An electrostatic transport system for lunar and Martian regolith particles was developed to realize In-Situ Resource Utilization for the successful long-term exploration of the Moon and Mars. The new system utilizes the dielectric elastomer actuator (DEA), which consists of a dielectric elastomer film sandwiched between elastic plate electrodes. When a high AC voltage is applied to the electrodes, the dielectric elastomer is driven by Maxwell stress and the resultant vibration is utilized to transport the regolith. The system has no mechanical drives and does not need complicated controls or high power consumption; thus, it is highly reliable for space application. In this study, the motions of regolith particles on a vibrating plate in the Earth and Moon environments were firstly investigated using a simple model calculation. Then, two types of vibration transport systems using DEA were developed based on the calculation results, and the basic characteristics of vibration transport for regolith were experimentally determined. The calculation result shows that the acceleration of the vibrating plate is the key factor for the success of vibration transport, and the lunar regolith simulant FJS-1 could be experimentally transported at a feed rate of approximately 1.95 g/s on the Earth using one of the developed system types when the plate acceleration exceeded 14.7 m/s(2). It is expected that the transport performance of the system will be improved in the Moon environment owing to the absence of air drag and the small gravitational force. (C) 2017 Elsevier B.V. All rights reserved.

A particle-size sorting system of lunar regolith using an electrostatic traveling wave is developed for In Situ Resource Utilization on the Moon to extract indispensable resources from the regolith and realize long-term exploration. The regolith is sorted by utilizing a balance between the electrostatic and gravitational forces, which are determined depending on particle size, in vacuum conditions where the particles are not subjected to air drag. In this study, the effect of particle charge on the particle motion is confirmed by conducting model experiments and numerical calculations based on the distinct element method. In addition, it was experimentally demonstrated that particles less than approximately 20 gm in diameter were efficiently separated from the bulk of a lunar regolith simulant FJS-1 in a vacuum condition (-1.5 x 10(-2) Pa), and the performance of the size sorting system on the Moon was predicted by the numerical calculations. The system utilizes only the electrostatic force, and it does not require any gas, liquid, or mechanical moving parts. (C) 2017 Elsevier B.V. All rights reserved.

To achieve reliable and autonomous regolith sampling from asteroids in space, the authors have developed a new sampling system that utilizes electrostatic force. This system consists of electrostatic capture and transport subsystems. Regolith particles on an asteroid are captured through parallel screen electrodes activated by the application of an alternating high voltage. The captured particles are then transported to a collection capsule from side to side basically along the electric flux lines in a zigzag path where an alternating electrostatic field is applied. It has been demonstrated that glass and sand particles can be transported in the horizontal direction that imitates micro-gravity on asteroids. The transport rate was increased by applying a high voltage of appropriate frequency. The demonstrated transport rate was approximately 3 g/min. The configuration of the path was improved to increase the transport performance. Numerical calculation using the discrete element method predicted that the transport of particles is successful if the gravity is less than 0.02-G. The process of sampling particles on asteroids will be easier than that on the Earth, because gravity is extremely low on small asteroids, particles are assumed to be highly charged because of cosmic rays, no air drag is exerted on the particles, and high voltage can be applied in vacuum where no gas discharge occurs. (C) 2016 Elsevier B.V. All rights reserved.

The authors have developed an electrostatic force-based sampler to reliably and autonomously sample asteroid regolith. After applying a rectangular high voltage between parallel screen electrodes mounted at the lower end of a tube, the resultant electrostatic force acts on nearby regolith particles. Some agitated particles are captured when passing through the screen electrode openings and transported to a collection capsule through the tube. In a microgravity environment, effective particle sampling was expected because particle motions are not affected by the negligible gravitational force. The authors confirmed the sampler's performance in a microgravity environment through numerical calculations and a model experiment. The calculation using the distinct element method predicted successful regolith capture, including conductive and insulative particles, under air and microgravity. The sampler shows much better performance in vacuum than in air. Lunar regolith simulant was sampled experimentally in a zero-g environment reproduced by the parabolic flight of an aircraft. A large amount of simulant (approximate to 900mg) containing small and large (diameter: >0.5mm) particles was successfully collected.

To realize reliable and autonomous sampling of regolith on the Moon and Mars, the authors have developed a unique sampling system that employs electrostatic force and mechanical vibration for the capture and transport of particles. A high alternating current (ac) voltage is applied between parallel screen electrodes mounted at the end of the sampling tube. Regolith particles on the surface of the Moon and Mars are captured using an electrostatic force, and they are passed through the openings of the screen electrodes. The captured particles are then transported through a tube to a capsule against gravity utilizing mechanical vibration. Experiments demonstrated that regolith is captured for a short time period if the open end of the sampling tube is immersed in the regolith layer. The captured regolith is transported upward through the inclined sampling tube against gravity. However, if the regolith in the vicinity of the fixed tube is depleted, the transport rate is decreased. The regolith particles are captured by the alternative electrostatic force. The capture rate increased with increases in the applied voltage. The electrostatic capture supplements the vibration capture, but the total collection rate is dependent on the amount of simulant captured at the tube entrance, or capture-controlled. (C) 2015 American Society of Civil Engineers.

To realize reliable and autonomous sampling of regolith on the Moon and Mars, the authors have developed a unique sampling system that employs electrostatic force and mechanical vibration for the capture and transport of particles. A high alternating current (ac) voltage is applied between parallel screen electrodes mounted at the end of the sampling tube. Regolith particles on the surface of the Moon and Mars are captured using an electrostatic force, and they are passed through the openings of the screen electrodes. The captured particles are then transported through a tube to a capsule against gravity utilizing mechanical vibration. Experiments demonstrated that regolith is captured for a short time period if the open end of the sampling tube is immersed in the regolith layer. The captured regolith is transported upward through the inclined sampling tube against gravity. However, if the regolith in the vicinity of the fixed tube is depleted, the transport rate is decreased. The regolith particles are captured by the alternative electrostatic force. The capture rate increased with increases in the applied voltage. The electrostatic capture supplements the vibration capture, but the total collection rate is dependent on the amount of simulant captured at the tube entrance, or capture-controlled. (C) 2015 American Society of Civil Engineers.

A unique shield system has been developed utilizing electrostatic force to remove dust breaking into bearings and mechanical seals of equipment used for space exploration. Because the performance of the former system was not satisfactory for mitigating dust intrusion, we added wire electrodes above the former system to improve the performance. As the result, approximately 95 % of dust was repelled from the gap. Moreover, we developed a numerical calculation algorithm using distinct element method for decreasing calculation load without decreasing calculation accuracy. It was predicted by the developed numerical method that the shield performance of the electrostatic dust shield system would be great on the Moon and Mars environment if dust would be charged strongly. This technology is expected to increase the reliability of equipment used in long-term manned and unmanned activities on the Lunar and Martian surface.

To realize reliable and autonomous regolith sampling from asteroids in space, the author has developed a new sampling system that uses electrostatic force. This system uses a combination of electrostatic capture and transport of particles. High voltage is applied between parallel screen electrodes of the sampling device. As a result of the electrostatic force, particles are captured by the screen electrodes. The captured particles are then transported by an electrostatic traveling wave and transferred to a collection capsule. It has been demonstrated that lunar soil simulant, iron particles, and crushed ice can be sampled if the end of the screen electrode is in contact with the regolith for a short period of time (within 1 s). Because gravity is extremely low on small asteroids, the process of sampling particles on asteroids will be easier than that on the Earth.

A unique shield system for lunar dust has been developed using electrostatic force to prevent dust from entering into bearings and mechanical seals of equipment used for lunar exploration. A single-phase rectangular high voltage is applied to insulated parallel-plate electrodes printed on the edges of the gap in the mechanical sealing part. It was demonstrated that more than 70% of the dust was repelled from the gap with very little power, and it was predicted by numerical calculations performed using the distinct element method that the shielding performance of the system would improve further in the low-gravity and vacuum environment of the Moon. This technology is expected to increase the reliability of equipment used in long-term manned and unmanned activities on the lunar surface.

An improved cleaning system has been developed that uses electrostatic force to remove sand from the surface of solar panels. A single-phase high voltage is applied to parallel wire electrodes embedded in the cover glass plate of a solar panel. It has been demonstrated that more than 90% of the adhering sand is repelled from the surface of the slightly inclined panel after the cleaning operation. The performance of the system was further improved by improving the electrode configuration and introducing natural wind on the surface of the panel, even when the deposition of sand on the panel is extremely high. The power consumption of this system is virtually zero. This technology is expected to increase the effective efficiency of mega solar power plants constructed in deserts at low latitudes. (C) 2014 Elsevier B.V. All rights reserved.

We have developed a numerical method to calculate the particle dynamics in electrophotographic two-component development system using Distinct Element Method(DEM).A characteristic of the method is that takes it account of particle conductivity and electric conduction in chains of carrier particles.Calculated results qualitatively agreed to the experimental results with respect to the amount of developed toner particles and the basic property of the Bead-Carry-Out(BCO)phenomenon under the varied contact condition between magnetic brush and photoconductor and the speed ratio between the development sleeve and photoconductor drum.

We have developed a numerical method for calculating the motion of toner and carrier particles in an electrophotographic two-component magnetic brush development system to improve system performances by using a three-dimensional distinct element method. Key features of this simulation method are that forces applied to toner and carrier particles include not only magnetic but also electrostatic forces involving a time-dependent electric current in the brush of conductive carrier particles and the air drag due to the airflow induced by the rotation of the development sleeve and photoreceptor drum. Numerical calculations were performed to investigate several subjects that have not been investigated thoroughly : chain formation of the carrier brush, effectiveness of noncontact development, bead-carry-out, and effect of airflow. It was confirmed that the calculation results agree with the experimental observations, and some countermeasures against image defects are proposed. It is expected that the presented numerical method can be used to improve the two-component magnetic brush development system in electrophotography.

Microspray mode of electrostatic inkjet has been examined experimentally for the application of precision film coating. One of the critical issues lies in productivity because the amount of liquid jetted from a single nozzle is too small to obtain sufficient coating speed. To overcome the situation, a possibility of jetting two types of functional liquids from multi-nozzle was investigated. Both end-nozzles were used as electrodes to control jetting direction. According to the increment of applied voltage, jetting mode was varied from dripping to stable cone-jet. Although the evolution of jetting mode was qualitatively the same as that of a single nozzle, the much higher voltage was required for the multi-nozzle to obtain the stable jetting mode. Calculated results suggested that the higher voltage adjusted the force from electric field at the tip of the cone jet. From coating experiments on a rotating drum, it was demonstrated that the multi-nozzle with control electrodes at high applied voltage could jet well-oriented fine droplets to acquire thin or thick flat film. It was confirmed that the coating speed was improved according to the number of the nozzles.

A unique shield system has been developed utilizing electrostatic force to remove dust breaking into bearings and mechanical seals of equipments used for lunar exploration. A single-phase rectangular voltage was applied to insulated parallel plate electrodes printed on a substrate at the clearance of the mechanical sealing part. Because the performance of the former system was not satisfactory at an inclined angle of 30°, we added support electrodes outside of the main electrodes so that the system with the support electrodes generates wide electrostatic field to improve the performance. As the result more than 80% of dust was repelled from the clearance, and it was predicted by the numerical calculation using the distinct element method that the cleaning performance to charged particles would be further improved in the low-gravity and vacuum environment of the Moon. This technology is expected to increase the reliability of equipment used in long-term manned and unmanned activities on the lunar surface.

To realize reliable regolith sampling for autonomous operation in space, the authors have developed a new sampling system that employs electrostatic force. This system employs a combination of electrostatic capture and transport of particles. High voltage is applied between parallel screen electrodes of the sampling device. Owing to electrostatic force, particles are captured at the screen electrode of the device. The captured particles are then transported by an electrostatic traveling wave and transferred to a collection capsule. It has been demonstrated that lunar soil simulant can be sampled if the end of the screen electrode is in touch with the regolith for short period, within one second. Because gravity is extremely low on small asteroids, the process of sampling particles on asteroids will be easier than that on the Earth.

A unique shield system has been developed utilizing electrostatic force to remove dust breaking into bearings and mechanical seals of equipments used for lunar exploration. A single-phase rectangular voltage was applied to insulated parallel plate electrodes printed on a substrate at the clearance of the mechanical sealing part. Because the performance of the former system was not satisfactory at an inclined angle of 30°, we added support electrodes outside of the main electrodes so that the system with the support electrodes generates wide electrostatic field to improve the performance. As the result more than 80% of dust was repelled from the clearance, and it was predicted by the numerical calculation using the distinct element method that the cleaning performance to charged particles would be further improved in the low-gravity and vacuum environment of the Moon. This technology is expected to increase the reliability of equipment used in long-term manned and unmanned activities on the lunar surface.

The removal of lunar dust adhered to an astronaut's spacesuit is critical for long-term lunar exploration. The author is developing a cleaning device that utilizes electrostatic force; this system employs a combination of electrostatic capture and electrostatic transport of dust. High voltage is applied between a screen electrode and an aluminum film deposited on a Mylar sheet positioned under the surface fabric of the spacesuit. By means of electrostatic force, dust adhered to the fabric is captured at the screen electrode of the device. The captured dust is then transported by an electrostatic traveling wave and transferred to a collection bag. The capture rate increased with the amount of dust adhered to the fabric and reached a value of 82%. Although small particles trapped between fabric fibers were difficult to remove, this system should be used in preliminary cleaning of spacesuits, saving valuable time for astronauts on the Moon. DOI: 10.1061/(ASCE)AS.1943-5525.0000143. (C) 2012 American Society of Civil Engineers.

In a non-magnetic single-component development system in electrophotography, formation of a thin and uniform toner layer on the development roller is important for obtaining high image quality. We conducted experimental and numerical investigations to clarify the dynamics of toner particles in this process. Two approaches were adopted for the investigation. One is experimental and the other is numerical simulation using the distinct element method. We manufactured a mock-up apparatus consisting of a supply roller, a development roller, and a doctor blade for forming a thin toner layer on the development roller. The thickness, surface roughness, and charge density of the formed toner layer were measured after the doctoring process. It was clarified that the thickness of the toner layer was increased, but the charge density was decreased, by increasing the applied voltage and rotational speed. These findings were confirmed by direct observation of the toner motion in the doctoring area with a high-speed microscope camera. Numerical calculations performed using an improved distinct element method revealed that the elastic energy applied to the toner particles, which is an index of toner degradation, was increased by increasing the stiffness and pressing force of the doctor blade, but decreased when the curvature of the blade tip was large. The present experimental and numerical results can be used to improve non-magnetic single-component development system in electrophotography. © 2012 The Japan Society of Mechanical Engineers.

We studied the mechanism of and countermeasures against a pale image defect observed in the halftone area following a solid image in a two-component magnetic brush electrophotographic development system. We build a model machine that consisted of a pseudo-photoreceptor drum, development sleeve, and stationary magnetic roller to perform direct observations of the toner and carrier particles in the development area. The image was formed on an insulated film electrode pasted onto the drum. Instead of a digital halftone image, an analog halftone image was formed on the pseudo-photoreceptor. A parameter experiment showed that the image defect was enhanced when the voltage difference between the solid area and halftone area was large, the AC voltage superposed on the DC development voltage was low, the development gap was large, and the ratio of the sleeve speed to the drum speed was low. However, the defect was almost independent of the toner-to-carrier concentration ratio as well as the frequency and waveform of the superposed AC voltage. The dynamic behavior of the toner particles in the development area was directly observed using a high-speed microscope camera, and the cause of the print defect was investigated.

The removal of lunar dust adhering to spacesuits is essential for the long-term exploration of the Moon. Because lunar dust is magnetic, a convenient cleaning device that utilizes magnetic force has been developed. The device can capture and separate lunar dust continuously with a multipole magnetic roller. The observed separation rate was 90%, but the capture rate was low, resulting in an overall cleaning rate of 40%. The rate increased when large amounts of dust adhered to the fabric. Although it was difficult to capture small particles trapped between fabric fibers, this device will be able to preliminarily clean spacesuits and save the precious activity time of astronauts on the Moon. DOI: 10.1061/(ASCE)AS.1943-5525.0000101. (C) 2012 American Society of Civil Engineers.

To realize a long-term lunar exploration, it is essential to develop a technology for transporting lunar soil for in situ resource utilization. We are developing a particle transport system that utilizes electrostatic traveling waves. The conveyer consists of parallel electrodes printed on a plastic substrate. Four-phase rectangular voltage is applied to the electrodes to transport particles on the conveyer. Mechanical vibration was applied to the conveyer to transport particles more efficiently. The results of our investigation are as follows: (1) The observed transport rate in air was 13.5 g/min for a conveyer with a width of 100 mm. By performing numerical calculations on the basis of the 3D distinct element method, we predicted that the system performance would improve in the high-vacuum and low-gravity environment on the moon. (2) Power consumption in this system is much less. It was only 10 W for a conveyer with an area of 1.0 m(2). (3) We demonstrated an inclined and curved transport path as well as a flat and straight transport path. In addition, we demonstrated that transportation of particles through a tube and accumulation of scattered particles were also possible. DOI: 10.1061/(ASCE)AS.1943-5525.0000094. (C) 2012 American Society of Civil Engineers.

Removing lunar dust adhering to astronaut space suits is critically important for long-term lunar exploration. We are developing an automatic cleaning system that uses electrostatic force. It employs an alternating electrostatic field that forms a barrier on the surface of fabrics. In this study, we applied single-phase rectangular voltage to parallel wire electrodes stitched into the insulating fabric of space suits. By applying mechanical vibration and operating the system in a vacuum, we realized high performance: the cleaning rate exceeded 80%. Flicking out particles smaller than 10 mu m in diameter that were trapped between fibers was difficult, but this system can perform preliminary space suit cleaning and save precious time for astronauts on the moon. DOI: 10.1061/(ASCE)AS.1943-5525.0000084. (C) 2011 American Society of Civil Engineers.

We developed electrostatic system for manipulating small particles with diameters in the range of several micrometers to 100 mu m. The electrostatic manipulation probe consists of a monopole pin electrode. When voltage is applied to the electrode, a dielectrophoresis force generated in the nonuniform electrostatic field is applied to the particle near the tip of the electrode. The particle is captured with the application of voltage, and then it is released from the probe by applying a high voltage of the opposite polarity. It is possible to manipulate not only insulative but also weakly conductive particles. A three-dimensional field calculation and a measurement of the adhesion force were conducted to evaluate the force balance for the capture and release of a particle. On the basis of these investigations, we demonstrated the manipulation of actual lunar dust returned by the Apollo 11 lunar surface mission. (C) 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

A unique shield system of lunar dust has been developed utilizing electrostatic force to remove dust breaking into bearings and mechanical seals of equipment used for lunar exploration. A single-phase rectangular voltage is applied to parallel plate electrodes printed on substrates at the gap of the mechanical sealing part. Approximately 60% of dust was repelled from the gap, and it was predicted by the numerical calculation using the distinct element method that the cleaning performance of the system would be further improved in the low-gravity and vacuum environment of the Moon. This technology is expected to increase the reliability of equipment used in long-term manned and unmanned activities on the lunar surface.

A system for removing lunar dust from the surface of solar panels and optical elements is of great importance for lunar exploration. We have developed a method of removing lunar dust using electrostatic traveling-waves generated by four-phase rectangular voltage applied to a transparent conveyer consisting of parallel ITO (indium tin oxide) electrodes printed on a glass substrate. On the basis of basic investigations, we have demonstrated the removal of actual lunar dust. A numerical investigation predicts that the performance will improve in the low-gravity environment on the Moon. (C) 2011 Elsevier B.V. All rights reserved.

A unique cleaning system has been developed utilizing electrostatic force to remove lunar dust adhered to the mechanical parts of equipment used for lunar exploration. A single-phase voltage is applied to parallel electrodes printed on a flexible substrate to remove the dust. More than 90% of adhered dust was repelled from the surface of the slightly inclined device in a vacuum, and the cleaning performance of the system would be further improved in the low-gravity environment of the Moon. This technology is expected to increase the reliability of equipment used in long-term manned and unmanned activities on the lunar surface. (C) 2011 Elsevier B.V. All rights reserved.

The dynamics of toner and carrier particles in a two-component development system used in electrophotography were studied to clarify the development characteristics and to reduce the image defects due to the bead-carry-out (BCO) phenomenon. The height of the developed toner line image and the density of carrier particles adhered to the photoreceptor surface after development were measured and the behavior of the toner and carrier particles was observed using a high-speed microscope camera. This study clarifies that development occurs not only in the contact area between the carrier brush and the photoreceptor but also in the pre- and postnip regions where the brush does not make contact with the photoreceptor and that the occurrence of BCO is reduced in the image area rather than in the nonimage area at a low dc development voltage at a high toner concentration and with the development sleeve at a high-speed ratio. The mechanisms of these phenomena are investigated using independent experimental and numerical analysis. (C) 2011 Society for Imaging Science and Technology. [DOI: 10.2352/J.ImagingSci.Technol.2011.55.3.030507]

Removal of lunar dust adhering to mechanical equipments is of critical importance for long-term lunar exploration. We are developing an automatic cleaning system that utilizes electrostatic force. It employs an alternating electrostatic field that forms a barrier on the surface of fabrics. In this study, single-phase rectangular voltage was applied to parallel wire electrodes stitched into the insulating fabric of spacesuits. It was observed that the cleaning rate exceeded 80%. High performance will be realized by applying mechanical vibration and operating the system in vacuum. Although it was difficult to flick out small particles of less than l0-pm diameter, this system can preliminary clean mechanical equipments on the Moon.

Applying micro spray of electrostatic inkjet to precision film coating was examined experimentally. Using a single nozzle, high quality coating was demonstrated by the authors elsewhere. A critical issue, however, lies in terms of productivity; the amount of liquid jetted from a nozzle was too small to obtain sufficiently high coating speed. To overcome the situation, a possibility of a multi-nozzle was tried in this report. The liquid was dilute dispersion of photo-sensitive pigment. As results, from seven nozzles of stainless steel multi-nozzle, jetting direction was fanned out toward the opposite plate electrode. By clogging the both end nozzles and making them as electrodes, the direction was remedied and parallel jets were obtained. According to the increment of applied voltage, jetting mode was varied from dripping mode to cone-jet mode. Although the variation of jetting mode was qualitatively the same as that of a single nozzle, the higher voltage was required for a multi-nozzle. Furthermore, the mode change and uniform distribution of droplets always started from the end nozzles. Again, high voltage was required to alleviate the fluctuation of the droplet size distribution. From simple line-coating experiments suggested that the multi-nozzle with dummy electrodes at high applying voltage could jet well-oriented fine and uniform droplets to acquire quality film coating.

Applying micro spray of electrostatic inkjet to precision film coating was examined experimentally. Using a single nozzle, high quality coating was demonstrated by the authors elsewhere. A critical issue, however, lies in terms of productivity; the amount of liquid jetted from a nozzle was too small to obtain sufficiently high coating speed. To overcome the situation, a possibility of a multi-nozzle was tried in this report. The liquid was dilute dispersion of photo-sensitive pigment. As results, from seven nozzles of stainless steel multi-nozzle, jetting direction was fanned out toward the opposite plate electrode. By clogging the both end nozzles and making them as electrodes, the direction was remedied and parallel jets were obtained. According to the increment of applied voltage, jetting mode was varied from dripping mode to cone-jet mode. Although the variation of jetting mode was qualitatively the same as that of a single nozzle, the higher voltage was required for a multi-nozzle. Furthermore, the mode change and uniform distribution of droplets always started from the end nozzles. Again, high voltage was required to alleviate the fluctuation of the droplet size distribution. From simple line-coating experiments suggested that the multi-nozzle with dummy electrodes at high applying voltage could jet well-oriented fine and uniform droplets to acquire quality film coating.

We have studied the dynamics of toner and carrier particles in a two-component magnetic brush development system used for electrophotography in order to improve the image defect due to the bead-carry-out (BCO) phenomenon. It has been confirmed that developed toner particles on the photoreceptor increases and the number density of the adhered carrier particles decreases when the effective AC voltage superposed on the DC development voltage is high. Because the developed toner particles reduce the surface voltage of the latent image on the photoreceptor, the BCO is improved when the amount of developed toner particles is high.

Applying micro spray of electrostatic inkjet to thick film coating was examined experimentally. High quality coating is expected by drops-on-drops of super fine and mono-diameter droplets. At first, the jetting states of two viscous solutions were observed to determine coating parameters. Then, with those parameters examined, the possibility of thick film coating was tested. According to the increment of applied voltage, jetting mode was varied from Mode 1, dripping, to Mode 2, jetting. The most favorable condition for coating was the stable cone-jet mode in the jetting mode, where a well-oriented thread was jetted from the stable Taylor Cone at the nozzle tip and broken up into mist during flight. From the coating experiments with the selected liquid and conditions of jetting, the possibility of uniform and thick film was demonstrated by piling up the droplets several times, whose diameters were less than 10 micrometers. The alternative methods to enhance breaking up of droplets and stabilize its process were also proposed.

This paper provides an overview of the recent progress of simulation technology of electrophotography. Numerical simulation is indispensable for reducing development term and cost, and improving image quality and reliability. Efficient simulation, which used to be impossible a decade ago, becomes possible utilizing highly efficient hardware and software. The dimension of calculations is progressed from one-dimension to three-dimension and more detailed simulation can be carried out. Almost all the processes of electrophotography;charging, exposure, development, transfer, fusing, cleaning, paper handling and adhesion of toner particle, are being investigated with simulations.

A non-magnetic and non-contact AC development process has been numerically investigated using two-dimensional dynamic model. Simulation of toner dynamics in the development process was carried out using the Finite Difference Method (FDM) for the electric field calculation and the Distinct Element Method (DEM) for the calculation of charged toner motion in the electric field. Distribution of the electric charge density on a photoreceptor, the electrostatic latent image, was derived from a spot profile of a laser beam. Calculated results showed fairly good agreement with experiments.

The Lunar Airborne Dust Toxicity Assessment Group (LADTAG) is working to determine the permissible limits for exposure to lunar dust. This standard will guide the design of airlocks and ports for EVA, as well as the requirements for filtering and monitoring the atmosphere in habitable vehicles and other modules. Rodent toxicity testing will be done using the respirable fraction of actual lunar soils (particles with physical size of less than 2.5 micrometers). We are currently separating this fine material from the coarser material that comprises &gt
95% of the mass of each soil sample. Sieving is not practical in this size range, so a new system was developed for this task. Collection and separation efficiencies are tracked as development and tests proceed. LADTAG's recommendation for permissible exposure limits will be delivered to the Constellation Program in 2010. © 2010 ASCE.

In order to realize a long-term lunar exploration, it is essential to develop a technology for transporting lunar soil for in-situ resource utilization. We are developing a particle transport system that uses electrostatic traveling-waves. The conveyer consists of parallel electrodes printed on a plastic substrate. Four-phase rectangular voltage is applied to the electrodes to transport particles on the conveyer. Ultrasonic vibration was applied to the conveyer to transport particles efficiently. The following points are the outline of our investigation: (1) The observed transport rate in air was 2 g/min. Through numerical calculations based on the 3D distinct element method, we predicted that the system performance would improve in the high vacuum and low-gravity environment on the moon. (2) The power consumption of this system is very less. It was only 4 W for a 1-m2 area of the conveyer. (3) We demonstrated an inclined and curved transport path as well as a flat and straight transport path. In addition, we demonstrated that transportation of particles through a tube and accumulation of scattered particles were also possible. © 2010 ASCE.

The authors used a simple model and a prototype machine to study statics and dynamics of a magnetic brush in a two-component development system in electrophotography In the model experiment, the authors measured the normal and tangential forces of the brush formed from a chain of magnetic carrier particles when it comes in contact with the photoreceptor to clarify the relationship between the tangential friction force and the diameter of the carrier particles, magnetic flux density, and the length of the brush. The tangential friction force increased with the magnetic flux density and decreased with an increase in the length of the brush; however, the total force was unaffected by the diameter of the carrier particles. On the other hand, numerical calculations performed using an improved distinct element method revealed that although the total force was not affected by the diameter of the carrier particles, the individual differential force acting on the magnetic particles of the chain was small, and the density of the carrier particles that come in contact with the photoreceptor drum was high when the size of the particles was small. In the investigation carried out using the prototype machine, it was found that the magnetic brush formed in the development area is inclined in a direction parallel to the magnetic field and that the chains are crushed by the photoreceptor drum. Although the total pressure applied on the photoreceptor was almost independent of the diameter of the carrier particles, the differential force exerted by individual chains is small and distributes dense when the size of the particles is small; on the other hand, it is large and distributes rough when the size of the particles is large as predicted by the model investigation. This result suggests that small carrier particles are advantageous in preventing any disturbances in the images developed on the photoreceptor The effects of the development gap and the thickness of the layer of supplied carrier particles have also been evaluated. (C) 2009 Society for Imaging Science and Technology. [DOI: 10.2352/J.ImagingSci.Technol.2009.53.6.060201]

Because manipulation of single particles is of great importance in the fields of electronics and biology, the author has been investigating an electrostatic manipulation system. The manipulation probe consisted of dipole pin electrodes. When voltage was applied between the electrodes, the dielectrophoresis and coulombic force generated in the non-uniform electrostatic field was applied to the particle near the tip of the electrode. The particle was captured by the application of voltage and then it is released from the probe by turning off the voltage application. It was possible to manipulate not only insulative but also conductive particles. However, if a particle was charged, the Coulomb adhesion force prevented the release of the particle even when the voltage application was turned off. This condition was generally observed for small particles. Asymmetric and coaxial electrode systems were developed so that the release of the attached particle was independent of the position of the probe. Instead of turning off the voltage application, high voltage was applied to the electrodes to blow off the particle by the ionic wind generated in a corona discharge field, and the applicability of this system was demonstrated. Further, a vibration separator was developed. A three-dimensional field calculation was conducted to calculate the dielectrophoretic force by using the finite difference method and the calculated force was compared to the measured force. It was deduced that the predominant force for the particle adhesion was not dielectrophoresis but Coulomb force generated due to triboelectrification. (C) 2009 Elsevier B.V. All rights reserved.

The generation of ozone in the plasma actuator that consists of simple parallel line electrodes separated by a thin dielectric layer was evaluated at the frequency less than 1000Hz. It was measured that the ozone generation was increased under the conditions of high applied voltage and high frequency but irrelevant to the gap between the electrodes. The measured ozone concentration under the conditions of 6kV-1000Hz applied voltage and 1.5liter/min flow rate was approximately 100ppm, which is much higher than the human safety standard value of 0.1ppm.

Applying micro spray of electrostatic inkjet to precision film coating was examined experimentally. High quality coating could by expected by drops-on-drops of super fine and mono-diameter droplets. At first, the most preferable jetting condition was determined through experiments with dilute dispersion of photo-sensitive pigment. Then, with those parameters examined, the surface quality of the coated films was evaluated through several coating tests. According to the increment of applied voltage, jetting mode was varied from Mode 1, dripping, to Mode 2, jetting. Most favorable condition for coating was found to be cone-jet mode in Mode 2, where well-oriented thread was jetted from the stable Taylor Cone at the nozzle tip and broken up into spray state during flight. Uniform and submicron film could be demonstrated by piling up the droplets several times, whose diameters were less than 10 micrometers, although unknown processes such as drying during flight, leveling phenomena on a coating substrate should be elucidated to meet industrial needs.

Transport and mitigation technology of lunar dust has been developed utilizing the electrostatic traveling wave applied to the electrostatic conveyer consisting of parallel electrodes. Four-phase rectangular voltage was applied to electrodes because it was most efficient compared to the sine or triangular wave. Traveling-wave propagation was achieved utilizing a set of positive and negative amplifiers controlled by a microcomputer. The power system was designed simple, small, and lightweight for the space application. The transport rate of more than 90% was realized in vacuum with this system under conditions of 700V voltage and less than 100Hz frequency. However, very small particles adhered mainly on the electrodes, probably due to the electrostatic image force, and they were not transported. The adhered dust was increased but saturated to the repeated operation. Because it is assumed that the lunar dust is charged by the irradiation of the solar wind and the cosmic ray, it was investigated whether initially charged particles can be transported efficiently with this system. The transport rates with positively charged particles (+0.6μC/g) and negatively charged particles (-0.6μC/g) were almost the same to the rate without charge. The power consumption of this system was measured and it was estimated that it takes only 0.08Wh for once operation of a 1m^2 conveyer. Numerical investigation was carried out with a three-dimensional hard-sphere model of the Distinct Element. Method to clarify the mechanism of the transport. This technology is expected to be utilized for the transport and mitigation of lunar dust for the lunar exploration.

A cleaning system for removing lunar dust from the surfaces of solar panels and optical lenses will be of great use for lunar exploration. Hence, we are developing a cleaning system based on electrostatic force generated by the electrostatic traveling-wave for removing lunar dust. We have developed an electrostatic cleaning plate with transparent ITO (Indium Tin Oxide) electrodes and demonstrated using lunar dust simulant that the decrease in the transmission rate of light is only by several percent by the application of ultrasonic vibrations in a vacuum even if lunar dust was initially charged. Based on these investigations, we have successfully demonstrated the electrostatic cleaning of real lunar dust returned by the Apollo 11 lunar surface mission. Finally, we have carried out a numerical simulation and proven that the performance of the system will improve in the low-gravity environment on the moon.

A print defect of streaking takes place in an offset printing machine after a ditch of a blanket drum collides with the ditch of another facing blanket drum and a proof cylinder. The streaking is visible just after the collision on a paper printed half-tone solid image. These experimental features suggest that the defect is caused by the vibration of blanket drums in the opposite direction due to the collision of these ditches, that is, caused by the alternation of the print pressure due to the relative displacement of a facing blanket drums. This hypothesis was proven by the experiment that the pitch and phase of streaking coincided with those of the relative displacement that determined the print pressure. The experimental results were confirmed by the numerical calculation based on a simple linear vibration model of eight-degree-of-freedom. In conclusion, the mechanism and characteristics of the vibration were clarified and the present investigation has been utilized for the improvement of the design.

We have studied friction force of magnetic carrier brushes to the photoconductor drum in two-component magnetic development system of electrophotography by a model experiment and the numerical simulation with the Distinct Element Method. Axial and lateral forces of chain-like brushes applied to the photoconductor were measured to clarify the relationship between the lateral friction force and the diameter of carrier particles, magnetic flux density, and the brush length. It was observed that the force was increased in accordance with the increase of the magnetic flux density and decreased with the brush length but the particle diameter did not affect the total force. On the other hand, the numerical calculation deduced that although the total force is not affected by the particle diameter, the individual differential force of the chain was small and the density of contact points of the brush was high for small particles.

Stability of a drop in a pin-to-plate electrohydrostatic system was examined both theoretically and experimentally. With this static model, the mechanism of electrostatic ink jetting process was estimated. The basic equations are the augmented Young-Laplace equation for drop shape and the Laplace equation for electric field. These coupled equations were solved by the Finite Element Method. By the initial condition of its shape, a drop could be deformed into anomalous shapes, such as "nipple" and "dog bone," as well as conical shape, often referred as Taylor cone with the increment of non-dimensional electric field. The concentration of electric field around the corner of a nozzle was the cause of these anomalous shapes. By this stability analysis, it was demonstrated that the electrostatic ink jetting modes, dripping mode and the onset of cone-jet mode, were governed by the force balance between forces from surface tension, pressure and electrostatic field.

We commenced basic research on the three-dimensional (3D) pattern formation of microgel beads for applications in biological tissue engineering. In this new technique, microgel beads are premagnetized by doping them with magnetic nanoparticles. Living cells will be included in the beads for actual use. If a nonuniform magnetic field is applied to a solution containing these magnetized beads, the beads will align, contact, and form a 3D structure. The structure is controlled by the seed pattern of the magnetic particles plugged in a substrate and the profile of the magnetic field distribution. We constructed tubes, which imitate blood vessels, for demonstration using gel beads whose diameters are of the order of several tens of micrometers. The diameter of the demonstrated tube was less than 0.5 mm and its length was 6.6 mm, although living cells were not included in the beads. Numerical calculations by using the discrete element method were conducted to confirm the formation of the tube and to predict the effect of centrifugal force, which will be applied to fill cells in the space between magnetically patterned beads. Although this unique technology is in the nascent stage, this 3D pattern formation technique by the control of the magnetic field has potential to be one of the effective engineering technologies for manufacturing 3D patterned biological tissues in the future.

We have investigated dynamics of a magnetic brush of carrier particles in the two-component development system of electrophotography by the numerical simulation with an improved Distinct Element Method and the experimental observation with a high-speed microscope camera. Two-dimensional magnetic field was calculated by superposing measured discrete magnetic flux densities on a development sleeve. It has been calculated and observed that magnetic chains of the brush grow up in the development area inclining in parallel in the direction of the magnetic field and they are crushed by a photoreceptor drum. The brush is depressed to backward before the center of the gap and springs just before the brush become free. The spring-back of the brush at the backward of the development area seems to cause a stripe defect of the developed toner images on the photoreceptor if the force applied by the brush to the photoreceptor is excessive. The differential force applied by individual chain is dense and small with small particles. On the other hand, it is rough and large with large particles. These suggest that small carrier particles are preferable to prevent disturbance of developed toner particles on the photoreceptor. The effects of the development gap and the thickness of supplied carrier particles have also evaluated.

Dynamics of toner particles in the magnetic single-component development system of electrophotography have been investigated to utilize for the improvement of the system. Two approaches have been adopted for the investigation: One is the direct observation of the toner motion in a development area with a high-speed microscope camera and another is the numerical simulation with the distinct element method. We have manufactured the mock-up apparatus that consisted of a pseudo-photoreceptor, development roller, stational magnetic roller inside it, and doctor blade to form thin toner layer on the development roller. The development roller, magnetic roller, and blade were diverted from a commercial printer. Thin line electrodes were embedded on the pseudo-photoreceptor drum to substitute for electrostatic latent images. The apparatus enabled high-speed observation of toner motion at the development gap with satisfactory image quality. Observed images showed that (1) toner particles formed chain-like clusters in the vicinity of the gap, (2) these chains vibrated at the development zone synchronized with an applied alternative electrostatic field, (3) at the latent image, chains crashed on the photoreceptor and then fell apart from the photoreceptor, and (4) at this moment, some of toner particles returned to the development roller but some adhered to the latent image to form a real image. Three-dimensional shapes of toner piles on the latent image were measured after the development by a scanned laser displacement meter. It has been clarified that both the width and height of the toner pile increased with an increase in the development voltage but these were saturated at the voltage higher than a threshold. Numerical simulation has been conducted to confirm the experimental results. The simulation method is based on a hard sphere model of the distinct element methtd with cyclic boundary condition. The method can be applied for the dynamics of small toner particles within reasonable calculation time.

Because a cleaning system of lunar dust on the solar panel and optical lens is of great importance for the lunar exploration, we are developing a cleaning system of lunar dust utilizing electrostatic force. Although it has been demonstrated that particles can be transported by the traveling-wave electric field formed by the parallel electrodes, some specific issues must be overcome to utilize this system for the lunar exploration. That is, a device must be transparent and highly efficient in the lunar environment. The electrostatic cleaner plate with transparent ITO electrodes was developed and it has been demonstrated that the decrease of the transmission rate of light was reduced only several percent by applying ultrasonic vibration in vacuum even if lunar dust was charged positively or negatively before operating the system. Finally, numerical simulation was conducted and it predicted that the performance will be further improved in the low gravity environment on the moon.

Applying micro spray state of electrostatic inkjet to precision film coating was examined experimentally. High quality coating could be expected by drops-on-drops of super fine and mono-diameter droplets. At first, the most preferable jetting condition was determined through experiments for two types of coating liquid, one of which was dilute dispersion and the other was viscous solution. Then, with those parameters examined, the surface quality of the coated films was evaluated through several coating tests. Along increasing applied voltage, jetting mode was varied from Mode 1, dripping mode, to Mode 2, jetting mode. The basics of jetting mode variation was equivalent for both types of coating liquid, although a larger nozzle had to be used for the viscous solution to avoid clogging. The most favorable condition for coating was the stable cone-jet mode in Mode 2, where a well-oriented thread was jetted from the stable Taylor cone at the nozzle tip and broken up into mist during flight. Both types of quality coating, a submicron film with the dilute dispersion and a thick film, over 10 micrometers, with the viscous liquid could be demonstrated by piling up the single-digit-micron-size droplets.

We have studied the dynamics of toner and carrier particles in a two-component development system used for electrophotography in order to improve the image defect due to the bead-carry-out (BCO) phenomenon. We have manufactured a mock-up apparatus consisting of a pseudo-photoreceptor drum, development sleeve, and stationary magnetic roller. We have measured the number density of carrier particles adhered to the photoreceptor surface after the development process and have observed the behavior of the toner and carrier particles using a high-speed color microscope camera. It has been confirmed that the number density of the adhered carrier particles increases when the DC development voltage is high, toner concentration is low, and speed ratio of the development sleeve to photoreceptor drum is low. It has been observed that depletion of toner particles from the tips of carrier chains occurs in the post-nip region of the development area. It is assumed that when the initial toner concentration is lower than the threshold value, 6 wt%, insulative toner particles do not affect the electrical conduction of the conductive carrier chains, and therefore, the electrical charge at the top of the chains, which is induced by the applied voltage, increases. This increase in the electrical charge causes an increase in the Coulomb force applied to the top of the chains, and the BCO phenomenon occurs. On the other hand, when the speed of the development sleeve is low, the number of toner particles developed on the latent image is not sufficient to neutralize the surface potential of the latent image. The effective voltage between the sleeve and photoreceptor drum is not sufficiently reduced in this case, and thus, the BCO phenomenon Occurs.

We have studied dynamics of magnetic brushes in the two-component development system of electrophotography by the numerical simulation with an improved Distinct Element Method (DEM) and experimental observation with a high-speed microscope camera. Two-dimensional magnetic field was calculated by superposing measured discrete magnetic flux densities on a development sleeve. It has been calculated and observed that magnetic brushes grow up in the development area inclining in parallel in the direction of the magnetic field and they are crushed by a photoreceptor drum. It has been evaluated that although the total pressure applied to the photoreceptor is almost irrelevant to the diameter of carrier particles, differential force applied by individual chain is dense and small with small particles but rough and large with large particles. This suggests that small carrier particles are preferable to prevent disturbance of developed toner particles on the photoreceptor.

An organic photoreceptor (OPC) drum for electrophotography is mainly manufactured by the dipcoating technology. However, large amount of coating solution is necessary for the dipcoating. In this report, we purposed a new coating method for the carrier generation layer of the OPC utilizing a liquid atomization phenomenon of the electrostatic inkjet system. Atomization of the carrier generation solution had been controlled by the applied voltage and the gap, and we have succeeded to coat a uniform film in 10 × 10 mm.

An electrostatic micro-ozone fan that utilizes the ionic wind induced in a pin-to-plate gas discharge field was developed for utilizing it in the micro-cooling system of electronic devices and a localized oxidization system, and its fundamental characteristics were elucidated through experiments and calculations. The fan consisted of a pin electrode and a plate electrode with a hole. When a high voltage was applied between the electrodes, the ionic wind containing ions and ozone flowed through the hole of the plate electrode toward a heated target. An experimental investigation indicated that the heat transfer could be enhanced by applying a positive voltage and approximately 10-ppm ozone could be generated and made to flow by utilizing the negative corona discharge. The experimental results were in good agreement with the numerical calculations performed in three steps, i.e., the calculation of the corona discharge field, calculation of the ionic wind induced by the migration of ions, and calculation of ozone generation in the corona discharge field. By performing a parametric experiment, the optimal geometry was deduced and local cooling was demonstrated by using a miniature fan. (C) 2008 Elsevier B.V. All rights reserved.

The author has developed five kinds of techniques on electrostatic separation of particle size utilizing the balance of the electrostatic and gravitational force. The first is an inclined plate conveyer system. A plate conveyer consisted of parallel electrodes was constructed and four-phase electrostatic traveling wave was applied to the electrodes to transport particles on the conveyer. Particles were separated with size under the voltage application of appropriate frequency based on the feature that small particles were transported upward against the gravity but large particles were apt to fall down. The second technique is an inclined tube system. The principle is common with that of the inclined plate system. The third technique utilizes a circular electrostatic conveyer similar with the mass spectroscopy but utilizes the feature that small particles fly high altitude compared to that of the large particle. The forth technique, a vortex system, also utilizes the difference of flying locus of small and large particles. The last technique is the combination of the linear conveyer and an electrostatic separation roller located at the end of the conveyer. Small particles were attached onto the roller charged by a charger roller. Although the yield was reduced to realize the high separation performance with the former four techniques, relatively high yield was realized without reducing the separation performance with the roller system. This technique is expected to be utilized to the separation of toner and carrier particles used in electrophotography. (c) 2008 Elsevier B.V. All rights reserved.

A preliminary investigation has been conducted on the three-dimensional micro fabrication utilizing the electrostatic inkjet phenomena. Suspension which disperses alumina nano particles to water was ejected and printed layer by layer to fabricate three-dimensional structures. We have demonstrated that the square shaped grid, 115μm-width, 140μm-height, was capable to fabricate by the electrostatic inkjet.

Electrostatic inkjet phenomena took place when strong electric field was applied to water pin electrode. In this paper we developed two new micro fabrication techniques utilizing electrostatic inkjet phenomena. First technique is to thin a metal rod The metal rod was set on a metal plate electrode. The diameter of the rod was controlled by the time of voltage application between the capillary tube and the metal rod The other is to punch a hole in a metal thin sheet. A shin metal sheet was set on the metal plate electrode. When the formation and locus of droplets that contained commercial etching liquid was controlled, small hole was punctured on the shin sheet. Hole diameter, less than 10 mu m to some 100 mu m was controlled by the voltage application between the sheet electrode and the capillary tube that was filled with the etching liquid

Transport and manipulation technologies of lunar soil and dust are under development utilizing the electrostatic force. Transport of particles is realized by an electrostatic conveyer consisting of parallel electrodes. Four-phase traveling electrostatic wave was applied to the electrodes to transport particles upon the conveyer and it was demonstrated that particles were efficiently transported under conditions of low frequency, high voltage, and the application of rectangular wave. Not only linear but also curved and closed transport was demonstrated. Numerical investigation was carried out with a three-dimensional bard-sphere model of the Distinct Element Method to clarify the mechanism of the transport and to predict performances in the lunar environment. This technology is expected to be utilized not only for the transport of bulk soil but also for the cleaning of a solar panel and an optical lens. Another technology is an electrostatic manipulation system to manipulate single particle. A manipulator consisted of two parallel pin electrodes. When voltage was applied between the electrodes, electrophoresis force generated in non-uniform electrostatic field was applied to the particle near the tip of the electrode. The particle was captured by the application of the voltage and released from the manipulator by turning off the voltage. It was possible to manipulate not only insulative but also conductive particles. Three-dimensional electrostatic field calculation was conducted to calculate the electrophoresis force and the Coulomb force.

Stability of a conducting drop hanging from a nozzle in an electric field was examined theoretically. With this static model, stability of electrostatic inkjet process was estimated The basic equations are the augmented roung-Laplace equation for drop shape and the Laplace equation for electric field. These coupled equations were solved by the Finite Element Method. By the initial condition of its shape, a drop could be deformed into different shapes, such as "conical shape," "nipple" or "dog bone" with the increment of non-dimensional electric field. The concentration of electric field around the corner of a nozzle was found to be the cause of these multiple shapes.

We have commenced basic research on the three-dimensional pattern formation of micro-gel beads for applications in biological tissue engineering. In this new technique, micro-gel beads are pre-magnetized by doping them with magnetic nanoparticles. Living cells will be included in beads for actual use. If a nonuniform magnetic field is applied to a solution containing these magnetized beads, the beads will align, contact, and form a 3D structure. The structure is controlled by the seed pattern of the magnetic particles plugged in a substrate and the profile of the magnetic field distribution. We have constructed tubes, which imitate blood vessels, for demonstration using gel beads whose diameters are of the order of several tens of micrometers. The diameter of the demonstrated tube was less than 0.5 mm and its length was 6.6 mm, although living cells were not included in the beads. Numerical calculations by using the discrete element method were conducted to confirm the formation of the tube and to predict the effect of centrifugal force, which will be applied to fill other tissues in the space between magnetically patterned beads. Although this unique technology is in the nascent stage, it can potentially be used to form three-dimensional, nonuniform, and heterogeneous artificial organs for tissue engineering.

Dynamics of toner particles in the magnetic single-component development system of electrophotography have been investigated to utilize for the improvement of the system. Two approaches have been adopted for the investigation: One is the direct observation of the toner motion in a development area with a high-speed microscope camera and another is the numerical simulation with the distinct element method We have manufactured the mock-up apparatus that consisted of a pseudo-photoconductor, development roller, stational magnetic roller inside it, and doctor blade to form thin toner layer on the development roller. The development roller, magnetic roller, and blade were diverted from a commercial printer. Thin line electrodes were embedded on the pseudo-photoconductor drum to substitute for electrostatic latent images. The apparatus enabled high-speed (8,000 fps) observation of toner motion at the development gap with satisfactory image quality. Observed images showed that (1) toner particles formed chain-like clusters in the vicinity of the gap, (2) these chains vibrated at the development zone synchronized with an applied alternative electrostatic field, (3) at the latent image, chains crashed on the photoconductor and then fell apart from the photoconduclor, and (4) at this moment, some of toner particles returned to the development roller but some adhered to the latent image to form a real image. Three-dimensional shapes of toner piles on the latent image were measured after the development by a scanned laser displacement meter. It has been clarified that both the width and height of the toner pile increased with an increase in the development voltage but these were saturated at the voltage higher than a threshold Numerical simulation has been conducted to confirm the experimental results. The simulation method is based on a hard sphere model of the distinct element method with cyclic boundary condition. The method can be applied for the dynamics of small toner particles within reasonable calculation time.

During the operation of a magnetic two-component development system used in electrophotography, some carrier particles adhere to a photoreceptor surface and cause serious image defects. This phenomenon is called "bead-carfy-out" or "carrier development." The author has observed the phenomenon using a high-speed CCD camera and has measured the number density of carrier particles that adhere to the photoreceptor surface after the development process under various conditions of the development voltage, toner particle concentration, and size of the carrier particles. The experimental results indicated the following characteristics. (1) Some particles were separated from the top of bead chains immediately after the chains separated from the photoreceptor at the outlet of the development nip. (2) A threshold voltage existed for the occurrence of bead-carry-out. (3) The threshold was low when the diameter of the carrier particles was small and the toner particle concentration was low. (4) The number density of the adhered carrier particles increases with an increase in the applied voltage and a decrease in the toner particle concentration. It has been clarified by a separate experiment that the effective conductivity of the bulk mixture of carrier and toner particles was significantly related to these characteristics. Because the carrier particles are conductive and toner particles are insulative, the latter disturbs the electrical conduction in the chain, and therefore, the electrical charge at the top of the chain induced by the voltage application is decreased at a critical concentration of the toner particles in the chain. This condition causes a reduction in the Coulomb force applied to the top of the chain and improves the bead-carry-out phenomenon. Quantitative characteristics of these features have also been elucidated by a numerical simulation. Some countermeasures against this phenomenon were also proposed based on the experiment and calculation.

This paper provides an overview of the recent progress of simulation technology in Japan for the development of electrophotography processes-charging, exposure, development, transfer, fusing, cleaning, and paper handling. By utilizing highly efficient hardware and software, the simulation technology has been improved significantly. Because charging, exposure, and fusing processes are based on the mechanics of continuous media, they are formulated as a set of multi-component, nonstationary, and nonlinear partial differential equations and are numerically solved by the iterative finite element method or finite differential method. In contrast, the discrete element method is used to simulate the dynamics of toner and/or carrier particles in the development, transfer, and cleaning processes. The method of direct observation with a high-speed microscope camera and particle tracking velocimetry are used to improve physical models and to confirm the adequacy of calculation results. Thus, the electrophotography processes are no longer a black box.

Experimental and theoretical research has been conducted to investigate basic characteristics of an ozone fan utilizing the ionic wind induced in the pin-to-plate corona discharge field. When a high voltage was applied between the electrodes, the ionic wind, which included ozone, flowed from the pin elecrode to a hole of the plate electrode. It was deduced that (1) the ozone concentration is almost linear with respect to the corona current, (2) the ozone concentration was high with the large pin diameter but almost irrelevant with the gap between the electrodes, (3) the energy efficiency of the negative corona was about 14 times higher that of the positive corona, but it was only several %, (4) the ozone generation was reduced at high temperature. It was estimated that the several ppm ozone could be generated and flowed utilizing the negative discharge and the ozone generation was almost eliminated by turning off the polarity.

Experimental and theoretical research has been conducted to investigate basic characteristics of an ozone fan utilizing the ionic wind induced in the pin-to-plate corona discharge field. When a high voltage was applied between the electrodes, the ionic wind, which included ozone, flowed from the pin electrode to a hole of the plate electrode. It was deduced that (1) the ozone concentration is almost linear with respect to the corona current, (2) the ozone concentration was high with the large pin diameter but almost irrelevant with the gap between the electrodes, (3) the energy efficiency of the negative corona was about 14 times higher that of the positive corona, but it was only several %, (4) the ozone generation was reduced at high temperature. It was demonstrated that the several ppm ozone could be generated and flowed utilizing the negative discharge and the ozone generation was almost eliminated by turning off the polarity.

A new paper separation and feed mechanism is proposed to realize a highly reliable paper handling system for printers and copiers. The paper-separation system consisted of a pair of parallel electrodes and a paper pile between the electrodes. Electrostatic separation of a piece of paper was possible from the top of the pile when the applied voltage exceeded the threshold needed to generate an electrostatic force larger than the weight of the paper. The threshold voltage was on the order of several kilovolts, and it agreed with the numerical value calculated using the finite element method (FEM) for the electrostatic field. Based on these basic investigations, a prototype mechanism for paper separation and feeding was constructed. It consisted of a roller-type separation electrode coated with an insulating film, a biased charger roller in contact with the separation roller to charge the insulating film on the separation roller, a ground electrode, and a paper pile situated between the electrodes. When an electrostatic field was applied between the biased charger roller and the ground electrode on which the paper pile was mounted, only the top sheet of paper separated, adhering electrostatically to the roller. The sheet was then fed rotating the separation roller. Using this system, reliable paper separation and feed was realized and a feed speed over 600mm/s was demonstrated. (C) 2006 Elsevier B.V. All rights reserved.

We have studied dynamics of magnetic brushes in two-component magnetic development system of electrophotography by a model experiment and the numerical simulation with the Distinct Element Method. Axial and lateral forces of chain-like brushes applied to the photoconductor were measured to clarify the relationship between the lateral friction force and the diameter of carrier particles, magnetic flux density, and the brush length. It was observed that the force was increased in accordance with the increase of the magnetic flux density and decreased with the brush length but the particle diameter did not affect the total force. On the other hand, the numerical calculation deduced that although the total force is not affected by the particle diameter, the individual differential force of the chain was small and the density of contact points of brushes was high for small particles.

A preliminary investigation was conducted to clarify fundamental characteristics of a micro fan utilizing ionic wind induced in the pin-to-plate gas discharge field. The fan was consisted of a pin electrode, a plate electrode with a hole and a heated plate under the plate electrode. When high voltage was applied between the electrodes, ionic wind flowed through the hole of the plate electrode toward the heated plate. This paper was focused on optimization of the electrode configuration and the enhancement of cooling effect by experiment and calculation. A numerical calculation was conducted by two steps. The corona discharge field was calculated with the finite element method and ionic wind induced by the migration of ions was calculated with the finite differential method. The experimental investigation deduced that: (1) The flow rate was increased with the increase of the hole diameter and the static pressure was increased with the increase of the plate thickness. (2) A gap〜to〜hole diameter ratio of 0.8 to 1.1 was found to be an optimal value that gives the highest power and efficiency. (3) The enhancement of the heat transfer coefficients was increased with the increase of the distance between the plate electrode and the heated plate. These experimental results were in good agreement with the calculated results.

We have investigated whether any force is generated by a spark discharge in a pin-to-plate system. Because it was difficult to measure the force directly over a short sparking period, three independent methods were employed to evaluate the magnitude of the force indirectly: (1) Axial vibration was observed for the pin electrode supported flexibly by a cantilever to the axial direction at the spark discharge that occurred periodically. The force was implicitly calculated in the case that the calculated vibration agreed with the measured. The result indicated that the force was almost ON during the spark period. The vibration was generated not by the force at the spark discharge but by alternative force of the Coulomb force at the period of no discharge and reaction force due to the ionic wind at the corona discharge. (2) A similar investigation was conducted whether the vibration magnitude depended on the spark current based on the assumption that the force at spark discharge depends on the spark current if any substantial force is generated at the spark discharge. We deduced that the force was not generated during the spark period and it was irrelevant to the spark current. (3) We made a hypothesis that axial vibration of the pin electrode could be observed if the spark discharge did not take place but the varying voltage was applied of which pattern was common with that with the spark discharge. To confirm the hypothesis an experiment was conducted with two parallel-connected pin-to-plate systems, the air gap of one system was slightly shorter than the other. The axial vibration was observed even in the system that the spark discharge did not take place and the vibration agreed also with the calculated. These three results suggested that no substantial force was generated at the spark period. (c) 2006 Elsevier B.V. All rights reserved.

Magnetic particles form chain-like clusters in the magnetic field. This phenomenon is of interest in two separate fields, one is a development system of the laser printer and another is an electromagnetic manipulation of biological cells. Experiments on the chain formation in air and oil have been performed in the ultra high magnetic field created by a superconducting magnet. It has been clarified that the chain length first increased and then decreased in accordance with the increase of the magnetic field. The result has been confirmed by a numerical calculation with the Distinct Element Method that included the mechanical contact force between particles and the magnetic force due to the field created by the coil and adjacent magnetized particles. A periodic boundary condition was employed to perform realistic calculation in a reasonable calculation time. The effect of the density and the diameter of particles was investigated experimentally. The effect of the dry friction between particles was also examined by comparing experimental results performed in air and oil. Lastly, it has been discussed that the static stability of the chain was determined by a minimization principle of the potential energy that consists of the gravitational and magnetic potential energy.

We have studied dynamics of magnetic brushes in two-component development system of electrophotography by a numerical simulation with an improved Distinct Element Method (DEM) and experimental observation with a high-speed microscope camera. Two-dimensional magnetic field was calculated by superposing measured discrete magnetic flux densities on a development sleeve. It has been calculated and observed that magnetic brushes grow up in the development area inclining in parallel in the direction of the magnetic field and they are crushed by a photoreceptor drum. It has been evaluated that although the total pressure applied to the photoreceptor is almost irrelevant to the diameter of carrier particles, differential force applied by individual chain is dense and small with small particles but rough and large with large particles. This suggests that small carrier particles are preferable to prevent disturbance of developed toner particles on the photoreceptor.

An investigation has been carried out on the control of a micro-droplet in electrostatic inkjet phenomena, because the electrostatic inkjet has a merit that the formation and locus of the droplet can be controlled by the application of the electric field and it is possible to treat highly viscous liquid. It was observed that a Taylor cone of the paste was formed at an end of a tube and the tip of the cone was broken to form a very small droplet at the beginning of the corona discharge. Droplets of paste that contains Ag nanoparticles are injected on a glass substrate to form electrode patterns. The formation of the droplet is controlled by the application of pulse voltage between the plate electrode and the fine tube that is filled with Ag paste. A multi-layered printing was realized by over-coating insulative glass paste on line electrodes. A direct 3D printing was also developed by taking advantage that highly viscous liquid can be ejected by the electrostatic inkjet system.

The authors have developed five kinds of techniques on electrostatic classification of particle size utilizing the balance of the electrostatic and gravitational force. The first is an inclined plate conveyer system. A plate conveyer consisted of parallel electrodes was constructed and four-phase traveling field was applied to the electrodes to transport particles on the conveyer. Particles were classified with size under the voltage application of appropriate frequency based on the feature that small particles were transported upward against the gravity but large particles were apt to fall down. The second technique was an inclined tube conveyer system. The principle is common with that of the inclined plate system. The third technique utilizes a circular electrostatic conveyer similar with the mass spectroscopy. The forth is also circular but utilizes the feature that a locus of the small particle is high compared to that of the large particle. The last is the combination of the linear conveyer and an electrostatic separation roller located at the end of the conveyer. Small particles were attached onto the roller charged by a charger roller. These techniques are expected to be utilized to the classification of toner and carrier particles used in electrophotography.

The authors have developed four kinds of techniques on electrostatic classification of particle size utilizing the balance of the electrostatic and gravitational force. The first is an inclined plate conveyer system. The plate conveyer consisted of parallel electrodes. Four-phase traveling field is applied to the electrodes to transport particles. The second is an inclined tube conveyer system. The third is a vortex electrode conveyer system. The last is the combination of the plate conveyer and an electrostatic separation roller. These techniques are expected to be utilized to the classification of toner and carrier particles used in electrophotography.

An electrohydrodynamic investigation has been carried out in-a pin-to-plate gas discharge system to clarify the mechanism of repulsive force generation between a pin and plate electrode at corona discharge. Numerical calculations have been conducted in two steps. First, the axi-cylindrical static corona discharge field was calculated with the finite-element method to deduce the Coulombic body force rho E applied to the air, where rho is the charge density and E is the electric field, and then the induced ionic wind was calculated with the finite differential method. The calculated pressure distribution on the plate electrode was on the order of 10 Pa which was in good agreement with the measured pressure distribution. The calculated air velocity at the center was several m/s and was confirmed by a time-of-flight experiment and the velocity distribution near the pin electrode also agreed with measurements using a laser Doppler velocimeter. Pressure and wind velocity were increased at high-applied voltage. These results confirm that the ionic wind is the cause of the repulsive force to the pin electrode at the corona discharge. (c) 2005 Elsevier B.V. All rights reserved.

We have been developing a mask-less printing technology for microelectronic circuits utilizing an electrostatic inkjet system. Drops of paste that contained Ag nano-particles were injected on a substrate by the electrostatic force to form electrode patterns. The formation of the drop was controlled by the application of pulse voltage between the plate electrode and a fine tube that contains Ag paste. It was demonstrated that line electrodes of 200 μm pitch were successfully printed on a glass substrate. A multi-layered printing was also realized by overcoating glass paste on the electrode.

We have been developing a mask-less printing technology for microelectronic circuits utilizing an electrostatic inkjet system. Drops of paste that contained Ag nano-particles were injected on a substrate by the electrostatic force to form electrode patterns. The formation of the drop was controlled by the application of pulse voltage between the plate electrode and a fine tube that contains Ag paste. It was demonstrated that line electrodes of 200 μm pitch were successfully printed on a glass substrate. A multi-layered printing was also realized by overcoating glass paste on the electrode.

Numerical and experimental investigations have been carried out on transport of particles in an electrostatic travelling field. A three-dimensional hard-sphere model of the distinct element method was developed to simulate the dynamics of particles. Forces applied to particles in the model were the Coulomb force, the dielectrophoresis force on polarized dipole particles in a non-uniform field, the image force, gravity and the air drag. Friction and repulsion between particle-particle and particle-conveyer were included in the model to replace initial conditions after mechanical contacts. Two kinds of experiments were performed to confirm the model. One was the measurement of charge of particles that is indispensable to determine the Coulomb force. Charge distribution was measured from the locus of free-fallen particles in a parallel electrostatic field. The averaged charge of the bulk particle was confirmed by measurement with a Faraday cage. The other experiment was measurements of the differential dynamics of particles on a conveyer consisting of parallel electrodes to which a four-phase travelling electrostatic wave was applied. Calculated results a-reed with measurements, and the following characteristics were clarified. (1) The Coulomb force is the predominant force to drive particles compared with the other kinds of forces, (2) the direction of particle transport did not always coincide with that of the travelling wave but changed partially. It depended on the frequency of the travelling wave, the particle diameter and the electric field, (3) although some particles overtook the travelling wave at a very low frequency, the motion of particles was almost synchronized with the wave at the low frequency and (4) the transport of some particles was delayed to the wave at medium frequency; the majority of particles were transported backwards at high frequency and particles were not transported but only vibrated at very high frequency.

In order to cope with image defects observed in the electrophotography using the single-component magnetic development system, a two dimensional numerical simulation has been carried out considering effects of multiple physics. The electrostatic field generated by the bias voltage applied and the electric charge on the photoreceptor and the toner particles are calculated using the finite difference method. The pressure equation is also solved by the finite difference method to obtain the flow field induced by motion of the photoreceptor and the development sleeve. The magnetic field is expressed by superposition of fields created by two-dimensional magnetic dipoles to extrapolate measured magnetic flux density on the development sleeve. Total force exerted on each toner particle by those fields are calculated and motion is tracked considering adhesion onto solid surfaces to estimate density distribution of toner particles on the photoreceptor. Two types of image defects are simulated. One is low-density area observed near a white line with dark background. The other is a phenomenon that large particles contained in the development particles are intensively developed on a non-image area close to a solid patch. Countermeasure against the image defect is also simulated.

Basic research has been carried out on the transport of a liquid drop and a soft body in an electrostatic travelling field. A conveyer consisting of parallel electrodes was constructed and a four-phase electrostatic travelling wave was applied to the electrodes to transport the drop on the conveyer. The following were clarified by the experiment. (1) Drops and soft bodies can be transported by virtue of the travelling wave in an insulative liquid that is insoluble to the drop, because the drop was charged on the conveyer by friction and driven by the Coulomb force. (2) A drop that covered less than three arrays of the parallel electrode can be transported in the travelling wave field. (3) A threshold voltage exists for the transport. (4) Although the transport was possible not only for insulative but also for conductive drops, the insulative drop can be transported efficiently. (5) The modes of transport can be classified into three categories, namely, a synchronous region where the motion of the liquid drop is in synchrony with the travelling wave, a delayed response regime, and a regime where transport does not occur. (6) Mixing of drops for a chemical reaction was demonstrated on the conveyer with scroll electrodes. A simple model was proposed to simulate the dynamics of the drop in the electrostatic travelling field.

This article describes an axial transient vibration and axial excitation response of a polygonal mirror scanner rotor driven by a flat-type brushless dc motor and supported by a passive thrust magnetic bearing and a radial air bearing. From results of experimental investigations, the following characteristics of the vibration have been deduced: (1) Repulsive magnetic force was induced between the rotor magnet and stator coils of the dc motor under current passage. The force caused axial static displacement and axial transient vibration. (2) Because the stiffness of the thrust magnetic bearing was small, large axial vibration took place due to the axial excitation. (3) Two types of damper were introduced to suppress the axial transient vibration and the axial excitation response; one was an eddy-current damper and the other was an air damper. It was demonstrated that the air damper was effective for reducing the axial vibration. (C) 2006 Society for Imaging Science and Technology.

We have been investigating an electrostatic manipulation of a small particle, such as toner and carrier particles. A manipulator consisted of two parallel pin electrodes. When voltage was applied between the electrodes, electrophoresis force generated in nonuniform electrostatic field was applied to the particle near the tip of the electrode. The particle was captured by the application of the voltage and released from the manipulator by turning off the voltage application. It was possible to manipulate not only insulative but also conductive particles. However, if the particle was charged, Coulomb force and adhesion force prevented to release the particle when the voltage was turned off. This condition was apt to take place for small particles, less than 200 fun in diameter. The third electrode was introduced near the dipole electrodes to blow off the particle by the ionic wind and the validity of this system was demonstrated. An uneven electrode system without the additional separation electrode was also developed to release the attached particle independently of the position of the manipulator. Three-dimensional calculation was conducted by the Finite Difference Method and compared to the measured force.

We have been developing an electrostatic inkjet system for printers and mask-less electronic micro-circuit printing. The system consisted of a tube filled with ink and a plate electrode. When voltage was applied between the electrodes, a droplet was formed and separated at the tip of the tube periodically. Optimizing this system we have demonstrated 1,600 dpi printing on paper. However the print speed was deadly slow because this system had only single nozzle. Therefore we have been developing a multi-nozzle system that consisted of two parallel tubes filled with ink and the metal plate electrode. Three-dimensional calculation of the electric field was conducted by the Finite Difference Method to deduce the cross-talk between the electrodes and it is proposed that a new system that the waveform of the applied voltage was adjusted to cancel the cross-talk between the adjacent nozzle.

Experimental and numerical investigations have been carried out on the bead-carry-out phenomenon of electromagnetic bead chains in two component development process of electrophotography. Electrostatic pull-off characteristics of chains were measured in a magnetic field and then it was clarified how the critical electrostatic pull-off field to break chains and the amount of pulled-off carriers depended on the bead diameter and the magnetic field. Magnetic bonding force and electrostatic pull-off force were estimated numerically to evaluate these experimental results. It was deduced that the bead-carry-out phenomenon could be predicted qualitatively from the comparison of calculated magnetic and electrostatic force.

For the purpose of analyzing the magnetic single-component development process of electrophotography, we measured 3D-figures and charge density of toner images on a photoreceptor drum and an OHP sheet with a co-focal laser focus displacement sensor and a Faraday cage. The results were as follows: (1) In a toner image on the photoreceptor, it was confirmed that mountain-like chain structures were formed parallel with development direction. (2) In a toner solid image, charge density in the center area is lager than that in the edge and volume density in the edge is lager than that in the center area.

This paper proposed new micro electrostatic driving mechanisms utilizing anisotropic feature of friction. One of the driving mechanisms consisted of parallel plate electrodes and a slanted-fiber sheet between the electrodes. When AC voltage was applied between the electrodes, alternative electrostatic force caused linear motion of the mechanism due to anisotropic feature of the friction between fibers and the lower electrode. The achieved velocity was about 10 mm/s in reverse of the fiber-slanted direction, and it roughly agreed with the numerical calculation based on a lamped dynamic model. Another mechanism was proposed because it was difficult to control friction coefficient and critical frequency of driving mechanism by the slanted-fiber sheet. It consisted of parallel plate electrodes and two slanted-plates made of polyester between the electrodes. The achieved velocity was about 5 mm/s. However, the driving direction of slanted-plate mover was opposite of the direction of slanted-fiber mover. Based on this experimental fact, relationship between the driving direction and the friction coefficient was investigated. We also proposed a rotational driving mechanism and a linear driving mover without a lead to provide voltage to the mover.

Electrohydrodynamic deformation of water surface was investigated in a pin-to-plate gas discharge system that consisted of a pin electrode made of metal and an ion-conductive water electrode. In the condition of a lower applied voltage than the corona threshold, because an extremely small electrostatic attractive force, a Coulomb force in the order of 10 mu N, was induced, water lifted up in the order of several tens of micrometres at the centre. Over the threshold voltage corona discharge took place and a relatively large repulsive force, in the order of 100 mu N, was induced due to the ionic wind. It depressed water in the order of several hundred micrometres at the centre. Deformation of the water level coincided with the pressure distribution on the metal plate electrode, if the surface tension of water and the Coulomb force was included in the estimation to derive the pressure distribution from the measured deformation of the water level. If the applied voltage was lower than the corona threshold, total force to the water electrode coincided with that to the pin electrode. However, it was larger than that to the pin electrode at the corona discharge because the reaction force due to the ionic wind was applied not only to the pin electrode but also to other parts of the electrode at the corona discharge.

A new paper separation and feed mechanism is proposed to realize a highly reliable paper handling system for printers. A prototype mechanism consisted of a plate or roller separation electrode coated with an insulated film, a ground electrode, and a paper pile between the electrodes. When high voltage was applied between the electrodes, charge was excited on the insulating film and eletrostatic force is applied to the paper. Electrostatic separation of a sheet of paper was realized at the top of the pile when the applied voltage exceeded a threshold voltage to generate electrostatic force large than the weight of a sheet of paper. The threshold voltage was about some kV, and it agreed with the numerical value obtained by the FEM calculations for the electrostatic field. In the next step the roller electrode was rotated to feed the attached paper. However the applied voltage had to be increased to separate subsequent papers, because charge on the insulated film was cancelled by the attached paper. Then a biased charger roller was settled in contact with the roller electrode to charge the insulating film on the roller separation electrode. In this system, reliable paper separation and feed was realized and a feed speed over 600 mm/s was demonstrated.

A fundamental investigation was conducted on electrostatic ink jet phenomena. High voltage was applied between an insulative capillary tube filled with ion conductive water and a metal plate electrode. A large water drop was formed and dropped from the tube at the dark discharge under conditions of appropriate voltage application and water level. The diameter of the drop was about one millimeter. At the beginning of corona discharge, however, a Taylor cone of water was formed at the tip of the tube and the tip of the cone was broken to form a very small droplet that was dispersed like mist at wide angle due to the Coulomb repulsive force of charged mist. When the applied voltage was further increased, water droplet was formed periodically. Application of adjusted pulse voltage can form a droplet of which formation is synchronized with the pulse. The diameter of the droplet depended on the applied voltage and the tube diameter. It was less than a Rayleigh's limit and agreed fairly well with a Vonnegut's limit. Preliminary printing on a paper was also demonstrated. This phenomenon is expected to be utilized for a new ink jet print head.

A preliminary, investigation was conducted on formation and control of micro droplet in electrostatic inkjet phenomena. High voltage was applied between an insulative capillary tube filled with ion-conductive water and a plate electrode. At the beginning of corona discharge, a Taylor cone was formed at the tip of the tube and the top of the cone was broken to form a very small droplet that was dispersed like mist at wide angle due to the Coulomb repulsive force of charged mist. When the applied voltage was further increased, water droplet was formed periodically. The charge to mass ratio of the droplet was measured and compared with the Rayleigh's limit. It was less than the limit because the droplet vibrated at the formation of the droplet. Another experimental set-up was constructed to control, the dropping position of the droplet. A ring electrode was settled between the capillary tube and the plate electrode to control the dropping position of the droplet.

Three kinds of techniques have been developed on electrostatic classification of particle size. The first utilizes linear electrostatic traveling field. A particle conveyer consisted of parallel electrodes was constructed and four-phase traveling electrostatic wave was applied to the electrodes to transport particles on the conveyer. Particles were classified with size under the voltage application of appropriate frequency based on the feature that the direction of particle transport was changed depending on the frequency of the traveling wave and the particle diameter. The second technique utilizes a circular electrostatic conveyer similar with the mass spectroscopy. Particles were classified with size because a locus of the particle in centrifugal field depended on the weight of the particle. The third is the combination of the linear conveyer and an electrostatic separation roller located at the end of the conveyer. Small particles were attached onto the roller charged by a charger roller. These techniques have been expected to be utilized to the classification of the particle size and a charge-to-mass ratio of toner and carrier particles used in electrophotography.

Two driving mechanisms were constructed and these characteristics were investigated. The mechanisms utilize force generated in a pin-to-plate gas discharge system that consisted of a rigid pin electrode and a plate electrode. One of the driving mechanisms utilizes force generated at dark discharge region, because attractive force, in the order of 10 fiN, was induced to the pin electrode due to the Coulomb force at this region. A stator consisted of parallel plate electrodes on a plastic plate and small linear movers were needle and/or plate electrodes on floating plastic plates. Experimental investigation deduced that (1) the speed of the movers was increased at high frequency of the applied voltage and a small air gap, but (2) the motion of the movers were out of tuning over a threshold frequency. Another driving mechanism utilizes force generated at corona discharge, because corona discharge took place over a certain threshold voltage and a relatively large repulsive force, in the order of 100 μN, was induced to the pin electrode due to the ionic wind. The force was almost tangential to the pin electrode even when the pin electrode inclined to the plate electrode. This force was utilized for driving small linear and rotational movers on water. The linear mover was an inclined pin electrode on a floating plate and the rotational mover consisted of two inclined pin electrodes on a floating disk at point-symmetrical positions. Experimental investigation deduced that (1) the driving force was induced over the corona onset voltage, (2) the driving force or torque were maximum when the inclination angle was 45 degrees, and (3) the speed of the movers was increased at high applied voltage and a small air gap.

A preliminary investigation was conducted on electrostatic formation of a liquid drop. High voltage was applied between an insulative capillary tube filled with water and a metal plate electrode. Formation of a water drop was observed at the dark discharge under conditions of appropriate voltage application and water level. Although the electrostatic attractive Coulomb force is small, in the order of 10 μN at the voltage lower than the corona onset, it is large enough to separate the water drop to the capillary tube against surface tension at certain conditions. The diameter of the drop was about one millimeter. At the beginning of corona discharge, however, water mist was dispersed at wide angle from the tip of the tube due to the Coulomb repulsive force of charged mist. When the applied voltage was further icreased, water mist became to be dispersed like spray, because the ionic wind prevented the separation and spread of the droplet. Application of adjusted pulse voltage can form a droplet of which formation is synchronized with the pulse. The diameter of the droplet depended on the applied voltage and the tube diameter. The droplet volume was in the order of several hundred picoliters. Preliminary inkjet printing on a paper was also demonstrated. This phenomenon is expected to be utilized for a new inkjet print head.

Experimental research was carried out on transport of particles and particle size classification in a traveling electrostatic field. Particle conveyors which consisted of parallel electrodes were constructed and a four phase traveling electrostatic wave was applied to the electrodes to transport particles on the conveyor. The following points were clarified by the experiment: (1) Particles were transported almost linearly with time. Transport rate was also linear with applied voltage but a threshold existed due to adhesion force. (2) The direction of particle transport did not always coincide with that of the traveling wave but it was in part changed depending on the frequency of the traveling wave, the particle diameter, and the electric field. Motion of particles at low frequency was nearly synchronized with the traveling wave but at medium frequency it was opposite to and slower than the wave. Particles were vibrated but not transported at high field frequency. (3) Particles were efficiently transported under conditions of high electrostatic field with a rectangular waveform. (4) Particles essentially moved along the electric flux line, but electrostatic interaction and particle-particle and particle-conveyor collisions made trajectories complex. (5) Particles were classified according to size under application of voltages of appropriate frequency.

This paper describes an analysis of a new electrostatic driving mechanism utilizing a slanted-fiber sheet. The mechanism consists of parallel plate electrodes and a slanted-fiber sheet between the electrodes. When AC voltage is applied between the electrodes, alternative electrostatic force causes linear motion of the mechanism due to anisotropic feature of the friction between fibers and the lower electrode. The achieved velocity is about 10 mm/s, and it roughly agreed with the numerical value based on a lamped dynamic model. This mechanism is expected to be utilized for precise positioning of a sheet of paper.

An experimental and analytical investigation has been performed on vibration induced in a driving mechanism of a photoconductor drum in a color laser printer. The mechanism consists of a flywheel supported by a dry journal bearing and driven through a belt and a pulley that is connected to a shaft of the photoreceptor drum. From the results of the investigation, the following characteristics were deduced: (1) Pulley runout induced a vertical harmonic pull force to the flywheel through the belt and caused the vibration of the flywheel. (2) When the pull force is large enough to support the flywheel, the shaft of which is always in contact with the stator ring of the dry bearing, the harmonic vertical forced vibration takes place by the harmonic vertical force due to the eccentricity of the pulley through the belt. (3) On the other hand whirling takes place when the pull force is low. The shaft vibrates in the air gap not only in vertical but also horizontal directions. (4) The driving mechanism must be constructed to have small runout of the pulley and sufficient static tension of the belt.

An experimental and analytical investigation has been performed on vibration induced in a driving mechanism of a photoconductor drum in a color laser printer. From results of the investigation, the following points were deduced : (1) A flywheel driven by a pulley through a belt caused forced and whirling vibrations. (2) A runout of the pulley attached to the photoreceptor drum to a shaft induced a vertical harmonic pull force to the flywheel through the belt and caused the vertical forced vibration of the flywheel. The driving mechanism must be constructed to be small runout of the pulley to the shaft and enough static tension of the belt.

It was investigated whether the electrostatic force was generated at the spark discharge on a pin electrode in a pin-to-plate gas discharge system. Because it was not possible to measure the force directly at a short sparking period, three independent metcods were employed to evaluate the existence of the force indirectly. (1) Axial vibration was observed at the intermittent spark discharge for the softly supported pin electrode. The force was explicitly calculated in the case that the calculated vibration was well agreed with the measured. This experiment indicated that the force was almost 0 N at the spark discharge. The vibration was generated not by the force at the spark discharge but by alternative ionic wind at corona discharge. (2) A similar experiment was conducted whether the vibration magnitude depended on the spark current. The current at the spark discharge was varied by a circuit resistor. The experiment deduced that the force did not generated at the spark period and it was independent on the current. (3) Axial vibration could be observed when the voltage pattern that was common with that with the spark discharge was applied, if no force was applied to the pin electrode. To confirm it an experiment was conducted with two parallel-connected pin-to-plate gas discharge systems, one of which air gap was shorter than the other. The axial vibration of the longer air gap, in which the spark discharge did not take place, was observed and vibration also agreed quantitatively with calculated one. These three results suggested that no substantial force was generated at the spark discharge.

Numerical and experimental investigations were carried out on transport of particles in an electrostatic traveling field. A 3D hard-sphere model of the Distinct Element Method was developed to simulate dynamics of particles. Forces applied to particles in the model were the Coulomb force, the electrostatic force to polarized particles in the non-uniform field, the gravity, and the air drag. Friction and repulsion between particle-particle and particle-conveyer were included in the model to replace initial conditions after mechanical contacts. Two kinds of experiments were performed to confirm the model. One was the measurement of charge of particles that is indispensable to determine the Coulomb force. Charge distribution was measured from locus of free-fallen particles in a parallel electrostatic field. Averaged charges of bulk particles were confirmed by the measurement with a Faraday cage. The other experiment was measurements of differential dynamics of particles on a conveyer consisting of parallel electrodes to which four-phase traveling electrostatic wave was applied. The calculated results agreed with measured and the following were clarified: (1) Coulomb force is most predominant to drive particles. (2) The direction of particle transport did not always coincide with that of the traveling wave but partially changed depending on the frequency of the traveling wave, the particle diameter, and the electric field. (3) Although some particles overtook the traveling wave at the very low frequency, the motion of particles was almost synchronized with the wave at the low frequency. (4) The transport of some particles delayed to the wave at medium frequency and almost all particles were transported backward at high frequency.

Three kinds of studies have been carried out on the statics and dynamics of carrier bead chains in an electromagnetic field to solve the three questions, that is, how the mechanical properties of chains are in a high magnetic field, what the effect of friction between beads is, and how the properties of chains vary by the introduction of toner particles. The followings were deduced from the experimental, theoretical and numerical investigations. (1) By the measurement on length and population of chains in the high magnetic field up to 1.0 T, reductions in these properties with the increase in magnetic field were observed in the field more than 0.1 T and the characteristics were confirmed by the numerical calculation with the Distinct Element Method. (2) The observation of chain forming process in oil, where the effect of friction between particles was supposed to be negligible, showed a good agreement with the theoretically estimated value by the assumption of the potential energy minimization. (3) The magnetic effect of toner particles on the chain length is negligible while the electric effect on the electric pull-off properties of chains is significant.

A new paper separation and feed mechanism is proposed to realize a highly reliable paper handling system for printers. A prototype mechanism consisted of a roller-type separation electrode coated with an insulating film, a ground electrode, and a paper pile between the electrodes. When electrostatic field was applied between the electrodes, it was confirmed that only the top paper was separated. However the applied voltage had to be increased to separate subsequent papers, because charge on the insulating film was cancelled by the attached paper. Then a biased charger roller was settled in contact with the separation electrode to charge the insulating film on the separation electrode. In this system, reliable paper separation and feed was realized and a feed speed over 600 mm/s was demonstrated.

Experimental, theoretical, and numerical investigations have been carried out to evaluate resonant frequency and stiffness of a magnetic bead chain in the magnetic field. Chains formed on a solenoid coil were vibrated by the sinusoidal wave and impulse wave to deduce resonant frequency. It showed weak dependency on the magnetic flux density and the bead diameter, because both the equivalent stiffness and the chain length were large in accordance with the increase of the magnetic flux density. These characteristics were confirmed by theoretical considerations based on an assumption of potential energy minimization and a numerical calculation with the Distinct Element Method. Stiffness of the chain was directly measured by observation of chain deflection in inclined gravitational field and the results agreed with the dynamically deduced characteristics. It was concluded that the resonant frequency was 20-60 Hz and the static stiffness at the top of the chain was 10(-4)-10(-2) N/m. The investigation is expected to be utilized for the improvement of the two-component magnetic brush development subsystem in electrophotography.

Electroaerodynamic investigation has been carried out in a pin-to-plate gas discharge system to clarify the mechanism of repulsive force generation between the pin and the plate electrode at corona discharge. Numerical calculation has been conducted by two steps. At the first place, corona discharge field was calculated to deduce volumetric force and then induced ionic wind was calculated. Calculated pressure distribution on the plate electrode was in the order of 10 Pa that was in good agreement with the measured. Calculated velocity at the center was several m/s that is confirmed by a time-of-flight experiment and the velocity distribution near the pin electrode also agreed with the measured with a laser Doppler velocimeter. These results confirm that the ionic wind is the cause of the repulsive force at the corona discharge.

A new mechanism of paper-separation system is proposed to realize a highly reliable paper handling system for printers. The system consists of a pair of parallel electrodes and paper pile between the electrodes. In this system, electrostatic separation of a piece of paper was realized always at the top of the pile when the applied voltage exceeded a threshold voltage to generate electrostatic force larger than the weight of a piece of paper. The threshold voltage was about some kV, and it agreed with the numerical value calculated by the finite element method for the electrostatic field. Additionally, lateral pull-off force of a paper from the attached electrode was measured to confirm the required force to feed the separated paper. The value was in the order of 10 μN/(mm)^2 that was also in the same order as the calculated pull-off force estimated from the electrostatic force between the plate electrode and the adhered paper and the friction coefficient between them.

This paper proposes new electrostatic driving mechanisms with slanted-fiber seats. One of the mechanisms consisted of a plate electrode and the seat with slanted-fibers. AC voltage was applied between the plate electrode and a ground electrode. Alternative electrostatic force caused linear motion of the mechanism due to anisotropic feature of the friction between fibers and the ground electrode. The demonstrated velocity was about 10 nm/s. Another mechanism consisted of the plate electrode and two seats of which fibers were slanted in opposite directions with each other. Rotation of the mechanism was realized because linear driving force was cancelled but torque was induces to the plate electrode. The demonstrated speed was in the order of 0.1 s^<-1>

A non-magnetic and non-contact AC development system has been numerically investigated using a two-dimensional dynamic model. Simulation of toner dynamics in the development process was carried out using the Finite Difference Method (FDM) for the electric field calculation and the Distinct Element Method (DEM) for the calculation of charged toner motion in the electric field. Calculated results showed fairly good agreement with experiments.

Electrostatic pull-off of electromagnetic bead chains is investigated to improve two-component magnetic development system of electrophotography by the estimation of forces applied to the beads. The dependency of the magnetic bonding force of chains on the magnetic field and bead diameter was clarified and the mechanism of the electrostatic pull-off was verified by the comparison of numerically calculated magnetic force with the measured electrostatic pull-off force.

Experimental and numerical investigations have been carried out on the bead-carry-out phenomenon of electromagnetic bead chains in two-component development process of electrophotography. Electrostatic pull-off characteristics were measured in a magnetic field and then it was clarified how the critical pull-off field intensity to break chains and the amount of pulled-off carriers depended on the bead diameter and the magnetic field. Magnetic bonding force and electrostatic pull-off force were estimated numerically to discuss these experimental results. It was clarified that the bead-carry-out phenomenon can be predicted qualitatively from the comparison of calculated magnetic force and electrostatic force.

A magnetic single-component development process in electrophotography has interesting characteristics on a magnetic and electrostatic interaction of toner particles. Magnetic force restrains toner adhesion to non-image area and this feature enhances the development. However, long chains made by magnetic interaction force between magnetic toner particles deteriorate toner-image quality on the photoreceptor. It is known from a past experimental study that the magnetic chain length is influenced not only by the magnetic field but also by the electrostatic charge of toner particles. This study confirmed it by using two-dimensional numerical analysis. Simulation of toner dynamics was carried out using the Finite Difference Method (FDM) for the electric field calculation and the Distinct Element Method (DEM) for the calculation of charged magnetic toner motion in the magnetic and electrostatic field. The following were deduced form the investigation. (1) The chain length of toner particles was shortened by the toner charge. (2) In the case that particles does not include wrong-sign toner, charge distribution does not change the chain formation but wrong-sign toner particles influence the chain length and number. (3) The magnetic chain was reconstructed under the application of AC biased potential at the development gap. (4) Toner particles with wrong-sign toner caused a defect of chain images.

New mechanisms of paper separation and feed systems were proposed to realize a highly reliable paper-handling system for printers. The new paper-separation system consisted of a pair of parallel electrodes and a paper pile between the electrodes. In this system, electrostatic separation of a piece of paper was realized always at the top of the pile when the applied voltage exceeded a threshold to generate electrostatic force larger than the weight of a paper. The threshold voltage was about some hundred volts, and it agreed with the numerical value calculated by the FEM for the electrostatic field. Additionally, lateral pull-off force of a paper from the attached electrode was measured to confirm the required force to feed the separated paper. The value was some muN/mm(2) that was also in the same order as the calculated pull-off force estimated from the friction coefficient between them and the electrostatic force between the plate electrode and the adhered paper. Two kinds of new paper-feed systems have been also developed. One consisted of a pair of parallel plate electrodes and two sheets with slanted fibers. In this system, vertical vibration of the electrodes was realized when the alternating electric field was applied between the electrodes. Paper attached between the sheets was fed in the horizontal direction in the order of 1 mm/s utilizing the vibration and anisotropic feature of the friction of slanted fibers. Another system consisted of an electrostatic particle conveyer with parallel electrodes, particles, and a sheet of paper on them. The paper is fed about 100 mm/s almost synchronized with the linear motion of particles driven by traveling electrostatic field.

A preliminary investigation was conducted on electrostatic inkjet phenomena. High voltage was applied between an insulative capillary tube filled with ion-conductive water and a metal plate electrode. Inkjet phenomenon was observed at the dark discharge under conditions of appropriate voltage application and water level. Although the electrostatic attractive Coulomb force is small, in the order of 10 muN at the voltage lower than the corona onset, it is large enough to separate a water drop against surface tension to the capillary tube at certain conditions. The diameter of the drop was about one millimeter. At the beginning of corona discharge, however, water mist was dispersed at wide angle from the tip of the tube due to the Coulomb repulsive force of charged mist. When the applied voltage was further increased, water mist became to be dispersed like spray, because the ionic wind prevented the separation and spread of the droplet. Application of adjusted pulse voltage can form a droplet of which formation is synchronized with the pulse. The diameter of the droplet depended on the applied voltage and the tube diameter. The droplet volume was in the order of several hundred picoliters. Preliminary printing on a paper was also demonstrated. This phenomenon is expected to be utilized for a new inkjet print head.

A basic research is being carried out on transport of particles and particle size classification in electrostatic traveling field. A particle conveyor consisting of parallel electrodes was constructed and four-phase traveling electrostatic wave was applied to the electrodes to transport particles on the conveyer. The following were clarified by the experiment and numerical simulation with the Distinct Element Method: (1) Particles were transported almost linearly with time. A transport rate was also linear with the applied voltage but a threshold existed due to adhesion force. (2) The direction of particle transport did not always coincide with that of the traveling wave but partially changed depending on the frequency of the traveling wave, the particle diameter, and the electric field. Particles were vibrated but not transported under high frequency field. (3) Particles were efficiently transported under conditions of low frequency, high voltage, and the application of rectangular wave. (4) Particles were classified with size under the voltage application of appropriate frequency.

Experimental, numerical, and theoretical investigations have been carried out on statics of a magnetic bead chain in the magnetic field. Chains formed on a solenoid coil were observed and chain lengths and slant angles were measured by a digital microscope. It was deduced that (1) the chain length depends on both the surface loading of magnetic particles and the magnetic flux density, and is almost independent of the particle diameter if the sufficient amount of particles are provided; (2) chains incline in the inclined magnetic field and the inclination of the chain is enlarged by the gravitational force. These configurations of chains are approximately determined to minimize the total potential energy that consisted of the gravitational and magnetic potential energy. These characteristics were qualitatively confirmed by the numerical calculation with the two-dimensional Distinct Element Method. The investigation is expected to be utilized for the improvement of the two-component magnetic brush development system in electrophotography.

Aerodynamic investigation has been carried out on the force in a pinto-plate gas discharge system to clarify the mechanism of force generation. Numerical calculation has been conducted with the vorticity-stream function method, where electrostatic force induced by charge in the corona discharge field is applied to the air. Calculated pressure distribution on the plate electrode was in the order of 10 Pa that was in good agreement with the measured pressure distribution. Calculated velocity at the center was several m/s that must be confirmed by a separate experiment.

Singular vibrations were observed in a pin-to-plate discharge system where the axial stiffness of a cantilever supporting the pin electrode was low. At the transition from dark to corona discharge, the pin electrode perpendicular to the plate electrode vibrated axially because of streamer corona. This vibration was forced by fluctuating electrostatic force caused by ionic wind. At more high voltage, the pin electrode started to vibrate when spark discharge took place. Although mechanisms of the vibrations are not clear, it is expected to be utilized for a new ozone-free charger and to clarify mechanism of "bead-carry-out" in electrophotography.

A preliminary experiment was conducted on an electrostatic ink jet phenomenon. High voltage was applied between an insulative capillary tube filled with water and a metal plate electrode. Ink jet phenomenon was observed at the dark discharge under conditions of appropriate tube diameter and water level. Although the electrostatic attractive force is small, in the order of 10 μN at the voltage lower than the corona onset, it is large enough to separate a water droplet against surface tension in the capillary tube at certain conditions. At the beginning of corona discharging, however, water mist was dispersed at wide angle from the tip of the tube. At higher voltage, water mist became to be dispersed like spray. Joule heat is assumed to be one of reasons of the mist generation. This phenomenon is expected to be utilized for a new ink jet print head.

Experimental and numerical investigations have been carried out on dynamics of electromagnetic particle chains in an electromagnetic field. Chains formed on a solenoid coil were observed and chain lengths and slant angles were measured. The chain length depends on both the density of magnetic particles and the magnetic flux density, but it is almost independent of the particle diameter. The inclination of a chain in the inclined magnetic field is enlarged by the gravitational force. The enlargement and collapse angle of a chain depend on magnetic flux density. These characteristics of chains and the chain forming process can be numerically simulated with the 3-D Distinct Element Method. Bead-carry-out phenomenon in a two-component development system in the laser printer was discussed by the comparison of calculated magnetic force and measured electrostatic force.

Experimental, numerical, and theoretical investigations have been carried out on statics of magnetic bead chain in magnetic field. Chains formed on a solenoid coil were observed and chain lengths and slant angles were measured. It was clarified that the chain length depends on both the density of magnetic particles and the magnetic flux density. It was also clarified that chains have inclinations in the inclined magnetic field and that the inclination of a chain is enlarged by the gravitational force. These configurations of chains are determined to minimize the total potential energy that consists of the gravitational and magnetic potential energy. These characteristics were also confirmed by the numerical calculation with the Distinct Element Method.

In a pin-to-plate gas discharge system, corona discharge took place over a threshold voltage and a relatively large repulsive force, in the order of 100μN, was induced to the pin electrode due to the ionic wind. The force was almost tangential to the pin electrode even when the pin electrode inclined to the plate electrode. The force was utilized for the driving force of small linear and rotational driving mechanisms on water. The linear mechanism was an inclined pin electrode on a floating plate and the rotational mechanism consisted of two pin electrodes on a floating disk at point-symmetrical positions. Experimental investigation deduced that (1) the driving force was induced over the corona onset voltage, (2) the driving force or torque were maximum when the inclination angle was 45 degrees, and (3) the speed of the mechanisms was increased at high applied voltage and a small air gap.

The following basic research is being carried out in our laboratory on electromechanics of particles, because it is a basis of digital printing technology: (1) Experimental, numerical, and theoretical investigations have been conducted on statics of magnetic bead chain in magnetic filed. Chains formed on a solenoid coil were observed and chain lengths and slant angles were measured. Stable configurations of chains were theoretically discussed in point of potential energy minimization. Numerical simulations were also per-formed using the Distinct Element Method considering magnetic interaction forces and the results were compared with the experimental results. (2) Dynamics of the magnetic bead chain has been also investigated. Chains were vibrated by the sine-wave excitation and an impact testing methods and the resonance frequency was deduced. Experimental results were confirmed by the theoretical consideration and the numerical calculation with the Distinct Element Method. (3) A technique to transport dielectric particles is developed utilizing traveling electrostatic field. A fundamental study is being carried out.

This article describes a transient contact phenomenon during start-stop operation of a polygonal mirror scanner rotor driven by a flat-type brushless DC motor and supported by a passive thrust magnetic bearing and a radial air bearing. From experimental investigations, the following characteristics have been clarified. The rotor is statically unstable in the very low speed region. This instability occurs because the stiffness of the air bearing is not induced without rotation, and it is small in the very low speed region, whereas the magnetic negative stiffness of the magnetic bearing exists even at zero speed. Dry contact between the rotor and the stator is induced at the speed lower than a threshold, because a static displacement due to the gravity and nonuniform magnetization of the magnetic bearing and forced vibration due to unbalance of the rotor exceed the air gap of the air bearing. Vertical support of the rotor results in the increase of the threshold speed, in the order of several tens percent, compared to horizontal support. Vibration due to unbalance of the rotor scarcely affects the contact phenomenon. Because dry contact reduces the lifetime of the air bearing, it is preferable to avoid frequent start-stop operations and to keep the rotor speed higher than the threshold. The instability is reduced by adopting a magnetic bearing composed of a pair of permanent magnets.

The electrostatic force acting on a pin electrode in a pin-to-plate corona discharge system was measured and numerically calculated by a static unipolar model. The model neglects the effects of diffusion and convection of charged particles. It is assumed that generation of ions takes place on a tip of the pin electrode and that surface electric field is less than the onset field of corona discharge. Numerical calculations were conducted using an iterative finite element method. Calculated voltage-current characteristics of the positive corona qualitatively agreed with the measured result that the corona discharge took place over a threshold voltage and the current was in the order of several ten microamperes. Trichel pulse was observed in case of negative corona and the negative corona current was large compared to the positive corona. Vertical electrostatic force was also measured and calculated. Although extremely small electrostatic pull force was induced if discharge did not take place, the force became repulsive and relatively large when the corona discharge took place. Force in negative corona was almost same with that in positive corona. Calculated force without discharge agreed with the measured but the calculation did not simulate repulsive characteristics at corona discharging. Convection of air must be included in the model. Effect of lean of the pin electrode has been also investigated. The present investigation is expected not only to realize a new ozone-free charger but also to clarify quantitative mechanisms of the bead carry-out in the magnetic brush development subsystem of electrophotography. © 2001, The Japan Society of Mechanical Engineers. All rights reserved.

Experimental, numerical, and theoretical investigations have been carried out on chain forming process of magnetic carrier beads in a magnetic brush development system of a laser printer. It was clarified that the chain length depends on both the density of magnetic carrier beads and the magnetic flux density and that the length is,determined to minimize the total potential energy that consists of the gravitational and magnetic potential energy. These characteristics were also confirmed by the numerical calculation with the Distinct Element Method.

The following singular phenomena were observed on dynamics of a pin electrode in a pin-to-plate gas discharge system. (1) When the axial stiffness of the support of the pin electrode I was low, vibration of the pin electrode perpendicular to the plate electrode was observed at the transition from the dark discharge to the corona discharge. (2) A spark-coupled-vibration took place for the softly supported pin electrode at the spark discharge (3) An electrostatic ink jet phenomenon was observed, when an insulative capillary tube filled with ink was used for the pin electrode. (4) On the contrary, when the plate electrode made of metal was replaced to water, repulsive reaction due to the corona wind changed the shape of water level (5) When the flexural rigidity of the pin electrode was extremely low, unstable vibration of the pin electrode, flutter, took place at the corona discharge due to the ionic wind. These phenomena are expected to be utilized for a new ozone free charger, a new ink jet system, and a driving system of a micromachine. In addition to these applications, the clarification of the dynamics is indispensable to improve the bead-carry-out in the two-component magnetic blush development subsystem of electrophotography.

Dynamics of a pin electrode in a pin-to-plate discharge system have been investigated to realize a new ozone-less charger of a laser printer. Vertical coupled vibration of the pin electrode was observed when the spark discharge took place. The force applied to the pin electrode at the spark discharge was implicitly evaluated and it was elucidated that the force was attractive, in the order of 1 mN, and it became large in accordance with the increase of the applied voltage. The frequency of the vibration was smaller than the natural frequency of the pin electrode. The force at the positive discharge was larger than that at the negative discharge but the decrease of the vibration frequency at the positive discharge was smaller than that at the negative discharge.

A stable and accurate numerical simulation technique is proposed to investigate performance of the transfer system using a biased transfer roller (BTR) in electrophotography. A one-dimensional layer-structured model was used to calculate distribution of electric field and current under air discharge. Concentration of generated ozone was also calculated. As results of calculations for a typical black and white laser printer, it was shown that (1) a transfer system using a semi-conductive BTR under constant current operation was robust against variation in resistance of media, and (2) concentration of ozone in the BTR system was two orders lower than that in the system using a conventional corona device.

Experimental, numerical, and theoretical investigations have been carried out on statics of a magnetic bead chain in the magnetic filed. Chains formed on a solenoid coil were observed and chain lengths and slant angles were measured by a digital microscope. It was deduced that (1) the chain length depends on both the weight of magnetic particles and the magnetic flux density; (2) chains have inclinations in the inclined magnetic field and that inclinations of the chains are enlarged by the gravitational force. These static configurations of chains are approximately determined to minimize. the total potential energy that consisted of the gravitational and magnetic potential energy. These characteristics were qualitatively confirmed by the numerical calculation with the two-dimensional Distinct Element Method. The investigation is expected to. be utilized for the improvement of the two-component magnetic brush development system in electrophotography.

The generation of ozone in a stable regime of DC corona discharge at a pin electrode is modeled to provide data that can be utilized for the evaluation of charging and transferring devices of electrophotography with respect to reducing the ozone emission. The results of a theoretical investigation show the following: (1) The ozone generation rates at a 5 liter/min air flow rate for a 50 mu m radius pin electrode are 0.085 ppm/mu A and 0.010 ppm/mu A for negative and positive charging corona, respectively. (2) The ozone generation rate increases with respect to the increase of the pin radius and can be assumed to be linear under normal operation conditions. (3) For positive charging corona, ozone is generated mainly at the surface of the pin electrode, whereas the ozone formation is displaced with a maximum generation rate located at 0.1-0.3 mm from the electrode for negative charging corona. (4) The ozone generation rate for the saw-toothed electrodes is about one-third that of a typical biased charging roller and only 1/140 to that of a corotron.

The electrostatic force acting on a pin electrode in a pin-to-plate corona discharge system was measured and numerically calculated by a static unipolar model. The model neglects the effects of diffusion and convection of charged particles. Numerical calculations were conducted using an iterative finite element method. Calculated voltage-current characteristics of the positive corona qualitatively agreed with the measured result that the corona discharge took place over a threshold voltage and the current was in the order of several ten microamperes. Trichel pulse was observed in case of negative corona and the negative corona current was large compared to the positive corona. Vertical electrostatic force was also measured and calculated. Although extremely small electrostatic pull force was induced if discharge did not take place, the force became repulsive and relatively large when the corona discharge took place. Force in negative corona was almost same with that in positive corona. Calculated force without discharge agreed with the measured but the calculation did not simulate repulsive characteristics at corona discharging. Convection of air must be included in the model. In addition to these technologies related to the electrophotography, a unique method to drive liquid, named " electrostatic Moses effect, " has found and reported. The method is expected to be utilized for a new ink jet printhead.

This paper describes a transient vibration during start-stop operation of a polygonal mirror scanner motor in a laser printer. Two types of abnormal vibration take place in the rotor driven by a flat-type brushless DC motor and supported by a passive thrust magnetic bearing and a radial air bearing. One is an axial displacement and vibration and another is a radial dry-contact at very low speed region. From results of theoretical and experimental investigations, the following characteristics and countermeasures have been deduced: (1) Repulsive magnetic force induced between the stator coils and rotor magnet of the motor causes the axial static displacement and the axial transient vibration. Soft start-stop scheme of the motor current is effective to reduce the axial vibration. (2) The rotor is statically unstable in the radial direction at very low speed region. This instability occurs because the stiffness of the air bearing is not induced without rotation and it is small at the very low speed region, whereas the magnetic negative stiffness of the magnetic bearing is existent even at a zero speed. Dry contact between the rotor and the stator shaft at the air bearing is induced at the speed lower than a threshold. Since the dry contact reduces the lifetime of the air bearing, it is preferable to avoid frequent start-stop operations and to keep the rotor speed higher than the threshold. The instability is reduced to adopt the magnetic bearing composed of a pair of permanent magnets.

The electrostatic force acting on a pin electrode in a pin-to-plate corona discharge system was measured and numerically calculated by a static unipolar model. The model neglects the effects of diffusion and convection of charged particles. It is assumed that generation of ions takes place on tip of the pin electrode and that surface electric field is less than the onset field of corona discharge. Numerical calculations were conducted using an iterative finite element method. Calculated voltage-current characteristics of the positive corona qualitatively agreed with the measured result that the corona discharge took place over a threshold voltage and the current was in the order of several ten microamperes. Trichel pulse was observed in case of negative corona and the negative corona current was large compared to the positive corona. Vertical electrostatic force was also measured and calculated. Although extremely small electrostatic pull force was induced if discharge did not take place, the force became repulsive and relatively large when the corona discharge took place. Force in negative corona was almost same with that in positive corona. Calculated force without discharge agreed with the measured but the calculation did not simulate repulsive characteristics at corona discharging. Convection of air must be included in the model. Effect of lean of the pin electrode has been also investigated. The present investigation is expected not only to realize a new ozone-free charger but also to clarify quantitative mechanisms of the bead carry-out in the magnetic brush development subsystem of electrophotography. In addition to these technologies related to the electrophotography, a unique method to drive liquid, named "electrostatic Moses effect," has found and reported. The method is expected to be utilized for a new ink jet printhead.

This article describes an axial transient vibration of a polygonal mirror scanner rotor driven by a flat-type brushless DC motor and supported by a passive thrust magnetic bearing and a radial air bearing. From results of theoretical and experimental investigations, the following characteristics of the vibration, countermeasures to suppress a static displacement, and the transient vibration have been deduced: (1) Repulsive magnetic force is,induced between the stator coils and rotor magnet under current passage. The force is proportional to the motor current. The force causes axial static displacement and axial transient vibration. (2) Parametric investigation deduced that:(a) higher stiffness of the magnetic bearing and lower acceleration current linearly reduce both the static displacement and the transient vibration; however, the former may reduce lifetime of the air bearing due to a dry contact with start and stop operation, and the latter prolongs the startup time; (b) soft start-stop scheme of the motor current is effective to reduce the vibration.

Theoretical and experimental investigations have been performed to clarify the mechanism of a self-excited chatter vibration induced in a paper-feed-roller system in an electrophotography copy machine. From results of the investigation, the following points were deduced: (1) The chatter vibration is induced only when a platen cover is pushed with a certain force and a paper does not exist between the roller and a platen glass, i.e., the roller slips against the platen glass. The experimental observation suggests that the vibration is a stick-slip vibration induced by the negative speed dependence of the friction coefficient. (2) Calculated results based on the present model qualitatively agreed with experimental observations, and several methods to suppress the vibration were proposed. (3) The paper-feed-roller system must be designed to be (a) high damping, (b) low negative speed dependence of the friction coefficient, (c) small press force, and (d) low arm angle. The resonance frequency of the platen cover must be designed to be away from the resonance frequency and its ultraharmonic ones of the roller system.

The generation of ozone in a stable regime of DC corona discharge at a pin electrode is modeled to provide data that can be utilized for the evaluation of charging and transferring devices of electrophotography with respect to reducing the ozone emission. The results of a theoretical investigation show the following: (1) The ozone generation rates of the 50 hum radius pin electrode are 0.085 ppm/muA and 0.010 ppm/muA under 5 liter/min air flow rate in case of negative corona and positive corona, respectively. The generation rate increases in accordance with the increase of the pin radius. Although the rate of ozone emission is nonlinear with respect to the discharge current, it can be assumed to be approximately linear within the usual design and operation conditions of electrophotography chargers. In case of the positive corona, ozone is formed just at the surface of the discharge electrode, but on the contrary, in case of the negative corona, ozone is formed at about 0.1 mm apart from the tip of the electrode. (2) The ozone generation rate of the charger with saw-tooth electrodes is reduced to about one third of that with a biased charger roller and it is only 1/140 of that with a corotron. The saw-tooth charger has a potential to realize virtually ozone-free charger.

The self-excited chatter vibration of a spring clutch used in an electrophotography fuser was investigated. From the results of theoretical and experimental investigations, the following points were deduced: (1) the vibration is induced by an asymmetric friction force due to asymmetric contact at the slipping surface; (2) Lissajous figures of the vibration were circular and the vibration was forward-whirling; and (3) calculated results based on the present model qualitatively agreed with experimental observations. Several methods of suppressing vibration were proposed. The spring clutch should be designed such that it has the following characteristics: (a) sufficient damping: (b) low friction coefficient; (c) sufficient gap during the slipping period and perfect fastening when transferring torque; and (d) small static offset displacement. These measures have been used to overcome the abnormal chatter vibration problem.

The electrophotography, such as a copier or a laser printer, requires a multi-pole magnet for its development system. Some of development magnets are produced by in-process magnetization of injection molded plastic magnet system. The process is nonlinear with respect to the relationship between a magnetization profile of the multi pole magnet and magnetic flux density in the vicinity of the cavity and a lot of trial-and-error FEM simulation must be conducted to determine the configuration of magnetization magnets for the development magnet. To realize the efficient design system, the design problem of the magnetization tool is formulated as the optimum design problem. In this problem, the global optimum design is not always required. Because the specifications about their magnetic flux densities have upper and lower limitations and it is the most important that all magnetic flux densities at poles are settled between two limitations within reasonable calculation time. Therefore, random step method with membership functions which are determined by the temporary optimum design is proposed. It is possible to search the quasi-optimum design in reasonable calculation time by the proposed method.

This paper describes an axial transient vibration of a polygonal mirror scanner rotor driven by a flat type brushless DC motor and supported by an axial magnetic beaing and a radial air bearing. From results of theoretical and experimental investigations, the following characteristics of the vibration and measures to suppress a static displacement and the transient vibration have been deduced: (1) Repulsive magnetic force is induced between the stator coils and rotor magnet under current passage. The force causes axial static displacement and axial transient vibration. (2) Parametric investigation deduced that; (a) high stiffness of the magnetic bearing and low acceleration current linearly reduce both the static displacement and the transient vibration, however, the former may reduce a lifetime of the air bearing due to a dry contact at the start and stop operation and the later prolongs the startup time; (b) soft start-stop scheme of the motor current is effective to reduce the vibration.

The self-excited chatter vibration of a spring clutch used in an electrophotography fuser was investigated. From the results of theoretical and experimental investigations, the following points were deduced: (1) the vibration is induced by an asymmetric friction force due to asymmetric contact at the slipping surface
(2) Lissajous figures of the vibration were circular and the vibration was forward-whirling
and (3) calculated results based on the present model qualitatively agreed with experimental observations. Several methods of suppressing vibration were proposed. The spring clutch should be designed such that it has the following characteristics: (a) sufficient damping
(b) low friction coefficient
(c) sufficient gap during the slipping period and perfect fastening when transferring torque
and (d) small static offset displacement. These measures have been used to overcome the abnormal chatter vibration problem.

A mathematical analysis has been performed on rotor dynamics of a high-speed polygonal mirror scanner motor in digital electrophotography. The rotor is assumed rigid and vertically supported by air bearings with an effective length that is not negligible compared to the rotor length. The model is a four-degree-of-freedom system that includes the gyroscopic effect and nonorthogonal force of the air bearing. The model also includes the effects of longitudinal bearing length and radially unstable magnetic stiffness of a driving motor and/or a magnetic bearing. A simulation program was coded to calculate complex eigenvalues, static and dynamic stability, critical speeds, unbalance responses, and external excitation responses. The results indicated that although the effects of bearing length and magnetic unstable stiffness were ignored in the past, these simplifications result in substantial error for the evaluation of rotor dynamics. The model is utilized to realize high-performance scanner motors.

Numerical calculations were performed to simulate charging characteristics of an electron beam printhead. Because the electric conduction in the gas discharge field is determined not only by electrostatic potential but also by ionic or electronic charge density, two coupled partial differential equations, the continuity equation of charge and Poisson's equation, were numerically solved by the finite-element method under the boundary condition that the electric field at a discharge electrode is a constant determined by a corona starting electric field strength. It was demonstrated that the calculated portion of the high charge density corresponds to the observed luminous and highly degraded portion. The calculation also confirmed that predominant charging particles on the printhead are not ions but electrons. The present method can be utilized for practical design of the charging process.

A feasibility study has been performed to simulate the transport of magnetic carriers in a two-component magnetic brush development subsystem of electrophotography. A fundamental model has been established for the magnetic force, which acts on magnetic particles in the magnetic field applied by a magnetic roller. Numerical calculations have been conducted using a simplified model that neglects the interactive magnetic force between carrier particles. The qualitative adequacy of the model has been confirmed by comparing the calculated distribution of the magnetic force with the experimentally observed adherence mode of carrier beads on the magnetic roller. The present method can be utilized to support the design of magnetic brush development subsystems.

Chatter vibration of a cleaner blade charged by a contact charger roller was mathematically investigated. From the results of the investigation, the following points were deduced: (1) The chatter vibration is basically induced by nonlinear negative damping due to negative speed dependence of the friction coefficient between the cleaner blade and a photoreceptor drum. Parametric excitation and forced vibration are also generated by the photoreceptor vibration induced by the alternating electrostatic force of the charger roller. (2) Calculated results based on the present model qualitatively agreed with experimental observations, and several methods to suppress the chatter vibration were proposed.

The generation of ozone in a stable regime of DC corona discharges at thin mires is modeled to provide data that can be utilized for the design of the charging and transferring devices of electrophotography, such as corotrons or scorotrons, with respect to reducing the ozone emission. The results of a theoretical investigation show the following: (1) Although the rate of the ozone emission is nonlinear with respect to the discharging current, it can be assumed to be approximately linear within the usual design and operating conditions of corotrons. (2) In the case of the positive corona, ozone is formed just at the surface of the discharge wire, but on the contrary, in the case of the negative corona ozone is formed about 0.1 mm from the wire. This yields the result that the ozone formation rate in the negative corona shows low dependence on materials used for the corona discharge mire but the rate in the positive corona is highly dependent on the wire materials. (3) The ozone formation rates are very small far from the discharge wire for both positive and negative discharges. This calculated result also supports the experimental evidence that the effect of materials used for the shield electrode is small for both positive and negative discharges.

Ozone formation by a contact charger roller was modeled on the basis of a one-dimensional static plasma reaction. The results of the investigation showed that though the calculated rate of ozone emission was about 1.7 times smaller than the experimental result, effects of applied ac voltage and its frequency qualitatively agreed with experiments. The following conclusions were deduced from the investigation: (1) the rate of ozone formation is roughly estimated using the present model; (2) the rate of ozone formation is large under high applied voltage and high-frequency operation, but the effect of the roller resistance is minor; and (3) it was proposed that a normalized cumulative charge density be minimized to suppress ozone formation. The present method may be utilized for the design of a contact charging subsystem and its operating conditions to reduce ozone emission.

A new numerical method has been developed to calculate secondary current distribution in electrochemical cells. The method is applicable in arbitrary two - dimensional systems which include non-uniform and/or anisotropical resistive electrodes with nonlinear polarization kinetics such as the Butler-Volmer polarization at electrolyte-electrode interfaces. The calculation uses a double iterative method employing the boundary element method (BEM) in the electrolyte region and the finite element method (FEM) in the electrode region. Parametric calculations for a corner electrode were performed to demonstrate the resent method.

A fundamental study is performed for local electrodeposition of copper utilizing thermal potential induced by Joule heating. The feasibility of the process for microelectronic applications is assessed by both experiment and mathematical modeling. The results of the investigation show that (i) a copper wire is coated under conditions of a.c. 50 Hz Joule heating in electrolyte containing 1.0 M CuSO4 and 0.5 M H2SO4 with relatively high deposition rate of about 0.4 mum min-1, (ii) the Joule heating current should be kept below the boiling point of the solution to realize uniform deposition, and (iii) results of calculations by the present model based on one-dimensional heat conduction agree well with experimental results.

A dynamic model of the porous sulphur electrode including diffusion of the reactant is developed to simulate charge-discharge characteristics of the sodium-sulphur cell and transient behaviour of the cell after termination of operation. From the results of investigations the following are clarified: (1) sodium ion concentration on the solid electrolyte side is low during charge, on the other hand, it is high during discharge; (2) an insulating film of sulphur is formed at the surface of the solid electrolyte in the deeply charged stage. This results in an increase of the cell resistance and thus restricts charge acceptance; (3) the resistance in the single phase region is larger than that in the two phase region; and (4) open circuit voltage in the single phase region, observed after termination of operation, is not equal to the equilibrium value but gradually approaches it according to the concentration relaxation. These characteristics agree well with experimental results.

Performance and thermal behavior of the sodium-sulfur cell of a central sodium tube type under high current density operations are investigated by thermal modeling and calculations and experimental verification. The following are clarified by comparing calculated results with experimental ones: (i) the cell temperature varies widely during the charge-discharge operations, and it becomes maximum at the end of discharge
(ii) the temperature distribution in the cell is roughly estimated from the measured value at the surface of the cell container
(iii) a hypothetical maximum of the energy efficiency is estimated by the calculation
(iv) though the thermal stress applied to the beta”-alumina solid electrolyte tube is small, the thermal fatigue of sealing parts of the cell and corrosion of a metal container of the sulfur electrode are accelerated under high current density operations
(v) dynamic behavior of the cell when the cell is short-circuited is investigated by experiments and calculations, and it is indicated that, in consequence of the high short-circuit current, the temperature rise becomes extremely high depending on the external resistance and the starting point of discharge depth. The induced thermal stress is small even then. The present method of the simulation is utilized to determine proper operating conditions of the cell under high current density operations and to assess the safety in the case that the cell is accidentally short-circuited. © 1989, The Electrochemical Society, Inc. All rights reserved.

The electric potential profile on the sulfur electrode container, and the cell voltage fluctuation have been monitored by in-test analysis methods. The. © 1986.