Generally, DLC films have good mechanical and tribological properties such as low friction coefficients, high wear resistance, and high hardness. And their mechanical properties can be varied widely by changing deposition conditions. However, they cannot be applied to machine elements such as gears, because their load capacities are not high enough for a high surface pressure. The present paper describes endurance performances of DLC films deposited POM gear pairs. POM is chemically stable, so that good adhesion of DLC films generally can not be obtained. Therefore, DLC films were deposited using PBIID (Plasma Based Ion Implantation and Deposition) Method under changing RF power and interlayers using HMDSO. As a result, DLC deposited POM gears had good endurance performances compared to no-DLC POM gear pairs.

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[in Japanese]

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We developed a new diagnostic method by using laser beam. The tooth surface is irradiated by zonal laser beam from oblique direction, and then irradiated laser beam line is shifted along the height of the tooth according to gear revolution. The variations of laser reflection between the initial and the present conditions are compared, and it can estimate a condition on a tooth surface such as initial or abnormal abrasion, pitting, etc. We developed a method of automatic and remote damage diagnosis on a gear tooth surface. By using this method, we can estimate and diagnosis automatically in consideration of influence of adjacent teeth by using an ideal measurement voltage based on each gear geometry.

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Traction drive CVT is a transmission changing the speed of output shaft continuously and smoothly. However, the speed ratio of the CVT is affected by the load torque - the increase of load torque generally makes the speed ratio lower. In this paper, effect of the load torque on the speed ratio of 2K-H type CVT equipping loading cam was investigated by the experiment focusing on the slip at contact zone in the unit. The experiment showed that the speed ratio drastically decreased when the load torque was quite small around zero, and that the change in speed ratio became moderate when the load torque became higher though the trend depended on the initial speed ratio. In addition, it was found that the slope of traction curve and traction coefficient at contact zone affected the speed ratio of the CVT.

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The simulation of rolling contact fatigue strength of traction drive elements was proposed. It can consider the effect of size and distribution of inclusions in the material and the traction force generates on the contact surface. The estimation formula of rolling contact fatigue strength which evaluates the shear stress was obtained by the experiment. The maximum size of inclusions which affect the fatigue strength was estimated by the observation of material and the statics of extremes. As the result of simulation, 820 MPa of average rolling contact fatigue strength was estimated. The error was 4% in the experimental result of 790 MPa.

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This paper describes improvement of the slip limit and power transmission efficiency of half-toroidal CVT (continuously valuable transmission) for automobile by using the power roller oflset In the CVT design, setting traction coefficient between power roller and disks must not exceed the slip limit On the other hand, the efficiency of half-toroidal CVT increases if the setting traction coefficient can be set low value. Hence, we should define the appropriate value of setting traction coefficient However the accurate value of slip limit considering the effects of deformation of CVT components has not been demonstrated. In this study, we calculated the effect of the slip limit of half-toroidal CVT on oflset of power roller which can cancel the effect of deformation of Hie CVT components and then discuss the possibility of improving the CVT efficiency.

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For the evaluation method of micro gear accuracy, the most suitable approach should be to use a pair of rotary encoders. The difficulty is that the diameter of the rotary encoder should be at least smaller than the reference diameter of a test gear in order to avoid the interference between the encoder and the mechanical coupling of the other encoder. Our target micro gears are supposed to have the reference diameter smaller than 1 mm. The authors here try to manufacture the grating disk whose diameter is smaller than 1 mm in order to achieve both the small width of the gratings and homogeneity of it by utilizing the combination of electron beam (EB) lithography and etching technique of silicon substrate. The optimum conditions were investigated to get adequate radial grating grooves with dummy sample patterns. Finally, a grating disk which has 1,000 gratings in the size of 1mm in diameter is successfully manufactured.

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A hypothesis was presented concerning the effect of the axial residual stress at the first thread root of a bolt on its fatigue strength. However, this has not yet been verified quantitatively since the residual stress which may exist locally around the thread root cannot be measured or estimated with sufficient accuracy. This study aims to quantify the effect of the residual stress on the fatigue strength. For this purpose, residual stress at the root of groove-rolled specimens were measured by X-ray method, and it was found that the maximum compressive residual stress was generated at the inner layer about 0.5 mm from the surface. In this report, simple 3-D FE analysis was done to calculate the axial residual stress distribution by using the interim FE model through the groove rolling process. The calculated results show that the circumferential plastic deformation affect significantly to the axial residual stress distribution in rolling process and the calculated axial residual stress distribution is similar to measured one.

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We are developing a multi-modal 2.5D display capable of stimulating tactile and force sensations to achieve a new human-friendly interface. In the present study, we extended the versatility of the operation in 2.5D space for object manipulation in 3D space. Although the surface rotation of the virtual tactile pad was limited around the z-axis in the previous display, the rotations around the jc-axis and ^-axis are managed by the centroid position of the operator's fingers in the new display. We conducted a series of evaluation experiments. In the experiments, subjects tried to compare the size of two virtual spheres to evaluate the 3D shape presentation capability of the present display. Since the sensation thresholds for each subject were low enough, we proved that operators could recognize a fine distinction of sphere radii generated by the proposed display.

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This study proposes a novel technique to display tactile sensation using electro-rheological fluid (ERF). ERF changes its Theological characteristics according to the electric field applied. The ERF used in this study generates relatively high yield stress and behaves as a solid when subjected to a strong electric field. Using this solid-liquid phase transition, we propose a device which provides a tactile sensation, i.e., tactile roughness display. Applying electric field at a specific position in an ERF chamber, the corresponding ERF turns to solid at the position. This solid-state ERF gives tactile sensation like a convex to a user. We develop in this study several prototypes, which may realize the above-mentioned idea, and characterize them. We obtained the following results through experiments. First, the tactile roughness display gives tactile sensation to a user. Second, as the strength of electric field increases, the probability of tactile sensation perception given by roughness tactile display increases. On the other hand, the quantity of increase in yield stress does not contribute to the probability.

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In recent years, tactile display technology in virtual reality and teleoperation is widely studied. However, it is still difficult to display complicated texture of objects in detail. It is particularly difficult to display tactile sensation without relative motion between finger and tactile display. Accordingly, we propose a novel tactile display, which has an ultrasonic vibrator and a movable strip of paper located between finger and the vibrator. The strip of paper provides a relative motion between finger and vibrator, that is, an active touch which is important for human to perceive roughness of an object. Using the tactile display we developed, we clarify the characteristic of tactile perception during active touch.

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In this paper, a display system that can present a virtual airflow and/or odor source on a screen is proposed. The system can give the user a sensation that airflow and/or odor is coming from a certain position on a computer screen. Four fans are used in the proposed display and are placed at the four corners of the screen. Airflows generated by the fans are collided with each other and deflected from their original courses. Thus, directed airflow is generated toward the user from a specific position on the screen (a virtual airflow source). By introducing odor vapor into the airflows, odor distribution spreading from a specific position on the screen (a virtual odor source) is generated. The results of airflow velocity and odor concentration measurements show that the virtual airflow/odor source can be moved to an arbitrary position on the screen by adjusting intensities of the airflows.

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Silicon dry etching technology makes it possible to fabricate rectangular structures by repeating two steps of etching process and protection process. Therefore, our research introduces the ability of Si dry etching technology in order to fabricate un-tapered, high precision microstructures containing rectangular grating patterns with narrow pitch of submicron level. In the present study, a high precision Si microstructure was fabricated using ICP-RIE apparatus. In these techniques, we have succeeded in fabricating about 40 μrn height, void-free gold microstructures in a space as narrow as 2.6 μm in large effective area of 60 mm squares. In this research, we are trying narrower space and high aspect ratio microstructures. Therefore, it is expected to be used in the production of a wide variety of micro-devices that have not yet been put into practice.

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We observe the elliptical motion generated by an annular stator of an ultrasonic motor using a high speed microscope. This observation clarifies the behavior to generate a torque of the ultrasonic motor. In this report, we show the generation of the elliptical motion by the high speed microscope. Using the setup, the amplitude of the elliptical motion and the motor power are examined by changing the voltage amplitude and frequency. The vibration amplitude of the elliptical motion is compared with the motor characteristics such as revolution and torque. The result indicates the optimal vibration amplitude to obtain the high torque.

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This paper proposes and presents an electro-conjugate fluid (ECF) micropump whose pumping sources are integrated inside flow channels three-dimensionally. ECF is a kind of functional and dielectric fluid. A strong and active jet flow of ECF is generated between electrodes surrounded by ECF, when high DC voltage is applied to the electrodes. To combine easy fabrication and high performance, we developed a novel ECF pumping source that consists of a triangular prism electrode and a slit electrode fabricated by MEMS technology. Thanks to the advantages of MEMS technology it is easy to integrate plenty of triangular prism and slit electrode pairs in a plane. The plane integration of these electrode pair results in the realization of ECF micropumps for high output power density. In order to obtain higher output power density, we make an attempt to integrate the triangular prism and slit electrode pair three-dimensionally in addition to the plane integration. To figure out the effectiveness of three-dimensional integration of ECF pumping sources, we develop the prototype and investigate the characteristics experimentally by using the prototype. The experimental results show that the ECF micropump by 3D integration can be a good candidate as a higher output power hydraulic power source.

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Electro-conjugate fluid (ECF) is a dielectric and functional fluid, which generates a powerful jet when electrodes inserted into it are subjected to direct current less than thousands of volts. As one essential research field on ECF, researchers have been conducting the study on electrodes. Several structures, e.g. planar parallel rod-like electrode array, ring-needle electrode pair and triangular-prism-slit (TPS) electrode pair, were proposed. Among them, the TPS electrode structure is often thought as the most promising candidate for future ECF applications thanks to its great merits of combining easy fabrication and relatively high performance. In this paper, in order to evaluate performance of the TPS electrode pair fabricated by MEMS technology, we conceive novel MEMS fabrication processes to utilize micro molds of thick photoresist and their electroplating. The relationships between output pressure and important parameters of the TPS electrode pair, including slit thickness, slit width, electrode gap, and tip angle are investigated. The experimental results show that thin slit thickness, narrow slit width, small gap are necessary in order to gain higher output pressure.

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For maintenance microrobots for small diameter pipes in power plants and so on, we proposed and developed a novel microgripper using valve division type flexible electro-rheological valves (FERVs). Each bendable arm consists of the FERV and a rubber chamber with several millimeters long. The FERV has plural short length ER valves in a rubber channel. Each ER valve controls the electro-rheological fluid (ERF) flow by changing the viscosity with the electric field. The FERV has high flexibility with sufficient pressure control range. The rubber chamber has plural walls inside to restrict the radial expansion and axially extends by the inner pressure controlled with the FERV. Arm large models and a gripper were fabricated and characterized.

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As a multi-DOF (degrees of freedom) microactuator system for maintenance microrobots for small diameter pipes in power plants and so on, we proposed a novel multi-DOF ER microactuator system using an alternating-pressure source. In the system, the alternating-pressure of low viscosity fluid is transmitted to ERF (electro-rheological fluid); the induced flow is rectified through ER microvalves and applied to each fluid power microactuator. The pipe connecting the pressure source and each actuator is only one for both outflow and inflow and is applicable small diameter due to the low viscosity fluid, which can solve the piping problem of multi-DOF ER microactuator systems. In this paper, the system was proposed and the basic characteristics were analyzed.

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In this paper, the effect of texture dimensions, which are textured area and aspect ratio of cross section, on sliding characteristic of the parallel plate was described. The sliding tests were carried out using block on disk type friction tester. The dimple patterns which have five kinds of dimensions were processed on block surface by laser processor. The friction coefficient, film thickness, pitch angle of block and behavior of oil flow were observed under varying the sliding velocity and viscosity of oil. The results showed that the friction reduction in mixed lubrication regime was influenced by the textured area, which was, friction coefficient was larger when textured area was smaller. The change of friction reduction was caused by the change of film thickness. In these experimental conditions, cavitation was not observed in contact area.

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In order to calculate the traction force between the contact surfaces of machine elements, such as a gear and traction drive, the influence of the asperity contact and the decrease of thickness of oil film by the heat generation of the contact surface were adapted to the visco-elastic-plastic model. The traction coefficient in case of using ATF and traction oil were calculated by using improved program, and compared with the experimental results in the same conditions. By the consideration of the decrease of film thickness, the traction coefficient increased in the region of the high slip ratio. Moreover, the maximum traction coefficient increased by considering asperity contact. As a result, the calculated results became close in the experimental results. Therefore, the effectiveness of those improvements was confirmed.

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CNx showed ultra low friction coefficient less than 0.01 in dry N_2. But clarification of ultra low friction mechanism is not completed. Our purpose is clarification of this ultra low friction mechanism, we think that extreme surface layer of CNx coatings is important to explain ultra low friction's mechanism. In this study, we investigate the properties and this extreme surface layer of the CNx coating by transmission micro scopy and electron energy-loss spectroscopy. And we clarify some characterization of bulk and surface layer of CNx.

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This study discusses the possibility to control the friction coefficient of Carbon Nanotube (CNT) films with a normal force oscillation motion method approach under micro newton loads application. In this study, vertically aligned multi-walled CNT films were used as an experimental sample due to their steady high friction coefficient. For this purpose, the oscillation method has been applied by increasing the oscillation amplitude of the bearing ball under various frequencies. The results from this dynamics approach clearly showed a decrement of high friction of CNT films with the increment of oscillation amplitude in micro-scale sliding contact.

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[in Japanese]

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The carbonaceous coating such as Diamond-Like Carbon (DLC) and Carbon Nitride (CNx) coating are one of the promising material as well as good tribological properties, especially low friction coefficient. It is assumed that ultraviolet light will change the DLC and CNx topmost surface to graphite-like layer because the light intensity exceeds C-N or C-C bonding energy, and then generated dangling bonds will combine each other. We hypothesized that ultraviolet light irradiation could make the CNx and DLC coating topmost surface graphitic. We prepared CNx and DLC coating irradiated ultraviolet light. Then these specimens and as-deposited CNx and DLC coating were tested in air to compare frictional property. CNx coating was synthesized with PVD as 0.1μm thickness on Si(100). The average friction coefficient of DLC without UV irradiation showed approximately 0.1, on the other hand, 254 and 365 nm UV irradiated DLC showed 0.02-0.05 friction coefficient.

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In application of bearings under the severe frictional conditions, nascent clean surfaces of bearing steel are created, so that the hydrocarbon components of greases can adsorb on and thus decompose by such reactive surfaces. As a result, generated hydrogen penetrates into the bearing steel and related hydrogen embrittlement occurs with anomalous structural change. Using controlled atmosphere cutting apparatus, therefore, this study investigated the decomposition behavior of greases with nascent clean surfaces of a carbon steel. Quadrupole mass spectrometer monitored the ion strength of fragment ions inside the test chamber and this spectrometry demonstrated that the behaviors of grease decomposition and the resultant hydrogen generation were greatly influenced by the types of base oils and the chemical structures of additives.

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Hydraulic systems have features of compact and high output power. However, in recent year, further downsizing and higher output power of hydraulic equipment have been demanded. As a result, operating pressure of hydraulic systems has been increasing and cavitation has significantly occurred with increasing pressure. The purpose of this study is to reduce the cavitation occurrence by eliminating bubbles in oil in high pressure condition. In this paper, the relation between the amount of the cavitation erosion and the bubble elimination is experimentally investigated.

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In a production process of rail vehicles, several panels such as a ceiling panel and side panels are assembled by fusion welding. The welding heat causes the assembled vehicles to be slightly distorted. In the next interior fitting process of the rail vehicle production stage, a huge number of parts must be fitted, such as air conditioning units and frame bars for straps, etc. It is very difficult for those parts to be fixed into the railway vehicles since the bolt holes are not in right positions because of the welding heat. So it is of very importance to measure shapes of the panels and the bolt holes after the welding process. In a previous study, we had developed a new type of laser coordinate measuring machine with a laser distance meter and two galvano mirrors. In this study we have improved the measuring accuracy of the developed system with larger galvano mirrors.

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