Traction drive technology is now in growing stage from the starting of development of a toroidal CVT in 1978. Technological innovations on traction fluid and steel-material make it possible to transmit high torque with long life. This paper shows current and prospect of traction drives as quiet, smooth and flexible power-transmitting machine-elements.

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The advanced actuators based on the various physical phenomena are developed actively, toward the innovation of the mechanical engineering systems such as a micro-mechanical system. This paper deals with the present state of the development of the advanced actuators, and the optical actuator system developed in our laboratory. The optical actuator systems are expected to be stronger against the EMI than the conventional mechatronics systems.

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A brief survey is made on researches presented at international tribology conferences held in Japan in 1990, 1995 and 2000. Trends in research subjects as well as collaboration of researchers from different nations and different organizations are shown on the basis of data compiled by the secretariat of the ITC Nagasaki 2000.

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In this paper, it was described that a new pivot bearing with 2-DOF applied continuously velocity joint (CVJ) was produced by way of trial, and analysed axial stiffness and contact pressure theoretically. A new pivot bearing swung smoothly within ±30degrees, and had high stiffness. It was thought that this pivot bearing could be apply to parallel mechanism, joint for robots and so on.

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To measure the EHL film thickness in a starved condition, a rolling contact apparatus with two successive rolling elements is made. The EHL film thickness and geometry is measured by white light interferometry because the film thickness in starved condition becomes thinner less than 1μm. In the case that inlet film thickness can be considered to be uniform, it is shown that a variation of film thickness with inlet film thickness predicted in the numerical analysis agrees with measurement results. Furthermore, in the case that the two ball successively passes on the same track, it is suggested that severe starvation may occurs in the side portion of contacts.

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A possible mechanism for the occurrence of numerous shallow cracks, which were observed on the rubbing surface of cemented carbide, was studied. The experiments were conducted using an apparatus simulated mechanical face seal composed of two kinds of ceramics rings and cemented carbide ring, with distilled water as the liquid to be sealed. The Vickers indentation formed between adjacent precracks produced cracks with almost the same length as the adjacent precracks. These results suggested that the cracking occurred by the tensile residual surface stress. A method to predict the magnitude of the tensile residual stress by measuring the surface profile of the cracking surface was also proposed.

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Direct observations of point contact elastohydrodynamic lubrication (EHL) films formed between a glass disk and a steel ball are conducted under pure sliding conditions. The numerical solutions of the thermal EHL theory based on Newtonian flow model are also obtained. Good qualitative agreement is obtained between the experimental and numerical results. The number of dimples produced in the EHL conjunction depends on the sliding speed and load. The possible mechanism is discussed. It is shown that the pressure spike plays an important role on the formation and position of the dimple.

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The nut loosening, which is the main cause of axial force deficiency in bolt-nut unit. A new type nut is proposed to constant axial force of the unit, and the deformations or friction force of the various nut are calculated by the FEM method. The validity of the numerical analyses is confirmed by some experiments. It is shown that the top face of the nut contracts in radial direction while its bearing surface expands by the force acting on mating threads ridges under wrench torque.

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This paper describes the calculations of waved air journal bearings used in a laser scanner motor. The waved bearing can achieve the higher load capacity and stiffness than that of circular bearing and be produced by the low cost because the shape is simpler than the herringbone bearing. However, this waved bearing has some problems. One of them is increasing power loss under high temperature and humidity environment. To investigate mechanism of increasing power loss, we calculated temperature in bearing clearance and inside shaft and bearing with two wall boundary conditions.

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Recently, brittle porous materials such as graphite and advanced ceramics have been often applied to aerostatic bearings because gas flow through these porous materials can be limited to a small amount. However, aerostatic bearings using these porous materials are prone to cause pneumatic hammer instability. Therefore, reducing the permeability of porous material only near the bearing surface is usually adopted as a very effective means for avoiding pneumatic hammer instability. In this paper, the static and dynamic characteristics of aerostatic circular thrust bearings with a restricted layer are investigated, theoretically and experimentally. In the theoretical calculations, several calculation models are presented and theoretical results obtained are discussed.

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An ultra-precision method of joining optical lenses in a cell has been developed by using a shrink fitter, which is made of plastics. This method gives contact pressure to the shrink fitter inserted between the optical lenses and the cell in various environmental temperature. Therefore, the contact pressure of the shrink fitted assembly decreased with time because of stress relaxation of the shrink fitter. Consequently, the assembly loosened and the radii of curvature of the lenses changed. We examined the effect of creep properties of the shrink fitter on its mounting performance for optical lenses theoretically and experimentally.

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Tribological properties of TiO_2 ceramics produced by spark plasuma sintering method were studied by the block-on-ring sliding wear tests under the wide range of contact load and the sliding velocity in room air. A block specimen was TiO_2 and a ring specimen was bearing steel. The wear rate of TiO_2 ceramics increases with sliding velocity until v=10.0m/s but then decreases at high velocity. It increases monotonously with load. TiO_2 ceramics shows high wear resistance compared with Al_2O_3 and SiC under v=0.1m/s. The wear properties of TiO_2 ceramics were discussed through SEM observations.

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Evalution of wear resistance of ceramics was carried out by a new solid particle impact test (slurry jet test). The alumina particles whose average diameter was 1.0, 10 and 170 μm were used as erodent. When the particles of 1.0 μm were impacted, transgranular fracture mainly occurred and wear rates were almost the same in the ceramics regardless of grain size. When the particles became large, intergranular fracture appeared on the worn surface. The wear rate of the ceramics with large grain size increased because of large occurred intergranular fracture.

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The film thickness and the concentration of thickener of grease which is composed by two phases has been measured in rolling point contacts by using FTIR microscope spectrometer under fully flooded condition because of the limit of film thickness by measuring range of FTIR. The results show that rolling speed, bulk concentration of thickener, and base oil viscosity influence film thickness and concentration of thickener.

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During the sliding between CN_x and ceramics, applying nitrogen as environmental gas provided very low friction as the level of 0.01 in friction coefficient. After several friction tests and chemical analysis, we found specific results on nitrogen lubricated sliding between CN_x coatings and ceramic balls. Lubrication effects of nitrogen in CN_x coating sliding against ceramics pin was only occurred for a Si_3N_4 pin. Higher pressure of nitrogen provided lower friction coefficient. In the case of low friction coefficient in nitrogen, there are few wear particles on the contact surfaces and an increase of sp^2 bonding. One of the lubrication effects of nitrogen is the decrease of wear particles on the sliding surfaces. A sp^2 rich structures which have low shear strength bonds was considered to cause low friction.

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Noncircular journal bearings, such as multi-lobe, offset, stepped journal bearings, have some advantages of relatively low manufacturing costs, stability, load carrying capacity and durability as compared with full circular journal bearings, so they are used widely for supporting the high speed rotating machinery. The stabilities of noncircular journal bearings are influenced by many bearing parameters such as clearance, preload factor, length-to-diameter ratio, feed hole location etc. However, it is not clear the effects of bearing orientation angle, which is equivalent to the location of applied load line, on the stabilities of bearings. In this study, the effects of bearing orientation angle on the stabilities of rotating shaft, supported symmetrically by two identical noncircular journal bearings, are examined experimentally. It was found that the stabilities of noncircular journal bearings are improved remarkably by suitable selection of optimal bearing orientation angles.

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On the meshing of the gear pair at the start of meshing and the end of meshing, the meshing of the addendum edge are occurred, when the actual double tooth contact begins and ends outside the geometric double tooth contact. Therefore, it is necessary to obtain equivalent meshing error at the edge of gear tooth tip on analyzing the meshing of the gear. In this study, the method for calculating equivalent meshing error at the edge of gear tooth tip was devised, and some calculation was carried out using the method. Then, the calculation results were compared with the results by the conventional calculation method.

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The present report describes geometrical tooth contact analyses of face gear. A new element for finite element analysis, Tooth Flank Film Element, will be proposed in order to solve a contact problem appearing in stress analysis of meshing gear pair. The Tooth Flank Film Element has not only node position, node displacement, and so on, but also tooth form deviation, normal vector of flank, and so on. This new element has still been on developing stage. In this report, tooth flank contact of face gear was discussed, using the Tooth Flank Film Element. As a result, the effect of misalignment on contact pattern was revealed. Furthermore, face gear with straight profile which has an advantage in cutting and grinding process was discussed, and its usefulness was confirmed.

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The present report describes finish-rolling of gears with shaving machine. In order to obtain the general information on die wheel design and the development of simulation program, plunge load of die wheel was measured. As a result, plunge load increases with the increase of die stroke on plunge process, and remains constant on dwell process. Furthermore, change in plunge load within short period has no definite frequency component. This fact shows that it is impossible to determine when, where, and how large plastic deformation is induced on tooth flank of work gear. Therefore, in order to develop the simulation program of finish-rolling with shaving machine, a new deformation model should be constructed.

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It is imperative to evaluate gear measuring instruments for ensuring the measured values of gears. In other words, it is very important to verify the measurement uncertainty of a gear measuring instrument. JGMA (Japan Gear Manufacturing Society) has organized a special committee for the purpose of proposing an international standard for the evaluation system for gear measuring instruments. On investigation it has been decided that our contribution should focus on a digital gear measuring instrument, because in Japan it had been researched and developed for the first time in the world. This paper describes two types of prototype machines which have been designed and manufactured on the basis of digital measuring method with some new ideas. These instruments are required to be ultrahigh accurate enough to calibrate an involute master.

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This report describes results of experiment on prototype instruments reported in 1st report. Possibility of calibrating a standard artifact (involute master) was verified by the results of experimental investigations.

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Sometimes, the pecluiar vibration behavior of a helical gearpair that appears at non-integer order of the meshirg frequency is generated because of the irregularity of tooth surface form having different cycles of transmission error from tooth mesh cycle. But, it is difficult to detect the spectrum of slight irregularity because there are few cycles of the irregularity on a measured tooth trace. In this research, we discuss about the possibility of Maximun Entropy Method for the spectral analysis of measured tooth surface form irregularity.

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The improvements of static transmission error of gear pair for gear noise reduction have already reached the limit, and it has become increasingly difficult to estimate the gear noise with transmission error, especially in high frequency bands. We have developed a new method of analyzing the vibration of a helical gear system, making it possible to predict the influence of the entire gear train (consisting of the gear blanks, shafts, bearings and the gears themselves) on gear noise. In addition, to consider the influence of gear case conveniently, we developed the simplified estimation of high frequency gear noise.

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Load sharing ratio of crossed helical gear was calculated by the based on stiffness at the point of contact between tooth surfaces. The stiffness was calculated by the displacement, which was analyzed by using a three dimensional finite element method (FEM) and theoretical elastic displacement. The theoretical analysis of displacement of contact was small. The FEM analysis showed that the bending stiffness reduce near the both sides of tooth. This reduction of bending, stiffness causes the load sharing ratio to change.

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The fatigue strength of steel is generally proportional to the hardness up to a certain point. However, the relationship between hardness and fatigue strength is more complicated for the case of high strength material, mainly because the defects in the material sensitively reduce the strength. This paper presents a determination of the defect size in carburized gear teeth and a method of strength evaluation based on this size

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It is reported that a clean steel with low oxygen content is effective to improve the fatigue strength. In this paper, the bending fatigue tests are carried out for carburized gears made of clean steel and ordinary steel with oxygen content of 5ppm and 8ppm, respectively. After removing the nonmartensitic layers by electropohshing, the fatigue strength of the clean steel gear is 28% higher than that of the ordinary steel gear. To discuss the influence of cleanliness, we estimate the fatigue strength considering the distribution of inclusions, and validate the estimated value.

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This paper presents a study on effect of gear-side case-hardening on residual stress and bending fatigue strength of case-hardened spur gears. The bending fatigue tests of case-hardened gears with different case depths and case-hardened parts (tooth surface and gear-side) were carried out, and the test results were examined on the basis of the residual stresses calculated by the three dimensional finite-element method (3D-FEM). Effects of the case depth, the residual stress and the gear-side case-hardening were determined to the considerable extent.

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A conical involute gear is an involute gear that external form is cone. The contact between tooth surfaces is the point contact. Therefore, in conical involute gear design, the evaluation of tooth surface strength is more important than bending strength. The evaluation of the strength of the conical involute gear is just entered on a research. The strength design of the conical involute gear has not been established yet. For the evaluation of tooth surface strength, experiments of the fatigue strength is needed. The authors developed a new testing machine for intersecting-axis conical involute gears. Using this testing machine, experiments on fatigue strength are perfomed in this paper. The circulating torque is kept constant and the number of times of contact is 10^7. The tooth surface life is evaluated by pitting area rate. As a result, the allowable load is obtained.

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The purpose of this study is to investigate the influence of shot peening on the surface durability of case-hardened steel rollers under a sliding-rolling contact condition. The compressive residual stress, the hardness and the surface roughness of the rollers increased by the shot peening. The failure mode of the rollers was spalling. The failure depth agreed almost with the depth where the amplitude A (τ_<yz>/HV) of the ratio of orthogonal shear stress to Vickers hardness became maximum near the case-core boundary. The surface durabilities of the shot-peened rollers were higher than that of the unpeened roller in these experiments. The coefficient of friction between the rollers decreased during the test, since the surface roughness of the rollers decreased by the running-in effect. The increases of the compressive residual stress and the hardness by the stronger shot peening contributed to the longer fatigue lives of the shot-peened rollers. Therefore, it could follows from this that the strong shot peening should be selected in order to improve the surface durability of the steel rollers in these experimental range.

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In order to evaluate the potential capability of planetary roller traction drives in a wide torque range and to promote its effective and widespread application such as assembling passenger cars, dependence of a power transmitting efficiency on load, speed were evaluated comparing with a rated driving condition. Experimental results showed that main factors for the efficiency were deduced to be the friction loss of oil seals and oil viscosity resistance. Moreover, rolling loss such as speed transmitting loss and elastic hysteresis were found out to be small.

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This paper describes the development of a tactile presentation system mounted on a mouse. Since human tactile receptors are distributed on entire fingertip surface, the matrix typed tactile presentation device is essential for the virtual reality for tactile sensation. In this paper, a tactile presentation system was designed using piezoelectric ceramic actuators (PZT ceramic actuator) for pressure stimulator because they can control precise displacement. The key part of the system, a Braille cell presenting Braille dots, was an array of eight PZT ceramic actuators (displacement of a PZT ceramic actuator is 1 mm/200 V). Three braille cells were mounted on a mouse to generate distributed pressure with 4-by-6 stimulating points. In order to examine the basic size of texture presented on the present display, recognition experiments were performed using virtual figures of 1.02 times to 3.06 times as large as size of the mouse cursor. It was found that if size of the virtual figures exceeded 2 times then human subjects could recognize the figures with high percentage of correct answers being more than 80 percent.

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In order to cause a tactile sensor to be thin shape, a new optical tactile sensor is developed by applying CT (Computed Tomography) algorithm. The present tactile sensor is comprised of infrared emitting diode array, the receiving phototransistor array and transparent silicon rubber plate. Infrared rays emitted from the diode array are directed into an end of the plate and their intensity distribution is measured by the phototransistor array mounted on the other end. If CT algorithm is directly applied to the tactile sensor, there are two defects such as shape of sensing area limited to a circle and long calculation time. Thus, a new CT algorithm oriented to tactile sensing is proposed to overcome these defects. In the present algorithm, a square sensing area is divided to an n-by-n array and algebraic equations are derived from relationship input and output light intensities on assumed light projections. To validate the present algorithm, a sires of simulation was performed and it was found that tactile image was completely reconstructed using SVD (Singular Value Decomposition) method for solution of the algebra equations. An experimental apparatus was developed on the basis of the simulated results. The apparatus was able to reconstruct pressure distribution. But, it needs improvement to prevent noise from the obtained pressure distribution.

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A small spherical stepping motor with two degrees of freedom is developed. The motor is composed of two sub stepping motors. Each sub motor is the two-phase permanent-magnet bipolar linear stepping type and the shape is semi-circle. The rotational axes of two sub motors cross at the same point, and this structure enables the developed motor to move in any direction. The experimental results show that the developed motor can hold the output shaft in any direction and has high positioning accuracy. The size of the motor is 75x75x68 [mm], which volume is less than 1/10 of the late developed spherical motor. This motor will be applied to the robotics eye with small CCD camera.

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A multi-DOF ultrasonic motor we developed can generate a multi-DOF rotation of a spherical rotor using three natural vibrations of a bar-shaped stator. However, the driving state of rotor has not been estimated when the three natural vibrations are voluntarily combined. In this study, a numerical simulation method for obtaining driving characteristics of the multi-DOF ultrasonic motor is proposed. First, the contact area and elasticity between the rotor and stator are modeled using nodes and linear springs, respectively. Then, a rotational axis is estimated considering frictional forces between the rotor and stator. Next, a rotational speed and an efficiency of the motor around the estimated rotational axis are calculated. Using the proposed method, the driving state of rotor is clarified. An appropriateness of the proposed simulation method is confirmed by comparing the calculated driving characteristics with the measured ones.

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In this study, a novel peristaltic micro pump using bimorph type PZT elements is proposed. There are two types such as single side type and double side type in the proposed pump. The pumping of liquid is realized by peristaltic motion of metal film with controlling driving voltage of 5 bimorph-type PZT elements that are laid on the metal film. In this paper, the peristaltic micro pump (20mm×20mm×2mm) is fabricated to verify the pumping principle and to examine the characteristics. Intermittent sinusoid driving method for PZT element is proposed to advance the pumping characteristics. The maximum output flow rate of 250mm^3/min is obtained and the maximum load pressure of 3.1kPa is obtained.

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Recently, Y. Otsubo et al reported that a kind of dielectric fluid such as dibutyl decanedioate produced jetflow by applying high voltage electrostatic field. The fluids are called Electro-conjugate Fluid (ECF). We proposed novel micromotors by making use of ECF. In this paper, firstly, a micromotor whose disk plate-type rotors are layered in multiple is proposed. High torque and high power density are produced with the multi-layered motor. Secondly, characteristics of the fabricated multi-layered motor are experimentally examined by comparison between a single-layered-rotor and a double-layered rotor. It is confirmed that the double-layered rotor produces twice as high torque and power as the single-layered rotor. Finally the I. D.φ9mm double-layered micromotor is fabricated. Characteristics of the fabricated motor are examined.

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Under the micromachine project of ISTF (Industrial Science and Technology Frontier ) program of MITI (present METI : Ministry of Economy, Trade and Industry ), a CCD micro camera of φ9.2x23mm was developed for visual inspection inside φ10mm pipe, which was carried on the top of a locomotive robot capable of transmitting the visual data wirelessly on microwave, receiving the energies in forms of microwave and laser beam. The CCD micro camera consists of such newly developed devices as a three dimensionally packaged LSI module for controlling CCD, electrostatic actuators of wobble and linear motion, a catadioptric lens, and visual data reconstruction circuits with wider dynamic range. These technologies and techniques have been being developed totally for 10 years, and on-the-way system had been presented in Exhibition Micromachine in each year. On this paper the final system is to be described introducing its specifications.

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This paper proposes a 3-d. o. f soft actuator composed of rubber balls, and describes the structure and the operational principle of this actuator. This actuator is made with six rubber balls. This rubber balls are fixed on the proper hexagon shaft. The actuator has three degrees of freedom. The shaft turns around x, y and z axes by pressure difference of six balls. A rotation movements around x and y axes are possible by adjusting the pressure of six rubber balls. A rotation movement around z axis can be realized by making the pressure of each ball change one after another.

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Ultrasonic motors have large and non-linear parameter space in geometry design. So it is difficult to optimize the geometry of the vibrator. In the present study, a new geometric design method for designing a linear ultrasonic motor is proposed. It is based on a contact analysis between slider and vibrator, finite element method and genetic algorithms. As a fitness function, only an output power of the vibrator obtained by contact analysis is evaluated. In this process, design parameters concerned with driving characteristics such as natural frequencies, amplitude of vibration, direction of displacement at contact points, arrangement of PZTs and factor of electro-mechanical transmission are taken into account. The proposed method is applied to a design problem in which designer might have difficulty in estimating the ideal condition of design parameters. Results of analysis show that the geometry of the vibrator having high output power is designed.

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Stators for the formerly developed multi-degree-of-freedom ultrasonic motors are not small enough compared with their rotors. In this study, a new type of multi-degree-of-freedom ultrasonic motor, whose stator is relatively small, is developed. First, the stator is designed in detail using a finite element analysis. An outline of the stator is square plate, which has four projections to be in contact with a spherical rotor. The rotor rotates around three perpendicular axes using three natural vibrations of the stator. Second, the designed stator is actually produced, and motion tests of the rotor are conducted. As a result, it is confirmed that the multi-degree-of-freedom motion of the rotor is experimentally produced.

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This paper deals with the dynamic characteristics of the water hydraulic drive system using tap water as a operating liquid, whose research and development is required from the view point of the environmental assessment and resources saving. The system using in the experiment is similar to a typical oil-hydraulic circuit consisting of a vortex pump, a relief valve, an electro-magnetic type on-off valve and a single rod cylinder. The step responses of pressure, piston displacement and load force in the operation condition of a low pressure as a tap water are obtained experimentally and the fundamental characteristics of a water hydraulic drive system are discussed

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PLZT element has a characteristic that mechanical strain is occurred by photostrictive effect when exposed to ultraviolet light. The photostrictive effect is multiple effect of photovoltaic effect and piezoelectric effect. The photovoltaic effect causes high voltage when exposed to ultraviolet light. There are some studies of optical actuator that makes use of photostrictive effect of PLZT elements. As a new type optical actuator using PLZT elements, this paper proposes an electrostatic optical motor driven by photovoltaic effect and electrostatic force in order to get large rotary motion. High voltage generated by photovoltaic effect causes electrostatic force. And the electrostatic optical motor makes rotational motion by this electrostatic force. This new type motor has some superior characteristics such as non-contact energy supply and large rotational motion and the like. A driving mechanism of the electrostatic optical motor is described, and a result of a fundamental experiment is shown and considered theoretically.

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