The hardness of hardened layer was measured for various case-carburized and induction hardened spur gears, and effective case depths of gears were obtained. The intergranular oxidation generated near the tooth surface of the gear by gas carburizing was observed with SEM, and then amounts of intergranular oxidation were obtained. The bending fatigue tests and the impact tests were carried out for these case-carburized and induction hardened gears, and then bending fatigue limits and impact breaking energies were obtained. On the basis of these obtained results, effects of carburized part, case depth, face width, intergranular oxidation and tempering on the bending fatigue and impact strength of the case-carburized gear were clarified. Effects of the heating condition (electric power, frequency, heating time) on hardened depth, microstructure and profiles of hardened layer of induction hardened gears, effects of heating condition, surface hardness, hardened depth, pre-treatment (as-rolling, thermal refining), material (S35C, S45C) and tempering on bending fatigue and impact strength of induction hardened gears were determined. Furthermore, the bending fatigue limits and impact breaking energies of case-carburized gears were compared with those of induction hardened gears.

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Tribology recognizes its significance largely through maintenance activities and, at the same time, maintenance embraces a great number of tribological machine items. Maintenance tribology has therefore played an important role in successful machinery operations. In particular, since most failures of machines having rotating parts are caused by damage to bearings, there exist increasing demands for detecting damaged bearings at an early stage. From this point of view, the author introduces some diagnostic evaluation methods of machinery abnormalities based on maintenance tribology. The topics introduced here include such research activities as oil monitoring and analysis, diagnostic monitoring by vibration, acoustic emission and ultrasonic technique.

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Since the accuracy of industrial applications are becoming a big issue in the industry, the high performance speed reducers are immense necessary part for the industrial applications such as multi-axis machining centers, robots, special purpose machines and etc. These speed reducers are yet in the developing stage. In this report, a speed reducer driven by roller gear cam mechanism is introduced and the characteristics of that are discussed by comparing them with the characteristics of worm gear mechanism and direct drive mechanism. As the characteristics, the positioning accuracy and repeatability, rotational fluctuations and influence of unbalance mass on motion are presented. Furthermore, two case studies are discussed.

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Recently, compact machine tool is demanded in manufacturing of small machines with high accuracy. However, the compact machine, i.e. downsizing of the machines, has problems, such as reduction of accuracy and decrease in the motion range. Accordingly, we focused on the downsizing of a parallel link manipulator which is known as having high rigidity and accuracy. And we developed the small parallel link manipulator. For the designing of manipulator, we proposed following things. The non-cylindrical link was adopted to avoid collision between links. And impact drive mechanism was used as an actuator. We confirmed that the manipulator had enough accuracy to handling small electronic parts by measuring the repeatability.

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The Stewart platform type of the parallel mechanism is used as motion bases for many industrial applications. The disadvantage of the Stewart platform type of the parallel mechanism is its limited workspace, wide installation area, and low frequency band. A rotational type of tripod parallel mechanism which has three legs rotating on ground has been proposed and developed for the new motion base. In order to evaluate the motion of the mechanism, a virtual motion simulator and a scale model has been developed. The analytical results show that the new parallel mechanism has larger workspace than the Stewart platform type of parallel mechanism. The developed scale model has high positioning accuracy for the motion base.

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Practical realization of service robots is in demand to compensate for the shrinking workforce due to aging populations. Robotics technologies can help support our aging populations in both social and work environments. We developed a manual control link mechanism using magnetic particle brakes. This mechanism can be used to support a positioning action passively. It meets the requirements of safety, low acoustic noise, and high efficiency. In this paper, we describe the design and the dynamics analysis of a prototype mechanism, including the self-weight compensation, which is realized by appropriate driving of the magnetic particle brakes, and the resistance torque display for the direct contact operation of the mechanism.

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This paper describes a synthesis method of elastic link mechanisms made of a single spring wire to manufacture compact and low cost mechanism. The mechanism is Euler beams and torsional coil springs which are serially connected. Stiffness equations of them are derived and unified. The stiffness equation of total mechanism is iteratively solved while updating posture angle of Euler beams then output displacement can be analyzed. By specifying desired trajectory of output point and stiffness on the trajectory, dimensions of the mechanism can then be determined by optimization. A forceps mechanism with four coil springs is synthesized and manufactured. The performance of the mechanism is validated with experiments and FEM analysis.

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In the present paper, the authors developed a mechanism for a step-climbing machine having torque assist mechanism. The mechanism reserves kinetic energy in spring, and releases it at appropriate timing to assist electric motors. The approach will be effective to achieve light-weight and low-energy consumption walking-assistance. After designing and fabricating a prototype torque assist mechanism, evaluation of essential driving force and energy consumption were carried out. Finally, step-climbing experiment using the prototype was demonstrated.

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This paper proposes a novel approach to synthesis of constant-diameter cam with a translating follower. The approach has some favorable features such as simple design calculation and easy programming, no requirement to numerically solve nonlinear equations. With the approach, the cam profile can be determined precisely and conveniently as well as the radius of curvature and the pressure angle. Moreover, some constraints which must be satisfied in the design are also clarified. The effectiveness and efficiency of the approach are sufficiently verified through a design example of constant-diameter cam.

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In the present paper, we describe the measurement of brain activation response during lathe operation in a VR lathe environment and an actual lathe environment by NIRS. The results show that in the VR lathe environment, oxyHb increased greatly in the temporal region of the motor cortex. Similarly, in the actual lathe environment, the increase in oxyHb was larger in the temporal region of the motor cortex than in other regions. The results also show that the brain activation response in the VR lathe environment was very similar to that which occurs during lathe operation in the actual lathe environment.

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We have proposed an XML schema for manufacturing cases and have developed the associated database. The manufacturing case data is composed of potions of material specifications, processing conditions, machine specifications and evaluation results. They are basically represented as text and multimedia data such as image, video image and sound are used partly. XML data in terms of text can be applied to share and to compare, but it is difficult to handle directly the multimedia data in XML for the purpose. We proposed an image search method and examined the possibility through the experiments on the appearance images of welding beads.

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Many industrial products or building equipments are standardized but not always designed taking user's sense to ease-of-use into account. The final objective of this research is to establish design system for user friendly engineering products. In the paper, possibility of utilization of electro myoelectric potential in engineering design is investigated. Electromyogram (EMG) occurred in stand-up motion from sitting position on chair under different handrail conditions is measured. Two performance index, median frequency and total sum of spectrum of EMG are examined. They show tendency for load level or degree of fatigue. Some results show effectiveness of usage of EMG information in engineering design or evaluation.

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We developed a new whole body motion support type mobile suit. This suit can be used separately for supporting the upper and/or lower limbs, for assisting ADL (Activities of Daily Living). We also developed a mobile lifter system which can bear both the equipped person and the suit. This suit and the lifter can be used by motor palsy patients suffering from stroke, spinal-cord-injury, and central nerve disorders. Using this device, these patients can recover normal gait with no risk of falling. In this paper, the brain activity during walking using the suit and normal gait without the suit are compared. According to multiple trials with the suit, the activity of the premotor area decreased. In addition, by walking while swinging bilateral arms (even though these arms were assisted by the suit), the activity in the supplementary motor area increased (this area of the brain is related with memory of motion). Finally, the brain activity during walking on the treadmill and in the sightly long corridor are compared. From the result of this experiment, it is effective for gait training to walk with locomotion, because of the improvement the motivation for training. We can conclude that this suit is suitable to assist patients in walking. Therefore it is important for patients to swing their arms during gait training in rehabilitation.

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Human safety is one of the most important issues in human-friendly robotics. We have presented a safety device to improve the safety of human-friendly robots for humans. The safety device consists of only mechanical components without actuators, controllers and batteries. The safety device locks the robot's joint after detecting the overdrive on the basis of the joints angular velocity. Furthermore, we have developed a human-friendly robot equipped with the safety devices. The robot has a 5-DOF arm. In this paper, we experimentally examine the usefulness of the safety devices. First, we explain the robot with the safety devices. Second, we experiment by using the 5-DOF arm of the robot Finally, from the experimental results, we examine the usefulness of the safety devices.

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In this paper, we analyzed the mechanical loss factor of the geared motor, which is composed of a 90W induction motor and a parallel gear reducer with total reduction ratio 9. Gear mesh was lubricated with the grease of NLGI consistency class 2. The loss factor was regarded as the sum of load independent part, at no loading, and dependent part. The loss of oil seal and grease was examined by the measurement of the geared motor. About the remaining loss, the friction loss of bearing was presumed by the coefficient of friction of bearing, which was measured by the unit testing of bearing, and investigating a temperature change of the grease, the friction loss of tooth flank was calculated by subtracting these losses. As a result, the high factor of loss was grease at no loading, and the friction of tooth flank at loading.

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An experimental investigation aiming to reduce windage loss in a gearbox is presented. The gear pair is operated like a gear pump with a tip cylinder fixed at the mesh approaching region. Experiments show that the gearbox can reach a low air pressure about -0.085MPa at 4000 rpm. Smaller clearances including the tooth tip clearance and the side clearance lead to lower air pressure.

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Power steering systems for automobile are mechanics to assist in steering. From soaring oil prices in recent years and environmental considerations, transmission efficiency of Rack & Pinion has been required to be improved. Rack & Pinion engages on non-intersecting and non-parallel axes. For this reason, sliding which is caused by the engage of gears and the restriction of the rack motion is existed. This sliding reduction is expected to improve transmission efficiency of rack & pinion. By the former research, the calculation method of specific sliding for rack & pinion is suggested. Six types of dimensions which are expected different performance are suggested, and using produced Rack & Pinion, the influence specific sliding exerts on the performance of Rack & Pinion was verified. As a result, it has been understood that not specific sliding but slide speed is related to the transmission efficiency of Rack & Pinion.

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In this study, we investigated two elliptical gears which were a single elliptical gear and a double elliptical gear to analyze the vibration of elliptical gears. The tooth root stress, the torque, the rotation speed and the circumferential vibration acceleration of the two elliptical gears and, for comparison, two circular gears with the same gear specifications as the two elliptical gears respectively were measured by the running test. The dynamic load factor and input torque variation of the four test gears were obtained from measured tooth root stress and input torque respectively. Furthermore, the instantaneous output powers of the motor driving elliptical gears were calculated to clarify the reason of the overload of the motor when driving elliptical gears.

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We had already reported estimation method of gear mesh excitation waveform with vibration measurement results and simulation to utilize for quality check of manufactured gear system. But it remains an unknown quantity and the exact mesh excitation waveform can't be estimated. In this paper, we improve excitation waveform estimation accuracy with vibration measurement results on the gearbox. But still amplitude error remains because of simulation accuracy.

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The influence of the complicated behavior of the components of a planetary gearset (i.e., sun gear, carrier, and ring gear) on transmission error is still unexplained. Accordingly, to elucidate that influence, the transmission error and misalignment of each component of one planetary gear set were experimentally measured at a time under a condition in which the fixed carrier position was varied. The measurement result shows that, under that condition, the state of misalignment fluctuates and the transmission error changes according to that fluctuation. Although the fluctuation of misalignment (in the form of eccentricity or inclination) is generally in a circular orbit, in this experiment, it was found to be in a near-elliptical orbit. By taking such misalignment fluctuation into account when calculating transmission error of the planetary gear set, it was found that the calculated behavior of transmission error replicates the above-described experimental measurements approximately.

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The aim of this study is to realize an ultrasonic motor which can be driven in a cryogenic temperature environment under a high intense magnetic field. We have fabricated and evaluated the ultrasonic motor made of titanium. The motor's diameter and length are 22 mm and 30.5 mm, respectively. We have succeeded in driving the ultrasonic motor at 4.5 K. The rotation speed was 215 rpm. We have also succeeded in driving the motor under the intense magnetic field of 7 T.

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In high temperature environment, it is difficult to use functional materials. Because functional materials a decrease their functional performance or lose their function in those environments. On the other hands, actuations in high temperature are strongly desired with increasing demand. In our study, we have proposed a new principle of actuator for actuation in high temperature. It uses volume expanding caused with the phase transition of working fluid. This actuator uses no functional materials to drive and has a potential for the high temperature actuators. In this paper, we report on experimental results of the actuator driven in 180℃ temperature environment. From this experiment, we confirm capability of this actuator.

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This paper proposes a representation method of the rotor posture for the spherical motor and the rotor posture sensor with two mouse speed sensing devices, which measure 2DOF circumferential speed. At first, several ideas of the posture sensors for the spherical motor are reviewed. Among the reviewed posture sensors, select a posture sensor with two mouse speed sensing devices. Introduce the rotor posture representation matrix. Then show how to get the rotor posture from the data from two mouse speed sensors. Select the mouse sensors which satisfy the specifications of the posture sensor for the developed spherical motor. Set two mouse sensors on the manufactured rotor holder and test the performances of rotor posture measurement. The problems of the developed posture sensor and the future works are also discussed.

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For a wearable device, it is required that it is small, light weight and soft from the viewpoint of the human friendliness. The rheumatic rubber artificial muscle is useful as the actuator to satisfy these demands. In this study, the power assist wear driven with a novel linearly harden type pneumatic rubber artificial muscle is developed to assist the shoulder motions.

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Recently, the need of colonoscopy is increasing because of the rise of colonic diseases including cancer of the colon. However, current colonoscopy depends on doctor's skill strongly. Therefore, a large intestine endoscope that can be inserted without any special techniques of doctors with high safety is required. In the previous research, the prototype changeable stiffness endoscope that changes own stiffness partially by air pressure was developed. However, we have never made a close investigation of the stiffness change pattern that can reduce load to the intestinal wall. In this report, an evaluation phantom which has sensors to measure load to the intestinal wall has been developed, in addition, the changeable stiffness endoscope has been improved. Using them, we have investigated the relation between stiffness change pattern and load to intestinal wall experimentally. From the experiments optimum stiffness change pattern to reduce the load in colonoscopy has been derived.

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This research deals with a method of friction control for a linear guideway, which is based on ultrasonic oscillations. Experiments were conducted by driving a single-axis guideway in sinusoidal motion as a simulation to a circular motion. The sinusoidal motion was controlled with the installation of a PI controller. The ultrasonic oscillations were applied at the guideway's carriage with 6 different oscillation patterns. Subsequently, their influence for the frictional characteristics was investigated. The investigation is focused at the inverting moving direction, when the carriage starts from zero velocity. It is observed that when the carriage was oscillated with a gradually increasing intensity, the static frictional force and the maximum displacement error had been reduced approximately by 39% and 29%, respectively.

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This paper describes a hydroinertia gas bearing with inclined supply holes, which may achieve higher speed of operation than conventional model. Our purpose is increasing to the maximum rotational speed by inclining supply holes. We developed the calculating method and made a device of measuring pressure distribution to confirm that verification. The results of the experiment show the regionaly negative pressure same as calculated results.

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Recently, larger stiffness and higher accuracy have been strongly required to an aerostatic spindle used for precision machine tools. The aerostatic spindle is usually composed by several aerostatic journal bearings and a couple of thrust bearings, but few reports have been published on the basic performance of an aerostatic spindle system. In this paper, the basic characteristics of the aerostatic spindle system are numerically investigated. In order to obtain the basic characteristics of the aerostatic spindle system, the non-linear orbit method was used. As a result, it was found that the basic characteristics of the aerostatic spindle system were largely affected by the arrangement of aerostatic journal bearings rather than that of aerostatic thrust bearings.

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This paper describes experimental study on vibration characteristics of oil film bearing spindle in oscillatory motion. Oil film bearings are widely used for HDD spindle motor. Recently, oil film bearing spindle is required to improve vibration characteristics because HDDs are widely used for mobile devices such as laptops, video cameras and car navigation systems. Many researchers have been studied vibration characteristics of oil film bearing spindle for HDD. However, most of them have been investigating about an experiment of vibration or impact. And, the vibration direction which is horizontal or perpendicular direction is single. However, HDDs are vibrated under oscillatory motion combined with horizontal and perpendicular direction vibrations. In this paper, we propose a new oscillation experiment apparatus and experimental methodology. And, we conducted the oscillating experiment of oil film bearing spindle for 2.5" HDD.

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A prediction method of the agitation torque and the quantity of oil in tapered roller bearings is developed using CFD analysis. The method was verified by experiments. Using this technique, we succeeded in controlling the oil flow in bearings and developed a low torque tapered roller bearing. The torque in this bearing is reduced due to low agitation resistance, while the quantity of oil around the sliding contact surfaces (i.e. the flange of the inner ring) is sufficient.

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In general, rolling bearings are applied with stationary fit to rotating axis. On the contrary, press fitting is required in fabrication of the bearing and the axis. Thus, request of running fit between bearing and rotating axis is increasing. However, if the running fit to rotating axis is applied, wear may occur due to the slip between the rotating axis and the inner diameter surface of inner ring in rolling bearing. This phenomenon is called as "creep" and affected by clearance, rotating speed and load. In this research, occurring situation was evaluated experimentally with changing clearance, rotating speed and load.

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Clarifying friction and the wear mechanism is very important because mechanical parts with friction and wear phenomena exist in a lot of mechanical systems. It involves to energy loss and material loss. However, because friction and the wear mechanism include complex phenomena, wear theory has not been established. In this study, friction and wear mechanism for various practical sliding materials was examined by in-situ observation method with a compact friction surface microscope. From the in-situ observation of friction and wear phenomena at the sliding interface and the measurement of friction force, it was found that deformation and fracture processes of the sliding materials (high polymer film material, brake material, and tool material) can be evaluated.

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It is one of the main subjects in tribology to systematize the wear theory. It is necessary to know the wear mode caused under the given condition by clarifying the various wear mechanisms. A lot of machines are operated in the lubricated condition. However, the wear mode diagram under the lubricated condition is not enough. In the present study, we aim to construct of the lubricated wear mode diagram for WJ2 which is the standard plane bearing material in a power plant. The sliding wear tests of WJ2 were carried out using a block-on-ring apparatus with various loads and sliding velocities. In order to classify wear modes, we investigated the relations among friction coefficient, worn surface, wear debris, specific wear amount of WJ2 and the minimum oil film thickness which were calculated from the EHL theory. As a result, the wear mode of WJ2 was classified into two types of large-scale adhesive wear and small-scale adhesive wear using the experimental result, and theoretical analyses.

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Tribological behavior of a copper-amorphous carbon (Cu-DLC) nanocomposite coating has been studied using linear reciprocating tribometers as a function of both environment (ambient air and ultra-high vacuum) and initial contact pressure. The Cu-DLC coating was deposited on a Si (100) wafer using a hybrid deposition process combining plasma enhanced chemical vapor deposition (PECVD) and DC magnetron sputtering of Cu target. In all cases, a selective transfer of mostly Cu and some C has been observed on the counterface. The evolution of such tribofilm with sliding cycles was found to depend on contact conditions. The chemical compositions and mechanical properties of tribofilm have thus been investigated with various techniques. As a result, it is found that the tribofilm showed similar hardness in various sliding condition. The stable hardness of tribofilm can maintain almost same contact conditions during sliding, which can stabilise the friction coefficient of Cu-DLC for various sliding conditions.

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Diamond-like Carbon (DLC) is a hard film composed primarily of carbon and possessed amorphous structure. It is known to have superior tribological properties such as low friction, high wear resistance and anti-seizure. In addition, DLC film is now widely used in a various industrial application due to improvements in its adhesive property. This paper shows the DLC film with sputtering method has the durability under high pressure contact.

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In this study, sintered and powder-forged rollers and gears with different densities and nickel contents were fatigue-tested using a roller testing machine and a gear testing machine in order to elucidate their fatigue strength. These experimental results were compared with the results of conventional steel ones. The hardness near the surface of the test specimens with higher nickel content was smaller than that of the other ones. The pores in the sintered rollers became smaller and were disappeared by the hot forging. The fatigue strength of the sintered rollers and gears was the lowest in this experimental range. The fatigue strength of the powder-forged rollers and gears was slightly lower than that of the steel ones. The fatigue strength of the test specimens increased as their density increased, and was hardly influenced by the nickel content in this experimental range. It was clear that the fatigue strength of the sintered and the powder-forged rollers and gears was proportional to the hardness for each pre-alloyed metal powder.

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This paper presents a study on effects of rim and web thickness on root stresses and bending fatigue strength of thin-rimmed helical gears with symmetric web arrangement of various rim and web thickness. Measurement of root stresses and bending fatigue test were carried out for thin-rimmed helical gears with symmetric web arrangement of various rim and web thickness. The changes of the root stresses from the beginning of engagement to the end of engagement, the meshing position (worst loading position), where the maximum root stress occurred, the effects of rim and web thickness on bending fatigue strength and bending fatigue cracks were clarified. Furthermore, the results obtained were compared with the solid helical gear results.

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