The environmental changes in the global level are now affecting the human social activities in various fields. And the automotive industry is no exception. It is definitely affected by such changes. We must respond to such radical changes. And to make it possible, I would like to give an outline of the trend in the automobile transmission field and its core technology of gear. Especially, I would like to give an account to the relevance of Continuous Variable Transmission (CVT) and the gear technology that manages both power faculty and fuel efficiency of automobiles.

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JIS gear accuracy class is not necessarily linked with the performance operation of gears, and hence it is important to find the relations between the tooth form accuracy and performance of gears. In the present study, we carried out the experiments to obtain the influence of tooth profile error on the friction loss and noise of spur gears. Nine kinds of tooth profile error with grinding with the similar error amount were used and also we prepared a barrel polished gear which had tip relief by grind. Test results showed that tooth profile error shapes affect the friction loss and noise very much even if the amount of error is the same. Further, it was found that the friction loss and noise have a certain correlation with each other and a barrel polishing showed the lowest friction loss and noise.

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We measured the friction losses of involute-cycloid composite tooth profile helical gear, modified cycloid tooth profile helical gear and involute helical gear using a power circulating-type gear testing machine, by the oil immersion formula, whose method is based on the oil temperature rise due to the power loss in the gear drives. It was found that the involute-cycloid composite tooth profile helical gear and the modified cycloid tooth profile helical gear have smaller friction loss than the involute helical gear. Furthermore, we calculated the gear friction losses of these helical gears. The calculated value agreed well with the experimental data.

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We measured the efficiency and the noise of the plastic worm gears with the module 0.5mm and the lead angle 5-8 degrees. As the result of the experiments, it was found that the application of the grease increased the efficiency more than 10 percents and the worm gear with the lead angle 8 degree provided 10 percents higher efficiency than that with the lead angle 5 degree.

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New polyamide resin Nylon 9T (PA9T) has excellent properties such as heat resistance, low water absorption, chemical resistance and wear resistance, which are required for gear applications. Injection molded plastic worm wheels are used in applications ranging from motion translation in copiers and printers to transmitting torque in automobile parts. In this study, the durability of injection molded plastic worm wheels was tested without lubrication under various torque and temperature conditions. The test was carried out on several engineering plastics including polyacetal (POM), Nylon 46 (PA46), PA9T, and PA9T wear resistant grades that are internal lubricated with polyolefin or PTFE or silicones.

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The unified theory of gears is explained through the base equations and its 3 examples of application At first, the problems of the present theories are presented and the coordinate systems and the base equations of the unified theory to solve them are explained. Then as the first application, a path of contact with no variation of bearing loads is obtained, which is a straight line coinciding with the contact normal with no transmission error and it is clarified that the most practical pair of tooth surfaces is the involute helicoid and its conjugate one to realize the path of contact. As the second one, a design example and its trial product of an hypoid gear pair with involute helicoids to realize the path of contact are presented. As the last one, the calculation method of the dynamic incremental loads and its example to be applied to helical gears are explained with the experimental result for verification.

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This paper presents a new method of profile design for strain wave gearing. The principles of this method are based on two approaches. The one is the tooth contact condition along the tooth trace and the other is the continuous meshing of teeth in the main perpendicular plane. The former condition is satisfied by coincidences between the direction of tooth profile and the tangent to projection of generator, which describe the neutral cylinder of flexible gear to the perpendicular plane. The latter condition is obtained by satisfying the Euler-Savary's theorem. The author obtained the analytical formulas to represent these conditions. The simulation of teeth meshing shows the utility of this method.

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This paper deals with the optimum design of the involute-cycloid composite tooth profile helical gear, which was developed as a non-involute tooth profile gear based on cycloid tooth profile. The involute-cycloid composite tooth profile helical gear has some design parameters such as pressure angle and rolling circle, which define the involute-cycloid composite tooth profile curve. In this study, we developed a method to calculate the tooth root stress and the tooth contact stress of the involute-cycloid composite tooth profile helical gear. Then we compared the results with the experimentally measured data, and the validity of the present calculation method was certified by the good agreement of the calculated values with the measured data. Furthermore, we discussed the effects of the design parameters on the tooth bending and tooth contact strengths of the involute-cycloid composite tooth profile helical gear.

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New Type WN Rack & Pinion is proposed whose radius of rack is larger than that of conventional design. TCA of New Type WN rack and pinion is compared by usual type WN rack & pinion and results of TCA is tested.

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As for the resarch of the arc tooth gear, formerly, a lot of research was done. However, it is several kinds that are only practicalized. For example, it is the Novkov gear of former USSR, Circarc gear in the United Kingdom and then Logix gear in Japan and so on. The arc tooth gear of the authors is a point symmetrical arctooth gear to the pace point, having the tooth end arc and a tooth origin arc to one tooth. In this repot, it report on the performance of this symmetrical arc tooth with gear.

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The coming to practical use of the symmetrical arc tooth gear starts in 1964. Atfirst, it used for gradually the heavy load from the light load. At present, it is used for the use field of the Involute gear which this geae quenched in the carbonization, too. The machine of this gear increase and the deceleration has about 5000 results. It reports on the process of this coming to practical use, and the followup surver, it introduces about the record article of the actual device and so on, too. In the actual device, it had encountered to the product accident, evaluating the strength of the symmetrical arc tooth gear, being surplus, too. It reports these experieces as much as possible using the figure and the photograph.

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P-S-N curves is required because of the estimation of the probability expression of the tooth surface pitting of the gear. Failure data assumes that it is the Weibull distribution, and failure probability is asked by using regression analysis on weibull chart. However, generally failure data separates from an approximation straight line, existence of a minimum life is expected. So failure data assumes that it is the three parameter Weibull distribution, and the way forward to asking minimum life was examined. As the result, to apply regression analysis to data which separated from an approximation straight line was suitable.

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This report shows that tooth surface shape along path of contact is closely related to gear whine noise. Designing tooth surface shape along path of contact can reach an appropriate tooth surface shape to reduce gear whine noise. Especially, crowning along path of contact is one of the most important factors to design tooth surface shape. In addition, this report shows an evaluation method of tooth surface shape on plane of action and along path of contact, and some important factors of tooth surface shape that are closely related to gear whine noise.

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Tooth frank form deviation of micrometers influences vibration and noise characteristics of gears. Its precise measurement is, therefore, crucial in quality control, but the calibration system of gear checkers with the traceability and uncertainty is not established yet in the sense of ISO standard. In this research, Virtual Gear Checker (VGC) has been developed, that is a computer program considering all mechanics and all possible error factors of real gear checkers, such as form error of component, movement error, sensing error and control system error. VGC can calculate measurement results of tooth frank form deviation from the specification and the value of error factors of real gear checkers. We can simulate the uncertainty of measured results for tooth frank form deviation much more easily and more quickly with VGC than with real gear checker. VGC makes it possible to establish the method for the inspection and calibration of gear checkers with the traceability and uncertainty.

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To guarantee tooth form accuracy of gears, three strong demands are now subjected: (a) to use production gear size artifact for checker calibration, (b) to clarify the uncertainty of measured results and (c) to give traceability to the results. For involute checker calibration, involute artifact has been widely used , because of its friendliness at usage. But, especially for item (b) and (c) above, involute artifact has big difficulty. Japan has proposed Double Ball Artifact to the ISO TC60 WG2 for involute checker calibration to solve these problems and to achieve far more accurate calibration work. The development of JIS on this matter is now on the way. This report introduces the outline of the work.

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Single flank gear meshing test is getting more popular in recent gear industry, for the reason of availability of inexpensive good Master Gear. However, you'll have to check its tooth profile error for investigating the cause of defects found during gear meshing test. Based on this fact, authors will offer the new method utilizing single flank gear meshing tester and the special master gear which is missing every other tooth. In this study, using the special master gear mentioned above, tooth profile error of the driven tested gear was measured. As a result, the measured curves obtained by this method and by ordinal tooth profile tester were well coincided each other. The result shows that it is possible to measure the tooth profile error of test gear, using the single flank gear meshing tester. More over the method is applicable for checking tooth profile error of very fine module gear providing that you have appropriate master gear.

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The purpose of this research is to derive the meaningful parameters and the new procedure of measurement of tooth flank topography to evaluate the individual gear accuracy objectively. For this purpose, the tooth flank topography is characterized as the curved surface and the parameters for tooth flank topography are derived from the 3-dimensional measured deviations of tooth flanks. For the first step, a new definition of the pitch deviation is proposed. The pitch deviation is calculated with multiple deviations of a tooth flank. According to this new definition, a pitch error should be expressed by the angle, not by the length, and it can be calculated from the measured conventional deviations. Actual gear flanks of a bevel gear are measured with the new measuring procedure and the new pitch deviation is calculated.

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AISIN AI has developed a Manual transmission (M/T) for compact FWD vehicles, which has being under production since 2000. This M/T has used for Europe compact FWD vehicles, TOYOTA YARIS and others. The performances like high shift comfort and low noise vibration etc have been achieved with low cost. This M/T is our main product, which is still evolving to the Automated Manual Transmission (AMT) and the overseas manufactured product in near future. We introduce the instance about the balance between high performance, reliability and cost including development story

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In order to develop a high torque gearbox, we built up a power circulating gearbox test-facilities to proving its performance. It is the common configuration that the back-to-back type gearboxes are driven by an electric motor and a dynamometer absorbs its power. Though that system is not only expensive but also energy consuming, we make it a power circulating system. The mechanical efficiency of whole system is proved 85% except lubricating power. That means the system needs only 15% of transmitting power. We also set up a noise proof room to the gearbox. It is proved good performance to isolating from other gearboxes and lubrication systems.

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This paper introduces Ultra Flat Strain Wave Gearing (CSD and SHD-type) developed in last year (2003). Strain wave gearing, also known as harmonic drive gearing, has been used in many applications, where lightweight and compact mechanical components are essential. This new product developed is more lightweight and compact than products in the past, CSF and SHF-type. There were many issues to be resolved in order to realize the ultra-flat design. New ideas and technologies were applied to develop CSD and SHD-type. Its exceedingly flat shape has never seen before hi a precision speed reducer.

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Bearing stiffness influences the performance of power transmissions. However, the stiffness evaluation of bearings subject to multiple loads has not been established. The purpose of the present study is to construct a evaluation method of the bearing stiffness. In the present report, a stiffness evaluation of deep groove ball bearings subject to radial and axial loads is proposed. The evaluation is based on the Hertzian contact theory. Being compared with experimental results, the evaluation can be confirmed in a valid method.

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Short & small size In-dash 6-discs DVD/CD Changer Mechanism has been developed as a suitable to put an In-dash to apply an entertainment system for rear seat to appreciate DVD contents. For playing DVD, we must allow to use a bigger pick-up and playing PCBs than that for CD's. In order to realize the mechanism of 1DIN size, while making the drive unit a thin shape and small to the limit, the parts layout were also elaborated. Moreover, the further thin shape mechanism has also been attained by adopting a unique drive unit traverse mechanism.

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A Micro-Gear with a module of 0.04mm made out of Ni-based Bulk Metallic Glass (BMG) was successfully completed basing on high-precision die-casting technologies. The Micro-Gear made out of Ni-base BMG has been assembled into 2.4mm diameter Planetary Gear-Head, attached onto a 2.0mm brushless DC Motor and operational life test at 0.1 mNm load has been performed. Result of the test, the Micro-Gear made out of Ni-based BMG showed 1/4 level in wearing compared with a conventional steel gear. From the result, a Micro-Gear made out of Ni-base BMG has been strongly acknowledged as making geared motor life much longer.

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A new differential gear mechanism is presented in this paper. By using this mechanism, it is possible to control the rotation of the target axis without any effect on axes passing through, and then because of easy to produce, 2 wheel drive bicycle is manufactured, i.e., the driving force from the rear wheel transmits to the front wheel in high transmission efficiency without any interference in steering. The basic working principle is based on the patent (JP03/03449).

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This paper describes a new reduction gear system where gear teeth have a pair of truncated cone; One is concave tooth and the other is convex. These convex teeth are generated on computer with simulation of the meshing condition of teeth. This procedure for gear cutting is generated by standard concave tooth. The experimental results of the efficiency and noise are worse than the inclined planetary system. Moreover, teeth of this system are destroyed. Therefore, reformed teeth were designed.

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The "Smoother-E/F" can control clutch operation automatically by replacing a dry clutch of 5 or 6 speeds manual transmission by fluid coupling and wet multi-clutches. The new system "Smoother-E Autoshift" has been achieved automatic gear shift-up and shift-down operation by adding an electromagnetic gearshift unit. Magnetic solenoids can reduce the gearshift time and elongate the durability period compared with electric motor, hydraulic piston, and pneumatic piston. "Smoother-E Autoshift" can improve the economical efficiency and the easy drive operation.

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This paper reports on investigation study to expand markets for a newly developed aerostatic lead screw. The accuracy of this aerostatic lead screw is "precision class (0.1μm〜1μm)". Its distinguished characteristics are no loss of accuracy with friction wear, easy to use and reasonable price. Expected fields of applications include focus drive of bio-microscope, 3-D measuring machine, IC exposure apparatus, biomedical robot, DVD pick up, inspection machine and others.

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The purpose of this study is to make clear analytically the fluctuation phenomenon of an aerostatic lead screw supposing to having an influence on its positioning accuracy. As the first step of its study, we succeeded measuring the fluctuation per 2π radian each screws experimentally, and considering theoretically. As the results, (1) The positioning accuracy was improved by using an air bearing effect, we call "Balancing effect". (2) It is assumed that the theoretical value of the female screw fluctuation is able to calculate by the balance of each axial loads.

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The present paper describes the development of fatigue test rig for plastic gears under high temperature. The test rig was dedigned for tests of fiber reinforced PA46 gears, so that it has much higher load capacity. Furthermore, even under relatively low temperature, PA46 gears could have advantages in the operation under which PV value is much higher. Therefore, the test rig being developed enables higher rotation speed. In addition, a new mechanism is adopted for mounting a test gear. It was contrived in consideration of thermal expansion of test gear.

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In this study, we investigated the properties of noise and vibration of plastic gear for power transmission. On the basis of experimental results, we discussed about the noise generation mechanism. It becomes clear as follows. (1) A plastic gear engaged with a steel gear is excited vibration heavily and the noise is radiated loudly from the plastic gear side rather than the mating steel gear side. (2) The vibration is caused by the the large tooth deflection of plastic gear in mesh cycle. (3) It is considered that one of the practical ways to reduce the noise of plastic gear is to reduce transmission error by appropriate profile modification.

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[in Japanese]

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Recently plastic micro gear is paid attention in mobile information instrument, small medical instruments, micro robot and so on. But it is not kwon abut power transmission characteristic of micro plastic gear. So we made plastic gear mold of module 0.15 and experimental apparatus for deformation and life of gear. And we carried on experiment two plastic materials, polyacetal and nylon with glass as comparison. In this result, deformation strength of nylon with glass is higher than that of polyacetal in micro gear of module 0.15. In life test, we know that nylon with glass gear is long life compared with polyacetal gear in the same loading torque conditions.

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Tooth strength of case hardened, nitrided or through hardened gears depends on the property and quality of gear material, manufacturing and the heat treatments. When Japanese designs gears, tooth bending fatigue strength data for the JIS gear steels is needed. Tooth bending endurance tests for JIS low-alloyed steels for gears and JIS wrought nitriding steels were conducted with pulsater over a six year period. It was found that the tooth bending fatigue strength of the case hardened SNC815, SCM420H and SCM822H gears is 500〜824N/mm^2, 490〜588N/mm^2 and 392〜530N/mm^2 respectively. Results for nitrided gears made from 31CrMol2 and others and for through hardened gears made from SNCM439 and SNCM630 were obtained. The maximum strength value in these tests was 157% of the maximum value of ISO's allowable stress data in case hardened gears, 142% in nitrided gears and 165% in through hardened gears respectively.

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It is important that the accurate measurement of strain and stress in the tooth for the reliable evaluation of strength or life of gear. In this paper, the method which is based on the image processing is applied in order to measure the strain near the fillet. The displacement of the point in the tooth flank is tracked, and then, the strain is calculated. The interrogation window size of cross-correlation method affect the accuracy and the resolution. In case of complicated profile such as fillet, the small size of the window is suitable.

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This paper presents a study on effects of case-carburized parts on residual stress and bending fatigue strength of case-carburized thin-rimmed spur gears with symmetric web arrangement. A heat conduction analysis and an elastic-plastic stress analysis during the case-carburizing process were carried out for various case-carburizing conditions by the three dimensional finite-element method (3D-FEM), considering changes of the thermal expansion coefficient and the yield stress with the temperature, and then residual stresses were obtained. Bending fatigue tests were carried out for different case-carburized thin-rimmed spur gears with symmetric web arrangement. Effects of case-carburized parts on the residual stress and the bending fatigue strength were examined. These results were also compared with those of solid gears.

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Fatigue failure patterns of a three-dimensional, extremely thin-walled spur gear used in a harmonic drive device are introduced in this paper. In order to solve strength design problem of this extremely thin-walled spur gear, mechanics models and responsive finite element methods are developed to do contact analyses, tooth load distribution and flexible bearing ball load calculations of the devices through 18 years of efforts of the author. Tooth load distribution and flexible bearing ball load are calculated by the presented contact analysis methods and stress analyses of the extremely thin-walled spur gear are conducted by using three-dimensional finite element method. The calculated stresses include bending stresses at the tooth root, contact stresses on tooth surfaces and structural stresses of the extremely thin-walled gear body itself. Contact stresses of the bearing balls are calculated by substituting bearing ball loads into Hertzian formula. Many experimental results and practical design experiences of the author show that the calculated results are reasonable. Finally, based on the fatigue failure patterns of the harmonic drive devices, strength design methods of every failure pattern are presented hi this paper.

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This paper describes a study on the surface durability of rolled sintered metal rollers. Sintered metal rollers were rolled under various amount of rolling using plunge feed type and axial intersection type rolling machines. The effect of rolling on the surface property was examined by measuring hardness and void rates near roller surfaces. Contact fatigue tests for these rolled sintered metal rollers were carried out. The effects of the rolling method and the amount of rolling on the surface durability of sintered metal rollers were determined, and these results were compared with the results for rollers as sintered.

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In order to compare the fatigue strength of powder forged gears with that of steel gears, the case-hardened powder forged rollers and gears with different Ni content and the case-hardened steel rollers and gears were fatigue-tested under a sliding-rolling contact condition. The surface hardness of the powder forged rollers and gears with the lower Ni content was almost equal to that of the steel rollers and gears. On the other hand, the hardness of the powder forged rollers and gears with the higher Ni content was smaller than that of the other rollers and gears. The compressive residual stress and the surface roughness of the powder forged rollers and gears were about equal to those of the steel rollers and gears. The failure mode of the test rollers was mainly spalling, and that of the test gears was mainly pitting. Using the relationship between the maximum amplitude of the ratio of stress to Vickers hardness and the fatigue life of the rollers and gears, it was denoted in this experimental range that the fatigue life of the powder forged rollers and gears with the higher Ni content was longer than that of the steel rollers and gears.

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Austempered Ductile Iron (ADI), which has much the same strength and toughness as usual steels, has been developed. ADI has many advantages in mechanical properties and manufacturing, such as weight reduction, good properties of vibration and noise, low cost in machining and heat treatment of blanks due to near-net-shape casting. In this paper, the load-carrying capacity, which indicates both surface durability and bending strength, of gear pairs with a combination of Austempered Ductile Iron (ADI) gear and hardened steel one is investigated using a power-circulating type gear testing machine. Especially, the performance of ADI gears treated with cermet-finish bobbing and several types of shot peening are examined. The impact strength of ADI gear is also examined with an impact testing machine for gears. Furthermore, the application example of ADI cast as one body with the gear and the nearby member is proposed.

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Austempered Ductile Iron (ADI), which has much the same strength and toughness as usual steels, has been developed. ADI has many advantages in mechanical properties and manufacturing, such as weight reduction, good properties of vibration and noise, low cost in machining and heat treatment of blanks due to near-net-shape casting. Using these advantages, it has been reported that ADI can be sufficiently applied as a medium hardness gear material. In addition, it is important to reduce the amount of the lubricant when many problems, i.e. global environment, resource conservation and cost reduction, etc., are considered. So it is necessary to examine the performance of ADI under oil-free condition or Minimal Quantity Lubrication (MQL) condition. In this paper, MQL condition is investigated using a disk machine which simulates the rolling and sliding action of gears. Then the surface failure strength of ADI gears under spray MQL condition is examined using a power-circulating type gear testing machine in comparison with steel gears which have almost the same hardness of ADI. As the results of experiments, the surface failure strength of ADI gears under MQL condition is larger than that of SCM435 gears.

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