近年、汎用加工機のNC制御機能の進化は著しく、歯車・ネジ加工において、新しい加工方法を確立することが可能となった。汎用加工機による歯車・ネジ加工の具現化には,一般的なパソコンの計算スピードの高速化並びに汎用工具の寿命延長が寄与している。廉価なパソコンによる形状解析が可能となり、形状を座標として認識することが容易となった。求められた座標を複数軸の同時制御可能な汎用機で、工具寿命の長い加工具を使用し、正確にトレースすることにより形状を作ることができる。

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In order to investigate the effect of cavitation shotless peening on fatigue strength of steel gears, the case-hardened steel rollers and gears cavitation shotless peened under different conditions were fatigue-tested using a roller testing machine and a gear testing machine. The hardness and the compressive residual stress of the test rollers and gears were increased by cavitation shotless peening. On the other hand, their surface roughness was not increased so much. In the fatigue tests, the fatigue life of most cavitation shotless peened rollers and gears was longer than that of the non-peened roller and gear. In particular, the fatigue life of cavitation shotless peened rollers and gears was significantly improved by using a modified nozzle for a high-speed water jet to obtain a greater peening effect. Therefore, it was found that the cavitation shotless peening is good for the increase in fatigue strength of steel gears.

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In earlier report, the authors carried out surface durability test with carburized steel roller and carburized steel roller with shot peened by two different methods. After examination, some micropitting were occurred on contact surface. In this study, we clarified the generation mechanism of micropitting by measuring the geometry of micropitting in detail. The object of the geometry measurement is a width of pit and the maximum depth of micropitting, and an angle that contact surface and crack formed. As a result of measurement, the maximum depth of micropitting was match shallower than the depth that predict by column to column contact of test rollers. Further, a strong correlation was confirmed the maximum depth of micropitting and the damage width along tool mark. Also, the damage width that vertical direction to tool marks was depending on tool mark width which increases along with the contact load. It is thought that micropitting was caused by asperity contact of contact surface after running-in process. Shapes in the contact asperity point were guessed by measurements of micropitting width and depth. The stress analysis was carried out for obtained asperity shape, and stress direction was calculated. Then, the stress that caused micropitting was determined by comparing stress direction and crack propagation angle. As a result, micropitting was caused by maximum shearing stress that increases along with high friction coefficient, and moves to contact surface.

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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, for example, weight reduction due to smaller density than that of steel, good properties of vibration and noise, low cost in machining and heat treatment of blanks due to near-net-shape casting. It has been reported that ADI can be sufficiently applied as a medium hardness gear material. Recently, two steps bending phenomenon of S-N curve for the bending fatigue strength of ADI is reported, and the fatigue phenomenon in long life region over 10,000,000 time number of cycles is discussed. However, the surface durability in long life region has not been clarified until now. In this paper, surface durability of ADI rollers in long life region is investigated using a disk machine which simulates the rolling and sliding action of gears. Furthermore, fatigue limit for surface durability of ADI is estimated by observations with crack initiation and propagation.

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In order to investigate the influence of shot peening on the surface durability of steel rollers, the steel ones treated by single and double shot peenings were fatigue-tested using two cylinders testing machine under a sliding-rolling contact condition. The hardness and the compressive residual stress of the test rollers were increased by shot peening. Their surface roughnesses were also increased by shot peening, and the surface roughness of the double shot-peened rollers was smaller than that of the single shot-peened ones. The cause of failure of all the test rollers was the spalling due to the subsurface cracking. The surface durability of the shot-peened rollers was larger than that of the non-peened roller. In particular, that of the double shot-peened rollers was the largest in this study.

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This paper describes a study on the surface durability of surface-rolled sintered metal gears. Sintered metal gears were made using hobs with different tooth profiles, and then surface-rolled under various amount of rolling using two types of rolling machines. Heat treatment was performed after surface-rolling. The effect of surface-rolling on the surface property was examined by measuring hardness and porosity near surfaces of rolled gears. Running tests for test gears were carried out. The effects of the amount of rolling on the surface durability of sintered metal gears were determined, and these results were compared with the results for as sintered gears and wrought steel gears.

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In order to evaluate the influence of artificial defects (holes) on rolling contact fatigue strength of steel rollers, the steel rollers with artificial defects were contact fatigue-tested under a sliding-rolling contact condition. The crack propagation behavior was investigated. The rolling contact fatigue strength of rollers with artificial defects was smaller than those of rollers with non-artificial defect. In the case of rollers with artificial defects, cracks occurred in the vicinity of holes. The initial crack propagated from the hole was parallel to the roller surface. Then the crack propagated in a range of 20 degrees -45 degrees for the crack that progressed in parallel with the surface. To examine what kind of subsurface stress affected the crack, internal stresses around hole were calculated with FEM. The factor that affected the initiation of cracks would be the maximum shear stress τ_<max>, and the factor that affected the propagation of cracks would be the orthogonal shear stress τ_<yz>.

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This paper describes a study on the load bearing capacity of newly developed high density sintered metal gears. Bending fatigue tests for gears of a newly developed high density sintered metal and contact fatigue tests for rollers were performed, respectively. Fatigue tests for surface-rolled sintered metal gears and rollers were also performed. Bending fatigue strength and surface durability of these gears and rollers, and the effect of surface-rolling on these strengths were determined. These results were compared with the results for wrought steel gears.

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Surface fatigue failure in gear teeth has been studied since a long time ago. Surface durability in carburized gears was controlled by occurrence of Spalling. However, recent researches have confirmed the occurrence of Micropittings and Flakings at carburized gears. These failures occur with lower load than Spalling does and also lead to tooth breakage. This paper focused on surface durability test of carburized gears, using the power circulating test rig. Micropittings occurred at beginning of the experiment and its number increased as the number of cycles increased. Flaking occurred after accumulation of Micropittings, and some cracks were also observed before Flakings occurrence. Based on failure process observation, we can conclude that is possible to create ten levels for failure rank in order to identify and classify failure situation on gear teeth.

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This paper described a study on effects of the case depth, the helix angle and the carburized part on the residual stress, bending fatigue strength and the bending fatigue crack path of case-carburized helical gears. A heat conduction analysis and an elastic-stress analysis during the case-hardening process of helical gears were carried out for various case-hardening conditions by the three-dimensional finite-element method (3D-FEM), and then residual stresses were obtained. The effects of the case depth, the helix angle and the carburized part (tooth surface, gear-side) on the residual stress were determined. Bending fatigue tests of case-carburized helical gear pairs of different case depths, helix angles and carburized parts were carried out, and S-N curves were obtained. Effects of the case depth, the helix angle and the carburized part on bending fatigue strength and the bending fatigue crack path of case-carburizing helical gears were determined. Furthermore, the relationship between the residual stress and the bending fatigue strength was examined.

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The influence of surface roughness on the change of the temperature of rolling-sliding contact surface was investigated by using the lubricating oil of various temperatures. First, the surfaces of case-carburized test rollers were finished by methods of grinding and hand finishing with the abrasive papers. Second, the surface temperature of the test rollers having different surface textures was measured under the condition of rolling-sliding contact. From these experiments, the following results are obtained: The surface temperature rises remarkably with the increase of normal load. The initial surface texture and the inlet oil temperature have considerable influence on surface temperature. The surface temperature greatly falls when the surface is smoother and the inlet oil temperature is lower under the high load condition. Therefore, in order to improve the surface durability of case-carburized power transmission gears, the smooth tooth surface texture and lubricating oil of low temperature are recommended.

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This paper presents a study on optimum profile of hardened layer for bending fatigue strength of induction hardened gears. The measurement of hardened layer and the bending fatigue test were carried out for induction hardened gears made of as-rolled and thermally refined S35C and S45C steels, and then profiles of hardened layer and S-N curves were obtained. Effects of the pre-treatment, the heating time, the electric power and the frequency on profile and micro structure of hardened layer of induction hardened gears were examined. The relationship between the bending fatigue strength and the profiles of hardened layer was determined. An optimum profile of the hardened layer for the bending fatigue strength of induction hardened S35C and S45C steel gears were indicated.

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This paper presents a study on bending fatigue strengths of induction hardened thin-rimmed spur gears with web arrangement. Bending fatigue tests were carried out for different induction hardened thin-rimmed spur gears with web arrangement. By measuring the case depth and observing the micro-structure of the case depth of the induction hardened gears, the effects the case depth, thickness of rim, heating time and web structure on the bending fatigue strength were determined.

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In the present paper, residual stresses and adhesion energies of DLC films were measured and discussed. DLC films consist of Cr/C gradient interlayer and a-C:H layer were deposited by UBM sputtering. Residual stresses of these films were calculated by the use of improved Stoney's equation. And adhesion energies were calculated by our contrived equation. Residual stresses increased with increasing substrate bias voltage under -300V, and decreased over -300V. And these decreased with CH_4 mixture ratio. Adhesion energies decreased with increasing substrate bias voltage. And these were increased with CH_4 mixture ratio. Residual stresses were found to be affected by hydrogen content, Ar ion assistant and substrate temperature. Adhesion energies strongly corresponded with Sp^3 fraction. Therefore, decreasing Sp^3 fraction brought the increase adhesion energy. In application of DLC films to gear tooth flanks, adhesion, hardness, and thickness of the films should be optimized, then DLC films could be expected to improve for their pitching and scuffing resistance.

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The present study describes surface modification of aluminum alloy by fine particle peening technique. Various fine particles, steel, zirconia, fused silica and fly-ash were accelerated with pressurized gas and were collided to the target surface with various gas pressure and treatment time. Micro Vickers hardness at loads of 3 and 10mN, surface profile and element distribution were measured with a micro indenter, profile meter and SEM/EDX system, respectively. As results, the significant increase of the hardness value, similar with that of quenched steel with relative smooth profile was obtained by the transfer of the steel particle accelerated with high gas pressure.

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Involute tooth profile is used to the tooth profile generally. But, with decreases number of teeth problem such as decrease of the strength with undercut and decrease of the contact ratio with the tip occurs. Against this, as tooth profile witch do not cause undercut even with small number of teeth, there are cycloid tooth profile that is formed with cycloid curve, and logix tooth profile, rack tooth profiles of which is formed with the accumulation of the minute involute curve. Therefore purpose of this research is to carry out design and production of 2 teeth gears for involute tooth profile, cycloid tooth profile and logix tooth profile as special tooth profile, quality analysis, and to examine its practicality from result of connection test.

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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 the positive deviated relative moving locus of two gears which construct the unit. One of the profile has a similar curve of the moving locus and the straight line. Another one is the generated curve by the former and the same straight line. It is expected that thiis profile has the high ratcheting torque which prevent the tooth flying due to the large load applied on teeth.

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The setting of Gleason hypoid gear generator was analyzed by vector analysis method. Numerical data are calculated and used for TCA by 3D/CAD drawing and also numerical method. Tested contact mark on the tooth surfaces of hypoid gear coincide well with the theoretical contact pattern estimated by 3D/CAD drawing and also numerical tooth contact analysis.

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Direct observation of rolling contact edge with plastic deformation due to high contact pressure is carried out by EHL oil film optical interference fringes testing machine. The position with the thinnest oil film thickness moves from an end of form to an inner side with increase of plastic deformation. This result supports the actual phenomenon in which the rolling fatigue pit on a contact end is not generated at the real end.

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Rolling contact fatigue test with three kinds of lubricating oil was carried out in order to clarify the influence of viscosity characteristics of lubricating oil on rolling fatigue strength of steel roller. Each lubricating oil was different in viscosity of base oil and blending quantity of the viscosity index improver. In case of the test under the lubricants with equivalent kinematic viscosity, the rolling contact fatigue life depended on the viscosity of the base oil and was longer in case that the base oil of the lubricant had the higher kinematic viscosity. In case of the rolling fatigue test under lubricant made from same base oil, the rolling contact fatigue life was longer in case of the rolling fatigue test under the lubricant with higher kinematic viscosity, Small spot marks with relatively high roughness would occur by non-destructive scuffing.

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Fluid motion has been investigated to give suggestions for more efficient lubrication feeding with respect to cooling tooth surfaces as early after finishing engagement. A pair of transparent helical gears made of PMMA was immersed in a water tank, which made the tooth space visible during engagement from the inside of the gear. The arrangement also made the speed of gears about 1/10 lower than that in practical gear operation owing to the Reynolds similarity principle. Flow behavior was three dimensionally visualized by using a high-speed camera which shot suspended polystyrene particles or nozzle injected milk. The observation clarified that there are marked sucked flow into tooth spaces just after engagement, which is mainly originated at around mesh ending region of leading side directed against the motion of gear movement and also directed axially toward the trailing side of mesh. However, another flow weakly exists at the trailing side axially getting into the spaces.

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In this paper, a new walking assist machine on which a flexible shaft is applied. A combination of the flexible shaft with a worm gear is successfully adopted on this walking assist machine to develop its appearance simple and its size compact. This walking assist machine is actively controlled with a hybrid control system witch control both torque and angle at ankle joint. In this control system, the torsion spring constant of the flexible shaft is took into account to control power and the rotating angle of the motor witch assist over 70% power of normal walking. Walking experiments using this machine show the walking assist machine is well fit to walking.

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Devices and machineries that can positioning operation precisely and in high speed are used in the read production site. These device work in high speed back and forth movement, too much load is added on power transmission parts. Therefore, they have been used mostly for transportation and assembly for light parts. Now we need the devices for the use to transport heavy items faster. But the conventional gears performance is not enough. The aim of this study is exploring the endurance of power transmission gears, using a back and forth experiment device to find some conditions for reformed devices. It was found that the thick one improves the thickness of the coating and the endurance performance improves, and that the change of housing materials from aluminum to iron produced, reduced the flexure of the device and the effect on the durability.

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This paper describes a new type of planetary gear drive with a high reduction ratio. The planetary gear drive is mechanically similar to a 2K-H type planetary gear, which has two sun gears and one carrier. The planetary gear drive has two pairs of an arc tooth profile gear and a pin roller, which mesh with each other. The planetary gear drive has little backlash, a high efficiency, a long fatigue limit, etc., because the tooth contact holds on concave and convex surfaces. In this study, we measured the vibration acceleration, the transmission error, the gear noise, and the efficiency on the new type planetary gear drive by the running tests. We discuss and report on the driving performance of the planetary gear drive.

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For the robot hand of which the miniaturization is required, a new joint drive mechanism is proposed in this paper. This mechanism is composed of three members. The first member is a convex sphere with a spiral groove on the surface, and this member is the driving element of this mechanism. The second member is a concave sphere which wraps the convex sphere. At one place on the inside of this concave sphere, an internal tooth is buried. This tooth meshes with the spiral groove. This member is driven element of this mechanism, and it does the swinging motion. The third member is a spherical bearing which supports the rotating convex sphere. This spherical bearing is the fixed element of this mechanism, and it has the guide plane which decides the direction of the swinging motion. Here, the details of this mechanism are explained.

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This paper describes the design and performance of external gear pumps. We have a method developed to calculate accurately the displacement volume of external gear pumps having a non-involute tooth profile and an involute tooth profile. Using this method, the displacement volumes of external gear pumps with an involute tooth profile, a cycloid tooth profile, an involute-cycloid composite tooth profile, a modified cycloid tooth profile and an asymmetric tooth profile are calculated. Then, the merits and the demerits of these tooth profiles are discussed with respect to the displacement volume. In addition, the gear pumps having some external tooth profiles were designed and manufactured, and the displacement volume of the gear pumps was measured. Consequently, it was confirmed from both the calculated and the experimental results that the displacement volume of the external gear pumps with the non-involute tooth profiles is larger than that of the involute tooth profile.

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This paper presents the procedure to simulate the transmission error in a planetary gear of star type. A planetary gear system is a kind of constrained geartrain. Accordingly a number of gear meshes between planet gears and a sun gear or a ring gear affect each others. Therefore a coupled analysis method of the transmission error is developed. Then this method is applied to study the effects of mesh phasing and tooth surface error on the transmission error and mesh excitation force. As a result, a sequential phasing has a great advantage for reducing transmission error and mesh excitation force compared with a simultaneous phasing. This effect is expected when planet gears have different tooth surface errors from one another as well as homogeneous tooth surface error.

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Planetary gears should carry equivalent torque through plural pinions in order to design low vibration systems. However, effective equalization methods on load sharing has not been found because the mechanism is far complicated. In present study, alternative numerical analysis method and measurement are developed which can evaluate structural properties and misalignments among components. Contact analysis of gears is conducted by an in-house simulation system of flexible multibody dynamics. Influence of bearing stiffness is investigated to find out factors in load sharing under quasi-static conditions. Some numerical results show that higher bearing stiffness of ring gear improves load sharing since it reduces unnecessary motions of ring gear. Moreover, an adequate support stiffness of carrier is revealed which optimizes both carrier and ring-gear motions. Finally, comparison between numerical and experimental results confirm the adequacy of the numerical method.

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The rotational transmission error of the strain wave gearing is the main cause of the tortional vibration. In this study confirmed the high frequency vibration generation in the strain wave gearing. First, the weighing device of the rotational transmission error was produced. This device can measure the rotational transmission error of the strain wave gearing can be measured in the high resolution evaluation. Next, do the Fourier transform of the rotation transmission error , and the error margin element of higher-order was confirmed. Moreover, the vibration of the output axis was measured, and the generation of the high frequency vibration was confirmed in reduction ratio 1/50.

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Reduction of mesh force is important to improve gear whine noise of an automotive transmission. Mesh force is defined by multiplication of transmission error and dynamic stiffness. To reduce mesh force, it is often hard to improve both of them simultaneously because they are incompatible with each other. In this study, a face width of a counter gear set in an automatic transmission is focused on as an example of incompatibility. In this case, it is possible to improve dynamic stiffness by decreasing flexural rigidity of a counter drive gear, but it leads to deterioration of transmission error. Influence of a face width upon mesh force is guessed by numerical methods considering both of them synthetically, and validity of the methods is verified through experimental analysis.

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Tooth surface measurement is applied for quality check of manufactured gear. But, gear unit's performance on vibration behavior cannot be checked completely, because there are other origins that may bring vibration problems such as misalignment, inadequate stiffness of shafts or bearings. Authors had already reported about excitation force estimation with vibration measurement results that can be applied for quality check and vibration diagnosis of gear unit. In this research, we discuss about precise phase estimation method. Also, vibration characteristics extraction on third harmonic component of mesh with misaligned gear pairs, and its potentiality of effectiveness is shown.

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Recently, for the connection of oil well tubes employed in an increasingly severer environment, special screw joints equipped with metal to metal seals are generally used. However, there are increasing in number, stricter oil well designs whereto screw joints of conventional properties have became inapplicable any longer. Under the above circumstance, the special screw joints with anti-leakage property, bearable specifically in an environment of the combined burdens of compression, external pressure and bending have become strongly demanded. Therefore, in order to increase the performance of the screw joints, it is necessary to analyze the internal stress distribution of the contact point of the screw joints. In this paper, the FEM model for calculating the contact problem of the screw joints was investigated. In the case of contact problem between a sphere and semi finite plane, the analytical stress distribution calculated using the FEM model, which consists of a cylinder with a curved surface and a rectangular parallelepiped, was the same as the theoretical one qualitatively.

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Bearing stiffness influences the performance of power transmissions. Various reports about the analysis of bearing stiffness have being published. In these reports, the method of Harris is the most general. Especially about the stiffness analysis of the tapered roller bearing, it is necessary to consider the contact field among the cones. However this problem about the contact field cannot be analyzed. Therefore, Palmgren suggested the method of Harris in considering of an empirical formula. In the present paper, the tooth flank film element applied for the issue of contact of the tapered roller and raceway. And we discussed the effect for evaluation of the bearing stiffness.

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The authors have developed the gear lapping machine which uses a nylon lap that enabled making tooth flanks of steel gears smooth: a maximum peak-valley height (Rz) of less than 1μm in a short time. The objective of this research is to develop a center-less gear lapping machine which can more efficiently make both tooth flanks of steel gears smooth without fixing the work gear on any shaft. This paper shows the mechanism of the center-less lapping process and the structure of the lapping machine designed and manufactured by the authors. Moreover, the work gears lapped using the new machine are evaluated with regard to the tooth roughness and the accuracy of the tooth profile.

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