The hobbing finish of hard gear tooth surfaces such as case-hardened gears is expected to be put to practical use for high efficiency production. This paper investigates the properties of wear and finished surfaces by the hob cutter made with cubic boron nitride (cBN) in high speed cutting at 900m/min of case hardened steel. The content rate of cBN in the tip ingredients relates to the wear rate, and high content cBN tips are superior to the wear resistance. High thermal conductivity of cBN tips contributes to the heat transfer of cutting temperature to chips, resulting in melting and adhesion of chips on the relief surface. Flaking wear on the cutting edge sometimes occurs and chippings do not occur newly though chippings exist after grinding. The finished surface roughness is influenced by the horning figure on the cutting edge. Round horning of the cutting edge leads to the smooth surface. Possibility of high speed finishing with cBN-tipped hobs is discussed by a point of view of grinding of cBN tips and properties of the finished surface in addition to wear properties.

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The high accurate and large amount of modification on tooth surface that was not able to be done in a past machine software of equipment succeeded with one passage by the form grinding. A newly developed software added A and Y-axis to the past one. That is 5-axis NC control simultaneously with the full-closed feedback systems. The bias modification including the tooth surface with a hollow lead became possible by that. It reports on various examples in this lecture.

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Relief grinding of helical involute pinion cutters using a trapezoid grinding wheel is investigated. Methods to calculate an exact wheel profile and a regrinding error are proposed. The methods were confirmed by the grinding test using the CNC Niles-type relief grinding machine.

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Two ideas for crowning of tooth surface to obtain point contact for forging gears is proposed. The numerical data. are calculated and used for CAD/CAM systems for forging of spiral bevel gears. Tooth contact of proposed gearing are confirmed by the 3D drawing of tooth surfaces. Master gears of electrode to work metallic pattern to forge a pair of spiral bevel gears were made and contact mark coincide well with 3D contact mark calculated by the theory proposed in this paper. The authors forged the spiral gear pair by the two methods.

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The movement behavior of tooth contact pattern is one of major characteristics for hypoid gears. Especially, the VH behavior (i.e. the movement of tooth contact pattern for Vertical and Horizontal displacement) is extremely important not only for mesh quality but also for lapping productivity. This paper visualized the VH behavior of heat-treated hypoid gears by analyzing their ease-off directly using the measured tooth flanks. As a result, it is clarified that the lapping productivity depends upon the VH behavior: (1) bad lapping productivity shows the identical movement directions of tooth contact pattern for the vertical and horizontal displacement. (2) good lapping productivity has a crossed movement directions of tooth contact pattern for vertical and horizontal displacement. (3) Large cutter radius has a good lapping productivity. All analysis results are confirmed by test.

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Face gears can be substituted for bevel gears or hypoid gears. They can be used only in restricted applications today. Recently, a new application of face gears for helicopter transmissions has been proposed and face gears have attracted special interest. The geometrical design method for face gear was also clarified. Especially, it has become clear how the inner and outer diameters of ring gear are defined. In this paper, for avoiding the influence of machining and assembling errors on tooth bearing, the design method of point-contact face gear is described. Concretely, the gear tooth surface is generated by the cutter gear with the same module as and larger number of teeth than the pinion. It was shown that the contact point was able to be located in a preferable place on the gear tooth surface by the appropriate choice of the addendum modification coefficient of the cutter gear. By tooth contact analysis on the example of designing gear, the effectiveness of the design method was confirmed.

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Face-worm gears for a high gear ratio were made and tested. It was found that the efficiency of meshing at a convex tooth surface is a little higher than that at a concave tooth surface. And also, tooth surface modification is indispensable for this type of face gears, to avoid edge contact by bending deformation of a pinion shaft.

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Meshing conditions of face gears with axis displacements are analyzed. Effects of four kinds of axis displacements based on bending deformation of a pinion shaft are investigated by means of contact clearance between the tooth surfaces. As a result, it was found that tooth surface modification is indispensable for face gears.

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A method of the geometrical design for the face gear drive has not been established. And, there is no method which determines an effective facewidth and a position of the effective portion. Therefore, it is difficult to design the face gear drive especially with offset because there are too many design parameters. In the present paper, the face gear drive with offset was discussed. In consideration of axode and hyperboloid, which were on the basis of a method for the geometrical design of the gear drive which rotate on crossed axes, a new concept "Design circle" was proposed. The position in which an effective facewidth exists was obtained approximately by the use of this concept.

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The tooth contact and transmission error of large-sized spiral bevel gears in Klingelnberg cyclo-palloid system are analyzed. The analysis method is based on simultaneous generations of tooth surface and simulations. The influence of alignment errors as assembling on the tooth contact of the spiral bevel gears was also investigated. These analyzed results were compared with experimental ones. As a result, two results showed a good agreement.

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Many of machine elements, such as gears, traction drives, rolling bearings, wheel/rails, and other things, are applied for a long time under the severe running conditions. These elements play the important role which is not to break down in security. Practically, phenomena called as pitting, spalling, flaking, and the other cause the serious problems. It is important to investigate a detailed stress state for the contacting surfaces precisely to guarantee and calculate contact stress strength and its life cycle. A large number of these elements are used practically in the conditions of three-dimensional contact stress state. To design the life of these elements has to calculate an auxiliary equation of the Hertzian theory. Because these auxiliary equations involve the complete integrals of the first and second kinds, numerical analysis are required. This paper presents how to calculate the contact stress using approximation equation by arithmetic geometric mean. As a result, numerical solution has simply and precisely accomplished. Added to these, contact stress state of crossed helical gearing were used to introduce something chosen as a typical case.

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The detection of failure in early stage of fatigue is important for a reliable evaluation of gear strength. From this viewpoint, some failure detection methods were applied to the fatigue process of tooth. Each method has good points and weak points in realtime process, quantitativeness and locating.

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We have developed a new type reducer having no eccentric crank input similar to Harmonic drive. By employing a train of movable pins and trochoid cam gears, it can get high torsional rigidity compared to Harmonic drive using elastic deformation. This reducer consists of the three components; The first one is an input cam having a concentric ellipse-shaped groove to keep a train of movable pins in it. The second one is an output cam having two teeth less than the number of pins. The third one is a fixed cam having equal number of teeth to the number of pins. When the input cam rotates 180 degree in a CCW direction, a pin turns around along a tooth of the fixed cam, by this motion, the output cam rotates in a CW direction by one tooth relative to the fixid cam. In this report, the design method of cam profile that provides the defined motion of the pins is presented, and pressure angle is analyzed by using polar complex vector.

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A 3 leg moving robot which has legs constructed by injection molding pantograph mechanism from polypropylene is herein suggested, and the velocity characteristics are measured in this paper. The injection molding pantograph mechanism has some natural frequencies in various directions with reference to the output point when an input wave is applied at an input point. Therefore, if the injection molding pantograph mechanisms are applied as legs, the robot employing pantograph mechanisms can move in various directions by actuating only one leg. A manufactured 3 leg vibration moving robot could move forward at 38mm/s, backward at 54mm/s and spin at 0.23rad/s by actuating one leg. By shifting the phase between each leg and the amplitude of the legs, the vibration propelled robot was able to accomplish a high speed of 167mm/s.

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The triple arm mechanism is a simple and basic spatial parallel mechanism with three degree of freedom, which consists of a based platform, a movable platform and three two-link-chains having the actuated prismatic joint. It is important to make clear the kinematics near the limit position for the parallel mechanism. Sensitivities analysis is useful to estimate the transmissibility, but sensitivities do not indicate the force to support the movable platform. In this paper, static analysis is done to make clear the force transmitting through the pair, and instantaneous screw axis indicating the motion of the movable platform is derived, and transmissibility characteristic is shown by means of the forces supporting the movable platform.

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In order to synthesize a parallel mechanism which satisfies conditions on output velocity characteristics and motion transmissibility given as design specifications, this paper focused on instantaneous center/screw axis. Output velocity characteristics, such as isotropy and translational/rotational velocities ratio, of planar mechanism with three degrees of freedom were generally investigated using three instantaneous centers of the output link. Input-output velocity relationship and transmission index of planar 3-RPR parallel mechanism were formulated using three centers. A kinematic synthesis method of this mechanism and a synthesis example were presented.

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This paper describes a kineto-static analysis of a spatial closed-loop link mechanism which is composed of elastic thin strips. The relation between elastic deformations and forces and moments at both ends of a rectangular thin strip was defined as a finite element model of a cantilever beam. A system of nonlinear equations with 32 variables to solve elastic deformations and output angular displacement of a four-bar elastic link mechanism was then derived. A simulation was carried out with optimization to solve the system of nonlinear equations.

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We developed a walking assist machine, which machine uses a spatial parallel link mechanism for the elderly or rehabilitants. The flat steps of the assist machine move in parallel with the ground and can support the legs of a person including the soles. The flat steps of the assist machine move in parallel with the ground and can support the legs of a person including the soles. To grasp the walking phase of each leg of the equipped person, pressure sensors were laid under the thenar eminence and the heel of the sole, and the pressure variation at each sensing point was measured. Furthermore, in order to support walking in indoors, we investigated the assist methods of turning around during walking and walking on a slope or stairs. A flexible link was installed in the mechanism for taking into account the twisting motions of the waist and ankle. To grasp the behavior of turning around during walking of the equipped person, pressure sensors were attached outside of the flexible link in both crural parts of the machine. As a result of the experiment wearing the machine, the equipped person could turn around during walking at will.

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This paper describes motion and stiffness control of a multi-DOFs linkage mechanism with elastic elements. The target mechanism is a closed-loop link mechanism with 5 DOFs consisting of rotary actuator and elastic manipulator formed by coil spring and linear actuator. To assign the robot with both planar position and stiffness of the output joint as an output vector, a method based on kinematics and static analysis and their inverse kinematics analysis is proposed. Verified with numerical simulation results, it has been proved that the proposed method are suitable and trajectory and stiffness of output link can be concurrently controlled.

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The helical cord is a unique machine element with high tensile stiffness and low bending stiffness, and therefore is used in various types of rubber belts as a tension member. However, the fatigue failure initiation site of the rubber belts is often the inside of the helical cord. In this study, the fatigue failure mechanism of the hybrid cord, which consists of the carbon fibers and the glass fibers, was investigated caring out some experiments and the mechanical analysis. Especially, the failure morphology of the damaged cords was observed using a three-dimensional X-ray CT scan.

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Performance for a frictional power transmission belt such as flat or V-ribbed belts is usually obtained by experiments using two pulleys system for instance and expressed as torque or horsepower of driven axis at the 2% ship ratio. On the other hand few theoretical studies on the performance have benn reported. We have already reported theoretical prediction method of the performance in which tension is set up by fixed pulley. In this paper, a formula to predict the performance in case of tension set up by dead weight (DW) is introduced. Then, validities of the formula are verified by experiments and finally comparison of the performance between fixed pulley system and DW system is described.

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The rubber belt for CVT in scooter is subjected to complex loadings, because the CVT performs as the variable speed device and as the power transmission. Therefore, various loads affects the CVT rubber belt, and the failure mechanism becomes complex. Therefore, there are many unclear points on the fatigue failure initiation and extension. In this study, the fatigue test is carried out under various conditions, and the failure mechanism of the CVT rubber belt is discussed.

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The fatigue failure mechanism of the CVT rubber belt was investigated using some experiments, FEM analysis and a simplified mechanical analysis. There are three major failure modes for the CVT rubber belts, namely adhesive rubber crack, bottom land crack and tension rubber crack. The paper focused on the adhesive rubber crack initiation mechanism. The crack was initiated along the interfaces between the adhesive rubber and the fiber reinforced rubber. The mechanical analysis revealed that the de-bonding of the interface was explained by the dishing deformation of the CVT belt that was wounded around the pulley. The contribution of the geometrical factors of the belt and pulley on the failure initiation was estimated by using the mechanical analysis.

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The transmission error in a synchronous belt was investigated experimentally in the case where the belt was generated the string vibration by resonance under the dynamics condition and the pulley speed ratio was 1:1. The period of the transmission error is 2 times per pitch. The tendency of occurrence can be estimated from the difference between the amplitudes of the string vibration due to the resonance. The transmission error in the belt greatly occurs in the first mode resonance of the string vibration.

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This paper was investigated the influence of transmitted torque, installation tension, pitch difference, and pulley alignment error on the transmission error in a helical synchronous belt having the error in the belt side face for the case where the flanged pulley was rotated in bidirectional operation under the quasi-static condition and the pulley speed ratio was 1:1. The transmission error in bidirectional operation increases when the transmitted torque increases. The transmission error can be reduced when the installation tension is set high, and when the pitch difference on the driving side is made small to some extent than that on the driven side. In addition, the rotation transmission accuracy is improved when the alignment between the driving and driven pulleys in the axial direction is set so that the belt on the driving side comes into contact with the pulley flange early.

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Fatigue failure mechanism in synchronous belts with steel cord was investigated. The belt failure was initiated near the tooth root, where the steel cords were broken. The steel cord was made for twisting steel wires. There are many kinds for the wire constitution. The bending stress of each wire is necessary to examine the bending strength of the twist cord, that wire constitution is different. The bending stress of the wire is found from a change of the curvature when a wire was bent. In this study, the geometrical calculating method of the wire curvature is proposed. In addition, the example of calculating the bending stress is shown by proposed method.

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This paper describes the load bearing capacity of plastic helical wheel meshed with metal worm. The test machine for plastic worm gears was newly developed, in which the center distance and shaft angle are variable and the transmission efficiency can be measured. Experiments were carried out using plastic helical or worm wheel and a commercial steel worm under various running conditions. The temperatures of plastic helical and worm wheels and the torques of the input and output shaft were measured. The effects of torques and rotational speeds on the gear teeth temperatures and the transmission efficiencies between meshing gear teeth were determined.

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The temperature rises by friction exothermic reaction and hysteresis exothermic reaction between tooth surfaces, elastic modulus lowers on the allowable stress of the plastic gear material, and the allowable stress lowers. Then, the strength of the tooth weakens on the face width central, since the heat radiation effect lowers. This study is the verification result between analytical result and experiment of developed plastic gear exclusive use exothermic reaction and heat conduction three-dimensional analysis software. Then, the simulation by the difference between the face width is carried out, and it is shown that it obtains allowable stress from the temperature distribution of the tooth and that the strength of plastic gear is not proportional to the face width.

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It is well known that the plastic gears have some advantages, that is lightweight, low noise and operation of oil-less conditions. But plastic gears have been used only low torque conditions. As FRP gears have acquired higher strength and stiffness than the plastic gears, FRP gears are now attracting attention and they have replaced metallic gear in order to reduce weight and noise. Although there have been many researches on metallic gears, we have seen few reports about FRP gears. At present, FRP gears are designed mainly based on little test data of plastic gears and experiences that engineers have. In this research, we investigated the bending fracture characteristic of FRP gears, to develop design criterion for FRP gears. According to the experiment results, tensile strength and bending fracture strength of gears were not direct proportion.

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The injection molding of plastic gears generally requires the structure of gear to have small rim thickness for achieving higher accuracy of its tooth geometry. The rim thickness greatly affects tooth bending stress, because of changes in stress distribution due to rim-web structure. In the present paper, the effect of rim thickness on endurance of injection molded POM gears was investigated. As a result, it was confirmed that the service life decreased with smaller rim thickness. Furthermore, maximum principal stress resulted from finite-element analysis could determine the effect of molded plastic gears.

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In this study, we investigated the properties of noise and vibration of plastic gear for power transmission. It becomes clear as follows. Tooth profile error of a plastic gear engaged with a steel gear has no great influence on the gear noise. Plastic gears that have tooth profiles with large negative pressure angle error show a tendency to generate low noise compared with plastic gears that have small tooth profile error when the plastic gears are used under high load conditions.

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Mesh frequency is affected by gear eccentricity. Large waviness in transmission error due to gear eccentricity is the prime cause of modulation. Large waviness causes an amplitude modulation of mesh frequency due to dynamic deflection of gear teeth. The waviness is calculated by the approximate formula of transmission error with gear eccentricity obtained by the authors. By assuming that the mesh wave is purely sinusoidal, the modulated spectrum is calculated theoretically and the obtained spectral components are known as sidebands. Sideband spectrum consists of two components, whose amplitudes are calculated by modulation indices. However, modulation indices can't be decided analytically, because amplitude modulation has strong relation to dynamic deflection of gear teeth. In this paper, amplitude modulation is confirmed by measurement of transmission error of gear eccentricity under load.

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In this research, a high-precision pitch artifact is proposed for calibration of pitch measuring instruments. This pitch artifact is composed of the combination and the alignment of balls and cylinders on a plane. Balls, cylinders and planes are possible to be manufactured with several-ten-nanometer-order accuracy. Therefore, this artifact can accomplish high dimensional accuracy. In addition, manufacturing of this artifact is not difficult because time-consuming special process is not needed. In this report, the concept, structure and feature of this pitch artifact are proposed and theoretical analysis is carried out.

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The purpose of this research is to extract the meaningful global parameters of 3-dimensional 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. The Oth order form deviation, which is regarded as a general representation of pitch deviations, the parameters for the 1st and 2nd order form deviations are derived. Using those parameters, the surface deviations of a tooth flank is characterized according to the order of the surface. They are calculated from the measured conventional deviations of actual bevel gear flanks and separation processes of measured deviations into four kinds of form deviations are automatically performed. The meaning of their representation is discussed for the parameters of each order form deviations.

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This paper describes a study on the quantitative measurement of the oil film thickness of the porous sintered sliding bearing by the ultrasonic method. The thickness of the oil film generated between shaft and porous sintered sliding bearing is so thin that the oil film thickness is very difficult to be measured. As a basic study of the measurement of oil film thickness of the bearing under running operation by means of the ultrasound, the clearance between the bearing and the shaft under no-running condition was measured by the ultrasonic method, and the relationship between the measured echo ratio and the oil film thickness (clearance) was obtained. The possibility of the measurement of the oil film thickness by the ultrasonic method was clarified by comparing the oil film thickness with the whirling shaft of the bearing under running operation.

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A new diagnostic method by using a laser reflection was developed. The variations of the laser reflection between the initial and the present conditions are compared, and it can estimate a condition on the tooth surface. To verify that our method can accurately diagnose a tooth surface of the lubricated gear, measurement experiment in the practical used gearbox was carried out. By attaching the cover, the response of measured data had more sensitive. Under the condition of force-feed lubrication, pitting could be detected in every range less than 1800rpm. Therefore, our method can diagnose a tooth surface of the lubricated gear in the practical used gearbox.

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The equipment measuring transmission errors of gears under load for assembled automotive transmissions is developed. This instrument can measure a manual transmission for front engine-front drive accurately without alteration and separate out the transmission error of each gear from measured data by discrete Fourier transform. Considering and adjusting resonance of the system united a test transmission with the measuring machine make measuring absolute value possible. The precision of measured transmission errors is confirmed by the comparison between measured values and calculated values from tooth surface. It is also shown that measured transmission errors correspond to gear whine noises.

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The automatic transmission uses a combination of 2 or 3 planetary gear trains to get a desired speed ratio. Reduction in the fuel consumption of automobiles has become an important project. The authors designed and made a gear train testing machine which can mount the planetary gear trains to be used for an automatic transmission of a passenger car. Single planetary gear train was used for the first and fourth speed stages while two planetary gear trains were used for the second speed stage. The theoretical efficiency of the combined internal gear trains is calculated using theoretical equation when oil churning and bearing losses are taken into account together with tooth meshing losses.

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A noble wedge ring type roller speed reducer with the speed ratio of 25 was developed. The normal force was given in accordance with the applied torque by producing a wedge between the loading ring and output ring, which enables to exclude the additional normal force mechanism. The power transmission performance was evaluated using the traction fluid under the test conditions such as step torque, step speed and sweep torque methods. As a result, the reduction speed ratio was stable under the test conditions, while the efficiency was about 90% at the maximum output torque.

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A power-split half-toroidal CVT, consisting of a variator and planetary-gear set, has features of stretching the speed-ratio range and decreasing the transmitting torque through the variator in high-speed cruising mode, while it has two issues of inversion of torque flow through the variator and discontinuity of output torque during mode change from direct to power-split mode. This paper confirms its inversion of torque flow by measuring the transmitting torque on the re-circulating shaft of the CVT-Box with speed ratio range of 1:6.33, and solves both the torque discontinuity and the torque-surge by a sequential control of variator-ratio and engaging pressures of a pair of mode-change clutches.

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Traction Drive have probabilities to change car from fossil fuel to real electoric motor.

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A noble planetary roller type traction drive with the speed ratio of 4.5 was developed as a speed reducer aiming at simplification and high efficiency of the device. The power was transmitted from the sun roller to the retainer through the centerlessly supported planetary roller, which enables to decrease a precision of processing of the rollers. Another feature was that the axial thrust between the wedge-shaped sun and planetary rollers provide the normal force. The power transmission performance was evaluated using the traction fluid under the test conditions taken a speed reducer of electric-powered wheel chair into consideration. As a result, the reduction speed ratio was stable under the test conditions, while the efficiency was about 90% at the maximum output torque. It was considered that the major cause of torque loss was the friction resistance on the bearings.

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A new type of the traction drive, which is driven in the transit-lubricated condition by piezoelectric actuators, is proposed. In it, the oil film is formed not by the rolling motion of the rollers but by the micro vertical vibrations of the wedge to the contacting surfaces. The performance of the new traction drive is compared with that of the friction drive. The transmissible force of the traction drive is about a third of the friction drive but the wear of the wedge of the traction drive is very small.

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