Yasuyoshi Tozaki

Performance evaluation of innovative micro-traction-drive-utilized angular-contact bearing

Traction drive makes oil film between two rollers, and power is transmitted by oil film shearing. It has the following characteristics. (I) Traction drive can be operated at low level of vibration and noise, so they are more suitable at higher speed rotations than gear. (2) Traction drive can change continuously the distance from the contact point of the rotating part to the axis of rotation: it is useful in continuously variable transmission (CVT). Generally-fixed-reduction-ratio-type traction drive is developed for the purpose of use by high-speed rotation taking advantage of the feature of characteristic (I). On the other hand the authors have developed a micro drive system for transmission; a micro-traction-drive based on the structure of an angular ball bearing is advantageous over geared speed reducers, for small scale equipment requiring high numbers of revolutions. A micro-traction-drive is easily manufactured by modifying angular bearings and tapered roller bearings for which preload inner race and outer race act as thrust force. The driving force is transmitted by the contact of the retainer with the rolling element in the rotating direction. The test of the experimental model of micro-traction-drive using an angular ball bearing of 10 mm inner diameter 30 mm outer diameter and 9 mm width was carried out. Power-absorbing-type test equipment was made and the input and output torque, number of revolutions, temperature, noise, and state of lubrication were measured. With the same test equipment, the micro-traction-drive was compared to the equivalent type planetary gear with outer diameter of32 mm on the market. In comparison with commercially available speed reducers, the planetary gear system, the newly developed micro-traction was found to bear superior performance in terms of allowable transmission torque, efficiency, noise, and other characteristics.

Non-steady state effects on oil film thickness and traction forces

The purpose of this study is to know the change of oil film thickness and traction forces, when the difference of rotational speed of two traction drive rollers becomes unsteadily large by torsional vibration or machine trouble. The simultaneous measurements of optical film thickness and traction forces are performed to investigate the elastohydrodynamic lubrication (EHL) film formation under flooded conditions, on the crowned roller and glass disc interferometry apparatus. The measured profile and thickness of film are compared to the theoretical values given by the two dimensional non-steady thermal EHL calculation. The traction forces measured simultaneously on the crowned roller in the rolling direction are compared to one calculated by two dimensional non-steady thermal non-Newtonian model.

Development of Micro Traction Drive Modified From Tapered Roller Bearings

A small traction drive that diverted a tapered roller bearing was developed for trial purposes, and the performance was evaluated. We expect that gears as a small transmission cause some problems with decrease of their size, deterioration of accuracy on hobbing, grinding, and heat treatment, tooth profile and lead measurement method and their accuracy, decreasing permissible transmission torque and so on. Authors developed the small size transmission system named a micro traction drive in consideration of these situations. Micro traction drive is a transmission by using of modified rolling bearings in so much transmitted power 70W. The traction force is easily generated by pre-load between inner race and outer race as thrust force. The driving force is transmitted by the contact of retainer combined output shaft with the rolling element in rotating direction. Authors reported on the traction drive that based on the angular contact ball bearing with retainer as an output shaft, and it has succeeded in the deceleration from a super-high velocity revolution about the 2-stage micro traction drive. However the micro traction drive based on the angular contact ball bearing is easy to drive at high speed, the risk of seizure increase along with torque because the contact area between retainer and rolling element is in condition with point contact and pure sliding. Authors developed a micro traction drive, which can transmit larger torque using tapered roller bearing with line contact between retainer and rolling element, and operating behaviours were compared under large torque conditions. As a result, tapered roller bearing type micro traction drive transmits torque bigger than 1.5 or more times of angular ball bearing type micro traction drive after taking consideration for difference of outer diameter. Efficiency was also satisfactory at 80%∼90%. The contact surface of roller, retainer, inner race and outer race was good after operation, and so we report that possibility of utilization of a micro traction drive using tapered roller bearing.Copyright

Evaluation of ultra high speed micro traction drive

Micro traction drive is a device to transmit driving force modified from angular ball bearing. The micro traction drive consists of an input/inner ring, an outer ring, a rolling element, a retainer/output shaft, and a casing. In addition, the micro traction drive of the tandem type that combined two bearings was developed to obtain a big reduction ratio. As a result, we are able to attain the reduction ratio 7.3. Traction oil on the market was sealed in the test piece for oil bath lubrication. Input shaft could be driven with a motor in ultra high speed. Power absorbing type test equipment was made the efficiency and temperature of micro traction drive operated at high speed were successfully measured. In the result of measurement, temperature rise are a few and it turns out a micro traction drive can be used by ultra high-speed.Copyright

The Experimental and Analytical Evaluation of High Speed Bevel Gears.

To reduce the size of reduction gears where big power is transmitted through crossed shafts, it is necessary to increase rotational speed and decrease the transmitted torque and load. To know dynamic behaviour of high speed bevel gears, the experiments were carried out and tooth root stress and temperature were measured. Also a spiral bevel gear set analysis has been developed that makes use of mesh stiffness calculations based on finite-element methods. The analysis enables the calculation of dynamic loads. And then, the following results were obtained. (1) A power absorbing gear testing machine (960 kW) could be operated up to high pitch line velocity (∼110 m/s) and it is found that dynamic loads is nine times as much as static loads under the condition of 110 m/s. (2) Analytical results of dynamic load agreed with the experimental results. It was confirmed that the analytical method has practical accuracy and usefulness.

円筒ウォームギヤの歯面荷重分布解析法の研究 : 第2報,歯当り解析プログラムの作成

Judging from manufacturing errors and deflections under load, worm gears do not operate in their ideal relative positions. It is important to predict the load distribution considering tooth profile and setting error. A method for determining the load distribution, Hertzian contact pressure and oil film thickness is presented in this paper. Using our empirical formula for bending deflections, we developed the matrix of transformation. The deflection along the load direction on any point of a contact line at the same meshing position is expressed by the matrix of transformation. Using this matrix, the load distribution of a worm and wheel is evaluated with numerical analysis. It is obvious that the calculated results agree comparatively with experimental ones under actual operating conditions. With this calculating method, the effects of various types of misalignment on tooth contact are clarified.