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. (1) 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 (1). 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 $10mm$ inner diameter, $30mm$ outer diameter, and $9mm$ 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 of $32mm$ 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.