Measurement of the transmission performance of traction drives and gears (Comparison of performance at 50000 rpm)

Abstract

A high speed electric motor with a small reducer and high power transmission efficiency realizes a powertrain system with high power density because electric motors can be miniaturized to increase the rotational speed. The transmission performance and behavior of meshing gears or traction drive transmission elements with a high-speed reducer have not been clarified at such high rotational speeds due to experimental difficulty. Therefore, a high-speed transmission tester was designed and built to enable experiments at 50,000 rpm, without the use of special motors or measuring instruments, by increasing the speed using the ratio of the test roller or gear radii. The measurement results almost agree with the known values and trends, confirming that this tester can be used to perform measurements at high speed. Because the traction coefficient and transmission efficiency do not decrease drastically at high rotational speed, discontinuity was not found in the mechanism of traction expression. At high rotational speed and low torque, a traction drive has a higher transmission efficiency than that of gears, and this is more pronounced at higher rotational speed. At low speed and high torque, gears are more efficient. Therefore, this study demonstrates that gears are suitable as transmission reduction elements below 25,000 rpm, and traction drives are suitable for rotation speed reduction above 25,000 rpm.

Keywords

• traction drive
• high speed
• transmission
• tribology
• gear
• electric vehicle