High-Speed 50,000 rpm Planetary Roller Reducer for Electric Vehicles: Design and Transmission Efficiency Analysis

Abstract

Planetary rollers produce no meshing vibration and exhibit low noise, so that they are suitable for use as reducers for high-speed electric motors. On the other hand, at high rotational speeds of tens of thousands of rpm, there is a concern that the transmission efficiency may decrease due to oil churning resistance in the traction portion and the bearings, windage associated with the rollers, and rolling viscous resistance in the traction portion. However, accurate transmission efficiency at high rotational speeds has not been measured, and loss factors have not been analyzed. Therefore, a planetary roller prototype and a high-speed tester were designed and manufactured, and transmission efficiency measurements at speeds of up to 50,000 rpm were performed. In addition, a model was constructed to calculate the loss caused by the load and rotation of each part that configures the reducer, and the calculations were confirmed to agree well with the experimental results. It was clarified that the planetary roller prototype has a high transmission efficiency of up to 98%, that the decrease in efficiency is small even at high rotational speeds, and that the spin loss due to the bearings and churning is small.