Bearing Ring Creep in EV Transmissions: Prediction and Prevention

Dr. Victor Brizmer

Summary

Lightweight design and higher power density are driving trends in electric vehicles (EVs). To meet these demands, EV motors are built for greater speed and torque, often using aluminum alloy housings as bearing seats in the power transmission system. A loose fit between the bearing outer ring (OR) and housing, used for easier assembly, can cause ring creep - a slow, unidirectional movement of the OR. Under high loads, this leads to significant wear on the softer housing, risking misalignment and damage to bearings and gears.

The present study identifies and examines the main wear mechanism occurring during ring creep in EV powertrains. A creep wear model based on the creep by strain mechanism has been developed with the SKF BEAST software, using friction and wear coefficients measured in an in-house Ring-on-Ring test. The predicted wear depth from the model aligned well with test results from the power transmission system. The study also presents solutions to mitigate ring creep wear.