The Rolling Bearing in the Electrified Power Train—Requirements and Solutions

Abstract

Climate change and global regulations for CO2 emission reduction are nowadays the drivers for the megatrend to E-mobility. Initiated with the hybridization of the power train the industry arrived today at the battery driven electric vehicle. Here one of the most important sub-assemblies is the E-axle, which consists of an electric machine and a reduction gearbox. Market requirements like rising power density, energy efficiency, maintenance free operation and cost efficiency require adequate technical solutions on component level. Especially the rolling bearing is subjected to high demanding operating conditions. High dynamics, poor lubrication, elevated temperature levels, risk of current leakage and others more need to be considered and call for a customized bearing design. For bearing dimensioning and development work on component level an SKF proprietary simulation software toolkit is available. By that it is possible to model the entire E-axle, to analyze the bearing reactions and to optimize the bearing components in terms of service life and efficiency. The simulation of cage deformation at high rotor speed is crucial to develop a high-speed cage design. The potential risk of electrical continuity which damages balls and raceways and reduce grease life, is another issue which asks for a technical solution. With the focus on bearing technology an E-axle and its specific operating conditions will be described, simulation tools and calculation results presented and the current SKF bearing portfolio for E-mobility applications introduced.