Ceramic Bearing Endurance Within a Transmission

Abstract

Abstract Fully ceramic bearings have been demonstrated to provide a forty to fifty percent reduction in weight over steel bearings. They can also provide improved reliability due to increased corrosion protection. One of the primary challenges to incorporating ceramic bearings is the coefficient of thermal expansion mismatch between the ceramic bearing races and its mating surfaces. The application of a tolerance ring was developed to address these challenges. The tolerance ring was applied between the inner bearing race and the pinion shaft to retain the race and absorb the thermal expansion differences, while maintaining an acceptable fit across the thermal operating range. The application of a ceramic bearing within a transmission was evaluated through a 300-hour endurance experiment. The experiment transmitted shaft speeds and torques through the transmission with a vertical load. The ceramic bearing successfully transmitted torque and speed through the duration of the experiment, and vibration did not increase over time. This experiment gives confidence that fully ceramic bearings may be utilized to improve power density and corrosion resistance. In addition, this experiment also demonstrated the ability of the newly commissioned Vehicle Innovative Powertrain Experimental Research facility at Aberdeen Proving Ground, Maryland to successfully perform experiments with novel technologies incorporated into a transmission.