As the trend shifts from Internal Combustion Engine (ICE) vehicles to Electric Vehicles (EVs), the operating speeds of prime movers have significantly increased. Commercial EV manufacturers prefer high-speed, low-torque motors coupled with transmissions over low-speed, high-torque motors due to higher efficiency and power density. This combination of high-speed, low-torque motors coupled with transmission is essential for achieving the required gradeability and enhances operational efficiency. However, the increased operating speeds of these EV transmissions have inherently increased the risk of ‘bearing creep’.
The “bearing creep” is the phenomenon where unintended relative motion occurs between bearing races and their mounting surfaces, leading to premature wear of mounting surfaces. This issue can lead to a series of failure modes such as increased gear mesh misalignment, bearing damage, seal damage, etc. These problems result into elevated transmission vibrations eventually leading to premature transmission system failure. Notably, bearing creep tends to be more severe in aluminum enclosures compared to those made of cast iron or steel, owing to greater difference in the coefficient of thermal expansion of aluminum and bearing steel.
This paper presents a comprehensive methodology to mitigate the bearing creep. This paper comprises of concept trade-off, design of experiments (DOE), parameter optimization, and design validation. Initially, the paper explores various potential solutions through concept trade-offs to identify the most effective solution to mitigate the bearing creep. A systematic DOE is then conducted to comprehend influence of different parameters on bearing creep resistance. A transfer function is generated to model the relationship between key design parameters and bearing creep resistance. Subsequently, parameter optimization techniques are applied to fine-tune the design, ensuring maximum resistance to creep. Finally, the optimized design is validated through testing for its performance. This study aims to demonstrate O-ring utilization as an effective anti-rotation feature for high-speed bearings in EV transmissions.