Automotive Intermediate Shaft Design & Bearing Selection for a Propulsion Switched Reluctance Motor in a Battery Electric Vehicle

Optimized half-shaft design is paramount to deliver power from a drive unit and gearbox to the wheels of a vehicle. An intermediate shaft must be able to deliver rotational force to the wheel with acceptable efficiency to prevent any sort of torque losses or torque steer when coupled with another shaft. Intermediate shafts must be optimized for torque delivery, stiffness, weight, and efficiency relative to the CV shaft it is coupled to. For the unique switched reluctance motor that is utilized in this study, the shaft will be supported by a fixed housing in which a bearing will be affixed. It is critical that through these studies an attempt is made to optimize all these conditions by selecting the best materials as well as study the effects of having a tubular shaft as opposed to one that is solid using computer software. This analysis was completed with specific constraints in mind with respect to both shaft performance as well as packaging constraints. Processes include design for manufacturing, simulations of both shaft integrity and simulating motor behavior under high stress drive-cycle scenarios. As for bearing selection, a motor such as this has never been integrated in an automobile powertrain before, as such, the loads it will undergo must be studied to determine which bearing will work best in terms of load capabilities, life, and durability, as well as protection when exposed to outdoor elements at speed. The best solution for this application is using a tubular shaft made from 4130 steel supported by a spherical roller bearing.