Influence of wheel bearing performance on In-wheel motor advanced applications

In-Wheel motor torque transmission concepts enable the realization of innovative solutions for the electric or hybrid new vehicle platforms. Protean Drive system integrates in the unused space behind the wheels and provides unique performances in terms of generated power, torque and compactness. The performance gain with respect to other more conventional arrangements is due to the full integration and synergies created with the mechanical components and in particular the wheel bearing. The final performance is connected to the ability of the wheel bearing to provide the required stiffness that controls the reduction of the air gap between the motor rotor and stator. This paper presents an overview of how the In-Wheel motor is connected to the chassis of the vehicle, through the wheel bearing, with special attention to the relationship between bearing stiffness and motor air-gap.