Maximum acceptable differential speed ratio of lateral torque-vectoring differentials for vehicles

Abstract

A lateral torque-vectoring differential consists of a slip clutch for torque vectoring from right to left, another slip clutch for torque vectoring from left to right, differential gears, and some planetary gears which generate the differential speeds of the slip clutches. The present authors introduced a design parameter, namely the maximum acceptable differential speed ratio, and showed that the design parameter is very useful to analyse the lateral torque-vectoring differentials. The minimum of the design parameter is determined by the vehicle driving condition in which the torque-vectoring differential should be activated. In order to find the most appropriate value of the design parameter, this paper studies possible influences — namely the vehicle track, vehicle cornering radius, dynamic tyre radius difference between right and left wheels, lateral torque vectoring, and tyre—road friction characteristic — on the maximum acceptable differential speed ratio. As a result, the lateral torque vectoring and tyre—road friction characteristic should be considered as much as the vehicle track or cornering radius; meanwhile the dynamic tyre radius variation is negligible. Finally, a determination method for the maximum acceptable differential speed ratio is proposed.