Design considerations and simulation of a rolling-contact gearless automotive differential

Abstract

This paper presents the design considerations, the kinematical simulation and the FE analysis of a differential mechanism which involves the rolling contact of two cam-track disks with four equally-spaced spherical rollers sliding in a cage much resembling a rolling bearing. The obvious benefit of this concept in the field of power transmissions is the potential replacement of gears in planetary reducers and differentials by cams. The side gears of a conventional open differential are replaced by two identical cam-track disks, while the spider gears are replaced by rolling elements that is, balls, cylinders or tapered cylinders. Practically, the well-known rolling bearing concept is generalized, where the circular tracks are replaced by wavy curves. In order to assess the performance of the mechanism, the shape of the tracks is considered for two distinct cases and a rigorous mathematical modeling follows regarding the kinematics of the mechanism. The results were validated through kinematical simulations and FE analysis was carried out coupled with fatigue life computation for a typical passenger vehicle differential, indicating that service life in the order of 200,000 km is feasible.