Non-Newtonian mixed elastohydrodynamics of differential hypoid gears at high loads

Abstract

Prediction of friction and transmission efficiency are design objectives in transmission engineering. Unlike spur and helical involute gears, there is a dearth of numerical analysis in the case of hypoid gear pairs. In particular, it is important to take into account the side leakage of the lubricant from the contact as the result of the lubricant entrainment at an angle to the elliptical contact footprint. In the automobile differential hypoid gears, high loads result in non-Newtonian behaviour of the lubricant, which may exceed its limiting shear stress, a fact which has not been taken into account in the open literature. This results in conditions which deviate from observed experimental tractive behaviour. The paper takes into account these salient practical features of hypoid gear pair analysis under high load. It highlights a non-Newtonian shear model, which limits the lubricant shear behaviour. Prediction of friction and transmission efficiency is in line with those reported in the literature.