Comparison of the Dynamics of Conventional and Worm-Gear Differentials

Abstract

The differential mechanism has been used for many years and a variety of unique designs have been developed for particular applications. This paper investigates the performance of both the conventional bevel-gear differential and the worm-gear differential as used in vehicles. The worm-gear differential is a design in which the bevel gears of the conventional differential are replaced by worm gear/worm wheel pairs. The resultant differential exhibits some interesting behavior which has made this differential desirable for use in high performance and off-road vehicles. In this work, an Euler-Lagrange formulation of the equations of motion of the conventional and worm-gear differentials allows comparison of their respective behavior. Additionally, each differential is incorporated into a full vehicle model to observe their effects on gross vehicle response. The worm-gear differential is shown to exhibit the desirable characteristics of a limited-slip differential while maintaining the conventional differential’s ability to differentiate output shaft speeds at all power levels.