Title: On the bias ratio of automotive worm-gear differentials

Authors: L.-C. Hsueh, H.-S. Yan

Addresses: Dept. of Power Mechanical Engineering, National Yunlin Polytechnic Institute, Huwei, Yuenlin, Taiwan. ' Dept. of Mechanical Engineering, National Cheng Kung University, Tainan, Taiwan

Abstract: An automotive worm-gear differential, which has the limited-slip action, is a planetary worm-gear train with two degrees of freedom. Bias ratio of an automotive gear differential is the output torque ratio of the low-speed shaft to the high-speed shaft. We derive mathematical expressions for bias ratios and mechanical efficiencies of automotive worm-gear differentials. The results shows that: (1) an alternative worm-gear differential will be locked up when making a turn of its sun gear is adjacent to the input shaft; (2) the desirable automotive worm-gear differential is the one with two worm-gear pairs and with its carrier adjacent to the input shaft; (3) the bias ratio of the desirable worm-gear differential is over 3; and (4) the bias ratio of a worm-gear differential is the smallest if the helical angle is 45°.

Keywords: worm-gear differentials; bias ratios; kinematic design; latent power; planetary gear trains; train value; automotive gear differentials; helical angle; vehicle design.

DOI: 10.1504/IJVD.1993.061836

International Journal of Vehicle Design, 1993 Vol.14 No.2/3, pp.212 - 225

Published online: 28 May 2014 *

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