Title: On the mechanical efficiency of continuously variable transmissions with planetary gear trains

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

Addresses: Department of Mechanical Engineering, National Cheng Kung University, Tainan, Taiwan 70101, ROC. ' Department of Mechanical Engineering, National Cheng Kung University, Tainan, Taiwan 70101, ROC

Abstract: A continuously variable transmission (CVT) consists of one planetary gear train (PGT) with two degrees of freedom and one continuously variable unit (CVU). Based on the concept of fundamental circuits, static equilibrium, and frictional loss, we present a systematic approach for the analysis of mechanical efficiency of CVT. By applying the technique of optimization, we synthesize CVT, subject to certain design constraints, with maximum mechanical efficiency. As a result, we conclude that: (1) a CVT with maximum mechanical efficiency is of input-coupled type, (2) the mechanical efficiency of a CVT depends only on its allowable maximum speed ratio (Rv)aoω and range of gear ratio, and (3) the mechanical efficiency of a CVT can only be improved by increasing (Rv)aoω the efficiency of PGT (ηpg), and the efficiency of CVU (ηv) for a fixed range of gear ratios.

Keywords: continuously variable transmission; CVT; continuously variable unit; CVU; frictional loss; fundamental circuit; planetary gear train; static equilibrium; gear ratios; vehicle design.

DOI: 10.1504/IJVD.1990.061615

International Journal of Vehicle Design, 1990 Vol.11 No.2, pp.176 - 187

Published online: 26 May 2014 *

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