Half-Toroidal Traction Drive Continuously Variable Transmission for Automobile Propulsion Systems (Traction Drive Materials, Transmission Design and Efficiency)

Environmental issues such as exhaust emission have stimulated the development of a flexible transmission for an engine-vehicle propulsion system. The authors have been researching and developing the rolling-type CVT, continuously variable transmission, of a half-toroidal traction drive for about 14 years. It represents engineering achievement in the fields of heat treatment technology of rolling elements which transmit tangential force at a maximum Hertzian pressure of 2.7 GPa, and of molecular design technology of synthetic traction fluid which works in the temperature range of -30 to 140°C. The paper shows the design principle of rolling element fatigue life and shear strength of traction fluid at high temperature, and discusses the performance of two types of CVTs of a single cavity with 80kW and a double cavity with 200 kW transmission capacity.