Advances in Automobile Engineering
Open Access

Performance comparison of half and full toroidal traction drive CVTs

2^nd International Conference and Exhibition on Automobile Engineering

December 01-02, 2016 Valencia, Spain

Rathindranath Maiti, Kumar Shanu and Vineet Sahoo

Indian Institute of Technology, Kharagpur, India

Posters & Accepted Abstracts: Adv Automob Eng

Abstract :

Toroidal CVT is an ideal automotive transmission system in terms of simplicity, fuel economy and performance. It consists of two discs forming a toroidal cavity and a power roller enclosed in a casing containing lubricant at very high pressure. In order to get the CVT with lesser mechanical losses, efficiencies of full-toroidal and the half-toroidal drives are estimated analytically. The present investigation aims at establishing the design guidelines for the geometry and dimension parameters of this CVT layout for uniform axial loading and optimal ratio range. First a kinematic analysis is done in order to find the speed ratios followed by the dynamic analysis where forces on different parts are analyzed. For estimating the torque losses through the bearings, the SKF model for the frictional torque calculation (in case of ball /roller bearing) or hydrodynamic lubrication theory (in case of journal bearing), is used. These frictional torque losses are distributed among the input and output shafts depending upon the ratios of the final input and output torque. A fully developed isothermal fluid film contact model between the discs and rollers, based on the results of EHL theory, is used to evaluate the slip and spin losses. With this method, the traction coefficient and slip can be predicted within 10% accuracy which makes the optimum control of the normal force of the power transmitting contact of a toroidal CVT. The effects on efficiency due to variation in traction drive parameters (half cone angle, cavity radius, fluid property) are also found out.

Biography :

Email: rmaiti@mech.iitkgp.ernet.in