400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 Web: www.sae.org 2005-01-1463 Comparison of Effi ciency Measurements and Simulation Resu lts for Automotive Traction Drives Farzad Samie and Burak Gecim General Motors Corporation Reprinted From: Transmissions and Drivelines Symposium–4WD/AWD (SP-1979) 2005 SAE World Congress Detroit, Michigan April 11-14, 2005 SAE TECHNICAL PAPER SERIESDownloaded from SAE International by American Univ of Beirut, Tuesday, July 31, 2018The Engineering Meetings Board has approved this paper for publication. It has successfully completed SAE’s peer review process under the supervision of the session organizer. This process requires aminimum of three (3) reviews by industry experts. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise,without the prior written permission of SAE. For permission and licensing requests contact: SAE Permissions 400 Commonwealth DriveWarrendale, PA 15096-0001-USAEmail: [email protected] Tel: 724-772-4028 Fax: 724-772-4891 For multiple print copies contact: SAE Customer ServiceTel: 877-606-7323 (inside USA and Canada)Tel: 724-776-4970 (outside USA)Fax: 724-776-1615Email: [email protected] ISSN 0148-7191Copyright © 2005 SAE International Positions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. A process is available by which discussionswill be printed with the paper if it is published in SAE Transactions. Persons wishing to submit papers to be considered fo r presentation or publication by SAE should send the manuscript or a 300 word abstract to Secretary, Engineering Meetings Board, SAE.Printed in USADownloaded from SAE International by American Univ of Beirut, Tuesday, July 31, 2018ABSTRACT Mechanical Efficiency of toroidal traction drives is the key parameter for transmission engineers worldwide to accept their use in continuously variable transmissions. In this work, the traction drive efficiencies are investigated analytically as well as experimentally as a function of speed, torque, speed ratio and temperature for two different CVU’s. In addition, creep at the traction contact is measured and compared with the prediction of the simulation model. In a stand-alone test rig, the drag torque associated with the power-roller thrust bearing is also measured. INTRODUCTION Traction drives, either in toroidal or in other embodiments, have been known for over a century [Heilich]. In the 1960's, a revolutionary CVT (Continuously Variable Transmission) employing a full- toroidal CVU (Continuously Variable Unit) was designed and tested at General Motors [Hewko]. There have been continuing efforts to improve the design of toroidal drives [Kraus], [Machida], [Fellows]. Tanaka et.al. had improved the design and development of half-toroidal drives, specifically in the area of ratio-change control [Tanaka, 1993, 1995]. More recently, the impact of optimized clamping on CVU efficiency is explored, [Gecim, 2004]. With the recent advancements in the areas of controls, material durability, and fluid rheology, the toroidal drives are once again considered as viable alternatives to the conventional step-gear transmissions. Rheological behavior of the traction fluid is a critical factor in the successful design and operation of toroidal drives. In this area, the investigations by Johnson and Tewaarwerk [Tewaarwerk, 1979,1980] are well known references. Winer and Bair reported measurements concerning lubricant limiting shear stress and glass transition [Bair, 1979a]. Recently published data for the new generation traction fluids show good high- temperature traction capacities, comparable to those achievable with Santotrac 50, an