400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 Web: www.sae.orgSAE TECHNICAL PAPER SERIES 2004-01-1634 Ratio Changing the Continuously Variable Transmission John E. Mahoney General Motors Corporation–Retired Joel M. Maguire and Shushan Bai General Motors Corporation Reprinted From: Transmissi on & Driveline Symposium 2004 (SP-1817) 2004 SAE World Congress Detroit, Michigan March 8-11, 2004Downloaded from SAE International by Brought to you by the University of Kansas (Technical reports: 1998 to Present), Saturday, August 25, 2018All 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]: 724-772-4891Tel: 724-772-4028 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] ISBN 0-7680-1319-4Copyright © 2004 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 of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE.Printed in USADownloaded from SAE International by Brought to you by the University of Kansas (Technical reports: 1998 to Present), Saturday, August 25, 20182004-01-1634 Ratio Changing the Continuously Variable Transmission John E. Mahoney General Motors Corporation–Retired Joel M. Maguire and Shushan Bai General Motors Corporation Copyright © 2004 SAE International ABSTRACT The ratio changing mechanics of the continuously variable transmissions are developed. The lever analogy of gear sets, comparison to step gear transmission mechanics, differential calculus analysis, and the step gear ratio changing equations are used. Power on up- shifts, power on downshifts , power off up-shifts, and power off downshifts are analyzed. Approaches to minimize the disturbances are considered. INTRODUCTION The purpose of this paper is to provide an understanding of the ratio changing mec hanics of the continuously variable transmission. The transmission output torque changes affect vehicle acceleration and driver awareness. The focus is therefore on what happens to output torque during the ratio changing transient. The methods can also be used to determine the speeds and torques of the engine and any member of the transmission. The ratio changing mechanics of the step gear automatic transmission were presented in SAE paper 311A at the 1961 SAE International Congress (see figure 1). This paper builds on that effort by showing how the principles can be extended to the CVT. The lever analogy was presented in SAE 810102. Knowledge of both these papers is of great use in understanding CVT ratio changing mechanics. The step gear automatic transmission ratio changes have implicit torque and vehicle acceleration changes during the shift transient that have required engineering attention to make them acceptable to the vehicle operator. The CVT has advantages over the step gear transmission in the number of ratios available and the ability to change ratio in a continuous and smooth manner. The transmission engineer needs to know how these apparent advantages affe ct vehicle acceleration and how that understanding can be applied to improve operator acceptance. The lever analogy of gear sets and three approac