400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 Web: www.sae.org SAE TECHNICAL PAPER SERIES 2003-01-3255 ATF Effects on Friction Stability in Slip-Controlled Torque Converter Clutches Timothy M. Cameron Mechanical Engineering Virginia Commonwealth University Samuel H. Tersigni, Tracy McCombs and Tze-Chi Jao Ethyl Petroleum Additives, Inc. Reprinted From: Lubri cants, Rheology and Tribolog y, and Driveline Fluids (SP–1810) Powertrain & Fluid Systems Conference & Exhibition Pittsburgh, Pennsylvania USA October 27-30, 2003Downloaded from SAE International by Univ of California Berkeley, Friday, July 27, 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: permissions@sae.orgFax: 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: Customer Service@sae.org ISSN 0148-7191Copyright © 2003 SAE InternationalPositions 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 discussions will be printed with the pap er if it is publishe d in SAE Transactions. Persons wishing to submit papers to be considered for presentation or publication by SAE should send themanuscript or a 300 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE. Printed in USADownloaded from SAE International by Univ of California Berkeley, Friday, July 27, 20182003-01-3255 ATF Effects on Friction Stability in Slip-Controlled Torque Converter Clutches Timothy M. Cameron Mechanical Engineering Virginia Commonwealth University Samuel H. Tersigni, Tracy McCombs and Tze-Chi Jao Ethyl Petroleum Additives, Inc. Copyright © 2003 SAE International ABSTRACT A model of an automotive powertrain equipped with a slip-controlled torque converter clutch (TCC) is presented that incorporates the clutch control system and the friction-related properties of the automatic transmission fluid (ATF) and cl utch friction material. Prior research has established that stability of a s lip-controlled TCC is enhanced by maintaining a positive slope of the coefficient of friction, µ, with respect to sliding speed, v. The model presented here agrees with this result, but suggests that it is neither a necessary nor sufficient condition guaranteeing stability. The model indicates that other factors affectin g stability at the equilibrium sliding speed include the magnitude of µ, the engine speed, the engine torque-speed slope, the ATF pressure, and the time constants of the clutch control system. This model will aid in the development of future wet clutch systems with improved friction stability performance. 1. INTRODUCTION Long-prevailing opinion has been that the slope of the coefficient of friction, µ, with respect to sliding speed, v, is the primary if not sole dete rminant of friction stability in slip-controlled torque converter clutches. This dependence of friction stability on µ-v slope is supported both by experiment and by mathematical powertrain models. Experimental evidence suggests, however, that other factors may affect stability, including the magnitude of µ, engine speed, pressu re and temperature of the automatic transmission fluid (ATF), as well as time constants associated with the clutch control system. Torque converters have been used for decades in automatic transmissions. Advantages of the torque converter include: decoupling of the engine from the driveline during idling,