400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 SAE TECHNICAL PAPER SERIES 2001-01-3594 ATF Additive Effects on Hot Spot Formation in Wet Clutches Donn Fairbank BorgWarner Transmission Systems Kenji Maruo NSK-Warner Shuqin Du and Timothy Newcomb BorgWarner Transmission Systems International Fall Fuels and Lubricants Meeting and Exposition San Antonio, Texas September 24-27, 2001Downloaded from SAE International by Brought to you by the University of Texas Libraries, Sunday, August 05, 2018The appearance of this I SSN code at the bottom of this page indicates SAE’s co nsent that copies of the paper may be made for personal or internal use of spec ific clients. This consent is given on the condition, however, that the copier pay a per article copy fee through the Copyright Clearance Center, Inc. Operations Center, 222 Rosewood Drive, Danvers, MA 01923 for copying beyond that permitted by Sections 107 or108 of the U.S. Copyright Law. This consent does not extend to other kinds of copying such as copying forgeneral distribution, for advertising or promotional purposes, for creating new collective works, or forresale. Quantity reprint rates can be obtained from the Customer Sales and Satisfaction Department.To request permission to reprint a technical paper or permission to use copyrighted SAE publications in other works, contact the SAE Publications Group. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior wr itten permission of the publisher. ISSN 0148-7191 Copyright © 2001 Society of Automotive Engineers, Inc. Positions and opinions advanced in this paper are those of the aut hor(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. A process is available by whic h discussions will be printed with the paper if it is p ublished in SAE Transactions. For permission to publish this paper in full or in part, contact the SAE Publications Group. Persons wishing to submit papers to be c onsidered for presentation or publication thr ough SAE should send the manuscript or a 3 00 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE. Printed in USAAll SAE papers, standards, and selected books are abstracted and indexed in theGlobal Mobility DatabaseDownloaded from SAE International by Brought to you by the University of Texas Libraries, Sunday, August 05, 20182001-01-3594 ATF Additive Effects on Hot Spot Formation in Wet Clutches Donn Fairbank BorgWarner Transmission Systems Kenji Maruo NSK-Warner Shuqin Du* and Timothy Newcomb BorgWarner Transmission Systems Copyright © 2001 Society of Automotive Engineers, Inc. * Now at Andrew Corporation ABSTRACT Wet clutch interfaces that operate in high-energy environments experience significant frictional heating. Under such conditions, thermoelastic or thermoplastic instabilities may lead to a transition from evenly distributed surface contacts to unevenly distributed regions that manifest themselves as hot spots on the separator plate. The critical power at which these instabilities occur depend on the thermal conductivity, thermal expansion, and stiffness of the components. Modeling has shown that for wet clutch interfaces the stiffness of the friction material has a dominant influence on the critical power. We have found that the lubricant additive package also plays a significant role in the onset of hot spots. I n this paper, we report the influence of antiwear systems on the occurrence of hot spots. INTRODUCTION HOT SPOT PHENOMENA I N WET CLUTCHES - During a heavy throttle wet clutch engagement in an automatic transmission, the sliding interface between the friction material and the separator must absorb a large amount of energy in a very short time. Any distortion or perturbation in this slipping interfa