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 2004-01-3027 ATF Friction Properties and Shift Quality T. M. Cameron Kettering University T. McCombs, M. Devlin, S. Tersigni and T.-C. Jao Afton Chemical Corporation Reprinted From: Oils , Rheology, Tribology, and Driveline Fluids (SP-1894) Powertrain & Fluid Systems Conference & Exhibition Tampa, Florida USA October 25-28, 2004Downloaded from SAE International by University of British Columbia, Saturday, July 28, 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 © 2004 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 University of British Columbia, Saturday, July 28, 2018 2004-01-3027 ATF Friction Properties and Shift Quality T. M. Cameron Kettering University T. McCombs, M. Devlin, S. Tersigni and T.-C. Jao Afton Chemical Corporation Copyright © 2004 SAE International ABSTRACT Multiple plate disk clutches are used extensively for shifting gears in automatic transmissions. In a shift from one gear to another one or more clutches is engaging or disengaging. In these active clutches the automatic transmission fluid (ATF) and friction material experience large changes in pressure P, temperature T, and sliding speed v. The coefficient of friction, µ, of the ATF and friction material depends on v, P and T, and also changes during clutch engagement. Changes in µ can lead to vibration and poor shift quality if the ATF and clutch friction material are improperly selected. An in-depth theoretical under standing of the cause of vibration in shifting clutches is crucial in the development of a suitable ATF to work with a particular friction material. To understand the relationship between ATF friction properties and shifting clutch vibration we present a theoretical model that identifies several possible causes: (1) self-excitation instability, (2) a reduction in friction holding torque during engagement, or (3) resonance caused by periodic pressure oscillations. The ATF and friction material properties that affect these sources of vibration include the friction level, µ, and the friction slopes with respect to sliding speed ∂ µ/∂v, pressure ∂µ/∂P, and temperature ∂µ/∂T. These properties must be carefully balanced to ensure that a clutch will deliver good shift quality and high torque capacity with effective vibration suppression. INTRODUCTION A vehicle powertrain experiences torsional, axial and bending vibrations that affect vehicle performance and occupant comfort. These vibrations and their effects are frequently referred to as noise, vibration and harshness (NVH). The numerous sources and transmission paths of NVH include engine firing pulses, valve motion, turbulent air flow, tire-road interactions and structural resonances at susceptible locations in the vehicle. Transfer path elemen