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 2003-01-3258 Development of New Automatic Transmission Fluid for Fuel Economy Kazuo Yamamori, Koji Saitou, Yasu shi Kobiki and Akiyoshi Ogawa Toyota Motor Corp. 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 Nottingham - Kings Meadow Campus, Saturday, August 11, 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: Customer [email protected] 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 Nottingham - Kings Meadow Campus, Saturday, August 11, 20182003-01-3258 Development of New Automatic Transmission Fluid for Fuel Economy Kazuo Yamamori, Koji Saitou, Yasushi Kobiki and Akiyoshi Ogawa Toyota Motor Corp. Copyright © 2003 SAE International ABSTRACT It is important to reduce the viscosity of automatic transmission fluid (ATF) in order to improve fuel economy. However, in general, low viscosity fluid can cause metal fatigue, wear, and seizure. It is necessary to increase the viscosity of the fluid at higher temperatures to maintain the durability of the automatic transmission (AT). The key point is the selection of the base oil and the viscosity index improver (VII) with both a high viscosity index (VI) and excellent shear stability. On the basis of this concept, a new generation high performance ATF named WS was developed. WS can achieve the highest level of fuel economy, while maintaining the durability of the AT. INTRODUCTION In recent years, the improvement of vehicle fuel economy has become a very important issue for global environmental protection in order to reduce CO 2 emissions and improve energy savings. Therefore, we have already developed ATF:T4 for the AT with a slip-controlled lock-up clutch system [1] and continuously variable transmission fluid (CVTF) for the continuously variable transmission (CVT) [2]. However, additional improvements in fuel econom y are desired. One of the most effective means of improving the transmission efficiency is to reduce the torque loss in the AT. Churning loss and friction loss occur in a start-up condition of the AT and play a key role in the torque loss of the AT. The churning loss and friction loss are largely determined by the viscosity of the ATF. Low viscosity ATF reduces the torque loss and improves transmission efficiency as shown in Figure 1. The low viscosity ATF has been studied and the effect on fuel economy has been reported [3]. However, too low a viscosity at high temperature can decrease the fatigue life of metals and increase oil leakage from the hydraulic control systems or oil seals. Therefore, it is required to reduce the viscosity as much as possible, while