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 2003-01-0248 A Five-Speed Starting Clutch Automatic Transmission Vehicle Chi-Kuan Kao, Anthony L. Smith and Patrick B. Usoro General Motors Corp. Reprinted From: Transmission & Driveline System s Symposium 2003 (SP-1760) 2003 SAE World Congress Detroit, Michigan March 3-6, 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 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 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, 2018ABSTRACT A wet multi-plate clutch, designated as the “s tarting clutch”, is used to replace the torque converter in the automatic transmission in order to improve vehicle fuel economy. The transmission ratio spread must be increased to compensate for the torque multiplication of the torque converter and avoid p enalizing the 0 -60 mph acceleration performance. The main challenge of this concept is the control of the starting clutch to ensure acceptable vehicle drivability. This paper describes the system of a five -speed starting clutch automatic transmission vehicle and shows vehicle test results. Vehicle test data show that (i) the fuel economy benefit of the starting clutch is significant, and (ii) a starting clutch transmission can be designed to equal or better the 0 -60 mph acceleration performance of a torque converter transmission by proper selection of the gear ratios. INTRODUCTION A torque converter is a hydro-mechanical device that connects the engine with the trans mission in an automatic transmission. The function of the torque converter is to provide fas t and smooth vehicle launch through its torque multiplication and driveline torsional damping capabilities. One major drawback of the torque converter is its relatively lower efficiency over the operating cycle. The torque converter efficiency can be improved by controlling the torque converter slip with a torque converter clutch (TCC) [1]. Further efficiency improvement can be achieved by replacing the torque converter with a wet clutch [2], designated as the “starting clutch”. The torsional damper spring is retained for its primary function of filtering engine-firing pulses when the clutch is locked. A viscous converter clutch (VCC) [3] is also used in some passenger cars to lockup torque converter clutch early with viscous damping to improve fuel economy without sacrificing drivability. A viscous converter clutch is a torque converter clutch with a viscous damper located between the torque converter clutch and turbine to improve drivability by damping engine torque fluctuation when early lockup the torque converter clutch [3]. Its drawback is that it adds addi