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 2006-01-0666 An Analytic Foundation for the Toyota Prius THS-II Powertrain with a Comparison to a Strong Parallel Hybrid-Electric Powertrain Jerome Meisel Georgia Institute of Technology Reprinted From: Advanced H ybrid Vehicle Powertrains 2006 (SP-2008) 2006 SAE World Congress Detroit, Michigan April 3-6, 2006 Downloaded from SAE International by Univ of Nottingham - Kings Meadow Campus, Sunday, August 12, 2018The Engineering Meetings Board has approved this paper for publication. It has successfully completed SAE's peer review process under th e supervision of the session organi zer. This process requires a minimum of three (3) reviews by industry experts. All 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]: 724-772-4028 Fax: 724-776-3036 For multiple print copies contact: SAE Customer Service Tel: 877-606-7323 (inside USA and Canada)Tel: 724-776-4970 (outside USA)Fax: 724-776-0790Email: [email protected] ISSN 0148-7191 Copyright © 2006 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 th e 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 publicat ion by SAE should send the manuscript or a 300 word abstract to Secretary, Engineering Meetings Board, SAE. Printed in USADownloaded from SAE International by Univ of Nottingham - Kings Meadow Campus, Sunday, August 12, 2018ABSTRACT Hybrid-electric powertrains for passenger vehicles and light trucks are generally being designed with two different configurations described as follows: The Toyota Hybrid System, THS-II, implemented in the 2004 Prius, the Lexus 400-H, and the Ford Hybrid Escape, is apower-split approach involving two electric machines and an internal combustion engine (ICE) mechanically coupled by a three-shaft planetary gear train. The second leading approach is a parallel hybrid-electric powertrain that generally includes a single electric machine and an ICE with a mating multi-ratio transmission. These parallel configurations are further divided as weak parallel and strong parallel. Honda uses a weak parallel powertrain in their Insight and Hybrid Civic. At Georgia Tech a strong (full), split-parallel hybrid powertrain has been implemented in a Ford Explorer. The vehicle is referred to as the Model GT. After presenting an analytic description of the THS-II operation, this paper then compares and contrasts the THS-II and Model GT powertrains outlining the advantages and disadvantages of each design. INTRODUCTION The main advantage of the Toyota THS-II powertrain over conventional powertrains with finite ratio transmissions is that the ICE speed is decoupled from the vehicle speed, giving an electrically controlled continuously variable transmission (CVT). However, there may be a penalty in mechanical energy loss that needs to be considered in choosing this design. This energy loss is due to the fact that a portion of the ICE output power may be routed through a mechanical to electrical to mechanical double energy mode conversion path in supplying driven-axle power from the engine. Also in other driving conditions, power must be supplied into the planetary system to obtain a desired engine speed. So the advantages of the electrical CVT in the THS-II system may be offset by added electric