The Engineering Meetings Board has approved this paper for publicat ion. It has successfully completed SAE’s peer review process under the supervision of the session organizer. 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 o r by any means, electronic, mechanical, photocopying, recording, or otherwi se, without the prior written permission of SAE. ISSN 0148-7191 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. SAE Customer Service: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: [email protected] SAE Web Address: http://www.sae.org Printed in USA 2009-01-1332 Development of New Hybrid System for Compact Class Vehicles Takuji Matsubara, Hideaki Yaguchi, Toshifumi Takaoka and Kunihiko Jinno Toyota Motor Corp. Copyright © 2009 SAE International ABSTRACT Toyota has been evolving a hybrid system since introducing the first mass-production hybrid vehicle in 1997 in response to the increasing automotive-related issues of CO2 emissions, energy security, and urban air pollution. This paper descri bes a newly developed hybrid system design and its perform ance. This system was developed with the main purpose to improve fuel consumption, especially for better real world fuel consumption; and to enhance its compatibility with multiple vehicle adoption by downsizing and reducing the weight of its components. At the same time, the hybrid system achieved improved power performance while satisfying stringent em ission regulations in the world. INTRODUCTION After the industrial revolution in the 19th and 20th centuries, automobiles hav e greatly contributed to humankind’s prosperity, and will continue to be an important factor in sustai ned development. On the other hand, in order to save energy resources and prevent global warming, there has been a pressing need in recent years to improve the fuel consumption of automobiles, thereby reducing CO2 emissions. At the same time, urban areas are facing a serious problem of air quality, prompting the enforcement of stricter automobile exhaust emission regulations worldwide. Under these circumstances, the hybrid vehicle draws attention as a system compatible with the improvement of fuel economy and the reduction of exhaust emissions. Toyota introduced the first mass production hybrid vehicle in 1997 with Toyota Hybrid System (THS). The vehicle achieved 100% fuel economy improvement, met stringent emission regulati ons around the world, and penetrated into the market as an environmentally friendly vehicle. The Toyota hybrid system was improved in 2003 not only in fuel economy and emissions, but also in power performance; and has had a good reputation in the market. This paper describes a newly developed hybrid system, its low fuel consumption technologies, and downsizing technology of each powertrain component. 1. OBJECTIVE OF THE DEVELOPMENT This Current hybrid vehicles have achieved the fuel consumption of about one hal f that of conventional vehicles at the drive cycle te sting; with Federal Test Procedure mode of the United States, Urban Driving Cycle (UDC) and Extra Urban Driving Cycle (EUDC) of Europe, and 10-15 mode of Japan all simulate urban driving. Improving the urban fuel consumption becomes possible by idle stop, regenerative braking, and EV (Electric Vehicle) drive at lo w road load; all of which are basic functions of hybrid v ehicle. However, it has been noted that hybrid systems do not maintain the same fuel consumption improvement dur