400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-0790 Web: www.sae.org SAE TECHNICAL PAPER SERIES 2007-01-4152 The Hydrid Transmission Peter A. J. Achten Innas BV Commercial Vehicle Engineering Congress and Exhibition Rosemont, Illinois October 30-November 1, 2007 Downloaded from SAE International by Brought to you by the University of Texas Libraries, Sunday, August 05, 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 © 2007 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 Brought to you by the University of Texas Libraries, Sunday, August 05, 2018Copyright © 2007 SAE International ABSTRACT The Floating Cup principle strongly increases the efficiency of hydraulic pumps, motors and transformers. Recent tests have proven an efficiency of up to 98%. For automobiles and other vehicles, this opens the oppor-tunity for the ‘Hydrid’: a full hydraulic hybrid transmissionbetween engine and wheels. The Hydrid has in-wheelhydraulic motors, hydraulic transformers for variabletraction control and a common pressure rail includingaccumulators for power management and energyrecuperation. The Hydrid offers the same advantages ashybrid electric drive trains, but without the cost penalty. AVOIDING DOUBLE TROUBLE Hybrid electric vehicles are compromises. The puremechanical transmission (Figure 1) is unparalleled whenit comes to cost, weight and efficiency. On the otherhand, gear transmissions and even CVT’s lack flexibilityregarding energy management, energy transformationand energy storage. Electric systems are in this respectmuch more convenient, but the power density and theefficiency are too poor to make a full electric drivefeasible. For that reason a compromise has been foundin creating mixed or so-called hybrid configurations of mechanical and electric drive trains. However, if a flexible, non-mechanical transmission principle could be found which would have the sameperformance, cost and efficiency as the existingmechanical transmissions, there would be no reason forthis mixed ‘double trouble’ hybrid configuration. In thisarticle, a full hydrostatic all-wheel drive train is proposed,which eliminates the complete mechanical drive trainbetween the engine and the wheels. Figure 2 shows themain components of this hydraulic hybrid transmission,in this paper further referred to as the ‘Hydrid’ [1]. In the Hydrid, all wheels have an in-wheel hydraulic unit. The units have a constant displacement and can operate in 4 quadrants (both forward and reverse, in propulsionand braking mode), which means the units can operateas a motor and a pump. The traction is controlled bymeans of hydra