SAE TECHNICAL PAPER SERIES Development of Hydromechanical Transmission (HMT) for Bulldozers Hiroyuki Mitsuya, Keiji Otani, Tsutomu Ishino, Ryouichi Maruyama, and Toshiyuki Akasaka Ksmatsu Ltd. The Engineering Society mA =For Advancing Mobility and Sea Air and Space, International Off-Highway & Powerplant Congress & Exposition Milwaukee, Wisconsin September 12-1 4, 1994 400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (41 2)776-4841 Fax:(412)776-5760 Downloaded from SAE International by University of New South Wales, Sunday, September 16, 2018The appearance of the ISSN code at the bottom of this page indicates SAE's consent that copies of the paper may be made for personal or internal use of specific clients. This consent is given on the condition, however, that the copierpaya $6.00perarticle copy fee through the Copyright Clearance Center, Inc. Operations Center, 222 Rosewood Drive, Danvers, MA 01 923for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent does not extend to other kinds of copying such as copying for general distribution, for advertising or promotional purposes, for creating new collective works, or for resale. SAE routinely stocks printed papers for a period of three years following date of publication. Direct your orders to SAE Customer Service Department. To obtain quantity reprint rates, permission to reprint a technical paper or permission to use copyrighted SAE publications in other works, contact the SAE Publications Group at (412) 776-4841. All SAE papers, standards, and selected books are abstracted and indexed in the Global Mobility Database. No part of this publication may by reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. ISSN 0148-7191 Copyright 1994 Society of Automotive Engineers, Inc. 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 paper if it is published in SAE transactions. For permission to publish this paper in full or in part, contact the SAE Publications Group. Persons wishing to submit papers to be considered for presentation or publication through SAE should send the manuscript or a 300 word abstract of a proposed manuscript to: Secretary, Engineering Activity Board, SAE. Printed in USA 90-1 ~~CIPG Downloaded from SAE International by University of New South Wales, Sunday, September 16, 2018Development of Hydromechanical Transmission (HMT) for Bulldozers Hiroyuki Mitsuya, Keiji Otani, Tsutomu Ishino, Ryouichi Maruyama, and Toshiyuki Akasaka Komatsu Ltd. ABSTRACT Conventional medium to large-sized bulldozers have a powertraincomprisedof a manually operated powershift transmission connected in series with a torque con- verter. There is a growing need, however, for a power train that is more efficient and easy to operate, thereby increasing bulldozer productivity. One answer to this growing demand is the hydromechanical transmission (HMT) developed by Komatsu for medium to large-sized bulldozers. The HMT consists of a powershift transmission combined in parallel with a hydrostatic transmission (HST) featuring a pair of hydraulic units. The HMT has a continuously variable shifting ratio and achieves high efficiency and automatic shifting. Additionally, it has an electronic controller that controls the transmission ratio to maintain engine speed at the maximum power point. As a result, bulldozers with the HMT demonstrate greatly improved productivity over bulldozers with the conventional powertrain. Furthermore, automatic shifting releases the operator from shifting operation, allowing the opera- tor to concentrate on operating the work equipment and thereby reducing operator fatigue. This paper explains t