SA E TECHNICAL PAPER SERIES The Engineering Society =For Advancing Mobility and sea ~ir and Space, New Transmission Control System for Bulldozers Makoto Toyama and Yoshikazu Asai Komatsu Ltd. Y-u-yL International Off-Highway & Powerplant Congress & Exposition Milwaukee, Wisconsin September 14-17,1992 400 COMMONWEALTH DRIVE, WARRENDALE, PA 15096-0001 U.S.A. Downloaded from SAE International by University of British Columbia, Sunday, August 19, 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. Thisconsent is given on thecondition, however, that the copier pay a$5.00 per article copy fee through the Copyright Clearance Center, Inc. Operations Center, 27 Congress St., Salem, MA 01970 for 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. All SAE papers, standards, and selected books are abstracted and indexed in the SAE 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. lSSN 0148-7191 Copyright 1992 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 Division. 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 Downloaded from SAE International by University of British Columbia, Sunday, August 19, 2018ABSTRACT A new transmission control system which realizes almost the same high level of operability as of a TORQFLOW (TIF) transmission (see Note 1) has been developed and introduced on an efficient HYDROSHIFT (HIS) transmission (see Note 2) for bull- dozers. To develop the system, comparison and evaluation were made between HIS transmission ma- chines without torque converter and TIF transmission machines with torque converter to ascertain the advan- tages and disadvantages of HIS transmission machines. As a result, the disadvantages inherent to HIS trans- mission machines, such as poor shifting characteristics, fine travel characteristics at low travel speed, and anti engine-stall characteristics were solved by electronically and synthetically controlling all clutches including those incorporated into the steering brake system, without sacrificing any advantages. Concerning the excess thermal load applied on the transmission clutch at ForwardIReverse (FIR) direc- tional change, the new system greatly lowers the thermal load on the clutch by interlocking the transmission and steering brakes to share the load, making it possible to reduce the transmission size. In addition, the system effectively lowers peak torque and shock at shifting, realizing excellent shifting characteristics compared with conventional models. An additional benefit of electronic control is that this system has an abnormality diagnostic function leading to reduced machine downti