SA E TECHNICAL PAPER SERIES Hydraulic Brake Control System for Off- Highway Vehicles James Kunz Komatsu-Dresser Co. Reprinted from: Vehicle Hydraulic Systems and DigitaliEiectrohydraulic Controls (SP-882) The Engineefiing Society Advancing m,,ity International Off-Highway & Powerplant --'r.nd % ~ir and space8 Congress and Exposition INTERNATIONAL Milwaukee, Wisconsin September 9-1 2,1991 400 COMMONWEALTH DRIVE, WARRENDALE, PA 15096-0001 U.S.A. Downloaded from SAE International by University of British Columbia, Tuesday, September 25, 2018Ths~tndudedrir th6 dume are abstrsfled and indexed in the SAE GWml MobIRy Lbtabase No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. ISSN 0148-71 91 Copyright 1991 Society of Automotive Eug~neers, Inc. Positions and opinions advanced in this paper are Persons wishing to submit papers to be considered for those of the author(s) and not necessarily those of presentation or publication through SAE should send SAE. The author is solely responsible for the content of the manuscript or a 300 word abstract of a proposed the paper. A process is available by which discussions manuscript to: Secretary, Engineering Activity Board, will be printed with the paper if it is published in SAE SAE. Transactions. For permission to publish this paper in full or in part, contact the SAE Publications Division. Printed in U.S.A. Downloaded from SAE International by University of British Columbia, Tuesday, September 25, 2018Hydraulic Brake Control System for Off- Highway Vehicles James Kunz Komatsu-Dresser Co. ABSTRACT In February of 1987, Dresser introduced a pair of new mechanical drive, off-highway trucks designed to operate in the 35 to 60 ton, rear-dump, classes. These trucks, designated 140M and 210M, replaced three previous models while covering the same payload range. One distinctive feature of these new vehicles was their hydraulic system and in particular the brake control portion of this system. This new hydraulic brake control system can be described as a closed-center arrangement using a pressure-compensated, variable displacement pump as an energy source with accumulator -based energy reserves for independent and redundant circuits. In the basic version, a pair of pressure regulating valves are used to control system pressure at the brakes. These valves can be actuated in FIGURE 1. DRESSER 210M HAULPAK DUMP TRUCK tandem by a treadle (foot pedal) or separately by hydraulic pilot pressure. A single, filtered hydraulic fluid is used throughout the system and is stored in a single reservoir vented to atmosp here. The basic system is capable of accommodating multiple-axle (i.e. more than two) arrangements but was originally applied to a two-axle vehicle using dry, disc-type (caliper and rotor) brakes on all wheels. In February of 1990, the Model 140M and 210M trucks were revised to offer rear axle oil-cooled brakes as an option. The brake control system was subsequently modified to provide for this change primarily by the use of an additional pressure regulating valve and redundant circuitry. Both the original and latest versions of this system are characterized by their use of a unique emergency brake control system. Through the use of logic-type control valves, a loss of hydraulic pressure in one circuit is used to force the remaining high pressure circuits into actuating the brakes. This paper will describe the arrangement and operation of this hydraulic brake control system and its function as an integral part of the overall vehicle hydraulic system. BACKGROUND Traditionally, off -highway vehicle brake systems have been complex and expensive often due to the use of compressed air and hydraulic oil in combination with redundant circuitry to provide for various methods of actuating the brakes in dif