SAE TECHNICAL PAPER SERIES Analysis of a New Automatic Transmission Control System for LEXUS LS400 Hiroji Taniguchi and Yasushi Ando Toyota Motor Corp. Reprinted from SP-854 - Automotive Transmission Advancements The Engineering Society EA =For Advancing Mobility Jr(lC and sea ~ir and space, International Congress and Exposition Detroit, Michigan February 25-March 1,1991 400 COMMONWEALTH DRIVE, WARRENDALE, PA 15096-0001 U.S.A. Downloaded from SAE International by University of New South Wales, Tuesday, September 18, 2018The pcpem induded in thS wlum are &traded and indexed in the SAE G@wI M&ty Database. 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 01 48-71 91 Copyright 1991 Society of Automotive Engineers, Inc. Positions and opinions advanced in this paper are Persons wishing to submit papers to be considered for those of the author@) 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 New South Wales, Tuesday, September 18, 2018Analysis of a New Automatic Transmission Control System for LEXUS LS400 Hiroji Taniguchi and Yasushi Ando Toyota Motor Corp. ABSTRACT 1. The shift quality should be very smooth A new automatic transmission, engineered from concept for "intelligent" and "anti-aging" (long life), has been designed and developed for TOYOTA's luxury passenger car. LEXUS LS400. This system, which has resulted in silky-smooth shift quality without changes in the long term, is composed of a transmission computer that inter- acts with engine computer, a number of sensors, an electronically controlled hydraulic unit with linear solenoid valves and assorted devices. As new control logic being developed with the aid of computer simulation to achieve distinction, the hydraulic and engine controls are combined in this system. There is a "feedback control", where the clutch pressure is controlled according to the rate of acceleration and compen- sated for dispersion to applied pressure, engine torque and/or the coefficient of dynamic friction of clutches, and at the same time engine torque is reduced by retarding ignition timing. ADVANCES made in recent years for the use of electronic control method for automatic transmissions (hereafter referred to as A/T) of passenger cars are remarkable, which is success- ful in improvements in fuel economy, drivability, shift quality, etc.. For the shift quality in particular, each automobile manufacturer is striving for further improvements. For example, the engine torque control during shifting to make it possible to suppress the jerk and shorten shift time or electronic control hydraulic pressure is already adopted. We also placed emphasis on following points on development of A/T for LEXUS LS400, considering the shift quality be used for the luxury car.(l)* under all driving conditions. For this purpose, it is necessary to control the clutch hydraulic pressure exactly as desired and to reduce the engine torque properly during shifting, in order to reduce the shift time and to minimize the disturbance in output torque variation. 2. The shift quality should be anti-aging (i.e., to maintain initial quality during long term). It is necessary to adopt the feedback control of clutch pressure in order to stabilize such shift characteristics as the shift time and output torque variations against dispersion and agi