Utilization of Motor-driven gearshift system

400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A.Tel: (724) 776-4841 Fax: (724) 776-5760SAE TECHNICAL PAPER SERIES1999-01-0745Utilization of Motor-Driven Gearshift SystemAtsuo OtaHonda R&D Co., Ltd.Satoru NaritaHonda R&D Co., Ltd.Reprinted From: 1999 Transmission and Driveline Systems Symposium(SP-1440)International Congress and ExpositionDetroit, Michigan March 1-4, 1999The appearance of this 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 copier pay a $7.00 per article copy fee through the Copyright Clearance Center, Inc.Operations Center, 222 Rosewood Drive, Danvers, MA 01923 for copying beyond that permitted by Sec-tions 107 or 108 of the U.S. Copyright Law. 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A process is available by which discussions will be printed with the paper if it is published in SAE T ransactions. 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 300word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE.Printed in USAAll SAE papers, standards, and selected books are abstracted and indexed in the Global Mobility Database1999-01-0745Utilization of Motor-Driven Gearshift SystemAtsuo OtaHonda R&D Co., Ltd.Satoru NaritaHonda R&D Co., Ltd. Copyright © 1999 Society of Automotive Engineers, Inc.ABSTRACTRecently, for passenger cars, hand operated gearshift systems have been made available by some manufactur-ers for the purpose of easy gearshift operation and to make driving more fun. For adapting such a system to an A TV (All T errain Vehicle), which is used mainly for agricul-ture and leisure, the whole system should be compact and lightweight. It is also necessary for the clutch to be engaged properly under various running conditions. This gearshift system performs both engaging and disengag-ing of the clutch and moving the gearshift spindle with one motor. Since this system is controlled by calculated engine speed, vehicle speed and gear position, suitable gear shifting is realized under various running conditions. For optimal clutch control, there is a reversing point for the decreasing and increasing of engine speed for each gearshift. This accelerates the clutch engagement speed and makes quick returning of the gearshift spindle. As a result of this, the shift feeling matches the rider’s will. It makes a beginning rider able to perform gear shifting under various running conditions. The shifting is made quickly and certainly, which is closer to a skilled rider’s ability. Adapting this system design made it possible to install it to an existing A TV engine.INTRODUCTIONA TVs currently have two types of drive systems designed for off-road usage; an automatic V-belt type CVT and a multiple-speed manual transmission. Compared to an automatic transmission, which does not require shifting operation, a manual transmission has been supported by the user because the power can be selected voluntarily by the rider. For automobiles, a hand operated gearshift system based on an automatic transmission system has been the most practical. The primary purpose of this system is to provide the rider with the ability to select the drive gear easily. This will improve the overall enjoyment of riding by realizing simple and speedy shift operation of the manual transmission.Considering this background, a hand operated gearshift system based on a multiple-speed gear transmission is considered to be a suitable drive system for an A TV. However, there are considerations for putting it to practi-cal use.1.The system should be lightweight and compact so asnot to sacrifice the A TV’s high running performance in off-road terrain.2.Under various running conditions, adequate shift tim-ing and clutch engagement should be realized.In consideration of the above, we have developed a shift mechanism which engages and disengages the clutch and shifts gears with one motor. The ECU (Electronic Control Unit) controls timing and speed of motor rotation based on various input information.In this thesis, the mechanism and control method of the developed system are compared to the operations of a manual shift system under actual running conditions.SYSTEM OUTLINEGEAR SHIFTING CONSTRUCTION – The gear shifting construction of the motor-driven gearshift system is shown in Fig.1. Whereas the construction of the manual shift used as the base is shown in Fig.2.The motor driven system is adding the control motor, the reduction gears to drive the gearshift spindle, and the angle sensor installed on the end of spindle, to the man-ual mechanism.The clutch system is constructed with a starting clutch and a change clutch. An automatic engaging centrifugal clutch is equipped as the starting clutch. The change clutch is connected with the gearshift spindle by link plates and the gear shifting mechanism. This system is shown in Fig.3.In general, gears in conventional constant mesh trans-mission for A TVs and motorcycles have convex dogs and dog holes. As shown in Fig.4, by replacing those dogs and dog holes with dogs similar to gear teeth which meshwith the space in-between those dogs (hereafter referred the space as the pockets), the dog could be downsized while maintaining its strength. With this downsizing, a chance of the dog engagement is increased in a dynamic condition, completion time for dog engagement and shift time is shorter.The weight increase is suppressed to 1.5kg for the engine itself and 2.0kg for the entire system. Since a manual shifting gear mechanism is utilized without any major changes, this system is easier to apply to existing A TV engines.Figure 1.Gearshift Construction of Motor DrivenGearshift SystemFigure 2.Gearshift Construction of Motor ShiftingCONTROL SYSTEM – The control system of the motor-driven gearshift system is shown in Fig.5.The sensors used in this system are an engine speed sensor, gear position sensor, vehicle speed sensor and angle sensor of gearshift spindle. Among these sensors, the engine speed sensor is combined with the ignition pulse generator for the ignition system. The gear posi-tion sensor and vehicle speed sensor are utilized also for the gear position and speed display on the meter respec-tively.The operating system receives input information for gear shifting from the gearshift switches and a release signal from the reverse interlock switch. The control output is only for the control motor.Reduction GearControl Motor Gearshift SpindleChange ClutchAngle SensorShift DrumGearshift SpindleGearshift Pedal TransmissionSub-Gearshift SpindleChange Clutch Shift DrumPocketsDogsFigure 5. Control System As shown in Fig.6, the ECU is composed of 8 bits micro-computer, input interface and MOS-FET H bridge to drivethe control motor. The contents of control are identifica-tion of the shifting mode based on input information,motor control and self-diagnosis of the system compo-nents. By utilizing the existing sensors, the increase inweight and cost are minimized and the system composi-tion is simplified.OPERATION METHOD – Gears are shift up and downposition by position as the rider presses the gearshiftswitches installed on the left-handlebar. T o achieve easeof operation, the gearshift switches are positioned close to the left handle grip. The upper part is for up-shift and the lower part is for down-shift. These positions are shown in Fig.7.Figure 6.ECU (Electronic Control Unit)Figure 7.Arrangement of Gearshift SwitchesShifting to reverse gear is allowed only when the gear is shifted to a neutral position and the interlock is released. Shifting is then done by pressing the down-shift switch.CONTROL METHODControl method of gearshift is based on the standard pat-tern of the gearshift spindle rotation, and the timing of the clutch engagement is quickened according to a reversing point for decreasing and increasing of engine speed. Control method and shifting characteristics in actual run-ning conditions are described below.BASIC GEARSHIFT CONTROL – Gear shifting is accomplished by rotating the gearshift spindle. Except for directions of the gearshift spindle rotation, the gear-shift control of up-shifting and down-shifting are basically the same.As shown in Fig.8, the gearshift control is divided into 3 stages as noted below and completed in this order.Gearshift Switches1.The stage shown in part A disengages the clutch androtates the shift drum.2.The stage shown in part B engages dogs and pock-ets, and holds the clutch disengaged.3.The stage shown in part C engages the clutch. During part A, the control motor rotates the shift spindle at the maximum speed, and disengages the clutch and rotates the shift drum quickly. At the end of this stage, the control motor is stopped through a short-circuit of the motor terminal. This is to suppress the impact of the shift mechanism when the shift spindle hits the stopper through the link plates.Figure 8.Basic Gearshift Control (Standard Pattern) During part B, the dogs are engaged into the pockets with adequate time to insure proper engagement. After that, the clutch is kept disengaged for a certain period to allow the rider to easily operate the throttle.During part C, to complete shifting smoothly, the clutch is slowly engaged after the shift spindle is returned at high speed to just before the position where the clutch starts to engage. Such control is realized by the gearshift spin-dle which is controlled by the control motor with PWM (Pulse Width Modulation). The Pulse Width is calculated by PID (Proportional Integral Derivative) control from the calculated target position of the shift spindle and mea-sure of its angle.This basic gearshift control is selected for slow traveling speed in which the rider does not intentionally operate the throttle. Adequate shift time and smooth clutch engagement can be achieved. Shifting characteristic of standard pattern in up-shift is shown in Fig.9.Figure 9.Shifting Characteristic of Standard Pattern in Up-shiftCLUTCH ENGAGEMENT CONTROL IN UP-SHIFT – T o obtain adequate clutch engagement, timing is variable under various running conditions. The clutch engage-ment point is made earlier than the basic gearshift control in case the engine speed changes during shift operation. Common throttle operation at up-shift is to close the throttle at the start of gear shifting, then the throttle is opened again when the process of shifting is complete. Given this, engine speed decreases from the start of gear shifting and then increases again when the throttle is opened. When a change in engine speed changes from decreasing to increasing is perceived, the system advances the clutch engagement time in the basic gear-shift control and engagement is quickened. This case is indicated by pattern B of Fig.10. And this shifting charac-teristic is shown in Fig.11.In case shifting is made without closing the throttle, and there is a continuous increase of engine speed detected, the quick clutch engagement is applied soon after waiting for the dog engagement completion point. This case is shown in Pattern A of Fig.10.Figure 10.Clutch Engagement Control in Up-shiftFigure 11.Shifting Characteristic of Pattern B in Up-shift CLUTCH ENGAGEMENT CONTROL IN DOWN-SHIFT – For down-shifting, the throttle is usually left closed, however, the throttle may be opened when the engine speed meets the next gear position. At this time, the engine speed increases during shifting, then decreases. In situations where engine speed changes are detected from increasing to decreasing during shift-ing, the clutch engagement is quickened. T o prevent quickening of the clutch engagement by a very small change of the engine speed, the control is limited only when the engine speed exceeds more than at the start of shifting. This case is shown in Pattern B of Fig.12. Shift-ing characteristic in this case is shown in Fig.13.As shown in Pattern A of Fig.12, in case the engine speed change point is detected before completion of dog engagement, quickening of the clutch engagement waitsfor its completion as well as up-shifting.By performing such clutch engagement control as men-tioned, the system provides natural feelings that match many riding conditions.Figure 12.Clutch Engagement Control in Down-shift Figure 13.Shifting Characteristic of Pattern B in Down-shiftCOMPARISON WITH MANUAL SHIFTThe actual running test was performed by an expert rider and a novice rider to compare the shifting characteristic of this system with that of manual shift. The A TV used for the test was a basic vehicle with a conventional shifting mechanism. The shifting characteristics of the expert and novice riders are shown in Fig.14 and Fig.15. It wasremarkable that the expert rider performed smooth clutch engagement to link the clutch engagement timing and the throttle control; whereas the novice rider did not link the throttle to the clutch engagement. The specification of test vehicle is shown in T able 1.Figure 14.Shifting Characteristic of Manual Gearshift in Up-shift by Expert RiderFigure 15.Shifting Characteristic of Manual Gearshift in Up-shift by novice RiderAs mentioned before, the shifting characteristic of the vehicle installed with this system on the same course is shown in Fig.11. The clutch engagement timing is linked to the throttle control by the novice rider, the same as that of the expert rider.Fig.16 shows a comparison of shift time by the expert rider in various running conditions. In slow riding, there is little difference between the manual shift vehicle and the vehicle installed with this system. However, in sporty riding, the distribution of shift time of the vehicle installed with this system shows quicker tendency. The following results are obtained from above.1.Since the clutch engagement timing is linked to throt-tle operation, and is done automatically, the same shifting action as that of expert riders is possible for novice riders.2.Down-shifting time is almost the same as that ofexpert riders. Up-shifting time is shortened depend-ing on riding conditions.TFigure 16.Shift Time of Up-shift and Down-shift CONCLUSIONThe following conclusions are obtained as the results of installation of the motor-driven gearshift system on A TVs.1.Monitoring engine speed, quick and smooth gearshifting operation like that of expert riders is possible for novice riders.2.By maximum utilization of mechanisms and existingcomponents on A TVs, a lightweight and compact system was constructed and the weight increase is suppressed to 2.0kg for the entire system.3.Modifications on the base engine are an installationof the control motor on the shift spindle, the angle sensor and reduction gears. Simple construction of the system made it possible to install on existing A TVengines.REFERENCES1.T.Shimada, T.Shichinohe, and H.Kobayashi, “Developmentof a New Concept for an A TV” SAE Paper 9600872.H.Furukawa, K.Hagiwara, T.Iwahashi, M.Fukuchi, Y.Saitoand Y.Y oshimura “Improvement of Automatic T ransmission Shift Quality by Robust Control“ HONDA R&D T echnical Review Vol.7, P.30-38 , 19953.K.Sawamura, Y.Saito, S.Kuroda, J.T akahashi and A.Katoh“Development of an Integrated Power T rain Control System with an Electronically Controlled Throttle“ Proceeding of JSAE, 962, P.101-104 ,1996。