大众汽车EPS介绍

Electro-mechanical Power Steering Design and Function Self-Study Program Course Number 892403 Volkswagen of America, Inc. Service Training Printed in U.S.A. Printed 12/04 Course Number 892403 ©2004 Volkswagen of America, Inc. All rights reserved. Information contained in this manual is based on the latest information available at the time of printing and is subject to the copyright and other intellectual property rights of Volkswagen of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, nor may these materials be modified or reposted to other sites without the prior expressed written permission of the publisher. All requests for permission to copy and redistribute information should be referred to Volkswagen of America, Inc. Always check Technical Bulletins and the latest electronic service repair information that may supersede any information included in this booklet. Trademarks: All brand names and product names used in this manual are trade names, service marks, trademarks, or registered trademarks; and are the property of their respective owners. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Electro-mechanical Power Steering with Dual Pinion, Electro-mechanical Power Steering Components System Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 System Overview Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Control Map Characteristics, The Steering Function, Straight-Line Stability Steering Mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 The Steering Gear Steering Electrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Steering Angle Sensor G85, Steering Torque Sensor G269, Rotor Speed Sender, Road Speed, Engine Speed (RPM) Sensor G28, Electro-mechanical Power Steering Motor V187, Power Steering Control Module J500, Electro-mechanical Power Steering Indicator Lamp K161, Special Features Functional Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Functional Diagram Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Diagnosis Knowledge Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Table of Contents Page i New! Important/Note! The Self-Study Program provides you with information regarding designs and functions. The Self-Study Program is not a Repair Manual! For maintenance and repair work, always refer to the current technical literature. ii 1 Introduction Steering Wheel Steering Column Universal Joint ShaftSteering Gear Electro-mechanical Power Steering Motor V187 Steering Torque Sensor G269 Power Steering Control Module J500 Electro-mechanical Power Steering with Dual Pinion The steering system components are: • Steering wheel • Steering Angle Sensor G85 • Steering column • Steering Torque Sensor G269 • Steering gear • Electro-mechanical Power Steering Motor V187 • Power Steering Control Module J500 Introduction 2 What You Should Know About the Electro-mechanical Power Steering System: With electro-mechanical power steering, there is no requirement for hydraulic assistance to support the steering. Eliminating hydraulic oil from the steering system helps to protect the environment. The electro-mechanical power steering system is a dual pinion type. This is characterized by two pinions (steering and drive pinions), which enable the necessary steering force to be transmitted to the steering rack. To assist the steering, an electric motor is actuated based on input response. The system provides the driver with assistance depending on the driving conditions (servotronic). The electro-mechanical power steering supports return of the steering wheel back to the center position via the “active return” function. This results in a well-balanced feeling and extremely accurate straight-line stability in every driving situation. With the straight-line stability function, a force is generated and applied to make it easier for the driver to steer the vehicle in a straight line when the vehicle is being affected constantly by side winds or driven up or down hills. 3 Introduction The Advantages of Electro-mechanical Power Steering The electro-mechanical power steering system offers the following advantages over a traditional hydraulic system: • no hydraulic components, for example power steering oil pump, hoses, oil tank, filter • no hydraulic fluid • space savings • reduction in noise • energy savings • no complex hose and wiring system The electric motor and control module are located directly on the steering gear. This results in a notable energy savings. Unlike hydraulically assisted steering, which requires a permanent circuit flow, the electro-mechanical power steering only draws energy when steering force is necessary. This input response performance leads to a reduction in fuel consumption. The driver has an optimal driving feeling in every situation thanks to: • good straight-line stability (return of the steering wheel to the center position is actively supported by the electro- mechanical power steering system) • direct but soft application of the steering input • no uncomfortable steering reactions over uneven driving surfaces The fuel consumption savings over 620 miles (1000 km) is approximately 0.5 gallons (2.0 liters). Introduction 4 Electro-mechanical Power Steering Components Steering Pinion Steering Torque Sensor G269 Power Steering Control Module J500 Electro-mechanical Power Steering Motor V187 Worm Gear Drive Pinion 5 System Overview System Overview Engine Speed (RPM) Sensor G28 ABS Control Module J104 Left Rear ABS Wheel Speed Sensor G46 Left Front ABS Wheel Speed Sensor G47 Data Bus On Board Diagnostic Interface J533 Instrument Cluster Control Module J285 Terminal 15 Electro-mechanical Power Steering Indicator Lamp K161 Power Steering Control Module J500 Engine Control Module (ECM) Steering Column Electronic Systems Control Module J527 Steering Angle Sensor G85 Steering Torque Sensor G269 Drivetrain CAN Data Bus Electro-mechanical Power Steering Motor V187 Right Rear ABS Wheel Speed Sensor G44 Right Front ABS Wheel Speed Sensor G45 6 Control Map Characteristics Steering assistance is controlled via a map, which is stored permanently in the program memory of Power Steering Control Module J500. The memory has a capacity for up to 16 different maps. Maps are activated in the factory depending on requirements (e.g. vehicle weight). However, maps can also be activated with the scan tool if the Power Steering Control Module J500 or steering system were to be serviced or replaced. Function V=0 mph (0 km/h) V=10 mph (15 km/h) V=31 mph (50 km/h) V=62 mph (100 km/h) V=155 mph (250 km/h) Steering Force lbs-ft (Nm) A ss is tin g Fo rc e lb s- ft (N m ) Heavy Vehicle Light Vehicle For any given vehicle, both a heavy and a light map are selected. Each map has five different characteristics that are calculated using vehicle speed. These maps determine the amount of steering assistance available to the driver. 4 (2.95) 3 (2.21) 2 (1.47) 1 (0.74) 0 0 2 (1.48) 4 (2.95) 6 (4.43) 8 (5.90) 7 1. The power steering assistance starts when the driver uses force to turn the steering wheel. 2. The force on the steering wheel causes a torsion bar in the steering gear to turn. The Steering Torque Sensor G269 detects the rotation and sends the calculated steering force figure to the Power Steering Control Module J500. 3. The Steering Angle Sensor G85 reports the current steering angle and steering speed. 4. Depending on the steering force, road speed, engine speed, steering angle, steering speed and maps stored in Power Steering Control Module J500, it calculates the necessary assisting force and actuates Electro-mechanical Power Steering Motor V187. The Steering Function Function 5. The steering assistance comes from a second pinion, which applies its energy in parallel on the steering rack. This pinion is driven by Electro-mechanical Power Steering Motor V187. The motor engages in the steering rack via a worm gear and drive pinion, which transmits the force required for steering assistance. 6. The sum of the turning force on the steering wheel and the assisting force is the effective force applied on the steering gear to move the rack. Turning Force at Steering Wheel Assisting Force Effective Force 8 The Steering Function for Parking Maneuvers 5. In this way, the largest amount of steering assistance is applied on the steering rack via the second pinion for parking maneuvers. 6. The sum of the turning force on the steering wheel and the maximum assisting force is the effective force applied on the steering gear for movement of the rack during parking maneuvers. Function 1. When parking the vehicle, the driver turns the steering wheel rapidly. 2. The torsion bar is turned. The Steering Torque Sensor G269 picks up the rotation and sends a signal to the Power Steering Control Module J500, indicating that a large amount of force has been placed on the steering wheel. 3. The Steering Angle Sensor G85 reports the current steering angle and steering speed. 4. Based on the large amount of steering force, the road speed of 0 mph (0 km/h), the engine speed, the large steering angle, the steering speed and the maps stored in it for V=0 mph (0 km/h), Power Steering Control Module J500 detects that a large amount of assisting force is required and actuates Electro-mechanical Power Steering Motor V187. Turning Force at Steering Wheel Assisting Force Effective Force V=0 mph (0 km/h) 9 1. When cornering in urban areas, the driver uses force to turn the steering wheel. 2. The torsion bar is turned. The Steering Torque Sensor G269 picks up the rotation and sends a signal to the Power Steering Control Module J500, indicating that a medium amount of force has been placed on the steering wheel. 3. The Steering Angle Sensor G85 reports the current steering angle and steering speed. The Steering Function in Urban Areas Function 4. Based on the medium amount of steering force, the road speed of 31 mph (50 km/h), the engine speed, the medium steering angle, the steering speed and the maps stored in it for V=31 mph (50 km/h), Power Steering Control Module J500 detects that a medium amount of assisting force is required and actuates Electro- mechanical Power Steering Motor V187. 5. In this way, a medium amount of steering assistance is applied on the steering rack via the second pinion during cornering. 6. The sum of the turning force on the steering wheel and the medium assisting force is the effective force applied on the steering gear for movement of the rack during cornering in urban areas. Turning Force at Steering Wheel Assisting Force Effective Force V=31 mph (50 km/h) 10 The Steering Function on Highways 4. Based on the small amount of steering force, the road speed of 62 mph (100 km/h), the engine speed, the small steering angle, the steering speed and the maps stored in Power Steering Control Module J500 for V=62 mph (100 km/h), it detects that a small amount of assisting force is required and actuates Electro-mechanical Power Steering Motor V187. 5. In this way, a small amount of steering assistance is applied on the steering rack via the second pinion during lane change maneuvers on the highway, or no assistance at all. 6. The sum of the turning force on the steering wheel and the minimum assisting force is the effective force applied on the steering gear to move the steering rack during lane changing maneuvers. Function 1. To change lanes, the driver imparts light force on the steering wheel. 2. The torsion bar is turned. The Steering Torque Sensor G269 picks up the rotation and sends a signal to the Power Steering Control Module J500, indicating that a small amount of force has been placed on the steering wheel. 3. The Steering Angle Sensor G85 reports the current steering angle and steering speed. Turning Force at Steering Wheel Assisting Force Effective Force V=62 mph (100 km/h) 11 1. If the driver reduces the force on the steering wheel during cornering, torsion bar tension is relieved. 2. In conjunction with the reduced steering force, inclusion of the steering angle and the steering speed, a return speed specification is calculated. This is compared with the steering angle speed. The result of this is the returning force required. 3. Return forces are applied on the steering wheels as a result of the running gear layout. The return forces are often too weak, due to friction in the steering system and in the axle (suspension), to bring the wheels back to the center position. The Active Return Function Function 4. Power Steering Control Module J500 calculates the necessary return force required from Electro-mechanical Power Steering Motor V187 by evaluating the steering force, road speed, engine speed, steering angle, steering speed and the map characteristics stored in Power Steering Control Module J500. 5. Electro-mechanical Power Steering Motor V187 is actuated and the wheels are returned to the straight-ahead position. Return Force Assisting Force Effective Force 12 Straight-Line Stability Straight-line stability is an extension of the active return function. An assisting force is generated to bring the wheels of the vehicle in the center position, when no force is applied. To do this, a difference is made between a short period algorithm and a long period algorithm. Long Period Algorithm The long period algorithm has the task of balancing deviations either side of the center position that occur over a long period of time. For example, deviations that could be caused when summer tires are changed for winter tires (used or with different diameter). 1. A constant side force is applied on the vehicle, e.g. side wind. 2. The driver applies force on the steering wheel to keep the vehicle in a straight line. 3. Power Steering Control Module J500 calculates the necessary force required from Electro-mechanical Power Steering Motor V187 to maintain the straight ahead position by evaluating the steering force, road speed, engine speed, steering angle, steering speed and the map characteristics stored in Power Steering Control Module J500. 4. Electro-mechanical Power Steering Motor V187 is actuated. The vehicle is brought into the straight-ahead position. The driver no longer has to steer against the resistance. Function Return Forces Assisting Force Effective Force Short Period Algorithm The short period algorithm is responsible for correcting deviations that occur briefly. This makes driving easier for the driver when, for example, permanent side winds make it necessary to steer against a resistance. 13 Electro-mechanical Power Steering Motor V187, Power Steering Control Module J500 and steering assistance sensors can be found on the second pinion. This design means that there is a mechanical connection between the steering wheel and steering rack. In this way, the vehicle can still be steered mechanically in the event of failure of Electro-mechanical Power Steering Motor V187. The Steering Gear The steering gear consists of Steering Torque Sensor G269, a torsion bar, a steering and drive pinion, a worm gear, Electro-mechanical Power Steering Motor V187, and Power Steering Control Module J500. The core of the electro-mechanical power steering is a steering rack with two teeth engaged in the steering gear. On the electro-mechanical power steering with dual pinion, the steering force required is transferred via the steering pinion and the drive pinion to the steering rack. The steering pinion transfers the steering force applied by the driver and the drive pinion transfers the assisting force from Electro-mechanical Power Steering Motor V187 via a worm gear. Steering Mechanics Steering Torque Sensor G269 Power Steering Control Module J500 Electro-mechanical Power Steering Motor V187 Drive PinionSteering Rack Steering Angle Sensor G85 Steering Column Steering Pinion 14 Steering Angle Sensor G85 Steering Electrics Airbag Spiral Spring/Return Spring With Slip Ring F138 Steering Angle Sensor G85 Steering Column Electronic Systems Control Module J527 The Steering Angle Sensor G85 can be found behind Airbag Spiral Spring/Return Spring With Slip Ring F138. It is located on the steering column between the steering column switch and the steering wheel. It sends the signal for steering angle analysis to Steering Column Electronic Systems Control Module J527 via the CAN data bus. The electronic system for analysis of the signals is located in Steering Column Electronic Systems Control Module J527. Effects of Failure In the event of signal failure, an emergency running mode is started. The missing signal is replaced by a substitute figure. Power steering assistance remains intact. Electro- mechanical Power Steering Indicator Lamp K161 will light up to indicate the fault. 15 Principles of Operation Basic components of Steering Angle Sensor G85 are: • Absolute and increment ring with two codes • Photoelectric beam pairs, each with one Light-Emitting Diode (LED) and one optical sensor. The code plate consists of two rings, an outer absolute ring and an inner increment ring. The increment ring is separated into five segments, each is 72°, and is read by a photoelectric beam pair. Within each segment the ring is split. The gap of the split is equal within the segments but different between the segments. This provides the code for the segments. The absolute ring determines the angle. It is read by six photoelectric beam pairs. Steering Angle Sensor G85 can detect a steering angle of up to 1044°. It accumulates the degrees after each turn of the steering wheel. In this way, it can detect that a full steering circle is complete when the 360° mark is exceeded. The design of the steering gear allows 2.76 turns of the steering wheel. Steering Electrics Increment Ring Steering Angle Sensor G85 Absolute Ring Increment Ring Steering Angle Sensor G85 Absolute Ring Segment 3 Segment 4 Segment 5 Segment 2 Segment 1 72º 16 Angle measurement is by means of the photoelectric beam principle. If, for purposes of simplification, the increment ring is used as an example, the light source is on one side of the segment ring and the optical sensor is on the other. When light shines through a gap onto a sensor, signal voltage is generated. When the light source is covered, voltage is interrupted. If the increment ring is moved, a sequence of signal voltages is given. This is precisely how the sequence of signal voltages occurs on each photoelectric beam pair of the absolute ring. All signal voltage sequences are processed by the Steering Column Electronic Systems Control Module J527. By comparing the signals, the system can calculate how far the rings have been moved. This is how the starting point for movement of the absolute ring is determined. Steering Electrics 17 The steering force is calculated directly at the steering pinion with help from the Steering Torque Sensor G269. The sensor works on the principle of magnetic resistance. It is a twin (redundant) sensor, which assures a high level of safety. The steering column and steering gear are joined together at Steering Torque Sensor G269 via a torsion bar. The co