Wuhan University of Technology Graduation Design (thesis)

Design of Electric Power Steering and Test Bench

School: School of International Education

Specialty amp; Class: Automotive Engineering gj1503

Name: Li Qin

Tutor: Wu Dongmei

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Abstract

Compared with traditional mechanical and hydraulic power steering systems, automotive electric power steering system (EPS) has the advantages of steering sensitivity, low energy consumption, good environmental compatibility and low cost. At present, many high-end vehicles are equipped with EPS, so the development of EPS has great practical significance and commercial value. In this design, the main design center of the rack-and-pinion steering gear is the summary of the steering system, the selection of the mechanical steering gear, the reasonable matching of the gear and rack to meet the requirements of the rational transmission ratio and strength of the steering gear, the trapezoidal structure design and optimization, and the design of the test bench. This design uses the rotation of steering wheel to drive the steering axle steering of the transmission mechanism, and the universal transmission device to drive the steering gear axle to rotate. The steering gear axle and the steering rack mesh with each other, so that the steering rack can move in a straight line and realize the steering of the automobile. This design realizes that the steering gear has simple structure, small axial dimension and fewer parts, so as to meet the requirements of sensitivity and stability of automobile steering. The calculation mainly carries out the design calculation and checking of the steering gear rack and the design checking of the steering gear axle. It mainly uses the experience parameters of automobile design and the theory of automobile design and automobile structure in the course of mechanical design in university. The result basically meets the strength requirement and is safe and reliable.

Key words: Steering Design of Gear and Rack Electric Power Steering System Bench Design

Catalog

Chapter 1 Introduction 1

1.1 Summary of steering system 4

1.2 Requirements for steering system 4

Chapter 2 Design of Electric Power Steering System 7

2.1 Composition of Electric Power Steering Mechanism 7

2.2 Working Principle of Electric Power Steering Mechanism 7

2.3 Characteristics of Electric Power Steering 8

2.4 Arrangement Scheme of Electric Power Steering Mechanism 8

2.4.1 Steering Shaft Booster 9

2.4.2 Pinion-assist type EPS 10

2.4.3 Rack-assist type EPS 10

2.5 Vehicle parameters 11

Table 2.1 Vehicle parameters 11

2.6 Basic Requirements for Power Steering Mechanism 12

2.7 Scheme Design of Gear-rack Steering Device 12

2.8 Electric Power Steering Key Parts 13

2.8.1 Motor 13

2.8.2 Electromagnetic Clutch 14

2.8.3 Torque Sensor 14

2.8.4 deceleration mechanism 14

2.9 Steering Shaft and Steering Pipe Structural Design 15

2.9.1 Calculation of Half Axis on Steering Shaft 16

2.9.2 Calculation of lower half axle of steering axle 16

Chapter 3 Steering gear design 18

3.1 Steering efficiency 18

3.1.1 Steering gear positive efficiency 18

3.1.2 Steering Reverse Efficiency 18

3.2 transmission clearance of steering gear pair △t 19

3.3 Determination of Calculating Load of Steering System 20

3.3.1 Steering Resistance Moment 20

3.3.2 Vehicle Steering Wheel Force 21

3.4 Worm Gear and Worm Design 22

3.4.1 Worm Gear and Worm Parameter Design 22

3.4.2 Worm Wheel Strength Check 23

3.5 Design of rack and pinion steering gear 23

3.5.1 Steering ratio 23

3.5.2 Gear Design 24

3.5.3 Gear Parameters Determination 24

3.5.4 Rack design 25

3.5.5 Gear Strength Checking 26

3.6 Force Analysis of Gear-rack Drive 27

3.7 Gear Shaft Design 28

Chapter 4 Steering trapezoid and Bench Design 30

4.1 Steering Trapezoidal Structure Scheme Analysis 30

4.1.1 Integral Steering Trapezoid 30

4.1.2 Disconnected Steering Trapezoid 30

4.2 Optimum Design of Integral Steering Trapezoidal Mechanism 31

4.3 Design of experimental bench 32

4.4 Channel Sensitive Intensity 33

Chapter 5 Summary 36

Reference 38

Acknowledgement 39

Appendix A 41

Chapter 1 Introduction

As a commodity, automobiles have a wide market in the world, and they bring huge profits to enterprises because of their large production batches. The diversity of automobile varieties can meet the needs of various production and life activities, and has good social benefits. The development of automobile industry has led to the development of many related enterprises and undertakings, including steel, petroleum, rubber, plastics, machine tools, roads, automobile sales, after-sales service, transportation, traffic management, financial industry, education and scientific research, thus solving the employment problem of a large number of people. Automobile is also one of the important criteria to measure people's living standards. Buying cars and the daily consumption resulting from it can promote the return of money. In the past hundred years, the automobile industry has been prosperous mainly because of the continuous progress of the market and science and technology. It is the gradual improvement of automobiles to meet the needs of users. Nowadays, not only in production activities, but also in daily life, people can not do without cars. For developed countries, choosing automobile industry as the pillar industry of national economy is the right choice.

Automobile is also a symbol of the development level of science and technology. A large number of new materials and structures are used in automobiles, especially modern micro-electronics technology to control and control, which greatly improves the performance of automobiles. In the process of developing automobiles, we need to concentrate a large number of outstanding scientific and technological talents, carry out thousands of research work, and apply the most advanced theory, the most accurate computing technology, the most modern design method and the most perfect technical testing means. The process of manufacturing automobiles should also have many latest achievements in the field of technology. Hundreds of automatic production lines have been used in factories and scientific means of production and management have been applied. Undoubtedly, automobile is a high-tech product, which can reflect the scientific and technological level of a society.

For automobile steering system, it is used to maintain or change the direction of the vehicle. When the vehicle steering, it ensures that there is a coordinated angular relationship between the steering wheels. The steering wheel is rotated manually by the driver of the mechanical steering system. The steering wheel is deflected by the steering gear and the steering transmission mechanism. Some cars also have anti-injury devices and steering dampers. A power steering vehicle is equipped with a power system, which can reduce the driver's hand power.

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