Graduation design of Wuhan University of Technology（Instructions）

Design of WG6820AI braking system for automatic driving pure electric bus

Institute：Institute of International Education

Professional class：Vehicle gj1403

Student name：Yin Weihao

Tutor：Yu Houyu

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本人郑重声明：所呈交的论文是本人在导师的指导下独立进行研究所取得的研究成果。除了文中特别加以标注引用的内容外，本论文不包括任何其他个人或集体已经发表或撰写的成果作品。本人完全意识到本声明的法律后果由本人承担。

作者签名：尹伟豪

2018年 5 月 7 日

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作者签名：尹伟豪 2018年 5月 7日

导师签名： 年 月 日

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ABSTRACT

In this paper, the structure and braking performance of various brakes are briefly described. Then the drum brake is used as the design object according to the vehicle parameters and vehicle conditions of a given vehicle, the dual loop brake system is adopted, and the brake driving mechanism of the pneumatic brake is adopted, and the basic parameters of the drum brake are determined. After the selection of the basic structure, this paper launches the following design for the brake. Parameters of brake system: selection and calculation of parameters such as braking force distribution coefficient, synchronous adhesion coefficient, braking strength, utilization ratio of adhesion coefficient and maximum braking moment; calculation of brake and its components and material selection; calculation of parking brake and emergency brake; calculation of brake drive mechanism. The design and type selection of the automatic brake actuator are briefly introduced. Use electric motor to connect pull wire to pull pedal to achieve automatic braking.

Then the drum brake was calculated and the structure of its main parts was designed. Finally, three dimensional model and engineering drawing of drum brake are established by using 3D modeling software CATIA, and the structural strength of brake shoe of drum brake is analyzed by finite element method through ANSYS.

Key words: brake system, drum brake, design

CATLOG

1 Introduction 8

1．1 Overview of braking system 8

1.2 The direction of thesis research 8

1.3 The design significance of the brake 9

2 Selection of brake type and scheme 10

2.1 Disc brake 10

2.1.1 Disc type disc brake 10

2.1.2 Clamp disc brake 10

2.1.3 Characteristics of disc brake 10

2.2 Drum brake 11

2.2.1 Collar slave brake 11

2.2.2 One way double collar shoe type and two way double collar shoe brake. 12

2.2.3 Double slave brake 13

2.2.4 Force increasing brake 14

2.3 Determination of type and scheme of brake 15

2.4 Automatic brake execution scheme 16

3 The selection of the main parameters of the brake system 17

3.1 Ideal pre and post power distribution curve 17

3.2 Determination of braking force distribution coefficient and synchronous adhesion coefficient 19

3.3 Rationality analysis of braking force distribution 21

3.3.1 utilization adhesion coefficient and braking efficiency 21

3.3.2 Calculation of braking force 22

4 Design and calculation of brake 24

4.1 Determination of main parameters of drum brake 24

4.1.1 Brake drum inner diameter D 24

4.1.2 Brake drum thickness n 25

4.1.3 The width of the friction lining B and the angle 25

4.1.4 The distance between the center of the brake and the opening force P of the shoe is e. 26

4.1.5 The starting angle of the friction plate 27

4.1.6 Position coordinates a and C of brake shoe support point 27

4.2 Calculation of torque on a hoof plate 27

4.2.1 Distribution law of radial pressure 28

4.2.1 Strength analysis of brake shoe based on ANSYS 34

4.3 Brake efficiency factor 35

4.4 Calculation of brake power 36

4.5 Calculation of parking brake 36

4.6 Calculation of emergency brake 38

4.7 Calculation of wear characteristics of friction plates 38

4.7.1 Calculation of the ratio of energy dissipation 38

4.7.2 Calculation of the average pressure P between the lining and the brake drum 40

4.7.3 Calculation of the thermal capacity and temperature rise of the brake 40

5 Evaluation of braking efficiency 42

5.1 Braking deceleration 42

5.2 braking distance 42

5.3 Stability of braking efficiency 43

5.4 Type selection of automatic brake actuator 44

6 Design of pressure control mechanism 45

6.1 calculate 45

6.2 Multi loop system of brake pipe 46

7 The structure design of the main parts of the brake 49

7.1 Structural design of brake drum 49

7.2 Structural design of brake shoe 50

7.3 Structural design of friction lining 51

7.4 Structural design of brake floor 51

7.5 Design of support form 51

7.6 Clearance adjustment device between hoofs and drums 52

8 Summary and experience 52

Reference 54

Acknowledgement 56

Appendix A: MATLAB programming in partial calculation process 57

Appendix B: ANSYS analysis file 60

Appendix C: Brake Three-dimensional graph 61

1 Introduction

1．1 Overview of braking system

Twenty-first Century is the era of rapid development of the automotive industry, the automotive industry has gradually become a pillar industry in many countries. With the rapid development of our national economy, the annual output and social quantity of automobiles are also increasing rapidly. The quality of automobile is related to whether our automobile industry can stride towards the world. Therefore, the improvement of automobile and related products is also very important.

With the improvement of the living standard and the rapid development of science and technology, people's life rhythm is getting faster and faster. The rapid development of the expressway and the increase of speed and the intensity of traffic flow are increasing. Therefore, the fast demand for traffic tools is becoming higher and higher. In order to cope with the threat of high speed to the safety of people, many regulations have put forward higher requirements for the safety of the car, and the reliability of the automobile brake system has become one of the most important aspects.