论文总字数：92056字

武汉理工大学毕业设计（论文）

双层公交客车转向系设计

学院（系）： 国际教育学院

专业班级： 车辆gj1604

学生姓名： 刘超

指导教师： 袁晓红

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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：刘超

2020年 5 月 31 日

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作者签名： 刘超 2020年 5 月 31 日

导师签名： 年 月 日

Abstract

The topic of this graduation project is the design of the double-decker bus steering system. The graduation project is centered on the design and verification of the circulating ball steering gear of the mechanical steering system, and the design and check calculation of the power steering mechanism. The first is an overview of automobile steering systems. It analyzes the working principles, advantages, disadvantages, and development status of various steering systems, and explains the working principles of various steering gears. The second is to do pre-design data preparation, choose the steering system plan, and determine the main performance parameters of the steering system. The third is the selection of the steering gear and the initial setting of various parameters, the selection of various data of the recirculating ball steering gear, and the stress analysis and data verification of its main components. The fourth is the design of the power steering mechanism. It first outlines the requirements of the power steering mechanism, and then selects the layout plan of the power steering mechanism and calculates various data. Fifth, the size design choice of steering transmission mechanism. Finally, three-dimensional modeling of the steering system is carried out to obtain part drawings and assembly drawings.

The steering system can maintain or change the direction of the car while driving.When the car is turning, the steering system can ensure that the angle relationship between the steering wheels is coordinated. The power of the mechanical steering system relies on the driver's hand to turn the steering wheel, and the steering wheel is deflected by the steering gear and the steering transmission mechanism. For power steering cars, it is also equipped with a power system. The power system can reduce the driver's hand strength. The steering system components include the steering control mechanism, steering gear and steering transmission mechanism.

Keywords: steering system; steering gear; recirculating ball type; power steering

Catalogue

Abstract i

1 Introduction 1

1.1 Research status of automobile steering system 1

1.1.1Mechanical steering system 2

1.1.2 Hydraulic Power Steering System (HPS) 2

1.1.3 Electronically controlled hydraulic power steering system (EHPS) 3

1.1.4 Electric Power Steering System (EPS) 5

1.1.5 Wire-controlled steering system (SBW) 7

1.2 Overview of steering system design 8

1.2.1 Requirements for the steering system 9

1.2.2 Steering control mechanism 10

1.2.3 Steering gear 11

1.3 Significance of the topic 12

2 The selection of the transformation department plan and the determination of the main parameters 13

2.1 Choice of steering system 13

2.1.1 Steering wheel 13

2.1.2 Steering shaft 13

2.1.3 Steering gear 14

2.1.4 Steering trapezoid 16

2.1.5 Selected data 17

2.2 Main performance parameters of steering system 17

2.2.1 Steering efficiency 17

2.2.2 Variable characteristics of transmission ratio 19

2.2.3 Steering gear angular transmission ratio and its changing law 22

2.2.4 The total number of turns of the steering wheel 22

3 Design of recirculating ball steering gear 23

3.1 Recirculating ball steering parameters 23

3.2 Screw, steel ball, nut transmission pair design 24

3.2.1Ball center distance, Screw outer diameter，Nut inner diameter 24

3.2.2 Steel ball diameter and quantity 26

3.2.3 Raceway section 26

3.2.4 Contact angle 26

3.2.5 Pitch and helix lead angle 27

3.2.6 Working steel ball circle 27

3.2.7 Selection of materials 28

3.3 Rack, gear fan transmission pair 28

3.3.1 Calculation of main parameters of tooth fan 29

3.3.2 Material selection of tooth fan shaft 31

3.4 Calculation and verification of steering gear 33

3.4.1 Drag torque 33

3.4.2 Contact stress between steel ball and raceway 35

3.4.3 Tooth bending stress 36

3.4.4 Steering rocker shaft diameter 36

4 Design and calculation of power steering structure 38

4.1 Requirements for power steering 38

4.2 Analysis of layout scheme of hydraulic power steering mechanism 38

4.3 Calculation of hydraulic power steering mechanism 41

4.3.1 Calculation of power cylinder size 41

4.3.2 Selection of distribution valve parameters 43

4.3.3 Evaluation index of power steering 46

5 Steering transmission mechanism 49

5.1 Integral steering trapezoidal design 49

5.2 Steering transmission mechanism arm, lever and ball pin 50

6 Conclusion 51

References 52

Appendix 53

Thanks 54

1 Introduction

1.1 Research status of automobile steering system

As an important part of the car chassis, the performance of the steering system directly affects the safety, steering stability and driving comfort of the car. It can ensure the driving safety of vehicles, reduce traffic accidents and protect the personal safety of drivers. With the rapid development of modern automotive technology, the steering system has evolved from the early pure mechanical steering system, hydraulic power steering system (HPS), electronically controlled hydraulic power steering system (EHPS) to today's electric power steering system (EPS) And wire steering system (SBW) ^[1].

The steering system is divided into a mechanical steering system and a power steering system according to the different steering power energy used.

The mechanical steering system refers to the steering system with manpower as the energy source. The component parts include steering transmission mechanism, steering control mechanism and steering gear. The core component of the steering system is the steering gear. The function of the steering gear is to transform the rotary motion of the steering mechanism into the linear motion of the transmission mechanism.

In addition to the three major mechanical components, the power steering system also contains a set of power steering devices. For the steering system using a hydraulic power assist system, the steering power assist device includes pumps, oil pipes, pistons, valves and oil storage tanks.

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