摘 要

悬架是现代汽车上的重要总成之一，它把车架（或车身）与车轴（或轮胎）弹性地连接起来。它的主要作用是传递作用在车轮和车身之间的一切力和力矩，比如支撑力、制动力和驱动力等，并且缓和由不平路面传给车身的冲击载荷、衰减由此引起的振动、保证乘员的舒适性、减小货物和车辆本身的动载荷。

本文对标致308车型的后悬架系统进行设计并对设计结果进行校核，保证设计满足汽车对安全方面的要求。通过查阅车型数据，确定后悬架类型为扭力梁式非独立悬架，通过计算选用确定悬架固有频率，后悬架刚度，后悬架静挠度和后悬架动挠度。设计计算螺旋弹簧的有关参数，弹簧中径，弹簧丝直径，旋绕比，弹簧圈数，节距和螺旋角，并对螺旋弹簧的变形和剪应力进行了计算和校核。还选取了双筒充气液力式减振器作为悬架的减振器，通过计算确定了减振器的主要参数，相对阻尼系数，阻尼系数，最大卸载力和工作缸直径等。

关键词：非独立悬架，螺旋弹簧，减振器

Abstract

Suspension is one of the most important assemblies in modern automobile. It connects the frame (or body) with the axle (or tire) flexibly. Its main function is to transfer the shear force and torque between the wheel and the car body, such as support force, braking force and driving force, etc. And ease the impact load transmitted to the body by the uneven road surface, reduce the vibration caused by it, ensure the comfort of the occupants, and reduce the dynamic load of the goods and the vehicle itself.

In this paper, the rear suspension system of Peugeot 308 is designed and the design results are checked to ensure that the design meets the safety requirements of the vehicle. By consulting the vehicle data, it is determined that the type of rear suspension is torsional beam non-independent suspension, and the natural frequency of suspension, stiffness of rear suspension, static deflection of rear suspension and dynamic deflection of rear suspension are determined by calculation. The relevant parameters of the spiral spring, the middle diameter of the spring, the diameter of the spring wire, the winding ratio, the number of coils, the pitch and the helix angle are designed and calculated, and the deformation and shear stress of the spiral spring are calculated and checked. The double cylinder inflatable hydraulic shock absorber is also selected as the shock absorber of the suspension. The main parameters of the shock absorber, relative damping coefficient, maximum unloading force and working cylinder diameter are determined by calculation.

Key Words：Non-independent suspension，spiral spring，shock absorber

Catalogue

Chapter 1 Introduction 1

1.1 The purpose and significance of this paper 1

1.2 Basic contents, objectives, technical programmes and measures to be taken of the study (design)............................................................................................................................................1

1.2.1 Basic elements of research (design) 2

1.2.2 Research objectives (design) 3

1.2.3 Technical options and measures to be taken 3

Chapter 2 Design and calculation of overall parameters of suspension system 5

2.1 Main technical parameters 5

2.2 Determination of suspension performance parameters 5

2.2.1 Selection of natural frequencies 5

2.2.2 Stiffness of rear suspension 6

2.2.3 Static deflection of rear suspension 6

2.2.4 Dynamic deflection of rear suspension 7

2.2.5 Elastic characteristic curve of suspension 7

2.3 Summary 8

Chapter 3 Design and calculation of Elastic elements 9

3.1 Determination of main parameters of spiral spring 9

3.1.1 Spring end structure 9

3.1.2 Middle diameter of spring 9

3.1.3 Spring Index (spinning ratio) 10

3.1.4 Number of spring coils 10

3.1.5 Spring pitch or helix angle 12

3.1.6 Spring height 12

3.1.6.1 Free height of spring H0 12

3.1.6.2 Press and height Hb 12

3.1.7 Outside and inside diameter of spring 13

3.2 Calculation and check of Spring stress 13

3.2.1 Calculation of deformation and shear stress of spring 13

3.2.2 Material and allowable stress of Helical Spring 13

3.2.3 Strength checking 13

3.3 Summary 15

Chapter 4 Design of suspension guiding Mechanism. 16

4.1 Design requirements for guiding mechanisms 16

4.2 Layout parameters of the guiding mechanism 16

4.2.1 Roll center.....................................................................................................................16

4.2.2 Roll axis........................................................................................................................17

4.2.3 Trim center....................................................................................................................17

4.2.4 Anti-braking pitch (anti-braking pitch angle)...............................................................18

4.2.5 Resistance to driving pitch (resistance to driving rear elevation).................................18

4.3 Control arm and thrust rod. 18

4.4 Summary 20

Chapter 5 Design of main parameters of shock Absorber 21

5.1 Selection and classification of shock absorbers 21

5.2 selection of relative damping coefficient ψ 21

5.3 Determination of damping coefficient δ of shock Absorber. 23

5.4 Determination of maximum unloading force F0 23

5.5 Determination of working cylinder diameter D of simple shock Absorber 24

5.6 Summary 25

Chapter 6 Conclusion 26

Reference 28

Acknowledgements  29

Chapter 1 Introduction

The automobile suspension system is an important part of the site platform, which directly affects the operational stability, ride comfort and safety of the vehicle, which is often included in the technical specification table as one of the standards to evaluate the performance and quality of the vehicle^[1].

1.1 The purpose and significance of this paper

At present, the rear suspension which is most widely used in ordinary family vehicles is torsional beam semi-independent suspension and multi-link suspension. Car buyers today are more likely to buy cars with independent rear suspensions, according to the results of an online survey.

They generally believe that independent suspension cars are more comfortable than non-independent suspension cars. So does the torsional beam non-independent suspension really have a lot of shortcomings? Since the 1970s, this classical structure still has strong vitality and is widely used in the front wheel drive of the rear suspension system of small and medium-sized family cars. In the past 40 years, the major automobile manufacturers have continuously improved and optimized the torque beam semi-independent suspension^[2]. The main components of the suspension are as follows: the torsional crossbeam is used to bear the main vertical and lateral torque; the longitudinal swinging arm is welded on the left and right sides of the torsional crossbeam; the elastic element and the connecting bracket are arranged in the front end of the torsional crossbeam. A longitudinal swing arm used to connect the body of a car; a spring shock absorber system.

Torque beam semi-independent suspension, although this kind of suspension is called semi-independent suspension, its essence is non-independent suspension. only by adding a balance bar to the torsional beam non-independent suspension can the wheels tilt to maintain the stability of the vehicle. The rear suspension has the advantages of low cost, light weight, simple suspension structure, small occupation area, easy to obtain large tail distance, good linear stability, low rear tire loss and so on. But the disadvantage is that although the balance rod is added to maintain the stability of the vehicle, when one wheel runs, the other wheel will still make the corresponding jump, so that the whole body vibration or tilt, so the comfort is poor. The independent suspension can improve the driving stability of the vehicle, but it has some shortcomings, such as complex structure, high cost, inconvenient maintenance and so on. At the same time, because of the complex structure of the car body, it will also occupy some of the driving space in the car^[3].

So how to combine the advantages of the two to design a more comfortable model? I think Peugeot 308 has provided a satisfactory answer for the majority of car enthusiasts.