摘 要

变速器是汽车传动系统中非常关键的部件，它的设计结果将直接影响到汽车的实际使用情况。变速器用于改变由发动机传递到驱动轮的扭矩和速度。目的是使汽车能够在各种驾驶条件下获得不同的牵引力和速度，例如当场启动，爬坡，转弯和加速。在有利的工作条件下工作。变速箱具有空档和倒档。变速箱在需要时还具有动力输出功能。

由于齿轮箱在低速挡工作时具有很大的力，因此普通齿轮箱的低速挡布置在轴的后支架附近，然后每个档的齿轮按从低档到高档的顺序排列。这不仅使轴具有足够的刚性，而且确保了易于组装。变速箱的整体结构刚度与轴和壳体的结构有关。通常，通过控制轴的长度，即齿轮的数量，以确保齿轮箱具有足够的刚度。

本文设计并研究了一种两轴五速手动变速器，解释了变速器的工作原理，对变速器的每个齿轮以及轴进行了详细的设计计算，并进行了强度检查，并选择了一些标准零件。设计了变速箱中的传动方案，并介绍了变速箱中各个组件的材料选择。

关键词：手动变速器；齿轮；轴；强度校核

Abstract

The transmission is a key part of the automobile transmission system, and its design will directly affect the actual performance of the automobile. The transmission is used to change the torque and speed transmitted by the engine to the driving wheels. The purpose is to enable the car to obtain different traction and speed under various driving conditions such as starting on the spot, climbing, turning, and accelerating. Work within favorable working conditions. The transmission has neutral and reverse gears. The transmission also has a power output function when needed.

Because the gearbox has a large force when working in the low gear, the low gear of the general gearbox is arranged near the rear support of the shaft, and then the gears of each gear are arranged in order from low gear to high gear. This not only makes the shaft sufficiently rigid, but also ensures easy assembly. The overall structural rigidity of the gearbox is related to the structure of the shaft and the housing. Generally, by controlling the length of the shaft, that is, the number of gears, to ensure that the gearbox has sufficient rigidity.

This paper designs and studies a two-shaft five-speed manual transmission, explains the working principle of the transmission, makes detailed design calculations for each gear and shaft of the transmission, and performs strength check, and selects some standard parts. The transmission scheme of the transmission design and tells about the selection of materials of various components in the transmission.

Key Words：manual transmission; gear; shaft; strength check.

Contents

Chapter 1 Introduction 1

1.1 Background, purpose and significance of the topic 1

1.2 Research status at home and abroad 3

1.3 Basic content and objectives of the design 5

Chapter 2 Overall Scheme Design of Manual Transmission 7

2.1 Design requirements of the transmission 7

2.2 Design content of the transmission 8

2.3 Layout scheme of transmission mechanism 8

2.3.1 Structural analysis and type selection of transmission mechanism 8

2.3.2 Reverse transmission layout plan 10

2.3.3 Scheme analysis of the main parts of the transmission 11

2.4 Summary of this chapter 12

Chapter 3 Selection of main parameters of transmission and design of main parts 13

3.1 Number of files 13

3.2 Transmission ratio range 13

3.3 Determination of the transmission ratio of each gear 14

3.3.1 Determination of the transmission ratio of the main reducer 14

3.3.2 Calculation of the lowest gear ratio 14

3.3.3 Selection of various gear ratios 16

3.3.4 Selection of center distance 16

3.3.5 Transmission dimensions 17

3.4 Selection of gear parameters 18

3.4.1 Modulus 18

3.4.2 Pressure angle 19

3.4.3 Helix angle β 19

3.4.4 Tooth width b 20

3.4.5 Coefficient of addendum height 20

3.5 Distribution of gear teeth of each gear and calculation of transmission ratio 20

3.6 Summary 27

Chapter 4 Strength Check of Transmission Gears and Shafts 28

4.1 Selection principle of gear materials 28

4.2 Material and heat treatment of transmission gear 29

4.3 Bending strength check of transmission gear 30

4.4 Gear contact stress check 34

4.5 Design of shaft structure 37

4.6 Checking the shaft 38

4.6.1 Calculation of shaft stiffness 38

4.6.2 Shaft strength calculation 42

4.7 Bearing selection and life calculation 44

4.8 Summary of this chapter 46

Chapter 5 Transmission Synchronizer and Design of Its Structural Elements 48

5.1 Function and classification of synchronizer 48

5.1.1 Structure of lock ring type synchronizer 48

5.1.2 Working principle of lock ring synchronizer 49

5.1.3 Determination of the main dimensions of the lock ring synchronizer 50

5.2 Determination of the main parameters of the synchronizer 51

5.2.1 Friction factor 51

5.2.2 Determination of the main dimensions of the synchronization ring 52

5.2.3 Locking angle 53

5.2.4 Transmission housing 53

5.3 Summary 54

Chapter 6 Conclusion 55

References 56

Thanks 57

Chapter 1 Introduction

1.1 Background, purpose and significance of the topic

For more than a century since the advent of automobiles, especially the mass production of automobiles and the great development of the automobile industry, automobiles have entered modern life for the development of the world economy and human development. Made an indelible contribution and set off an epoch-making revolution. As an important part of the automobile transmission system, the transmission directly affects the power and economy of the automobile, the reliability and portability of the operation, and the smoothness and efficiency of the transmission. Although the traditional manual transmission has the disadvantages of large shift shock, large displacement, and troublesome operation, it is still widely used in modern automobiles due to its advantages of high transmission efficiency, mature manufacturing technology, and low cost. ^[1]。

The car is an important means of transportation. Its design and manufacturing level is an important indicator to measure the level of scientific and technological development of various countries. The automobile industry is a capital-intensive, technology-intensive, talent-intensive, comprehensive and economical industry. Almost without exception, the industrialized countries in the world regard the automobile industry as the pillar industry of the national economy ^[2]. The development, production, sales, and operation of automobiles are closely related to many fields of the national economy, and play an important role in promoting social economic construction and scientific and technological development. The automobile is also a sign of the development level of social material life. The car ownership increases with the increase of national per capita income. In many developed countries, the number of cars is huge and has spread to millions of families, which has led to major changes in people’s social lifestyles ^[3]。

In 1886, the first car born in the world was not equipped with a transmission. It was not until 1902 that France produced the first car with a transmission. At present, most cars still use a mechanical transmission, transfer case and final drive to form the vehicle's driveline. Its simple structure, convenient operation, and low cost are still the main assemblies commonly used in automotive transmission systems ^[4]. Since piston-type internal combustion engines are widely used in automobiles, the torque and speed change range is small, and complex use conditions require that the traction force and speed of the car can be changed in a relatively large range ^[5]. A gearbox is provided for this in the drive train. Mechanical manual transmissions are widely used in various automobiles due to their advantages of simple structure, high transmission efficiency, low manufacturing cost and reliable operation. Mechanical manual transmission will still dominate for a long time in China's light and medium truck transmission system ^[6]。