论文总字数：55391字

摘 要

制动系统作为汽车当中一个极其重要的系统，是强制使行驶中的汽车减速或停车和使下坡行驶的汽车的车速保持稳定以及使已停止的汽车在原地（包括斜坡上）驻留不动的机构^[1]。近这些年来，随着我国的高速公路的迅速建设发展以及汽车的平均车速的进一步提高还有道路上的车流密度的日益增大,人们的出行安全就更加需要保障，而为了保证行车的安全、停车的可靠,汽车制动系统的稳定工作和可靠性也就显得日益重要；同时，开发出一个具有良好性能的汽车制动系统对于开拓市场和提高汽车销量都有着决定性的重要作用。

双层公交客车是有着上、下两层乘坐空间的大型公交车，有着载客量大，节省停泊空间的优点，虽然双层公交车的使用较容易受到建筑物的高度限制，但相比起要达到相同载客量的挂接式公交车，双层公交车在转向及上落斜坡方面会比挂接式公交车更加灵活。本次设计根据其中一款双层公交客车（金龙 XMQ6112SGBEVM）的相关数据和特点，通过理论分析和计算对其制动系统结构进行了设计。

关键词：双层公交客车；制动系；盘式制动器；气压盘式制动器。

Abstract

As an extremely important system among automobiles, the braking system is the one to force the deceleration or to stop of the running car and to stabilize the speed of the downhill car and to keep the stopped car in place (including on the slope)^[1]. Since 2000, with the rapid construction and development of highways in China and the further increase in average vehicle speeds and the increasing density of traffic on the roads, most people pay more attention on the safety when they are driving, and in order to ensure the safety of driving and the reliability of parking, the stable operation and reliability of automotive brake systems are becoming increasingly important, the development of a car brake system with a good performance has a decisive and important role in opening up the market and increasing car sales as well.

The double-decker bus is a bus with two upper and lower floors, which has the advantages of large passenger capacity and saving parking space. Although the double-decker bus is more susceptible to height restrictions of buildings, it will be more flexible in terms of turning and ascending and descending slopes compared to mounted buses that have the same passenger capacity. This paper designs the main structure of the braking system through theoretical analysis and calculation based on the relevant data and characteristics of a double-decker bus (Jinlong XMQ6112SGBEVM).

Key Words：Double-decker bus, Brake system, Disc brake, Air disc brake.

Contents

Chapter One Introduction 1

1.1 The background and significance of the thesis research 1

1.2 Application of brakes at home and abroad 1

1.2.1 Application of brakes abroad 1

1.2.2 Application of brakes at home 1

1.3 Classification and characteristics of disc brakes 2

1.4 The content of the paper 6

Chapter Two Overall design of the braking system 7

2.1 Preliminary selection of system main parameters 7

2.1.1 Drawing of ideal braking force distribution curve 7

2.1.2 Preliminary Selection of Synchronous Adhesion Coefficient and Braking Force Distribution Coefficient 10

2.2 Calculation and selection of main brake parameters 12

2.2.1 Front and rear axle braking force determination 12

2.2.2 Determination of brake type 12

2.2.3 Brake main component type and parameter determination 14

2.2.4 Calculation and selection of brake efficiency factors 17

2.2.5 Calculation of braking torque 17

2.3 Effective radius of lining pad 18

Chapter Three The Design and Calculation of brake driving mechanism 20

3.1 Brake chamber 22

3.2 Gas tank 23

3.3 Air compressor 25

Chapter Four Brake system design performance check 26

4.1 The energy capacity check 26

4.2 Braking distance check 28

Chapter Five Conclusion 29

References 30

Acknowledge 32

Chapter One Introduction

1.1 The background and significance of the thesis research

With the continuous increase in the per capita car ownership in China, cars have already became a convenient tool in people's lives, but due to the impact of urban traffic pressure, many people choose to travel by bus, and this situation directly causes the bus to be overcrowded, and therefore the braking performance of the bus is directly related to the personal safety of many people, so the safety of the bus is getting more and more attention. According to some relevant information, among the traffic accidents caused by the problems of the vehicle itself, the accidents caused by the failure of the brake system account for almost 45% of the total, and the reasons for some major traffic accidents often are the braking distance is too long and the braking deceleration is too small^[1]. As a result, the braking performance of the bus plays an important role in the driving safety.

As an important member of the bus, double-decker buses have a larger passenger volume than that of ordinary buses, so it is even more necessary to ensure the safety of passengers and drivers, and an excellent braking system is an important guarantee for the vehicle driving safety. Meanwhile, on the other hand, the current double-decker bus has the problem that it is not pretty easy for passengers who seat on the second floor to get off the bus. Certainly, a good braking system can improve this problem in a certain degree, thereby increasing the competitiveness of double-decker buses in the market.

1.2 Application of brakes at home and abroad

1.2.1 Application of brakes abroad

Disc brakes had a very important position in the whole history of automobiles, and the first kind to be widely used is the hydraulic disc brake. However, several years later, due to the structural characteristics of hydraulic disc brakes and the problem that brake fluid will vaporize at high temperatures, its application range was also mainly limited to cars and light trucks^[2]. Since the 1980s, the research of air disc brakes has entered a substantial stage, and in the early 1980s, a company called WABCO began to develop the first generation of air disc brakes and then it gradually entered a substantial application stage. In the mid-to-late 1980s, another company called Meritor also began to develop and produce air disc brakes in small-scale at the same time. Then in the mid-1990s, the third company called Knorr began to orderly produce air disc brakes which had a structure of double push discs. However, due to the price reason, at first, air disc brakes were only used on city buses and buses with higher single prices and strict environmental protection requirements. But since 2000, air brake disc started as the standard configuration of public buses , and later it gradually extended the scope of application to other commercial vehicles^[3].

1.2.2 Application of brakes at home

The development of the domestic automobile industry is much later than the automobile industry in foreign country, and it was also affected by the foreign technical blockade, so that China still has some backward technology in the technology of automobile brake systems. At the same time, almost 80% of the active safety components which are purchased by mainstream domestic independent brands are foreign brands such as Bosch and TRW. The development process and the calibration of the technology are totally completed by the above-mentioned companies themselves, which makes the technology relatively blocked. It is difficult for domestic independent brands such as Wuhan Yuanfeng to reach the level of foreign brands in terms of product quality or price in such a short time, but this is also a direction for China's auto industry to break the technological monopoly^[4].

Similarly, domestic research on air disc brakes began in nearly 2000. About a year later, in 2001, the above-mentioned Wuhan Yuanfeng Company started the research on this product, and Yuanfeng company became the first company launched its own series of products in Chian, and in recent years this has achieved a batch supply. The main markets of Yuanfeng company are Beijing Public Transport and Suzhou Jinlong, and the products have already became serial. After that, other domestic manufacturers quickly followed up for research and development, such as Wuhan Wanxiang, Zhejiang Asia-Pacific, etc., but there are few manufacturers that have formed industrialized products and market scale. At present, the products of Wuhan Yuanfeng and Wuhan Wanxiang occupy the vast majority of domestic air disc brakes in the domestic market^[3]. At the beginning, the products of the main domestic manufacturers were mainly developed with reference to WABCO's single-push disc air disc brake. Because of its simple structure, the manufacturing process is much simpler and more reliable than the double-push disc pneumatic disc brake. Therefore, domestic manufacturers are relatively skillful in this technology.

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