Air spring was born in the mid-nineteenth century. In 1847, John Lewis invented air spring. The air spring was used for vibration isolation of mechanical equipment in the early stage. The earliest patent for suspension components of vehicles appeared in 1901. It was used as vibration absorber of tramcar suspension. In the early 1930s, Vanstone Tire Company first applied air springs to the automotive industry. With the support of Henry Ford I and Thomas Alva Edison, Harvey Firestone developed the air spring suspension system AIREDE in 1934. In 1944, General Motors cooperated with Vanstone to conduct the first-round test on its bus. The test results show the inherent superiority of the air suspension system.

With the development of China's road transport industry, people put forward higher requirements for vehicle ride comfort and handling stability. In the traditional passive suspension, the parameters can not be changed once they are determined, which limits the further improvement of vehicle performance. The semi-active suspension with adjustable damping or stiffness parameters can automatically adjust the suspension parameters according to the driving state of the vehicle and the magnitude of road excitation, so that the suspension parameters can always be kept in the optimal setting state, which improves the ride comfort and handling stability of the vehicle. The air spring suspension has the characteristics of low natural vibration frequency, adjustable spring stiffness, low vibration and noise, and long service life. Air spring suspension can effectively solve the above problems.

At present, some researches on semi-active air spring suspension have been carried out at home and abroad, especially in the design of air spring suspension, the control of air spring suspension and the matching technology of vehicle. There are many companies with air suspension project in our country, but few companies have air suspension design and development technology, and the scale is very limited. Changchun Automobile Research Institute began the research of air suspension technology as early as 1957. Many universities and research institutes have done a lot of work and achieved many important research results. In 1990, domestic bus factories purchased air suspension and air suspension chassis from abroad for loading. At present, major domestic automobile factories, research institutes, colleges and universities have developed air suspension design and theoretical research. For example, Zhengzhou Yutong Company, Xiamen Jinlong Company and Suzhou Jinlong Company have independently developed and introduced air suspension products since 2002. They mainly choose Neway, Koman and Reyco air suspension. Dongfeng Automobile Research Institute has designed hybrid air suspension, and China Heavy Vehicle Group Corporation has installed floating bridge air suspension on the Steyr vehicle. Chongqing Highway Science Research Institute of the Ministry of Communications has studied the guiding mechanism of the non-independent air suspension of bus. Beijing University of Technology has also carried out the bench test of the air spring of Hino RC420 bus, and has carried out the analysis of the static and dynamic characteristics of the air spring and the volume characteristics of the air chamber. South China University of Technology has studied the vibration transmission characteristics of the air suspension, and has obtained some initial results. Step by step research results. However, compared with developed countries such as Europe and the United States, China's technological research in this area is still in an obvious backward position and basically belongs to the import stage. As for the research and design of the test-bed, there are only a few colleges and universities in China, some of which are still limited to the simulation stage, and there are basically no detailed and comprehensive scientific research results.

With the popularization of the application of air suspension, the research of air suspension has also been paid attention to. The development of automobile air suspension abroad has experienced the change of "leaf SPRING-AIR bag composite suspension-passive all-air suspension-active all-air suspension (ECAS electronic controlled air suspension system)". At present, such as Audi A6 wagon, LS-400 car produced by Toyota Company of Japan, S-Series 2000 car produced by Benz Company and Lincoln car and Ford car of the United States are equipped with electronic control air suspension system.

2. 研究的基本内容与方案

The main design contents of this graduation project are as follows:

2.1 Understand the structure, function and basic principle of automobile suspension

2.2 Selection of rear air suspension system for buses is completed.

2.3 Complete the design of rear air suspension system of bus.

1) Making the general assembly drawing of the rear air suspension of the bus.（Design drawings must contain assembly drawings and part drawings）

2) Drawing the parts of the main parts of the rear air suspension of the bus.（Three-dimensional drawing needs to be transformed into two-dimensional drawing in Mechanical drawing）