With the rapid development of national economy, the output of automobiles has increased year by year, reaching 7.2 million in 2006. There are more and more cars in China, and their models are becoming more and more complicated. Especially with the rapid development of high technology and the wide application of some new technologies and materials in automobiles, it is more difficult to diagnose and eliminate automobile faults. This paper mainly introduces the fault analysis and maintenance methods of automobile clutch. Clutch is an important assembly necessary for manual transmission vehicles. Without the clutch, the car will not start and it is difficult to shift gears. In the process of using the car, the clutch will inevitably have such and such faults, which will directly affect the normal operation of the car. Nowadays, cars are rapidly entering families, and the degree of privatization of cars has increased. Car failures will affect everyone. It is of great practical significance to analyze and study the phenomena and causes of clutch failure, and explore the troubleshooting methods and maintenance techniques of clutch failure. This paper focuses on the clutch failure of Beijing Hyundai Motor Co., Ltd., so as to correctly understand the clutch failure and better use and maintain the clutch. 2 clutch overview In automobiles, the clutch is an important assembly in the transmission system of manual automobiles and electronically controlled mechanical automatic transmissions, and it is a necessary independent component to ensure that such automobiles can start and shift gears. 2. 1 Overview of clutch function and development 2. 1. 1 Clutch function The clutch is installed between the engine and the transmission to separate or engage the front and rear power connections. Its function is: 1) to make the car start smoothly; 2) Interrupt the power to the transmission system and cooperate with gear shifting 3) Prevent the transmission system from being overloaded 2. 1.2 The development of clutch. Multi-disc clutch, the pioneer of disc clutch used today, appeared after 1925. The main advantage of multi-disc clutch is that the clutch is engaged smoothly and there is no impact when it is started automatically. From the late 1920s to 1930s, only engineering vehicles, racing cars and high-powered cars used multi-disc clutches. With years of practical experience and technical improvement, people gradually tend to single-chip dry friction clutch, because it has the advantages of small moment of inertia of driven parts, good heat dissipation, simple structure, convenient adjustment, compact volume and complete separation. And some structural measures have been taken to achieve smooth joint, so now large, medium and small models are widely used. Now the single-chip dry friction clutch has been quite perfect in structural design. The driven plate with axial elasticity is adopted to improve the riding comfort when the clutch is engaged. The clutch driven plate assembly is equipped with a torsional damper, which can prevent the torsional vibration of the transmission system and reduce the noise and dynamic load of the transmission system. With the improvement of people's requirements for automobile comfort, the clutch is constantly improved on the original basis, and more and more dual-mass flywheel torsional dampers are applied to passenger cars, which can effectively reduce the noise of transmission system. 2.2 Types of clutches, working principles and requirements 2.2. 1 Types of clutches Automobile clutches include friction clutches, hydraulic couplings and electromagnetic clutches. The hydraulic coupling transmits torque through working fluid (oil), and the shell is connected with the pump wheel as a whole, which is the driving part; The turbine is opposite to the pump wheel and is a driven part. When the rotating speed of the pump impeller is low, the turbine cannot be driven, and the driving part and the driven part are separated. With the increase of pump impeller speed, the turbine is driven, and the driving part and the driven part are in a joint state. The electromagnetic clutch controls the engagement and disengagement of the clutch by turning on and off the coil. If the magnetic powder is placed between the driving and driven parts, the meshing force between them can be enhanced. This kind of clutch is called magnetic powder electromagnetic clutch. At present, the clutch matching with manual gearbox is mostly dry friction clutch, which can be divided into single disc, double disc and multi-disc according to the number of driven discs. Friction clutches can be divided into wet clutches and dry clutches. Working principle of clutch 2.2.2 Working principle of clutch: The driving part and driven part of clutch use friction between contact surfaces, or use liquid as transmission medium (hydraulic coupling) or magnetic transmission (electromagnetic clutch) to transmit torque, so that they are temporarily separated and gradually engaged, and the two parts are allowed to rotate with each other during transmission. At present, the friction clutch pressed by spring is widely used in automobiles. 2.2.2. 1 working principle of friction clutch: the engine flywheel is the transmission part of the clutch. The driven disc with friction plate and the driven disc hub are connected with the driven shaft (transmission drive shaft) through sliding splines. The compression spring compresses the driven disc on the end face of the flywheel. The torque of the engine is transmitted to the driven disk through the friction between the flywheel and the driven disk, and then the wheels are driven through the driven shaft and a series of components in the transmission system. The greater the pressure of the spring, the greater the torque that the clutch can transmit. 2.2.3 The basic requirements that the friction clutch should meet (1) ensure that it can transmit the maximum torque from the engine, and there is still a certain torque transmission margin. (2) When it can be separated, it can be completely separated, and the joint is soft and has good heat dissipation ability. (3) The moment of inertia of the driven part should be as small as possible. In this way, when shifting the clutch, the rotational speed of the part connected with the input shaft of the transmission is relatively easy to change, thus reducing the impact between gears.