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1 the structure and principle of hydraulic torque converter, hydraulic torque converter, as an important part of modern auto transmission, is installed between the engine and the transmission, and the hydraulic oil (ATF) is used as the working medium, and the engine power is transferred to the transmission smoothly. And drive the oil pump of the hydraulic control system. Hydraulic torque converter is usually made up of three components, namely, pump wheel, turbine and guide wheel. The pump wheel is rigidly connected with the torque converter housing and rotates along with the engine flywheel, which is the input element of the torque converter. The turbine is connected to the input shaft of the gear shift system through the spline hole and is the output element. The guide wheel is fixed on the guide wheel shaft or guide wheel bushing in one-way direction through one-way clutch. The torque converter is assembled to form a closed working chamber which can withstand a certain pressure. The cavity is filled with ATF. When the engine works, the ATF flows from the center of the centrifugal pump wheel to the outer edge. After the impact of the turbine and the guide wheel, it flows back to the center of the pump wheel and then forms a circulating flow in the torque converter. The output power of the engine is transmitted to the turbine by the pump wheel through the ATF and input to the input shaft of the gear transmission system. 2 fault diagnosis of hydraulic torque converter, the common faults in the mechanical part of the torque converter have no gear, acceleration, low speed performance, low transmission efficiency, high oil temperature, and torque converter. 2.1 the failure analysis of the torque converter is the failure analysis of the torque converter, which means that the power transfer interrupts in the torque converter, that is, there is no driving response when the torque converter enters any position. The reasons for this phenomenon usually come from two aspects: first, there is no working fluid in the torque converter. Because there is no mechanical connection between the pump wheel and the turbine in the torque converter, the power is transmitted by oil as a medium. If there is no oil power, it will not be able to pass. The two is that the turbine is connected to the turbine shaft loosely or is stuck. The turbine blade is disconnected from the turbine hub hub welding place, the spline hub is connected with the turbine shaft to connect with the spline damage or the bearing damage in the torque converter will cause the turbine and the turbine shaft to be loosened or stuck, and the power can not be exported through the turbine. 2.2 the failure analysis of the torque converter with weak acceleration and poor high speed performance is mainly manifested by the insufficiency of the acceleration when the torque converter fault leads to the acceleration performance, but the driving condition at high speed is very normal. It is known from the working principle of torque converter that the speed difference between the pump wheel and the turbine in the torque converter is larger than that in the starting or accelerating conditions. Under the impact of the liquid flow, the unidirectional clutch locks the guide wheel, making the torque converter play a role in increasing the torque. If the one-way clutch damage can not lock the guide wheel, this effect will disappear, and the acceleration performance will be poor. Another situation is that the motor is normal at low speed and speed, but the engine speed and speed can not be improved correspondingly at high speed. The engine power is obviously insufficient, especially when the speed of the accelerator pedal is relaxed or the gear handle is placed at the N position at high speed, it can feel the speed obviously descend too fast. The ride comfort is worse. This phenomenon is usually caused by the slip of the one-way clutch of the guide wheel. Because the turbine speed exceeds the coupling speed of the torque converter, the fluid flow through the turbine will impact the back of the guide blade. If the one-way clutch can not achieve good skidding, the turbine motion resistance will become larger, the engine speed and speed increase difficult, and the performance of the vehicle is poor at high speed. 2.3 the failure analysis of the low transmission efficiency and high oil temperature of the torque converter analysis the low transmission efficiency and high oil temperature of the torque converter, which usually shows that the engine work normally and the oil consumption increases, the transmission and transmission oil temperature is very high, and the transmission oil is very easy to deteriorate, and the white smoke is taken at the refueling port seriously. The reason may be the shortage of oil in the torque converter or the clogging of the heat pipe and the wear of the thrust bearing of the torque converter. The blade gap between the pump wheel, the turbine and the guide wheel is too large. The fluid will lose a part of the energy in the form of heat energy and increase the temperature of the oil. The stagnation of the guide wheel one-way clutch causes the turbine to not rotate when the speed is high, and the liquid flow affects the back of the guide wheel and consumes energy. If the lock clutch can not be locked normally at work, a part of the energy loss will be lost in the torque converter, so the transmission efficiency is low and the oil temperature of the transmission is too high. 2.4 fault analysis of abnormal torque of hydraulic torque converter. Torque converter abnormal noise usually appears as two types of roar noise and sharp metal sound. The roar noise is mainly caused by the vibration noise caused by the imbalance of the torque converter or the incorrect installation position, as well as the incorrect clearance between the blades of the torque converter, the unidirectional clutch of the guide wheel can not achieve reliable locking and skidding, and causes the friction noise of the fluid flow, and the sharp metal sound communication is often the motion interference of the internal component of the torque converter. The percussion or friction of metal caused by friction material loss and clutch slip. 3 conclusion the hydraulic torque converter is installed between the engine and the transmission. The working condition of the torque converter directly affects the transmission of engine power and the performance of the vehicle. The hydraulic torque converter itself is a seal. It needs professional maintenance equipment for its disintegration and maintenance, and the general maintenance shop does not have the maintenance conditions, which brings inconvenience to the maintenance. Therefore, to ensure that the torque converter works reliably, it is necessary to do routine maintenance and repair work. If necessary, go to the professional repair shop for maintenance.