The torque converter is located at the forefront of the automatic transmission, installed on the flywheel of the engine,

Its function is similar to that of a clutch in a car with a manual transmission. It uses the change of kinetic energy in the process of oil circulation to transfer the power of the engine to the input shaft of the automatic transmission, and can automatically and steplessly change the transmission ratio and the torque ratio within a certain range according to the changes in the resistance of the car. Certain deceleration and torque increase function.

　　The transmission gear mechanism in the automatic transmission adopts two types: ordinary gear type and planetary gear type. The common gear type transmission is adopted by only a few models due to its large size and relatively small maximum transmission. The gear transmission in most automatic transmissions for cars uses planetary gears.

　　 One of the important components of the automatic transmission is mainly composed of the sun gear (also called the center wheel), the inner ring gear, the planet carrier and the planet gear. The planetary gear mechanism is a mechanism that realizes the speed change. The change of the speed ratio is realized by using different elements as the active part and restricting the movement of different elements. In the process of changing the speed ratio, the entire planetary gear set still moves, and the power transmission is not interrupted, thus realizing the power shift.

　　 The shift actuator is mainly used to change the active element in the planetary gear or limit the movement of a certain element, change the direction and speed ratio of power transmission, and it is mainly composed of multi-plate clutches, brakes and one-way overrunning clutches. The role of the clutch is to transmit power to a certain element of the planetary gear mechanism to make it an active part. The function of the brake is to hold a certain element in the planetary gear mechanism and make it immobile. The one-way overrunning clutch is also one of the shifting elements of the planetary gear transmission. Its function is basically the same as that of the multi-disc clutch and brake. It is also used to fix or connect some sun gears, planet carriers, and ring gears in several planetary rows. And other basic components, let the planetary gear changer form gears with different transmission ratios. Principle or electronic automatic control principle, according to a certain rule to control the work of the shift actuator in the gear changer to realize automatic shift.