There are three common types of automatic transmission: at, CVT, AMT and DSG. At that time, at was widely used, and at almost became the pronoun of automatic transmission.

　　At is composed of hydraulic torque converter, planetary gear and hydraulic operation system, which ends the variable speed and torque conversion by means of hydraulic transmission and gear combination. Among them, the hydraulic torque converter is an important component, which is composed of pump wheel, turbine and guide wheel, and has the effect of transmitting torque and gathering and dispersing.

　　Compared with at, CVT saves the cluttered and clumsy gear combination variable speed drive, but two groups of belt wheels for variable speed drive. By changing the touch radius of the driving wheel and the driven wheel, the transmission belt can be changed. Because the gear transmission is canceled, the transmission ratio can be changed at will, the speed change is smoother, and there is no sudden jump feeling of shifting.

　　AMT and hydraulic automatic transmission (at) are the same step automatic transmission. On the basis of the general manual transmission, it replaces the separation and engagement of the original manual operated agglomerator and the gear selection and shifting behavior of the transmission by adding the electric equipment controlled by microcomputer to end the automatic shifting.

　　There is a significant difference between DSG transmission and traditional automatic transmission. DSG did not choose hydraulic torque converter from the beginning. This transmission is not produced on the basis of the traditional concept of automatic transmission. It describes that DSG engineers have taken a new technological road with remoulding ability, which connects the flexibility of manual transmission with the convenience of traditional automatic transmission.

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