Working Principle of Automatic Transmission Hydraulic Torque Converter

The hydraulic torque converter is located at the front end of the hydraulic automatic transmission and mounted on the engine flywheel. Its function is similar to that of the clutch in a vehicle, and it can automatically and steplessly adjust the transmission ratio and torque ratio within a certain range according to changes in vehicle driving resistance, featuring a certain speed reduction and torque increase performance. Currently, the three-element locked-up integrated hydraulic torque converter composed of an impeller, a turbine, and a stator is widely adopted.

As shown in Figure 6, the impeller is integrated with the torque converter housing and serves as the driving element; the turbine is connected to the output shaft via splines and acts as the driven element; the stator is arranged between the impeller and the turbine, and fixed to the transmission housing through an overrunning clutch and a stator sleeve.

After the engine starts, the crankshaft drives the impeller to rotate via the flywheel. The centrifugal force generated by rotation throws the working fluid between the impeller blades from the inner edge to the outer edge along the blades; this part of the working fluid has both a circumferential component velocity rotating with the impeller and an axial component velocity rushing toward the turbine. The working fluid impacts the turbine blades, driving the turbine to rotate in the same direction as the impeller.