In comparison to a normal dry clutch, the torque converter clutch (TC or TCC) runs with multiple, higher starting torques. It is made up by an oil-filled hydraulic torque converter, the associated torque converter lock-up clutch, and a downstream dry clutch.
- The hydrodynamic torque converter consists of an impeller, a turbine wheel, and a stator which build a closed, circular housing. The impeller, which is driven directly by the engine, converts the mechanical energy from the engine into hydrodynamic energy. In the turbine wheel, connected to the transmission's input shaft, the oil flow direction is reversed once it emerges from the impeller. The stator, located between impeller and turbine wheel, has the task of reversing the flow of oil emerging from the turbine once again, and re-directs it to the impeller. This redirection of flow delivers a corresponding level of torque to the stator, thereby increasing the turbine torque. The ratio of turbine torque to impeller torque is known as conversion (torque increase). The greater the difference in the speeds of the impeller and turbine, the higher the torque. Maximum torque conversion is generated when the turbine wheel is stationary. As turbine speed rises, the level of torque conversion declines (output speed). No further torque conversion takes place once a 'turbine wheel-impeller' speed synchronization of approx. 80% is reached. At this point, the torque converter is locked up; consequently, the output torque is identical with the engine torque.
- The torque converter lock-up clutch upstream of the torque converter has been designed as a hydraulic multidisk clutch. It's task is to lock up the converter, i.e. to generate the mechanical connection between the engine and the transmission; thus, it limits torque converter operation to the range of its ultimate economic efficiency.
- The third major assembly of the torque converter clutch (TCC) is a dry clutch. This dry clutch will always be used once the torque converter is locked up and a gear change takes place.