Torque Converter Lock-up Clutch (TCC)
The TCC is a device which eliminates converter slip which helps to improve fuel consumption.
The TCC is engaged and released in a controlled manner. During the controlled phase, a slight speed difference between the impeller and the turbine wheel is established. This ensures that the engine's rotating vibration is not phased on to the transaxle. The result is optimum shift quality.
An electronic pressure-regulating valve determines pressure regulation of the TCC piston.
When the piston is open, the oil pressure behind the TCC piston is equal to the pressure in the turbine zone. The direction of flow is through the turbine shaft and through the space behind the piston to the turbine chamber.
The direction of flow is reversed through a valve in the hydraulic selector unit, engaging the TCC. At the same time the space behind the TCC piston is vented. The oil pressure passes from the turbine chamber to the TC piston and presses the piston against the converter cover. The turbine is thus blocked by way of the linings between the piston and the cover, permitting rigid through drive with no slip or reduced slip to the mechanical stage of the transaxle.