Patent ID: 7234578

Claim:
A torque converter comprising: a pump vane wheel connected so as to be rotatable with an output shaft of an engine of a vehicle; a turbine vane wheel connected so as to be rotatable with an input shaft of a transmission; a stator vane wheel secured to a housing of the transmission via a one-way clutch; a lock-up clutch mechanism which operates so as to control a slip amount of the turbine vane wheel and the pump vane wheel in accordance with a fluid pressure applied to a piston chamber of the lock-up clutch mechanism; a hydraulic pressure map defining the relationship between a parameter which influences a back pressure of a lock-up piston of the lock-up clutch mechanism and the back pressure of the lock-up piston; a sensor for measuring the parameter which influences the back pressure of the lock-up piston; and a lock-up pressure controlling unit for determining a value equivalent to the back pressure of the lock-up piston from the hydraulic pressure map and the parameter measured by the sensor and, the lock-up pressure controlling unit outputting a lock-up pressure to be applied to the piston chamber by compensating the value equivalent to the back pressure of the lock-up piston.