Control device of a lock-up mechanism

A lock-up mechanism control device comprising:

• a lock-up mechanism arranged in parallel with a hydraulic torque transmitting mechanism transmitting a rotatory power of a pump impeller connected with an output shaft of an engine to a turbine impeller connected with a wheel side element, the lock-up mechanism controlling a slip value between a rotational speed of the pump impeller and a rotational speed of the turbine impeller in response to hydraulic pressure supplied to the lock-up mechanism;
• target slip value calculating means for calculating a target slip value which remains fixed to completion of control of the lock-up mechanism based on driving conditions of a vehicle;
• actual slip value detecting means for detecting an actual slip value from the difference between the rotational speed of the pump impeller and the rotational speed of the turbine impeller;
• intermediate slip value setting means for setting an intermediate slip value between the actual slip value and the target slip value;
• hydraulic pressure controlling means for controlling the hydraulic pressure supplied to the lock-up mechanism in order for the actual slip value to coincide with the intermediate slip value;
• and
• intermediate slip value renewal means for reducing the intermediate slip value to a renewed intermediate slip value closer to the target slip value than the intermediate slip value when the actual slip value reaches the intermediate slip value and for reducing the renewed intermediate slip value based on a time until the actual slip value reaches the renewed intermediate slip value after the intermediate slip value is renewed.