Patent ID: 7769517

Claim:
A lock-up clutch control apparatus for controlling a lock-up clutch provided in a torque converter installed between an engine and a transmission in a vehicle, comprising: a differential pressure generator which engages, causes a slip of or disengages the lock-up clutch by adjusting differential pressure supplied to the lock-up clutch; a sensor for detecting a rotational speed of the engine; a sensor for detecting an input rotational speed to the transmission; and a controller for conducting proportional integration control by using a command signal to the differential pressure generator, in order that an actual slip rotational speed, which is a difference between the engine rotational speed and the input rotational speed to the transmission, can become a target slip rotational speed, wherein the controller is programmed: to calculate a variation rate of the target slip rotational speed and determine whether the absolute value of the variation rate is equal to or less than a predetermined target slip rotational speed variation rate; to conduct integration accumulating a difference between the target slip rotational speed and the actual slip rotational speed; to determine whether an accumulated integration value is equal to or higher than a predetermined integration value; and to stop the integration when the accumulated integration value is equal to or higher than the predetermined integration value and when the absolute value of the variation rate of the target slip rotational speed is equal to or less than the predetermined target slip rotational speed variation rate, while the vehicle moves at a constant speed.