Lock-up control device

Abstract

A lock-up control device controls an engaging force of a lock-up clutch, which shares engine output with a torque converter to transmit it toward an input shaft of a transmission of a car. First, target driving force is produced based on accelerator pedal opening and car velocity. Then, required torque is produced based on a gear ratio and the target driving force. Target engine speed is produced based on the required torque, wherein the target engine speed is set to avoid occurrence of abnormal sounds and abnormal vibrations. Thus, the lock-up clutch is controlled in such a way that real engine speed does not become less than the target engine speed in case of a gear change corresponding to a shift-up operation, for example. Basically, the lock-up clutch is controlled to have engaging force, which is made as maximal as possible to improve fuel efficiency. In other words, the lock-up clutch is controlled to be as tightly as possible. Or, the lock-up clutch which is initially set at a tight state is turned off just after the gear change start timing if it is predicted that the real engine speed after the gear change will become lower than the target engine speed.