Lockup control system for automatic transmission

摘要

A lockup control system controls a lockup state of the automatic transmission employing a torque converter with a lockup clutch. The lockup control system executes a lockup clutch engagement pressure control for decreasing an engagement differential pressure of the lockup clutch at a predetermined differential pressure for a predetermined time period under a coast lockup state. Further, the lockup control system executes a learning control for obtaining the predetermined differential pressure by adding a differential pressure correction value to a differential pressure learning value by which the torque converter generates a slight slip under the coast lockup state. Therefore, even during the coast lockup state, both of suppressing vibrations by a lowering of a lockup capacity and maintaining a responsibility for re-increasing the differential pressure are ensured.