Control device and control method for lock-up clutch

A control device for a lock-up clutch comprising:

• a control unit configured to control an engagement state of the lock-up clutch of a torque converter provided between an engine and an automatic transmission, and to perform a slip lock-up control by performing a feedback control of an engagement hydraulic pressure of the lock-up clutch to be a first slip amount during coasting;
• an abnormality determination unit configured to determine an abnormality when a state occurs with a slip amount of the lock-up clutch being equal to or greater than a second slip amount that is greater than the first slip amount;
• a release control unit configured to release the lock-up clutch when the abnormality is determined by the abnormality determination unit;
• and
• a prohibition unit configured to allow the control unit to raise the engagement hydraulic pressure of the lock-up clutch by a prescribed pressure, and to prohibit determination by the abnormality determination unit, when a transmission ratio of the automatic transmission is downshifted in response to a driver's downshifting operation of the automatic transmission during coasting while the slip lock-up control is performed.