Lock-up clutch control device for vehicle, and lock-up clutch control method

A vehicular lockup clutch control method for a vehicle in which a torque converter is mounted between an engine and a transmission, wherein the torque converter includes a lockup clutch, the vehicular lockup clutch control method comprising:

• controlling engagement of the lockup clutch by a control unit;
• performing a learning control by the control unit when the lockup clutch shifts into an engaged state while the vehicle is running, wherein the learning control is configured to:
• calculate a lockup transmission torque estimated value based on a difference between an engine torque and a torque converter transmission torque;
• and
• obtain a learning value of an initial pressure as a hydraulic pressure command value at a start of the control of engagement of the lockup clutch, based on an elapsed time period from an event of commanding of the initial pressure to an event that the lockup transmission torque estimated value exceeds a capacity excess determination transmission torque threshold value;
• detecting a state of clutch capacity excess, and performing an operation of a learning value correction of reducing the learning value, by the control unit, in response to a situation where the lockup transmission torque estimated value exceeds the capacity excess determination transmission torque threshold value in a predetermined time period after commanding of the initial pressure;
• setting a quantity of the learning value correction for detection of the state of clutch capacity excess, depending on a maximum value of the quantity of the learning value correction during the learning control, in response to a first detection of the state of clutch capacity excess;
• and
• updating the learning value by subtracting the set quantity of the learning value correction from the learning value obtained.