Lock-up clutch control device

A lock-up clutch control device for controlling the engagement hydraulic pressure of a lock-up clutch of a torque converter disposed between an engine and a transmission, the device comprising

• base hydraulic pressure calculation device that calculates, based on an input torque from the engine, a base hydraulic pressure Pb for engaging the lock-up clutch,
• input rotational speed calculation device that detects an input rotational speed of the transmission,
• cylinder cut-off detection device that detects a cylinder cut-off state of the engine,
• correction factor calculation device that calculates, based on the input rotational speed of the transmission detected by the input rotational speed calculation device and the cylinder cut-off state of the engine, a correction factor α, which is greater than 0 but less than 1, for correcting the base hydraulic pressure Pb, and
• commanded hydraulic pressure calculation device that calculates a commanded hydraulic pressure Pc of the lock-up clutch from the base hydraulic pressure Pb and the correction factor α, wherein
• the commanded hydraulic pressure calculation device calculates the commanded hydraulic pressure Pc as a present value from the base hydraulic pressure Pb and the correction factor α by adding to a previous value of the commanded hydraulic pressure a value obtained by multiplying a differential pressure between the base hydraulic pressure Pb and the previous value of the commanded hydraulic pressure Pc by the correction factor α, and the commanded hydraulic pressure Pc is made to converge to the base hydraulic pressure Pb by repeating the calculation a predetermined number of times.