Patent ID: 7085640

Claim:
A lockup control device for a lockup clutch of a torque converter for a vehicle, the torque converter comprising a pump impeller connected to an engine and a turbine runner connected to an automatic transmission, and transmitting a torque between the pump impeller and the turbine runner via a fluid and the lockup clutch according to a tightening force of the lockup clutch, the device comprising: a mechanism which regulates the tightening force; a sensor which detects a rotation speed of the pump impeller; a sensor which detects a rotation speed of the turbine runner; a sensor which detects a running condition of the engine; and a programmable controller programmed to: calculate a real relative rotation speed of the pump impeller and the turbine runner from the rotation speed of the pump impeller and the rotation speed of the turbine runner; determine a target relative rotation speed based on the running condition of the engine; perform feedback control of the mechanism based on a difference between the target relative rotation speed and the real relative rotation speed to cause the difference to decrease; perform feedforward control of the mechanism in combination with the feedback control; determine whether or not a variation in a feedforward control amount applied to the mechanism by the feedforward control has exceeded a predetermined value; and correct a feedback control amount applied to the mechanism by the feedback control in a direction to moderate an effect of the variation when the variation has exceeded the predetermined value.