Patent ID: 6942597

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 an engaging force of the lockup clutch, the device comprising: a mechanism which regulates the engaging force; a sensor which detects a rotation speed of the pump impeller, the rotation speed of the pump impeller being equal to an engine rotation speed; 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 a 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 a feedforward control of the mechanism in an increasing direction of the engaging force based on a predetermined feedforward control value, in combination with the feedback control; determine from the engine rotation speed whether or not the engine is in a predetermined engine-stall prevention condition; and prohibit the feedforward control from being performed when the engine is in the predetermined engine-stall prevention condition.