Patent ID: 6860834

Claim:
An engaging force control device of a lockup clutch for use with a torque converter for a vehicle, the lockup clutch engaging a pump impeller connected to an engine with a turbine runner connected to an input shaft of an automatic transmission according to an engaging force, comprising: a sensor which detects an engine rotation speed (EngREV); a sensor which detects an input rotation speed (PriREV) of the automatic transmission; an engaging force regulating mechanism which regulates the engaging force of the lockup clutch; and a programmable controller programmed to: calculate a relative rotation speed (ω SLPR ) of the pump impeller and the turbine runner from the engine rotation speed (EngREV) and the input rotation speed (PriREV) of the automatic transmission; compare an initial engine rotation speed (ST_EREV) which corresponds to an engine rotation speed when control of the engaging force is started, with a predetermined target engine rotation speed (TGT_EREV); set a target relative rotation speed (ω SLPT ), when the initial engine rotation speed (ST_EREV) is equal to or greater than the predetermined target engine rotation speed (TGT_EREV), according to a difference between the target engine rotation speed (TGT_EREV) and the input rotation speed (PriREV) of the automatic transmission; set the target relative rotation speed (ω SLPT ), when the initial engine rotation speed (ST_EREV) is smaller than the predetermined target engine rotation speed (TGT_EREV), to gradually vary from an initial relative rotation speed (ST_EREV) which corresponds to the relative rotation speed (ω SLPR ) of the pump impeller and the turbine runner when control of the engaging force is started, to a predetermined target change-over relative rotation speed (CHG_SREV); and control the engaging force regulating mechanism such that the relative rotation speed (ω SLPR ) coincides with the target relative rotation speed (ω SLPT ).