Patent ID: 7387591

Claim:
In an external control fan clutch controlling method, in which a valve member is activated by an electromagnet to control the On/Off of an oil circulation passage and in which an effective contact area of oil in a torque transmission clearance between a drive side and a driven side is increased/decreased to control a rotating torque transmission from the drive side to the driven side, the method comprising: controlling On/Off of said valve member by a PID control on the basis of at least one signal of a radiator cooling liquid temperature, a fan speed, a transmission oil temperature, a vehicle speed, an engine speed, an accelerator (throttle) position, compressor pressure of an air conditioner, and an On/Off signal of the air conditioner, determining individual gains of said PID control by a gain matrix containing an optimum fan speed demanded by an engine side, an actually metered fan speed, and the engine speed, and outputting a control signal so that the PID control is made on the basis of the determined gains.