A viscous clutch according to the present invention, which is composed of a main body having a fluid storage chamber of a concave shape formed at a central portion thereof and a cover having a concave fluid operation chamber formed at a central portion thereof, comprises: a fan housing in which the main body is stacked on an upper side of the cover so that an opening of the fluid operation chamber can be covered; a drive shaft which extends in a vertical direction and has a lower end inserted through a bottom plate of the main body; a rotor fixedly coupled to the lower end of the drive shaft so as to be rotatable in the fluid operation chamber; a rotary assembly integrally coupled to the main body so as to cover an opening of the fluid storage chamber; a coil core mounted on an upper surface of the rotary assembly and generating an electromagnetic force when an electric current is applied from the outside; and a valve assembly for opening or closing a fluid outlet according to whether or not an electric current is applied to the coil core.

A cooling control system includes a prime mover, a fan to be rotated under rotational power of an output shaft of the prime mover, a housing to which the fan is attached, a rotor to be rotated under rotational power of the prime mover, the rotor and the housing, under the agency of a fluid, rotating together, a fluid setting circuit to determine an injection quantity of the fluid to be introduced into the gap, a fan rotation detection device to detect a fan actual rotation speed, a target rotation obtaining circuit to obtain a fan target rotation speed. The integral controlling circuit does not execute the integral control with a difference between the fan actual rotation speed and a fan target rotation speed being greater than or equal to a threshold, and executes the integral control with the difference being less than the threshold.

A vehicle heating system having a first viscous clutch and a pump and viscous clutch mechanism. The first viscous clutch has a first clutch input member. The pump and viscous clutch mechanism has a pump and a second viscous clutch. The pump includes a pump input member, while the second viscous clutch includes a second clutch input member. One of the pump input member and the second clutch input member is drivingly coupled to a portion of the first viscous clutch.