Abstract: A viscous fan drive which includes a moveable component in the scavenge or fill passageway that moves relative to pressure that is proportional to slip speed. The force which moves the component into and out of the passageway is directly proportional to the slip speed of the fan drive. This balances the fill and scavenge flow.

Abstract: A hydraulically controlled fan drive system (12) having a method of engagement includes a housing assembly (20) containing a hydraulic fluid (48) and an engaging circuit (36). The engaging circuit (36) includes a pitot tube (152) coupled within the housing assembly (20) that receives at least a portion of the hydraulic fluid (48). An engaging circuit (36) engages the housing assembly (20) to a fan shaft (44) in response to supply of the hydraulic fluid (48) from the pitot tube (152). An electrical control circuit (40) having a relief valve assembly (225) coupled to a main controller (176) is used to control the fluid pressure within the pitot tube (152) that controls the engagement of the housing assembly (20).

Abstract: A hydraulically controlled fan drive system for controlling the cooling of an engine and having a method of engagement includes a housing assembly containing a hydraulic fluid and an engaging circuit. The engaging circuit includes a pitot tube coupled within the housing assembly that receives at least a portion of the hydraulic fluid as the housing assembly rotates to drive a clutch pack (and coupled fan) via static pressure. A fluid controller having binary control adjusts the static pressure within the pitot tube at a given rotational speed, thereby controlling the engagement of the clutch pack to a fully engaged drive (utilizing friction type engagement), a fully disengaged drive, and at least two partially engaged clutch positions (i.e. partially engaged utilizing a wet viscous type clutch engagement). To control static pressure release, the fluid controller may utilize a dual spool system valving arrangement or a parallel fixed orifice binary control.

Abstract: An electronically-controlled viscous coupling is coupled to a water pump to control the coolant flow rate of engine coolant to an engine at a given engine speed to maximize fuel economy and minimize emissions. The viscous coupling has a stationary electrical coil that, when excited by electrical current, induces the driven disk to flex away from an input disk within the viscous, thereby increasing the size of the shear area, thereby decreasing the amount of torque produced to drive the water pump shaft and impellers that control the coolant flow rate. A carrier coupled to the back of the driven disk maximizes the amount of flex allowed to the driven disk, thereby assuring a maximum decrease in rotational speed of the impellers at a given engine speed and ensuring that the driven disk does not contact the stationary coil.

Abstract: An electronically-controlled viscous coupling is coupled to a water pump to control the coolant flow rate of engine coolant to an engine at a given engine speed to maximize fuel economy and minimize emissions. The viscous coupling has a stationary electrical coil that, when excited by electrical current, induces the driven disk to flex away from an input disk within the viscous, thereby increasing the size of the shear area, thereby decreasing the amount of torque produced to drive the water pump shaft and impellers that control the coolant flow rate. A carrier coupled to the back of the driven disk maximizes the amount of flex allowed to the driven disk, thereby assuring a maximum decrease in rotational speed of the impellers at a given engine speed and ensuring that the driven disk does not contact the stationary coil.