Patent ID: 7503444

Claim:
An actuator for actuating a fan to cool an engine in an engine mounted viscous fan clutch wherein the fan clutch includes a work area, and a viscous fluid that is contained within a fluid reservoir and flows through the work area during engagement of the clutch and is prevented from flowing through the work area during disengagement of the clutch, the actuator comprising: a controller; a current source capable of transmitting varying electrical currents wherein said current source is connected to and in communication with said controller; a valve arm that controls the flow of the viscous fluid between the reservoir and the work area of the clutch and is moveable in the range between a closed position and an open position, wherein in said closed position the viscous fluid is retained within the reservoir and wherein in said open position the viscous fluid flows out from the reservoir to the work area; a valve shaft connected to said valve arm; a position sensor for detecting the position of said valve arm, said position sensor including a stationary capacitive plate and a rotating capacitive plate fixedly attached to and moveable with said valve arm, and wherein said position sensor is in communication with said controller; and a first shape memory alloy actuation wire having a first end and a second end, said first end is connected to said valve shaft and said second end is connected to said current source, and wherein said first shape memory alloy actuation wire is moveable between an activated length and a deactivated length; and a second shape memory alloy actuation wire having a first end and a second end, said first end is connected to said valve shaft and said second end is connected to said current source and is positioned in the range of 175 degrees −185 degrees from said second end of said first shape memory alloy actuation wire, and wherein said second shape memory alloy actuation wire is moveable between an activated length and a deactivated length; wherein when said first shape memory alloy actuation wire is subjected to an electrical current it is forced into its said activated state and wherein said second shape memory alloy actuation wire is subjected to an electrical current it is forced into its said activated state and varying electrical currents to said first and second shape memory alloy actuation wires force said valve shaft to rotate to a position in a range of positions between the valve arm closed position and the valve arm open position.