ELECTRONICALLY CONTROLLED VISCOUS FAN DRIVE WITH BUSHING

摘要

A viscous shear fan drive mechanism for a cooling fan. A moveable valve disk is provided which controls the quantity of fluid in the operating chamber. An electronic actuation system activates piston and shaft members which move the valve disk against the bias of a return spring to open the fill holes, allow fluid communication between the reservoir and working chambers, and allow rotation of the cooling fan. Without activation of the electronic actuation system, the flow of fluid to the working chamber is prevented. A non-magnetic or insulating bushing member adjacent the piston and shaft members prevents the system from sticking in the actuation condition when power is eliminated.