Abstract: A viscous fan drive in which the output drive to the fan is controlled by the movement of viscous fluid from a fluid reservoir and into the operating and working chamber of the coupling during normal operation. The input-coupling assembly and cover member are formed with a unique combination of continuous and non-continuous radially extending lands and grooves designed to distribute the viscous fluid in a continuous film throughout the shear zone so as to maximize output fan speed at a given input speed. An armature-venting feature is designed to simplify the opening and closing of the valve disk in an electronic version of the viscous fan drive depending upon the desired operating condition.

Abstract: An improved valve disk having a modified cylinder region that includes a first arc section and a second arc section separated by a pair of non-arced sections. These arc sections are positioned to correspond to fill holes in an electronically controlled viscous coupling system. The arc sections have sufficient length and height to seal over the fill holes when the viscous coupling is in a disengaged position. The arc sections each have a face/end portion that each seal to the reservoir cover when the viscous coupling is in the disengaged position. To ensure proper location of the arc sections relative to the fill holes, the valve disk is pinned or otherwise coupled to the input coupling assembly in a way that prevents rotational movement of the valve disk.

Abstract: A viscous fan drive having improved pumping efficiency from removing fluid from a fluid operating chamber to a fluid reservoir chamber is achieved by providing a wiper element that is located within the radial clearance between the clutch and the housing that effectively seals leakage paths leading (upstream) and trailing the wiper. The wiper element includes a radial tang that is positioned within a corresponding slot of the cover wall. The wiper element also has a pair of spaced apart arms extending from the radial tang portion each having a radial outer surface that has a similar radius as the cover wall and a radial inner surface has a similar radius as the clutch. The wiper element also preferably includes details designed to seal the radial inner surface to the outer periphery of the clutch during fan drive operation and a locating detail to aid in assembly.