Temperature responsive, pneumatically actuated, fluid shear, cooling fan clutch and control therefor

Claim 1

A cooling fan device for use with an internal combustion engine, comprising: a viscous fluid coupling means which includes an input means drivingly connected to the engine, an output means provided with a fan for cooling a radiator of the engine and rotatable relative to said input means, said input and output means defining therebetween a fluid-tight working chamber into which an amount of viscous fluid can be admitted to hydrodynamically transmit rotational power from said input means to said output means, said output means having a partition means for separating from said working chamber a reservoir chamber provided in said output means for storing an additional amount of the viscous fluid, said partition means having formed therein a hole for permitting the flow of the viscous fluid from said working chamber to said reservoir chamber, and a viscous fluid valve means operable to close said hole thereby causing a decrease in the amount of the viscous fluid within said working chamber to reduce the power transmitted from said input means to said output means, and means for controlling the operation of said viscous fluid valve means, said control means including means for sensing the temperature of engine cooling water, a slidable plug on the reservoir chamber side of said partition means, an inner cover secured to said input means to form an air chamber therein, said inner cover having a center opening through which said slidable plug extends in sealing relationship therewith, a diaphragm dividing said air chamber into two opposed chambers, the outer periphery of said diaphragm being fixed to said input means and the inner periphery of said diaphragm being attached to an inner end of said slidable plug, said viscous fluid valve means being secured to an outer end of said plug to open or close said hole of said partition means, changeover valve means connected to a source of suction air pressure and a source of atmospheric air pressure, passage means connecting said changeover valve means and a first one of said opposed chambers, said changeover valve means being for regulating in accordance with the temperature of the engine cooling water the supply of suction pressure and atmospheric pressure through said passage means into said first opposed chamber defined by said diaphragm for moving said plug and said fluid valve means secured thereto to effect control of viscous fluid flowing to said working chamber and provide variation in the speed of rotation of said fan.