Fluid coupling device having improved response time

A fluid coupling device comprising a rotatable output coupling assembly including a housing member and a cover member, said members cooperating to define a fluid chamber therebetween, valve means associated with said cover member to separate said fluid chamber into a fluid operating chamber and a fluid reservoir chamber, an input coupling member disposed in said fluid operating chamber and being rotatable relative to said output coupling assembly, said valve means being operable to control the flow of fluid between said reservoir chamber and said operating chamber, and including means associated with said valve means to effect the operation thereof in response to variations in a predetermined temperature condition, said input coupling member including a hub portion and a disc-like portion, said disc-like portion having forward and rearward axially-spaced surfaces, said forward surface and the adjacent surface of said cover member each forming a plurality of annular lands and grooves which are interdigitated to define a forward shear space, said rearward surface and the adjacent surface of said housing member each forming a plurality of annular lands and grooves which are interdigitated to define a rearward shear space, said disc-like portion defining a plurality of radially-extending fluid passages, each of said fluid passages communicating between the inner radial periphery of said disc-like portion and the outer radial periphery thereof, each of said fluid passages being in fluid communication with each of said grooves defined by the lands formed by said forward surface, and with each of said grooves defined by the lands formed by said rearward surface, said forward lands and grooves and said rearward lands and grooves being substantially uninterrupted by said radially-extending fluid passages.

A fluid coupling device comprising a first rotatable coupling assembly defining an axis of rotation, enclosure means associated with said first rotatable coupling assembly to define a fluid chamber therebetween, valve means associated with said first rotatable coupling assembly and disposed to separate said fluid chamber into a fluid operating chamber and a fluid reservoir chamber, a second rotatable coupling member disposed in said fluid operating chamber and being rotatable relative to said first rotatable coupling assembly, said valve means being operable to control the flow of fluid between said reservoir and said operating chamber, and including means associated with said valve means to effect the operation thereof in response to variations in a predetermined condition, said second coupling member including a hub portion and a disc-like portion, said disc-like portion having first and second axially-spaced surfaces, said first surface cooperating with the adjacent surface of said first coupling assembly to define a first viscous shear space, said second surface cooperating with with the adjacent surface of said first coupling assembly to define a second viscous shear space, said disc-like portion defining at least one fluid passage communicating between the inner radial periphery of said disc-like portion and the outer radial periphery thereof, said fluid passage communicating at least intermittently with each of said first and second viscous shear spaces over at least a major portion of the radial extent of said shear spaces, said fluid passage comprising a machined bore of generally circular cross-section.