Viscous fluid coupling and external actuator assembly therefor

A fluid coupling device of the type including a first rotatable coupling assembly defining an axis of rotation, said first coupling assembly including a first coupling member and a cover member cooperating to define a fluid chamber therebetween;

• valve means associated with said first 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 coupling member, said first coupling assembly cooperating with said second coupling member to define a viscous shear space therebetween, said valve means being operable to control the flow of fluid between said reservoir chamber and said operating chamber;
• means operable to pump fluid from said operating chamber into said reservoir chamber in response to a difference in speed of rotation of said first and second coupling members;
• said valve means including a plate-like member disposed generally perpendicular to said axis of rotation and defining a fluid inlet port, and a valve member comprising a generally flat member disposed to move in a plane parallel to said plate-like member, and closely spaced thereto, said valve member being movable between an open position permitting fluid flow through said inlet port, and a closed position substantially blocking fluid flow through said inlet port;
• means biasing said valve member toward one of said open and closed positions;
• and an actuator assembly operably associated with said first coupling assembly and with said valve member and operable to move said valve member toward the other of said open and closed positions, in position to the force of said biasing means, said actuator assembly including a source of an electromagnetic field;
• characterized by:
• (a) an armature member, including a plurality of armature segments, disposed in said reservoir chamber and operably associated with said valve member to rotate therewith;
• (b) said actuator assembly including a ferromagnetic housing portion disposed adjacent said source of said electromagnetic field;
• (c) said actuator assembly disposed adjacent a forward surface of said cover member;
• (d) a plurality of electromagnetic pole pieces, each disposed within said cover member and having a forward end portion extending axially forward to a location adjacent said forward surface of said cover member, said pole pieces being disposed in an annular pattern about said axis of rotation, whereby said forward end portions are disposed axially adjacent said ferromagnetic housing portion and closely spaced axially thereto as said first coupling assembly rotates relative to said actuator assembly;
• and
• (e) each of said plurality of pole pieces being disposed adjacent one of said armature segments and in operative association therewith, whereby, upon energization of said source of said electromagnetic field, a flux path is established which includes said ferromagnetic housing portion, said armature segments, and said electromagnetic pole pieces.