Viscous clutch with front-mounted electromagnetic coil, modular valve and front hub subassemblies for a viscous clutch, and method of making

A method of making a viscous clutch, the method comprising:

• providing a mounting bracket having a center shaft;
• rotatably mounting a rotor on the center shaft, wherein mounting the rotor further includes positioning a housing base adjacent to the center shaft and the rotor;
• assembling a modular valve subassembly by:
• securing a reed valve element to an outer pole made of a ferromagnetic material;
• securing a spring to an armature;
• and
• securing the spring to the outer pole such that, when the modular valve subassembly is fully assembled, the armature is movable relative to the outer pole and further such that at least a seal portion of the reed valve element is located axially between the outer pole and the armature;
• securing the previously-assembled modular valve subassembly to the rotor;
• rotatably mounting a housing cover on the center shaft and securing the housing cover to the housing base;
• and
• securing an electromagnetic coil to the center shaft at or near a front end thereof, wherein one or more wires for the electromagnetic coil extend rearward through a bore in the center shaft.

A modular valve subassembly for a viscous clutch, the modular valve subassembly comprising:

• a pole, wherein the pole includes a body having an annular shape, and wherein the pole is made of a ferromagnetic material;
• an armature made of a ferromagnetic material, wherein the armature is configured as a plate;
• a spring securing the armature to the pole such that the armature is movable relative to the pole;
• and
• a reed valve element secured to the pole, the reed valve element positioned at least partially between the armature and the pole and having a seal portion movable relative to the pole, wherein the reed valve element and the spring are secured to the pole at locations spaced from each other.

A viscous clutch assembly, comprising:

• a center shaft that is rotationally fixed;
• a rotor rotatably supported on the center shaft;
• a housing positioned adjacent to the rotor and rotatably supported on the center shaft;
• a working chamber, wherein the rotor and the housing define at least portions of a boundary of the working chamber such that a shear fluid present in the working chamber can transmit torque between the rotor and the housing;
• a reservoir carried by the rotor and rotationally fixed to the rotor, the reservoir having an outlet bore;
• an electromagnetic coil rotationally fixed to the center shaft at or near a front end of the center shaft;
• a valve subassembly operable to control flow of a shear fluid between the reservoir and the working chamber through the outlet bore, wherein the valve subassembly is controllable using magnetic flux generated by the electromagnetic coil, the valve subassembly including:
• an outer pole having an annular body;
• an armature;
• a spring pivotally securing the armature to the outer pole;
• and
• a reed valve element pivotally secured to the outer pole and having a seal portion arranged adjacent to the outlet bore, wherein selective actuation of the armature by applied magnetic flux exerts a force on the reed valve element to pivotally actuate the reed valve element against a spring bias force such that the seal portion selectively covers and uncovers the outlet bore;
• and
• a front hub subassembly including:
• a flux guide;
• a set of bearings;
• and
• a magnetic flux insulator sleeve positioned adjacent to and radially in between the set of bearings and the flux guide,
• wherein the front hub subassembly is engaged between the center shaft and the housing with the flux guide extending axially across a portion of the housing with a front end of the flux guide separated from the electromagnetic coil by an air gap and with an opposite rear end of the flux guide separated from the outer pole by another air gap.