Abstract: A system for controlling the engagement and disengagement of a viscous type coupling is accomplished by controlling the relative positioning of a spring loaded valve arm relative to a fluid port through the use of an electrically-activated, temperature-sensitive member, such as a NiTi wire. The characteristics of shape memory alloy materials are such that they are hard above a predetermined temperature, but soft and ductile below a predetermined temperature. When engagement or disengagement of the coupling is desired, electrical current is introduced through the member, therein heating it above a predetermined temperature to harden it. This hardening causes the valve arm to either move to either cover or uncover a fluid port, depending upon the design arrangement of the valve arm relative to the fluid port. A controller coupled to a plurality of engine operating sensors and a power source controls the electrical activation as a function of a desired operating condition.

Abstract: A system for controlling the engagement and disengagement of a viscous type coupling is accomplished by controlling the relative positioning of a spring loaded valve arm relative to a fluid port through the use of an electrically-activated, temperature-sensitive wire. The characteristics of wire are such that the wire is hard above a predetermined temperature, but soft and ductile below a predetermined temperature. When engagement or disengagement of the coupling is desired, electrical current is introduced through the wire, therein heating the wire above a predetermined temperature to harden the wire. This hardening causes the valve arm to either move to either cover or uncover a fluid port, depending upon the design arrangement of the valve arm relative to the fluid port. A controller coupled to a plurality of engine operating sensors and a power source controls the electrical activation as a function of a desired operating condition.