Temperature-responsive fluid coupling device

A temperature-responsive fluid coupling device for driving a cooling fan of an internal combustion engine, said coupling device comprising:

• a driving shaft driven so as to be rotated by said engine;
• a housing member rotatably mounted on said driving shaft;
• a rotor located in a hollow interior of said housing and connected with said driving shaft;
• a partition plate dividing said hollow interior into a reservoir chamber for a viscous fluid and a working chamber accommodating said rotor therein;
• a fluid return passage formed in said partition plate to cause said viscous fluid to return from said reservoir chamber to said working chamber;
• a valve plate rotating on said partition plate in response to changes in temperatures of a cooling water in an engine radiator so as to control a fluid communication through said fluid return passage;
• a pumping passage formed in said housing to transfer said viscous fluid from said working chamber to said reservoir chamber;
• and
• a ball check valve mechanism installed in said fluid return passage and said pumping passage, respectively;
• said valve mechanism including a ball check valve located in a slidable state in a radial direction, a spring biasing said ball check valve toward its closed position, and a cap member supporting said spring and limiting a distance of a sliding movement of said ball check valve;
• said spring having a load which is so established such that in a stopping process of said engine at first said fluid return passage is brought and maintained in its closed state and next said pumping passage is brought and maintained in its closed state respectively.