Viscous fluid coupling

Claim 1

A viscous fluid coupling comprising: an input member driven by an engine and having a rotor, an output member supported rotatably on said input member, a partition fixed to said output member and separating the internal space of said output member into a reservoir chamber for viscous fluid and a working chamber that accommodates said rotor, a first return hole and a second return hole which are formed in said partition for refluxing viscous fluid from said reservoir chamber to said working chamber, valve means comprising a single valve plate to control the opening and closing of said first and second return holes so that the transmission of torque from said input member to said output member is performed in three stages, and said valve means controlling the opening and closing of said first return hole with a rotating movement on the partition by being associated with a spiral bimetal that operates by detecting the temperature of the air passing the radiator; and controlling the opening and closing of said second return hole with a movement in an axial direction of the rotor by being associated with a thermostat that operates by detecting the temperature of the water in a vortex chamber of a water pump.