Fluid friction coupling

Claim 1

A fluid friction coupling, especially for a cooling fan of a fluid-cooled internal combustion engine, comprising: (a) a rotor rotatable about a rotation axis, (b) a housing rotatable about the rotation axis in relation to the rotor, containing a reservoir for shear fluid and a working chamber separated from the reservoir by a first partition and enclosing the rotor, forming at least one shear gap, (c) a pump device which in the relative rotation of the rotor and the housing pumps shear fluid by way of a first opening of the first partition in the region of the external diameter of the rotor from the working chamber into the reservoir, (d) a temperature-dependently controllable valve device for the control of the supply of shear fluid from the reservoir to the working chamber by way of a second opening of the first partition placed closer to the rotation axis than the first opening, (e) an annular buffer chamber encircling said rotation axis within said housing, a second partition extending transversely of said rotation axis located within said housing separating said buffer chamber from said working chamber, at least one inlet opening in said second partition near the inner diameter of said buffer chamber, at least one constricted opening in said second partition at the external diameter of said buffer chamber, whereby when the rotor and/or housing are not rotating, said buffer chamber receives a part of the shear fluid contained in the housing and delivers it again through said at least one constricted opening when the rotor and/or housing are in rotation.