Fluid friction couplings

Abstract

A fluid friction coupling or clutch unit is disclosed. The coupling includes a housing which is substantially filled with a viscous liquid. The housing comprises inner and outer parts which are concentrically disposed and rotate about an axis. The fluid friction coupling also includes mutually interleaved inner and outer plates within the housing, the inner plates being coupled to rotate with the inner part of the housing and outer plates being coupled to rotate with the outer part of the housing. The individual inner and outer plates are separated from each other and are axially displaceable so as to vary the size of the gap between them. Annular disc springs are disposed within the gaps between the plates. The annular disc springs are shaped as truncated cones. They act to spread the plates apart. In a preferred embodiment, the fluid friction coupling also includes a pressure body connected to the inner and outer plates. The pressure body is actuated by a hydraulically or mechanically driven piston which applies a counterforce to the inner and outer plates in opposition to the resilience of the annular disc springs. Thus, the size of the gaps between the plates can be regulated by the pressure applied to the plates.