Fluid friction clutch with reserve chamber in the primary disk

A fluid friction clutch having a driving primary part and a secondary driven part, comprising:

• an input shaft;
• said driving primary part comprising a primary disk positioned within said secondary driven part and being attached to said input shaft;
• a tappet coaxially arranged within said input shaft, said tappet being axially movable in response to variation of an external temperature source;
• a fixed baffle extending radially outward from said primary disk;
• a work chamber between said primary disk and said secondary driven part and adapted to be filled with a viscous fluid;
• a reserve chamber positioned within said primary disk;
• a temperature-controlled fluid connection between said reserve chamber and said work chamber, wherein said fluid connection includes a valve orifice arranged in the end face of said primary disk and an overflow orifice arranged on the peripheral circumference of said primary disk, said overflow orifice being controlled by said fixed baffle, a closure element for closing said valve orifice of said fluid connection, and a lever extending from said tappet to said closure element, whereby said closure element is controlled by said tappet;
• and
• a bimetallic strip, one end of said strip being attached to said lever and the other end being braced against the interior of said primary disk, whereby said strip closes said valve orifice when the internal temperature reaches a predetermined level.