Rotary vibration damper

In a rotary vibration damper, particularly in a piston engine having a drive shaft, for varying the flow volume rate of a liquid damping medium, the rotary vibration damper being connected to the engine drive shaft and having an output shaft, a cylindrical casing connected to one of the engine drive shaft or the output shaft, spur gears supported in a planetary gear-type system in the cylindrical casing, a central spur gear mounted on the other one of the drive or output shafts and meshing with the spur gears of the planetary gear type system to form a gear pump for a closed circuit of the damping medium, and a conveying conduit for the damping medium forming the closed circuit and connecting the pressure and suction sides of the gear pump, the improvement comprising:

• a reservoir chamber for the damping medium in the pressure side of the conveying conduit, the reservoir chamber having an elastically variable volume;
• a piston valve on the pressure side of the conveying conduit, said piston valve having a piston whose axial position is controlled as a function of the engine speed, said piston being adapted by its axial position to vary the cross section of said conveying conduit and serve as a throttle member;
• and
• a short circuit connection, between the pressure and suction sides of the conveying conduit, which is closed off by an excess pressure valve and which bridges the piston valve.