Torque Amplification Phenomenon in Viscous Couplings. Effects of Camber of Inner Disk Blade.

Viscous couplings, which are mainly used in the power train of four-wheel-drive vehicles, normally operate in the viscous mode, where torque is transmitted by viscous shearing force between sets of disks alternately coupled to the input and output. Under an extreme condition, in which relative speed between the disks is largely increased, two disks come into contact with each other, resulting in a torque amplification called the hump mode. Although some theoretical and experimental studies have been made to explain the hump phenomenon, they seemed to be inadequate. In this paper the effects of the camber of the inner disk blade on the hump phenomenon were examined by means of numerical calculations. A slight camber of the disk was found to cause considerable torsional moment on the blades, resulting in an increase of the attack angle of the blade and axial thrust on the inner disk.