Hydroviscous Drive and Some New Developments

The hydroviscous drive (HVD) is a kind of variable speed coupling in which power is transmitted from the driving part to the driven part through the viscous shear of the interposed oil film. The HVD has been employed in industrial applications for more than twenty years, especially in the speed regulation of fans, pumps and blowers, and also for the controlled acceleration of high inertia loads. Its advantages include the selection of a continuously variable speed and a fast response together with isolation as well as direct drive. Further applications are foreseen, such as in brakes and dynamometers. This paper presents a systematic theoretical and experimental analysis of the HVD. More significantly, some new ideas and developments, for instance the hydroviscous mechanical drive, which uses a combination of the HVD and planetary gear train, will be discussed.