Hydrokinetic couplers

Hydrokinetic (or hydrodynamic) couplings are turbomachines that transmit mechanical power between the shaft of a motor and that of a servo-driven machine, at variable transmission ratios close to unity, through the intermediary of the hydraulic power of a liquid.

Several constructive solutions are possible. A distinction is made between constant-fill (or closed) hydrokinetic couplings and controlled-fill (or adjustable, open, also known as clutches) hydrokinetic couplings.

This last category allows clutch disengagement and, in a certain operating range, gear ratio adjustment. But these hydrokinetic couplings are much more complicated, and also feature a heat exchanger, drain system and feed pumps.

Today, the main advantage of hydrokinetic couplings is their operational flexibility: they adapt to rapid load changes without affecting the engine, they dampen torsional vibrations and perform clutch-disengagement maneuvers without mechanical friction, i.e. without wear or shock. As a result, they provide excellent engine protection and enable machines to be started up at heavy starting speeds.

For notations and symbols, see end of article.