Method and apparatus for prefill of wet clutches

Apparatus for controlling a wet clutch, including

• a pump for providing a housing with a hydraulic fluid,
• a piston being movably disposed in the housing, the piston being movable into an extended position by a preloaded spring and into a retracted position by applying an engagement pressure on the piston by the hydraulic fluid, wherein in the retracted position torque is transmittable through the clutch,
• a fluid conduit connecting the pump and the housing,
• an electroproportional valve disposed between the pump and the housing for regulating the pressure of the hydraulic fluid in the housing, the electroproportional valve being configured to prefill the housing by applying a prefill pressure on the piston, thereby prefilling the fluid conduit and the housing with the hydraulic fluid, the prefill pressure being lower than the engagement pressure required to move the piston into the retracted position, and
• providing a controller for controlling the pressure applied to the piston by taking into account at least one of a temperature of a transmission fluid, a radial pressure distribution of the transmission fluid inside a clutch housing affected by a rotational speed of the clutch, and a time between shifts.