The distribution plate (or valve plate) in a hydraulic motor or pump serves to distribute flow between high- and low-pressure circuits; it enables the generation of output torque when high-pressure oil acts on the pistons and facilitates the discharge of high-pressure oil from piston chambers-where torque output has ceased-during the low-pressure (return) phase.
In high-speed piston motors (typically of the axial type), the swash plate and the distribution plate remain stationary. When pressurized oil passes through the distribution plate into the cylinder bore and reaches the base of the piston, the piston is forced outward by the oil pressure.
The distribution plate operates via relative motion against the pump cylinder block to switch between the pump's suction and discharge flow paths.
In certain specific applications, such as diaphragm compressors, the distribution plate features a specialized design. For instance, one design incorporates an integrally formed conical block at the center of the plate's base, surrounded by an annular array of oil channels; these channels contain outwardly inclined oil passages designed to reduce fluid flow resistance and enhance compression efficiency.