Hydraulic Variable Pump

A hydraulic variable displacement pump has a method of increasing or reducing displacement either manually, hydraulically or electronically. The method of displacement change depends upon the pump’s structure, differing between piston and vane pumps.

A hydraulic variable displacement pressure-compensated vane pump works quite differently from a piston pump. Instead of reciprocating pistons, the rotating group of a vane pump is exposed to suction and pressure chambers inside the housing. The vanes move outward and inward inside the cam ring which is offset compared to the axis of the rotating group. There exists a control piston in a hydraulic variable vane pump, but this time it pushes against the cam ring. When downstream pressure rises, the control piston pushes the cam ring towards the center of the housing, reducing the difference in alignment between it and the rotating group. This reduces effective displacement, reducing flow to reduce downstream pressure.