VARIABLE DISPLACEMENT VANE PUMP WITH DUAL CONTROL CHAMBERS

摘要

A traditional variable-displacement vane pump is designed to operate at an equilibrium pressure which meets the worst case scenario. Thus, at lower speeds energy will be wasted as the pump will supply working fluid at a greater pressure than is required. A variable capacity vane pump (20) is provided which has a pump control ring (40) which is moveable to alter the volumetric displacement of the pump (20). The pump ring (40) is moved by at least first and second control chambers (76, 80), which act on the pump control ring (40) when pressurized working fluid is supplied to them to move the pump control ring (40) to alter the volumetric capacity of the pump (20). When pressurized fluid is supplied to only the first control chamber (76), the pump operates at a first equilibrium pressure and when pressurized fluid is also supplied to the second chamber (80), the pump operates at a second equilibrium pressure. If desired, pressurized fluid can also be supplied only to the second control chamber (80) to operate the pump (20) at a third equilibrium pressure and/or additional control chambers can be provided if required.