Rotary hydraulic vane pump with improved undervane porting

Abstract

The pump has a multi-vane rotor operating within a cam ring to pump oil to a component such as a power steering gear. The pump rotor sandwiched between stationary thrust and pressure plates is supplied with oil from a surrounding fluid chamber through aligned intake ports in the two plates. Fluid chambers formed between the reciprocating vanes of the rotor discharges oil into axially aligned discharge ports of the thrust and pressure plates. The discharge port of the thrust plate is hydraulically connected to the discharge port of the pressure plate . Pressure oil in the discharge port of the pressure plate feeds into a system pressure chamber outboard of the pressure plate. Oil in the system pressure chamber is fed back to a first side chamber of the rotor through at least one simple flow passage in the pressure plate. The first side chamber is formed between inner and outer lands on the rotor. A second side chamber is similarly formed on the opposite side of the rotor and is hydraulically interconnected to the first side chamber by the undervane passages. With the pump rotating, the undervane chambers are pressurized by the supply of pressure oil to the side chambers through the straight through passage in the pressure plate to assure engagement of the vanes with the operative surface of the cam ring.