This application relates to improvements in the piston for an under vane pressure regulating valve.
Vane pumps in compressors are known and, typically, include a plurality of vanes that extend outwardly of a rotor. The vanes are brought into contact with a cam surface of a casing or stator. As the rotor turns, the vanes move radially inwardly and outwardly of the rotor moving an entrapped fluid. The rotor is mounted within the casing. The distance between the outer surface of the rotor and the cam surface changes, such that the vanes are driven inwardly and outwardly, allowing filling and pressurizing of a fluid.
One feature commonly used in vane pumps and compressors is under vane pressure. This assists in biasing a vane outwardly of the rotor.
Valves are known to regulate the pressure of the fluid delivered to the under vane cavities to properly bias the vane. These valves are generally comprised of a valve set, a piston installed into a sleeve, installed into a housing bore. Typically, these valves have had a piston with a flat forward face or sometimes a “nosed” face with a central protrusion. A pressure from fluid in the under vane cavity is placed on this forward face and may move the vane to allow this fluid to communicate with an outlet leading to a pump chamber. Fluids reacting off the flat or “nosed” face and moving toward the outlet have a significant axial component as well as a radial component.
Thus, in the past, contaminants entrained in this fluid have sometimes been forced into a space between a radially outer surface of the piston, and a radially inner surface of a sleeve by pressure delta and fluid forces.
This is undesirable and can lead to valve seizure.