Piston-to-shoe interface lubrication method

摘要

Methods and apparatus are provided for lubricating a piston-to-shoe interface in a hydraulic motor or pump. Piston assemblies are installed in a housing that are each adapted to receive a reciprocating drive force and are each configured, in response thereto, to cyclically move between an intake direction and a discharge direction. Each piston assembly includes a piston and a piston shoe, and the piston, the piston shoe, or both have a plurality of pockets formed in a surface that defines a piston-to-shoe interface. When the pistons cyclically move, liquid is supplied to each piston-to-shoe interface to form a hydrostatic bearing at each piston-to-shoe interface. A portion of the liquid that is supplied to each piston-to-shoe interface is selectively supplied to and from one or more of the plurality of pockets.

主权项

1. A method for lubricating a piston-to-shoe interface in an axial piston machine that comprises a plurality of piston assemblies that are each adapted to receive a reciprocating drive force and configured, in response thereto, to cyclically move between an intake direction and a discharge direction, wherein each piston assembly comprises (1) a piston that includes a first end and a substantially rounded second end, the substantially rounded second end having a plurality of pockets formed in at least a portion of an outer surface thereof, and (2) an associated piston shoe including a cam engagement surface and a skirt portion, the skirt portion having an inner surface that defines a cavity within which the substantially rounded second end is inserted, the skirt portion engaging the substantially rounded second end to define the piston-to-shoe interface between the inner surface of the skirt portion and the outer surface of the substantially rounded second end, the method comprising the steps of:
supplying the reciprocating drive force to each of the plurality of pistons to cause each piston to cyclically move between the intake direction and the discharge direction, whereby liquid is supplied from a liquid source to each piston-to-shoe interface to form a hydrostatic bearing at each piston-to-shoe interface; and while supplying the reciprocating drive force to each of the plurality of pistons, simultaneously:
selectively supplying a portion of the liquid that is supplied to each piston-to-shoe interface to one or more of the plurality of pockets; andselectively supplying a portion of the liquid that is supplied to each piston-to-shoe interface from one or more of the plurality of pockets,thereby providing a dynamically continuous process of simultaneously supplying liquid to, and supplying liquid from, one or more of the plurality of pockets in dependence on relative orientation of each piston to its associated piston shoe and resultant load at each point of the piston-to-shoe interface,wherein at least some of the pockets are isolated from the liquid source in some of the relative orientations.