Axial piston pump with port plate having balance feed aperture relief feature

A piston pump configured to displace a fluid comprising:

• a housing that defines an internal space, the housing having a fluid inlet into the internal space, the housing having a fluid outlet out of the internal space;
• a rotating group that is supported for rotation within the internal space of the housing, the rotating group including a rotor member with a bore therein and a piston supported for movement within the bore as the rotating group rotates to change a volume of a pump chamber that is cooperatively defined by the piston and the rotor member;
• a biasing member;
• and
• a ported member that is moveably disposed within the internal space of the housing between the rotating group and the housing, the ported member including a first face facing the rotating group and a second face facing the fluid inlet and the fluid outlet, the ported member including an intake port that fluidly connects the fluid inlet and the pump chamber as the rotating group rotates within the internal space, the ported member including a discharge port that fluidly connects the pump chamber and the fluid outlet as the rotating group rotates within the internal space, the ported member including a balance aperture configured to pass fluid between the biasing member and the pump chamber as the rotating group rotates within the internal space such that the biasing member biases the ported member toward a balanced position within the internal space;
• the balance aperture having a rim at the first face, the rim being clefted at a relief feature of the first face, the relief feature recessed into the first face;
• wherein the rim includes a rounded portion with a first end and a second end that are separated by a junction portion of the relief feature;
• wherein the relief portion has an outer boundary that intersects the rim at the first end and the second end;
• and
• wherein the outer boundary is shaped as a rounded lobe of the rim, with the outer boundary expanding in width as the relief feature spans in a direction away from the rim;
• and
• wherein the relief feature has a width that gradually increases as the relief feature spans in a direction away from the outer boundary toward the junction portion.

A method of operating an axial piston pump comprising:

• rotating a rotating group of the axial piston pump within an internal space of a housing of the axial piston pump, the housing having a fluid inlet into the internal space and a fluid outlet out of the internal space;
• moving a piston of the rotating group reciprocally in an axial direction within a bore of the rotating group to move a fluid through a pump chamber that is cooperatively defined by the piston and the rotor member;
• moving the fluid through a ported member that is moveably disposed within the internal space of the housing between the rotating group and the housing, the ported member including a first face facing the rotating group and a second face facing the fluid inlet and the fluid outlet, wherein moving the fluid through the ported member includes:
• moving the fluid from the fluid inlet to the pump chamber via an intake port of the ported member as the rotating group rotates within the internal space;
• moving the fluid from the pump chamber to the fluid outlet via a discharge port of the ported member as the rotating group rotates within the internal space;
• and
• passing the fluid between the pump chamber and a biasing member via a balance aperture of the ported member as the rotating group rotates within the internal space such that the biasing member biases the ported member toward a balanced position within the internal space, including passing the fluid through a clefted rim of the balance aperture defined at the first face, the rim being clefted at a relief feature of the first face, the relief feature recessed into the first face, the rim including a rounded portion with a first end and a second end that are separated by a junction portion of the relief feature, the relief feature having an outer boundary that intersects the rim at the first end and the second end, the outer boundary being shaped as a rounded lobe of the rim with the outer boundary expanding in width as the relief feature spans in a direction away from the rim, and the relief feature having a width that gradually increases as the relief feature spans in a direction away from the outer boundary toward the junction portion.