Fluid device with pressurized roll pockets

A fluid device comprising:

• a valve housing defining a first fluid port and a second fluid port;
• a valve member disposed in the valve housing, the valve member defining a first plurality of fluid passages in fluid communication with the first fluid port and a second plurality of fluid passages in fluid communication with the second fluid port, the valve member having a first axial end;
• a valve plate having a valve surface that contacts the first axial end of the valve member, the valve plate defining a plurality of commutating passages and a plurality of recesses, the commutating passages in commutating fluid communication with the first and second pluralities of fluid passages of the valve member;
• a displacement assembly in commutating fluid communication with the valve member, the displacement assembly including:
• a ring defining a central bore and a plurality of roll pockets disposed about the central bore;
• a plurality of rolls disposed in the plurality of roll pockets;
• a rotor disposed in the central bore, the rotor being adapted to rotate and orbit in the central bore of the ring, wherein the ring, the plurality of rolls and the rotor define a plurality of expanding and contracting volume chambers;
• and
• wherein fluid from the first and second ports is communicated to each of the roll pockets during movement of the rotor so that when the volume chamber immediately before one of the roll pockets and the volume chamber immediately after that roll pocket are both in fluid communication with one of the first and second ports, that roll pocket is in fluid communication with the other of the first and second ports.

A method for pressuring a roll pocket in a displacement assembly of a fluid device, the method comprising:

• providing a fluid device having a displacement assembly including:
• a ring defining a central bore and a plurality of roll pockets disposed about the central bore;
• a plurality of rolls disposed in the plurality of roll pockets;
• a rotor disposed in the central bore, wherein the ring, the plurality of rolls and the rotor define a plurality of expanding and contracting volume chambers;
• communicating fluid from a first port of the fluid device and a second port of the fluid device to each of the roll pockets so that when the volume chamber immediately before one of the roll pockets and the volume chamber immediately after that roll pocket are both in fluid communication with one of the first and second ports, that roll pocket is in fluid communication with the other of the first and second ports.