Variable displacement hydraulic pump/motor with hydrostatic valve plate

Abstract

A variable displacement hydraulic axial piston machine includes (a) a housing having an outlet opening; (b) a barrel mounted in the housing for rotation about a rotation axis; (c) a plurality of pistons movable in respective bores in the barrel; (d) a valve plate coupled to the barrel and having a fluid passage therein that ends at an outlet opening; and (e) a flow tube connecting the outlet opening in the valve plate to the outlet opening in the housing. The barrel and the valve plate are pivotally movable together about a pivot axis transverse the rotation axis for varying the displacement of the pistons in the bores. An end of the flow tube connects to the valve plate while allowing for axial movement of the flow tube relative to the valve plate in a direction parallel to the rotational axis of the barrel.

1 . A variable displacement hydraulic axial piston machine, comprising:
 a housing having an outlet opening;   a rotatable member rotatably-mounted in the housing for rotation about an axis;   a valve plate having a fluid passage therein that ends at an outlet opening, a barrel mounted between the valve plate and the rotatable member, the barrel being coupled to the valve plate for rotation relative to the valve plate and the barrel being pivotally coupled to the rotatable member for rotation about a rotation axis, the barrel including a plurality of piston bores;   a plurality of pistons movable in respective bores in the barrel and coupled to the rotatable member for rotation with the rotatable member, the barrel and the valve plate being pivotally movable together about a pivot axis transverse the rotation axis for varying the displacement of the pistons in the bores;   a flow tube connecting the outlet opening of the valve plate to the outlet opening in the housing, the flow tube having a first connector at a first end that connects the flow tube to the valve plate in a direction parallel to the rotational axis of the barrel while allowing for axial movement of the flow tube relative to the valve plate in a direction parallel to the rotational axis of the barrel, and a second end opposite the first end, the flow tube having a second connector at the second end that connects the flow tube to the outlet opening in the housing for axial movement in a direction coaxial with the pivot axis while allowing for angular movement of the flow tube about the pivot axis.   
     
     
         2 . A machine as set forth in  claim 1 , where the first connector includes an end section of the flow tube that is received in a bore in the valve plate with a slip fit. 
     
     
         3 . A machine as set forth in  claim 1 , where the second end of the flow tube is parallel to the pivot axis. 
     
     
         4 . A machine as set forth in  claim 1 , where the barrel includes a plurality of circumferentially-spaced cylindrical bores. 
     
     
         5 . A machine as set forth in  claim 1 , where the valve plate is movable relative to the housing. 
     
     
         6 . A machine as set forth in  claim 1 , where the flow tube is formed as a separate structure from the valve plate. 
     
     
         7 . A machine as set forth in  claim 1 , where the first end of the flow tube is movable axially within the bore of the valve plate. 
     
     
         8 . A machine as set forth in  claim 1 , where the second end of the flow tube is received in a bore that is coaxial with the pivot axis. 
     
     
         9 . A machine as set forth in  claim 1 , where the second end of the flow tube is received in a bore with a slip fit for rotation about the pivot axis. 
     
     
         10 . A machine as set forth in  claim 1 , wherein a radial opening extends through the first end of the flow tube for enabling a flow of fluid from the flow tube to an internal fluid passage in the valve plate that intersects the bore in the valve plate. 
     
     
         11 . A machine as set forth in  claim 1 , wherein the valve plate includes a planar surface into which a port opening is integrated. 
     
     
         12 . A machine as set forth in  claim 11 , wherein housings for setting pistons are attachable to the planar surface of the valve plate. 
     
     
         13 . A machine as set forth in  claim 1 , wherein a plurality of interconnecting grooves form a balancing region on a surface of the valve plate to enable the valve plate to move directly over a guide path formed by the housing with reduced friction. 
     
     
         14 . A machine as set forth in  claim 1 , comprising a sensor mounted to monitor an angular position of the flow tube about the pivot axis relative to the housing. 
     
     
         15 . A machine as set forth in  claim 14 , where the sensor includes a rotatable portion connected to the second end of the flow tube and a fixed portion that is fixed relative to the housing, the sensor providing an output indicative of the relative position of the rotatable portion relative to the fixed portion. 
     
     
         16 . A variable displacement hydraulic axial piston machine, comprising:
 a housing;   a rotatable member rotatably-mounted in the housing for rotation about a rotation axis;   a barrel coupled to the rotatable member, the barrel including a plurality of piston bores;   a plurality of pistons movable in respective bores and coupled to the rotatable member for rotation with the rotatable member;   a valve plate coupled to the barrel and constrained in the housing for rotation with the barrel, the barrel and the valve plate being pivotally movable together about a pivot axis transverse the rotation axis for varying the displacement of the pistons in the bores;   a working fluid within the housing;   wherein the housing, the working fluid, and the valve plate cooperate to define a hydrostatic pad between the valve plate and the housing to decrease friction and wear from the relative movement between the housing and the valve plate.   
     
     
         17 . A machine as set forth in  claim 16 , where the valve plate includes a plurality of grooves in a surface that faces a corresponding surface of the housing. 
     
     
         18 . A machine as set forth in  claim 16 , where the valve plate includes a planar surface that faces a corresponding surface of the barrel. 
     
     
         19 . A variable displacement hydraulic axial piston machine, comprising:
 a housing;   a rotatable member rotatably-mounted in the housing for rotation about a rotation axis;   a barrel coupled to the rotatable member, the barrel including a plurality of piston bores;   a plurality of pistons movable in respective bores and coupled to the rotatable member for rotation with the rotatable member;   a valve plate coupled to the barrel and constrained in the housing for rotation with the barrel, the barrel and the valve plate being pivotally movable together about a pivot axis transverse the rotation axis for varying the displacement of the pistons in the bores;   wherein valve plate includes a planar running surface facing a corresponding surface of the barrel.   
     
     
         20 . (canceled) 
     
     
         21 . A variable displacement hydraulic axial piston machine, comprising:
 a housing having an outlet opening;   a rotatable member rotatably-mounted in the housing for rotation about an axis;   a valve plate having a fluid passage therein that ends at an outlet opening,   a barrel mounted between the valve plate and the rotatable member, the barrel being coupled to the valve plate for rotation relative to the valve plate and the barrel being pivotally coupled to the rotatable member for rotation about a rotation axis, the barrel including a plurality of piston bores;   a plurality of pistons movable in respective bores in the barrel and coupled to the rotatable member for rotation with the rotatable member, the barrel and the valve plate being pivotally movable together about a pivot axis transverse the rotation axis for varying the displacement of the pistons in the bores;   a flow tube connecting the outlet opening of the valve plate to the outlet opening in the housing;   a rotary sensor attached to the flow tube on the pivot axis to monitor the angular position of the valve plate within the housing.