Axial piston pump auxiliary cam assembly

Abstract

An auxiliary cam assembly for an axial piston pump includes an auxiliary cam plate and an auxiliary cam retainer. The auxiliary cam plate is configured to be coupled a rotatable shaft. A central shaft opening extends through the auxiliary cam plate. A plurality of piston openings surround the central opening and extend through the auxiliary cam plate. A circumferential cut is formed in and extends around the outer peripheral surface of the auxiliary cam plate. The auxiliary cam retainer has a plurality of ramps formed therein, and each ramp slopes upwardly from a first end to a second end. A plurality of substantially flat pads are disposed between each of the ramps, and each pad extends between the first end of one ramp and the second end of another ramp.

What is claimed is: 
     
         1 . An auxiliary cam assembly for an axial piston pump, comprising:
 an auxiliary cam plate configured to be coupled a rotatable shaft and including a main body having a first side, a second side, and an outer peripheral surface;   a central shaft opening extending between the first side and the second side for receiving the rotatable shaft;   a plurality of piston openings surrounding the central opening and extending between the first side and the second side, each piston opening for receiving at least a portion of a piston;   a circumferential cut extending around the outer peripheral surface of the auxiliary cam plate;   an auxiliary cam retainer having an engagement side, a non-engagement side, an inner peripheral surface, and an outer peripheral surface, at least a portion of the engagement side contacting the auxiliary cam plate first side;   a plurality of ramps formed in the engagement side, each ramp sloping upwardly from a first end to a second end; and   a plurality of substantially flat pads integrally formed on the engagement side and disposed between each of the ramps, each substantially flat pad extending between the first end of one ramp and the second end of another ramp.   
     
     
         2 . The assembly of  claim 1 , wherein:
 the auxiliary cam plate and the auxiliary cam retainer each exhibit a compliance under load; and   the compliance of the auxiliary cam plate is substantially matched to that of the auxiliary cam retainer via the circumferential cut.   
     
     
         3 . The assembly of  claim 1 , wherein:
 the circumferential cut is configured as a circumferential groove; and   the circumferential groove is disposed midway between the first side and the second side of the auxiliary cam plate.   
     
     
         4 . The assembly of  claim 1 , wherein the circumferential cut is configured as an undercut. 
     
     
         5 . The assembly of  claim 1 , wherein the circumferential cut has a predetermined depth. 
     
     
         6 . The assembly of  claim 1 , wherein the ramps and pads are evenly distributed around the engagement side of the auxiliary cam retainer. 
     
     
         7 . The assembly of  claim 1 , wherein the ramps and pads are unevenly distributed around the engagement side of the auxiliary cam retainer. 
     
     
         8 . The assembly of  claim 1 , wherein:
 each ramp has a length between its first end and its second end; and   the length of each ramp is equal.   
     
     
         9 . The assembly of  claim 1 , wherein:
 each ramp has a length between its first end and its second end; and   the length of each ramp is not equal.   
     
     
         10 . The assembly of  claim 1 , wherein each ramp slopes upwardly from its first end to its second end at a predetermined, fixed angle. 
     
     
         11 . The assembly of  claim 10 , wherein the predetermined, fixed angle is between 8 and 20 arc minutes. 
     
     
         12 . The assembly of  claim 1 , wherein the first end of each ramp is offset its second end by a predetermined depth. 
     
     
         13 . The assembly of  claim 12 , wherein the predetermined depth is between 0.0005 inches and 0.0015 inches. 
     
     
         14 . The assembly of  claim 1 , wherein each pad has a predetermined circumferential width. 
     
     
         15 . The assembly of  claim 14 , wherein the predetermined circumferential width is between 1 and 6 degrees. 
     
     
         16 . An axial piston pump, comprising:
 a pump housing;   a rotor rotationally mounted within the pump housing, the rotor including a shaft and a plurality of axial piston bores, the rotor configured, upon receipt of an input torque on the shaft, to rotate about a rotational axis;   a plurality of pistons, each piston movably disposed within, and extending from, one of the plurality of axial piston bores;   a hanger non-rotationally mounted within the pump housing and having a opening through which the shaft extends, the hanger disposed at an angle relative to the rotational axis;   an auxiliary cam plate disposed adjacent the hanger, the auxiliary cam plate coupled to the shaft and configured to rotate therewith, the auxiliary cam plate including a main body having a first side, a second side, and an outer peripheral surface,   a central opening extending between the first side and the second side, the shaft extending through the central opening;   a plurality of piston openings surrounding the central opening and extending between the first side and the second side, each piston extending at least partially into one of the piston openings;   a circumferential cut formed in and extending around the outer peripheral surface of the auxiliary cam plate; and   an auxiliary cam retainer coupled to the hanger and having an engagement side, a non-engagement side, an inner peripheral surface, and an outer peripheral surface, at least a portion of the engagement side contacting the auxiliary cam plate first side,   a plurality of ramps formed in the engagement side, each ramp sloping upwardly from a first end to a second end; and   a plurality of substantially flat pads integrally formed on the engagement side and disposed between each of the ramps, each substantially flat pad extending between the first end of one ramp and the second end of another ramp.   
     
     
         17 . The pump of  claim 16 , wherein:
 the auxiliary cam plate and the auxiliary cam retainer each exhibit a compliance under load; and   the compliance of the auxiliary cam plate is substantially matched to that of the auxiliary cam retainer via the circumferential cut.   
     
     
         18 . The pump of  claim 16 , wherein:
 each ramp slopes upwardly from its first end to its second end at a predetermined, fixed angle; and   the first end of each ramp is offset its second end by a predetermined depth.   
     
     
         19 . The pump of  claim 16 , wherein each pad has a predetermined circumferential width. 
     
     
         20 . The pump of  claim 16 , wherein:
 the rotor is configured to rotate about the rotational axis in a first direction; and   each ramp slopes upwardly in the first direction.