Dual output variable displacement axial piston pump and method thereof

Abstract

A variable displacement axial pump, including: a housing including first and second inlet ports and first and second outlet ports; a shaft arranged to receive rotational torque; an axis of rotation for the shaft; swash plate located in the housing; a first cylinder block located in the housing and including first and second through-bores and first and second pistons at least partly disposed in the first and second through-bores, respectively, and connected to the swash plate; and a second cylinder block located in the housing and including third and fourth through-bores and third and fourth pistons at least partly disposed in the third and fourth through-bores, respectively, and connected to the swash plate. The shaft is arranged to rotate, with respect to the swash plate, the first and second cylinder blocks about the axis of rotation.

1 . A variable displacement axial pump, comprising:
 a housing including:
 first and second inlet ports; and, 
 first and second outlet ports; 
   a shaft arranged to receive rotational torque;   an axis of rotation for the shaft;   a swash plate located in the housing;   a first cylinder block located in the housing and including:
 first and second through-bores; and, 
 first and second pistons at least partly disposed in the first and second through-bores, respectively, and connected to the swash plate; and, 
   a second cylinder block located in the housing and including:
 third and fourth through-bores; and, 
 third and fourth pistons at least partly disposed in the third and fourth through-bores, respectively, and connected to the swash plate, wherein the shaft is arranged to rotate, with respect to the swash plate, the first and second cylinder blocks about the axis of rotation. 
   
     
     
         2 . The variable displacement axial pump of  claim 1 , wherein:
 the first and second pistons are arranged to:
 draw first fluid, via the first inlet port, into the first and second through-bores, respectively; and, 
 expel the first fluid from the first and second through-bores, respectively, into the first outlet port; and, 
   the third and fourth pistons are arranged to:
 draw second fluid, via the second inlet port, into the third and fourth through-bores, respectively; and, 
 expel the second fluid from the third and fourth through-bores, respectively, into the second outlet port. 
   
     
     
         3 . The variable displacement axial pump of  claim 2 , further comprising:
 an actuator arranged to pivot the swash plate about an axis transverse to the axis of rotation, wherein in a first circumferential position of the swash plate, with respect to the axis, and at a constant rotational speed for the shaft:
 the first cylinder block is arranged to expel the first fluid into the first outlet port at a first flow rate; 
 the second cylinder block is arranged to expel the second fluid into the second outlet port at a second flow rate; and, 
 the first and second flow rates are equal. 
   
     
     
         4 . The variable displacement axial pump of  claim 3 , wherein in a second circumferential position of the swash plate, different from the first circumferential position of the swash plate, with respect to the axis, and at the constant rotational speed for the shaft:
 the first cylinder block is arranged to expel the first fluid into the first outlet port at a third flow rate different from the first flow rate; and,   the second cylinder block is arranged to expel the second fluid into the second outlet port at a fourth flow rate different from the second flow rate.   
     
     
         5 . The variable displacement axial pump of  claim 2 , further comprising:
 an actuator arranged to pivot the swash plate about an axis transverse to the axis of rotation, wherein in a first circumferential position of the swash plate, with respect to the axis, and at a constant rotational speed for the shaft:
 the first cylinder block is arranged to expel the first fluid into the first outlet port at a first flow rate; 
 the second cylinder block is arranged to expel the second fluid into the second outlet port at a second flow rate; and, 
 the first and second flow rates are not equal. 
   
     
     
         6 . The variable displacement axial pump of  claim 5 , wherein in a second circumferential position of the swash plate, different from the first circumferential position of the swash plate, with respect to the axis, and at the constant rotational speed for the shaft:
 the first cylinder block is arranged to expel the first fluid into the first outlet port at a third flow rate different from the first flow rate; and,   the second cylinder block is arranged to expel the second fluid into the second outlet port at a fourth flow rate different from the second flow rate.   
     
     
         7 . The variable displacement axial pump of  claim 1 , further comprising:
 an actuator arranged to pivot the swash plate about an axis transverse to the axis of rotation, wherein in a first circumferential position of the swash plate, with respect to the axis and with the first, second, third and fourth through-bores aligned with the first, second, third and fourth ports, respectively, the swash plate is arranged to simultaneously:   displace the first piston in a first axial direction by a first distance;   displace the second piston in a second axial direction, opposite the first axial direction, by the first distance;   displace the third piston in the second axial direction by a second distance; and,   displace the fourth piston in the first axial direction by the second distance.   
     
     
         8 . The variable displacement axial pump of  claim 7 , wherein in a second circumferential position of the swash plate, with respect to the axis, different from the first circumferential position of the swash plate and with the first, second, third and fourth through-bores aligned with the first, second, third and fourth ports, respectively, the swash plate is arranged to simultaneously:
 displace the first piston in a first axial direction by a third distance, different from the first distance;   displace the second piston in the second axial direction, by the third distance;   displace the third piston in the second axial direction by a fourth distance, different from the second distance; and,   displace the fourth piston in the first axial direction by the fourth distance.   
     
     
         9 . The variable displacement axial pump of  claim 1 , further comprising:
 an actuator arranged to pivot the swash plate about an axis transverse to the axis of rotation, wherein pivoting, with the actuator, the swash plate in a first circumferential direction about the axis is arranged to simultaneously:
 increase displacement, in a first axial direction, of the first piston within the first through-bore; 
 increase displacement, in a second axial direction opposite the first axial direction, of the second piston in the second through-bore; 
 increase displacement, in the second axial direction, of the third piston in the third through-bore; and, 
 increase displacement, in the first axial direction, of the fourth piston in the fourth through-bore. 
   
     
     
         10 . The variable displacement axial pump of  claim 9 , wherein pivoting, with the actuator, the swash plate in a second circumferential direction, opposite the first circumferential direction, about the axis is arranged to simultaneously:
 decrease displacement, in the first axial direction, of the first piston within the first through-bore;   decrease displacement, in the second axial direction, of the second piston in the second through-bore;   decrease displacement, in the second axial direction, of the third piston in the third through-bore; and,   decrease displacement, in the first axial direction, of the fourth piston in the fourth through-bore.   
     
     
         11 . The variable displacement axial pump of  claim 1 , wherein the swash plate is an only swash plate for the variable displacement axial pump. 
     
     
         12 . A variable displacement axial pump, comprising:
 a housing including:
 first and second inlet ports; and, 
 first and second outlet ports; 
   a shaft arranged to receive rotational torque;   an axis of rotation for the shaft;   only one swash plate located in the housing fixed to prevent rotation with respect to the axis of rotation;   a first cylinder block located in the housing, non-rotatably connected to the shaft, and including:
 first and second through-bores; and, 
 first and second pistons at least partly disposed in the first and second through-bores, respectively, and connected to the swash plate; 
   a second cylinder block located in the housing, non-rotatably connected to the shaft, and including:
 third and fourth through-bores; and, 
 third and fourth pistons at least partly disposed in the third and fourth through-bores, respectively, and connected to the swash plate; and, 
   an actuator arranged to rotate the swash plate about an axis transverse to the axis of rotation, wherein:
 the shaft is arranged to rotate the first and second cylinder blocks; 
 the first cylinder block is arranged to expel first fluid from the first outlet port at a first flow rate; and, 
 the second cylinder block is arranged to expel second fluid from the second outlet port at a second flow rate. 
   
     
     
         13 . A variable displacement axial pump, comprising:
 a housing including:
 first and second inlet ports; and, 
 first and second outlet ports; 
   a shaft arranged to receive rotational torque;   an axis of rotation for the shaft;   only one swash plate located in the housing and fixed to prevent rotation with respect to the shaft;   a first cylinder block located in the housing, non-rotatably connected to the shaft, and including:
 first and second through-bores; and, 
 first and second pistons at least partly disposed in the first and second through-bores, respectively, and connected to the swash plate; 
   a second cylinder block located in the housing, non-rotatably connected to the shaft, and including:
 third and fourth through-bores; and, 
 third and fourth pistons at least partly disposed in the third and fourth through-bores, respectively, and connected to the swash plate; and, 
   an actuator arranged to rotate the swash plate about an axis transverse to the axis of rotation, wherein for rotation of the shaft about the axis of rotation the swash plate is arranged to displace:
 the first piston to draw first fluid into the first through-bore via the first inlet port; 
 the second piston to expel second fluid from the second through-bore into the first outlet port; 
 the third piston to draw third fluid into the third through-bore via the second inlet port; and, 
 the fourth piston to expel fourth fluid from the fourth through-bore into the second outlet port. 
   
     
     
         14 . A method of using the variable displacement axial pump of  claim 1 , comprising:
 rotating the shaft about the axis of rotation;   rotating, with the shaft, the first and second cylinder blocks about the axis of rotation and with respect to the swash plate;   axially displacing, with the swash plate, the first, second, third and fourth pistons;   drawing first fluid, via the first inlet port and using the first and second pistons, into the first and second through-bores, respectively;   expelling, using the first and second pistons, the first fluid from the first and second through-bores, respectively, into the first outlet port;   drawing second fluid, via the second inlet port and using the third and fourth pistons, into the third and fourth through-bores, respectively; and,   expelling, using the third and fourth pistons, the second fluid from the third and fourth through-bores, respectively, into the second outlet port.   
     
     
         15 . The method of  claim 14 , further comprising:
 aligning, in a first axial direction, the first, second, third and fourth through-bores with the first inlet port, the first outlet port, the second inlet port and the second outlet port, respectively; and,   simultaneously displacing, with the swash plate:
 the first piston a first distance, in the first axial direction, within the first through-bore; 
 the second piston the first distance, in a second axial direction opposite the first axial direction, within the second through-bore; 
 the third piston a second distance, in the second axial direction, within the third through-bore; and, 
 the fourth piston the second distance, in the first axial direction, within the fourth through-bore. 
   
     
     
         16 . The method of  claim 15 , further comprising:
 pivoting, using the actuator, the swash plate about the axis;   aligning, in the first axial direction, the first, second, third and fourth through-bores with the first inlet port, the first outlet port, the second inlet port and the second outlet port, respectively; and,   simultaneously displacing, with the swash plate:
 the first piston a third distance, in the first axial direction, within the first through-bore; 
 the second piston the third distance, in the second axial direction, within the second through-bore; 
 the third piston a fourth distance, in the second axial direction, within the third through-bore; and, 
 the fourth piston the fourth distance, in the first axial direction, within the fourth through-bore, wherein:
 the third distance is different from the first distance; and, 
 the fourth distance is different from the second distance. 
 
   
     
     
         17 . A method of using the variable displacement axial pump of  claim 12 , comprising:
 rotating the shaft about the axis of rotation at a constant speed;   rotating, with the shaft, the first and second cylinder blocks about the axis of rotation; and,   for a constant speed of rotation of the shaft:
 displacing, with the swash plate, the first and second pistons; 
 drawing first fluid, with the first and second pistons and from the first inlet port, into the first cylinder block; 
 expelling, with the first and second pistons and from the first cylinder block, the first fluid into the first outlet port at a first flow rate; 
 displacing, with the swash plate, the third and fourth pistons; 
 drawing second fluid, with the third and fourth pistons and from the second inlet port, into the second cylinder block; and, 
 expelling, with the third and fourth pistons and from the second cylinder block, the second fluid into the second outlet port at a second flow rate. 
   
     
     
         18 . The method of  claim 17 , further comprising:
 pivoting, using the actuator, the swash plate in a first circumferential direction with respect to the axis; and,   for the constant speed of rotation of the shaft:
 displacing, with the swash plate, the first and second pistons; 
 drawing the first fluid, with the first and second pistons and from the first inlet port, into the first cylinder block; 
 expelling, with the first and second pistons and from the first cylinder block, the first fluid into the first outlet port at a third flow rate, less than the first flow rate; 
 displacing, with the swash plate, the third and fourth pistons; 
 drawing the second fluid, with the third and fourth pistons and from the second inlet port, into the second cylinder block; and, 
 expelling, with the third and fourth pistons and from the second cylinder block, the second fluid into the second outlet port at a fourth flow rate, less than the second flow rate. 
   
     
     
         19 . The method of  claim 18 , further comprising:
 pivoting, using the actuator, the swash plate in a second circumferential direction, opposite the first circumferential direction; and,   for the constant speed of rotation of the shaft:
 displacing, with the swash plate, the first and second pistons; 
 drawing the first fluid, with the first and second pistons and from the first inlet port, into the first cylinder block; 
 expelling, with the first and second pistons and from the first cylinder block, the first fluid into the first outlet port at a fifth flow rate, greater than the third flow rate; 
 displacing, with the swash plate, the third and fourth pistons; 
 drawing the second fluid, with the third and fourth pistons and from the second inlet port, into the second cylinder block; and, 
 expelling, with the third and fourth pistons and from the second cylinder block, the second fluid into the second outlet port at a sixth flow rate, greater than the fourth flow rate. 
   
     
     
         20 . A method of using the variable displacement axial pump of  claim 13 , comprising:
 rotating the shaft about the axis of rotation; and,   rotating, with the shaft, the first and second cylinder blocks about the axis of rotation;   displacing, with the swash plate, the first, second, third and fourth pistons; and,   simultaneously:
 drawing, with the first piston, first fluid into the first through-bore via the first inlet port; 
 expelling, with the second piston, second fluid from the second through-bore into the first outlet port; 
 drawing, with the third piston, third fluid into the third through-bore via the first inlet port; and, 
 expelling, with the fourth piston, fourth fluid from the fourth through-bore into the second outlet port.