Variable displacement hydraulic pump with electromechanical actuator and method thereof

Abstract

A pump, including: inlet port and outlet ports; a cylinder block including a piston disposed in a through-bore; a swash plate engaged with the piston; a drive shaft non-rotatably connected to the drive shaft, arranged to rotate the cylinder block to draw fluid through the inlet port into the through-bore and to expel the fluid from the through-bore and through the outlet port and including an axis of rotation; an axis transverse to the axis of rotation; and an actuator including a roller screw; a nut disposed about the roller screw and in threaded contact with the roller screw; an actuator pin; and an electric motor arranged to rotate the roller screw or the nut to axially displace the actuator pin to pivot the swash plate or the cylinder block about the axis and control an amount of the fluid expelled from the through-bore.

1 . A variable displacement hydraulic pump, comprising:
 an inlet port;   an outlet port;   a cylinder block including a first piston disposed in a first through-bore;   a swash plate engaged with the first piston;   a drive shaft:
 non-rotatably connected to the cylinder block; 
 arranged to rotate the cylinder block to draw fluid through the inlet port into the first through-bore and to expel the fluid from the first through-bore and through the outlet port; and, 
 including an axis of rotation; 
   an axis transverse to the axis of rotation; and,   an actuator including:
 a roller screw; 
 a nut disposed about the roller screw and in threaded contact with the roller screw; 
 an actuator pin engaged with the roller screw; and, 
 an electric motor arranged to rotate the roller screw or the nut to axially displace the actuator pin to:
 pivot the swash plate about the axis and control an amount of the fluid expelled from the first through-bore; or, 
 pivot the cylinder block about the axis and control an amount of the fluid expelled from the first through-bore. 
 
   
     
     
         2 . The variable displacement hydraulic pump of  claim 1 , wherein the actuator includes a resilient element urging the roller screw in a first axial direction. 
     
     
         3 . The variable displacement hydraulic pump of  claim 1 , wherein:
 the electric motor is arranged to rotate the roller screw or the nut to axially displace the actuator pin to pivot the swash plate about the axis;   the cylinder block includes:
 a second through-bore; and, 
 a second piston disposed in the second through-bore and engaged with the swash plate; and, 
   rotation of the cylinder block is arranged to:
 displace the first piston within the first through-bore; 
 displace the second piston within the second through-bore; 
 draw the fluid through the inlet port into the second through-bore; and, 
 expel the fluid from the second through-bore and through the outlet port. 
   
     
     
         4 . The variable displacement hydraulic pump of  claim 1 , wherein:
 the electric motor is arranged to rotate the roller screw or the nut to pivot the cylinder block about the axis;   the cylinder block includes:
 a second through-bore; and, 
 a second piston disposed in the second through-bore and engaged with the swash plate; and, 
   rotation of the cylinder block is arranged to:
 displace the first piston within the first through-bore; 
 displace the second piston within the second through-bore; 
 draw the fluid through the inlet port into the second through-bore; and, 
 expel the fluid from the second through-bore and through the outlet port. 
   
     
     
         5 . The variable displacement hydraulic pump of  claim 1 , wherein:
 the electric motor is arranged to rotate the roller screw to axially displace the actuator pin to pivot the swash plate about the axis;   the electric motor is arranged to rotate the roller screw in a first circumferential direction about the axis of rotation to displace the actuator pin in a first axial direction;   the actuator pin is arranged to pivot the swash plate about the axis in a second circumferential direction to increase the amount of fluid expelled from the first through-bore;   the electric motor is arranged to rotate the roller screw in a third circumferential direction, opposite the first circumferential direction, about the axis of rotation to displace the actuator pin in a second axial direction, opposite the first axial direction; and,   the actuator pin is arranged to pivot the swash plate about the axis in a fourth circumferential direction, opposite the second circumferential direction to decrease the amount of fluid expelled from the first through-bore.   
     
     
         6 . The variable displacement hydraulic pump of  claim 1 , wherein:
 the electric motor is arranged to rotate the nut to axially displace the actuator pin to pivot the swash plate about the axis;   the electric motor is arranged to rotate the nut in a first circumferential direction about the axis of rotation to displace the actuator pin in a first axial direction;   the actuator pin is arranged to pivot the swash plate about the axis in a second circumferential direction to increase the amount of fluid expelled from the first through-bore;   the electric motor is arranged to rotate the nut in a third circumferential direction, opposite the first circumferential direction, about the axis of rotation to displace the actuator pin in a second axial direction, opposite the first axial direction; and,   the actuator pin is arranged to pivot the swash plate about the axis in a fourth circumferential direction, opposite the second circumferential direction to decrease the amount of fluid expelled from the first through-bore.   
     
     
         7 . The variable displacement hydraulic pump of  claim 1 , wherein:
 the electric motor is arranged to rotate the roller screw to axially displace the actuator pin to pivot the cylinder block about the axis;   the electric motor is arranged to rotate the roller screw in a first circumferential direction about the axis of rotation to displace the actuator pin in a first axial direction;   the actuator pin is arranged to pivot the cylinder block about the axis in a second circumferential direction to increase the amount of fluid expelled from the first through-bore;   the electric motor is arranged to rotate the roller screw in a third circumferential direction, opposite the first circumferential direction, about the axis of rotation to displace the actuator pin in a second axial direction, opposite the first axial direction; and,   the actuator pin is arranged to pivot the swash plate about the axis in a fourth circumferential direction, opposite the second circumferential direction to decrease the amount of fluid expelled from the first through-bore.   
     
     
         8 . The variable displacement hydraulic pump of  claim 1 , wherein:
 the electric motor is arranged to rotate the nut to axially displace the actuator pin to pivot the cylinder block about the axis;   the electric motor is arranged to rotate the nut in a first circumferential direction about the axis of rotation to displace the actuator pin in a first axial direction;   the actuator pin is arranged to pivot the cylinder block about the axis in a second circumferential direction to increase the amount of fluid expelled from the first through-bore;   the electric motor is arranged to rotate the nut in a third circumferential direction, opposite the first circumferential direction, about the axis of rotation to displace the actuator pin in a second axial direction, opposite the first axial direction; and,   the actuator pin is arranged to pivot the cylinder block about the axis in a fourth circumferential direction, opposite the second circumferential direction to decrease the amount of fluid expelled from the first through-bore.   
     
     
         9 . The variable displacement hydraulic pump of  claim 1 , wherein:
 the actuator pin is arranged to pivot the swash plate about the axis; and,   the actuator pin is arranged to pivot the swash plate about the axis to control an extent of displacement of the first piston within the first through-bore.   
     
     
         10 . The variable displacement hydraulic pump of  claim 1 , wherein:
 the actuator pin is arranged to pivot the cylinder block about the axis; and,   the actuator pin is arranged to pivot the cylinder block about the axis to control an extent of displacement of the first piston within the first through-bore.   
     
     
         11 . A variable displacement hydraulic pump, comprising:
 an inlet port;   an outlet port;   a cylinder block including:
 a through-bore; and, 
 a piston at least partially disposed in the through-bore; 
   a drive shaft:
 non-rotatably connected to the cylinder block; 
 arranged to rotate the cylinder block to displace the piston to draw fluid through the inlet port into the through-bore and expel the fluid from the through-bore and through the outlet port; and, 
 including an axis of rotation; 
   an axis transverse to the axis of rotation;   an actuator including:
 a roller screw; 
 a nut disposed about and in contact with the roller screw; 
 an actuator pin engaged with the roller screw and the swash plate; and, 
 an electric motor arranged to rotate the roller screw to axially displace the actuator pin to:
 pivot the swash plate about the axis and control an amount of the fluid expelled from the through-bore; or, 
 pivot the cylinder block about the axis and control an amount of the fluid expelled from the through-bore. 
 
   
     
     
         12 . A variable displacement hydraulic pump, comprising:
 an inlet port;   an outlet port;   a cylinder block including:
 a through-bore; and, 
 a piston at least partially disposed in the through-bore; 
   a drive shaft:
 non-rotatably connected to the drive shaft; 
 arranged to rotate the cylinder block to displace the piston to draw fluid through the inlet port into the through-bore and expel the fluid from the through-bore and through the outlet port; and, 
 including an axis of rotation; 
   an axis transverse to the axis of rotation;   an actuator including:
 a roller screw; 
 a nut disposed about and in contact with the roller screw; 
 an actuator pin engaged with the roller screw and the swash plate; and, 
 an electric motor arranged to rotate the nut to axially displace the actuator pin to:
 pivot the swash plate about the axis and control an amount of the fluid expelled from the through-bore; or, 
 pivot the cylinder block about the axis and control an amount of the fluid expelled from the through-bore. 
 
   
     
     
         13 . A method of operating the variable displacement hydraulic pump of  claim 1 , comprising:
 rotating, with the drive shaft, the cylinder block;   drawing the fluid through the inlet port and into the first through-bore;   expelling the fluid from the first through-bore and through the outlet port;   rotating, with the electric motor, the roller screw or the nut;   axially displacing the actuator pin; and,   pivoting, with the actuator pin:
 the swash plate about the axis and controlling an amount of the fluid expelled from the first through-bore; or, 
 the cylinder block about the axis and controlling an amount of the fluid expelled from the first through-bore. 
   
     
     
         14 . The method of  claim 13 , further comprising:
 blocking, with a resilient element in the actuator, axial displacement of the actuating pin.   
     
     
         15 . The method of  claim 13 , further comprising:
 pivoting, with the actuator pin, the swash plate about the axis;   rotating, with the electric motor, the roller screw in a first circumferential direction about the axis of rotation;   displacing, with the roller screw, the actuator pin in a first axial direction;   pivoting, with the actuator pin, the swash plate about the axis in a second circumferential direction;   increasing the amount of fluid expelled from the first through-bore;   rotating, with the electric motor, the roller screw in a third circumferential direction, opposite the first circumferential direction, about the axis of rotation;   displacing, with the roller screw, the actuator pin in a second axial direction, opposite the first axial direction;   pivoting, with the actuator pin, the swash plate about the axis in a fourth circumferential direction, opposite the second circumferential direction; and,   decreasing the amount of fluid expelled from the first through-bore.   
     
     
         16 . The method of  claim 13 , further comprising:
 pivoting, with the actuator pin, the cylinder block about the axis;   rotating, with the electric motor, the roller screw in a first circumferential direction about the axis of rotation;   displacing, with the roller screw, the actuator pin in a first axial direction;   pivoting, with the actuator pin, the cylinder block about the axis in a second circumferential direction;   increasing the amount of fluid expelled from the first through-bore;   rotating, with the electric motor, the roller screw in a third circumferential direction, opposite the first circumferential direction, about the axis of rotation;   displacing, with the roller screw, the actuator pin in a second axial direction, opposite the first axial direction;   pivoting, with the actuator pin, the cylinder block about the axis in a fourth circumferential direction, opposite the second circumferential direction; and,   decreasing the amount of fluid expelled from the first through-bore.   
     
     
         17 . The method of  claim 13 , further comprising:
 pivoting, with the actuator pin, the swash plate about the axis;   rotating, with the electric motor, the nut in a first circumferential direction about the axis of rotation;   displacing, with the roller screw, the actuator pin in a first axial direction;   pivoting, with the actuator pin, the swash plate about the axis in a second circumferential direction;   increasing the amount of fluid expelled from the first through-bore;   rotating, with the electric motor, the nut in a third circumferential direction, opposite the first circumferential direction, about the axis of rotation;   displacing, with the roller screw, the actuator pin in a second axial direction, opposite the first axial direction;   pivoting, with the actuator pin, the swash plate about the axis in a fourth circumferential direction, opposite the second circumferential direction; and,   decreasing the amount of fluid expelled from the first through-bore.   
     
     
         18 . The method of  claim 13 , further comprising:
 pivoting, with the actuator pin, the cylinder block about the axis;   rotating, with the electric motor, the nut in a first circumferential direction about the axis of rotation;   displacing, with the roller screw, the actuator pin in a first axial direction;   pivoting, with the actuator pin, the cylinder block about the axis in a second circumferential direction;   increasing the amount of fluid expelled from the first through-bore;   rotating, with the electric motor, the nut in a third circumferential direction, opposite the first circumferential direction, about the axis of rotation;   displacing, with the roller screw, the actuator pin in a second axial direction, opposite the first axial direction;   pivoting, with the actuator pin, the cylinder block about the axis in a fourth circumferential direction, opposite the second circumferential direction; and,   decreasing the amount of fluid expelled from the first through-bore.   
     
     
         19 . The method of  claim 13 , further comprising:
 pivoting, with the actuator pin, the swash plate about the axis; and,   controlling, with the swash plate, an extent of displacement of the first piston within the first through-bore.   
     
     
         20 . The method of  claim 12 , further comprising:
 pivoting, with the actuator pin, the cylinder block about the axis; and,   controlling, with the swash plate, an extent of displacement of the first piston within the first through-bore.