Hydraulic unit having orifice plate displacement control

Abstract

A hydraulic unit is disclosed. The hydraulic unit may have a rotatable body at least partially defining a plurality of barrels, a plurality of plungers associated with the plurality of barrels, and a swashplate tiltable to vary a displacement of the plurality of plungers relative to the plurality of barrels. The hydraulic unit may also have an orifice plate located adjacent the rotatable body. The orifice plate may include an inlet port, a discharge port, and a first plurality of control orifices located between first ends of the inlet and discharge ports. The hydraulic unit may further have a first plurality of control valves, each of the first plurality of control valves being associated with a different control orifice of the first plurality of control orifices.

1 . A hydraulic unit, comprising:
 a rotatable body at least partially defining a plurality of barrels;   a plurality of plungers associated with the plurality of barrels;   a swashplate tiltable to vary a displacement of the plurality of plungers relative to the plurality of barrels;   an orifice plate located adjacent the rotatable body and having:
 an inlet port; 
 a discharge port; and 
 a first plurality of control orifices located between first ends of the inlet and discharge ports; and 
   a first plurality of control valves, each of the first plurality of control valves associated with a different control orifice of the first plurality of control orifices.   
   
   
       2 . The hydraulic unit of  claim 1 , wherein each of the first plurality of control valves is configured to selectively communicate an associated one of the first plurality of control orifices with the inlet port. 
   
   
       3 . The hydraulic unit of  claim 1 , wherein communication of the first plurality of control orifices with the inlet port affects a tilt angle of the swashplate. 
   
   
       4 . The hydraulic unit of  claim 1 , further including:
 a second plurality of control orifices located between second ends of the inlet and discharge ports; and   a second plurality of control valves, each of the second plurality of control valves associated with a different control orifice of the second plurality of control orifices and being configured to selectively communicate an associated one of the second plurality of control orifices with the discharge port.   
   
   
       5 . The hydraulic unit of  claim 1 , further including at least one resilient member configured to urge the swashplate toward one of a minimum and a maximum displacement position. 
   
   
       6 . The hydraulic unit of  claim 1 , further including a metering slot extending from an end of at least one of the inlet and discharge ports. 
   
   
       7 . The hydraulic unit of  claim 1 , further including:
 a sensing device configured to generate a signal indicative of a performance demand change; and   a controller in communication with the sensing device and the first plurality of control valves, the controller being configured to:
 determine a desired tilt angle change of the swashplate based on the performance demand change; and 
 selectively activate the first plurality of control valves based on the desired tilt angle change. 
   
   
   
       8 . The hydraulic unit of  claim 1 , wherein the performance demand change is associated with a flow output. 
   
   
       9 . The hydraulic unit of  claim 1 , wherein the performance demand change is associated with at least one of a torque output, a speed, and a noise. 
   
   
       10 . A method of pressurizing fluid, comprising:
 rotating a plurality of plungers past an inlet port during a retraction stroke of the plurality of plungers to draw in fluid;   rotating the plurality of plungers past a discharge port during an extension stroke of the plurality of plungers to expel fluid; and   selectively changing a force on the plurality of plungers at multiple locations near an end-of-stroke motion of the plurality of plungers to affect a displacement of the plurality of plungers.   
   
   
       11 . The method of  claim 10 , where selectively changing includes selectively changing the force on the plurality of plungers at multiple locations near both a top-dead-center and a bottom-dead center of the plurality of plungers. 
   
   
       12 . The method of  claim 10 , wherein changing the force on the plurality of plungers near the end-of-stroke motion affects a tilt angle of a swashplate operatively engaged with the plurality of plungers. 
   
   
       13 . The method of  claim 12 , wherein changing the force on the plurality of plungers near the end-of-stroke motion affects a compression amount of a resilient member opposing tilting of the swashplate. 
   
   
       14 . The method of  claim 10 , further including gradually communicating the plurality of plungers with at least one of the inlet port and the discharge port during rotation of the plurality of plungers. 
   
   
       15 . The method of  claim 10 , further including:
 sensing a performance demand change;   determining a desired displacement change of the plurality of plungers based on the performance demand; and   selectively changing the force on the plurality of plungers based on the desired displacement change.   
   
   
       16 . The method of  claim 15 , wherein the performance demand change is associated with at least one of a flow output, a torque output, a speed, a pulsation, and a noise. 
   
   
       17 . A method of converting power, comprising:
 directing pressurized fluid into a plurality of pumping chambers as the plurality of pumping chambers rotate past an inlet port;   expanding a volume of the pumping chambers with the pressurized fluid to generate a mechanical output;   discharging the pressurized fluid from the plurality of pumping chambers as the plurality of pumping chambers rotate past a discharge port; and   selectively changing a pressure of the plurality of pumping chambers at multiple locations between first ends of the inlet and discharge ports to affect the mechanical output.   
   
   
       18 . The method of  claim 17 , wherein selectively changing further includes selectively changing the pressure at multiple locations between second ends of the inlet and discharge ports to affect the mechanical output. 
   
   
       19 . The method of  claim 17 , further including gradually communicating the plurality of pumping chambers with at least one of the inlet port and the discharge port during rotation of the plurality of pumping chambers. 
   
   
       20 . The method of  claim 17 , further including:
 sensing a demand change in at least one of a speed and a torque of the mechanical output;   determining a desired expansion amount based on the performance demand; and   selectively changing the pressure of the plurality of pumping chambers based on the desired expansion amount.