US3738111A - Variable displacement pump control system - Google Patents

Variable displacement pump control system Download PDF

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Publication number
US3738111A
US3738111A US00197699A US3738111DA US3738111A US 3738111 A US3738111 A US 3738111A US 00197699 A US00197699 A US 00197699A US 3738111D A US3738111D A US 3738111DA US 3738111 A US3738111 A US 3738111A
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US
United States
Prior art keywords
line
pressure
pump
pilot
control valve
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00197699A
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English (en)
Inventor
E Fletcher
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Deere and Co
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Deere and Co
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Filing date
Publication date
Application filed by Deere and Co filed Critical Deere and Co
Application granted granted Critical
Publication of US3738111A publication Critical patent/US3738111A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
    • F04B1/04—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinders in star- or fan-arrangement
    • F04B1/0404—Details or component parts
    • F04B1/0435—Arrangements for disconnecting the pistons from the actuated cam
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/04—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
    • F15B11/05—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed specially adapted to maintain constant speed, e.g. pressure-compensated, load-responsive
    • F15B11/055—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed specially adapted to maintain constant speed, e.g. pressure-compensated, load-responsive by adjusting the pump output or bypass
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20538—Type of pump constant capacity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20546—Type of pump variable capacity
    • F15B2211/20553—Type of pump variable capacity with pilot circuit, e.g. for controlling a swash plate
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/635—Circuits providing pilot pressure to pilot pressure-controlled fluid circuit elements

Definitions

  • the pistons are returned by the fluid pressure in the inlet line, and the displacement of the pump is controlled by varying the pressure in the drive chamber of the pump, in creasing pressure in the drive chamber resisting the return of the pistons to decrease the piston strokes.
  • the pressure in the chamber is supplied by the charge pump through a pilot-operated stroke control valve, which is biased toward a dump position, wherein it exhausts the pressurized fluid from the chamber, and is shiftable to an alternate position wherein it connects the charge pump to the chamber in response to pressure in a pilot line connected to the pump discharge.
  • This invention relates to a control system for a variable displacement hydraulic pump and more particularly to a control system for a hydraulic pump wherein the displacement is varied by controlling the pressure in the drive chamber of the pump to limit the return or intake stroke of the pump pistons and thereby control the pump displacement.
  • the stroke control system utilizes a charge pump, which supplies pressurized fluid to the pump inlet at a relatively high pressure, without interruptions for other hydraulic functions, thereby eliminating the need for the return springs in the pump.
  • An important feature of the invention resides in the utilization of the charge pump pressure to pressurize the pump crankcase or drive chamber, the flow of pressurized fluid to and from the crankcase being controlled by a stroke control valve responsive to the pump output pressure.
  • Another feature of the invention is the provision of means for making the system responsive to the load pressureat a hydraulic function in addition to the pump output pressure, providing a demand compensated system.
  • An important advantage of this invention resides in the fact that it eliminates the need for a quick dump valve to get the pump in the stroke rapidly and further eliminates the loss due to the constant drainage from v the high pressure outlet while the pump is operating at less than full stroke.
  • Still another feature of the invention resides in the fact that the oil flow in the crankcase is directly related to the pump output, rather than the inverse relationship, so that there is maximum oil flow in the crankcase at maximum pump displacement, reducing the operating temperature of the pump.
  • FIG. 1 is a schematic illustration of one embodiment of the invention, wherein the stroke control valve is responsive to the pump output pressure.
  • FIG. 2 is a schematic illustration of a second embodiment of the invention wherein the system is modified so that the stroke control valve is also responsive to the load pressure.
  • the hydraulic system includes a variable displacement radial piston hydraulic pump 10 having a plurality of radially arranged cylinders 12 with pistons 14 mounted for reciprocation therein, only a single cylinder and piston being schematically illustrated in the drawings since pumps of this type are well known.
  • the inner end of each cylinder opens into a central, closed drive chamber or crankcase 16, in which an eccentric type drive mechanism 18 rotates, the drive mechanism engaging the inner ends of the piston 14 to reciprocate the pistons in response to the rotation of the drive mechanism.
  • the fluid pressure is supplied to and exhausted from the crankcase 16 by means of a regulating line 20.
  • each cylinder 12 The outer or closed end of each cylinder 12 is connected to an inlet line 22 and an outlet line 24 respectively having check valves 26 and 28, which permit the flow of fluid only from the inlet line to the cylinder and from the cylinder to the discharge line 24.
  • each cylinder is connected to the inlet and discharge lines through appropriate manifolding and includes its own pair of check valves.
  • the discharge line 24 supplies pressurized fluid to one or more bydraulic functions, indicated by the functional box 30 in FIG. 1.
  • a fixed displacement charge pump 32 draws fluid from a reservoir and discharges it into an outlet line 36, which is conventionally provided with a filter 38 and a check valve 40 which permits flow of fluid only from the charge pump.
  • the hydraulic function 30 is connected to the outlet line 36 via a return line 42.
  • a pressure regulating valve 44 is disposed in the outlet line 36 to maintain the pressure therein at a predetermined level, the pressure regulating valve 44 dumping the fluid in the outlet line to a reservoir when the predetermined pressure is reached, so that flow from the charge pump in excess of that required by the main pump is returned to the reservoir, preferably through a cooler (not shown).
  • the charge pump outlet line 36 is connected to the main pump inlet line 22, so that the charge pressure tends to return the piston 14 during the intake stroke of the pistons.
  • the charge pump outlet line 36 is also connected to the inlet of a pilot-operated stroke control valve 46, which is preferably a two-position spool-type valve of known construction. In the position shown in FIG. 1, the stroke control valve 46 connects the charge pump outlet line 36 to the regulating line 20, while in the alternate or exhaust position, the outlet line 36 is blocked and the regulating line 20 is connected to the reservoir.
  • a pilot-operated stroke control valve 46 which is preferably a two-position spool-type valve of known construction.
  • the valve 46 is biased toward its exhaust position by a spring 48, which acts on one end of the valve, while the opposite end of the valve is connected to the discharge line 24 by a pilot line 50, which applies the discharge pressure to the end of the valve in opposition to the spring 48.
  • a spring 48 which acts on one end of the valve
  • pilot line 50 which applies the discharge pressure to the end of the valve in opposition to the spring 48.
  • the hydraulic system includes a hydraulic function or load represented by a two-way hydraulic cylinder 52 having its opposite ends connected to hydraulic lines 54 and 56, respectively provided with check valves 58 and 60, which permit flow of fluid only to the hydraulic cylinder.
  • Bypass lines 62 and 64 are respectively connected to the hydraulic lines 54 and 56 to bypass the check valves 58 and 60 to permit exhaust of the fluid from the cylinder.
  • a three-position control valve 66 is connected to the main pump discharge line 24, the return line 42, and the hydraulic lines 54, 56, 62, and 64.
  • the control valve 66 is illustrated in its neutral position, wherein all of the hydraulic lines are blocked, and is shiftable downwardly therefrom to connect the bypass line 64 to the return line 42 and the line 54 to the pump discharge line 24, so that the upper end of the cylinder 52 is pressurized and the lower end is connected to the return line. As is apparent, the valve is shiftable in the opposite direction from the neutral position to pressurize the line 56 and exhaust the upper end of the cylinder via the line 62.
  • a pilot line 68 communicates with the end of the pilot-operated stroke control valve 46 on the opposite end from the pilot line 50 and is connected to the upper hydraulic cylinder line 54 through a hydraulic line 70 having a check valve 72 and to the lower cylinder line 56 by a line 74 having a check valve 76, the check valves 72 and 76 permitting the flow of fluid only from the line 54 or 56 to the pilot line 68, depending on which line is pressurized.
  • the pilot line 68 is connected to the reservoir via a drain line 78 having a flowrestricting orifice 80.
  • the second embodiment of the invention operates in the same manner as the embodiment described in FIG. 1, except that the stroke control valve 46 is responsive to both the pressure in the discharge line 24 and the pressure in either of the hydraulic lines 54 or 56 to the load, depending upon which line is pressurized.
  • the stroke control valve 46 is responsive to both the pressure in the discharge line 24 and the pressure in either of the hydraulic lines 54 or 56 to the load, depending upon which line is pressurized.
  • a hydraulic system comprising: a main variable displacement hydraulic pump having an inlet line and a discharge line; a pump regulating means responsive to pressure in a pump regulating line to respectively decrease or increase pump displacement in response to an increase or decrease in the pump regulating line pressure; a charge pump means having an inlet line connected to a reservoir and an outlet line connected to the main pump inlet line for supplying fluid thereto; a pilot-operated stroke control valve means connected to the reservoir, the charge pump outlet line and the regulating lines; means biasing the valve toward a first position wherein it connects the pump regulating line to the reservoir to decrease the pressure therein and increase the pump displacement; and a first pilot line operatively connected to the stroke control valve and the main pump discharge line for shifting the valve against said biasing means when the force exerted by fluid pressure in the pilot line exceeds the force exerted by the biasing means into a second position wherein it connects the charge pump outlet line to the pressure regulating line to increase the pressure therein and reduce the pump displacement.
  • a hydraulic system comprising: a main variable displacement hydraulic pump having a plurality of cylinders with inner ends opening into a closed drive chamber and closed outer ends connected to an inlet line and a discharge line, a piston mounted in each cylinder and drive means within the chamber engageable with the inner ends of the pistons to reciprocate the pistons, the pressure in the inlet line returning the pistons into driving engagement with the drive means and the pressure in the chamber opposing said engagement, so that the piston strokes are dependent upon the relative pressuresin the inlet line and the drive chamber; a pump regulating line connected to the drive chamber; a charge pump having an outlet line connected to the main pump inlet line for supplying pressurized fluid to the outer ends of the cylinders; a pilot-operated stroke control valve shiftable between a first-position, wherein it connects the pump regulating line to the reservoir to decrease the pressure in the drive chamber and increase the piston strokes, and a second position, wherein it connects the pump regulating line to the charge pump discharge line to increase the pressure in the drive chamber and decrease

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Reciprocating Pumps (AREA)
  • Control Of Positive-Displacement Pumps (AREA)
US00197699A 1971-11-11 1971-11-11 Variable displacement pump control system Expired - Lifetime US3738111A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US19769971A 1971-11-11 1971-11-11

Publications (1)

Publication Number Publication Date
US3738111A true US3738111A (en) 1973-06-12

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ID=22730400

Family Applications (1)

Application Number Title Priority Date Filing Date
US00197699A Expired - Lifetime US3738111A (en) 1971-11-11 1971-11-11 Variable displacement pump control system

Country Status (6)

Country Link
US (1) US3738111A (it)
CA (1) CA967809A (it)
DE (1) DE2254590A1 (it)
FR (1) FR2160171A5 (it)
GB (1) GB1344798A (it)
IT (1) IT972396B (it)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3995973A (en) * 1975-09-04 1976-12-07 Deere & Company Variable displacement hydraulic system
FR2339074A1 (fr) * 1976-01-23 1977-08-19 Caterpillar Tractor Co Pompe a piston
US4519752A (en) * 1982-09-03 1985-05-28 Applied Power Inc. Control system for a variable displacement pump
US4648803A (en) * 1985-09-17 1987-03-10 Deere & Company Control circuit and control valve for radial piston pump
US4840544A (en) * 1985-02-06 1989-06-20 Aisin Seiki Kabushiki Kaisha Hydraulic pump assembly associated with accumulator
US4945816A (en) * 1985-12-02 1990-08-07 Black Gold Development Corporation Radial piston hydraulic motor with rotary cam position encoder and valve control system
US6651545B2 (en) * 2001-12-13 2003-11-25 Caterpillar Inc Fluid translating device
EP1555432A1 (en) * 2004-01-19 2005-07-20 Delphi Technologies, Inc. Hydraulic pump

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3987622A (en) * 1976-02-02 1976-10-26 Caterpillar Tractor Co. Load controlled fluid system having parallel work elements
US3990236A (en) * 1976-02-23 1976-11-09 Caterpillar Tractor Co. Load responsive pump controls of a fluid system
JPS5393265A (en) * 1977-01-26 1978-08-16 Girling Ltd System of hydraulic pressure
US4475870A (en) * 1980-08-19 1984-10-09 Karl Eickmann Hydraulic arrangement

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2851952A (en) * 1957-06-27 1958-09-16 Lane Edwin Leonard Hydraulic pumps
US3002462A (en) * 1957-08-13 1961-10-03 Racine Hydraulics & Machinery Fluid translating apparatus
US3302585A (en) * 1962-09-24 1967-02-07 Abex Corp Control for variable displacement pump or motor
US3412683A (en) * 1966-08-25 1968-11-26 Ulrich Mfg Co Hydraulic system control
US3422726A (en) * 1966-06-27 1969-01-21 Nathan Gottlieb Motorized spindle
US3444689A (en) * 1967-02-02 1969-05-20 Weatherhead Co Differential pressure compensator control
US3465680A (en) * 1967-05-31 1969-09-09 Sundstrand Corp Hydraulic pump or motor unit

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2851952A (en) * 1957-06-27 1958-09-16 Lane Edwin Leonard Hydraulic pumps
US3002462A (en) * 1957-08-13 1961-10-03 Racine Hydraulics & Machinery Fluid translating apparatus
US3302585A (en) * 1962-09-24 1967-02-07 Abex Corp Control for variable displacement pump or motor
US3422726A (en) * 1966-06-27 1969-01-21 Nathan Gottlieb Motorized spindle
US3412683A (en) * 1966-08-25 1968-11-26 Ulrich Mfg Co Hydraulic system control
US3444689A (en) * 1967-02-02 1969-05-20 Weatherhead Co Differential pressure compensator control
US3465680A (en) * 1967-05-31 1969-09-09 Sundstrand Corp Hydraulic pump or motor unit

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3995973A (en) * 1975-09-04 1976-12-07 Deere & Company Variable displacement hydraulic system
FR2339074A1 (fr) * 1976-01-23 1977-08-19 Caterpillar Tractor Co Pompe a piston
US4519752A (en) * 1982-09-03 1985-05-28 Applied Power Inc. Control system for a variable displacement pump
US4840544A (en) * 1985-02-06 1989-06-20 Aisin Seiki Kabushiki Kaisha Hydraulic pump assembly associated with accumulator
US4648803A (en) * 1985-09-17 1987-03-10 Deere & Company Control circuit and control valve for radial piston pump
US4945816A (en) * 1985-12-02 1990-08-07 Black Gold Development Corporation Radial piston hydraulic motor with rotary cam position encoder and valve control system
US6651545B2 (en) * 2001-12-13 2003-11-25 Caterpillar Inc Fluid translating device
EP1555432A1 (en) * 2004-01-19 2005-07-20 Delphi Technologies, Inc. Hydraulic pump

Also Published As

Publication number Publication date
GB1344798A (en) 1974-01-23
FR2160171A5 (it) 1973-06-22
CA967809A (en) 1975-05-20
IT972396B (it) 1974-05-20
DE2254590A1 (de) 1973-05-17

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