US20210040944A1 - Electric displacement control for an open circuit variable displacement pump - Google Patents
Electric displacement control for an open circuit variable displacement pump Download PDFInfo
- Publication number
- US20210040944A1 US20210040944A1 US16/866,714 US202016866714A US2021040944A1 US 20210040944 A1 US20210040944 A1 US 20210040944A1 US 202016866714 A US202016866714 A US 202016866714A US 2021040944 A1 US2021040944 A1 US 2021040944A1
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- United States
- Prior art keywords
- control
- spool
- servo
- valve
- force
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- 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.)
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- 238000006073 displacement reaction Methods 0.000 title claims abstract description 34
- 239000012530 fluid Substances 0.000 claims abstract description 20
- 230000006835 compression Effects 0.000 claims description 3
- 238000007906 compression Methods 0.000 claims description 3
- 230000003247 decreasing effect Effects 0.000 claims description 2
- 238000000034 method Methods 0.000 claims 4
- 230000004913 activation Effects 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
Images
Classifications
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- 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
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/002—Hydraulic systems to change the pump delivery
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- 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
- F04B1/12—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis
- F04B1/26—Control
- F04B1/28—Control of machines or pumps with stationary cylinders
- F04B1/29—Control of machines or pumps with stationary cylinders by varying the relative positions of a swash plate and a cylinder block
- F04B1/295—Control of machines or pumps with stationary cylinders by varying the relative positions of a swash plate and a cylinder block by changing the inclination of the swash plate
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- 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
- F04B17/00—Pumps characterised by combination with, or adaptation to, specific driving engines or motors
-
- 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
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/22—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by means of valves
Definitions
- the present invention is directed to a control system for a hydraulic variable displacement pump, and more particularly a control system for an open circuit variable displacement pump which is adjustable by means of a servo piston that shifts inside of a servo cylinder.
- Control systems for an open circuit variable displacement pump are known in the art.
- a control device is used to set various power levels for the variable displacement pump that are reliably maintained by automatically regulating the control device without requiring any external control intervention.
- Electric displacement controls (EDC) for a pump regulate the speed of a machine function such as speed of a conveyor belt or drilling speed on a drill rig.
- EDCs typically replace PVG-like valves allowing cost reductions as well as lowering the hydraulic losses across the valve for better system efficiency. While useful, problems still exist with respect to cost and space while still meeting application requirements.
- a solution to these problems involves an EDC concept that includes use of a two-way, two or three position, spool type valve located in the pump servo bore and having an orifice to vent fluid from the servo bore to the pump case.
- the spool type valve meters fluid from system pressure to the servo bore and the flow rate across the valve depends on a force balanced between a feedback spring force on one side of the spool and a solenoid actuator force on another side of the spool.
- An objective of the present invention is to provide an electric displacement system that reduces the cost of manufacturing and still meets application requirements.
- Another objective of the present invention is to provide an electric displacement system that reduces the space needed and still meets application requirements.
- An electric displacement control system has a hydraulic variable displacement pump that operates in an open hydraulic circuit.
- a servo piston is disposed within a servo bore that is connected to the hydraulic variable displacement pump.
- Located in the servo bore is a control spool valve having an orifice that vents fluid pressure from the servo bore to a pump case. The flow rate of the system depends upon a fluid force between a feedback spring on a first side of the control spool valve and a solenoid actuator force on a second side of the control spool valve.
- the control spool valve is located in a housing and has a plug with a system pressure access to a porting hole, a moveable control spool, a feedback compression spring at a first side and a solenoid actuator at a second side.
- the control spool valve is a two-way, two-position spool type valve or a two-way, three-position spool type valve.
- the control spool valve has a groove where fluid in the groove is connected with a fluid in the servo bore and fluid volume at a solenoid actuator. An axis of the of the control spool valve is aligned with an axis of the servo bore.
- a feedback spring Positioned between the servo piston and a first side of the control spool valve is a feedback spring.
- FIG. 1 is a schematic view of an electric displacement control system
- FIG. 2 is a schematic view of an electric displacement control system.
- an electric displacement control system 10 includes a variable displacement pump 12 .
- the variable displacement pump 12 has an inlet 14 and an outlet 16 .
- the outlet 16 is connected to a control device 18 via a pressure line 20 .
- Control device 18 has a control piston 22 mounted within a housing 24 and is adapted to shift or move longitudinally.
- a first end 26 of the control piston 22 has an actuator 27 that is exposed to high pressure fluid that exerts hydraulic force toward a second end 28 having an adjustable spring 30 .
- the housing 24 has a first port 32 , a second port 34 , and a third port 36 .
- the first port 32 is positioned to selectively align with pressure line 20 .
- the second port 34 is positioned to selectively align with drain line 37 that extends between the control device 18 and a tank 38 .
- the third port 36 is positioned to selectively align with pressure line 40 .
- the control device 18 has a first position that permits flow through the control device 18 between drain line 36 and pressure line 40 .
- the control device 18 has a second position where fluid flows from pressure line 20 to pressure line 40 .
- the pressure line 40 extends from the control device 18 and a spool type valve 42 .
- the spool type valve 42 is of any type and preferably is a two-way two position spool valve 42 A for a zero flow and minimum fail-safe control design, or a two-way three position spool valve 42 B for a full flow and maximum pressure fail-safe control design.
- the spool valve 42 is located in a pump servo bore 44 and the axis of the spool valve 42 is aligned with the axis of the servo bore 44 .
- the spool valve 42 includes a plug 46 with a system pressure access to a porting hole 48 , a moveable control spool 50 , a feedback compression spring 52 on one end, and a solenoid actuator 54 on the opposite end.
- a groove 56 on the control spool 50 selectively permits flow from the outlet 16 , through the control spool 50 to pressure line 40 .
- the two-way three position spool valve 42 B has a pair of plugs 46 A and 46 B on each side of the groove 56 .
- the servo bore 44 has an orifice 58 to maintain a pressure differential between servo pressure and case pressure. Fluid pressure from the spool valve 42 acts upon a servo piston 60 moving the piston 60 against the force of a return spring 62 . Movement of the servo piston 60 adjusts the variable displacement pump 12 as required via an activation link 64 . This adjustment results in a change in the deflection angle of a swashplate.
- moveable control 50 When the actuator force is decreased, moveable control 50 is pushed by feedback spring 56 against the solenoid actuator 54 and system pressure is communicated to the servo piston 60 .
- the servo piston 60 moves out of the servo bore 44 and force from the feedback spring 56 is lowered until spring force and solenoid actuator force are balanced again. With maximum solenoid force, system pressure is blocked at porting hole 48 and fluid in servo bore is all vented to case as the pump bias system returns the pump 12 to maximum displacement.
- the two-way three-position spool valve 42 B operates in a similar manner to move the control member 50 between maximum and minimum displacement, but also provides an emergency or fail safe when electrical power to the solenoid actuator 54 is lost. More specifically, when solenoid force drops below a preset minimum force from the feedback spring 52 moves the control member 50 all the way against the solenoid actuator which blocks system pressure. Pump displacement would be returned to maximum as all fluid would be vented to the pump case through the orifice.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Control Of Positive-Displacement Pumps (AREA)
Abstract
Description
- This application claims the benefit of the priority of U.S. Provisional Application No. 62/884,380 filed on Aug. 8, 2019, the contents of this application is hereby incorporated by reference in its entirety.
- The present invention is directed to a control system for a hydraulic variable displacement pump, and more particularly a control system for an open circuit variable displacement pump which is adjustable by means of a servo piston that shifts inside of a servo cylinder.
- Control systems for an open circuit variable displacement pump are known in the art. In one example, as disclosed in U.S. Publication No. 2015/0050165 by Zavadinka, a control device is used to set various power levels for the variable displacement pump that are reliably maintained by automatically regulating the control device without requiring any external control intervention. Electric displacement controls (EDC) for a pump regulate the speed of a machine function such as speed of a conveyor belt or drilling speed on a drill rig. EDCs typically replace PVG-like valves allowing cost reductions as well as lowering the hydraulic losses across the valve for better system efficiency. While useful, problems still exist with respect to cost and space while still meeting application requirements.
- A solution to these problems involves an EDC concept that includes use of a two-way, two or three position, spool type valve located in the pump servo bore and having an orifice to vent fluid from the servo bore to the pump case. The spool type valve meters fluid from system pressure to the servo bore and the flow rate across the valve depends on a force balanced between a feedback spring force on one side of the spool and a solenoid actuator force on another side of the spool.
- An objective of the present invention is to provide an electric displacement system that reduces the cost of manufacturing and still meets application requirements.
- Another objective of the present invention is to provide an electric displacement system that reduces the space needed and still meets application requirements.
- These and other objectives will be apparent to those having skill in the art based upon the following written description, drawings, and claims.
- An electric displacement control system has a hydraulic variable displacement pump that operates in an open hydraulic circuit. A servo piston is disposed within a servo bore that is connected to the hydraulic variable displacement pump. Located in the servo bore is a control spool valve having an orifice that vents fluid pressure from the servo bore to a pump case. The flow rate of the system depends upon a fluid force between a feedback spring on a first side of the control spool valve and a solenoid actuator force on a second side of the control spool valve.
- The control spool valve is located in a housing and has a plug with a system pressure access to a porting hole, a moveable control spool, a feedback compression spring at a first side and a solenoid actuator at a second side. Preferably the control spool valve is a two-way, two-position spool type valve or a two-way, three-position spool type valve. The control spool valve has a groove where fluid in the groove is connected with a fluid in the servo bore and fluid volume at a solenoid actuator. An axis of the of the control spool valve is aligned with an axis of the servo bore. Positioned between the servo piston and a first side of the control spool valve is a feedback spring.
-
FIG. 1 is a schematic view of an electric displacement control system; and -
FIG. 2 is a schematic view of an electric displacement control system. - Referring to the figures, an electric
displacement control system 10 includes avariable displacement pump 12. Thevariable displacement pump 12 has aninlet 14 and anoutlet 16. Theoutlet 16 is connected to acontrol device 18 via apressure line 20. -
Control device 18 has acontrol piston 22 mounted within ahousing 24 and is adapted to shift or move longitudinally. Afirst end 26 of thecontrol piston 22 has anactuator 27 that is exposed to high pressure fluid that exerts hydraulic force toward asecond end 28 having anadjustable spring 30. - The
housing 24 has afirst port 32, asecond port 34, and athird port 36. Thefirst port 32 is positioned to selectively align withpressure line 20. Thesecond port 34 is positioned to selectively align withdrain line 37 that extends between thecontrol device 18 and atank 38. Thethird port 36 is positioned to selectively align withpressure line 40. Thecontrol device 18 has a first position that permits flow through thecontrol device 18 betweendrain line 36 andpressure line 40. Thecontrol device 18 has a second position where fluid flows frompressure line 20 topressure line 40. - The
pressure line 40 extends from thecontrol device 18 and a spool type valve 42. The spool type valve 42 is of any type and preferably is a two-way twoposition spool valve 42A for a zero flow and minimum fail-safe control design, or a two-way threeposition spool valve 42B for a full flow and maximum pressure fail-safe control design. - The spool valve 42 is located in a
pump servo bore 44 and the axis of the spool valve 42 is aligned with the axis of theservo bore 44. The spool valve 42 includes aplug 46 with a system pressure access to aporting hole 48, amoveable control spool 50, afeedback compression spring 52 on one end, and asolenoid actuator 54 on the opposite end. Agroove 56 on thecontrol spool 50 selectively permits flow from theoutlet 16, through thecontrol spool 50 topressure line 40. The two-way threeposition spool valve 42B has a pair of plugs 46A and 46B on each side of thegroove 56. - The
servo bore 44 has anorifice 58 to maintain a pressure differential between servo pressure and case pressure. Fluid pressure from the spool valve 42 acts upon aservo piston 60 moving thepiston 60 against the force of areturn spring 62. Movement of theservo piston 60 adjusts thevariable displacement pump 12 as required via anactivation link 64. This adjustment results in a change in the deflection angle of a swashplate. - In operation, using the two-way two
position spool valve 42A, with no or minimum solenoid force, fluid pressure flows fromoutlet 16, throughcontrol spool 50 topressure line 40. This results in sending thepump 12 to minimum displacement. - As solenoid force increases, the
spool valve 42A moves toward and againstfeedback spring 52 reducing flow to the servo. As a result, the pump bias system returnspump 12 displacement to maximum while compressing thefeedback spring 52 until the spring force and the actuator force are balanced. - When the actuator force is decreased,
moveable control 50 is pushed byfeedback spring 56 against thesolenoid actuator 54 and system pressure is communicated to theservo piston 60. Theservo piston 60 moves out of the servo bore 44 and force from thefeedback spring 56 is lowered until spring force and solenoid actuator force are balanced again. With maximum solenoid force, system pressure is blocked at portinghole 48 and fluid in servo bore is all vented to case as the pump bias system returns thepump 12 to maximum displacement. - The two-way three-
position spool valve 42B operates in a similar manner to move thecontrol member 50 between maximum and minimum displacement, but also provides an emergency or fail safe when electrical power to thesolenoid actuator 54 is lost. More specifically, when solenoid force drops below a preset minimum force from thefeedback spring 52 moves thecontrol member 50 all the way against the solenoid actuator which blocks system pressure. Pump displacement would be returned to maximum as all fluid would be vented to the pump case through the orifice.
Claims (12)
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US16/866,714 US20210040944A1 (en) | 2019-08-08 | 2020-05-05 | Electric displacement control for an open circuit variable displacement pump |
CN202010486933.1A CN112343806B (en) | 2019-08-08 | 2020-06-01 | Electric displacement control for open circuit variable displacement pump |
CN202020974579.2U CN212803539U (en) | 2019-08-08 | 2020-06-01 | Electric displacement control system for open circuit variable displacement pump |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US201962884380P | 2019-08-08 | 2019-08-08 | |
US16/866,714 US20210040944A1 (en) | 2019-08-08 | 2020-05-05 | Electric displacement control for an open circuit variable displacement pump |
Publications (1)
Publication Number | Publication Date |
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US20210040944A1 true US20210040944A1 (en) | 2021-02-11 |
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ID=74498045
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US16/866,714 Pending US20210040944A1 (en) | 2019-08-08 | 2020-05-05 | Electric displacement control for an open circuit variable displacement pump |
Country Status (2)
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US (1) | US20210040944A1 (en) |
CN (1) | CN212803539U (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN112343806B (en) * | 2019-08-08 | 2023-08-29 | 丹佛斯动力系统公司 | Electric displacement control for open circuit variable displacement pump |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20150285214A1 (en) * | 2014-04-03 | 2015-10-08 | Danfoss Power Solutions Gmbh & Co Ohg | Switchable hydrostatic adjusting device |
WO2017083839A1 (en) * | 2015-11-15 | 2017-05-18 | Eaton Corporation | Hydraulic pump control system |
-
2020
- 2020-05-05 US US16/866,714 patent/US20210040944A1/en active Pending
- 2020-06-01 CN CN202020974579.2U patent/CN212803539U/en active Active
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20150285214A1 (en) * | 2014-04-03 | 2015-10-08 | Danfoss Power Solutions Gmbh & Co Ohg | Switchable hydrostatic adjusting device |
WO2017083839A1 (en) * | 2015-11-15 | 2017-05-18 | Eaton Corporation | Hydraulic pump control system |
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CN212803539U (en) | 2021-03-26 |
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