EP0086772B1 - Load responsive system controls - Google Patents

Load responsive system controls Download PDF

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Publication number
EP0086772B1
EP0086772B1 EP81902366A EP81902366A EP0086772B1 EP 0086772 B1 EP0086772 B1 EP 0086772B1 EP 81902366 A EP81902366 A EP 81902366A EP 81902366 A EP81902366 A EP 81902366A EP 0086772 B1 EP0086772 B1 EP 0086772B1
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EP
European Patent Office
Prior art keywords
control
pressure
orifice
differential
load
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
Application number
EP81902366A
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German (de)
English (en)
French (fr)
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EP0086772A4 (en
EP0086772A1 (en
Inventor
Tadeusz Budzich
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Caterpillar Inc
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Caterpillar Inc
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Publication date
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Publication of EP0086772A1 publication Critical patent/EP0086772A1/en
Publication of EP0086772A4 publication Critical patent/EP0086772A4/en
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    • 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
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/161—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load
    • F15B11/165—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load for adjusting the pump output or bypass in response to demand
    • 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
    • F15B2211/20576—Systems with pumps with multiple pumps
    • 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
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30505—Non-return valves, i.e. check valves
    • 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
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30525—Directional control valves, e.g. 4/3-directional control valve
    • 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
    • F15B2211/30—Directional control
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/321—Directional control characterised by the type of actuation mechanically
    • F15B2211/324—Directional control characterised by the type of actuation mechanically manually, e.g. by using a lever or pedal
    • 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
    • F15B2211/40—Flow control
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • F15B2211/40507—Flow control characterised by the type of flow control means or valve with constant throttles or orifices
    • 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
    • F15B2211/40—Flow control
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • F15B2211/40515—Flow control characterised by the type of flow control means or valve with variable throttles or orifices
    • 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
    • F15B2211/40—Flow control
    • F15B2211/42—Flow control characterised by the type of actuation
    • F15B2211/428—Flow control characterised by the type of actuation actuated by fluid pressure
    • 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
    • F15B2211/40—Flow control
    • F15B2211/45—Control of bleed-off flow, e.g. control of bypass flow to the return line
    • 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
    • F15B2211/50—Pressure control
    • F15B2211/505—Pressure control characterised by the type of pressure control means
    • F15B2211/50509—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means
    • F15B2211/50536—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using unloading valves controlling the supply pressure by diverting fluid to the return line
    • 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
    • F15B2211/50—Pressure control
    • F15B2211/52—Pressure control characterised by the type of actuation
    • F15B2211/528—Pressure control characterised by the type of actuation actuated by fluid pressure
    • 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
    • F15B2211/50—Pressure control
    • F15B2211/57—Control of a differential pressure
    • 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
    • F15B2211/63—Electronic controllers
    • 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
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7052—Single-acting output members
    • 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
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7053—Double-acting output members
    • 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
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7058—Rotary output members
    • 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
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders

Definitions

  • This invention relates generally to a fluid control system and more particularly to load responsive system controls, which permit variation in the level of control differential between the discharge pressure of a pump and the load pressure signal, while this control differential is automatically maintained constant at each controlled level.
  • the variation is preferably in response to an external control signal.
  • this invention relates to signal modifying controls of a load responsive system, which supply control signals to the output flow control of a pump, to adjust and regulate the pressure differential across an orifice positioned between the system pump and a fluid motor operating a load.
  • Load responsive systems in which pump output flow controls respond to the load pressure signal to maintain a constant pressure differential between pump discharge pressure and load pressure, are well known in the art.
  • flow through an orifice positioned between a system pump and a fluid motor operating a load, is proportional to the area of the orifice and independent of system load.
  • load responsive systems are very desirable for a number of reasons. Not only do they provide exceptional control of a load, but they permit operation of the load at very high system efficiency.
  • load responsive fluid control systems are shown in US-A-2892312 and US-A-3444689.
  • US-A-4282898 discloses a system capable of selectively operating at one of either a high or a low flow rate with only a single pressurise of source.
  • Another object of this invention is to provide load responsive system control, in which control of system load can either be accomplished by variation in area of an orifice between the system pump and a fluid motor, while the pressure differential across this orifice is maintained constant at a specific level, or by control of pressure differential, acting across this orifice while the area of the orifice remains constant.
  • a pump a fluid motor subjected to a load pressure; control orifice means between the pump and the fluid motor; flow control means to regulate the discharge pressure of the pump; and first control means to control the flow control means to maintain a constant pressure differential across said control orifice means; characterized in that the first control means has pilot valve means controlling an actuating means for operating the flow control means, the pilot valve means being subjected on one side to a load pressure signal and on the other side to a pump discharge pressure signal, and operating in conjunction with the flow control means to maintain a predetermined constant pressure differential across the pilot valve means;
  • second control means responsive to an external signal, to modify the desired load pressure or pump discharge pressure signal and thus, in conjunction with the first control means, the level of the desired constant pressure differential across the control orifice means.
  • control action preferably responsive to an external control signal, can be superimposed upon conventional constant pressure differential control of a load responsive system, providing a system with dual parallel control inputs.
  • level of controlled pressure differential be adjusted to any desired value chosen by the operator during the conventional mode of operation of the load responsive control, but the load can be fully controlled through change in the control differential, in any control position of the load responsive direction control valve.
  • Fig. 1 is a diagrammatic representation of load responsive control for adjustment in level of control differential from a certain preselected level to zero level, with fluid motor, system pump and pump controls shown schematically;
  • the hydraulic system shown therein comprises a fluid pump 10, equipped with a flow changing mechanism 11, operated by an output flow control 12.
  • the output flow control 12 regulates delivery of the pump 10 into a load responsive circuit, composed of a differential control, generally designated as 13, regulating the level of pr essure differential developed across schematically shown variable orifice 14, interposed between the pump 10 and a fluid motor 15 operating load W.
  • the pump 10 may be of fixed or variable displacement type. With the pump 10 being of fixed displacement type, the output flow control 12, in a well known manner, regulates, through flow changing mechanism 11, delivery from pump to load responsive circuit, by bypassing part of the pump flow to a system reservoir 16.
  • the output flow control 12 in a well known manner, regulates through flow changing mechanism 11 delivery from pump to load responsive circuit, by changing the pump displacement.
  • the differential control 13 is shown separated, in actual application the differential control 13 would be most likely an integral part of pump output flow control 12.
  • the output flow control 12 may be supplied with fluid energy from the pump 10 through discharge line 17 and line 18, or from a separate source of fluid energy, namely a pump 19 provided with a bypass valve 20.
  • Discharge line 17 of pump 12 is connected through a load check 21, variable orifice 14 and line 22 to the fluid motor 15 and through line 23 to a fluid motor 24, subjected to load W l .
  • Load pressure signal Pw is transmitted through line 22 and a signal check valve 25 to fixed or variable orifice 26.
  • load pressure signal from the fluid motor 24 is transmitted through a signal check valve 27 and line 28 to upstream of fixed or variable orifice 26 and downstream of signal check valve 25.
  • the differential control 13 communicates through line 29 with downstream of fixed or variable orifice 26 and through line 30 with the output flow control 12 of pump 10.
  • the differential control 13 comprises a housing 31 having an inlet chamber 32, a control chamber 33 and an exhaust chamber 34, interconnected by bore 35, guiding a control spool 36.
  • the control spool 36 is equipped with a land 37 provided with throttling slots 38 and positioned, between control and inlet chambers, a land 39 separating inlet and exhaust chambers and a flange 40.
  • a control spring 41 is interposed in the exhaust chamber between the flange 40 of control spool 36 and the housing 31.
  • the exhaust chamber 34 and the control chamber 33 are selectively interconnected by metering orifice, created by a stem 43 guided in circular bore 42 and provided with metering slots 44.
  • the stem 43 is connected to an actuator 45, responsive to external control signal 46.
  • a differential pressure control 13a of Fig. 2 is identical to the differential control 13 of Fig. 1, with the exception that metering orifice 42 and the stem 43 with its metering slots 44 were substituted by fixed orifice 42a.
  • Fig. 3 the same components used in Fig. 1 are designated by the same numerals.
  • the only difference between load responsive system controls of Figs. 1 and 3 is the phasing of the differential control 13 and the load pressure signals from fluid motors 15 and 24 to the output flow control 12 of pump 10.
  • Fig. 2 the load pressure signal from downstream of signal check valves 25 and 27 is directly transmitted through line 47 to the output flow control 12.
  • the discharge pressure signal from pump 10 is transmitted to the output flow control 12, through discharge line 17, load check 21, fixed or variable orifice 26 and line 30, with differential control 13 connected to this signal transmitting path.
  • Fig. 4 the same components used in Figs 1 and 3 are designated by the same numerals.
  • the load responsive system of Fig. 4 shows one differential control 13 connected to signal transmitting line 30 in the same way as in the circuit of Fig. 1 and a second differential control 13 connected to signal transmitting line 48 in the same way as in the circuit of Fig. 3.
  • Fig. 5 the same components used in Fig. 1 are designated by the same numerals.
  • the differential control assembly 50 of Fig. 4 is phased into the circuitin the same way as the differential control 13 of Fig. 1 and performs an identical function.
  • the differential control assembly 50 is shown for purpose of better demonstration, composed of two components, those two components should be combined and preferably incorporated into assembly of output flow control 12.
  • the differential control assembly 50 includes a variable orifice valve 51, provided with a housing 52, having an inlet chamber 53, an outlet chamber 54, circular bore 55, positioned between those chambers and guiding a stem 56 equipped with metering slot 57.
  • the stem 56 is connected to the actuator 45 responsive to an external control signal 46.
  • the differential control assembly 50 also includes a flow control valve 58, provided with a housing 59 having an inlet chamber 60 and an exhaust chamber 61, connected by bore 62, axially guiding a metering pin 63, provided with a metering slot 64.
  • the metering pin 63 is provided with a stop 65 and is biased towards position as shown by a spring 66, contained in the exhaust chamber.
  • variable orifice valve 51 is connected by line 28 with downstream of signal check valves 25 and 27, while the outlet chamber 54 is connected by line 67 with the inlet chamber 60, of the flow control valve 58, which in turn is connected by line 30 with the output flow control 12 of pump 10.
  • Fig. 6 the same components used in Fig. 5 are designated by the same numerals.
  • the basic load responsive system of Fig. 6 is similar to the system of Fig. 5, with the exception that variable orifice 14 was substituted by a load responsive direction control valve, generally designated as 68 and a differenttype of a differential valve 68a was used.
  • the direction control valve 68 comprises a housing 69 having an inlet chamber 70, first and second load chambers 71 and 72, first and second exhaust chambers 73 and 74, load pressure sensing ports 75 and 76 and bore 77, guiding a valve spool 78.
  • the valve spool 78 has lands 79, 80 and 81 provided with metering slots 82, 83, 84 and 8.5 and signal slots 86 and 87 and is actuated by control lever 88.
  • Load pressure sensing ports 75 and 76 are connected by line 89 to upstream of the signal check valve 25.
  • load pressure sensing ports of a load responsive direction control valve 90 controlling through fluid motor 91 load W 2 , are connected by a line to upstream of the signal check valve 27. Downstream of signal check valves 25 and 27 is connected by line 28 to inlet port 93 of differential valve, generally designated as 68a.
  • the differential valve 68a comprises a housing 94, retaining a coil 95, guiding an armature 96 of a solenoid, generally designated as 97.
  • the armature 96 is provided with a conical surface 98 selectively engageable with the sealing edge 99 of the inlet port 93 and venting passage 100.
  • a retaining spring 101 can be interposed between the armature 96 and the housing 94.
  • the coil 95 is connected by a sealed connector 102 to outside of the housing 94, external signal 46 being applied to the sealed connector 102.
  • the outlet port 103 of the differential valve 68a is connected by line 30 with the output flow control 12 and is also connected by line 104 with orifice leading to the reservoir 16.
  • the orifice can be of a fixed or variable type. If the orifice is of a variable type it may be of a type and contained within the flow control valve 58 of Fig. 5, construction of which was described in detail when referring to Fig. 5.
  • a differential pressure controller 68b is similar to the differential controller 68a of Fig. 6, with the exception that the throttling member 98, with its conical surface 98a engaging sealing edge 99, is biased by a spring 101a instead of by armature 96.
  • variable output flow pump 10 of Figs. 1,3,4,5 and 6 is provided with the flow changing mechanism 11 and the output flow control 12.
  • First pressure control signal is transmitted from discharge line 17, through fixed or variable orifice 26, line 29, the differential control 13 and line 30 to the output flow control 12, as per control arrangement shown in Fig. 3.
  • a second pressure control signal 105 is transmitted directly from the largest system load to control space 106 of the output flow control 12.
  • the output flow control 12, well known in the art, comprises a pilot valve 107, guided in a bore 108 and equipped with lands 109, 110 and 111, defining annular spaces 112, 113 and space 114.
  • the pilot valve 107 is biased by a control spring 115, contained within control space 106.
  • Bore 108 is provided with an exhaust core 116, connected to the system reservoir 11 and a control core 117, connected to a chamber 118 and through leakage orifice 119 also connected to the exhaust core 116.
  • the chamber 118 contains a piston 120 operating the flow changing mechanism 11 and biased by a spring 121.
  • Annular space 112 is connected by line 122 with discharge pressure of the pump 19 and the flow changing mechanism 11 is connected by line 123 with the system reservoir 16.
  • FIG. 8 the basic arrangements of the flow changing mechanism 11 and the output flow control 1 of the fluid pump 10 are the same, as those shown in Fig. 7, however, the output flow control 12 of Fig. 8 responds to different pressure control signals.
  • Space 114 is directly connected by line 125 with the discharge line 17 and control space 106 is subjected to control pressure signal 124, which is a load pressure signal, modified by the differential control 13.
  • FIG. 9 shows the basic arrangement of Fig. 8 with the fluid energy for pump controls being supplied to annular space 112 from separate pump 19, instead of using energy supplied by the pump 10.
  • Fig. 9 shows the pump controls connected into basic system as shown in Fig. 1.
  • the stem 43 or 56 of the actuator 45 of Figs. 1, 3, 4 and 5 is biased by a spring 126 towards position of zero orifice and is directly operated by a lever 127, which provides the external signal 46.
  • the stem 43 or 56 of the actuator 45 of Figs. 1, 3, 4 and 5 is biased by a spring 128 towards position of zero orifice and is directly operated by a piston 129. Fluid pressure is supplied to the piston 129 from a pressure generator 130, operated by a lever 131.
  • the stem 43 or 56 of the actuator 45 of Figs. 1, 3, 4 and 5 is biased by a spring 132 towards position of zero orifice and is directly operated by a solenoid 133, connected by a line to an input current control 134, operated by a lever 135 and supplied from an electrical power source 136.
  • the stem 43 of the differential control 13 is biased by a spring 137 towards position, where it isolates the inlet chamber 33 from the exhaust chamber 34 and is controlled by a solenoid 138.
  • the electrical control signal, amplified by amplifier 139, is transmitted from a logic circuit or a microprocessor 140, subjected to inputs 141, 142 and 143.
  • a logic circuit or a microprocessor 144 supplied with control signals 145, 146 and 147 transmits an external control signal to the differential control 68a through an amplifier 148.
  • output flow control 12 is a differential pressure relief valve, which in a well known manner, by bypassing fluid from the pump 10 to the reservoir 16, maintains discharge pressure P, of pump 10 at a level, higher by a constant pressure differential, than P 2 pressure signal delivered to the output flow control 12.
  • pump flow control 16 is a differential pressure compensator, well known in the art, which by changing displacement of pump 10 maintains discharge pressure P, of pump 10 at a level, higher by a constant pressure differential, than P 2 pressure signal delivered to the output flow control 12. Therefore irrespective of the characteristics of pump 10 the load responsive output flow control 12 will always automatically maintain, between two of its control inputs, namely P 2 and P, pressures, a preselected constant pressure differential, irrespective of the variation in its discharge pressure level.
  • load responsive output flow controls either in the form of differential pressure relief valve, or in the form of differential pressure compensator, are well known in the art and will be described in greater detail when referring to Figs. 7, 8 and 9.
  • the P 2 pressure is always the maximum load pressure Pw, developed in one of the fluid motors subjected to maximum load. Therefore, in a conventional load responsive system the pump output flow control will always maintain a constant pressure differential between the pump discharge pressure P, and the maximum load pressure Pw, irrespective of the magnitude of Pw pressure, maintaining the relationship of AP P, Pw constant.
  • Such a system will always maintain a constant pressure differential AP across orifice 14, positioned between system pump and fluid motor. With constant pressure differential acting across the orifice, flow through the orifice will be proportional to the area of the orifice and independent of the pressure level in the fluid motor.
  • variable orifice 14 the fluid flow to the fluid motor 15 and velocity of the load W can be controlled, each specific area of variable orifice 14 corresponding to a specific velocity of load W, which will remain constant, irrespective of the variation in magnitude of load W.
  • control spool 36 biased by the control spring 41, will move from right to left, connecting by throttling slots 38 the inlet chamber 32 with the control chamber 33. Rising pressure in the control chamber 33, reacting on cross-sectional area of control spool 36, will move it back into a modulating position, in which sufficient flow of pressure fluid will be throttled from the inlet chamber 32 to the control chamber 33, to maintain the control chamber 33 at a constant pressure, equivalent to preload in the control spring 41.
  • the area of the metering orifice will be varied.
  • each specific area of metering slots 44 will correspond to a specific constant flow level from the control chamber 33 to the exhaust chamber 34 and from the inlet chamber 32 to the control chamber 33, irrespective of the magnitude of the pressure in the inlet chamber 32. Therefore each specific position of stem 43, within the zone of metering slots 44, will correspond to a specific flow level and therefore a specific pressure drop ⁇ Px through fixed orifice 26, irrespective of the magnitude of the load pressure Pw.
  • P 1 Pw ⁇ Py, P 1 - P 2 ⁇ P maintained constant by pump control and Pw P 2 A Px.
  • the pressure differential, acting across orifice 14 and the flow through orifice 14 can be controlled from maximum to minimum by the differential control 13, each flow level automatically being controlled constant by the output flow contol 12, irrespective of the variation in the load pressure Pw. From inspection of the basic equation APy ⁇ P ⁇ Px it becomes apparent that with ⁇ Px 0, ⁇ Py ⁇ P and that the system will revert to the mode of operation of conventional load responsive system, with maximum constant ⁇ P of the output flow control 12.
  • each specific area of the variable orifice 14 pressure differential ⁇ Py, acting across orifice 14, can be varied by the differential control 13 through the output flow control 12, each specific pressure differential ⁇ Py corresponding to a specific constant flow into the fluid motor 15, irrespective of the variation in the magnitude of the load pressure PwTherefore fluid flow into fluid motor 15 can be controlled either by variation in the area of variable orifice 14, or by variation in pressure differential ⁇ Py, each of those control methods displaying identical control characteristics and controlling flow, which is independent of the magnitude of the load pressure. Action of one control can be superimposed upon the action of the other, providing a unique system, in which, for example, a command signal from the operator, through the use of variable orifice 14, can be corrected by signal 46 from a computing device, acting through the differential control 13.
  • a differential control, genera111y designated as 13a is similar to the differential control 13 of Fig. 1.
  • the variable metering orifice, operated by actuator 45 of Fig. 1 was substituted by fixed metering orifice 42a, the pressure regulating section of both controls remaining the same.
  • the differential control 13a, of Fig. 2 will generate a constant ⁇ Px across fixed orifice 26 decreasing, by exactly the same amount, the control pressure differential of the load responsive system.
  • the arrangement of Fig. 2 is very useful to reduce comparatively large controlled pressure differential of output flow control 12 to a lower level, thus increasing system efficiency, while response of output flow control 12 is not affected.
  • the differential control 13 is identical to the differential control 13 of Fig. 1 and performs in an identical way, by modifying a control signal transmitted to the output flow control 12 of pump 10.
  • the differential control 13 of Fig. 3 modifies the control signal of pump discharge pressure P 1 instead of modifying the control signal of load pressure Pw, as shown in the system of Fig. 1.
  • the control load pressure signal Pw is transmitted directly from fluid motors 15 and 24, through logic system of signal check valves 25 and 27 and line 47 to the output flow control 12.
  • Fig. 4 the load responsive control systems of Fig. 1 and Fig. 3 have been combined into a single system.
  • the other differential control 13 responding to external control signal 46, by modifying load pressure signal, will perform in an identical way, as previously described when referring to the load responsive control of Fig. 1, varying the level of control pressure differential APy from maximum level of ⁇ P to zero.
  • the other differential control 13 responding to external control signal 49, by modifying pump discharge pressure signal will perform in an identical way, as previously described when referring to the load responsive control of Fig. 3, varying the level of control pressure differential AP from minimum level of AP to any desired higher level. Therefore, combined load responsive control of Fig. 4 is capable of controlling the pressure differential ⁇ Py from zero to any desired maximum value.
  • a differential control 50 which although different in construction performs in a very similar way as the differential control 13 of Fig. 1.
  • the flow control valve 58, of differential control 50 is provided with the housing 59 guiding the metering pin 63, which is subjected to inlet pressure in the inlet chamber 60, to the reservoir pressure in the exhaust chamber 61 and to the biasing force of spring 66.
  • each specific pressure level corresponding to a specific position of metering pin 63, in respect to the housing 59 and also corresponding to the specific biasing force of spring 66.
  • Each specific position of metering pin 63, in respect to the housing 59 will correspond to a specific flow area of metering slot 64, interconnecting the inlet chamber 60 with the exhaust chamber 61.
  • the shape of metering slot 64 and the characteristics of biasing spring 66 are so selected that variation in the effective orifice area of metering slot 64, in respect to pressure in the inlet chamber 60, will provide a relatively constant flow from the inlet chamber 60 to the exhaust chamber 61.
  • the shape of metering slot 64 may be so selected, that any desired relationship between the flow from the inlet chamber 60 and its pressure level can be obtained.
  • the flow control 58 provides a constant flow from the inlet chamber 60, irrespective of its pressure level.
  • the flow control 58 could be substitued by a conventional flow control valve, well known in the art.
  • Constant flow to the inlet chamber 60 is supplied from fluid motors 15 or 24 through a logic system of signal check valves 21 and 25, the variable orifice valve 51 and line 67.
  • the variable orifice valve 51, upstream offlow control valve 58, is provided with circular bore 55, guiding a stem 56, provided with metering slots 57.
  • the load pressure signal can be modified on its way to the output flow control 12, each value of pressure drop ⁇ Px, maintained constant by the differential control 50, corresponds to a specific value of pressure differential ⁇ Py, following the basic relationship of APy ⁇ P ⁇ Px.
  • the control characteristics of the load responsive control of Fig. 5 will be identical to those described when referring to Fig. 1, the pressure differential ⁇ Py being varied and maintained constant at each specific level by the differential control 50 in response to external control signal 46 between maximum value equal to ⁇ P and zero.
  • variable orifice valve 51 of Fig. 5 was substituted by the fixed orifice 42a of Fig. 2. Then controlled increase in flow through fixed orifice 42a, with increase in the load pressure, will proportionally increase the pressure differential ⁇ Px and therefore proportionally decrease the pressure differential APy,
  • Fig. 6 the load responsive system of Fig. 6 is similar to that of Fig. 5 with the exception that variable orifice 14 of Fig. 5 was substituted in Fig. 6 by a load responsive four way valve, generally designated as 68 and a different type of a differential valve 68a was used.
  • the differential control 68a which can be substituted by the differential control 13 of Fig. 1, or the differential control 50 of Fig. 5, is connected to load pressure sensing ports 75 and 76 of four way valve 68. With the valve spool 78 in its neutral position, as shown in Fig. 6 load pressure sensing ports 75 and 76 are blocked by the land 80 and therefore effectively isolated from the load pressure existing in load chamber 71 or 72.
  • the output flow control 12 will automatically maintain the discharge pressure of pump 10 at a minimum level equal to the load responsive system AP. Displacement of the valve spool 78 from its neutral position in either direction first connects with signal slot 86 or 87 load chamber 71 or 72 with load pressure sensing port 75 or 76, while load chambers 71 and 72 are still isolated by the valve spool 78 from the inlet chamber 70 and first and second exhaust chambers 73 and 74. With the variable orifice valve68a open, the load pressure signal will be transmitted to the output flow control 12, permitting it to react, before metering orifice is open to the fluid motor 15.
  • valve spool 78 Further displacement of the valve spool 78 in either direction will create, in a well known manner, through metering slot 83 or 84 a metering orifice between one of the load chambers and the inlet chamber 70, while connecting the other load chamber, through metering slot 82 or 85, with one of the exhaust chambers, in turn connected to the system reservoir 16.
  • the metering orifice can be varied by displacement of valve spool 78, each position corresponding to a specific flow level into fluid motor 15, irrespective of the magnitude of the load W i .
  • the differential valve generally designated as 68a, contains the solenoid, generally designated as 97, which consists of the coil 95 secured in the housing 94 and the armature 96, slidably guided in the coil 95.
  • the armature 96 is provided with conical surface 98; which, in cooperation with sealing edge 99, regulates the pressure differential ⁇ Px between inlet port 93 and outlet port 103.
  • the comparatively weak spring 101 can be interposed between the armature 96 and the housing 94, to permit a back flow under deenergized conditionof the coil 95 from outlet port 103 to inlet port 93. This feature may be of importance, when using a shuttle valve logic system instead of the check valve logic system of Fig. 6.
  • the sealed connector 102 in the housing 94 connects the coil 95 with external terminals, to which the external signal 46 can be applied.
  • a solenoid is an electromechanical device, using the principle of electromagnetics, to produce output forces from electrical input signals.
  • the force developed on the solenoid armature 96 is a function of input current. As the current is applied to the coil 95, each specific current level will correspond to a specific force level transmitted to the armature. Therefore the contact force between the conical surface 98 of the armature 96 and sealing edge 99 of the housing 94 will vary and be controlled by the input current.
  • venting passage 100 can be connected directly through the cone of conical surface 98 with inlet port 93 and the lower end of venting passage 100 enlarged, to slidably engage a balancing pin, of diameter smaller than diameter of inlet port 93. In this way the effective area subjected to pressure differential is greatly reduced, permitting reduction in the size of the solenoid 97.
  • a balancing pin of diameter smaller than diameter of inlet port 93.
  • the load W 1 can be proportionally controlled by action of differential control 68a, each value of pressure differential APy being automatically maintained at a constant level by the output flow control 12 and corresponding to a specific flow level into fluid motor 15, irrespective of the magnitude of the load W 1 .
  • the load W 2 is controlled by the direction control valve 90, which may be identical to the direction control valve 68.
  • a differential pressure controller performs a similar function as the differential pressure controller 68a, but is capable of providing, in a well known manner, a fixed pressure differential between inlet port 93 and outlet port 103, this pressure differential being proportional to preload in the spring 101 a.
  • Control AP of the system will be reduced by this pressure differential providing the controlling pressure differential APy of a much smaller value.
  • the arrangement of Fig. 6a is very useful to reduce comparatively large controller pressure differential of output flow control 12 to a lower level, thus increasing system efficiency, while response of output flow control 12 is not affected.
  • a load responsive output flow control of a pump is shown. If the pump 10 is of a fixed displacement type, the flow changing mechanism 11 becomes a differential pressure relief valve, well known in the art. If the pump 10 is of a variable displacement type, the flow changing mechanism 11 becomes a differential pressure compensator, well known in the art.
  • the pilot valve 107 on one side is subjected to a load pressure signal 105, together with the biasing force of control spring 115 and on the other side to pump discharge pressure, signal which, as shown in Fig. 7, can be modified by the differential control 13.
  • the pilot valve 107 will reach a modulating position, in which it will control the position of piston 120, to regulate the discharge pressure in discharge line 17, to maintain a constant pressure differential between pressure in space 114 and pressure in control space 106.
  • This constant pressure differential is dictated by the preload in the control spring 115 and is equal to the quotient of this preload and cross-sectional area of the pilot valve 107.
  • the pilot valve 107 in control of flow changing mechanism 11, uses energy supplied by the pump 19.
  • load responsive system pressure signal 124 is directly supplied from the system load and a small leakage is provided from control space 94.
  • load pressure signal is modified by the differential control 13 and becomes pressure signal 124.
  • Fig. 9 shows the pump controls connected into a basic system as shown in Fig. 1.
  • the differential control 13 is connected to space 106 and as described when referring to Fig. 1 modifies the control signal to vary the effective pressure differential across an orifice connecting the pump 10 and the load.
  • the differential control 13 is shown separately connected to the schematically shown output flow control of the pump.
  • the components of the differential control 13 would become an integral part of the output flow control of the pump 10.
  • the stem 43 or 56 of the actuator 45 of Figs. 1, 3, 4 and 5 is biased by a spring 126 towards position of zero orifice and is directly operated by a lever 127, which provides the external signal 46 in the form of manual input.
  • Fig. 11 the stem 43 or 56 of the actuator 45 of Figs. 1, 3, 4 and 5 biased by a spring 128 towards position of zero orifice and is directly operated by a piston 129. Fluid pressure is supplied, in a well know manner, to the piston 129 from a pressure generator 130, operated by a lever 131. Therefore the arrangement of Fig. 11 provides the external signal 46 in the form of a fluid pressure signal.
  • the stem 43 or 56 of the actuator 45 of Figs. 1, 3, 4 and 5 is biased by a spring 132 towards position of zero orifice and is directly operated, in a well known manner, by a solenoid 133, connected by a line to an input current control 134, operated by a lever 135 and supplied from an electrical power source 136. Therefore the arrangement of Fig. 12 provides the external signal 46 in the form of an electric current, proportional to displacement of lever 123.
  • the stem 43 of the differential control 13 is biased by a spring 137 towards position, where it isolates the inlet chamber 33 from the exhaust chamber 34.
  • the stem 43 is completely pressure balanced, can be made to operate through a very small stroke and controls such low flows, at such low pressures, that the influence of flow forces is negligible.
  • the area of metering slots 44 is so selected that it provides a linear function in respect to displacement of the stem 43 and a constant pressure is maintained in front of the orifice, the flow force will also be linear and will add to the spring force, changing slightly the combined rate of the spring.
  • the stem 43 is directly coupled to a solenoid 138.
  • a solenoid is an electromechanical device using the principle of electromagnetics to produce output forces from electrical input signals.
  • the position of solenoid armature when biased by a spring, is a function of the input current. As the current is applied to the coil, the resulting magnetic forces generated move the armature from its deenergized position to its energized position. When biased by a spring, for each specific current level there is a corresponding particular position, which the solenoid will attain. As the current is varied from zero to maximum rating, the armature will move one way from a fully retracted to a fully extended position in a predictable fashion, depending on the specific level of current at any one instant.
  • solenoid 126 Since the forces developed by solenoid 126 are very small, so is the input current which is controlled by a logic circuit or a microprocessor 128.
  • the microprocessor 128 will then, in response to different types of transducers, either directly control the system load, in respect to speed, force and position, or can superimpose its action upon the control function of an operator, to perform the required work in minimum time, with a minimum amount of energy, within the maximum capability of the structure of the machine and within the envelope of its horsepower.
  • control signal from a logic circuit or microprocessor 144 in a similar way as described in Fig. 13, is directly transmitted through the amplifier 148 to the differential pressure control 68a, where, through a solenoid and throttling valve combination, in a manner as previously described, regulates the pressure differential in response to input current.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Servomotors (AREA)
  • Flow Control (AREA)
EP81902366A 1981-08-20 1981-08-20 Load responsive system controls Expired EP0086772B1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1981/001121 WO1983000726A1 (en) 1981-08-20 1981-08-20 Load responsive system controls

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EP0086772A1 EP0086772A1 (en) 1983-08-31
EP0086772A4 EP0086772A4 (en) 1986-02-10
EP0086772B1 true EP0086772B1 (en) 1988-11-09

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EP (1) EP0086772B1 (enrdf_load_stackoverflow)
JP (1) JPS58501284A (enrdf_load_stackoverflow)
DE (1) DE3176929D1 (enrdf_load_stackoverflow)
WO (1) WO1983000726A1 (enrdf_load_stackoverflow)

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DE4313597B4 (de) * 1993-04-26 2005-09-15 Linde Ag Verfahren zum Betreiben einer verstellbaren hydrostatischen Pumpe und dafür ausgebildetes hydrostatisches Antriebssystem
US20060219436A1 (en) * 2003-08-26 2006-10-05 Taylor William P Current sensor
CN101968067A (zh) * 2010-10-24 2011-02-09 绍兴市肯特机械电子有限公司 一种高精度的泵控系统

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2892312A (en) * 1958-01-27 1959-06-30 Deere & Co Demand compensated hydraulic system
US3444689A (en) * 1967-02-02 1969-05-20 Weatherhead Co Differential pressure compensator control

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL169628C (nl) * 1971-06-29 1982-08-02 Ind En Handelmaatschappij Kopp Regelinrichting voor het lastonafhankelijk besturen van hydraulische aandrijfapparaten.
US4075842A (en) * 1976-10-05 1978-02-28 Tadeusz Budzich Load responsive fluid control system
US4282898A (en) * 1979-11-29 1981-08-11 Caterpillar Tractor Co. Flow metering valve with operator selectable boosted flow
US4285195A (en) * 1980-01-02 1981-08-25 Tadeusz Budzich Load responsive control system

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2892312A (en) * 1958-01-27 1959-06-30 Deere & Co Demand compensated hydraulic system
US3444689A (en) * 1967-02-02 1969-05-20 Weatherhead Co Differential pressure compensator control

Also Published As

Publication number Publication date
DE3176929D1 (en) 1988-12-15
EP0086772A4 (en) 1986-02-10
JPS58501284A (ja) 1983-08-04
EP0086772A1 (en) 1983-08-31
WO1983000726A1 (en) 1983-03-03
JPH025922B2 (enrdf_load_stackoverflow) 1990-02-06

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