EP1092095B2 - Hydraulic circuit - Google Patents

Hydraulic circuit Download PDF

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Publication number
EP1092095B2
EP1092095B2 EP99936360A EP99936360A EP1092095B2 EP 1092095 B2 EP1092095 B2 EP 1092095B2 EP 99936360 A EP99936360 A EP 99936360A EP 99936360 A EP99936360 A EP 99936360A EP 1092095 B2 EP1092095 B2 EP 1092095B2
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EP
European Patent Office
Prior art keywords
pressure
consumer
load
bypass channel
control
Prior art date
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Expired - Lifetime
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EP99936360A
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German (de)
French (fr)
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EP1092095A1 (en
EP1092095B1 (en
Inventor
Thomas Weickert
Erich Adlon
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Bosch Rexroth AG
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Bosch Rexroth AG
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Classifications

    • 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
    • F15B11/003—Systems with load-holding 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
    • 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
    • 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
    • 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
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/25—Pressure control functions
    • F15B2211/253—Pressure margin control, e.g. pump pressure in relation to load 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
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30525—Directional control valves, e.g. 4/3-directional control valve
    • F15B2211/3053—In combination with a pressure compensating valve
    • F15B2211/3054—In combination with a pressure compensating valve the pressure compensating valve is arranged between directional control valve and output member
    • 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
    • F15B2211/31—Directional control characterised by the positions of the valve element
    • F15B2211/3144—Directional control characterised by the positions of the valve element the positions being continuously variable, e.g. as realised by proportional 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
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/329—Directional 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
    • F15B2211/505—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
    • F15B2211/50545—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using braking valves to maintain a back 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
    • F15B2211/605—Load sensing circuits
    • F15B2211/6051—Load sensing circuits having valve means between output member and the load sensing circuit
    • F15B2211/6054—Load sensing circuits having valve means between output member and the load sensing circuit using shuttle 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
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
    • 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
    • F15B2211/78—Control of multiple 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
    • F15B2211/80—Other types of control related to particular problems or conditions
    • F15B2211/88—Control measures for saving energy

Definitions

  • the invention relates to a hydraulic circuit for controlling at least one lower-load and higher-load consumer according to the preamble of patent claim 1.
  • Such circuits are used inter alia for controlling mobile machines, such as excavators.
  • Such circuits are used inter alia for controlling mobile machines, such as excavators.
  • Such a load-sensing circuit is known, for example, from EP 0 566 449 AS.
  • This circuit has a variable displacement pump, which can be controlled so that it produces at its output a pressure which is higher than the highest load pressure of the hydraulic consumers by a certain amount.
  • a load-sensing controller is provided, which can be acted upon by the pump pressure in the direction of reducing the stroke volume and the highest pressure at the consumers and by a compression spring in the direction of increasing the stroke volume.
  • the setting in the variable displacement difference between the pump pressure and the highest load pressure corresponds to the force of the aforementioned compression spring.
  • Each of the consumers is associated with an adjustable orifice plate with a downstream pressure compensator, via which the pressure drop across the orifice plate is kept constant, so that the hydraulic fluid flowing to the respective consumer depends on the opening cross section of the orifice and not on the load pressure of the consumer or on the pump pressure.
  • the pressure compensators of all actuated hydraulic consumers are adjusted in the closing direction, so that all hydraulic fluid flows to the individual. Consumers are reduced by the same proportion. That is, with downstream pressure compensator, the flow rates to the consumers are always in proportion to the opening cross-sections of the orifices. Due to this load-independent flow distribution (LUDV), all driven consumers move at a speed reduced by the same amount.
  • LUDV load-independent flow distribution
  • variable displacement pump is usually equipped with a pressure control and with a power control, via which the maximum possible pump pressure or the maximum deliverable by the variable displacement power (excavator performance) are adjustable. These pressure and power controls are superimposed on the load-sensing control.
  • WO95 / 32364 discloses a control arrangement via which, when a limit load pressure is exceeded, only the load pressure of the lower-load hydraulic consumer is reported to the load-sensing regulator of the variable displacement pump.
  • This limit load pressure is chosen so that the supply of the other hydraulic consumer is guaranteed.
  • this is achieved by the spring chamber of the pressure compensator of the lower-load consumer via a pressure limiting valve assembly is connected to the tank.
  • the pressure relief valve opens the connection to the tank, so that the spring chamber of the pressure balance of the lower-load consumer relieved and the control piston is brought into its open position, in which the load pressure of this consumer is reported in the load pressure signaling line.
  • a disadvantage of this control arrangement is that a partial volume flow is discharged to the tank and thus can not be used for the consumer control. The efficiency of this control is therefore comparatively low. Another disadvantage is that generated by the return of the hydraulic fluid to the tank heat in the system and thus pump power is destroyed.
  • the present invention seeks to provide a control arrangement by which a sufficient supply of all consumers is guaranteed with minimal device complexity.
  • a particularly simple circuit is obtained when the pressure compensator upstream measuring orifice is formed by a proportional directional control valve, wherein the bypass channel in response to the valve spool position of the proportional directional control valve is alsêtbar. Due to the control of the bypass channel dependent on the control of the proportional valve, the individual pressure compensator only acts in the fine control range, in which comparatively small hydraulic fluid volume flows through the pressure compensator.
  • the structure can be further simplified if the bypass channel is formed in the valve spool of the proportional directional control valve and is controllable by a control edge of the valve spool bore.
  • a check valve arrangement is provided therein.
  • two working connections of a consumer are controlled via the proportional valve.
  • the bypass channel is assigned to only one of the working ports, so that, for example, in the lifting function, a flow through the bypass.
  • bypass channel is opened only after a certain stroke of the proportional valve, so that no bypass flow is formed at the beginning of the control.
  • the valve spool of the proportional directional valve is preferably formed with a central speed part and two outer direction parts, which are each associated with a terminal of the consumer.
  • the bypass channel extends within the valve spool from Geschwindkeitsteil towards the direction part, so that the pressure compensator is bypassed.
  • the pressure loss in the bypass channel can be minimized if it opens with oblique and radial bores in the outer circumference of the valve spool.
  • a part of a circuit diagram for a hydraulic circuit for controlling a mobile implement, such as an excavator is shown.
  • This excavator has several consumers, such as a boom, a spoon, a handle, a chassis drive and a slewing drive, which are supplied by a variable displacement pump 2 with hydraulic fluid.
  • a cylinder 4 for actuating a spoon and a cylinder 6 for actuating the excavator boom are shown as a consumer schematically.
  • the hydraulic fluid delivered by the variable displacement pump is led via a pump line 12 with branch lines 12a, 12b to the two consumers 4 and 6, respectively.
  • an adjustable orifice plate 14a, 14b is formed in each branch of the pump line 12 (12a, 12b. As will be explained in more detail below, these orifices 14a, 14b are designed as speed parts of a proportional valve.
  • a pressure compensator 16a, 16b Downstream of each metering orifice 14a, 14b, a pressure compensator 16a, 16b is connected in each case.
  • the control piston of this 2-way pressure compensator is acted upon in the opening direction via a control line 18 with the pressure downstream of the orifice 14a, 14b and in the closing direction via a load control line 20 with the highest load pressure, which is tapped from a load pressure signaling line 22. About this the highest load pressure is also led to the load-sensing controller 8.
  • the volume flow of the load at the lower end of the load decreases to a value which is predetermined by the maximum pump power. A large part of the power is destroyed in the regulating pressure compensator of this consumer.
  • the load-lower consumer b is assigned a bypass channel 32 in the control illustrated in FIG. 1, which allows a bypass of the pressure compensator 16a.
  • the bypass channel 32 branches off downstream of the orifice plate 14a and opens into the working line 24a to the consumer 6.
  • a suitable control device 34 is provided which shuts off the bypass channel 32 in the basic position and aufêtt depending on the opening cross section of the orifice 14a.
  • the switching device provided with the reference numeral 34 may be any device which is suitable for shutting off the bypass channel 32 and réelle juryn in response to the control of the orifice plate 14a.
  • FIG. 2 the circuit diagram of a valve disc 35 of a valve block for realizing the circuit shown in Fig. 1 is shown.
  • the valve disc 35 includes the pressure compensator 16a, a proportional valve 36, through the speed part of the orifice plate 14a is formed and the bypass channel 32, and the other, described in more detail below connection lines of the hydraulic elements.
  • the proportional valve 36 in addition to the orifice 14 a and a directional part for controlling the load A, B, and the control of the bypass channel 32 are integrated.
  • the proportional valve 36 has a pump port P, two working ports A, B, which are connected to the cylinder chambers of a differential cylinder b or with a hydraulic motor. Furthermore, an output port P1 to the pressure compensator 16a, a bypass port U, two input ports R, S of the directional part and a tank port T are formed on the proportional valve 36.
  • valve spool 38 of the proportional valve 36 are biased by two compression springs 41a, 41b in their basic position. In this basic position, ports P, A, B, U and S are shut off while ports P1 and R are connected to the tank.
  • valve spool 38 The end faces of the valve spool 38 are subjected to control pressures P ST , so that it can be moved out of its spring-biased basic position.
  • the output port P1 is connected via the pump line 12a to the input port Q of the pressure compensator 16a.
  • the control line 18 via which the pressure downstream of the orifice 14a (proportional valve 36) is reported to the left in Fig. 2 end face of the pressure compensator 16a.
  • the load pressure of the consumer 6 is connected via the load-sensing line 20 to the load pressure signaling line 22 and guided to the spring side of the pressure compensator 16 a.
  • the output terminal C of the pressure compensator 16a is connected via lines 40, 42 to the input terminals R and S of the directional part. In the lines 40, 42 there are two check valves 56a, 56b, which prevent a backflow of the hydraulic fluid from the direction part to the pressure compensator 16a.
  • the tank connection T is connected via a tank line 44 to the tank.
  • the pressure compensator 16a By the pressure compensator 16a, the pressure drop across the metering orifice 14a is kept constant and independent of the load pressure when the proportional valve 36 is actuated, so that the volume flow to the consumer 6 is proportional to the opening cross section of the metering orifice 14a.
  • valve spool 38 When applying a control pressure P ST, for example, to the left end face of the proportional valve 36, the valve spool 38 is shifted to the right, so that the orifice plate 14a for connecting the terminals P, P1 is turned on. In the fine control range, that is to say in the first part of the valve spool stroke, the connection to the bypass duct connection U is still blocked.
  • the hydraulic fluid is supplied via the working line 12a to the input terminal Q and via the control line 18 to the left end side of the control piston of the pressure compensator 16a, so that it is moved to its control position for keeping constant the pressure drop across the orifice plate 14a.
  • the thus adjusted hydraulic fluid flow is then passed via the line 40, the terminals R, A to the working port of the consumer 6, while via the working port B and the tank line 44, the hydraulic fluid from the consumer 6 is fed back to the tank.
  • the connection S is closed.
  • the bypass channel 32 is opened by the valve spool 38, so that the hydraulic fluid directly into the Line 40 flows.
  • the volume flow to the pressure compensator 16a is reduced or even completely shut off, so that a larger volume flow to the consumer 6 is performed. This increase in the volume flow also leads to a drop in the system pressure when the load-bearing consumer 4 is driven to the stop.
  • Fig. 3 shows a section through a directional control valve segment, by which the circuit shown in Fig. 2 is realized.
  • the directional control valve segment has a valve plate 52, in which receiving bores for the valve spool 38, the pressure compensator 16a, two pressure relief valves 54a, 54b and the two non-return or load-holding valves 56a, 56b are formed.
  • the valve plate 52 In the valve plate 52 are further provided the two working ports A, B, two control terminals 58a, 58b for controlling the proportional valve 36, a pump port P, at least one connection for the load pressure signaling line 22 and a tank connection.
  • the valve spool 38 has in its central region a control collar 60, which forms the orifice plate 14a in cooperation with a web 62 of the valve bore.
  • the valve slide 38 is biased by the two compression springs 41a, 41b into its basic position, in which no flow through the metering orifice 14a takes place.
  • the control of the proportional valve 36 is effected by applying a control pressure to the two control terminals 58a and 58b, which are connected via control lines to the spring chamber 64a and 64b of the proportional valve 36.
  • a nozzle is formed with a check valve, through which a damping of the valve spool movement is possible.
  • the control collar 60 is provided in the region of its end faces with a plurality of control notches 64 and 66, via the pressure medium from a connected to the pump port P annulus 68 can be performed to the input terminal Q, so that the lower in Fig. 3 end face of the control piston 72nd the pressure compensator 16a with the pressure downstream of the orifice can be acted upon.
  • the orifice plate 14a is formed by cooperation of the control notches 64 with the one control edge of the web 62, while with a shift to the left the control notches 66 open the connection from the annulus 68 to the pressure compensator 16a out ,
  • the input port Q of the pressure compensator 16a is formed as an axial connection, so that the fluid pressure also acts on the lower end face 70 of the control piston 72.
  • the output terminal C is formed as a radial connection and opens into the lines 40 and 42. In these lines 40, 42, the load-holding valves 56a, 56b are arranged, which prevent backflow from the valve spool 38 to the pressure compensator 16a out and allow a flow in the reverse direction.
  • each working port A, B is associated with a directional part, via a working port A and B with a Line 40, 42 or with the tank T is connectable.
  • the right-trained in Fig. 3 direction part for the terminal B has three axially spaced control covenants 74, 76 and 78.
  • the control covenants 76 and 78 are each provided with control notches 80 and 82, which arranged to the between these control cords 76, 78 Open radially recessed section.
  • the working part A associated direction part of the valve spool 38 is formed only by two spaced control covenants 84, 86.
  • control notches 88 are formed, which correspond in function to the control notches 80 of the control collar 78.
  • a plurality of circumferentially distributed oblique holes 90 which are connected to a common axial bore 92. This passes through the control collar 8 to the left end portion of the valve spool 38.
  • the end stop 94 of the valve spool is screwed into the axial bore 92, so that the left end portion is closed.
  • valve slide 38 shows a detailed representation of the valve slide 38 in the middle region of this axial bore 92.
  • a retention valve is provided in the axial bore 92, the valve body 96 is biased by a compression spring 97 against a valve seat 98.
  • a radial hole star 100 and an oblique hole star 102 Downstream of the valve body 96 open a radial hole star 100 and an oblique hole star 102.
  • the radial hole star 100 is blocked by a web 104 of the receiving bore 103 of the valve spool 38.
  • the oblique bore star 102 opens into the radially recessed portion between the control collars 84 and 86.
  • the biased against the valve seat 98 valve body 96 prevents hydraulic fluid from the port A can flow into the axial bore 92. A flow in the opposite direction is practically not prevented because the compression spring 97 is weak.
  • the geometry of the radial bore star 100 and the oblique bore star 102 is selected such that upon a displacement of the valve spool 38 to the left over these stars 100, 102, the connection from the working port A to the tank port T can be opened.
  • control notches in the right end face area of the control collar 84 are used.
  • valve spool 38 is moved in the illustration of FIG. 3 to the right, so that the control notches 64 in conjunction with the web 62 control the connection from the pump port P to the input port Q of the pressure compensator on.
  • the upper end face 105 of the control piston 72 lying at the top in FIG. 3 is acted upon by the force of a control spring 106 and by the load pressure, which is tapped by a circumferential groove 110 via a control edge and an angular bore 108 in the control piston 72.
  • a control spring 106 By the pressure applied to the input terminal Q downstream of the metering orifice 14a of the control piston 72 is deflected upward and the output port C open until an equilibrium of forces on the control piston 72 is established.
  • the load holding valve 56a is opened and the hydraulic fluid via the line 40 and the control collar 86 with the control notches 88 to the working port A out.
  • connection between the working port B and the tank port T is opened up via the control collar 76 and the control notches 82 assigned to the working port B, so that the hydraulic fluid can flow back from the consumer into the tank.
  • the oblique bores 90 of the bypass channel 32 are not yet opened by the control edge 107.
  • control edge 107 controls the bypass channel 82, so that the hydraulic fluid or at least a partial volume flow to the working port A is performed.
  • the system pressure drops, so that the load lower consumer 6 can be operated at a higher speed.
  • bypass channel 32 is assigned only to the working port A, which is required for the lifting function of the consumer.
  • the other working port B a further bypass channel can be assigned, which would then have an identical structure as the above-described working port.
  • a load-lower consumer for example, a boom is controlled.
  • the bypass channel 32 is opened in the manner described above, so that the hydraulic fluid flow Q increases to the lower-load consumer (dashed line). Due to this increase of the hydraulic fluid volume flow to the lower-load consumer, the pressure from the system pressure p SYS drops to a lower level p *.
  • the pressure level p * can be adjusted so that the pressure drops, for example, from a pressure of 240 bar to a pressure p * of 200 bar.
  • bypass channel 32 is integrated into the proportional valve 36.
  • bypass channel is realized via external circuits.
  • a LUDV circuit for controlling at least one lastniedrigeren and a higher-load load, each consumer an orifice plate and a downstream pressure compensator are assigned to keep the pressure drop across the orifice constant.
  • the pressure compensator of the lower-load consumer is assigned an openable bypass channel, via which the pressure compensator of this consumer can be bypassed.

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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)

Abstract

The invention relates to a load-independent flow regulation circuit for controlling at least one low load consumer (6) and one high load consumer (4), wherein each consumer (4, 6) is allocated a metering orifice (14a, 14b) and a downstream pressure regulator (16a, 16b) to constantly maintain pressure drop above the metering orifice (16a). A controllable bypass duct (32) is allocated to the pressure regulator of the low load consumer through which the pressure regulator of said consumer may be circumvented.

Description

Die Erfindung betrifft eine hydraulische Schaltung zur Ansteuerung zumindest eines lastniedrigeren und eines lasthöheren Verbrauchers gemäß dem Oberbegriff des Patentanspruchs 1.The invention relates to a hydraulic circuit for controlling at least one lower-load and higher-load consumer according to the preamble of patent claim 1.

Derartige Schaltungen (auch Load-Sensing-Schaltungen genannt) werden unter anderem zur Ansteuerung von mobilen Arbeitsmaschinen, beispielsweise von Baggern eingesetzt. Über die zentrale Schaltung werden hydraulisch betätigte Aggregate der Arbeitsmaschine, beispielsweise ein Drehwerk, der Fahrantrieb, ein Löffel, ein Stiel oder eine am Baggerausleger montierte Klemmeinrichtung angesteuert.Such circuits (also called load-sensing circuits) are used inter alia for controlling mobile machines, such as excavators. About the central circuit hydraulically actuated units of the machine, such as a slewing, the drive, a spoon, a handle or a mounted on the excavator jaw clamping device are driven.

Eine derartige Load-Sensing-Schaltung ist beispielsweise aus der EP 0 566 449 AS bekannt. Diese Schaltung hat eine Verstellpumpe, die derart geregelt werden kann, daß sie an ihrem Ausgang einen Druck erzeugt, der um einen bestimmten Differenzbetrag über dem höchsten Lastdruck der hydraulischen Verbraucher liegt. Zur Regelung ist ein Load-Sensing-Regler vorgesehen, der vom Pumpendruck in Richtung der Verringerung des Hubvolumens und vom höchsten Druck an den Verbrauchern sowie von einer Druckfeder in Richtung der Vergrößerung des Hubvolumens beaufschlagbar ist. Die sich bei der Verstellpumpe einstellende Differenz zwischen dem Pumpendruck und dem höchsten Lastruck entspricht der Kraft der vorgenannten Druckfeder.Such a load-sensing circuit is known, for example, from EP 0 566 449 AS. This circuit has a variable displacement pump, which can be controlled so that it produces at its output a pressure which is higher than the highest load pressure of the hydraulic consumers by a certain amount. To control a load-sensing controller is provided, which can be acted upon by the pump pressure in the direction of reducing the stroke volume and the highest pressure at the consumers and by a compression spring in the direction of increasing the stroke volume. The setting in the variable displacement difference between the pump pressure and the highest load pressure corresponds to the force of the aforementioned compression spring.

Jedem der Verbraucher ist eine verstellbare Meßblende mit einer nachgeschalteten Druckwaage zugeordnet, über die der Druckabfall an der Meßblende konstant gehalten wird, so daß die zum jeweiligen Verbraucher fließende Hydraulikfluidmenge vom Öffnungsquerschnitt der Meßblende und nicht vom Lastdruck des Verbrauchers oder vom Pumpendruck abhängt. In demjenigen Fall, in dem die Verstellpumpe mit maximalem Volumen fördert und der Hydraulikfluidstrom trotzdem nicht ausreicht, um den vorgegebenen Druckabfall über den Meßblenden aufrechtzuerhalten, werden die Druckwaagen aller betätigten hydraulischen Verbraucher in Schließrichtung verstellt, so daß alle Hydraulikfluidströme zu den einzelnen. Verbrauchern um den gleichen Anteil verringert werden. Das heißt, bei nachgeschalteter Druckwaage stehen die Volumenströme zu den Verbrauchern immer im Verhältnis der Öffnungsquerschnitte der Meßblenden. Aufgrund dieser lastunabhängigen Durchflußverteilung (LUDV) bewegen sich alle angesteuerten Verbraucher mit einer prozentual um den gleichen wert verringerten Geschwindigkeit.Each of the consumers is associated with an adjustable orifice plate with a downstream pressure compensator, via which the pressure drop across the orifice plate is kept constant, so that the hydraulic fluid flowing to the respective consumer depends on the opening cross section of the orifice and not on the load pressure of the consumer or on the pump pressure. In the case where the variable displacement pump delivers and the hydraulic fluid flow is still insufficient to maintain the predetermined pressure drop across the orifice plates, the pressure compensators of all actuated hydraulic consumers are adjusted in the closing direction, so that all hydraulic fluid flows to the individual. Consumers are reduced by the same proportion. That is, with downstream pressure compensator, the flow rates to the consumers are always in proportion to the opening cross-sections of the orifices. Due to this load-independent flow distribution (LUDV), all driven consumers move at a speed reduced by the same amount.

Die eingangs genannte Verstellpumpe ist üblicherweise mit einer Druckregelung und mit einer Leistungsregelung ausgestattet, über die der maximal mögliche Pumpendruck bzw. die maximale von der Verstellpumpe abgebbare Leistung (Baggerleistung) einstellbar sind. Diese Druck- und Leistungsregelungen sind der Load-Sensing-Regelung überlagert.The above-mentioned variable displacement pump is usually equipped with a pressure control and with a power control, via which the maximum possible pump pressure or the maximum deliverable by the variable displacement power (excavator performance) are adjustable. These pressure and power controls are superimposed on the load-sensing control.

Mit einer Steueranordnung der vorstehend geschilderten Art kann es dann zu Problemen kommen, wenn ein hydraulischer Verbraucher gegen einen praktisch unendlichen Widerstand arbeitet. Dies kann beispielsweise dann der Fall sein, wenn der hydraulische Verbraucher ein Löffel ist, der auf Anschlag gefahren wird. Bei einem Fahren auf Anschlag baut sich an dem entsprechenden hydraulischen Verbraucher ein Druck auf, der etwa dem durch die Druckregelung vorgegebenen Maximaldruck (Baggerleistung) entspricht. Wird nun ein weiterer hydraulischer Verbraucher, beispielsweise ein Fahrantrieb oder ein Ausleger angesteuert, kann dieser nur mit einer geringeren Geschwindigkeit bewegt werden, da aufgrund des hohen Druckes am erstgenannten Verbraucher (Löffel) bereits bei geringen Hydraulikfluidströmen zum anderen hydraulischen Verbraucher (Fahrantrieb) die Leistungsregelung der Verstelipumpe anspricht.With a control arrangement of the type described above, problems can arise when a hydraulic consumer works against a virtually infinite resistance. This may for example be the case when the hydraulic consumer is a spoon, which is driven to stop. When driving on stop, a pressure builds up on the corresponding hydraulic consumer, which corresponds approximately to the maximum pressure (excavator performance) predetermined by the pressure regulation. Now, if another hydraulic consumer, such as a traction drive or a boom driven, this can only be moved at a lower speed, because due to the high pressure on the first consumer (spoon) already at low hydraulic fluid flows to the other hydraulic consumer (traction drive), the power control of Flushing pump responds.

Um diesen Nachteil auszuräumen, wird in der WO95/32364 der Anmelderin eine Steueranordnung offenbart, über die bei Überschreiten eines Grenzlastdruckes lediglich der Lastdruck des lastniedrigeren hydraulischen Verbrauchers an den Load-Sensing-Regler der Verstellpumpe gemeldet wird. Dieser Grenzlastdruck ist so gewählt, daß die Versorgung des anderen hydraulischen Verbrauchers gewährleistet ist. Beim Gegenstand der WO95/32364 wird dies erreicht, indem der Federraum der Druckwaage des lastniedrigeren Verbrauchers über eine Druckbegrenzungsventilanordnung mit dem Tank verbindbar ist. Bei Überschreiten eines Grenzlastdruckes öffnet das Druckbegrenzungsventil die Verbindung zum Tank, so daß der Federraum der Druckwaage des lastniedrigeren Verbrauchers entlastet und der Regelkolben in seine Öffnungsstellung gebracht wird, in der der Lastdruck dieses Verbrauchers in die Lastdruckmeldeleitung gemeldet wird.In order to overcome this disadvantage, in WO95 / 32364 the Applicant discloses a control arrangement via which, when a limit load pressure is exceeded, only the load pressure of the lower-load hydraulic consumer is reported to the load-sensing regulator of the variable displacement pump. This limit load pressure is chosen so that the supply of the other hydraulic consumer is guaranteed. In the subject matter of WO95 / 32364 this is achieved by the spring chamber of the pressure compensator of the lower-load consumer via a pressure limiting valve assembly is connected to the tank. When a limit load pressure is exceeded, the pressure relief valve opens the connection to the tank, so that the spring chamber of the pressure balance of the lower-load consumer relieved and the control piston is brought into its open position, in which the load pressure of this consumer is reported in the load pressure signaling line.

Nachteilig bei dieser Steueranordnung ist, daß ein Teilvolumenstrom zum Tank hin abgeführt wird und somit nicht für die Verbraucheransteuerung verwendet werden kann. Der Wirkungsgrad dieser Steuerung ist daher vergleichsweise gering. Ein weiterer Nachteil besteht darin, daß durch die Rückführung des Hydraulikfluids hin zum Tank Wärme im System erzeugt und somit Pumpenleistung vernichtet wird.A disadvantage of this control arrangement is that a partial volume flow is discharged to the tank and thus can not be used for the consumer control. The efficiency of this control is therefore comparatively low. Another disadvantage is that generated by the return of the hydraulic fluid to the tank heat in the system and thus pump power is destroyed.

Demgegenüber liegt der Erfindung die Aufgabe zugrunde, eine Steueranordnung zu schaffen, durch die bei minimalem vorrichtungstechnischen Aufwand eine hinreichende Versorgung sämtlicher Verbraucher gewährleistet ist.In contrast, the present invention seeks to provide a control arrangement by which a sufficient supply of all consumers is guaranteed with minimal device complexity.

Diese Aufgabe wird durch eine hydraulische Schaltung mit den Merkmalen des Patentanspruchs 1 gelöst.This object is achieved by a hydraulic circuit having the features of patent claim 1.

Durch die Maßnahme, einen Bypasskanal vorzusehen, über den die der Meßblende nachgeschaltete Druckwaage umgehbar ist, ist es nicht erforderlich, zur Begrenzung des Systemdruckes die Druckwaage abzuregeln oder Hydraulikfluid in den Tank abzuführen. Der sich einstellende Systemdruck kann durch entsprechende Wahl des Bypassquerschnittes vorbestimmt werden. Aufgrund des reduzierten Systemdruckes kann der lastniedrigere Verbraucher mit einer größeren Hydraulikfluidmenge versorgt werden, die beispielsweise in eine Geschwindigkeitserhöhung eines Auslegers oder ähnliches umgesetzt werden kann.By the measure to provide a bypass channel through which the metering orifice downstream pressure balance is bypassed, it is not necessary to adjust the pressure regulator to limit the system pressure or dissipate hydraulic fluid into the tank. The resulting system pressure can be predetermined by appropriate choice of the bypass cross-section become. Due to the reduced system pressure of the load lower consumer can be supplied with a larger amount of hydraulic fluid, which can be implemented, for example, in a speed increase of a boom or the like.

Eine besonders einfach aufgebaute Schaltung erhält man, wenn die der Druckwaage vorgeschaltet Meßblende durch ein Proportionalwegeventil ausgebildet wird, wobei der Bypasskanal in Abhängigkeit von der Ventilschieberstellung des Proportionalwegeventils aufsteuerbar ist. Durch die von der Ansteuerung des Proportionalventils abhängige Aufsteuerung des Bypasskanals wirkt die Individualdruckwaage lediglich im Feinsteuerbereich, in dem vergleichsweise geringe Hydraulikfluidvolumenströme die Druckwaage durchströmen.A particularly simple circuit is obtained when the pressure compensator upstream measuring orifice is formed by a proportional directional control valve, wherein the bypass channel in response to the valve spool position of the proportional directional control valve is aufsteuerbar. Due to the control of the bypass channel dependent on the control of the proportional valve, the individual pressure compensator only acts in the fine control range, in which comparatively small hydraulic fluid volume flows through the pressure compensator.

Der Aufbau läßt sich weiter vereinfachen, wenn der Bypasskanal im Ventilschieber des Proportionalwegeventils ausgebildet ist und durch eine Steuerkante der Ventilschieberbohrung auf steuerbar ist.The structure can be further simplified if the bypass channel is formed in the valve spool of the proportional directional control valve and is controllable by a control edge of the valve spool bore.

Um die Rückströmung vom Verbraucher durch den Bypasskanal zu verhindern, wird in diesem eine Rückschlagventilanordung vorgesehen.In order to prevent the backflow from the consumer through the bypass channel, a check valve arrangement is provided therein.

Bei einer bevorzugten Variante der Erfindung werden über das Proportionalventil zwei Arbeitsanschlüsse eines Verbrauchers angesteuert. In einigen Fällen, beispielsweise bei doppeltwirkenden Hydraulikzylindern, ist es ausreichend, wenn der Bypasskanal lediglich einem der Arbeitsanschlüsse zugeordnet ist, so daß beispielsweise in der Hebenfunktion eine Durchströmung des Bypasses erfolgt. Selbstverständlich ist es auch möglich, beiden Arbeitsanschlüssen Bypasskanäle zuzuordnen.In a preferred variant of the invention, two working connections of a consumer are controlled via the proportional valve. In some cases, for example, in double-acting hydraulic cylinders, it is sufficient if the bypass channel is assigned to only one of the working ports, so that, for example, in the lifting function, a flow through the bypass. Of course, it is also possible to assign bypass channels to both work ports.

Wie vorstehend bereits erwähnt, kann es vorteilhaft sein, wenn der Bypasskanal erst nach einem bestimmten Hub des Proportionalventils aufgesteuert wird, so daß zu Beginn der Regelung keine Bypassströmung entsteht.As already mentioned above, it may be advantageous if the bypass channel is opened only after a certain stroke of the proportional valve, so that no bypass flow is formed at the beginning of the control.

Der Ventilschieber des Proportionalwegeventils wird vorzugsweise mit einem mittigen Geschwindigkeitsteil und zwei außenliegenden Richtungsteilen ausgebildet, die jeweils einem Anschluß des Verbrauchers zugeordnet sind. Der Bypasskanal erstreckt sich dabei innerhalb des Ventilschiebers vom Geschwindkeitsteil hin zum Richtungsteil, so daß die Druckwaage umgangen wird.The valve spool of the proportional directional valve is preferably formed with a central speed part and two outer direction parts, which are each associated with a terminal of the consumer. The bypass channel extends within the valve spool from Geschwindkeitsteil towards the direction part, so that the pressure compensator is bypassed.

Der Druckverlust im Bypasskanal läßt sich minimieren, wenn dieser mit Schräg- und Radialbohrungen im Außenumfang des Ventilschiebers mündet.The pressure loss in the bypass channel can be minimized if it opens with oblique and radial bores in the outer circumference of the valve spool.

Sonstige vorteilhafte Weiterbildungen der Erfindung sind Gegenstand der weiteren Unteransprüche.Other advantageous developments of the invention are the subject of the other dependent claims.

Im folgenden werden bevorzugte Ausführungsbeispiele der Erfindung anhand schematischer Zeichnungen näher erläutert. Es zeigen:

  • Fig. 1 ein Schaltschema einer erfindungsgemäßen Schaltung mit Bypasskanal;
  • Fig. 2 eine Ventilscheibe eines Ventilblocks für eine Schaltung gemäß Fig. 1;
  • Fig. 3 einen Schnitt durch ein Ventilsegment für eine Schaltung gemäß Fig. 1;
  • Fig. 4 eine Detaildarstellung des Ventilsegments aus Fig. 3 und
  • Fig. 5 ein Diagramm zur Verdeutlichung des Systemdruckaufbaus bei der Ansteuerung eines lasthöheren und eines lastniedrigeren Verbrauchers.
In the following preferred embodiments of the invention will be explained in more detail with reference to schematic drawings. Show it:
  • Fig. 1 is a circuit diagram of a circuit according to the invention with bypass channel;
  • FIG. 2 shows a valve disk of a valve block for a circuit according to FIG. 1; FIG.
  • 3 shows a section through a valve segment for a circuit according to FIG. 1;
  • Fig. 4 is a detailed view of the valve segment of Fig. 3 and
  • Fig. 5 is a diagram for illustrating the system pressure build-up in the control of a higher-load and a lower-load consumer.

In Fig. 1 ist ein Teil eines Schaltschemas für eine hydraulische Schaltung zur Ansteuerung eines mobilen Arbeitsgerätes, beispielsweise eines Baggers dargestellt. Dieser Bagger hat mehrere Verbraucher, wie beispielsweise einen Ausleger, einen Löffel, einen Stiel, einen Fahrwerksantrieb und einen Drehwerksantrieb, die von einer Verstellpumpe 2 mit Hydraulikfluid versorgt werden. Bei dem in Fig. 1 dargestellten Ausführungsbeispiel sind schematisch ein Zylinder 4 zur Betätigung eines Löffels und ein Zylinder 6 zur Betätigung des Baggerauslegers als Verbraucher dargestellt.In Fig. 1, a part of a circuit diagram for a hydraulic circuit for controlling a mobile implement, such as an excavator is shown. This excavator has several consumers, such as a boom, a spoon, a handle, a chassis drive and a slewing drive, which are supplied by a variable displacement pump 2 with hydraulic fluid. In the embodiment shown in Fig. 1, a cylinder 4 for actuating a spoon and a cylinder 6 for actuating the excavator boom are shown as a consumer schematically.

Eine Einstellung des Hubvolumens der Verstellpumpe erfolgt über einen Load-Sensing-Regler 8, der in Abhängigkeit vom Pumpendruck einerseits und vom höchsten Lastdruck an den Verbrauchern 4, 6 und der Kraft einer Druckfeder 10 andererseits das Hubvolumen der Verstellpumpe regelt. Das von der Verstellpumpe geförderte Hydraulikfluid wird über eine Pumpenleitung 12 mit Zweigleitungen 12a, 12b zu den beiden Verbrauchern 4 bzw. 6 geführt.An adjustment of the stroke volume of the variable displacement pump via a load-sensing controller 8, on the other hand, controls the stroke volume of the variable depending on the pump pressure on the one hand and the highest load pressure to the consumers 4, 6 and the force of a compression spring 10. The hydraulic fluid delivered by the variable displacement pump is led via a pump line 12 with branch lines 12a, 12b to the two consumers 4 and 6, respectively.

In jedem Zweig der Pumpenleitung 12 (12a, 12b) ist eine einstellbare Meßblende 14a, 14b ausgebildet. wie im folgenden noch näher erklärt wird, sind diese Meßblenden 14a, 14b als Geschwindigkeitsteile eines Proportionalventils ausgeführt.In each branch of the pump line 12 (12a, 12b) an adjustable orifice plate 14a, 14b is formed. As will be explained in more detail below, these orifices 14a, 14b are designed as speed parts of a proportional valve.

Stromabwärts jeder Meßblende 14a, 14b, ist jeweils eine Druckwaage 16a, 16b geschaltet. Der Regelkolben dieser 2-Wege-Druckwaagen ist in Öffnungsrichtung über eine Steuerleitung 18 mit dem Druck stromabwärts der Meßblende 14a, 14b und in Schließrichtung über eine Laststeuerleitung 20 mit dem höchsten Lastdruck beaufschlagt, der von einer Lastdruckmeldeleitung 22 abgegriffen wird. Über diese ist der höchste Lastdruck auch zum Load-Sensing-Regler 8 geführt.Downstream of each metering orifice 14a, 14b, a pressure compensator 16a, 16b is connected in each case. The control piston of this 2-way pressure compensator is acted upon in the opening direction via a control line 18 with the pressure downstream of the orifice 14a, 14b and in the closing direction via a load control line 20 with the highest load pressure, which is tapped from a load pressure signaling line 22. About this the highest load pressure is also led to the load-sensing controller 8.

Vom Ausgangsanschluß der Druckwaage 16a, 16b führt eine Arbeitsleitung 24a, 24b zu den jeweiligen Verbrauchern 4 bzw. 6. Der Lastdruck der Verbraucher 4, 6 wird über Zweigleitungen 26a, 26b abgegriffen und zu einem Wechselventil 28 geführt, an dessen Ausgang die Lastdruckmeldeleitung 22 angeschlossen ist.From the output terminal of the pressure compensator 16a, 16b leads a working line 24a, 24b to the respective consumers 4 and 6. The load pressure of the consumer 4, 6 is tapped via branch lines 26a, 26b and led to a shuttle valve 28, connected to the output of the load pressure signaling line 22 is.

Die Ansteuerung der einstellbaren Meßblenden 14a, 14b erfolgt über manuell betätigbare Steuereinrichtungen 30a, 30b, die mit den Meßblenden 14a bzw. 14b in Wirkverbindung stehen.The control of the adjustable orifices 14a, 14b via manually operable control means 30a, 30b, which are in operative connection with the orifices 14a and 14b.

Durch eine Schaltung der vorbeschriebenen Art ist eine klassische "LUDV"-Schaltung realisiert, bei der über die Druckwaagen 16a, 16b der Druckabfall über den Meßblenden 14a, 14b lastdruckunabhängig konstant gehalten wird. Beim Ausschöpfen der vollen Pumpenleistung werden üblicherweise beide Druckwaagen 16a, 16b zurückgeregelt, so daß der Hydraulikfluidvolumenstrom zu den beiden Verbrauchern 4, 6 um den gleichen Prozentanteil reduziert wird. Wie eingangs bereits beschrieben wurde, kann bei diesen Schaltungen dann ein Problem auftreten, wenn der lasthöhere Verbraucher (Löffel 4) auf Anschlag gefahren wird, so daß der Lastdruck dieses Verbrauchers im Bereich des Pumpenmaximaldruckes angesiedelt ist. Schaltet man nun zusätzlich einen lastniedrigeren Verbraucher hinzu, so geht der Volumenstrom des lastniedrigeren Verbrauchers auf einen Wert zurück, der durch die maximale Pumpenleistung vorgegeben ist. Ein großer Teil der Leistung wird in der abregelnden Druckwaage dieses Verbrauchers vernichtet.By a circuit of the type described above, a classic "LUDV" circuit is realized, in which the pressure drop across the metering orifices 14a, 14b is kept constant independent of the load pressure via the pressure compensators 16a, 16b. When exhausting the full pump power usually both pressure compensators 16a, 16b are back regulated, so that the hydraulic fluid flow to the two consumers 4, 6 is reduced by the same percentage. As has already been described, a problem can occur in these circuits when the load-carrying consumer (spoon 4) is driven to stop, so that the load pressure of this consumer is located in the region of the pump maximum pressure. If, in addition, a load with a lower load is added, the volume flow of the load at the lower end of the load decreases to a value which is predetermined by the maximum pump power. A large part of the power is destroyed in the regulating pressure compensator of this consumer.

Um dies zu verhindern, wird bei der in Fig. 1 dargestellten Regelung dem lastniedrigeren Verbraucher b ein Bypasskanal 32 zugeordnet, der eine Umgehung der Druckwaage 16a ermöglicht. Der Bypasskanal 32 zweigt stromabwärts der Meßblende 14a ab und mündet in der Arbeitsleitung 24a zum Verbraucher 6. Im Bypasskanal 32 ist eine geeignete Steuereinrichtung 34 vorgesehen, die den Bypasskanal 32 in der Grundstellung absperrt und in Abhängigkeit vom Öffnungquerschnitt der Meßblende 14a aufsteuert. Durch diese Schaltung wird der Hydraulikfluidvolumenstrom zum Verbraucher 6 hin nicht durch die Druckwaage 16a abgeregelt, so daß sich ein niedrigerer Systemdruck als bei einem System ohne Bypasskanal 32 einstellt. Dies ermöglicht es, den Ausleger 6 mit einer größeren Geschwindigkeit auszufahren. Die mit dem Bezugszeichen 34 versehene Schalteinrichtung kann dabei eine beliebige Einrichtung sein, die geeignet ist, um den Bypasskanal 32 abzusperren und in Abhängigkeit von der Ansteuerung der Meßblende 14a aufzusteuern.In order to prevent this, the load-lower consumer b is assigned a bypass channel 32 in the control illustrated in FIG. 1, which allows a bypass of the pressure compensator 16a. The bypass channel 32 branches off downstream of the orifice plate 14a and opens into the working line 24a to the consumer 6. In the bypass channel 32, a suitable control device 34 is provided which shuts off the bypass channel 32 in the basic position and aufsteuert depending on the opening cross section of the orifice 14a. By this circuit, the hydraulic fluid flow to the consumer 6 through is not regulated by the pressure compensator 16 a, so that sets a lower system pressure than in a system without bypass channel 32. This makes it possible to extend the boom 6 at a greater speed. The switching device provided with the reference numeral 34 may be any device which is suitable for shutting off the bypass channel 32 and aufzusteuern in response to the control of the orifice plate 14a.

In Fig. 2 ist das Schaltschema einer Ventilscheibe 35 eines Ventilblockes zur Realisierung der in Fig. 1 abgebildeten Schaltung dargestellt. Die Ventilscheibe 35 enthält die Druckwaage 16a, ein Proportionalventil 36, durch dessen Geschwindigkeitsteil die Meßblende 14a ausgebildet ist und den Bypasskanal 32, sowie die sonstigen, im folgenden näher beschriebenen Verbindungsleitungen der Hydraulikelemente. Bei dem in Fig. 2 dargestellten Ausführungsbeispiel sind im Proportionalventil 36 neben der Meßblende 14a auch noch ein Richtungsteil zur Ansteuerung der Verbraucher A, B, sowie die Ansteuerung des Bypasskanals 32 integriert.In Fig. 2, the circuit diagram of a valve disc 35 of a valve block for realizing the circuit shown in Fig. 1 is shown. The valve disc 35 includes the pressure compensator 16a, a proportional valve 36, through the speed part of the orifice plate 14a is formed and the bypass channel 32, and the other, described in more detail below connection lines of the hydraulic elements. In the embodiment shown in FIG. 2, in the proportional valve 36 in addition to the orifice 14 a and a directional part for controlling the load A, B, and the control of the bypass channel 32 are integrated.

Das Proportionalventil 36 hat einen Pumpenanschluß P, zwei Arbeitsanschlüsse A, B, die mit den Zylinderräumen eines Differentialzylinders b oder mit einem Hydromotor verbunden sind. Des weiteren sind ein Ausgangsanschluß P1 zur Druckwaage 16a, ein Bypass-Anschluß U, zwei Eingangsanschlüsse R, S des Richtungsteils und ein Tankanschluß T am Proportionalventil 36 ausgebildet.The proportional valve 36 has a pump port P, two working ports A, B, which are connected to the cylinder chambers of a differential cylinder b or with a hydraulic motor. Furthermore, an output port P1 to the pressure compensator 16a, a bypass port U, two input ports R, S of the directional part and a tank port T are formed on the proportional valve 36.

Die beiden Stirnseiten des Ventilschiebers 38 des Proportionalventils 36 sind durch zwei Druckfedern 41a, 41b in ihre Grundposition vorgespannt. In dieser Grundposition sind die Anschlüsse P, A, B, U und S abgesperrt, während die Anschlüsse P1 und R mit dem Tank verbunden sind.The two end faces of the valve spool 38 of the proportional valve 36 are biased by two compression springs 41a, 41b in their basic position. In this basic position, ports P, A, B, U and S are shut off while ports P1 and R are connected to the tank.

Die Stirnflächen des Ventilschiebers 38 sind mit Steuerdrücken PST beaufschlagt, so daß dieser aus seiner federvorgespannten Grundposition herausbewegbar ist.The end faces of the valve spool 38 are subjected to control pressures P ST , so that it can be moved out of its spring-biased basic position.

Der Ausgangsanschluß P1 ist über die Pumpenleitung 12a mit dem Eingangsanschluß Q der Druckwaage 16a verbunden. Wie bereits vorstehend erläutert, zweigt von der Pumpenleitung 12a die Steuerleitung 18 ab, über die der Druck stromabwärts der Meßblende 14a (Proportionalventil 36) an die in Fig. 2 linke Stirnseite der Druckwaage 16a gemeldet ist. Der Lastdruck des Verbrauchers 6 ist über die Lastmeldeleitung 20 mit der Lastdruckmeldeleitung 22 verbunden und zur Federseite der Druckwaage 16a geführt. Der Ausgangsanschluß C der Druckwaage 16a ist über Leitungen 40, 42 mit den Eingangsanschlüssen R bzw. S des Richtungsteils verbunden. In den Leitungen 40, 42 befinden sich zwei Rückschlagventile 56a, 56b, die eine Rückströmung des Hydraulikfluids vom Richtungsteil zur Druckwaage 16a verhindern.The output port P1 is connected via the pump line 12a to the input port Q of the pressure compensator 16a. As already explained above, branches off from the pump line 12a, the control line 18, via which the pressure downstream of the orifice 14a (proportional valve 36) is reported to the left in Fig. 2 end face of the pressure compensator 16a. The load pressure of the consumer 6 is connected via the load-sensing line 20 to the load pressure signaling line 22 and guided to the spring side of the pressure compensator 16 a. The output terminal C of the pressure compensator 16a is connected via lines 40, 42 to the input terminals R and S of the directional part. In the lines 40, 42 there are two check valves 56a, 56b, which prevent a backflow of the hydraulic fluid from the direction part to the pressure compensator 16a.

Der Tankanschluß T ist über eine Tankleitung 44 mit dem Tank verbunden. Durch die Druckwaage 16a wird bei Ansteuerung des Proportionalventils 36 der Druckabfall über der Meßblende 14a lastdruckunabhängig konstant gehalten, so daß der Volumenstrom zum Verbraucher 6 proportional zum Öffnungsquerschnitt der Meßblende 14a ist.The tank connection T is connected via a tank line 44 to the tank. By the pressure compensator 16a, the pressure drop across the metering orifice 14a is kept constant and independent of the load pressure when the proportional valve 36 is actuated, so that the volume flow to the consumer 6 is proportional to the opening cross section of the metering orifice 14a.

Bei Anlegen eines Steuerdruckes PST beispielsweise an die linke Stirnfläche des Proportionalventils 36 wird der Ventilschieber 38 nach rechts verschoben, so daß die Meßblende 14a zur Verbindung der Anschlüsse P, P1 aufgesteuert wird. Im Feinsteuerbereich, das heißt im ersten Teil des Ventilschieberhubes ist die Verbindung zum Bypasskanalanschluß U noch versperrt. Das Hydraulikfluid wird über die Arbeitsleitung 12a zum Eingangsanschluß Q und über die Steuerleitung 18 zur linken Stirnseite des Regelkolbens der Druckwaage 16a geführt, so daß diese in ihre Regelposition zum Konstanthalten des Druckabfalls über der Meßblende 14a verschoben wird.When applying a control pressure P ST, for example, to the left end face of the proportional valve 36, the valve spool 38 is shifted to the right, so that the orifice plate 14a for connecting the terminals P, P1 is turned on. In the fine control range, that is to say in the first part of the valve spool stroke, the connection to the bypass duct connection U is still blocked. The hydraulic fluid is supplied via the working line 12a to the input terminal Q and via the control line 18 to the left end side of the control piston of the pressure compensator 16a, so that it is moved to its control position for keeping constant the pressure drop across the orifice plate 14a.

Der derart eingestellte Hydraulikfluidstrom wird dann über die Leitung 40, die Anschlüsse R, A zum Arbeitsanschluß des Verbrauchers 6 geführt, während über den Arbeitsanschluß B und die Tankleitung 44 das Hydraulikfluid vom Verbraucher 6 zurück zum Tank geführt wird. Der Anschluß S ist verschlossen.The thus adjusted hydraulic fluid flow is then passed via the line 40, the terminals R, A to the working port of the consumer 6, while via the working port B and the tank line 44, the hydraulic fluid from the consumer 6 is fed back to the tank. The connection S is closed.

Beim weiteren Auf steuern der Meßblende 14a, wird der Bypasskanal 32 durch den Ventilschieber 38 aufgesteuert, so daß das Hydraulikfluid direkt in die Leitung 40 einströmt. Der Volumenstrom zur Druckwaage 16a wird verringert oder gar ganz abgesperrt, so daß ein größerer Volumenstrom zum Verbraucher 6 geführt wird. Diese Vergrößerung des Volumenstroms führt auch dann zu einem Absinken des Systemdrucks, wenn der lasthöhere Verbraucher 4 auf Anschlag gefahren ist.Upon further control on the metering orifice 14 a, the bypass channel 32 is opened by the valve spool 38, so that the hydraulic fluid directly into the Line 40 flows. The volume flow to the pressure compensator 16a is reduced or even completely shut off, so that a larger volume flow to the consumer 6 is performed. This increase in the volume flow also leads to a drop in the system pressure when the load-bearing consumer 4 is driven to the stop.

Fig. 3 zeigt einen Schnitt durch ein Wegeventilsegment, durch das die in Fig. 2 dargestellte Schaltung realisiert ist. Das Wegeventilsegment hat eine Ventilplatte 52, in der Aufnahmebohrungen für den Ventilschieber 38, die Druckwaage 16a, zwei Druckbegrenzungsventile 54a, 54b und die beiden Rückschlag- oder Lasthalteventile 56a, 56b ausgebildet sind. In der Ventilplatte 52 sind des weiteren die beiden Arbeitsanschlüsse A, B, zwei Steueranschlüsse 58a, 58b zur Ansteuerung des Proportionalventils 36, ein Pumpenanschluß P, zumindest ein Anschluß für die Lastdruckmeldeleitung 22 und ein Tankanschluß vorgesehen.Fig. 3 shows a section through a directional control valve segment, by which the circuit shown in Fig. 2 is realized. The directional control valve segment has a valve plate 52, in which receiving bores for the valve spool 38, the pressure compensator 16a, two pressure relief valves 54a, 54b and the two non-return or load-holding valves 56a, 56b are formed. In the valve plate 52 are further provided the two working ports A, B, two control terminals 58a, 58b for controlling the proportional valve 36, a pump port P, at least one connection for the load pressure signaling line 22 and a tank connection.

Der prinzipielle Grundaufbau dieses Wegeventilsegmentes ist bereits aus dem Stand der Technik bekannt und beispielsweise in der eingangs genannten WO95/32364 beschrieben.The fundamental basic structure of this directional control valve segment is already known from the prior art and described, for example, in the aforementioned WO95 / 32364.

Der Ventilschieber 38 hat in seinem mittleren Bereich einen Steuerbund 60, der im Zusammenwirken mit einem Steg 62 der Ventilbohrung die Meßblende 14a ausbildet. In der Darstellung gemäß Fig. 3 ist der Ventilschieber 38 durch die beiden Druckfedern 41a, 41b in seine Grundposition vorgespannt, in der keine Durchströmung der Meßblende 14a stattfindet.The valve spool 38 has in its central region a control collar 60, which forms the orifice plate 14a in cooperation with a web 62 of the valve bore. In the illustration according to FIG. 3, the valve slide 38 is biased by the two compression springs 41a, 41b into its basic position, in which no flow through the metering orifice 14a takes place.

Die Ansteuerung des Proportionalventils 36 erfolgt durch Anlegen eines Steuerdruckes an die beiden Steueranschlüsse 58a bzw. 58b, die über Steuerleitungen mit dem Federraum 64a bzw. 64b des Proportionalventils 36 verbunden sind. In der Steuerleitung zwischen den Steueranschlüssen 58a, 58b und den Federräumen 64a bzw. 64b ist eine Düse mit einem Rückschlagventil ausgebildet, durch die eine Dämpfung der Ventilschieberbewegung möglich ist.The control of the proportional valve 36 is effected by applying a control pressure to the two control terminals 58a and 58b, which are connected via control lines to the spring chamber 64a and 64b of the proportional valve 36. In the control line between the control terminals 58a, 58b and the spring chambers 64a and 64b, a nozzle is formed with a check valve, through which a damping of the valve spool movement is possible.

Der Steuerbund 60 ist im Bereich seiner Stirnflächen mit einer Vielzahl von Steuerkerben 64 bzw. 66 versehen, über die Druckmittel aus einem mit dem Pumpenanschluß P verbundenen Ringraum 68 zum Eingangsanschluß Q geführt werden kann, so daß die in Fig. 3 untere Stirnfläche des Regelkolbens 72 der Druckwaage 16a mit dem Druck stromabwärts der Meßblende beaufschlagbar ist.The control collar 60 is provided in the region of its end faces with a plurality of control notches 64 and 66, via the pressure medium from a connected to the pump port P annulus 68 can be performed to the input terminal Q, so that the lower in Fig. 3 end face of the control piston 72nd the pressure compensator 16a with the pressure downstream of the orifice can be acted upon.

Bei einer Verschiebung des Wegeventilschiebers 38 nach rechts (Fig. 3) wird die Meßblende 14a durch Zusammenwirken der Steuerkerben 64 mit der einen Steuerkante des Steges 62 gebildet, während bei einer Verschiebung nach links die Steuerkerben 66 die Verbindung vom Ringraum 68 zur Druckwaage 16a hin aufsteuern.With a displacement of the directional control valve spool 38 to the right (FIG. 3), the orifice plate 14a is formed by cooperation of the control notches 64 with the one control edge of the web 62, while with a shift to the left the control notches 66 open the connection from the annulus 68 to the pressure compensator 16a out ,

Der Eingangsanschluß Q der Druckwaage 16a ist als Axialanschluß ausgebildet, so daß der Fluiddruck auch auf die untere Stirnfläche 70 des Regelkolbens 72 wirkt. Der Ausgangsanschluß C ist als Radialanschluß ausgebildet und mündet in den Leitungen 40 bzw. 42. In diesen Leitungen 40, 42 sind die Lasthalteventile 56a, 56b angeordnet, die eine Rückströmung vom Ventilschieber 38 zur Druckwaage 16a hin verhindern und eine Durchströmung in umgekehrter Richtung ermöglichen.The input port Q of the pressure compensator 16a is formed as an axial connection, so that the fluid pressure also acts on the lower end face 70 of the control piston 72. The output terminal C is formed as a radial connection and opens into the lines 40 and 42. In these lines 40, 42, the load-holding valves 56a, 56b are arranged, which prevent backflow from the valve spool 38 to the pressure compensator 16a out and allow a flow in the reverse direction.

Die Verbindung der Leitungen 40, 42 mit den Arbeitsanschlüssen A bzw. B oder dem Tankanschluß T erfolgt jeweils über ein Richtungsteil des Ventiischiebers 38. Das heißt, jedem Arbeitsanschluß A, B ist ein Richtungsteil zugeordnet, über das ein Arbeitsanschluß A bzw. B mit einer Leitung 40, 42 oder mit dem Tank T verbindbar ist.The connection of the lines 40, 42 with the working ports A and B or the tank port T takes place in each case via a directional part of the Ventiischiebers 38. That is, each working port A, B is associated with a directional part, via a working port A and B with a Line 40, 42 or with the tank T is connectable.

Das in Fig. 3 rechts ausgebildete Richtungsteil für den Anschluß B hat drei im Axialabstand ausgebildete Steuerbünde 74, 76 und 78. Die Steuerbünde 76 und 78 sind jeweils mit Steuerkerben 80 bzw. 82 versehen, die sich zu dem zwischen diesen Steuerbünden 76, 78 angeordneten, radial zurückgesetzten Abschnitt hin öffnen.The right-trained in Fig. 3 direction part for the terminal B has three axially spaced control covenants 74, 76 and 78. The control covenants 76 and 78 are each provided with control notches 80 and 82, which arranged to the between these control cords 76, 78 Open radially recessed section.

Das dem Arbeitsanschluß A zugeordnete Richtungsteil des Ventilschiebers 38 ist lediglich durch zwei beabstandete Steuerbünde 84, 86 gebildet. Im Steuerbund 86 sind Steuerkerben 88 ausgebildet, die in der Funktion den Steuerkerben 80 des Steuerbundes 78 entsprechen.The working part A associated direction part of the valve spool 38 is formed only by two spaced control covenants 84, 86. In the control collar 86 control notches 88 are formed, which correspond in function to the control notches 80 of the control collar 78.

Im Axialabstand zu der rechten Stirnfläche des Steuerbundes 86 münden am Außenumfang mehrere, am Umfang verteilte Schrägbohrungen 90, die mit einer gemeinsamen Axialbohrung 92 verbunden sind. Diese durchsetzt den Steuerbund 8 bis zum linken Endabschnitt des Ventilschiebers 38. Bei der dargestellten Variante ist der Endanschlag 94 des Ventilschiebers in die Axialbohrung 92 eingeschraubt, so daß deren linker Endabschnitt verschlossen ist.At an axial distance to the right end face of the control collar 86 open at the outer periphery a plurality of circumferentially distributed oblique holes 90 which are connected to a common axial bore 92. This passes through the control collar 8 to the left end portion of the valve spool 38. In the illustrated variant, the end stop 94 of the valve spool is screwed into the axial bore 92, so that the left end portion is closed.

Fig. 4 zeigt eine Detaildarstellung des Ventilschiebers 38 im Mittelbereich dieser Axialbohrung 92.4 shows a detailed representation of the valve slide 38 in the middle region of this axial bore 92.

Demgemäß ist in der Axialbohrung 92 ein Rückhalteventil vorgesehen, dessen Ventilkörper 96 über eine Druckfeder 97 gegen einen Ventilsitz 98 vorgespannt ist.Accordingly, a retention valve is provided in the axial bore 92, the valve body 96 is biased by a compression spring 97 against a valve seat 98.

Stromabwärts des Ventilkörpers 96 münden ein Radialbohrungsstern 100 und ein Schrägbohrungsstern 102. Der Radialbohrungsstern 100 ist durch einen Steg 104 der Aufnahmebohrung 103 des Ventilschiebers 38 versperrt. Der Schrägbohrungsstern 102 mündet in dem radial zurückgesetzten Abschnitt zwischen den Steuerbünden 84 und 86. Der gegen den Ventilsitz 98 vorgespannte Ventilkörper 96 verhindert, daß Hydraulikfluid vom Anschluß A in die Axialbohrung 92 einströmen kann. Eine Durchströmung in Gegenrichtung wird praktisch nicht verhindert, da die Druckfeder 97 schwach ist.Downstream of the valve body 96 open a radial hole star 100 and an oblique hole star 102. The radial hole star 100 is blocked by a web 104 of the receiving bore 103 of the valve spool 38. The oblique bore star 102 opens into the radially recessed portion between the control collars 84 and 86. The biased against the valve seat 98 valve body 96 prevents hydraulic fluid from the port A can flow into the axial bore 92. A flow in the opposite direction is practically not prevented because the compression spring 97 is weak.

Die Geometrie des Radialbohrungssterns 100 und des Schrägbohrungssterns 102 ist derart gewählt, daß bei einer Verschiebung des Ventilschiebers 38 nach links über diese Sterne 100, 102 die Verbindung vom Arbeitsanschluß A zum Tankanschluß T aufsteuerbar ist. Alternativ könnten für die Aufsteuerung selbstverständlich auch Steuerkerben im rechten Stirnflächenbereich des Steuerbundes 84 verwendet werden.The geometry of the radial bore star 100 and the oblique bore star 102 is selected such that upon a displacement of the valve spool 38 to the left over these stars 100, 102, the connection from the working port A to the tank port T can be opened. Alternatively, of course, for the Aufsteuerung also control notches in the right end face area of the control collar 84 are used.

Falls nun an den Steueranschluß 58a ein Steuerdruck angelegt wird, wird der Ventilschieber 38 in der Darstellung nach Fig. 3 nach rechts bewegt, so daß die Steuerkerben 64 im Zusammenwirken mit dem Steg 62 die Verbindung vom Pumpenanschluß P zum Eingangsanschluß Q der Druckwaage auf steuern.If now to the control terminal 58a, a control pressure is applied, the valve spool 38 is moved in the illustration of FIG. 3 to the right, so that the control notches 64 in conjunction with the web 62 control the connection from the pump port P to the input port Q of the pressure compensator on.

Die in Fig. 3 oben liegende Stirnfläche 105 des Regelkolbens 72 ist von der Kraft einer Regelfeder 106 und vom Lastdruck beaufschlagt, der über eine Steuerkante und eine Winkelbohrung 108 im Regelkolben 72 von einer Umfangsnut 110 abgegriffen wird. Durch den am Eingangsanschluß Q anliegenden Druck stromabwärts der Meßblende 14a wird der Regelkolben 72 nach oben ausgelenkt und der Ausgangsanschluß C aufgesteuert bis sich ein Kräftegleichgewicht über dem Regelkolben 72 einstellt. Das Lasthalteventil 56a wird geöffnet und das Hydraulikfluid über die Leitung 40 und den Steuerbund 86 mit den Steuerkerben 88 zum Arbeitsanschluß A geführt. Gleichzeitig wird über den dem Arbeitsanschluß B zugeordneten Steuerbund 76 und die Steuerkerben 82 die Verbindung zwischen dem Arbeitsanschluß B und dem Tankanschluß T aufgesteuert, so daß das Hydraulikfluid vom Verbraucher in den Tank zurückströmen kann. In diesem Feinsteuerbereich sind die Schrägbohrungen 90 des Bypasskanals 32 noch nicht durch die Steuerkante 107 aufgesteuert.The upper end face 105 of the control piston 72 lying at the top in FIG. 3 is acted upon by the force of a control spring 106 and by the load pressure, which is tapped by a circumferential groove 110 via a control edge and an angular bore 108 in the control piston 72. By the pressure applied to the input terminal Q downstream of the metering orifice 14a of the control piston 72 is deflected upward and the output port C open until an equilibrium of forces on the control piston 72 is established. The load holding valve 56a is opened and the hydraulic fluid via the line 40 and the control collar 86 with the control notches 88 to the working port A out. At the same time, the connection between the working port B and the tank port T is opened up via the control collar 76 and the control notches 82 assigned to the working port B, so that the hydraulic fluid can flow back from the consumer into the tank. In this fine control range, the oblique bores 90 of the bypass channel 32 are not yet opened by the control edge 107.

Bei einer weiteren Verschiebung des Ventilschiebers 38 steuert die Steuerkante 107 den Bypasskanal 82 auf, so daß das Hydraulikfluid oder zumindest ein Teilvolumenstrom zum Arbeitsanschluß A geführt wird. Der Systemdruck sinkt ab, so daß der lastniedrigere Verbraucher 6 mit höherer Geschwindigkeit betätigt werden kann.In a further displacement of the valve spool 38, the control edge 107 controls the bypass channel 82, so that the hydraulic fluid or at least a partial volume flow to the working port A is performed. The system pressure drops, so that the load lower consumer 6 can be operated at a higher speed.

Bei einer Ansteuerung des Ventilschiebers 38 in umgekehrter Richtung hat der Bypasskanal keine Wirkung, da die umgekehrte Durchströmung von A zum Eingangsanschluß Q der Druckwaage 16a durch den auf dem Ventilsitz 98 aufliegenden Ventilkörper 96 verhindert wird.In a control of the valve spool 38 in the reverse direction of the bypass channel has no effect, since the reverse flow from A to the input terminal Q of the pressure compensator 16a is prevented by the resting on the valve seat 98 valve body 96.

Im vorbeschriebenen Ausführungsbeispiel ist der Bypasskanal 32 lediglich dem Arbeitsanschluß A zugeordnet, der für die Hebenfunktion des Verbrauchers erforderlich ist. Selbstverständlich kann auch dem anderen Arbeitsanschluß B ein weiterer Bypasskanal zugeordnet werden, der dann einen identischen Aufbau wie der vorbeschriebene Arbeitsanschluß aufweisen würde.In the embodiment described above, the bypass channel 32 is assigned only to the working port A, which is required for the lifting function of the consumer. Of course, the other working port B, a further bypass channel can be assigned, which would then have an identical structure as the above-described working port.

In dem Diagramm gemäß Fig. 5 sind die Druck- und Volumenstromverhältnisse der vorbeschriebenen Vorgänge in Abhängigkeit von der Zeit dargestellt. Es sei angenommen, daß zunächst ein lasthöherer Verbraucher, beispielsweise ein Löffel auf Anschlag gefahren wird. Der entsprechende Druckverlauf ist in Fig. 5 mit durchgezogenen Linien dargestellt. Demgemäß steigt der Lastdruck an diesem Verbraucher sehr schnell an und erreicht zum Zeitpunkt t1 ein Maximum, das durch die Pumpenleistung psys vorgegeben ist.In the diagram according to FIG. 5, the pressure and volume flow conditions of the above-described processes are shown as a function of time. It is assumed that initially a higher-load consumer, such as a spoon is driven to the stop. The corresponding pressure curve is shown in FIG. 5 by solid lines. Accordingly, the load pressure at this consumer increases very rapidly and reaches a maximum at time t1, which is predetermined by the pump power p sys .

Nach Erreichen dieses Maximaldruckes wird ein lastniedrigerer Verbraucher, beispielsweise ein Ausleger zugesteuert. Bei der Ansteuerung des diesem Verbraucher zugeordneten Proportionalventils 36 wird der Bypasskanal 32 in der vorbeschriebenen Weise aufgesteuert, so daß der Hydraulikfluidstrom Q zum lastniedrigeren Verbraucher ansteigt (gestrichelte Linie). Aufgrund dieses Anstieges des Hydraulikfluidvolumenstroms zum lastniedrigeren Verbraucher sinkt der Druck vom Systemdruck pSYS auf ein niedrigeres Niveau p* ab. Durch geeignete Wahl des Bypasskanaldurchmessers kann das Druckniveau p* eingestellt werden, so daß der Druck beispielsweise von einem Druck von 240 bar auf einen Druck p* von 200 bar absinkt.After reaching this maximum pressure, a load-lower consumer, for example, a boom is controlled. In the control of the consumer associated with this proportional valve 36, the bypass channel 32 is opened in the manner described above, so that the hydraulic fluid flow Q increases to the lower-load consumer (dashed line). Due to this increase of the hydraulic fluid volume flow to the lower-load consumer, the pressure from the system pressure p SYS drops to a lower level p *. By a suitable choice of the bypass channel diameter, the pressure level p * can be adjusted so that the pressure drops, for example, from a pressure of 240 bar to a pressure p * of 200 bar.

Zu Beginn der Ansteuerung des lastniedrigeren Verbrauchers erfolgt keine Beeinflussung des Druckes p, da der Bypasskanal zu Beginn der Ansteuerung noch nicht aufgesteuert ist.At the beginning of the control of the lower-load consumer there is no influence on the pressure p, since the bypass channel is not yet open at the beginning of the control.

Selbstverständlich ist die Erfindung keinesfalls darauf festgelegt, daß der Bypasskanal 32 in das Proportionalventil 36 integriert ist. Es sind auch andere Lösungen vorstellbar, bei denen der Bypasskanal über externe Schaltungen realisiert ist.Of course, the invention is by no means limited to the fact that the bypass channel 32 is integrated into the proportional valve 36. Other solutions are conceivable in which the bypass channel is realized via external circuits.

Offenbart ist ein LUDV-Schaltung zur Ansteuerung zumindest eines lastniedrigeren und eines lasthöheren Verbrauchers, wobei jedem Verbraucher eine Meßblende und eine nachgeschaltete Druckwaage zum Konstanthalten des Druckabfalls über der Meßblende zugeordnet sind. Der Druckwaage des lastniedrigeren Verbrauchers ist ein aufsteuerbarer Bypasskanal zugeordnet, über den die Druckwaage dieses Verbrauchers umgehbar ist.Disclosed is a LUDV circuit for controlling at least one lastniedrigeren and a higher-load load, each consumer an orifice plate and a downstream pressure compensator are assigned to keep the pressure drop across the orifice constant. The pressure compensator of the lower-load consumer is assigned an openable bypass channel, via which the pressure compensator of this consumer can be bypassed.

Claims (9)

  1. A hydraulic circuit for controlling at least one of a lower-load consumer and a higher-load consumer (4, 6),
    comprising a power-controlled variable adjustment pump (2) having a setting which is variable as a function of the highest load pressure of said consumers (4, 6),
    wherein an adjustable metering orifice (14a, 14b) including a downstream pressure compensator (16a, 16b) is provided between said variable adjustment pump (2) and each consumer (4, 6), the control piston (72) of said pressure compensator being adapted to be subjected to the highest one of the load pressures tapped from said consumers (4, 6) in the closing direction, and to the pressure downstream of said metering orifice (14a, 14b) in the opening direction, characterized in that
    the output (P1) of the metering orifice (14a) associated with the lower-load consumer (6) is adapted to be connected with at least one work port (A) for the lower-load consumer (6) via a bypass channel (32) so as to bypass the metering orifice (14a) downstream of the measuring orifice (14a), so that when the bypass channel (32) is controlled open, the system pressure drops to a lower level than when the bypass channel (32) is closed, and the hydraulic fluid flow to the lower-load consumer increases.
  2. The hydraulic circuit according to claim 1, characterized in that said metering orifice (14a, 14b) is formed by a proportional valve (36) whereby said work port (A, B) may be connected to the pump port (P) or to a reservoir (T), and in that said bypass channel (32) may be controlled open in accordance with the valve spool position of said proportional valve (36).
  3. The hydraulic circuit according to claim 2, characterized in that said bypass channel (32) is formed in said valve spool (38) and may be controlled open by a control land of said proportional valve (36).
  4. The hydraulic circuit according to any one of the preceding claims, characterized in that in said bypass channel (32) a check valve (96, 97, 98) is arranged which prevents a hydraulic fluid flow from said consumer (6) to said metering orifice (14a).
  5. The hydraulic circuit according to any one of claims 2 to 4, characterized in that said proportional valve (36) includes two work ports (A, B) for said consumer (6), and in that a bypass channel (32) is associated to each work port (A, B).
  6. The hydraulic circuit according to any one of claims 2 to 5, characterized in that said bypass channel (32) is controlled open only following a predetermined stroke of said valve spool (36).
  7. The hydraulic circuit according to any one of claims 2 to 6, characterized in that said valve spool (38) includes a velocity component having an approximately central arrangement and forming said metering orifice (14a), as well as two directional components through which the hydraulic fluid may be conveyed from the output port (Q) of said pressure compensator (16a) to a work port (A, B) or from said other work port (A, B) to a reservoir port (T), respectively, wherein said bypass channel (32) extends from said velocity component to one of said directional components.
  8. The hydraulic circuit according to any one of claims 4 to 7, characterized in that said bypass channel (32) opens via oblique bores (90) in the range of said velocity component on the one hand, and via a radial bore star (10 0) and/or an oblique bore star (102) downstream from said check valve (96, 97, 98) in the range of a directional component on the other hand.
  9. The hydraulic circuit according to any one of the preceding claims, characterized in that said variable displacement pump (2) is pressure-controlled.
EP99936360A 1998-06-29 1999-05-31 Hydraulic circuit Expired - Lifetime EP1092095B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19828963 1998-06-29
DE19828963A DE19828963A1 (en) 1998-06-29 1998-06-29 Hydraulic switch system for the operation of low- and high-load units
PCT/DE1999/001591 WO2000000747A1 (en) 1998-06-29 1999-05-31 Hydraulic circuit

Publications (3)

Publication Number Publication Date
EP1092095A1 EP1092095A1 (en) 2001-04-18
EP1092095B1 EP1092095B1 (en) 2003-03-26
EP1092095B2 true EP1092095B2 (en) 2007-04-18

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EP99936360A Expired - Lifetime EP1092095B2 (en) 1998-06-29 1999-05-31 Hydraulic circuit

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US (1) US6367365B1 (en)
EP (1) EP1092095B2 (en)
JP (1) JP4520041B2 (en)
KR (1) KR100636863B1 (en)
DE (2) DE19828963A1 (en)
WO (1) WO2000000747A1 (en)

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DE10041061A1 (en) * 2000-08-22 2002-03-07 Still Gmbh Hydraulic shift arrangement
DE10058032A1 (en) * 2000-11-23 2002-05-29 Mannesmann Rexroth Ag Hydraulic control arrangement
DE10332120A1 (en) * 2003-07-15 2005-02-03 Bosch Rexroth Ag Control arrangement and method for controlling at least two hydraulic consumers
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KR20010071687A (en) 2001-07-31
EP1092095A1 (en) 2001-04-18
EP1092095B1 (en) 2003-03-26
JP4520041B2 (en) 2010-08-04
JP2002519596A (en) 2002-07-02
DE19828963A1 (en) 1999-12-30
US6367365B1 (en) 2002-04-09
DE59904746D1 (en) 2003-04-30
KR100636863B1 (en) 2006-10-19
WO2000000747A1 (en) 2000-01-06

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