EP0502411A2 - Hydraulic system for controlling a loaddriven actuator - Google Patents

Hydraulic system for controlling a loaddriven actuator Download PDF

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Publication number
EP0502411A2
EP0502411A2 EP92103245A EP92103245A EP0502411A2 EP 0502411 A2 EP0502411 A2 EP 0502411A2 EP 92103245 A EP92103245 A EP 92103245A EP 92103245 A EP92103245 A EP 92103245A EP 0502411 A2 EP0502411 A2 EP 0502411A2
Authority
EP
European Patent Office
Prior art keywords
valve
pressure
consumer
magnet
pilot
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.)
Withdrawn
Application number
EP92103245A
Other languages
German (de)
French (fr)
Other versions
EP0502411A3 (en
Inventor
Günter Winkels
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Deere and Co
Original Assignee
Deere and Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Deere and Co filed Critical Deere and Co
Publication of EP0502411A2 publication Critical patent/EP0502411A2/en
Publication of EP0502411A3 publication Critical patent/EP0502411A3/en
Withdrawn legal-status Critical Current

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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
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an 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
    • F15B2211/20—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
    • F15B2211/21—Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge
    • F15B2211/212—Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge the pressure sources being accumulators
    • 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
    • F15B2211/40—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
    • F15B2211/415—Flow control characterised by the connections of the flow control means in the circuit
    • F15B2211/41572—Flow control characterised by the connections of the flow control means in the circuit being connected to a pressure source and an 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
    • F15B2211/40—Flow control
    • F15B2211/42—Flow control characterised by the type of actuation
    • F15B2211/426—Flow control characterised by the type of actuation electrically or electronically
    • 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
    • F15B2211/50518—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using pressure relief 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
    • F15B2211/50—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
    • F15B2211/515—Pressure control characterised by the connections of the pressure control means in the circuit
    • F15B2211/5151—Pressure control characterised by the connections of the pressure control means in the circuit being connected to a pressure source and a 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
    • F15B2211/50—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
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/615—Filtering means
    • 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
    • F15B2211/625—Accumulators
    • 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

Definitions

  • the invention relates to a hydraulic system for controlling a force moving a consumer with a pilot-controlled main valve and with a pilot valve controlled by a magnet, the main valve being switchable by means of the pilot valve into a position supplying a pressure medium to the consumer and a pressure medium discharging from it.
  • Hydraulic systems for controlling the position or the contact pressure of a consumer are widely known and z. B. used to control the distance of a device from the ground.
  • pressure cylinders can be supplied to lifting cylinders via a main valve if it comes from a blocking position is switched into a through position.
  • the changeover takes place via a pilot valve which is operated remotely and, when actuated accordingly, reduces a pilot pressure behind the main valve, so that this is pushed into the open position by means of a pressure applied to the other side of the main valve.
  • the same control is carried out with a second main valve and a second pilot valve if pressure medium is to flow out of the lifting cylinders to a storage container.
  • the object on which the invention is based is seen in designing a hydraulic system for controlling a force which moves a consumer, in particular for controlling its contact force, with a pilot-controlled main valve and with a pilot valve controlled by a magnet such that with only one main and one pilot valve a preselectable pressure is automatically applied to the consumer during a control.
  • the pilot valve is opened and thus reduces pressure behind the main valve as soon as a pressure present at the pilot valve exceeds the force acting on the other side of the pilot valve, ie the counteracting force.
  • This other force could be built up by means of a spring, a magnet or some other pressure.
  • Such an increase in pressure occurs when the consumer z. B. moved with a device due to the nature of the ground away from the ground and no longer on this lies on.
  • the opening of the main valve then causes the pressure medium to flow out of the consumer, so that the device can lower itself until the pilot-controlled pressure is reached again at the consumer.
  • the pressure at which the pilot valve responds and the main valve is actuated can be varied. Such changeability is useful if the operating conditions of the device worn by the consumer change and an adjustment is necessary or desired.
  • the response pressure in the pilot valve can act in a simple manner if it works against the force of a spring, since this is constant and can be calculated.
  • a proportional pressure relief valve with a pilot control and a magnet with changeable application voltage and reverse characteristic is already known [BOSCH - For hydraulics - Product information - HP / VEK 2-BEY 013/5 De, En, Fr (3.90)]; however, it is not known to use such a valve to control the contact pressure or the position of a consumer.
  • the main valve is designed so that the amount of pressure medium flowing through it can be adjusted, the lowering speed of the consumer can be changed so that when the pilot valve responds, the consumer can be moved at a variable speed until a certain support pressure is reached.
  • a hydraulic system 10 contains a reservoir 12, a pump 14, a valve 16, a main valve 18, a pilot valve 20 and a consumer 22.
  • Such a hydraulic system 10 is used to control the lifting and / or lowering of an object engaging the consumer 22, or generally to control its position and, if it is placed on a floor, to control its contact force.
  • the object can be an implement, that is attached to a vehicle, or a header on a harvester, a shovel on a loader or excavator, or a grapple on a forestry machine.
  • numerous other application examples are conceivable.
  • Pressure medium is stored in the reservoir 12 in the form of liquid, in particular oil, which can be pressurized by the pump 14.
  • the pump 14 is designed as a continuously pumping constant current pump which is driven by a motor, not shown.
  • a suction line 24 extends between the pump 14 and the reservoir 12.
  • the delivery rate of the pump 14 is assumed to be 18 l / min.
  • the valve 16 is designed as a two-position valve with three connections, which supplies pressure medium coming from the pump 14 in a position -a to the reservoir 12 and in a position -b- to the consumer 22.
  • a spring 26 and, on the other hand, a magnet 28 are provided for adjusting the valve 16. In a normal switching position, the spring 26 presses the valve 16 into its position -a-. Since the valve 16 is designed as a so-called black-and-white valve, it can only assume one of the positions mentioned, but not an intermediate position.
  • a pressure line 30 extends between the pump 14 and the valve 16
  • a line 32 extends between the valve 16 and the reservoir
  • a line 34 extends from the valve 16 to the consumer 22.
  • a branch 36 leads from the pressure line 30 to a conventional pressure relief valve 38, which opens at a set maximum permissible pressure and allows pressure medium to flow into the reservoir 12.
  • the maximum allowable pressure is above the normal operating pressure of the consumer 22nd
  • a spring-loaded check valve 40 is provided in line 34, which can open in the direction of consumer 22.
  • the main valve 18 is designed as a two-position valve with two connections and is connected on the inlet side to a line 42 and on the outlet side to a line 44. While line 42 establishes a connection between line 34 leading to consumer 22 and main valve 18, line 44 leads to reservoir 12. Position -c- interrupts the flow from the two possible positions -c- and -d- through the main valve 18 and thus the connection between the line 34 and the storage container 12, and the other position -d- provides a connection between the lines 42 and 44, the volume flow flowing through being variably throttled, as will be explained later. It is assumed for the exemplary embodiment that the maximum flow rate is 35 l / min.
  • the main valve 18 is on one side, i.e.. H. with a view of Figure 1 right, acted upon by a spring 46.
  • a pilot line 48 opens on the same side as the spring 46, and on the opposite side the main valve 18 is acted upon by a pressure present in a pilot line 50.
  • the pilot line 50 is connected to the line 42 and is therefore always subject to the pressure at the consumer 22.
  • the pilot valve 20 is connected to a further line 52, which branches off from the line 34 and leads to the reservoir 12. One after the other are on the line 52 a filter 54, a throttle 56, an orifice 58 and the pilot valve 20 are provided.
  • the pilot line 48 branches off between the throttle 56 and the orifice 58 to the main valve 18.
  • a third pilot line 60 is connected on the one hand between the orifice 58 and the pilot valve 20 to the line 52 and on the other hand to one side of the pilot valve 20.
  • a leakage oil line 62 is connected at one end to the pilot valve 20 and at the other end between the pilot valve 20 and the reservoir 12 to the line 52.
  • the pilot valve 20 is acted upon on one side by a spring 64, which counteracts the pressure present in the pilot line 60.
  • the pressure prevailing at the consumer 22 is always present in the pilot line 60, possibly noticeably reduced as a result of flow losses in the throttle 56 and the orifice 58.
  • a magnet 66 acts on the side opposite the spring 64 and together with the pressure in the pilot line 60 to the pilot valve 20.
  • the magnet 66 is advantageously designed as a proportional magnet; in any case, it is a magnet 66 with a known constant hysteresis.
  • the pilot valve 20 In the idle state, the pilot valve 20 is pushed by the spring 64 into a blocking position, in which the connection between the line 34 and the reservoir 12 via the line 52 is interrupted.
  • the magnet 66 In the idle state, the magnet 66 is not actuated, and the pressure present in the pilot line 60 with the associated surface is not sufficient to overcome the force of the spring 64. To compress the spring 64, the magnet 66 must also always be effective.
  • the magnet 66 In order to get from the blocking position -e- into a through position -f-, the magnet 66 must also be activated.
  • the magnet 66 is an electromagnet with an inverted one Characteristic curve as can be seen from FIG. 2.
  • the magnitude of the voltage / current that can be applied to it is variable and is specified by means of a potentiometer 68 via a switch 74. Depending on the size of the applied voltage or the applied current, the force with which the magnet 66 counteracts the spring 64 and thus allows pressure medium to flow out of the line 34 is greater or less.
  • the potentiometer 68 is located on a harvesting machine on a driver platform and can be adjusted from there. The control is selected so that the pilot valve 20 opens completely when the magnet 66 is at full voltage / current.
  • the consumer 22 is designed as a single-acting, linearly movable hydraulic motor, the piston of which can lift a load.
  • a pressure accumulator 70 is connected to the line 34, the input into the pressure accumulator 70 being able to be changed by means of a throttle 72 in order to make the hydraulic system 10 more rigid or more flexible.
  • Figure 1 shows the hydraulic system 10 in its idle state, in which the magnets 28 and 66 are de-energized.
  • the spring 16 pushes the valve 16 into its circulating position -a-, by means of the spring 46 the main valve 18 into its blocking position -c- and by means of the spring 64 the pilot valve 20 into its blocking position -e-; the pressure medium delivered by the pump 14 thus flows via the valve 16 directly into the reservoir 12 without moving the consumer 22.
  • the magnet 28 is in turn activated and thus the valve 16 is pushed into its through position -b-.
  • the magnet 66 is activated so that the force applied by it, together with the force resulting from the pressure in the pilot line 60, stands opposite the spring 64, projects beyond it and shifts the pilot valve 20 into its opening -f-position.
  • This control means that the consumer 22 is always moved by the load acting on it into a position in which the load only acts on it with a predetermined force. For example, a cutting mechanism of a combine harvester should be lowered by means of the consumer 22 until it rests on the ground with a certain force.
  • the position control it is first necessary to establish a relationship between the support pressure of the consumer 22 or the device attached to it, which builds up in the line 34, and the voltage on the magnet 66.
  • the consumer 22 is completely retracted in order to reduce the pressure in the line 34 as much as possible.
  • the magnets 28 and 66 are energized by means of a further switch, not shown, so that the valve 16 assumes its through position and conveys pressure medium to the consumer 22.
  • the switch 74 is closed so that voltage is applied to the magnet 66, which should, however, be the highest possible voltage / current at the start of the adjustment process.
  • the consumer 22 In order for the position control process to take effect, the consumer 22 must extend a certain amount, i.e. H. the load will be lifted.
  • the potentiometer 68 In order to activate the pressure-proportional position control, the potentiometer 68 is connected to the magnet 66 by closing the switch 74 and this is energized with a certain voltage, which generates the preset force directed against the spring 64. The pilot valve 20 is therefore biased.
  • the magnet 28 is energized so that the valve 16 allows pressure medium to flow into the line 34.
  • the application of a voltage to the magnets 28, 66 takes place for a time of, for. B. 5-6 seconds; this period can also be maintained by means of a timer in the form of a relay or the like. If the pressure at the consumer 22 is too high, the consumer 22 lowers in accordance with the previous statements regarding the adjustment process.
  • the pilot valve 20 opens the connection to the storage container 12
  • the pressure in the pilot line 48 decreases and the pressure in the pilot line 50 shifts the main valve 18 into its through position -d-, in which pressure medium can flow out of the consumer 22 into the reservoir 12.
  • the pressure medium can flow off until the pressure increase in the lines 34, 52 is reduced and the spring 64 manages to close the passage through the pilot valve 20, which causes the pilot pressure on the right side of the main valve 18 to rise and this increases also closes. This means that the consumer 22 lowers the load until it z. B. is supported on the floor. It can be clearly seen that by changing the voltage on the magnet 66, the time or pressure point at which the pilot valve 20 opens and initiates the control process can be changed.
  • the switch 74 is opened so that no voltage can be applied to the magnet 66 via the potentiometer 68.
  • the maximum flow rate through the main valve 18 can be changed manually, for which purpose, for example, an adjusting screw 76 can be used, as shown in FIG. 3. So the maximum flow rate of 35 l / min to z. B. 30 l / min can be reduced. This has the consequence that during a lowering process with unchanged Inflow of pressure medium from the pump 14 at 18 l / min can only flow from the consumer 22 at 12 l / min; the lowering speed slows down.
  • an electrically adjustable adjusting device could also be used.
  • a valve block 78 is shown in FIG. 3, which contains in particular the magnets 28 and 66, the valve 16, the main valve 18, the pilot valve 20 and the adjusting screw 76.
  • the previously used reference numerals are entered in the valve block 78 at the relevant points.
  • a detailed explanation is not necessary since the connections and the function are the same, with the exception that the valve 16 is not pilot-controlled directly by means of the magnet 28, but rather. However, this is already known from TM-1352, pages 270-20-5 and 270-20-7 to 270-20 9, Mar-86, by JOHN DEERE, so that no explanation is required here either.
  • the set screw 76 is screwed into a housing 82 so that it can move longitudinally and acts at one end on the spring 46, which presses a slide 84 of the main valve 18 against a seat 86. The further the set screw 76 is moved towards the spring 46 and preloads it accordingly, the less the slide 84 can with a comparable pressure dodge, so that the passage cross-section can be changed.
  • pilot valve 20 Since the pilot valve 20 operates under full voltage / current as a so-called black-white valve or open-close valve and thus does not allow any intermediate positions, it is also excellently suitable for any manual control that may be desired.
  • the hydraulic system according to the invention is particularly suitable for controlling the contact pressure of the consumer, but also for controlling its position.

Abstract

2.1 Hydraulic systems (10) of the said type are used, e.g. in harvesters, to lower a harvesting attachment to a level at which it is supported with a predetermined force on the ground. In order to achieve this aim, conventional hydraulic systems are provided with a multiplicity of valves which are controlled in a complicated manner. 2.2 It is proposed to use a proportional pressure-relief valve as a pilot valve (20) for a main valve (18) permitting the lowering operation, which pilot valve (20) can be preloaded by means of a magnet (66) variable in its voltage. 2.3 Hydraulic systems (10) of this type are used in the positional control of harvesting attachments on harvesters. <IMAGE>

Description

Die Erfindung betrifft ein Hydrauliksystem zur Steuerung einer einen Verbraucher bewegenden Kraft mit einem pilotgesteuerten Hauptventil und mit einem von einem Magneten gesteuerten Pilotventil, wobei das Hauptventil mittels des Pilotventils in eine ein Druckmittel dem Verbraucher zuführende und eine Druckmittel von diesem abführende Stellung schaltbar ist.The invention relates to a hydraulic system for controlling a force moving a consumer with a pilot-controlled main valve and with a pilot valve controlled by a magnet, the main valve being switchable by means of the pilot valve into a position supplying a pressure medium to the consumer and a pressure medium discharging from it.

Hydrauliksysteme zur Steuerung der Lage oder des Auflagedrucks eines Verbrauchers sind vielfach bekannt und werden z. B. dazu verwendet, den Abstand eines Geräts vom Boden zu steuern.Hydraulic systems for controlling the position or the contact pressure of a consumer are widely known and z. B. used to control the distance of a device from the ground.

In einer ersten Ausführung (TM-1352, Seiten 270-20-5 und 270-20-7 bis 270-20-9, Mar-86, von JOHN DEERE) kann Hubzylindern Druckmittel über ein Hauptventil zugeführt werden, wenn dieses aus einer Sperrstellung in eine Durchgangsstellung geschaltet wird. Die Umschaltung erfolgt über ein Pilotventil, das ferngesteuert betätigt wird und bei entsprechender Betätigung einen Pilotdruck hinter dem Hauptventil abbaut, so daß dieses mittels eines auf der anderen Seite des Hauptventils angelegten Drucks in die Durchgangsstellung geschoben wird. Die gleiche Steuerung erfolgt mit einem zweiten Hauptventil und einem zweiten Pilotventil, wenn Druckmittel aus den Hubzylindern zu einem Vorratsbehälter abfließen soll. Mit diesem Hydrauliksystem ist lediglich ein gesteuertes Anheben oder Absenken eines Geräts möglich, hingegen keine selbsttätige Lagesteuerung des Geräts.In a first version (TM-1352, pages 270-20-5 and 270-20-7 to 270-20-9, Mar-86, by JOHN DEERE), pressure cylinders can be supplied to lifting cylinders via a main valve if it comes from a blocking position is switched into a through position. The changeover takes place via a pilot valve which is operated remotely and, when actuated accordingly, reduces a pilot pressure behind the main valve, so that this is pushed into the open position by means of a pressure applied to the other side of the main valve. The same control is carried out with a second main valve and a second pilot valve if pressure medium is to flow out of the lifting cylinders to a storage container. With this hydraulic system, only a controlled raising or lowering of a device is possible, however no automatic position control of the device.

Nach einer anderen Steuerungsart [Bosch-Hydraulik, Systeminformation, Schaltungen und Komponenten für Mähdrescher, K6/VKD 2 - BEY 017/5 De(5.84), Seiten 4 und 5] werden hinter einemhandbetätigten Dreistellungsventil zwei Zweistellungsventile und ein einstellbares Druckbegrenzungsventil geschaltet, wobei das Druckbegrenzungsventil und ein Zweistellungsventil dazu benötigt werden, das andere Zweistellungsventil bei Erreichen eines vorgegebenen Drucks aus einer Sperr- in eine Durchgangsstellung zu bewegen. Der mit diesem Hydrauliksystem einhergehende Aufwand an Ventilen und Steuerverbindungen ist zu hoch.According to another type of control [Bosch hydraulics, system information, circuits and components for combine harvesters, K6 / VKD 2 - BEY 017/5 De (5.84), pages 4 and 5], behind a manually operated three-position valve, two two-position valves and one adjustable pressure relief valve are switched, whereby the Pressure relief valve and a two-position valve are required to move the other two-position valve from a blocking position into a through position when a predetermined pressure is reached. The expense of valves and control connections associated with this hydraulic system is too high.

Die der Erfindung zugrunde liegende Aufgabe wird darin gesehen, ein Hydrauliksystem zur Steuerung einer einen Verbraucher bewegenden Kraft, insbesondere zur Steuerung dessen Auflagekraft, mit einem pilotgesteuerten Hauptventil und mit einem von einem Magneten gesteuerten Pilotventil so auszubilden, daß mit nur einem Haupt- und einem Pilotventil automatisch ein vorwählbarer Druck an dem Verbraucher während einer Steuerung anliegt.The object on which the invention is based is seen in designing a hydraulic system for controlling a force which moves a consumer, in particular for controlling its contact force, with a pilot-controlled main valve and with a pilot valve controlled by a magnet such that with only one main and one pilot valve a preselectable pressure is automatically applied to the consumer during a control.

Diese Aufgabe ist erfindungsgemäß durch die Merkmale des Patentanspruchs 1 gelöst worden, wobei in den weiteren Patentansprüchen Merkmale aufgeführt sind, die die Lösung in vorteilhafter Weise weiterentwickeln.This object has been achieved according to the invention by the features of patent claim 1, features being listed in the further patent claims which further develop the solution in an advantageous manner.

Auf diese Weise wird das Pilotventil geöffnet und baut somit Druck hinter dem Hauptventil ab, sobald ein an dem Pilotventil anstehender Druck die auf der anderen Seite des Pilotventils anstehende, d. h. entgegenwirkende Kraft überschreitet. Diese andere Kraft könnte mittels einer Feder, eines Magneten oder eines anderen Drucks aufgebaut werden. Eine derartige Druckerhöhung tritt dann ein, wenn sich der Verbraucher z. B. mit einem Gerät aufgrund der Bodenbeschaffenheit von dem Boden weg bewegt und nicht mehr auf diesem aufliegt. Das Öffnen des Hauptventils bewirkt dann ein Abströmen des Druckmittels aus dem Verbraucher, so daß sich das Gerät absenken kann, bis an dem Verbraucher der vorgesteuerte Druck wieder erreicht ist.In this way, the pilot valve is opened and thus reduces pressure behind the main valve as soon as a pressure present at the pilot valve exceeds the force acting on the other side of the pilot valve, ie the counteracting force. This other force could be built up by means of a spring, a magnet or some other pressure. Such an increase in pressure occurs when the consumer z. B. moved with a device due to the nature of the ground away from the ground and no longer on this lies on. The opening of the main valve then causes the pressure medium to flow out of the consumer, so that the device can lower itself until the pilot-controlled pressure is reached again at the consumer.

Wenn die an dem Magnet anlegbare Spannung oder Stromstärke, jedenfalls deren Anlagekraft an der Steueröffnung veränderbar ist, kann der Druck, bei dem das Pilotventil anspricht und das Hauptventil betätigt wird, variiert werden. Eine derartige Änderbarkeit ist dann sinnvoll, wenn die Einsatzverhältnisse des von dem Verbraucher getragenen Geräts wechseln und eine Anpassung erforderlich oder gewünscht ist.If the voltage or current that can be applied to the magnet, or at least its contact force at the control opening, can be changed, the pressure at which the pilot valve responds and the main valve is actuated can be varied. Such changeability is useful if the operating conditions of the device worn by the consumer change and an adjustment is necessary or desired.

Auf einfache Weise kann der Ansprechdruck in dem Pilotventil wirken, wenn er gegen die Kraft einer Feder arbeitet, da diese konstant und vorberechenbar ist.The response pressure in the pilot valve can act in a simple manner if it works against the force of a spring, since this is constant and can be calculated.

Es ist zwar bereits ein Proportional-Druckbegrenzungsventil mit einer Pilotsteuerung und einem Magneten mit änderbarer Anlegespannung und umgekehrter Kennlinie bekannt [BOSCH - Für Hydraulik - Produktinformation - HP/VEK 2-BEY 013/5 De, En, Fr (3.90)]; es ist hingegen nicht bekannt, ein derartiges Ventil zur Steuerung des Auflagedrucks oder der Lage eines Verbrauchers zu verwenden.A proportional pressure relief valve with a pilot control and a magnet with changeable application voltage and reverse characteristic is already known [BOSCH - For hydraulics - Product information - HP / VEK 2-BEY 013/5 De, En, Fr (3.90)]; however, it is not known to use such a valve to control the contact pressure or the position of a consumer.

Wird das Hauptventil so ausgebildet, daß die durch es fließende Druckmittelmenge einstellbar ist, kann die Senkgeschwindigkeit des Verbrauchers verändert werden, so daß beim Ansprechen des Pilotventils der Verbraucher mit veränderlicher Geschwindigkeit bis zum Erreichen eines bestimmten Abstützdrucks bewegt werden kann.If the main valve is designed so that the amount of pressure medium flowing through it can be adjusted, the lowering speed of the consumer can be changed so that when the pilot valve responds, the consumer can be moved at a variable speed until a certain support pressure is reached.

Es ist zwar allgemein bekannt, z. B. auch aus der erstgenannten Druckschrift, die Durchflußmenge des Druckmittels durch das Hauptventil veränderlich zu machen; nach diesem Stand der Technik ist aber keine Steuerung der Abstützkraft möglich.While it is well known, e.g. B. also from the first-mentioned document to make the flow rate of the pressure medium through the main valve variable; after this State of the art, however, no control of the support force is possible.

Eine hervorragende Wirkung wird mit dem erfindungsgemäßen Hydrauliksystem erzielt, wenn es zur Lagesteuerung eines Geräts an einer landwirtschaftlich nutzbaren Maschine, insbesondere eines Erntevorsatzes an einer Erntemaschine verwendet wird, weil dort die Einsatzverhältnisse ständig wechseln, weil unterschiedliche Abstützdrücke und unterschiedliche Senkgeschwindigkeiten gewünscht werden. Auch bei Bau- und Forstmaschinen, oder bei der Dreipunktregelung von Ackerschleppern kann dieses Hydrauliksystem vorteilhaft verwendet werden.An excellent effect is achieved with the hydraulic system according to the invention if it is used to control the position of a device on an agriculturally usable machine, in particular a header on a harvesting machine, because the conditions of use change there constantly because different support pressures and different lowering speeds are desired. This hydraulic system can also be used to advantage in construction and forestry machines, or in the three-point control of agricultural tractors.

In der Zeichnung ist ein nachfolgend näher beschriebenes Ausführungsbeispiel der Erfindung dargestellt. Es zeigt:

Fig.1
einen Schaltplan eines erfindungsgemäßen Hydrauliksystems in schematischer Darstellung,
Fig.2
eine Kennlinie eines Magneten und
Fig.3
eine Darstellung eines Ventilblocks des Hydrauliksystems im Schnitt.
In the drawing, an embodiment of the invention described below is shown. It shows:
Fig. 1
1 shows a circuit diagram of a hydraulic system according to the invention in a schematic representation,
Fig. 2
a characteristic of a magnet and
Fig. 3
a representation of a valve block of the hydraulic system in section.

Ein erfindungsgemäßes Hydrauliksystem 10 enthält einen Vorratsbehälter 12, eine Pumpe 14, ein Ventil 16, ein Hauptventil 18, ein Pilotventil 20 und einen Verbraucher 22.A hydraulic system 10 according to the invention contains a reservoir 12, a pump 14, a valve 16, a main valve 18, a pilot valve 20 and a consumer 22.

Ein derartiges Hydrauliksystem 10 dient der Hub- und/oder Senksteuerung eines an dem Verbraucher 22 angreifenden Gegenstands, oder allgemein zu dessen Lagesteuerung und, wenn er auf einem Boden aufgelegt wird, zu dessen Auflagekraftsteuerung. Der Gegenstand kann ein Arbeitsgerät sein, das an ein Fahrzeug angehängt ist, oder ein Erntevorsatz an einer Erntemaschine, eine Schaufel an einem Lader oder Bagger oder ein Greifer an einer Forstmaschine. Darüber hinaus sind zahlreiche andere Anwendungsbeispiele denkbar.Such a hydraulic system 10 is used to control the lifting and / or lowering of an object engaging the consumer 22, or generally to control its position and, if it is placed on a floor, to control its contact force. The object can be an implement, that is attached to a vehicle, or a header on a harvester, a shovel on a loader or excavator, or a grapple on a forestry machine. In addition, numerous other application examples are conceivable.

In dem Vorratsbehälter 12 wird Druckmittel in der Form von Flüssigkeit, insbesondere Öl bevorratet, das von der Pumpe 14 unter Druck gesetzt werden kann.Pressure medium is stored in the reservoir 12 in the form of liquid, in particular oil, which can be pressurized by the pump 14.

Die Pumpe 14 ist als eine dauernd fördernde Konstantstrompumpe ausgebildet, die von einem nicht gezeigten Motor angetrieben wird. Zwischen der Pumpe 14 und dem Vorratsbehälter 12 erstreckt sich eine Saugleitung 24. Die Fördermenge der Pumpe 14 sei mit 18 l/min angenommen.The pump 14 is designed as a continuously pumping constant current pump which is driven by a motor, not shown. A suction line 24 extends between the pump 14 and the reservoir 12. The delivery rate of the pump 14 is assumed to be 18 l / min.

Das Ventil 16 ist als ein Zweistellungsventil mit drei Anschlüssen ausgebildet, das von der Pumpe 14 kommendes Druckmittel in einer Stellung -a- dem Vorratsbehälter 12 und in einer Stellung -b- dem Verbraucher 22 zuführt. Zur Verstellung des Ventils 16 ist einerseits eine Feder 26 und andererseits ein Magnet 28 vorgesehen. In einer normalen Schaltstellung drückt die Feder 26 das Ventil 16 in seine Stellung -a-. Da das Ventil 16 als sogenanntes Schwarz-Weiß-Ventil ausgebildet ist, kann es nur eine der genannten Stellungen, hingegen keine dazwischenliegende Stellung einnehmen. Zwischen der Pumpe 14 und dem Ventil 16 erstreckt sich eine Druckleitung 30, zwischen dem Ventil 16 und dem Vorratsbehälter eine Leitung 32 und von dem Ventil 16 zu dem Verbraucher 22 eine Leitung 34.The valve 16 is designed as a two-position valve with three connections, which supplies pressure medium coming from the pump 14 in a position -a to the reservoir 12 and in a position -b- to the consumer 22. A spring 26 and, on the other hand, a magnet 28 are provided for adjusting the valve 16. In a normal switching position, the spring 26 presses the valve 16 into its position -a-. Since the valve 16 is designed as a so-called black-and-white valve, it can only assume one of the positions mentioned, but not an intermediate position. A pressure line 30 extends between the pump 14 and the valve 16, a line 32 extends between the valve 16 and the reservoir, and a line 34 extends from the valve 16 to the consumer 22.

Von der Druckleitung 30 führt eine Abzweigung 36 zu einem herkömmlichen Druckbegrenzungsventil 38, das bei einem eingestellten zulässigen Höchstdruck öffnet und Druckmittel in den Vorratsbehälter 12 abströmen läßt. Der zulässige Höchstdruck liegt über dem normalen Betriebsdruck des Verbrauchers 22.A branch 36 leads from the pressure line 30 to a conventional pressure relief valve 38, which opens at a set maximum permissible pressure and allows pressure medium to flow into the reservoir 12. The maximum allowable pressure is above the normal operating pressure of the consumer 22nd

In der Leitung 34 ist ein federbelastetes Rückschlagventil 40 vorgesehen, das in Richtung zu dem Verbraucher 22 hin öffnen kann.A spring-loaded check valve 40 is provided in line 34, which can open in the direction of consumer 22.

Das Hauptventil 18 ist als Zweistellungsventil mit zwei Anschlüssen ausgebildet und eingangsseitig an eine Leitung 42 und ausgangsseitig an eine Leitung 44 angeschlossen. Während die Leitung 42 eine Verbindung zwischen der zu dem Verbraucher 22 führenden Leitung 34 und dem Hauptventil 18 herstellt, führt die Leitung 44 zu dem Vorratsbehälter 12. Von den beiden möglichen Stellungen -c- und -d- unterbricht die Stellung -c- den Durchfluß durch das Hauptventil 18 und somit die Verbindung zwischen der Leitung 34 und dem Vorratsbehälter 12, und die andere Stellung -d- erbringt eine Verbindung zwischen den Leitungen 42 und 44, wobei der hindurchfließende Volumenstrom veränderlich drosselbar ist, wie dies später noch erläutert wird. Es sei für das Ausführungsbeispiel angenommen, daß die maximale Durchflußmenge 35 l/min betrage.The main valve 18 is designed as a two-position valve with two connections and is connected on the inlet side to a line 42 and on the outlet side to a line 44. While line 42 establishes a connection between line 34 leading to consumer 22 and main valve 18, line 44 leads to reservoir 12. Position -c- interrupts the flow from the two possible positions -c- and -d- through the main valve 18 and thus the connection between the line 34 and the storage container 12, and the other position -d- provides a connection between the lines 42 and 44, the volume flow flowing through being variably throttled, as will be explained later. It is assumed for the exemplary embodiment that the maximum flow rate is 35 l / min.

Das Hauptventil 18 wird auf einer Seite, d. h. mit Blick auf Figur 1 rechts, von einer Feder 46 beaufschlagt. Auf der gleichen Seite wie die Feder 46 mündet eine Pilotleitung 48 ein, und auf der gegenüberliegenden Seite wird das Hauptventil 18 von einem in einer Pilotleitung 50 anstehenden Druck beaufschlagt. Die Pilotleitung 50 ist an die Leitung 42 angeschlossen und unterliegt somit stets dem am Verbraucher 22 anstehenden Druck.The main valve 18 is on one side, i.e.. H. with a view of Figure 1 right, acted upon by a spring 46. A pilot line 48 opens on the same side as the spring 46, and on the opposite side the main valve 18 is acted upon by a pressure present in a pilot line 50. The pilot line 50 is connected to the line 42 and is therefore always subject to the pressure at the consumer 22.

Das Pilotventil 20 ist in eine weitere Leitung 52 geschaltet, die von der Leitung 34 abzweigt und zu dem Vorratsbehälter 12 führt. Hintereinander folgend sind in der Leitung 52 ein Filter 54, eine Drossel 56, eine Blende 58 und das Pilotventil 20 vorgesehen. Die Pilotleitung 48 zweigt zwischen der Drossel 56 und der Blende 58 zu dem Hauptventil 18 ab.The pilot valve 20 is connected to a further line 52, which branches off from the line 34 and leads to the reservoir 12. One after the other are on the line 52 a filter 54, a throttle 56, an orifice 58 and the pilot valve 20 are provided. The pilot line 48 branches off between the throttle 56 and the orifice 58 to the main valve 18.

Eine dritte Pilotleitung 60 ist einerseits zwischen der Blende 58 und dem Pilotventil 20 an die Leitung 52 und andererseits an eine Seite des Pilotventils 20 angeschlossen. Eine Leckölleitung 62 ist einenends mit dem Pilotventil 20 und anderenends zwischen dem Pilotventil 20 und dem Vorratsbehälter 12 mit der Leitung 52 verbunden. Schließlich wird das Pilotventil 20 auf einer Seite von einer Feder 64 beaufschlagt, der der in der Pilotleitung 60 anstehende Druck entgegenwirkt. In der Pilotleitung 60 herrscht stets der an dem Verbraucher 22 anstehende Druck, gegebenenfalls kaum merklich reduziert infolge von Strömungsverlusten in der Drossel 56 und der Blende 58. Auf der der Feder 64 entgegengesetzten Seite und zusammen mit dem Druck in der Pilotleitung 60 wirkt ein Magnet 66 auf das Pilotventil 20. Der Magnet 66 ist vorteilhafterweise als Proportionalmagnet ausgebildet; jedenfalls ist es ein Magnet 66 mit einer bekannten konstanten Hysterese.A third pilot line 60 is connected on the one hand between the orifice 58 and the pilot valve 20 to the line 52 and on the other hand to one side of the pilot valve 20. A leakage oil line 62 is connected at one end to the pilot valve 20 and at the other end between the pilot valve 20 and the reservoir 12 to the line 52. Finally, the pilot valve 20 is acted upon on one side by a spring 64, which counteracts the pressure present in the pilot line 60. The pressure prevailing at the consumer 22 is always present in the pilot line 60, possibly noticeably reduced as a result of flow losses in the throttle 56 and the orifice 58. A magnet 66 acts on the side opposite the spring 64 and together with the pressure in the pilot line 60 to the pilot valve 20. The magnet 66 is advantageously designed as a proportional magnet; in any case, it is a magnet 66 with a known constant hysteresis.

Das Pilotventil 20 wird im Ruhezustand von der Feder 64 in eine Sperrstellung -e- geschoben, in der die Verbindung zwischen der Leitung 34 und dem Vorratsbehälter 12 über die Leitung 52 unterbrochen ist. In dem Ruhezustand wird der Magnet 66 nicht betätigt, und der in der Pilotleitung 60 anstehende Druck reicht mit der dazugehörigen Fläche nicht aus, die Kraft der Feder 64 zu überkommen. Zur Kompression der Feder 64 muß stets auch der Magnet 66 wirksam werden.In the idle state, the pilot valve 20 is pushed by the spring 64 into a blocking position, in which the connection between the line 34 and the reservoir 12 via the line 52 is interrupted. In the idle state, the magnet 66 is not actuated, and the pressure present in the pilot line 60 with the associated surface is not sufficient to overcome the force of the spring 64. To compress the spring 64, the magnet 66 must also always be effective.

Um aus der Sperrstellung -e- in eine Durchgangsstellung -f-zu gelangen, muß zusätzlich der Magnet 66 aktiviert werden. Der Magnet 66 ist ein Elektromagnet mit einer umgekehrten Kennlinie, wie sie aus Figur 2 zu ersehen ist. Die an ihm anlegbare Spannung/Stromstärke ist in ihrer Größe veränderlich und wird mittels eines Potentiometers 68 über einen Schalter 74 vorgegeben. Je nach der Größe der angelegten Spannung bzw. der angelegten Stromstärke ist die Kraft, mit der der Magnet 66 der Feder 64 entgegenwirkt und somit Druckmittel von der Leitung 34 abströmen läßt, größer oder kleiner. Das Potentiometer 68 befindet sich bei einer Erntemaschine auf einer Fahrerplattform und kann von dort aus eingestellt werden. Die Steuerung ist so gewählt, daß das Pilotventil 20 vollkommen öffnet, wenn der Magnet 66 unter voller Spannung/ Stromstärke steht.In order to get from the blocking position -e- into a through position -f-, the magnet 66 must also be activated. The magnet 66 is an electromagnet with an inverted one Characteristic curve as can be seen from FIG. 2. The magnitude of the voltage / current that can be applied to it is variable and is specified by means of a potentiometer 68 via a switch 74. Depending on the size of the applied voltage or the applied current, the force with which the magnet 66 counteracts the spring 64 and thus allows pressure medium to flow out of the line 34 is greater or less. The potentiometer 68 is located on a harvesting machine on a driver platform and can be adjusted from there. The control is selected so that the pilot valve 20 opens completely when the magnet 66 is at full voltage / current.

Der Verbraucher 22 ist als ein einfach wirkender, linear beweglicher Hydraulikmotor ausgebildet, dessen Kolben eine Last anheben kann. Parallel zu dem Verbraucher 22 ist ein Druckspeicher 70 an die Leitung 34 angeschlossen, wobei der Eingang in den Druckspeicher 70 mittels einer Drossel 72 verändert werden kann, um das Hydrauliksystem 10 steifer oder beweglicher zu gestalten.The consumer 22 is designed as a single-acting, linearly movable hydraulic motor, the piston of which can lift a load. In parallel to the consumer 22, a pressure accumulator 70 is connected to the line 34, the input into the pressure accumulator 70 being able to be changed by means of a throttle 72 in order to make the hydraulic system 10 more rigid or more flexible.

Nach alledem stellt sich die Funktion des Hydrauliksystems 10 wie folgt dar.After all, the function of the hydraulic system 10 is as follows.

RuhestellungResting position

Figur 1 zeigt das Hydrauliksystem 10 in seinem Ruhezustand, in dem die Magneten 28 und 66 spannungslos sind. Mittels der Feder 26 wird in diesem Ruhezustand das Ventil 16 in seine Umlaufstellung -a-, mittels der Feder 46 das Hauptventil 18 in seine Sperrstellung -c- und mittels der Feder 64 das Pilotventil 20 in seine Sperrstellung -e- gedrückt; das von der Pumpe 14 geförderte Druckmittel fließt also über das Ventil 16 direkt in den Vorratsbehälter 12, ohne den Verbraucher 22 zu bewegen.Figure 1 shows the hydraulic system 10 in its idle state, in which the magnets 28 and 66 are de-energized. In this idle state, the spring 16 pushes the valve 16 into its circulating position -a-, by means of the spring 46 the main valve 18 into its blocking position -c- and by means of the spring 64 the pilot valve 20 into its blocking position -e-; the pressure medium delivered by the pump 14 thus flows via the valve 16 directly into the reservoir 12 without moving the consumer 22.

HubvorgangLifting process

Um den Verbraucher 22 im Sinne eines Hubs auszufahren, wird lediglich der Magnet 28 über einen nicht gezeigten Schalter betätigt, d. h. aktiviert, so daß das Ventil 16 seine Durchgangsstellung -b- einnimmt und das Druckmittel in die Leitung 34 über das Rückschlagventil 40 zu dem Verbraucher 22 gelangt, der ausfährt, sobald der Druckspeicher 70 seinen Betriebsdruck erreicht hat. Das Hauptventil 18 und das Pilotventil 20 bleiben in ihrer Sperrstellung -c- bzw. -e-. Der Hubvorgang wird beendet, sobald an dem Magnet 28 keine Spannung mehr angelegt wird, was z. B. durch das Öffnen des Schalters möglich ist.In order to extend the consumer 22 in the sense of a stroke, only the magnet 28 is actuated via a switch (not shown), i. H. activated so that the valve 16 assumes its through position -b- and the pressure medium in line 34 passes through the check valve 40 to the consumer 22, which extends as soon as the pressure accumulator 70 has reached its operating pressure. The main valve 18 and the pilot valve 20 remain in their blocking position -c- or -e-. The lifting process is ended as soon as no more voltage is applied to the magnet 28, which, for. B. is possible by opening the switch.

SenkvorgangLowering process

Zum Absenken einer an dem Verbraucher 22 angreifenden Last, d. h. zum Einfahren des Hydraulikkolbens, wird wiederum der Magnet 28 aktiviert und somit das Ventil 16 in seine Durchgangsstellung -b- geschoben. Außerdem wird der Magnet 66 aktiviert, so daß die von ihm aufgebrachte Kraft zusammen mit der sich aus dem Druck in der Pilotleitung 60 ergebenden Kraft der Feder 64 gegenübersteht, diese überragt und das Pilotventil 20 in seine den Durchgang öffnende Stellung -f-verschiebt. Nachdem der an dem Hauptventil 18 auf der rechten Seite anstehende Druck sich nun durch das geöffnete Pilotventil 20 zum Vorratsbehälter 12 abbauen kann, bewirkt der an dem Verbraucher 22 anstehende und sich durch die Leitung 34 und die Pilotleitung 50 an der anderen, linken Seite des Hauptventils 18 angelegte Pilotdruck, daß das Hauptventil 18 seine Durchgangsstellung -d- einnimmt, in der Druckmittel von dem Verbraucher 22 zu dem Vorratsbehälter 12 abfließen kann. Allerdings kann nur die Menge abfließen, die sich aus der Differenz zwischen der maximalen Durchströmmenge durch das Hauptventil (35 1/min) und der von der Pumpe 14 geförderten Menge (18 l/min) ergibt; in diesem Fall sind dies 17 l/min, wenn der Durchgang durch das Hauptventil 18 nicht gedrosselt wird.In order to lower a load acting on the consumer 22, ie to retract the hydraulic piston, the magnet 28 is in turn activated and thus the valve 16 is pushed into its through position -b-. In addition, the magnet 66 is activated so that the force applied by it, together with the force resulting from the pressure in the pilot line 60, stands opposite the spring 64, projects beyond it and shifts the pilot valve 20 into its opening -f-position. After the pressure at the main valve 18 on the right side can now be reduced through the opened pilot valve 20 to the reservoir 12, the pressure at the consumer 22 and through line 34 and the pilot line 50 on the other, left side of the main valve 18 applied pilot pressure that the main valve 18 assumes its through position -d-, in which pressure medium can flow from the consumer 22 to the reservoir 12. However, only the amount that flows from the difference between the maximum flow rate through the main valve (35 1 / min) and that from the pump can flow away 14 delivered quantity (18 l / min) results; in this case, this is 17 l / min if the passage through the main valve 18 is not throttled.

Lagesteuerung bei voreingestelltem Abstützdruck des Verbrauchers 22Position control with a preset support pressure of the consumer 22

Diese Steuerung bewirkt, daß der Verbraucher 22 von der an ihm angreifenden Last stets in eine Stellung bewegt wird, in der die Last nur noch mit einer vorbestimmten Kraft an ihm angreift. Beispielsweise soll mittels des Verbrauchers 22 ein Schneidwerk eines Mähdreschers soweit abgesenkt werden, bis es mit einer bestimmten Kraft auf dem Boden aufliegt.This control means that the consumer 22 is always moved by the load acting on it into a position in which the load only acts on it with a predetermined force. For example, a cutting mechanism of a combine harvester should be lowered by means of the consumer 22 until it rests on the ground with a certain force.

Zum Einleiten der Lagesteuerung ist es zunächst erforderlich, eine Beziehung zwischen dem Abstützdruck des Verbrauchers 22 bzw. des an ihm angehängten Geräts, der sich in der Leitung 34 aufbaut, und der Spannung an dem Magnet 66 herzustellen. Zuerst wird der Verbraucher 22 ganz eingefahren, um den Druck in der Leitung 34 soweit wie möglich abzubauen. Dann werden in diesem Einstellungsvorgang mittels eines weiteren nicht gezeigten Schalters die Magneten 28 und 66 bestromt, so daß das Ventil 16 seine Durchgangsstellung einnimmt und Druckmittel zu dem Verbraucher 22 fördert. Außerdem wird der Schalter 74 geschlossen, so daß Spannung an dem Magnet 66 angelegt wird, die jedoch zu Beginn des Einstellvorgangs die höchstmögliche Spannung/Stromstärke sein sollte. Obwohl an dem Verbraucher 22 ein noch geringer Druck ansteht, der auch in der Pilotleitung 60 herrscht, wird dieser zusammen mit der von dem Magnet 66 aufgebauten Kraft das Pilotventil 20 in seine Durchgangsstellung -f-verschieben. Somit nimmt auch das Hauptventil 18 seine Durchgangsstellung -d- ein. Das Potentiometer 68 wird nun kontinuierlich so lange verstellt und somit die Spannung an dem Magnet 66 reduziert, bis die Kraft des Magneten 66 zusammen mit der aus dem Pilotdruck in der Pilotleitung 60 geringer wird als die der Feder 64. Sobald dieser Fall eintritt, wird das Pilotventil 20 seine Sperrstellung -e- und darauffolgend das Hauptventil 18 seine Sperrstellung -c-einnehmen, und der Verbraucher 22 wird ausfahren. Die Stellung des Potentiometers 68, bei der sich der Verbraucher 22 bewegt, wird festgehalten, und zur Einstellung eines bestimmten Abstützdrucks wird das Potentiometer 68 um einen zu ermittelnden Betrag zurückverstellt.To initiate the position control, it is first necessary to establish a relationship between the support pressure of the consumer 22 or the device attached to it, which builds up in the line 34, and the voltage on the magnet 66. First, the consumer 22 is completely retracted in order to reduce the pressure in the line 34 as much as possible. Then, in this setting process, the magnets 28 and 66 are energized by means of a further switch, not shown, so that the valve 16 assumes its through position and conveys pressure medium to the consumer 22. In addition, the switch 74 is closed so that voltage is applied to the magnet 66, which should, however, be the highest possible voltage / current at the start of the adjustment process. Although there is still a low pressure at the consumer 22, which also exists in the pilot line 60, this will, together with the force built up by the magnet 66, move the pilot valve 20 into its through position -f-. The main valve 18 thus also assumes its through position -d-. The potentiometer 68 is now continuously adjusted so that the voltage on the magnet 66 is reduced until the force of the magnet 66 together with that from the pilot pressure in the pilot line 60 becomes lower than that of the spring 64. As soon as this occurs, the pilot valve 20 will assume its blocking position -e- and subsequently the main valve 18 its blocking position -c-, and the consumer 22 will extend . The position of the potentiometer 68, at which the consumer 22 is moving, is recorded, and the potentiometer 68 is adjusted back by an amount to be determined in order to set a specific support pressure.

Damit der Lagesteuerungsvorgang wirksam werden kann, muß der Verbraucher 22 ein bestimmtes Maß ausgefahren, d. h. die Last angehoben werden. Um die druckproportionale Lagesteuerung zu aktivieren, wird das Potentiometer 68 durch Schließen des Schalters 74 an den Magnet 66 angeschlossen und dieser mit einer bestimmten Spannung bestromt, die die voreingestellte, gegen die Feder 64 gerichtete Kraft erzeugt. Das Pilotventil 20 wird also vorgespannt. Außerdem wird der Magnet 28 bestromt, so daß das Ventil 16 Druckmittel in die Leitung 34 strömen läßt. Das Anlegen einer Spannung an die Magneten 28, 66 erfolgt für eine Zeit von z. B. 5 - 6 Sekunden; diese Zeitdauer kann auch mittels eines Zeitglieds in der Form eines Relais oder dergl. eingehalten werden. Ist der Druck an dem Verbraucher 22 zu hoch, senkt sich der Verbraucher 22 gemäß den vorherigen Ausführungen zu dem Einstellvorgang.In order for the position control process to take effect, the consumer 22 must extend a certain amount, i.e. H. the load will be lifted. In order to activate the pressure-proportional position control, the potentiometer 68 is connected to the magnet 66 by closing the switch 74 and this is energized with a certain voltage, which generates the preset force directed against the spring 64. The pilot valve 20 is therefore biased. In addition, the magnet 28 is energized so that the valve 16 allows pressure medium to flow into the line 34. The application of a voltage to the magnets 28, 66 takes place for a time of, for. B. 5-6 seconds; this period can also be maintained by means of a timer in the form of a relay or the like. If the pressure at the consumer 22 is too high, the consumer 22 lowers in accordance with the previous statements regarding the adjustment process.

Bei der Aktivierung der Auflagedrucksteuerung wird der Einstelldruck an dem Pilotventil 20 immer von der Ausgangsspannung bzw. dem Ausgangsstrom I bzw. U = 0 angefahren. Das bedeutet, daß als Fehler nur die Wiederholgenauigkeit eingeht und nicht die Hysterese. Mit diesem Hydrauliksystem 10 ist man somit in der Lage, nur durch Betätigen eines Schalters zum Bestromen der Magneten 28 und 66 den Druck im System und somit die Abstützkraft immer auf den gleichen Wert anzufahren.When the contact pressure control is activated, the set pressure at the pilot valve 20 is always approached by the output voltage or the output current I or U = 0. This means that only the repeat accuracy is taken into account and not the hysteresis. With this hydraulic system 10 one is thus in a position to operate the pressure in the magnets 28 and 66 only by actuating a switch System and thus the support force always to approach the same value.

Tritt aufgrund irgendeines Ereignisses an dem Verbraucher 22 und somit in der Leitung 34 eine Druckerhöhung in dem Druckmittel ein, die ausreichend groß ist, mit der Kraft des Magneten 66 die Kraft der Feder 64 zu übersteuern, so öffnet das Pilotventil 20 die Verbindung zu dem Vorratsbehälter 12, der Druck in der Pilotleitung 48 baut sich ab und der Druck in der Pilotleitung 50 verschiebt das Hauptventil 18 in seine Durchgangsstellung -d-, in der Druckmittel aus dem Verbraucher 22 in den Vorratsbehälter 12 abfließen kann. Das Druckmittel kann so lange abfließen, bis die Druckerhöhung in den Leitungen 34, 52 abgebaut ist und es der Feder 64 gelingt, den Durchgang durch das Pilotventil 20 zu schließen, was bewirkt, daß der Pilotdruck auf der rechten Seite des Hauptventils 18 ansteigt und dieses ebenfalls schließt. Dies bedeutet, daß der Verbraucher 22 die Last absenkt, bis sie sich mit der vorher bestimmten Kraft z. B. auf dem Boden abstützt. Es ist klar erkennbar, daß durch eine Änderung der Spannung an dem Magnet 66 der Zeit- bzw. Druckpunkt verändert werden kann, bei dem das Pilotventil 20 öffnet und den Steuervorgang einleitet.If, due to any event on the consumer 22 and thus in the line 34, there is a pressure increase in the pressure medium which is sufficiently large to override the force of the spring 64 with the force of the magnet 66, the pilot valve 20 opens the connection to the storage container 12, the pressure in the pilot line 48 decreases and the pressure in the pilot line 50 shifts the main valve 18 into its through position -d-, in which pressure medium can flow out of the consumer 22 into the reservoir 12. The pressure medium can flow off until the pressure increase in the lines 34, 52 is reduced and the spring 64 manages to close the passage through the pilot valve 20, which causes the pilot pressure on the right side of the main valve 18 to rise and this increases also closes. This means that the consumer 22 lowers the load until it z. B. is supported on the floor. It can be clearly seen that by changing the voltage on the magnet 66, the time or pressure point at which the pilot valve 20 opens and initiates the control process can be changed.

Soll die zuletzt beschriebene Lagesteuerung nicht in Betrieb sein, wird der Schalter 74 geöffnet, so daß über das Potentiometer 68 keine Spannung an dem Magnet 66 angelegt werden kann.If the position control described last is not to be in operation, the switch 74 is opened so that no voltage can be applied to the magnet 66 via the potentiometer 68.

Wie eingangs erwähnt wurde, kann die maximale Durchflußmenge durch das Hauptventil 18 manuell verändert werden, wozu beispielsweise eine Stellschraube 76 verwendet werden kann, wie sie in Figur 3 gezeigt ist. So kann die maximale Durchflußmenge von 35 l/min auf z. B. 30 l/min gesenkt werden. Dies hat zur Folge, daß während eines Senkvorgangs bei ungeändertem Zustrom von Druckmittel von der Pumpe 14 mit 18 l/min nur noch 12 l/min aus dem Verbraucher 22 abfließen können; die Senkgeschwindigkeit verlangsamt sich somit. Anstatt einer manuell betätigbaren Stellschraube 76 könnte auch eine elektrisch verstellbare Stellvorrichtung verwendet werden.As mentioned at the beginning, the maximum flow rate through the main valve 18 can be changed manually, for which purpose, for example, an adjusting screw 76 can be used, as shown in FIG. 3. So the maximum flow rate of 35 l / min to z. B. 30 l / min can be reduced. This has the consequence that during a lowering process with unchanged Inflow of pressure medium from the pump 14 at 18 l / min can only flow from the consumer 22 at 12 l / min; the lowering speed slows down. Instead of a manually operated adjusting screw 76, an electrically adjustable adjusting device could also be used.

Zum Ende dieser Beschreibung anhand der schematischen Darstellung nach Figur 1 sei darauf hingewiesen, daß sich die Angaben links und rechts oder gegenüberliegend und dergl. nur mit Blick auf Figur 1 der Zeichnung beziehen. Selbstverständlich können bei einer praktischen Ausgestaltung, wie sie z. B. in Figur 3 gezeigt ist, Federn, Magneten, Leitungen, Pilotleitung auch an anderen Stellen angreifen, solange dadurch die Funktion des erfindungsgemäßen Hydrauliksystems 10 beibehalten wird.At the end of this description with reference to the schematic representation according to FIG. 1, it should be pointed out that the information on the left and right or opposite and the like only relate to FIG. 1 of the drawing. Of course, with a practical design, as z. B. is shown in Figure 3, springs, magnets, lines, pilot line attack at other points, as long as the function of the hydraulic system 10 according to the invention is maintained.

In Figur 3 ist ein Ventilblock 78 gezeigt, in dem insbesondere die Magneten 28 und 66, das Ventil 16, das Hauptventil 18, das Pilotventil 20 und die Stellschraube 76 enthalten sind. In den Ventilblock 78 sind an den betreffenden Stellen die bisher verwendeten Bezugszeichen eingetragen. Eine detaillierte Erläuterung erübrigt sich, da die Verbindungen und die Funktion die gleichen sind, mit der Ausnahme, daß das Ventil 16 nicht direkt mittels des Magneten 28, sondern pilotgesteuert ist. Dies ist jedoch bereits aus TM-1352, Seiten 270-20-5 und 270-20-7 bis 270-20 9, Mar-86, von JOHN DEERE bekannt, so daß es auch hierzu keiner Erläuterung bedarf.A valve block 78 is shown in FIG. 3, which contains in particular the magnets 28 and 66, the valve 16, the main valve 18, the pilot valve 20 and the adjusting screw 76. The previously used reference numerals are entered in the valve block 78 at the relevant points. A detailed explanation is not necessary since the connections and the function are the same, with the exception that the valve 16 is not pilot-controlled directly by means of the magnet 28, but rather. However, this is already known from TM-1352, pages 270-20-5 and 270-20-7 to 270-20 9, Mar-86, by JOHN DEERE, so that no explanation is required here either.

Die Stellschraube 76 ist über eine Hülse 80 in ein Gehäuse 82 längsbeweglich eingeschraubt und wirkt einenends auf die Feder 46, die einen Schieber 84 des Hauptventils 18 gegen einen Sitz 86 preßt. Je weiter die Stellschraube 76 auf die Feder 46 zubewegt wird und diese entsprechend vorspannt, desto weniger kann der Schieber 84 bei vergleichbarem Druck ausweichen, so daß hiermit der Durchlaßquerschnitt verändert werden kann.The set screw 76 is screwed into a housing 82 so that it can move longitudinally and acts at one end on the spring 46, which presses a slide 84 of the main valve 18 against a seat 86. The further the set screw 76 is moved towards the spring 46 and preloads it accordingly, the less the slide 84 can with a comparable pressure dodge, so that the passage cross-section can be changed.

Durch die Verwendung eines Magneten 66 mit einer definierten Kennlinie (Hysterese), die durch eine einfache oder komplizierte mathematische Formel beschrieben werden kann, ist es möglich, die von dem Magnet 66 ausgehende Kraft in jeder seiner Stellungen und unter jeder seiner Spannungen bzw. Stromstärken genau zu errechnen. Da diese Kraft gleichzeitig den Steuerdruck darstellt, kann durch ihre Änderung der Zeitpunkt oder das Ausmaß des Öffnens und Schließens des Pilotventils 20 verändert werden.By using a magnet 66 with a defined characteristic (hysteresis), which can be described by a simple or complicated mathematical formula, it is possible to accurately measure the force emanating from the magnet 66 in any of its positions and under any of its voltages or currents to calculate. Since this force also represents the control pressure, changing the time or the extent to which the pilot valve 20 opens and closes can be changed.

Da das Pilotventil 20 unter voller Spannung/Stromstärke als sogenanntes Schwarz-Weiß-Ventil oder Offen-Zu-Ventil arbeitet und somit keine Zwischenstellungen zuläßt, eignet es sich hervorragend auch zu einer gegebenenfalls gewünschten manuellen Steuerung.Since the pilot valve 20 operates under full voltage / current as a so-called black-white valve or open-close valve and thus does not allow any intermediate positions, it is also excellently suitable for any manual control that may be desired.

Das erfindungsgemäße Hydrauliksystem eignet sich insbesondere zur Auflagedrucksteuerung des Verbrauchers, aber auch zu dessen Lagesteuerung.The hydraulic system according to the invention is particularly suitable for controlling the contact pressure of the consumer, but also for controlling its position.

Claims (7)

Hydrauliksystem (10) zur Steuerung einer einen Verbraucher bewegenden Kraft (22) mit einem pilotgesteuerten Hauptventil (18) und mit einem von einem Magneten (66) gesteuerten Pilotventil (20), wobei das Hauptventil (18) mittels des Pilotventils (20) in eine ein Druckmittel dem Verbraucher (22) zuführende und eine Druckmittel von diesem abführende Stellung schaltbar ist, dadurch gekennzeichnet, daß das Pilotventil (20) zusätzlich von dem an dem Verbraucher (22) anstehenden Druck beaufschlagt wird, der der Kraft des Magneten (66) entgegenwirkt.Hydraulic system (10) for controlling a force (22) which moves a consumer with a pilot-controlled main valve (18) and with a pilot valve (20) controlled by a magnet (66), the main valve (18) being connected by means of the pilot valve (20) a pressure medium feeding the consumer (22) and a pressure medium discharging from this position can be switched, characterized in that the pilot valve (20) is additionally acted upon by the pressure applied to the consumer (22), which counteracts the force of the magnet (66) . Hydrauliksystem nach Anspruch 1, dadurch gekennzeichnet, daß die an dem Magnet (66) anlegbare Spannung oder Stromstärke veränderbar ist.Hydraulic system according to Claim 1, characterized in that the voltage or current intensity which can be applied to the magnet (66) can be changed. Hydrauliksystem nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der Druck an dem Pilotventil (20) gegen die Kraft einer Feder (64) arbeitet.Hydraulic system according to claim 1 or 2, characterized in that the pressure on the pilot valve (20) works against the force of a spring (64). Hydrauliksystem nach Anspruch 1, 2 oder 3, dadurch gekennzeichnet, daß die Durchflußmenge des Hauptventils (18) veränderlich einstellbar ist.Hydraulic system according to claim 1, 2 or 3, characterized in that the flow rate of the main valve (18) is variably adjustable. Hydrauliksystem nach einem oder mehreren der vorherigen Ansprüche für die Lagesteuerung eines Geräts an einer landwirtschaftlich nutzbaren Maschine, insbesondere eines Erntevorsatzes an einer Erntemaschine.Hydraulic system according to one or more of the preceding claims for controlling the position of a device on an agricultural machine, in particular a header on a harvesting machine. Hydrauliksystem nach einem oder mehreren der vorherigen Ansprüche, dadurch gekennzeichnet, daß der Magnet (66) als Proportionalmagnet ausgebildet ist.Hydraulic system according to one or more of the preceding claims, characterized in that the magnet (66) is designed as a proportional magnet. Hydrauliksystem nach einem oder mehreren der vorherigen Ansprüche, dadurch gekennzeichnet, daß das Pilotventil (20) unter maximaler Spannung/Stromstärke als Schwarz-Weiß-Ventil wirkt.Hydraulic system according to one or more of the preceding claims, characterized in that the pilot valve (20) acts as a black and white valve under maximum voltage / current.
EP19920103245 1991-03-04 1992-02-26 Hydraulic system for controlling a loaddriven actuator Withdrawn EP0502411A3 (en)

Applications Claiming Priority (2)

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DE4106845 1991-03-04
DE4106845A DE4106845A1 (en) 1991-03-04 1991-03-04 HYDRAULIC SYSTEM FOR CONTROLLING A POWER MOVING A CONSUMER

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EP0502411A2 true EP0502411A2 (en) 1992-09-09
EP0502411A3 EP0502411A3 (en) 1993-02-03

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US5355773A (en) 1994-10-18
EP0502411A3 (en) 1993-02-03
DE4106845C2 (en) 1993-03-04

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