EP0205925B1 - Control device for hydraulic power equipment - Google Patents

Control device for hydraulic power equipment Download PDF

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Publication number
EP0205925B1
EP0205925B1 EP19860106864 EP86106864A EP0205925B1 EP 0205925 B1 EP0205925 B1 EP 0205925B1 EP 19860106864 EP19860106864 EP 19860106864 EP 86106864 A EP86106864 A EP 86106864A EP 0205925 B1 EP0205925 B1 EP 0205925B1
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EP
European Patent Office
Prior art keywords
control valve
pump
reference value
directional control
signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19860106864
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German (de)
French (fr)
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EP0205925A2 (en
EP0205925A3 (en
Inventor
Erich Dipl.-Ing. Eckhardt
Gerhard Dipl.-Ing. Nonnenmacher
Roman Ing. Romes
Franz Dipl.-Ing.(Fh) Schwede
Dieter Dipl.-Ing. Weigle
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Robert Bosch GmbH
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Robert Bosch GmbH
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Publication of EP0205925A2 publication Critical patent/EP0205925A2/en
Publication of EP0205925A3 publication Critical patent/EP0205925A3/en
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Publication of EP0205925B1 publication Critical patent/EP0205925B1/en
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B21/00Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
    • F15B21/08Servomotor systems incorporating electrically operated control means
    • F15B21/087Control strategy, e.g. with block diagram

Definitions

  • the invention relates to a control device for hydraulic machines according to the preamble of the main claim.
  • Such machines are usually controlled with the aid of directional control valves which, in addition to the neutral position and the maximum working position, have a fine control range in which only part of the pump delivery flow is directed to the consumer (working cylinder, hydraulic motor).
  • the pump is designed as a variable displacement pump. In such hydraulic circuits, throttle losses inevitably occur in the neutral position (circulating pressure at maximum flow rate) and in the fine control range (outflow of unused hydraulic fluid), which worsen the energy balance of the system.
  • control device with the characterizing features of the main claim has the advantage that it is very simple and allows to work with the least losses, d. that is, always adjust the pump so that it only provides the flow required by the consumers.
  • Figures 1-4 show control devices for hydraulic machines in a schematic representation.
  • 10 is an adjustable pump that draws pressure medium from a container 11 and displaces it into a delivery line 12.
  • the delivery line leads to a 4/3-way valve 13 with proportional behavior, which can be actuated by electromagnets 14, 15.
  • Two lines 16, 17 lead from the directional control valve to the pressure chambers 18, 19 of a double-acting working cylinder 20.
  • the actuator 22 of the adjustable pump 10 is actuated by two actuating pistons 23, 24 pressurized by pressure medium, of which the one with the smaller diameter 24 is pressurized via a line 25 connected to the delivery line.
  • a line 26 leads from the larger area piston 23 to a 3/3-way valve 27 with proportional behavior; it is actuated by an electromagnet 28 against the force of a control spring 29, which is supported on the actuating piston 23.
  • a line 30 leads from the directional control valve 27 to the delivery line 12 on the one hand, and a line 31 to the container 11 on the other hand.
  • the control of the directional control valves 13, 27 takes place via an adjusting device 32 designed as a setpoint device with an actuating lever 32 ', the angular position of which is converted into a proportional electrical signal, e.g. B. by a setpoint transmitter 33 designed as a rotary potentiometer.
  • the setpoint signals of the electrical setpoint generator thus formed lead via two lines 35, 36 to the electromagnets 14, 15 of the directional control valve 13, and from a summing point 38 and its amplifier 44 a line 39 leads to the electromagnet 28 of the directional control valve 27.
  • the control lever 32 'of the setpoint generator can be pivoted to both sides (- ⁇ ; + ⁇ ) and generates and sends corresponding setpoint signals to the directional control valves.
  • Power amplifiers 42, 43 which supply the magnetic current, are arranged in the lines 35, 36.
  • the pump 10 is driven by an internal combustion engine 48.
  • a position signal for the directional control valve 27 and thus for the pump 10 is also obtained with the electrical setpoint generator 33.
  • the speed of the internal combustion engine 48 is also included in the control circuit.
  • An electronic divider 52 is inserted in line 39 before summing point 50, and the speed of the internal combustion engine is entered via line 53 as a divisor.
  • the power amplifier 45 which supplies the magnetic current, is located in line 39 behind the divider element.
  • Figure 3 follows that of Figure 1, but with the difference that here a second cylinder 55 with associated 4/3-way proportional valve 156 is provided, and a second actuator 57 with lever 57 'and electrical Setpoint generator 58. Details are - so far not readily understandable - only taken into account insofar as a line 59 is led from the actuating device 57 to a second summing point 60 of the line 39, so that one also operates from the actuation of the second consumer 55 Signal is given to the directional control valve 27, whereby the pump flow is increased according to this additional need.
  • a combination of the last-mentioned exemplary embodiment with that according to FIG. 2 represents the exemplary embodiment according to FIG. 4, where the internal combustion engine 48 is again included in the control circuit. Their load state is compared in an electronic control unit 62 with a target value for the maximum load. Two lines 63, 64 lead from the control device 62 to electrical limiters 65 and 66, which can reduce the setpoint signals of the actuating devices 32, 57. When a predetermined limit is reached, e.g. B. the power limit of the internal combustion engine, the setpoints for the adjustment of the directional control valves 13, 56 are reduced according to a preprogrammed priority plan. The pump 10 is then reset as in the case of the previous exemplary embodiments.
  • a predetermined limit e.g. B. the power limit of the internal combustion engine
  • the device according to the invention also has the advantage that an energy saving is achieved with conventional directional valves, which otherwise can only be achieved with load-sensing technology. Furthermore, the device according to the invention also offers intervention options for higher-level signals that far exceed previously known limit load regulations or power regulations. As can be seen from the above, the device makes use of the consideration of electrically adjusting the control valves to avoid long rods and hydraulic lines; the same applies to the pump.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Valve Device For Special Equipments (AREA)

Description

Stand der TechnikState of the art

Die Erfindung geht aus von einer Steuereinrichtung für hydraulische Arbeitsmaschinen nach der Gattung des Hauptanspruchs. Die Steuerung derartiger Arbeitsmaschinen erfolgt überlicherweise mit Hilfe von Wegeventilen, die außer der Neutralstellung und der maximalen Arbeitsstellung einen Feinsteuerbereich haben, in dem nur ein Teil des Pumpenförderstroms zum Verbraucher (Arbeitszylinder, Hydromotor) geleitet wird. Die Pumpe ist dabei als Verstellpumpe ausgebildet. In solchen Hydraulikkreisen entstehen zwangsläufig in der Neutralstellung (Umlaufdruck bei maximalem Förderstrom) und im Feinsteuerbereich (Abströmen nicht genutzter Hydraulikflüssigkeit) Drosselverluste, die die Energiebilanz der Anlage verschlechtern.The invention relates to a control device for hydraulic machines according to the preamble of the main claim. Such machines are usually controlled with the aid of directional control valves which, in addition to the neutral position and the maximum working position, have a fine control range in which only part of the pump delivery flow is directed to the consumer (working cylinder, hydraulic motor). The pump is designed as a variable displacement pump. In such hydraulic circuits, throttle losses inevitably occur in the neutral position (circulating pressure at maximum flow rate) and in the fine control range (outflow of unused hydraulic fluid), which worsen the energy balance of the system.

Um solche Verluste zu vermeiden, ist es bekannt, sogenannte load-sensing-Systeme einzusetzen, die jedoch eine besondere Gattung von Regelventilen, Steuerleitungen und spezielle Pumpensteuerungen erfordern. Der Aufwand für die Leistungsbegrenzung ist hoch. Trotzdem sind solche Wegeventile nicht frei von Drosselverlusten, vor allem bei hohem Durchfluß.In order to avoid such losses, it is known to use so-called load-sensing systems, which, however, require a special type of control valve, control lines and special pump controls. The effort to limit performance is high. Nevertheless, such directional control valves are not free from throttling losses, especially at high flow rates.

Aus der DE-A-1 807 171 ist eine Einrichtung zur elektrohydraulischen Fernsteuerung bekanntgeworden, wie sie dem Oberbegriff des Anspruchs 1 entspricht. Auch diese bekannte Einrichtung ist noch nicht optimal ausgelegt, d. h. sie erwies sich als verbesserungsfähig.From DE-A-1 807 171 a device for electro-hydraulic remote control has become known, as it corresponds to the preamble of claim 1. This known device is also not yet optimally designed, ie it has proven to be capable of improvement.

Vorteile der ErfindungAdvantages of the invention

Die erfindungsgemäße Steuereinrichtung mit den kennzeichnenden Merkmalen des Hauptanspruchs hat demgegenüber den Vorteil, daß sie sehr einfach ist und es erlaubt, mit geringsten Verlusten zu arbeiten, d. h., die Pumpe stets so einzustellen, daß sie nur gerade den von den Verbrauchern benötigten Förderstrom erbringt.The control device according to the invention with the characterizing features of the main claim has the advantage that it is very simple and allows to work with the least losses, d. that is, always adjust the pump so that it only provides the flow required by the consumers.

Durch die in den Unteransprüchen aufgeführten Maßnahmen sind Weiterbildungen der im Hauptanspruch angegebenen Merkmale möglich.The measures listed in the subclaims allow further developments of the features specified in the main claim.

Zeichnungdrawing

Mehrere Ausführungsbeispiele der Erfindung sind in der Zeichnung dargestellt und in der nachfolgenden Beschreibung näher erläutert. Die Figuren 1-4 zeigen Steuereinrichtungen für hydraulische Arbeitsmaschinen in schematischer Darstellung.Several embodiments of the invention are shown in the drawing and explained in more detail in the following description. Figures 1-4 show control devices for hydraulic machines in a schematic representation.

Beschreibung der ErfindungsbeispieleDescription of the invention examples

In Figur 1 ist mit 10 eine verstellbare Pumpe bezeichnet, die Druckmittel aus einem Behälter 11 ansaugt und dieses in eine Förderleitung 12 verdrängt. Die Förderleitung führt zu einem 4/3-Wegeventil 13 mit Proportionalverhalten, das durch Elektromagnete 14, 15 betätigbar ist. Vom Wegeventil führen zwei Leitungen 16, 17 zu den Druckräumen 18, 19 eines doppeltwirkenden Arbeitszylinders 20.In FIG. 1, 10 is an adjustable pump that draws pressure medium from a container 11 and displaces it into a delivery line 12. The delivery line leads to a 4/3-way valve 13 with proportional behavior, which can be actuated by electromagnets 14, 15. Two lines 16, 17 lead from the directional control valve to the pressure chambers 18, 19 of a double-acting working cylinder 20.

Das Stellglied 22 der verstellbaren Pumpe 10 wird durch zwei druckmittelbeaufschlagte Stellkolben 23, 24 betätigt, von denen derjenige mit dem kleineren Durchmesser 24 über eine an die Förderleitung angeschlossene Leitung 25 mit Druck beaufschlagt wird. Vom flächengrößeren Kolben 23 führt eine Leitung 26 zu einem 3/3-Wegeventil 27 mit proportionalem Verhalten; es wird über einen Elektromagneten 28 entgegen der Kraft einer Regelfeder 29 betätigt, welche sich am Stellkolben 23 abstützt. Vom Wegeventil 27 führt einerseits eine Leitung 30 zur Förderleitung 12, andererseits eine Leitung 31 zum Behälter 11.The actuator 22 of the adjustable pump 10 is actuated by two actuating pistons 23, 24 pressurized by pressure medium, of which the one with the smaller diameter 24 is pressurized via a line 25 connected to the delivery line. A line 26 leads from the larger area piston 23 to a 3/3-way valve 27 with proportional behavior; it is actuated by an electromagnet 28 against the force of a control spring 29, which is supported on the actuating piston 23. A line 30 leads from the directional control valve 27 to the delivery line 12 on the one hand, and a line 31 to the container 11 on the other hand.

Die Ansteuerung der Wegeventile 13, 27 erfolgt über eine als Sollwertgeber ausgebildete Stelleinrichtung 32 mit Stellhebel 32', dessen Winkelstellung in ein proportionales elektrisches Signal umgeformt wird, z. B. durch einen als Drehpotentiometer ausgebildeten Sollwertgeber 33. Die so gebildeten Sollwertsignale des elektrischen Sollwertgebers führen über zwei Leitungen 35, 36 zu den Elektromagneten 14, 15 des Wegeventils 13, und von einem Summierpunkt 38 und dessen Verstärker 44 führt eine Leitung 39 zum Elektromagneten 28 des Wegeventils 27. Der Stellhebel 32' des Sollwertgebers ist nach beiden Seiten (- α ; + α ) schwenkbar und erzeugt und schickt entsprechende Sollwertsignale zu den Wegeventilen. In den Leitungen 35, 36 sind Leistungsverstärker 42, 43 angeordnet, die den Magnetstrom liefern.The control of the directional control valves 13, 27 takes place via an adjusting device 32 designed as a setpoint device with an actuating lever 32 ', the angular position of which is converted into a proportional electrical signal, e.g. B. by a setpoint transmitter 33 designed as a rotary potentiometer. The setpoint signals of the electrical setpoint generator thus formed lead via two lines 35, 36 to the electromagnets 14, 15 of the directional control valve 13, and from a summing point 38 and its amplifier 44 a line 39 leads to the electromagnet 28 of the directional control valve 27. The control lever 32 'of the setpoint generator can be pivoted to both sides (-α; + α) and generates and sends corresponding setpoint signals to the directional control valves. Power amplifiers 42, 43, which supply the magnetic current, are arranged in the lines 35, 36.

Die Pumpe 10 ist von einer Brennkraftmaschine 48 angetrieben. Mit dem elektrischen Sollwertgeber 33 wird zusätzlich zum Stellungssignal für das Wegeventil 13 auch ein Stellungesignal für das Wegeventil 27 und damit für die Pumpe 10 gewonnen.The pump 10 is driven by an internal combustion engine 48. In addition to the position signal for the directional control valve 13, a position signal for the directional control valve 27 and thus for the pump 10 is also obtained with the electrical setpoint generator 33.

In der Leitung 39 ist noch ein Summierpunkt 50 mit Verstärker 45 vorgesehen, dem ein Signal zugeführt wird, welches bewirkt, daß die Verstellung der Pumpe mittels des Stellhebels 32 gegenüber der Verstellung des Wegeventils 13 einen etwa konstanten Vorlauf besitzt, d. h. die Pumpe wird früher verstellt als das Wegeventil 13.In line 39 there is also a summing point 50 with amplifier 45, to which a signal is supplied which has the effect that the adjustment of the pump by means of the actuating lever 32 has an approximately constant advance relative to the adjustment of the directional valve 13, i. H. the pump is adjusted earlier than the directional control valve 13.

Beim Ausführungsbeispiel nach Figur 2 ist auch die Drehzahl der Brennkraftmaschine 48 mit in den Steuerkreis einbezogen. In die Leitung 39 ist vor dem Summierpunkt 50 ein elektronisches Divierdierglied 52 eingesetzt, dem über eine Leitung 53 als Divisor die Drehzahl der Brennkraftmaschine eingegeben wird. Außerdem befindet sich in der Leitung 39 hinter dem Divierdierglied wieder der Leistungsverstärker 45, der den Magnetstrom liefert. Mit dieser Anordnung erreicht man, daß die Verstellung der Pumpe proportional zur Verstellung der Wegeventile erfolgt, dividiert durch die Drehzahl der Brennkraftmaschine; d. h. der Förderstrom bleibt unabhängig von der Drehzahl, weil z. B. bei langsam drehender Brennkraftmaschine die Pumpe weiter ausgestellt wird als bei hoher Drehzahl.In the embodiment according to FIG. 2, the speed of the internal combustion engine 48 is also included in the control circuit. An electronic divider 52 is inserted in line 39 before summing point 50, and the speed of the internal combustion engine is entered via line 53 as a divisor. In addition, the power amplifier 45, which supplies the magnetic current, is located in line 39 behind the divider element. With this arrangement it is achieved that the adjustment of the pump is proportional to the adjustment of the directional valves, divided by the speed of the internal combustion engine; d. H. the flow rate remains independent of the speed, because z. B. with a slowly rotating internal combustion engine, the pump is turned off more than at high speed.

Das Ausführungsbeispiel nach Figur 3 schließt sich an dasjenige nach Figur 1 an, jedoch mit dem Unterschied, daß hier ein zweiter Arbeitszylinder 55 mit zugehörigem 4/3-Wege-Proportionalventi 156 vorgesehen ist, sowie eine zweite Stelleinrichtung 57 mit Stellhebel 57' und elektrischem Sollwertgeber 58. Auf Einzelheiten ist - so weit nicht ohne weiteres verständlich - nur insoweit eingegangen, als von der Stelleinrichtung 57 eine Leitung 59 zu einem zweiten Summierpunkt 60 der Leitung 39 geführt ist, so daß also auch von der Betätigung des zweiten Verbrauchers 55 her ein Signal zum Wegeventil 27 gegeben wird, wodurch der Pumpenförderstrom entsprechend diesem Zusatzbedarf erhöht wird.The embodiment of Figure 3 follows that of Figure 1, but with the difference that here a second cylinder 55 with associated 4/3-way proportional valve 156 is provided, and a second actuator 57 with lever 57 'and electrical Setpoint generator 58. Details are - so far not readily understandable - only taken into account insofar as a line 59 is led from the actuating device 57 to a second summing point 60 of the line 39, so that one also operates from the actuation of the second consumer 55 Signal is given to the directional control valve 27, whereby the pump flow is increased according to this additional need.

Eine Kombination des zuletztgenannten Ausführungsbeispiels mit demjenigen nach Figur 2 stellt das Ausführungsbeispiel nach Figur 4 dar, wo also wieder die Brennkraftmaschine 48 in den Steuerkreis einbezogen ist. Deren Lastzustand wird in einem elektronischen Steuergerät 62 mit einem Sollwert für die Maximallast verglichen. Vom Steuergerät 62 führen zwei Leitungen 63, 64 zu elektrischen Begrenzern 65 und 66, die die Sollwertsignale der Stelleinrichtungen 32, 57 verringern können. Beim Erreichen eines vorgegebenen Grenzwertes, z. B. der Leistungsgrenze der Brennkraftmaschine, werden nach einem vorprogrammierten Prioritätsplan die Sollwerte für die Verstellung der Wegeventile 13, 56 reduziert. Die Zurückstellung der Pumpe 10 erfolgt dann wie im Fall der vorherigen Ausführungsbeispiele.A combination of the last-mentioned exemplary embodiment with that according to FIG. 2 represents the exemplary embodiment according to FIG. 4, where the internal combustion engine 48 is again included in the control circuit. Their load state is compared in an electronic control unit 62 with a target value for the maximum load. Two lines 63, 64 lead from the control device 62 to electrical limiters 65 and 66, which can reduce the setpoint signals of the actuating devices 32, 57. When a predetermined limit is reached, e.g. B. the power limit of the internal combustion engine, the setpoints for the adjustment of the directional control valves 13, 56 are reduced according to a preprogrammed priority plan. The pump 10 is then reset as in the case of the previous exemplary embodiments.

Die erfindungsgemäße Einrichtung hat darüber hinaus noch den Vorteil, daß mit herkömmlichen Wegeventilen eine Energieeinsparung erzielt wird, die sonst allenfalls mit load-sensing-Technik erreicht werden kann. Des weiteren bietet die erfindungsgemäße Einrichtung auch Eingriffsmöglichkeiten für übergeordnete Signale, die bisher bekannte Grenzlastregelungen oder Leistungsregelungen weit übertreffen. Die Einrichtung macht sich, wie aus Obigem zu erkennen ist - die Überlegung zunutze, zur Vermeidung langer Gestänge und Hydraulikleitungen die Verstellung der Regelventile elektrisch vorzunehmen; dasselbe gilt auch für die Pumpe.The device according to the invention also has the advantage that an energy saving is achieved with conventional directional valves, which otherwise can only be achieved with load-sensing technology. Furthermore, the device according to the invention also offers intervention options for higher-level signals that far exceed previously known limit load regulations or power regulations. As can be seen from the above, the device makes use of the consideration of electrically adjusting the control valves to avoid long rods and hydraulic lines; the same applies to the pump.

Claims (6)

  1. Control device for hydraulic power machines with an adjustable pump (10) whose actuating piston (23, 24), acted upon by pressure, for its actuating element (22) can be driven via an electrically actuable control valve (27) and controls the compression means via an electrically actuable directional control valve (13, 56) to at least one load (20, 55), it being possible for both the directional control valve (13, 56) and the electrically actuable control valve (27) to be driven by at least one electrical reference value generator (32, 57) which can be actuated by an actuating lever (32', 57'), characterised in that in the line (39) leading from the reference value generator (32, 57) to the electromagnet (28) of the control valve (27) a summing point (50) is provided to which a signal is fed which causes the adjustment of the pump (10) to have an approximately constant advance with respect to the adjustment of the directional control valve (13, 56).
  2. Device according to Claim 1, characterised in that both the directional control valve (13, 56) and the control valve (27) are proportionally operating valves.
  3. Device according to one of Claims 1 or 2, characterised in that upon actuation of the electrical reference value generator (32, 57) a signal is fed to the control valve (27) associated with the pump movement, which signal is slightly larger than corresponds to the movement of the directional control valve (13, 56).
  4. Device according to one of Claims 1 to 3, characterised in that a speed of rotation signal is fed from the drive machine (48) driving the pump (10) to an electronic dividing element (52) which engages in the actuation circuit for the control valve (27).
  5. Device according to one of Claims 1 to 4, characterised in that a plurality of loads (20, 55) are supplied by the pump (10), to each of which loads an electrically actuable directional control valve (13, 56) is assigned.
  6. Device according to Claim 5, characterised in that in the lines leading from the reference value generator (32, 57) to the electromagnets (28, 14, 15) of the valves (27, 13, 56) electrical limiters (65, 66) are provided for reducing the reference value signals, the limiters (65, 66) connecting to an electronic control device (62) to which the load signal (PDM) of the drive machine (48) of the pump (10) and a reference value (Pref) for the maximum load of the drive machine (48) are fed.
EP19860106864 1985-06-19 1986-05-21 Control device for hydraulic power equipment Expired - Lifetime EP0205925B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3521815 1985-06-19
DE19853521815 DE3521815A1 (en) 1985-06-19 1985-06-19 CONTROL DEVICE FOR HYDRAULIC WORKING MACHINES

Publications (3)

Publication Number Publication Date
EP0205925A2 EP0205925A2 (en) 1986-12-30
EP0205925A3 EP0205925A3 (en) 1989-03-22
EP0205925B1 true EP0205925B1 (en) 1992-02-05

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EP19860106864 Expired - Lifetime EP0205925B1 (en) 1985-06-19 1986-05-21 Control device for hydraulic power equipment

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DE (2) DE3521815A1 (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2648584B1 (en) * 1989-06-16 1991-10-11 Rexroth Sigma METHOD AND SYSTEM FOR REGULATING THE MIDDLE CURRENT THROUGH A LOAD, AND ELECTRIC REMOTE CONTROL DEVICE OF THE MANIPULATOR TYPE USING THE SAME
FR2650635A1 (en) * 1989-08-07 1991-02-08 Rexroth Sigma Method for operating at least one variable output pump in an electrohydraulic plant, and electrohydraulic plant implementing this method
DE4129858A1 (en) * 1991-09-07 1993-03-11 Kiwa Maschinenfabrik Gmbh METHOD AND CIRCUIT FOR CONTROLLING, IN PARTICULAR A CRANE SYSTEM
DE19545657A1 (en) * 1995-12-07 1997-06-12 Rexroth Mannesmann Gmbh Hydraulic valve arrangement with a pressure-controlled directional valve
CN107917117A (en) * 2016-10-11 2018-04-17 张利 A kind of mechanical hydraulic servo cylinder

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1807171A1 (en) * 1968-11-06 1970-06-18 Bosch Gmbh Robert Device for the electro-hydraulic remote control of hydraulic directional control valves
GB1385099A (en) * 1972-08-25 1975-02-26 Coventry Climax Eng Ltd Industrial fork lift truck
SE435750B (en) * 1979-06-15 1984-10-15 Akermans Verkstad Ab DEVICE FOR RESTRICTING FROM A HYDRAULIC DEVICE WITHOUT POWER
JPS5899501A (en) * 1981-12-03 1983-06-13 Ishikawajima Harima Heavy Ind Co Ltd Hydraulic pump control circuit

Also Published As

Publication number Publication date
EP0205925A2 (en) 1986-12-30
DE3683805D1 (en) 1992-03-19
EP0205925A3 (en) 1989-03-22
DE3521815A1 (en) 1987-01-02

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