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EP0615024A2 - Load-independent speed control of hydraulic actuators for construction machines - Google Patents

Load-independent speed control of hydraulic actuators for construction machines Download PDF

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Publication number
EP0615024A2
EP0615024A2 EP94101011A EP94101011A EP0615024A2 EP 0615024 A2 EP0615024 A2 EP 0615024A2 EP 94101011 A EP94101011 A EP 94101011A EP 94101011 A EP94101011 A EP 94101011A EP 0615024 A2 EP0615024 A2 EP 0615024A2
Authority
EP
European Patent Office
Prior art keywords
pressure
control
line
load
orifice
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.)
Granted
Application number
EP94101011A
Other languages
German (de)
French (fr)
Other versions
EP0615024A3 (en
EP0615024B1 (en
Inventor
Walter Kolb
Gustav Leidinger
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.)
CNH Industrial Baumaschinen GmbH
Original Assignee
O&K Orenstein and Koppel GmbH
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 O&K Orenstein and Koppel GmbH filed Critical O&K Orenstein and Koppel GmbH
Publication of EP0615024A2 publication Critical patent/EP0615024A2/en
Publication of EP0615024A3 publication Critical patent/EP0615024A3/en
Application granted granted Critical
Publication of EP0615024B1 publication Critical patent/EP0615024B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2221—Control of flow rate; Load sensing arrangements
    • E02F9/2232—Control of flow rate; Load sensing arrangements using one or more variable displacement pumps
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2203—Arrangements for controlling the attitude of actuators, e.g. speed, floating function
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2221—Control of flow rate; Load sensing arrangements
    • E02F9/2225—Control of flow rate; Load sensing arrangements using pressure-compensating valves
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2278—Hydraulic circuits
    • E02F9/2296—Systems with a variable displacement pump
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/04—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
    • F15B11/044—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed by means in the return line, i.e. "meter out"
    • F15B11/0445—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed by means in the return line, i.e. "meter out" with counterbalance valves, e.g. to prevent overrunning or for braking
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20546—Type of pump variable capacity
    • F15B2211/20553—Type of pump variable capacity with pilot circuit, e.g. for controlling a swash plate
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30525—Directional control valves, e.g. 4/3-directional control valve
    • F15B2211/3053—In combination with a pressure compensating valve
    • F15B2211/30535—In combination with a pressure compensating valve the pressure compensating valve is arranged between pressure source and directional control valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30525—Directional control valves, e.g. 4/3-directional control valve
    • F15B2211/3053—In combination with a pressure compensating valve
    • F15B2211/3055—In combination with a pressure compensating valve the pressure compensating valve is arranged between directional control valve and 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
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/3056—Assemblies of multiple valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/31—Directional control characterised by the positions of the valve element
    • F15B2211/3144—Directional control characterised by the positions of the valve element the positions being continuously variable, e.g. as realised by proportional valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/35—Directional control combined with flow control
    • F15B2211/351—Flow control by regulating means in feed line, i.e. meter-in control
    • 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
    • F15B2211/35—Directional control combined with flow control
    • F15B2211/353—Flow control by regulating means in return line, i.e. meter-out control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/605—Load sensing circuits
    • F15B2211/6051—Load sensing circuits having valve means between output member and the load sensing circuit
    • F15B2211/6054—Load sensing circuits having valve means between output member and the load sensing circuit using shuttle valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/75—Control of speed of the output member

Definitions

  • the invention relates to a load pressure-independent control of the speed of hydraulic control elements, such as cylinders, hydraulic motors or the like., With premature loads on construction machines, such as wheel loaders, excavators or the like. With at least one pressure medium from a tank-delivering pump with a variable delivery volume by a controller and at least one control slide with at least one control piston for actuating the control element or elements.
  • the conventional hydraulic systems When pulling, i.e. leading load, the conventional hydraulic systems are only able to influence the speed of the adjusting element, such as cylinders, hydraulic motors or the like, by means of a throttle effect. Since the oil flow flowing through the throttle is dependent on the load pressure, the adjustment speed is therefore also dependent on the load pressure.
  • the adjusting element such as cylinders, hydraulic motors or the like
  • the term 'independent of the load pressure' refers to the adjustment speed of the individual control elements, such as in particular cylinders, which is independent of the load pressure which acts on the control elements by external forces.
  • This independence is achieved by a so-called load-sensing system, which essentially consists of a central, hydraulically adjustable variable displacement pump with a hydraulically actuated adjusting element for regulating the delivery pressure and a hydraulic pressure signaling device for transmitting the load pressure applied to a controlled working cylinder or another adjusting element to the adjusting element the variable displacement pump.
  • This pressure signaling device thus transmits the pending load pressure to the actuator of the variable pump, which acts on the corresponding control slide with a delivery pressure which is a design-dependent constant differential pressure above the pending load pressure. If several working cylinders or other control elements are actuated at the same time, the highest load pressure is reported to the control element of the variable pump via corresponding shuttle valves in the branches of the pressure signaling device.
  • variable displacement pump Due to the control of the corresponding control spool with a constant differential pressure above the load pressure applied to the working cylinder or other actuating elements, that of the working cylinder or the another actuating device operated tool moves at a substantially constant, depending on the position of the spool, which facilitates the operation of such tools.
  • the variable displacement pump due to the load-sensing system, only delivers the flow rate assigned to the respective working cylinder or control element, as a result of which no flow rate-dependent losses occur and the efficiency of the hydraulic drive device is increased.
  • the object of the invention is to be able to control the speed of a pulling load independently of the load pressure.
  • the pressure compensator is used in the connecting line of the space of the control element to the control slide, in particular to the associated control piston, that the return area of the associated control piston is designed as a differential pressure orifice, and that the pressure signal of the oil flow before it passes through the Differential pressure orifice can be brought about via a line to the side of the pressure compensator facing away from the spring chamber.
  • the goal is also achieved in that the pressure compensator is inserted into the line between the outlet of the slide, in particular the associated control piston, and the tank, that the return area of the associated control piston is designed as a differential pressure orifice, and that the pressure message of the oil flow before it passes through the differential pressure orifice via a line to the side of the pressure compensator facing away from the spring chamber.
  • the pressure compensator In the connecting line from the space of the actuator to the spool, the pressure compensator is used so that it performs its intended function when the oil flow flows from this space to the spool.
  • the return opening in the associated control piston which up to now has been designed as a free passage or, depending on requirements, also as a throttle opening, is designed here as a differential pressure orifice according to the desired flow characteristics.
  • the pressure messages for the pressure compensator are such that the pressure in the line to the differential pressure orifice is directed to the side of the pressure compensator facing away from the spring chamber.
  • FIG. 1 now shows the lowering of the working device of a wheel loader, not shown, in this example, as a bucket 1, under the dead weight G.
  • a pressure resulting from the weight G and possibly the payload of the bucket 1 builds up.
  • the control piston 5 arranged in the control slide 4 in the direction of the position shown, oil flows out via the lines 6 and 7 and further via a differential pressure orifice 8 into the tank 9.
  • the pressure of the line 7 is directed to the spring-facing side 10 of the pressure compensator 11 provided between the line 6 and the control slide 4.
  • the pressure in the control line 12 is passed through a shuttle valve 13 into the spring chamber 14 of the pressure compensator 11.
  • the shuttle valve 13 blocks the connection from the load pressure signaling line 15, which is only acted upon by the suction pressure and which taps the pressure through the differential pressure orifice 8 'which is common in load-sensing systems.
  • Different supply lines to further control pistons 21, 22 are designated by 20.
  • the pressure compensator 11 reduces the pressure in the line 6 of the cover-side space 2 to a value which is reduced so far in accordance with its spring force that a constant pressure drop which is analogous to the spring force is set at the differential pressure orifice 8.
  • the oil flow passing through the differential pressure orifice 8 and thus the lowering speed of the blade 1 is independent of the load pressure and only dependent on the opening cross section of the differential pressure orifice 8, which is predetermined by the respective position of the associated control piston 5.
  • further control pistons 21 and 22 can be provided in the control valve 4.
  • control pistons 21, 22 as well as the control piston 5 can be used in the usual way in load-sensing systems with pressure compensators, not shown here, for the mutually unaffected simultaneous actuation of pushing Loads in the lines 20 from the pump 17 to the respective control piston 5, 21, 22 can be equipped.
  • a corresponding pressure compensator - not shown here for the sake of a better overview - can also be assigned to the control pistons 21 and / or 22 if pulling loads are also to be controlled here independently of the load pressure.
  • F ground pressure
  • the delivery flow is metered by pressure into the annular space 18 of the hydraulic cylinder 3, it being necessary to ensure that the oil displaced from the cover-side space 2 of the cylinder 3 is not throttled by the pressure compensator 11, because this is as small as possible Flow resistance should flow into the tank 9.
  • the pressure of the oil flow directed to the adjustment of the cylinder 3 in the annular space 18 is passed via the load pressure signaling line 15 and the shuttle valve 13 into the spring chamber 14 of the pressure compensator 11.
  • the shuttle valve 13 blocks the connection of the control line 12, which is only pressurized in the tank 9.
  • FIG. 3 shows the lifting of the bucket 1 which may contain a payload, the same components again being provided with the same reference numerals.
  • the delivery flow is metered by pressure into the cover-side space 2 of the cylinder 3, it being necessary to ensure that the inflowing oil is not throttled by the pressure compensator 11.
  • the pressure to adjust the cylinder 3 in the room 2 oil flow is passed via the load pressure signal line 15 and the shuttle valve 13 into the spring chamber 14 of the pressure compensator 11.
  • the shuttle valve 13 blocks the connection from the control line 12 which is only acted upon by the pressure in the tank 9.
  • the pressure of the cover-side space 2 of the cylinder 3 acts, which is equal to that in the load pressure reporting line 15 .
  • the same hydraulic pressure thus acts on both end faces of the piston 23 of the pressure compensator 11. For this reason, the piston 23 of the pressure compensator 11 is guided into the end position with the spring force, the passage from the line 7 to the line 6 being released.
  • FIGS. 4 to 6 show equivalent controls according to FIGS. 1 to 3.
  • the pressure compensator 11 is inserted between the outlet 25 of the slide 4 and the tank 9, functionally the same conditions and also in all three operating states in the corresponding lines analog pressures prevail, which is described as follows:
  • FIG. 4 shows, analogously to FIG. 1, the lowering of the working device designed as a blade 1.
  • a pressure builds up resulting from the weight G and possibly the payload of the blade 1.
  • oil flows out into the tank 9 via the lines 6, 26.
  • the pressure of line 6 is passed via line 29 to the spring-side 27 of the pressure compensator 11 provided between the outlet 25 of the control slide 4 and the tank 9.
  • the pressure in line 26 is passed via a shuttle valve 13 into the spring chamber 14 of the pressure compensator 11.
  • the shuttle valve 13 blocks the connection from the load pressure signaling line 15, which is only acted upon by the suction pressure and which taps the pressure through the differential pressure orifice 8 'which is common in load-sensing systems.
  • An additional quantity of oil required to fill the annular space 18 of the cylinder 3 in addition to the flow rate of the pump 17 controlled by the regulator 16 is supplemented by a suction valve 19 which is arranged in the pressure medium supply line 20 '.
  • the pressure compensator 11 reduces the pressure in the line 6 of the cover-side space 2 of the cylinder 3 to a value so far reduced in accordance with its spring force that a constant pressure drop which is analogous to the spring force is established at the differential pressure orifice 8.
  • the oil flow passing through the differential pressure orifice 8 and thus the lowering speed of the blade 1 is thus independent of the load pressure and only dependent on the opening cross section of the differential pressure orifice 8, which is predetermined by the respective position of the control piston 5.
  • further control pistons 21 and 22 can be provided in the control valve 4.
  • control pistons 21, 22 and also the control piston 5 can, in the usual way in load-sensing systems, with pressure compensators, not shown here, for the mutually unaffected simultaneous actuation of pressing loads in the lines 20 from the pump 17 to the respective control piston 5, 21 , 22 be equipped.
  • a corresponding pressure compensator - not shown here for the sake of a better overview - can also be assigned to the control piston 21 and / or 22, provided that pulling loads are to be controlled here independently of the load pressure.
  • the shuttle valve 13 blocks the connection of the line 26 which is only pressurized in the tank 9
  • the only effect on page 27 is the low dynamic pressure in the line 29 of the oil flowing out of the cover-side space 2 into the tank 9. Therefore, the piston 23 of the pressure compensator 11 is guided into the end position, the passage from the line 26 to the tank 9 being released without the pressure compensator 11 taking effect.
  • FIG. 6 shows the lifting of the bucket 1, with the same components again being provided with the same reference symbols.
  • FIG. 7 can be seen analogously to FIG. 1, with the actuator cylinder being replaced by a hydraulic motor 28 in this example.
  • the pulling load can be predetermined here by a torque T generated by external influences, which causes the hydraulic motor 28 to become the pump, so that it pumps 6 pressure oil into the line.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Operation Control Of Excavators (AREA)

Abstract

Load-independent speed control of hydraulic actuators in the case of leading loads, in particular for construction machines, is proposed, comprising at least one pump, at least one control spool, and at least one pressure balance. The pressure balance is inserted either in the connecting line of the space, to be emptied in a controlled manner, of the actuator, designed as hydraulic cylinder, to the control spool or else in the line between the outlet of the control spool and the tank. The return area of the associated control piston is designed as a differential-pressure orifice. The pressure indication before the passage of the oil flow through the differential-pressure orifice to the pressure balance can be brought about via a line to the side of the pressure balance remote from the spring chamber. <IMAGE>

Description

Die Erfindung betrifft eine lastdruckunabhängige Steuerung der Geschwindigkeit von hydraulischen Stellelementen, wie Zylindern, Hydromotoren oder dgl., bei vorauseilenden Lasten an Baumaschinen, wie beispielsweise Radladern, Baggern oder dgl., mit mindestens einer Druckmittel aus einem Tank fördernden Pumpe mit durch einen Regler veränderlichem Fördervolumen und mindestens einem Steuerschieber mit mindestens einem Steuerkolben zur Betätigung des bzw. der Stellelemente.The invention relates to a load pressure-independent control of the speed of hydraulic control elements, such as cylinders, hydraulic motors or the like., With premature loads on construction machines, such as wheel loaders, excavators or the like. With at least one pressure medium from a tank-delivering pump with a variable delivery volume by a controller and at least one control slide with at least one control piston for actuating the control element or elements.

Bei ziehender, d.h. voreilender Last sind die gebräuchlichen Hydrauliksysteme lediglich imstande, die Geschwindigkeit des Verstellelementes, wie Zylinder, Hydromotoren oder ähnliche, über eine Drosselwirkung zu beeinflussen. Da der über die Drossel fließende Ölstrom abhängig vom Lastdruck ist, ist demnach auch die Verstellgeschwindigkeit lastdruckabhängig.When pulling, i.e. leading load, the conventional hydraulic systems are only able to influence the speed of the adjusting element, such as cylinders, hydraulic motors or the like, by means of a throttle effect. Since the oil flow flowing through the throttle is dependent on the load pressure, the adjustment speed is therefore also dependent on the load pressure.

Der Begriff 'lastdruckunabhängig' bezieht sich auf die Verstellgeschwindigkeit der einzelnen Stellelemente, wie insbesondere Zylinder, die unabhängig von dem Lastdruck ist, der durch äußere Kräfte auf die Stellorgane wirkt. Diese Unabhängigkeit wird durch ein sogenanntes Load-Sensing-System erzielt, das im wesentlichen eine zentrale hydraulisch verstellbare Verstellpumpe mit einem hydraulisch betätigbaren Verstellorgan zur Regelung des Förderdrucks und eine hydraulische Druckmeldeeinrichtung zur Übertragung des an einem angesteuerten Arbeitszylinder oder einem anderen Stellelement anstehenden Lastdruckes an das Stellorgan der Verstellpumpe umfaßt. Diese Druckmeldeeinrichtung übermittelt so den anstehenden Lastdruck an das Stellorgan der Verstellpumpe, die den entsprechenden Steuerschieber mit einem Förderdruck beaufschlagt, der um einen auslegungsbedingten konstanten Differenzdruck über dem anstehenden Lastdruck liegt. Werden mehrere Arbeitszylinder oder andere Stellelemente gleichzeitig angesteuert, so wird über entsprechende Wechselventile in den Verzweigungen der Druckmeldeeinrichtung der höchste anstehende Lastdruck dem Stellorgan der Verstellpumpe gemeldet.The term 'independent of the load pressure' refers to the adjustment speed of the individual control elements, such as in particular cylinders, which is independent of the load pressure which acts on the control elements by external forces. This independence is achieved by a so-called load-sensing system, which essentially consists of a central, hydraulically adjustable variable displacement pump with a hydraulically actuated adjusting element for regulating the delivery pressure and a hydraulic pressure signaling device for transmitting the load pressure applied to a controlled working cylinder or another adjusting element to the adjusting element the variable displacement pump. This pressure signaling device thus transmits the pending load pressure to the actuator of the variable pump, which acts on the corresponding control slide with a delivery pressure which is a design-dependent constant differential pressure above the pending load pressure. If several working cylinders or other control elements are actuated at the same time, the highest load pressure is reported to the control element of the variable pump via corresponding shuttle valves in the branches of the pressure signaling device.

Aufgrund der Ansteuerung des entsprechenden Steuerschiebers mit einem konstanten Differenzdruck über dem am Arbeitszylinder oder anderen Stellelementen anstehenden Lastdruck wird das von dem Arbeitszylinder bzw. dem anderen Stellelement betätigte Arbeitsgerät mit einer im wesentlichen gleichbleibenden, von der Stellung des Steuerschiebers abhängigen Geschwindigkeit bewegt, was die Bedienung solcher Arbeitsgeräte erleichtert. Darüber hinaus liefert die Verstellpumpe aufgrund des Load-Sensing-Systems nur den dem jeweiligen Arbeitszylinder bzw. Stellelement zugemessenen Förderstrom, wodurch keine förderstromabhängigen Verluste auftreten und der Wirkungsgrad der hydraulischen Antriebsvorrichtung erhöht wird.Due to the control of the corresponding control spool with a constant differential pressure above the load pressure applied to the working cylinder or other actuating elements, that of the working cylinder or the another actuating device operated tool moves at a substantially constant, depending on the position of the spool, which facilitates the operation of such tools. In addition, due to the load-sensing system, the variable displacement pump only delivers the flow rate assigned to the respective working cylinder or control element, as a result of which no flow rate-dependent losses occur and the efficiency of the hydraulic drive device is increased.

Bei lastdruckunabhängigen Hydrauliksystemen ist bei drückender Last, d.h. bei einer durch den Förderstrom der Pumpe zu bewegenden Last die Geschwindigkeit unabhängig vom Lastdruck. Um so nachteiliger wird es empfunden, wenn unter Beibehaltung der Bewegungsrichtung beim Wechsel der Lastrichtung die Geschwindigkeit nicht mehr lastdruckunabhängig, sondern nur mehr nach der Drosselcharakteristik kontrolliert werden kann.With hydraulic systems that are independent of load pressure, for a load to be moved by the pump flow, the speed is independent of the load pressure. It is all the more disadvantageous if, while maintaining the direction of movement when changing the load direction, the speed can no longer be controlled independently of the load pressure, but only according to the throttle characteristic.

Der internationalen Patentanmeldung WO 92/15799 ist ein Load-Sensing-System zu entnehmen, das ein Ventil beinhaltet, das den Durchfluß steuernde Einrichtungen aufweist und das zwischen den den Durchfluß erfassenden Einrichtungen und sogenannten Absorptionseinrichtungen angeordnet ist. Tenor dieser internationalen Patentanmeldung ist jedoch nicht die lastdruckunabhängige Steuerung der Geschwindigkeit von hydraulischen Stellelementen, wie Zylindern, Hydromotoren oder dgl., bei vorauseilenden Lasten, sondern die Kontrolle und Energierückgewinnung bei Beaufschlagung von Zylindern, wobei der hier sich im System aufbauende Druck über dieses Ventil den Absorptionseinrichtungen zugeführt wird.International patent application WO 92/15799 shows a load-sensing system which contains a valve which has flow control devices and which is arranged between the flow detection devices and so-called absorption devices. However, the tenor of this international patent application is not the load pressure-independent control of the speed of hydraulic actuating elements, such as cylinders, hydraulic motors or the like, with leading loads, but the control and energy recovery when cylinders are acted on, the pressure building up in the system via this valve Absorption devices is supplied.

Ziel des Erfindungsgegenstandes ist es, die Geschwindigkeit auch einer ziehenden Last kontrolliert lastdruckunabhängig steuern zu können.The object of the invention is to be able to control the speed of a pulling load independently of the load pressure.

Dieses Ziel wird erfindungsgemäß dadurch erreicht, daß die Druckwaage in die Verbindungsleitung des Raumes des Stellelementes zum Steuerschieber, insbesondere zum zugehörigen Steuerkolben, eingesetzt ist, daß der Rücklaufbereich des zugehörigen Steuerkolbens als Differenzdruckblende ausgebildet ist, und daß die Druckmeldung des Ölstromes vor dem Durchtritt durch die Differenzdruckblende über eine Leitung auf die der Federkammer abgewandte Seite der Druckwaage herbeiführbar ist.This goal is achieved in that the pressure compensator is used in the connecting line of the space of the control element to the control slide, in particular to the associated control piston, that the return area of the associated control piston is designed as a differential pressure orifice, and that the pressure signal of the oil flow before it passes through the Differential pressure orifice can be brought about via a line to the side of the pressure compensator facing away from the spring chamber.

Gemäß nebengeordnetem Hauptpatentanspruch wird das Ziel darüber hinaus auch dadurch erreicht, daß die Druckwaage in die Leitung zwischen dem Ausgang des Schiebers, insbesondere des zugehörigen Steuerkolbens, und dem Tank eingesetzt ist, daß der Rücklaufbereich des zugehörigen Steuerkolbens als Differenzdruckblende ausgebildet ist, und daß die Druckmeldung des Ölstromes vor dem Durchtritt durch die Differenzdruckblende über eine Leitung auf die der Federkammer abgewandte Seite der Druckwaage herbeiführbar ist.According to the secondary main patent claim, the goal is also achieved in that the pressure compensator is inserted into the line between the outlet of the slide, in particular the associated control piston, and the tank, that the return area of the associated control piston is designed as a differential pressure orifice, and that the pressure message of the oil flow before it passes through the differential pressure orifice via a line to the side of the pressure compensator facing away from the spring chamber.

Weiterbildungen der nebengeordneten Hauptpatentansprüche sind den zugehörigen Unteransprüchen zu entnehmen.Further developments of the subordinate main patent claims can be found in the associated subclaims.

Das aus dem St.d.T. bekannte Hydrauliksystem wird nun durch die erfindungsgemäße Funktion des kontrollierten lastdruckunabhängigen Absenkens bei vorauseilenden Lasten erweitert. Diese kann sinngemäß und ohne gegenseitige Beeinflussung nicht nur bei einem, sondern auch bei mehreren Stellelementen angewandt werden, die z.B. über Steuerkolben betätigt werden.The from the St.d.T. Known hydraulic system is now expanded by the function according to the invention of the controlled lowering of the load pressure independent of leading loads. This can be used analogously and without mutual interference not only with one, but also with several control elements that e.g. are actuated via control pistons.

In die Verbindungsleitung des Raumes des Stellorgans zum Steuerschieber wird die Druckwaage so eingesetzt, daß sie ihre bestimmungsgemäße Funktion dann ausübt, wenn der Ölstrom von diesem Raum zum Steuerschieber fließt. Die Rücklauföffnung im zugehörigen Steuerkolben, die bislang als freier Durchgang oder je nach Erfordernissen auch als Drosselöffnung ausgeführt ist, wird hier nach der gewünschten Durchflußcharakteristik als Differenzdruckblende ausgebildet. Die Druckmeldungen zur Druckwaage erfolgen so, daß der Druck in der Leitung zur Differenzdruckblende auf die der Federkammer abgewandte Seite der Druckwaage geleitet wird. Hingegen wird über das Wechselventil der jeweils höhere Druck zwischen der Steuerleitung, welche den Druck nach der Differenzdruckblende abgreift und der bei Load-Sensing-Systemen bisheriger Bauart schon vorhandenen Lastdruckmeldeleitung über eine Steuerleitung in die Federkammer der Druckwaage gemeldet.In the connecting line from the space of the actuator to the spool, the pressure compensator is used so that it performs its intended function when the oil flow flows from this space to the spool. The return opening in the associated control piston, which up to now has been designed as a free passage or, depending on requirements, also as a throttle opening, is designed here as a differential pressure orifice according to the desired flow characteristics. The pressure messages for the pressure compensator are such that the pressure in the line to the differential pressure orifice is directed to the side of the pressure compensator facing away from the spring chamber. On the other hand, the higher pressure between the control line, which taps the pressure after the differential pressure orifice, and the load pressure signaling line already present in load-sensing systems of the previous type is reported via a control line into the spring chamber of the pressure compensator via the shuttle valve.

Der wesentliche Unterschied zwischen den nebengeordneten Patentansprüchen besteht darin, daß beim Patentanspruch 1 die Druckwaage in die Verbindungsleitung des kontrolliert zu entleerenden Raumes des Stellelementes zum Steuerschieber eingesetzt wird, während beim Patentanspruch 2 die Druckwaage zwischen dem Ausgang des Schiebers und dem Tank eingesetzt wird.The main difference between the independent claims is that in claim 1, the pressure compensator in the connecting line of the controlled space to be emptied of the control element is used for the control slide, while in claim 2 the pressure compensator is used between the outlet of the slide and the tank.

In sämtlichen Betriebszuständen herrschen in den entsprechenden Leitungen jedoch analoge Drücke.However, analog pressures prevail in the corresponding lines in all operating states.

Die Erfindung ist in der Zeichnung dargestellt und wird wie folgt beschrieben. Es zeigen:

Figur 1 -
Steuerung im Betriebszustand Absenken der Arbeitsvorrichtung unter deren Eigengewicht gem. Anspruch 1
Figur 2 -
Steuerung im Betriebszustand Aufpressen der Arbeitsvorrichtung, d.h. Absenken gegen eine das Eigengewicht übersteigende Gegenkraft gem. Anspruch 1
Figur 3 -
Steuerung im Betriebszustand Anheben der Arbeitsvorrichtung gem. Anspruch 1
Figur 4 -
Steuerung im Betriebszustand Absenken der Arbeitsvorrichtung unter deren Eigengewicht gem. Anspruch 2
Figur 5 -
Steuerung im Betriebszustand Aufpressen der Arbeitsvorrichtung, d.h. Absenken gegen eine das Eigengewicht übersteigende Gegenkraft gem. Anspruch 2
Figur 6 -
Steuerung im Betriebszustand Anheben der Arbeitsvorrichtung gem. Anspruch 2
Figur 7 -
Steuerung einer alternativen Arbeitsvorrichtung gem. Figur 1

Der in Figur 1 gezeigte Betriebszustand ist derjenige, bei dem erfindungsgemäß das Absenken unter vorauseilender Last kontrolliert lastdruckunabhängig gesteuert werden soll. Bei den in den Figuren 2 und 3 dargelegten Betriebszuständen wird nachgewiesen, daß aus der erfindungsgemäßen Anordnung keine Beeinträchtigung ihrer Funktion aufgrund des Vorhandenseinseiner Druckwaage resultiert.The invention is illustrated in the drawing and is described as follows. Show it:
Figure 1 -
Control in the operating state lowering the working device under its own weight acc. Claim 1
Figure 2 -
Control in the operating state pressing on the working device, ie lowering against a counterforce exceeding the dead weight acc. Claim 1
Figure 3 -
Control in operating state lifting the working device acc. Claim 1
Figure 4 -
Control in the operating state lowering the working device under its own weight acc. Claim 2
Figure 5 -
Control in the operating state pressing on the working device, ie lowering against a counterforce exceeding the dead weight acc. Claim 2
Figure 6 -
Control in operating state lifting the working device acc. Claim 2
Figure 7 -
Control of an alternative working device acc. Figure 1

The operating state shown in FIG. 1 is the one in which the lowering under the leading load is to be controlled in a controlled manner independently of the load pressure. In the set out in Figures 2 and 3 Operating conditions it is demonstrated that the arrangement according to the invention does not impair its function due to the presence of a pressure compensator.

Figur 1 zeigt nun das Absenken der in diesem Beispiel als Schaufel 1 ausgebildeten Arbeitsvorrichtung eines nicht weiter dargestellten Radladers unter dem Eigengewicht G. Im deckelseitigen Raum 2 des Zylinders 3 baut sich ein aus dem Gewicht G und evtl. Nutzlast der Schaufel 1 resultierender Druck auf. Bei Betätigung beispielsweise des im Steuerschieber 4 angeordneten Steuerkolbens 5 in Richtung der dargestellten Position fließt Öl über die Leitungen 6 und 7 und weiter über eine Differenzdruckblende 8 in den Tank 9 ab. Der Druck der Leitung 7 wird auf die federabgewandte Seite 10 der zwischen der Leitung 6 und dem Steuerschieber 4 vorgesehenen Druckwaage 11 geleitet. Der Druck in der Steuerleitung 12 wird über ein Wechselventil 13 in die Federkammer 14 der Druckwaage 11 geleitet. Das Wechselventil 13 sperrt dabei die Verbindung von der nur mit dem Nachsaugedruck beaufschlagten Lastdruckmeldeleitung 15, die den Druck nach der bei Load-Sensing-Systemen üblichen Differenzdruckblende 8' abgreift. Eine zusätzliche über den Förderstrom der über einen Regler 16 angesteuerten Pumpe 17 hinaus benötigte Ölmenge zur Auffüllung des Ringraumes 18 des Zylinders 3 wird über ein Nachsaugeventil 19 ergänzt, das in der Druckmittelzuführleitung 20' angeordnet ist. Mit 20 sind verschiedene Zuleitungen zu weiteren Steuerkolben 21,22 bezeichnet.FIG. 1 now shows the lowering of the working device of a wheel loader, not shown, in this example, as a bucket 1, under the dead weight G. In the cover-side space 2 of the cylinder 3, a pressure resulting from the weight G and possibly the payload of the bucket 1 builds up. When actuating, for example, the control piston 5 arranged in the control slide 4 in the direction of the position shown, oil flows out via the lines 6 and 7 and further via a differential pressure orifice 8 into the tank 9. The pressure of the line 7 is directed to the spring-facing side 10 of the pressure compensator 11 provided between the line 6 and the control slide 4. The pressure in the control line 12 is passed through a shuttle valve 13 into the spring chamber 14 of the pressure compensator 11. The shuttle valve 13 blocks the connection from the load pressure signaling line 15, which is only acted upon by the suction pressure and which taps the pressure through the differential pressure orifice 8 'which is common in load-sensing systems. An additional amount of oil required to fill the annular space 18 of the cylinder 3 via the delivery flow of the pump 17, which is controlled by a regulator 16, is supplemented by a suction valve 19 which is arranged in the pressure medium supply line 20 '. Different supply lines to further control pistons 21, 22 are designated by 20.

Dadurch vermindert die Druckwaage 11 in der diesem Element eigentümlichen Weise den in der Leitung 6 anstehenden Druck des deckelseitigen Raumes 2 auf einen entsprechend ihrer Federkraft so weit verminderten Wert, daß sich an der Differenzdruckblende 8 ein konstantes, der Federkraft analoges Druckgefälle einstellt. Damit ist der durch die Differenzdruckblende 8 durchtretende Ölstrom und somit die Absenkgeschwindigkeit der Schaufel 1 lastdruckunabhängig und nur mehr abhängig vom Öffnungsquerschnitt der Differenzdruckblende 8, welche durch die jeweilige Stellung des zugehörigen Steuerkolbens 5 vorgegeben wird. Im Steuerventil 4 können, wie bereits dargelegt, weitere Steuerkolben 21 und 22 vorgesehen sein. Die Steuerkolben 21,22 wie auch der Steuerkolben 5 können in bei Load-Sensing-Systemen üblicher Weise mit hier nicht dargestellten Druckwaagen für die gegenseitig unbeeinflußte gleichzeitige Betätigung von drückenden Lasten in den Leitungen 20 von der Pumpe 17 zum jeweiligen Steuerkolben 5,21,22 ausgerüstet sein.As a result, the pressure compensator 11, in the manner peculiar to this element, reduces the pressure in the line 6 of the cover-side space 2 to a value which is reduced so far in accordance with its spring force that a constant pressure drop which is analogous to the spring force is set at the differential pressure orifice 8. Thus, the oil flow passing through the differential pressure orifice 8 and thus the lowering speed of the blade 1 is independent of the load pressure and only dependent on the opening cross section of the differential pressure orifice 8, which is predetermined by the respective position of the associated control piston 5. As already explained, further control pistons 21 and 22 can be provided in the control valve 4. The control pistons 21, 22 as well as the control piston 5 can be used in the usual way in load-sensing systems with pressure compensators, not shown here, for the mutually unaffected simultaneous actuation of pushing Loads in the lines 20 from the pump 17 to the respective control piston 5, 21, 22 can be equipped.

In analoger Weise wie die Druckwaage 11, kann auch eine entsprechende - hier der besseren Übersicht halber nicht dargestellte - Druckwaage den Steuerkolben 21 und/oder 22 zugeordnet werden, sofern auch hier ziehende Lasten lastdruckunabhängig gesteuert werden sollen. Der im Betriebszustand nach Figur 1 höhere Druck der Steuerleitung 12, die den Druck hinter der Differenzdruckblende 8 abgreift gegenüber der Lastdruckmeldeleitung 15, wird über die Steuerleitung 24 in die Federkammer 14 der Druckwaage 11 gemeldet.In an analogous manner to the pressure compensator 11, a corresponding pressure compensator - not shown here for the sake of a better overview - can also be assigned to the control pistons 21 and / or 22 if pulling loads are also to be controlled here independently of the load pressure. The higher pressure of the control line 12 in the operating state according to FIG. 1, which taps the pressure behind the differential pressure orifice 8 compared to the load pressure signaling line 15, is reported via the control line 24 into the spring chamber 14 of the pressure compensator 11.

Figur 2 zeigt das Aufpressen der Schaufel 1 gegen einen äußeren Widerstand (F = Bodendruck), wie es z.B. beim Aufdrücken der Schaufel 1 gegen den Boden der Fall ist, wobei gleiche Bauteile mit gleichen Bezugszeichen versehen sind. Beim Aufpressen der Schaufel 1 erfolgt das Zumessen des Förderstromes durch Druck in den Ringraum 18 des Hydraulikzylinders 3, wobei gewährleistet sein muß, daß das aus dem deckelseitigen Raum 2 des Zylinders 3 verdrängte Öl nicht durch die Druckwaage 11 abgedrosselt wird, weil dieses mit möglichst geringem Strömungswiderstand in den Tank 9 abfließen soll. Der Druck des zur Verstellung des Zylinders 3 in den Ringraum 18 geleiteten Ölstromes wird über die Lastdruckmeldeleitung 15 und das Wechselventil 13 in die Federkammer 14 der Druckwaage 11 geleitet. Das Wechselventil 13 sperrt dabei die Verbindung von der nur mit dem Druck im Tank 9 beaufschlagten Steuerleitung 12. Auf der der Federkammer 14 abgewandten Seite 10 der Druckwaage 11 wirkt lediglich der geringe Staudruck des aus dem deckelseitigen Raum 2 in den Tank 9 abfließenden Öls. Deshalb wird der Kolben 23 der Druckwaage 11 in die Endstellung geführt, wobei der Durchgang von der Leitung 6 zur Leitung 7 ohne Wirksamwerden der Druckwaage 11 freigegeben ist.Figure 2 shows the pressing of the blade 1 against external resistance (F = ground pressure), as it is e.g. when the blade 1 is pressed against the ground, the same components being provided with the same reference numerals. When the blade 1 is pressed on, the delivery flow is metered by pressure into the annular space 18 of the hydraulic cylinder 3, it being necessary to ensure that the oil displaced from the cover-side space 2 of the cylinder 3 is not throttled by the pressure compensator 11, because this is as small as possible Flow resistance should flow into the tank 9. The pressure of the oil flow directed to the adjustment of the cylinder 3 in the annular space 18 is passed via the load pressure signaling line 15 and the shuttle valve 13 into the spring chamber 14 of the pressure compensator 11. The shuttle valve 13 blocks the connection of the control line 12, which is only pressurized in the tank 9. On the side 10 of the pressure compensator 11 facing away from the spring chamber 14, only the low dynamic pressure of the oil flowing out of the cover-side space 2 into the tank 9 acts. Therefore, the piston 23 of the pressure compensator 11 is guided into the end position, the passage from line 6 to line 7 being released without the pressure compensator 11 taking effect.

Figur 3 zeigt das Anheben der ggf. eine Nutzlast beinhaltenden Schaufel 1, wobei auch hier gleiche Bauteile wiederum mit gleichen Bezugszeichen versehen sind. Beim Anheben der Schaufel 1 erfolgt das Zumessen des Förderstromes durch Druck in den deckelseitigen Raum 2 des Zylinders 3, wobei gewährleistet werden muß, daß das zufließende Öl nicht durch die Druckwaage 11 abgedrosselt wird. Der Druck des zur Verstellung des Zylinders 3 in den Raum 2 geleiteten Ölstromes wird über die Lastdruckmeldeleitung 15 und das Wechselventil 13 in die Federkammer 14 der Druckwaage 11 geleitet. Das Wechselventil 13 sperrt dabei die Verbindung von der nur mit dem Druck im Tank 9 beaufschlagten Steuerleitung 12. Auf der der Federkammer 14 abgewandten Seite 10 der Druckwaage 11 wirkt der Druck des deckelseitigen Raumes 2 des Zylinders 3, der gleich dem in der Lastdruckmeldeleitung 15 ist. Auf beiden Stirnflächen des Kolbens 23 der Druckwaage 11 wirkt somit der gleiche Hydraulikdruck. Aus diesem Grund wird der Kolben 23 der Druckwaage 11 mit der Federkraft in die Endstellung geführt, wobei der Durchgang von der Leitung 7 zur Leitung 6 freigegeben wird.FIG. 3 shows the lifting of the bucket 1 which may contain a payload, the same components again being provided with the same reference numerals. When the bucket 1 is raised, the delivery flow is metered by pressure into the cover-side space 2 of the cylinder 3, it being necessary to ensure that the inflowing oil is not throttled by the pressure compensator 11. The pressure to adjust the cylinder 3 in the room 2 oil flow is passed via the load pressure signal line 15 and the shuttle valve 13 into the spring chamber 14 of the pressure compensator 11. The shuttle valve 13 blocks the connection from the control line 12 which is only acted upon by the pressure in the tank 9. On the side 10 of the pressure compensator 11 facing away from the spring chamber 14, the pressure of the cover-side space 2 of the cylinder 3 acts, which is equal to that in the load pressure reporting line 15 . The same hydraulic pressure thus acts on both end faces of the piston 23 of the pressure compensator 11. For this reason, the piston 23 of the pressure compensator 11 is guided into the end position with the spring force, the passage from the line 7 to the line 6 being released.

Die Figuren 4 bis 6 zeigen äquivalente Steuerungen gemäß den Figuren 1 bis 3. Die Druckwaage 11 ist in diesen Fällen zwischen dem Ausgang 25 des Schiebers 4 und dem Tank 9 eingesetzt, wobei funktional die gleichen Gegebenheiten und auch in allen drei Betriebszuständen in den entsprechenden Leitungen analoge Drücke herrschen, was wie folgt beschrieben wird:FIGS. 4 to 6 show equivalent controls according to FIGS. 1 to 3. In these cases, the pressure compensator 11 is inserted between the outlet 25 of the slide 4 and the tank 9, functionally the same conditions and also in all three operating states in the corresponding lines analog pressures prevail, which is described as follows:

Figur 4 zeigt in Analogie zu Figur 1 das Absenken der als Schaufel 1 ausgebildeten Arbeitsvorrichtung. Im deckelseitigen Raum 2 des Zylinders 3 baut sich ein aus dem Gewicht G und evtl. Nutzlast der Schaufel 1 resultierender Druck auf. Bei Betätigung beispielsweise des im Steuerschieber 4 angeordneten Steuerkolbens 5 in Richtung der dargestellten Position fließt Öl über die Leitungen 6,26 in den Tank 9 ab. Der Druck der Leitung 6 wird über die Leitung 29 auf die federabgewandte Seite 27 der zwischen dem Ausgang 25 des Steuerschiebers 4 und dem Tank 9 vorgesehenen Druckwaage 11 geleitet. Der Druck in der Leitung 26 wird über ein Wechselventil 13 in die Federkammer 14 der Druckwaage 11 geleitet. Das Wechselventil 13 sperrt dabei die Verbindung von der nur mit dem Nachsaugedruck beaufschlagten Lastdruckmeldeleitung 15, die den Druck nach der bei Load-Sensing-Systemen üblichen Differenzdruckblende 8' abgreift. Eine zusätzliche über den Förderstrom der durch den Regler 16 angesteuerten Pumpe 17 hinaus benötigte Ölmenge zur Auffüllung des Ringraumes 18 des Zylinders 3 wird über ein Nachsaugeventil 19 ergänzt, das in der Druckmittelzuführleitung 20' angeordnet ist.FIG. 4 shows, analogously to FIG. 1, the lowering of the working device designed as a blade 1. In the space 2 on the cover side of the cylinder 3, a pressure builds up resulting from the weight G and possibly the payload of the blade 1. When actuating, for example, the control piston 5 arranged in the control slide 4 in the direction of the position shown, oil flows out into the tank 9 via the lines 6, 26. The pressure of line 6 is passed via line 29 to the spring-side 27 of the pressure compensator 11 provided between the outlet 25 of the control slide 4 and the tank 9. The pressure in line 26 is passed via a shuttle valve 13 into the spring chamber 14 of the pressure compensator 11. The shuttle valve 13 blocks the connection from the load pressure signaling line 15, which is only acted upon by the suction pressure and which taps the pressure through the differential pressure orifice 8 'which is common in load-sensing systems. An additional quantity of oil required to fill the annular space 18 of the cylinder 3 in addition to the flow rate of the pump 17 controlled by the regulator 16 is supplemented by a suction valve 19 which is arranged in the pressure medium supply line 20 '.

Dadurch vermindert die Druckwaage 11 den in der Leitung 6 anstehenden Druck des deckelseitigen Raumes 2 des Zylinders 3 auf einen entsprechend ihrer Federkraft so weit verminderten Wert, daß sich an der Differenzdruckblende 8 ein konstantes, der Federkraft analoges Druckgefälle einstellt. Damit ist der durch die Differenzdruckblende 8 durchtretende Ölstrom und somit die Absenkgeschwindigkeit der Schaufel 1 lastdruckunabhängig und nur mehr abhängig vom Öffnungsquerschnitt der Differenzdruckblende 8, welche durch die jeweilige Stellung des Steuerkolbens 5 vorgegeben wird. Im Steuerventil 4 können darüber hinaus weitere Steuerkolben 21 und 22 vorgesehen sein. Die Steuerkolben 21,22 sowie auch der Steuerkolben 5 können, in bei Load-Sensing-Systemen üblicher Weise, mit hier nicht dargestellten Druckwaagen für die gegenseitig unbeeinflußte gleichzeitige Betätigung von drückenden Lasten in den Leitungen 20 von der Pumpe 17 zum jeweiligen Steuerkolben 5,21,22 ausgerüstet sein.As a result, the pressure compensator 11 reduces the pressure in the line 6 of the cover-side space 2 of the cylinder 3 to a value so far reduced in accordance with its spring force that a constant pressure drop which is analogous to the spring force is established at the differential pressure orifice 8. The oil flow passing through the differential pressure orifice 8 and thus the lowering speed of the blade 1 is thus independent of the load pressure and only dependent on the opening cross section of the differential pressure orifice 8, which is predetermined by the respective position of the control piston 5. In addition, further control pistons 21 and 22 can be provided in the control valve 4. The control pistons 21, 22 and also the control piston 5 can, in the usual way in load-sensing systems, with pressure compensators, not shown here, for the mutually unaffected simultaneous actuation of pressing loads in the lines 20 from the pump 17 to the respective control piston 5, 21 , 22 be equipped.

In analoger Weise wie die Druckwaage 11 kann auch eine entsprechende - hier der besseren Übersicht halber nicht dargestellte - Druckwaage dem Steuerkolben 21 und/oder 22 zugeordnet werden, sofern auch hier ziehende Lasten lastdruckunabhängig gesteuert werden sollen. Der im Betriebszustand nach Figur 4 höhere Druck der Leitung 26, welche den Druck hinter der Differenzdruckblende 8 abgreift, gegenüber der Lastdruckmeldeleitung 15, wird über die Steuerleitung 24 in die Federkammer 14 der Druckwaage 11 gemeldet.In an analogous manner to the pressure compensator 11, a corresponding pressure compensator - not shown here for the sake of a better overview - can also be assigned to the control piston 21 and / or 22, provided that pulling loads are to be controlled here independently of the load pressure. The higher pressure of the line 26 in the operating state according to FIG. 4, which taps the pressure behind the differential pressure orifice 8 compared to the load pressure reporting line 15, is reported via the control line 24 into the spring chamber 14 of the pressure compensator 11.

Figur 5 zeigt das Aufpressen der Schaufel 1 gegen einen äußeren Widerstand (F = Bodendruck), wie es z.B. beim Aufdrücken der Schaufel 1 gegen den Boden der Fall ist, wobei gleiche Bauteile mit gleichen Bezugszeichen versehen sind. Beim Aufpressen der Schaufel 1 erfolgt das Zumessen des Förderstroms durch Druck in den Ringraum 18 des Hydraulikzylinders 3, welcher gewährleistet sein muß, daß das aus dem deckelseitigen Raum 2 verdrängte Öl nicht durch die Druckwaage 11 abgedrosselt wird, weil dieses mit möglichst geringem Strömungswiderstand in den Tank 9 abfließen soll. Der Druck des zur Verstellung des Zylinders 3 in den Ringraum 18 geleiteten Ölstroms wird über die Lastdruckmeldeleitung 15 und das Wechselventil 13 in die Federkammer 14 der Druckwaage 11 geleitet. Das Wechselventil 13 sperrt dabei die Verbindung von der nur mit dem Druck im Tank 9 beaufschlagten Leitung 26. Auf der der Federkammer 14 abgewandten Seite 27 wirkt lediglich der in der Leitung 29 herrschende geringe Staudruck des aus dem deckelseitigen Raum 2 in den Tank 9 abfließenden Öls. Deshalb wird der Kolben 23 der Druckwaage 11 in die Endstellung geführt, wobei der Durchgang von der Leitung 26 zum Tank 9 ohne Wirksamwerden der Druckwaage 11 freigegeben ist.FIG. 5 shows the pressing of the blade 1 against external resistance (F = ground pressure), as is the case, for example, when pressing the blade 1 against the ground, the same components being provided with the same reference symbols. When the blade 1 is pressed on, the delivery flow is metered by pressure into the annular space 18 of the hydraulic cylinder 3, which must be ensured that the oil displaced from the cover-side space 2 is not throttled by the pressure compensator 11 because this has the lowest possible flow resistance in the Tank 9 should drain. The pressure of the oil flow directed into the annular space 18 for the adjustment of the cylinder 3 is passed via the load pressure signaling line 15 and the shuttle valve 13 into the spring chamber 14 of the pressure compensator 11. The shuttle valve 13 blocks the connection of the line 26 which is only pressurized in the tank 9 The only effect on page 27 is the low dynamic pressure in the line 29 of the oil flowing out of the cover-side space 2 into the tank 9. Therefore, the piston 23 of the pressure compensator 11 is guided into the end position, the passage from the line 26 to the tank 9 being released without the pressure compensator 11 taking effect.

Figur 6 zeigt das Anheben der Schaufel 1, wobei auch hier gleiche Bauteile wiederum mit gleichen Bezugszeichen versehen sind. Beim Anheben der Schaufel 1 erfolgt das Zumessen des Förderstroms durch Druck in den deckelseitigen Raum 2 des Zylinders 3, wobei gewährleistet werden muß, daß das aus dem kolbenstangenseitigen Raum 18 verdrängte Öl nicht durch die Druckwaage 11 abgedrosselt wird. Der Druck des zur Verstellung des Zylinders 3 in den Raum 2 geleiteten Ölstroms wird über die Lastdruckmeldeleitung 15 und das Wechselventil 13 in die Federkammer 14 der Druckwaage 11 geleitet. Das Wechselventil 13 sperrt dabei die Verbindung von der nur mit dem Druck im Tank 9 beaufschlagten Leitung 26. Auf der der Federkammer 14 abgewandten Seite 27 der Druckwaage 11 wirkt über die Leitung 29 der Druck des deckelseitigen Raumes 2 des Zylinders 3, der gleich dem der Lastdruckmeldeleitung 15 ist. Auf beiden Stirnflächen des Kolbens 23 der Druckwaage 11 wirkt somit der gleiche Hydraulikdruck. Aus diesem Grund wird der Kolben 23 der Druckwaage 11 mit der Federkraft in die Endstellung geführt, wobei der Durchgang von der Leitung 26 zum Tank 9 freigegeben wird.FIG. 6 shows the lifting of the bucket 1, with the same components again being provided with the same reference symbols. When the bucket 1 is raised, the delivery flow is metered by pressure into the cover-side space 2 of the cylinder 3, it being necessary to ensure that the oil displaced from the piston rod-side space 18 is not throttled by the pressure compensator 11. The pressure of the oil flow directed to the adjustment of the cylinder 3 in the space 2 is passed via the load pressure signaling line 15 and the shuttle valve 13 into the spring chamber 14 of the pressure compensator 11. The shuttle valve 13 blocks the connection of the line 26, which is only pressurized with the pressure in the tank 9. On the side 27 of the pressure compensator 11 facing away from the spring chamber 14, the pressure of the cover-side space 2 of the cylinder 3 acts via the line 29, which is equal to that of the Load pressure reporting line 15 is. The same hydraulic pressure thus acts on both end faces of the piston 23 of the pressure compensator 11. For this reason, the piston 23 of the pressure compensator 11 is guided into the end position with the spring force, the passage from the line 26 to the tank 9 being released.

Figur 7 ist analog zu Figur 1 zu sehen, wobei in diesem Beispiel das Stellelement Zylinder durch einen Hydromotor 28 ersetzt ist. Die ziehende Last kann hier durch ein durch äußere Einflüsse erzeugtes Drehmoment T vorgegeben werden, das bewirkt, daß der Hydromotor 28 zur Pumpe wird, so daß diese in die Leitung 6 Drucköl fördert.FIG. 7 can be seen analogously to FIG. 1, with the actuator cylinder being replaced by a hydraulic motor 28 in this example. The pulling load can be predetermined here by a torque T generated by external influences, which causes the hydraulic motor 28 to become the pump, so that it pumps 6 pressure oil into the line.

Bei Betätigung beispielsweise des im Steuerschieber 4 angeordneten Steuerkolbens 5 in Richtung der dargestellten Position fließt das von der Pumpe (Hydromotor 28) geförderte Öl über die Leitungen 6 und 7 und weiter über die Differenzdruckblende 8 in den Tank 9 ab. Im weiteren sind die Verhältnisse gleich , wie unter Figur 1 beschrieben. Die über den Förderstrom der Pumpe 17 hinaus benötigte Ölmenge zur Speisung des zur Pumpe gewordenen Hydromotors 28 wird über ein Nachsaugeventil 19 ergänzt, das in der Druckmittelzuführleitung 20' angeordnet ist. Als Beispiel für den Einsatz von Hydromotoren 28 kann das Schardrehwerk bei Gradern genannt werden.When, for example, the control piston 5 arranged in the control slide 4 is actuated in the direction of the position shown, the oil pumped by the pump (hydraulic motor 28) flows out via the lines 6 and 7 and further via the differential pressure orifice 8 into the tank 9. Furthermore, the conditions are the same as described under Figure 1. The amount of oil required to supply the hydraulic motor 28 that has become a pump, in addition to the flow rate of the pump 17, is supplemented by a suction valve 19 which is arranged in the pressure medium supply line 20 '. The coulter slewing gear for graders can be cited as an example of the use of hydraulic motors 28.

Claims (7)

Lastdruckunabhängige Steuerung der Geschwindigkeit von hydraulischen Stellelementen, wie Zylindern (3), Hydromotoren (28) oder dgl., bei vorauseilenden Lasten an Baumaschinen, wie beispielsweise Radladern, Baggern, Gradern oder dgl., mit mindestens einer Druckmittel aus einem Tank (9) fördernden Pumpe (17) mit durch einen Regler (16) veränderlichem Fördervolumen und mindestens einem Steuerschieber (4) mit mindestens einem Steuerkolben (5,21,22) zur Betätigung des bzw. der Stellelemente (3,28), dadurch gekennzeichnet, daß eine Druckwaage (11) in die Verbindungsleitung (6) des Raumes (2) des Stellelementes (3) bzw. vom Stellelement (28) zum Steuerschieber (4), insbesondere zum zugehörigen Steuerkolben (5) eingesetzt ist, daß der Rücklaufbereich des zugehörigen Steuerkolbens (5) als Differenzdruckblende (8) ausgebildet ist, und daß die Druckmeldung des Ölstromes vor dem Durchtritt durch die Differenzdruckblende (8) über eine Leitung (7) auf die der Federkammer (14) abgewandte Seite (10) der Druckwaage (11) herbeiführbar ist.Load pressure-independent control of the speed of hydraulic control elements, such as cylinders (3), hydraulic motors (28) or the like, in the case of premature loads on construction machines, such as wheel loaders, excavators, graders or the like, with at least one pressure medium from a tank (9) Pump (17) with a delivery volume which can be varied by a controller (16) and at least one control slide (4) with at least one control piston (5, 21, 22) for actuating the control element (s) (3,28), characterized in that a pressure compensator (11) in the connecting line (6) of the space (2) of the control element (3) or from the control element (28) to the control slide (4), in particular to the associated control piston (5), that the return area of the associated control piston (5 ) is designed as a differential pressure orifice (8), and that the pressure signal of the oil flow before it passes through the differential pressure orifice (8) via a line (7) facing away from the spring chamber (14) Side (10) of the pressure compensator (11) can be brought about. Lastdruckunabhängige Steuerung der Geschwindigkeit von hydraulischen Stellelementen, wie Zylindern (3), Hydromotoren (28) oder dgl., bei vorauseilenden Lasten an Baumaschinen, wie beispielsweise Radladern, Baggern, Gradern oder dgl., mit mindestens einer Druckmittel aus einem Tank (9) fördernden Pumpe (17) mit durch einen Regler (16) veränderlichem Fördervolumen und mindestens einem Steuerschieber (4) mit mindestens einem Steuerkolben (5,21,22) zur Betätigung des bzw. der Stellelemente (3), dadurch gekennzeichnet, daß eine Druckwaage (11) in die Leitung zwischen dem Ausgang (25) des Schiebers (4), insbesondere des zugehörigen Steuerkolbens (5) und dem Tank (9) eingesetzt ist, daß der Rücklaufbereich des zugehörigen Steuerkolbens (5) als Differenzdruckblende (8) ausgebildet ist, und daß die Druckmeldung vor dem Durchtritt des Ölstromes durch die Differenzdruckblende (8) über eine Leitung (29) auf die der Federkammer (14) abgewandte Seite (27) der Druckwaage (11) herbeiführbar ist.Load pressure-independent control of the speed of hydraulic control elements, such as cylinders (3), hydraulic motors (28) or the like, in the case of premature loads on construction machines, such as wheel loaders, excavators, graders or the like, with at least one pressure medium from a tank (9) Pump (17) with a delivery volume that can be varied by a controller (16) and at least one control slide (4) with at least one control piston (5, 21, 22) for actuating the control element (s) (3), characterized in that a pressure compensator (11 ) in the line between the outlet (25) of the slide (4), in particular the associated control piston (5) and the tank (9), that the return area of the associated control piston (5) is designed as a differential pressure orifice (8), and that the pressure message before the oil flow passes through the differential pressure orifice (8) via a line (29) to the side (27) of the pressure compensator (11) facing away from the spring chamber (14) is cash. Steuerung nach Anspruch 1, gekennzeichnet durch eine den Druck nach der Differenzdruckblende (8) abgreifende Steuerleitung (12), die zu einem Wechselventil (13) führt.Control system according to claim 1, characterized by a control line (12) tapping the pressure after the differential pressure orifice (8), which leads to a shuttle valve (13). Steuerung nach Anspruch 2, gekennzeichnet durch eine den Druck nach der Differenzdruckblende (8) abgreifende Steuerleitung (26), die zu einem Wechselventil (13) führt.Control system according to claim 2, characterized by a control line (26) tapping the pressure after the differential pressure orifice (8), which leads to a shuttle valve (13). Steuerung nach den Ansprüchen 1 und 3, dadurch gekennzeichnet, daß über das Wechselventil (13) der jeweils höhere Druck zwischen der Steuerleitung (12) und einer Lastdruckmeldeleitung (15) über eine weitere Steuerleitung (24) vom Wechselventil (13) zur Federkammer (14) der Druckwaage (11) gemeldet wird.Control according to claims 1 and 3, characterized in that the respective higher pressure between the control line (12) and a load pressure signaling line (15) via a further control line (24) from the shuttle valve (13) to the spring chamber (14) via the shuttle valve (13) ) the pressure compensator (11) is reported. Steuerung nach den Ansprüchen 2 und 4, dadurch gekennzeichnet, daß über das Wechselventil (13) der jeweils höhere Druck zwischen der Leitung (26) und einer Steuerleitung (15) über eine Steuerleitung (24) vom Wechselventil (13) zur Federkammer (14) der Druckwaage (11) gemeldet wird.Control according to claims 2 and 4, characterized in that the respective higher pressure between the line (26) and a control line (15) via a control line (24) from the shuttle valve (13) to the spring chamber (14) via the shuttle valve (13). the pressure compensator (11) is reported. Steuerung nach einem oder mehreren der Ansprüche 1 bis 6, gekennzeichnet durch ein Nachsaugeventil (19), das im Bereich der Druckmittelzuführleitung (20') vorgesehen ist und den Ringraum (18) des als Zylinder (3) ausgebildeten Stellelementes auffüllt bzw. den zur Pumpe gewordenen Hydromotor (28) speist.Control according to one or more of claims 1 to 6, characterized by a suction valve (19) which is provided in the region of the pressure medium supply line (20 ') and fills the annular space (18) of the actuating element designed as a cylinder (3) or the one to the pump Hydromotor (28) feeds.
EP94101011A 1993-03-12 1994-01-25 Load-independent speed control of hydraulic actuators for construction machines Expired - Lifetime EP0615024B1 (en)

Applications Claiming Priority (2)

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DE4307872A DE4307872C2 (en) 1993-03-12 1993-03-12 Load pressure-independent control of the speed of hydraulic control elements
DE4307872 1993-03-12

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EP0615024A2 true EP0615024A2 (en) 1994-09-14
EP0615024A3 EP0615024A3 (en) 1996-09-25
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AT (1) ATE200538T1 (en)
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DE59409720D1 (en) 2001-05-17
DE4307872C2 (en) 2001-05-17
ATE200538T1 (en) 2001-04-15
DE4307872A1 (en) 1994-09-22
EP0615024A3 (en) 1996-09-25
EP0615024B1 (en) 2001-04-11
ES2155837T3 (en) 2001-06-01

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