EP0719947B1 - Load-sensing circuit - Google Patents

Load-sensing circuit Download PDF

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Publication number
EP0719947B1
EP0719947B1 EP95120626A EP95120626A EP0719947B1 EP 0719947 B1 EP0719947 B1 EP 0719947B1 EP 95120626 A EP95120626 A EP 95120626A EP 95120626 A EP95120626 A EP 95120626A EP 0719947 B1 EP0719947 B1 EP 0719947B1
Authority
EP
European Patent Office
Prior art keywords
pressure
load
force
working
valve body
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
EP95120626A
Other languages
German (de)
French (fr)
Other versions
EP0719947A3 (en
EP0719947A2 (en
Inventor
Werner Hörmann
Reinhold Schniederjan
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.)
Brueninghaus Hydromatik GmbH
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Brueninghaus Hydromatik GmbH
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Publication date
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Publication of EP0719947A2 publication Critical patent/EP0719947A2/en
Publication of EP0719947A3 publication Critical patent/EP0719947A3/en
Application granted granted Critical
Publication of EP0719947B1 publication Critical patent/EP0719947B1/en
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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
    • E02F9/2225—Control of flow rate; Load sensing arrangements using pressure-compensating valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/08—Regulating by delivery pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/161—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load
    • F15B11/165—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load for adjusting the pump output or bypass in response to demand
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B2205/00—Fluid parameters
    • F04B2205/09—Flow through the 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20546—Type of pump variable capacity
    • F15B2211/20553—Type of pump variable capacity with pilot circuit, e.g. for controlling a swash plate
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/25—Pressure control functions
    • F15B2211/253—Pressure margin control, e.g. pump pressure in relation to load pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30525—Directional control valves, e.g. 4/3-directional control valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • F15B2211/40515—Flow control characterised by the type of flow control means or valve with variable throttles or orifices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—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
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/605—Load sensing circuits
    • F15B2211/6058—Load sensing circuits with isolator 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
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/67—Methods for controlling pilot pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders

Definitions

  • the invention relates to a load-sensing circuit according to the preamble of Claim 1.
  • load-sensing circuits are known from practice and for example in the "hydraulic training, issued by Mannesmann Rexroth, Drive and control technology in mobile drive machines ", RE 00 315 / 9.82 on page 68 in hydraulic-mechanical design described.
  • These known load-sensing circuits are very susceptible to vibration, so that unstable conditions can often occur; aggravating in addition there are the high volume capacities in the relatively large distances between the hydraulic pump and the consumers bridging hoses and especially strong in mobile applications Fluctuations in oil temperature, drive speed and in vehicles such as such as excavators with multiple consumers the movement of changing masses (Boom, stick, spoon).
  • Load sensing circuits in electro-hydraulic Execution show a more stable operating behavior, but a considerable one faces greater design effort.
  • the volume flow feedback device comprises the first and second measuring surfaces, wherein the first measuring area is larger than the second measuring area. If for example the throttle cross section of the pressure difference between the Working pressure and the load pressure with the flow of a corresponding volume flow generating variable throttle increases and thus this pressure difference is reduced, the control valve controls the hydraulic pump for a longer time Delivery volume and thus larger volume flow until this at the variable throttle the original one, before enlarging the throttle cross section existing pressure difference generated. The larger volume flow accelerates the or the consumer, so that the working pressure and the load pressure in the same Dimensions increase. This increase in pressure creates the different sizes Measuring surfaces a force component corresponding to the measuring surface difference greater hydraulic force of the pressure difference.
  • This force component is a measure of the increase in volume flow and thus represents the feedback force represents, which acts against the counterforce, which is preferably the adjusting force is a compression spring.
  • the counterforce which is preferably the adjusting force is a compression spring.
  • the feedback device ensures that after each adjustment of the hydraulic pump greater or smaller delivery volume the resultant acting on the control valve the feedback force and the counterforce to a smaller or larger value is set.
  • the setpoint setting of the Control valve changed so that a new adjustment of the hydraulic pump to an even larger or smaller delivery volume only with a smaller or larger, counteracting pressure difference between the Working pressure and the load pressure can be carried out. It results in in this way a decreasing with increasing funding volume and, conversely, with decreasing delivery volume increasing p-V characteristic curve, the one Load sensing circuit with so-called proportional behavior.
  • the feedback device is advantageously as one Flow feedback device designed, being the force generated by the feedback device can be mechanical force.
  • the delivery volume feedback device comprises at least one displacement spring, on the actuator adjusting the delivery volume of the hydraulic pump and attacks on the valve body and the action of the latter by the Counterforce with increasing adjustment of the hydraulic pump to a larger or smaller funding volume reduced or increased. In this way a smaller or Larger pressure difference required to turn the hydraulic pump to a larger one or set a smaller delivery volume.
  • the invention is between the valve body and a first, double-acting and stationary actuating cylinder, a second, single-acting, from the counterforce towards a fixed stop Actuated actuating cylinder clamped, the actuating piston under the Effect of the working pressure acts on the valve body against the counterforce, the actuating piston of the first actuating cylinder being the working pressure and has measuring surfaces acted upon by the load pressure and under which Effect of the pressure difference between the working pressure and the load pressure above the second actuating cylinder acts on the valve body against the counterforce.
  • valve body takes over together with the first actuating cylinder the load-sensing function and, with the second actuating cylinder, pressure control, which is superimposed on the load sensing, i.e. instead of the latter in Function occurs when the hydraulic force enters the second actuating cylinder System stops at the fixed stop.
  • the pressure control points when using the delivery volume feedback device the same proportional behavior as the load sensing control.
  • the characteristics of which approximate a performance hyperbola there is a power regulation instead of the pressure can as well as that of the aforementioned pressure control by simultaneous Use of the volume flow feedback device according to the measurement area difference be modified.
  • Figure 1 shows a load sensing circuit for a zero stroke controlled Hydraulic pump 1 adjustable delivery volume V, two in the open circuit consumers 2 connected in parallel, such as two hydraulic motors over two Working lines 3 drives hydraulically.
  • the hydraulic pump 1 is with a Drive motor, not shown, mechanically coupled and via a main working line 4 to the two working lines 3 and via a suction line 5 connected to the tank 6.
  • One of the consumers 2 leads Return line 7 also to tank 6.
  • the hydraulic pump 1 is designed, for example, as an axial piston pump, the Actuator 8 for adjusting its delivery volume V via the piston rod 9 with the actuating piston 10 of a hydraulic cylinder 11 in a differential design is mechanically coupled.
  • the actuating piston 10 defines in the hydraulic cylinder 11 with its smaller, circular end face a pressure chamber 12 and with its opposite, larger, circular end face one Pressure chamber 13.
  • the pressure chamber 12 is connected via a first signal pressure line 14 the main working line 4 and via a second signal pressure line 15 to the Pressure chamber 13 connected.
  • the load sensing circuit consists of a control valve 16 in the second Signal pressure line 15, a volume flow feedback device 17 and each an adjusting throttle 18 in the two working lines 3.
  • the control valve 16 which is shown symbolically in FIG. 7, divides the second Signal pressure line 15 in a first, connected to the pressure chamber 12 Signal pressure line section 19 and a second, to the pressure chamber 13 connected signal pressure line section 20. It is considered a throttling 3/2-way valve with a working connection P to the first signal pressure line section 19, a working connection A to the second signal pressure line section 20 and a working connection T to a leading to the tank 6 Relief line 21 formed.
  • the valve body 22 of the control valve 16 has at its two ends a first measuring surface MF 1 and a second measuring surface MF 2 .
  • the first measuring area MF 1 is larger than the second measuring area MF 2 and defines a working pressure control chamber 23 which is connected to the first signal pressure line section 19 via a working pressure control line 24.
  • the second measuring surface MF 2 defines a load pressure control chamber 25, which is connected via a load pressure control line 26 to a shuttle valve 27 in a connecting line 28.
  • the connecting line 28 connects those working line sections 3, 29 to one another which are arranged in the flow direction after the adjusting throttles 18, ie between these and the consumers 2.
  • a preloaded compression spring 30 is arranged in the load pressure control chamber 25, which acts on the valve body 22 in FIG. 1 to the left in the direction of a first working position, in which the working connections A and T are connected to one another, while the working connection P is blocked.
  • the volume flow feedback device 17 comprises the two differently sized measuring surfaces MF 1 and MF 2 on the valve body 22 and serves to generate a feedback force F R acting on the valve body, as described below.
  • the function of the load-sensing circuit according to FIG. 1 is as follows:
  • the zero-stroke-controlled hydraulic pump 1 is actuated by the actuating or working pressure p A, which may be present in the pressure chamber 12 of the hydraulic cylinder 11, and is removed from the main working line 4 via the first actuating pressure line 14.
  • p A which may be present in the pressure chamber 12 of the hydraulic cylinder 11
  • p A acted upon by a compression spring, not shown, in the pressure chamber 12 in the direction of the maximum delivery volume, as long as the control valve 16 assumes its aforementioned first working position.
  • the pressure chamber 13 of the hydraulic cylinder 11 is relieved via the second signal pressure line section 20, the opened working connections A and T of the control valve 16 and the relief line 21 to the tank 6, while the full setting or Working pressure p A builds up and acts on the actuating piston 11 in the direction of its right end position in FIG. 1, which corresponds to the maximum delivery volume V of the hydraulic pump 1.
  • the preload (setting force or counterforce F G ) of the compression spring 30 is selected such that it is equal to the hydraulic force of that pressure difference ⁇ p between the working pressure p A of the hydraulic pump 1 which was reduced in front of the adjusting throttle 18 and the load pressure p L of the consumer which was reduced after the adjusting throttle 18 2, which, acting on both measuring surfaces MF 1 and MF 2 of the valve body 22, is formed on the adjusting throttle 18 which is set to the largest throttle cross section and through which the maximum volume flow Q of the hydraulic pump 1 flows; in this case the other adjustment throttle 18 is completely closed.
  • the pressure difference ⁇ p increases accordingly and shifts the valve body 22 in FIG. 1 to the right into a second working position, in which when the working connection T is blocked, the working connections A and P are open and the two signal pressure line sections 19 and 20 connect with each other.
  • the actuating or working pressure p A now acts on the larger, circular piston surface of the actuating piston 10, thus displacing it to the left in FIG.
  • the feedback force F R thus increases the action on the valve body 22 by the counterforce F G and thus sets the control valve 16 to a larger setpoint of the volume flow Q. This results in the pQ characteristic curve shown in FIG. 2, which increases with decreasing volume flow Q and characterizes a proportional operating behavior of the hydraulic pump 1.
  • the operating behavior of the hydraulic pump 1 follows the same characteristic curve if the throttle cross section of the variable throttle 18 is increased.
  • the pressure difference ⁇ p thus falls, so that the valve body 22 transfers to the first working position and the hydraulic pump 1 is swung out to a larger delivery volume V until it promotes the larger volume flow Q which causes the original pressure difference ⁇ p at the adjusting throttle 18 , ie until force equilibrium is established on valve body 22.
  • the larger volume flow Q increases the load on the hydraulic pump 1, so that the working pressure p A and the load pressure p L increase to the same extent.
  • the hydraulic force of the working pressure p A acting on the larger measuring surface MF 1 increases by a larger amount corresponding to the measuring surface difference than the hydraulic force of the load pressure p L acting on the smaller measuring surface MF 2 .
  • the resulting feedback force F R acts on the valve body 22 in the opposite direction to the counter force F G , whereby the control valve 16 is set to a smaller setpoint of the volume flow Q.
  • the result is the same pQ characteristic curve, shown in FIG. 2 and falling with increasing volume flow Q, which characterizes a proportional operating behavior of the hydraulic pump 1.
  • Control valve 16 also takes over the function of a Regulation with which the delivery volume V of the hydraulic pump 1 changes Loads are adjusted such that the volume flow Q delivered with the adjusting throttle 18 matches the setpoint.
  • the volume flow Q delivered by the hydraulic pump 1 is divided into two partial volume flows, which the consumers 2, in accordance with the set throttle cross sections and the loads acting on the consumers 2 at the branches of the working lines 3 from the main working line 4 drive at appropriate speed.
  • the respectively higher load pressure p L acts via the shuttle valve 27 and the load pressure control line 26 on the second measuring surface MF 2 of the valve body 22, while the same working pressure p A in both working lines 3 acts on the first measuring surface MF 1 .
  • the smaller of the pressure difference ⁇ p occurring at both adjusting throttles 18 acts on the valve body 22; in other words, the control and regulation described above only controls or regulates the consumer 2 which is subject to greater loads in the manner described above.
  • the load-sensing circuit according to FIG. 3 differs from that according to FIG. 1 with an otherwise identical construction and function by an override device 31 for changing the size of the first and second measuring surfaces MF 1 , MF 2 . pressure difference ⁇ p.
  • the override device 31 comprises a third measuring surface MF 3 , which is formed on the valve body 22, defines a control pressure chamber 32 and can be acted upon by an external control pressure p S against the counterforce F G of the compression spring 30 via a control pressure line 33 connected thereto, by the pressure difference Increase ⁇ p as required; this function of the override device 31 which causes the hydraulic pump 1 to pivot back to a smaller delivery volume as the control pressure p S increases is also referred to as a negative control function.
  • control pressure line 33 can be connected to the pressure space opposite the control pressure space 32, designated by reference numeral 34 in FIG.
  • FIG. 4 shows a load-sensing circuit which, instead of the hydraulic override device 31, comprises an override device 35 which is designed as an electrically controllable input part, for example in the form of a switching magnet or control magnet, for the control valve 16 and, with appropriate control, the valve body 22 with a Additional force is applied, which either acts against the counterforce F G of the compression spring 30 (when performing the negative control function) or in the opposite direction (when performing the positive control function).
  • an override device 35 which is designed as an electrically controllable input part, for example in the form of a switching magnet or control magnet, for the control valve 16 and, with appropriate control, the valve body 22 with a Additional force is applied, which either acts against the counterforce F G of the compression spring 30 (when performing the negative control function) or in the opposite direction (when performing the positive control function).
  • the load sensing arrangement according to FIG. 5 differs from that according to FIG. 1 with otherwise the same construction and function in that instead of the volume flow feedback device 17 with measuring surfaces MF 1 and MF 2 of different sizes, they are of the same size and therefore have the reference symbols MF ' 1 and MF ' 2 designated measuring surfaces and a delivery volume feedback device 36 are used in the form of a displacement measuring spring which acts on the actuator 8 of the hydraulic pump 1 and on the end of the valve body 22 opposite the compression spring 30.
  • the measuring spring 36 detects the delivery volume setting of the hydraulic pump 1 by acting on the valve body 22 with increasing delivery volume V with a correspondingly increasing feedback force F R and with decreasing delivery volume V with a correspondingly decreasing feedback force F R against the counterforce F G of the compression spring 30.
  • the invention also extends to exemplary embodiments, both the Volume flow feedback device 17 and the delivery volume feedback device 36 use.
  • Figure 7 shows a load sensing circuit with superimposed pressure or power control. It comprises a first, double-acting and stationary actuating cylinder 37, a second, single-acting actuating cylinder 38 and the control valve 16 according to FIG. 1, but without the measuring surfaces acted upon by the differential pressure ⁇ p. These are designed as measuring surfaces MF ' 1 and MF' 2 of the same size on the actuating piston 39 of the first actuating cylinder 37.
  • the first measuring surface MF ' 1 defines the working pressure control chamber 23, which is connected to the main working line 4 via the working pressure control line 24.
  • the second measuring surface MF ' 2 defines the load pressure control chamber 25, which is connected via the load pressure control line 26 to the shuttle valve 27 in the connecting line 28 connecting the working line sections 29.
  • the pressure difference .DELTA.p taken off at the adjusting throttle 18 associated with the higher-load consumer acts on the actuating piston 39 of the first actuating cylinder 37 and acts on the second actuating cylinder 38 in FIG. 7 to the left in the direction of the valve body 22 via its piston rod 40.
  • the actuating piston 42 of the second actuating cylinder 38 has an annular piston surface 43 which, together with an annular cylinder surface 44 of the same size, defines a likewise annular pressure chamber 45 which is penetrated by the piston rod 46 and is connected to the second actuating pressure line section 15, 20 via a control line 47 ,
  • the actuating piston 42 acts on the valve body 22 of the control valve 16 against the counterforce F G of the adjustable compression spring 30 in the direction of the second, under the action of the working pressure p A of sufficient size present in the pressure chamber 45 and taken from the first actuating pressure line section 15, 20 by the first actuating pressure line 14 working position.
  • the feedback device is designed here as a delivery volume feedback device 36 which, in the case of the aforementioned pressure control, comprises a position measuring spring and, in the case of the aforementioned power control, an arrangement of a plurality of travel measuring springs connected in series with different characteristic curves which approximate a performance hyperbola.
  • the displacement spring or displacement spring arrangement 36 engages on the piston rod 9 of the actuating piston 10 of the hydraulic cylinder 11 and on the end of the valve body 22 opposite the actuating cylinders 37, 38 and acted upon by the compression spring 30.
  • the measuring spring or measuring spring arrangement 36 is tensioned with increasing swiveling back of the hydraulic pump 1 to a smaller delivery volume V, so that the resulting feedback force F R acts in the same direction with the compression spring 30, ie the valve body 22 in the direction of the first working position and via this and the actuating piston 42, the second actuating cylinder 38 is urged against a stationary stop 48.
  • the valve body 22 takes over together with the first actuating cylinder 37 Load-sensing function and together with the second actuating cylinder 38 Pressure or power control, with the p-V characteristics of both the load sensing control as well as the pressure or power control of the characteristic of Displacement spring 36, for example the characteristic shown in FIG. 6, or the Power hyperbola correspond to the position measuring spring arrangement 36.
  • the measuring surfaces MF ' 1 and MF' 2 are larger than the piston surface 43 and the cylinder surface 44, in such a way that during the load sensing function the hydraulic force of the pressure difference ⁇ p acting on the measuring surfaces MF ' 1 and MF' 2 is greater than the hydraulic force of the working pressure p A acting on the cylinder surface 44 and thus keeps the second actuating cylinder 38 at a distance from the fixed stop 46; as a result, the effect of the working pressure p A on the actuating piston 42 and thus the valve body 22 is switched off.

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

Description

Die Erfindung betrifft eine Load-Sensing-Schaltung nach dem Oberbegriff des Anspruches 1.The invention relates to a load-sensing circuit according to the preamble of Claim 1.

Derartige Load-Sensing-Schaltungen sind aus der Praxis bekannt und beispielsweise in dem von der Firma Mannesmann Rexroth ausgegebenen "Hydraulik-Training, Antriebs- und Steuerungstechnik in mobilen Antriebsmaschinen", RD 00 315/9.82 auf Seite 68 in hydraulisch-mechanischer Ausführung beschrieben. Diese bekannten Load-Sensing-Schaltungen sind stark schwingungsanfällig, so daß häufig instabile Zustände auftreten können; erschwerend hinzukommen die hohen Volumenkapazitäten in den in der Praxis die relativ großen Abstände zwischen der Hydropumpe und den Verbrauchern überbrückenden Schläuchen und insbesondere bei mobilen Anwendungen starke Schwankungen der Öltemperatur, der Antriebsdrehzahl sowie bei Fahrzeugen wie etwa Baggern mit mehreren Verbrauchern die Bewegung sich verändernder Massen (Ausleger, Stiel, Löffel). Load-Sensing-Schaltungen in elektro-hydraulischer Ausführung zeigen ein stabileres Betriebsverhalten, dem jedoch ein erheblich größerer konstruktiver Aufwand gegenübersteht. Such load-sensing circuits are known from practice and for example in the "hydraulic training, issued by Mannesmann Rexroth, Drive and control technology in mobile drive machines ", RE 00 315 / 9.82 on page 68 in hydraulic-mechanical design described. These known load-sensing circuits are very susceptible to vibration, so that unstable conditions can often occur; aggravating in addition there are the high volume capacities in the relatively large distances between the hydraulic pump and the consumers bridging hoses and especially strong in mobile applications Fluctuations in oil temperature, drive speed and in vehicles such as such as excavators with multiple consumers the movement of changing masses (Boom, stick, spoon). Load sensing circuits in electro-hydraulic Execution show a more stable operating behavior, but a considerable one faces greater design effort.

Weiterhin ist eine Load-Sensing-Schaltung gemäß Oberbegriff des Anspruchs 1 mit einer Rückmeldeeinrichtung aus der DE-A 29 10 611 bekannt.Furthermore, a load-sensing circuit according to the preamble of claim 1 with a feedback device known from DE-A 29 10 611.

Die Volumenstrom-Rückmeldeeinrichtung umfaßt die erste und zweite Meßfläche, wobei die erste Meßfläche größer als die zweite Meßfläche ist. Wenn beispielsweise der Drosselquerschnitt einer die Druckdifferenz zwischen dem Arbeitsdruck und dem Lastdruck bei Durchfluß eines entsprechenden Volumenstroms erzeugenden Verstelldrossel vergrößert und damit diese Druckdifferenz reduziert wird, steuert das Regelventil die Hydropumpe so lange auf größeres Fördervolumen und damit größeren Volumenstrom, bis dieser an der Verstelldrossel die ursprüngliche, vor der Vergrößerung des Drosselquerschnitts vorhandene Druckdifferenz erzeugt. Der größere Volumenstrom beschleunigt den oder die Verbraucher, so daß der Arbeitsdruck und der Lastdruck in gleichem Maße ansteigen. Dieser Druckanstieg erzeugt an den unterschiedlich großen Meßflächen eine um eine der Meßflächendifferenz entsprechende Kraftkomponente größere hydraulische Kraft der Druckdifferenz. Diese Kraftkomponente ist ein Maß für die Zunahme des Volumenstroms und stellt somit die Rückmeldekraft dar, die gegen die Gegenkraft wirkt, die vorzugsweise die Einstellkraft einer Druckfeder ist. Um die Hydropumpe erneut auf größeres Fördervolumen auszuschwenken, ist eine der Kraftkomponente entsprechend geringere Druckdifferenz erforderlich. Dies bedeutet eine geringere Zunahme des Volumenstroms und damit kleinere Regelabweichungen bzw. geringeres Überschwingen und infolgedessen eine verbesserte Stabilität.The volume flow feedback device comprises the first and second measuring surfaces, wherein the first measuring area is larger than the second measuring area. If for example the throttle cross section of the pressure difference between the Working pressure and the load pressure with the flow of a corresponding volume flow generating variable throttle increases and thus this pressure difference is reduced, the control valve controls the hydraulic pump for a longer time Delivery volume and thus larger volume flow until this at the variable throttle the original one, before enlarging the throttle cross section existing pressure difference generated. The larger volume flow accelerates the or the consumer, so that the working pressure and the load pressure in the same Dimensions increase. This increase in pressure creates the different sizes Measuring surfaces a force component corresponding to the measuring surface difference greater hydraulic force of the pressure difference. This force component is a measure of the increase in volume flow and thus represents the feedback force represents, which acts against the counterforce, which is preferably the adjusting force is a compression spring. To enlarge the hydraulic pump again Swinging out the delivery volume is one of the force components lower pressure difference required. This means a smaller increase of the volume flow and thus smaller control deviations or less Overshoot and consequently improved stability.

Eine weitere Load-Sensing-Schaltung ist aus der DE-A 29 13 534 bekannt, wobei die Rückmeldung durch einen separaten, auf einem Regelventilkolben wirkenden Kolben mit zwei entgegengesetzten Meßfläche erfolgt und die erste Meßflächen durch den Arbeitsdruck der Pumpe und die zweite Meßfläche durch den Lastdruck beaufschlagt wird. Neben dem erheblichen konstruktiven Aufwand ist vor allem die Anfälligkeit gegenüber Schwingungen von Nachteil.Another load-sensing circuit is known from DE-A 29 13 534, the feedback from a separate, on a control valve piston acting piston with two opposite measuring surface and the first measuring surfaces by the working pressure of the pump and the second measuring surface is acted upon by the load pressure. In addition to the considerable constructive Effort is the disadvantage of susceptibility to vibrations.

In der Druckschrift DE 32 00 885 A1 ist ein Leistungsregler für eine hydrostatische Pumpe offenbart, bei der zur Begrenzung des Regelbereichs der Leistungsregelung zu großen Fördermengen hin ein auf einen ersten, mit einem Lastdruck beaufschlagten Kolben wirkender zweiter Kolben vorgesehen ist, dessen zwei entgegengesetzten Kolbenflächen mit dem Lastdruck und einem Arbeitsdruck beaufschlagt sind. Überschreitet die an dem zweiten Kolben angreifende resultierende Kraft aufgrund der sich entsprechend einem Volumenstrom durch eine Drossel einstellenden Druckdifferenz eine durch eine Feder vorgebbare Kraft, so wirkt der zweite Kolben über den ersten Kolben auf das Regelventil, so daß die Pumpe in Richtung kleinerer Fördermenge verstellt wird. In the document DE 32 00 885 A1 there is a power controller for a hydrostatic pump disclosed to limit the control range the output control for large quantities at a first, with a second piston acting under a load pressure is provided is, the two opposite piston surfaces with the load pressure and are subjected to a working pressure. Exceeds that on the second Resulting force acting on the piston due to the corresponding movement Volume flow through a throttle pressure difference one through If a force can be specified by a spring, the second piston acts via the first Piston on the control valve, so that the pump towards smaller Flow rate is adjusted.

Es ist Aufgabe der Erfindung, eine Load-Sensing-Schältung der eingangs genannten Art so weiterzubilden, daß mit geringem konstruktiven Aufwand ein stabileres Betriebsverhalten erreicht wird.It is an object of the invention to provide a load-sensing circuit at the beginning mentioned type so that with little design effort more stable operating behavior is achieved.

Diese Aufgabe wird durch die kennzeichnenden Merkmale des Anspruches 1 im Zusammenwirken mit dessen gattungsbildenden Merkmalen gelöst. Die Rückmeldeeinrichtung sorgt dafür, daß nach jeder Einstellung der Hydropumpe auf größeres oder kleineres Fördervolumen die am Regelventil wirkende Resultierende der Rückmeldekraft und der Gegenkraft auf einen kleineren bzw. größeren Wert eingestellt ist. Damit ist die Sollwert-Einstellung des Regelventils derart verändert, daß eine erneute Verstellung der Hydropumpe auf noch größeres oder kleineres Fördervolumen nur mit einer kleineren bzw. größeren, gegen die Gegenkraft wirkenden Druckdifferenz zwischen dem Arbeitsdruck und dem Lastdruck durchgeführt werden kann. Es ergibt sich auf diese Weise eine mit zunehmendem Fördervolumen abfallende und, umgekehrt, mit abnehmendem Fördervolumen ansteigende p-V- Kennlinie, die eine Load-Sensing-Schaltung mit sog. Proportionalverhalten kennzeichnet. Diese weist im Gegensatz zu den aus dem Stand der Technik bekannten Load-Sensing-Schaltungen mit sog. Integralverhalten, d.h. mit Kennlinien mit der Steigung Null, ein erheblich stabileres Betriebsverhalten auf, weil das Fördervolumen bei einer kleinen Regelabweichung nur langsam, bei einer großen Regelabweichung jedoch schnell verändert wird. Die Schwingungsanfälligkeit eines solchen Systems ist sehr gering.This object is achieved by the characterizing features of claim 1 Interaction with its generic characteristics solved. The feedback device ensures that after each adjustment of the hydraulic pump greater or smaller delivery volume the resultant acting on the control valve the feedback force and the counterforce to a smaller or larger value is set. The setpoint setting of the Control valve changed so that a new adjustment of the hydraulic pump to an even larger or smaller delivery volume only with a smaller or larger, counteracting pressure difference between the Working pressure and the load pressure can be carried out. It results in in this way a decreasing with increasing funding volume and, conversely, with decreasing delivery volume increasing p-V characteristic curve, the one Load sensing circuit with so-called proportional behavior. This has in contrast to the load-sensing circuits known from the prior art with so-called integral behavior, i.e. with characteristic curves with the slope Zero, a significantly more stable operating behavior because of the delivery volume with a small control deviation only slowly, with a large control deviation however is changed quickly. The susceptibility to vibration of a such system is very small.

Die Rückmeldeeinrichtung ist vorteilhafterweise als eine Förderstrom-Rückmeldeeinrichtung ausgebildet, wobei die von der Rückmeldeeinrichtung erzeugte Kraft eine mechanische Kraft sein kann.The feedback device is advantageously as one Flow feedback device designed, being the force generated by the feedback device can be mechanical force.

Die Fördervolumen-Rückmeldeeinrichtung umfaßt wenigstens eine Wegmeßfeder, die an dem das Fördervolumen der Hydropumpe verstellenden Stellglied sowie am Ventilkörper angreift und die Beaufschlagung des letzteren durch die Gegenkraft mit zunehmender Verstellung der Hydropumpe auf größeres oder kleineres Fördervolumen reduziert bzw. verstärkt. Auf diese Weise eine kleinere bzw. größere Druckdifferenz erforderlich, um die Hydropumpe erneut auf größeres bzw. kleineres Fördervolumen einzustellen.The delivery volume feedback device comprises at least one displacement spring, on the actuator adjusting the delivery volume of the hydraulic pump and attacks on the valve body and the action of the latter by the Counterforce with increasing adjustment of the hydraulic pump to a larger or smaller funding volume reduced or increased. In this way a smaller or Larger pressure difference required to turn the hydraulic pump to a larger one or set a smaller delivery volume.

Gemäß einer Weiterbildung der Erfindung ist zwischen dem Ventilkörper und einem ersten, doppeltwirkenden und ortsfesten Stellzylinder ein zweiter, einfachwirkender, von der Gegenkraft in Richtung eines ortsfesten Anschlags beaufschlagter Stellzylinder eingespannt, dessen Stellkolben unter der Wirkung des Arbeitsdrucks den Ventilkörper gegen die Gegenkraft beaufschlagt, wobei der Stellkolben des ersten Stellzylinders die vom Arbeitsdruck und vom Lastdruck beaufschlagbaren Meßflächen aufweist und unter der Wirkung der Druckdifferenz zwischen dem Arbeitsdruck und dem Lastdruck über den zweiten Stellzylinder den Ventilkörper gegen die Gegenkraft beaufschlagt. Der Ventilkörper übernimmt gemeinsam mit dem ersten Stellzylinder die Load-Sensing-Funktion und mit dem zweiten Stellzylinder eine Druckregelung, die dem Load-Sensing überlagert ist, d.h. statt letzterem in Funktion tritt, wenn die hydraulische Kraft den zweiten Stellzylinder in Anlage am ortsfesten Anschlag hält.According to a development of the invention is between the valve body and a first, double-acting and stationary actuating cylinder, a second, single-acting, from the counterforce towards a fixed stop Actuated actuating cylinder clamped, the actuating piston under the Effect of the working pressure acts on the valve body against the counterforce, the actuating piston of the first actuating cylinder being the working pressure and has measuring surfaces acted upon by the load pressure and under which Effect of the pressure difference between the working pressure and the load pressure above the second actuating cylinder acts on the valve body against the counterforce. The valve body takes over together with the first actuating cylinder the load-sensing function and, with the second actuating cylinder, pressure control, which is superimposed on the load sensing, i.e. instead of the latter in Function occurs when the hydraulic force enters the second actuating cylinder System stops at the fixed stop.

Die Druckregelung weist bei Einsatz der Fördervolumen-Rückmeldeeinrichtung das gleiche proportionale Verhalten wie die Load-Sensing-Regelung auf.The pressure control points when using the delivery volume feedback device the same proportional behavior as the load sensing control.

Bei Ausbildung der Fördervolumen-Rückmeldeeinrichtung mit einer oder mehreren Wegmeßfedern, deren Kennlinien einer Leistungshyperbel angenähert sind, ergibt sich statt der Druck- eine Leistungsregelung. Deren Kennlinie kannn ebenso wie die der vorerwähnten Druckregelung durch gleichzeitige Verwendung der Volumenstrom-Rückmeldeeinrichtung entsprechend der Meßflächendifferenz abgewandelt werden.When designing the delivery volume feedback device with one or several measuring springs, the characteristics of which approximate a performance hyperbola there is a power regulation instead of the pressure. Their characteristic can as well as that of the aforementioned pressure control by simultaneous Use of the volume flow feedback device according to the measurement area difference be modified.

Ferner ist es möglich, mit Hilfe einer Übersteuerungseinrichtung zum Verändern der Größe der die Meßflächen beaufschlagenden Druckdifferenz zwischen dem Arbeitsdruck und dem Lastdruck die Kennlinien der Load-Sensing-Regelung und ggfs. der Druck- oder Leistungsregelung gezielt zu verändern.It is also possible to use an override device to Changing the size of the pressure difference acting on the measuring surfaces The characteristics of the load-sensing control between the working pressure and the load pressure and possibly the pressure or power control change.

Weitere Merkmale und Vorteile der Erfindung ergeben sich aus den verbleibenden Ansprüchen.Further features and advantages of the invention result from the remaining ones Claims.

Nachstehend ist der Stand der Technik und die Erfindung anhand Zweier bevorzugter Ausführungsbeispiele unter Bezugnahme auf die Zeichnung näher beschrieben. Es zeigen:

Fig. 1
einen Schaltplan einer Load-Sensing-Schaltung in einer ersten Ausgestaltung nach dem Stand der Technik,
Fig. 2
ein Diagramm, das die Kennlinie der Load-Sensing-Schaltung nach Figur 1 zeigt,
Fig. 3
einen vereinfachten Schaltplan einer Load-Sensing-Schaltung in einer zweiten Ausgestaltung nach dem Stand der Technik,
Fig. 4
einen vereinfachten Schaltplan einer Load-Sensing-Schaltung in einer dritten Ausgestaltung nach dem Stand der Technik,
Fig. 5
einen vereinfachten Schaltplan einer Load-Sensing-Schaltung gemäß einem bevorzugten Ausführungsbeispiel der Erfindung,
Fig. 6
ein Diagramm, das die Kennlinie der Load-Sensing-Schaltung nach Figur 5 zeigt, und
Fig. 7
einen vereinfachten Schaltplan einer Load-Sensing-Schaltung gemäß einem weitere bevorzugten Ausführungsbeispiel der Erfindung.
The prior art and the invention are described in more detail below using two preferred exemplary embodiments with reference to the drawing. Show it:
Fig. 1
2 shows a circuit diagram of a load-sensing circuit in a first embodiment according to the prior art,
Fig. 2
2 shows a diagram showing the characteristic curve of the load-sensing circuit according to FIG. 1,
Fig. 3
a simplified circuit diagram of a load sensing circuit in a second embodiment according to the prior art,
Fig. 4
a simplified circuit diagram of a load-sensing circuit in a third embodiment according to the prior art,
Fig. 5
1 shows a simplified circuit diagram of a load-sensing circuit according to a preferred exemplary embodiment of the invention,
Fig. 6
a diagram showing the characteristic of the load sensing circuit of Figure 5, and
Fig. 7
a simplified circuit diagram of a load sensing circuit according to another preferred embodiment of the invention.

Figur 1 zeigt eine Load-Sensing-Schaltung für eine nullhubgeregelte Hydropumpe 1 verstellbaren Fördervolumens V, die im offenen Kreislauf zwei parallelgeschaltete Verbraucher 2 wie etwa zwei Hydromotoren über zwei Arbeitsleitungen 3 hydraulisch antreibt. Die Hydropumpe 1 ist mit einem nicht gezeigten Antriebsmotor mechanisch gekoppelt und über eine Hauptarbeitsleitung 4 an die beiden Arbeitsleitungen 3 sowie über eine Saugleitung 5 an den Tank 6 angeschlossen. Von den Verbrauchern 2 führt je eine Rücklaufleitung 7 ebenfalls zum Tank 6.Figure 1 shows a load sensing circuit for a zero stroke controlled Hydraulic pump 1 adjustable delivery volume V, two in the open circuit consumers 2 connected in parallel, such as two hydraulic motors over two Working lines 3 drives hydraulically. The hydraulic pump 1 is with a Drive motor, not shown, mechanically coupled and via a main working line 4 to the two working lines 3 and via a suction line 5 connected to the tank 6. One of the consumers 2 leads Return line 7 also to tank 6.

Die Hydropumpe 1 ist beispielsweise als Axialkolbenpumpe ausgebildet, deren Stellglied 8 zur Verstellung ihres Fördervolumens V über die Kolbenstange 9 mit dem Stellkolben 10 eines Hydrozylinders 11 in Differentialbauweise mechanisch gekoppelt ist. Der Stellkolben 10 definiert im Hydrozylinder 11 mit seiner kleineren, kreisringförmigen Stirnfläche einen Druckraum 12 und mit seiner gegenüberliegenden, größeren, kreisförmigen Stirnfläche einen Druckraum 13. Der Druckraum 12 ist über eine erste Stelldruckleitung 14 an die Hauptarbeitsleitung 4 und über eine zweite Stelldruckleitung 15 an den Druckraum 13 angeschlossen.The hydraulic pump 1 is designed, for example, as an axial piston pump, the Actuator 8 for adjusting its delivery volume V via the piston rod 9 with the actuating piston 10 of a hydraulic cylinder 11 in a differential design is mechanically coupled. The actuating piston 10 defines in the hydraulic cylinder 11 with its smaller, circular end face a pressure chamber 12 and with its opposite, larger, circular end face one Pressure chamber 13. The pressure chamber 12 is connected via a first signal pressure line 14 the main working line 4 and via a second signal pressure line 15 to the Pressure chamber 13 connected.

Die Load-Sensing-Schaltung besteht aus einem Regelventil 16 in der zweiten Stelldruckleitung 15, einer Volumenstrom-Rückmeldeeinrichtung 17 und je einer Verstelldrossel 18 in den beiden Arbeitsleitungen 3. Das Regelventil 16, das schaltsymbolisch in Fig. 7 dargestellt ist, teilt die zweite Stelldruckleitung 15 in einen ersten, an den Druckraum 12 angeschlossenen Stelldruckleitungsabschnitt 19 und einen zweiten, an den Druckraum 13 angeschlossenen Stelldruckleitungsabschnitt 20. Es ist als ein drosselndes 3/2-Wegeventil mit einem Arbeitsanschluß P an den ersten Stelldruckleitungsabschnitt 19, einem Arbeitsanschluß A an den zweiten Stelldruckleitungsabschnitt 20 und einem Arbeitsanschluß T an eine zum Tank 6 führende Entlastungsleitung 21 ausgebildet.The load sensing circuit consists of a control valve 16 in the second Signal pressure line 15, a volume flow feedback device 17 and each an adjusting throttle 18 in the two working lines 3. The control valve 16, which is shown symbolically in FIG. 7, divides the second Signal pressure line 15 in a first, connected to the pressure chamber 12 Signal pressure line section 19 and a second, to the pressure chamber 13 connected signal pressure line section 20. It is considered a throttling 3/2-way valve with a working connection P to the first signal pressure line section 19, a working connection A to the second signal pressure line section 20 and a working connection T to a leading to the tank 6 Relief line 21 formed.

Der Ventilkörper 22 des Regelventils 16 weist an seinen beiden Enden eine erste Meßfläche MF1 und eine zweite Meßfläche MF2 auf. Die erste Meßfläche MF1 ist größer als die zweite Meßfläche MF2 und definiert einen Arbeitdruck-Steuerraum 23, der über eine Arbeitsdruck-Steuerleitung 24 an den erste Stelldruckleitungsabschnitt 19 angeschlossen ist. Die zweite Meßfläche MF2 definiert einen Lastdruck-Steuerraum 25, der über eine Lastdruck-Steuerleitung 26 an ein Wechselventil 27 in einer Verbindungsleitung 28 angeschlossen ist. Die Verbindungsleitung 28 verbindet diejenigen Arbeitsleitungsabschnitte 3, 29 miteinander, die in Strömungsrichtung nach den Verstelldrosseln 18, d.h. zwischen diesen und den Verbrauchern 2 angeordnet sind. Im Lastdruck-Steuerraum 25 ist eine vorgespannte Druckfeder 30 angeordnet, die den Ventilkörper 22 in Figur 1 nach links in Richtung einer ersten Arbeitsstellung beaufschlagt, in der die Arbeitsanschlüsse A und T miteinander verbunden sind, während der Arbeitsanschluß P gesperrt ist.The valve body 22 of the control valve 16 has at its two ends a first measuring surface MF 1 and a second measuring surface MF 2 . The first measuring area MF 1 is larger than the second measuring area MF 2 and defines a working pressure control chamber 23 which is connected to the first signal pressure line section 19 via a working pressure control line 24. The second measuring surface MF 2 defines a load pressure control chamber 25, which is connected via a load pressure control line 26 to a shuttle valve 27 in a connecting line 28. The connecting line 28 connects those working line sections 3, 29 to one another which are arranged in the flow direction after the adjusting throttles 18, ie between these and the consumers 2. A preloaded compression spring 30 is arranged in the load pressure control chamber 25, which acts on the valve body 22 in FIG. 1 to the left in the direction of a first working position, in which the working connections A and T are connected to one another, while the working connection P is blocked.

Die Volumenstrom-Rückmeldeeinrichtung 17 umfaßt die beiden unterschiedlich großen Meßflächen MF1 und MF2 am Ventilkörper 22 und dient zur Erzeugung einer am Ventilkörper angreifenden Rückmeldekraft FR, wie nachstehend beschrieben ist.The volume flow feedback device 17 comprises the two differently sized measuring surfaces MF 1 and MF 2 on the valve body 22 and serves to generate a feedback force F R acting on the valve body, as described below.

Die Funktion der Load-Sensing-Schaltung nach Figur 1 ist wie folgt: Die nullhubgeregelte Hydropumpe 1 wird durch den im Druckraum 12 des Hydrozylinders 11 herrschenden, über die erste Stelldruckleitung 14 von der Hauptarbeitsleitung 4 abgenommenen Stell- bzw. Arbeitsdruck pA und ggfs. durch eine nicht gezeigte Druckfeder im Druckraum 12 in Richtung maximalen Fördervolumens beaufschlagt, solange das Regelventil 16 seine vorerwähnte erste Arbeitsstellung einnimmt. In dieser ist der Druckraum 13 des Hydrozylinders 11 über den zweiten Stelldruckleitungsabschnitt 20, die geöffneten Arbeitsanschlüsse A und T des Regelventils 16 sowie die Entlastungsleitung 21 zum Tank 6 hin entlastet, während sich infolge des gesperrten Arbeitsanschlusses P im Druckraum 12 der volle Stell- bzw. Arbeitsdruck pA aufbaut und den Stellkolben 11 in Richtung seiner in Figur 1 rechten Endstellung beaufschlagt, die dem maximalen Fördervolumen V der Hydropumpe 1 entspricht.The function of the load-sensing circuit according to FIG. 1 is as follows: The zero-stroke-controlled hydraulic pump 1 is actuated by the actuating or working pressure p A, which may be present in the pressure chamber 12 of the hydraulic cylinder 11, and is removed from the main working line 4 via the first actuating pressure line 14. acted upon by a compression spring, not shown, in the pressure chamber 12 in the direction of the maximum delivery volume, as long as the control valve 16 assumes its aforementioned first working position. In this, the pressure chamber 13 of the hydraulic cylinder 11 is relieved via the second signal pressure line section 20, the opened working connections A and T of the control valve 16 and the relief line 21 to the tank 6, while the full setting or Working pressure p A builds up and acts on the actuating piston 11 in the direction of its right end position in FIG. 1, which corresponds to the maximum delivery volume V of the hydraulic pump 1.

Die Vorspannung (Einstellkraft oder Gegenkraft FG) der Druckfeder 30 ist so gewählt, daß sie gleich der hydraulischen Kraft derjenigen Druckdifferenz Δp zwischen dem vor der Verstelldrossel 18 abgenommenen Arbeitsdruck pA der Hydropumpe 1 und dem nach der Verstelldrossel 18 abgenommenen Lastdruck pL des Verbrauchers 2 ist, die, an beiden Meßflächen MF1 und MF2 des Ventilkörpers 22 wirkend, an derjenigen Verstelldrossel 18 entsteht, die auf größten Drosselquerschnitt eingestellt ist und vom maximalen Volumenstrom Q der Hydropumpe 1 durchströmt wird; in diesem Fall ist die jeweils andere Verstelldrossel 18 vollständig geschlossen.The preload (setting force or counterforce F G ) of the compression spring 30 is selected such that it is equal to the hydraulic force of that pressure difference Δp between the working pressure p A of the hydraulic pump 1 which was reduced in front of the adjusting throttle 18 and the load pressure p L of the consumer which was reduced after the adjusting throttle 18 2, which, acting on both measuring surfaces MF 1 and MF 2 of the valve body 22, is formed on the adjusting throttle 18 which is set to the largest throttle cross section and through which the maximum volume flow Q of the hydraulic pump 1 flows; in this case the other adjustment throttle 18 is completely closed.

Unter diesen Bedingungen steht die hydraulische Kraft der vom maximalen Volumenstrom Q an der Verstelldrossel 18 erzeugten Druckdifferenz Δ p im Gleichgewicht mit der Vorspannung oder Gegenkraft FG der Druckfeder 30, so daß das Regelventil 16 seine in Figur 1 gezeigte Ausgangsstellung einnimmt, in der sämtliche Arbeitsanschlüsse A, P und T gesperrt sind.Under these conditions, the hydraulic force of the pressure difference Δ p generated by the maximum volume flow Q at the adjusting throttle 18 is in equilibrium with the pretension or counterforce F G of the compression spring 30, so that the control valve 16 assumes its starting position shown in FIG. 1, in which all working connections A, P and T are locked.

Wenn nun beispielsweise der Drosselquerschnitt der Verstelldrossel 18 verringert wird, steigt die Druckdifferenz Δp entsprechend an und verschiebt den Ventilkörper 22 in Figur 1 nach rechts in eine zweite Arbeitsstellung, in der bei gesperrtem Arbeitsanschluß T die Arbeitsanschlüsse A und P geöffnet sind und die beiden Stelldruckleitungsabschnitte 19 und 20 miteinander verbinden. Der Stell- bzw. Arbeitsdruck pA beaufschlagt nun die größere, kreisförmige Kolbenfläche des Stellkolbens 10, verschiebt diesen somit in Figur 1 nach links und schwenkt damit die Hydropumpe 1 auf kleineres Fördervolumen V zurück, bis sie denjenigen, reduzierten Volumenstrom Q fördert, der an der Verstelldrossel 18 die ursprüngliche, der Vorspannung FG der Druckfeder 30 entsprechende Druckdif-Druckdifferenz Δp verursacht, d.h. bis sich am Ventilkörper 22 erneut Kraftgleichgewicht einstellt. Entsprechend dem reduzierten Volumenstrom Q verringert sich die Belastung der Hydropumpe 1, so daß der Arbeitsdruck pA und der Lastdruck pL um den gleichen Wert fallen. Da der Lastdruck pL jedoch an der kleineren der beiden Meßflächen MF1 und MF2 wirkt, nimmt seine hydraulische Kraft um ein der Meßflächendifferenz MF1-MF2 entsprechendes geringeres Maß ab als die hydraulische Kraft des die größere Meßfläche MF1 beaufschlagenden Arbeitsdrucks pA. Die Differenz zwischen der hydraulischen Kraft der Druckdifferenz Δp vor und derjenigen nach dem vorgenannten Zurückschwenken der Hydropumpe 1 auf kleineres Fördervolumen V ist ein Maß für die resultierende Verringerung des Volumenstroms Q. Diese Kraftdifferenz an den die Rückmeldeeinrichtung 17 bildenden Meßflächen MF1 und MF2 wird hier als Rückmeldekraft FR bezeichnet, die am Ventilkörper 22 gleichsinnig mit der Vorspannung FG der Druckfeder 30 wirkt. Die Rückmeldekraft FR verstärkt also die Beaufschlagung des Ventilkörpers 22 durch die Gegenkraft FG und stellt somit das Regelventil 16 auf einen größeren Sollwert des Volumenstroms Q ein. Damit ergibt sich die in Figur 2 dargestellte, mit abnehmendem Volumenstrom Q ansteigende p-Q-Kennlinie, die ein proportionales Betriebsverhalten der Hydropumpe 1 kennzeichnet.If, for example, the throttle cross section of the adjusting throttle 18 is reduced, the pressure difference Δp increases accordingly and shifts the valve body 22 in FIG. 1 to the right into a second working position, in which when the working connection T is blocked, the working connections A and P are open and the two signal pressure line sections 19 and 20 connect with each other. The actuating or working pressure p A now acts on the larger, circular piston surface of the actuating piston 10, thus displacing it to the left in FIG. 1 and thus swiveling the hydraulic pump 1 back to a smaller delivery volume V until it delivers the reduced volume flow Q that starts the adjusting throttle 18 causes the original pressure differential pressure difference Δp corresponding to the preload F G of the compression spring 30, ie until a force equilibrium is established again on the valve body 22. In accordance with the reduced volume flow Q, the load on the hydraulic pump 1 is reduced, so that the working pressure p A and the load pressure p L fall by the same value. However, since the load pressure p L acts on the smaller of the two measuring surfaces MF 1 and MF 2 , its hydraulic force decreases by a smaller amount corresponding to the measuring surface difference MF 1 -MF 2 than the hydraulic force of the working pressure p A acting on the larger measuring surface MF 1 , The difference between the hydraulic force of the pressure difference Δp before and that after the aforementioned pivoting back of the hydraulic pump 1 to a smaller delivery volume V is a measure of the resulting reduction in the volume flow Q. This difference in force at the measuring surfaces MF 1 and MF 2 forming the feedback device 17 becomes here referred to as feedback force F R , which acts on the valve body 22 in the same direction as the preload F G of the compression spring 30. The feedback force F R thus increases the action on the valve body 22 by the counterforce F G and thus sets the control valve 16 to a larger setpoint of the volume flow Q. This results in the pQ characteristic curve shown in FIG. 2, which increases with decreasing volume flow Q and characterizes a proportional operating behavior of the hydraulic pump 1.

Das Betriebsverhalten der Hydropumpe 1 folgt der gleichen Kennlinie, wenn der Drosselquerschnitt der Verstelldrossel 18 vergrößert wird. Damit fällt die Druckdifferenz Δ p, so daß der Ventilkörper 22 in die erste Arbeitsstellung überführt und damit die Hydropumpe 1 so lange auf größeres Fördervolumen V ausgeschwenkt wird, bis sie denjenigen, größeren Volumenstrom Q fördert, der an der Verstelldrossel 18 die ursprüngliche Druckdifferenz Δp verursacht, d.h. bis sich Kraftgleichgewicht am Ventilkörper 22 einstellt. Durch den größeren Volumenstrom Q erhöht sich die Belastung der Hydropumpe 1, so daß der Arbeitsdruck pA und der Lastdruck pL im gleichen Maße ansteigen. Die hydraulische Kraft des an der größeren Meßfläche MF1 wirkenden Arbeitsdrucks pA nimmt um ein der Meßflächendifferenz entsprechendes größeres Maß zu als die hydraulische Kraft des die kleinere Meßfläche MF 2 beaufschlagenden Lastdrucks pL. Die dadurch in bereits beschriebener Weise entstehende Rückmeldekraft FR wirkt am Ventilkörper 22 gegensinnig zur Gegenkraft FG, womit das Regelventil 16 auf einen kleineren Sollwert des Volumenstroms Q eingestellt ist. Es ergibt sich die gleiche, in Figur 2 gezeigte, mit zunehmendem Volumenstrom Q fallende p-Q-Kennlinie, die ein proportionales Betriebsverhalten der Hydropumpe 1 kennzeichnet.The operating behavior of the hydraulic pump 1 follows the same characteristic curve if the throttle cross section of the variable throttle 18 is increased. The pressure difference Δ p thus falls, so that the valve body 22 transfers to the first working position and the hydraulic pump 1 is swung out to a larger delivery volume V until it promotes the larger volume flow Q which causes the original pressure difference Δp at the adjusting throttle 18 , ie until force equilibrium is established on valve body 22. The larger volume flow Q increases the load on the hydraulic pump 1, so that the working pressure p A and the load pressure p L increase to the same extent. The hydraulic force of the working pressure p A acting on the larger measuring surface MF 1 increases by a larger amount corresponding to the measuring surface difference than the hydraulic force of the load pressure p L acting on the smaller measuring surface MF 2 . The resulting feedback force F R acts on the valve body 22 in the opposite direction to the counter force F G , whereby the control valve 16 is set to a smaller setpoint of the volume flow Q. The result is the same pQ characteristic curve, shown in FIG. 2 and falling with increasing volume flow Q, which characterizes a proportional operating behavior of the hydraulic pump 1.

Das nach der vorstehenden Beschreibung zur Steuerung der Hydropumpe 1 eingesetzte Regelventil 16 übernimmt gleichzeitig auch die Funktion einer Regelung, mit der das Fördervolumen V der Hydropumpe 1 bei wechselnden Belastungen derart verstellt wird, daß der geförderte Volumenstrom Q dem mit der Verstelldrossel 18 eingestellten Sollwert übereinstimmt.That according to the above description for controlling the hydraulic pump 1 Control valve 16 also takes over the function of a Regulation with which the delivery volume V of the hydraulic pump 1 changes Loads are adjusted such that the volume flow Q delivered with the adjusting throttle 18 matches the setpoint.

Wenn beispielsweise die Belastung des Verbrauchers 2 so stark ansteigt, daß der Antriebsmotor gedrückt wird und damit die Hydropumpe 1 einem dem Drehzahl-Abfall entsprechenden kleineren Volumenstrom Q fördert, wird der Ventilkörper 22 in gleicher Weise wie bei der vorbeschriebenen Steuerung in die erste Arbeitsstellung verschoben und damit die Hydropumpe 1 so lange auf größeres Fördervolumen V ausgeschwenkt, bis sie denjenigen Volumenstrom Q fördert, der an der Verstelldrossel 18 die ursprüngliche Druckdifferenz Δ p erzeugt. In entsprechender Weise wird bei zu geringer Belastung des Verbrauchers 2 und dementsprechendem Höherdrehen des Antriebsmotors und der Hydropumpe 1 letztere auf kleineres Fördervolumen eingestellt, bis der geförderte Volumenstrom Q dem Bedarf des Verbrauchers angepaßt ist.For example, if the load on the consumer 2 increases so much that the drive motor is pressed and thus the hydraulic pump 1 one Speed drop corresponding smaller volume flow Q promotes the Valve body 22 in the same manner as in the control described in shifted the first working position and thus the hydraulic pump 1 for so long larger delivery volume V swung out until it reaches that volume flow Q promotes the original pressure difference Δ p on the adjusting throttle 18 generated. In a corresponding manner, the load on the Consumer 2 and accordingly cranking up the drive motor and Hydraulic pump 1 the latter set to a smaller delivery volume until the volume flow Q is adapted to the needs of the consumer.

Wenn die bisher geschlossene Verstelldrossel 18 ebenfalls geöffnet wird, teilt sich der von der Hydropumpe 1 geförderte Volumenstrom Q entsprechend den eingestellten Drosselquerschnitten und den an den Verbrauchern 2 wirkenden Belastungen an den Abzweigungen der Arbeitsleitungen 3 von der Hauptarbeitsleitung 4 in zwei Teilvolumenströme, die die Verbraucher 2 mit entsprechender Geschwindigkeit antreiben. Der jeweils höhere Lastdruck pL wirkt über das Wechselventil 27 und die Lastdruck-Steuerleitung 26 auf die zweite Meßfläche MF2 des Ventilkörpers 22, während der in beiden Arbeitsleitungen 3 gleiche Arbeitsdruck pA die erste Meßfläche MF1 beaufschlagt. Auf diese Weise wirkt am Ventilkörper 22 die jeweils kleinere der sich an beiden Verstelldrosseln 18 einstellenden Druckdifferenz Δ p; mit anderen Worten, die vorbeschriebene Steuerung und Regelung steuert bzw. regelt in der vorbeschriebenen Weise lediglich den stärker belasteten Verbraucher 2.If the previously closed adjustment throttle 18 is also opened, the volume flow Q delivered by the hydraulic pump 1 is divided into two partial volume flows, which the consumers 2, in accordance with the set throttle cross sections and the loads acting on the consumers 2 at the branches of the working lines 3 from the main working line 4 drive at appropriate speed. The respectively higher load pressure p L acts via the shuttle valve 27 and the load pressure control line 26 on the second measuring surface MF 2 of the valve body 22, while the same working pressure p A in both working lines 3 acts on the first measuring surface MF 1 . In this way, the smaller of the pressure difference Δ p occurring at both adjusting throttles 18 acts on the valve body 22; in other words, the control and regulation described above only controls or regulates the consumer 2 which is subject to greater loads in the manner described above.

Die Load-Sensing-Schaltung nach Figur 3 unterscheidet sich bei ansonsten gleicher Konstruktion und Funktion von derjenigen nach Figur 1 durch eine Übersteuerungseinrichtung 31 zum Verändern der Größe der die erste und zweite Meßfläche MF1, MF2. beaufschlagenden Druckdifferenz Δp. Die Übersteuerungseinrichtung 31 umfaßt eine dritte Meßfläche MF3, die am Ventilkörper 22 ausgebildet ist, einen Steuerdruckraum 32 definiert und über eine an diesen angeschlossene Steuerdruckleitung 33 mit einem externen Steuerdruck pS gegen die Gegenkraft FG der Druckfeder 30 beaufschlagt werden kann, um die Druckdifferenz Δp nach Bedarf zu erhöhen; diese mit steigendem Steuerdruck pS ein Zurückschwenken der Hydropumpe 1 auf kleineres Fördervolumen bewirkende Funktion der Übersteuerungseinrichtung 31 wird auch als Negativ-Control-Funktion bezeichnet. Andererseits ist auch eine sog. Positiv-Control-Funktion möglich, mit der bei steigendem Steuerdruck die Hydropumpe 1 auf größeres Fördervolumen V ausgeschwenkt wird; zu diesem Zweck kann die Steuerdruckleitung 33 an den dem Steuerdruckraum 32 gegenüberliegenden, in Figur 3 mit dem Bezugszeichen 34 bezeichneten Druckraum angeschlossen sein.The load-sensing circuit according to FIG. 3 differs from that according to FIG. 1 with an otherwise identical construction and function by an override device 31 for changing the size of the first and second measuring surfaces MF 1 , MF 2 . pressure difference Δp. The override device 31 comprises a third measuring surface MF 3 , which is formed on the valve body 22, defines a control pressure chamber 32 and can be acted upon by an external control pressure p S against the counterforce F G of the compression spring 30 via a control pressure line 33 connected thereto, by the pressure difference Increase Δp as required; this function of the override device 31 which causes the hydraulic pump 1 to pivot back to a smaller delivery volume as the control pressure p S increases is also referred to as a negative control function. On the other hand, a so-called positive control function is also possible, with which the hydraulic pump 1 is pivoted out to a larger delivery volume V when the control pressure increases; For this purpose, the control pressure line 33 can be connected to the pressure space opposite the control pressure space 32, designated by reference numeral 34 in FIG.

Figur 4 zeigt eine Load-Sensing-Schaltung, die statt der hydraulischen Übersteuerungseinrichtung 31 eine Übersteuerungseinrichtung 35 umfaßt, die als elektrisch ansteuerbarer Eingangsteil, beispielsweise in Form eines Schaltmagneten oder Regelmagneten, für das Regelventil 16 ausgebildet ist und bei entsprechender Ansteuerung den Ventilkörper 22 mit einer Zusatzkraft beaufschlagt, die entweder gegen die Gegenkraft FG der Druckfeder 30 (bei Durchführung der Negativ-Control-Funktion) oder in entgegengesetzte Richtung (bei Durchführung der Positiv-Control-Funktion) wirkt.FIG. 4 shows a load-sensing circuit which, instead of the hydraulic override device 31, comprises an override device 35 which is designed as an electrically controllable input part, for example in the form of a switching magnet or control magnet, for the control valve 16 and, with appropriate control, the valve body 22 with a Additional force is applied, which either acts against the counterforce F G of the compression spring 30 (when performing the negative control function) or in the opposite direction (when performing the positive control function).

Die erfindungsgemäße Load-Sensing-Sthaltung nach Figur 5 unterscheidet sich bei ansonsten gleicher Konstruktion und Funktion von derjenigen nach Figur 1 dadurch, daß statt der Volumenstrom-Rückmeldeeinrichtung 17 mit unterschiedlich großen Meßflächen MF1 und MF2 gleichgroße und deshalb mit den Bezugszeichen MF'1 und MF'2 bezeichnete Meßflächen sowie eine Fördervolumen-Rückmeldeeinrichtung 36 in Form einer Wegmeßfeder verwendet werden, die am Stellglied 8 der Hydropumpe 1 und an dem der Druckfeder 30 gegenüberliegenden Ende des Ventilkörpers 22 angreift. Die Wegmeßfeder 36.erfaßt die Fördervolumen-Einstellung der Hydropumpe 1, indem sie den Ventilkörper 22 bei zunehmendem Fördervolumen V mit entsprechend zunehmender Rückmeldekraft FR und bei abnehmendem Fördervolumen V mit entsprechend abnehmender Rückmeldekraft FR gegen die Gegenkraft FG der Druckfeder 30 beaufschlagt. Auf diese Weise wird die Beaufschlagung des Ventilkörpers 22 durch die Gegenkraft FG und damit die Sollwert-Einstellung des Regelventils 16 derart verändert, daß sich die in Figur 6 gezeigte, mit zunehmendem Fördervolumen V abfallende und, umgekehrt, mit abnehmendem Fördervolumen V ansteigende p-V-Kennlinie ergibt, die eine Load-Sensing-Schaltung mit sog. Proportionalverhalten kennzeichnet.The load sensing arrangement according to FIG. 5 differs from that according to FIG. 1 with otherwise the same construction and function in that instead of the volume flow feedback device 17 with measuring surfaces MF 1 and MF 2 of different sizes, they are of the same size and therefore have the reference symbols MF ' 1 and MF ' 2 designated measuring surfaces and a delivery volume feedback device 36 are used in the form of a displacement measuring spring which acts on the actuator 8 of the hydraulic pump 1 and on the end of the valve body 22 opposite the compression spring 30. The measuring spring 36 detects the delivery volume setting of the hydraulic pump 1 by acting on the valve body 22 with increasing delivery volume V with a correspondingly increasing feedback force F R and with decreasing delivery volume V with a correspondingly decreasing feedback force F R against the counterforce F G of the compression spring 30. In this way, the action on the valve body 22 by the counterforce F G and thus the setpoint setting of the control valve 16 is changed such that the pV- shown in FIG. 6 decreases with increasing delivery volume V and, conversely, increases with decreasing delivery volume V. Characteristic results that characterizes a load-sensing circuit with so-called proportional behavior.

Die Erfindung erstreckt sich auch auf Ausführungsbeispiele, die sowohl die Volumenstrom-Rückmeldeeinrichtung 17 als auch die Fördervolumen-Rückmeldeeinrichtung 36 verwenden.The invention also extends to exemplary embodiments, both the Volume flow feedback device 17 and the delivery volume feedback device 36 use.

Figur 7 zeigt eine Load-Sensing-Schaltung mit überlagerter Druck- bzw. Leistungsregelung. Sie umfaßt einen ersten, doppeltwirkenden und ortsfesten Stellzylinder 37, einen zweiten, einfachwirkenden Stellzylinder 38 und das Regelventil 16 nach Figur 1, allerdings ohne die vom Differenzdruck Δp beaufschlagbaren Meßflächen. Diese sind als Meßflächen MF'1 und MF'2 gleicher Größe am Stellkolben 39 des ersten Stellzylinders 37 ausgebildet. Die erste Meßfläche MF'1 definiert den Arbeitsdruck-Steuerraum 23, der über die Arbeitsdruck-Steuerleitung 24 an die Hauptarbeitsleitung 4 angeschlossen ist. Die zweite Meßfläche MF'2 definiert den Lastdruck-Steuerraum 25, der über die Lastdruck-Steuerleitung 26 an das Wechselventil 27 in der die Arbeitsleitungsabschnitte 29 verbindenden Verbindungsleitung 28 angeschlossen ist. Die an der dem höherbelasteten Verbraucher zugeordneten Verstelldrossel 18 abgenommene Druckdifferenz Δp wirkt am Stellkolben 39 des ersten Stellzylinders 37 und beaufschlagt über dessen Kolbenstange 40 den zweiten, in einer Führung 41 längsverschiebbar geführten Stellzylinder 38 in Figur 7 nach links in Richtung des Ventilkörpers 22.Figure 7 shows a load sensing circuit with superimposed pressure or power control. It comprises a first, double-acting and stationary actuating cylinder 37, a second, single-acting actuating cylinder 38 and the control valve 16 according to FIG. 1, but without the measuring surfaces acted upon by the differential pressure Δp. These are designed as measuring surfaces MF ' 1 and MF' 2 of the same size on the actuating piston 39 of the first actuating cylinder 37. The first measuring surface MF ' 1 defines the working pressure control chamber 23, which is connected to the main working line 4 via the working pressure control line 24. The second measuring surface MF ' 2 defines the load pressure control chamber 25, which is connected via the load pressure control line 26 to the shuttle valve 27 in the connecting line 28 connecting the working line sections 29. The pressure difference .DELTA.p taken off at the adjusting throttle 18 associated with the higher-load consumer acts on the actuating piston 39 of the first actuating cylinder 37 and acts on the second actuating cylinder 38 in FIG. 7 to the left in the direction of the valve body 22 via its piston rod 40.

Der Stellkolben 42 des zweiten Stellzylinders 38 weist eine kreisringförmige Kolbenfläche 43 auf, die gemeinsam mit einer kreisringförmigen Zylinderfläche 44 gleicher Größe einen ebenfalls kreisringförmigen Druckraum 45 definiert, der von der Kolbenstange 46 durchsetzt und über eine Steuerleitung 47 an den zweiten Stelldruckleitungsabschnitt 15, 20 angeschlossen ist. Der Stellkolben 42 beaufschlagt unter der Wirkung des im Druckraum 45 anstehenden, über den zweiten Stelldruckleitungsabschnitt 15, 20 von der ersten Stelldruckleitung 14 abgenommenen Arbeitsdrucks pA ausreichender Größe den Ventilkörper 22 des Regelventils 16 gegen die Gegenkraft FG der einstellbaren Druckfeder 30 in Richtung der zweiten Arbeitsstellung.The actuating piston 42 of the second actuating cylinder 38 has an annular piston surface 43 which, together with an annular cylinder surface 44 of the same size, defines a likewise annular pressure chamber 45 which is penetrated by the piston rod 46 and is connected to the second actuating pressure line section 15, 20 via a control line 47 , The actuating piston 42 acts on the valve body 22 of the control valve 16 against the counterforce F G of the adjustable compression spring 30 in the direction of the second, under the action of the working pressure p A of sufficient size present in the pressure chamber 45 and taken from the first actuating pressure line section 15, 20 by the first actuating pressure line 14 working position.

Die Rückmeldeeinrichtung ist hier als Fördervolumen-Rückmeldeeinrichtung 36 ausgebildet, die im Falle der vorerwähnten Druckregelung eine Wegmeßfeder und im Falle der vorerwähnten Leistungsregelung eine Anordnung mehrerer, in Reihe geschalteter Wegmeßfedern mit unterschiedlichen Kennlinien umfaßt, die einer Leistungshyperbel angenähert sind. Die Wegmeßfeder bzw. Wegmeßfeder-Anordnung 36 greift an der Kolbenstange 9 des Stellkolbens 10 des Hydrozylinders 11 und an dem den Stellzylindern 37, 38 gegenüberliegenden, von der Druckfeder 30 beaufschlagten Ende des Ventilkörpers 22 an. Somit wird die Wegmeßfeder bzw. Wegmeßfeder-Anordnung 36 mit zunehmendem Zurückschwenken der Hydropumpe 1 auf kleineres Fördervolumen V gespannt, so daß die dabei entstehende Rückmeldekraft FR gleichsinnig mit der Druckfeder 30 wirkt, d.h. der Ventilkörper 22 in Richtung der ersten Arbeitsstellung und über diesen und den Stellkolben 42 der zweite Stellzylinder 38 gegen einen ortsfesten Anschlag 48 beaufschlagt wird.The feedback device is designed here as a delivery volume feedback device 36 which, in the case of the aforementioned pressure control, comprises a position measuring spring and, in the case of the aforementioned power control, an arrangement of a plurality of travel measuring springs connected in series with different characteristic curves which approximate a performance hyperbola. The displacement spring or displacement spring arrangement 36 engages on the piston rod 9 of the actuating piston 10 of the hydraulic cylinder 11 and on the end of the valve body 22 opposite the actuating cylinders 37, 38 and acted upon by the compression spring 30. Thus, the measuring spring or measuring spring arrangement 36 is tensioned with increasing swiveling back of the hydraulic pump 1 to a smaller delivery volume V, so that the resulting feedback force F R acts in the same direction with the compression spring 30, ie the valve body 22 in the direction of the first working position and via this and the actuating piston 42, the second actuating cylinder 38 is urged against a stationary stop 48.

Der Ventilkörper 22 übernimmt gemeinsam mit dem ersten Stellzylinder 37 die Load-Sensing-Funktion und gemeinsam mit dem zweiten Stellzylinder 38 die Druck- oder Leistungsregelung, wobei die p-V-Kennlinien sowohl der Load-Sensing-Regelung als auch der Druck- oder Leistungsregelung der Kennlinie der Wegmeßfeder 36, beispielsweise der in Figur 6 gezeigten Kennlinie, bzw. der Leistungshyperbel der Wegmeßfeder-Anordnung 36 entsprechen.The valve body 22 takes over together with the first actuating cylinder 37 Load-sensing function and together with the second actuating cylinder 38 Pressure or power control, with the p-V characteristics of both the load sensing control as well as the pressure or power control of the characteristic of Displacement spring 36, for example the characteristic shown in FIG. 6, or the Power hyperbola correspond to the position measuring spring arrangement 36.

Die Meßflächen MF'1 und MF'2 sind größer als die Kolbenfläche 43 und die Zylinderfläche 44, und zwar derart, daß während der Load-Sensing-Funktion die hydraulische Kraft der an den Meßflächen MF'1 und MF'2 wirkenden Druckdifferenz Δp größer als die hydraulische Kraft des an der Zylinderfläche 44 wirkenden Arbeitsdrucks pA ist und somit den zweiten Stellzylinder 38 im Abstand vom ortsfesten Anschlag 46 hält; dadurch ist die Wirkung des Arbeitsdrucks pA auf den Stellkolben 42 und damit den Ventilkörper 22 ausgeschaltet. Bei Überschreiten des Wertes, bei dem die Druck- bzw. Leistungsregelung die Load-Sensing-Funktion übersteuern soll, übersteigt die hydraulische Kraft des an der Kolbenfläche 43 und an der Zylinderfläche 44 wirkenden Arbeitsdrucks pA die hydraulische Kraft der an den Meßflächen MF'1 und MF'2 wirkenden Druckdifferenz Δ p und verschiebt den zweiten Stellzylinder 38 gegen den ortsfesten Anschlag 48. Dadurch sind der zweite Stellzylinder 38 und der Stellkolben 39 des ersten Stellzylinders 37 stillgelegt, und der Arbeitsdruck pA verschiebt den Stellkolben 42 des zweiten Stellzylinders 38 in Figur 7 nach links und überführt auf diese Weise den Ventilkörper 22 in die zweite Arbeitsstellung; die Hydropumpe wird entsprechend der Kennlinie der Wegmeßfeder 36 bzw. der Leistungshyperbel der Wegmeßfeder-Anordnung 36 auf kleineres Fördervolumen V zurückgeschwenkt.The measuring surfaces MF ' 1 and MF' 2 are larger than the piston surface 43 and the cylinder surface 44, in such a way that during the load sensing function the hydraulic force of the pressure difference Δp acting on the measuring surfaces MF ' 1 and MF' 2 is greater than the hydraulic force of the working pressure p A acting on the cylinder surface 44 and thus keeps the second actuating cylinder 38 at a distance from the fixed stop 46; as a result, the effect of the working pressure p A on the actuating piston 42 and thus the valve body 22 is switched off. If the value at which the pressure or power control is to override the load-sensing function is exceeded, the hydraulic force of the working pressure p A acting on the piston surface 43 and on the cylinder surface 44 exceeds the hydraulic force of the pressure on the measuring surfaces MF ' 1 and MF ' 2 acting pressure difference Δ p and displaces the second actuating cylinder 38 against the fixed stop 48. As a result, the second actuating cylinder 38 and the actuating piston 39 of the first actuating cylinder 37 are shut down, and the working pressure p A displaces the actuating piston 42 of the second actuating cylinder 38 in Figure 7 to the left and in this way transfers the valve body 22 into the second working position; the hydraulic pump is pivoted back to a smaller delivery volume V in accordance with the characteristic curve of the displacement spring 36 or the power hyperbola of the displacement spring arrangement 36.

Claims (9)

  1. Load-sensing circuit for a zero-stroke-regulated hydraulic pump (1) with adjustable delivery volume (V) driving at least one consumer (2) via at least one working line (3), with a control valve (16) which can be set to a nominal value of the volume flow (Q) of the hydraulic pump (1),
    the valve body (22) of which, under the effect of a counter-force (FG) setting the nominal value, can be pressurised via a first measurement surface (MF1, MF'1) by the working pressure (pA) of the hydraulic pump (1) against the counter-force (FG) towards a working position and via a second measurement surface (MF2, MF'2) by the load pressure (pL) of the consumer (2) in the same direction as the counter-force (FG) towards another working position,
    or the valve body (22) of which, under the effect of the counter-force (FG) setting the nominal value, can be pressurised via a pressure difference (Δp) acting on an actuator piston (39) in the opposite direction to the counter-force (FG),
    where the control valve (16) in the one working position provokes an adjustment of the hydraulic pump (1) towards a smaller and in the other working position towards a greater delivery volume (V),
    characterised by
    a feedback device (17, 36) to generate a feedback force (FR) corresponding to the set delivery volume (V) of the hydraulic pump (1) which acts on the valve body (22) and changes the pressurisation of the valve body (22) by the counter-force (FG) and hence the nominal value setting of the control valve (16) in the opposite direction to the changes of the delivery volume (V),
    where the feedback device comprises a delivery volume feedback device (36) which is formed with at least one position measurement spring (36) which acts on the actuator (8) adjusting the delivery volume (V) of the hydraulic pump (1) and on the valve body (22).
  2. Load-sensing circuit according to claim 1, characterised in that the characteristic curve(s) of the position measurement spring (36) resemble a power hyperbola.
  3. Load-sensing circuit according to claim 1 or 2, characterised in that the working pressure (pA) is taken in the flow direction before and the load pressure (pL) in the flow direction after a choke point (18) in the working line (3).
  4. Load-sensing circuit according to claim 3, characterised in that the choke position (18) is an adjustment choke.
  5. Load-sensing circuit according to at least one previous claim,
    characterised by an overdrive device (31, 35) to change the size of the pressure difference (Δp) acting on the measurement surfaces (MF1, MF2) between the working pressure (pA) and the load pressure (pL).
  6. Load-sensing circuit according to at least one previous claim,
    characterised in that between the valve body (22) and a first double-action stationary actuating cylinder (37) is clamped a second single-action actuating cylinder (38) pressurised by the counter-force (FG) in the direction of a stationary stop (48), the actuating piston (42) of which cylinder, under the effect of the working pressure (pA), pressurises the valve body (22) against the counter-force (FG), and in that the adjustment piston (39) of the first actuating cylinder (37) has the measurement surfaces (MF'1, MF'2) which can be subjected to the working pressure (pA) and the load pressure (pL), and under the effect of the pressure difference (Δp) between the working pressure (pA) and the load pressure (pL) via the second actuating cylinder (38) pressurises the valve body (22) against the counter-force (FG).
  7. Load-sensing circuit according to claim 6, characterised in that the piston surface (43), pressurised by the working pressure (pA), of the actuating piston (42) of the second actuating cylinder (38) is smaller than the measurement surfaces (MF'1, MF'2) of the adjustment piston (39) of the first adjustment cylinder (37) which can be subjected to the working pressure (pA) and the load pressure (pL).
  8. Load-sensing circuit according to at least one previous claim,
    characterised in that between the valve body (22) and a first double-action stationary actuating cylinder (37) is clamped a second single-action actuating cylinder (38) which is pressurised by the counter-force (FG) in the direction of a stationary stop (48), the actuating piston (42) of which cylinder, under the effect of the working pressure (pA), pressurises the valve body (22) against the counter-force (FG), and that the actuating piston (39) of the first actuating cylinder (37) has the measurement surfaces (MF'1, MF'2) which can be subjected to the working pressure (pA) and the load pressure (pL) and under the effect of the pressure difference (Δp) between the working pressure (pA) and the load pressure (pL) via the second actuating cylinder (38) pressurises the valve body (22) against the counter-force (FG).
  9. Load-sensing circuit according to claim 8, characterised in that the piston surface (43), pressurised by the working pressure (pA), of the actuating piston (42) of the second actuating cylinder (38) is smaller than the measurement surfaces (MF'1, MF'2) of the actuating piston (39) of the first actuating cylinder (37) which can be subjected to the working pressure (pA) and the load pressure (pL).
EP95120626A 1994-12-29 1995-12-27 Load-sensing circuit Expired - Lifetime EP0719947B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4447154A DE4447154C2 (en) 1994-12-29 1994-12-29 Load-sensing circuit
DE4447154 1994-12-29

Publications (3)

Publication Number Publication Date
EP0719947A2 EP0719947A2 (en) 1996-07-03
EP0719947A3 EP0719947A3 (en) 1998-02-11
EP0719947B1 true EP0719947B1 (en) 2004-07-21

Family

ID=6537452

Family Applications (1)

Application Number Title Priority Date Filing Date
EP95120626A Expired - Lifetime EP0719947B1 (en) 1994-12-29 1995-12-27 Load-sensing circuit

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EP (1) EP0719947B1 (en)
DE (2) DE4447154C2 (en)

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DE19713934B4 (en) * 1997-04-04 2004-06-03 Brueninghaus Hydromatik Gmbh Load pressure-controlled flow regulator with flushing circuit
DE10134747B4 (en) * 2001-07-17 2017-05-04 Liebherr-Machines Bulle S.A. Method and device for load-dependent control of the fluid supply of a fluid circuit
DE10209964A1 (en) * 2002-03-06 2003-09-25 Zf Lenksysteme Gmbh System for controlling a hydraulic variable pump
DE102005016181B4 (en) * 2005-04-08 2018-05-09 Robert Bosch Automotive Steering Gmbh Regulating device for a hydraulic conveyor
DE102006002959A1 (en) * 2006-01-21 2007-07-26 Zf Lenksysteme Gmbh Hydraulic system for use in vehicles, has current regulating piston, where height of application of pressure of current regulating piston, for adjustment to pressure is changed, according to flow against lateral pressure
DE102006014074B4 (en) * 2006-03-28 2017-04-06 Robert Bosch Gmbh Dosing system and method for dispensing an additive in an exhaust system of an internal combustion engine
DE102007039589A1 (en) * 2007-08-22 2009-02-26 Voigt, Dieter, Dipl.-Ing. Regular oil pump with adjustment-dependent oil pressure control
DE102008031768A1 (en) * 2008-07-04 2010-01-07 Alpha Fluid Hydrauliksysteme Müller GmbH Regulating arrangement for proportional angle adjustment in driving or lifting units comprises a tension spring connected at its ends directly to the lifting component of a hydraulic linear motor component
DE102012112879B4 (en) 2012-12-21 2014-08-07 Pierburg Gmbh Valve device for a hydraulic circuit and oil pump control arrangement
DE102013216395B4 (en) * 2013-08-19 2019-01-17 Danfoss Power Solutions a.s. CONTROL DEVICE FOR HYDRAULIC ADJUSTING PUMPS AND ADJUSTING PUMP WITH A CONTROL DEVICE

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DE2910611A1 (en) * 1979-03-17 1980-09-18 Bosch Gmbh Robert HYDRAULIC SYSTEM
DE2913534A1 (en) * 1979-04-04 1980-10-16 Bosch Gmbh Robert Flow and pressure control for variable delivery pump - has flow control valve operated by throttle differential and limited pilot pressure
US4292805A (en) * 1979-09-24 1981-10-06 Rexnord Inc. Servo-valve convertible construction
DE3200885A1 (en) * 1982-01-14 1983-07-21 Robert Bosch Gmbh, 7000 Stuttgart Output regulator for a hydrostatic pump
DE3340332C2 (en) * 1983-11-08 1988-11-10 Hydromatik GmbH, 7915 Elchingen Power control device for a hydrostatic drive with flow rate adjustment
DE3805061A1 (en) * 1988-02-18 1989-08-31 Linde Ag HYDRAULIC SWITCHING ARRANGEMENT
DE69314735T2 (en) * 1992-08-31 1998-02-19 Kayaba Industry Co Ltd Control device for consumers
KR0120281B1 (en) * 1994-07-29 1997-10-22 석진철 Apparatus for controlling input horse power and discharge of a pump in load sensing system of an excavator

Also Published As

Publication number Publication date
DE4447154C2 (en) 2002-05-29
EP0719947A3 (en) 1998-02-11
EP0719947A2 (en) 1996-07-03
DE4447154A1 (en) 1996-07-11
DE59510929D1 (en) 2004-08-26

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