EP3940246A1 - Valve assembly and method for control of a lifting mechanism or a mounted implement - Google Patents

Abstract

A valve arrangement and a method for controlling a lifting mechanism or attachment of a mobile working device are disclosed, with a double-acting lifting cylinder being controlled via a directional control valve. This is designed with two control edges, which simultaneously change an inflow cross section and an outflow cross section, so that, for example, a pressure setting on the lifting cylinder in the "lowering" direction is possible.

Description

The invention relates to a valve arrangement for controlling a lifting mechanism or attachment according to the preamble of patent claim 1 and a method for controlling such a lifting mechanism or attachment.

Such valve arrangements are used, for example, to control the working function of mobile working devices, in particular agricultural vehicles such as tractors with power lifts, combine harvesters with a mower deck control, forage harvesters with a head control or municipal machines with power lifts.

For example, modern tractors are designed with a rear linkage and a front linkage, with the pressure medium often being supplied according to an LS control, i.e. depending on the highest load pressure of the consumers. The rear or the front linkage can each be double-acting, with the pressure chambers of a lifting cylinder of the linkage, which are effective in the "lift"/"support" or "lower"/"press" direction, for example, being connected to a pressure medium source or Can be connected to a return in order to implement the respective functions (lowering, pushing, lifting, supporting, neutral position or floating position).

The continuously adjustable directional valve is controlled via an electrical control unit of the work machine, with the setpoint values being set, for example, via a front control panel or a rear control panel of the work machine.

In various work processes, for example lowering with cold oil or releasing jammed catch hooks, and for operating various attachments, for example cultivators, packer rollers, etc., it is necessary to provide the pressure chamber of the lifting cylinder acting in the "push" direction with a defined hydraulic volume flow and apply limited pressure. This can be done, for example, by suitable control of the continuously adjustable directional control valve and/or via separate pressure control valves (pressure-limiting or pressure-reducing valve).

In the pamphlets DE 10 2004 033 315 A1 and DE 10 2006 004 423 B4 generic valve arrangements are shown, in which the limitation of the pressure in the direction "pressing"/"lowering" effective pressure chamber of the lifting cylinder and the pressure medium flow paths connected to it takes place via a pressure-limiting valve.

The two pamphlets DE 10 2017 219 942 A1 and EP 2 884 118 A1 each show generic valve arrangements in which the pressure is limited by means of a pressure-reducing valve. A similar solution is in the US10321621B2 disclosed.

In the pamphlet DE 101 38 389 A1 describes a valve assembly with a continuously adjustable directional valve that is designed with an electronic pressure control.

A continuously adjustable (double-acting) directional control valve suitable for controlling such hoists is in DE 10 2013 207 299 A1 shown with the directional control valve having intermediate positions for passive movement, ie movement due to gravity or the like.

When using hydromechanical valves for pressure regulation, for example the above-mentioned pressure-limiting or pressure-reducing valves, the system costs are increased by the additional pressure-regulating valves.

This disadvantage is eliminated in the solutions described below with a regulation of the pressure via the directional control valve, with a pressure sensor value, for example, being used as a feedback variable. A disadvantage, however, is that the performance of the control is highly dependent on the signal processing chain: pressure sensor - processing in the control algorithm - control of the valve - reaction of the valve and possibly also the dynamics of the pressure supply. In addition, a valve slide of the continuously adjustable directional control valve has to pass through a neutral position during control, which has a disruptive effect on control technology.

In contrast, the invention is based on the object of creating a valve arrangement and a method for controlling a mobile working device in which the pressure limitation is simplified compared to the solutions described at the outset.

With regard to the valve arrangement, this object is achieved by the combination of features of patent claim 1 and with regard to the method by the features of the independent patent claim 11 .

Advantageous developments of the invention are the subject matter of the dependent claims.

The valve arrangement according to the invention and the method according to the invention are designed to control a lifting cylinder of a lifting gear or attachment of a mobile working device, in particular an agricultural vehicle, and has a proportionally/continuously adjustable directional control valve. This has a first working connection, which is in fluid communication with a first Actuating direction (e.g. lifting) is effective pressure chamber of the lifting cylinder. Another working port is in fluid communication with a second pressure chamber of the lifting cylinder that is effective in a second actuating device (e.g. lowering). The directional control valve also has a return/tank connection and a pressure connection, with opening cross-sections (measuring orifices) between the connections being able to be opened or closed by adjusting a slide of the directional control valve in order to control the pressure medium supply to or from the lifting cylinder. According to the invention, the slide is designed with two active lowering control edges, via which, when the slide is adjusted, an inflow cross section in the direction of one of the pressure chambers can be opened and at the same time, preferably in opposite directions, an outflow cross section in the pressure medium flow path from the pressure chamber in the direction of the return connection (tank). - or is controllable. Accordingly, when the directional control valve is adjusted into the active-lowering range, the slide assumes its own pressure control position, in which a dynamic pressure balance is established, which is dependent on the inflow and outflow cross-sections opened via the active-lowering control edges. This results in a defined pressure drop, which is called "block pressure" in the concept according to the invention, without lifting gear movement and the associated "volume flow disturbance" over the discharge edge determining the discharge cross section in a specific slide position. By varying the slide deflection and thus the adjustment of the opening cross sections mentioned, the "block pressure" can then be set directly without lifting gear movement.

To put it simply, when the slide is moved into the active-lowering range, the pressure chamber of the cylinder that is effective in the "press"/"lower" direction is subjected to an inflowing pressure medium volume flow, with a defined outflow cross-section also being present at the same time, so that a predictable "block pressure" sets, whereby the consumer volume flow is equal to zero. In this case, the “block pressure” is increased by increasing the volume flow from the pressure chamber (outflow cross section opened). If the pressure medium volume flow to the consumer is increased (enlargement of the inlet cross section), the "block pressure" is reduced accordingly.

According to an advantageous development of the invention, the directional control valve is designed with adjustment ranges “float position” and/or “neutral” and/or “passive lowering” and/or “raise” in addition to the “active lowering” slide adjustment range described above.

The “active lowering” slide adjustment range can be configured adjacent to the “passive lowering” slide adjustment range. This makes it possible to form a continuous, overlapping transition between the two adjustment ranges.

A load-pressure-independent volume flow can be formed by configuring the valve arrangement as an LS valve arrangement with an LS pressure compensator connected upstream of the directional control valve and an LS pressure regulator of the pump.

To further improve operational safety, a pressure-limiting valve can be provided in a pressure medium flow path between one or both working connections and the pressure chamber/pressure chambers connected thereto.

This pressure-limiting valve (secondary pressure-limiting valve) can intercept overpressure situations induced by disturbances, so that in such a situation pressure medium can be routed in the direction of return. This can be necessary, for example, if the lifting gear has to move upwards due to a contour in the ground.

The functionality of the method according to the invention and the valve arrangement according to the invention can be further improved if a position sensor is provided, via which the position of the lifting mechanism/attachment is detected. This For example, the position sensor can detect the stroke of the lifting cylinder, a lifting gear angle or the like. In principle, the signal from this position sensor can be used to calculate the theoretical volume flow or, alternatively, the speed of the hoist, so that control can be intervened if there are deviations from the target values. This will be discussed later.

A further or additional possibility for making interventions in the regulation that are necessary due to disturbances is to use a pressure sensor, via which the pressure in the respective pressure chamber of the lifting cylinder or in the pressure medium flow path leading to it is detected. Depending on the signal from this pressure sensor, the slide position can then be corrected in accordance with the control deviation via a control algorithm using a control unit. This concept is also explained in more detail in the specific description.

The control of the directional control valve is particularly simple if it is designed to be controlled electrohydraulically.

The support of the lifting cylinder in a predetermined desired position is improved if a non-return valve that can be opened is assigned to the pressure chamber that is effective in the support direction. This can be brought into the open position mechanically or hydraulically in order to allow the pressure medium to flow out. In this case, for example, the stroke of the slide can be transmitted to the check valve via a coupling mechanism in order to open it.

• Figur 1 einen vereinfachten Hydraulikschaltplan einer Ventilanordnung zur Ansteuerung eines Hubwerks;
• Figur 2 eine Detaildarstellung eines Wegeventils der Ventilanordnung gemäß Figur 1;
• Figur 3 eine qualitative Darstellung der sich bei der Verstellung des Wegeventils gemäß Figur 2 einstellenden Querschnittsverläufe;
• Figur 4 einen Teilbereich der Darstellung gemäß Figur 3, wobei der Verlauf eines "Blockdrucks" dargestellt ist, der sich nach dem erfindungsgemäßen Konzept einstellt;
• Figur 5 eine Darstellung gemäß Figur 3, bei der der "Blockdruck" durch eine geeignete Ansteuerung des Wegeventils vergleichsweise moderat ansteigt und
• Figur 6 eine ebenfalls auf Figur 3 basierende Darstellung, in der die Querschnittsverläufe im Hinblick auf eine Varianz der Rücklaufkennlinien modifiziert sind.

Preferred exemplary embodiments of the invention are explained in more detail below using schematic drawings. Show it:

• figure 1 a simplified hydraulic circuit diagram of a valve assembly for controlling a lifting mechanism;
• figure 2 a detailed representation of a directional control valve of the valve arrangement according to FIG figure 1 ;
• figure 3 a qualitative representation of the adjustment of the directional valve according to figure 2 adjusting cross-section courses;
• figure 4 a portion of the representation according to figure 3 , wherein the course of a "block pressure" is shown, which is set according to the concept of the invention;
• figure 5 a representation according to figure 3 , in which the "block pressure" rises comparatively moderately through suitable control of the directional control valve and
• figure 6 one also up figure 3 based representation, in which the cross-sections are modified with regard to a variance of the return characteristics.

The invention is explained below using a hitch assembly of a tractor. In principle, however, the valve arrangement according to the invention can also be used with other double-acting consumers of a mobile working device.

As explained at the outset, modern tractors are designed with a lifting mechanism 2 which has a double-acting lifting cylinder 4 (also called lifting mechanism cylinder) which is controlled via a valve arrangement 6 according to the invention. In the illustrated embodiment, the lifting cylinder 4 is designed as a differential cylinder with a bottom-side pressure chamber 8 and an annular space 10 which has the Valve assembly 6 with a variable displacement pump 12 or a pressure medium sink, in the present case a tank T can be connected. In the exemplary embodiment shown, the lifting mechanism 2 is designed as a rear lifting mechanism, with a piston rod 14 of the lifting cylinder 4 actuating an arm 18 pivotably mounted on a lifting shaft 16 and other coupling elements on which, for example, an attachment such as a packer roller 20, a seed drill or a plow is attached .

The illustrated valve arrangement 6 for controlling the hoist 2 is designed as an LS control with a continuously adjustable directional control valve 22 forming a metering orifice and an LS pressure compensator 24 connected upstream thereof. In a manner known per se, such an LS control ensures that the pressure in front of the measuring orifice that is opened in each case is only a specific pressure difference above the individual load pressure, regardless of the pump pressure. However, the invention in no way presupposes such an LS control.

According to the hydraulic circuit diagram in figure 1 is the pressure connection of the variable displacement pump 12 embodied, for example, as an axial piston pump, connected via an inlet channel 26 to a pressure connection P′ of the pressure compensator 24 . This is biased by a spring 28 into a basic position in which an output port D of the pressure compensator 24 is shut off. The pressure in the inlet channel 26 is tapped off via a control channel 30 and guided to a control surface of the pressure compensator 24 which acts in the opening direction against the force of the spring 18 . As mentioned, the spring 28 and the pressure in an LS channel 32 act in the opposite direction. Depending on this measuring orifice opening, the pressure compensator 24 adjusts to a control position in which the pressure drop across the measuring orifice is kept constant and approximately corresponds to the pressure equivalent of the force of the spring 28, so that a constant pressure medium volume flow through the measuring orifice (directional valve 22) is guaranteed is.

The delivery pressure of the variable displacement pump 4 present in the inlet channel 26 is set in an LS control as a function of the highest load pressure present at the consumers of the tractor. This load pressure--in the illustrated embodiment the load pressure on the lifting cylinder 4--is reported to an LS pressure regulator 34, via which the variable displacement pump is set in a manner known per se. However, as mentioned above, such an LS control, in which the delivery flow of the pump is adjusted as a function of the highest load pressure, is not a prerequisite for the system according to the invention.

An outlet port D of the pressure compensator 24 is connected to a pressure port P of the directional control valve 22 via an inlet line 36 . This also has a return port T, an LS relief port LSE and a further pressure port P′, with this and the LS relief port LSE being in fluid communication with the LS line 32 . The LS discharge connection LSE is assigned an LS outlet connection LSR, which in turn is connected to the tank T via an LS return line 43 . As will be explained in more detail below, an LS pressure relief can be carried out by opening the LS return line.

The directional control valve 22 also has an outlet port P‴, which is connected via a channel 38 to the pressure port P′ and thus also to the LS line 32 . A working port A is connected via a working line 40 to the bottom pressure chamber 8 of the lifting cylinder 4 . Another working connection B is connected via a working line 42 to the annular space 10 of the lifting cylinder 4 through which the piston rod 14 passes.

In the representation according to figure 1 is a slide 44 of the directional valve 22 biased via centering springs 46, 48 in a neutral position, which is based on the following figure 2 is explained in more detail.

The directional control valve 22 is adjusted via a pilot valve arrangement 50, which is shown in accordance with FIG figure 1 is formed by two electro-hydraulic pilot elements 52, 54. The control of the pilot valve arrangement 54 takes place by means of a control unit 56, which is designed with suitable control software. The control oil required to control the pilot valve arrangement 50 is provided via a control oil supply 58 which is connected to the two pilot control elements 52 , 54 via a pilot line 60 . The control oil required for actuating the pilot valve assembly 50 can be discharged to the tank T via the LS return line 43 .

The position of the slide 44 is detected by a displacement sensor 62 and reported to the control unit 56, so that the pilot valve arrangement 50 is also actuated as a function of the signal from the displacement sensor 62.

Further details of the directional control valve 22 are shown on the enlarged view in FIG figure 2 explained.

As explained above, the spool 44 of the directional control valve 22 is biased into a neutral position N by the two centering springs 46, 48, in which the ports P, P", P'" and A are shut off. The working connection B is connected to the tank connection T, so that the pressure medium can flow from the working line 42 to the tank T via a tank channel 64 . Furthermore, the LS relief connections LSE and LSR are connected to one another, so that the LS line to tank T is also relieved.

When the valve slide 44 is adjusted to the left (view from figure 2 ) in the "Lift" area, a metering orifice 65 connecting the two ports P and P'" is opened, so that pressure medium can flow from the pressure port P via the port P'" and the channel 38 to the pressure port P" and then from there via the Working port A and the working line 40 in the bottom Pressure chamber 8 of the lifting cylinder 4 is funded. Its annular space 10 is connected to the tank T via the working line 42, the working connection B, the tank connection T and the tank channel 64, so that the pressure medium can flow out of the decreasing annular space 10. The piston of the lifting cylinder 4 extends and the implement is raised or at least supported accordingly.

When the valve slide 44 is adjusted from its in figure 2 _{If the} basic position shown is moved to the right, it is moved into a "sink passive (S _passive ) area" in which the connections P, P'" and P" are blocked. The two working ports A, B are both connected to the tank port T. The LS pressure relief is also open to the LS return line 43, so that the attachment, in the present case the packer roller 20, is subjected to the lifting cylinder 4 in the retracting direction due to its own weight, so that the pressure medium from the decreasing pressure chamber 8 to the tank T is pushed out. From this, pressure medium can flow into the expanding annular space 10 .

With a further adjustment of the slide 44, the "lowering _active (S _active ) area" is reached, in which, similar to the lifting area, the two ports P and P‴ are connected to one another, so that pressure medium from the supply line 36 is guided into the channel 38 via the orifice plate 65. In the S _active area, a control edge of the slide 44 opens an inflow cross section 66 between the connections P" and B. Simultaneously or at least overlapping, a drain cross section 68 is opened via a further control edge, through which the working connection B and thus the flow in the direction " Lowering / pressing "effective annular space 10 is connected to the tank T. The adjustment of the cross sections 66, 68 is preferably carried out in opposite directions.

As explained at the outset, without a hoisting gear movement, a defined pressure drop occurs over this discharge cross section 68 in a specific slide deflection, with varying the slide deflection, ie by opening or closing This defined pressure drop ("block pressure") can be varied by controlling the inlet cross section 66 or the outlet cross section 68 . The inflow cross section 66 and the outflow cross section 68 preferably change in opposite directions, so that when the volume flow from the consumer increases, the “block pressure” is increased, while when the volume flow to the consumer decreases, the “block pressure” is reduced. Depending on the deflection of the slide, a dynamic pressure equilibrium is established, as a result of which a fine adjustment of the pressure on the lifting cylinder 4 in the "lowering" direction is possible.

With a further adjustment of the slide 44 to the right (view after figure 2 ) a floating position ("Float") is set, in which the two working connections A, B are both connected to the tank T. Furthermore, the LS pressure relief is effective.

In this floating position, the hoist 2 is not subjected to a force, so that the implement rests on the ground solely due to its own weight.

In order to prevent an undesired lowering of the lifting cylinder 4, in figure 1 Illustrated embodiment is provided in the working line 40, a pilot operated check valve 70, which prevents pressure medium from flowing out of the pressure chamber 8 in its closed position. The check valve 70 can be opened mechanically, electrically or hydraulically when the slide 44 is moved into the “float” and “ _{active/passive lowering” ranges.} This can be done, for example, by the slide 44 being mechanically coupled to the check valve 70 so that this is opened when the slide 44 is moved into the aforementioned ranges. Of course, hydraulic or electromechanical actuation is also possible.

Instead of the check valve 70, corresponding check valves can also be integrated into the directional control valve 22. These serve in particular to prevent the attachment/power lift from lowering due to a leak.

In one embodiment of the invention, according to figure 1 optionally, a pressure sensor 72 can be provided, via which the pressure in the annular space 10 or in the working line 42 is recorded and reported to the control unit 56 . If the signal from the pressure sensor 72 deviates from setpoint values, for example due to an inaccurate deflection of the slide 44 or other disturbances, the slide position can then be corrected via the control algorithm of the control unit 56 according to the control deviation. In order to efficiently reduce excessive pressure due to pressure medium volume flows, the " _passive lowering" area can be included in this control in order to use only one control edge opening in the "tank/return" direction without the pressure medium flowing in. This is necessary, for example, when the attachment has to move out of the way due to a rising ground contour while the pressure/ground immersion depth remains the same.

In order to intercept overpressure situations induced by disturbances, a secondary pressure-limiting valve 74, 76 can be provided according to the invention, via which the pressure in working line 42 or working line 40 is limited, so that the pressure medium is released when the pressure set at pressure-limiting valve 74, 76 is exceeded drains towards tank T. This can be necessary, for example, when the lifting mechanism 2 has to give way due to a ground contour, so that the pressure-limiting valve 74 in the working line 42 then opens.

A further option consists in detecting the deflection of the lifting cylinder 4 using a position sensor 78 . In the embodiment according to figure 1 this is designed as an angle sensor with which the angle of attack of the arm 18 is detected. This makes it possible, for example, to increase the theoretical volume flow the "push side" (alternatively the cylinder speed/hoist speed, which are approximately proportional over large ranges). With knowledge of this theoretical volume flow, the following improvements of the system can be brought about, for example.

In this way, when lowering to a theoretical volume flow, the pump volume flow can be actively refilled without causing a pressure build-up. Due to tolerances, this theoretical volume flow is not fully utilized.

The associated advantage is better filling of the lifting cylinder 4, so that the transition to pressure control is continuous. A further advantage is that when lowering the slider 44 can be deflected further without building up pressure. In this way, the single-acting lowering speed can possibly be maximized, since the control edge determining the outflow cross section 68 is then completely open.

A further improvement is that when evading through a ground contour, the tank drain can be opened in a controlled manner on the "push side" depending on the theoretical pressure medium volume flow and the target pressure. The advantage of this is that the pressure rises only moderately when evading, even without "closed-loop pressure control", or in a system with pressure control, the controller is supported by the pilot control.

Furthermore, it is possible to limit the volume flow by reducing the "press pressure" when lowering in the "press pressure control". In the case where the "push pressure" is already 0 bar and the hoist 2 is still too fast, the spool position can be further changed to "carry" the In addition, the discharge edge towards tank T must be closed. This then corresponds to a switchover to the "lowering range" without pressure control.

In the case of "lowering" without pressure control, you can automatically switch to "press-pressure control" if the volume flow falls below a minimum speed.

For further clarification are in the figure 3 qualitatively shown cross-sectional profiles that occur in the above-described adjustment of the slide 44. The areas "Lift", "Neutral" and "Freedom/Float", in particular their exact start and the gradients, are only shown as an example in this figure.

the inside figure 3 The upper cross-sectional course shows the opening cross-section in the above-described adjustment ranges of the slide 44 between the pressure chamber 8 ("carrying") and the return (T). Accordingly, this cross-section is opened in the two "sink areas" and is then open in the "Float".

The opening cross-section of the pump 12 in the direction of the pressure chamber 8 ("carrying") is only opened in the "lifting" area and decreases with increasing adjustment of the slide 44 in the "neutral" direction.

According to the concept according to the invention, at the end of the “lowering _passive ” adjustment range, a defined flow cross section 68 is opened from the annular space 10 (“press”) to the return (T). This cross-section is then closed again at the transition from the "Sinking _active " area to the "Float" area.

In the "lowering _active " adjustment range, an inflow cross-section is then opened in accordance with the above statements, which connects the pressure medium between the pump 12 and the annular space 10 and which is then closed again in the area of free movement ("float").

In this area, the two pressure chambers 8 ("carrying") and 10 ("pressing") are then connected to the tank T, so that pressure medium can flow around.

As shown in the detail view in FIG. 4, without a movement of the lifting mechanism 2 (consumer volume flow 0), _{a predictable pressure occurs in the “lowering active} ” area, which is referred to as “block pressure” in this application. As mentioned above, increasing the flow of fluid from the consumer (lift cylinder 4) to the tank T increases the "block pressure", while decreasing the flow of fluid to the consumer reduces the "block pressure".

By suitably setting the outflow cross-section towards tank T, the increase in the "block pressure" can be influenced with increasing deflection and thus increasing pump quantity. This is quite evident in figure 5 shown, from which it can be seen that with increasing inflow volume and simultaneous increase in the outflow cross section 68 towards the tank T, the increase in the “block pressure” compared to the increase according to FIG figure 4 can be flattened so that the "block pressure" increases only moderately.

As in figure 6 indicated, in the "lowering _active " area, the course of the cross section when the pressure medium connection is opened from the pressure chamber 8 ("carry") to the return (T) and the course of the opening cross section from the annular space 10 ("press") to the return (T) can also be varied . So can, as in figure 6 indicated by dashed lines, the full outflow cross section 68 effective in the "lowering" direction, ie the cross section determining the pressure medium connection from the pressure chamber 8 to the tank T, must already be set to a maximum before the in figure 6 pressure control range indicated by dashed lines is reached. As in figure 6 for those with the term "variance" marked opening cross-section courses indicated, these areas can also overlap each other more or less.

A valve arrangement and a method for controlling a lifting mechanism or attachment of a mobile working device are disclosed, with a double-acting lifting cylinder being controlled via a directional control valve. This is designed with two control edges, which simultaneously change an inflow cross section and an outflow cross section, so that, for example, a pressure setting on the lifting cylinder in the "lowering" direction is possible.

Reference list:

2

hoist

4

lifting cylinder 4

6

valve assembly

8th

pressure room

10

annulus

12

variable displacement pump

14

piston rod

16

lifting shaft

18

poor

20

packer roller

22

directional valve

24

pressure compensator

26

inlet channel

28

feather

30

control channel

32

LS line

34

LS pressure regulator

36

inlet line

38

channel

40

working line

42

working line

43

LS return line

44

slider

46

centering spring

48

centering spring

50

pilot valve arrangement

52

pre-control element

54

pre-control element

56

control unit

58

control oil supply

60

pilot line

62

displacement transducer

64

tank channel

65

metering orifice

66

inlet cross-section

68

drain cross-section

70

check valve

72

pressure sensor

74

pressure relief valve

76

pressure relief valve

78

position sensor

Claims (11)

Valve arrangement for controlling a hoist or an attachment of a mobile working device, in particular an agricultural utility vehicle, with a continuously adjustable directional control valve (22) which has a working connection (A) which is in pressure medium connection with a pressure chamber which is effective in a first actuating direction ("lifting") (8) of the lifting cylinder (4) and which has a further working connection (B) which is in fluid communication with a second pressure chamber (10) of the lifting cylinder (4) which is effective in a second direction of actuation ("lowering"), the directional control valve (22) has a tank connection (T) and a pressure connection (P), whereby opening cross-sections between the connections can be opened or closed by adjusting a slide (44) of the directional control valve (22), characterized in that the slide (44) has two active sinks has control edges, via which during the adjustment of the slide (44) in an active sink area (lowering _active) a supply cross-section (66) in Ric direction to one of the pressure chambers (8, 10) and at the same time a flow cross section (68) from the pressure chamber (8, 10) in the direction of the tank connection (T), preferably in the opposite direction, can be opened or closed. Valve arrangement according to claim 1, wherein the directional control valve (22) has a slide adjustment range "floating position" and/or "neutral" and/or "passive lowering" ( _passive lowering) and/or "lifting". Valve arrangement according to patent claim 2, wherein the spool adjustment range “active lowering” (lowering _active ) is adjacent to the spool adjustment range “passive lowering” (lowering _passive ). Valve arrangement according to one of the preceding claims, wherein an LS pressure compensator (24) is provided in an inlet to the directional control valve (22). Valve arrangement according to one of the preceding claims, with a pressure-limiting valve (74, 76) in a pressure medium flow path between a working connection (A, B) and the pressure chamber (8, 10) connected thereto. Valve arrangement according to one of the preceding claims, with a position sensor (78) for detecting a position of the lifting mechanism/attachment. Valve arrangement according to one of the preceding claims, with a pressure sensor (72) in the pressure medium flow path to one of the pressure chambers (8, 10). Valve arrangement according to Patent Claim 6 or 7, with a control unit (56) which is designed, preferably in the manner of a "closed-loop control", as a function of the pressure signal from the pressure sensor (72) and/or as a function of the signal from the position sensor (76 ) to adjust/correct the slider position. Valve arrangement according to one of the preceding claims, in which the directional control valve (22) is controlled electrohydraulically. Valve arrangement according to one of the preceding patent claims, with at least one pilot-operated check valve (70) arranged in the pressure medium flow path to the first pressure chamber (8) or integrated in the directional control valve (22). Method for controlling a hoist or an attachment of a mobile working device, in particular an agricultural utility vehicle, with a continuously adjustable directional control valve (22) which has a working connection (A) which is in pressure medium connection with a pressure chamber which is effective in a first actuating direction ("lifting") (8) and which has a further working connection (B) which is in fluid communication with a second pressure chamber (10) effective in a second actuation direction ("lowering"), the directional control valve (22) also having a tank connection (T) and has a pressure connection (P), opening cross-sections between the connections being able to be opened or closed by adjusting a slide (44) of the directional control valve (22), with the steps: - Adjusting the slide (44) in an active lowering adjustment range (lowering _active ) in which - Via a first "active lowering control edge" an inflow cross section (66) to a pressure chamber (10) effective in the "lowering" direction is opened and simultaneously or overlapping via a second "active lowering control edge" a discharge cross section (68) from the pressure chamber (8) to the tank (T) is controlled open or closed, so that a dynamic pressure balance is established.

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