EP1736671B1 - Load sensing control system and load sensing directional valve - Google Patents

Abstract

The linear saturation (LS) control device has a path valve (1), the valve slide (10) of which enables consumer connections (A, B) to be made for two consumers to an input connection (P) and an output connection (T). The flow path can be connected to two successive or overlapping pressure limiting chambers (24, 28) with pressure limiting valves (6, 8).

Description

The invention relates to a LS control arrangement according to the preamble of patent claim 1 and a suitable for such a control arrangement LS-way valve.

Such LS control arrangements are for example from the DE 197 15 020 A1 or from the published by the applicant data sheet RD 64 282 (control block M4) and are used, for example, in mobile work equipment to provide their consumers with pressure medium. Each of the consumers is assigned an LS directional control valve, via which the speed and the direction of the pressure medium volume flow conveyed by a pump are controlled. The pump pressure is adjusted in LS systems so that it is above the maximum load pressure of the consumer by a certain control Δp, for example 20 bar. The pressure medium volume flow over a set by an inlet control edge of the LS-way valve inlet orifice is kept constant independent of the load in the mentioned known solutions by a LS or individual pressure compensator. A pressure compensator piston of the individual pressure compensator is biased by a spring in the opening direction, in addition to the force of the spring acts downstream of the inlet orifice metered load pressure also in the opening direction. In the closing direction of the pressure compensator piston acts upstream of the inlet orifice and downstream of the individual pressure compensated tapped inlet pressure. In the prior art, the individual pressure compensator upstream of the inlet orifice plate, in principle, the individual pressure compensator also as in one of the US Pat. No. 4,787,294 known Embodiment be arranged downstream of the inlet orifice.

The individual pressure compensator responds to changes in load pressure and is displaced in the closing direction at a load pressure increase in the opening direction and at a load pressure reduction. As a result, the pressure in the inlet to the inlet orifice plate is regulated by the individual pressure compensator in such a way that the force acting in the closing direction by this inlet pressure is in equilibrium, with the force of the spring acting in the opening direction and the force equivalent of the load pressure. Accordingly, the pressure in the inlet is always adjusted by the constant, the spring force corresponding amount higher than the load pressure, so that above the inlet orifice a constant pressure drop and thus a constant flow exists (load pressure independent flow control).

In the known mobile control block M4 can be individually limited to protect the consumer-side machine equipment, the load pressure at the two load ports of a piston axis each by a pressure relief valve. When this pressure relief valve responds, the actual load pressure is forfeited to the individual pressure compensator, so that the above-described volume flow control can be disabled for the consumer connection. The pressure medium volume flow set via the inlet metering orifice can be reduced, for example, if the consumer is driven against a high resistance, which would actually require an inlet pressure above the set maximum pressure. In this case, however, the inlet pressure will not exceed the value set on the pressure relief valve by more than the spring force. Because every consumer connection has a pressure relief valve is assigned, different pressure settings can be set for each consumer connection.

However, operating conditions may occur in which different maximum pressures must be achieved in a direction of movement of the consumer at different operating speeds. For example, it may be necessary to run the consumer at a higher speed with only a low pressure, but at a lower speed with a higher pressure.

In another application z. B. causes the speed of a lowering movement of a crane jib by a so-called flow rate control. For this purpose, a lowering brake valve is opened by the inlet pressure in the hydraulic cylinder determining the movement of the crane jib. Since the opening pressure of the lowering brake valve has an influence on the lowering speed of the crane jib, this opening pressure must be kept as constant as possible in order to avoid possible vibrations. For this purpose, the above-described pressure relief valve can be set to limit the load pressure, so that the inlet volume flow control is ineffective when the pressure relief valve is triggered. By the kinematics of the crane boom, however, this can be moved when lowering into positions in which a higher pressure is required than the set opening pressure. This is z. B. a small area at the end of the lowering movement, wherein the crane boom is in a position of a load reversal in which its own weight requires a much higher inlet pressure - in this area, the crane boom should be moved for safety reasons only at low speed at higher pressure.

Such operating conditions can not be mastered with the known solutions described at the outset, since the supply pressure can only be limited to one value by the pressure limiting valve assigned to a consumer connection.

Other LS control arrangements of the type mentioned are in the publications DE 196 51 967 A1 . EP 1 069 317 A2 and DE 101 07 532 A1 described.

In contrast, the present invention seeks to provide an LS control arrangement and a suitable LS-way valve, which allow a multi-stage supply pressure limitation.

This object is achieved with respect to the LS control arrangement by the feature combination of claim 1 and with respect to the LS-way valve by the features of the independent claim 14.

According to the invention, a LS control oil flow path for tapping the load pressure is successively or overlapping connected to two pressure limiting chambers when adjusting a valve spool of the LS-way valve from the basic position in one direction, each of which a pressure relief valve is assigned to LS-pressure limiting. The load pressure can be limited to different values in different stroke ranges of the valve slide so that a supply pressure limitation in the manner described above is made possible.

In this case, it is preferred if the maximum pressure in the pressure limiting chamber connected to the LS control oil flow path during a first partial lift is set to a higher pressure than that in the second pressure limiting chamber, which is effective during a subsequent partial stroke. In this case, it may be allowed that in a transition region both pressure limiting chambers with the LS control oil flow path are connected, since then in each case the set to the lower value pressure relief valve responds and thus limits the inlet pressure in the second partial stroke.

In a concrete solution, the valve spool has a pressure limiting channel that forms part of the LS control oil flow path. This pressure limiting channel opens on the one hand during the adjustment of the valve spool in one direction in a connected to the associated load port working control chamber and on the other hand during the first partial stroke of the valve spool in the first pressure limiting chamber during the second partial stroke in the second pressure limiting chamber.

In order to keep the size of the pressure relief valves and the control oil loss as low as possible, a Lastabgriffsdüse is formed in the pressure limiting channel between the load tap and the pressure relief valve.

The valve spool is of particularly simple construction if two spaced peripheral recesses are formed on its outer circumference, in each of which a nozzle channel passing through the pressure limiting passage communicates with the valve spool, ie the pressure limiting channel is during the first partial stroke via the first peripheral recess and the associated first nozzle channel the first pressure-limiting chamber and during the further partial stroke via the second circumferential recess and the second nozzle channel is connected to the second pressure-limiting chamber. The start of operation and the functional range of the second pressure relief valve can then be determined by the position and length of the peripheral recesses in the valve spool. This very simple Construction makes it possible to realize the LS directional control valve with the exception of the control piston with series components.

The peripheral recesses are preferably designed as pockets for minimizing leaks.

In the neutral position of the LS-way valve, the LS control chamber is connected to a drain chamber via one of the pressure-limiting chambers and a tank groove on the valve slide.

In the other adjustment direction of the valve spool, the load pressure is picked up via an LS channel and reported to the LS control chamber.

The peripheral recesses are designed such that they shut off the connection between the LS control chamber and the pressure limiting chambers when adjusting the valve spool in the second adjustment direction, wherein during a relatively small stroke, a connection may still be approved.

The construction of the valve spool is particularly simple when the LS channel and the pressure limiting channel open on the one hand in the same piston collar.

This piston collar can be designed with a control edge over which the first pressure limiting chamber is connected to a drain chamber in the second partial stroke of the valve slide.

As already mentioned, the individual pressure compensator of LS control arrangement of the metering orifice may be connected upstream, wherein a pressure compensator piston in the opening direction of a pressure compensator spring and the limited Load pressure and in the closing direction of the pressure in the area between the individual pressure compensator and the metering orifice is acted upon.

Other advantageous developments of the invention are the subject of further subclaims.

• Figur 1 ein stark vereinfachtes Schaltschema einer Kolbenachse eines Mobilsteuerblocks mit zweistufiger Zulaufdruckbegrenzung;
• Figur 2 Teilhübe eines Ventilschiebers eines LS-Wegeventils aus Figur 1 bei Verstellung in einer Richtung und
• Figur 3 Teilhübe des Ventilschiebers bei einer Verstellung in der anderen Richtung.

In the following, a preferred embodiment of the invention is explained in more detail with reference to schematic drawings. Show it:

• FIG. 1 a highly simplified schematic diagram of a piston axis of a mobile control block with two-stage supply pressure limitation;
• FIG. 2 Partial strokes of a valve spool of a LS-way valve FIG. 1 with adjustment in one direction and
• FIG. 3 Partial strokes of the valve spool with an adjustment in the other direction.

FIG. 1 shows a schematic circuit diagram of a valve disc of a mobile control block, through which a piston axis for the pressure medium supply of a consumer, for example, an actuating cylinder of a crane jib is formed. Such a mobile control block has an input member, an end member, and a plurality of directional control elements each associated with a consumer of the mobile implement. This in FIG. 1 a directional control valve element of the valve control block forming a LS control arrangement 1 has a pressure port P, two consumer ports A, B, a drain port T and a control oil drain Y. Usually, such directional control valves are still with other terminals, such as a LS connection, connections for tapping the individual load pressure at the consumer connections and with control connections. Since these do not contribute to the understanding of the invention, they have been for simplicity in the illustration according to FIG. 1 omitted. The LS control arrangement 1 has a continuously adjustable directional control valve 2, an individual pressure compensator 4 and two adjustable pressure relief valves 6, 8 for limiting the load pressure. The basic structure of such a LS control arrangement is already known from the prior art described above (RD 64 282), so that only the components essential for understanding the invention are described here.

The continuously adjustable directional control valve 2 has a valve spool 10, which by a not shown Zentrierfederanordnung in his in FIG. 1 shown basic position 0 is biased. The valve spool 10 can be moved electrically or hydraulically from its illustrated basic position to the left (working positions A) or to the right (working positions B). In a hydraulic pilot control pressure reducing valves, for example, can be used to pressurize the valve spool 10 for adjusting with a control pressure difference. The valve spool 10 is guided in a valve bore 12 of the valve disc. This is in the illustration according to FIG. 1 from right to left in the radial direction to a first discharge chamber 14, a working chamber 16, an inlet chamber 18, a further working chamber 20, a second discharge chamber 22, a first pressure limiting chamber 24, a LS control chamber 26 and a second pressure limiting chamber 28 expands.

The valve spool 10 is designed with four control circuits, wherein the in FIG. 1 the right-hand control collar as tank collar 30, the two middle piston collars as Tax code 32 and tax code 34 and the in FIG. 1 left, slightly longer piston collar is referred to as end collar 38. The aforementioned bundles are spaced from each other by piston necks. The tank collar 30 closes the valve bore 12 to the right frontally to a spring or control chamber, not shown. On the right annular end surface of the control collar 32, a control control edge 40 designed with fine control notches and an inlet control edge 42 are formed on the other annular end face. Accordingly, a further feed control edge 44 and a further flow control edge 46 are provided on the second control collar 34. In the illustrated basic position, the inlet control edges 44, 42 block the pressure medium connection from the inlet chamber 18 to the two adjacent working chambers 16 , 20 off. Their connection to the outer drainage chambers 14, 22 is locked in the basic position 0 by the two flow control edges 40, 46. The tank control edge 48 is located within the second discharge chamber 22, which is connected via a circumferential tank groove 50 on the outer circumference of the end collar 38 with the adjacent pressure-limiting chamber 24. On the outer circumference of the end collar 38 are further provided two pocket-shaped or flattened circumferential recesses 52, 54, the circumferential recess 52 having a greater axial length than the further circumferential recess 54. In the illustrated basic position opens the smaller circumferential recess 54 in the LS control chamber 26, the larger circumferential recess 52 connects the pressure limiting chamber 24 with the LS control chamber 26th

The valve spool 10 is penetrated by a pressure limiting channel 56 which is drilled in the illustrated embodiment of the left end face of the end collar 38 ago as axially parallel bore and closed by a sealing plug 58. The pressure limiting channel 56 extends in the axial direction of the basic position 0 to beyond the working chamber 20 and then flows through a Lastabgriffsdüse 60 in the outer periphery of the control collar 34. In the basic position 0, the Lastabgriffsdüse 60 is covered by the annular web between the chambers 18, 20 and thus closed , The pressure-limiting channel 56 also opens out via a first radial nozzle channel 62 in the larger circumferential recess 52 and via a second radial nozzle channel 64 in the smaller circumferential recess 54 (nozzle channels radially). Accordingly, in the home position, the LS control chamber 26 and the right pressure limiting chamber 24 and the pressure limiting channel 56 are connected to the drain chamber 22 and thus pressure relieved.

In the illustrated embodiment is in the valve spool 10 from the other side (right in FIG. 1 ) Drilled in the axial direction LS channel 66, which is also closed by a sealing plug 58 and the one side opens via a radial bore 68 in the basic position 0 in the pressure limiting chamber 28 and on the other hand via a radially extending Lastabgriffsbohrung 70 on the outer circumference of the control collar 32 opens. This Lastabgriffsbohrung 70 is covered by the web between the inlet chamber 18 and the working chamber 16 in the basic position 0. The inlet chamber 18 is connected via an inlet channel 72 to an outlet port A of the individual pressure compensator 4, the input port P is connected via a pump channel 74 with a LS-pump 76, which as Variable or can be designed as a constant pump with bypass pressure compensator. The control of this LS pump 76 is carried out - as stated - depending on the highest load pressure of the driven loads, the pump pressure is adjusted so that it is above the control Δp above this highest load pressure.

The individual pressure compensator 4 is designed in the version shown with a load-holding function. This is achieved by blocking the connection between P and A in its spring-biased basic position as long as no pump pressure is built up. Such an individual pressure compensator 4 thus operates in the load holding function similar to a check valve. In the illustrated embodiment, the pump pressure in the pump channel 74 is tapped via a control line 78 in the control positions (b) and acts on the pressure compensator piston in the direction of his in FIG. 1 Closing position marked with (c). In the opening direction, ie, in the direction of the control positions identified by (b), the pressure compensator piston is acted upon on the one hand by the force of the pressure compensator spring 80 and by the individual load pressure, which is tapped via an LS control line 80 connected to the LS control chamber 26.

The two working chambers 16, 20 are connected via a feed channel 82 and a return passage 84 to the load ports A, B. Depending on the control of the directional control valve 2, the return passage 84 can also act as a flow channel and then correspondingly the flow channel 82 are in the pressure medium return. The pressure limiting valve 6 is connected via a load pressure limiting channel 86 to the pressure limiting chamber 24, accordingly, the other pressure limiting chamber 28 via a further load pressure limiting channel 88 with the further pressure relief valve 8 connected. Upon reaching the maximum value set at one of the pressure relief valves 6, 8, this opens a connection to the control oil drain Y, so that the pressure in the corresponding pressure limiting chamber 24, 28 is limited to this maximum value. This maximum pressure is executed in both pressure relief valves 6, 8 mechanically or electrically / hydraulically changeable. The drain port T is connected via a drain passage 90 with the two drain chambers 14, 22.

It is now assumed that by adjusting the directional control valve 2 from its illustrated basic position 0 pressure medium flow through the consumer port A to the consumer and should run from this via the consumer port B to the tank T out, so that, for example, a lowering movement of a crane jib can be effected. For this purpose, the valve spool 10 according to FIG. 1 shifted to the left, wherein when driving through the total stroke the in FIG. 2 positions A1, A2 and A3 are overrun. At the beginning of the adjustment of the valve spool 10 to the left (A1) the connection of the pressure limiting channel 56 is opened with the working chamber 20 via the Lastabgriffsdüse 60 before the Zulaufsteuerkante 44 opens the connection between the inlet chamber 18 and the working chamber 20 and the flow control edge 40, the pressure medium connection between the drain chamber 14 and connected to the load port B working chamber 16 opens. The Lastabgriffsbohrung 70 remains covered by the bridge between the chambers 16, 18. During this first partial stroke, the connection between the drainage chamber 22 and the first pressure-limiting chamber 24 which is opened by the tank groove 50 in the basic position is also shut off. The LS control chamber 26 is over the larger circumferential recess 52 with the Pressure limiting chamber 24 connected and thus also the pressure limiting channel 56 connected to the LS control chamber 26 - ie, in the LS control chamber 26 and in the pressure limiting chamber 24, the pressure in the working chamber 20 is reported with the pressure relief valve closed. During the further adjustment of the valve spool 10, an inlet orifice plate between the inlet chamber 18 and the working chamber 20 is opened via the inlet control edge 44 and conveyed in accordance with pressure medium to the consumer port A. The flowing away from the consumer pressure fluid flows through the consumer port B, the return passage 84, the up-regulated by the flow control edge 40 drain cross section between the working chamber 16 and the drain chamber 14 to the tank T out. The load pressure building up downstream of the inlet orifice plate is then reported via the load tap nozzle 60, the pressure limiting channel 56, the first nozzle channel 62 and the longer circumferential recess 52 to both the LS control chamber 26 and the pressure limiting chamber 24 until the A2 position is reached. wherein the maximum load pressure building up in the pressure limiting chamber is limited by the pressure limiting valve 6, which is set to a higher pressure than the other pressure relief valve 8. The load pressure applied in the LS control chamber 26 is applied via the LS control line 80 to the pressure compensator piston of the individual pressure compensator 4 in the opening direction. As long as this load pressure is below the value set on the pressure limiting valve 6, the individual pressure compensator 4 operates in the manner described in the introduction and regulates a pressure in the inlet channel 72 which is always higher by a value corresponding to the constant amount of the force of the pressure compensator spring 80 than the individual one Load pressure, so that the pressure drop across the inlet orifice kept constant independent of the load pressure can be and thus depends only on the opening cross-section. When the pressure limiting valve 6 is opened, the load pressure effective in the opening direction on the individual pressure compensator can not exceed this preset maximum value, so that the inlet pressure in the inlet channel 72 is correspondingly limited. D. h., At the beginning of the stroke of the valve spool, the pressure relief valve 6 is effective, so that the inlet pressure is limited to a relatively high value at low pressure medium flow rate. Upon further displacement of the valve spool 10 (positions A2, A3) the connection between the pressure limiting chamber 24 and the LS control chamber 26 is shut off via the longer recess 52 and via the smaller circumferential recess 54 the connection of the pressure limiting channel 56 to the left pressure limiting chamber 28 via the further nozzle channel 64 turned on. The tapped via the Lastabgriffsdüse 60 load pressure is also reported via the first nozzle channel 62 in the LS control chamber 26, but since it is not connected to the pressure limiting chambers 24, 28 in the positions A2, A3, flows from the LS control chamber 26 virtually no Control oil, so that no pressure drop over the first nozzle channel 62. The maximum load pressure in the pressure limiting channel 56 and thus in the LS control chamber 26 is limited in the positions A2, A3 by the set to a lower pressure relief valve 8, whose input is connected via the load pressure limiting channel 88 to the pressure limiting chamber 28. The Lastabgriffsdüse 60 ensures that even when the pressure relief valve 8 is open via the first nozzle channel 62 is not directly the load pressure is reported, since the control oil flow through the open pressure relief valve 8 at the Lastabgriffsdüse 60, a pressure drop. The actual pressure in the pressure limiting channel 56 and thus in the LS control chamber 26 is thus somewhat above the maximum pressure set at the pressure limiting valve 8 - its set value is adjusted until the desired maximum load pressure is reached. Accordingly, when the pressure limiting valve 8 responds, the inlet pressure is set to a lower value at a higher pressure medium volume flow. During the adjustment of the valve spool 10 in the direction of the position A3, the connection between the discharge chamber 22 and the pressure limiting chamber 24 is opened via the tank control edge 48, so that the latter is pressure-relieved. Furthermore, in the above-described positions A1, A2, A3, the load tap hole 70 remains covered by the web between the inlet chamber 18 and the working chamber 16. As described above, the function start and the functional range of the second pressure limiting valve are determined by the geometry of the circumferential recesses 52, 54. It is not necessarily required that the pressure limiting channel 56 is connected in succession to the pressure limiting chamber 24 and the pressure limiting chamber 28 - it is also possible to connect the pressure limiting channel 56 with two pressure limiting chambers 24, 28 in a transition region - the pressure is then in any case limited to the lower, predetermined by the pressure relief valve 8 value.

If the consumer is now to be supplied with pressure medium via the consumer connection B and the pressure medium flowing away from the consumer flows through the consumer connection A to the tank T, the valve slide will be released from its in FIG. 1 shown basic position 0 to the right in the direction of the positions B1, B2 according to FIG. 3 postponed. During this adjustment of the valve spool 10 to the right, the Lastabgriffsbohrung 70 opens to the with the consumer port B At the same time or a little later, the inlet orifice plate 42 is opened via the inlet control edge 42 between the inlet chamber 18 and the working chamber 16 and opened according to the flow control edge 46, a flow area between the working chamber 20 and the drain chamber 22. At the very beginning of the shift out of the basic position (0) out the nozzle channel 64 of the valve spool 10 is still open to the pressure limiting chamber 28 so that when the load pressure at the load port B is exceeded, the set to a lower value pressure relief valve 8 can open and some control oil to control oil drain Y flows off - but this loss is relatively low and can be accepted.

The downstream of the inlet orifice in the working chamber 16 applied pressure is reported via the Lastabgriffsbohrung 70, the LS channel 66 and the radial bore 68 in the LS control chamber 26. This load pressure is not limited, so that the individual pressure compensator 4 is always acted upon by the actual load pressure in the opening direction. During the entire stroke (B1, B2) of the valve slide 10, the load tap nozzle 60 remains covered by the web between the inlet chamber 18 and the working chamber 20, so that no load pressure can be tapped over it.

The above construction can be realized in a very simple manner with mass-produced components, wherein only the geometry of the spool by providing the peripheral recesses and the pressure-limiting channel and the Lastabgriffsdüse 60 must be adjusted. In principle, it is also possible to open the pressure limiting channel 56 and the LS channel in different piston collars.

As already mentioned, the individual pressure compensator can also be connected downstream of the metering orifice. Instead of the pocket-shaped circumferential recesses 52, 54, circumferential annular grooves can also be selected - although this variant can be produced more easily, it has the disadvantage that the leakage is increased.

Disclosed are an LS control arrangement and an LS directional control valve, via which the load pressure in an adjustment direction of the LS directional control valve can be limited to two different maximum values.

LIST OF REFERENCE NUMBERS

1

LS control arrangement

2

way valve

4

Individual pressure compensator

6

Pressure relief valve

8th

Pressure relief valve

10

valve slide

12

valve bore

14

drain chamber

16

working chamber

18

inlet chamber

20

further working chamber

22

2nd drainage chamber

24

Pressure control chamber

26

LS-control chamber

28

Pressure control chamber

30

tank Bund

32

control collar

34

control collar

36

tank Bund

38

Dead end

40

Flow control edge

42

Inlet control edge

44

further inlet control edge

46

further flow control edge

48

Tank control edge

50

Tanknut

52

circumferential

54

smaller circumferential recess

56

Pressure relief channel

58

sealing plug

60

Lastabgriffsdüse

62

1. nozzle channel

64

2nd nozzle channel

66

LS-channel

68

radial bore

70

Lastabgriffsbohrung

72

inlet channel

74

pump channel

76

pump

78

control line

80

LS control line

82

forward channel

84

Return channel

86

Load pressure relief channel

88

further load pressure limiting channel

90

drain channel

Claims (14)

1. Load-sensing control arrangement having a directional control valve (2) by means of whose valve slide (10), on displacement out of the basic position in one direction, a first consumer port (A) and, on displacement in the other direction, a second consumer port (B) can be connected to an inlet port (P) and the respective other consumer port can be connected to an outlet port (T), an opening cross-section of an inlet restrictor, which is assigned an individual pressure regulator (4) for keeping constant the drop in pressure across the inlet restrictor, being determined by means of an inlet control edge (42, 44), and having a load-sensing control oil flow path by means of which the load pressure downstream of the inlet restrictor can be sensed and signalled through the valve slide (10) to a load-sensing control chamber (26) of the directional control valve (2), a maximum pressure in the load-sensing control oil flow path being limitable by means of a pressure-limiting valve, characterised in that the load-sensing control oil flow path, during the displacement of the valve slide (10) out of the basic position in the one direction, can be connected in succession or in an overlapping manner to two pressure-limiting chambers (24, 28) which are each assigned a pressure-limiting valve (6, 8) for load-sensing pressure limitation.
2. Load-sensing control arrangement according to patent claim 1, wherein the maximum pressure in a pressure-limiting chamber (24) active during a first partial stroke is limited to a higher pressure than in the second pressure-limiting chamber (28).
3. Load-sensing control arrangement according to patent claim 1 or 2, wherein there is formed in the valve slide (10) a pressure-limiting channel (56) which, during displacement in the one direction, on the one hand, opens out in a working chamber (20) connected to the first consumer port (A) and, on the other hand, during a first partial stroke opens out in the first pressure-limiting chamber (24) and, during a further partial stroke, opens out in the second pressure-limiting chamber (28).
4. Load-sensing control arrangement according to patent claim 3, having a load-sensing nozzle (60) in that opening-out region of the pressure-limiting channel (56) which is on the working chamber side.
5. Load-sensing control arrangement according to patent claim 4, wherein two spaced circumferential recesses (52, 54), in each of which a respective nozzle channel (62, 64) connected to the pressure-limiting channel (56) opens out, are formed on the outer circumference of the valve slide (10), the pressure-limiting channel (56) being connected by way of a first circumferential recess (52) and a first nozzle channel (62) in the first displacement region to the first pressure-limiting chamber (24) and, during the second partial stroke, by way of the second circumferential recess (54) and the second nozzle channel (64) to the second pressure-limiting chamber (28).
6. Load-sensing control arrangement according to patent claim 5, wherein the circumferential recesses (52, 54) are constructed in the form of pockets.
7. Load-sensing control arrangement according to any one of patent claims 3 to 6, having a tank groove (50) by way of which, in a basic position (0) of the valve slide (10), the first pressure-limiting chamber (24) is connected to an outlet chamber (22) connected to the outlet port (T).
8. Load-sensing control arrangement according to any one of the preceding patent claims, having a load-sensing channel (66) which extends through the valve slide (10) and which, on displacement of the valve slide (10) in the second direction, for load-sensing, connects a working chamber (16) assigned to the second consumer port (B) to the load-sensing control chamber (26).
9. Load-sensing control arrangement according to patent claims 5 and 8, wherein the first circumferential recess (52) is in a form such that, during the displacement of the valve slide (10) in the second direction, it blocks the connection between the load-sensing control chamber (26) and the first pressure-limiting chamber (24).
10. Load-sensing control arrangement according to any one of the claims related to patent claims 8 and 3, wherein the load-sensing channel (66) and the pressure-limiting channel (56) open out in the same piston collar (38).
11. Load-sensing control arrangement according to any one of the preceding patent claims, wherein, during the second partial stroke, a control edge (48) of a piston collar (38) connects the first pressure-limiting chamber (24) to an outlet chamber (22).
12. Load-sensing control arrangement according to any one of the preceding patent claims, wherein the individual pressure regulator (4) is connected upstream of the inlet restrictor, and the pressure regulator piston is acted upon in the opening direction by the force of a pressure regulator spring (80) and by the load pressure and, in the closing direction, by the pressure between the individual pressure regulator (4) and the inlet restrictor.
13. Load-sensing control arrangement according to any one of the preceding patent claims, wherein the pressure-limiting valves (6, 8) are constructed to be displaceable.
14. Load-sensing directional control valve, especially for a load-sensing control arrangement according to any one of the preceding patent claims, by means of whose valve slide (10), on displacement out of a basic position in one direction, a first consumer port (A) and, on displacement in the other direction, a second consumer port (B) can be connected to an inlet port (P) and the respective other consumer port can be connected to an outlet port (T), an opening cross-section of an inlet restrictor being determined by means of an inlet control edge (42, 44), and having a load-sensing control oil flow path by means of which the load pressure downstream of the inlet restrictor can be sensed and signalled through the valve slide (10) to a load-sensing control chamber (26), characterised in that the load-sensing control oil flow path, during the displacement out of the basic position in the one direction, can be connected in succession or in an overlapping manner to two pressure-limiting chambers (24, 28) in which the maximum pressure can be limited to different values.

Images