EP1623123B1 - Hydraulic control arrangement - Google Patents

Abstract

What is disclosed is a hydraulic control arrangement for controlling a consumer, comprising a continuously adjustable directional control valve, an individual pressure compensator associated to the latter, as well as shut-off blocks arranged downstream from the directional control valve. In accordance with the invention, in the case of a insufficient supply of the consumer the pressure compensator is subjected not to the pressure in the supply (load pressure) but to a higher pressure, so that the control pressure difference at the supply control edge is raised.

Description

The invention relates to a hydraulic control arrangement for controlling a consumer according to the preamble of claim 1.

From the DE 100 45 404 C2 an LS control arrangement is known in which a hydraulic consumer, for example a double-acting cylinder for moving a load via a continuously adjustable directional control valve with pressure medium can be supplied. In the pressure medium inlet to the cylinder and in the drain from the cylinder each check valves are provided, wherein the inlet-side check valve is brought by the pressure downstream of the directional control valve in an open position. The drain-side check valve can be brought by pressing a poppet in an open position, which allows the drainage of the pressure fluid from the consumer to the directional control valve.

In the known solution takes place via the drain-side blocking block a flow control by feedback of the discharge pressure before the flow-determining slide control edge of the continuously adjustable directional control valve on the topping piston of the blocking block.

The problem with this solution is that, for example, in the case of a "pulling load", the pressure in the inlet may drop below the pressure in the outlet, with the danger of a shortage of the inlet-side cylinder chamber occurring in the inlet. Such an undersupply can lead to cavitations, by which the consumer or the associated Hydraulic switching elements can be damaged. Such an operating state can occur, for example, when a load is first raised, then overcomes a dead center and then acts pulling on the hydraulic consumer.

From the DE 199 31 142 C2 a similarly constructed control arrangement is known in which, however, the flow control does not take place via the blocking block, but an inlet control is carried out via an upstream of the directional control valve individual pressure compensator. This is acted upon in the opening direction by the force of a spring and the pressure in the inlet to the consumer. Also in this solution, it can in the case of a pulling load to the problems described above, further, the running pressure medium flow should be controlled independent of load pressure.

In principle, several methods are known to avoid an undersupply. For example, suction valves can be provided, via which pressure medium can be sucked out of the tank in the event of insufficient supply. Due to the low differential pressure between the cylinder suction side and the tank pressure, however, such suction valves must have a very large cross section.

Another possibility is the use of bias valves in the pressure fluid outlet. However, there is the problem that the inlet pressure, especially for small loads, must be raised very high, resulting in high energy losses.

Alternatively, lowering brake valves can be used, but also a high pressure on the Need to supply side to control the flow on the drain side.

The invention has for its object to provide a hydraulic control arrangement for controlling a consumer, in particular a double-acting consumer, in which the risk of undersupply is minimized.

This object is achieved by a control arrangement having the features of patent claim 1.

According to the invention, the control arrangement has a continuously adjustable directional control valve to which an individual pressure balance is assigned. This is acted upon in the opening direction by the force of a spring and a control pressure and in the closing direction of a pressure in the inlet upstream of the directional control valve. In the normal operating state of the control arrangement, for example when lifting a load, the control pressure corresponds to the pressure in the inlet downstream of the directional control valve, d. H. the load pressure and thus corresponds to a conventional LS control.

At risk of undersupply, ie when the pressure drops in the inlet and at a pressure load in the process (for example, a pulling load), the control pressure is raised so that it is higher than the pressure in the inlet downstream of the directional control valve. By this increase in the effective control in the opening direction, the control pressure gradient is raised at the inlet-side control edge of the directional control valve, so that a larger pressure fluid flow is promoted to the inlet-side cylinder chamber and a shortage can be prevented.

According to the invention, this control pressure is maintained at a constant, elevated level in the event of an undersupply. This raised control pressure can be tapped off, for example, in the pressure medium flow path between the outflow-side blocking block and a sequence control edge of the directional control valve.

Alternatively, the control pressure can also be tapped from any other available constant pressure source.

In a preferred embodiment, the locking block has a poppet which can be acted upon by an unblocking control pressure for unlocking. In this variant, it is possible to use the set, for example via a pressure reducing valve Entsperrsteuerdruck as control pressure.

In this case, it is preferred to apply the discharge-side pressure to the poppet, so that it is acted upon in the upstroke direction by the release-control pressure and in the opposite direction by the pressure in the discharge, so that a substantially load-independent discharge control is made possible.

In a particularly preferred embodiment, the inlet and outlet pressures are tapped downstream of the directional control valve and upstream of the respective check valve and the respective higher pressure via a shuttle valve to the spring chamber of the individual pressure compensator.

In an alternative solution, these two pressures can still be compared with the Entsperrsteuerdruck and the largest of these pressures via a shuttle valve assembly are guided to the effective in the opening direction control surface of the individual pressure compensator.

In a further advantageous embodiment of the invention, the pounding piston of the blocking block is acted upon in the lifting direction by a spring. In this case, a compression spring can be made weaker, over which a pilot piston guided in the blocking piston is biased into its closed position.

The check valve can be executed with or without seat difference.

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

• Figur 1 ein Schaltschema eines Ausführungsbeispiels einer LS-Steueranordnung;
• Figur 2 eine vergrößerte Darstellung der Steueranordnung aus Figur 1 und
• Figur 3 ein weiteres Ausführungsbeispiel einer erfindungsgemäßen Steueranordnung.

In the following two preferred embodiments of the invention will be explained in more detail with reference to schematic drawings. Show it:

• Figure 1 is a circuit diagram of an embodiment of a LS control arrangement;
• Figure 2 is an enlarged view of the control arrangement of Figure 1 and
• Figure 3 shows another embodiment of a control arrangement according to the invention.

FIG. 1 shows a valve disk 1 of a mobile control block, via which a consumer of a mobile working device can be supplied with pressure medium. The valve disc 1 receives an LS control arrangement with a continuously adjustable directional control valve 2, an individual pressure compensator 4 and two shut-off valves 6, 8, via which the consumer, for example a Hydraulic cylinder 10 pressure medium from a pump, for example a variable displacement pump 12 can be fed and via which the pressure medium from the load 10 to a tank T is traceable.

A cylinder chamber 14 of the hydraulic cylinder 10 is connected to a working port A and an annular space 16 to a working port B, the tank is connected to a tank port S and the variable displacement pump 12 to a pressure port P (perpendicular to the plane in Figure 1).

According to Figure 1, a pressure compensator piston 15 of the individual pressure compensator 4 - in the following called pressure balance - in a pressure compensator bore 17 of the valve disc 1 is guided axially displaceable. The pressure compensator piston 15 has a central annular groove, via which it is divided into a control collar 18 and a rear spring collar 20. On the control collar 18, a plurality of control notches are provided which form a control edge 22, via which the connection of a connected to the pressure port P pressure chamber 24 to an adjacent pressure channel 28 up or is zuusteuerbar. The pressure compensator piston 15 is biased by means of a control spring 30 supported on an end face of the pressure compensator bore 17 in a direction in which the connection between the pressure chamber 24 and the pressure channel 28 is opened. A control spring 30 receiving spring chamber is connected to a control channel 34 which leads to the output of a shuttle valve 36. The left in Figure 1 end face of the pressure compensator bore 16 defines with the adjacent end face of the control collar 18 a control chamber 38 which is acted upon via a further control channel with the pressure in the pressure channel 28. In the further control channel 40, a damping throttle 42 is further provided for damping high-frequency vibrations. Of the Pressure channel 28 branches according to Figure 1 in two directional control valve 2 leading channels 44, 46. Details of this directional control valve 2 and the two locking blocks 6, 8 will be explained with reference to FIG.

The continuously adjustable directional control valve 2 has a valve slide 48 which is received in a valve bore 50 of the valve disc 1 axially displaceable. The valve spool 48 is biased via a centering spring arrangement 52, 53 in its illustrated basic position. From this basic position, the valve spool 48 can be moved mechanically, electrically or hydraulically into working positions, which will be discussed in more detail later. In the illustrated embodiment, the actuation of the valve spool 48 via one or two proportional solenoids (not shown).

The valve bore 50 is provided with a plurality of annular spaces. In this case, a central control pressure chamber 52 to a control terminal X (not shown) is connected, via which the control pressure chamber 52 can be acted upon by a constant Entsperrsteuerdruck. On both sides of the control pressure chamber 52, two annular return chambers 54, 56 are provided, which are connected via the tank channels R with the return port T (see Figure 1). On both sides of the return chambers 54, 56 two further annular spaces are provided, wherein the left in Figure 2 annulus are referred to below as Zulaufraum 58 and the right as drainage chamber 60. Adjacent to the inflow or outflow space 58, 60 are two pressure chambers 63, 65 which are connected to the channels 44 and 46, respectively. Between the central control pressure chamber 52 and the two return spaces 54, 56 of the other two annular spaces 62, 65 are provided in the valve bore 50 further.

The valve spool 50 has in the region of these annular spaces 62, 64 two narrow annular webs 66, 68 which shut off the connection between the central control pressure chamber 52 and the two adjacent annular spaces 62, 64 in the basic position shown in FIG.

At the valve spool 50 further two control collars 70, 72 are formed, in the annular end faces each control notches are provided so that at each control collar 70, 72 a flow control edge 74 and an inlet control edge 76 is formed. The geometry of the control collars 70, 72 with the control notches formed thereon is designed so that in the illustrated basic position of the inlet chamber 58 and the drain chamber 60 are open to the respective adjacent return chamber 54, 56, so that these pressure chambers are depressurized. The connection between the inlet space 58 and the discharge space 60 to the outer pressure chambers 63, 65 is controlled via the inlet control edge 74.

The two blocking blocks 6, 8 shown enlarged in Figure 2 each have an identical structure, so that in the following only the blocking block 6 is described. Each locking block 6, 8 has a locking piston 78, which is biased against a valve seat 80. The locking piston 78 is guided in a bore 79 of the disc 1. In the illustrated blocking position, the connection between an inlet chamber 82 and a working chamber 84 or the connection between a discharge chamber 86 and a working chamber 88 is shut off leak-free. The locking piston 78 is designed as a hollow piston, wherein in its designed as a cone piston crown a pilot cone 90 is guided, which is biased by a pilot spring 94 against a pilot seat 92. About this pilot spring 94 and the locking piston 78 against its valve seat 80th biased. The pilot poppet 90 has an axially projecting from the pilot seat 92 projection 96 which projects in the direction of the inlet chamber 82 and the discharge chamber 86 out.

In the remote from the locking piston 78 end portion of the bore 79 of a further designed as a stepped piston poppet 98 is guided axially displaceable, the piston rod 100 extends in the direction of the projection 96 of the pilot poppet 90. In the poppet 98 receiving end portion of the bore 79 opens a Entsperrsteuerraum 102, which is connected via a connecting channel 104 with the annular space 62. Accordingly, a Entsperrsteuerraum 106 of the blocking block 8 is connected via a further connecting channel 108 with the annular space 64.

The inlet chamber 82 of the blocking block 6 is connected via an intermediate channel 110 to the inlet chamber 58 and corresponding to the drain chamber 86 of the blocking block 8 via a further intermediate channel 112 to the drain chamber 60. The space 101 on the rod side of the piston 98 is connected to the space 82 via a throttle, depending on the necessary damping.

In the exemplary embodiment illustrated in FIG. 1, the inlet chamber 58 and the outlet chamber 60 are each connected via a control line 116 or 118 to the two inputs of the shuttle valve 36. This means that the larger of the two pressures Y _A , Y _B picked up in the inlet space 58 and in the discharge space 60 is reported to the control channel 34 via the shuttle valve.

To describe the function of this control arrangement is first assumed that the hydraulic cylinder 10 is acted upon by a pulling load L. Accordingly, must Pressure medium are conveyed via the working port A in the cylinder chamber 14 and the pressure medium from the annular space 16 of the hydraulic cylinder via the working port B to drain.

For this purpose, the valve spool 48 of the continuously variable directional control valve 2 is shifted in the illustration of Figure 1 to the right, so that through the inlet control edge 76, the connection between the annular space 62 and the inlet space 58 and the connection between the drain chamber 60 and the return chamber 56 via the flow control edge 74 is turned on. The pressure medium can then flow from the variable displacement pump 12 via the pressure chamber 24, the pressure compensator 4 opened as described below, the pressure channel 28 into the channel 44 and from there via the controlled from the inflow control edge 76 cross section of the directional control valve 4 in the intermediate channel 110 and from there into the inlet chamber 82 of the blocking block 6 flow.

As soon as the pressure in the inlet chamber 82 is greater than the pressure equivalent of the pilot spring 94 plus the load pressure at the working port A, the locking piston 78 is lifted from its valve seat 80, so that the pressure medium can flow into the cylinder chamber 14.

The pressure compensator 4 is acted upon in the closing direction of the pressure in the control channel 40 and thus the pressure in the channel 44 and in the opening direction of the force of the control spring 30 and the pressure in the control channel 34. With sufficient pressure medium supply to the consumer 10, the pressure in the inlet chamber 58 is greater than the pressure in the drain chamber 60, so that correspondingly in the spring chamber 32 of the individual pressure compensator 4, the pressure is applied downstream of the controlled from the inlet control edge 76 cross section. That is, by this inlet control edge 76 of the effective Determined cross-section of an inlet orifice, wherein the pressure compensator piston 15 is adjusted in its control position such that the pressure drop across this orifice is held constant load pressure independent.

The applied in the control pressure chamber 52 control pressure PX is guided through the annular space 64 and the connecting channel 108 in the Entsperrsteuerraum 106, so that the poppet 98 of the locking block 8 is brought in the illustration of Figure 2 to the right in abutment against the projection 96 of the pilot poppet 90. The Entsperrsteuerdruck is chosen so that it is sufficient to lift the pilot cone 90 via the poppet 98 from its pilot seat 92 against the force of the pilot spring 94 and against the force acting on the seat load pressure. When pilot control is open, the spring chamber 120, which is connected via a diaphragm 122 with the working chamber 88 and thus acted upon by the pressure at the working port B, via the feedforward control with the discharge chamber 86 and via the intermediate channel 112, the discharge chamber 60, via the Sequence control edge 74 controlled flow cross section of the directional control valve 2, the return chamber 56 and the return R connected to the tank T and thus relieved of pressure in the closing direction. The pressure compensated locking piston 78 can then be lifted by the poppet 98 from its valve seat, so that the pressure medium along the aforementioned pressure medium flow path to the tank T can flow out. The running pressure medium volume flow is throttled at the flow control edge 74 of the valve spool 48, so that 56 sets a pressure gradient between the drain chamber 60 and the return chamber. When pulling the load, the flow control takes place practically by the feedback of the pressure in the discharge chamber 86, which acts on the end face of the piston rod 100 and the annular surface of the poppet 98, so that this one hand from Entsperrsteuerdruck in Entsperrsteuerraum 106 and on the other hand by the pressure equivalent of the pilot spring 94 and the pressure acting on the piston rod 100 pressure is applied. That is, on the outlet side, a flow regulator is formed by the blocking block 8 and the outlet-side measuring orifice, in which the control pressure difference results from the pressures or pressure equivalents acting on the topping piston. The pressure in the flow is thus regulated by pulling force through a structurally fixed constant, independent of the load pressure at port B and thus in the annulus 16 pressure. This means that there is a load pressure-independent control both on the inlet side and on the outlet side.

If the pressure on the inlet side now drops when the load is pulled, for example as a result of an insufficient regulating pressure gradient at inlet control edge 76 in the event of undersupply of cylinder chamber 14 until it is less than the outlet-side pressure, the larger of these pressures, ie the pressure in the drainage chamber 60 is reported in the control channel 34. This control pressure is - as described above - substantially constant and is located in the spring chamber 32 of the individual pressure compensator 4. Due to this increased, constant pressure, the control pressure gradient at the inlet control edge 76 of the directional valve in the inlet to the cylinder chamber 14 is raised and the pressure medium volume flow in the inlet increases until a pressure medium volumetric flow equilibrium is established between inflow and outflow - an undersupply of the consumer can be caused by this increase in the control pressure gradient reliably prevented. An essential aspect of the invention is seen in the fact that when the pressure drops in the inlet below the pressure in the sequence, the individual pressure compensator is acted upon with such a constant, higher pressure than in the feed, that the Control pressure drop is raised at the inlet control edge.

If necessary, this applied in the control channel 34 pressure could also be tapped from any constant pressure source.

In the embodiment shown in Figure 3, such an embodiment is realized. The basic structure of this embodiment corresponds to that of Figure 2, so that only the essential differences will be discussed here. The control arrangement according to Figure 3 also has a directional control valve 2, an individual pressure compensator 4 and two locking blocks 6, 8. The two on both sides of the control pressure chamber 52 arranged annular ribs 66, 68 are formed so that the two annular spaces 62, 64 in the basic position of the continuously adjustable directional control valve 2 are connected to the two return spaces 54, 56, so that the back sides of the two topping pistons 98 are depressurized.

Furthermore, the control arrangement according to FIG. 3 has a second shuttle valve 128, by means of which the pressure in the inlet space 58 is compared with the pressure in the annular space 64, while the pressure in the discharge space 60 is compared with the pressure in the annular space 62 via a third shuttle valve 130. The outputs of the two shuttle valves 128, 130 are connected to the inputs of the shuttle valve 36, whose output is connected via the control channel 34 to the spring chamber 32 of the individual pressure compensator 4.

That is, in this embodiment, the largest of the pressures in the inlet space 58, in the drain chamber 60 or in the annular spaces 62, 64 applied Entsperrsteuerdruck reported in the spring chamber 32 and this constant pressure for Raising the control pressure gradient used at the inlet control edge 76 in order to avoid a shortage.

The inventive construction eliminates the need to provide Nachsaugventile or the like. Since a shortage of the consumer is almost impossible, and cavitation phenomena at the control edges of the directional control valve 2 can be avoided. Furthermore, air discharges on the suction side of the cylinder are avoided. Another advantage is the fact that the increase in the inlet pressure is much lower than is the case with the solutions described above with bias valves in the process or in a lowering-brake valve. In the illustrated embodiment, the locking piston 78 is the rear side with the same diameter as the valve seat 80 executed. But it could also be a blocking block with a seat difference can be used.

Disclosed is a hydraulic control arrangement for controlling a consumer, with a continuously adjustable directional control valve, an individual pressure compensator associated therewith and blocking blocks arranged downstream of the directional control valve. According to the invention, the pressure compensator is subjected to a higher pressure instead of the pressure in the inlet (load pressure) in the event of an undersupply of the consumer, so that the control pressure difference at the inlet control edge is raised.

LIST OF REFERENCE NUMBERS

1

valve disc

2

way valve

4

Individual pressure compensator

6

locking block

8th

locking block

10

hydraulic cylinders

12

pump

14

cylinder space

15

Pressure regulator piston

16

annulus

17

Pressure compensator bore

18

control collar

20

spring shackle

22

control edge

24

pressure chamber

28

pressure channel

30

control spring

32

spring chamber

34

control channel

36

shuttle valve

38

control room

40

another control channel

42

damping throttle

44

channel

46

channel

48

valve slide

50

valve bore

52

Control pressure chamber

54

Return Room

56

Return Room

58

feed space

60

drain space

62

annulus

63

pressure chamber

64

annulus

65

pressure chamber

66

ring land

68

ring land

70

control collar

72

control collar

74

Flow control edge

76

Inlet control edge

78

blocking piston

79

drilling

80

valve seat

82

inlet chamber

84

working chamber

86

drain chamber

88

working chamber

90

pilot poppet

92

pilot seat

94

pilot spring

96

head Start

98

topping

100

piston rod

101

Annular space at the pounding piston

102

Entsperrsteuerraum

104

connecting channel

106

Entsperrsteuerraum

108

connecting channel

110

intermediate channel

112

intermediate channel

114

slide

116

control line

118

control line

120

spring chamber

122

cover

128

2nd shuttle valve

130

3rd shuttle valve

Claims (8)

1. A hydraulic control arrangement for controlling a consumer (10), comprising a continuously adjustable directional control valve (2) whereby two work ports (A, B) connected to the consumer (10) may be connected to a pressure or supply port (P) or to a drain port (T), wherein a releasable shut-off block (6, 8) is provided in at least one working line acting as a drain line, and comprising an individual pressure compensator (4) associated to the continuously adjustable directional control valve (2) and adapted to be subjected to the force of a spring (30) and to a control pressure in the opening direction and to a pressure upstream from the directional control valve (2) in the closing direction, characterized in
   that the control pressure is determined by a comparing means (36, 128, 130) for the comparison of the effective load pressure in the supply with a constant pressure, wherein the individual pressure compensator (4) is pressurized by the constant pressure, if this is higher than the effective load pressure in the supply.
2. The hydraulic control arrangement in accordance with claim 1, wherein the control pressure in the pressure medium flow path is tapped between the shut-off block (6, 8) on the drain side and a drain control edge (74) of the directional control valve (2).
3. The hydraulic control arrangement as claimed in any preceding claim, wherein the shut-off block (6, 8) includes a topping piston (98) adapted to be subjected to a release control pressure (P_x) for releasing, and wherein the control pressure corresponds to the release control pressure.
4. The hydraulic control arrangement comprising a shut-off block (6, 8) in accordance with claim 3, wherein the topping piston (98) is subjected to the load pressure on the drain side in the closing direction of the shut-off block (6, 8).
5. The hydraulic control arrangement in accordance with claim 1, wherein one respective shut-off block (6, 8) is associated to the pressure medium supply and to the pressure medium drain, and the higher one of the pressures between the shut-off blocks (6, 8) and the directional control (2) valve is tapped via a shuttle valve (36) as a control pressure.
6. The hydraulic control arrangement in accordance with claim 4, wherein the highest of the following pressures: release control pressure, pressure downstream from a supply metering orifice of the directional control valves (2), and pressure downstream from a drain measuring orifice, is tapped via a shuttle valve assembly (128, 130, 36) as a control pressure.
7. The hydraulic control arrangement as claimed in any preceding claim, wherein the shut-off block (6, 8) includes a shut-off piston (78) biased against a valve seat (80) which in turn is provided with a pilot seat (92) against which a pilot cone (90) is biased by means of a pilot spring (94), wherein the pilot cone (90) is adapted to be raised from the pilot seat (92) by means of a topping piston (98), and the topping piston (98) is biased by a pressure spring in a direction away from the shut-off piston (6, 8).
8. The hydraulic control arrangement as claimed in any preceding claim, wherein the shut-off block (6, 8) is designed without a seat difference.

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