EP1452744B1 - Hydraulic control device - Google Patents

Abstract

Hydraulic control arrangement (1) for controlling a consumer comprises two adjustable measuring diaphragms (16, 18) arranged in a pressure inlet and a pressure outlet. At least the pressure inlet is assigned a pressure balance (20) loaded in the closing direction by a pressure upstream of the pressure inlet and in the opening direction by a lower status pressure and the force of a spring. The status pressure is measured at a control channel (24) connecting sections of the pressure inlet and pressure outlet upstream of the measuring diaphragms. Preferred Features: A fixed nozzle (22) and an adjustable nozzle (28) are arranged in series in the control channel and the status pressure between the nozzles is measured.

Description

The invention relates to a hydraulic control arrangement according to the preamble of patent claim 1.

Such control arrangements are based on the load-sensing principle and are disclosed for example in DE 197 15 020 A1. This document shows an LS control block, in which a consumer is supplied via an LS-way valve with pressure medium. The proportionally adjustable directional control valve has a spool, which forms a direction / speed part with a valve housing. About the direction part of the pressure medium supply and the pressure medium flow is controlled to or from the consumer and the speed part is the pressure medium flow before. In the known solution, the speed part is formed by a respective arranged in the inlet and return adjustable metering orifice whose opening cross-section is changed by the axial displacement of a spool. The measuring orifice is preceded by a pressure compensator, which is acted upon in the opening direction by the force of a spring and the load pressure downstream of the inlet orifice and in the closing direction of the pressure upstream of the inlet orifice plate.

If such an LS control block is now to be used to control a lifting cylinder with an oppressive load, then a lowering brake valve is assigned to it on the outlet side. Such a lowering brake valve is in principle a check valve that can be unlocked by the pressure in the inlet and thus allows a controlled lowering under oppressive load. It was found that such a system with LS control block and lowering valve at certain Operating conditions to vibrations tends. This susceptibility to vibration results from the fact that the lowering brake valve, as mentioned above, is actuated by the pressure in the inlet, ie by the pressure downstream of the inlet measuring orifice. If this supply pressure is insufficient, the lowering brake valve is closed and controlled according to the return. The pressure in the inlet then rises again and the lowering brake valve opens - the pressure in the inlet is thus dependent on the opening degree of the lowering brake valve. This opening and closing of the Senkdruckbremsventils when lowering a load caused fluctuations in the inlet, which have an effect on the upstream pressure compensator and possibly on the driven depending on the effective load pressure variable.

In contrast, the invention has the object to provide a hydraulic control arrangement for controlling a consumer, in which the susceptibility to vibration is reduced.

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

According to the invention, the signaling pressure is not tapped downstream of the inlet-side orifice but on a control channel which connects a portion upstream of the inlet-side orifice with a portion upstream of the outlet-side orifice. This reporting pressure has a much lower dependence on pressure fluctuations, so that - for example, when using a Senkbremsventils- the resulting vibrations do not affect-as in the prior art described above-directly on the reporting pressure, as it were a "smoothed" reporting pressure at the pressure compensator and / or the variable displacement pump of the LS system is applied. The control channel only needs to be designed so that the tapped pressure is less than the effective pressure on the pressure compensator in the closing direction.

From DE 38 02 672 C2, a control arrangement is known in which in an LS system, the message pressure is also tapped at a pressure divider. In this variant, however, the control line containing the pressure divider extends between an area upstream of the inlet orifice plate and a tank channel and not, as in the invention, between the upstream sections in front of the metering orifices (as seen in the pressure medium flow direction).

In a particularly preferred embodiment, the control channel includes a fixed and an adjustable nozzle, wherein the reporting pressure is tapped in a portion between these two nozzles. That is, the reporting pressure is practically tapped at a pressure divider between the high pressure (inlet) and the low pressure (drain).

In this variant, the adjustable nozzle is changed depending on the setting of the inlet orifice. More specifically, the adjustable nozzle is adjusted inversely proportional to the inlet orifice, that is, the cross section of the adjustable nozzle is reduced with increasing stroke of the directional control valve.

In a particularly preferred variant, the hydraulic control arrangement has an LS-way valve, via which a speed part is formed. The speed part of the LS directional control valve forms the inlet orifice plate and the drain orifice plate, the control channel being integrated with the pressure divider (fixed nozzle, adjustable nozzle) in a spool valve of the LS directional control valve.

In a particularly preferred embodiment of the invention, the spool has a central annular groove, which is arranged in the basic position in the region of a pressure port of the directional control valve and via which a connection to the inlet-side or outlet-side connection is controlled in axial displacement of the spool.

In the construction described above, a control collar adjoining the annular groove, via which the connection to the outflow connection can be opened, is provided with a radial nozzle bore which has an opening cross section tapering towards the return connection. This nozzle bore forms the adjustable nozzle and opens into an axial bore of the spool. In this axial bore further opens a radially extending control oil inlet bore, via which the axial bore can be connected to a pressure chamber leading to the pressure chamber pressure. This control oil inlet bore thus corresponds to the fixed nozzle of the control channel. The signaling pressure which occurs between these two nozzles (nozzle bore, control oil inlet bore) is tapped off via an LS connection and, if appropriate via a shuttle valve arrangement, reported to the upstream pressure compensator and / or to the variable displacement pump.

The production of the spool is particularly simple if the inlet bore and the nozzle bore are formed on the same control collar.

The peripheral mouth region of the nozzle bore is formed in a preferred embodiment by an axially extending notch, which tapers towards the discharge port and becomes shallower, so that the effective diameter of the nozzle bore with increasing stroke of the spool (inlet control) is smaller.

The invention can be used particularly advantageously in a control arrangement with a variable displacement pump and with a lowering brake valve.

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

• Figur 1 ein stark schematisiertes Schaltschema einer erfindungsgemäßen Steueranordnung zur Betätigung eines Hubzylinders mit drückender Last;
• Figur 2 ein Schaltsymbol eines LS-Wegeventils der Steueranordnung aus Figur 1
• Figur 3 eine Schnittdarstellung eines LS-Wegeventils gemäß Figur 1 und
• Fig. 4, 5 Betriebsstellungen des LS-Wegeventils aus Fig. 3.

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

• Figure 1 is a highly schematic circuit diagram of a control arrangement according to the invention for actuating a lifting cylinder with pressing load;
• FIG. 2 shows a circuit symbol of a LS directional control valve of the control arrangement from FIG. 1
• Figure 3 is a sectional view of a LS-way valve according to Figure 1 and
• Fig. 4, 5 operating positions of the LS-way valve of FIG. 3rd

FIG. 1 shows a greatly simplified circuit diagram of a hydraulic control arrangement 1 according to the invention, via which a hydraulic consumer, for example a lifting cylinder 2 of a mobile working device, via which, for example, a main arm of a construction site vehicle is supported, can be controlled. The lifting cylinder 2 is supplied by a variable displacement pump 4 with pressure medium, wherein the pressure medium flow between this and the lifting cylinder 2 is controlled by a LS-way valve 6. The basic structure of such a LS-way valve 1 is known from the initially discussed DE 197 15 020 A1. The proportionally adjustable directional control valve 6 controls via the pressure medium flow between the variable displacement pump, the consumer (lifting cylinder 2) and a tank T. In the embodiment shown in Figure 1 is the simplicity Half only one position of the directional control valve 6 is shown, in which an annular space 8 of the lifting cylinder 2 is connected via a supply line 10 to a working port A. A bottom-side cylinder chamber 12 of the lifting cylinder 2 is connected via a drain line 14 to a working port B, which in turn is connected via the directional part of the directional control valve 6 to the tank T.

By a speed part of the directional control valve 6, a Zulaufmessblende 16 and a drain metering orifice 18 are formed, the switching position shown in the figure 1 of the directional control valve 6 between a pressure port P and the working port A (inlet orifice 16) and between a tank port T and the working port B ( Drain aperture 18) are arranged. The inlet orifice 16 is preceded by a pressure compensator 20, which is acted upon in the closing direction by the pressure upstream of the inlet orifice 16, that is the pressure in the region of the pressure port P and in the opening direction by the force of a spring and a signaling pressure in a control line 22. This signaling pressure is tapped via the control line 22 at a control channel 24, which extends according to Figure 1 between an area of the pressure fluid flow path upstream of the inlet orifice 16 and upstream of the drain metering orifice 18. In the control channel 24, a pressure divider with a fixed nozzle 26 and an adjustable nozzle 28 is arranged, wherein the control line 22 branches off between these two nozzles 26, 28. The adjustable nozzle 28 is associated with the drain side (low pressure) and the fixed nozzle 26 of the inlet side (high pressure).

The adjustable nozzle 28 can be adjusted depending on the setting position of the LS-way valve, more specifically depending on the setting of the speed part and thus the opening cross-section of the metering orifices 16 and 18 vary.

The pressure in the control line 22 is applied to the input of a LS shuttle valve 30 whose output is guided to the control valve 32 of the variable displacement pump 4. The other input of the shuttle valve 30 is connected to an LS reporting line 34 through which the highest of the load pressures of other consumers of the mobile implement to the shuttle valve 30 is performed. That is, the delivery of the variable displacement pump 4 is controlled in response to the highest load pressure or the signal pressure in the control line 22. In the present embodiment, it is assumed that this reporting pressure is higher than the highest of the load pressures in the LS reporting line 34.

The lifting cylinder 2 is provided for supporting a pressing load. In order to prevent an uncontrolled lowering of this load, the lifting cylinder 2 is associated with a lowering brake valve 36. This lowering brake valve is basically a check valve that can be unlocked by a back pressure, in the present case by the pressure in the supply line 10 and bring in an open position, so that the pressure fluid can flow out of the cylinder chamber 12 via the drain line 14. The peculiarity of the invention lies in the fact that the control pressure acting on the pressure compensator 20 in the opening direction and optionally also the pressure for regulating the variable displacement pump 4 is not tapped off downstream of the inlet orifice 16, as in the prior art described above, but at the pressure divider which passes through the Nozzle 26, 28 is formed. This pressure is below the pressure upstream of the inlet orifice plate 16 and, depending on the setting of the nozzle 28, above the pressure in the outlet upstream of the drainage orifice 18. It has been found that this pressure is much less susceptible to opening. and closing movements of the lowering brake valve, so that the vibration susceptibility to conventional solutions is significantly improved.

As will be explained in more detail below, such a control channel 24 can be integrated with a pressure divider 26, 28 with minimal device complexity in the spool of a directional control valve, as is known in principle from DE 197 15 020 A1.

The circuit symbol of such a LS-way valve 6 is shown in FIG.

In its spring-biased home position, the pressure port P is shut off and the working ports A, B, and control ports S, LS connected to the tank port T.

If a spool 38 is displaced to the left in the illustration according to FIG. 2, then the tank connection T is connected to the working connection B, while the working connection A is connected to the pressure connection P - the pressure medium path which is shown by way of example in FIG.

The metering orifices 16, 18 are arranged in the inlet or in the outlet. The control channel 24 connects the respectively upstream of the orifices 16, 18 located pressure medium paths with each other and contains the fixed nozzle 26 and the adjustable nozzle 28. The reporting pressure is tapped via the control line 22 between this pressure divider. This corresponding pressure is also reported in an LS line.

In these adjusting positions (spool 38 in Figure 2 to the left) is pressure medium via the working port A guided in the annular space 8 and flows out of the cylinder chamber 12 via the lowering brake valve 36, not shown, and the working port B to the tank T down. About the upstream pressure compensator 20, the pressure drop across the inlet metering orifice 16 is held constant load pressure independent, so that a constant pressure medium flow is passed to the consumer (LS control). The lifting cylinder 2 is thus lowered in these adjusting positions of the directional control valve 6 as a function of the opening of the lowering brake valve 36.

To extend the lifting cylinder of the spool 38 is shifted in the illustration of Figure 2 to the right, so that the pressure port P to the working port B and the working port A is connected to the tank port T. The load pressure at the working connection B is tapped off via a nozzle 40 and led to the control connection S. This nozzle 40 is formed by the nozzle 28 in the solution described below.

FIG. 3 shows a section of a directional valve 6 with which the switching symbol shown in FIG. 2 is realized.

The directional control valve 6 has a valve housing 42, in which the spool 38 is guided axially displaceable. This is biased by a centering spring, not shown in the basic position shown in Figure 3 (see also Figure 2).

On the valve housing 42, the terminals P, T, A, B and the LS or S port are formed. The valve housing 42 is penetrated in the axial direction by a valve bore 44, in which in the region of the aforementioned ports annular spaces 46, 48, 50, 52, 54 and 56 are formed are. The annular space 46 and two adjacent annular spaces 58, 60 are assigned to the LS port, the two annular spaces 48, 56 to the tank port T, the annular space 50 to the working port A, the annular space 54 to the working port B and the annular space 52 the pressure port P, that is in the pressure chambers formed by the annular spaces, the pressure at the associated connection is approximately equal.

The spool 38 has a central annular groove 62 bounded by two adjacent control collars 64,66. In the distance left (view of Figure 3) from the control collar 64 two annular collars 68, 70 are arranged, between which a radially recessed circumferential groove 72 remains. A circumferential groove 74 remains between the control collar 64 and the annular collar 68. On the right (view according to FIG. 3), a guide collar 66 is provided, which is spaced apart from the control collar 66 via a further circumferential groove 78.

The axial lengths of the above-described frets and grooves are selected such that in the illustrated spring-biased home position of the working port P is shut off (see Figure 2) and the two working ports A, B and the LS port to the tank port T are connected.

On control edges 80, 82 of the control collar 66 and on a control edge 84, 86 of the control collar 64 and the annular collar 68 axially extending control notches are formed via which a connection to the adjacent pressure chamber is gradually aufsteuerbar.

The spool 38 has an axial bore which forms the control channel 24. This axially extending control channel 24 is shut off on one side by a screwed into the right end face de spool 38 screw plug 88. The of the screw 88 adjacent end portion terminates in a radial bore 90 which opens at the outer periphery of the circumferential groove 72 of the spool 38 and thus establishes a connection between the LS port and the control channel.

In the limited by the two control edges 80, 82 control collar 66 are still two lying on a diagonal control oil inlet holes 92 formed on the one hand in the control channel 24 and on the other hand in the outer peripheral region of the control collar 66 between two adjacent control notches. That is, in the basic position of the spool 38 shown in Figure 3, the mouth areas of the inlet holes 92 are shut off. According to FIG. 3, the mouth region of the inlet bores 92 is formed with a relatively small axial distance from the control edge 80. Approximately in the axial region in which the control notch 80 associated Steuerkerben, two also disposed on a diagonal nozzle bores 94 are provided in the control collar 66, the one hand in the control channel 24 and peripherally each in a along the outer circumference extending notch 96 open. This notch tapers in both the width (along the outer circumference) and in the depth (in the radial direction) to the right. That is, the maximum width and depth of the notch 96 are respectively achieved in the peripheral mouth region of the nozzle bores 94. These notches, with an approximately triangular cross section can be formed, for example, by milling on the outer circumference of the spool 38.

In the illustrated basic position of the spool 38, the notches 96 and the nozzle bores 94 are open to the working port B with maximum cross-section. That is, in the home position, the LS port and the control channel 24 are above the nozzle bores 94 and the notches 96 connected to the working port B and thus to the tank port T.

To lower the lifting cylinder 2, the spool 38 is moved to the left in a figure 4 corresponding position. In this case, the connection from the pressure port P to the working port A is controlled via the control edge 84 with the associated control notches, while the connection from the working port B to the tank port T is opened via the control edge 82 with the associated control notches. The cross-section opened by the control edge 84 corresponds to the effective cross-section of the inlet orifice 16. As can be seen in FIG. 4, when the spool 38 is displaced to the left (depressions), the orifice cross-section of the control oil inlet bores 92 is opened so that pressure medium from the working port P, ie upstream of the open-loop orifice plate 16 can enter via the control oil inlet holes 92 in the control channel 24 of the spool 38. As can be further seen in Figure 4, the effective flow area of the notch 96 is reduced from the home position. However, there is still a connection to the working port B, so that the control oil from the control channel 24 throttled down to the tank port B can flow down. That is, the pilot oil supply bore 92 has a constant cross-section in the sink mode, while the nozzle bores 24 with the notches 96 have a stroke-dependent cross-section which decreases as the stroke increases. Thus, the fixed nozzle 26 is formed by the inlet bores 92, and the adjustable nozzle 28 is formed by the nozzle bore 94 with the notches 96. These two nozzles 26, 28 form a pressure divider, the tapping between these adjusting pressure via the control channel 24, the radial bore 90 and the LS port and the LS shuttle valves or the pressure compensator 20 and the control valve 32 of the Variable displacement pump is guided. By reducing the effective cross section of the adjustable nozzle 28 (nozzle holes 94, notches 96), the control oil is accumulated in the control channel and thus a higher pressure in the control line 22 is reported, so that correspondingly with increasing slide stroke, the pressure in the inlet is increased.

The self-adjusting pressure by means of pressure medium and control oil flow path corresponds to that, as it is shown in Figure 1.

To extend the lifting cylinder 2, the spool is moved from the basic position to a position shown in Figure 5 to the right, in which the connection from the pressure port P to the working port B is turned on by the control edge 80 with the associated control notches. In these positions, the winding cross-section of the radial bores 90 remains closed, while the nozzle bores 94 and the notches 96 to the working port B are completely opened. The right in Figure 5, connected to the tank port T annular space 56 is controlled by the control edge 82 to the working port B out. Accordingly, pressure medium can flow from the pressure port P via the working port B into the cylinder space 12 of the lifting cylinder 2, while the pressure medium 8 displaced from the annular space via the working port A to the tank port T. The pressure at the working port B is controlled via the opened nozzle bore 94, the control channel 24, the radial bore 90, the annular space 60 and the annulus 46 tapped and reported to the LS (S) connection. The control of the variable displacement pump 4 then takes place as a function of this pressure at the working connection B. The cross section opened by the control edge 80 corresponds to the effective cross section of the drain measuring orifice 18.

The solution according to the invention is characterized by a very simple structure, wherein compared to the prior art described in the introduction according to DE 197 15 020 A1, the channel guidance within the control slide is simplified.

Disclosed is a hydraulic arrangement with a Zulaufmessblende and a drain metering orifice, wherein at least the inlet orifice is associated with a pressure compensator. The pressure compensator is acted upon in the opening direction by a control pressure which is tapped off on a control channel which extends between sections located downstream of the inlet measuring orifice and the drain metering orifice.

LIST OF REFERENCE NUMBERS

1

control arrangement

2

lifting cylinder

4

variable

6

LS-way valve

8th

annulus

10

supply line

12

cylinder space

14

drain line

16

Supply measuring orifice

18

Drain measuring orifice

20

pressure compensator

22

control power

24

control channel

26

jet

28

adjustable nozzle

30

LS shuttle valve

32

control valve

34

LS-signaling line

36

lowering valve

38

spool

42

valve housing

44

valve bore

46

annulus

48

annulus

50

annulus

52

annulus

54

annulus

56

annulus

58

annulus

60

annulus

62

ring groove

64

control collar

66

control collar

68

collar

70

collar

72

groove

74

circumferential groove

76

guide collar

78

circumferential groove

80

control edge

82

control edge

84

control edge

86

control edge

88

Screw

90

radial bore

92

Control oil supply boreholes

94

nozzle bores

96

score

Claims (10)

1. A hydraulic control arrangement for controlling a consumer, with two adjustable measuring diaphragms (16, 18) arranged in a pressure-medium inlet and a pressure-medium outlet, wherein a pressure balance (20) is associated with at least the inlet measuring diaphragm (16) and is acted upon in the closing direction by a pressure upstream of the inlet measuring diaphragm and in the opening direction by a lower status pressure and the force of a spring, characterised in that the status pressure is measured at a control channel (24) which connects together portions of the pressure-medium inlet and the pressure-medium outlet which are located upstream of the measuring diaphragms (16, 18).
2. A control arrangement according to claim 1, wherein a lowering brake valve (36) is connected in the outlet and can be opened by the pressure in the inlet.
3. A control arrangement according to claim 1 or 2, wherein a fixed nozzle (22) [sic - recte 26] and an adjustable nozzle (28) are connected in series in the control channel (24), and the status pressure is measured between the nozzles (26, 28).
4. A control arrangement according to claim 3, wherein the adjustable nozzle (28) is adjustable as a function of the setting of the measuring diaphragms (16, 18).
5. A control arrangement according to claim 4, wherein the measuring diaphragms (16, 18) are formed by a velocity part of a proportionally adjustable LS directional-control valve (6), and the control channel (24) with the nozzles (26, 28) is preferably integrated into a control slider (38) of the directional-control valve (6).
6. A control arrangement according to claim 5, wherein the control slider (38) has an approximately central annular groove (62) arranged in the region of a pressure connection (P) of the directional-control valve (6) and, by means of its displacement, a connection to an inlet or a return of the consumer can be opened up.
7. A control arrangement according to claim 6, wherein, in a control collar (66) associated with the return and adjacent to the annular groove, a radial nozzle bore (94) is provided, the control-oil outlet cross-section of which can be reduced when the inlet measuring diaphragm (16) is opened up and which leads into an axial bore of the control slider (38), which axial bore is connected by means of a control-oil inlet bore (92) of the control slider (38) to a pressure chamber (52) which is arranged downstream of the inlet measuring diaphragm (16) and is connected to the pressure connection (P), and which axial bore leads to an LS connection for measuring the status pressure.
8. A control arrangement according to claim 7, wherein the inlet bores (92) are formed in the control collar (66) between the nozzle bores (94) and the annular groove (62).
9. A control arrangement according to claim 7 or 8, wherein the nozzle bores (94) each have a radial bore portion leading into a broad end portion of an axially extending notch (96) which tapers away from the annular groove (62) and becomes flatter.
10. A control arrangement according to any one of the preceding claims, characterised by a variable displacement pump (4) which is controllable by means of the status pressure.

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