EP1643138B1 - Hydraulic control device - Google Patents

Abstract

Hydraulic control arrangement regulates a constant low pressure in a flow pipe (16). A run-off pressure balance (60) is impinged by a constant pressure in the flow pipe in the opening direction. Preferred Features: The constant pressure is adjusted using a pressure limiting valve (48) adjusted to a low pressure and connected to a call circuit (36) connected via a nozzle (43) to the flow pipe. A blocking non-return valve (66) is arranged between the pressure balance and the consumer.

Description

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

Such a hydraulic control arrangement is off DE 198 00 721 known.

Such hydraulic control arrangements are used for example in cranes, mobile work equipment, aerial work platforms or drilling rigs for controlling hydraulic consumers, such as hydraulic cylinders or hydraulic motors. In this case, different control concepts, such as the LS system are used, in which the highest load pressure of the driven load is reported to a variable and this is controlled so that in a pump line is present at a certain pressure difference Ap over the load pressure lying pump pressure. The adjustable metering orifices of a LS control are assigned individual pressure balances, which maintain a pressure difference independent of the load pressure via the respective metering orifices. In the case of the control arrangements designated in a conventional manner with LS control, these individual pressure compensators are arranged upstream of the metering orifice, in the special case of a LUDV control the individual pressure compensators are provided downstream of the metering orifices.

In the DE 102 16 958 B3 is a running as a LS system control arrangement shown in the connections of a hydraulic motor via a continuously adjustable directional control valve with a variable or a tank can be connected. The continuously adjustable directional control valve forms an inlet and a flow meter orifice, wherein the inlet orifice is preceded by an individual pressure compensator. In the pressure medium flow and the pressure medium return are each one Expander scale arranged, of which when driving the consumer only the return pressure compensator lying in the return is effective, which is in the flow "discharge pressure balance" is then fully open and thus ineffective. With the effective discharge pressure compensator, the pressure medium volume flow in the return is regulated when the load is pulled, so that no uncontrolled operating state can occur. An appropriate solution is also in the US 4,184,410 disclosed.

A disadvantage of such hydraulic control arrangements is that the control of the return pressure compensator located in the return is relatively expensive, since this must be acted upon by the pressure in a line leading to the tank and on the other by the applied pressure between the flow meter and the discharge pressure balance.

On the other hand, the object of the invention to provide a hydraulic control arrangement, which allows a simple pressure fluid flow control in the process with low device complexity.

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

According to the invention, the hydraulic control arrangement has an outlet pressure balance arranged in the respective return, which is acted upon in the opening direction - not by the tank pressure as in the prior art described above - but by a constant low pressure in a feed line leading to the consumer. As a result, the channel guidance between the metering orifice and the metering orifice and the pressure compensator-containing control block and the drainage pressure compensator-containing sink module much easier be configured because no own tank line must be performed to the sink module, so that it is connected only via a flow line and a return line with the directional control valve containing control block.

In a preferred embodiment of the invention, the regulation of this constant pressure in the flow line by a supply pressure compensator, which is also acted upon in the opening direction by a constant pressure.

This constant pressure can be adjusted for example via a pressure relief valve. This is connected via a Lastmeldeleitung and a nozzle to the flow line and forms together with the inlet pressure compensator a pilot-operated pressure reducing valve. This regulates in the supply line a pressure which is higher by the pressure equivalent of the pressure compensator spring than the value set at the pressure limiting valve. D. h., In the flow to the consumer, the flow control is replaced by a pressure control.

This pressure limiting valve is preferably designed to be adjustable, so that a lowering is possible even with a positive load.

In a particularly preferred embodiment, a pilot-operated check valve is provided in the region between the discharge pressure balance and the associated working port of the consumer, which is preferably also unlocked from said control pressure.

In the case in which the discharge pressure balance is in the pressure medium flow, it is bypassable by means of a bypass line, in which a bypass check valve opening in the direction of the consumer is arranged.

As an alternative to the bypass check valve with the bypass line, a directional control valve can be provided which acts in a spring-biased basic position, the discharge pressure compensator in the opening direction with the constant pressure in the supply line, while in the closing direction of the pressure compensator respectively the pressure between the discharge pressure compensator and the adjustable drain metering orifice is effective. About the directional control valve, the discharge pressure balance is acted upon in each case in the opening direction with the constant pressure in the flow. In the case in which the "discharge pressure balance" is arranged in the pressure medium flow, this pressure balance is then fully open, while throttling the draining pressure medium volume flow at a pulling load.

The drain pressure compensator practically vorsteuernde directional control valve is acted upon in the direction of its basic position by the flow pressure and in the direction of its switching position of the pressure between the drain metering and the discharge pressure balance.

The control arrangement according to the invention is preferably designed as a LS control arrangement with a variable displacement pump which can be controlled as a function of a load pressure signal of the load tapped via an LS line.

According to the invention, it is preferred if this load pressure signal is differently limited as a function of the pressure medium flow direction, so that, for example, when lifting a load, a higher load pressure signal is allowed than is the case when lowering a load.

In an advantageous embodiment of the invention, the consumer is a hydraulic cylinder over which, for example, a crane arm is supported.

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

• Figur 1 ein Schaubild einer hydraulischen Steueranordnung zur Ansteuerung eines Kranarms, mit einem Steuerblock und einem Senkenmodul und
• Figur 2 ein weiteres Ausführungsbeispiel eines Senkenmoduls für eine Steueranordnung gemäß Figur 1.

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

• FIG. 1 a diagram of a hydraulic control arrangement for controlling a crane arm, with a control block and a sink module and
• FIG. 2 a further embodiment of a sink module for a control arrangement according to FIG. 1 ,

In the FIG. 1 shown control assembly 1 is used to control a designed as a differential cylinder lifting cylinder 2, via which a crane arm 4 of a crane or a boom of a mobile device is supported. The control arrangement 1 is designed as a LS system, wherein pressure medium is sucked via a variable displacement pump 6 from a tank T and conveyed via a control block 8 to the lifting cylinder 2 and is returned by this via a drain module 10 and the control block 8 to the tank T. The variable displacement pump 6 is controlled by means of a pump controller 12 in response to the tapped via an LS line 14 highest load pressure of all supplied by the variable displacement 6 consumers so that it generates at its output a pressure by a predetermined difference Δp above this highest load pressure of all consumers. For this purpose, the pump regulator 12 is acted upon by the pump pressure and in terms of increasing the stroke volume of the highest load pressure and a spring in terms of a reduction of the stroke volume. The difference between the pump pressure and the highest load pressure then corresponds to the force of this spring (for example, 20 bar).

The output of the variable displacement pump 6 is connected to a pump port P of the control block 8, the tank T is connected to a tank port T and two working ports A, B of the control block 8 via two working lines, which are mentioned in the following flow line 16 and return line 18, with an annular space 20 and a cylinder chamber 22 of the lifting cylinder 2 connected.

In one setting of the control block 8 pressure fluid from the working port A flows into the annulus 20 and from the cylinder chamber 22 via the sink module 10 and the control block 8 back to the tank T. The line 16 is then the flow line, while the line 18 is the return line. The control block 8 can also be controlled so that the line 18 (here called return line) the flow line and the line 16 (here called feed line) is the return line.

When pressure medium supply to the cylinder chamber 22 of the lifting cylinder 2 extends, so that the crane arm 4 is pivoted about a pivot joint 24 to the right and the load m is raised. In the opposite control of the control block 8, the pressure medium supply takes place in the annular space 20 so that the lifting cylinder 2 enters and accordingly the load m is lowered.

The in FIG. 1 shown control block 8 has a continuously adjustable directional control valve 26 which is hydraulically pilot operated in the illustrated embodiment. This precontrol can be done, for example, by means of pressure reducing valves, not shown, via which a control supply pressure is reduced to a suitable control pressure. The continuously adjustable directional control valve 26 has a pressure port P and two working ports A, B, which are shut off in the illustrated spring-biased home position (0). A tank connection T of the directional control valve 26 is connected via a tank channel 28 to the tank connection T of the control block 8 (closed center system).

The pressure port P of the control block 8 is connected to the input port P of the directional control valve 26 via an inlet channel 30, in which an individual or inlet pressure compensator 32 is arranged. This is acted upon in the opening direction by the force of a pressure compensator spring 34 and the pressure in the respective flow line 16 and 18, which is tapped via a signaling line 36. In the closing direction, the pressure compensator 32 is acted upon by the pressure at the input P of the directional control valve, which is tapped via a control channel 38 from the inlet channel 30.

In the control positions of the directional control valve 26 marked with (a), a metering orifice 40 between the inlet connection P and the working connection A of the directional control valve 26 is opened via a control edge. Accordingly, a drain metering orifice 42 between the working port B and the tank port T of the directional control valve 26 is opened. The pressure downstream of the inlet metering orifice 40 is reported to the reporting line 36.

At the control positions indicated by (b), the metering orifice is between the input port P and the working port B, while the drain metering orifice is between the working port A and the tank port T. In these control positions, the pressure is also reported downstream of the metering orifice in the reporting line 36.

In the control positions (a) via the directional control valve 26, the pressure in the message line 36 via a nozzle 43 in a lowering-pressure limiting channel 44 and in the control positions (b) also via a nozzle (not shown in detail) in a lifting-pressure limiting channel 46 reported. In the drain pressure limiting channel 44, a lowering pressure relief valve 48 and the lifting pressure limiting channel 46, a lifting pressure relief valve 50 is arranged, the first-mentioned pressure relief valve 48 is set to a much lower pressure (25 bar) than the latter pressure relief valve 50 (250 bar). The two pressure-limiting channels 44, 46 open into the tank channel 28 downstream of the pressure-limiting valves 48, 50. The pressure relief valve 48 limits in the control positions (a) and the pressure limiting valve 50 in the control positions (b) of the directional control valve 26 via the line 36 to the individual pressure compensator 32 and to the pump controller 12 reported pressure to the value set at the respective pressure relief valve.

The two working ports A, B of the continuously variable directional valve are connected via a flow channel 52 and a return passage 54 to the working ports A, B of the control block 8, to which the flow line 16 and the return line 18 are connected.

In the return line 18, the sink module 10 is arranged. This has according to FIG. 1 a pressure port P ', a working port A' and a control port X, which is connected via a line 56 to the flow line 16.

The input port P 'is connected via a channel 58, which forms part of the return line 18 to the working port A'. In the channel 58, a discharge pressure compensator 60 is provided, which in the opening direction by the force of a weak spring 61 (eg 3 bar) and the pressure in a control line 62 is applied, which is connected to the line 56. In the closing direction acts on the pressure compensator piston (not shown) of the pressure compensator 60, the pressure in the region between the input port P 'and the discharge pressure compensator 60. This control pressure is tapped via a line 64 from the channel 58.

In the area between the discharge pressure compensator 60 and the working port A 'is still a pilot-operated check valve 66 is provided, which is unlocked via a Entsperrkanal 68 which is connected to the line 56.

The discharge pressure compensator 60 can be bypassed by means of a bypass line 70, which branches off in the area between the input port P 'and the discharge pressure compensator 60 from the channel 58 and re-opens in the area between the latter and the check valve. In the bypass line 70, a bypass check valve 72 is provided which opens in the direction of the cylinder chamber 22 and blocks a flow of pressure medium in the opposite direction.

To lift the load m, the directional control valve 26 is displaced by appropriate control of the control block 8 in one of his (b) marked control positions, in which the input port P of the directional control valve 26 is connected to the working port B, while the working port A connected to the tank T. is. The variable displacement pump 6 delivers depending on the maximum load pressure of the consumer pressure medium via the inlet pressure compensator 32, the directional control valve 26, the working port B of the control block 8, the input port P 'of the sink module 10, the opening bypass check valve 72, the check valve 66 and the working port A' of the sink module 10 in the cylinder chamber 22, so that the lifting cylinder 2 extends. That's from the downsizing Annulus 20 displaced pressure fluid flows through the then to be regarded as return line flow line 16, the working port A of the control block 8, the flow channel 52, the working port A of the directional control valve 26, the tank port T, the tank channel 28 and the tank port T of the control block 8 back to the tank T. As is known, the pressure across the metering orifice 40 is kept constant by the inlet pressure compensator 32 in a manner independent of the load pressure and pump pressure. The discharge pressure compensator 60 is shut off in this operating state, since the high pressure downstream of the metering orifice 40 is present in the control chamber acting in the closing direction via the line 64.

To retract the lifting cylinder 2, the control block 8 is reversed and the directional control valve 26 is moved to one of its (a) marked control positions in which the pressure medium is conveyed into the annular space 20 and displaced from the cylinder chamber 22.

On the one hand, the inlet metering orifice 40 and the metering orifice 42 of the directional control valve 26 are coordinated so that at a given by the pressure compensator spring 34 pressure difference over the inlet metering orifice 40 the annular space 20 of the lifting cylinder would flow a larger amount of pressure medium than taking into account the area ratio of the cylinder chamber 22 via the drain metering orifice 42 is displaced at the pressure difference predetermined by the discharge pressure compensator 60. The pressure in the annular space 20 therefore increases until the pressure limiting valve 48 responds and limits the pressure in the signaling line 36 to the value set at it. The inlet pressure compensator 32 now works together with the pressure relief valve 48 as a pilot-operated pressure reducing valve and regulates in the flow line 16 a pressure which is higher by the pressure equivalent of the pressure compensator spring 34 than the value set at the pressure relief valve 48. In the flow to the lifting cylinder 2 so the flow control is replaced by a pressure control, so that the discharge pressure compensator 60 is applied via the line 56 and the control line 62 in the opening direction with a constant pressure. The coordination between the metering orifice and the drain metering aperture does not have to be very accurate. The inlet metering orifice 40 must simply be one piece larger than the metering orifice 42.

On the other hand, the pressure relief valve 48 is set to a pressure such that, taking into account the pressure equivalent of the pressure compensator spring 34, the pressure in the supply line 16 is so high that it is sufficient to open via the line 56 and the Entsperrkanal 68, the pilot operated check valve 66 and open to keep.

If, for example, the pressure relief valve 48 is set to 25 bar and the pressure equivalent of the pressure compensator spring 34 is 10 bar, then the inlet pressure compensator 32 in the supply line 16 regulates a pressure of 35 bar. But to open the check valve 66 may already suffice 30 bar. Of course, the pump controller 12 is set so that the pump pressure is slightly higher than 35 bar at a message of 25 bar.

The discharge pressure compensator 60 is thus acted upon in the opening direction by the constant pressure in the supply line 16 and by the force of the weak spring 61. In the closing direction, the discharge pressure compensator 60 is acted upon by the pressure in the line 18, that is, by the pressure upstream of the drain metering orifice 42. The discharge pressure compensator 60 therefore in each case opens so far that the pressure upstream of the drain metering orifice 42 is equal to the pressure in the supply line 16 plus the pressure equivalent of the spring 61. Because the pressure in the flow line is constant, is then the pressure upstream of the drain metering orifice 42 is constant. The pressure downstream of the drain metering orifice 42 is the constant tank pressure. Thus, the pressure difference across the drain metering orifice 42 is constant. The displaced from the cylinder chamber 22 of the lifting cylinder 2 pressure medium quantity and thus the lowering speed of the crane arm 4 can be independent of load control by proportional adjustment of the drain measuring aperture.

The essential difference of the above-described solution to the prior art is thus that the discharge pressure compensator 60 is acted upon in the opening direction not by the tank pressure, but by a constant, relatively low pressure.

At the in FIG. 1 illustrated embodiment, the pressure medium supply to the cylinder chamber 22 via the bypass line 70 of the sink module 10th

FIG. 2 shows a further embodiment of a drain module 10, in which instead of the bypass line 70 with the check valve 72, a 3/2-way valve 74 is used. The basic structure of the sink module 10 is the same as in the embodiment according to FIG FIG. 1 , In the channel 58, the discharge pressure compensator 60 is arranged, between which and the working port A ', the pilot-operated check valve 66 is formed. The control pressure required for unlocking is tapped via the unlocking channel 68 from the control line 62 connected to the control connection X. The pressure compensator 60 is acted upon by the spring 61 in the illustrated embodiment, a force corresponding to a pressure of 5 bar in the opening direction and in the closing direction of the pressure in the line 64, which is tapped from the channel 58.

The 3/2-way valve 74 is biased by means of a 10bar spring 76 and the pressure in the control line 62 in a basic position (a), in which the control line 62 is connected to a pressure compensator channel 78 through which the discharge pressure compensator 60 in addition to the force of Spring 61 is acted upon in the opening direction.

The 3/2-way valve 74 is acted upon in the direction of its switching position (b) by the pressure in the channel 58, which corresponds to the pressure in the conduit 64. The 3/2-way valve 74 is thus displaced against the force of the 10bar spring 76 in its switching position (b) when the pressure difference between the pressure in the channel 58 and the pressure in the control line 62 is more than 10 bar. In this switching position (b), the channel 58 is connected to the pressure compensator channel 78, so that the discharge pressure compensator 60 is pressure-balanced on the front side and experiences an excess of force in the opening direction by the 5bar spring 61.

When lifting the load m (extension of the lifting cylinder 2), the directional control valve 26 of the control block 8 - as in the embodiment described above - moved to one of his (b) marked positions, so that the pressure medium via the inlet pressure compensator 32, the directional control valve 26 and the return line 18 to the input terminal P 'of the sink module 10 ( FIG. 2 ). The annular space 20 of the lifting cylinder 2 is then connected via the control block 8 to the tank T. Correspondingly, the lower pressure in the annular space 20 is applied to the control connection X of the sink module 10, while the in FIG. 2 right control surface of the 3/2-way valve 74 is acted upon by the pressure downstream of the directional control valve 26 - the 3/2-way valve is switched to its (b) characterized switching position in which the pressure compensator 60 - as described above - from the 5bar- Spring 61 completely is controlled and has no effect. The pressure medium can then flow via the channel 58, the pressure compensator 60, the opening check valve 66 and the working port A 'in the cylinder chamber 22.

To lower the directional control valve 26 is moved in one of its (a) marked control positions, so that the pressure medium is conveyed into the annular space 20 and displaced from the cylinder chamber 22. In normal operation (no pulling load), the 3/2-way valve 74 is then biased by the force of the 10bar spring 76 and the pressure in the flow line 16 in its designated (a) switching position and the discharge pressure compensator 60 remains in its open position.

In the case of a pulling load, the pressure in the annular space 20 decreases and the pressure upstream of the drain metering orifice 42 increases due to the larger displaced pressure medium volume flow, so that correspondingly the pressure compensator 60 is moved to an equilibrium position in which the outflowing pressure medium volume flow is throttled. The 3/2-way valve 74 remains due to the comparatively strong 10bar spring 76 in its (a) marked position.

The pressure applied to the inlet pressure compensator 32 in the opening direction pressure when lifting the load (extension of the lifting cylinder 2) via the lifting-pressure limiting valve 50 to a relatively high value (250 bar) limited while lowering the maximum load signal pressure via the drain pressure relief valve 48 to a much lower value (25 bar) is set. In the illustrated embodiment, the pilot-operated check valve 66 is releasable with a control pressure corresponding to about 50 bar in the illustrated embodiment. The pressure compensator spring 34 is selected so that the supply pressure compensator 32 starts at a pressure of about 25 bar with the flow control.

Also in the case of FIG. 2 explained embodiment, only two lines 16, 18 must be provided between the control block 8 and the sink module 10.

In the case of FIG. 1 explained control arrangement is a sink module 10 is provided only in the line 18 (return line). In principle, a corresponding drain module can also be arranged in the supply line 16, which then becomes correspondingly effective in order to bring about a sequence control when lifting the load m. This may be necessary, for example, when over the lifting cylinders 22 when lifting the load a dead center is run over.

Disclosed is a hydraulic control arrangement for controlling a consumer, with an adjustable metering orifice and an associated inlet pressure compensator and a drain module arranged in the drain from the consumer. This has a discharge pressure balance, which is acted upon according to the invention in the opening direction by a constant low pressure in the flow.

LIST OF REFERENCE NUMBERS

1

control arrangement

2

lifting cylinder

4

kranarm

6

variable

8th

control block

10

lowering module

12

pump regulator

14

LS line

16

supply line

18

Return line

20

annulus

22

cylinder space

24

pivot

26

way valve

28

tank channel

30

inlet channel

32

Meter-in compensator

34

Compensator spring

36

reporting line

38

control channel

40

Supply measuring orifice

42

Drain measuring orifice

43

jet

44

Lower pressure relief channel

46

Raise pressure relief channel

48

Lower pressure relief valve

50

Raise pressure relief valve

52

forward channel

54

drain channel

56

management

58

channel

60

Pressure compensator

61

feather

62

control line

64

management

66

unlockable check valve

68

Entsperrkanal

70

bypass line

72

Pass check valve

74

3/2-way valve

76

10bar Pen

78

Pressure balance channel

Claims (12)

1. A hydraulic control arrangement for controlling a hydraulic consumer (2), with an adjustable inlet metering orifice (40), via which pressure medium flows to the hydraulic consumer by means of a feed line (16), with an inlet pressure-maintaining valve (32) arranged upstream of the inlet metering orifice (40) and with an outlet pressure-maintaining valve (60) which, in order to regulate the outlet flow of the quantity of pressure medium discharged from the hydraulic consumer (2) to a tank (T) during lowering under compressive load, is arranged in a return line (18) between an adjustable outlet metering orifice (42) and the hydraulic consumer (2) and is acted upon in the closing direction by the pressure upstream of the outlet metering orifice (42), characterised in that a constant low pressure is set in the feed line (16) in order to regulate the outlet flow and in that the outlet pressure-maintaining valve (60) is acted upon in the opening direction by the constant pressure in the feed line (16).
2. A control arrangement according to claim 1, wherein the inlet pressure-maintaining valve (32) is acted upon by a constant pressure in the opening direction in order to set the constant pressure in the feed line (16).
3. A control arrangement according to claim 2, wherein the constant pressure can be set by means of a lowering pressure-limiting valve (48) which is set to the low pressure and which, during lowering, is connected to a signalling line (36) connected to the feed line (16) via a nozzle (43) and which, together with the inlet pressure-maintaining valve (32), forms a pilot-controlled pressure-reducing valve.
4. A control arrangement according to claim 3, wherein the lowering pressure-limiting valve (48) is adjustable.
5. A control arrangement according to any one of the preceding claims, wherein the inlet metering orifice (40) and the outlet metering orifice (42) are formed by a continuously adjustable directional-control valve (26).
6. A control arrangement according to any one of the preceding claims, wherein an unblockable non-return valve (66) is arranged between the outlet pressure-maintaining valve (60) and the consumer (2).
7. A control arrangement according to any one of the preceding claims, with a bypass line (70) which bypasses the outlet pressure-maintaining valve (60) and in which a bypass non-return valve (72) opening in the direction of the consumer (2) is arranged.
8. A control arrangement according to any one of claims 1 to 6, wherein the control pressure is tapped via a directional-control valve (74) which in its starting position (a) connects a control line (78), conducting the control pressure, to a line (62) acted upon by the inlet pressure, and in a switching position (b) connects the control line (78) to a line portion (58) conducting the pressure between the outlet metering orifice (42) and the outlet pressure-maintaining valve (60).
9. A control arrangement according to claim 8, wherein the directional-control valve (74) is acted upon in the direction of the starting position (a) by the feed pressure and in the closing direction by the pressure between the outlet pressure-maintaining valve (60) and the outlet metering orifice (42).
10. A control arrangement according to claim 6, wherein the unblockable non-return valve (66) is unblockable by the control pressure.
11. A control arrangement according to any one of the preceding claims, with a variable displacement pump (6) which is actuatable as a function of a load-pressure signal from the consumer, which load-pressure signal is tapped via an LS line (14).
12. A control arrangement according to any one of the preceding claims, wherein the consumer (2) is a hydraulic cylinder.

Images