EP3236085B1 - Amplifier valve for a closed-center-system working hydraulic system for an agricultural or civil engineering working machine - Google Patents

Description

The invention relates to one which generates an amplified secondary load pressure signal by means of a pump pressure of a pressure line due to a primary load pressure signal generated by one or more controllers in a primary load signal line, the amplifier valve having a primary load pressure signal and a booster spring on the one hand and the amplified secondary load pressure signal on the other hand having controllable control valve, the input side is connected to the pressure line and the output side with a shut-off valve.

Furthermore, the invention also relates to a working hydraulics of a land or building usable vehicle to which vehicle in its rear and / or front area a hydraulic adjusting and / or drive system having attachments are coupled, wherein a hydraulic system of the respective attachment by means of a hydraulic coupling system the working hydraulics can be connected and both within the work hydraulics and within the hydraulic system each control units are assigned functionally, wherein in the working hydraulics, a variable is provided whose delivery volume in response to a load pressure of the hydraulic load of the working hydraulics and the implement associated hydraulic system adjustable is, is provided as part of the regulation of the variable displacement pump at least one hydraulic load signal line which is connected to the control units, and wherein between a secondary Lastsig nalleitung, which is connected to the arranged within the working hydraulics control units, and a primary load signal line which is connected to the control units of the hydraulic system, a consisting of a control valve and a shut-off valve amplifier valve is arranged, which due to a generated by one of the control units of the hydraulic system primary Load pressure signal by means of a pump pressure of a pressure line generates a secondary load pressure signal.

In the past, in the case of vehicles that could be used for agricultural or construction purposes, the working hydraulics were usually designed as open-center systems. In an open center system always promotes a constant pump at power demand with their maximum power consumption their constant maximum flow. This results in a high power loss and a correspondingly high heating of the pressure medium. Even if there is no power requirement, the full amount of oil is promoted and power loss generated.

For this reason, in the meantime, closed-center systems with hydraulic pumps that can be changed in their delivery volume, that is to say variable-displacement pumps, which in the meantime only supply a volume flow and pressure which is appropriate to the demand, are now used. In this case, the variable displacement pump is controlled by a so-called load-sensing system, which consists of a load signal line and a pressure compensator associated with the adjustment of the variable displacement pump. About the load signal line is from each of the control valves, which are assigned to the individual consumers of the working hydraulics, the highest load pressure reported to the pressure compensator and the variable only builds the load pressure plus a small pressure surplus.

This makes it possible that the variable displacement pump is pivoted back into a stand-by state, as soon as the control valves are in their neutral position and demand no flow. The pump pressure settles so that the pressure difference Δp _LS between the load pressure p _{LS of} the pressure compensator and the delivery pressure of the pump p _p always remains the same. If one or more valves are actuated, the pressure is passed on via the load signal line to the pressure compensator, which determines the energy requirement of the system by comparing the load pressure p _LS and the pump pressure p _p . Pump pressure and pump flow are always automatically adapted to the respective requirements.

The respective highest load pressure p _LS is reported by the corresponding control valve to the variable displacement pump, whereupon the variable displacement pump only builds up the load pressure plus a low pressure surplus (rule - Δp). In a parallel operation of multiple consumers, the pump flow is divided by the use of so-called section pressure compensators regardless of the various load pressures on the consumer, as it corresponds to the ratio of the opening cross-sections of the control valves.

To the hydraulic circuit of the working hydraulics of the agricultural or construction vehicle usable equipment can be coupled via so-called remote connections work tools, said coupled equipment hydraulic consumers, for example in the form of hydraulic cylinders or hydraulic motors. Since these consumers are each controlled or operated via a control valve, the remote connections are at least two connections, namely a working line and a return line. The hydraulic coupling system for the implements can also be designed as a power beyond connection, in which case the pressure line is connected via a corresponding remote coupling with the implement and there is a corresponding switching valve for controlling the hydraulic functions on the implement. In the case of agricultural vehicles, such power beyond connections can be provided in their front and rear areas, in which there is also a three-point power lift for receiving the respective implement.

When this power beyond connection is combined with a load sensing system, the power beyond connection system is expanded to include a connector for a primary load signal line leading to the implement controllers. This ensures that the variable displacement pump of the agricultural vehicle supplies the control valves of the attachment only with pressure medium when the corresponding hydraulic power is needed. Therefore, this system regulates the flow rate and pressure to meet the needs. In the primary load signal line, the load pressure increases as the operator of the implement retrieves one of its hydraulic functions. However, when using the Load Sensing system for a work implement coupled to the vehicle, considerable pressure losses can occur in the connection elements between the pump and the attachment so that the control variable for the hydraulic pump Δp _LS collapses. This has the consequence that the variable displacement pump can not provide sufficient volume flow. However, such pressure losses can also occur in the working hydraulics of the agricultural or construction-economical vehicle, since many hydraulic functions are activated at the same time during working operations.

An intensifier valve for a trained as a closed-center system working hydraulics of a land or building economics usable machine of the type specified in the preamble of claim 1 is known from the EP 1-843-047-A2 or from the DE 11 2004 002 768 B4 known.

In the FIGS. 3 to 8 This document discloses a hydraulic control system in which an implement is operated via power beyond ports. In this case, the respective load pressure of the load can be reported as a load-sensing signal via a load signal line to the control system. In addition, it is provided that the control system has means to influence at least one of the load-sensing signals.

In order to change the load-sensing signal such that the consumer or consumers receive a larger flow of oil, resulting in a rapid action of the consumer or the consumer should result, a compensating valve and a shut-off valve existing compensator is provided. In this case, the compensation valve should lift a load sensing pressure applied to it by a fixed amount .DELTA.p, the sum of the load-sensing pressure and the fixed amount .DELTA.p representing the corrected load-sensing pressure. The shut-off valve should shut off the compensator when the load-sensing pressure applied to the compensation valve goes against a tank pressure.

FIGS. 7 and 8 of FIG DE 11 2004 002 768 B4 show an embodiment of the compensator, in which the shut-off valve shown in its two switching positions is connected downstream of the compensation valve. The shut-off valve receives on the input side a corrected by the compensation valve pressure. In this case, the shut-off valve does not control the compensation valve in the sense of its shutdown. Instead, the compensation valve should always generate the increase of the pressure in the load-sensing line LS ₁ or LS ₄₀ by the amount Δp, ie not only when the consumer is in operation and the pressure in the load-sensing line LS ₁ or LS _{40 represents} the load of the consumer. This happens even when the consumer is not in operation, so that the pressure in the load-sensing line LS ₁ or LS ₄₀ corresponds to the pressure p _T in the tank line. In a branch of the load-sensing line LS ₁ or LS ₄₀ , which is designed as a tank line, a relief member is arranged,

It is an object of the present invention to provide a booster valve for a trained as a closed-center system working hydraulics of a land or building economics usable machine, by means of which the hydraulic consumers can be operated without delay and at the desired operating speed.

This object is achieved on the basis of the respective preamble of claims 1 and 12 by their characterizing features. Advantageous embodiments are given in the dependent claims of claim 1, which in each case taken alone or in combination may represent an aspect of the invention.

Thereafter, the booster valve amplifies a load pressure signal (p _LS ) generated by one or more controllers in a primary load signal line by means of a pressure increase from a pressure line. The booster valve has a controllable on the one hand via the load pressure signal and an amplifier spring and on the other hand via an amplified load pressure signal control valve, said control valve is connected on the input side to the pressure line and the output side with a shut-off valve. In this case, the primary load signal line, the secondary load signal line, leading to a control of the control valve signal line and a return to the tank should be connected to one another in a designed as a blocking position first working position of the shut-off valve. The relief according to the invention integrated in the shut-off valve via the return has the advantage that the amounts of oil that are permanently withdrawn from the primary and the secondary load signal line, are very low. Consequently, it is achieved that the volume of oil withdrawn from the volume flow is very low and a delay-free control, both of the booster valve and an adjustment of a closed-center system operated variable pump is possible.

In contrast, the relief member after the DE 11 2004 002 768 B4 arranged directly in a branch of the primary load signal line, wherein the relief member may be formed as a diaphragm or flow control valve. An orifice would dissipate a large amount of oil at a high load-sensing pressure while the amount of oil drained from the flow regulator would be constant regardless of the load-sensing pressure. Accordingly, the document teaches that when the consumer is not driven, the load-sensing pressure in the primary load signal line corresponds to the pressure _pT in the tank line due to the relief member. In the process, a considerable volume of oil flows into the tank via the tank line. Incidentally, in the blocking position of the shut-off valve the secondary load signal line connected via a shuttle valve to the tank, so that also emerges from this a significant volume of oil. As a result, upon actuation of a control valve, firstly the reduced amount of oil in the load signal lines must be compensated, which leads to a delayed response of the booster valve.

In a further embodiment of the invention, it is provided that the shut-off valve is designed as a 5/2-way valve, which blocks an output side of the control valve provided connecting line in its first switching position and the secondary load signal line with both the primary load signal line and serving to control the control valve signal line and a return connects and which connects in its second switching position, the connecting line to the secondary load signal line and the primary load signal line with both the signal line and the return. About the connecting line the shut-off valve in a corresponding switching position of the control valve, the amplified load pressure signal is supplied, which is locked in the first switching position relative to the secondary load signal line. In the second switching position, the amplified load pressure signal is forwarded to the secondary load signal line. In these two switching positions, the primary load signal line is always connected to the control valve controlling the signal line and the return line in combination.

It can further be provided that in the first switching position of the shut-off valve, a connection of the primary load signal line to the secondary load signal line and the return and in the second switching position, a connection of the primary load signal line and the signal line are throttled to the return.

In addition, it is provided that the control valve is pilot-controlled via the shut-off valve, wherein the primary load pressure signal is transmitted via the shut-off valve in the two switching positions on the signal line. In this case, an end face of a spool of the control valve in each switching position of the shut-off valve via the signal line with the load pressure signal is applied, this being connected in a flow position of the shut-off additionally with a controlled return and in a blocking position of the shut-off valve with a controlled return and with the secondary load pressure line is. The control pressure of the signal line acts on the front side of the spool of the control valve, wherein the spool at this first end face is acted upon by the force of an amplifier spring whose spring preload is variable.

It is also essential that in the switching position of the control valve for a load pressure amplification of the secondary load signal line the shut-off valve is acted upon exclusively with the delivery pressure p _{p of} the variable. Consequently, the control valve on the input side, that is not supplied via a working port, a load pressure and this transmitted together with the pump pressure to the shut-off valve.

It is further provided that the control valve is designed as a 3/3-way valve having a blocking position and two working positions, wherein in the first working position, the pressure line is connected to the connecting line leading to the shutdown valve and wherein in the second working position, the connecting line and between the control valve and the shut-off valve extending signal line are interconnected. From the connecting line branches off a control line via which the spool of the control valve is acted upon at a second end face, ie in the first working position of the control valve with the amplified load pressure signal. The increased load pressure is thus adjusted via the spring bias of the spool by means of the booster spring. In the second operating position of the control valve, this connects the signal line to the control line, so that the primary load pressure acts on both sides of the control slide.

Within the primary load signal line, a diaphragm and an oil filter can be arranged, these, starting from the consumer, the shut-off valve, ie its control and its corresponding working port are connected upstream.

The control valve and the shut-off valve may be arranged within a common valve housing, which is preferably designed as a plate-like way valve block. A corresponding directional valve block may be sandwiched together with further directional control valve blocks, this arrangement being ultimately closed by a cover plate.

With regard to the embodiment of the control valve is provided that a spool of this control valve has a blind bore extending in the axial direction and two transverse to this control bores, wherein the spool on the front side a trained as a coil spring booster spring is acted upon, whose spring preload is adjustable via a trained as a set screw actuator.

The shut-off valve should be designed such that its valve slide is formed as a hollow piston and is provided in its outer circumferential surface with a control groove, via which the connecting line to the secondary load signal line is connectable, and that via an interior of the valve spool and provided in this transverse holes in both switching positions of Valve spool the primary load pressure line is connected to both the control line and the return line. The design of the valve spool provided in the shut-off valve makes it possible for the primary load-pressure line to be connected to the secondary load-pressure line at the same time as the front-end pressurization of the valve spool via its interior and at least one transverse bore in its blocking position.

Finally, a hydraulic control system for a working hydraulics of a land or building economy usable vehicle should be provided, to the vehicle in its rear and / or front area attachments can be coupled, which have a hydraulic actuator and / or drive system. In this case, a hydraulic system of the respective attachment by means of a hydraulic coupling system with a hydraulic circuit of the working hydraulics can be connected, both within the hydraulic circuit and within the hydraulic system hydraulic consumers each control devices are assigned functionally. Furthermore, a variable displacement pump is provided in the hydraulic circuit, the delivery volume in response to a load pressure of the hydraulic load of the hydraulic circuit and the implement associated hydraulic system is regulated, wherein at least one hydraulic load signal line is provided as part of the regulation of the variable, which is connected to the control units. Between a first line section of the load signal line, which is connected to the arranged within the hydraulic circuit controllers, and a second line section of the load signal line, which is connected to the control units of the hydraulic system, an amplifier valve is to be arranged, which is generated due to one of the control units of the hydraulic system primary load pressure signal from a pump pressure of a pressure line generates a secondary load pressure signal. This booster valve should, as stated above, be arranged and constructed within the hydraulic control system.

The invention is not limited to the specified combination of the features of independent claims 1 and 13 with the claims dependent thereon. It also results in ways to combine individual features, as far as they emerge from the claims, the advantages of the claims, the following description of the embodiment or at least from the drawings. The reference of the claims to the drawings by corresponding use of the reference number is not intended to limit the scope of the claims.

Figur 1

eine als Closed-Center-System ausgebildete Arbeitshydraulik für ein land- oder bauwirtschaftlich nutzbares Fahrzeug, an das über Power-Beyond-Anschlüsse ein Hydrauliksystem eines Anbaugeräts ankuppelbar ist, wobei innerhalb der Arbeitshydraulik ein erfindungsgemäßes Verstärkerventil angeordnet ist,

Figur 2

ein an die Arbeitshydraulik nach Figur 1 ankuppelbares Hydrauliksystem eines Anbaugeräts,

Figur 3

ein Abschaltventil in einer als Durchflussstellung ausgebildeten zweiten Arbeitsstellung,

Figur 4

das Abschaltventil in einer als Sperrstellung ausgebildeten ersten Arbeitsstellung und

Figur 5

einen Längsschnitt durch das aus einem Regelventil und dem Abschaltventil bestehende Verstärkerventil.

For further explanation of the invention reference is made to the drawing, in which an embodiment of this is shown in simplified form. Show it:

FIG. 1

a trained as a closed-center system working hydraulics for a land or building economics usable vehicle to the power beyond connections a hydraulic system of an attachment can be coupled, wherein within the working hydraulics, an inventive amplifier valve is arranged,

FIG. 2

one to the working hydraulics FIG. 1 Coupling hydraulic system of an attachment,

FIG. 3

a shut-off valve in a second working position designed as a flow position,

FIG. 4

the shut-off valve in a trained as a blocking position first working position and

FIG. 5

a longitudinal section through the consisting of a control valve and the shut-off valve amplifier.

In the FIG. 1 is 1 denotes a working hydraulics, which is provided for example for an agricultural tractor or an agricultural system vehicle. This working group 1 is designed as a closed-center system, in which the pressure medium from a tank 2 via a variable displacement pump 3, preferably as an axial piston unit is designed according to the bent axis principle, two as a double-acting hydraulic cylinders 4 and 5 trained consumers 6 and 7 supplies. The hydraulic cylinders 4 and 5 are associated with control devices 8 and 9, which are designed as electromagnetically operated, provided with spring centering 4/4-way valves. The hydraulic cylinders 4 and 5 may be provided, for example, each for lifting devices of a front and a rear linkage.

The pressure medium is conveyed by the variable displacement pump 3 via a pressure line 10 to the control units 8 and 9, where it can get into corresponding positions of these control units 8 and 9 in a return line 11 and thus back into the tank 2. In this position, the respective control units 8 and 9 whose working lines 12, 13, 14 and 15 are shut off.

As already stated, the delivery volume of the variable displacement pump 3 can be adjusted, for which purpose a single-acting adjusting cylinder 16 is provided. In this case, this adjusting cylinder 16 is connected to a secondary load signal line 17 via a pressure compensator 18 and a pressure regulator 19. The secondary load signal line 17 is connected to each of the control units 8 and 9 in such a way that a pressure on the pressure compensator 18 can be passed through it, if via the respective control unit 8 or 9, a pressure medium applied to the hydraulic cylinder 4 or 5 takes place.

After FIG. 1 is the variable displacement pump 3 in its standby mode, ie, in a variable displacement pump according to the bent axis principle, the corresponding axial piston unit is in a state with a small swing angle and thus low displacement volume. In this state, the variable displacement pump 3 promotes only a very small amount of hydraulic oil and only builds up a low pressure. The pump pressure p _p settles in such a way that the pressure difference Δp _LS between the load pressure p _{LS of} the pressure compensator 18 and the delivery pressure p _{p of} the variable displacement pump 3 always remains the same.

If, however, as already stated, one of the two or both control devices 8, 9 is actuated, the pressure in the secondary load signal line 17 rises and this increased load pressure p _LS acts on the pressure compensator 18, via which the pressure regulator 19 is piloted. This load pressure p _LS acts in the same direction as a pressure spring 20 provided on the pressure compensator 18, so that the pressure compensator 18 determines the energy requirement of the system by comparing the load pressure p _LS and the pump pressure p _p can. The pump pressure p _p and the pump flow rate are automatically adjusted to the respective requirements. The respective highest load pressure p _LS is thus reported by the respective control unit 8 and / or 9 to the variable displacement pump 3, and this only builds up the load pressure plus a slight pressure surplus (rule - Δp).

Lead from the secondary load signal line 17 line sections 17a and 17b to the respective control unit 8 and 9, wherein between the secondary load signal line 17 and these line branches 17a and 17b each a shuttle valve 21 is arranged. Furthermore, 10 section pressure compensators 22 and 23 are provided in the leading to the control units 8 and 9 sections of the pressure line. These are in a parallel operation of multiple consumers 6, 7 ensure that the pump flow independent of the various load pressures is distributed to the consumers 6, 7, as it corresponds to the ratio of the opening cross-sections of the control units 8 and 9.

Overall, this achieves that the power consumption of the variable displacement pump 3 is permanently adapted to the needs. The efficiency is considerably greater, especially in the fine control range, than in a so-called open center system. The actuating speeds of the consumers 6 and 7 is not influenced by changing load pressures, so that a countersteering is not required.

After FIG. 1 Furthermore, a so-called power beyond connection system 24 is provided, which for the hydraulic connection of the working hydraulics 1 with a in the FIG. 2 shown hydraulic system 25 of an attachment is used. For this purpose, the pressure line 10 has a remote port 26 labeled P, a primary load signal line 17 'having a remote port 27 labeled LS, and the return line 11 having a remote port 28 labeled T. By coupling the in FIG. 2 shown hydraulic system 25 of the attachment corresponding lines with the aforementioned lines 10, 17, 11 are connected. These are in the FIG. 2 correspondingly denoted by 10 ', 17 "and 11' and lead to control devices 29 and 30, which are associated with consumers 31 and 32. The consumer 31 is a double-acting hydraulic cylinder 33, while the consumer 32 as a hydraulic motor 34th is trained.

In this case too, the load pressure in the corresponding section 17 "of the primary load signal line 17 'is to be monitored, since a higher delivery volume and a higher pressure are also to be requested from these control devices 29 and 30 in the event of an adjustment to their working position on the variable displacement pump 3 Individual branches of the load signal line 17 "are also assigned shuttle valves 21. In the corresponding branches of the pressure line 10 'are also section pressure compensators 35 and 36th

According to the invention, in an area of the working hydraulics 1 adjacent to the power beyond connection system 24, a booster valve 37 which, in the event of actuation of the control devices 29 and / or 30 of the working device, increases a load pressure _pSsecondary in the secondary load signal line 17 connected to the pressure compensator 18 should. This pressure increase is necessary because the pressure losses between the variable displacement pump 3 and the hydraulic system 25 of the attachment due to the hydraulic couplings, hose lines, etc. may be greater than the control variable Δp _LS , so that a maximum flow for the supply of the load 31 and 32 not more can be provided. As continues from the FIG. 1 As can be seen, the booster valve 37 consists of a control valve 38 and a shut-off 39th

However, a corresponding booster valve 37 may also be used when it is necessary to increase the primary load pressure for consumers who are part of the working hydraulics, as if no attachment hydraulically powered is coupled to the agricultural or construction vehicle. For further explanation of the booster valve 37 and its function is on the following FIGS. 3 and 4 directed.

The FIGS. 3 and 4 each show an enlarged view of the hydraulic scheme of the booster valve 37 and its connection to the working hydraulics 1 and with the primary load signal line 17'.Dabei differ FIGS. 3 and 4 characterized in that the shut-off valve 39 in the FIG. 3 in its second working position, namely a flow position, and in the FIG. 4 in its first working position, which corresponds to a blocking position is located.

The control valve 38 is designed as a 3/3-way valve, which is actuated hydraulically and in addition on a front side by spring force. The corresponding switching positions of the control valve are in the FIGS. 3 and 4 with a middle position 0 and working positions a and b, wherein in the switching position a, which corresponds to a first working position, the pressure line 10 is connected to a leading from the control valve 38 to the shut-off valve 39 connecting line 40. This switching position a takes the control valve 38 in both FIGS. 3 and 4 on. From the connecting line 40 branches off a control line 41, which acts on the control valve 38 at a first end face 42. At a second end face 43 of the control valve 38, this is acted upon via an amplifier spring 44, whose spring bias is variable, and via a signal line 45.

The signal line 45 is also connected via a line branch 45a to a working port of the control valve 38. As part of a corresponding design of the booster valve 37 such lines are formed as extending in a valve housing bores, cross sections, annular grooves, etc., which are therefore shown only in the hydraulic scheme as lines or line sections. Furthermore, located at the inlet of the pressure medium from the pressure line 10 in the control valve 38, a diaphragm 46th

Based on the flow direction of the pressure medium from the pressure line 10, the shut-off valve 39 is connected downstream of the control valve 38. This shut-off valve 39 is designed as a 5/2-way valve and thus has two switching positions a and b. The switching position a, the shut-off valve 39 in the FIG. 4 occupies, it is the first switching position in which a connection of the connecting line 40 is locked to the secondary load signal line 17. How continues the FIG. 4 can be removed, the secondary load signal line 17 ', the primary load signal line 17, the signal line 45 and the return line 11 are connected to each other in this switching position a, ie the first working position.

In the FIG. 3 is the shut-off valve 39 in its switching position b, which represents a flow position. In this only the pressure fluid from the pressure line 10 into the secondary load signal line 17 passes. In this switching position b of the shut-off valve 39, the primary load signal line 17 ', the return line 11 and the signal line 45 are also connected to each other. As well as from the Figures 3 and 4 It can be seen, in the switching position a is the connection between the primary load signal line 17 'and the return line 11 and the signal line 45 throttled via a throttle 47, while I in the switching position b between the primary load signal line 17' and the signal line 45 on the one hand and the return line eleventh on the other hand, a throttle 48 is arranged.

Furthermore goes from the FIGS. 3 and 4 shows that the shut-off valve is acted upon at one end face of the primary load pressure of the load signal line 17 'and thus is shifted at an increased primary load pressure in its switching position b. At the other end face of the shut-off valve, a valve spring 49 and a pressure p _{T of} the return line 11 act. Furthermore, it can be seen from the figures that an aperture 50 and an oil filter 51 are arranged in the primary load signal line 17 '.

A structural design of the booster valve 37 goes out of the FIG. 5 which shows this booster valve 37 in a longitudinal section. The control valve 38 and the shut-off valve 39 each take a switching position, which with the FIG. 4 matches. The booster valve 37 has a valve housing 52 which is designed as a plate-like way valve block. In the valve housing 52 receiving bores 53 and 54 are provided, wherein the receiving bore 53 receives a slidably guided in this control spool 55 of the control valve 38.

This spool 55 has a concentric blind bore 56 extending from the transverse control bores 57 and 58. In the illustrated position of the spool 55, the pressure medium of the pressure line 10 passes through a connecting piece 59, the control bore 57 and the blind bore 56 in the connecting line 40. At the same time the spool 55 is the end face, so applied to the end face 42 with the pressure of the connecting line 40 , On the side facing away from this end face other end face 43 of the spool 55 is acted upon by a spring plate 60 with the force of the booster spring 44. This is arranged in a spring housing 61, wherein the spring preload can be changed via a trained as a set screw actuator 62.

The connecting line 40 communicates with the receiving bore 54, wherein in this receiving bore 54, a valve spool 63 of the shut-off valve 39 is slidably disposed. At the end of the receiving bore 54 is in this a connecting piece 64, to which the primary load signal line 17 'is connected, screwed. The valve spool 63 is designed as a hollow piston and provided on its outer circumferential surface with a control groove 65.

In the FIG. 5 takes the valve spool 63 a position in which this shuts off the connecting line 40. At the other end of the receiving bore 54, a connecting piece 66 for the return line 11 is screwed into this. Transverse to the receiving bore 54 extends the secondary load signal line 17 which is inserted via a further connecting piece 67 in the valve housing. In this case, this primary load signal line 17 via a transverse control bore 68 with a spring chamber 69 and thus the end face of the valve spool 63 as well as a longitudinal bore 70 of the valve spool 63 and the throttle 48 with the primary load signal line 17 'in connection. As is apparent from the sectional view, there is also a connection between this spring chamber and the connecting piece 66 of the return line eleventh

reference numeral

1

hydraulics

2

tank

3

variable

4

hydraulic cylinders

5

hydraulic cylinders

6

consumer

7

consumer

8th

control unit

9

control unit

10

pressure line

10 '

pressure line

11

Return line

11 '

Return line

12

working line

13

working line

14

working line

15

working line

16

adjusting cylinder

17

secondary load signal line

17 '

primary load signal line

17 "

Load signal line of 25

17a

Line branch of 17

17b

Line branch of 17

18

pressure compensator

19

pressure regulator

20

Compression spring of 18

21

shuttle valve

22

Section pressure compensator

23

Section pressure compensator

24

Power beyond connection system

25

Hydraulic system of an attachment

26

Remote connection P

27

Remote connection LS

28

Remote connection T

29

control unit

30

control unit

31

consumer

32

consumer

33

double-acting hydraulic cylinder

34

hydraulic motor

35

Section pressure compensator

36

Section pressure compensator

37

booster valve

38

control valve

39

shut-off valve

40

connecting line

41

control line

42

first face of 38

43

second face of 38

44

amplifier spring

45

signal line

45a

Line branch of 45

46

cover

47

throttle

48

throttle

49

Valve spring of 39

50

cover

51

oil filter

52

valve housing

53

location hole

54

location hole

55

Spool of 38

56

Blind hole in 55

57

control bore

58

control bore

59

Connection piece for 10

60

spring plate

61

spring housing

62

actuator

63

Valve slide of 39

64

Connecting piece for 17 '

65

Steering groove of 63

66

Connecting piece for 11

67

Connection piece for 17

68

control bore

69

spring chamber

70

Longitudinal bore in 63

p _LS

Pressure in load signal line 17

p _{LS17 '}

Pressure in the line section 17 '

p _p

Delivery pressure of the variable displacement pump 3

p _T

Pressure in the return line 11

Δp _LS

Pressure difference between delivery pressure p _p and load pressure p _LS

Claims (13)

1. Amplifier valve (37) for a closed-centre-system working hydraulic system (1) of an agricultural or civil engineering working machine, which generates an amplified secondary load pressure signal by means of a pump pressure (p_p) of a pressure line (10) on the basis of a primary load pressure signal generated by one or more control devices (8, 9, 39, 30) in a primary load signal line (17'), wherein the amplifier valve (37) has a control valve (38), which can be controlled on the one hand via the primary load pressure signal and an amplifying spring (44) and on the other hand via the amplified secondary load pressure signal, and which is connected on the inlet side to the pressure line (10) and on the outlet side to a cut-off valve (39), characterized in that in a first working position (a) of the cut-off valve (39), formed as a blocking position, the primary load signal line (17'), a secondary load signal line (17) carrying the secondary load pressure signal, a signal line (45) leading to an actuation of the control valve (38) and a return line (11) into a tank (2) are connected to each other via this cut-off valve (39).
2. Amplifier valve according to claim 1, characterized in that the cut-off valve (39) is formed as a 5/2-way valve, which in its first switching position (a) blocks a connecting line (40) provided on the outlet side of the control valve (38) and connects the primary load signal line (17') both to the secondary load signal line (17) and to a signal line (45) serving to control the control valve (38) and a return line (11), and which in its second switching position (b) connects the connecting line (40) to the secondary load signal line (17) and the primary load signal line (17') to both the signal line (45) and the return line (11).
3. Amplifier valve according to claim 2, characterized in that in the first switching position (a) of the cut-off valve (39) a connection of the primary load signal line (17') towards the secondary load signal line (17) and towards the return line (11) is restricted, and in its second switching position (b) a connection of the primary load signal line (17') and the signal line (45) towards the return line (11) is restricted.
4. Amplifier valve according to claim 1, characterized in that the control valve (38) is pilot controlled via the cut-off valve (39), wherein the primary load pressure signal is transmitted to the signal line (45) via the cut-off valve (39) in both of its switching positions (a and b).
5. Amplifier valve according to claim 1, characterized in that in each switching position (a and b) of the cut-off valve (39) a front face (43) of a control spool (55) of the control valve (38) is acted on by the primary load pressure signal via the signal line (45), wherein in a flow position (b) of the cut-off valve (39) it is additionally connected to a controlled return line (11) and in a blocking position (a) of the cut-off valve (39) it is connected to a controlled return line (11) and to the secondary load pressure line (17).
6. Amplifier valve according to claim 1, characterized in that in the switching position (a) of the control valve (38), for an increase in the load pressure in the secondary load signal line (17), the cut-off valve (39) is acted on exclusively by the feed pressure p_p of the variable displacement pump (3).
7. Amplifier valve according to claim 1, characterized in that the control valve (38) is formed as a 3/3-way valve which has a blocking position (0) and two working positions (a and b), wherein in its first working position (a) the pressure line (10) is connected to a connecting line (40) leading to the cut-off valve (39), and wherein in its second working position (b) the connecting line (40) and a signal line (45) running between the control valve (38) and the cut-off valve (39) are connected to each other.
8. Amplifier valve according to claim 1, characterized in that a diaphragm (50) and an oil filter (51) are arranged in the primary load signal line (17').
9. Amplifier valve according to claim 1, characterized in that the control valve (38) and the cut-off valve (39) are arranged in a common valve housing (52) which is preferably implemented as a directional control valve block formed plate-like.
10. Amplifier valve according to claim 7, characterized in that a control spool (55) of the control valve (38) has a blind hole (56) running in the axial direction and two control holes (57 and 58) running transverse thereto, wherein on its front face the control spool (55) is acted on via an amplifying spring (44) formed as a helical spring, the spring preload of which can be altered via an adjustment element (62) formed as an adjusting screw.
11. Amplifier valve according to claim 2, characterized in that a valve spool (63) of the cut-off valve (39) is formed as a hollow piston and is provided in its external lateral surface with a control groove (65), via which the connecting line (40) can be connected to the secondary load signal line (17), and in that in both switching positions of the valve spool (63) the primary load pressure line (17') is connected both to the signal line (45) and to the return line (11) via an internal space of the valve spool (63) and via transverse holes (68) provided therein.
12. Amplifier valve according to claim 11, characterized in that in the blocking position (a) of the valve spool (63) the primary load pressure line (17'), when the valve spool (63) is simultaneously acted on by pressure on its front face, is connected to the secondary load pressure line (17) via the internal space (70) of the valve spool (63) and at least one transverse hole (68).
13. Working hydraulic system (1) for an agricultural or civil engineering vehicle, to the rear and/or front area of which vehicle attachment units having a hydraulic adjustment system and/or drive system can be coupled, wherein a hydraulic system (25) of the respective attachment unit can be connected to a hydraulic circuit of the working hydraulic system (1) by means of a hydraulic coupling system (24) and in each case control devices (8, 9, 29, 30) are functionally allocated to hydraulic consumers (6, 7, 31, 32) both within the hydraulic circuit and within the hydraulic system (25), wherein in the working hydraulic system (1) a variable displacement pump (3) is provided, the displacement volume of which can be regulated as a function of a load pressure (p_LS) of the hydraulic consumers of the working hydraulic system (1) and of the hydraulic system (25) allocated to the attachment unit, wherein, within the framework of the regulation of the variable displacement pump (3), at least one hydraulic load signal line (17, 17') is provided, which is connected to the control devices (8, 9, 29, 30), and wherein arranged between a secondary load signal line (17), which is connected to the control devices (8 and 9) arranged within the working hydraulic system (1), and a primary load signal line (17'), which is connected to the control devices (29 and 30) of the hydraulic system (25), is an amplifier valve which generates a secondary load pressure signal by means of a pump pressure of a pressure line (10) on the basis of a primary load pressure signal (p_LSprimary) generated by one of the control devices (29 and 30) of the hydraulic system (25), characterized by an arrangement of the amplifier valve within the hydraulic circuit of the working hydraulic system and the formation thereof according to one of claims 1 - 12.

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