DE10062428A1 - Servo-assisted pressure feed valve has flow regulating valve in control oil flow path to transfer cavity - Google Patents

Abstract

The pressure feed valve has a servo valve body (40) prestressed in its closed position. A rearward transfer cavity (58) of the transfer piston (44) can be pressurized at control pressure via a flow regulating valve (48) in the control oil flow path to the transfer cavity to raise the servo effect of the control spring so that the control oil can be taken to the transfer cavity regardless of viscosity or pressure.

Description

The invention relates to a pilot-operated pressure feed valve according to the preamble of claim 1.

Such pressure feed valves are used for example for Absi Protection of hydraulic circuits for chassis and slewing gear drives used, either as a closed or open Hydraulic circuit can be executed. For example at the An swiveling the uppercarriage or accelerating the excavator Hydraulic motor pressurized with a high hydraulic pressure, so that this Movements are initiated comparatively quickly and the build up significant acceleration with correspondingly high masses moments of inertia are exposed. These sudden strains can damage the hydraulic system. You are there strives to carry out speed changes such that smooth transitions between the driving / turning states are made. When a hydraulic fluid quantity jump occurs, the mo mentally working consumers, for example the slewing gear or the Suspension damped, accelerated or decelerated (shockless function).

Due to the suction function of the pressure feed valve, pressure can medium in the event of a pressure reversal, d. H. when the pressure rises in the never the pressure branch of the hydraulic system is discharged to the high pressure branch become.

DE 197 44 337 A1 of the applicant is of the generic type Pressure feed valve disclosed, in which a pilot valve body ei ner pilot stage via a control spring against a pilot valve seat is biased. The control spring is on a booster piston supported, the rear end face to increase the Steuerfe preload via a with the pressure at the input of the Pilot valve, d. H. in the spring chamber of the main stage Pressure is applied. With such a construction  set an approximately parabolically increasing switching delay, whereby the maximum pressure that can be limited is reached when the translator piston has reached its end position in which the control spring with the maximum preload is applied. Opens the next time you climb then the pilot stage, so that the spring chamber is relieved and the main level is limited to limit the system pressure.

The problem with this solution is that the translation is filled room takes place via an upstream nozzle and is therefore very viscous is dependent on the state. That is, the response behavior of the pressure feed valve changes depending on the pressure and on the operating temperature.

In contrast, the invention is based on the object of the invention to develop the pressure feed valve according to the invention such that the one flows of a change in viscosity of the pressure medium are minimal.

This task is carried out by a pressure feed valve with the characteristics len of claim 1 solved.

According to the invention, instead of the egg in the control oil flow path A stream is arranged in the translator room of the pilot stage used gel valve, through which the control oil volume flow in the translation Space is kept independent of viscosity, so that a uniform Filling the translator room regardless of the pressure and temperature of the Tax oil is guaranteed. By using a Flow control valve instead of a nozzle turns a practically linear Pressure increase over time and also a linear Δp-Q behavior on.

The pressure feed valve according to the invention is particularly compact built up when the current regulator is integrated in the booster piston is. There is a pressure compensator piston in an inner bore of the over set piston, whereby through the rear peripheral edge of the Pressure compensator piston open a jacket bore opening in the or is controllable and a in a bottom of the pressure compensator piston Orifice plate is formed. The up or over the pressure compensator piston  controllable cross-section thus forms the variable orifice of the Flow control valve.

In an alternative embodiment, the metering orifice is limited by an annular gap between a ball and the inner circumferential wall of the pressure compensator piston, the ball being biased against a valve seat in a basic position. This ball interacts with a piston of a directional control valve, via which the translator chamber can be connected to a control connection, so that a quick controlled intermediate relief of the translator piston 24 and its return movement into its basic position is made possible.

Through a suitable choice of the active surfaces of the ball on the valve seat side and the piston of the directional valve can be a predetermined transmission Set the ratio above which the switch-on and switch-off point of the pressure relief valve is adjustable.

The pilot valve body is advantageously with an in Effective area difference in the closing direction.

The valve spool on the main stage can be used to reduce the leakage fe biased against a seat edge.

Other advantageous developments of the invention are counter stood the further subclaims.

The following are preferred embodiments of the invention explained in more detail using schematic drawings. Show it:

Figure 1 is a longitudinal section through a first embodiment egg NES pressure feed valve.

FIG. 2 shows an enlarged illustration of a pilot control stage of the pressure feed valve from FIG. 1;

Fig. 3 is a circuit symbol of the pressure feed valve of Fig. 1;

Fig. 4 shows a dynamic characteristic of the pressure-one feed valves according to the invention;

5 shows a longitudinal section through another embodiment of a pressure-feed valve.

Fig. 6 shows a section through a pilot stage of the pressure feed valve and

Fig. 7 is a circuit symbol of the pressure feed valve in FIG. 4.

The embodiment shown in Fig. 1 in longitudinal section egg nes pressure feed valve 1 has a cartridge-shaped valve housing 2 in which an axial pressure port P and a radial bore 4 formed by a low pressure or tank port T are formed. A control connection Y is also provided at an axial distance from the low-pressure connection T and can be connected to an external control line or a line leading to the low-pressure. In a valve bore 2 axially penetrating the valve bore 6 , a valve spool 8 leads a main stage 10 of the pressure feed valve 1 ge. The main stage 10 is designed in a sliding seat construction, the valve slide 8 being prestressed against a circumferential seat edge 14 of the housing 2 via a compression spring 12 . The valve slide 12 can be provided with a chamfer in the area of the contact area on the seat edge 14 with a surface difference, which then acts in the closing direction. In the bottom of the cup-shaped valve slide 8 , a nozzle bore 16 is formed through which control oil from the pressure port P can enter the rear spring chamber 18 of the compression spring 12 .

The valve bore 6 is radially expanded at an axial distance from the radial bore star 4 , so that between the outer circumference of the valve slide 8 and the inner circumference of the valve bore 6 a receiving space is formed for a suction ring 20 , the right axial position of which in FIG. 1 is represented by a radial collar 22 of the valve slide 8 is limited. The other, low-pressure axial position of the valve slide 20 is limited by a radial shoulder of the valve bore 6 . The pressure chamber receiving the suction ring 20 is connected via an annular throttle gap 24 to a parallel bore 26 , via which the pressure at the low-pressure port P is tapped. That is, after the suction ring is on the one hand open by the pressure at the low pressure port T and on the other hand the pressure on the spring chamber 18 be.

The main stage 10 is assigned a pilot control stage 28 , which is accommodated in a pilot control housing 30 which is screwed into the housing 2 of the main stage 10 . The compression spring 12 is supported on the left end face of the pilot control housing 30 in FIG. 1. The front bathing of the pilot housing 30 is penetrated by a connecting channel 34 which on the one hand opens via radial bores in the spring chamber 18 and on the other hand in a radially expanded pilot spring chamber 36 . The connecting channel 34 is expanded in the mouth area to a Ven valve seat 38 for a pilot valve body 40 . The pilot control spring space 36 is connected via a connecting bore 32 to an annular space in which the control connection Y opens.

The pilot valve body 40 is biased towards the valve seat 38 via a control spring 42 . This control spring 42 is supported on a in the pilot housing 30 axially displaceable booster piston 44 , the right end portion of the pilot valve piston 40 in FIG. 1 being immersed in an inner bore 46 of the booster piston 44 . The diameter of the end face of this sealingly guided in the inner bore 46 end portion of the pilot valve body 40 is smaller than the diameter of the valve seat 38 , so that the pilot valve body 40 is designed with a difference in area.

The pilot valve body 40 is penetrated by an axial bore 49 , via which the pressure in the spring chamber 18 is reported into the inner bore 46 of the booster piston 44 .

The flow control valve 48 is shown enlarged in FIG. 2. In a radially enlarged part of the inner bore 46 of the booster piston 44 , a flow control valve 48 is received, the pressure compensator piston 50 is biased via a control spring 52 supported on a locking screw 54 in the basic position against a radial shoulder of the inner bore 46 . The spring chamber of the flow control valve 48 receiving the control spring 52 is connected via a bore 56 to a translator chamber 58 , which is limited on the one hand by the right-hand end face of the translator piston 44 in FIG. 1 and on the other hand by the end face of a spindle 60 against which the translator piston 44 is biased in its basic position shown by the force of the control spring 42 . That is, the axial length of the spring chamber 36 can be changed by the axial position of the spindle 60 and fixed by means of a lock nut 62 with respect to the pilot valve housing 30 .

In the sectional view according to FIG. 2, the pressure compensator piston 50 has an approximately H-shaped cross section, a bottom 64 being formed in the region between the two ring end faces of the pressure compensator piston 50 . The ring end face 66 on the left in FIG. 2 lies against the radial shoulder of the inner bore 46 , while the outer peripheral edge of the right end face forms a control edge 68 , via which the cross section of the bore 56 can be controlled or opened. The bottom 64 is penetrated by a bore which forms a measuring orifice 70 of the flow control valve 48 . The bare from the control edge 68 bare bore 56 accordingly forms the variable orifice.

The valve shown also has an emergency opening, which is actuated for towing or oil drainage at the consumer (engine, cylinder). In the solution shown, this emergency opening is possible by unscrewing the pilot valve housing 30 from the housing 2 , in which case the spring chamber 18 is connected to the control connection Y. This emergency opening can be adjusted by turning the pilot control housing 36 with respect to the housing 2 .

In Fig. 3, the circuit symbol of the pressure inlet valve described above is shown, the emergency opening being symbolized by the manually actuated directional control valve 70 , via which the connection from P to T can be opened directly. According to this circuit symbol, the Ven tilschieber 8 of the main stage 10 is acted upon in the opening direction by the pressure at the pressure port P and in the closing direction by the pressure regulated via the pilot stage 28 , the bias of the Steuerfe the 36 by means of the translation piston 44 is variable. The backward term translator room 58 is ver through the control valve 48 with the orifice 70 and the pressure compensator with the pressure compensator piston 50 with control oil ver, which is tapped from the pressure port P. The pressure compensator piston 50 throttles the opening cross section of the drilling 56 in such a way that the pressure drop across the measuring orifice 70 remains constant, so that the volume flow into the booster chamber 58 remains constant regardless of viscosity and pressure.

FIG. 4 shows the characteristic of a dynamic characteristic of such a pressure feed valve 1 .

In the illustrated basic position of the pressure feed valve 1 , the translation piston 44 is in its stop position on the spindle 60 , so that the compression spring 36 is acted upon with a minimal preload. In the event of a pressure increase, for example caused by acceleration of the travel or slewing gear, this pressure is reported via the nozzle bore 16 into the spring chamber 18 . The pressure rises steeply up to the value p _min . When this connection point is reached, the pilot valve body 40 is lifted off the valve seat 38 so that the spring chamber is connected to the connection Y and control oil can flow out of the spring chamber 18 and the valve slide 8 opens the connection between the pressure connection P and the low pressure connection T. At the same time, control oil flows via the axial bore 48 to the flow control valve 48 . The pressure compensator piston 50 is brought into a re gel position by the pressure of the control oil against the force of the control spring 52 , so that a constant control oil flow is established in the booster chamber 58 . Due to the rising pressure in the booster chamber 58 of the booster piston 44 is moved in the representation of Figure 1 to the left, so that the bias of the control spring 36 increases and the pilot valve body 40 is controlled closed again. - by this return movement of the pilot valve body 40 increases the pressure at the pressure connection P continues to be linear, but the slope after reaching the cut-in point is flatter than before this point in time.

After a predetermined switching delay, the booster piston 44 reaches its left end position, so that the compression spring 36 is subjected to the maximum prestress. If the pressure increases further, the pilot valve body 40 is brought into its control position against the force of the compression spring 42 , in which the pressure at the pressure connection P is limited to the maximum value p _max .

In the event of pressure reversal, that is to say a reduction in pressure at the pressure port P and a build-up of pressure at the low-pressure port T, the control oil can be displaced very quickly via the fully open bore 36 , the orifice plate 70 , the axial bore 48 , so that the booster piston 44 is relieved and returned to its illustrated starting position moves. This return movement takes place according to the characteristic curve in FIG. 4 much faster than the pressure build-up described above, so that the valve described can be used both individually and for mutual support, for example in an AVG circuit. Since such circuits are known per se, for the sake of simplicity, reference is made to the existing specialist literature.

The course of the switching time delay can be influenced in particular by the size of the orifice plate 70 and the spring rate of the control spring 52 and by a suitable choice of the diameter of the bore 56 . As already mentioned above, the minimum bias of the control spring 42 can be changed by changing the axial position of the spindle 60 , so that a certain time correction is also possible.

Fig. 5 shows a further embodiment of a pressure-feed valve 1 according to the invention, which differs in principle only by the design of the flow control valve 48 and by the addition of a directional valve 72 cooperating with the flow control valve 48 from the solution described above. In the construction shown in FIG. 5, the main stage 10 and the area of the pilot stage 28 with the biased against the valve seat 38 before the control valve body 40 are identical to the embodiment described above, for example, so that only the newly added features are discussed below.

FIG. 6 shows an enlarged illustration of that area of the pilot control stage 28 in which the flow control valve 48 and the aforementioned directional valve 72 are arranged. In the variant shown in FIGS . 5 and 6, the cup-shaped pressure compensator piston 50 is in turn biased via the control spring 52 with its annular end face 66 against a radial shoulder 74 of the inner bore 46 . The control spring 52 is supported on a shoulder of a bush 76 which is inserted into an inner bore of the spindle 60 . The bushing 76 is fixed in its axial position by means of a sleeve 77 screwed into the spindle 60 . The end face of the pressure compensator piston 50 which is removed from the radial shoulder 74 forms the control edge 68 , via which the cross section of the bore 56 can be controlled. In this embodiment, the bore 56 is partially closed in the basic position of the pressure balance piston 50 .

In contrast to the exemplary embodiment described above, the measuring orifice 70 is formed by an annular gap between the inner circumferential wall of a bottom bore 78 of the pressure compensator piston 50 and the outer periphery of a ball 80 inserted into this bottom bore 78 . This is pressed in the basic position shown via a piston 82 of the directional valve 72 in a contact position on a peripheral edge of the radial shoulder 74 . The piston 82 is in turn biased by a spring 84 supported on the sleeve 77 in its bearing position against the ball 80 . The piston 82 has a conical section 86 , which can be brought into abutment against a seat 88 formed by an inner peripheral edge of the bush 76 .

As can be seen in particular from FIG. 5, the spring 84 in the receiving space 90 is connected via an axial channel 92 and a transverse bore 94 in the bushing 76 to the pilot spring space 36 , so that the pressure at the control connection Y acts in the space 90 . Accordingly, in the basic position shown, ie when the cone surface 86 of the piston 82 is lifted from the seat 88, the translator chamber 58 is acted upon by the pressure at the control connection Y and is thus largely relieved.

The use of a ball 80 to close the connection to the axial bore 48 and to limit the inner diameter of the ring-shaped measuring orifice 70 has the particular advantage that it is very easy to manufacture and is self-centering, so that even with a slight tilting of the piston 82 proper function is guaranteed.

The directional control valve 72 makes it possible to increase the pressure in the booster chamber 58 and thus the pretension of the transverse spring 42 by means of a switchable pressure increase via the control connection Y, the shockless function being maintained. This switchable pressure increase can be necessary especially when driving in difficult terrain.

When the pressure at the pressure connection P increases as described above, the ball 80 is lifted against the force acting on the back of the ball in the closing direction from the peripheral edge of the radial shoulder 74 , so that the control oil can flow through the opened annular measuring orifice 70 into the spring chamber for the control spring 52 . By the axial displacement of the ball 80 , the conical surface 86 is pressed against the seat 88 , so that the connection of the translator room to the Steueran circuit Y is blocked. The pressure in the translator room 58 increases as a result, so that the switching delay described above occurs. The switch-on point and the switch-off point (indicated in FIG. 4) can be tuned in the variant shown in FIGS . 5 and 6 by suitable selection of the diameter ratio between the outer diameter of the ball and the diameter of the seat 88 , so that the switch-off point in Dependence on this translation ratio is below the cut-in point by a predetermined value.

In the suction function, that is, when the pressure at the low-pressure connection T is higher than at the pressure connection P, the suction ring 20 is shifted to the right in the illustration according to FIG. 1, so that it runs onto the radial collar 22 and the valve slide 8 into it Is brought open position in which the connection from T to P is open and pressure medium can flow from T to P. After the suction ring 20 also contributes to the damping of the valve spool movement in the pressure limiting function.

With the construction described above, the repeatability of the shockless function in the same direction (e.g. when pushing a slewing gear) is made possible by the possible quick intermediate relief via the 3/2-way valve 72 . Such a function is required in the load sensing system.

Otherwise, the function corresponds to that of the above Embodiment, so that no further explanations are given becomes.

Fig. 7 shows the circuit symbol of the game Ausführungsbei described above, which differs from that of the Schaltsym bols shown in Fig. 4 only by the addition of the 3/2-way valve 72 , through which the translator room 58 either with the Druckan circuit P or with the control connection Y is connectable. The directional control valve 72 is acted upon by the force of the spring 84 and the pressure at the Steueran circuit Y in its basic position and in the opposite direction (connection to P) by the pressure at the pressure port P.

Disclosed is a pilot operated pressure feed valve in which a pilot valve body via one on a booster piston supported control spring is biased into its closed position. On the translator piston's rear translator room can be accessed via a Apply a control pressure to the flow control valve to the preload increase the control spring. The flow control valve enables one Viscosity and pressure independent supply of control oil in the over setter room.  

LIST OF REFERENCE NUMBERS

1

Pressure feed

2

casing

4

Radial bore star

6

valve bore

8th

valve slide

10

main stage

12

compression spring

14

seat edge

16

nozzle bore

18

spring chamber

20

anti-cavitation

22

radial collar

24

throttle gap

26

parallel hole

28

pilot stage

30

pilot housing

32

connecting bore

34

connecting channel

36

Pilot spring space

38

Pilot valve seat

40

Pilot valve body

42

control spring

44

Booster piston

46

internal bore

48

Flow control valve

49

axial bore

50

Pressure regulator piston

52

Rule feather

54

Screw

56

drilling

58

Booster chamber

60

spindle

62

locknut

64

ground

66

Annular face

68

control edge

70

orifice

72

way valve

74

radial shoulder

76

Rifle

78

bottom hole

80

Bullet

82

piston

84

feather

86

conical surface

88

Seat

90

room

92

axial

94

cross hole

Claims (10)

1. Pilot-operated pressure feed valve with a through a nozzle bore ( 16 ) valve spool ( 8 ) through which a connection between a pressure port (P) and a low pressure port (T) is controllable and via a compression spring ( 12 ) in it Close position is biased, the spring chamber ( 18 ) via a pilot stage ( 28 ) can be connected to a control connection (Y), the pilot stage ( 28 ) having a pilot valve body ( 40 ) which is supported by means of a control spring supported on a translation piston ( 44 ) ( 42 ) is biased against a pilot valve seat ( 38 ) and a from the rear end face of the booster piston ( 44 ) limited translator chamber ( 58 ) can be acted upon by a control pressure to increase the bias of the control erfeder, characterized in that in the control oil flow path to Translator room ( 58 ) a flow control valve ( 48 ) is arranged. 2. Pilot-operated pressure feed valve, wherein the flow control valve ( 48 ) has an in an inner bore ( 46 ) of the booster piston ( 44 ) guided pressure compensator piston ( 50 ), in the bottom ( 64 ) of which a measuring orifice ( 70 ) is formed and with it rear circumferential edge ( 68 ) a bore ( 56 ) opening in the translator space ( 58 ) can be controlled and which is biased into a stop position by means of a control spring ( 52 ). 3. Pilot operated pressure feed valve according to claim 2, where at the bottom ( 64 ) with respect to the two end faces is axially offset in NEN. 4. Pilot-operated pressure feed valve according to claim 2, where the orifice ( 70 ) is limited by an annular gap between a ball ( 80 ) guided in the bottom of the pressure compensator piston ( 50 ) and the peripheral surface of a bottom bore ( 78 ). 5. Pilot-operated pressure feed valve according to claim 2 or 3, with a directional control valve ( 72 ) via which the translator space ( 58 ) can be connected to the control connection (Y). 6. Pilot-operated pressure feed valve according to claim 4 and 5, wherein a piston ( 82 ) of the directional valve ( 72 ) by means of a spring ( 84 ) is biased into an abutment position on the ball ( 80 ) so that it in turn abuts against a radial shoulder ( 74 ) an inner bore ( 46 ) of the booster piston ( 44 ) is pressed. 7. Pilot-controlled pressure feed valve according to one of the preceding claims, wherein the pilot valve body ( 40 ) is designed with an effective area difference in the closing direction. 8. Pilot-operated pressure feed valve according to one of the preceding claims, wherein the valve slide ( 8 ) is biased against a seat edge ( 14 ). 9. Pilot-operated pressure feed valve according to one of the claims 5 to 8, wherein the outer diameter of the ball ( 80 ) is larger than the diameter of a seat ( 88 ) of the piston ( 82 ). 10. Pilot-operated pressure feed valve according to one of the preceding claims, wherein the basic position of the booster piston ( 44 ) can be changed in the axial direction.