EP1710443B1 - Hydromechanical filtering valve and load sensing circuit - Google Patents

Abstract

The hydromechanic valve for filtering pressure fluctuations of a specific frequency has a slide (40) with two end surfaces, to which pressure can be applied from two control lines. One line (48) applies pressure to a surface (44) to open the valve, while the second (46) applies pressure to the other surface (42) to close it. The second line is fitted with a second valve (52) which filters out pressure fluctuations with a frequency above a threshold value. An independent claim is included for LS-control systems for hydraulic fluid which contain the valve.

Description

The invention relates to a hydromechanical filter valve for filtering pressure oscillations of certain frequency and / or amplitudes of a pressure signal applied in a control or pressure line. The invention further relates to an LS control arrangement.

Particularly in the case of load-sensing systems (LS systems) pressure oscillations can occur in the LS line, via which the highest load pressure of several consumers is tapped and fed to a pump regulator, which then results in oscillations of the pump pressure. It was found that, especially in mobile hydraulics, the low-frequency vibrations can lead to mechanical vibrations of hydraulic consumers and are therefore unacceptable.

In LS systems such pressure oscillations can be reduced by changing the valves or pump regulators, for example, the springs of the individual pressure compensators of the LS system are designed so that the unwanted vibrations are reduced. There are also known solutions in which a throttle check valve or the like has been installed in the LS line; However, it has been found that such solutions allow improvement only in certain operating points, but otherwise are ineffective.

In contrast, the present invention seeks to provide a hydromechanical filter valve, with the unwanted pressure fluctuations reliably can be eliminated. The invention is further based on the object to provide an LS control arrangement, are minimized in the low-frequency fluctuations of the pump pressure with low device complexity.

This object is achieved with regard to the hydraulic filter valve by the features of claim 1 and with respect to the LS control arrangement by the features of claim 14.

According to the invention, the hydromechanical filter valve has a connection between an inlet and a drain on or zusteuenden valve body, which is designed with two pressurized surfaces, one in the throttle direction and the other acts in the opening direction. Both surfaces are acted upon via a respective branching off from the inlet control line with the inlet pressure, wherein in the control line, which is acted upon in the throttle direction effective area with control oil, a valve device is provided, the control signals or their shares with the frequency range to be filtered or with greatly reduced amplitude lets through. In this case, signal components with a frequency above a cutoff frequency are not transmitted or only attenuated and signal components with a frequency below the cutoff frequency are essentially transmitted.

Accordingly, the invention is based on the fact that the voltage applied in the inlet pressure signal is present at a control edge of the filter valve and simultaneously passed to its two control surfaces, wherein in the opening direction, the pressure signal is substantially unchanged, while in the throttle direction by the arranged in the control line valve means only pressure signals acting in the frequency range to be filtered or below act. That is, via the valve device in the control line pressure signals are locked at a relatively high frequency, so that it practically acts as a low-pass filter. As a result, at lower frequencies or rates of pressure rise or decay on both sides of the valve body, the same forces act and remain in their home position (minimum flow or maximum flow depending on design). In the event that the pressure fluctuations are relatively high-frequency, they are filtered via the valve device in the control line, that the relatively high-frequency component of the pressure signal acts only on the other control surface in the opening direction - the valve body is then moved accordingly in the opening direction and the high-frequency pressure signal pass through. Comparatively low-frequency pressure fluctuations are reliably blocked via the filter valve, however. By using such a hydromechanical filter valve in an LS line of a LS control arrangement, fluctuations of the pump pressure in the harmful area can be reliably prevented.

In a particularly preferred embodiment, the effective as a low-pass filter, arranged in the control line valve means is designed by a filter choke and a series-connected filter volume. By designing the throttle diameter and the filter volume while the frequency response of this low-pass filter can be adapted to the present operating conditions.

In order to keep the filter valve open for a short time even after a rapid increase in pressure, can be provided in the other, leading to the control direction effective in the opening direction control line a throttle check valve.

The valve body of the filter valve is preferably biased by a spring in the direction of its closed position.

According to the invention, it is preferred if the filter valve is designed with negative coverage, so that the valve body never fully closes, so that very slow pressure changes that do not lead to unwanted vibrations in the system, the valve can happen. That is, the filter valve according to the invention is designed not as a high-pass filter but as a band-stop filter, with very slow pressure fluctuations and high-frequency pressure fluctuations are transmitted while a harmful frequency range lying in between is blocked.

This frequency range is often in the range between 5 and 20 hertz in LS control arrangements in mobile technology.

The valve device preferably has a variable filter throttle, so that the throttling effect becomes greater with increasing vibration. In the open position, the filter choke has a large diameter. In the throttle position this has a small diameter. For stronger vibrations, therefore, the slide remains longer in a throttle position.

According to another embodiment of the invention, the valve body of the filter valve is biased by a compression spring in the opening direction, so that the filter valve is turned on in the rest position and a strong throttling of each pressure signal is avoided and only at a certain dynamics, a throttling is made.

In the case in which the LS control arrangement is provided for controlling a plurality of consumers, preferably each individual metering orifice assigned to a consumer is assigned an individual pressure balance. However, the valve according to the invention is needed only once, in the LS line between the valve block and the pump. Not every valve disk needs to be assigned a separate filter valve.

The pump for supplying pressure medium to the consumer can be designed as a variable displacement pump or as a fixed displacement pump with bypass pressure compensator.

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

• Figur 1 ein Schaltbild einer LS-Steueranordnung mit einem ersten Ausführungsbeispiel eines hydromechanischen Filterventils;
• Figur 2 das hydromechanische Filterventil aus Figur 1;
• Figur 3 Druckschwankungen des Pumpendrucks und des Lastdrucks bei einer herkömmlichen LS-Steueranordnung;
• Figur 4 Schwankungen des Pumpendrucks und des LS-Drucks bei einer erfindungsgemäßen LS-Steueranordnung entsprechend Fig. 1;
• Fig. 5 ein zweites Ausführungsbeispiel eines hydromechanischen Filterventils;
• Fig. 6 ein drittes Ausführungsbeispiel eines hydromechanischen Filterventils;
• Figur 7 Druckschwankungen des Pumpendrucks und des LS-Drucks bei einer herkömmlichen LS-Steueranordnung;
• Figur 8 Schwankungen des Pumpendrucks und des LS-Drucks bei einer erfindungsgemäßen LS-Steueranordnung nach Fig. 6 bei geringer Schieberdämpfung; und
• Figur 9 Schwankungen des Pumpendrucks und des LS-Drucks bei einer erfindungsgemäßen LS-Steueranordnung nach Fig. 6 bei starker Schieberdämpfung.

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

• FIG. 1 a circuit diagram of a LS control arrangement with a first embodiment of a hydromechanical filter valve;
• FIG. 2 the hydromechanical filter valve FIG. 1 ;
• FIG. 3 Pressure fluctuations of the pump pressure and the load pressure in a conventional LS control arrangement;
• FIG. 4 Variations in the pump pressure and the LS-pressure in a LS control arrangement according to the invention accordingly Fig. 1 ;
• Fig. 5 a second embodiment of a hydromechanical filter valve;
• Fig. 6 a third embodiment of a hydromechanical filter valve;
• FIG. 7 Pressure fluctuations of the pump pressure and the LS pressure in a conventional LS control arrangement;
• FIG. 8 Variations in the pump pressure and the LS-pressure in a LS control device according to the invention after Fig. 6 at low slide damping; and
• FIG. 9 Variations in the pump pressure and the LS-pressure in a LS control device according to the invention after Fig. 6 with strong slider damping.

FIG. 1 shows a circuit diagram of a LS control arrangement 1 of a mobile implement, such as a tractor. This has a large number of consumers 2 who have a mobile control block with one after each FIG. 1 trained valve disk are supplied by a variable displacement pump 4 with pressure medium. In the illustration according to FIG. 1 only one consumer is shown, which is for example a lifting cylinder 2 of a hoist. The direction of movement and speed of the hydraulic cylinder 2 is adjusted by means of a proportionally adjustable directional control valve 6, the speed part of which forms a metering orifice 8, via which the pressure medium volume flow to the consumer 2 is set. The hydraulic cylinder 2 is shown Embodiment designed as a differential cylinder and is divided by a piston 10 in a bottom-side cylinder chamber 12 and a penetrated by a piston rod annular space 14. A working port A of the directional control valve 6 is connected via a feed line 16 to the cylinder chamber 12 and a working port B of the directional control valve 6 via a return line 18 to the annular space 14 of the hydraulic cylinder 2. A pressure connection of the variable displacement pump 4 is connected via a supply line 20 to an input port P of the directional control valve whose tank port T opens into a tank 24 via a discharge line 22. In the supply line 20, an individual pressure compensator 26 is arranged, which is acted upon in the closing direction via a control line 28 from the pressure upstream of the metering orifice 8 and in the opening direction of the pressure in a LS line 30. About this LS line 30, the load pressure of the consumer 2 is tapped. The individual pressure compensator 26 is further acted upon in the opening direction by the force of a spring 32. The individual pressure compensator 26 forms, together with the metering orifice 8, a flow regulator, via which the pressure drop across the inlet metering orifice 8 can be kept constant independently of the load pressure. Such LS control arrangements with upstream pressure compensator are known from the prior art, so that further embodiments are dispensable.

In the area between the individual pressure compensator 26 and the proportionally adjustable directional control valve 6, a check valve 31 is provided, which opens in the direction of the directional control valve 6. In the illustrated spring-biased home position (0), the ports P, A, B of the directional control valve 6 are shut off and the LS line 30 is connected to the drain line 22, so that it is depressurized. When moving the directional control valve 6 in one of his (a) marked positions of the pressure port P is connected to the working port B and the working port A to the tank port T, so that pressure medium depending on the setting of the metering orifice 8 conveyed into the annular space 14 and due to the retraction movement of the piston 10 the cylinder chamber 12 is displaced to the tank 24 out. When setting the directional control valve 6 in one of his (b) marked positions, the pressure medium is conveyed via the metering orifice into the cylinder chamber 12 and displaced out of the annular space 14 to the tank 24.

The LS line 30 leads to a pump controller 34, via which the variable displacement pump 4 is controlled such that the pump pressure in the supply line 20 is always above a predetermined pressure difference .DELTA.p above the highest load pressure in the LS line 30 (LS system).

As already mentioned, it can in particular in applications in mobile hydraulics to pressure fluctuations in the LS line 30 come, resulting in pressure fluctuations of the pump pressure, in particular the frequencies in the range between 5 and 20 Hertz are harmful and to discontinuities in the control of the or the consumer can lead. To minimize such undesirable pressure fluctuations, a hydromechanical filter valve 36 according to the first embodiment is arranged in the LS line, the structure of which FIG. 2 is explained.

This filter valve 36 is designed as a continuously adjustable valve with negative overlap and biased by a compression spring 38 in the direction of a basic position (a), in which the connection between the inlet side of the filter valve 36 and the drain side (bottom in FIG. 2 ) is still open, so that Control oil from the pump controller 34 and from this back to the tank 24 can flow. A slider 40 of the filter valve 36 is designed with two control surfaces 42, 44, wherein the control surface 42 in terms of a reduction of the flow cross-section and the control surface 44 in terms of increasing the flow cross-section of the filter valve 36 is effective. From the inlet of the filter valve 36 branches to a limited by the control surface 42 control line 46 and to a limited by the control surface 44 control chamber 48 from a control line 48, ie at the control edge of the slider 40 and the two control surfaces 42, 44 is in principle the Inlet pressure 30 on. In the control surface 44 associated control line 48, a throttle check valve 50 is arranged, which ensures that the filter valve 36 is still kept open after a rapid increase in pressure for a short time, so that some tax oil is allowed to drain.

In the control surface 42 associated control line 46, a filter choke 52 and a filter volume 54 are arranged in series with each other. The filter choke 52 and the filter volume 54 together form a low-pass filter whose frequency response u.a. depends on the diameter of the filter throttle 52 and the size of the filter volume 54. The smaller the diameter of the filter throttle 52 and the greater the volume of the filter volume 54, the lower must be a frequency in order to reach the spring side (control surface 42) of the filter valve 36. That through the filter choke 52 and the filter volume 54 comparatively high frequencies of the LS signal are filtered out.

In the opening direction acts on the slider 40 of the filter valve 36, the LS signal virtually unchanged. In the closing direction, the LS signal with the help of Filter choke 52 and the filter volume 54 filtered so that the high frequencies are disabled. Thus, at low frequencies, substantially the same forces act on both control surfaces 42, 44 of the slider, so that it remains in its rest position (a). In the case where the frequency is relatively high, ie with a rapid increase in pressure, this LS signal in the control line 46 is filtered out or delayed, while it is impressed unchanged on the control surface 44 in the control line 48, so that the slider 40 is moved in the opening direction (b) in a control position. Such an LS signal is thus transmitted from the filter valve 36 to the pump controller 34 out.

The remaining at rest negative coverage together with the hydraulic capacity on the outlet side of the filter valve 36 is a low-pass filter. The size of the negative coverage can determine which frequencies the filter valve can happen in any case. In this case, however, care must be taken that this frequency does not overlap with the blocking frequency specified via the filter throttle 52 and the filter volume 54, since otherwise the filter valve 36 is ineffective.

The filter valve 36 thus represents a band rejection filter that allows lower and higher frequencies to pass, but blocks a medium frequency range, for example 5 to 20 Hertz. Strictly speaking, a certain range of pressure rise rates are blocked. Very slow and very fast rising pressure signals are little affected while a certain range of pressure rise rates are blocked by the filter valve 36. The rate of pressure rise together with a certain amplitude gives a frequency - In this respect pressure increase rate and frequency are basically proportional to each other, although the factor depends on the amplitude. In the above embodiments, therefore, for the sake of simplicity of frequencies is spoken.

In the LS system undesirable frequencies can be filtered out by the filter valve according to the invention selectively, without deteriorating the dynamics of the response when switching valves that are used to control the hydraulic consumers. By suitable design of the filter choke 52 and the associated filter volume 54, the desired filtered frequency range can be easily adapted to the existing operating conditions.

The pressure differences between the two control surfaces 42, 44 may be relatively low. The forces acting in the opening direction are correspondingly small. At the same time act on the control edge of the filter valve 36 flow forces in the closing direction. If their proportion is too large, the filter valve can not open far enough and thus not work properly. For a given pressure difference on the control surfaces 42, 44, the slide diameter should therefore not fall below a certain minimum level to ensure proper functioning. At the same time, the influence of the slider friction on the valve function becomes smaller, the larger its diameter. An upper limit for the slide diameter is given by the fact that the slide displaces control oil in the direction of an end face even during its movement (depending on the direction of movement). By the throttle valves 52, 50, this control oil displacement itself leads to a pressure increase on the corresponding front side and could thus falsify the operation of the valve. In applications in mobile hydraulics, a slide diameter of about 8 mm has been found to be the preferred measure.

The function of the invention has already been tested in practice. FIG. 3 shows the time-dependent course of the LS-pressure and the pump pressure (pressure in the supply line 20) in a conventional system. It can be seen that due to the variations in the load pressure in the LS line 30, the pump pressure is subject to considerable fluctuations, which lead to mechanical vibrations of hydraulic consumers.

When using the filter valve 36 according to the invention, the pressure fluctuations in the LS line 30 according to FIG. 4 be reduced to a minimum, with only high-frequency vibrations reach the pump controller 34, but which are harmless to the function of the LS control arrangement. Accordingly, in the supply line 20, a pump pressure, the pressure fluctuations have a much lower amplitude of the harmful frequency than in the prior art - such pressure fluctuations are harmless and affect the control of the consumer 2 practically not.

Fig. 5 shows a hydrodynamic filter valve 136 according to a second embodiment of the present invention, instead of the filter valve 36 in the LS control arrangement of Fig. 1 is usable. This filter valve 136 is designed as a continuously adjustable valve and biased by a compression spring 138 in the direction of a rest position (a), in which the connection between the inlet side of the filter valve 136 and the drain side (bottom in FIG. 5 ) is open, so that Control oil from the pump controller 34 and from this back to the tank 24 can flow. In the throttle position (b) of the slider 140 pressure fluid can only throttled flow from the pump regulator and from this back to the tank. The slide 140 of the filter valve 136 is designed with two control surfaces 142, 144, wherein the control surface 142 in terms of increasing the flow cross-section and the control surface 144 in the sense of reducing the flow cross-section of the filter valve 136 is effective. From the inlet of the filter valve 136 branches to a limited by the control surface 142 control chamber 148 and to a limited by the control surface 144 control chamber 146 from a control line, ie at the control edge of the slider 140 and the two control surfaces 142, 144 is in principle the Supply pressure of the LS line 30 at. At the control surface 142, the pressure in the LS line 30 acts without damping or throttling.

In the control surface 146 associated control surface 146, a filter throttle 152 and a filter volume 154 are arranged in series with each other. In parallel with the filter throttle 152, a check valve 156 which opens toward the control surface 144 is provided, in the open position of which control oil can be supplied from the LS line 30 via the filter volume 154 of the control surface 144. The filter throttle 152 and the check valve 156 together form a throttle check valve. The filter choke 152 and the filter volume 154 together form a low-pass filter whose frequency response depends on the diameter of the filter choke 152 and the size of the filter volume 154. The smaller the diameter of the filter throttle 152 and the larger the volume of the filter volume 154, the lower must be a frequency of the LS-pressure, so that this from the control surface 144 of the filter valve 136 to the LS line 30 down. That is, through the filter throttle 152 and the filter volume 154 is allowed that the slider 140 only delayed from its throttle position (b) in its rest position (a) back, so that comparatively high frequencies of the LS signal can be filtered out.

In the opening direction acts on the slide 140 of the filter valve 136, the LS signal virtually unchanged. In the throttle direction, the control oil is filtered at the control surface 144 by means of the filter choke 52 and the filter volume 54 such that it returns only delayed to the LS line 30, whereby the comparatively high frequencies are disabled. Thus, at low frequencies below a lower cutoff frequency, substantially the same forces act on both control surfaces 142, 144 of the slider, so that it remains in its rest position (a). All signals of the LS line 30 are transmitted in principle unhindered, so that the dynamics is not hindered.

In the case where the frequency is relatively high, ie, above a lower cutoff frequency, control oil is directed to the control surface 142 via the control line 148 and to the control surface 144 via the opened check valve 156 as the pressure increases, so that the spool 144 is initially in the Rest position (a) remains. With rapid pressure reduction in the limited by the control surface 144 pressure chamber control oil is reduced in the limited by the control surface 144 pressure chamber on the filter volume 154 and the filter throttle 152 only delayed to the LS line 30, while control oil in the control line 148 unchanged on the control surface 142nd acts. As a result, the slider 140 is displaced against the force of the spring 138 in the throttle direction (b) in its throttle position. An LS signal with relative high frequencies in the LS line 30 is thus forwarded by the filter valve 136 to the pump controller 34 back only throttled.

Depending on the diameter of the filter throttle 152 and the size of the filter volume 154 and in dependence on the frequency and amplitude of the vibrations of the pressure in the LS line 30, a transition between the rest position (a) and the throttle position (b) after a certain number to oscillations until the throttle position is completely set and thereby further vibrations in an unwanted frequency range can be prevented.

After a decay of the vibrations that contain frequency components above the cutoff frequency, in the LS line 30, the slider 140 is moved by the compression spring 138 back into the rest position (a).

At frequencies of the pressure in the LS line 30 that are below a lower cutoff frequency, the filter choke 152 and the filter volume 154 have little or no effect. Thus, the filter valve 136 according to the second embodiment has a notch filter effect. For the other effects and advantages of the filter valve 136 according to the second embodiment, reference is made to the comments on the first embodiment.

Fig. 6 shows a filter valve 236 according to the third embodiment, which differs from the filter valve 136 according to the second embodiment by a variable throttling of the control oil volume flow from the filter volume 254 to the control line 246. The hydrodynamic filter valve 236 according to the third embodiment of the present invention is instead of the filter valve 36 in the LS control arrangement of Fig. 1 usable and is also designed as a continuously adjustable valve and is biased by a compression spring 238 in the direction of a rest position (a), in which the connection between the inlet side of the filter valve 236 and the drain side (bottom in FIG. 6 ) is open, so that control oil from the pump controller 34 and from this back to the tank 24 can flow. In the throttle position (b) of the slider 240 pressure fluid can only throttled flow from the pump regulator and from this back to the tank. The slider 240 of the filter valve 236 is designed with two control surfaces 242, 244, wherein the control surface 242 in terms of increasing the flow cross-section and the control surface 244 in terms of reducing the flow cross-section of the filter valve 236 is effective. From the inlet of the filter valve 236 branches to one of the control surface 242 limited control chamber 248 and to a limited by the control surface 244 control chamber from a control line 246, ie at the control edge of the slider 240 and the two control surfaces 242, 244 is in principle the Supply pressure of the LS line 30 at. At the control surface 242, the pressure in the LS line 30 acts without damping or throttling.

In the control surface 246 associated with the control surface 244, a check valve 256 and a filter volume 254 are arranged in series. Between the inlet of the filter valve 236 and the filter volume 254 is a variable filter throttle, which is determined by a control edge and in Fig. 6 is provided by a large diameter filter choke 252a and a small diameter filter choke 252b. The variable filter throttle 252a, 252b is arranged in the slider 240 and is switched in response to the position of the slider 240. The The large-diameter throttle 252a is switched to the rest position (a); the throttle diameter is reduced in the throttle position (b) to the small diameter throttle 252b. The check valve 256 opens to the control surface 244, wherein in its open position, the pressure in the LS line 30 via the filter volume 254 rests against the control surface 144. The variable filter choke 252a, 252b and the filter volume 254 together form a low-pass filter whose frequency response depends on the diameter of the variable filter choke 252a, 252b and thus on the slide position of the filter valve and on the size of the filter volume 254.

In the opening direction acts on the slider 240 of the filter valve 236, the LS signal virtually unchanged. In the throttle direction, the control oil on the control surface 244 is filtered by means of the large diameter filter choke 252a and the filter volume 254 such that it returns only delayed to the LS line 30, thereby blocking the comparatively high frequencies. Thus, at low frequencies below a lower cut-off frequency, substantially the same forces act on both control surfaces 242, 244 of the slide, so that it remains in its rest position (a). All signals of the LS line 30 are transmitted in principle unhindered, so that the dynamics is not hindered.

Also, in the case where the frequency is relatively high, ie above a cutoff frequency, control oil is directed to the control surface 242 via the control line 248 and the control surface 244 via the opened check valve 256 with increasing pressure, so that the slider 240 in the first Rest position (a) remains. With a comparatively rapid pressure reduction in the LS line 30, the pressure in the through the control surface 244 limited pressure chamber degraded relatively slowly over the filter choke 252 a large diameter, while the control oil in the control line 248 acts unchanged on the control surface 242. As a result, the slider 240 is displaced against the force of the spring 238 in the throttle direction in its throttle position (b). An LS signal with relatively high frequencies in the LS line 30 is thus forwarded by the filter valve 136 to the pump controller 34 only throttled.

At higher frequencies, the pressure difference across the filter choke is still higher due to the faster pressure change, so that the slider 240 is further displaced in the throttle direction. The control edge in the filter valve reduces the throttle diameter, so that a smaller filter throttle is effective. It is achieved an improved filter effect.

Due to the larger diameter of the filter throttle 252a, it is possible that a one-time, rapid change of the LS pressure with less delay than in the second embodiment via the filter valve 236 is forwarded. Vibrations above the cut-off frequency at which the feed pressure drops to the filter valve 236 several times in succession are damped by the filter valve 236 over an extended period of time due to the small diameter filter choke 252b. Thus, with a filter valve 236 according to the third embodiment, a better differentiation can be made between the states "vibrations" and "no vibrations".

Fig. 7 shows a simulation without oscillation choke, while the 8 and 9 Simulations with a filter valve according to the second embodiment demonstrate. In Fig. 8 There is a slider damping of 50 Ns / m, at the still disturbing low-frequency vibrations in the LS-pressure and pump pressure are present, while in Fig. 9 a slider damping of 500 Ns / m is present, whereby disturbing low-frequency vibrations are no longer present.

With the filter valves 136, 236 according to the second and third embodiments, a high dynamics in the reporting of LS pressure signals to the pump can be achieved, with a stable system behavior is maintained.

At the in FIG. 1 illustrated embodiment of the present invention, a variable displacement pump 4 is provided. In principle, instead of the variable displacement pump 4, it is also possible to use a constant displacement pump with a bypass pressure compensator, with the LS pressure then being applied to the inlet pressure compensator.

At the in FIG. 1 As shown, the individual pressure compensator is acted upon in the opening direction by the pressure downstream of the metering orifice 8 and in the closing direction by the pressure upstream of the metering orifice 8 and is connected upstream of the directional control valve 6. Of course, then the filter valve 36 can also be used in LUDV systems (load pressure independent flow behavior), in which the individual pressure compensator of the metering orifice is connected downstream and is acted upon in the opening direction of the highest load pressure of the consumer. In principle, the filter valve can be used in all hydraulic systems in which low-frequency vibrations are to be eliminated, as long as it is installed in a line that serves only to forward pressure signals. Due to the strong throttling of the pressure signal in case of unwanted Vibrations can not be used in pipes through which larger volume flows flow. The valve can only influence the signal transmission, not the line transmission.

Disclosed are a filter valve for filtering pressure fluctuations of certain frequency and / or amplitude of a pressure signal and designed with such a filter valve LS control arrangement. The filter valve has a valve body with two oppositely effective control surfaces, both of which can be acted upon via a control line with the inlet pressure. In the control line leading to the control surface effective in the throttle direction, a valve device with a low-pass filter function is arranged, via which higher-frequency control signals can be filtered out.

LIST OF REFERENCE NUMBERS

1

LS control arrangement

2

hydraulic cylinders

4

variable

6

way valve

8th

metering orifice

10

piston

12

cylinder space

14

annulus

16

supply line

18

Return line

20

supply line

22

drain line

24

tank

26

Individual pressure compensator

28

control line

30

LS line

31

check valve

32

feather

34

pump regulator

36

filter valve

38

compression spring

40

pusher

42

control surface

44

control surface

46

control line

48

control line

50

Speed Controller

52

filter inductor

54

filter volume

136

filter valve

138

compression spring

140

pusher

142

control surface

144

control surface

146

control line

148

control line

152

filter inductor

154

filter volume

156

check valve

236

filter valve

238

compression spring

240

pusher

242

control surface

244

control surface

246

control line

248

control line

251

choke line

252a

filter inductor

252b

filter inductor

254

filter volume

256

check valve

Claims (16)

1. Hydromechanical filtering valve for filtering pressure fluctuations of a certain frequency and/or amplitude, with a valve body (40; 140; 240) which comprises two control faces (42, 44; 142; 144) and via which a connection between an inlet and an outlet can be controlled so as to be opened or closed, wherein one control face (42; 142) is active in the throttling direction and the other control face (44; 144) is active in the opening direction, and both control faces (42, 44; 142, 144) can be acted upon by the inlet pressure via a control line (46, 48; 146, 148; 246) in each case branching off the inlet, wherein a valve device is provided in the control line (46; 146; 246) leading to the control face (42; 142) which is active in the throttling direction, which device does not pass control signal components at a frequency which is higher than a cutoff frequency, or only passes them in an attenuated form, and passes control signal components at a lower frequency.
2. Filtering valve according to Claim 1, wherein the valve device has a filter throttle (52; 152; 252a, 252b).
3. Filtering valve according to Claim 2, wherein the valve device has a filter volume (54; 154; 254).
4. Filtering valve according to any one of the preceding Claims, wherein it is constructed with negative overlap.
5. Filtering valve according to Claims 2 and 3, wherein the filter throttle (52; 152; 252a, 252b) and the filter volume (54; 154; 254) are designed such that frequencies in the range between 5 and 20 hertz are filtered out.
6. Filtering valve according to Claims 2 and 3, wherein the filter throttle (52; 152; 252a, 252b) and the filter volume (54; 154; 254) are connected in series.
7. Filtering valve according to any one of Claims 2 to 6, wherein the filter throttle (152) is part of a throttle check valve (152, 156).
8. Filtering valve according to any one of the preceding Claims, wherein the valve device has a variable filter throttle (252a, 252b).
9. Filtering valve according to Claim 8, wherein the variable filter throttle (252a, 252b) has a large diameter in the open position (a) of the filtering valve and a small diameter in the throttling position (b).
10. Filtering valve according to any one of Claims 1 to 6, wherein the valve body (140, 240) of the filtering valve (136, 236) is biased in the opening direction.
11. Filtering valve according to any one of Claims 1 to 6, wherein a throttle check valve (50) is disposed in the control line (48) to the control face which acts in the opening direction.
12. Filtering valve according to any one of Claims 1 to 6, wherein the valve body (40) of the filtering valve (36) is biased in the throttling direction via a compression spring (38).
13. Hydromechanical filtering valve according to any one of the preceding Claims which acts as a band-stop filter via which a frequency range is not passed or only passed in an attenuated form.
14. LS control arrangement with a filtering valve (36; 136; 236) according to any one of the preceding Claims, wherein the LS control arrangement has an adjustable metering orifice (8) for setting a pressure medium volumetric flow between a pump (4) and a hydraulic consumer (2), wherein the pump pressure in an inlet line (20) can be set in accordance with a load pressure of the consumer (2) which is tapped off via an LS line (30), and the filtering valve (36; 136; 236) is disposed in the LS line (30) between valves and the pump (4).
15. LS control arrangement according to Claim 14, with a plurality of consumers (2) which can in each case be supplied with pressure medium via a metering orifice (8) and with which an individual pressure-maintaining valve (26) is in each case associated.
16. LS control arrangement according to Claim 14 or 15, wherein the pump is a variable-displacement pump (4) or a fixed-displacement pump with a bypass pressure-maintaining valve.

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