WO2015131918A1

WO2015131918A1 - Valve apparatus

Info

Publication number: WO2015131918A1
Application number: PCT/EP2014/003289
Authority: WO
Inventors: Winfried RÜB
Original assignee: Hydac Filtertechnik Gmbh
Priority date: 2014-03-01
Filing date: 2014-12-09
Publication date: 2015-09-11
Also published as: DE102014005410A1

Abstract

A valve apparatus having at least one valve device (10), the control slide (12) of which is guided in a valve housing (14) so as to be longitudinally movable under the action of two pilot pressures (xA, xB) which act on said control slide in opposite directions, which valve housing has at least two working ports (A, B) for the connection of a hydraulic consumer (16) and has a pressure supply port (P) for the connection of a pressure supply source and has a return port (T) to which a reservoir tank (20) is preferably connectable, is characterized in that in each case one further valve device (22) is provided for comparing a load pressure (p_L), which is assignable to the respective working port (A, B), with a supply pressure (p_v), which is assignable to the pressure supply port (P), in order thereby for the action of the respective pilot pressure (xA, xB) on the control slide (12) of the former valve device (10) to be activated or deactivated.

Description

valve device

The invention relates to a valve device having at least one valve device, the spool is guided längsverfahr- under the action of two oppositely acting on him pilot pressures in a valve housing having at least two Nutzanschlüsse for connecting a hydraulic consumer and a Druckversorgungsanschius for connecting a pressure supply source and a return port to which preferably a storage tank can be connected.

Conventional hydraulic control systems are often used to move loads. Regular load consumers, such as cylinders or hydraulic motors, must be approached in the stroke direction. Energetically favorably designed controls adapt the necessary pump pressure to the currently prevailing load on the hydraulic consumer. There may be short-term errors during the adaptation. Should the pump pressure become lower than the load pressure, the load unintentionally sinks back into the "pump channel", in which load-side oil from the consumer flows back into the pump channel, ie via the pressure supply connection in the direction of the pressure supply source connected to it.

To counteract this unwanted backflow, you build from today's point of view regularly a check valve in the supply line, the blocks the possible return in the direction of the pump channel. However, check valves fundamentally cause throttle losses during operation, which preclude an energetically favorable operation. If, as shown in the prior art, a load-controlling directional control valve is seated between the pump line and the hydraulic consumer, then the check valve is placed regularly in front of the directional control valve in the flow direction. This solution is particularly typical for controlling industrial hydraulics in stationary applications. As a source of pressure supply so-called constant pressure networks are often used.

In the case of mobile control systems, the most varied directional valves are used again. In the case of the throttle valves used, a distinction is made between so-called open center valves and closed center valves. In the neutral position of open center valves, the flow rate of a constant displacement pump through the open center channel directly into the return port, ie directed directly to the tank. If an open center valve is actuated, then the outflow via the center channel is throttled at the same time and a connection to the hydraulic consumer is opened, wherein the connection to the consumer is fed by a parallel pump channel via a check valve. In the case of multiple pump systems used, there are correspondingly a plurality of parallel channels and associated non-return valves, as shown, for example, for a valve device in US Pat. No. 7,475,502 B2.

For throttle valves with closed center positions in neutral position, a constant flow must be diverted otherwise, or one uses control pumps and puts them in zero delivery. Instead of check valves in the pump supply and pilot operated check valves are used. This one sets downstream of the directional valve to the consumer in Neutral position leak-free to hold in position (US 7 475 502 B2). In this case, you need then no check valve in the supply line. In contrast to compensated valves, in which a LS-pressure compensator of the valve orifice is upstream or downstream, the open center valves are also in large mobile machines with pump control in use because they have prevailed in this field and are available accordingly. From a technical point of view, these solutions make little sense, because the open center position of the valve must first be closed before the pump pressure can rise. The necessary closing stroke of the center position reduces the resolution of the valve in cooperation with variable displacement pumps. For valves that interact with so-called. Pressure compensators, either the check valve is arranged in front of or behind the pressure compensator or the pressure compensator itself is pre-controlled via a corresponding logic circuit (DE

10 2012 014 359 A1).

Based on this prior art, the invention has the object to further improve the known valve devices while maintaining their other benefits to the effect that can be dispensed with throttle losses in the above context on check valves and that is still avoided with certainty that at an increase of the load pressure on the pump pressure, the amount of fluid displaced by the load can not unintentionally flow back into the pump channel. This object is achieved by a valve device having the features of patent claim 1 in its entirety.

Characterized in that according to the characterizing part of patent claim 1, in each case a further valve device is provided in order to be able to allocate a load pressure, which can be assigned to the respective user connection, to a pressure Comparing supply port assignable supply pressure in order to activate or switch off the respective pilot pressure on the spool of the one valve device is achieved in a functionally reliable manner with low component expenditure, that even at much higher load pressures than the pressure of the pressure supply source (pump pressure) fluid under any circumstances unintentionally can flow back into the so-called pump channel via the pressure supply connection in the valve housing.

In general, if the load pressure is greater than the pressure of the pressure supply source, the pilot pressures acting on the valve spool are either short-circuited or connected to the return port. If, on the other hand, the currently prevailing load pressure is less than the pressure of the pressure supply source, the pilot pressures are separated from one another and insofar actively act on the valve spool of the valve device.

The comparison pressures, as they are present at the pressure supply port of the valve housing of the valve device, as well as each of the hydraulic load coming load pressure are constantly on the other valve leinrichtung, preferably formed of a logic valve, on the control sides and also the other valve device is constantly with its connections connected to the respective assignable pilot pressure and the return port. If the load applied to the hydraulic load rises above the supply pressure, then the respectively addressed pilot pressure is switched to the return port, at which the tank or ambient pressure essentially prevails, and thus switched off or deactivated, with the result that the valve spool valve closes and in any case blocks the fluid-carrying connection between the addressed hydraulic consumer at one of the user terminals and the pressure supply connection and pump channel. The same thing happens with moving loads with load pressures greater than the pressure of the pressure supply source, so that the valve device according to the invention as a whole realizes the aforementioned pump channel blocking non-return function; without, however, comparable to the check valve function to generate high pressure losses. This has no equivalent in the prior art.

If a load stops, for example because the hydraulic cylinder is driving as a load, then P-Pu = load. In this case, the spool of the valve device may then not be moved to neutral, because the load may also be present at a gripping cylinder, which must not open for safety reasons under any circumstances. Therefore, the further valve device, in particular in the form of a 2/2 logic valve, preferably additionally receives on its pressure control side the effect of a compression spring that is weakly designed by the spring force, but nevertheless ensures that the pressure equality of Supply pressure and load pressure, the pilot pressure is not relieved or switched off, but remains in the activated position, which allows the spool to continue to supply the gripping cylinder with fluid pressure and thus keep closed.

The valve device according to the invention is regularly provided for the control of a single hydraulic consumer; However, it can be interconnected with other valve devices for multiple control hydraulic consumers. In particular, the valve device according to the invention can be expanded in terms of control technology in a sense in order to be able to use so-called LS control pumps as the pressure supply source. The spool of the valve device can be used unchanged for such LS control systems without this being changed constructively; In particular, no load signaling channels are to be introduced along the slide axis. In a particularly preferred embodiment of the valve device according to the invention is further provided that this is supplemented by a discharge current regulator. Preferably, the valve device is further supplemented by at least one release valve, which can be actuated by the respective higher of the two pilot pressures in the direction of a release position in which a pressure-conducting connection between the respective load pressure and the input side of the relief current regulator is established.

In this case, the higher, that is the more active, of the two pilot pressures should act on the release valve, preferably in the form of a 2/2-way switching valve, for passing on the respectively prevailing load pressures to the load-signaling line. In the neutral position of the release valve both pilot pressures of the spool are no load and the release valve remains closed so far. There will be no load reported. To ensure that the load-sensing line is actually safely relieved of load, the unloading current controller is connected to the load-sensing line. This current regulator limits the leakage current to a small, preferably fixed value, for example about 0.5 to 1 liter per minute. In order to ensure a maximum pressure, a maximum operating pressure in the pump regulator of the LS control pump can be set or can be realized by a pressure limiting valve, which is connected to the relief current regulator.

Overall, can be saved with the valve device solution according to the invention throttle losses of a check valve in the main flow of the hydraulic fluid circuit. Furthermore, space can be saved over known solutions by using two small-building logic valves for two hydraulic consumers, in which a correspondingly large dimensioned check valve is used. Since the control axis or the spool of the valve device itself does not need to report a load signal, commercially available valves can be used to this extent. ne load message are used, which in turn is cost-effective and reliable.

If the control slide does not need to contain any load signaling channels in its interior, then other functions can be accommodated there, for example in the form of brake or discharge valves and check valves for regeneration circuits, etc. Thus, it is also possible with LS valves to perform such additional functions to save space in the spool valve. The additional logic functions for the load message in the valve housing require little installation space and thus do not force any relevant enlargement of the valve housing.

In the following, the valve device solution according to the invention will be explained in more detail with reference to the drawing. In a schematic and not to scale representation, the

Fig. 1 in the manner of a hydraulic circuit diagram, the basic structure of the valve device; Fig. 2 in the manner of a construction representation of the essential

Parts of the valve device with two different types of valve devices used;

Fig. 3 and 4 in turn in the form of hydraulic circuit diagrams with conventional

Circuit symbols the use of the valve device according to FIGS. 1 and 2 for control systems with LS control pumps.

Fig. 1 shows an embodiment of the valve device according to the invention with a first valve means 10, the spool 12 under the action of two oppositely attacking pilot pressures xA, xB in a valve housing 14 is guided longitudinally movable. The valve housing 14 has two Nutzanschlüsse A, B for connecting a hydraulic consumer 16. In the present embodiment, the hydraulic consumer 16 is formed from a conventional hydraulic working cylinder, the piston side is fluidly connected to the terminal A and the rod side with the user port B. Viewing in the direction of FIG. 1, the valve device 10 on its the user terminals A, B, a pressure supply port P for connecting a pressure supply source, for example in the form of a hydraulic pump 18, on. Furthermore, the housing 14 is equipped with a return connection T, to which, as shown in FIG. 1, a storage tank 20 is connected in which there is regular tank or ambient pressure. According to the illustration according to FIG. 1, the valve device 10 is designed as a 4/3 proportional valve.

As shown in FIG. 1 further shows, each utility port A, B is assigned a structurally identical further or second valve device 22, which is shown in accordance with representation of FIG. 1 in its locked position respectively. As the control lines 24 reproduced by dashed lines indicate, the respective further valve device 22 makes it possible to compare a load pressure pi which can be assigned to the respective utility connection A, B with a supply pressure pv which can be assigned to the pressure supply connection P, in order to control the respective pilot pressure xA, xB at the control spool 12 to activate or disconnect a valve device 10. The comparative pressures in the form of the load pressure pi and the supply pressure pv, which are to be compared with one another, therefore also remain permanently at the respective further valve device 22 on the control side, as with its respective input and output ports 26 and 28 with the respective assignable control pressure xA, xB or is acted upon by the return pressure pR. Furthermore, on the same side of the respective further valve device 22, in which the supply pressure pv is connected as the control input. is, the pressure of an energy storage, here in the form of a compression spring 30, which at a pressure balance between the supply pressure pv and the respective load pressure p_ the pilot pressure xA, xB can be made such that the spool 12 of a valve device 10 by no means in its neutral position arrives. The further valve device 22 is designed in the manner of a 2/2 logic valve, which results more closely from the illustration according to FIG. 2. In particular, the 2/2 logic valve is designed in the manner of a switching valve with a valve piston 34 which can be moved longitudinally in a control housing 32 and which is widened in its diameter towards its free ends, forming a control piston 36. As seen in the direction of FIG. 2, the upper control piston 36 is responsible for controlling the pressurized connection between the respective pilot pressure xA, xB and the return pressure pR. As is further apparent from FIG. 2, the spool 12 is subdivided into individual extended segments and is held in its neutral position shown in FIG. 2 by two counteracting compression springs 38. Furthermore, the connections P, A, B, T are shown as annular channel inlets in the valve housing 14 shown as an indication. If, for example, via a pilot valve not shown in greater detail, which can be actuated by a joystick, the pilot pressure xA increases and no pilot pressure is present at xB, the control spool 12 is deflected to the right as seen in FIGS. 1 and 2. This results in a fluid-carrying connection between the pressure supply source 18 via the pressure supply port P to the user port A and the hydraulic cylinder 16 extends with its piston rod unit accordingly. The displaced on the rod side fluid (oil) passes through the user port B to the return port T. If now on the piston rod side an additional load, the hydraulic consumer 1 6 tries to bring back on its piston side fluid in the direction of the pump channel and in the direction of the pressure supply port P. therefore rises on the service connection side A of the load pressure p. at. At the 2/2-logic valve 22 is now according to the representations of FIGS. 1 and 2, the load pressure p. compared with the supply pressure pv. If the load pressure in the present case is higher than the supply pressure pv, the 2/2 logic valve is shifted from its blocking position shown in FIG. 1 into a switched-through position and the pilot pressure xA, which is present on the inlet side 26 of the valve 22, On the output side 28 is switched to the return or tank pressure pR in the direction of the storage tank 20. In that regard, therefore, the pilot pressure xA decreases, to the zero level of the pilot pressure xB, so that the valve or spool 12 of the first valve device 10 due to the two compression springs 38 (FIG. 2) again reaches its neutral position with the result that the service port A is closed relative to the pressure supply port P, so that so far on the piston side of the hydraulic consumer 16 with increasing load no fluid medium can flow back to the pressure supply side of the valve device.

If this is not the case, but a corresponding control edge geometry ensures that in any case a connection to the return side T for the hydraulic consumer 16 is made on the load side, so that so far superfluous fluid in a throttled manner to the tank side T can flow out. If, on the other hand, the supply pressure pv is greater than the load pressure p_, for example on the service connection side A, the logic valve 22 remains in its closed position shown in FIG. 1 and the pilot-operated pressure xA remains the fluid-conducting connection between the pressure supply source and the utility connection A. If the conditions are reversed, ie if the pilot pressure x B is active, the above-described conditions turn correspondingly and increased loads on the B side are likewise reliably controllable on the hydraulic consumer 16. The embodiment of FIGS. 3 and 4 will be explained only insofar as they differ significantly from the preceding embodiment. The same designations and specifications are used for the same components. The statements made so far then also apply to the modified embodiments of FIGS. 3 and 4, which serve a total of the control of two hydraulic consumers 16. FIG. 3 shows a possible extension of the solution according to FIGS. 1 and 2 in cooperation with the aforementioned LS control pumps as a hydraulic pump 18. The LSKV valve is an LS copy valve and the LSAV valve is an LS shut off valve. The LSKV valve is connected with its control sides once to an LSmax line and connected on its opposite side via a throttle or orifice 40 with the storage tank side 20. By means of counteracting pairs of check valves 42, 44, the respective higher pressure at the respective service connection side A, B can be brought to the LSmax line side. The pertinent rule control for a LS-control pump 18 is common, so that will not be discussed in more detail here at this point. The advantages described for FIGS. 1 and 2 for the valve device according to the invention also arise for the embodiment according to FIG. 3, which uses an LS control pump as the feed for the pressure supply source. In any case, the advantage of this arrangement is that the valve device according to the invention can also be used for LS control systems without the control spool 12 of the first valve device 10 having to be changed and without additional load signaling channels having to be introduced along the spool axis.

The solution according to FIG. 4 is modified compared to the solution according to FIG. 3 insofar as the valve device is additionally supplemented there by a relief flow regulator 50. Further, the hydraulic circuit for each consumer 16 is supplemented by a so-called. Release valve 52, which according to Representation of FIG. 4 is held by a compression spring in its locked position. The respective release valve 52 can be actuated by the respective higher of the two pilot pressures xA, xB in the direction of its release position, in which a pressure-carrying connection between the respective load pressure pi. of each consumer 16 and the input side LSmax of the discharge current regulator 50 is made. For the pertinent passing of the respective highest pressure in the form of the pilot pressure xA, xB to the said release valve 52, a shuttle valve 54 is used, whose output side 56 is connected to one of the control sides of the release valve 52 druckfüh- rend, which is opposite to the pressure spring side in this case ,

Furthermore, as already stated above, the input side LSmax of the discharge flow regulator 50 is connected to the LS copy valve LSKV, which in turn in conjunction with an LS cut-off valve LSAV controls the LS control pump 18, which supplies the supply pressure pv for the entire valve device , According to the representation according to FIG. 4, the relief flow regulator 50 is designed by means of an adjustable throttle 58 or diaphragm in such a way that the load-sensing pressure (LS pressure) is constantly relieved to the return pressure p R, preferably to limit a maximum predeterminable pressure to the current regulator system 50 is still a pressure relief valve 60 is connected.

The respective higher, that is to say the active, of the two pilot control pressures xA, xB thus acts on the release valve 52, preferably in the form of a 2/2-switching valve, a load pressure p_ prevailing on the useful connections A, B, respectively, to the load-signaling line LS. In the neutral position for the first valve device 10 shown in FIG. 4, both pilot or control pressures xA, xB are unloaded and the assignable release valve 52 remains closed. It is so far no load reported. In order to ensure that the load-signaling line LS is actually reliably relieved of load, the load-indicating line LS of the latter is also connected to the load-signaling line LS shown discharge relief regulator 50 connected, which limits the leakage current to a small, fixed value, eg 0.5 to 1 liter per minute, via the throttle 58.

Claims

P a n t a n s p r e c h e

Valve device with at least one valve device (10), the control slide (12) under the action of two oppositely acting on him pilot pressures (xA, xB) in a valve housing (14) is moved longitudinally, the at least two Nutzanschlüsse (A, B) for connecting a hydraulic consumer (16) and a pressure supply connection (P) for connecting a pressure supply source (18) and a return port (T), to which preferably a storage tank (20) can be connected, characterized in that in each case a further valve means (22) is present for comparing a load pressure (p) that can be assigned to the respective utility connection (A, B) with a supply pressure (p _v ) that can be assigned to the pressure supply connection (P), in order to reduce the respective pilot pressure (xA, xB) at the control spool (12) of the one Valve device (10) to activate or switch off.

Valve device according to claim 1, characterized in that the comparative pressures to be compared in the form of the load pressure (pO and the supply pressure (p _v ) as well as permanently pending on the respective further valve means (22), as this with its input and Ausgangsansehl uss with the respective assignable control pressure (xA, xB) or with the return pressure (PR) is acted upon.

Valve device according to claim 1 or 2, characterized in that the respective further valve device (22) on the same side in which the supply pressure (pv) is present as a control input, an energy storage, in particular in the form of a compression spring (30), which at pressure balance between supply pressure (p _v ) and respective load pressure (pO the pilot pressure (xA, xB)) can stand that the spool (12) of a valve device (10) never gets into its neutral position.

4. Valve device according to one of the preceding claims, characterized in that the one valve device (10) from a directional control valve, preferably a 4/3-proportional valve, is formed and that the respective further valve device (22) in the manner of a 2/2 Logic valve is formed.

5. Valve device according to one of the preceding claims, characterized in that the 2/2-way logic valve is designed in the manner of a switching valve with a in a control housing (32) längsver negotiated valve piston (34), which under its free ends under Formation of control piston (36) is widened in diameter, of which a control piston (36) controls the pressure-carrying connection between the pilot pressure (xA, xB) and the return pressure (ρι.

6. Valve device according to one of the preceding claims, characterized in that it is supplemented by a discharge current regulator (50).

7. Valve device according to one of the preceding claims, characterized in that it is supplemented by at least one release valve (52) which is actuated by the respective higher of the two pilot pressures (xA, xB) in the direction of a release position, in which a pressure-carrying connection between the respective load pressure (p and the input side (LSmax) of the relief current regulator (50) is made.

8. Valve device according to one of the preceding claims, characterized in that the input side (LSmax) of the discharge current regulator (50) is connected to a LS-copying valve, which in Connected to an LS shut-off valve, an LS control pump that supplies the supply pressure (pv).

9. Valve device according to one of the preceding claims, characterized in that the relief flow regulator (50) by means of an adjustable throttle or orifice the load-sensing pressure (LS pressure) constantly relieved to the return pressure (P) and preferably to limit a maximum specified pressure is equipped with a pressure relief valve.

10. Valve device according to one of the preceding claims, characterized in that for the transmission of the respective highest pressure, either in the form of the pilot pressure (xA, xB) or in the form of the prevailing load pressure (p to the release valve, a shuttle valve (54) is used whose output side (56) is connected in pressure-carrying manner to one of the control sides of the release valve (52).