Valve

Abstract

A valve, in particular a 2 / 2-way seat valve, having a valve piston (12) which is guided longitudinally movably in a valve housing (10) and controls a fluid flow between two connection points (1, 2) in the valve housing (10), and having an orifice (24), the free orifice cross section of which is predeterminable by a pilot control piston (26), is characterized in that there is a further orifice (28), the free orifice cross section of which is likewise activatable by the pilot control piston (26).

Description

[0001] HYDAC FLUIDTECHNIK GMBH

[0002] Justus-von-Liebig-Straße, 66280 Sulzbach / Saar, Germany

[0003] valve

[0004] The invention relates to a valve, in particular a 2 / 2-way seat valve, with a valve piston which is guided longitudinally in a valve housing and which controls a fluid flow between two connection points in the valve housing, and with an orifice whose free orifice cross-section can be predetermined by a pilot piston.

[0005] DE 10 2020 007 098 A1 discloses a valve, particularly in the form of a 2 / 2-way seat valve, which integrates a pressure-limiting function into a common valve body to implement thermal overpressure protection. The valve body has at least one inlet and one outlet, which can be connected to or separated from one another in a fluid-conducting manner by means of a valve piston controlled by a solenoid system. The valve piston further has two orifice bores, one of which is designed as a fixed orifice and the other as a variable orifice. The variable orifice is controlled by a pilot piston having a control cone at one of its free ends, with which the free opening cross-section of the variable orifice can be specified. The hydraulic pilot control achieved with the known valve makes it possible to move the valve piston in seat valves with reduced force.In a "normally closed" valve, the valve piston initially separates two pressure chambers in the unactuated position, thus preventing fluid flow. To open, a volume flow-dependent force balance acting on the valve piston is controlled by means of an orifice, which is controlled via a pilot tip of the pilot piston and is known as a pilot orifice.

[0006] By trapping compressible gas in the pressure chamber, brief pressure increases, usually in the form of pressure surges, can lead to compression and, consequently, to a volume flow through the inlet orifice, in the form of the stationary orifice, into a pilot chamber with the pilot piston. The resulting force equilibrium then unintentionally leads to a brief opening of the valve piston, which is technically referred to as spitting.

[0007] To counteract this behavior, the ability to influence one or more components of the force balance with respect to these volume flows resulting from undesired compression must be improved.

[0008] The operating principle of pilot control is based on the one hand on the pressure drop that occurs across a hydraulic orifice and on the other hand on the pressure-imposed force on a given area, i.e. the compressive force. In the unactuated position, the valve piston is held closed by a pressure and spring force acting in the direction of the valve seat. The compression spring used for this acts on the opposite side of the valve seat on the valve piston. When pressure is applied in the opposite direction, the valve opens automatically when the pressure force acting on the valve seat, equivalent to the spring, is exceeded. In pilot-operated valves, such as those offered by the patent holder (2 / 2-way seat valve / solenoid-operated pilot-operated / normally closed / screw-in valve UNF-350 bar / WS12Z-01), a pilot control tip opens a pilot control orifice located in the valve piston.The volume flow established through this orifice creates a pressure drop, which in turn reduces the spring-side pressure force to such an extent that an area subjected to system pressure can exceed both the spring force and the spring-side pressure force. With the resulting force equilibrium, the valve piston follows the pilot control tip.

[0009] To counteract the "spitting" effect, an additional compression spring acting on the valve piston is used. This, as a further component in the force balance, results in a lower pressure force acting on the spring side and thus a larger volume flow through the pilot orifice. The disadvantages of this solution are the associated increased component expenditure and the fact that the volume flows occurring during the spitting effect can only be counteracted to a limited extent via the pilot orifice.

[0010] Based on this prior art, the invention is based on the object of improving the valve solutions described above.

[0011] A valve having the features of patent claim 1 in its entirety solves this problem.

[0012] By providing an additional orifice in the valve according to the invention, whose free orifice cross-section can also be controlled by the pilot control piston, it is possible to enlarge the free orifice cross-section, which is responsible for the volume flow-dependent pressure differential. Such an enlarged orifice area ensures a lower pressure differential when the valve is closed than that required to open the valve piston. When the pilot control piston is actuated, a sliding edge mechanically coupled to the pilot control piston closes another variable orifice, while the pilot control orifice is simultaneously opened. This ensures that the pressure differential required to open the valve piston can be achieved via such a reduced orifice cross-section. This effectively prevents unintentional "spitting" of the valve.

[0013] Further advantageous embodiments of the valve according to the invention are the subject of the subclaims.

[0014] In the following, the valve according to the invention is explained in more detail using two embodiments according to the drawing. In a schematic representation and not to scale, the

[0015] Figure 1 shows, in the form of a longitudinal section, a first embodiment of the valve according to the invention;

[0016] Figures 2 and 3 show a lower section of the valve according to Figure 1, once in the unactuated and once in the actuated position;

[0017] Figures 3 and 4 show an embodiment of the valve according to the invention which is modified compared to Figures 1 to 3 in the unactuated and actuated positions, respectively.

[0018] The valve shown in longitudinal section in Figure 1 is in the form of a so-called 2 / 2-way seat valve, with a valve piston 12 which is guided longitudinally in a valve housing 10 and which controls a fluid flow between two connection points 1, 2 in the valve housing 10. The valve housing 10 is configured as a so-called screw-in cartridge according to the illustration in Figure 1 and can thus be introduced via a screw-in section 14 into a valve or housing block (not shown in detail), in which fluid guides are introduced to continue the two fluid connection points 1, 2. In this case, one connection point 1 can be connected optionally to a pressure supply device, such as a hydraulic pump, or a low-pressure side, such as a tank connection, whereas connection point 2 can lead to a hydraulic consumer, such as a hydraulically actuated working cylinder.The connection point 1 is introduced into the valve housing 10 in the axial direction concentric to a longitudinal axis 16 of the valve. The connection point 2, on the other hand, is formed from a fluid chamber between the valve block and the valve housing 10, into which bores 18, 20 open, which radially penetrate the valve housing 10 transversely to the longitudinal axis 16. The free diameter of the upper bores 18 of the associated row of bores, as viewed in the direction of Figure 1, is each smaller than the diameter of a bore 20 of the lower row of bores. Furthermore, the bores 18, 20 of each row of bores are separated from one another in every travel position of the valve piston 12 during normal operation by a circumferential separating web 22 along the inner circumferential side of the valve housing 10.

[0019] The valve piston 12 contains a first orifice 24, the free orifice cross-section of which can be predetermined by a pilot piston 26. Furthermore, a further second orifice 28 is present, the free orifice cross-section of which can also be controlled by the pilot piston 26. As the orifice cross-section of one orifice 24 is increasingly opened by the pilot piston 26, the pilot piston 26 controls the free orifice cross-section of the further second orifice 28.

[0020] Viewed in the direction of Figure 1, the pilot piston 26 has a control part 30 on its one free, downward-facing end face, which, while forming one orifice 24, engages at least partially in an associated opening 32 in the valve piston 12, which opens in the direction of one connection point 1 in the valve housing 10. The control part 30 is preferably formed from a valve cone which is tapered in the direction of the opening 32 axially introduced in the valve piston 12.

[0021] Furthermore, the pilot control piston 26 has a control edge 34 on its outer circumference, which, while forming the further orifice 28, at least partially extends over an associated opening 36 radially introduced in the valve piston 12, which opens in the direction of the further connection point 2 in the valve housing 10 via the upper row of bores with the individual bores 18. While the opening 32 is formed by an axially stepped bore beginning at the lower free end face of the valve piston 12, the free diameter of which decreases in the direction of the conical control part 30 and is arranged concentrically to the longitudinal axis 16 of the valve, the further opening 36 is realized by a radial bore in the valve piston 12 transverse to the longitudinal axis 16, wherein the free bore diameter of the radial opening 36 is selected to be larger than the free bore diameter for the axial opening 32 in the region of the engagement of the control part 30 in the corresponding opening 32.

[0022] As shown in particular in Figures 2 and 3, the control edge 34 is formed by an annular shoulder 38 in the pilot piston 26, to which a cylindrical guide surface 40 of the pilot piston 26, with a wider diameter, adjoins in the direction of the control part 30. This guide surface 40, guided longitudinally along the inner circumference of the valve piston 12, changes the free orifice cross-section of the further orifice 28. The pilot piston 26 extends in a rod-like configuration concentric with the longitudinal axis 16 of the valve. On its lower end face, which faces the axial opening 32, a pilot spring 42 is supported in the usual manner on both sides, once on an annular shoulder of the pilot piston 26 and once on an inner circumferential shoulder of the valve piston 12.In this respect, the pilot spring 42 extends in a pilot chamber 44, formed by an outer peripheral side of the pilot piston 26 and an adjacent inner peripheral side of the valve piston 12, wherein the pilot chamber 44 opens into the axial opening 32 in the valve piston 12 when the orifice 24 is released.

[0023] At its upper end, as viewed in the direction of Figure 1, the pilot control piston 26 is operatively connected at one end to a magnet armature 48 via a drag connection 46, which is conventional. The other free end of the magnet armature is supported on an armature spring 50 designed as a compression spring, whereby the armature spring 50 in question is only partially shown in Figure 1, but completely in Figures 4 and 5. The magnet armature 48 is guided so as to be longitudinally movable in a pole tube 52 and can be controlled by means of a coil with its coil winding (not shown) of a conventional electromagnetic actuating device (not shown), i.e. when the coil winding of the coil is energized, the magnet armature 48 moves upwards, as viewed in the direction of its initial position shown in Figure 1, against the action of the armature spring 50, up to a maximum of an end part 54, with which the upper free end of the pole tube 52 is firmly crimped.For the sake of simplicity, a conventional magnetic separation in the pole tube 52 has been omitted. This separation is located approximately at the height of the upper end of the magnet armature 58 in the position shown in Figure 1. Furthermore, the magnet armature 48 has a compensating channel 56, which connects the two pressure chambers upstream and downstream of the direction of travel of the magnet armature 48 in a media-conducting manner. At a stepped inner end of the lower region of the pole tube 52, which is accommodated inside the valve housing 10 via a further screw-in section 58, another compression spring, designed as a piston spring 60, extends between the pole tube 52 and the upper free end face of the valve piston 12.

[0024] When the magnetic system is actuated, the magnetic armature 48 moves upwards (as viewed in Figure 1) against the action of the armature spring 50. After overcoming the drag play of the drag connection 46 in the axial direction, the pilot piston 26 is also raised, and the conical control part 30 moves from its closed position shown in Figures 1 and 2 into its open position shown in Figure 3, in which the orifice cross-section of the first orifice 24 is visibly exposed. This leads to an open position of the valve in which the connection points 1, 2 are fluidically connected to one another as shown in Figure 3, and the valve piston 12, raised to this extent, moves against the spring action of the piston spring 60.The already mentioned pilot spring 42 only has the task of releasing the control part 30 with its low spring stiffness from the valve piston 12 to release the variable orifice 24 in order to avoid inhibitions during operation.

[0025] The annular shoulder 38, which forms the control edge 34 for the second variable orifice 28, corresponds in terms of its annular surface to the annular surface of the pilot piston 26, against which the pilot spring 42 rests. The cylindrical guide surface 40 of the pilot piston 26 has an axial length such that in a raised position of the pilot piston 26, the radial opening 36 is largely or preferably completely closed, whereas a third orifice 62, as a constant orifice with a preferably constant opening cross-section, which passes through the valve piston 12 transversely to the longitudinal axis 16, remains free from the cylindrical guide surface 40 of the pilot piston 26. In this respect, the center axis of the associated bore 64, which opens at its free end into the orifice 62 with its orifice opening, is located above the center axis of the radial opening 36 in the form of the radial bore, as seen in the direction of travel of the pilot piston 26 in the direction of the piston spring 60.

[0026] Further recessed on the outer circumference of the pilot piston 26 is a circumferential space formed as a recess 66, the axial length of which, viewed parallel to the longitudinal axis 16, is slightly larger than the distance between the center axis of the radial bore 36 and the top side of the valve piston 12, against which the piston spring 60 engages. The depth of the groove-like recess 66 is predetermined by the annular shoulder 38 with the control edge 34.

[0027] The radial opening 36 opens outwardly into a circumferential annular space 68 of the valve piston 12, which, as already explained in the direction of view of the figures, is bounded at the bottom by the separating web 22 and at the top by a further separating web 70. Likewise, the bore 64, as part of the third orifice 62, opens into the corresponding annular space 68. The axial length of the annular space 68 between the two separating webs 22, 70 is in any case dimensioned such that, in every travel position of the valve piston 12, the annular space 68 remains in overlap with the respective bore 18 of the associated row of bores.

[0028] Furthermore, an obliquely running transverse channel 72 is introduced into the pilot control piston 26, which opens with one free end into the pilot control chamber 44 with the pilot control spring 42 and with its other free end into the recess 66 in the pilot control piston 26. The center axis of the transverse channel 72 runs at an angle of 65° to the center axis of the radial bore 36. Furthermore, the lower boundary of the transverse channel 72 exiting at the top opens flush with the outer control edge 34 at the height of the annular shoulder 38.

[0029] The valve according to the invention can be controlled in such a way that when the pilot orifice 24 is opened, a volume flow flows via this 24 and the further, variable-stroke orifice 28, which leads to a pressure drop in the flow direction behind the further orifice 28 in such a way that an equilibrium of the pressure forces acting on the valve piston 12 is established and that the volume flow flowing through the two orifices 24, 28 causes the valve piston 12 to follow a pilot piston 26 raised from its initial state by means of the actuating magnet device, with the result that the further orifice 28, which is designed as having a variable stroke, is closed to the extent that the pilot orifice 24 is opened. As a result, the valve between the connections 1, 2 is opened in that, as shown in Figure 3, the valve piston 12 is raised accordingly.By means of the solution shown with the various orifices 24, 28, 62, a component of the force balance acting on the valve piston 12 is influenced in such a way that the volume flow-dependent influence is reduced, with the result that the undesired spitting, which is accompanied by an undesired, brief opening of the valve piston 12, is avoided in any case.

[0030] The modified embodiment according to Figures 4 and 5 will only be explained insofar as it differs significantly from the previously described embodiment according to Figures 1 and 3.

[0031] Compared to the solution according to Figures 1 to 3, the modified embodiment differs in that the third orifice 62 opens into the pilot chamber 44 with a constant opening cross-section at its bottom side, opposite the axial opening 32. Otherwise, the other free end of the associated bore 64 is also designed to open into the annular space 68 of the valve piston 12.

[0032] Another difference is that the radial opening 36 is designed to run obliquely and, starting from the annular space 68 in the valve piston 12, opens at the other end into an annular groove 74 on the inside of the valve piston 12. The annular groove has an annular, end-face boundary wall 76 which, as shown in Figure 4, delimits an annular gap 78 with the control edge 34 of the pilot piston 26, which can be closed according to the open valve position according to Figure 5 by moving over the control edge 34. The annular gap 78 thus forms the further second orifice 28 with a variable cross-section.Even in the completely closed state of the second orifice 28, in which the annular gap 78 is closed, a fluid-carrying connection is still established between the piston chamber with the piston spring 60 and the connection 2, namely via the transverse channel 72, which permanently opens into the pilot control chamber 44, and the third orifice 62 connected to this pilot control chamber 44. In this respect, the advantages achieved also apply to the modified embodiments according to Figures 4 and 5, as described above for the embodiment according to Figures 1 to 3.

[0033] The axial length of the annular groove 74, formed from an annular recess 76 in the valve piston 12, is larger than the bore diameter of the obliquely introduced radial opening 36, which opens at the bottom into the lower end wall boundary of the annular groove 74. When the annular gap 78 is closed according to Figure 5, the cylindrical guide surface 40 on the outer circumference of the pilot piston 26 completely covers the annular groove 74 and thus also closes the annular gap 78.

Claims

Patent claims 1 . Valve, in particular a 2 / 2-way seat valve, with a valve piston (12) which is guided longitudinally displaceably in a valve housing (10) and which controls a fluid flow between two connection points (1, 2) in the valve housing (10) and with an orifice (24) whose free orifice cross-section can be predetermined by a pilot piston (26), characterized in that a further orifice (28) is provided whose free orifice cross-section can also be controlled by the pilot piston (26).

2. Valve according to claim 1, characterized in that with increasing release of the orifice cross-section of one orifice (24) by means of the pilot piston (26), the latter controls the orifice cross-section of the further orifice (28).

3. Valve according to claim 1 or 2, characterized in that the pilot piston (26) has on its one free end face a control part (30) which, while forming one orifice (24), engages at least partially in an associated opening (30) in the valve piston (12), which opens in the direction of the one connection point (1) in the valve housing (10).

4. Valve according to one of the preceding claims, characterized in that the control part (30) is formed from a valve cone which tapers conically in the direction of the opening (32) axially introduced in the valve piston (12).

5. Valve according to one of the preceding claims, characterized in that the pilot piston (26) has on its outer circumference a control edge (34) which, forming the further orifice (28), at least partially forms an associated orifice formed in the valve piston (12) passes over the radially introduced opening (36), which opens in the direction of the further connection point (2) in the valve housing (10).

6. Valve according to one of the preceding claims, characterized in that the control edge (34) is formed by an annular shoulder (38) in the pilot piston (26), to which a cylindrical guide surface (40) of enlarged diameter of the pilot piston (26) is connected, which guide surface is guided longitudinally along the inner circumference of the valve piston (12) and changes the free orifice cross-section of the further orifice (28).

7. Valve according to one of the preceding claims, characterized in that the opening (36) radially introduced in the valve piston (12) is formed as part of the further orifice (28) from at least one radial bore in the valve piston (12), which opens with one end in the direction of the annular shoulder (38) as part of the control edge (34) of the pilot control piston (26) or in an annular groove (74) in the valve piston (26) which cooperates with the control edge (34) of the pilot control piston (26).

8. Valve according to one of the preceding claims, characterized in that the valve piston (12) delimits on the outer circumference an annular space (68) arranged in a recess in it, into which the respective radial bore (36) opens with its other end as part of the further orifice (28), and in that the annular space (68) in each travel position of the valve piston (12) engages over a branch as part of the further connection point (2) in the valve housing (10) in a fluid-conducting manner.

9. Valve according to one of the preceding claims, characterized in that a third orifice (62) with a preferably constant orifice cross-section is arranged in the valve piston (12), which opens with its one end into the annular space (68) and with its other end into a pilot chamber (44) with the pilot piston (26) or into a recess (66) on the outer circumference of the pilot piston (26).

10. Valve according to one of the preceding claims, characterized in that the pilot piston (26) has a transverse channel (72) which, coming from the pilot chamber (44), opens into the recess (66) on the outer circumference of the pilot piston (26).

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