Bidirectional proportional valve with electromagnetic actuator

Abstract

The invention relates to an electromagnetic actuator (10) for a bidirectional proportional valve (1), comprising: an actuator rod (18) that is oriented along a longitudinal axis L and is suitable and intended for connection to a valve piston (26, 27) of the proportional valve (1); a valve armature (2) that is fastened to the actuator rod (18); and a solenoid coil (15) that is arranged radially around the valve armature (2); a magnetic sleeve (12) that is arranged radially between the solenoid coil (15) and the valve armature (2); and a non-magnetic ring (13) that interrupts the magnetic sleeve (12) in the longitudinal direction L, wherein the actuator (10) is designed such that, by corresponding electrical actuation of the solenoid coil (15), the valve armature (2) and thus the actuator rod (18) can be moved along the longitudinal axis L on account of the resultant magnetic field, both in one direction and in the opposite direction, wherein the valve armature (2) is constructed from a plurality of annular or disc-shaped elements arranged in a row along the longitudinal axis L, and wherein at least one of the elements is a permanent magnet (4), at least one element (3) is a magnetic disc (3) with the same diameter as the permanent magnet (4), and at least one element is a magnetic additional element (5) having a diameter that is between 40% and 85% of the diameter of the permanent magnet (4).

Description

[0001] File: 28337 WO / CAH - 1 -

[0002] Bidirectional proportional valve with electromagnetic actuator

[0003] The invention relates to an electromagnetic actuator for a bidirectional proportional valve, and to such a bidirectional proportional valve, in particular for hydraulic applications.

[0004] The electromagnetic actuator comprises an actuator rod aligned along a longitudinal axis L, which can be connected to a valve piston of the proportional valve. This connection can be direct mechanical or indirect via intermediate pieces or via a pneumatic or hydraulic connection. It further comprises a valve armature mounted on the actuator rod, a solenoid coil arranged radially around the valve armature, a magnetic sleeve arranged radially between the solenoid coil and the valve armature, and a non-magnetic ring that interrupts the magnetic sleeve in the longitudinal direction L.

[0005] The actuator is designed so that, through appropriate electrical control of the solenoid coil, it can move the valve armature and thus the actuator rod along the longitudinal axis L due to the resulting magnetic field, both in one direction and in the opposite direction. In this way, the valve piston within the valve block can be moved precisely. This allows different fluid lines within the valve block to be connected to each other or shut off from each other.

[0006] CN 118499304 A describes a bidirectional electromagnetic proportional valve. It depicts a hydraulic 4 / 3-way valve comprising an electromagnetic actuator with a bidirectional solenoid coil. Radially between the solenoid coil and the valve armature is a magnetic sleeve, interrupted longitudinally by a non-magnetic ring. The generated magnetic field changes direction when the current to the solenoid coil is reversed. The valve armature is mounted on the actuator rod, which is longitudinally displaceable. [File: 28337 WO / CAH -2 -]

[0007] The generated magnetic field attracts or repels the valve armature accordingly, causing it to be moved back and forth longitudinally. The actuator rod is connected to the valve piston, which is thus moved in one direction or the opposite direction. The return spring pushes the valve piston back into its neutral position. By selectively activating the solenoid coil, the valve piston can be moved to the desired position within the valve block, thereby connecting, shutting off, or throttling the hydraulic lines within the valve block as required. The longitudinal length of the valve armature influences the stroke of the solenoid valve.

[0008] These well-known, electromagnetically controlled valves, however, exhibit significant hysteresis when switching back and forth. This means that, with the same control signal, the flow rate varies depending on the direction from which the valve is switched to that position. This hysteresis must be compensated for in bidirectional proportional valves, which is particularly important for high-pressure hydraulic valves. This can be achieved, for example, by using feedback from a position sensor in the valve piston, actuator rod, or valve armature and adjusting the control signal accordingly. However, the additional sensors and control system are complex, prone to errors, and result in increased costs.

[0009] The object of the invention is now to develop an improved electromagnetic bidirectional proportional valve, as well as an improved electromagnetic actuator for such a valve, so that they do not require hysteresis compensation.

[0010] The problem is solved, firstly, by an electromagnetic actuator according to claim 1. Further advantageous features are specified in the corresponding dependent claims.

[0011] The embodiment according to the invention is characterized in that the valve armature is constructed from several ring-shaped or disc-shaped elements arranged in a row along the longitudinal axis L, wherein at least one of the File: 28337 WO / CAH -3 -

[0012] The system consists of a permanent magnet, at least one element is a magnetic disk with the same diameter as the permanent magnet, and at least one element is a magnetic accessory element with a diameter between 40% and 85% of the diameter of the permanent magnet. Specifically, its diameter is 50% to 65% of the diameter of the permanent magnet. Here, "diameter" generally refers to the outer diameter of the elements.

[0013] Extensive development tests and calculations have shown that designing the valve armature with one or more additional elements that have a smaller diameter than the permanent magnet significantly reduces the valve's hysteresis. This eliminates the need for sensor-based compensation and corrected control without compromising the valve's accuracy.

[0014] Due to the smaller diameter of the additional element, the effect of the magnetic field on the valve armature is altered, which has a surprisingly positive effect on suppressing hysteresis. The longitudinal length of the valve armature determines the valve stroke. Thanks to the modular design of the valve armature, consisting of several interconnected elements, the armature, and thus the entire electromagnetic actuator, can be adapted to different valves with minimal modifications.

[0015] The magnetic discs and magnetic accessories can be made of magnetic steel in particular.

[0016] The actuator rod is made of a non-magnetic material.

[0017] Another preferred embodiment is designed such that the valve armature comprises two elements of the same diameter, which are permanent magnets, and an element arranged centrally between them, which is a magnetic disk, preferably with the same diameter as the permanent magnet. This enables clear back-and-forth switching. File: 28337 WO / CAH -4 -

[0018] Furthermore, it is advantageous if the valve armature includes an additional magnetic disk with the same diameter as the permanent magnet, and which is arranged not between, but to the side of the permanent magnets. This allows the valve stroke to be increased.

[0019] Additionally, it is advantageous if the valve armature includes one or more further magnetic elements with a diameter between 40% and 85% of the diameter of the permanent magnet. This allows the valve hysteresis to be reduced even further.

[0020] In particular, the magnetic add-on elements can all have the same diameter.

[0021] In an alternative design, the magnetic additional element adjacent to the permanent magnets can have a larger diameter than the other magnetic additional element located further out.

[0022] In this and the other embodiments, particularly advantageous sequences of the elements of the valve armature in the longitudinal direction L are described.

[0023] In a preferred embodiment, one or more additional magnetic elements are arranged only on one side of the permanent magnet(s), the additional elements having a diameter between 40% and 85% of the diameter of the permanent magnet.

[0024] Particularly preferably, the valve armature is constructed such that one or more additional magnetic elements with a diameter between 40% and 85% of the diameter of the permanent magnet are arranged on both sides of the permanent magnet(s). That is, the element(s) designed as a permanent magnet are located in the center, and the additional magnetic elements are located on both sides on the outside. File: 28337 WO / CAH -5 -

[0025] Smaller diameter magnetic additive elements. This design has proven particularly advantageous for suppressing hysteresis.

[0026] In particular, the valve armature can be constructed asymmetrically along the longitudinal axis L with respect to the magnetic additional elements, or it can be constructed symmetrically along the longitudinal axis L.

[0027] These variations allow the valve armature, and therefore the stroke and switching behavior of the valve, to be specifically adapted to different conditions.

[0028] The design features described above can be implemented individually or in combination, depending on the application.

[0029] Furthermore, the problem for the bidirectional electromagnetic proportional valve is solved by an embodiment according to claim 11. The bidirectional proportional valve comprises a valve block with several fluid lines, at least one valve piston which is arranged in a cavity of the valve block and can be moved linearly back and forth along a longitudinal axis L, so that the fluid lines can be connected to or shut off from each other and the opening between the fluid lines can also be selectively throttled. It further comprises an electromagnetic actuator which is connected to at least one valve piston via an actuator rod, so that the movement of the actuator rod is transmitted directly or indirectly to the valve piston. The valve according to the invention is characterized in that the electromagnetic actuator is designed according to one of the preceding claims.

[0030] The valve according to the invention is particularly advantageous for use as a hydraulic valve, since the hysteresis in valves according to the prior art has a particularly detrimental effect due to the high pressures.

[0031] The valve according to the invention can also be used advantageously in pneumatic applications. File: 28337 WO / CAH -6 -

[0032] The embodiment according to the invention offers particularly significant advantages when the valve is designed as a so-called spool-in-spool valve. In this design, a second valve piston is provided, which is arranged inside the first valve piston and which can move axially back and forth within it.

[0033] Further advantageous features of the invention are explained using exemplary embodiments with reference to the drawings. These features can be advantageously implemented not only in the combination shown, but also individually combined with one another. The figures show in detail:

[0034] Fig. 1 Bidirectional proportional valve according to the invention with electromagnetic actuator according to the invention.

[0035] Figs. 2-6 Further embodiments of the electromagnetic actuator according to the invention

[0036] Fig. 7 Flow control signal diagram for valve with strong hysteresis (state of the art actuator)

[0037] Fig. 8 Flow control signal diagram for valve according to the invention

[0038] The figures are described in more detail below. Identical reference numbers denote identical or analogous parts or components.

[0039] Fig. 1 shows the bidirectional proportional valve 1 according to the invention with the electromagnetic actuator 10 according to the invention. As an example, a hydraulic bidirectional proportional valve is shown in the neutral position. Various fluid lines 28 – here designed as hydraulic channels – are provided in the valve block 20, leading to different fluid connections – here designed as hydraulic connections – of the valve 1.

[0040] The cavity 21 contains the valve pistons 26, 27, which can be moved back and forth along the longitudinal axis L and thus control the various fluid lines. 28File: 28337 WO / CAH -7 -

[0041] Valve 1 can connect or shut off the fluid lines, or reduce the opening between them. This allows valve 1 to selectively reduce or completely shut off the pressure at its fluid connections relative to the pressure of an external pressure source and connect the fluid connection to a pressureless tank.

[0042] The valve pistons 26, 27 are pressed into their central position by the return springs 24, 25. The support cover 22 closes the valve block 20 on one side. The bidirectional electromagnetic actuator 10 presses at least one of the valve pistons 26, 27 – here, valve piston 27 directly and valve piston 26 indirectly – into the desired position along the longitudinal axis L, thus achieving the desired valve opening. For this purpose, the actuator rod 18 is connected to the valve piston 27. The actuator 10 and the valve block 20 are screwed together via the connecting element 23. The actuator rod 18 is supported and guided in the actuator by the sliding bearing bushings 17. The actuator rod 18 is made of a non-magnetic material. It is located on one end in the cover 16 and on the other end in the magnetic sleeve 12. The magnetic sleeve 12 is interrupted longitudinally by the non-magnetic ring 13.Thus, the actuator's neutral position is predetermined. The magnetic sleeve 12 concentrically surrounds the valve armature 2, which is mounted on the actuator rod 18. The solenoid coil 15 also concentrically surrounds the magnetic sleeve 12. The valve armature 2 is radially located inside the magnetic sleeve 12, and the solenoid coil 15 is radially located outside the magnetic sleeve 12. All components are housed within the actuator casing 11. A connection 14 for controlling the solenoid coil 15 is also provided.

[0043] Conventional actuators have so far had the disadvantage of exhibiting a large hysteresis when switching the valve back and forth.

[0044] In contrast, the actuator 20 according to the invention is designed such that the hysteresis is greatly reduced and only occurs to a very small degree. This is achieved by the fact that the valve armature 2 consists of several ring-shaped or disc-shaped elements. File: 28337 WO / CAH -8 -

[0045] The valve armature consists of elements arranged in series to form the valve armature 2. At least one of these elements is a permanent magnet, at least one element is a magnetic disk with the same diameter as the permanent magnet, and at least one element is an additional magnetic element with a diameter between 40% and 85% of the permanent magnet's diameter. Extensive development tests and calculations have shown that such a valve armature can significantly reduce hysteresis. As previously described, the outer diameter of the elements is always a crucial factor.

[0046] In the embodiment shown here, the valve armature 2 comprises two elements in the center, designed as permanent magnets 4, and an element between them, designed as a magnetic disk 3. Furthermore, another magnetic disk 3 is present on the outer surface of one of the permanent magnets 4. These magnetic disks 3 have essentially the same diameter as the permanent magnets 4. Additionally, the valve armature 2 includes two additional magnetic elements 5, which are arranged on the other outer surface (viewed in the longitudinal direction L) of the permanent magnets 4 and have a smaller diameter than the permanent magnets 4. Their diameter is in the range between 40% and 85% of the diameter of the permanent magnets. Here, the additional element 5 adjacent to the permanent magnet 4 has a larger diameter than the adjacent additional element 5 located further outwards.The number and thickness in the longitudinal direction of the additional elements 5 can be adjusted as required.

[0047] The illustrated embodiment is an example of an asymmetrical design of the valve armature 2, in which the additional elements 5 are arranged on the side of the valve armature 2 facing the valve block 20. The further magnetic disk 3, with the same diameter as the permanent magnet 4, is arranged on the side facing away from the valve block 20.

[0048] The length of the valve armature 2 in the longitudinal direction L determines the stroke of the valve 1. This can be determined, among other things, by the number and thickness in the longitudinal direction L of the armature. File: 28337 WO / CAH -9 -

[0049] magnetic discs 3 and magnetic additional elements 5 are adapted.

[0050] When the solenoid coil 15 is activated, the valve armature 2 is moved from its central position in one direction or the other, depending on the strength and direction of the magnetic field. This movement then moves the actuator rod 18 and thus the valve piston 27 along its longitudinal axis L. The direction of the magnetic field can be reversed by reversing the polarity of the voltage used to activate the solenoid coil 15.

[0051] Figures 2-6 show further advantageous embodiments for the construction of the valve armature 2 in the actuator 10 according to the invention. Depending on the design and requirements of the valve 1, the appropriate version of the valve armature 2 can be used to reduce the hysteresis and still achieve sufficient valve stroke.

[0052] Figure 2 shows an asymmetrical valve armature 2, which is a mirror image of the embodiment shown in Figure 1. That is, the magnetic auxiliary element(s) 5 are arranged on the side of the valve armature 2 facing away from the valve block 20. The additional magnetic disk 3 is arranged on the side facing the valve block 20. The auxiliary element 5 adjacent to the permanent magnet 4 has a larger diameter than the auxiliary element 5 located further out. Both auxiliary elements 5 have a smaller diameter than the permanent magnet 4. Their diameters are between 40% and 85% of the diameter of the permanent magnet 4. As before, a magnetic disk 3 is located in the center between the two disk-shaped permanent magnets 4.

[0053] Figures 3 and 4 again show an asymmetrically constructed valve armature 2. Here, the two additional magnetic elements 5 have the same diameter. The further magnetic disk 3, which is arranged outside the permanent magnets 4, increases the valve lift. File: 28337 WO / CAH - 10 -

[0054] Figures 5 and 6 depict symmetrical valve armatures 2 in which magnetic auxiliary elements 5 are provided on both sides of the permanent magnets 4. As previously described, the auxiliary elements 5 are each designed with graduated diameters. All auxiliary elements 5 have a diameter between 40% and 85% of the diameter of the permanent magnets 4. For example, the inner auxiliary elements 5 can have diameters between 65% and 85%, and the outer auxiliary elements 5 between 40% and 60%.

[0055] In the other embodiment according to Fig. 6, the additional elements 5 all have the same diameter. For example, the diameter of all additional elements is between 40% and 65% of the diameter of the permanent magnets 4.

[0056] Figures 7 and 8 show the valve characteristics from comparative tests as a diagram; that is, the flow rate Q of the bidirectional proportional valve is plotted against the control voltage U. This is done once for adjusting to the maximum voltage in one direction and then to the maximum voltage in the other direction, and back to zero. This reveals the hysteresis of the respective valve in the flow rate Q at the same control voltage (applied once from one direction and once from the other).

[0057] Figure 7 illustrates this valve characteristic for a valve with a state-of-the-art actuator. The difference in flow rate Q is enormous at low desired flow rates, depending on whether the valve is moved into this position from one side (i.e., from a lower control voltage) or from the other side (i.e., from a higher control voltage). These valves absolutely require hysteresis compensation using sensors, as described earlier. However, this increases the complexity and cost.

[0058] In contrast, Fig. 8 shows the valve characteristic for a valve according to the invention with an actuator according to the invention that suppresses hysteresis. The hysteresis is shown for both a higher pressure level p2 and a lower pressure level p1. [File: 28337 WO / CAH - 11 -]

[0059] The flow rate is extremely low. Therefore, these valves require no additional compensation, which is a tremendous advantage for the valves according to the invention. File: 28337 WO / CAH

[0060] - 12 -

[0061] Reference symbol list

[0062] 1 Electromagnetic bidirectional proportional valve (valve) 2 Valve armature

[0063] 3 magnetic discs

[0064] 4 permanent magnets

[0065] 5 magnetic accessories

[0066] 10 Electromagnetic actuator

[0067] 11 actuator housings

[0068] 12 magnetic sleeves

[0069] 13 non-magnetic ring

[0070] 14 connection

[0071] 15 Magnetic coil

[0072] 16 sealing caps

[0073] 17 Plain bearing bushing

[0074] 18 actuator rod

[0075] 20 Valve block

[0076] 21 Cavity

[0077] 22 support covers

[0078] 23 Connecting element

[0079] 24 return springs

[0080] 25 additional return springs

[0081] 26 valve pistons

[0082] 27 more valve pistons

[0083] 28 fluid lines (especially hydraulic channels)

[0084] L Axial direction

[0085] R Radial direction

[0086] Qflow rate

[0087] U control voltage

Claims

File: 28337 WO / CAH - 13 - Patent claims 1. Electromagnetic actuator (10) for a bidirectional proportional valve (1) comprising an actuator rod (18) aligned along a longitudinal axis L and suitable and intended to be connected to a valve piston (26, 27) of the proportional valve (1), a valve armature (2) mounted on the actuator rod (18), a solenoid coil (15) arranged radially around the valve armature (2), a magnetic sleeve (12) arranged radially between the solenoid coil (15) and the valve armature (2), and a non-magnetic ring (13) interrupting the magnetic sleeve (12) in the longitudinal direction L. wherein the actuator (10) is designed such that by appropriate electrical control of the solenoid coil (15) the valve armature (2) and thus the actuator rod (18) can be moved along the longitudinal axis L due to the resulting magnetic field, both in one direction and in the opposite direction, characterized in that that the valve armature (2) is constructed from several ring-shaped or disc-shaped elements arranged in a row along the longitudinal axis L, wherein at least one of the elements is a permanent magnet (4), at least one element is a magnetic disk (3) with the same diameter as the permanent magnet (4) and at least one element is a magnetic auxiliary element (5) with a diameter between 40% and 85% of the diameter of the permanent magnet (4).

2. Actuator (10) according to claim 1 characterized by that the valve armature (2) comprises two elements of the same diameter, which are a permanent magnet (4), and an element which is arranged in the middle between these, and which is a magnetic disk (3), preferably with the same diameter as the permanent magnet (4).

3. Actuator (10) according to claim 1 or 2 characterized by this, File: 28337 WO / CAH - 14 - that the valve armature (2) includes another magnetic disk (3) which has the same diameter as the permanent magnet and which is arranged not between, but to the side of the permanent magnets (4).

4. Actuator (10) according to any of the preceding claims characterized by that the valve armature (2) comprises one or more additional magnetic elements (5) with a diameter between 40% and 85% of the diameter of the permanent magnet (4).

5. Actuator (10) according to claim 4 characterized by that the magnetic accessories (5) all have the same diameter.

6. Actuator (10) according to claim 4 characterized by that each magnetic additional element (5) adjacent to the permanent magnets (4) has a larger diameter than the other magnetic additional element (5).

7. Actuator (10) according to any of the preceding claims characterized by that only on one side of the permanent magnet(s) (4) one or more additional magnetic elements (5) with a diameter between 40% and 85% of the diameter of the permanent magnet (4) are arranged.

8. Actuator (10) according to one of claims 1 to 6 characterized by that one or more additional magnetic elements (5) with a diameter between 40% and 85% of the diameter of the permanent magnet (4) are arranged on both sides of the permanent magnet(s) (4). File: 28337 WO / CAH - 15 - 9. Actuator (10) according to any of the preceding claims characterized by that the valve armature (2) is constructed asymmetrically along the longitudinal axis L with respect to the magnetic additional elements (5).

10. Actuator (10) according to one of claims 1 to 8 characterized by that the valve armature (2) is symmetrically constructed of several elements along the longitudinal axis L with respect to the magnetic additional elements (5).

11. Bidirectional proportional valve (1) comprising a valve block (20) with several fluid lines (28), at least one valve piston (26, 27) which is arranged in a cavity (21) of the valve block (20) and can be moved linearly back and forth along a longitudinal axis L, further comprising an electromagnetic actuator (10) which is connected via an actuator rod (18) to at least one valve piston (26, 27) such that the movement of the actuator rod (18) is transmitted directly or indirectly to the valve piston (26, 27) in such a way that the fluid lines (28) are connected to each other or shut off from each other, wherein the opening between the fluid lines (28) can also be selectively throttled, characterized by that the electromagnetic actuator (10) is designed according to one of the preceding claims.

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