Solenoid valve

Abstract

The invention relates to a solenoid valve (1), in particular for electrically continuously adjustable shock absorbers of a vehicle, having a valve body (2) which separates a working chamber (3) from a compensating chamber (4) and has an aperture (6) which can be closed by a slide (5) and connects the working chamber (3) to the compensating chamber (4), having an energisable coil (8) that is arranged on a coil former (7), a pole tube (9) which is arranged at least in regions within the coil former (7), and a magnet armature (11) which is mounted movably in the pole tube (9) with respect to a longitudinal axis (10) of the coil (8), wherein the magnet armature (11) acts on the slide (5), with the result that the aperture (6) of the valve body (2) can be reversibly closed by means of a movement of the magnet armature (11). In order to be able to achieve a desired characteristic particularly precisely and at the same time to ensure easy production, according to the invention a pin is provided which is mounted movably in the valve body (2), which pin is acted on by the magnet armature (11), on the one hand, and by a working pressure of the working chamber (3), on the other hand, even in the closed state of the valve.

Description

[0001] solenoid valve

[0002] The invention relates to a solenoid valve, in particular for electrically continuously adjustable shock absorbers of a vehicle, with a valve body which separates a working chamber from a compensation chamber and has a diaphragm which can be closed by a slide and which connects the working chamber to the compensation chamber, a coil which is arranged on a coil body and can be energized, a pole tube which is arranged at least partially within the coil body and a magnet armature which is mounted in the pole tube so as to be movable with respect to a longitudinal axis of the coil, wherein the magnet armature acts on the slide so that the diaphragm of the valve body can be reversibly closed by a movement of the magnet armature.

[0003] Solenoid valves of the type mentioned above are known from the prior art. They feature an orifice through which a working chamber is fluidically connected to a compensation chamber, such that when the orifice is open, fluid can flow from the working chamber through the orifice into the compensation chamber. When the solenoid valve is used on a shock absorber, the working chamber is usually part of the shock absorber, so that by changing the orifice, flow resistance or pressure loss between the working chamber and compensation chamber can be changed in order to make the damper harder or softer by changing the valve position. Thus, by changing the valve position of the solenoid valve, the orifice in a vehicle's shock absorber can be opened or closed depending on a current in the coil, usually proportional to a current in the coil, whereby damper behavior can be changed by actuating the solenoid valve.

[0004] The disadvantages of state-of-the-art solenoid valves have been found to be that, on the one hand, they can only be manufactured with great effort and, on the other hand, a desired characteristic curve is sometimes difficult to achieve when used in a damper.

[0005] This is where the invention comes in. The object of the invention is to provide a solenoid valve of the type mentioned above that is easy to manufacture and simultaneously enables a specific, desired damping characteristic to be achieved when used in a shock absorber.

[0006] This object is achieved according to the invention by a solenoid valve of the type mentioned at the outset, in which a pin is provided which is movably mounted in the valve body and on which pin the magnet armature acts on the one hand and a working pressure of the working chamber on the other hand, even when the valve is in the closed state.

[0007] The pin is usually mounted in the valve body so as to be movable approximately parallel to the stroke direction of the magnet armature, along which the armature is movable in the pole tube. The pin usually penetrates the valve body or projects through an opening, in particular a bore, in a wall of the valve body, which wall delimits the working chamber, so that when the orifice is closed, a force acts on the magnet armature via the pin, the magnitude of which depends on a pressure difference between the working pressure in the working chamber and the pressure in the compensation chamber, as well as the diameter of the pin. In this way, by selecting a diameter, a characteristic curve of the solenoid valve or shock absorber can be set very easily, wherein the solenoid valve according to the invention can also be manufactured using very simple means.

[0008] It is advantageous if a spring is provided which connects the valve body to the slide, by means of which a force acts on the slide when the solenoid valve is closed in the direction of a position in which the orifice is released by the slide. The spring thus creates a solenoid valve which is open when de-energized. In this way, a design is achieved in which a position of the magnet armature increases continuously along a stroke direction with increasing current strength, preferably proportional to the current strength, so that a positioning of the magnet armature, and thus a position of the slide relative to the orifice, can be precisely specified via the current strength. The stroke direction is defined as a movement of the magnet armature in a direction in which the slide closes the orifice. The stroke direction is usually parallel to the longitudinal axis of the pole tube.A movement of the solenoid armature opposite to the stroke direction thus causes the orifice to open. This makes it possible to specifically influence the valve characteristic by changing the current strength. The orifice opens or closes to a predefined degree, thereby achieving a desired pressure drop across the orifice, which makes it easier or more difficult for hydraulic fluid to flow from the working chamber into the compensation chamber.

[0009] To achieve a desired characteristic curve of the solenoid valve, it is often desirable to design the solenoid valve such that the pole tube conducts a magnetic flux to varying degrees along an axial extent within the coil body, so that the magnetic flux is, so to speak, forced into the magnet armature in certain areas. For this purpose, it is known from the prior art to design the pole tube in several parts, for example, from document EP 3 524 847 B1. However, it has been shown that it is more advantageous if the pole tube is designed in one piece, with the pole tube extending, in particular, over the entire axial extent of the coil body.

[0010] When the solenoid valve is used in a shock absorber, pressurized hydraulic fluid is usually present in an area within the pole tube where the magnet armature is movably arranged. A multi-part pole tube is therefore disadvantageous in that the pole tube no longer seals the space containing the hydraulic fluid from the coil body, which is why prior art solenoid valves with split pole tubes require additional sealing. However, this can be omitted if the pole tube is constructed in one piece over the entire axial extent of the coil body. In order to simultaneously achieve certain magnetic properties in the pole tube, it can also be constructed with a cross-section of varying thicknesses even with a one-piece design.

[0011] It is advantageous if the pole tube has a stroke range that is longer than the magnet armature and within which the magnet armature can move, whereby the stroke range is preferably located within an axial extension of the coil body. The stroke range thus corresponds to the range in which the magnet armature can move, so that the length of the stroke range generally corresponds to the length of the magnet armature plus a possible stroke of the magnet armature. The magnet armature can be moved within the stroke range along or against a stroke direction, which stroke direction is usually parallel to the longitudinal axis of the pole tube. A movement in the stroke direction causes the valve to close, and a movement of the magnet armature against the stroke direction causes the valve to open.

[0012] In order to achieve a movement of the magnet armature in the pole tube with particularly low resistance, it is advantageous if the pole tube has a constant inner contour in the stroke area, in particular a cylindrical surface.

[0013] To achieve the desired movement of the magnet armature when the coil is energized in a particularly efficient manner, it is preferably provided that the pole tube has a taper in the stroke area. This ensures that the magnetic circuit closes via the magnet armature, which is thus moved along the stroke direction when the coil is energized.

[0014] It is preferably provided that the taper extends to a slide-side end of the stroke range.

[0015] It is preferably provided that the taper extends over less than 50 percent of an axial extent of the stroke range in order to achieve a particularly efficient movement of the magnet armature.

[0016] It is advantageous if the taper is designed in such a way that the taper appears approximately V-shaped in an axial section.

[0017] In order to be able to produce the taper in a simple manner without changing an inner contour of the pole tube, it is preferably provided that an outer diameter of the pole tube is reduced in the region of the taper.

[0018] It is advantageous if the wall thickness of the pole tube in the area of ​​the taper is at least partially less than 50 percent, in particular less than 30 percent, of the maximum wall thickness of the pole tube in the stroke area.

[0019] For example, the pole tube can be essentially tubular with a wall thickness of approximately 6 mm, which tapers to less than 1.5 mm in some areas. This results in poor conductivity of the pole tube with respect to the magnetic flux in the taper area, so that the magnetic circuit is closed via the magnet armature, while simultaneously providing a seal against the coil body despite the reduced wall thickness.

[0020] To prevent relative movement between the pole tube and the coil former, the space between the pole tube and the coil former is typically filled with potting compound, at least in some areas, especially in the area of ​​a tapered section. A plastic that is not magnetically conductive is typically used as the potting compound.

[0021] In order to achieve a certain characteristic of the solenoid valve, as a force on the magnet armature depending on a current through the coil, it can be advantageous if an insert, in particular a ring, is inserted into the pole tube.

[0022] The insert is a separate component that is typically inserted into the pole tube after the magnet armature has been positioned in the pole tube. The insert can be connected to the pole tube by gluing, welding, soldering, or a press fit, for example, to achieve low magnetic resistance between the pole tube and the insert.

[0023] Preferably, the insert, in particular a ring, is made of a magnetic material, in particular the same material as the pole tube. The magnetic circuit can then be closed via the pole tube, the magnet armature, and the insert, which is preferably designed as a ring. By varying the design parameters for the magnet armature, the pole tube, and the ring, a wide variety of possibilities exist for achieving a desired characteristic curve.

[0024] If the insert is designed as a ring, it is preferably provided that a rotation axis of the ring is coaxial with a longitudinal axis of the pole tube.

[0025] Particularly preferably, the insert axially defines a stroke range, preferably at a slide-side end of the stroke range. It is advantageous if a shoulder is arranged at a slide-side end of the magnet armature, with a contour of the shoulder corresponding to an inner contour of the insert. Thus, the magnetic circuit can be closed via the magnet armature and the shoulder attached to it, as well as the ring.

[0026] The magnet armature and insert are preferably designed to be rotationally symmetrical to the longitudinal axis of the pole tube, although in principle a different cross-section would also be possible, for example a square cross-section.

[0027] It is advantageous if a shoulder length corresponds approximately to the length of a stroke by which the magnet armature can be moved in the pole tube.

[0028] As a rule, the pole tube, the magnet armature and the ring are matched to one another in such a way that the shoulder is arranged essentially axially outside the insert when the aperture is open and essentially axially inside the insert when the aperture is closed.

[0029] It has proven effective for the pole tube to be made of a magnetic material, particularly steel. The pin can be designed in a variety of ways, each of which is suitable for transferring a force acting on the pin due to a working pressure in the working chamber to the slider and, via the slider, to the magnet armature.

[0030] In order to achieve particularly simple manufacture, it is preferably provided that the pin has a substantially cylindrical element on which a stop element, in particular a spring washer or a press ring, is arranged.

[0031] The diameter of the pin can, for example, depend on the desired characteristic curve of the shock absorber for which the solenoid valve is used, and can be between 0.5 mm and 5 mm, preferably between 0.2 mm and 2 mm. With a higher vehicle mass, a harder damper setting is desired, which requires a smaller pin diameter. In principle, the pin could also be formed as a single piece with a stop. However, manufacturing such a component, which must meet very high accuracy requirements in terms of cylindricity and diameter tolerances, is very complex. For this reason, it has proven useful to form the pin in two parts, namely with a cylindrical element on which a separate stop element is arranged. If the stop element is designed as a spring washer, this can be very easily pressed onto the cylindrical element, creating a force-fitting connection.

[0032] A particularly cost-effective way to manufacture the pin is to use a needle roller as the cylindrical element. Needle rollers are manufactured in large quantities for rolling bearings, with high precision in terms of diameter tolerances and cylindricity, so these components, which are available at very low cost, are ideal for forming the pin. A spring washer, for example, can then be pressed onto a corresponding needle roller, providing a stop for the pin and preventing it from passing through the opening in the valve body into the working chamber.

[0033] It is therefore preferred that the stop element is non-positively connected to the cylindrical element.

[0034] It is advantageous if a distance between the stop element and the valve body in the open state of the valve corresponds at least to a stroke by which the magnet armature can be moved in the pole tube.

[0035] Further features, advantages, and effects of the invention will become apparent from the following exemplary embodiments. Reference is made to the drawings, which show:

[0036] Fig. 1 shows a first embodiment of a solenoid valve according to the invention in a sectional view;

[0037] Fig. 2a to 2c different states of the solenoid valve of Fig. 1;

[0038] Fig. 3 shows another embodiment of a solenoid valve;

[0039] Fig. 4 Characteristic curves of a shock absorber depending on a valve position. Fig. 1 shows a first embodiment of a solenoid valve 1 according to the invention in a sectional view. As can be seen, the solenoid valve 1, which is preferably used for electrically continuously adjustable shock absorbers of a vehicle, has a valve body 2 which separates a working chamber 3 from a compensation chamber 4. The valve body 2 has a plurality of orifices 6 formed by openings which can be closed by a slide 5. When the orifices 6 are closed by the slide 5, a pressure difference across the orifices 6 is changed, so that an overflow of hydraulic fluid from the working chamber 3 into the compensation chamber 4 is made more difficult or easier, whereby a characteristic of the shock absorber can be changed.

[0040] To actuate the slide 5, a magnetic armature 11 is provided, which is mounted in a pole tube 9 for movement parallel to a stroke direction 15. To actuate the magnetic armature 11, the pole tube 9 is arranged in a coil body 7, which carries a coil 8, so that by energizing the coil 8, the magnetic armature 11 can be moved in the stroke direction 15.

[0041] Thus, when current is applied to the coil 8, a magnetic flux is generated through the pole tube 9. The pole tube 9 has a taper 16 in the region of a slide-side end of a stroke range 14, at which the magnet armature 11 is movable, so that the magnetic flux is forced into the magnet armature 11 and thus causes the magnet armature 11 to move.

[0042] Despite the taper 16, the pole tube 9 is formed in one piece, so that the pole tube 9 seals an inner area of ​​the solenoid valve 1 filled with hydraulic fluid from the coil body 7 and no separate seal is required.

[0043] As can be seen, a ring 18 is arranged at a slide-side end of the stroke range 14 in the pole tube 9, which ring forms a stop for a magnet armature 11. A length of the ring 18 in the direction of the longitudinal axis 10 of the pole tube 9, i.e. in the axial direction or in the stroke direction 15, corresponds approximately to a stroke of the magnet armature 11. The magnet armature 11 also has a shoulder 24 at its end, which corresponds to the dimensions of the ring 18, so that the shoulder 24 can slide into the ring 18. In the open situation of the solenoid valve 1 shown in Fig. 1, in which the slide 5 does not close the orifice 6, the shoulder 24 of the magnet armature 11 is arranged almost completely outside the ring 18.When the valve is closed, the shoulder 24 lies axially within the ring 18 and is separated from the ring 18 only by an air gap of one or a few millimeters, in particular less than 1 mm, preferably 0.05 mm to 0.8 mm, so that the magnetic circuit can also be closed via the magnet armature 11 and the ring 18.

[0044] As can be seen, the magnetic armature 11 acts on the slide 5, which is connected to the valve body 2 via a spring 13. Thus, when the valve is closed or when the orifice 6 is closed by the slide 5, the spring 13 exerts a force on the magnetic armature 11 opposite to the stroke direction 15, so that the magnetic armature 11 assumes the open position shown in Fig. 1 when de-energized.

[0045] In addition, when the valve is closed, the working pressure prevailing in the working chamber 3 also acts on the slide 5 and the magnet armature 11 via a pin 12 which is movably mounted in the valve body 2, counter to the stroke direction 15. Accordingly, the magnet armature 11 is opened via pin 12 at constant current and increasing pressure in the working chamber 3 until an equilibrium between magnetic force 20, spring force 21 and force via pin 12 is established, whereby a damping behavior can be set.

[0046] To achieve particularly cost-effective manufacturing while maintaining high precision, the pin 12 is formed by a needle roller onto which a press ring is pressed. The press ring forms a stop so that the needle roller cannot slide through the bore in the valve body 2, in which the needle roller is mounted, into the working chamber 3.

[0047] At one end of the pole tube 9, which is opposite the slide-side end, the pole tube 9 is fixed in a housing 25 by means of a casting compound 17. Furthermore, at this end, which is opposite the slide-side end, a plug 19 is visible, via which the coil 8 can be supplied with power.

[0048] Fig. 2a to 2c show the solenoid valve 1 of Fig. 1 in different operating states.

[0049] Fig. 2a shows an open state of the solenoid valve 1, in which the slide s does not close the orifice 6. This operating state occurs, for example, when the coil 8 is de-energized.

[0050] In Fig. 2a the forces essentially acting on the slide 5 are also shown, namely a magnetic force 20 which is exerted by the armature when the coil 8 is energized in the direction of a closing movement of the slide 5 or a stroke direction 15, a spring force 21 which is exerted by the spring 13 against the stroke direction 15 on the slide 5, and a pin force 22 which acts on the slide 5 via a cross-sectional area of ​​the pin 12 and a working pressure in the working chamber 3 from the pin 12, also against the stroke direction 15.

[0051] Furthermore, Fig. 2a shows a flow direction or a flow 23 of a fluid from the working chamber 3 through the orifice 6 into the compensation chamber 4 as an example.

[0052] Fig. 2b shows a state between fully open and closed solenoid valve 1, for example, at a current corresponding to 50 percent of a maximum current, where the maximum current can be, for example, 1.8 amperes. In this state, the orifice 6 is 50 percent closed by the slide 5.

[0053] Fig. 2c shows another operating state, in which the aperture 6 is completely closed by the slide 5. This operating state corresponds to a state of maximum current through the coil 8, for example, a current of 1.8 amperes. In this state, a maximum-hard damping characteristic curve is thus obtained.

[0054] Fig. 3 shows a further embodiment of a solenoid valve 1 according to the invention. In contrast to the solenoid valve 1 shown in Fig. 1 to 2c, here only the plug 19 for energizing the coil 8 is not arranged above, but at an end of the pole tube 9 opposite the slide-side end.

[0055] Fig. 4 shows, by way of example, a diagram with different damper characteristics of a shock absorber on which a solenoid valve according to the invention is arranged, wherein a volume flow of the hydraulic fluid via the orifice 6 is entered on an abscissa and a pressure loss across the orifice 6 is entered on an ordinate. The different damper characteristics shown result depending on the position of the solenoid valve 1, wherein a lowest characteristic curve shown in a dash-dotted line corresponds to an open solenoid valve position, i.e. a de-energized situation of the solenoid valve, and a top characteristic curve shown in a solid line corresponds to a characteristic when the solenoid valve 1 is completely closed, i.e. when the coil 8 is energized with maximum current.A middle characteristic curve, which is drawn in dashed lines, shows a damper characteristic curve which results when the aperture is half open, for example when the current through the coil is 50 percent of a maximum current.

[0056] With a solenoid valve 1 according to the invention, a desired characteristic curve, in particular of a shock absorber, can be achieved in a particularly simple and simultaneously highly precise manner, especially since both a taper 16 of the pole tube 9 and the dimensions of the ring 18 are available as design parameters, each of which influences the characteristic curve. At the same time, the solenoid valve 1 according to the invention can be manufactured very easily and cost-effectively thanks to the possibility of producing the pin 12, in particular using a needle roller.

Claims

Claims 1. A solenoid valve (1), in particular for electrically continuously adjustable shock absorbers of a vehicle, comprising a valve body (2) which separates a working chamber (3) from a compensation chamber (4) and has a diaphragm (6) which can be closed by a slide (5) and which connects the working chamber (3) to the compensation chamber (4), a coil (8) which can be energized and is arranged on a coil body (7), a pole tube (9) arranged at least partially within the coil body (7), and a magnet armature (11) which is movably mounted in the pole tube (9) with respect to a longitudinal axis (10) of the coil (8), wherein the magnet armature (11) acts on the slide (5) so that the diaphragm (6) of the valve body (2) can be reversibly closed by a movement of the magnet armature (11), characterized in that a pin (12) which is movably mounted in the valve body (2) is provided,on which pin (12) the solenoid armature (11) and a working pressure of the working chamber (3) act on the one hand, even when the valve is closed.

2. Solenoid valve (1) according to claim 1, characterized in that a spring (13) is provided which connects the valve body (2) to the slide (5), by means of which spring a force acts on the slide (5) in the closed state of the solenoid valve (1) in the direction of a position in which the aperture (6) is released by the slide (5).

3. Solenoid valve (1) according to claim 1 or 2, characterized in that the pole tube (9) is formed in one piece, wherein the pole tube (9) extends in particular over an entire axial extent of the coil body (7).

4. Solenoid valve (1) according to one of claims 1 to 3, characterized in that the pole tube (9) has a stroke range (14) which is longer than the magnet armature (11) and in which stroke range (14) the magnet armature (11) is movable, wherein the stroke range (14) is preferably located within an axial extension of the coil body (7).

5. Solenoid valve (1) according to claim 4, characterized in that the pole tube (9) has a constant inner contour in the stroke area (14), in particular a cylindrical surface.

6. Solenoid valve (1) according to claim 4 or 5, characterized in that the pole tube (9) has a taper (16) in the stroke area (14).

7. Solenoid valve (1) according to claim 6, characterized in that the taper (16) extends to a slide-side end of the stroke range (14).

8. Solenoid valve (1) according to claim 6 or 7, characterized in that the taper (16) extends over less than 50 percent of an axial extent of the stroke range (14).

9. Solenoid valve (1) according to one of claims 6 to 8, characterized in that the taper (16) appears approximately V-shaped in an axial section.

10. Solenoid valve (1) according to one of claims 6 to 9, characterized in that an outer diameter of the pole tube (9) is reduced in the region of the taper (16).

11. Solenoid valve (1) according to one of claims 6 to 10, characterized in that a wall thickness of the pole tube (9) in the region of the taper (16) is at least partially less than 50 percent, in particular less than 30 percent, of a maximum wall thickness of the pole tube (9) in the stroke region (14).

12. Solenoid valve (1) according to one of claims 1 to 11, characterized in that a space between the pole tube (9) and the coil body (7) is at least partially filled with casting compound (17), in particular in the region of a taper (16).

13. Solenoid valve (1) according to one of claims 1 to 12, characterized in that an insert, in particular a ring (18), is inserted into the pole tube (9).

14. Solenoid valve (1) according to claim 13, characterized in that the insert consists of a magnetic material, in particular of the same material as the pole tube (9).

15. Solenoid valve (1) according to claim 13 or 14, characterized in that the insert axially delimits a stroke range (14), preferably at a slide-side end of the stroke range (14).

16. Solenoid valve (1) according to one of claims 13 to 15, characterized in that a shoulder (24) is arranged on a slide-side end of the magnet armature (11), wherein a contour of the shoulder (24) corresponds to an inner contour of the insert.

17. Solenoid valve (1) according to claim 16, characterized in that a shoulder length corresponds approximately to a length of a stroke by which the magnet armature (11) is movable in the pole tube (9).

18. Solenoid valve (1) according to claim 16 or 17, characterized in that the shoulder (24) is arranged substantially outside the insert when the aperture (6) is open and substantially inside the insert when the aperture (6) is closed.

19. Solenoid valve (1) according to one of claims 1 to 18, characterized in that the pole tube (9) consists of a magnetic material, in particular of a steel.

20. Solenoid valve (1) according to one of claims 1 to 19, characterized in that the pin (12) has a substantially cylindrical element on which a stop element, in particular a spring washer or a press ring, is arranged.

21. Solenoid valve (1) according to claim 20, characterized in that the cylindrical element is formed by a needle roller 22. Solenoid valve (1) according to claim 21, characterized in that the stop element is non-positively connected to the cylindrical element.

23. Solenoid valve (1) according to one of claims 1 to 22, characterized in that a distance between the stop element and the valve body (2) in the open state of the valve corresponds at least to a stroke by which the magnet armature (11) is movable in the pole tube (9).

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