SOLENOID VALVE

Description

[0001] The invention relates to a solenoid valve with a valve housing in which an electrical coil and a magnetic armature are arranged, and with a valve element that can be actuated by the magnetic armature in an axial actuation direction for opening and closing the solenoid valve. The electrical coil, when supplied with energy, generates a magnetic flux that forms a magnetic circuit which is closed via the valve housing and the magnetic armature, thereby exerting a magnetic force on the magnetic armature. This force attracts the magnetic armature axially in the direction of the coil in order to open or close the valve element. The coil is arranged on a coil carrier, and an end section of the coil carrier axially facing the magnetic armature is designed as an end stop for the magnetic armature to limit axial movement of the magnetic armature and thus limit the stroke of the valve element. The coil is at least partially integrated into the coil carrier.The invention further relates to an internal combustion engine.

[0002] Internal combustion engines often use electromagnetically actuated injection or injection valves to supply liquid or gaseous fuels to the combustion chamber. These valves are commonly referred to as solenoid valves. Solenoid valves offer the advantage over conventional mechanically actuated valves that they allow for highly flexible valve control, independent of the engine speed. For example, the opening time, duration, and lift of the valve can be variably controlled, thus increasing the degree of freedom in fuel metering. Large engines, particularly large gas engines, frequently employ a pre-chamber principle, in which the gaseous fuel is not fed directly into the combustion chamber, but rather into a pre-chamber located upstream of it. The combustible gas / air mixture is then ignited in the pre-chamber, typically by means of spark plugs and / or compression.Starting in the pre-chamber, the combustion process spreads into the associated combustion chamber. On one side of the solenoid valve, which in its assembled state faces the combustion chamber or pre-chamber, at least one valve opening is typically provided in the valve housing, which is closed by a valve element. By appropriately controlling the solenoid valve, the valve opening is opened and closed as desired to introduce a specific quantity of fuel into the combustion chamber or pre-chamber.

[0003] Such solenoid valves typically feature a valve housing containing an electrical coil that can be energized to generate a magnetic field. A movable magnetic armature is also included, which is usually moved axially by the generated magnetic field. The valve element is typically connected to and actuated by the magnetic armature. When the solenoid valve is actuated by applying a voltage to the electrical coil, the magnetic armature and the associated valve element move, opening the valve and allowing fuel to be injected into the combustion chamber or pre-chamber. The fuel is usually pre-compressed to a specific pressure and supplied to the solenoid valve via a suitable feed port.Most solenoid valves also contain a return spring against which the magnetic armature is moved, ensuring that the valve opening closes again even if the power supply fails after the solenoid valve has been actuated.

[0004] Such solenoid valves are known, for example, from EP 1 517 341 A2, US 2002 / 0000529 A1, US 2019 / 211786 A1.

[0005] To limit the valve stroke, i.e., the distance the valve element can travel, to a specific maximum value, a stroke limiter is usually integrated into the valve, typically in the form of one or more separate components. A disadvantage of this is that these stroke limiting devices require a corresponding amount of installation space within the valve, which is generally very limited anyway. Furthermore, the associated material and manufacturing costs are also a disadvantage. DE 10 2012 224240 A1, for example, discloses a solenoid valve with a magnetic assembly comprising a coil and a magnetic core, as well as a magnetic armature interacting with it. The magnetic assembly is arranged on a support element that has an outer pole ring and an inner pole ring. A shoulder can be provided on the side of the outer pole ring facing the magnetic armature, which serves as an armature stop.

[0006] It is therefore an object of the invention to provide a solenoid valve that is as simple and compact as possible and in which the valve stroke can be limited in a simple way.

[0007] The object is achieved according to the invention in that the coil carrier is made of a plastic and the magnetic conductivity of the coil carrier is negligibly low compared to the other parts forming the magnetic circuit, so that the magnetic flux of the magnetic circuit runs radially inside the coil, axially through a first valve housing section, axially below the coil via a second valve housing section adjoining the first valve housing section and extending radially outwards, from the second valve housing section via a third valve housing section adjoining it radially outwards, and is closed via the movable magnetic armature.The plastic coil carrier reduces the noise and mechanical stress on the magnetic armature and the end section when the magnetic armature hits the end section of the coil carrier, whereby, due to the magnetically non-conductive coil carrier, the magnetic flux is closed not via the coil carrier, but via the valve housing with the magnetic armature.

[0008] The coil is at least partially integrated into the coil carrier, for example, by being at least partially encased in plastic. Preferably, the coil is completely integrated into the coil carrier, for example, by being encased in plastic. This provides a simple way to limit the valve stroke without the need for separate components.

[0009] Preferably, when the solenoid valve is actuated, the coil generates a magnetic flux that flows to the magnetic armature via a magnetically conductive outer wall of the valve housing. A magnetically conductive flux element is provided in the valve housing, which directs at least a portion of the magnetic flux flowing across the outer wall of the valve housing into an end face of the magnetic armature facing the coil. This reduces the lateral forces acting on the magnetic armature, thereby minimizing frictional losses of the solenoid valve.

[0010] In order to advantageously guide the magnetic flux into the magnetic armature, the flux element is preferably arranged transversely to the direction of actuation between the outer wall of the valve housing and the end section of the coil carrier, and in the direction of actuation between the coil and the magnetic armature.

[0011] The flux element is preferably designed as a flux ring, particularly preferably as a closed flux ring. This allows the magnetic flux to be advantageously introduced into the magnetic armature at any point in the circumferential direction. Furthermore, a flux ring is easy to manufacture.

[0012] Preferably, the flux element has a higher magnetic conductivity than the outer wall of the valve housing, so that the magnetic resistance is reduced and as much of the magnetic flux as possible can be directed into the end face of the magnetic armature.

[0013] It has proven particularly advantageous if the flow element has a cross-section in the form of a trapezoid, preferably a right-angled trapezoid, because this allows a large contact area to be formed with the outer wall of the valve housing.

[0014] Advantageously, the valve housing forms a cylinder in the area of ​​the magnetic armature, and the magnetic armature forms a piston that is axially movable within the cylinder. In the direction of actuation, a compression chamber is formed between a first armature end face of the magnetic armature, facing away from the coil, and an opposing valve housing wall. At least one throttle opening is arranged in the magnetic armature, connecting the first armature end face with an opposing second armature end face. This forms a pneumatic damper that reduces the speed at which the valve element strikes the valve seat.

[0015] Preferably, a sealing element is arranged on the circumferential surface of the magnetic armature to seal the compression chamber in order to improve the effect of the damper.

[0016] Preferably, a valve opening is provided at an axial end of the valve housing, and at least one supply opening for a preferably gaseous medium is provided on the valve housing, which is connected to the valve opening inside the valve housing. This allows the solenoid valve to be advantageously used as a gas injection valve for an internal combustion engine.

[0017] Preferably, the magnetic armature has an armature shaft and the valve element has a valve shaft separate from the armature shaft, wherein, when the solenoid valve is actuated, the magnetic armature actuates the valve shaft via the armature shaft. This decouples the movement of the magnetic armature from the valve element during the closing movement of the solenoid valve, thereby reducing the wear of the valve element and the valve seat.

[0018] Preferably, a plastic buffer element is arranged between the armature shaft and the valve stem. This prevents direct contact between the armature shaft and the valve stem, thereby reducing noise and wear.

[0019] To reduce the friction losses of the solenoid valve, it is advantageous if the buffer element is made of a tribologically optimized plastic, preferably a plastic containing polytetrafluoroethylene (PTFE).

[0020] Preferably, a spring element is arranged in the valve housing, which exerts a restoring force on the valve element to hold the valve element in the closed position when the solenoid valve is not actuated. This ensures that the valve is closed as soon as the power supply to the coil is interrupted.

[0021] The problem is further solved with an internal combustion engine having a cylinder head and at least one combustion chamber by arranging at least one solenoid valve according to the invention on the cylinder head to supply a preferably gaseous fuel to the combustion chamber or to a pre-chamber located upstream of the combustion chamber.

[0022] The present invention is described below with reference to the Figur 1 This is explained in more detail, and it shows, by way of example, schematically and without limitation, an advantageous embodiment of the invention. It shows Fig.1 A sectional view of an electromagnetically actuated actuator in the form of a valve.

[0023] In Fig.1 Figure 1 shows an advantageous embodiment of the solenoid valve 1 according to the invention. The illustrated solenoid valve 1 is designed as a dry-running solenoid valve 1, which is intended to inject a gaseous fuel into the combustion chamber or a pre-chamber upstream of the combustion chamber of an internal combustion engine (not shown). The solenoid valve 1 has a valve housing 2, which here is essentially cylindrical and has a valve axis A. To the left of the valve axis A, the solenoid valve 1 is shown in the closed state, and to the right of the valve axis A, in the open state. A mounting section B is provided at a first axial end E1 of the valve housing 2, here in the form of a thread, with which the solenoid valve 1 can be attached to a cylinder head (not shown) of an internal combustion engine. Of course, other types of mounting would also be possible.

[0024] An electrical coil 3 is provided in the valve housing 2, extending in a ring shape around the central valve axis A. The coil 3 can be supplied with energy in the form of an electrical voltage or an electric current via suitable electrical connections (not shown) in order to generate an (electro)magnetic field in a known manner. Depending on the design of the solenoid valve 1, the connections can, for example, be located radially on the outside of the valve housing 2 or at a second axial end E2 of the valve housing 2, opposite the first axial end E1. The coil 3 need not be a single piece; several coil segments could also be arranged distributed around the valve axis A and be electrically connected.

[0025] The coil 3 is arranged on a coil carrier 4, which is essentially annular in design analogous to the coil 3 and is arranged in a designated annular opening in the valve housing 2. According to the invention, the coil carrier 4 is made of a suitable plastic and is therefore essentially non-conductive magnetically. "Essentially" means that the magnetic conductivity of the coil carrier 4 is negligibly low compared to the other parts forming the magnetic circuit M. The coil 3 is at least partially integrated into the coil carrier 4, so that the coil 3 is at least partially surrounded by the coil carrier 4. However, the coil 3 can also be completely integrated into the coil carrier, for example, by encasing the coil 3 in the plastic, so that only the electrical connections of the coil 3 (not shown) are appropriately routed out of the coil carrier 4.The coil 3 and the coil carrier 4 therefore preferably form a single component.

[0026] A magnetic armature 5 is arranged in the valve housing 2 and is movable in an axial actuation direction in the direction of the valve axis A. The magnetic armature 5 interacts magnetically with the coil 3 to actuate the valve and has an armature end face 5A facing the coil 3 for this purpose. In the illustrated example, the magnetic armature 5 is essentially cylindrical, with a first axial armature end face 5A facing away from the coil 3 and a second armature end face 5B facing the coil 3, as well as a circumferential armature surface 5U. A central cylindrical armature shaft 6 is arranged on the magnetic armature 5, for example, on the second armature end face 5B in the illustrated example. This shaft is guided axially within a cylindrical opening in the valve housing 2 and is movable in the axial direction synchronously with the magnetic armature 5.The armature shaft 6 can be formed in one piece with the magnetic armature 5 or connected to the magnetic armature 5 in another suitable manner.

[0027] A valve opening 9 is arranged on the valve housing 2 of the solenoid valve 1, specifically at the first axial end E1 of the valve housing 2. The valve opening 9 can be opened and closed by means of a valve element 8, which is actuated by the magnetic armature 5. The valve element 8 is connected to a substantially cylindrical valve stem 7, which extends along the valve axis A inside the valve housing 2. The armature stem 6 and the valve stem 7 can be rigidly connected to each other, for example, as a single piece. Preferably, however, they are designed as separate components so that the movement of the armature stem 6 can be decoupled from the movement of the valve stem 7, as will be explained in more detail below.In the illustrated solenoid valve 1, a spring element 11 is also arranged inside the valve housing 2, which exerts a restoring force on the valve stem 7 and the associated valve element 8, so that the valve element 8 is in the closed position (in . Fig.1 to the left of the valve axis A) returns to close the valve opening 8.

[0028] To actuate the solenoid valve 1, an electric current or voltage is applied to the coil 3, generating a magnetic flux in the coil 3. This magnetic flux exerts an electromagnetic attraction on the magnetic armature 5, causing the armature 5 to move in the actuation direction against the spring force of the spring element 11 towards the coil 3. The armature shaft 6, connected to the magnetic armature 5, presses against the valve stem 7, thereby moving the valve element 8 from the closed position, in which the valve opening 9 is closed (to the left of the valve axis A), to the open position, in which the valve opening 9 is released (to the right of the valve axis A), as indicated by the downward-pointing arrow along the valve axis A. Fig.1 This is indicated. The available travel between the closed position and the open position is also referred to as the valve stroke.

[0029] As soon as the energy supply to coil 3 is interrupted or reaches a sufficiently low level at which the restoring force of the spring element 11 (possibly supported by a pressure force acting on the underside of the valve element 8 in the combustion chamber) exceeds the magnetic attraction of coil 3, the valve element 8 is moved from the open position back to the closed position, as indicated by the upward-pointing arrow along the valve axis A in Fig.1 This has been indicated. Of course, with appropriate control of coil 3, stepless control or regulation of the valve lift would also be possible, allowing valve positions between the closed and open positions to be achieved. For example, it would be conceivable that the valve lift could be continuously controlled or regulated depending on the applied coil voltage or current. This would allow, for instance, the flow rate of the preferably gaseous fuel to be continuously adjusted to a specific, predetermined combustion process.

[0030] The valve element 8 has a substantially conical valve disc 8a, which, in the closed position, seals against a valve seat of the valve housing 2, as shown to the left of the valve axis A. In the open position, the valve element 8 is lifted from the valve seat in the actuation direction and exposes a specific cross-section of the valve opening 9, as shown to the right of the valve axis A. This allows a preferably pre-compressed medium, such as a gaseous fuel, to flow from a feed opening 10, located laterally on the valve housing 2, through the interior of the valve housing 2 to the valve opening 9, as indicated by the arrows in the figure. Fig.1 This is indicated. Of course, several feed openings 10 can also be provided. The medium can be supplied to the feed opening 10, for example, from a storage device (not shown). The medium, e.g., fuel, can be supplied via the valve opening 9 to a combustion chamber or pre-chamber of an internal combustion engine (not shown).

[0031] In the illustrated example, the valve element 8 seals the valve seat from the outside. However, the reverse configuration is also possible, where the valve element 8 is entirely located within the valve housing 2 and seals the valve seat from the inside, as is the case with a known needle valve. The valve seat does not necessarily have to be located directly on the valve housing 2, but could, for example, be formed by a separate valve seat element attached to the valve housing 2. This allows for the advantageous use of different materials for the valve housing 2 and the valve seat element. Since the valve seat is a relatively mechanically stressed area due to the closing movement of the valve element 8, a valve seat ring made of a suitable, low-wear material, such as hardened steel, can be used as the valve seat element.For the remaining valve seat housing 2, a more cost-effective material can preferably be used in this case.

[0032] The spring element 11, which biases the valve element 8 towards the valve seat in the closed state, is designed here as a helical spring that surrounds the valve stem 7 in an annular manner. The helical spring is arranged in a designated space within the valve housing 2, which is also supplied with gaseous fuel. A shoulder is formed on the valve stem 7, to which a disc is attached. The helical spring is arranged axially between the disc and a shoulder in the valve housing and exerts a spring force axially on the valve stem 7, in this case upwards. Of course, other suitable spring elements 11 could also be used, such as disc springs, etc., and it would also be conceivable for the spring element 11 to have a non-linear spring characteristic to influence the opening characteristic of the solenoid valve, such as a progressive or degressive spring characteristic.Of course, the illustrated version is only an example and other versions of the solenoid valve 1 would also be possible.

[0033] The valve stem 7 and the valve element 8 are made of a material suitable for the expected temperatures, forces, and pressures that occur during the operation of the solenoid valve 1. If, for example, a metallic material is chosen, it should also be sufficiently corrosion-resistant to the medium, e.g., a gaseous fuel, for which the solenoid valve 1 is intended.

[0034] When the electrical coil 3 is energized, a magnetic flux is generated, forming a magnetic circuit M. The magnetic circuit M is closed via the valve housing 2 and the magnetic armature 5, as shown in Fig.1 This is indicated. A magnetic force acts on the magnetic armature 5, attracting it axially towards the coil 3, thereby opening (or conversely closing) the valve element 8. The magnetic flux of the magnetic circuit M runs radially within the coil 3 in a substantially axial direction through a first valve housing section 2a, axially below the coil 3 via a second valve housing section 2b adjoining the first valve housing section 2a and extending radially outwards. From the second valve housing section 2b, the magnetic flux runs via a third valve housing section 2c, which adjoins it and simultaneously forms the outer wall of the valve housing 2. The magnetic circuit M is finally closed by the movable magnetic armature 5, which in the example shown is arranged axially above the coil 3. The coil 3 including...The coil carrier 4 is therefore located here in an annular recess, which is formed in a radial direction between the first and third valve housing sections 2a, 2c.

[0035] The valve housing 2, at least in the area around the coil 3 where the magnetic circuit M is formed, is made of a magnetically conductive material, such as a ferromagnetic metal. Preferably, however, the entire valve housing 2 is made of the same ferromagnetic material, which simplifies its manufacture. Similarly, the magnetic armature 5, at least in the area of ​​the magnetic circuit 5, is also made of a magnetically conductive material to close the magnetic circuit 5. Preferably, however, the entire magnetic armature 5 is made of the same material, which simplifies its manufacture.

[0036] The armature shaft 6 is preferably non-magnetically conductive, at least in the region of the magnetic circuit 5, in order to avoid generating disruptive lateral magnetic forces on the armature shaft 6, which could, for example, negatively affect the actuating force of the valve element 8 due to increased friction. The solenoid valve 1 is designed here as a so-called dry-running valve. This means that no separate lubricant is provided for lubricating the moving parts of the solenoid valve 1. Particularly when relatively dry gases are used as fuel, it is advantageous for such dry-running valves to minimize the friction between the armature shaft 6 and the section of the valve housing 2 in which the armature shaft 6 is guided (here, the first housing section 2a).To achieve this, it is therefore particularly advantageous for dry-running valves if no or minimal lateral forces act on the magnetic armature 5 and on the armature shaft 6 in order to reduce friction in the guide of the armature shaft 6.

[0037] Preferably, at least one magnetically conductive flux element 12 is arranged in the valve housing 2 to direct at least a portion of the magnetic flux of the magnetic circuit M flowing across the magnetically conductive outer wall of the valve housing, here the third housing section 2c, into the second armature end face 5B of the magnetic armature 5 facing the coil 3 (or vice versa, depending on the direction of the magnetic flux). Preferably, at least 80%, particularly preferably at least 90%, and especially 100% of the magnetic flux is directed into the magnetic armature 5 via the flux element 12. The flux element 12 is arranged radially, i.e., transversely to the direction of actuation, in a region adjacent to the outer wall 2c of the valve housing 2. The flux element 12 extends radially inwards from the outer wall 2c of the valve housing 2 within the valve housing 2.In the direction of actuation, the flux element 12 is arranged between the coil 3 and the magnetic armature 5.

[0038] By using the flux element 12, a larger proportion of the magnetic flux can flow axially into the magnetic armature 5, or the proportion of the magnetic flux flowing radially from the valve housing outer wall 2c into the magnetic armature 5 is reduced. This reduces lateral forces acting on the magnetic armature 5, thereby reducing frictional forces between the armature shaft 6 and the valve housing 2. This reduction in friction losses subsequently allows the actuation speed of the valve element 8 to be increased, enabling highly dynamic opening and closing operations. It is particularly advantageous if the flux element 12 has a higher magnetic permeability than the valve housing outer wall 2c.This allows the magnetic resistance of the preferred magnetic circuit to be reduced and consequently the proportion of magnetic flux flowing through the flux element 12 into the armature end face 5B to be increased.

[0039] The arrangement of the flux element 12 can advantageously also be used to reduce the radial extent of the solenoid valve 1, for example, the diameter of the valve housing 2, while maintaining essentially the same actuating force of the valve element 8, since the magnetic armature 5 can be made smaller in the radial direction. Alternatively, the actuating force of the valve element 8 could also be increased while maintaining the same size of the solenoid valve 1. At the same time, the efficiency of force generation is also increased, so that a smaller coil 3 can potentially be used. Preferably, the flux element 12, as in the illustrated example, is designed as a preferably closed flux ring, which is arranged radially between an end section 4a of the coil carrier 4 and the outer wall 2c of the valve housing. In the axial direction, the flux ring 12 is arranged between the coil 3 and the magnetic armature 5.The flux element 12 is preferably made of a material with good magnetic conductivity, e.g. made of the same material as the magnetic armature 5 and / or the valve housing 2 or the magnetically conductive section of the valve housing 2.

[0040] According to the invention, an end section 4a of the coil carrier 4, which faces axially towards the magnetic armature 5, is designed as an end stop for the magnetic armature 5. This allows the axial movement of the magnetic armature 5 to be limited, thereby limiting the valve stroke of the valve element 8. In the illustrated example, the flux element 12 is arranged radially between the end section 4a of the coil carrier 4 and the outer wall 2c of the valve housing. Here, the flux element 12 is essentially flush with a step on the inside of the outer wall 2c of the valve housing and flush with an axial end surface of the first housing section 2a facing the magnetic armature 5. The end section 4a of the coil carrier 4 projects beyond the end surface by a certain length I, as shown in Fig.1 This is illustrated. The design of the coil carrier 4, including the end section 4a, allows this length I to be predetermined, thus limiting the valve stroke easily without the need for separate components. The entire coil carrier 4, or at least the end section 4a, could be made of a suitable material, particularly a plastic, with certain spring and / or damping properties. This reduces the noise and mechanical stress on the magnetic armature 5 and the end section 4a when the magnetic armature 5 impacts the end section 4a. This is advantageous for reducing noise emissions and increasing service life.

[0041] When the valve element 8 returns from the open position to the closed position after actuation of the solenoid valve 1, the valve element 8 typically strikes the valve seat due to the restoring force of the spring element 11. This can lead to undesirable noise and increased mechanical stress on both the valve element 8 and the valve seat, potentially resulting in increased wear on the valve element 8 and / or the valve seat. This can be particularly true for spring elements 11 with high restoring forces, which are advantageous for high closing speeds. To prevent this, a further advantageous embodiment of the solenoid valve 1 incorporates pneumatic damping. For this purpose, the valve housing 2 forms a cylinder in the area of ​​the magnetic armature 5, and the magnetic armature 5 forms a piston that is axially movable within the cylinder.In the direction of actuation, a compression chamber KR is formed between the first armature end face 5A of the magnetic armature 5, facing away from the coil 3, and an opposing valve housing wall 2d of the valve housing 2. At least one throttle opening 13 is also arranged in the magnetic armature 5, which connects the first armature end face 5A with an opposing second armature end face 5B. A suitable sealing element for sealing the compression chamber KR is also preferably arranged on the circumferential surface 5U of the magnetic armature 5, for example in the form of a known piston sealing ring or O-ring. Preferably, the valve housing 2 is, as in . Fig.1The illustration also shows a pressure relief opening, in particular a pressure relief bore, which connects the space below the magnetic armature 5 with the space in which the spring element 11 is arranged. This provides pressure relief for the space below the magnetic armature 5, preventing the movement of the magnetic armature 5 from being dampened when the solenoid valve 1 opens. For optimal pressure relief, the pressure relief bore is preferably arranged so that it is aligned with the throttle opening 13.

[0042] This achieves simple and effective damping of the magnetic armature 5 when the solenoid valve 1 closes. The damping characteristic can be influenced by the design of the solenoid valve 1, in particular by the size of the first armature end face 5A, the volume of the compression chamber KR, the effectiveness of the seal of the magnetic armature 5 in the cylinder, and the number, shape, and cross-section of the throttle opening(s) 13. The pneumatic damping reduces the velocity at which the valve element 8 strikes the valve seat to preferably a maximum of 0.5 m / s, thus reducing noise and wear. Preferably, the damping characteristic is selected such that the movement at the beginning of the closing motion is essentially undamped and that the damping only begins shortly before the valve reaches the closed position.This allows the solenoid valve 1 to close quickly while still achieving the gentlest possible contact with the valve seat. Rapid opening and closing of the solenoid valve 1 is advantageous for achieving the most precise flow control of the preferably gaseous medium and for performing multiple sequential opening and closing cycles in a short time.

[0043] Previously, the armature shaft 6 and the valve stem 7 were often rigidly connected, for example, as a single piece or welded together. Particularly in relatively large solenoid valves 1, such as those used in large engines, the moving components of the solenoid valve 1, especially the magnetic armature 5, the armature shaft 6, the valve stem 7, and the valve element 8, have comparatively large masses, which cause inertial forces that are not negligible when the solenoid valve 1 is actuated. Due in particular to the mass of the magnetic armature 5 and the armature shaft 6, an inertial force can therefore occur when the solenoid valve 1 closes, which acts on the valve element 8 via the valve stem 7.In the example shown, when the valve element 8 strikes the valve seat in the closed position, an additional upward pulling force is exerted due to this inertial force, which can have a negative impact on noise generation and on the wear of the valve element and / or the valve seat.

[0044] According to a further advantageous embodiment of the solenoid valve 1, the armature shaft 6 and the valve stem 7 are therefore designed separately, with a buffer element 15 made of plastic advantageously arranged between the armature shaft 6 and the valve stem 7. This separate design allows the movement of the magnetic armature 5, including the armature shaft 6, to be decoupled from the movement of the valve element 8, including the valve stem 7, during the closing movement. This reduces the load on the valve element 8 and the valve seat because, when the solenoid valve 1 closes, only the inertial force of the masses of the valve element 8 and the valve stem 7 acts on the valve element 8 and the valve seat. Furthermore, the arrangement of the buffer element 15 prevents direct, especially metallic, contact between the armature shaft 6 and the valve stem 7, thus minimizing noise generation and wear on the contact surface.

[0045] The buffer element 15 is preferably made of a tribologically optimized plastic, such as a polytetrafluoroethylene (PTFE)-filled plastic, so that the friction between the circumferential surface of the buffer element 15 and the valve housing 2 is as low as possible. This is particularly advantageous for dry-running valves without additional lubricant, because it further improves the efficiency of the solenoid valve 1 and / or increases the actuation force. If the end section 4a of the coil carrier 4 is used as an end stop for the magnetic armature 5, as shown, the buffer element 15 can also be advantageously designed to compensate for any temperature-dependent changes in the valve stroke.For this purpose, a suitable material is used for the buffer element 15, and the buffer element 15 is dimensioned such that the (maximum) valve stroke when the magnetic armature 5 is in contact with the end stop of the coil carrier 4 is as constant as possible across the temperature range. It is sufficient if the compensation is implemented at least within a temperature range expected for the application of the solenoid valve 1.

[0046] Finally, it should be noted that the depicted solenoid valve 1 is of course only an example and is simplified to illustrate the basic structure and function. The specific design, such as dimensions, material selection, design of the valve element 8, etc., is naturally the responsibility of the expert and depends on the application of the solenoid valve 1.

Claims

1. Solenoid valve (1) with a valve housing (2), in which an electric coil (3) and a magnet armature (5) are arranged, and with a valve element (8) which can be actuated by the magnet armature (5) in an axial actuation direction for opening and closing the solenoid valve (1), wherein, when supplied with energy, the electric coil (3) generates a magnetic flux which forms a magnetic circuit (M) which is closed via the valve housing (2) and the magnetic armature (5), thereby exerting a magnetic force on the magnetic armature (5) through which the magnet armature (5) is axially attracted in the direction of the coil (3), in order to open or close the valve element (8), wherein the coil (3) is arranged on a coil carrier (4), wherein an end section (4a), axially facing the magnet armature (5), of the coil carrier (4) is designed as an end stop for the magnet armature (5) in order to limit an axial movement of the magnet armature (5), so as to limit a valve lift of the valve member (8), wherein the coil (3) is at least partially integrated into the coil carrier (4), characterized that the coil carrier (4) is formed from a plastic and the magnetic conductivity of the coil carrier (4) is negligibly small compared to the other parts forming the magnetic circuit (M), in that the magnetic flux of the magnetic circuit (M) runs radially within the coil (3) axial through a first valve housing section (2a), axially below the coil (3) via a second valve housing section (2b) extending radially outwards and adjoining the first valve housing section (2a), from the second valve housing section (2b) via an adjoining, radially outer, third valve housing section (2c) and is closed via the movable magnet armature (5).

2. Solenoid valve (1) according to claim 1, characterized in that the coil (3) is completely integrated into the coil carrier (4), preferably by the coil (3) being encapsulated by the plastic.

3. Solenoid valve (1) according to claim 1 or 2, characterized in that the coil (3) generates the magnetic flux when the solenoid valve (1) is actuated, said magnetic flux flowing to the magnet armature (5) over the magnetically conductive valve housing outer wall (2c) of the valve housing (2), wherein a magnetically conductive flux element (12) is provided in the valve housing (2), said flux element introducing at least part of the magnetic flux flowing over the valve housing outer wall (2c) into an armature end face (5B), facing the coil (3), of the magnetic armature (5).

4. Solenoid valve (1) according to claim 3, characterized in that the flux element (12) is arranged, transversely to the actuation direction, between the valve housing outer wall (2c) and the end section (4a) of the coil carrier (4), and is arranged, in the actuation direction, between the coil (3) and the magnet armature (5).

5. Solenoid valve (1) according to claim 3 or 4, characterized in that the flux element (12) is designed as a preferably closed flux ring.

6. Solenoid valve (1) according to one of claims 3 through 5, characterized in that the flux element (12) has a higher magnetic conductivity than the valve housing outer wall (2c).

7. Solenoid valve (1) according to one of claims 3 through 6, characterized in that the flux element (12) has a cross-section in the form of a trapezoid, and preferably a rectangular trapezoid.

8. Solenoid valve (1) according to one of claims 1 through 7, characterized in that the valve housing (2) forms a cylinder in the region of the magnet armature (5), and the magnet armature (5) forms a piston which is axially movable in the cylinder, wherein, in the actuation direction, a compression space (KR) is formed between a first armature end face (5A), facing away from the coil (3), of the magnet armature (5) and an opposite valve housing wall (2d), wherein at least one throttle opening (13) is arranged in the magnet armature (5) and connects the first armature end face (5A) to an opposite, second armature end face (5B).

9. Solenoid valve (1) according to claim 8, characterized in that a sealing element (14) for sealing the compression space (KR) is arranged on the peripheral surface (5U) of the magnet armature (5).

10. Solenoid valve (1) according to one of claims 1 through 9, characterized in that a valve opening (9) is provided in an axial end (E1) of the valve housing (2), and at least one feed opening (10) for a preferably gaseous medium is provided in the valve housing (2), the feed opening being connected to the valve opening (9) within the valve housing (2).

11. Solenoid valve (1) according to one of claims 1 through 10, characterized in that the magnet armature (5) has an armature shaft (6), and the valve element (8) has a valve shaft (7) which is separate from the armature shaft (6), wherein the magnet armature (5) actuates the valve shaft (7) via the armature shaft (6) when the solenoid valve (1) is actuated.

12. Solenoid valve (1) according to claim 11, characterized in that a buffer element (15) made of plastic is arranged between the armature shaft (6) and the valve shaft (7).

13. Solenoid valve (1) according to claim 12, characterized in that the buffer element (15) is formed from a tribologically-optimized plastic, and preferably from a plastic that contains polytetrafluoroethylene.

14. Solenoid valve according to one of claims 1 through 13, characterized in that a spring element (11) is arranged in the valve housing (2) and exerts a restoring force on the valve element (8) in order to hold the valve element (8) in the closed position when the solenoid valve (1) is in the non-actuated state.

15. Internal combustion engine having a cylinder head and at least one combustion chamber, wherein, on the cylinder head, at least one solenoid valve (1) according to one of claims 1 through 14 is arranged in order to supply a preferably gaseous fuel to the combustion chamber or a prechamber upstream of the combustion chamber.