Electromagnetic valve

Abstract

To reduce friction of a dry-type electromagnetic valve as easily as possible.SOLUTION: A dry-type electromagnetic valve 1 includes: a valve casing 2 arranging an electric coil 3 and a magnetic movable element 5 inside; and a valve member 8 which is operable by the magnetic movable element 5 in an operation direction of an axial line direction that opens / closes the electromagnetic valve 1. In the valve casing 2, a magnetically conductive magnetic flux member 12 is provided in order for the coil 3 to reduce friction of the dry-type electromagnetic valve 1 causing magnetic flux flowing in the magnetic movable element 5 via a magnetically conductive valve casing outer wall 2c of the valve casing 2 during operation of the electromagnetic valve 1. The magnetic flux member 12 is assumed to introduce to a movable element end surface 5B facing the coil 3 of the magnetic movable element 5 at least 80%, preferably at least 90%, or 100% in particular, of magnetic flux flowing via the valve casing outer wall 2c.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a dry solenoid valve for injecting gaseous fuel into a combustion chamber or pre-combustion chamber of an internal combustion engine, the solenoid valve comprising a valve casing having an electric coil and a magnetic armature disposed therein, and a valve member operable by the magnetic armature in an axial operating direction to open and close the solenoid valve, wherein, when the solenoid valve is operated, the coil generates a magnetic flux that flows through the magnetic armature via a magnetically conductive outer wall of the valve casing.The present invention also relates to an internal combustion engine.

[0002] In internal combustion engines, mechanically, hydraulically, or electromagnetically operated injection or injection valves are often used to supply liquid or gaseous fuel to the combustion chamber. Electromagnetically operated injection or injection valves are commonly referred to as solenoid valves. Solenoid valves have the advantage of providing highly flexible valve control, regardless of the engine's speed. For example, this allows for variable control of the opening time, opening duration, and valve travel, thereby increasing the flexibility in metering fuel. Large engines, particularly large gas engines, often use the pre-chamber principle, in which gaseous fuel is not supplied directly to the combustion chamber but to a pre-chamber located upstream of the combustion chamber. In this case, the combustible gas / air mixture is ignited in the pre-chamber, typically via a spark plug and / or via compression. Combustion begins in the pre-chamber and spreads to the combustion chamber connected to it. In the installed state, the solenoid valve generally has at least one valve opening in the valve housing on the side facing the combustion chamber or pre-combustion chamber, which is closed by a valve element. By controlling the solenoid valve accordingly, the valve opening can be opened or closed as desired, so that a predetermined amount of fuel is introduced into the combustion chamber or pre-combustion chamber.

[0003] In general, solenoid valves typically have a valve casing in which an electric coil is arranged that can be supplied with energy to generate a magnetic field. Furthermore, a movable magnetic armature is provided, which is usually movable in the axial direction of the solenoid valve by the generated magnetic field. A valve member is usually connected to the magnetic armature and operated by the magnetic armature. When the solenoid valve is operated by applying a voltage to the electric coil, the magnetic armature and the valve member connected to the magnetic armature move to open the valve opening, thereby injecting or spraying fuel into the combustion chamber or pre-combustion chamber. For this purpose, fuel is usually pre-compressed to a predetermined pressure and supplied to the solenoid valve through an appropriate supply opening. A return spring is usually also provided in the solenoid valve, against which the magnetic armature is moved. After the solenoid valve is operated, the return spring acts to close the valve opening again even if the energy supply fails.

[0004] Solenoid valves for liquid fuels have the advantage that they usually have low friction between moving parts, since the fuel itself can often be used as a valve lubricant. EP 2 496 823 A1 discloses, for example, a fuel injector for liquid fuels with an electromagnetic actuator. The actuator has a coil and a disk-shaped armature connected to the valve member. The valve member controls the fuel pressure in a control chamber above the nozzle needle, causing the nozzle needle to lift off the valve seat. Other generic fuel injectors are disclosed, for example, in DE 103 12 319 A1 and EP 0 604 914 A1.

[0005] In contrast, in solenoid valves for gaseous fuels, fuel cannot be used as a valve lubricant due to its lack of lubrication properties. Therefore, such valves are often referred to as so-called dry valves, which do not have additional lubrication means. Therefore, especially in the case of dry solenoid valves, it is important to minimize friction despite the lack of lubricant in order to achieve as efficient electromagnetic force generation as possible. For example, German Patent No. 112012003736 discloses a natural gas injector having a coil and an armature connected to an armature tube. A sealing disk that seals the valve opening is arranged at the end of the armature tube. U.S. Patent Application Publication No. 2019032808 also discloses an injector for gaseous fuels, which has a coil arranged in a magnetically conductive coil support. The injector further includes an inner magnetic armature and an outer magnetic armature surrounding the inner magnetic armature. The inner magnetic armature and the outer magnetic armature each have a sealing portion that closes the valve opening.

[0006] SUMMARY OF THE INVENTION The object of the present invention is therefore to reduce the friction of a dry solenoid valve as simply as possible.

[0007] This problem is solved according to the invention by providing a magnetically conductive flux element in the valve housing, which directs at least 80%, preferably at least 90%, and particularly preferably 100% of the magnetic flux flowing through the valve housing outer wall to the end face of the magnetic armature facing the coil. The flux element advantageously redirects the magnetic flux toward the magnetic armature, thereby reducing the amount of magnetic flux flowing from the valve housing outer wall in the operating direction into the magnetic armature transverse to the operating direction. This reduces the lateral forces on the magnetic armature and, as a result, reduces friction in the guides of the magnetic armature.

[0008] In order to guide the magnetic flux advantageously into the magnetic armature, the magnetic flux member is preferably arranged in a region of the valve housing adjacent to the valve housing outer wall transverse to the operating direction and is arranged between the coil and the magnetic armature in the operating direction.

[0009] The flux member is preferably configured as a flux ring, particularly preferably as a closed flux ring, so that the magnetic flux can be introduced into the magnetic armature at any point in the circumferential direction. Furthermore, the flux ring can be easily manufactured.

[0010] Preferably, the magnetic flux member has a higher magnetic permeability than the valve casing outer wall, so that the magnetic reluctance is reduced and the maximum amount of magnetic flux can be introduced to the end face of the magnetic armature.

[0011] It has proven particularly advantageous if the flux element has a cross section in the shape of a trapezoid, preferably a right-angled trapezoid, since this allows a large contact surface to be formed with the outer wall of the valve housing.

[0012] Preferably, the coil is arranged on a coil support, and the end of the coil support facing the magnetic armature in the axial direction is formed as an end stop for the magnetic armature, thereby limiting the axial movement of the magnetic armature to limit the valve stroke of the valve member. Preferably, the coil support is made of plastic, and the coil is completely integrated into the coil support. This achieves a simple means of limiting the valve stroke without requiring a separate component.

[0013] Advantageously, the valve casing forms a cylinder in the region of the magnetic armature, the magnetic armature forming an axially movable piston in the cylinder, a compression chamber being formed between a first armature end face facing away from the coil and the opposite valve casing wall in the operating direction, and at least one throttle opening is arranged in the magnetic armature, connecting the first armature end face with the opposite second armature end face, thereby forming a pneumatic damper that reduces the speed at which the valve member contacts the valve seat.

[0014] Preferably, a seal member for sealing the compression chamber is disposed on the circumferential surface of the magnetic mover, thereby improving the damping effect.

[0015] Preferably, a valve opening is provided at an axial end of the valve housing, which is provided with at least one supply opening for a preferably gaseous medium, which supply opening is connected to the valve opening inside the valve housing, so that the solenoid valve can be used advantageously as a gas injection valve for an internal combustion engine.

[0016] Preferably, the magnetic armature has an armature shaft, and the valve member has a valve shaft, in which case, when the solenoid valve is operated, the magnetic armature operates the valve shaft via the armature shaft, and in which case, a buffer member made of plastic is arranged between the armature shaft and the valve shaft, so that, when the solenoid valve is closed, the movement of the magnetic armature is decoupled from the valve member, thereby reducing wear on the valve member and the valve seat.

[0017] Preferably, a buffer element made of plastic is arranged between the armature shaft and the valve shaft, which prevents direct contact between the armature shaft and the valve shaft, thereby reducing noise and wear.

[0018] In order to reduce the friction losses of the solenoid valve, the buffer element is advantageously made from a tribologically optimized plastic, preferably a plastic containing polytetrafluoroethylene.

[0019] Preferably, a spring element is arranged in the valve casing, which exerts a restoring force on the valve element, thereby keeping it in a closed position when the solenoid valve is in a deactivated state, thereby ensuring that the valve is closed as soon as the coil is deenergized.

[0020] The object is furthermore achieved by an internal combustion engine having a cylinder head and at least one combustion chamber, in which at least one solenoid valve according to the invention is arranged for supplying a fuel, preferably in gaseous form, to the combustion chamber or to a pre-combustion chamber arranged upstream of the combustion chamber.

[0021] The invention will now be explained in more detail with reference to FIG. 1, which shows, by way of example, schematic and non-limiting example, one advantageous configuration of the invention. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view of a solenoid valve in one advantageous configuration;

[0023] FIG. 1 shows one advantageous configuration of a solenoid valve 1 according to the invention. The solenoid valve 1 shown is designed as a dry valve and is intended to inject gaseous fuel into a combustion chamber or a pre-combustion chamber arranged upstream of the combustion chamber of an internal combustion engine (not shown). The solenoid valve 1 has a valve casing 2, which here is substantially cylindrical and has a valve axis A. To the left of the valve axis A, the solenoid valve 1 is shown in a closed state, and to the right of the valve axis A, it is shown in an open state. A first axial end E1 of the valve casing 2 is provided with a mounting part B, here in the form of a screw thread, by means of which the solenoid valve 1 can be mounted to a cylinder head (not shown) of the internal combustion engine. Of course, other types of mounting are also possible.

[0024] An electric coil 3 is provided within the valve casing 2 and extends in an annular manner around the central valve axis A. Energy in the form of a voltage or current can be supplied to the coil 3 via a suitable electrical connection (not shown), which generates an (electro)magnetic field in a well-known manner. Depending on the structural design of the solenoid valve 1, the connection can be located, for example, on the radially outer side of the valve casing 2 or on a second axial end E2 of the valve casing 2 opposite the first axial end E1. However, the coil 3 does not have to be formed as a single piece; it can instead consist of several electrically connected coil segments distributed around the valve axis A. The coil 3 is preferably arranged on a coil support 4, which here is formed substantially annularly like the coil 3 and is arranged in an annular opening provided for this purpose in the valve casing 2. The coil support 4 is preferably non-magnetically conductive. This essentially means that the magnetic conductivity of the coil support 4 is negligibly small compared to the other parts forming the magnetic circuit M. The coil 3 and the coil support 4 preferably form one common component. The coil 3 is here entirely integrated within the coil support 4, i.e. it is surrounded on all sides by the coil support 4, with only the electrical connections of the coil 3 (not shown) being suitably led out from the coil support 4. The coil support 4 may, for example, be made of a suitable plastic which is poured around the coil 3.

[0025] A magnetic armature 5 is also arranged in the valve casing 2, movable in the axial operating direction along the valve axis A. The magnetic armature 5 magnetically cooperates with the coil 3 to operate the valve and has an armature end face 5A facing the coil 3. In the illustrated example, the magnetic armature 5 is substantially cylindrical and has a first axial armature end face 5A facing away from the coil 3, an opposite second armature end face 5B facing the coil 3, and an armature circumferential surface 5U. A central cylindrical armature shaft 6 is arranged in the magnetic armature 5, for example, on the second armature end face 5B in the illustrated example. The armature shaft 6 is axially guided in a cylindrical opening in the valve casing 2 and is axially movable simultaneously with the magnetic armature 5. The armature shaft 6 may be formed integrally with the magnetic armature 5 or may be connected to the magnetic armature 5 in another suitable manner.

[0026] A valve opening 9 is further arranged in the valve casing 2 of the solenoid valve 1, here at the first axial end E1 of the valve casing 2. The valve opening 9 can be opened and closed via a valve member 8 operable by the magnetic armature 5. The valve member 8 is connected to a substantially cylindrical valve stem 7, which extends along a valve axis A inside the valve casing 2. The armature stem 6 and the valve stem 7 may be rigidly connected to each other, for example formed as a single unit. However, they are preferably formed as separate components, which allows the movement of the armature stem 6 to be decoupled from the movement of the valve stem 7, as will be explained in more detail below. The illustrated solenoid valve 1 also includes a spring 11 arranged in the valve casing 2. The spring 11 applies a return force to the valve stem 7 and the valve member 8 connected to it, so that when the solenoid valve 1 is in a non-operated state, the valve member 8 returns to a closed position (to the left of the valve axis A in FIG. 1 ) and closes the valve opening 8.

[0027] To operate the solenoid valve 1, a current or voltage is applied to the coil 3, which generates a magnetic flux. The magnetic flux exerts an electromagnetic attractive force on the magnetic armature 5, which moves the magnetic armature 5 in the operating direction against the spring force of the spring member 11 toward the coil 3. In this case, the armature stem 6 connected to the magnetic armature 5 presses against the valve stem 7, thereby moving the valve member 8 from a closed position (left side of the valve axis A) in which the valve opening 9 is closed to an open position (right side of the valve axis A) in which the valve opening 9 is opened, as indicated by the downward arrow along the valve axis A in FIG. 1 . The available distance between the closed and open positions is also referred to as the valve stroke.

[0028] As soon as the energy supply to the coil 3 is interrupted or the restoring force of the spring element 11 (possibly assisted by the pressure in the combustion chamber acting on the underside of the valve element 8) reaches a sufficiently low level that it overcomes the magnetic attractive force of the coil 3, the valve element 8 returns from the open position to the closed position, as indicated by the upward arrow along the valve axis A in FIG. 1 . Of course, by controlling the coil 3 accordingly, the valve stroke can also be infinitely controlled or adjusted, so that multiple valve positions between the closed and open positions can also be realized. For example, it is conceivable that the valve stroke can be infinitely controlled or adjusted depending on the applied coil voltage or coil current. This makes it possible, for example, to infinitely adapt the flow rate of a fuel, preferably gaseous, to a predetermined set combustion process.

[0029] The valve member 8 has a substantially conical valve plate 8a, which in the closed position (shown to the left of the valve axis A) sealingly abuts against a valve seat in the valve casing 2. In the open position (shown to the right of the valve axis A), the valve member 8 is lifted from the valve seat in the operating direction, freeing a predetermined cross-section of the valve opening 9. This allows a preferably pre-compressed medium, such as a gaseous fuel, to flow through a supply opening 10, which is arranged at the side of the valve casing 2 here, as indicated by the arrow in FIG. 1 , through the interior of the valve casing 2 and toward the valve opening 9. Of course, multiple supply openings 10 may also be provided. The medium can be supplied to the supply opening 10, for example, from a reservoir (not shown). Via the valve opening 9, the medium, for example, a fuel, can be supplied, for example, to a combustion chamber or pre-combustion chamber of an internal combustion engine (not shown).

[0030] In the illustrated example, the valve member 8 closes the valve seat from the outside. However, the opposite variant is also possible, in which the valve member 8 is arranged entirely within the valve casing 2 and closes the valve seat from the inside, as in, for example, well-known needle valves or injectors for liquid fuels. The valve seat does not have to be arranged directly on the valve casing 2, but can instead be formed, for example, by a separate valve seat member arranged on the valve casing 2. This advantageously allows different materials to be used for the valve casing 2 and the valve seat member. Since the valve seat is a relatively highly mechanically loaded area due to the closing movement of the valve member 8, a valve seat ring made of a suitable, low-wear material, such as hardened steel, can be used as the valve seat member. In this case, a less expensive material can be advantageously used for the remaining valve casing 2.

[0031] The spring element 11, which preloads the valve element 8 in the closed position toward the valve seat, is here in the form of a coil spring, which annularly surrounds the valve stem 7. The coil spring is arranged in a space provided for the coil spring in the valve casing 2, through which the gaseous fuel also flows. A shoulder is formed on the valve stem 7, and a disk is arranged on the shoulder. The coil spring is arranged axially between the disk and a step in the valve casing and applies a spring force axially, here upward, to the valve stem 7. Of course, other suitable spring elements 11, such as disc springs, may also be used, and the spring element 11 may have a non-linear spring characteristic curve, for example, a progressive or regressive spring characteristic curve, in order to influence the opening characteristic of the solenoid valve. Of course, it is to be understood that the illustrated configuration is merely exemplary, and other configurations of the solenoid valve 1 are also possible.

[0032] The valve stem 7 and the valve member 8 are manufactured from a material suitable for the anticipated temperatures, forces and pressures that occur during operation of the solenoid valve 1. If a metallic material is selected, this material should also be sufficiently corrosion-resistant to the media in which the solenoid valve 1 is intended to be used, such as gaseous fuels.

[0033] When the electric coil 3 is energized, a magnetic flux is generated that forms a magnetic circuit M. As shown in FIG. 1, the magnetic circuit M is closed via the valve casing 2 and the magnetic armature 5. This causes a magnetic force to act on the magnetic armature 5, which is attracted axially toward the coil 3, thereby opening (or conversely closing) the valve member 8. The magnetic flux of the magnetic circuit M here runs essentially axially through the first valve casing part 2a, radially inside the coil 3, and then axially below the coil 3, through the second valve casing part 2b, which extends radially outward from the first valve casing part 2a. The magnetic flux then runs from the second valve casing part 6b through the radially outward third valve casing part 6c, which simultaneously forms the outer valve casing wall of the valve casing 2. The magnetic circuit M is finally closed via a movable magnetic armature 5, which in the illustrated example is arranged axially above the coil 3. The coil 3 including the coil support 4 is thus mounted here in an annular recess formed radially between the first and third valve casing parts 6a, 6c.

[0034] The valve casing 2 consists of a magnetically conductive material, for example a ferromagnetic metal, at least in the region around the coil 3 where the magnetic circuit M is formed. Preferably, however, the entire valve casing 2 is made of the same ferromagnetic material, which simplifies the manufacture of the valve casing 2. Similarly, the magnetic armature 5 also consists of a magnetically conductive material, at least in the region of the magnetic circuit M, in order to close the magnetic circuit M. Preferably, however, the entire magnetic armature 5 is made of the same material, which simplifies the manufacture.

[0035] Preferably, however, the armature shaft 6 is non-conductive at least in the region of the magnetic circuit 5 to prevent undesirable lateral magnetic forces from being generated towards the armature shaft 6, which could potentially negatively affect the operating force of the valve member 8, for example by increasing friction. The solenoid valve 1 is configured as a so-called dry valve, i.e., no separate lubricant is provided for lubricating the moving parts of the solenoid valve 1. Especially when a relatively dry gas is used as fuel, it is important for such dry valves to minimize friction between the armature shaft 6 and the part of the valve casing 2 in which the armature shaft 6 is guided (here, the first casing part 6a). To achieve this, it is therefore advantageous if there are no or only minimal lateral forces acting on the magnetic armature 5 and the armature shaft 6, in order to reduce friction in the guiding of the armature shaft 6.

[0036] According to the invention, therefore, at least one magnetically conductive flux element 12 is arranged in the valve casing 2, which allows at least 80%, preferably at least 90%, and particularly preferably 100%, of the magnetic flux of the magnetic circuit M flowing through the magnetically conductive valve casing outer wall, here the third casing part 2c, to be guided to the second armature end face 5B of the magnetic armature 5 facing the coil 3 (or in the opposite direction, depending on the direction of the magnetic flux). The flux element 12 is arranged here in the radial direction, i.e. transverse to the operating direction, in the region of the valve casing 2 adjacent to the valve casing outer wall 2c. The flux element 12 extends radially inward from the valve casing outer wall 2c within the valve casing 2. In the operating direction, the flux element 12 is arranged between the coil 3 and the magnetic armature 5.

[0037] The use of the flux member 12 allows a larger amount of magnetic flux to flow axially into the magnetic armature 5, or reduces the amount of magnetic flux that flows radially from the valve casing outer wall 2c into the magnetic armature 5. This reduces the lateral force acting on the magnetic armature 5, thereby reducing the frictional force between the armature shaft 6 and the valve casing 2. This reduction in frictional losses further increases the operating speed of the valve member 8, thereby achieving highly dynamic opening and closing operations. It is particularly advantageous if the flux member 12 has a higher magnetic permeability than the valve casing outer wall 2c. This reduces the magnetic reluctance of the appropriate magnetic circuit, thereby increasing the amount of magnetic flux that flows through the flux member 12 to the armature end face 5B.

[0038] This can be advantageously used, for example, to reduce the radial extension of the solenoid valve 1, e.g., the diameter of the valve casing 2, without substantially changing the operating force of the valve member 8, since the magnetic armature 5 can be made smaller in the radial direction. Alternatively, the operating force of the valve member 8 can be increased for a solenoid valve 1 of the same overall size. At the same time, the force generation efficiency is increased, so that a smaller-sized coil 3 can be used, if necessary. Preferably, the flux member 12 in the illustrated example is configured as a closed flux ring, which is arranged radially between one end 4a of the coil carrier 4 and the outer wall 2c of the valve casing. In the axial direction, the flux ring 12 is arranged between the coil 3 and the magnetic armature 5. The flux member 12 is preferably made of a material with high magnetic permeability, e.g., the same material as the magnetic armature 5 and / or the valve casing 2 or the magnetically permeable parts of the valve casing 2.

[0039] In another advantageous configuration of the solenoid valve 1, the coil 3 is arranged on a coil support 4, the end 4a of which axially faces the magnetic armature 5 being configured as an end stop for the magnetic armature 5. This makes it possible to limit the axial movement of the magnetic armature 5 in the operating position in order to limit the valve stroke of the valve member 8. In the illustrated example, the flux element 12 is arranged radially between the end 4a of the coil support 4 and the outer valve casing wall 2c. The flux element 12 is arranged substantially flush with the inner step of the outer valve casing wall 2c and with the axial end face of the first casing part 2a facing the magnetic armature 5.

[0040] As shown in FIG. 1, the end 4a of the coil support 4 protrudes from the end face by a predetermined length l. This length l can be set by the structural configuration of the coil support 4, including the end 4a, so that the valve stroke can be easily limited without requiring a separate component. In this case, the entire coil support 4 or at least the end 4a can be made of a suitable material, for example, with specific spring and / or damping properties. This reduces the noise generated when the magnetic armature 5 hits the end 4a and the mechanical load on the magnetic armature 5 and the end 4a. This is advantageous for reducing noise generation and increasing the service life.

[0041] When the valve member 8 returns from the open position to the closed position after operation of the solenoid valve 1, the valve member 8 normally abuts against the valve seat due to the restoring force of the spring member 11. This can lead to undesirable noise generation on the one hand and to increased mechanical loads on the valve member 8 and the valve seat on the other hand, which can lead to increased wear on the valve member 8 and / or the valve seat. This may be particularly true for spring members 11 with a large restoring force that is favorable for high closing speeds. To prevent this, in one further advantageous configuration of the solenoid valve 1, the solenoid valve 1 is provided with pneumatic damping means.

[0042] For this purpose, the valve casing 2 forms a cylinder in the region of the magnetic armature 5, which forms an axially movable piston in the cylinder. In the operating direction, a compression chamber KR is formed between a first armature end face 5A of the magnetic armature 5 facing away from the coil 3 and the opposite valve casing wall 2d of the valve casing 2. Furthermore, at least one throttle opening 13 is arranged in the magnetic armature 5, which connects the first armature end face 5A with the opposite second armature end face 5B.

[0043] A suitable sealing member for sealing the compression chamber KR is preferably arranged on the peripheral surface 5U of the magnetic armature 5, for example in the form of a well-known piston seal ring or O-ring. Preferably, a pressure relief opening, in particular a pressure relief hole, is also provided in the valve casing 2, as shown in FIG. 1, connecting the space below the magnetic armature 5 to the space in which the spring member 11 is arranged. This allows pressure relief in the space below the magnetic armature 5 to be achieved, so as to prevent damping of the movement of the magnetic armature 5 even when the solenoid valve 1 is open. For good pressure relief, the pressure relief hole is preferably arranged to align with the throttle opening 13.

[0044] This allows for simple and efficient damping of the magnetic armature 5 when the solenoid valve 1 is closed, the damping characteristics of which can be influenced by the structural design of the solenoid valve 1, in particular the size of the first armature end face 5A, the volume of the compression chamber KR, the effectiveness of the sealing of the magnetic armature 5 in the cylinder and the number, extension and cross-section of the throttle openings 13. Pneumatic damping allows the speed at which the valve member 8 abuts on the valve seat to be reduced, preferably to a maximum of 0.5 m / s, thereby reducing noise and wear.

[0045] Preferably, the damping characteristic is selected so that the closing operation is essentially undamped at the beginning and only damped immediately before the closed position. This allows the solenoid valve 1 to close rapidly, while still achieving the softest possible contact with the valve seat. Rapid opening and closing of the solenoid valve 1 is advantageous for achieving the most accurate possible metering of the gaseous medium and for enabling multiple successive opening and closing operations to be performed in a short time.

[0046] Conventionally, the armature shaft 6 and the valve shaft 7 have often been firmly connected to each other, for example, by being integrally formed or welded. In particular, in the case of a relatively large solenoid valve 1 used in a large engine, the moving components of the solenoid valve 1, particularly the magnetic armature 5, the armature shaft 6, the valve shaft 7, and the valve member 8, have a relatively large mass, generating a non-negligible inertial force when the solenoid valve 1 is operated. Therefore, due to the mass of the magnetic armature 5 and the armature shaft 6, in particular, an inertial force may be generated that acts on the valve member 8 via the valve shaft 7 when the solenoid valve 1 is closed. In the illustrated example, when the valve member 8 abuts against the valve seat in the closed position, this inertial force generates an additional upward pulling force, which may have a negative effect on noise generation and wear of the valve member and / or valve seat.

[0047] Therefore, in another advantageous configuration of the solenoid valve 1, the armature shaft 6 and the valve shaft 7 are formed separately from each other, with a buffer element 15, preferably made of plastic, being arranged between the armature shaft 6 and the valve shaft 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 member 8, including the valve shaft 7, during the closing operation. This reduces the load on the valve member 8 and the valve seat, since only the inertial force of the masses of the valve member 8 and the valve shaft 7 acts on the valve member 8 and the valve seat when the solenoid valve 1 is closed. The arrangement of the buffer element 15 also prevents direct contact, especially metal contact, between the armature shaft 6 and the valve shaft 7, thereby reducing noise generation and wear on the contact surfaces.

[0048] The buffer element 15 is preferably made of a tribologically optimized plastic, such as a plastic filled with polytetrafluoroethylene (PTFE), so that there is minimal friction between the periphery of the buffer element 15 and the valve housing 2. This is particularly advantageous in dry valves without additional lubricants, since it further improves the efficiency and / or increases the operating force of the solenoid valve 1. If the end 4a of the coil support 4 serves 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 so that the (maximum) valve stroke when the magnetic armature 5 abuts against the end stop of the coil support 4 remains as constant as possible over temperature. In this case, it is sufficient for the compensation to be achieved at least within the temperature range to be expected for use of the solenoid valve 1.

[0049] Finally, it should be noted that the illustrated solenoid valve 1 is of course to be understood as merely exemplary and is shown in a simplified form to clarify its basic structure and functional form. The specific structural design, such as the dimensioning, material selection, and design of the valve member 8, are of course left to those skilled in the art and will depend on the field of use of the solenoid valve 1.

Claims

1. A dry solenoid valve (1) for injecting gaseous fuel into a combustion chamber or pre-combustion chamber of an internal combustion engine, comprising: a valve casing (2) having an electric coil (3) and a magnetic armature (5) disposed therein; and a valve member (8) operable in an axial operating direction by the magnetic armature (5) for opening and closing the solenoid valve (1), wherein, when the solenoid valve (1) is operated, the coil (3) generates a magnetic flux that flows through the magnetic armature (5) through a magnetically conductive valve casing outer wall (2c) of the valve casing (2). A solenoid valve (1) is provided in the valve casing (2) with a magnetically conductive flux member (12), which introduces at least 80%, preferably at least 90%, and particularly preferably 100% of the magnetic flux flowing through the valve casing outer wall (2c) to the armature end face (5B) of the magnetic armature (5) facing the coil (3).

2. 2. The solenoid valve (1) according to claim 1, wherein the magnetic flux member (12) is arranged in a region of the valve casing (2) adjacent to the valve casing outer wall (2c) transverse to the operating direction and is arranged between the coil (3) and the magnetic armature (5) in the operating direction.

3. 3. The solenoid valve (1) according to claim 1 or 2, wherein the flux element (12) is preferably configured as a closed flux ring.

4. 4. The solenoid valve (1) according to claim 1, wherein the magnetic flux element (12) has a higher magnetic permeability than the valve casing outer wall (2c).

5. 5. The solenoid valve (1) according to any one of claims 1 to 4, wherein the flux member (12) has a cross section in the shape of a trapezoid, preferably a right-angled trapezoid.

6. 6. The solenoid valve (1) according to claim 1, wherein the coil (3) is arranged on a coil support (4), the end (4a) of the coil support (4) facing the magnetic armature (5) in the axial direction being formed as an end stop for the magnetic armature (5), thereby limiting the axial movement of the magnetic armature (5) in the operating position in order to limit the valve stroke of the valve member (8).

7. 7. The solenoid valve (1) according to claim 6, wherein the coil support (4) is made of plastic and the coil (3) is completely integrated within the coil support (4).

8. 8. The solenoid valve according to claim 1, wherein the valve casing (2) forms a cylinder in the region of the magnetic armature (5), the magnetic armature (5) forming a piston axially movable in the cylinder, a compression chamber (KR) being formed between a first armature end face (5A) of the magnetic armature (5) facing away from the coil (3) and the oppositely positioned valve casing wall (2d) in the operating direction, and at least one throttle opening (13) is arranged in the magnetic armature (5), which connects the first armature end face (5A) with a second armature end face (5B) located on the opposite side.

9. 9. The solenoid valve (1) according to claim 8, wherein a seal member (14) for sealing the compression chamber (KR) is arranged on a peripheral surface (5U) of the magnetic armature (5).

10. 10. The solenoid valve (1) according to claim 1, wherein the axial end (E1) of the valve casing (2) is provided with a valve opening (9), and the valve casing (2) is provided with at least one supply opening (10) for a preferably gaseous medium, which supply opening (10) is connected to the valve opening (9) inside the valve casing (2).

11. 11. The solenoid valve (1) according to claim 1, wherein the magnetic mover (5) has a mover shaft portion (6), the valve member (8) has a valve shaft portion (7) separate from the mover shaft portion (6), and when the solenoid valve (1) is operated, the magnetic mover (5) operates the valve shaft portion (7) via the mover shaft portion (6).

12. 12. The solenoid valve (1) according to claim 11, wherein a buffer element (15) made of plastic is arranged between the armature stem (6) and the valve stem (7).

13. 13. The solenoid valve (1) according to claim 12, wherein the buffer element (15) is made from a tribologically optimized plastic, preferably a plastic containing polytetrafluoroethylene.

14. 14. The solenoid valve (1) according to claim 1, wherein a spring element (11) is arranged in the valve casing (2), and the spring element (11) exerts a restoring force on the valve element (8), thereby keeping the valve element (8) in a closed position when the solenoid valve (1) is in an inoperative state.

15. 15. An internal combustion engine with a cylinder head and at least one combustion chamber, in which at least one solenoid valve (1) according to any one of claims 1 to 14 is arranged for supplying a fuel, preferably in gaseous form, to a combustion chamber or a pre-combustion chamber arranged upstream of the combustion chamber.

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