solenoid valve

Abstract

Dry-running electromagnetic valve (1) comprising a valve housing (2) in which an electric coil (3) and an armature (5) are arranged, and a valve spool (8) which can be operated by the armature (5) in an axial operating direction for opening and closing the electromagnetic valve (1), the coil (3) generating a magnetic flow when the electromagnetic valve (1) is operated, which magnetic flow flows via a magnetically conductive valve housing outer wall (2c) of the valve housing (2) to the armature (5), in order to reduce the friction of the electromagnetic valve, it is provided according to the invention that in the valve housing (2) a magnetically conductive magnetic flux element (12) is provided, which introduces at least 80%, preferably at least 90%, particularly preferably 100% of the magnetic flow flowing through the valve housing outer wall (2c) into an armature end face (5B) of the armature (5) facing the coil (3).

Description

TECHNICAL FIELD

[0001] The invention relates to an electromagnetic valve for gaseous fuel injection into a combustion chamber or a pre-chamber of an internal combustion engine, which electromagnetic valve comprises a valve housing in which an electric coil and an armature are arranged, and a valve plug which can be operated in an axial operating direction by the armature for opening and closing the electromagnetic valve, a magnetic flow being generated by the coil when the electromagnetic valve is operated, which magnetic flow flows via a magnetically conductive outer wall of the valve housing to the armature. Furthermore, the invention relates to an internal combustion engine. BACKGROUND

[0002] In internal combustion engines, fuel injection valves or injection valves, which can be mechanically, hydraulically or electromagnetically operated, are mostly used for delivering liquid or gaseous fuel to a combustion chamber. Fuel injection valves or injection valves, which can be electromagnetically operated, are usually referred to as electromagnetic valves. Electromagnetic valves have the advantage that a very flexible valve control can be achieved independently of the rotational speed of the internal combustion engine. Thus, for example, the opening point in time, the opening duration and the valve stroke can be variably controlled, thereby increasing the degree of freedom in metering the fuel. In large displacement engines, in particular large gas engines, the pre-chamber principle is often used, wherein gaseous fuel is not delivered directly to the combustion chamber, but to a pre-chamber which is arranged in front of the combustion chamber. The combustible fuel / air mixture is then ignited in the pre-chamber, usually by means of a spark plug and / or by compression. The combustion spreads from the pre-chamber to the combustion chamber connected thereto. On the side of the electromagnetic valve which faces the combustion chamber or the pre-chamber in the assembled state, at least one valve port is usually provided on the valve housing, which valve port is closed by a valve plug. By correspondingly actuating the electromagnetic valve, the valve port is opened and closed in the desired manner in order to introduce a quantity of fuel into the combustion chamber or the pre-chamber.

[0003] Common electromagnetic valves usually have a valve housing in which an electric coil is arranged, which can be supplied with electrical voltage in order to generate a magnetic field. Furthermore, a movable armature is provided, which can be moved in the axial direction of the electromagnetic valve by the generated magnetic field. A valve plug is usually connected to the armature and is operated thereby. If the electromagnetic valve is operated by applying electrical voltage to the electric coil, the armature and the valve plug connected thereto are moved and open the valve port in order to inject or inject fuel into the combustion chamber or the pre-chamber. For this purpose, the fuel is usually pre-compressed to a certain pressure and delivered to the electromagnetic valve via a suitable supply port. Usually, a return spring is also provided in the electromagnetic valve, against which the armature is moved, and which ensures that the valve port is closed again even in the event of a power failure after operating the electromagnetic valve.

[0004] Electromagnetic valves for liquid fuels have the advantage that the fuel itself can usually be used as a lubricant for the valve, which is why such valves usually have low friction between the moving parts. For example, a fuel injector for liquid fuels with an electromagnetic actuator is disclosed in EP 2496823 A1. The actuator has a coil and a disc-shaped armature / anchor connected to a valve needle. The fuel pressure in a control chamber above the needle is controlled via the valve needle to lift the needle from the valve seat. Other fuel injectors of the same type are disclosed, for example, in DE 103 12 319 A1 and EP 0604914 A1.

[0005] However, in the case of electromagnetic valves for gaseous fuels, the fuel cannot be used as a lubricant for the valve due to the lack of lubricating properties. Therefore, such valves are usually referred to as so-called dry-running valves without additional lubrication. It is therefore particularly important for electromagnetic valves that are dry-running that, despite the lack of lubricant, low friction is maintained as far as possible in order to achieve the most efficient electromagnetic force generation. For example, DE 112 01 2 003 736 T5 discloses a natural gas injector with a coil and an armature connected to an armature tube. A sealing disc is arranged on the end of the armature tube, with which the valve port is sealed. US 2019032808 A1 also discloses a gaseous fuel injector with a coil arranged in a magnetically conductive coil carrier. An inner armature and an outer armature surrounding the inner armature are also provided in the injector, on which inner armature and outer armature sealing sections for closing the valve port are arranged. SUMMARY

[0006] It is therefore an object of the present application to provide an electromagnetic valve to reduce the friction of a dry-running electromagnetic valve in as simple a manner as possible.

[0007] This object is achieved according to the application in that a magnetically conductive magnetic flux element is provided in the valve housing, which introduces at least 80%, preferably at least 90%, particularly preferably 100% of the magnetic flow flowing through the valve housing outer wall into the armature end face of the armature facing the coil. By means of the magnetic flux element, the magnetic flow can be diverted in an advantageous manner towards the armature, so that the portion of the magnetic flow flowing into the armature from the valve housing outer wall transversely to the operating direction along the operating direction can be reduced. The side forces acting on the armature can thereby be reduced, so that the friction in the guidance of the armature can be reduced.

[0008] In order to introduce the magnetic flow in an advantageous manner into the armature, the magnetic flux element is preferably arranged transversely to the operating direction in a region adjoining the valve housing outer wall of the valve housing and between the coil and the armature in the operating direction.

[0009] The magnetic flux element is preferably configured as a magnetic flux ring, particularly preferably as a closed magnetic flux ring. The magnetic flux can thus be introduced into the armature in an advantageous manner at any position in the circumferential direction. Furthermore, the magnetic flux ring is easy to manufacture.

[0010] Preferably, the magnetic flux element has a higher magnetic permeability than the outer wall of the valve housing, thereby reducing the magnetic resistance and enabling the largest possible portion of the magnetic flux to be introduced into the end face of the armature.

[0011] It has proved to be particularly advantageous if the magnetic flux element has a trapezoidal, preferably a right-angled trapezoidal, cross section, since a large contact surface with the outer wall of the valve housing can be formed in this way.

[0012] The coil is preferably arranged on a coil carrier, wherein an end section of the coil carrier which faces the armature in the axial direction is configured as an end stop for the armature for limiting the axial movement of the armature in the operating position in order to limit the valve stroke of the valve core. The coil carrier is preferably composed of plastic in this case, and the coil is fully integrated in the coil carrier. This provides a simple possibility of limiting the valve stroke without the need for separate components.

[0013] The valve housing advantageously forms a cylinder in the region of the armature, and the armature forms a piston which can be moved axially in the cylinder, wherein a compression chamber is configured between a first armature end face of the armature facing away from the coil and an opposite valve housing wall in the operating direction, wherein at least one orifice is provided in the armature which connects the first armature end face to an opposite second armature end face. A pneumatic damper is thus formed which reduces the speed with which the valve core hits the valve seat.

[0014] Preferably, a sealing element for sealing the compression chamber is provided on the peripheral surface of the armature in order to improve the effect of the damper.

[0015] Preferably, a valve port is provided at an axial end of the valve housing, and at least one supply port for a preferably gaseous medium is provided on the valve housing which connects to the valve port inside the valve housing. The solenoid valve can thus be used advantageously as a gas blow-in valve for an internal combustion engine.

[0016] Preferably, the armature has an armature rod and the valve core has a valve rod, wherein the armature operates the valve rod via the armature rod when the solenoid valve is operated, wherein a damping element made of plastic is provided between the armature rod and the valve rod. The movement of the armature is thus decoupled from the valve core in the closing movement of the solenoid valve, and in this way the wear of the valve core and the valve seat can be reduced.

[0017] Preferably, a damping element made of plastic is arranged between the armature rod and the valve rod. Direct contact between the armature rod and the valve rod is thereby avoided, so that noise generation and wear can be reduced.

[0018] If the damping element is composed of a plastic that is optimized in terms of tribology, preferably a plastic that contains polytetrafluoroethylene, it is advantageous to reduce the frictional losses of the solenoid valve.

[0019] Preferably, a spring element is arranged in the valve housing, which exerts a return force on the valve core in order to hold the valve core in the closed position in the state in which the solenoid valve is not operated. It is thereby ensured that the valve is closed in any case as soon as the supply of power to the coil is interrupted.

[0020] Furthermore, the object is also achieved by an internal combustion engine having a cylinder head and at least one combustion chamber, by the provision of at least one solenoid valve according to the application on the cylinder head for feeding preferably gaseous fuel to the combustion chamber or to a prechamber upstream of the combustion chamber. BRIEF DESCRIPTION OF DRAWINGS

[0021] The application is explained below with reference to the Figure 1 The application is explained below with reference to the

[0022] Figure 1 is a sectional view of an advantageous design of a solenoid valve. DETAILED DESCRIPTION

[0023] Figure 1 An advantageous design of a solenoid valve 1 according to the application is shown in Fig. 1. The solenoid valve 1 shown is designed as a dry-running solenoid valve and is provided for blowing gaseous fuel into a combustion chamber of an internal combustion engine (not shown) or into a prechamber upstream of the combustion chamber. The solenoid valve 1 has a valve housing 2 which is designed here as a substantially cylindrical body and has a valve axis A. The solenoid valve 1 is shown in the closed state on the left of the valve axis A and in the open state on the right of the valve axis A. At a first axial end E1 of the valve housing 2, a fastening section B is provided (which is in the form of a thread here), with which the solenoid valve 1 can be fastened to a not shown cylinder head of an internal combustion engine. Of course, other types of fastening are also possible.

[0024] In the valve housing 2, an electric coil 3 is provided, which extends in a ring shape around the central valve axis A. The coil 3 can be supplied with energy in the form of a voltage or a current via suitable (not shown) electrical terminals in order to generate an (electro)magnetic field in a known manner. The terminals can be provided, depending on the design of the solenoid valve 1, for example at the radially outer side of the valve housing 2 or at a second axial end portion E2 of the valve housing 2 opposite the first axial end portion El. However, the coil 3 does not have to be designed as a unit, but can also be provided in a distributed manner with a plurality of coil segments which are electrically connected to one another. The coil 3 is preferably provided on a coil carrier 4, which is embodied here in a ring shape which is essentially similar to the coil 3 and is arranged in a ring-shaped opening provided for this purpose in the valve housing 2. The coil carrier 4 is preferably non-magnetic. By "essentially" is meant that the magnetic permeability of the coil carrier is negligible compared to the other components of the magnetic circuit M. The coil 3 and the coil carrier 4 are preferably formed as a common component. The coil 3 is here completely integrated in the coil carrier 4, i.e. is completely surrounded by the coil carrier 4, only the not shown electrical terminals of the coil 3 protruding in a suitable manner from the coil carrier 4. The coil carrier 4 can for example be formed from a suitable plastic, with which the coil 3 is for example injection-moulded.

[0025] In addition, in the valve housing 2, an armature 5 is provided, which is movable in an axial operating direction in the direction of the valve axis A. The armature 5 interacts magnetically with the coil 3 for operating the valve and for this purpose has an armature end face 5A facing the coil 3. In the example shown, the armature 5 is designed in the form of a substantially cylindrical body, with an axial first armature end face 5A facing away from the coil 3 and an opposite second armature end face 5B facing the coil 3 and an armature peripheral surface 5U. On the armature 5, for example on the second armature end face 5B in the example shown, a central cylindrical armature rod 6 is provided, which is axially guided in a cylindrical opening of the valve housing 2 and can move in the axial direction in synchronism with the armature 5. The armature rod 6 can be formed integrally with the armature 5 or connected to the armature 5 in another suitable manner.

[0026] In addition, a valve port 9 is provided on the valve housing 2 of the solenoid valve 1, which is provided here at the first axial end E1 of the valve housing 2. The valve port 9 can be opened and closed by a valve core 8, which can be operated by the armature 5. The valve core 8 is connected here to a substantially cylindrical valve rod 7, which extends inside the valve housing 2 along the valve axis A. The armature rod 6 and the valve rod 7 can be rigidly connected to one another, for example designed as one piece. However, it is preferred that they are designed as separate components, so that the movement of the armature rod 6 can be decoupled from the movement of the valve rod 7, as will be explained in more detail below. In the solenoid valve 1 shown, a spring element 11 is also provided inside the valve housing 2, which exerts a restoring force on the valve rod 7 and the valve core 8 connected thereto, so that the valve core 8 returns to a closed position (left of the valve axis A) in the de-energized state of the solenoid valve 1, in order to close the valve port 8. Figure 1

[0027] In order to operate the solenoid valve 1, an electric current or a voltage is applied to the coil 3, wherein a magnetic flow is generated by the coil 3. By means of the magnetic flow, an electromagnetic attraction is exerted on the armature 5, by means of which the armature 5 is moved in the operating direction against the spring force of the spring element 11 in the direction of the coil 3. The armature rod 6 connected to the armature 5 presses the valve rod 7 at the same time, so that the valve core 8 is moved from the closed position, in which the valve port 9 is closed (left of the valve axis A), into the open position, in which the valve port 9 is open (right of the valve axis A), as is represented by the arrow pointing in the direction of the valve axis A in Figure 1

[0028] As soon as the supply of the coil 3 is interrupted or reaches a sufficiently low level, at which the restoring force of the spring element 11 (if necessary, assisted by the pressure acting on the underside of the valve core 8 in the combustion chamber) exceeds the magnetic attraction of the coil 3, the valve core 8 is moved back from the open position into the closed position, as is represented by the arrow pointing in the direction of the valve axis A in Figure 1

[0029] ​​​The valve core 8 has here a substantially conical valve disc 8a, which in the closed position seals against the valve seat of the valve housing 2, as shown on the left of the valve axis A. In the open position, the valve core 8 is lifted from the valve seat in the operating direction and releases the defined cross section of the valve opening 9, as shown on the right of the valve axis A. Thereby, a preferably pre-compressed medium, for example a gaseous fuel, can flow from a supply opening 10, which is here provided on the side of the valve housing 2, through the interior of the valve housing 2 to the valve opening 9, as indicated by the arrow. Of course, a plurality of supply openings 10 can also be provided. The medium, for example, can be delivered to the supply opening 10 from a not shown storage container. The medium, for example fuel, can be delivered via the valve opening 9 to a combustion chamber or a pre-chamber of a not shown internal combustion engine. Figure 1

[0030] In the shown example, the valve core 8 closes the valve seat from the outside, however, the opposite solution is of course also possible, in which the valve core 8 is completely arranged in the valve housing 2 and closes the valve seat from the inside, as in a known needle valve or injector for liquid fuel. The valve seat does not have to be arranged directly on the valve housing 2, but can for example be formed by a separate valve seat element arranged on the valve housing 2. Thereby, it is advantageous that different materials can be used for the valve housing 2 and the valve seat element. Since the valve seat is a region with a high mechanical load due to the closing movement of the valve core 8, as a valve seat element for example a valve seat ring made of a suitable low-wear material, such as a quenched steel, can be used. In this case, a more economical material can preferably be used for the remaining part of the valve housing 2.

[0031] The spring element 11, which pre-tensions the valve core 8 in the closed state in the direction of the valve seat, is here configured in the form of a coil spring, which encloses the valve stem 7 in a ring shape. The coil spring is arranged in a space provided for it in the valve housing 2, which space is also traversed by the gaseous fuel. On the valve stem 7, a shoulder is configured, on which a washer is arranged. In the valve housing, the coil spring is arranged axially between the washer and the shoulder and exerts a spring force axially upward on the valve stem 7 here. Of course, other suitable spring elements 11, such as disc springs, etc., can also be used, and it is also conceivable that the spring element 11 has a non-linear spring characteristic curve, such as a progressive or a decreasing spring characteristic curve, in order to influence the opening behavior of the solenoid valve. Of course, the shown embodiment should only be understood as exemplary, other embodiments of the solenoid valve 1 are also possible.

[0032] ​The valve stem 7 and the valve core 8 are made of a material which is suitable for the expected temperatures, forces and pressures which occur during the operation of the solenoid valve 1. If a metallic material is chosen, for example, this material should in addition also have sufficient corrosion resistance with respect to the media, for example gaseous fuel, which are conventionally used with the solenoid valve 1.

[0033] When the electric coil 3 is supplied with electric current, a magnetic flow is generated which constitutes a magnetic circuit M. The magnetic circuit M is closed via the valve housing 2 and the armature 5, as is indicated in Figure 1 Thereby, a magnetic force acts on the armature 5, which is attracted in axial direction by the magnetic force towards the coil 3, so that the valve core 8 is opened (or vice versa closed). The magnetic flow of the magnetic circuit M here passes in radial direction within the coil 3 in substantially axial direction through the first valve housing section 2a, below the coil 3 in axial direction via the second valve housing section 2b which extends radially outwards and which adjoins the first valve housing section 2a. From the second valve housing section 2b, the magnetic flow extends via the third valve housing section 2c which adjoins the second valve housing section and which is located radially outside, which at the same time constitutes the valve housing outer wall of the valve housing 2. The magnetic circuit M is finally closed via the movable armature 5, which in the example shown is arranged in axial direction above the coil 3. The coil 3 together with the coil carrier 4 is thus located in this case in an annular recess which is configured radially between the first and the third valve housing section 2a, 2c.

[0034] The valve housing 2 is made of a magnetically conductive material, such as a ferromagnetic metal, at least in the region around the coil 3 which constitutes the magnetic circuit M. However, it is preferred that the entire valve housing 2 is made of the same ferromagnetic material, which facilitates the manufacture of the valve housing 2. In a similar manner, the armature 5 is also made of a magnetically conductive material at least in the region of the magnetic circuit 5, in order to close the magnetic circuit 5. However, it is preferred that the entire armature 5 is made of the same material, which simplifies the manufacture.

[0035] However, the armature rod 6 is preferably non-magnetically conductive at least in the region of the magnetic circuit 5, in order not to generate disturbing lateral magnetic forces on the armature rod 6 which, for example due to increased friction, can have a negative effect on the operating force of the valve core 8. The solenoid valve 1 is designed as a so-called dry-running valve, which means that no separate lubricant is provided for lubricating the movable parts of the solenoid valve 1. In particular, if a relatively dry gas is used as fuel, it is important in such a dry-running valve to reduce the friction between the armature rod 6 and the section of the valve housing 2 in which the armature rod 6 is guided, here the first housing section 2a, to a minimum. In order to achieve this, it is therefore advantageous that no or as little lateral force as possible acts on the armature 5 and the armature rod 6, in order to reduce the friction in the guidance of the armature rod 6.

[0036] According to the application, at least one magnetically permeable flux element 12 is therefore provided in the valve housing 2, in order to introduce at least 80%, preferably at least 90%, particularly preferably 100% of the magnetic flow through the magnetically permeable outer wall of the valve housing (here the third housing section 2c) into the second armature end face 5B of the armature 5 facing the coil 3 (or vice versa, depending on the direction of the magnetic flow). The flux element 12 is here arranged radially, i.e. transversely to the operating direction, in a region adjoining the valve housing outer wall 2c of the valve housing 2. The flux element 12 extends radially inwards from the valve housing outer wall 2c in the valve housing 2. The flux element 12 is arranged between the coil 3 and the armature 5 in the operating direction.

[0037] By using the flux element 12, a larger proportion of the magnetic flow can flow axially into the armature 5, or the proportion of the magnetic flow flowing radially from the valve housing outer wall 2c into the armature 5 is reduced. The side forces acting on the armature 5 can thereby be reduced, and the friction between the armature rod 6 and the valve housing 2 can be reduced. By reducing the friction losses, the operating speed of the valve core 8 can in turn be increased, so that very dynamic opening and closing processes can be achieved. It is particularly advantageous if the flux element 12 has a higher magnetic permeability than the valve housing outer wall 2c. The magnetic resistance of the preferred magnetic circuit can thereby be reduced, and the proportion of the magnetic flow flowing into the armature end face 5B via the flux element 12 can be increased.

[0038] This can be used, for example, in an advantageous manner to reduce the radial extension of the solenoid valve 1, here for example the diameter of the valve housing 2, while the operating force of the valve core 8 remains essentially unchanged, since the armature 5 can be designed to be smaller in the radial direction. Alternatively, the operating force of the valve core 8 can also be increased while the structural dimensions of the solenoid valve 1 remain the same. The efficiency of the force generation is also increased, so that a smaller coil 3 can be used, as appropriate. Preferably, the flux element 12 is designed as a preferably closed flux ring, as in the example shown, which is arranged radially between one end section 4a of the coil carrier 4 and the valve housing outer wall 2c. The flux ring 12 is arranged axially between the coil 3 and the armature 5. The flux element 12 is preferably made of a material having a high magnetic permeability, for example of the same material as the armature 5 and / or the valve housing 2 or the magnetically permeable section of the valve housing 2.

[0039] According to a further advantageous design of the solenoid valve 1, the coil 3 is arranged on a coil carrier 4, an end section 4a of the coil carrier 4 which faces the armature 5 in axial direction being configured as an end stop for the armature 5. Thereby, the axial movement of the armature 5 in the operating position can be limited, in order to thereby limit the valve stroke of the valve core 8. In the example shown, the magnetic 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. The magnetic flux element 12 is arranged essentially flush with a step on the inner side of the valve housing outer wall 2c and is arranged flush with an axial end face of the first housing section 2a which faces the armature 5.

[0040] As shown in Figure 1 , the end section 4a of the coil carrier 4 exceeds the end face by a defined length I. By the design of the coil carrier 4 including the end section 4a, this length I can be given in advance, so that the valve stroke can be limited in a simple manner without the need for separate components. Here, the entire coil carrier 4 or at least the end section 4a can be made, for example, of a suitable material which has certain damping properties and / or damping properties. Thereby, the noise and the mechanical load of the armature 5 when it hits the end section 4a can be reduced. This contributes to a reduction of noise emissions and to an increased service life.

[0041] When the valve core 8 is returned from the open position to the closed position after operating the solenoid valve 1, the valve core 8 usually hits against the valve seat due to the return force of the spring element 11. This can lead to an unintended emission of noise on the one hand and to an increased mechanical stress of the valve core 8 and the valve seat, which can lead to an increased wear on the valve core 8 and / or the valve seat. This can be the case in particular with spring elements 11 having a large return force which contributes to a high closing speed. In order to prevent this, according to a further advantageous design of the solenoid valve 1, a pneumatic damping is provided in the solenoid valve 1.

[0042] The valve housing 2 is thereby configured as a cylinder in the region of the armature 5, while the armature 5 is configured as a piston which can move in axial direction in the cylinder. In operating direction, a compression chamber KR is configured between a first armature end face 5A of the armature 5 which faces away from the coil 3 and an opposite valve housing wall 2d of the valve housing 2. Furthermore, at least one throttle opening 13 is provided in the armature 5 which connects the first armature end face 5A with an opposite second armature end face 5B.

[0043] Furthermore, a suitable sealing element, for example in the form of a known piston sealing ring or O-ring, is preferably provided on the peripheral surface 5U of the armature 5 for sealing the compression chamber KR. As shown in Figure 1As is shown in the figures, a pressure relief opening, in particular a pressure relief hole, is preferably provided in the valve housing 2, which connects the space below the armature 5 to the space in which the spring element 11 is arranged. This achieves a pressure relief of the space below the armature 5, in order to avoid a damping of the movement of the armature 5 even when the electromagnetic valve 1 is opened. For a good pressure relief effect, the pressure relief hole is preferably arranged in alignment with the throttle hole 13.

[0044] A simple and effective damping of the armature 5 when the electromagnetic valve 1 is closed is thus achieved, wherein the damping characteristic can be influenced by the design of the electromagnetic valve 1, in particular by the size of the first armature end face 5A, by the volume of the compression chamber KR, the sealing effect of the armature 5 in the cylinder and the number, course and cross section of the throttle holes 13. By means of the pneumatic damping, the speed of the valve core 8 hitting the valve seat can be reduced to preferably a maximum of 0.5 m / s, so that noise and wear can be reduced.

[0045] The damping characteristic is preferably chosen such that a substantially undamped movement is achieved at the beginning of the closing movement and the damping is only started before the closing position is reached. In this way, the electromagnetic valve 1 can be closed quickly and nevertheless a soft landing on the valve seat can be achieved. A quick opening and closing of the electromagnetic valve 1 is advantageous for achieving a precise metering of the preferably gaseous medium and for being able to carry out a plurality of successive opening and closing processes in a short time.

[0046] Hitherto, the armature rod 6 and the valve rod 7 were often rigidly connected to one another, for example made or welded in one piece. In particular in the case of comparatively large electromagnetic valves 1, as they are used for example in large displacement engines, the moving parts of the electromagnetic valve 1, in particular the armature 5, the armature rod 6, the valve rod 7 and the valve core 8 have a large weight, which causes non-negligible inertial forces when the electromagnetic valve 1 is operated. In particular due to the weight of the armature 5 and the armature rod 6, an inertial force arises when the electromagnetic valve 1 is closed, which acts via the valve rod 7 on the valve core 8. In the example shown, when the valve core 8 hits the valve seat in the closed position, an additional upward pulling force arises due to this inertial force, which can have a negative effect on noise generation and wear of the valve core and / or the valve seat.

[0047] According to a further advantageous design of the solenoid valve 1, the armature rod 6 and the valve rod 7 are thus designed separately from one another, wherein advantageously a damping element 15 made of plastic is arranged between the armature rod 6 and the valve rod 7. By virtue of this separate design, the movement of the armature 5 together with the armature rod 6 can be decoupled from the movement of the valve core 8 together with the valve rod 7 in the closing movement. As a result, the load on the valve core 8 and the valve seat can be reduced, since only the inertial forces of the weight of the valve core 8 and the valve rod 7 act on the valve core 8 and the valve seat when the solenoid valve 1 is closed. Furthermore, as a result of the provision of the damping element 15, direct contact, in particular metallic contact, between the armature rod 6 and the valve rod 7 is also prevented, so that in this way noise generation and wear on the contact surfaces can be reduced.

[0048] The damping element 15 is preferably composed of a plastic which is optimized in terms of tribology, for example a plastic filled with polytetrafluoroethylene (PTFE), so that as little friction as possible arises between the peripheral surface of the damping element 15 and the valve housing 2. This is advantageous in particular in the case of a lubricant-free operating valve, since as a result the efficiency of the solenoid valve 1 and / or the operating force can be further improved. If the end section 4a of the coil carrier 4 is used as an end stop for the armature 5, as shown, the damping element 15 can furthermore be designed in an advantageous manner for compensating possible temperature-dependent changes in the valve stroke. To this end, a suitable material is used for the damping element 15, and the damping element 15 is dimensioned such that the (maximum) valve stroke is as temperature- independent as possible when the armature 5 comes to rest on the end stop of the coil carrier 4. It is sufficient here for the compensation to be achieved at least in a temperature range which is expected for the application of the solenoid valve 1.

[0049] Finally, it should be stated that the solenoid valve 1 shown is of course only to be understood as being exemplary and simplified for the purpose of illustrating the basic structure and the principle of action. The specific design structure, such as the dimensions of the valve core 8, the material selection, the design, etc., is of course the responsibility of the person skilled in the art and depends on the field of application of the solenoid valve 1.

Claims

1. A dry running solenoid valve (1) for injecting gaseous fuel into a combustion chamber or a pre-chamber of an internal combustion engine, the solenoid valve comprising: Valve housing (2) in which an electric coil (3) and an armature (5) are arranged, and a valve spindle (8) which can be operated by the armature (5) in an axial operating direction in order to open and close the electromagnetic valve (1), the electric coil (3) generating a magnetic flow when the electromagnetic valve (1) is operated, which flows via a magnetically conductive valve housing outer wall (2c) of the valve housing (2) to the armature (5), characterized in that the armature (5) has an armature rod (6) and the valve spindle (8) has a valve rod (7) which is separate from the armature rod (6), wherein the armature (5) operates the valve rod (7) by means of the armature rod (6) when the electromagnetic valve (1) is operated, and a damping element (15) made of plastic is arranged between the armature rod (6) and the valve rod (7).

2. The electromagnetic valve (1) according to claim 1, characterized in that: The damping element (15) consists of a tribologically optimized plastic.

3. The electromagnetic valve (1) according to claim 2, characterized in that: The damping element (15) consists of a plastic containing polytetrafluoroethylene.

4. The electromagnetic valve (1) according to claim 1, characterized in that: In the valve housing (2) a magnetically conductive flux element (12) is arranged, which introduces at least 80% of the magnetic flow flowing through the valve housing outer wall (2c) into an armature end face (5B) of the armature (5) facing the electric coil (3).

5. The solenoid valve (1) according to claim 4, characterized in that: The flux element introduces at least 90% of the magnetic flow flowing through the valve housing outer wall (2c) into an armature end face (5B) of the armature (5) facing the electric coil (3).

6. The solenoid valve (1) according to claim 5, characterized in that: The flux element introduces 100% of the magnetic flow flowing through the valve housing outer wall (2c) into an armature end face (5B) of the armature (5) facing the electric coil (3).

7. The electromagnetic valve (1) according to claim 4, characterized in that: The flux element (12) is arranged in a region adjoining the valve housing outer wall (2c) of the valve housing (2) transversely to the operating direction and between the electric coil (3) and the armature (5) in the operating direction.

8. The electromagnetic valve (1) according to claim 4 or 7, characterized in that: The flux element (12) is configured as a flux ring.

9. The solenoid valve (1) according to claim 8, characterized in that: The flux element (12) is configured as a closed flux ring.

10. The electromagnetic valve (1) according to any one of claims 4 to 7, characterized in that: The flux element (12) has a higher magnetic permeability than the valve housing outer wall (2c).

11. The electromagnetic valve (1) according to any one of claims 4 to 7, characterized in that: The flux element (12) has a trapezoidal cross section.

12. The solenoid valve (1) according to claim 11, characterized in that: The flux element (12) has a right-angled trapezoidal cross section.

13. The electromagnetic valve (1) according to any one of claims 1 to 7, characterized in that: The electric coil (3) is arranged on a coil carrier (4), an end section (4a) of the coil carrier (4) facing the armature (5) in the axial direction being configured as an end stop for the armature (5) for limiting the axial movement of the armature (5) in the operating position in order to limit the valve stroke of the valve spindle (8).

14. The solenoid valve (1) according to claim 13, characterized in that: The coil carrier (4) consists of plastic and the electric coil (3) is completely integrated in the coil carrier (4).

15. The electromagnetic valve (1) according to any one of claims 1 to 7, characterized in that: The valve housing (2) is configured as a cylinder in the region of the armature (5) and the armature (5) is configured as a piston which can be moved axially in the cylinder, wherein a compression chamber (KR) is configured between a first armature end face (5A) of the armature (5) facing away from the electric coil (3) and an opposite valve housing wall (2d) in the operating direction, wherein at least one throttle opening (13) is arranged in the armature (5) which connects the first armature end face (5A) to an opposite second armature end face (5B).

16. The solenoid valve (1) according to claim 15, characterized in that: A sealing element (14) for sealing the compression chamber (KR) is arranged on a peripheral surface (5U) of the armature (5).

17. The electromagnetic valve (1) according to any one of claims 1 to 7, characterized in that: A valve port (9) is provided at one axial end (E1) of the valve housing (2), and at least one supply port (10) for a medium is provided on the valve housing (2) and is connected to the valve port (9) within the valve housing (2).

18. The solenoid valve (1) according to claim 17, characterized in that: The medium is a gaseous medium.

19. The electromagnetic valve (1) according to any one of claims 1 to 7, characterized in that: A spring element (11) is provided in the valve housing (2) and exerts a return force on the valve core (8) for holding the valve core (8) in a closed position in a state in which the solenoid valve (1) is not operated.

20. An internal combustion engine comprising a cylinder head and at least one combustion chamber, wherein at least one solenoid valve (1) according to any one of claims 1 to 19 is provided on the cylinder head for delivering fuel to the combustion chamber or to a pre-chamber upstream of the combustion chamber.

21. The internal combustion engine of claim 20, wherein: The fuel is a gaseous fuel.

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