Gas injector

Abstract

In order to increase the service life of a gas injector (1), a guide bushing (20) is provided in the gas injector (1) and the valve shaft (13) is arranged in the guide bushing (20) in an axially and radially guided manner, the valve shaft (13) is mounted in the housing (2) in an axially movable manner by means of a second link plate (26), and a centring bushing (21) is provided in the gas injector (1), which centring bushing (21) is either fixedly connected to the valve shaft (13) in the region of the second axial end of the valve shaft (13) and has a centring recess (22) in which the first axial end of the magnetic armature shaft (11) is arranged with radial play, or is fixedly connected to the magnetic armature shaft (11) in the region of the first axial end of the magnetic armature shaft (11) and has a centring recess (22) in which the second axial end of the valve shaft (13) is arranged with radial play.

Description

[0001] Gas injector

[0002] The present invention relates to a gas injector with a housing having a gas inlet and a gas outlet, which are connected to each other in the housing by a flow channel, wherein an electromagnet is arranged in the housing which interacts with a magnetic armature of the gas injector to move a valve stem in an axial direction, wherein a valve element is arranged at a first axial end of the valve stem which interacts with a valve seat of the gas injector to open or close the gas injector, wherein the valve element is lifted from the valve seat in an open position to open the gas outlet, and rests against the valve seat in a closed position to close the gas outlet, wherein the magnetic armature has a magnetic armature shaft separate from the valve stem and a first axial end of the magnetic armature shaft acts on a second axial end of the valve stem opposite the first axial end of the valve stem.to move the valve stem, wherein the magnetic armature with the magnetic armature shaft is axially movably mounted in the housing by a first guide plate in the region of a second axial end opposite the first axial end of the magnetic armature shaft, and wherein a spring element is provided in the gas injector which biases the valve stem towards the closed position. The gas injector is intended in particular for use in injecting gaseous fuel into an internal combustion engine, for example, injecting it into a combustion chamber, a pre-chamber, an intake manifold, or an intake tract of the internal combustion engine.

[0003] Internal combustion engines often use electromagnetically actuated gas injectors to supply liquid or gaseous fuels for combustion. In gas engines using gaseous fuels such as compressed natural gas (CNG) or hydrogen, port fuel injection (PFI) is frequently employed. In this case, the gas injector is often referred to as a port fuel valve. The gaseous fuel, at the required pressure, is injected by the gas injector into the intake manifold or intake tract leading to the cylinder of the internal combustion engine. In contrast, there are gas injectors that inject the fuel directly into the cylinder (direct injection, DI).This has the advantage that the injection window can also be extended beyond the closing time of the intake valve, which offers potential in the volumetric power density of the combustion engine (increase in the mixture calorific value in MJ / m). 3(in the cylinder). This also allows for the implementation of post-injection for NOx emission reduction. In large engines, especially large gas engines, a pre-chamber principle is frequently used, in which the gaseous fuel is not fed directly into the combustion chamber. Instead, a portion of the fuel is fed into a pre-chamber located upstream of the combustion chamber, and the majority of the fuel is added via intake manifold injection. The combustible gas / air mixture is then ignited in the pre-chamber, usually by means of spark plugs and / or compression. From the pre-chamber, the combustion spreads into the associated combustion chamber. A gas injector can also be used to inject the fuel into a pre-chamber.

[0004] Electromagnetically actuated gas injectors typically have a housing with at least one valve opening on one discharge side, which can be closed by a movable valve element. An electromagnet is arranged or integrated within the housing, which can be supplied with electrical energy to generate a magnetic field. A movable magnetic armature is also provided, which is usually moved axially by the generated magnetic field along the solenoid valve. The valve element is usually connected to the magnetic armature and actuated by it. When the gas injector is actuated by applying an electrical voltage to the electromagnet, the magnetic armature and the associated valve element move, and the valve opening is opened to release the gaseous fuel.By appropriately controlling the gas injector, the valve opening is opened and closed as desired to release a specific quantity of gaseous fuel. The gaseous fuel is typically pre-compressed to a certain pressure and fed to the gas injector via a suitable feed port. Most gas injectors also incorporate a return spring against which the magnetic armature moves. This spring ensures that the valve opening closes again after the gas injector is activated, particularly in the event of a power failure.

[0005] Direct injection (DI) processes place high demands on mixture formation in the cylinder. Consequently, the gas injector must be capable of highly dynamic operation (in terms of very short switching times), and the leakage requirements are also stricter compared to port fuel injection (PFI) injectors. Furthermore, the loads from temperature and cylinder pressure are more challenging for gas injectors in terms of strength and wear. Finally, the limited installation space in the cylinder head presents a significant challenge due to the proximity of the intake and exhaust valves and the spark plug.

[0006] The gas injector is supplied with gaseous fuel at a predetermined pressure from a fuel rail or via the cylinder head. The injection pressure of the gaseous fuel is typically between 0 and 60 bar differential pressure relative to the ambient pressure. The injection process, and in particular the quantity of gaseous fuel, is controlled by a control unit, specifically via the opening time of the injection valve (injection window). This allows for precise metering of the delivered amount of gaseous fuel.

[0007] The primary requirements for a gas injector are a high flow rate to ensure the necessary gas quantities are delivered within the short possible opening times. Equally important is the gas injector's wear resistance due to the very high switching frequency. Wear resistance is particularly challenging with oil-free gaseous fuels, such as hydrogen, which lack lubrication of the valve components. Minimizing leakage from the gas injector is also crucial to prevent, or at least largely prevent, the escape of gaseous fuel when the injector is closed.

[0008] Gas injectors are therefore subject to high demands regarding wear and the associated service life. Common gas injectors must have service lives in the range of several hundred million switching cycles. The switching frequency of the gas injector is typically in the range of 5 to 20 Hz, depending on the engine speed. It is therefore essential to design the gas injector to be wear-resistant. Wear is primarily caused by relative movement between two contacting components of the gas injector. Critical components are therefore the bearings of the moving parts of the gas injector and the components against which a moving part of the gas injector strikes during opening or closing, often at high speed.

[0009] The object of the present invention is to provide a gas injector with an improved service life.

[0010] This problem is solved according to the invention by providing a guide bushing in the gas injector and by having the valve stem axially and radially guided in the guide bushing, by having the valve stem axially movable in the housing by means of a second guide plate, and by providing a centering bushing in the gas injector which is either fixedly connected to the valve stem in the region of the second axial end of the valve stem and which has a centering recess in which the first axial end of the magnetic armature stem is arranged with radial play, or which is fixedly connected to the magnetic armature stem in the region of the first axial end of the magnetic armature stem and which has a centering recess in which the second axial end of the valve stem is arranged with radial play.

[0011] This type of bearing arrangement for the valve stem and the magnetic armature shaft – essentially a Gerber carrier – results in a particularly low-friction and low-wear bearing arrangement. This is due, firstly, to the fact that the bearing arrangement using the guide plate is very wear-resistant. Secondly, it results from the fact that there is no relative axial movement between the centering bushing and the valve stem or magnetic armature shaft, thus preventing any wear.

[0012] This can reduce wear and tear on the gas injector and increase its service life.

[0013] To create a rigid connection, the valve stem and centering bushing, or the magnetic armature shaft and centering bushing, can be manufactured as a single piece, allowing for a simple design with few components. Alternatively, the centering bushing can be rigidly connected to the valve stem by firmly positioning the second axial end of the valve stem in the centering recess, or the centering bushing can be rigidly connected to the magnetic armature shaft by firmly positioning the first axial end of the magnetic armature shaft in the centering recess. In this design, the valve stem or magnetic armature shaft can be of a simpler design.

[0014] In a particularly preferred embodiment, the centering bushing is rigidly connected to the valve stem in the region of the second axial end of the valve stem, and the second guide plate is connected to the valve stem via the centering bushing. In this configuration, the centering bushing, and thus also the valve stem, is supported in the housing via the second guide plate.

[0015] Advantageously, the valve stem is arranged in a gas volume within the housing, and this gas volume is connected to the gas outlet. The magnetic armature stem has a central recess connected to the gas inlet, and a connecting opening on the magnetic armature stem links this central recess to the gas volume. This central gas flow allows for a simpler geometric and structural design of the electromagnet and magnetic armature, as the gas flow does not need to pass through them. Furthermore, it is advantageous to incorporate a gas damper in the gas injector to reduce opening and closing slam, significantly extending the injector's service life.

[0016] The present invention is explained in more detail below with reference to Figures 1 to 6, which show exemplary, schematic, and non-limiting advantageous embodiments of the invention.

[0017] Fig. 1 shows an embodiment of a gas injector according to the invention.

[0018] Fig. 2 shows a section through the guide bushing,

[0019] Fig. 3 shows an embodiment of a handlebar plate,

[0020] Fig. 4 shows an embodiment of a gas injector according to the invention with a gas damper, Figs. 5a to 5d show embodiments of the arrangement of the second control plate on the valve stem and

[0021] Fig. 6 shows an alternative embodiment of a gas damper of a gas injector according to the invention.

[0022] The gas injector 1 according to the invention is shown in an advantageous embodiment in Fig. 1, although not all of the illustrated features of the gas injector 1 necessarily have to be implemented. The gas injector 1 is preferably used as a direct injector for injecting gaseous fuel into the combustion chamber of an internal combustion engine, or for injecting fuel into a pre-chamber. However, the gas injector 1 could also be used as an injection valve for injecting gaseous fuel into the intake manifold or intake port of the internal combustion engine.

[0023] The gas injector 1 has a housing 2 with a gas inlet 3 and a gas outlet 4, which are connected to each other within the housing 2 by a flow channel 5. The housing 2 can be made in multiple parts if necessary to facilitate the assembly of the gas injector 1. The gas outlet 4 can be closed by a valve element 6. A valve seat 7 is provided at the gas outlet 4. The valve element 6 interacts with the valve seat 7 of the gas injector 1 in a manner known per se to open or close the gas injector 1, wherein the valve element 6 is lifted from the valve seat 7 in an open position O and rests against the valve seat 7 in a closed position C. In Fig. 1, the open position O is shown on one side and the closed position C on the other.

[0024] It should be noted that the design of the valve element 6 and the valve seat 7 is irrelevant to the invention. Likewise, it is irrelevant whether the valve element 6 opens outwards (as in Fig. 1) or inwards. Furthermore, an electromagnet 8 is provided in the housing 2 of the gas injector 1. This electromagnet essentially comprises an electrical coil 9 that can be energized to generate a magnetic field 12. The necessary electrical leads for the electromagnet 8 are not shown in Fig. 1. These leads can be arranged and routed arbitrarily on the gas injector 1.

[0025] The gas injector 1 also has a magnetic armature 10 in its housing 2, the magnetic armature 10 being arranged to be axially movable (in the direction of the longitudinal axis of the gas injector 1) within the housing 2. During operation of the gas injector 1, the electromagnet 8 interacts with the magnetic armature 10 of the gas injector 1 to actuate the gas injector 1, i.e., to open or close it. The magnetic armature 10 is attracted by the magnetic field 12 generated by the electromagnet 8, which allows the magnetic armature 10 to move within the gas injector 1.

[0026] It should be noted, however, that for the invention it is irrelevant how the electromagnet 8 and the magnetic armature 10 are specifically designed and arranged.

[0027] The magnetic armature 10 comprises a magnetic armature shaft 11. The magnetic armature shaft 11 can be formed integrally with the magnetic armature 10, or a magnetic armature shaft 11 can be connected to the magnetic armature 10 (as in Fig. 1) to form an armature assembly. In any case, the magnetic armature 10 and the magnetic armature shaft 11 are always moved together.

[0028] A valve stem 13 is movably arranged in the housing 2. The valve element 6 is arranged at a first axial end of the valve stem 13, which faces the valve seat 7. The valve element 6 and the valve stem 13 can be manufactured as a single piece (as in Fig. 1), but could also be manufactured as separate components.

[0029] The valve stem 13 and the magnetic armature stem 11 are designed separately, i.e., as two distinct components, and are not rigidly connected. A first axial end of the magnetic armature stem 11, facing the valve stem 13, acts on a second axial end of the valve stem 13, opposite the first axial end of the valve stem 13 (with the valve element 6), which also faces the magnetic armature stem 11, in order to move the valve stem 13.

[0030] The axial movement of the magnetic armature 10 causes an axial movement of the magnetic armature shaft 11. This shaft acts on the valve stem 13 to transmit this axial movement to the valve stem 13 and thus to the valve element 6, in the embodiment according to Fig. 1 to open the gas injector 1. It can be provided that the first axial end of the magnetic armature shaft 11 rests against the second axial end of the valve stem 13, as in Fig. 1. In this case, the magnetic armature shaft 11 acts directly on the valve stem 13. However, it is also conceivable that another component, for example a spacer or a radial circumferential web of another component, is arranged between the first axial end of the magnetic armature shaft 11 and the second axial end of the valve stem 13, so that the magnetic armature shaft 11 acts indirectly on the valve stem 13.

[0031] The housing 2 of the gas injector 1 also contains a spring element 14, such as a coil spring as shown in Fig. 1, which biases the valve stem 13 towards the closed position C. The spring element 14 thus ensures that the gas injector 1 is closed and, more importantly, remains closed.

[0032] When the electromagnet 8 is de-energized, the spring element 14 pushes the valve stem 13 into the closed position C. Simultaneously, the magnetic armature stem 11 and the magnetic armature 10 are also moved back to their initial position in the gas injector 1 along with the valve stem 13. Therefore, to open the gas injector 1, the spring force of the spring element 14 must also be overcome.

[0033] It should be noted, however, that for the invention it is irrelevant how the spring element 14 is specifically designed and arranged, in particular on which movable component of the gas injector 1 the spring element 14 acts.

[0034] A magnetic field guide ring 31 can optionally be provided in the gas injector 1. The magnetic field guide ring 31 is, for example, made of an austenitic steel that has no or only extremely low magnetic conductivity. Such a magnetic field guide ring 31 allows the magnetic field 12 to be guided in a controlled manner in order to enable a high magnetic force on the magnetic armature 10 and to prevent or minimize a magnetic short circuit across the housing 2. This magnetic field guide ring 31 can be gas-tightly welded or soldered to the adjacent parts, as indicated in Fig. 1, or arranged in the housing 2 in another suitable manner.

[0035] The gas injector 1 also includes an opening stop 15, against which a moving component of the gas injector 1 abuts axially during opening to define the open position. In the embodiment shown in Fig. 1, the magnetic armature 10 or the magnetic armature shaft 11 of the magnetic armature 10 abuts axially against the opening stop 15. In the embodiment shown in Fig. 1, the opening stop 15 is designed as a disk arranged in the housing 2. Depending on the design of the gas injector 1, however, the opening stop 15 can also be designed differently or arranged in a different location (as in Fig. 4).

[0036] In the embodiment according to Fig. 1, the gaseous medium G is supplied centrally and guided centrally in the gas injector 1 (indicated by the arrows in Fig. 1), although this is not a necessary requirement. For the central gas guidance, the magnetic armature 10 and the magnetic armature shaft 11 are designed with a central recess 16. The central recess 16 is connected to the gas inlet 3, for example, by the magnetic armature shaft 11 being open at the second axial end opposite the first axial end (as in Fig. 1). The valve stem 13 is arranged in a gas volume 17 of the housing 2, the gas volume 17 being connected to the gas outlet 4. The gas volume 17 is also connected to the recess 16 in the magnetic armature shaft 11, for example, via a connecting opening 18 in the shell of the hollow magnetic armature shaft 11, which connects the recess 16 to the gas volume 17.In the case of a disc as an opening stop 15, an opening can optionally be provided in the disc (as in Fig. 1) through which the gaseous medium G can pass. The central gas guide allows for a geometrically simple design of the electromagnet in particular.

[0037] To ensure central gas flow, a sealing element 30, such as an O-ring or a sealing ring (like a piston ring) or a sealing ring combination (e.g. consisting of several sealing rings), can also be provided between housing 2 and magnetic armature 10 or magnetic armature shaft 11.

[0038] It should be noted, however, that the central gas flow is not a necessary condition for the gas injector 1 and that the gaseous medium G can also be guided differently within the gas injector 1. For example, the gaseous medium G could also be fed radially into the gas injector 1 and guided between the housing 2 and the magnetic armature 10 or the magnetic armature shaft 11, or guided differently within the gas injector 1 between the gas inlet 3 and the gas outlet 4.

[0039] Essential to the invention for the gas injector 1 is the type of bearing arrangement for the moving components of the gas injector 1, namely the bearing arrangement of the valve stem 13 and the magnetic armature 10 with the magnetic armature shaft 11. This bearing arrangement is crucial for the wear in the gas injector 1 and thus for its service life. The bearing arrangement according to the invention largely reduces frictional components, thereby reducing wear in the gas injector 1. For this purpose, a guide bushing 20 is provided in the gas injector 1. The valve stem 13 is axially and radially guided in the guide bushing 20. A clearance fit can be provided between the guide bushing 20 and the valve stem 13, for example, to minimize guiding forces and thus friction. Preferably, a clearance of 5 pm to 20 pm is provided. Preferably, the guide bushing 20 is arranged in the region of the first axial end of the valve stem 13, i.e., in the region of the valve element 6.

[0040] Secondly, the valve stem 13 is also supported in the housing 2 by a second guide plate 26. Preferably, the second guide plate 26 is arranged in the region of the second axial end of the valve stem 13.

[0041] The second control plate 26 supports and holds the valve stem 13 in the gas injector 1 and centers the valve stem 13 radially. The second control plate 26 allows the valve stem 13 to move axially back and forth within the housing 2. Simultaneously, the second control plate 26 generates a restoring force during axial deflection, which assists the spring element 24. This restoring force is, however, generally significantly smaller than the spring force of the spring element 14.

[0042] The second control plate 26 can also be designed to absorb most of the lateral forces (in the radial direction) of the spring element 14, because the control plate 26 is rigid in the radial direction. In this case, the second control plate 26 should therefore be positioned close to the point of application of the spring element 14.

[0043] The valve stem 13 is thus supported at a first axial end in the guide bushing 20 and at the other second axial end via the second guide plate 26. The valve stem 13 therefore runs in the guide bushing 20 with virtually no load and with low wear.

[0044] In the area of ​​the second axial end of the valve stem 13, which faces the magnetic armature shaft 11, a centering bushing 21 is provided, which is either firmly connected to the valve stem 13 in the area of ​​the second axial end of the valve stem 13 or is firmly connected to the magnetic armature shaft 11 in the area of ​​the first axial end of the magnetic armature shaft 11, which faces the valve stem 13.

[0045] The centering bushing 21 has a centering recess 22. In the centering recess 22, either the first axial end of the magnetic armature shaft 11, facing the valve stem 13, is arranged with radial play and is axially movable (if the centering bushing 21 is fixedly connected to the valve stem 13), or the second axial end of the valve stem 13, also facing the magnetic armature shaft 11, is arranged with radial play and is axially movable (if the centering bushing 21 is fixedly connected to the magnetic armature shaft 11). The radial play between the centering recess 22 and the magnetic armature shaft 11 or the valve stem 13 is preferably greater than the radial play between the guide bushing 20 and the valve stem 13 and is, for example, 20 pm to 150 pm. The radial play allows the magnetic armature shaft 11 or valve stem 13 to pivot freely within the centering recess 22. Centering recess 22 mounted.This results in a flexible connection between the magnetic armature shaft 11 and the valve shaft 13.

[0046] Due to its fixed arrangement on the valve stem 13 or magnetic armature stem 11, the centering bushing 21 also moves axially with the valve stem 13 or the magnetic armature stem 11.

[0047] The fixed connection of the centering bushing 21 to the valve stem 13 or the magnetic armature shaft 11 can be achieved by designing the centering bushing 21 as a single component with the valve stem 13 (as in Fig. 5d) or as a single component with the magnetic armature shaft 11 (as in Fig. 5c). However, the centering bushing 21 can also be designed as a separate component, as shown in the embodiments of Fig. 1, Fig. 4, Fig. 5a, and Fig. 5b. When the centering bushing 21 is designed as a separate component, the fixed connection can be achieved by firmly arranging the second axial end of the valve stem 13 in the centering recess 22 of the centering bushing 21 or by firmly arranging the first axial end of the magnetic armature shaft 11 in the centering recess 22. For example, the centering bushing 21 can be pressed onto the valve stem 13 or the magnetic armature stem 11.

[0048] Since the magnetic armature shaft 11 and the valve stem 13, and thus necessarily also the centering bushing 21, are moved together, no relative movement in the axial direction occurs between the centering recess 22 and the magnetic armature shaft 11 or the valve stem 13. Therefore, the magnetic armature shaft 11 or the valve stem 13 is essentially friction-free and thus subject to low wear in the centering recess 22.

[0049] Figures 5a to 5d describe possible embodiments of the centering bushing 21 and the arrangement of the second control plate 26. In Figures 5a and 5b, the centering bushing 21 is designed as an independent component and could be rigidly connected either to the valve stem 13 or to the magnetic armature shaft 11. Accordingly, either the magnetic armature shaft 11 is mounted with radial play in the centering recess 22, or the valve stem 13. In Figure 5a, the second control plate 26 is arranged on the valve stem 13 via a spring plate 33, against which the spring element 14 rests, and in Figure 5b via a retaining ring 34. The spring plate 33 and the retaining ring 34 are each rigidly connected to the valve stem 13 and consequently move axially with the valve stem 13. However, it would also be possible to fix the second control plate 26 directly to the valve stem 13.

[0050] In the embodiment according to Fig. 5c, the centering bushing 21 is formed integrally with the magnetic armature shaft 11. The valve stem 13 is arranged with a radial gap in the centering recess 22 of the centering bushing 21. In the embodiment according to Fig. 5d, the centering bushing 21 is formed integrally with the valve stem 13, and the magnetic armature shaft 11 is arranged with a radial gap in the centering recess 22 of the centering bushing 21. In both embodiments, the second guide plate 26 is firmly connected to the valve stem 13 via a retaining ring 34 (as in the embodiment according to Fig. 5b).

[0051] In the embodiment according to Fig. 1 and Fig. 4, the second control plate 26 is rigidly connected to the valve stem 13 via the centering bushing 21. In this case, the centering bushing 21 must therefore be rigidly connected to the valve stem 13, and the magnetic armature shaft 11 is arranged with radial play in the centering recess 22 of the centering bushing 21.

[0052] In the embodiments shown in Figs. 1, 4, 5a, 5c, and 5d, the magnetic armature shaft 11 rests axially against the valve stem 13 in the centering bushing 21 in order to act on the valve stem 13 in the axial direction. However, it would also be conceivable, for example, that a circumferential rib 35 projecting into the centering recess 22 is formed (as in Fig. 5b), against which the valve stem 13 rests on one side and the magnetic armature shaft 11 on the other. Instead of a circumferential rib 35, a spacer could also be provided in the centering recess 22. In these cases, the magnetic armature shaft 11 acts on the valve stem 13 in the axial direction via the circumferential rib 35 (or the spacer).

[0053] In order to also fully support the magnetic armature shaft 11 in the housing 2, a first guide plate 23 is provided, via which the magnetic armature 10 with the magnetic armature shaft 11 is supported in the housing 2 in the area of ​​the second axial end opposite the first axial end of the magnetic armature shaft 11.

[0054] The valve stem 13 and the magnetic armature stem 11 are thus formed in the form of a Gerber carrier by the guide bushing 20, the first and second control plate 23, 26 and the centering bushing 21 and are mounted in the housing 2.

[0055] The first handlebar plate 23 is preferably connected radially to the housing 2 on the outside. For example, the first handlebar plate 23 could be clamped radially to the outside of the housing 2. For this purpose, the handlebar plate 23 could be bonded to the housing 2 radially on the outside, for example by welding or gluing at a weld point 25. A clamping ring 24 can also be provided (as, for example, in Fig. 1) with which the first handlebar plate 23 is axially clamped in the housing 2. However, any other fastening of the first handlebar plate 23 to the housing 2 is conceivable. The first handlebar plate 23 is connected radially to the magnetic armature 10 or the magnetic armature shaft 11 on the inside, for example by welding or pressing it on.

[0056] The first control plate 23 supports and holds the magnetic armature 10 with the magnetic armature shaft 11 on one side within the gas injector 1 and centers the magnetic armature 10 with the magnetic armature shaft 11 radially. The first control plate 23 allows the magnetic armature 10 with the magnetic armature shaft 11 to move axially back and forth within the housing 2. Simultaneously, the first control plate 23 generates a restoring force during axial deflection, which assists the spring element 24. This restoring force is, however, generally significantly smaller than the spring force of the spring element 14. The first control plate 23 can also be designed to absorb any lateral forces from the electromagnet 8. In this case, the first control plate 23 should therefore be positioned close to the magnetic armature 10.

[0057] The magnetic armature shaft 11 is thus pivotally mounted at a first axial end via the centering bushing 21 and at the other second axial end via the first handlebar plate 23.

[0058] The second handlebar plate 26 is preferably connected radially to the housing 2 on the outside. For example, the second handlebar plate 26 could be clamped radially to the outside of the housing 2. For this purpose, the second handlebar plate 26 could be bonded to the housing 2 radially on the outside, for example by welding or gluing it at a weld point 25. A clamping ring 24 can also be provided (as, for example, in Fig. 1) with which the second handlebar plate 26 is axially clamped in the housing 2. However, any other fastening of the first handlebar plate 23 to the housing 2 is conceivable.

[0059] A guide plate 23, 26 is a known component and essentially consists of a radially outer ring 27 and a radially inner ring 28, which are connected to each other by several spring arms 29, as shown in Fig. 3. The guide plate 23, 26 is fastened via the two rings 27, 28. The spring arms 29 are preferably as flexible as possible so that they exert minimal resistance in the axial direction during axial deflection. In the radial direction, the spring arms 29 are sufficiently rigid to ensure stable radial guidance of the magnetic armature 10 with the magnetic armature shaft 11 or the valve stem 13. Of course, the illustrated guide plate is only an example; in particular, the number of spring arms 29 and the design, e.g., the width and radial orientation of the spring arms 29, can be adapted to a desired guiding characteristic.The advantage of the handlebar plate 23, 26 is the particularly low-friction and low-wear bearing, since there are hardly any guiding forces during axial movement, but a sufficiently precise bearing in the radial direction is still ensured.

[0060] The combination described above of the bearing of the valve stem 13 in the guide bushing 20 and by means of the second control plate 26 and the bearing of the magnetic armature stem 11 by means of the first control plate 23, as well as the articulated connection between valve stem 13 and magnetic armature stem 11, results in a particularly low-friction and low-wear bearing of the moving components of the gas injector 1, which can increase the service life of the gas injector 1.

[0061] Fig. 2 shows a section AA through the guide bushing 20, from which it can be seen that at least one axially through-hole 19 is provided on the guide bushing 20, through which the gaseous medium G can flow.

[0062] The magnetic armature 10 with magnetic armature shaft 11 can be made in two parts. In a two-part design, the magnetic armature 10 can be made of a magnetically conductive material and the magnetic armature shaft 11 of a magnetically non-conductive material, in particular plastic. The magnetic armature 10 can be pressed, overmolded (in the case of plastic), or bonded to the magnetic armature shaft 11 to form an armature assembly that moves together. The plastic magnetic armature shaft 11 also allows for a favorable material pairing for the design of a stop, for example, an opening stop 15. For this purpose, the opening stop 15 could be made of metal, and the magnetic armature shaft 11 could bear against the opening stop 15.The two-part design of the magnetic armature 10 with magnetic armature shaft 11 also allows for easy adjustment of the actuating stroke of the gas injector 1 when the magnetic armature shaft 11 comes to rest against the opening stop 15. The axial position of the magnetic armature shaft 11 relative to the magnetic armature 10 determines the actuating stroke and can be easily adjusted during manufacturing. If the opening stop surface has a small axial distance to the axial contact surface (direct or indirect) between the magnetic armature shaft 11 and the valve stem 13, thermal expansion of the magnetic armature shaft 11, especially when made of plastic, has less of an effect on the actuating stroke of the gas injector 1. Therefore, in the embodiment shown in Fig. 1, the opening stop is located near the centering bushing 21.

[0063] An axial contact surface between the magnetic armature shaft 11 and the valve stem 13 can be adapted to reduce contact stresses, particularly on a magnetic armature shaft 11 made of plastic. Fig. 4 shows an embodiment of the gas injector 1 with a gas damper 40. The gas injector 1 is essentially designed like the one described in Fig. 1, which is why these components are not described again. In the embodiment according to Fig. 4, the magnetic field guide ring 31 and the clamping rings 24 are missing, and the opening stop 15 is arranged in a different location and here interacts with the magnetic armature 10.

[0064] The gas damper 40 comprises a compression chamber 41 formed between the magnetic armature 10 and the housing 2. For this purpose, the first sealing element 30 is arranged between the magnetic armature 10 or the magnetic armature shaft 11. A further sealing element 32, such as an O-ring or a sealing ring (e.g., a piston ring) or a combination of sealing rings (e.g., consisting of several sealing rings), is arranged axially spaced between the magnetic armature 10 and the housing 2. The compression chamber 41 is formed between the two sealing elements 30 and 32. The compression chamber 41 is thus bounded by the magnetic armature 10 or the magnetic armature shaft 11, the housing 2, and the two sealing elements 30 and 32. The compression chamber 41 is connected to the gas inlet 3 via at least one throttle opening 42 in the housing 2. However, the throttle opening can, in principle, be arranged at various locations, for example, also in the magnetic armature 10.

[0065] When the magnetic armature 10 is moved with the magnetic armature shaft 11, causing the compression chamber 41 to enlarge (when the gas injector 1 opens in the embodiment according to Fig. 1 or Fig. 4), a negative pressure is created in the compression chamber 41 because the gaseous medium cannot flow quickly enough into the expanding compression chamber 41 through the throttle opening 42. This negative pressure thus slows down and dampens this movement, for example, the opening movement. When the magnetic armature 10 is moved with the magnetic armature shaft 11, causing the compression chamber 41 to shrink (when the gas injector 1 closes in the embodiment according to Fig. 1 or Fig. 4), a positive pressure is created in the compression chamber 41 because the gaseous medium cannot flow quickly enough out of the shrinking compression chamber 41 through the throttle opening 42. This positive pressure thus slows down and dampens this movement, for example, the closing movement.It is obvious that the damping effect can be adjusted in particular by the dimensioning of the throttle opening 42 or also by the number of throttle openings 42.

[0066] This damping reduces opening shocks at the opening stop 15, as well as closing shocks between valve element 6 and valve seat 7. These shocks are caused by the high opening and closing speeds and represent a high mechanical load on the gas injector 1. The damping reduces the opening and closing speeds, which significantly reduces the mechanical load. It has been shown that a reduction in opening and closing speeds by a factor of 4 increases the service life (in number of switching cycles) of the gas injector 1 by a factor of 20 to 30.

[0067] Fig. 6 shows an alternative embodiment of a gas damper 40 of the gas injector 1. In this embodiment, the first guide plate 26 is designed as a gas-tight diaphragm, so that no gaseous medium can flow through the diaphragm. The compression chamber 41 is thus formed by the diaphragm, the magnetic armature 10 or the magnetic armature shaft 11, the housing 2, and the sealing element 32. The throttle opening 42 is formed here in the magnetic armature 10 or the magnetic armature shaft 11 and connects the central recess 16, and thus also the associated gas inlet 3, with the compression chamber 41. The function of the gas damper 40 is the same as described with reference to Fig. 4.

[0068] From the above description, it is evident that when using the gas injector 1, relative movement occurs between the sealing element 30 (Fig. 1 or Fig. 4) and the magnetic tank 10 or the magnetic armature shaft 11, or between the sealing element 32 (Fig. 4 or Fig. 6) and the housing 2 (or a part of the housing 2) of the gas injector 1. This movement can lead to increased wear of the respective sealing element 30, 32, or the surface against which the sealing element 30, 32 rests. To at least reduce this wear (which helps to increase the service life of the gas injector 1), the surface (on the magnetic tank 10, the magnetic armature shaft 11, or the housing 2) against which the sealing element 30, 32 rests can be modified within the possible range of movement of the sealing element 30, 32.

[0069] It can be provided that the surface (on the magnetic tank 10, the magnetic armature shaft 11, or the housing 2) against which the sealing element 30, 32 rests has increased hardness within the possible range of motion of the sealing element 30, 32 compared to the magnetic tank 10, the magnetic armature shaft 11, or the housing 2 outside this range of motion. To achieve this, a special material, such as hardened steel, can be used in one of these surface areas, or the surface in one of these ranges of motion can be treated. The surface treatment can be carried out by nitriding or by coating. Coating can be carried out, for example, using the known process of physical vapor deposition (PVD). Coating can, for example, apply an amorphous carbon layer (DLC) or a chromium nitride layer.

[0070] In one of the movement ranges of a sealing element 30, 32, an improved surface finish compared to the magnetic tank 10, the magnetic armature shaft 11, or the housing 2 outside this movement range can also be provided. This can be achieved, for example, by honing, fine grinding, or fine turning in this movement range. The improved surface finish can be provided as an alternative to, or in addition to, increased hardness. It is also conceivable not to directly modify the surface of the magnetic tank 10, the magnetic armature shaft 11, or the housing 2 in one of the movement ranges of a sealing element 30, 32, but rather to use a separate bushing that has at least one of these properties.

Claims

Patent claims 1. Gas injector, in particular for use in injecting gaseous fuel into an internal combustion engine, comprising a housing (2) with a gas inlet (3) and a gas outlet (4) which are connected to each other in the housing (2) by a flow channel (5), wherein an electromagnet (8) is arranged in the housing (2) which interacts with a magnetic armature (10) of the gas injector (1) to move a valve stem (13) in an axial direction, wherein a valve element (6) is arranged at a first axial end of the valve stem (13) which interacts with a valve seat (7) of the gas injector (1) to open or close the gas injector (1), wherein the valve element (6) is lifted from the valve seat (7) in an open position (O) to open the gas outlet (4), and the valve element (6) is in a closed position (C) against the valve seat (7) to close the gas outlet (4),wherein the magnetic armature (10) has a magnetic armature shaft (11) separate from the valve stem (13) and a first axial end of the magnetic armature shaft (11) acts on a second axial end of the valve stem (13) opposite the first axial end of the valve stem (13) to move the valve stem (13), wherein the magnetic armature (10) with the magnetic armature shaft (11) is axially movably mounted in the housing (2) by a first guide plate (23) in the region of a second axial end opposite the first axial end of the magnetic armature shaft (11), and wherein a spring element (14) is provided in the gas injector (1) which biases the valve stem (13) in the direction of the closed position (C), characterized in that a guide bushing (20) is provided in the gas injector (1) and the valve stem (13) is arranged axially and radially guided in the guide bushing (20), that the valve stem (13) is guided by a second The handlebar plate (26) is axially movable and mounted in the housing (2).and that a centering bushing (21) is provided in the gas injector (1), which is either fixedly connected to the valve stem (13) in the region of the second axial end of the valve stem (13) and which has a centering recess (22) in which the first axial end of the magnetic armature stem (11) is arranged with radial play, or which is fixedly connected to the magnetic armature stem (11) in the region of the first axial end of the magnetic armature stem (11) and which has a centering recess (22) in which the second axial end of the valve stem (13) is arranged with radial play.

2. Gas injector according to claim 1, characterized in that the valve stem (13) and the centering bushing (21) or the magnetic armature stem (11) and the centering bushing (21) are made in one piece.

3. Gas injector according to claim 1, characterized in that the centering bushing (21) is firmly connected to the valve stem (13) by the second axial end of the valve stem (13) is fixedly arranged in the centering recess (22), or the centering bushing (21) is fixedly connected to the magnetic armature shaft (11) by the first axial end of the magnetic armature shaft (11) being fixedly arranged in the centering recess (22).

4. Gas injector according to one of claims 1 to 3, characterized in that the second control plate (26) is connected to the valve stem (13) via a spring plate (33) on which the spring element (14) rests axially, or via a retaining ring (34).

5. Gas injector according to claim 4, characterized in that the spring element (14) is arranged on the centering bushing (21).

6. Gas injector according to claim 1, characterized in that the centering bushing (21) is firmly connected to the valve stem (13) in the region of the second axial end of the valve stem (13) and the second guide plate (26) is connected to the valve stem (13) via the centering bushing (21).

7. Gas injector according to one of claims 1 to 6, characterized in that an opening stop (15) is provided in the gas injector (1) and the valve stem (13), the centering bushing (21), the magnetic armature (10) or the magnetic armature stem (11) is designed to bear axially against the opening stop (15) in the open position (O).

8. Gas injector according to one of claims 1 to 7, characterized in that the valve stem (13) is arranged in a gas volume (17) in the housing (2) and the gas volume (17) is connected to the gas outlet (4), that the magnetic armature stem (11) is designed with a central recess (16) which is connected to the gas inlet (3) and that a connecting opening (18) is provided on the magnetic armature stem (11) which connects the central recess (16) to the gas volume (17).

9. Gas injector according to one of claims 1 to 8, characterized in that a sealing element (30) is arranged between the magnetic armature (10) and the housing (2) or between the magnetic armature shaft (11) and the housing (2).

10. Gas injector according to one of claims 1 to 8, characterized in that two axially spaced sealing elements (30, 32) are arranged between the magnetic armature (10) and the housing (2) or between the magnetic armature shaft (11) and the housing (2), such that a compression volume (41) of a gas damper (40) is formed between the two axially spaced sealing elements (30, 32), the housing (2) and the magnetic armature (10) or magnetic armature shaft (11), and that a throttle opening (42) is provided on a component of the gas injector (1) which connects the gas inlet (3) with the compression volume (41).

11. Gas injector according to one of claims 1 to 8, characterized in that the magnetic armature (10) with the magnetic armature shaft (11) is mounted at the end opposite the first axial end of the magnetic armature shaft (11) with a first guide plate (26) in the form of a gas-tight membrane in the housing (2), that a sealing element (32) is arranged axially between the gas-tight membrane and the first axial end of the magnetic armature shaft (11) between the magnetic armature (10) and the housing (2) or between the magnetic armature shaft (11) and the housing (2), such that a compression volume (41) of a gas damper (40) is formed between the gas-tight membrane, the sealing element (32), the housing (2) and the magnetic armature (10) or magnetic armature shaft (11), and that a throttle opening (42) is provided on a component of the gas injector (1) which connects the gas inlet (3) with the compression volume (41).

12. Gas injector according to one of claims 9, 10 or 11, characterized in that a surface of the magnetic armature (10) or the magnetic armature shaft (11) or the housing (2) in a movement area in which one of the sealing elements (30, 32) bears against the surface is modified compared to a surface away from the movement area, preferably is hardened, nitrided, coated or has an increased surface quality.

13. Gas injector according to one of claims 1 to 12, characterized in that the radial clearance between guide bushing (20) and valve stem (13) is smaller than the radial clearance between centering recess (21) and the valve stem (13) or magnetic armature stem (11).

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