Gas injector with improved needle guide

Abstract

The invention relates to a gas injector for blowing in gaseous fuel, in particular hydrogen, comprising an actuatable closing element (6) which releases and closes a through-opening (20) located on a sealing seat (5) of a valve body (21), the closing element (6) being embodied as part of a valve needle (4). The valve needle (4) has at least one guide element (25) for guiding the valve needle (4) in the valve housing (21) during an axial movement of the valve needle in the axial direction X-X. According to the invention, a particle deflector (28, 29, 30, 31) is fluidically connected upstream of the at least one guide element (25), said particle deflector being responsible for holding particles away from the circumferential guide surface (26) of the guide element (25).

Description

Technical Field

[0001] The present invention relates to a gas injector for directly injecting a gaseous fuel, such as hydrogen, methane, etc., into the combustion chamber of an internal combustion engine, and the gas injector has an improved needle guide portion. Background Art

[0002] Gas injectors are known from the prior art in different configurations. Compared with fuel injectors for liquid fuels, there are significant differences in the technical requirements for gas injectors. The problem here is that, in addition to the lack of lubrication by liquid fuel, the volume of the gaseous medium is also significantly larger. This can lead to problems in terms of precise metering for the injection process. In addition, high temperatures are generated during operation, especially in the region of the sealing area between the closing element and the valve seat of the gas injector. Due to the combustion gases during operation that reach the sealing area between the closing element and the valve seat, the temperature at this sealing area may increase, which leads to increased component wear and may lead to increased distortion of the components. Thereby, in particular, leakage at the valve seat area may occur.

[0003] For example, a gas metering valve for an internal combustion engine is known from DE102020201973A1, which has a housing in which a gas chamber is constructed. A movable valve element is arranged in the gas chamber, and the valve element can be moved by an electric actuator against the force of a return spring, and the valve element cooperates with a valve seat to open and close the valve. The valve needle implemented together with the closing element has at least one guiding region. The valve needle is opened towards the combustion chamber by means of the closing element, so that this is an outward-opening gas metering valve.

[0004] Due to its main centering function for the sealing seat and in order to avoid bearing tilting with a corresponding wear tendency, the guide portion of the valve needle should in principle be designed with a very small guide clearance. In order to center the valve needle well and to achieve as large a contact surface as possible to reduce wear, the guide surface is usually configured circumferentially.

[0005] The disadvantage in this configuration of the needle guide portion may be that, due to the circumferentially closed guide surface, particles flowing upstream from the gas injector in the gaseous fuel are pressed into the narrow guide clearance and trapped therein. As a result, mechanical jamming due to tilting and / or adhesive and abrasive wear manifestations, and even a tendency to galling may occur. This is particularly serious especially in the case of a dry-running guide portion.

[0006] As an alternative to the closed guide part, an interrupted guide part is known, in which surface cuts or notches in the guide region enable the flow-through. Although this type of guide part configuration enables the particles in the gas to flow through the flow part formed by the cuts, jamming is thus largely avoided to a great extent. However, the disadvantage of this solution is that the circumferential surface left for indicating the guiding property is significantly reduced and tilting may occur. Summary of the Invention

[0007] In contrast, the gas injector for injecting a gaseous medium, in particular for injecting gaseous hydrogen, having the features of claim 1 has the advantage that, in the case of a large surrounding guide surface, the removal of particles in the gas can still be achieved simultaneously. The guide surface is advantageously protected against particles in the fluid flow. According to the invention, this is achieved in that a particle deflector is connected upstream of at least one guide element at the valve needle in terms of fluid technology, and this particle deflector is responsible for keeping the particles away from the circumferential guide surface of the guide element.

[0008] The dependent claims show preferred expansion schemes of the invention.

[0009] Particularly advantageously, the particle deflector has an inner opening for the flow of the gaseous fuel, and this inner opening extends in a tapered manner narrowing in the flow direction. In this way, the fluid flow is guided radially inwards towards the valve axis, thus away from the radially outer guide region. In addition, a radial pressure drop is established by the fluid acceleration caused by the nozzle-shaped narrowing of the particle deflector, and the particles tend to deflect towards the flow-through opening on the needle side of the guide element because the static pressure present in the guide region of the guide surface is higher than that in the main flow field (Bernoulli effect).

[0010] To further enhance this effect, it is advantageous to provide at least one very small pressure equalization path, which is smaller than the particles to be intercepted having the corresponding particle size. Here, the pressure equalization path is radially more outward than the inner opening of the particle deflector. The pressure equalization path can "extract" the higher static pressure above the particle deflector at the start of the flow of the particle deflector. Therefore, in the region between the particle deflector and the guide element, there is a higher pressure than in the radially inner region of the transition between the reduced-diameter opening and the flow-through opening of the particle deflector, so that the outflow of particles towards the radially outer guide region can be avoided.

[0011] Advantageously, the particle deflector and the guide element can be implemented as thin-walled annular flanges or continuations, which sink / embed into each other, so that there is a stroke overlap, which particularly effectively protects the guide region from the particles of the air flow in the form of a labyrinth seal.

[0012] The gas injector is preferably an outward-opening injector. Description of the Drawings

[0013] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings:

[0014] Figure 1 A schematic cross-sectional view showing a known gas injector in a closed state is shown;

[0015] Figure 2 Shows Figure 1 A schematic cross-sectional view of the combustion chamber side end of the gas injector in the open state shown in

[0016] Figure 3 A schematic cross-sectional view showing the guide element of the valve needle according to the first and second embodiments of the present invention and the particle deflector fluid-technologically connected upstream thereof in a view with open and closed valves;

[0017] Figure 4 A schematic cross-sectional view showing the guide element of the valve needle according to the third and fourth embodiments of the present invention and the particle deflector fluid-technologically connected upstream thereof in a view with open and closed valves. Detailed Description of the Specific Embodiments

[0018] Hereinafter, different embodiments of the present invention will be described in detail with reference to Figures 1 to 4 Detailed description of different embodiments of the present invention.

[0019] Figure 1 Exemplarily and highly simplified, a gas injector 1 with an electromagnetic actuator 10 is shown. The electromagnetic actuator 10 includes an electromagnetic coil 3 for acting on an axially movable armature 2, wherein the electromagnetic actuator 10 is generally used to manipulate a closing element 6. The armature 2 is operatively connected to the valve needle 4, i.e., in contact in any case. Here, the valve needle 4 includes a closing element 6 at its downstream end, which releases and closes a through-opening 20 at a sealing seat 5 of the valve body 21, wherein the closing element 6 is implemented, for example, as a valve disk of the valve needle 4. In this regard, a blowing-in cross-section can be released at the sealing seat 5. The reference numeral 8 denotes a return element of the gas injector configured as a helical spring. The closing element 6 is held, for example, by a valve spring 7 in the closed position shown in Figure 1 In the closed position shown in

[0020] If the electromagnetic coil 3 is energized, a magnetic field is formed, the magnetic force of which causes the armature 2 to move in the direction of the closing element 6, which is indicated by the arrow 11. Here, for example, an armature column 9 connected to the armature 2 abuts against the valve needle 4, such that the closing element 6 can be lifted at the sealing seat 5 against the spring force of the valve spring 7, and the through-opening 20 is opened. Here, the armature 2 moves, for example, until a stroke stop 16 for the armature 2, which represents the fully open state of the gas injector.

[0021] To close the gas injector 1, the energization of the electromagnetic coil 3 is stopped, so that the reset element 8 resets the armature 2 back to the Figure 1 initial position shown in. At the same time, the valve spring 7 also resets the closing element 6 to the Figure 1 closing position shown in. Thus, due to the movement direction of the closing element 6, this valve type is an outward-opening valve.

[0022] Instead of the electromagnetic actuator 10 described above, the closing element 6 can also be actuated by a piezoelectric actuator (not shown). In addition to mechanical transmission, the valve needle 4 can also perform its opening movement outward in a hydraulic transmission manner. It is also conceivable that the valve needle 4 is opened by the pressure increase of the medium to be introduced in a purely hydraulic manner. In addition, an embodiment of indirectly controlling the valve needle 4 by a servo principle can also be realized.

[0023] The gas injector 1 is supplied with the gaseous fuel to be introduced, especially hydrogen, through the schematically shown gas supply line 12. For example, a pressure sensor 13 is arranged in the gas supply line 12, which is connected to the control unit 14. The gas flow direction is indicated by the arrow 15.

[0024] In order to guide the valve needle 4 in the valve housing, especially also in the valve body 21 belonging to the valve housing, during the axial movement of the valve needle 4 along the axial direction X-X of the gas injector 1, the valve needle 4 has at least one guiding element 25. In the shown simplified embodiment, the valve needle 4 has two guiding elements 25.

[0025] For a better understanding of the present invention, the downstream end region of the gas injector 1 is shown enlarged as a partial view in Figure 2 . Here, the lower downstream guiding element 25 can be seen, which is either integrally formed with the valve needle 4 or reliably and fixedly mounted on the rod of the valve needle. The precise guiding of the valve needle 4 in the valve body 21 during its axial movement is achieved by the circumferential guiding surface 26, which is precisely machined for unobstructed guiding. At least one flow-through opening 27 is provided in the guiding element 25; normally, three to ten flow-through openings 27 are formed.

[0026] The guiding part of the valve needle 4 should in principle be designed with a very small guiding clearance due to its main centering function for the sealing seat 5 and also to avoid bearing tilting with a corresponding wear tendency. For the good centering of the valve needle 4 and for the largest possible contact surface to reduce wear, the guiding surface 26 is usually configured circumferentially.

[0027] A disadvantage of this configuration of the needle guide is that, due to the circumferentially closed guide surface 26, particles in the gaseous fuel that reach the guide region from upstream in the gas injector 1 can be pressed into the narrow guide gap and become stuck therein. As a result, mechanical jamming due to tilting and / or adhesive and abrasive wear manifestations, and even a tendency to galling, may occur. This is particularly severe in the case of a dry-running guide.

[0028] Instead of a closed guide, an interrupted guide is known, in which surface cuts or notches in the guide region enable through-flow. Although this guide configuration offers the possibility that particles in the gas flow through the flow pockets formed by the cuts, and thus jamming is largely avoided here. However, the disadvantage of this solution is that the peripheral surface left for representing the guiding performance is significantly reduced, and tilting may occur.

[0029] In order to avoid particles entering the guide region in the case of a guide with a circumferentially closed guide surface 26 as shown in Figure 2 now, at the core of the present invention, a design element in terms of fluid mechanics is proposed, which keeps the flow away from the guide contact region and thus also keeps the particles away from the guide contact region due to their mass inertia.

[0030] Therefore, a design solution is described according to the present invention, which has a large circumferential guide surface 26, and in which the particles can still be discharged at the same time. Advantageously, inside the gas injector 1, particle deflectors 28, 29, 30, 31 are fluid-technologically connected upstream of at least one guide element 25, which are responsible for keeping the particles away from the circumferential guide surface 26 of the guide element 25.

[0031] Figure 3 shows a schematic cross-sectional view of the guide element 25 of the valve needle 4 and the particle deflectors 28, 29 fluid-technologically connected upstream thereof according to the first and second embodiments of the present invention in a diagram with an open and closed valve. Here, Figure 3 the left side shows the state of the valve needle 4 with the guide element 25 in the case of the valve being closed, while on the Figure 3 right side shows the state of the valve needle 4 with the guide element 25 in the case of the valve being fully open. In this regard, a scale for the entire valve needle stroke is shown by a double arrow 35.

[0032] In addition to showing the two maximum movement states of the valve needle 4 together in Figure 3 two different embodiments of the particle deflector according to the present invention are also shown. Here, Figure 3One embodiment of the particle deflector 28 integrally formed with the valve body 21 or another section of the valve housing is shown on the left. The particle deflector 28 is here a component section which, for example, has an inner opening for the flow of gaseous fuel with an inclination extending inwards towards the valve axis X-X, and this inner opening extends in a tapered manner. In this way, the fluid flow marked by the arrow 32 is directed towards the valve axis X-X and thus towards the flow-through opening 27.

[0033] Furthermore, acceleration is achieved through the nozzle-like narrowing of the particle deflector 28. Due to the radial pressure drop established by this acceleration, the particles tend to deflect in the direction of the flow-through opening 27 on the valve needle side because the static pressure present in the guiding area of the guiding surface 26 is higher than that in the main flow field (Bernoulli effect). To further enhance this effect, very small pressure equalization paths 33, which are smaller than the particles to be intercepted with the corresponding particle size, can additionally be integrated. The pressure equalization paths 33 can be, for example, grooves formed by means of a laser. The pressure equalization paths 33 can "extract" the higher static pressure above the particle deflector 28 at the start of the flow in the particle deflector 28. Thus, in the area between the particle deflector 28 and the guiding element 25, there is a higher pressure than in the radial inner area of the constricted opening of the particle deflector 28 leading to the flow-through opening 27, so that the outflow of particles towards the radial outside of the guiding area can be avoided. Instead of a single pressure equalization path 33, a plurality of pressure equalization paths 33 can also be arranged in a peripherally distributed manner.

[0034] As shown on the right in Figure 3 the particle deflector 29 can also be an independent component which can optionally be inserted into a section of the valve body 21, for example specially provided for this purpose and equipped with a receiving shoulder, and can be fixed there, and which has the same function as described above.

[0035] The maximum outlet diameter of the inner opening of the particle deflectors 28, 29 should not be greater than the maximum radial extension scale of the flow-through opening 27, thus ensuring an optimized flow transition.

[0036] Figure 4 A schematic cross-sectional view of the guiding element 25 of the valve needle 4 according to the third and fourth embodiments of the present invention and the particle deflector fluid-technologically connected upstream is shown in the illustration with the valve in the open and closed states. Here, Figure 4 the state of the valve needle 4 with the guiding element 25 in the closed state of the valve is shown on the left in Figure 4 while the state of the valve needle 4 with the guiding element 25 in the fully open state of the valve is shown on the right in

[0037] In addition to in Figure 4In addition to showing the two maximum movement states of the valve needle 4, two different embodiments of the particle deflector according to the present invention are also shown. Figure 4 On the left side, an embodiment of a particle deflector 30 is shown which is integrally formed with the valve body 21 or with another section of the valve housing. The particle deflector 30 is a component section which, for example, has an inner opening for the flow of gaseous fuel with an inclination extending inwardly toward the valve axis XX, which inner opening narrows conically. In this way, the fluid flow marked by the arrow 32 is guided toward the valve axis XX and thus toward the throughflow opening 27. Figure 4 In the two embodiments shown in FIG. 1 , the same results are obtained as described above according to Figure 3 The fluid mechanics effect as described in the two embodiments.

[0038] In order to further enhance the Bernoulli effect achieved by the geometric design, a very small pressure equalization path 33 can also be integrated, which is smaller than the particles to be intercepted with the corresponding particle size, or a plurality of such pressure equalization paths 33 can be integrated. Figure 4 Shown on the left.

[0039] Figure 4 The two variants of embodiment are characterized in particular in that the particle deflectors 30, 31 have a thin-walled annular flange 36 in the downstream direction. This annular flange 36 pointing toward the guide element 25 is a circular cylindrical stroke overlap front (vorsatz) which extends into a likewise thin-walled annular flange-shaped continuation 37 of the guide element 25 and thus of the axially movable valve needle 4 pointing upstream. The annular flange 36 of the particle deflectors 30, 31 and the continuation 37 of the guide element 25 have a large axial overlap length. Therefore, in particular in the case of large needle strokes, the penetration of particles into the guide area is very effectively avoided. In this regard, this advantageous design has the structure of a labyrinth seal.

[0040] As in Figure 4 As shown on the right in FIG. 1 , the particle deflector 31 can also be a separate component which can be optionally inserted into a section of the valve body 21 provided specifically for this purpose, for example provided with a receiving shoulder, and can be fixed there and has the same function as described above.

[0041] The maximum outlet diameter of the inner openings of the particle deflectors 30 , 31 in the region of the annular collar 36 should not be larger than the maximum radial extension of the throughflow opening 27 , in order to ensure an optimized flow transition.

[0042] For all the embodiments described it should be noted that the features shown in these embodiments may be combined arbitrarily.

Claims

1. A gas injector for injecting a gaseous fuel, in particular hydrogen, the gas injector comprising: An actuable closing element (6) that releases and closes a through-opening (20) at a sealing seat (5) of a valve body (21), wherein the closing element (6) is embodied as part of a valve needle (4); At least one guiding element (25) for guiding the valve needle (4) in the valve housing (21) during an axial movement of the valve needle in the axial direction X-X, Characterized in that a particle deflector (28, 29, 30, 31) is fluid-technically connected upstream of the at least one guiding element (25), the particle deflector being responsible for keeping particles away from a circumferential guiding surface (26) of the guiding element (25).

2. The gas injector according to claim 1, wherein The particle deflectors (28, 30) are integrally formed with the valve housing (21).

3. The gas injector according to claim 1, characterized in that, The particle deflectors (29, 31) are separate components and can be inserted into and fixed in a section of the valve body (21) configured therefor.

4. The gas injector according to one of the above-mentioned claims, characterized in that, The particle deflectors (28, 29, 30, 31) have inner openings for the flow of the gaseous fuel, the inner openings extending in a tapered manner narrowing in the flow direction.

5. The gas injector according to claim 4, wherein At least one pressure equalization path (33) is formed at a diameter that is larger than an opening width of the inner opening of the particle deflectors (28, 29, 30, 31).

6. The gas injector according to claim 4, characterized in that, The at least one pressure equalization path (33) is arranged such that the fluid pressure present in the flow connection in the region between the particle deflector (28) and the guiding element (25) is greater than in the outlet region of the inner opening of the particle deflectors (28, 29, 30, 31).

7. The gas injector according to claim 5 or 6, characterized in that, The opening width of the pressure equalization path (33) is smaller than the particles to be intercepted with their corresponding particle sizes.

8. The gas injector according to claim 5 or 6 or 7, characterized in that, The at least one pressure equalization path (33) is a laser-machined groove.

9. The gas injector according to one of the above claims, characterized in that, The particle deflectors (30, 31) have downstream thin-walled annular flanges (36), and the guiding element (25) of the valve needle (4) has an upstream-pointing thin-walled annular flange-shaped continuation (37) of the guiding element (25), wherein the annular flange (36) is radially sunk into the continuation (37).

10. The gas injector according to one of the above claims, characterized in that, The maximum outlet diameter of the inner opening of the particle deflectors (28, 29, 30, 31) is not greater than the maximum radial extension dimension of a flow-through opening (27) introduced into the guiding element (25).

11. The gas injector according to one of the above claims, characterized in that, The closing element (6) is an outward-opening closing element (6).

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