Gas injector with improved needle guiding
Patent Information
- Application Number
- EP2023792938
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-12-13
- Filing Date
- 2023-10-17
- Publication Date
- 2025-10-22
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Gas injectors for internal combustion engines face challenges with particle-induced mechanical jamming and wear due to the lack of lubrication and high temperatures, particularly in the sealing area between the closing element and valve seat, leading to potential leaks and reduced guiding properties.
A particle deflector is fluidly connected upstream of the guide element, creating a conical inner opening that directs fluid flow radially inward and utilizes a radial pressure gradient to deflect particles away from the guide surface, combined with a labyrinth seal design to prevent particle entry.
This design effectively prevents particle entry into the guide area, reducing mechanical jamming and wear while maintaining a large circumferential guide surface for precise centering and reduced wear, enhancing the reliability and longevity of the gas injector.
Smart Images
Figure 1.1
Abstract
Description
[0001] Description
[0002] title
[0003] State of the art
[0004] The present invention relates to a gas injector for injecting a gaseous fuel, e.g. hydrogen or methane or the like, directly into a combustion chamber of an internal combustion engine with an improved needle guide.
[0005] Gas injectors are known from the prior art in various designs. Compared to fuel injectors for liquid fuels, the technical requirements for gas injectors are significantly different. In addition to the lack of lubrication from a liquid fuel, a significantly larger volume of the gaseous medium is particularly problematic. This can result in problems with the precise metering for an injection process. Furthermore, high temperatures arise during operation, particularly in the sealing area between a closing element and a valve seat of the gas injector. The combustion gases during operation, which reach the sealing area between the closing element and the valve seat, can result in increased temperatures in the sealing area, which leads to increased wear and possibly increased distortion of the components. This can cause leaks in the seat area in particular.
[0006] For example, DE 10 2020 201 973 A1 discloses a gas metering valve for an internal combustion engine, which has a housing in which a gas chamber is formed. A movable valve element is arranged in the gas chamber. This movable valve element can be moved by an electric actuator against the force of a return spring and interacts with a valve seat to open and close the valve. A valve needle, which is designed together with a closing element, has at least one guide area. The valve needle opens with the closing element toward the combustion chamber, thus resulting in an outward-opening gas metering valve.
[0007] The valve needle guides must be designed with very small guide clearances due to their essential centering function of the sealing seat and to prevent bearing tilting, which can lead to wear. To ensure good centering of the valve needle and the largest possible contact surface to reduce wear, a guide surface is typically designed to be circumferential.
[0008] A disadvantage of this type of needle guide design can be that the circumferentially closed guide surface can force particles in the gaseous fuel that pass from upstream in the gas injector to the guide area into the narrow guide gap and become trapped. This can result in mechanical jamming due to tilting and / or adhesive and abrasive wear phenomena, including scuffing. This is particularly critical for dry-running guides.
[0009] Interrupted guides, in which surface grindings or recesses in the guide area create the flow, are known as alternatives to closed guides. This type of guide design does offer the possibility of particles in the gas flowing through the flow pockets formed by the grindings, thus largely eliminating jamming. However, the disadvantage of this solution is that the outer surface area remaining for the guide properties is significantly reduced, and tilting can occur.
[0010] Disclosure of the invention
[0011] The gas injector according to the invention for injecting a gaseous medium, in particular for injecting gaseous hydrogen, with the features of claim 1, has the advantage that, despite a large circumferential guide surface, the removal of particles in the gas is nevertheless possible. The guide surface is advantageously protected from particles in the fluid flow. This is achieved according to the invention by a particle deflector fluidically arranged upstream of the at least one guide element on the valve needle, which ensures that particles are kept away from the circumferential guide surface of the guide element.
[0012] The subclaims show preferred developments of the invention.
[0013] It is particularly advantageous that the particle deflector has an inner opening for the flow of the gaseous fuel, which tapers conically in the direction of flow. This directs the fluid flow radially inward toward the valve axis and thus away from the guide area located further radially outward. Furthermore, the buildup of a radial pressure gradient due to the acceleration of the fluid through the nozzle-like constriction of the particle deflector tends to deflect the particles toward the needle-side flow openings of the guide element, since a higher static pressure prevails in the guide area of the guide surface than in the main flow field (Bernoulli effect).
[0014] To further enhance this effect, it is advantageous to provide at least one very small pressure equalization path that is smaller than the particles to be blocked and their corresponding particle sizes. This pressure equalization path is located radially further outward than the inner opening of the particle deflector. The pressure equalization path can "tap" the higher static pressure above and upstream of the particle deflector at the start of flow through the particle deflector. In the area between the particle deflector and the guide element, a higher pressure then prevails than in the radially inner region of the transition from the reduced-diameter opening of the particle deflector to the flow-through openings, so that any flow of particles radially outward toward the guide area can be prevented.
[0015] Advantageously, the particle deflector and the guide element can be designed with thin-walled annular collars or extensions that dip into each other so that a stroke overlap is present, which, in the manner of a labyrinth seal, protects the guide area particularly effectively from particles of the gas flow.
[0016] The gas injector is preferably an outward-opening injector.
[0017] drawing
[0018] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawings:
[0019] Figure 1 is a schematic sectional view of a known gas injector in the closed state,
[0020] Figure 2 is a schematic sectional view of the combustion chamber side
[0021] End of the gas injector of Figure 1 in the open state,
[0022] Figure 3 is a schematic sectional view of a guide element of the
[0023] Valve needle with a particle deflector arranged upstream of the valve according to a first and second embodiment of the invention in a representation with the valve open and closed and
[0024] Figure 4 is a schematic sectional view of a guide element of the
[0025] Valve needle with a particle deflector arranged upstream of the flow path according to a third and fourth embodiment of the invention in a representation with the valve open and closed.
[0026] Preferred embodiments of the invention
[0027] The invention is described in detail below according to various exemplary embodiments with reference to Figures 1 to 4. Figure 1 shows, by way of example and in a highly simplified manner, a gas injector 1 with a magnetic actuator 10. The magnetic actuator 10 comprises a magnetic coil 3 for acting on an axially movable armature 2, wherein the magnetic actuator 10 generally serves to actuate a closing element 6. The armature 2 is operatively connected to a valve needle 4, i.e. can be brought into contact in any case. The valve needle 4 comprises, at its downstream end, the closing element 6, which opens and closes a through-opening 20 at a sealing seat 5 of a valve body 21, wherein the closing element 6 is designed, for example, as a valve disk of the valve needle 4. In this respect, an injection cross-section can be opened at the sealing seat 5. The reference numeral 8 denotes a return element of the gas injector designed as a helical spring. The closing element 6 is, for example,held in the closed position shown in Figure 1 on the sealing seat 5 by means of a valve spring 7.
[0028] When the solenoid coil 3 is energized, a magnetic field is created, the magnetic force of which moves the armature 2 in the direction of the closing element 6, as indicated by the arrow 11. An armature bolt 9, connected to the armature 2, for example, comes into contact with the valve needle 4, so that the closing element 6 can lift off the sealing seat 5 against the spring force of the valve spring 7, and the through opening 20 is opened. The armature 2 is moved, for example, up to a stroke stop 16 for the armature 2, which represents the fully open state of the gas injector.
[0029] To close the gas injector 1, the current supply to the solenoid coil 3 is stopped, so that the return element 8 returns the armature 2 to the initial position shown in Figure 1. At the same time, the valve spring 7 also returns the closing element 6 to the closed position shown in Figure 1. Due to the direction of movement of the closing element 6, this valve type is an outward-opening valve.
[0030] As an alternative to the described magnetic actuator 10, the closing element 6 can also be actuated by a piezo actuator (not shown). In addition to mechanical transmission, the valve needle 4 can also perform its outward opening movement hydraulically. It is also conceivable to open the valve needle 4 purely hydraulically via a pressure increase of the medium being introduced. In addition, embodiments with indirect control of the valve needle 4 via a servo principle are also feasible.
[0031] The gas injector 1 is supplied with a gaseous fuel, in particular hydrogen, to be injected via a schematically indicated gas supply line 12. A pressure sensor 13, for example, is arranged in the gas supply line 12 and is connected to a control unit 14. The direction of gas flow is indicated by arrows 15.
[0032] To guide the valve needle 4 in a valve housing, in particular also in the valve body 21 belonging to the valve housing, during its axial movement along the axial direction XX of the gas injector 1, the valve needle 4 has at least one guide element 25. In the simplified embodiment shown, the valve needle 4 has two guide elements 25.
[0033] Figure 2 shows an enlarged partial view of the downstream end region of the gas injector 1 for a better understanding of the invention. This shows a lower, downstream guide element 25, which is either formed integrally with the valve needle 4 or securely and firmly attached to its shaft. The precise guidance of the valve needle 4 in the valve body 21 during its axial movement is achieved via a circumferential guide surface 26, which is precisely machined to ensure jam-free guidance. At least one flow opening 27 is provided in the guide element 25; normally, between three and ten flow openings 27 are formed.
[0034] The guides of the valve needle 4 are generally designed with very small guide clearances due to their essential centering function of the sealing seat 5 and to prevent bearing tilting, which would lead to wear. To ensure good centering of the valve needle 4 and the largest possible contact surface to reduce wear, the guide surface 26 is typically designed to be circumferential.
[0035] A disadvantage of this type of needle guide design can be that the circumferentially closed guide surface 26 forces particles in the gaseous fuel, which pass from upstream in the gas injector 1 to the guide area, into the narrow guide gap and become trapped. This can result in mechanical jamming due to tilting and / or adhesive and abrasive wear phenomena, including scuffing. This is particularly critical for dry-running guides.
[0036] Interrupted guides, in which surface grindings or recesses in the guide area create the flow, are known as alternatives to closed guides. This type of guide design does offer the possibility of particles in the gas flowing through the flow pockets formed by the grindings, thus largely eliminating jamming. However, the disadvantage of this solution is that the outer surface area remaining for the guide properties is significantly reduced, and tilting can occur.
[0037] In order to prevent particles from entering the guide area in a guide with a circumferentially closed guide surface 26, as shown in Figure 2, a fluid-mechanical design element is now proposed as the core of the invention, which keeps the flow away from the guide contact area and thus also the particles due to their mass inertia.
[0038] According to the invention, a design solution is therefore described that has a large circumferential guide surface 26 while still allowing the removal of particles. Particularly advantageously, a particle deflector 28, 29, 30, 31 is fluidically arranged upstream of at least one guide element 25 inside the gas injector 1, ensuring that particles are kept away from the circumferential guide surface 26 of the guide element 25.
[0039] Figure 3 shows a schematic sectional view of a guide element 25 of the valve needle 4 with a particle deflector 28, 29 arranged upstream of the valve needle in accordance with a first and second exemplary embodiment of the invention, depicted with the valve open and closed. The left side of Figure 3 shows the state of the valve needle 4 with the guide element 25 when the valve is closed, while the right side of Figure 3 shows the state of the valve needle 4 with the guide element 25 when the valve is fully open. The double arrow 35 indicates the dimension of the entire valve needle stroke.
[0040] In addition to the representation of the two maximum states of movement of the valve needle 4 together in Figure 3, two different embodiments of the particle deflector according to the invention are also shown. Figure 3 shows on the left-hand side an embodiment of the particle deflector 28 which is formed integrally together with the valve body 21 or another section of the valve housing. The particle deflector 28 is a component section which, for example, has an inner opening for the flow of the gaseous fuel with an incline running inwards towards the valve axis XX and which tapers conically. In this way, the fluid flow marked with arrows 32 is guided towards the valve axis XX and thus to the flow-through openings 27.
[0041] Furthermore, the buildup of a radial pressure gradient due to acceleration through the nozzle-like constriction of the particle deflector 28 tends to deflect the particles toward the needle-side flow openings 27, since a higher static pressure prevails in the guide area of the guide surface 26 than in the main flow field (Bernoulli effect). To further enhance this effect, a very small pressure equalization path 33, which is smaller than the particles to be deflected with their corresponding particle sizes, can be integrated. This pressure equalization path 33 can, for example, be a laser-formed groove. The pressure equalization path 33 can "tap" the higher static pressure upstream of the particle deflector 28 at the start of the flow of the particle deflector 28.In the area between the particle deflector 28 and the guide element 25, a higher pressure prevails than in the radially inner area of the transition from the reduced-diameter opening of the particle deflector 28 to the flow-through openings 27, so that a radially outward flow of particles towards the guide area can be excluded. As an alternative to a single pressure equalization path 33, several pressure equalization paths 33 can also be provided distributed over the circumference. As shown on the right-hand side of Figure 3, the particle deflector 29 can also be an independent component, which can therefore optionally be inserted and fastened in a section of the valve body 21 specially designed for this purpose, e.g. with receiving shoulders, and in this case has the same functionality as previously described.
[0042] The maximum outlet diameter of the inner opening of the particle deflector 28, 29 should not be larger than the maximum radial extension of the flow openings 27, so that an optimal flow transition is ensured
[0043] Figure 4 shows a schematic sectional view of a guide element 25 of the valve needle 4 with a particle deflector 30, 31 arranged upstream of the valve needle in accordance with a third and fourth exemplary embodiment of the invention, depicted with the valve open and closed. The left side of Figure 4 shows the state of the valve needle 4 with the guide element 25 when the valve is closed, while the right side of Figure 4 shows the state of the valve needle 4 with the guide element 25 when the valve is fully open. The double arrow 35 indicates the dimension of the entire valve needle stroke.
[0044] In addition to the representation of the two maximum states of movement of the valve needle 4 together in Figure 4, two different embodiments of the particle deflector according to the invention are also shown. On the left-hand side, Figure 4 shows an embodiment of the particle deflector 30 which is formed as a single piece together with the valve body 21 or 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 the gaseous fuel which tapers conically and runs with an incline towards the valve axis XX. In this way, the fluid flow marked with arrows 32 is directed towards the valve axis XX and thus to the flow-through openings 27. The fluid mechanical effect also arises in the two embodiments shown in Figure 4, as previously described for the first two embodiments according to Figure 3.To further enhance the Bernoulli effect achieved through the geometric design, a very small pressure equalization path 33, which is smaller than the particles to be held back with their corresponding particle sizes, or several such pressure equalization paths 33 can be integrated. This is indicated on the left side of Figure 4.
[0045] The two embodiments of Figure 4 are characterized in particular by the fact that the particle deflector 30, 31 has a downstream, thin-walled annular collar 36. This annular collar 36, directed towards the guide element 25, represents a circular-cylindrical stroke overlap attachment which engages in a likewise thin-walled, upstream, annular collar-shaped extension 37 of the guide element 25 and thus of the axially movable valve needle 4. The annular collar 36 of the particle deflector 30, 31 and the extension 37 of the guide element 25 have a large axial overlap length. This very effectively prevents particles from penetrating the guide area, particularly with large needle strokes. This advantageous design therefore has the structure of a labyrinth seal.
[0046] As shown in Figure 4 on the right-hand side, the particle deflector 31 can also be an independent component, which can therefore optionally be inserted and fastened in a section of the valve body 21 specially designed for this purpose, e.g. with receiving shoulders, and in this case has the same functionality as previously described.
[0047] The maximum outlet diameter of the inner opening of the particle deflector 30, 31 in the area of the annular collar 36 should not be larger than the maximum radial extent of the flow openings 27, so that an optimal flow transition is ensured.
[0048] For all described embodiments, it should be noted that any combination of the features shown in the embodiments is possible.
Claims
Claims 1 . Gas injector for injecting a gaseous medium, in particular hydrogen, comprising: an actuatable closing element (6) which opens and closes a through-opening (20) on a sealing seat (5) of a valve body (21), wherein the closing element (6) is designed as part of a valve needle (4), at least one guide element (25) for guiding the valve needle (4) in a valve housing (21) during its axial movement along an axial direction XX, characterized in that a particle deflector (28, 29, 30, 31) is fluidically connected upstream of the at least one guide element (25), which ensures that particles are kept away from the circumferential guide surface (26) of the guide element (25).
2. Gas injector according to claim 1, characterized in that the particle deflector (28, 30) is formed in one piece together with the valve housing (21).
3. Gas injector according to claim 1, characterized in that the particle deflector (29, 31) is an independent component and can be inserted and fastened in a section of the valve housing (21) designed for this purpose.
4. Gas injector according to one of the preceding claims, characterized in that that the particle deflector (28, 29, 30, 31) has an inner opening for the flow of the gaseous fuel, which tapers conically in the flow direction. Gas injector according to claim 4, characterized in that at least one pressure equalization path (33) is provided, which is radially formed with a larger diameter than the opening width of the inner opening of the particle deflector (28, 29, 30, 31). Gas injector according to claim 4, characterized in that the at least one pressure equalization path (33) is arranged such that in a flow connection in the region between the particle deflector (28) and the guide element (25), a higher fluid pressure prevails than in the outlet region of the inner opening of the particle deflector (28, 29, 30, 31). Gas injector according to claim 5 or 6, characterized in that the opening width of the pressure equalization paths (33) is smaller than the particles to be kept out with their corresponding particle sizes.Gas injector according to claim 5, 6, or 7, characterized in that the at least one pressure equalization path (33) is a laser-formed groove. Gas injector according to one of the preceding claims, characterized in that the particle deflector (30, 31) has a downstream, thin-walled annular collar (36), and the guide element (25) of the valve needle (4) has a thin-walled, upstream, annular collar-shaped extension (37) of the guide element (25), wherein the annular collar (36) dips radially within the extension (37). Gas injector according to one of the preceding claims, characterized in that the maximum outlet diameter of an inner opening of the particle deflector (28, 29, 30, 31) is not greater than the maximum radial extent of flow openings (27) provided in the guide element (25). Gas injector according to one of the preceding claims, characterized in that the closing element (6) is an outwardly opening closing element (6).