Gas injector with improved needle guide

Abstract

The present invention relates to a 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). The valve needle (4) has 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. According to the invention, a circumferential and pocket-shaped particle deflector (28) formed in the valve housing (21) 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).

Description

State of the art

[0001] 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.

[0002] 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 lead to leaks in the seat area in particular.

[0003] DE 10 2020 201 973 A1, for example, 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 member, has at least one guide area. The valve needle opens with the closing member toward the combustion chamber, so that the gas metering valve opens outward.

[0004] Due to their essential centering function of the sealing seat and to prevent bearing tilting and the associated tendency for wear, the valve needle guides must generally be designed with very small guide clearances. To ensure good centering of the valve needle and the largest possible contact surface to reduce wear, a guide surface is usually designed to be circumferential.

[0005] A disadvantage of this type of needle guide design can be that the circumferentially closed guide surface forces particles in the gaseous fuel that travel from upstream in the gas injector to the guide area into the narrow guide gap and become trapped. The result can be mechanical jamming due to tilting and / or adhesive and abrasive wear phenomena, including scuffing. This is particularly critical for dry-running guides.

[0006] 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. Disclosure of the invention

[0007] 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 in that a circumferential, pocket-shaped particle deflector formed in the valve housing is fluidically arranged upstream of the at least one guide element, which ensures that particles are kept away from the circumferential guide surface of the guide element.

[0008] The subclaims show preferred developments of the invention.

[0009] It is particularly advantageous that the particle deflector is a recess in the wall of a through opening in the valve body, which widens conically in the direction of flow. Since the recess has a nose-shaped contour in cross-section, the fluid flow running along the wall is directed radially inwards towards the valve axis and thus away from the guide area further radially outwards. This redirected gas flow meets the axially incoming main gas flow and deflects it in the desired manner inwards towards the valve axis and thus towards the through-flow openings of the guide element. The area at the sensitive outer guide surface of the guide element is thus largely kept out of the gas flow, so that the risk of clogging by particles entrained in the gas flow at the very narrow guide gap in the area of ​​the guide surface is greatly reduced.

[0010] The gas injector is preferably an outward-opening injector. drawing

[0011] Preferred embodiments of the invention will now be described in detail with reference to the accompanying drawings. In the drawings: Fig. 1 a schematic sectional view of a known gas injector in the closed state, Fig. 2 a schematic sectional view of the combustion chamber end of the gas injector of Fig. 1 in the open state, Fig. 3 a schematic sectional view of a guide element of the valve needle with a pocket-shaped particle deflector arranged upstream of the valve needle according to an embodiment of the invention. Preferred embodiments of the invention

[0012] The following is based on the Fig. 1 to 3 the invention is described in detail according to various embodiments.

[0013] Fig. 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 the closing element 6 at its downstream end, 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. The through-opening 20 at the sealing seat 5 is the fluidically continued end of a through-opening 19 in the valve body 19, through which the gas flows in the direction of the sealing seat 5. An injection cross-section can be opened at the sealing seat 5.Reference numeral 8 denotes a return element of the gas injector, designed as a helical spring. The closing element 6 is actuated, for example, by means of a valve spring 7 in the position shown in . Fig. 1 shown, closed position on the sealing seat 5.

[0014] 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. In this case, an armature bolt 9, connected, for example, to the armature 2, 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.

[0015] To close the gas injector 1, the current supply to the solenoid coil 3 is stopped so that the reset element 8 returns the armature 2 to the position shown in Fig. 1. At the same time, the valve spring 7 also returns the closing element 6 to the position shown in Fig. 1. Due to the direction of movement of the closing element 6, this valve type is an outward-opening valve.

[0016] 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 introduced medium. In addition, embodiments with indirect control of the valve needle 4 via a servo principle are also feasible.

[0017] 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 the arrows 15.

[0018] 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.

[0019] In the Fig. 2, the downstream end region of the gas injector 1 is shown enlarged as a partial view 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.

[0020] 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 avoid 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 usually designed to be circumferential.

[0021] A disadvantage of this type of needle guide design can be that the circumferentially closed guide surface 26 forces particles in the gaseous fuel that 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 seizure. This is particularly critical for dry-running guides.

[0022] 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.

[0023] To prevent particles from entering the guide area in a guide with a circumferentially closed guide surface 26, as shown in Fig. 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 inertia.

[0024] According to the invention, a design solution is therefore described that enables the removal of particles. Particularly advantageously, a particle deflector 28 is fluidically arranged upstream of the 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.

[0025] In the Fig. Figure 3 shows a schematic sectional view of a guide element 25 of the valve needle 4 with a particle deflector 28 arranged upstream of the valve body 21 according to an exemplary embodiment of the invention. It can be seen that the particle deflector 28 represents a circumferential, pocket-shaped recess in the wall of the valve body 21, which expands the through-opening 19 over a short axial extent, with the recess having a nose-shaped contour in cross-section.

[0026] The nose-shaped contour is characterized by the fact that the pocket-shaped particle deflector 28 experiences a continuously widening enlargement of the diameter of the through-opening 19 in the flow direction shortly before the guide element 25, which then returns quite abruptly radially inwards to the “normal” dimension of the through-opening 19 for a strong flow deflection.

[0027] The pocket-shaped recess serving as a particle deflector 28 is formed in the valve body 21, for example, by milling. However, other machining methods for forming the recess are also conceivable.

[0028] The gas flow flowing along the wall of the valve body 21 is kept away from the guide gap on the guide surface 26 thanks to the particle deflector 28 due to the strong deflection in the recess, so that potential particles cannot get into the small guide gap, but are guided through the large flow openings 27 in the valve needle 4.

[0029] The radially outer gas flow is redirected via a rounded transition from the conically widening section of the recess to its base 30, through which gas is redirected almost at a right angle back into the gas space of the through-opening 19. This redirected gas flow meets the axially incoming main gas flow, marked by arrow 31, and redirects it in the desired manner inward toward the valve axis XX and thus toward the through-flow openings 27. The area at the guide surface 26 of the guide element 25 is thus largely kept out of the gas flow, so that the risk of clogging by particles entrained in the gas flow at the very narrow guide gap in the area of ​​the guide surface 26 is greatly reduced. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 201 973 A1

[0003]

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) at a sealing seat (5) of a valve body (21), the closing element (6) being 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 by that a circumferential and pocket-shaped particle deflector (28) formed in the valve housing (21) 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 by that the particle deflector (28) is formed directly on the valve housing (21). [3] Gas injector according to claim 1 or 2, characterized by that the particle deflector (28) represents a recess in the wall of the valve body (21) which widens a through opening (19) of the valve body (21) over an axial extent. [4] Gas injector according to claim 3, characterized by that the recess has a conically widening section which merges via a rounded transition to a base (30), wherein the base (30) is designed such that a gas flow can be deflected back into the gas space of the through-opening (19), so that the recess has a nose-shaped contour in cross section. [5] Gas injector according to claim 4, characterized by that the base (30) of the recess is largely aligned at right angles to the axial direction XX. [6] Gas injector according to one of the preceding claims, characterized in that the recess serving as a particle deflector (28) can be introduced into the valve body (21) by milling. [7] Gas injector according to one of the preceding claims, characterized in that the closing element (6) is an outwardly opening closing element (6).

Images