INJECTOR FOR INJECTING GAS

Abstract

The present invention relates to an injector for injecting gas, in particular hydrogen, preferably for directly injecting hydrogen, comprising an injector housing for holding injector components, a valve needle movably arranged along its longitudinal axis in the injector housing and configured to selectively close or release an injection opening for the flow of hydrogen therethrough, and a valve, preferably a solenoid valve, which is adapted to transfer the valve needle into a closing or releasing state by a movement along its longitudinal axis. The injector is characterized in that the valve needle is a hollow needle adapted to pass a gas, in particular hydrogen, flowing through the injection port through the interior of the hollow needle.

Claims

1. Injector for injecting gas, comprising: an injector housing for holding injector components, a valve needle which is arranged movably along its longitudinal axis in the injector housing and is configured to selectively close or open an injection opening for the flow of gas, for example hydrogen, through it, and a valve which is configured to transfer the valve needle into a closing or releasing state by a movement along its longitudinal axis, wherein the valve needle is a hollow needle configured to guide a gas flowing through the injection port through the interior of the hollow needle.

2. Injector according to claim 1, wherein the injector is further configured to guide all of the gas flowing through the injection port through the interior of the hollow needle.

3. Injector according to claim 1, wherein the hollow needle comprises, starting from its interior, at least one flow channel extending laterally outwardly.

4. Injector according to claim 1, wherein the hollow needle comprises a flange-like projection at its end facing the injection opening which serves to seal the at least one injection opening located in a valve plate.

5. Injector according to claim 1, wherein the valve comprises an armature element which is movable relative to the longitudinal axis of the hollow needle and is firmly connected to the hollow needle.

6. Injector according to claim 5, wherein the armature element comprises a through hole for passing gas from a connection side of the injector to the interior of the hollow needle.

7. Injector according to claim 5, wherein the armature element and the hollow needle consist of different materials.

8. Injector according to claim 5, further comprising an elastic element which is configured to urge the armature element in a direction away from a connection side, to bias the hollow needle connected to the armature element in the direction of the injection opening.

9. Injector according to claim 1, further comprising a needle guide which is arranged in the injector housing, circumferentially surrounds the hollow needle on its outer side and is configured to permit only a movement of the hollow needle parallel to its longitudinal direction, wherein preferably the needle guide has a clearance in the longitudinal direction of the injector housing.

10. Injector according to claim 9, wherein the hollow needle on its outer side and/or the needle guide on its inner side comprises/comprise a coating for low-wear sliding.

11. Injector according to claim 9, wherein at least one guide tape is arranged between the hollow needle and the needle guide, which guide tape serves as a sliding partner between the hollow needle and the needle guide.

12. Injector according to claim 6, wherein the valve is a solenoid valve and comprises an annular solenoid coil circumferentially surrounding the armature element and capable of generating magnetic field lines to move the armature element towards the connection side of the injector.

13. Injector according to claim 5, wherein the hollow needle and the armature element are formed rotationally symmetrical or rotationally symmetrical with respect to a common axis of rotation, wherein the common axis of rotation is parallel or identical to the longitudinal axis of the hollow needle.

14. Injector according to claim 1, wherein the injector is configured to inject gas into a combustion chamber without the admixture of air via the at least one injection opening.

15. Internal combustion engine with gas direct injection, comprising an injector according to claim 1.

16. Injector according to claim 1, wherein the gas is hydrogen.

17. Injector according to claim 3, wherein in an open state of the injector, water can flow around the end of the hollow needle facing the injection opening on the inside and outside.

18. Injector according to claim 6, wherein a cavity of the hollow needle and the through hole of the armature element are coaxially arranged and/or are aligned with each other.

19. Injector according to claim 6, wherein the armature element is a magnetizable body which is moved in the longitudinal direction of the hollow needle upon actuation of a solenoid valve and, by connection with the hollow needle, lifts the latter off the injection opening or places it thereon

20. Injector according to claim 9, wherein the needle guide has a clearance in the longitudinal direction of the injector housing.

Description

[0045] Further features, details and advantages of the invention will be apparent from the following description of figures. The Figures show in:

[0046] FIG. 1: a sectional view through an injector according to the invention, and

[0047] FIG. 2: a detailed sectional view of another option for pressing the armature and needle.

[0048] The following detailed description of the figures refers to an injector for injecting hydrogen, although it is clear to the person skilled in the art that the invention also includes an injector for injecting gas.

[0049] FIG. 1 shows a longitudinal section of the injector 1 according to the invention for injecting hydrogen into a combustion chamber 16. The injector 1 comprises an injector housing 2 in which various components of the injector 1 are located. On the connection side, a gas connection 11 is provided for introducing a hydrogen into the injector 1. First of all, the hydrogen or another combustible fluid is passed through a bore of a cover 29 extending approximately centrally in the injector housing 2 and, following this, through a fluid channel of an armature counterpart 27, a through-opening 10 of the armature 5 and the hollow interior 12 of a hollow needle 3 to the end of the hollow needle 3 remote from the connection side 11.

[0050] Depending on the position of the hollow needle 3 relative to the valve plate 9, the injection openings 4 piercing the valve plate 9 are closed or opened. In the state shown in FIG. 1, the injection openings 4 are closed by pressing the hollow needle 3 against the valve plate 9, since the end face of the hollow needle 3 covers the opening contours of the injection openings 4. To improve the tightness, sealing elements 30 can be provided which extend around the opening contours of the injection openings 4 and contact the end face of the hollow needle 3 in a sealing state of the hollow needle 3. When the injection openings 4 are closed by the end face of the hollow needle 3, the fluid flow of hydrogen is stopped at this point of the injector 1 and there is no downstream flow of hydrogen beyond the valve plate 9.

[0051] If, on the other hand, the injection openings 4 are unblocked, which is implemented by lifting the hollow needle 3 away from the valve plate 9, the hydrogen introduced into the injector 1 at a certain pressure flows out of the interior 12 of the hollow needle 3 and exits via the plurality of injection openings 4 on the side of the valve plate 9 spaced from the hollow needle 3. After flowing through a check valve 20, 21, 23, which may optionally be provided in the injector 1, the pressurized hydrogen flows through the injection cap 18, which may also optionally be provided and which comprises at least one through opening 17. After passing through this injection cap 18, the hydrogen delivered by the injector 1 is then typically located outside the injector 1 in a combustion chamber 16. An admixture of air and a compression of the hydrogen-air mixture then generally takes place there, which then ignites or is ignited.

[0052] The check valve 20, 21, 23, which is located on the side of the valve plate 9 facing away from the hollow needle 3, serves to keep a very high pressure prevailing in the combustion chamber away from the at least one injection opening 4. Otherwise, it could happen that the very high pressure prevailing in the combustion chamber acts via the at least one injection opening 4 on the end face of the hollow needle 3 closing the injection opening 4 and moves it away from its position closing the at least one injection opening 4. In a subsequent operating step of the injector 1, the hydrogen required for combustion would then no longer be introduced into the combustion chamber 16, but rather a mixture that has already been at least partially burned, which can lead to an interruption of the combustion process or, at best, to a lower performance of the combustion process.

[0053] The check valve 20, 21, 23 comprises a valve tappet 20, a valve guide 21 and a valve spring 23, which urges the valve tappet in a closing direction, so that an outflow of hydrogen via the opening contour 19 of the check valve 20, 21, 23 only occurs if a pressure prevails on the side of the check valve 20, 21, 23 facing the valve plate 9 which is greater, at least by the restoring force of the valve tappet 20 exerted by the valve spring 23, than the pressure prevailing on the side facing away from the check valve 20, 21, 23 towards the valve plate 9. An inflow of fluid from the side of the check valve 20, 21, 23 arranged in the injection tube 22 facing the combustion chamber is thus prevented.

[0054] The valve needle 3, which is configured as a hollow needle 3, can be moved back and forth in the longitudinal direction of the injector 1. The movement of the valve needle 3 is controlled by a valve 5, 6, which in the present representation of FIG. 1 is a solenoid valve. The hollow needle 3 is firmly connected to an armature element 5, which in turn reacts to the magnetic force generated by a coil 6. The coil 6 can optionally have current flowing through it in such a way that the resulting magnetic force moves the armature element 5 in the direction of the gas connection 11. This movement also moves the hollow needle 3, which is firmly connected to the armature element 5, so that the hollow needle 3 is raised relative to the valve plate 9. This opens the injection openings 4 in the valve plate 9 so that hydrogen can flow through the valve plate 9. Possible ways of fastening the hollow needle 3 to the armature element 5 include, for example, pressing, a screw-in connection in the armature element 5, gluing or other relevant fastening options.

[0055] For precise guidance of the hollow needle 3 along the longitudinal axis or axis of rotation X of the injector or of the hollow needle 3 itself, a needle guide 14 is provided which circumferentially encloses an outer side of the hollow needle 3. In the contact area between the needle guide 14 and the outer side of the hollow needle 3, sliding friction occurs, so that it can be advantageous if one of the two contact surfaces or even both contact surfaces has a special coating, in particular a coating with carbon. It has been shown that such a coating containing carbon is advantageous with regard to the tribological requirements of the two sliding components.

[0056] The needle guide 14 can be configured in such a way that it extends from the valve plate 9 and protrudes inwardly at a certain distance from the latter, in order to come into contact with the outside of the hollow needle 3 only at the certain distance from the valve plate 9. Regardless of the specific design of the needle guide 14, the hollow needle 3 pierces the needle guide 14 in such a way that the end of the valve needle 3 facing the valve plate 9 is still completely guided through the needle guide 14 even in a state lifted from the valve plate 9. Like the armature element 5 and the hollow needle 3, the needle guide can be rotationally symmetrical or rotationally symmetrical to the axis of rotation X of the injector 1.

[0057] A flange-like projection is provided at the end of the hollow needle 3 facing the valve plate 9, which facilitates covering of the at least one injection opening 4 in the valve plate 9. In addition, the hollow needle 3 may also have further flow channels 7 extending obliquely or perpendicularly to its longitudinal direction, through which a hydrogen introduced into the hollow needle 3 can flow out. The advantage of this is that the hydrogen introduced into the injector 1 flows around the side of the hollow needle 3 facing the injection openings 4 on both sides, i.e. from the inside and from the outside. In this way, the stroke of the valve needle 3 or the armature element 5 can be minimized and yet the required flow of hydrogen can be realized. This is because the flow can be split into an external flow (via flow channel 7) and an internal flow through the outlet hole of hollow needle 3 facing valve plate 9. The flange-like projection 8, also known as the plate, is therefore flowed around on both sides.

[0058] An air gap 24 is provided between the needle guide 14 and the armature element 5, which allows some movement of the needle guide in the longitudinal direction of the injector 1. The needle guide 14 performs its primary task regardless of its exact arrangement position, so that even the slight play in the longitudinal direction of the injector 1 does not change this. In particular, however, in the event of compression of the injector housing 2, for example caused by fastening the injector 1 to a motor or thermal expansion or contraction, this air gap 24 serves as a reserve so that a change in length of the injector housing 2 in the longitudinal direction can be compensated for without introducing a force on the needle guide 14. On the side of the armature element 5 facing away from the hollow needle 3, an armature counterpart 27 is provided in which an elastic spring element 13 in the form of a spiral spring is arranged, which forces the armature element 5 in the direction of the valve plate 9. Thus, without actuating the valve 5, 6, the hollow needle 3 is urged in the direction of the valve plate 9 and closes the at least one injection opening 4. Similar to the armature element five, the armature counterpart 27 also has a through opening, the center of which may be arranged in the longitudinal center axis X of the injector 1. A simple implementation for introducing the elastic spring element 13 into the armature counterpart 27 is here to change the diameter of the through-opening of the armature counterpart 27. The step thus created is thereby used as a stop surface for the elastic spring element 13, so that design modifications beyond this are not necessary. The through opening through the armature counterpart 27 can be realized by two bores of different diameter, which have the same bore center axis. It can also be provided that the central axis of the bore is identical to the central axis of the armature element 5.

[0059] In order to improve the magnetic flux when the valve 5, 6 is implemented as a solenoid valve, the coil 6 can be surrounded on its outside by a back iron 25, in which the magnetic field can propagate particularly well. Similarly, the housing component directly surrounding the armature element 5 and the armature counterpart 27 also preferably consists of a magnetizable material. Thus, it can be advantageous if the pole tube 28, which is a component of the injector housing 2, is also made of iron or another ferromagnetic material. The same applies to the armature counterpart 27, which advantageously also consists of a magnetizable material.

[0060] A visualized representation of the magnetic field lines is illustrated by reference character 15. These have a direction that is counterclockwise when looking at FIG. 1. This pulls the armature element 5 toward the armature counterpart 27 and lifts the hollow needle 3 from the valve plate 9 or from the injection openings 4 that penetrate through the valve plate 9, so that hydrogen can flow in toward the check valve, from where hydrogen is ultimately introduced into the combustion chamber 16 via the injection cap 18.

[0061] FIG. 2 shows a detailed sectional view of a further option for pressing armature element 5 and needle 3, showing the upper half of the relevant area when connecting armature element 5 and needle 3. recognizes that two guide tapes 31 are arranged between needle 3 and needle guide 14, which are spaced apart from one another in the longitudinal direction of injector 1. It may be provided that the contact area 32 for pressing between needle 3 and armature element 5 is provided precisely in the area of the distance between the two guide tapes 31 extending in the longitudinal direction of the injector 1. As a result, a uniform force acts on the two guide tapes 31 when sliding between the needle 3 and the needle guide 14. It is also no longer possible for a single guide tape 31 to tend to warp due to the application of a force that is not uniformly balanced as a result of the pressing, and to no longer slide cleanly along the needle guide 14.

[0062] It is clear to the person skilled in the art that the design of the interference fit between armature 5 and needle 3 shown in FIG. 2 must not be understood as restrictive, but that the invention also includes the provision of only one guide tape 31 or more than two guide tapes 31 with identical arrangement of armature 5 and needle 3.