VALVE AND METHOD FOR PRODUCING A VALVE

Abstract

A valve is provided, in particular an injection valve, having a valve seat and a valve needle which extends along a closing direction for the most part, the valve seat having a valve-seat surface, and a valve-closing element is mounted on an end of the valve needle facing the valve seat, the valve-closing element being able to be moved between an open position and a closed position, and the valve-closing element together with the valve-seat surface forming a sealing seat in the closed position, the valve-closing element having a greater core hardness and/or surface hardness than the valve-seat surface.

Claims

1-10. (canceled)

11. An injection valve, comprising: a valve seat having a valve-seat surface; a valve needle which extends along a closing direction, a valve-closing element being mounted on an end of the valve needle facing the valve seat, the valve-closing element being able to be moved between an open position and a closed position, the valve-closing element forming a sealing seat together with the valve-seat surface in the closed position; wherein the valve-closing element has at least one of: i) a greater core hardness than the valve-seat surface, and ii) a greater surface hardness than the valve-seat surface.

12. The valve as recited in claim 11, wherein the valve-seat surface is adapted to a form of the valve-closing element, and the valve-closing element has a spherical form.

13. The valve as recited in claim 11, wherein the valve-closing element has a surface region and in the closed position, the valve-closing element is in contact with the valve-seat surface in the surface region, the valve-closing element having a greater surface hardness in the surface region than the valve-seat surface.

14. The valve as recited in claim 13, wherein the surface region of the valve-closing element includes a diffusion layer, and the diffusion layer has a greater surface hardness than the valve-seat surface.

15. The valve as recited in claim 13, wherein the surface region includes a layer made of a coating material, the layer having a greater surface hardness than the valve-seat surface, the layer being an amorphous carbon layer.

16. The valve as recited in claim 15, wherein a surface of the valve-closing element is at least partially made up of the layer.

17. The valve as recited in claim 15, wherein the layer has a coating thickness between 0 and 50 micrometers.

18. The valve as recited in claim 15, wherein the layer has a coating thickness between 1 and 20 micrometers, and especially preferably, between 1.5 and 5 micrometers.

19. The valve as recited in claim 15, wherein the layer has a coating thickness between 1.5 and 5 micrometers.

20. A method for producing a valve, comprising: in a first production step, developing a valve-closing element from a base body material; in a second production step, nitrifying the valve-closing element; and in a third production step, boronizing the valve-closing element.

21. The method as recited in claim 20, further comprising: in a fourth production step, coating the valve-closing element with the coating material so that the layer made of the coating material is formed in a surface region of the valve-closing element.

22. The method as recited in claim 20, wherein in the second production step, the valve-closing element is nitrified in such a way that a nitrification depth amounts to between 1 and 100 micrometers.

23. The method as recited in claim 20, wherein in the second production step, the valve-closing element is nitrified in such a way that a nitrification depth amounts to between 5 and 50 micrometers.

24. The method as recited in claim 20, wherein in the second production step, the valve-closing element is nitrified in such a way that a nitrification depth amounts to between 10 and 20 micrometers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIGS. 1 through 5 show a valve according to different specific embodiments of the present invention in a schematic cross-sectional view.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0026] In all instances, identical components have been provided with the same reference numerals in the various figures and thus are generally also identified or mentioned only once.

[0027] FIG. 1 shows a valve 1 according to one specific embodiment of the present invention in a schematic cross-sectional view. In particular, valve 1 shown here is an injection valve for the injection of fuel into a combustion chamber (not shown). Valve 1 includes a valve seat 10 and a valve needle 20 which extends along a closing direction 101 for the most part. A valve-closing element 21, such as a valve-closing ball, is mounted on an end of valve needle 20 facing valve seat 10. In other words, valve needle 20 in particular includes valve-closing element 21 and a valve-needle base body 20′ to which valve-closing element 21 is welded. Valve-closing element 21 is able to be moved between an open position and a closed position. In this instance, the valve is shown in a closed position of valve-closing element 21. Valve seat 10 has a valve-seat surface 11, which forms a sealing seat together with valve-closing element 21 in the closed position of valve-closing element 21. Moreover, the valve in particular includes a restoring spring 40, which is configured in such a way that valve-closing element 21 is moved from the open position to the closed position and is retained in the closed position until a magneto armature 30 of valve 1 lifts valve needle 20 off, counter to a spring force of restoring spring 40. During the opening of valve 1, the armature is preferably first accelerated along a free armature travel 31 and then strikes a stop element 41 so that valve-closing element 21 is moved from the closed position into the open position. In addition, FIG. 1 exemplarily illustrates a further restoring spring 40′, a further stop element 41′ and a further armature free travel 31′ for a closing operation of valve 1. In particular, valve 1 has a spring cup 42′ in this instance.

[0028] For example, valve-closing element 21 is a valve ball which sits on valve seat 10 having a conical geometry and thereby forms the sealing seat. A contact region between valve-closing element 21 and a valve-seat surface 11 of valve seat 10 in particular is linear and the the contact region is enlarged by wear, for example.

[0029] FIG. 2 shows a schematic cross-sectional view of a valve 1 according to a specific embodiment of the present invention; the specific embodiment shown here is essentially identical with the specific embodiment according to FIG. 1. According to the present invention, it is provided that valve-closing element 21 has a greater core hardness and/or surface hardness than valve-seat surface 11, so that a valve 1 is provided which has relatively low wear and/or has only a predefined wear. In an advantageous manner, this particularly makes it possible to place a predefined number and/or a predefined size of spray-discharge orifices 12 downstream from the sealing seat up to a wear region in the sealing seat, which, however, are not adversely affected by wear of the valve seat or are affected relatively little by such wear. FIG. 2 shows a valve-closing element 21 which was produced in a diffusion-method step and includes a diffusion layer 22. This advantageously realizes surface hardening of valve-closing element 21, the diffusion method in particular including a nitriding method, boration method and/or a kolsterization method. In the diffusion-method step, a certain substance in a gaseous state, in a plasma state or in a liquid state preferably diffuses into a material surface of valve-closing element 21 and forms a relatively hard diffusion layer 22. In an advantageous manner, this particularly allows for the realization of a surface hardness and/or corrosion resistance in a predefined manner and for a selective weldability of valve-closing element 21 on valve-needle base element 20′. According to the present invention, it is preferably provided that valve-closing element 21 has a support hardness for realizing a material pairing that features a predefined hardness difference so that in particular a hardness of valve-closing element 21 is greater than a hardness of valve seat 10. For instance, valve-closing element 21 has a relatively hard solid material so that greater core hardness and/or surface hardness of valve-closing element 21 is realized in comparison with valve seat 10 (at least in the area of the sealing seat). For instance, valve-closing base element 21 is produced from titanium, ceramics, tungsten or from an alloy that includes titanium, ceramics or tungsten or another material.

[0030] FIG. 3 shows a schematic cross-sectional view of a valve 1 according to a specific embodiment of the present invention; in particular, the specific embodiment shown here is essentially identical with one of the preceding specific embodiments, but in this case, valve-seat surface 11 is adapted to a form (in particular to a surface in a surface region 21′) of valve-closing element 21. Here, a state of valve 1 prior to and after the breaking-in process (see reference numerals 11 and 11′) is illustrated; during the breaking-in process, valve-closing element 21 penetrates valve seat 10 to such an extent that a defined or predefined wear is generated in the region of the sealing seat. This advantageously makes it possible for valve seat 10 to realize a damping effect during the closing of valve 1, and a noise level during the closing of valve 1 is reduced, in particular, in comparison with the related art.

[0031] FIG. 4 shows a schematic cross-sectional view of a valve 1 according to one specific embodiment of the present invention. In particular, the specific embodiment shown here is essentially identical with one of the preceding specific embodiments, and a layer 23 is depicted, which is situated in a surface region 21′ of valve-closing element 21 in this case. Here, layer 23 forms a surface of valve-closing element 21. The layer is an amorphous carbon layer (DLC: diamond-like carbon), for instance, or a titanium layer (such as a titanium-aluminum-nitride layer). Preferably, layer 23 is configured in such a way that layer 23 is subject to wear itself (i.e. is adapted to the valve-seat form of valve seat 10) so that valve-seat surface 11 itself is not deformed by layer 23. In this way, a relatively high tightness of the sealing seat is advantageously realized. In this case, a main portion of the surface of valve-closing element 21 is provided with layer 23.

[0032] FIG. 5 shows a schematic cross-sectional view of a valve 1 according to a specific embodiment of the present invention; in particular, the specific embodiment shown here is essentially identical with one of the preceding specific embodiments, and valve-closure element 21 is partially coated in this case.

[0033] Valve-closing element 21 is preferably coated in such a way that valve-closing element 21 includes layer 23 in a region that faces valve seat 10. Especially preferably, the region facing valve seat 10 includes a sealing region (to form the sealing seat) and/or a guide region and/or further tribologically stressed regions.