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. An injection valve, comprising: a valve seat having a valve-seat surface; and 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, or ii) a greater surface hardness than the valve-seat surface; and wherein the valve-closing element includes a base body material and at least one diffusion layer with nitrogen and boron diffused into the base body material, the at least one diffusion layer being produced by (i) conducting a nitrifying diffusion on the valve-closing element, the nitrifying diffusion including diffusing nitrogen into the base body material by providing a nitrogen-containing substance in at least one of: a gaseous state, a liquid state, or a plasma state; and (ii) conducting a boronizing diffusion on the valve-closing element, the boronizing diffusion including diffusing boron into the base body material by providing a boron-containing substance in at least one of: a gaseous state, a liquid state, or a plasma state.

2. The valve as recited in claim 1, wherein the valve-seat surface is adapted to a form of the valve-closing element, and the valve-closing element has a spherical form.

3. The valve as recited in claim 1, 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.

4. The valve as recited in claim 3, wherein the surface region of the valve-closing element includes the diffusion layer, and the diffusion layer has a greater surface hardness than the valve-seat surface.

5. The valve as recited in claim 3, 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.

6. The valve as recited in claim 5, wherein a surface of the valve-closing element is at least partially made up of the layer.

7. The valve as recited in claim 5, wherein the layer has a coating thickness between 0 and 50 micrometers.

8. The valve as recited in claim 5, wherein the layer has a coating thickness between 1 and 20 micrometers.

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

10. The valve as recited in claim 1, wherein the valve-closing element includes a body formed from the base body material.

11. The valve as recited in claim 1, wherein a center of the valve-closing element is formed from the base body material.

12. The valve as recited in claim 1, wherein the nitrogen is diffused into the base body material in the at least one diffusion layer to a depth of between 1 and 100 micrometers.

13. The valve as recited in claim 1, wherein the nitrogen is diffused into the base body material in the at least one diffusion layer to a depth of between 5 and 50 micrometers.

14. The valve as recited in claim 1, wherein the nitrogen is diffused into the base body material in the at least one diffusion layer to a depth of between 10 and 20 micrometers.

15. The valve as recited in claim 1, wherein the boron is diffused into the base body material in the at least one diffusion layer to a depth of between 1 and 100 micrometers.

16. The valve as recited in claim 1, wherein the boron is diffused into the base body material in the at least one diffusion layer to a depth of between 5 and 90 micrometers.

17. The valve as recited in claim 1, wherein the nitrogen is diffused into the base body material in the at least one diffusion layer to a depth of between 15 and 30 micrometers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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

(2) 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.

(3) 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.

(4) 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.

(5) 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.

(6) 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.

(7) 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.

(8) 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. 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.