Spark Plug Housing Having a Galvanic Nickel and Zinc-Containing Protective Layer and a Silicon-Containing Sealing Layer, Spark Plug Having Said Housing, and Method for Producing Said Housing

Abstract

The disclosure relates to a housing for a spark plug, having a bore along the longitudinal axis X of the housing, the housing comprises an outer side and an inner side and a galvanically applied nickel and zinc-containing protective layer is arranged on at least one part of the outer side of the housing. A sealing layer, which contains silicon, is arranged on the nickel and zinc-containing protective layer.

Claims

1. A housing for a spark plug, the housing having an outer side and an inner side, comprising: a bore along a longitudinal axis of the housing; an electrochemically applied nickel- and zinc-containing protective layer disposed on at least part of the outer side of the housing; and a sealing layer is disposed on the nickel- and zinc-containing protective layer wherein the sealing layer comprises silicon.

2. The housing as claimed in claim 1, wherein the sealing layer is free from chromium.

3. The housing as claimed in claim 1, wherein the sealing layer has a layer thickness of 10 nm to 10 μm.

4. The housing as claimed in claim 1, wherein the nickel- and zinc-containing protective layer has a layer thickness of 1 μm to 30 μm on the housing.

5. The housing as claimed in claim 1, wherein at least one of a first interlayer is applied between the housing and the nickel- and zinc-containing protective layer, a second interlayer is applied between the nickel- and zinc-containing protective layer and the sealing layer, and an outer layer is applied on the sealing layer.

6. The housing as claimed in claim 5, wherein: The first interlayer is applied between the housing and the nickel and zinc-containing protective layer; and the first interlayer has a layer thickness of 1 nm to 1000 nm.

7. The housing as claimed in claim 5, wherein: the second interlayer is applied between the nickel- and zinc-containing protective layer and the sealing layer; and the second interlayer has a layer thickness of 1 nm to 1000 nm.

8. The housing as claimed in claim 5, wherein: the outer layer is applied on the sealing layer; and the outer layer has a layer thickness E of 1 nm to 2000 nm.

9. The housing as claimed in claim 5, wherein: the nickel- and zinc-containing protective layer and the sealing layer are formed on the entire outer side of the housing; the nickel- and zinc-containing protective layer and the sealing layer are formed on at least part of the inner side of the housing; and the at least one of the first interlayer, the second interlayer, and the outer layer are formed on the entire outer side of the housing, and on at least part of the inner side of the housing.

10. A spark plug, comprising: a housing as claimed in claim 1; an insulator disposed in the housing; a central electrode disposed in the insulator; and a ground electrode disposed on a combustion chamber-side end of the housing, wherein the ground electrode and the central electrode are configured to constitute a spark gap.

11. A method for producing a housing as claimed in claim 1, comprising: providing a housing for a spark plug having a nickel- and zinc-containing protective layer applied to the housing by means of an electrochemical coating process, and a second interlayer; washing the provided housing coated with the nickel- and zinc—containing protective layer; and applying a sealing layer to the washed nickel- and zinc-containing protective layer and the second interlayer.

12. The method for producing a housing as claimed in claim 11, further comprising: cleaning a surface of the housing coated with at least the nickel- and zinc-containing protective layer before washing the provided housing.

13. The method for producing a housing as claimed in claim 11, further comprising: the production method after the applying of the sealing layer to the nickel- and zinc-containing protective layer or to the second interlayer a drying step drying the housing after applying the sealing layer to remove at least one of water and solvents from the application of the sealing layer from a surface of the housing.

14. The method for producing a housing as claimed in claim 13, further comprising: curing the sealing layer during polycondensation and after drying the housing.

15. The method for producing a housing as claimed in claim 11, further comprising: applying an outer layer to the sealing layer.

16. The method for producing a housing as claimed in claim 11, wherein the sealing layer is applied using a coating technique selected from the group consisting of a sol-gel operation, CCVD and PVD.

17. The method for producing a housing as claimed in claim 11, wherein silanes with functionalization selected from the group consisting of alkoxysilanes, aminosilanes, and acrylosilanes, are used for the sealing layer.

18. The method for producing a housing as claimed in claim 17, wherein silanes without functionalization selected from the group consisting of alkyltrialkoxysilanes are also used for the sealing layer.

19. The housing as claimed in claim 3, wherein the sealing layer has a layer thickness of 100 nm to 1 μm.

Description

DRAWING

[0038] FIG. 1 shows an example of a corrosion control layer system according to the invention on a housing

[0039] FIG. 2 shows a further example of a corrosion control layer system according to the invention on a housing

[0040] FIG. 3 shows an example of a spark plug with the housing according to the invention

[0041] FIG. 4 shows illustratively the production method for a housing according to the invention

DESCRIPTION OF THE WORKING EXAMPLE

[0042] FIG. 1 shows an example of a corrosion control layer system according to the invention, consisting of the nickel- and zinc-containing protective layer 210 and of the silicon-containing sealing layer 220. The nickel- and zinc—containing protective layer 210 is applied on the surface of a housing 2. Applied in turn to the nickel- and zinc—containing protective layer 210 is the silicon-containing sealing layer 220.

[0043] The nickel- and zinc-containing protective layer 210 has a layer thickness B. The layer thickness is measured perpendicularly to the housing surface. Since the nickel- and zinc-containing protective layer 210 is applied by means of electroplating on the housing 2, the layer thickness B of the nickel- and zinc-containing protective layer 210 may differ at different sites on the housing 2. On its inner side 204, for example, the housing 2 may have no nickel- and zinc-containing protective layer 210 or only partially a nickel- and zinc-containing protective layer. Preferably, the housing 2 has a nickel- and zinc-containing protective layer 210 on its entire outer side 205.

[0044] The silicon-containing sealing layer 220 has a layer thickness A. In the case of a silicon-containing sealing layer 220 applied by means of a dipping bath in a silane solution, the resulting silicone-containing sealing layer 220 generally has a very uniform layer thickness A. In particular, the silicon-containing sealing layer 220 may be formed on the entire surface of the housing 2, including at sites on the housing 2 at which there is no nickel- and zinc—containing protective layer 210, such as regions of the inner side 204 of the housing 2, for example.

[0045] FIG. 2 shows a further example of a corrosion control layer system according to the invention, consisting of the nickel- and zinc-containing protective layer 210 and of the silicon-containing sealing layer 220 and also of the first interlayer 301 and the second interlayer 302 and the outer layer 303. Applied on the surface of a housing 2 is the first interlayer 301. Applied in turn on the latter is the nickel- and zinc-containing protective layer 210. The second interlayer 302 is disposed between the nickel- and zinc-containing protective layer 210 and the silicon—containing sealing layer 220. Applied in turn on the silicon-containing sealing layer 220 is the outer layer 303.

[0046] The nickel- and zinc-containing protective layer 210 has a layer thickness B. The first interlayer 301 has a layer thickness C and second interlayer 302 has a layer thickness D. The layer thicknesses are measured perpendicularly to the housing surface. If the nickel- and zinc-containing protective layer 210 is applied by means of electroplating on the housing 2, the layer thickness B of the nickel- and zinc-containing protective layer 210 may be different at different sites on the housing 2. On its inner side 204, for example, the housing 2 may have no nickel- and zinc—containing protective layer 210 or only partially a nickel- and zinc-containing protective layer 210.

[0047] The silicon-containing sealing layer 220 has a layer thickness A. In the case of the silicon-containing sealing layer 220 applied by means of a dipping bath in a silane solution, the resulting silicone-containing sealing layer 220 generally has a very uniform layer thickness A. In particular, the silicon-containing sealing layer 220 may be formed on the entire surface of the housing 2, including at sites on the housing 2 at which there is no nickel- and zinc—containing protective layer 210, such as regions of the inner side 204 of the housing 2, for example. The outer layer 303 has a layer thickness E.

[0048] In further embodiments of the housing 2 with the corrosion control layer system according to the invention, the corrosion control layer system, besides the nickel- and zinc-containing protective layer 210 and the sealing layer 220, may comprise only the outer layer 303 or only the first or second interlayer 301, 302, or the outer layer 303 in combination with the first or second interlayer 301, 302.

[0049] FIG. 3 shows a spark plug 1 in a half-sectional view. The spark plug 1 comprises a housing 2. Inserted in the housing 2 is an insulator 3. The housing 2 and the insulator 3 each have a bore along their longitudinal axis X. As a result of the bore, the housing 2 has an outer side 205 and an inner side 204. The longitudinal axis of the housing 2, the longitudinal axis of the insulator 3 and the longitudinal axis of the spark plug 1 are coincident. Inserted in the insulator 3 is a central electrode 4. Furthermore, a connection bolt 8 extends into the insulator 3. Disposed on the connection bolt 8 is a connection nut 9, via which the spark plug 1 can be contacted electrically with a voltage source which is not shown here. The connection nut 9 forms the end of the spark plug 1 that faces away from the combustion chamber.

[0050] Located in the insulator 3, between the central electrode 4 and the connection bolt 8, is a resistance element 7, also called CCM (Ceramic Compound Material). The resistance element 7 provides an electrically conducting connection between the central electrode 4 and the connection bolt 8. The resistance element 7 is constructed, for example, as a layer system from a first contact-CCM 72a, a resistance—CCM 71 and a second contact-CCM 72b. The layers of the resistance element 7 differ in their physical composition and in the resulting electrical resistance. The first contact-CCM 72a and the second contact-CCM 72b may have a different electrical resistance or an identical electrical resistance. The resistance element 7 may also comprise only one layer of resistance-CCM or two or more different layers of resistance-CCM with different physical compositions and resistances.

[0051] A shoulder of the insulator 3 lies on a housing seat formed on the inner side of the housing. In order to seal off the air gap between the inner side of the housing and the insulator 3, an inner seal 10 is disposed between the insulator shoulder and the housing seat, and, when the insulator 3 is clamped in the housing 2, this inner seal 10 undergoes plastic deformation and so seals off the air gap.

[0052] Disposed in an electrically conducting manner on the housing 2, on its end face on the combustion chamber side, there is arranged a ground electrode 5. The ground electrode 5 and the central electrode 4 are arranged with respect to one another in such a way that a spark gap is formed between them, at which the ignition spark is generated.

[0053] The housing 2 has a shaft. A polygon 21, a shrink recess and a screw thread 22 are formed on this shaft. The screw thread 22 serves for screwing the spark plug 1 into an internal combustion engine. Disposed between the screw thread 22 and the polygon 21 is an outer sealing element 6. In this working example, the outer sealing element 6 is configured as a fold seal.

[0054] The housing 2 consists of a steel, such as carbon steel, for example. Applied on the housing 2, more particularly on its outer side, is a nickel- and zinc-containing protective layer 210. The nickel- and zinc-containing protective layer 210 has a layer thickness B, with B preferably being not less than 1 μm and not more than 30 μm. The nickel- and zinc-containing protective layer 210 serves as passive corrosion control. Also applied on the nickel- and zinc—containing protective layer 210 is a silicon-containing sealing layer 220. The silicon-containing sealing layer 220 has a layer thickness A, with A preferably being not less than 10 nm and not more than 1000 nm.

[0055] FIG. 4 shows, schematically, a detail of the illustrative sequence of the method for producing a housing 2 according to the invention:

[0056] In a first, optional step S1, the housing 2, which has been coated beforehand, by means of electroplating, with at least the nickel- and zinc-containing protective layer 210 and optionally with one or two interlayers, and its surface is cleaned. For this purpose, the housing 2 coated with at least the nickel- and zinc-containing protective layer 210 is placed into a bath containing a highly alkaline cleaner and is additionally bombarded with ultrasound in the bath for around 5 min. The optional cleaning step serves, on the one hand, for removing particles, dirt and passivating agent which hinder application of the sealing layer 220; on the other hand, the surface to which the sealing layer 220 is to be applied is hydrolyzed and/or activated, so that the sealing layer 220 has a good attachment possibility. Optionally, before the optional cleaning, the housing 2 may have not only the nickel- and zinc-containing protective layer 210 but also a first interlayer 301 and/or a second interlayer 302.

[0057] In the second step S2, the cleaned housing 2 is washed with demineralized water, for example, so that possible residues of cleaning agent are removed.

[0058] In the third step S3, the sealing layer 220 is applied. Application in this case may take place, for example, by silanization of the coated housing 2. In that case, the housing 2 is immersed into a silane solution or sprayed with a silane solution. In this step, the silane binds to the hydrolyzed surface of the housing 2 and begins to cross-link, causing the sealing layer 220 to form.

[0059] In the optional fourth step S4, the housing 2 is dried and the sealing layer 220 cures. In that case the housing 2, after the silanization, is placed, for example, into a drying oven at around 130° C. for around 15 min. Here, possible residues of water or residues of solvent, from the bath, for example, are removed from the sealing layer 220. At the same time, the crosslinking of the silanes with one another is concluded, causing the sealing layer 220 to cure. The drying step is particularly advantageous, since it supports and accelerates the crosslinking of the silanes with one another.

[0060] In the final step S5 shown here, the housing 2 cools before it is passed on for further processing operations, such as, for example, application of an outer layer 303 to the silicon-containing sealing layer 220, or assembly of the spark plug 1.