Spark plug housing including an electroplated or a chemically applied nickel-containing protective layer and a silicon-containing sealing layer, and a spark plug including this housing, and method for manufacturing this housing

Abstract

A housing for a spark plug. The housing includes a bore along the longitudinal axis X of the housing, as the result of which the housing has an outer side and an inner side, and an electroplated or chemically applied nickel-containing protective layer situated on at least one portion of the outer side of the housing and a sealing layer situated on the nickel-containing protective layer. The sealing layer contains silicon. A first intermediate layer is applied between the housing and the nickel-containing protective layer and/or a second intermediate layer is applied between the nickel-containing protective layer and the sealing layer and/or a cover layer is applied on the sealing layer. The sealing layer may be free of chromium.

Claims

1. A spark plug, comprising: a housing including a bore along a longitudinal axis of the housing, as a result of which the housing has an outer side and an inner side, an electroplated or chemically applied nickel-containing protective layer situated on at least one portion of the outer side of the housing, and a sealing layer situated on the nickel-containing protective layer, wherein the sealing layer contains silicon; an insulator situated in the housing; a center electrode situated in the insulator; and a ground electrode situated at the combustion chamber-side end of the housing, the ground electrode and the center electrode being configured for jointly forming a spark gap, wherein the sealing layer contains silicon, wherein the sealing layer is made by silanization of a surface of the housing, which is covered by the nickel-containing protective layer.

2. A housing for a spark plug, comprising: a bore along a longitudinal axis of the housing, as a result of which the housing has an outer side and an inner side; an electroplated or chemically applied nickel-containing protective layer situated on at least one portion of the outer side of the housing; and a sealing layer situated on the nickel-containing protective layer, wherein the sealing layer contains silicon, wherein the sealing layer contains silicon, wherein the sealing layer is made by silanization of a surface of the housing, which is covered by the nickel-containing protective layer.

3. The housing as recited in claim 2, wherein the sealing layer is free of chromium.

4. The housing as recited in claim 2, wherein at least one of: (i) a first intermediate layer is situated between the housing and the nickel-containing protective layer, (ii) a second intermediate layer is situated between the nickel-containing protective layer and the sealing layer, or (iii) a cover layer is situated on the sealing layer.

5. The housing as recited in claim 4, wherein at least one of the first intermediate layer has a layer thickness of 1 nm to 1000 nm, (ii) the second intermediate layer has a layer thickness of 1 nm to 1000 nm, or (iii) the cover layer has a layer thickness of 1 nm to 2000 nm.

6. The housing as recited in claim 4, wherein the nickel-containing protective layer and the sealing layer, and at least one of: (i) the first intermediate layer, (ii) the second intermediate layer, or (iii) the cover layer, are formed on an entire outer side of the housing and on at least one portion of the inner side of the housing.

7. The housing as recited in claim 2, wherein the sealing layer has a layer thickness of 10 nm to 10 μm.

8. The housing as recited in claim 2, wherein the sealing layer has a layer thickness of 100 nm to 1 μm.

9. The housing as recited in claim 2, wherein the nickel-containing protective layer has a layer thickness of 1 μm to 30 μm on the housing.

10. A method for manufacturing a housing, comprising the following steps: providing a housing for a spark plug including a nickel-containing protective layer, which was applied onto the housing using an electroplating coating method or a chemical coating method; after the providing, rinsing the housing coated with the nickel-containing protective layer; and after the rinsing, applying a sealing layer onto the nickel-containing protective layer, wherein the sealing layer contains silicon, wherein the sealing layer is made by silanization of a surface of the housing, which is covered by the nickel-containing protective layer.

11. The method as recited in claim 10, wherein the housing includes an intermediate layer suited on the nickel-containing protective layer, wherein in the applying step, the sealing layer is applied onto the intermediate layer.

12. The method as recited in claim 10, further comprising: before the rinsing step, cleaning the surface of the housing coated with the nickel-containing protective layer.

13. The method as recited in claim 10, further comprising: after the applying of the sealing layer onto the nickel-containing protective layer, drying the housing to remove possible water or solvent from the application of the sealing layer from the surface of the housing.

14. The method as recited in claim 13, wherein after the drying step, a polycondensation step occurs, in which the sealing layer cures.

15. The method as recited in claim 10, further comprising: applying a cover layer onto the sealing layer.

16. The method as recited in claim 10, wherein a sol-gel process, or CCVD, or PVD is utilized as a coating method for the applying of the sealing layer.

17. The method as recited in claim 10, wherein silanes with functionalization including alkoxysilanes, or aminosilanes, or acrylsilanes, are utilized for the sealing layer.

18. The method as recited in claim 17, wherein, additionally, silanes without functionalization, including alkyl trialkoxysilanes, are also utilized for the sealing layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an example of a nickel-containing protective layer on a housing according to the related art.

(2) FIG. 2A shows an example of a corrosion-protection-layer system according to the present invention on a housing.

(3) FIG. 2B shows a second example of a corrosion-protection-layer system according to the present invention on a housing.

(4) FIG. 3 shows an example of a spark plug including the housing according to the present invention.

(5) FIG. 4 shows, by way of example, the method for manufacturing a housing according to the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(6) FIG. 1 shows an example of a nickel-containing protective layer 210 on a housing 2 according to the related art. Layer thickness B of nickel-containing protective layer 210 is plotted on the left side. The percentage of defects 215, which reach housing 2, is plotted on the right side. In this schematic representation, it is apparent that, as layer thickness B increases, the number of defects 215, which extend through entire nickel-containing protective layer 210 up to housing 2, decreases.

(7) FIG. 2A shows an example of a corrosion-protection-layer system according to the present invention, made up of nickel-containing protective layer 210 and silicon-containing sealing layer 220. Nickel-containing protective layer 210 is applied on the surface of a housing 2. Silicon-containing sealing layer 220 is applied onto nickel-containing protective layer 210. Nickel-containing protective layer 210 has a layer thickness B. The layer thickness is measured perpendicularly to the housing surface. If nickel-containing protective layer 210 has been applied on housing 2 with the aid of electroplating, layer thickness B of nickel-containing protective layer 210 may be different at various points of housing 2. For example, housing 2 may include no nickel-containing protective layer 210 or only partially include a nickel-containing protective layer 210 on its inner side 204. Preferably, housing 2 includes a nickel-containing protective layer 210 on its entire outer side 205.

(8) Silicon-containing sealing layer 220 has a layer thickness A. In the case of a silicon-containing sealing layer 220, which is applied with the aid of a dipping bath in a silane solution, a highly uniform layer thickness A generally results for silicon-containing sealing layer 220. In particular, silicon-containing sealing layer 220 may be formed on the entire surface of housing 2, also at points of housing 2 at which there is no nickel-containing protective layer 210, such as areas of inner side 204 of housing 2.

(9) FIG. 2B shows a second example of a corrosion-protection-layer system according to the present invention, made up of nickel-containing protective layer 210 and silicon-containing sealing layer 220 as well as first intermediate layer 301 and second intermediate layer 302 and cover layer 303. First intermediate layer 301 is applied on the surface of a housing 2. Nickel-containing protective layer 210 is in turn applied thereon. Second intermediate layer 302 is situated between nickel-containing protective layer 210 and silicon-containing sealing layer 220. Cover layer 303 is in turn applied on silicon-containing sealing layer 220. Nickel-containing protective layer 210 has a layer thickness B. First intermediate layer 301 has a layer thickness C and second intermediate layer 302 has a layer thickness D. The layer thicknesses are measured perpendicularly to the housing surface. If nickel-containing protective layer 210 has been applied on housing 2 with the aid of electroplating, layer thickness B of nickel-containing protective layer 210 may be different at various points of housing 2. For example, housing 2 may include no nickel-containing protective layer 210 or only partially include a nickel-containing protective layer 210 on its inner side 204. Silicon-containing sealing layer 220 has a layer thickness A. In the case of a silicon-containing sealing layer 220, which is applied with the aid of a dipping bath in a silane solution, a highly uniform layer thickness A generally results for silicon-containing sealing layer 220. In particular, silicon-containing sealing layer 220 may be formed on the entire surface of housing 2, also at points of housing 2 at which there is no nickel-containing protective layer 210, such as areas of inner side 204 of housing 2. Cover layer 303 has a layer thickness E.

(10) In further embodiments of housing 2 including the corrosion-protection-layer system according to the present invention, the corrosion-protection-layer system may include, alongside nickel-containing protective layer 210 and sealing layer 220, only cover layer 303 or only first intermediate layer 301 or second intermediate layer 302 or cover layer 303 in combination with first intermediate layer 301 or second intermediate layer 302.

(11) FIG. 3 shows a spark plug 1 in a bisected view. Spark plug 1 includes a housing 2. An insulator 3 is inserted into housing 2. Housing 2 and insulator 3 each include a bore along its longitudinal axis X. Due to the bore, housing 2 includes an outer side 205 and an inner side 204. The longitudinal axis of housing 2, the longitudinal axis of insulator 3, and the longitudinal axis of spark plug 1 coincide. A center electrode 4 is inserted into insulator 3. Moreover, a terminal stud 8 extends into insulator 3. A terminal nut 9 is situated at terminal stud 8, via which spark plug 1 is electrically contactable to a voltage source (not represented here). Terminal nut 9 forms the end of spark plug 1 facing away from the combustion chamber.

(12) A resistor element 7, also referred to as CCM (ceramic compound material), is located in insulator 3 between center electrode 4 and terminal stud 8. Resistor element 7 connects center electrode 4 to terminal stud 8 in an electrically conductive manner. Resistor element 7 is designed, for example, as a layer system made up of a first contact CCM 72a, a resistor CCM 71, and a second contact CCM 72b. The layers of resistor element 7 differ with respect to their material composition and the resultant electrical resistance. First contact CCM 72a and second contact CCM 72b may have a different electrical resistance or an identical electrical resistance. Resistor element 7 may also include only one layer of resistor CCM or multiple various layers of resistor CCM having different material compositions and resistances.

(13) Insulator 3 rests via one shoulder on a housing seat formed at the housing inner side. In order to seal the air gap between the housing inner side and insulator 3, an inner seal 10 is situated between the insulator shoulder and the housing seat, which is plastically deformed when insulator 3 is clamped in housing 2.

(14) A ground electrode 5 is electrically conductively situated at housing 2 on its combustion chamber-side end face. Ground electrode 5 and center electrode 4 are situated with respect to one another in such a way that a spark gap forms between them, at which the ignition spark is generated.

(15) Housing 2 includes a shaft. A polygon 21, a shrink recess, and a thread 22 are formed on this shaft. Thread 22 is utilized for screwing spark plug 1 into an internal combustion engine. An outer sealing element 6 is situated between thread 22 and polygon 21. Outer sealing element 6 is designed as a folded-wall seal ring in this exemplary embodiment.

(16) Housing 2 is made up of a steel, for example carbon steel. A nickel-containing protective layer 210 is applied on housing 2, in particular on its outer side. Nickel-containing protective layer 210 has a layer thickness B, B preferably being not less than 1 μm and not greater than 30 μm. Nickel-containing protective layer 210 is utilized as passive corrosion protection. A silicon-containing sealing layer 220 is also applied on nickel-containing protective layer 210. Silicon-containing sealing layer 220 has a layer thickness A, A preferably being not less than 10 nm and not greater than 1000 nm.

(17) FIG. 4 schematically shows a section of the exemplary sequence of the method for manufacturing a housing 2 according to the present invention.

(18) In a first optional step S1, housing 2, which was previously coated with a nickel-containing protective layer 210 with the aid of electroplating or a chemical coating method, and its surface are cleaned. For this purpose, housing 2 coated with nickel-containing protective layer 210 is placed into a bath with a high alkaline cleaning agent and is additionally irradiated with ultrasound in the bath for approximately 5 minutes. The optional cleaning step is utilized, on the one hand, for removing particles, dirt, and passivation agents, which obstruct an application of sealing layer 220; on the other hand, the surface, onto which sealing layer 220 is to be applied, is hydrolyzed and activated, so that sealing layer 220 has a good bonding possibility. Optionally, before the optional cleaning, housing 2 may also include, alongside nickel-containing protective layer 210, a first intermediate layer 301 and/or a second intermediate layer 302.

(19) In second step S2, cleaned housing 2 is rinsed with, for example, demineralized water, so that possible residue of cleaning agents is removed.

(20) In third step S3, sealing layer 220 is applied. The application may take place, for example, via a silanization of housing 2. In this case, housing 2 is dipped into a silane solution or is sprayed with a silane solution. In this step, the silane bonds to the hydrolyzed surface of housing 2 and begins to cross-link, thereby creating sealing layer 220.

(21) In optional fourth step S4, a drying of housing 2 and the curing of sealing layer 220 take place. After the silanization, housing 2 is placed, for example, into a drying oven at approximately 130° C. for approximately 15 minutes. Possible water residue or solvent residue, for example from the bath, is removed from sealing layer 220. Simultaneously, the cross-linking of the silanes with one another is concluded, as the result of which sealing layer 220 cures. The drying step is particularly advantageous, since, as a result, the cross-linking of the silanes with one another is supported and accelerated.

(22) In final step S5 shown here, housing 2 cools down before it is forwarded for further processing, such as an application of a cover layer 303 onto silicon-containing sealing layer 220 or an assembly of spark plug 1.