Spark plug

Abstract

A spark plug having a center conductor, an insulator surrounding the center conductor, at least two electrodes forming a spark gap, and a spark plug body surrounding the insulator and having an external thread arranged at the front end of the spark plug for screwing in to an internal combustion engine. A component that is attached to the front end of the spark plug and comes into contact with fuel during operation is formed as a sintered powder injection molded part, referred to as a metal injection molded (MIM) component.

Claims

1. A method of manufacturing a spark plug component, comprising the steps of: mixing a nickel-based metal powder with a binder material to form a feedstock material comprising the nickel-based metal powder mixed with the binder material; providing the feedstock material to an injection mold machine; injection molding the feedstock material in the injection mold machine to form a metal injection molded (MIM) spark plug component in the form of a green part; removing the binder material from the green part to form the MIM spark plug component in the form of a powder metal structure; sintering the powder metal structure to form the MIM spark plug component in the form of a MIM spark plug cap or MIM spark plug ground electrode; and attaching the MIM spark plug component to a spark plug body without polishing a surface of the spark plug component, wherein during the attaching step, an unpolished surface of the MIM spark plug component is attached to the spark plug body.

2. The method of claim 1, further comprising the step of welding an annular section of the MIM spark plug component to a front end of a spark plug body.

3. The method of claim 2, wherein the annular section of the MIM spark plug component is welded along an entire circumference to the front end of the spark plug body.

4. The method of claim 1, wherein the nickel-based metal powder includes a nickel-based alloy having nickel, iron, and chromium, with nickel as the main constituent.

5. The method of claim 1, wherein the MIM spark plug cap or the MIM spark plug ground electrode has a modulus of elasticity that is at least 5% smaller than a modulus of elasticity of a spark plug cap or a spark plug ground electrode formed by fusion metallurgy.

6. The method of claim 5, wherein the MIM spark plug cap or the MIM spark plug ground electrode has a modulus of elasticity that is at least 10% smaller than a modulus of elasticity of a spark plug cap or a spark plug ground electrode formed by fusion metallurgy.

7. The method of claim 1, wherein the MIM spark plug component is the MIM spark plug cap, wherein the MIM spark plug cap is cupped-shaped and has multiple through holes.

8. The method of claim 7, wherein the MIM spark plug cap defines a prechamber containing a spark gap formed between a ground electrode and a center electrode.

9. The method of claim 1, wherein the MIM spark plug component is the MIM spark plug ground electrode.

10. The method of claim 9, further comprising the step of welding a precious metal reinforcement to the MIM spark plug ground electrode.

11. The method of claim 9, wherein the MIM spark plug ground electrode has an annular section and a conical section with a plurality of legs extending between the annular section and the conical section.

12. The method of claim 11, wherein at least two legs of the plurality of legs have a through hole to allow air to flow through.

13. The method of claim 11, further comprising the step of welding a precious metal reinforcement to the conical section of the MIM spark plug ground electrode.

14. The method of claim 13, wherein the precious metal reinforcement is an annular precious metal reinforcement.

15. The method of claim 1, wherein the sintering step decreases the porosity of the MIM spark plug component to 10% or less.

16. The method of claim 15, wherein the sintering step decreases the porosity of the MIM spark plug component to 5% or less.

17. A method of manufacturing a spark plug component, comprising the steps of: mixing a nickel-based metal powder with a binder material to form a feedstock material comprising the nickel-based metal powder mixed with the binder material; providing the feedstock material to an injection mold machine; injection molding the feedstock material in the injection mold machine to form a metal injection molded (MIM) spark plug component in the form of a green part; removing the binder material from the green part to form the MIM spark plug component in the form of a powder metal structure; and sintering the powder metal structure to form the MIM spark plug component in the form of a MIM spark plug cap or MIM spark plug ground electrode, wherein the MIM spark plug cap or the MIM spark plug ground electrode has a nominal geometry directly following the sintering step, wherein the nominal geometry includes at least part of an annular surface, and wherein the MIM spark plug cap or the MIM spark plug ground electrode has a modulus of elasticity that is at least 5% smaller than a modulus of elasticity of a spark plug cap or a spark plug ground electrode formed by fusion metallurgy.

18. A method of manufacturing a spark plug component, comprising the steps of: mixing a nickel-based metal powder with a binder material to form a feedstock material comprising the nickel-based metal powder mixed with the binder material, wherein the nickel-based metal powder includes a nickel-based alloy having nickel, iron, and chromium, with nickel as the main constituent; providing the feedstock material to an injection mold machine; injection molding the feedstock material in the injection mold machine to form a metal injection molded (MIM) spark plug component in the form of a green part; removing the binder material from the green part to form the MIM spark plug component in the form of a powder metal structure; and sintering the powder metal structure to form the MIM spark plug component in the form of a MIM spark plug cap or MIM spark plug ground electrode, wherein the sintering step decreases the porosity of the MIM spark plug component to 10% or less.

Description

DRAWINGS

(1) Preferred exemplary embodiments of the invention will hereinafter be described in conjunction with the appended drawings, wherein like designations denote like elements, and wherein:

(2) FIG. 1 a partially sectional view of a spark plug according to one embodiment;

(3) FIG. 2 a spark plug according to another embodiment, shown in longitudinal section; and

(4) FIG. 3 a partially sectional view of a third embodiment.

DESCRIPTION

(5) FIGS. 1 to 3 each show a spark plug 1 with a center conductor 2, an insulator 3 surrounding the center conductor 2, and a spark plug body 4 surrounding the insulator 3. Arranged at the front end of the spark plug 1 is an external thread 5 on the spark plug body 4, by means of which the spark plug 1 can be screwed into an internal combustion enginenot shownin a manner that is generally known. The spark plug 1 has at least two electrodes 6, 7, namely a center electrode 6 that is connected in an electrically conductive manner to the center conductor 2, and a ground electrode 7 connected in an electrically conductive manner to the spark plug body 4. The center electrode 6 forms, together with the ground electrode 7, a spark gap 10, which forms a spark air gap. The center electrode 6 and the ground electrode 7 each contain a precious metal reinforcement 8 or 9, respectively, which borders the spark gap 10. The reinforcements 8, 9 are made of precious metal, in particular platinum and/or iridium or an alloy thereof, and can each be welded to the electrode 6, 7.

(6) In the embodiment from FIG. 1, the MIM component that is attached to the front end of the spark plug 1 and comes into contact with fuel during operation is the ground electrode 7, which surrounds the center electrode 6 in an annular shape and hence is designed as an annular electrode. The ground electrode 7 from FIG. 1 has an annular section 11 that rests against the spark plug body 4. The annular section 11 is welded along its entire circumference to the spark plug body 4. The ground electrode 7 from FIG. 1 also has multiple through holes 71 distributed about the circumference, and a conical section 72 at the front end.

(7) In the embodiment of the spark plug 1 shown in FIG. 2, the ground electrode 7 is likewise implemented as a MIM component, and likewise has an annular section 11 and multiple through holes 71 and conical sections 72. The front end of the spark plug body 4 of the spark plug 1 shown in FIG. 2 is flanged over the annular section 11 in order to secure the ground electrode 7 by positive engagement. After its attachment to the spark plug body in the region of its end sections that bear the reinforcements 9 of the conical sections 72, the ground electrode 7 shown in FIG. 2 is bent slightly toward the center electrode 6, or away from it, in order to adjust the spark gap 10 to its nominal dimension with high precision. This plastic bending deformation of the ground electrode 7 is simplified by the lower modulus of elasticity of the ground electrode 7 produced as a MIM component. High precision in the spark gap width can be ensured more easily.

(8) In the embodiment shown in FIG. 3, the spark plug 1 has, at its front end, a prechamber 12 that contains the electrodes 6, 7 and that is delimited by a cupped MIM cap component 13 which contains an annular section by which it is attached to the front end of the spark plug body 4. The MIM component 13 has multiple through holes 14.

(9) It is to be understood that the foregoing is a description of one or more preferred exemplary embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.

(10) As used in this specification and claims, the terms for example, e.g., for instance, such as, and like, and the verbs comprising, having, including, and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.

(11) TABLE-US-00001 List of Reference Numerals 1 Spark plug 2 Center conductor 3 Insulator 4 Spark plug body 5 External thread 6 Center electrode 7 Ground electrode 8 Reinforcement 9 Reinforcement 10 Spark gap 11 Annular section 12 Prechamber 13 MIM component 14 Through holes 71 Through holes 72 Conical sections