SPARK PLUG AND METHOD FOR PRODUCING A SPARK PLUG

Abstract

A spark plug with an improved heat-dissipating capacity of the center electrode. The spark plug includes a ground electrode, a center electrode and a ceramic insulator, which is designed to accommodate the center electrode. The center electrode has a center-electrode head which lies in the direction of an electrical connection region of the spark plug and which includes an end face that is in contact with an electrically conductive connection element disposed between the electrical connection region and the center-electrode head. At its outer periphery, the center-electrode head is at least regionally in heat-conducting contact with the ceramic insulator and forms a heat-conducting contact region.

Claims

1-13. (canceled)

14. A spark plug, comprising: a ground electrode; a center electrode; and a ceramic insulator designed to accommodate the center electrode; wherein the center electrode includes a center-electrode head which lies in a direction of an electrical connection region of the spark plug, the center electrode head having an end face that is in contact with an electrically conductive connection element situated between the electrical connection region and the center-electrode head, and the center-electrode head, at its outer periphery, being at least regionally in heat-conducting contact with the ceramic insulator and forming a heat-conducting contact region.

15. The spark plug as recited in claim 14, wherein the entire outer periphery of the center-electrode head forms a heat-conducting contact region with the ceramic insulator.

16. The spark plug as recited in claim 14, wherein the outer periphery of the center-electrode head is in direct contact with the insulator.

17. The spark plug as recited in claim 14, wherein a press-fit connection is between the center-electrode head and the insulator.

18. The spark plug as recited in claim 15, wherein the heat-conducting contact region between the center-electrode head and the insulator is gas-tight.

19. The spark plug as recited in claim 15, wherein the heat-conducting contact region has a length of at least 1 mm in the axial direction of the spark plug.

20. The spark plug as recited in claim 19, wherein the length is 1.5 to 4.5 mm,

21. The spark plug as recited in claim 14, wherein a diameter of the center-electrode head in the heat-conducting contact region is at least 2 mm.

22. The spark plug as recited in claim 21, wherein the diameter is 2 to 4 mm.

23. The spark plug as recited in claim 14, wherein a ratio a length of the heat-conducting contact region to a diameter of the heat-conducting contact region is at least 0.75.

24. The spark plug as recited in claim 14, wherein a diameter of the center-electrode head is greater than a center-electrode section facing the combustion chamber, and a shoulder, which is in heat-conducting contact with the ceramic insulator, is in a transition region between the center-electrode head and the center-electrode section facing the combustion chamber.

25. The spark plug as recited in claim 14, wherein the center-electrode head has a cup-like region at the end face.

26. A method for producing a spark plug, comprising: introducing the center electrode into a cavity of a ceramic insulator so that the center-electrode head comes to lie on a shoulder developed in the cavity of the ceramic insulator; press-fitting the center electrode with the ceramic insulator; and developing a heat-conducting contact region between an outer periphery of the center-electrode head and the ceramic insulator.

27. The method as recited in claim 26, wherein the press-fitting is carried out with the aid of a stamp.

28. The method as recited in claim 26, further comprising: introducing an electrically conductive connection element into the cavity of the ceramic insulator so that the center-electrode head is connected to the electrical connection region of the spark plug in an electrically conductive manner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] An exemplary embodiment of the present invention is described in detail below with reference to the figures.

[0021] FIG. 1 a part-sectional view of a spark plug according to an advantageous further refinement of the present invention.

[0022] FIG. 2 a sectional view of a segment of the spark plug from FIG. 1.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0023] As shown in FIG. 1, spark plug 1 includes a ground electrode 2 and a center electrode 3. A ceramic insulator 7 is provided in such a way that center electrode 3 projects slightly from insulator 7 in the known manner. Center electrode 3 is made from one material but may also have a core-jacket structure, e.g., a jacket from a nickel-containing material and a core made from a copper-containing material, which improves a heat dissipation from the center-electrode base facing the combustion chamber to insulator 7. In addition, a noble metal pin for generating a spark plasma may be provided on the side of the combustion chamber.

[0024] Insulator 7 itself is partially surrounded by a housing 6. Reference numeral 13 denotes an electrical connection region of spark plug 1. An electrically conductive connection is provided from electrical connection region 13 to center electrode 3 via a connection stud and a connection element 8 made from an electrically conductive glass, for example.

[0025] Center electrode 3 has a center-electrode head 5, which points in the direction of electrically conductive connection element 8. An end face 10 of center-electrode head 5 is in contact with electrically conductive connection element 8.

[0026] A diameter of center-electrode head 5 is larger than a diameter of a center-electrode section 4 facing the combustion chamber. In a transition region between center-electrode head 5 and center-electrode section 4 facing the combustion chamber, a shoulder 12 is developed on center-electrode head 5, which comes to rest on a correspondingly developed section of insulator 7.

[0027] An outer periphery of center-electrode head 5 is in heat-conducting contact with ceramic insulator 7, so that a heat-conducting contact region 9 is developed between the outer periphery of center-electrode head 5 and ceramic insulator 7.

[0028] Heat-conducting contact region 9 is shown in greater detail in FIG. 2. According to the advantageous further refinement depicted there, the entire outer periphery of center-electrode head 5 forms a heat-conducting contact region 9 with ceramic insulator 7. In other words, the entire outer periphery of center-electrode head 5 including its shoulder 12 is in direct contact with insulator 7, so that neither an air gap nor an electrically conductive connection element 8, as in conventional spark plugs, is provided between these components.

[0029] For this purpose, a press-fit connection is developed especially between center-electrode head 5 and insulator 7. This also improves the gas tightness of heat-conducting contact region 9 between center-electrode head 5 and insulator 7.

[0030] In the axial direction X-X of spark plug 1, heat-conducting contact region 9 advantageously has a length L of at least 1 mm, and in particular of 1.5 to 4.5 mm because this makes it possible to provide an especially large heat-exchange surface between center-electrode head 5 and insulator 7.

[0031] In addition, a diameter D of center-electrode head 5 in heat-conducting contact region 9 advantageously amounts to at least 2 mm, and in particular 2 to 4 mm; a ratio L/D of length L of heat-conducting contact region 9 to diameter D of heat-conducting contact region 9 is at least 0.75. Heat-conducting contact region 9 is able to be enlarged to a maximum size by varying ratio L/D as a function of the dimensioning of spark plug 1.

[0032] In the direction of its end face 10, center-electrode head 5 has a cup-like region 11, and thus a concave region, which is oriented in the direction of electrically conductive connection element 8. As a result, a particularly large heat-conducting contact region 9 is obtained at a reduced volume of center-electrode head and excellent contacting of electrically conductive connection element 8. Moreover, center electrode 3 is thus form-fittingly seated in the insulator and in electrically conductive connection element 8, so that center electrode 3 is stabilized and centered in ceramic insulator 7.