SPARK PLUG FOR INTERNAL COMBUSTION ENGINES

Abstract

A spark plug (1) for internal combustion engines has a center electrode (6) arranged along a central axis (2) of the spark plug (1), which electrode (6) is enclosed by an insulator (5) at least in portions, and a housing (9) in which the insulator (5) is received, at least in portions. A gap (20) is formed, at least in portions, between the insulator (5) and the housing (9). The gap (20) is at least partially filled with a material (23) having a thermal conductivity (λ)≥1 W/(m*K).

Claims

1.-8. (canceled)

9. A spark plug (1) for internal combustion engines, comprising a center electrode (6) arranged along a central axis (2) of the spark plug (1), the center electrode being at least in portions enclosed by an insulator (5); and a housing (9) in which the insulator (5) is received, at least in portions, wherein a gap (20) is formed, at least in portions, between the insulator (5) and the housing (9), and wherein the gap (20) is at least partially filled with a material (23) having a thermal conductivity (λ)≥1 W/(m*K).

10. The spark plug according to claim 9, wherein the material (23) has a thermal conductivity (λ)≥4 W/(m*K).

11. The spark plug according to claim 9, wherein the material (23) has a thermal conductivity (λ)≥6 W/(m*K).

12. The spark plug according to claim 9, wherein the material (23) has a melting point (Θ)<200° C.

13. The spark plug according to claim 9, wherein the material (23) has a melting point (Θ)<100° C.

14. The spark plug according to claim 9, wherein the material (23) is a metal, a metal alloy, or a suspension comprising metal particles.

15. The spark plug according to claim 9, wherein the material (23) is a bismuth alloy.

16. The spark plug according to claim 9, wherein the material (23) is Rose's metal.

17. The spark plug according to claim 9, wherein an outer side (21) of the insulator (5) and/or an inner side (22) of the housing (9) is coated at least in a region of the gap (20).

18. The spark plug according to claim 9, wherein an outer side (21) of the insulator (5) and/or an inner side (22) of the housing (9) has, at least in a region of the gap (20), a structure that increases a surface of the outer side (21) and/or the inner side (22).

19. The spark plug according to claim 9, wherein an outer side (21) of the insulator (5) and/or an inner side (22) of the housing (9) has, at least in a region of the gap (20), grooves or notches that increases a surface of the outer side (21) and/or the inner side (22).

20. The spark plug according to claim 9, wherein the spark plug (1) has a front end (3) directed towards a combustion chamber in an installed state and a rear end (4) directed away from the combustion chamber in the installed state, and wherein part of the gap (20) filled with the material (23) runs from an insulator seat (19) in a region of the front end (3) of the spark plug (1) towards the rear end (4).

Description

BRIEF DESCRIPTION OF THE DRAWING

[0029] The FIGURE shows a portion of a spark plug in a partially cut side view.

DETAILED DESCRIPTION

[0030] In the FIGURE, the left side of spark plug 1 is shown uncut. The right side of the spark plug 1, on the other hand, is shown cut along a cutting plane that passes through a central axis 2 of the spark plug 1 and is parallel to the viewing plane.

[0031] The spark plug 1 has a front end 3 directed toward a combustion chamber of an internal combustion engine in the installed state and a rear end 4 directed away from the combustion chamber in the installed state.

[0032] An insulator 5 made of an electrically insulating material, in particular ceramic, extends from the front end 3 up to the rear end 4 of the spark plug 1.

[0033] An electrically conductive center electrode 6 and an electrically conductive connecting bolt 7 are arranged along the central axis 2. The center electrode 6 is almost completely enclosed and the connecting bolt 7 is at least partially enclosed by the insulator 5. The connecting bolt 7 can be connected to a current conductor (not shown).

[0034] An electrically conductive glass seal 8 received inside the insulator 5 is located between the center electrode 6 and the connecting bolt 7.

[0035] The insulator 5 is received in a metallic housing 9. This has an external thread 11 for screwing into a cylinder head and an external hexagon for attaching a tool.

[0036] In the region of the front end 3, in the illustrated embodiment of the spark plug, an outer electrode 13 is arranged on the housing 9, which protrudes from the housing 9 towards the central axis 2, such that an ignition gap 15 is formed between the outer electrode 13 and a free end 14 of the central electrode 6.

[0037] The insulator 5 has a shoulder 16 in the region of the front end 3 of the spark plug 1, which rests against an inner shoulder of the housing 9 either directly or via a sealing ring 17. Together, the shoulder 16 of the insulator 5 and the inner shoulder 18 of the housing 9 form the insulator seat 19.

[0038] Starting from the insulator seat 19 and extending in the direction of the rear end 4 of the spark plug 1, a gap 20 is formed between an outer side 21 of the insulator 5 and an inner side 22 of the housing 9. Thus, the gap 20 has the shape of a hollow cylinder arranged between the insulator 5 and the housing 9.

[0039] A thermally conductive material 23 is arranged in at least a part of the gap 20 adjacent to the insulator seat. The thermally conductive material 23 can be filled into the gap 20 in a molten state during the manufacture of the spark plug. Alternatively, the thermally conductive material 23 can be arranged in a solid or deformable state in the gap 20 during manufacture.

[0040] The heat-conducting material 23 arranged in the gap 20 is at least partially, but in particular completely, melted during operation, that is, when the internal combustion engine is running. It forms a good heat-conducting connection between the insulator 5 and the housing 9.

[0041] The outer side 21 of the insulator 5 and/or the inner side 22 of the housing 9 can/may have a specially shaped or machined surface, for example a surface with a very low surface roughness, such that it can be wetted very well.

[0042] Spark plugs 1 of a different design can also be used, as long as a heat-conducting material 23 is received, in particular filled, in the gap 20 between the insulator 5 and the housing 9.

LIST OF REFERENCE SIGNS

[0043] 1 Spark plug [0044] 2 Central axis [0045] 3 Front end [0046] 4 Rear end [0047] 5 Insulator [0048] 6 Center electrode [0049] 7 Connecting bolt [0050] 8 Glass seal [0051] 9 Housing [0052] 10 --- [0053] 11 External thread [0054] 12 Attachment point [0055] 13 Outer electrode [0056] 14 Free end of center electrode [0057] 15 Ignition gap [0058] 16 Shoulder [0059] 17 Sealing ring [0060] 18 Inner shoulder [0061] 19 Insulator seat [0062] 20 Gap [0063] 21 Outer side of insulator [0064] 22 Inner side of housing