Spark plug with fine wire ground electrode

1. A spark plug for a spark-ignited internal combustion engine, said spark plug comprising:

a generally tubular ceramic insulator;

a conductive shell surrounding at least a portion of said ceramic insulator, said shell including at least one ground electrode;

a center electrode disposed in said ceramic insulator, said center electrode having an upper terminal end and a lower sparking end in opposing relation to said ground electrode with a spark gap defining the space therebetween;

said ground electrode extending from an anchored end adjacent said shell to a distal end adjacent said spark gap, said ground electrode including a ledge formed on said distal end, said ledge having at least one inset planar surface;

a sparking tip located on said distal end of said ground electrode, said sparking tip having a base end attached to said inset planar surface of said ledge and a side peripheral surface extending from said base end;

said inset planar surface intersecting said distal end of said ground electrode and completely covering said base end of said sparking tip, said inset planar surface being oversized in area relative to said base end so as to extend outwardly therefrom to provide an exposed peripheral interface portion of said inset planar surface adjacent said base end;

said ledge further including an inset back wall spaced from said distal end and intersecting said planar surface, said peripheral surface of said sparking tip directly abutting said back wall of said ledge; and

at least one weld bonding said base end of said sparking tip to said inset planar surface, and at least one weld bonding said peripheral surface of said sparking tip to said back wall of said ledge.

2. The spark plug of claim 1 , wherein said inset back wall has a contour along a length thereof and a cross-section profile.

3. The spark plug of claim 2 , wherein the contour of said inset back wall is generally planar along its length.

4. The spark plug of claim 2 , wherein the contour of said inset back wall is curved along its length.

5. The spark plug of claim 2 , wherein the contour of said inset back wall has a generally planar portion and a curved portion along its length.

6. The spark plug of claim 1 , wherein said inset back wall is substantially orthogonal to said inset planar surface.

7. The spark plug of claim 6 , wherein said inset back wall has at least one of a tapered or a curved cross-section profile.

8. The spark plug of claim 1 , wherein said inset back wall is not orthogonal to said inset planar surface.

9. The spark plug of claim 8 , wherein said inset back wall has at least one of a tapered or a curved cross-section profile.

10. The spark plug of claim 1 , wherein said at least one weld comprises a resistance weld between said base end of said sparking tip and said inset planar surface.

11. The spark plug of claim 1 , wherein said at least one weld disposed on said peripheral surface of said sparking tip comprises a laser weld.

12. The spark plug of claim 1 , wherein said ground electrode includes at least one exposed upper surface extending between said anchored end and said distal end, said exposed surface intersecting and abutting said sparking tip at said back wall of said ledge, and wherein said at least one weld comprises a weld disposed at the intersection between said exposed surface and said sparking tip.

13. The spark plug of claim 1 , wherein said sparking tip comprises one of gold, a gold alloy, a platinum group metal or a tungsten alloy.

14. The spark plug of claim 13 , wherein said platinum group metal comprises at least one element selected from the group consisting of platinum, iridium, rhodium, palladium, ruthenium and rhenium.

15. The spark plug of claim 14 , wherein said platinum group metal further comprises at least one element selected from the group consisting of nickel, chromium, iron, manganese, copper, aluminum, cobalt, tungsten, yttrium, zirconium, hafnium, lanthanum, cerium and neodymium.

16. The spark plug of claim 13 , further comprising a firing tip attached to said sparking end of said center electrode.

17. The spark plug of claim 1 , wherein said sparking tip is a multi-layer sparking tip having a free end portion and a base end portion.

18. The spark plug of claim 17 , wherein said free end portion comprises one of gold, a gold alloy, a platinum group metal or a tungsten alloy and said base end portion comprises one of nickel or a nickel-based alloy.

19. The spark plug of claim 18 , wherein said platinum group metal comprises at least one element selected from the group consisting of platinum, iridium, rhodium, palladium, ruthenium and rhenium.

20. The spark plug of claim 19 , wherein said platinum group metal further comprises at least one element selected from the group consisting of nickel, chromium, iron, manganese, copper, aluminum, cobalt, tungsten, yttrium, zirconium, hafnium, lanthanum, cerium and neodymium.

21. The spark plug of claim 18 , further comprising a firing tip attached to said sparking end of said center electrode.

22. The spark plug of claim 21 , wherein said sparking tip comprises one of gold, a gold alloy, a platinum group metal or a tungsten alloy.

23. The spark plug of claim 1 , wherein said sparking tip has a regular cross-section extending continuously between said base end and a free end thereof.

24. The spark plug of claim 23 , wherein said sparking tip is generally cylindrical, with said base and free ends being generally circular.

25. The spark plug of claim 1 , wherein said ground electrode also includes a thermally conductive core located proximate said sparking tip.

26. The spark plug of claim 25 , wherein said thermally conductive core extends at least partially under said inset planar surface.

27. The spark plug of claim 26 , wherein said thermally conductive core is also located proximate at least a portion of said inset back wall.

28. The spark plug of claim 25 , wherein said thermally conductive core extends entirely under said base end of said sparking tip.