Image Number 3 for United States Patent #8115372.
A spark plug for an internal combustion engine, includes: a cylindrical insulating body; a center electrode; a cylindrical metal shell; and a ground electrode, as defined herein, wherein the noble metal tip is bonded to the ground electrode via a molten bond, and when viewed in a cross-section including a center axis of the noble metal tip along a longitudinal direction of the ground electrode, a sum of a cross-sectional area of a base-end-side molten bond (A) positioned at a base end side of the ground electrode and a cross-sectional area of a front-end-side molten bond (B) positioned at a front end side of the ground electrode is equal to or greater than 4 mm.sup.2, and the cross-sectional area of the front-end-side molten bond (B) is 1.1 to 1.3 times greater than that of the base-end-side molten bond (A).
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