Patent ID: 9083155
Filing Date: 2015-07-14
Classification: H01T

Abstract:
1. A spark plug comprising: a center electrode; a ground electrode; and a noble metal tip resistance-welded to at least one of the center electrode and the ground electrode, wherein the noble metal tip has a flat discharge surface, a bottom surface embedded in the electrode to which the noble metal tip is resistance-welded, and a side surface whose width constantly increases from the discharge surface toward the bottom surface, on a predetermined cross section containing a vertical line passing through the centroid of the discharge surface, a maximum thickness along a direction parallel to the vertical line is defined as the maximum thickness t of the noble metal tip, and a straight line which passes through a portion of the bottom surface where the noble metal tip has the maximum thickness and is parallel to the discharge surface is defined as a first straight line, on a first half cross section of two half cross sections formed by dividing the predetermined cross section by the vertical line, a maximum width along a direction orthogonal to the vertical line is defined as the maximum width Rw on a second half cross section of the two half cross sections which differs from the first half cross section, a maximum width along the direction orthogonal to the vertical line is defined as the maximum width Rw relations h on the predetermined cross section containing the vertical line, the noble metal tip has a bottom surface portion which is concave toward the discharge surface, and on each of the first half cross section and the second half cross section, a distance h