Patent ID: 6720716
Filing Date: 2004-04-13
Classification: H01T

Abstract:
A spark plug comprising:a cylindrical metallic housing; a center electrode accommodated in said metallic housing, with one end protruding and extending from one end of said metallic housing; a center electrode tip fixed to said one end of said center electrode and extending in the same direction as an axis of said center electrode; a ground electrode having a proximal portion fixed to said one end of the metallic housing and a distal portion extending toward said one end of said center electrode; and a columnar ground electrode tip fixed to an end surface of said distal portion of the ground electrode, with an apical surface of said ground electrode tip opposed to an apical surface of said center electrode tip via a discharge gap, wherein an acute angle is formed between an axis of said distal portion of the ground electrode and said axis of said center electrode when said ground electrode is projected on a virtual plane including said axis of the center electrode and a cross-sectional centroid of a proximal end of said ground electrode where the ground electrode is fixed to said metallic housing, said ground electrode tip extends along an axis crossing with the axis of the distal portion of the ground electrode, so that said ground electrode tip protrudes from the end surface of the distal portion of said ground electrode and extends toward said center electrode, an axis of said center electrode tip is in a cross or skew relationship with an axis of said ground electrode tip, said round electrode tip protrudes toward said center electrode by a protruding length in a range from 0.3 mm to 1.5 mm with respect to the side surface of said distal portion of said ground electrode, said center electrode tip has a cylindrical shape with a cross sectional area in a range from 0.07 mm2 to 0.79 mm2, and said around electrode tip has a cylindrical shape with a cross sectional area in a range from 0.07 mm2 to 1.13 mm2.