Patent ID: 9444229
Filing Date: 2016-09-13
CPC Classification: H01T

Claim Text:
1. A spark plug for an internal combustion engine, comprising: a cylindrical ground electrode; a cylindrical insulator held inside the ground electrode and projecting toward a distal end side of the spark plug beyond a distal end of the ground electrode; and a center electrode held inside the insulator and projecting toward the distal end side beyond a distal end of the insulator, the spark plug being configured to generate a discharge between the ground electrode and the center electrode when applied with a high-frequency voltage at the center electrode, wherein a line segment of an imaginary line extends in a plug radial direction to connect a start point on a surface of the ground electrode and an outer peripheral surface of the insulator, the line segment and the outer peripheral surface of the insulator intersect at an intersection point, the line segment has a first length, and an axial distance between the intersection point and the distal end of the insulator is a second length, and the ground electrode is provided on the surface thereof with a shortest discharge forming portion as the start point locally along a plug circumferential direction at which a value of a sum of the first length and the second length becomes minimum.