| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug for an internal combustion engine wherein the front end as a portion of an earth electrode opposed to the center electrode is arranged extending from an intake valve arranged in the combustion chamber of the internal combustion engine to an exhaust valve in a direction perpendicular to the flowing direction of air when viewing the earth electrode from the direction of the axis of the center electrode, for achieving a longer life by increasing the volume of a site where spark occurs, to suppress the wear of the earth electrode. SOLUTION: The front end of the earth electrode when viewed from the direction of the axis of the center electrode is divided into a front end upstream portion on the upstream side in the flowing direction of air and a front end downstream portion on the downstream side in the flowing direction of air by a virtual plane which passes through the axial center of the center electrode and which is perpendicular to the flowing direction of air from the intake valve to the exhaust valve. In this case, the area of the front end downstream portion is set to be larger than the area of the front end upstream portion. COPYRIGHT: (C)2010,JPO&INPIT
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