| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug which can maintain ignitability even by making the discharge gap small. SOLUTION: At least either of a center electrode 32 and a ground electrode facing apart each other is made of an iridium alloy, and the distance R1 between the center electrode 32 and the ground electrode 42 is less than 1.1 mm, and, further, the cross-section area S1, S2 of the center electrode and the ground electrode where the distance R2 from the center point P of the both electrodes is not more than 0.6 mm, is 0.95 mm2 or less.
|
