| 摘要 |
A spark plug according to the present invention includes a tubular metal shell, an insulator, a center electrode, a ground electrode, and a shield. The insulator is retained in the metal shell. The center electrode is secured in the insulator such that an end portion of the center electrode protrudes out of the insulator. The ground electrode includes a base portion, a tip portion, and a joining portion that joins together the base and tip portions. The base portion is fixed to the metal shell. The tip portion faces the side surface of the end portion of the center electrode through a spark gap in a direction perpendicular to the longitudinal direction of the spark plug. The shield shields the joining portion of the ground electrode from directly facing outside of the spark plug in the longitudinal direction of the spark plug, thereby securing the reliability of the joining portion.
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