Patent attributes
The spark plug is provided with: an insulator; a main metal fitting in which a shelf portion for locking the insulator is provided; and a cap joined to the main metal fitting by way of a melted portion. The cap forms an auxiliary chamber, and includes an injection port penetrating from an inner surface to an outer surface. There is a gap extending from the auxiliary chamber to the melted portion, between a first surface connecting an inner peripheral surface of the main metal fitting and an outer peripheral surface of the main metal fitting on a tip end side of the shelf portion, and a second surface of the cap, connecting an inner surface and an outer surface thereof, and the gap includes an opening portion which opens into the auxiliary chamber in a radial direction.
