SPARK PLUG AND IGNITION SYSTEM

摘要

A spark plug has a center electrode containing a shaft portion, a tip portion joined to a forward end portion of the shaft portion, and a joint portion joining the shaft portion and the tip portion together. In the spark plug, the distance between the surface of the center electrode and an inner edge of the insulator is 0.3 mm or greater. The inner edge is a forward-end-side edge of an inner circumferential surface of a small diameter portion of the insulator, the small diameter portion being a part of a portion of the insulator for accommodating the tip portion and having the smallest inner diameter.

主权项

1. A spark plug comprising:
a tubular insulator having an axial hole extending therethrough along an axial line; a center electrode disposed at an end of the axial hole on a forward end side; and a ground electrode forming a gap between the ground electrode and a forward end portion of the center electrode, wherein the center electrode includes a shaft portion, a tip portion joined to a forward end portion of the shaft portion, and a joint portion joining the shaft portion and the tip portion together; an end of the joint portion on the forward end side is located on a rear end side in the direction of the axial line in relation to an inner edge of the insulator, which is a forward-end-side edge of an inner circumferential surface of a small diameter portion of the insulator, the small diameter portion being a part of an accommodation portion of the insulator that accommodates the tip portion, and having the smallest inner diameter therein; and a distance between the inner edge and a surface of the center electrode is 0.3 mm or greater.