SPARK PLUG

摘要

A spark plug includes an insulator having a through hole formed in the direction of an axis, a rod-shaped center electrode inserted in the through hole and extending in the direction of the axis, a metal shell disposed around an outer circumference of the insulator, and a ground electrode electrically conducted with the metal shell and adapted to define a gap between the ground electrode and the center electrode. A front end part of the insulator has a front end surface, an outer circumferential surface and a curved surface region formed between the front end surface and the outer circumferential surface. In a cross section including the axis, a front end of an inner circumferential surface of the metal shell faces the curved surface region in a direction perpendicular to the axis. The curved surface region has a curvature radius of 0.2 mm to 0.8 mm.

主权项

1. A spark plug, comprising:
an insulator having a through hole formed in the direction of an axis of the spark plug; a rod-shaped center electrode inserted in the through hole and extending in the direction of the axis; a metal shell disposed around an outer circumference of the insulator; and a ground electrode electrically conducted with the metal shell and adapted to define a gap between the ground electrode and the center electrode, wherein a front end part of the insulator has a front end surface, an outer circumferential surface extending toward the rear from the front end surface in the direction of the axis and a curved surface region formed between the front end surface and the outer circumferential surface; wherein, in a cross section including the axis, a front end of an inner circumferential surface of the metal shell faces the curved surface region in a direction perpendicular to the axis; and wherein the curved surface region has a curvature radius of 0.2 mm to 0.8 mm.