Spark plug

摘要

A sparkplug includes a ground electrode forming a gap with a front end surface of the center electrode. A front end portion of the ground electrode includes an opposed surface facing the center electrode, and a pair of tapered surfaces sandwiching the opposed surface. A shortest distance between the center electrode and a boundary formed by the opposed surface and the tapered surface is equal to or less than 1.2 times a distance of the gap. At least a part of a cross section of the core portion is disposed in a region at a front side of the straight line that passes a rear end of a line segment corresponding to the tapered surface and is vertical to the line segment. A shortest distance between the line segment and the cross section of the core portion is 0.2 mm or more and 1.5 mm or less.

主权项

1. A sparkplug, comprising:
a center electrode extending in an axial direction; an insulator with an axial hole extending in the axial direction, the center electrode being disposed to be inserted into the axial hole; a metal shell disposed at an outer circumference of the insulator; and a ground electrode that electrically connects to the metal shell, the ground electrode forming a gap with a front end surface of the center electrode, wherein the ground electrode includes a rod-shaped main body portion, the main body portion including a base material and a core portion, the base material forming at least a part of a surface of the ground electrode, the core portion being buried in the base material and having a higher thermal conductivity than the base material, a front end portion of the main body portion of the ground electrode is disposed at a position facing a front end surface of the center electrode, the front end portion of the main body portion includes a tapered front end portion, the tapered front end portion including an opposed surface and a pair of tapered surfaces, the opposed surface being a surface facing the center electrode, the tapered surfaces being configured to sandwich the opposed surface, when the front end surface of the center electrode is projected along the axial direction, at least a part of the tapered end portion is disposed in a range overlapping the projected front end surface of the center electrode, a shortest distance between the center electrode and a boundary formed by the opposed surface and the tapered surface is equal to or less than 1.2 times a distance of the gap, and a perpendicular cross section of the ground electrode includes a front end of the core portion perpendicular to the axial direction, wherein at least a part of a cross section of the core portion is disposed in a region at a front end side of a straight line that passes a rear end of a line segment corresponding to the tapered surface and is vertical to the line segment, and a shortest distance between the line segment and the cross section of the core portion is 0.2 mm or more to 1.5 mm or less.