Ignition plug

摘要

An ignition plug includes an insulator having an axial hole extending therethrough in the direction of an axis, a center electrode inserted into a forward end portion of the axial hole, and a metallic shell disposed externally of the insulator. The insulator includes a step portion engaged with an inner circumferential portion of the metallic shell and a leg portion extending forward from the forward end of the step portion. The porosity of the leg portion is 3.0% or less. Among three regions of the leg portion that are radially trisected in a cross section perpendicular to the axis, the outermost region is defined as a first region and the innermost region is defined as a second region. The porosity of the first region is equal to or more than 1.20 times the porosity of the second region.

主权项

1. An ignition plug comprising:
an insulator having an axial hole extending in the direction of an axis; a center electrode inserted into a forward end portion of the axial hole; and a metallic shell disposed externally of the insulator, wherein the insulator includes a step portion engaged with an inner circumferential portion of the metallic shell and a leg portion extending forward from a forward end of the step portion, the porosity of the leg portion of the insulator is 3.0% or less, and the porosity of a first region is equal to or more than 1.20 times the porosity of a second region, where the first region is an outermost region of three regions of the leg portion that are radially trisected in a cross section perpendicular to the axis, and the second region is an innermost region of the three regions.