| 摘要 |
<p>A resistor-containing spark plug 100 has an alumina insulator 2 coated with a glaze layer 2d, the glaze layer 2d has a lead component content of 1 mol% or lower in terms of PbO and containing a silicon component, a boron component, a zinc and/or alkaline earth metal component, and an alkali metal component. The insulator 2 has, in an axially central position thereof, a projection part protruding from the outer circumferential surface thereof and extending in a circumferential direction. That main body of the insulator 2 which is located adjacent to the projection part on the rear side thereof, which is the side opposite to the front side facing the center electrode 3 in the axial direction, has a base portion having a cylindrical outer circumference. The outer circumference of the base portion is covered with the glaze layer 2d which, when examined by the method as provided for in JIS B 0601, gives a surface roughness curve having a maximum height Ry of 10 mu m or smaller. <IMAGE></p> |
