| 摘要 |
<p>PROBLEM TO BE SOLVED: To effectively suppress cracking of an insulating material due to thermal shock, while more reliably preventing penetration of the insulating material.SOLUTION: An ignition plug 1 comprises: a main metal fitting 3; and a cylindrical insulator 2 which is arranged on an inner periphery of the main metal fitting 3 and has a shaft hole 4 extending in an axial line CL1 direction, and whose tip end is located on a further end side than a tip end of the main metal fitting 3. A distance along the axial line CL1 from the tip end of the main metal fitting 3 to the tip end of the insulator 2 is 0.5 mm or greater. Equations C≥1.07 mm and V≤3.9 mmare satisfied where: C denotes a thickness of the insulator at a cross section passing through an inner periphery surface tip end 3A of the main metal fitting 3 and perpendicular to the axial line CL1; and V denotes a volume of the insulator 2 within the range of 0.5 mm rear side from the tip end of the insulator 2 in the axial line CL1 direction.</p> |
