| 摘要 |
A spark plug 1 that suppresses a breakage of an insulator due to the thermal shock while ensuring the prevention of a spark penetration in the insulator has a metal shell 3 and a cylindrical ceramic insulator 2 disposed in an inner circumference of the metal shell 3, having an axial hole 4 extending in an axial line CL direction, and having a tip located in more tip side than a tip of the metal shell 3, and a distance along the axial line CL1 from the tip of the metal shell 3 to the tip of the ceramic insulator 2 is 0.5 mm or more. It satisfies C ‰¥ 1.07 mm and V ‰¤ 3.9 mm 3 , where C is a thickness of the ceramic insulator in a cross section passing an inner circumference surface tip 3A of the metal shell 3 and orthogonal to the axial line CL1 and V is a volume of the ceramic insulator 2 within a range of 0.5 mm from the tip of the ceramic insulator 2 to a rear end side in the axial line CL1 direction. |
