| 摘要 |
PROBLEM TO BE SOLVED: To prevent an ignition plug from breaking at a rear end part of an insulator more securely even when a rear end-side barrel part is long or when a flat part of the insulator is small in area.SOLUTION: An ignition plug 1 includes an insulator 2 having a shaft hole 4, main metal fittings 3 arranged at an outer periphery of the insulator 2, and a terminal electrode 6 having a leg part 6A inserted into a rear end side of the shaft hole 4 and a head part 6B exposed from a rear end of the insulator 2. The insulator 2 is formed such that a length L of a region exposed from a rear end of the main metal fittings 3 is 28 to 34 mm and an area of the flat part 2F is 25 mmor less. An ignition plug 1 like this is such that a thickness (t) of the thinnest part 2A of an insulator 2 is 1.0 mm or larger within a range of 5.5 mm from the rear end of the insulator 2 to a tip side in the direction of an axis CL1. Further, an area D of a region AR where a projection region PA1 of a flat part 2F and a projection region PA2 of a flat part 6F overlap is 8 mmor larger. |
