| 摘要 |
PROBLEM TO BE SOLVED: To provide an easy-to-manufacture spark plug for an internal combustion engine capable of ensuring stabilized ignitability regardless of the attachment posture to the internal combustion engine, while suppressing the horizontal flying spark, and to provide a method for manufacturing the same.SOLUTION: A spark plug 1 has a housing 2, an insulator 3, a center electrode 4, a ground electrode 5 and tip protrusion 6. The proximal end of the tip protrusion 6, i.e., protrusion proximal end 61, is joined to the apical surface 21 of the housing 2, while protruding farther inside than the inner peripheral edge of the apical surface of the housing 2. When the amount of protrusion of the protrusion proximal end 61 from the tip inner peripheral edge 211 is dimension A, the inside corner 62 of the protrusion proximal end 61 is formed so that the outer shape of the cross-section by a plane including the plug central axis is confined on the arc C side of a virtual curve L connecting the tip inner peripheral edge 211 and the inner end edge 63 of the tip protrusion 6 by an arc having a radius of dimension A. |
