| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug having a through-hole piercing the ground electrode through which a turbulent flow of the air-fuel mixture is efficiently blown on the discharge gap to develop a superior ignition performance. SOLUTION: The spark plug 100 has a ground electrode 4 having a through-hole 43 defined by a first and second lengthwise faces 431, 432 to reduce its diameter to the inside 44 from the outside 45 of the electrode 43. In a first section cut in a plane vertical to an axis O passing through a discharge gap g, a first and second lengthwise lines 431', 432' are formed on the first cut section, and when the top end face 34 of a center electrode 3 is projected on the first cut section, two extension lines s1, s2 from the first and second lengthwise lines 431', 432' intersect on a projection plane 34' at one end 41 of the ground electrode 4 away from the intersection point s3 of the two extension lines s1, s2. COPYRIGHT: (C)2007,JPO&INPIT
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