| 摘要 |
The spark plug has a center electrode (3) arranged in an axial hole of an insulator (2), and a metallic base surrounding the hole. A ground electrode includes an end (41) made of precious metal. An axial distance between an end surface of the end (41) and an inner circumferential surface of a body (4a) of the ground electrode is not less than 0.3 millimeter. The plug corresponds to a preset relation. - The preset relation is defined as theta 1+ theta 2 at most 93 degree, where theta 1 and theta 2 are angles included between two respective sets of straight lines (s1-s4). The straight line (s2) connects a lateral edge of another end of the ground electrode to the end (41), and the line (s4) contains the lateral edge at a front end surface of the center electrode. |
