| 摘要 |
Provided is a novel technique for improving the durability of a spark plug. The spark plug comprises: a central electrode extending in the axial direction; an insulator having a shaft hole extending in the axial direction with the central electrode inserted into the shaft hole; a main metal fitting disposed around the insulator; a first ground electrode electrically connected to the main metal fitting and forming a first gap in conjunction with the front end surface of the central electrode; and a second ground electrode electrically connected to the main metal fitting, bonded to the main metal fitting, and extending from the main metal fitting to a position facing the lateral surface of the central electrode to form a second annular gap between the lateral surface of the central electrode and the inner peripheral surface of itself. Here, the ratio of the size of the first gap to the size of the second gap is between 0.80 and 1.25. |
