| 摘要 |
The purposes of the present invention are to reduce capacitance, and to ensure impact resistance of a central electrode. This spark plug is provided with a main metal fitting, an insulator, a resistor, a central electrode, and a seal body. The main metal fitting is a substantially cylindrical member having a ground electrode provided to the tip side. The insulator is a cylindrical member which is held inside the main metal fitting, and which has, provided therein, an axial hole provided with: a small-diameter section; an intermediate-diameter section which has a larger diameter than the small-diameter section, and which is connected to the rear end of the small-diameter section via a stepped section; and a large-diameter section which has a larger diameter than the intermediate-diameter section, and which is disposed further towards the rear-end side than the intermediate-diameter section. The resistor has at least a portion thereof disposed inside the large-diameter section. The central electrode is provided with: a flange section which protrudes in the radial direction inside the intermediate-diameter section, and comes into contact with the stepped section; and a leg section which extends from the flange section to the tip side, and which is disposed inside the small-diameter section. The seal body is an electrically conductive member which is disposed further towards the rear-end side than the stepped section, and which electrically connects the central electrode and the resistor. The rear end of the seal body is positioned inside the intermediate-diameter section. |
