| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce a capacitive discharge current, and to effectively suppress electrode wear and noise. <P>SOLUTION: A spark plug 1 working as an ignition plug, comprises a insulator 2 having a shaft hole 4 extending in an axis line CL1; a cylindrical main fitting 3 provided on the outer periphery of the insulator 2; a rod-shaped electrode 8 inserted in the shaft hole 4; and a ground electrode 27 disposed at a tip end portion of the main fitting 3, and forming a spark discharging clearance 33 between the ground electrode 27 and the tip end portion of the electrode 8. A cylindrical resistor 9 is provided between the inner peripheral surface of the insulator 2 and the outer peripheral surface of the electrode 8, in at least a part of a range from the tip end of the main fitting 3 to a part separated from a rear end of the main fitting 3 to a rear end side by 5 mm, along the axis CL1. The length along the axis line CL1 of the resistor 9 within a range from the tip end of the main fitting 3 to the rear end of the main fitting 3 is not less than 36% of the length along the axis line CL1 of the main fitting 3. <P>COPYRIGHT: (C)2012,JPO&INPIT |
