| 摘要 |
<P>PROBLEM TO BE SOLVED: To more certainly increase ejection length of flame to attain excellent ignitability. <P>SOLUTION: An ignition plug 1 includes: a center electrode 5 which extends in a direction of an axial line CL1; an insulator 2 into which the center electrode 5 is inserted; a main metal fitting 3 which stores the tip of the center electrode 5 at an inner periphery; a plurality of ground electrodes 27 which form spark discharge gaps 33 between their sides and the outer peripheral surface of the tip of the center electrode 5; and a cap 28 which is located closer to the tip side in the direction of the axial line CL1 than the ground electrodes 27. A sub combustion space 35 formed by the rear end side of the cap 28 and the inner peripheral surface of the main metal fitting 3 is provided closer to the tip side in the direction of the axial line CL1 than the ground electrodes 27, and a vent hole 34 which connects the sub combustion space 35 with the outside is formed in the cap 28. When a distance between the center of an opening on the rear end side of the vent hole 34 and the center of an opening on the tip side of the vent hole 34 is T(mm), and the minimum inner diameter of the vent hole 34 is A(mm), 1.0≤T/A is satisfied. <P>COPYRIGHT: (C)2013,JPO&INPIT |
