| 摘要 |
PURPOSE:To make the certain removement of adhered carbon possible by using a surface discharge plug, and combining an ignition power source whose voltage rise time and discharge duration can attain their fixed values in a discharge waveform with the above-metioned plug. CONSTITUTION:An insulating material 2 is abutedly received in the tip step seat surface 16 of the inner cavity 1a of a main body fitting 1 having engine fastening screws at its tip part, and a conical recess 2f broadening toward its tip is formed on a central part of the end surface 2e of an ignition part of the small diametral part 2b of the insulating material 2. The bottom 2h of the recess 2f is provided with a central electrode tip 3a, and a creeping discharge clearance 4 passing along the recess 2f and a flat surface 2g is formed between the tip peripheral edge 3b of the above-mentioned tip 3a and a tip inner wall 1d forming the earthing electrode of the main body fitting 1, and a surface discharge plug 10 composed in this way is combined with an ignition power source in which voltage rise time is shorter than 10mus and discharge duration is longer than 1ms in discharge waveform to form a desired ignition device.
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