| 摘要 |
PURPOSE:To well perform ignition or the like of a mixture by an ignition plug, by opening the point end of an insertion hole of the ignition plug in a cylinder head to the central part of a combustion chamber while forming in this opening part a semispherical cavity having a predetermined diameter. CONSTITUTION:An engine 10 opens to a ceiling wall 16a of its combustion chamber 16 four intake and exhaust ports 17, 18 in total in openings 17a, 18a. Here a point end part 36a of an insertion hole 36 of an ignition plug 37, provided in a cylinder head 13, is opened to a position, surrounded by each opening 17a, 18a of each port 17, 18 in a bottom surface 13a of the cylinder head 13, that is, the central part in the roof-shaped ceiling wall 16a of the combustion chamber 16. And the point end part 36a is formed in a semispherical cavity in a contour larger than the hole size of an internal thread part 36c, for screwing the ignition plug 37, successively placed to the upper of the part 36a. In this way, ignition of mixture by the ignition plug 37 or growth and propagation or the like of a flame in the beginning of the ignition can be well performed. |
