| 摘要 |
PROBLEM TO BE SOLVED: To suppress the occurrence of knocking in an internal combustion engine having a cylinder block in which a cylinder head part and a cylinder block part are integrally casted.SOLUTION: A cylinder block part 4 is formed with a groove part 16 which is continuous in the whole circumference of the upper end edge of a cylinder 3. The groove part 16 is a recess for protecting the tip portion of a tool used in boring processing when the boring processing of the cylinder 3 is stopped, and is set for increasing the service life of the tool used in the boring processing. On the outer peripheral edge of a piston crown surface 8, a protruding wall 17 is provided to cover a portion of the groove part 16, which lies apart from an ignition plug 14 and becomes relatively low in temperature. |
