| 摘要 |
PROBLEM TO BE SOLVED: To increase the effect such as knocking suppression due to intension of a reverse squish stream at the initial time in an expansion process while preventing the interference of an air intake valve and an air exhaust valve even when a valve lift amount at an air intake top dead center is large. SOLUTION: In the engine generating a tumble stream in a combustion chamber 6 by an air intake stream and forming squish areas 5a, 5b in a peripheral fringe part of a crown face of a piston 5, a recessed part 11 is provided in a predetermined region including projection faces of the air intake valve 9 and the air exhaust valve 10 in the crown face of the piston 5. A bottom face of the recessed part 11 is formed into a chevron shape which has a pair of inclined bottom faces 11a, 11b substantially in parallel with both inclined faces of a ceiling part in the combustion chamber and in which a ridge line part 11c is positioned in a central part substantially to divide the tumble stream into two air streams T1, T2 turning reversely to each other in a compression process.
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