| 摘要 |
PROBLEM TO BE SOLVED: To provide an engine capable of reducing the combustion noise. SOLUTION: In this engine E provided with a piston P having a top surface T facing to a cylinder head CH, a central part of the top surface T has a recessed part DP forming a combustion chamber between the cylinder head CH and the central part, and Helmholtz type resonance cavities 2, 3, 4, 5, 6 are provided in the periphery of the recessed part DP of the top surface T. A part of the sound wave of the combustion noise generated in the combustion chamber is reduced by these Helmholtz type cavities 2, 3, 4, 5, 6, provided in the periphery.
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