| 摘要 |
PURPOSE:To suppress gas from leaking and reduce a number of rings, by providing an annular groove on the peripheral surface, opposed to the ceramic coating internal wall surface of a cylinder in its top dead center side, of a piston and fitting the plural piston rings to be mounted to the bottom half of the peripheral surface of the piston. CONSTITUTION:A piston 3 in an internal-combustion engine provides on the peripheral surface in a side of the top dead center a plurality of stripes of annular grooves 19 to be opposed to the internal wall surface of a ceramic coating 18 in a cylinder 1 in a side of the top dead center over almost a half stroke. While the piston is constituted such that a plurality of piston rings 21 are fitted into ring grooves 20 on the peripheral surface in a side of the bottom dead center of the piston and opposed to a non-ceramic coating internal wall surface of the cylinder 1 over the full stroke of the piston. In this way, the piston, dropping the pressure of gas in a combustion chamber due to diffusion in the annular groove and reducing a leak of the gas from the piston ring, enables a number of piston rings to be decreased. |
