| 摘要 |
A piston structure for a direct-injection, spark-ignition engine which properly stratifies a mixture adjacent to the spark plug in a stratified-combustion operation without impairing the reliable ignition of the spark plug. In the direct-injection, spark-ignition engine, the central portion of the roof of the combustion chamber is located at a higher level than its peripheral portion, the spark plug is disposed in the central portion, the fuel injector is disposed on the left side of the central portion, and the fuel injector injects fuel so that the fuel contacts the tumble flow produced in the combustion chamber in such a manner that the mixture is concentrated adjacent to the spark plug and ignited in the area in which the tumble flow turns clockwise. On the piston, a cavity having the bottom surface along which the tumble flow flows and extending to both sides of the cylinder axis is formed, and a step provided on the left side of the cylinder axis on the bottom surface of the cavity for guiding the tumble flow upwardly in the area in which the tumble flow turns.
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