| 摘要 |
PURPOSE:To suppress dilution of lubricating oil caused by fuel injection by promoting atomization of injected fuel. CONSTITUTION:An ignition plug is arranged on a center part of an inner wall surface of a cylinder head, while a fuel injection valve 14a is arranged on a circumferential part of the inner wall surface of the cylinder head. A groove 15 is formed on a top face 2a of a piston 2, which groove 15 is determined by a pair of side wall surfaces gradually widened from a lower part of the ignition plug to the side of the fuel injection valve 14a while substantially straightly extending, and a substantially flat bottom wail surface. A portion of the top face 2a of the piston 2 around the groove 15 is formed to be a flat surface. Fuel is injected from the fuel injection valve 14a into the groove 15 under a low load operation of an engine. The fuel injection timing is advanced under a high load operation of the engine, and the fuel is injected mainly to the flat top face 2a around the groove 15.
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