| 摘要 |
PROBLEM TO BE SOLVED: To improve fuel consumption by forming a mixture layer near an ignition plug during operation with a partial load according to air flow and the shape of a piston and prevent the formation of carbon fouling on the ignition plug when an engine is started. SOLUTION: A fuel injection valve is provided at a position facing to a combustion chamber 16 on the intake port side of the outer edge of a cylinder on one side in the cross direction of a cylinder head and a swirl causing means to cause swirl of fuel spray in a cylinder is arranged in an intake passage. The top face of the piston is formed with a recession 64 comprising a portion opposing to the intake port and the ignition plug recessed, and a protrusion 66 is formed so as to surround the recession 64 from each side in the axis direction C of a crankshaft and the discharge port side. As a result, a cavity 68 is formed by the recession and the protrusion 66 on the intake port side. The protrusion 66 comprises protruded portions positioning on each side in the axis direction C of the crankshaft and a discharge side protruded portion positioning on the discharge port side, and the discharge side protruded portion is provided with a spray guide recession 70 in the portion intersected by a virtual plane.
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