Internal combustion engine

An internal combustion engine comprising:

• a cylinder formed by a cylinder block;
• a cylinder head covering one end of the cylinder;
• a piston having a top surface facing the cylinder head and configured to reciprocate in the cylinder;
• an ignition plug disposed in a central portion of the cylinder head in a combustion chamber formed between the cylinder, the cylinder head, and the piston;
• an intake port and an exhaust port provided in the cylinder head with the ignition plug sandwiched therebetween;
• and
• a fuel injection nozzle configured to supply fuel to the combustion chamber, wherein
• the top surface of the piston is provided with a pair of side guide portions extending along an intake and exhaust direction connecting the intake port to the exhaust port, protruding toward the cylinder head, and disposed on both end sides in a crankshaft direction orthogonal to a cylinder axial direction that is a reciprocating direction of the cylinder and the intake and exhaust direction,
• a passage portion extending in a direction intersecting an extension direction and making an inner surface and an outer surface of each of the side guide portions communicate with each other, is formed in each of the side guide portions,
• a sub-chamber accommodating the ignition plug is provided in the combustion chamber,
• an injection port making the combustion chamber and the sub-chamber communicate with each other and configured to inject flame from the sub-chamber to the combustion chamber, is formed in the sub-chamber, and
• the passage portion is formed on an extension line of the injection port when viewed in the cylinder axial direction.