Internal combustion engine

An internal combustion engine comprising:

• a main combustion chamber sandwiched between a cylinder head and a piston facing the cylinder head;
• an intake port formed within the cylinder head and connected to the main combustion chamber at an intake opening;
• an exhaust port formed within the cylinder head and connected to the main combustion chamber at an exhaust opening;
• a sub-chamber provided on the cylinder head between the intake opening and the exhaust opening, and connected to the main combustion chamber through a plurality of through-holes;
• a fuel injector injecting fuel into the sub-chamber;
• and
• a spark plug performing ignition in the sub-chamber, wherein
• a tumble flow at a position of the sub-chamber flows from a first side to a second side as seen from the sub-chamber,
• the plurality of through-holes include:
• a first through-hole formed in a part on the first side of a side wall of the sub-chamber;
• and
• a second through-hole different from the first through-hole and formed in a part on the second side of the side wall of the sub-chamber,
• a diameter of the first through-hole is larger than a diameter of the second through-hole, and
• the fuel injector preferentially injects fuel to a direction of the second side over a direction of the first side.