Internal combustion engine and method for manufacturing the same

A method for manufacturing an internal combustion engine, the internal combustion engine including:

• an air supply manifold extending in one direction;
• a plurality of cylinders arranged at a predetermined interval in the one direction in which the air supply manifold extends;
• a plurality of swirl chambers connected to ends of the respective cylinders to form swirls;
• and
• an air supply port including a connecting part arranged on one side surface of the air supply manifold and a swirl chamber introduction part that connects the connecting part and the swirl chamber in a downstream side of the connecting part, a plurality of air supply ports being provided with respect to the air supply manifold, wherein
• an air supply inlet for supplying air into the air supply manifold is provided on an end of the air supply manifold,
• air that is supplied from the air supply inlet to the air supply manifold flows along the one direction in which the air supply manifold extends,
• connecting parts of respective air supply ports are arranged on the one side surface of the air supply manifold along the one direction in which the air supply manifold extends at an interval in the one direction,
• a central axis of the connecting part of one of the air supply ports inclines with a predetermined inclination angle in a direction away from the air supply inlet with respect to an orthogonal direction orthogonal to the one direction in which the air supply manifold extends,
• the inclination angle of the central axis of the connecting part of the one of the air supply ports provided on the air supply manifold is larger than an inclination angle of the central axis of the connecting part of other air supply ports located on a side closer to the air supply inlet than the one of the air supply ports, the method comprising:
• a connecting part manufacturing step of manufacturing the connecting parts by an air supply manifold mold for forming the air supply manifold;
• a swirl chamber introduction part manufacturing step of manufacturing the swirl chamber introduction parts by a cylinder head mold for forming the swirl chamber and the ends of the cylinder;
• and
• an air supply port manufacturing step of connecting the connecting parts and the swirl chamber introduction parts to manufacture the air supply ports.