US Patent 7874278 Intake port of internal combustion engine

An internal combustion engine wherein the top wall surface of the intake air inflow passage part of the intake port is formed by a first top wall surface and a second top wall surface lower than the first top wall surface and wherein a lower layer flow passage and an upper layer flow passage are formed at the height position of the second top wall surface as a boundary. When the intake valve opens, a lower layer flow flowing through the inside of the lower layer flow passage passes through the intake valve opening region, flows to the circumferential direction of the combustion chamber, and generates a swirl, while an upper layer flow flowing through the inside of the upper layer flow passage passes through the helical part and flows into the combustion chamber.