PURPOSE: To reduce the emission of HC by conducting EGR at the center of air intake pipe by using an air intake port having a coaxial double structure consisting of the inside and outside ports.
CONSTITUTION: The air intake port 4 has a coaxial double structure consisting of the inside port 4a and the outside port 4b. A part of exhaust gas is sent through the EGR flow rate control lever groove 10 from the EGR path 9 into the inside port 4a of the air intake port 4. Thus, because the EGR gas-mixed gas is present at the central part of the combustion chamber 6 where NOx is prone to generate, the generation of NOx is reduced, and at the same time, becuase a layer consisting of combustible mixed gas alone is formed in and around the wall surface 6a of the combustion chamber 6, the combustion speed is comparatively fast and hence combustion is fully accelerated, greatly reducing the emission of HC.
NAKAGAWA YASUHIKO
SUZUKI SUZUO
MATSUMOTO YASUO
