INTAKE AIR COMPOSITION VARIABLE INTERNAL COMBUSTION ENGINE AND METHOD FOR CONTROLLING THE SAME

PROBLEM TO BE SOLVED: To make intake air composition appropriate according to an engine operation state. SOLUTION: A gas separation device 24 is disposed at a downstream side of a catalyst 22 in an exhaust pipe 21, exhaust gas purified by a catalyst 22 is made to flow into a gas separation device 24, and nitrogen and a carbon dioxide are separated from the exhaust gas. The nitrogen and the carbon dioxide separate by the gas separation device 24 are introduced to an intake air passage of the engine 11 with its mix rate and/or mix quantity (intake system introduction quantity) which is changed according to an engine operation state. Consequently, the composition of intake air (concentration of the nitrogen and the carbon dioxide) can be changed to a composition suitable for the engine operation state according to the engine operation state, and theoretical thermal efficiency and actual efficiency are improved while reducing the occurrence of the knocking and the formation of NOx. COPYRIGHT: (C)2011,JPO&INPIT