| 摘要 |
PROBLEM TO BE SOLVED: To surely minimize the air-fuel ratio of the exhaust gas discharged from a combustion chamber in the use of gas fuel. SOLUTION: In this gas fuel internal combustion engine in which the air-fuel ratio of air-fuel mixture to be burnt in the combustion chamber is kept at a lean air-fuel ratio, an NOx catalyst is arranged in its exhaust passage. When the accumulated NOx quantity in the NOx catalyst exceeds an allowable quantity, the air-fuel ratio of the exhaust gas discharged from the combustion chamber is temporarily switched to a rich air-fuel ratio. A part (QRc) of the fuel increment necessary for switching the air-fuel ratio of the exhaust gas discharged from the combustion chamber from the lean air-fuel ratio to the rich air-fuel ratio is injected in the initial stage of a compression stroke, and the remainder (QRp) is injected in a combustion stroke. COPYRIGHT: (C)2004,JPO
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