| 摘要 |
PROBLEM TO BE SOLVED: To largely reduce an exhaust amount of NOx in a super-lean region combustion without using a reduction catalyst of NOx. SOLUTION: After the determination of an operating region based on revolutions and loads of an engine (S1), a mixture is fired by compression autoignition combustion when the operating region is in the super-lean region of low or medium range of loads of a low or medium range of revolutions (S2), and is fired by spark ignition combustion as in the ordinary case when the operation is in other regions (S3). Because the combustion style in the super- lean region is made to be the compression autoignition combustion, the mixture is fired under the temperature of producing NOx, the use of NOx reduction catalysts becomes unnecessary.
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