| 摘要 |
PROBLEM TO BE SOLVED: To enhance NOx purification efficiency and to supress reduction of purification efficiency of HC and CO by providing a plurality of exhaust passages provided with a NOx absorber and shifting rich spike starting time in each of the NOx absorbers when making an exhaust air-fuel ratio in the plurality of exhaust passages rich. SOLUTION: NOx absorbers 38 and 39 are disposed to first and second exhaust passages 35 and 36, respectively, and an exhaust emission control device 40 is provided in a common exhaust passage 37 at a downstream side of these passages. When an air-fuel ratio of exhaust gas is lean, each of the NOx absorbers 38, 39 absorbs NOx, and when air fuel ratio of entering exhaust gas is rich, each of the NOx absorbers 38, 39 releases absorbed NOx. In this exhaust emission control device, in order to sufficiently supplement reducing agent required for relasing and reducing NOx absorbed by the NOx absorbers 38, 39, rich degree is heightened. At this time, at the time of rich spike, spike starting time in each of NOx absorbers 38, 39 are shifted by a predetermined time, thereby efficiently carrying out exhaust emission control.
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