To provide an exhaust emission control device provided with a nitrogen oxides storage and reduction type catalyst capable of remarkably improving purifying performance for NOx in exhaust gas on the whole by monitoring the change of the NOx storable quantity caused by the degradation of the catalyst, and allowing the introduction of rich spike at appropriate timing.
This exhaust emission control device 1 provided with the nitrogen oxides storage and reduction type catalyst 2 and executing the rich spike when the NOx integrated value NOx mass computed from the operating state of an engine E is larger than a specified first decision value NOxSL, is provided with an NOx sensor 13 in the downstream side of the nitrogen oxides storage and reduction type catalyst 2 and constituted to correct the specified first decision value NOxSL when the detected value RSNOx of the NOx sensor 13 immediately after the execution of the rich spike is larger than a specified second decision value RSSL.
TSUNODA HIROSHI
YAMADA HIROYUKI
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