To provide an exhaust emission control device of an internal combustion engine, the device capable of quickly and properly obtaining an SCR catalyst purification action even at a cold start or a low load, and avoiding a thermal effect on an SCR catalyst during DPF regeneration treatment.
Exhaust gas is purified in an exhaust passage (18) of an internal combustion engine (10) which includes an exhaust turbine (20a) and a DPF device (34) provided on the downstream side with respect to the exhaust turbine. An exhaust emission control device includes, particularly, a first SCR catalyst (24) provided on the upstream side with respect to the DPF device, a second SCR catalyst (50) provided on the downstream side with respect to the DPF device, an exhaust bypass passage (42) for bypassing the first SCR catalyst, a reflux control passage (44) for opening and closing the exhaust bypass passage, and an exhaust temperature sensor (22) for detecting a temperature on the upstream side of the first SCR catalyst. When a detection value of the exhaust temperature sensor is a threshold or above, a reflux control valve is set to be in an opened state. When the detection value is less than the threshold, the reflux control valve is set to be in a closed state.
OKADA KOJIRO
KIMURA HIROYUKI
MATSUDA SEIJI
MORIMOTO KENJI
ISOBE YUSUKE
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