| 摘要 |
Provided is a control method for an exhaust gas aftertreatment device, with which the timing for returning to a rich state after an S purge and the urea water injection timing after particulate matter (PM) regeneration can be reliably controlled. A DOC (25), a NOx storage reduction catalyst (26), and a DPF (27) are connected to the exhaust pipe (20) of an engine (E), downstream from an exhaust pipe injector (23) provided on the exhaust pipe (20), with the NOx in the exhaust gas being stored by the NOx storage reduction catalyst (26) when the air-fuel ratio is lean, and the stored NOx being reduced/purified when the air-fuel ratio is rich. When a prescribed amount of PM has accumulated in the DPF (27) the exhaust gas temperature is raised and the PM is regenerated, after which the exhaust gas temperature is raised further to perform an S purge of the sulfur stored in the NOx storage reduction catalyst (26), with enrichment being prohibited during the PM regeneration period and the S purge period. When the S purge is completed the prohibition of enrichment is continued until the difference between the inlet temperature of the DOC (25) and the outlet temperature of the NOx storage reduction catalyst (26) is equal to or less than a set threshold value. |
