Patent ID: 8857158

Claim:
An exhaust gas treatment method for an internal combustion engine, comprising a collecting step of collecting particulate matter contained in an exhaust gas discharged from the internal combustion engine in a filter, and an active regeneration step of post-injecting a fuel to heat the exhaust gas to a combustion temperature of the particulate matter in a diesel oxidation catalyst so that the particulate matter collected in the filter is burned and removed by the heated exhaust gas, the exhaust gas treatment method comprising: detecting an exhaust gas temperature at an inlet of the filter during the active regeneration step, determining whether or not a shift of an operating condition of the internal combustion engine from a high rotation or high load operating condition to a low rotation and low load operating condition including an idling condition occurs within a set time during the active regeneration step; increasing an exhaust gas flow by performing at least one operation from among fully opening a throttle valve provided in an intake pipe or an exhaust pipe and not reducing a rotation speed during the low load operating condition to or below a set value, when the exhaust gas temperature at the inlet of the filter is determined to equal or exceed the combustion temperature of the particulate matter during the active regeneration step and the operating condition of the internal combustion engine is determined to shift within the set time; and reducing a combustion speed of the particulate matter performed in parallel with increasing the exhaust gas flow by reducing an oxygen concentration of the filter while continuing the post-injection as is.