Patent ID: 8769934

Claim:
An exhaust purifying system for an internal combustion engine capable of a lean burn operation, comprising: a NOx storage-reduction catalyst (NSR catalyst) disposed in an exhaust passage of the internal combustion engine; a NOx selective catalytic reduction (SCR) disposed downstream of the NSR catalyst; means for detecting sulfur poisoning of the SCR; and means for increasing a bed temperature of the SCR when the poisoning detecting means detects sulfur poisoning of the SCR, wherein: the internal combustion engine includes a plurality of cylinder groups; the temperature increasing means includes means for performing a bank control in which a rich air-fuel ratio is set for a first cylinder group and a lean or stoichiometric air-fuel ratio is set for a second cylinder group; and the bank control is performed when the sulfur poisoning of the SCR is detected and a distance driven from performance of a preceding bank control is longer than a predetermined distance.