Patent ID: 7127883

Claim:
An exhaust gas purifying apparatus of an internal combustion engine, comprising: a light-off catalyst provided in an exhaust passage and having an O 2 storage capability such that said light-off catalyst passes, there through, at least CO in an exhaust gas to a downstream side of said light-off catalyst when the internal combustion engine is operating under a condition where the oxygen concentration of the exhaust gas is reduced; exhaust gas purifying means provided in the exhaust passage at a downstream position of and in series with said light-off catalyst, said exhaust gas purifying means having a NOx catalyst for adsorbing NOx in the exhaust gas when an air-fuel ratio of the exhaust gas is lean and releasing the adsorbed NOx when the oxygen concentration of the exhaust gas is reduced, said exhaust gas purifying means further having a three-way catalyst that reacts with the released NOx; wherein the light-off catalyst has an oxygen storage capability of a first value and the three-way catalyst of the exhaust gas purifying means has an oxygen storage capability of a second value greater than said first value, said first and second values being per one liter of catalyst; and NOx regeneration control means for repeatedly releasing NOx adsorbed by the NOx catalyst every first interval outside the temperature range where SOx is releasable, and separate SOx regeneration control means independent from said NOx regeneration control means for repeatedly releasing SOx adsorbed by the NOx catalyst every second interval, said second interval being longer than the first interval and determined independently from said first interval.