Patent ID: 6911184

Claim:
An exhaust gas purifying apparatus used for an internal combustion engine, which can select an operation at a fuel-lean air-fuel ratio and an operation at a fuel-stoichiometric or rich air-fuel ratio, and which apparatus comprises: an NO x storage-and-reduction type catalyst disposed in an exhaust gas flow passage and exhibiting a saturated NO x storage amount of 5 g or more as NO 2 with respect to 1 liter of a catalyst volume at 500° C.; NO x storage amount estimating means for estimating an actual NO x storage amount of the NO x storage-and-reduction type catalyst; air-fuel ratio adjusting means for adjusting an exhaust gas atmosphere to reduction components lean or reduction components rich; and a controlling device for controlling the air-fuel ratio adjusting means based on an estimated value estimated by the NO x storage amount estimating means so that the actual NO x storage amount becomes 50% or less of the saturated NO x storage amount.