Patent ID: 6988359

Claim:
An exhaust gas control apparatus for an internal combustion engine, comprising: a first catalyst portion disposed in an exhaust passage of the internal combustion engine; a second catalyst portion disposed in the exhaust passage downstream of the first catalyst portion; and a controller which performs stoichiometric feedback control by: (i) obtaining a value that changes according to at least an amount of oxygen stored in the first catalyst portion, as an obtained value; (ii) controlling a stoichiometric air-fuel ratio of the internal combustion engine such that the obtained value substantially matches a feedback target value; (iii) calculating a value that changes according to at least an amount of oxygen stored in the second catalyst portion, as a calculated value, based on at least a state of exhaust gas flowing into the second catalyst portion; and (iv) changing the feedback target value according to the calculated value such that a relationship between the feedback target value and a maximum amount of oxygen able to be stored in the first catalyst portion changes with changes in a relationship between the calculated value and a maximum amount of oxygen able to be stored in the second catalyst portion.