Patent ID: 8266893

Claim:
An exhaust gas purification apparatus of an internal combustion engine, the exhaust gas purification apparatus comprising a storage reduction type NOx catalyst provided in an exhaust system of the internal combustion engine, wherein the exhaust gas purification apparatus conducts catalyst recovery control for releasing sulfur oxide stored in the NOx catalyst, wherein an adding period for carrying out a continuous intermittent fuel addition to a section upstream of the NOx catalyst of the exhaust system and a suspend period during which the intermittent fuel addition is stopped are repeated in the catalyst recovery control, and wherein the intermittent fuel addition is carried out in such a manner that an air-fuel ratio detected by an air-fuel ratio sensor provided in the exhaust system during the adding period comes to a target air-fuel ratio which is richer than a stoichiometric air-fuel ratio, wherein the exhaust gas purification apparatus includes a control unit configured to: set a fuel adding amount at one time in the intermittent fuel addition during the adding period based on temperature of the exhaust gas; limit the fuel adding amount to a predetermined value or less when the fuel adding amount set based on the temperature of the exhaust gas exceeds the predetermined value, set the predetermined value such that a fuel adding amount per unit time during the adding period becomes equal to or less than an allowable upper limit value at and below which the NOx catalyst fully purifies an unburned fuel component; and set the predetermined value to Q 1 max·t/N, wherein Q 1 max denotes the allowable upper limit value, t denotes an elapsed time from the start of the adding period, and N denotes a number of times of the fuel addition to the exhaust system from the start of the adding period.