| abstract |
Exhaust gas control device of an internal combustion engine with: a NOx catalyst (50b) provided at an exhaust passage (18, 19); NOx catalyst temperature detecting means (48a, 48b) for detecting a temperature of the NOx catalyst (50b); exhaust air-fuel ratio detecting means (47) for detecting an air-fuel ratio of the exhaust gas in the exhaust passage (18, 19); and an exhaust air-fuel control means (30) for controlling the air-fuel ratio of the exhaust gas in the exhaust passage (18, 19) based on the temperature of the NOx catalyst (50b) detected by the NOx catalyst temperature detecting means (48a, 48b) and the air-fuel ratio of the Exhaust gas detected by the exhaust air-fuel ratio detection means (47), wherein, when the air-fuel ratio of the exhaust gas detected by the exhaust-gas-fuel-ratio detecting means (47) is lean from a first predetermined air-fuel ratio at which an upper limit of allowable amount of generated smoke is reached and which is greater than a stoichiometric air-fuel ratio, the exhaust air-fuel ratio control means (30) controls the air-fuel ratio of the exhaust gas to the first predetermined air-fuel ratio, and intermittently controls the air-fuel ratio of the exhaust gas ... |