| 摘要 |
<p>Provided is an exhaust purification system for an internal combustion engine. The exhaust purification system comprising: a NO X purifying catalyst arranged in an exhaust passage of the internal combustion engine, wherein the NO X purifying catalyst comprises a base metal supported on a catalyst support; an oxygen sensor arranged at the downstream side of the NO X purifying catalyst in the exhaust passage; and an air-fuel ratio control means for controlling the air-fuel ratio of exhaust gas flowing into the NO X purifying catalyst; wherein when the NO X purifying catalyst suffers from predetermined oxygen poisoning, the air-fuel ratio control means controls the air-fuel ratio of the exhaust gas, which flows into the NO X purifying catalyst, to a first air-fuel ratio wherein the first air-fuel ratio is richer than a theoretical air-fuel ratio, and then the air-fuel ratio control means switches the air-fuel ratio of the exhaust gas, which flows into the NO X purifying catalyst, to a second air-fuel ratio on the basis of an output value from the oxygen sensor wherein the second air-fuel ratio is leaner than the first air-fuel ratio.</p> |
