Exhaust gas purification system comprises catalyst in exhaust gas passage of I.C. engine, catalyst downstream of first catalyst, and regulator

摘要

Exhaust gas purification system comprises a first catalyst (22) in the exhaust gas passage (21) of an I.C. engine (11) for accelerating an oxidation reaction of the conversion of nitrogen oxide to nitrogen dioxide; a second catalyst (23) downstream of the first catalyst for adsorbing and reducing the nitrogen oxides; and a regulator (29) which regulates an air-fuel ratio of an air-fuel mixture conveyed to the engine before the second catalyst is active. Preferred Features: The regulating unit regulates the air-fuel ratio of the air-fuel mixture to the lean side after the first catalyst is active and before the second catalyst is active.