Air-fuel ratio control system for internal combustion engines

摘要

An air-fuel ratio control system controls the air-fuel ratio of a mixture supplied to an internal combustion engine. An exhaust gas purifying-device arranged in the exhaust system of the engine accommodates a nitrogen oxide absorbent for absorbing nitrogen oxides in exhaust gases emitted from the engine. Nitrogen oxides absorbed by the nitrogen oxide absorbent is reduced by enriching the air-fuel ratio of the mixture supplied to the engine. The degree of the enriching of the air-fuel ratio is set to a larger value as a flow rate or flow velocity of the exhaust gases increases.