Importance

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Abstract

An air-fuel ratio control apparatus for internal combustion engine includes exhaust gas purifying catalysts mounted on the upstream and downstream sides of an exhaust passage of an internal combustion engine, a fuel injector for injection of a desired quantity of fuel into a cylinder of the internal combustion engine in accordance with an engine operating condition, and an ECU. The ECU changes an air-fuel ratio to lean and rich magnitudes by alternately increasing and decreasing the quantity of fuel injection. The lean/rich changeover of the exhaust air-fuel ratio is performed at an interval including a period during which the lean and rich components in the exhaust gas react with the upstream catalyst and a period thereafter during which an unreacted exhaust gas passes through the upstream catalyst.

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First Claim