| 摘要 |
An air fuel ratio control apparatus for an internal combustion engine can freely change an oscillation width of an amount of oxygen occlusion so as to adapt to or diagnose catalyst degradation without changing the settings of the period or width of the air fuel ratio oscillation. The apparatus includes a first air fuel ratio feedback control section that adjusts the air fuel ratio of a mixture supplied to an engine in accordance with an output value of an upstream air fuel ratio sensor and a predetermined control constant thereby to make the air fuel ratio periodically oscillate in rich and lean directions, and an average air fuel ratio oscillation section that operates the control constant based on an amount of oxygen occlusion of the catalyst so that an average air fuel ratio obtained by averaging the periodically oscillating air fuel ratio is caused to oscillate in the rich and lean directions.
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