Engine exhaust purification device

摘要

An oxygen storage amount of the catalyst (3) is estimated using a detection result from a front A/F sensor (4). An HC storage amount is calculated as a time integral of the product of the storage rate by the catalyst (3), the air-fuel ratio and the intake air amount, and a target air-fuel ratio is corrected so that a deficiency relative to a target amount of the oxygen storage amount is compensated based on this computation result.