EXHAUST GAS PURIFICATION DEVICE FOR ENGINE AND EXHAUST GAS PURIFICATION METHOD

摘要

The first target A/ F directing toward a richer side from the initial target A/F to the theoretical A/F is calculated; and the first estimated catalyst's oxygen amount is calculated based on the detected A/F and the theoretical A/F. Until the first estimated catalyst's oxygen amount reaches the first target catalyst's oxygen amount, calculations of the first target A/ F and of the first estimated catalyst's oxygen amount continue. After the first estimated catalyst's oxygen amount reaches the first target catalyst's oxygen amount, the second target A/F directing toward a richer side from the theoretical A/F to the final target A/F is calculated; and the second estimated catalyst's oxygen amount is calculated based on the detected A/F and the final target A/F. Until the second estimated catalyst's oxygen amount reaches the second target catalyst's oxygen amount, calculations of the second target A/F and of the second estimated catalyst's oxygen amount continue.