EXHAUST EMISSION PURIFICATION METHOD AND EXHAUST EMISSION PURIFICATION SYSTEM

摘要

In an exhaust emission purification method and an exhaust emission purification system where forced regeneration start timing of a DPF for purifying the PM (particulate matters) in exhaust gas is judged based on the comparison of a differential pressure across the DPF with a predetermined differential pressure threshold across the DPF, a differential pressure threshold (”Ps) across the DPF is set by multiplying a reference differential pressure threshold (”Ps0) across the DPF by a coefficient( ±(”M)) which varies stepwise or continuously depending on the mileage (”M) of a vehicle after previous forced regeneration. Consequently, the PM can be removed by burning while the amount of PM accumulated unevenly in the DPF is still small, and excessive temperature rise in the DPF resulting from excessive accumulation of PM during forced regeneration and melting-loss of DPF due to excessive temperature rise can be prevented.