METHOD FOR CONTROLLING EXHAUST GAS PURIFICATION SYSTEM, AND EXHAUST GAS PURIFICATION SYSTEM

In regeneration control, when the catalyst temperature index temperature (Tg2) using the temperature of the oxidation catalyst (12a) as an index is below a predetermined first determination temperature (Tc1), the engine speed of idling is brought to a predetermined first target engine speed (Neil) which is higher than the engine speed of idling (Nei0) in the ordinary operation, and, further, multi-injection is carried out. On the other hand, when the catalyst temperature index temperature (Tg2) is the predetermined first determination temperature (Tc1) or above, the engine speed of idling is brought to a predetermined second target engine speed (Nei2), which is lower than the predetermined first target engine speed (Nei1) and is higher than the engine speed of idling (Nei0) in ordinary operation, and, further, post injection is carried out, followed by raising of the temperature of an exhaust gas flown into a DPF apparatus (12b) to a predetermined second determination temperature (Tc2). According to the above constitution, in the regeneration control of the DPF apparatus (12b) in an internal combustion engine (10), the regeneration can be forcibly carried out with high efficiency while enhancing the temperature rise efficiency of the exhaust gas, and, at the same time, excessive rise in the exhaust temperature, a deterioration in fuel consumption, and the occurrence of noise are suppressed.