Method for controlling exhaust gas purification system and exhaust gas purification system

摘要

When the operating state of an internal combustion engine (10) is under low load, the supply of unburned fuel is controlled by using post-injection without using direct injection into an exhaust pipe. Under medium load, the supply of the unburned fuel is controlled by using both the post-injection and the direct injection into the exhaust pipe. Under high load, the supply of the unburned fuel is controlled by using the direct injection into the exhaust pipe without using the post-injection. Thus, in air-fuel ratio rich control performed during regeneration to recover the purification capability of an exhaust gas purification apparatus, both black smoke and white smoke are reduced when the supply of the unburned fuel for supplying the unburned fuel into exhaust gas is controlled.