METHOD AND DEVICE FOR TREATING EXHAUST GAS OF INTERNAL COMBUSTION ENGINE

摘要

In an exhaust gas treatment device in which a diesel oxidation catalyst and a DPF are provided in an exhaust pipe of an internal combustion engine, abnormal combustion in the DPF, occurring when the internal combustion engine varies from a high load condition to a low load condition, poses a problem. To solve this problem, in the present invention, a DPF abnormal combustion causing operation is determined to have occurred when the internal combustion engine shifts from a high rotation or high load operation region ± to a low rotation, low load operation region ² within a set time T 1 . When it is determined that a DPF abnormal combustion causing operation has occurred, abnormal combustion of PM collected in the DPF is suppressed by fully opening an intake throttle valve 44 in order to increase an exhaust gas flow so that heat is removed by sensible heat of the exhaust gas, thereby cooling a DPF device 52, and continuing a late post-injection in order to reduce an oxygen concentration of the DPF. As a result, an abnormal temperature increase in the DPF device 52 can be suppressed early.