Exhaust gas cleaning system having particulate filter

摘要

In an exhaust gas cleaning system of an internal combustion engine having a diesel particulate filter (DPF), measuring accuracy of a collection quantity of particulate matters collected by the DPF is estimated based on an accelerator position change rate and an exhaust gas flow rate. When the measuring accuracy is high, the collection quantity is calculated based on a pressure difference and the exhaust gas flow rate at the DPF. If the measuring accuracy is low, an increment value of the collection quantity is calculated based on a quantity of the particulate matters discharged from an engine main body. Then, the collection quantity is calculated by adding the collection quantity increment value to the previous collection quantity calculated based on the pressure difference and the exhaust gas flow rate while the measuring accuracy is high.