Patent ID: 6952920

Claim:
An exhaust gas cleaning system comprising: a particulate filter disposed in an exhaust passage of an engine configured and arranged to accumulate particulate matter in an exhaust gas discharged from the engine; a pressure difference detecting section configured and arranged to detect a pressure difference in the exhaust passage between before and after the particulate filter; an exhaust gas flow rate determining section configured and arranged to determine an exhaust gas flow rate; an exhaust gas temperature detecting section configured and arranged to detect a temperature of the exhaust gas passing through the particulate filter; and an accumulation state determining section configured and arranged to determine an accumulation state of the particulate matter in the particulate filter by obtaining a reference equivalent surface area of a passage inside the particulate filter based on the pressure difference detected in the pressure difference detecting section, the exhaust gas flow rate determined in the exhaust gas flow rate determining section, and the temperature of the exhaust gas detected in the exhaust gas temperature detecting section, the accumulation state determining section being further configured to obtain an adjusted equivalent surface area by adjusting the reference equivalent surface area based on a temperature of the particulate filter and the exhaust gas flow rate.