Patent ID: 7171803

Claim:
An exhaust gas purification system of an internal combustion engine, which includes a particulate filter disposed in an exhaust passage of the engine for collecting exhaust particulate matters and calculates an deposition state of the exhaust particulate matters deposited in the particulate filter based on operating states of the engine including a differential pressure between an inlet and an outlet of the particulate filter to determine whether the particulate filter should be regenerated or not, the exhaust gas purification system comprising: absolute pressure calculating means for calculating an absolute pressure of exhaust gas at an upstream portion or inside the particulate filter; converting means for converting a mass flow rate of the exhaust gas flowing through the particulate filter into a volumetric flow rate based on the absolute pressure; and deposition state calculating means for calculating the deposition state based on the volumetric flow rate and the differential pressure, wherein the absolute pressure calculating means includes filter downstream pressure loss calculating means for calculating a pressure loss in the exhaust passage between the outlet of the particulate filter and a tailpipe based on the operating states of the engine and a filter pressure loss calculating means for calculating a pressure loss in the particulate filter, and the absolute pressure calculating means calculates the absolute pressure by adding an atmospheric pressure, the pressure loss in the exhaust passage between the outlet of the particulate filter and the tailpipe, and the pressure loss in the particulate filter.