Patent ID: 6966178

Claim:
An exhaust gas purification system for an internal combustion engine, the exhaust gas purification system having a particulate filter in an exhaust passage for collecting particles included in exhaust gas and for burning and removing the particles accumulated in the particulate filter for recovering the particulate filter, the exhaust gas purification system comprising: a pressure drop detecting unit that detects a pressure drop of the particulate filter; a regeneration determining unit that defines an accumulation characteristic of a relationship between the accumulation amount ML of the particles and the pressure drop, wherein: the regeneration determining unit defines a first characteristic line, which is a straight line passing an initial point in which the accumulation amount ML is zero, and a second characteristic line, which is a straight line having a smaller slope value compared with a slope of the first characteristic line; the accumulation characteristic is defined by the first characteristic line and the second characteristic line; the pressure drop increases along with the first characteristic line from the initial point to a predetermined increasing transitional point, and increases along with the second characteristic line from the increasing transitional point; the regeneration determining unit calculates the accumulation amount ML based on the accumulation characteristic and an operating condition of the internal combustion engine which includes at least the pressure drop; and the regeneration determining unit determines whether the accumulation amount ML exceeds a predetermined regeneration-starting amount MLth for determining whether the regeneration of the particulate filter needs to be performed; a exhaust particle detecting unit that detects a combusting condition of the particles accumulated in the particulate filter; and a correcting unit that corrects the accumulation characteristic so that the second characteristic line is substantially parallely shifted to a direction, in which the accumulation amount ML becomes large when the particles are in the combusting condition.