Patent ID: 7707827

Claim:
An exhaust gas purifying apparatus for an internal combustion engine comprising: a filter provided in an exhaust pipe of the engine and having multiple exhaust gas passages defined by porous partitioning walls, for trapping diesel particulates contained in exhaust gas from the engine by the porous partitioning walls when the exhaust gas passes through the porous partitioning walls, wherein the diesel particulates accumulated in the filter are forcibly combusted to re-generate the filter when an accumulated amount of the trapped diesel particulates exceeds a predetermined amount; a means for estimating the accumulated amount of the diesel particulates from a pressure loss at the filter, based on an accumulation characteristic in which the pressure loss is related to the accumulated amount of the diesel particulates; a means for detecting a flow velocity of the exhaust gas passing through the porous partitioning walls; and a means for correcting the accumulation characteristic depending on the flow velocity of the exhaust gas detected by the flow velocity detecting means, wherein the accumulation characteristic has a first characteristic line in a first range, in which the accumulated amount of the diesel particulates changes from a zero point to a transition point, and a second characteristic line in a second range, in which the accumulated amount of the diesel particulates changes from the transition point to a further larger amount, an increasing ratio of the pressure loss with respect to an increase of the accumulated amount of the diesel particulates is constant in the first range, so that the pressure loss increases in proportion to the increase of the accumulated amount of the diesel particulates in the first range, the pressure loss also increases in proportion to the increase of the accumulated amount of the diesel particulates in the second range, but in a slower manner than the pressure loss in the first range, and the accumulation characteristic correcting means corrects the accumulation characteristic in accordance with the first characteristic line, when the flow velocity of the exhaust gas detected by the flow velocity detecting means is in the first range.