Patent ID: 8171723
Filing Date: 2012-05-08
Classification: F01N,Y02A,Y02T

Abstract:
1. An abnormality detection system for an internal combustion engine that determines whether a NOx discharge amount exceeds a prescribed regulation value due to deterioration of a NOx selective catalytic reduction catalyst arranged in an exhaust passage of the internal combustion engine or due to an irregularity in an amount or quality of aqueous urea solution that is supplied to the NOx selective catalytic reduction catalyst, comprising: An Electronic Control Unit (ECU) having: a determination-required region setting unit that sets a determination-required region to a region within which a NOx removal efficiency falls in either a case where the NOx discharge amount exceeds the regulation value due to deterioration of the NOx selective catalytic reduction catalyst or a case where the NOx discharge amount exceeds the regulation value due to an irregularity in the amount or quality of aqueous urea solution that is supplied to the NOx selective catalytic reduction catalyst, and in which a temperature of the NOx selective catalytic reduction catalyst is within a predetermined first temperature range; a first abnormality region setting unit that sets a first abnormality region to a region within which the NOx removal efficiency falls when the NOx discharge amount exceeds the regulation value due to deterioration of the NOx selective catalytic reduction catalyst, within which the NOx removal efficiency does not fall when the NOx discharge amount exceeds the regulation value due to an irregularity in the amount or quality of aqueous urea solution that is supplied to the NOx selective catalytic reduction catalyst, and in which the temperature of the NOx selective catalytic reduction catalyst is within a predetermined second temperature range having a lower limit that is higher than an upper limit of the first temperature range; a second abnormality region setting unit that sets a second abnormality region to a region within which the NOx removal efficiency falls when the NOx discharge amount exceeds the regulation value due to an irregularity in the amount or quality of aqueous urea solution that is supplied to the NOx selective catalytic reduction catalyst, within which the NOx removal efficiency does not fall when the NOx discharge amount exceeds the prescribed regulation value due to deterioration of the NOx selective catalytic reduction catalyst, and in which the temperature of the NOx selective catalytic reduction catalyst is within the second temperature range; and an abnormality factor determination unit that determines that the NOx discharge amount exceeds the regulation value due to deterioration of the NOx selective catalytic reduction catalyst, if it is determined that the NOx removal efficiency is within the determination-required region when the temperature of the NOx selective catalytic reduction catalyst is within the first temperature range and it is then determined that the NOx removal efficiency falls within the first abnormality region when the temperature of the NOx selective catalytic reduction catalyst is brought into the second temperature range, the abnormality factor determination unit determining that the NOx discharge amount exceeds the regulation value due to an irregularity in the amount or quality of aqueous urea solution that is supplied to the NOx selective catalytic reduction catalyst, if it is determined that the NOx removal efficiency is within the determination-required region when the temperature of the NOx selective catalytic reduction catalyst is within the first temperature range and it is then determined that the NOx removal efficiency falls within the second abnormality region when the temperature of the NOx selective catalytic reduction catalyst is brought into the second temperature range.