| 摘要 |
PROBLEM TO BE SOLVED: To provide a failure detecting device for an exhaust emission control system for an internal combustion engine, capable of discriminating in which structural element of the exhaust emission control system a failure occurs, when detecting the failure of the exhaust emission control system including an SCR catalyst.SOLUTION: The failure detecting device is provided for detecting the failure of the exhaust emission control system for the internal combustion engine, which includes the SCR catalyst provided in an exhaust passage, and a reducing agent supply means for adding urea water into exhaust gas upstream of the SCR catalyst. The failure detecting device includes a unit for acquiring a NOx amount flowing into the SCR catalyst by measuring or estimating it, a unit for acquiring a NOx amount flowing out of the SCR catalyst by measuring it, a unit for acquiring the rate of the NOx eliminated by the SCR catalyst in accordance with the acquired flowing-in NOx amount and flowing-out NOx amount, and a failure site discriminator for discriminating a failure of the SCR catalyst, a failure of the reducing agent supply or a failure of a NOx sensor in accordance with the elimination rate in a steady state and a time required for stabilizing the transient fluctuation of the elimination rate in a transient state. |
