| 摘要 |
The abnormality of an NH 3 sensor is judged highly accurately. For this purpose, an abnormality judging system for an exhaust gas purification apparatus of an internal combustion engine comprises a selective catalytic reduction NOx catalyst which is provided at an exhaust gas passage of the internal combustion engine and which reduces NOx by using NH 3 as a reducing agent, a supply device which supplies the reducing agent from an upstream side from the NOx catalyst, a NOx sensor which detects NOx and NH 3 on a downstream side from the NOx catalyst, and an NH 3 sensor which detects NH 3 on a downstream side from the NOx catalyst, wherein it is judged that the NH 3 sensor has any abnormality if an absolute value of a difference between an estimated NH 3 concentration as a difference between a detection value of the NOx sensor and an estimated value of a NOx concentration and an NH 3 concentration detected by the NH 3 sensor is not less than a threshold value when NH 3 flows out from the selective catalytic reduction NOx catalyst. |
