| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an NOx sensor abnormality detection device for detecting abnormality of an NOx sensor at high accuracy, and an exhaust emission control system using it. <P>SOLUTION: This NOx sensor abnormality detection device stops an urea adding valve to add urea water to an NOx catalyst (S306), in a high NOx operating condition that an NOx amount emitted from an engine is not less than a predetermined value (S302: Yes), and when an engine operating condition is a steady condition (S304: Yes). When addition of the urea water from the urea adding valve is stopped, an urea amount adsorbed in the NOx catalyst is reduced. Then, the NOx sensor abnormality detection device determines the NOx sensor as abnormal when adsorption amount of urea in the NOx catalyst becomes 0 (S308: Yes) and an absolute value of a difference between an estimation value of the NOx amount estimated based on an engine speed NE and a command injection amount Q and a detection value of the NOx amount detected from output signals of the NOx sensor exceeds a predetermined value (S312: Yes). <P>COPYRIGHT: (C)2009,JPO&INPIT |
