| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control system for an internal combustion engine which can determine that a selective reduction catalyst is oxidized and catalyzed. <P>SOLUTION: The exhaust emission control system includes a selective reduction catalyst and a NH<SB POS="POST">3</SB>sensor for detecting the concentration of NH<SB POS="POST">3</SB>in exhaust downstream of the same. When the temperature of the selective reduction catalyst is not lower than its activating temperature and is higher than deterioration determining temperature set within a high temperature region where the maximum storage capacity of the reduction agent is reduced and, in addition, when the detection value of the NH<SB POS="POST">3</SB>sensor is a light deterioration determining value or less after supplying through an injector the amount of urea water making the detection value of the NH<SB POS="POST">3</SB>sensor larger than the light deterioration determining value, the selective reduction catalyst is determined to be in an oxidative deterioration state that NH<SB POS="POST">3</SB>or urea water is oxidized into NOx. <P>COPYRIGHT: (C)2013,JPO&INPIT |
