| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control system for an internal combustion engine capable of utilizing NOx purification function by a second selective reduction catalyst at a downstream side to the maximum while suppressing discharge of a reduction agent from a tail pipe. <P>SOLUTION: This exhaust emission control system includes: a first selective reduction catalyst and a second selective reduction catalyst, provided in series in an exhaust pipe; a second consumption amount estimation part 51 estimating an NOx amount flowing into the second selective reduction catalyst and an NOx purification rate of the second selective reduction catalyst and estimating an NH<SB POS="POST">3</SB>amount consumed for purifying the flowing amount of NOx by the second selective reduction catalyst on the basis of the NOx purification rate and the NOx amount; a target NH<SB POS="POST">3</SB>concentration determination part 52 determining a target value VNH3<SB POS="POST">CMD</SB>for an NH<SB POS="POST">3</SB>sensor so that NH<SB POS="POST">3</SB>in the amount equivalent to the estimated NH<SB POS="POST">3</SB>consumption amount is re-adsorbed in the second selective reduction catalyst; and a controller 53 determining a corrected injection amount G<SB POS="POST">UREA</SB>_<SB POS="POST">FB</SB>so that an output value VNH3 of the sensor becomes the determined target value VNH3<SB POS="POST">CMD</SB>. <P>COPYRIGHT: (C)2013,JPO&INPIT |
