| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust fuel injection type exhaust emission control system capable of preventing the occurrence of excessive HC slip while keeping a NOx eliminating rate as high as possible.SOLUTION: The exhaust emission control system includes an exhaust fuel injection device for injecting fuel to the upstream side of an LNT, exhaust fuel injection control means for controlling the exhaust fuel injection amount of the exhaust fuel injection device, a post-catalyst LAF sensor for detecting the air-fuel ratio of exhaust gas on the downstream side of the LNT, and downstream air-fuel ratio estimating means for estimating the air-fuel ratio of the exhaust gas on the downstream side of the LNT. The exhaust fuel injection control means controls an exhaust fuel injection amount Gfuel_ex so that a NOx eliminating parameter P_LNT equivalent to an air-fuel ratio difference between an output value AFact_ds for the post-catalyst LAF sensor and an ideal exhaust air-fuel ratio AF_exh_id_ds calculated by the downstream air-fuel ratio estimating means becomes a predetermined target value P_LNT_cmd, not zero. |
