| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control system which continuously keeps an NOx eliminating rate high, while suppressing the occurrence of ammonia slip. <P>SOLUTION: The exhaust emission control system includes a slip determining part 34 for determining the occurrence of ammonia slip in accordance with an output value NH3<SB>CONS</SB>of an ammonia sensor 26, a reference injection amount calculating part 31, and a switching injection amount calculating part 32. The reference injection amount calculating part 31 calculates a reference injection amount G<SB>UREA_BS</SB>based on a parameter correlative to the operating condition of an engine. The switching injection amount calculating part 32 sets a switching injection amount G<SB>UREA_SW</SB>to a negative value in response to the determination that the ammonia slip occurs to reduce a urea injection amount G<SB>UREA</SB>, and sets the switching injection amount G<SB>UREA_SW</SB>to a positive value in response to the fact that a storage amount estimated value ST<SB>UREA</SB>falls below a predetermined switching storage amount ST<SB>UREA_SW</SB>to increase the urea injection amount G<SB>UREA</SB>. <P>COPYRIGHT: (C)2011,JPO&INPIT |
