| 摘要 |
<P>PROBLEM TO BE SOLVED: To accurately estimate the amount of an ammonia-producing compound stored in a catalyst. <P>SOLUTION: A catalyst 22 suitable for reducing NOx in exhaust gas by ammonia under the existence of excessive oxygen is arranged in an exhaust gas passage of an internal combustion engine so as to supply liquid containing an ammonia-producing compound to the catalyst 22 through the medium of a flow control valve 33. On the basis of the elapsed time after the ammonia-producing compound is stored in the catalyst 22, the amount of the ammonia-producing compound stored in the catalyst 22 is estimated. When the presumed stored amount of the ammonia-producing compound exceeds the predetermined maximum stored amount, the supply of liquid including the ammonia-producing compound is stopped. <P>COPYRIGHT: (C)2008,JPO&INPIT |
