| 摘要 |
<P>PROBLEM TO BE SOLVED: To enhance estimating accuracy of an ammonia consumption amount in a NOx catalyst, and to optimize NOx purification. <P>SOLUTION: An SCR catalyst 13 is provided in an exhaust pipe 11 of an engine, and a urea water adding valve 15 is disposed on the upstream side. An ECU 40 controls a urea water addition amount by the urea water adding valve 15 based on an ammonia adsorption amount of the SCR catalyst 13. Regarding calculation of the ammonia adsorption amount, the ECU 40 detects a temperature of the SCR catalyst 13, and calculates a reaction ratio which is a ratio of an ammonia reaction amount with respect to an NOx reaction amount in the SCR catalyst 13 based on the temperature of the SCR catalyst. Further, the ammonia consumption amount in the SCR catalyst 13 is calculated based on the reaction ratio, and the ammonia adsorption amount is calculated based on the ammonia consumption amount. <P>COPYRIGHT: (C)2010,JPO&INPIT |
