| 摘要 |
<P>PROBLEM TO BE SOLVED: To highly precisely detect an addition error of a reducing agent added from an addition valve for reducing an exhaust gas purifying catalyst for an internal combustion engine on a basis of an air-fuel ratio and accurately decide abnormality of the addition valve. <P>SOLUTION: In case the reducing agent is added in an exhaust port from the addition valve, an air-fuel ratio detected by an air-fuel ratio sensor is reduced to a value lower than an air-fuel ratio by fuel injected in a combustion chamber from a fuel injection valve. By periodically accumulating a value equivalent to a reducing agent addition amount appearing on a change of an air-fuel ratio, an estimated addition amount is determined (S186). Therefor, a high-precise estimated addition amount can be determined. By comparing the estimated addition amount with a decision value (S190), an addition error is highly precisely detected, and this way enables accurate decision of abnormality (S194)/accurate decision of normality (S196). <P>COPYRIGHT: (C)2005,JPO&NCIPI |
