| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an internal combustion engine capable of switching the reducing agent concentration in exhaust gas in the proper timing, while using ammonia generated when enriching the air-fuel ratio by enhancing the reducing agent concentration in the exhaust gas, for reducing NOx in lean burn operation being low in the reducing agent concentration in the exhaust gas. <P>SOLUTION: An NOx purifying device 11 has the function for holding the ammonia. A residual quantity ΣNH3 of the ammonia held in this NOx purifying device 11 is calculated (S13 to S15, S18, S22 to S24 and S26). When the residual quantity ΣNH3 exceeds an upper limit ammonia threshold value NH3THH when performing reduction, the reduction is finished, and is transferred to the lean burn operation (S19 and S20). When the residual quantity ΣNH3 becomes less than a lower limit ammonia threshold value NH3THL in the lean burn operation, the reduction is started (S27 and S28). <P>COPYRIGHT: (C)2005,JPO&NCIPI |
