| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine, which includes a SCR catalyst, a reductant solution addition part and a NOx sensor installed in the exhaust passage, for suppressing a reduction in the NOx eliminating rate of the SCR catalyst by adequately controlling the addition of reductant solution while suppressing the water crack of the NOx sensor.SOLUTION: When an exhaust gas temperature is within a temperature range where the sensor may be exposed to water and the estimated adsorption amount of reductant adsorbed to the SCR catalyst is not smaller than a predetermined amount, the exhaust emission control device stops the energization of the sensor, and then controls the addition part on the basis of the estimated exhaust amount of NOx to be exhausted from the internal combustion engine. When the exhaust gas temperature is within the temperature range and the estimated adsorption amount is smaller than the predetermined amount, the exhaust emission control device stops the energization of the sensor, and then increases the exhaust gas temperature up to a temperature exceeding the temperature range and controls the addition part on the basis of a detection value obtained by starting the energization of the sensor after increasing the exhaust gas temperature. |
