| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent discharging of SOx absorbed by occulusion reduction type NOx catalyst when a car is stopped or driven with extremely low speed. SOLUTION: After SOx is absorbed by an NOx catalyst 17 by a specific amount, an ECU 30 determines a discharging timing of SOx. The ECU 30 performs stoichi controlling of an air-fuel ratio of the exhaust gas for discharging SOx from the NOx catalyst 17 while keeping temperature of the exhaust gas at a specified value or higher. That is, it performs high temperature stoichi controlling for discharging SOx. However, when the running speed of a car sensed by a vehicular speed sensor 27 is not higher than a lower limit value, that is, the car is stopped or driven with extremely low speed, the high temperature stoichi controlling is suspended. Low temperature stoichi controlling where the exhaust air-fuel ratio is kept in stoichi state and the exhaust gas temperature is kept lower than SOx discharge reduction temperature is executed, so that SOx discharging from the NOx catalyst is suspended to thereby discontinue a SOx discharging treatment.</p> |
