| 摘要 |
PROBLEM TO BE SOLVED: To properly cause NOX to be released from a NOX absorbent. SOLUTION: The NOX absorbent 23 is arranged in an engine exhaust gas passage, when an air/fuel ratio is lean and a NOX ammonia sensor in the engine exhaust gas passage, downstream of the NOX absorbent. When the ammonia concentration starts to increase, after switching the air/fuel ratio into being rich for releasing the NOX from NOX absorbent 23, the air/fuel ratio is switched from lean to rich. |
