| 摘要 |
PROBLEM TO BE SOLVED: To stabilize regeneration of a catalyst device by providing the catalystic device which adsorbs a sulfur component when an exhaust air-fuel ratio is at least lean and releases it at a high temperature and in a reduction atmosphere, and controlling so that sulfur component is desorbed through estimating the frequency at which sulfur component is desorbed. SOLUTION: In this emission control unit, a catalyst temperature of a NOx adsorption catalyst is estimated (S1) based on exhaust temperature information, and an S frequency indicating regeneration degree of the NOx adsorption catalyst from S poisoning is calculated (S2). A catalyst temperature Tcat of the NOx adsorption catalyst is judged (S4) and when it is ZSTEMP or more, control mode is set in a S purge mode (S5) judging that S purging is likely to occur. In this way, regeneration in which SOx is released from a NOx adsorption catalyst is controlled and kept to a predetermined degree. Therefore, by heating the NOx adsorption as assistance under the condition where a temperature of the NOx adsorption catalyst is high, SOx is released and regenerated in a catalyst temperature region appropriate for a SOx release rate at which a sulfur regeneration rate is slow. |
