| 摘要 |
PROBLEM TO BE SOLVED: To surely regenerate a storage type NOx catalyst while suppressing deterioration of fuel consumption by changing an execution condition of regenerating means according to the degree of reduction of a catalyst purifying function, and operating the regenerating means when the execution condition is materialized according to the degree of reduction of the catalyst purifying function. SOLUTION: A storage type NOx catalyst 25 of an exhaust emission catalyst control device 23 storages NOx since nitrate is generated from NOx in exhaust at the time of combustion operation in a lean mode, and exhaust emission control is carried out. In this time, it is judged whether the poisoning S rate of the NOx catalyst 25 attains a S-purge judgment reference value or not. Namely, a condition is changed to regenerate catalyst purifying function according to the degree of reduction of purifying function estimated by comparing the poisoning S rate of the NOx catalyst 25 and a plurality of S-purge judgment reference value with each other. When the execution condition is set up, it is judged that the poisoning S rate of the NOx catalyst 25 attains a start reference value to switch a control mode into a S-purge mode, and elimination of SOx stored in the NOx catalyst 25 is started. |
