Assume that a boundary on the air-fuel ration operation is changed from a boundary (i) to a boundary (ii). Then, after the boundary is changed, a high EGR operation region where a target EGR rate is set to a high value overlaps partially with a rich operation region. Therefore, when it is determined that the current operating point exists in the overlapped region, the target EGR rate is forcibly lowered. In addition, the boundary on a drive cam for an intake valve is changed from a boundary (I) to a boundary (II) thereby a region where a small cam is selected is enlarged.

The invention provides an exhaust purification device capable of suppressing the temporal decrease in NOx catalyst removal efficiency due to soot accumulation. The invention provides an exhaust purification device using an air injection nozzle to inject pressurized air into a casing of a catalyst reactor containing an NOx catalyst as a catalyst and removing soot adhering to the NOx catalyst, wherein it is determined and externally notified that there is abnormal deterioration in the NOx catalyst when the pressure difference P in exhaust between the upstream and downstream sides of the NOx catalyst has increased by at least a first reference pressure difference increase Pt1, which is the allowable amount of pressure difference increase, above the pressure difference Pi in exhaust between the upstream and downstream sides of the catalyst in the initial state at the same exhaust flow rate Ve.

The invention provides an exhaust purification device capable of suppressing the temporal decrease in NOx catalyst removal efficiency due to soot accumulation. The invention provides an exhaust purification device using an air injection nozzle to inject pressurized air into a casing of a catalyst reactor containing an NOx catalyst as a catalyst and removing soot adhering to the NOx catalyst, wherein it is determined and externally notified that there is abnormal deterioration in the NOx catalyst when the pressure difference P in exhaust between the upstream and downstream sides of the NOx catalyst has increased by at least a first reference pressure difference increase Pt1, which is the allowable amount of pressure difference increase, above the pressure difference Pi in exhaust between the upstream and downstream sides of the catalyst in the initial state at the same exhaust flow rate Ve.

The invention provides an exhaust purification device capable of suppressing the temporal decrease in NOx catalyst removal efficiency due to soot accumulation. The invention provides an exhaust purification device using an air injection nozzle to inject pressurized air into a casing of a catalyst reactor containing an NOx catalyst as a catalyst and removing soot adhering to the NOx catalyst, wherein it is determined and externally notified that there is abnormal deterioration in the NOx catalyst when the pressure difference P in exhaust between the upstream and downstream sides of the NOx catalyst has increased by at least a first reference pressure difference increase Pt1, which is the allowable amount of pressure difference increase, above the pressure difference Pi in exhaust between the upstream and downstream sides of the catalyst in the initial state at the same exhaust flow rate Ve.