Abstract: A diesel engine 100 is provided with a common rail type fuel injection device. A controller 14 controls a common rail pressure and an engine control parameter other than the common rail pressure, respectively, to target values that are determined on the basis of the engine load. The controller 14 corrects the engine control parameter other than the common rail pressure when the common rail pressure does not coincide with the target common rail pressure in a transient state of the diesel engine, thereby preventing an air-fuel ratio in the combustion region from becoming lean.

Abstract: An exhaust emission control device includes a first detection unit for detecting a NOx adsorption amount and an oxygen storage amount of a three-way catalyst and a NOx purification catalyst during rich spike, a second detection unit for detecting the oxygen storage amount of the three-way catalyst and the NOx purification catalyst until the output of a second air-fuel sensor becomes lean after the rich spike, and a deterioration determination unit for determining deterioration of the NOx purification catalyst based on a detected value of the first detection unit and that of the second detection unit.

Abstract: A diesel engine 100 is provided with a common rail type fuel injection device. A controller 14 controls a common rail pressure and an engine control parameter other than the common rail pressure, respectively, to target values that are determined on the basis of the engine load. The controller 14 corrects the engine control parameter other than the common rail pressure when the common rail pressure does not coincide with the target common rail pressure in a transient state of the diesel engine, thereby preventing an air-fuel ratio in the combustion region from becoming lean.

Abstract: An exhaust emission control device includes a NOx purification catalyst, a three-way catalyst provided upstream of the NOx purification catalyst, a first air-fuel ratio sensor provided upstream of the three-way catalyst, a second air-fuel ratio provided downstream of the NOx purification catalyst, a rich spike unit for changing an exhaust gas air-fuel ratio from lean to rich for a predetermined period to reduce and purify NOx adsorbed by the NOx purification catalyst, a first detection unit for detecting a NOx adsorption amount and an oxygen storage amount of the three-way catalyst and the NOx purification catalyst during rich spike, a second detection unit for detecting the oxygen storage amount of the three-way catalyst and the NOx purification catalyst until the output of the second air-fuel sensor becomes lean after the rich spike, and a deterioration determination unit for determining deterioration of the NOx purification catalyst based on a detected value of the first detection unit and that of the seco