There is provided a technology pertaining to abnormality diagnosis of an NSR catalyst that enables the diagnosis that the NSR catalyst is abnormal to be made even when the degree of deterioration of the NSR catalyst is relatively small yet. An abnormality diagnosis apparatus is applied to an exhaust gas purification apparatus having an NSR catalyst and a fuel addition valve. The abnormality diagnosis apparatus includes a controller configured to perform a specific fuel addition process and diagnose the NSR catalyst. The controller starts the specific fuel addition process when the NSR catalyst is in a specific start condition, and diagnoses the NSR catalyst on the basis of the quantity of NOx flowing out of the NSR catalyst over a specific period in the period from when the specific fuel addition process is started to when the temperature of the NSR catalyst reaches the thermal desorption temperature.

A method and apparatus are disclosed for controlling the operation of an aftertreatment system for a motor vehicle having a Lean NO.sub.x Trap and a tail pipe for conveying exhaust gasses from the LNT to the external environment. Values are calculated for a NO.sub.x content in the exhaust gasses flowing in the tail pipe and the quantity of NO.sub.x stored in the LNT. A DeNO.sub.x request index is calculated as a function of these values. A raw threshold value of the DeNO.sub.x request index is calculated as a function of a LNT temperature and of an exhaust gas mass flow. A corrected threshold value of the DeNO.sub.x request index is calculated as a function of the raw threshold value of the DeNO.sub.x request index and of a correction factor. A DeNO.sub.x regeneration is initiated when the calculated value of the DeNO.sub.x request index is larger than the corrected threshold value.

At a time of an abnormality diagnosis, for a NOx storage reduction catalyst, a predetermined fuel addition process is started when the temperature of the NOx storage reduction catalyst is lower than a predetermined temperature and a NOx storage amount in the NOx storage reduction catalyst is equal to or more than a predetermined storage amount. Then, the abnormality diagnosis for the NOx storage reduction catalyst is performed based on a comparison between an integrated value of a NOx outflow amount after the predetermined fuel addition process is started and before the temperature of the NOx storage reduction catalyst reaches the predetermined temperature and an integrated value of the NOx outflow amount after the temperature of the NOx storage reduction catalyst reaches the predetermined temperature during the execution of the predetermined fuel addition process.

A three-way catalyst, an NSR catalyst, and an SCR catalyst are provided in this order for an exhaust gas passage, wherein the air-fuel ratio (AFR) is set to a first AFR which is a rich AFR before the AFR is switched from a theoretical AFR to a lean AFR, and then the AFR is set to a second AFR which is higher than the first AFR and lower than the theoretical AFR if a NOx occlusion amount is less than a threshold value during a period until an NH.sub.3 adsorption amount of the SCR catalyst becomes a predetermined adsorption amount, while the AFR is set to a third AFR which is higher than the first AFR and lower than the second AFR if the NOx occlusion amount is not less than the threshold value.

An exhaust purification system includes a NOx-occlusion-reduction-type catalyst that occludes NOx in exhaust in a lean state and reduces and purifies the occluded NOx in exhaust in a rich state, and a NOx purge rich control unit that executes NOx purge of reducing and purifying the occluded NOx by putting the exhaust into the rich state by fuel injection control, where a catalyst temperature of the NOx-occlusion-reduction-type catalyst is equal to or higher than a catalyst temperature threshold value and a NOx occlusion amount of the NOx-occlusion-reduction-type catalyst is equal to or higher than an NOx occlusion amount threshold value, and executes the NOx purge when the catalyst temperature is lower than a catalyst temperature threshold value.

A method and apparatus are disclosed for controlling the operation of an aftertreatment system for a motor vehicle having a Lean NO.sub.x Trap and a tail pipe for conveying exhaust gasses from the LNT to the external environment. Values are calculated for a NO.sub.x content in the exhaust gasses flowing in the tail pipe and the quantity of NO.sub.x stored in the LNT. A DeNO.sub.x request index is calculated as a function of these values. A raw threshold value of the DeNO.sub.x request index is calculated as a function of a LNT temperature and of an exhaust gas mass flow. A corrected threshold value of the DeNO.sub.x request index is calculated as a function of the raw threshold value of the DeNO.sub.x request index and of a correction factor. A DeNO.sub.x regeneration is initiated when the calculated value of the DeNO.sub.x request index is larger than the corrected threshold value.

In an internal combustion engine, a hydrocarbon feed valve and an exhaust purification catalyst are arranged in an engine exhaust passage. A first NOX removal method which injects hydrocarbons from the hydrocarbon feed valve within a predetermined range of period so that the reducing intermediate generated thereby reduces the NOX contained in the exhaust gas and a second NOX removal method which makes the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst a first target rich air-fuel ratio by a period which is longer than this predetermined range are used. When the NOX removal method is switched from the second NOX removal method to the first NOX removal method, the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst is made a second target air-fuel ratio which is smaller than the first target rich air-fuel ratio.

A twin charged engine is provided comprising a catalytic converter; a first compressor which, when operated, increases engine load; a second compressor which extracts energy from the exhaust gases to increase the overall engine efficiency; and a controller configured to operate one of at least two modes. A first mode is a standard operating mode in which the system is configured to optimise the efficiency of running of the engine. A second mode is for use under special conditions.

A three-way catalyst, an NSR catalyst, and an SCR catalyst are provided in this order for an exhaust gas passage, wherein the air-fuel ratio (AFR) is set to a first AFR which is a rich AFR before the AFR is switched from a theoretical AFR to a lean AFR, and then the AFR is set to a second AFR which is higher than the first AFR and lower than the theoretical AFR if a NOx occlusion amount is less than a threshold value during a period until an NH.sub.3 adsorption amount of the SCR catalyst becomes a predetermined adsorption amount, while the AFR is set to a third AFR which is higher than the first AFR and lower than the second AFR if the NOx occlusion amount is not less than the threshold value.

A method is disclosed for operating an internal combustion engine of a motor vehicle in which exhaust gas from the internal combustion engine is fed to at least one catalytic converter in an emission control system of the motor vehicle. A power that the internal combustion engine can supply is adjusted via a control device of the motor vehicle as a function of an emission of at least one pollutant contained in the exhaust gas into an environment of the motor vehicle. A quantity of a volumetric percentage of the at least one catalytic converter causing the at least one pollutant to be converted is ascertained, and the power supplied by the internal combustion engine is adjusted as a function of said quantity of the volumetric percentage.