Systems and methods of the present invention related to an exhaust gas purification system comprising: (a) a first injector for injecting ammonia or a compound decomposable to ammonia into the exhaust gas; (b) a diesel particulate filter including an inlet and an outlet, wherein the filter includes a selective catalyst reduction (SCR) catalyst and an oxidation catalyst; (c) a second injector for injecting ammonia or a compound decomposable to ammonia into the exhaust gas, located downstream of the filter; and (d) a downstream catalyst comprising a selective catalytic reduction catalyst, located downstream of the second injector.

Systems, apparatuses, and methods include an upstream exhaust analysis circuit structured to determine a characteristic of an exhaust gas stream entering a nitrous oxide (NOx) storage catalyst; a prediction circuit structured to predict a downstream NOx concentration of an exhaust gas stream exiting the NOx storage catalyst based on a model of a NOx storage capacity or a dynamic response of the NOx storage catalyst; a downstream exhaust analysis circuit structured to determine a downstream NOx concentration of the exhaust gas stream exiting the NOx storage catalyst; and a comparison circuit structured to compare the predicted downstream NOx concentration to the determined downstream NOx concentration, and determine a health of the NOx storage catalyst based on the comparison.

A method for monitoring a gas sensor (14) which comprises two electrochemical measuring cells (20, 30) and which is arranged in an exhaust tract (10) of an internal combustion engine (11), wherein the sensor elements (20, 30) exhibit a substantially identical sensitivity towards a first gas component and a different sensitivity towards a second gas component and are insensitive towards further gas components. In an operating state in which an exhaust gas stream at the gas sensor (14) contains less of the second gas component than of the first gas component a concentration of the first gas component is calculated from each of the sensor signals from the sensor elements (20, 30) and a defect in a sensor element (20, 30) is deduced from the concentrations of the first gas component.

A control apparatus (12): creates a torque correction table indicating a relationship between a change rate of an intake air amount, a change of the main injection amount and the main injection timing of a fuel injection apparatus (8) in the torque value of a diesel engine (1) in a lean state; measures an intake air amount in a rich state by using an MAF sensor (11); calculates a change rate of the measured intake air amount for the intake air amount in the lean state; obtains a correction value of the main injection amount and a correction value of the main injection timing of the fuel injection apparatus (8) based on the calculated change rate and the torque correction table; and performs an injection of the fuel in the rich state at the main injection amount and the main injection timing, corrected by the respective correction values.

Rich spike is carried out in an efficient manner. In an exhaust gas purification apparatus for an internal combustion engine which performs lean burn operation, the apparatus includes an NOx storage reduction catalyst, a controller to carry out rich spike, to calculate a storage amount of NOx, to calculate a storage amount of nitrates, and calculate a nitrate ratio, wherein the controller controls a timing at which the rich spike is carried out, based on the nitrate ratio.

Various embodiments may include a method for monitoring a nitrogen oxide trap comprising: monitoring a storage capacity of the nitrogen oxide trap; deactivating nitrogen oxide trap regeneration based on the monitored storage capacity; and upon a predetermined event, reactivating nitrogen oxide trap regeneration.

An exhaust gas control apparatus for an internal combustion engine includes a NO.sub.X storage reduction catalyst, a selective catalytic reduction catalyst, and an electronic control unit configured to shift an operation state of the engine from a rich operation state to a lean operation state, in a case where an acquired temperature of the NO.sub.X storage reduction catalyst is higher than a storage limit temperature, and an acquired NH.sub.3 adsorption amount is equal to or larger than a lower limit adsorption amount when a lean operation restart request is made, and not to shift the operation state from the rich operation state to the lean operation state in a case where the acquired temperature of the NO.sub.X storage reduction catalyst is higher than the storage limit temperature and the acquired NH.sub.3 adsorption amount is smaller than the lower limit adsorption amount when the lean operation restart request is made.

Methods and systems are provided for an aftertreatment system. In one example, a method comprises regenerating a NO.sub.x trap during an engine shut-down event. The method further comprises reversing a direction of flow of a gas through a HP-EGR passage during the regenerating.

A method for operating an engine system that includes an internal combustion engine and an exhaust aftertreatment device. The method includes: carrying out a filling control in order to regulate a filling level of the exhaust aftertreatment device as a function of a predefined filling level setpoint value, a lambda setpoint value for a lambda regulation being predefined as a manipulated variable, adapting the filling control with the aid of an adaptation variable that indicates a correction value for the lambda setpoint value, and storing an adaptation value as a function of an operating range of the engine system, the adaptation value in question being updated with the value of the adaptation variable for the instantaneous operating range.

A rich-wait-time threshold value is set based on the NOx discharge amount per unit time discharged from an internal combustion engine. When the elapsed time, i.e. either the elapsed engine operation time since rich control was performed on a lean NOx trap catalyst device, or the elapsed engine operation time since the engine was started, becomes equal to or greater than the rich-wait-time threshold value, a determination that the rich control be started is added as a necessary condition for starting the rich control. Accordingly, an exhaust gas purification system for an internal combustion engine, an internal combustion engine, and an exhaust gas purification method for an internal combustion engine are provided, with which the execution timing of the rich control for recovering the NOx occlusion capacity of the lean NOx trap catalyst device is rendered more appropriate, and thus NOx reduction is performed with little fuel consumption deterioration.