A method includes: initiating a low engine-out NOx (LEON) mode by controlling a component of a vehicle having an aftertreatment system to decrease an instantaneous engine-out NOx (EONOx) amount; comparing a temperature of the aftertreatment system during the LEON mode to a warm-operation threshold temperature; responsive to determining that the temperature of the aftertreatment system exceeds the warm-operation threshold temperature, disengaging the LEON mode; responsive to determining that the temperature of the aftertreatment system is below the warm-up operation threshold temperature, comparing information indicative of an operating status of the vehicle to a LEON exit threshold; and disengaging the LEON mode responsive to determining that the information indicative of the operating status of the vehicle during the LEON mode exceeds the LEON exit threshold.

An exhaust emission control system of an engine is provided, which includes a NO.sub.x catalyst disposed in an exhaust passage for storing NO.sub.x within exhaust gas when an air-fuel ratio of the exhaust gas is lean, and reducing the stored NO.sub.x when the air-fuel ratio is approximately stoichiometric or rich. A processor executes a NO.sub.x reduction controlling module for performing a NO.sub.x reduction control in which a fuel injector performs a post injection to control the air-fuel ratio to a target ratio, and an EGR controlling module for controlling an EGR valve to recirculate EGR gas. In the NO.sub.x reduction control, the EGR controlling module controls an opening of the EGR valve to a target opening smaller than when the NO.sub.x reduction control is not performed. The NO.sub.x reduction controlling module starts the control after the EGR valve opening is controlled to the target opening.

An exhaust emission control system of an engine, including an NO.sub.x catalyst disposed in an exhaust passage for storing NO.sub.x within exhaust gas when an air-fuel ratio of the exhaust gas is lean, and reducing the stored NO.sub.x when the air-fuel ratio is approximately stoichiometric or rich, is provided. The system includes an SCR catalyst disposed in the exhaust passage downstream of the NO.sub.x catalyst and for purifying NO.sub.x within exhaust gas by causing a reaction with ammonia, a controller executing a NO.sub.x reduction controlling module for executing a control in which the air-fuel ratio is controlled to a target air-fuel ratio so that the stored NO.sub.x is reduced, and an ammonia adsorption amount acquiring module for acquiring an ammonia adsorption amount of the SCR catalyst by detection or estimation. The NO.sub.x reduction controlling module controls the target air-fuel ratio to be leaner as the ammonia adsorption amount increases.

An exhaust emission control system of an engine including a NO.sub.x catalyst disposed in an exhaust passage and for storing NO.sub.x within exhaust gas when an air-fuel ratio of the exhaust gas is lean, and reducing the stored NO.sub.x when the air-fuel ratio is approximately stoichiometric or rich, is provided. The system includes a SCR catalyst disposed downstream of the NO.sub.x catalyst and for purifying NO.sub.x by causing a reaction with ammonia, and a processor configured to execute a NO.sub.x reduction controlling module for controlling the air-fuel ratio to a target ratio so that the stored NO.sub.x is reduced. The controlling module limits the performance of the NO.sub.x reduction control when a temperature of the SCR catalyst is above a given temperature and loosens the limitation in a given engine operating state in which an exhaust gas flow rate is above a given rate despite the SCR catalyst temperature.

An exhaust emission control system is provided, which includes a NO.sub.x storage catalyst provided in an exhaust passage of an engine and configured to store NO.sub.x, a urea SCR catalyst provided in the exhaust passage, downstream of the NO.sub.x storage catalyst, and a NO.sub.x reduction controlling module configured to set a NO.sub.x reduction condition and, when the NO.sub.x reduction condition is satisfied, performs NO.sub.x reduction processing in which an air-fuel ratio of exhaust gas is set to be one of near a stoichiometric air-fuel ratio and rich, and the NO.sub.x stored in the NO.sub.x storage catalyst is reduced, the NO.sub.x reduction condition being set looser for the NO.sub.x reduction processing performed the first time after the engine is started than the NO.sub.x reduction processing performed the second and subsequent times after the engine is started.

Methods and systems are provided for partially regenerating a lean NO.sub.x trap in response to an engine shutdown request. In one example, an engine shutdown is delayed so that a low-temperature storing region of the lean NO.sub.x trap is regenerated without regenerating a high-temperature storing region of the lean NO.sub.x trap. A battery charge is replenished during the shutdown, wherein the charge may be consumed during a subsequent engine operation.

A control apparatus is applicable to an internal combustion engine having an exhaust passage arranged with an NSR catalyst and an SCR catalyst, wherein when it is necessary to decrease NH.sub.3 adsorbed to the SCR catalyst, then an air-fuel ratio of an air-fuel mixture to be combusted in the internal combustion engine is controlled to a predetermined lean air-fuel ratio which is higher than a theoretical air-fuel ratio if a temperature of the SCR catalyst is not less than a lower limit temperature at which NH.sub.3 can be oxidized, while the air-fuel ratio of the air-fuel mixture to be combusted in the internal combustion engine is controlled to a predetermined weak lean air-fuel ratio which is lower than the predetermined lean air-fuel ratio and which is higher than the theoretical air-fuel ratio if the temperature of the SCR catalyst is less than the lower limit temperature.

Methods and systems are provided for an exhaust aftertreatment arrangement. In one example, a system includes a LNT upstream of an SCR with an oxygen storage component arranged therebetween, and where a rich operation of an engine is limited based on an oxygen load of the oxygen storage component when an exhaust gas temperature is higher than a limit temperature.

A control device of an internal combustion engine using a neural network. When a value of an operating parameter of the engine is outside a preset range, the number of nodes of a hidden layer one layer before an output layer of the neural network is increased and training data obtained by actual measurement with respect to a newly acquired value of an operating parameter of the engine is used to learn a weight of the neural network so that a difference between the output value changing corresponding to the value of the operating parameter of the engine and training data corresponding to the value of the operating parameter of the engine becomes smaller.

An engine control device is provided, which includes an oxidation catalyst provided in an exhaust passage to oxidize unburned fuel within exhaust gas, a NO.sub.x catalyst provided integrally with or downstream of the oxidation catalyst, a PM filter provided in the exhaust passage downstream of the oxidation catalyst to capture fine particulate matter within the exhaust gas, a fuel injector, and a controller. When the particulate matter is accumulated by a given amount, the controller starts a PM filter regeneration control to remove the particulate matter, and after this control is started and when the accumulation amount decreases by a given amount, the controller starts a NO.sub.x catalyst regeneration control to switch between a first state in which an air-fuel ratio of the exhaust gas is a stoichiometric air-fuel ratio or less and a second state in which the air-fuel ratio is higher than the stoichiometric air-fuel ratio.