A method and an exhaust treatment system are provided for treatment of an exhaust stream that comprises nitrogen oxides NO.sub.x. The method comprises using a first slip-catalyst SC.sub.1, arranged at a first device to create a first impact on a first amount of nitrogen oxides NO.sub.x.sub._.sub.1 An NO.sub.x-storing catalyst may store nitrogen oxides NO.sub.x. The first slip-catalyst SC.sub.1 may reduce nitrogen oxides NO.sub.x, and/or oxidize potential additive in the exhaust stream. This first impact is actively controlled, based on the first amount of nitrogen oxides NO.sub.x.sub._.sub.1 reaching the first device. The method also comprises a second impact on a second amount of nitrogen oxides NO.sub.x.sub._.sub.2 reaching a second device. The active control of the first impact may be by active control of the dosage of additive at the first device, and/or through an active control of an exhaust environment, for example, a temperature for the exhaust stream.

An exhaust treatment system is provided for treatment of an exhaust stream, where the system comprises a first dosage device, arranged to supply a first additive into said exhaust stream and a first reduction catalyst device, arranged downstream for reduction of nitrogen oxides in said exhaust stream through the use of said first additive, and for the generation of heat through at least one exothermal reaction with said exhaust stream. A particulate filter arranged downstream of said first reduction catalyst device to catch soot particles. A second dosage device arranged downstream of said particulate filter to supply a second additive into said exhaust stream and a second reduction catalyst device, arranged downstream of said second dosage device for reduction of nitrogen oxides in said exhaust stream through the use of at least one of said first and said second additive.

A treatment system for providing treatment of an exhaust stream comprising nitrogen oxides NO.sub.x, in which nitrogen monoxide NO and nitrogen dioxide NO.sub.2 are comprised. When the exhaust stream passes through the treatment system, oxidation occurs of compounds comprising nitrogen, carbon and/or hydrogen. An amount of nitrogen oxides NO.sub.x reaching a reduction catalyst device downstream of the oxidizing component in the exhaust treatment system is reduced. A ratio (NO.sub.2/NO.sub.x).sub.det between an amount of nitrogen dioxide NO.sub.2 reaching a reduction catalyst device and the amount of nitrogen oxides NO.sub.x reaching the reduction catalyst device is determined. An active control of at least one parameter related to the combustion engine is carried out, based on the determined ratio, so that the amount of nitrogen oxides NO.sub.x reaching the reduction catalyst device is increased, if the determined ratio (NO.sub.2/NO.sub.x).sub.det exceeds an upper threshold value (NO.sub.2/NO.sub.x).sub.threshold.sub._.sub.high.

Methods and systems for operating an engine during and after regeneration of a particulate filter are described. In one example, exhaust flow is increased and exhaust temperature is decreased in response to ceasing regeneration of a particulate filter so that SCR efficiency may be improved in a short amount of time.

Technical solutions are described for limiting exposure of components of an emissions control system to rich exhaust conditions. An example an emissions control system includes an oxygen storage component; and a controller that limits exposure of the oxygen storage component to rich exhaust conditions. The limiting includes determining an air-to-fuel equivalence ratio in exhaust gas in response to an engine receiving a request to generate torque, the request including a displacement of a pedal; determining an amount of oxygen in the exhaust gas based on the air-to-fuel equivalence ratio; determining an oxygen level stored by the oxygen storage component; and if the oxygen level is above a predetermined threshold, lowering a torque generation rate of the engine, which specifies amount of torque generated per unit displacement of the pedal.

The disclosure provides a method and a device for closed-loop control of a temperature of a component in an exhaust-gas tract of an internal combustion engine. The exhaust-gas tract has a temperature sensor arranged upstream of the component. The method includes providing a control circuit for the closed-loop control of the temperature of the component and detecting a measurement signal by the temperature sensor during the operation of the internal combustion engine. The measurement signal is characteristic of an exhaust-gas temperature. The measurement signal is used as a measured controlled variable for the control circuit for the closed-loop control of the temperature of the component. The method also includes determining a temperature model for the exhaust-gas temperature of the exhaust gas upstream of the component. The temperature model is used as a predictor for the control circuit. Also, a modeled controlled variable is provided from the temperature model.

Methods and systems are provided for regenerating and purging a particulate filter of an exhaust treatment system for a combustion engine. In one example, a method may include flowing exhaust gas in a reverse direction through the particulate filter to purge particulate matter to an intake manifold of the engine for combusting. The duration of purging may be based on a regeneration achieved during a previous regeneration of the particulate filter during a deceleration fuel shut-off event.

An object is to enable an exhaust gas purification system to bring about satisfactory oxidation of fuel in an oxidation catalyst in a temperature raising process of a filter, thereby allowing fuel supply to be performed at as low a temperature as possible. In the exhaust gas purification system, when the temperature of the exhaust gas flowing into the oxidation catalyst exceeds a specific threshold temperature that is determined based on the cetane number of fuel, a controller performs the temperature raising process. If the quantity of heat generated in the oxidation catalyst per unit time is smaller than a specific value while the temperature raising process is being performed, the temperature raising process in progress is suspended. The temperature raising process is resumed later on when the temperature of the exhaust gas flowing into the oxidation catalyst exceeds an updated threshold temperature higher than the specific threshold temperature.

An internal combustion engine of a hybrid drive vehicle includes an exhaust gas purification catalyst in an exhaust passage. An internal combustion engine control device is configured to continuously rotate the internal combustion engine for a predetermined time period after an engine start. The internal combustion engine control device prohibits a fuel-cut within the predetermined time period after the engine start, thereby suppressing the frequent repetition of the start and stop of the internal combustion engine due to an accelerator pedal operation and suppressing oxygen storage in the exhaust gas purification catalyst associated with the fuel-cut. As a result, exhaust gas purification performance at the time of restarting the internal combustion engine is ensured.

A method for controlling an exhaust gas purification apparatus as a catalyst oxygen purge control method during a cold engine period of an exhaust gas purification apparatus including a three way catalyst (TWC) converter purifying exhaust gas exhausted from the engine includes determining whether a fuel cut condition of an injector which injects the fuel to the combustion chamber is satisfied; performing a fuel cut of the injector when the fuel cut condition is satisfied; determining heat load of the three way catalyst by use of a temperature detector and an exhaust gas flow rate detector; measuring oxygen storage capacity (OSC) stored in the three way catalyst according to the heat load; determining an inflection point by use of variation amount of the OSC; and controlling oxygen purge period differently around the inflection point.