A method of purifying exhaust gas discharged from an engine using a three-way catalyst may include: calculating, by a controller, an oxygen mass flow rate flowing into the three-way catalyst based on an air-fuel ratio and an exhaust gas flow rate measured by a front oxygen sensor arranged at a front end of the three-way catalyst; calculating, by the controller, an oxygen storage capacity (OSC) and an oxygen storage amount (OSA) of the three-way catalyst by integrating the oxygen mass flow rate; correcting, by the controller, the calculated oxygen storage amount based on an actual voltage measurement value of the exhaust gas measured by a rear oxygen sensor arranged at a rear end of the three-way catalyst; and controlling, by the controller, a control variable related to performance of the three-way catalyst based on the corrected oxygen storage amount and the oxygen storage capacity.

A method and a control device for regulating a modeled fill level of an exhaust gas component reservoir of a catalytic converter of an internal combustion engine. Regulation of the modeled fill level is accomplished using a system model. An actual maximum storage capacity of the catalytic converter for the exhaust gas component is ascertained during operation of the internal combustion engine and is taken into consideration in regulating the modeled fill level.

A catalyst abnormality diagnostic device is configured to diagnose an abnormality of a first purification catalyst having an oxygen storage capacity and a second purification catalyst having the oxygen storage capacity and a function of a particulate filter provided on an exhaust passage on a downstream side of the first purification catalyst. The catalyst abnormality diagnostic device adjusts a fuel injection amount so that an air-fuel ratio of an exhaust gas is repeatedly in a rich state and a lean state, obtains a first determination value indicating a catalytic performance of the first purification catalyst, obtains a second determination value indicating a catalytic performance of the second purification catalyst, and determines whether there is an abnormality in one or both of the first purification catalyst and the second purification catalyst on the basis of the first determination value, the second determination value, and a predetermined determination reference value.

An internal combustion engine makes available exhaust gas which can be treated by means of a catalytic converter and a particle filter. A method for determining the particle load of the particle filter comprises steps of determining the storage capacity of the catalytic converter for oxygen and determining the particle load of the particle filter on the basis of the determined storage capacity in the controller.

The invention relates to a method for adjusting a fuel/air ratio of an internal combustion engine (10), comprising a catalyst volume (26) with a first catalyst partial volume (26.1) and a second catalyst partial volume (26.2). The second catalyst partial volume (26.2) is arranged downstream from the first catalyst partial volume (26.1). An actual filling level of an exhaust gas constituent in the catalyst volume (26) is calculated from operating parameters of the internal combustion engine (10) and the exhaust system (14) using a computing model, and is adjusted to a nominal value by modifying the fuel/air ratio. The adjustment is carried out first for the second catalyst partial volume (26.2) and only later for the first catalyst partial volume (26.1).

An internal combustion engine comprises an exhaust purification catalyst, a downstream side air-fuel ratio sensor which is arranged at a downstream side of the exhaust purification catalyst, and an air flow meter which detects an amount of intake air. The control system of the internal combustion engine controls the exhaust air-fuel ratio to a target air-fuel ratio by feedback control, sets the target air-fuel ratio at a lean air-fuel ratio when the output air-fuel ratio of the downstream side air-fuel ratio sensor becomes a rich air-fuel ratio, and sets the target air-fuel ratio at a rich air-fuel ratio when the output air-fuel ratio of the downstream side air-fuel ratio sensor becomes a lean air-fuel ratio. When a change in the amount of intake air occurs so that it increases, the lean degree is set lower than before, in at least part of the time period during which the target air-fuel ratio is set to the lean air-fuel ratio, and the rich degree is set lower than before, in at least part of the timer period during which the target air-fuel ratio is set to the rich air-fuel ratio.

A controller for an internal combustion engine of a spark ignition type is provided. When stopping combustion in a cylinder in a situation in which a crankshaft of the internal combustion engine is rotating, one of a fuel cut process and a fuel feeding process is selectively executed. When combustion is resumed in the cylinder in which the combustion has been stopped, an enrichment process is executed to control a fuel injection valve so that an air-fuel ratio is set to be richer than a stoichiometric air-fuel ratio. When the enrichment process is executed, a decrease amount of an oxygen storage amount of the three-way catalyst corresponding to the enrichment process is set.

The present invention provides a catalyst diagnosis device that enables precisely grasping a variation of AFR and diagnosing a deteriorated condition of the catalyst based on the variation. A timer counts elapsed time Tosc until downstream AFU (AFRd) meets a predetermined threshold condition when the fuel injection quantity is corrected by increasing or decreasing it so that as to the AFRu, the transition from either of leanness or richness to the other is repeated with the stoichiometric area between the leanness and the richness. An OSA calculating section calculates an Oxygen Storage Amount (OSA) as a function of the AFR, Mfuel, Ne and Tosa. An OPA calculating section calculates an Oxygen Purge Amount (OPA) as a function of the AFR, Mfuel, Ne and Topa. A deterioration diagnosing section diagnoses a deteriorated condition of the catalyst C on the basis of at least one of the OSA and OPA.

An exhaust gas purification system for vehicle includes: a housing disposed on an exhaust pipe to receive a exhaust gas discharged from an engine and to exhaust the exhaust gas passed rearward; a front end catalyst disposed in the housing to purify the exhaust gas flowing into the housing through a front end of the housing; a rear end catalyst disposed in the housing to purify the exhaust gas passing through the front end catalyst before the exhaust gas flows out to a rear end of the housing; and a controller connected to the exhaust pipe at a front end of the housing to control a concentration of unburned fuel contained in the exhaust gas flowing into the housing.

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.