A vehicle includes an internal combustion engine, an exhaust purification catalyst, and an air fuel ratio sensor. The internal combustion engine is structured to be motored by an electric motor generator. The exhaust purification catalyst is structured to purify exhaust gas of the internal combustion engine. The air fuel ratio sensor is located upstream of the exhaust purification catalyst and structured to sense an air fuel ratio. When a quantity of oxygen stored in the exhaust purification catalyst is larger than a reference value, it is determined that inflow of oxygen into the exhaust purification catalyst has an insignificant effect on exhaust performance. Then, fuel injection of the internal combustion engine is stopped, the internal combustion engine is motored, and air fuel ratio learning is performed for learning of a sensed value of the air fuel ratio sensor.

A method (200) for operating an exhaust gas system (120) that includes a first catalytic converter (122) and at least one second catalytic converter (124), which are both arranged downstream from an internal combustion engine (110) The internal combustion engine (110) is controlled to generate a rich exhaust gas having a first rich gas portion, (220) a fill level of the second catalytic converter (124) is ascertained with respect to at least one lean gas component that is storable in the second catalytic converter and, if the ascertained fill level drops below (230) a minimum fill level, (240) the internal combustion engine (110) is controlled to generate a lean exhaust gas. The internal combustion engine (110) is then controlled to generate a rich exhaust gas having a second rich gas portion, and subsequently controlled (210) to generate the rich exhaust gas having the first rich gas portion.

A control unit configured to control an electric turbocharger and an EGR valve. While an internal combustion engine is stopped, an oxygen-free period, which is a period during which oxygen surrounding an exhaust gas purifier used for an oxidation reaction runs out, is estimated based on a temperature of the exhaust gas purifier. Before entering the oxygen-free period, the EGR valve is opened and the electric turbocharger is driven. Air surrounding the exhaust gas purifier is replaced with fresh air. After replacement with the fresh air has been completed, the electric turbocharger is stopped.

An exhaust gas control apparatus for an internal combustion engine includes: a catalyst disposed in an exhaust passage of the engine and configured to be able to occlude oxygen; an air-fuel ratio sensor that detects an air-fuel ratio of an out-flow exhaust gas; and an air-fuel ratio control device that controls an air-fuel ratio of an in-flow exhaust gas to a target air-fuel ratio. The device executes air-fuel ratio reduction control in which the target air-fuel ratio is set to a rich setting air-fuel ratio, and corrects a parameter related to the air-fuel ratio reduction control such that an amount of a reducing gas supplied to the catalyst is decreased when a minimum air-fuel ratio obtained when the detected air-fuel ratio is varied to a rich side is richer than the rich setting air-fuel ratio or an average value of detected air-fuel ratios of the in-flow exhaust gas.

An exhaust gas control apparatus for an internal combustion engine includes: a catalyst disposed in an exhaust passage of the engine and configured to be able to occlude oxygen; an air-fuel ratio sensor that detects an air-fuel ratio of an out-flow exhaust gas; and an air-fuel ratio control device that controls an air-fuel ratio of an in-flow exhaust gas to a target air-fuel ratio. The device executes air-fuel ratio reduction control in which the target air-fuel ratio is set to a rich setting air-fuel ratio, and corrects a parameter related to the air-fuel ratio reduction control such that an amount of a reducing gas supplied to the catalyst is decreased when a minimum air-fuel ratio obtained when the detected air-fuel ratio is varied to a rich side is richer than the rich setting air-fuel ratio or an average value of detected air-fuel ratios of the in-flow exhaust gas.

A state estimation apparatus includes: a rate calculating configured to calculate, based on both a flow rate and an air-fuel ratio of exhaust gas flowing into an oxygen storage catalyst, a rate of change in an oxygen storage amount in the oxygen storage catalyst; a limit calculating unit configured to calculate a limit rate which is a limit value for the rate of change; and a storage-amount updating unit configured to update, based on the rate of change and the limit rate, an estimated value of the oxygen storage amount. Moreover, the storage-amount updating unit is further configured to: update, when the rate of change does not exceed the limit rate, the estimated value based on the rate of change; and update, when the rate of change exceeds the limit rate, the estimated value based on the limit rate.

To keep catalyst purification efficiency high and prevent deterioration of emission performance. Therefore, an internal combustion engine control device according to an aspect of the present invention includes: an oxygen storage ratio calculation unit that calculates an oxygen storage ratio of a catalyst based on a catalytic reaction model having at least a detection value of a first exhaust gas sensor disposed on an upstream side of the catalyst as an input; a statistical model calculation unit that predicts a catalyst downstream exhaust gas concentration using a statistical model having an oxygen storage ratio as an input and a catalyst downstream exhaust gas concentration as an output; and an air-fuel ratio correction amount calculation unit that calculates an air-fuel ratio correction amount of an air-fuel mixture of an internal combustion engine based on a future catalyst downstream exhaust gas concentration calculated by the statistical model calculation unit.

A catalyst having an oxygen storage capacity is provided in an exhaust passage of an internal combustion engine. A catalyst temperature calculating device calculates an oxygen storage amount of the catalyst to a value greater than or equal to zero and less than or equal to than a maximum value based on an amount of oxygen and an amount of unburned fuel components in a fluid flowing into the catalyst. A temperature calculation process calculates a temperature of the catalyst assuming that an amount of temperature rise of the catalyst is larger when an increase amount of the oxygen storage amount is large than when the increase amount of the oxygen storage amount is small in a case where the oxygen storage amount increases.

A method of recognizing deactivation of an exhaust gas catalytic converter is disclosed. For this purpose, coverage of storage sites of the exhaust gas catalytic converter with rich gas components is modeled (60) and the deactivation is recognized from a proportion of the occupied storage sites in a total number of storage sites.

Methods and systems are provided for enabling diagnostics of an exhaust catalyst regardless of a level of oxygen stored in the catalyst. In one example, a method may include initiating diagnostics of the catalyst in response to an oxygen sensor coupled downstream of the catalyst recording a measurement that crosses a stoichiometric air-fuel ratio output more than a threshold number of times.