A method for the onboard diagnosis in a vehicle having a catalytic convertor and a lambda-controlled internal combustion engine in the running operation of the vehicle, includes determining the currently maximum possible oxygen storage capacity of the catalytic convertor as well as a measured temporal duration between the lean spike of the pre-catalyst lambda probe and the post-catalyst lambda probe takes place by means of an OSC diagnosis. The method also includes determining a theoretical residual oxygen content and determining a theoretical temporal duration. When the quotient between the measured temporal duration (Δt) and the theoretical temporal duration (Δt.sub.theo) lies within a predefined range delimited by a first and a second threshold value (SW1; SW2), thus:

[00001]$\mathrm{SW}1\le \frac{\Delta t}{\Delta t_{\mathrm{theo}}}\le \mathrm{SW}2,$

it is determined that the pre-catalyst lambda probe and the post-catalyst lambda probe operate without flaw.

To keep medium purification efficiency at a high level and prevent deterioration of emission performance. An aspect of the present invention includes: a downstream equivalence ratio calculation unit that calculates a catalyst downstream exhaust gas equivalence ratio by using a catalyst statistical model that receives at least a detection value of an air-fuel ratio sensor on an upstream side of a catalyst and outputs a catalyst downstream exhaust gas equivalence ratio; an oxygen output calculation unit that calculates an output value of an oxygen sensor by using an oxygen sensor statistical model that receives the catalyst downstream exhaust gas equivalence ratio and outputs an output value of the oxygen sensor on the downstream side of the catalyst; a downstream equivalence ratio correction unit that corrects the catalyst downstream exhaust gas equivalence ratio calculated by the downstream equivalence ratio calculation unit based on a calculation result of the oxygen output calculation unit and the detection value of the oxygen sensor; and an air-fuel ratio control unit that controls an air-fuel ratio of an air-fuel mixture of an internal combustion engine based on the corrected catalyst downstream exhaust gas equivalence ratio and air-fuel ratio target value.

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 internal combustion engine and capable of occluding oxygen; an air-fuel ratio sensor that detects the air-fuel ratio of an out-flow exhaust gas that flows out of the catalyst; and an air-fuel ratio control device that controls the air-fuel ratio of an in-flow exhaust gas that flows into the catalyst. The air-fuel ratio control device starts slightly rich control in which the air-fuel ratio of the in-flow exhaust gas is controlled such that the air-fuel ratio of the out-flow exhaust gas is maintained at a slightly rich setting air-fuel ratio that is richer than a stoichiometric air-fuel ratio, when the air-fuel ratio of the out-flow exhaust gas is reduced to be equal to or less than a rich-side switching air-fuel ratio that is richer than the stoichiometric air-fuel ratio.

A method for controlling an internal combustion engine with a catalytic converter for exhaust-gas aftertreatment, comprising specification of a target fill level profile is proposed, which fluctuates between an upper threshold value and a lower threshold value, of at least one exhaust-gas component that can be stored in the catalytic converter, determination of a present fill level of the at least one exhaust-gas component in the catalytic converter on the basis of a theoretical catalytic converter model, and control of the internal combustion engine so as to generate an exhaust gas with a target concentration of the at least one exhaust-gas component such that a deviation between the present fill level and the present target fill level in accordance with the target fill level profile is reduced. A processing unit and a computer program product for carrying out a method of said type, and a vehicle which is configured for carrying out the method, are likewise proposed.

Operating an internal combustion engine (110) having at least two combustion chambers (1-6) and at least one exhaust-gas catalytic converter (130). In one example, a beginning of the load operation phase of the internal combustion engine (110) that adjoins a coasting phase is detected. A combustion chamber of the at least two combustion chambers (1-6) is determined as the first combustion chamber; and one of other the combustion chambers is selected as the purging combustion chamber. An exhaust gas of the purging combustion chamber is directed into the same exhaust-gas catalytic converter (130) as an exhaust gas of the first combustion chamber. A first fuel quantity is fed into the purging combustion chamber such that the first fuel quantity, prior to igniting the fuel in the purging combustion chamber, is discharged to be partially or fully non-combusted in the direction of the exhaust-gas catalytic convertor (130).

Aspects of the present invention relate to a controller (104) and method (400) for controlling operation of an internal combustion engine (101). The controller (104) is configured to: receive a first request signal indicative of a request to stop fuel being supplied to the engine (101), and cause an intake valve (301) of a cylinder (103) of the internal combustion engine (101) to remain closed during the current revolution of the internal combustion engine (101) and revolutions of the internal combustion engine (101) immediately following the current revolution of the internal combustion engine (101) in dependence on at least one of: the intake valve (301) being closed at the time of receiving the first request signal; or a next opening of the intake valve having not been scheduled. The controller (104) is also configured to cause injection of fuel into the cylinder (103) and subsequently cause the intake valve (301) to remain closed during revolutions of the internal combustion engine (101) immediately following a next closing of the intake valve (301), in dependence on at least one of: the intake valve (301) being open at the time of receiving the first request signal; and a next opening of the intake valve (301) having already been scheduled at the time of receiving the first request signal and said next opening of the intake valve (301) is to be performed.