An internal combustion engine includes an upstream side exhaust purification catalyst and a downstream side exhaust purification catalyst. The control device includes a storage amount estimating device which estimates the oxygen storage amount of the downstream side exhaust purification catalyst, and can execute fuel cut control which cuts the feed of fuel to the combustion chamber during operation of the internal combustion engine when the engine speed is the lowest reference speed or more. The control device lowers the lowest reference speed when the storage amount estimated by the storage amount estimating device has become a given limit storage amount or less, compared with when it is larger than the limit storage amount. As a result, a control device can effectively keep the oxygen storage amount of the downstream side exhaust purification catalyst from decreasing to zero.

An internal combustion engine control device and a catalyst deterioration diagnostic method according to the present invention control the amount of fuel to be supplied to an internal combustion engine such that the air-fuel ratio of the exhaust on the downstream side of the exhaust purification catalyst is alternately switched between rich and lean, measure the oxygen storage capability of the exhaust purification catalyst during a measurement period within a reversal period of the air-fuel ratio, and diagnose deterioration of the exhaust purification catalyst based on a measurement value of the oxygen storage capability. A time point at which the output of an exhaust sensor indicates that the air-fuel ratio of the exhaust on the downstream side of the exhaust purification catalyst begins to change from a vicinity of a stoichiometric air-fuel ratio to rich or lean is set as the time of end of the measurement period.

The concepts described herein relate to a system, method, and/or apparatus for monitoring a NOx sensor that is arranged in an exhaust gas feedstream of an internal combustion engine downstream of an exhaust aftertreatment system to detect a fault related to the NOx sensor. This includes utilizing a catalyst efficiency model to detect occurrence of a fault that may indicate an in-range biased or stuck NOx sensor.

Deterioration of a selective catalytic reduction (SCR) catalyst can be diagnosed with sufficient accuracy, by making use of a sensor for measuring an air fuel ratio of exhaust gas flowing into an exhaust gas purification apparatus, which is equipped with the SCR catalyst, and a sensor for measuring an air fuel ratio of exhaust gas flowing out from the exhaust gas purification apparatus.

The invention relates to a method for operating an internal combustion engine comprising at least one turbocharger, at least one catalytic converter and a variable valve train, a valve overlap parameter being determined in at least one operating mode of the internal combustion engine and being used to set the valve train. According to the invention, the valve overlap parameter is adapted on the basis of at least one parameter for the condition of the catalytic converter and/or at least one parameter for the condition of the turbocharger, prior to being used to set the valve train. The invention also relates to an internal combustion engine.

The disclosure relates to internal combustion engines in general, and teaches various methods and apparatus for operating engines with an exhaust-gas turbocharger. Some embodiments include a method for operating an internal combustion engine having a fresh-gas tract for the supply of fresh gas to a cylinder, and an exhaust tract for the discharge of exhaust gas. They may include determining a value of a first operating condition of a catalytic converter arranged in the exhaust tract; determining a value of a second operating condition of the catalytic converter; calculating, as a function of the determined value, a first value for a maximum admissible scavenged-over quantity of fresh gas into the exhaust tract during scavenging operation; and setting the maximum admissible scavenged-over quantity to a second value lower than the first value if the value of the second operating condition reaches a predefined 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.

A control device for an internal combustion engine is provided. The control device includes an electronic control unit. The electronic control unit is configured to set a target air-fuel ratio to a rich air-fuel ratio from a time at which fuel cut control for terminating fuel supply to a combustion chamber during operation of the internal combustion engine is terminated to a time at which an output air-fuel ratio of a downstream-side air-fuel ratio sensor becomes a rich determination air-fuel ratio or lower, temporarily set the target air-fuel ratio to the rich air-fuel ratio after the output air-fuel ratio of the downstream-side air-fuel ratio sensor becomes the rich determination air-fuel ratio or lower, and thereafter set the target air-fuel ratio to a lean air-fuel ratio.

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.

The invention relates to a method for operating a drive device that, for purifying of exhaust gas, comprises at least one catalytic converter having an oxygen storage. wherein upstream of the catalyst a pre-catalyst molecular mass of a first substance, and a pre-catalyst molecular mass of oxygen is determined. According to the invention, in order to calculate a post-catalytic converter lambda value, a post-catalytic converter oxygen molecular mass is determined by considering the reaction equation for the reaction of the oxygen with the first substance, and, in order to determine the post-catalytic converter oxygen molecular mass, a second reaction equation that describes a reaction of the first substance with the oxygen stored in the oxygen storage, and a third reaction equation that describes the introduction of oxygen from the exhaust gas into the oxygen storage are additionally considered, wherein a fill level of the oxygen storage is entered in a reaction rate of the second reaction equation and in a reaction rate of the third reaction equation. The invention further relates to a drive device