Method and device for determining the oxygen storage capacity of an emission control system

A method for determining a hydrocarbon gas storage capacity of an emission control system in an exhaust duct of an internal combustion engine, having a first exhaust gas analyzer probe situated in front of the emission control system in a direction of flow and a second exhaust gas analyzer probe situated in back of the emission control system, the method comprising:

• in a first phase, operating the internal combustion engine at a lean (λ>1) air-to-fuel ratio;
• in a second phase, operating the internal combustion engine at a rich (λ<1) air-to-fuel ratio;
• and
• determining a hydrocarbon gas storage capacity from an oxygen discharge from the emission control system during the second phase;
• wherein parameters of a step response of an output signal of the second exhaust gas analyzer probe is determined based on a sudden change in a lambda value of the air-fuel mixture supplied to the internal combustion engine, and the oxygen discharge is corrected using the parameters of the step response.

A method for determining the oxygen storage capacity of an emission control system in an exhaust duct of an internal combustion engine, having a first exhaust gas analyzer probe situated in front of the emission control system in a direction of flow and a second exhaust gas analyzer probe situated in back of the emission control system, the method comprising:

• in a first phase, operating the internal combustion engine using an air-fuel mixture having a rich (λ<1) air-to-fuel ratio;
• in a second phase, operating the engine at a lean (λ>1) air-to-fuel ratio;
• and
• determining an oxygen storage capacity of the emission control system from an oxygen input into the emission control system during the second phase;
• wherein a correction of at least one of the oxygen input and an oxygen discharge is determined as a function of a probe delay Ts and a probe time constant τs of the first exhaust gas analyzer probe, of an average mass flow rate of exhaust gas, and of a magnitude of a lambda increase of an air-fuel mixture supplied to the internal combustion engine in the first phase and the second phase, and stored in characteristics maps, and the at least one of the oxygen input and the oxygen discharge during operation of the internal combustion engine is taken from the characteristics maps.

A device for determining an oxygen storage capacity of an emission control system in an exhaust duct of an internal combustion engine, comprising:

• a first exhaust gas analyzer probe situated in front of the emission control system in a direction of flow;
• a second exhaust gas analyzer probe situated in back of the emission control system;
• and
• an engine control unit assigned to the internal combustion engine, the engine control unit including at least one of a circuit and a program sequence, with the aid of which an air-fuel mixture supplied to the engine is controlled in such a manner, that in a first phase, the internal combustion engine is operated using an air-fuel mixture having a rich (λ<1) air-to-fuel ratio, and in a second phase, the engine is operated at a lean (λ>1) air-to-fuel ratio, and that an oxygen storage capacity of the emission control system is determined from an oxygen input into the emission control system during the second phase, wherein a further at least one of a circuit and program sequence for determining parameters of a step response of an output signal of the first exhaust gas analyzer probe, based on an abrupt change in a lambda value of the air-fuel mixture supplied to the internal combustion engine is provided in the engine control unit, and a program sequence for correcting the oxygen input using the parameters of the step response, is provided in the engine control unit.

A device for determining an oxygen storage capacity of an emission control system in an exhaust duct of an internal combustion engine, comprising:

• a first exhaust gas analyzer probe situated in front of the emission control system;
• a second exhaust gas analyzer probe situated in back of the emission control system;
• and
• an engine control unit assigned to the internal combustion engine, the engine control unit including at least one of a circuit and a program sequence, with the aid of which an air-fuel mixture is supplied to the engine is controlled in such a manner, that in a first phase, the internal combustion engine is operated at a lean (λ>1) air-to-fuel ratio, and in a second phase, the engine is operated at a rich (λ<1) air-to-fuel ration, the engine control unit including a program sequence for determining a hydrocarbon gas storage capacity from an oxygen discharge from the emission control system, wherein a further at least one of a circuit and program sequence for determining parameters of a step response of an output signal of the oxygen discharge, using the parameter of the step response, is provided in the engine control unit.