Method and device for operating an internal combustion engine
View Patent ↗An internal combustion engine has a plurality of cylinders and an exhaust tract into which a mixture which is situated in the respective cylinder is introduced in the respective discharge strokes. A combustion misfire rate is determined as a function of at least one operating variable of the internal combustion engine. A temperature in the exhaust tract is determined as a function of the combustion misfire rate.
1. A method for operating an internal combustion engine with a number of cylinders and an exhaust gas tract, in which a mixture present in the respective cylinder is brought into the respective exhaust cycles, with the method comprising the steps of:
determining a misfire rate as a function of at least one operating variable of the internal combustion engine, and
determining a temperature in the exhaust gas tract as a function of the misfire rate and as a function of whether the fault causing the misfire lies in an ignition system or in an injection system of the internal combustion engine.
2. The method according to claim 1 , wherein, depending on a determined spark time of the respective assigned spark plug, it is determined whether a misfire is to be assigned to a fault in the ignition system.
3. A device for operating an internal combustion engine with a number of cylinders in an exhaust gas tract, in which a mixture located in the respective cylinder is brought into the respective exhaust cycles, to the device being operable to
determine a misfire rate as a function of at least one operating variable of the internal combustion engine, and to
determine a temperature in the exhaust gas tract as a function of the misfire rate and as a function of whether the fault causing the misfire lies in an ignition system or in an injection system of the internal combustion engine.
4. The device according to claim 3 , being further operable to determine, depending on a determined spark time of the respective assigned spark plug, whether a misfire is to be assigned to a fault in the ignition system.
5. A method for operating an internal combustion engine with a number of cylinders and an exhaust gas tract, in which a mixture present in the respective cylinder is brought into the respective exhaust cycles, with the method comprising the steps of:
determining a misfire rate as a function of at least one operating variable of the internal combustion engine, and
determining a temperature in the exhaust gas tract as a function of the misfire rate, wherein the temperature in the exhaust gas tract on explicit cutoff of a fuel delivery of at least one of the cylinders during the operation of the internal combustion engine is determined as a function of a physical estimation model for the explicit cutoff of the fuel delivery in at least one of the cylinders and in the case of a detected misfire a characteristic value which is representative of a virtual number of cylinders with explicit cutoff of the delivery of fuel, is determined as a function of the misfire rate and the temperature in the exhaust gas tract is determined as a function of the characteristic value as input variable for the physical cutoff model.
6. The method according to claim 5 , wherein the temperature in the exhaust gas tract is determined as a function of a fault causing misfires.
7. The method according to claim 5 , wherein the characteristic value is determined as a function of an air/fuel mixture determined for the respective misfire.
8. The method according to claim 5 , wherein the temperature in the exhaust gas catalyzer is determined as the temperature in the exhaust gas tract.
9. The method according to claim 5 , wherein, depending on a determined spark time of the respective assigned spark plug, it is determined whether a misfire is to be assigned to a fault in the ignition system.
10. The method according to claim 5 , wherein the characteristic value is determined as a function of a heat capacity ratio of a heat capacity of the mixture in the respective cylinder on a misfire to the heat capacity of air.
11. The method according to claim 10 , wherein the characteristic value is determined only in the case of a fault cause in the injection system for the misfire as a function of the heat capacity ratio.
12. A device for operating an internal combustion engine with a number of cylinders in an exhaust gas tract, in which a mixture located in the respective cylinder is brought into the respective exhaust cycles, to the device being operable to
determine a misfire rate as a function of at least one operating variable of the internal combustion engine,
determine a temperature in the exhaust gas tract as a function of the misfire rate, wherein the temperature in the exhaust gas tract is determined on explicit cutoff of a fuel delivery of at least one of the cylinders during the operation of the internal combustion engine as a function of a physical estimation model for the explicit cutoff of the fuel delivery in at least one of the cylinders, and
in the case of a detected misfire, to determine a characteristic value which is representative of a virtual number of cylinders with explicit cutoff of the delivery of fuel, as a function of the misfire rate and to determine the temperature in the exhaust gas tract as a function of the characteristic value as input variable for the physical cutoff model.
13. The device according to claim 12 , being further operable to determine the temperature in the exhaust gas tract as a function of a fault causing misfires.
14. The device according to claim 12 , being further operable to determine the characteristic value as a function of an air/fuel mixture determined for the respective misfire.
15. The device according to claim 12 , being further operable to determine the temperature in the exhaust gas catalyzer as the temperature in the exhaust gas tract.
16. The device according to claim 12 , being further operable to determine, depending on a determined spark time of the respective assigned spark plug, whether a misfire is to be assigned to a fault in the ignition system.
17. The device according to claim 12 , being further operable to determine the characteristic value as a function of a heat capacity ratio of a heat capacity of the mixture in the respective cylinder on a misfire to the heat capacity of air.
18. The device according to claim 17 , being further operable to determine the characteristic value only in the case of a fault cause in the injection system for the misfire as a function of the heat capacity ratio.