Patent Application
20070272210
The invention is explained in detail below with reference to schematic drawings.
They are as follows:
Elements with the same design or function are labeled in all the figures with the same reference symbols.
An internal combustion engine comprises an intake tract 1, an engine block 2, a cylinder head 3 and an exhaust gas tract 4. The intake tract 1 preferably comprises a throttle valve 5, a manifold 6 and an intake pipe 7, which is routed to a cylinder Z1 via an intake port in a combustion chamber 9 in an engine block 2. The engine block 2 also comprises a crankshaft 8 that is connected to piston 11 of a cylinder Z1 by means of a connecting rod 10. The internal combustion engine preferable comprises in addition to the cylinder Z1 additional cylinders Z1-Z4. The internal combustion engine is preferably arranged in a motor vehicle.
The cylinder head 3 also preferably includes both an injection valve 18 and a spark plug 19. Alternatively, the injection valve 18 can also be arranged accordingly in the intake pipe 7. The exhaust gas tract 4 preferably includes an exhaust gas catalytic converter 23, which is preferably embodied as a three-way catalytic converter.
A control device 25 is provided to which sensors have been allocated, said sensors detecting the different measured quantities and in each case determining the value of the measured quantity. Operating variables include the measured quantities and quantities of the internal combustion engine derived from these. Operating variables can be representative of the current operating condition of the internal combustion engine. The control device 25 determines, as a function of at least one of the operating variables, at least one controlling variable, which is then converted into one adjusting signal or a plurality of adjusting signals for controlling the final control elements by means of corresponding actuators. The control device 25 can also be referred to as a device for controlling an internal combustion engine.
The sensors are a pedal position indicator 26 which detects the position of a gas pedal 27, an air mass flow meter 28 which detects an air mass flow upstream of the throttle valve 5, a temperature sensor 32 which detects the intake air temperature, an intake pipe pressure sensor 34 which detects the intake pipe pressure in a manifold 6, a crankshaft angle sensor 36 which detects a crankshaft angle to which a rotational speed of the internal combustion engine is then allocated. In addition, provision has also been made for an exhaust sensor 38, which is arranged upstream of the exhaust gas catalytic converter 23 and which, for example, detects a residual oxygen content of the exhaust gas and the measuring signal of which is characteristic of an air-to-fuel ratio in the combustion chamber 9 of cylinders Z1-Z4.
Depending on the embodiment of the invention, there can be any subset of the mentioned sensors or there can even be additional sensors.
The final control elements are, for example, the throttle valve 5, the gas intake and the gas discharge valves 12, 13, the injection valve 18 and/or the spark plug 19.
Lean operation AFL of the internal combustion engine is characterized in that a smaller amount of fuel is fed in for the combustion process of the internal combustion engine than can be combusted with the amount of air fed in for the combustion process, in particular with the oxygen contained therein.
During stoichiometric operation of the internal combustion engine, exactly the same amount of fuel that can be combusted with the oxygen is fed in for the combustion process. In this context, quasi-stoichiometric means that the air-to-fuel ratio is stoichiometric at a preferably predetermined low tolerance. For example, during the quasi-stoichiometric operation, preferably within a very small range around the stoichiometric air-to-fuel ratio, lean operation AFL and rich operation of the internal combustion engine are alternated. In principle, the quasi-stoichiometric operation can also be referred to as stoichiometric operation.
In lean operation AFL, an opening degree of the throttle valve 5 is adjusted to the maximum and an engine load is preferably adjusted by means of an amount of fuel MFF to be dispensed. On the other hand, during the quasi-stoichiometric operation, the load of the internal combustion engine is preferably adjusted by means of the opening degree of the throttle valve 5. The opening degree of the throttle valve 5 acts on a mass air flow MAF through to the combustion chamber 9. An efficiency of the internal combustion engine is higher than that achieved during the quasi-stoichiometric operation AFS owing to the unthrottled mass air flow MAF in lean operation AFL through to the combustion chamber. However, in lean operation AFL, the internal combustion engine is more prone to error conditions. These error conditions can be generated by the unexpected values of command variables, which are operating variables, for example an unexpected fuel pressure, an unexpectedly large amount of metered fuel MFF and/or an unexpected air-to-fuel ratio in favor of the amount of fuel dispensed MFF that can be generated by the unexpectedly large amount of fuel MFF. The unexpectedly large amount of metered fuel MFF or the unexpected air-fuel ratio can for example be generated by a tank aeration and/or a crankshaft housing aeration, through which the fuel fumes from a fuel tank or from a crankshaft housing of the internal combustion engine can reach the intake tract 1 and/or the combustion chamber 9 and/or the exhaust gas tract 4.
When an error condition occurs, a bit is set in an error memory on a storage medium of the control unit 25 in a preferred manner. This bit is then representative of the occurrence of the error condition, in particular for the presence of the implausible operating variables. In lean operation, in order to test the operating variable, a test can then be carried out to determine whether or not the bit has been set.
In lean operation, the unexpectedly amount of fuel dispensed MFF or the unexpected air-to-fuel ratio acts directly on a torque generated by the internal combustion engine, because on the basis of lean operation AFL there is sufficient oxygen in the internal combustion engine in order to combust the unexpectedly large amount of fuel MFF. During quasi-stoichiometric operation, the unexpectedly large amount of fuel MFF or the unexpected air-to-fuel ratio no longer acts so strongly on the generated torque as it does in lean operation AFL, because hardly any oxygen or no oxygen at all has been provided for the combustion of the unexpectedly large amount of fuel MFF.
When testing whether or not a value of any operating variable is plausible PLAUS, for example a value of the amount of fuel MFF to be dispensed, the value of any operating variable is preferably determined by means of a model calculation on the basis of a first measured quantity of the internal combustion engine. A check value of any operating variable is then preferably determined as a function of a second measured quantity. Subsequently, the value and the check value of any operating variable can be compared with one another. For example, a tolerance band can be specified as a function of the value of any operating variable and a test can be carried out to determine whether or not the check value of any operating variable lies within the tolerance band. Alternatively, the tolerance band can be predetermined by the check value of any operating variable and a test can be carried out to determine whether or not the value of any operating variable lies within the tolerance band. Alternatively, the tolerance band can be specified as a function of the first and/or the second measured quantity and a test can be carried out to determine whether or not the value of any operating variable lies within the tolerance band. During the operation of the internal combustion engine, the value and the check value or the tolerance band of any operating variable is preferably determined continuously and used for mutual plausibility.
A program (
In a step S2, the value LAMB_AV of the air-to-fuel ratio is determined as a function of the mass air flow MAF up to the combustion chamber 9 and as a function of the metered mass air flow MFF. The mass air flow MAF up to the combustion chamber 9 can for example be determined as a function of the mass air flow upstream of the throttle valve 5 and as a function of the opening degree of the throttle valve 5. The amount of fuel dispensed MFF can for example be selected on the basis of a desired value of the amount of fuel dispensed MFF and/or determined as a function of the duration of an activation of the injection valve 18 and/or as a function of a fuel pressure by means of which the fuel is metered by means of the injection valve 18.
In a step S3, a test is carried out to determine whether or not the value LAM_AV of the air-to-fuel ratio is plausible PLAUS and preferably as a function of a measuring signal of the exhaust gas sensor 38. If the condition of a step S3 has been met, the process is continued once more in a step S1. If the condition of a step S3 has not been met, the process is continued in a step S4.
In a step S4, a test is carried out to determine whether or not the internal combustion engine is currently being operated in lean operation. If the condition of a step S4 has not been met, an error measure ERROR is initiated. If the condition of a step S4 has been met, the process is continued in a step S6. In a step S6, a changeover to quasi-stoichiometric operation AFS of the internal combustion engine takes place.
The program then remains in a step S7 for a specified length of time DUR.
In a step S8, a counter CTR can be incremented by one unit.
In a step S9, the value LAMB_AV of the air-to-fuel ratio is determined anew.
In a step S10, a test is carried out to determine whether or not the newly determined value LAMB_AV of the air-to-fuel ratio is plausible PLAUS and whether or not the counter CTR is below a maximum CTR MAX value of the counter CTR. This can contribute to preventing, an error, which is for example generated on the basis of lean operation AFL of the internal combustion engine, from being generated time and again by changing over to lean operation AFL.
In a step S11, a changeover to lean operation AFL takes place.
The program can end in a step S12. However, the program is preferably ended at regular intervals during the operation of the internal combustion engine.
The invention is not limited to the given examples of the invention. For example, in the program, as an alternative to the value LAMB_AV of the air-to-fuel ratio, a different operating variable of the internal combustion chamber can be determined and tested, for example, the amount of fuel dispensed MFF.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 022 106.0 | May 2006 | DE | national |
This application claims priority of German application No. 10 2006 022 106.0 DE filed May 11, 2006, which is incorporated by reference herein in its entirety.
