CN106968822B

CN106968822B - Method for operating an internal combustion engine

Info

Publication number: CN106968822B
Application number: CN201611044092.9A
Authority: CN
Inventors: C.旺德林; R.埃克; T.库恩; T.霍尔曼; U.舒尔茨
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2015-11-25
Filing date: 2016-11-24
Publication date: 2021-02-02
Anticipated expiration: 2036-11-24
Also published as: DE102015223319A1; CN106968822A

Abstract

Method for operating an internal combustion engine of a vehicle having a fuel injection system, wherein at least one first injection valve is assigned to each cylinder for direct injection and the fuel injection system has at least one second injection valve, which is not cylinder-specific, for intake pipe injection, wherein system-specific and/or motor-specific cylinder-specific filling differences and/or mixture distribution differences are determined by modulating the injection quantity injected by means of the direct injection and cylinder-specific quantity corrections are determined therefrom in order to compensate for a larger or smaller quantity resulting from the intake pipe injection, characterized in that cylinder-specific quantity corrections are determined for all cylinders, a drift in the injected quantity of the at least one second injection valve for intake pipe injection is inferred by means of a comparison of the cylinder-specific quantity corrections for all cylinders, and the drift is corrected by changing the injection quantity injected by the at least one second injection valve.

Description

Method for operating an internal combustion engine

Technical Field

The invention is based on a method for operating an internal combustion engine of a vehicle having a fuel injection system in which at least one first injection valve is assigned to each cylinder for direct injection and which has at least one second injection valve that is not cylinder-specific for intake manifold injection, wherein system-specific and/or motor-specific cylinder-specific filling differences and/or mixture distribution differences are determined by modulating the injection quantity injected by means of the direct injection and cylinder-specific quantity corrections are determined therefrom in order to compensate for larger or smaller quantities caused by the intake manifold injection. The invention also relates to a computer program which is set up to carry out each step of the method according to the invention; and a storage medium readable by a machine, on which the computer program according to the present invention is stored. Finally, the invention relates to an electronic control unit with a computing device, which implements a computer program and thus implements the execution of the method.

Background

Methods for operating an internal combustion engine are known, in which fuel is dispensed into an intake manifold by means of a first injection valve and directly into a combustion chamber of the internal combustion engine by means of a second injection valve. In this case, a first injection valve is preferably used in one operating mode and a second injection valve is preferably used in another operating mode. Such a combination of a so-called PFI injection (intake pipe injection) and a so-called DI injection (direct injection) achieves the advantage of using both injection types for optimal mixture formation and combustion. Thus, for example, in terms of full load and dynamics of the motor, it is more advantageous to use direct injection in order to avoid knocking, while in part load, intake pipe injection is more advantageous in order to reduce the number of soot particles and the hydrocarbon content of the exhaust gas produced during combustion. The fuel supply takes place in the low-pressure circuit during the intake pipe injection and in the high-pressure circuit during the direct injection. Here, fuel supply systems with and without return and systems regulated as required are used. Generally, a system is used in which one valve is used for direct injection and one valve is used for intake pipe injection per cylinder. However, for reasons of simplicity and also for reasons of cost saving, there are also solutions with a smaller number of valves for intake pipe injection than the number of cylinders. Due to different intake manifold geometries, pressure fluctuations and/or tolerances of the cylinder entry ends and/or different mixture distributions in the intake manifold injection mixture formation section, and/or due to the installation position of the valve for the intake manifold injection (this valve is also referred to below as intake manifold injector for short), and/or due to different maps of the intake manifold injector, different filling of the cylinder with fuel can now result, which is based on the intake manifold injection. Since the intended function of the PFI injection and of the DI injection is a prerequisite for an optimum exhaust emission value, there is a desire for an optimum diagnosis of the injection valves, in particular of the PFI injection valves, which are not used individually, i.e. simultaneously for a plurality of cylinders.

Disclosure of Invention

Advantages of the invention

According to the method of the invention, cylinder-specific quantity corrections of all cylinders (direct injection) are determined and a drift of the injected quantity of the at least one second injection valve for intake pipe injection, i.e. the PFI injection valve, is inferred by means of a comparison of the cylinder-specific quantity corrections of all cylinders, and is corrected by changing the injection quantity caused by the at least one second injection valve for intake pipe injection. The corrections modify each other's approval based on cylinder-individualized DI amounts. The basic idea here is to identify and to specifically correct systematic shifts of the PFI injection valves in the direction of larger or smaller quantities by means of a comparison of the DI quantity corrections with respect to all cylinders. The method according to the invention thus provides for a correction of the injection quantity injected by means of the PFI injection valve and not only by a DI quantity correction. Thereby making the best use of the possible PFI operating area. In particular, an inadmissible drift can be seen due to a malfunction of the PFI injector, as will be explained in more detail below.

In an advantageous embodiment of the method according to the invention, it is provided that, in the case of at least two injection valves which are not cylinder-specific, a group of cylinders is assigned for the intake pipe injection of each of the two injection valves which are not cylinder-specific, and that, when a cylinder-specific quantity correction, i.e. a DI quantity correction, of the cylinders of the first group deviates from a cylinder-specific quantity correction, i.e. a DI quantity correction, of the second cylinder of the second group, a correction offset is formed and subtracted from the injected quantity (which is assigned to the injection valve of the group which is not cylinder-specific for the intake pipe injection). Thus here the DI amount modification of the cylinders of the first grouping is compared to the DI amount modification of the cylinders of the second grouping and a modified offset is formed by the difference of the DI amount modification of the cylinders of the second grouping and the DI amount modification of the cylinders of the first grouping and is taken into account when PFI injection of the cylinders of the first grouping. The consideration here means that the correction offset is subtracted from the amount injected by means of PFI injection. This occurs, for example, when the PFI injection valves of the cylinders of the first group inject in principle an excessive injection quantity. The correction offset is added if the PFI injection valves of the cylinders of the first grouping inject an excessively small injection quantity on the contrary. Thus, in other words, if the PFI injection valves of the first group inject an excessively large injection quantity, the subtraction means subtracting a positive value, and if the PFI injection valves inject an excessively small quantity in principle, a negative value is subtracted, that is, a positive value is added.

Generally, the correction is implemented as a factor. If, for example, in a four-cylinder motor, the DI amount correction is 1.1 for cylinder 1, 1.1 for cylinder 2, 0.9 for cylinder 3 and 0.9 for cylinder 4, then two PFI amount corrections 1.1 and 0.9 are obtained. In the correction of the non-zero average value, for example, when moving toward the rich direction, when the DI amount of the first cylinder is corrected to be 1.2, the DI amount of the second cylinder is 1.2, the DI amount of the third cylinder is 1, and the DI amount of the fourth cylinder is 1, for example, the PFI values are 1.2 and 1.

In addition, according to a very advantageous embodiment of the method, it is provided that the correction offset value of the cylinders of each group is compared with a predeterminable value and a fault signal is output when the correction offset value of the cylinders of each group exceeds the predeterminable value. If, for example, such a predefinable limit value is exceeded in a group, it can be assumed that: there is drift of the PFI injection valves of this group.

In addition, according to an advantageous embodiment, it is provided that the correction offset value of the cylinders of the first group is compared with the correction offset value of the cylinders of the second group and a fault signal is output if the correction offset value of the cylinders of the first group deviates from the correction offset value of the cylinders of the second group by a predeterminable value. A fault is thus identified when the corrective value of the PFI injection of the cylinder of the first grouping exceeds the corrective value of the PFI injection of the cylinders of the other grouping by a certain amount. In this case, an inadmissible drift of the PFI injection valve due to a malfunction of the PFI injection valve is inferred.

Furthermore, a variant of the method according to the invention also makes it possible to identify a modified map of the PFI injection valve. In this case, it is provided that, in the case of at least two non-cylinder-specific injection valves for intake manifold injection, each of the two non-cylinder-specific injection valves for intake manifold injection is assigned to a group of cylinders, and cylinder-specific quantity corrections, i.e. DI quantity corrections, of the individual cylinders of the first group are compared with one another, and a fault signal is output if the cylinder-specific quantity corrections of the cylinders of the first group exceed or fall below a threshold value depending on the operating point. A fault signal is thus output if the correction value is lower, depending on the operating point, than the injection quantity to be injected in its entirety, for example by means of a DI injection valve. The same applies when the correction value is lower than the entire injected DI amount. Thus as the cylinder-individual volume corrections for the DI injection become increasingly far apart from each other relative to a PFI injection valve, it must be considered that: the map of the associated PFI injector has been changed in such a way that one cylinder input receives more and more fuel and the other cylinder input receives less and less fuel. This can be compensated for by means of DI injection via an over correction. However, if the correction value exceeds or falls below the total injection-to-be-injected amount by means of the DI injection, a failure is determined. Finally, it can also be seen from the aforementioned quantity correction values: whether a deposit has already formed at or in the injection valve for direct injection (DI injection valve) is then removed by a defined and pre-calculated so-called flush injection.

The cylinder-specific filling difference and/or mixture distribution difference, which is subject to the motor, is advantageously determined by determining a cylinder-specific lambda difference and/or a rotational speed difference. In this case, the individual lambda differences of the cylinders are determined by means of a single cylinder lambda measurement. The difference in rotational speed can be determined by operating a stationarity regulator.

The method can advantageously be implemented as a computer program. For this purpose, the computer program is configured to: each step of the method for operating the internal combustion engine of the vehicle is carried out, in particular when the computer program is run on a controller. Such a controller has a computing device implementing the computer program. The computer program itself can be stored on a machine-readable storage medium, which enables the computer program to be run on a conventional electronic control unit.

Drawings

Embodiments of the invention are illustrated in the drawings and will be explained in more detail in the following description.

Fig. 1 schematically shows a part of an internal combustion engine, which can be operated with a method according to an embodiment of the invention, and a fuel injection system of the internal combustion engine;

fig. 2 shows schematically an intake pipe injection into a cylinder of the internal combustion engine according to fig. 1;

fig. 3 shows schematically the direct injection of fuel into the cylinder of the internal combustion engine according to fig. 1.

Detailed Description

The internal combustion engine 1, which is realized as a gasoline motor, has a plurality of cylinders 10, only one of which is schematically illustrated in fig. 1. In the cylinder block 10, a piston 11 is arranged, which is connected to a crankshaft 12 of the internal combustion engine 1. The cylinder 10 has at least one inlet valve 13 and at least one outlet valve 14. The inlet valve 13 connects the inner chamber of the cylinder 10 to an inlet line 15, and the outlet valve 14 connects the inner chamber of the cylinder 10 to the exhaust system of the internal combustion engine 1. The first injection valve 16 for the direct injection of the fuel, which is ultimately in the interior of the cylinder 10, is embodied as a high-pressure injection valve. A second injection valve 17 for intake pipe injection of fuel is arranged in the intake pipe 15. The two

injection valves

16, 17 are supplied with fuel by a fuel injection system 2, which is explained in more detail below. In order to stock the fuel 21, a fuel tank 20 is provided. Fuel is pumped into the line 22 via an electric fuel pump 23. The fuel pump 23 is a low-pressure pump. Via line 22a, the second injection valve 17 for intake pipe injection is supplied with fuel. Line 22b leads to a high-pressure pump 24, which supplies the first injection valves 16 for direct injection with fuel at high pressure. For such a high-pressure circuit, the low-pressure pump 23 serves as a fuel prefeed pump.

The electronic control unit 3 controls the internal combustion engine 1 and the fuel injection system 2.

In the present case, it is provided that each cylinder 10 of the internal combustion engine 1 is assigned a first injection valve 16 for injecting fuel directly into the interior of the cylinder 10, while the second injection valves 17 are not arranged individually for the cylinders, i.e., no valve 17 for the intake manifold injection is assigned to each cylinder 10. In fact, the injection valves 17 are each associated with a plurality of or all of the cylinders 10, i.e. the number of injection valves 17 for the intake manifold injection of fuel is smaller than the number of cylinders 10.

In the intake manifold injection shown in fig. 2, fuel 21 is injected into the interior of the cylinder 10 by means of the second injection valve 17 via the intake manifold 15 and the inlet valve 13. In the direct injection shown in fig. 3, the fuel is injected directly into the interior of the cylinder by means of the first injection valve 16.

The method according to the invention is described, for example, in connection with a four-cylinder inline internal combustion engine with a PFI valve associated for each of two cylinder/DI valves. It is clear that the invention is not limited thereto, but can also be applied in particular in six-cylinder motors or motors with other numbers of cylinders, in which a distribution into at least two groups of cylinders is effected, which each have a PFI injection valve assigned to it.

The method is illustrated by means of different scenarios. In the first case, it is assumed that one PFI valve 17 injects in principle an excessive injection quantity. In this case, the cylinder-specific quantity correction of the DI injection valves 16 assigned to the cylinder of the PFI injection valve 17 is slightly smaller in a trend with respect to the DI quantity correction of the DI injection valves 16 assigned to the cylinders of the other PFI injection valves 17. At this time, a smaller cylinder-specific DI quantity correction of the DI injection valves 16 of this cylinder group relative to the DI quantity correction of the DI injection valves 16 of the other cylinder group is determined as a correction offset, for example by subtracting the DI quantity correction of the DI injection valves 16 of one group and the injection quantity of the DI injection valves 16 of the other group, and the correction offset is used in order to correct the injection quantity to be injected which is assigned to the PFI injection valves 17 of the first group, in which case the quantity to be injected by means of the PFI injection valves 17 is thus reduced by the correction offset value. If this correction value of the PFI injection valve (also referred to below simply as PFI correction value) exceeds a specific absolute value that can be set in advance, a fault message is output and, for example, an MIL lamp (fault indicator lamp) associated with the request for maintenance is switched on. If the PFI correction value exceeds a specific relative magnitude in comparison with the correction values of the other PFI injection valves 17, i.e. of the PFI injection valves assigned to the cylinders of the other group, a fault report is likewise output. The two values, i.e. the absolute value and the relative value (compared to the other PFI injectors 17), can also be compared to the value from the past (which was determined, for example, in the last driving cycle) in order to take into account the degree of deterioration, for example, the drift speed, together.

In the following description of the process according to the invention it is considered that: the PFI injection valve 17 injects in principle an excessively small fuel quantity. In this case, the cylinder-specific correction of the amount injected by the DI injection valve 16 (hereinafter referred to simply as DI amount correction) of one PFI injection valve 17 tends to be higher relative to such correction of the other PFI injection valves 17. In this case, the larger cylinder-specific DI amount correction of the more-injected DI valve is used as the correction offset, and the amount to be injected of the concerned PFI injection valve 17 is increased by this amount. It is also applicable here that a fault is inferred if this PFI correction value exceeds a specific absolute value and/or a fault is inferred if this PFI correction value exceeds a specific relative value compared to the correction values of the other PFI injectors 17. In this case too, the two (absolute and relative) values can be compared with the values determined in the past, in order to thereby determine the degree of deterioration.

Another malfunction of the PFI injection valve 17 is a changed shot. Such a modified beam pattern can also be determined by means of the method according to the invention. In this case, the cylinder-specific DI quantity corrections of the PFI injection valves of one grouping of cylinders are increasingly separated from each other. The reason for this is to change the map of the associated PFI injector 17 in such a way that one cylinder input receives more and less fuel. This can be compensated by DI amount correction of the corresponding cylinder. However, if the correction value is lower, depending on the operating point, than the entire quantity to be injected, for example, by means of the DI injection valve 16, a fault is detected. A fault is also detected if the correction value is below the total injection quantity to be injected, depending on the operating point, of the injection quantity to be injected by means of the DI injection valve 16. Here, the threshold value can also be predetermined.

The method is described above with the aid of a four-cylinder inline combustion engine. The method can of course also be applied in V motors, for example in V6 motors. In this case, for example, one PFI injection valve 17 can always operate three cylinders. This method can be employed even in the case of a larger motor, such as the W18 motor, in which one PFI injection valve 17 always operates six cylinders. Generally, approval is made between PFI paths because the PFI injection relationship and the mixture formation relationship of the paths are comparable.

The aforementioned corrections of the DI injection and of the PFI injection and the DI and PFI corrections can also be determined and evaluated in the framework of a system-related determination of zone data by filtering and/or in relation to the operating region in order to identify problems in time and to ensure vehicle availability, for example by early communication in service.

Finally, a variant of the method is also described, which variant serves to identify: when flushing by means of DI injection is required. This is because it is possible to identify from the correction values: whether deposits are built up at DI injection valve 16 and in DI injection valve 16. This deposit is then removed or avoided by a defined and pre-calculated so-called flush jet at the valve of the direct injection. Using the method described above, it is possible to identify individually: one or more flushing jets are required for which cylinders which are assigned to the PFI injection valve 17.

It is assumed that, in a four-cylinder inline motor, the cylinders 1, 2 and thus the DI injection valves 16 are assigned to the PFI injection valves a, and the cylinders 3 and 4 and the DI injection valves assigned to these cylinders are assigned to the PFI injection valves B. If it is now recognized for the PFI injector a by means of a correction value, for example, exceeding a threshold value that can be set in advance: for this system, i.e. the cylinders 1 and 2, a flushing spray is required, which is carried out without influencing the cylinders 3, 4. The system with cylinders 3, 4 can be operated continuously in the optimum operating point. The same applies to the opposite case. The method of course also achieves the recognition that: whether the flush jet was successful. This is again done by comparing the correction values before and after the injection. If these correction values change, it must be assumed that the valve is full of soot.

Claims

1. Method for operating an internal combustion engine (1) of a vehicle having a fuel injection system (2), in which at least one first injection valve (16) is assigned to each cylinder for direct injection and which has at least one second injection valve (17) that is not cylinder-specific for intake pipe injection, wherein a system-dependent and/or motor-dependent cylinder-specific fuel filling difference and/or mixture distribution difference is determined by modulating the injection quantity injected by means of the direct injection and a cylinder-specific injection quantity correction is determined therefrom in order to compensate for a larger or smaller quantity caused by the intake pipe injection, characterized in that the cylinder-specific injection quantity corrections of all cylinders are determined and the injected second injection valve (17) for intake pipe injection is inferred by means of a comparison of the cylinder-specific injection quantity corrections of all cylinders A drift of the quantity and the drift is corrected by varying the injection quantity injected by the at least one second injection valve (17).

2. Method according to claim 1, characterized in that in the case of at least two non-cylinder-specific second injection valves (17), each of the two non-cylinder-specific second injection valves (17) is assigned to a group of cylinders, and in the case of a cylinder-specific injection quantity correction of a cylinder of a first group deviating from a cylinder-specific injection quantity correction of a cylinder of a second group, a correction offset is formed and subtracted from the quantity injected by the non-cylinder-specific second injection valve (17) assigned to the first group.

3. Method according to claim 2, characterized in that the correction offset is selected positively/negatively in dependence on the larger/smaller quantity injected by the second non-cylinder-specific injection valve (17) assigned to the first grouping.

4. A method according to claim 2, characterised in that the correction offset of the cylinders of each grouping is compared with an absolute value which can be set in advance, and a fault signal is output when the correction offset of the cylinders of each grouping exceeds the absolute value.

5. A method according to claim 2, wherein the corrected offset for the cylinders of the first grouping is compared with the corrected offset for the cylinders of the second grouping and a fault signal is output when the corrected offset for the cylinders of the first grouping deviates from the corrected offset for the cylinders of the second grouping by a value that can be preset.

6. Method according to claim 1, characterized in that in the case of at least two second injection valves (17) which are not cylinder-specific, each of the two second injection valves (17) is assigned to one group of cylinders, and that the cylinder-specific injection quantity corrections of the individual cylinders of the first group are compared with each other and a fault signal is output when the cylinder-specific injection quantity corrections of the cylinders of the first group exceed or fall below a predeterminable value depending on the operating point.

7. Method according to one of the preceding claims, wherein the cylinder-specific difference in fuel filling and/or the mixture distribution caused by the system and/or by the motor is determined by determining a cylinder-specific difference in lambda and/or a difference in rotational speed.

8. Method according to claim 7, characterized in that the cylinder-specific lambda difference is determined by means of a single cylinder lambda measurement.

9. The method of claim 7, wherein determining the difference in rotational speed is accomplished by operating an actuator.

10. Storage medium readable by a machine, on which a computer program is stored, which computer program is set up to carry out the individual steps of the method according to one of claims 1 to 9.

11. Electronic controller (50) having a computing device which implements a computer program which is set up to carry out the individual steps of the method according to one of claims 1 to 9.