CN107023411B

CN107023411B - Method for operating an internal combustion engine

Info

Publication number: CN107023411B
Application number: CN201611044041.6A
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: 2022-02-01
Anticipated expiration: 2036-11-24
Also published as: DE102015223316A1; CN107023411A

Abstract

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) which is not cylinder-specific for intake pipe injection, characterized in that a system-specific and/or motor-specific cylinder-specific filling difference and/or mixture distribution difference is determined by varying the injection quantity injected by means of the Direct Injection (DI) and a motor-specific cylinder-specific correction is determined therefrom in order to compensate for a greater or lesser quantity resulting from the intake pipe injection (PFI).

Description

Method for operating an internal combustion engine

Technical Field

The invention relates to a method for operating an internal combustion engine of a vehicle having a fuel injection system in which at least one first injection valve for direct injection is associated with each cylinder and which has at least one second injection valve for intake pipe injection that is not cylinder-specific. 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 which is configured to: by means of the method according to the invention, cylinder-specific filling differences and/or mixture distribution differences are determined by means of the injection quantity injected by direct injection, and from these motor-specific and cylinder-specific quantity corrections are determined in order to compensate for the greater or lesser quantity resulting from the injection through the intake manifold.

Background

It is known from practice that internal combustion engines can be operated in so-called dual operation, in which the cylinder of the internal combustion engine is acted upon with fuel in parallel by at least one injector injected via the intake manifold and a plurality of injectors injected directly. The combination of intake pipe injection and direct injection enables the use of the advantages of both injection modes 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, only a different filling of the cylinder with fuel as a result of the intake manifold injection results.

Disclosure of Invention

The method according to the invention for operating an internal combustion engine of a vehicle with a fuel injection system in which a first injection valve for direct injection is assigned to each cylinder and which has at least one second injection valve for intake pipe injection which is not cylinder-specific, makes it possible to identify and compensate cylinder and individual filling differences and/or mixture composition differences for a system with intake pipe injection injectors which are not cylinder-specific.

In this case, the method provides for the system and/or motor-specific filling and/or mixture distribution differences to be determined by varying the injection quantity injected by means of direct injection, and for motor-specific and cylinder-specific corrections to be determined therefrom in order to compensate for the greater or lesser quantity injected via the intake manifold. This achieves, for example, a critical improvement in comfort through better operating stability, but of course also a reduction in exhaust emissions and a reduction in energy consumption. This is achieved by minimizing the mix deviation for cylinder personalization. It is also advantageous for the exhaust gas aftertreatment system, for example a 3-way catalyst, based on less strongly HC and CO-loaded raw exhaust gas to be loaded to a lesser extent. It is also advantageous to reduce the number of valves for intake pipe injection, i.e. the number of intake pipe injectors, by the method according to the invention without adverse consequences with regard to exhaust emissions, performance and comfort.

Advantageously, according to one embodiment of the method, the determination of the cylinder-specific filling difference and/or mixture distribution difference and the determination of the motor-specific and cylinder-specific correction are carried out in repeated processes for compensating a larger or smaller quantity caused by the intake pipe injection (PFI), wherein in each process an incremental cylinder-specific correction is determined in order to compensate a larger or smaller quantity caused by the intake pipe injection (PFI). These repeated processes and incremental cylinder-specific modifications represent to some extent a learning method.

According to an advantageous embodiment of the method, it is provided that the system-dependent and/or motor-dependent cylinder-dependent filling difference and/or mixture distribution difference is determined by determining a cylinder-dependent lambda difference and/or a rotational speed difference.

In this case, according to an advantageous embodiment, it is provided that the individual lambda difference of the cylinders is determined by means of a single cylinder lambda measurement. By means of such a per se known individual cylinder lambda determination, a cylinder-specific mixture composition in the selected operating point is detected by means of one or more lambda sensors and then cylinder-specifically correlated.

In addition, according to an advantageous embodiment, it is provided that the determination of the rotational speed difference is carried out by means of a known running stability controller. The individual compression and decompression of the cylinders is determined by means of a rotational speed signal measured, for example, by a transmitter wheel and a normalized mean value is formed across all cylinders. The upward and downward deviations are compensated by means of correcting the individual injection quantities of the cylinders.

The cylinder-specific, quantitative DI correction enables a precise setting of the lambda value (lambda = 1) and/or an optimal running stability. Depending on the speed profile and/or the cylinder-specific lambda, incremental cylinder-specific corrections or changes in the directly injected injection quantity, also referred to as DI quantity, are carried out for so long as a specific higher quantity is reached. This correction is performed in a learning process to some extent in an iterative process.

According to an advantageous embodiment of the method, it is provided that the cylinder-specific DI correction and thus the compensation of a larger or smaller quantity, both implicitly and by way of the intake manifold injection, is provided in a load-dependent and rotational speed-dependent manner to a cylinder-specific pilot control of the injection quantity injected by means of direct injection.

In a further embodiment of the method, it is provided that the cylinder-specific correction of the injection quantity injected by the direct injection is provided to a cylinder-specific pilot control of the injection quantity produced by the intake pipe injection, also referred to as PFI injection, as a function of load and as a function of rotational speed.

In a further embodiment of the method, it is provided that a cylinder-specific correction of the injection quantity injected by direct injection is provided to at least one pilot control of the injection quantity resulting from Direct Injection (DI) and from intake pipe injection (PFI) which is cylinder-specific as a function of load and rotational speed, wherein the distribution of the quantity injected by Direct Injection (DI) and the distribution of the quantity resulting from intake pipe injection (PFI) are carried out as a function of the real-time relationship of the injection quantities resulting from direct injection and intake pipe injection (PFI).

The cylinder-specific DI quantity correction can thus be taken into account and provided to the pilot control of the DI injection and the pilot control of the PFI injection and to the two pilot controls or to the common pilot control of the DI injection and the PFI injection.

The method can 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 executed, in particular when the computer program runs on a computing device or a controller. The computer program enables the implementation of the method on a conventional electronic control unit without structural changes having to be made at the control unit. In this case, it is stored, for example, on a storage medium that can be read by a machine. By running a computer program on a conventional electronic control unit, an electronic control unit according to the invention is obtained which is configured to: by means of the method according to the invention, cylinder-specific filling differences and/or mixture distribution differences are determined by means of the injection quantity injected by direct injection, and from these motor-specific and cylinder-specific quantity corrections are determined in order to compensate for the greater or lesser quantity resulting from the injection through the intake manifold.

Drawings

Embodiments of the invention are illustrated in the accompanying drawings and are explained in further 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 provides that a system-and/or motor-specific filling difference and/or mixture distribution difference is determined by varying the injection quantity injected by means of Direct Injection (DI), and a motor-specific and cylinder-specific correction is determined therefrom in order to compensate for the greater or lesser quantity resulting from the intake pipe injection (PFI). This is done in that a cylinder-specific filling difference and/or a mixture distribution difference, which is conditioned on the system and/or the motor, is 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, for example, by means of a so-called single cylinder lambda measurement. By means of the individual cylinder lambda determination, cylinder-specific mixture compositions at the selected operating point are detected by means of one or more lambda sensors and can be cylinder-specifically modified.

The rotational speed difference is determined, for example, by means of a running stationarity regulator. In this case, the individual compression and decompression of the cylinders is measured by means of the rotational speed signal and a normalized mean value is formed for all cylinders. The upward and downward deviations can be compensated by means of correcting the individual injection quantities of the cylinders.

By means of the method according to the invention, the system-dependent/motor-dependent cylinder-dependent filling and mixture distribution differences are determined by a change in the cylinder-dependent quantity of the directly injected injection quantity as a function of the quantity distribution between the direct injection and the intake pipe injection. This is achieved by the abovementioned running stability controller and/or by the abovementioned individual cylinder lambda measurement. These motor-specific and cylinder-specific corrections (hereinafter referred to as DI corrections) are stored in the motor controller and checked and adapted at suitable time intervals in order to be able to indicate and balance the operating-time and aging effects.

By means of the DI correction in terms of the individual quantities of the cylinders, i.e. by changing the injection quantity to be injected directly, an exact setting of the lambda value (lambda = 1) and/or optimum running stability is ensured. For example, if the cylinder-specific injection quantity is too small, an excessively small rotational speed profile and/or an excessively lean cylinder-specific lambda is determined, which leads to an incremental cylinder-specific correction or a change in the directly injected injection quantity (hereinafter referred to as DI quantity) up to a specific, higher quantity. By means of this incremental cylinder-individual correction, a learning method can be discussed to a certain extent.

The cylinder-specific DI correction and thus the compensation of a larger or smaller quantity (PFI larger or smaller) by the intake manifold injection is learned as described above as a function of load and speed and can be taken into account in the precontrol unit for the PFI quantity calculation and/or the DI quantity calculation in the manner described below.

According to a first exemplary embodiment, such a cylinder-specific learned DI correction is taken into account in a pre-control of the cylinder-specific DI quantity in a further operation as a function of load and rotational speed.

According to a further embodiment, the cylinder-specific learned DI quantity is corrected in a pilot control which takes into account the cylinder-specific PFI quantity in a further operation depending on load and rotational speed.

In a third exemplary embodiment, in the pilot control of the cylinder-specific learned DI quantity, which is taken into account in the further operation depending on the load and the rotational speed, the cylinder-specific PFI and DI quantity, a correction quantity assignment of PFI-DI is effected in accordance with the real-time PFI-DI split, i.e. the PFI-DI ratio.

The method described makes it possible to dispense with the individual dosing of fuel to the cylinders for intake manifold injection. In fact, also with the aid of so-called single injection, i.e. only one valve for intake manifold injection or in the case of one valve for intake manifold injection for both cylinders, etc., a precise cylinder-specific correction is possible by the method according to the invention.

The method can be implemented as a computer program and stored as a computer program in the controller 3 of the vehicle. The controller also includes the above-mentioned pre-control section.

Claims

1. Method for operating an internal combustion engine (1) of a vehicle with a fuel injection system (2), in which at least one first injection valve (16) is associated with each cylinder for direct injection and which has at least one second injection valve (17) that is not cylinder-specific for intake pipe injection, no valve for intake pipe injection being associated with each cylinder, the number of injection valves for intake pipe injection of fuel being smaller than the number of cylinders, characterized in that a system-and/or motor-specific filling difference and/or mixture distribution difference is determined by varying the injection quantity injected by means of the Direct Injection (DI) and a motor-and cylinder-specific correction is determined therefrom in order to compensate for a greater or lesser quantity caused by the intake pipe injection (PFI).

2. Method according to claim 1, characterized in that the determination of the cylinder-specific filling difference and/or mixture distribution difference and the determination of the motor-specific and cylinder-specific corrections for compensating for a larger or smaller amount caused by the intake pipe injection (PFI) are carried out in repeated processes, wherein in each process an incremental cylinder-specific correction is determined in order to compensate for a larger or smaller amount caused by the intake pipe injection (PFI).

3. Method according to claim 1, characterized in that the cylinder-specific filling difference and/or the mixture distribution difference, which are caused by the system and/or by the motor, are determined by determining a cylinder-specific lambda difference and/or a rotational speed difference.

4. A method according to claim 3, characterized in that the cylinder-specific lambda difference is determined by means of a single cylinder lambda measurement.

5. A method according to claim 3, characterized in that said determination of said difference in rotational speed is effected by operating a stationarity regulator.

6. Method according to any of the preceding claims 1 to 5, characterized in that a cylinder-specific correction of the injection quantity injected by direct injection is provided to a cylinder-specific pilot control of the injection quantity injected by means of Direct Injection (DI) in a load-and rotational speed-dependent manner.

7. Method according to any of the preceding claims 1 to 5, characterized in that a cylinder-specific correction of the injection quantity injected by direct injection is provided to the cylinder-specific pre-control of the injection quantity caused by means of injection (PFI) through the intake pipe, depending on load and rotational speed.

8. Method according to any one of the preceding claims 1 to 5, characterized in that a cylinder-specific correction of the injection quantity injected by direct injection is provided to at least one pre-control of the cylinder-specific injection quantity caused by Direct Injection (DI) and the injection quantity caused by intake pipe injection (PFI) in a load-and rotational speed-dependent manner, wherein the distribution of the quantity injected by Direct Injection (DI) and the distribution of the quantity caused by intake pipe injection (PFI) is carried out in dependence on the real-time ratio of the injection quantities caused by Direct Injection (DI) and intake pipe injection (PFI).

9. 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 any one of claims 1 to 5.

10. An electronic control unit (3) configured to: cylinder-specific filling differences and/or mixture distribution differences are determined by means of the injection quantity injected by direct injection, and from this motor-specific and cylinder-specific quantity corrections are determined by means of the method according to any one of claims 1 to 5 in order to compensate for the greater or lesser quantity caused by the intake pipe injection.