WO2014202202A1

WO2014202202A1 - Method and control system for correcting the injection duration of injectors of an internal combustion engine

Info

Publication number: WO2014202202A1
Application number: PCT/EP2014/001634
Authority: WO
Inventors: Andreas Mehr; Carsten ENGLER; Michael Walder; Robby Gerbeth; Alexander Bernhard; Frank Schwanz; Christian Wolf
Original assignee: Mtu Friedrichshafen Gmbh
Priority date: 2013-06-20
Filing date: 2014-06-16
Publication date: 2014-12-24
Also published as: DE102013211731A1

Abstract

The invention relates to a method for correcting the injection duration of injectors (1) of an internal combustion engine (2), the method comprising the following steps: Determining an injection duration set value (3); detecting a pressure in a single memory (4) of an injector (1) and determining a measured injection duration (27) based on the pressure; determining the actual value (31) of the injection duration based on the measured injection duration (27); comparing the injection duration set value (3) and the injection duration actual value (31), and calculating an injection duration correction value (13) based on the comparison, and applying the injection duration correction value (13) to the correction of a duration of current feed (21) for the injector (1).

Description

DESCRIPTION

METHOD AND CONTROL DEVICE FOR CORRECTING THE INJECTION TIME OF INJECTORS OF AN INTERNAL COMBUSTION ENGINE

The invention relates to a method for correcting the injection duration of injectors of an internal combustion engine according to claim 1 and to a control device for a

Internal combustion engine according to the preamble of claim 10.

From the German patent application DE 31 26 393 AI a fuel injection system with a common memory and a plurality of injectors is known, wherein the individual injectors are each associated with individual memory. Each individual memory is assigned a high-pressure converter, that is to say a device for measuring the pressure of a pressure in the individual memory. Based on the pressure drop in the individual memories is injected

Fuel quantity determined. This is also corrected. However, the fuel injection system known from the cited document does not correspond to a modern injection system with several injectors, in particular no modern injection system, which has a common high-pressure accumulator, namely a so-called common rail, wherein injectors of the injection system each have a single accumulator as an additional buffer volume , Accordingly, the known method for correcting the amount of injected fuel is not applicable to a modern injector. It can be seen that the injected fuel quantity depends on the duration of injection and thus, in particular, on the duration of energization of an injector, whereby a nozzle needle of the injector is displaced and opened by the energization. If the energization ends, the nozzle needle is moved back into its closed position. Thus, the duration of injection - briefly the injection duration - of the injector is determined over the Bestromungsdauer, which in turn is determined by the injection amount of fuel, in particular depending on an injection start pressure applied to the injector at the beginning of the injection. Typically, in a control device for the internal combustion engine, a characteristic map is stored, which comprises global energization duration values for all injectors of the internal combustion engine as a function of an amount of fuel to be injected and the injection start pressure. Become accordingly identical values are taken from this map for all injectors. It turns out, however, that different injectors respond differently to an energization, thus having different injection durations with identical energization duration. The injectors of a

Internal combustion engine are therefore as far as possible initially before or at the beginning of commissioning of the internal combustion engine, equal, so that they inject an amount of fuel injected in default by the control device identically. It also shows that the response of the injectors varies over their lifetime. Thus it is

desirable, the injectors also during the operating time of the internal combustion engine in

With regard to the duration of injection and thus to be able to equate the injected fuel quantity.

The invention has for its object to provide a method and a control device for an internal combustion engine, with the aid of which the injection duration of injectors can be corrected. It should be possible in particular to equate different injectors of the internal combustion engine not only initially with regard to the injected fuel quantity, but also during the operating time of the internal combustion engine.

The object is achieved by providing a method with the steps of claim 1. As part of the process, a nominal injection duration is determined. In this case, the injection duration desired quantity with the amount of fuel to be injected, in particular the

fuel mass to be injected or the volume of fuel to be injected, functionally linked - in the sense of a physical or mathematical dependency. This includes that the injection duration desired variable is preferably identical to the fuel quantity to be injected, particularly preferably to the fuel volume to be injected. A pressure in an individual memory of an injector during an injection event is detected, and a measured injection duration is determined on the basis of the detected pressure. Based on this measured injection duration, an actual injection duration size is determined. The injection duration setpoint and the

Actual injection duration are compared with each other and an injection duration correction variable is calculated on the basis of the comparison of the two variables. Finally, the injection duration correction variable is used for the correction of an energization duration for the injector. In the context of the method, it is therefore possible, the energization of a single injector with regard to an amount of fuel to be injected or a

correct actual injection duration. Furthermore, it is possible to inject different injectors of the internal combustion engine in terms of their injection duration and thus the injected Equalize fuel quantity when the method is performed for all injectors of the internal combustion engine. In this case, the method can readily both initially before or at a first start of the internal combustion engine, as well as during their operating time

be performed to compensate for a later occurring, injector-individual drift.

The pressure in the individual memory is preferably detected and stored as a time-resolved pressure curve. The actual, measured injection duration is then determined from the stored pressure profile, preferably by determining an injection start and an injection end. A method suitable for this purpose is known from the German patent application DE 10 2009 056 381 AI, wherein it is apparent that an injection period from the injection end and the

Start of injection can be determined, for example, in which the start of injection is subtracted from the injection end.

The comparison of the injection duration setpoint and the actual injection duration is carried out in a preferred embodiment of the method directly by the two variables are compared directly. In another embodiment of the method, it is possible that a first derived variable is determined from the injection duration desired size, while from the

Injection duration actual size, a second derived variable is determined, and wherein the comparison of the injection duration target variable with the injection duration actual size is carried out indirectly or indirectly such that the first derived variable is compared with the second derived variable.

The method is feasible for each injection event. It is thus possible to carry out the method for a pilot injection, for a main injection and / or for a secondary injection.

A method is preferred which is characterized in that the injection duration correction variable is stored in a correction map associated with the injector.

Alternatively, it is possible for the injection duration correction variable to be stored in a correction map, which is provided as a global field for all injectors, but includes a parameter for assigning the registered values to the individual injectors, so that the injection duration correction variable is individual for the considered injectors in the

Map can be filed. This alternative procedure ultimately results in the same result as the previously described procedure, in which each injector is assigned its own correction map. In both cases, one results Injektorindividuelle assignment of the injection duration correction variable, so that an injector-individual correction of the energization duration for the injectors of the internal combustion engine is possible.

Particularly preferably, a global energization duration predetermined for all injectors is offset with the injection duration correction variable stored in the injector-individually in order to determine an individual energization duration for each injector. In this way, it is in particular possible to equate the various injectors with regard to their injection duration and thus also with regard to the injected fuel quantity. A method is preferred which is characterized in that the actual duration of the injection duration is read from a size characteristic field, which preferably comprises values averaged over a plurality of injectors. The size map includes values for the actual duration of the injection duration as a function of the measured injection duration. Preferably, the map includes the injection start pressure as a further parameter on which the injection duration actual size depends. The size map is not in a preferred embodiment of the method

injector-individual but global to all injectors, preferably including values averaged over an order of magnitude of about one hundred injectors. It is assumed that the actual duration of the spray duration deviates only slightly from the mean value stored in the size characteristic field for a given injection duration. The method is therefore based on the idea to equate the injectors in terms of their response to the energization, it being assumed that the actual injection duration of the injectors is different for the same Bestromungsdauer. It is further assumed that the injectors have an approximately equal injection duration actual size for a given injection duration. The injection start pressure responds to the pressure applied to the injector before or immediately at the start of injection. In this case, this pressure corresponds both to a pressure prevailing in the individual memory at that time and to the same time in the individual memory

common high-pressure accumulator prevailing pressure. These are namely in fluid communication with each other, and there is no fuel flow instead of with the injector closed, so that an identical static pressure prevails both in the common high-pressure accumulator and in the individual accumulator. It is therefore possible to detect the injection start pressure by means of a pressure sensor provided in the region of the common high-pressure accumulator, while the pressure in the individual accumulator for determining the duration of injection is detected by means of a pressure sensor provided thereon. Because the pressure in the common high-pressure accumulator less varied in time than the pressure in the individual memories, it is advantageous than

Input variable for maps, which include values dependent on the injection start pressure, to use the injection start pressure measured in the area of the common high-pressure accumulator.

The injection duration correction variable is also preferably used in the correction map

Dependence on the injection start pressure stored. It is obvious that the injection start pressure is a quantity from which the actually injected fuel quantity depends on the injection duration. Therefore, it makes sense in principle to consider a dependency of the variables considered here on the initial injection pressure.

A method is also preferred in which the injection duration desired value is a

amount of fuel to be injected, in particular a fuel mass to be injected or preferably a fuel volume to be injected, is used. Accordingly, the injection duration actual size is preferably an injected fuel quantity, in particular a

injected fuel mass or preferably an injected fuel volume determined, namely on the basis of the measured injection duration.

The injection duration desired value is preferably determined by the control device for the

Internal combustion engine, in particular depending on a power demand or

Determined torque demand on the internal combustion engine, preferably also from a map. Another parameter is the determination of the injection duration setpoint

preferably a speed of preferably designed as a reciprocating engine

Internal combustion engine.

A method is preferred in which the injection duration setpoint and the actual injection duration are directly offset from one another. In this case, the injection duration correction variable is preferably determined as the difference between the injection duration setpoint size and the actual injection duration size. From the injection duration setpoint and the injection duration correction variable, a corrected injection duration setpoint is preferably calculated. On the basis of this corrected injection duration target variable, a supply duration for the injector is preferably determined, which is corrected with regard to the injection duration or the injected fuel quantity. In this case, it is provided in a preferred embodiment of the method that the injection duration setpoint and the actual duration of the injection duration are the quantities of fuel to be injected or injected Fuel quantity can be determined. As a spray duration correction quantity then goes from the process, a deviation of the actually injected fuel amount of the

amount of fuel to be injected. On the basis of this deviation, a corrected amount of fuel to be injected is calculated, from which finally a corrected energization time for the injector is determined.

Alternatively, a method is preferred, which is characterized in that based on the

Duration of injection setpoint a desired energization time for the injector is determined. From the actual injection duration, a virtual lighting duration is determined. In the context of this embodiment of the method, the injection duration target variable is compared indirectly with the actual duration of the injection duration by calculating the desired energization duration with the virtual energization duration. In this case, the target energization duration represents a first derived variable and the virtual energization duration represents a second derived variable which are offset with one another in order to indirectly compare the injection duration target variable and the injection duration actual variable. The injection duration correction variable is preferably calculated as the difference between the desired energization duration and the virtual energization duration. A corrected energization duration for the injector is calculated from the desired energization duration and the injection duration correction variable. The injection duration correction variable is preferably added to the desired energization duration. In this case, the injection duration correction quantity is signed, the direction of the correction, that is to say for a longer or a shorter energization duration, being defined by the sign.

It is possible that the lighting duration is actually determined as a duration - either in units of time or in units of a crank angle of the internal combustion engine - or used in the context of the method. Alternatively, it is possible that the energization period is characterized indirectly by specifying a pair of values from the start of energization and end of energization. Here is the mathematical relationship between the

On the one hand and on the other hand, the energizing time on the one hand and the beginning of the energization on the other hand obviously, so that the corresponding information can be easily converted into each other. It is possible that the injection duration correction variable comprises a pair of values corresponding to a correction value for the start of energization and a

Correction value for the Bestromungsende has. Alternatively, it is also possible for the injection duration correction variable to have only one correction value for either the start of energization or the end of energization. However, preferred is a method in which the

Energizing duration is directly characterized by a value directly indicative thereof, wherein the injection duration correction quantity is also indicated as a value by which the energization period is corrected as such.

A method is preferred in which the desired energization duration and the virtual energization duration are read out from an injector characteristic map, which preferably comprises values averaged over a multiplicity of injectors. In particular, the desired energization duration and the virtual energization duration are preferably read from the same injector characteristic field. The injector map also preferably includes the injection start pressure as an additional parameter, on which the duration of the application of power stored in the map depends. In particular, therefore, depends on the stored in the injector map energization duration

preferably from the injection duration setpoint, particularly preferably from an amount of fuel to be injected, and from the injection start pressure.

A method is also preferred, which is characterized in that the injection duration correction variable is weighted. The weighting serves, in particular, to compensate for outliers and thus for a certain damping or deceleration of the control according to the method in order, in particular, to prevent the energization period from being regulated as a result of short-term events. In this respect, a controlled over the duration of the duration of the injection duration by means of the weighting is smoothed. Preferably, the injection duration correction quantity is reduced in weighting while maintaining the sign with respect to its magnitude. This can be done, for example, by a

Weighting factor is multiplied by the injection duration correction quantity. Of course, other forms of weighting, in particular by using a

Weighting parameter possible. The weighting parameter is preferably read out from a characteristic field which determines its values as a function of the fuel to be injected

Fuel quantity and the injection start pressure includes. Instead of the injected

Fuel quantity can also be deposited as a parameter in the map of this associated setpoint for the energization. In a preferred embodiment of the method, the injection duration correction variable and / or the corrected injection duration are still corrected on the basis of a value which originates from a separate correction for the start of energization. In this way it is ensured that a correction of the start of energization has no influence on the correction of the energization duration and thus ultimately on the energization end of the injection. Finally, a method is preferred which is characterized in that it is carried out for each injector of the internal combustion engine. Each injector is assigned a correction map. For each injector so own injector individual injection duration correction quantities are preferably deposited depending on the amount of fuel to be injected and the injection start pressure. The injectors of the internal combustion engine are made equal by means of the method. It is provided according to an embodiment of the method that the various injectors initially, so at the time commissioning of

Internal combustion engine to be assimilated. Alternatively or additionally, it is provided that the injectors with the aid of the method during the operating time of the internal combustion engine

be equalized to compensate for injector drift over the life of the injectors. Equalization of the injectors is understood to mean that each injector is assigned an individual energization duration in such a way that the injection durations of the different injectors are the same, as a result of which the individual injectors are dependent on a target specification

Injectors injected fuel quantities are the same.

Finally, the object is also achieved by providing a control device for controlling an internal combustion engine having the features of claim 10. The

Control device is characterized in that it is set up for carrying out a method according to one of the previously described embodiments. It is possible that the method steps are firmly implemented in a hardware of the control device. Alternatively or additionally, a computer program product is loaded into the control device, which comprises instructions on the basis of which the control device carries out the method when the computer program product is running on the control device.

It is possible that the control device has separate devices for carrying out different method steps. For example, it is possible that the

Control device comprises an engine control unit, which determines the injection duration setpoint and corrected by means of the injection duration correction quantity an energization duration for an injector and energized the injector. It is possible that in a separate

Analyzer the individual storage pressure of the injector detected and based on the detected pressure, the measured injection time is determined. In this case, an actual injection duration variable is also preferably determined in the analysis device on the basis of the measured injection duration. The comparison of the injection duration setpoint with the actual injection duration and the calculation of the Injection duration correction variable may be performed in the engine controller or, alternatively, in the separate analyzer. In this case, the analysis device is preferably operatively connected to the engine control unit, so that in particular data between the two

Devices are interchangeable.

In an alternative embodiment of the control device is provided that this comprises only a device, in particular an engine control unit, on which the entire process takes place. The control device preferably has a first interface via which it is operatively connected to a single accumulator pressure sensor. It preferably has a second one

Interface via which it is operatively connected to at least one injector to energize it. Finally, the control device preferably has a third interface via which it is operatively connected to a pressure sensor in the region of the common high-pressure accumulator, with the aid of this pressure sensor in particular determining the start of injection pressure as the input variable for the various characteristic diagrams.

The method and the control device are intended for use in one

Internal combustion engine having an injection system, which preferably has a

having common high-pressure accumulator and particularly preferably single memory as additional buffer volumes in the region of the individual injectors. The internal combustion engine is preferably designed as a reciprocating piston engine. It can be used to power land vehicles, watercraft, especially ships, or aircraft. In the area of land vehicles, especially heavy vehicles such as self-propelled

Harvesting vehicles, construction machinery, open-pit mining vehicles, railcars or

Locomotives for trains and defense vehicles such as tanks in question. The internal combustion engine can also be used for stationary applications, for example for emergency power supply, in peak load operation or in continuous load operation. For example, a use of the internal combustion engine in a combined heat and power plant is conceivable. Also, the stationary operation of auxiliary or auxiliary equipment, such as

Fire pumps on drilling rigs, is possible. A liquid or gaseous fuel is preferably injected via the injection system, for example gasoline, diesel, heavy oil, methanol, ethanol, a higher alcohol, natural gas, biogas, lean gas or special gas. This list is not exhaustive. By means of the injection system, any, fluid Be injected with fuels for use in an internal combustion engine with

Single point injection, multi-point injection and / or direct injection are suitable.

The invention will be explained in more detail below with reference to the drawing. Showing:

1 is a schematic block diagram of the energization of an injector according to an embodiment of the method, and

2 shows a schematic block diagram representation of a correction of the energization duration in FIG

Frame of an embodiment of the method.

1 shows a block diagram in which the energization of an injector 1 of an internal combustion engine 2 is shown schematically. In the context of the embodiment of the method is as an injection duration target value 3 of an engine control unit based on a Lei stungs wish or a load or torque demand and preferably also dependent on a current speed of the internal combustion engine an amount of fuel to be injected, preferably as fuel mass or particularly preferably as fuel Volume, determined. In addition, an injection start pressure 5 is determined, preferably in the region of a common high-pressure accumulator by a pressure sensor. From an injector map 7, depending on the injection duration setpoint 3, in this case of the fuel quantity to be injected, and depending on the injection start pressure 5, a target energization time 9 is read out. In this case, the injector characteristic map 7 is not designed individually for individual injectors, but rather comprises values obtained in the context of averaging over a plurality of injectors, preferably of the order of magnitude of about one hundred injectors. The target energization time 9, which is determined here for the injector 1, is therefore a global one

Bestromungsdauer, which is determined identically for all injectors 1 at the same input values for the map 7, namely the injection duration target size 3 and the injection start pressure 5. The injection duration target variable 3 and the injection start pressure 5 are also used as an input variable in a correction map 11, from which an injection duration correction variable 13 is read out depending on the injection duration target variable 3 and the injection start pressure 5. The correction map 11 includes injector-individual correction values, in this case it is tuned to the injector 1 or comprises the values of the injection duration correction variable 13 determined for it. The injection duration setpoint quantity 3, that is to say the quantity of fuel to be injected and the injection start pressure 5, are preferably filtered before the correction characteristic field 11 is read out. For this purpose, two transmission members 15, 17 are provided in the illustrated embodiment, wherein the transmission members 15, 17 are preferably formed as a low-pass and more preferably as PT1 members. The filtering prevents the internal combustion engine 2 from swinging open due to the regulation in the context of the method, since an algorithm for evaluating the individual accumulator pressure over the injected one

Fuel quantity is directly coupled to a speed controller of the internal combustion engine 2. The transmission elements 15, 17 preferably each have two time constants. A first time constant is defined for the stationary operation of the internal combustion engine 2, that is to say for operating states in which a load point of the internal combustion engine 2 does not change. A second time constant is provided for a transient operation of the internal combustion engine 2, in which the load point changes. The use of the time constant is preferably switched by the engine control unit according to an operating state of the internal combustion engine 2, in particular via a bit which can be set to zero or to one depending on the operating state.

The injection duration correction variable 13 is here a summand, which is added in an addition element 19- with a positive or negative sign - to the target energization time 9. In this way, a corrected energization duration 21 is calculated, with which the injector 1 is driven.

The steps illustrated in FIG. 1 are preferably carried out by a control device 23, in particular by the engine control unit. Accordingly, the

Control device 23 indicated here by a dashed line.

2 shows a block diagram which schematically illustrates the correction of the energization duration in the context of an embodiment of the method. In particular, it is shown in FIG. 2 how the injection duration correction variable 13 is obtained or how the injector-specific correction characteristic map 11 is fed. For this purpose, either by the engine control unit or - as shown in Figure 2 - detected by a separate analysis device 25, a pressure in an individual memory 4 of the injector 1, namely in particular as time-resolved pressure curve, wherein on the basis of the pressure or the time-resolved pressure curve, a measured injection duration 27 is determined.

Based on the measured injection duration 27 is from a size map 29, which is designed as a quantitative map, preferably as a mass map or volume map, an injection duration actual size 31 - in the dargstellten embodiment as actually injected fuel or - there it is determined on the basis of a calculation - determined as a virtually injected amount of fuel. The values for the actual injection duration 31 stored in the size map 29 preferably also depend on the

Injection start pressure 5 from which is also taken into account when reading the size map 29. The size map 29 is a global map, which is the same for all injectors 1. It preferably includes values averaged over a plurality of injectors, preferably of the order of about one hundred injectors. Based on the injection duration actual size 31 from the injector map 7 is a virtual

Bestromungsdauer 33 read out, wherein - as already stated in connection with Figure 1 - the injector map 7, the values for the energization duration as a function of the

Injection start pressure 5 includes, which is also used so far to read the virtual Bestromungsdauer 33 from the injector map 7. It is preferably accessed here on the same injector map 7, which is also addressed in connection with Figure 1. This is possible because the actual injection duration 31 represents an actual or virtually injected quantity of fuel, while in FIG

Duration of spray duration 3 represents an amount of fuel to be injected. Analogously to FIG. 1, also in FIG. 2, parallel to the determination of the virtual

Bestromungsdauer 33, the target Bestromungsdauer 9 from the injector map 7 using the injection duration target size 3 and the injection start pressure 5 read.

In the illustrated embodiment of the method, the injection duration target size 3 and the injection duration actual size 31 are indirectly compared with each other by determining the desired energization time 9 as the first derived variable on the basis of the injection duration target size 3, wherein from the injection duration actual size 31 as the second derived size the virtual lighting duration 33 is determined. The target energization time 9 is then offset against the virtual energization duration 33, the virtual energization duration 33 being subtracted from the desired energization duration 9 in a subtraction element 35. In this way, it is preferable to calculate as the difference of these values an unweighted injection duration correction variable 37, which is determined by a

Weighting element 39 is weighted. The weighting in the weighting element 39 is preferably parameterizable, wherein a weighting parameter is read from a map, not shown, as a function of the fuel quantity to be injected and the injection start pressure and used for weighting. The weighting in the weighting element 39 is preferably designed such that it takes about thirty to fifty cycles of the process until all the injectors 1 of the

Internal combustion engine 2 are equal. The compensation by the method is thus preferably delayed by means of the weighting element 39 in order to be able to compensate for outliers and to prevent the regulation from occurring immediately when an outlier occurs

or running quickly into a boundary.

In a preferred embodiment of the method, a result from a calculation of the start of energization is additionally added to ensure that a correction of the start of energization has no influence on the correction of the energization duration.

In this way, the injection duration correction variable 13 is ultimately calculated and in the injector-specific map 11 for the injector 1 considered here depending on the

Duration of injection setpoint 3 and the injection start pressure 5 stored or stored. In this way, the correction map 11 is constantly re-fed in the course of the process, wherein - as shown in Figure 1 - the always current injection duration correction variable 13 is available to the injector 1 from the target energization time 9 and the injection duration Correction quantity 13 to calculate the corrected energization duration 21. It is possible that all the steps shown in FIG

Determination of the injection duration target size 3, which can be provided by the engine control unit, are performed in the analysis device 25. Alternatively, it is possible for the steps illustrated in FIG. 2 to be carried out by the engine control unit, while only the measured injection duration 27 is determined by the analysis device 25. Finally, it is possible that no separate analysis device 25 is provided, but that it is rather implemented in quasi the engine control unit, so that the measured injection duration 27 is also calculated by the engine control unit.

Overall, it is apparent that with the aid of the method and the control device 23 it is possible to correct the energization duration for different injectors 1 of an internal combustion engine 2 not only initially but also during the operating time to compensate an injector drift, whereby the injectors 1 can ultimately be assimilated.

Claims

1. A method for correcting the injection duration of injectors (1) of an internal combustion engine (2) with the following steps:

Determining a duration of injection duration (3);

Detecting a pressure in a single reservoir (4) of an injector (1) and determining a measured injection duration (27) from the pressure;

- Determining a duration of injection actual size (31) based on the measured injection duration (27);

- Compare the injection duration target size (3) and the injection duration actual size (31), as well

Calculating an injection duration correction quantity (13) from the comparison, and

- Using the injection duration correction variable (13) for correcting a Bestromungsdauer (21) for the injector (1).

2. The method according to claim 1, characterized in that the injection duration correction variable (13) in a the injector (1) associated correction map (11) is stored.

3. The method according to any one of the preceding claims, characterized in that the injection duration actual size (31) from a size map (29) is read, the

preferably via a plurality of injectors (1) averaged values.

4. The method according to any one of the preceding claims, characterized in that as the injection duration target size (3) an amount of fuel to be injected is used, wherein an injected fuel quantity is determined as the injection duration actual size (31).

5. The method according to any one of the preceding claims, characterized in that the injection duration target size (3) and the injection duration actual size (31) are offset directly with each other, wherein the injection duration correction quantity (13) as a difference of the injection duration target size (3) and the injection duration actual variable (31) is determined, and wherein from the injection duration setpoint (3) and the injection duration correction variable (13) a corrected injection duration setpoint is calculated, based on which a Bestromungsdauer for the injector (1) is determined. Method according to one of the preceding claims 1 to 4, characterized in that on the basis of the injection duration target size (3) a target energization time (9) for the injector (1) is determined, from the injection duration actual size (31) a virtual lighting duration (33) is determined, and wherein the injection duration desired variable (3) with the injection duration actual size (31) is compared by the desired energization time (9) with the virtual

Bestromungsdauer (33) is calculated, wherein the injection duration correction quantity (13) is calculated as the difference of the target energization time (9) and the virtual lighting duration (33), and wherein a corrected energization time (21) for the injector (1) from the Target energization duration (9) and the injection duration correction variable (13), preferably by addition, is calculated.

Method according to one of the preceding claims, characterized in that the desired energization duration (9) and the virtual energization duration (33) are read from an injector characteristic map (7), which preferably comprises values averaged over a plurality of injectors (1).

Method according to one of the preceding claims, characterized in that the injection duration correction variable (13) is weighted.

Method according to one of the preceding claims, characterized in that the method for each injector (1) of the internal combustion engine (2) is performed, each injector (1) is assigned a correction map (11), wherein the injectors (1) using of the procedure. 10. Control device (23) for an internal combustion engine (2), characterized in that the control device (23) is set up for carrying out a method according to one of claims 1 to 9.