CN107237700B

CN107237700B - Method for adjusting fuel metering

Info

Publication number: CN107237700B
Application number: CN201710193598.4A
Authority: CN
Inventors: D.A.弗赖施泰特; A.布劳; M.胡梅尔
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2016-03-29
Filing date: 2017-03-28
Publication date: 2022-04-26
Anticipated expiration: 2037-03-28
Also published as: CN107237700A; DE102016205107A1

Abstract

The invention relates to aMethod for adjusting the dosing of fuel in an internal combustion engine, in which fuel is introduced into at least one cylinder by at least two different fuel injectors, wherein the total fuel quantity (M) to be introduced into the at least one cylinder (102) is a function of the total fuel quantity_G) Is carried out by means of an adjustment of individual fuel quantities, the total fuel quantity being distributed to the respective individual fuel quantities (M) of the at least two different fuel injectors_S1、M_S2、M_D) And wherein the adjustment of each individual fuel quantity is carried out solely by means of the respective fuel injector in the following cases: in this case, the respective individual fuel quantity (M) for introducing the respective fuel injector is taken into account_S1、M_S2、M_D) And the respective fuel injector is introducing the total fuel quantity (M)_G) The corresponding proportion of the dosing duration.

Description

Method for adjusting fuel metering

Technical Field

The invention relates to a method for adjusting a fuel metering in an internal combustion engine, and to a computing unit and a computer program for carrying out the method.

Background

For the otto motor, two methods for fuel injection are generally known, namely intake pipe injection and direct injection. However, intake manifold injection is increasingly being replaced by direct injection, since direct injection, in particular in operating regions with high load demands, can lead to higher power gains with lower fuel consumption and to more targeted injection strategies.

Furthermore, there are also otto motors with a combination of intake pipe injection and direct injection, so-called dual system. This is precisely advantageous in view of increasingly stringent emission requirements or emission limits, since, in contrast to direct injection, for example, in the medium load range and in the operating range with lower load dynamics (Lastdynamik), intake manifold injection leads to better emission values, whereas direct injection is advantageous in the high rotational speed or load range. Likewise, a reduction in the tendency to knock is achieved by direct injection, which can be used in a targeted manner for protecting the internal combustion engine when a tendency to knock or even knock itself is already recognized or is likely to occur in a specific operating point. The coupling of the two injection modes thus combines the respective advantages of the individual injection systems in different operating regions and enables a novel optimization of the motor characteristics.

Another type of internal combustion engine is an internal combustion engine in which a plurality of fuel injectors for introducing fuel into cylinders are provided for one injection pattern. For example, in an internal combustion engine with intake pipe injection, two fuel injectors for the same injection (i.e., intake pipe injection) can be provided, to which the amount of fuel to be introduced into the cylinders is distributed. In this case, reference is made to the so-called multipoint injection system (mehreinsprinzsystem).

Disclosure of Invention

According to the invention, a method for adjusting a fuel metering in an internal combustion engine, a computing unit and a computer program for carrying out the method are provided having features according to the invention. Advantageous embodiments are subject matter of the preferred embodiments and the following description.

The method according to the invention is used for adjusting the fuel metering, in particular within the scope of mixture adaptation, in an internal combustion engine in which fuel is introduced into at least one cylinder by at least two different fuel injectors. In this case, the adjustment of the total fuel quantity to be introduced into the at least one cylinder is carried out by means of an adjustment of individual fuel quantities, that is to say for each fuel path or each individual cylinder, which are distributed to the respective individual fuel quantities of the at least two different fuel injectors, wherein the adjustment of each individual fuel quantity is carried out in the following cases: in this case, the ratio of the respective metering duration of the respective fuel injector for introducing the respective individual fuel quantity to the respective metering duration of the respective fuel injector when the total fuel quantity is introduced solely by means of the respective fuel injector is taken into account.

In the case of a regulation of the fuel-air ratio for an internal combustion engine, it is possible to superimpose a pilot control on the regulation. The pre-control is mainly used for: the system deviations in the fuel-air ratio are corrected by means of a fuel quantity adjustment, and the adjustment corrects (ausregeln) the actual disturbance. However, the following can occur, in particular as a result of ageing or wear of the components used: due to the changing operating conditions, the pilot control retains the deviation and therefore the pilot control itself should be recalibrated or "adapted".

In particular, a so-called mixture adaptation can be used to compensate for a misadjustment or deviation of the pilot control (due to the mentioned possible aging effects) which occurs over a longer operating period. The mixture adaptation, for example, corrects the deviation of the fuel/air ratio when a deviation of the ideal lambda value (i.e. a lambda value of 1) is measured after combustion and, as a result, after the air path error has been eliminated, the pre-calculated fuel quantity deviates from the ideal situation, for example, due to dynamic influences or permanently in the steady-state operating point. In this way, a fuel path adjustment (i.e., a fuel quantity adjustment) is necessary in order to permanently reach a lambda value of 1 during operation. Preferably, the dosing duration comprises: a control period, i.e. a period during which a control signal is applied to the injector; and/or the duration of opening, i.e. the duration during which the injector is actually open.

In conventional internal combustion engines, in which one fuel injector is provided for each cylinder, or in which only one fuel injector is provided for all cylinders, for example, for the introduction of fuel, the mixture adaptation can be very simply linked linearly to the opening duration of the respective fuel injector, for example, in order to obtain an adjustment of the respective pilot value for the fuel metering.

In internal combustion engines, fuel is introduced into the combustion chamber or chamber of a cylinder by two or more different fuel injectors which together deliver a total fuel quantity for the respective cylinder, for which there are different possibilities for distributing the total fuel quantity to the individual fuel injectors. Depending on the operating region, different distribution ratios (Aufteilung) can be advantageous, for example, for minimizing fuel consumption and/or pollutant emissions. When, for a distribution ratio, one of the fuel injectors is now operated in the limit region, i.e., for example in the region of its minimum adjustable opening duration, significantly greater unreliability occurs for the fuel metering in the limit region than in the case of longer opening durations. The reason for this is, for example, the short opening duration which is difficult to set. If, within the scope of the adjustment of the fuel metering, the adjustment of the respective pilot value of the fuel metering is now effected linearly to the distribution ratio (i.e. the respective portion of the individual fuel quantity of the respective fuel injector in the total fuel quantity), then a possible unreliability occurs precisely in the limit region of the actuation of the fuel injector. This effect is even greater for fuel injectors for intake pipe injection than in the case of fuel injectors for direct injection. The reason for this is that less precise injectors are generally used for intake manifold injection than in the case of direct injection. For direct injection, for example, piezo injectors are used, but for port injection piezo injectors are not used, since historically there were injectors that had to be opened for a longer time due to the front (voragerungen) and therefore the fineness (Feinheit) and the faster opening were not necessary or were already unnecessary. Another reason is that for the injectors of the intake manifold injection, less current is used for opening and therefore also the unreliability occurs more strongly in the case of low loads.

Now the invention starts here, the method is: in the adjustment of the fuel metering and the consequent adjustment of the pilot control value for the individual fuel quantity for reaching the total fuel quantity, the proportion of the mentioned metering duration of the fuel injector concerned is taken into account. In this way, it is possible to take into account the limit region in particular in a different manner than a longer metering duration in the operation of the respective fuel injector. For example, for a distribution ratio for which the fuel injector is operated in the limit region of its minimum possible opening duration, only very small adjustments can be made for the fuel injector, while more drastic adjustments are made for the other fuel injectors, so that overall the total fuel quantity is adjusted as desired. Thereby significantly reducing unreliability. In this case, it can be advantageous if the respective metering duration is already acquired and stored on the control unit before the internal combustion engine is used normally for the first time, for example, within the range measured on a test stand, so that the control unit can be accessed during the implementation of the adjustment.

Preferably, the adjustment of each individual fuel quantity is effected by means of an adjustment of an adaptation value, which is obtained in the following case: in this case, the respective metering duration of the respective fuel injector is taken into account when the total fuel quantity is introduced only by means of the respective fuel injector. In this way, it is possible to take into account the respective proportion of the dosing duration very simply and quickly.

Advantageously, the adaptation value is adjusted in the form of a weighting factor in the following cases: in this case, the ratio of the respective metering duration of the respective fuel injector for introducing the respective individual fuel quantity to the respective metering duration of the respective fuel injector when the total fuel quantity is introduced solely by means of the respective fuel injector is taken into account. By means of such a weighting, simple and adaptive consideration of the respective unreliability can now be achieved when adjusting the respective individual fuel quantity or the respective metering duration.

Advantageously, the adaptation value is obtained in one or more predetermined operating regions of the internal combustion engine. Such an operating region, which is determined, for example, by means of the rotational speed and/or the load requirement of the internal combustion engine, can be selected, for example, with regard to a smooth operation in which deviations can be easily detected.

Preferably, the adaptation value is obtained taking into account the lambda value and in particular the lambda regulation of the exhaust gas of the internal combustion engine. In this case, it can also be advantageous to select a corresponding operating range, for example an operating range in which a lambda value of 1 is set. In this way, it is possible to very easily detect the deviation and to adjust the dosing duration accordingly.

As an internal combustion engine, it is advantageous to use an internal combustion engine in which the at least two different fuel injectors comprise: at least one fuel injector for intake pipe injection and at least one fuel injector for direct injection, and/or at least two fuel injectors for intake pipe injection, and/or at least two fuel injectors for direct injection. As already mentioned, there is a great unreliability in operation in the limit region, in particular for fuel injectors for intake manifold injection. Nevertheless, even with fuel injectors for direct injection, unreliability can occur when operating in the limit range. In this respect, the proposed method is advantageous for any type of internal combustion engine in which fuel is introduced to the cylinders by means of two or more fuel injectors.

The computing unit according to the invention, for example, a control unit of a motor vehicle, is designed in particular in terms of program technology for: the method according to the invention is carried out.

It is also advantageous to implement the method in the form of a computer program, since this results in particularly low costs, especially when the executed controller is also used for other tasks and is therefore already present. Suitable data carriers for providing the computer program are in particular magnetic, optical and electrical memories such as, for example, hard disks, flash memories, EEPROMs, DVDs and other memories. It is also feasible to download the program via a computer network (internet, intranet, etc.).

Drawings

Further advantages and embodiments of the invention emerge from the description and the drawing.

The invention is schematically illustrated in the drawings by means of embodiments and described hereinafter with reference to the drawings. In the drawings:

fig. 1a and 1b schematically show schematic views of two internal combustion engines which can use the method according to the invention;

FIG. 2 schematically shows a cylinder of an internal combustion engine, which cylinder is capable of using a method according to the invention;

fig. 3 shows schematically, in a preferred embodiment, a possible distribution ratio of the total fuel quantity when carrying out the method according to the invention; and is

Fig. 4 shows, in a preferred embodiment, a schematic illustration of the adjustment of the opening duration as dosing duration when carrying out the method according to the invention.

Detailed Description

Fig. 1a shows schematically and in a simplified manner an internal combustion engine 100, which can be used with the method according to the invention. The internal combustion engine 100 illustratively has four cylinders 102 and an intake pipe 106 connected to each of the cylinders 102.

The intake manifold 106 has one fuel injector 107 and one fuel injector 113 per cylinder 102, which are arranged in a respective section of the intake manifold shortly before the cylinder. For the sake of simplicity, only one of all

fuel injectors

107, 113, respectively, is provided with a reference numeral.

Both

fuel injectors

107 and 113 serve for intake pipe injection, for example for gasoline, and only for this injection mode. The

fuel injectors

107 and 113 are supplied with gasoline by a low-pressure pump 150 via a low-pressure line 151. For the sake of simplicity, only the low-pressure line 151 leading to the respective one of the

fuel injectors

107 and 113 is shown, but it goes without saying that each of the

fuel injectors

107 and 113 is connected to a low-pressure line.

Further, each cylinder 102 has a fuel injector 111 for direct injection. For the sake of simplicity, only one of the fuel injectors 111 is provided with a reference numeral. The fuel injector 111 is used only for direct injection of gasoline and is connected with a high-pressure line 162 to a high-pressure accumulator 161, a so-called rail or common rail. For the sake of simplicity, only the high-pressure line 162 leading to one of the fuel injectors 111 is shown, but it goes without saying that each of the fuel injectors 111 is connected to a high-pressure line.

The high-pressure accumulator 161 is in turn supplied with gasoline by a high-pressure pump 160. The high-pressure pump 160 is usually driven by the internal combustion engine. The fuel injectors 111, the high-pressure line 162, the high-pressure accumulator 16 and the high-pressure pump 160 are part of a high-pressure system 165 of the internal combustion engine 100. Both low-pressure pump 150 and high-pressure pump 160 can be connected, for example, to a common tank for gasoline, not shown here.

In the presently illustrated example, fuel is introduced into each cylinder 102 by three different fuel injectors, namely intake manifold injection

respective fuel injectors

107 and 113 and direct injection respective fuel injector 111. However, it is also conceivable and common in practice to introduce fuel into each cylinder by, for example, two fuel injectors, which are each injected exclusively by the intake manifold. Furthermore, it is also conceivable and common in practice to introduce fuel into each cylinder, for example by means of one fuel injector injected by the intake manifold and one fuel injector for direct injection, respectively.

Fig. 1b shows schematically and in a simplified manner another internal combustion engine 200, which can be used with the method according to the invention. The internal combustion engine 200 illustratively has four cylinders 102 and an intake pipe 206 connected to each of the cylinders 102.

The intake manifold 206 here has two common fuel injectors 207 and 213 for, for example, gasoline for all cylinders 102, which are arranged, for example, shortly after a throttle valve, not shown here. The fuel injectors 207 and 213 thus serve intake pipe injection. Furthermore, each cylinder 102 has a fuel injector 111 for direct injection of, for example, gasoline.

Regarding the fuel supply system, the internal combustion engine 200 corresponds to the internal combustion engine 100. In this connection, reference is made to the description there. It is also conceivable and usual here, as also explained with reference to fig. 1a, to provide only fuel injectors for intake pipe injection; or one fuel injector injected by the intake pipe and one fuel injector injected directly, respectively, introduces fuel into each cylinder, which in the present case means that only one of the two fuel injectors injected by the intake pipe is provided.

The difference between the

internal combustion engines

100 and 200 is the manner of intake pipe injection. For example, the intake manifold injection shown in fig. 1a allows individual fuel metering for each cylinder, as can be used, for example, for higher-class (hhwertig) internal combustion engines, whereas the intake manifold injection shown in fig. 1b is simpler in terms of its construction and its actuation. It goes without saying that the intake manifold injection according to fig. 1a can also be combined with the intake manifold injection according to fig. 1b and vice versa, i.e. for example, a separate fuel injector for the intake manifold injection is provided for each cylinder and additionally a common fuel injector for the intake manifold injection is provided for all cylinders.

Fig. 2 shows a cylinder 102 of the internal combustion engine 100 schematically and in a simplified manner, but in greater detail than fig. 1 a. The cylinder 102 has a combustion chamber 103 which is enlarged or reduced by the movement of a piston 104. The position of the piston can be specified here, for example, with reference to the so-called top dead center (OT), in which the piston has reached its (with reference to the drawing) highest point.

The cylinder 102 has an intake valve 105 for introducing air or a fuel-air-mixture into the combustion chamber 103. The air is delivered through an intake pipe 106, which is part of the air delivery, where the

fuel injectors

107 and 113 are located. The drawn air is introduced into the combustion chamber 103 of the cylinder 102 through the intake valve 105. A throttle valve 112 is used in the intake system to set the required mass flow of air into the cylinder 102.

The internal combustion engine is capable of operating during intake pipe injection. During this intake pipe injection, for example, gasoline is injected into the intake pipe 106 as fuel by means of the

fuel injectors

107 and 113, so that an air-fuel mixture is formed there, which is introduced into the combustion chamber 103 of the cylinder 102 via the intake valve 105. The metered fuel quantity can be distributed to the two

fuel injectors

107 and 113 as required.

The internal combustion engine can also be operated during direct injection. For this purpose, the fuel injector 111 is arranged at the cylinder 102 so as to inject, for example, gasoline as fuel directly into the combustion chamber 103. For such direct injection, the air-fuel mixture required for combustion is formed directly in the combustion chamber 103 of the cylinder 102.

Furthermore, the cylinder 102 is provided with an ignition device 110 in order to generate an ignition spark for starting combustion in the combustion chamber 103.

After combustion, combustion exhaust is expelled from the cylinder 102 through an exhaust pipe 108. The exhaust is effected in dependence of the opening of an exhaust valve 109 also arranged at the cylinder 102. The intake and

exhaust valves

105, 109 open and close to perform a four-stroke operation of the engine 100 in a known manner.

The internal combustion engine 100 can be operated with direct injection, intake manifold injection or with hybrid operation. This enables the selection of a correspondingly optimal operating mode for operating the internal combustion engine 100 depending on the current operating point. Therefore, when the internal combustion engine 100 is operated at a low rotation speed and a low load, the internal combustion engine can be operated in an intake pipe injection operation, and when the internal combustion engine is operated at a high rotation speed and a high load, the internal combustion engine can be operated in a direct injection operation.

However, it is expedient in the context of a large operating range to operate the internal combustion engine 100 in a mixed mode in which the fuel quantity to be supplied to the combustion chamber 103 is delivered in portions by intake manifold injection and direct injection, wherein the fuel quantity delivered by means of intake manifold injection can in turn be guided in portions by two fuel injectors injected by intake manifold.

Furthermore, a computing unit designed as a controller 115 is provided for controlling the internal combustion engine 100. The controller 115 can cause the internal combustion engine 100 to operate with direct injection, intake manifold injection, or hybrid operation. Furthermore, a lambda probe 120 provided in the exhaust pipe 108 can be read out by the controller 115.

The functional manner of the internal combustion engine 100 explained in detail with reference to fig. 2 can also be applied to the internal combustion engine 200 according to fig. 1b, which has only the following differences: two common fuel injectors for intake manifold injection are provided for all combustion chambers or cylinders.

Fig. 3 shows a schematic representation of a possible distribution ratio of the total fuel quantity when carrying out the method according to the invention in a preferred embodiment.

For a specific operating range or operating point, which can be predefined, for example, by means of a rotational speed and load range or a rotational speed and load point, the total fuel quantity M can be set_GThe total fuel quantity should be introduced into one cylinder or each of the cylinders.

This total fuel quantity M_GWhich can then in turn be distributed to the individual fuel injectors by means of which fuel is introduced into the cylinder or cylinders concerned. In the present example, with a single fuel quantity M_S1And M_S2To effect injection into the inlet lineDistribution over two fuel injectors and in a single fuel quantity M_DTo effect dispensing to a fuel injector that injects directly.

It goes without saying that for a total of only two fuel injectors, that is to say for example for two fuel injectors for intake manifold injection or for one fuel injector for intake manifold injection and one fuel injector for direct injection there is a distribution to only two fuel injectors accordingly.

In this case, the individual fuel quantity M_S1、M_S2And M_DBy suitable opening duration of the associated fuel injector

、

And

to be implemented. It goes without saying that a corresponding actuation period of the fuel injector is required.

Now, in the mentioned operating region or operating point, it is also possible not to dispense fuel to the respective fuel injector, but rather to dispense fuel of the total quantity M_GIt is also possible to dose by only one fuel injector. The opening duration is required for the respectively selected fuel injector

、

And/or

Is open for a duration of time.

These opening durations can advantageously be recorded in the range of the test stand measurements and stored in a memory on the executing computing unit.

The opening duration corresponding to the respective individual fuel quantity and the opening duration associated with the use of only one fuel injector can now be, for example, G_S1=

/

、G_S2=

/

And G_D=

/

The weighting factor is obtained.

Fig. 4 schematically shows, in a preferred embodiment, the adjustment of the opening duration in the implementation of the method according to the invention.

In certain operating regions or operating points, preferably in steady-state operating points, in which the lambda value is to be kept at 1, mixture adaptation or adjustment of the fuel metering can now be carried out. As already mentioned above, although the fuel metering can be adjusted within the range of the regulation, it is expedient and advantageous to adjust the pilot control value from time to time.

A predetermined total fuel quantity M delivered individually by one of the fuel injectors_GIn this case, each of the fuel injectors is tested in succession, for example, with the aid of the lambda value or in the range of the lambda control. Thus, for example, it is possible to determine: of fuel injectors actually injecting by means of an intake pipeMetered Total Fuel quantity M'_G,S1Greater or less than the total fuel quantity M expected originally_G. This can be determined, for example, by means of a deviation of the lambda value lambda from a setpoint value. The same applies to the actually metered total fuel quantity M 'of the other fuel injectors of the intake manifold injection or of the directly injected fuel injectors'_G,S2And M'_G,D。

The reason for this deviation may be, for example, aging or contamination of the fuel injector, so that, for example, less fuel is metered in than provided for the same opening duration.

By means of the deviation of the current lambda value lambda from the setpoint value (typically lambda = 1) and the knowledge about the setpoint fuel quantity present in the motor control unit, a fuel quantity difference can be calculated in the form of a difference between the setpoint fuel quantity (from the motor control unit) and the actual fuel quantity (from the lambda value).

Taking into account the duration of opening of the associated fuel injector

、

And

and corresponding fuel quantity differences, of which only Δ M is shown here_S1In case of, now, the adaptation value A can be obtained_S1、A_S2Or A_DThe opening duration can be adjusted taking into account the adaptation value

、

And

in order to re-reach the total fuel quantity M by means of each of the fuel injectors_G. For example, it may be necessary to slightly increase these opening durations for this purpose (for example by increasing the amplitude of the adaptation value a as a factor).

For adjusting the total fuel quantity M in the case of the respective opening duration_GIs distributed to the single fuel quantity M_S1、M_S2And M_DIn the above case, as shown on the left in fig. 3, the adaptation value a can now also be used_S1、A_S2And/or A_DBut now with a weighting factor G_S1、G_S2And/or G_DTo achieve weighting.

In this way, possible non-linearities of the correlation of the opening duration of the individual fuel injectors and the fuel quantity can be taken into account, in particular in the limit region.

Claims

1. Method for adjusting the fuel metering in an internal combustion engine (100, 200) in which fuel is introduced into at least one cylinder (102) by means of at least two different fuel injectors (107, 111, 113, 207, 213),

wherein the total fuel quantity (M) to be introduced into the at least one cylinder (102) is used_G) By means of a single fuel quantity (M)_S1、M_S2、M_D) Is distributed to respective individual fuel quantities of the at least two different fuel injectors (107, 111, 113, 207, 213), and

wherein the adjustment of each individual fuel quantity is based on the respective fuel injector (107, 111, 113, 207, 213) for introducing the respective individual fuel quantity (M)_S1、M_S2、M_D) And the respective fuel injector (107, 111, 113, 207, 213) introduces the total fuel quantity (M) only by means of the respective fuel injector (107, 111, 113, 207, 213)_G) Corresponding dosage ofThe ratio of the time durations.

2. The method according to claim 1, wherein for each of said individual fuel quantities (M)_S1、M_S2、M_D) By means of the adaptation value (A)_S1、A_S2、A_D) Is achieved, the adaptation value is based on the respective fuel injector (107, 111, 113, 207, 213) introducing the total fuel quantity (M) solely by means of the respective fuel injector (107, 111, 113, 207, 213)_G) The corresponding dosing duration in time.

3. The method according to claim 2, wherein the adaptation value (a)_S1、A_S2、A_D) For introducing a respective individual fuel quantity (M) based on a respective fuel injector (107, 111, 113, 207, 213)_S1、M_S2、M_D) And the respective fuel injector (107, 111, 113, 207, 213) introduces the total fuel quantity (M) solely by means of the respective fuel injector (107, 111, 113, 207, 213)_G) The proportion of the respective metering duration of time is weighted by a weighting factor (G)_S1、G_S2、G_D) The form of (c) is adjusted.

4. Method according to claim 2 or 3, wherein said adaptation value (A)_S1、A_S2、A_D) Is carried out in one or more predetermined operating regions of the internal combustion engine (100, 200).

5. Method according to claim 4, wherein said adaptation value (A)_S1、A_S2、A_D) Is based on the lambda value and the lambda regulation of the exhaust gas of the internal combustion engine (100, 200).

6. A method according to any one of claims 1 to 3, wherein the adjustment is performed in an additive or multiplicative manner depending on the operating region.

7. The method according to any one of claims 1 to 3, wherein the following internal combustion engine (100, 200) is used as the internal combustion engine (100, 200), in which internal combustion engine (100, 200) the at least two different fuel injectors comprise:

at least one fuel injector (107, 113, 207, 213) for intake pipe injection and at least one fuel injector (111) for direct injection, and/or

At least two fuel injectors (107, 113, 207, 213) for intake pipe injection and/or

At least two fuel injectors for direct injection.

8. The method of any of claims 1 to 3, wherein said dosing duration comprises an opening duration(s) (c

、

、

) And/or a duration of the maneuver.

9. A computing unit (115) which is set up for: carrying out the process according to any one of claims 1 to 8.

10. A machine-readable storage medium having stored thereon a computer program which, when executed on a computing unit (115), causes the computing unit (115) to carry out the method according to any one of claims 1 to 8.