Method for operating an internal combustion engine

Abstract

Method for operating an internal combustion engine (2), wherein an engine control unit sets an exhaust gas recirculation rate for the internal combustion engine (2) depending on a provided temperature (TAGR) of the cooled recirculated exhaust gas, - wherein the supplied temperature (TAGR) of the cooled recirculated exhaust gas is determined depending on a specification of an efficiency (ηcooler, Δηcooler) of the cooler (8), - where the information about the efficiency of the cooler (8) is determined by: - Determining the temperature (TAGR) of the recirculated exhaust gas cooled by the cooler (8) using a temperature detector (9); and - Determining the information on the efficiency (ηcooler, Δηcooler) of the cooler (8) depending on the measured temperature (TAGR) of the cooled recirculated exhaust gas.

Description

Technical field

[0001] The invention relates to engine systems for internal combustion engines with exhaust gas recirculation, which have a cooler for cooling the recirculated exhaust gas in the exhaust gas recirculation section. State of the art

[0002] In internal combustion engine systems, exhaust gas recirculation (EGR) is used to reduce the nitrogen oxide (NOx) content of the exhaust gas. Due to the increased soot content in the exhaust gas caused by EGR, the amount of recirculated exhaust gas (specified by the EGR rate) is limited as a compromise between the NOx and soot content in the exhaust gas by means of a constant EGR rate.

[0003] The recirculated exhaust gas is typically passed through a cooler (EGR cooler) for cooling. Cooling the recirculated exhaust gas allows for a higher EGR rate at constant intake manifold pressure and can therefore significantly reduce raw emissions.

[0004] Modern control concepts, such as model-based charge control (MCC), allow for the regulation of the exhaust gas recirculation (EGR) rate and have the advantage over conventional air mass controllers of being able to keep combustion engine emissions within tighter tolerances. The required control variable, the EGR rate, is generally calculated using an air system model, which, for modeling the temperature of the cooled exhaust gas, assumes a model of an intact, ideal cooler.

[0005] However, the efficiency of the EGR cooler can change during engine operation, resulting in variations in cooling capacity. This variation in cooling capacity, due to the changing density of the recirculated exhaust gas, leads to a change in the EGR rate and can therefore cause significant fluctuations in the engine's emissions.

[0006] Furthermore, since the cooler for cooling the recirculated exhaust gas (EGR cooler) has an emission-relevant significance, the legislator requires that the cooling function be monitored as part of the on-board diagnostics.

[0007] DE 10 2004 041 767 A1 discloses a method for diagnosing an exhaust gas recirculation cooler during normal engine operation by determining a parameter characteristic of the cooler function, e.g. the efficiency or a temperature downstream of the cooler, and comparing it with a predetermined target value in order to detect a fault in case of deviations.

[0008] DE 100 03 060 C2 describes an exhaust gas recirculation fault diagnostic system that detects a fault condition in the EGR system by frequency analysis of a signal generated from the EGR cooler temperature when the amplitude of the main frequency exceeds or falls below a threshold value.

[0009] The object of the present invention is to provide an EGR rate control in such a way as to reduce fluctuations in nitrogen oxide emissions. Disclosure of the invention

[0010] This problem is solved by the method according to claim 1.

[0011] Further advantageous embodiments of the invention are specified in the dependent claims.

[0012] According to one aspect, a method is provided for providing information on the efficiency of a recirculated exhaust gas cooler in an internal combustion engine. The method comprises the following steps: - Measuring the temperature of the recirculated exhaust gas cooled by the cooler; - Determining the efficiency of the cooler depending on the measured temperature of the cooled recirculated exhaust gas.

[0013] The efficiency of the cooler can be determined as an absolute value. Alternatively, the efficiency of the cooler can be determined as a change in the cooler's efficiency relative to a reference cooler's efficiency, depending on the cooler model temperature. The cooler model temperature of the cooled recirculated exhaust gas is determined according to a cooler model for a reference cooler, depending on the mass flow rate of the recirculated exhaust gas.

[0014] According to another aspect, a method for detecting a fault in the cooler is provided, wherein an indication of the efficiency of a cooler is determined according to the above method, wherein the fault of the cooler is determined depending on a threshold value.

[0015] According to another aspect, a method for operating an internal combustion engine is provided, wherein an engine control unit sets an exhaust gas recirculation rate for the internal combustion engine depending on a provided temperature of the cooled recirculated exhaust gas, wherein the provided temperature of the cooled recirculated exhaust gas is determined depending on the information about the efficiency of the cooler, which is determined according to the above method.

[0016] One aspect of the present invention is to provide a method for determining an efficiency value for an EGR cooler, i.e., a value for the absolute efficiency or for a change in the cooler's efficiency, so that a fault in the EGR cooler can be detected using this efficiency value. Furthermore, an engine control unit can be operated depending on the temperature of the recirculated exhaust gas, wherein the temperature of the recirculated exhaust gas is not the temperature detected by a temperature sensor in the recirculation line, but rather a temperature calculated from the efficiency value.

[0017] Furthermore, the efficiency of even an intact cooler can change within certain limits, thus affecting the exhaust gas temperature after the EGR cooler and consequently the EGR rate. This change in efficiency is caused, for example, by soot buildup in the EGR cooler. However, such soot buildup can dissipate during certain operating phases, resulting in changes in cooler efficiency over the vehicle's lifetime. While current air system models always assume a constant, fixed cooler model, the invention proposes modifying the cooler model using the calculated efficiency change Δη. Kühler or based on the absolute efficiency η KühlerThe monitoring function is used to correct or adapt the temperature reading. This adaptation preferably occurs in small increments. This is advantageous because changes in the cooler's efficiency are only observable over longer periods. This measure results in a higher-quality modeled temperature of the recirculated exhaust gas after the EGR cooler and thus also in a more accurate calculation of the EGR rate. Furthermore, adapting the cooler's efficiency ensures that the dynamic quality of the temperature reading, calculated from the efficiency, is reliable, unlike the dynamics of the temperature detector.

[0018] Furthermore, the information regarding the efficiency of the low-pass filter can be filtered. In particular, the time constant of the low-pass filter can be made dependent on a release time, where the release time indicates the total time during which one or more release conditions are met.

[0019] According to one embodiment, the efficiency rating can be determined depending on one or more release conditions. The release conditions may include: - the exhaust gas temperature exceeds a certain predetermined exhaust gas threshold temperature; - The exhaust gas mass flow rate of the recirculated exhaust gas exceeds a certain predetermined exhaust gas mass flow threshold; and - the EGR rate exceeds a certain predetermined EGR rate threshold.

[0020] Furthermore, if the information about the efficiency of the cooler is determined by the information about a change in the efficiency of the cooler with respect to a reference efficiency, the threshold value can be determined depending on an exhaust gas mass flow through the cooler according to a cooler model.

[0021] The cooler model can describe the relationship between the cooler's efficiency and the exhaust gas mass flow rate through the cooler, whereby the cooler model is adapted depending on a determined cooler efficiency at a specific exhaust gas mass flow rate. In particular, the adaptation of the cooler model can be carried out by interpolation depending on a cooler model of the reference cooler and a cooler model of a hidden cooler.

[0022] According to another aspect, an engine control unit is intended to provide information about the efficiency of a recirculated exhaust gas cooler in an internal combustion engine. The engine control unit is designed to - to receive information about the temperature of the recirculated exhaust gas cooled by the cooler; and - to determine the efficiency of the cooler depending on the temperature of the cooled recirculated exhaust gas.

[0023] According to one embodiment, the engine control unit can be provided for detecting a fault in the radiator, wherein the engine control unit is configured to determine an indication of the efficiency of a radiator according to the above methods and to detect a fault in the radiator depending on a threshold value.

[0024] According to another aspect, a computer program product with program code for carrying out the above procedure is provided when the program is executed in an engine control unit. Brief description of the drawings

[0025] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 a schematic representation of an engine system with exhaust gas recirculation; Fig. 2 a schematic block diagram illustrating a method for monitoring the function of the EGR cooler and for providing an efficiency correction value; Fig. 3 a schematic representation illustrating the adaptation of the conventional cooler model by a determined change in the efficiency of the EGR cooler; Fig. 4 a schematic representation of a method for monitoring the function of an EGR cooler based on a determined absolute efficiency of the EGR cooler; and Fig. 5 a representation of the dependence of the cooler efficiency on an EGR mass flow of the recirculated exhaust gas with an illustration of an estimation or interpolation of the existing cooler efficiency at a specific EGR mass flow. Description of embodiments

[0026] Fig. Figure 1 shows a schematic representation of an engine system 1 with an internal combustion engine 2, which has four cylinders 3. Air is supplied to the cylinders 3 of the internal combustion engine 2 via corresponding intake valves (not shown) from an air supply 4, e.g., in the form of an intake manifold, which is required for combustion. The exhaust gas produced by the combustion in the cylinders 3 is discharged from the internal combustion engine 2 via an exhaust system 5.

[0027] An exhaust gas recirculation line 6 is provided between the exhaust stream 5 and the intake 4. This line includes an exhaust gas recirculation valve 7 (EGR valve) to introduce a portion of the exhaust gas discharged through the exhaust stream 5 into the intake 4. The EGR valve 7 is variably adjustable to achieve a desired exhaust gas recirculation rate (EGR rate) in the engine system 1. The EGR rate is defined as the ratio between the exhaust gas mass flow m AGRthrough the return line 6 to the total mass flow m 22 the amount of gas flowing into cylinder 3 of the internal combustion engine 2. The amount of gas flowing into cylinder 3 is determined by the sum of the air mass flow m drawn in by the internal combustion engine 2. 21 and the recirculated exhaust gas mass flow m AGR certainly.

[0028] The recirculation of exhaust gas into the air intake 4 serves to reduce the nitrogen oxide produced by combustion in the cylinders 3. According to an exhaust gas recirculation control system, which actuates the EGR valve 7 depending on exhaust gas values, combustion and / or operating parameters of the combustion engine 3, the EGR rate is essentially kept constant. The exhaust gas recirculation control system takes into account, in addition to the intake air mass flow m 21 also the temperature T AGRof the recirculated exhaust gas (EGR temperature), as this affects the density of the exhaust gas. It is particularly desirable to reduce the temperature of the exhaust gas so that the desired EGR rate, determined by the exhaust gas recirculation control, can be increased without increasing the intake air mass flow. 21 to reduce.

[0029] An exhaust gas cooler 8 (EGR cooler) is therefore provided between the exhaust gas line 5 and the EGR valve 7. The EGR cooler 8 cools the exhaust gas flowing through the recirculation line 6 using cooling water or the like. The temperature T AGR The temperature of the cooled recirculated exhaust gas is measured using a temperature detector 9 located between the EGR cooler 8 and the EGR valve 7. Furthermore, the temperature of the exhaust gas flowing into the EGR cooler 8 is measured as T3, and the temperature of the cooling water used for cooling in the EGR cooler 8 is measured as T. Kühlwasser denoted by the temperature T. KühlwasserThe temperature of the cooling water can be determined, for example, with a suitable cooling water temperature detector (not shown).

[0030] The exhaust gas temperature T3 of the exhaust gas after leaving the combustion engine 3 is either detected by a further temperature detector (not shown) or determined according to a model from operating parameters such as injection quantity, temperature of the mass flow admitted via the intake valves into the cylinders 3 and other operating parameters, such as speed, load torque, ignition timing and the like, according to a map or an underlying function of an engine model. T3=f(T22,Injection quantity,etc.) where T 22 corresponds to the temperature of the gas (air, exhaust gas) introduced into the combustion engine, which is derived from the temperature T 21 the air drawn in from the environment, the EGR temperature T AGR and the EGR rate.

[0031] In Fig. Figure 2 is a block diagram to represent a function for determining an efficiency correction value Δη. Kühler_Korrektur and schematically illustrated in a block diagram for the purpose of identifying a fault in the EGR cooler 8.

[0032] In an efficiency change calculation unit 10, the EGR temperature T is used as a basis. AGR , which is measured by the temperature detector 9, depending on a modeled temperature value T of the temperature value present in an intact EGR cooler 8 AGR_Modell at the position of the temperature detector 9, depending on a temperature reading of the exhaust gas when leaving the combustion engine 2 and depending on the temperature of the coolant T Kühlwasser a change in efficiency Δη Kühler calculated according to the following formula: ΔηKu¨bler=TAGR−TAGRModellT3−TCooling water

[0033] The temperature value T present in an intact EGR cooler 8 AGR_Modellis provided by a cooler model 22.

[0034] In a release unit 11, release conditions are checked and a release signal FS is generated depending on whether the release conditions are met. The release conditions can, for example, include the requirement that the calculation of the efficiency change of the EGR cooler 8 is only considered if the exhaust gas temperature T3 exceeds a certain predefined exhaust gas threshold temperature T. 3_SW exceeds. Furthermore, one of the release conditions may be that the efficiency change calculation is only valid with a sufficiently large exhaust gas mass flow rate (dm). AGR this is done via the return line 6, since otherwise the temperature T measured by the temperature detector 9 would be incorrect. AGR This does not allow for a sufficiently precise statement about the actual cooling capacity of the EGR cooler 8. Consequently, the exhaust gas mass flow rate dm through the recirculation line 6 is AGR with a mass flow threshold dmAGR_SW The EGR rate is compared to an EGR rate threshold, and the enable signal FS is only activated if the exhaust gas mass flow exceeds the mass flow threshold or the EGR rate exceeds the EGR rate threshold. Other enable conditions are also conceivable. In general, the enable conditions should ensure that the determined efficiency change Δη Kühler It will only be taken into account further if it is ensured with sufficient reliability that the deviation from the efficiency η Kühler a functioning cooler can be reliably detected with low susceptibility to errors.

[0035] When the release signal FS is activated, a counter in a counter unit 12 is continuously incremented depending on a counting cycle clk, thus accumulating a total time t. kumuliertThe output of comparator unit 13 indicates the time during which the enable signal FS is activated. The counter value of counter unit 12 is compared with a counter threshold ZSW in a comparator unit 13, and an output of comparator unit 13 is forwarded to a debouncing unit 14. The output of comparator unit 13 thus indicates with a logic level when the enable conditions were / are met for a minimum duration specified by the counter threshold ZSW.

[0036] The calculated change in efficiency Δη KühlerThe signal is fed to a low-pass filter 15. The filter output of the low-pass filter 15 is only calculated if the enable signal FS indicates that the enable conditions are met, i.e., only under favorable operating conditions of the combustion engine 2. A high filter time constant in the range of several seconds, minutes, or even hours increases the robustness of the calculation, so that even changes in the dynamics of the temperature detector 9, e.g., due to soot deposits, have only a minor influence on the resulting filtered efficiency change Δη. Kühler_gefiltert have.

[0037] If the total duration during which the enable signal is activated exceeds the duration specified by the counter threshold ZSW, the filtered efficiency change Δη Kühler_gefiltert , which is supplied to the debouncing unit 14, as debounced efficiency change Δη Kühler_entprelltThe signal is then applied to a further comparator unit 16. In this further comparator unit 16, the debounced efficiency change is compared with an efficiency change threshold WGDS, and a fault is detected if the efficiency change is greater than the efficiency change threshold WGDS. This determines whether the efficiency of the EGR cooler 8 has changed by more than a certain amount, thus enabling the detection of a defect in the EGR cooler 8.

[0038] To perform engine control, information about the exhaust gas recirculation (EGR) rate is generally required. However, since the EGR rate depends heavily on the temperature of the recirculated exhaust gas, information about the current temperature T is also necessary. AGR of the recirculated exhaust gas. However, the behavior of the temperature detector 9 is sluggish and therefore unsuitable for this purpose. Therefore, it is proposed to measure the temperature T AGRto derive the recirculated exhaust gas from the exhaust gas temperature and the efficiency of the EGR cooler 8 at a specific mass flow rate.

[0039] Since the efficiency η Kühler Since the EGR cooler 8 can change during the lifetime of the engine system 1, it makes sense to model the cooler for modeling the temperature T. AGR to adapt the cooled recirculated exhaust gas. Starting from a conventional cooler model 20, which depends on the exhaust gas temperature T3, the coolant temperature T Kühlwasser and the efficiency η Kühler_intakt of the intact EGR cooler 8 (of a reference cooler) a temperature specification for the temperature T AGR_Modell of the recirculated cooled exhaust gas and depending on the efficiency change Δη determined in the efficiency change unit 10 Kühler or the debounced efficiency change Δη Kühler_entprelltdetermined. Depending on the efficiency change Δη determined in the efficiency change calculation unit 10. Kühler or the debounced efficiency change Δη Kühler_entprellt as efficiency change correction value Δη Kühler_Korrektur and depending on the modeled temperature T AGR_Modell as well as the exhaust gas temperature T3 and the coolant temperature T Kühlwasser Can the temperature T previously used by the exhaust gas recirculation control AGR of the cooled recirculated exhaust gas.

[0040] In adaptation block 21, the efficiency change Δη is adjusted depending on the determined change in efficiency. Kühler_Korrektur the adapted temperature T AGR_adaptiert determined after the EGR cooler 8 according to the following formula: TAGR_adapted=TAGR_Model−Δη*(T3−TCoolingWater)

[0041] In adaptation unit 21, further measures, such as a maximum limit on the efficiency change Δη or the definition of a learning rate, can be applied, as are well known for adaptation procedures.

[0042] The in Fig. The 3 adaptation methods shown make it possible to determine an instantaneous value of the recirculated cooled exhaust gas T. AGR_adaptiert to obtain a temperature reading that, unlike the temperature reading from the temperature detectors 9, represents an instantaneous value of the recirculated exhaust gas temperature. This avoids a time delay in the temperature value due to the inertia of the temperature detector 9, allowing the exhaust gas recirculation control to react more quickly to temperature changes in the recirculated exhaust gas in order to adjust the EGR rate to the desired value.

[0043] According to another embodiment, in Fig. Figure 4 shows a schematic representation of the inventive method for monitoring the EGR cooler. In comparison to the embodiment of the Fig. The release unit 11, the counter unit 12, and the first comparator unit 13 are identically designed.

[0044] An efficiency calculation unit 30 is calculated from the temperature reading of the temperature detector T. AGR from the exhaust gas temperature T3 and the coolant temperature T Kühlwasser an efficiency η Kühler of the cooler according to the following formula: ηKu¨bler=T3−TAGRT3−TCooling water

[0045] The efficiency η Kühler is fed to a filter unit 31, which performs low-pass filtering with an efficiency of η. Kühler carries out. The efficiency η Kühler is permanently available. The filtered efficiency of the cooler η Kühler_gefiltertHowever, it is only calculated if the release conditions are met according to the release signal FS (see embodiment of the Fig. 2) are present. Furthermore, filter unit 31 receives the cumulative total release time t. kumuliert as output of counter unit 12.

[0046] The total release time t kumuliert This can then correspond to or depend on the filter time constant. This results in an average value of the absolute efficiency. This increases the robustness of the calculation, so that changes in the dynamics of the temperature detector 9, e.g., due to soot deposits or differing dynamics of the temperature detector 9 and the engine model for calculating the exhaust gas temperature T3, have only a minor influence on the result. The filtering of the efficiency η Kühler is described by the following equation: ηCooler_filtered=∫ηCooler_dTtcumulative

[0047] The efficiency η Kühlerwill be during the total release time t kumuliert integrated and through the cumulative total release time t kumuliert divided.

[0048] In addition to the embodiment of the Fig. 2 is used in the embodiment of the Fig. 4 of the exhaust gas mass flow dm AGR filtered by the return line 6, by operating it during the total release time t kumuliert is integrated and through the total release time t kumuliert The values ​​are divided to calculate the average efficiency. Filtering is performed according to the following equation: dmAGR_filtered=∫dmAGRdTtcumulative

[0049] The filtration of the exhaust gas mass flow dm AGR is carried out in the mass flow filter 32. The cumulative total release time t kumuliertIf a total release time threshold (GZS) is exceeded (detected by the first comparator unit 13), the debouncing units 14 and a further debouncing unit 33 are used to debounce the exhaust gas mass flow dm AGR the filtered efficiency η Kühler_gefiltert of the cooler as well as the exhaust gas mass flow rate (dm) AGR_gefiltert Provided as debounced values. This means robust debounced values ​​are available for the cooler efficiency η. Kühler_entprellt and a corresponding exhaust gas mass flow rate (dm²). AGR_entprellt available. These are used in the adaptation model for adapting the cooler efficiency η. Kühler used. Furthermore, an error can be detected by comparison in the further comparator unit 16 if the efficiency η Kühler_entprellt the EGR cooler 8 falls below a certain efficiency threshold WGS.

[0050] The efficiency threshold WGS is not constant in this embodiment, but depends on the mass flow rate dm³.AGR ab. The efficiency threshold WGS is calculated from an efficiency threshold offset WGSoff and a variable value that results from a characteristic map 34.

[0051] In Fig. Figure 5 shows characteristic curves of a cooler model for the efficiency η. Kühler the EGR cooler 8 depends on the exhaust gas mass flow rate dm AGR for an intact cooler (reference cooler) and the efficiency η Kühler_Bypass_offen The curves are shown for an EGR cooler 8 that is completely bypassed. The characteristic curves are usually determined by measurements on an engine test bench for an internal combustion engine 2.

[0052] In the presentation of the Fig. Within the two characteristic curves for the intact cooler and the hidden EGR cooler 8, 5 is an example of a debounced efficiency η calculated from the temperature reading of the temperature detector 9 as described above. Kühler above the exhaust gas mass flow dm AGRplotted. The plotted operating point η Kühler_Adaption , dm AGR_Adaption This refers to the current cooling behavior or its performance. To move from this operating point to the adapted characteristic curve of the EGR cooler 8 as a function of the exhaust gas mass flow dm AGR To be able to conclude, the values ​​between the characteristic curve for η are Kühler_intakt and η Kühler_Bypass_offen For each value of the exhaust gas mass flow, interpolated so that the dashed characteristic curve for η Kühler-korrigiert This results in the following: Interpolation can be performed, for example, by assigning dm to each value of the exhaust gas mass flow rate. AGR the difference between the efficiencies for η Kühler_intakt and η Kühler_Bypass_offen is divided in a ratio in which the correction value of the efficiency n Kühler_Adaption the difference between efficiencies for η Kühler_intakt and η Kühler_Bypass_offen at point dm AGR_Adaption shares. The following applies: α=(ηCooler_Adaptation(dmAGR_Adaption−ηCooler_Bypass_open(dmAGR_Adaption))(ηCooler_intact(dmAGR_Adaptation)−ηCooler_Bypass_open(dmAGR_Adaptation)) ηCooler_corrected(dmAGR)=α⋅(ηCooler_intact(dmAGR)−ηCooler_Bypass_open(dmAGR))

[0053] This interpolation can be performed, for example, in a control unit of the internal combustion engine 3.

[0054] When determining the corrected characteristic curve, it is advisable to limit the adaptation. For example, the adaptation should be performed in limited, adjustable step sizes to increase the robustness of the adaptation method. If, for example, the currently valid characteristic curve for the corrected cooler efficiency η Kühler_korrigiert above the calculated operating point η Kühler , dm AGR If the characteristic curve (i.e., all values ​​of the efficiencies η) is located, then, for example, the characteristic curve (i.e., all values ​​of the efficiencies η) can be determined. Kühler) by a fixed percentage of the absolute value of the efficiency or of the difference value of the efficiencies η Kühler_intakt for the intact cooler and the efficiency η Kühler_Bypass_offen to be adapted for the bypassed cooler.

[0055] The efficiency threshold WGS is now determined as the sum of the constant efficiency threshold offset WGSoff and an efficiency difference value Δη determined from a characteristic map 34, which depends on the exhaust gas mass flow dm AGR_entprellt is provided. The exhaust gas mass flow dm AGR_entprellt The dependent efficiency threshold WGS makes it possible to increase the robustness of the monitoring by shifting the dependent efficiency threshold towards smaller EGR mass flows according to the efficiency characteristic Δη. Kühler_korrigiert is increased.

[0056] Using the corrected efficiency curve, which is exemplified as a dashed efficiency curve in Fig. 5 is shown in Fig. 5 schematically the adaptation of the cooler efficiency η Kühler shown. The adaptation of the temperature T AGR is calculated using the corrected cooling efficiency η Kühler_korrigiert , which results from the characteristic curve of the Fig. 5 results, and the exhaust gas temperature T3 and the coolant temperature T Kühlwasser carried out. The following applies: TAGR_Adapted=T3−ηCooler_corrected(T3−TCooling water)

[0057] If the corrected efficiency curve is available, the adapted temperature T can be determined in the air system model using the same algorithms as before for an intact cooler. AGR_adaptiert calculated for the current real cooler state, which has a very good dynamic compared to the temperature indication provided with inertia by the temperature detector 9.

Claims

[1] Method for operating an internal combustion engine (2) wherein an engine control unit sets an exhaust gas recirculation rate for the internal combustion engine (2) depending on a provided temperature (TAGR) of the cooled recirculated exhaust gas, - wherein the supplied temperature (TAGR) of the cooled recirculated exhaust gas is determined depending on a specification of an efficiency (ηcooler, Δηcooler) of the cooler (8), - where the information about the efficiency of the cooler (8) is determined by: - Determining the temperature (TAGR) of the recirculated exhaust gas cooled by the cooler (8) using a temperature detector (9); and - Determining the information on the efficiency (ηcooler, Δηcooler) of the cooler (8) depending on the measured temperature (TAGR) of the cooled recirculated exhaust gas. [2] Method according to claim 1, comprising the further steps: - Providing an exhaust gas temperature (T3) as the temperature of the exhaust gas leaving the combustion engine (2); - Providing a cooling water temperature (TCooling Water) as the temperature of the cooling water flowing through the radiator (8); and - Determining the information about the efficiency of the cooler (8) continues to depend on the exhaust gas temperature (T3) and the coolant temperature. [3] Method according to claim 1 or 2, wherein an absolute value of the efficiency (ηcooler) is determined as an indication of the efficiency of the cooler (8). [4] Method according to claim 1 or 2, comprising the following further steps: - Determining the mass flow rate (dmEGR) of the recirculated exhaust gas; - Determining a cooler model temperature of the cooled recirculated exhaust gas according to a cooler model for a reference cooler as a function of the mass flow rate (dmEGR) of the recirculated exhaust gas; and - Determining a statement about a change in the efficiency of the cooler with respect to a reference efficiency of the reference cooler as a statement about the efficiency of the cooler (8) further dependent on the cooler model temperature. [5] Method according to any one of claims 1 to 4, wherein the information about the efficiency (ηcooler, Δηcooler) is filtered by a low-pass filter. [6] Method according to claim 5, wherein the time constant of the low-pass filtering is performed depending on a release time (tcumulative), wherein the release time (tcumulative) indicates the total time during which one or more release conditions are satisfied. [7] Method according to any one of claims 1 to 5, wherein the efficiency (ηcooler, Δηcooler) is determined depending on one or more release conditions; wherein the release conditions comprise: - the exhaust gas temperature (T3) exceeds a certain predetermined exhaust gas threshold temperature; - The exhaust gas mass flow rate (dmEGR) of the recirculated exhaust gas exceeds a certain predetermined exhaust gas mass flow threshold; and - the EGR rate exceeds a certain predetermined EGR rate threshold.

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