CN112196678B

CN112196678B - Method for determining at least one adaptive value of an exhaust gas recirculation rate

Info

Publication number: CN112196678B
Application number: CN202010637408.5A
Authority: CN
Inventors: A.尼霍夫; M.马祖尔; W.戈特沙尔克; S.贝伦特; R.格拉鲍斯基
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2019-07-08
Filing date: 2020-07-03
Publication date: 2023-01-10
Anticipated expiration: 2040-07-03
Also published as: CN112196678A; DE102019210027A1

Abstract

The invention relates to a method for determining an exhaust gas recirculation rate r during operation of an internal combustion engine (1) _EGR One or more methods of adapting a value; wherein the internal combustion engine (1) has at least one cylinder (3) with an inlet side (4) and an outlet side (5), wherein an air inlet line (6) with a raw air inlet (7) is provided on the inlet side (4), wherein an exhaust gas line (9) and an exhaust gas recirculation line (10) connecting the exhaust gas line (9) to the air inlet line (6) are provided on the outlet side (5), wherein a recirculated EGR exhaust gas mass flow can be set at least by means of a first regulating valve (11) arranged in the exhaust gas recirculation line (9)

。

Description

Method for determining at least one adaptive value of an exhaust gas recirculation rate

Technical Field

The invention relates to a method for determining (or regulating) at least one adaptive value of an exhaust gas recirculation rate (or for determining an Exhaust Gas Recirculation (EGR) rate r) during the operation of an internal combustion engine _EGR One or more adapted values of).

An internal combustion engine having at least one cylinder with an inlet side and an outlet side for discharging combustion gases from the cylinder into an exhaust gas line and an external low-pressure (or high-pressure) exhaust gas recirculation device, in which the external exhaust gas recirculation device comprises at least one exhaust gas recirculation line connecting the exhaust gas line to an air inlet line of the internal combustion engine. In the exhaust gas recirculation line, a (first) control valve is provided, by means of which the exhaust gas mass flow from the exhaust gas line can be returned adjustably back into the air supply line. A cooling device and a filter device for temperature control of the exhaust gas recirculation mass flow can also be arranged in the exhaust gas recirculation line.

Technical Field

In order to regulate the exhaust gas recirculation rate, in particular in Otto combustion processes and in diesel combustion processes, in internal combustion engines having an (external low-pressure or external high-pressure) exhaust gas recirculation device (EGR device — exhaust gas recirculation device), a high degree of accuracy is required for modeling the exhaust gas recirculation rate. The requirements for accuracy are mainly set by the emission limits, which are set by some law, the combustion stability required for the operation of the internal combustion engine and the consumption of fuel.

The accuracy of the exhaust gas recirculation rate may be affected by a number of factors. For example, the accuracy may be affected by manufacturing tolerances of various components of the exhaust gas recirculation device. In particular, these manufacturing tolerances can be checked during the end-of-line inspection process (i.e., during the production of the internal combustion engine or motor vehicle) and compensated for by individual adjustment. Furthermore, the accuracy may be affected by the effect of the length of time the internal combustion engine is operating, for example by the accumulation of smoke in the cooling device, a malfunction of the pressure sensor, etc.

It is these run-time effects that are to be recognized by suitable measures and compensated for if necessary.

It has hitherto been known to correct the mass balance (mass flow in the cylinder, mass flow of raw or fresh air and mass flow of recirculated exhaust gas), for example as a function of the pressure difference across the (first) valve which regulates the exhaust gas recirculation rate. It is also known to perform a multi-model adaptation of camshaft phasing.

DE 10 2004 029 642 A1 discloses a method for self-learning parameterization of parameterizable models and for determining systematic errors in systematic models. An accurate determination of the mass of fresh air fed to the engine and a calculation of model parameters for describing the systematic errors of the sensors used here are exemplarily explained.

DE 10 2011 017 779 A1 discloses a method for determining a low-pressure exhaust-gas recirculation mass flow in an air system of an internal combustion engine. The fresh air mass flow is determined by a fresh air mass sensor.

DE 10 2016 205 A1 discloses a method and a device for determining a fresh air mass flow into an internal combustion engine. An alternative solution to determining the fresh air mass flow using a hot film air flow meter is suggested. This is related to the pressure difference over the charge air cooler.

Disclosure of Invention

It is an object of the present invention to at least partially solve the problems occurring in the prior art. In particular, a method for adjusting the exhaust gas recirculation rate is proposed, wherein the adjustment is to be carried out with greater accuracy by adaptation.

The features listed individually may be supplemented by explanatory facts in the description and/or by details in the figures, in which further embodiments of the invention are shown.

The invention relates to a method for determining an exhaust gas recirculation rate r during operation of an internal combustion engine _EGR Or for adjusting one or more adaptation values of the exhaust gas recirculation rate. Internal combustion engines have an exhaust gas recirculation device (external low pressure or external high pressure). The internal combustion engine furthermore has at least one cylinder (with a combustion chamber for combusting at least air and fuel and for driving a piston which moves in the cylinder), which has an input side (for introducing air and possibly exhaust gases from the exhaust gas recirculation line and possibly fuel and/or additives) and an output side (for discharging combustion gases from the cylinder into the exhaust gas line). An air supply line with a raw air inlet or a fresh air inlet and possibly a second regulating valve (throttle valve) is arranged or connected on the input side. On the output side, an exhaust gas line and an exhaust gas recirculation line connecting the exhaust gas line to the air supply line (upstream or downstream of the second control valve, if present) are arranged or connected. At least a first control valve arranged in the exhaust gas recirculation line can regulate (i.e. can adjust the mass flow) the recirculated EGR exhaust gas mass flow (fed back from the exhaust gas line via the exhaust gas recirculation line into the air supply line and into the cylinder via the inlet side)

(e.g. in [ kg ]Hour/hour]In terms of exhaust gas mass flow). The method at least comprises the following steps:

a) Operating the internal combustion engine at one or more operating points; wherein for a first group having a plurality of operating condition points i, wherein i =1 to n (where n is a natural number), the first regulating valve is at least partially open; and for a second group having a plurality of operating condition points j, where j =1 to 1m (where m is a natural number), the first regulating valve is closed;

b) Determining a measured or modeled or lambda value of lambda control (e.g. of the exhaust gas in the exhaust gas duct) for each operating point and calculating an EGR factor f for each pair of operating points _EGRij (ii) a And

c) According to the conditions

Establishing a mass balance at least for a first set (or two sets) of operating mode points (from, for example, model values or measurements), wherein the operating mode points j of the second set

(when the first regulating valve is closed, there is no EGR exhaust gas mass flow

Is the mass flow through the cylinder;

is the original air mass flow input into the cylinder); and calculating the air coefficient f for each operating condition point of the two groups _Luftij ；

d) The exhaust gas recirculation rate (preferably at any operating point) is calculated and adjusted (or corrected to be modeled, measured or calculated) according to the following conditions:

in particular, a second regulating valve (throttle valve) is additionally arranged in the air supply line (for example in the case of an otto engine). In particular, the recirculated EGR exhaust gas mass flow (fed back from the exhaust gas line via the exhaust gas recirculation line into the air supply line and entering the cylinder via the inlet side) can then be regulated by a first control valve arranged in the exhaust gas recirculation line

(e.g. in [ kg/h ]]Exhaust gas mass flow in units) and the total mass flow or the cylinder mass flow can be regulated by means of a second regulating valve

(i.e. EGR exhaust gas Mass flow)

And the original air mass flow from the environment into the air supply line to the cylinders

The sum of).

The above (non-exhaustive) division of method steps a) to d) is only used for differentiation, and not to force an order and/or dependency. The frequency of the steps may also vary, for example, during operation of the internal combustion engine. The method steps may also overlap each other at least partially in time. In particular, steps a) to d) are carried out in the stated order, wherein steps b) to d) are carried out in particular during step a). Steps b) and c), and optionally also b) to d), are carried out in particular repeatedly.

In particular, according to step d), by taking into account the EGR factor f _EGRij And air coefficient f _Luftij The exhaust gas recirculation rate (for the current operating point) is calculated and set on the internal combustion engine for each current operating point. The current state of the internal combustion engine or of the component influencing the exhaust gas recirculation rate is taken into account in particular by these coefficients.

In particular, it should be ensured that the exhaust gas recirculation rate set for an operating point (which must comply with emission limits, for example) is also actually set.

In particular, on the basis of steps b) and c), the state of the exhaust gas recirculation device is checked (continuously or periodically during the operation of the internal combustion engine) in order to actually be able to achieve the "nominal exhaust gas recirculation rate" set for the current operating point. Determining coefficients for each operating point according to steps b) and c).

In particular, the coefficients are combined to form a characteristic curve for carrying out step d), so that suitable coefficients for this can be determined from this characteristic curve for any operating point.

To carry out step d), the coefficients are preferably combined in each case for the EGR coefficient f _EGR And for air factor f _Luft The value of (c).

For the EGR coefficient and the air coefficient, which combine the respective coefficients for all operating points, the calculated coefficients can be checked mathematically before they are actually used for adjusting the exhaust gas recirculation rate. In particular, the determined coefficients can be used (for example in the step-wise control range) for setting the exhaust gas recirculation rate only if the check is successful (i.e. if the result is reasonable).

In particular, in the air supply line, a raw air valve can be provided as a further (third) regulating valve upstream of the opening of the exhaust gas recirculation line into the air supply line. In particular, the original air valve is used to generate a defined pressure difference over the first regulating valve. As a result, greater accuracy can be achieved in operating conditions with generally lower pressure differentials. Alternatively, for example, a waste gas valve may also be used in the waste gas line, for example in a diesel combustion process.

In particular, the internal combustion engine does not comprise any means for supercharging or increasing the supercharging pressure of the internal combustion engine.

In particular or alternatively, the internal combustion engine comprises means for supercharging or increasing the supercharging pressure of the internal combustion engine. In particular, exhaust gas turbochargers or similar devices are provided, in which a compressor can be driven, for example by a turbine arranged in the exhaust gas flow, which compressor can build up a pressure increase in the air supply line.

In particular, the device is arranged in the exhaust gas line between the outlet side and the exhaust gas recirculation line and in the air inlet line between the exhaust gas recirculation line and the inlet side. In this case, the exhaust gas recirculation device forms an external low-pressure exhaust gas recirculation device.

Alternatively, the device is arranged in the exhaust line such that the exhaust gas recirculation line is provided between the output side and the device (i.e. upstream of the device). In particular, the device is arranged in the air supply line between the exhaust gas recirculation line and the raw air inlet (i.e. upstream of the exhaust gas recirculation line). In this case, the exhaust gas recirculation device forms an external high-pressure exhaust gas recirculation device.

In particular, the second regulating valve is arranged upstream of the exhaust gas recirculation line, and preferably downstream of the device.

In particular, the EGR coefficient f may be calculated in step b) for each operating point _EGRij . The EGR factor compensates for deviations of the EGR exhaust mass flow from the "nominal EGR exhaust mass flow". In particular, the composition or composition of the exhaust gas in the exhaust gas line can be determined by means of a lambda sensor. By comparing the detected control variables of the hybrid control or the detected lambda value with the "nominal lambda value", for example, the EGR coefficient can be determined.

In particular, the air ratio f can be determined in step c) for each operating point of at least a first group or two groups _Luftij . For this purpose, depending on the conditions

To take into account the mass balance at least for the first group of operating points, wherein the operating point j of the second group (when the first regulating valve is closed)

The air factor compensates for deviations of the raw air mass flow from the "nominal raw air mass flow". The change occurring at the second regulating valve can be recognized and entered by the air factorAnd (4) line compensation.

In particular, the mass flow through the cylinder can be determined from data available from a control device of the internal combustion engine (for example from data from an injection device for the fuel, from measured values determined by a pressure sensor, a characteristic curve, etc.).

In particular, the results determined in each of steps b) and c) may be used for the other respective steps c) and b). In particular, the determined values can also be checked against one another in this way (for example with regard to plausibility).

In particular, errors or deviations of the raw air mass flow and of the EGR exhaust gas mass flow are identified by the method and compensated for by the coefficients mentioned. For this purpose, the operation is carried out via operating points in the EGR operation (i.e. the first control valve is at least partially open) and the non-EGR operation (i.e. the first control valve is closed), the determined values being compared with one another (to form operating point pairs i and j) and characteristic values (coefficients) being formed. It should therefore be realized, in particular, that other error sources (i.e. in addition to the EGR exhaust gas mass flow and the raw air mass flow) are eliminated. These two determined coefficients are detected and calculated, in particular, by means of a least-squares method (see, for example, EP 1 715 165 A2 and DE 10 2004 029 A1) at a specific number of operating point points.

In particular, the adaptation of the primary air mass flow and the EGR exhaust gas mass flow can be decoupled from one another by this method (that is to say by calculating two coefficients).

In particular, each operating point comprises a fixed operating state of the internal combustion engine.

In particular, the stable operating conditions include: at least the following parameters have a deviation during steps b) and c), respectively, of, for example, at most 5%, preferably at most 2% (i.e. the variation of the respective parameter over the time interval considered necessary for carrying out step b) or c):

crankshaft speed of the internal combustion engine (driven by the piston moving in the cylinder);

EGR exhaust gas mass flow

Original air mass flow or fresh air mass flow

Lambda value (of exhaust gas).

In particular, the primary air mass flow

Determined by a sensor or model.

In particular, the sensor is a (known) hot-film air quality sensor.

In particular, changes occurring in the hot-film air mass sensor (which, for example, influence the control accuracy of the second control valve or throttle valve) are compensated for by the air factor.

Especially by taking into account parameters

·P _US (the first pressure in the exhaust gas recirculation line upstream of the first regulator valve),

·p _DS (second pressure in the exhaust gas recirculation line downstream of the first regulating valve), and

·T _US (exhaust gas temperature in the region of the first regulating valve or upstream of the first regulating valve)

Determining EGR exhaust mass flow

In particular, the EGR exhaust gas mass flow is determined, for example, according to the following (known) equation (wherein detection can also be carried out by means of sensors or a characteristic map):

wherein the content of the first and second substances,

A _eff : an effective cross-sectional area of the first regulator valve;

r: specific gas constant;

Ψ: a flow function;

k: an isentropic index.

In particular, the number of operating mode points of the first group corresponds to the number of operating mode points of the second group. Selecting the coefficients f determined for the individual operating mode points _EGRij And f _Luftij And respectively combined by the least square method into a factor f which is suitable for the entire operating characteristic curve of the internal combustion engine (and which is used to calculate and set the exhaust gas recirculation rate according to step d) _EGR And f _Luft 。

In particular, the first and second groups each include at least five different operating points.

In particular, the process is carried out continuously (or preferably) periodically (i.e. at certain time intervals).

A motor vehicle is further proposed, which has at least one internal combustion engine and a control device (control unit), wherein the internal combustion engine has an exhaust gas recirculation device (external low pressure or external high pressure) and at least one cylinder with an input side and an output side. An air supply line with a primary air inlet (and possibly a second control valve) is arranged on the supply side. On the output side, an exhaust gas line and an exhaust gas recirculation line connecting the exhaust gas line to the air supply line (upstream or downstream of the second control valve, if present) are arranged. During operation of the internal combustion engine, the recirculated EGR exhaust gas mass flow can be adjusted at least by means of a first regulating valve arranged in the exhaust gas recirculation line

(if present, the primary air mass flow is regulated by a second regulating valve

Or total or cylinder mass flow) in order to set the exhaust gas recirculation rate r _EGR . At least the setting of the exhaust gas recirculation rate and the adjustment of at least one control valve (possibly two control valves or all control valves) is carried out by the control device. The control device is embodied or designed, configured or programmed to be suitable for carrying out the described method.

The statements relating to the method can be transferred in particular to motor vehicles and vice versa.

Furthermore, the method may also be performed by a processor of a computer or a control device.

Therefore, a system for data processing is also suggested, which system comprises a processor adapted/configured such that it is capable of performing the method or parts of the steps of the proposed method.

A computer-readable storage medium may be provided, comprising instructions which, when executed by a computer/processor, cause the computer/processor to perform the method or at least a part of the steps of the proposed method.

Statements made to the method can be transferred in particular to a motor vehicle or a computer-implemented method (that is to say a computer or a processor, a system for data processing, a computer-readable storage medium) and vice versa.

In particular, the method can be carried out as described below, wherein the description of the individual steps is valid even independently of the order described here and can be combined with other features of the method.

After starting the internal combustion engine, the preconditions can be queried in step 1).

In this case, to determine to what extent the preconditions for the adaptable (low-pressure or high-pressure external) exhaust gas recirculation device are present, the following can be checked: first, the inductive and physical plausibility and accuracy of the mass flow controllers associated with the EGR system, i.e., the first regulating valve and the possible second regulating valve, are queried. The determination of the plausibility or accuracy itself is carried out beforehand, for example by means of a so-called end-of-line test (bandinde-shufang) in so-called idling engine controls or before the current corresponding start of the internal combustion engine. That is, in step 1), the current feature value is checked for presence or for formal validity. In addition, the operating conditions (operating mode, characteristic curve region, etc.) which are adapted to the system or are appropriate for the method are checked.

If the precondition is satisfied, it can be queried in step 2) whether a stable operating point exists. In step 2), it is checked whether the operating point at the present time of observation meets the criteria describing steady-state operation (e.g. crankshaft speed, raw air mass flow, EGR mass flow, mixture ratio, i.e. lambda value, etc.). These standards may be specifically defined for current external low pressure exhaust gas recirculation devices. The so-called steady-state operation, which is present in a plurality of dimensions, is a prerequisite for a further successful implementation of the system adaptation or the method described. In order to reliably detect what is known as steady-state operation, purposefully selected operating parameters are observed during their respective times, the gradient is calculated over a correspondingly adjusted time range, and the gradient is compared in each case with specific limits, i.e. with the permissible limit values (minimum and maximum) signed in the sense of steady-state operation. The case of steady-state operation via said query is that all parameters of the above-mentioned relevant choices satisfy the respective criteria at the current observation point in time at the same time and therefore the steady-state operation in terms of system adaptation is present in the form of a logical and operation.

If a stable operating point exists, the use of an external low-pressure exhaust gas recirculation device can be queried in step 3). In this case, it can be adaptively determined by the EGR system whether the internal combustion engine is operated without the use of exhaust gas recirculation (i.e. mainly closing the first control valve) or intentionally with the use of exhaust gas recirculation (i.e. mainly at least partially opening the first control valve and possibly a further (third) control valve (original air valve) in the position control mode). The distinction between the two operating states (with or without the use of an exhaust gas recirculation device) which are assumed by the system adaptation or the method at the respective observation time is of particular (decisive) significance for further logically and physically correct processing of the obtained further data or measurement data.

In a next step 4), characteristic values for a comprehensive factorial description of the so-called mixing deviation or correction requirement are determined and stored by the lambda control. The physical basis for the system adaptability of the external low-pressure exhaust gas recirculation device observed here is the determination of characteristic values which describe the suitability for observationThe correction of the multiplication, i.e. multiplication, of the lambda control over a defined observation time range is effected in order to adjust the "actual value" of the current air ratio lambda to the "setpoint value" of the air ratio lambda specified in the engine control (for example provided in the control device). One or more, for example three, individually determined characteristic values (for example, the manipulated variables lambda control, the mixture adaptation offset and the mixture adaptation gain) with specific physical significance are used as a basis, which describe the so-called lambda control action. In this step, the three characteristic values obtained by the system adaptation or the method are used, together with further operating characteristic values, to calculate a characteristic value (EGR coefficient f) described above for the overall factorization from the point of view of lambda control, which describes the so-called mixing deviation or correction requirement, on the basis of a so-called mixing basic calculation chain (Gemisch-grundhenkenkey) present in the engine control unit _EGRij ). The operating characteristic values necessary for this purpose are obtained as input variables of the above equation within a defined time range at a defined sampling frequency, i.e. therefore in a certain number of sampling steps. The above equation is solved at the same frequency, i.e. in each sampling step, in order to determine a characteristic value which describes the so-called hybrid deviation or correction requirement in terms of lambda control overall factorization. The quantities of characteristic values are stored in specific memory locations in association with the two operating modes.

In the operation of an internal combustion engine without an exhaust gas recirculation device (i.e. mainly closing the first control valve and, if present, fully opening the original air valve), a mass balance of all gas mass flows present in the internal combustion engine and flowing during the operation of the engine is additionally formed by a parameterable number of sampling steps in order to determine a factorial correction value (air factor f) for the measured values of a so-called hot-film air mass sensor _Luftij ) So that the above-mentioned factorial correction value (air factor f) for the measured values of the so-called hot-film air quality sensor is applied _Luftij ) The mass balance is then correct. The factorial correction value (air factor f) _Luftij ) But also in a specific memory location (e.g. in the control device).

By a further step 5) the data stored in step 4) can be queried. For reasons of physical reliability and mathematical stability, in particular the same number of characteristic values of the factorial lambda correction obtained by step 4 on the basis of the engine operating point should be stored in both operating states (with or without the use of an exhaust gas recirculation device) in order to represent a further usable state in terms of system adaptation or the method. The amount of data that is definitely available in terms of system adaptation or the method can be parameterized.

In a further step 6), the above-mentioned factorized air correction value (air factor f) by step 4) (or method steps b) and c)) can be selected if there is sufficient data _Luftij ) And factorial lambda correction (EGR coefficient f) _EGRij ) The number of data occupied storage locations and the storage locations are fed to a so-called least squares method, for example based on a so-called matrix solver. Alternatively, iterative or analytical methods can also be used as calculation methods. This procedure according to step 6) is particularly necessary and sensible, since the mass flow of exhaust gas to the recirculating EGR is relevant at separately observed or evaluated operating points

And primary air mass flow

The physical statement of the final adaptive correction requirement of (i.e. the core task and the final goal of the described system adaptation of the exhaust gas recirculation device of the invention or of the method) may differ in size and sign compared to the physical statement at another operating point. The system adaptation or the function of the method is defined in that only one factorial air correction value (i.e. only one air factor f) is available for the entire engine operating characteristic _Luft ) And only one comparable factorial lambda correction (i.e. only one EGR-coefficient f) _EGR ). Therefore, it is necessary to determine a solution for a mathematical reliability check, in particular for two coefficients. If the solution is successful, these two coefficients can be applied to the raw air mass flow and the EGR exhaust gas mass flow andall steps (steps 1) to 6) or a) to d)) are started to be performed again.

Furthermore, a control device for an internal combustion engine is proposed, wherein the internal combustion engine is designed with an (externally low-pressure or externally high-pressure) exhaust gas recirculation device having at least one (first) control valve, and means are provided which are suitable for carrying out the method steps in the manner proposed here.

Furthermore, the invention also relates to a computer program product comprising instructions for causing a control device to perform (at least partly) the method steps specified herein.

If the control device and/or the exhaust gas recirculation device and/or the (first) regulating valve can be monitored and/or controlled for this purpose by means of sensors and/or actuators by the control device, reference can be made in full to the further description and the system can be supplemented.

It is noted that the numbers ("first", "second", … …) used herein are mainly (only) used to distinguish several similar objects, sizes or processes, and especially do not necessarily specify any dependency and/or order of these objects, sizes or processes on each other. If dependencies and/or sequences are required, they are explicitly stated herein or will be apparent to those skilled in the art when studying the specifically described schemes. If a component can appear more than once ("at least one"), then the description of one of the components can apply equally to most or part of the components, but this is not mandatory.

Drawings

The invention and the technical environment are explained in more detail below with reference to the drawings. It should be noted that the invention is not limited to the embodiments mentioned. Unless explicitly stated otherwise, it is possible in particular to extract part of the aspects of the fact explained in the figures and to combine them with other constituents and findings in the present description. It should be particularly noted that the drawings and in particular the scale shown are purely schematic, in which:

fig. 1 shows a motor vehicle with an internal combustion engine and a control device.

Detailed Description

Fig. 1 shows a motor vehicle 19 with an internal combustion engine 1 and a control device 20.

The internal combustion engine 1 has an external low-pressure exhaust gas recirculation device 2 and a plurality of cylinders 3 with an input side 4 and an output side 5. On the input side 4, an air supply line 6 is arranged, which air supply line 6 has a raw air inlet 7 and a filter arranged on the raw air inlet 7, a raw air valve 26 and a second control valve 8. On the output side 5, an exhaust gas line 9 and an exhaust gas recirculation line 10 are arranged, which exhaust gas recirculation line 10 connects the exhaust gas line 9 to the air supply line 6 upstream of the second control valve 8 and downstream of the original air valve 26. During operation of the internal combustion engine 1, the recirculated EGR exhaust gas mass flow is regulated by a first control valve 11 arranged in the exhaust gas recirculation line 10

And the primary air mass flow is regulated by means of a second regulating valve 8

Or total or cylinder mass flow (sum of original air mass flow and EGR exhaust gas mass flow) to adjust the exhaust gas recirculation rate r _EGR . At least the exhaust gas recirculation rate is set by the control device 20 and the

control valves

8, 11, 26 are set.

Primary air mass flow

Determined by the hot film air mass sensor 15. The changes occurring on the hot-film air mass sensor 15, which for example affect the control accuracy of the second regulating valve 8, are compensated by the air factor.

By taking into account the first pressure p in the exhaust gas recirculation line 10 upstream of the first regulating valve 11 _US 16. The second pressure p in the exhaust gas recirculation line 10 downstream of the first regulating valve 11 _DS 17 and the temperature T of the exhaust gas upstream of the first regulating valve _US 18 determining EGR exhaust mass flow

For determining a stable operating state, the rotational speed of the crankshaft 14 of the internal combustion engine 1, which is driven by the piston moving in the cylinder 4, can also be taken into account.

The internal combustion engine 1 comprises means for supercharging or increasing the supercharging pressure of the internal combustion engine 1. For this purpose, an exhaust-gas turbocharger 21 is provided, by means of which a compressor 23 arranged in the air supply line 6 can be driven by a turbine 22 arranged in the exhaust-gas flow of the exhaust-gas line 9.

A filter 24 and a cooler 25 are arranged in the exhaust gas recirculation line 10. The exhaust gas recirculation line 10 opens into the air supply line 6 upstream of the second control valve 8.

List of reference numerals

1. Internal combustion engine

2. Exhaust gas recirculation device

3. Cylinder

4. Input side

5. Output side

6. Air input line

7. Original air inlet

8. Second regulating valve

9. Waste gas line

10. Exhaust gas recirculation line

11. First regulating valve

12 EGR exhaust gas mass flow

13. Primary air mass flow

14. Crankshaft

15. Hot film air quality sensor

16. First pressure p _US

17. Second pressure p _DS

18. Temperature T _US

19. Motor vehicle

20. Control device

21. Turbocharger

22. Turbine engine

23. Compressor with a compressor housing having a plurality of compressor blades

24. Filter

25. Cooling device

26. Original air valve

Claims

1. Method for determining an exhaust gas recirculation rate r during operation of an internal combustion engine (1) _EGR The internal combustion engine (1) having an external exhaust gas recirculation device (2); wherein the internal combustion engine (1) has at least one cylinder (3) with an input side (4) and an output side (5), wherein an air supply line (6) with a raw air inlet (7) is provided on the input side (4), wherein an exhaust gas line (9) and an exhaust gas recirculation line (10) connecting the exhaust gas line (9) to the air supply line (6) are provided on the output side (5), wherein a recirculated EGR exhaust gas mass flow can be set at least by means of a first regulating valve (11) arranged in the exhaust gas recirculation line (9)

Wherein the method comprises at least the following steps:

a) Operating the internal combustion engine (1) in one or more operating points, wherein for a first group of one or more operating points i, i =1 to n, the first regulating valve (11) is at least partially open, and for a second group of one or more operating points j, j =1 to m, the first regulating valve (11) is closed,

b) Determining a measured or modeled value or mixture ratio of the manipulated variable of the air/fuel ratio adjustment for each operating point, and calculating an EGR factor f for each operating point _EGRij (ii) a And is provided with

c) According to the conditions

Establishing a mass balance of at least a first set of operating points, wherein the operating points j of a second set

Calculating an air factor f for each operating point of the group _Luftij Wherein, in the process,

representing the original air mass flow input into at least one cylinder (3), and wherein,

is the mass flow through the cylinder;

d) The exhaust gas recirculation rate is calculated and set according to the following conditions:

2. a method according to claim 1, characterized in that each operating point comprises a stable operating state of the internal combustion engine (1).

3. The method of claim 2, wherein the stable operating state comprises: at least the following parameters have a deviation of at most 5% during steps b) and c):

the rotational speed of a crankshaft (14) of the internal combustion engine (1);

EGR exhaust gas mass flow

Primary air mass flow

The mixing ratio.

4. The method according to any one of the preceding claims, characterized in thatCharacterized in that the raw air mass flow is determined by a sensor

5. The method of claim 4, wherein the sensor is a hot film air quality sensor (15).

6. Method according to claim 1, characterized in that the parameters are taken into account

·p _US A first pressure (16) in the exhaust gas recirculation line (9) upstream of the first regulating valve (11),

·p _DS a second pressure (17) in the exhaust gas recirculation line (9) downstream of the first regulating valve (11), and

·T _US (18) Determining the EGR exhaust gas mass flow at the exhaust gas temperature in the region of the first control valve (11) or upstream of the first control valve (11)

7. The method of claim 1, wherein the number of operating condition points of the first group corresponds to the number of operating condition points of the second group; wherein the coefficients f determined for the individual operating mode points are selected _EGRij And f _Luftij And are combined by the least square method to form coefficients f suitable for the entire operating characteristic curve of the internal combustion engine (1) _EGR And f _Luft 。

8. The method of claim 1, wherein the first and second sets each include at least five different operating condition points.

9. The method of claim 1, wherein the method is performed periodically.

10. A motor vehicle (19) having at least an internal combustion engine (1) and a control device (20), wherein the internal combustion engine (1) has an exhaust gas recirculation device (2) and at least one cylinder (3) having an input side (4) and an output side (5); wherein an air supply line (6) with a raw air inlet (7) is provided on the inlet side (4), wherein an exhaust gas line (9) and an exhaust gas recirculation line (10) connecting the exhaust gas line (9) to the air supply line (6) are arranged on the outlet side (5), wherein, during operation of the internal combustion engine (1), a recirculated EGR exhaust gas mass flow can be set at least by means of a first regulating valve (11) arranged in the exhaust gas recirculation line (10)

So as to adjust the exhaust gas recirculation rate r _EGR (ii) a Wherein at least the exhaust gas recirculation rate is set by a control device (20) and at least one control valve (11) is set; wherein the control device (20) is designed to be adapted to perform a method according to any of the preceding claims.

11. A control device (20) of an internal combustion engine (1), the internal combustion engine (1) having a low-pressure exhaust gas recirculation device (2), said control device (20) comprising at least one regulating valve (11) and means adapted to perform the steps of the method according to any one of claims 1 to 9.