DE102013216024B4 - Method for lambda control of an internal combustion engine and control device - Google Patents

Abstract

Method for lambda control of an internal combustion engine (11), comprising the following steps: - measuring or determining a temperature of an exhaust gas flow or an exhaust gas-carrying component of an exhaust system (17) of the internal combustion engine (11) at a predetermined position using at least one sensor (23); - Measuring an exhaust gas lambda by means of a lambda probe (22) arranged in the exhaust system and transmitting a measured lambda value (λW) to an exhaust gas temperature model (28) of the internal combustion engine (11); - Determining the temperature of the exhaust gas flow or the exhaust gas-carrying component at the predetermined position by means of the exhaust gas temperature model (28) as a function of the measured lambda value (λW); - checking whether a maximum permissible adjustment deviation between the temperature (TS) measured or determined by means of the sensor (23) and the temperature (TS) measured by means of the exhaust gas temperature model (28) certain temperature (TATM) is exceeded - if the maximum permissible Justi deviation (JA) is exceeded, correcting the lambda measurement and/or a combustion lambda of the internal combustion engine (11).

Description

The invention relates to a method for lambda control of an internal combustion engine and a control device which is designed to carry out the method according to the invention.

It is known to determine the oxygen concentration in a gas mixture using an oxygen-sensitive gas probe, a lambda probe. The lambda probe provides an actual probe signal which is dependent on the oxygen content of the gas mixture and which can be, for example, a probe voltage in the case of jump lambda probes or a current intensity in the case of linear lambda probes (linear probes). This sensor signal is converted into the lambda value using a stored characteristic curve or a corresponding calculation rule. The most prominent applications are internal combustion engines, in which the lambda value of the exhaust gas is determined using lambda probes installed in the exhaust gas duct in order to regulate the air-fuel ratio with which the engine is operated depending on the lambda value determined. This procedure is generally referred to as lambda control.

A distinction is made between step lambda probes (also step response lambda probes) and broadband lambda probes. Stepped lambda probes can deliver a signal curve according to the Nernst principle, which has only slight gradients for an exhaust gas lambda less than one and greater than one and shows a sudden change in the area around an exhaust gas lambda equal to 1. Thus, jump lambda probes are usually only used for combustion engines that are controlled when lambda is equal to 1. In contrast, broadband lambda probes show sufficient sensitivity in the entire lambda range, which is why they can be used more widely than jump lambda probes, but on the other hand are significantly more expensive than these.

In practice, however, converting the probe signal into a lambda value is made more difficult by the fact that the probe signal not only depends on the composition of the exhaust gas, but is also influenced by additional interference, which means that the characteristic curve is not constant under all conditions. In the case of jump probes, it is known, for example, that the probe temperature, ie the temperature of the measuring element of the probe, has an influence on the accuracy of the conversion rule or the characteristic curve. This has an effect in particular in the rich lambda range, i.e. with lambda values less than 1. Furthermore, changes in the characteristic curve result from increasing aging of the measuring element of the probe over the operating time. In addition, various exhaust gas components such as lead, manganese, phosphorus or zinc can cause progressive poisoning of the measuring element and thus a change in the characteristic.

Methods for correcting measured lambda values can be used to compensate for these influences. A disadvantage of the known methods is that the lambda values determined have only limited accuracy. In practice, for example, a lambda value obtained from the probe signal of a jump lambda probe shows deviations from lambda values that were obtained with a broadband lambda probe under the same conditions or that were calculated for synthetic gas mixtures of known compositions, despite a temperature correction.

the DE 26 49 272 A1 discloses a lambda control with a lambda jump probe at a low engine or lambda probe temperature. The lambda regulation takes place in that a current supplied to the lambda probe is changed in accordance with a predetermined curve matched to the output signal of the lambda probe in such a way that an equalization of an output voltage behavior of the lambda probe is achieved.

The object of the invention is now to provide a method for lambda control of an internal combustion engine and a control device which are characterized by increased accuracy.

• - Messen oder Bestimmen einer Temperatur eines Abgasstroms oder eines abgasführenden Bauteils einer Abgasanlage der Verbrennungskraftmaschine an einer vorbestimmten Position mittels wenigstens eines Sensors;
• - Messen eines Abgas-Lambdas mittels einer in der Abgasanlage angeordneten Lambdasonde und Übermitteln eines gemessenen Lambda-Wertes an ein Abgastemperaturmodell der Verbrennungskraftmaschine;
• - Bestimmen der Temperatur des Abgasstroms oder des abgasführenden Bauteils an der vorbestimmten Position mittels des Abgastemperaturmodells in Abhängigkeit des gemessenen Lambda-Wertes;
• - Überprüfen, ob eine maximal zulässige Justierabweichung zwischen der mittels des Sensors gemessenen oder bestimmten Temperatur und der mittels des Abgastemperaturmodells bestimmten Temperatur überschritten ist,
• - wenn die maximal zulässige Justierabweichung überschritten ist, Korrigieren
  • - der Lambda-Messung, und/oder
  • - eines Verbrennungs-Lambdas der Verbrennungskraftmaschine.

This object is achieved by a method for lambda control of an internal combustion engine, which includes the following steps:

• - Measuring or determining a temperature of an exhaust gas flow or an exhaust-carrying component of an exhaust system of the internal combustion engine at a predetermined position by means of at least one sensor;
• - Measuring an exhaust gas lambda by means of a lambda probe arranged in the exhaust system and transmitting a measured lambda value to an exhaust gas temperature model of the internal combustion engine;
• - Determining the temperature of the exhaust gas flow or the exhaust gas-carrying component at the predetermined position using the exhaust gas temperature model as a function of the measured lambda value;
• - Check whether a maximum permissible adjustment deviation between the temperature measured or determined by the sensor and the temperature determined using the exhaust gas temperature model is exceeded,
• - if the maximum permissible adjustment deviation is exceeded, correct
  • - the lambda measurement, and/or
  • - A combustion lambda of the internal combustion engine.

To carry out the method, a temperature of the exhaust gas flow or the exhaust gas-carrying component of the exhaust system of the internal combustion engine is measured and/or determined at a predetermined position (in particular simultaneously) in two different ways. The method can be carried out at discrete points in time or continuously. Using the method according to the invention, an inaccurate lambda control z. B. be avoided or prevented due to aging of the lambda probe.

The method is preferably carried out during a constant operating point and/or during full load of the internal combustion engine, ie z. B. at a constant speed and / or full load driving of a motor vehicle, which uses the internal combustion engine to drive it, performed. This means that (thermal) inertia on the part of the sensor is irrelevant.

On the one hand, the temperature is measured or determined using the at least one sensor. This can be done in that the at least one sensor comprises or is at least one temperature sensor. Thus, the temperature can be measured using the temperature sensor. Alternatively, the at least one sensor can include at least one pressure sensor. The temperature can thus be determined by measuring a pressure of the exhaust gas flow using the at least one pressure sensor and then converting it into a temperature corresponding to the pressure. The conversion can take place using an exhaust gas mass flow, a gas constant and the measured pressure. The exhaust gas mass flow can be determined from a speed and a load of the internal combustion engine. However, the direct measurement of the temperature using the temperature sensor is preferable, as this is cheaper than the pressure sensor and it also offers greater accuracy due to the fact that there is no conversion.

On the other hand, the temperature (at the predetermined position, ie at the position of the sensor) is determined using an exhaust gas temperature model. The exhaust gas temperature model is a mathematical model and is designed to determine (model) temperatures in the exhaust system of the internal combustion engine as a function of a measured lambda value of a real exhaust gas lambda. In addition to the lambda value, other input variables, such as e.g. B. the speed and / or load of the internal combustion engine are available. The lambda value is measured using a lambda probe.

After the temperature of the exhaust gas flow or the exhaust gas-carrying component has been measured and/or determined in two different ways at the predetermined position (at the same time), it is checked whether a maximum permissible adjustment deviation between the temperature measured or determined by means of the sensor and the temperature determined by means of the Exhaust temperature model certain temperature is exceeded. If this maximum permissible misalignment is exceeded, ie z. B. an amount of a difference between the two temperatures is greater than the maximum permissible adjustment deviation, it can be concluded that an input variable of the exhaust gas temperature model is incorrect. Since the sensors of the other input variables are not subject to pronounced aging, it can be concluded that the temperature difference is due to aging of the lambda probe.

This knowledge can now be used to counteract an incorrect, measured lambda value by correcting the lambda measurement and/or a combustion lambda of the internal combustion engine. In this case, the correction can take place until the deviation falls below the maximum permissible adjustment deviation, in particular until the deviation falls below a maximum permissible adjusted deviation which is less than the maximum permissible deviation from adjustment. The maximum permissible adjustment deviation can also be equal to 0, whereby the correcting step is carried out as soon as there is a deviation (of any magnitude) between the temperature measured or determined using the sensor and the temperature determined using the exhaust gas temperature model.

Provision is preferably made here for the method to be carried out with a non-stoichiometric exhaust gas flow (with an exhaust gas lambda not equal to 1). The non-stoichiometric exhaust gas flow can be a rich exhaust gas flow with an exhaust gas lambda of less than 1 and can thus be brought about by a non-stoichiometric (eg rich) operating point of the internal combustion engine. The internal combustion engine is typically an Otto engine.

Provision is preferably made for the lambda probe to be a jump lambda probe. The lambda probe can therefore be a voltage jump probe (Nernst probe) or a resistance jump be probe The correction according to the invention achieves such a high level of precision in determining the lambda value that the field of application of the jump lambda probe can be significantly expanded. While in the prior art jump lambda probes are essentially used for internal combustion engines controlled lambda equal to 1, the area of application of a jump lambda probe, which is processed using the method according to the invention, can be extended to lambda ranges not equal to 1, which conventionally can only be controlled with expensive broadband lambda probes.

The lambda control is preferably a continuous lambda control. A more precise lambda regulation and a lambda regulation with an exhaust gas lambda (and thus combustion lambda) not equal to 1 are thus ensured.

Provision is preferably made for correcting the lambda measurement to include correcting heating of the lambda probe. The temperature of the lambda probe has a significant influence on the lambda value measured by the lambda probe. This applies in particular to jump lambda probes when the exhaust gas lambda to be measured is less than 1. The lambda probe is heated by the heating, the heating being regulated to a desired setpoint temperature of the lambda probe. An actual temperature of the lambda probe is determined by an internal resistance of the lambda probe and/or by the exhaust gas temperature model. However, as the lambda probe ages, the internal resistance changes. As a result, the lambda probe is often operated at too high a temperature, which can assume critical proportions with regard to component protection of the lambda probe. In addition, the output signal of the lambda probe changes due to the excessively high temperature of the lambda probe (in particular of jump lambda probes in the case of a rich exhaust gas lambda). As a result, without correcting the lambda measurement, the internal combustion engine would be operated too richly, which would be detrimental to the fuel consumption of the internal combustion engine. However, correcting the heating of the lambda probe prevents this disadvantage. The heating can be corrected in particular by correcting an (assumed) internal resistance of the lambda probe, which counteracts the cause of the incorrect operating temperature of the lambda probe caused by aging.

According to a preferred embodiment of the invention, it is provided that the correction of the lambda measurement includes a correction of the (already) measured lambda value. A signal from the lambda probe, e.g. B. be understood as a probe voltage, which is corrected. In this way, a measured lambda value can be corrected (subsequently), e.g. B. by applying a correction factor to the lambda value. In the context of the present invention, the term “application of a correction factor” means a suitable offsetting of the correction factor with the object to be corrected, which can include multiplication, division, addition and subtraction. It is therefore understood that the term "correction factor" is understood to mean not only multipliers, but also other operands. In addition, the lambda value can also be corrected by using a corrected characteristic curve.

• - Messen oder Bestimmen der Temperatur des Abgasstroms oder des abgasführenden Bauteils der Abgasanlage der Verbrennungskraftmaschine an der vorbestimmten Position mittels des wenigstens einen Sensors;
• - Messen des Abgas-Lambdas mittels der in der Abgasanlage angeordneten Lambdasonde und Übermitteln des gemessenen Lambda-Wertes an das Abgastemperaturmodell der Verbrennungskraftmaschine;
• - Bestimmen der Temperatur des Abgasstroms oder des abgasführenden Bauteils an der vorbestimmten Position mittels des Abgastemperaturmodells in Abhängigkeit des gemessenen Lambda-Wertes;
• - Überprüfen, ob eine maximal zulässige Kalibrierabweichung zwischen der mittels des Sensors gemessenen oder bestimmten Temperatur und der mittels des Abgastemperaturmodells bestimmten Temperatur überschritten ist,
• - wenn die maximal zulässige Kalibrierabweichung überschritten ist, Kalibrieren des Abgastemperaturmodells.

It is preferably provided that the method also includes the following steps, in particular in the case of a stoichiometric exhaust gas flow:

• - Measuring or determining the temperature of the exhaust gas flow or the exhaust-carrying component of the exhaust system of the internal combustion engine at the predetermined position by means of the at least one sensor;
• - Measuring the exhaust gas lambda by means of the lambda probe arranged in the exhaust system and transmitting the measured lambda value to the exhaust gas temperature model of the internal combustion engine;
• - Determining the temperature of the exhaust gas flow or the exhaust gas-carrying component at the predetermined position using the exhaust gas temperature model as a function of the measured lambda value;
• - checking whether a maximum permissible calibration deviation between the temperature measured or determined by means of the sensor and the temperature determined by means of the exhaust gas temperature model is exceeded,
• - if the maximum permissible calibration deviation is exceeded, calibrating the exhaust gas temperature model.

Thus, with a stoichiometric exhaust gas flow (i.e. a stoichiometric operating point of the internal combustion engine), which z. B. can also be set exactly by means of a jump lambda probe, a calibration of the exhaust gas temperature model. The maximum permissible calibration deviation can also be equal to 0, which means that a calibration takes place as soon as there is a deviation in the temperatures.

Provision is preferably made for the exhaust gas temperature model to be calibrated by adapting the temperature determined at the predetermined position using the exhaust gas model. As a result, the maximum permissible calibration deviation, ins in particular, a maximum permissible calibrated deviation, which is smaller than the calibration deviation, is no longer exceeded.

Provision is preferably made for the method to include an enriching step if the temperature measured or determined by means of the sensor or a temperature determined by means of the exhaust gas temperature model exceeds a maximum permissible temperature at any (in particular predefined) position. Enrichment can take place in the short term, thereby ensuring component protection of components that are in contact with the exhaust gas flow. Using the exhaust gas temperature model, temperatures can be determined at any predefined position (both of the exhaust gas flow and of the exhaust gas-carrying components). If it is recognized that a temperature determined in this way or the temperature measured by the sensor is greater than a maximum permissible temperature predefined for the respective position, the temperature of the exhaust gas flow is lowered by enriching the internal combustion engine.

Furthermore, a control device, which is designed to carry out the method according to the invention, is made available. The control device is distinguished by a more precisely controlled air/fuel ratio of the internal combustion engine. It typically includes an internal combustion engine, an exhaust system, an engine controller (an engine control unit) and other components required for the operation of the internal combustion engine.

In addition, a motor vehicle is made available which includes the control device according to the invention. During its operation, the motor vehicle is characterized by reduced fuel consumption and reduced reliability.

Further preferred configurations of the invention result from the remaining features mentioned in the dependent claims.

• 1 eine Regeleinrichtung,
• 2 einen Zusammenhang zwischen einer Spannungsfunktion und einer Temperatur einer Lambdasonde, und
• 3 einen Teil eines Verfahrensablaufs zur Lambda-Regelung.

The invention is explained below in exemplary embodiments with reference to the associated drawings. Show it:

• 1 a control device,
• 2 a relationship between a voltage function and a temperature of a lambda probe, and
• 3 part of a procedure for lambda control.

1 shows an example of a control device 10 according to a preferred embodiment of the invention, which can be part of a motor vehicle. The control device includes an internal combustion engine 11 whose fuel supply takes place via an injection system 12 . The injection system 12 can be an intake manifold injection or a direct injection. The internal combustion engine 11 is also supplied with air via an intake tract 14 . If necessary, the amount of air supplied can be regulated via a controllable actuating element 16 arranged in the intake tract 14, for example a throttle valve.

An exhaust gas flow generated by the internal combustion engine 11 is discharged into the environment via an exhaust system 17 with an exhaust gas duct (an exhaust pipe) 18 , with environmentally relevant exhaust gas components being converted by a catalytic converter 20 .

A lambda probe 22 is arranged within the exhaust gas duct 18 at a position close to the engine, which lambda probe is in particular a comparatively inexpensive jump lambda probe. If necessary, a further lambda probe 24 can be arranged downstream of the catalytic converter 20, which can also be a jump lambda probe or a broadband lambda probe.

The signals from the lambda probes 22 and 24 are transmitted to an engine controller 26 . If Nernst sensors are used as jump lambda sensors, the sensor signals are sensor voltages. The probe voltage U _S is the probe voltage of the lambda probe 22. Other signals from sensors (not shown) also go into the engine control 26. In this way, the engine controller also receives data from the internal combustion engine 11 which, for example, include the current engine speed n and the current relative engine load L as input variables and characterize the operating point of the internal combustion engine 11 . The engine controller 26 controls various components of the internal combustion engine 11 in a known manner as a function of the incoming signals. In particular, depending on the probe _{voltage U S of} the lambda probe 22 close to the engine, the air-fuel mixture to be supplied to the internal combustion engine 11 is regulated, for which purpose the engine controller 26 regulates a fuel quantity to be supplied via the fuel injection system 12 and/or an air quantity to be supplied via the intake system 14.

In addition, the exhaust system includes a sensor 23, which is a temperature sensor in the example shown. By means of the temperature sensor as a sensor 23, the temperature of the exhaust gas flow or an exhaust-carrying component of the exhaust gas position measured at a predetermined position and the engine control 26 is transmitted. Depending on which type of temperature sensor is used, different signals can be transmitted to the engine controller 26 . In an exemplary use of a thermocouple as a temperature sensor, a voltage can be transmitted to the engine controller 26 . As an alternative to the temperature sensor, the sensor 23 can also be a pressure sensor, with a pressure of the exhaust gas flow being measured and then converted into a temperature of the exhaust gas flow.

The engine controller 26 also includes an exhaust gas temperature model 28, which is designed as a calculation model to determine (to model) temperatures in the exhaust system 17 of the internal combustion engine 11 _{, in addition to other input variables, depending on a measured lambda value λ W of a real exhaust gas lambda.} Exhaust gas temperature model 28 can thus be designed to determine the temperature of a component and/or the exhaust gas flow at any predetermined positions in exhaust system 17 (in particular at the position of sensor 23 and lambda probe 22). For this purpose, the exhaust gas temperature model 28 can contain a corresponding algorithm in computer-readable form.

The engine control 26 can also contain algorithms in computer-readable form as well as suitable characteristic curves and characteristic diagrams.

The lambda probe 22 includes a heater, which is designed to heat the lambda probe 22 and regulates the lambda probe 22 to a predetermined setpoint temperature. An actual temperature of the lambda probe 22 can be determined by an internal resistance of the lambda probe 22 and/or a temperature TATM determined by the exhaust gas temperature model 28 at the position of the lambda probe 22 .

However, the internal resistance of the lambda probe 22 changes as the aging of the lambda probe 22 progresses, as a result of which the target temperature of the lambda probe 22 is no longer maintained due to an incorrectly determined actual temperature. This can lead to the lambda probe 22 being operated too hot. On the one hand, this can lead to a reduced service life of the lambda probe 22, but on the other hand to an incorrectly dimensioned combustion lambda of the internal combustion engine 11 in non-stoichiometric operation.

In 2 the relationship between a voltage function supplied by a lambda probe 22 (a Nernst probe) and the temperature of the lambda probe 22 can be seen.

It is assumed below that the combustion lambda corresponds to the exhaust gas lambda at the position of the lambda probe 22 . Assuming that the engine controller 26 is to regulate the internal combustion engine 11 to a non-stoichiometric combustion lambda of 0.98. Furthermore, it is assumed that the engine control does not take into account aging of the lambda probe 22 (contrary to the method according to the invention). The engine control thus assumes that the lambda probe 22 is being operated at the intended target temperature and determines the current exhaust gas lambda on the basis of the continuous characteristic curve, which is to be used for a correct target temperature. The engine controller 26 thus regulates the combustion lambda in such a way that the lambda probe 22 _{outputs a probe voltage U S} of approximately 0.75 volts. Due to the aging of the lambda probe 22 that was not taken into account, however, as described above, it is operated hotter than assumed by the engine controller 26 . Thus, the engine controller 26 should actually use the lower dashed line for a corrected lambda measurement. It follows from this that the probe voltage U _S of approx. 0.75 volts (wrongly) sought by the engine controller 26 actually corresponds to a combustion lambda of 0.93 instead of 0.98. The fact that the combustion lambda is now actually richer than desired causes an undesired increase in fuel consumption due to additional enrichment.

If the measured lambda value λ _{W deviates} from the actual exhaust gas lambda, which results in a combustion lambda that is too lean (and thus the internal combustion engine 11 that is operated with an incorrect characteristic curve or in an incorrect area of a characteristic map), it can happen that the internal combustion engine 11 is operated too hot.

For the above-mentioned reasons, a significantly more expensive linear lambda probe (linear probe) was previously used for operating the internal combustion engine 11 at non-stoichiometric operating points and in particular for continuous lambda control, which is not affected by the technical problems mentioned.

3 shows a method sequence for lambda control of internal combustion engine 11 according to a preferred embodiment of the invention during continuous lambda control. In this context, only the aspects of the lambda control according to the present invention are to be discussed in a preferred embodiment. Well-known processes for lambda control are not discussed.

First, in step 100, it is determined whether a lambda value λ _W determined by engine control 26 using lambda probe 22 is equal to 1.

If the lambda value λ _{W is} equal to 1, it can be checked according to block I whether a calibration of the exhaust gas temperature model 28 should take place and this can be carried out if necessary. For this purpose, it is first checked whether a maximum permissible calibration deviation KA between a temperature T _S measured or determined by means of sensor 23 and the temperature TATM determined by means of exhaust gas temperature model 28 (at the same position at the same time) has been exceeded. For this purpose, a difference can be formed between the temperature T _S measured or determined by means of the sensor 23 and the temperature TATM determined by means of the exhaust gas temperature model 28 . If the magnitude of the difference is greater than a maximum permissible calibration deviation KA, the exhaust gas temperature model is calibrated. If the difference is less than or equal to the maximum permissible calibration deviation KA, the lambda value can be checked again according to step 100 . The exhaust gas temperature model 28 is calibrated in step 104. For this purpose, the exhaust gas temperature model 28 can be adjusted to such an extent that a new temperature TATM corresponds to the _{temperature T S measured or determined by the sensor 23 .} This can be done, for example, via a suitable application of a correction factor to algorithms of the exhaust gas temperature model 28 . Alternatively, it can also be sufficient that a deviation determined using the new temperature TATM does not exceed a maximum permissible calibrated deviation kA (not equal to 0), which is smaller than the calibration deviation. You can then continue with step 100.

The calibration of the exhaust gas temperature model 28 with a lambda value equal to 1 is possible because an exhaust gas lambda equal to 1 can be measured relatively exactly even with lambda probes 22 that have already aged, and the internal combustion engine 11 can therefore be operated relatively exactly with a combustion lambda equal to 1. The reason for this is in 2 evident. If the probe voltage U _{S , which corresponds to a lambda value λ W} equal to 1 at the correct probe temperature according to the solid line, is transferred to the lower dashed line, there is only a minimal deviation of the measured lambda value λ _W from the actual exhaust gas lambda. With a measured lambda value λ _W equal to 1, it can thus be assumed with a high level of certainty that a lambda probe 22 operated at the wrong temperature is not the reason for exceeding the maximum permissible calibration deviation KA.

As an example of the method steps according to block I, with a lambda value equal to 1, the temperature T _S measured or determined by the sensor 23 can be 800° C. and the temperature TATM determined by the exhaust gas temperature model 28 can be 750° C. With a maximum permissible calibration deviation of e.g. B. 20 °C this means that a calibration is being carried out. After the calibration, the temperature TATM determined using the exhaust gas temperature model 28 is 800°C.

The temperatures of the exhaust gas flow or of the general components (at any position) of the exhaust gas system 17 that can be determined using the exhaust gas temperature model 28 are dependent on one another. Thus, these other determinable temperatures were also calibrated. This will e.g. For example, a temperature of the lambda probe 22 determined by the exhaust gas temperature model 28 is also calibrated. This can in turn be used for more precise heating of lambda probe 22 and/or for more precise selection of a suitable characteristic curve according to FIG 2 be used.

If the lambda value λ _{W is} not equal to 1, it can be checked according to block II whether the lambda measurement and/or the combustion lambda of the internal combustion engine 11 should be corrected. For this purpose, step 110 first checks whether a maximum permissible adjustment deviation YES between the temperature T _S measured or determined by means of sensor 23 and the temperature TATM determined by means of exhaust gas temperature model 28 at the position of sensor 23 has been exceeded. For this purpose, a difference can again be formed between the temperature T _S measured or determined by means of the sensor 23 and the temperature TATM determined by means of the exhaust gas temperature model 28 . If the absolute value of the difference is greater than the maximum permissible adjustment deviation YES, the lambda measurement and/or the combustion lambda of internal combustion engine 11 is corrected in accordance with correction block K. If the difference is less than or equal to the maximum permissible adjustment deviation YES, the lambda value can be checked according to step 100 .

The correction of the lambda measurement according to step 122 can include a step of correcting the heating of the lambda probe 22 . A deviation in the measured lambda value λ _W due to an incorrectly controlled temperature of the lambda probe 22 is thus corrected. This can be done by correcting an internal resistance of the lambda probe 22 that is stored in the engine controller 26 (that is, incorrectly assumed due to aging). This correction of the temperature T _S leads to the determination of the lambda value λ _{W of} the motor controller 26 already has a correct probe voltage U _S available.

Another way of correcting the lambda measurement according to step 122 can be done by not directly influencing the measurement of the lambda probe 22, so that it _{outputs a changed probe voltage U S} , but only making the correction later by the engine controller 26 when determining the lambda Value λ _{W is} performed. This can be done by applying a correction factor to the probe voltage U _S . In addition, the lambda value can also be corrected by using a corrected characteristic curve (e.g. based on a corresponding characteristic curve according to 2 is changed).

A further (alternative or additional) possibility of correction is step 124, which includes a (direct) correction of the combustion lambda of internal combustion engine 11. This can be done by changing the fuel supply to internal combustion engine 11 . If the temperature TATM determined by means of the exhaust gas temperature model 28 is greater than the temperature T _S determined by means of the sensor 23, this can be corrected by means of enrichment.

In order to ensure improved component protection, it can also be provided that if the temperature T _S measured or determined by means of sensor 23 or a temperature determined by means of the exhaust gas temperature model at any position exceeds a maximum permissible temperature, the correction of the combustion lambda takes one step of fattening. This can be done at short notice and thus ensure component safety.

The corrections can be carried out until, according to step 112, a maximum permissible adjusted deviation jA between a temperature T _S measured or determined by means of sensor 23 and the temperature TATM determined by means of exhaust gas temperature model 28 at the position of sensor 23 is no longer exceeded. The adjusted deviation jA is smaller than the adjustment deviation JA. For this purpose, a difference can be formed between the temperature T _S measured or determined by means of the sensor 23 and the temperature TATM determined by means of the exhaust gas temperature model 28 . If the absolute value of the difference is greater than the maximum admissible adjusted deviation jA, the lambda measurement and/or the combustion lambda of the internal combustion engine 11 is corrected again in accordance with the correction block K. Otherwise the correction is complete. Alternatively, the correction can be made until the temperature TATM equals the temperature T _S , which represents a special case with an adjusted deviation jA equal to 0. As a further alternative, the correction can also already be completed when the difference is less than or equal to the maximum permissible adjustment deviation YES. Furthermore, block II can also be controlled (ie by a controller).

As an example of the method steps according to block 11, with a lambda value λ _{W not equal to 1, the temperature T S} measured or determined by the sensor 23 can be 850° C. and the temperature TATM determined by the exhaust gas temperature model 28 can be 750° C. With a maximum permissible adjustment deviation of e.g. B. 50 °C this means that a correction is carried out. For this purpose, at least one of the corrections mentioned above is carried out until the difference between the temperatures T _S and T _{ATM is} less than or equal to the maximum permissible adjusted deviation jA from z. B. is 20 °C. In the example, the correction is thus completed at a temperature TATM of 830 °C.

The method described allows the measured lambda value to be adapted due to aging of the lambda probe 22 . Limit position probes can also be adapted. Boundary position sensors are lambda sensors 22 which have properties on the outer edge of a permissible specification (due to series scatter).

In addition, depending on the circumstances and trust in the (possibly adapted in a different way) lambda value λ _W to reliably achieve a desired construction teleprotection lambda, e.g. B. 4% additionally fattened. This means that with a component protection lambda of z. B 0.9, which is actually 0.92 due to a deviation, resulting in a real lambda value of 0.88 after enrichment. Thus, the internal combustion engine has hitherto been operated richer than actually required for component protection. The resulting increased consumption of fuel can be reduced or eliminated by the method according to the invention.

If the sensor 23 is a temperature sensor, it is usually more sluggish than the exhaust gas temperature model, which means that the temperature sensor, which z. B. can be a thermocouple, should have a relatively large diameter for reasons of robustness and therefore a thorough heating of the thermocouple requires a certain period of time. However, the dynamics of the sensor 23 are not decisive for the proposed method if this is carried out during constant travel. A temperature sensor also has the advantage that the temperature of the exhaust gas flow can be determined very precisely for a constant operating point. Even when driving under full load, the sensor 23 have reached the real temperature after approx. 2 to 3 seconds at the latest, so that it can be checked whether the maximum permissible exhaust gas temperature is not exceeded and then, if necessary, a targeted enrichment can take place.

In summary, it can be stated that using the sensor 23 (e.g. a temperature sensor) and the corresponding modeled temperature T _ATM (at the same position as that of the sensor 23) of the exhaust gas temperature model 28, it is possible to calibrate the exhaust gas temperature model 28 in stoichiometric operation , since in stoichiometric operation a very precise combustion lambda can be set by the lambda probe 22 (a jump lambda probe).

In non-stoichiometric operation, it is now possible, by comparing the temperature TATM modeled (by means of the exhaust gas temperature model 28) and the temperature T _S measured by means of sensor 23, to determine a temperature deviation for a correction of the lambda measurement (e.g. by means of a correction the lambda value λ _W ), and/or a combustion lambda of the internal combustion engine 11 . In addition, enrichment can be carried out for a short time if a maximum permissible temperature of the exhaust gas flow or the exhaust gas-carrying components is exceeded for a specific position. These temperatures can also be modeled using the exhaust gas temperature model 28 . These temperatures can also be used to infer how warm lambda probe 22 is.

As a result, an adjustment (adaptation) of the lambda probe 22 in non-stoichiometric operation is possible with a high level of accuracy. On the other hand, it is possible to avoid short-term overlapping of a permissible component temperature. This results in better component protection during a service life to be guaranteed and more efficient use of fuel during high-load operation of the internal combustion engine 11. In addition, the accuracy during a catalytic converter diagnosis, oxygen storage capacity measurement and lambda diagnosis is higher. The sensor 23 can also be used for boost pressure control, exhaust gas aftertreatment and catalytic converter heating.

It makes sense for the sensor 23 to be arranged where it is also useful outside of the method according to the invention. A sensible installation option is installation in an area that extends from a manifold of the exhaust system to a funnel upstream of the catalytic converter. Ideally, the sensor 23 z. B. in the vicinity of a collector (not shown) of the exhaust system 17 is positioned.

In addition to being used in a motor vehicle, the method can also be used wherever a lambda probe is used in order to control a non-stoichiometric mixture in particular. These include e.g. B. Engines in the shipping industry, motorcycle engines and gas engines for heating systems in buildings.

Reference List

10

control device

11

internal combustion engine

12

injection system

14

intake tract

16

actuator

17

exhaust system

18

exhaust duct

20

catalyst

22

lambda probe

23

sensor

24

further lambda probe

26

engine control

28

exhaust temperature model

λW

measured lambda value

U.S

probe voltage

TS

temperature measured or determined by the sensor

TATM

temperature determined by means of the exhaust gas temperature model

KA

maximum allowable calibration deviation

no

maximum allowable calibrated deviation

YES

maximum permissible adjustment deviation

Yes

maximum allowable adjusted deviation

I

Block I

II

Block II

K

correction block

Y

Condition fulfilled (yes / ja)

N

Condition not met (no / no)

Claims (3)

Method for lambda control of an internal combustion engine (11), comprising the following steps: - measuring or determining a temperature of an exhaust gas flow or of an exhaust gas-carrying component an exhaust system (17) of the internal combustion engine (11) at a predetermined position by means of at least one sensor (23); - Measuring an exhaust gas lambda by means of a lambda probe (22) arranged in the exhaust system and transmitting a measured lambda value (λ _W ) to an exhaust gas temperature model (28) of the internal combustion engine (11); - Determining the temperature of the exhaust gas flow or the exhaust gas-carrying component at the predetermined position by means of the exhaust gas temperature model (28) as a function of the measured lambda value (λ _W ); - Check whether a maximum permissible adjustment deviation between the temperature (T _{S ) measured or determined by means of the sensor (23) and the temperature (T ATM} ) determined by means of the exhaust gas temperature model (28) is exceeded, - if the maximum permissible adjustment deviation (YES) is exceeded, correcting - the lambda measurement, and/or - a combustion lambda of the internal combustion engine (11). procedure after claim 1 , characterized in that the method is carried out with a non-stoichiometric exhaust gas flow. Method according to one of the preceding claims, characterized in that the lambda probe (22) is a jump lambda probe. 4.A method according to any one of the preceding claims, characterized in that the lambda control is a continuous lambda control. 5. The method according to any one of the preceding claims, characterized in that the correction of the lambda measurement comprises correcting a heating of the lambda probe (22). 6. The method according to any one of the preceding claims, characterized in that the correction of the lambda measurement includes a correction of the measured lambda value (λ _W ). 7. The method according to any one of the preceding claims, characterized in that the method further comprises the following steps, in particular in the case of a stoichiometric exhaust gas flow: - measuring or determining the temperature of the exhaust gas flow or of the exhaust gas-carrying component of the exhaust system (17) of the internal combustion engine (11). the predetermined position by means of the at least one sensor (23); - Measuring the exhaust gas lambda by means of the lambda probe (22) arranged in the exhaust system and transmitting the measured lambda value (λ _W ) to the exhaust gas temperature model (28) of the internal combustion engine (11); - Determining the temperature of the exhaust gas flow or the exhaust gas-carrying component at the predetermined position by means of the exhaust gas temperature model (28) as a function of the measured lambda value (λ _W ); - Check whether a maximum permissible calibration deviation between the temperature (T _{S ) measured or determined by means of the sensor (23) and the temperature (T ATM} ) determined using the exhaust gas temperature model is exceeded, - if the maximum permissible calibration deviation is exceeded, calibrating the exhaust gas temperature model (28). 8. The method according to any one of the preceding claims, characterized in that the method comprises a step of enriching when the temperature (T _S ) measured or determined by means of the sensor (23) or a temperature determined by means of the exhaust gas temperature model at any position has a maximum permissible temperature is exceeded. 9. control device (10), designed to carry out the method according to any one of the preceding claims.

Images