DE102013216024A1 - Method for lambda control of an internal combustion engine and control device - Google Patents

Abstract

The invention relates to a method for regulating the lambda 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 by means of at least one Sensor (23); - Measuring an exhaust gas lambda by means disposed in the exhaust system lambda probe (22) 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 stream or the exhaust gas-carrying component at the predetermined position by means of the exhaust gas temperature model (28) in dependence on the measured lambda value (λW); - Check whether a maximum permissible adjustment deviation between the temperature (TS) measured or determined by means of the sensor (23) and the temperature (TATM) 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). In addition, the invention relates to a control device (10), which is designed for carrying out the method according to the invention.

Description

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

It is known to determine the oxygen concentration in a gas mixture by means of an oxygen-sensitive gas probe, a lambda probe. In this case, the lambda probe provides an actual probe signal which is dependent on the oxygen content of the gas mixture and which may 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 probe signal is converted by means of a stored characteristic curve or a corresponding calculation rule into the lambda value. The most prominent application cases are internal combustion engines in which the lambda value of the exhaust gas is determined by means of lambda probes installed in the exhaust gas duct in order to regulate the air-fuel ratio with which the engine is operated as a function of the determined lambda value. This procedure is generally referred to as lambda control.

There are differentiated leap lambda probes (also step response lambda probe) and broadband lambda probes. Jump lambda probes can provide a Nernst-principle signal curve, which has only small slopes in the case of an exhaust lambda smaller than one and greater than one and exhibits a sudden change in the region around an exhaust lambda equal to 1. Thus, jump lambda probes are usually used only for the internal combustion engines, which are regulated at lambda equal to 1. In contrast, broadband lambda probes exhibit sufficient sensitivity over the entire lambda range, which is why they allow a wider use than jump lambda probes, but on the other hand are considerably more expensive than these.

However, a conversion of the probe signal into a lambda value is made more difficult in practice by the fact that the probe signal not only depends on the exhaust gas composition but is also influenced by additional disturbing influences which cause the characteristic curve not to be constant under all conditions. In the case of jump probes, for example, it is known that the probe temperature, that is to say 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 especially in the rich lambda range, ie at lambda values of less than 1. Furthermore, changes in the characteristic curve resulting 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 curve.

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

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

The invention is based on the object 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 comprises the following steps:

• - Measuring or determining a temperature of an exhaust gas stream or an exhaust gas-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 stream or the exhaust gas-carrying component at the predetermined position by means of the exhaust gas temperature model in dependence of the measured lambda value;
• Checking 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 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.

For carrying out the method, therefore, a temperature of the exhaust gas flow or of the exhaust gas-conducting 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 may be performed at discrete times or continuously. By means of the method according to the invention, an inaccurate lambda control z. B. avoided due to aging of the lambda probe or prevented.

The method is preferably during a constant operating point and / or during full load of the internal combustion engine, ie z. B. at a constant speed and / or a full load travel of a motor vehicle, which uses the internal combustion engine to drive it, performed. As a result, a (thermal) inertia by the sensor does not matter.

On the one hand, the temperature is measured or determined by means of the at least one sensor. This can be done by the at least one sensor comprising or being at least one temperature sensor. Thus, the temperature can be measured by means of the temperature sensor. Alternatively, the at least one sensor may comprise at least one pressure sensor. Thus, the temperature can be determined by measuring a pressure of the exhaust gas flow by means of the at least one pressure sensor and then converting it to a temperature corresponding to the pressure. The conversion can be carried out by means of an exhaust gas mass flow, a gas constant and the measured pressure. The exhaust gas mass flow can be determined from a rotational speed and a load of the internal combustion engine. However, the direct measurement of the temperature by means of the temperature sensor is preferable, since this is cheaper than the pressure sensor and it also provides a higher accuracy due to the attributable conversion.

On the other hand, the temperature (at the predetermined position, ie at the position of the sensor) is determined by means of an exhaust gas temperature model. The exhaust gas temperature model is a mathematical model and 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, the exhaust gas temperature model in addition to the lambda value still other input variables, such. B. the speed and / or load of the internal combustion engine are available. The lambda value is measured by means of a lambda probe.

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

As a result of this knowledge, a wrong, measured lambda value can now be counteracted by correcting the lambda measurement and / or a combustion lambda of the internal combustion engine. The correction can be carried out until the maximum allowable adjustment deviation is exceeded, in particular until a maximum allowable adjusted deviation is exceeded, which is less than the maximum allowable adjustment deviation. The maximum permissible adjustment deviation can also be equal to 0, whereby the step of correcting is carried out as soon as there is an (arbitrarily high) deviation of the temperature measured or determined by the sensor and the temperature determined by means of the exhaust gas temperature model.

Preferably, it is provided that the method is carried out at a non-stoichiometric exhaust gas flow (with an exhaust lambda not equal to 1). The non-stoichiometric exhaust stream may be a rich exhaust stream having an exhaust lambda less than 1, and thus be effected by a non-stoichiometric (eg, rich) operating point of the internal combustion engine. The internal combustion engine is typically a gasoline engine.

It is preferably provided that the lambda probe is a jump lambda probe. The lambda probe may therefore be a voltage jump probe (Nernst probe) or a resistance jump probe. As a result of the correction according to the invention, such a high precision of the lambda value determination is achieved that the field of application of the jump Lambda sensor can be significantly extended. While in the prior art leaky lambda probes are essentially used for Lambda equal to 1 controlled internal combustion engines, the scope of a jump lambda probe, which is processed by the method according to the invention can be extended to lambda ranges not equal to 1, which can be controlled conventionally only with expensive broadband lambda probes.

The lambda control is preferably a continuous lambda control. Thus, a more accurate lambda control and a lambda control at an exhaust lambda (and thus combustion lambda) is guaranteed equal to 1.

It is preferably provided that correcting the lambda measurement comprises correcting heating of the lambda probe. The temperature of the lambda probe has a significant influence on the lambda value measured by means of the lambda probe. This is especially true for jump lambda probes for exhaust lambda smaller than 1 to be measured. The lambda probe is heated by the heating, wherein the heating is controlled 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. With increasing aging of the lambda probe, however, the internal resistance changes. As a result, the lambda probe is often operated at too high a temperature, which can assume critical dimensions with regard to component protection of the lambda probe. In addition, changes due to the high temperature of the lambda probe, the output of the lambda probe (in particular of jump lambda probes at a rich exhaust lambda). As a result, the internal combustion engine would be operated too rich without correcting the lambda measurement, which would be detrimental to the fuel consumption of the internal combustion engine. By correcting the heating of the lambda probe but this disadvantage is prevented. The correction of the heating can in particular be carried out by means of a correction of an (assumed) internal resistance of the lambda probe, which counteracts the cause of the aging-related, incorrect operating temperature of the lambda probe.

According to a preferred embodiment of the invention, it is provided that correcting the lambda measurement comprises correcting the (already) measured lambda value. Under the measured lambda value and a signal of the lambda probe, z. B. a probe voltage to be understood, which is corrected. Thus, a measured lambda value can be (subsequently) corrected, for. By applying a correction factor to the lambda value. In the context of the present invention, the term "applying a correction factor" is understood to mean a suitable accounting of the correction factor with the object to be corrected, which may include a multiplication, division, addition and subtraction. It is therefore understood that the term "correction factor" not only multipliers, but also other computational variables are understood. In addition, the lambda value can also be corrected by using a corrected characteristic.

• – 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 further comprises the following steps, in particular in the case of a stoichiometric exhaust gas stream:

• - Measuring or determining the temperature of the exhaust gas stream or the exhaust gas-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 stream or the exhaust gas-carrying component at the predetermined position by means of the exhaust gas temperature model in dependence 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 allowable calibration deviation is exceeded, calibrate the exhaust gas temperature model.

Thus, in a stoichiometric exhaust stream (ie, a stoichiometric operating point of the internal combustion engine), which z. B. can also be adjusted exactly by means of a jump lambda probe, carried out a calibration of the exhaust gas temperature model. The maximum allowable calibration deviation can also be equal to 0, whereby a calibration takes place as soon as a deviation of the temperatures is present.

It is preferably provided that the calibration of the exhaust gas temperature model takes place by means of adaptation of the temperature determined by means of the exhaust gas model at the predetermined position. As a result, the maximum permissible calibration deviation, in particular a maximum permissible calibrated deviation, which is smaller than the calibration deviation, is no longer exceeded.

It is preferably provided that the method comprises a step of enriching, if the measured by means of the sensor or certain temperature or a temperature determined by means of the exhaust gas temperature model at any (in particular predefined) position exceeds a maximum allowable temperature. The enrichment can take place in the short term, which ensures component protection of components in contact with the exhaust gas stream. By means of the exhaust gas temperature model, temperatures can be determined at any predefined position (of both the exhaust gas flow and the exhaust gas-carrying components). If it is detected that such a determined temperature or the temperature measured by means of the sensor is greater than a predefined maximum permissible temperature for the respective position, the temperature of the exhaust gas flow is lowered by means of enrichment of the internal combustion engine.

Furthermore, a control device, which is designed for carrying out the method according to the invention, is provided. The control device is characterized by a precise regulated 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 operation of the internal combustion engine.

Moreover, a motor vehicle is provided which comprises the control device according to the invention. The motor vehicle is characterized during its operation by a reduced fuel consumption and a reduced reliability.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

1 a control device,

2 a relationship between a voltage function and a temperature of a lambda probe, and

3 a 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 may be part of a motor vehicle. The control device comprises an internal combustion engine 11 , whose fuel supply via an injection system 12 he follows. In the injection system 12 it may be a port injection or a direct injection. The internal combustion engine 11 is also via an intake 14 supplied with air. Optionally, the amount of air supplied via a in the intake 14 arranged controllable actuator 16 For example, a throttle valve to be regulated.

One from the internal combustion engine 11 generated exhaust gas flow is via an exhaust system 17 with an exhaust duct (an exhaust pipe) 18 released into the environment, with environmentally relevant exhaust gas constituents through a catalyst 20 be implemented.

Inside the exhaust duct 18 is a lambda probe at a position close to the engine 22 arranged, which is in particular a relatively inexpensive jump lambda probe. Optionally, another lambda probe 24 downstream of the catalyst 20 may be arranged, which may also be a jump lambda probe or a broadband lambda probe.

The signals of the lambda probes 22 and 24 be to a motor control 26 transmitted. In the case of using Nernstsonden as Sprunglambdasonden so the probe signals are probe voltages. The probe voltage U _S is the probe voltage of the lambda probe 22 , Other signals not shown sensors also go into the engine control 26 one. Thus, the engine control also receives data of the internal combustion engine 11 , which include, for example, the current engine speed n and the current relative engine load L as inputs, and the operating point of the internal combustion engine 11 mark. The engine control 26 controls in dependence on the incoming signals in a known manner various components of the internal combustion engine 11 at. In particular, as a function of the probe voltage U _S, the lambda probe close to the engine is used 22 a regulation of the internal combustion engine 11 supplied air-fuel mixture, for which the engine control 26 one about the fuel injection system 12 amount of fuel to be supplied and / or via the intake system 14 regulates the amount of air to be supplied.

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 For example, the temperature of the exhaust gas flow or an exhaust gas carrying component of the exhaust system is measured at a predetermined position and the engine control 26 transmitted. Depending on which type of temperature sensor is used, different signals can be sent to the motor controller 26 be transmitted. In an exemplary Using a thermocouple as a temperature sensor can supply a voltage to the motor control 26 be transmitted. As an alternative to the temperature sensor, the sensor 23 also be a pressure sensor, wherein a pressure of the exhaust gas flow is measured and then converted into a temperature of the exhaust gas flow.

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

Also the engine control 26 can contain algorithms in computer-readable form as well as suitable characteristics and maps.

The lambda probe 22 includes a heater which is used to heat the lambda probe 22 is formed and the lambda probe 22 regulated to a predetermined target temperature. An actual temperature of the lambda probe 22 can by an internal resistance of the lambda probe 22 and / or one of the exhaust gas temperature model 28 at the position of the lambda probe 22 determined temperature T _ATM .

The internal resistance of the lambda probe 22 However, changes with progressive aging of the lambda probe 22 , Due to an incorrectly determined actual temperature, the target temperature of the lambda probe 22 no longer respected. This can cause the lambda probe 22 is operated too hot. On the one hand, this can lead to a reduced lifetime of the lambda probe 22 on the other hand, however, also to a wrong sized combustion lambda of the internal combustion engine 11 in a non-stoichiometric operation.

In 2 is the relationship between one of a lambda probe 22 (a Nernst probe) supplied voltage and the temperature of the lambda probe 22 seen.

It is assumed below that the combustion lambda the exhaust lambda at the position of the lambda probe 22 equivalent. Suppose the engine control 26 should the internal combustion engine 11 to a non-stoichiometric combustion lambda of 0.98. Further assumed, the engine control takes into account (contrary to the method according to the invention) an aging of the lambda probe 22 Not. Thus, the engine control assumes that the lambda probe 22 is operated at the intended target temperature and determines the current exhaust lambda due to the solid curve, which is to be used for a correct target temperature. Thus controls the engine control 26 the combustion lambda such that the lambda probe 22 a probe voltage U _S of about 0.75 volts outputs. Due to the unaccounted for aging of the lambda probe 22 However, this is operated as described above, hotter than the engine control 26 accepted. Thus, the engine control should 26 for a corrected lambda measurement, actually use the lower dashed line. It follows that the (erroneous) of the engine control 26 The desired probe voltage U _S of approximately 0.75 volts actually corresponds to a combustion lambda of 0.93 instead of 0.98. The now fatter than desired adjusted combustion lambda causes an undesirably increased fuel consumption by an additional enrichment.

In the case of a deviation of the measured lambda value λ _W from the actual exhaust lambda, which results in an excessively lean combustion lambda (and thus the internal combustion engine 11 which is operated with a wrong characteristic, or in a wrong area of a map), it can happen that the internal combustion engine 11 is operated too hot.

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

3 shows a procedure for the lambda control of the internal combustion engine 11 according to a preferred embodiment of the invention during a continuous lambda control. In this case, only the aspects of the lambda control according to the present invention in a preferred embodiment will be discussed. General known processes for lambda control will not be discussed.

First, in step 100 determines if any of the engine control 26 by means of the lambda probe 22 determined lambda value λ _{W is} equal to 1.

If the lambda value λ _{W is} equal to 1, then block I be checked if a calibration of the exhaust gas temperature model 28 should take place and if necessary, these are carried out. For this purpose, it is first checked whether a maximum allowable calibration deviation KA between one by means of the sensor 23 measured or determined temperature T _S and by means of the exhaust gas temperature model 28 (at the same position at the same time) certain temperature T _{ATM is} exceeded. For this purpose, a difference between the by means of the sensor 23 measured or determined temperature T _S and by means of the exhaust gas temperature model 28 certain temperature T _{ATM are} formed. If the amount of the difference is greater than a maximum allowable calibration deviation KA, calibration of the exhaust temperature model is performed. If the difference is less than or equal to the maximum allowable calibration deviation KA, it may be possible to recheck the lambda value according to step 100 be continued. The calibration of the exhaust gas temperature model 28 takes place in step 104 , This can be the exhaust gas temperature model 28 be adjusted so far that a new temperature T _ATM by means of the sensor 23 measured or specific temperature T _S corresponds. This may be, for example, via a suitable application of a correction factor to algorithms of the exhaust gas temperature model 28 respectively. Alternatively, it may also be sufficient that a deviation determined by means of the new temperature T _ATM does not exceed a maximum permissible calibrated deviation kA (not equal to 0), which is smaller than the calibration deviation. Subsequently, with step 100 be continued.

The calibration of the exhaust gas temperature model 28 at a lambda value equal to 1 is therefore possible, as even with already-aged lambda probes 22 an exhaust lambda equal to 1 measured relatively accurately and thus the internal combustion engine 11 can be operated relatively accurately with a combustion lambda equal to 1. The reason is in 2 seen. If one transmits to the lower dashed line that 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, only a minimal deviation of the measured lambda value λ _W from the actual exhaust gas lambda. Thus, with a measured lambda value λ _W equal to 1, it can be assumed with high certainty that not an lambda probe operated at the wrong temperature 22 the reason for exceeding the maximum allowable calibration deviation KA is.

As an example of the method steps according to block I can at a lambda value equal to 1 by means of the sensor 23 measured or determined temperature T _S 800 ° C and by means of the exhaust gas temperature model 28 certain temperature T _{ATM be} 750 ° C. At a maximum allowable calibration deviation of z. B. 20 ° C, this means that a calibration is performed. After calibration, this is done by means of the exhaust gas temperature model 28 certain temperature T _ATM 800 ° C.

The means of the exhaust gas temperature model 28 determinable temperatures of the exhaust gas flow or the exhaust gas-carrying components (at any position) of the exhaust system 17 are interdependent. Thus these other determinable temperatures were also calibrated. This z. B. also one of the exhaust gas temperature model 28 certain temperature of the lambda probe 22 calibrated. This can in turn for a more accurate heating of the lambda probe 22 and / or for a more accurate selection of a suitable characteristic according to 2 be used.

If the lambda value λ _{W is} not equal to 1, then according to block II be checked whether a correction of the lambda measurement, and / or the combustion lambda of the internal combustion engine 11 to be carried out. This is done first according to step 110 Check if a maximum allowable calibration deviation is YES between the sensor 23 measured or determined temperature T _S and by means of the exhaust gas temperature model 28 at the position of the sensor 23 certain temperature T _{ATM is} exceeded. For this purpose, in turn, a difference between the means of the sensor 23 measured or determined temperature T _S and by means of the exhaust gas temperature model 28 certain temperature T _{ATM are} formed. If the amount of the difference is greater than the maximum allowable adjustment deviation, YES, a correction is made to the lambda measurement and / or the combustion lambda of the internal combustion engine 11 performed according to the correction block K. If the difference is less than or equal to the maximum allowable calibration deviation, then the lambda value check may be performed in accordance with step 100 be continued.

The correction of the lambda measurement according to step 122 may include a step of correcting the heating of the lambda probe 22 include. Thus, a deviation of the measured lambda value λ _W due to an incorrectly controlled temperature of the lambda probe 22 Fixed. This can be done by one in the engine control 26 stored (ie due to aging erroneously assumed) internal resistance of the lambda probe 22 is corrected. This correction of the temperature T _S leads to that for determining the lambda value λ _{W of} the engine control 26 already a correct probe voltage U _S is available.

Another way of correcting the lambda measurement according to step 122 can be done by measuring the lambda probe 22 is not directly affected so that it outputs a modified probe voltage U _S , but the correction first subsequently by the engine control 26 is performed in the determination of the lambda value λ _W. 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 (eg to a corresponding characteristic according to FIG 2 is changed).

Another (alternative or additional) possibility of correction is in step 124 , which is a (direct) correction of the combustion lambda of the internal combustion engine 11 includes. This can be done by changing the fuel supply to the internal combustion engine 11 respectively. If the by means of the exhaust gas temperature model 28 certain temperature T _ATM greater than that by means of the sensor 23 certain temperature T _S , this can be corrected by means of a Anfettens.

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

The corrections can be made until after step 112 a maximum allowable adjusted deviation jA between one by means of the sensor 23 measured or determined temperature T _S and by means of the exhaust gas temperature model 28 at the position of the sensor 23 certain temperature T _{ATM is} no longer exceeded. The adjusted deviation jA is smaller than the adjustment deviation YES. For this purpose, a difference between the by means of the sensor 23 measured or determined temperature T _S and by means of the exhaust gas temperature model 28 certain temperature T _{ATM are} formed. If the amount of the difference is greater than the maximum allowable adjusted deviation jA, a new correction of the lambda measurement and / or the combustion lambda of the internal combustion engine 11 performed according to the correction block K. Otherwise, the correction is complete. Alternatively, the correction may be made until the temperature T _ATM equals the temperature T _S , which is a special case with an adjusted deviation jA equal to zero. As a further alternative, the correction may already be completed when the difference is less than or equal to the maximum allowable adjustment deviation YES. Furthermore, the block II also controlled (ie by a controller) done.

As an example of the method steps according to block II can at a lambda value λ _W not equal to 1 by means of the sensor 23 measured or determined temperature T _S 850 ° C and by means of the exhaust gas temperature model 28 certain temperature T _{ATM be} 750 ° C. At a maximum allowable adjustment deviation of z. B. 50 ° C, this means that a correction is performed. For this purpose, at least one of the above-mentioned corrections is performed until the difference of the temperatures T _S and T _{ATM is} less than or equal to the maximum allowable adjusted deviation jA of z. B. 20 ° C is. In the example, the correction is thus completed at a temperature T _ATM of 830 ° C.

The described method is an adaptation of the measured lambda value due to aging of the lambda probe 22 possible. In addition, an adaptation of boundary layer probes can take place. Boundary probes are lambda probes 22 which have properties at the outer edge of an acceptable specification (due to a series spread).

In addition, depending on the circumstances and trust of the (possibly adapted by other means) lambda value λ _W for the reliable achievement of a desired Bauteleschutzlambda z. B. 4% additionally greased. This means that if a component protection lambda of z. B 0.9, which in reality is 0.92 due to a deviation, results in a real lambda value after enrichment of 0.88. Thus, the internal combustion engine has been operated fatter than actually required for component protection. The resulting excess consumption of fuel can be reduced or eliminated by the method according to the invention.

Is the sensor 23 a temperature sensor, this is usually slower than the exhaust gas temperature model, that is, the temperature sensor, which z. B. may be a thermocouple, for reasons of ruggedness should have a relatively large diameter and therefore a heating of the thermocouple requires a period of time. For the proposed method is the dynamics of the sensor 23 however, not crucial if done during a cruise. A temperature sensor also has the advantage that the temperature of the exhaust stream for a constant operating point can be determined very accurately. Even at full load, the sensor should 23 After approx. 2 to 3 seconds, the actual temperature has reached the latest so that it can be checked whether the maximum permissible exhaust gas temperature is not exceeded and, if necessary, targeted enrichment can then take place.

In summary, it can be stated that it is using the sensor 23 (eg 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 is possible, in stoichiometric operation, the exhaust gas temperature model 28 to calibrate, since in stoichiometric operation, a very accurate combustion lambda through the lambda probe 22 (a jump lambda probe) is adjustable.

In non-stoichiometric operation, it is now possible by means of an adjustment of the (by means of the exhaust gas temperature model 28 ) modeled temperature T _ATM and that by means of the sensor 23 measured temperature T _s a temperature deviation for a correction of the lambda measurement (eg., By means of a correction of the lambda value λ _W ), and / or a combustion lambda of the internal combustion engine 11 to use. In addition, in the short term when exceeding a, for a given position in each case the maximum permissible temperature of the exhaust gas stream or the exhaust gas-carrying components enrichment can be performed. These temperatures can also by means of the exhaust gas temperature model 28 be modeled. Based on these temperatures can also be deduced how warm the lambda probe 22 is.

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

It makes sense to use the sensor 23 thus arranged there where it is also useful outside the method according to the invention. A useful possibility of installation is an installation in an area that extends from a manifold of the exhaust system to a funnel upstream of the catalyst. Ideally, the sensor will 23 z. B. in the vicinity of a collector (not shown) of the exhaust system 17 positioned.

In addition to use in a motor vehicle, the method can also be used wherever a lambda probe is used in order to control a mixture which is in particular non-stoichiometric. These include z. As motors in the shipping industry, motorcycle engines and gas engines for heating systems of buildings.

LIST OF REFERENCE NUMBERS

10

 control device

11

 Internal combustion engine

12

 injection

14

 intake system

16

 actuator

17

 exhaust system

18

 exhaust duct

20

 catalyst

22

 lambda probe

23

 sensor

24

 further lambda probe

26

 motor control

28

 Exhaust gas temperature model

λ _W

 measured lambda value

U _S

 probe voltage

T _S

 temperature measured by the sensor

T _ATM

 temperature determined by the exhaust gas temperature model

KA

 maximum permissible calibration deviation

kA

 maximum permissible 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 / yes)

N

 Condition not fulfilled (no / no)

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 2649272 A1 [0006]

Claims (9)

Method for lambda control of an internal combustion engine ( 11 ), comprising the following steps: measuring or determining a temperature of an exhaust gas stream or of an exhaust gas-carrying component of an exhaust gas 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 arranged in the exhaust system ( 22 ) 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 stream or of 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 sensor ( 23 ) measured or determined temperature (T _S ) and by means of the exhaust gas temperature model ( 28 ) exceeded certain temperature (T _ATM ), - when the maximum allowable adjustment deviation (YES) is exceeded, correcting - the lambda measurement, and / or - a combustion lambda of the internal combustion engine ( 11 ). A method according to claim 1, characterized in that the method is carried out at a non-stoichiometric exhaust gas stream. Method according to one of the preceding claims, characterized in that the lambda probe ( 22 ) is a jump lambda probe. Method according to one of the preceding claims, characterized in that the lambda control is a continuous lambda control. Method according to one of the preceding claims, characterized in that correcting the lambda measurement correcting a heating of the lambda probe ( 22 ). Method according to one of the preceding claims, characterized in that the correction of the lambda measurement comprises correcting the measured lambda value (λ _W ). Method according to one of the preceding claims, characterized in that the method further comprises, in particular in the case of a stoichiometric exhaust gas flow, the following steps: measuring or determining the temperature of the exhaust gas stream or of the exhaust gas-carrying component of the exhaust gas system ( 17 ) of the internal combustion engine ( 11 ) at the predetermined position by means of the at least one sensor ( 23 ); Measuring the exhaust gas lambda by means of the lambda probe arranged in the exhaust system ( 22 ) 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 stream or of 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 sensor ( 23 ) measured and determined temperature (T _S ) and the temperature determined by the exhaust gas temperature model (T _ATM ) is exceeded, - when the maximum allowable calibration deviation is exceeded, calibration of the exhaust gas temperature model ( 28 ). Method according to one of the preceding claims, characterized in that the method comprises a step of enriching, when the means of the sensor ( 23 ) measured or determined temperature (T _S ) or a temperature determined by means of the exhaust gas temperature temperature at any position exceeds a maximum allowable temperature. Regulating device ( 10 ), adapted for carrying out the method according to one of the preceding claims.

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