DE102018219978B3 - Method for operating a drive device and corresponding drive device - Google Patents

Abstract

The invention relates to a method for operating a drive device (1) having an internal combustion engine (2) and an exhaust tract (3), in which a storage catalytic converter (12) for purifying exhaust gas of the internal combustion engine (2), a first lambda probe (13) upstream of the engine Storage catalytic converter (12) and a second lambda probe (14) downstream of the storage catalytic converter (12) are arranged, wherein a lambda value for controlling a mixture composition for the internal combustion engine (2) and an oxygen filling state of an oxygen storage of the storage catalytic converter (12) from a measurement signal of the first lambda probe ( 13). It is provided that a measurement signal of the second lambda probe (14) when present within a certain range of values for determining an offset value for the measurement signal of the first lambda probe by means of a trim control and in the presence of the determined range of values is used to set the oxygen filling state to a certain value. The invention further relates to a drive device (1).

Description

The invention relates to a method for operating a drive device with an internal combustion engine and an exhaust gas tract in which a storage catalytic converter for purifying exhaust gas of the internal combustion engine, a first lambda probe upstream of the storage catalytic converter and a second lambda probe are arranged downstream of the storage catalytic converter, wherein a lambda value for controlling a mixture composition for the internal combustion engine and an oxygen filling state of an oxygen storage of the storage catalytic converter are determined from a measurement signal of the first lambda probe. The invention further relates to a drive device.

From the prior art, for example, the publication DE 10 2016 220 850 B3 known. This describes a method for operating a drive device with a drive unit and an exhaust gas purification device, wherein the exhaust gas purification device comprises a flowed through by an exhaust stream of the drive unit catalyst and upstream of the catalyst disposed in the exhaust stream first lambda probe and a downstream of the catalyst arranged in the exhaust stream second lambda probe wherein an oxygen filling value of an oxygen storage of the catalytic converter is determined on the basis of a first lambda sensor provided by the first lambda signal and an offset value.

During a calibration step, an oxygen fill value is set to a first value corresponding to an empty oxygen reservoir or a second value corresponding to a full oxygen reservoir, the oxygen fill value is set to a default fill value, and the offset value is adjusted based on the second lambda signal. It is provided that, after the calibration step, a lambda signal waveform of the second lambda signal is monitored, and the calibration step is repeated when an extreme value is detected in the lambda signal waveform.

It is an object of the invention to propose a method for operating a drive device, which has advantages over known methods, in particular the implementation of both a trim control and an accounting of the oxygen filling state, each with high accuracy possible.

This is achieved according to the invention with a method for operating a drive device having the features of claim 1. It is provided that a measurement signal of the second lambda probe is used when present within a certain range of values for determining an offset value for the measurement signal of the first lambda probe by means of a trim control and in the presence of the predetermined range of values for setting the oxygen filling state to a specific value.

The drive device serves, for example, to drive a motor vehicle, in particular thus to provide a drive torque directed at the driving of the motor vehicle. The drive device has at least the internal combustion engine and the exhaust gas tract through which exhaust gas of the internal combustion engine is discharged, in particular in the direction of an external environment of the drive device. In the exhaust tract. is the storage catalyst, which is used to clean the exhaust gas of the internal combustion engine. The storage catalyst is present for example in the form of a NO _x storage catalytic converter. The exhaust gas tract, the exhaust gas of the internal combustion engine, in particular the entire exhaust gas generated by the internal combustion engine, is supplied. The exhaust gas supplied to the exhaust gas flows through the storage catalytic converter in which pollutants contained in the exhaust gas are converted into safer products, in particular by oxidation and / or reduction of the pollutants.

The storage catalyst has an oxygen storage or works as such. This means that in the presence of lean exhaust gas - that is in the case of excess oxygen in an operation of the internal combustion engine with lambda greater than one - oxygen from the exhaust gas passes into the oxygen storage and is cached in this. On the other hand, if rich exhaust gas is present - as a result of operation of the internal combustion engine when there is excess fuel with lambda less than one - oxygen previously stored is withdrawn. In this way, at least over a certain period of time, it is ensured that the stoichiometric ratio with lambda equal to one necessary for exhaust gas purification can be provided at least approximately in the storage catalytic converter.

The drive device has at least two lambda probes, namely the first lambda probe and the second lambda probe. The first lambda probe is arranged upstream of the storage catalytic converter so that it can be used to determine the oxygen content in the exhaust gas at this point. The first lambda probe is arranged for this purpose in such a way that it protrudes at least regionally into the exhaust gas or is in fluid communication with the exhaust gas, for example, the exhaust gas flows over it. On the other hand, the second lambda probe is arranged downstream of the storage catalytic converter and serves to determine it the oxygen content in the exhaust gas at this point. Like the first lambda probe, the second lambda probe protrudes at least regionally into the exhaust gas or is in fluid communication therewith, so that it is in particular overflowed by the exhaust gas. For example, the first lambda probe is designed as a broadband lambda probe and the second lambda probe as a jump lambda probe.

The measurement signal of the first lambda probe is used to control the mixture composition for the internal combustion engine. In that regard, the composition of the internal combustion engine supplied fuel-air mixture results as a function of the measured signal of the first lambda probe. To compensate for a possible error, in particular an offset error, the first lambda probe, the lambda value, which is ultimately based on the control of the mixture composition, for example, determined from the measured signal of the first lambda probe and the offset value. In particular, the lambda value results from the sum of the measurement signal and the offset value. In this way, the accuracy of the control of the mixture composition can be significantly improved. Alternatively, the offset value may also be used to correct the mixture composition after it has been determined by the control.

The offset value can be determined, for example, based on a measurement signal of the second lambda probe, in particular in the context of the trim control. Accordingly, therefore, the measurement signal of the second lambda probe is used to determine an error of the first lambda probe and finally to correct. However, because the exhaust gas downstream of the lambda probe must first pass through the storage catalytic converter before it reaches the second lambda probe, the latter initially reacts very slowly to a change in the exhaust gas composition, not least because of the storage capacity, in particular the oxygen storage capacity, of the storage catalytic converter. For storing or temporarily storing the oxygen, the storage catalytic converter has the oxygen storage.

Due to the sluggish reaction, the trim control can only be carried out very slowly, ie with a large time constant, in order to ensure a stable control loop. However, this means that the offset value can only be adjusted very slowly to compensate for the measurement error of the first lambda probe. Accordingly, this measurement error initially causes an undesirable deviation in the mixture composition, which can lead to increased pollutant emissions of the drive device. The trim control is, for example, a PI control, ie a trim control by means of a PI controller. Alternatively, the trim control may be a PID trim control.

In addition to the lambda value for regulating the mixture composition, the oxygen filling state of the oxygen storage device is determined from the measurement signal of the first lambda probe and-optionally-the offset value. Based on the measurement signal of the first lambda probe, the amount of oxygen entering the storage catalytic converter per unit of time is determined with lean exhaust gas, in particular with the additional use of an exhaust gas mass flow. The exhaust gas mass flow corresponds to the amount of exhaust gas which flows through the exhaust gas tract and in particular the storage catalytic converter per unit time. If, on the other hand, rich exhaust gas is present, it is calculated or at least estimated how much oxygen is discharged from the oxygen storage of the storage catalytic converter through the exhaust gas.

In other words, using the measurement signal of the first lambda probe, an oxygen balance is performed to determine the oxygen-filled state of the oxygen storage. The oxygen filling state describes the amount of oxygen present in the oxygen storage, preferably based on a normalization value. This normalization value is, for example, a maximum amount of oxygen that can be temporarily stored in the oxygen reservoir, so that the oxygen filling state can assume values between 0% and 100%. It should be understood that the described oxygen fill state is a calculated value that ideally, but not necessarily, matches the actual oxygen fill state of the oxygen store. The (modeled) oxygen filling state can thus deviate at least temporarily from the actual oxygen filling state.

In order to improve the accuracy of both the determination of the offset value by means of the trim control and the determination of the oxygen filling state, it is now provided to make the use of the measurement signal of the second lambda probe dependent on its value. If the measuring signal of the second lambda probe lies in the specific value range, then it is taken as the basis for the trim control, but does not or at best indirectly influences the oxygen filling state via the trim control and corresponding to the offset value. However, if the measurement signal is outside the value range, it is used to set the oxygen filling state while the trim control is interrupted.

In other words, the measurement signal of the second lambda probe is only used to carry out the trim control if it lies in the specific value range. If it is outside the value range, then the trim control is interrupted, so that according to the offset value is at least not influenced by the trim control. The range of values is in particular determined such that the measuring signal of the second lambda probe lying in the value range has a particularly high accuracy. If, on the other hand, the measurement signal of the second lambda probe is outside the value range, it can be assumed that the accuracy of the measurement signal is lower. Accordingly, the measurement signal of the second lambda probe is only used for trim control, if it has a high accuracy.

This results in a high accuracy of the offset value and accordingly in a very accurate control of the mixture composition. Despite its lower accuracy outside the specific range of values, the measurement signal of the second lambda probe can still be used to determine the oxygen filling state, because this only requires a statement as to whether the exhaust gas is significantly rich or clearly lean. Overall, therefore, with the described method for operating the drive device, an accurate determination of both the mixture composition and the oxygen filling state is achieved.

A further embodiment of the invention provides that the trim control is suspended as long as the measurement signal of the second lambda probe is outside the specific value range. This has already been pointed out above. The suspension of the trim control may cause the offset value to remain constant as long as the second lambda probe's measurement signal is outside the specified range of values. However, it may alternatively be provided to adapt the offset value in another way, that is not by means of the trim control. With the described procedure, a particularly high accuracy of the trim control and thus of the offset value is achieved.

Within the scope of a further embodiment of the invention, it is provided that the oxygen filling state is determined from the measuring signal of the first lambda probe only if the measuring signal of the second lambda probe lies within the specific value range. It has already been explained above that the oxygen filling state results from an oxygen balancing, which is carried out on the basis of the measuring signal of the first lambda probe and-optionally-the offset value. This oxygen balancing is omitted if the measurement signal of the second lambda probe is outside the value range. Rather, in this case, the oxygen filling state is preferably determined solely as a function of the measuring signal of the second lambda probe, so that the measuring signal of the first lambda probe remains disregarded. This also serves to achieve a particularly high accuracy, namely the oxygen filling state.

A development of the invention provides that when the measurement signal of the second lambda probe is present on a first side of the range of values, a first value and, if the second lambda probe is present on a second side of the value range opposite the first side, a second value is used as the determined value , If, therefore, the measuring signal of the second lambda probe exceeds a first limit limiting the range of values on the first side, then the oxygen filling state is set to the first value. This also applies if the measurement signal of the second lambda probe on the first side is outside the value range.

If, on the other hand, the measuring signal of the second lambda probe exceeds a second limit limiting the range of values on the second side, the oxygen filling state is set to the second value. This in turn also applies if the measuring signal of the second lambda probe is present on the second side of the value range. The range of values and thus both the first limit and the second limit are preferably selected such that upon leaving the range of values, it can be concluded that the exhaust gas present downstream of the storage catalyst is either completely rich or completely lean, ie at least significantly of a stoichiometric ratio differs.

From this it can be concluded that the sour storage is either completely filled or completely emptied, so that the oxygen filling state corresponding to the first value or the second value can be assigned. This results in a high accuracy of the determined oxygen filling state, because it is not determined by means of the oxygen balancing on the basis of the measured value of the first lambda probe, but is determined on the basis of the measuring signal of the second lambda probe.

A further embodiment of the invention provides that the value used is a value corresponding to a completely filled oxygen storage and the value corresponding to a value corresponding to a completely empty oxygen storage. This has already been indicated above. Leaves the measuring signal of the second Lambda probe the range of values in the direction of the first side, so the exhaust gas present downstream of the storage catalyst is lean. Accordingly, the oxygen storage is completely filled. Conversely, rich exhaust gas is present downstream of the storage catalytic converter if the measurement signal of the second lambda probe leaves the value range in the direction of the second side. It can be concluded in this respect that the oxygen storage is completely emptied. Consequently, therefore, the oxygen filling state is set to a value corresponding to a completely empty oxygen storage. From this procedure, the high accuracy results in the determination of the oxygen filling state.

A further embodiment of the invention provides that the oxygen filling state is regulated immediately after setting to the predetermined value to a default filling state. The default charge state is the state to which the oxygen storage of the storage catalyst is to be adjusted. He therefore indicates the amount of oxygen, which should be cached after the rules in the oxygen storage. If the measurement signal of the second lambda probe is outside the specific range of values, a control period is initiated within which the internal combustion engine is controlled in such a way that the oxygen filling state changes in the direction of the default filling state.

The default fill state is preferably different from the first value and the second value, for example, it is centered or approximately midway between them. The default filling state thus corresponds, for example, to a half oxygen-loaded oxygen storage. It should be noted again that the oxygen filling state corresponds to a theoretical filling state of the oxygen storage. The amount of oxygen actually present in the oxygen storage does not necessarily have to correspond to the oxygen filling state, although ideally this is the case.

Operation of the internal combustion engine to control the oxygen fill state to the default fill state is accomplished by appropriate adjustment of the blend composition. It has already been explained above that the trim control is preferably suspended if the measurement signal of the second lambda probe is outside the specified value range. In this case, the offset value is not determined by the trim control, but adjusted by the determined correction value. If the measurement signal of the second lambda probe is within the specific range of values, the offset value is determined by means of the trim control, so that within the range of values a slow, but very accurate control is made, whereby the offset value can be adjusted very precisely to a possible fault of the first lambda probe and insofar as an accurate correction of the measurement signal of the first lambda probe takes place.

If, on the other hand, the measurement signal of the second lambda probe is outside the specific range of values, then an adjustment of the offset value which is only rough but extremely rapid is to be undertaken. For this purpose, the offset value is adjusted with the determined correction value. For example, the correction value is added to the previous offset value to obtain a new offset value. Of course, however, a subtraction is possible. The correction value can basically be chosen arbitrarily. For example, it is constant. Alternatively, however, a variable correction value can also be realized.

It can be provided that the offset value is adjusted by the correction value only if the measurement signal of the second lambda probe is at least a certain difference value outside the specific value range. It can thus be provided that the adjustment takes place only when the measurement signal is spaced from the respective nearest limit of the range of values by an amount which is at least equal to or greater than the determined difference value. It can be provided that the correction value is determined as a function of the measurement signal of the first lambda probe and / or the second lambda probe. By way of example, the further the measurement signal of the second lambda probe lies outside the determined value range, the greater the correction value is selected. Larger deviations mean a stronger correction or adjustment of the offset value. Thus, the offset value can be adapted particularly fast to the actual conditions or the error of the first lambda probe. Overall, this is a particularly accurate. Determining the offset value and correspondingly a very good correction of a fault of the first lambda probe possible.

A further embodiment of the invention provides that a broadband lambda probe is used as the first lambda probe and / or a jump lambda probe is used as the second lambda probe. Compared to the broadband lambda probe, the jump lambda probe has only a relatively small lambda window, within which the respective measurement signal changes. For example, the lambda window of the jump lambda probe lies in a range of approximately 0.98 to 1.02, within which the measurement signal supplied by the lambda probe changes. Outside of this Lambdafensters the measurement signal remains constant or at least almost constant.

Using the broadband lambda probe, on the other hand, a lambda window can be covered, which is several times larger than the lambda window of the jump lambda probe. For example, the lambda window of the broadband lambda probe is in an area bounded by a lower bound and an upper bound, the lower bound being, for example, 0.8 to 0.9 and the upper bound 1.1 to 1.2. Of course, both lambda probes can be designed either as a broadband lambda probe or as a jump lambda probe. However, the first lambda probe is particularly preferably designed as a broadband lambda probe and the second lambda probe is designed as a jump lambda probe. With such a design of the lambda probes a highly accurate control of the mixture composition is possible.

Finally, it can be provided within the scope of a further embodiment of the invention that the oxygen filling state is determined by means of a model, in particular integrally, from the measured value of the first lambda probe. The oxygen filling state is preferably determined solely on the basis of the measured value of the first lambda probe, so that the measured value of the second lambda probe is not considered. This is sufficient to establish an accounting of the oxygen input into the oxygen storage and the oxygen discharge from the oxygen storage. However, it can also be provided to use, in addition to the measurement signal of the first lambda signal, the measurement signal of the second lambda signal for determining the oxygen filling state as long as the measurement signal of the second lambda probe lies within the determined value range.

In this way, the accuracy can be further increased because also the amount of oxygen leaving the storage catalyst is determined more accurately. If the second lambda probe is designed as a jump lambda probe, a linearization of the measured value of the second lambda probe can be carried out for this purpose, for example. The determination of the oxygen filling state is particularly preferably carried out integrally, ie starting from a defined value, for example the first value or the second value, which is used to reset the oxygen filling state under the conditions mentioned.

The invention further relates to a drive device, in particular for carrying out the method according to the statements in this description, with an internal combustion engine and an exhaust tract, in which a storage catalytic converter for purifying exhaust gas of the internal combustion engine, a first lambda probe upstream of the storage catalytic converter and a second lambda probe downstream of the Storage catalytic converter are arranged, wherein a lambda value for controlling a mixture composition for the internal combustion engine and an oxygen filling state of an oxygen storage of the storage catalytic converter are determined from a measurement signal of the first lambda probe. It is provided that the drive device is adapted to a measurement signal of the second lambda probe when present within a certain range of values for determining an offset value for the measurement signal of the first lambda probe by means of a trim control and in the presence of the determined range of values for setting the oxygen filling state to a specific value to use.

The advantages of such an embodiment of the drive device or such an approach has already been discussed. Both the drive device and the method for its operation can be further developed according to the statements in the context of this description, so that reference is made to this extent.

• 1 eine schematische Darstellung einer Antriebseinrichtung mit einer Brennkraftmaschine und einem Abgastrakt,
• 2 eine schematische Darstellung einer Regelstrecke der Antriebseinrichtung, sowie
• 3 zwei Diagramme, anhand welchen ein Verfahren zum Betreiben der Antriebseinrichtung beschrieben wird.

The invention will be explained in more detail with reference to the embodiments illustrated in the drawings, without any limitation of the invention. Showing:

• 1 a schematic representation of a drive device with an internal combustion engine and an exhaust tract,
• 2 a schematic representation of a controlled system of the drive device, as well
• 3 two diagrams by which a method for operating the drive device will be described.

The 1 shows a schematic representation of a drive device 1 that have an internal combustion engine 2 as well as an exhaust tract 3 features. In the embodiment shown here, the internal combustion engine 2 several cylinders, each with a combustion chamber 4 on. Each of the cylinders has at least one inlet valve 5 and at least one exhaust valve 6 , About each of the intake valves 5 can the respective cylinder fresh gas from a fresh gas tract 7 whereas, through each of the exhaust valves 6 Exhaust gas from the corresponding cylinder can escape, namely in the direction of the exhaust tract 3 ,

The fresh gas is at the intake valves 5 by means of a compressor 8th provided which part of an exhaust gas turbocharger 9 is. In addition to the compressor 8th shows the exhaust gas turbocharger 9 a turbine 10 on, which via an exhaust pipe 11 , which is part of the exhaust tract 3 is, to the exhaust valves 6 fluidically connected. Downstream of the turbine 10 is a storage catalyst 12 in front. Upstream of the storage catalyst 12 is a first lambda probe 13 and downstream of a second lambda probe 14 in front. Downstream of the second lambda probe 14 the exhaust tract opens 3 , For example via a tailpipe, in an external environment of the drive device 1 on. It should be noted that the exhaust gas turbocharger 9 purely optional. He can also be omitted accordingly.

The 2 shows a control loop 15 the drive device 1 , In a controlled system 16 of the control loop 15 lie the internal combustion engine 2 and the storage catalyst 12 in front. The lambda probes 13 and 14 or the measured values supplied by these are also indicated schematically. A mixture composition for the internal combustion engine 2 is by means of a lambda controller 17 determined. This receives at least the measured value of the first lambda probe 13 as an input variable, in particular a lambda value, which results from the measured value of the first lambda probe 13 and an offset value is determined. Of course, it can also be provided, the lambda controller 17 the measured value of the first lambda probe 13 and to supply the offset value separately from each other.

The measured value of the first lambda probe 13 flows - either uncorrected or corrected by the offset value - in an oxygen balancing, by means of which an oxygen filling state of an oxygen storage of the storage catalyst 12 is calculated. The oxygen balance 18 serves as an oxygen balance regulator, thus performing a control of the oxygen fill state to a default fill state. The input is the control loop 15 a lambda setpoint 19 on. The oxygen balance 18 In addition, an exhaust gas mass flow 20 and the default fill state 21 fed. Furthermore, the control loop includes 15 a trim controller 22 which is a correction of the lambda desired value 19 or a correction of the measured value of the first lambda probe 13 , By means of the trim controller 22 In particular, the offset value is determined. The trim controller 22 has as input the measured value of the second lambda probe 14 on.

In the operation of the drive device 1 it is intended by means of the lambda controller 17 a mixture composition for the internal combustion engine 2 to regulate. In this case, a lambda value for regulating the mixture composition from the measurement signal of the first lambda probe 13 and the offset value. The offset value can either be used directly for the correction of the measurement signal of the first lambda probe, so that the lambda controller 17 already the corrected lambda value is supplied. Alternatively, as shown here, first by means of the lambda controller 17 a lambda control is performed and the result of the lambda control of the determination of the lambda value is corrected with the offset value. In addition, using the oxygen balance 18 an oxygen filling state of the oxygen storage of the storage catalyst 12 determined and adjusted to a default filling state.

Because the reading of the first lambda probe 13 Usually erroneous, the already mentioned offset is using the trim controller 22 certainly. It is provided, the measurement signal of the second lambda probe 14 when present within a certain range of values for determining the offset value by means of the trim controller 22 and, if present outside the determined range of values, to set the oxygen fill state to a particular value. For this purpose, reference is made to the further statements in the context of this description.

The 3 shows two diagrams, wherein in an upper of the diagrams of the measuring signal of the first lambda probe 13 and the offset value determined lambda value λ over time t is applied. In a lower of the diagrams, however, is the measurement signal U the second lambda probe 14 over time t shown. In the lower diagram is a certain value range 23 indicated, which extends purely by way of example from 0.40 V to 0.75 V. Of course, another value for the lower limit and / or the upper limit may be provided. In the specific range of values 23 is no concrete statement about the oxygen filling state of the storage catalytic converter 12 or an oxygen storage of the storage catalyst 12 possible. For this reason, when the measurement signal is present U the second lambda probe 14 in the range of values 23 the trim control by means of the trim controller 22 for determining the offset value.

On the other hand lies the measuring signal U the second lambda probe 14 outside the range of values 23 , it may be provided to suspend the trim control. For example, it is provided in this case to adjust the offset value by a certain correction value. The correction value may, for example, be constant or a function of the measurement signal of the first lambda probe 13 and / or the measurement signal of the second lambda probe 14 be determined. It is particularly preferably provided that the correction value from the oxygen filling state and / or an exhaust gas mass flow through the exhaust gas tract 3 is determined.

It becomes clear that the measuring signal of the second lambda probe 14 in the period of t _o ≦ t <t ₁ outside the range of values 23 is present. For this reason, a regeneration period is initiated at the time t = t ₁ , during which the storage catalytic converter 12 or its oxygen storage is regenerated. This includes filling or emptying the oxygen storage device in dependence on the measurement signal of the second lambda probe 14 , In the exemplary embodiment illustrated here, there is an excess of oxygen, so that the oxygen reservoir is filled, in particular completely filled.

Accordingly, the oxygen storage is emptied during the regeneration period. For this purpose, the internal combustion engine 2 operated with a richer mixture composition than before, ie for t <t ₁ . This can be seen directly on the lambda value according to the upper diagram. The regeneration period extends from t ₁ to t ₂ . At the end of the regeneration period, ie at t = t ₂ , the offset value is adjusted with the determined correction value. This is also evident in the course of the measurement signal of the first lambda probe 13 to recognize, wherein the offset value is denoted by Δλ ₁ . The correction value becomes, in particular, from the oxygen filling state of the storage catalytic converter 12 and / or the exhaust gas mass flow determined.

Subsequently, in the period t ₂ <t <t _3, the mixture composition is again carried out by regulation based on the lambda value. However, since the measurement signal of the second lambda probe according to the lower diagram continues to be outside the specific range of values, a regeneration period is again initiated, which differs from t ₃ to t ₄ extends. Again at the end of the regeneration period, the offset value is adjusted, the correction value in the upper diagram now being shown as Δλ ₂ is designated. For t> t ₄ , the offset value is again determined by means of the trim control. It can be seen that the measurement signal of the second lambda probe 13 increases.

It can be provided that the offset value is adapted via the correction value only when the measurement signal of the second lambda probe 14 at least by a certain difference value outside the specified value range 23 lies. This criterion is at the time t ₅ and subsequently not met. Although a regeneration period is initiated again, because the measured value of the first lambda probe 13 outside the specified range, however, at the end of this regeneration period, the offset value will not be adjusted with the determined correction value. As a result of regenerating the storage catalytic converter in the last-described regeneration period, the measurement signal of the second lambda probe increases 14 such that it is subsequently in the determined range of values. As a result, after the regeneration period, the offset value is merely adjusted by means of the trim control using the trim controller 22 certainly.

It is not necessary in this respect, again a regeneration of the storage catalyst 12 initiate and / or adjust the offset value. Rather, could in the manner described, the offset value significantly faster to a fault of the first lambda probe 13 adjusted as would have been possible with the help of the trim control alone. Accordingly, a more accurate control of the mixture composition for the internal combustion engine is faster 2 possible, resulting in a lower pollutant emission of the internal combustion engine 2 follows.

Additionally or alternatively, it is provided, the oxygen filling state of the storage catalyst 12 to set to a certain value when the measurement signal of the second lambda probe 14 is outside the specified range. By way of example, if the measurement signal is present, a first value is used on a first side of the value range, and a second value is used as the determined value on the presence of the measurement signal on a second side opposite the first side. The first value corresponds to a completely filled oxygen storage, whereas the second value corresponds to a completely empty oxygen storage. In this way, a particularly accurate determination of the oxygen filling state of the oxygen storage of the storage catalyst 12 respectively.

Claims (10)

Method for operating a drive device (1) with an internal combustion engine (2) and an exhaust tract (3), in which a storage catalytic converter (12) for purifying exhaust gas of the internal combustion engine (2), a first lambda probe (13) upstream of the storage catalytic converter (12) and a second lambda probe (14) downstream of the storage catalytic converter (12) are arranged, wherein a lambda value for controlling a mixture composition for the internal combustion engine (2) and an oxygen filling state of an oxygen storage of the storage catalytic converter (12) from a measurement signal of the first lambda probe (13) are determined , characterized in that a measurement signal of the second lambda probe (14) when present within a certain range of values for determining an offset value for the measurement signal of the first lambda probe by means of a trim control and in the presence of the predetermined range of values Set the oxygen fill state to a specific value. Method according to Claim 1 , characterized in that the trim control is suspended as long as the measurement signal of the second lambda probe (14) is outside the certain range of values. Method according to one of the preceding claims, characterized in that the oxygen filling state is determined from the measuring signal of the first lambda probe (13) only if the measuring signal of the second lambda probe (14) lies within the determined value range. Method according to one of the preceding claims, characterized in that in the presence of the measurement signal of the second lambda probe (14) on a first side of the value range (23) a first value and in the presence of the measurement signal of the second lambda probe (14) on one of the first side opposite second side of the value range (23) a second value is used as a specific value. Method according to one of the preceding claims, characterized in that as the first value corresponding to a completely filled oxygen storage value and the second value is used a value corresponding to a completely empty oxygen storage. Method according to one of the preceding claims, characterized in that the oxygen filling state is regulated immediately after setting to the predetermined value to a default filling state. Method according to one of the preceding claims, characterized in that the offset value is adjusted by a specific correction value when the measurement signal of the second lambda probe (14) is outside the determined value range (23). Method according to one of the preceding claims, characterized in that a broadband lambda probe is used as first lambda probe (13) and / or a jump lambda probe is used as second lambda probe (14). Method according to one of the preceding claims, characterized in that the oxygen filling state is determined by means of a model, in particular integrally, from the measured value of the first lambda probe (13). Drive device (1), in particular for carrying out the method according to one or more of the preceding claims, with an internal combustion engine (2) and an exhaust tract (3), in which a storage catalytic converter (12) for purifying exhaust gas of the internal combustion engine (2), a first Lambda probe (13) upstream of the storage catalytic converter (12) and a second lambda probe (14) downstream of the storage catalytic converter (12) are arranged, wherein a lambda value for controlling a mixture composition for the internal combustion engine (2) and an oxygen filling state of an oxygen storage of the storage catalytic converter (12) a measurement signal of the first lambda probe (13) are determined, characterized in that the drive device (1) is adapted to a measurement signal of the second lambda probe (14) when present within a certain range of values for determining an offset value for the measurement signal of the first lambda probe by means of a Trim control and at Vorlie outside of the specified range of values to set the oxygen fill state to a particular value.

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