Method for operating a drive device for a motor vehicle and corresponding drive device

Abstract

The invention relates to a method for operating a drive device for a motor vehicle, wherein the drive device has an exhaust-gas-generating drive unit, and by means of an exhaust gas probe an exhaust gas value describing a composition of the exhaust gas is determined, and for a plurality of systems of the drive device a state value describing the state of the respective system is determined, in each case as part of a system diagnosis. According to the invention, for each of the plurality of systems, it is defined in at least one system defect data set whether a system defect of the respective system affects the exhaust gas value, wherein if the exhaust gas value departs from an exhaust gas range, the system defect data sets of the systems are first put on a checklist of system defect data sets to be checked, and then, those system defect data sets for which it is defined that the exhaust gas value is not affected are removed from the checklist, wherein for the system defect data sets remaining on the checklist, a device diagnosis is carried out to detect the system defect of the respective system based on the state value. The invention further relates to a drive device for a motor vehicle.

Description

[0001] Method for operating a drive device for a motor vehicle and corresponding drive device

[0002] DESCRIPTION:

[0003] The invention relates to a method for operating a drive device for a motor vehicle, wherein the drive device has a drive unit that generates exhaust gases, and an exhaust gas value describing the composition of the exhaust gas is determined by means of an exhaust gas probe, and a status value describing a state of the respective system is determined for several systems of the drive device as part of a system diagnosis. The invention further relates to a drive device for a motor vehicle.

[0004] For example, the prior art document DE 10 2021 003 415 A1 is known. This document describes a control unit for monitoring the emission behavior of a machine, wherein the monitoring is carried out based on a first emission influence of a component of the machine. The control unit is designed and configured to perform the following steps: determining a first defect measure of a first component of the machine, determining a first emission influence based on the determined first defect measure, and monitoring the emission behavior of the machine based on the first emission influence.

[0005] It is an object of the invention to propose a method for operating a drive device which has advantages over the prior art, in particular detects a system defect in one of the systems of the drive device with high reliability even if the system diagnosis of the respective system does not indicate such a defect.

[0006] This is achieved according to the invention with a method for operating a drive device for a motor vehicle with the features of claim 1. It is provided that for each of the plurality of systems, it is stored in at least one system defect data record whether a system defect of the respective system affects the exhaust gas value, wherein when the exhaust gas value leaves an exhaust gas value range, the system defect data records are first placed on a checklist of system defect data records to be checked and then those system defect data records for which no influence on the exhaust gas value is stored are removed from the checklist, wherein for the system defect data records remaining on the checklist, a device diagnosis is carried out to detect the system defect of the respective system on the basis of the status value.

[0007] Advantageous embodiments with useful further developments of the invention are specified in the dependent claims. It should be noted that the exemplary embodiments explained in the description are not limiting; rather, any variations of the features disclosed in the description, the claims, and the figures are feasible.

[0008] The drive device serves to drive the motor vehicle, i.e. to provide a drive torque directed towards driving the motor vehicle. The drive device is preferably a component of the motor vehicle, but can of course also be separate from it. To provide the drive torque, the drive device has the drive unit, which is preferably designed as an internal combustion engine. During operation of the drive device, fuel and fresh gas are supplied to the drive unit at least temporarily, wherein the fresh gas contains fresh air at least temporarily. In addition, the fresh gas can comprise exhaust gas, provided that exhaust gas recirculation is implemented, in which the exhaust gas generated by the drive unit is at least partially recirculated into the drive unit, namely as a component of the fresh gas.The fuel and fresh gas supplied to the drive unit form a fuel-fresh gas mixture with a specific composition, which is reacted in the drive unit.

[0009] During operation of the drive unit, exhaust gas is produced due to the chemical reaction between fuel and fresh gas, which is discharged towards the outside environment of the drive device or the motor vehicle. Preferably, the exhaust gas is first fed to an exhaust gas aftertreatment device before being released into the outside environment, since the exhaust gas generated by the drive unit contains pollutants. In the exhaust gas aftertreatment device, the pollutants are at least partially converted into less hazardous products. Only after passing through the exhaust gas aftertreatment device is the exhaust gas discharged into the outside environment. The exhaust gas aftertreatment device is available, for example, as a vehicle catalyst, in particular as a three-way catalyst, oxidation catalyst, NO xStorage catalyst or SCR catalyst. However, it can also be designed as a particulate filter, in particular as a gasoline particulate filter or as a diesel particulate filter, preferably with an integrated vehicle catalyst, for example with a catalytic coating.

[0010] The drive system has several systems, each of which represents a part of the drive system. Systems include, for example, components of the drive system or drive unit, but additionally or alternatively also software programs that run on a control unit of the drive system. The systems therefore include any elements of the drive system, in particular those that influence the composition and / or throughput of the exhaust gas. Throughput refers to the amount of exhaust gas per unit of time, in particular an exhaust gas mass flow or an exhaust gas volume flow.Purely by way of example, the systems of the drive device comprise one or more of the following systems: high-pressure fuel pump, fuel pressure sensor, load sensor, mixture adaptation, tank ventilation valve, exhaust gas aftertreatment device, lambda probe, in particular pre-cat lambda probe or post-cat lambda probe, temperature sensor, ambient pressure sensor, charger, in particular compressor and / or exhaust gas turbocharger, boost pressure sensor, intake manifold leak test, camshaft adjuster, crankcase ventilation, EVAP system, in particular tank leak test, expansion valve test or fuel tank shut-off valve test, cooling system, cylinder imbalance sensor, idle speed controller, cold start strategy, valve lift switchover, exhaust flap, knock sensor and ignition detection.

[0011] System diagnostics are performed for each of the drive system's systems, during which the status value is determined. The status value describes the status of the respective system and is determined to monitor the individual system. During system diagnostics, only one of the systems is considered at a time; accordingly, a separate system diagnosis is performed for each of the systems. This procedure is commonly referred to as on-board diagnostics (OBD). It can provide an indication of a possible system defect in individual systems.

[0012] Furthermore, the exhaust gas probe is used to determine the exhaust gas value, which describes the composition of the exhaust gas. The exhaust gas value therefore provides an indication of the concentration of at least one exhaust gas component in the exhaust gas. The exhaust gas probe can, for example, be provided and arranged to measure raw emissions from the drive unit or to measure tailpipe emissions. In the former case, it is arranged fluidically between the drive unit and the exhaust gas aftertreatment device; in the latter case, it is arranged downstream of the exhaust gas aftertreatment device, i.e. fluidically between the exhaust gas aftertreatment device and a tailpipe through which the exhaust gas is released into the outside environment. The exhaust gas value can be used to monitor the emissions of the drive unit. For example, if an exhaust gas threshold is exceeded, the exhaust gas value can be used to detect a device defect in the drive unit.

[0013] However, the exhaust gas value determined using the exhaust gas sensor is primarily used to detect a system defect in one of the systems, particularly a system defect in the system that caused the exhaust gas value to exceed the exhaust gas threshold. This particularly indicates a potential system defect in one of the systems without having to first check multiple systems, for example, during a repair of the drive system. This process can also be referred to as "pinpointing."

[0014] Of course, only a single exhaust gas value can be used. Preferably, however, multiple exhaust gas values ​​are used, which are available in particular for several different exhaust gas components. In this respect, it is provided to determine at least one exhaust gas value using at least one exhaust gas probe. Further preferably, each of these exhaust gas values ​​is assigned to one of several exhaust gas value ranges. The procedure described for the system defect data sets is carried out, for example, if one or more of the exhaust gas values ​​leave their respective assigned exhaust gas value range.

[0015] The diagnosis of the multiple systems as a whole is carried out as part of a system diagnosis. In contrast to the system diagnosis, this does not just look at a single system, but rather at several systems. The system diagnosis provides feedback as to which of the systems has the system defect or at least for which of the systems this is the case with a certain probability. In order to carry out the system diagnosis, a record is stored for each of the systems as to whether the system defect in the respective system affects the exhaust gas value, particularly in a data store. For example, a flag is stored for each of the systems in the data store which has a first state if the system defect in the respective system affects the exhaust gas value and a second value if this is not the case. The system defect data records are used for this purpose. At least one system data record is stored for each of the systems.However, it can also be provided that for one or more of the systems, several system data records are stored, which describe different types of system defects.

[0016] If the exhaust gas value now leaves the exhaust gas value range, i.e. lies outside the exhaust gas value range, the system diagnosis is carried out, and only then. As part of the system diagnosis, first all system defect data records or at least some of the system defect data records are placed on the checklist, which specifies or lists the system defect data records to be checked. Subsequently, all system defect data records for which no influence on the exhaust gas value is stored are removed from the checklist, i.e. whose system is not the cause of the exhaust gas value leaving the exhaust gas value range, or at most is unlikely to be the cause. Therefore, those system defect data records whose systems potentially caused the exhaust gas value to deviate from the exhaust gas value range remain on the checklist.

[0017] At this point, it should be noted that in this description, systems, system data sets, and system defects are sometimes referred to in the plural. It goes without saying that any number of systems, system data sets, and system defects can exist, i.e., no system, no system data set, and no system defect, or just one system, just one system data set, and just one system defect. This applies in particular when system data sets are to be removed from the checklist. In this case, depending on whether the respective condition applies, no system data set, just one system data set, or multiple system data sets can be removed from the checklist.After the checklist has been provided, the remaining system defect data records on the checklist are further reviewed using the status value assigned to their respective system as part of the system diagnosis in order to determine the potential system defect. The status value is used to determine the probability that the respective system caused the deviation of the exhaust gas value from the exhaust gas value range. In other words, the system diagnosis of the corresponding system is performed for each of the remaining system defect data records. It should be noted that the system status values ​​used during the system diagnosis correspond to the status values ​​determined during the system diagnosis. The status values ​​are therefore not redetermined for the system diagnosis; instead, the values ​​previously determined for the system diagnosis are used.

[0018] Preferably, the system defect is subsequently identified for one of the remaining system data sets on the checklist, or the system assigned to it, based on its respective status value, i.e., at the end of the device diagnosis or after the device diagnosis. For example, this occurs for the system whose status value has exceeded or is closest to a status threshold assigned to the system.

[0019] In this way, the system responsible for the exhaust gas deviation from the emission range can be identified with a high degree of certainty. Accordingly, the system can be replaced or initiated as part of the maintenance of the drive system or the vehicle without any further diagnostic effort.

[0020] Optionally, the system defect records removed from the checklist can also be written to a checklist. For example, the checklist is emptied beforehand. If the checklist is completely empty after the system defect records have been removed, i.e., no system defect records are contained in it, the system defect record with the worst—usually the highest—status value stored for the system is preferentially selected from the checklist. The system error is detected for this system.

[0021] Preferably, this is only the case if the status value has also exceeded a threshold value assigned to the system. This threshold value is preferably selected to be lower than the status threshold value, the exceedance of which alone would indicate a system defect. Therefore, to detect a system defect, the exhaust gas value must first leave the exhaust gas value range, the checklist must be empty or all system defect data records must be removed from it, and the status value of the system with the worst status value must also exceed the threshold value. The described procedure is preferably applied after performing the system diagnosis.

[0022] A further development of the invention provides that for each of the multiple system defect data sets, the direction in which the system defect of the respective system affects the exhaust gas value is stored, and when the exhaust gas value leaves the exhaust gas value range in a certain direction, those system defect data sets for which no influence on the exhaust gas value in the certain direction is stored are removed from the checklist. In addition to the information as to whether the system defect of the respective system affects the exhaust gas value at all, information is also stored as to the direction in which the exhaust gas value changes due to the system defect. Consequently, the change in the exhaust gas value in the certain direction or its departure from the exhaust gas value range in this direction can be determined with even greater accuracy as to which system is responsible for this.

[0023] For this purpose, if the exhaust gas value lies outside the exhaust gas value range, the direction in which the exhaust gas value has left the exhaust gas value range is determined, for example, whether the exhaust gas value is smaller than a lower limit of the exhaust gas value range or larger than an upper limit of the exhaust gas value range. Depending on the direction in which the exhaust gas value lies outside the exhaust gas value range, those system defect data records are removed from the checklist for which no influence on the exhaust gas value in this direction is recorded or for which only an influence in the opposite direction is recorded. This further improves the accuracy of the described method.

[0024] A further development of the invention provides that for at least one of the systems, several system defect data sets are stored for different types of system defect and their influence on the exhaust gas value. It can happen that different changes in the exhaust gas value occur with different types of system defect or different system defects in the system. If, for example, the high-pressure fuel pump delivers too high a pressure, this will have a different effect on the exhaust gas value than if it delivers too low a pressure. Depending on the exhaust gas component for which the exhaust gas value is being determined, for example, excessive pressure causes a change in the exhaust gas value, whereas excessive pressure has no effect on the exhaust gas value or, at most, a significantly smaller effect. By storing the different types of system defect and their respective influence on the exhaust gas value, the accuracy can be further improved.The system is preferably recorded multiple times in the checklist, namely for each of the different types of system defects. This is done in the form of multiple system defect records for the system.

[0025] A further development of the invention provides that the exhaust gas value is one of several exhaust gas values ​​that are determined for different exhaust gas components and / or for different operating states of the drive device and / or for different configurations of the drive unit. Therefore, there is not just a single exhaust gas value, but several exhaust gas values ​​are used to carry out the device diagnosis. In particular, the device diagnosis is carried out when one of the several exhaust gas values ​​leaves its respective assigned exhaust gas value range, i.e. lies outside of it. The exhaust gas values ​​are available, for example, for different exhaust gas components. They can be determined using different exhaust gas probes. However, they are preferably determined using the same exhaust gas probe, namely in particular by exploiting a cross-sensitivity of the exhaust gas probe. For example, the exhaust gas probe is a NO X- Sensor that has a NHs cross-sensitivity. Using the exhaust gas sensor, an exhaust gas value for NO X and an exhaust gas value for NH3 is determined.

[0026] Additionally or alternatively, the multiple exhaust gas values ​​are determined for different operating states of the drive system. One of the exhaust gas values ​​is thus determined for a first operating state, and another of the exhaust gas values ​​is determined for a second operating state that differs from the first operating state. The first operating state is, for example, a warm-up operating state, and the second operating state is a normal operating state.The warm-up operating state preferably exists as long as at least one of the following conditions is met: the exhaust gas aftertreatment device is heated, a temperature of the exhaust gas aftertreatment device is less than a temperature threshold value, an air mass flowing through the exhaust gas aftertreatment device since the start of operation of the drive device is less than an air mass threshold value and a quantity of heat introduced into the exhaust gas aftertreatment device since the start of operation is less than a heat quantity threshold value. For example, the warm-up state exists as long as at least one of the mentioned conditions is met. However, it can also be provided that several or all of the mentioned conditions must be met. If the conditions or the conditions for the warm-up state are no longer met, the normal operating state exists.

[0027] Additionally or alternatively, different configurations of the drive system or drive unit can be stored for at least one of the systems. For example, if the drive unit has multiple cylinder banks, the system defects can be stored for each of the cylinder banks, along with their respective impact on the exhaust emissions. For this purpose, multiple system defect data sets are stored for the affected system(s).

[0028] If exhaust gas values ​​are used for two different exhaust gas components and for two different operating states of the drive system, a total of four exhaust gas values ​​are available. For the above examples, these are: a first exhaust gas value for NO X during warm-up operation, a second exhaust gas value for NO Xduring normal operating conditions, a third exhaust gas value for NH3 during warm-up operating conditions, and a fourth exhaust gas value for NH3 during normal operating conditions. A separate exhaust gas value range is defined for each of these exhaust gas values, upon exceeding which the system diagnosis is performed. Furthermore, for each of the exhaust gas values, it is stored for each of the system defect data sets whether the system defect of the respective system affects the respective exhaust gas value. The procedure described enables a particularly detailed system diagnosis.

[0029] A further development of the invention provides that an exhaust gas measurement value is measured using the exhaust gas probe, and the exhaust gas value is determined from the exhaust gas measurement value by cumulating the values ​​over a distance traveled by the vehicle and normalizing them using the distance traveled and / or by normalizing them using a model value determined using an exhaust gas model. The exhaust gas value is therefore not measured directly using the exhaust gas probe, but rather determined from the measured exhaust gas value. This at least partially eliminates influences that may be due, for example, to different distances traveled and / or different driving styles.

[0030] To determine the exhaust gas value, the measured exhaust gas value is first cumulated, i.e., summed up or integrated, particularly since the vehicle began driving. The start of driving refers, in particular, to the start of the drive system or drive unit after the vehicle has been switched off. The cumulative exhaust gas value is then normalized using the distance traveled since the vehicle began driving, so that the exhaust gas value is ultimately expressed as mass or weight per unit of distance, for example, as grams per kilometer.

[0031] Additionally or alternatively, the exhaust gas value is determined from the measured exhaust gas value by normalizing it using the model value. The model value is the result of the exhaust gas model, which is used to calculate the theoretical exhaust gas value. For example, the exhaust gas model uses at least one operating variable of the drive device or drive unit as an input variable, for example an operating point of the drive unit, which describes the drive torque currently provided by the drive unit and / or the current speed of the drive unit. The model value supplied by the exhaust gas model as an output variable describes the composition of the exhaust gas in the event that all systems are fully functional. For example, the exhaust gas model assumes that all systems are in a new condition.

[0032] Particularly preferably, the exhaust gas value is derived from the measured exhaust gas value by cumulating it over the distance traveled by the vehicle and normalizing it using both the distance traveled and the model value. Consequently, the exhaust gas value does not directly describe the composition of the exhaust gas, but only indirectly, namely by describing the deviations of the exhaust gas composition from a modeled exhaust gas composition. The described procedure largely eliminates influences attributable to uncontrollable boundary conditions, such as the driver's driving behavior, thus enabling reliable system diagnosis.

[0033] A further development of the invention provides that the measurement of the exhaust gas value is carried out continuously, in particular throughout a driving cycle of the motor vehicle. The exhaust gas value is measured, for example, at short intervals, i.e., several times during the driving cycle. The driving cycle extends from the start of the journey to the end of the journey of the motor vehicle. However, it is particularly preferred that the exhaust gas value for the driving cycle be calculated only once, for example, at the start of the driving cycle or at the end of the driving cycle. In this respect, in the case of multiple driving cycles, the exhaust gas value is determined only once for each of the driving cycles. This enables reliable implementation of the device diagnosis.

[0034] A further development of the invention provides that at least for the system defect data records remaining on the checklist, the state value of the respective system is normalized using a state threshold value. If the state value is exceeded, the system defect of the respective system is detected independently of the exhaust gas measurement value. As already explained above, the respective state value is determined for each of the systems. This applies at least to those systems for which system defect data records remain on the checklist, but can of course be provided for all systems. For each of the systems, the state threshold value is also defined. If the state value exceeds the state threshold value, the system defect of the respective system is detected independently of the exhaust gas measurement value. Such a procedure is provided in particular in the context of system diagnostics, i.e. when diagnosing the individual systems.This procedure can also be referred to as on-board diagnostics.

[0035] Within the scope of device diagnostics, the state threshold is preferably used to normalize the state value. The normalized state value is therefore available as the state value divided by the state threshold. The normalized state value allows a statement to be made about the state of the respective system. Within the scope of device diagnostics, the normalized state value is always preferably used instead of the state value, even if this is not specifically indicated. The described procedure enables a further improvement in the accuracy of device diagnostics.

[0036] A further development of the invention provides that, within the framework of the device diagnosis, at least one of the following diagnostic types is performed for the system defect data records remaining on the checklist: correlation diagnosis, linkage diagnosis, statistical diagnosis, and intrusive diagnosis. Typically, several system defect data records remain on the checklist after the exhaust gas value has been evaluated. In order to further narrow down the checklist and thus ultimately be able to make a plausible statement about the system defect of one of the systems, at least one of the aforementioned diagnostic types is performed before the system defect of the system is identified, for example, based on the system defect data records still remaining on the checklist using the status value of the respective system. It can be provided that only one of the aforementioned diagnostic types is performed.Preferably, however, several diagnostic types are used, in particular all diagnostic types for the remaining system defect data records on the checklist. The diagnostic types are preferably used in the specified order, but a different order is also possible in principle. The use of at least one diagnostic type enables a reliable statement about the system defect of a particular system.

[0037] A further development of the invention provides that, within the framework of the correlation diagnosis, at least the system defect data sets remaining on the checklist are checked for the presence of a temporal correlation between a temporal profile of the exhaust gas value and a temporal profile of the status value for the respective system. If the correlation is present for at least one of the system defect data sets, all system defect data sets for which the correlation is not determined are removed from the checklist. By means of the correlation diagnosis, the temporal profile of the exhaust gas value is to be correlated with the temporal profiles of the status values ​​of those systems for which at least one system defect data set remains on the checklist.Ultimately, each of the system defect data sets, or at least the remaining system defect data sets on the checklist, is assigned a correlation measure that reflects the degree of dependence between the evolution of the exhaust gas value and the evolution of the condition value for the respective system. The correlation measure is presented, for example, in the form of a correlation coefficient.

[0038] If, during the correlation diagnosis, it is determined that a change in the temporal progression of the exhaust gas value coincides with a change in the temporal progression of the condition value for at least one of the system defect data sets, it is assumed that the change in the exhaust gas value was caused by the respective system. Consequently, only those system defect data sets for which such a correlation is determined, i.e., the correlation coefficient exceeds a certain threshold, are retained on the checklist. Those system defect data sets for which no correlation is determined, i.e., whose correlation coefficient is less than or equal to the threshold, are removed from the checklist.Removal from the checklist is preferably only performed if the correlation exists for one of the system defect records. This approach can typically significantly reduce the number of system defect records remaining on the checklist, allowing efficient detection of the system defect.

[0039] A further development of the invention provides that for at least a first of the system defect data records of a first of the systems, a linking condition is stored that establishes a relationship between a first change in the state value and a second change in the state value assigned to a second system. Within the scope of the linking diagnosis, those system defect data records for which the respective linking condition is not met are removed from the checklist. The linking diagnosis uses physical relationships to link the individual system defect data records to one another.This is based on the observation that a first system in the first system defect data set and a second system in the second system defect data set are physically connected, so that a change in the state value of the first system must also result in a change in the state value of the second system, or vice versa. This connection is formulated using the connection condition that links the two system defect data sets. The change in the state value of the first system is also referred to as the first state value change, and the change in the state value of the second system is also referred to as the second state value change.

[0040] The linking condition can, for example, be one of the following conditions: both the first state value change and the second state value change are different from zero, both the first state value change and the second state value change are different from zero and have the same sign, both the first state value change and the second state value change are different from zero and have the same amount within a certain tolerance.

[0041] For example, for each of the system defect data sets, a link condition is formulated to each of the other system defect data sets. Purely as an example, the first system defect data set concerns the load sensor, and the second system defect data set concerns the mixture adaptation. A defect in the load sensor inevitably also affects the mixture adaptation, so that a change in the state value of the load sensor also results in a change in the state value of the mixture adaptation. The described procedure enables the efficient elimination of the system defect data sets from the checklist.

[0042] A further development of the invention provides that, within the framework of the statistical diagnosis, a dispersion of the temporal progression of the status value for the respective system is determined at least for the system defect data records remaining on the checklist, and those system defect data records for which the dispersion is greater are removed from the checklist. The background of the statistical diagnosis is the verification of the status values ​​for their accuracy. It is assumed that status values ​​for which the temporal progression shows a smaller fluctuation or a smaller control are more reliable than those for which the fluctuation or dispersion is greater. For example, a standard deviation over the temporal progression of the status value for the respective system is calculated for each of the system defect data records.

[0043] It may be planned to remove all system defect data records from the checklist for which the standard deviation exceeds a certain threshold. Additionally or alternatively, only the system defect data record with the smallest standard deviation is retained, in particular only if the difference between the standard deviation of this system defect data record and the standard deviation of the system defect data record with the next smallest standard deviation is greater than a further threshold. Statistical diagnostics are used to verify the statistical validity of the status values. This ensures the effective implementation of the facility diagnostics.

[0044] A further development of the invention provides that, within the scope of the intrusive diagnosis, a fourth system defect data set is selected for a third of the system defect data sets, at least from the remaining system defect data sets on the checklist, for whose associated system a change in an operating state of the drive unit causes a different, in particular opposing, change in the exhaust gas value and / or the state value as for the system of the third system defect data set, wherein, after the change has been made, the system defect data set for which the change in the exhaust gas value and / or the state value does not occur is removed from the checklist. The intrusive diagnosis comprises an active intervention in the operation of the drive unit, namely the change in the operating state.For example, the change in the operating state includes a change in the composition of the fuel-fresh gas mixture, a change in the drive torque provided and / or a change in the speed of the drive unit.

[0045] The third and fourth system defect data sets are selected from those system defect data sets that react differently, particularly in opposite ways, to the change in operating state. The change in operating state is then implemented. The exhaust gas value and / or the status values ​​of the systems assigned to the system defect data sets are then evaluated. If the specified change in the exhaust gas value or the specified change in the status value does not occur for one or more system defect data sets, they are removed from the checklist. This effectively eliminates further system defect data sets. Particularly preferred is to only permit and execute intrusive diagnostics if the measured exhaust gas value exceeds a certain threshold. In this case, an error message is usually generated, in particular the MIL (Malfunction Indicator Lamp) is activated.

[0046] A further development of the invention provides that, using an exhaust component model, an exhaust component concentration of at least one exhaust component of the exhaust gas is determined and corrected using a correction factor determined from the exhaust gas value. If an exhaust component threshold value is exceeded by the exhaust component concentration, a defect in the drive system is detected. The exhaust component model serves to determine the exhaust component concentration, in particular in terms of flow between the drive unit and the exhaust gas aftertreatment system. The exhaust component model assumes that all systems of the drive system are fully functional, in particular in mint condition.

[0047] The correction factor is intended to take the actual condition of the systems into account, particularly for an exhaust component or for exhaust components for which no measured value is available from a sensor. For this purpose, the exhaust gas value is used to determine the correction factor. The correction factor is then used to correct the exhaust component concentration, for example, by multiplication. If the corrected exhaust component concentration exceeds the exhaust component threshold value, it is assumed that the exhaust emissions of the drive system are no longer within the permissible range, and a defect in the drive system is detected accordingly. This ensures reliable operation of the drive system within the intended specifications.

[0048] In other words, the exhaust component concentration of at least one exhaust component of the exhaust gas is first determined using the exhaust component model, namely for a fault-free drive system in which all systems are operating faultlessly, in particular, in mint condition. The exhaust component concentration is then corrected using the correction factor. The correction factor is thus used to describe the exhaust component concentration of an exhaust component for which no measured value is available.

[0049] The invention further relates to a drive device for a motor vehicle, in particular for carrying out the method according to the statements in the context of this description, wherein the drive device has a drive unit generating exhaust gas and is provided and designed to determine an exhaust gas value describing a composition of the exhaust gas by means of an exhaust gas probe and to determine a state value describing a state of the respective system for several systems of the drive device in each case within the scope of a system diagnosis.

[0050] It is provided that for each of the plurality of systems, it is stored in at least one system defect data record whether a system defect of the respective system affects the exhaust gas value, wherein the drive device is further provided and designed to, when the exhaust gas value leaves an exhaust gas value range, first place the system defect data records of the systems on a checklist of system defect data records to be checked and then remove those system defect data records from the checklist for which no influence on the exhaust gas value is stored, wherein a device diagnosis is carried out for the system defect data records remaining on the checklist to detect the system defect of the respective system on the basis of the status value.

[0051] The advantages of such a design of the drive device or such a procedure have already been pointed out. Both the drive device and the method for its operation can be further developed according to the explanations in this description, so reference is made to these in this regard.

[0052] The features and feature combinations described in the description, in particular the features and feature combinations described in the following description of the figures and / or shown in the figures, can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments are also considered to be encompassed by the invention that are not explicitly shown or explained in the description and / or the figures, but which follow from or can be derived from the explained embodiments.

[0053] The invention will be explained in more detail below with reference to the exemplary embodiments shown in the drawings, without limiting the invention.

[0054] Figure 1 is a schematic representation of a method for operating a drive device for a motor vehicle.

[0055] Figure 1 shows a schematic representation of a method for operating a drive system for a motor vehicle. The drive system has a drive unit generating exhaust gas and an exhaust gas probe, by means of which an exhaust gas value is determined that describes the composition of the exhaust gas from the drive unit. In module 1 of the method, a state value describing a state of the respective system is to be determined for several systems of the drive system as part of a system diagnosis. The state values ​​obtained in this way are normalized in module 2, namely using a state threshold value assigned to the respective system.

[0056] In a module 3, several system defect data sets are also stored, which are assigned to the systems. At least one of the system defect data sets is assigned to each of the systems. It can also be provided that several system defect data sets are assigned to at least one of the systems. In a module 4, an exhaust gas measurement value is determined using the exhaust gas probe and transferred to a module 5. Module 5 has a model value as a further input value, which is determined in a module 6. The model value is determined using an exhaust gas model and describes the composition of the exhaust gas when the drive system is fully functional. In module 5, an exhaust gas value is determined from the exhaust gas measurement value and the model value. This value is therefore in standardized form and can therefore also be referred to as a standardized exhaust gas value.

[0057] Module 7 checks for a deviation of the exhaust gas value from an exhaust gas value range. If a deviation is found, module 8 removes all system defect data records from the checklist for which no influence on the exhaust gas value is stored. Subsequently, several different diagnoses are carried out as part of a device diagnosis, which take place in modules 9, 10, 11 and 12. Module 9 performs a correlation diagnosis, module 10 a linkage diagnosis, module 11 a statistical diagnosis and module 12 an intrusive diagnosis. During each of the diagnoses, as many of the system data records as possible are removed from the checklist. If several system defect data records remain on the checklist, module 13 selects the system defect data record for whose assigned system the highest status value is available.Subsequently, a module 14 for the system detects a system defect in the remaining system defect data set. Furthermore, it is preferably provided that, if a threshold value is exceeded by the exhaust gas value or the measured exhaust gas value, a module 15 immediately detects a device defect in the drive system. Furthermore, it can be provided that intrusive diagnostics are enabled only in this case using a module 16. Additionally or alternatively, it can be provided that evaluation of the remaining system defect data set is enabled only in this case using a module 17 and is otherwise prevented.

[0058] Finally, it may be provided to directly compare the status values ​​of the multiple systems with a status threshold assigned to the respective system. If the status value exceeds the status threshold, the system defect of the corresponding system is immediately detected. This is indicated by arrow 18. Using the described procedure, the system in which the system defect exists is efficiently singled out. This eliminates the need for time-consuming troubleshooting or system diagnostics of the other systems.

[0059] LIST OF REFERENCE SYMBOLS:

[0060] 1 building block

[0061] 2 building blocks

[0062] 3 building blocks

[0063] 4 building blocks

[0064] 5 building blocks

[0065] 6 building blocks

[0066] 7 building blocks

[0067] 8 building blocks

[0068] 9 building blocks

[0069] 10 building blocks

[0070] 11 building blocks

[0071] 12 building blocks

[0072] 13 building blocks

[0073] 14 building blocks

[0074] 15 building blocks

[0075] 16 building blocks

[0076] 17 building blocks

[0077] 18 Arrow

Claims

PATENT CLAIMS:

1. A method for operating a drive device for a motor vehicle, wherein the drive device has a drive unit generating exhaust gas and an exhaust gas value describing a composition of the exhaust gas is determined by means of an exhaust gas probe, and for several systems of the drive device, a state value describing a state of the respective system is determined within the framework of a system diagnosis, characterized in that for each of the several systems, at least one system defect data record is stored as to whether a system defect of the respective system affects the exhaust gas value, wherein when the exhaust gas value leaves an exhaust gas value range, the system defect data records of the systems are first placed on a checklist of system defect data records to be checked and then those system defect data records for which no influence on the exhaust gas value is stored are removed from the checklist,For the system defect records remaining on the checklist, a device diagnosis is carried out to detect the system defect of the respective system based on the status value.

2. Method according to claim 1, characterized in that for each of the plurality of system defect data sets, it is stored in each case in which direction the system defect of the respective system affects the exhaust gas value, and when the exhaust gas value leaves the exhaust gas value range in a certain direction, those system defect data sets are removed from the checklist for which no influence on the exhaust gas value in the certain direction is stored.

3. Method according to one of the preceding claims, characterized in that the exhaust gas value is one of several exhaust gas values ​​which are determined for different exhaust gas components and / or for different operating states of the drive device and / or for different configurations of the drive unit.

4. Method according to one of the preceding claims, characterized in that an exhaust gas measured value is measured by means of the exhaust gas probe and the exhaust gas value is determined from the exhaust gas measured value by cumulating over a distance traveled by the vehicle and normalizing by means of the distance traveled and / or by normalizing by means of a model value determined using an exhaust gas model.

5. Method according to one of the preceding claims, characterized in that for the system defect data records remaining on the checklist, at least one of the following types of diagnosis is carried out within the framework of the device diagnosis: correlation diagnosis, linkage diagnosis, statistical diagnosis and intrusive diagnosis.

6. Method according to one of the preceding claims, characterized in that within the framework of the correlation diagnosis, at least the system defect data records remaining on the checklist are checked for the presence of a temporal correlation between a temporal course of the exhaust gas value and a temporal course of the state value for the respective system, wherein if the correlation is present for at least one of the system defect data records, all system defect data records for which the correlation is not determined are removed from the checklist.

7. Method according to one of the preceding claims, characterized in that for at least a first of the system defect data records of a first of the systems at least one linking condition is stored which establishes a connection between a first state value change of the state value assigned to the first system and a second state value change of the state value assigned to a second system, wherein as part of the linking diagnosis those system defect data records are removed from the checklist for which the respective linking condition is not fulfilled.

8. Method according to one of the preceding claims, characterized in that within the framework of the statistical diagnosis at least for the A dispersion of the temporal course of the condition value for the respective system is determined from the system defect data records remaining in the checklist and those system defect data records for which the dispersion is greater are removed from the checklist.

9. Method according to one of the preceding claims, characterized in that, within the scope of the intrusive diagnosis, for a third of the system defect data sets, a fourth system defect data set is selected at least from the system defect data sets remaining on the checklist, for whose associated system a change in an operating state of the drive unit causes a different, in particular opposing, change in the state value as for the system of the third system defect data set, wherein after making the change, that one of the system defect data sets for which the change in the state value does not occur is removed from the checklist.

10. Drive device for a motor vehicle, in particular for carrying out the method according to one or more of the preceding claims, wherein the drive device has a drive unit generating exhaust gas and is provided and designed to determine an exhaust gas value describing a composition of the exhaust gas by means of an exhaust gas probe and to determine a state value describing a state of the respective system for several systems of the drive device within the framework of a system diagnosis, characterized in that for each of the several systems it is stored in at least one system defect data record whether a system defect of the respective system affects the exhaust gas value, wherein the drive device is further provided and designed toIf the exhaust gas value leaves an exhaust gas value range, the system defect data records of the systems are first placed on a checklist of system defect data records to be checked and then those system defect data records are removed from the checklist for which no influence on the exhaust gas value is stored, whereby for the system defect data records remaining on the checklist, Device diagnosis is performed to detect the system defect of the respective system based on the status value.

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