Method for operating a drive unit for a motor vehicle, corresponding drive unit and computer program product

Abstract

The invention relates to a method for operating a drive unit (2) for a motor vehicle (1), which has an exhaust-generating drive unit and a component that influences the composition of the exhaust gas, wherein an aging value of an aging parameter describing the condition of the component is determined and, if a threshold value is exceeded, a fault in the component is detected by the aging value. It is provided that an operating parameter describing the operation of the drive unit is determined and the threshold value is selected depending on the operating parameter. The invention further relates to a drive unit (2) for a motor vehicle (1) and a computer program product.

Description

[0001] The invention relates to a method for operating a drive unit for a motor vehicle, which has an exhaust-generating drive unit and a component that influences the composition of the exhaust gas, wherein an aging value of an aging parameter describing the condition of the component is determined and, if a threshold value is exceeded by the aging value, a fault of the component is detected, an operating parameter describing the operation of the drive unit is determined and the threshold value is selected depending on the operating parameter. The invention further relates to a drive unit for a motor vehicle and a computer program product.

[0002] For example, the prior art includes German patent application DE 10 2019 220 343 A1. This describes a method for controlling an SCR catalyst, comprising: detecting concentration values ​​in the exhaust gas downstream of the catalyst, wherein at least one concentration value for NH3 and one concentration value for NO3 are recorded. x is recorded; calculation of modeled concentration values ​​for NH3 and NO x downstream of the catalyst based on a catalyst model, wherein the model includes an aging parameter which at least partially describes the aging of the modeled catalyst; comparing the measured concentration values ​​with the modeled concentration values; and, depending on the result of the comparison, changing the change parameter of the model and / or changing a predetermined dosage of a reducing agent in the SCR catalyst.

[0003] Furthermore, publication GB 2 475 318 A discloses a method for diagnosing a catalytic device of an engine exhaust aftertreatment system, wherein the method comprises at least one phase for estimating an aging index of the catalytic device. The estimation of the aging index is provided to include the following steps: determining the operating temperature of the catalytic device, determining an aging factor as a function of at least the determined operating temperature, determining the time period that the catalytic device has spent at the determined operating temperature, calculating a contributing aging coefficient as a function of the aging factor of the time period, and increasing a cumulative aging parameter by adding the contributing aging coefficient.

[0004] German patent application DE 41 39 560 A1 describes a method for obtaining a value for assessing the aging state of a catalytic converter connected to an internal combustion engine using a pre-catalyst signal measured by a gas probe located upstream of the catalytic converter and a post-catalyst signal measured by a gas probe located downstream of the catalytic converter. The method is performed during steady-state operation of the internal combustion engine. The pre- and post-catalyst signals are multiplied together, and the products are averaged over several oscillations of the pre-catalyst signal. The resulting average value can then be used to assess the aging state of the catalytic converter.

[0005] Further documents known from the prior art include US 2014 / 0 208 721 A1, DE 198 39 791 A1 and EP 3 201 444 B1.

[0006] The object of the invention is to propose a method for operating a drive unit for a motor vehicle which has advantages over known methods, in particular avoiding false detection of the fault of the component and thus unnecessary replacement of the component.

[0007] According to the invention, this is achieved by a method for operating a drive unit for a motor vehicle with the features of claim 1. It is provided that the determination of the operating parameter and the selection of the threshold value are carried out depending on the operating parameter such that the threshold value is lower when the drive unit is operating with high dynamics than when the drive unit is operating with low dynamics, wherein the fuel consumption of the drive unit relative to a distance traveled by the motor vehicle is used as the operating parameter.

[0008] Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims. It should be noted that the exemplary embodiments described in the description are not limiting; rather, any variations of the features disclosed in the description, the claims, and the figures are possible.

[0009] The method is designed for operating the drive system. It is preferably implemented or carried out by means of a control unit for the drive system. The drive system or its control unit is preferably an integral part of the motor vehicle, but can of course also be separate from it, particularly until the drive system or the control unit is mounted on or in the motor vehicle. The drive system serves to propel the motor vehicle, i.e., to provide a drive torque directed towards propelling the motor vehicle. To provide the drive torque, the drive system includes the drive unit. The drive unit is preferably an internal combustion engine, in particular a gasoline engine or a diesel engine.

[0010] During operation, the drive unit is supplied with fuel and fresh gas at least intermittently, with the fresh gas containing fresh air at least intermittently. Additionally, the fresh gas may contain exhaust gas if exhaust gas recirculation is implemented, in which the exhaust gas generated by the drive unit is at least partially returned to the drive unit 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 then reacted within the drive unit.

[0011] During operation of the engine, exhaust gas is produced due to the chemical reaction of fuel and fresh air. This exhaust gas is discharged towards the outside environment of the engine or vehicle. Since the exhaust gas generated by the engine contains pollutants, it is preferably subjected to an exhaust aftertreatment system before being released into the environment. In the exhaust aftertreatment system, the pollutants are at least partially converted into less harmful products. Only after passing through the exhaust aftertreatment system is the exhaust gas discharged into the environment, in particular through an exhaust pipe of the engine.

[0012] The exhaust aftertreatment system preferably comprises at least one vehicle catalyst, in particular a three-way catalyst, an oxidation catalyst, an NO catalyst x- a storage catalyst or an SCR catalyst. The vehicle catalyst may be integrated into a particulate filter, particularly a gasoline particulate filter or a diesel particulate filter. For this purpose, the particulate filter is, for example, provided with a catalytic coating. The conversion rate, and thus the conversion efficiency of the exhaust aftertreatment system, which converts the pollutants into less harmful products, depends in particular on the composition of the exhaust gas supplied to the exhaust aftertreatment system or the vehicle catalyst, as well as on the temperature of the exhaust aftertreatment system.

[0013] The components of the exhaust gas produced by the engine are also referred to as raw emissions. Raw emissions describe the composition of the exhaust gas upstream of the exhaust aftertreatment system, or in terms of flow characteristics, between the engine and the exhaust aftertreatment system. As the exhaust gas passes through the aftertreatment system, some of the substances contained within it are transformed, thus changing its composition. The substances present in the exhaust gas downstream of the aftertreatment system, which constitute the exhaust gas, are also referred to as tailpipe emissions, since this is the composition of the exhaust gas released into the environment through the engine's tailpipe.

[0014] As mentioned, the amount of pollutants contained in the tailpipe emissions depends on the raw emissions, but also on the conversion efficiency of the exhaust aftertreatment system or the vehicle's catalytic converter. This efficiency is temperature-dependent. Specifically, the conversion efficiency decreases the greater the temperature of the exhaust aftertreatment system or the vehicle's catalytic converter deviates from its operating temperature; in other words, the greater the absolute difference between the temperatures. The temperature of the exhaust aftertreatment system or the vehicle's catalytic converter refers, for example, to the temperature of a ceramic honeycomb structure coated with the catalytic material.

[0015] The exhaust aftertreatment system and / or the catalytic converter, for example, represents the component that influences the composition of the exhaust gas. This component is understood to be, in particular, a device that is located between the engine and the tailpipe. The exhaust gas from the engine flows through and / or over this component and is designed and configured to alter the composition of the exhaust gas, at least temporarily. In principle, the component can also be a device separate from the exhaust aftertreatment system or the vehicle's catalytic converter. For example, the component can also be a sensor or probe, such as a lambda sensor or similar device. Naturally, it is also possible for the engine to have multiple components.In this case, the explanations for the component are preferably applicable to each of the multiple components.

[0016] The aging value is determined for the component. The aging value is a measure of the aging parameter that describes the component's condition. Specifically, the aging value initially corresponds to a first value and changes as the component ages, moving towards a second value that differs from the first. For example, the aging value increases with the component's aging. If the aging value exceeds the threshold, meaning it is greater than the threshold, it is assumed that the component can no longer modify the exhaust gas composition as desired due to aging. In the case of a vehicle's catalytic converter, this manifests itself, for example, in the inability to sufficiently convert a specific exhaust gas component.

[0017] Accordingly, when the aging value exceeds the threshold, a component fault is detected. Preferably, in this case, a fault signal is generated and / or an error message is displayed to the vehicle user. The drive system or drive unit may be operated depending on the fault signal. As long as the fault signal is not present, i.e., the aging value is less than or equal to the threshold, normal operation of the drive system or drive unit is permitted. However, if the fault signal is present, i.e., the aging value is greater than the threshold, the operation of the drive system or drive unit may be restricted.For example, it is intended that the rated power of the drive unit or drive system will not be limited, or at most only to a first value, as long as the fault signal is not present. However, if the fault signal is present, the power is limited to a second value, which is preferably lower than the first value. This takes into account the fact that the component can no longer influence the exhaust gas in the desired way.

[0018] If a vehicle is operated very dynamically, fuel consumption increases over the distance traveled, resulting in more emissions per unit of distance. Consequently, the threshold must be set strictly, i.e., relatively low, to reliably prevent emissions from exceeding a predetermined limit. However, this also means that the component may, even after only a short period of aging, exhibit an aging value that exceeds the threshold, necessitating its replacement. Therefore, if the threshold were set to reliably prevent emissions from exceeding the limit even under consistently high power output from the drive system or power unit, the component would be replaced in numerous vehicles unnecessarily.

[0019] For this reason, according to the invention, the operating parameter describing the operation of the drive unit is first determined, and then the threshold value is selected depending on the operating parameter. The operating parameter is chosen such that it behaves differently under a lower load on the drive unit than under a higher load. For example, the operating parameter increases more slowly under a lower load than under a higher load.

[0020] The operating parameter preferably describes the operation of the drive unit from the moment the component is installed. When the component is installed, for example, during a component replacement, the operating parameter is reset, specifically to an initial value. From the moment the component is installed, the operating parameter continuously describes the operation of the drive unit. In other words, the operating parameter describes the operation of the drive unit while the component is part of the drive system, specifically completely and continuously, i.e., for the entire period during which the component is part of the drive system.

[0021] The threshold value is then determined based on the operating parameter. The determination of the operating parameter and the selection of the threshold value, depending on the operating parameter, are carried out in such a way that the threshold value is lower when the drive unit operates with high dynamics than when it operates with low dynamics. Ultimately, this means that greater component aging is tolerated as long as the drive unit is operated with low dynamics or low load. This prevents premature component replacement.

[0022] According to the invention, the fuel consumption of the drive unit, relative to a distance traveled by the motor vehicle, is used as an operating parameter. A further development of the invention provides that one of the following quantities and / or its time-dependent profile is additionally used as an operating parameter: torque of the drive unit, speed of the drive unit, power of the drive unit, and operating time of the drive unit. The operating parameter describes the operation of the drive system or the drive unit. It can be determined from at least one of the aforementioned quantities and / or its respective time-dependent profile. It can be determined from just one of the aforementioned quantities, or from several, or even all of them.

[0023] Torque describes the torque currently provided by the drive unit, and speed describes the current rotational speed of the drive unit. Similarly, power refers to the instantaneous power output of the drive unit. The operating time of the drive unit describes the duration for which the drive unit was operated to provide torque or drive torque during the operation of the drive system. Fuel consumption describes the amount of fuel consumed by the drive unit during its operation. These parameters enable a targeted determination of the operating parameters and thus a precise selection of the threshold value.

[0024] A further development of the invention provides that at least one of the following parameters is used as an aging parameter: the operating time of the component, the age of the component, and the oxygen storage capacity of the component. Operating time is understood to be the length of a cumulative period over which exhaust gas has been supplied to the component. Age is the absolute age of the component, for example, its calendar age, particularly from the time of its installation in the drive unit. Oxygen storage capacity is understood to be the component's ability to temporarily store oxygen during its operation. Typically, the oxygen storage capacity decreases with increasing age of the component, making it a reliable measure of aging. Each of the aforementioned parameters enables a reliable determination of the component's aging.

[0025] A further development of the invention provides that the threshold value is determined from the operating parameter using a mathematical relationship, a table, or a characteristic map. The operating parameter thus serves as the input for the mathematical relationship, the table, or the characteristic map. The threshold value, on the other hand, represents an output. Using the relationship, the table, or the characteristic map, the operating parameter is directly converted into the threshold value. This enables a reliable determination of the threshold value as a function of the operating parameter.

[0026] A further development of the invention provides that the threshold value is chosen to be lower the more the operating parameter indicates a heavy load on the component. This has already been explained. The heavier the load on the drive unit and thus also on the component, the smaller the remaining margin within which the component can reliably influence the exhaust gas. For this reason, the threshold value is chosen such that it is lower the heavier the load on the component. Conversely, the threshold value is higher the lower the load. This ensures, on the one hand, reliable compliance with limit values ​​even under high load on the drive unit, and on the other hand, prevents premature replacement of the component under low load on the drive unit.

[0027] The invention provides that the operating parameter is determined in relation to a distance traveled by the motor vehicle. The distance traveled is preferably understood to be the distance covered by the motor vehicle since the component was installed in the drive system. The operating parameter thus describes the load on the drive unit in relation to this distance. This results in a particularly reliable assessment of the load on the drive unit.

[0028] A further development of the invention provides that, based on the operating parameter, a threshold value data set containing a threshold is selected from several threshold value data sets. The threshold value is contained within the threshold value data set, so that the threshold value is ultimately determined as a function of the operating parameter. This results in an adjustment of the threshold value depending on the operating parameter; thus, the threshold value is selected depending on the load of the drive unit. The multiple threshold value data sets are stored, in particular, in a data memory of the control unit, with which the described method is executed. The use of the multiple threshold value data sets enables targeted adjustment of the threshold values ​​to different values ​​of the operating parameter.

[0029] A further development of the invention provides that different reference values ​​for the operating parameter are stored in the threshold data sets. To select the threshold data set, a correlation value is determined for each threshold data set between the reference value stored therein and an actual value of the operating parameter, and the threshold data set with the correlation value indicating the highest agreement is selected. The threshold data sets are thus provided for different values ​​of the operating parameter. Preferably, the threshold data sets differ consistently with respect to their reference values; that is, they do not contain identical reference values.

[0030] The correlation value describes the degree of agreement between the respective reference value and the actual value of the operating parameter. For example, the correlation value is a difference between the reference value and the actual value, specifically the absolute value of such a difference. Ultimately, the threshold data set is selected for which the determined correlation value indicates the highest agreement between the reference value and the actual value. If the difference is used, the threshold data set with the lowest correlation value is chosen. The described procedure enables the efficient selection of the threshold data set that best describes the operation of the drive unit.

[0031] The invention further relates to a drive unit for a motor vehicle, in particular for carrying out the method as described in this description, wherein the drive unit comprises an exhaust gas-generating drive unit and a component that influences the composition of the exhaust gas, and wherein the drive unit is designed and configured to determine an aging value of an aging parameter describing the condition of the component and to detect a component defect when a threshold value is exceeded. The drive unit is also designed and configured to determine an operating parameter describing the operation of the drive unit and to select the threshold value depending on the operating parameter.It is provided that the determination of the operating parameter and the selection of the threshold value are carried out depending on the operating parameter in such a way that the threshold value is lower when the drive unit is operating with high dynamics than when the drive unit is operating with low dynamics, whereby the fuel consumption of the drive unit in relation to a distance traveled by the motor vehicle is used as the operating parameter.

[0032] The advantages of such a drive system design and such a procedure have already been mentioned. Both the drive system and the method for operating it may be further developed as explained in this description, and reference is made to those explanations.

[0033] Furthermore, the invention relates to a computer program product comprising commands that cause the drive device to execute the described method as described herein. For the advantages and possible further developments, reference is made to the description in its entirety.

[0034] The features and combinations of features described in the description, in particular those described in the following figure description and / or shown in the figures, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention, in particular the scope of the claims. Thus, embodiments that are not explicitly shown or explained in the description and / or the figures, but which emerge from or can be derived from the explained embodiments, particularly within the scope of the claims, are also to be considered as encompassed by the invention.

[0035] The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawing, without limiting the invention. The only embodiment shown is... Fig. 1 A schematic representation of a motor vehicle with a drive unit which has an exhaust gas generating drive unit and a component which influences the composition of the exhaust gas.

[0036] The Fig. Figure 1 shows a schematic representation of a motor vehicle 1, which has a drive unit 2 that in turn has an exhaust-generating drive unit. The drive unit 2 also has a component that influences the composition of the exhaust gas. In the illustrated embodiment, this component is in the form of an exhaust aftertreatment device, which is fluidically arranged between the drive unit and an exhaust pipe 3 of the motor vehicle. Exhaust gas generated by the drive unit is expelled into the external environment of the motor vehicle 1 via the exhaust pipe 3.

[0037] The drive unit 2 also has a control unit 4. During operation of the drive unit, the control unit 4 determines a value for an aging parameter that describes the condition of the component. This value is also referred to as the aging value. The aging value is compared to a threshold value. If the aging value exceeds the threshold value, a fault in the component, for example, the exhaust aftertreatment system, is detected.

[0038] Additionally, an operating parameter describing the operation of the drive unit is determined. The threshold value is not fixed but is selected based on the operating parameter. This is done such that the threshold value is higher the lower the load on the drive unit during operation. Thus, if the drive unit is continuously operated at a comparatively low power output, this is reflected in a higher threshold value. Conversely, the threshold value is lower when the drive unit is under a heavier load. Accordingly, with a lower load on the drive unit, a component failure is only detected at a higher aging threshold than with a higher load. This approach reliably prevents unnecessary component replacement. REFERENCE MARK LIST: 1 motor vehicle 2 Drive unit 3 tailpipe 4 Control unit

Claims

[1] Method for operating a drive unit (2) for a motor vehicle (1) which has an exhaust gas-generating drive unit and a component influencing the composition of the exhaust gas, wherein an aging value of an aging parameter describing a state of the component is determined and, if a threshold value is exceeded by the aging value, a fault of the component is detected, wherein an operating parameter describing an operation of the drive unit is determined and the threshold value is selected depending on the operating parameter, characterized by, that the determination of the operating parameter and the selection of the threshold value depending on the operating parameter is carried out in such a way that the threshold value is lower when the drive unit is operating with high dynamics than when the drive unit is operating with low dynamics, wherein the fuel consumption of the drive unit is used as the operating parameter in relation to a distance traveled by the motor vehicle (1). [2] Method according to claim 1, characterized by , that at least one of the following parameters is used as an aging parameter: an operating time of the component, an age of the component and an oxygen storage capacity of the component. [3] Method according to any one of the preceding claims, characterized by that the threshold value is determined from the operating parameter using a mathematical relationship, a table or a characteristic map. [4] Method according to any one of the preceding claims, characterized by, that the threshold value is chosen to be lower the more the operating parameter indicates a heavy load on the component. [5] Method according to any one of the preceding claims, characterized by , that a threshold data set containing a threshold is selected from several threshold data sets based on the operating parameter. [6] Method according to claim 5, characterized by , that different comparison values ​​for the operating parameter are stored in the threshold data sets, whereby to select the threshold data set, a correlation value is determined for each of the threshold data sets between the comparison value stored in this set and an actual value of the operating parameter, and the threshold data set with the correlation value indicating the highest agreement is selected. [7] Drive unit (2) for a motor vehicle (1), in particular for carrying out the method according to one or more of the preceding claims, wherein the drive unit (2) has an exhaust gas-generating drive unit and a component influencing the composition of the exhaust gas, and wherein the drive unit (2) is provided and configured to determine an aging value of an aging parameter describing the condition of the component and to detect a component defect when a threshold value is exceeded by the aging value, wherein the drive unit (2) is also provided and configured to determine an operating parameter describing the operation of the drive unit and to select the threshold value depending on the operating parameter, characterized by, that the determination of the operating parameter and the selection of the threshold value depending on the operating parameter is carried out in such a way that the threshold value is lower when the drive unit is operating with high dynamics than when the drive unit is operating with low dynamics, wherein the fuel consumption of the drive unit is used as the operating parameter in relation to a distance traveled by the motor vehicle (1). [8] Computer program product comprising instructions that cause the drive device (2) according to claim 7 to execute the method according to one or more of claims 1 to 6.

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