Method for operating an exhaust gas cleaning device of a motor vehicle and corresponding exhaust gas cleaning device
By measuring signal gradient and signal delay, the second λ sensor and vehicle catalyst in the motor vehicle exhaust gas cleaning device can be quickly and accurately diagnosed, solving the problem of inaccurate diagnosis in the prior art and improving the operational reliability of the device.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- AUDI AG
- Filing Date
- 2021-07-21
- Publication Date
- 2026-06-12
AI Technical Summary
Existing technologies struggle to quickly and accurately diagnose the effectiveness of the second λ sensor and the vehicle catalytic converter in motor vehicle exhaust cleaning devices, leading to potentially inaccurate fault identification.
By measuring the signal gradient and signal delay between the signal transitions of the first and second λ sensors, and combining the signal gradient and signal delay thresholds, faults in the second λ sensor and the vehicle catalyst can be identified, ensuring the accuracy of the diagnosis.
It enables rapid and reliable diagnosis of the second λ sensor and vehicle catalyst, avoids false identification, and improves the operational reliability of the exhaust gas cleaning device.
Smart Images
Figure CN116171346B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for using an exhaust gas cleaning device / exhaust purification device for operating a motor vehicle, wherein the exhaust gas cleaning device includes a vehicle catalytic converter, a first λ sensor disposed upstream of the vehicle catalytic converter, and a second λ sensor disposed downstream of the vehicle catalytic converter. This invention also relates to an exhaust gas cleaning device for a motor vehicle. Background Technology
[0002] For example, document DE 10 2004 055 231 B3 is known from the prior art. This document describes a method for achieving λ regulation in an internal combustion engine using a catalyst in the exhaust manifold and at least one λ sensor arranged within the catalyst. In this arrangement of upstream sensors, a signal delay occurs, which reduces the speed of the λ regulator. To compensate, the measurement signal from the first λ sensor is provided to a λ evaluation unit, which corrects for the delay in the measurement signal. The corrected λ sensor signal is then provided to the λ regulation unit. Both λ sensors are connected to one λ regulation unit.
[0003] Furthermore, document DE 10 2016 213 767 A1 discloses a method for diagnosing the exhaust system of an internal combustion engine using at least one three-way catalytic converter, at least one four-way catalytic converter, and at least one binary λ sensor, wherein the effectiveness of at least one binary λ sensor and / or at least one four-way catalytic converter is checked based on λ changes when the internal combustion engine switches from lean-burn operation to a fuel-rich operation after inertial operation to purge at least one three-way catalytic converter.
[0004] Finally, document US 2016 / 0 160 778A1 describes a diagnostic system for internal combustion engines. The diagnostic system calculates a first characteristic curve of air-fuel ratio change as the air-fuel ratio passes through a first air-fuel ratio range leaner than the stoichiometric air-fuel ratio, and a second characteristic curve of air-fuel ratio change as the air-fuel ratio passes through a second air-fuel ratio range including the stoichiometric air-fuel ratio. The diagnostic system diagnoses sensor bias based on the first and second characteristic curves. Summary of the Invention
[0005] The object of this invention is to provide a method for operating an exhaust gas cleaning device for motor vehicles, which has advantages over known methods, particularly in that it allows for simple verification of the effectiveness of a second λ sensor and / or the vehicle's catalyst.
[0006] According to the invention, this is achieved using a method for operating an exhaust gas cleaning device for a motor vehicle having the features of claim 1. Herein, a signal gradient is determined over the time interval between a first signal transition of a measurement value of a first λ sensor along a first direction and a second signal transition of the measurement value along a second direction opposite to the first direction; and a signal delay of the measurement value of the second λ sensor is determined after the second signal transition, wherein the signal delay corresponds to the time interval between the second signal transition and the response of the measurement value of the second λ sensor to the second signal transition; and wherein a fault in the second λ sensor is identified if the signal gradient is less than a signal gradient threshold and the signal delay is greater than a signal delay threshold, and / or a fault in the vehicle catalytic converter is identified if the signal gradient is less than a signal gradient threshold and the signal delay is less than a signal delay threshold.
[0007] Advantageous designs and suitable improvements of the invention are described in the dependent claims.
[0008] This method is used to operate an exhaust gas cleaning device. The exhaust gas cleaning device is, for example, a component of a motor vehicle, but it can also exist separately from the motor vehicle. The exhaust gas cleaning device is preferably part of the motor vehicle's drive system, which is used to drive the motor vehicle and, in this respect, to provide drive torque intended to drive the motor vehicle. To generate drive torque, the drive system has at least one drive unit.
[0009] Drive units, particularly drive motors, generate exhaust gases during operation, which are discharged along the direction of the external environment. In flow technology, an exhaust gas cleaning device exists between the drive motor and the external environment. This device cleans the exhaust gases by converting pollutants into safer byproducts. The exhaust gases generated by the drive motor are conveyed to the cleaning device and, after passing through it, are discharged into the external environment.
[0010] Exhaust gas cleaning is achieved by an exhaust gas cleaning device using the vehicle's catalytic converter. Vehicle catalytic converters include, for example, three-way catalytic converters, oxidation catalytic converters, and storage catalytic converters, especially for NOx emissions. x A storage catalyst, or an SCR catalyst, is present. A particulate filter may be integrated into the vehicle catalyst. Regarding the flow direction of exhaust gas through the exhaust gas cleaning device or through the vehicle catalyst, a first λ sensor is located upstream of the vehicle catalyst, while a second λ sensor is arranged downstream of the vehicle catalyst regarding the flow direction of exhaust gas.
[0011] A λ sensor is used to determine the combustion air ratio λ. For this purpose, the λ sensor specifically measures the residual oxygen content present in the exhaust gas. Each λ sensor provides a corresponding measurement value. The first λ sensor is preferably a broadband λ sensor, while the second λ sensor is a jump-type λ sensor. In this case, the measurement value of the first λ sensor is preferably given in the form of the combustion air ratio λ, and the measurement value of the second λ sensor is given as a voltage.
[0012] A broadband λ sensor is characterized by its ability to determine the combustion air ratio over a wide range. For example, a broadband λ sensor for this purpose has a pump cell / pump unit and a Nernstzelle cell, with a measurement space between them. The measurement space is technically connected to the exhaust gas line guiding the exhaust gas via a diffusion channel that passes through the pump cell. The current intensity flowing through the pump cell is set such that a combustion air ratio of λ = 1 exists in the measurement space. For this purpose, the measurement value from the Nernstzelle cell is used, specifically adjusted to correspond to a combustion air ratio of λ = 1.
[0013] In comparison, the abrupt λ sensor has a simpler construction and, for example, consists of only a Nernst cell. The characteristic curve of the abrupt λ sensor is characterized by a large gradient in its measured value within the range of the combustion air ratio at λ = 1. Therefore, the gradient of the measured value is significantly larger near λ = 1 than outside this range.
[0014] For example, the measurement value of the first λ sensor is used to perform λ adjustment on the drive unit or drive assembly. On the other hand, the measurement value of the second λ sensor is used to perform corrective adjustment. The corrective adjustment is used to compensate for possible deviations of the first λ sensor in order to perform λ adjustment more accurately.
[0015] Because the second λ sensor is crucial for the accuracy of λ adjustment, it is essential to diagnose its faults as quickly as possible to enable appropriate countermeasures. For example, it may be stipulated that the rated power of the drive unit or drive assembly be reduced when the second λ sensor malfunctions. To diagnose the second λ sensor, the signal gradient and signal delay of its measured value are determined. This determination is performed in time in relation to the first and second signal transitions of the first λ sensor's measured value. Therefore, the signal gradient is determined over the time between the first and second signal transitions, and the signal delay is determined over the time after the second signal transition.
[0016] The signal gradient is understood as the slope of the measurement value of the second λ sensor over time, while the signal delay describes the lag (Nachlauf) of the measurement value of the second λ sensor. Therefore, the signal delay corresponds to the time between the second signal transition and the response of the second λ sensor's measurement value to that transition. The first and second signal transitions should be understood as transitions in the measurement value of the first λ sensor, i.e., the gradient of the measurement value, especially the absolute value of the gradient, exceeding the gradient threshold. Therefore, whether the measurement value increases or decreases is primarily irrelevant. What matters is that the designed gradient exceeds the gradient threshold.
[0017] To perform diagnostics on the second lambda sensor, the signal gradient and signal delay are evaluated. In principle, it can be stipulated that if the signal gradient is less than a signal gradient threshold, a fault in the second lambda sensor is identified. The signal gradient threshold is understood to be a threshold value for the signal gradient, preferably determined empirically, and when the signal gradient is less than this threshold, the second lambda sensor can be considered faulty. However, it is important to note that the measurement signal of the second lambda sensor does not immediately follow the measurement signal of the first lambda sensor, but is also related to the vehicle's catalyst, particularly its state.
[0018] Therefore, to avoid misidentifying the second λ sensor's malfunction due to the influence of the vehicle's catalytic converter, signal delay is used in addition to signal gradient to diagnose the second λ sensor. Thus, a malfunction of the second λ sensor is only identified if the signal delay is also greater than a signal delay threshold, even if the signal gradient is less than a signal gradient threshold. The signal delay threshold is preferably determined empirically and has a value from which a malfunction of the second λ sensor can be considered, especially if the signal gradient is also additionally less than the signal gradient threshold.
[0019] In this regard, to identify a fault in the second λ sensor, it is insufficient for the signal gradient to be less than a signal gradient threshold. The signal delay must also be greater than a signal delay threshold. In other words, even if the signal gradient is less than the signal gradient threshold, a fault in the second λ sensor can only be identified if the signal delay is simultaneously greater than the signal delay threshold. This achieves reliable diagnosis of the second λ sensor.
[0020] Additionally or alternatively, signal gradient and signal delay can be used for the diagnosis of vehicle catalytic converters. As previously explained, the measurement value of the second λ sensor does not simply follow the measurement value of the first λ sensor, and the measurement value of the second λ sensor is also additionally related to the state of the vehicle catalytic converter. Now, if the signal gradient is less than a signal gradient threshold and, furthermore, the signal delay is less than a signal delay threshold, a catalytic converter malfunction is identified. In other words, if the signal gradient is less than the signal gradient threshold, and if the signal delay is less than the signal delay threshold, then only a catalytic converter malfunction is identified.
[0021] Preferably, the diagnosis of the second λ sensor and / or the vehicle catalyst is performed in two stages. First, only the signal gradient is compared to a signal gradient threshold, and while signal delay is to be determined, it is initially disregarded. Only in the second step is the signal delay compared to a signal delay threshold if the signal gradient is less than the signal gradient threshold. If the signal delay is greater than the signal delay threshold, a fault in the second λ sensor is identified. Additionally or alternatively, the effectiveness of the vehicle catalyst can be identified. However, if the signal delay is less than the signal delay threshold, a fault in the vehicle catalyst is identified. Additionally or alternatively, the effectiveness of the second λ sensor can be identified.
[0022] The described approach enables particularly accurate diagnostics of the second λ sensor and / or the vehicle catalyst. In particular, by considering not only one parameter, the signal gradient, but also another parameter, the signal delay, during diagnostics, it effectively avoids misidentifying faults in the second λ sensor. This approach also makes it possible to (optionally) make inferences about the condition of the vehicle catalyst.
[0023] The improved embodiment of the present invention specifies that the maximum gradient occurring between the first signal transition and the second signal transition of the measured value of the second λ sensor is used as the signal gradient. For this purpose, the gradient of the measured value of the second λ sensor between the first signal transition and the second signal transition is determined, for example, continuously or periodically. The maximum gradient occurring within this time period is used as the signal gradient. Preferably, the signal gradient is designed, i.e., it corresponds to the absolute value of the maximum gradient between the two signal transitions. This achieves high accuracy in the diagnosis of the second λ sensor.
[0024] An improved embodiment of the present invention specifies that the duration between the second signal transition and the sign change of the gradient of the measurement value of the second λ sensor is used as the signal delay. As already explained, the signal delay is the time elapsed before the measurement value of the second λ sensor indicates a response to the second signal transition. The criterion for this response is the sign change of the gradient of the measurement value of the second λ sensor. This sign change occurs because the second signal transition describes a change in the direction of the measurement value of the first λ sensor along a direction different from that observed in the first signal transition. The measurement value of the first λ sensor changes in a first direction in the first signal transition, while in the second signal transition it changes in a second direction opposite to the first direction. Accordingly, the signal delay can be determined with high precision based on the sign change.
[0025] The improved embodiment of the present invention specifies that if the measured value of the first λ sensor changes from a value greater than or equal to 1 to a value less than or equal to 1, or from a value less than or equal to 1 to a value greater than or equal to 1, a first signal transition and / or a second signal transition are identified by a value difference greater than a specific value difference. Therefore, for the existence of a first or second signal transition, it is always necessary that the measured value of the first λ sensor changes by a specific value difference during the corresponding signal transition, wherein the value difference should be understood as the difference between the measured value of the first λ sensor immediately before the corresponding signal transition and its measured value immediately after the corresponding signal transition.
[0026] Within the range of signal transitions, the measured value changes, for example, from a value greater than 1 to a value equal to 1 or less than 1. It can also change from a value equal to 1 to a value less than 1, and vice versa. A measured value of 1 from the first λ sensor is here understood to correspond to a measured value of the stoichiometric combustion air ratio. Similarly, a measured value greater than 1 from the first λ sensor corresponds to excess air, and a value less than 1 corresponds to insufficient air in the exhaust gas.
[0027] For example, the value difference must meet the following conditions: at least 0.01, at least 0.02, at least 0.03, at least 0.04, or at least 0.05, with the latter two values being preferred. It can also be specified that the value difference used to identify the first signal transition is greater than the value difference used to identify the second signal transition. For example, the former is at least 1.5 times, at least 1.75 times, or at least 2.0 times greater than the latter. In this case, for example, the first signal transition is identified only when the value difference is at least 0.05, at least 0.075, or at least 0.10; conversely, the second signal transition is identified when the value difference is between 0.01 and 0.05 (or greater).
[0028] Particularly preferably, the first signal transition is identified only when the measurement value of the first λ sensor indicates a change from excess air to insufficient air. The second signal transition is identified only when, for example, a change from insufficient air to at least a stoichiometric air-fuel ratio or to excess air is detected. This achieves high accuracy in the diagnosis of the second λ sensor.
[0029] An improved embodiment of the present invention specifies that the effectiveness of the second λ sensor is identified when the signal gradient exceeds a signal gradient threshold. If the signal gradient is greater than the signal gradient threshold, the second λ sensor can be reliably considered to be functioning. In this case, the evaluation of signal delay is unnecessary. For example, the effectiveness of the second λ sensor can be determined immediately after the second signal transition and without needing to determine the signal delay, i.e., when the signal gradient exceeds the signal gradient threshold. This enables a particularly fast evaluation. For example, it is specified that the signal delay is determined only when the signal gradient is less than the signal gradient threshold. Conversely, when the signal gradient exceeds the signal gradient threshold, the signal delay is not determined.
[0030] The improved embodiment of this invention specifies that the validity of the second λ sensor is identified when the signal gradient is less than a signal gradient threshold and, additionally, when the signal delay is less than a signal delay threshold. In other words, a malfunction of the second λ sensor is identified only when, on the one hand, the signal gradient is less than the signal gradient threshold, and on the other hand, the signal delay is greater than the signal delay threshold. If either condition is not met, the validity of the second λ sensor is determined. As previously explained, the evaluation of the signal delay can even be cancelled based on the signal gradient. Thus, the second λ sensor can be diagnosed quickly and accurately.
[0031] The improved embodiment of the present invention specifies that a fault in the second λ sensor is always identified when the signal delay exceeds a signal delay threshold. If the signal delay is evaluated, for example, based on the value of the signal gradient, then a fault in the second λ sensor is always identified as long as the signal delay is greater than the signal delay threshold. Therefore, whether the signal delay evaluation is performed solely based on the value of the signal gradient, or whether the signal delay is always determined independently of the value of the signal gradient, is particularly insignificant. If the aforementioned criteria are met, then a fault in the second λ sensor is always identified.
[0032] The improved embodiment of the present invention specifies that when the signal delay exceeds a signal delay threshold, the signal gradient is compared with a signal gradient threshold. Specifically, when the signal gradient is less than another signal gradient threshold, a malfunction of the vehicle catalytic converter is identified; when the signal gradient exceeds another signal gradient threshold, the effectiveness of the vehicle catalytic converter is identified. Therefore, in addition to diagnosing the second λ sensor, diagnosing the vehicle catalytic converter can also be performed.
[0033] While a fault in the second λ sensor is always assumed when the signal delay exceeds a signal delay threshold, a definitive conclusion about the state of the vehicle's catalytic converter can be made using an additional signal gradient threshold. This additional signal gradient threshold is lower than the signal gradient threshold. When the signal gradient is less than the signal gradient threshold, a fault in the vehicle's catalytic converter is suspected. For this reason, a more differentiated approach is taken when using the additional signal gradient threshold.
[0034] If the signal gradient is less than another signal gradient threshold, then in addition to confirming a fault in the second λ sensor, a fault in the vehicle catalytic converter can also be identified. Conversely, if the signal gradient exceeds another signal gradient threshold, i.e., the signal gradient lies between the first and second signal gradient thresholds, then the effectiveness, at least limited effectiveness, of the vehicle catalytic converter can be identified. The described approach enables not only the diagnosis of the second λ sensor but also, additionally, the diagnosis of the vehicle catalytic converter.
[0035] An improvement of the present invention specifies that the additional signal gradient threshold is selected to be less than the stated signal gradient threshold. This has already been noted previously. For example, the additional signal gradient threshold is a maximum of 75%, a maximum of 60%, or a maximum of 50% of the stated signal gradient threshold. This selection of the additional signal gradient threshold enables differentiated treatment of the effectiveness of the vehicle catalyst.
[0036] The present invention also relates to an exhaust gas cleaning device for motor vehicles, particularly for performing a method according to an embodiment within the scope of the specification, wherein the exhaust gas cleaning device has a vehicle catalyst, a first λ sensor disposed upstream of the vehicle catalyst, and a second λ sensor disposed downstream of the vehicle catalyst.
[0037] This specification stipulates that the exhaust gas cleaning device is configured and designed to determine a signal gradient over the time between a first signal transition of a measurement value of a first λ sensor along a first direction and a second signal transition of the measurement value along a second direction opposite to the first direction, and to determine a signal delay of the measurement value of the second λ sensor after the second signal transition, wherein the signal delay is equivalent to the time between the second signal transition and the response of the measurement value of the second λ sensor to the second signal transition, and wherein if the signal gradient is less than a signal gradient threshold and the signal delay is greater than a signal delay threshold, then a fault in the second λ sensor is identified, and / or if the signal gradient is less than a signal gradient threshold and the signal delay is less than a signal delay threshold, then a fault in the vehicle catalytic converter is identified.
[0038] The advantages of this design and approach for the exhaust gas cleaning device have been pointed out. The exhaust gas cleaning device and its operation method can be improved based on the implementation scheme within the scope of this instruction manual, and can therefore be referenced in this regard.
[0039] The features and combinations thereof described in the specification, especially those described in the following description of the drawings and / or shown in the drawings, may be used not only in the combinations given but also in other combinations or individually, without departing from the scope of the invention. Therefore, embodiments not explicitly shown or illustrated in the specification and / or drawings, but which arise from or can be derived therefrom by combination of features, are also considered to be covered by the invention. Attached Figure Description
[0040] The invention will now be described in more detail with the aid of embodiments shown in the accompanying drawings, without limiting the scope of the invention. Herein:
[0041] Figure 1 A schematic diagram of the drive system of a motor vehicle is shown, and
[0042] Figure 2Two diagrams are shown to illustrate a method for using an exhaust gas cleaning device to operate a drive unit. Detailed Implementation
[0043] Figure 1 A schematic diagram of a motor vehicle drive unit 1 is shown. The drive unit 1 has a drive unit 2 that generates exhaust gases; in the embodiment shown here, it includes an internal combustion engine. The exhaust gases generated by the drive unit 2 are conveyed to an exhaust gas purification device 3, which, in addition to a vehicle catalytic converter 4, also has a first λ sensor 5 and a second λ sensor 6. The first λ sensor 5 is arranged upstream of the vehicle catalytic converter 4 with respect to the exhaust gas flow direction, and the second λ sensor 6 is arranged downstream of the vehicle catalytic converter 4. The measurement value of the first λ sensor 5 is conveyed to a first regulator 7, which performs λ regulation on the drive unit 2. The measurement value of the second λ sensor 6 is then conveyed to a second regulator 8, which performs corrective regulation, correcting for any deviation in the measurement value of the first λ sensor 5.
[0044] Figure 2 Two graphs are shown to illustrate the method used to operate the exhaust gas cleaning device 3 for driving the drive unit 1. The upper graph shows the change of the measurement value of the first λ sensor 5 over time t. Here, the measurement value is interpreted as the combustion air ratio λ, where λ = 1 corresponds to a stoichiometric combustion air ratio. The lower graph shows the change of the measurement value of the second λ sensor 6 over time t. These measurements are interpreted as voltages, where a voltage U0 exists at the stoichiometric combustion air ratio.
[0045] Diagnostic testing of the second λ sensor 6 is performed within the scope of the method used to operate the exhaust gas cleaning device 3. The drive unit 2 is operated such that the measurement value of the first λ sensor 5 over time t exhibits multiple signal transitions, particularly a first signal transition 9 and a second signal transition 10. The two signal transitions 9 and 10 are clearly visible in the curve 11 showing the change in the measurement value of the first λ sensor 5 over time t. For example, the drive unit 2 is specified to be operated such that at time point t0, starting from the stoichiometric combustion air ratio, a combustion air ratio greater than 1 is set, particularly a combustion air ratio of 1.05.
[0046] To generate the first signal transition 9, at time point t1, the drive unit 2 is controlled such that the combustion air ratio drops below 1, specifically to 0.95. Therefore, the first signal transition 9 includes a change of 0.1 in the difference between the measured values of the first λ sensor 5 and the actual measured value. To generate the second signal transition 10 at time point t2, the drive unit 2 is controlled such that the combustion air ratio is adjusted from a value less than 1 to a value of 1. This value is then maintained at least until time point t3.
[0047] Based on the states of the second λ sensor 6 and the vehicle catalyst 4, different variation curves 12, 13, and 14 are generated for the measurements of the second λ sensor 6. Variation curve 12 shows the measurement over time t when both the second λ sensor 6 and the vehicle catalyst 4 are active. Variation curve 13 shows the measurement over time t when the second λ sensor 6 is faulty but the vehicle catalyst 4 is active. Variation curve 14 shows the measurement over time of the second λ sensor 6 when it is active, but this variation curve 14 deviates from variation curve 12 due to the given operating state of the vehicle catalyst 4.
[0048] For the purpose of diagnosing the second λ sensor 6, the signal gradients 15, 16, or 17 of the curves 12, 13, and 14 between signal transitions 9 and 10 are determined. This is only illustrative. If the corresponding signal gradient 15, 16, or 17 is greater than a signal gradient threshold, the second λ sensor 6 is considered valid. For curve 12, the above condition is met, thus the validity of the second λ sensor 6 can be determined immediately. For comparison, curve 13 is shown, for which the signal gradient 16 is less than the signal gradient threshold. In this case, a fault in the second λ sensor 6 can be identified immediately.
[0049] However, for curve 14, the signal gradient is less than the signal gradient threshold, even though the second λ sensor 6 is functional in principle. For this reason, it is stipulated that the signal delay Δt must be determined after the second signal transition 10, at least when the signal gradient is less than the signal gradient threshold. The signal delay Δt describes the time elapsed before the measurement of the second λ sensor 6 reacts to the second signal transition 10. It can be seen that for curves 12 and 14, the reaction occurs almost immediately, and thus the corresponding signal delays are less than the signal delay thresholds, respectively. However, for curve 13, the signal delay Δt is greater than the signal delay threshold. In this case, a fault in the second λ sensor 6 can be identified.
[0050] By utilizing signal gradient and signal delay, the functionality or malfunction of the second λ sensor 6 can be reliably identified. Therefore, if the signal delay Δt is greater than the signal delay threshold even when the signal gradient is less than the threshold, then a malfunction of the second λ sensor 6 is identified. Otherwise, the second λ sensor 6 is still identified as functional even though the signal gradient is less than the threshold. This approach reliably diagnoses the second λ sensor 6 and optionally the vehicle catalyst 4.
[0051] List of reference numerals in the attached diagram:
[0052] 1. Drive unit
[0053] 2 drive units
[0054] 3. Exhaust gas cleaning device
[0055] 4. Vehicle Catalyst
[0056] 5 First λ sensor
[0057] 6 Second λ sensor
[0058] 7 First regulator
[0059] 8 Second regulator
[0060] 9 First signal transition
[0061] 10 Second signal transition
[0062] 11. Variation Curve
[0063] 12 variation curves
[0064] 13 Variation Curve
[0065] 14. Variation Curve
[0066] 15 signal gradient
[0067] 16 signal gradients
[0068] 17 signal gradient
Claims
1. A method for operating an exhaust gas cleaning device (3) of a motor vehicle, wherein, The exhaust gas cleaning device (3) has a vehicle catalyst (4), a first λ sensor (5) arranged upstream of the vehicle catalyst (4) and a second λ sensor (6) arranged downstream of the vehicle catalyst (4), characterized in that a signal gradient (15, 16, 17) is determined in the time between a first signal jump (9) of the measurement value of the first λ sensor (5) along a first direction and a second signal jump (10) of the measurement value along a second direction opposite to the first direction, and a signal delay of the measurement value of the second λ sensor (6) is determined after the second signal jump (10), wherein the signal delay is equivalent to the time between the second signal jump (10) and the response of the measurement value of the second λ sensor (6) to the second signal jump (10), and if the signal gradient (15, 16, 17) is less than a signal gradient threshold and the signal delay is less than a signal delay threshold, then a fault in the vehicle catalyst (4) is identified.
2. The method of claim 1, wherein, If the signal gradient (15, 16, 17) is less than the signal gradient threshold and the signal delay is greater than the signal delay threshold, then the fault of the second λ sensor (6) is identified.
3. The method according to claim 1 or 2, characterized in that, The maximum gradient of the measured value of the second λ sensor (6) between the first signal transition (9) and the second signal transition (10) is used as the signal gradient (15, 16, 17).
4. The method according to claim 1 or 2, characterized in that, The duration between the sign change of the second signal transition (10) and the gradient of the measurement value of the second λ sensor (6) is used as the signal delay.
5. The method according to claim 1 or 2, characterized in that, When the measured value of the first λ sensor (5) changes from a value greater than or equal to 1 to a value less than or equal to 1, or from a value less than or equal to 1 to a value greater than or equal to 1, the first signal transition (9) and / or the second signal transition (10) are identified.
6. The method according to claim 1 or 2, characterized in that, The effectiveness of the second λ sensor (6) is identified when the signal gradient (15, 16, 17) exceeds the signal gradient threshold.
7. The method according to claim 1 or 2, characterized in that, The effectiveness of the second λ sensor (6) is identified when the signal gradient (15, 16, 17) is less than the signal gradient threshold and additionally when the signal delay is less than the signal delay threshold.
8. The method according to claim 1 or 2, characterized in that, The fault of the second λ sensor (6) is always identified when the signal delay exceeds the signal delay threshold.
9. The method according to claim 1 or 2, characterized in that, When the signal delay exceeds the signal delay threshold, the signal gradient (15, 16, 17) is compared with the signal gradient threshold. When the signal gradient (15, 16, 17) is less than another signal gradient threshold, the vehicle catalyst (4) is identified as faulty. When the signal gradient exceeds another signal gradient threshold, the vehicle catalyst (4) is identified as effective. The other signal gradient threshold is selected to be less than the signal gradient threshold.
10. An exhaust gas cleaning device (3) for a motor vehicle, the exhaust gas cleaning device being used to perform the method according to any one of claims 1-9, wherein, The exhaust gas cleaning device (3) has a vehicle catalyst (4), a first λ sensor (5) arranged upstream of the vehicle catalyst (4) and a second λ sensor (6) arranged downstream of the vehicle catalyst (4). The exhaust gas cleaning device (3) is characterized in that it is configured and designed to determine a signal gradient (15, 16, 17) over a time between a first signal transition (9) of the measurement value of the first λ sensor (5) along a first direction and a second signal transition (10) of the measurement value along a second direction opposite to the first direction, and to determine a signal delay of the measurement value of the second λ sensor (6) after the second signal transition (10), wherein the signal delay is equivalent to the time between the second signal transition (10) and the response of the measurement value of the second λ sensor (6) to the second signal transition (10). If the signal gradient (15, 16, 17) is less than a signal gradient threshold and the signal delay is less than a signal delay threshold, then a fault in the vehicle catalyst (4) is identified.