Method and device for testing and ensuring the functionality of an exhaust gas aftertreatment system of an internal combustion engine

Abstract

The invention relates to a method for checking and ensuring the functional capability of an exhaust gas aftertreatment system (100) of an internal combustion engine, wherein the exhaust gas aftertreatment system (100) has an exhaust gas catalytic converter (110) and a voltage source (140), wherein the exhaust gas catalytic converter (110) has an exhaust gas catalytic region (112) and an electric heating device (114), which is selectively supplied with electrical energy from the voltage source (140), wherein the method comprises the following steps: - determining an actual value (302) which characterizes the ohmic resistance of the heating device (114), wherein the actual value (302) is determined using the current intensity supplied to the heating device (114) and the voltage supplied to the heating device (114) from the voltage source (140), - providing a setpoint value (304) which characterizes the expected ohmic resistance of the heating device (114), wherein the setpoint value (304) takes into account a specific heating behavior of the heating device (114) and an expected long-term behavior of the exhaust gas catalytic converter (110).

Description

Technical Field

[0001] The invention relates to a method and a device for testing and ensuring the functionality of an exhaust gas aftertreatment system of an internal combustion engine. Background Art

[0002] Exhaust gas aftertreatment systems are provided, in particular in vehicles with an internal combustion engine, for carrying out exhaust gas aftertreatment in order to reduce pollutants in the exhaust gas from the internal combustion engine. In this respect, the exhaust gas aftertreatment system has at least one exhaust gas catalytic converter, which binds the pollutants in the exhaust gas catalytic converter by means of a chemical conversion by oxidation or by reduction. In this respect, the exhaust gas catalytic converter usually has an exhaust gas catalytic region in which the chemical conversion—catalysis—takes place.

[0003] Since the exhaust gas catalytic effect performed in the exhaust gas catalytic region requires a certain minimum temperature for effective exhaust gas aftertreatment, the necessary operating temperature for the exhaust gas catalytic region is mostly in the range of ≥200° C. In order to quickly bring the exhaust gas catalytic region into the desired temperature range, according to one embodiment, the exhaust gas catalytic converter has a heating device, which is set up to heat the exhaust gas catalytic region to the desired temperature range during operation of the exhaust gas aftertreatment system. According to one embodiment, the heating device is conventionally powered by electrical energy from a voltage source. The heating device is arranged in the exhaust gas aftertreatment system in the vicinity of the exhaust gas catalytic region so that heat transfer can be advantageously carried out quickly and with low losses. Therefore, the heating device is arranged in the flow area of ​​the exhaust gas. Functional failures of the heating device or other components of the exhaust gas aftertreatment system may occur during the operating time of the exhaust gas aftertreatment system. In particular, a heating device that is permanently exposed to the exhaust gas during the operating time may form a functional failure that affects the operability of the exhaust gas aftertreatment system.

[0004] For example, the internal resistance of the heating device may change during its operating period. Another malfunction, such as damage to the heating device, may cause a short circuit. Malfunctions of the heating device and / or the exhaust gas aftertreatment system may affect their functional capacity and / or even damage the vehicle. Summary of the invention

[0005] The object of the present invention is to provide a method and a device with which it is possible to reliably test and ensure the functional capacity of an exhaust gas aftertreatment system of an internal combustion engine.

[0006] This object is achieved by a method and a device according to the invention for testing and ensuring the functionality of an exhaust gas aftertreatment system of an internal combustion engine. Advantageous developments of the disclosure are described below.

[0007] According to the present disclosure, a method for checking and ensuring the functional capability of an exhaust gas aftertreatment system of an internal combustion engine, wherein the exhaust gas aftertreatment system has an exhaust gas catalytic converter and a voltage source, wherein the exhaust gas catalytic converter has an exhaust gas catalytic region and an electric heating device, and the electric heating device is selectively supplied with electric energy from the voltage source, specifically the following steps:

[0008] - determining an actual value which characterizes the ohmic resistance of the heating device, wherein the actual value is determined using the current intensity supplied to the heating device from the voltage source and the voltage supplied to the heating device,

[0009] - providing a nominal value which characterizes the expected ohmic resistance of the heating device, wherein the nominal value takes into account the specific heating behavior of the heating device and the expected long-term behavior of the exhaust gas catalytic converter,

[0010] - Comparison of actual values ​​with nominal values ​​in order to verify and ensure that the heating device functions according to the specified heating behavior and the expected long-term behavior.

[0011] The exhaust gas catalytic converter has an exhaust gas catalytic region in which catalytic action takes place and an electric heating device, which is designed to heat the exhaust gas catalytic region. According to one embodiment, the electric heating device is arranged upstream of the exhaust gas catalytic region in the direction of exhaust gas flow, but it is also conceivable that the electric heating device is arranged downstream of the exhaust gas catalytic region in the direction of exhaust gas flow. According to another embodiment, the exhaust gas catalytic converter has two electric heating devices, one of the two electric heating devices is arranged upstream of the exhaust gas catalytic region in the direction of exhaust gas flow, and the other of the two electric heating devices is arranged downstream of the exhaust gas catalytic region in the direction of exhaust gas flow. The electric heating device is selectively supplied with electrical energy from a voltage source, for example from a battery or from a battery. Only when the exhaust gas catalytic region has a temperature below a threshold temperature required for effective exhaust gas aftertreatment, the exhaust gas catalytic region must be heated to a specific temperature by means of the electric heating device. This is the case, for example, immediately after a low-temperature start of an internal combustion engine. Therefore, the exhaust gas catalytic region does not have to be permanently heated by the electric heating device.

[0012] According to one embodiment, the electric heating device has a honeycomb structure or a matrix structure through which the current flows directly from the voltage source, wherein the honeycomb structure or the matrix structure acts as an ohmic resistor. As a result, the honeycomb structure or the matrix structure generates heat and transfers the heat to the exhaust gas catalytic region and / or to the exhaust gas. The temperature of the heating device is therefore directly related to the electrical energy transmitted from the voltage source.

[0013] The ohmic resistance of the heating device can change during the operating period of the heating device, for example due to deposits in the honeycomb structure or in the matrix structure or due to changes in the metal structure. It is also conceivable that the ohmic resistance can change due to damage to the matrix structure and / or the honeycomb structure. Damage to the honeycomb structure and / or the matrix structure of the heating device can lead to severe changes in the ohmic resistance of the heating device and / or even to short circuits in the heating device. Such damage has an influence on the flow behavior of electrical energy through the heating device, whereby the ohmic resistance of the heating device and thus the heat transfer to the exhaust gas catalytic region is changed.

[0014] The ohmic resistance can be determined by means of the current intensity and the voltage. Thus, the ohmic resistance of the heating device can be determined by means of the current intensity supplied to the heating device from the voltage source and the voltage supplied to the heating device. Damage or changes in the honeycomb structure or matrix structure of the heating device can be derived from the ohmic resistance of the heating device. Thus, changes or damage to the heating device during the operating time of the heating device can be detected by determining the ohmic resistance of the heating device.

[0015] According to the disclosed method, a setpoint value is provided, which characterizes the expected ohmic resistance of the heating device. The expected ohmic resistance or the corresponding setpoint value takes into account the specific heating behavior of the heating device and the expected long-term behavior of the exhaust gas catalytic converter. The specific heating behavior of the heating device depends, for example, on the construction of the heating device and in particular on the construction of the honeycomb structure or matrix structure of the heating device. The specific heating behavior of the heating device can be detected / measured, for example, when developing the heating device and stored in a memory. This specific heating behavior is taken into account when providing the setpoint value.

[0016] The expected long-term behavior of the exhaust gas catalytic converter can also be determined when developing the heating device and when testing the heating device. The expected long-term behavior maps, for example, a specific service life of the exhaust gas catalytic converter. According to one embodiment, the service life of the exhaust gas catalytic converter is 5 years or 80,000 vehicle kilometers. According to another embodiment, the service life of the exhaust gas catalytic converter is 10 years or 160,000 vehicle kilometers. Longer service lives are also conceivable. According to one embodiment, the expected long-term behavior of the heating device of the exhaust gas catalytic converter over the entire service life is mapped and stored in a memory.

[0017] The setpoint value thus takes into account the heating behavior and the corresponding long-term behavior of the exhaust gas catalytic converter and is provided as a function of the current operating time of the exhaust gas catalytic converter. The setpoint value changes during the operating time of the exhaust gas catalytic converter. In summary, setpoint values ​​are thus provided which are generated as a function of the current operating time of the exhaust gas catalytic converter and the specific heating behavior.

[0018] According to the disclosure, the actual value is compared with the rated value in order to check and ensure whether the heating device functions according to the specific heating behavior and the expected long-term behavior. The actual value is determined by means of the current intensity supplied to the heating device and the voltage supplied to the heating device. The current intensity supplied to the heating device can be determined and the voltage supplied to the heating device can also be determined, so that the actual value determination can be implemented in a simple manner accordingly. Due to changes in the exhaust gas catalytic converter, in particular due to changes in the heating device, the actual value may change during the operating time. The rated value is provided according to the specific heating behavior and the expected long-term behavior. Therefore, the rated value also changes during the operating time of the exhaust gas catalytic converter or during the operating time of the heating device. The actual value and the rated value can therefore change in the same way during the operating time of the heating device.

[0019] The comparison of the actual value with the setpoint value thus provides a relatively good and robust check over the entire operating time of the exhaust gas catalytic converter or over the entire operating time of the heating device of the exhaust gas catalytic converter: whether the heating device functions according to the specific heating behavior and the expected long-term behavior, and thus ensures that the exhaust gas aftertreatment system is operated within a predetermined operating range. If, for example, the actual value deviates too strongly from the setpoint value due to damage to the heating device, it can be determined in a relatively simple manner: the heating device no longer functions as specified. Thus, for example, an entry can be made into an error memory or a prompt can be output to the operator of the internal combustion engine. In summary, the method according to the present disclosure can be carried out relatively simply, but still provides reliable values ​​about the functional capacity of the heating device and thus also about the functional capacity of the exhaust gas aftertreatment system.

[0020] According to one embodiment, in order to compare the actual value with the rated value, a first difference is formed from the actual value and the rated value, and the first difference is compared with a first threshold value, wherein if the first difference deviates from the first threshold value by at least a first specific value, it is recognized that the heating device does not function according to a specific heating behavior and an expected long-term behavior. For example, the first difference can be formed in the following manner, in which the actual value is subtracted from the rated value or in which the rated value is subtracted from the actual value. It is also conceivable to parameterize the actual value or the rated value before forming the difference, wherein the value is represented as a function with one or more variables. For example, the first threshold value can be stored in a memory and compared continuously with the first difference. For example, the first threshold value may change during the operating time of the exhaust gas catalytic converter. The first specific value can also be stored in a memory. The first specific value can also change during the operating time of the exhaust gas catalytic converter. If, for example, it is recognized that the first difference deviates from the first threshold value positively or negatively by a first value, a malfunction of the exhaust gas aftertreatment system can be recognized. This comparison can be simply performed and provides a relatively reliable result during the operating time of the exhaust gas catalytic converter. In particular, due to the variability of the first threshold value and the first specific value, a robust check of the functional capability of the exhaust gas aftertreatment system can be achieved over the entire service life of the exhaust gas catalytic converter. According to another embodiment, the setpoint values ​​and / or actual values ​​are added over a specific operating time before the added setpoint values ​​are compared with the corresponding added actual values.

[0021] According to one embodiment, the exhaust gas aftertreatment system has a voltage measuring device, which is arranged at the end of a transmission cable assigned to a heating device, wherein the transmission cable transmits electrical energy from a voltage source to the heating device during operation of the heating device, wherein the voltage measuring device is set up to determine a measurement signal, which characterizes the voltage reaching the heating device during operation, and wherein the actual value is determined using the measurement signal of the voltage measuring device. According to this embodiment, electrical energy is transmitted from the voltage source to the heating device by means of a transmission cable. One end of the transmission cable is assigned to the heating device, and the other end of the transmission cable is assigned to the voltage source. The voltage measuring device is arranged at the end assigned to the heating device. Therefore, the measurement signal takes into account the transmission losses from the voltage source to the heating device. As a result, the method is additionally more detailed and more reliable.

[0022] According to another embodiment, the voltage measuring device or an additional voltage measuring device is arranged directly at the heating device, the additional voltage measuring device being set up to determine a further or additional measurement signal, the further or additional signal representing the voltage supplied to the honeycomb structure or matrix structure of the heating device during operation, the voltage reaching the honeycomb structure or matrix structure. The measurement signal according to this embodiment takes into account the additional transmission losses in the heating device. According to another embodiment, the additional voltage measuring device is arranged at the ground line of the electric heating device, the additional voltage measuring device being set up to determine an additional measurement signal, the additional measurement signal representing the voltage in the ground line.

[0023] According to one embodiment, the method additionally comprises the following steps:

[0024] - comparing a measurement signal of the voltage measuring device with a voltage setpoint value, which characterizes the expected voltage reaching the heating device from the voltage source during operation of the heating device, wherein, in order to compare the measurement signal with the voltage setpoint value, a difference is formed using the measurement signal and the voltage setpoint value, and the difference is compared with a second threshold value, wherein if the second difference deviates from the second threshold value by at least a second specific value, it is recognized that the transmission cable and / or other components of the exhaust gas aftertreatment system are not functioning according to their intended functionality.

[0025] The measurement signal characterizes the voltage delivered to the heating device during operation, and therefore characterizes the voltage reaching the heating device. The voltage rated value characterizes the expected voltage sent to the heating device. Correspondingly, the voltage rated value characterizes the voltage transmitted from the transmission cable to the electric heating device. Therefore, the voltage rated value also takes into account the resistance losses of the transmission cable. For example, the voltage rated value can be stored in a memory, and in addition, the long-term behavior of the transmission cable can be taken into account, which has been determined in advance and stored in the memory. The second difference is composed of the measurement signal and the voltage rated value. Here, the measurement signal can be subtracted from the voltage rated value, or the voltage rated value can be subtracted from the measurement signal. The measurement signal and / or the voltage rated value can also be parameterized or the measurement signal and the voltage rated value can be processed in other ways to simplify the difference formation.

[0026] The second threshold value can also be stored in the memory and continuously compared with the second difference. The second specific value can also be stored in the memory. According to one embodiment, the second threshold value and the second value may change during the operating time of the exhaust gas aftertreatment system. Thus, an advantageously robust check of the functional capability of the transmission cable or other components of the exhaust gas aftertreatment system, which transmit electrical energy from the voltage source to the heating device, can be achieved over the entire operating time of the exhaust gas aftertreatment system. If, for example, the transmission cable has a break or other damage and no longer transmits electrical energy from the voltage source to the heating device as expected, this can be identified according to this embodiment. In summary, it is therefore possible to additionally distinguish possible sources of error in addition to checking the functional capability of the exhaust gas aftertreatment system.

[0027] According to one embodiment, the setpoint value and / or the setpoint voltage value take into account the current ambient conditions. For example, the current ambient condition may be the ambient temperature. The ambient conditions may influence the heating behavior of the heating device and / or the transmission behavior of electrical energy from the voltage source to the heating device. If the ambient conditions are taken into account in the setpoint value and / or the voltage setpoint value, the method can advantageously continue to reliably and robustly check the functional capacity of the exhaust gas aftertreatment system even when the ambient conditions change.

[0028] According to one specific embodiment, the setpoint value and / or the voltage setpoint value is provided as a characteristic diagram. The characteristic diagram can be, for example, a mathematical model that takes into account different parameters and provides corresponding setpoint values ​​and / or corresponding voltage setpoint values ​​as a function of the currently prevailing parameters for reliable comparison of the setpoint value or voltage setpoint value with the actual value or with the measurement signal. Providing the setpoint value and / or the voltage setpoint value by means of a characteristic diagram is a relatively simple way to take into account environmental conditions or parameters of the exhaust gas aftertreatment system or the internal combustion engine and thus to achieve an advantageously reliable check and assurance of the functional capability of the exhaust gas aftertreatment system.

[0029] According to one embodiment, the determination of the actual value and / or the determination of the measurement signal is determined using a test current intensity supplied to the heating device and a test voltage supplied to the heating device from a voltage source. The test current intensity and the test voltage can be supplied to the heating device, for example, in a specific test run. According to one embodiment, the test run can be performed, for example, before starting the internal combustion engine. Therefore, the test current intensity and the test voltage can be specifically selected in order to obtain a value that is as representative as possible of the actual value or the measurement signal. It is therefore possible to specifically check and ensure the functional capability of the exhaust gas aftertreatment system. Because there is an unaffected result, the method is additionally reliable and accurate. The test current intensity and the test voltage can be kept constant over the service life of the exhaust gas aftertreatment system, so that values ​​that are well comparable to each other can be determined over the entire service life of the exhaust gas aftertreatment system.

[0030] According to one embodiment, the test voltage is 0.5 V to 5 V. Due to the test voltage being within the range according to this embodiment, negative influences on the determination of the actual value or on the determination of the measurement signal can be reduced. In addition, due to these relatively low voltages, resistance changes due to intense heating of the heating element, which have a negative influence on the determination of the actual value or on the determination of the measurement signal, are reduced.

[0031] According to one embodiment, the voltage source is configured to output a maximum voltage of 36 volts or more. According to another embodiment, the voltage source is configured to output a voltage of 48 volts or more. In the case of a vehicle that is driven by an electric motor in addition to an internal combustion engine, for example, the electric motor is supplied with electrical energy from the voltage source, because the internal combustion engine does not have to be operated permanently during the operating time of the vehicle because the electric motor can also drive the vehicle, so the exhaust gas catalytic region cools relatively quickly. It is therefore meaningful to provide a heating device at the exhaust gas catalytic converter in the case of such a vehicle so that if the internal combustion engine is in operation, the exhaust gas catalytic region is heated to the desired temperature interval. The voltage source of such a vehicle is configured to output a voltage of 36 volts or more. Therefore, the voltage source that supplies electrical energy to the electric motor can also supply electrical energy to the electric heating device. The number of voltage sources can be reduced in this way.

[0032] According to one embodiment, the selective energy supply from the voltage source to the electric heating device is controlled by comparing the actual value with the rated value and / or by comparing the measurement signal with the voltage rated value. As a result, the control of the electric heating device can be adapted according to the knowledge from the comparison or comparisons. According to another embodiment, the energy supply from the voltage source to the electric heating device can also be regulated. The control or regulation described according to these embodiments makes it possible to operate the electric heating device in an adapted manner and safely over its entire service life. As a result, the functional capability can be advantageously checked and ensured in a simple and reliable manner.

[0033] According to another embodiment, a device for testing and ensuring the functional capability of an exhaust gas aftertreatment system of an internal combustion engine has a control unit, which is designed to control the above method. The device can be, for example, an engine control unit. It is also conceivable that the device is part of the engine control unit or is installed as an additional control unit, for example, in a vehicle with an internal combustion engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Exemplary embodiments and developments of the method according to the disclosure are shown in the drawings and are explained in more detail in the following description.

[0035] Figure 1shows a schematic diagram of an exhaust gas aftertreatment system having a control unit,

[0036] Figure 2 A block diagram of a method for testing and ensuring the functionality of an exhaust gas aftertreatment system is shown. DETAILED DESCRIPTION

[0037] Figure 1 An exhaust gas aftertreatment system 100 of an internal combustion engine is shown in a schematic diagram, wherein the exhaust gas aftertreatment system 100 has an exhaust gas catalytic converter 110, a voltage source 140 and a control unit 200. The exhaust gas catalytic converter 110 has an exhaust gas catalytic region 112 and an electric heating device 114. The exhaust gas catalytic region 112 is configured to reduce harmful substances from the exhaust gas 102. The heating device 114 is configured to heat the exhaust gas catalytic region 112. The heating device 114 is arranged upstream of the exhaust gas catalytic region 112 in the exhaust gas flow direction. The exhaust gas catalytic converter 110 additionally has an exhaust gas inlet region 120 and an exhaust gas outlet region 130. The exhaust gas inlet region 120 is configured to allow the exhaust gas 102 to flow into the exhaust gas catalytic converter 110. The exhaust gas outlet region 130 is configured to allow the exhaust gas 102 to flow out of the exhaust gas catalytic converter 110.

[0038] A voltage source 140, such as a battery or a cell, is designed to supply electrical energy to the heating device 114. In this regard, the exhaust gas aftertreatment system 100 has a transmission cable 142 and the heating device 114 has a current connection 116. The electrical energy flows to the heating device 114 via the transmission cable 142 and the current connection 116.

[0039] According to this embodiment, the exhaust gas aftertreatment system 100 has a voltage measuring device 170. The voltage measuring device 170 is arranged at the end of the transmission cable 142 assigned to the heating device 114. The voltage measuring device 170 is therefore arranged in the vicinity of the heating device 114. The voltage measuring device 170 is designed to detect a value that characterizes the incoming voltage transmitted from the voltage source 140 to the heating device 114. Therefore, the voltage measuring device 170 detects a value that takes into account the transmission losses of the transmission cable 142.

[0040] The control unit 200 has a computing unit 210, a program / data memory 220 and an error memory 230. According to this specific embodiment, the detected measurement data of the voltage measuring device 170 are transmitted to the control unit 200. In addition, the measurement data of the voltage source 140 are transmitted to the control unit 200. The control unit 200 is designed to control the exhaust gas aftertreatment system 100 and also to test the exhaust gas aftertreatment system 100 with respect to its functional capability.

[0041] According to one embodiment, the control unit 200 is configured to execute Figure 2, for checking and ensuring the functional capability of the exhaust gas aftertreatment system 100. Therefore, the control unit 200 is designed to determine an actual value 302, which characterizes the ohmic resistance of the heating device 114. In this case, at least one first actual value condition 310 and a second actual value condition 312 are taken into account for determining the actual value. The first actual value condition 310 is the current intensity supplied to the heating device 114. The second actual value condition 312 is the voltage supplied to the heating device 114. According to this embodiment, the control unit 200 is additionally designed to provide a setpoint value 304. For example, this provision can be made from the program / data memory 220. In this case, the setpoint value 304 characterizes the expected ohmic resistance of the heating device 114. According to this embodiment, the provision of the setpoint value 304 includes a first setpoint value condition 314, a second setpoint value condition 316 and a third setpoint value condition 318. The first setpoint value condition 314 takes into account the specific heating behavior of the heating device 114. The second setpoint condition 316 takes into account the expected long-term behavior of the exhaust gas catalytic converter 110. The third rated value condition 318 takes into account environmental conditions, such as ambient temperature.

[0042] The control unit 200 is further configured to carry out a comparison of the actual value 302 with the setpoint value 304. In this respect, the calculation unit 210 of the control unit 200 can be used. In order to compare the actual value 302 with the setpoint value 304, according to this embodiment, a first difference is formed from the actual value 302 and the setpoint value 304 by means of a first difference formation 380. The first difference is then compared with a first threshold value 360. For example, the threshold value 360 ​​can be stored in the program / data memory 220. According to one embodiment, the first difference is formed continuously during the operation of the exhaust gas aftertreatment system 100. According to this embodiment, the control unit 200 is configured to detect that the heating device 114 is not functioning as expected if the first difference deviates from the first threshold value 360 ​​by at least a first specific value 400. The first specific value 400 can also be stored in the program / data memory 220 and can be provided therefrom. This first result formation 420 is also carried out using the calculation unit 210. As long as it is detected that the heating device 114 is not functioning as intended, an error entry can be made to the error memory 230. Furthermore, it is conceivable to display the error by means of an error display device to an operator of the internal combustion engine or a driver of a vehicle equipped with an internal combustion engine having exhaust gas aftertreatment system 100 .

[0043] The control unit 200 is additionally configured to determine a measurement signal 306. When determining the measurement signal 306, a first measurement signal condition 320 is included. In this case, the first measurement signal condition 320 characterizes a signal measured by means of the voltage measuring device 170 at the end of the transmission cable 142 facing the heating device 114. According to this embodiment, the control unit 200 is additionally configured to provide a voltage setpoint value 308 by means of the program / data memory 220. According to this embodiment, the voltage setpoint value 308 depends on a first voltage setpoint value condition 322 and a second voltage setpoint value condition 324. The first voltage setpoint value condition 322 takes into account the expected voltage that should reach the heating device 114. The second voltage setpoint condition 324 takes into account at least one environmental parameter.

[0044] The control unit 200 is additionally configured by means of the calculation unit 210 to perform a second difference formation 390 using the measurement signal 306 and the voltage setpoint value 308. According to this embodiment, the control unit 200 is additionally configured by means of the calculation unit 210 to compare the result of the second difference formation 390 with a second threshold value 370. The second threshold value 370 can be stored in the program / data memory 220 of the control unit 200. With the second difference formation 340 and the comparison of the second difference formation 390 with the second threshold value 370, it can be determined whether the transmission of electrical energy from the voltage source 140 to the heating device 114 functions as intended. For this check, a second result formation 430 is performed. Here, if the second difference deviates from the second threshold value 370 by at least a second specific value 410, it is detected that the transmission cable 142 does not function according to its intended functionality. The second specific value 410 can be stored in the program / data memory 220 of the control unit 200.

[0045] The method according to this embodiment makes it possible, on the one hand, to check whether the exhaust gas aftertreatment system 100 functions as intended and, if necessary, to determine which components of the exhaust gas aftertreatment system 100 do not function as intended. In addition, in the case of a problem that is determined, the control of the exhaust gas aftertreatment system 100 can be adapted in order to ensure that the functional capacity continues to be ensured. Overall, the exhaust gas aftertreatment system 100 is designed in a simple manner despite the testing possibilities, does not require additional components and still allows the functional capacity of the exhaust gas aftertreatment system 100 to be tested. Overall, the method and the device are thus correspondingly reliable and robust.

Claims

1. A method for checking and ensuring the functional capability of an exhaust gas aftertreatment system (100) of an internal combustion engine, wherein the exhaust gas aftertreatment system (100) has an exhaust gas catalytic converter (110) and a voltage source (140), wherein the exhaust gas catalytic converter (110) has an exhaust gas catalytic region (112) and an electric heating device (114), wherein the electric heating device is selectively supplied with electrical energy from the voltage source (140), wherein the method comprises the following steps: - determining an actual value (302) which characterizes the ohmic resistance of the heating device (114), wherein the actual value (302) is determined using the current intensity supplied to the heating device (114) and the voltage supplied to the heating device (114) from the voltage source (140), - providing a setpoint value (304) which characterizes an expected ohmic resistance of the heating device (114), wherein the setpoint value (304) takes into account a specific heating behavior of the heating device (114) and an expected long-term behavior of the exhaust gas catalytic converter (110), wherein the specific heating behavior depends on the configuration of the heating device (114), wherein the expected long-term behavior maps a specific service life of the exhaust gas catalytic converter (110), - comparing the actual value (302) with the nominal value (304) in order to verify and ensure that the heating device (114) functions according to the specific heating behavior and the expected long-term behavior, In order to compare the actual value (302) with the setpoint value (304), a first difference is formed from the actual value (302) and the setpoint value (304), and the first difference is compared with a first threshold value (360), wherein if the first difference deviates from the first threshold value (360) by at least a first specific value (400), it is recognized that the heating device (114) is not functioning according to the specific heating behavior and the expected long-term behavior.

2. A method according to claim 1, wherein the exhaust gas aftertreatment system (100) has a voltage measuring device (170), which is arranged at the end of a transmission cable (142) assigned to the heating device (114), and the transmission cable transmits electrical energy from the voltage source (140) to the heating device (114) during operation of the heating device (114), wherein the voltage measuring device (170) is set up to determine a measurement signal (306), which represents the voltage reaching the heating device (114) during operation, and wherein the actual value (302) is determined using the measurement signal (306) of the voltage measuring device (170).

3. The method according to claim 2, wherein the method comprises the following steps: - comparing a measurement signal (306) of the voltage measuring device (170) with a voltage setpoint value (308), the voltage setpoint value (308) characterizing an expected voltage from the voltage source (140) arriving at the heating device (114) during operation of the heating device (114), wherein for comparing the measurement signal (306) with the voltage setpoint value (308), a second difference is formed from the measurement signal and the voltage setpoint value (308), and the second difference is compared with a second threshold value (370), wherein if the second difference deviates from the second threshold value (370) by at least a second specific value (410), it is detected that the transmission cable (142) is not functioning according to its intended functionality.

4. The method according to claim 3, wherein the rated value (304) and / or the voltage rated value (308) take into account current environmental conditions.

5. The method according to claim 3 or 4, wherein the setpoint value (304) and / or the voltage setpoint value (308) is provided as a characteristic diagram.

6. A method according to any one of claims 1 to 4, wherein the determination of the actual value (302) and / or the determination of the measurement signal (306) are determined using a test current intensity supplied to the heating device (114) and a test voltage supplied to the heating device (114) from the voltage source (140). The method according to claim 6 , wherein the test voltage is 0.5 volts to 5 volts.

8. The method according to any one of claims 1 to 4, wherein the voltage source (140) is configured to output a maximum voltage of greater than or equal to 36 volts.

9. A method according to any one of claims 1 to 4, wherein the selective energy supply from the voltage source (140) to the electric heating device (114) is controlled by comparing the actual value (302) with the rated value (304) and / or by comparing the measurement signal (306) with the voltage rated value (308).

10. A device for testing and ensuring the functional capability of an exhaust gas aftertreatment system (100) of an internal combustion engine, wherein the device has a control unit (200) which is designed to control the method according to any of the preceding claims.

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