Methods for testing the exhaust system of a motor vehicle and motor vehicle

Abstract

The invention relates to a method for testing whether a catalyst (11) is arranged in an exhaust tract (8) of a motor vehicle through which exhaust gas from an internal combustion engine (2) flows, wherein the internal combustion engine (2) is operated during a first time period (Z1) with a combustion air ratio which has a first value during the first time period (Z1). The internal combustion engine (2) is operated during a second time period (Z2) following the first time period (Z1), during which the combustion air ratio with which the internal combustion engine (2) is operated during the second time period (Z2) has a second value greater than the first value.The internal combustion engine (2) is operated during a third time period (Z3) which follows the second time period (Z2), during which the combustion air ratio with which the internal combustion engine (2) is operated during the third time period (Z3) has a lower third value than the second value.

Description

[0001] The invention relates to a method for testing an exhaust system of a motor vehicle according to the preamble of claim 1. The invention also relates to a motor vehicle.

[0002] EP 2 718 689 B1 discloses a method for monitoring a subsystem installed in a motor vehicle. DE 10 2014 209 794 A1 discloses a method for diagnosing the removal of an exhaust aftertreatment component in the exhaust system of an internal combustion engine. US 11 098 630 B2 discloses a method for detecting a removed or defective particulate filter in the exhaust aftertreatment system of an internal combustion engine. DE 10 2016 212 636 A1 discloses a detection device for recognizing the presence of a particulate filter in the exhaust system of a motor vehicle. Furthermore, DE 10 2010 030 633 A1 discloses a method for determining the condition of a component located in the exhaust system of an internal combustion engine.

[0003] The object of the present invention is to provide a method and a motor vehicle so that it can be advantageously tested whether a catalyst is arranged in an exhaust tract through which exhaust gas from an internal combustion engine flows.

[0004] This problem is solved according to the invention by a method with the features of claim 1 and by a motor vehicle with the features of claim 14. Advantageous embodiments of the invention are the subject of the dependent claims.

[0005] A first aspect of the invention relates to a method for checking whether a catalyst is arranged in an exhaust tract of a motor vehicle through which exhaust gas from an internal combustion engine flows. In other words, the method is a method for checking the presence of the catalyst in the exhaust tract. As will be explained in detail below, the method can be used to determine whether the catalyst is, and in particular still is, arranged in the exhaust tract or whether the catalyst has been removed from the exhaust tract, i.e., taken out, and thus whether the catalyst is absent.

[0006] In order to determine with particular precision and ease whether the catalyst is still installed in the exhaust system, the method provides that the internal combustion engine, also referred to as an internal combustion engine or combustion power engine, and designed, for example, as a reciprocating engine, is operated for a first period of time, in particular continuously and thus without interruption, with a combustion air ratio also referred to as lambda (A), which has a first value during this first period of time, in particular continuously and thus without interruption. For example, during this first period of time, the internal combustion engine is operated in its fired mode, in particular continuously and thus without interruption.During operation of the internal combustion engine, combustion processes take place within the engine, particularly in the combustion chambers. Specifically, within each operating cycle, one combustion process occurs in the respective combustion chamber. During each combustion process, a mixture, also known as a fuel-air mixture, is burned, resulting in the exhaust gas of the internal combustion engine. This mixture comprises, for example, a liquid or gaseous fuel and air, also referred to as combustion air. This air flows through the intake manifold of the internal combustion engine (also called the intake tract) during operation and is directed into the combustion chamber via the intake tract.For example, during the process of the motor vehicle, propulsion is provided by means of the internal combustion engine, in particular by means of the fired operation of the internal combustion engine.

[0007] The internal combustion engine, for example, has an output shaft, which, particularly if the internal combustion engine is a reciprocating piston engine, is a crankshaft. The internal combustion engine can provide drive torque for propelling the vehicle via the output shaft. Specifically, the output shaft is rotatably mounted on the engine housing element about an output shaft axis of rotation relative to a housing element of the internal combustion engine. During combustion, the output shaft is driven by the combustion process and thus rotated about its output shaft axis relative to the housing element, in particular such that the output shaft is driven via connecting rods and pistons, which partially define the combustion chambers.

[0008] In particular, the internal combustion engine is a four-stroke engine. In particular, each working cycle of the internal combustion engine comprises, in particular precisely, two complete revolutions of the output shaft and thus, in particular, in particular precisely, a crankshaft angle of 720 degrees.

[0009] In this method, the internal combustion engine is operated during a second period that follows, in particular directly, the first period, during which the air-fuel ratio, with which the internal combustion engine is operated during the second period, in particular continuously and thus without interruption, has a higher value than the first value. In particular, the internal combustion engine is also operated in its fired mode during the second period, in particular continuously and thus without interruption.

[0010] In this method, the internal combustion engine is operated during a third period that follows, in particular directly, the second period, during which the air-fuel ratio with which the internal combustion engine is operated during the third period, in particular continuously and thus without interruption, has a lower value than the second value. Preferably, the internal combustion engine is operated in its fired mode during the third period, in particular continuously and thus without interruption.

[0011] The characteristic that the second time period preferably follows directly after the first time period means that no other time period lies between the first and second time periods. Similarly, the characteristic that the third time period preferably follows directly after the second time period means that no other time period lies between the second and third time periods.

[0012] For example, the process is carried out by means of an electronic computing device, in particular of the motor vehicle, wherein the electronic computing device is, for example, a control unit or, at least or exactly, comprises a control unit. For example, by means of the electronic computing device, the internal combustion engine is operated with the respective air-fuel ratio during the respective period of time, so that, for example, the air-fuel ratio, and thus the respective value of the air-fuel ratio, is set, in particular regulated, by means of the electronic computing device.

[0013] In this process, at a first time point belonging to the first and / or second time period, i.e., within the first and / or second time period, a measurement is taken using a nitrogen oxide sensor at a measuring point located downstream of the catalyst in the direction of exhaust gas flow through the exhaust tract. This measurement characterizes the nitrogen oxide (NOx) contained in the exhaust gas. The measurement of this quantity at the first time point yields an initial measured value, which characterizes the initial quantity of nitrogen oxides present in the exhaust gas at that time point. This means that the first measured value is determined as a function of the measurement of the quantity at the first time point. For example, the nitrogen oxide sensor provides a sensor signal, particularly an electrical one, which characterizes the quantity measured by the nitrogen oxide sensor and, for example, the first measured value.The electronic computing device receives, for example, the sensor signal, whereby, for example, the electronic computing device determines the first measured value depending on the sensor signal.

[0014] The characteristic that the first time point belongs to the first time period and / or the second time period means, in particular, the following: if the time periods and the values ​​of the combustion air ratio are illustrated and considered, for example, using a diagram, such that the diagram has an abscissa and an ordinate perpendicular to the abscissa, with time plotted on the abscissa in such a way that time increases from left to right, and with the measured quantity plotted on the ordinate in such a way that it increases from bottom to top, and if a time course of the measured quantity is entered into the diagram, particularly during the aforementioned time periods, this time course of the measured quantity can be entered into the diagram as a discontinuous course, which may have two jumps.The first time period ends, for example, at a first end time, at which the second time period begins. This means that, for example, the first end time coincides with a first start time, at which the second time period begins. The first of the aforementioned jumps in the time course occurs at the first end time, at which the measured quantity essentially jumps from the first value to the second value. The second time period extends, for example, continuously and thus without interruption, from the first start time to a second end time, at which the second time period ends and the third time period begins. Thus, the second end time coincides with a second start time, at which the third time period begins.A second jump in the time course thus occurs, for example, at the second start time, at which the measured quantity jumps, so to speak, from the second value to the third value. If, for example, the first time point is chosen as the first end time or the first start time, meaning the first time point is the first start time or the first end time, then the first time point belongs to both the first and the second time periods, since, in the scenario described above, the first time period ends and the second time period begins at the first time point. However, if, for example, a time point is used that lies before the end time and within the first time period, then the first time point, with respect to both the first and second time periods, belongs exclusively to the first time period.For example, if the first point in time is chosen to be one that follows the first end point in time and lies within the second time period, then the first point in time, in relation to the first time period and the second time period, belongs exclusively to the second time period.

[0015] In actual reality, the temporal progression of the measured quantity will not exhibit the two jumps, since the measured quantity cannot have two different values ​​at the same time. Therefore, in actual or absolute reality, it will probably be the case that if, at a first point in time, the measured quantity has the first value, and thus, at a second point in time following a first point in time, it has the second value, the first time period ends at the first point in time and the second time period begins at the second point in time.If the first point in time is the first actual point in time, then, with respect to both the first and second time periods, the first point in time belongs exclusively to the first time period. Conversely, if the second actual point in time is used as the first point in time, then, with respect to both the first and second time periods, the first point in time belongs exclusively to the second time period. The use of the phrase "and / or" above, indicating that the first point in time can belong to both the first and / or the second time period, reflects the theoretical and / or model-based consideration of the time periods, the measured quantity, and, in particular, the temporal progression of the measurement calculation described above.

[0016] In this method, at a second time point belonging to the second and / or third time period, and thus lying within the second and / or third time period and following the first time point, the measured quantity is measured at the measuring point using the nitrogen oxide sensor. This yields a second measured value, which characterizes a second quantity of nitrogen oxides contained in the exhaust gas at the second time point. This means that the second measured value is determined as a function of the measurement of the measured quantity at the second time point. The preceding and following explanations regarding the first measured value are readily applicable to the second measured value and vice versa. Thus, for example, the nitrogen oxide sensor provides the sensor signal, in particular the electrical signal, which is received by, for example, the electronic processing unit.For example, the electronic computing device determines the second measured value depending on the signal.

[0017] The preceding and following explanations regarding the first point in time, particularly concerning its belonging to the first and / or second time period, can readily be applied to the second point in time and its belonging to the second and / or third time period. Thus, if, for example, the second point in time is chosen to be the second end point or the second start point, meaning that the second point in time is the second end point or the second start point, then the second point in time belongs, so to speak, to both the second and third time periods, since the second time period ends and the third time period begins at the second point in time.If the second point in time is chosen to be one that follows the first point in time, precedes the second start time or the second end time, and lies within the second time period, then the second point in time, with respect to both the second and third time periods, belongs exclusively to the second time period. If the second point in time is chosen to be one that follows the first point in time and follows both the second end time or the second start time, and lies within the third time period, then the second point in time, with respect to both the second and third time periods, belongs exclusively to the third time period. As already explained regarding the first point in time, in actual, or rather absolute, reality, the timeline likely does not exhibit this second jump, since the timeline cannot have two different values ​​at the same point in time.Thus, in actual reality, it is more likely that the second time period ends at a third point in time, at which the measured quantity has the second value, and the third time period begins at a fourth point in time, which follows the third point in time and at which the measured quantity has the third value. If, for example, the third point in time is used as the second point in time, then the second point in time, in relation to the second and third time periods, belongs exclusively to the second time period. If the fourth point in time is chosen as the second point in time, then the second point in time, in relation to the second and third time periods, belongs exclusively to the third time period.With regard to the second point in time, the phrase "and / or" is also used above in relation to the second point in time belonging to the second time period and / or the third time period, in order to take account of the consideration of the time period, the measured quantity and the values ​​described above, which is carried out theoretically and, for example, using the diagram.

[0018] In the method according to the invention, a difference between the measured values ​​is determined, in particular by means of the electronic computing device.

[0019] Furthermore, the method according to the invention provides that, in particular by means of the electronic computing device, it is checked, depending on the difference, whether the catalyst is arranged in the exhaust tract, i.e., whether the catalyst is present in the exhaust tract. In particular, the method according to the invention provides that, in particular by means of the electronic computing device, it is checked, depending on the difference, whether the catalyst is arranged in the exhaust tract, i.e., installed, or not. The method according to the invention utilizes the knowledge that with increasing air-fuel ratio, i.e., towards higher values ​​of the air-fuel ratio, the amount of nitrogen oxides contained in the exhaust gas downstream of the catalyst tends to increase.In other words, if the internal combustion engine is operated lean, particularly during its combustion phase, the exhaust gas downstream of the catalyst contains a larger quantity of nitrogen oxides than if the internal combustion engine is operated rich or richer, particularly during its combustion phase. The invention also utilizes the knowledge that the catalyst, when present in the exhaust system, affects the quantity of nitrogen oxides in the exhaust gas downstream of the catalyst, thus influencing the quantity of nitrogen oxides contained in the exhaust gas downstream of the catalyst, particularly in comparison to when the catalyst is not, or would not be, located in the exhaust system.It was found that the aforementioned difference between the aforementioned measured values ​​represents a particularly advantageous indicator, or can be used as a particularly advantageous indicator, to determine, based on the indicator, whether or not the catalyst is present in the exhaust system.

[0020] Based on the indicator, i.e., depending on the difference between measured values, the inventive method can thus be used to check whether the catalyst is arranged in the exhaust system or not, without using additional, separate sensors. In order to be able to check particularly precisely, i.e., meaningfully, whether the catalyst is arranged in the exhaust system or not using the inventive method, a defined adjustment or setting of the air-fuel ratio is carried out, also referred to as mixture adjustment or mixture control, first towards a lean mixture and then, in particular, again towards a rich mixture.If the catalytic converter is actually located in the exhaust system, i.e., installed, then the catalytic converter can be used to ensure that the internal combustion engine is initially operated with the combustion air ratio having the first value and then with the combustion air ratio having the second value, and since the second value is greater than the first value, there is thus an increase in the combustion air ratio from the first time period to the second time period, also referred to as an increase, i.e. an adjustment or setting of the combustion air ratio towards leaner.Since the internal combustion engine is then operated with the second value of the air-fuel ratio and subsequently with the third value, and since the third value is lower than the second, a reduction in the air-fuel ratio occurs from the second to the third time period, thus resulting in a richer mixture. If the catalytic converter is indeed installed in the exhaust system, it can at least partially, and in particular at least predominantly, compensate for the increase in the amount of nitrogen oxides in the exhaust gas resulting from the increase in the air-fuel ratio, so that downstream of the catalytic converter, a significantly lower amount of nitrogen oxides is contained in the exhaust gas than if the catalytic converter were not located in the exhaust system.Therefore, the aforementioned difference allows for a particularly precise, and thus particularly meaningful and robust, test of whether the catalyst is located in the exhaust system, in particular whether the catalyst is located in the exhaust system or not.

[0021] It is most preferably provided that during the first time period, the first value of the combustion air ratio is kept at least substantially constant, particularly continuously and thus without interruption. It is more preferably provided that during the second time period, the second value of the combustion air ratio is kept at least substantially constant, particularly continuously and thus without interruption. It is more preferably provided that during the third time period, the third value of the combustion air ratio is kept constant, particularly continuously and thus without interruption.

[0022] To enable particularly advantageous testing of the exhaust system, especially regarding whether or not the catalytic converter is located within it, one embodiment of the invention provides for determining the difference by subtracting the first measured value from the second. Another embodiment is characterized in that the difference is compared with a reference value, also referred to as a comparison value. Based on this comparison, it is then determined whether the catalytic converter is located within the exhaust system. In other words, a comparison is performed, for example, using an electronic computing device, in which the difference is compared with the reference value. Based on this comparison, it is then determined whether the catalytic converter is located within the exhaust system.This allows for a particularly precise, and therefore meaningful and robust, test to determine whether the catalyst is located in the exhaust system, in particular or not.

[0023] In particular, the method provides that the motor vehicle, especially the internal combustion engine, is operated depending on the difference. This difference-dependent operation of the motor vehicle includes, for example, the output of at least one warning signal, perceptible visually, audibly, and / or haptically to a person inside the vehicle, particularly by means of an electrical or electronic playback device of an electric motor vehicle. This warning signal is output, for example, when the difference is greater than the reference value.

[0024] In a further, particularly advantageous embodiment of the invention, it is provided that if the difference is greater than the reference value, it is determined that the catalyst is not located in the exhaust system, i.e., that the exhaust system is free of the catalyst. In other words, if the comparison reveals that the difference is greater than the reference value, it is determined that the catalyst is not located in the exhaust system, and thus that the exhaust system is free of the catalyst. Conversely, if the difference is less than or equal to the reference value, it is determined that the catalyst is located in the exhaust system, i.e., installed.The rationale behind this embodiment is, in particular, that if the catalyst is actually located in the exhaust system, the increase in the amount of nitrogen oxides in the exhaust system resulting from the increased air-fuel ratio can be at least partially compensated for by the catalyst. Therefore, if the catalyst is indeed located in the exhaust system, the nitrogen oxide sensor will not detect an increase in the amount of nitrogen oxides in the exhaust gas, or will detect a smaller increase than if the exhaust system were free of the catalyst. This allows for a particularly precise, and thus robust and informative, test of whether or not the catalyst is located in the exhaust system.Preferably, a three-way catalyst is used as the catalyst, so that it can be tested particularly advantageously and meaningfully whether the catalyst is located in the exhaust tract or not.

[0025] In order to be able to test particularly precisely and therefore meaningfully and robustly whether the exhaust system has the catalyst, i.e. whether the catalyst is arranged in the exhaust system, it is provided in a further embodiment of the invention that the first value is at least 0.95, in particular at least 0.99.

[0026] Another embodiment is characterized in that the first value is at most 1.05, in particular at most 1.02. This makes it particularly advantageous to check whether the catalyst is located in the exhaust system.

[0027] It has proven particularly advantageous if the first value is 1.00. This allows for a particularly precise differentiation between the first and second values, or between the first and second time intervals, by increasing the combustion air ratio from the first to the second value. This makes it particularly advantageous, precise, and robust to test whether the catalyst is located in the exhaust system.

[0028] Another, particularly advantageous embodiment is characterized in that the second value is greater than 1.05, and in particular greater than 1.08. This allows for a particularly advantageous determination, based on the first and second values, of whether the exhaust system contains a catalyst or not, and thus whether the catalyst is located in the exhaust system or not.

[0029] To enable particularly advantageous testing of the exhaust system, especially with regard to whether the catalyst is located within the exhaust system, a further embodiment of the invention provides that the second value is at most 1.2, and in particular at most 1.15. This ensures particularly low-emission operation of the internal combustion engine, while simultaneously allowing for advantageous testing of the exhaust system.

[0030] In order to be able to test the exhaust system in a particularly advantageous way to determine whether the catalyst is arranged in the exhaust system, it is further provided in the invention that the second value is 1.10.

[0031] In a further, particularly advantageous embodiment of the invention, the third value corresponds to the first value. This ensures particularly low-emission operation of the internal combustion engine, allowing for a particularly low-emission test to determine whether the catalyst is located in the exhaust system.

[0032] Finally, it has proven particularly advantageous for realizing a particularly beneficial testing of the exhaust system if the respective time period is at least 10 s (seconds).

[0033] A second aspect of the invention relates to a motor vehicle, also referred to simply as a vehicle, and preferably configured as a motor car, in particular as a passenger car, which is configured to carry out a method according to the first aspect of the invention. Advantages and advantageous embodiments of the first aspect of the invention are to be regarded as advantages and advantageous embodiments of the second aspect of the invention and vice versa.

[0034] Further details of the invention will become apparent from the following description of a preferred embodiment with the accompanying drawings. These show: Fig. 1 a schematic representation of a drive system of a motor vehicle; Fig. 2. A diagram illustrating a method for checking whether a catalyst is arranged in an exhaust system of the propulsion unit and thus of the motor vehicle; and Fig. 3. Another diagram to further illustrate the procedure.

[0035] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0036] Fig. Figure 1 shows a schematic representation of a drive unit 1 of a motor vehicle, also referred to simply as a vehicle and preferably designed as a motor car, in particular as a passenger car, whose interior, also referred to as passenger cell, passenger compartment or cabin, is formed by a structure of the motor vehicle designed, for example, as a self-supporting body. During a journey of the motor vehicle, persons such as the driver of the motor vehicle may be located in the interior.

[0037] The drive unit 1 comprises an internal combustion engine 2, also referred to as an internal combustion engine or combustion power unit, by means of which the motor vehicle can be driven or is driven. The internal combustion engine 2 comprises a housing element 3, which is also referred to as the engine block. In particular, the housing element 3 is a cylinder housing, especially a cylinder crankcase. The internal combustion engine 2 has combustion chambers 4. Each combustion chamber 4 is partially delimited by a respective cylinder 5, wherein the cylinders 5 are formed by the housing element 3, and are thus cylinders of the housing element 3. A respective piston is mounted in each cylinder 5 so as to be movably movable, wherein the respective combustion chamber 4 is partially delimited by the respective piston mounted in the respective cylinder 5 so as to be movably movable.Each piston is articulated via a connecting rod to an output shaft 6 of the internal combustion engine 2. For example, the internal combustion engine 2 is a reciprocating engine, so the output shaft 6 is, for example, a crankshaft. Each piston is translationally movable within its respective cylinder 5 relative to the housing element 3. Since the pistons are articulated via the connecting rods to the output shaft 6, the translational movements of the pistons can be converted into a rotational movement of the output shaft 6, which, during its rotational movement, rotates about an output shaft axis relative to the housing element 3.

[0038] The internal combustion engine 2 is or is operable in a fired operation. In the fired operation of the internal combustion engine 2, which, for example, powers the motor vehicle in its fired operation, combustion processes take place in the combustion chambers 4, in particular in all combustion chambers 4, of the internal combustion engine 2, and thus in the internal combustion engine 2, in particular such that within each working cycle of the internal combustion engine 2 taking place in the fired operation, each combustion process takes place in the respective combustion chamber 4, in particular exactly one of the combustion processes. The internal combustion engine 2 is designed as a four-stroke engine, so that each working cycle of the internal combustion engine 2 comprises exactly two complete revolutions of the output shaft 6, thus exactly 720 degrees of crankshaft angle.The combustion processes taking place in the combustion chambers 4 drive the pistons and connecting rods, which in turn drive the output shaft 6, causing the output shaft 6 to rotate around its axis of rotation relative to the housing element 3. This allows the internal combustion engine 2 to provide drive torque via the output shaft 6 to propel the motor vehicle.

[0039] The drive unit 1 has an intake tract 7, also referred to as an inlet tract, through which air can flow or is flowing. During operation, the air flowing through the intake tract 7 is directed into the combustion chambers 4 via the intake tract 7. In each combustion process, a mixture, also referred to as a fuel-air mixture, is combusted, in particular ignited and burned. This mixture comprises the air introduced into the respective combustion chamber 4 and, for example, a liquid or gaseous fuel. Exhaust gas from the internal combustion engine 2 results from the combustion of the respective mixture. Preferably, the internal combustion engine 2 is designed as a spark-ignition engine, in particular as a gasoline engine. The drive unit 1 also has an exhaust tract 8, through which the exhaust gas from the combustion chambers 4 can flow or is flowing.This means that in the fired operation, the exhaust gas flows out of the combustion chambers 4, into the exhaust tract 8 and flows through the exhaust tract 8.

[0040] An exhaust aftertreatment device 9, through which the exhaust gas flows or through which it flows, is arranged in the exhaust tract 8. The exhaust aftertreatment device 9 comprises a first catalyst 10, a second catalyst 11, and a particulate filter 12. For example, the particulate filter 12 is designed as a gasoline particulate filter (GPF). In the direction of flow of the exhaust gas flowing through the exhaust tract 8 and thus the exhaust aftertreatment device 9, the catalyst 10 is arranged upstream of the particulate filter 12 and upstream of the catalyst 11, and in the direction of flow of the exhaust gas flowing through the exhaust tract 8, the particulate filter 12 is arranged downstream of the catalyst 10 and upstream of the catalyst 11, which is thus located downstream of the catalyst 10 and downstream of the particulate filter 12.

[0041] For example, the internal combustion engine 2 is arranged in an engine compartment formed by the vehicle body. The catalyst 10 is also arranged in the engine compartment. The particulate filter 12 is also arranged in the engine compartment. Alternatively, the catalyst 11 may be arranged outside the engine compartment, specifically in the vertical direction of the vehicle below a floor of the vehicle body, also referred to as the underbody, in particular such that the catalyst 11 is completely overlapped, i.e., covered, by the floor in the vertical direction of the vehicle. Therefore, the catalyst 11 is, for example, a so-called underfloor catalyst (UB-cat).

[0042] Preferably, catalyst 10 is a three-way catalyst. Preferably, catalyst 11 is a three-way catalyst. For example, the particulate filter 12 has a catalytic coating which, for example, acts like a three-way catalyst, is a three-way catalyst, or forms a three-way catalyst.

[0043] The exhaust system 8 also includes a first sensor 13, a second sensor 14, a third sensor 15, a fourth sensor 16, a fifth sensor 17, and a sixth sensor 18. The first sensor 13 is, for example, a first lambda sensor, which can detect, or is measured, the residual oxygen content in the exhaust gas, particularly during combustion operation. The second sensor 14 is a nitrogen oxide sensor, also known as a NOx sensor, which can detect any nitrogen oxides present in the exhaust gas, particularly during combustion operation. For example, the second sensor 14 is also configured to measure the residual oxygen content in the exhaust gas, so that, particularly during combustion operation of the internal combustion engine 2, the residual oxygen content in the exhaust gas can be measured, or is detected, by means of the second sensor 14.It can be seen that sensor 13 is located upstream of the catalyst 11 and, in this case, also upstream of the particulate filter 12 and downstream of at least part of the catalyst 10. The second sensor 14 is located downstream of the catalyst 11 and also downstream of the particulate filter 12 and downstream of the catalyst 10. The residual oxygen content in the exhaust gas measured or to be measured by means of sensor 13 is or will be measured at a first measuring point, and the nitrogen oxides contained in the exhaust gas measured or to be measured by means of sensor 14 are or will be measured at a second measuring point, wherein the first measuring point is arranged upstream of the catalyst 11, upstream of the particulate filter 12 and downstream of at least a part of the catalyst 10, and wherein the second measuring point is arranged downstream of the first measuring point, downstream of the catalyst 11, downstream of the particulate filter 12 and downstream of the catalyst 10.

[0044] Sensor 15, for example, is a second λ-probe, by means of which a residual oxygen content in the exhaust gas is measured upstream of the catalyst 10 and thus upstream of the first measuring point, upstream of the second measuring point, upstream of the catalyst 11, and upstream of the particulate filter 12, or is measured, particularly during combustion operation. Sensors 16 and 17 are pressure sensors by means of which a respective pressure in the exhaust tract 8, and thus, for example, of the exhaust gas, can be detected, or is detected, particularly during combustion operation. It can be seen that sensor 16 is arranged upstream of the catalyst 11 and upstream of at least part of the particulate filter 12, and downstream of at least part of the catalyst 10. Sensor 17 is arranged upstream of the catalyst 11 and downstream of at least part of the particulate filter 12, and downstream of the catalyst 10.Sensor 18 is a temperature sensor used to measure, or to measure, the temperature of the exhaust gas downstream of the catalyst 11.

[0045] Based on Fig. 1 and Fig. Section 2 below describes and explains a method by which it is tested whether the catalyst 11 is arranged in the exhaust tract 8, in particular whether it is not. To illustrate the method, Figure 2 shows... Fig. 2 a diagram on whose abscissa 19 time is plotted, where time is, for example, along the abscissa 19 and relative to the image plane of Fig. 2 increases from left to right, that is, progresses or advances. On the ordinate 20 of the in Fig. In diagram 2, the quantity of nitrogen oxides contained in the exhaust gas is plotted such that the quantity is shown along the ordinate 20 and relative to the plane of the diagram. Fig. 2 is applied in a rising pattern from bottom to top.

[0046] Furthermore, for example, a combustion air ratio is plotted on the ordinate 20, with which the internal combustion engine 2 is operated in the fired operation during the process, wherein, for example, the combustion air ratio is plotted along the ordinate 20 and with respect to the image plane of Fig. 2 increases from bottom to top.

[0047] In order to be able to test, particularly advantageously, precisely, and robustly, and thus meaningfully, whether the catalyst 11 is arranged in the exhaust tract 8, in particular whether it is or not, the internal combustion engine 2 is operated for a first period of time Z1 with the combustion air ratio having a first value, such that, for example, the combustion air ratio has the first value during the period of time Z1, in particular continuously or without interruption. In the case of the Fig. In the embodiment shown in Figure 2, the first value is 1. This ensures that the internal combustion engine 2 is operated in fired mode during the first time period Z1.

[0048] In this process, the internal combustion engine 2 is operated in fired mode during a second time period Z2 that directly follows the first time period Z1, wherein during the second time period Z2 the combustion air ratio with which the internal combustion engine 2 is operated has a second value that is larger than the first value, which is the case when the Fig. In embodiment 1.1 shown in 2, the combustion engine 2 is operated in fired mode during a third time period Z3, which immediately follows the second time period Z2. During the third time period Z3, the combustion air ratio with which the combustion engine 2 is operated has a lower value than the second value, which is lower in the case of the Fig. 2 shown embodiment 1 is, that is, is.

[0049] Recognizable from Fig. 2 is that in the Fig. In the embodiment shown in Figure 2, the first time interval Z1 ends at a first time t1, at which the second time interval Z2 begins. The first time t1 is thus simultaneously a first end time and a first start time, since the second time interval Z2 begins at the first start time and the first time interval Z1 ends at the first end time. Fig. 2 is thus a consideration or illustration of the process, particularly a theoretical or model-based one, in which, at the first time point t1, the air-fuel ratio undergoes a jump, changing from the first value to the second value, i.e., from 1 to 1.1. Therefore, in this theoretical and model-based consideration of the process, the first time point t1 belongs to the first time interval z1 and the second time interval z2.

[0050] In the aforementioned model or theoretical consideration or illustration of the process, the second time interval Z2 ends at a second time t2, at which the third time interval Z3 begins. The second time t2 is thus simultaneously a second start time and a second end time, since the second time interval Z2 ends at the second end time and the third time interval Z3 begins at the second start time. It is also evident that the second time interval Z2 extends continuously and thus without interruption from time t1 to time t2. At the second time t2, a second change in the air-fuel ratio occurs, which at the second time t2 changes from the second value to the third value, i.e., from 1.1 to 1, or rather, changes back. Therefore, the second time t2 belongs to both the time interval Z2 and the third time interval Z3.It is also apparent that the second time t2 follows the time t1 in time and is spaced apart from the time t1.

[0051] During time intervals Z1, Z2, and Z3, a measurement is taken by means of sensor 14, designed as a nitrogen oxide sensor, at the second measuring point located downstream of the catalyst 11. This measurement characterizes the nitrogen oxides (NOx) contained in the exhaust gas at the second measuring point. Thus, the measurement is taken by the nitrogen oxide sensor at the second measuring point at time t1 and time t2. A time course of the measurement taken by sensor 14 is shown in the Fig. The diagram shown is plotted and labeled 21. By measuring the quantity, respective measured values ​​are determined, which form the temporal profile 21. In other words, the temporal profile 21 comprises the measured values ​​that follow one another in time. Thus, at time t1, specifically, a first of the measured values ​​is recorded, and at time t2, specifically, a second of the measured values ​​is recorded. The first measured value characterizes a first quantity of nitrogen oxides contained in the exhaust gas at the second measuring point at time t1, and the second measured value characterizes a second quantity of nitrogen oxides contained in the exhaust gas at the second measuring point at time t2. Fig. 2 The first measurement is labelled M1, and the second measurement is labelled M2.

[0052] In this method, a difference, also denoted by Δ, between the first and second measured values ​​is determined, in particular by means of an electronic computing device, specifically by subtracting the first measured value from the second measured value. The difference is then compared with a reference value using the electronic computing device. In the Fig. In the illustrated embodiment 2, the difference is less than or equal to the reference value, since in the Fig. In the embodiment shown in Figure 2, the catalyst 11 is actually arranged in the exhaust tract 8. If the difference is less than or equal to the reference value, it is determined that the catalyst 11 is arranged in the exhaust tract 8.

[0053] Fig.Figure 3 shows an embodiment in which the catalyst 11 is not arranged in the exhaust tract 8, and thus the exhaust tract 8 is free of the catalyst 11. The difference is greater than the reference value, so it is determined that the catalyst 11 is not arranged in the exhaust tract. Reference symbol list 1 Drive unit 2 Internal combustion engine 3 Housing element 4 Combustion chamber 5 cylinders 6 Output shaft 7 Intake tract 8 Abstract 9 Exhaust aftertreatment system 10 Catalyst 11 Catalyst 12 particulate filters 13 Sensor 14 Sensor 15 Sensor 16 Sensor 17 Sensor 18 Sensor 19 Abscissa 20 ordinates 21 Time course M1 first measured value M2 second measured value t1 first time point t2 second time point Z1 first time period Z2 second time period Z3 third time period Δ Difference QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 2 718 689 B1

[0002] DE 10 2014 209 794 A1

[0002] US 11 098 630 B2

[0002] DE 10 2016 212 636 A1

[0002] DE 10 2010 030 633 A1

[0002]

Claims

[1] Method for checking whether a catalyst (11) is arranged in an exhaust tract (8) of a motor vehicle through which exhaust gas from an internal combustion engine (2) flows, characterized by , that: - the internal combustion engine (2) is operated during a first time period (Z1) with a combustion air ratio which has a first value during the first time period (Z1); - the internal combustion engine (2) is operated during a second period (Z2) following the first period (Z1), during which the air-fuel ratio with which the internal combustion engine (2) is operated during the second period (Z2) has a second value greater than the first value; - the internal combustion engine (2) is operated during a third period (Z3) following the second period (Z2), during which the air-fuel ratio with which the internal combustion engine (2) is operated during the third period (Z3) has a lower third value than the second value; - at a first time point (t1) belonging to the first time period (Z1) and / or the second time period (Z2), a measurement quantity which characterizes nitrogen oxides contained in the exhaust gas is measured by means of a nitrogen oxide sensor (14) at a measuring point arranged downstream of the catalyst (11), whereby a first measurement value (M1) is determined which characterizes a first quantity of nitrogen oxides contained in the exhaust gas at the first time point (t1); - at a second time point (t2) belonging to the second time period (Z2) and / or the third time period (Z3) and following the first time point (t1), the measured quantity is measured at the measuring point using the nitrogen oxide sensor (14), thereby determining a second measured value (M2) which characterizes a second quantity of nitrogen oxides contained in the exhaust gas at the second time point (t2); - a difference (Δ) between the measured values ​​(M1, M2) is determined; and - depending on the difference (Δ), it is checked whether the catalyst (11) is located in the exhaust tract (8). [2] Method according to claim 1, characterized by , that the difference (Δ) is determined by subtracting the first measurement (M1) from the second measurement (M2). [3] Method according to claim 1 or 2, characterized by, that the difference (Δ) is compared with a reference value, whereby, depending on the comparison of the difference (Δ) with the reference value, it is checked whether the catalyst (11) is arranged in the exhaust tract (8). [4] Method according to claim 3, characterized by , that: - then, if the difference (Δ) is greater than the reference value, it is determined that the catalyst (11) is not located in the exhaust tract (8); and - then, if the difference (Δ) is less than or equal to the reference value, it is determined that the catalyst (11) is located in the exhaust tract (8). [5] Method according to any one of the preceding claims, characterized by , that the catalyst (11) is a three-way catalyst. [6] Method according to any one of the preceding claims, characterized by that the first value is at least 0.95, in particular at least 0.

99. [7] Method according to any one of the preceding claims, characterized by, that the first value is at most 1.05, in particular at most 1.

02. [8] Method according to any one of the preceding claims, characterized by , that the first value is 1.

00. [9] Method according to any one of the preceding claims, characterized by , that the second value is greater than 1.05, in particular greater than 1.

08. [10] Method according to any one of the preceding claims, characterized by , that the second value is at most 1.20, in particular at most 1.

15. [11] Method according to any one of the preceding claims, characterized by , that the second value is 1.

10. [12] Method according to any one of the preceding claims, characterized by , that the third value corresponds to the first value. [13] Method according to any one of the preceding claims, characterized by that the respective time interval (Z1, Z2, Z3) is at least ten seconds. [14] Motor vehicle designed to carry out a method according to any of the preceding claims.

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