Method for diagnosing a level meter

Abstract

The invention relates to a method for diagnosing a level meter for a tank system (100), wherein the tank system (100) has at least a first tank region (111) and a second tank region (112), wherein the level meter has a first sensor (101) for determining a first fill level (114) in the first tank region (111) and a second sensor (102) for determining a second fill level (115) in the second tank region (112), wherein the method comprises the following steps: a) determining a first value (126) of the first sensor (101) and a second value (127) of the second sensor (102) for a first completely filled quantity (138) of the tank system (100); b) defining a transition region (133) in which a change in the first fill level (114) and the second fill level (115) is to be expected; c) determining a third value (128) of the first sensor (101) and a fourth value (129) of the second sensor (102) for a second completely filled quantity (139) of the tank system (100), wherein at least part of the transition region (133) lies between the first and the second completely filled quantity (138, 139); d) detecting a fault in the level meter if a change between the first value (126) and the third value (128) is less than a predefined threshold value and / or a change between the second value (127) and the fourth value (129) is less than a further predefined threshold value. The invention also relates to a corresponding control device and to a computer program.

Description

[0001]202400227 1 DESCRIPTION Method for diagnosing a fill level measuring device TECHNICAL FIELD The present disclosure relates to methods and control devices for diagnosing fill level measuring devices, which are used, for example, in fuel tanks of motor vehicles. BACKGROUND OF THE INVENTION The current fill level in fuel tanks can be determined using measuring devices with one or more sensors. Such sensors are designed, for example, as lever sensors that have a movable arm with a float. Depending on the fill level, the arm assumes different angles, which are translated into a variable resistance via a sliding contact. The fill level can be derived from the resistance measurement in a control device. Particular challenges for determining the total fill level arise with so-called saddle tanks, which have a saddle, i.e., an elevation, in the tank bottom.Such an increase results, for example, from a recess in the tank housing, which is provided to guide a drive shaft past the tank system in all-wheel or rear-wheel drive. The tank is divided by the saddle into different areas that are not fully accessible to a single sensor. Therefore, in saddle tanks, multiple sensors are generally required to accurately determine the tank contents. Due to the different tank areas in saddle tanks, fault diagnosis of the various sensors is also difficult. The diagnostic options depend, among other things, on the fill level in the different areas. With conventional approaches, a reliable diagnosis is not possible under certain conditions. SUMMARY AND EMBODIMENTS Therefore, an object of the present disclosure is to facilitate the diagnosis of a fill level measuring device with multiple sensors,as used, for example, in a saddle tank, particularly simple and reliable. This object is achieved by a method for diagnosing a fill level measuring device for a tank system and a control unit according to the independent patent claims. Advantageous embodiments and further developments emerge from the respective dependent claims.the following description and the drawings. Thus, according to a first aspect, a method for diagnosing a fill level measuring device for a tank system is provided. The tank system has at least a first tank area and a second tank area, and the fill level measuring device has a first sensor for determining a first fill level in the first tank area and a second sensor for determining a second fill level in the second tank area. The method comprises the following steps: (a) determining a first value of the first sensor and a second value of the second sensor at a first total fill level of the tank system; (b) defining a transition range in which a change in the first fill level and the second fill level is to be expected; (c) determining a third value of the first sensor and a fourth value of the second sensor at a second total fill level of the tank system,wherein at least a portion of the transition region lies between the first and the second total fill quantity; (d) detecting an error in the fill level measuring device if a change between the first value and the third value is smaller than a predetermined threshold and / or a change between the second value and the fourth value is smaller than a further predetermined threshold. 202400227 3 According to a further aspect, a control device is provided which is configured to carry out the method described above. According to a further aspect, a computer program is provided which comprises instructions which, when the computer program is executed by a computer, cause the computer to carry out the method described above. According to a further aspect, a storage medium with a computer program is provided, wherein the computer program comprises instructions,which, when the computer program is executed by a computer, cause the computer to carry out the method described above. In the context of the present disclosure, a tank system is defined, for example, as a storage device for a tank content, in particular a liquid tank content, such as a fuel for an internal combustion engine. According to one embodiment, the tank system comprises a container configured to receive the tank content. The container may have a raised portion in a container base, for example, a web or a saddle. The raised portion may be configured such that it divides the storage space for the tank content into at least a first tank area and a second tank area. The raised portion may form a boundary between the first and second tank areas. When the tank system is aligned as intended, for example, horizontally,The first and second tank areas can be fluidically separated from each other by the elevation. The intended orientation can be defined with respect to a typical arrangement of the tank system in a motor vehicle. The motor vehicle itself can be aligned horizontally. A third tank area can comprise an area above the first and / or the second tank area, in particular again with respect to the aforementioned intended orientation. The third tank area can be defined based on an area of ​​the container above a horizontal plane, wherein the plane rests on the elevation and / or comprises the lowest 202400227 4 vertex of the elevation. The third tank area can be designed such that tank contents can pass from the first to the second tank area via this third tank area, or vice versa.for example, by the tank contents spilling over. In other words, the third tank region can fluidically connect the first and second tank regions. In the context of the present disclosure, the fill level measuring device is defined, for example, as a device configured to determine the fill level of the tank contents in the tank system, in particular the current total fill quantity in the tank system. For this purpose, the fill level measuring device has at least two sensors configured to determine a respective fill level in at least the first tank region or the second tank region. The first and / or second sensor can also be configured to determine a third fill level in the third tank region, in particular when the first and second tank regions are completely filled. According to one embodiment, one or more of the sensors each have a float configuredto float on the surface of a liquid tank. The fill level in the corresponding tank area can be derived from the position of the float. For this purpose, the float can be connected to an arm, whereby an angle assumed by the arm can be indicative of the fill level. The angle and / or the fill level can be determined, for example, via a resistance measurement, whereby the resistance changes depending on the angle assumed by the arm. This can be implemented via a sliding contact. Other measurement principles are conceivable, for example, using ultrasound, microwaves, optical waves, radar, or even conductivity or capacitive measurement. Consequently, the first, second, third, and fourth values ​​can be electrical resistances or fill levels. These values ​​can be values ​​measured directly by the respective sensor or can be derived from measured values.in particular by means of a control unit. For example, resistance values ​​can be measured, but the first to fourth values ​​indicate corresponding first or second fill levels. In the context of the present disclosure, a transition range is defined, for example, as a contiguous interval between two total fill levels. The total fill levels can refer to the total tank content present in the tank system, for example, the tank content in all existing tank areas. The transition range can be defined by changes occurring in both the first fill level and the second fill level, for example, changes due to transverse or longitudinal accelerations and / or due to consumption of the tank content, for example, for the movement of the motor vehicle. In the context of the present disclosure, the change in a quantity can be positively defined,for example, as the amount of the associated difference. In the context of the present disclosure, an error is defined, for example, as improper behavior of the respective sensor. The error can, for example, consist of a sensor jamming, in which the sensor values ​​do not correspond, at least in some areas, to the respective fill level. The sensor can jam in an upper position, a lower position, or any intermediate position. Alternatively or additionally, an error can be defined as a suspected improper behavior of the respective sensor, i.e., as a suspected error. The previously described method and / or the previously described control unit can be advantageous for performing a particularly reliable diagnosis of the fill level measuring device. Such a reliable diagnosis can enable error detection under previously unconsidered operating conditions of the tank system.where conventional diagnostic approaches have led to erroneous results. In a tank system with separate first and second tank zones, diagnosis can be particularly challenging because, for certain total fill volumes of the tank system, the two tank zones may have different fill levels, for example, one of the two tank zones may be essentially empty and / or one of the two tank zones may be essentially full. In these cases, the respective sensor may display constant values, regardless of whether it is functioning properly or is faulty. Accordingly, errors may not be detectable, such as a possible sensor jam. If measured values ​​from both sides of the transition zone or measured values ​​between which at least part of the transition zone lies are used for the diagnosis,The problem described above can be solved or at least mitigated. For example, the transition area can be selected such that, when the sensors are functioning properly, the measured values ​​of at least the first sensor change on one side of the transition area, and the measured values ​​of at least the second sensor change on the other side of the transition area. Furthermore, the transition area can be selected such that the measured values ​​of both sensors change in the transition area. Therefore, if at least part of the transition area lies between the measured values, it can be expected thatthat both a change in the values ​​of the first sensor and a change in the values ​​of the second sensor are greater than appropriately selected respective thresholds. Accordingly, the method described in this disclosure can exclude the problematic cases described above, and malfunctions of both sensors can be reliably detected and assigned. In summary, the method can make it possible to find, confirm, and correct errors in any tank condition.especially when the total fill level is outside the transition range. Errors can be indicated, for example, to the driver of a motor vehicle using a so-called "malfunction indicator lamp." Such a display may be required by law. According to one embodiment, the values ​​assigned to the second total fill level are determined at a later time than the values ​​assigned to the first total fill level. If the second total fill level is less than the first total fill level, this may correspond to a consumption of the tank contents. If, however, the second total fill level is greater than the first total fill level, this may correspond to refueling. Of course, refueling can also occur in the first case, as long as the filled tank content is less than the consumed tank content. Likewise, consumption can also occur in the second case.as long as the consumed tank content is smaller than the filled one. According to one embodiment, the transition range lies entirely between the first and second total fill levels. Such an embodiment can be advantageous because, due to the change in the total fill level, sufficiently large changes in the first and second fill levels are to be expected, so that the corresponding predetermined threshold values ​​are exceeded in the event of an error. According to one embodiment, at least one-tenth of the transition range lies between the first and second total fill levels, in particular at least one-fifth, in particular at least half, in particular at least three-quarters. Such an embodiment can be advantageous for performing diagnostics more frequently or even in the event of unusual tank behavior, for example, only when the total fill level is high.is operated exclusively at a medium total fill level or exclusively at a low total fill level. According to one embodiment, the transition region comprises a total fill level that corresponds to the maximum fill level of the first tank area. Such an embodiment can be advantageous because, with such a total fill level, a spillover of tank contents between the first and second tank areas or vice versa can be expected, and thus a change in the values ​​of the first and second sensors. This can be the case in particular when a conveying device conveys tank contents from the second to the first tank area, for example because the first tank area is then largely filled, in particular to such an extent that spillover is likely under normal operating conditions. According to one embodiment, the transition region corresponds to a regionby the total filling quantity varying by at least 5% of the maximum filling quantity of the first and second tank areas, in particular by at least 10%, in particular by at least 40%. According to one embodiment, the total filling quantity in the area varies by at most 75% of the maximum filling quantity of the first and second tank areas, in particular by at most 50%, in particular by at most 25%.in particular by a maximum of 10%. The range may depend on the filling volume and / or geometry of the tank system. In the described range, spillover between the first and second tank areas, or vice versa, may be expected, and consequently, a change in the values ​​of both sensors. Alternatively or additionally, a sufficient change in the values ​​of both sensors may be expected in the range due to the consumption of tank contents. According to one embodiment, the transition range is determined by complementary movements of the first and second sensors. The complementary movements may correspond quantitatively or only qualitatively. They may be caused by spillover. According to one embodiment, the tank system further comprises a conveying device, in particular a suction jet pump, which is configured to convey tank contents from the second tank area to the first tank area. Such an embodiment may be advantageousto empty the second tank area, in particular if a removal device of the tank system is configured to remove tank contents from the first tank area. According to one embodiment, the tank system further comprises a removal device configured to remove tank contents from the first tank area, for example, from the first and third tank areas, in particular only from the first tank area. 202400227 9 According to a further embodiment, a fault in the first sensor is detected if the change between the first value and the third value is smaller than the predetermined threshold, and / or a fault in the second sensor is detected if the change between the second value and the fourth value is smaller than the further predetermined threshold. The changes can be defined as positive values,for example, as the amounts of the respective differences. Because value changes for both sensors are to be expected with a suitable choice of the transition range, a fault can be concluded if no changes occur. According to one embodiment, the second total fill quantity is smaller than the first total fill quantity, and the second total fill quantity is selected at the boundary of the transition range, particularly if the values ​​associated with the second total fill quantity are measured at a later time than the values ​​associated with the first total fill quantity. Such an embodiment can be advantageous because the distance between the total fill quantities can be minimized, while simultaneously ensuring reliable diagnosis. The small distance can increase the number of diagnoses. According to one embodiment, a fault in the fill level measuring device is further detectedif a tank content level represented by the first value is lower by a predetermined distance than a tank content level represented by the second value and / or if a tank content level represented by the third value is lower by a further predetermined distance than a tank content level represented by the fourth value. The predetermined distances can be zero or have a finite value. The tank content levels can be determined by a corresponding liquid level. In particular, if a conveying device conveys tank content from the second tank area to the first tank area, the tank content level of the first area can at least not be permanently below the tank content level of the second area. If overflow is possible, this can, however, be the case briefly. 202400227 10 According to one embodiment, a fault in the first sensor is inferred,If the total fill quantity is greater than the maximum total fill quantity of the transition area, in particular, a first sensor clamped at the bottom, and / or a fault in the second sensor is concluded if the total fill quantity is less than the minimum total fill quantity of the transition area, in particular, a second sensor clamped at the top. Preferably, the total fill quantity is an actual total fill quantity at the current time. For example, if one of the sensors is corrupted, the total fill quantity determined by the sensors could be incorrect and not correspond to the actual total fill quantity. The actual total fill quantity would then have to be determined in another way, for example based on the tank content consumption, e.g., fuel consumption. If the total fill quantity is greater than the maximum fill quantity of the transition area,The first tank area should be substantially full. Therefore, if the first sensor is functioning properly, the first sensor should indicate a higher tank content level than the second sensor, independent of the second sensor. On the other hand, the second tank area should be substantially empty if the total fill level is less than the minimum fill level of the transition area. Therefore, if the second sensor is functioning properly, the second sensor should indicate a lower tank content level than the first sensor, independent of the first sensor. According to one embodiment, the method further comprises: checking whether a stability condition is met before the first and third values ​​are determined and / or before the second and fourth values ​​are determined and / or before the fifth and sixth values ​​are determined. Such an embodiment can be advantageous to preventthat the diagnosis is distorted by an inclination of the tank system and / or excessive movement of the tank contents. 202400227 11 According to one embodiment, the stability condition comprises at least one of the following conditions: that a derivative of the values ​​of the first sensor and / or a derivative of the values ​​of the second sensor is less than a predetermined gradient threshold; that a derivative of the sum of the values ​​of the first and second sensors is less than a further predetermined gradient threshold; that an inclination of the vehicle is less than a predetermined inclination threshold, in particular determined by means of a change in ambient pressure; that a stopping or stationary state of the vehicle is determined for a predetermined minimum period of time. Such an embodiment can be advantageous to at least limit the influences of an inclination of the tank system and / or excessive movement of the tank contents. According to one embodiment,If the stability condition is met, a total fill level is determined based on the first and second values ​​and / or the third and fourth values ​​and / or the fifth and sixth values, and the total fill level is compared with consumption values ​​of the tank contents, in particular based on the consumption of an internal combustion engine. The stability condition can include at least one of the following conditions: that a derivative of the values ​​of the first sensor and / or a derivative of the values ​​of the second sensor is less than a predetermined gradient threshold; that a derivative of the sum of the values ​​of the first and second sensors is less than a further predetermined gradient threshold. Such an embodiment can be advantageousto verify the plausibility of the determined total fill level and, for example, to detect an inclination of the tank system. According to one embodiment, the method further comprises: determining a fifth value of the first sensor and a sixth value of the second sensor at a third total fill level of the tank system, wherein the change between the first total fill level and the third total fill level corresponds to a predetermined tank content consumption integral or a predetermined distance traveled by a motor vehicle having the tank system. For example, for the fuel tank of an internal combustion engine, the tank content consumption integral can correspond to the integral of the injected fuel between the first and the third total fill levels. This can be determined based on a fuel pressure and respective injection times. The third value of the first sensor and the fourth value of the second sensor are determinedif a change between the first value and the fifth value is smaller than a third predetermined threshold and / or a change between the second value and the sixth value is smaller than a fourth predetermined threshold. If this condition is met, a suspected error variable can be set. The corresponding suspected error can subsequently be confirmed or refuted based on the third and fourth values. Such an embodiment can be advantageous because a larger number of diagnoses are possible. Only if the values ​​of one of the two sensors do not show a sufficient change is the more complex method for confirming or refuting the suspected error performed. According to one embodiment, error recovery and / or error confirmation of a previously detected error is based on repeatedly performing the described method. Such an embodiment can be advantageousif a faulty sensor subsequently functions properly again, for example, if the sensor jams are eliminated by shaking. The error is corrected in the area of ​​the total filling quantity in which the error was initially detected, for example, on the corresponding side of the transition area, and / or at least in the transition area. Furthermore, the embodiment can be advantageous for correctly confirming a previously detected error. BRIEF DESCRIPTION OF THE DRAWINGS Further advantages and advantageous embodiments and developments of the method and the control unit will become apparent from the following,in connection with the figures illustrated embodiments. They show: 202400227 13 Figure 1 shows a saddle tank with a control unit according to an embodiment of the present disclosure; Figure 2 shows aspects of a method for diagnosing a fill level measuring device for a tank system during proper operation according to an embodiment of the present disclosure; Figures 3 to 6 show further aspects of a method for diagnosing a fill level measuring device in the event of a fault according to an embodiment of the present disclosure. Same,Similar or similarly functioning elements are provided with the same reference numerals in the figures. In some figures, individual reference numerals have been omitted to improve clarity. The figures and the relative sizes of the elements shown in the figures are not to be considered to scale. Rather, individual elements may be exaggerated for clarity and / or clarity. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS Figure 1 shows a saddle tank system 100 with a web 110 arranged on the tank bottom. The web 110 may result from a recess formed on the underside of the tank. Such a recess may be provided, for example,to guide a drive shaft past the tank system 100 in all-wheel or rear-wheel drive. A first tank region 111 and a second tank region 112 of the fuel chamber are fluidically separated from one another by the web 110. A third tank region 113 is arranged above the web 110 and above the first and second tank regions 111, 112. A fluid connection between the two tank regions 111, 112 is established via this third tank region 113. The dashed line in Figure 1 running through the apex of the web 110 separates the three tank regions 111, 112, 113 from one another. 202400227 14 A first sensor 101 is configured to determine a first fill level 114 in the first tank region 111. A second sensor 102 is configured to determine a second fill level 115 in the second tank area 112. Both sensors 101,102 are designed as lever sensors. A float arranged on a lever arm changes the angle assumed by the lever arm depending on the tank content level. By means of a sliding contact, the angle can be translated into a resistance. The tank content level in the respective area 111, 112 is then derived from the measured resistance value by means of the control unit 150. In the tank system 100 shown, the second sensor 102 functions properly, while the first sensor 101 is stuck in a lower position, which is why the float is not at the level of the first fill level 114. The tank system 100 further comprises a conveying device 104, which is configured to convey tank content from the second tank area 112 into the first tank area 111. The conveying device 104 can be, for example, a suction jet pump. In addition, the tank system 100 comprises a removal device 103, which is configuredTank contents are to be removed from the first tank area 101. The control device 150, arranged outside the tank, is connected via signal lines to the first and second sensors 101, 102, as well as to the removal device 103 and the conveying device 104. It is configured to carry out a method for diagnosing the fill level measuring device for the tank system 100. Aspects of such a method are illustrated in more detail in Figures 2 to 6. Figure 2 shows measured values ​​122 of the first sensor and measured values ​​123 of the second sensor, which are each determined as resistance values ​​121, plotted against a tank content consumption 120, here a fuel consumption. In the schematic and simplified representation of Figure 2, at 0 l fuel consumption, which corresponds to 65 l total fill volume of the tank system, both sensors show a minimum resistance value of 70 Ω. This minimum 202400227 15resistance value corresponds to a maximum filling of the respective tank areas111,112. A third tank area is not provided as shown in Figures 2 to 6. However, at a consumption of 65 l or a total fill level of 0 l, both tank areas 111, 112 are empty and the sensors indicate a maximum resistance value of 250 Ω. At a consumption value of 25 l, the total fill level of 40 l corresponds to the maximum fill level in the first tank area 111. At a total tank volume of 65 l, the transition area 133 comprises a range of 25 l, which includes the aforementioned consumption value of 25 l. The transition region 133 is characterized in that both sensors 101, 102 change their values, either due to longitudinal or transverse acceleration of the tank system 100 and / or due to a consumption-related change in the tank content level. A control device, such as shown in Figure 1, is configured to carry out a methodwhich comprises the following steps: (a) determining a first value 126 of the first sensor 101 and a second value 127 of the second sensor 102 at a first total fill level 138 of the tank system 100; (b) defining a transition range 133 in which a change in the first fill level 114 and the second fill level 115 is to be expected; (c) determining a fifth value 130 of the first sensor 101 and a sixth value 131 of the second sensor 102 at a third total fill level 140 of the tank system 100, wherein the change between the first total fill level 138 and the third total fill level 140 corresponds to a predetermined tank content consumption integral 132, for example 15 l.or a predetermined distance traveled by a motor vehicle comprising the tank system; (d) if a change between the first value 126 and the fifth value 130 is smaller than a third predetermined threshold value and / or a change between the second value 127 and the sixth value 131 is smaller than a fourth predetermined threshold value, determining a third value 128 of the first sensor 101 and a fourth value 129 of the second sensor 102 at a second total fill quantity 139 of the tank system 100, wherein at least a part of the transition region 133 lies between the first and the second total fill quantities 202400227 16138, 139; (d) detecting an error in the fill level measuring device,if a change between the first value 126 and the third value 128 is smaller than a predetermined threshold and / or a change between the second value 127 and the fourth value 129 is smaller than another predetermined threshold. Detecting an error may also be or include setting a suspected error variable. In the method described above, in addition to taking into account the preprocessed total fuel level, a diagnostic-internal fuel level is calculated based on the sum of the raw values ​​of the sensor resistances or only lightly filtered sensor resistances. The preprocessed total fuel level may be derived from heavily filtered measured values ​​of sensors 101, 102. A full tank can be considered as a condition by expanding or increasing the fuel consumption threshold, for example, the tank consumption integral 132 introduced above, when both sensors 101,102 indicate the lowest resistance. Tilt conditions can be taken into account, especially while driving. A longitudinal tilt, for example, based on a typical arrangement of the tank system 100 in a motor vehicle, can be determined based on the ambient pressure. A transverse tilt can be taken into account by observing tank content levels only when the vehicle is stationary. Furthermore, determined changes in the total fill level, which are derived from raw resistance values, can be verified for plausibility based on the tank content consumption, especially if the derivative of the tank content level, calculated based on the sum of the only slightly filtered sensor resistances,is smaller than a calibratable or specified threshold. The plausibility check can be performed continuously. In the case of a fuel tank for an internal combustion engine, the tank consumption can be determined, for example, via the injected fuel. 202400227 17 Parking on an incline can, on the one hand, be taken into account by the plausibility check just described. Additionally or alternatively, the end of the diagnosis can be delayed if an incline has been detected.even if the consumption integral has reached the threshold. Figure 3 illustrates the behavior of the sensor values ​​in a fault situation. Here, the first sensor 101 is stuck in an upper position. However, in the blind area 134, such a jamming of the first sensor 101 cannot be deduced from the measured values. Due to the conveyance of tank contents from the second tank area 112 into the first tank area 111, the first tank area 111 remains largely constantly filled in the blind area 134. Accordingly, the first sensor 101 would display constant values ​​anyway, corresponding to an upper position of the lever sensor 101. The blind area 134 ends at or near the transition area 133, because there, a movement of both sensors 101,102 is to be expected. Only outside the blind area 134 do the measured values ​​122 of the faulty first sensor 101 deviate from the values ​​124 expected for a properly functioning sensor. A diagnosis based on measured values ​​from the blind area 134 would therefore not be able to reliably diagnose the aforementioned error, i.e., detect a jammed first sensor 101. For example, a suspected error variable can be set after the consumption integral 132 or distance integral has been reached within the blind area. The consumption or distance integral can be extended if only one sensor within the original consumption or distance integral shows a significant change in resistance. The extension can be maintained as long asuntil the transition range 133 is exceeded. Figure 4 illustrates the behavior of the tank system 100 with a first sensor 101 stuck in the lower position. This results in measured values ​​122 from the faulty sensor 101 that deviate from the values ​​124 expected from a properly functioning sensor. A diagnosis can be made here based on the exclusion range 136. For example, a certain consumption may be detected and no inclination may be present as a stability condition. If the tank content level 114 determined by the first sensor 101 is lower than the tank content level 115 determined by the second sensor, then a fault in the first sensor 101 can be detected while a vehicle comprising the tank system 100 is stationary and / or if the derivative of the total fill level is less than a calibratable threshold. For example, the above-mentioned error of the first sensor 101 can be detected,If, in the exclusion area 136, measured values ​​122 of the first sensor 101 are constant over a certain consumption 120 and / or measured values ​​123 of the second sensor 102 vary over the consumption 120. This may be due to the fact that a conveying device conveys tank contents from the second tank area 112 to the first tank area 111 and therefore the tank content level in the first tank area 111 should typically be higher,at least if disturbing influences such as vehicle tilt or spillage of the tank contents from the first tank area 111 are negligible. Figure 5 illustrates the behavior of the sensor values ​​in another error case. Here, the second sensor 102 is stuck in a lower position. However, in the blind area 135, such a jamming of the second sensor 102 cannot be deduced from the measured values. Due to the conveyance of tank contents from the second tank area 112 into the first tank area 111, the second tank area 111 remains essentially empty. Accordingly, the second sensor 101 would display constant values ​​anyway, corresponding to a lower position of the lever sensor 101. The blind area 135 ends at or near the transition area 133, because there, a movement of both sensors 101,102 is to be expected. Only outside the blind area 135 do the measured values ​​123 of the faulty second sensor 102 deviate from the values ​​125 expected for a properly functioning sensor. A diagnosis based on measured values ​​from the blind area 135 would therefore not be able to reliably diagnose the aforementioned error, i.e., detect a jammed second sensor 102. For example, a suspected error variable can be set within the blind area 135 if an error was previously detected. A correction of the error is only possible if, after filling the tank, a minimum consumption of 202400227 19 has been reached, with values ​​that show raw resistances for the first sensor that are less than the full filling level, for example, less than 70 ohms. Figure 6 illustrates the behavior of the tank system 100 with a second sensor 102 clamped in the upper position. This results in measured values ​​123 of the faulty sensor 102,which deviate from the values ​​125 expected from a properly functioning sensor. A diagnosis can be made here based on the exclusion range 137. If the tank content level 114 determined by the first sensor 101 is lower than the tank content level 115 determined by the second sensor, then a fault in the second sensor 102 can be detected while a vehicle comprising the tank system 100 is stationary and / or if the derivative of the total fill level is smaller than a calibrated threshold. For example, the aforementioned fault in the second sensor 102 can be detected if, in the exclusion range 137, measured values ​​123 of the second sensor are constant over a certain consumption 120 and / or measured values ​​122 of the first sensor 101 vary over the consumption 120. This can be due tothat a conveying device conveys tank contents from the second tank area 112 to the first tank area 111, and therefore the tank content level in the first tank area 111 should typically be higher, at least if disruptive influences such as vehicle tilt or spillage of the tank contents from the first tank area 111 are negligible. The invention is not limited to the description based on the exemplary embodiments. Rather, the invention encompasses any novel feature and any combination of features, which in particular includes any combination of features in the exemplary embodiments and patent claims. 202400227 20 REFERENCE SYMBOL, 100 Tanksystem 101 first sensor102 second sensor103 removal device104 conveyor device 110 Steg111 First tank area 112 Second tank area 113 Third tank area 114 First fill level 115 Second fill level 120 Consumption 121 Sensor value 122 Measured values ​​of the first sensor 123 Measured values ​​of the second sensor 124 Expected values ​​of the first sensor 125 Expected values ​​of the second sensor 126 First value 127 Second value 128 Third value 129 Fourth value 130 Fifth value 131 Sixth value 132 Consumption integral 133 Transition area 134 First blind area 135 Second blind area 136 First exclusion area 137 Second exclusion area 138 First total fill level 139 Second total fill level 202400227 21140 Third total fill level 150 Control device

Claims

202400227 22 PATENT CLAIMS1. Method for diagnosing a fill level measuring device for a tank system (100), wherein the tank system (100) has at least a first tank region (111) and a second tank region (112), wherein the fill level measuring device has a first sensor (101) for determining a first fill level (114) in the first tank region (111) and a second sensor (102) for determining a second fill level (115) in the second tank region (112), wherein the method comprises the following steps: - determining a first value (126) of the first sensor (101) and a second value (127) of the second sensor (102) at a first total fill quantity (138) of the tank system (100); - defining a transition region (133) in which a change in the first fill level (114) and the second fill level (115) is to be expected;- Determining a third value (128) of the first sensor (101) and a fourth value (129) of the second sensor (102) at a second total fill level (139) of the tank system (100), wherein at least a portion of the transition region (133) lies between the first and second total fill levels (138, 139); - Determining an error in the fill level measuring device if a change between the first value (126) and the third value (128) is smaller than a predetermined threshold value and / or a change between the second value (127) and the fourth value (129) is smaller than a further predetermined threshold value.

2. Method according to the preceding claim, wherein the transition region (133) lies entirely between the first and second total fill levels (138, 139).

3. Method according to one of the preceding claims, wherein the transition region (133) comprises a total filling quantity which corresponds to the maximum filling quantity of the first tank region (111); 202400227 234. Method according to one of the preceding claims, wherein the transition region (133) corresponds to a region in which the total filling quantity varies by at least 5% of the maximum filling quantity of the first and second tank regions (111, 112), in particular by a maximum of 50%.

5. Method according to one of the preceding claims, wherein the tank system (100) further comprises a conveying device (104), in particular a suction jet pump, which is configured to convey tank contents from the second tank region (112) into the first tank region (111), and further comprises a removal device (103) which is configured to remove tank contents from the first tank region (111).6.Method according to one of the preceding claims, wherein a fault in the first sensor (101) is detected if the change between the first value (126) and the third value (128) is smaller than the predetermined threshold, and / or a fault in the second sensor (102) is detected if the change between the second value (127) and the fourth value (129) is smaller than the further predetermined threshold.

7. Method according to one of the preceding claims, wherein the second total filling quantity (139) is smaller than the first total filling quantity (138) and the second total filling quantity (139) is selected at the boundary of the transition region (133).8.Method according to one of the preceding claims, wherein an error in the fill level measuring device is further determined if a tank content level represented by the first value (126) is lower by a predetermined distance than a tank content level represented by the second value (127) and / or if a tank content level represented by the third value (128) is lower by a further predetermined distance than a tank content level represented by the fourth value (129).

9. Method according to the preceding claim, wherein an error in the first sensor (101) is inferred if the total fill quantity is greater. 202400227 24 than the maximum total filling quantity of the transition region (133), and / or a fault of the second sensor (102) is concluded if the total filling quantity is less than the minimum total filling quantity of the transition region (133).

10. Method according to one of the preceding claims, wherein the method further comprises:- checking whether a stability condition is met before the first and third values ​​(126, 128) are determined and / or before the second and fourth values ​​(127, 129) are determined.11.Method according to the preceding claim, wherein the stability condition comprises at least one of the following conditions: that a derivative of the values ​​of the first sensor (101) and / or a derivative of the values ​​of the second sensor (102) is less than a predetermined gradient threshold value; that a derivative of the sum of the values ​​of the first and second sensors (101, 102) is less than a further predetermined gradient threshold value; that an inclination of the vehicle is less than a predetermined inclination threshold value, in particular determined by means of a change in ambient pressure; that a holding of the vehicle is determined for a predetermined minimum period of time.12.Method according to one of claims 10 or 11, wherein, if the stability condition is met, a total fill level is determined based on the first and second value (126, 127) and / or on the third and fourth value (128, 129) and the total fill level is compared with consumption values ​​of the tank contents.

13. Method according to one of the preceding claims, further comprising:- determining a fifth value (130) of the first sensor (101) and a sixth value (131) of the second sensor (102) at a third total fill quantity (140) of the tank system (100), wherein the change between the first total fill quantity (138) and the third total fill quantity (140) corresponds to a. 202400227 25 predetermined tank content consumption integral (132) or a predetermined distance traveled by a motor vehicle having the tank system (100); wherein the determination of the third value (128) of the first sensor (101) and the fourth value (129) of the second sensor (102) occurs when a change between the first value (126) and the fifth value (130) is smaller than a third predetermined threshold value and / or a change between the second value (127) and the sixth value (131) is smaller than a fourth predetermined threshold value.

14. Control unit (150) which is configured to carry out the method according to one of claims 1 to 13.

15. Computer program which comprises instructions which, when the computer program is executed by a computer, cause the computer to carry out the method according to one of claims 1 to 13.

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