Method and apparatus for diagnosing a fuel sensor, fuel cell system, vehicle, computer program product and storage medium

Abstract

The technology disclosed herein relates to a method for diagnosing a fuel sensor (30) of a fuel cell system (10), wherein the fuel cell system (10) further comprises a fuel cell (11) with an anode (12) and a cathode (13), a cathode system (38) with the cathode (13) and an anode system (38) with the anode (12), an anode inlet (21), an anode outlet (22), an anode inlet path (15) for directing fuel into the anode inlet (21) and an anode outlet path (16) for directing anode exhaust gas from the anode outlet (22), comprising the steps of: determining a sudden pressure increase in the anode system (38), determining fuel behavior in the anode system (38) via the pressure increase using the fuel sensor (30) and diagnosing the fuel sensor (30) based on the determined fuel behavior.The technology further relates to a device (80), a fuel cell system (10), a vehicle (100) and a computer program product (40) for carrying out the method, as well as a computer-readable storage medium (50) on which the computer program product (40) is stored.

Description

[0001] The technology disclosed herein relates to a method and a device for diagnosing fuel cell sensors. The technology further relates to a device, a fuel cell system, a vehicle, and a computer program for executing the method. The method also relates to a computer-readable storage medium on which such a computer program is stored.

[0002] Various fuel cell systems for mobile applications are known in the prior art. In a vehicle, fuel cell systems are typically configured to generate electricity for the vehicle's drive motor. Typical fuel cell systems comprise a fuel cell stack. The fuel cell stack includes several fuel cell elements, each with two electrodes and a membrane arrangement between the two electrodes. Within the fuel cell stack, fuel reacts with an oxidizer via reverse electrolysis, thereby generating electricity. The fuel can be supplied to the fuel cell stack from at least one fuel tank in the vehicle. The oxidizer can be drawn from the ambient air.

[0003] Furthermore, it is known to control the operation of the fuel cell system depending on current operating conditions and / or operating parameters within the fuel cell system. For example, the fuel behavior in the anode system of the fuel cell is monitored using fuel sensors to prevent fuel insufficient supply to the fuel cell and unnecessarily high fuel consumption. However, fuel sensors introduce a degree of uncertainty. Various influences, such as liquid water in and / or on the sensors or other relevant components of the fuel cell system, can cause the fuel sensors to deliver erroneous measurements. Inaccurate or malfunctioning fuel sensors can lead to faulty, and therefore inefficient and dangerous, operating conditions.

[0004] The purpose of the present technology is to create improved methods and devices for diagnosing the fuel sensor system of a fuel cell system.

[0005] The aforementioned problem is solved by the claims. In particular, the aforementioned problem is solved by the method according to claim 1 and by the device, the fuel cell system, the vehicle, the computer program product, and the computer-readable storage medium according to the dependent claims. Further advantages of the disclosed technology will become apparent from the subclaims, the description, and the figures. Features described in connection with the method also apply in connection with the device, the fuel cell system, the vehicle, the computer program product, and the storage medium, and vice versa, so that the disclosure always makes and / or can make reciprocal references to the individual aspects.

[0006] According to a first aspect of the present technology, a method for diagnosing the fuel cell sensor of a fuel cell system is proposed. In addition to the fuel cell sensor, the fuel cell system comprises a fuel cell with an anode and a cathode, a cathode system, and an anode system. The anode system further includes an anode inlet, an anode outlet, an anode inlet path for directing fuel into the anode inlet, and an anode outlet path for directing anode exhaust from the anode outlet. The method comprises the following steps: - Detecting a sudden pressure increase in the anode system, - Determining fuel behavior in the anode system via pressure increase using fuel sensors and - Diagnosing fuel sensor technology based on the determined fuel behavior.

[0007] Within the framework of the technology described here, the correlation between a sudden pressure increase and the resulting fuel behavior in the anode system, which can be evaluated for diagnostic purposes, was identified. Using a functioning fuel sensor, specific changes in the fuel fraction in the anode system should be detected under certain operating conditions during pressure surges. If the fuel behavior correlates with the pressure surges, it can be concluded that the fuel sensor is functioning correctly. Ultimately, this enables efficient and safe operation of the fuel cell system. Based on the fuel behavior as measured by the pressure increase, not only a qualitative but also a quantitative diagnosis of the fuel sensor can be performed. That is, it is possible not only to diagnose whether the fuel sensor is faulty, but also to determine the extent of the fault.The magnitude of the error can refer, for example, to an error in sensor accuracy and / or the corresponding maximum possible measurement accuracy. The usable measurement accuracy affects, for instance, the safety margin of various control concepts within the fuel cell system. The safety margin can be understood as at least a defined setpoint.

[0008] In this context, a sudden pressure increase can be understood as a pressure jump and / or a gas pressure rise within a defined short time to a defined high pressure. The pressure increase can also be understood as a pressure increase triggered by a defined gas injection into the anode system. The defined gas injection can be understood as the injection or introduction of fuel, pure fuel, and / or a gas with a known and / or predefined gas composition. A sudden pressure increase can be understood as a pressure increase of more than 0.5 bar or more than 1 bar within a time of less than 2 seconds, less than 1 second, or less than 0.2 seconds, for example, within approximately 0.1 seconds.

[0009] The abrupt pressure increase can be measured, calculated, and / or modeled using physical and / or virtual pressure sensors. At least one pressure sensor can be used to determine the pressure increase. The pressure increase can be determined in the anode, at the anode, in the anode inlet path, and / or in the anode outlet path. For example, the fuel cell system can have a pressure sensor to determine the pressure increase in the anode inlet path upstream of the anode input. The fuel behavior in the anode system can be measured, calculated, and / or modeled using physical and / or virtual fuel sensors. At least one pressure sensor can be used to determine the fuel behavior. The fuel behavior can be determined in the anode, at the anode, in the anode inlet path, and / or in the anode outlet path.The fuel cell system can, for example, include a fuel sensor, particularly a hydrogen sensor, for determining the fuel behavior and, in particular, the behavior of a fuel fraction in the anode outlet path downstream of the anode outlet. "Determining" in this context can be understood as measuring, calculating, modeling, and / or estimating. For example, measured values ​​can be obtained using pressure sensors, fuel sensors, and / or a virtual model, which are then processed by a computing unit to infer the desired values. Determining the fuel behavior can therefore include determining the behavior of the fuel fraction in the total fluid within the anode system, i.e., within the anode inlet path, within the anode, and / or within the anode outlet path.Determining fuel behavior can be understood as using fuel sensors to measure and / or calculate how the fuel quantity at at least one point in the anode system behaves over a defined period, for example, 10 seconds, after the pressure increase—that is, whether it changes or remains unchanged. Determining fuel behavior via pressure increase can be carried out by operating the fuel cell system with as constant system parameters as possible during this time and / or during a corresponding pressure increase period. For example, the fuel cell system can be operated in such a way that the power generated by the fuel cell remains as constant as possible during the pressure increase period.

[0010] The sudden pressure increase can be determined within a defined pressure increase time. The fuel behavior can be determined during and / or after the pressure increase time. The pressure increase time can encompass a period between a defined time before the pressure increase and a defined time after the pressure increase. The fuel behavior can also be determined within the pressure increase time. The pressure increase time can be a period from a time before the pressure increase to a time of less than 60 seconds, less than 30 seconds, or less than 15 seconds after the pressure increase. The total pressure increase time can be less than 60 seconds, less than 30 seconds, or less than 15 seconds.

[0011] Determining fuel behavior via pressure increase can be understood as determining the fuel behavior in relation to the pressure increase. For example, the fuel behavior can be determined in relation to a pressure before the pressure increase, a pressure after and / or during the pressure increase, and a pressure difference between the pressure before and after the pressure increase. In this context, pressure can be understood to refer specifically to the gas pressure present in and / or measured in the anode inlet path, the anode, and / or the anode outlet path. For diagnosing fuel sensor issues, the fuel behavior after the pressure increase, and especially a defined time after the pressure increase, can be considered and / or used for diagnostic purposes.Determining fuel behavior using fuel sensors means that fuel sensors are used to ascertain the fuel's behavior. In addition to fuel sensors, other components and / or models can also be used to determine fuel behavior. In this context, "fuel" can be understood to mean hydrogen.

[0012] Diagnostics can be understood as the systematic analysis and identification of faults, malfunctions, and / or anomalies in the fuel sensor system. Based on the determined pressure-dependent fuel behavior, diagnostics can identify absolute and / or relative faults in the fuel sensor system, enabling targeted repair, maintenance, and / or adjustment of the fuel sensor system and / or the fuel cell system. Diagnostics can include fault detection and / or fault analysis. Fault detection first determines whether a fault exists. If a fault is present, a corresponding indicator and / or warning signal can be generated and / or output. Fault analysis determines the cause of the fault. This cause can be determined based on the fuel behavior.The procedure can be used to control the fuel cell system based on the diagnosis of the fuel sensor. For example, depending on the diagnosis—that is, whether the fuel sensor exhibits sensor inaccuracy, no sensor inaccuracy, a defined large sensor inaccuracy, and / or a defined small sensor inaccuracy—control concepts for operating the fuel cell system can be designed differently. In this context, "control" can be understood as adjusting, controlling, and / or regulating. Errors in the fuel sensor can be determined as qualitative or absolute errors and / or as quantitative or relative errors.

[0013] According to one embodiment of the technology described here, the method comprises the following steps: - Determining fuel consumption as a measured value over time, - Determining a target fuel consumption behavior as a setpoint over time and - Diagnosing the fuel sensor system based on the determined measured value and based on the determined target value.

[0014] In this way, any errors can be detected easily and reliably. Diagnosis can be performed by comparing the measured fuel behavior with a target fuel behavior for error detection and / or analysis. Depending on the deviation of the fuel behavior or the measured value from the target fuel behavior or the target value, various errors and / or error causes can be identified. In particular, it is possible not only to quickly and reliably determine whether the fuel sensor is fundamentally faulty, but also the extent of the error. For example, not only a steady-state error between the target value and the measured value, but also the dynamic behavior of the fuel sensor can be determined and / or evaluated. The fuel cell system can then be monitored based on the determined dynamic behavior of the fuel sensor.The term "assessment value" can be understood as a measured value.

[0015] Furthermore, it is possible that the proposed procedure includes the following steps: - Determining the difference between the measured value and the target value over time and - Diagnosing fuel sensor issues based on the measured difference, - where the difference is determined a predefined time after the pressure increase.

[0016] The sudden pressure increase is used here as a starting point for determining fuel behavior. Fuel behavior reacts with a delay to the pressure increase. Therefore, the most meaningful data for diagnosis can be specifically determined within the defined time after the pressure increase. Based on the measured difference within this defined time after the pressure increase, particularly accurate statements about the sensor accuracy of the fuel sensor can be made quickly and easily. The difference can be determined over time. This means that not only a single difference value, but several difference values ​​can be determined, based on which the fuel sensor can be diagnosed.

[0017] Furthermore, the procedure may include the following steps: - Defining a tolerance range for the determined target value between an upper tolerance value and a lower tolerance value and - Diagnosing a faulty fuel sensor when the measured value after pressure increase is outside the tolerance range for a defined period of time.

[0018] In this way, fuel sensor diagnostics can also be performed particularly easily and reliably. If the measured value after the pressure increase remains outside the tolerance range for a defined period of time, the diagnosis can be made by concluding that the fuel sensor is faulty. The defined period can be between 1 and 30 seconds after the pressure increase, between 2 and 20 seconds after the pressure increase, and / or less than 15 seconds after the pressure increase.

[0019] Furthermore, the procedure may include the following steps: - Defining a tolerance range for the determined target value between an upper tolerance value and a lower tolerance value and - Diagnosing a quantitative error value of the fuel sensor when the measured value after the pressure increase is within the tolerance range for a defined period of time.

[0020] In this way, the fuel cell sensor can also be diagnosed particularly easily and reliably. If the measured value after the pressure increase remains within the tolerance range for a defined period, the diagnosis can be made by concluding that the fuel cell sensor is fundamentally functional and can determine the fuel behavior at least within a permissible tolerance range. The defined period can be between 1 and 30 seconds after the pressure increase, between 2 and 20 seconds after the pressure increase, and / or less than 15 seconds after the pressure increase. The quantitative error value can be understood as a relative error value that lies within a defined tolerance and on which safety margins for the fuel cell system's control concepts can be based.

[0021] In the method proposed here, the target value can be determined based on the following relationship: y2H2Soll=p1⋅y1H2+Δpp2, where y 2H2Soll = Fuel quantity fraction in the anode system after pressure increase, p1 = Pressure in the anode system before the pressure increase, p2 = pressure in the anode system after the pressure increase, Δp = differential pressure, y 1H2 = Fuel quantity fraction in the anode system before pressure increase.

[0022] Using the relationship shown, the target value can be determined quickly and reliably based on simple pressure values ​​before and after the pressure increase, as well as depending on the fuel fraction before the pressure increase. This relationship was developed within the framework of the technology proposed here, based on the ideal gas law. p1VRT=N1total(state before printer increase), ΔpVRT=ΔNH2(change of state due to the increase in pressure), p2VRT=N2total(state after printer increase), as well as the sensor relationship N1H2=N1total⋅y1H2, and N2H2=N1H2+ΔNH2=(N1tot+ΔNH2)⋅y2H2, N1tot⋅y1H2+ΔpVRT=(N1tot+ΔpVRT)⋅y2H2, p1VRT⋅y1H2+ΔpVRT=(p1VRT+ΔpVRT)⋅y2H2, p1⋅y1H2+Δp=(p1+Δp)⋅y2H2, derived. where: N = amount of substance, V = Anode system volume, R = Gas constant, T = temperature in the anode system, □1 = State before the pressure jump, □2 = State after the pressure jump.

[0023] According to another embodiment of the technology proposed here, the method comprises the following steps: - Providing a predefined faulty fuel behavior and - Operating the fuel cell system to cause the sudden pressure increase after the predefined faulty fuel behavior has been detected.

[0024] This means that if a specific fuel behavior is detected, a pressure surge can be actively triggered to subsequently and / or concurrently perform the fuel sensor diagnostics described above. This allows for particularly reliable monitoring of the fuel sensor system during operation of the fuel cell system. In particular, it ensures continuously that a functioning fuel sensor system is being used. Additionally, the diagnostic process can be performed with every regular, sudden pressure increase or with predefined pressure increases.

[0025] The predefined faulty fuel behavior of the procedure described here can exhibit a predefined increase in the fuel fraction in the anode system. This means that if a predefined increase in the fuel fraction is detected, it can raise suspicion of a malfunction in the fuel sensor. Subsequently, a sudden pressure increase is actively triggered to diagnose the fuel sensor as described above. In this way, the diagnosis can be carried out in a targeted and efficient manner. The predefined increase in the fuel fraction can include an unexplained increase during an operating condition such as a purge process, in which no increase in the fuel fraction should actually occur.

[0026] Furthermore, it is possible that the predefined faulty fuel behavior exhibits a predefined drop in the fuel fraction within the anode system. This means that if a predefined drop in the fuel fraction is detected, it can also raise suspicion of a malfunction in the fuel sensor. Subsequently, a sudden pressure increase can be actively triggered to diagnose the fuel sensor as described above. In this way, the diagnosis can also be carried out in a targeted and efficient manner. The predefined drop in the fuel fraction can include an unexplained drop in an operating condition such as during fuel supply through the anode inlet path, in which no drop in the fuel fraction should actually occur.

[0027] Furthermore, it is possible that the predefined faulty fuel behavior in the procedure described here exhibits a predefined constant fuel fraction in the anode system. If a predefined constant fuel fraction is detected, this can also raise suspicion of a malfunction in the fuel sensor. Subsequently, a sudden pressure increase is actively triggered to diagnose the fuel sensor as described above. In this way, the diagnosis can also be carried out in a targeted and correspondingly efficient manner. The predefined constant fuel fraction can include an inexplicable continuity in an operating state such as during fuel supply through the anode inlet path, in which a constant fuel fraction should not actually occur.A constant fuel quantity can be normal, for example, at extremely high purge rates and / or extremely high nitrogen partial pressures. A constant fuel quantity can be understood as a constant or substantially constant fuel fraction over time, which, for example, changes by less than 20%, less than 10%, or less than 5% over a period of less than 150 seconds or less than 100 seconds.

[0028] Furthermore, it is possible that the procedure includes the following steps: - Determine that a defined operating time of the fuel cell system has been exceeded without a sudden pressure increase being detected, and then - Operating the fuel cell system to cause a sudden pressure increase.

[0029] This means that a pressure surge and the resulting diagnosis can be carried out specifically after a defined operating time has been exceeded. In this way, faulty and / or inaccurate behavior of the fuel sensor can be detected before it leads to noticeable and / or irreversible effects on the operation of the fuel cell system.

[0030] Another aspect of the technology described here concerns a device with a control unit, wherein the control unit is configured to perform a procedure as described above. The device thus offers the same advantages as described in detail with reference to the procedure. The device can be configured to perform the following steps in a fuel cell system as described above: - Detecting a sudden pressure increase in the anode system, - Determining fuel behavior in the anode system via pressure increase using fuel sensors and - Diagnosing fuel sensor technology based on the determined fuel behavior.

[0031] The device can also be configured to perform the process steps described above. For this purpose, the control unit can include a control unit, an ECU, a computer, sensors and / or actuators, which can be configured to carry out the respective process.

[0032] In accordance with another aspect of the technology described herein, a fuel cell system with the described device is proposed. The fuel cell system also comprises a fuel cell with an anode and a cathode, a cathode system with the cathode, and an anode system with the anode, an anode input, an anode output, an anode inlet path for directing fuel into the anode input, an anode outlet path for directing anode exhaust from the anode output, and fuel sensors. The fuel cell system can be configured to execute a process as described above. The fuel cell system can be configured as a PEM fuel cell system.

[0033] The fuel cell system is preferably configured for mobile applications such as vehicles. The fuel cell system can be configured to generate electricity for at least one of the vehicle's drive units. The drive unit can be a machine, for example, an electric motor, used to propel the vehicle. The term "fuel cell" can refer to a single fuel cell or, in particular, a fuel cell stack with multiple fuel cell elements. In its simplest form, the fuel cell is an electrochemical energy converter that converts fuel and oxidant into reaction products, generating electricity and heat in the process. The anode and cathode of a single fuel cell can be separated by an ion-selective or ion-permeable separator.If the fuel cell is configured in the form of a fuel cell stack, the anode can be understood as an anode area of ​​the fuel cell stack and the cathode as a cathode area of ​​the fuel cell stack.

[0034] Another aspect of the proposed technology concerns a vehicle with a fuel cell system as described above, wherein the fuel cell system is configured to generate electricity in the vehicle. The vehicle may have at least one electric motor for propelling the vehicle, and the fuel cell system may be configured to supply power to this at least one electric motor. Thus, the vehicle offers the same advantages as described in detail with regard to the fuel cell system. The term "vehicle" can refer to a motor vehicle such as a motorized two-wheeler, a passenger car, or a truck. It can also refer to a road vehicle, an aircraft, a watercraft, a rail vehicle, or a robot.The term "vehicle" can also include a purely electric vehicle and a hybrid electric vehicle, which, in addition to at least one electric motor, has an internal combustion engine for propulsion. The term "vehicle" can also include a fuel cell vehicle and / or a so-called FCEV (Fuel Cell Electric Vehicle).

[0035] Furthermore, the technology disclosed herein comprises a computer program product and a computer-readable, in particular non-volatile, storage medium on which the computer program product is stored. Thus, the computer program product and the computer-readable storage medium also offer the advantages described above. The computer program product may include instructions which, when executed by a computer, for example, a computer of a control unit and / or device of the vehicle, cause it to execute the proposed method in a vehicle as described above.

[0036] The computer program product can be implemented as machine-readable instruction code in any suitable programming language and / or machine language, such as Java, C++, C#, and / or Python. The computer program product can be stored on a machine-readable storage medium such as a data disk, removable drive, volatile or non-volatile memory, or onboard memory / processor. The instruction code can program a computer and other programmable devices, such as a control unit, to perform the desired functions. Furthermore, the computer program product can be made available on a network, such as the internet, from which it can be downloaded by a user as needed.The computer program product can be implemented using software, one or more special electronic circuits (i.e., in hardware), or in any hybrid form (i.e., using software components and hardware components).

[0037] Further features and combinations of features of the proposed technology will become apparent from the following description of various embodiments, which are schematically illustrated in the figures. All features and / or advantages arising from the claims, the description, and the figures, including design details and spatial arrangements, can be significant both individually and in combination with one another.

[0038] They each show schematically: Fig. 1 a fuel cell system according to an embodiment of the present technology, Fig. 2 a vehicle with a fuel cell system according to an embodiment of the present technology, Fig. 3 a computer-readable storage medium with a computer program product stored thereon according to an embodiment of the present technology, Fig. 4 a flowchart to explain a process according to an embodiment of the present technology and Fig. 5 a diagram to explain a diagnosis of a fuel sensor of the in Fig. 1 fuel cell system shown.

[0039] Elements with the same function and mode of operation are each provided with the same reference symbols in the figures.

[0040] Fig. Figure 1 shows a fuel cell system 10 according to a possible embodiment in the form of a PEM fuel cell system. The depicted fuel cell system 10 comprises an anode system 38, a cathode system 39, and a fuel cell 11. The fuel cell 11 has an anode 12, which can be considered part of the anode system 38, and a cathode 13, which can be considered part of the cathode system 39. The fuel cell 11 has an anode input 21, an anode output 22, a cathode input 23, and a cathode output 24. The cathode system 39 has a cathode inlet path 26 and a cathode outlet path 27. The anode system 38 has an anode inlet path 15, an anode outlet path 16, a recirculation path 17, an injector / ejector 18, a purge path 19, and a purge valve 25. Fuel can be supplied as primary fluid from a [missing information] via the anode inlet path 15. Fig. The fuel tank 70 of a vehicle 100, as depicted in Figure 2, is routed to the injector / ejector 18. Anode gas can also be routed as a mixed gas from the injector / ejector 18 into the fuel cell 11 via the anode inlet path 15. Anode exhaust gas can be routed out of the fuel cell 11 via the anode outlet path 16. Anode exhaust gas from the fuel cell 11 can be routed or drawn into the injector / ejector 18 as secondary fluid via the recirculation path 17 and then routed back into the fuel cell 11 via the anode inlet path 15. Anode exhaust gas from the fuel cell 11 or from the anode 12 can be routed into the cathode outlet path 27 via the purge path 19 (not shown in detail). In the injector / ejector 18 there is a mixing area 29 in which anode exhaust gas from the recirculation path 17 can be mixed with fuel in the anode inlet path 15.

[0041] The fuel cell system 10 shown comprises a fuel sensor 30 with a hydrogen sensor for determining the hydrogen fraction in the anode exhaust gas in the anode outlet path 16 near the anode output 22 or directly downstream of the anode output 22. The fuel cell system 10 also comprises a pressure sensor 31 with a pressure sensor for determining the gas pressure in the anode inlet path 15 downstream of the injector / ejector 18 and upstream of the anode input 21. Furthermore, the fuel cell system 10 includes a device 80 and a control unit 20, the control unit 20 being configured for diagnosing the fuel sensor 30.

[0042] In Fig. Figure 2 shows a vehicle 100 in the form of a passenger car. The vehicle 100 has a fuel cell system 10 as described above, comprising a fuel cell 11 and a fuel tank 70. The vehicle 100 also has two electric motors 60 for propelling the vehicle 100. The fuel cell system 10 is configured to generate electrical current in the vehicle 100, which can be used to power the electric motors 60. In addition, the vehicle 100 has a control unit 20 configured to execute a procedure according to the technology described herein. The control unit 20 can be configured as part of the device 80 described above and is not geographically limited to the device described herein. Fig. The position shown in point 2 is to be considered in a limited way.

[0043] Fig. Figure 3 shows a computer-readable and non-volatile storage medium 50 on which a computer program product 40 is stored. The storage medium 50 is in the form of a flash drive. The computer program product 40 comprises instructions which, when executed by a computer, cause the computer program product 40 to execute the described method in the fuel cell system 10 shown. The term "computer" can refer to a part of the control unit 20 and / or the device 80 described above.

[0044] With reference to Fig. Section 4 describes a method for diagnosing a fuel sensor 30 of a fuel cell system 10 as described above. In a first step S1, a sudden pressure increase in the anode system 38 is detected. In a second step S2, the fuel behavior in the anode system 38 is determined via the pressure increase using the fuel sensor 30. In a third step S3, the fuel sensor 30 is diagnosed based on the determined fuel behavior.

[0045] One possible implementation variant for diagnosing the fuel sensor system 30 will then be described with reference to Fig. 5 described. Fig. Figure 5 shows a diagram illustrating fuel consumption over time. The y-axis represents the fuel fraction y. H2plotted in the anode system 38. In the example shown, a sudden pressure increase occurs after approximately 1 second (not shown). The pressure increase correlates with a calculated target value 83 over time, which corresponds to a target fuel behavior. The target value 83 is determined according to the following equation: y2H2Soll=p1⋅y1H2+Δpp2.

[0046] In addition to the target value 83, an upper tolerance value 85 and a lower tolerance value 86 are defined. More precisely, the upper tolerance value 85 and the lower tolerance value 86 define a tolerance range 84 relative to the determined target value 83. Furthermore, in Fig. 5. A determined value 82 is displayed over time. The determined value 82 corresponds to a fuel behavior, and more precisely a fuel quantity proportion behavior, which was determined using the fuel sensor 30. The determined value 82 can therefore be understood as a measured value determined physically and / or virtually by the fuel sensor 30. The tolerance range 84 corresponds to the following relationship: |y2H2Sett−y2H2Determine|<ε where Y 2H2Ermit = Determined fuel quantity fraction in the anode system (determined value 82), ε = permissible distance (upper tolerance value 85, lower tolerance value 86) to the target value 83.

[0047] As in Fig. As can be seen in step 5, the measured value 82 approaches the target value 83 over the first few seconds after the sudden pressure increase. After approximately 5 seconds, the measured value 82 is within the tolerance range 84. After approximately 8 seconds, a difference 87 develops between the target value 83 and the measured value 83, which then hardly changes. These times can, of course, vary depending on the fuel cell system and the sensor. The difference 87 and / or a corresponding difference value can be considered a relative error and / or an error in the sensor accuracy of the fuel cell sensor 30. That is, based on the difference 87, the fuel cell sensor 30 in the example shown can be diagnosed as having an acceptable measurement inaccuracy in the direction of the lower tolerance value 86.Based on this diagnosis, a safety margin can then be set for various control concepts of the fuel cell system 10. A larger difference 87 results in a larger safety margin being set than a smaller difference 87. The procedure described here can therefore be carried out to control the fuel cell system 10 based on the diagnosis of the fuel sensor 30. Under the in . Fig. The time shown in section 5 can be understood as the pressure increase time described above, during which not only the sudden pressure increase takes place, but also the fuel behavior is determined and the fuel sensor system 30 is diagnosed.

[0048] The technology disclosed here allows for further design principles in addition to those illustrated. That is to say, the technology should not be considered limited to the embodiments explained with reference to the figures.

[0049] For example, the fuel cell system 10 is not limited to a fuel cell system 10 with a recirculation path 17 or with an injector / ejector 18. The fuel behavior and the pressure behavior can be determined at different positions in the anode system 38, in addition to or as an alternative to the positions shown. This is particularly the case when no current is drawn from the fuel cell 11.

[0050] Furthermore, it is possible that a faulty fuel sensor 30 is diagnosed if the measured value 82 is consistently outside the tolerance range 84 or does not fall within the tolerance range 84 for a defined period of time, for example, 15 seconds or less, after the pressure increase. If a diagnosis of the fuel sensor 30 with regard to a pressure jump is desired, but no sudden pressure increase could be detected within a defined time, it is possible to deliberately trigger the sudden pressure increase. That is, the fuel cell system 10 can be operated in such a way that the desired sudden pressure increase occurs. Such a procedure is carried out within the framework of the method proposed here, in particular, after a predefined faulty fuel behavior has been detected. Reasons for a potentially faulty orUndesirable fuel behavior is manifold. Within the framework of the technology proposed here, a predefined increase in a fuel fraction in the anode system 38, a predefined decrease in a fuel fraction in the anode system 38, and a predefined constant fuel fraction in the anode system 38 were identified as reliable indicators of faulty fuel behavior. Reference symbol list 10 Fuel cell systems 11 Fuel cell 12 Anode 13 Cathode 15 Anode inlet path 16 Anode outlet path 17 Recirculation pathway 18 Injector / Ejector 19 Purge Trail 20 Control unit 21 Anode input 22 Anode output 23 Cathode input 24 Cathode output 25 Purge valve 26 Cathode inlet path 27 Cathode outlet path 29 Mixing area 30 Fuel sensors 31 Pressure sensors 38 anode system 39 Cathode system 40 Computer program product 50 storage medium 60 electric motor 70 fuel tanks 80 Device 82 assessed value 83 Target value 84 Tolerance range 85 upper tolerance value 86 lower tolerance value 87 difference 100 vehicles

Claims

[1] Method for diagnosing a fuel sensor (30) of a fuel cell system (10), wherein the fuel cell system (10) further comprises a fuel cell (11) with an anode (12) and a cathode (13), a cathode system (38) with the cathode (13) and an anode system (38) with the anode (12), an anode inlet (21), an anode outlet (22), an anode inlet path (15) for directing fuel into the anode inlet (21) and an anode outlet path (16) for directing anode exhaust gas from the anode outlet (22), comprising: - Determining a sudden pressure increase in the anode system (38), - Determining fuel behavior in the anode system (38) via pressure increase using the fuel sensor (30) and - Diagnosing the fuel sensor system (30) based on the determined fuel behavior. [2] Method according to claim 1, comprising: - Determining the fuel behavior as a measured value (82) over time, - Determining a target fuel behavior as a setpoint (83) over time and - Diagnosing the fuel sensor system (30) based on the determined measured value (82) and based on the determined target value (83). [3] Method according to claim 2, comprising: - Determining a difference (87) between the measured value (82) and the target value (83) over time and - Diagnosing the fuel sensor system (30) based on the determined difference (87), - where the difference (87) is determined a predefined time after the pressure increase. [4] Method according to any one of claims 2 to 3, comprising: - Defining a tolerance range (84) for the determined target value (83) between an upper tolerance value (85) and a lower tolerance value (86) and - Diagnosing a faulty fuel sensor (30) when the measured value (82) after the pressure increase is outside the tolerance range (84) for a defined period of time. [5] Method according to any one of claims 2 to 4, comprising: - Defining a tolerance range (84) for the determined target value (83) between an upper tolerance value (85) and a lower tolerance value (86) and - Diagnosing a quantitative error value of the fuel sensor (30) when the determined value (82) after the pressure increase is within the tolerance range (84) for a defined period of time. [6] Method according to any one of claims 2 to 5, wherein the target value (83) is determined based on the following relationship: y2H2Soll=p1⋅y1H2+Δpp2, where Y 2H2Soll = Fuel quantity fraction in the anode system (target value) after pressure increase, P1 = Pressure in the anode system before the pressure increase, P2 = Pressure in the anode system after the pressure increase, Δp = differential pressure, y 1H2 = Fuel quantity fraction in the anode system before pressure increase. [7] Method according to any one of the preceding claims, comprising: - Providing a predefined faulty fuel behavior and - Operating the fuel cell system (10) to cause the sudden pressure increase after the predefined faulty fuel behavior has been detected. [8] Method according to claim 7, wherein the predefined faulty fuel behavior has a predefined increase and / or a predefined decrease of a fuel quantity fraction in the anode system (38). [9] Method according to one of claims 7 to 8, wherein the predefined faulty fuel behavior has a predefined constant fuel quantity fraction in the anode system (38). [10] Method according to any one of the preceding claims, comprising: - Determine that a defined operating time of the fuel cell system has been exceeded without a sudden pressure increase being detected, and then - Operating the fuel cell system (10) to cause a sudden pressure increase. [11] Device (80) comprising a control unit (20) configured to perform a method according to any of the preceding claims. [12] Fuel cell system (10) comprising a fuel cell (11) with an anode (12) and a cathode (13), a cathode system (38) with the cathode (13) and an anode system (38) with the anode (12), an anode inlet (21), an anode outlet (22), an anode inlet path (15) for directing fuel into the anode inlet (21) and an anode outlet path (16) for directing anode exhaust gas from the anode outlet (22), a fuel sensor system (30) and a device (80) according to claim 11. [13] Vehicle (100) with a fuel cell system (10) according to claim 12, wherein the fuel cell system (10) is configured to generate electrical current in the vehicle (100). [14] Computer program product (40), comprising instructions which, when the computer program product (40) is executed by a computer, cause it to execute the method according to one of claims 1 to 10 in a fuel cell system (10) according to claim 12 and / or in a vehicle (100) according to claim 13. [15] Computer-readable storage medium (50) with a computer program product (40) stored thereon according to claim 14.

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