Method and device for checking a fuel concentration sensor

Abstract

The invention relates to a device (103) for checking a fuel concentration sensor (323) which is designed to ascertain an estimated value of the concentration of fuel (211) in a gas mixture (403). For a measuring process for ascertaining an estimated value of the fuel concentration, the device (103) is designed to: produce a supply or removal of a target quantity of thermal energy (402, 412) to or from the gas mixture (403); ascertain a measuring process temperature measurement value of the gas mixture (403), using a temperature sensor (404) of the fuel concentration sensor (323), as a result of the supply or removal of the target quantity of thermal energy (402, 412); and ascertain the estimated value of the fuel concentration on the basis of the measuring process temperature measurement value. Additionally, for a testing process for testing the fuel concentration sensor (323), the device (103) is designed to: produce a supply or removal of a test quantity of thermal energy (402, 412) to or from the gas mixture (403), said test quantity deviating from the target quantity of thermal energy (402, 412); ascertain a test process temperature measurement value of the gas mixture (403), using the temperature sensor (404), as a result of the supply or removal of the test quantity of thermal energy (402, 412); and detect an impairment of the fuel concentration sensor (323) on the basis of the test process temperature measurement value of the gas mixture (403).

Description

[0001] Method and device for testing a fuel concentration sensor

[0002] The technology disclosed here relates to a method and a corresponding device for checking, in particular for recalibrating, a fuel concentration sensor.

[0003] An electrically powered vehicle may have a fuel cell system with a fuel cell stack having one or more fuel cells. The fuel cell system is configured to generate electrical energy for operating the vehicle's electric drive motor based on a fuel, in particular based on hydrogen (H2). The fuel for the fuel cell stack is typically supplied from a pressure vessel to the fuel cell stack. The amount of fuel supplied to the fuel cell stack can be varied by a valve.

[0004] The fuel cell system typically has at least one fuel concentration sensor configured to detect a measured value of the fuel concentration in the exhaust gas of the fuel cell stack. Alternatively or additionally, the fuel cell system may have a fuel concentration sensor configured to detect fuel in the vicinity of the fuel cell system (e.g., in the vicinity of the pressure vessel valve), e.g., to detect a leak in the fuel cell system. Aging of a fuel concentration sensor may lead to measurement inaccuracies. Alternatively or additionally, the fuel concentration sensor may fail, which could compromise the safety of the fuel cell system. It is a preferred object of the technology disclosed here to reduce or eliminate at least one disadvantage of a previously known solution or to propose an alternative solution.It is a preferred object of the technology disclosed herein to detect deterioration of a fuel concentration sensor in an efficient, reliable and precise manner, in particular to enable efficient and safe operation of a fuel cell system.

[0005] The problem(s) are solved by the subject matter of the independent patent claims. The dependent claims represent preferred embodiments.

[0006] According to one aspect, a device for checking a fuel concentration sensor is described, which is configured to determine an estimated value of the fuel concentration of fuel (in particular hydrogen, such as EL) in a gas mixture. The fuel concentration sensor can be part of a fuel cell system. The gas mixture can comprise, in particular, an exhaust gas from the fuel cell system.

[0007] The fuel cell system can be designed for mobile applications such as motor vehicles (e.g., passenger cars, motorcycles, commercial vehicles, etc.), in particular for providing (electrical) energy for at least one (electric) drive motor for propulsion of the motor vehicle. Alternatively or additionally, the fuel cell system can be designed for a stationary application. The fuel cell system comprises a fuel cell stack, wherein the fuel cell stack is an electrochemical energy converter that converts fuel and oxidant into reaction products, thereby producing electricity and heat.

[0008] The device is configured to add or remove a desired amount of thermal energy from the gas mixture for a measurement process to determine an estimated value of the fuel concentration. For this purpose, a main temperature control element (e.g., a main heating element) of the fuel concentration sensor can be caused to add or remove the desired amount of thermal energy from the gas mixture.

[0009] The device is further configured to use a temperature sensor of the fuel concentration sensor to determine at least one measurement process temperature measured value of the gas mixture (i.e., the temperature of the gas mixture) as a result of the supply or removal of the desired amount of thermal energy. The estimated value of the fuel concentration can then be determined based on the measurement process temperature measured value.

[0010] The estimated fuel concentration can be determined using a predefined (possibly analytical) model. The model can accept a temperature measurement (and possibly a humidity measurement and / or a pressure measurement) as an input and provide an estimated fuel concentration as an output. This allows for efficient and precise fuel concentration estimates.

[0011] The device is further configured to cause a test amount of thermal energy to be added to or removed from the gas mixture during a test process for checking the fuel concentration sensor, which deviates (e.g., by 10% or more) from the target amount of thermal energy. Thus, one or more thermal conditions for detecting a temperature measurement value (compared to the measurement process) can be changed for the test process.

[0012] Using the temperature sensor, at least one test process temperature measurement of the gas mixture can then be determined as a result of the addition or removal of the test quantity of thermal energy. Furthermore, an impairment of the fuel concentration sensor can be detected efficiently and reliably based on the test process temperature measurement of the gas mixture. The impairment of the fuel concentration sensor, in particular of the temperature sensor of the fuel concentration sensor, can be detected particularly reliably based on the deviation (in particular based on a missing or insufficient deviation) of the test process temperature measurement from the measurement process temperature measurement.

[0013] A change in one or more thermal conditions used to detect a temperature reading should typically result in a corresponding (expected) change in the temperature reading detected by the temperature sensor. If the expected change in the temperature reading detected by the temperature sensor is not detected, this may indicate a malfunction of the fuel concentration sensor.

[0014] The device can be configured to compare the test process temperature measured value with the measurement process temperature measured value. An impairment of the fuel concentration sensor can be detected in a particularly reliable manner based on the comparison, in particular such that an impairment of the fuel concentration sensor is detected (possibly only) if the test process temperature measured value deviates from the measurement process temperature measured value by less than a predefined deviation threshold. The deviation threshold can depend on the deviation of the test quantity from the target amount of thermal energy. In particular, the deviation threshold can increase with increasing deviation of the test quantity from the target amount of thermal energy.

[0015] The device can be designed to cause the gas mixture to be heated to a desired temperature for the measuring process to determine the estimated value of the fuel concentration and then to be heated to or from a

[0016] From the switch-off time, the active supply or active removal of thermal energy to or from the gas mixture is prevented. In particular, it can be ensured that the one or more temperature control elements (in particular all temperature control elements) of the fuel concentration sensor are deactivated from the switch-off time. A temporal progression of measurement process temperature measured values ​​of the gas mixture from the switch-off time can then be determined using the temperature sensor. The estimated value of the fuel concentration can then be determined in a particularly precise manner on the basis of the temporal progression of measurement process temperature measured values, in particular on the basis of the temporal gradient of the temporal progression of measurement process temperature measured values ​​(and using the model).

[0017] Furthermore, the device can be configured to heat the gas mixture to the target temperature during the fuel concentration sensor testing process, and to (continue to) actively supply or remove thermal energy to or from the gas mixture at or from the shutdown point. Thus, one or more temperature control elements of the fuel concentration sensor can (continue to) operate from the shutdown point.

[0018] Using the temperature sensor, a temporal progression of the gas mixture temperature measurements during the test process can then be determined from the shutdown point. Furthermore, an impairment of the fuel concentration sensor can be detected particularly precisely based on the temporal progression of the gas mixture temperature measurements during the test process, in particular based on a temporal gradient of the temporal progression of the temperature measurements during the test process. Furthermore, the temporal progression of the temperature measurements during the test process can be compared with the corresponding temporal progression of the temperature measurements during the measurement process in order to detect an impairment of the fuel concentration sensor in a particularly robust manner.

[0019] The device can be configured to ensure, for the measuring process for determining the estimated value of the fuel concentration, that a constant thermal target output for tempering the gas mixture is achieved during a specific measuring period by at least one tempering element of the fuel concentration sensor (overall and / or for the entire measuring period). On the other hand, for the checking process for checking the fuel concentration sensor, a constant thermal test output for tempering the gas mixture is achieved during the measuring period by at least one tempering element of the fuel concentration sensor (overall and / or for the entire measuring period), wherein the test output differs (by 10% or more) from the target output. In this way, any impairment of the fuel concentration sensor can be detected in a particularly robust manner based on temperature measurements.

[0020] The device can be configured to determine a measurement process humidity measured value of the gas mixture (ie the humidity of the gas mixture) as a result of the supply or removal of the desired amount of thermal energy for the measurement process for determining the estimated value of the fuel concentration using a humidity sensor of the fuel concentration sensor, and to determine the estimated value of the fuel concentration (using the model) on the basis of the measurement process humidity measured value.

[0021] Furthermore, the device can be configured to determine a checking process humidity measured value of the gas mixture (i.e. the humidity of the gas mixture) as a result of the supply or withdrawal of the test quantity of thermal energy for the checking process for checking the fuel concentration sensor using the humidity sensor, and to detect an impairment of the fuel concentration sensor on the basis of the checking process humidity measured value of the gas mixture, in particular on the basis of a deviation or a missing or insufficient deviation of the checking process humidity measured value from the measuring process humidity measured value.

[0022] For example, within the scope of a first check procedure, it can be checked whether the temperature sensor of the fuel concentration sensor is impaired based on the temperature measurement value of the gas mixture during the check procedure. Furthermore, within the scope of a subsequent second check procedure, it can be checked whether the humidity sensor of the fuel concentration sensor is impaired based on the humidity measurement value of the gas mixture during the check procedure (particularly if it was determined in the first check procedure that there is no impairment of the temperature sensor).

[0023] By taking moisture measurements into account, any impairment of the fuel concentration sensor can be detected in a particularly precise and robust manner.

[0024] The device can be configured to determine a fuel concentration estimate for the fuel concentration sensor during the test process based on the temperature measurement and the predefined model. An impairment of the fuel concentration sensor can then be detected in a particularly robust and precise manner based on the fuel concentration estimate during the test process, in particular based on the deviation (or the lack of or insufficient deviation) of the fuel concentration estimate during the test process from the fuel concentration estimate determined during the measurement process.

[0025] The device can be configured to cause the main temperature control element of the fuel concentration sensor to supply or remove the target amount of thermal energy from the gas mixture for the test process for testing the fuel concentration sensor. Furthermore, an additional temperature control element of the fuel concentration sensor can be caused to supply or remove thermal energy from the gas mixture, so that the test amount of thermal energy deviating from the target amount is effectively supplied to or removed from the gas mixture. Thus, an additional temperature control element can be provided and used to effect the change in one or more thermal conditions for a test process. This allows for particularly robust detection of a fuel concentration sensor impairment.

[0026] The device can be configured to perform repeated, in particular periodic, measuring processes and checking processes, in particular such that after N measuring processes (if necessary exactly) a checking process is carried out, with N>1, e.g., N>4. Thus, a repeated check of the fuel concentration sensor can be carried out during operation of the fuel concentration sensor in order to ensure particularly safe operation of a fuel cell system.

[0027] The device can be configured to initiate at least one safety measure if an impairment of the fuel concentration sensor is detected. Examples of safety measures include:

[0028] • deactivation of the fuel cell system in which the fuel concentration sensor is installed; and / or

[0029] • issuing a warning to a user of the fuel cell system. This can ensure particularly safe operation of the fuel cell system.

[0030] The device can be configured to effect a recalibration of the fuel concentration sensor (in particular of the predefined model for determining an estimated value of the fuel concentration) on the basis of the determined checking process temperature measurement value and / or the checking process humidity measurement value.

[0031] According to another aspect, a fuel concentration sensor is described which includes the device described in this document.

[0032] According to a further aspect, a fuel cell system is described which includes the device described in this document.

[0033] According to a further aspect, a (road) motor vehicle (in particular a passenger car or a truck or a bus or a motorcycle) is described which comprises the device and / or the fuel cell system described in this document.

[0034] According to a further aspect, a method for testing a fuel concentration sensor is described, which is configured to determine an estimated value of the fuel concentration of fuel (in particular of H2) in a gas mixture. The method comprises, for a measuring process for determining an estimated value of the fuel concentration: causing a desired amount of thermal energy to be added to or removed from the gas mixture; determining, using a temperature sensor of the fuel concentration sensor, a measurement temperature measurement value (the temperature) of the gas mixture as a result of the addition or removal of the desired amount of thermal energy; and determining the estimated value of the fuel concentration based on the measurement temperature measurement value.

[0035] Furthermore, the method for a test procedure for testing the fuel concentration sensor comprises: causing a test amount of thermal energy to be added to or removed from the gas mixture that deviates from the target amount of thermal energy; determining, from the temperature sensor, a test procedure temperature reading (the temperature) of the gas mixture as a result of the addition or removal of the test amount of thermal energy; and detecting deterioration of the fuel concentration sensor based on the test procedure temperature reading of the gas mixture.

[0036] According to another aspect, a software (SW) program is described. The SW program can be configured to be executed on a processor (e.g., on a vehicle control unit) and thereby to carry out the method described in this document.

[0037] According to a further aspect, a storage medium is described. The storage medium can comprise a software program configured to be executed on a processor and thereby to carry out the method described in this document.

[0038] It should be noted that the methods, devices, and systems described in this document can be used both alone and in combination with other methods, devices, and systems described in this document. Furthermore, any aspects of the methods, devices, and systems described in this document can be combined in a variety of ways. In particular, the features of the claims can be combined in a variety of ways. Furthermore, features listed in parentheses are to be understood as optional features.

[0039] The invention will be described in more detail below using exemplary embodiments.

[0040] Figure 1 shows an exemplary fuel cell system with a fuel cell stack; Figure 2 shows an exemplary structure of a fuel cell;

[0041] Figure 3 shows an exemplary fuel cell system with a fuel concentration sensor;

[0042] Figure 4a shows an exemplary fuel concentration sensor;

[0043] Figure 4b shows exemplary temporal courses of temperature measured values;

[0044] Figure 4c shows exemplary temperature measurements; and

[0045] Figure 5 is a flowchart of an exemplary method for checking a fuel concentration sensor of a fuel cell system.

[0046] As stated at the beginning, this document deals with the efficient, reliable and precise verification of a fuel concentration sensor, in particular for use in a fuel cell system.

[0047] Fig. 1 shows a fuel cell system 100 with a fuel cell stack 102 with at least one fuel cell 101. The fuel cell system 100 is intended, for example, for mobile applications such as motor vehicles, in particular for providing energy for at least one electric drive motor for propulsion of a motor vehicle. A fuel cell 101 is an electrochemical energy converter that converts fuel and oxidant into reaction products, thereby producing electricity and heat. A fuel cell 101 comprises (as shown in Fig. 2) an anode 201 and a cathode 202, which are separated by an ion-selective or ion-permeable separator 203. The anode 201 is supplied with fuel 211. Preferred fuels 211 are: hydrogen (EL), low-molecular-weight alcohol, biofuels, or liquefied natural gas. The cathode 202 is supplied with oxidant 212.Preferred oxidizing agents 212 are air, oxygen, and peroxides. The ion-selective separator 203 can be designed, for example, as a proton exchange membrane (PEM). A cation-selective polymer electrolyte membrane is preferably used. Materials for such a membrane include, for example, Nafion®, Flemion®, and Aciplex®.

[0048] A fuel cell system 100 comprises, in addition to the at least one fuel cell 101, peripheral system components (BOP (balance-of-plant) components) that can be used in the operation of the at least one fuel cell 101. Typically, several fuel cells 101 are combined to form a fuel cell stack 102. Furthermore, the fuel cell system 100 typically comprises at least one pressure vessel, in particular a pressure tank, 110, which is used to provide the fuel 211 for the one or more fuel cells 101. The pressure vessel 110 is connected to the one or more fuel cells 101 via one or more lines 112.

[0049] The anode 201 and the cathode 202 of a fuel cell 101 or a fuel cell stack 102 can be connected to contact parts 204. An operating voltage is typically present between the contact parts 204 (e.g., approximately IV for a fuel cell 101), and a current can be provided. By connecting several fuel cells 101 in series (i.e., by providing a stack or fuel cell stack 102), the operating voltage of a fuel cell stack 102 can be increased. The fuel cells 101 of the fuel cell stack 102 generally each comprise two separator plates (not shown). The ion-selective separator 203 of a fuel cell 101 is generally arranged between two separator plates. One separator plate, together with the ion-selective separator 203, forms the anode 201.The additional separator plate arranged on the opposite side of the ion-selective separator 203 forms, together with the ion-selective separator 203, the cathode 202. Gas channels for fuel 211 and for oxidant 212 are preferably provided in the separator plates.

[0050] The separator plates can be designed as monopolar plates and / or as bipolar plates. In other words, a separator plate expediently has two sides, one side, together with an ion-selective separator 203, forming the anode 201 of a first fuel cell 101, and the second side, together with another ion-selective separator 203 of an adjacent second fuel cell 101, forming the cathode 202 of the second fuel cell 101.

[0051] Between the ion-selective separators 203 and the separator plates, so-called gas diffusion layers or gas diffusion layers (GDL) are usually provided.

[0052] Fig. 3 shows further details of a fuel cell system 300. Fuel 211 is supplied from the pressure vessel 110 to the anode inlet of the anode 201 of the fuel cell stack 102 via lines 112, 311. If necessary, fuel 211 can be recirculated from the anode exhaust line 313 of the anode 201 back to the inlet of the anode 201 (via the fuel recirculation conveyor 312). The gas from the anode 201 can first be passed through a water separator 314 to separate water from the gas. The separated water can be fed into a water tank (not shown). The gas (which primarily comprises fuel 211) then passes via a recirculation line 316 from the water separator 314 via the recirculation conveyor 312 back to the inlet line 311 and to the inlet of the anode 201.A fuel concentration sensor (which may be configured as described in this document) may be arranged on the recirculation path, in particular on the recirculation line 316.

[0053] On the cathode side, oxidant 212 can be fed via the oxidant conveyor 205 to the cathode inlet via a cathode supply line 321. Furthermore, exhaust gas from the cathode 202 can be conducted away from the cathode 202 from the cathode outlet via a cathode exhaust line 322. When ambient air is used as the oxidant 212, the exhaust gas from the cathode 202 typically primarily comprises nitrogen. Furthermore, a bypass line with a bypass valve 324 can be arranged on the cathode side, via which the oxidant 212 can be fed past the cathode 202 directly from the cathode supply line 321 to the cathode exhaust line 322.

[0054] The fuel cell system 300 may further include a purge valve 317, which allows the anode 201 to be purged, e.g., to reduce the amount of water in the anode 201. The purge valve 317 may be arranged downstream of the water separator 314. The purge valve 317 may be connected to the exhaust line 322 of the cathode 202 via a purge line 315, so that a mixture of the gas from the cathode 202 and the exhaust gas from the anode 201 is conducted out of the fuel cell system 300 via the exhaust line 322. The concentration of fuel 211 in this exhaust mixture may be measured by a fuel concentration sensor 323.

[0055] The fuel cell system 100 thus typically comprises an anode subsystem (with one or more anode-side components) formed by the fuel-carrying components of the fuel cell system 100, 300. An anode subsystem can have at least one anode supply line 311 leading to the anode inlet (from at least one pressure vessel 110, at least one tank shut-off valve (TAV), and optionally at least one pressure reducer), an anode chamber in the fuel cell stack 102, at least one anode exhaust line 313 leading away from the anode outlet, at least one water separator 314 (=AWS), at least one anode purge valve 317 (=APV) (also referred to as a purge valve), at least one active or passive fuel recirculation promoter 312 (=ARE or ARB) and / or at least one recirculation line 316, as well as optionally other elements.The main task of the anode subsystem is the supply and distribution of fuel 211 to the electrochemically active surfaces of the anode compartment and the removal of anode exhaust gas.

[0056] Furthermore, the fuel cell system 100, 300 comprises a cathode subsystem (with one or more cathode-side components). The cathode subsystem is formed from the oxidant-carrying components. A cathode subsystem can have at least one oxidant feeder 205, at least one cathode supply line 321 leading to the cathode inlet, at least one cathode exhaust line 322 leading away from the cathode outlet, a cathode chamber in the fuel cell stack 102, and other elements. The main task of the cathode subsystem is to supply and distribute oxidant 212 to the electrochemically active surfaces of the cathode chamber and to remove unused oxidant 212 and / or reaction products.

[0057] During operation of the fuel cell system 100, 300, the fuel concentration sensor 323 can repeatedly record measured values ​​relating to the concentration of fuel 211 in the exhaust gas of the fuel cell system 100, 300, particularly in the exhaust line 322. The operation of the fuel cell system 100, 300 can be adjusted depending on the measured values ​​of the concentration sensor 323. This allows for efficient and safe operation of the fuel cell system 100, 300.

[0058] It may happen that the measurement accuracy of the fuel concentration sensor 323 is impaired, e.g., due to aging. Alternatively or additionally, a failure of the fuel concentration sensor 323 in the exhaust line 322 or of another fuel concentration sensor of the fuel cell system 100, 300 may occur. This document describes measures that enable the efficient and reliable detection of a deterioration of a fuel concentration sensor 323.

[0059] Fig. 4a shows an exemplary fuel concentration sensor 323, which is designed to detect measured values ​​relating to the fuel concentration in a gas mixture 403. The gas mixture 403 can comprise, for example, air and optionally fuel 211. The sensor 323 comprises a temperature control element 401, in particular a heating element, which is designed to supply the gas mixture 403 with a defined target amount of thermal energy 402. For example, the gas mixture 403 can be heated to a defined target temperature by the temperature control element 401. Alternatively or additionally, a specific thermal power can be continuously emitted by the temperature control element 401 in order to continuously supply the gas mixture 403 with a defined amount of thermal energy.

[0060] The fuel concentration sensor 323 includes a temperature sensor 404 configured to detect one or more (temperature) measured values ​​related to the temperature of the gas mixture 403. The temperature sensor 404 can be arranged at a defined distance from the temperature control element 401. Furthermore, the fuel concentration sensor 323 can include a humidity sensor 405 configured to detect one or more (humidity) measured values ​​related to the humidity of the gas mixture 403. Furthermore, the fuel concentration sensor 323 can include a pressure sensor 406 configured to detect one or more (pressure) measured values ​​related to the pressure of the gas mixture 403.

[0061] The (control and / or evaluation) device 103 can be configured to determine an estimated value for the fuel concentration in the gas mixture 403 based on at least one temperature measurement value (from the temperature sensor 404). For this purpose, a predefined model (e.g., an analytical model) can be used. This can utilize the fact that the thermal conductivity of the gas mixture 403 depends on the fuel concentration in the gas mixture 403, with the thermal conductivity of the gas mixture 403 typically increasing with increasing fuel concentration.

[0062] When determining the estimated fuel concentration, one or more humidity measurements (from humidity sensor 405) and / or one or more pressure measurements (from pressure sensor 406) can also be taken into account. This can further increase the accuracy of the estimated value.

[0063] Fig. 4b shows exemplary temporal profiles of the (detected) temperature 420 of the gas mixture 403. The gas mixture 403 can be heated to a target temperature 421 by the temperature control element 401. It can then (at a

[0064] From the switch-off point in time, the supply of thermal energy 402 can be stopped, and the time profile 431, 432 of the temperature 420 can be recorded (using the temperature sensor 404), wherein the temperature 420 drops starting from the target temperature 421. The time gradient 441, 442 with which the temperature 420 drops depends on the thermal conductivity of the gas mixture 403, wherein the magnitude of the gradient 441, 442 typically increases with increasing thermal conductivity (i.e. with increasing fuel concentration) of the gas mixture 403. Fig. 4b shows a first time profile 431 of the temperature 420 with a first gradient 441 for a first fuel concentration. Furthermore, Fig. 4b shows a second time profile 432 of the temperature 420 with a second gradient 442 for a second fuel concentration.The first gradient 441 is smaller in magnitude than the second gradient 442, from which it can be concluded that the first fuel concentration is smaller than the second fuel concentration.

[0065] The recorded time course 431, 432 can be evaluated using the predefined model to determine an estimate of the fuel concentration.

[0066] Fig. 4c shows temperature measurement values ​​451, 452 for an alternative measurement method, in which the gas mixture 403 is continuously heated by the temperature control element 401 with a specific thermal (target) power, resulting in a specific, constant temperature 420 of the gas mixture 403, which depends on the thermal conductivity of the gas mixture 403 and thus on the fuel concentration. The resulting temperature 451, 452 typically increases with increasing thermal conductivity (and thus with increasing fuel concentration).

[0067] A malfunction of the temperature sensor 404 (and / or the humidity sensor 405) can lead to a reduction in the accuracy of the fuel concentration estimate. Typically, it is not easy to verify whether the fuel concentration estimate determined by the fuel concentration sensor 323 is correct. In particular, with a fuel concentration estimate of 0%, it is not easy to determine whether the estimate is correct or whether the fuel concentration sensor 323 is defective.

[0068] The fuel concentration sensor 323 can be configured (during a testing process, to determine an estimated value of the fuel concentration, in particular to detect a temperature measurement and / or a humidity measurement) to cause a test amount of thermal energy 402 that deviates from the target amount to be supplied to the gas mixture 403. This can be achieved by appropriate operation of the temperature control element 401. Alternatively or additionally, this can be achieved by providing an additional temperature control element 411 that is configured to supply (or withdraw) thermal energy 412 from the gas mixture 403 for testing the fuel concentration sensor 323. The additional temperature control element 411 can comprise a heating element (e.g., a heating resistor) and / or a cooling element (e.g., a process control element).The test amount of thermal energy 402, 412 may be (by at least 10%) higher or lower than the target amount.

[0069] In the measurement method illustrated in connection with Fig. 4b, for example, additional thermal energy 412 can be added to (or removed from) the gas mixture 403 during the recording of the temporal profile 433 of the temperature 420 of the gas mixture 403. This typically results in the gradient 443 of the recorded temporal profile 433 being reduced (or increased), as shown by way of example in Fig. 4b. This change in the temporal profile 433 of the temperature 420, in particular the gradient 443, can be detected, and based on this, it can be checked whether the fuel concentration sensor 323 is functioning correctly.

[0070] In the measurement method illustrated in connection with Fig. 4c, the thermal power can be increased (or reduced) compared to the target power, resulting in the detected temperature 453 of the gas mixture 403 increasing (or decreasing). This temperature increase of the gas mixture 403 can be detected, and based on this, it can be checked whether the fuel concentration sensor 323 is functioning correctly.

[0071] To measure the concentration of hydrogen 211 in a fuel cell system 100, 300, two test methods can be used, for example. With the heat loss measurement method, a heating element 401 (e.g., with a heating wire) can be heated cyclically, and the heat loss can be measured during and / or after the switch-off time. With a thermal conductivity measurement, the heating element 401 can be constantly heated, and the heat output arriving at a nearby temperature sensor 404 can be measured. Both methods exploit the physical effect that a higher H2 concentration in the air 403 leads to a changed (in particular, an increased) thermal conductivity of the air 403. The ^ concentration can then be determined from the changed thermal conductivity.

[0072] Especially when used in a vehicle, the ^ concentration (e.g. to detect a leak) should be determined with sufficient certainty (according to ISO26262, in particular according to ASIL D).

[0073] An H2 sensor 323 can be configured such that the H2 sensor 323 normally indicates a hydrogen concentration of 0%, and only indicates a value deviating from 0% when an elevated hydrogen concentration is present. If the reading is 0%, it typically cannot be reliably determined that there is no elevated hydrogen concentration; it could also indicate a malfunction of the hydrogen sensor 323. Integrity according to ISO 26262 with ASIL D typically requires very low failure rates of the hydrogen sensor 323, which can be achieved through repeated, particularly continuous, recalibration and / or functional testing of the hydrogen sensor 323 (as described in this document).

[0074] For this purpose, energy can be specifically introduced (or removed) from the environment of the EE sensor 323, for example, using an additional temperature control element 411, so that one or more sub-sensors 404, 405 (in particular the temperature sensor 404 and / or the humidity sensor 405) of the EE sensor 323 experience a change in value. This change can be used to draw conclusions about the state (e.g., the accuracy, the reaction speed, etc.) of the EE sensor 323. As already explained, the main temperature control element 401 of the H2 sensor 323 can be used to effect the change in temperature in the environment of the H2 sensor 323. If necessary, conclusions can be drawn about the condensation or icing of the sensor membrane of the H2 sensor 323, since the condensation or icing of the sensor membrane of the H2 sensor 323 leads to a change in the temperature and / or humidity measurement.

[0075] Fig. 5 shows a (possibly computer-implemented) method 500 for checking a fuel concentration sensor 323 configured to determine an estimated value of the fuel concentration of fuel 211 (in particular, H2) in a gas mixture 403. The fuel concentration sensor 323 may be part of a fuel cell system 100, 300. The method 500 may be executed by a device 103.

[0076] For a measurement process to determine an estimated value of the fuel concentration, the method 500 comprises causing 501 a target amount of thermal energy 402, 412 to be added to or removed from the gas mixture 403. This can be effected, for example, by a main temperature control element 401 of the fuel concentration sensor 323. Furthermore, the method comprises determining 502, using a temperature sensor 404 of the fuel concentration sensor 323, at least one measurement process temperature measured value of the gas mixture 403 as a result of the addition or removal of the target amount of thermal energy 402, 412. If necessary, a temporal profile 431, 432 of measurement process temperature measured values ​​can be determined.

[0077] Method 500 further includes determining 503 the estimated fuel concentration based on the measured temperature value. Typically, a predefined model is used that allows the estimated fuel concentration to be determined based on the measured temperature value.

[0078] Furthermore, the method 500 includes, for a test procedure for testing the fuel concentration sensor 323, causing 504 a test amount of thermal energy 402, 412 to be added to or removed from the gas mixture 403 that deviates from the target amount of thermal energy 402, 412. The test amount may, for example, deviate by 10% or more from the target amount (which is used to determine estimated fuel concentration values). The addition or removal of the test amount of thermal energy 402, 412 can be effected by the main temperature control element 401 and, if appropriate, by an additional temperature control element 411 of the fuel concentration sensor 323.

[0079] The method 500 further comprises determining 505, using the temperature sensor 404, at least one test process temperature measurement value of the gas mixture 403 as a result of the supply or withdrawal of the test amount of thermal energy 402, 412.

[0080] Furthermore, the method 500 includes detecting 506 an impairment of the fuel concentration sensor 323 based on the checking process temperature measurement value of the gas mixture 403. The impairment of the fuel concentration sensor 323 can be detected, in particular, based on a deviation, or on the basis of a missing or insufficient deviation, of the checking process temperature measurement value from the measuring process temperature measurement value. The measures described in this document allow an impairment of a fuel concentration sensor 323 of a fuel cell system 100, 300 to be detected efficiently and reliably. Furthermore, a recalibration of the fuel concentration sensor 323 can be performed. Thus, the safety of the fuel cell system 100, 300 can be increased efficiently and reliably.

[0081] The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and figures are intended only to illustrate the principle of the proposed methods, devices, and systems by way of example.

[0082] List of reference symbols

[0083] 100, 300 fuel cell system

[0084] 101 Fuel Cell

[0085] 102 fuel cell stacks

[0086] 103 (Control and / or evaluation) device

[0087] 110 pressure vessels

[0088] 112 Fuel line

[0089] 201 Anode

[0090] 202 Cathode

[0091] 203 Separator

[0092] 204 Contact part (electrode)

[0093] 205 Oxidant Booster

[0094] 211 Fuel (especially hydrogen)

[0095] 212 Oxidizing agents (especially air)

[0096] 311 Anode lead

[0097] 312 Fuel recirculation conveyor

[0098] 313 Anode exhaust line

[0099] 314 water separator

[0100] 315 Purgel line

[0101] 316 Recirculation line

[0102] 317 Purge valve

[0103] 321 Oxidant supply line

[0104] 322 Cathode exhaust line

[0105] 323 Fuel concentration sensor

[0106] 324 Bypass valve

[0107] 401 Main temperature control element

[0108] 402 thermal energy

[0109] 403 Gas mixture

[0110] 404 Temperature sensor

[0111] 405 Humidity sensor

[0112] 406 pressure sensor

[0113] 411 Additional temperature control element 412 thermal energy

[0114] 420 Temperature (gas mixture)

[0115] 421 Target temperature

[0116] 431-433 temporal course of temperature 441-443 temporal gradient

[0117] 451-453 Temperature measurement value

[0118] 500 Procedure for checking a fuel concentration sensor

[0119] 501-506 Procedural steps

Claims

Claims 1) Device (103) for checking a fuel concentration sensor (323) which is designed to determine an estimated value of a fuel concentration of fuel (211) in a gas mixture (403); wherein the device (103) is designed - for a measurement process to determine an estimated value of the fuel concentration - to cause a desired amount of thermal energy (402, 412) to be added to or removed from the gas mixture (403); - to determine a measurement process temperature measurement value of the gas mixture (403) as a result of the supply or withdrawal of the desired amount of thermal energy (402, 412) using a temperature sensor (404) of the fuel concentration sensor (323); and - to determine the estimated fuel concentration based on the measured temperature value; and - for a check procedure to check the fuel concentration sensor (323) - to cause a test amount of thermal energy (402, 412) to be added to or removed from the gas mixture (403) which deviates from the target amount of thermal energy (402, 412); - to determine a test process temperature measurement value of the gas mixture (403) by means of the temperature sensor (404) as a result of the supply or withdrawal of the test quantity of thermal energy (402, 412); and - to detect an impairment of the fuel concentration sensor (323) on the basis of the test process temperature measurement value of the gas mixture (403). 2) Device (103) according to claim 1, wherein the device (103) is arranged - to compare the verification process temperature measurement value with the measurement process temperature measurement value; - to detect an impairment of the fuel concentration sensor (323) based on the comparison, in particular such that an impairment of the fuel concentration sensor (323) is detected if the verification process temperature measured value deviates from the measurement process temperature measured value by less than a deviation threshold value; wherein the deviation threshold value depends in particular on a deviation of the test quantity from the target quantity of thermal energy (402, 412). 3) Device (103) according to one of the preceding claims, wherein the device (103) is arranged - for the measurement process to determine the estimated value of the fuel concentration - to cause the gas mixture (403) to be heated to a desired temperature (421), and from a switch-off point onwards, an active supply or active removal of thermal energy (402, 412) to or from the gas mixture (403) is prevented; - to determine, using the temperature sensor (404), a time profile (431, 432) of the measuring process temperature measured values of the gas mixture (403) from the switch-off time; and - to determine the estimated value of the fuel concentration on the basis of the temporal progression (431, 432) of the measuring process temperature measured values, in particular on the basis of a temporal gradient (441, 442) of the temporal progression (431, 432) of the measuring process temperature measured values; and - for the fuel concentration sensor check procedure (323) - to cause the gas mixture (403) to be heated to the desired temperature (421), and from the switch-off time onwards an active supply or an active withdrawal of thermal energy (402, 412) to or from the gas mixture (403) takes place; - to determine, using the temperature sensor (404), a time profile (433) of the test process temperature measured values of the gas mixture (403) from the switch-off time; and - to detect an impairment of the fuel concentration sensor (323) on the basis of the temporal profile (433) of the checking process temperature measured values of the gas mixture (403), in particular on the basis of a temporal gradient (443) of the temporal profile (433) of the checking process temperature measured values. 4) Device (103) according to one of the preceding claims, wherein the device (103) is arranged - for the measuring process for determining the estimated value of the fuel concentration, to ensure that during a measuring period a constant thermal target power for tempering the gas mixture (403) is effected by at least one tempering element (401, 411) of the fuel concentration sensor (323); - for the testing process for testing the fuel concentration sensor (323), to ensure that a constant thermal test power for tempering the gas mixture (403) is effected by the at least one tempering element (401, 411) of the fuel concentration sensor (323) during the measurement period; wherein the test power differs from the target power. 5) Device (103) according to one of the preceding claims, wherein the device (103) is arranged - for the measurement process to determine the estimated value of the fuel concentration - using a moisture sensor (405) of the fuel Concentration sensor (323) a measuring process humidity Measured value of the gas mixture (403) due to the supply or extraction of the desired amount of thermal energy (402, 412); and - to determine the estimated fuel concentration based on the moisture measured during the measurement process; and - for the fuel concentration sensor check procedure (323) - to determine, using the humidity sensor (405), a test process humidity measurement value of the gas mixture (403) as a result of the supply or withdrawal of the test quantity of thermal energy (402, 412); and - to detect an impairment of the fuel concentration sensor (323) on the basis of the check process humidity measurement value of the gas mixture (403). 6) Device (103) according to claim 5, wherein the device (103) is arranged - to check, as part of a first check process, on the basis of the check process temperature measurement value of the gas mixture (403), whether the temperature sensor (404) of the fuel concentration sensor (323) is impaired or not; and - to check, in the context of a subsequent second check process, on the basis of the check process humidity measurement value of the gas mixture (403), whether the humidity sensor (405) of the fuel concentration sensor (323) is impaired or not. 7) Device (103) according to one of the preceding claims, wherein the device (103) is arranged - for the measurement process to determine the estimated value of the fuel concentration, to determine the estimated value of the fuel concentration using a predefined model; the model takes a temperature measurement as input and Output variable provides an estimate of the fuel concentration; and - for the fuel concentration sensor check procedure (323) - to determine a verification process estimate of the fuel concentration based on the verification process temperature measurement and the predefined model; and - to detect an impairment of the fuel concentration sensor (323) on the basis of the verification process estimate of the fuel concentration, in particular on the basis of a deviation of the verification process estimate of the fuel concentration from the estimate of the fuel concentration determined during the measuring process. 8) Device (103) according to one of the preceding claims, wherein the device (103) is arranged - for the measuring process for determining the estimated value of the fuel concentration, to cause a main temperature control element (401) of the fuel concentration sensor (323) to supply or withdraw the desired amount of thermal energy (402) from the gas mixture (403); and - for the fuel concentration sensor check procedure (323) - to cause the main temperature control element (401) of the fuel concentration sensor (323) to supply or withdraw the desired amount of thermal energy (402) from the gas mixture (403); and - to cause an additional temperature control element (411) of the fuel concentration sensor (323) to supply or withdraw thermal energy (412) from the gas mixture (403) so that the test quantity of thermal energy (402, 412) deviating from the target quantity is effectively supplied to the gas mixture (403) is added or removed. 9) Device (103) according to one of the preceding claims, wherein the device (103) is configured to carry out measuring operations and checking operations repeatedly, in particular periodically, in particular such that after each N measuring operations a checking operation is carried out, with N>1. 10) Device (103) according to one of the preceding claims, wherein - the device (103) is configured to effect at least one safety measure if an impairment of the fuel concentration sensor (323) is detected; and - the security measure includes, - the deactivation of a fuel cell system (100, 300) in which the fuel concentration sensor (323) is installed; and / or - issuing a notice to a user of the fuel cell system (100, 300). 11) Device (103) according to one of the preceding claims, wherein the fuel (211) is hydrogen, in particular H2. 12) Method (500) for testing a fuel concentration sensor (323) which is configured to determine an estimated value of a fuel concentration of fuel (211) in a gas mixture (403); the method (500) comprising - for a measurement process to determine an estimated value of the fuel concentration - causing (501) a desired amount of thermal energy (402, 412) to be added to or removed from the gas mixture (403); - Determining (502), using a temperature sensor (404) of the fuel concentration sensor (323), a measuring process temperature measured value of the gas mixture (403) as a result of the Supplying or removing the desired amount of thermal energy (402, 412); and - determining (503) the estimated value of the fuel concentration on the basis of the measurement process temperature measurement value; and - for a verification process to check the fuel Concentration sensor (323) - causing (504) a test amount of thermal energy (402, 412) to be added to or removed from the gas mixture (403) which deviates from the target amount of thermal energy (402, 412); - determining (505), using the temperature sensor (404), a Verification process temperature measurement value of the gas mixture (403) as a result of the supply or withdrawal of the test amount of thermal energy (402, 412); and - Detecting (506) an impairment of the fuel concentration sensor (323) on the basis of the Verification process temperature measurement value of the gas mixture (403).

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