Method, control device and computer program for determining a leak in a fuel cell system, and seality analysis device and fuel cell system

Abstract

The invention relates to a method, a control device (160) and a computer program for determining leaks in a fuel cell system, as well as a tightness analysis device (180) and a fuel cell system (100) and the use of a hydrogen sensor (131) arranged in a fuel cell system (100) for determining leaks in a fuel cell system (100). A method according to the invention comprises: receiving a hydrogen signal from a hydrogen sensor (151) arranged in an exhaust system (150); if the received hydrogen signal indicates a hydrogen concentration value in the exhaust system (150) that exceeds a predetermined hydrogen concentration threshold, transmitting a diagnostic signal that causes the fuel cell system (100) to shift to a diagnostic operating mode; it is determined that the membrane of the fuel cell (110) of the fuel cell system (100) is at least partially unsealed if the hydrogen signal received during a diagnostic operation of the fuel cell system (100) substantially drops, or it is determined that the membrane of the fuel cell (110) of the fuel cell system (100) is at least partially unsealed if the hydrogen signal received during the diagnostic operation of the fuel cell system (100) substantially does not drop. If the membrane or the purge valve (137) is at least partially unsealed, it is determined that the purge valve (137) arranged in the anode line system (130) is at least partially unsealed, and a control signal is sent which indicates that the membrane or the purge valve (137) is at least partially unsealed.

Description

Technical Field

[0001] The present invention relates to a method, a control device, and a computer program for determining a leak in a fuel cell system, in particular for locating the leak, and to a leak tightness analysis device and a fuel cell system, and also to the use of a hydrogen sensor arranged in a fuel cell system for determining a leak in the fuel cell system, in particular for locating the leak. Background Art

[0002] A fuel cell system is usually fueled with a gas mixture substantially consisting of hydrogen. For this purpose, it is desirable that the fueled gas mixture has a hydrogen concentration of more than 99%. This high hydrogen concentration in the gas mixture can avoid premature aging of the fuel cell and efficiency losses. Hydrogen sensors based on the principle of thermal conductivity measurement are known from the prior art. Here, the thermal conductivity of the entire gas mixture is determined, from which the concentration of hydrogen in the gas mixture can be derived, since the thermal conductivity of hydrogen is significantly greater than that of many other gas components in the gas mixture.

[0003] For example, US 8,795,917 B2, CN 114,838,937 A, JP 2010 / 067573 A, US10,581,100 B2, and US11,201,340 B2 are known from the prior art. Summary of the Invention

[0004] The task underlying the present invention essentially lies in locating the point of a leak when determining a leak in a fuel cell system.

[0005] This task is solved by the method according to independent claim 1, the control device according to claim 6, the leak tightness analysis device according to claim 8, the fuel cell system according to claim 9, the computer program according to claim 10, the computer program product according to claim 11, and the use of the hydrogen sensor arranged in the exhaust gas line of the fuel cell system according to claim 12. Advantageous design options are described in the dependent claims.

[0006] The idea underlying the present invention basically lies in that when detecting a leak in a fuel cell system, the leak is located by evaluating the signal of a hydrogen sensor arranged in the exhaust pipe of the fuel cell system, in particular whether the leak is caused by the membrane of the fuel cell or by a purge valve arranged in the anode pipeline system of the fuel cell system. For this purpose, first, a leak in the fuel cell system is detected by means of a hydrogen sensor arranged in the exhaust system, and then the fuel cell system is switched to a diagnostic operating mode during which there must be no gas mixture that has previously interacted with the cathode in the exhaust system of the fuel cell system. By evaluating the variation process of the hydrogen sensor signal received by the hydrogen sensor arranged in the exhaust system of the fuel cell system during the diagnostic operating mode, the leak can be located. If the variation process of the hydrogen signal basically decreases during the diagnostic operating mode, it can be determined that the membrane of the fuel cell of the fuel cell system is unsealed. However, if the variation process of the hydrogen signal basically does not decrease during the diagnostic operating mode, in particular is basically constant or even increases, the unsealed point can be assigned to the purge valve.

[0007] Therefore, according to a first aspect of the present invention, a method for detecting a leak in a fuel cell system including an exhaust system is disclosed. The method includes: receiving a hydrogen signal from a hydrogen sensor arranged in the exhaust system. Here, the hydrogen signal represents the hydrogen concentration in the gas mixture present in the exhaust system. The method according to the present invention further includes: if the received hydrogen signal indicates a hydrogen concentration value in the exhaust system exceeding a predetermined hydrogen concentration threshold, sending a diagnostic signal that causes the fuel cell system to switch to a diagnostic operating mode; if the hydrogen signal received during the diagnosis of the fuel cell system basically decreases, it is determined that the membrane of the fuel cell of the fuel cell system is at least partially unsealed, or if the hydrogen signal received during the diagnosis of the fuel cell system basically does not decrease, it is determined that the purge valve arranged in the anode pipeline system is at least partially unsealed; and sending a control signal indicating that the membrane or the purge valve is at least partially unsealed.

[0008] Therefore, by means of the method according to the present invention, in particular after a leak in the fuel cell system has generally been detected and the fuel cell system has been switched to the diagnostic operating mode, the unsealed point in the fuel cell system can be located by evaluating the hydrogen signal of the hydrogen sensor arranged in the exhaust system of the fuel cell system.

[0009] According to a preferred design of the method according to the invention, sending a diagnostic signal includes: sending a cathode inlet valve closing signal, the cathode inlet valve closing signal causing the closing of a cathode inlet valve arranged in the cathode input pipeline of the cathode pipeline system, and / or sending a cathode outlet valve closing signal, the cathode outlet valve closing signal causing the closing of a cathode outlet valve arranged in the cathode discharge pipeline of the cathode pipeline system. Herein, the cathode input pipeline is configured to supply a gas mixture with oxygen to the cathode of the fuel cell system. The cathode discharge pipeline is configured to discharge the gas mixture with oxygen supplied to the cathode of the fuel cell system into the exhaust system.

[0010] According to this preferred design, during the diagnostic operating mode of the fuel cell system, it can be excluded by means of the method according to the invention that there is a gas mixture in the exhaust system of the fuel cell system that has previously interacted with the cathode of the fuel cell of the fuel cell system, so that leaks can be located according to the invention. Herein, the increased hydrogen concentration in the exhaust system may originate from the anode pipeline system (especially in the case of a non-sealed purge valve), or from the cathode pipeline system (especially in the case of a non-sealed membrane of the fuel cell of the fuel cell system). By closing the cathode pipeline connected to the cathode of the fuel cell of the fuel cell system, leaks can be located in a simple manner.

[0011] Furthermore, it can be advantageous herein that sending the diagnostic signal further includes: sending a bypass valve opening signal, the bypass valve opening signal causing at least partial opening of a cathode bypass valve arranged in a cathode bypass pipeline connecting the cathode input pipeline and the cathode discharge pipeline. Herein, determining that at least part of the membrane of the fuel cell of the fuel cell system is not sealed may include determining that the hydrogen signal received during the diagnostic operation of the fuel cell system indicates a hydrogen concentration value that is substantially zero. Additionally or alternatively, determining that at least part of the purge valve of the fuel cell system is not sealed may include determining that the hydrogen signal received during the diagnostic operation of the fuel cell system indicates a hydrogen concentration value greater than zero.

[0012] Since the exhaust system is flushed with a gas mixture from the cathode pipeline system and having oxygen that does not flow past the cathode of the fuel cell, so that the possible hydrogen present in the exhaust system can only come from the anode system due to a potentially non-sealed purge valve, the diagnosis and location of leaks can be accelerated by sending a bypass valve opening signal.

[0013] According to another advantageous design of the method according to the invention, sending a diagnostic signal includes: sending a throttle valve closing signal, the throttle valve closing signal causing the closing of a throttle valve arranged downstream of the cathode outlet valve in the cathode discharge pipeline.

[0014] According to such an advantageous embodiment of the method according to the invention, the complete separation of the cathode pipeline system from the exhaust system can be caused by closing the throttle valve. If hydrogen is still detected in the exhaust system by means of a hydrogen sensor immediately afterwards, the hydrogen must come from the anode pipeline system due to a leaky purge valve.

[0015] According to another preferred embodiment of the method according to the invention, the control signal is furthermore configured to control an operator interface for displaying a warning to the operator of the fuel cell system. The warning notifies the operator that a leak in the membrane or the purge valve has been determined.

[0016] According to another aspect of the invention, a control device is disclosed, which is configured to perform the steps of the method according to any one of the preceding claims.

[0017] Preferably, the control device comprises: a first control device section for performing the step of receiving a hydrogen signal from a hydrogen sensor; a second control device section for performing the step of sending a diagnostic signal; a third control device section for performing the step of determining that the membrane or the purge valve is at least partially leaky; and a fourth control device section for performing the step of sending a control signal.

[0018] According to yet another aspect of the invention, a leak tightness analysis device for a fuel cell system is disclosed, which comprises: a hydrogen sensor configured to generate a hydrogen signal representative of the hydrogen concentration in a gas mixture present in the exhaust system of the fuel cell system; and a control device according to the invention.

[0019] According to yet another aspect of the invention, a fuel cell system is disclosed, which comprises: an anode; a cathode separated from the anode by means of a membrane; an anode pipeline system in which a purge valve is arranged; an exhaust system fluidly connected to the anode pipeline system; and a leak tightness analysis device according to the invention.

[0020] According to yet another aspect of the invention, a computer program is disclosed, which comprises instructions that, when executed by a computing unit, cause the computing unit to perform the method according to the invention for determining a leak in a fuel cell system.

[0021] According to yet another aspect of the invention, a computer-readable medium is disclosed, on which a computer program according to the invention is stored.

[0022] According to yet another aspect of the invention, the use of a hydrogen sensor arranged in the exhaust system of a fuel cell system for determining a leak in a fuel cell system by means of the method according to the invention is disclosed. Description of the Drawings

[0023] By implementing the teachings described herein and observing the appended single drawing, other advantages and features of the present invention become apparent to those skilled in the art, wherein:

[0024] Figure 1 A schematic diagram showing a fuel cell system for a vehicle according to the present invention,

[0025] Figure 2 Showing, in the case of an unsealed membrane or an unsealed purge valve, an exemplary variation process of a hydrogen signal of a hydrogen sensor arranged in an exhaust system of a fuel cell system in Figure 1 and a chart showing an exemplary variation process of a hydrogen signal of a hydrogen sensor arranged in an exhaust system of a fuel cell system, and

[0026] Figure 3 Showing an exemplary flowchart of a method for determining a leak in a fuel cell system according to the present invention Figure 1 of the fuel cell system. DETAILED DESCRIPTION

[0027] In the scope of the present disclosure, the term "gas mixture" describes a mixture composed of different gaseous components, such as hydrogen, nitrogen, air, and / or inert gases, for example argon.

[0028] In the scope of the present disclosure, the term "signal" describes raw data that is converted into a form that can be transmitted via a selected transport medium for data transmission. This can be done in analog or digital form, where the data is first sampled and the data is transformed into discrete (often binary-coded) values, which are then sent as current pulses or voltages of different heights through the medium. In addition, in the scope of the present disclosure, signals can be sent or received continuously. For example, digital signals are sent and received at intervals of several milliseconds.

[0029] In the scope of the present disclosure, the term "diagnostic operating mode of a fuel cell system" describes the following operating mode of a fuel cell system, in which different components and elements of the fuel cell system for diagnosing a cathode outlet valve are controlled and operated in a different manner than in a normal operating mode, and the normal operating mode includes a possible purge process of an anode pipeline system.

[0030] Within the scope of the present disclosure, a "sufficiently sealed point" is described as follows: The corresponding component blocks the corresponding connection path in the closed or intact state, such that the gas mixture flowing through the pipeline can essentially not flow through the component. However, also within the scope of the present disclosure is that a component having a leakage rate of about 0.1 standard milliliters per minute [Sml / min] under an overpressure of about 600 mbar can also be referred to as "sufficiently sealed". Thus, within the scope of the present disclosure, if the leakage rate through a component is above the mentioned 0.1 Sml / min under an overpressure of about 600 mbar, the component can be referred to as "unsealed".

[0031] Figure 1 FIG. shows a schematic view of a fuel cell system 100 for a vehicle according to the present invention. The fuel cell system 100 includes a fuel cell 110, such as a fuel cell stack. Here, as is known from the prior art, the fuel cell 110 includes an anode and a cathode separated from each other by a membrane. For example, the fuel cell 110 can be a so-called PEM fuel cell, where the membrane is a proton exchange membrane, and protons formed at the anode can pass through the proton exchange membrane to reach the cathode.

[0032] The fuel cell system 100 further includes a tank 120 in which a gas mixture consisting essentially of hydrogen is preferably stored under pressure. The tank 120 can further have a valve (not explicitly shown in Figure 1 ), by means of which the inflow and outflow of the gas mixture into and from the tank 120 can be controlled.

[0033] Figure 1The fuel cell system 100 further includes an anode pipeline system 130, which is configured to convey the gas mixture flowing out of the tank 120 to the anode of the fuel cell 110 and discharge or convey back the gas mixture flowing past the anode. To this end, the anode pipeline system 130 includes an anode input pipeline 132, which is fluidly connected to the tank 120 and conveys the gas mixture flowing out of the tank 120 to the anode pipeline 134, and the anode pipeline 134 in turn conveys the gas mixture to the anode of the fuel cell 110. The anode pipeline system 130 further includes an anode discharge pipeline 136, which is fluidly connected to the anode pipeline 134 and can discharge the gas mixture flowing through the anode pipeline 134 and convey it to the exhaust system 150. The anode pipeline system 130 further includes an anode return pipeline 138, which fluidly connects the anode discharge pipeline 136 to the anode input pipeline 132, and a recirculation pump 139 is arranged in the anode return pipeline 138, and the recirculation pump is configured to redirect the gas mixture flowing through the anode discharge pipeline 136 back to the anode input pipeline 132. Therefore, a loop (Kreislauf) is formed among the anode input pipeline 132, the anode pipeline 134, the anode discharge pipeline 136, and the anode return pipeline 138, and the gas mixture can be circulated by means of the recirculation pump 139 and guided in the loop (Kreis).

[0034] The anode pipeline system 130 further includes a purge valve 137, which is arranged in the anode discharge pipeline 136 downstream of the orifice point of the anode return pipeline 138 and is configured to release or block the anode discharge pipeline 136. In the normal operating mode of the fuel cell 110, the purge valve 137 is closed, so that the above-described loop and circulation process of the gas mixture can be provided by means of the recirculation pump 139.

[0035] In addition, a gas sensor 131, such as a hydrogen sensor, is provided in the anode discharge pipeline 136, and the gas sensor is configured to generate a hydrogen signal, which represents the hydrogen concentration at a position between the anode pipeline 134 and the purge valve 137 in the anode discharge pipeline 136. Here, the gas sensor 131 can be a gas sensor based on the principle of thermal conductivity. The hydrogen signal of the hydrogen sensor 131 is preferably a digital signal or data, which can be processed by a data processing device, and the data processing device can include a processor and a memory.

[0036] During the normal operating mode of the fuel cell system 100, an elevated nitrogen concentration is formed within the aforementioned loop, so that the signal of the gas sensor 131 additionally represents the nitrogen concentration within the anode pipeline system. In particular, it can be stated qualitatively that the gas mixture located within the anode pipeline system 130 during the normal operating mode of the fuel cell system 100 consists almost solely of hydrogen and nitrogen, i.e., the sum of the hydrogen concentration and the nitrogen concentration within the anode pipeline system 130 totals 100%. Thus, the hydrogen concentration as well as the nitrogen concentration within the anode pipeline system 130 can be determined based on the signal of the gas sensor 131.

[0037] The fuel cell system 100 additionally includes a cathode pipeline system 140, which consists of a cathode input pipeline 142, a cathode pipeline 144 connected to the cathode, and a cathode discharge pipeline 146. Additionally, the cathode pipeline system 140 includes a cathode bypass pipeline 148, which fluidly connects the cathode input pipeline 142 to the cathode discharge pipeline 146, and a cathode bypass valve 149 for blocking or releasing the cathode bypass pipeline 148 is arranged in the cathode bypass pipeline. The cathode discharge pipeline 146 can discharge the air supplied to the cathode through the cathode input pipeline 142 into the exhaust system 150. In the cathode input pipeline 142, a pressure sensor 141 for detecting the pressure within the cathode input pipeline 142 and a cathode inlet valve 145 are arranged, and the cathode inlet valve can be, for example, a throttle butterfly valve. Similarly, the cathode discharge pipeline 146 has a cathode outlet valve 147 and a pressure sensor 143 arranged downstream thereof in the cathode discharge pipeline for detecting the pressure within the cathode discharge pipeline 146. Additionally, a compressor 170, a water separator 172, and a throttle valve 174 for compressing air are arranged in the cathode pipeline system 140.

[0038] The throttle valve 174 is arranged in the cathode discharge pipeline 146 at a position downstream of the orifice point where the bypass pipeline 168 enters the cathode discharge pipeline, and is configured to release or block the cathode discharge pipeline 146. By closing the throttle valve, the cathode pipeline system 140 can be blocked, so that the gas mixture flow between the compressor 170 and the throttle valve 174 is deactivated or paused.

[0039] Figure 1 The fuel cell system 100 additionally has a vehicle electrical grid branch 102, which includes an electrical consumer. In particular, the vehicle electrical grid branch 102 describes at least a part of the electrical system, which can store and distribute the electrical energy generated by the fuel cell 110.

[0040] As already described, both the anode pipeline system 130 and the cathode pipeline system 140 lead to an exhaust system 150, in which a hydrogen sensor 151 is arranged, which is configured to generate a hydrogen signal that indicates the hydrogen concentration in the gas mixture (in particular the exhaust gas) present in the exhaust system 150. The hydrogen sensor 151 can here be a gas sensor based on the principle of thermal conductivity.

[0041] It can furthermore be seen from Figure 1 that a control device 160 is provided, which can be connected to all components of the fuel cell system 100. Although no separate lines are shown for this purpose in Figure 1 , this electrical connection line can exist in the form of connection lines or connection conductors or wireless communication devices. The control device 160 can have a plurality of control device sections, such as a first control device section 162, a second control device section 164, a third control device section 166 and a fourth control device section 168, which will be discussed in more detail below with reference to Figure 3 which.

[0042] The control device 160 can have a processor or computing unit and a memory. Alternatively, the control device 160 can be a processor or computing unit that is connected to a memory. The processor can be a central processing unit (CPU). The processor can furthermore be another general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor, or the processor can be any conventional processor, etc.

[0043] The memory includes, but is not limited to, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM) or portable read-only memory (e.g., CD-ROM). The memory is configured to store the associated program commands and the associated data.

[0044] The hydrogen sensor 151 and the control device 160 together form a leak analysis device 180 for the fuel cell system 100.

[0045] Figure 2A graph showing exemplary change processes 210, 220 of a hydrogen signal recorded by a hydrogen sensor 151 disposed in an exhaust system 150 of a fuel cell system 100. In particular, the change process 210 depicts the hydrogen signal received by the hydrogen sensor 151 when the membrane of the fuel cell 110 is at least partially unsealed, while the change process 220 shows the hydrogen signal of the hydrogen sensor 151 when the purge valve 137 is at least partially unsealed.

[0046] In Figure 2 it, the first time point t1 indicates the time point when a leak in the fuel cell system 100 occurs. The time point t2 indicates the time point when the fuel cell system 100 is switched to the diagnostic operating mode. In particular, the cathode inlet valve 145 and / or the cathode outlet valve 147 are closed at the time point t2 for this purpose. After the time point t2, the hydrogen signal of the hydrogen sensor 151 is then evaluated according to the present invention in order to locate the detected leak in the fuel cell system 100. For example, at the time point t3, which can be about 5 seconds after the time point t2.

[0047] In Figure 2 before the time point t1 in, the two change processes 210, 220 of the hydrogen signal of the hydrogen sensor 151 respectively indicate that the hydrogen concentration threshold C_H2, such as a hydrogen concentration value of 8%, is not exceeded. Therefore, a leak in the fuel cell system 10 can generally be determined based on exceeding the hydrogen concentration threshold C_H2.

[0048] Before the time point t1, the fuel cell system 100 is furthermore in the normal operating mode, in which the purge valve 137 is closed and the recirculation pump 139 is activated. As already described, during the normal operating mode of the fuel cell system 100, the gas mixture from the tank 120, in particular the hydrogen mixture, circulates or persists in a loop between the anode input line 132, the anode line 134, the anode discharge line 136 and (due to the closed purge valve 137) the anode return line 138. If during this normal operating mode, a hydrogen concentration in the exhaust system 150 above a predetermined hydrogen concentration threshold C_H2, such as 8%, is determined before the time point t1, then according to the present invention, the already detected general leak in the fuel cell system 100 can additionally be located by performing a purge process and then evaluating the hydrogen signal at the time point t3.

[0049] When starting the purging process of the anode pipeline system 130 at time point t1, the purge valve 137 is simultaneously opened and the recirculation pump 139 is deactivated, so that the gas mixture flowing out of the tank 120 at this time point, especially the hydrogen mixture, is directly guided to the exhaust system 150 through the anode input pipeline 132, the anode pipeline 134 and the anode discharge pipeline 136. If it is determined during the purging process of the anode pipeline system 130 that the hydrogen signal has basically risen (for example, at the time point t2 in Figure 2 ), the purging process can be determined to be ended and terminated again, that is, the purge valve 137 is closed, and the recirculation pump 139 is activated again, so that the fuel cell system 100 switches back to the normal operating mode.

[0050] Below, an exemplary embodiment of the method for detecting and localizing a Figure 3 leak in the fuel cell system 100 according to the present invention will be described additionally with reference to the flowchart shown in Figure 1 the fuel cell system 100 according to the present invention will be described additionally with reference to the flowchart shown in

[0051] Figure 3 The method starts at step 300 and then reaches step 310, where a hydrogen signal is received from the hydrogen sensor 151 by the control device 160, especially the first control device section 162. At this point, it should be noted again that the control device 160, especially the first control device section 162, continuously receives the hydrogen signal of the hydrogen sensor 151. Therefore, during the execution of the method according to the present invention, the (digital) hydrogen signal of the hydrogen sensor 151 is received persistently and continuously, for example, at a predetermined time interval (such as a few milliseconds).

[0052] In the subsequent step 320, it is determined whether the received hydrogen signal indicates a hydrogen concentration exceeding a predetermined hydrogen concentration threshold C_H2. In particular, when the predetermined hydrogen concentration threshold C_H2 is exceeded, there is an increased risk of ignition of the gas mixture present in the exhaust system 150. If it is determined in step 320 that the received hydrogen signal indicates a hydrogen concentration not exceeding the predetermined hydrogen concentration threshold C_H2, the method returns to step 310 again. As long as the method stays at steps 310 and 320, the fuel cell system 100 can be diagnosed as sealed.

[0053] However, if it is determined at step 320 that the received hydrogen signal indicates a hydrogen concentration value exceeding a predetermined hydrogen concentration threshold C_H2, the method proceeds to step 330, where the control device 160, in particular the second control device section 164, sends a diagnostic signal that causes the fuel cell system 100 to switch to a diagnostic operating mode. Sending the diagnostic signal may include sending a cathode inlet valve closing signal that causes the cathode inlet valve 145 to close. Additionally or alternatively, sending the diagnostic signal includes sending a cathode outlet valve closing signal that causes the cathode outlet valve 147 to close. Additionally or alternatively, sending the diagnostic signal may include sending a throttle valve closing signal that causes the throttle valve 174 to close.

[0054] Generally, the sending of the diagnostic signal causes the gas mixture that has flowed through the cathode line 144 and has thus interacted with the cathode not to reach the exhaust line, and it is also not possible for the gas mixture having hydrogen to flow from the anode line system to the cathode. If, for example, the cathode inlet valve 145 and / or the cathode outlet valve 147 are closed, the gas mixture, in particular air, delivered by the compressor 170 can flow directly into the exhaust system 150 without contacting the cathode of the fuel cell 110. The closing of the throttle valve 174 causes the gas mixture flowing through the exhaust system 150 to no longer be able to originate from the cathode line system 140. Instead, the gas mixture flowing through the exhaust system 150 then originates from the anode line system 130.

[0055] In a subsequent step 340, after a predetermined duration, such as about 5 seconds (see the time period between t2 and t3 in Figure 2 ), after the measured time point t2 at which the purging process of the anode line system 130 ends, a hydrogen signal is received from the hydrogen sensor 151 and the hydrogen signal is evaluated at a subsequent step 350. That is, the time point t2 also indicates the end of hydrogen emission.

[0056] If it is determined at step 350 that the hydrogen signal received at time point t3 has a substantially decreasing course, the method reaches step 360, at which the membrane is diagnosed as not being sealed. In particular, due to the diagnostic operation of the fuel cell system 100, it can be excluded that the hydrogen present in the exhaust system 150 and detected by the hydrogen sensor 151 originates from the cathode line system 140. Thus, in the case of a substantially decreasing hydrogen signal at time point t3, it can be assumed that the hydrogen previously present in the exhaust system 150 originated from the cathode line system 140, in particular due to a non-sealed membrane of the fuel cell 110. Due to the diagnostic operation of the fuel cell system, for example by closing the cathode inlet valve 145 and / or the cathode outlet valve 147, the hydrogen flowing through the non-sealed membrane can no longer flow into the exhaust system 150, and thus the hydrogen signal substantially decreases.

[0057] However, if it is determined at step 350 that the hydrogen signal received at time point t3 has a substantially non-decreasing course, the method reaches step 370, at which the purge valve 137 is diagnosed as not being sealed. In particular, due to the diagnostic operation of the fuel cell system 100, it can be excluded that the hydrogen present in the exhaust system 150 and detected by the hydrogen sensor 151 originates from the cathode line system 140. Thus, in the case of a substantially non-decreasing hydrogen signal at time point t3, it can be assumed that the hydrogen previously present in the exhaust system 150 originated from the anode line system 130, in particular due to a non-sealed purge valve 137. Due to the diagnostic operation of the fuel cell system, for example by closing the cathode inlet valve 145 and / or the cathode outlet valve 147, the hydrogen flowing through the purge valve 137 can continue to flow into the exhaust system 150, and thus the hydrogen signal does not decrease. For example, the hydrogen signal can be substantially constant.

[0058] The determination at step 360 or 370 is carried out by the control device 160, in particular by the third control device section 166.

[0059] After steps 360, 370, the method reaches step 380 respectively, at which, before the method ends at step 390, the control device 160, in particular the fourth control device section 168, can send a control signal which indicates that the membrane or the purge valve 137 is at least partially not sealed.

[0060] To accelerate the diagnosis described above, it may be advantageous to additionally at least partially open the cathode bypass valve 149 after closing the cathode inlet valve 145 and / or the cathode outlet valve 147. Thus, the transmission of the diagnostic signal can additionally or alternatively also include the transmission of a bypass valve opening signal, which causes the cathode bypass valve 149 to be at least partially opened. Thereby, it can be achieved that the gas mixture previously present in the exhaust system 150 can be flushed out of the exhaust system 150 more quickly by the fresh gas mixture conveyed by the compressor 170. Here, determining that the membrane of the fuel cell 110 of the fuel cell system 100 is at least partially unsealed (see step 350) can include: determining that the hydrogen signal received during the diagnostic operation of the fuel cell system indicates a hydrogen concentration value that is substantially zero.

[0061] However, if the hydrogen signal received during the diagnostic operation of the fuel cell system 100 indicates a hydrogen concentration value greater than zero, the purge valve 137 can again be diagnosed as at least partially unsealed. Here, due to the unsealed purge valve 137, the gas mixture in the exhaust pipe is composed of the gas mixture with hydrogen from the anode pipeline system 130 and the fresh gas mixture from the cathode pipeline system 140.

[0062] Therefore, the method utilizes that the hydrogen signal of the hydrogen sensor 151 arranged in the exhaust system of the fuel cell system can be used to additionally localize the leak in the case of a generally detected leak in the fuel cell system 100, in particular assigned to the membrane or the purge valve 137. This can be done in a simple manner by evaluating the hydrogen signal of the hydrogen sensor 151 arranged in the exhaust system 150 by blocking the gas mixture flowing through the cathode of the fuel cell 110.

Claims

1. A method for determining a leak in a fuel cell system (100) including an exhaust system (150), the method comprising: - receiving a hydrogen signal from a hydrogen sensor (151) disposed in the exhaust system (150), wherein the hydrogen signal represents the hydrogen concentration in a gas mixture present in the exhaust system (150); - sending a diagnostic signal if the received hydrogen signal indicates a hydrogen concentration value in the exhaust system (150) that exceeds a predetermined hydrogen concentration threshold, the diagnostic signal causing the fuel cell system (100) to switch to a diagnostic operating mode; - determining that at least a part of the membrane of the fuel cell (110) of the fuel cell system (100) is not sealed if the hydrogen signal received during the diagnostic operation of the fuel cell system (100) substantially decreases, or determining that at least a part of the purge valve (137) disposed in the anode pipeline system (130) is not sealed if the hydrogen signal received during the diagnostic operation of the fuel cell system (100) does not substantially decrease; and - sending a control signal indicating that at least a part of the membrane or the purge valve (137) is not sealed.

2. The method according to claim 1, wherein sending the diagnostic signal includes: - sending a cathode inlet valve closing signal that causes the closing of a cathode inlet valve (145) disposed in a cathode input pipeline (142) of a cathode pipeline system (140), wherein the cathode input pipeline (142) is configured to supply a gas mixture having oxygen to a cathode of the fuel cell system; and / or - sending a cathode outlet valve closing signal that causes the closing of a cathode outlet valve (147) disposed in a cathode discharge pipeline (146) of the cathode pipeline system (140), wherein the cathode discharge pipeline (146) is configured to discharge the gas mixture having oxygen supplied to the cathode of the fuel cell system (100) into the exhaust system (150).

3. The method according to claim 2, wherein sending the diagnostic signal further includes: - sending a bypass valve opening signal that causes at least a partial opening of a cathode bypass valve (149) disposed in a cathode bypass pipeline (148) connecting the cathode input pipeline (145) and the cathode discharge pipeline (146); wherein determining that at least a part of the membrane of the fuel cell (110) of the fuel cell system (100) is not sealed includes determining that the hydrogen signal received during the diagnostic operation of the fuel cell system (100) indicates a hydrogen concentration value that is substantially zero; and / or wherein determining that at least a part of the purge valve (137) of the fuel cell system (100) is not sealed includes determining that the hydrogen signal received during the diagnostic operation of the fuel cell system (100) indicates a hydrogen concentration value greater than zero.

4. The method according to any one of the preceding claims, wherein sending the diagnostic signal includes: - Send a throttle valve closing signal, which causes the throttle valve (145) arranged downstream of the cathode outlet valve (147) in the cathode discharge pipeline (142) to close.

5. The method according to any one of the preceding claims, wherein the control signal is configured to control an operator interface to display a warning to an operator of the fuel cell system (100), wherein the warning notifies the operator that a leak in the membrane or the purge valve (137) has been detected.

6. A control device (160) configured to perform the steps of the method according to any one of the preceding claims.

7. The control device (160) according to claim 6, the control device comprising: - A first control device section (162) for performing the step of receiving a hydrogen signal from a hydrogen sensor (151), - A second control device section (164) for performing the step of sending a diagnostic signal, - A third control device section (166) for performing the step of determining that the membrane or the purge valve (137) is at least partially unsealed, and - A fourth control device section (168) for performing the step of sending a control signal.

8. A leak analysis device (180) for a fuel cell system (100), the leak analysis device comprising: - A hydrogen sensor (151) configured to generate a hydrogen signal representing the hydrogen concentration in a gas mixture present in the exhaust system (150) of the fuel cell system (100); and - The control device (160) according to any one of claims 6 and 7.

9. A fuel cell system (100), the fuel cell system comprising: - An anode, - A cathode separated from the anode by means of a membrane, - An anode pipeline system (130) in which a purge valve (137) is arranged, - An exhaust system (150) fluidly connected to the anode pipeline system (130), and - The leak analysis device (180) according to claim 8.

10. A computer program comprising instructions that, when executed by a computing unit, cause the computing unit to perform the method according to any one of claims 1 to 5.

11. A computer-readable medium having stored thereon the computer program according to claim 10.

12. Use of a hydrogen sensor (151) arranged in the exhaust system (150) of a fuel cell system (100) for determining a leak in the fuel cell system (100) by means of the method according to any one of claims 1 to 5.

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