Fuel cell system, gas tank system, and method for monitoring a gas tank system

Abstract

A method for monitoring a gas tank system comprises removing a predefined mass flow of gas from a high-pressure line system of the gas tank system, wherein each tank is connected to the high-pressure line system via a first valve device, which is in an open state, and carrying out a functional test on each of the first valve devices. During the functional test, all the first valve devices, except the first valve device currently to be examined, are closed, and therefore in a testing state the entire predefined mass flow is only removed from the tank that is connected to the high-pressure line system via the first valve device currently to be examined, and a test pressure is recorded, which in the testing state has stably settled in the high-pressure line system. In further steps of the method, at least a smallest of the recorded test pressures is compared with a reference pressure, and a fault signal is generated by means of a control device if the compared test pressure deviates from the reference pressure by more than a threshold value.

Description

[0001] Description

[0002] title

[0003] Technical area

[0004] The present invention relates to a fuel cell system, in particular for a motor vehicle, a gas tank system, in particular for a fuel cell system, and a method for monitoring a gas tank system.

[0005] State of the art

[0006] Fuel cells are increasingly being used as energy converters, including in vehicles, to convert chemical energy stored in a fuel, such as hydrogen, together with oxygen, directly into electrical energy. Fuel cells have an anode, a cathode, and an electrolytic membrane arranged between the anode and cathode. Oxidation of the fuel occurs at the anode, and reduction of the oxygen occurs at the cathode.

[0007] The fuel is typically supplied to the fuel cell via a line system from a tank in which the gaseous fuel is stored at high pressure. A separating or shut-off valve is typically provided between the tank and a high-pressure section of the line system. The high-pressure section is typically further connected to a line section connected to the fuel cell via a pressure regulator or flow control device. US Pat. No. 7,484,521 B2 describes a tank system for a fuel cell system comprising multiple tanks. Each tank is connected to a high-pressure line system via a respective valve. Furthermore, a pressure sensor is provided in the high-pressure line system, which outputs a pressure detected in the high-pressure line system to a control device.

[0008] Disclosure of the invention

[0009] Against this background, the present invention provides a method for monitoring a gas tank system having the features of claim 1, a gas tank system having the features of claim 6 and a fuel cell system having the features of claim 10.

[0010] According to a first aspect of the invention, a method for monitoring a gas tank system comprises withdrawing a predetermined, e.g. constant or substantially constant, mass flow of gas from a high-pressure line system of the gas tank system, each tank being connected to the high-pressure line system via a first valve device in the open state, and performing a functional test on each of the first valve devices. The functional test comprises closing all of the first valve devices except for a first valve device currently to be checked, so that in a test state, the entire predetermined mass flow is withdrawn only from the tank which is connected to the high-pressure line system by the first valve device currently to be checked.

[0011] High-pressure line system is connected, and a test pressure is detected that is stationary in the high-pressure line system during the test state. In further steps of the method, at least one of the smallest of the detected test pressures is compared with a reference pressure, and an error signal is generated by a control device if the compared test pressure deviates from the reference pressure by more than a threshold value.

[0012] According to a second aspect of the invention, a gas tank system, in particular for a fuel cell system, is provided. The gas tank system comprises a plurality of tanks for holding gas, a high-pressure line system, a number of first valve devices corresponding to the number of tanks, each of which is switchable between an open state in which it connects the respective tank to the high-pressure line system and a closed state in which it separates the respective tank from the high-pressure line system, a pressure sensor for detecting a pressure in the high-pressure line system, and a control device which is signal-conductingly connected to the first valve devices and to the pressure sensor and is configured to cause the gas tank system to carry out a method according to the first aspect of the invention.

[0013] According to a third aspect of the invention, a fuel cell system, which can be designed in particular for use in a motor vehicle, comprises a gas tank system according to the second aspect of the invention and a consumer system with a fuel cell arrangement which has a fuel supply connection connected to the second valve device.

[0014] One idea underlying the invention is to test the functionality of isolation valve devices or first valve devices arranged between a respective tank and a high-pressure line system, in particular to check for the presence of an impermissibly high pressure loss in the isolation valve devices, by sequentially delivering a mass flow of gas, which is supplied by the tank system from several tanks, from a single tank and recording the steady-state pressure in the high-pressure line system. For this purpose, a functional test is performed for each first valve device.This means that all of the first valve devices are switched one after the other so that a test state is created for each first valve device and the associated tank in which the entire predetermined mass flow is taken only from the tank that is connected to the high-pressure line system by the first valve device currently being tested. In this test state, a higher mass flow flows through the respective valve device compared to a state in which all of the first valve devices are open. This is associated with high flow velocities in the respective valve device and thus with higher pressure losses. Consequently, a pressure loss can be reliably determined in the test situation. The resulting steady-state pressures can be different for the various first valve devices.At least the pressure value recorded at the first valve device at which the lowest steady-state pressure is established during the test condition is compared with a reference value. If the compared test pressure deviates from the reference pressure by more than a threshold value, it is concluded that an unacceptably high pressure loss is occurring at this first valve device. In this case, an error signal is generated by an electronic control device, e.g., in the form of an output and / or an entry in a data memory.

[0015] An advantage of the invention is that the testing of the first valve devices can be performed during operation, i.e., while a predetermined mass flow is being drawn. Because the entire mass flow is passed through only one valve device during the functional test of the first valve devices, significant pressure losses occur at each valve device, which facilitates the comparability of the measurement results and ultimately the detection of inadmissible pressure losses.

[0016] Advantageous embodiments and further developments emerge from the further subclaims and from the description with reference to the figures of the drawing.

[0017] According to some embodiments, it can be provided that the highest of the recorded test pressures is used as the reference pressure. Thus, a fixed reference pressure does not necessarily have to be used; instead, a reference value dependent on the respective mass flow is used, which is available as a measured value. This further simplifies the implementation of the method.

[0018] According to some embodiments, it can be provided that only the smallest of the recorded test pressures is compared with the reference value. Thus, the number of comparisons that are performed is reduced. This advantageously reduces the required computing power. According to some embodiments, it can be provided that performing the functional test additionally comprises storing the respectively recorded test pressure in a data memory together with an index identifying the first valve device currently to be tested, wherein the generation of the error signal comprises outputting the index of that first valve device in which the test pressure deviates from the reference pressure by more than the threshold value in the test state.This not only detects the occurrence of an excessively high pressure loss at a first valve device, but also makes it possible to locate or identify the valve device where this pressure loss occurs. For this purpose, the recorded test pressures are stored together with information about which of the first valve devices was open when the respective test pressure was recorded.

[0019] According to some embodiments, the functional test can only be performed if a pressure gradient in the high-pressure line system is within a predetermined range when the predetermined mass flow is being drawn. This ensures that the functional test is only performed when no pressure equalization between the tanks is taking place or when a possible pressure equalization between the tanks has already ended. This ensures that the recorded steady-state test pressures are not affected by any equalization processes, and the detection of inadmissible pressure losses becomes even more precise and reliable.

[0020] According to some embodiments, each first valve device may include a filter. In this case, a high pressure loss in the respective valve device may be due, for example, to a clogged filter. The method according to the invention allows such a condition to be detected particularly quickly and reliably.

[0021] According to some embodiments, it can be provided that each first valve device has a switchable solenoid valve that can be switched between the open state and the closed state, e.g., by means of the control device. According to some embodiments, it can be provided that the gas tank system has a second valve device that can be switched between an open state and a closed state for connecting the high-pressure line system to a consumer system. The second valve device can be designed, e.g., as a switchable solenoid valve, in particular as a flow-controllable valve. Optionally, the second valve device can be connected to the control device in a signal-conducting manner.

[0022] The features and advantages disclosed herein in connection with one aspect of the invention are also disclosed for the respective other aspects. In particular, the control device can initiate all method steps and carry out various steps itself, such as steps for determining values ​​based on measured physical quantities, comparing measured quantities with reference values, outputting signals and the like. For example, the control device can have a computing unit, such as a CPU, an ASIC, an FPGA or the like, and a data memory, in particular a non-volatile data memory such as a flash memory, an SD memory or the like, which is readable by the computing unit. The data memory can store software that is executable by the computing unit in order to cause the system to carry out the steps of the method.

[0023] The invention is explained below with reference to the figures of the drawings. The figures show:

[0024] Fig. 1 is a schematic representation of a hydraulic circuit diagram of a fuel cell system according to an embodiment of the invention; and

[0025] Fig. 2 is a flowchart of a method according to an embodiment of the invention.

[0026] In the figures, the same reference numerals designate identical or functionally equivalent components, unless otherwise stated. Fig. 1 schematically shows a fuel cell system 200 that can be used, for example, in a vehicle. The fuel cell system 200 comprises a gas tank system 100 and a consumer system 205.

[0027] As shown only schematically in Fig. 1, the consumer system 205 has a fuel cell arrangement 210. The fuel cell arrangement 210 has at least one fuel cell, but preferably a plurality of fuel cells connected electrically in series, which are designed to convert chemical energy stored in a gaseous fuel, such as hydrogen, together with oxygen, directly into electrical energy. As further shown schematically in Fig. 1, the fuel cell arrangement 210 has a fuel supply connection 211, via which gaseous fuel can be supplied to the fuel cell arrangement 210, in particular to an anode of the at least one fuel cell.

[0028] The gas tank system 100 is explained below in connection with the fuel cell system 200, but is not limited to this use. As shown schematically in Fig. 1, the gas tank system 100 comprises a plurality of tanks 1, a high-pressure line system 2, a number of first valve devices 3 corresponding to the number of tanks 1, an optional pressure regulator or flow control device 5, a pressure sensor 4, and a control device 6. Optionally, the gas tank system 100 can further comprise a refueling connection or supply connection 20.

[0029] Fig. 1 shows, purely by way of example, a gas tank system 100 with three tanks 1A, 1B, 1C. However, the invention is not limited thereto. Generally, at least two tanks 1 are provided, although more than three tanks 1 may also be provided. Each tank 1 is designed to store gas, in particular hydrogen. For example, each tank 1 can be configured to store gas at a pressure of up to 800 bar.

[0030] The high-pressure line system 2 can in particular have a connecting line 21, a plenum 24 connected to the connecting line 21 and a number of connecting lines 23 corresponding to the number of tanks 1, each connecting the plenum 24 to the respective tank 1. As shown in Fig. 1 purely by way of example, the first tank 1A can thus be connected to the plenum 24 via a first connecting line 23A, the second tank 1B via a second connecting line 23B and the third tank 1C via a third connecting line 23C. The connecting line 21 connects the plenum 24 to the consumer system 205. Optionally, a supply line 22 can also be provided, which is connected to the plenum 24 and the optional supply device 20.

[0031] The first valve devices 3 can each have a switchable solenoid valve 3 that can be switched between a closed state and an open state. In general, each first valve device 3 can be switched between a closed state and an open state. Optionally, each first valve device 3 can also have a filter 30, as shown schematically in Fig. 1. As shown schematically in Fig. 1, each valve device 3 is arranged between the tank 1 and the high-pressure line system 2. For example, each first valve device 3 can be arranged in a respective connecting line 23, as shown by way of example in Fig. 1. In the open state, the respective first valve device 3 connects the respective tank 1 to the high-pressure line system 2. In the closed state, the respective first valve device 3 separates the tank 1 and the high-pressure line system 2 from one another.

[0032] The optional pressure regulator or flow control device 5 can also be switched between a closed state and an open state. For this purpose, the flow control device 5 can, for example, have a switchable solenoid valve that can be switched between a closed state and an open state. Generally, the pressure regulator 5 is designed to vary a gas flow and / or a pressure of the gas flowing through the pressure regulator. As shown schematically in Fig. 1, the flow control device 5 is arranged between the consumer system 205 and the high-pressure line system 2, in particular between the consumer system 205 and the connecting line 21. In the open state, the second valve device 5 connects the consumer system 205 to the high-pressure line system 2. In the closed state, the second valve device 5 separates the consumer system 205 and the high-pressure line system 2 from one another.

[0033] The tanks 1 are thus connected in parallel to each other to the high-pressure line system 2. When the first valve devices 3 and the flow control device 5 are open, the tanks 1 jointly supply a gas mass flow to the consumer system 205.

[0034] The supply line 22 is connected to the supply connection 20, which can be designed, for example, as a plug-in connection for a tank nozzle. As shown in Fig. 1, a check valve 8 can be arranged in the supply line 22, which closes the supply connection 20 against the escape of gas from the high-pressure line system 2.

[0035] As shown in Fig. 1, the pressure sensor 4 is connected to the high-pressure line system 2 and is configured to detect a pressure in the high-pressure line system 2. As shown in Fig. 1, the pressure sensor 4 can, for example, detect a pressure in the plenum 24.

[0036] The control device 6 is shown only schematically as a block in Fig. 1 and is implemented as an electronic control device 6. As shown by way of example in Fig. 1, the control device 6 can have a computing unit 61, such as a CPU, an ASIC, an FPGA or the like, and a data memory 62, in particular a non-volatile data memory such as a flash memory, an SD memory or the like, which is readable by the computing unit 61. As shown schematically in Fig. 1, the control device 6 is connected to the first valve device 3, optionally to the second valve device 5 and to the pressure sensor 4 in a signal-conducting manner, for example by wire, such as via a bus system. Alternatively, a wireless connection can also be provided, e.g. via WiFi or the like.

[0037] The control device 6 is configured to cause the gas tank system 100 to execute the method M shown in Fig. 2 for monitoring the gas tank system 100. For example, software executable by the computing unit 61 can be stored in the data memory 62 to cause the system 100 to execute the method M.

[0038] In step M1, a predetermined mass flow of gas is withdrawn from the high-pressure line system 2 of the gas tank system 100, e.g., through the consumer system 205. In this case, all first valve devices 3 are open. Any flow control device 5 provided is also open. Optionally, in step M1, a temporal pressure profile in the high-pressure line system 2 can be recorded using the pressure sensor 4, and the control device 6 can determine a pressure gradient from the pressure profile. In step M1, the mass flow is thus supplied jointly from all tanks 1A-1C.

[0039] In optional step M10, the control device 6 can check whether the determined pressure gradient during withdrawal M1 of the predetermined mass flow lies within a predetermined range. If this is not the case, as indicated by the symbol in step M10 in Fig. 2, the method M can return to step M1. If the control device 6 determines in step M10 that the pressure gradient in the high-pressure line system 2 lies within the predetermined range during withdrawal M1 of the predetermined mass flow, as indicated by the "+" symbol in Fig. 2, the method proceeds to step M2.

[0040] In step M2, a functional test is performed on each of the first valve devices 3. Initially, all of the first valve devices 3 are closed except for the first valve device 3 currently being tested (step M21). This creates a test state in which the entire predetermined mass flow is drawn only from the tank 1 that is connected to the high-pressure line system 2 by the first valve device 3 currently being tested. For example, in Fig. 1, the valve devices 3A, 3B, and 3C can be tested one after the other. If the valve device 3A is the valve device 3 currently being tested, the control device 6, in the example of Fig. 1, outputs a control signal to the first valve devices 3B, 3C to switch them to the closed state. Thus, the entire mass flow from the tank 1A flows via the valve device 3A.If the valve device 3B is the valve device 3 currently being checked, the control device 6 in the example of Fig. 1 outputs a control signal to the first valve devices 3A, 3C to switch them to the closed state. Thus, the entire mass flow from the tank 1B flows via the valve device 3B. If the valve device 3C is the valve device 3 currently being checked, the control device 6 in the example of Fig. 1 outputs a control signal to the first valve devices 3A, 3B to switch them to the closed state. Thus, the entire mass flow from the tank 1C flows via the valve device 3C.

[0041] During the functional test, a test pressure which is stationary in the test state in the high-pressure line system 2 is also detected (step M22) by means of the pressure sensor 4. If, for example, the first valve device 3A is checked (valve devices 3B, 3C are closed), a stationary pressure is detected in the plenum 24. For example, a pressure which is established after a predetermined time has elapsed after the test state has been established or after the first valve devices 3 have been closed except for the first valve device 3 to be tested can be detected as the stationary test pressure. Alternatively, the detected pressure can be continuously evaluated by the control device 6, wherein a detected pressure is determined as the test pressure after a pressure gradient in the high-pressure line system 2 lies within a predetermined range.

[0042] Optionally, the respectively recorded test pressure for each first valve device 3 is saved M23 in the data memory 62 together with an index identifying the first valve device 3 currently to be checked. For example, the index can contain information in numerical or alphanumeric form which uniquely identifies the respective valve device. For example, the first valve device 3A can have the index “V1”. If, for example, the first valve device 3A is being checked, i.e. if the first valve devices 3B, 3C are closed, the test pressure recorded in step M22 can be saved in the data memory 62 together with the index “V1”. The recorded test pressures can also be saved without saving an index, e.g. in the chronological order in which they were recorded.The steps M21 and M22 and optionally step M23 are thus repeated for each combination of the first valve devices 3 in which all first valve devices 3 are closed, except for one valve device 3 that is currently to be checked.

[0043] Subsequently, step M3 is carried out, in which the control device 6 compares at least the smallest of the recorded test pressures with a reference pressure. A largest of the recorded test pressures can be used as the reference pressure, for example. This means that the control device 6 can first evaluate the test pressures stored in the data memory 62 such that the computing device 61 reads out the largest of the test pressures and the smallest test pressure from the data memory 62. The largest test pressure can be used as the reference pressure. The smallest test pressure is compared with the reference pressure, for example a difference between the reference pressure and the smallest test pressure being formed and compared with a threshold value. Optionally, this is done not only for the smallest of the recorded test pressures but for several or all of the recorded test pressures. However, it is also conceivable that only the smallest of the recorded test pressures is compared with the reference value.

[0044] If the test pressure compared with the reference value deviates from the reference pressure by more than the threshold value, as indicated in Fig. 2 by the symbol "+" at step M3, the method M proceeds to step M4. In step M4, the control device 6 generates an error signal. Step M4 can, for example, comprise the writing of an error entry into the data memory 62 by the computing unit 61. For example, the computing unit 61 can output the index of the first valve device(s) 3 for which the test pressure deviates from the reference pressure by more than the threshold value in the test state, and write the index as an error entry in the data memory 62. Alternatively or in addition to writing an error entry into the data memory 62, the control device 6 can output a warning signal when the error entry is generated, e.g. in the form of an acoustic and / or optical warning signal.If no deviation by more than the threshold value is detected in step M3, as indicated in Fig. 2 by the symbol “-”, the method can, for example, return to step M1, as shown purely by way of example in Fig. 2.

[0045] Although the present invention has been explained above using exemplary embodiments, it is not limited thereto but can be modified in a variety of ways. In particular, combinations of the above embodiments are also conceivable.

Claims

Claims 1. A method (M) for monitoring a gas tank system (100), comprising: Withdrawing (M1) a predetermined mass flow of gas from a high-pressure line system (2) of the gas tank system (100), wherein each tank (1) is connected to the high-pressure line system (2) via a first valve device (3) in the open state; performing (M2) a functional test on each of the first valve devices (3) according to the following procedure: Closing (M21) all first valve devices (3) except for a first valve device (3) currently to be tested, so that in a test state the entire predetermined mass flow is taken only from that tank (1) which is connected to the high-pressure line system (2) by the first valve device (3) currently to be tested; and Detecting (M22) a test pressure which is stationary in the high-pressure line system (2) in the test state; Comparing (M3) at least one of the smallest of the recorded test pressures with a reference pressure; and Generating (M4) an error signal by means of a control device (6) if the compared test pressure deviates from the reference pressure by more than a threshold value.

2. Method (M) according to claim 1, wherein a largest of the recorded test pressures is used as the reference pressure.

3. Method (M) according to claim 1 or 2, wherein only the smallest of the recorded test pressures is compared with the reference value.

4. Method (M) according to one of the preceding claims, wherein the carrying out (M2) of the functional test additionally comprises storing (M23) of the respectively detected test pressure in a data memory (62) together with an index identifying the first valve device (3) currently to be tested, and wherein the generation (M4) of the error signal comprises the output of the index of that first valve device (3) in which the test pressure deviates from the reference pressure by more than the threshold value in the test state. Method (M) according to one of the preceding claims, wherein the performance (M2) of the functional test only occurs if, when the predetermined mass flow is withdrawn (M1), a pressure gradient in the high-pressure line system (2) lies within a predetermined range.A gas tank system (100), in particular for a fuel cell system (200), comprising: a plurality of tanks (1) for holding gas; a high-pressure line system (2); a number of first valve devices (3) corresponding to the number of tanks (1), each of which is switchable between an open state, in which it connects the respective tank (1) to the high-pressure line system (2), and a closed state, in which it separates the respective tank (1) from the high-pressure line system (2); a pressure sensor (4) for detecting a pressure in the high-pressure line system (2); and a control device (6) which is connected to the first valve devices (3) and to the pressure sensor (4) in a signal-conducting manner and is configured to cause the gas tank system (100) to carry out a method (M) according to one of the preceding claims. Gas tank system (100) according to claim 6, wherein each first valve device (3) comprises a filter (30).

8. The gas tank system (100) according to claim 6 or 7, wherein each first valve device (3) comprises a switchable solenoid valve that can be switched between the open state and the closed state.

9. The gas tank system (100) according to any one of claims 6 to 8, additionally comprising: a flow control device (5) that can be switched between an open state and a closed state for connecting the high-pressure line system (2) to a consumer system (205).

10. A fuel cell system (200), in particular for a motor vehicle, comprising: a gas tank system (100) according to one of claims 6 to 9; a consumer system (205) with a fuel cell arrangement (210) having a fuel supply connection (211) connected to the second valve device (5).

Images