Fuel cell system

Abstract

The present invention provides a configuration or method for detecting an abnormality in an ejector in a fuel cell system that includes a hydrogen circulation system including an ejector. [Solution] The fuel cell system comprises a fuel cell stack, an injector, a first pipe, a second pipe, an ejector, a pressure sensor, and a control unit. The first pipe is connected to the hydrogen supply port of the fuel cell stack, and the second pipe is connected to the exhaust port of the fuel cell stack. The ejector is located on the output side of the injector and guides the hydrogen gas injected from the injector and the gas in the second pipe to the first pipe. The pressure sensor measures the pressure in the first pipe or the second pipe. The control unit controls the injection of hydrogen gas by the injector based on the pressure measured by the pressure sensor. The control unit detects an abnormality in the ejector based on a parameter representing the time change of the pressure measured by the pressure sensor.

Description

Technical Field

[0001] The present invention relates to a fuel cell system.

Background Art

[0002] A fuel cell generates electric power through an oxidation-reduction reaction between hydrogen as fuel and oxygen as an oxidant. Therefore, a fuel cell system is configured to supply hydrogen gas to the fuel cell according to a command. However, a part of the hydrogen supplied to the fuel cell may be discharged without being consumed. For this reason, in order to effectively use fuel, a fuel cell system including a hydrogen circulation system that re-injects the hydrogen discharged from the fuel cell into the fuel cell has been proposed and put into practical use.

[0003] In such a background, there has been proposed a fuel cell system including a fuel cell, an anode supply pipe, a fuel gas supply unit that adjusts the supply amount of fuel gas by opening and closing a valve, an ejector provided between the fuel gas supply unit and the anode supply port, an anode circulation pipe connecting the anode discharge port and the ejector, a circulation stop unit capable of stopping the circulation of fuel gas in the anode circulation pipe, a pressure sensor for detecting the pressure between the ejector and the anode supply port, and a control device (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As mentioned above, fuel cell systems equipped with a hydrogen circulation system are known. As an example of a hydrogen circulation system, a configuration has been proposed in which an ejector is provided at the junction of the main flow path and the circulation path. The ejector is located on the output side of the injector and uses the negative pressure created by the hydrogen gas injected from the injector to draw in hydrogen gas from the circulation path, and combines the hydrogen gas drawn in from the circulation path with the hydrogen gas injected from the injector.

[0006] However, malfunctions can occur in the ejector of a hydrogen circulation system. For example, water contained in the gas flowing in from the circulation path may freeze, causing the ejector to become blocked. In this case, insufficient hydrogen may be supplied to the fuel cell, potentially degrading its performance or characteristics. Therefore, a method for detecting malfunctions in the ejector that constitutes the hydrogen circulation system is required.

[0007] An object relating to one aspect of the present invention is to provide a configuration or method for detecting an abnormality in an ejector in a fuel cell system that includes a hydrogen circulation system including an ejector. [Means for solving the problem]

[0008] A fuel cell system according to one aspect of the present invention comprises a fuel cell stack, an injector for injecting hydrogen gas, a first pipe connected to a hydrogen supply port of the fuel cell stack, a second pipe connected to an exhaust port of the fuel cell stack, an ejector provided on the output side of the injector and guiding the hydrogen gas injected from the injector and the gas in the second pipe to the first pipe, a pressure sensor for measuring the pressure in the first pipe or the second pipe, and a control unit that controls the injection of hydrogen gas by the injector based on the pressure measured by the pressure sensor. The control unit determines whether or not an abnormality has occurred in the ejector based on a parameter representing the time change of the pressure measured by the pressure sensor.

[0009] In the above configuration, when the ejector is operating normally, the hydrogen gas ejected from the injector passes through the ejector and is supplied to the fuel cell stack via the first piping. On the other hand, when the ejector is blocked, the hydrogen gas ejected from the injector is supplied to the fuel cell stack via the second piping. Therefore, the length of the path from the injector to the pressure sensor differs depending on whether the ejector is operating normally or blocked. Consequently, the time change of the pressure measured by the pressure sensor during hydrogen supply from the injector to the fuel cell stack differs depending on whether the ejector is operating normally or blocked. Therefore, the control unit can determine whether or not an abnormality has occurred in the ejector based on the time change of the pressure measured by the pressure sensor.

[0010] In the fuel cell system described above, if an exhaust and drain valve is provided for the second piping, the control unit may determine whether or not an abnormality has occurred in the ejector when the exhaust and drain valve is closed. This configuration allows for accurate determination of whether or not an abnormality has occurred in the ejector.

[0011] In the fuel cell system described above, the control unit may inject hydrogen gas into the injector for a predetermined time when the pressure drops to a predetermined threshold, and determine whether or not an abnormality has occurred in the ejector based on the time from the start of hydrogen gas injection by the injector until the pressure reaches its peak. Alternatively, the control unit may inject hydrogen gas into the injector when the pressure drops to a predetermined threshold, and determine whether or not an abnormality has occurred in the ejector based on the pressure at a predetermined time after the start of hydrogen gas injection by the injector. Furthermore, the control unit may inject hydrogen gas into the injector when the pressure drops to a predetermined threshold, and determine whether or not an abnormality has occurred in the ejector based on the slope of the pressure with respect to time while the injector is injecting hydrogen gas. [Effects of the Invention]

[0012] According to the above embodiment, in a fuel cell system equipped with a hydrogen circulation system including an ejector, abnormal operation of the ejector can be detected. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows an example of a fuel cell system according to an embodiment of the present invention. [Figure 2] This is a diagram illustrating an example of how a fuel cell system operates. [Figure 3] This diagram illustrates the flow of hydrogen gas supplied to a fuel cell. [Figure 4] This figure shows an example of a method for detecting ejector blockage. [Figure 5] This flowchart shows an example of a method for detecting ejector blockage. [Figure 6] This figure shows variations in methods for detecting ejector blockage. [Figure 7] This is a flowchart corresponding to the method shown in Figure 6. [Figure 8] This figure shows other variations in methods for detecting ejector blockage. [Figure 9] This is a flowchart corresponding to the method shown in Figure 8. [Modes for carrying out the invention]

[0014] Figure 1 shows an example of a fuel cell system according to an embodiment of the present invention. The fuel cell system 1 according to an embodiment of the present invention supplies power to a load 100. When the fuel cell system 1 is mounted on a vehicle (for example, an electric vehicle, an industrial vehicle such as a forklift), the load 100 is, for example, an inverter circuit that drives a motor (such as a driving motor or a cargo handling motor). Also, when the fuel cell system 1 is a generator such as an industrial stationary generator, a household stationary generator, or an emergency stationary generator, the load 100 is, for example, industrial machinery or home appliances.

[0015] The fuel cell system 1 includes a fuel cell 11. The fuel cell 11 is composed of a plurality of fuel cells (for example, a polymer electrolyte fuel cell (PEFC)) connected in series / parallel to each other. Each fuel cell can generate electric power through an electrochemical reaction between hydrogen and oxygen. Note that a fuel cell composed of a plurality of fuel cells may be called a fuel cell stack.

[0016] The fuel cell system 1 includes a DC / DC converter 12 and a power storage device 13. The DC / DC converter 12 converts the output voltage of the fuel cell system 1 into a specified predetermined voltage. The power output via the DC / DC converter 12 is supplied to the load 100 and stored in the power storage device 13. Also, the power output via the DC / DC converter 12 may be provided to auxiliary machines within the fuel cell system 1. The power storage device 13 is composed of, for example, a capacitor and cooperates with the fuel cell 11 to supply power to the load 100.

[0017] The fuel cell system 1 includes a fuel tank 14, an injector 15, and a pressure sensor 16. The fuel tank 14 is a storage container for hydrogen gas. The injector 15 injects the hydrogen gas supplied from the fuel tank 14 based on a command given from a control unit 41 described later. The hydrogen gas injected from the injector 15 is guided to the hydrogen supply port (anode supply port) of the fuel cell 11 through a hydrogen supply pipe (anode supply pipe) 21. Note that the hydrogen supply pipe 21 is an example of a first pipe connected to the hydrogen supply port of the fuel cell 11. The pressure sensor 16 measures the pressure within the hydrogen supply pipe 21. That is, the pressure sensor 16 substantially measures the pressure of the hydrogen gas at the hydrogen supply port of the fuel cell 11.

[0018] As air system auxiliary machines, the fuel cell system 1 includes an air compressor 17, an air pressure regulating valve 18, etc. The air compressor 17 compresses the air outside the fuel cell system 1 and supplies it to the fuel cell 11. That is, oxygen is supplied to the fuel cell 11 by the air compressor 17. The air pressure regulating valve 18 can adjust the pressure and flow rate of the air supplied to the fuel cell 11.

[0019] The fuel cell system 1 includes a hydrogen circulation system including a circulation pipe (anode circulation pipe) 22, a gas-liquid separator 23, and an ejector 24. The circulation pipe 22 is an example of a second pipe connected to the anode exhaust port of the fuel cell 11. The fuel cell system 1 may further include a pressure sensor 25 that measures the pressure in the circulation pipe 22. The gas-liquid separator 23 is provided in the middle of the circulation pipe 22 and separates liquid water from the anode exhaust gas exhausted from the fuel cell 11. Here, the anode exhaust gas exhausted from the fuel cell 11 contains hydrogen that was not consumed in the fuel cell 11. That is, the anode exhaust gas from which liquid water has been separated by the gas-liquid separator 23 contains residual hydrogen. Then, this anode exhaust gas is led to the ejector 24 through the circulation pipe 22.

[0020] The ejector 24 is provided at the output side of the injector 15 (the direction in which hydrogen is injected) and at the junction of the hydrogen supply pipe 21 and the circulation pipe 22. When the injector 15 injects hydrogen gas and the hydrogen gas passes through the ejector 24, the pressure inside the ejector 24 decreases and becomes close to a vacuum state, so the gas in the circulation pipe 22 is sucked in. As a result, when the hydrogen gas injected from the injector 15 is led to the hydrogen supply pipe 21, the gas in the circulation pipe 22 is also led to the hydrogen supply pipe 21. That is, the ejector 24 can lead the hydrogen gas injected from the injector 15 and the gas in the circulation pipe 22 to the hydrogen supply pipe 21. Thereby, the hydrogen discharged without being consumed in the fuel cell 11 can be re-introduced into the fuel cell 11.

[0021] The fuel cell system 1 includes a radiator 31 and a water pump 32 as cooling system auxiliary devices. The radiator 31 exchanges heat between the refrigerant (for example, water) discharged from the fuel cell 11 and the outside air. The refrigerant heat-exchanged in the radiator 31 is circulated by the water pump 32. The water pump 32 supplies the refrigerant sent from the radiator 31 to the fuel cell 11.

[0022] The exhaust and drain valve 33 sends the liquid water separated by the gas-liquid separator 23 to the diluent 34. The liquid water sent to the diluent 34 is stored in a tank inside the diluent 34. In addition, a portion of the anode exhaust gas may be directed to the diluent 34 by the exhaust and drain valve 33. The anode exhaust gas sent to the diluent 34 may be diluted with air discharged via the air pressure regulating valve 18 and then discharged outside the fuel cell system 1.

[0023] The fuel cell system 1 comprises a control unit 41 and a memory unit 42. The control unit 41 is configured as a microcomputer or the like and controls the operation of the fuel cell system 1 based on a power command value sent from the load 100. The power command value represents the power required by the load 100. The control unit 41 then controls the injector 15, the air compressor 17, and the DC / DC converter 12 based on the power command value. At this time, the control unit 41 may also control the operation of the fuel cell system 1 by referring to the pressure measured by the pressure sensor 16. The control unit 41 may also control the air pressure regulating valve 18, the water pump 32, and the exhaust and drain valve 33. The memory unit 42 can store the program and various parameter values ​​used by the control unit 41. The memory unit 42 may include non-volatile memory and volatile memory.

[0024] Figure 2 shows an example of the operation of the fuel cell system 1. The vertical axis of the graph in Figure 2 represents the gas pressure in the hydrogen supply pipe 21 as measured by the pressure sensor 16. In the following description, the pressure measured by the pressure sensor 16 may be referred to as "pressure P". The gas flowing through the hydrogen supply pipe 21 is mainly hydrogen gas. In Figure 2, the open / close instructions given from the control unit 41 to the injector 15 are such that an H level indicates an open state and an L level indicates a closed state.

[0025] When the fuel cell 11 is generating electricity, the control unit 41 controls the injector 15 to supply hydrogen to the fuel cell 11. At this time, the control unit 41 controls the injector 15 to be open for a predetermined time. As a result, the injector 15 injects hydrogen gas for the predetermined time. The control unit 41 also controls the air compressor 17 to supply oxygen (actually, air containing oxygen) to the fuel cell 11. Then, electricity is generated in the fuel cell 11 by an electrochemical reaction between hydrogen and oxygen. At this time, hydrogen is consumed in the fuel cell 11, so the pressure P measured by the pressure sensor 16 decreases.

[0026] The control unit 41 constantly monitors the pressure P. When the pressure P drops to a predetermined lower threshold level (P1 in Figure 2), the control unit 41 controls the injector 15 to the open state. As a result, the injector 15 injects hydrogen gas, and the pressure P measured by the pressure sensor 16 increases. At this time, the control unit 41 controls the injector 15 so that the pressure P rises to a predetermined upper threshold level (P2 in Figure 2). For example, the control unit 41 may control the injector 15 using the value measured by the pressure sensor 16. However, the configuration of the fuel tank 14, injector 15, ejector 24, and hydrogen supply piping 21 is known, and the capacity of the fuel cell 11 is also known. Therefore, the time required to raise the pressure P from "P1" to "P2" can be calculated in advance. Therefore, when the pressure P drops to the lower threshold level P1, the control unit 41 may control the injector 15 to the open state for a predetermined time calculated in advance, thereby substantially raising the pressure P to the upper threshold level P2.

[0027] Subsequently, the control unit 41 repeats the operation of controlling the injector 15 as described above in response to a request from the load 100. As a result, the fuel cell 11 generates the power required by the load 100. The interval at which the injector 15 injects hydrogen is, for example, several tens to several hundreds of milliseconds. The period during which the injector 15 is controlled to be in the open state and injects hydrogen (i.e., the "predetermined time" described above) is, for example, several milliseconds.

[0028] Figure 3 illustrates the flow of hydrogen gas supplied to the fuel cell 11. Note that the gas-liquid separator 23 is omitted in Figure 3. The injector 15 supplies hydrogen to the fuel cell 11 in accordance with the on / off instructions given by the control unit 41 shown in Figure 1. That is, when the on / off instruction indicates an open state, the injector 15 injects hydrogen gas. When the on / off instruction indicates a closed state, the injector 15 stops injecting hydrogen gas. The control unit 41 controls the injector 15 based on the pressure P measured by the pressure sensor 16.

[0029] When the ejector 24 is operating normally, as shown in Figure 3A, the hydrogen gas injected from the injector 15 passes through the ejector 24 and is guided to the hydrogen supply port of the fuel cell 11 via the hydrogen supply pipe 21. The exhaust gas containing hydrogen discharged from the anode exhaust port of the fuel cell 11 flows through the circulation pipe 22 and is guided to the hydrogen supply port of the fuel cell 11 by the ejector 24.

[0030] In contrast, when the ejector 24 is blocked, as shown in Figure 3B, the hydrogen gas injected from the injector 15 is guided to the circulation pipe 22. In this case, the hydrogen gas injected from the injector 15 is guided to the anode exhaust port of the fuel cell 11 via the circulation pipe 22. That is, the hydrogen gas injected from the injector 15 is supplied to the fuel cell 11 by flowing back through the circulation pipe 22. It should be noted that the fuel cell 11 can generate electricity even when hydrogen is supplied from the anode exhaust port.

[0031] Figure 4 shows an example of a method for detecting blockage of the ejector 24. The vertical axis of the graph shown in Figure 4 represents the gas pressure (i.e., pressure P) in the hydrogen supply pipe 21 as measured by the pressure sensor 16.

[0032] Figure 4A shows the time change of pressure P in the case where the ejector 24 is operating normally (i.e., the case shown in Figure 3A). At times T1 to T2, with hydrogen gas injection from the injector 15 stopped, hydrogen is consumed as the fuel cell 11 generates electricity, and the pressure P gradually decreases. Then, at time T2, when the pressure P drops to the lower threshold level P1, the control unit 41 controls the injector 15 to the open state. As a result, hydrogen gas is injected from the injector 15, and the pressure P increases.

[0033] The control unit 41 controls the injector 15 to be in the open state for a predetermined time, and then returns it to the closed state. Therefore, after the injection of hydrogen gas from the injector 15 stops, the pressure P decreases as hydrogen is consumed in the fuel cell 11. That is, each time the injector 15 injects hydrogen gas, a peak in pressure P appears on the time axis. In the case shown in Figure 4A, the peak in pressure P appears at time T3.

[0034] The control unit 41 detects the time from when the injector 15 starts injecting hydrogen gas (time T2 in Figure 4A) to when the pressure P reaches its peak in response to that injection (time T3 in Figure 4A). In the following description, this time may be referred to as the "monitoring time". In this case, time T2 corresponds to the start time of the monitoring time, and time T3 corresponds to the end time of the monitoring time. The monitoring time is also an example of a parameter that represents the time change of pressure P.

[0035] In the example shown in Figure 4A, the monitoring time X1 is obtained. Since the injector 15 is controlled by the control unit 41, the time when the injector 15 starts injecting hydrogen gas is known. Furthermore, the time when the pressure P reaches its peak can be detected by monitoring the pressure sensor 16.

[0036] Figure 4B shows the time change of pressure P in the case where the ejector 24 is blocked (i.e., the case shown in Figure 3B). In this example, at time T4, the pressure P drops to the lower threshold level P1, and the control unit 41 controls the injector 15 to the open state. As a result, hydrogen gas is injected from the injector 15, and the pressure P rises. The control unit 41 then detects the monitoring time. In this embodiment, as shown in Figure 4B, a peak in pressure P appears at time T5, and the monitoring time X2 is obtained.

[0037] The control unit 41 determines whether or not an abnormality has occurred in the ejector 24 based on the monitoring time. Here, the pressure sensor 16 is installed in the hydrogen supply pipe 21 connected to the hydrogen supply port of the fuel cell 11. When the ejector 24 is operating normally, as shown in Figure 3A, the hydrogen gas injected from the injector 15 is supplied to the fuel cell 11 via the hydrogen supply pipe 21. In other words, the path from the hydrogen gas injected from the injector 15 to the pressure sensor 16 is short. For this reason, as soon as the injector 15 starts injecting hydrogen gas, the pressure P detected by the pressure sensor 16 rises sharply.

[0038] In contrast, in the case where the ejector 24 is blocked, as shown in Figure 3B, the hydrogen gas injected from the injector 15 is supplied to the fuel cell 11 via the circulation pipe 22. That is, compared to the case where the ejector 24 is operating normally, the path from the hydrogen gas injected from the injector 15 to the pressure sensor 16 is longer. Specifically, the hydrogen gas injected from the injector 15 flows through the circulation pipe 22 and is supplied to the fuel cell 11 from the anode exhaust port side. Then, as the pressure inside the fuel cell 11 rises, the pressure P detected by the pressure sensor 16 rises. For this reason, after the injector 15 starts injecting hydrogen gas, the pressure P detected by the pressure sensor 16 rises more slowly compared to the case where the ejector 24 is operating normally.

[0039] As a result, the monitoring time X2 detected when the ejector 24 is blocked is longer than the monitoring time X1 detected when the ejector 24 is operating normally. Therefore, the control unit 41 sets a judgment threshold that is greater than X1 and less than or equal to X2. The control unit 41 can then determine whether or not an abnormality has occurred in the ejector 24 by comparing the detected monitoring time with the judgment threshold. Specifically, if the detected monitoring time is greater than the judgment threshold, the control unit 41 determines that an abnormality has occurred in the ejector 24. Note that the monitoring times X1 and X2 can be obtained in advance by measurement or simulation. Therefore, the judgment threshold can be appropriately determined based on the monitoring times X1 and X2.

[0040] Note that the ejector 24 may experience poor flow before it becomes completely blocked. In this case, the detected monitoring time will be greater than X1 and less than X2. Therefore, by appropriately setting the judgment threshold, the control unit 41 can detect signs of impending blockage of the ejector 24. For example, by setting a judgment threshold close to X1, the control unit 41 may detect signs of impending blockage of the ejector 24. Alternatively, by setting a judgment threshold close to X2, the control unit 41 may detect that the ejector 24 is blocked.

[0041] Figure 5 is a flowchart illustrating an example of a method for detecting blockage of the ejector 24. The control unit 41 constantly monitors the pressure in the hydrogen supply pipe 21 using the pressure sensor 16.

[0042] In S1, the control unit 41 monitors whether the pressure P measured by the pressure sensor 16 has fallen to the lower threshold level P1. If the pressure P falls to the lower threshold level P1, the control unit 41 proceeds to S2.

[0043] In S2, the control unit 41 controls the injector 15 to the open state. This starts the injection of hydrogen gas. In S3, the control unit 41 determines the start time of the monitoring period. Here, S2 and S3 are executed substantially simultaneously. Therefore, the start time of hydrogen gas injection is acquired as the start time of the monitoring period. Then, when a predetermined time has elapsed from the start of hydrogen gas injection, the control unit 41 controls the injector 15 to the closed state in S4. This stops the injection of hydrogen gas.

[0044] In S5, the control unit 41 detects the peak of pressure P. The control unit 41 then obtains the time when the peak of pressure P appears as the end time of the monitoring period. Subsequently, in S6, the control unit 41 calculates the monitoring period from the start time and end time of the monitoring period.

[0045] In S7, the control unit 41 compares the monitoring time with a preset determination threshold. If the monitoring time is less than or equal to the determination threshold, the control unit 41 determines that the ejector 24 is functioning normally. On the other hand, if the monitoring time is greater than the determination threshold, the control unit 41 determines that an abnormality has occurred in the ejector 24.

[0046] Thus, in the fuel cell system 1 according to the embodiment of the present invention, it is possible to determine whether or not an abnormality has occurred in the ejector 24 based on the time change of pressure P measured by the pressure sensor 16. In many cases, the fuel cell system is equipped with a sensor (i.e., pressure sensor 16) for monitoring the pressure in the hydrogen supply piping. Therefore, it is not necessary to add a dedicated part to detect abnormalities in the ejector that constitutes the hydrogen circulation system. Furthermore, the monitoring time, which is a parameter for determining whether or not an abnormality has occurred in the ejector, can be easily calculated by monitoring the pressure in the hydrogen supply piping.

[0047] Figure 6 shows variations in the method for detecting blockage of the ejector 24. In the method shown in Figure 6, the control unit 41 detects the pressure P at a time ΔT elapsed from the start time of hydrogen gas injection. Time ΔT is set to be shorter than the time for which the injector 15 is controlled to be in the open state (i.e., the time for which the injector 15 injects hydrogen gas). The value of pressure P at a time ΔT elapsed from the start time of hydrogen gas injection is an example of a parameter that represents the time change of pressure P.

[0048] In the case where the ejector 24 is operating normally, as shown in Figure 6A, when the injector 15 starts injecting hydrogen gas at time T2, the pressure P then increases. The control unit 41 then acquires the output data of the pressure sensor 16 at a time ΔT elapsed from time T2. In this embodiment, pressure P3 is detected at time T2+ΔT.

[0049] In the case where the ejector 24 is blocked, as shown in Figure 6B, when the injector 15 starts injecting hydrogen gas at time T4, the pressure P then rises. The control unit 41 then acquires the output data of the pressure sensor 16 at a time ΔT elapsed from time T4. In this embodiment, pressure P4 is detected at time T4+ΔT.

[0050] As explained with reference to Figure 4, in the case where the ejector 24 is blocked, the pressure P measured by the pressure sensor 16 rises slowly compared to the case where the ejector 24 is operating normally. Therefore, in the example shown in Figure 4, P4 becomes smaller than P3.

[0051] Therefore, the control unit 41 sets a pressure determination threshold that is greater than P3 and less than or equal to P4. The control unit 41 can then determine whether or not an abnormality has occurred in the ejector 24 by comparing the pressure P at a time ΔT elapsed from the start time of hydrogen gas injection with the pressure determination threshold. Specifically, if the detected pressure P is less than the pressure determination threshold, the control unit 41 determines that an abnormality has occurred in the ejector 24. Pressures P3 and P4 can be obtained in advance by measurement or simulation.

[0052] Figure 7 is a flowchart corresponding to the method shown in Figure 6. Note that S1 and S2 are substantially the same in Figures 5 and 7.

[0053] The control unit 41 starts a timer in S2 when it starts injecting hydrogen gas into the injector 15. This timer measures time ΔT. When this timer expires, the control unit 41 detects the pressure P using the pressure sensor 16 in S11. In the following description, the pressure measured by the pressure sensor 16 at the time ΔT elapsed from the start of hydrogen gas injection may be referred to as "Px".

[0054] In S12, the control unit 41 compares the pressure Px detected in S11 with the pressure determination threshold. If the pressure Px is greater than the pressure determination threshold, the control unit 41 determines that the ejector 24 is functioning normally. On the other hand, if the pressure Px is less than the pressure determination threshold, the control unit 41 determines that an abnormality has occurred in the ejector 24. Note that, according to the method shown in Figures 6 and 7, it is not necessary to detect the peak of the pressure P, and it is possible to determine whether or not an abnormality has occurred in the ejector 24 by detecting the pressure P at a time ΔT elapsed from the start time of hydrogen gas injection.

[0055] Figure 8 shows another variation of the method for detecting blockage of the ejector 24. In the method shown in Figure 8, the control unit 41 detects the slope of pressure P with respect to time during the period when the injector 15 is injecting hydrogen gas. The slope of pressure P with respect to time is an example of a parameter that represents the time change of pressure P.

[0056] In the case where the ejector 24 is operating normally, as shown in Figure 8A, when the injector 15 starts injecting hydrogen gas at time T2, the pressure P increases thereafter. Then, the control unit 41 acquires the pressure P values ​​at two sampling points (T2+ΔT1, T2+ΔT2) during the period when the injector 15 is injecting hydrogen gas. Note that ΔT in Figure 8 represents the difference between ΔT1 and ΔT2. The control unit 41 then calculates the slope G1 from ΔT and the difference in the pressure P values ​​at the two sampling points (ΔP1 in Figure 8A).

[0057] In the case where ejector 24 is blocked, as shown in Figure 8B, when injector 15 starts injecting hydrogen gas at time T4, the pressure P increases thereafter. Then, the control unit 41 acquires the pressure P values ​​at two sampling points (T4+ΔT1, T4+ΔT2) during the period when injector 15 is injecting hydrogen gas. The control unit 41 then calculates the slope G2 from ΔT and the difference between the pressure P values ​​at the two sampling points (ΔP2 in Figure 8B).

[0058] As explained with reference to Figure 4, in the case where the ejector 24 is blocked, the pressure P measured by the pressure sensor 16 rises slowly compared to the case where the ejector 24 is operating normally. Therefore, in the example shown in Figure 4, the slope G2 becomes smaller than the slope G1.

[0059] Therefore, the control unit 41 sets a tilt determination threshold that is greater than G1 and less than or equal to G2. The control unit 41 can then determine whether or not an abnormality has occurred in the ejector 24 by comparing the tilt G detected during the period in which the injector 15 is injecting hydrogen gas with the tilt determination threshold. Specifically, if the detected tilt G is less than the tilt determination threshold, the control unit 41 determines that an abnormality has occurred in the ejector 24. Note that the tilts G1 and G2 can be obtained in advance by measurement or simulation.

[0060] Figure 9 is a flowchart corresponding to the method shown in Figure 8. Note that S1 and S2 are substantially the same in Figures 5 and 9.

[0061] In S21, the control unit 41 detects pressure P at two sampling points separated by a time ΔT from each other during the period when the injector 15 is injecting hydrogen gas. The control unit 41 then calculates the difference between the two detected values ​​(i.e., the pressure difference ΔP). Subsequently, in S22, the control unit 41 calculates the slope G by dividing the pressure difference ΔP by the time difference ΔT between the two sampling points.

[0062] In S23, the control unit 41 compares the tilt G with the tilt determination threshold. If the calculated tilt G is greater than the tilt determination threshold, the control unit 41 determines that the ejector 24 is functioning normally. On the other hand, if the calculated tilt G is less than the tilt determination threshold, the control unit 41 determines that an abnormality has occurred in the ejector 24.

[0063] <Variations> As described above, the control unit 41 can determine whether or not an abnormality has occurred in the ejector 24 while controlling the power generation of the fuel cell 11. At this time, the control unit 41 determines whether or not an abnormality has occurred in the ejector 24 based on the time change of pressure P measured by the pressure sensor 16. On the other hand, the control unit 41 periodically or as needed opens the exhaust drain valve 33 to discharge unwanted substances (e.g., water vapor, nitrogen gas, etc.) in the hydrogen circulation path including the circulation piping 22. However, when the exhaust drain valve 33 is open, the pressure in the circulation piping 22 may temporarily decrease, and the pressure P measured by the pressure sensor 16 may also decrease. In this case, even if the control unit 41 monitors the pressure P, it cannot accurately determine whether or not an abnormality has occurred in the ejector 24. Therefore, it is preferable that the control unit 41 does not determine whether or not an abnormality has occurred in the ejector 24 when the exhaust drain valve 33 is open. In other words, it is preferable that the control unit 41 determines whether or not an abnormality has occurred in the ejector 24 when the exhaust drain valve 33 is closed.

[0064] In the example described above, the control unit 41 uses a pressure sensor 16 provided on the hydrogen supply port side of the fuel cell 11 to determine whether or not an abnormality has occurred in the ejector 24. However, the fuel cell system 1 is not limited to this configuration. For example, in a configuration where a pressure sensor 25 is provided on the anode exhaust port side of the fuel cell 11, the control unit 41 may determine whether or not an abnormality has occurred in the ejector 24 based on the pressure measured by the pressure sensor 25. However, in this case, the logic of the determination is reversed compared to the case where the pressure sensor 16 is used. For example, when the procedure shown in Figure 5 is performed using the pressure sensor 25, an abnormality is determined to have occurred in the ejector 24 when the monitoring time is less than the determination threshold.

[0065] <Note> The technical concepts that can be understood from the above embodiments and modified examples are described below. [Note 1] Fuel cell stack and An injector that sprays hydrogen gas, A first pipe connected to the hydrogen supply port of the fuel cell stack, A second pipe connected to the exhaust port of the fuel cell stack, An ejector is provided on the output side of the injector and guides the hydrogen gas injected from the injector and the gas in the second pipe to the first pipe, A pressure sensor for measuring the pressure inside the first pipe or the second pipe, The system includes a control unit that controls the injection of hydrogen gas by the injector based on the pressure measured by the pressure sensor, The control unit determines whether or not an abnormality has occurred in the ejector based on a parameter representing the time change of the pressure measured by the pressure sensor. A fuel cell system characterized by the following features. [Note 2] An exhaust drain valve is provided for the second piping. The control unit determines whether or not an abnormality has occurred in the ejector when the exhaust and drain valve is closed. The fuel cell system described in Appendix 1, characterized by the features described herein. [Note 3] The control unit, When the pressure drops to a predetermined threshold, hydrogen gas is injected into the injector for a predetermined time. Based on the time from the start of hydrogen gas injection by the injector until the pressure reaches its peak, it is determined whether or not an abnormality has occurred in the ejector. A fuel cell system as described in Appendix 1 or 2, characterized by the above. [Note 4] The control unit, When the pressure drops to a predetermined threshold, hydrogen gas is injected into the injector. Based on the pressure measured after a predetermined time has elapsed since the start of hydrogen gas injection by the injector, it is determined whether or not an abnormality has occurred in the ejector. A fuel cell system as described in any one of the appendices 1 to 3, characterized by the above. [Note 5] The control unit, When the pressure drops to a predetermined threshold, hydrogen gas is injected into the injector. Based on the slope of the pressure with respect to time when the injector is injecting hydrogen gas, it is determined whether or not an abnormality has occurred in the ejector. A fuel cell system as described in any one of the appendices 1 to 4, characterized by the above. [Explanation of Symbols]

[0066] 1. Fuel cell system 11 Fuel Cell 15 Injectors 16. Pressure Sensor 21 Hydrogen supply piping 22 Circulation piping 24 Ejectors 33 Exhaust drain valve 41 Control Unit

Claims

1. Fuel cell stack and An injector that sprays hydrogen gas, A first pipe connected to the hydrogen supply port of the fuel cell stack, A second pipe connected to the exhaust port of the fuel cell stack, An ejector is provided on the output side of the injector and guides the hydrogen gas injected from the injector and the gas in the second pipe to the first pipe, A pressure sensor for measuring the pressure inside the first pipe or the second pipe, The system includes a control unit that controls the injection of hydrogen gas by the injector based on the pressure measured by the pressure sensor, The control unit determines whether or not an abnormality has occurred in the ejector based on a parameter representing the time change of the pressure measured by the pressure sensor. A fuel cell system characterized by the following features.

2. An exhaust drain valve is provided for the second piping. The control unit determines whether or not an abnormality has occurred in the ejector when the exhaust and drain valve is closed. The fuel cell system according to claim 1.

3. The control unit, When the pressure drops to a predetermined threshold, hydrogen gas is injected into the injector for a predetermined time. Based on the time from the start of hydrogen gas injection by the injector until the pressure reaches its peak, it is determined whether or not an abnormality has occurred in the ejector. The fuel cell system according to claim 1.

4. The control unit, When the pressure drops to a predetermined threshold, hydrogen gas is injected into the injector. Based on the pressure measured after a predetermined time has elapsed since the start of hydrogen gas injection by the injector, it is determined whether or not an abnormality has occurred in the ejector. The fuel cell system according to claim 1.

5. The control unit, When the pressure drops to a predetermined threshold, hydrogen gas is injected into the injector. Based on the slope of the pressure with respect to time when the injector is injecting hydrogen gas, it is determined whether or not an abnormality has occurred in the ejector. The fuel cell system according to claim 1.

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