Fuel cell system

Abstract

In a fuel cell system (10) in which fuel gas is supplied from a fuel tank (16) to a fuel cell (14) via an injector (32), when a power generation current (Ifc) of the fuel cell (14) is equal to or greater than a detected effective current threshold value (Ith), the fuel gas is injected from the fuel tank (16) to the fuel cell (14) via the injector (32). The failure determination of an injector (32) is performed on the basis of a fuel gas pressure command value (Pcom) and a gas pressure detection value (Pa) detected by a pressure sensor (50) provided downstream of the injector (32).

Description

Technical Field

[0001] The present invention relates to a fuel cell system including a fuel cell for generating electricity by utilizing an electrochemical reaction between an oxidant gas and a fuel gas. Background Art

[0002] In recent years, in order to ensure that more people have access to appropriate, reliable, sustainable and advanced energy, research and development of fuel cells that contribute to energy efficiency has been carried out.

[0003] For example, Patent Document 1 discloses a technology in which, in a fuel cell system in which hydrogen gas supplied from a hydrogen tank is supplied to a fuel cell stack via a plurality of injectors, a pressure sensor is arranged downstream of the plurality of injectors to detect a closing failure of the injectors.

[0004] This technology includes: a normal mode in which one of the plurality of injectors is driven; and a high load mode in which two or more of the plurality of injectors are driven when the required power is equal to or greater than a predetermined value. Under the feasible conditions of the normal mode, a drive command is issued to all of the plurality of injectors one by one, and when the pressure measured by the pressure sensor after the time when the drive command is issued is less than a predetermined threshold value, it is detected that one of the injectors driven based on the drive command is in a closed fault.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japan JP2018-101572A Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, in the fuel cell system disclosed in Patent Document 1, in normal mode, drive commands are issued to all of the multiple injectors one by one, and pressure sensors arranged downstream of the injectors measure pressures, so there is a problem that it takes a long time to complete the detection of the multiple injectors.

[0010] Furthermore, since the detection of the closing failure is not performed in the high load mode but is performed in the normal mode, there is a problem that the timing for detecting the closing failure is limited and the detection cannot be performed efficiently.

[0011] The object of the present invention is to solve the above-mentioned problems.

[0012] Solutions for solving problems

[0013] An aspect of the present invention relates to a fuel cell system, which has a fuel cell that generates electricity through an electrochemical reaction between an oxidant gas and a fuel gas and supplies electricity to a load. The fuel cell system includes: a fuel container that contains fuel gas; a fuel supply flow path that guides the fuel gas supplied from the fuel container to the fuel cell; a plurality of injectors that are arranged in the fuel supply flow path and regulate the pressure of the fuel gas and supply it to the fuel cell; a pressure sensor that detects the pressure of the fuel gas at the downstream side of the plurality of injectors; a control device that controls power generation of the fuel cell; and a failure determination unit that performs failure determination of the injector, the control device opens and closes the plurality of injectors according to a fuel gas pressure command value based on a request from the load to cause the fuel gas to be ejected into the fuel supply flow path, and when the current value output from the fuel cell is greater than a detection effective current threshold, the failure determination unit performs failure determination of the injector based on the fuel gas pressure command value and a gas pressure detection value detected by the pressure sensor.

[0014] Effects of the Invention

[0015] According to the present invention, the failure determination unit performs failure determination by opening and closing the plurality of injectors. Therefore, the time until the failure determination of the plurality of injectors is finalized can be shortened, and failure determination can be performed efficiently.

[0016] The above-mentioned objects, features and advantages can be easily understood from the following description of the embodiments described with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic configuration diagram of a fuel cell system according to an embodiment in which a fuel cell is electrically connected to a load.

[0018] Figure 2 This is a flowchart for explaining the operation of the fuel cell system.

[0019] Figure 3 It is a timing chart for explaining the operation of the fuel cell system.

[0020] Figure 4 It is a timing chart for explaining the operation of the fuel cell system according to the modification. DETAILED DESCRIPTION

[0021] [Implementation Method]

[0022] [structure]

[0023] Figure 1The schematic structure diagram of a fuel cell system 10 according to an embodiment in which a fuel cell is electrically connected to a load is shown. In the fuel cell system 10, a fuel cell stack (also simply referred to as a fuel cell) 14 is electrically connected to a load 12. The fuel cell stack 14 is composed of a plurality of power generation cells 26 stacked in layers.

[0024] The fuel cell system 10 is used by being assembled in a mobile body such as a fuel cell automobile, a ship, a submarine, an aircraft, a spacecraft, a robot, an industrial vehicle, and a forklift. The fuel cell stack 14 supplies power to a main load 12, i.e., an electric motor (motor) for driving the mobile body, and an auxiliary load, i.e., an auxiliary device. Furthermore, the fuel cell system 10 is also used to supply power to various devices in fixed-placement industrial equipment and the like.

[0025] The fuel cell system 10 is composed of a fuel cell stack 14, a fuel container 16 as a hydrogen tank, an oxidant gas supply device 18, a fuel gas supply device 20, a heat medium supply device (not shown) and a control device 22 for controlling these, wherein the heat medium supply device is used as the auxiliary device to adjust the temperature of the fuel cell stack 14. The control device 22 may be divided into two or more control devices instead of one.

[0026] The oxidant gas supply device 18 includes a compressor (CP) 24 which is an auxiliary device for compressing introduced air and supplying the compressed air to the fuel cell stack 14 .

[0027] The fuel gas supply device 20 includes a plurality of injectors (INJ) 32 (a first injector 32a and a second injector 32b) for regulating the pressure of the fuel gas, an ejector 36, and a gas-liquid separator 38. The first injector 32a and the second injector 32b are connected in parallel.

[0028] Fuel gas is supplied from the fuel container 16 to the supply port of the injector 32. The injector 32 has a piston driven by an electromagnetic coil inside, and the ejection port is opened and closed by the forward and backward movement of the piston, thereby ejecting a predetermined amount of fuel gas. In addition, there may be more than three injectors 32. Preferably, the specifications of the plurality of injectors 32 are the same, but they may also be of different specifications. The most suitable specification of the injector 32 is selected according to the required ejection amount of fuel gas and the operation mode. The maximum ejection amount that the injector 32 can eject depends on the effective cross-sectional area of ​​the ejection port of the injector 32.

[0029] The fuel cell stack 14 includes a stacked body formed by stacking a plurality of power generation cells 26 of a solid polymer fuel cell (PEFC), and the stacked body is sandwiched by a pair of end panels to form the fuel cell stack 14. Each power generation cell 26 includes: an electrolyte membrane-electrode structure 46 formed by sandwiching a solid polymer electrolyte membrane (electrolyte membrane) 44 by a cathode electrode 43 and an anode electrode 45; and a pair of separators 47 and 48 sandwiching the electrolyte membrane-electrode structure 46. The separators 47 and 48 are formed of a carbon plate or a metal plate. The fuel cell stack 14 is not limited to a solid polymer fuel cell, and can also be composed of a well-known fuel cell such as a solid electrolyte fuel cell (SOFC).

[0030] A cathode flow path (oxidant gas flow path) 40 is formed on one side of the separator 48 facing the membrane electrode assembly 46. The cathode flow path connects the oxidant gas inlet communication port 101 with the oxidant gas outlet communication port 102. A heat medium flow path 49 is formed on the other side of the separator 48.

[0031] The other separator 47 has an anode flow path (fuel gas flow path) 42 formed on one side thereof facing the membrane electrode assembly 46. The anode flow path connects the fuel gas inlet communication port 103 and the fuel gas outlet communication port 104. The separator 47 also has a heat medium flow path 49 formed on the other side thereof.

[0032] In the anode electrode 45, by supplying the fuel gas (hydrogen), hydrogen ions (protons) and electrons are generated from hydrogen molecules due to the electrode reaction caused by the catalyst. The hydrogen ions pass through the solid polymer electrolyte membrane 44 and move to the cathode electrode 43. In addition, as the fuel gas, it is sufficient as long as a part of it contains hydrogen, and it can also be a hydrogen-containing reformed gas generated by reforming hydrocarbon fuel.

[0033] The electrons generated from the hydrogen molecules pass through the load 12 from the negative terminal 106 and move to the cathode electrode 43 via the positive terminal 108 .

[0034] In cathode electrode 43, the hydrogen ions and the electrons react with oxygen contained in the oxidant gas (air) supplied by compressor 24 by the action of the catalyst to generate water. The oxidant gas may be pure oxygen as long as it contains oxygen.

[0035] A voltage sensor 110 for detecting the generated voltage Vfc is provided between the wiring connecting the negative terminal 106 of the fuel cell stack 14 and the load 12 and the wiring connecting the positive terminal 108 and the load 12. In addition, a current sensor 112 for detecting the generated current Ifc (current value) output from the fuel cell stack 14 is provided in the wiring connecting the positive terminal 108 and the load 12. The current sensor 112 is directly connected to the positive terminal 108 of the fuel cell stack 14. That is, a voltage converter such as a DC / DC converter is not inserted between the current sensor 112 and the positive terminal 108 of the fuel cell stack 14. As a result, the current sensor 112 can detect the generated current Ifc output from the fuel cell stack 14 with good accuracy.

[0036] The electric power generated by the fuel cell stack 14 is also used to drive auxiliary equipment such as the compressor 24 .

[0037] The compressor 24 draws and pressurizes air from the external air intake port 114. The pressurized air is supplied as oxidant gas to the cathode flow path 40 in the fuel cell stack 14 from the oxidant gas inlet communication port 101. The oxidant gas flowing through the cathode flow path 40 is supplied to the cathode electrode 43.

[0038] The fuel container 16 is a container that contains high-purity hydrogen gas (fuel gas) compressed to a high pressure. The fuel container 16 is provided with an electromagnetically operated shutoff valve at a hydrogen supply port.

[0039] The fuel gas ejected from the fuel container 16 passes through the injectors 32 (first injector 32a, second injector 32b) and ejector 36 provided in the fuel gas ejection pipe 54 (fuel supply flow path), and is supplied to the anode flow path 42 in the fuel cell stack 14 through the fuel gas supply pipe 56 (fuel supply flow path), and further through the fuel gas inlet communication port 103. The fuel gas flowing through the anode flow path 42 is supplied to the anode electrode 45.

[0040] The fuel gas supply piping 56 is provided with: a temperature sensor 55 that detects the temperature of the fuel gas supplied to the fuel cell stack 14; and a pressure sensor 50 that detects the pressure of the fuel gas supplied to the fuel cell stack 14. The pressure sensor 50 has two pressure sensors 51 and 52. The pressure sensor 50 detects the pressure of the fuel gas after pressure regulation (after pressure reduction) by the injector 32. In the present embodiment, in order to ensure redundancy, two pressure sensors 50 are provided in parallel. Thus, even if one of the two pressure sensors 51 and 52 fails, the remaining one can be used to continue control. The specifications of the two pressure sensors 51 and 52 are the same.

[0041] Furthermore, the pressure sensor 50 may be one, or may be three or more. In addition, the specifications of the two pressure sensors 50 may be different from each other. In this case, the pressure sensor 51 on one side may be used to detect a region where the pressure of the fuel gas is relatively low, and the pressure sensor 52 on the other side may be used to detect a region where the pressure of the fuel gas is relatively high.

[0042] The pressure value of the fuel gas detected by the pressure sensor 51 is set to P1, and the pressure value of the fuel gas detected by the pressure sensor 52 is set to P2. Moreover, the pressure value of the fuel gas flowing through the fuel gas supply pipe 56 is P1 or P2. Alternatively, the average value {Pa=(P1+P2) / 2} of the gas pressure detection value P1 detected by the pressure sensor 51 and the gas pressure detection value P2 detected by the pressure sensor 52 may be set as the pressure value of the fuel gas. Alternatively, either P1 or P2 may be used as the pressure value of the fuel gas.

[0043] Hereinafter, the pressure value detected by the pressure sensor 50 will be referred to as a gas pressure detection value Pa.

[0044] In the fuel cell stack 14 , the oxidant gas and the fuel gas flowing through the cathode electrode 43 and the anode electrode 45 cause electrochemical reactions to generate electricity. The generated power is then supplied to the load 12 through the positive terminal 108 and the negative terminal 106 .

[0045] The oxidant gas in which a part of oxygen is consumed in the fuel cell stack 14 is discharged to the outside (into the atmosphere) through the oxidant gas outlet communication port 102 as nitrogen-rich oxidant exhaust gas.

[0046] Fuel gas partially consumed in the fuel cell stack 14 flows into the inlet 120 of the gas-liquid separator 38 as hydrogen-containing gas, namely, fuel exhaust gas, through the fuel gas outlet communication port 104. The fuel exhaust gas discharged from the anode flow path 42 is supplied to the gas-liquid separator 38.

[0047] The gas-liquid separator 38 separates the fuel exhaust gas into a gas component and a liquid component (liquid water) containing reaction-generated water. The gas component of the fuel exhaust gas includes hydrogen gas that is not used for electrochemical reaction and is discharged in the fuel cell stack 14, nitrogen that permeates from the cathode flow path 40 to the anode flow path 42 through the electrolyte membrane 44, and a gas component of the reaction-generated water. The gas component is discharged from the gas discharge port 122 of the gas-liquid separator 38 and is supplied to the suction port of the ejector 36 through the reed valve 126 in the circulation pipe 124. The pilot valve 126 is a check valve that prevents the gas component from flowing back from the ejector 36 to the gas-liquid separator 38.

[0048] The liquid component of the fuel exhaust gas may be mixed with the oxidant exhaust gas from the liquid discharge port 136 of the gas-liquid separator 38 through the drain valve 60 and discharged to the outside (atmosphere) via a diluter (not shown).

[0049] The control device 22 comprehensively controls the above-described components of the fuel cell system 10 .

[0050] The control device 22 is constituted by an ECU (Electronic Control Unit). The ECU is constituted by a computer having one or more processors (CPU), a memory, an input / output interface, and a circuit. The one or more processors (CPU) execute a program (computer executable instruction) not shown) stored in the memory.

[0051] The control device 22 performs overall control related to power generation of the fuel cell system 10 .

[0052] The control device 22 includes a timer 64 as a timing device (Japanese: タイマ), and a memory 65 for recording various information in a storage device (Japanese: メモリ).

[0053] The control device 22 includes a failure determination unit 66 for performing failure determination of the injector 32 .

[0054] The processor (CPU) of the control device 22 executes the program to control the operation of the fuel cell system 10 .

[0055] A power switch 62 for turning the fuel cell system 10 on and off is connected to the control device 22. The power switch 62 starts and continues (ON) or ends (OFF) the power generation operation of the fuel cell stack 14 of the fuel cell system 10.

[0056] [action]

[0057] The fuel cell system 10 according to the present embodiment is basically configured as described above. Figure 2 The flowchart shown in the figure illustrates the operation. Furthermore, the control device 22 repeatedly executes the operation at a predetermined cycle. Figure 2 Flowchart of the process.

[0058] When the power switch 62 is turned on, the control device 22 performs failure determination control of the fuel cell system 10. Specifically, the failure determination unit 66 of the control device 22 performs failure determination control of a shutdown failure of the injector 32 that ejects hydrogen gas, which is a fuel gas supplied to the fuel cell stack 14.

[0059] During normal power generation operation, the control device 22 causes the fuel cell stack 14 to output power based on a request from the load 12. Specifically, the control device 22 refers to the correspondence stored in the memory 65, causes the injector 32 to eject a fuel gas amount greater than the fuel gas pressure command value Pcom corresponding to the required current from the load 12, and causes the fuel cell stack 14 to output a power generation current Ifc corresponding to the required current.

[0060] In step S1 , the failure determination unit 66 determines whether the generated current Ifc is equal to or greater than the detection effective current threshold value Ith.

[0061] Here, the detection effective current threshold value Ith will be described.

[0062] The control device 22 can make the fuel cell stack 14 output a generated current Ifc greater than a predetermined value. The predetermined value of the generated current Ifc (current value) is referred to as the detection effective current threshold value Ith. Preferably, the control device 22 maintains the detection effective current threshold value Ith at a fixed value while the fault determination unit 66 is performing the fault determination.

[0063] The detection effective current threshold Ith is the maximum current value that can be output by the fuel cell stack 14 using the maximum amount of hydrogen gas (maximum amount of fuel gas) that can be ejected by only one of the multiple injectors 32. Alternatively, the detection effective current threshold Ith is a specific current value set based on the maximum current value.

[0064] As another embodiment, the effective current threshold Ith is detected when two injectors 32 (first injector 32a, second injector 32b) are driven simultaneously, using a fixed amount of fuel gas ejected by only one of the injectors 32 to make the fuel cell stack 14 output a fixed current value. A fixed amount of fuel gas means that the ejection amount of the injector 32 per unit time is fixed. Since one injector 32 ejects a fixed amount of fuel gas, it is possible to accurately detect the pressure change of the fuel gas ejected by the other injector 32. When the ejection amount of fuel gas from one injector 32 changes, it will interfere with the ejection amount of fuel gas ejected by the other injector 32, making it difficult for the pressure sensor 50 provided downstream of the two injectors 32 to accurately detect the pressure change of the fuel gas.

[0065] Sometimes the control device 22 causes the fuel cell stack 14 to output a generated current Ifc greater than the detection effective current threshold value Ith based on the required current from the load 12. In this case, the amount of fuel gas ejected by one injector 32 is insufficient for the required current, so it is necessary to drive both injectors 32 simultaneously. One of the two injectors 32 ejects the maximum amount of fuel gas, and the other injector 32 ejects the amount of fuel gas that is insufficient for the maximum amount of fuel gas ejected by one injector 32.

[0066] If the generated current Ifc (current value) is greater than the detection effective current threshold value Ith, it is not limited to a fixed value and may also change with time. In this case, in the present embodiment, one injector 32 ejects a fixed maximum amount of fuel gas, and the other injector 32 changes the amount of fuel gas ejected according to the required current from the load 12.

[0067] If the generated current Ifc is smaller than the detection effective current threshold value Ith in step S1 (step S1: No), the fault determination unit 66 advances the process to step S2. In step S2, the fault determination unit 66 does not perform a fault determination (does not perform a fault determination).

[0068] When the generated current Ifc is equal to or greater than the detection effective current threshold value Ith in the determination of step S1 (step S1 : Yes), the failure determination unit 66 advances the process to step S3 .

[0069] In step S3 , the failure determination unit 66 determines whether a difference value obtained by subtracting the gas pressure detection value Pa detected by the pressure sensor 50 from the fuel gas pressure command value Pcom is equal to or larger than a first detection difference value Ef.

[0070] The first detection difference Ef includes a control error related to the control and a detection error of the pressure sensor 50 .

[0071] When the difference between the fuel gas pressure command value Pcom and the gas pressure detection value Pa is smaller than the first detection difference Ef (step S3 : NO), the failure determination unit 66 advances the process to step S4 .

[0072] In step S4 , the failure determination section 66 determines that the injector 32 has no failure.

[0073] On the other hand, when the difference between the fuel gas pressure command value Pcom and the gas pressure detection value Pa is greater than the first detection difference value Ef (step S3: Yes), the fault determination unit 66 advances the process to step S5. In addition, when the process advances to step S5, the timer 64 is activated to start measuring the elapsed time tm, and a flag in fault detection is set.

[0074] In step S5 , the failure determination unit 66 determines whether the elapsed time tm in the state of proceeding to step S5 has elapsed a first failure determination time Tf which is a predetermined time after the flag in failure detection is asserted (tm≧Tf).

[0075] When the first failure determination time Tf has not elapsed (step S5 : NO), the failure determination unit 66 advances the process to step S6 .

[0076] In step S6 , the failure determination unit 66 is in the process of determining the failure of the injector 32 and the process returns to step S1 .

[0077] When the first failure specific time Tf has elapsed after the flag indicating that the failure is being detected is asserted (step S5 : Yes), the failure determination unit 66 advances the process to step S7 .

[0078] In step S7 , the failure determination portion 66 determines that the injector 32 is faulty.

[0079] When a failure of the injector 32 is identified, the control device 22 may operate a warning device such as a lamp or a buzzer for indicating the failure.

[0080] Then, refer to Figure 3 The timing diagram shows Figure 2 An example of processing according to the flowchart.

[0081] At time point t0, the control device 22 refers to the correspondence relationship in the memory 65 recording the relationship between the generated current Ifc and the fuel gas pressure command value Pcom based on the required current from the load 12. In this case, the control device 22 drives the injector 32 based on the fuel gas pressure command value Pcom corresponding to the generated current Ifc. Alternatively, the correspondence relationship may be switched based on the temperature Ta of the hydrogen gas flowing through the fuel gas supply pipe 56 detected by the temperature sensor 55.

[0082] In this case, in this embodiment, if Figure 3 As shown, after time point t0, the first injector 32a and the second injector 32b are opened and closed repeatedly at the same time and inject a predetermined amount of fuel gas.

[0083] The relationship between the amount of fuel gas injected from each of the first injector 32 a and the second injector 32 b and the fuel gas pressure command value Pcom is stored in advance in the memory 65 as a correspondence relationship.

[0084] In this example, when the fuel gas pressure command value Pcom is small, one injector 32 ejects fuel gas, and when the fuel gas pressure command value Pcom increases, two injectors 32 eject fuel gas. Alternatively, in consideration of the durability of the plurality of injectors 32, the first injector 32a and the second injector 32b may be switched so that the time for each injector 32 to be driven for the fuel gas pressure command value Pcom is equal.

[0085] The fuel gas ejected from the injector 32 is consumed by (A) power generation due to the electrochemical reaction in the fuel cell stack 14, (B) movement from the anode electrode 45 to the cathode electrode 43 via the electrolyte membrane 44, and (C) discharge from the gas-liquid separator 38 to the outside via the liquid discharge port 136. The gas pressure detection value Pa detected by the pressure sensor 50 is determined based on the amount of fuel gas ejected from the injector 32 and supplied to the fuel cell stack 14 and the consumption of the fuel gas (A), (B), and (C) described above.

[0086] In the present embodiment, the first injector 32a and the second injector 32b are opened simultaneously for predetermined times Ta1 and Tb1, respectively, to eject a predetermined amount of hydrogen gas to the fuel gas supply pipe 56. The time Ta1 and the time Tb1 may be the same or different. In addition, the first injector 32a and the second injector 32b may be opened at different timings.

[0087] The flow rate of the fuel gas injected by the injector 32 within a predetermined time can be adjusted by changing the duty ratio of opening and closing. The duty ratios of the first injector 32a and the second injector 32b may be the same or different.

[0088] As the injector 32 opens, the fuel gas is ejected to the fuel gas supply pipe 56, and after time t1, the gas pressure detection value Pa detected by the pressure sensor 50 increases at a rising speed Pv0. Then, at time t2, the gas pressure detection value Pa reaches a maximum value Pmax.

[0089] When the gas pressure detection value Pa is higher than the fuel gas pressure command value Pcom, the failure determination unit 66 starts failure determination. Alternatively, the failure determination may be started from the time when the gas pressure detection value Pa reaches the maximum value Pmax.

[0090] Alternatively, the fault determination unit 66 may start fault determination when the fuel gas pressure command value Pcom corresponding to the generated current Ifc is within a predetermined range. The predetermined range is determined based on the error in pressure control, i.e., the control error. Alternatively, the fault determination may be started within a predetermined range of the fuel gas pressure command value Pcom where the control error is reduced.

[0091] After the time point t2 , inside the fuel cell stack 14 on the downstream side of the injector 32 , as the fuel gas is consumed mainly by the electrochemical reaction, the gas pressure detection value Pa gradually decreases at a decreasing speed Pv1 .

[0092] In this case, the control device 22 drives the injector 32 to eject the fuel gas based on the correspondence relationship stored in advance in the memory 65 so that the detected gas pressure value Pa remains equal to or higher than the fuel gas pressure command value Pcom even when the detected gas pressure value Pa drops to the minimum.

[0093] In this embodiment, when the gas pressure detection value Pa reaches the maximum value Pmax (time point t3), the first injector 32a of the first injector 32a and the second injector 32b has a closing failure. The closing failure means that the ejection port of the injector 32 is closed and the fuel gas cannot be ejected.

[0094] exist Figure 3 At time point t3, when the first injector 32a has a closing failure, the gas pressure detection value Pa detected by the pressure sensor 50 decreases from the maximum value Pmax at a decreasing speed Pv2 faster than when there is no closing failure. Furthermore, when the gas pressure detection value Pa is lower than the fuel gas pressure command value Pcom, the control device 22 issues a command to the second injector 32b based on feedback control to increase the injection amount and thereby increase the gas pressure detection value Pa.

[0095] In this case, the first injector 32a has a closure failure and does not eject fuel gas. The remaining normal second injector 32b increases the ejection amount of fuel gas by a feedback equivalent amount (FB equivalent amount), so the falling speed Pv3 (|Pv2|>|Pv3|) of the gas pressure detection value Pa temporarily decreases (time point t4 to time point t5).

[0096] When the gas pressure detection value Pa further decreases and falls below the first detection threshold value Pf even if the injection amount of the fuel gas is increased by the feedback amount, the failure determination unit 66 detects a failure of the first injector 32a (time t6, refer to step S3: Yes).

[0097] At this time point t6, the failure of the first injector 32a has not yet been determined. In addition, the first detection threshold value Pf is a pressure value that is lower than the fuel gas pressure command value Pcom by the first detection difference value Ef. As described above, the first detection difference value Ef is set in consideration of the control error related to the control and the detection error of the pressure sensor 50.

[0098] The control error is caused by a deviation between the actual amount of fuel gas consumed due to the power generation state of the fuel cell stack 14 and the amount of fuel gas ejected from the injector 32 based on the fuel gas pressure command value Pcom.

[0099] The error of the pressure sensor 50 is caused by the detection error of the pressure sensor 50 itself and the state (pressure distribution, flow rate, temperature, etc.) of the fuel gas flowing inside the fuel gas supply pipe 56. The influence of the pressure distribution, flow rate, and temperature may be reflected in the gas pressure detection value Pa to more accurately grasp the detection error of the pressure sensor 50 itself.

[0100] After the fault is detected at time t6, the fault determination unit 66 monitors whether the state in which the gas pressure detection value Pa drops below the first detection threshold value Pf continues. If the state is maintained even after the first fault determination time Tf has passed (see step S5: Yes), it is determined that the fault is determined (time t8, see step S7).

[0101] When the failure determination unit 66 determines that the first injector 32a is faulty, the control device 22 sets the maximum amount of fuel gas that can be ejected by the normal second injector 32b to an upper limit value, and uses an amount of fuel gas that does not exceed the upper limit value to continue power generation of the fuel cell stack 14. The maximum amount of fuel gas that can be ejected depends on the effective cross-sectional area of ​​the second injector 32b, and the duty cycle of the second injector 32b is generally about 85% to 100%.

[0102] In this case, the amount of fuel gas ejected from the injector 32 may be insufficient for the required current from the load 12, so it is necessary to quickly limit the generated current Ifc output from the fuel cell stack 14. This is because when the amount of fuel gas supplied from the injector 32 is insufficient for the required current from the load 12, insufficient supply of fuel gas occurs in the anode electrode 45, and the electrolyte membrane-electrode structure 46 is damaged, which affects the durability.

[0103] The generated current Ifc corresponding to the maximum amount of fuel gas that can be ejected by the normally driven second injector 32b is set as the limiting current value. The limiting current value in this embodiment is the same as the detection effective current threshold Ith. Moreover, when the required current from the load 12 exceeds the limiting current value, current is supplied to the load 12 from a battery, etc., not shown in the figure.

[0104] [Modifications]

[0105] The above-described embodiment can be modified as follows.

[0106] Figure 4 is a timing diagram for explaining the operation of the modified example. Figure 4 In Figure 3 The same reference numerals are used for common items, and detailed description thereof will be omitted.

[0107] exist Figure 4 In the timing diagram, the actions from time point t1 to time point t4 are the same as Figure 3 The difference is that at time point t5', the second injector 32b also fails.

[0108] exist Figure 4 In the timing diagram, Figure 3 Compared with the timing diagram of FIG. 1 , a second detection difference Es is set in which the difference between the fuel gas pressure command value Pcom and the gas pressure detection value Pa is larger than the first detection difference Ef. That is, two detection differences, the first detection difference Ef and the second detection difference Es, are set. The second detection difference Es is larger than the first detection difference Ef (Es>Ef). In this case, since the first injector 32a has already failed at time point t3, and the second injector 32b has failed at time point t5′, the falling speed Pv4 of the gas pressure detection value Pa after time point t5′ is faster than the previous falling speed Pv3.

[0109] After the difference obtained by subtracting the gas pressure detection value Pa from the fuel gas pressure command value Pcom exceeds the first detection difference Ef at time t6', the failure of the first injector 32a is determined at time t8' when the first failure determination time Tf has elapsed.

[0110] On the other hand, at time t7', the gas pressure detection value Pa drops below the detection threshold value Ps. That is, after the difference between the fuel gas pressure command value Pcom and the gas pressure detection value Pa exceeds the second detection difference Es, at time t9 after the second failure determination time Ts has passed, the failure of the second injector 32b is also determined.

[0111] When the failure of the two injectors 32 is confirmed, the control device 22 stops the power generation of the fuel cell stack 14. In this case, a warning device such as a lamp or a buzzer for indicating the failure may be operated.

[0112] According to this modification, even if two injectors 32 supplying fuel gas fail successively, the failure is detected quickly and power generation of the fuel cell stack 14 is stopped, thereby preventing damage to the fuel cell stack 14 due to insufficient supply of fuel gas.

[0113] The present invention is not limited to the above-mentioned embodiments, and various changes can be made without departing from the scope of the main purpose of the present invention. For example, the number of injectors 32 is not limited to two, and can also be three or more. In this case, it is preferred that the fault judgment is performed when all three or more injectors 32 are driven. The detection effective current threshold Ith of the power generation current Ifc is a fixed current value output by the fuel cell when all the remaining injectors 32 except one of the multiple injectors are driven at the same time and different fixed amounts of fuel gas are used. More preferably, the detection effective current threshold Ith of the power generation current Ifc is a current value in the state where the fuel cell stack 14 is generating electricity using the maximum amount of fuel gas that can be ejected by at least one of the multiple injectors.

[0114] [Note]

[0115] Regarding the above disclosure, the following additional notes are further disclosed.

[0116] (Supplementary Note 1) A fuel cell system 10 includes a fuel cell 14, which generates electricity through an electrochemical reaction between an oxidant gas and a fuel gas and supplies electricity to a load 12. In the fuel cell system, there are: a fuel container 16, which contains fuel gas; fuel supply flow paths 54, 56, which guide the fuel gas supplied from the fuel container 16 to the fuel cell 14; a plurality of injectors 32, which are arranged in the fuel supply flow path, regulate the pressure of the fuel gas and supply it to the fuel cell; a pressure sensor 50, which detects the pressure of the fuel gas at the downstream side of the plurality of injectors 32. The pressure of the fuel gas; a control device 22, which controls the power generation of the fuel cell; and a fault judgment unit 66, which performs fault judgment on the injector 32, the control device 22 opens and closes the plurality of injectors 32 according to a fuel gas pressure command value Pcom formed based on a requirement from a load to cause the fuel gas to be ejected into the fuel supply flow path, and when the current value output from the fuel cell 14 is greater than a detection effective current threshold value Ith, the fault judgment unit 66 performs fault judgment on the injector 32 based on the fuel gas pressure command value and a gas pressure detection value Pa detected by the pressure sensor 50.

[0117] Through this structure, when the current value output from the fuel cell is above the detection effective current threshold, the injector failure judgment is performed based on the fuel gas pressure command value and the gas pressure detection value detected by the pressure sensor. Therefore, the change in the gas pressure of the fuel gas can be detected while a stable amount of fuel gas flows through the fuel supply flow path, and the injector failure judgment can be reliably performed.

[0118] In addition, since the pressure of the fuel gas is detected at the downstream side of the plurality of injectors, the failure of each injector is not determined individually, and thus the failure of the injector can be detected quickly. Thus, the insufficient supply of the fuel gas caused by the failure of the injector can be detected quickly and dealt with, and the degradation of the fuel cell can be effectively suppressed.

[0119] (Note 2) In the fuel cell system described in Note 1, the fault judgment unit may determine that the injector is faulty when the difference between the fuel gas pressure command value and the gas pressure detection value exceeds the first detection difference Ef.

[0120] This reduces the influence of a control error related to the control of the fuel cell and a detection error of the pressure sensor, and enables reliable detection of a failure of the injector.

[0121] (Supplementary Note 3) In the fuel cell system according to Supplementary Note 1, the failure determination unit may start failure determination when the gas pressure detection value is higher than the fuel gas pressure command value.

[0122] Thus, the temporal change of the gas pressure detection value can be detected with high accuracy while the gas pressure detection value is decreasing.

[0123] (Supplementary Note 4) In the fuel cell system according to Supplementary Note 1, when the fuel gas pressure command value corresponding to the current value is within a predetermined range, failure determination may be started.

[0124] Thus, the fuel gas pressure command value can be detected in a state where the fuel gas pressure command value is stable with respect to the current value and the control error is small, and thus a failure of the injector can be reliably detected.

[0125] (Supplementary Note 5) In the fuel cell system described in Supplementary Note 1, the multiple injectors may be two injectors, and the detection effective current threshold may be a maximum current value that the fuel cell can output using only one injector or a current value based on the maximum current value.

[0126] Thus, a gas pressure detection value that is sufficiently lower than the fuel gas pressure command value can be detected, and a fault determination can be made reliably and quickly. In addition, when only one of the injectors is used to make the maximum current value that the fuel cell can output, the other injector is also driven at the same time, so no matter which of the two injectors fails, a fault determination can be made.

[0127] (Supplementary Note 6) In the fuel cell system according to Supplementary Note 1, the failure determination unit may perform failure determination in a state where all of the plurality of injectors are driven.

[0128] Thus, no matter which of the plurality of injectors fails, the gas pressure detection value decreases with respect to the fuel gas pressure command value, so that the failure of the injector can be detected quickly.

[0129] (Supplementary Note 7) In the fuel cell system described in Supplementary Note 6, the detection effective current threshold may be a fixed current value output by the fuel cell using fixed amounts of fuel gas different from each other ejected from all of the plurality of injectors except one.

[0130] Thus, all the remaining injectors except one injector eject fixed amounts of fuel gas that are different from each other, so even if one of the injectors has a shutdown failure, the injector with the failure can be identified because the falling speed of the gas pressure detection value is different. In addition, the one injector can make the ejection amount of fuel gas variable according to the required current to be changed by the fuel cell.

[0131] (Supplementary Note 8) In the fuel cell system described in Supplementary Note 7, the failure determination unit may perform failure determination on the injector when at least one of the plurality of injectors is causing the injectors to discharge a maximum amount of fuel gas that can be discharged.

[0132] This makes it possible to detect a sufficiently reduced gas pressure detection value, and to reliably and quickly perform a failure determination.

[0133] (Supplementary Note 9) In the fuel cell system described in Supplementary Note 2, when the gas pressure detection value is lower than the fuel gas pressure command value, the control device may instruct the plurality of injectors to increase the amount of fuel gas to be ejected.

[0134] Thus, the injectors that are not defective supply an increased amount of fuel gas, thereby compensating for the shortage of fuel gas that should be supplied by the defective injectors, thereby suppressing the shortage of fuel gas supply to the anode electrode.

[0135] (Note 10) In the fuel cell system described in Note 2, when it is determined that at least one of the multiple injectors is faulty, the control device may limit the current output from the fuel cell to a current value below that which the fuel cell can output using the maximum amount of fuel gas that can be ejected by an injector without faults.

[0136] This can suppress the shortage of fuel gas supply to the anode electrode and suppress the degradation of the fuel cell stack.

[0137] (Note 11) In the fuel cell system described in Note 2, the fault judgment unit may determine that a plurality of the injectors are faulty when a difference obtained by subtracting the gas pressure detection value from the fuel gas pressure command value exceeds a second detection difference Es that is larger than the first detection difference.

[0138] This makes it possible to quickly detect that two or more injectors have failed.

[0139] Furthermore, the present invention is not limited to the above-mentioned disclosure, and various structures can be adopted without departing from the gist of the present invention.

Claims

1. A fuel cell system comprising a fuel cell, wherein the fuel cell generates electricity through an electrochemical reaction between an oxidant gas and a fuel gas and supplies the electricity to a load, wherein the fuel cell system comprises: a fuel container containing fuel gas; a fuel supply flow path that guides the fuel gas supplied from the fuel container to the fuel cell; a plurality of injectors, the plurality of injectors being disposed in the fuel supply flow path and regulating the pressure of the fuel gas to supply the fuel cell; a pressure sensor that detects a pressure of the fuel gas at a downstream side of the plurality of injectors; a control device that controls power generation of the fuel cell; as well as a fault determination unit for determining a fault of the injector, The control device opens and closes the plurality of injectors according to a fuel gas pressure command value based on a request from the load to eject fuel gas into the fuel supply flow path. When a current value output from the fuel cell is equal to or greater than a detection effective current threshold, the failure determination unit performs failure determination of the injector based on the fuel gas pressure command value and a gas pressure detection value detected by the pressure sensor.

2. The fuel cell system according to claim 1, characterized in that: The failure determination unit determines that the injector has a failure when a difference value obtained by subtracting the gas pressure detection value from the fuel gas pressure command value exceeds a first detection difference value during the failure determination of the injector.

3. The fuel cell system according to claim 1, characterized in that: The failure determination unit starts failure determination when the gas pressure detection value is a value higher than the fuel gas pressure command value.

4. The fuel cell system according to claim 1, characterized in that: When the fuel gas pressure command value corresponding to the current value is within a predetermined range, failure determination is started.

5. The fuel cell system according to claim 1, characterized in that: Multiple injectors are two injectors, The detection effective current threshold is a maximum current value that can be output by the fuel cell using only one injector, or a current value based on the maximum current value.

6. The fuel cell system according to claim 1, characterized in that: The failure determination unit performs failure determination in a state where all of the plurality of injectors are driven.

7. The fuel cell system according to claim 6, characterized in that: The detection effective current threshold is a fixed current value that is output by the fuel cell using fixed amounts of fuel gas different from each other ejected by all of the plurality of injectors except one.

8. The fuel cell system according to claim 7, characterized in that: The failure determination unit performs failure determination of the injector when at least one of the plurality of injectors is caused to inject a maximum amount of fuel gas that can be injected.

9. The fuel cell system according to claim 2, characterized in that: When the gas pressure detection value is lower than the fuel gas pressure command value, the control device instructs the plurality of injectors to increase the amount of fuel gas to be injected.

10. The fuel cell system according to claim 2, characterized in that: When it is determined that at least one of the plurality of injectors is faulty, the control device limits the current output from the fuel cell to a current value that can be output by the fuel cell using the maximum amount of fuel gas that can be ejected by an injector without fault.

11. The fuel cell system according to claim 2, characterized in that: The failure determination unit determines that the plurality of injectors have a failure when a difference value obtained by subtracting the gas pressure detection value from the fuel gas pressure command value exceeds a second detection difference value that is larger than the first detection difference value.

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