Fuel cell system

Abstract

To provide a fuel cell system capable of implementing a fault diagnosis of a shut valve which opens and closes a supply path of a fuel while continuing power generation of a fuel cell.SOLUTION: A fuel cell system 1 comprises a fuel cell 10, a plurality of fuel tanks 311, a fuel supply path 32, a shut valve 331, a pressure sensor 103, and a diagnosis section 120. The fuel supply path 32 includes a plurality of upstream paths 321, an aggregation part 322 where each upstream path 321 is aggregated, and a downstream path 323 which connects the aggregation part 322 and the fuel cell 10. In the fuel cell system 1, the shut valve 331 is provided in each upstream path 321. The diagnosis section 120 calculates an estimation amount of a pressure variation amount of a fuel which flows in the downstream path 323 based on a power generation state of the fuel cell 10 in an operation state where a part of the shut valves 331 is in a closed state and a supply of the fuel to the fuel cell 10 is continued. The diagnosis section 120 diagnoses a fault of the shut valve 331 based on the estimation amount and a detection result of the pressure sensor 103.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to fuel cell systems. [Background technology]

[0002] Conventionally, in a gas fuel supply system for a vehicle, a system is known in which a shut-off valve provided in a gas fuel supply pipe is determined to be in a faulty state based on the rate of pressure drop of the gas fuel when the shut-off valve is fully closed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-274311 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the present inventors have considered performing a fault diagnosis of a shutoff valve provided in a fuel supply path that supplies fuel containing hydrogen from a fuel tank to a fuel cell in a fuel cell system using the technology described in Patent Document 1. According to the inventors' considerations, if a fault diagnosis of the shutoff valve is performed with the shutoff valve closed, as in Patent Document 1, the supply of fuel to the fuel cell will be stopped, making it impossible for the fuel cell to continue generating power.

[0005] An object of the present disclosure is to provide a fuel cell system that can perform a fault diagnosis on a shutoff valve that opens and closes a fuel supply path while continuing to generate power in the fuel cell. [Means for solving the problem]

[0006] The invention described in claim 1 is 1. A fuel cell system, comprising: a fuel cell (10) that outputs electrical energy through an electrochemical reaction between a fuel containing hydrogen and oxygen; a plurality of fuel tanks (311) storing fuel including hydrogen; a fuel supply path (32) including a plurality of upstream paths (321) connected to a plurality of fuel tanks, respectively, a collection section (322) that collects the plurality of upstream paths, and a downstream path (323) that connects the collection section to the fuel cell; a plurality of shutoff valves (331) provided in the plurality of upstream paths, respectively; a pressure sensor (103) for detecting the pressure of fuel flowing through the downstream path; a diagnostic unit (120) for diagnosing a failure of the shutoff valve; The diagnostic unit, in an operating state in which some of the multiple shutoff valves are closed and the shutoff valves are controlled so that fuel is continuously supplied to the fuel cell, calculates an estimate of the pressure fluctuation of the fuel flowing through the downstream path based on the power generation state of the fuel cell, and diagnoses a failure of the shutoff valve based on the estimate and the detection result of the pressure sensor.

[0007] In this way, if multiple fuel tanks are provided and some of the multiple shutoff valves provided in the multiple fuel tanks are closed to diagnose shutoff valve failure, it is possible to diagnose shutoff valve failure while continuing to supply fuel to the fuel cell.

[0008] Here, it is conceivable that a shutoff valve failure diagnosis would be performed by comparing the amount of change in the pressure sensor's detection value with a predetermined judgment threshold. However, when fuel is continuously supplied to the fuel cell, the amount of hydrogen consumed changes depending on the power generation state of the fuel cell, which in turn causes fluctuations in fuel pressure. For this reason, it is desirable to obtain an estimate of the amount of pressure fluctuation in the fuel flowing through the downstream path based on the power generation state of the fuel cell, and then diagnose a shutoff valve failure based on this estimate and the detection result of the pressure sensor.

[0009] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a fuel cell system according to a first embodiment. [Figure 2] 4 is a flowchart showing the flow of control processing executed by a diagnostic unit of the fuel cell system according to the first embodiment. [Figure 3] 4 is a flowchart showing the flow of a fault diagnosis process executed by a diagnosis unit of the fuel cell system according to the first embodiment. [Figure 4] FIG. 10 is an explanatory diagram for explaining a method for selecting a shutoff valve to be diagnosed. [Figure 5] FIG. 10 is an explanatory diagram for explaining the amount of pressure fluctuation of fuel when some of the shutoff valves are closed. [Figure 6] FIG. 4 is an explanatory diagram for explaining the relationship between the number of shutoff valves that are closed and the amount of fluctuation in fuel pressure. [Figure 7] FIG. 10 is an explanatory diagram for explaining a method for estimating the amount of pressure fluctuation of fuel when some of the shutoff valves are closed. [Figure 8] FIG. 10 is an explanatory diagram for explaining a method for measuring the amount of pressure fluctuation of the fuel when some of the shutoff valves are closed. [Figure 9] 10 is a flowchart showing the flow of control processing executed by a diagnostic unit of a fuel cell system according to a second embodiment. [Figure 10] 10 is a flowchart showing the flow of control processing executed by a diagnostic unit of a fuel cell system according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, parts that are the same as or equivalent to those described in the preceding embodiments will be given the same reference numerals, and their description may be omitted. Furthermore, in the embodiments, when only some of the components are described, the components described in the preceding embodiments can be applied to the remaining components. The following embodiments can be partially combined with each other, even if not specifically stated, as long as there is no particular problem with the combination.

[0012] (First embodiment) This embodiment will be described with reference to Figs. 1 to 8. In this embodiment, an example will be described in which a fuel cell system 1 of the present disclosure is applied to a fuel cell vehicle (so-called FCV). The fuel cell system 1 of this embodiment is configured as a system that generates electric power to be supplied to a traction motor that drives the fuel cell vehicle. Specifically, the fuel cell system 1 includes a fuel cell 10, an air supply unit 20, a fuel supply unit 30, an air discharge unit 40, a fuel discharge unit 50, and a control unit 100.

[0013] The fuel cell 10 outputs electrical energy through an electrochemical reaction between air as an oxidant and hydrogen as a reducing agent. Specifically, the fuel cell 10 is configured as a cell stack CS in which multiple solid polymer battery cells C are stacked. The solid polymer battery cells C are also called PEFCs (short for Polymer Electrolyte Fuel Cells).

[0014] The battery cell C is composed of an electrolyte membrane, a hydrogen electrode constituting the anode, an oxygen electrode constituting the cathode, and separators forming air and fuel flow paths. The battery cell C outputs electrical energy to an external circuit (not shown) through the electrochemical reaction of hydrogen and oxygen shown in the following reaction formulas F1 and F2. The power output from each battery cell C is supplied to a load device or battery via a power converter PW such as an inverter.

[0015] (Fuel electrode) 2H2→4H+ +4e - …(F1)

[0016] (Oxygen electrode) 4H + +O2+4e - →2H2O …(F2) An air supply unit 20 including an air flow path and a fuel supply unit 30 including a fuel flow path are connected to the fuel cell 10. Air serving as an oxidizing agent and fuel containing hydrogen serving as a reducing agent are supplied to the fuel cell 10 via the air supply unit 20 and the fuel supply unit 30.

[0017] The air supply unit 20 uses atmospheric air as a supply source and includes an air supply path 21 that guides the air from the supply source to the fuel cell 10, and a blower 22 arranged in the air supply path 21. The blower 22 is an electric device that controls the amount of air supplied to the fuel cell 10 as an oxidant, and its operation is controlled in response to a control signal from the control unit 100. The air supply path 21 is composed of piping and the like.

[0018] The fuel supply unit 30 uses a hydrogen storage device 31 as a fuel supply source and supplies hydrogen from the supply source to the fuel cell 10 via a fuel supply path 32. The fuel supply unit 30 is configured to include the hydrogen storage device 31, a fuel supply path 32 that guides hydrogen from the hydrogen storage device 31 to the fuel cell 10, and a valve device 33 provided in the fuel supply path 32.

[0019] The hydrogen storage device 31 is composed of a plurality of fuel tanks 311 in which fuel containing hydrogen is stored. The fuel is stored in a compressed state in each fuel tank 311. Each fuel tank 311 has a structure with excellent gas barrier properties to prevent hydrogen permeation.

[0020] The fuel supply path 32 is configured with piping or the like so that the fuel stored in each fuel tank 311 can be supplied to the fuel cell 10. The fuel supply path 32 includes a plurality of upstream paths 321 connected to each of the plurality of fuel tanks 311, a collecting section 322 that collects the plurality of upstream paths 321, and a downstream path 323 that connects the collecting section 322 to the fuel cell 10. The number of upstream paths 321 provided is the same as the number of fuel tanks 311. The collecting section 322 is configured with a multi-way joint that has the same number of input ports as the upstream paths 321 and one output port. One end of the downstream path 323 is connected to the output port of the collecting section 322, and the other end is connected to the fuel cell 10.

[0021] The valve device 33 is a device that opens and closes the multiple upstream paths 321. The valve device 33 is configured to include multiple shutoff valves 331 that are provided in the multiple upstream paths 321, respectively. The shutoff valves 331 are configured, for example, as solenoid valves that open and close the valves by changing the state of conduction. The state of conduction to the shutoff valves 331 is controlled in response to a control signal from the control unit 100. Note that a normally closed valve is adopted as the shutoff valve 331 in this embodiment.

[0022] The air discharge unit 40 includes an air discharge path 41 that discharges the air that has passed through the air electrode side of the fuel cell 10 from the fuel cell 10 as off-gas, and a pressure regulating valve 42 that adjusts the pressure on the air electrode side of the fuel cell 10. The air discharge path 41 is formed of piping or the like.

[0023] The fuel discharge unit 50 includes a fuel discharge path 51 that discharges the fuel that has passed through the fuel electrode side of the fuel cell 10 as off-gas from the fuel cell 10, and an exhaust valve 52 that purges the off-gas on the fuel electrode side of the fuel cell 10. The fuel discharge path 51 is formed of piping or the like.

[0024] Here, in the fuel cell 10, water produced by the electrochemical reaction between hydrogen and oxygen is discharged together with the off-gas. The off-gas discharged from the fuel electrode side of the fuel cell 10 may contain unreacted hydrogen. For this reason, the fuel cell system 1 is designed so that the hydrogen concentration in the off-gas is reduced by recycling or by using a catalyst before it is discharged to the outside.

[0025] Next, we will explain the control unit 100, which is an electronic control device of the fuel cell system 1. The control unit 100 is configured by a computer including a processor and memory. The memory includes not only ROM and RAM but also auxiliary storage devices, etc. The memory is a non-transitory tangible storage medium.

[0026] A group of sensors including a current sensor 101 that detects the output current from the fuel cell 10, a voltage sensor 102 that detects the potential difference across the fuel cell 10, and a pressure sensor 103 that detects the pressure of the fuel supplied to the fuel cell 10, as well as an operation panel (not shown) are connected to the input side of the control unit 100. The pressure sensor 103 is provided downstream of the shutoff valve 331. In this embodiment, the pressure sensor 103 is provided in the downstream path 323 of the fuel supply path 32. The pressure sensor 103 may also be provided in the collection unit 322, for example.

[0027] The output side of the control unit 100 is connected to various devices of the fuel cell system 1, such as the fuel cell 10, blower 22, multiple shutoff valves 331, pressure regulating valve 42, and exhaust valve 52. The control unit 100 has, as functional units, an equipment control unit 110 that controls the various devices of the fuel cell system 1 and a diagnosis unit 120 that diagnoses failures in the various devices of the fuel cell system 1. The equipment control unit 110 and the diagnosis unit 120 may be configured using common hardware or may be configured using separate hardware.

[0028] Here, in the fuel cell system 1, if some of the shutoff valves 331 are left open for some reason, there is a risk that a large amount of hydrogen will be released into the atmosphere, so it is necessary to diagnose abnormalities in each of the shutoff valves 331.

[0029] In the fuel cell system 1, when each shutoff valve 331 is closed while the fuel cell 10 is generating electricity, fuel is consumed by the fuel cell 10, causing a drop in fuel pressure in the fuel supply unit 30. On the other hand, if the fuel pressure in the fuel supply unit 30 does not drop even when all of the shutoff valves 331 are closed, it is believed that some of the shutoff valves 331 are left open for some reason. In this way, there is a strong correlation between the open / closed state of each shutoff valve 331 and the fuel pressure in the fuel supply unit 30, and it is possible to diagnose the presence or absence of an open valve malfunction in each shutoff valve 331 based on the amount of change in fuel pressure when each shutoff valve 331 is closed.

[0030] However, if an attempt is made to perform a failure diagnosis on the valve device 33 with each shutoff valve 331 closed, the supply of fuel to the fuel cell 10 will be stopped, and the fuel cell 10 will be unable to continue generating power.

[0031] In light of these, the fuel cell system 1 of this embodiment is configured to be able to perform failure diagnosis of the shutoff valves 331 that open and close the fuel supply path while continuing power generation by the fuel cell 10. That is, the fuel cell system 1 of this embodiment is configured to diagnose failure of some of the shutoff valves 331 by the diagnosing unit 120 while some of the shutoff valves 331 are closed and the remaining shutoff valves 331 are open during power generation by the fuel cell 10. Specifically, the diagnosing unit 120 obtains an estimated amount of pressure fluctuation of the fuel flowing through the downstream path 323 from the power generation state of the fuel cell 10 in an operating state where some of the shutoff valves 331 are closed and the shutoff valves 331 are controlled so that fuel supply to the fuel cell 10 continues. Then, the diagnosing unit 120 diagnoses failure of the shutoff valves 331 based on the estimated amount of pressure fluctuation of the fuel flowing through the downstream path 323 and the detection result of the pressure sensor 103.

[0032] The control processing executed by the diagnosis unit 120 of the fuel cell system 1 will be described below with reference to Fig. 2 etc. The control routine shown in Fig. 2 is executed by the diagnosis unit 120 periodically or irregularly when the start switch of the fuel cell vehicle is turned on.

[0033] 2, the diagnosis unit 120 first determines in step S10 whether the fuel cell 10 is generating power. The diagnosis unit 120 determines whether the fuel cell 10 is generating power based on, for example, the sensor output of the current sensor 101 and the sensor output of the voltage sensor 102.

[0034] If the fuel cell 10 is generating electricity, the diagnosis unit 120 executes a fault diagnosis process in step S20 to diagnose whether or not the shutoff valve 331 is faulty, and if the fuel cell 10 is not generating electricity, the diagnosis unit 120 exits this process. Details of the fault diagnosis process executed by the diagnosis unit 120 will be described with reference to the flowchart in Figure 3.

[0035] As shown in FIG. 3, in step S100, the diagnosing unit 120 selects a shutoff valve 331 to be diagnosed from among the multiple shutoff valves 331. As shown in FIG. 4, the diagnosing unit 120 of this embodiment selects a shutoff valve 331 to be diagnosed based on the required amount of power generation required for the fuel cell 10. Specifically, the diagnosing unit 120 calculates the required supply amount of fuel required for the fuel cell 10 from the required amount of power generation. The diagnosing unit 120 then selects from the multiple shutoff valves 331 a shutoff valve 331 that can ensure the required supply amount even when closed. At this time, the diagnosing unit 120 selects one or more shutoff valves 331 as the diagnosis target. It is desirable that the diagnosing unit 120 preferentially selects, from among the multiple shutoff valves 331, a shutoff valve 331 that has not been recently diagnosed for a fault.

[0036] Next, in step S110, the diagnosis unit 120 forcibly closes the shutoff valve 331 to be diagnosed. When the shutoff valve 331 operates normally, as shown in the upper part of Fig. 5, when a command to close the shutoff valve 331 is output, the fuel pressure decreases over time as shown in the middle and lower parts of Fig. 5. The amount of fuel pressure decrease at this time increases as the number of shutoff valves 331 to be closed increases, for example, as shown in Fig. 6.

[0037] On the other hand, when the shutoff valve 331 is not operating normally and remains open, even if a command to close the shutoff valve 331 is output, the fuel pressure does not decrease as it does when the shutoff valve 331 is operating normally, as indicated by the dashed line in the lower part of Fig. 5. Note that in Fig. 5, when a command to close the shutoff valve 331 is output to the abnormal shutoff valve 331, the fuel pressure decreases over time, but the behavior of the fuel pressure is not limited to this, and there are also cases where, for example, the fuel pressure does not change even over time.

[0038] Next, in step S120, the diagnosis unit 120 acquires the output value of the pressure sensor 103 and starts counting the timer. The diagnosis unit 120 stores the output value of the pressure sensor 103 in memory as the initial pressure immediately after the shutoff valve 331 is closed.

[0039] Next, in step S130, the diagnosis unit 120 obtains an estimate of the amount of fuel pressure fluctuation when some of the shutoff valves 331 are closed. For example, the diagnosis unit 120 obtains the amount of power generated by the fuel cell 10, and then obtains the amount of fuel consumed by the fuel cell 10 from that amount of power generated. The diagnosis unit 120 also obtains the total volume of the fuel supply unit 30 connected to the fuel cell 10 from the volume of the fuel supply path 32 and fuel tank 311 that communicate with the fuel cell 10 (i.e., the volume of the fuel tank 311 upstream of the open shutoff valves 331). Then, as shown in Fig. 7, the diagnosis unit 120 obtains the amount of pressure fluctuation estimated from the amount of fuel consumed and the total volume of the fuel supply unit 30 connected to the fuel cell 10.

[0040] Next, in step S140, the diagnosis unit 120 determines whether a predetermined time has elapsed since the timer started counting. If the predetermined time has not elapsed, the diagnosis unit 120 returns to step S130, and if the predetermined time has elapsed, the diagnosis unit 120 proceeds to step S150. In step S150, the diagnosis unit 120 acquires the output value of the pressure sensor 103 and resets the timer count. The diagnosis unit 120 stores the output value of the pressure sensor 103 in memory as a comparison pressure after the predetermined time has elapsed since the shutoff valve 331 was closed.

[0041] Next, in step S160, the diagnosis unit 120 determines the amount of pressure fluctuation of the fuel flowing through the downstream path 323 as a measurement amount based on the detection results of the pressure sensor 103 during a period from when some of the shutoff valves 331 are closed until a predetermined time has elapsed. The diagnosis unit 120 determines the measurement amount of the pressure fluctuation of the fuel based on the initial pressure and the comparison pressure, as shown in Fig. 8. The diagnosis unit 120 determines the pressure difference between the initial pressure and the comparison pressure as the measurement amount.

[0042] Next, in step S170, the diagnosis unit 120 compares the measured amount of fuel pressure fluctuation with the estimated amount. The diagnosis unit 120 determines whether the difference between the measured amount of fuel pressure fluctuation and the estimated amount is smaller than a predetermined reference amount. In other words, the diagnosis unit 120 determines whether the value obtained by subtracting the measured amount from the estimated amount of fuel pressure fluctuation is smaller than the reference amount. Note that the reference amount is set to, for example, the amount of fuel pressure fluctuation expected when the shutoff valve 331 to be diagnosed is closed.

[0043] If the difference between the estimated amount and the measured amount is equal to or greater than a predetermined reference amount, it is considered that the shutoff valve 331 to be diagnosed is not closed. For this reason, in step S180, the diagnosing unit 120 diagnoses that the shutoff valve 331 to be diagnosed has an open valve malfunction, meaning that the shutoff valve 331 cannot be closed. Then, in step S190, the diagnosing unit 120 notifies the user of the open valve malfunction of the shutoff valve 331. Examples of ways to notify the user include turning on a warning light or outputting a warning sound from a speaker.

[0044] On the other hand, if the difference between the measured amount and the estimated amount is smaller than the predetermined reference amount, it is considered that the shutoff valve 331 to be diagnosed is closed normally. Therefore, in step S200, the diagnosing unit 120 diagnoses that the shutoff valve 331 to be diagnosed does not have an open valve malfunction.

[0045] Next, in step S210, the diagnosing unit 120 determines whether or not the failure diagnosis has been completed for all of the shutoff valves 331. If the failure diagnosis has not been completed for all of the shutoff valves 331, the diagnosing unit 120 returns to step S100 and selects a shutoff valve 331 to be diagnosed from among the other shutoff valves 331 for which the failure diagnosis has not been performed. On the other hand, if the failure diagnosis has been completed for all of the shutoff valves 331, the diagnosing unit 120 executes post-processing in step S220, such as returning the shutoff valve 331 to be diagnosed to an open state, and then exits this process.

[0046] The fuel cell system 1 described above diagnoses a failure of the shutoff valves 331 in an operating state in which some of the multiple shutoff valves 331 are closed and the shutoff valves 331 are controlled so as to continue supplying fuel to the fuel cell 10. The fuel cell system 1 of this embodiment calculates an estimate of the pressure fluctuation amount of the fuel flowing through the downstream path 323 of the fuel supply path 32 based on the power generation state of the fuel cell 10, and performs a failure diagnosis of the shutoff valves 331 based on this estimate and the detection result of the pressure sensor 103. In this way, if the configuration is such that a failure of the shutoff valves 331 is diagnosed with some of the multiple shutoff valves 331 provided in the multiple fuel tanks 311 being closed, it is possible to diagnose a failure of the shutoff valves 331 in a state in which the supply of fuel to the fuel cell 10 is continued.

[0047] Here, it is conceivable that a failure diagnosis of the shutoff valve 331 is performed by comparing the amount of change in the detection value of the pressure sensor 103 with a predetermined judgment threshold. However, when fuel is continuously supplied to the fuel cell 10, the amount of hydrogen consumed changes depending on the power generation state of the fuel cell 10, which in turn causes fluctuations in the fuel pressure. For this reason, as in the present invention, it is desirable to obtain an estimate of the amount of pressure fluctuation of the fuel flowing through the downstream path 323 based on the power generation state of the fuel cell 10, and to diagnose a failure of the shutoff valve 331 based on this estimate and the detection result of the pressure sensor 103.

[0048] The fuel cell system 1 of this embodiment also has the following features. (1) When diagnosing a fault in the shutoff valve 331, the diagnosing unit 120 obtains an estimate of the amount of fuel pressure fluctuation based on the amount of fuel consumed in the fuel cell 10 and the volume of the fuel supply path 32 and fuel tank 311 that communicate with the fuel cell 10. When fuel is consumed in the fuel cell 10, the pressure in the fuel cell 10 fluctuates, and therefore the amount of fuel pressure fluctuation is strongly correlated with the amount of fuel consumed in the fuel cell 10. For this reason, the amount of fuel pressure fluctuation can be accurately estimated based on the amount of fuel consumed in the fuel cell 10 and the volume of all parts that communicate with the fuel cell 10.

[0049] (2) The diagnosing unit 120 obtains, as a measured amount, the amount of pressure fluctuation of the fuel flowing through the downstream path 323 based on the detection results of the pressure sensor 103 during a period from when some of the shutoff valves 331 are closed until a predetermined time has elapsed. Then, the diagnosing unit 120 compares the measured amount with the estimated amount to diagnose a failure of the shutoff valves 331. This makes it possible to obtain the actual amount of pressure fluctuation of the fuel when some of the shutoff valves 331 are closed.

[0050] (3) When the difference between the measured amount and the estimated amount is equal to or greater than the reference amount, the diagnosis unit 120 determines that an open malfunction has occurred, in which the open state of the shutoff valve 331 is maintained. This makes it possible to appropriately determine whether an open malfunction of the shutoff valve 331 has occurred.

[0051] (4) When the difference between the measured amount and the estimated amount is smaller than the reference amount, the diagnosing unit 120 determines that an open valve malfunction has not occurred in the shutoff valve 331. This makes it possible to appropriately determine whether the shutoff valve 331 has an open valve malfunction.

[0052] (5) When it is determined that no open valve malfunction has occurred in the malfunction diagnosis of some of the shutoff valves 331, the diagnosing unit 120 closes the other shutoff valves 331 and diagnoses the malfunction of the other shutoff valves 331. This makes it possible to perform malfunction diagnosis on each of the multiple shutoff valves 331. When diagnosing the malfunction of the other shutoff valves 331, the diagnosing unit 120 sets at least one of the part of the shutoff valves 331 for which malfunction diagnosis was previously performed to an open state.

[0053] (6) The diagnosing unit 120 selects one of the multiple shutoff valves 331 to be closed so as to ensure the necessary supply amount of fuel required by the fuel cell 10, and diagnoses a malfunction by closing the selected shutoff valve 331. This makes it possible to appropriately determine an open malfunction of the shutoff valve 331 while minimizing the impact on the fuel cell system 1 of the opening and closing of the shutoff valve 331.

[0054] (Second embodiment) Next, a second embodiment will be described with reference to Fig. 9. In this embodiment, differences from the first embodiment will be mainly described.

[0055] When the fuel pressure in the portion of the fuel supply path 32 that communicates with the fuel cell 10 is low, the amount of pressure fluctuation caused by the opening and closing of the shutoff valve 331 is also small. A small amount of pressure fluctuation caused by the opening and closing of the shutoff valve 331 can be a factor in reducing the accuracy of failure diagnosis of the shutoff valve 331. Furthermore, when an attempt is made to perform failure diagnosis of the shutoff valve 331 when the fuel pressure in the portion that communicates with the fuel cell 10 is low, there is a risk that it may become difficult to properly supply fuel to the fuel cell 10.

[0056] In contrast to these, the diagnosis unit 120 of this embodiment is configured not to diagnose a failure of the shutoff valve 331 when the detection value of the pressure sensor 103 is equal to or lower than a predetermined reference pressure. This processing will be described with reference to Fig. 9. The control routine shown in Fig. 9 is executed by the diagnosis unit 120 periodically or irregularly when the start switch of the fuel cell vehicle is on.

[0057] 9, the diagnosis unit 120 first determines in step S10A whether or not the fuel cell 10 is generating power. If the fuel cell 10 is generating power, the diagnosis unit 120 proceeds to step S20A, and if the fuel cell 10 is not generating power, the diagnosis unit 120 exits this process. In step S20A, the diagnosis unit 120 determines whether or not the fuel pressure detected by the pressure sensor 103 is equal to or lower than a predetermined reference pressure. The reference pressure is a pressure at which a fault diagnosis of the shutoff valve 331 can be performed, and is determined through simulation, experiment, etc.

[0058] If the fuel pressure exceeds the predetermined reference pressure, the diagnosing unit 120 executes a fault diagnosis process in step S30A to diagnose whether or not there is a fault in the shutoff valve 331. This fault diagnosis process is the same as in the first embodiment, and therefore a description thereof will be omitted.

[0059] On the other hand, if the fuel pressure is equal to or lower than the predetermined reference pressure, the diagnosis unit 120 skips step S30A and exits this process. In other words, if the detection value of the pressure sensor 103 is equal to or lower than the predetermined reference pressure, the diagnosis unit 120 does not perform a failure diagnosis of the shutoff valve 331.

[0060] The rest of the configuration is the same as that of the first embodiment. The fuel cell system 1 of this embodiment can obtain the same effects as those of the first embodiment that are achieved by a configuration common to or equivalent to that of the first embodiment.

[0061] The fuel cell system 1 of this embodiment also has the following features. (1) In this embodiment, the diagnosing unit 120 does not diagnose a failure of the shutoff valve 331 when the detection value of the pressure sensor 103 is equal to or lower than a predetermined reference pressure. As described above, when the fuel pressure detected by the pressure sensor 103 is small, the amount of pressure fluctuation caused by the opening and closing of the shutoff valve 331 is also small. For this reason, when the detection value of the pressure sensor 103 is small, it is desirable not to diagnose a failure of the shutoff valve 331, as in this embodiment.

[0062] (Third embodiment) Next, a third embodiment will be described with reference to Fig. 10. In this embodiment, differences from the first and second embodiments will be mainly described.

[0063] When the amount of power generation by the fuel cell 10 fluctuates greatly per unit time, the amount of fuel consumed by the fuel cell 10 also fluctuates. For this reason, if a fault diagnosis of the shutoff valve 331 is performed when the amount of power generation by the fuel cell 10 fluctuates greatly, there is a concern that the opening and closing of the shutoff valve 331 will have a significant impact on the fuel cell system 1. Furthermore, when the amount of power generation by the fuel cell 10 fluctuates greatly, there is a risk that the accuracy of estimating the amount of fuel pressure fluctuation when some of the shutoff valves 331 are closed will decrease.

[0064] In contrast to these, the diagnosis unit 120 of this embodiment is configured to diagnose a failure in the shutoff valve 331 when the amount of fluctuation in the amount of power generated by the fuel cell 10 is within a predetermined range. This processing will be explained with reference to Fig. 10. The control routine shown in Fig. 10 is executed by the diagnosis unit 120 periodically or irregularly when the start switch of the fuel cell vehicle is on.

[0065] 10, the diagnostic unit 120 first determines in step S10B whether the fuel cell 10 is generating power. If the fuel cell 10 is generating power, the diagnostic unit 120 proceeds to step S20B, and if the fuel cell 10 is not generating power, the diagnostic unit 120 exits this process. In step S20B, the diagnostic unit 120 determines whether the fuel pressure detected by the pressure sensor 103 is equal to or lower than a predetermined reference pressure.

[0066] If the fuel pressure exceeds a predetermined reference pressure, the diagnostic unit 120 proceeds to step S30B, and if the fuel pressure is equal to or less than the predetermined reference pressure, the diagnostic unit 120 exits this process. In step S30B, the diagnostic unit 120 further determines whether the fluctuation in the amount of power generated by the fuel cell 10 is within a predetermined range. The amount of power generated by the fuel cell 10 can be determined based on the sensor output of the current sensor 101 and the sensor output of the voltage sensor 102. The predetermined range is set, for example, based on the fluctuation range of the amount of power generated when the fuel cell 10 is in a steady operating state.

[0067] If the fluctuation amount of the power generation amount of the fuel cell 10 is within a predetermined range, the diagnosing unit 120 executes a fault diagnosis process in step S40B to diagnose whether or not there is a fault in the shutoff valve 331. This fault diagnosis process is the same as in the first embodiment, and therefore a description thereof will be omitted.

[0068] On the other hand, if the amount of fluctuation in the amount of power generated by the fuel cell 10 is outside the predetermined range, the diagnosing unit 120 returns to the determination process of step S30B. In other words, if the amount of fluctuation in the amount of power generated by the fuel cell 10 is outside the predetermined range, the diagnosing unit 120 waits until the amount of fluctuation in the amount of power generated by the fuel cell 10 falls within the predetermined range, and does not perform a fault diagnosis on the shutoff valve 331.

[0069] The rest of the configuration is the same as that of the first and second embodiments. The fuel cell system 1 of this embodiment can obtain the same effects as those of the first and second embodiments, which are achieved by a configuration common to or equivalent to those of the first and second embodiments.

[0070] The fuel cell system 1 of this embodiment also has the following features. (1) In this embodiment, the diagnosing unit 120 performs a fault diagnosis on the shutoff valve 331 when the fluctuation amount of the power generation amount of the fuel cell 10 is within a predetermined range. This makes it possible to suppress the influence on the fuel cell system 1 caused by the opening and closing of the shutoff valve 331.

[0071] (Modification of the third embodiment) As in the third embodiment, it is desirable not to diagnose a malfunction of the shutoff valve 331 when the detection value of the pressure sensor 103 is equal to or lower than a predetermined reference pressure, but this is not limiting. The diagnosing unit 120 may also be configured to diagnose a malfunction of the shutoff valve 331 when the detection value of the pressure sensor 103 is equal to or lower than a predetermined reference pressure.

[0072] (Other embodiments) Representative embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments and can be modified in various ways, for example, as follows.

[0073] The diagnosis unit 120 in the above embodiment is configured to obtain an estimated amount of fuel pressure fluctuation based on the amount of fuel consumed in the fuel cell 10 and the volumes of the fuel supply path 32 and fuel tank 311 that communicate with the fuel cell 10, but is not limited to this. The diagnosis unit 120 may also obtain an estimated amount of fuel pressure fluctuation using a method different from that described above.

[0074] The diagnosing unit 120 in the above-described embodiment is configured to determine the pressure fluctuation amount of the fuel flowing through the downstream path 323 as a measured amount based on the detection results of the pressure sensor 103 during a period from when some of the shutoff valves 331 are closed until a predetermined time has elapsed, but is not limited to this. The diagnosing unit 120 may also determine the measured amount of the pressure fluctuation amount of the fuel using a method different from that described above.

[0075] The diagnosing unit 120 in the above-described embodiment is configured to determine that an open circuit malfunction has occurred in which the open state of the shutoff valve 331 is maintained when the difference between the measured amount and the estimated amount is equal to or greater than a reference amount, but is not limited to this. For example, the diagnosing unit 120 may be configured to determine that an open circuit malfunction has occurred in which the open state of the shutoff valve 331 is maintained when the estimated amount is equal to or greater than a certain amount and the difference between the measured amount and the estimated amount is equal to or greater than a reference amount.

[0076] The diagnosing unit 120 in the above-described embodiment is configured to determine that an open valve malfunction has not occurred in the shutoff valve 331 when the difference between the measured amount and the estimated amount is smaller than the reference amount, but is not limited to this. For example, the diagnosing unit 120 may be configured to determine that an open valve malfunction has occurred in which the open state of the shutoff valve 331 is maintained when the estimated amount is equal to or greater than a certain amount and the difference between the measured amount and the estimated amount is smaller than the reference amount.

[0077] When no open failure has occurred in some of the shutoff valves 331, it is desirable for the diagnosing unit 120 to close the other shutoff valves 331 and diagnose the failure of the other shutoff valves 331, but this is not necessarily required.

[0078] Furthermore, it is desirable that the diagnosing unit 120 selects one of the multiple shutoff valves 331 to be closed so as to ensure the necessary supply of fuel required by the fuel cell 10, and diagnoses a failure of the selected shutoff valve 331, but this is not necessarily required.

[0079] In the above embodiment, an example has been described in which the fuel cell system 1 of the present disclosure is applied to a fuel cell vehicle, which is a mobile body, but the fuel cell system 1 can also be applied to mobile bodies such as ships and airplanes, stationary power generation devices, etc. Furthermore, the fuel cell 10 may be one other than a PEFC.

[0080] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle.

[0081] In the above-described embodiments, when numerical values ​​such as the number, values, amounts, ranges, etc. of components of the embodiments are mentioned, they are not limited to the specific numbers unless they are specifically stated as essential or are clearly limited to a specific number in principle.

[0082] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., the shapes, positional relationships, etc. are not limited to those unless otherwise specified or when they are limited in principle to specific shapes, positional relationships, etc.

[0083] The controller and method of the present disclosure may be implemented on a special-purpose computer by configuring a processor and memory programmed to perform one or more functions embodied in a computer program. The controller and method of the present disclosure may be implemented on a special-purpose computer by configuring a processor with one or more dedicated hardware logic circuits. The controller and method of the present disclosure may be implemented on one or more special-purpose computers configured with a processor and memory programmed to perform one or more functions in combination with a processor configured with one or more hardware logic circuits. The computer program may also be stored on a computer-readable non-transitory tangible storage medium as instructions executed by a computer. [Explanation of symbols]

[0084] 1. Fuel cell system 10 fuel cell 103 Pressure Sensor 120 Diagnostic Department 31 Fuel tank 32 Fuel supply route 321 Upstream Route 322 Assembly area 323 Downstream Route

Claims

1. 1. A fuel cell system, comprising: a fuel cell (10) that outputs electrical energy by an electrochemical reaction between a fuel containing hydrogen and oxygen; a plurality of fuel tanks (311) in which fuel including hydrogen is stored; a fuel supply path (32) including a plurality of upstream paths (321) connected to the plurality of fuel tanks, respectively, a collection section (322) that collects the plurality of upstream paths, and a downstream path (323) that connects the collection section and the fuel cell; a plurality of shutoff valves (331) provided in the plurality of upstream paths, respectively; a pressure sensor (103) for detecting the pressure of the fuel flowing through the downstream path; a diagnosis unit (120) that diagnoses a failure of the shutoff valve, the diagnosing unit, in an operating state in which some of the plurality of shutoff valves are closed and the shutoff valves are controlled so as to continue supplying fuel to the fuel cell, calculates an estimated amount of pressure fluctuation of the fuel flowing through the downstream path based on a power generation state of the fuel cell, and diagnoses a failure of the shutoff valve based on the estimated amount and the detection result of the pressure sensor.

2. 2. The fuel cell system according to claim 1, wherein the diagnosing unit determines the estimated amount based on the amount of fuel consumed by the fuel cell and the volumes of the fuel supply path and the fuel tank that communicate with the fuel cell in the operating state.

3. 3. The fuel cell system according to claim 1, wherein the diagnosing unit determines a pressure fluctuation amount of the fuel flowing through the downstream path as a measured amount based on detection results of the pressure sensor during a period from when some of the shutoff valves are closed until a predetermined time has elapsed, and compares the measured amount with the estimated amount to diagnose a failure of the shutoff valves.

4. 4. The fuel cell system according to claim 3, wherein the diagnosing unit determines that an open circuit failure has occurred in which the shutoff valve remains open when the difference between the measured quantity and the estimated quantity is equal to or greater than a predetermined reference quantity.

5. 4. The fuel cell system according to claim 3, wherein the diagnosing unit determines that the open malfunction of the shutoff valve has not occurred when the difference between the measured amount and the estimated amount is smaller than a reference amount.

6. 6. The fuel cell system according to claim 5, wherein, when it is determined in the failure diagnosis of some of the shutoff valves that the open valve failure has not occurred, the diagnosing unit sets at least one of some of the shutoff valves to the open state and sets other shutoff valves other than some of the shutoff valves to the closed state, and diagnoses the other shutoff valves for a failure.

7. 3. The fuel cell system according to claim 1, wherein the diagnosing unit selects one of the plurality of shutoff valves to be closed so as to ensure a necessary supply amount of fuel required by the fuel cell, and diagnoses a fault by closing the selected shutoff valve.

8. 3. The fuel cell system according to claim 1, wherein the diagnosing unit diagnoses a fault in the shutoff valve when a fluctuation in the amount of power generated by the fuel cell falls within a predetermined range.

9. 3. The fuel cell system according to claim 1, wherein the diagnosing unit does not diagnose a failure of the shutoff valve when the detected value of the pressure sensor is equal to or lower than a predetermined reference pressure.

Images