Fuel cell system

Abstract

A fuel cell system (1) without DCDC converter is provided with a FC (11), a storage battery (12), an inverter (13), a hydrogen system (21), an air system (22), a FC relay (18) provided between the FC (11) and the inverter (13), a storage battery relay (19) provided between the storage battery (12) and the inverter (13), and a control device (20) which controls the hydrogen system (21), the air system (22), the FC relay (18) and the storage battery relay (19). At the time of system start, the control device (20) starts supplying hydrogen from the hydrogen system (21) to the FC (11) and supplying air from the air system (22) to the FC (11) after connecting both relays (18, 19).

Description

Technical Field

[0001] The technology disclosed in this specification relates to a fuel cell system having a fuel cell that receives a supply of fuel and oxidant to generate electricity. Background Technology

[0002] Conventionally, such technology includes, for example, the "air-cooled fuel cell system" described in Patent Document 1. This system comprises: a fuel cell that receives a supply of fuel and oxidant to generate electricity; a battery that is charged with the power from the fuel cell; a load device that is driven by the power from the fuel cell or the battery; a fuel supply unit that supplies fuel to the fuel cell; and an oxidant supply unit that supplies oxidant to the fuel cell. This system is configured as a simple fuel cell system without a DC-DC converter. The system controls the state of charge of the battery by intermittently stopping the oxidant supply (suppressing FC current) by either generating electricity from the oxidant or by closing the oxidant valve. Therefore, in this system, oxidant valves are provided at the cathode side inlet and outlet of the fuel cell to intermittently stop the oxidant supply when oxidant is insufficient.

[0003] Here, a DC-DC converter is a device that converts DC to DC, performing DC-DC conversion on the voltage used in the system.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2022-185247 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] Furthermore, in the fuel cell system described in Patent Document 1, it can be assumed that a relay is installed between the load device and the fuel cell or between the load device and the battery. The relay is disconnected when the system stops and connected when the system starts. In this case, if fuel and oxidant are supplied to the fuel cell before the relay is connected when the system starts, a high voltage will be applied rapidly. As a result, the fuel cell may deteriorate. In addition, if fuel remains in the fuel cell before the relay is disconnected when the system stops, a high current will flow through the fuel cell and the relay when the system restarts, and the fuel cell and the relay may deteriorate due to this high current.

[0009] This disclosure is made in view of the above circumstances, and its first objective is to prevent the rapid application of a high voltage to the fuel cell during startup of a fuel cell system in which a relay is provided between the load device and the fuel cell, and between the load device and the battery, thereby suppressing the degradation of the fuel cell caused by the high voltage. A second objective of this disclosure is, in addition to the first objective, to prevent the flow of a high current in the fuel cell and the relay during system restart due to residual fuel in the fuel cell when the fuel cell system is stopped, thereby suppressing the degradation of the fuel cell and the relay caused by such a high current.

[0010] Solution for solving the problem

[0011] (1) In order to achieve the first objective mentioned above, one aspect of the technology disclosed in this application is that, in a fuel cell system having a fuel cell that receives a supply of fuel and oxidant to generate electricity, and without a DC-DC converter, i.e., a DCDC converter, the system comprises: a battery that is charged with the power of the fuel cell; a load device that is driven by the power of the fuel cell or the battery; a fuel supply device for supplying fuel to the fuel cell; an oxidant supply device for supplying oxidant to the fuel cell; at least one of a first relay and a second relay, wherein the first relay is used to switch the connection and disconnection of the wiring between the fuel cell and the load device, and the second relay is used to switch the connection and disconnection of the wiring between the battery and the load device; and a control device for controlling the fuel supply device and the oxidant supply device, and controlling at least one of the first relay and the second relay, wherein, when the fuel cell system is started, the control device starts supplying fuel from the fuel supply device to the fuel cell and supplying oxidant from the oxidant supply device to the fuel cell after connecting at least one of the first relay and the second relay.

[0012] According to the structure described in (1) above, when the fuel cell system without a DC-DC converter is started, fuel is supplied to the fuel cell from the fuel supply device and oxidant is supplied to the fuel cell from the oxidant supply device after at least one of the first and second relays is connected. Therefore, when at least one of the first and second relays is connected when the fuel cell system is started, the voltage applied to the fuel cell is suppressed to the same voltage as the battery.

[0013] (2) In order to achieve the first objective mentioned above, the structure of (1) above preferably further includes: a pressure sensor for measuring the pressure of fuel supplied to the fuel cell; an exhaust and drainage passage for the flow of exhaust and drainage from the fuel cell; and an exhaust and drainage valve for opening and closing the exhaust and drainage passage. When the fuel cell system is started, the control device opens the exhaust and drainage valve for a specified time before connecting at least one of the first relay and the second relay, provided that the measured value of the pressure sensor is above a specified pressure that requires depressurization of the exhaust and drainage passage.

[0014] According to the structure described in (2) above, in addition to the function of the structure described in (1) above, when the fuel cell system is started, before connecting at least one of the first relay and the second relay, the exhaust drain valve is opened for a predetermined time if the pressure of the fuel supplied to the fuel cell reaches or exceeds a predetermined pressure that requires depressurization of the exhaust drain passage. Therefore, before the fuel cell generates electricity, the fuel remaining in the fuel cell, etc., is discharged into the exhaust drain passage.

[0015] (3) In order to achieve the second objective mentioned above, in the structure of (2) above, it is preferable that when the fuel cell system stops, after the control device controls the pressure of the fuel supplied from the fuel supply device to the fuel cell to the stop pressure and stops the supply of oxidant from the oxidant supply device to the fuel cell, the exhaust drain valve is opened for a predetermined time and the relay in the first relay and the second relay that is in a connected state is disconnected.

[0016] According to the structure described in (3) above, in addition to the function of the structure described in (2) above, when the fuel cell system stops, the pressure of the fuel supplied from the fuel supply device to the fuel cell is controlled to a stop pressure, and the supply of oxidant from the oxidant supply device to the fuel cell is stopped. Then, the exhaust drain valve is opened for a predetermined time, and the relays that are connected in the first and second relays are disconnected. Therefore, before the fuel cell stops generating electricity, the fuel remaining in the fuel cell, etc., is discharged into the exhaust drain passage.

[0017] (4) In order to achieve the first objective mentioned above, in the structure of (1) above, it is preferable that when the fuel system is started, the control device starts to supply fuel from the fuel supply device to the fuel cell and to supply oxidant from the oxidant supply device to the fuel cell after a predetermined time has elapsed after connecting at least one of the first relay and the second relay.

[0018] According to the structure described in (4) above, in addition to the function of the structure described in (1) above, when the fuel cell system is started, fuel and oxidant are supplied to the fuel cell after at least one of the first relay and the second relay is connected and a predetermined time has elapsed. Therefore, when at least one of the first relay and the second relay is connected when the fuel cell system is started, the voltage applied to the fuel cell is suppressed to the same voltage as the battery during the predetermined time period before the fuel cell begins to generate electricity.

[0019] (5) In order to achieve the second objective mentioned above, the structure of (1) above preferably also includes a pressure sensor for measuring the pressure of the fuel supplied to the fuel cell. When the fuel cell system stops, after the control device stops supplying fuel to the fuel cell from the fuel supply device and stops supplying oxidant to the fuel cell from the oxidant supply device, and the change in the measured value of the pressure sensor per unit time becomes below a predetermined value, the relay in the first relay and the second relay that is in a connected state is disconnected.

[0020] According to the structure described in (5), in addition to the function of the structure described in (1), when the fuel cell system stops, the supply of fuel from the fuel supply device to the fuel cell and the supply of oxidant from the oxidant supply device to the fuel cell are stopped. Then, after the pressure change of the fuel supplied to the fuel cell decreases, the relays that are connected in the first and second relays are disconnected. Therefore, after the fuel supply to the fuel cell is sufficiently reduced, the fuel cell stops generating electricity.

[0021] (6) In order to achieve the second objective mentioned above, the structure of (1) above preferably also includes a galvanometer for measuring the output current of the fuel cell. When the fuel cell system stops, after the control device stops supplying fuel from the fuel supply device to the fuel cell and stops supplying oxidant from the oxidant supply device to the fuel cell, the measured value of the galvanometer becomes below a predetermined value after a predetermined time, and then disconnects the relay in the first relay and the second relay that is in a connected state.

[0022] According to the structure described in (6), in addition to the function of the structure described in (1), when the fuel cell system stops, the supply of fuel from the fuel supply device to the fuel cell and the supply of oxidant from the oxidant supply device to the fuel cell are stopped. Then, after the output current of the fuel cell decreases, the relays that are connected in the first and second relays are disconnected. Therefore, after the output current of the fuel cell decreases sufficiently, the fuel cell stops generating electricity.

[0023] The effects of the invention

[0024] According to the structure described in (1) above, for a fuel cell system in which a relay is provided at least on one side between the load device and the fuel cell and between the load device and the battery, when the fuel cell system is started, it is possible to prevent the rapid application of high voltage to the fuel cell, thereby suppressing the deterioration of the fuel cell caused by high voltage.

[0025] According to the structure described in (2), in addition to the effects of the structure described in (1), when the fuel cell system is started, it is possible to prevent the generation of high current due to the reaction of fuel remaining in the fuel cell, etc., thereby suppressing the degradation of the fuel cell caused by the high current and the degradation of at least one of the first relay and the second relay caused by the high current.

[0026] According to the structure described in (3), in addition to the effects of the structure described in (2), when the fuel cell system is stopped, it is possible to prevent fuel residue in the fuel cell, etc., and to prevent high current from being generated due to the reaction of fuel residue in the fuel cell, etc. when the fuel cell system is restarted, thereby suppressing the deterioration of the fuel cell caused by the high current and the deterioration of at least one of the first relay and the second relay caused by the high current.

[0027] According to the structure described in (4), in addition to the effects of the structure described in (1), when the fuel cell system is started, it is possible to prevent the rapid application of high voltage to the fuel cell, thereby suppressing the degradation of the fuel cell caused by high voltage.

[0028] According to the structure described in (5), in addition to the effects of the structure described in (1), when the fuel cell system is stopped, it is possible to prevent fuel residue from remaining in the fuel cell, etc., and to prevent high current from being generated due to the reaction of fuel residue in the fuel cell, etc. when the fuel cell system is restarted, thereby suppressing the deterioration of the fuel cell caused by the high current and the deterioration of at least one of the first relay and the second relay caused by the high current.

[0029] According to the structure described in (6), in addition to the effects of the structure described in (1), when the fuel cell system is stopped, it is possible to prevent fuel residue in the fuel cell, etc., and to prevent high current from being generated due to the reaction of fuel residue in the fuel cell, etc. when the fuel cell system is restarted, thereby suppressing the deterioration of the fuel cell caused by the high current and the deterioration of at least one of the first relay and the second relay caused by the high current. Attached Figure Description

[0030] Figure 1 A structural diagram of a fuel cell system is shown, relating to the first embodiment.

[0031] Figure 2In the first embodiment, (A) is a graph showing an example of the relationship between FC current and FC voltage when the inverter in the fuel cell system consumes power, and (B) is a graph showing an example of the relationship between battery current and battery voltage when the inverter in the fuel cell system consumes power.

[0032] Figure 3 In the first embodiment, (A) is a graph showing an example of the relationship between FC current and FC voltage when there is no power consumption by the inverter in the fuel cell system, and (B) is a graph showing an example of the relationship between battery current and battery voltage when there is no power consumption by the inverter in the fuel cell system.

[0033] Figure 4 The first embodiment is illustrated by a flowchart showing an example of the control content during the startup of a fuel cell system.

[0034] Figure 5 The first embodiment is illustrated by a flowchart showing an example of the control content when the fuel cell system stops.

[0035] Figure 6 The second embodiment is illustrated by a flowchart showing an example of the control content during the startup of a fuel cell system.

[0036] Figure 7 The second embodiment is illustrated by a flowchart showing an example of the control content when the fuel cell system stops.

[0037] Figure 8 In the second embodiment, the behavior of various parameters related to control during startup is illustrated by timing diagrams.

[0038] Figure 9 This involves a comparative diagram, which uses timing diagrams to illustrate the behavior of various parameters related to control during startup.

[0039] Figure 10 In the second embodiment, the behavior of various parameters related to control during stop is illustrated by timing diagrams.

[0040] Figure 11 This involves a comparative approach, using timing diagrams to illustrate the behavior of various parameters related to control at the time of stop.

[0041] Figure 12 The third embodiment is illustrated by a flowchart showing an example of the control content when the fuel cell system stops. Detailed Implementation

[0042] <First Implementation Method>

[0043] The first embodiment of a fuel cell system embodied in an electric vehicle will now be described in detail with reference to the accompanying drawings.

[0044] [Regarding the structure of fuel cell systems]

[0045] exist Figure 1 The fuel cell system 1 according to this embodiment is illustrated by a schematic structural diagram. Figure 1 As shown, the fuel cell system 1 of this embodiment is configured as a DC-DC converter-free system. That is, the fuel cell system 1 includes an FC stack (hereinafter referred to as "FC") 11, a battery 12, and an inverter 13 (or motor). The fuel cell system 1 is a simple DC-DC converter-free system in which these devices 11-13 are connected in parallel and without a DC-DC converter. Here, a DC-DC converter is a device that converts DC to DC, and is a device that performs DC-DC conversion on the voltage used in the system.

[0046] The fuel cell system 1 includes a hydrogen system 21 and an air system 22. The hydrogen system 21 is an example of a "fuel supply device" of the present disclosure for supplying fuel to the FC 11. The air system 22 is an example of an "oxidant supply device" of the present disclosure for supplying oxidant to the FC 11. In this embodiment, the fuel is hydrogen (hydrogen gas), and the oxidant is air. The FC 11 is an example of a "fuel cell" of the present disclosure that receives hydrogen from the hydrogen system 21 and air from the air system 22 to generate electricity. The electricity generated by the FC 11 is supplied to a battery 12 and an inverter 13.

[0047] Battery 12 is connected to FC 11 via first wiring 14a, 14b. Power generated by FC 11 is charged to battery 12 via first wiring 14a, 14b. Battery 12 is connected to inverter 13 via first wiring 14a, 14b and second wiring 15a, 15b. Second wiring 15a is connected to first wiring 14a. Second wiring 15b is connected to first wiring 14b. Power charged to battery 12 is supplied to inverter 13 via first wiring 14a, 14b and second wiring 15a, 15b. Inverter 13 is driven by receiving power from FC 11 and / or battery 12 via first wiring 14a, 14b and second wiring 15a, 15b. Inverter 13 is an example of a "load device" of the present disclosure driven by power from FC 11 or battery 12. Near the output port of FC 11, a galvanometer 17 is provided in the first wiring 14a for measuring the “output current” of FC 11, i.e., the FC current.

[0048] An FC relay 18 is provided on the first wiring 14a between FC 11 and inverter 13 for switching the connection and disconnection of the wiring 14a. FC relay 18 is an example of the "first relay" of the present disclosure. Additionally, a battery relay 19 is provided on the first wiring 14a between battery 12 and inverter 13 for switching the connection and disconnection of the wiring 14a. Battery relay 19 is an example of the "second relay" of the present disclosure. FC relay 18 is disposed in the first wiring 14a between the connection P1 of the first wiring 14a and the second wiring 15a and the ammeter 17. Battery relay 19 is disposed in the first wiring 14a between the connection P1 of the first wiring 14a and the second wiring 15a and the battery 12. Here, each relay 18 and 19 is a component that receives electrical signals from the outside and performs circuit connection / disconnection and switching, and has a known structure.

[0049] The hydrogen system 21 is located on the anode side of the FC 11. The hydrogen system 21 includes a hydrogen supply passage 31, an exhaust and drainage passage 32, a filling passage 33, and a circulation passage 34.

[0050] Hydrogen supply passage 31 is a passage for supplying hydrogen from hydrogen tank 41, where hydrogen is stored, to FC 11. Exhaust and drainage passage 32 is a passage for discharging hydrogen (i.e., hydrogen exhaust gas) discharged from FC 11.

[0051] In addition, the hydrogen system 21 includes, in the hydrogen supply passage 31, a hydrogen valve 51, a hydrogen pressure reducing valve 52, an injector 53 and an ejector 54 in sequence from the hydrogen tank 41 side.

[0052] The filling passage 33 is a passage for filling hydrogen from the filling port 42 into the hydrogen tank 41. The circulation passage 34 is a passage that connects the exhaust drainage passage 32 (which specifically includes the gas-liquid separator 56) to the ejector 54, and is a passage for circulating hydrogen waste gas to the ejector 54.

[0053] Hydrogen valve 51 is a valve that switches the supply and cut-off of hydrogen from hydrogen tank 41 to hydrogen supply passage 31. This valve 51 is, for example, composed of multiple devices including a solenoid valve. Hydrogen pressure reducing valve 52 is a pressure regulating valve for reducing the pressure of hydrogen. This valve 52 is, for example, composed of a solenoid valve. Injector 53 is a device that injects hydrogen from hydrogen tank 41 downstream. Injector 53 is, for example, composed of a solenoid valve. Injector 53 is configured such that the opening of the injection port is adjusted by the movement of a needle valve, thereby adjusting the hydrogen injection pressure (hydrogen pressure). Ejector 54 uses the hydrogen injected from injector 53 to generate a negative pressure, which attracts hydrogen waste gas flowing in circulation passage 34, mixes the hydrogen waste gas with hydrogen, and then injects it downstream from outlet 54a.

[0054] The hydrogen system 21, in the exhaust and drainage passage 32, sequentially includes a gas-liquid separator 56 and an exhaust and drainage valve 57, starting from the FC 11 side. The gas-liquid separator 56 is an electrically operated device that separates moisture from hydrogen waste gas. The exhaust and drainage valve 57 is a valve that switches between discharging and shutting off hydrogen waste gas and moisture from the gas-liquid separator 56. This valve 57 is, for example, a solenoid valve.

[0055] In the hydrogen system 21, a pressure sensor 16 is provided in the hydrogen supply passage 31 between the ejector 54 and the FC 11. The pressure sensor 16 is used to measure the pressure of the hydrogen ejected from the outlet 54a of the ejector 54 (outlet hydrogen pressure), that is, the pressure of the hydrogen supplied to the FC 11 (fuel pressure).

[0056] On the other hand, an air system 22 is provided on the cathode side of the FC 11. The air system 22 includes an air supply passage 61 and an air exhaust passage 62. The air supply passage 61 is a passage for supplying air to the FC 11 from outside the fuel cell system 1. The air exhaust passage 62 is a passage for discharging air (i.e., exhaust gas) discharged from the FC 11.

[0057] Furthermore, the air system 22 includes an air compressor 71 in the air supply passage 61. The air compressor 71 is an electric device that supplies air to the FC 11. In this embodiment, no air valves or other devices are provided in the air supply passage 61 between the air compressor 71 and the FC 11, or in the air discharge passage 62. That is, in this embodiment, air is directly supplied to the FC 11 from the air compressor 71 and exhaust air is directly discharged from the FC 11 to the outside.

[0058] In addition, the fuel cell system 1 of this embodiment also includes a cooling system 23 for cooling the FC 11. The cooling system 23 includes an air passage 81 for circulating air and an electrically powered cooling fan 82 for cooling the air flowing in the passage 81. That is, in this embodiment, a closed cathode system is configured such that the cooling system 23 is separate from the air system 22.

[0059] The fuel cell system 1 also includes a control device 20 for controlling the system 1. The control device 20 includes, for example, an arithmetic processing unit such as a CPU, a storage unit including a ROM storing control programs and control data processed by the CPU, a RAM used for various operating areas of the control processing, and an input / output interface unit. The control device 20 executes various controls of the fuel cell system 1 according to the control programs stored in the storage unit. In particular, in this embodiment, the control device 20 controls the hydrogen system 21, the air system 22, the FC relay 18, and the battery relay 19.

[0060] In this embodiment, the control device 20 controls the FC relay 18, the battery relay 19, the hydrogen system 21 (hydrogen valve 51, hydrogen pressure reducing valve 52, ejector 53, gas-liquid separator 56, exhaust and drain valve 57), the air system 22 and the like (air compressor 71 and cooling fan 82) based on the measured value of the pressure sensor 16, so as to control the fuel cell system 1.

[0061] [Operation of Fuel Cell System]

[0062] In the fuel cell system 1 configured as described above, hydrogen supplied from the hydrogen supply passage 31 to the FC 11 is used for power generation of the FC 11, and then is discharged as hydrogen exhaust gas from the FC 11 through the exhaust and drain passage 32 to the outside of the fuel cell system 1. In addition, air supplied from the air supply passage 61 to the FC 11 is used for power generation of the FC 11, and then is discharged as air exhaust gas from the FC 11 through the air discharge passage 62 to the outside of the fuel cell system 1.

[0063] The electric power generated by the FC 11 is supplied to the battery 12 to charge the battery 12, or is supplied to the inverter 13 to drive the inverter 13. Further, electric power is also supplied from the battery 12 to the inverter 13.

[0064] (Regarding System Without DCDC Converter)

[0065] As described above, the fuel cell system 1 of the present embodiment is configured as a system without a DCDC converter. Therefore, in the fuel cell system 1, the voltage of the FC 11 (FC voltage) is equal (or substantially equal) to the voltage of the battery 12 (battery voltage). Therefore, the FC current depends on the battery voltage. In other words, this fuel cell system 1 supplies the electric power generated by the FC 11 to the battery 12 and the inverter 13 without converting the FC voltage. In addition, the FC current is the current of the electric power generated by the FC 11. Further, the battery voltage is the voltage of the battery 12.

[0066] In this fuel cell system 1, as described above, the FC voltage is equal to the battery voltage, so the FC 11 performs "passive power generation" (Japanese: 成り行き発電) corresponding to the battery voltage during power generation. Further, in this fuel cell system 1, when the state of charge of the battery 12 becomes high, the hydrogen injection pressure of the ejector 53 is controlled to a stop pressure and the air compressor 71 is stopped to make the FC voltage lower than the battery voltage, so as to perform "low-current power generation" in which the power generation of the FC 11 is intermittently stopped. Thereby, the fuel economy of the fuel cell system 1 can be improved. In this embodiment, the state in which the FC 11 is in the "passive power generation" state is referred to as a "passive power generation mode", and the state in which the FC 11 is in the "low-current power generation" state is referred to as a "low-current power generation mode".

[0067] exist Figure 2 In the diagram, graph (A) shows an example of the relationship between FC current and FC voltage when the inverter 13 in the fuel cell system 1 consumes power, and graph (B) shows an example of the relationship between battery current and battery voltage under the same condition. Figure 2 As shown, when inverter 13 consumes power, and the battery voltage is "47V", the FC voltage in "momentum generation" is also "47V" as the battery voltage. Therefore, the FC current in "momentum generation" is "50A". Thus, in "momentum generation", "FC output = 47V × 50A ≈ 2.3kW". At this time, the battery current is "100A", therefore, "battery output = 47V × 100A = 4.7kW". Furthermore, by adding the FC output and the battery output, the power consumed in inverter 13 is "2.3kW + 4.7kW = 7.0kW". In addition, the FC output is the power generated and output from FC 11. The battery output is the power output from battery 12.

[0068] exist Figure 2 In the "intermittent stop" mode, the FC voltage and battery voltage are "aV" lower than "47V", and the battery current is "150A" higher than "100A".

[0069] exist Figure 3 In the diagram, graph (A) shows an example of the relationship between FC current and FC voltage in the fuel cell system 1 when there is no power consumption from inverter 13, and graph (B) shows an example of the relationship between battery current and battery voltage under the same condition. Figure 3 As shown, when inverter 13 has no power consumption, and the battery voltage is "49V", the FC voltage in "momentum generation" is the same as the battery voltage, also "49V". Therefore, the FC current in "momentum generation" becomes "30A". Thus, in "momentum generation", "FC output = 49V × 30A ≈ 1.5kW". At this time, the battery current is "-30A", therefore, "battery output = 49V × (-30A) ≈ -1.5kW". Therefore, in inverter 13, "power consumption = 1.5kW + (-1.5kW) = 0kW".

[0070] exist Figure 3 During "intermittent stop", the FC voltage and battery voltage are "bV" lower than "49V", and the battery current is "0A".

[0071] [Control of fuel cell systems]

[0072] Next, the control of the fuel cell system 1 performed by the control device 20 will be explained. Figure 4 The flowchart illustrates an example of the control procedures during startup of the fuel cell system 1 according to this embodiment. The control program described in the flowchart is stored in the storage unit of the control device 20.

[0073] When processing is transferred Figure 4 In the routine, in step 100, the control device 20 takes the hydrogen pressure remaining in FC 11 based on the measurement value of the pressure sensor 16.

[0074] Next, in step 110, the control device 20 determines whether the pressure of the incoming hydrogen is above a specified pressure. Here, the specified pressure is the pressure at which the exhaust drainage passage 32 needs to be depressurized, for example, "20 kPaG". If the determination result is affirmative, the control device 20 causes the process to proceed to step 120; if the determination result is negative, the process jumps to step 130.

[0075] In step 120, the control device 20 opens the exhaust valve 57 for a predetermined time in order to release hydrogen pressure from the hydrogen supply passage 31. Here, the predetermined time is, for example, "200ms".

[0076] In step 130, which proceeds from step 110 or step 120, control device 20 connects FC relay 18 and battery relay 19. That is, it connects wiring 14a between battery 12 and FC 11, and connects wiring 14a and 15a between battery 12 and inverter 13.

[0077] Next, in step 140, the control device 20 begins supplying hydrogen from the hydrogen system 21 to the FC 11. At this time, the control device 20 controls the hydrogen injection pressure of the injector 53 to a target pressure. Here, the target pressure is, for example, "70 kPaG".

[0078] Next, in step 150, the control device 20 begins supplying air from the air system 22 to the FC 11. At this time, the control device 20 drives the air compressor 71.

[0079] Therefore, in step 160, the control device 20 starts the FC 11 to generate electricity, temporarily ending the subsequent processing.

[0080] According to the above-described system startup control, when the fuel cell system 1 starts up, after connecting the FC relay 18 and the battery relay 19, the control device 20 begins supplying hydrogen from the hydrogen system 21 to the FC 11 and air from the air system 22 to the FC 11. More specifically, when the fuel cell system 1 starts up, before connecting the FC relay 18 and the battery relay 19, if the pressure sensor 16 reaches a predetermined pressure that requires depressurization of the exhaust drain passage 32, the control device 20 opens the exhaust drain valve 57 for a predetermined time.

[0081] In addition, Figure 5 The flowchart illustrates an example of the control procedures for when the fuel cell system 1 according to this embodiment stops. The control program described in the flowchart is stored in the storage unit of the control device 20.

[0082] When processing is transferred Figure 5 In the routine case where FC 11 is generating electricity in step 200, in step 210, the control device 20 controls the hydrogen pressure supplied from the hydrogen system 21 to the FC 11 to a stop pressure. Here, the stop pressure is, for example, "5 kPaG". At this time, the control device 20 controls the hydrogen injection pressure of the injector 53.

[0083] Next, in step 220, control device 20 stops supplying air from air system 22 to FC 11. At this time, control device 20 stops air compressor 71.

[0084] Next, in step 230, the control device 20 opens the exhaust valve 57 for a predetermined time in order to release hydrogen pressure from the hydrogen supply passage 31. Here, the predetermined time is, for example, "200ms".

[0085] Next, in step 240, the control device 20 disconnects the FC relay 18 and the battery relay 19. That is, it disconnects the wiring 14a between the battery 12 and the FC 11, and disconnects the wiring 14a and 15a between the battery 12 and the inverter 13.

[0086] Therefore, in step 250, the control device 20 stops FC 11 from generating electricity, temporarily ending the subsequent processing.

[0087] According to the above-described system shutdown control, when the fuel cell system 1 stops, the control device 20 controls the pressure of the hydrogen supplied from the hydrogen system 21 to the FC 11 to the stop pressure and stops the supply of air from the air system 22 to the FC 11. Then, it opens the exhaust drain valve 57 for a specified time and disconnects the FC relay 18 and the battery relay 19, which are in a connected state.

[0088] [Regarding the role and effects of fuel cell systems]

[0089] According to the structure of the fuel cell system 1 of the above-described embodiment, since it is a system without a DC-DC converter and the FC current depends on the battery voltage, the fuel cell system 1 can be made into a simpler structure.

[0090] According to the structure of this embodiment, when the fuel cell system 1 without a DC-DC converter is started, after connecting both the FC relay 18 and the battery relay 19, it begins to supply hydrogen from the hydrogen system 21 to the FC 11 and air from the air system 22 to the FC 11. Therefore, when the fuel cell system 1 is started, when both the FC relay 18 and the battery relay 19 are connected, the FC voltage applied to the FC 11 is suppressed to the same voltage as the battery voltage of the battery 12. That is, in the conventional example where the control of this embodiment is not performed, the FC voltage at startup becomes higher than... Figure 3 The voltage "cV" shown is "49V". In contrast, in this embodiment, as... Figure 3 As shown, the FC voltage during startup is suppressed to "49V", the same as the battery voltage. Therefore, in the fuel cell system 1 equipped with an FC relay 18 corresponding to the inverter 13 and FC 11, and a battery relay 19 corresponding to the inverter 13 and battery 12, when the fuel cell system 1 starts up, it is possible to prevent the rapid application of high voltage to FC 11, thereby suppressing the degradation of FC 11 caused by high voltage.

[0091] Furthermore, according to the structure of this embodiment, when the fuel cell system 1 is started, before connecting both the FC relay 18 and the battery relay 19, the exhaust drain valve 57 is opened for a predetermined time while the hydrogen pressure supplied to the FC 11 is above a predetermined pressure. Therefore, before the FC 11 generates electricity, the hydrogen remaining in the FC 11 is discharged into the exhaust drain passage 32. Thus, when the fuel cell system 1 is started, it is possible to prevent the generation of high current due to the reaction of hydrogen remaining in the FC 11, thereby suppressing the deterioration of the FC 11 and the deterioration of the relays 18 and 19 caused by the high current.

[0092] Furthermore, according to the structure of this embodiment, when the fuel cell system 1 stops, the hydrogen pressure supplied from the hydrogen system 21 to the FC 11 is controlled to a stop pressure, and the air supply from the air system 22 to the FC 11 is stopped. Then, the exhaust drain valve 57 is opened for a predetermined time, and the two relays 18 and 19, which are currently connected, are disconnected. Therefore, before the FC 11 stops generating electricity, the hydrogen remaining in the FC 11 is discharged into the exhaust drain passage 32. Thus, when the fuel cell system 1 stops, hydrogen residue in the FC 11 is prevented, and a high current is prevented from being generated due to the reaction of the hydrogen remaining in the FC 11 when the fuel cell system 1 restarts. This suppresses the degradation of the FC 11 caused by the high current, as well as the degradation of at least one of the FC relay 18 and the battery relay 19 caused by the high current. Additionally, it prevents the application of high voltage and the flow of high current to the FC 11, thereby suppressing the degradation of the FC 11 caused by high voltage and the degradation of the two relays 18 and 19 caused by high current.

[0093] Furthermore, according to the structure of this embodiment, the air system 22 includes an air compressor 71, from which air is directly supplied to the FC 11, and from which exhaust gas is directly discharged. Therefore, no air valves or the like are provided on the supply side of the air system 22 except for the air compressor 71, and no air valves or the like are provided on the discharge side of the air system 22. This simplifies the air system 22, thereby reducing the cost of the fuel cell system 1.

[0094] <Second Implementation Method>

[0095] Next, a second embodiment of the fuel cell system, specifically a fuel cell system mounted on an electric vehicle, will be described in detail with reference to the accompanying drawings. Furthermore, in the following description, structural elements identical to those in the first embodiment will be labeled with the same reference numerals and their descriptions will be omitted; the description will focus on the differences.

[0096] [Control of fuel cell systems]

[0097] In this embodiment, the structure of the control system 1 differs from that in the first embodiment. Figure 6 The flowchart illustrates an example of the control procedures during startup of the fuel cell system 1 according to this embodiment. The control program described in the flowchart is stored in the storage unit of the control device 20.

[0098] When processing is transferred Figure 6In the routine, in step 300, the control device 20 connects the FC relay 18 and the battery relay 19. That is, it connects the wiring 14a between the battery 12 and the FC 11, and connects the wiring 14a and 15a between the battery 12 and the inverter 13.

[0099] Next, in step 310, the control device 20 waits for a predetermined time T1 to elapse. That is, the control device 20 waits for the predetermined time T1 to elapse since the relays 18 and 19 were connected.

[0100] Next, in step 320, the control device 20 begins supplying hydrogen from the hydrogen system 21 to the FC 11. At this time, the control device 20 controls the hydrogen injection pressure of the injector 53 to a target pressure. Here, the target pressure is, for example, "70 kPaG".

[0101] Next, in step 330, the control device 20 begins supplying air from the air system 22 to the FC 11. At this time, the control device 20 drives the air compressor 71.

[0102] Therefore, in step 340, the control device 20 causes FC 11 to start generating electricity, temporarily ending the subsequent processing.

[0103] According to the above-described start-up control, when the fuel cell system 1 is started, after the control device 20 connects the FC relay 18 and the battery relay 19, a predetermined time T1 is elapsed before it begins to supply hydrogen from the hydrogen system 21 to the FC 11 and air from the air system 22 to the FC 11.

[0104] In addition, Figure 7 The flowchart illustrates an example of the control procedures for when the fuel cell system 1 according to this embodiment stops. The control program described in the flowchart is stored in the storage unit of the control device 20.

[0105] When processing is transferred Figure 7 In the routine case where FC 11 is generating electricity in a power source or is intermittently stopped in step 400, in step 410, control device 20 stops supplying hydrogen from hydrogen system 21 to FC 11. At this time, control device 20 stops the drive of injector 53.

[0106] Next, in step 420, control device 20 stops supplying air from air system 22 to FC 11. At this time, control device 20 stops air compressor 71.

[0107] Next, in step 430, the control device 20 takes the hydrogen pressure at the outlet of the injector 53 based on the measurement value of the pressure sensor 16.

[0108] Next, in step 440, the control device 20 determines whether the hydrogen pressure at the outlet of the injector 53 remains unchanged. Here, if the change in the measured value of the hydrogen pressure measured by the pressure sensor 16 per unit time is below a predetermined value, the control device 20 determines that the hydrogen pressure injected from the injector 53 remains unchanged. If the determination result is positive, the control device 20 moves the process to step 450; if the determination result is negative, it repeats the process of step 440.

[0109] Next, in step 450, the control device 20 disconnects the FC relay 18 and the battery relay 19. That is, it disconnects the wiring 14a between the battery 12 and the FC 11, and disconnects the wiring 14a and 15a between the battery 12 and the inverter 13.

[0110] Therefore, in step 460, the control device 20 stops FC 11 from generating electricity, temporarily ending the subsequent processing.

[0111] According to the above-described system shutdown control, when the fuel cell system 1 stops, after the control device 20 stops supplying hydrogen from the hydrogen system 21 to the FC 11 and stops supplying air from the air system 22 to the FC 11, and after the change in the measured value of the pressure sensor 16 per unit time becomes below a predetermined value, the two connected components of the FC relay 18 and the battery relay 19 are disconnected.

[0112] [Regarding the role and effects of fuel cell systems]

[0113] According to the structure of the fuel cell system 1 of the above-described embodiment, when the fuel cell system 1 without a DC-DC converter is started, both the FC relay 18 and the battery relay 19 are connected, and hydrogen and air are supplied to the FC 11 after a predetermined time T1. Therefore, when the fuel cell system 1 is started, during the predetermined time T1 before the FC 11 begins generating electricity, while the FC relay 18 and the battery relay 19 are connected, the voltage applied to the FC 11 is suppressed to the same voltage as the battery 12. Therefore, when the fuel cell system 1 is started, it is possible to prevent the rapid application of a high voltage to the FC 11, thereby suppressing the degradation of the FC 11 caused by high voltage.

[0114] Here, in Figure 8 The timing diagram illustrates the behavior of various parameters related to the aforementioned startup control. Figure 9 In this diagram, the behavior of various parameters related to startup control, which differs from the startup control described in this embodiment, is illustrated using timing diagrams. Figure 7 , Figure 8In this context, (a) represents the FC voltage, (b) represents the FC current, (c) represents the outlet pressure (IN outlet pressure) of injector 53, and (d) represents the FAN (fan) duty cycle, assumed to be the output of air compressor 71. These parameters (a) to (d) will be discussed later. Figure 10 , Figure 11 The same applies to China.

[0115] like Figure 7 As shown, according to the startup control of this embodiment, firstly, at time t1, FC relay 18 and battery relay 19 are turned on. Then, after a predetermined time T1, at time t2, the INJ outlet pressure and FANFAN duty cycle increase sharply almost simultaneously. That is, hydrogen and air are supplied to FC 11, and FC 11 becomes a power generator. At this time, the FC voltage behaves at approximately "maximum 48 (V)," avoiding high voltage.

[0116] In contrast, such as Figure 8 As shown, in the proportional control during startup, hydrogen and air are first supplied to FC11 at time t1. Then, after a predetermined time, FC relay 18 and battery relay 19 are activated at time t2. Consequently, the FC voltage behaves as "maximum 68 (V)," making high voltage unavoidable. Such high voltage will affect the degradation of FC11.

[0117] Furthermore, according to the structure of this embodiment, when the fuel cell system 1 stops, the supply of hydrogen from the hydrogen system 21 (injector 53) to the FC 11 is stopped, and the supply of air from the air system 22 (air compressor 71) to the FC 11 is also stopped. Afterwards, once the pressure change of the hydrogen supplied to the FC 11 decreases, both the FC relay 18 and the battery relay 19 are disconnected. Therefore, after the hydrogen supply to the FC 11 is sufficiently reduced, the FC 11 stops generating electricity. Thus, when the fuel cell system 1 stops, hydrogen residue in the FC 11 can be prevented, and high currents caused by the reaction of hydrogen residue in the FC 11 can be prevented when the fuel cell system 1 restarts, thereby suppressing the degradation of the FC 11 and the FC relay 18 and battery relay 19 caused by such high currents.

[0118] Here, in Figure 10 In this diagram, the behavior of various parameters related to the aforementioned stop control is illustrated using timing diagrams. Figure 11 In the figure, the behavior of various parameters related to a stop control that is different from the stop control in this embodiment is illustrated by timing diagrams.

[0119] like Figure 10As shown, according to the shutdown control of this embodiment, for FC 11 in the power generation process, the supply of hydrogen and air to FC 11 is stopped at time t1. Then, at time t2, when the FC current and INJ outlet pressure decrease, the FC relay 18 and battery relay 19 are disconnected. In this case, the FC voltage (≈ battery voltage) becomes "maximum 52 (V)" and does not become high voltage. Furthermore, although the INJ outlet pressure drops to "-90.4 (kPaG)" at time t2, since oxygen that would affect the deterioration of FC 11 is not mixed in, it can be considered a problem.

[0120] In contrast, such as Figure 11 As shown, in the control during the proportional shutdown, for the FC 11 generating electricity, the FC relay 18 and battery relay 19 are disconnected at time t1, and the supply of hydrogen and air to the FC 11 is stopped immediately afterward at time t2. Consequently, the FC voltage behavior becomes "maximum 67.6 (V)," making high voltage unavoidable. Furthermore, at time t3 when the FC voltage begins to decrease, the INJ outlet pressure becomes "-64.7 (kPaG)," thus considered to have an impact on the degradation of the FC 11.

[0121] <Third Implementation Method>

[0122] Next, a third embodiment of a fuel cell system specifically designed for use in an electric vehicle will be described in detail with reference to the accompanying drawings.

[0123] [Control of fuel cell systems]

[0124] In this embodiment, the control structure of the fuel cell system differs from that of the second embodiment. Figure 12 The flowchart illustrates an example of the control procedures for when the fuel cell system 1 according to this embodiment stops. The control program described in the flowchart is stored in the storage unit of the control device 20.

[0125] When processing is transferred Figure 12 During the routine, in steps 400 to 420, the control device 20 executes the... Figure 7 The same process applies to the flowchart. Then, in step 500, the control device 20 takes in the FC current measured by the ammeter 17.

[0126] Next, in step 510, the control device 20 determines whether a predetermined time has elapsed since the input FC current reached a state of "FC current ≈ 0". Here, "FC current ≈ 0" means that the FC current is below a predetermined value, i.e., a value approximately equal to "0". If the determination result is positive, the control device 20 executes steps 450 and 460. Conversely, if the determination result is negative, the control device 20 repeats step 510.

[0127] According to the above-described stop control, when the fuel cell system 1 stops, after the control device 20 stops supplying hydrogen from the hydrogen system 21 to the FC 11 and stops supplying air from the air system 22 to the FC 11, and after a predetermined time when the measured value of the ammeter 17 is below a predetermined value, the two connected components of the FC relay 18 and the battery relay 19 are disconnected.

[0128] [Regarding the role and effects of fuel cell systems]

[0129] The structure of the fuel cell system 1 according to the above-described embodiment differs from that of the second embodiment in its function and effect, as follows: Specifically, when the fuel cell system 1 without a DC-DC converter is stopped, the supply of hydrogen from the hydrogen system 21 (injector 53) to the FC 11 is stopped, and the supply of air from the air system 22 (air compressor 71) to the FC 11 is also stopped. Afterwards, after the output current of the FC 11 decreases, both the FC relay 18 and the battery relay 19 are disconnected. Therefore, after the output current of the FC 11 has sufficiently decreased, the FC 11 stops generating electricity. Thus, when the fuel cell system 1 is stopped, hydrogen residue in the FC 11, etc., can be prevented, and high currents caused by the reaction of hydrogen residue in the FC 11, etc., can be prevented when the fuel cell system 1 is restarted, thereby suppressing the degradation of the FC 11 and the FC relay 18 and battery relay 19 caused by such high currents.

[0130] <Other Implementation Methods>

[0131] Furthermore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying part of the structure without departing from the spirit of the disclosure.

[0132] (1) In the above embodiments, the fuel cell system 1 is configured to have both an FC relay 18 and a battery relay 19, and the relays 18 and 19 are controlled when the fuel cell system 1 starts and stops. Alternatively, the fuel cell system can also be configured to have both an FC relay and a battery relay, and either the FC relay or the battery relay is controlled when the fuel cell system starts and stops. Or, the fuel cell system can also be configured to have either an FC relay or a battery relay, and the FC relay or the battery relay is controlled when the fuel cell system starts and stops.

[0133] (2) In each of the embodiments, the fuel cell system 1 is specifically designed to be installed in an electric vehicle, but it can also be designed to be installed in a device other than an electric vehicle.

[0134] (3) In each of the embodiments, air valves or the like are not provided on the supply side and the discharge side of the air system 22, but air valves or the like may be provided.

[0135] (4) In the embodiments described above, a closed cathode system in which the cooling system 23 and the air system 22 are separate has been described. In contrast, an open cathode system in which the cooling system and the air system are shared can also be applied. That is, the air system can be omitted, and the oxidant supply device can be composed only of the cooling system.

[0136] (5) In the first embodiment, such as Figure 4 As shown in steps 140 and 150 of the flowchart, the control device 20 starts supplying air to the FC 11 from the air system 22 after it starts supplying hydrogen from the hydrogen system 21 to the FC 11. Conversely, it is also possible to start supplying hydrogen from the hydrogen system 21 to the FC 11 after it starts supplying air from the air system 22 to the FC 11, or to start supplying air from the air system 22 to the FC 11 and hydrogen from the hydrogen system 21 to the FC 11 simultaneously.

[0137] (6) In the first embodiment, such as Figure 5 As shown in steps 210 and 220 of the flowchart, the control device 20 stops supplying air from the air system 22 to the FC 11 after stopping the supply of hydrogen from the hydrogen system 21 to the FC 11. Conversely, the supply of hydrogen from the hydrogen system 21 to the FC 11 can also be stopped after the supply of air from the air system 22 to the FC 11 is stopped, or the supply of air from the air system 22 to the FC 11 and the supply of hydrogen from the hydrogen system 21 to the FC 11 can be stopped simultaneously.

[0138] Industrial availability

[0139] The technology disclosed herein can be used, for example, in fuel cell systems mounted on electric vehicles.

[0140] Explanation of reference numerals in the attached figures

[0141] 1: Fuel cell system; 11: FC (fuel cell); 12: Battery; 13: Inverter (load device); 14a: First wiring; 14b: First wiring; 15a: Second wiring; 15b: Second wiring; 16: Pressure sensor; 17: Ammeter; 18: FC relay (first relay); 19: Battery relay (second relay); 20: Control device; 21: Hydrogen system (fuel supply device); 22: Air system (oxidant supply device); 23: Cooling system (oxidant supply device); 32: Exhaust and drain passage; 53: Injector (fuel supply device); 57: Exhaust and drain valve; 71: Air compressor (oxidant supply device); 82: Cooling fan (oxidant supply device).

Claims

1. A fuel cell system comprising a fuel cell for generating electricity by receiving a supply of fuel and oxidant, and without a DC-DC converter, wherein the fuel cell system is characterized by having: A storage battery, which is charged with the power of the fuel cell; A load device, which is powered by the fuel cell or the storage battery; A fuel supply device for supplying fuel to the fuel cell; An oxidant supply device for supplying the oxidant to the fuel cell; At least one of a first relay and a second relay, wherein the first relay is used to switch the connection and disconnection of the wiring between the fuel cell and the load device, and the second relay is used to switch the connection and disconnection of the wiring between the battery and the load device; as well as A control device for controlling the fuel supply device and the oxidizer supply device, and for controlling at least one of the first relay and the second relay. When the fuel cell system is started, the control device, after connecting at least one of the first relay and the second relay, begins to supply fuel from the fuel supply device to the fuel cell and to supply oxidant from the oxidant supply device to the fuel cell.

2. The fuel cell system according to claim 1, characterized in that, The fuel cell system also features: A pressure sensor for measuring the pressure of the fuel supplied to the fuel cell; An exhaust and drainage passage for the flow of exhaust and drainage from the fuel cell; as well as An exhaust drain valve, used to open and close the exhaust drain passage. When the fuel cell system is started, the control device opens the exhaust drain valve for a specified time before connecting at least one of the first relay and the second relay, provided that the pressure sensor readings exceed a specified pressure requiring depressurization of the exhaust drain passage.

3. The fuel cell system according to claim 2, characterized in that, When the fuel cell system stops, the control device, after controlling the pressure of the fuel supplied from the fuel supply device to the fuel cell to a stop pressure and stopping the supply of oxidant from the oxidant supply device to the fuel cell, opens the exhaust drain valve for a predetermined time and disconnects the relay that is connected between the first relay and the second relay.

4. The fuel cell system according to claim 1, characterized in that, When the fuel system is started, the control device, after a predetermined time has elapsed following the connection of at least one of the first relay and the second relay, begins to supply fuel from the fuel supply device to the fuel cell and to the fuel cell from the oxidant supply device.

5. The fuel cell system according to claim 1, characterized in that, The fuel cell system also includes a pressure sensor for measuring the pressure of the fuel supplied to the fuel cell. When the fuel cell system stops, the control device disconnects the connected relay of the first relay and the second relay after the change in the measured value of the pressure sensor per unit time becomes below a predetermined value after the fuel supply from the fuel supply device to the fuel cell and the oxidant supply from the oxidant supply device to the fuel cell have stopped.

6. The fuel cell system according to claim 1, characterized in that, The fuel cell system also includes a galvanometer for measuring the output current of the fuel cell. When the fuel cell system stops, after the control device stops supplying fuel from the fuel supply device to the fuel cell and stops supplying oxidant from the oxidant supply device to the fuel cell, and after a predetermined time, the ammeter reading falls below a predetermined value, the connected relay of the first relay and the second relay disconnects.

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