Fuel cell system

Abstract

In the present invention, a DC-DC converter-less fuel cell system (1) comprises: an FC (11); a battery (12); an inverter (13); a hydrogen system (21); an air system (22); an FC relay (18) provided between the FC (11) and the inverter (13); a battery relay (19) provided between the battery (12) and the inverter (13); and a control device (20) for controlling the hydrogen system (21), the air system (22), the FC relay (18), and the battery relay (19). When the system is started, the control device (20) connects both relays (18, 19), and then commences supplying hydrogen from the hydrogen system (21) to the FC (11) and supplying air from the air system (22) to the FC (11).

Description

fuel cell system

[0001] The technology disclosed in this specification relates to a fuel cell system equipped with a fuel cell that generates electricity by receiving a supply of fuel and an oxidant.

[0002] A known example of this type of technology is the "air-cooled fuel cell system" described in Patent Document 1 below. This system includes a fuel cell that generates electricity by receiving a supply of fuel and oxidant, a battery that charges the fuel cell, a load device driven by the power of 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. This system controls the battery's state of charge by either running the power or by intermittently stopping the system by closing the oxidant valve (reducing the FC current). To achieve this, this system includes oxidant valves at the cathode inlet and outlet of the fuel cell that intermittently stop the supply of oxidant when the oxidant runs low.

[0003] Here, the DCDC converter is a device that converts DC (direct current) to DC (direct current), and converts the voltage used in the system into DC.

[0004] Japanese Patent Application Laid-Open No. 2022-185247

[0005] In the fuel cell system described in Patent Document 1, a relay may be provided between the load device and the fuel cell or between the load device and the battery, with the relay opened when the system is shut down and closed when the system is started. In this case, if fuel and oxidizer are supplied to the fuel cell before the relay is closed during system startup, a sudden high voltage may be applied. This may result in fuel cell degradation. Furthermore, if fuel remains in the fuel cell before the relay is opened during system shutdown, a high current may flow through the fuel cell and the relay when the system is restarted, which may cause degradation of the fuel cell and the relay.

[0006] The disclosed technology has been made in consideration of the above circumstances, and its first object is to prevent a high voltage from being suddenly applied to the fuel cell when the fuel cell system is started up, and to suppress deterioration of the fuel cell due to high voltage, in a fuel cell system in which a relay is provided at least between a load device and a fuel cell or between the load device and a battery. The disclosed technology's second object, in addition to the first object, is to prevent high current from flowing through the fuel cell and the relay when the system is restarted due to fuel remaining in the fuel cell when the fuel cell system is stopped, and to suppress deterioration of the fuel cell and the relay due to that high current.

[0007] (1) In order to achieve the first object, one aspect of the technology disclosed in the present application is a fuel cell system that includes a fuel cell that generates electricity by receiving a supply of fuel and an oxidant, but does not include a DC-DC converter, and includes a battery that charges the fuel cell with power, a load device that is driven by the power of the fuel cell or the battery, a fuel supply device that supplies fuel to the fuel cell, an oxidant supply device that supplies oxidant to the fuel cell, and at least one of a first relay that switches between connection and disconnection of wiring between the fuel cell and the load device and a second relay that switches between connection and disconnection of wiring between the battery and the load device, and a control device that controls the fuel supply device and the oxidant supply device and also controls at least one of the first relay and the second relay, and the control device connects at least one of the first relay and the second relay when the fuel cell system is started up, and then starts supplying fuel from the fuel supply device to the fuel cell and supplying oxidant from the oxidant supply device to the fuel cell.

[0008] According to the configuration (1) above, this fuel cell system, which does not include a DCDC converter, 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 at least one of the first relay and the second relay is connected during startup. Therefore, when at least one of the first relay and the second relay is connected during startup of the fuel cell system, the voltage applied to the fuel cell is suppressed to the same voltage as the battery.

[0009] (2) In order to achieve the first object, the configuration of (1) above preferably further comprises a pressure sensor for measuring the pressure of the fuel supplied to the fuel cell, an exhaust drainage passage through which exhaust and wastewater from the fuel cell flow, and an exhaust drainage valve for opening and closing the exhaust drainage passage, and when the fuel cell system is started, the control device preferably opens the exhaust drainage valve for a predetermined time before connecting at least one of the first relay and the second relay if the measurement value of the pressure sensor reaches or exceeds a predetermined pressure that requires depressurization of the exhaust drainage passage.

[0010] According to the configuration (2), in addition to the effects of the configuration (1), when the fuel cell system is started, before at least one of the first relay and the second relay is connected, if the pressure of the fuel supplied to the fuel cell reaches or exceeds a predetermined pressure that requires depressurization of the exhaust drainage passage, the exhaust drainage valve opens for a predetermined time, so that fuel remaining in the fuel cell, etc. is discharged into the exhaust drainage passage before the fuel cell generates electricity.

[0011] (3) In order to achieve the second object, in the configuration of (2) above, when the fuel cell system is stopped, it is preferable that the control device controls the pressure of the fuel supplied from the fuel supply device to the fuel cell to a stop pressure and stops the supply of oxidant from the oxidant supply device to the fuel cell, then opens the exhaust drain valve for a predetermined time and opens the connected one of the first relay and the second relay.

[0012] According to the configuration (3), in addition to the effects of the configuration (2), when the fuel cell system is shut down, the pressure of the fuel supplied from the fuel supply device to the fuel cell is controlled to the shut-down pressure, and the supply of oxidant from the oxidant supply device to the fuel cell is stopped. The exhaust and drain valve then opens for a predetermined time, and the connected one of the first and second relays is opened. Therefore, before the fuel cell stops generating power, any fuel remaining in the fuel cell is drained to the exhaust and drain passage.

[0013] (4) In order to achieve the first object, in the configuration of (1) above, it is preferable that, when the fuel system is started, the control device connects at least one of the first relay and the second relay, and then, after a predetermined time has elapsed, starts supplying fuel from the fuel supply device to the fuel cell and supplying oxidant from the oxidant supply device to the fuel cell.

[0014] According to the configuration (4) above, in addition to the effects of the configuration (1) above, when the fuel cell system is started up, at least one of the first relay and the second relay is connected, and after a predetermined time has elapsed, the supply of fuel and oxidant to the fuel cell is started. Therefore, when at least one of the first relay and the second relay is connected when the fuel cell system is started up, the voltage applied to the fuel cell is suppressed to the same voltage as the battery for a predetermined time until the fuel cell starts generating electricity.

[0015] (5) In order to achieve the second object, it is preferable that the configuration of (1) above further includes a pressure sensor for measuring the pressure of the fuel supplied to the fuel cell, and that when the fuel cell system is stopped, the control device 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, and then opens the connected one of the first relay and the second relay after the change per unit time of the measurement value of the pressure sensor becomes equal to or less than a predetermined value.

[0016] According to the configuration (5), in addition to the effects of the configuration (1), when the fuel cell system is shut down, the supply of fuel from the fuel supply device to the fuel cell is stopped, and the supply of oxidant from the oxidant supply device to the fuel cell is stopped. After that, once the pressure change of the fuel supplied to the fuel cell has decreased, the connected one of the first relay and the second relay is opened. Therefore, the fuel cell stops generating electricity after the supply of fuel to the fuel cell has decreased sufficiently.

[0017] (6) In order to achieve the second object, it is preferable that the configuration of (1) further includes an ammeter for measuring the output current of the fuel cell, and that when the fuel cell system is stopped, the control device 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, and then opens the connected one of the first relay and the second relay after the measurement value of the ammeter has been below a predetermined value for a predetermined time.

[0018] According to the configuration (6) above, in addition to the effects of the configuration (1) above, when the fuel cell system is shut down, the supply of fuel from the fuel supply device to the fuel cell is stopped, and the supply of oxidant from the oxidant supply device to the fuel cell is stopped. After that, once the output current of the fuel cell has dropped, the connected one of the first relay and the second relay is opened. Therefore, once the output current of the fuel cell has dropped sufficiently, the fuel cell stops generating electricity.

[0019] According to the above configuration (1), in a fuel cell system in which a relay is provided at least either between the load device and the fuel cell or between the load device and the battery, it is possible to prevent a high voltage from being suddenly applied to the fuel cell when the fuel cell system is started, and to suppress deterioration of the fuel cell due to high voltage.

[0020] According to the configuration (2) above, in addition to the effect of the configuration (1) above, it is possible to prevent the generation of a high current due to the reaction of fuel remaining in the fuel cell, etc., when the fuel cell system is started up, and it is possible to suppress deterioration of the fuel cell due to the high current and deterioration of at least one of the first relay and the second relay due to the high current.

[0021] According to the configuration (3) above, in addition to the effect of the configuration (2) above, it is possible to prevent fuel from remaining in the fuel cell, etc. when the fuel cell system is stopped, and it is possible to prevent the generation of a high current due to a reaction of fuel remaining in the fuel cell, etc. when the fuel cell system is restarted, and it is possible to suppress deterioration of the fuel cell due to the high current and deterioration of at least one of the first relay and the second relay due to the high current.

[0022] According to the configuration (4) above, in addition to the effect of the configuration (1) above, it is possible to prevent a high voltage from being suddenly applied to the fuel cell when the fuel cell system is started, and it is possible to suppress deterioration of the fuel cell due to high voltage.

[0023] According to the configuration (5) above, in addition to the effect of the configuration (1) above, it is possible to prevent fuel from remaining in the fuel cell, etc. when the fuel cell system is stopped, and it is possible to prevent the generation of a high current due to a reaction of fuel remaining in the fuel cell, etc. when the fuel cell system is restarted, and it is possible to suppress deterioration of the fuel cell due to the high current and deterioration of at least one of the first relay and the second relay due to the high current.

[0024] According to the configuration (6) above, in addition to the effect of the configuration (1) above, it is possible to prevent fuel from remaining in the fuel cell, etc. when the fuel cell system is stopped, and it is possible to prevent the generation of a high current due to a reaction of fuel remaining in the fuel cell, etc. when the fuel cell system is restarted, and it is possible to suppress deterioration of the fuel cell due to the high current and deterioration of at least one of the first relay and the second relay due to the high current.

[0025] 1 is a schematic diagram of a fuel cell system according to a first embodiment; FIG. 2 is a graph showing an example of the relationship between (A) FC current and FC voltage, and (B) battery current and battery voltage, when power is consumed by the inverter in the fuel cell system according to the first embodiment; FIG. 3 is a graph showing an example of the relationship between (A) FC current and FC voltage, and (B) battery current and battery voltage, when power is not consumed by the inverter in the fuel cell system according to the first embodiment; FIG. 4 is a flowchart showing an example of control content at startup of the fuel cell system according to the first embodiment; FIG. 5 is a flowchart showing an example of control content at shutdown of the fuel cell system according to the first embodiment; FIG. 6 is a flowchart showing an example of control content at startup of the fuel cell system according to a second embodiment; FIG. 7 is a flowchart showing an example of control content at shutdown of the fuel cell system according to the second embodiment; FIG. 8 is a timing chart showing the behavior of various parameters related to control at startup according to the second embodiment; FIG. 9 is a comparative example of the behavior of various parameters related to control at startup according to the time chart; FIG. 10 is a timing chart showing the behavior of various parameters related to control at shutdown according to the second embodiment; 10 is a flowchart showing an example of control content when the fuel cell system is stopped according to a third embodiment of the present invention;

[0026] First Embodiment A first embodiment of a fuel cell system embodied in a fuel cell system mounted on an electric vehicle will now be described in detail with reference to the drawings.

[0027] [Configuration of the Fuel Cell System] Figure 1 is a schematic diagram showing the configuration of a fuel cell system 1 according to this embodiment. As shown in Figure 1, the fuel cell system 1 of this embodiment is configured as a DCDC converter-less system that does not have a DCDC converter. That is, the fuel cell system 1 includes an FC stack (hereinafter simply referred to as "FC") 11, a battery 12, and an inverter 13 (or a motor). These devices 11 to 13 are connected in parallel in the fuel cell system 1, making it a simple DCDC converter-less system that does not have a DCDC converter. Here, the DCDC converter is a device that converts DC (direct current) to DC (direct current), and converts the voltage used in the system into DC.

[0028] This 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" in the disclosed technology, which supplies fuel to the FC11. The air system 22 is an example of an "oxidizer supply device" in the disclosed technology, which supplies oxidizer to the FC11. In this embodiment, the fuel is hydrogen (hydrogen gas), and the oxidizer is air. The FC11 is an example of a "fuel cell" in the disclosed technology, which generates electricity by receiving a supply of hydrogen from the hydrogen system 21 and a supply of air from the air system 22. The electricity generated by the FC11 is supplied to the battery 12 and the inverter 13.

[0029] The battery 12 is connected to the FC 11 via first wiring 14a and 14b. Electric power generated by the FC 11 is charged to the battery 12 via the first wiring 14a and 14b. The battery 12 is connected to the inverter 13 via the first wiring 14a and 14b and the second wiring 15a and 15b. The second wiring 15a is connected to the first wiring 14a. The second wiring 15b is connected to the first wiring 14b. Electric power charged in the battery 12 is supplied to the inverter 13 via the first wiring 14a and 14b and the second wiring 15a and 15b. The inverter 13 is driven by power supplied from the FC 11 and / or the battery 12 via the first wiring 14a and 14b and the second wiring 15a and 15b. The inverter 13 corresponds to an example of a "load device" of the disclosed technology, which is driven by power from the FC 11 or the battery 12. An ammeter 17 for measuring the FC current, which is the "output current" of the FC 11, is provided on the first wiring 14a immediately adjacent to the output port of the FC 11.

[0030] An FC relay 18 is provided on the first wiring 14a between the FC 11 and the inverter 13, switching between connection and disconnection of the wiring 14a. The FC relay 18 corresponds to an example of a "first relay" in the disclosed technology. Furthermore, a battery relay 19 is provided on the first wiring 14a between the battery 12 and the inverter 13, switching between connection and disconnection of the wiring 14a. The battery relay 19 corresponds to an example of a "second relay" in the disclosed technology. The FC relay 18 is disposed on the first wiring 14a between a connection portion P1 between the first wiring 14a and the second wiring 15a and the ammeter 17. The battery relay 19 is disposed on the first wiring 14a between a connection portion P1 between the first wiring 14a and the second wiring 15a and the battery 12. Each of the relays 18 and 19 receives an electrical signal from an external device and turns on / off or switches an electrical circuit, and has a known configuration.

[0031] The hydrogen system 21 is provided on the anode side of the FC 11. The hydrogen system 21 includes a hydrogen supply passage 31, an exhaust drain passage 32, a filling passage 33, and a circulation passage .

[0032] The hydrogen supply passage 31 is a passage for supplying hydrogen from a hydrogen tank 41 in which hydrogen is stored to the FC 11. The exhaust / drain passage 32 is a passage for discharging hydrogen (i.e., hydrogen off-gas) and drainage water discharged from the FC 11.

[0033] The hydrogen system 21 also 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 this order from the hydrogen tank 41 side.

[0034] The filling passage 33 is a passage for filling hydrogen into the hydrogen tank 41 from the filling port 42. The circulation passage 34 is a passage that connects the exhaust / drainage passage 32 (more specifically, including the gas-liquid separator 56) and the ejector 54, and is a passage for circulating and supplying hydrogen off-gas to the ejector 54.

[0035] The hydrogen valve 51 is a valve that switches between supplying and blocking hydrogen from the hydrogen tank 41 to the hydrogen supply passage 31. This valve 51 is composed of multiple devices including, for example, a solenoid valve. The hydrogen pressure reducing valve 52 is a pressure regulating valve for reducing the pressure of hydrogen. This valve 52 is composed of, for example, a solenoid valve. The injector 53 is a device that injects hydrogen guided from the hydrogen tank 41 downstream. The injector 53 is composed of, for example, a solenoid valve. The injector 53 is configured to adjust the hydrogen discharge pressure (hydrogen pressure) by, for example, adjusting the opening of an injection port by moving a needle valve. The ejector 54 generates negative pressure by the hydrogen injected from the injector 53, uses this negative pressure to suck in hydrogen off-gas flowing through the circulation passage 34, mixes the hydrogen off-gas with hydrogen, and discharges the mixture downstream from an outlet 54a.

[0036] The hydrogen system 21 further includes, in the exhaust / drain passage 32, a gas-liquid separator 56 and an exhaust / drain valve 57, in this order from the FC11 side. The gas-liquid separator 56 is an electrically operated device that separates moisture from the hydrogen off-gas. The exhaust / drain valve 57 is a valve that switches between discharging and blocking the hydrogen off-gas and moisture from the gas-liquid separator 56. This valve 57 is, for example, configured as a solenoid valve.

[0037] In the hydrogen system 21, a pressure sensor 16 is provided in the hydrogen supply passage 31 between the ejector 54 and the FC11. This pressure sensor 16 is a sensor for measuring the pressure of hydrogen discharged from the outlet 54a of the ejector 54 (outlet hydrogen pressure), i.e., the pressure of hydrogen supplied to the FC11 (fuel pressure).

[0038] On the other hand, the 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 discharge passage 62. The air supply passage 61 is a passage for supplying air from outside the fuel cell system 1 to the FC 11. The air discharge passage 62 is a passage for discharging air (i.e., air off-gas) discharged from the FC 11.

[0039] The air system 22 also includes an air compressor 71 in the air supply passage 61. The air compressor 71 is an electrically operated device that supplies air to the FC11. In this embodiment, no device such as an air valve is provided in the air supply passage 61 or the air discharge passage 62 between the air compressor 71 and the FC11. That is, in this embodiment, air is directly supplied from the air compressor 71 to the FC11, and air off-gas is directly discharged from the FC11 to the outside.

[0040] In addition, the fuel cell system 1 of this embodiment further includes a cooling system 23 that cools the FC 11. This cooling system 23 includes an air passage 81 that circulates air, and an electric cooling fan 82 that cools the air flowing through the passage 81. That is, in this embodiment, the cooling system 23 and the air system 22 are configured as separate closed cathode systems.

[0041] The fuel cell system 1 further includes a control device 20 for controlling the system 1. The control device 20 has, for example, an arithmetic processing unit such as a CPU, a storage unit including a ROM for storing control programs and control data processed by the CPU, and a RAM used as various work areas for control processing, and an input / output interface unit. The control device 20 executes various controls of the fuel cell system 1 in accordance with the control programs stored in the storage unit. In particular, in this embodiment, the control device 20 controls a hydrogen system 21, an air system 22, an FC relay 18, and a battery relay 19.

[0042] In this embodiment, the control device 20 controls the FC relay 18, battery relay 19, hydrogen system 21 (hydrogen valve 51, hydrogen pressure reducing valve 52, injector 53, gas-liquid separator 56, exhaust drain valve 57) and air system 22 (air compressor 71 and cooling fan 82) in order to control the fuel cell system 1 based on the measurement value of the pressure sensor 16.

[0043] [Operation of the fuel cell system] In the fuel cell system 1 configured as described above, hydrogen supplied from the hydrogen supply passage 31 to the FC11 is used for power generation in the FC11, and then discharged from the FC11 as hydrogen off-gas via the exhaust drain passage 32 to the outside of the fuel cell system 1. In addition, air supplied from the air supply passage 61 to the FC11 is used for power generation in the FC11, and then discharged from the FC11 as air off-gas via the air discharge passage 62 to the outside of the fuel cell system 1.

[0044] 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. The inverter 13 is also supplied with electric power from the battery 12.

[0045] [Regarding the DCDC converter-less system] As described above, the fuel cell system 1 of this embodiment is configured as a DCDC converter-less system. Therefore, in the fuel cell system 1, the voltage of the FC 11 (FC voltage) is equal to (or approximately equal to) the voltage of the battery 12 (battery voltage). As a result, the FC current depends on the battery voltage. In other words, this fuel cell system 1 supplies the power generated by the FC 11 to the battery 12 and the inverter 13 without converting the FC voltage. Note that the FC current is the current of the power generated by the FC 11. Furthermore, the battery voltage is the voltage of the battery 12.

[0046] In this fuel cell system 1, since the FC voltage is equal to the battery voltage as described above, the FC 11 performs "run-of-the-run power generation" according to the battery voltage when generating power. In addition, in this fuel cell system 1, when the charging rate of the battery 12 becomes high, the hydrogen injection pressure of the injector 53 is controlled to the stop pressure and the air compressor 71 is stopped, thereby lowering the FC voltage below the battery voltage and intermittently stopping power generation of the FC 11, thereby performing "small current power generation." This can improve the fuel efficiency of the fuel cell system 1. In this embodiment, the state in which the FC 11 performs "run-of-the-run power generation" is referred to as the "run-of-the-run power generation mode," and the state in which the FC 11 performs "small current power generation" is referred to as the "small current power generation mode."

[0047] FIG. 2 is a graph showing an example of (A) the relationship between FC current and FC voltage and (B) the relationship between battery current and battery voltage in this fuel cell system 1 when power is consumed by the inverter 13. As shown in FIG. 2, when power is consumed by the inverter 13 and the battery voltage is 47 V, the FC voltage during "run-of-the-road power generation" is equal to the battery voltage, i.e., 47 V. As a result, the FC current during "run-of-the-road power generation" is 50 A. Therefore, during "run-of-the-road power generation," the "FC output = 47 V × 50 A ≒ 2.3 kW" is obtained. In this case, the battery current is 100 A, so the "battery output = 47 V × 100 A = 4.7 kW" is obtained. By adding up the FC output and the battery output, the inverter 13 calculates "power consumption = 2.3 kW + 4.7 kW = 7.0 kW." The FC output is the power generated by the FC 11 and output from the FC 11. The battery output is the power output from the battery 12 .

[0048] In FIG. 2, the FC voltage and battery voltage in "intermittent stop" are "aV" which is lower than "47V", and the battery current is "150A" which is higher than "100A".

[0049] FIG. 3 is a graph showing an example of (A) the relationship between FC current and FC voltage, and (B) the relationship between battery current and battery voltage in this fuel cell system 1 when there is no power consumption in the inverter 13. As shown in FIG. 3, when there is no power consumption in the inverter 13 and the battery voltage is "49 V," the FC voltage during "run-of-the-road power generation" is equal to the battery voltage, i.e., "49 V." As a result, the FC current during "run-of-the-road power generation" is "30 A." Therefore, during "run-of-the-road power generation," "FC output = 49 V × 30 A ≒ 1.5 kW." In this case, the battery current is "-30 A," so "battery output = 49 V × (-30 A) ≒ -1.5 kW." Therefore, in the inverter 13, "power consumption = 1.5 kW + (-1.5 kW) = 0 kW."

[0050] In FIG. 3, the FC voltage and battery voltage in the "intermittent stop" state are "bV" which is lower than "49V", and the battery current is "0A".

[0051] [Control of the fuel cell system] Next, a description will be given of the control of the fuel cell system 1 executed by the control device 20. Fig. 4 is a flowchart showing an example of the control content at the start-up of the fuel cell system 1 according to this embodiment. The control program according to this flowchart is stored in the storage unit of the control device 20.

[0052] When the process proceeds to the routine of FIG. 4, the control device 20 acquires the hydrogen pressure remaining in the FC 11 based on the measurement value of the pressure sensor 16 in step 100 .

[0053] Next, in step 110, the control device 20 determines whether the pressure of the introduced hydrogen is equal to or greater than a predetermined pressure. Here, the predetermined pressure is a pressure at which depressurization of the exhaust / drain passage 32 is required, such as 20 kPaG. If the result of this determination is positive, the control device 20 proceeds to step 120, and if the result of this determination is negative, the control device 20 proceeds to step 130.

[0054] In step 120, the control device 20 opens the exhaust drain valve 57 for a predetermined time to release the hydrogen pressure from the hydrogen supply passage 31. Here, the predetermined time is, for example, 200 ms.

[0055] In step 130, moving from step 110 or step 120, the control device 20 connects the FC relay 18 and the battery relay 19. That is, the control device 20 connects the wiring 14a between the battery 12 and the FC 11, and also connects the wirings 14a and 15a between the battery 12 and the inverter 13.

[0056] Next, in step 140, the control device 20 starts supplying hydrogen from the hydrogen system 21 to the FC11. At this time, the control device 20 controls the hydrogen injection pressure by the injector 53 to a target pressure. Here, the target pressure is, for example, 70 kPaG.

[0057] Next, in step 150, the control device 20 starts supplying air from the air system 22 to the FC 11. At this time, the control device 20 drives the air compressor 71.

[0058] As a result, the control device 20 starts power generation by the FC 11 in step 160, and then temporarily ends the subsequent processing.

[0059] According to the control at system startup described above, when starting up the fuel cell system 1, the control device 20 connects both the FC relay 18 and the battery relay 19, and then starts supplying hydrogen gas from the hydrogen system 21 to the FC 11 and air from the air system 22 to the FC 11. More specifically, when starting up the fuel cell system 1, before connecting both the FC relay 18 and the battery relay 19, if the measurement value of the pressure sensor 16 reaches or exceeds 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.

[0060] 5 is a flowchart showing an example of control procedures when the fuel cell system 1 is stopped according to this embodiment. A control program according to this flowchart is stored in the storage unit of the control device 20.

[0061] 5, if the FC11 is generating electricity in step 200, the control device 20 controls the hydrogen pressure supplied from the hydrogen system 21 to the FC11 to a stop pressure in step 210. 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.

[0062] Next, in step 220, the control device 20 stops the supply of air from the air system 22 to the FC 11. At this time, the control device 20 stops the air compressor 71.

[0063] Next, in step 230, the control device 20 opens the exhaust / drain valve 57 for a predetermined time to release the hydrogen pressure from the hydrogen supply passage 31. Here, the predetermined time is, for example, 200 ms.

[0064] Next, in step 240, the control device 20 opens the FC relay 18 and the battery relay 19. That is, the wiring 14a between the battery 12 and the FC 11 is opened, and the wirings 14a and 15a between the battery 12 and the inverter 13 are opened.

[0065] As a result, in step 250, the control device 20 stops the power generation of the FC 11, and temporarily ends the subsequent processing.

[0066] According to the above-mentioned control when the system is stopped, when the fuel cell system 1 is stopped, the control device 20 controls the pressure of the hydrogen gas supplied from the hydrogen system 21 to the FC11 to the stop pressure and stops the supply of air from the air system 22 to the FC11, then opens the exhaust drain valve 57 for a predetermined time and opens both of the connected FC relay 18 and battery relay 19.

[0067] [Regarding the function and effect of the fuel cell system] According to the configuration of the fuel cell system 1 of this embodiment described above, since it is a DCDC converter-less system and the FC current depends on the battery voltage, the fuel cell system 1 can be configured more simply.

[0068] According to the configuration of this embodiment, this fuel cell system 1, which does not include a DC-DC converter, starts supplying hydrogen gas from the hydrogen system 21 to the FC 11 and supplying air from the air system 22 to the FC 11 after both the FC relay 18 and the battery relay 19 are connected at startup. Therefore, when the fuel cell system 1 starts up, 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 a conventional example in which the control of this embodiment is not executed, the FC voltage at startup becomes "cV," which is higher than "49 V" shown in FIG. 3. In contrast, in this embodiment, the FC voltage at startup is suppressed to "49 V," the same as the battery voltage, as shown in FIG. 3. Therefore, in a fuel cell system 1 in which an FC relay 18 and a battery relay 19 are provided between the inverter 13 and the FC11 and between the inverter 13 and the battery 12, respectively, it is possible to prevent a high voltage from being suddenly applied to the FC11 when the fuel cell system 1 is started, and to suppress deterioration of the FC11 due to high voltage.

[0069] Furthermore, according to the configuration of this embodiment, when the fuel cell system 1 is started, the exhaust drain valve 57 opens for a predetermined time if the hydrogen pressure supplied to the FC 11 is equal to or higher than a predetermined pressure before both the FC relay 18 and the battery relay 19 are connected. Therefore, before the FC 11 generates electricity, hydrogen gas remaining in the FC 11 and the like is discharged to the exhaust drain passage 32. Therefore, when the fuel cell system 1 is started, it is possible to prevent the generation of a high current due to a reaction of hydrogen gas remaining in the FC 11 and the like, and it is possible to suppress deterioration of the FC 11 due to that high current and of the relays 18 and 19 due to that high current.

[0070] Furthermore, according to the configuration of this embodiment, when the fuel cell system 1 is shut down, the hydrogen pressure supplied from the hydrogen system 21 to the FC 11 is controlled to the shutdown pressure, and the supply of air from the air system 22 to the FC 11 is stopped. Thereafter, the exhaust / drain valve 57 opens for a predetermined time, and both connected relays 18 and 19 are opened. Therefore, before the FC 11 stops generating power, hydrogen gas remaining in the FC 11 and other components is discharged to the exhaust / drain passage 32. This prevents hydrogen from remaining in the FC 11 and other components when the fuel cell system 1 is shut down. This prevents high current from being generated by the reaction of hydrogen remaining in the FC 11 and other components when the fuel cell system 1 is restarted. This prevents deterioration of the FC 11 due to the high current and deterioration of at least one of the FC relay 18 and the battery relay 19 due to the high current. Furthermore, this prevents high voltage from being applied to the FC 11 and high current from flowing, thereby preventing deterioration of the FC 11 due to the high voltage and deterioration of the relays 18 and 19 due to the high current.

[0071] Furthermore, according to the configuration of this embodiment, the air system 22 includes an air compressor 71, and air is directly supplied to the FC 11 from the air compressor 71, and air off-gas is directly discharged from the FC 11. Therefore, no air valves or the like other than the air compressor 71 are provided on the supply side of the air system 22, and no air valves or the like are provided on the discharge side of the air system 22. This simplifies the air system 22, and reduces the cost of the fuel cell system 1.

[0072] Second Embodiment Next, a second embodiment of a fuel cell system implemented as a fuel cell system mounted on an electric vehicle will be described in detail with reference to the drawings. In the following description, the same components as those in the first embodiment will be assigned the same reference numerals and description thereof will be omitted, and differences will be mainly described.

[0073] [Regarding Control of Fuel Cell System] This embodiment differs from the first embodiment in the control content of the fuel cell system 1. Figure 6 is a flowchart showing an example of the control content at the start-up of the fuel cell system 1 according to this embodiment. The control program according to this flowchart is stored in the storage unit of the control device 20.

[0074] 6 , the control device 20 connects the FC relay 18 and the battery relay 19 in step 300. That is, the control device 20 connects the wiring 14a between the battery 12 and the FC 11, and also connects the wirings 14a and 15a between the battery 12 and the inverter 13.

[0075] Next, in step 310, the control device 20 waits for the lapse of a predetermined time T1. That is, the control device 20 waits for the lapse of the predetermined time T1 after connecting the relays 18 and 19.

[0076] Next, in step 320, the control device 20 starts supplying hydrogen from the hydrogen system 21 to the FC11. At this time, the control device 20 controls the hydrogen injection pressure by the injector 53 to a target pressure. Here, the target pressure is, for example, "70 kPaG."

[0077] Next, in step 330, the control device 20 starts supplying air from the air system 22 to the FC 11. At this time, the control device 20 drives the air compressor 71.

[0078] As a result, the control device 20 starts power generation by the FC 11 in step 340, and then temporarily ends the subsequent processing.

[0079] According to the above-described startup control, when the fuel cell system 1 is started, the control device 20 connects both the FC relay 18 and the battery relay 19, and then, after a predetermined time T1 has elapsed, starts supplying hydrogen gas from the hydrogen system 21 to the FC11 and air from the air system 22 to the FC11.

[0080] 7 is a flowchart showing an example of control procedures when the fuel cell system 1 is stopped according to this embodiment. A control program according to this flowchart is stored in the storage unit of the control device 20.

[0081] 7, if the FC11 is generating electricity naturally or is intermittently stopped in step 400, the control device 20 stops the supply of hydrogen gas from the hydrogen system 21 to the FC11 in step 410. At this time, the control device 20 stops the operation of the injector 53.

[0082] Next, in step 420, the control device 20 stops the supply of air from the air system 22 to the FC 11. At this time, the control device 20 stops the air compressor 71.

[0083] Next, in step 430 , the control unit 20 acquires the hydrogen pressure at the outlet of the injector 53 based on the measurement value of the pressure sensor 16 .

[0084] Next, in step 440, the control device 20 determines whether there is any change in the hydrogen pressure at the outlet of the injector 53. Here, the control device 20 determines that there is no change in the hydrogen pressure injected from the injector 53 when the change per unit time of the hydrogen pressure measured by the pressure sensor 16 is equal to or less than a predetermined value. If the result of this determination is positive, the control device 20 proceeds to step 450, and if the result of this determination is negative, the control device 20 repeats the processing of step 440.

[0085] Next, in step 450, the control device 20 opens the FC relay 18 and the battery relay 19. That is, the wiring 14a between the battery 12 and the FC 11 is opened, and the wirings 14a and 15a between the battery 12 and the inverter 13 are opened.

[0086] As a result, in step 460, the control device 20 stops the power generation of the FC 11, and temporarily ends the subsequent processing.

[0087] According to the control at the time of system shutdown described above, when the fuel cell system 1 is shut down, the control device 20 stops the supply of hydrogen gas from the hydrogen system 21 to the FC11 and the supply of air from the air system 22 to the FC11, and then opens both of the connected FC relay 18 and the battery relay 19 after the change per unit time of the measurement value of the pressure sensor 16 falls below a predetermined value.

[0088] [Operations and Effects of the Fuel Cell System] According to the configuration of the fuel cell system 1 of this embodiment described above, when this fuel cell system 1, which does not include a DCDC converter, is started, both the FC relay 18 and the battery relay 19 are connected, and after the predetermined time T1 has elapsed, the supply of hydrogen gas and air to the FC 11 begins. Therefore, when the FC relay 18 and the battery relay 19 are connected when the fuel cell system 1 is started, the voltage applied to the FC 11 is kept at the same voltage as the battery 12 for the predetermined time T1 until the FC 11 starts generating electricity. Therefore, when the fuel cell system 1 is started, it is possible to prevent a high voltage from being suddenly applied to the FC 11, and to suppress deterioration of the FC 11 due to high voltage.

[0089] Here, Fig. 8 shows a time chart illustrating the behavior of various parameters related to the above-described startup control. Fig. 9 shows a time chart illustrating the behavior of various parameters related to startup control for comparison, which is different from the startup control of this embodiment. In Figs. 7 and 8, (a) indicates the FC voltage, (b) indicates the FC current, (c) indicates the outlet pressure (IN outlet pressure) of the injector 53, and (d) indicates the fan duty assuming the output of the air compressor 71. These parameters (a) to (d) are also the same as those in Figs. 10 and 11, which will be described later.

[0090] As shown in Figure 7, according to the startup control of this embodiment, first, at time t1, the FC relay 18 and battery relay 19 are turned on. After a predetermined time T1 has elapsed, at time t2, the INJ outlet pressure and FANFAN duty increase sharply almost simultaneously. In other words, the supply of hydrogen gas and air to the FC11 begins, and the FC11 begins to generate electricity as it goes. At this time, the FC voltage behaves as "maximum 48 (V)," making it possible to avoid high voltage.

[0091] In contrast, as shown in Figure 8, in the start-up control of the comparative example, first, at time t1, the supply of hydrogen gas and air to the FC 11 is started. After a predetermined time has elapsed, at time t2, the FC relay 18 and battery relay 19 are turned on. As a result, the FC voltage becomes "maximum 68 (V)," and high voltage cannot be avoided. Such high voltage will affect the deterioration of the FC 11.

[0092] Furthermore, according to the configuration of this embodiment, when the fuel cell system 1 is shut down, the supply of hydrogen gas 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 stopped. After that, once the pressure change of the hydrogen gas supplied to the FC 11 has decreased, both the FC relay 18 and the battery relay 19 are opened. Therefore, the FC 11 stops generating power only after the supply of hydrogen gas to the FC 11 has sufficiently decreased. This prevents hydrogen gas from remaining in the FC 11 and other components when the fuel cell system 1 is shut down, and prevents the generation of a high current due to a reaction of the hydrogen gas remaining in the FC 11 and other components when the fuel cell system 1 is restarted. This prevents deterioration of the FC 11 due to the high current, and also suppresses deterioration of the FC relay 18 and the battery relay 19 due to the high current.

[0093] Here, Fig. 10 shows a time chart illustrating the behavior of various parameters related to the above-described stop control, and Fig. 11 shows a time chart illustrating the behavior of various parameters related to a comparative stop control that is different from the stop control of this embodiment.

[0094] As shown in Figure 10, according to the shutdown control of this embodiment, the supply of hydrogen gas and air to the FC11 during natural power generation is stopped at time t1. Thereafter, at time t2 when the FC current and INJ outlet pressure have dropped, the FC relay 18 and battery relay 19 are turned off. In this case, the FC voltage (≈ battery voltage) is a maximum of 52 (V) and does not become a high voltage. At time t2, the INJ outlet pressure drops to -90.4 (kPaG), but this is not considered to be a problem because oxygen, which would affect the deterioration of the FC11, is not mixed in.

[0095] In contrast, as shown in Figure 11, in the control during shutdown in the comparative example, the FC relay 18 and battery relay 19 are turned off at time t1 in the FC11 that is generating electricity, and immediately thereafter at time t2, the supply of hydrogen gas and air to the FC11 is stopped. As a result, the FC voltage becomes "maximum 67.6 (V)", and high voltage cannot be avoided. Furthermore, at time t3 when the FC voltage begins to drop, the INJ outlet pressure becomes "-64.7 (kPaG)", which is thought to affect the degradation of the FC11.

[0096] Third Embodiment Next, a third embodiment of a fuel cell system embodied in a fuel cell system mounted on an electric vehicle will be described in detail with reference to the drawings.

[0097] [Regarding the control of the fuel cell system] This embodiment differs from the second embodiment in the control content of the fuel cell system. Figure 12 is a flowchart showing an example of the control content when the fuel cell system 1 is stopped according to this embodiment. The control program according to this flowchart is stored in the memory unit of the control device 20.

[0098] 12, the control device 20 executes the same processes as those in the flowchart of FIG. 7 in steps 400 to 420. Then, in step 500, the control device 20 acquires the FC current measured by the ammeter 17.

[0099] Next, in step 510, the control device 20 determines, based on the captured FC current, whether or not a predetermined time has elapsed in the state of "FC current ≈ 0." Here, the state of "FC current ≈ 0" indicates that the FC current is equal to or less than a predetermined value, and means a value close to "0." If the result of this determination is positive, the control device 20 executes the processes of steps 450 and 460. On the other hand, if the result of this determination is negative, the control device 20 repeats the process of step 510.

[0100] According to the above-mentioned shutdown control, when the fuel cell system 1 is shut down, the control device 20 stops the supply of hydrogen gas from the hydrogen system 21 to the FC11 and the supply of air from the air system 22 to the FC11, and then opens both of the connected FC relay 18 and battery relay 19 after the measurement value of the ammeter 17 has been below a predetermined value for a predetermined time.

[0101] [Regarding the Functions and Effects of the Fuel Cell System] The configuration of the fuel cell system 1 of this embodiment described above differs from the second embodiment in the following functions and effects. Specifically, when this fuel cell system 1, which does not include a DC-DC converter, is shut down, the supply of hydrogen gas 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 stopped. After the output current of the FC 11 decreases, both the FC relay 18 and the battery relay 19 are opened. Therefore, the FC 11 stops generating power only after the output current of the FC 11 has sufficiently decreased. This prevents hydrogen gas from remaining in the FC 11 and other components when the fuel cell system 1 is shut down. This prevents the generation of high current due to a reaction of hydrogen gas remaining in the FC 11 and other components when the fuel cell system 1 is restarted. This suppresses degradation of the FC 11 due to the high current, as well as degradation of the FC relay 18 and the battery relay 19 due to the high current.

[0102] <Other Embodiments> The disclosed technology is not limited to the above-described embodiments, and can be implemented by appropriately modifying part of the configuration within the scope of the disclosed technology.

[0103] (1) In each of the above embodiments, the fuel cell system 1 is provided with both the FC relay 18 and the battery relay 19, and both relays 18, 19 are controlled when the fuel cell system 1 is started up and stopped. However, the fuel cell system may also be provided with both an FC relay and a battery relay, and the FC relay or the battery relay may be controlled when the fuel cell system is started up and stopped. Alternatively, the fuel cell system may be provided with an FC relay or a battery relay, and the provided FC relay or battery relay may be controlled when the fuel cell system is started up and stopped.

[0104] (2) In each of the above embodiments, the fuel cell system 1 is embodied in an electric vehicle. However, the fuel cell system may also be embodied in a vehicle other than an electric vehicle.

[0105] (3) In the above embodiments, no air valves or the like are provided on the supply side and discharge side of the air system 22, but air valves or the like may be provided.

[0106] (4) In the above embodiments, a closed cathode system in which the cooling system 23 and the air system 22 are separate has been described. However, the present invention can also be applied to an open cathode system in which the cooling system and the air system are shared. In other words, the air system can be omitted, and the oxidizer supply device can be configured with only the cooling system.

[0107] (5) In the first embodiment, as shown in steps 140 and 150 of the flowchart in Fig. 4, the control device 20 starts the supply of hydrogen from the hydrogen system 21 to the FC11, and then starts the supply of air from the air system 22 to the FC11. Alternatively, it is also possible to start the supply of air from the air system 22 to the FC11, and then start the supply of hydrogen from the hydrogen system 21 to the FC11, or to start the supply of air from the air system 22 to the FC11 and the supply of hydrogen from the hydrogen system 21 to the FC11 simultaneously.

[0108] (6) In the first embodiment, as shown in steps 210 and 220 of the flowchart in Fig. 5, the control device 20 stops the supply of hydrogen from the hydrogen system 21 to the FC11, and then stops the supply of air from the air system 22 to the FC11. However, it is also possible to stop the supply of air from the air system 22 to the FC11, and then stop the supply of hydrogen from the hydrogen system 21 to the FC11, or to stop the supply of air from the air system 22 to the FC11 and the supply of hydrogen from the hydrogen system 21 to the FC11 simultaneously.

[0109] The disclosed technology can be used, for example, in a fuel cell system mounted on an electric vehicle.

[0110] REFERENCE SIGNS LIST 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 (oxidizer supply device) 23 cooling system (oxidizer supply device) 32 exhaust drain passage 53 injector (fuel supply device) 57 exhaust drain valve 71 air compressor (oxidizer supply device) 82 cooling fan (oxidizer supply device)

Claims

1. A fuel cell system having a fuel cell that generates electricity by receiving a supply of fuel and an oxidant, and no DCDC converter, comprising: a battery that charges the fuel cell with power; a load device driven by the power of the fuel cell or the battery; a fuel supply device for supplying the fuel to the fuel cell; an oxidant supply device for supplying the oxidant to the fuel cell; at least one of a first relay for switching between connection and disconnection of wiring between the fuel cell and the load device and a second relay for switching between connection and disconnection of wiring between the battery and the load device; and a control device for controlling the fuel supply device and the oxidant supply device, and for controlling at least one of the first relay and the second relay, wherein the control device connects at least one of the first relay and the second relay when the fuel cell system is started, and then starts supplying fuel from the fuel supply device to the fuel cell and supplying oxidant from the oxidant supply device to the fuel cell.

2. A fuel cell system as claimed in claim 1, further comprising: a pressure sensor for measuring the pressure of the fuel supplied to the fuel cell; an exhaust and drain passage through which exhaust and drain from the fuel cell flow; and an exhaust and drain valve for opening and closing the exhaust and drain passage, wherein the control device, when starting up the fuel cell system, opens the exhaust and drain valve for a predetermined time if the measurement value of the pressure sensor reaches or exceeds a predetermined pressure that requires depressurization of the exhaust and drain passage before connecting at least one of the first relay and the second relay.

3. A fuel cell system as described in claim 2, wherein, when the fuel cell system is stopped, the control device controls the pressure of the fuel supplied from the fuel supply device to the fuel cell to a stop pressure and stops the supply of oxidant from the oxidant supply device to the fuel cell, then opens the exhaust drain valve for a predetermined time and opens the connected relay of the first relay and the second relay.

4. A fuel cell system as described in claim 1, characterized in that, when the fuel system is started, the control device connects at least one of the first relay and the second relay, and then, after a predetermined time has elapsed, starts supplying the fuel from the fuel supply device to the fuel cell and the oxidant from the oxidant supply device to the fuel cell.

5. A fuel cell system as claimed in claim 1, further comprising a pressure sensor for measuring the pressure of the fuel supplied to the fuel cell, wherein the control device, when the fuel cell system is stopped, stops the supply of fuel from the fuel supply device to the fuel cell and stops the supply of oxidant from the oxidant supply device to the fuel cell, and then opens the connected one of the first relay and the second relay after the change per unit time of the measurement value of the pressure sensor falls below a predetermined value.

6. A fuel cell system as claimed in claim 1, further comprising an ammeter for measuring the output current of the fuel cell, wherein when the fuel cell system is shut down, the control device 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, and then opens the connected one of the first relay and the second relay after the measured value of the ammeter has remained below a predetermined value for a predetermined time.

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