Fuel cell system

Abstract

To prevent a high voltage from being applied to a fuel cell and a large current from flowing and suppress deterioration of the fuel cell due to the high voltage at the time of startup in a fuel cell system in which a relay is provided in at least one of a connection between a load device and the fuel cell and a connection between the load device and a battery.SOLUTION: 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).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[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. [Background technology]

[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's power, 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 electricity or by intermittently stopping the system by closing an 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 DC-DC converter is a device that converts DC (direct current) to DC (direct current), and converts the voltage used in the system into DC. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-185247 Summary of the Invention [Problem to be solved by the invention]

[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 when the system is started, a high voltage may be applied suddenly. This may result in deterioration of the fuel cell. Furthermore, if fuel remains in the fuel cell before the relay is opened when the system is shut down, a high current may flow through the fuel cell and the relay when the system is restarted, which may cause deterioration of the fuel cell and the relay.

[0006] This disclosed technology was 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 second object of this disclosed technology, 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. [Means for solving the problem]

[0007] In order to achieve the first object, the technology described in claim 1 is a fuel cell system having a fuel cell that generates electricity by receiving a supply of fuel and an oxidant, and not having a DC-DC converter, the system including 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 fuel to the fuel cell, an oxidant supply device for supplying oxidant to the fuel cell, and 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, and 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.

[0008] According to the configuration of the above technology, this fuel cell system, which does not include a DC-DC 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] In order to achieve the above-mentioned first object, the technology described in claim 2 is the technology described in claim 1, further comprising 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 the control device is intended to open the exhaust drainage valve for a predetermined time when the measurement value of the pressure sensor reaches or exceeds a predetermined pressure that requires depressurization of the exhaust drainage passage before connecting at least one of the first relay and the second relay when starting up the fuel cell system.

[0010] According to the configuration of the above technology, in addition to the function of the technology described in claim 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. Therefore, before the fuel cell generates power, fuel remaining in the fuel cell, etc. is discharged into the exhaust drainage passage.

[0011] In order to achieve the second object, the technology described in claim 3 is the technology described in claim 2, in which, 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.

[0012] According to the configuration of the above technology, in addition to the effect of the technology described in claim 2, when the fuel cell system is stopped, the pressure of the fuel supplied from the fuel supply device to the fuel cell is controlled to the stop pressure, and the supply of oxidant from the oxidant supply device to the fuel cell is stopped. After that, the exhaust drain valve opens for a predetermined time, and the connected relay of the first relay and the second relay is opened. Therefore, before the fuel cell stops generating power, fuel remaining in the fuel cell, etc. is discharged to the exhaust drain passage.

[0013] In order to achieve the first object, the technology described in claim 4 is the technology described in claim 1, in which the control device connects at least one of the first relay and the second relay when the fuel 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 after a predetermined time has elapsed.

[0014] According to the configuration of the above technology, in addition to the effect of the technology described in claim 1, when the fuel cell system is started, at least one of the first relay and the second relay is connected, and after a predetermined time has passed, 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, 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] In order to achieve the second object, the technology described in claim 5 is the technology described in claim 1, further comprising a pressure sensor for measuring the pressure of the fuel supplied to the fuel cell, and the control device is configured to open the connected one of the first relay and the second relay when the fuel cell system is stopped, after stopping the supply of fuel from the fuel supply device to the fuel cell and stopping the supply of oxidant from the oxidant supply device to the fuel cell, and 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 of the above technology, in addition to the function of the technology described in claim 1, when the fuel cell system is stopped, 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 relay of the first relay and the second relay is opened. Therefore, the fuel cell stops generating power after the supply of fuel to the fuel cell has decreased sufficiently.

[0017] In order to achieve the second object, the technology described in claim 6 is the technology described in claim 1, further comprising an ammeter for measuring the output current of the fuel cell, and 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 of the above technology, in addition to the function of the technology described in claim 1, when the fuel cell system is stopped, 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 decreased, the connected one of the first relay and the second relay is opened. Therefore, once the output current of the fuel cell has decreased sufficiently, the fuel cell stops generating power. [Effects of the Invention]

[0019] According to the technology described in claim 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 technology described in claim 2, in addition to the effect of the technology described in claim 1, it is possible to prevent the generation of high current due to the reaction of fuel remaining in the fuel cell, etc. when the fuel cell system is started, 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 technology described in claim 3, in addition to the effect of the technology described in claim 2, 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 the 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 technology described in claim 4, in addition to the effect of the technology described in claim 1, 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.

[0023] According to the technology described in claim 5, in addition to the effect of the technology described in claim 1, 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 the 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 technology described in claim 6, in addition to the effect of the technology described in claim 1, 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 the 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. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a configuration diagram illustrating a fuel cell system according to a first embodiment. [Figure 2] 5 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 when power is consumed in the inverter in the fuel cell system according to the first embodiment. [Figure 3] 5 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 when there is no power consumption in the inverter in the fuel cell system according to the first embodiment. [Figure 4] 5 is a flowchart showing an example of control content at the start-up of the fuel cell system according to the first embodiment. [Figure 5] 5 is a flowchart showing an example of control content when the fuel cell system is stopped in the first embodiment. [Figure 6] 10 is a flowchart showing an example of control content at the start-up of a fuel cell system according to a second embodiment. [Figure 7]10 is a flowchart showing an example of control content when the fuel cell system is stopped according to the second embodiment. [Figure 8] 10 is a timing chart showing the behavior of various parameters related to control at startup according to the second embodiment. [Figure 9] For comparison, the behavior of various parameters related to control at startup is shown in a time chart. [Figure 10] 10 is a timing chart showing the behavior of various parameters related to control during stopping according to the second embodiment. [Figure 11] For comparison, the behavior of various parameters related to control during stopping is shown in a time chart. [Figure 12] 10 is a flowchart showing an example of control content when the fuel cell system is stopped according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

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

[0027] [Fuel cell system configuration] FIG. 1 is a schematic diagram showing a fuel cell system 1 according to this embodiment. As shown in FIG. 1, the fuel cell system 1 of this embodiment is configured as a DCDC converterless 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 converterless 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, and is for supplying fuel to the FC 11. The air system 22 is an example of an "oxidant supply device" in the disclosed technology, and is for supplying an oxidant to the FC 11. In this embodiment, the fuel is hydrogen (hydrogen gas), and the oxidant is air. The FC 11 generates electricity by receiving a supply of hydrogen from the hydrogen system 21 and a supply of air from the air system 22, and is an example of a "fuel cell" in the disclosed technology. The electricity generated by the FC 11 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. The 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. The 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 FC11, is provided on the first wiring 14a immediately adjacent to the output port of the FC11.

[0030] An FC relay 18 is provided on the first wiring 14a between the FC 11 and the inverter 13, for 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, for 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. Here, each of the relays 18 and 19 is a component that receives an electrical signal from an external device and turns on / off or switches an electrical circuit, and has a well-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), for example, by 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, and uses this negative pressure to suck in hydrogen off-gas flowing through the circulation passage 34, mix the hydrogen off-gas with hydrogen, and discharge the resulting 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 configured, for example, by 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 FC 11. 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 FC 11 (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 the outside of 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 driven 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] This 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] [About the operation of fuel cell systems] In the fuel cell system 1 configured as described above, hydrogen supplied from the hydrogen supply passage 31 to FC11 is used for power generation in FC11, and then discharged from 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 FC11 is used for power generation in FC11, and then discharged from 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] [About DC / DC converter-less systems] As described above, the fuel cell system 1 of this embodiment is configured as a DC-DC 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). This means that 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. The FC current is the current of the power generated by the FC 11. The battery voltage is the voltage of the battery 12.

[0046] In this fuel cell system 1, the FC voltage is equal to the battery voltage as described above, so that 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 improves 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," "FC output = 47 V × 50 A ≒ 2.3 kW" is obtained. In this case, the battery current is 100 A, so "battery output = 47 V × 100 A = 4.7 kW" is obtained. By adding up the FC output and the battery output, the inverter 13 obtains "power consumption = 2.3 kW + 4.7 kW = 7.0 kW." The FC output is the power generated by 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, if 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" is obtained. In this case, the battery current is -30 A, so "battery output = 49 V × (-30 A) ≒ -1.5 kW" is obtained. Therefore, in the inverter 13, "power consumption = 1.5 kW + (-1.5 kW) = 0 kW" is obtained.

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

[0051] [Regarding fuel cell system control] 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. A 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 taken-in hydrogen is equal to or greater than a predetermined pressure. Here, the predetermined pressure is the pressure at which depressurization of the exhaust / drain passage 32 is required, and is, for example, 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, it 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 FC 11. 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, the control device 20 opens the exhaust drain valve 57 for a predetermined time if the measurement value of the pressure sensor 16 reaches or exceeds a predetermined pressure that requires depressurization of the exhaust drain passage 32.

[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 FC 11 is generating electricity in step 200, the control device 20 controls the hydrogen pressure supplied from the hydrogen system 21 to the FC 11 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 power generation by the FC 11, and temporarily ends the subsequent processing.

[0066] According to the above-mentioned control at the time of system shutdown, when the fuel cell system 1 is shut down, the control device 20 controls the pressure of the hydrogen gas supplied from the hydrogen system 21 to the FC11 to the shutdown 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 the FC relay 18 and the battery relay 19 that are connected.

[0067] [About the action and effects of fuel cell systems] According to the configuration of the fuel cell system 1 of this embodiment described above, the system is a DC-DC converter-less system in which the FC current depends on the battery voltage, so the fuel cell system 1 can have a simpler configuration.

[0068] According to the configuration of this embodiment, the 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 during startup. Therefore, when both the FC relay 18 and the battery relay 19 are connected during startup of the fuel cell system 1, 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 during startup becomes "cV," which is higher than "49 V" shown in FIG. 3. In contrast, in this embodiment, the FC voltage during 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 corresponding FC relays 18 and battery relays 19 are provided between the inverter 13 and the FC 11 and between the inverter 13 and the battery 12, respectively, a high voltage can be prevented from being suddenly applied to the FC 11 during startup of the fuel cell system 1, and deterioration of the FC 11 due to the high voltage can be suppressed.

[0069] Furthermore, according to the configuration of this embodiment, when the fuel cell system 1 is started, before both the FC relay 18 and the battery relay 19 are connected, if the hydrogen pressure supplied to the FC 11 is equal to or greater than a predetermined pressure, the exhaust drain valve 57 opens for a predetermined time. 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. This makes it possible to prevent the generation of a high current due to a reaction of hydrogen gas remaining in the FC 11 and the like when the fuel cell system 1 is started, and to suppress deterioration of the FC 11 due to that high current and of the relays 18 and 19 due to the 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 shut-down 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 a 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 the fuel cell system, which is 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 explanations will be omitted, and differences will be mainly described.

[0073] [Regarding fuel cell system control] This embodiment differs from the first embodiment in the control content of the fuel cell system 1. Fig. 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. A 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, it 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 a predetermined time T1 to elapse. That is, the control device 20 waits for the predetermined time T1 to elapse 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 FC 11. 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 starts supplying hydrogen gas from the hydrogen system 21 to the FC11 and air from the air system 22 to the FC11 after a predetermined time T1 has elapsed.

[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 FC 11 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 FC 11 in step 410. At this time, the control device 20 stops driving 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 controller 20 captures the hydrogen pressure at the outlet of the injector 53 based on the measurement 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 power generation by 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 becomes equal to or less than a predetermined value.

[0088] [About the action and effects of fuel cell systems] 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 DC-DC converter, starts up, 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 starts up, 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 starts up, 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 the high voltage.

[0089] Here, Fig. 8 shows the behavior of various parameters related to the above-mentioned startup control in the form of a time chart. Fig. 9 shows the behavior of various parameters related to startup control in a comparative example that differs from the startup control of this embodiment in the form of a time chart. In Figs. 7 and 8, (a) shows the FC voltage, (b) shows the FC current, (c) shows the outlet pressure (IN outlet pressure) of the injector 53, and (d) shows 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 FC 11 begins, and the FC 11 begins to generate power as it goes. At this time, the FC voltage behaves to a maximum of approximately 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 makes it possible to suppress deterioration of the FC 11 due to the high current, as well as 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 control when the engine is stopped. Fig. 11 shows a time chart illustrating the behavior of various parameters related to a control when the engine is stopped, which is a comparative example different from the control when the engine is stopped in 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 FC 11 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) reaches a maximum of 52 V and is not 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 degradation of the FC 11, 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 for the FC 11 that is generating electricity, and immediately thereafter at time t2, the supply of hydrogen gas and air to the FC 11 is stopped. As a result, the FC voltage behaves as "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 is "-64.7 (kPaG)," which is thought to affect the degradation of the FC 11.

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

[0097] [Regarding fuel cell system control] This embodiment differs from the second embodiment in the control content of the fuel cell system. Fig. 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 storage 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 control at the time of shutdown, 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 measurement value of the ammeter 17 has been below a predetermined value for a predetermined time.

[0101] [About the action and effects of fuel cell systems] The configuration of the fuel cell system 1 of this embodiment described above differs in its operation and effect from the second embodiment as follows. 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 that, the output current of the FC 11 decreases, and then 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 high currents from being generated due to reactions of the hydrogen gas remaining in the FC 11 and other components when the fuel cell system 1 is restarted. This prevents degradation of the FC 11 due to the high current, and also suppresses degradation of the FC relay 18 and the battery relay 19 due to the high current.

[0102] <Another embodiment> 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 the FC relay and the 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, but the fuel cell system may also be embodied in a vehicle other than an electric vehicle.

[0105] (3) In the above-described 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 oxidant 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 FC11, and then starts the supply of air from the air system 22 to FC11. However, it is also possible to start the supply of air from the air system 22 to FC11, and then start the supply of hydrogen from the hydrogen system 21 to FC11, or to start the supply of air from the air system 22 to FC11 and the supply of hydrogen from the hydrogen system 21 to 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 stopped the supply of hydrogen from the hydrogen system 21 to FC11 and then stopped the supply of air from the air system 22 to FC11. However, it is also possible to stop the supply of air from the air system 22 to FC11 and then stop the supply of hydrogen from the hydrogen system 21 to FC11, or to stop the supply of air from the air system 22 to FC11 and the supply of hydrogen from the hydrogen system 21 to FC11 simultaneously. [Industrial Applicability]

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

[0110] 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 (1st Relay) 19 Battery relay (second relay) 20 Control device 21 Hydrogen system (fuel supply system) 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 that generates electricity by receiving a supply of fuel and an oxidant and does not have a DC-DC converter, a battery that charges the fuel cell; 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; including 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; 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; Equipped with 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. A fuel cell system characterized by:

2. 2. The fuel cell system according to claim 1, a pressure sensor for measuring the pressure of the fuel supplied to the fuel cell; an exhaust and drainage passage through which exhaust and drainage from the fuel cell flow; an exhaust drain valve for opening and closing the exhaust drain passage; Further provided with The control device opens the exhaust drain valve for a predetermined time when the measurement value of the pressure sensor reaches or exceeds a predetermined pressure that requires depressurization of the exhaust drain passage before connecting at least one of the first relay and the second relay at the start of the fuel cell system. A fuel cell system characterized by:

3. 3. The fuel cell system according to claim 2, 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, and then opens the exhaust drain valve for a predetermined time and opens the connected relay of the first relay and the second relay. A fuel cell system characterized by:

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

5. 2. The fuel cell system according to claim 1, a pressure sensor for measuring the pressure of the fuel supplied to the fuel cell; When the fuel cell system is stopped, the control device stops the supply of the fuel from the fuel supply device to the fuel cell and the supply of the 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 a change per unit time in the measurement value of the pressure sensor becomes equal to or less than a predetermined value. A fuel cell system characterized by:

6. 2. The fuel cell system according to claim 1, further comprising an ammeter for measuring an output current of the fuel cell; When the fuel cell system is stopped, the control device stops the supply of the fuel from the fuel supply device to the fuel cell and the supply of the oxidant from the oxidant supply device to the fuel cell, and then, after the measured value of the ammeter has been equal to or less than a predetermined value for a predetermined time, opens the connected one of the first relay and the second relay. A fuel cell system characterized by:

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