Fuel cell system

Abstract

A fuel cell system is provided. Even if the pressure of the fuel gas supplied to the discharger is reduced, the concentration of the fuel gas supplied to the fuel cell from the discharger can be adjusted, and deterioration caused by oxidation of the fuel cell can be suppressed. A fuel cell system is provided with an FC stack, a hydrogen gas supply passage, a hydrogen exhaust gas circulation passage, an ejector, an exhaust drain valve, a hydrogen gas pressure sensor, and a control device. The control device variably controls the time ratio between the opening time and the closing time for each control cycle of the exhaust / drain valve, and controls the number of opening / closing operations per unit time of the exhaust / drain valve by setting the opening time to be constant and variably controlling the closing time. The control device controls the number of opening and closing operations of the exhaust / drain valve on the basis of the pressure measurement value of the pressure sensor so as to adjust the concentration of hydrogen gas in the hydrogen exhaust gas circulating through the hydrogen exhaust gas circulation path to the hydrogen gas supply path.

Description

Technical Field

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

[0002] Conventionally, a "fuel cell system" described in Patent Document 1 below is known as such a technology. This system includes: a fuel cell; a fuel gas supply passage for supplying fuel gas to the fuel cell; an injector disposed in the fuel gas supply passage; an ejector disposed in the fuel gas supply passage and between the injector and the fuel cell; and a fuel exhaust gas recirculation passage for recirculating fuel exhaust gas discharged from the fuel cell to the ejector. The ejector generates a negative pressure by injecting fuel gas from the injector, and uses this negative pressure to draw fuel exhaust gas from the fuel exhaust gas recirculation passage, mixes the fuel exhaust gas with the fuel gas, and supplies it to the fuel cell.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2022-121309 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] However, in the fuel cell system described in Patent Document 1, the pressure of the fuel gas supplied to the injector sometimes decreases. In this system, when the fuel in the fuel tank decreases, the pressure of the fuel gas supplied to the injector decreases, and the flow rate of the fuel gas injected from the injector to the exhaust device decreases. As a result, the negative pressure generated in the exhaust device decreases, the amount of fuel exhaust gas drawn into the exhaust device decreases, and the recirculation efficiency of the fuel exhaust gas to the exhaust device decreases. Consequently, the concentration of the fuel gas supplied to the fuel cell decreases, and the power generation performance of the fuel cell may decrease.

[0008] On the other hand, when hydrogen is used as fuel, sometimes a hydrogen alloy tank is used instead of a fuel tank, which allows the built-in hydrogen alloy to absorb hydrogen. In this case, the pressure of the hydrogen discharged from the tank varies greatly depending on the temperature of the hydrogen alloy tank. In particular, when the temperature of the tank decreases, the pressure of the hydrogen supplied to the injector decreases, leading to the same problem as described above.

[0009] This disclosure is made in view of the above circumstances, and its object is to provide a fuel cell system that can adjust the concentration of fuel gas supplied from the exhaust to the fuel cell and suppress the reduction of the power generation performance of the fuel cell even if the pressure of the fuel gas supplied to the exhaust is reduced.

[0010] Solution for solving the problem

[0011] To achieve the above objectives, the technology described in the first invention is a fuel cell system comprising a fuel cell that generates electricity by receiving a supply of fuel gas and an oxidant gas. The fuel cell system comprises: a fuel gas supply passage for supplying fuel gas to the fuel cell; a fuel exhaust gas discharge passage for discharging fuel exhaust gas discharged from the fuel cell to the outside; a fuel exhaust gas recirculation passage for circulating at least a portion of the fuel exhaust gas from the fuel exhaust gas discharge passage back to the fuel gas supply passage; a fuel gas supply unit disposed in the fuel gas supply passage for supplying fuel gas; and an exhaust device disposed downstream of the fuel gas supply unit in the fuel gas supply passage for discharging the fuel gas supplied by the fuel gas supply unit into the fuel exhaust gas recirculation passage. The system includes: a circulating fuel exhaust gas mixture and ejection; an exhaust drain valve disposed in the fuel exhaust gas discharge passage for discharging fuel exhaust gas to the outside; a pressure sensor disposed in the fuel gas supply passage for measuring the pressure of the fuel gas upstream of the exhaust device; and a control device for controlling the exhaust drain valve, wherein the control device is configured to: variably control the ratio of the opening time to the closing time of the exhaust drain valve in each control cycle, and control the number of opening and closing actions of the exhaust drain valve per unit time by setting the opening time constant and variably controlling the closing time; the control device controls the number of opening and closing actions of the exhaust drain valve based on the pressure measurement value of the pressure sensor, thereby adjusting the concentration of fuel gas in the fuel exhaust gas circulating through the fuel exhaust gas circulation passage to the fuel gas supply passage.

[0012] According to the structure of the above technology, the control device variably controls the ratio of the opening time to the closing time of the exhaust drain valve in each control cycle, and controls the number of opening and closing operations of the exhaust drain valve per unit time by setting the opening time constant and the closing time variable. Setting the opening time constant is to prevent the exhaust drain valve from being over-opened. Here, the longer the closing time, the fewer the number of opening and closing operations of the exhaust drain valve per unit time, and the shorter the total opening time of the exhaust drain valve per unit time. As a result, the circulation flow rate of fuel exhaust gas circulating to the fuel gas supply passage via the fuel exhaust gas recirculation passage is reduced. On the other hand, the shorter the closing time, the more the number of opening and closing operations, and the longer the total opening time of the exhaust drain valve per unit time. As a result, gases (nitrogen, water, etc.) generated by the power generation of the fuel cell are discharged at a high frequency, thus increasing the concentration of fuel gas in the fuel exhaust gas circulating to the fuel gas supply passage via the fuel exhaust gas recirculation passage. In addition, the control device controls the number of opening and closing operations of the exhaust drain valve based on the pressure measurement value of the fuel gas upstream of the exhaust outlet. Therefore, by adjusting the number of opening and closing operations based on the fuel gas pressure, the concentration of fuel gas in the fuel exhaust gas mixed with fuel gas in the exhaust device can be adjusted. Thus, even if the pressure of the fuel gas supplied to the exhaust device decreases, the concentration of fuel gas supplied from the exhaust device to the fuel cell can be adjusted, thereby suppressing a decrease in the power generation performance of the fuel cell.

[0013] To achieve the above objectives, the main point of the technology described in the second invention is that, in the technology described in the first invention, an ammeter is also included, which is used to measure the output current of the fuel cell. In addition to performing control corresponding to the pressure measurement value, the control device also controls the number of times the exhaust and drain valves open and close based on the current measurement value of the ammeter, so as to adjust the concentration of fuel gas in the fuel exhaust gas.

[0014] According to the structure of the above-described technology, in addition to the functions of the technology described in the first invention, the control device, besides performing control corresponding to the pressure measurement value, also controls the number of times the exhaust and drain valves open and close based on the current measurement value of the fuel cell. Therefore, by adjusting the number of times the exhaust and drain valves open and close based on the generation of gases (nitrogen, water, etc.) produced by the fuel cell's power generation, the concentration of fuel gas in the fuel exhaust gas mixed with fuel gas in the exhaust device is adjusted.

[0015] To achieve the above objectives, the main point of the technology described in the third invention is that, in the technology described in the second invention, the control device performs the following control: the higher the current measurement value, the shorter the closing time of each control cycle of the exhaust and drain valve.

[0016] Based on the structure of the above-described technology, in addition to the effects of the technology described in the second invention, when the measured current value of the fuel cell increases, the closing time of each control cycle of the exhaust drain valve decreases, the number of opening and closing actions of the exhaust drain valve increases, and the total opening time of the exhaust drain valve increases. Therefore, when the output current of the fuel cell increases, the amount of gas (nitrogen, water, etc.) generated by the fuel cell during power generation increases, and the concentration of fuel gas in the fuel exhaust gas discharged into the fuel exhaust gas discharge passage decreases. However, by increasing the number of operations of the exhaust drain valve, the gas generated during fuel cell power generation is discharged at a high frequency, suppressing the decrease in fuel gas concentration.

[0017] In order to achieve the above objectives, the main idea of ​​the technology described in the fourth invention is that, in the technology described in any one of the first to third inventions, the control device performs the following control: the higher the pressure measurement value, the longer the closing time of each control cycle of the exhaust and drain valve is.

[0018] According to the structure of the above-described technology, in addition to the effects of the technology described in any of the first to third inventions, the control device also performs the following control: when the pressure measurement value increases, the closing time of the exhaust drain valve in each control cycle is extended. This reduces the number of opening and closing operations of the exhaust drain valve, and shortens the total opening time of the exhaust drain valve. In this case, the pressure of the fuel gas supplied to the exhaust unit is high, and the exhaust gas contains a sufficient concentration of fuel gas, so the number of opening and closing operations of the exhaust drain valve can also be reduced. On the other hand, the control device performs the following control: when the pressure measurement value decreases, the closing time of the exhaust drain valve in each control cycle is shortened. This increases the number of opening and closing operations of the exhaust drain valve, and lengthens the total opening time of the exhaust drain valve. In this case, the pressure of the fuel gas supplied to the exhaust unit is low, and gases (nitrogen, water, etc.) generated by the fuel cell's power generation are discharged at a high frequency, resulting in insufficient fuel gas concentration in the exhaust gas. Therefore, the concentration of fuel gas in the exhaust gas can be increased by increasing the number of opening and closing operations of the exhaust drain valve.

[0019] The effects of the invention

[0020] According to the technology described in the first invention, even if the pressure of the fuel gas supplied to the exhaust device decreases, the concentration of the fuel gas supplied from the exhaust device to the fuel cell can be adjusted, thereby suppressing the reduction in the power generation performance of the fuel cell.

[0021] According to the technology described in the second invention, similarly to the technology described in the first invention, even if the flow rate of the fuel gas supplied to the exhaust device decreases, the concentration of the fuel gas supplied from the exhaust device to the fuel cell can be adjusted, thereby suppressing the reduction in the power generation performance of the fuel cell.

[0022] According to the technology described in the third invention, in addition to the effects of the technology described in the second invention, it is also possible to increase the concentration of fuel gas supplied from the exhaust device to the fuel cell, thereby suppressing the reduction in the power generation performance of the fuel cell.

[0023] According to the technology described in the fourth invention, in addition to the effects of the technology described in any one of the first to third inventions, the number of times the exhaust drain valve is operated can be controlled based on the difference in the concentration of fuel gas in the fuel exhaust gas, thereby suppressing the reduction in the power generation performance of the fuel cell. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating the structure of a fuel cell system according to one embodiment.

[0025] Figure 2 This is a timing diagram illustrating the opening and closing operation of an exhaust and drain valve according to one embodiment.

[0026] Figure 3 This is a timing diagram illustrating the opening and closing operation of an exhaust and drain valve according to one embodiment.

[0027] Figure 4 This is a graph illustrating the relationship between hydrogen concentration and hydrogen pressure and tank temperature of hydrogen absorbed by and released from a hydrogen alloy tank, as described in one embodiment.

[0028] Figure 5 This is a flowchart illustrating the control of hydrogen waste gas recirculation volume as described in one embodiment.

[0029] Figure 6 This is a shutdown time mapping that illustrates the relationship between shutdown time and inlet gas pressure and FC current in one implementation. Detailed Implementation

[0030] Hereinafter, with reference to the accompanying drawings, a detailed description will be given of one embodiment of a fuel cell system specifically designed for use in an electric vehicle.

[0031] [Regarding the structure of fuel cell systems]

[0032] exist Figure 1 The diagram below illustrates the fuel cell system 1 according to this embodiment. Figure 1 As shown, the fuel cell system 1 of this embodiment includes an FC stack 11, a battery 12, and an inverter 13 (or a motor).

[0033] Furthermore, the fuel cell system 1 in this embodiment is a simple system without a DC-DC converter, where the aforementioned devices 11-13 are connected in parallel. Here, a DC-DC converter is a device that converts DC voltage to another DC voltage, and is a device that maintains a DC state while converting the voltage used in the system.

[0034] The fuel cell system 1 also includes a hydrogen system 21 and an air system 22. In this embodiment, the fuel gas is hydrogen, and the oxidant gas is air. The FC stack 11 receives a supply of hydrogen from the hydrogen system 21 and a supply of air from the air system 22 to generate electricity. The FC stack 11 corresponds to an example of a "fuel cell" of the present disclosure. The electricity generated by the FC stack 11 is supplied to a battery 12 and an inverter 13.

[0035] Battery 12 is connected to FC stack 11 via first wirings 14a and 14b. Power generated by FC stack 11 is charged into battery 12 via first wirings 14a and 14b. Battery 12 is connected to inverter 13 via first wirings 14a and 14b and second wirings 15a and 15b. Second wiring 15a is connected to first wiring 14a. Second wiring 15b is connected to first wiring 14b. Power charged into battery 12 is supplied to inverter 13 via first wirings 14a and 14b and second wirings 15a and 15b. Inverter 13 is driven by power supplied from FC stack 11 and / or battery 12 via first wirings 14a and 14b and second wirings 15a and 15b. Near the output port of FC stack 11, a current meter 17 is provided on first wiring 14a to measure the FC current IFC, which is the "output current" of FC stack 11.

[0036] An FC relay 18 is provided on the first wiring 14a between the FC stack 11 and the inverter 13 for switching the connection and opening of this wiring 14a. Additionally, a battery relay 19 is provided on the first wiring 14a between the battery 12 and the inverter 13 for switching the connection and opening of this wiring 14a. The FC relay 18 is disposed in the first wiring 14a between the connection point C1 of the first wiring 14a and the second wiring 15a and the ammeter 17. The battery relay 19 is disposed in the first wiring 14a between the connection point C1 of the first wiring 14a and the second wiring 15a and the battery 12. Here, each relay 18 and 19 is a component that receives electrical signals from the outside and performs circuit connection / disconnection and switching, and has a known structure.

[0037] The hydrogen system 21 is located on the anode side of the FC stack 11. The hydrogen system 21 includes a hydrogen supply passage 31, an exhaust and drainage passage 32, a hydrogen waste gas circulation passage 33, and a hydrogen alloy tank 41.

[0038] Hydrogen supply passage 31 is a passage for supplying hydrogen from the hydrogen alloy tank 41 that absorbs hydrogen to the FC reactor 11. Hydrogen supply passage 31 corresponds to an example of the "fuel gas supply passage" of this disclosure. The hydrogen alloy tank 41 contains a hydrogen alloy capable of absorbing and releasing hydrogen. The hydrogen alloy tank 41 corresponds to an example of the "fuel gas supply unit" of this disclosure. Exhaust and drainage passage 32 is a passage for discharging hydrogen waste gas and wastewater discharged from the FC reactor 11. Exhaust and drainage passage 32 corresponds to an example of the "fuel waste gas discharge passage" of this disclosure.

[0039] In addition, the hydrogen system 21 has an injector 53 and an exhaust device 54 located downstream of the hydrogen alloy tank 41 in the hydrogen supply passage 31.

[0040] The hydrogen exhaust gas recirculation passage 33 is a passage connecting the exhaust and drainage passage 32 (more specifically, including the gas-liquid separator 56) to the discharger 54, and is used to circulate hydrogen exhaust gas through the discharger 54 to the hydrogen supply passage 31. The hydrogen exhaust gas recirculation passage 33 is equivalent to an example of the "fuel exhaust gas recirculation passage" of the present disclosure.

[0041] Injector 53 is a device that injects hydrogen gas from hydrogen alloy tank 41 toward exhaust device 54. Injector 53 is, for example, a solenoid valve. Injector 53 is configured, for example, to adjust the opening of the injection port by moving a needle valve, thereby adjusting the hydrogen injection pressure (hydrogen pressure). Injector 53 corresponds to an example of the "fuel gas supply unit" of the present disclosure.

[0042] The discharger 54 generates a negative pressure by injecting hydrogen gas from the ejector 53, and uses this negative pressure to draw in hydrogen waste gas flowing in the hydrogen waste gas circulation passage 33, mixes the hydrogen waste gas with hydrogen gas, and ejects it from the outlet 54a toward the FC stack 11.

[0043] The hydrogen system 21 also includes a gas-liquid separator 56 and a gas exhaust valve 57 arranged sequentially from the FC stack 11 side in the exhaust drainage passage 32. The gas-liquid separator 56 is an electrically operated device that separates moisture from hydrogen waste gas. The gas exhaust valve 57 is a valve that switches between the discharge of hydrogen waste gas and moisture from the gas-liquid separator 56 and the cutting off of this discharge. This valve 57 is, for example, a solenoid valve. In this embodiment, the gas exhaust valve 57 is configured to change the number of opening and closing actions of the valve core relative to the valve seat per unit time by controlling the amount of supplied current.

[0044] In the hydrogen system 21, a pressure sensor 16 is installed in the hydrogen supply passage 31 between the hydrogen alloy tank 41 and the injector 53. The pressure sensor 16 is used to measure the pressure (inlet gas pressure) PH1 of the hydrogen supplied to the injector 53.

[0045] On the other hand, an air system 22 is provided on the cathode side of the FC stack 11. The air system 22 includes an air supply passage 61 and an air exhaust passage 62. The air supply passage 61 is a passage for supplying air from outside the fuel cell system 1 to the FC stack 11. The air exhaust passage 62 is a passage for discharging air (i.e., exhaust gas) discharged from the FC stack 11.

[0046] Furthermore, the air system 22 includes an air compressor 71 in the air supply passage 61. The air compressor 71 is an electrically powered device that supplies air to the FC stack 11. In this embodiment, no air valves or similar devices are installed in the air supply passage 61 and the air discharge passage 62 between the air compressor 71 and the FC stack 11. That is, in this embodiment, air is directly supplied to the FC stack 11 from the air compressor 71, and exhaust gas is directly discharged from the FC stack 11 to the outside.

[0047] Furthermore, the fuel cell system 1 of this embodiment also includes a cooling system 23 for cooling the FC stack 11. The cooling system 23 includes an air passage 81 for circulating air and an electrically powered cooling fan 82 for cooling the air flowing in the passage 81. That is, in this embodiment, it is configured as a "cathode-closed system" with the cooling system 23 and the air system 22 separated.

[0048] The fuel cell system 1 also includes a control device 20 for controlling the system 1. The control device 20 includes, for example, a processing unit such as a CPU, a storage unit, and an input / output interface unit. The storage unit includes a ROM storing control programs and control data processed by the CPU, and RAM used for various operating areas of the control processing. The control device 20 executes various controls of the fuel cell system 1 according to the control programs stored in the storage unit.

[0049] exist Figure 2 and Figure 3 The opening and closing actions of the exhaust and drain valve 57 are illustrated using a timing diagram. In this embodiment, as... Figure 2 , Figure 3 As shown, the control device 20 is configured to: variably control the time ratio of the opening time TOP to the closing time TCL of the exhaust drain valve 57 in each control cycle P1 (duty cycle control), and control the number of opening and closing actions of the exhaust drain valve 57 per unit time TU by setting the opening time TOP to be constant and variably controlling the closing time TCL. Figure 2 This illustrates the case of extending the shutdown time of the TCL. Figure 3 This illustrates the case of TCL with shortened shutdown time. From... Figure 2 , Figure 3It can be seen that when the closing time TCL is shortened, compared with the case of extending the closing time TCL, the number of opening and closing actions of the exhaust and drain valve 57 per unit time TU increases, and the total opening time per unit time TU becomes longer.

[0050] [Regarding actions related to fuel cell systems]

[0051] In the fuel cell system 1 configured as described above, the hydrogen supplied to the FC stack 11 from the hydrogen supply passage 31 is used for power generation in the FC stack 11. After being used as hydrogen exhaust gas, it is discharged from the FC stack 11 to the outside of the fuel cell system 1 via the exhaust drainage passage 32, and circulated back into the hydrogen supply passage 31 via the hydrogen exhaust gas recirculation passage 33 and the exhaust device 54. Meanwhile, the air supplied to the FC stack 11 from the air supply passage 61 is used for power generation in the FC stack 11. After being used as air exhaust gas, it is discharged from the FC stack 11 to the outside of the fuel cell system 1 via the air exhaust passage 62.

[0052] The electricity generated by the FC stack 11 is either fed into the battery 12 or used to drive the inverter 13. In addition, power is also supplied from the battery 12 to the inverter 13.

[0053] The fuel cell system 1 of this embodiment is configured such that, electrically, the voltage of the FC stack 11 (FC voltage) is equal to (or approximately equal to) the voltage of the battery 12 (battery voltage). Therefore, the current (FC current) IFC of the FC stack 11 depends on the battery voltage. In other words, the power generated by the FC stack 11 can be supplied to the battery 12 and the inverter 13 without converting the FC voltage. Furthermore, the FC current IFC is the current generated by the power produced by the FC stack 11. Additionally, the battery voltage is the voltage of the battery 12.

[0054] In this fuel cell system 1, the FC voltage is equal to the battery voltage, so the FC stack 11 generates electricity on demand, corresponding to the battery voltage. Furthermore, in this fuel cell system 1, when the battery 12's charging rate increases, the hydrogen injection pressure of the injector 53 is controlled to a stop pressure, causing the air compressor 71 to stop. This results in "low-current power generation," where the FC voltage drops below the battery voltage, intermittently stopping the FC stack 11's power generation. Therefore, the fuel consumption rate of the fuel cell system 1 can be improved.

[0055] In this embodiment, a hydrogen alloy tank 41 is used in the hydrogen system 21, therefore the pressure of the hydrogen gas discharged from the hydrogen alloy tank 41 varies significantly depending on the temperature of the tank 41. Figure 4 The diagram illustrates the relationship between the "hydrogen concentration" and "hydrogen pressure" of hydrogen absorbed by and released from the hydrogen alloy tank, and the "tank temperature (THC)". For example... Figure 4As shown, as the tank temperature (THC) decreases within the range of 0~60°C, the relationship between hydrogen pressure and hydrogen concentration decreases. Figure 4 In the process, at each tank temperature (THC), the hydrogen pressure is higher during absorption than during release.

[0056] from Figure 4 As can be seen, in this embodiment, when the tank temperature (THC) decreases, the pressure of the hydrogen supplied to the injector 53 decreases, the negative pressure generated in the exhaust device 54 decreases, and the circulation efficiency of the hydrogen waste gas to the exhaust device 54 decreases. Therefore, the pressure of the hydrogen waste gas mixed with hydrogen in the exhaust device 54 decreases, and the pressure of the hydrogen supplied from the exhaust device 54 to the FC stack 11 decreases. As a result, the concentration of hydrogen supplied to the FC stack 11 does not increase, and the power generation efficiency of the FC stack 11 decreases. Therefore, in this embodiment, to address the above problems, the control device 20 performs control on the circulation volume of the hydrogen waste gas flowing to the exhaust device 54 as follows. In this control, the control device 20 controls the exhaust drain valve 57 based on the measurements of the pressure sensor 16 and the ammeter 17.

[0057] [Regarding the control of hydrogen waste gas recirculation volume]

[0058] Next, the "hydrogen waste gas recirculation volume control" performed by control device 20 will be explained. Figure 5 The flowchart illustrates one example of the control process. The control program described in the flowchart is stored in the storage unit of the control device 20. In this embodiment, the control device 20 performs the "hydrogen waste gas recirculation control" when performing "on-demand power generation" corresponding to the battery voltage and when performing "low-current power generation" to stop the power generation intermittently of the FC stack 11.

[0059] When processing is transferred Figure 5 In the illustrated routine, control device 20 acquires the inlet gas pressure PH1 and FC current IFC of injector 53 in step 100. The inlet gas pressure PH1 is obtained based on the measurement value of pressure sensor 16. The FC current IFC is obtained based on the measurement value of ammeter 17.

[0060] Next, in step 110, the control device 20 calculates the closing time TCL of the exhaust drain valve 57 in one control cycle P1 based on the acquired inlet gas pressure PH1 and FC current IFC.

[0061] Control device 20, for example, can be controlled by reference Figure 6 The shutdown time TCL is calculated using the shutdown time mapping shown. This shutdown time mapping is set with a relationship between the shutdown time TCL and the inlet gas pressure PH1 and the FC current IFC. Figure 6The mapping is set such that the higher the inlet gas pressure PH1 is in the range of "50~600 (kPaG)", the longer the closing time TCL is in the range of "10~50 (ms)". Additionally, it is set such that the higher the FC current IFC is in the range of "0~150 (A)", the shorter the closing time TCL is in the range of "25~10 (ms)". In this embodiment, by controlling the closing time TCL of each control cycle P1 in the duty cycle control, the number of opening and closing actions of the exhaust / drain valve 57 per unit time TU is controlled, thereby controlling the total opening time per unit time.

[0062] Next, in step 120, the control device 20 controls the number of opening and closing actions of the exhaust / drain valve 57 per unit time TU by combining a calculated closing time TCL with a constant opening time TOP (e.g., "200ms"). The control device 20 temporarily terminates the subsequent processing.

[0063] According to the above control, the control device 20 controls the number of times the exhaust drain valve 57 opens and closes based on the measured value of the pressure sensor 16, thereby adjusting the circulation flow rate of hydrogen waste gas circulating through the hydrogen waste gas circulation passage 33 to the hydrogen supply passage 31. In addition to controlling the operation according to the pressure measured value of the pressure sensor 16, the control device 20 also controls the number of times the exhaust drain valve 57 opens and closes based on the current measured value of the ammeter 17, thereby adjusting the circulation flow rate of the hydrogen waste gas.

[0064] Based on the above control, the control device 20 performs the following control: the higher the current measurement value of the ammeter 17, the shorter the closing time TCL of each control cycle P1 of the exhaust drain valve 57. Additionally, the control device 20 performs the following control: the higher the pressure measurement value of the pressure sensor 16, the longer the closing time TCL of each control cycle P1 of the exhaust drain valve 57.

[0065] [Regarding the role and effects of fuel cell systems]

[0066] According to the structure of the fuel cell system 1 of this embodiment described above, the control device 20 variably controls the ratio of the opening time TOP to the closing time TCL of the exhaust drain valve 57 in each control cycle P1, and controls the number of opening and closing operations of the exhaust drain valve 57 per unit time TU by setting the opening time TOP constant and variably controlling the closing time TCL. Setting the opening time TOP constant is to prevent the exhaust drain valve 57 from being over-opened. Here, the longer the closing time TCL, the fewer the number of opening and closing operations of the exhaust drain valve 57 per unit time TU, and the shorter the total opening time of the exhaust drain valve 57 per unit time TU. As a result, the circulation flow rate of hydrogen exhaust gas circulating to the hydrogen supply passage 31 via the hydrogen exhaust gas circulation passage 33 is reduced. On the other hand, the shorter the closing time TCL, the more the number of opening and closing operations, and the longer the total opening time of the exhaust drain valve 57 per unit time TU. As a result, gases (nitrogen, water, etc.) generated during power generation in the FC reactor 11 are discharged at a high frequency, thus increasing the concentration of hydrogen in the hydrogen exhaust gas circulating through the hydrogen exhaust gas recirculation path 33 to the hydrogen supply path 31. Furthermore, the control device 20 controls the number of times the exhaust drain valve 57 opens and closes based on the inlet gas pressure PH1 (pressure measurement value) of the hydrogen upstream of the exhaust device 54. Therefore, by adjusting the number of opening and closing operations according to the hydrogen concentration, the concentration of hydrogen in the hydrogen exhaust gas mixed with hydrogen in the exhaust device 54 is adjusted. Thus, even if the pressure of the hydrogen supplied to the exhaust device 54 decreases, the concentration of hydrogen supplied from the exhaust device 54 to the FC reactor 11 can be adjusted, thereby suppressing the reduction in the power generation performance of the FC reactor 11.

[0067] According to the structure of this embodiment, in addition to controlling the inlet gas pressure PH1 (pressure measurement value), the control device 20 also controls the number of times the exhaust drain valve 57 opens and closes based on the FC current IFC (current measurement value), which is the output current of the FC stack 11. Therefore, by adjusting the number of times the exhaust drain valve 57 opens and closes according to the generation status of gases (nitrogen, water, etc.) produced by the power generation of the FC stack 11, the concentration and pressure of hydrogen in the hydrogen exhaust gas mixed with hydrogen in the exhaust fan 54 can be adjusted. Therefore, even if the flow rate of hydrogen supplied to the exhaust fan 54 decreases, the concentration of hydrogen supplied from the exhaust fan 54 to the FC stack 11 can be adjusted, thereby suppressing the reduction in the power generation performance of the FC stack 11.

[0068] According to the structure of this embodiment, when the FC current IFC increases, the closing time of the exhaust drain valve 57 in each control cycle P1 becomes shorter, the number of opening and closing operations of the exhaust drain valve 57 increases, and the total opening time of the exhaust drain valve 57 becomes longer. Therefore, when the output current of the FC stack 11 increases, the amount of gas (nitrogen, water, etc.) generated by the power generation of the FC stack 11 increases, and the concentration of hydrogen in the hydrogen waste gas discharged into the exhaust drain passage 32 decreases. However, by increasing the number of operations of the exhaust drain valve 57, the gas generated during the power generation of the FC stack 11 is discharged at a higher frequency, which can suppress the decrease in hydrogen concentration. Therefore, the concentration of hydrogen supplied from the exhaust device 54 to the FC stack 11 can be increased, thereby suppressing the decrease in the power generation performance of the FC stack 11.

[0069] According to the structure of this embodiment, when the hydrogen inlet gas pressure PH1 increases, the control device 20 controls the vent valve 57 to extend the closing time TCL of each control cycle P1. This reduces the number of opening and closing operations of the vent valve 57, and shortens the total opening time of the vent valve 57. In this case, the pressure of the hydrogen supplied to the exhaust device 54 is high, resulting in a sufficient concentration of hydrogen in the hydrogen waste gas, thus reducing the number of opening and closing operations of the vent valve 57. On the other hand, when the hydrogen inlet gas pressure PH1 decreases, the control device 20 controls the vent valve 57 to shorten the closing time TCL of each control cycle P1. This increases the number of opening and closing operations of the vent valve 57, and lengthens the total opening time of the vent valve 57. In this case, the pressure of the hydrogen supplied to the exhaust device 54 is low, and gases (nitrogen, water, etc.) generated by the power generation of the FC stack 11 are discharged at a high frequency, resulting in insufficient hydrogen concentration in the hydrogen waste gas. Therefore, the concentration of hydrogen in the hydrogen exhaust gas can be increased by increasing the number of times the exhaust valve 57 is opened and closed. Thus, the number of times the exhaust valve 57 is operated can be controlled according to the difference in the concentration of hydrogen in the hydrogen exhaust gas, thereby suppressing the reduction in the power generation performance of the FC reactor 11.

[0070] Furthermore, according to the structure of this embodiment, the air system 22 includes an air compressor 71, from which air is directly supplied to the FC stack 11, and exhaust gas is directly discharged from the FC stack 11. Therefore, on the supply side of the air system 22, only the air compressor 71 is provided; no air valves or the like are provided, and on the exhaust side of the air system 22, no air valves or the like are provided. This simplifies the air system 22 and reduces the cost of the fuel cell system 1.

[0071] <Other Implementation Methods>

[0072] Furthermore, the present disclosure is not limited to the above-described embodiments, and can also be implemented by appropriately modifying a part of the structure without departing from the spirit of the disclosure.

[0073] (1) In the above embodiment, the control device 20 uses both the pressure measurement value of the pressure sensor 16 and the current measurement value of the ammeter 17 to control the exhaust and drain valve 57, but it is also possible to use only the pressure measurement value of the pressure sensor 16.

[0074] (2) In the above embodiment, a hydrogen alloy tank 41 is provided as a fuel gas supply unit, but a hydrogen tank filled with hydrogen can also be provided.

[0075] (3) In the above embodiments, the fuel cell system 1 is specifically installed in an electric vehicle, but it can also be specifically installed in a place other than an electric vehicle.

[0076] (4) In the above embodiment, no air valve or the like is provided on the supply side and the discharge side of the air system 22, but air valves or the like may be provided.

[0077] (5) In the above embodiment, the fuel cell system 1 is configured as a cathode-closed system with separate cooling system 23 and air system 22. In contrast, the fuel cell system can also be configured as a cathode-open system that shares the cooling system and air system.

[0078] Industrial availability

[0079] The technology disclosed herein can be used, for example, in fuel cell systems installed in electric vehicles.

[0080] Explanation of reference numerals in the attached figures

[0081] 1. Fuel Cell System

[0082] 11 FC stack (fuel cell)

[0083] 16 Pressure Sensors

[0084] 17. Ammeter

[0085] 20 Control devices

[0086] 31 Hydrogen supply pathway (fuel gas supply pathway)

[0087] 32. Exhaust and drainage passage (fuel exhaust gas discharge passage)

[0088] 33. Hydrogen exhaust gas recirculation path (fuel exhaust gas recirculation path)

[0089] 41 Hydrogen Alloy Tank (Fuel Gas Supply Unit)

[0090] 53 Injector (Fuel Gas Supply Unit)

[0091] 54 Discharge device

[0092] 57. Exhaust and drain valve

Claims

1. A fuel cell system comprising a fuel cell that generates electricity by receiving a supply of fuel gas and an oxidant gas, the fuel cell system being characterized in that it comprises: A fuel gas supply passage for supplying the fuel gas to the fuel cell; A fuel exhaust gas discharge passage for discharging fuel exhaust gas discharged from the fuel cell to the outside; A fuel exhaust gas recirculation passage for circulating at least a portion of the fuel exhaust gas from the fuel exhaust gas discharge passage to the fuel gas supply passage; A fuel gas supply unit, disposed in the fuel gas supply passage, is used to supply the fuel gas; An exhaust device, which is disposed downstream of the fuel gas supply unit in the fuel gas supply passage, is used to mix the fuel gas supplied by the fuel gas supply unit with the fuel exhaust gas circulating through the fuel exhaust gas circulation passage and then spray it out. An exhaust drain valve is configured in the fuel exhaust gas discharge passage for discharging the fuel exhaust gas to the outside; A pressure sensor, configured in the fuel gas supply passage, is used to measure the pressure of the fuel gas upstream of the exhaust device; and Control device, which is used to control the exhaust and drain valve, in, The control device is configured to: variably control the ratio of the opening time to the closing time of the exhaust / drain valve in each control cycle; and control the number of opening and closing actions of the exhaust / drain valve per unit time by setting the opening time constant and variably controlling the closing time. The control device controls the number of opening and closing actions of the exhaust drain valve based on the pressure measurement value of the pressure sensor, so as to adjust the concentration of the fuel gas in the fuel exhaust gas circulating through the fuel exhaust gas circulation passage to the fuel gas supply passage.

2. The fuel cell system according to claim 1, characterized in that, It also includes an ammeter used to measure the output current of the fuel cell. In addition to controlling the pressure measurement value, the control device also controls the number of opening and closing actions of the exhaust drain valve based on the current measurement value of the ammeter, so as to adjust the concentration of the fuel gas in the fuel exhaust gas.

3. The fuel cell system according to claim 2, characterized in that, The control device performs the following control: the higher the measured current value, the shorter the closing time of the exhaust and drain valve in each control cycle.

4. The fuel cell system according to any one of claims 1 to 3, characterized in that, The control device performs the following control: the higher the pressure measurement value, the longer the closing time of the exhaust and drain valve in each control cycle.

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