Fuel cell system and method for controlling fuel cell system

Abstract

The invention relates to a fuel cell system and a control method of the fuel cell system. When the determination unit (146) determines that the fuel cell stack (12) is in a wet state, the control unit (142) executes water drainage in the first water drainage mode during power generation at the time of stop, and when the determination unit (146) determines that the fuel cell stack (12) is not in a wet state, the control unit (142) executes water drainage in the second water drainage mode during power generation at the time of stop.

Description

Technical Field

[0001] The present invention relates to a fuel cell system and a control method of the fuel cell system. Background Art

[0002] In recent years, in order to ensure that more people have access to appropriate, reliable, sustainable and advanced energy, research and development of fuel cells that contribute to energy efficiency has been carried out.

[0003] A power generation system having a fuel cell stack is called a fuel cell system. A fuel cell stack has a plurality of power generation cells. The power generation cells generate electricity through an electrochemical reaction between a fuel gas (hydrogen-containing gas) and an oxidant gas (oxygen-containing gas). The power generation cells generate water when generating electricity. The generated water is retained in the fuel cell stack, etc. When the operation of the fuel cell system is stopped in a low temperature environment, the water retained in the fuel cell stack, etc. may freeze. When water freezes in a fuel cell system, etc., it hinders the flow of gas, so the fuel cell stack cannot generate electricity.

[0004] Patent Document 1 discloses that purging is performed when the operation of a fuel cell system ends. Purge is a process for discharging impurities such as water and nitrogen from a fuel cell stack.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2021-180076 Summary of the invention

[0008] Problems to be solved by the invention

[0009] It is desirable to properly drain water from the fuel cell stack.

[0010] The object of the present invention is to solve the above-mentioned problems.

[0011] Solutions for solving problems

[0012] The first invention relates to a fuel cell system, comprising: a fuel cell stack, which comprises a plurality of power generation cells for generating electricity using an oxidant gas and a fuel gas; an oxidant gas supplier, which supplies the oxidant gas to the fuel cell stack; a supply path, in which the oxidant gas supplied to the fuel cell stack flows; a discharge path, in which the oxidant gas discharged from the fuel cell stack flows; a temperature sensor, which detects the temperature of the fuel cell stack, i.e., the stack temperature; and a control device, which controls the oxidant gas supplier, wherein in the fuel cell system, the control device comprises: a control unit, which causes the power generation cells to continue generating electricity when the power generation is stopped after obtaining an indication of stopping power generation until a predetermined condition is satisfied; an acquisition unit, which acquires the stack temperature before the power generation is stopped; and a determination unit, which determines whether the fuel cell stack is at least at the stack temperature acquired by the acquisition unit. Whether it is in a wet state, the control unit can selectively perform either drainage in a first drainage mode or drainage in a second drainage mode during the power generation during stop. In the drainage in the first drainage mode, the oxidant gas of a first flow rate is supplied from the oxidant gas supplier to the fuel cell stack, thereby discharging water retained in the fuel cell stack. In the drainage in the second drainage mode, the oxidant gas of a second flow rate less than the first flow rate is supplied from the oxidant gas supplier to the fuel cell stack, thereby discharging water retained in the fuel cell stack. When the determination unit determines that the fuel cell stack is in the wet state, the control unit performs drainage in the first drainage mode during the power generation during stop. When the determination unit determines that the fuel cell stack is not in the wet state, the control unit performs drainage in the second drainage mode during the power generation during stop.

[0013] The second invention relates to a control method for a fuel cell system, the fuel cell system comprising: a fuel cell stack comprising a plurality of power generation cells for generating electricity using an oxidant gas and a fuel gas; an oxidant gas supplier for supplying the oxidant gas to the fuel cell stack; a supply path through which the oxidant gas supplied to the fuel cell stack flows; a discharge path through which the oxidant gas discharged from the fuel cell stack flows; a temperature sensor for detecting the temperature of the fuel cell stack, i.e., the stack temperature; and a control device for controlling the oxidant gas supplier. In the control method for the fuel cell system, the control device causes the power generation cells to continue generating electricity when stopped after obtaining an indication of stopping power generation until a predetermined condition is satisfied, and the control device obtains the stack temperature before the power generation when stopped, and the control device controls the control method based at least on the obtained stack temperature before the power generation when stopped. , to determine whether the fuel cell stack is in a wet state, the control device can selectively perform either drainage in a first drainage mode or drainage in a second drainage mode during the stop power generation, in the drainage in the first drainage mode, a first flow rate of the oxidant gas is supplied from the oxidant gas supplier to the fuel cell stack, thereby discharging water retained in the fuel cell stack, and in the drainage in the second drainage mode, a second flow rate of the oxidant gas less than the first flow rate is supplied from the oxidant gas supplier to the fuel cell stack, thereby discharging water retained in the fuel cell stack, the control device performs the drainage in the first drainage mode during the stop power generation when it is determined that the fuel cell stack is in the wet state, and performs the drainage in the second drainage mode during the stop power generation when it is determined that the fuel cell stack is not in the wet state.

[0014] Effects of the Invention

[0015] According to the present invention, water can be appropriately discharged from a fuel cell stack.

[0016] The above-mentioned objects, features and advantages will be easily understood from the following description of the embodiments described with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the fuel cell system.

[0018] Figure 2 This is an exploded perspective view of a power generation cell included in a fuel cell stack.

[0019] Figure 3 This is a schematic diagram of the first spacer.

[0020] Figure 4This is a schematic diagram of the second spacer.

[0021] Figure 5 This is a flowchart of the wetness determination process for the fuel cell stack.

[0022] Figure 6 : is a diagram showing the wetness determination correspondence relationship.

[0023] Figure 7 (A) is a graph showing the time change of the current indication value. Figure 7 (B) is a graph showing the temporal change in the temperature value of the cooling medium. Figure 7 (C) is a diagram showing the temporal change of the time measured by the timer. Figure 7 (D) is a graph showing the temporal change of the wetness flag.

[0024] Figure 8 This is a flowchart of the water discharge process performed during power generation at stop. DETAILED DESCRIPTION

[0025] [1 Structure of the fuel cell system 10]

[0026] Figure 1 1 is a schematic diagram of the structure of the fuel cell system 10. The fuel cell system 10 is mounted on a vehicle (fuel cell vehicle), for example. In addition, the fuel cell system 10 can also be mounted on a ship, an aircraft, a robot, etc. In addition, the fuel cell system 10 can also be used as a power source in equipment, homes, etc.

[0027] In the fuel cell system 10, fuel gas and oxidant gas are used as reaction gases. Fuel gas is a hydrogen-containing gas. Oxidant gas is an oxygen-containing gas such as air. The fuel gas and the oxidant gas are each supplied to the fuel cell stack 12 to perform an electrochemical reaction. Moreover, in this specification, the fuel gas discharged from the fuel cell stack 12 without being used for the electrochemical reaction is also referred to as fuel exhaust. In addition, in this specification, the oxidant gas discharged from the fuel cell stack 12 without being used for the electrochemical reaction is also referred to as oxidant exhaust.

[0028] The fuel cell system 10 includes a fuel cell stack 12, a tank 14, an anode system 16, a cathode system 18, and a cooling system 20. The fuel cell system 10 also includes a control device 22. Electric power generated by the fuel cell stack 12 is supplied to a load 21. The tank 14 is filled with high-pressure fuel gas.

[0029] The fuel cell stack 12 includes a fuel gas supply interface 22a for supplying fuel gas to the interior of the fuel cell stack 12, and a fuel gas exhaust interface 22b for exhausting fuel gas exhaust from the interior of the fuel cell stack 12. The fuel cell stack 12 includes an oxidant gas supply interface 22c for supplying oxidant gas to the interior of the fuel cell stack 12, and an oxidant gas exhaust interface 22d for exhausting oxidant exhaust from the interior of the fuel cell stack 12. The fuel cell stack 12 includes a cooling medium supply interface 22e for supplying cooling medium to the interior of the fuel cell stack 12, and a cooling medium exhaust interface 22f for exhausting cooling medium from the interior of the fuel cell stack 12. The fuel cell stack 12 includes a drainage interface 22g for draining water retained in the interior of the fuel cell stack 12. The drainage interface 22g is disposed at the lower portion of the fuel cell stack 12.

[0030] Here, use Figure 2 to Figure 4 The structure of the fuel cell stack 12 will be described. Figure 2 1 is an exploded perspective view of a power generation cell 24 included in the fuel cell stack 12. The fuel cell stack 12 is formed by stacking a plurality of power generation cells 24 in the direction of arrow A. A compressive load in the stacking direction is applied to the plurality of power generation cells 24 in the fuel cell stack 12.

[0031] The power generation cell 24 has a horizontally long rectangular shape. The power generation cell 24 includes an electrolyte membrane-electrode structure 26 and a pair of separators (a first separator 28 and a second separator 30). The surface 28a of the first separator 28 faces the first surface 26a of the electrolyte membrane-electrode structure 26. The surface 30a of the second separator 30 faces the second surface 26b of the electrolyte membrane-electrode structure 26. The electrolyte membrane-electrode structure 26 is sandwiched by the first separator 28 and the second separator 30.

[0032] The cross-sections of the first separator 28 and the second separator 30 are formed of corrugated metal thin plates. In two adjacent power generation cells 24, the first separator 28 of one power generation cell 24 and the second separator 30 of the other power generation cell 24 are joined to each other. A refrigerant flow path (not shown) for the cooling medium to flow is formed between the first separator 28 and the second separator 30.

[0033] The electrolyte membrane-electrode structure 26 includes an MEA (Membrane Electrode Assembly) 32 and a resin frame 34. The MEA 32 includes an electrolyte membrane 36, a cathode electrode 40, and an anode electrode 38. The electrolyte membrane 36 is interposed between the cathode electrode 40 and the anode electrode 38. The resin frame 34 protrudes outward from the outer periphery of the MEA 32.

[0034] An oxidant gas supply through hole 42a, a cooling medium supply through hole 44a, and a fuel gas discharge through hole 46b are provided at one end edge portion in the long side direction of the power generation cell 24 (the end edge portion in the direction of the arrow symbol B1). The oxidant gas supply through hole 42a is connected to the oxidant gas supply interface 22c. In the oxidant gas supply through hole 42a, the oxidant gas flows in the direction of the arrow symbol A2. The cooling medium supply through hole 44a is connected to the cooling medium supply interface 22e. In the cooling medium supply through hole 44a, the cooling medium flows in the direction of the arrow symbol A2. The fuel gas discharge through hole 46b is connected to the fuel gas discharge interface 22b. In the fuel gas discharge through hole 46b, the fuel gas flows in the direction of the arrow symbol A1.

[0035] A fuel gas supply passage 46a, a cooling medium discharge passage 44b, and an oxidant gas discharge passage 42b are provided at the other end edge portion in the long side direction of the power generation cell 24 (the end edge portion in the direction of the arrow symbol B2). The fuel gas supply passage 46a is connected to the fuel gas supply interface 22a. In the fuel gas supply passage 46a, the fuel gas flows in the direction of the arrow symbol A2. The cooling medium discharge passage 44b is connected to the cooling medium discharge interface 22f. In the cooling medium discharge passage 44b, the cooling medium flows in the direction of the arrow symbol A1. The oxidant gas discharge passage 42b is connected to the oxidant gas discharge interface 22d. In the oxidant gas discharge passage 42b, the oxidant gas flows in the direction of the arrow symbol A1.

[0036] Figure 3 It is a schematic diagram of the first spacer 28 . Figure 3 FIG. 2 shows the surface 28a of the first separator 28. The first separator 28 is formed in a rectangular shape. The oxidant gas flow path 50 is formed on the surface 28a of the first separator 28. Figure 2 When viewed in the direction of arrow A1 or arrow A2, the oxidant gas flow path 50 overlaps the cathode electrode 40 of the electrolyte membrane-electrode assembly 26. The oxidant gas flow path 50 extends along the longitudinal direction of the power generation cell 24 (direction of arrow B).

[0037] The oxidant gas flow path 50 includes a plurality of first flow path protrusions 52 and a plurality of first flow path grooves 54. The first flow path protrusions 52 protrude in the direction of arrow symbol A2. The first flow path grooves 54 are recessed in the direction of arrow symbol A1. The first flow path protrusions 52 and the first flow path grooves 54 each extend in a wavy manner in the direction of arrow symbol B. In the oxidant gas flow path 50, the first flow path protrusions 52 and the first flow path grooves 54 are alternately arranged in the flow path width direction (arrow symbol C direction).

[0038] Two first supply parts 55a and 55b are formed on the surface 28a of the first separator 28. The first supply part 55a includes a plurality of first supply protrusions 56a and a plurality of first supply grooves 57a extending from the oxidant gas supply passage 42a toward the oxidant gas flow path 50. The first supply part 55b includes a plurality of first supply protrusions 56b and a plurality of first supply grooves 57b extending from the oxidant gas flow path 50 toward the oxidant gas discharge passage 42b.

[0039] A first sealing portion 58 is formed on the surface 28a of the first separator 28 to prevent leakage of the reaction gas (oxidant gas or fuel gas) or the cooling medium. The first sealing portion 58 includes a plurality of first connecting hole sealing portions 60 and a first flow path sealing portion 62. The first connecting hole sealing portion 60 and the first flow path sealing portion 62 protrude in the direction of the arrow symbol A2. One first connecting hole sealing portion 60 is formed for one connecting hole (oxidant gas supply connecting hole 42a, etc.). Each first connecting hole sealing portion 60 surrounds the connecting hole individually. The first flow path sealing portion 62 surrounds the area where the oxidant gas flow path 50, the first supply portion 55a, 55b, and the connecting holes for the reaction gas to flow (oxidant gas supply connecting hole 42a, oxidant gas discharge connecting hole 42b, fuel gas supply connecting hole 46a, fuel gas discharge connecting hole 46b) are arranged. Each of the plurality of first connecting hole sealing portions 60 and the first flow path sealing portion 62 is pressed against the resin frame portion 34 of the electrolyte membrane-electrode structure 26.

[0040] The first communication hole sealing portion 60 surrounding the oxidizing gas supply communication hole 42a includes a passage 63a. The passage 63a connects the oxidizing gas supply communication hole 42a with the first supply portion 55a adjacent to the oxidizing gas supply communication hole 42a. Figure 3 63a, but in fact, there are multiple channels 63a. Similarly, the first communication hole sealing portion 60 surrounding the oxidant gas discharge communication hole 42b is provided with a channel 63b. The channel 63b connects the oxidant gas discharge communication hole 42b with the first supply portion 55b adjacent to the oxidant gas discharge communication hole 42b. Figure 3 Although one channel 63b is shown in the figure, a plurality of channels 63b are actually provided.

[0041] The oxidant gas is supplied from the oxidant gas supply passage 42a to the oxidant gas flow path 50 via the channel 63a and the first supply portion 55a. The oxidant gas flows through the oxidant gas flow path 50 and is supplied to the cathode electrode 40. The oxidant exhaust gas without the electrochemical reaction is discharged from the oxidant gas flow path 50 to the oxidant gas discharge passage 42b via the first supply portion 55b and the channel 63b.

[0042] A first bypass-preventing convex portion 64 is formed on the surface 28a of the first separator 28. The first bypass-preventing convex portion 64 is disposed between the end portion (the first end portion flow path protrusion 52a) in the flow path width direction of the oxidant gas flow path 50 and the first flow path sealing portion 62. The first bypass-preventing convex portion 64 prevents the oxidant gas supplied from the oxidant gas supply passage 42a from flowing between the first end portion flow path protrusion 52a and the first flow path sealing portion 62 and being supplied to the oxidant gas discharge passage 42b. In other words, the first bypass-preventing convex portion 64 prevents the oxidant gas from bypassing.

[0043] The first bypass blocking convex portion 64 has a plurality of first bypass protrusions 65 extending in the direction of arrow symbol C. A plurality of first bypass protrusions 65 are arranged along the direction of arrow symbol B. The first bypass protrusion 65 protrudes in the direction of arrow symbol A2. The height of the first bypass protrusion 65 is slightly lower than the height of the first flow path sealing portion 62. The first bypass protrusion 65 is not subjected to a compressive load in the direction of arrow symbol A. Therefore, there is a small gap between the first bypass protrusion 65 and the resin frame portion 34 of the electrolyte membrane-electrode structure 26.

[0044] Figure 4 It is a schematic diagram of the second spacer 30 . Figure 4 FIG. 3 shows the surface 30a of the second separator 30. The second separator 30 is formed in a rectangular shape. A fuel gas flow path 66 is formed on the surface 30a of the second separator 30. Figure 2 When viewed in the direction of arrow A1 or arrow A2, the fuel gas flow path 66 overlaps the anode electrode 38 of the membrane electrode assembly 26. The fuel gas flow path 66 extends in the longitudinal direction of the power generation cell 24 (direction of arrow B).

[0045] The fuel gas flow path 66 includes a plurality of second flow path protrusions 68 and a plurality of second flow path grooves 70. The second flow path protrusions 68 protrude in the direction of arrow symbol A1. The second flow path grooves 70 are recessed in the direction of arrow symbol A2. The second flow path protrusions 68 and the second flow path grooves 70 each extend in a wavy manner in the direction of arrow symbol B. In the fuel gas flow path 66, the second flow path protrusions 68 and the second flow path grooves 70 are alternately arranged in the flow path width direction (arrow symbol C direction).

[0046] Two second supply parts 71a and 71b are formed on the surface 30a of the second separator 30. The second supply part 71a includes a plurality of second supply protrusions 72a and a plurality of second supply grooves 73a extending from the fuel gas supply passage 46a toward the fuel gas flow path 66. The second supply part 71b includes a second supply protrusion 72b and a plurality of second supply grooves 73b extending from the fuel gas flow path 66 toward the fuel gas discharge passage 46b.

[0047] A second sealing portion 74 is formed on the surface 30a of the second separator 30 to prevent leakage of the reaction gas (oxidant gas or fuel gas) or the cooling medium. The second sealing portion 74 includes a plurality of second connecting hole sealing portions 76 and a second flow path sealing portion 78. The second connecting hole sealing portion 76 and the second flow path sealing portion 78 protrude in the direction of the arrow symbol A1. One second connecting hole sealing portion 76 is formed relative to one connecting hole (fuel gas supply connecting hole 46a, etc.). Each second connecting hole sealing portion 76 surrounds the connecting hole individually. The second flow path sealing portion 78 surrounds the area where the fuel gas flow path 66, the second supply portion 71a, 71b, and the connecting holes (oxidant gas supply connecting hole 42a, oxidant gas discharge connecting hole 42b, fuel gas supply connecting hole 46a, fuel gas discharge connecting hole 46b) for the reaction gas flow are arranged. The plurality of second connecting hole sealing portions 76 and the second flow path sealing portion 78 are each pressed against the resin frame portion 34 of the electrolyte membrane-electrode structure 26.

[0048] The second communication hole sealing portion 76 surrounding the fuel gas supply communication hole 46a includes a passage 79a. The passage 79a connects the fuel gas supply communication hole 46a with the second supply portion 71a adjacent to the fuel gas supply communication hole 46a. Figure 4 , but in fact, there are multiple channels 79a. Similarly, the second connecting hole sealing portion 76 surrounding the fuel gas discharge connecting hole 46b is provided with a channel 79b. The channel 79b connects the fuel gas discharge connecting hole 46b with the second supply portion 71b adjacent to the fuel gas discharge connecting hole 46b. Figure 4 Although only one channel 79b is shown in the figure, a plurality of channels 79b are actually provided.

[0049] The fuel gas is supplied from the fuel gas supply passage 46a to the fuel gas flow path 66 via the channel 79a and the second supply portion 71a. The fuel gas flows through the fuel gas flow path 66 and is supplied to the anode electrode 38. The fuel exhaust gas without the electrical chemical reaction is discharged from the fuel gas flow path 66 to the fuel gas discharge passage 46b via the second supply portion 71b and the channel 79b.

[0050] A second bypass preventing convex portion 80 is formed on the surface 30a of the second separator 30. The second bypass preventing convex portion 80 is disposed between the end portion (the second end portion flow path protrusion 68a) in the flow path width direction of the fuel gas flow path 66 and the second flow path sealing portion 78. The second bypass preventing convex portion 80 prevents the fuel gas supplied from the fuel gas supply passage 46a from flowing between the second end portion flow path protrusion 68a and the second flow path sealing portion 78 and being supplied to the fuel gas discharge passage 46b. In other words, the second bypass preventing convex portion 80 prevents the fuel gas from bypassing.

[0051] The second bypass blocking convex portion 80 has a plurality of second bypass protrusions 82 extending in the direction of arrow symbol C. A plurality of second bypass protrusions 82 are arranged along the direction of arrow symbol B. The second bypass protrusion 82 protrudes in the direction of arrow symbol A1. The height of the second bypass protrusion 82 is slightly lower than the height of the second flow path sealing portion 78. The second bypass protrusion 82 is not subjected to a compressive load in the direction of arrow symbol A. Therefore, there is a small gap between the second bypass protrusion 82 and the resin frame portion 34 of the electrolyte membrane-electrode structure 26.

[0052] Back to Figure 1 , the structure of the fuel cell system 10 is described. The anode system 16 includes a fuel gas supply path 84, a fuel gas discharge path 86, a circulation path 88, a first drain path 90, and a second drain path 92. In addition, the anode system 16 includes an ejector 94, an ejector 96, a gas-liquid separator 98, a first drain valve 100, and a second drain valve 102.

[0053] The fuel gas supply path 84 is connected to the discharge port of the tank 14 and the fuel gas supply port 22a of the fuel cell stack 12. The fuel gas supply path 84 is provided with an ejector 94 and an ejector 96. The ejector 96 is disposed closer to the fuel cell stack 12 than the ejector 94.

[0054] The fuel gas discharge path 86 is connected to the fuel gas discharge port 22 b of the fuel cell stack 12 and the supply port of the gas-liquid separator 98 . The circulation path 88 is connected to the discharge port of the gas-liquid separator 98 and the ejector 96 .

[0055] The first drain passage 90 is connected to the drain port of the gas-liquid separator 98 and the inlet of the diluter 121. The outlet of the diluter 121 is connected to the drain port of the vehicle. The first drain passage 90 is provided with a first drain valve 100. The second drain passage 92 is connected to the drain interface 22g of the fuel cell stack 12 and the first drain passage 90. The second drain passage 92 is provided with a second drain valve 102.

[0056] The cathode system 18 includes an oxidant gas supply path 106, an oxidant gas discharge path 108 (discharge path), and a bypass path 110. The cathode system 18 also includes a compressor 112 (oxidant gas supplier), a humidifier (HUM) 114, a first sealing valve 116, a second sealing valve 118, and a bypass valve 120.

[0057] The oxidant gas supply path 106 is connected to the air intake port of the vehicle and the oxidant gas supply interface 22c of the fuel cell stack 12. The oxidant gas supply path 106 is provided with a compressor 112, a first sealing valve 116, and a humidifier supply path 114A of the humidifier 114. The portion of the oxidant gas supply path 106 disposed upstream of the humidifier 114 is referred to as the oxidant gas supply path 106A. The portion of the oxidant gas supply path 106 disposed downstream of the humidifier 114 is referred to as the oxidant gas supply path 106B. The oxidant gas supply path 106A is provided with a compressor 112 and a first sealing valve 116. The first sealing valve 116 is disposed near the humidifier 114 relative to the compressor 112.

[0058] The oxidant gas discharge path 108 is connected to the oxidant gas discharge port 22d of the fuel cell stack 12 and the inlet of the diluter 121. The oxidant gas discharge path 108 is provided with a humidifier discharge path 114B of the humidifier 114 and a second sealing valve 118. The portion of the oxidant gas discharge path 108 disposed upstream of the humidifier 114 is referred to as the oxidant gas discharge path 108A. The portion of the oxidant gas discharge path 108 disposed downstream of the humidifier 114 is referred to as the oxidant gas discharge path 108B. The oxidant gas discharge path 108B is provided with a second sealing valve 118.

[0059] The bypass passage 110 is connected to a portion between the compressor 112 and the first sealing valve 116 in the oxidizing gas supply passage 106A and a portion downstream of the second sealing valve 118 in the oxidizing gas discharge passage 108B. The bypass passage 110 is provided with a bypass valve 120 .

[0060] The anode system 16 and the cathode system 18 are connected to each other via a connection path 132. The connection path 132 connects the circulation path 88 of the anode system 16 and the oxidant gas supply path 106B of the cathode system 18. The connection path 132 is provided with a relief valve 134.

[0061] The cooling system 20 includes a cooling medium supply path 122 and a cooling medium discharge path 124 . The cooling system 20 also includes a pump 126 , a radiator 128 , and a temperature sensor 130 .

[0062] The cooling medium supply path 122 is connected to the fluid discharge port of the radiator 128 and the cooling medium supply interface 22e of the fuel cell stack 12. The cooling medium supply path 122 is provided with a pump 126. The cooling medium discharge path 124 is connected to the cooling medium discharge interface 22f of the fuel cell stack 12 and the fluid supply port of the radiator 128. A temperature sensor 130 is installed in the cooling medium discharge path 124. The temperature sensor 130 detects the temperature of the cooling medium flowing in the cooling medium discharge path 124. The temperature of the cooling medium flowing in the cooling medium discharge path 124 is equivalent to the internal temperature of the fuel cell stack 12 (stack temperature).

[0063] Furthermore, the impedance measuring device 148 may be mounted on the fuel cell stack 12. For example, the impedance measuring device 148 measures the impedance of the fuel cell stack 12 by superimposing an alternating current on the outputs of the plurality of power generation cells 24.

[0064] The control device 22 can be composed of an ECU (Electronic Control Unit). The control device 22 includes a computing unit 136 and a storage unit 138. The computing unit 136 is, for example, a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). That is, the computing unit 136 can be composed of a processing circuit. The computing unit 136 executes the program stored in the storage unit 138 to control each device. Alternatively, at least a portion of the computing unit 136 is implemented by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). Alternatively, at least a portion of the computing unit 136 is implemented by a circuit including discrete devices.

[0065] The calculation unit 136 includes an acquisition unit 140, a control unit 142, a timing unit 144, and a determination unit 146. The acquisition unit 140 acquires information from electronic components (sensors, ECU, etc.) other than the control device 22. The control unit 142 controls the operation of the ejector 94, the compressor 112, the pump 126, each valve, etc. The timing unit 144 measures the execution time of the drainage control described later by a timer (Japanese: タイマ). The determination unit 146 determines whether the fuel cell stack 12 is in the expected wet state and whether it is in the wet state.

[0066] The storage unit 138 is composed of a volatile memory (not shown) and a non-volatile memory (not shown) as a computer-readable storage medium. Examples of volatile memory include RAM (Random Access Memory). Examples of non-volatile memory include ROM (Read Only Memory), flash memory, etc. Data, etc. are stored in the volatile memory, for example. Programs, forms, correspondences, etc. are stored in the non-volatile memory, for example. Alternatively, the processor, integrated circuit, etc. described above may include at least a portion of the storage unit 138.

[0067] [2 Flow of Fluid in Fuel Cell System 10]

[0068] [2-1 Flow of Fluid in Anode System 16]

[0069] The injector 94 injects the fuel gas supplied from the tank 14 to the downstream of the fuel gas supply path 84. The fuel gas injected from the injector 94 is supplied to the fuel gas supply port 22a of the fuel cell stack 12 via the fuel gas supply path 84. The fuel gas that has not reacted inside the fuel cell stack 12 is discharged as a fuel exhaust gas from the fuel gas discharge port 22b of the fuel cell stack 12. The fuel exhaust gas includes hydrogen that has not reacted with oxygen, nitrogen in the oxidant gas that has passed through the electrolyte membrane 36, and moisture generated by the reaction between oxygen and hydrogen.

[0070] The fuel exhaust is supplied to the gas-liquid separator 98 via the fuel gas exhaust path 86. The gas-liquid separator 98 separates the fuel exhaust into a gas component (fuel exhaust) and a liquid component (water). The fuel exhaust discharged from the gas-liquid separator 98 is supplied to the ejector 96 via the circulation path 88. In the ejector 96, the fuel exhaust sucked from the gas-liquid separator 98 merges with the fuel gas injected from the injector 94.

[0071] [2-2 Flow of Fluid in Cathode System 18]

[0072] The compressor 112 ejects the oxidant gas (air) sucked from the outside of the vehicle to the downstream of the oxidant gas supply path 106. The oxidant gas ejected from the compressor 112 is supplied to the oxidant gas supply port 22c of the fuel cell stack 12 via the oxidant gas supply path 106. The oxidant gas that has not reacted inside the fuel cell stack 12 is discharged as an oxidant exhaust gas from the oxidant gas exhaust port 22d of the fuel cell stack 12. The oxidant exhaust gas includes various components contained in the oxidant gas and moisture generated by the reaction of oxygen and hydrogen.

[0073] The oxidant exhaust gas is discharged to the diluter 121 via the oxidant gas discharge path 108. The oxidant exhaust gas includes moisture. In the humidifier 114, a part of the moisture contained in the oxidant exhaust gas is used to humidify the oxidant gas flowing through the humidifier supply path 114A.

[0074] [2-3 Flow of Fluid in Cooling System 20]

[0075] The pump 126 ejects the cooling medium toward the cooling medium supply port 22e of the fuel cell stack 12. The cooling medium ejected from the pump 126 is supplied to the cooling medium supply port 22e of the fuel cell stack 12 via the cooling medium supply path 122. The cooling medium flowing inside the fuel cell stack 12 is discharged from the cooling medium discharge port 22f of the fuel cell stack 12. The cooling medium discharged from the cooling medium discharge port 22f is supplied to the radiator 128 via the cooling medium discharge path 124. The cooling medium that has radiated heat in the radiator 128 is sucked into the pump 126.

[0076] [3 Water discharge during power generation at stoppage]

[0077] When the operation of the vehicle stops, the control device 22 stops the operation of the fuel cell system 10. The operation unit 136 (control unit 142) of the control device 22 makes the electrolyte membrane 36 in an appropriate wet state and uniformly wets the electrolyte membrane 36 before stopping the power generation of the fuel cell system 10 so as to generate electricity. This is called stop-time power generation. When the power generation is stopped, the control unit 142 performs power generation control so that the output current value of the fuel cell stack 12 becomes a predetermined value. When the power generation is stopped, the fuel gas, the oxidant gas and the cooling medium are supplied to the fuel cell stack 12, and the power is supplied from the fuel cell stack 12 to the load 21 (such as a battery).

[0078] In addition, the control unit 142 causes water to be drained from the fuel cell stack 12 during power generation when stopped. It is also called scavenging. For example, the control unit 142 increases the flow rate of the reaction gas compared to normal power generation, thereby draining water from the fuel cell stack 12 and each exhaust path. Specifically, the control unit 142 controls the flow rate of the oxidant gas ejected from the compressor 112 (the flow rate of the oxidant gas supplied to the fuel cell stack 12). Moreover, even if the flow rate of the fuel gas is increased, water can be drained from the fuel cell stack 12. Among them, when the flow rate of the fuel gas is increased during power generation when stopped, the fuel gas will be wasted. Therefore, it is preferred to increase the oxidant gas, thereby draining water from the fuel cell stack 12. In this specification, the control of discharging water from the fuel cell stack 12 (and the oxidant gas exhaust path 108) during power generation when stopped is referred to as drainage control or scavenging control. In addition, water includes high humidity air containing water vapor in addition to liquid water retained in the fuel cell stack 12 and the oxidant gas exhaust path 108.

[0079] During power generation at stop, the control unit 142 can perform drainage control in the cathode system 18 in either the first drainage mode or the second drainage mode. When the determination unit 146 determines that the fuel cell stack 12 is in a wet state, the control unit 142 performs drainage in the first drainage mode. When the determination unit 146 determines that the fuel cell stack 12 is not in a wet state, the control unit 142 performs drainage in the second drainage mode. The wet state refers to a state in which the water content in the fuel cell stack 12 is above a predetermined amount, and refers to a state in which the humidity in the fuel cell stack 12 is above a predetermined humidity.

[0080] In the first drainage mode, a first flow rate of oxidant gas is ejected from the compressor 112. In the second drainage mode, a second flow rate of oxidant gas is ejected from the compressor 112. The first flow rate is greater than the second flow rate. Therefore, drainage in the first drainage mode can drain more water from the fuel cell stack 12 than drainage in the second drainage mode.

[0081] For example, in Figure 3 The first bypass blocking convex portion 64, the first supply portions 55a, 55b, etc. shown in the figure are prone to retaining water. When the flow rate of the oxidant gas to the fuel cell stack 12 is increased, the water content of the electrolyte membrane 36 is reduced. As a result, the water retained in the first bypass blocking convex portion 64 is absorbed by the electrolyte membrane 36 and is easily discharged to the oxidant gas flow path 50. The water discharged to the oxidant gas flow path 50 is discharged to the outside of the fuel cell stack 12. That is, by performing drainage in the first drainage mode, it is possible to promote the discharge of water retained in the first bypass blocking convex portion 64. In addition, by performing drainage in the first drainage mode, it is possible to promote the discharge of water retained in the first supply portions 55a, 55b.

[0082] Similarly, in Figure 4 The second bypass blocking convex portion 80, the second supply portions 71a, 71b, etc. shown in the figure are prone to retaining water. When the flow rate of the oxidant gas to the fuel cell stack 12 is increased, the water retained in the second bypass blocking convex portion 80, etc. is absorbed by the electrolyte membrane 36 and is easily discharged to the oxidant gas flow path 50. The water discharged to the oxidant gas flow path 50 is discharged to the outside of the fuel cell stack 12. That is, by performing drainage in the first drainage mode, the drainage of the water retained in the second bypass blocking convex portion 80 can also be promoted. In addition, by performing drainage in the first drainage mode, the drainage of the water retained in the second supply portions 71a, 71b can also be promoted.

[0083] [3-1 Determination of Wetness of Fuel Cell Stack 12]

[0084] Figure 5 This is a flowchart of the wetness determination process for the fuel cell stack 12 . Figure 6 1 is a diagram showing the wetness determination map 150 . Figure 7 (A) is a graph showing the time change of the current indication value. Figure 7 (B) is a graph showing the temporal change in the temperature value of the cooling medium. Figure 7 (C) is a diagram showing the temporal change of the time measured by the timer. Figure 7 (D) is a graph showing the temporal change of the wetness flag.

[0085] As described above, whether to perform drainage in the first drainage mode or the second drainage mode is determined based on whether the fuel cell stack 12 is in a wet state. Whether the fuel cell stack 12 is in a wet state is determined during operation of the fuel cell system 10 (during operation of the vehicle). Figure 5 , an example of the wetness determination of the fuel cell stack 12 is described.

[0086] Moreover, when using Figure 5 In the wet determination process described below, when the wet state is expected to continue for a predetermined time, the fuel cell stack 12 is determined to be in a wet state. The expected wet state refers to a state in which the fuel cell stack 12 is likely to be in a wet state. Here, the expected wet state is determined based on the output current of the fuel cell stack 12 and the temperature of the fuel cell stack 12. Moreover, the output current of the fuel cell stack 12 is substantially equivalent to the current indication value from the ECU of the vehicle. In addition, the temperature of the fuel cell stack 12 is substantially equivalent to the temperature of the fluid discharged from the fuel cell stack 12. Therefore, in the wet determination process described below, whether it is an expected wet state is determined based on the current indication value (output current value) from the ECU of the vehicle and the temperature value (stack temperature) detected by the temperature sensor 130. Moreover, the temperature of the oxidant exhaust gas may also be used instead of the temperature of the cooling medium.

[0087] In step S1, the determination unit 146 determines whether the fuel cell stack 12 is in the estimated wet state. The determination unit 146 uses, for example, Figure 6 The wetness determination correspondence 150 is shown. The wetness determination correspondence 150 associates the combination of the current indication value and the temperature value of the cooling medium with the state of the fuel cell stack 12 (whether it is the expected wetness state). Figure 6 As shown, the wetness determination correspondence 150 associates the combination of the current indication value less than the current threshold value Ith and the temperature value of the cooling medium less than the temperature threshold value Tth with the expected wetness state. The wetness determination correspondence 150 makes such a correspondence association because the fuel cell stack 12 is likely to become wet when the output current value of the fuel cell stack 12 is relatively small and the temperature of the fuel cell stack 12 is relatively low.

[0088] The acquisition unit 140 acquires the current indication value of the fuel cell stack 12 from the ECU of the vehicle. In addition, the acquisition unit 140 acquires the temperature value of the cooling medium from the temperature sensor 130. The determination unit 146 determines whether the fuel cell stack 12 is in the expected wet state based on the current indication value, the temperature value of the cooling medium, and the wet determination correspondence 150.

[0089] If the fuel cell stack 12 is in the expected wet state (step S1: Yes), the process proceeds to step S2. Figure 7 As shown in (A), between time point t1 and time point t2, the current indication value is less than the current threshold value Ith. Figure 7 As shown in (A), between time point t3 and time point t4, the current indication value is less than the current threshold value Ith. Figure 7 As shown in (B), after time point t1, the temperature value of the cooling medium is less than the temperature threshold value Tth. The determination unit 146 determines that the fuel cell stack 12 is in the expected wet state between time point t1 and time point t2. In addition, the determination unit 146 determines that the fuel cell stack 12 is in the expected wet state between time point t3 and time point t4.

[0090] On the other hand, if the fuel cell stack 12 is not in the expected wet state (step S1: No), the process proceeds to step S7. Figure 7 As shown in (B), between time point t0 and time point t1, the temperature value of the cooling medium is greater than the temperature threshold value Tth. Figure 7As shown in (A), between time point t2 and time point t3, the current indication value is greater than the current threshold value Ith. Between time point t0 and time point t1, the determination unit 146 determines that the fuel cell stack 12 is not in the expected wet state. In addition, between time point t2 and time point t3, the determination unit 146 determines that the fuel cell stack 12 is not in the expected wet state.

[0091] In step S2, the timing unit 144 determines whether timing is in progress. If timing is in progress (step S2: Yes), the process proceeds to step S4. On the other hand, if timing is not in progress (step S2: No), the process proceeds to step S3.

[0092] When the process moves from step S2 to step S3, the timing unit 144 starts timing by the timer. Figure 7 As shown in (C), at time point t1 and time point t3, the timer starts counting. Moreover, between time point t1 and time point t2, the timer continues counting. In addition, between time point t3 and time point t4, the timer continues counting. When step S3 is completed, the process transfers to step S4.

[0093] When transferring from step S2 or step S3 to step S4, the determination unit 146 compares the measured time of the timer with the predetermined time Cth. The predetermined time Cth is a time threshold for determining whether the fuel cell stack 12 is in a wet state. In the wet determination process, when the wet state is expected to occur continuously for the predetermined time Cth, it is determined that the fuel cell stack 12 is in a wet state. When the measured time is longer than the predetermined time Cth (step S4: Yes), the process transfers to step S5. For example, if Figure 7 As shown in (C), at time point t4, the time measured by the timer is equal to or longer than the predetermined time Cth. On the other hand, when the measured time is less than the predetermined time Cth (step S4: No), the process returns to step S1.

[0094] When transferring from step S4 to step S5, the determination unit 146 sets the wet flag to "1". Figure 7 As shown in (D), at time point t4, the wet flag is set to "1." When step S5 is completed, the process moves to step S6.

[0095] When transferring from step S5 or step S8 described later to step S6, the control unit 142 determines whether there is an instruction to stop the operation of the fuel cell system 10. The driver of the vehicle performs a disconnection operation on an ignition switch (also called a power switch) not shown in the figure to stop the operation of the vehicle. When the acquisition unit 140 acquires a disconnection signal accompanying the disconnection operation of the ignition switch, the control unit 142 determines that there is an instruction to stop the operation of the fuel cell system 10. When there is an instruction to stop the operation of the fuel cell system 10 (step S6: Yes), Figure 5 The series of processing shown ends. On the other hand, when there is no instruction to stop the operation of the fuel cell system 10 (step S6: No), the process returns to step S1.

[0096] When the process moves from step S1 to step S7, the timing unit 144 resets the timer. Figure 7 As shown in (C), the timer is reset between time point t0 and time point t1 and between time point t2 and time point t3. When step S7 is completed, the process transfers to step S8.

[0097] In step S8, the control unit 142 sets the wet flag to "0". Figure 7 As shown in (D), between time point t0 and time point t4, the wet flag is set to "0." When step S8 is completed, the process moves to step S6.

[0098] [3-2 Water discharge processing performed during power generation at stoppage]

[0099] Figure 8 Flow chart of the drainage process performed during power generation at stop. Figure 5 If the result of the determination in step S6 is "yes", the Figure 8 In the drainage process described below, it is possible to switch from the first drainage mode to the second drainage mode in drainage control.

[0100] In step S11, the timer 144 sets the drainage time for executing the drainage control. Here, the timer 144 sets the drainage setting time stored in the storage unit 138 as the drainage time. When step S11 is completed, the process moves to step S12.

[0101] In step S12, the timing unit 144 starts timing by the timer. That is, the timing unit 144 starts timing the execution time of the drainage control. When step S12 is completed, the process transfers to step S13.

[0102] In step S13, the determination unit 146 determines the Figure 5The wet flag set in the process shown in the figure is used to determine whether the fuel cell stack 12 is in a wet state. When the wet flag is set to 1 (step S13: "1"), the process is transferred to step S14. That is, when the fuel cell stack 12 is in a wet state, the process is transferred to step S14. On the other hand, when the wet flag is set to 0 (step S13: "0"), the process is transferred to step S19. That is, when the fuel cell stack 12 is not in a wet state, the process is transferred to step S19.

[0103] When transferring from step S13 to step S14, or when transferring from step S16 described later to step S14, the control unit 142 performs drainage in the first drainage mode. The control unit 142 controls the operation of the compressor 112 in the first drainage mode so that the flow rate of the oxidant gas ejected from the compressor 112 becomes the first flow rate. Thus, the oxidant gas of the first flow rate is supplied to the fuel cell stack 12 and the oxidant gas discharge path 108. In this case, the oxidant gas with a relatively large flow rate is supplied to the fuel cell stack 12 and the oxidant gas discharge path 108. A large amount of oxidant gas is supplied, so that the water retained in the fuel cell stack 12 and the oxidant gas discharge path 108 can be fully discharged. Moreover, the control unit 142 controls the rotation speed of the pump 126 to the first rotation speed in the first drainage mode. When step S14 ends, the process is transferred to step S15.

[0104] In step S15, the control unit 142 compares the measured time (first execution time) of the timer with the drainage time. When the measured time is greater than the drainage time (step S15: Yes), the drainage control ends. In this case, the control unit 142 stops the compressor 112 and the pump 126. In addition, the control unit 142 closes each valve in sequence. On the other hand, when the measured time is less than the drainage time (step S15: No), the process moves to step S16.

[0105] When transferring from step S15 to step S16, the determination unit 146 determines whether the fuel cell stack 12 is in a wet state. For example, the determination unit 146 may perform a wet determination based on the wet determination correspondence 150. When the wet determination correspondence 150 is used, when the combination of the current indication value (predetermined value) and the temperature value of the cooling medium is within the expected wet state, the determination unit 146 determines that the fuel cell stack 12 is in a wet state. Alternatively, the determination unit 146 performs a wet determination based on the impedance value of the fuel cell stack 12. The impedance value of the fuel cell stack 12 is measured by the impedance measuring device 148. When the fuel cell stack 12 is in a wet state (step S16: yes), the process returns to step S14. On the other hand, when the fuel cell stack 12 is not in a wet state (step S16: no), the process transfers to step S17.

[0106] When the process moves from step S16 to step S17, the timer 144 calculates the remaining drainage time by subtracting the first drainage execution time, which is the drainage execution time in the first drainage mode, from the drainage setting time stored in the storage unit 138. The timer 144 sets the remaining drainage time as the drainage time (second execution time). When step S17 is completed, the process moves to step S18.

[0107] In step S18, the timer 144 resets the timer and then starts counting again. That is, the timer 144 starts counting the execution time of the drainage control in the second drainage mode. When step S18 is completed, the process moves to step S19.

[0108] When transferring from step S13, step S18 or step S20 described later to step S19, the control unit 142 performs drainage in the second drainage mode. When transferring from step S18 to step S19, the control unit 142 switches the drainage mode from the first drainage mode to the second drainage mode. The control unit 142 controls the operation of the compressor 112 in the second drainage mode so that the flow rate of the oxidant gas ejected from the compressor 112 becomes the second flow rate. Thus, the second flow rate of oxidant gas is supplied to the fuel cell stack 12 and the oxidant gas discharge path 108. In this case, the oxidant gas with a smaller flow rate than the first drainage mode and a larger flow rate than the normal power generation is supplied to the fuel cell stack 12 and the oxidant gas discharge path 108. By switching from drainage in the first drainage mode to drainage in the second drainage mode, the fuel cell stack 12 is appropriately drained, and the fuel cell stack 12 can be prevented from being excessively dried. In addition, the control unit 142 controls the rotation speed of the pump 126 to the second rotation speed in the second drainage mode. The second rotation speed is greater than the first rotation speed. When step S19 is completed, the process proceeds to step S20.

[0109] In step S20, the control unit 142 compares the measured time of the timer with the drainage time. When the measured time is greater than the drainage time (step S20: Yes), the drainage control ends. In this case, the control unit 142 stops the compressor 112 and the pump 126. In addition, the control unit 142 closes each valve in sequence. On the other hand, when the measured time is less than the drainage time (step S20: No), the process returns to step S19.

[0110] As described above, when the fuel cell stack 12 is wet, the controller 142 performs drainage in the first drainage mode. When the fuel cell stack 12 is no longer wet before a predetermined drainage time (drainage setting time) has elapsed, the controller 142 performs drainage in the second drainage mode.

[0111] and, Figure 8 In the series of processes shown, step S17 and step S18 can be omitted. That is, the timer unit 144 may not count the second execution time for executing drainage in the second drainage mode. In this case, the control unit 142 executes drainage in the second drainage mode until the time measured by the timer reaches the drainage time set in step S11.

[0112] [4 Effects of the above-mentioned embodiments]

[0113] When the water content of the fuel cell stack 12 is too high, the water may freeze. In addition, when the water content of the fuel cell stack 12 is too high, iron components are easily dissolved from metal components into water. Water containing iron components deteriorates the electrolyte membrane 36. Therefore, it is preferable to appropriately drain water from the fuel cell stack 12 so that the water content of the fuel cell stack 12 does not increase.

[0114] When the amount of oxidant gas supplied to the fuel cell stack 12 is increased, it is possible to promote the drainage of water from the fuel cell stack 12. On the other hand, when the fuel cell stack 12 is dried more than necessary, the fuel cell stack 12 may be degraded.

[0115] In the above embodiment, when the fuel cell stack 12 is in a wet state, the control unit 142 performs drainage in the first drainage mode. That is, during power generation at stop, the control unit 142 makes the supply amount of oxidant gas to the fuel cell stack 12 relatively large. As a result, it is possible to promote drainage from the fuel cell stack 12, especially drainage from the first blocking bypass convex portion 64, the first supply portion 55a, 55b, the second blocking bypass convex portion 80, the second supply portion 71a, 71b, etc. On the other hand, when the fuel cell stack 12 is not in a wet state, the control unit 142 performs drainage control in the second drainage mode. That is, during power generation at stop, the control unit 142 makes the supply amount of oxidant gas to the fuel cell stack 12 relatively small. According to the above embodiment, it is possible to promote drainage from the portion of the fuel cell stack 12 that is not easy to drain. In addition, according to the above embodiment, it is possible to suppress excessive drying of the fuel cell stack 12 and drain water from the fuel cell stack 12. That is, according to the above embodiment, it is possible to appropriately drain water from the fuel cell stack 12.

[0116] In the above embodiment, the control unit 142 switches the drainage control from the first drainage mode to the second drainage mode when the fuel cell stack 12 changes from a wet state to a predetermined dry state during the drainage control. Thus, according to the above embodiment, the drainage control is switched from the first drainage mode to the second drainage mode, so that the fuel cell stack 12 is appropriately drained, and the fuel cell stack 12 can be prevented from being excessively dried.

[0117] In the above embodiment, the control unit 142 performs drainage control by setting a predetermined drainage setting time as the drainage time. According to the above embodiment, it is possible to prevent the drainage control from being performed for a longer time than necessary.

[0118] In the drainage control in the first drainage mode, the power consumption of the compressor 112 increases. In the above embodiment, the control unit 142 makes the rotation speed of the pump 126 during drainage in the first drainage mode lower than the rotation speed of the pump 126 during drainage in the second drainage mode. Therefore, according to the above embodiment, the increase in the power consumption of the entire fuel cell system 10 can be suppressed.

[0119] [5 Notes]

[0120] In connection with the above disclosure, the following supplementary notes are also disclosed.

[0121] (Note 1)

[0122] The first disclosure relates to a fuel cell system, comprising: a fuel cell stack 12, which comprises a plurality of power generation cells 24 for generating electricity using an oxidant gas and a fuel gas; an oxidant gas supplier 112, which supplies the oxidant gas to the fuel cell stack; a supply path 106, in which the oxidant gas supplied to the fuel cell stack flows; a discharge path 108, in which the oxidant gas discharged from the fuel cell stack flows; a temperature sensor 130, which detects the temperature of the fuel cell stack, i.e., the stack temperature; and a control device 22, which controls the oxidant gas supplier. In the fuel cell system 10, the control device comprises: a control unit 142, which causes the power generation cell to continue generating electricity when the power generation is stopped after obtaining an indication of stopping power generation until a predetermined condition is satisfied; an acquisition unit 140, which acquires the stack temperature before the power generation is stopped; and a determination unit 146, which determines the temperature of the stack based at least on the information acquired by the acquisition unit. The stack temperature is used to determine whether the fuel cell stack is in a wet state. The control unit can selectively perform either drainage in a first drainage mode or drainage in a second drainage mode during the stopped power generation. In the drainage in the first drainage mode, a first flow rate of the oxidant gas is supplied from the oxidant gas supplier to the fuel cell stack, thereby discharging water retained in the fuel cell stack. In the drainage in the second drainage mode, a second flow rate of the oxidant gas less than the first flow rate is supplied from the oxidant gas supplier to the fuel cell stack, thereby discharging water retained in the fuel cell stack. When the determination unit determines that the fuel cell stack is in the wet state, the control unit performs drainage in the first drainage mode during the stopped power generation. When the determination unit determines that the fuel cell stack is not in the wet state, the control unit performs drainage in the second drainage mode during the stopped power generation.

[0123] According to the above structure, it is possible to promote drainage from the part of the fuel cell stack that is difficult to drain. In addition, according to the above structure, it is possible to suppress excessive drying of the fuel cell stack and drain water from the fuel cell stack. In other words, according to the above structure, it is possible to appropriately drain water from the fuel cell stack.

[0124] (Note 2)

[0125] In the fuel cell system according to Supplementary Note 1, the determination unit may determine whether the fuel cell stack is in the wet state based on the stack temperature and an output current value of the fuel cell stack.

[0126] (Note 3)

[0127] In the fuel cell system described in Note 2, it may be that before the start of power generation during the stop, the determination unit obtains the stack temperature and the output current value, and when the stack temperature is less than a predetermined temperature threshold and the output current value is less than a predetermined current threshold, the determination unit determines that the fuel cell stack is in the expected wet state, and when the expected wet state reaches a predetermined time Cth before the start of power generation during the stop, the determination unit determines that the fuel cell stack is in the wet state.

[0128] (Note 4)

[0129] In the fuel cell system described in Note 1, the power generation cell may also include: a structure 26, which includes an electrolyte membrane 36, an anode electrode 38, and a cathode electrode 40; and a pair of separators 28, 30, wherein the pair of separators sandwich the structure, and each of the separators includes: a reaction gas flow path 50, 66, wherein the oxidant gas or the fuel gas flows in the reaction gas flow path; a sealing portion 62, 78, wherein the sealing portion surrounds the reaction gas flow path; and a bypass suppression portion 64, 80, wherein the bypass suppression portion is formed between the end portions 52a, 68a of the reaction gas flow path in the flow path width direction and the sealing portion to suppress the bypass of the oxidant gas or the fuel gas.

[0130] At the normal flow rate of the oxidant gas during power generation at stop (the second flow rate of the oxidant gas in the second drainage mode), water accumulated in the bypass suppression portion is not easily discharged. On the other hand, the first flow rate of the oxidant gas in the first drainage mode can promote drainage from the bypass suppression portion.

[0131] (Note 5)

[0132] In the fuel cell system described in Note 1, the determination unit may also determine whether the fuel cell stack is in the wet state during drainage in the first drainage mode, and when the determination unit determines that the fuel cell stack is no longer in the wet state during drainage in the first drainage mode, the control unit switches the drainage from the first drainage mode to the drainage in the second drainage mode.

[0133] According to the above structure, the drainage control of the first drainage mode is switched to the drainage control of the second drainage mode, so that the fuel cell stack is appropriately drained, which can prevent the fuel cell stack from being excessively dried. In addition, even when the fuel cell stack is no longer in a wet state (that is, in a predetermined dry state), drainage in the second drainage mode is performed, thereby draining liquid water retained in the exhaust device (such as the second sealing valve, etc.) provided in the exhaust path. As a result, it is possible to prevent the fuel cell system from being unable to generate electricity when it is started due to freezing of liquid water retained in the exhaust device when it is stopped.

[0134] (Note 6)

[0135] In the fuel cell system described in Note 5, the control unit may measure the execution time of drainage in the first drainage mode, i.e., the first execution time, and the control unit may determine the execution time of drainage in the second drainage mode, i.e., the second execution time based on the first execution time, and the control unit may execute drainage in the second drainage mode during the second execution time.

[0136] (Note 7)

[0137] In the fuel cell system described in Note 5, the control unit may measure the execution time of drainage in the first drainage mode, i.e., the first execution time, and the control unit subtracts the first execution time from the preset drainage time to thereby determine the execution time of drainage in the second drainage mode, i.e., the second execution time, and the control unit executes drainage in the second drainage mode during the second execution time.

[0138] (Note 8)

[0139] In the fuel cell system described in any one of Notes 1 to 7, there is a refrigerant supply pump 126, which supplies cooling medium to the fuel cell stack, and the control device makes the speed of the refrigerant supply pump when draining in the first drain mode lower than the speed of the refrigerant supply pump when draining in the second drain mode.

[0140] According to the above configuration, it is possible to suppress an increase in power consumption of the entire fuel cell system.

[0141] (Note 9)

[0142] The second disclosure relates to a control method for a fuel cell system, the fuel cell system comprising: a fuel cell stack, which comprises a plurality of power generation cells for generating electricity using an oxidant gas and a fuel gas; an oxidant gas supplier, which supplies the oxidant gas to the fuel cell stack; a supply path, in which the oxidant gas supplied to the fuel cell stack flows; a discharge path, in which the oxidant gas discharged from the fuel cell stack flows; a temperature sensor, which detects the temperature of the fuel cell stack, i.e., the stack temperature; and a control device, which controls the oxidant gas supplier. In the control method for the fuel cell system, the control device causes the power generation cells to continue generating electricity when stopped after obtaining an indication of stopping power generation until a predetermined condition is satisfied, and the control device obtains the stack temperature before the stopped power generation, and the control device controls the control device based at least on the obtained stack temperature before the stopped power generation. , to determine whether the fuel cell stack is in a wet state, the control device can selectively perform either drainage in a first drainage mode or drainage in a second drainage mode during the stop power generation, in the drainage in the first drainage mode, a first flow rate of the oxidant gas is supplied from the oxidant gas supplier to the fuel cell stack, thereby discharging water retained in the fuel cell stack, and in the drainage in the second drainage mode, a second flow rate of the oxidant gas less than the first flow rate is supplied from the oxidant gas supplier to the fuel cell stack, thereby discharging water retained in the fuel cell stack, the control device performs the drainage in the first drainage mode during the stop power generation when it is determined that the fuel cell stack is in the wet state, and performs the drainage in the second drainage mode during the stop power generation when it is determined that the fuel cell stack is not in the wet state.

[0143] According to the above structure, it is possible to promote drainage from the part of the fuel cell stack that is difficult to drain. In addition, according to the above structure, it is possible to suppress excessive drying of the fuel cell stack and drain water from the fuel cell stack. In other words, according to the above structure, it is possible to appropriately drain water from the fuel cell stack.

[0144] Furthermore, the present invention is not limited to the above disclosure, and various structures can be adopted without departing from the gist of the present invention.

Claims

1. A fuel cell system comprising: A fuel cell stack including a plurality of power generation cells for generating power using an oxidant gas and a fuel gas; an oxidant gas supplier that supplies the oxidant gas to the fuel cell stack; a supply passage through which the oxidant gas supplied to the fuel cell stack flows; an exhaust passage through which the oxidant gas exhausted from the fuel cell stack flows; a temperature sensor for detecting the temperature of the fuel cell stack, ie, the stack temperature; and a control device for controlling the oxidant gas supplier, In the fuel cell system, The control device comprises: a control unit that causes the power generation cell to continue power generation during stop after receiving an instruction to stop power generation until a predetermined condition is satisfied; an acquisition unit that acquires the stack temperature before the power generation at the stop time; and a determination unit that determines whether the fuel cell stack is in a wet state based at least on the stack temperature acquired by the acquisition unit, The control unit can selectively perform any one of drainage in a first drainage mode and drainage in a second drainage mode during the stop power generation, wherein in the drainage in the first drainage mode, the oxidant gas of a first flow rate is supplied from the oxidant gas supplier to the fuel cell stack, thereby draining water retained in the fuel cell stack, and in the drainage in the second drainage mode, the oxidant gas of a second flow rate less than the first flow rate is supplied from the oxidant gas supplier to the fuel cell stack, thereby draining water retained in the fuel cell stack, When the determination unit determines that the fuel cell stack is in the wet state, the control unit performs water drainage in the first water drainage mode during the stop power generation. When the determination unit determines that the fuel cell stack is not in the wet state, the control unit performs water drainage in the second water drainage mode during the stop power generation.

2. The fuel cell system according to claim 1, characterized in that: The determination unit determines whether the fuel cell stack is in the wet state based on the stack temperature and an output current value of the fuel cell stack.

3. The fuel cell system according to claim 2, characterized in that: Before the stop-time power generation starts, the determination unit acquires the stack temperature and the output current value, When the stack temperature is lower than a predetermined temperature threshold and the output current value is lower than a predetermined current threshold, the determination unit determines that the fuel cell stack is in the expected wet state; when the expected wet state reaches a predetermined time before power generation starts during the stop, the determination unit determines that the fuel cell stack is in the wet state.

4. The fuel cell system according to claim 1, characterized in that: The power generation cell comprises: A structure comprising an electrolyte membrane, an anode electrode, and a cathode electrode; and a pair of spacers, wherein the pair of spacers sandwich the structure, Each of the spacers comprises: a reaction gas flow path, wherein the oxidant gas or the fuel gas flows through the reaction gas flow path; a sealing portion surrounding the reaction gas flow path; and The bypass suppressing portion is formed between an end portion of the reaction gas flow path in the flow path width direction and the sealing portion, and suppresses the bypass of the oxidant gas or the fuel gas.

5. The fuel cell system according to claim 1, characterized in that: The determination unit further determines whether the fuel cell stack is in the wet state during water discharge in the first water discharge mode, When the determination unit determines that the fuel cell stack is no longer in the wet state during water discharge in the first water discharge mode, the control unit switches the water discharge in the first water discharge mode to the water discharge in the second water discharge mode.

6. The fuel cell system according to claim 5, characterized in that: The control unit measures a first execution time of drainage in the first drainage mode, that is, a first execution time. The control unit determines a second execution time, that is, an execution time of drainage in the second drainage mode, based on the first execution time. The control unit executes water discharge in the second water discharge mode during the second execution time.

7. The fuel cell system according to claim 5, characterized in that: The control unit measures a first execution time of drainage in the first drainage mode, that is, a first execution time. The control unit subtracts the first execution time from a preset drainage time to thereby determine a second execution time which is a drainage execution time in the second drainage mode. The control unit executes water discharge in the second water discharge mode during the second execution time.

8. The fuel cell system according to any one of claims 1 to 7, characterized in that: A refrigerant supply pump is provided, the refrigerant supply pump supplies a cooling medium to the fuel cell stack, The control device makes the rotation speed of the refrigerant supply pump when the water is drained in the first water drain mode lower than the rotation speed of the refrigerant supply pump when the water is drained in the second water drain mode.

9. A control method for a fuel cell system, the fuel cell system comprising: A fuel cell stack including a plurality of power generation cells for generating power using an oxidant gas and a fuel gas; an oxidant gas supplier that supplies the oxidant gas to the fuel cell stack; a supply passage through which the oxidant gas supplied to the fuel cell stack flows; an exhaust passage through which the oxidant gas exhausted from the fuel cell stack flows; a temperature sensor for detecting the temperature of the fuel cell stack, ie, the stack temperature; and a control device for controlling the oxidant gas supplier, In the control method of the fuel cell system, The control device causes the power generation cell to continue power generation during stop after receiving the instruction to stop power generation until a predetermined condition is satisfied. The control device acquires the stack temperature before the power generation during the stop, The control device determines whether the fuel cell stack is in a wet state based on at least the acquired stack temperature before the power generation at the stop time, The control device can selectively perform any one of drainage in a first drainage mode and drainage in a second drainage mode during the stop power generation, wherein in the drainage in the first drainage mode, the oxidant gas of a first flow rate is supplied from the oxidant gas supplier to the fuel cell stack, thereby draining water retained in the fuel cell stack, and in the drainage in the second drainage mode, the oxidant gas of a second flow rate less than the first flow rate is supplied from the oxidant gas supplier to the fuel cell stack, thereby draining water retained in the fuel cell stack, The control device performs water drainage in the first water drainage mode during the stop power generation when it is determined that the fuel cell stack is in the wet state. The control device performs water drainage in the second water drainage mode during the stop-time power generation when it is determined that the fuel cell stack is not in the wet state.

Images