Fuel cell system

Abstract

The invention relates to a fuel cell system. The control device (24) executes first power generation control in a state in which the first refrigerant flow path (120) and the second refrigerant flow path (140) are blocked, and causes the refrigerant in the second refrigerant flow path (140) heated by the heater (144) to flow into the first refrigerant flow path (120) when the control device (24) executes second power generation control.

Description

Technical Field

[0001] The present invention relates to a 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 system with a fuel cell stack is called a fuel cell system. The 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. Part of the generated water is retained inside the fuel cell stack. When the operation of the fuel cell system is stopped in a low temperature environment, the water retained inside the fuel cell stack 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 a method for stopping a fuel cell system, wherein, in order to promote drying of a membrane electrode assembly (MEA) of a power generation cell, when an ignition switch is turned off, a drainage power generation process is performed after a drying power generation process is performed. The humidification amount of the oxidant gas supplied to the fuel cell stack during the drying power generation process is determined to be less than the humidification amount of the oxidant gas supplied to the fuel cell stack during the drainage power generation process.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2016-058188 Summary of the invention

[0008] Problems to be solved by the invention

[0009] A technology for satisfactorily drying power generating cells is desired.

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

[0011] Solutions for solving problems

[0012] One aspect of the present invention relates to a fuel cell system, comprising: a fuel cell stack including a power generation cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas; a radiator for cooling the fuel cell stack; a valve body that can switch between connection and disconnection between a first refrigerant flow path and a second refrigerant flow path, the first refrigerant flow path circulates a refrigerant between the fuel cell stack and the radiator, the second refrigerant flow path being different from the first refrigerant flow path; a heater that heats the refrigerant flowing in the second refrigerant flow path; and a control device that performs power generation control on the power generation cell, the control device being capable of executing a first power generation control and a second power generation control that is different from the first power generation control, the second power generation control being a power generation control for drying an electrolyte membrane provided in the power generation cell, the control device executing the first power generation control in a state where the first refrigerant flow path and the second refrigerant flow path are disconnected, and when performing the second power generation control, the control device causes the refrigerant in the second refrigerant flow path heated by the heater to flow into the first refrigerant flow path.

[0013] Effects of the Invention

[0014] According to the present invention, the power generating cells can be dried satisfactorily.

[0015] 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

[0016] Figure 1 This is a schematic diagram of the fuel cell system.

[0017] Figure 2 : is a flowchart showing the procedure of the power generation control process.

[0018] Figure 3 : is a flowchart showing the procedure of post-stop processing.

[0019] Figure 4 It is a timing chart showing the operation of each part of the fuel cell system when the post-processing is stopped. DETAILED DESCRIPTION

[0020] [1 Structure of the fuel cell system 10]

[0021] Figure 1 1 is a schematic diagram of the structure of the fuel cell system 10. The fuel cell system 10 is installed in a vehicle (fuel cell vehicle), for example. The fuel cell system 10 can also be installed in a mobile object such as a ship, an aircraft, or a robot. In addition, the fuel cell system 10 can also be used as a power source for fixed installation in equipment, homes, etc.

[0022] 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 for electrochemical reaction. Moreover, in this specification, the fuel gas discharged from the fuel cell stack 12 without being used for 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 electrochemical reaction is also referred to as oxidant exhaust.

[0023] The fuel cell system 10 includes a fuel cell stack 12, a tank 14, an anode system 16, a cathode system 18, a cooling system 20, and an air conditioning system 22. In addition, the fuel cell system 10 includes a control device 24. The power generated by the fuel cell stack 12 is supplied to a load 26. The load 26 includes a drive motor of a fuel cell vehicle, a battery, and a heater 144. The tank 14 is filled with high-pressure fuel gas.

[0024] The fuel cell stack 12 includes a fuel gas supply interface 12a that supplies fuel gas to the interior of the fuel cell stack 12, and a fuel gas exhaust interface 12b that exhausts the fuel gas exhaust from the interior of the fuel cell stack 12. The fuel cell stack 12 includes an oxidant gas supply interface 12c that supplies oxidant gas to the interior of the fuel cell stack 12, and an oxidant gas exhaust interface 12d that exhausts the oxidant exhaust from the interior of the fuel cell stack 12. The fuel cell stack 12 includes a coolant supply interface 12e that supplies coolant to the interior of the fuel cell stack 12, and a coolant exhaust interface 12f that exhausts the coolant from the interior of the fuel cell stack 12.

[0025] The fuel cell stack 12 includes a plurality of power generation cells 28. Each of the plurality of power generation cells 28 has the same structure. The power generation cell 28 includes an electrolyte membrane-electrode structure 30, a first separator 32, and a second separator 34. The electrolyte membrane-electrode structure 30 is sandwiched between the first separator 32 and the second separator 34. Figure 1 One power generating cell 28 among a plurality of power generating cells 28 is shown.

[0026] For example, the cross-sections of the first separator 32 and the second separator 34 are formed of corrugated metal thin plates. In two adjacent power generation cells 28, the first separator 32 of one power generation cell 28 and the second separator 34 of the other power generation cell 28 are joined to each other. A cell cooling flow path (not shown) is formed between the first separator 32 and the second separator 34. The cell cooling flow path is connected to the refrigerant supply port 12e and the refrigerant discharge port 12f.

[0027] The electrolyte membrane-electrode structure 30 includes an electrolyte membrane 36, an anode electrode 38, and a cathode electrode 40. The electrolyte membrane 36 is located between the anode electrode 38 and the cathode electrode 40. An anode flow path 42 is formed between the first separator 32 and the anode electrode 38. The anode flow path 42 is connected to the fuel gas supply interface 12a and the fuel gas exhaust interface 12b. A cathode flow path 44 is formed between the second separator 34 and the cathode electrode 40. The cathode flow path 44 is connected to the oxidant gas supply interface 12c and the oxidant gas exhaust interface 12d.

[0028] The anode system 16 includes a fuel gas supply path 84, a fuel gas discharge path 86, a circulation path 88, and a drain path 90. The anode system 16 also includes an ejector 94, an ejector 96, a gas-liquid separator 98, and a drain valve 100.

[0029] The fuel gas supply path 84 connects the discharge port of the tank 14 to the fuel gas supply port 12a 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 between the ejector 94 and the fuel cell stack 12.

[0030] The fuel gas discharge path 86 connects the fuel gas discharge port 12 b of the fuel cell stack 12 and the supply port of the gas-liquid separator 98 . The circulation path 88 connects the discharge port of the gas-liquid separator 98 and the ejector 96 .

[0031] The drain passage 90 connects 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 a drain port provided in the vehicle. The drain passage 90 is provided with a drain valve 100.

[0032] 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 114 (HUM), a first sealing valve 116, a second sealing valve 118, and a bypass valve 119.

[0033] The oxidant gas supply path 106 connects the air intake port (not shown) of the vehicle to the oxidant gas supply interface 12c 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 between the compressor 112 and the humidifier 114.

[0034] The oxidant gas discharge path 108 connects the oxidant gas discharge interface 12d of the fuel cell stack 12 to 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.

[0035] 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 to 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 119.

[0036] The cooling system 20 includes a refrigerant flow path 120 . In addition, the cooling system 20 includes a pump 126 , a radiator 128 , a temperature sensor 130 , and a flow dividing valve 132 .

[0037] The refrigerant flow path 120 circulates the refrigerant between the fuel cell stack 12 and the radiator 128. The refrigerant is, for example, water containing ethylene glycol. The refrigerant flow path 120 includes a refrigerant supply path 122, a refrigerant discharge path 124, and a shunt path 125. The refrigerant supply path 122 connects the fluid discharge port of the radiator 128 to the refrigerant supply interface 12e of the fuel cell stack 12. The refrigerant discharge path 124 connects the refrigerant discharge interface 12f of the fuel cell stack 12 to the fluid supply port of the radiator 128. The shunt path 125 branches from the refrigerant discharge path 124 and merges with the refrigerant supply path 122.

[0038] The refrigerant supply path 122 is provided with a pump 126. For example, the pump 126 is provided between a portion where a partial flow path 148B described later is connected to the refrigerant supply path 122 and a portion where a partial flow path 148A described later is connected to the refrigerant supply path 122. Alternatively, the pump 126 may be provided in the refrigerant discharge path 124. The radiator 128 is a radiator that radiates heat from the refrigerant in the refrigerant flow path 120. The radiator 128 may also include a fan.

[0039] The refrigerant discharge path 124 is provided with a temperature sensor 130. Alternatively, the refrigerant supply path 122 is provided with a temperature sensor 130. The temperature sensor 130 detects the temperature of the refrigerant in the refrigerant flow path 120 (refrigerant temperature). Alternatively, the temperature sensor 130 detects the outlet temperature of the reaction gas. In this case, for example, the fuel gas discharge interface 12b is provided with a temperature sensor 130. The above-mentioned refrigerant temperature or the above-mentioned outlet temperature is equivalent to the internal temperature of the fuel cell stack 12 (stack temperature).

[0040] The flow divider valve 132 is provided at a confluence portion where the flow divider path 125 and the refrigerant supply path 122 merge. Alternatively, the flow divider valve 132 may be provided at a branch portion where the flow divider path 125 branches off from the refrigerant discharge path 124. The flow divider valve 132 can adjust the opening degree. The amount of refrigerant supplied to the radiator 128 is adjusted according to the opening degree of the flow divider valve 132. The opening degree of the flow divider valve 132 is controlled by the control device 24.

[0041] The air conditioning system 22 includes a refrigerant flow path 140 . The air conditioning system 22 also includes a pump 142 , a heater 144 , and a valve body 146 .

[0042] The refrigerant flow path 140 is provided separately from the refrigerant flow path 120 of the cooling system 20. That is, the refrigerant flow path 140 is different from the refrigerant flow path 120. A temperature sensor 160 is provided in the refrigerant flow path 140. The refrigerant flow path 140 of the air conditioning system 22 is connected to the refrigerant flow path 120 of the cooling system 20 via a communication path 148. The communication path 148 has a partial flow path 148A and a partial flow path 148B.

[0043] The material of the refrigerant flowing in the refrigerant flow path 140 of the air conditioning system 22 is the same as the material of the refrigerant flowing in the refrigerant flow path 120 of the cooling system 20. The refrigerant flowing in the refrigerant flow path 140 exchanges heat with, for example, air taken in from the vehicle interior. The heat-exchanged air is supplied to, for example, the vehicle interior.

[0044] The refrigerant flow path 140 of the air conditioning system 22 is provided with a pump 142. The heater 144 is a heater for heating the refrigerant in the refrigerant flow path 140 of the air conditioning system 22. The heating of the refrigerant by the heater 144 is controlled by the control device 24, for example.

[0045] The valve body 146 switches the connection and blocking between the refrigerant flow path 120 of the cooling system 20 and the refrigerant flow path 140 of the air conditioning system 22. The switching is performed by the control device 24. The valve body 146 may also be a three-way valve. In this case, the valve body 146 is provided at the connection portion between the refrigerant flow path 140 and the partial flow path 148A and the connection portion between the refrigerant flow path 140 and the partial flow path 148B.

[0046] The control device 24 may be composed of an ECU (Electronic Control Unit). The control device 24 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 may be composed of a processing circuit.

[0047] The operation unit 136 includes an acquisition unit 150, a power generation control unit 152, and a heat control unit 154. The acquisition unit 150, the power generation control unit 152, and the heat control unit 154 can be realized by executing the program stored in the storage unit 138 by the operation unit 136. At least a part of the acquisition unit 150, the power generation control unit 152, and the heat control unit 154 can also be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). In addition, at least a part of the acquisition unit 150, the power generation control unit 152, and the heat control unit 154 can also be realized by a circuit including discrete devices. The acquisition unit 150 acquires information from electronic components (sensors, ECU, etc.) other than the control device 24. The power generation control unit 152 controls the operation of the ejector 94, the compressor 112, the pump 126, and each valve. The heat control unit 154 controls the operation of the diverter valve 132, the heater 144, the valve body 146, etc.

[0048] The storage unit 138 is a computer-readable storage medium. The storage medium is composed of a volatile memory (not shown) and a non-volatile memory (not shown). 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, mapping tables, etc. are stored in the non-volatile memory, for example. Alternatively, at least a portion of the storage unit 138 may be provided in the processor, integrated circuit, etc. described above.

[0049] [2 Flow of Fluid in Fuel Cell System 10]

[0050] [2-1 Flow of Fluid in Anode System 16]

[0051] 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 12a 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 12b 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.

[0052] 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. The fuel exhaust sucked from the gas-liquid separator 98 merges with the fuel gas injected from the injector 94 in the ejector 96.

[0053] [2-2 Flow of Fluid in Cathode System 18]

[0054] 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 12c 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 12d 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.

[0055] 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, part of the moisture contained in the oxidant exhaust gas is used to humidify the oxidant gas flowing through the humidifier supply path 114A.

[0056] [2-3 Flow of Fluid in Cooling System 20]

[0057] The pump 126 ejects the refrigerant toward the refrigerant supply port 12e of the fuel cell stack 12. The refrigerant ejected from the pump 126 is supplied to the refrigerant supply port 12e of the fuel cell stack 12 via the refrigerant supply path 122. The refrigerant that has circulated inside the fuel cell stack 12 is discharged from the refrigerant discharge port 12f of the fuel cell stack 12. The refrigerant discharged from the refrigerant discharge port 12f is supplied to the radiator 128 via the refrigerant discharge path 124. The refrigerant that has released heat in the radiator 128 reaches the pump 126.

[0058] Then, part of the refrigerant discharged from the refrigerant discharge port 12f flows into the refrigerant supply path 122 via the bypass path 125 without passing through the radiator 128. The inflow amount is adjusted by the opening degree of the bypass valve 132.

[0059] [2-4 Flow of Fluid in Air Conditioning System 22]

[0060] Heater 144 heats the refrigerant in refrigerant flow path 140 . In a state where refrigerant flow path 120 of cooling system 20 and refrigerant flow path 140 of air conditioning system 22 are blocked (first state), the refrigerant heated by heater 144 circulates in refrigerant flow path 140 by pump 142 .

[0061] In the state (second state) where the refrigerant flow path 120 of the cooling system 20 is connected to the refrigerant flow path 140 of the air conditioning system 22, the refrigerant heated by the heater 144 flows into the refrigerant flow path 120. That is, in the second state, the refrigerant heated by the heater 144 flows into the partial flow path 148A of the communication path 148 via the valve body 146. The refrigerant flowing into the partial flow path 148A flows into the refrigerant flow path 120 of the cooling system 20 to merge with the refrigerant in the refrigerant flow path 120.

[0062] After that, the refrigerant flows into the fuel cell stack 12 via the refrigerant supply path 122, circulates inside the fuel cell stack 12, and flows into the refrigerant supply path 122 via the refrigerant discharge path 124 or the branch path 125. A portion of the refrigerant that has flowed into the refrigerant supply path 122 flows into the refrigerant flow path 140 of the air conditioning system 22 via the partial flow path 148B of the communication path 148. The refrigerant that has flowed into the refrigerant flow path 140 reaches the pump 142.

[0063] In this way, in the second state, the refrigerant circulates in the refrigerant flow path 140 of the air conditioning system 22 , the refrigerant flow path 120 of the cooling system 20 , and the fuel cell stack 12 .

[0064] [3 Power generation control]

[0065] The power generation control unit 152 can execute first power generation control and second power generation control. Figure 2 1 is a flowchart showing the order of the power generation control process. The power generation control unit 152 does not execute the power generation control process when it has not received the system start command for starting the fuel cell system 10. When the power generation control unit 152 receives the system start command, the power generation control process moves to step S1.

[0066] In step S1, the power generation control unit 152 performs the first power generation control. The power generation control unit 152 continues the first power generation control until receiving an instruction for stopping the fuel cell system 10, i.e., a system stop instruction. When the power generation control unit 152 receives the system stop instruction, it ends the first power generation control. When the first power generation control ends, the fuel cell system 10 becomes a system stop. Thereafter, the power generation control process transfers to step S2.

[0067] In step S2, the power generation control unit 152 monitors the temperature (stack temperature) detected by the temperature sensor 130 during system stop. The power generation control unit 152 compares the stack temperature with a predetermined temperature threshold. For example, the temperature threshold is selected from a range of 0°C to 5°C. When the stack temperature is above the temperature threshold (No in step S2), the power generation control unit 152 compares the stack temperature with the temperature threshold again after a predetermined time has passed. When the stack temperature is lower than the temperature threshold (Yes in step S2), the power generation control process executes step S3.

[0068] In step S3, the power generation control unit 152 executes the second power generation control. When the second power generation control is completed, the power generation control process is completed. When the power generation control process is completed, the power generation control unit 152 does not execute the power generation control process until it receives the system startup command again.

[0069] The system start command is supplied when the switch (start switch) of the fuel cell system 10 is turned on. The system stop command is supplied when the switch of the fuel cell system 10 is turned off. The switch of the fuel cell system 10 corresponds to, for example, an ignition switch of a vehicle.

[0070] The first power generation control is a power generation control for supplying electric power corresponding to the demand to the load 26. That is, the first power generation control is a control for performing normal power generation. The power generation control unit 152 controls the operation of the ejector 94, the compressor 112, the pump 126, each valve, etc. based on the predetermined normal power generation conditions, so that the power generation cell 28 performs normal power generation.

[0071] The second power generation control is a power generation control for drying the electrolyte membrane 36 provided in the power generation single cell 28. Before executing the second power generation control, the power generation control unit 152 controls the operations of the ejector 94, the compressor 112, the pump 126, each valve, etc. to perform preheating. In the case of performing preheating, the power generation control unit 152 controls the compressor 112 so that the air-fuel ratio (Japanese: stoichiometric ratio) of the oxidant gas supplied to the fuel cell stack 12 is relatively small. That is, the power generation control unit 152 sets the air-fuel ratio of the oxidant gas during preheating to be smaller than the air-fuel ratio of the oxidant gas during the first power generation control. Thereby, during preheating, low-efficiency power generation with a lower power generation efficiency than normal power generation is implemented in the power generation single cell 28. Since low-efficiency power generation is implemented, the calorific value of the power generation single cell 28 increases during preheating. That is, the calorific value of the power generation single cell 28 during preheating is greater than the calorific value of the power generation single cell 28 during the first power generation control.

[0072] When the temperature detected by the temperature sensor 130 reaches a target temperature described later, the power generation control unit 152 ends the preheating and starts the second power generation control. In this case, the power generation control unit 152 controls the operations of the ejector 94, the compressor 112, the pump 126, each valve, etc. based on established dry power generation conditions to cause the power generation single cell 28 to perform dry power generation.

[0073] The air-fuel ratio of the oxidant gas supplied to the fuel cell stack 12 during dry power generation is set to be larger than the air-fuel ratio of the oxidant gas supplied to the fuel cell stack 12 during normal power generation. The power generation control unit 152 controls the compressor 112 so that the air-fuel ratio of the oxidant gas supplied to the fuel cell stack 12 during dry power generation is greater than the air-fuel ratio of the oxidant gas supplied to the fuel cell stack 12 during normal power generation. Therefore, during dry power generation, the discharge efficiency of the water remaining in the fuel cell stack 12 to the outside is improved. That is, the water discharge efficiency during dry power generation is greater than the water discharge efficiency during normal power generation. Thereby, the retention of water inside the fuel cell stack 12 is reduced.

[0074] Moreover, it may also be that the humidification amount of the oxidant gas supplied to the fuel cell stack 12 during the second power generation control is less than the humidification amount of the oxidant gas supplied to the fuel cell stack 12 during the first power generation control. For example, it may also be that during the second power generation control, the oxidant gas branches from the oxidant gas supply path 106A and is supplied to the fuel cell stack 12 via a humidifier bypass flow path (not shown) that merges with the oxidant gas supply path 106B without passing through the humidifier 114. On the other hand, during the first power generation control, the oxidant gas supplied to the oxidant gas supply path 106A is supplied to the fuel cell stack 12 via the humidifier 114 and the oxidant gas supply path 106B.

[0075] [4 Thermal Control]

[0076] In the implementation of the first power generation control, the heat control unit 154 drives the pump 126 and closes the diverter valve 132. It is also possible that the heat control unit 154 adjusts the opening of the diverter valve 132. In addition, in the implementation of the first power generation control, the heat control unit 154 causes the valve body 146 to block the refrigerant flow path 120 of the cooling system 20 and the refrigerant flow path 140 of the air conditioning system 22. Therefore, in the implementation of the first power generation control, the refrigerant in the refrigerant flow path 140 of the air conditioning system 22 is not supplied to the fuel cell stack 12. In the implementation of the first power generation control, only the refrigerant in the refrigerant flow path 120 of the cooling system 20 is supplied to the fuel cell stack 12.

[0077] As described later, in the present embodiment, in order to maintain the temperature of the power generation cell 28 sufficiently high when the second power generation control is performed, the refrigerant heated by the heater 144 flows into the refrigerant flow path 120. Therefore, it is preferable that the refrigerant in the refrigerant flow path 140 is sufficiently heated by the heater 144 when the second power generation control starts. Therefore, when the preheating starts, the heat control unit 154 turns on the heater 144 in advance to raise the temperature of the refrigerant in the refrigerant flow path 140 to a predetermined temperature.

[0078] When the heater 144 performs heating, the power output from the power generation cell 28 due to preheating may be supplied to the heater 144, or the power stored in the battery may be supplied to the heater 144. Furthermore, when the control device 24 receives a power consumption instruction to consume the power stored in the battery, the heat control unit 154 sets the power supply path so that the power stored in the battery is supplied to the heater 144. In this case, the power stored in the battery is consumed by the heater 144.

[0079] Then, the above-mentioned power consumption command is supplied when the remaining capacity of the battery is equal to or greater than a predetermined remaining capacity threshold value. In addition, the above-mentioned predetermined temperature is set to be higher than the refrigerant temperature detected by the temperature sensor 130 during the preheating operation.

[0080] Before the second power generation control starts, the heat control unit 154 controls the valve body 146 to connect the refrigerant flow path 120 of the cooling system 20 with the refrigerant flow path 140 of the air conditioning system 22. More specifically, before the preheating ends, the heat control unit 154 connects the refrigerant flow path 120 of the cooling system 20 with the refrigerant flow path 140 of the air conditioning system 22. The timing for connecting the refrigerant flow path 120 of the cooling system 20 with the refrigerant flow path 140 of the air conditioning system 22 may be a timing when a predetermined time has passed since the start of preheating. When the refrigerant flow path 120 of the cooling system 20 is connected to the refrigerant flow path 140 of the air conditioning system 22, the power generation cell 28 is heated by the heat generated by the power generation cell 28 and the heat of the refrigerant heated by the heater 144. Therefore, compared with the case where the power generation cell 28 is dried only by the heat generated by the power generation cell 28, the power generation cell 28 can be dried quickly and fully.

[0081] When performing the second power generation control, the heat control unit 154 compares the refrigerant temperature detected by the temperature sensor 130 with the target temperature at predetermined time intervals. The heat control unit 154 adjusts the opening of the diverter valve 132 according to the temperature detected by the temperature sensor 130. In this case, the heat control unit 154 makes the opening of the diverter valve 132 smaller as the temperature detected by the temperature sensor 130 increases. As a result, the temperature of the fuel cell stack 12 can be maintained at the target temperature.

[0082] [5 Stop post-processing]

[0083] Figure 3 : is a flowchart showing the procedure of post-stop processing. Figure 4 It is a timing chart showing the operation of each part of the fuel cell system 10 when the post-processing is stopped.

[0084] exist Figure 4 In the above, “refrigerant temperature” refers to the temperature detected by the temperature sensor 130. That is, “refrigerant temperature” refers to the temperature of the refrigerant in the refrigerant flow path 120. Figure 4 In the above, "impedance (HFR)" refers to the impedance of the fuel cell stack 12, that is, the high frequency impedance (High Frequency Resistance) of the fuel cell stack 12. Alternatively, the impedance may be detected by an impedance sensor that detects the AC impedance of the plurality of power generation cells 28 as a whole. Figure 4 The "diverter valve (CMV)" mentioned here corresponds to the diverter valve 132. Figure 4 The "valve body" mentioned here corresponds to valve body 146. Figure 4 The “heater” mentioned here corresponds to the heater 144 .

[0085] After the first power generation control ends, if the stack temperature is lower than the temperature threshold, the post-stop process starts, and the process proceeds to step S11 .

[0086] In step S11, the control device 24 starts preheating. At this time, the control device 24 controls the pump 126 to circulate the refrigerant of the cooling system 20. In addition, the control device 24 controls the diverter valve 132 to reduce the amount of refrigerant supplied to the radiator 128. In addition, the heat control unit 154 turns on the pump 142 and the heater 144 to increase the temperature of the refrigerant in the air-conditioning system 22 to a predetermined temperature. Thereafter, the post-processing is stopped and transferred to step S12. Alternatively, the heater 144 may already be turned on. Due to the start of preheating, low-efficiency power generation starts in the power generation cell 28, and the refrigerant temperature in the refrigerant flow path 120 gradually rises as time passes (see Figure 4 ). As the refrigerant temperature rises, the water content in the power generation cell 28 decreases, so the impedance of the fuel cell stack 12 increases (see Figure 4 ).

[0087] In step S12, the control device 24 controls the valve body 146 to connect the refrigerant flow path 120 of the cooling system 20 with the refrigerant flow path 140 of the air conditioning system 22. During this connection, the refrigerant temperature of the refrigerant flow path 140 of the air conditioning system 22 is higher than the refrigerant temperature of the refrigerant flow path 120 of the cooling system 20. Therefore, the refrigerant in the refrigerant flow path 120 of the cooling system 20 is heated by the refrigerant in the refrigerant flow path 140 of the air conditioning system 22.

[0088] In step S13, the control device 24 compares the refrigerant temperature detected by the temperature sensor 130 with the target temperature. If the refrigerant temperature is lower than the target temperature (No in step S13), step S13 is repeated. On the other hand, if the refrigerant temperature is higher than the target temperature (Yes in step S13), the post-processing is stopped and transferred to step S14.

[0089] In step S14, the control device 24 terminates the preheating and starts the second power generation control. As a result, the power generation by the power generation cell 28 is switched from low-efficiency power generation to dry power generation (high-efficiency power generation). The refrigerant temperature temporarily drops due to this switch, but rises again due to the refrigerant heated by the heater 144 (see Figure 4 ). When the second power generation control starts, the post-stop process is transferred to step S15.

[0090] In step S15, the control device 24 starts the process of adjusting the opening of the diverter valve 132 according to the refrigerant temperature. For example, when the refrigerant temperature exceeds the target temperature, the control device 24 starts the process of adjusting the opening of the diverter valve 132 according to the refrigerant temperature. As a result, the refrigerant temperature is adjusted to be close to the target temperature (see Figure 4 ). When the opening of the diverter valve 132 starts to be adjusted, the post-processing is stopped and transferred to step S16.

[0091] In step S16, the control device 24 determines whether the power generation cell 28 is dry. For example, the control device 24 obtains the impedance of the fuel cell stack 12 at each predetermined time interval. When the impedance of the fuel cell stack 12 obtained does not reach the target impedance, the control device 24 determines that the power generation cell 28 is not dry. On the other hand, when the impedance of the fuel cell stack 12 obtained reaches the target impedance, the control device 24 determines that the power generation cell 28 is dry. When it is determined that the power generation cell 28 is not dry (in step S16, No), the process of step S16 is repeated. On the other hand, when it is determined that the power generation cell 28 is dry (in step S16, Yes), the post-processing is stopped and transferred to step S17.

[0092] In step S17, the control device 24 ends the second power generation control. In this case, the supply of fuel gas and oxidant gas to the fuel cell stack 12 is stopped, so that the power generation of the power generation cell 28 stops. In addition, the control device 24 ends the control of the pump 126 and the diverter valve 132 of the cooling system 20, and ends the control of the pump 142 and the heater 144 of the air conditioning system 22. When each control ends, the post-stop process transfers to step S18.

[0093] In step S18, the control device 24 controls the valve body 146 to block the refrigerant flow path 120 of the cooling system 20 and the refrigerant flow path 140 of the air conditioning system 22. When the refrigerant flow path 120 of the cooling system 20 and the refrigerant flow path 140 of the air conditioning system 22 are blocked, the post-stop process ends.

[0094] [6 Effects of the above embodiment]

[0095] In the above-mentioned embodiment, the control device 24 regularly measures the stack temperature during the period when the start switch is off, that is, when it is idle. When the stack temperature is lower than a predetermined temperature threshold, the control device 24 performs a second power generation control (dry power generation control) after performing preheating (low-efficiency power generation control). In the second power generation control, the control device 24 causes the refrigerant in the refrigerant flow path 140 of the air-conditioning system 22 heated by the heater 144 to flow into the refrigerant flow path 120 of the cooling system 20. Thus, the power generation cell 28 can be heated by the heat generated by the power generation cell 28 and the heat of the heated refrigerant. Therefore, even if the heat generated by the power generation cell 28 is suppressed, the temperature of the fuel cell stack 12 can be raised to the target temperature. As a result, the power generation cell 28 can be properly dried.

[0096] [7 Modifications of the above embodiment]

[0097] The above-mentioned embodiment may be modified as described below.

[0098] For example, the power generation control unit 152 may perform power generation control for charging the battery during the period from when the first power generation control is stopped to when the second power generation control is started.

[0099] [8 Notes]

[0100] In connection with the above disclosure, the following supplementary notes are also disclosed.

[0101] (Note 1)

[0102] The present disclosure relates to a fuel cell system 10, comprising: a fuel cell stack 12, which includes a power generation cell 28 for generating electricity through an electrochemical reaction between a fuel gas and an oxidant gas; a heat radiator 128, which is used to cool the fuel cell stack; a valve body 146, which can switch between connection and blockage between a first refrigerant flow path 120 and a second refrigerant flow path 140, wherein the first refrigerant flow path circulates a refrigerant between the fuel cell stack and the heat radiator, and the second refrigerant flow path is different from the first refrigerant flow path; a heater 144, which cools the refrigerant flowing in the second refrigerant flow path. agent heating; and a control device 24, which performs power generation control on the power generation cell, the control device is capable of executing a first power generation control and a second power generation control different from the first power generation control, the second power generation control is a power generation control for drying the electrolyte membrane 36 possessed by the power generation cell, the control device executes the first power generation control in a state where the first refrigerant flow path and the second refrigerant flow path are blocked, and when performing the second power generation control, the control device causes the refrigerant in the second refrigerant flow path heated by the heater to flow into the first refrigerant flow path.

[0103] According to the above, the power generation cell can be heated by the heat generated by the power generation cell and the heat of the heated refrigerant. Therefore, even if the heat generated by the power generation cell is suppressed in order to suppress the degradation of the power generation cell, the temperature of the fuel cell stack can be increased to the target temperature. As a result, the power generation cell can be appropriately dried.

[0104] (Note 2)

[0105] In the fuel cell system described in Supplementary Note 1, the air conditioning system 22 may include the heater and the second refrigerant flow path.

[0106] (Note 3)

[0107] The fuel cell system described in Supplementary Note 1 may be configured such that, after receiving a system stop command for stopping the fuel cell system, the control device performs the second power generation control when the temperature of the fuel cell stack is lower than a predetermined temperature threshold.

[0108] According to the above, even if the fuel cell system is stopped in a low-temperature environment, freezing of water can be suppressed.

[0109] (Note 4)

[0110] The fuel cell system described in Supplement 1 may be configured such that the control device performs the second power generation control after preheating the fuel cell stack, and the air-fuel ratio of the oxidant gas supplied to the fuel cell stack is different during the preheating and the second power generation control.

[0111] According to the above, compared with the first power generation control, the amount of heat generated by the power generation cells can be increased, or the efficiency of discharging water accumulated inside the fuel cell stack to the outside can be improved.

[0112] (Note 5)

[0113] In the fuel cell system described in Supplementary Note 4, the air-fuel ratio in the preheating may be smaller than the air-fuel ratio in the first power generation control, and the air-fuel ratio in the second power generation control may be larger than the air-fuel ratio in the first power generation control.

[0114] According to the above, compared with the first power generation control, after the heat amount of the power generation cells is increased, it is possible to suppress the water generated by the power generation from accumulating inside the fuel cell stack.

[0115] (Note 6)

[0116] The fuel cell system recorded in Note 1 may also be that the first refrigerant flow path has: a refrigerant supply path 122, which connects the refrigerant supply interface 12e of the fuel cell stack with the fluid discharge port of the heat radiator; and a refrigerant discharge path 124, which connects the refrigerant discharge interface 12f of the fuel cell stack with the fluid supply port of the heat radiator, and when the second power generation control is performed, the control device causes the refrigerant in the second refrigerant flow path heated by the heater to flow into the refrigerant supply path.

[0117] According to the above, the heated coolant flowing into the first coolant flow path can be supplied to the fuel cell stack without passing through the radiator.

[0118] (Note 7)

[0119] The fuel cell system recorded in Note 6 may also be that the first refrigerant flow path has a bypass path 125 connecting the refrigerant supply path and the refrigerant discharge path, and the control device adjusts the flow rate of the refrigerant released by the heat emitter according to the temperature of the refrigerant detected by the temperature sensor 130 provided in the first refrigerant flow path.

[0120] (Note 8)

[0121] The fuel cell system recorded in Note 1 may also be that the control device performs the second power generation control after preheating the fuel cell stack, and during the preheating and before performing the second power generation control, the control device causes the refrigerant in the second refrigerant flow path heated by the heater to flow into the first refrigerant flow path.

[0122] According to the above content, the temperature of the fuel cell stack can be maintained at the target temperature. Moreover, when the temperature of the fuel cell stack is lower than the target temperature and the flow divider valve is in a closed state, it is possible to suppress the situation where the temperature of the first refrigerant flow path and the second refrigerant flow path is difficult to rise. In addition, when the temperature of the fuel cell stack is higher than the target temperature and the flow divider valve is in an open state, the temperature of the refrigerant flowing into the heater due to the radiator is reduced, thereby further extending the time for the power generated by the power generation cell to be consumed by the heater.

[0123] 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 power generation cells for generating power through an electrochemical reaction between a fuel gas and an oxidant gas; a heat radiator for cooling the fuel cell stack; a valve body capable of switching connection and blocking between a first refrigerant flow path and a second refrigerant flow path, the first refrigerant flow path allowing refrigerant to circulate between the fuel cell stack and the radiator, the second refrigerant flow path being different from the first refrigerant flow path; a heater configured to heat the refrigerant flowing in the second refrigerant flow path; as well as a control device for controlling power generation of the power generation cell, the control device is capable of executing a first power generation control and a second power generation control different from the first power generation control, The second power generation control is a power generation control for drying an electrolyte membrane provided in the power generation cell. The control device performs the first power generation control in a state where the first refrigerant flow path and the second refrigerant flow path are blocked. When the second power generation control is performed, the control device causes the refrigerant in the second refrigerant flow path heated by the heater to flow into the first refrigerant flow path.

2. The fuel cell system according to claim 1, characterized in that: The air conditioning system includes the heater and the second refrigerant flow path.

3. The fuel cell system according to claim 1, characterized in that: The control device performs the second power generation control when the temperature of the fuel cell stack is lower than a predetermined temperature threshold value after receiving a system stop command for stopping the fuel cell system.

4. The fuel cell system according to claim 1, characterized in that: The control device performs the second power generation control after warming up the fuel cell stack, In the warm-up and the second power generation control, the air-fuel ratio of the oxidant gas supplied to the fuel cell stack is different.

5. The fuel cell system according to claim 4, characterized in that: The air-fuel ratio in the preheating is smaller than the air-fuel ratio in the first power generation control, and the air-fuel ratio in the second power generation control is larger than the air-fuel ratio in the first power generation control.

6. The fuel cell system according to claim 1, characterized in that: The first refrigerant flow path includes: a refrigerant supply path connecting the refrigerant supply interface of the fuel cell stack with the fluid discharge port of the radiator; and a refrigerant discharge path connecting the refrigerant discharge interface of the fuel cell stack with the fluid supply port of the radiator. When the second power generation control is performed, the control device causes the refrigerant in the second refrigerant flow path heated by the heater to flow into the refrigerant supply path.

7. The fuel cell system according to claim 6, characterized in that: The first refrigerant flow path includes a branch path connecting the refrigerant supply path and the refrigerant discharge path. The control device adjusts the flow rate of the refrigerant that radiates heat by the radiator, based on the temperature of the refrigerant detected by the temperature sensor provided in the first refrigerant flow path.

8. The fuel cell system according to claim 1, characterized in that: The control device performs the second power generation control after warming up the fuel cell stack, During the preheating and before the second power generation control is executed, the control device causes the refrigerant in the second refrigerant flow path heated by the heater to flow into the first refrigerant flow path.

Images