Fuel cell system

Abstract

The invention relates to a fuel cell system. The control device (24) causes the heater (144) to consume power generated from the power generation unit cell (28) in a state in which the first refrigerant flow path (120) and the second refrigerant flow path (140) are connected to each other when the control device (24) performs the second power generation control in a state in which the remaining capacity of the storage battery (26A) is equal to or greater than a predetermined remaining capacity threshold value.

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] Regarding fuel cells, there is a fuel cell system that includes: a fuel cell stack including power generation cells; and a storage battery that stores the power generated by the power generation cells. The fuel cell system can be mounted on a mobile body such as a vehicle. In a fuel cell system mounted on a mobile body, power generation is sometimes performed while the mobile body is stopped.

[0004] Patent Document 1 discloses a fuel cell system shutdown method that performs a drain power generation process after performing a drying power generation process when an ignition switch is turned off in order to promote drying of a membrane electrode assembly (MEA) of a power generation cell.

[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] When the remaining capacity of the battery provided in the fuel cell system is relatively high, the power generated by the power generating cell cannot be supplied to the battery. Therefore, a technology for efficiently consuming the power generated by the power generating cell 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 through an electrochemical reaction between a fuel gas and an oxidant gas; a storage battery that can store electricity generated from the power generation cell; a heat radiator that is used to cool 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 heat 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 controls the The power generation cell performs power generation control. In the fuel cell system, the control device is capable of executing a first power generation control and a second power generation control based on a system stop instruction for stopping the fuel cell system. The second power generation control includes a low-efficiency power generation control for causing the power generation cell to generate power at a power generation efficiency lower than the power generation efficiency in the first power generation control. When the second power generation control is performed when the remaining capacity of the battery is above a predetermined remaining capacity threshold, the control device causes the heater to consume the power generated from the power generation cell while the first refrigerant flow path and the second refrigerant flow path are interconnected.

[0013] Effects of the Invention

[0014] According to the present invention, the temperature of the refrigerant heated by the heater rises slowly compared to a case where the first refrigerant flow path and the second refrigerant flow path are not connected. Therefore, the time during which the power generated by the power generation cell is consumed by the heater can be increased compared to a case where the first refrigerant flow path and the second refrigerant flow path are not connected. Therefore, even when the remaining capacity of the battery is large, the second power generation control can be continued for a relatively long time. As a result, the power generated by the power generation cell can be consumed well.

[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 1 is a flowchart showing the procedure of the heat control process in the implementation of the second power generation control. DETAILED DESCRIPTION

[0019] [1 Structure of the fuel cell system 10]

[0020] 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.

[0021] 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.

[0022] 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 battery 26A that stores the power generated by the fuel cell stack 12; a drive motor 26B of the vehicle; and a heater 144. The tank 14 is filled with high-pressure fuel gas.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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 .

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] The cooling system 20 includes a refrigerant flow path 120 . In addition, the cooling system 20 includes a pump 126 , a radiator 128 , a first temperature sensor 130 , and a flow dividing valve 132 .

[0036] 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.

[0037] 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. In addition, 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 128F.

[0038] The first temperature sensor 130 is a first temperature detection device that detects the temperature of the refrigerant in the refrigerant flow path 120 (refrigerant temperature). The first temperature sensor 130 is provided in the refrigerant discharge path 124. Alternatively, the first temperature sensor 130 may be provided in the refrigerant supply path 122. Alternatively, the first temperature sensor 130 detects the outlet temperature of the reaction gas. In this case, for example, the first temperature sensor 130 is provided in the fuel gas discharge interface 12b. 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).

[0039] 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.

[0040] The air conditioning system 22 includes a refrigerant flow path 140 . The air conditioning system 22 also includes a pump 142 , a heater 144 , a valve body 146 , and a second temperature sensor 160 .

[0041] 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. The refrigerant flow path 140 of the air conditioning system 22 and the refrigerant flow path 120 of the cooling system 20 can be connected via a communication path 148. The communication path 148 has a partial flow path 148A and a partial flow path 148B.

[0042] 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.

[0043] 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.

[0044] The valve body 146 can switch 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 can also be a three-way valve. In this case, the valve body 146 is respectively provided at the connection part of the refrigerant flow path 140 and the partial flow path 148A and the connection part of the refrigerant flow path 140 and the partial flow path 148B.

[0045] The second temperature sensor 160 is a second temperature detection device that detects the temperature of the refrigerant (refrigerant temperature) in the refrigerant flow path 140. In this embodiment, the temperature of the refrigerant on the downstream side of the heater 144 is detected, but the temperature of the heater 144 may be detected as the temperature of the refrigerant in the refrigerant flow path 140.

[0046] The control device 24 may be constituted by 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 constituted by a processing circuit. The computing unit 136 includes an acquisition unit 150, a power generation control unit 152, and a heat control unit 154. The computing unit 136 executes a program stored in the storage unit 138, thereby realizing the acquisition unit 150, the power generation control unit 152, and the heat control unit 154.

[0047] Alternatively, at least one of the acquisition unit 150, the power generation control unit 152, and the heat control unit 154 may be implemented by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). Alternatively, at least one of the acquisition unit 150, the power generation control unit 152, and the heat control unit 154 may be implemented by a circuit including discrete devices.

[0048] 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, the valves, etc. The heat control unit 154 controls the operation of the diverter valve 132, the heater 144, the valve body 146, etc.

[0049] 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.

[0050] [2 Flow of Fluid in Fuel Cell System 10]

[0051] [2-1 Flow of Fluid in Anode System 16]

[0052] 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.

[0053] 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.

[0054] [2-2 Flow of Fluid in Cathode System 18]

[0055] 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.

[0056] 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.

[0057] [2-3 Flow of Fluid in Cooling System 20]

[0058] 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.

[0059] 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.

[0060] [2-4 Flow of Fluid in Air Conditioning System 22]

[0061] 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 .

[0062] 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.

[0063] 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.

[0064] 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 .

[0065] [3 Power generation control]

[0066] The power generation control unit 152 can execute a first power generation control for supplying electric power in accordance with a request to the load 26 , and a second power generation control for drying the electrolyte membrane 36 included in the power generation cell 28 .

[0067] 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.

[0068] In step S1, the power generation control unit 152 performs the first power generation control for supplying power corresponding to the request to the load 26. The power generation control unit 152 continues the first power generation control until receiving the system stop command, which is an instruction for stopping the fuel cell system 10. The power generation control unit 152 ends the first power generation control when receiving the system stop command. When the first power generation control ends, the power generation control process is transferred to step S2.

[0069] In step S2, the power generation control unit 152 compares the temperature (stack temperature) detected by the first temperature sensor 130 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 is transferred to step S3.

[0070] In step S3, the power generation control unit 152 performs the second power generation control. When a predetermined time has passed since the start of the second power generation control, or when the impedance of the fuel cell stack 12 reaches the target impedance, or when the temperature of the fuel cell stack 12 reaches a predetermined temperature, the power generation control unit 152 determines that the power generation cell 28 is dry. In this case, the power generation control unit 152 ends the second power generation control. When the second power generation control ends, the power generation control process ends. When the power generation control unit 152 ends the second power generation control, it does not execute the power generation control process until it receives the system startup command again.

[0071] 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.

[0072] In the first power generation control, the power generation control unit 152 controls the operation of the ejector 94, the compressor 112, the pump 126, the valves, etc., so that the power generation cell 28 performs normal power generation. In the execution of the first power generation control, the power generation control unit 152 controls the ejector 94 and the compressor 112 based on the required power generation so that the power generation of the power generation cell 28 becomes the required power generation. The required power generation is calculated by the power generation control unit 152 based on the accelerator opening, the vehicle speed, the road gradient, etc., for example.

[0073] The second power generation control includes low-efficiency power generation control for causing the power generation cell 28 to generate power at a power generation efficiency lower than that in the first power generation control, and dry power generation control for heating and drying the fuel cell stack 12 in order to dry the electrolyte membrane 36 included in the power generation cell 28 .

[0074] In the low-efficiency power generation control, power generation is performed at a low-efficiency operation point where power generation loss is greater than the normal operation point in the first power generation control. In the execution of the low-efficiency power generation control, the power generation control unit 152 controls the ejector 94 and the compressor 112 so that the air-fuel ratio of the oxidant gas supplied to the fuel cell stack 12 is relatively small. More specifically, the power generation control unit 152 sets the air-fuel ratio of the oxidant gas during the second power generation control to be smaller than the air-fuel ratio of the oxidant gas during the first power generation control. That is, the ratio of the oxidant gas to the fuel gas during the execution of the second power generation control is made smaller than the ratio of the oxidant gas to the fuel gas during the execution of the first power generation control.

[0075] Thus, the amount of oxidant gas supplied to the fuel cell stack 12 during the second power generation control is less than the amount of oxidant gas supplied to the fuel cell stack 12 during the first power generation control. As a result, during the second power generation control, low-efficiency power generation with a power generation efficiency lower than that of normal power generation is performed by the power generation cell 28. Since low-efficiency power generation is performed, the calorific value of the power generation cell 28 increases during the second power generation control. That is, the calorific value of the power generation cell 28 during the second power generation control is greater than the calorific value of the power generation cell 28 during the first power generation control.

[0076] After the low-efficiency power generation control ends, the dry power generation control begins. For example, when the temperature detected by the first temperature sensor 130 reaches the target temperature, the low-efficiency power generation control is switched to the dry power generation control. In the dry power generation control, power generation is performed at the normal operation point in the first power generation control, the operation point with a smaller power generation loss than the normal operation point, or the operation point equal to the normal operation point. That is, the power generation control unit 152 controls the ejector 94 and the compressor 112 so that the power generation cell 28 performs steady-state operation at the same normal operation point as the first power generation control, or the power generation cell 28 performs power generation in a high air-fuel ratio state in which the ratio of the oxidant gas to the fuel gas supplied to the fuel cell stack 12 is increased.

[0077] [4 Heat Control]

[0078] In the implementation of the first power generation control, the heat control unit 154 drives the pump 126 provided in the refrigerant flow path 120. In addition, in the implementation of the first power generation control, the heat control unit 154 sets the opening of the diverter valve 132 so that the refrigerant discharged from the fuel cell stack 12 to the refrigerant discharge path 124 is not supplied to the refrigerant supply path 122 via the diverter path 125 but is supplied to the radiator 128. Alternatively, the heat control unit 154 may adjust the opening of the diverter valve 132.

[0079] In addition, in the implementation of the first power generation control, the thermal control unit 154 controls the valve body 146 so that the refrigerant flow path 120 of the cooling system 20 and the refrigerant flow path 140 of the air conditioning system 22 are blocked. 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. In addition, in the implementation of the first power generation control, the thermal control unit 154 controls the valve body 146 so that the refrigerant flow path 120 of the cooling system 20 and the refrigerant flow path 140 of the air conditioning system 22 are connected only during an arbitrary period.

[0080] Figure 3 1 is a flowchart showing the procedure of the heat control process in the implementation of the second power generation control. In the implementation of the second power generation control, the heat control unit 154 executes a predetermined heat control process. When the second power generation control starts, the heat control process moves to step S11.

[0081] In step S11, the heat control unit 154 drives the pump 126 provided in the refrigerant flow path 120 and the pump 142 provided in the refrigerant flow path 140. The pump 126 and the pump 142 may be driven by the power supplied from the battery 26A or by the power generated from the power generation cell 28 by the second power generation control. In addition, the heat control unit 154 sets the opening of the diverter valve 132 so that the refrigerant discharged from the fuel cell stack 12 to the refrigerant discharge path 124 is not supplied to the radiator 128 but to the refrigerant supply path 122. When the pump 126 and the pump 142 are driven and the opening of the diverter valve 132 is set, the heat control process is transferred to step S12.

[0082] In step S12, 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. 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 the second power generation control.

[0083] 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 can be 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 heated only by the heat generated by the power generation cell 28, the power generation cell 28 can be heated quickly and sufficiently. After 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 heat control process is transferred to step S13.

[0084] In step S13, the thermal control unit 154 determines whether the remaining capacity of the battery 26A is greater than or equal to a predetermined remaining capacity threshold. For example, the remaining capacity of the battery 26A is obtained from a capacity sensor or the like provided in the battery 26A. When the remaining capacity of the battery 26A is less than the predetermined remaining capacity threshold (No in step S13), the thermal control process is transferred to step S14. On the other hand, when the remaining capacity of the battery 26A is greater than or equal to the predetermined remaining capacity threshold (Yes in step S13), the thermal control process is transferred to step S15.

[0085] In step S14, the heat control unit 154 charges the battery 26A and drives the heater 144 using the power supplied from the battery 26A. That is, the heat control unit 154 sets the power supply path so that the power generated from the power generation cell 28 by the second power generation control is supplied to the battery 26A. In addition, the heat control unit 154 sets the power supply path so that power is supplied from the battery 26A to the heater 144. In this way, the heater 144 can be driven while suppressing the power consumption of the battery 26A. When the heater 144 starts to be driven using the power supplied from the battery 26A, the heat control process is transferred to step S16.

[0086] In step S15, the heat control unit 154 drives the heater 144 using the power generated from the power generation cell 28 by the second power generation control. That is, the heat control unit 154 sets the power supply path so that the power generated from the power generation cell 28 is supplied to the heater 144 and the heater 144 consumes the power. In this way, the heater 144 can be driven while suppressing excessive power accumulation in the storage battery 26A. When the power generated from the power generation cell 28 is started to be used to drive the heater 144, the heat control process is transferred to step S16.

[0087] In step S16, the heat control unit 154 compares the refrigerant temperature detected by the first temperature sensor 130 with the target temperature. If the refrigerant temperature is higher than the target temperature (Yes in step S16), the heat control process moves to step S17. On the other hand, if the refrigerant temperature is lower than the target temperature (No in step S16), the heat control process moves to step S18.

[0088] In step S17, the heat control unit 154 adjusts the opening of the diverter valve 132 according to the refrigerant temperature detected by the first temperature sensor 130. The opening of the diverter valve 132 is adjusted so that the greater the temperature detected by the first temperature sensor 130, the greater the amount of refrigerant supplied to the radiator 128. In this way, the temperature of the fuel cell stack 12 can be maintained at the target temperature. When the opening of the diverter valve 132 is adjusted, the heat control process is transferred to step S18.

[0089] In step S18, the heat control unit 154 compares the refrigerant temperature detected by the second temperature sensor 160 with a predetermined temperature threshold. The temperature threshold is set to be higher than the above-mentioned target temperature. When the temperature of the refrigerant flowing through the refrigerant flow path 140 is higher than the temperature threshold (in step S18, yes), the heat control process is transferred to step S19. On the other hand, when the temperature of the refrigerant flowing through the refrigerant flow path 140 is lower than the temperature threshold (in step S18, no), the heat control process returns to step S17.

[0090] In step S19, the heat control unit 154 cuts off the power supplied to the heater 144 to stop the heater 144. When the heater 144 stops, the heat control process returns to step S17.

[0091] The above heat control process is performed during the implementation of the second power generation control. When the second power generation control is completed, the heat control unit 154 stops the pump 126 and the pump 142. In addition, if the heater 144 is not stopped in the above-mentioned step S19, when the second power generation control is completed, the heat control unit 154 stops the heater 144.

[0092] [5 Effects of the above-mentioned embodiments]

[0093] In the above-mentioned embodiment, after the first power generation control is ended based on the system stop instruction, when the stack temperature is lower than the temperature threshold, the control device 24 starts the second power generation control. First, the control device 24 sets the air-fuel ratio of the oxidant gas in the second power generation control to be smaller than the air-fuel ratio of the oxidant gas in the first power generation control to perform low-efficiency power generation control. Thereafter, the control device 24 sets the air-fuel ratio of the oxidant gas to be greater than the air-fuel ratio of the oxidant gas in the first power generation control to perform dry power generation control. Thus, the electrolyte membrane 36 can be dried well. As a result, the startup of the power generation cell 28 at low temperature can be well implemented. In addition, the degradation of the electrolyte membrane 36 caused by freezing of water is suppressed.

[0094] When the second power generation control is performed when the remaining capacity of the battery 26A is above a predetermined remaining capacity threshold, the control device 24 causes the heater 144 to consume the power generated by the power generation cell 28 while the refrigerant flow path 120 of the cooling system 20 and the refrigerant flow path 140 of the air-conditioning system 22 are interconnected.

[0095] As a result, the temperature of the refrigerant heated by the heater 144 rises slowly compared to the case where the refrigerant flow path 120 and the refrigerant flow path 140 are not connected. Therefore, the time during which the power generated by the power generation cell 28 is consumed by the heater 144 can be increased compared to the case where the refrigerant flow path 120 and the refrigerant flow path 140 are not connected. Therefore, even when the remaining capacity of the storage battery 26A is large, the second power generation control can be continued for a relatively long time. In this way, according to the embodiment, the power generated by the power generation cell 28 can be consumed well.

[0096] In addition, the control device 24 controls the diverter valve 132 provided in the coolant flow path 120 according to the coolant temperature detected by the first temperature sensor 130, thereby adjusting the flow rate of the coolant radiated by the radiator 128. In this way, the temperature of the fuel cell stack 12 can be maintained at the target temperature while the heater 144 consumes the power generated by the power generation cell 28.

[0097] More specifically, when the temperature of the fuel cell stack is lower than the target temperature, the control device 24 sets the diverter valve 132 to a closed valve state. Thus, it is possible to suppress a situation where the temperature of the refrigerant flow path 140 and the refrigerant flow path 120 is difficult to rise. In addition, when the temperature of the fuel cell stack is higher than the target temperature, the control device 24 sets the diverter valve 132 to an open valve state. Thus, the temperature of the refrigerant flowing into the heater 144 can be reduced by the radiator 128, and as a result, the time during which the power generated by the power generation cell 28 is consumed by the heater 144 can be further extended.

[0098] In addition, when the temperature of the refrigerant flowing through the refrigerant flow path 140 is above a predetermined temperature threshold, the control device 24 stops the heater 144 from consuming power. This can prevent the refrigerant from being overheated. In particular, even when the heater 144 fails, the refrigerant can be prevented from being overheated.

[0099] [6 Variations of the above embodiment]

[0100] The above-mentioned embodiment may be modified as described below.

[0101] (First Modification)

[0102] Alternatively, when the remaining capacity of the battery 26A is less than a predetermined remaining capacity threshold, the thermal control unit 154 may drive the heater 144 using both the power supplied from the battery 26A and the power generated from the power generating cell 28 by the second power generation control. In addition, in the present modification, when the remaining capacity of the battery 26A is greater than or equal to the predetermined remaining capacity threshold, the thermal control unit 154 drives the heater 144 using only the power generated from the power generating cell 28 by the second power generation control.

[0103] (Second Modification)

[0104] When the radiator 128 includes the fan 128F, the control device 24 may perform fan control as follows.

[0105] That is, when the first power generation control is performed, the control device 24 drives the fan 128F. The fan 128F may be driven by the power supplied from the storage battery 26A or by the power generated from the power generation cell 28 by the first power generation control. In addition, the control device 24 may adjust the rotation speed of the fan 128F according to the temperature detected by the first temperature sensor 130 during the execution of the first power generation control.

[0106] On the other hand, when the second power generation control is performed in a state where the remaining capacity of the battery 26A is greater than the remaining capacity threshold, the control device 24 stops the fan 128F. As a result, the temperature of the fuel cell stack 12 can be increased compared to the case where the fan 128F is not stopped, and as a result, the electrolyte membrane 36 can be dried efficiently. In addition, in the second power generation control performed when the start switch is turned off, the noise level can be reduced.

[0107] [7 Notes]

[0108] Regarding the above disclosure, the following supplementary notes are further disclosed.

[0109] (Note 1)

[0110] The present disclosure relates to a fuel cell system 10, comprising: a fuel cell stack 12, which includes a power generation cell 28 that generates electricity through an electrochemical reaction of a fuel gas and an oxidant gas; a storage battery 26A that can store the electricity generated by the power generation cell; a heat radiator 128 that is used to cool the fuel cell stack; a valve body 146 that can switch between connection and blockage between a first refrigerant flow path 120 and a second refrigerant flow path 140, the first refrigerant flow path circulates a refrigerant between the fuel cell stack and the heat radiator, the second refrigerant flow path being different from the first refrigerant flow path; a heater 144 that heats the refrigerant flowing in the second refrigerant flow path; and A control device 24, which controls power generation of the power generation cell. In the fuel cell system, the control device is capable of executing a first power generation control and a second power generation control based on a system stop instruction for stopping the fuel cell system. The second power generation control includes a low-efficiency power generation control for causing the power generation cell to generate power at a power generation efficiency lower than the power generation efficiency in the first power generation control. When the second power generation control is performed when the remaining capacity of the battery is above a predetermined remaining capacity threshold, the control device causes the heater to consume the power generated from the power generation cell while the first refrigerant flow path and the second refrigerant flow path are interconnected.

[0111] According to the above, the temperature of the refrigerant heated by the heater rises slowly compared to the case where the first refrigerant flow path and the second refrigerant flow path are not connected. Therefore, the time during which the power generated by the power generation cell is consumed by the heater can be increased compared to the case where the first refrigerant flow path and the second refrigerant flow path are not connected. Therefore, even when the remaining capacity of the battery is large, the second power generation control can be continued for a relatively long time. As a result, the power generated by the power generation cell can be consumed well.

[0112] (Note 2)

[0113] In the fuel cell system recorded in Note 1, it may also be provided with a first temperature detection device 130 capable of detecting the temperature of the fuel cell stack, and 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; 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 a bypass path 125, which connects the refrigerant supply path with the refrigerant discharge path, and a bypass valve 132 with adjustable opening is provided at the connecting part of the bypass path and the refrigerant supply path, or the connecting part of the bypass path and the refrigerant discharge path, and the control device controls the bypass valve according to the temperature of the fuel cell stack to adjust the flow rate of the refrigerant released by the heat radiator.

[0114] According to the above content, the temperature of the fuel cell stack can be maintained at the target temperature while the heater consumes the power generated by the power generation cell. Moreover, when the temperature of the fuel cell stack is lower than the target temperature and the diverter 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 diverter 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.

[0115] (Note 3)

[0116] In the fuel cell system recorded in Note 1, the heat emitter may include a fan 128F, and when the second power generation control is performed in a state where the remaining capacity of the battery is above the remaining capacity threshold, the control device causes the heater to consume the power generated from the power generation cell while stopping the fan.

[0117] According to the above, the heating value of the power generation cell can be increased compared to the case where the fan is not stopped, and as a result, the electrolyte membrane can be dried efficiently. In addition, during the execution of the second power generation control, the noise level can be reduced compared to the case where the fan is driven.

[0118] (Note 4)

[0119] In the fuel cell system described in Note 1, there may be a second temperature detection device 160 capable of detecting the temperature of the second refrigerant flow path, and when the temperature of the second refrigerant flow path is above a predetermined temperature threshold, the control device stops the heater from consuming the power.

[0120] According to the above, it is possible to suppress the refrigerant from being excessively heated. In particular, even when the heater fails, it is possible to suppress the refrigerant from being excessively heated.

[0121] (Note 5)

[0122] In the fuel cell system according to Supplementary Note 1, the air-fuel ratio of the oxidant gas in the low-efficiency power generation control may be smaller than the air-fuel ratio of the oxidant gas in the first power generation control.

[0123] According to the above, the amount of heat generated by the power generation cell increases compared to the first power generation control, so the electrolyte membrane can be dried well. As a result, degradation of the electrolyte membrane due to freezing of water is suppressed.

[0124] 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 storage battery capable of storing the electric power generated by the power generation cell; 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, wherein the first refrigerant flow path circulates refrigerant between the fuel cell stack and the radiator, and the second refrigerant flow path is 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, In the fuel cell system, The control device is capable of executing a first power generation control and a second power generation control based on a system stop instruction for stopping the fuel cell system. The second power generation control includes low-efficiency power generation control for causing the power generation cell to generate power at the power generation efficiency lower than the power generation efficiency in the first power generation control. When the second power generation control is performed in a state where the remaining capacity of the battery is above a predetermined remaining capacity threshold, the control device causes the heater to consume the power generated by the power generation cell in a state where the first refrigerant flow path and the second refrigerant flow path are connected to each other.

2. The fuel cell system according to claim 1, characterized in that: A first temperature detection device capable of detecting the temperature of the fuel cell stack is provided, The first refrigerant flow path comprises: a refrigerant supply path connecting a refrigerant supply interface of the fuel cell stack with a fluid discharge port of the radiator; a refrigerant discharge path connecting the refrigerant discharge interface of the fuel cell stack with the fluid supply port of the radiator; and a shunt path connecting the refrigerant supply path with the refrigerant discharge path, A flow divider valve whose opening degree can be adjusted is provided at a connection portion between the flow divider passage and the refrigerant supply passage, or at a connection portion between the flow divider passage and the refrigerant discharge passage. The control device controls the diverter valve according to the temperature of the fuel cell stack to adjust the flow rate of the refrigerant that releases heat from the radiator.

3. The fuel cell system according to claim 1, characterized in that: The radiator has a fan. When the second power generation control is performed in a state where the remaining capacity of the storage battery is equal to or greater than the remaining capacity threshold, the control device causes the heater to consume the power generated by the power generation cell while stopping the fan.

4. The fuel cell system according to claim 1, characterized in that: A second temperature detection device capable of detecting the temperature of the second refrigerant flow path is provided, The control device causes the heater to stop consuming the electric power when the temperature of the second refrigerant flow path is equal to or higher than a predetermined temperature threshold.

5. The fuel cell system according to any one of claims 1 to 4, characterized in that: The air-fuel ratio of the oxidant gas in the low-efficiency power generation control is smaller than the air-fuel ratio of the oxidant gas in the first power generation control.

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