Fuel cell system

Abstract

The present application provides a kind of fuel cell system (100), with: temperature detection part (52), it detects the temperature of each of multiple fuel cells (1);Cooling system (40), it has the cooling medium supply unit (42) of cooling medium supply to each of multiple fuel cells (1);Power storage device (53);And control portion (102).When the temperature (Ta) of first fuel cell (1A) detected by temperature detection part (52) becomes specified temperature (T1) or more, control portion (102) controls cooling system (40), so that with the temperature of second fuel cell (1B) lower than first fuel cell (1A) corresponding cooling capacity to cool first fuel cell (1A) and second fuel cell (1B), and execute the output limit of first fuel cell (1A), further make the power corresponding to the output limit of first fuel cell (1A) from power storage device (53) discharge.

Description

Technical Field

[0001] This invention relates to a fuel cell system having multiple fuel cells. Background Technology

[0002] In recent years, in order to ensure that more people have access to affordable, reliable, sustainable, and advanced energy, technologies related to fuel cells that contribute to energy efficiency are being developed. Among these fuel cell-related technologies, technologies related to cooling fuel cell systems having multiple fuel cells are known. Such a fuel system is described, for example, in Patent Document 1.

[0003] In the fuel cell system described in Patent Document 1, when the first fuel cell and the second fuel cell are generating electricity, when the temperature of the first fuel cell reaches or exceeds a set temperature, the second fuel cell is cooled with a cooling capacity higher than the cooling capacity determined based on the temperature of the second fuel cell. Then, when the temperature of the first fuel cell reaches or exceeds a threshold temperature, the output of the first fuel cell is limited, and the output of the second fuel cell is made to correspond to the amount of the output limit.

[0004] In the system described in Patent Document 1, when the temperature of one fuel cell exceeds a set temperature, the speed of the electric fan of the coolant pump and radiator of the coolant circulation system of the other fuel cell is increased to enhance cooling capacity. Therefore, the power consumption of the fuel cell system increases, accompanied by a deterioration in fuel efficiency.

[0005] Existing technical documents Patent documents Patent document 1: Japanese Patent Application Publication No. 2020-144984 (JP2020-144984A). Summary of the Invention

[0006] A fuel cell system according to one embodiment of the present invention comprises: a plurality of fuel cells; a temperature detection unit that detects the temperature of each of the plurality of fuel cells; a cooling system having a cooling medium supply unit that supplies a cooling medium to each of the plurality of fuel cells; an energy storage device; and a control unit that controls the output of the cooling system, the plurality of fuel cells, and the charging and discharging of the energy storage device based on the temperature detected by the temperature detection unit. When the temperature of the first fuel cell detected by the temperature detection unit reaches or exceeds a predetermined temperature, the control unit controls the cooling system to cool the first and second fuel cells with a cooling capacity corresponding to the temperature of the second fuel cell, which is lower than that of the first fuel cell, and performs an output limit on the first fuel cell, thereby discharging the power corresponding to the output limit on the first fuel cell from the energy storage device. Attached Figure Description

[0007] The objectives, features, and advantages of the present invention are further illustrated by the following description of embodiments in conjunction with the accompanying drawings.

[0008] Figure 1 This is a diagram showing a schematic structure of a single unit system constituting an embodiment of the fuel cell system of the present invention; Figure 2 This is a block diagram that schematically illustrates the control structure of a fuel cell system according to an embodiment of the present invention; Figure 3 This is a diagram illustrating the structure of the cooling system of a fuel cell system according to an embodiment of the present invention; Figure 4 This is a block diagram that schematically illustrates the structure of a cooling control device included in a fuel cell system according to an embodiment of the present invention; Figure 5 It is shown by Figure 4 A flowchart of an example of the processing performed by the controller. Detailed Implementation

[0009] The following is for reference Figures 1-5 Embodiments of the present invention will be described. The fuel cell system of the present invention has multiple fuel cells. This fuel cell system can be installed in large fuel cell vehicles, such as fuel cell buses. Hereinafter, each of the multiple fuel cells will be referred to as a unit system. The fuel cell system has multiple unit systems, thereby increasing the overall power generation and providing sufficient power to the drive motor of a large fuel cell vehicle.

[0010] Multiple unit systems have the same structure. Figure 1 This is a diagram showing the schematic structure of a single unit system (fuel cell) 101. (See diagram for example.) Figure 1 As shown, the unit system 101 includes a fuel cell stack 1, a fuel gas supply / discharge unit 2 for supplying fuel gas to and discharging fuel gas from the fuel cell stack 1, an oxidant gas supply / discharge unit 3 for supplying oxidant gas to and discharging oxidant gas from the fuel cell stack 1, and a cooling medium supply / discharge unit 4 for supplying cooling medium to and discharging cooling medium from the fuel cell stack 1. The fuel gas (anode gas) is, for example, hydrogen. The oxidant gas (cathode gas) is, for example, oxygen-containing air. The cooling medium (coolant) is, for example, water, a coolant containing ethylene glycol or propylene glycol.

[0011] The fuel cell stack 1 is constructed by stacking multiple power generation units. Each power generation unit has an electrolyte membrane, an anode separator facing one side of the electrolyte membrane, and a cathode separator facing the other side of the electrolyte membrane. The electrolyte membrane is, for example, a solid polymer electrolyte membrane. An anode electrode is formed on one side of the electrolyte membrane, and fuel gas is supplied to the anode electrode through an anode flow channel between the anode separator and the anode electrode. An oxidant electrode is formed on the other side of the electrolyte membrane, and oxidant gas is supplied to the cathode electrode through a cathode flow channel between the cathode separator and the cathode electrode. Between adjacent pairs of power generation units, the anode separator and the cathode separator are arranged in a single, integrated manner, and a cooling medium flows between these anode separators and cathode separators.

[0012] At the anode electrode, the fuel gas (hydrogen) supplied via the anode channel is ionized by the catalyst and moves through the electrolyte membrane towards the cathode electrode. The generated electrons are extracted as electrical energy via an external circuit. At the cathode electrode, the oxidant gas (oxygen) supplied via the cathode channel reacts with hydrogen ions introduced from the anode electrode and electrons moving from the anode electrode to produce water. The generated water imparts appropriate humidity to the electrolyte membrane, and any remaining water is discharged to the outside.

[0013] The fuel gas supply / discharge unit 2 includes a fuel gas tank 21 storing fuel gas, a fuel gas supply channel PA11 for guiding the fuel gas in the fuel gas tank to the fuel gas inlet of the fuel cell stack 1, and a fuel gas discharge channel PA12 for supplying fuel gas (fuel exhaust) flowing out of the fuel gas outlet of the fuel cell stack 1. A sealing valve 22 and an injector 23 are arranged in the fuel gas supply channel PA11. The sealing valve 22 is a solenoid valve that opens and closes using electromagnetic force and is located between the fuel gas tank 21 and the injector 23. The sealing valve 22 opens or closes the flow channel between the fuel gas tank 21 and the injector 23. The injector 23 has one or multiple electromagnetic injectors connected in parallel. Fuel gas is injected by driving the injector 23, and the injected fuel gas flows to the fuel cell stack 1.

[0014] A gas-liquid separator (not shown) is connected to the fuel gas discharge channel PA12. In the gas-liquid separator, the fuel exhaust gas introduced through the fuel gas discharge channel PA12 is separated into fuel gas and water. The separated fuel gas is drawn into an ejector (not shown) located downstream of the injector 23 and introduced into the fuel gas supply channel PA11. The separated water is discharged to the outside through the drain channel.

[0015] The oxidant gas supply / discharge unit 3 includes a pump (compressor) 31 for generating high-pressure oxidant gas, an oxidant gas supply channel PA21 for guiding the oxidant gas to the oxidant gas inlet of the fuel cell stack 1, and an oxidant gas discharge channel PA22 for supplying oxidant gas (oxidant exhaust) flowing from the oxidant gas outlet of the fuel cell stack 1. The pump 31 compresses air drawn in from the atmosphere and supplies it to the fuel cell stack 1 as oxidant gas. A bypass channel PA23 connects the oxidant gas supply channel PA21 and the oxidant gas discharge channel PA22, bypassing the fuel cell stack 1 and guiding the oxidant gas from the oxidant gas supply channel PA21 to the oxidant gas discharge channel PA22.

[0016] A humidifier 32 is connected to the oxidant gas supply channel PA21 and the oxidant gas discharge channel PA22. The humidifier 32 is positioned between the bypass channel PA23 and the fuel cell stack 1. In the humidifier 32, the moisture contained in the oxidant exhaust gas from the oxidant gas discharge channel PA22 is used to humidify the oxidant gas in the oxidant gas supply channel PA21. Sealing valves 33 and 34 are respectively installed between the oxidant gas supply channel PA21 and the oxidant gas discharge channel PA22, and between the bypass channel PA23 and the humidifier 32. Sealing valves 33 and 34 are solenoid valves that open and close using electromagnetic force; as sealing valves 33 and 34 open and close, channels PA21 and PA22 are opened or closed. A bypass valve 35 with an adjustable opening degree, also using electromagnetic force, is installed in the bypass channel PA23.

[0017] The cooling medium supply / discharge unit 4 includes a cooling device 41, a cooling medium supply channel PA31 connecting the cooling device 41 and the fuel cell stack 1 to a cooling medium inlet, and a cooling medium discharge channel PA32 connecting the cooling device 41 and the fuel cell stack 1 to a cooling medium outlet. The cooling device 41 includes an electric pump 42 installed in the cooling medium supply channel PA31 that pressurizes the cooling medium to the fuel cell stack 1. The cooling device 41 is included in a cooling system 40. The cooling system 40 includes a radiator 43 that cools the cooling medium by heat exchange with external air, and an electric fan 44 that delivers cooling air to the radiator 43. Sometimes, the entire cooling system including the radiator 43 and the electric fan 44 is referred to as a cooling device.

[0018] A bypass channel PA33, which bypasses the radiator 43, connects the cooling medium supply channel PA31 and the cooling medium discharge channel PA32. A thermal valve 45 is installed at the connection between the cooling medium supply channel PA31 and the bypass channel PA33. When the thermal valve 45 opens the cooling medium supply channel PA31 towards the radiator, the flow through the bypass channel PA33 is cut off. Thus, as... Figure 1As shown by the solid arrow, the cooling medium flows through the cooling medium discharge channel PA32 to the radiator 43, where it is cooled. When the radiator side of the cooling medium supply channel PA31 is closed by the thermal valve 45, the flow from the radiator 43 to the thermal valve 45 is cut off. Thus, as... Figure 1 As shown by the dashed arrow, the cooling medium flowing through the cooling medium discharge channel PA32 bypasses the radiator 43 and flows in the bypass channel PA33, thus preventing the cooling of the cooling medium.

[0019] The thermal valve 45 opens and closes according to the temperature of the cooling medium. That is, the thermal valve 45 is open when the temperature of the cooling medium is above a specified temperature, and closed when the temperature is below the specified temperature. The thermal valve 45 is configured to have an adjustable opening, allowing a portion of the cooling medium (a specified proportion of cooling medium) to flow around the radiator 43. A temperature sensor 51 is connected to the cooling medium supply channel PA31, which detects the temperature of the cooling medium at the inlet of the fuel cell stack 1 (inlet coolant temperature). A temperature sensor 52 is connected to the cooling medium discharge channel PA32, which detects the temperature of the cooling medium at the outlet of the fuel cell stack 1 (outlet coolant temperature). Hereinafter, the outlet coolant temperature will sometimes be referred to simply as the coolant temperature. The coolant temperature is related to the temperature of the fuel cell stack 1.

[0020] The electricity generated by the fuel cell stack 1 is supplied to the drive motor 55 via a power control unit (PCU) 50. A chargeable and dischargeable energy storage device, namely a battery (BAT) 53, is connected to the power control unit 50. The power control unit 50 includes a DC-DC converter that boosts or bucks the electricity supplied from the fuel cell stack 1 and the battery 53, and an inverter that converts direct current into three-phase alternating current and supplies it to the drive motor 55. The fuel cell system of this embodiment has multiple fuel cell stacks 1 (unit system 101), therefore, electricity from multiple fuel cell stacks 1 is supplied to the power control unit 50. The power control unit 50, battery 53, and drive motor 55 are not provided for each unit system 101, but rather for the entire fuel cell system.

[0021] Figure 2 This is a block diagram that schematically illustrates the control structure of a fuel cell system 100 according to an embodiment of the present invention. Figure 2As shown, the fuel cell system 100 includes a host controller (host ECU) 61, a main controller (main ECU) 62, and multiple individual controllers (individual ECUs) 63. Each controller 61 to 63 is configured as a computer having a CPU (central processing unit), ROM (read-only memory), RAM (random access memory), and peripheral circuitry. Sometimes, the host controller 61, the main controller 62, and the multiple individual controllers 63 are collectively referred to as controller 102. Controller 102 (e.g., the main controller 62) also functions as a battery controller for controlling the charging and discharging of the battery 53.

[0022] The host controller 61 and the main controller 62, as well as the main controller 62 and the individual controllers 63, are interconnected via communication protocols such as CAN (Controller Area Network). Multiple individual controllers 63 are configured with the same number as multiple (e.g., four) unit systems 101 (FC_A, FC_B, FC_C, FC_D) in a corresponding relationship. The individual controllers 63 control the power generation and cooling device 41 of the unit systems 101. Figure 2 The example shown is a fuel cell system 100 with four individual controllers 63, but the number of individual controllers 63 can be more than four.

[0023] The fuel cell system 100 of this embodiment is mounted in a vehicle. The host controller 61 calculates the required power generation of the vehicle (required power generation), i.e., the overall required power generation for the fuel cell system 100. More specifically, the host controller 61 calculates the target drive torque of the drive motor 55 based on a signal from an accelerator pedal opening sensor that detects the accelerator pedal opening, and calculates the required power generation needed for the drive motor 55 to generate the target drive torque. Alternatively, the host controller 61 calculates the required power generation based on a signal from a battery sensor that detects the state of charge (SOC) of the battery 53, such that the remaining capacity of the battery 53 is a predetermined value. The remaining capacity (SOC) of the battery 53 can also be calculated by the battery ECU (not shown), and the battery ECU can also send the SOC to the host controller 61.

[0024] The main controller 62 determines the power generation of each unit system (individual power generation requirement) based on the required power generation. More specifically, the main controller 62 determines whether output limitation of unit system 101 is required based on signals from individual controllers 63, and determines the individual power generation requirement based on the determination result. Whether output limitation is required can also be determined separately by each individual controller 63. In this case, the main controller 62 determines the power generation of each unit system (individual power generation requirement) based on the determination of each individual controller 63 regarding whether output limitation of unit system 101 is required. When, for example, the stack outlet temperature of a single unit system 101 among the four unit systems 101 exceeds a specified temperature, the main controller 62 limits the output of unit system 101 to reduce the stack outlet temperature. At this time, the discharge of battery 53 is increased by an amount corresponding to the output limitation to maintain the power supplied to motor 55.

[0025] Figure 3 This is a diagram showing the structure of the cooling system of the entire fuel cell system, specifically the structure of cooling system 40. (See diagram 40 for details.) Figure 3 As shown, multiple unit systems 101 have cooling devices 41 (electric pumps 42, thermal valves 45) arranged side by side and connected to a confluence section 46 via flow channels PA34. When the thermal valve 45 is open, the cooling medium of the fuel cell stack 1 flows through the flow channels PA34 to the confluence section 46 due to the drive of the electric pump 42. The cooling medium confluent in the confluence section 46 flows into the radiator 43 via the flow channels PA35 and the inlet 43a, where it is cooled.

[0026] The cooling medium passing through radiator 43 flows out from outlet 43b and through flow channel PA36 to branch section 47. At branch section 47, the cooling medium is evenly distributed into multiple flow channels PA37, and the distributed cooling medium flows through flow channels PA37 to the cooling device 41 of each unit system 101. When the thermal valve 45 is closed, the flow of cooling medium from flow channel PA37 is stopped, and the cooling medium discharged from electric pump 42 does not flow to radiator 43, but instead circulates in fuel cell stack 1 through thermal valve 45.

[0027] Thus, in this embodiment, the cooling devices 41 of multiple unit systems 101 (FC_A, FC_B, FC_C, FC_D) are arranged side by side, and the multiple cooling devices 41 are connected to a single heat sink 43 via a confluence section 46 and a branch section 47, constituting a cooling system 40. Therefore, compared to the case where a heat sink 43 and an electric fan 44 are provided in each unit system, the number of parts in the cooling system 40 can be reduced. Figure 3 In the diagram, 1A to 1D represent the fuel cell stacks 1 contained in the unit systems FC_A, FC_B, FC_C, and FC_D, respectively.

[0028] The lower the coolant temperature and the higher the flow rate of the cooling medium, the greater the cooling capacity of the cooling system 40 for the fuel cell stack 1. Regarding the coolant temperature, increasing the speed of the electric fan 44 can lower it. Regarding the flow rate of the cooling medium, increasing the speed of the electric pump 42 can increase it.

[0029] Regarding the fuel cell system 100 with such a cooling system 40, the coolant temperature of each unit system 101 may sometimes deviate. For example, sometimes the coolant temperature of a single unit system 101 (FC_A) (the coolant temperature of the fuel cell stack 1A) may exceed a predetermined temperature. In this case, to lower the coolant temperature of the fuel cell stack 1A, increasing the cooling capacity of the cooling system 40 results in increased power consumption, making it difficult to effectively cool the entire fuel cell system. Therefore, in this embodiment, a cooling control device is configured as follows to suppress power consumption and effectively cool the entire fuel cell system.

[0030] Figure 4 This is a block diagram schematically illustrating the structure of the cooling control device 70 included in the fuel cell system 100 of this embodiment. The fuel cell system 100 includes four unit systems 101 ( Figure 2 However, for ease of explanation, the structure of the cooling control device 70 will be described below as having a pair of unit systems 101 (FC_A, FC_B) in the fuel cell system 100.

[0031] like Figure 4 As shown, the cooling control device 70 has a controller 102 ( Figure 2 Each of the pair of unit systems 101 (FC_A, FC_B) connected to the controller 102 includes a temperature sensor 52 (52A, 52B), a cooling device 41 (41A, 41B), a gas supply / exhaust unit 103 (103A, 103B), an input unit 71, an electric fan 44, and a battery 53.

[0032] Gas supply / discharge unit 103 is Figure 1 The term "gas supply / discharge unit 2" and "oxidizer gas supply / discharge unit 3" are collectively referred to as such. The gas supply / discharge unit 103 includes an injector 23, sealing valves 22, 33, and 34, a gas pump 31, and a bypass valve 35. By controlling the gas supply / discharge unit 103A, the output of unit system 101 (FC_A) can be controlled. By controlling the gas supply / discharge unit 103B, the output of unit system 101 (FC_B) can be controlled. The input unit 71 is a command unit for indicating power requirements, including, for example, an accelerator pedal opening sensor that detects the opening degree of the accelerator pedal.

[0033] The controller 102 functions as the cooling control unit 102A, the power control unit 102B, and the battery control unit 102C by executing programs pre-stored in the memory.

[0034] The cooling control unit 102A outputs control signals to the cooling device 41 and the electric fan 44 to control the operation of the cooling system 40. For example, when the coolant temperatures Ta and Tb detected by temperature sensors 52A and 52B are both lower than the specified temperature T1, the cooling control unit 102A controls the cooling device 41A (electric pump 42) of unit system FC_A to flow at a coolant flow rate Qa corresponding to the coolant temperature Ta, and controls the cooling device 41B of unit system FC_B to flow at a coolant flow rate Qb corresponding to the coolant temperature Tb. That is, the cooling control unit 102A controls the cooling devices 41A and 41B respectively according to the coolant temperatures Ta and Tb (conventional control).

[0035] When the coolant temperature Ta of only unit system FC_A reaches a predetermined temperature T1 or higher, the cooling control unit 102A sets the coolant flow rate Qb of unit system FC_B with a lower coolant temperature to a target flow rate Qα, and controls the cooling device 41A of unit system FC_A (coolant regulation control) in such a way that the coolant flow rate Qa reaches the target flow rate Qα. In this case, instead of lowering the coolant temperature Ta by increasing the cooling capacity, the coolant temperature Ta is lowered by suppressing the power generation of fuel cell stack 1 (output limitation), as described later. As a result, the power consumption of cooling system 40 can be suppressed without increasing the speed of electric pump 42 and electric fan 44. Afterwards, when the coolant temperature Ta falls below the predetermined temperature T2 (< T1), the cooling control unit 102A ends the coolant regulation control and resumes normal control.

[0036] Until the aforementioned coolant regulation control begins, the power control unit 102B outputs a control signal to the gas supply / discharge unit 103 in a manner that generates electricity corresponding to the power required by the input unit 71, controlling the output of the fuel cell stack 1 (conventional control). When the coolant regulation control begins (Ta≥T1), the output (power generation) of the unit system FC_A and FC_B is gradually reduced to a predetermined value. That is, the power control unit 102B limits the output of the unit system FC_A and FC_B (output limit control). As a result, the coolant temperature Ta can be reduced. Afterwards, when the coolant temperature Ta becomes below the predetermined temperature T2, the power control unit 102B ends the output limit and resumes conventional control.

[0037] The battery control unit 102C controls the charging and discharging of the battery 53. Under normal control conditions where the output limit of the unit system 101 is released, the power supplied to the drive motor 55 is provided by the generation of the unit system 101 and the discharging of the battery 53. Thus, the unit system 101 and the battery 53 can output the required power, and the drive motor 55 can generate the target torque.

[0038] Figure 5 It is by Figure 4 The flowchart illustrates an example of a process executed by the controller (CPU) 102 according to a pre-stored program. The process shown in the flowchart begins, for example, upon the activation of the vehicle's power switch. Figure 5 As shown, firstly, in S1 (S: processing step), the controller 102 reads signals from temperature sensors 52A and 52B and input unit 71. Next, in S2, the controller 102 determines whether either the coolant temperature Ta or Tb of the multiple unit systems 101 is above a predetermined temperature T1. The predetermined temperature T1 is the temperature at which the temperature of the cooling medium needs to be reduced. For example, when the temperature of the cooling medium opened by the thermal valve 45 is set to the predetermined coolant temperature, the predetermined temperature T1 is set to a temperature above the predetermined coolant temperature. Therefore, when S2 is affirmative (S2: yes), the cooling medium has already been supplied to the radiator 43.

[0039] When S2 is affirmative (S2: Yes), the process proceeds to S3; when it is negative (S2: No), it returns to S1. In S3, controller 102 calculates the target flow rate Qα for unit systems 101 (FC_A, FC_B). The target flow rate Qα for unit system FC_A is the same as the target flow rate Qα for unit system FC_B. The relationship between coolant temperature and target flow rate Qα is pre-stored in the memory of controller 102. This relationship is, for example, that the higher the coolant temperature, the greater the target flow rate Qα. In S2, controller 102 calculates the target flow rate Qα based on this pre-determined relationship and the lowest coolant temperature among multiple coolant temperatures Ta and Tb. It is assumed that coolant temperatures Ta and Tb have a relationship of Ta ≥ Tb. In this case, for example, when coolant temperature Ta is above a specified temperature T1 and coolant temperature Tb is below a specified temperature T1, controller 102 calculates the target flow rate Qα based on coolant temperature Tb.

[0040] Next, in S4, the controller 102 controls the cooling device 41 (electric pump 42) of each unit system 101 with the coolant flow rates Qa and Qb of each unit system 101 as the target flow rate Qα. It also controls the speed of the electric fan 44. That is, the controller 102 performs the aforementioned coolant regulation control. At this time, the thermal valve 45 of each unit system 101 remains open. Thus, the controller 102 calculates the target flow rate Qα based on the lowest coolant temperature Tb among the cooling temperatures Ta and Tb, thereby suppressing the target flow rate Qα and reducing power consumption.

[0041] Next, in S5, controller 102 outputs control signals to gas supply / discharge units 103A and 103B, gradually reducing the outputs of unit systems FC_A and FC_B to predetermined values. That is, controller 102 performs output limiting control on unit systems FC_A and FC_B. The output of not only the high-temperature unit system FC_A but also the low-temperature unit system FC_B is limited because, following the rise in coolant temperature Ta of unit system FC_A, it is predicted that the coolant temperature Tb of unit system FC_B will rise. In other words, the rise in coolant temperature Ta can be attributed to the high ambient temperature, such as external air temperature; in this case, the coolant temperature Tb can also be assumed to rise. In S5, controller 102 limits the outputs of all unit systems FC_A and FC_B, thus effectively reducing the coolant temperatures Ta and Tb.

[0042] Furthermore, in S5, the controller 102 controls the discharge operation of the battery 53 in such a way that the power conducted by the battery 53 is equivalent to the power that limits the output of the unit system 101. As a result, the entire fuel cell system can output the required power corresponding to the input of the input unit 71. Consequently, the drive torque of the drive motor 55 can be maintained at the target drive torque corresponding to the operation of the accelerator pedal.

[0043] Next, in S6, the controller 102 determines whether either the coolant temperature Ta or Tb detected by the temperature sensors 52A and 52B is lower than the specified temperature T2. The specified temperature T2 can be lower than the specified temperature T1; for example, the specified temperature T2 is set to a value lower than the specified temperature T1. S6 is repeated until S6 is affirmative (S6: Yes).

[0044] When S6 is affirmative (S6: Yes), proceed to S7. In S7, controller 102 terminates the coolant regulation control of cooling system 40 and enters normal control. Furthermore, the output limit of unit system 101 is released, and normal control is entered. This concludes the processing of cooling control device 70.

[0045] exist Figure 5The document describes the handling when unit system 101 has two components (FC_A and FC_B), but... Figure 2 As shown, when unit system 101 has 4 units (FC_A, FC_B, FC_C, FC_D), it also executes the same... Figure 5 The same process applies. Assume that among the four unit systems 101, for example, unit system FC_A has the highest coolant temperature Ta, and unit system FC_B has the lowest coolant temperature Tb. In this case, the target flow rates Qα calculated in S3 for unit systems FC_C and FC_D are the same as the target flow rate Qα for unit system FC_B. Furthermore, the output restriction levels for unit systems FC_C and FC_D in S5 are also the same as those for unit system FC_B; all unit systems 101 (FC_A, FC_B, FC_C, FC_D) are restricted in the same way. That is, the output of all unit systems 101 gradually decreases to the specified value. Then, when the coolant temperature of fuel cell stacks 1A to 1D falls below the specified temperature T2, in S7, the coolant regulation control of all unit systems 101 (FC_A, FC_B, FC_C, FC_D) ends, and the output restriction is also lifted.

[0046] The following effects can be achieved by adopting this implementation method.

[0047] (1) The fuel cell system 100 includes: a plurality of fuel cell stacks 1 (1A to 1D); a temperature sensor 52 that detects the temperature of each of the plurality of fuel cell stacks 1; a cooling system 40 having a cooling device 41 (electric pump 42, etc.) that supplies a cooling medium to each of the plurality of fuel cell stacks 1; a battery 53; and a controller 102 that controls the output of the cooling system 40, the plurality of fuel cell stacks 1, and the charging and discharging of the battery 53 based on the temperature detected by the temperature sensor 52. Figure 1 , Figure 2 , Figure 4 Multiple fuel cell stacks 1 include fuel cell stack 1A of unit system FC_A and fuel cell stack 1B of unit system FC_B. Figure 3 Assume that the temperature (coolant temperature) Tb of fuel cell stack 1B is lower than the temperature (coolant temperature) Ta of fuel cell stack 1A. In this case, when the temperature Ta of fuel cell stack 1A detected by temperature sensor 52A becomes above a predetermined temperature T1, controller 102 controls cooling system 40 to cool fuel cell stack 1A and fuel cell stack 1B with cooling capacity corresponding to the temperature Tb of fuel cell stack 1B, and performs output limiting on fuel cell stacks 1A and 1B, thereby discharging the power corresponding to the output limiting on fuel cell stacks 1A and 1B from battery 53.

[0048] With this structure, when the coolant temperature Ta reaches or exceeds a predetermined temperature T1, there is no need to increase the cooling capacity of the unit system FC_A (e.g., by increasing the rotational speed of the electric pump 42), thus suppressing the power consumption of the fuel cell system 100. Furthermore, by cooling the fuel cell stacks 1A and 1B with a cooling capacity corresponding to the coolant temperature Tb of the unit system FC_B on the low-temperature side, the target flow rate Qα of the coolant in the unit system FC_A on the high-temperature side decreases. As a result, the rotational speed of the electric pump 42 of the unit system FC_A decreases, thereby reducing the power consumption of the unit system FC_A.

[0049] (2) The above-mentioned fuel cell stack 1A is the fuel cell stack with the highest temperature among the multiple fuel cell stacks 1A to 1D. Therefore, when the temperature (coolant temperature) Ta of at least one of the multiple fuel cell stacks 1A to 1D becomes above the specified temperature T1, the temperature of fuel cell stack 1A is controlled (coolant regulation control, output limit control) to start decreasing, so that the temperature of the multiple fuel cell stacks 1A to 1D can be reliably suppressed below the specified temperature T1.

[0050] (3) When the temperature (coolant temperature) Ta of fuel cell stack 1A detected by temperature sensor 52A becomes above a specified temperature T1, controller 102 controls cooling system 40 to cool all multiple fuel cell stacks 1A to 1D using cooling capacity corresponding to the temperature (coolant temperature) Tb of fuel cell stack 1B. Figure 5 Therefore, it is also possible to suppress the power consumption of unit systems 101 (e.g., unit systems FC_C, FC_D) whose coolant temperature is not above the specified temperature T1.

[0051] (4) Fuel cell stack 1B is the lowest temperature fuel cell stack among the multiple fuel cell stacks 1A to 1D. As a result, the target flow rate of coolant Qα can be suppressed to a minimum, which can significantly reduce power consumption.

[0052] (5) When the temperature (coolant temperature) Ta of the high-temperature fuel cell stack 1A detected by temperature sensor 52A becomes above the specified temperature T1, controller 102 performs output limiting on all multiple fuel cell stacks 1A to 1D. Figure 5 This allows for the effective cooling of multiple fuel cell stacks 1A to 1D.

[0053] (6) When the controller 102 applies output limits to all multiple fuel cell stacks 1A to 1D, if the temperature (coolant temperature) Ta of fuel cell stack 1A detected by temperature sensor 52A is lower than the specified temperature T2 which is lower than the specified temperature T1, the output limit on all multiple fuel cell stacks 1A to 1D is lifted. Figure 5Therefore, the conversion to conventional control is carried out collectively, rather than on a unit-by-unit basis, making the process easier.

[0054] (7) The cooling system 40 also includes a radiator 43 for cooling the cooling medium, flow channels PA36 and PA37 for guiding the cooling medium passing through the radiator 43 to the multiple fuel cell stacks 1A to 1D via branch sections 47, and flow channels PA34 and PA35 for guiding the cooling medium passing through the multiple fuel cell stacks 1A to 1D to the radiator 43 via confluence sections 46. Thus, multiple cooling devices 41 share the radiator 43, thereby enabling the cooling system 40 to be constructed at a low cost.

[0055] The above embodiments can be modified in various ways. Several modifications will be described below. In the above embodiments, a temperature sensor 52 that detects the coolant outlet temperature constitutes a temperature detection unit for detecting the temperature of the fuel cell. However, other parts related to the temperature of the fuel cell (fuel cell stack 1) can also be detected, and the configuration of the temperature detection unit is not limited to the above description. In the above embodiments, an electric pump 42 that supplies cooling medium to each of the plurality of fuel cell stacks 1 is configured as a cooling medium supply unit. However, the configuration of the cooling device, i.e., the cooling system 40, which has a cooling medium supply unit, is not limited to the above description.

[0056] In the above embodiment, a battery 53 for storing electricity generated in the fuel cell is used as the energy storage device, but a capacitor can also be used as the energy storage device. In the above embodiment, a fuel cell system 100 having four unit systems 101 is exemplified, but the number of unit systems 101 is not limited to those described above, as long as each unit system FC_A contains a fuel cell stack 1A (first fuel cell) and each unit system FC_B contains a fuel cell stack 1B (second fuel cell). In this case, a fuel cell that is colder than the first fuel cell can be used as the second fuel cell.

[0057] In the above embodiments, the fuel cell with the highest temperature among the multiple fuel cells (fuel cell stacks 1A to 1D) (fuel cell stack 1A) is designated as the first fuel cell, but the first fuel cell may not necessarily be the highest temperature. In the above embodiments, the fuel cell with the lowest temperature among the multiple fuel cells (fuel cell stacks 1A to 1D) (fuel cell stack 1B) is designated as the second fuel cell, but the second fuel cell may not necessarily be the lowest temperature. In the above embodiments, when the temperature (coolant temperature) Ta of fuel cell stack 1A becomes a predetermined temperature T1 or higher, all fuel cells are cooled using a cooling capacity corresponding to the temperature (coolant temperature) Tb of fuel cell stack 1B, but it is also possible to cool only a portion of the fuel cells.

[0058] In the above embodiment, when the temperature (coolant temperature) Ta of the fuel cell stack 1A reaches or exceeds a predetermined temperature T1, the controller 102, acting as the control unit, performs output limiting on all fuel cells (fuel cell stacks 1A to 1D), but may also perform output limiting on a portion of the fuel cells. In the above embodiment, when the coolant temperature reaches or exceeds a predetermined temperature T1 (first predetermined temperature), output limiting on all fuel cells begins; when the coolant temperature falls below a predetermined temperature T2 (second predetermined temperature), output limiting on all fuel cells is lifted, but may also lift output limiting on a portion of the fuel cells.

[0059] In the above embodiment, the cooling system 40 has a single radiator 43 (heat exchanger) for each of the multiple unit systems 101, and the radiator 43 and the multiple unit systems 101 are connected via a branch 47 and flow channels PA36, PA37 (supply flow channels), a confluence 46 and flow channels PA34, PA35 (return flow channels), but the structure of the cooling system is not limited to the above description.

[0060] In the above embodiments, an example of applying the fuel cell system 100 to a fuel cell vehicle was described. However, the fuel cell system of the present invention can be applied to various mobile bodies having multiple fuel cells, and can also be applied to devices other than mobile bodies.

[0061] It is possible to combine the above-described embodiments with one or more variations, and it is also possible to combine the variations with each other.

[0062] Using this invention, it is possible to suppress the power consumption of the fuel cell system and cool the fuel cell.

[0063] The present invention has been described above in conjunction with preferred embodiments, but those skilled in the art should understand that various modifications and changes can be made without departing from the scope of the claims.

Claims

1. A fuel cell system, characterized in that, have: Multiple fuel cells (1); Temperature detection unit (52) detects the temperature of each of the plurality of fuel cells (1); Cooling system (40) having a cooling medium supply unit (42) that supplies cooling medium to each of the plurality of fuel cells (1). Energy storage device (53); and The control unit (102) controls the output of the cooling system (40), the plurality of fuel cells (1), and the charging and discharging of the energy storage device (53) based on the temperature detected by the temperature detection unit (52). When the temperature (Ta) of the first fuel cell (1A) detected by the temperature detection unit (52) becomes above a predetermined temperature (T1), the control unit (102) controls the cooling system (40) to cool the first fuel cell (1A) and the second fuel cell (1B) with a cooling capacity corresponding to the temperature (Tb) of the second fuel cell (1B) which is lower than the first fuel cell (1A), and performs an output limit on the first fuel cell (1A), thereby discharging the power corresponding to the output limit on the first fuel cell (1A) from the energy storage device (53).

2. The fuel cell system according to claim 1, characterized in that, The first fuel cell (1A) is the fuel cell with the highest temperature among the plurality of fuel cells (1).

3. The fuel cell system according to claim 2, characterized in that, When the temperature (Ta) of the first fuel cell (1A) detected by the temperature detection unit (52) reaches or exceeds the specified temperature (T1), the control unit (102) controls the cooling system (40) to cool all the plurality of fuel cells (1) with a cooling capacity corresponding to the temperature (Tb) of the second fuel cell (1B).

4. The fuel cell system according to claim 1, characterized in that, The second fuel cell (1B) is the lowest temperature fuel cell among the plurality of fuel cells (1).

5. The fuel cell system according to claim 1, characterized in that, When the temperature of the first fuel cell (1A) detected by the temperature detection unit (52) reaches or exceeds the specified temperature (T1), the control unit (102) performs output limiting on all of the plurality of fuel cells (1).

6. The fuel cell system according to claim 5, characterized in that, The specified temperature (T1) is the first specified temperature. When the control unit (102) performs output restriction on all of the plurality of fuel cells (1), if the temperature (Ta) of the first fuel cell (1A) detected by the temperature detection unit (52) is lower than the second specified temperature (T2) which is lower than the first specified temperature, the output restriction on all of the plurality of fuel cells (1) is lifted.

7. The fuel cell system according to any one of claims 1 to 6, characterized in that, The cooling system (40) further includes: a heat exchanger (43) for cooling the cooling medium, supply channels (PA36, PA37) for guiding the cooling medium that has passed through the heat exchanger (43) to the plurality of fuel cells (1) via a branch (47), and a return channel (PA34, PA35) for guiding the cooling medium that has passed through the plurality of fuel cells (1) to the heat exchanger (43) via a confluence (46).

8. The fuel cell system according to claim 7, characterized in that, The cooling medium supply unit (42) is an electric pump. The cooling system (40) also has a thermistor (45) that switches according to the temperature of the cooling medium, allowing or disallowing the flow of the cooling medium that has passed through each of the plurality of fuel cells (1) to the heat exchanger (43).

9. The fuel cell system according to claim 8, characterized in that, The thermal valve (45) is configured to allow the flow of the cooling medium to the heat exchanger (43) when the temperature of the cooling medium is above the specified coolant temperature, and to prohibit the flow of the cooling medium to the heat exchanger (53) when the temperature of the cooling medium is below the specified coolant temperature. The specified temperature (T1) is above the specified coolant temperature.

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