Fuel battery system

Abstract

Provided is a fuel battery system comprising: a fuel battery that is obtained by laminating a plurality of fuel battery cells; a fuel supply path that is for supplying fuel to the fuel battery; an oxidizing agent supply path that is for supplying an oxidizing agent to the fuel battery; and a porous body that is disposed between adjacent fuel battery cells and that constitutes a flow path through which a cooling medium flows, said fuel battery system further comprising a cooling medium circulation flow path that is for circulating the cooling medium through the porous body, wherein the cooling medium circulation flow path is configured such that the cooling medium can exchange heat with the fuel and / or the oxidizing agent, and is configured from a closed loop through which only the cooling medium is circulated.

Description

fuel cell system

[0001] The technology disclosed in this specification relates to a fuel cell system equipped with a fuel cell that generates electricity by receiving a supply of fuel and an oxidant.

[0002] A known example of this type of technology is a "fuel cell stack system" described in Patent Document 1 below. This system includes a fuel cell in which multiple fuel cell units are stacked, an anode gas flow path (fuel supply passage) that supplies fuel to the fuel cell, a cathode gas flow path (oxidant supply passage) that supplies oxidant to the fuel cell, and a porous body disposed between adjacent fuel cell units and forming a flow path through which a cooling medium flows. In this system, the cooling medium vaporized after flowing through the porous body is used to humidify the oxidant.

[0003] Japanese Patent Application Laid-Open No. 2008-305627

[0004] In the system described in Patent Document 1, the fuel cell can be cooled by flowing a cooling medium through the porous body between the fuel cell cells. However, the cooling medium that flows through the porous body is also used to humidify the oxidant and is consumed. As a result, it becomes difficult to obtain sufficient cooling performance when the cooling medium is consumed, and it is necessary to periodically replenish the cooling medium. Furthermore, the degree of cooling (cooling amount) of the fuel cell is determined by the flow rate of the fuel used in the reaction. Therefore, simply flowing the cooling medium through the porous body poses a problem in terms of controllability of the cooling amount.

[0005] This disclosed technology has been made in consideration of the above circumstances, and its purpose is to provide a fuel cell system that enables the cooling medium to be used efficiently to cool the fuel cell while reducing consumption of the cooling medium.

[0006] (1) In order to achieve the above object, one aspect of the present disclosure is a fuel cell system including a fuel cell formed by stacking a plurality of fuel cell cells, a fuel supply passage for supplying fuel to the fuel cell, an oxidant supply passage for supplying an oxidant to the fuel cell, and a porous body disposed between adjacent fuel cell cells and constituting a flow path through which a cooling medium flows, further including a cooling medium circulation flow path for circulating the cooling medium in the porous body, the cooling medium circulation flow path being configured so that the cooling medium can exchange heat with at least one of the fuel and the oxidant, and being configured as a closed loop through which only the cooling medium circulates.

[0007] According to this aspect, the cooling medium is circulated through the porous body arranged between the fuel cell cells by the cooling medium circulation flow path, thereby cooling each fuel cell cell and thus the entire fuel cell. Here, the cooling medium is drawn up into the porous body by its capillary force. Furthermore, the cooling medium is vaporized in the porous body upon receiving heat from the fuel cell cells, thereby removing heat from the fuel cell cells and cooling them. Furthermore, in the cooling medium circulation flow path, the cooling medium is cooled by heat exchange with at least one of the fuel and the oxidant, and is returned to the fuel cell. Furthermore, since the cooling medium circulation flow path is configured as a closed loop in which only the cooling medium circulates, the cooling medium is not released to the outside.

[0008] The technology described in (2) is the same as the above-mentioned (1), except that it is provided with a heat exchanger arranged in the cooling medium circulation flow path, in which the cooling medium is configured to be able to exchange heat with the fuel, and a first fan that blows air toward the heat exchanger to cool the heat exchanger.

[0009] According to this aspect, in the cooling medium circulation passage, the cooling medium is cooled by heat exchange with the fuel by the heat exchanger. Furthermore, since the heat exchanger is cooled by the air blown by the first fan, cooling of the cooling medium in the heat exchanger is promoted.

[0010] The technology described in (3) is the same as the above (2), except that it includes a temperature sensor for measuring the temperature of the fuel cell and a first control unit for controlling the first fan, and the first control unit controls the first fan so that the airflow volume corresponds to the measurement value of the temperature sensor.

[0011] According to this aspect, the first control unit controls the first fan to send air at a volume corresponding to the temperature of the fuel cell measured by the temperature sensor, thereby adjusting the amount of cooling of the fuel cell according to the temperature of the fuel cell.

[0012] The technology described in (4) is based on the above-described aspect (1), and is further provided with a heat exchanger that is arranged in the cooling medium circulation flow path and that is configured so that the cooling medium can exchange heat with the fuel, an oxidant bypass passage that passes the oxidant from the oxidant supply passage through the heat exchanger, bypassing the fuel cell, and returning the oxidant to the oxidant supply passage, and a valve device that opens and closes the connection between the oxidant supply passage and the oxidant bypass passage, and that opens and closes the oxidant bypass passage with a variable opening.

[0013] According to this aspect, in the coolant circulation passage, the coolant is cooled by heat exchange with the fuel in the heat exchanger. Furthermore, by variably opening and closing the valve device, the oxidant that has bypassed the fuel cell passes through the heat exchanger via the oxidant bypass passage and returns to the oxidant supply passage. This promotes cooling of the coolant in the heat exchanger.

[0014] The technology described in (5) is the same as the above (4), but includes a temperature sensor for measuring the temperature of the fuel cell and a second control unit for controlling the valve device, and the second control unit controls the valve device so that the oxidant flowing through the oxidant bypass passage has a flow rate that corresponds to the measurement value of the temperature sensor.

[0015] According to this aspect, the second control unit controls the valve device so that the flow rate of the oxidant flowing through the oxidant bypass passage corresponds to the temperature of the fuel cell measured by the temperature sensor, and therefore the amount of cooling of the fuel cell is adjusted according to the temperature of the fuel cell.

[0016] The technology described in (6) is based on the above-mentioned (1) aspect, and is further provided with a heat exchanger that is arranged in the cooling medium circulation flow path and that is configured so that the cooling medium can exchange heat with the fuel, and a second fan that is arranged in the cooling medium circulation flow path between the outlet side of the porous body and the heat exchanger and that imparts a flow to the cooling medium.

[0017] According to this aspect, in the cooling medium circulation flow path, the cooling medium is cooled by heat exchange with the fuel by the heat exchanger. Also, in the cooling medium circulation flow path from the outlet side of the porous body to the heat exchanger, a flow is imparted to the cooling medium by the second fan, thereby accelerating the cooling of the cooling medium in the heat exchanger.

[0018] The technology described in (7) is the same as the above (6), but includes a temperature sensor for measuring the temperature of the fuel cell and a third control unit for controlling the second fan, and the third control unit controls the second fan so that the flow of cooling medium applied by the second fan has a flow rate corresponding to the measurement value of the temperature sensor.

[0019] According to this aspect, the third control unit controls the second fan so that the flow rate of the cooling medium applied by the second fan corresponds to the temperature of the fuel cell measured by the temperature sensor, and therefore the amount of cooling of the fuel cell is adjusted according to the temperature of the fuel cell.

[0020] According to the technology described in (1), the cooling medium can be efficiently used to cool the fuel cell while suppressing consumption of the cooling medium.

[0021] According to the technique described in (2), the cooling efficiency of the fuel cell by the cooling medium can be improved.

[0022] According to the technique described in (3), it is possible to improve the controllability of the cooling amount of the fuel cell.

[0023] According to the technique described in (4), the cooling efficiency of the fuel cell by the cooling medium can be improved.

[0024] According to the technique described in (5), it is possible to improve the controllability of the cooling amount of the fuel cell.

[0025] According to the technique described in (6), the cooling efficiency of the fuel cell by the cooling medium can be improved.

[0026] According to the technology described in (7), it is possible to improve the controllability of the cooling amount of the fuel cell.

[0027] FIG. 1 is a schematic configuration diagram showing a fuel cell system according to a first embodiment; FIG. 2 is a schematic configuration diagram showing a cooling system according to the first embodiment; FIG. 3 is an image diagram showing a part of the FC stack shown in FIG. 2 according to the first embodiment; FIG. 4 is a schematic configuration diagram showing a fuel cell system according to a second embodiment; FIG. 5 is a schematic configuration diagram showing a fuel cell system according to a third embodiment; and FIG. 6 is a schematic configuration diagram showing a fuel cell system according to a fourth embodiment.

[0028] Hereinafter, an embodiment in which the fuel cell system is embodied as a fuel cell system mounted on an electric vehicle will be described.

[0029] First Embodiment A first embodiment will be described in detail with reference to the drawings.

[0030] [Main Configuration of Fuel Cell System] Figure 1 shows a schematic configuration diagram of a fuel cell system 1 of this embodiment. As shown in Figure 1, the fuel cell system 1 of this embodiment includes an FC stack 11, a hydrogen system 21, an air system 22, and a cooling system 23. Figure 2 shows a schematic diagram of the cooling system 23. Figure 3 shows an image diagram of a portion of the FC stack 11 shown in Figure 2.

[0031] [About the FC stack] The FC stack 11 generates power by receiving a supply of fuel and an oxidant. In this embodiment, the fuel is hydrogen gas, and the oxidant is air. The FC stack 11 generates power by receiving a supply of hydrogen gas from a hydrogen system 21 and a supply of air from an air system 22. The power generated by the FC stack 11 is supplied to a battery and an inverter (not shown). The cooling system 23 uses a cooling medium to cool the FC stack 11. The FC stack 11 corresponds to an example of a "fuel cell" in the disclosed technology.

[0032] As shown in Figures 1 and 2, in this embodiment, the FC stack 11 is configured by stacking a plurality of fuel cell units 13. Between adjacent fuel cell units 13, block-shaped porous bodies 18 are arranged, forming flow paths through which cooling water flows. The porous bodies 18 are substances having numerous fine gaps and pores therein. Examples of the porous bodies 18 include sponges, sponge-like materials, filters, porous ceramics, and porous metals. The porous bodies 18 have properties such as breathability and absorbency, and are used in a variety of fields. The cooling water corresponds to an example of the "cooling medium" in this disclosed technology.

[0033] [Hydrogen System] The hydrogen system 21 is provided on the anode side of the FC stack 11. The hydrogen system 21 includes a hydrogen supply passage 31, a hydrogen discharge passage 32, and a filling passage 33.

[0034] The hydrogen supply passage 31 is a passage for supplying hydrogen gas from a hydrogen tank 41 in which hydrogen gas is stored to the FC stack 11. The hydrogen discharge passage 32 is a passage for discharging hydrogen gas (i.e., hydrogen off-gas) discharged from the FC stack 11.

[0035] The hydrogen supply passage 31 is provided with a hydrogen tank 41, a hydrogen valve 51, a hydrogen pressure reducing valve 52, and an injector 53. The filling passage 33 is a passage for filling the hydrogen tank 41 with hydrogen gas from a filling port .

[0036] The hydrogen valve 51 is a valve that switches between supplying and blocking hydrogen gas from the hydrogen tank 41 to the hydrogen supply passage 31, and is composed of multiple devices including, for example, a solenoid valve. The hydrogen pressure reducing valve 52 is a pressure adjustment valve for reducing the pressure of hydrogen gas, and is composed of, for example, a solenoid valve. The injector 53 is a device that injects hydrogen gas guided from the hydrogen tank 41 downstream, and is composed of, for example, a solenoid valve. The injector 53 is configured to adjust the discharge pressure of the hydrogen gas (hydrogen pressure) by, for example, adjusting the opening of an injection port by moving a needle valve.

[0037] An exhaust drain valve 57 is provided in the hydrogen discharge passage 32. The exhaust drain valve 57 is a valve that switches between discharging and blocking the hydrogen off-gas and moisture from the FC stack 11, and is configured by, for example, a solenoid valve.

[0038] [Air System] The air system 22 is provided on the cathode side of the FC stack 11. The air system 22 includes an air supply passage 61, an air discharge passage 62, and an air compressor 71.

[0039] The air supply passage 61 is a passage for supplying air from outside the fuel cell system 1 to the FC stack 11. The air discharge passage 62 is a passage for discharging air (i.e., air off-gas) discharged from the FC stack 11.

[0040] The air compressor 71 is an electrically operated device that supplies air to the FC stack 11. In this embodiment, no devices such as air valves are provided in the air supply passage 61 between the air compressor 71 and the FC stack 11, and in the air discharge passage 62 downstream of the FC stack 11. In other words, the FC stack 11 in this embodiment is configured so that air is directly supplied from the air compressor 71 and air off-gas is directly discharged from the FC stack 11 to the outside.

[0041] 1 and 2, the cooling system 23 includes a cooling water circulation channel 81 that circulates cooling water through each porous body 18. A heat exchanger 82 and a water tank 83 are provided in the cooling water circulation channel 81. The cooling water circulation channel 81 corresponds to an example of a "cooling medium circulation channel" in the disclosed technology.

[0042] The heat exchanger 82 is disposed on the cooling water circulation flow path 81 downstream of the FC stack 11. In this embodiment, the heat exchanger 82 is configured so that the cooling water flowing through the cooling water circulation flow path 81 can exchange heat with the hydrogen gas flowing through the hydrogen supply passage 31.

[0043] In this embodiment, the heat exchanger 82 is provided with a first fan 88 for blowing air to cool the heat exchanger 82. The first fan 88 is, for example, an electric fan driven by an electric motor.

[0044] The water tank 83 is disposed on the cooling water circulation flow path 81, upstream of the FC stack 11. The water tank 83 is configured to store cooling water that has been heat exchanged (cooled) in the heat exchanger 82 and liquefied (condensed).

[0045] The FC stack 11 is provided with an inlet shroud 85 on the inlet side of the cooling water, and an outlet shroud 86 on the outlet side of the cooling water. The inlet shroud 85 covers the inlet side of the FC stack 11 to allow cooling water to flow into each of the inlet sides of the multiple porous bodies 18. The downstream end of the cooling water circulation channel 81 is connected to an inlet 85a of the inlet shroud 85. The outlet shroud 86 covers the outlet side of the FC stack 11 to collect cooling water (water vapor) flowing out from the outlet sides of the multiple porous bodies 18. The upstream end of the cooling water circulation channel 81 is connected to an outlet 86a of the outlet shroud 86. The cooling water circulation channel 81 is configured as a closed loop in which only cooling water circulates. In other words, the cooling water circulation channel 81 is a closed channel that does not communicate with the outside.

[0046] As shown in Fig. 2, cooling water flows through the central tube 82a of the heat exchanger 82. Hydrogen gas supplied to the FC stack 11 flows around this central tube 82a. Hydrogen gas at about "20°C" flows into the heat exchanger 82. Cooling water at about "60°C" flows into the central tube 82a. The hydrogen gas is heated to about "55°C" in the heat exchanger 82 and supplied to the FC stack 11. The cooling water is cooled from "60°C" to about "52°C" and flows into the water tank 83. The cooling water flowing from the water tank 83 to the FC stack 11 is drawn into the porous body 18 by the capillary force of the porous body 18.

[0047] As shown in FIG. 3 , one fuel cell 13 is composed of an electrode material 14, which serves as a heat source, and a pair of separators 15 that sandwich the electrode material 14. The electrode material 14 is composed of an electrolyte membrane sandwiched between a pair of catalyst layers. Cooling water is drawn into the porous body 18 from its inlet side (lower side in FIG. 3 ) due to the capillary force of the porous body 18. At this time, heat generated by the electrode material 14 is transferred to the porous body 18 via the separators 15, causing the cooling water in the porous body 18 to transform into steam, which evaporates and dissipates heat from the outlet side (upper side in FIG. 3 ). The latent heat of vaporization of the porous body 18 at this time cools the fuel cell 13. The heat transfer coefficient of latent heat of vaporization is significantly higher than that of air-cooling or water-cooling.

[0048] [Regarding Control of the Fuel Cell System] The fuel cell system 1 further includes a control device 10 for controlling the system 1. The control device 10 has, for example, an arithmetic processing unit such as a CPU, a storage unit including a ROM for storing control programs and control data processed by the CPU, and a RAM used as various work areas for control processing, and an input / output interface unit. The control device 10 executes various controls of the fuel cell system 1 in accordance with the control programs stored in the storage unit. In particular, in this embodiment, the control device 10 controls a cooling system 23 for controlling the cooling of the FC stack 11.

[0049] To control the cooling system 23, the FC stack 11 is provided with a temperature sensor 89 for measuring the temperature of the FC stack 11. This temperature sensor 89 is placed in a position relative to the FC stack 11 that allows it to measure the average temperature of the entire FC stack 11. Alternatively, the temperature sensor 89 can be configured such that multiple temperature sensors are placed at multiple locations on the FC stack 11 and the average value of the measurements from the multiple temperature sensors is calculated.

[0050] In this embodiment, the control device 10 is configured to control the first fan 88 so that the airflow rate corresponds to the measurement value of the temperature sensor 89. In other words, when the temperature of the FC stack 11 becomes high, the control device 10 is configured to increase the airflow rate of the first fan 88 to increase the amount of condensation of the cooling water in the heat exchanger 82 in order to lower the temperature of the FC stack 11. In this embodiment, the control device 10 corresponds to an example of the "first control unit" of the disclosed technology.

[0051] [Operation of the fuel cell system] In the fuel cell system 1 configured as described above, hydrogen gas supplied from the hydrogen supply passage 31 to the FC stack 11 is used for power generation in the FC stack 11, and then discharged from the FC stack 11 as hydrogen off-gas via the hydrogen discharge passage 32 to the outside of the fuel cell system 1. In addition, air supplied from the air supply passage 61 to the FC stack 11 is used for power generation in the FC stack 11, and then discharged from the FC stack 11 as air off-gas via the air discharge passage 62 to the outside of the fuel cell system 1.

[0052] The electric power generated by the FC stack 11 is supplied to a battery to charge the battery, or is supplied to an inverter to drive the inverter. The inverter is also supplied with electric power from the battery.

[0053] [Operations and Effects of the Fuel Cell System] According to the configuration of the fuel cell system 1 of this embodiment described above, cooling water is circulated through the porous body 18 arranged between the plurality of fuel cells 13 by the cooling water circulation channel 81, thereby cooling each fuel cell 13 and cooling the entire FC stack 11. Here, the cooling water is drawn up into the porous body 18 by its capillary force. Furthermore, in the porous body 18, the cooling water is vaporized upon receiving heat from the fuel cell 13, thereby removing heat from the fuel cell 13 and cooling it. Furthermore, in the cooling water circulation channel 81, the cooling water is cooled by heat exchange with hydrogen gas and returned to the FC stack 11. Furthermore, because the cooling water circulation channel 81 is configured as a closed loop in which only cooling water circulates, the cooling water is not released to the outside. Therefore, the cooling water can be used efficiently to cool the FC stack 11 while reducing consumption of cooling water.

[0054] In this embodiment, the cooling water is drawn up by the capillary force of the porous body 18, so that the cooling water circulates through the cooling water circulation channel 81 without the use of any power equipment. This allows the FC stack 11 to be cooled without using electrical power. Furthermore, by disposing the porous body 18 between adjacent fuel cell cells 13, the dimensions of the FC stack 11 in the stacking direction can be reduced. For example, in conventional air-cooled systems, an air flow channel with a thickness of about 3 mm was required between adjacent fuel cell cells. However, in this embodiment, the thickness of the porous body 18 can be set to 1 mm, allowing the stacking dimensions of the FC stack 11 to be reduced.

[0055] According to the configuration of this embodiment, in the cooling water circulation flow path 81, the cooling water is cooled by heat exchange with hydrogen gas by the heat exchanger 82. Furthermore, the heat exchanger 82 is cooled by the air blown by the first fan 88, which promotes the cooling (heat exchange) of the cooling water in the heat exchanger 82. This improves the cooling efficiency of the FC stack 11 by the cooling water.

[0056] Furthermore, according to the configuration of this embodiment, the control device 10 controls the first fan 88 so that the airflow rate corresponds to the temperature of the FC stack 11 measured by the temperature sensor 89. Therefore, the amount of cooling of the FC stack 11 is adjusted according to the temperature of the FC stack 11. This improves the controllability of the amount of cooling of the FC stack 11. In other words, the amount of cooling of the FC stack 11 can be controlled according to the temperature of the FC stack 11.

[0057] Furthermore, according to the configuration of this embodiment, the air system 22 includes an air compressor 71, and air is directly supplied to the FC stack 11 from the air compressor 71, and air off-gas is directly discharged from the FC stack 11. Therefore, no air valves or the like other than the air compressor 71 are provided on the supply side of the air system 22, and no air valves or the like are provided on the discharge side of the air system 22. This allows the air system 22 to be simplified, and the cost of the fuel cell system 1 to be reduced.

[0058] Second Embodiment Next, a second embodiment will be described in detail with reference to the drawings. In the following description, components equivalent to those in the first embodiment will be denoted by the same reference numerals, and differences will be mainly described.

[0059] [Cooling System] This embodiment differs from the first embodiment in the configuration of the cooling system 23. Fig. 4 is a schematic diagram showing the fuel cell system 1 of this embodiment. As shown in Fig. 4, in this embodiment, the heat exchanger 82 is not provided with a first fan 88. Instead, a second fan 91 is arranged in the cooling water circulation flow path 81 between the outlet side (outlet shroud 86) of the porous body 18 of the FC stack 11 and the heat exchanger 82, for imparting flow to the cooling water (water vapor) in the flow path 81. The second fan 91 is, for example, an electric fan driven by an electric motor.

[0060] [Regarding Control of the Fuel Cell System] In this embodiment, the control device 10 is configured to control the second fan 91 so that the flow of water vapor imparted by the second fan 91 in the cooling water circulation flow path 81 is at a flow rate corresponding to the measurement value of the temperature sensor 89. In other words, when the temperature of the FC stack 11 becomes high, the control device 10 is configured to increase the flow rate of water vapor caused by the rotation of the second fan 91 in order to lower the temperature of the FC stack 11, and to actively send water vapor generated in the porous body 18 to the heat exchanger 82, thereby promoting the conversion of cooling water into water vapor in the porous body 18. In this embodiment, the control device 10 corresponds to an example of the "third control unit" of the disclosed technology.

[0061] [Operations and Effects of the Fuel Cell System] The configuration of the fuel cell system 1 of this embodiment described above can achieve operations and effects equivalent to those of the first embodiment. In particular, unlike the first embodiment, this embodiment imparts a flow to the coolant (steam) by the second fan 91 in the coolant circulation flow path 81 from the outlet side of the porous body 18 to the heat exchanger 82, thereby accelerating the cooling of the coolant (steam) in the heat exchanger 82. This can improve the cooling efficiency of the FC stack 11 by the coolant.

[0062] According to the configuration of this embodiment, the control device 10 controls the second fan 91 so that the flow of water vapor imparted by the second fan 91 has a flow rate that corresponds to the temperature of the FC stack 11 measured by the temperature sensor 89. Therefore, the amount of cooling of the FC stack 11 is adjusted according to the temperature of the FC stack 11. This improves the controllability of the amount of cooling of the FC stack 11. In other words, the amount of cooling of the FC stack 11 can be controlled according to the temperature of the FC stack 11.

[0063] Third Embodiment Next, a third embodiment will be described in detail with reference to the drawings.

[0064] [Cooling System] This embodiment differs from the previous embodiments in the configuration of the cooling system 23. Fig. 5 is a schematic diagram showing the fuel cell system 1 of this embodiment. As shown in Fig. 5, in this embodiment, a second fan 91 is not provided in the cooling water circulation flow path 81. Instead, a water pump 93 is provided in the cooling water circulation flow path 81 between the inlet side (inlet shroud 85) of the porous body 18 of the FC stack 11 and the water tank 83 to pump the cooling water in the flow path 81. The water pump 93 is, for example, an electric pump driven by an electric motor.

[0065] [Regarding Control of the Fuel Cell System] In this embodiment, the control device 10 is configured to control the water pump 93 so that the flow rate of the cooling water flowing from the cooling water circulation flow path 81 to the FC stack 11 corresponds to the measurement value of the temperature sensor 89. In other words, when the temperature of the FC stack 11 becomes high, the control device 10 increases the amount of water absorbed by the porous body 18, thereby increasing the amount of evaporation of the cooling water in the porous body 18.

[0066] [Operations and Effects of the Fuel Cell System] The configuration of the fuel cell system 1 of this embodiment described above can achieve operations and effects equivalent to those of the previous embodiments. In addition, unlike the previous embodiments, this embodiment uses a water pump 93 to pump cooling water through the cooling water circulation flow path 81 between the inlet side of the porous body 18 and the water tank 83, thereby increasing the amount of water supplied to the porous body 18. This improves the cooling efficiency of the FC stack 11 using cooling water.

[0067] According to the configuration of this embodiment, the control device 10 controls the water pump 93 so that the flow rate of the cooling water pumped by the water pump 93 corresponds to the temperature of the FC stack 11 measured by the temperature sensor 89. Therefore, the amount of cooling of the FC stack 11 is adjusted according to the temperature of the FC stack 11. This improves the controllability of the amount of cooling of the FC stack 11. In other words, the amount of cooling of the FC stack 11 can be controlled according to the temperature of the FC stack 11.

[0068] Fourth Embodiment Next, a fourth embodiment will be described in detail with reference to the drawings.

[0069] [Cooling System] This embodiment differs from the previous embodiments in the configuration of the cooling system 23. Fig. 6 is a schematic diagram showing the configuration of the fuel cell system 1 of this embodiment. As shown in Fig. 6, in this embodiment, the heat exchanger 82 is not provided with a first fan 88, and the cooling water circulation passage 81 is not provided with a second fan 91 or a water pump 93. Instead, the air supply passage 61 is provided with an air bypass passage 64 and a valve device 66.

[0070] The air bypass passage 64 is connected so that air from the air supply passage 61 bypasses the FC stack 11, passes through the heat exchanger 82, and returns to the air supply passage 61. That is, the upstream end of the air bypass passage 64 is connected to the air supply passage 61 immediately downstream of the air compressor 71. The downstream end of the air bypass passage 64 is connected to the air supply passage 61 immediately upstream of the FC stack 11.

[0071] The valve device 66 is configured to open and close the connection between the air supply passage 61 and the air bypass passage 64, and to open and close the air bypass passage 64 with a variable opening degree. The valve device 66 is made up of a first solenoid valve 67, a second solenoid valve 68, and a third solenoid valve 69. The first solenoid valve 67 is disposed at the upstream end of the air bypass passage 64. The third solenoid valve 69 is disposed at the downstream end of the air bypass passage 64. The second solenoid valve 68 is disposed in the air supply passage 61, between a connection position with the upstream end of the air bypass passage 64 and a connection position with the downstream end of the air bypass passage 64. In this embodiment, all of the solenoid valves 67 to 69 are configured to have variable opening degrees.

[0072] [Regarding Control of the Fuel Cell System] In this embodiment, the control device 10 controls the valve device 66 so that the air flowing through the air bypass passage 64 is at a flow rate that corresponds to the measurement value of the temperature sensor 89. In other words, when the temperature of the FC stack 11 becomes high, the control device 10 is configured to control the opening and closing and the degree of opening of the valve device 66 so that more air flows through the air bypass passage 64 in order to lower the temperature of the FC stack 11. In other words, by flowing air through the air bypass passage 64, the air is used for heat exchange in the heat exchanger 82, and more stable heat exchange (cooling) of the coolant is achieved in the heat exchanger 82.

[0073] For example, when heat exchange (cooling) of the cooling water in the heat exchanger 82 is sufficient by heat exchange with hydrogen gas alone, the control device 10 closes the first solenoid valve 67 and the third solenoid valve 69 and opens only the second solenoid valve 68. As a result, air does not flow into the air bypass passage 64. On the other hand, when heat exchange (cooling) of the cooling water in the heat exchanger 82 is sufficient by heat exchange with hydrogen gas alone, or when the amount of cooling of the cooling water in the heat exchanger 82 needs to be controlled, the control device 10 opens all of the solenoid valves 67 to 69 and controls the apertures of each of the solenoid valves 67 to 69. As a result, air flows into the air bypass passage 64 and the flow rate thereof is controlled. In this embodiment, the control device 10 corresponds to an example of a "second control unit" of the disclosed technology.

[0074] [Regarding the Functions and Effects of the Fuel Cell System] The configuration of the fuel cell system 1 of this embodiment described above can achieve functions and effects equivalent to those of the previous embodiments. In addition, unlike the previous embodiments, this embodiment differs from the previous embodiments in that the valve device 66 is opened and closed to a variable degree of opening, causing air that has bypassed the FC stack 11 to pass through the heat exchanger 82 via the air bypass passage 64 and return to the air supply passage 61. This promotes cooling of the coolant in the heat exchanger 82. This improves the cooling efficiency of the FC stack 11 by the coolant.

[0075] According to the configuration of this embodiment, the control device 10 controls the valve device 66 so that the flow rate of air flowing through the air bypass passage 64 corresponds to the temperature of the FC stack 11 measured by the temperature sensor 89. Therefore, the amount of cooling of the FC stack 11 is adjusted according to the temperature of the FC stack 11. This improves the controllability of the amount of cooling of the FC stack 11. In other words, the amount of cooling of the FC stack 11 can be controlled according to the temperature of the FC stack 11.

[0076] <Other Embodiments> The disclosed technology is not limited to the above-described embodiments, and can be implemented by appropriately modifying part of the configuration within the scope of the disclosed technology.

[0077] (1) In each of the above embodiments, the fuel cell system 1 is mounted on an electric vehicle. However, the fuel cell system may also be mounted on a device other than an electric vehicle.

[0078] (2) In the above-described embodiments, no air valves or the like are provided on the supply side and discharge side of the air system 22, but air valves or the like may be provided.

[0079] (3) In each of the above embodiments, a closed cathode system in which the cooling system and the air system are separate has been described. However, the present invention can also be applied to an open cathode system in which the cooling system and the air system are shared.

[0080] The disclosed technology can be used, for example, in a fuel cell system mounted on an electric vehicle.

[0081] REFERENCE SIGNS LIST 1 fuel cell system 10 control device (first control unit, second control unit, third control unit) 11 FC stack (fuel cell) 13 fuel cell cell 18 porous body 21 hydrogen system 22 air system 31 hydrogen supply passage (fuel supply passage) 61 air supply passage (oxidant supply passage) 64 air bypass passage (oxidant bypass passage) 66 valve device 81 cooling water circulation passage (cooling medium circulation passage) 82 heat exchanger 88 first fan 89 temperature sensor 91 second fan

Claims

1. A fuel cell system comprising: a fuel cell formed by stacking a plurality of fuel cell cells; a fuel supply passage for supplying fuel to the fuel cell; an oxidant supply passage for supplying an oxidant to the fuel cell; and a porous body disposed between adjacent fuel cell cells and constituting a flow path through which a cooling medium flows; further comprising a cooling medium circulation flow path for circulating the cooling medium in the porous body, wherein the cooling medium circulation flow path is configured so that the cooling medium can exchange heat with at least one of the fuel and the oxidant, and is configured as a closed loop through which only the cooling medium circulates.

2. A fuel cell system according to claim 1, comprising: a heat exchanger arranged in the cooling medium circulation flow path, the cooling medium being configured to be able to exchange heat with the fuel; and a first fan that blows air towards the heat exchanger to cool the heat exchanger.

3. A fuel cell system as described in claim 2, comprising a temperature sensor for measuring the temperature of the fuel cell, and a first control unit for controlling the first fan, wherein the first control unit controls the first fan so that the airflow rate corresponds to the value measured by the temperature sensor.

4. A fuel cell system according to claim 1, comprising: a heat exchanger arranged in the cooling medium circulation flow path, and configured so that the cooling medium can exchange heat with the fuel; an oxidant bypass passage which passes the oxidant from the oxidant supply passage, bypassing the fuel cell, through the heat exchanger and returning it to the oxidant supply passage; and a valve device which opens and closes the connection between the oxidant supply passage and the oxidant bypass passage, and which opens and closes the oxidant bypass passage with a variable opening.

5. A fuel cell system as described in claim 4, comprising a temperature sensor for measuring the temperature of the fuel cell, and a second control unit for controlling the valve device, wherein the second control unit controls the valve device so that the oxidant flowing through the oxidant bypass passage has a flow rate corresponding to the measurement value of the temperature sensor.

6. A fuel cell system according to claim 1, comprising: a heat exchanger disposed in the cooling medium circulation flow path, and configured so that the cooling medium can exchange heat with the fuel; and a second fan disposed in the cooling medium circulation flow path between the outlet side of the porous body and the heat exchanger, for imparting a flow to the cooling medium.

7. A fuel cell system as described in claim 6, comprising a temperature sensor for measuring the temperature of the fuel cell, and a third control unit for controlling the second fan, wherein the third control unit controls the second fan so that the flow of the cooling medium applied by the second fan is at a flow rate corresponding to the value measured by the temperature sensor.

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