Fuel cell system

Abstract

To detect a moisture content in a power generation cell with accuracy and reduce a water storage amount in a fuel cell stack.SOLUTION: A fuel cell system (10) determines whether or not an anode gas and a cathode gas are in a dew condensation state on the basis of a humidity of the anode gas detected by a first humidity sensor provided in a power generation cell (22) and a humidity of the anode gas detected by a second humidity sensor provided in the power generation cell (22), and adjusts a water content of the gas that is determined to be in the dew condensation state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system. [Background technology]

[0002] A fuel cell system generates electricity by supplying an anode gas (hydrogen gas) and a cathode gas (oxygen gas) to a fuel cell stack. The fuel cell stack generates electricity through an electrochemical reaction between the anode gas and the cathode gas.

[0003] Patent Document 1 below discloses a method for operating a fuel cell system. In this method, the amount of water in a fuel cell stack (fuel cell) is estimated, and a scavenging process is performed based on the estimation result. In the scavenging process, scavenging gas is supplied to the fuel cell stack when the ignition is turned off. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-35389 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-described operating method, the amount of water in the fuel cell stack is estimated, and if the estimated amount of water differs significantly from the amount of water in the fuel cell stack, the amount of water in the fuel cell stack cannot be reduced.

[0006] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0007] One aspect of the present invention is a fuel cell system that adjusts the moisture content of cathode gas and anode gas supplied to a fuel cell stack having a plurality of stacked power generation cells, and includes: a first humidity sensor provided in at least one of the power generation cells for detecting the humidity of the cathode gas; a second humidity sensor provided in at least one of the power generation cells for detecting the humidity of the anode gas; and a control device that determines whether the anode gas and the cathode gas are in a condensed state based on the humidity of the anode gas detected by the first humidity sensor and the humidity of the anode gas detected by the second humidity sensor, and reduces the moisture content of gases determined to be in a condensed state. [Effects of the Invention]

[0008] According to one aspect of the present invention, a humidity sensor is provided inside the power-generating cell, so the amount of moisture in the power-generating cell can be accurately detected. Furthermore, according to another aspect of the present invention, by reducing the gas moisture content determined to be in a condensed state, it is possible to suppress the accumulation of liquid water inside the power-generating cell even when the ignition is on. This reduces the amount of water accumulated in the fuel cell stack. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a fuel cell system according to a first embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view of a power generating cell. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a diagram showing the first separator piece. [Figure 5] FIG. 5 is a diagram showing the second separator piece. [Figure 6] FIG. 6 is a diagram showing the locations of the first humidity sensor and the second humidity sensor according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] [First embodiment] FIG. 1 is a schematic diagram showing the configuration of a fuel cell system 10 according to a first embodiment. The fuel cell system 10 is mounted on a mobile body. Examples of the mobile body include a vehicle, a submarine, a spaceship, a ship, an aircraft, and a robot. The vehicle may be a four-wheeled vehicle (automobile), or may be a two-wheeled or three-wheeled vehicle.

[0011] The fuel cell system 10 includes a fuel cell stack 12 , a cathode gas supply device 14 , an anode gas supply device 16 , a coolant supply device 18 , and a control device 20 .

[0012] The fuel cell stack 12 contains a plurality of power generating cells 22. The power generating cells 22 are stacked to form a stack. Each power generating cell 22 generates electricity through an electrochemical reaction between a cathode gas and an anode gas. The cathode gas is an oxidant gas containing oxygen, such as air, and the anode gas is a fuel gas containing hydrogen, etc.

[0013] The fuel cell stack 12 is provided with a cathode gas input unit 12-1 for inputting cathode gas and a cathode gas output unit 12-2 for outputting cathode gas. The fuel cell stack 12 is also provided with an anode gas input unit 12-3 for inputting anode gas and an anode gas output unit 12-4 for outputting anode gas. The fuel cell stack 12 is also provided with a refrigerant input unit 12-5 for inputting a refrigerant and a refrigerant output unit 12-6 for outputting the refrigerant. The refrigerant may be a liquid or a gas, as long as it is a substance that can be used as a medium for cooling the heat generated by the fuel cell stack 12.

[0014] The cathode gas supply device 14 supplies cathode gas to the fuel cell stack 12. The cathode gas supply device 14 includes a cathode supply passage 24, a cathode discharge passage 26, a cathode pump 28, and a humidifier 30.

[0015] One end of the cathode supply channel 24 is connected to a cathode pump 28, and the other end of the cathode supply channel 24 is connected to a cathode gas input port 12-1 of the fuel cell stack 12. The cathode gas flowing through the cathode supply channel 24 is supplied to each power generation cell 22.

[0016] One end of the cathode discharge channel 26 is connected to the cathode gas output section 12-2, and the other end of the cathode discharge channel 26 is open to the atmosphere. The cathode gas flowing out from each power generation cell 22 is discharged to the cathode discharge channel 26.

[0017] The cathode pump 28 supplies the cathode gas to the cathode supply channel 24. The cathode pump 28 is configured to be able to adjust the amount of cathode gas supplied. The amount of cathode gas supplied by the cathode pump 28 is controlled by the control device 20.

[0018] The humidifier 30 humidifies the cathode gas flowing through the cathode supply channel 24 with moisture collected from the cathode discharge channel 26. The humidifier 30 is configured to be able to adjust the amount of humidification of the cathode gas. The amount of humidification of the cathode gas is controlled by the control device 20.

[0019] For example, the humidifier 30 includes a recovery unit disposed on the cathode discharge channel 26, a humidifier disposed on the cathode supply channel 24, a bypass path bypassing the humidifier, and an on-off valve disposed on the bypass path. The humidifier generates water vapor from the moisture recovered by the recovery unit and introduces the generated water vapor into the cathode supply channel 24. The bypass path branches off from the cathode supply channel 24 closer to the cathode pump 28 than the humidifier and is connected to a cathode supply channel 24 closer to the fuel cell stack 12 than the humidifier, bypassing the humidifier. In this case, the humidifier 30 can adjust the amount of humidification of the cathode gas by adjusting the amount of cathode gas supplied to the humidifier according to the opening degree of the on-off valve. The opening degree of the on-off valve is controlled by the control device 20.

[0020] The anode gas supply device 16 supplies anode gas to the fuel cell stack 12 and recovers anode gas discharged from the fuel cell stack 12. The anode gas supply device 16 includes a circulation path 32, a purge path 34, an anode gas tank 36, a circulation pump 38, an ejector 40, and a discharge valve 42.

[0021] One end of the circulation path 32 is connected to the anode gas input port 12-3 of the fuel cell stack 12, and the other end of the circulation path 32 is connected to the anode gas output port 12-4 of the fuel cell stack 12. The anode gas flowing in from the anode gas input port 12-3 is supplied to each power generation cell 22. The anode gas flowing out from each power generation cell 22 is discharged from the anode gas output port 12-4 to the circulation path 32. A circulation pump 38 is provided in the circulation path 32. An ejector 40 is provided in the circulation path 32 between the circulation pump 38 and the anode gas input port 12-3.

[0022] The purge path 34 branches off from the circulation path 32 between the anode gas output port 12-4 and the circulation pump 38. A discharge valve 42 is provided in the purge path 34.

[0023] The anode gas tank 36 stores the anode gas. The anode gas tank 36 is configured to be able to supply the anode gas to the circulation path 32 and to be able to adjust the amount of the anode gas supplied. The amount of the anode gas supplied is controlled by the control device 20.

[0024] For example, the anode gas tank 36 has an anode gas supply path that connects the circulation path 32 and the anode gas tank 36, and a flow rate control valve provided on the anode gas supply path. In this case, the anode gas tank 36 can adjust the amount of anode gas supplied by adjusting the flow rate of the flow rate control valve. The flow rate control valve is controlled by the control device 20.

[0025] The circulation pump 38 supplies the anode gas discharged from the fuel cell stack 12 via the circulation path 32 to the ejector 40. The circulation pump 38 is capable of adjusting the amount of anode gas supplied. The amount of anode gas supplied by the circulation pump 38 is controlled by the control device 20.

[0026] The ejector 40 supplies the anode gas supplied from the anode gas tank 36 or the circulation pump 38 to the fuel cell stack 12 .

[0027] The discharge valve 42 is configured to be openable and closable. When the discharge valve 42 is open, the anode gas discharged from the fuel cell stack 12 to the circulation path 32 flows into the purge path 34. Conversely, when the discharge valve 42 is closed, the anode gas discharged from the fuel cell stack 12 to the circulation path 32 flows into the circulation pump 38. The opening and closing of the discharge valve 42 is controlled by the control device 20.

[0028] The coolant supply device 18 cools the fuel cell stack 12. The coolant supply device 18 has a coolant supply path 44, a coolant discharge path 46, and a cooler 48.

[0029] One end of the coolant supply path 44 is connected to the cooler 48, and the other end of the coolant supply path 44 is connected to the coolant input port 12-5. The coolant flowing through the coolant supply path 44 is supplied between the power generating cells 22.

[0030] One end of the coolant discharge path 46 is connected to the coolant output portion 12-6, and the other end of the coolant discharge path 46 is connected to the cooler 48. The coolant flowing between the power generating cells 22 flows out from the coolant output portion 12-6 to the coolant discharge path 46.

[0031] The cooler 48 cools the coolant supplied from the fuel cell stack 12 via the coolant discharge path 46, and supplies the cooled coolant to the fuel cell stack 12 via the coolant supply path 44. The cooler 48 is configured to be able to adjust the temperature of the coolant supplied to the fuel cell stack 12. The temperature of the coolant is controlled by the control device 20.

[0032] For example, the cooler 48 includes a radiator provided between the refrigerant discharge path 46 and the refrigerant supply path 44, a radiator bypass path that bypasses the radiator, and an on-off valve provided in the radiator bypass path. The radiator cools the refrigerant supplied via the refrigerant discharge path 46 and sends the cooled refrigerant to the refrigerant supply path 44. The radiator bypass path branches off from the refrigerant discharge path 46, which is closer to the fuel cell stack 12 than the radiator, and is connected to the refrigerant supply path 44, which is closer to the fuel cell stack 12 than the radiator, and does not pass through the radiator. In this case, the cooler 48 can adjust the amount of refrigerant supplied to the radiator according to the opening degree of the on-off valve, thereby adjusting the temperature of the refrigerant. The opening degree of the on-off valve is controlled by the control device 20.

[0033] The control device 20 comprehensively controls the entire fuel cell system 10. The control device 20 can execute power generation operations to generate electricity in the fuel cell stack 12. For example, when a power generation execution command is given from an input device (not shown), the control device 20 executes the power generation operation. In this case, the control device 20 supplies current to each power generation cell 22. Furthermore, the control device 20 controls the cathode gas supply device 14 to supply cathode gas to the fuel cell stack 12, and controls the anode gas supply device 16 to supply anode gas to the fuel cell stack 12.

[0034] FIG. 2 is a schematic cross-sectional view of the power generating cell 22. The power generating cell 22 is a polymer electrolyte fuel cell. The power generating cell 22 has a membrane electrode assembly 50 and a separator 52. The membrane electrode assembly 50 is hereinafter referred to as an MEA 50. The separator 52 has a first separator piece 54 and a second separator piece 56. The first separator piece 54 and the second separator piece 56 are joined together to form the separator 52. The separator 52 sandwiches the MEA 50.

[0035] Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2. The MEA 50 includes an electrolyte membrane 58, an anode catalyst layer 60, an anode diffusion layer 62, a cathode catalyst layer 64, a cathode diffusion layer 66, and an outer frame film 68 (see Fig. 2).

[0036] The electrolyte membrane 58 is composed of a solid polymer electrolyte membrane or the like. The anode catalyst layer 60 is provided on one side of the electrolyte membrane 58. The anode diffusion layer 62 is provided on the side of the anode catalyst layer 60 opposite the side facing the electrolyte membrane 58. The cathode catalyst layer 64 is provided on the other side of the electrolyte membrane 58. The cathode diffusion layer 66 is provided on the side of the cathode catalyst layer 64 opposite the side facing the electrolyte membrane 58.

[0037] The outer frame film 68 (FIG. 2) is a member that forms the outer frame of the MEA 50. The outer frame film 68 may be the electrolyte membrane 58 (see FIG. 2). In this case, the electrolyte membrane 58 is formed so as to protrude outward from the anode catalyst layer 60, the anode diffusion layer 62, the cathode catalyst layer 64, and the cathode diffusion layer 66. The outer frame film 68 may be a resin film (not shown). In this case, the resin film may be connected to the outer periphery of the electrolyte membrane 58, or may be sandwiched between the outer periphery of the anode catalyst layer 60 and the outer periphery of the cathode catalyst layer 64.

[0038] 4 is a diagram showing the first separator piece 54. The first separator piece 54 has a cathode inlet hole 70, a cathode outlet hole 72, an anode inlet hole 74, and an anode outlet hole 76. The cathode inlet hole 70, the cathode outlet hole 72, the anode inlet hole 74, and the anode outlet hole 76 are spaced apart from one another.

[0039] The cathode inlet hole 70 communicates with the cathode supply channel 24 (FIG. 1) through a cathode input channel (not shown) provided within the fuel cell stack 12. The cathode outlet hole 72 communicates with the cathode exhaust channel 26 (FIG. 1) through a cathode output channel provided within the fuel cell stack 12.

[0040] The anode inlet hole 74 communicates with the circulation path 32 (FIG. 1) via an anode input path (not shown) provided within the fuel cell stack 12. The anode outlet hole 76 communicates with the circulation path 32 via an anode output path provided within the fuel cell stack 12.

[0041] The cathode inlet hole 70 and the anode outlet hole 76 are located, for example, at a first edge of the first separator piece 54. The cathode outlet hole 72 and the anode inlet hole 74 are located, for example, at a second edge of the first separator piece 54. The second edge is the edge portion opposite the first edge.

[0042] A plurality of grooves 78 are formed on the inner surface of the first separator piece 54. The inner surface of the first separator piece 54 faces the MEA 50. The plurality of grooves 78 are disposed approximately in the center of the inner surface of the first separator piece 54 and extend along the longitudinal direction of the first separator piece 54.

[0043] Additionally, a first line seal member 80 is provided on the inner surface of the first separator piece 54. The first line seal member 80 surrounds the plurality of grooves 78, the cathode inlet hole 70, and the cathode outlet hole 72. A cathode gas flow path 82 is formed between the MEA 50 surrounded by the first line seal member 80 and the first separator piece 54.

[0044] The cathode gas flow path 82 includes a cathode inlet space 84, a cathode outlet space 86, and a plurality of grooves 78. The cathode inlet space 84 is the space between the outer frame film 68 and the first separator piece 54, which communicates with the cathode inlet hole 70 (see FIG. 2). The cathode outlet space 86 is the space between the outer frame film 68 and the first separator piece 54, which communicates with the cathode outlet hole 72 (see FIG. 2). The plurality of grooves 78 communicate the cathode inlet space 84 and the cathode outlet space 86 (see FIG. 4).

[0045] 5 is a diagram showing the second separator piece 56. The second separator piece 56 has a cathode inlet hole 70, a cathode outlet hole 72, an anode inlet hole 74, and an anode outlet hole 76 at positions corresponding to the holes in the first separator piece 54.

[0046] A plurality of grooves 88 are formed on the inner surface of the second separator piece 56. The plurality of grooves 88 are disposed approximately in the center of the inner surface of the second separator piece 56 and extend along the longitudinal direction of the second separator piece 56.

[0047] Additionally, a second line seal member 90 is provided on the inner surface of the second separator piece 56. The second line seal member 90 surrounds the plurality of grooves 88, the anode inlet hole 74, and the anode outlet hole 76. An anode gas flow path 92 is formed between the MEA 50 surrounded by the second line seal member 90 and the first separator piece 54.

[0048] The anode gas flow path 92 includes an anode inlet space 94, an anode outlet space 96, and a plurality of grooves 88. The anode inlet space 94 is the space between the outer frame film 68 and the second separator piece 56, which communicates with the anode inlet hole 74 (see FIG. 2). The anode outlet space 96 is the space between the outer frame film 68 and the second separator piece 56, which communicates with the anode outlet hole 76 (see FIG. 2). The plurality of grooves 88 communicate the anode inlet space 94 and the anode outlet space 96 (see FIG. 5).

[0049] A plurality of grooves 98 (see FIG. 3) are formed on the outer surface of the first separator piece 54 and the outer surface of the second separator piece 56. The outer surface of the first separator piece 54 is the surface opposite the inner surface of the first separator piece 54, and the outer surface of the second separator piece 56 is the surface opposite the inner surface of the second separator piece 56.

[0050] When another power generating cell 22 is adjacent to the first separator piece 54, the grooves 98 formed in the outer surface of the first separator piece 54 and the grooves 98 formed in the outer surface of the second separator piece 56 of the other power generating cell 22 form a refrigerant flow path 100. Similarly, when another power generating cell 22 is adjacent to the second separator piece 56, the grooves 98 formed in the outer surface of the second separator piece 56 and the grooves 98 formed in the outer surface of the first separator piece 54 of the other power generating cell 22 form a refrigerant flow path 100.

[0051] A coolant flows into the coolant flow path 100 from a coolant input path (not shown) provided inside the fuel cell stack 12. The coolant input path is connected to a coolant supply path 44 (FIG. 1) of the coolant supply device 18. The coolant flowing through the coolant flow path 100 flows out to a coolant output path (not shown) provided inside the fuel cell stack 12. The coolant output path is connected to a coolant discharge path 46 (FIG. 1) of the coolant supply device 18. Note that inside the fuel cell stack 12, the coolant, anode gas, and cathode gas do not mix with each other.

[0052] The fuel cell system 10 further includes a first humidity sensor 102 (FIG. 4) for detecting the humidity (relative humidity) of the cathode gas and a second humidity sensor 104 (FIG. 5) for detecting the humidity (relative humidity) of the anode gas. In this embodiment, the first humidity sensor 102 and the second humidity sensor 104 are provided in one of the plurality of power generating cells 22.

[0053] The first humidity sensors 102 are provided in the cathode inlet space 84 and the cathode outlet space 86 of the cathode gas flow channel 82. Each of the first humidity sensors 102 is, for example, formed to have a thin thickness and attached to the inner surface of the first separator piece 54. Meanwhile, the second humidity sensors 104 are provided in the anode inlet space 94 and the anode outlet space 96 of the anode gas flow channel 92. Each of the second humidity sensors 104 is, for example, formed to have a thin thickness and attached to the inner surface of the second separator piece 56.

[0054] In this way, the first humidity sensor 102 is provided in the cathode gas flow path 82 inside the power generating cell 22, and the second humidity sensor 104 is provided in the anode gas flow path 92 inside the power generating cell 22. This allows the moisture content of the power generating cell 22 to be detected more accurately than when the sensors are provided outside the power generating cell 22.

[0055] The control device 20 determines the condensation state of the cathode gas based on the humidity detected by each first humidity sensor 102. The control device 20 makes the determination during power generation operation of the fuel cell stack 12. For example, the control device 20 may determine that the cathode gas is in a condensation state when at least one of the humidities detected by each first humidity sensor 102 exceeds a first threshold. Alternatively, the control device 20 may determine that the cathode gas is in a condensation state when a difference between the humidities detected by each first humidity sensor 102 exceeds the first threshold. Alternatively, the control device 20 may determine that the cathode gas is in a condensation state when an average of the humidities detected by each first humidity sensor 102 per unit time exceeds the first threshold. The first threshold is, for example, 100%.

[0056] When the control device 20 determines that the cathode gas is in a condensed state, it reduces the moisture content of the cathode gas. In this case, the control device 20 executes at least one of a gas amount increase operation and a humidification reduction operation. The gas amount increase operation is an operation that controls the cathode pump 28 to increase the amount of cathode gas supplied compared to the time when it was determined that the cathode gas was in a condensed state. The humidification reduction operation is an operation that controls the humidifier 30 to reduce the amount of humidification of the cathode gas compared to the time when it was determined that the cathode gas was in a condensed state.

[0057] In this way, the control device 20 determines whether the cathode gas is in a condensed state during the power generation operation of the fuel cell stack 12, and if the cathode gas is in a condensed state, reduces the water content of the cathode gas. This makes it possible to prevent liquid water from accumulating inside the power generation cells 22 even if scavenging gas is not supplied when power generation operation is stopped.

[0058] Meanwhile, the control device 20 determines the condensation state of the anode gas based on the humidity detected by each second humidity sensor 104. The control device 20 makes this determination during power generation operation of the fuel cell stack 12. For example, the control device 20 may determine that the anode gas is in a condensation state when at least one of the humidities detected by each second humidity sensor 104 exceeds a second threshold. Alternatively, the control device 20 may determine that the anode gas is in a condensation state when the difference between the humidities detected by each second humidity sensor 104 exceeds the second threshold. Alternatively, the control device 20 may determine that the anode gas is in a condensation state when the average of the humidities detected by each second humidity sensor 104 exceeds the second threshold. The second threshold is, for example, 100%.

[0059] If the control device 20 determines that the anode gas is in a condensed state, it reduces the moisture content of the anode gas. In this case, the control device 20 opens the exhaust valve 42 to allow the anode gas exhausted from the fuel cell stack 12 to flow into the purge path 34. At the same time, the control device 20 performs at least one of a gas supply operation and a gas increase operation.

[0060] The gas supply operation is an operation of controlling the anode gas tank 36 to supply the anode gas to the ejector 40. The gas increase operation is an operation of controlling the circulation pump 38 to increase the amount of anode gas supplied to the ejector 40.

[0061] In the gas supply operation, the control device 20 may supply an amount of anode gas corresponding to the amount of anode gas flowing through the purge path 34. In this case, a flow sensor for detecting the amount of anode gas is provided in the purge path 34. The control device 20 supplies the anode gas from the anode gas tank 36 to the ejector 40 based on the amount of anode gas detected by the flow sensor.

[0062] In this way, the control device 20 determines whether the anode gas is in a condensed state during the power generation operation of the fuel cell stack 12, and if the anode gas is in a condensed state, reduces the water content of the anode gas. This makes it possible to prevent liquid water from accumulating inside the power generation cells 22 even if scavenging gas is not supplied when power generation operation is stopped.

[0063] Second Embodiment In the second embodiment, explanations that overlap with those in the first embodiment will be omitted. In this embodiment, the locations where the first humidity sensor 102 and the second humidity sensor 104 are installed are different from those in the first embodiment.

[0064] Fig. 6 is a diagram showing the installation locations of the first humidity sensor 102 and the second humidity sensor 104 according to the second embodiment. Fig. 6 shows a cross section taken along line III-III in Fig. 2. In this embodiment, the first humidity sensor 102 and the second humidity sensor 104 are provided inside the MEA 50.

[0065] The first humidity sensor 102 is provided in at least one of the first cathode interlayer portion, the second cathode interlayer portion, and the third cathode interlayer portion. The first cathode interlayer portion is between the electrolyte membrane 58 and the cathode catalyst layer 64. The second cathode interlayer portion is between the cathode catalyst layer 64 and the cathode diffusion layer 66. The third cathode interlayer portion is between the separator 52 (first separator piece 54) and the cathode diffusion layer 66. The third cathode interlayer portion may be between the first separator piece 54 and the cathode diffusion layer 66 in the portion where the groove 78 is formed, or between the first separator piece 54 and the cathode diffusion layer 66 in the portion where the groove 98 is formed. FIG. 6 shows an example in which the first humidity sensor 102 is provided in the first cathode interlayer portion.

[0066] When two or more first humidity sensors 102 are provided in the cathode interlayer portion, the control device 20 determines whether the cathode gas is in a condensed state based on the humidity detected by each of the first humidity sensors 102. For example, when at least one of the humidities detected by each of the first humidity sensors 102 exceeds a first threshold value, or when the difference, sum, average, etc. of the humidities detected by each of the first humidity sensors 102 exceeds a first threshold value, the control device 20 determines that the cathode gas is in a condensed state.

[0067] When the first humidity sensor 102 is provided in one cathode interlayer portion, the control device 20 determines that the cathode gas is in a condensed state when the humidity detected by the first humidity sensor 102 exceeds a first threshold value.

[0068] The second humidity sensor 104 is provided in at least one of the first anode interlayer portion, the second anode interlayer portion, and the third anode interlayer portion. The first anode interlayer portion is between the electrolyte membrane 58 and the anode catalyst layer 60. The second anode interlayer portion is between the anode catalyst layer 60 and the anode diffusion layer 62. The third anode interlayer portion is between the separator 52 (second separator piece 56) and the anode diffusion layer 62. The third anode interlayer portion may be between the second separator piece 56 and the anode diffusion layer 62 in the portion where the groove 88 is formed, or between the second separator piece 56 and the anode diffusion layer 62 in the portion where the groove 98 is formed. FIG. 6 shows an example in which the second humidity sensor 104 is provided in the first anode interlayer portion.

[0069] When two or more second humidity sensors 104 are provided in the anode interlayer portions, the control device 20 determines whether the anode gas is in a condensed state based on the humidity detected by each second humidity sensor 104. For example, when at least one of the humidities detected by each second humidity sensor 104 exceeds a second threshold value, or when the difference, sum, average, etc. of the humidities detected by each first humidity sensor 102 exceeds a second threshold value, the control device 20 determines that the anode gas is in a condensed state.

[0070] When the second humidity sensor 104 is provided in one anode interlayer portion, the control device 20 determines that the anode gas is in a condensed state when the humidity detected by the second humidity sensor 104 exceeds a second threshold value.

[0071] As described above, in this embodiment, the first humidity sensor 102 and the second humidity sensor 104 are provided inside the MEA 50. This makes it possible to locally detect locations in the power generating cell 22 where liquid water is likely to accumulate.

[0072] The first or second embodiment may be modified as follows.

[0073] (Variation 1) When the control device 20 determines that at least one of the cathode gas and the anode gas is in a condensed state, the control device 20 may execute a refrigerant temperature increasing operation to increase the temperature of the refrigerant by controlling the cooler 48. This allows the condensation to be resolved more quickly than when the refrigerant temperature increasing operation is not executed.

[0074] (Variation 2) Both the first humidity sensor 102 of the first embodiment and the first humidity sensor 102 of the second embodiment may be employed. In this case, the control device 20 determines whether the cathode gas is in a condensed state based on the detection results of at least one first humidity sensor 102 provided in the cathode gas flow path 82 and at least one first humidity sensor 102 provided inside the MEA 50.

[0075] For example, if the difference, sum, average, etc. between the humidity detected by the first humidity sensor 102 provided in the cathode gas flow path 82 and the humidity detected by the first humidity sensor 102 provided inside the MEA 50 exceeds a first threshold value, the control device 20 determines that the cathode gas is in a condensed state.

[0076] Similarly, both the second humidity sensor 104 of the first embodiment and the second humidity sensor 104 of the second embodiment may be employed. In this case, the control device 20 determines whether the anode gas is in a condensed state based on the detection results of at least one second humidity sensor 104 provided in the anode gas flow path 92 and at least one second humidity sensor 104 provided inside the MEA 50.

[0077] For example, if the difference, sum, average, etc. between the humidity detected by the second humidity sensor 104 provided in the anode gas flow path 92 and the humidity detected by the second humidity sensor 104 provided inside the MEA 50 exceeds a second threshold value, the control device 20 determines that the anode gas is in a condensed state.

[0078] (Variation 3) The first humidity sensor 102 and the second humidity sensor 104 may be provided in the plurality of power generating cells 22. In this case, the control device 20 determines that the cathode gas is in a condensed state when the difference, sum, average, etc. between the humidity detected by the first humidity sensor 102 provided in the plurality of power generating cells 22 exceeds a first threshold value. Similarly, the control device 20 determines that the anode gas is in a condensed state when the difference, sum, average, etc. between the humidity detected by the second humidity sensor 104 provided in the plurality of power generating cells 22 exceeds a second threshold value.

[0079] Temperature differences tend to occur among the multiple power-generating cells 22 during power generation operation of the fuel cell stack 12. That is, among the multiple stacked power-generating cells 22, the power-generating cell 22 located at the center in the stacking direction tends to have the highest temperature. On the other hand, among the multiple stacked power-generating cells 22, the power-generating cells 22 located on both sides in the stacking direction tend to have the lowest temperatures.

[0080] Therefore, the first humidity sensor 102 and the second humidity sensor 104 may be provided to each of the power generating cells 22 located on both sides in the stacking direction of the power generating cells 22, and to the power generating cell 22 located in the center in the stacking direction of the power generating cells 22. This makes it possible to set the determination conditions for determining that condensation has occurred, taking into account the temperature difference that occurs among the multiple power generating cells 22 when the fuel cell stack 12 is operating to generate electricity.

[0081] The judgment conditions are a first threshold value, a second threshold value, etc. When changing the judgment conditions, the control device 20 changes the first threshold value, the second threshold value, etc. in response to a user operation so that they become values ​​given from an input device (not shown).

[0082] The technical ideas and effects that can be understood from the above description will be described below.

[0083] One aspect of the present invention is a fuel cell system (10) that adjusts the moisture content of cathode gas and anode gas supplied to a fuel cell stack (12) having a plurality of stacked power generation cells (22), and includes a first humidity sensor (102) provided in at least one of the power generation cells for detecting the humidity of the cathode gas, a second humidity sensor (104) provided in at least one of the power generation cells for detecting the humidity of the anode gas, and a control device (20) that determines whether the anode gas and the cathode gas are in a condensed state based on the humidity of the anode gas detected by the first humidity sensor and the humidity of the anode gas detected by the second humidity sensor, and adjusts the moisture content of gases that are determined to be in a condensed state.

[0084] According to one aspect of the present invention, a humidity sensor is provided inside the power-generating cell, thereby enabling accurate detection of the moisture content of the power-generating cell. Furthermore, according to another aspect of the present invention, by adjusting the moisture content of at least one of the anode gas and the cathode gas, it is possible to suppress accumulation of liquid water inside the power-generating cell even when the ignition is on. This reduces the amount of water accumulated in the fuel cell stack.

[0085] The power-generating cell may have a membrane electrode assembly (50) and a separator (52) that sandwiches the membrane electrode assembly, and the first humidity sensor and the second humidity sensor may be provided between the membrane electrode assembly and the separator, thereby enabling accurate detection of the amount of moisture in the flow path within the power-generating cell.

[0086] The first humidity sensor may be disposed in at least one of a cathode inlet space (84) between the membrane electrode assembly and the separator, the cathode inlet space communicating with a cathode inlet hole (70) formed in the separator, and a cathode outlet space (86) between the membrane electrode assembly and the separator, the cathode outlet space communicating with a cathode outlet hole (72) formed in the separator, and the second humidity sensor may be disposed in at least one of an anode inlet space (94) between the membrane electrode assembly and the separator, the anode inlet space communicating with an anode inlet hole (74) formed in the separator, and an anode outlet space (96) between the membrane electrode assembly and the separator, the anode outlet hole (76) formed in the separator. This makes it possible to accurately detect the moisture content in a relatively wide space in the flow path of the power generation cell.

[0087] The power-generating cell may have a membrane electrode assembly and a separator that sandwiches the membrane electrode assembly, and the first humidity sensor and the second humidity sensor may be provided inside the membrane electrode assembly, thereby making it possible to accurately detect the amount of moisture in the membrane electrode assembly in the power-generating cell.

[0088] The membrane electrode assembly may include an electrolyte membrane (58), an anode catalyst layer (60) disposed on one side of the electrolyte membrane, an anode diffusion layer (62) disposed between the anode catalyst layer and the separator, a cathode catalyst layer (64) disposed on the other side of the electrolyte membrane, and a cathode diffusion layer (66) disposed between the cathode catalyst layer and the separator, wherein the first humidity sensor is disposed between the electrolyte membrane and the anode catalyst layer and / or between the anode catalyst layer and the anode diffusion layer, and the second humidity sensor is disposed between the electrolyte membrane and the cathode catalyst layer and / or between the cathode catalyst layer and the cathode diffusion layer. This allows localized detection of areas in the power generation cell where liquid water is likely to accumulate.

[0089] The fuel cell system includes a cathode pump (28) for supplying the cathode gas to the fuel cell stack and a humidifier (30) for humidifying the cathode gas supplied from the cathode pump, and when the control device determines that the cathode gas is in a condensed state, the control device may execute at least one of a gas increase operation for controlling the cathode pump to increase the amount of the cathode gas supplied and a humidification decrease operation for controlling the humidifier to decrease the amount of humidification of the cathode gas. This reduces the water content of the cathode gas and eliminates the condensed state of the cathode gas.

[0090] The fuel cell system includes a circulation pump (38) provided in a circulation path for returning the anode gas discharged from the fuel cell stack to the fuel cell stack, an ejector (40) provided in the circulation path (32) from the circulation pump to the fuel cell stack, an anode gas tank (36) connected to the ejector and storing the anode gas that can be supplied to the circulation path, and a discharge valve (42) provided in a purge path (34) branching off from the circulation path from the fuel cell stack to the circulation pump, and when the control device determines that the anode gas is in a condensed state, the control device may execute at least one of a gas supply operation in which the control device opens the discharge valve to allow the anode gas discharged from the fuel cell stack to flow into the purge path and controls the anode gas tank to supply the anode gas to the ejector, and a gas increase operation in which the control device controls the circulation pump to increase the supply amount of the anode gas supplied to the ejector. This reduces the moisture content of the anode gas, eliminating the condensation state of the anode gas.

[0091] The fuel cell system may include a cooler (48) that cools a refrigerant supplied from the fuel cell stack and supplies the cooled refrigerant to the fuel cell stack, and the control device may execute a refrigerant temperature lowering operation to control the cooler to lower the temperature of the refrigerant when it determines that at least one of the cathode gas and the anode gas is in a condensed state. This allows the condensation to be resolved more quickly than if the refrigerant temperature lowering operation was not executed.

[0092] The plurality of power generating cells may be stacked, and the first humidity sensor and the second humidity sensor may be provided to each of the power generating cells located on both sides of the stacking direction of the power generating cells and to the power generating cell located at the center of the stacking direction of the power generating cells. This makes it possible to set a determination condition for determining whether condensation has occurred, taking into account the temperature difference that occurs among the plurality of power generating cells during power generation operation of the fuel cell stack. [Explanation of symbols]

[0093] 10...Fuel cell system 12...Fuel cell stack 20...Control device 22...Power generation cell 28...Cathode pump 30...Humidifier 32...Circulation path 34...Purge path 36...Anode gas tank 38...Circulation pump 40... Ejector 42... Discharge valve 48...Cooler 50...Membrane electrode assembly (MEA) 52...Separator 54...First separator piece 56... Second separator piece 58... Electrolyte membrane 60... anode catalyst layer 62... anode diffusion layer 64... cathode catalyst layer 66... ​​cathode diffusion layer 68...Outer frame film 70...Cathode inlet hole 72: Cathode outlet hole 74: Anode inlet hole 76...Anode outlet hole 78, 88, 98...Grooves 82: Cathode gas flow path 84: Cathode inlet space 86: Cathode outlet space 92: Anode gas flow path 94...Anode inlet space 96...Anode outlet space 100... refrigerant flow path 102... first humidity sensor 104...Second humidity sensor

Claims

1. A fuel cell system for adjusting the water content of a cathode gas and an anode gas supplied to a fuel cell stack having a plurality of stacked power generation cells, comprising: a first humidity sensor provided in at least one of the power generation cells for detecting the humidity of the cathode gas; a second humidity sensor provided in at least one of the power generation cells for detecting the humidity of the anode gas; a control device configured to determine whether the anode gas and the cathode gas are in a dew condensation state based on the humidity of the cathode gas detected by the first humidity sensor and the humidity of the anode gas detected by the second humidity sensor, and to reduce the gas water content when it is determined that the gas is in a dew condensation state; A fuel cell system comprising the above components.

2. The fuel cell system according to claim 1, wherein the power generation cell has a membrane electrode assembly and a separator sandwiching the membrane electrode assembly; the first humidity sensor and the second humidity sensor are provided between the membrane electrode assembly and the separator. A fuel cell system.

3. The fuel cell system according to claim 2, wherein the first humidity sensor is disposed in at least one of a cathode inlet space between the membrane electrode assembly and the separator communicating with a cathode inlet hole formed in the separator and a cathode outlet space between the membrane electrode assembly and the separator communicating with a cathode outlet hole formed in the separator; the second humidity sensor is disposed in at least one of an anode inlet space between the membrane electrode assembly and the separator communicating with an anode inlet hole formed in the separator and an anode outlet space between the membrane electrode assembly and the separator communicating with an anode outlet hole formed in the separator. A fuel cell system.

4. The fuel cell system according to any one of claims 1 to 3, wherein the power generation cell has a membrane electrode assembly and a separator sandwiching the membrane electrode assembly; the first humidity sensor and the second humidity sensor are provided inside the membrane electrode assembly. A fuel cell system.

5. The fuel cell system according to claim 4, wherein The membrane electrode assembly has an electrolyte membrane, an anode catalyst layer disposed on one surface of the electrolyte membrane, an anode diffusion layer disposed between the anode catalyst layer and the separator, a cathode catalyst layer disposed on the other surface of the electrolyte membrane, and a cathode diffusion layer disposed between the cathode catalyst layer and the separator. The first humidity sensor is disposed at least on one of between the electrolyte membrane and the cathode catalyst layer and between the cathode catalyst layer and the cathode diffusion layer. The second humidity sensor is disposed at least on one of between the electrolyte membrane and the anode catalyst layer and between the anode catalyst layer and the anode diffusion layer, a fuel cell system.

6. A fuel cell system according to any one of claims 1 to 5, a cathode pump for supplying the cathode gas to the fuel cell stack, a humidifier for humidifying the cathode gas supplied from the cathode pump, and having when the control device determines that the cathode gas is in a dew condensation state, the control device executes at least one of a gas increasing operation of controlling the cathode pump to increase the supply amount of the cathode gas and a humidification decreasing operation of controlling the humidifier to decrease the humidification amount of the cathode gas, a fuel cell system.

7. A fuel cell system according to any one of claims 1 to 6, a circulation pump provided in a circulation path for returning the anode gas discharged from the fuel cell stack to the fuel cell stack, an ejector provided in the circulation path from the circulation pump to the fuel cell stack, an anode gas tank connected to the ejector and storing the anode gas that can be supplied to the circulation path, a discharge valve provided in a purge path branched from the circulation path from the fuel cell stack to the circulation pump, and having when the control device determines that the anode gas is in a dew condensation state, the control device executes at least one of a gas supply operation of opening the discharge valve to flow the anode gas discharged from the fuel cell stack into the purge path and controlling the anode gas tank to supply the anode gas to the ejector and a gas increasing operation of controlling the circulation pump to increase the supply amount of the anode gas supplied to the ejector, a fuel cell system.

8. A fuel cell system according to claim 6 or 7, comprising a cooler that cools the refrigerant supplied from the fuel cell stack and supplies the cooled refrigerant to the fuel cell stack, wherein when the control device determines that at least one of the cathode gas and the anode gas is in a dew condensation state, the control device controls the cooler to perform a refrigerant temperature increase operation for increasing the temperature of the refrigerant.

9. A fuel cell system according to any one of claims 1 to 8, wherein a plurality of the power generation cells are stacked, and the first humidity sensor and the second humidity sensor are provided for each of the power generation cells located at both ends in the stacking direction of the power generation cells and the power generation cell located at the center in the stacking direction of the power generation cells.

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