JP2011258396A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a performance of a fuel cell while suppressing moisture from becoming too much and an electrolyte membrane from being dried during power generation of the fuel cell.SOLUTION: The present invention relates to a fuel cell system including a flooding detection section, a membrane dry detection section, a fastening mechanism, and a fastening load control section. The fastening mechanism is configured to apply a fastening load to a fuel cell in a stacking direction and is capable of applying a uniform fastening load to a single cell and applying fastening loads different in accordance with areas in the single cell. When the flooding detection section detects occurrence of flooding, the fastening load control section drives the fastening mechanism to decrease the fastening load at least in a flooding area that is an area preset as an area where flooding easily occurs and when the membrane dry detection section detects the lack of moisture in an electrolyte membrane, the fastening load control section drives the fastening mechanism to increase a fastening load at least in a membrane dry area preset as an area where the lack of moisture in the electrolyte membrane easily occurs.

Description

  The present invention relates to a fuel cell system.

  During power generation of the fuel cell, liquid water may stay in the gas flow path in the fuel cell and suppress the gas flow in the gas flow path. Suppression of the gas flow due to such stagnation of liquid water can cause a decrease in power generation performance of the fuel cell. Therefore, in order to maintain the performance of the fuel cell, it is important to ensure drainage from the fuel cell. As one method for ensuring drainage from such a fuel cell, conventionally, when the fuel cell system is stopped, the tightening load of the fuel cell stack is reduced based on the amount of water in the fuel cell stack, and the fuel cell Has been proposed (see, for example, Patent Document 1).

JP 2007-115492 A JP 2007-005229 A

  However, when the tightening load of the fuel cell stack is reduced to enhance the drainage performance from the fuel cell, the electrolyte membrane is partially dried due to the increased drainage performance, and the fuel cell performance cannot be sufficiently secured. Could also occur. In addition, ensuring the cell performance by ensuring drainage from the fuel cell has been strongly desired not only when the fuel cell is stopped, but also when the fuel cell continues to generate power. When the fuel cell is stopped, even if the electrolyte membrane dries, it does not necessarily directly affect the subsequent power generation.However, when the fuel cell continues to generate power, drying the electrolyte membrane immediately reduces the battery performance. May cause. For this reason, during power generation of the fuel cell, even in order to ensure drainage from the fuel cell, it has been difficult to adopt the measure of reducing the tightening load that may cause the electrolyte membrane to dry. .

  The present invention has been made to solve the above-described conventional problems, and aims to ensure the performance of a fuel cell while suppressing excessive moisture and drying of an electrolyte membrane during power generation of the fuel cell. To do.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1]
A fuel cell system comprising a fuel cell having a single cell including an electrolyte membrane and an electrode,
A flooding detection unit for detecting occurrence of flooding in the fuel cell;
A membrane dryness detection unit for detecting water shortage in the electrolyte membrane provided in the fuel cell;
A fastening mechanism that applies a fastening load to the fuel cell in the stacking direction of the electrolyte membrane and the electrode, and can apply a uniform fastening load to the single cell, and varies depending on a region in the single cell. A fastening mechanism capable of applying a fastening load;
When the flooding detection unit detects the occurrence of flooding, the fastening mechanism is driven to reduce at least the fastening load of the flooding region that is a region preset as a region where flooding is likely to occur in the single cell, When the membrane drying detection unit detects water shortage of the electrolyte membrane, the membrane is a region set in advance as a region where water shortage in the electrolyte membrane is likely to occur at least in the single cell by driving the fastening mechanism. A fuel cell system comprising: a fastening load control unit that increases the fastening load in the dry region.

  According to the fuel cell system described in Application Example 1, when flooding occurs, the flooding can be eliminated by reducing at least the fastening load in the flooding region. When water shortage of the electrolyte membrane occurs, at least the membrane Membrane drying can be eliminated by increasing the fastening load in the drying region.

[Application Example 2]
In the fuel cell system according to application example 1, when the flooding detection unit detects flooding, the fastening load control unit reduces the fastening load of the entire single cell by driving the fastening mechanism. Thereafter, when the membrane drying detection unit detects water shortage of the electrolyte membrane, the fastening mechanism is driven to increase the fastening load of the membrane drying region as compared to other regions. According to the fuel cell system described in Application Example 2, even if flooding occurs in any region in the single cell, the flooding can be eliminated by reducing the fastening load of the entire single cell. . In addition, by reducing the fastening load of the entire single cell, in the case where insufficient moisture of the electrolyte membrane occurs in the membrane drying region, the electrolyte membrane can be increased by increasing the fastening load of the membrane drying region as compared with other regions. The lack of moisture can be solved.

[Application Example 3]
The fuel cell system according to Application Example 1, wherein the fastening load control unit is configured to fasten the entire single cell by driving the fastening mechanism when the membrane dryness detection unit detects water shortage of the electrolyte membrane. A fuel cell system that increases a load, and then, when the flooding detection unit detects flooding, drives the fastening mechanism to reduce the fastening load in the flooding region as compared to other regions. According to the fuel cell system described in Application Example 3, even if the electrolyte membrane has insufficient moisture in any region of the single cell, the electrolyte membrane has insufficient moisture by increasing the fastening load of the entire single cell. Can be solved. Further, when flooding occurs in the flooding area by increasing the fastening load of the entire single cell, the flooding can be eliminated by reducing the fastening load in the flooding area compared to other areas. .

[Application Example 4]
4. The fuel cell system according to any one of application examples 1 to 3, wherein the flooding detection unit detects a voltage drop in the fuel cell and serves as a flow path through which a reaction gas used for an electrochemical reaction flows. A fuel cell system for detecting occurrence of flooding when an increase in pressure loss is detected in a gas flow path in a fuel cell formed in a battery. According to the fuel cell system described in the application example 4, the flooding can be detected with high accuracy by combining the voltage drop of the fuel cell and the increase of the pressure loss in the gas flow path in the fuel cell.

[Application Example 5]
The fuel cell system according to any one of Application Examples 1 to 4, wherein the membrane dryness detection unit detects the voltage drop in the fuel cell and detects the increase in resistance in the fuel cell. A fuel cell system that detects water shortage in an electrolyte membrane. According to the fuel cell system described in Application Example 5, it is possible to accurately detect the moisture shortage of the electrolyte membrane by combining the voltage drop of the fuel cell and the resistance increase in the fuel cell.

[Application Example 6]
The fuel cell system according to any one of Application Examples 1 to 5, wherein the flooding region is formed from an in-cell gas flow path formed in the single cell as a flow path through which a reaction gas to be subjected to an electrochemical reaction flows. It is a region near the reaction gas outlet from which the reaction gas is discharged outside the single cell, and the membrane drying region is a reaction gas to which the reaction gas is supplied from outside the single cell to the gas flow path in the cell. A fuel cell system in the vicinity of the supply port. According to the fuel cell system described in Application Example 6, the region near the reaction gas discharge port through which the reaction gas having a relatively high humidity flows is set as a flooding region, and the reaction gas supply port through which the reaction gas having a relatively low humidity flows. By setting the vicinity region as the membrane drying region, flooding and water shortage of the electrolyte membrane can be appropriately suppressed.

[Application Example 7]
The fuel cell system according to Application Example 6, wherein the single cell is disposed so as to sandwich a membrane-electrode assembly in which electrodes are formed on both surfaces of the electrolyte membrane, and the membrane-electrode assembly. A gas separator having a pair of gas diffusion layers made of a conductive porous body and irregularities disposed on the gas diffusion layer to form the in-cell gas flow path between the gas diffusion layer and the gas diffusion layer And the in-cell gas flow path is a groove-shaped flow path parallel to each other for guiding the reaction gas so as to go straight from the reaction gas supply port side to the reaction gas discharge port side. The first flow path includes a first flow path and a second flow path, and one end of the first flow path is opened on the reaction gas supply port side and the other end is closed. The second flow path has one end disposed in the vicinity of the reaction gas supply port. Fuel cell system but with the closure and the other end is open in the reaction gas outlet side. According to the fuel cell system described in Application Example 7, in particular, water shortage of the electrolyte membrane easily occurs on one end side of the first flow path, and the other end portions of the first and second flow paths. Since flooding is likely to occur on the side, the effect of suppressing flooding and lack of moisture in the electrolyte membrane can be significantly obtained.

[Application Example 8]
8. The fuel cell system according to Application Example 6 or 7, wherein the in-cell gas flow path is a flow path through which an oxidizing gas containing oxygen flows as the reaction gas. According to the fuel cell system described in Application Example 8, the upstream side of the oxidation gas flow path, which is the flow path on the cathode side where generated water is generated in response to the electrochemical reaction, is set as the membrane drying region, and the downstream side is flooded. By setting the area, it is possible to accurately suppress the deterioration of the battery performance due to the insufficient moisture of the electrolyte membrane and the flooding.

[Application Example 9]
A fuel cell system comprising a fuel cell having a single cell including an electrolyte membrane and an electrode,
A flooding detection unit for detecting occurrence of flooding in the fuel cell;
A membrane dryness detection unit for detecting water shortage in the electrolyte membrane provided in the fuel cell;
A fastening mechanism that applies a fastening load to the fuel cell in the stacking direction of the electrolyte membrane and the electrode, and can apply a uniform fastening load to the single cell, and varies depending on a region in the single cell. A fastening mechanism capable of applying a fastening load;
When the flooding detection unit detects the occurrence of flooding, by driving the fastening mechanism, at least reduce the fastening load of the flooding region, which is a region where flooding is determined to occur in the single cell, When the membrane dryness detection unit detects water shortage of the electrolyte membrane, the membrane is a region where at least the water shortage in the electrolyte membrane is determined to occur in the single cell by driving the fastening mechanism A fuel cell system comprising: a fastening load control unit that increases the fastening load in the dry region.

  According to the fuel cell system described in Application Example 9, when flooding occurs, the flooding can be eliminated by reducing at least the fastening load in the flooding region, and when water shortage of the electrolyte membrane occurs, at least the membrane Membrane drying can be eliminated by increasing the fastening load in the drying region.

  The present invention can be realized in various forms other than those described above. For example, the present invention can be realized in the form of a control method for a fuel cell system.

1 is a block diagram illustrating a schematic configuration of a fuel cell system 10. FIG. 3 is a schematic cross-sectional view showing a configuration of a single cell 70. FIG. 7 is a plan view showing the shape of a gas separator 77. FIG. It is explanatory drawing which shows arrangement | positioning of the flooding area | region E and the film | membrane drying area | region D. FIG. It is a flowchart showing a fastening load control processing routine. It is explanatory drawing which shows an example of a current-voltage characteristic (IV characteristic). It is a flowchart showing a fastening load control processing routine. It is a flowchart showing a fastening load control processing routine.

A. Configuration of the fuel cell system 10:
FIG. 1 is a block diagram showing a schematic configuration of a fuel cell system 10 according to a first embodiment of the present invention. The fuel cell system 10 includes a fuel cell 15, a hydrogen tank 20, a hydrogen circulation pump 23, a compressor 30, pressure sensors 42 and 43, and a control unit 45.

  The fuel cell 15 is a polymer electrolyte fuel cell, and includes a stack 18 formed by stacking a plurality of single cells 70 as a power generator. The stack 18 is configured by sequentially arranging a current collecting plate and an insulating plate (not shown) having output terminals, and end plates 16 and 17 at both ends of a laminated body formed by laminating a plurality of single cells 70. ing. Further, the fuel cell 15 is provided with a voltage sensor 40 that detects the voltage of each single cell 70 constituting the fuel cell 15. Further, the fuel cell 15 is provided with a resistance measuring unit 44 for measuring the resistance of the entire stack 18. The resistance measurement unit 44 measures the AC impedance between the positive and negative bipolar terminals by detecting the alternating current flowing between the bipolar terminals when the AC voltage is input to the bipolar terminals of the stack 18 while sweeping the frequency. It is a known device. Further, the fuel cell 15 is provided with a fastening portion 50.

  The fastening portion 50 includes a fastening mechanism that holds the stack 18 in a state where a fastening load is applied in the stacking direction of the single cells 70. The stack 18 is fixed on an end plate 16 which is one end. A fastening portion 50 that can change the fastening load applied to the stack 18 via the end plate 17 is provided on the end plate 17 side that is the other end. The fastening portion 50 includes a plurality of springs 51 and a plurality of actuators 52 that apply a fastening load to the end plate 17 via the springs 51. Each actuator 52 includes a servo motor (not shown), and the magnitude of the fastening load applied to the end plate 17 by each actuator 52 can be adjusted by the drive control of the servo motor. The fastening load applied to the stack 18 can be made uniform in the cell plane or can be made different in the cell plane by the drive control of the servo motor provided in each actuator 52. The stack 18 is further provided with a load cell 53 at a position corresponding to each actuator 52 so that a fastening load applied by the actuator 52 can be detected. When driving the servo motor, feedback control is performed based on the detection signal of the load cell 53. The configuration of the fuel cell 15 and the fastening load control by the fastening portion 50 will be described in detail later.

  The hydrogen tank 20 is a storage device that stores hydrogen gas as a fuel gas, and is connected to the stack 18 via a hydrogen supply channel 25. On the hydrogen supply flow path 25, a hydrogen cutoff valve 21 and a modulatable pressure valve 22 are provided in order from the hydrogen tank 20. The adjustable pressure valve 22 is a pressure regulating valve capable of adjusting the hydrogen pressure (hydrogen amount) supplied from the hydrogen tank 20 to the fuel cell 15. The hydrogen tank 20 may be a hydrogen cylinder that stores high-pressure hydrogen gas, or a hydrogen storage alloy that stores hydrogen by storing a hydrogen storage alloy and storing the hydrogen in the hydrogen storage alloy.

  A hydrogen discharge channel 26 is further connected to the stack 18. A purge valve 24 is provided in the hydrogen discharge channel 26. Further, a connection flow path 27 is provided by connecting the hydrogen supply flow path 25 and the hydrogen discharge flow path 26. The connection flow path 27 is connected to the hydrogen supply flow path 25 on the downstream side of the adjustable pressure valve 22 and is connected to the hydrogen discharge flow path 26 on the upstream side of the purge valve 24. The connection flow path 27 is provided with a hydrogen circulation pump 23 that generates a driving force when hydrogen circulates in the flow path.

  Hydrogen supplied from the hydrogen tank 20 via the hydrogen supply flow path 25 is supplied to the electrochemical reaction in the fuel cell 15 and discharged to the hydrogen discharge flow path 26. The hydrogen discharged to the hydrogen discharge channel 26 is guided again to the hydrogen supply channel 25 via the connection channel 27. As described above, in the fuel cell system 10, hydrogen is part of the hydrogen discharge passage 26, the connection passage 27, part of the hydrogen supply passage 25, and the fuel gas passage formed in the fuel cell 15. (These flow paths are collectively referred to as a hydrogen circulation flow path). When the fuel cell 15 generates power, the purge valve 24 is normally closed. However, when impurities (nitrogen, water vapor, etc.) in the circulating hydrogen increase, the purge valve 24 is appropriately opened, Part of the hydrogen gas with increased impurity concentration is discharged outside the system. Further, when the amount of hydrogen in the hydrogen circulation channel is insufficient due to the consumption of hydrogen due to the progress of the electrochemical reaction or the opening of the purge valve 24, the hydrogen tank 20 is transferred from the hydrogen tank 20 to the hydrogen circulation channel via the adjustable pressure valve 22. And hydrogen is supplemented.

  The compressor 30 is a device that takes in air from the outside, compresses it, and supplies it as an oxidizing gas to the fuel cell 15, and is connected to the stack 18 via an air supply flow path 31. In addition, an air discharge channel 32 is further connected to the stack 18. The air supplied from the compressor 30 via the air supply flow path 31 is subjected to an electrochemical reaction in the fuel cell 15 and discharged to the outside of the fuel cell 15 via the air discharge flow path 32. The air supply flow path 31 and the air discharge flow path 32 are provided with pressure sensors 42 and 43 for detecting the pressure of the oxidizing gas in the flow path in the vicinity of the connection portion with the stack 18, respectively.

  The control unit 45 is configured as a logic circuit centered on a microcomputer, and more specifically, a CPU that executes predetermined calculations in accordance with a preset control program, and controls necessary for executing various arithmetic processes by the CPU. A ROM in which programs, control data, and the like are stored in advance, a RAM in which various data necessary for performing various arithmetic processes in the CPU, and an input / output port for inputting and outputting various signals are also provided. The control unit 45 outputs a drive signal to the compressor 30, the hydrogen cutoff valve 21, the adjustable pressure valve 22, the hydrogen circulation pump 23, the purge valve 24, the actuator 52, and the like. Also, detection signals are acquired from the voltage sensor 40, the pressure sensors 42, 43, and the like.

B. Configuration of the fuel cell 15:
FIG. 2 is a schematic cross-sectional view showing the configuration of the single cell 70 constituting the fuel cell 15. The single cell 70 includes an electrolyte membrane 71 and an anode 72 and a cathode 73 that are electrodes including a catalyst formed on both surfaces of the electrolyte membrane 71. In addition, gas diffusion layers 74 and 75 are provided to sandwich the electrolyte membrane 71 on which the electrodes are formed from both sides. Further, gas separators 76 and 77 are provided on the gas diffusion layers 74 and 75. An in-cell fuel gas flow path 78 through which the fuel gas flows is formed between the gas separator 76 and the gas diffusion layer 74, and an in-cell oxidation through which an oxidizing gas flows between the gas separator 77 and the gas diffusion layer 75. A gas flow path 79 is formed. Although not shown in FIG. 2, an inter-cell refrigerant flow path through which a refrigerant flows is formed between adjacent single cells 70.

  The electrolyte membrane 71 is a proton-conductive ion exchange membrane formed of a solid polymer material, for example, a fluorine-based resin, and exhibits good electrical conductivity in a wet state. The anode 72 and the cathode 73 include a catalyst (for example, platinum or a platinum alloy), and are formed by supporting these catalysts on a conductive carrier (for example, carbon particles). The gas diffusion layers 74 and 75 can be formed of a conductive member having gas permeability, such as carbon paper or carbon cloth. The gas separators 76 and 77 are made of a gas-impermeable conductive member, for example, a dense carbon that is made impermeable by compressing carbon, baked carbon, or a metal material such as stainless steel. The gas separators 76 and 77 are members that form part of the wall surfaces of the in-cell fuel gas flow path 78 and the in-cell oxidizing gas flow path 79 described above. An uneven shape is formed.

FIG. 3 is a plan view showing the shape of the surface in contact with the gas diffusion layer 75 in the gas separator 77, that is, the surface forming the in-cell oxidizing gas flow path 79. In the figure, the longitudinal direction of the gas separator 77 is represented as the A direction, and the direction perpendicular to the A direction is represented as the B direction. The gas separator 77 has holes 60 to 65 formed in the vicinity of the outer periphery along two sides in the B direction. When a fuel cell is assembled by stacking a plurality of single cells 70, holes provided at corresponding positions of the separators overlap each other to form a flow path that penetrates the fuel cell in the stacking direction of the gas separators. Specifically, the hole 63 forms an oxidizing gas supply manifold that distributes the oxidizing gas to the in-cell oxidizing gas flow path 79 (shown as O ₂ in in the figure), and the hole 62 is formed in each cell. An oxidizing gas discharge manifold in which oxidizing gas collects from the oxidizing gas flow path 79 is formed (shown as O ₂ out in the figure). The hole 60 forms a fuel gas supply manifold that distributes the fuel gas to each in-cell fuel gas flow path 78 (indicated as H ₂ in in the figure), and the hole 65 has a fuel gas flow in each cell. A fuel gas discharge manifold that collects fuel gas from the passage 78 is formed (indicated as H ₂ out in the figure). The hole 61 forms a refrigerant supply manifold that distributes the refrigerant to each inter-cell refrigerant flow path (indicated as CLT in in the figure), and the hole 64 collects the refrigerant from each inter-cell refrigerant flow path. A refrigerant discharge manifold is formed (indicated as CLT out in the figure).

  In the gas separator 77 shown in FIG. 3, in a region other than the region where the holes 60 to 65 are formed, a substantially rectangular shape in which the in-cell oxidizing gas flow path 79 is formed so as to overlap the cathode 73 and the gas diffusion layer 75. This region is hereinafter referred to as a power generation region C. In FIG. 3, the power generation region C is surrounded by a broken line. A connecting portion between the power generation region C and the hole 63 constitutes an oxidizing gas supply port through which the oxidizing gas flows from the oxidizing gas supply manifold to the in-cell oxidizing gas flow path 79 in the fuel cell 15. Further, the connecting portion between the power generation region C and the hole 62 constitutes an oxidizing gas discharge port through which oxidizing gas is discharged from the in-cell oxidizing gas flow path 79 to the oxidizing gas discharge manifold in the fuel cell 15. In the middle of the power generation region C, a plurality of linear convex portions 80 and groove channels 81 are formed extending in the A direction. Each linear protrusion 80 is formed to have substantially the same length in which the relative positions in the A direction in the gas separator 77 are aligned with each other. Further, in the power generation region C, the region between the end portions of the plurality of linear convex portions 80 and the hole portions 60 to 62, and the end portion of the plurality of linear convex portions 80 and the portion between the hole portions 63 to 65. In this region, a plurality of convex portions 86 formed apart from each other are formed. The plurality of linear protrusions 80 and the plurality of protrusions 86 are in contact with the gas diffusion layer 75 and constitute part of the wall surface of the oxidizing gas flow channel in the cell. Further, in FIG. 3, it is arranged on the gas separator 77 to ensure the sealing property of the in-cell oxidizing gas flow path with the electrolyte membrane 71, and each hole 60 between other adjacent gas separators. The arrangement of the sealing member 88 that secures the sealing performance of the manifold formed by ˜65 is also described. In addition, in FIG. 3, the site | part which contacts an adjacent member is attached | subjected and shown. The oxidizing gas that has flowed into the in-cell oxidizing gas flow path from the oxidizing gas supply manifold formed by the hole 63 is guided to the space formed between the convex portions 86 on the upstream side, and into the space formed by the groove flow path 81. Distributed. The fuel gas flowing through the space formed by each groove channel 81 is guided to the space formed between the convex portions 86 on the downstream side, and is discharged to the oxidizing gas discharge manifold formed by the hole 62.

  Here, the plurality of groove flow paths 81 formed in the gas separator 77 are alternately arranged, the first groove flow paths 82 having the outlet side blocking portions 84 and the second groove paths 81 having the inlet side blocking portions 85. And a groove channel 83. The outlet-side blocking portion 84 and the inlet-side blocking portion 85 are formed in a shape that blocks the cross section of the arranged groove channel 81 without a gap. The outlet side blocking portion 84 and the inlet side blocking portion 85 can be formed of, for example, ceramics, carbon, metal, resin, or rubber, and at least a part thereof can be formed porous. Such closed portions 84 and 85 are fixed at predetermined positions of the groove channel 81 formed on the gas separator 77 by welding, adhesion, pressure bonding, or the like.

  When the oxidizing gas is supplied from the oxidizing gas supply manifold to the in-cell oxidizing gas channel 79, the oxidizing gas flows into the first groove channel 82 whose inlet is not blocked by the inlet side blocking portion 85. To do. Since the first groove channel 82 is provided with the outlet side blocking portion 84, the oxidizing gas that has flowed into the first groove channel 82 flows from the downstream end of the first groove channel 82. Cannot be discharged. Therefore, the oxidizing gas flowing into the first groove channel 82 spreads into the gas diffusion layer 75 having gas permeability. Then, in the gas diffusion layer 75, it diffuses into a region where the linear convex portion 80 provided along the first groove flow path 82 contacts and flows into the second groove flow path 83. Thereafter, the second groove channel 83 is discharged from the opened downstream end to the oxidizing gas discharge manifold side.

  The configuration of the in-cell fuel gas channel 78 formed on the gas separator 76 and the manner in which the fuel gas flows in the in-cell fuel gas channel 78 can be the same. At this time, the sealing member (a member corresponding to the sealing member 88 shown in FIG. 3) disposed on the gas separator 76 includes the in-cell fuel gas flow path 78 formed on the gas separator 76 and the holes 60 and 65. It is formed in a shape that communicates with each other.

  When the fuel cell generates electricity, water is generated at the cathode as the electrochemical reaction proceeds. At least a portion of the water produced at the cathode is vaporized into the oxidizing gas and is directed downstream of the oxidizing gas stream. Therefore, the oxidizing gas flowing in the in-cell oxidizing gas flow path 79 has a higher humidity on the downstream side, and in the in-cell oxidizing gas flow path 79, liquid water is more likely to be generated on the downstream side. In particular, since the first groove channel 82 is provided with the outlet side blocking portion 84 on the downstream side, water vapor in the oxidizing gas and liquid water generated in the channel are discharged from the first groove channel 82. It becomes difficult to be done. The downstream region of the second groove channel 83 and the region provided with the plurality of convex portions 86 in the vicinity of the hole 62 (oxidizing gas discharge manifold) are the humidity in the oxidizing gas flowing through the in-cell oxidizing gas channel. It can be said that is the highest part. Therefore, it can be said that the downstream region of the first groove channel 82 and the second groove channel 83 and the region near the hole 62 are the regions where flooding is most likely to occur. In addition, flooding means that the flow of gas to the catalyst provided in the electrode is hindered by the presence of excess liquid water in the electrode or in-cell gas flow path, and the progress of the electrochemical reaction is suppressed. .

  Further, the upstream region of the first groove channel 82 and the region provided with the plurality of convex portions 86 in the vicinity of the hole 63 (oxidizing gas supply manifold) are located in other regions in the in-cell oxidizing gas channel 79. This is a region where an oxidizing gas having a lower humidity flows. Thus, in the region where the dried gas flows, the moisture in the electrolyte membrane is taken away by the dried gas, and the electrolyte membrane is likely to be deficient in moisture. Therefore, it can be said that the upstream region of the first groove channel 82 and the region near the hole 63 are regions where the electrolyte membrane is most likely to dry. FIG. 4 is an explanatory view showing the arrangement of the above-described region where flooding is most likely to occur (hereinafter referred to as flooding region E) and the region where electrolyte membrane is most likely to dry (hereinafter referred to as membrane drying region D). .

  In the fuel cell system 10 of this embodiment, the fastening load can be changed separately in the flooding region E and the membrane drying region D in the power generation region C. Specifically, the actuator 52 provided in the fastening portion 50 includes two actuators 52, that is, an actuator disposed on the flooding region side and an actuator disposed on the film drying region side. By making the fastening load by one actuator 52 stronger than the fastening load by the other actuator 52, the end plate 17 is tilted, and the fastening load applied to the region on the one actuator 52 side can be relatively strengthened. it can.

C. Control related to fastening load:
FIG. 5 is a flowchart showing a fastening load control processing routine that is repeatedly executed during power generation by the fuel cell 15 in the CPU of the control unit 45. This routine is started when the power generation of the fuel cell 15 is started.

  When this routine is started, the CPU of the control unit 45 acquires the voltage of each single cell 70 constituting the fuel cell 15 from the voltage sensor 40 (step S100). And it is judged whether the single cell 70 whose voltage value is less than a reference value exists (step S110). FIG. 6 is an explanatory diagram showing an example of current-voltage characteristics (IV characteristics) as output characteristics of the fuel cell. As shown in FIG. 6, the fuel cell has a certain relationship between the output current and the output voltage, and the voltage value is determined when the output current value is determined. Such IV characteristics are determined for each fuel cell, and the IV characteristics vary depending on the flow rate of gas supplied to the fuel cell and the power generation conditions such as the operating temperature of the fuel cell. In the fuel cell system 10 of this embodiment, for each power generation condition such as the supply gas flow rate and the fuel cell temperature, a voltage value corresponding to the output current value is a reference voltage for determining that the fuel cell is generating power without any problem. A value (voltage value of the single cell 70) is determined in advance and stored in the control unit 45 as a map. When making the determination in step S110, the power generation condition and output current value at that time are further acquired, the reference voltage value is acquired with reference to the map, and each single cell 70 acquired in step S100 is acquired. It is determined whether or not the voltage falls below the reference voltage value. In step S110, when the voltages of all the single cells 70 are equal to or higher than the reference voltage value, it is determined that the fuel cell 15 is generating power without any trouble, and this routine is finished.

  In step S110, when the voltage of any single cell 70 is less than the reference voltage value, the CPU of the control unit 45 derives the pressure loss in the oxidizing gas flow path in the stack 18 (step S120). . In the present embodiment, the pressure loss is the detection value of the pressure sensor 42 that is the pressure of the oxidizing gas introduced into the stack 18 and the detection value of the pressure sensor 43 that is the pressure of the oxidizing gas discharged from the stack 18. It is calculated as a difference.

  Thereafter, the CPU of the control unit 45 determines whether or not the pressure loss obtained in step S120 exceeds the reference value (step S130). No flooding occurs in the stack 18, and the pressure loss when the gas flows through the stack 18 without hindrance depends on the flow rate and pressure of the gas supplied to the stack 18 and the power generation amount (hydrogen and oxygen of the fuel cell 15). Depending on the amount of consumption), it can be obtained in advance by experiment or simulation. In the present embodiment, the reference pressure loss obtained as described above is stored in the control unit 45 as a map for each supply gas condition and power generation amount. In step S130, the reference pressure loss is compared with the pressure loss derived in step S120 with reference to such a map.

  In step S130, when it is determined that the pressure loss exceeds the reference value and the pressure loss is higher than normal, it can be determined that the cause of the voltage drop is due to flooding. In this case, the CPU of the control unit 45 controls each actuator 52 of the fastening unit 50 to uniformly reduce the fastening load applied to the stack 18 (step S140). The fastening load applied to the stack 18 during normal power generation of the fuel cell 15 includes the durability of each member constituting the stack 18, the magnitude of contact resistance between the members, and the sealing by a seal member provided in the stack 18. It is set appropriately in consideration of reliability of performance. When the fastening load is reduced in step S140, the value is lower than the normal fastening load set as described above, and is set in advance as a value within which the magnitude of contact resistance and the reliability of the sealing performance are within an allowable range. Control to change the fastening load to the set value is performed.

  When the fastening load applied to the stack 18 is reduced, the gas diffusibility in the electrode and the gas diffusion layer is increased, and the amount of liquid water retained in the electrode and the gas diffusion layer can be increased. Further, since the volume of the voids in the electrode and the gas diffusion layer is increased, the liquid water staying in the electrode and the gas diffusion layer is easily discharged. Accordingly, when flooding occurs in any part of the stack 18, it is possible to eliminate the flooding by uniformly reducing the fastening load applied to the stack 18.

  When a predetermined time elapses after the operation of reducing the fastening load is performed in step S140, the CPU of the control unit 45 acquires the detection signal of the voltage sensor 40 again, and determines whether or not the voltage of each single cell 70 has recovered. Judgment is made (step S150). The time from when the fastening load is reduced until it is determined whether or not the voltage is restored depends on the power generation conditions such as the supply gas flow rate and the fuel cell temperature, and the conditions related to the amount of generated water (current power generation amount and integrated power generation amount). ) Etc., the time required to eliminate flooding may be set appropriately and stored as a map. When it is determined in step S150 that the voltage has recovered, the CPU of the control unit 45 drives each actuator 52 of the fastening unit 50 to uniformly return the fastening load (step S200). This routine ends.

  When it is determined in step S150 that the voltage has not recovered, the CPU of the control unit 45 acquires the resistance value of the stack 18 measured by the resistance measurement unit 44 (step S160). Then, it is determined whether or not the measured resistance value of the stack 18 is higher than a reference value preset and stored as a normal resistance value (step S170). The resistance value of the stack 18 is affected by the activation overvoltage, the resistance overvoltage, and the concentration overvoltage in the stack 18. Of the resistance overvoltage, it is considered that the overvoltage related to the internal resistance of each member and the activation overvoltage do not change, and the main cause of the fluctuation of the resistance value can be considered as a change in the resistance of the electrolyte membrane. Therefore, it is possible to determine the degree of moisture shortage (film drying) of the electrolyte membrane 71 based on the resistance value. However, when the fastening load applied to the stack 18 is decreased, the resistance overvoltage increases due to an increase in contact resistance, and the concentration overvoltage decreases due to an increase in the void volume in the electrode or the like. Therefore, as a reference value of the resistance used in step S170, it is determined that film drying has not occurred and the fuel cell 15 is generating electricity without any problems in consideration of resistance overvoltage and concentration overvoltage when the fastening load is reduced. A resistance value is set in advance.

  When it is determined in step S170 that the resistance value has increased, it can be determined that the cause of the voltage not recovering even when the fastening load is decreased is film drying. In this case, the CPU of the control unit 45 controls each actuator 52 of the fastening unit 50 to return the fastening load on the membrane drying region D side (step S180).

  The operation of reducing the fastening load in step S140 acts in the direction of eliminating flooding as described above. However, by increasing the gas diffusibility in the electrode and the gas diffusion layer, moisture is removed from the electrolyte membrane by the gas. The amount may also increase, resulting in a shortage of water in the electrolyte membrane. Further, from the beginning of reducing the fastening load in step S140, it is conceivable that one of the causes of the voltage drop is a lack of moisture in the electrolyte membrane in addition to the occurrence of flooding. Such a shortage of water in the electrolyte membrane is particularly likely to occur in a region where a gas having a relatively low humidity flows, that is, the membrane drying region D described above. Therefore, in step S180, by returning the fastening load on the membrane drying region D side, the gas diffusibility in the membrane drying region D is suppressed, and the removal of moisture from the electrolyte membrane in the membrane drying region D is suppressed, Eliminates moisture deficiencies in electrolyte membranes.

  Thereafter, the CPU of the control unit 45 acquires the detection signal of the voltage sensor 40 again, and determines whether or not the voltage of each single cell 70 has been recovered (step S190). Then, when the voltage recovers, each actuator 52 of the fastening portion 50 is driven to return the fastening load to a normal state where the whole is uniform (step S200), and this routine is finished.

  In step S130, when the pressure loss is equal to or less than the reference value and no increase in pressure loss is recognized, the CPU of the control unit 45 acquires the resistance value of the stack 18 measured by the resistance measurement unit 44 (step S210). Then, it is determined whether or not the acquired resistance value is higher than the reference value (step S220). The processes in steps S210 and S220 are processes for determining film drying, similar to steps S160 and S170 described above. However, since the process of lowering the fastening load is not performed in steps S210 and 220, the reference value used in step S220 is the resistance value when the fuel cell 15 generates power without trouble when a normal fastening load is applied. Are preset and used.

  When it is determined in step S220 that the resistance value has increased, it can be determined that the cause of the voltage drop is not the flooding but the moisture shortage (film drying) of the electrolyte membrane 71. In this case, the CPU of the control unit 45 controls each actuator 52 of the fastening unit 50 to increase the fastening load on the film drying region D side higher than usual (step S230). When the fastening load is partially increased in step S230, the durability of the constituent members is within an allowable range, and the influence on the sealing performance due to the change of the fastening pressure in the plane is set in advance as the allowable range. Control to change the fastening load to the set value is performed.

  Thereafter, the CPU of the control unit 45 acquires the detection signal of the voltage sensor 40 again, and determines whether or not the voltage of each single cell 70 has been recovered (step S240). When the voltage recovers, each actuator 52 of the fastening portion 50 is driven to return the fastening load to a normal state where the whole is uniform (step S250), and this routine is finished.

  When it is determined in steps S170 and S220 that the resistance value has not increased, the CPU of the controller 45 determines that the cause of the voltage drop is due to other factors that are neither flooding nor film drying (step S1). S260), this routine is finished.

  According to the fuel cell system 10 configured as described above, the fastening load applied to the stack 18 can be changed uniformly as a whole, and compared to the fastening load on the flooding region E side, the membrane drying region D side It is possible to perform control to increase the fastening load. Therefore, it becomes possible to suppress the shortage of water in the electrolyte membrane while suppressing flooding.

  Here, the problems related to the amount of moisture in the electrolyte, such as flooding and membrane drying, can be solved by controlling the flow rate of gas supplied to the fuel cell, the amount of moisture in the supplied gas, or the amount of power generation (the amount of generated water). There is. However, since flooding and membrane drying are generally defects that occur in a part of the cell surface, the above-mentioned problems can be solved by controlling the supply gas and power generation amount, that is, controlling the moisture amount in the entire fuel cell. It is difficult to resolve properly. On the other hand, in the present embodiment, the above-described problem can be solved efficiently by a simple configuration in which the actuator is driven to vary the fastening pressure applied to the stack in the plane.

  In this embodiment, when the voltage drop of the stack 18 is determined in step S110, the voltage is detected for all the single cells 70. However, the voltage of the entire stack 18 can be detected and determined. is there. However, by detecting the voltage of all the single cells 70 and making a determination for each single cell, even if one cell falls below the reference value, measures are taken to prevent deterioration in performance due to flooding or film drying more quickly. It becomes possible to detect well. And while the degree of performance degradation due to flooding or film drying is small, the performance degradation can be recovered more quickly.

  In this embodiment, when it is determined that the pressure loss is increased in step S130 and flooding is considered to occur, the fastening load of the entire stack 18 is once reduced uniformly. For this reason, the flooding can be eliminated not only in the above-described flooding area E but also in the case where flooding occurs in any position in the cell plane.

  Further, in FIG. 5, after the fastening load is reduced in step S140, when the voltage is not recovered in step S150, the resistance value is immediately measured to determine whether or not the film is dried. Also good. For example, when the voltage is not recovered in step S150, the pressure loss may be derived again to check whether the flooding has been eliminated. When the flooding has not been eliminated, the state in which the fastening load is reduced may be maintained, and the flooding may be subsequently eliminated for a predetermined time. Even if the degree of flooding is particularly large due to some factor, flooding can be reliably eliminated.

  Further, in FIG. 5, when it is determined in step S170 that the resistance value has increased, only the fastening load on the membrane drying region D side is restored, but a different configuration may be used. For example, the fastening load of the entire stack 18 may be temporarily restored, and then the fastening load on the membrane drying region D side may be increased from the normal state as in step S230. By increasing the fastening load on the membrane drying region D side as compared with other regions, it is possible to obtain a similar effect that achieves both elimination of flooding and elimination of membrane drying.

D. Second embodiment:
In the first embodiment, when a drop in the voltage of the fuel cell is detected, first, whether or not flooding has occurred is determined first, and whether or not film drying has occurred is determined later. It is also good. Hereinafter, as a second embodiment, when a voltage drop of the fuel cell is detected, first, it is determined whether or not film drying has occurred first and then whether or not flooding has occurred is described later. . Since the fuel cell system 10 of the second embodiment has the same configuration as that of the first embodiment, detailed description thereof is omitted. FIG. 7 is a flowchart showing a fastening load control process routine executed in place of the process shown in FIG. 5 in the CPU of the control unit 45 of the fuel cell system 10 of the second embodiment.

  In the process shown in FIG. 7, the CPU of the control unit 45 acquires the voltage of each single cell 70 from the voltage sensor 40 (step S300), as in step S100, and the voltage value is the reference value as in step S110. It is determined whether or not there is a single cell 70 that falls below (step S310). When the voltage of any single cell 70 is less than the reference voltage value, the control unit 45 acquires the resistance value of the stack 18 measured by the resistance measurement unit 44 (step S320), and acquires the acquired resistance value. Is determined to be higher than the reference value (step S330). The processes in steps S320 and S330 are the same as those in steps S210 and S220 in FIG.

  When it is determined in step S330 that the resistance value is higher than the reference value, it can be determined that the cause of the voltage drop is film drying. Therefore, the CPU of the control unit 45 causes each actuator of the fastening unit 50 to 52 is driven to perform control to uniformly increase the fastening load applied to the stack 18 (step S340). When increasing the fastening load in step S340, control for changing the fastening load to a value higher than the normal fastening load and set in advance as a value within which the durability of each member is within an allowable range. Is done. By increasing the fastening load of the entire stack 18, the gas diffusibility in the electrode and the gas diffusion layer is lowered, moisture tends to stay in the electrode and the gas diffusion layer, and the amount of moisture taken away by the gas can be suppressed. it can. Therefore, even when film drying is progressing at any location, it is possible to eliminate this film drying by uniformly increasing the fastening load applied to the stack 18. Further, by uniformly increasing the fastening load, the contact resistance between the constituent members of the stack 18 decreases, and such a decrease in contact resistance also contributes to an increase in the voltage of the stack 18.

  After increasing the fastening load, after a predetermined time has elapsed, the CPU of the control unit 45 determines whether or not the voltage of each single cell 70 has recovered (step S350), and when the voltage is recovered, the fastening unit The 50 actuators 52 are driven to return the fastening load applied to the entire stack 18 (step S400), and this routine ends. Note that the time from when the fastening load is increased to when it is determined whether or not the voltage is restored depends on the power generation conditions such as the flow rate of the supply gas and the fuel cell temperature, and the conditions related to the amount of generated water (current power generation amount and integration The time required for recovering the water content of the electrolyte membrane 71 may be appropriately set based on the power generation amount) and stored as a map.

  When it is determined in step S350 that the voltage has not recovered, the CPU of the control unit 45 derives the pressure loss in the oxidizing gas flow path in the stack 18 in the same manner as in step S120 (step S360). It is determined whether or not the pressure loss has exceeded the reference value (step S370). When the determination in step S370 is made, the fastening load is in an increased state. In such a state, the pressure loss when the gas flows through the stack 18 without any trouble is the flow rate of the fuel gas and the oxidizing gas supplied to the stack 18. It can be obtained in advance by experiment or simulation according to the pressure and the power generation amount (consumption of hydrogen and oxygen) in the fuel cell 15. In the present embodiment, the reference pressure loss obtained as described above is stored in the control unit 45 as a map for each supply gas condition and power generation amount.

  If it is determined in step S370 that the pressure loss has increased, it can be determined that the occurrence of flooding is the cause of the voltage not recovering even if the fastening load is increased. In this case, the CPU of the control unit 45 controls each actuator 52 of the fastening unit 50 to return the fastening load on the flooding region E side (step S380).

  When the film drying is suppressed by the operation of increasing the fastening load in step S340, flooding may occur due to a decrease in the amount of moisture removed from the electrode or gas diffusion layer by the gas. Further, from the beginning of increasing the fastening load in step S340, it may be considered that flooding has occurred in addition to film drying as one of the causes of voltage drop. Such flooding is particularly likely to occur in a region where a gas with relatively high humidity flows, that is, the above-described flooding region E. Therefore, in step S380, the fastening load on the flooding region E side is restored to improve the gas diffusibility in the flooding region E, thereby promoting the discharge of liquid water in the flooding region E.

  Thereafter, the CPU of the control unit 45 acquires the detection signal of the voltage sensor 40 again, and determines whether or not the voltage of each single cell 70 has been recovered (step S390). When the voltage recovers, each actuator 52 of the fastening portion 50 is driven to return the fastening load to a normal state where the whole is uniform (step S400), and this routine is finished.

  In step S330, when the resistance value is equal to or less than the reference value and no increase in resistance value is recognized, the CPU of the control unit 45 derives the pressure loss in the oxidizing gas flow path in the stack 18 (step S410). It is determined whether or not the derived pressure loss is increased compared to the reference value (step S420). The processes in steps S410 and S420 are the same as those in steps S120 and S130.

  When it is determined in step S420 that the pressure loss has increased, it can be determined that the cause of the voltage drop is the occurrence of flooding. In this case, the CPU of the control unit 45 controls each actuator 52 of the fastening unit 50 to lower the fastening load on the flooding region E side than usual (step S430). When the fastening load is partially reduced in step S430, the value is lower than the normal fastening load, and the value is set in advance as a value in which the contact resistance and the reliability of the sealing performance are within the allowable range. Then, control for changing the fastening load is performed.

  Thereafter, the CPU of the control unit 45 acquires the detection signal of the voltage sensor 40 again, and determines whether or not the voltage of each single cell 70 has been recovered (step S440). When the voltage recovers, each actuator 52 of the fastening portion 50 is driven to return the fastening load to a normal state where the whole is uniform (step S450), and this routine is finished.

  When it is determined in steps S370 and S420 that the pressure loss has not increased, it is determined that the cause of the voltage drop is due to other factors that are neither flooding nor film drying (step S460). finish.

  According to the fuel cell system 10 of the second embodiment configured as described above, the fastening load applied to the stack 18 can be changed uniformly as a whole, and the fastening load on the flooding region E side can be changed to the membrane drying. Control to make it smaller than the fastening load on the region D side can be performed. Therefore, it is possible to obtain the same effect as that of the first embodiment that suppresses the water shortage of the electrolyte membrane while suppressing the flooding.

  In this embodiment, when it is determined that the resistance value has increased in step S330 and it is considered that film drying has occurred, the fastening load of the entire stack 18 is once increased uniformly. . For this reason, the film drying can be solved not only in the above-described film drying region D but also in the case where the film drying occurs at any position in the cell plane.

  In FIG. 7, when it is determined that the voltage has not recovered in step S350 after increasing the fastening load of the entire stack 18 in step S340, the pressure loss is immediately derived to determine the presence or absence of flooding. However, different configurations may be used. For example, when the voltage is not recovered in step S350, a resistance value may be derived again to check whether film drying has been eliminated. When the film drying has not been eliminated, the state in which the fastening load is increased may be maintained, and the film drying may subsequently be eliminated for a predetermined time. Even if the degree of film drying is particularly large due to some factor, it becomes possible to reliably eliminate film drying.

  Further, in FIG. 7, when it is determined in step S370 that the pressure loss has increased, only the fastening load on the flooding region E side is restored, but a different configuration may be used. For example, the fastening load of the entire stack 18 may be restored once, and then only the fastening load on the flooding region E side may be reduced in the same manner as in step S430. By reducing the fastening load on the flooding region E side as compared with other regions, the same effect can be obtained that achieves both elimination of flooding and elimination of film drying.

E. Third embodiment:
In the first and second embodiments, when flooding or film drying is first detected, the fastening load of the entire stack 18 is once changed, but a different configuration may be used. When flooding or film drying is highly likely to occur at a specific location, control may be performed to increase the fastening load on the flooding area E side when detecting flooding and to decrease the fastening load on the film drying area D side when detecting film drying. . Such a configuration will be described below as a third embodiment. Since the fuel cell system 10 of the third embodiment has the same configuration as that of the first embodiment, detailed description thereof is omitted. FIG. 8 is a flowchart showing a fastening load control process routine executed in place of the process shown in FIG. 5 in the CPU of the control unit 45 of the fuel cell system 10 of the third embodiment.

  In FIG. 8, steps S500 to S530 are the same processes as steps S100 to S130. Here, when the CPU of the control unit 45 determines that the pressure loss has increased in step S530, it determines that the cause of the voltage drop is the occurrence of flooding, and reduces the fastening load on the flooding region E side. Control is performed (step S540). This step S540 is the same processing as step S430. Thereafter, when recovery of pressure loss is detected (step S550), the CPU of the controller 45 temporarily returns the fastening load (step S560), and determines whether or not the voltage is recovered (step S570). If the voltage is recovered, this routine is terminated. If the voltage has not recovered, the CPU of the controller 45 continues to measure the resistance value (step S580), determines whether or not the resistance value has increased (step S590), and the resistance value has increased. If so, the fastening load on the membrane drying region D side is increased (step S600). Steps S580 to S600 are the same steps as steps S210 to 230. Thereafter, when the recovery of the resistance value is detected (step S610), the CPU of the control unit 45 restores the fastening load (step S620), and if the voltage is recovered (step S630), the routine ends. To do.

  If it is determined in step S530 that the pressure loss has not increased, the CPU of the control unit 45 executes the processes in and after step S580 without performing the process related to the elimination of flooding. Further, when it is determined in step S590 that the resistance value has not increased and in step S630 it is determined that the voltage has not recovered, the CPU of the control unit 45 causes the film to dry even if flooding occurs. However, it is determined that this is due to other factors (step S260), and this routine is terminated.

  According to the fuel cell system 10 of the third embodiment configured as described above, the fastening load on the flooding region E side is reduced when flooding is detected, and the membrane drying region D side is detected when membrane drying is detected. The fastening load is increased. Therefore, it is possible to obtain the same effect as that of the first embodiment that suppresses the water shortage of the electrolyte membrane while suppressing the flooding. In FIG. 8, when a voltage drop is detected in step S510, the presence / absence of flooding is determined first and then the presence / absence of film resistance is determined. However, the order may be reversed.

F. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

F1. Modification 1:
In the first to third embodiments, it is determined that there is a possibility that flooding or film drying has occurred if there is even one single cell whose voltage is lower than the reference value among the single cells 70 constituting the stack 18. However (steps S100, S110, S300, S310, S500, S510), different configurations may be used. For example, when the voltage of a predetermined number of single cells of 2 or more falls below a reference value, it may be determined that flooding or film drying may have occurred. Alternatively, when the output voltage of the entire stack falls below the reference value, it may be determined that there is a possibility that flooding or film drying has occurred.

  Note that even if the IV characteristics of the fuel cell deteriorate due to flooding or membrane drying, it may not be detected as a voltage drop. For example, the fuel cell stack is connected in parallel to the secondary battery with respect to the load, and power can be supplied to the load from both the fuel cell stack and the secondary battery, and the DC / DC provided in the wiring A configuration in which the output of the fuel cell stack and the secondary battery is controlled by the voltage command value of the DC converter is conceivable. In such a configuration, when the voltage command value of the DC / DC converter is set in order to obtain the desired power corresponding to the load request from the fuel cell stack, the fuel cell is deteriorated when the IV characteristic of the fuel cell is deteriorated. The voltage of the stack does not decrease, but the output current of the fuel cell stack decreases, and the insufficient power is supplemented from the secondary battery. Therefore, in such a configuration, it is only necessary to determine a decrease in the output current value of the fuel cell instead of a decrease in the voltage of the fuel cell, and it is only necessary to determine a decrease in the IV characteristic of the fuel cell stack.

F2. Modification 2:
In the first to third embodiments, it is determined that flooding occurs when the pressure loss increases when the voltage drops (when the IV characteristic decreases). However, even if the occurrence of flooding is determined by a different configuration, good. For example, flooding is the cause of the voltage drop when a high load operation (operation in which the amount of generated water is greater than the reference value) is performed when the voltage drop (IV characteristic drop) exceeds the predetermined reference value. You may judge that there is.

  In addition, as a voltage reduction factor other than flooding and film drying, for example, deterioration of each member (a catalyst layer, a gas diffusion layer, etc.) constituting the stack can be considered. It is considered that the voltage drop due to such deterioration of the member proceeds very slowly as compared with the voltage drop due to flooding or film drying, and the degree of voltage drop is accumulated slowly over a long time. In addition, unlike the problems relating to the amount of water in the fuel cell such as flooding and membrane drying, it is extremely difficult to achieve recovery by control. Therefore, when the accumulated time since the start of use of the fuel cell stack is long and a voltage drop determined to be caused by other factors occurs, the reference used for the voltage drop judgment (steps S110, S310, S510, etc.) The value may be corrected. This makes it possible to omit an operation by detecting a voltage drop due to a cause that is difficult to recover in subsequent processing.

F3. Modification 3:
In the first to third embodiments, the occurrence of flooding is determined based on the pressure loss on the oxidizing gas flow path side. However, instead of or in addition to such a configuration, the pressure on the fuel gas flow path side is determined. A determination based on loss may be made. Due to the nature of the fuel cell system, if there is a high possibility that the flow path where flooding occurs is on the specific gas flow path side, it may be determined only on the flow path side where flooding is likely to occur. By determining, the accuracy of flooding detection can be improved.

F4. Modification 4:
In the first to third embodiments, in the fastening portion 50, the two actuators 52 are provided corresponding to the flooding region E and the film drying region D. However, three or more actuators are provided, and the fastening pressure is in-plane. You may control more finely the grade which varies. Further, the degree to which the fastening load on the flooding area E side is decreased compared to the normal fastening load or the degree to which the fastening load on the membrane drying area D side is increased compared to the normal fastening load is only one stage each. Instead of being changeable, it may be changeable in two or more stages. Depending on the degree of flooding detected or the degree of film drying, the control of varying the fastening load in the plane may be performed more finely.

F5. Modification 5:
In the first to third embodiments, the in-cell oxidizing gas flow path includes a first groove flow path 82 having an outlet-side blocking portion 84 and a second groove flow path 83 having an inlet-side blocking portion 85. Although it is configured by alternately arranging, different flow path shapes may be used. In the first to third embodiments, the upstream side of the oxidizing gas flow is the film drying region D and the downstream side is the flooding region E in the cell plane. However, different configurations may be used. Ease of stagnation of liquid water and ease of membrane drying depends on the shape of the gas flow path (gas flow direction) in the cell surface, gas flow rate and power generation amount (the amount of generated water), environmental temperature, and temperature in the fuel cell. Influenced by distribution. Therefore, depending on the assumed operating conditions of the fuel cell and the environment in which the fuel cell is installed, an area that is prone to flooding and an area that is prone to membrane drying are set in advance for each fuel cell used experimentally or by simulation. In addition, the fastening load may be adjusted for each region.

F6. Modification 6:
In the first to third embodiments, in the cell plane, an area considered to be easily flooded is set as a flooding area in advance, and an area considered to be easily dried is set as a film drying area. The area where the film is dry or the area where the film is dry may be determined each time based on the actually detected value. For example, the temperature of a plurality of locations in a single cell surface is measured by a temperature sensor, an area having a relatively low temperature is determined as a flooding area, an area having a relatively high temperature is determined as a film drying area, Similar control may be performed. In this case, the actuator to be driven is selected from the actuators provided in the fastening portion so that the fastening load in the determined region can be changed, and the driving direction is determined according to the flooding and the film drying. That's fine. Further, in the cell plane, the membrane drying region may be set by detecting the resistance distribution, or the flooding region may be set by detecting the pressure loss distribution in the in-cell gas flow path. .

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 15 ... Fuel cell 16, 17 ... End plate 18 ... Stack 20 ... Hydrogen tank 21 ... Hydrogen cutoff valve 22 ... Modulatable pressure valve 23 ... Hydrogen circulation pump 24 ... Purge valve 25 ... Hydrogen supply flow path 26 ... Hydrogen Discharge flow path 27 ... Connection flow path 30 ... Compressor 31 ... Air supply flow path 32 ... Air discharge flow path 40 ... Voltage sensor 42, 43 ... Pressure sensor 44 ... Resistance measurement part 45 ... Control part 50 ... Fastening part 51 ... Spring 52 ... Actuator 53 ... Load cell 60 to 65 ... Hole 70 ... Single cell 71 ... Electrolyte membrane 72 ... Anode 73 ... Cathode 74, 75 ... Gas diffusion layer 76, 77 ... Gas separator 78 ... In-cell fuel gas flow path 79 ... In the cell Oxidizing gas flow path 80 ... Linear convex part 81 ... Groove flow path 82 ... First groove flow path 83 ... Second groove flow path 84 ... Outlet side blocking part 85 ... Inlet side blocking part 86 ... Convex part 88 ... Seal member

Claims (9)

A fuel cell system comprising a fuel cell having a single cell including an electrolyte membrane and an electrode,
A flooding detection unit for detecting occurrence of flooding in the fuel cell;
A membrane dryness detection unit for detecting water shortage in the electrolyte membrane provided in the fuel cell;
A fastening mechanism that applies a fastening load to the fuel cell in the stacking direction of the electrolyte membrane and the electrode, and can apply a uniform fastening load to the single cell, and varies depending on a region in the single cell. A fastening mechanism capable of applying a fastening load;
When the flooding detection unit detects the occurrence of flooding, the fastening mechanism is driven to reduce at least the fastening load of the flooding region that is a region preset as a region where flooding is likely to occur in the single cell, When the membrane drying detection unit detects water shortage of the electrolyte membrane, the membrane is a region set in advance as a region where water shortage in the electrolyte membrane is likely to occur at least in the single cell by driving the fastening mechanism. A fuel cell system comprising: a fastening load control unit that increases the fastening load in the dry region. The fuel cell system according to claim 1, wherein
When the flooding detection unit detects flooding, the fastening load control unit drives the fastening mechanism to reduce the fastening load of the entire single cell, and then the membrane dryness detection unit detects the electrolyte membrane. A fuel cell system that, when water shortage is detected, drives the fastening mechanism to increase the fastening load in the membrane drying region as compared to other regions. The fuel cell system according to claim 1, wherein
The fastening load control unit increases the fastening load of the entire single cell by driving the fastening mechanism when the membrane dryness detection unit detects water shortage of the electrolyte membrane, and then the flooding detection unit When the flooding is detected, the fastening mechanism is driven to reduce the fastening load in the flooding region as compared with other regions. The fuel cell system according to any one of claims 1 to 3,
The flooding detection unit detects a voltage drop in the fuel cell and causes a pressure loss in a gas flow path in the fuel cell formed in the fuel cell as a flow path through which a reaction gas used for an electrochemical reaction flows. A fuel cell system that detects the occurrence of flooding when an increase is detected. The fuel cell system according to any one of claims 1 to 4,
The membrane dry detection unit detects a water shortage in the electrolyte membrane when a voltage drop is detected in the fuel cell and a resistance increase in the fuel cell is detected. The fuel cell system according to any one of claims 1 to 5,
The flooding region is a reactive gas discharge port through which the reactive gas is discharged out of the single cell from an in-cell gas flow path formed in the single cell as a flow path through which a reactive gas to be subjected to an electrochemical reaction flows. Is a neighborhood region of
The membrane drying region is a region near a reaction gas supply port through which the reaction gas is supplied from outside the single cell to the in-cell gas flow path. The fuel cell system according to claim 6, wherein
The single cell comprises a pair of gas diffusion layers comprising a membrane-electrode assembly in which electrodes are formed on both surfaces of the electrolyte membrane, and a conductive porous body disposed so as to sandwich the membrane-electrode assembly. And a gas separator disposed on the gas diffusion layer and formed with irregularities for forming the in-cell gas flow path with the gas diffusion layer,
The in-cell gas flow passages are mutually parallel groove-like flow passages that guide the reaction gas so as to go straight from the reaction gas supply port side to the reaction gas discharge port side, and are arranged alternately. And a second flow path,
The first flow path has one end opened on the reaction gas supply port side and the other end closed.
The fuel cell system, wherein one end portion of the second flow path disposed in the vicinity of the reaction gas supply port is closed and the other end portion is opened on the reaction gas discharge port side. The fuel cell system according to claim 6 or 7, wherein
The in-cell gas channel is a channel through which an oxidizing gas containing oxygen flows as the reaction gas. A fuel cell system comprising a fuel cell having a single cell including an electrolyte membrane and an electrode,
A flooding detection unit for detecting occurrence of flooding in the fuel cell;
A membrane dryness detection unit for detecting water shortage in the electrolyte membrane provided in the fuel cell;
A fastening mechanism that applies a fastening load to the fuel cell in the stacking direction of the electrolyte membrane and the electrode, and can apply a uniform fastening load to the single cell, and varies depending on a region in the single cell. A fastening mechanism capable of applying a fastening load;
When the flooding detection unit detects the occurrence of flooding, by driving the fastening mechanism, at least reduce the fastening load of the flooding region, which is a region where flooding is determined to occur in the single cell, When the membrane drying detection unit detects water shortage of the electrolyte membrane, the membrane is determined to be at least a region where water shortage occurs in the electrolyte membrane in the single cell by driving the fastening mechanism. A fuel cell system comprising: a fastening load control unit that increases the fastening load in the dry region.

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