JP4856437B2 - Fuel cell stack - Google Patents

Description

  The present invention relates to a fuel cell stack capable of detecting a stacking load of a single cell.

  In a fuel cell stack mounted on a fuel cell vehicle or the like, end plates are arranged at both ends of a laminate formed by laminating a plurality of single cells and are held in a state where a load is applied to the laminate. . As means for applying a load to the laminate, Patent Document 1 proposes a technique for holding the laminate via an elastic member, and a predetermined pressure acts on the laminate by tightening or loosening a nut as necessary. It has become.

  By the way, in this type of fuel cell stack, the surface pressure received by the single cell stack is not necessarily uniform in each region, and there are regions where the surface pressure is large and regions where the surface pressure is small. For this reason, if the surface pressure is too high, the seal portion is liable to deteriorate, and if the surface pressure is too low, the electric resistance increases and the performance of the fuel cell stack deteriorates.

Therefore, in the fuel cell stack described in Patent Document 2, a sensor for detecting the stack load distribution is arranged at one end of the single-cell stack, and the hydraulic pressure is set at a position corresponding to the sensor at the other end. It has been proposed to appropriately adjust the stacking load in each region based on the information from the sensor by arranging the pressure generating member of the formula.
Japanese Patent Laid-Open No. 11-97054 (paragraphs 0013 to 0015, FIGS. 1 and 4) JP 2001-93564 A (paragraphs 0070 to 0072, FIG. 13)

  However, in the fuel cell stack described in Patent Document 2, since the sensor is disposed outside the end plate for holding the stacked body, it is necessary to further provide a member for supporting the sensor outside the sensor. There is a problem that the fuel cell stack becomes larger.

  In addition, in a fuel cell stack, a structure in which both ends of a single cell stack are sandwiched and held between metal end plates is generally used, so that the end plate functions as a cooling plate when used in a low temperature environment. There is a problem that the power generation efficiency is lowered due to excessive cooling of the fuel cell stack. Therefore, it has been proposed to provide a heat insulating layer between the laminated body of the single cell and the end plate. From the viewpoint of cost reduction, a separator similar to that used for the single cell is provided as a dummy cell. It has been proposed that the reaction gas flow path formed in the above function as a heat insulating layer.

  However, in order to reduce the size of the fuel cell stack, if the sensor S for detecting the pressure distribution is sandwiched between the separators 200 and 201 as shown in FIG. Even if it acts, the detection point Q1 of the sensor S is provided in a region where the convex portion of the reaction gas flow path 200a formed in the separator 200 and the convex portion of the reaction gas flow path 201a formed in the separator 201 face each other. And the case where the detection point Q2 of the sensor S is provided in the region where the concave portion of the reactive gas flow channel 200a and the concave portion of the reactive gas flow channel 201a are opposed to each other, A large stack load is output at the detection point Q1, and a low stack load is output at the detection point Q2, resulting in failure to accurately measure the stack load distribution.

  The present invention solves the above-mentioned conventional problems, and provides a fuel cell stack that can improve the detection accuracy of the stack load distribution without increasing the size of the apparatus in which dummy cells are provided. Let it be an issue.

  The present invention is a fuel cell stack in which a dummy cell in which a pair of separators are stacked in a state where each reaction gas flow channel is opposed to each other is disposed at both ends in the stacking direction of a single cell, And a sheet-like pressure distribution detecting means for measuring a stack load distribution of the single cell in a region corresponding to the electrode surface of the single cell between the separators, and both surfaces of the pressure distribution detecting means are sandwiched between conductive sheets. It is characterized by being.

  According to the present invention, by providing the conductive sheet, the output due to the shape of the separator (reactive gas flow path) is reduced, that is, the region where the stacking load is high (the part that is not the reactive gas flow path is opposed). In the region), it is difficult to deform by the conductive sheet, and the lamination load is outputted low, and in the region where the lamination load is outputted low (region where the reaction gas flow channel is opposed), the lamination load adjacent by the conductive sheet As a result, the stacking load is output to a high level in response to the deformation force in a high region. As a result, the stacking load is averaged to some extent as a whole and output. Further, since it is not necessary to provide a sensor outside the end plate for holding the single cell stack, the apparatus can be miniaturized. Note that the conductive sheet may be rigid or flexible as long as the pressure distribution can be measured relatively uniformly.

  For example, the conductive sheet is carbon paper. Since the same carbon paper as that used for a single cell (for example, a diffusion layer) can be used, it is possible to reduce the number of parts and reduce the cost by diverting the carbon paper to a conductive sheet.

  According to the present invention, in the fuel cell stack provided with the dummy cells, it is possible to improve the accuracy of the stack load distribution without increasing the size of the apparatus.

  FIG. 1 is an exploded perspective view showing a fuel cell stack according to the present embodiment, FIG. 2 is an enlarged cross-sectional view showing the main part of the fuel cell stack according to the present embodiment, and FIG. 3 shows a pressure distribution detecting means used in a dummy cell. a) is a perspective view, (b) is an AA sectional view of (a), FIG. 4 is a sectional view showing details of an end portion of the fuel cell stack of the present embodiment, and FIG. 5 is a fuel cell stack of the present embodiment. FIG. 6 is a schematic diagram for explaining the operation of the fuel cell stack according to the present embodiment.

  As shown in FIG. 1, the fuel cell stack FC of the present embodiment includes a stacked body 2 in which a plurality of single cells 1 are connected in series, end plates 3 and 4, a movable plate 5, dummy cells 6A and 6B, The slide rail 7 and the actuator 8 are included.

  As shown in FIG. 2, the unit cell 1 is abbreviated as MEA (Mebrane Electrode Assembly), in which an anode 11 is provided on one surface of an electrolyte membrane 10 and a cathode 12 is provided on the other surface. ), And a pair of separators 13 and 14 are laminated on both sides of the MEA.

  The electrolyte membrane 10 is formed of, for example, a hydrogen ion (proton) exchange membrane made of a solid polymer material. The anode 11 has a smaller area than the electrolyte membrane 10 (see FIG. 1), and includes an anode electrode 11a on which a catalyst such as platinum is supported, and a diffusion layer 11b laminated outside the anode electrode 11a. It is configured. Similarly, the cathode 12 is formed to have a smaller area than the electrolyte membrane 10 (see FIG. 1), a cathode electrode 12a carrying a catalyst such as platinum, and a diffusion layer 12b laminated outside the cathode electrode 12a. It consists of and. Each diffusion layer 11b, 12b is formed of a conductive material such as carbon paper.

  The separator 13 is formed in a plate shape with a conductive material such as a metal, is provided facing the anode 11 side, and an anode gas flow in which hydrogen (fuel gas) flows on the surface facing the anode 11. A passage (reaction gas passage) Pa is formed. The separator 14 is formed in a plate shape with a conductive member such as a metal, is provided facing the cathode 12 side, and cathode gas in which air (oxidant gas) flows on the surface facing the cathode 12. A flow path (reactive gas flow path) Pc is formed.

  As shown in FIG. 1, each of the end plates 3 and 4 is made of a thick metal plate, has an area larger than the end surface of the laminate 2, and is disposed at both ends of the laminate 2. . The end plate 3 is formed with mounting holes 3a for fixing the slide rails 7 at the four corners, and the end plate 4 is formed with insertion holes 4a through which the slide rails 7 are inserted. The end plate 4 has a plurality of through holes 4b into which the actuators 8 are inserted. The actuator 8 is set so as to be disposed on the surface (electrode surface) on which the anode electrode 11a and the cathode electrode 12a of the single cell 1 are laminated. The number of actuators 8 is not limited to eight and can be changed as appropriate.

  The movable plate 5 is made of a metal plate and is disposed inside the end plate 4. The movable plate 5 has slide holes 5a through which the slide rails 7 are inserted.

  The dummy cell 6 </ b> A is provided between one end (on the right side in the drawing) of the laminate 2 and the movable plate 5. This dummy cell 6A is capable of detecting a lamination load distribution in addition to a function as a heat insulating layer, and includes a tactile sensor (pressure distribution detecting means) S, conductive sheets 6a and 6b, separators 6c and 6d, It consists of

  As shown in FIGS. 3A and 3B, the tactile sensor S is provided such that film-like resin sheets 61 and 62 formed using polyethylene terephthalate (PET) or the like as a base material face each other. A row electrode 61a in which a plurality of linear electrodes 61a1, 61a1,... Are arranged in parallel is provided on the upper surface of the resin sheet 61, and a plurality of linear electrodes 62a1, 62a1 are provided on the lower surface of the resin sheet 62. Are arranged in parallel. A column electrode 62a is provided. Each electrode 61a1 of the row electrode 61a and each electrode 62a1 of the column electrode 62a are formed by covering the surface of the silver paste 63 with the conductive ink 64, respectively. As such a tactile sensor S, specifically, a tactile sensor manufactured by Nitta Corporation is preferably used. In the tactile sensor S formed in this way, each intersection of the row electrode 61a and the column electrode 62a becomes a detection point. When no load is applied, the electric resistance value at the detection point becomes almost infinite, As the load increases, the contact area increases and the electrical resistance value decreases. For example, the electrical resistance value is converted into a digital value in 256 steps, so that the digital value and the pressure are output in a substantially proportional relationship.

  As shown in FIG. 1, the conductive sheets 6 a and 6 b are formed of, for example, a rigid member, and are provided on both surfaces of the tactile sensor S. Further, as shown in FIG. 2, the conductive sheets 6a and 6b are brought into contact with each other at the edge (only one edge is shown) to conduct. Here, the rigidity of the conductive sheets 6a and 6b has a hardness that does not deform due to the shape of each of the anode gas flow path Pa of the separator 6c and the cathode gas flow path Pc of the separator 6d. For example, carbon paper is preferably used. By using carbon paper for the conductive sheets 6a and 6b in this way, the diffusion layers 11b and 12b used in the single cell 1 can be used as they are, so that an increase in the number of parts can be prevented and cost reduction can be achieved. It becomes possible.

  As shown in FIG. 2, the dummy cell 6B is composed only of separators 6e and 6f. The separator 6e is the same as the separator 13 (6c), the separator 6f is the same as the separator 14 (6d), and the concave portion of the anode gas flow path Pa and the concave portion of the cathode gas flow path Pc Are stacked so as to face each other and overlap each other. Thereby, a space composed of an air layer is formed by the anode gas flow path Pa and the cathode gas flow path Pc, and this space functions as a heat insulating layer. Therefore, even if the end plate 3 is made of metal due to the heat insulating function of the dummy cell 6B, the unit cell 1 is excessively cooled when used in a low temperature environment, and the power generation efficiency is reduced. Can be prevented.

  The dummy cell 6A also has a heat insulating function due to the air layers of the anode gas flow path Pa formed in the separator 6c and the cathode gas flow path Pc formed in the separator 6d, similarly to the dummy cell 6B. Even if the movable plate 5 is made of metal, it is possible to prevent a problem that the power generation efficiency is lowered due to excessive cooling of the single cell 1 when used in a low temperature environment.

  Further, since the separators 6c and 6d used for the dummy cell 6A and the separators 6e and 6f used for the dummy cell 6B are the same as the separators 13 and 14 used for each single cell 1 of the laminate 2, the number of parts can be reduced. This makes it possible to reduce costs.

  As shown in FIG. 1, in the state where the end plate 3, the dummy cell 6B, the laminated body 2, the dummy cell 6A, the movable plate 5, and the end plate 4 are laminated, four slide rails 7 are attached to the end plate 4 respectively. It is inserted into the hole 4 a, inserted into each slide hole 5 a of the movable plate 5, and fixed to each mounting hole 3 a of the end plate 3 with a nut (not shown). Then, each actuator 8 is inserted into the through hole 4b of the end plate 4 and fixed to the end plate 4 with its tip in contact. The actuator 8 includes a pressing portion 8a (see FIG. 4) capable of moving forward and backward at the tip, and the pressing portion 8a is operated in a protruding direction and a backward direction by a control device 100 described later. When the pressing portion 8a protrudes, the stacking load on the stacked body 2 is increased, and when the pressing portion 8a moves backward, the stacking load on the stacked body 2 is decreased. The end plates 3 and 4 are fixed to the vehicle body if the fuel cell stack FC of the present embodiment is mounted on a vehicle.

  As shown in FIG. 4, the movable plate 5 has a recess 5c formed on the surface facing the dummy cell 6A, and a plate-like insulator (insulator) 9 is incorporated in the recess 5c. The insulator 9 is formed with an area that can cover one surface of the dummy cell 6A. Furthermore, a recess 9a is formed in the insulator 9 on the surface facing the dummy cell 6A, and a terminal T made of a conductive material is incorporated in the recess 9a. The terminal T has a planar shape such that one surface is in surface contact with the separator 6c (see FIG. 2) of the dummy cell 6A, and a rod-shaped protrusion t passes through the insulator 9, the movable plate 5 and the end plate 4 on the other surface. Then, it protrudes from the surface of the end plate 4. The protrusion t is connected to one terminal of the external load. Although not shown, the end plate 3 is also provided with a terminal electrically connected to the dummy cell 6B, and this terminal is connected to the other terminal of the external terminal.

  The control device 100 includes pipes 101, 101,..., A pump 102, an on-off valve 103, a cell voltage sensor 104, a control unit 105, and the like. The pump 102 is operated by, for example, hydraulic pressure or air pressure. One end of the flow path 101 is connected to the actuator 8, and the other end is joined to another pipe 101 and connected to the pump 102. Each channel 101 is provided with an on-off valve 103. When the on-off valve 103 is opened, the operating pressure is input to the actuator 8, and when the on-off valve 103 is closed, the input of the operating pressure to the actuator 8 is stopped. Is done. The cell voltage sensor 104 can detect the electromotive force output from each single cell 1.

  The control unit 105 includes a CPU (Central Processing Unit), a memory, an input / output port, and the like, and is electrically connected to the tactile sensor S, the pump 102, each on-off valve 103, and the cell voltage sensor 104. In this control unit 105, a signal having surface pressure distribution information acting on the fuel cell stack FC is input from the tactile sensor S, and an operation signal and a stop signal for the pump 102, an open / close signal for the on-off valve 103, and an activation of each single cell 1. Power information is output. Therefore, the control unit 105 determines the surface pressure distribution obtained from the tactile sensor S based on the output from the cell voltage sensor 104, that is, when the single cell 1 whose electromotive force is lower than the reference is detected. Considering this, the load on the laminate 2 is appropriately adjusted by opening the on-off valve 103 of the actuator 8 that needs to be operated and operating the pump 102.

Next, the operation of the fuel cell stack FC of this embodiment will be described.
When hydrogen is supplied from the outside of the fuel cell stack FC into each single cell 1 through a flow passage (not shown), the hydrogen is supplied to the anode gas flow path Pa formed in the separator 13 as shown in FIG. And is diffused over the entire surface of the anode electrode 11a through the diffusion layer 11b. When air humidified by a humidifier (not shown) is supplied from outside the fuel cell stack FC into each single cell 1 through a flow passage (not shown), the humidified air is formed in the separator 14. The cathode gas flow path Pc is supplied and diffused to the entire surface of the cathode electrode 12a through the diffusion layer 12b. In the anode electrode 11a, the supplied hydrogen is decomposed into protons and electrons by the action of the catalyst, the protons pass through the electrolyte membrane 10, and the electrons move to the cathode electrodes 12a through an external load (such as a traveling motor). In the cathode electrode 12a, protons that have permeated through the electrolyte membrane 10 and electrons that have passed through the external load react with oxygen in the air by the action of the catalyst to generate water. Electrons generated by the anode electrode 11a flow to the terminal T through the separator 13 of the single cell 1, the separator 6d of the dummy cell 6A, the conductive sheet 6b, the conductive sheet 6c, and the separator 6c of the dummy cell 6A. Then, the electrons returning from the terminal T to the fuel cell stack FC through the external load flow to the separator 6e, the separator 6f of the dummy cell 6B, and the separator 14 of the single cell 1 through a terminal (not shown). Although not shown, the separator 13 of each single cell 1 is formed with a flow passage through which the refrigerant passes so that the fuel cell stack FC is not excessively heated.

  By the way, in the fuel cell stack FC of the present embodiment, rubber seals formed at the edges of the diffusion layers 11b and 12b of each single cell 1 and the anode gas flow path Pa and the cathode gas flow path Pc by long-term use. The elasticity of the part decreases. As a result, the stacking load acts in the direction of dropping (decreasing). At this time, it is necessary to operate the actuator 8 in the direction in which the stacking load is increased. However, a uniform stacking load is not necessarily applied to the entire electrode surface of the single cell 1 (the surface of the anode electrode 11a and the surface of the cathode electrode 12a). However, there are a region with a high stacking load and a region with a low stacking load. If the stacking load is too low, the electrical resistance of the electrode surface increases and the catalyst and the like are likely to deteriorate. Conversely, if the stacking load is too high, the diffusion layers 11b and 12b and the seal portion are likely to deteriorate. Therefore, since it is necessary to adjust so that an appropriate lamination load acts uniformly on the electrode surface, the lamination of which region of the electrode surface of the single cell 1 is high and which region is low. It is necessary to accurately measure the load distribution.

  Therefore, in the present embodiment, a structure in which the tactile sensor S is sandwiched between the conductive sheets 6a and 6b is provided between the separators 6c and 6d, for example, as illustrated in FIG. When the detection point Q1 of the tactile sensor S is located in a region where the convex portion 6c1 and the convex portion 6d1 of the cathode gas flow path Pc face each other, when the load F acts on the detection point Q1, the load F becomes conductive. Buffered by the conductive sheets 6a and 6b, that is, the stacking load on the detection point Q1 is relaxed, and the detection output at the detection point Q1 is compared to the case where the conductive sheets 6a and 6b are not provided (see FIG. 7). Get smaller. On the other hand, when the detection point Q2 of the tactile sensor S is located in a region where the concave portion of the anode gas flow path Pa and the concave portion of the cathode gas flow path Pc face each other, when the load F acts on the detection point Q2, Detection of the tactile sensor S by the laminated load acting on the region where the convex portions 6c2, 6c3 of the adjacent anode gas flow channel Pa and the convex portions 6d2, 6d3 of the cathode gas flow channel Pc face each other is transmitted through the conductive sheets 6a, 6b. Since it acts on the point Q2, the detection output at the detection point Q2 becomes larger than when the conductive sheets 6a and 6b are not provided (see FIG. 7). Therefore, since the detection values at the respective detection points Q1, Q2,... Are averaged to some extent and output, the accuracy of the stack load distribution can be improved. Moreover, since the tactile sensor S is disposed not between the end plates 3 and 4 but between the separators 6c and 6d, the fuel cell stack FC can be reduced in size.

  Accordingly, based on the output from the cell voltage sensor 104, that is, when the control unit 105 determines that the output is lower than the reference, the corresponding actuator 8 is pressed in the region where the surface pressure is detected to be low. The protrusion amount of the portion 8a is increased to increase the stacking load, and the load corresponding to the electrode surface of the single cell 1 is adjusted to be uniform over the entire electrode surface. If necessary, the protruding amount of the pressing portion 8a of the actuator 8 is reduced to adjust the stacking load to be low. As described above, in the fuel cell stack FC, an appropriate stacking load always acts on the stacked body 2 of the single cells 1, so that the performance of the fuel cell stack FC can be improved.

  Further, in the fuel cell stack FC, the MEA repeatedly expands and contracts depending on the temperature, that is, when the temperature rises during power generation and the MEA expands and the outside air temperature is low (for example, in a low temperature environment such as below freezing point). ), The actuators 8 can be controlled in real time by the control device 100 shown in FIG. That is, when the MEA expands and the stacking load becomes excessively high, the protruding amount of the pressing portion 8a of the actuator 8 is reduced by the control from the control unit 104, and the movable plate 5 approaches the end plate 4. By moving in the direction, the stacking load on the stacked body 2 is reduced. Further, when the MEA contracts and the stacking load becomes excessively small, the protruding amount of the pressing portion 8a of the actuator 8 is increased by the control from the control unit 104, and the movable plate 5 is moved away from the end plate 4. To increase the stacking load on the stacked body 2. By automatically controlling in this way, the fuel cell stack FC can always be operated with the optimum stacking load, and the performance of the fuel cell stack FC can be improved.

  The present invention is not limited to the above-described embodiment. For example, instead of the tactile sensor S as the surface pressure distribution detecting means, point-like pressure sensors are arranged in a grid pattern. May be.

  Further, the conductive sheets 6a and 6b are not limited to carbon paper, and are conductive and have an anode gas flow path Pa formed in the separator 6c and a cathode gas flow formed in the separator 6d. For example, a plate made of metal such as iron may be used as long as it has rigidity enough to prevent deformation by the path Pc.

  In the above-described embodiment, the conductive sheets 6a and 6b have been described by taking, as an example, those having rigidity such as carbon paper. However, the present invention is not limited to this, and the surface pressure distribution can be measured relatively uniformly. As long as it is a thing, it may have some flexibility, such as a carbon cloth.

It is a partially exploded perspective view which shows the fuel cell stack of this embodiment. It is sectional drawing of the fuel cell stack of this embodiment. The pressure distribution detection means used for a dummy cell is shown, (a) is a perspective view, (b) is AA sectional drawing of (a). It is sectional drawing which shows the detail of the edge part of the fuel cell stack of this embodiment. 1 is an overall configuration diagram for automatically controlling a load on a fuel cell stack according to an embodiment. It is the schematic explaining the effect | action in the fuel cell stack of this embodiment. It is sectional drawing which shows the conventional fuel cell stack.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Single cell 2 Stack 6A, 6B Dummy cell 6a, 6b Conductive sheet 6c, 6d, 6e, 6f, 13, 14 Separator 8 Actuator 11a Anode electrode 12a Cathode electrode FC Fuel cell stack pa Anode gas flow path (reaction gas flow path )
Pc cathode gas channel (reactive gas channel)
S Tactile sensor (pressure distribution detection means)

Claims (2)

A fuel cell stack in which a dummy cell is disposed at both ends in the stacking direction of a single cell in which a pair of separators are stacked in a state where the reaction gas flow paths face each other,
One dummy cell is provided with sheet-like pressure distribution detection means for measuring the stack load distribution of the single cell in a region corresponding to the electrode surface of the single cell between the separators, and both surfaces of the pressure distribution detection means are A fuel cell stack, which is sandwiched between conductive sheets.   The fuel cell stack according to claim 1, wherein the conductive sheet is carbon paper.

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