JP5177964B2 - Fuel cell stack - Google Patents

Description

  The present invention relates to a fuel cell stack. More specifically, the present invention relates to a technique for stably operating a fuel cell stack.

  Generally, a polymer electrolyte fuel cell stack is configured as follows. First, a membrane electrode assembly (hereinafter referred to as “MEA”) is constructed by joining an anode to one surface of a solid polymer membrane and a cathode to the other surface. Next, a cell is configured by sandwiching the MEA between an anode side plate provided with a fuel flow path facing the anode of the MEA and a cathode side plate provided with an oxidant flow path facing the cathode of the MEA. Further, a stacked body is formed by stacking a plurality of cooling plates with the cooling plates interposed between the cells, and an end plate is attached to both ends of the stacked body and tightened to constitute a polymer electrolyte fuel cell stack.

  In the polymer electrolyte fuel cell stack, fuel gas such as reformed gas is circulated through the anode side plate, and oxidant gas such as air is circulated through the cathode side plate to cause an electrochemical reaction through the electrolyte membrane. To generate DC power. Since the electrochemical reaction is an exothermic reaction, the normal operating temperature of the polymer electrolyte fuel cell stack (for example, about 70 to 80 [° C.]) is obtained by circulating cooling water through the cooling plate and cooling each cell. Is maintained.

  In the polymer electrolyte fuel cell stack, the cells at both ends adjacent to the end plate are easily affected by outside air. For this reason, the temperature of the cells at both ends tends to be lower than the cells at other portions. When the temperature of the cell decreases, the water vapor in the reaction gas flowing through the flow path of the anode side plate or the cathode side plate may condense in the flow path, and the condensed water formed by condensing the water vapor is the flow of the reaction gas. This causes a decrease in battery performance.

In view of such a current situation, there is a demand for a technique for suppressing a temperature drop of cells at both ends in a polymer electrolyte fuel cell stack. In Patent Document 1, a flow path for flowing cooling water is provided to the end plates at both ends, the temperature is raised to a temperature close to the operating temperature, and the cooling water discharged after power generation is supplied to the flow path provided on the entire end plate. A technique for heating and heating the cells at both ends is disclosed. Patent Document 2 discloses a technique for suppressing a temperature drop of cells at both ends.
JP 2001-68141 A JP 2002-184449 A

  As described in Patent Document 1 and Patent Document 2, it is a factor of an increase in manufacturing cost that the end plate or the conductive plate has a special structure, or that a part dedicated to heat insulation or heating is installed in the vicinity of the end plate.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a technique for stably operating the fuel cell stack while suppressing the temperature drop of the end unit cell while reducing the cost. .

  In order to solve the above problems, a fuel cell stack according to an aspect of the present invention includes a laminate in which a plurality of unit cells each provided with an electrolyte membrane are provided between a fuel electrode and an oxidant electrode, and the unit cell includes: In order to guide the generated current to the outside, a pair of current collectors that are in contact with the unit cells located at both ends of the laminate, a pair of end plates to which a clamping force for fastening the laminate is applied, and the pair of pairs And an insulator that is disposed between at least one of the current collectors and the end plate, and insulates between the current collector and the end plate. A space is formed between the end plate and the current collector.

  According to this aspect, since a space is formed between the current collector and the end plate, it is difficult for heat to be transferred from the current collector to the end plate, and the heat escapes to the outside through the end plate or the insulator. Can be suppressed. Therefore, it is possible to suppress the temperature drop of the unit cell located at the end of the stacked body with which the current collector is in contact and to operate the fuel cell stack stably.

  The insulator may include a pressing portion that presses the current collector when the stacked body is sandwiched, and a recess that becomes a closed space when the pressing portion presses the current collector. Good. Thereby, since the clamping force applied to the end plate presses the current collector through the insulator, the cell and the current collector at the end can be firmly adhered to each other, and contact failure and contact resistance can be reduced.

  The pressing portion may be configured by a rib. Thereby, the strength of the insulator itself can be improved and the current collector can be pressed uniformly.

The plurality of recesses are formed by a plurality of intersecting ribs, and when the ribs press the current collector, the openings of the recesses are closed by the current collector and closed to each other. It may be. Thereby, the strength of the insulator itself can be further improved, and the current collector can be pressed more uniformly. In addition, since the plurality of spaces are closed to each other, it is difficult for the heat generated by the current collector to be transmitted to the adjacent space, and the diffusion of the heat of the cell at the end can be suppressed.

  The rib may be recessed in a region in contact with the current collector from a region in contact with the current collector. Thereby, since the current collector can be arranged inside the region where the insulator does not contact the current collector, the fuel cell stack can be made compact.

The insulator is provided with a flow path through which a fluid that cools the stacked body flows, and a partition is formed between the flow path and the pressing portion. when pressing the laminate, and space provided on the flow path side than the partition wall, also a space in which the opening is closed is closed by the collector of the concave portion be formed so as not to communicate Good. As a result, the air heated by the heat generated from the current collector does not reach the vicinity of the flow path through the space, so that it is possible to prevent the air from being cooled by the fluid flowing through the flow path.

The insulator is provided on a side opposite to the current collector, and is pressed and closed by the end plate when the end plate presses the pressed portion. And a concave portion that becomes an open space. Thereby, since the closed space is formed on both end faces of the insulator, it is possible to suppress the heat generated in the unit cell located at the end of the stacked body from being transmitted to the outside. As a result, the temperature drop of the cell at the end can be suppressed and the fuel cell stack can be operated stably.

  The insulator may be made of resin. Thereby, the shape of a recessed part, a rib, etc. can be simply formed in an insulator by integral molding, and the manufacturing cost and material cost of a fuel cell stack can be reduced.

  A combination of the above-described elements as appropriate can also be included in the scope of the invention for which patent protection is sought by this patent application.

  According to the present invention, it is possible to stably operate the fuel cell stack while suppressing the temperature reduction of the cell at the end while reducing the cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, an example of a fuel cell system that can suitably use the fuel cell stack according to the present embodiment will be described.

(First embodiment)
FIG. 1 is a schematic diagram showing the overall configuration of a fuel cell system 10 according to the first embodiment. Note that the schematic diagram of FIG. 1 is a diagram schematically showing mainly the functions and connections of each component, and does not limit the positional relationship or arrangement of each component.

  The fuel cell system 10 includes a power supply unit 20. The power supply unit 20 includes a reforming device 40, a fuel cell stack 50, a fuel wet heat exchanger 60, an oxidant wet heat exchanger 70, a converter 90, an inverter 92, and a control device 100. The fuel moist heat exchanger 60 and the oxidant moist heat exchanger 70 of the present embodiment humidify the gas to be humidified to a predetermined humidity by bubbling the gas to be humidified using the water stored in the tank. can do.

  The reformer 40 is supplied with clean water that has been subjected to water treatment by the water treatment device 42 as reforming water. The water treatment device 42 treats water from the clean water using a reverse osmosis membrane and an ion exchange resin. The water subjected to the water treatment by the water treatment device 42 is used for steam reforming of the reformer included in the reforming device 40.

  The battery off-gas, which is the reformed gas that is discharged unreacted in the fuel cell stack 50, is sent to the reformer 40 via the gas-liquid separator 44. In the gas-liquid separator 44, only the gas component of the battery off gas is taken out and sent to the reformer 40, where it is used as fuel for the burner. The gas-liquid separator 44 also has a heat exchange function that allows the battery off gas and the reforming water to exchange heat, and the reforming water is heated by the heat of the battery off gas.

  The DC power generated in the fuel cell stack 50 is converted into DC power having a predetermined voltage (for example, 24V) by the converter 90, and then converted to AC power (for example, 100V) by the inverter 92. The AC power converted by the inverter 92 is output to the system 94. Further, the DC power of a predetermined voltage converted by the converter 90 is used as a power source for the control device 100 or the like.

  The control device 100 controls the amount of power generated by the fuel cell stack 50 by adjusting the amount of fuel supplied from the reformer 40 and the amount of air supplied from the outside. In addition, the control device 100 controls the amount of cooling water by adjusting the opening of a control valve provided in the piping for cooling water and the circulation pump. Further, the control device 100 transmits and receives electrical signals to and from the converter 90 and the inverter 92 and controls these various devices. The control device 100 can perform infrared communication with the remote controller 96. The user can set the operation of the fuel cell system 10 using the remote controller 96.

(Fuel cell stack)
Next, the fuel cell stack 50 will be described in detail. FIG. 2 is a perspective view showing an overview of the fuel cell stack 50. FIG. 3 is a side view of the fuel cell stack 50 of FIG. 2 as viewed from the A1 direction. FIG. 4 is a side view of the fuel cell stack 50 of FIG. 2 as viewed from the A2 direction. FIG. 5 is a side view of the fuel cell stack 50 of FIG. 2 as viewed from the A3 direction.

  The fuel cell stack 50 includes a stacked body 51 in which a plurality of cells are stacked, a pair of current collectors 53a and 53b (hereinafter referred to as current collector 53 as appropriate), and a pair of end plates 110a and 110b (hereinafter referred to as end plates as appropriate). 110), and insulators 55a and 55b (hereinafter referred to as insulator 55 as appropriate) that are disposed between the current collector 53 and the end plate 110 and insulate between the current collector 53 and the end plate 110; Is provided.

  The laminated body 51 is formed by laminating a plurality of cells each provided with a solid polymer film 52 as an electrolyte film between an anode 54 as a fuel electrode and a cathode 56 as an oxidant electrode shown in FIG. The current collectors 53 are in contact with the cells located at both ends of the stacked body 51 in order to guide the current generated by the cells to the outside. The end plate 110 is fastened by a fastening mechanism so that a fastening force for fastening the laminated body 51 is applied to both ends of the laminated body 51 via the current collector 53 and the insulator 55.

  The fuel cell stack 50 is fastened by a fastening mechanism including a plurality of spring members 108 having a W-shaped cross section for applying a compressive load in the cell stacking direction to the bolts 104, nuts 106, and the stacked body 51.

  The fuel cell stack 50 generates power using hydrogen gas as a fuel and air as an oxidant. Specifically, in each cell (unit cell) constituting the fuel cell stack 50, an electrode reaction represented by the formula (1) occurs at the anode 54 in contact with one surface of the solid polymer film 52. On the other hand, at the cathode 56 in contact with one surface of the solid polymer film 52, an electrode reaction represented by the formula (2) occurs. Each cell is cooled by cooling water flowing through the cooling water plate 58 and adjusted to an appropriate temperature of about 70 to 80 ° C.

(Insulator)
Further, the insulator 55a will be described. FIG. 6 is a perspective view of the insulator 55a according to the present embodiment as viewed from the side where the current collector is disposed. FIG. 7 is a top view of the insulator 55a according to the present embodiment as viewed from the side in contact with the end plate 110a. 8 is a cross-sectional view taken along the line BB ′ of FIG. FIG. 9 is a perspective view of the insulator 55a according to the present embodiment as viewed from the side in contact with the end plate 110a. FIG. 10 is a schematic diagram showing that a space is formed between the insulator 55 and the current collector plate according to the present embodiment. FIG. 11 is an enlarged cross-sectional view of a part of FIG.

  As shown in FIG. 4 and FIG. 7, the insulator 55a has an oxidant inlet 120 through which air flows, a cooling water air vent 122 for venting cooling water, A fuel inlet 124 through which hydrogen gas flows in and a cooling water outlet 126 through which cooling water is discharged are formed. The insulator 55a and the end plate 110a are overlapped and tightened so that each flow path formed in the insulator 55a protrudes from a through hole provided in the end plate 110a.

  Further, as shown in FIG. 5, the insulator 55b has an oxidant drain outlet 128 that discharges excess components contained in air and a cooling water inlet 130 into which cooling water flows, on a surface facing the end plate 110b. A fuel drain outlet 132 for discharging excess components contained in the hydrogen gas, a fuel outlet 134 for discharging unreacted hydrogen gas in the cell, and an oxidant exhaust for discharging unreacted air in the cell. An outlet 136 is formed. The insulator 55b and the end plate 110b are overlapped and tightened so that each flow path formed in the insulator 55b protrudes from a through hole provided in the end plate 110b.

  As shown in FIGS. 6 and 8, a plurality of vertical ribs 140 provided in the longitudinal direction of the insulator 55a and the vertical ribs 140 intersect the surface of the insulator 55a on the side where the current collector 53a is disposed. A plurality of lateral ribs 142 are provided. The insulator according to the present embodiment is a resin member, and can be easily formed in a shape such as a recess and a rib by integral molding, and the manufacturing cost and material cost of the fuel cell stack can be reduced. . As the resin material, PPS (polyphenylene sulfide) containing glass fiber is preferable. This material is thermally stable, has very few eluents that increase electrical conductivity, and has high steam resistance, so that the fuel cell stack can maintain stable power generation over a long period of time.

  The vertical rib 140 and the horizontal rib 142 formed on the insulator 55a function as a pressing portion that presses the current collector 53a when the stacked body 51 is sandwiched. In addition, a concave portion 144 that is a closed space when the insulator 55 a presses the current collector 53 a is formed as a region surrounded by the vertical rib 140 and the horizontal rib 142.

  When such an insulator 55a is disposed between the end plate 110a and the current collector 53a, as shown in FIG. 10, when the stacked body 51 is sandwiched, the current collector 53a and the end plate 110a are disposed. Since the space 160 filled with air is formed, heat is hardly transmitted from the current collector 53a to the end plate 110a, and heat can be prevented from escaping to the outside through the end plate 110a and the insulator 55a. Therefore, the temperature drop of the cell located at the end of the stacked body 51 with which the current collector 53a is in contact can be suppressed, and the fuel cell stack 50 can be stably operated. In addition, like the insulator 55a according to the present embodiment, the strength of the insulator 55a itself can be improved and the current collector 53a can be pressed uniformly by configuring the pressing portion with a rib. it can.

  Further, a plurality of recesses 144 provided in insulator 55a according to the present embodiment are formed by a plurality of intersecting vertical ribs 140 and horizontal ribs 142, and vertical ribs 140 and horizontal ribs 142 form current collector 53a. A plurality of spaces are closed when pressed. Therefore, since the plurality of spaces are closed and not in communication with each other, the heat generated by the current collector 53a is not easily transmitted to the adjacent space, and the diffusion of the heat of the cell at the end can be suppressed.

  In addition, the vertical rib 140 and the horizontal rib 142 formed on the insulator 55a have regions 140a and 142a that are in contact with the current collector 53a and regions 140b and 142b that are in contact with the stacked body 51 without the current collector 53a. It is recessed. As a result, as shown in FIGS. 10 and 11, the current collector 53a can be disposed in a region 154 that is recessed from the surface 148 where the insulator 55a does not contact the current collector 53a. It can be made compact.

  The insulator 55a is provided with a cooling water discharge port 126 as a flow path through which a fluid for making the temperature of the stacked body 51 appropriate. In the insulator 55a, partition ribs 152 functioning as partition walls are formed between the cooling water discharge ports 126 and the vertical ribs 140 and horizontal ribs 142 that function as pressing portions. The partition rib 152 includes a space provided on the cooling water discharge port 126 side from the partition rib 152 and a space provided on the current collector side from the partition rib 152 when the vertical rib 140 and the horizontal rib 142 press the laminated body 51. It is formed so as not to communicate with 156. As a result, the air heated by the heat generated from the current collector 53a does not reach the vicinity of the cooling water discharge port 126 via the space 156, so that the air is cooled by the fluid flowing through the cooling water discharge port 126. Can be suppressed.

  As shown in FIGS. 7 and 9, the insulator 55a includes a plurality of vertical ribs 240 provided in the longitudinal direction of the insulator 55a on the surface where the insulator 55a is in contact with the end plate 110a. And a plurality of lateral ribs 242 intersecting with each other. The vertical ribs 240 and the horizontal ribs 242 function as pressed parts that are pressed against the end plate 110a. Moreover, it has the recessed part 244 used as the space closed when the end plate 110a pressed the vertical rib 240 and the horizontal rib 242. FIG.

  With this configuration, the fuel cell stack 50 according to the present embodiment forms closed spaces on both end surfaces of the insulator 55a, so that heat generated in the cells located at the end portions of the stacked body 51 is transmitted to the outside. This can be suppressed. As a result, the temperature drop of the cell at the end can be suppressed and the fuel cell stack 50 can be operated stably.

  Next, the difference between the insulator 55b and the insulator 55a will be mainly described. FIG. 12 is a top view of the insulator 55b according to the present embodiment as viewed from the side where the current collector 53b is disposed.

  As shown in FIG. 12, on the surface of the insulator 55b on the side where the current collector 53b is disposed, a plurality of vertical ribs 340 provided in the longitudinal direction of the insulator 55b and a plurality of horizontal ribs crossing the vertical ribs 340 are provided. Ribs 142 are provided.

  The vertical rib 340 and the horizontal rib 342 formed on the insulator 55b function as a pressing portion that presses the current collector 53b when the stacked body 51 is sandwiched. In addition, a concave portion 344 that becomes a closed space when the insulator 55 b presses the current collector 53 b is formed as a region surrounded by the vertical rib 340 and the horizontal rib 342.

  When such an insulator 55b is disposed between the end plate 110b and the current collector 53b, as shown in FIG. 10, when the stacked body 51 is sandwiched, the current collector 53b and the end plate 110b are interposed. Since the space 160 filled with air is formed, heat is hardly transmitted from the current collector 53b to the end plate 110b, and heat can be prevented from escaping to the outside through the end plate 110b and the insulator 55b. Therefore, the temperature drop of the cell located at the end of the stacked body 51 with which the current collector 53b is in contact can be suppressed, and the fuel cell stack 50 can be operated stably.

  Further, the vertical rib 340 and the horizontal rib 342 formed on the insulator 55b are formed from the regions 340b and 342b in which the regions 340a and 342a in contact with the current collector 53b are in contact with the stacked body 51 without the current collector 53b. It is recessed. As a result, as shown in FIGS. 10 and 11, the current collector 53b can be disposed in a region 350 that is recessed from the surface 348 where the insulator 55b does not contact the current collector 53b. It can be made compact. Note that the structure of the surface of the insulator 55b on the side in contact with the end plate 110b is substantially the same as the structure of the surface of the insulator 55a on the side in contact with the end plate 110a, and thus the description thereof is omitted.

(Second Embodiment)
FIG. 13 is a diagram schematically showing a schematic configuration of the fuel cell stack 150 according to the second embodiment. Note that portions other than the insulator 153 and a detailed configuration of the insulator 153 are omitted as appropriate.

  The insulator 153 is an oxidation for supplying the air humidified and heated by the oxidant wet heat exchanger 70 in the fuel cell system 10 shown in FIG. 1 to the cathode in the stack 151 of the fuel cell stack 150. An agent inlet 228 is provided.

  The air as the humidified reaction gas may generate water droplets in the middle of the path from the oxidant inlet 228 to the cathode. Intrusion into the manifold of the laminate 151 in such a state of water droplets is not preferable in view of the reaction during power generation.

  Therefore, the insulator 153 according to the present embodiment suppresses water droplets from entering the manifold of the multilayer body 151 by providing the oxidant drain outlet 230 at a position immediately before the manifold inlet of the multilayer body 151. Can do.

  In addition, by forming the insulator 153 with a resin, it is possible to obtain a sufficient electrical resistance to the reaction gas containing moisture as compared with the case where the insulator is formed of metal or the like.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added based on the knowledge of those skilled in the art. The form can also be included in the scope of the present invention.

1 is a schematic diagram showing an overall configuration of a fuel cell system according to a first embodiment. It is a perspective view which shows the general view of a fuel cell stack. FIG. 3 is a side view of the fuel cell stack of FIG. 2 when viewed from the A1 direction. FIG. 3 is a side view of the fuel cell stack of FIG. 2 when viewed from the A2 direction. FIG. 3 is a side view when the fuel cell stack of FIG. 2 is viewed from the A3 direction. It is the perspective view which looked at the insulator which concerns on this Embodiment from the side by which a collector is arrange | positioned. It is the top view which looked at the insulator which concerns on this Embodiment from the side which contact | connects an end plate. It is B-B 'sectional drawing of FIG. It is the perspective view which looked at the insulator which concerns on this Embodiment from the side which contact | connects an end plate. It is a schematic diagram which shows that the space is formed between the insulator and current collector which concern on this Embodiment. It is sectional drawing to which a part of FIG. 8 was expanded. It is the top view which looked at the insulator which concerns on this Embodiment from the side by which a collector is arrange | positioned. It is the figure which showed typically schematic structure of the fuel cell stack which concerns on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Fuel cell system, 20 Power supply unit, 50 Fuel cell stack, 51 Laminated body, 52 Solid polymer film, 53 Current collector, 54 Anode, 55 Insulator, 56 Cathode, 110 End plate, 140 Vertical rib, 142 Horizontal rib 144 Recess, 152 Partition rib.

Claims (4)

A laminate in which a plurality of single cells each provided with an electrolyte membrane are laminated between a fuel electrode and an oxidant electrode;
A pair of current collectors respectively in contact with the unit cells located at both ends of the laminated body in order to guide the current generated by the unit cells to the outside;
A pair of end plates to which a tightening force for tightening the laminate is applied;
An insulator disposed between at least one of the pair of current collectors and the end plate, and insulating between the current collector and the end plate;
With
A space is formed between the end plate and the current collector,
The insulator is
A rib as a pressing portion that presses the current collector when the laminate is sandwiched;
A recess that becomes a closed space when the rib presses the current collector;
The recess is formed by a plurality of intersecting ribs, and when the rib presses the current collector, the opening of the recess is closed by the current collector and closed to each other. A fuel cell stack characterized by a plurality of spaces.   2. The fuel cell stack according to claim 1, wherein a region where the rib contacts the current collector is recessed from a region where the rib does not contact the current collector. 3. The insulator is provided with a flow path through which a fluid for cooling the stacked body flows, and a partition is formed between the flow path and the pressing portion,
The partition wall, the space in which the pressing portion when the pressing the laminate, and space provided in the flow path side than the partition wall, the opening of the front Ki凹 portion is closed is closed by the collector The fuel cell stack according to claim 1, wherein the fuel cell stack is formed so as not to communicate with the fuel cell stack. The insulator is
A pressed portion provided on the opposite side of the current collector and pressed against the end plate;
A recess that is closed by the end plate when the end plate presses the pressed portion;
The fuel cell stack according to claim 1, comprising:

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