JP2005100701A - Fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable secure application of a desired fastening load with a simple structure without being influenced by temperature. <P>SOLUTION: A fuel cell stack 10 is equipped with a plurality of fuel cells 12, and a laminate 14 is formed by laminating the fuel cells 12 in the direction shown as an arrow A. Outside the laminate 14, terminal plates 16a, 16b, insulating plates 18a, 18b and end plates 20a, 20b are formed. Outside the end plate 20a, a volume-variable bag member 54 is formed, and in a liquid chamber 56 formed in the bag member 54, stored liquid 58 expanding at a temperature equal to or lower than a predetermined temperature is sealed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell stack in which a plurality of fuel cells in which a solid polymer electrolyte membrane is disposed between a pair of electrodes and a metal separator and a plurality of fuel cells are laminated.

  For example, in a polymer electrolyte fuel cell, an electrolyte membrane / electrode structure in which an anode electrode and a cathode electrode are arranged on both sides of an electrolyte membrane made of a polymer ion exchange membrane (cation exchange membrane) is sandwiched between separators. doing. This type of fuel cell is normally used as a fuel cell stack by laminating a predetermined number of electrolyte membrane / electrode structures and separators.

  In a fuel cell, a fuel gas supplied to the anode side electrode, for example, a hydrogen-containing gas, is hydrogen-ionized on the electrode catalyst and moves to the cathode side electrode through an appropriately humidified electrolyte membrane. The electrons generated in the meantime are taken out to an external circuit and used as direct current electric energy. Since the cathode side electrode is supplied with an oxidant gas, for example, an oxygen-containing gas such as air, hydrogen ions, electrons and oxygen gas react with each other to generate water at the cathode side electrode.

  By the way, when the contact resistance in the fuel cell increases, the internal resistance loss increases and the terminal voltage decreases. For this reason, it is necessary to apply a desired tightening force to the entire fuel cell stack so that the surface pressure applied to the electrode surface is uniform in order to reduce the contact resistance.

  Therefore, for example, a solid polymer electrolyte fuel cell of Patent Document 1 is known. As shown in FIG. 6, the fuel cell includes a cell 3 in which an electrolyte membrane / electrode structure 1 is sandwiched between a pair of separators 2, and the cell 3 includes an end plate with a current collector plate 4 interposed therebetween. 5 is tightened and held. A piston 6 is provided on the end plate 5, and pack-filled water 7 is accommodated between the piston 6 and the end plate 5. A heater 8 for heating the packed water 7 as a heat medium is fixed to the end plate 5.

  In such a configuration, the outer peripheral portion of the pack material of the pack-filled water 7 is pressurized by air from an air pressure source (not shown), and the pack water of the pack-filled water 7 that is a heat medium under the action of the heater 8. Is heated to control the cell 3 to a predetermined clamping pressure.

Japanese Unexamined Patent Publication No. 2000-123854 (FIG. 2)

  However, in the above-mentioned Patent Document 1, since the cell heating control is performed using the heater 8, the configuration and the control are complicated. For this reason, the problem that the cost of the whole fuel cell rises is pointed out.

  The present invention solves this type of problem, and provides a fuel cell stack capable of reliably applying a desired tightening load without being influenced by temperature with a simple and inexpensive configuration. For the purpose.

  The fuel cell stack of the present invention includes a variable volume bag member disposed at an end of the fuel cell stack, and a container that is accommodated in the bag member and expands at a predetermined temperature or less. ing.

  When the temperature is low, the electrolyte membrane / electrode structure constituting each fuel cell is reduced to shorten the overall length of the fuel cell stack, and the tightening load of the fuel cell stack is likely to be reduced only by the elasticity of the metal separator itself. At that time, the volume of the contents in the bag member expands below a predetermined temperature, and the volume of the bag member increases. For this reason, the reduction | decrease of each fuel cell can be supplemented by the volume increase of a bag member, and the fall of the clamping load of the whole fuel cell stack is relieve | moderated.

  Moreover, it is preferable that the container contains at least water, and it is preferable that a heat insulating member is interposed between the bag member and the metal separator.

  According to the present invention, it is only necessary to house a container whose volume expands below a predetermined temperature in the bag member, and for example, heating control by a heater becomes unnecessary. For this reason, with a simple and inexpensive configuration, it is possible to effectively prevent a decrease in tightening load due to a decrease in temperature, and reliably prevent leakage of reaction gas and the like.

  Furthermore, the volume of the water contained in the contents expands when frozen. This makes it possible to reliably increase the volume of the bag member with an extremely economical configuration. At that time, if the contents are a mixture of water and a solvent, the freezing point and volume expansion coefficient of the contents can be changed by setting the type and amount of the solvent, thereby improving versatility. Is planned.

  Moreover, even if the contents in the bag member are frozen, the metal separator is not cooled too much under the action of the heat insulating member. Therefore, in the fuel cell close to the bag member, power generation failure due to a temperature drop is not caused particularly at low temperature startup, and low temperature startup is efficiently performed.

  FIG. 1 is a schematic configuration explanatory view of a fuel cell stack 10 according to the first embodiment of the present invention.

  The fuel cell stack 10 includes a plurality of fuel cells 12, and the stacked body 14 is configured by stacking the fuel cells 12 in the direction of arrow A. Terminal plates 16a and 16b, insulating plates 18a and 18b, and end plates 20a and 20b are sequentially arranged on the outer side of the laminate 14. A load 21 is connected to the terminal plates 16a and 16b.

  As shown in FIG. 2, the fuel cell 12 includes an electrolyte membrane / electrode structure 22, and first and second metal separators 24 and 26 that sandwich the electrolyte membrane / electrode structure 22.

  One end edge of the fuel cell 12 in the direction of arrow B communicates with each other in the direction of arrow A, which is the stacking direction, and an oxidant gas supply communication hole 30a for supplying an oxidant gas, for example, an oxygen-containing gas. A cooling medium discharge communication hole 32b for discharging the medium and a fuel gas discharge communication hole 34b for discharging a fuel gas, for example, a hydrogen-containing gas, are arranged in the direction of arrow C (vertical direction).

  The other end edge of the fuel cell 12 in the direction of the arrow B communicates with each other in the direction of the arrow A, the fuel gas supply communication hole 34a for supplying the fuel gas, and the cooling medium supply communication hole for supplying the cooling medium. 32a and an oxidant gas discharge communication hole 30b for discharging the oxidant gas are arranged in the direction of arrow C.

  The electrolyte membrane / electrode structure 22 includes, for example, a solid polymer electrolyte membrane 36 in which a perfluorosulfonic acid thin film is impregnated with water, anode-side electrodes 38 disposed on both surfaces of the solid polymer electrolyte membrane 36, and A cathode side electrode 40 (see FIGS. 1 and 2).

  The anode side electrode 38 and the cathode side electrode 40 include a gas diffusion layer made of carbon paper or the like, and an electrode catalyst layer in which porous carbon particles having a platinum alloy supported on the surface are uniformly applied to the surface of the gas diffusion layer. Have The electrode catalyst layers are bonded to both surfaces of the solid polymer electrolyte membrane 36 so as to face each other with the solid polymer electrolyte membrane 36 interposed therebetween.

  As shown in FIG. 2, on the surface 24a of the first metal separator 24 facing the electrolyte membrane / electrode structure 22, an oxidant gas flow communicating with the oxidant gas supply communication hole 30a and the oxidant gas discharge communication hole 30b. A path 42 is provided. The oxidant gas flow path 42 includes, for example, a plurality of grooves extending in the direction of arrow B.

  A fuel gas flow path 44 that communicates with the fuel gas supply communication hole 34 a and the fuel gas discharge communication hole 34 b is formed on the surface 26 a of the second metal separator 26 facing the electrolyte membrane / electrode structure 22. The fuel gas channel 44 includes, for example, a plurality of grooves extending in the arrow B direction.

  As shown in FIG. 2, a cooling medium flow between the surface 24b of the first metal separator 24 and the surface 26b of the second metal separator 26 communicates with the cooling medium supply communication hole 32a and the cooling medium discharge communication hole 32b. A path 46 is formed. The cooling medium flow path 46 is integrally configured to extend in the direction of arrow B by overlapping a plurality of grooves provided in the first and second metal separators 24 and 26.

  A first seal member 50 is integrally provided on both surfaces 24a and 24b of the first metal separator 24 by molding or the like. The first seal member 50 is made of, for example, silicone rubber, and surrounds the oxidant gas flow path 42 on the surface 24a, and the oxidant gas flow path 42 passes through the oxidant gas supply communication hole 30a and the oxidant gas flow path 42. It is formed to communicate with the agent gas discharge communication hole 30b. The first seal member 50 is formed on the surface 24b so as to surround the cooling medium flow path 46 and to communicate the cooling medium flow path 46 with the cooling medium supply communication hole 32a and the cooling medium discharge communication hole 32b.

  A second seal member 52 is integrally provided on both surfaces 26a and 26b of the second metal separator 26 by molding or the like. The second seal member 52 is made of, for example, silicone rubber, and surrounds the fuel gas passage 44 on the surface 26a, and the fuel gas passage 44 is connected to the fuel gas supply passage 34a and the fuel gas discharge passage. It communicates with 34b. The second seal member 52 surrounds the cooling medium flow path 46 on the surface 26 b and communicates the cooling medium supply communication hole 32 a and the cooling medium discharge communication hole 32 b with the cooling medium flow path 46.

  As shown in FIG. 1, a variable volume bag member 54 is disposed outside the end plate 20a, which is a heat insulating member, and a liquid chamber 56 formed in the bag member 54 has a predetermined temperature. The container 58 whose volume expands below is enclosed. The container 58 contains at least water, and a solvent, for example, alcohols or ethers is mixed as necessary. By setting the type and amount of the solvent, the freezing point and the volume expansion coefficient of the contents 58 can be changed.

  The bag member 54 is provided with a plate portion 60 configured to be thinner than the end plate 20a. On one surface of the plate portion 60, for example, a flexible metal plate material such as an aluminum thin plate or a stainless thin plate is provided. 62 is fixed by welding, brazing, adhesion or the like. A liquid chamber 56 is formed between the metal plate 62 and the plate portion 60.

  As shown in FIG. 3, a liquid sealing port 64 for filling the liquid chamber 56 with the contents 58 is formed on the outer surface 60 a of the plate portion 60, and the liquid sealing port 64 is provided with a sealing washer 66 and a sealing bolt 68. Is blocked through. A sensor mounting port 70 is provided at a position diagonal to the liquid sealing port 64, and a pressure sensor 74 is attached to the sensor mounting port 70 via a washer 72. The pressure sensor 74 detects the liquid pressure of the contents 58 in the liquid chamber 56, and may be provided as necessary.

  Four bolt holes 76 are formed through the plate portion 60, and tie rods 78 are inserted into the bolt holes 76, and the tie rods 78 fasten and fix the end plates 20a and 20b with a predetermined tightening load.

  The operation of the fuel cell stack 10 configured as described above will be described below.

  As shown in FIG. 1, in the fuel cell stack 10, a fuel gas such as an oxidant gas that is an oxygen-containing gas such as air, a hydrogen-containing gas, In addition, a cooling medium such as pure water, ethylene glycol, or oil is supplied.

  For this reason, as shown in FIG. 2, in each fuel cell 12, an oxidant gas is introduced into the oxidant gas flow path 42 of the first metal separator 24 from the oxidant gas supply communication hole 30a, and this oxidant gas is supplied to the electrolyte. It moves along the cathode side electrode 40 of the membrane / electrode structure 22. The fuel gas is introduced into the fuel gas flow path 44 of the second metal separator 26 from the fuel gas supply communication hole 34 a and moves along the anode side electrode 38 of the electrolyte membrane / electrode structure 22.

  Therefore, in the electrolyte membrane / electrode structure 22, the oxidant gas supplied to the cathode side electrode 40 and the fuel gas supplied to the anode side electrode 38 are consumed by an electrochemical reaction in the electrode catalyst layer, thereby generating power. Is done.

  Next, the oxidant gas consumed by being supplied to the cathode side electrode 40 is discharged in the direction of arrow A along the oxidant gas discharge communication hole 30b. Similarly, the fuel gas consumed by being supplied to the anode electrode 38 is discharged in the direction of arrow A along the fuel gas discharge communication hole 34b.

  Further, the cooling medium supplied to the cooling medium supply communication hole 32 a is introduced into the cooling medium flow path 46 between the first and second metal separators 26 and then circulates in the direction of arrow B. The cooling medium is discharged from the cooling medium discharge communication hole 32b after the electrolyte membrane / electrode structure 22 is cooled.

  By the way, when the fuel cell stack 10 is started at a low temperature, the electrolyte membrane / electrode structure 22 constituting each fuel cell 12 is particularly reduced and the dimension in the stacking direction (arrow A direction) is reduced. Specifically, as shown in FIG. 4, the length L in the stacking direction of the fuel cell stack 10 becomes shorter as the starting temperature decreases.

  When the length L of the fuel cell stack 10 is shortened, the tightening load of the fuel cell stack 10 is reduced even if the elastic forces of the first and second metal separators 24 and 26 themselves are acting. When the temperature T is reached, the tightening load becomes equal to or less than the limit load, and the tightening failure of the fuel cell stack 10 is likely to occur.

  Therefore, in the first embodiment, as shown in FIG. 1, a variable volume bag member 54 is disposed on the end plate 20a, and a liquid chamber 56 formed in the bag member 54 has a predetermined volume. A container 58 that is frozen at a temperature T1 (see FIG. 4) or less and expands in volume is enclosed. For this reason, the contents 58 are frozen at a temperature T1 or lower to expand the volume, and the volume of the bag member 54 is increased.

  As a result, the metal plate member 62 constituting the bag member 54 is deformed so as to protrude toward the end plate 20 a, and a load is applied in the tightening direction of the fuel cell stack 10. In particular, the load drop of the fuel cell stack 10 can be effectively mitigated at the time of low temperature startup, and the fuel cell stack 10 can be reliably maintained above the limit load.

  Accordingly, in the fuel cell stack 10, for example, heating control by a heater is not required, and the configuration is simple and inexpensive, effectively preventing a decrease in tightening load accompanying a temperature decrease, and leaking fuel gas or oxidant gas. The effect that it becomes possible to prevent reliably is acquired.

  Moreover, the fuel cell stack 10 is configured such that a desired tightening load is applied through the elasticity of the first and second metal separators 24 and 26 constituting each fuel cell 12 and the expansion of the accommodation 58. Has been. For this reason, for example, it is not necessary to provide the fuel cell stack 10 with a spring or the like so as to apply a tightening load, and the entire fuel cell stack 10 can be easily downsized.

  Furthermore, since the volume of the water contained in the accommodation 58 expands when frozen, the volume of the bag member 54 can be reliably increased with an extremely economical configuration. At that time, if the container 58 is a mixed liquid of water and a solvent, it becomes possible to change the freezing point and volume expansion coefficient of the container 58 by setting the type and amount of the solvent. The versatility can be improved.

  Further, even if the contents 58 in the bag member 54 are frozen, the fuel cell 12 is not excessively cooled under the heat insulating action of the end plate 20a. Therefore, the fuel cell 12 in the vicinity of the bag member 54 has an advantage that efficient low-temperature start-up is performed without causing power generation failure due to a temperature drop particularly at low-temperature start-up. Even if the bag member 54 is disposed between the fuel cell 12 at the end in the stacking direction and the end plate 20a with a heat insulating member interposed therebetween, the same effect can be obtained.

  FIG. 5 is a schematic configuration diagram of a fuel cell stack 90 according to the second embodiment of the present invention. The same components as those of the fuel cell stack 10 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The fuel cell stack 90 includes a plate 92 disposed outside the end plate 20a, and a bag member 96 having a variable volume is accommodated in an opening 94 in the plate 92. In the bag member 96, an accommodation 58 is enclosed. A plurality of pistons 98 are disposed in the opening 94 so as to be movable forward and backward toward the end plate 20a. The position of each piston 98 is set corresponding to a desired portion of the end plate 20a so that a load can be applied to the fuel cell stack 90 satisfactorily. In place of the plurality of pistons 98, a single piston (not shown) may be used.

  In the second embodiment configured as described above, the contents 58 in the bag member 96 are frozen at a low temperature to expand the volume, and the volume of the bag member 96 is increased. For this reason, each piston 98 disposed in the opening 94 is pressed by the bag member 96 and protrudes toward the end plate 20a, and the end plate 20a is pressurized to apply a load in the tightening direction to the fuel cell stack 90. Is done.

  As a result, in the second embodiment, a desired tightening load can be reliably applied to the fuel cell stack 90 at the time of low-temperature startup, and fuel gas and oxidant gas can be leaked with a simple and inexpensive configuration. The same effects as those of the first embodiment can be obtained, for example, it can be prevented. Note that the bag member 96 can be accommodated in the end plate 20a or the insulating plate 18a without using the plate 92.

  In the first and second embodiments, the fuel cell stacks 10 and 90 are clamped and held via the tie rods 78, but the present invention is not limited to this. For example, the structure which hold | maintains the fuel cell stacks 10 and 90 in a box-shaped casing may be sufficient. Furthermore, you may provide the bag member 96 in the rear part for every piston 98 separately.

1 is a schematic configuration explanatory diagram of a fuel cell stack according to a first embodiment of the present invention. 2 is an exploded perspective view of a fuel cell constituting the fuel cell stack. FIG. FIG. 4 is a partially exploded perspective view of a bag member constituting the fuel cell stack. It is a related figure of temperature, stack length, and clamping load. FIG. 5 is a schematic configuration explanatory diagram of a fuel cell stack according to a second embodiment of the present invention. 2 is a cross-sectional view of a main part of a fuel cell of Patent Document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 90 ... Fuel cell stack 12 ... Fuel cell 14 ... Laminated body 16a, 16b ... Terminal plate 18a, 18b ... Insulation plate 20a, 20b ... End plate 22 ... Electrolyte membrane and electrode structure 24, 26 ... Metal separator 36 ... Solid Polymer electrolyte membrane 38 ... Anode side electrode 40 ... Cathode side electrode 50, 52 ... Seal members 54, 96 ... Bag member 56 ... Liquid chamber 58 ... Container 92 ... Plate 94 ... Opening 98 ... Piston

Claims (3)

A fuel cell stack in which a plurality of fuel cells in which a solid polymer electrolyte membrane is disposed between a pair of electrodes and a metal separator are alternately stacked,
A variable volume bag member disposed at an end of the fuel cell stack;
A container that is accommodated in the bag member and has a volume that expands below a predetermined temperature; and
A fuel cell stack comprising:   2. The fuel cell stack according to claim 1, wherein the container contains at least water. 3. The fuel cell stack according to claim 1, wherein a heat insulating member is interposed between the bag member and the metal separator.

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