JP2005093169A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell equipped with a sealing means of a structure of which a clearance between an electrode part and a sealing part surrounding the electrode part is large at assembly of a cell but gets small at the completion of the cell. <P>SOLUTION: Of the fuel cell, of which, at least either of a pair of sealing means keeping airtightness between an anode and an anode-side separator plate, and between a cathode and a cathode-side separator plate has a gas-suction inlet for pressurization, is composed of at least one elastic tube arranged on the surface of the separator plate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell using a polymer electrolyte used for a portable power source, a power source for portable devices, a power source for electric vehicles, a home cogeneration system, and the like.

  Fuel cells using polymer electrolytes generate electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen, which is a reaction gas, and an oxidant gas containing oxygen such as air. It is something to be made. Its basic structure consists of a polymer electrolyte membrane that selectively transports hydrogen ions, and an anode and a cathode disposed on both sides thereof. This is called MEA (membrane electrode assembly). The electrode is composed of a catalyst layer mainly composed of carbon powder supporting a platinum group metal catalyst, and a gas diffusion layer having both air permeability and electronic conductivity disposed on the outer surface of the catalyst layer.

  Next, a gas seal material or a gasket is disposed around the electrode with a polymer electrolyte membrane interposed so that the reaction gas to be supplied does not leak outside or the two kinds of reaction gases are mixed with each other. The sealing material and gasket are assembled in advance by being integrated with the electrode and the polymer electrolyte membrane. This is called MESA (membrane electrode sealing material assembly). Outside the MESA, a conductive separator plate is disposed for mechanically fixing the MESA and for connecting adjacent MEAs electrically in series with each other. In the portion of the separator plate that comes into contact with the MEA, a reaction gas is supplied to the electrode surface, and a gas flow path for carrying away the generated gas and surplus gas is formed. Although the gas flow path can be provided separately from the separator plate, a method of providing a gas flow path by providing a groove on the surface of the separator plate is generally used.

In order to supply the reaction gas to the gas flow path of the separator plate, a piping jig that branches the piping for supplying the reaction gas to the number of separator plates to be used and connects the branch destination directly to the groove of the separator plate is required. It becomes. This jig is called a manifold, and the type that connects directly from the reaction gas supply pipe as described above is called an external manifold. There is a type of this manifold called an internal manifold with a simplified structure. The internal manifold is a separator plate in which a gas flow path is formed with a through-hole, through the gas flow path to the hole, and a reaction gas is directly supplied from the hole.
Since the fuel cell generates heat during operation, it is necessary to cool it with cooling water or the like in order to maintain the battery at a good temperature. Usually, a cooling unit for flowing cooling water every 1 to 3 cells is inserted between the separator plate and the separator plate. In many cases, a cooling water channel is provided on the back surface of the separator plate to form a cooling unit. After alternately stacking these MESA, separator plates, and cooling units, stacking 10 to 200 cells, sandwiching them with end plates through current collector plates and insulating plates, fixing them from both ends with fastening bolts, The general laminated battery structure is surrounded by a heat insulating material.

Since the gasket of such a polymer electrolyte fuel cell performs gas sealing while making contact between the separator plate and the electrode, high dimensional accuracy and / or sufficient elasticity and gasket fastening allowance are required. Therefore, the conventional gasket used is a sheet-like flat gasket made of resin or rubber, an O-ring made of rubber, or the like.
Recently, as seen in Patent Document 1 and Patent Document 2, the load necessary for sealing the gasket in order to reduce the stack fastening load and reduce the weight, simplification, and cost of the structural member. Attempts have been made to reduce the thickness of the gasket, and not only an O-ring shape but also a gasket having a triangular or semicircular cross section has been attempted. In addition, when the gasket such as an O-ring has a certain cross-sectional area, an attempt is made to configure the gasket on the separator plate side.

  In a gasket configuration such as an O-ring that seals with the electrolyte membrane interposed therebetween, sealing is performed by pressing the electrolyte membrane against the separator plate with the O-ring. For this reason, a double gas seal configuration of an anode side gas seal and a cathode side gas seal is necessary, and there is a problem that the size of the seal portion is increased. Furthermore, it is necessary to form a groove in the separator plate for the O-ring, and there is a restriction that the thickness of the separator plate cannot be reduced in order to ensure the groove dimension. In view of such problems, a space-saving seal configuration has been attempted.

There is an O-ring or a flat gasket configuration that seals with a commonly used electrolyte membrane in between. In the O-ring, it is necessary to form a groove in the separator plate for the O-ring, and there is a restriction that the thickness of the separator plate cannot be reduced in order to secure the groove dimension. For this reason, an increase in volume and cost in the laminated battery and a complicated shape of the separator plate are necessary, which has been a cause of deterioration in the yield during the processing of the separator plate.
Moreover, when assembling the laminated battery, the separator plate is placed below, the MESA or MEA is placed thereon, the separator plate or the gasket and the separator plate are stacked thereon, and the steps are stacked. At that time, the gasket or separator plate placed on the MEA was assembled by the guide of the assembly jig. However, there are dimensional errors in each part, and from the viewpoint of assembly of electrodes, gaskets, and separator plates, a clearance is required between the gas seal part and the electrode part to ensure workability or manufacturing yield. Met.

  If the clearance is small, the reliability at the time of assembly is low, seal failure may occur due to part of the electrode biting into the seal part, etc., or the seal part may hit the electrode, reducing the battery performance, Excessive surface pressure worked, causing damage to the electrolyte membrane and a decrease in durability. In particular, the assembling property could not be ensured unless the clearance between the gasket and the MEA was large. For this reason, the reaction gas sometimes bypasses through the clearance between the gas flow path of the separator plate, the gasket, and the electrode. The surrounding clearance varies from cell to cell due to errors in assembly of the MEA or gasket, causing pressure loss variation between cells. When there is a variation in pressure loss between the cells, the reaction gas corresponding to the pressure loss of each cell flows in each cell in the laminated battery, and therefore the flow rate of the reaction gas varies. As a result, the battery performance varied, causing problems such as a decrease in generated voltage, a decrease in durability, and a decrease in stability during low-power operation. These symptoms were remarkable on the fuel gas side where the utilization rate of the reaction gas was relatively large.

Further, when the clearance between the gasket and the electrode is reduced in order to reduce the clearance, there is a need to improve the accuracy of the component dimensions, leading to a decrease in yield and an increase in component cost. In particular, in the molded separator plate, there is a limit to the processing accuracy of the guide portion used at the time of assembly, and therefore there is a limit to the improvement of the accuracy of the guide portion, and it is difficult to reduce the clearance. Therefore, after the separator plate is molded, the guide portion is added by post-processing. As a result, the cost has been increased.
Moreover, in the flat-shaped gasket, although the volume occupied by the gasket can be reduced, the above-described problems relating to the assembly and the problems relating to the bypass of the reaction gas in the clearance portion exist in common. Furthermore, an excessive fastening force is required to ensure the surface pressure required for the seal, which has been an obstacle to reducing the weight, compactness, and cost of the stack fastening member. In Patent Document 3, a tubular sealing material is used as an alternative to the O-ring for the purpose of reducing the fastening force and increasing the clearance in the thickness direction. However, it was not effective for bypassing the reaction gas through the gasket-electrode clearance.
JP-A-11-233128 JP 2002-141082 A JP-A-11-233128

As described above, the clearance between the electrode portion and the seal portion surrounding the electrode portion is limited due to the processing accuracy of the parts. This clearance is preferably large in terms of battery assembly workability and yield, but there is a disadvantage that the reaction gas bypasses the clearance portion. Thus, it has been difficult to reduce the clearance.
SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel cell having a sealing means configured such that a clearance between an electrode portion and a seal portion surrounding the electrode portion is large when the battery is assembled, but is small in a completed battery. And

The present invention includes a polymer electrolyte membrane, an anode and a cathode sandwiching the polymer electrolyte membrane, an anode separator plate having a gas flow path for supplying fuel gas to the anode, and a gas flow path for supplying oxidant gas to the cathode The present invention relates to a cell stack including a cathode-side separator plate and a fuel cell including a pair of sealing means for maintaining airtightness between an anode and an anode-side separator plate and airtightness between a cathode and a cathode-side separator plate.
The fuel cell according to the present invention is characterized in that at least one of the sealing means has at least one stretchable tube disposed on the surface of the separator plate having a pressurizing gas suction port.

  According to the present invention, at least one of the pair of sealing means on the anode side and the cathode side takes the sealing structure of an elastic tube having a gas inlet for pressurization disposed on the surface of the separator plate, and is elastic after stacking. By injecting gas into the tube and deforming it, the clearance required during assembly can be greatly reduced. As a result, the reliability of the seal can be improved, the yield during mass production can be improved, the cost can be greatly reduced, and the battery can be made more compact. Moreover, the fall of the battery performance by a reactive gas bypassing a clearance part can be suppressed.

  According to the present invention, at least one of a pair of sealing means for maintaining an airtightness between the anode and the anode-side separator plate and an airtightness between the cathode and the cathode-side separator plate has a pressurizing gas inlet and is disposed on the surface of the separator plate. It is characterized in that it consists of at least one stretchable tube.

By applying the above-described seal structure, the clearance between the electrode portion and the seal portion surrounding the electrode portion is large when the battery is assembled, but can be reduced in a completed battery. Therefore, it is possible to secure a sealing property and to assemble with high reliability. In addition, since the accuracy of the guide portion necessary for the separator plate during assembly can be reduced, post-processing on the separator plate can be eliminated, and the yield in manufacturing can be improved. Accordingly, the cost can be reduced.
On the other hand, in the completed battery, since the clearance can be reduced, the bypass of the reaction gas can be reduced and the battery performance can be prevented from being lowered.
Furthermore, according to the present invention, as the space occupied by the gasket is reduced, the battery can be reduced in weight, size and cost by reducing the stack volume and the stack fastening force.

In a preferred embodiment of the present invention, the stretchable tube is composed of two stretchable tubes surrounding the sealed portion, and the hardness of the outer stretchable tube is higher than that of the inner stretchable tube, and the stretchability is high. small.
In another preferred embodiment of the present invention, at least a part of the seal portion of the stretchable tube is fixed to the separator plate.
In another preferred embodiment of the present invention, the separator plate has a protrusion for preventing the expansion of the stretchable tube to the outside of the seal portion. The protrusion preferably has a curved edge portion in contact with the elastic tube, and the curvature radius of the edge portion is preferably 0.5 mm or more and 2 mm or less.
In still another preferred embodiment of the present invention, the cell stack has a pressurized gas manifold hole, and is configured to inject gas from the manifold hole into the pressurized gas inlet of the stretchable tube. ing.

The stretchable tube, which is a feature of the present invention, will be described. Necessary requirements for the stretchable tube include (1) flexible deformation by injection of pressurized gas and (2) high chemical durability. Examples of the material satisfying these include fluorine rubber, polyisobrene, butyl rubber, ethylene propylene rubber, silicone rubber, nitrile rubber, thermoplastic elastomer, and composite materials thereof.
The following effects can be obtained by arranging a plurality of elastic tubes made of such a material at the seal site so that the outer elastic tube has high hardness and low elasticity.
(I) High reliability is obtained with a double seal.
(Ii) The inner elastic tube can be deformed inward to reduce the clearance more effectively and reduce the reaction gas bypass.

When at least a part of the seal part is fixed to the separator plate, the elastic tube has the same effect as arranging a plurality of elastic tubes and deforming the inner elastic tube inward. can get. For fixing the stretchable tube, an adhesive layer is preferably used or fixed by baking.
When the separator plate has a protrusion on the outside of the seal portion, the stretchable tube can be prevented from bulging outward. Further, when a plurality of elastic tubes are provided, the same effect as that of deforming the inner elastic tube inward can be obtained. When the edge portion of the protrusion that contacts the stretchable tube is processed into a curved surface, mechanical damage to the stretchable tube can be reduced and durability can be improved. In consideration of the thickness of the separator plate and the clearance between the electrode and the separator plate, the radius of curvature R is preferably 0.5 mm or more and 2 mm or less when processing into the curved surface of the edge portion.

Embodiment 1
1 is a front view of an anode separator plate according to the present embodiment, FIG. 2 is a cross-sectional view of the cell stack taken along line II-II in FIG. 1, and FIG. 3 is a state in which a pressurizing gas is injected into an elastic tube. FIG. 4 is a sectional view taken along line IV-IV in FIG. 1.
The MEA 10 includes a polymer electrolyte membrane 11, and an anode 12 and a cathode 13 that sandwich the polymer electrolyte membrane 11. The anode 12 and the cathode 13 are composed of catalyst layers 14 and 15 and gas diffusion layers 16 and 17, respectively. The anode separator plate 20 is made of a graphite plate or a carbon plate formed by molding a mixture of carbon powder and a binder, and has a pair of manifold holes for fuel gas 22, a manifold hole for oxidant gas 25, and a manifold hole for cooling water 23. . The anode separator plate 20 further has a fuel gas flow path 24 communicating with the pair of manifold holes 22 on the surface facing the anode, and a flow of cooling water communicating with the pair of manifold holes 23 on the back surface. A path 27 is provided. In the example of FIG. 1, the gas flow path 24 is configured by four parallel grooves. A cover plate 26 for preventing the gasket from drooping into the groove is provided at a portion communicating with the manifold hole 22 of the gas flow path 24, and the gas flow path of this portion is in a tunnel shape. This cover plate is described in, for example, Japanese Patent Application Laid-Open No. 2000-133289, and is cited here.

  Similarly, the cathode separator plate 30 has a pair of fuel gas manifold holes, an oxidant gas manifold hole and a cooling water manifold hole, and a pair of oxidant gas holes on the surface facing the cathode. An oxidant gas flow path 35 communicates with the manifold holes, and a cooling water flow path 37 communicates with the pair of cooling water manifold holes on the back surface.

Next, the stretchable tube for sealing will be described.
First, the anode-side stretchable tube 40 attached to the anode-side separator plate 20 surrounds a pipe 46 disposed so as to surround the fuel gas flow path 24, and a pair of manifold holes 22, 23, and 25. The pipes 42, 43 and 45, the pipe 48 arranged so as to surround the pressurized gas manifold hole 28, and a connecting portion for connecting these pipes together. The stretchable tube 40 is bonded to the separator plate 20 with an adhesive layer 41. Similarly, a stretchable tube 50 is bonded to the surface of the cathode side separator plate 30 facing the cathode by an adhesive layer 51. Similar to the elastic tube 40, the elastic tube 50 includes a portion surrounding the cathode, a portion surrounding each pair of manifold holes, a portion surrounding the manifold hole communicating with the pressurized gas manifold hole 28, and these integrally connected. It consists of parts to do.

The cell stack is assembled as shown in FIG. 2 using the separator plates 20 and 30 with the stretchable tubes 40 and 50 attached as described above, and fastened with a predetermined fastening pressure. A pressurized gas is then injected into the stretchable tubes 40 and 50 and expanded to establish a seal structure.
With reference to FIG. 4, a structure for injecting the pressurizing gas from the pressurized gas manifold hole 28 to the stretchable tubes 40 and 50 will be described. The pressurized gas manifold hole 28 of the anode side separator plate 20, the pressurized gas manifold hole 38 of the cathode side separator plate 30, and the pressurized gas manifold hole provided in the polymer electrolyte membrane corresponding thereto are taken. Then, the pressurized gas is fed from the pressurized gas supply source. On the other hand, the pressurized gas injection portions 49 and 59 of the stretchable tubes 40 and 50 pass through the holes 29 of the separator plate 20 and the holes 39 of the separator plate 30, respectively, and open on the back surface of the separator plate. Since the holes 29 and 39 communicate with the pressurized gas manifold hole, the pressurized gas supplied to the pressurized gas manifold holes 28 and 38 is supplied to the pressurized gas injection portion 49. And 59 into the elastic tubes 40 and 50, causing the tubes 40 and 50 to expand.

By appropriately expanding the tubes 40 and 50, as shown in FIG. 3, the space between the polymer electrolyte membrane 11 and the anode separator plate 20 and the cathode separator plate 30 sandwiching the polymer electrolyte membrane 11 is hermetically sealed. The reaction gas supplied to the passages 24 and 35 and the anode 12 and the cathode 13 does not leak to the outside.
Between the anode side separator plate 20 and the cathode side separator plate 30, the cooling water channels 27 and 37 face each other to form one cooling water channel. In order to prevent the coolant supplied to the flow path and the gas supplied to the pressurized gas manifold hole from leaking to the outside, an O-ring 55 or the like is installed between the separator plates 20 and 30. .

<< Embodiment 2 >>
5 and 6 are cross-sectional views of the main part of the battery according to the present embodiment. FIG. 5 shows a state where no pressurized gas is injected into the stretchable tube, and FIG. 6 shows a state where pressurized gas is injected into the stretchable tube. The present embodiment is the same as the first embodiment except that the protrusions 26 and 36 are provided on the outer peripheral edges of the separator plates 20 and 30. The protrusions 26 and 36 prevent the elastic tubes 40 and 50 from bulging outward from the separator plate.

<< Embodiment 3 >>
7 and 8 are cross-sectional views of the main part of the battery according to the present embodiment. FIG. 7 shows a state where no pressurized gas is injected into the stretchable tube, and FIG. 8 shows a state where pressurized gas is injected into the stretchable tube. In the present embodiment, two elastic tubes 40a, 40b and 50a, 50b are used in place of the elastic tubes 40 and 50 of the first embodiment. The outer tubes 40b and 50b were made of fluororubber with high rubber hardness, and the inner tubes 40a and 50a were made of fluororubber with low hardness. According to this embodiment, the effect of the double seal structure and the hardness of the outer peripheral stretchable tube are higher than the inner one, so that the deformation of the inner stretchable tube is MEA as shown in FIG. The effect limited to the deformation toward the side is obtained.

<< Embodiment 4 >>
A front view of the anode separator plate according to this embodiment is shown in FIG. The anode-side separator plate 120 is made of a graphite plate or a molded carbon plate, and has a pair of fuel gas manifold holes 122, an oxidant gas manifold hole 125, and a cooling water manifold hole 123. The anode-side separator plate 120 further has a fuel gas flow path 124 communicating with the pair of manifold holes 122 on the surface facing the anode, and the flow of cooling water communicating with the pair of manifold holes 123 on the back surface. Has a road.

On the surface of the anode side separator plate 120 facing the anode, an anode side elastic tube 140 disposed so as to surround the fuel gas flow path 124 is attached by an adhesive layer. On the other hand, around each pair of manifold holes 122, 123, and 125, O-rings 142, 143, and 145 are mounted in grooves surrounding the manifold holes. An O-ring 148 is mounted in a groove provided so as to surround the pressurizing gas manifold 128 for injecting gas into the pressurized gas injection portion of the stretchable tube 140. A cover plate 126 for preventing the gasket from drooping into the groove is installed at a portion communicating with the manifold 122 of the gas flow path 124, and the gas flow path of this portion is in a tunnel shape. A part of the O-ring 142 is arranged over the cover plate 126.
Here, the anode side separator plate has been described, but the cathode side separator plate can also have the same configuration. Those skilled in the art will readily understand that the gas passage for injecting gas from the pressurizing gas manifold 128 to the pressurized gas injection portion of the stretchable tube 140 can be configured in the same manner as in the first embodiment.

In the above embodiment, both the pair of sealing means for keeping the airtightness between the anode and the anode-side separator plate and the airtightness between the cathode and the cathode-side separator plate are constituted by the stretchable tube having the gas inlet for pressurization according to the present invention. did. However, the stretchable tube of the present invention can be applied to only one of the pair of sealing means.
The battery is usually assembled by assembling one separator plate, MEA, and the other separator plate in that order on an assembly jig with guide pins raised. When the stretchable tube of the present invention is applied to only one of the sealing means, in the case of adopting such an assembly method, the stretchable tube is preferably attached to the separator plate assembled on the MEA.

Examples of the present invention will be described below.
Example 1
Carbon powder acetylene black (Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd., particle size 35 nm) was mixed with an aqueous dispersion of polytetrafluoroethylene (PTFE) (D1 manufactured by Daikin Industries, Ltd.) and dried. A water repellent ink containing 20% by weight of PTFE was prepared. This ink is applied and impregnated on one side of carbon paper (TGPH060H manufactured by Toray Industries, Inc.) which is the base material of the gas diffusion layer, heat treated at 300 ° C. using a hot air dryer, and a gas having a thickness of about 200 μm. A diffusion layer was formed.

On the other hand, 66 parts by weight of a catalyst body in which 50% by weight of a Pt catalyst is supported on Ketjen Black (Ketjen Black EC, Ketjen Black International Co., Ltd., particle size 30 nm), which is carbon powder, It was mixed with 33 parts by weight (polymer dry weight) of perfluorocarbon sulfonic acid ionomer (5% by weight Nafion dispersion manufactured by Aldrich, USA) as a binder, and the resulting mixture was molded to a thickness of 10 to 20 μm. A catalyst layer was formed.
The gas diffusion layer and the catalyst layer obtained as described above were bonded to both surfaces of a polymer electrolyte membrane (Nafion 112 membrane manufactured by DuPont, USA) to prepare a membrane electrode assembly (MEA). The size of the polymer electrolyte membrane is the same as the size of the separator plate described later, and the polymer electrolyte membrane is punched with holes of a size corresponding to the manifolds for fuel gas, cooling water, and oxidant gas described later. It processed by.

In this example, a polymer electrolyte fuel cell having the configuration according to the first embodiment was manufactured. The structure of each component of the fuel cell will be described.
First, the separator plate will be described. A gas impervious isotropic graphite plate (thickness 3 mm) was machined to form manifold holes for fuel gas, oxidant gas, and cooling water, and gas passages and cooling water passages. As shown in FIG. 1, the anode-side separator plate has a gas flow path composed of four parallel grooves (groove width of 1.5 mm), and a cooling water flow composed of six parallel grooves on the back surface. Has a road. The cathode-side separator plate has a gas flow path composed of seven grooves parallel to one surface, and a cooling water flow path composed of six grooves parallel to the other surface.

Next, the elastic tubes 40 and 50 constituting the pair of gaskets are made of fluoro rubber, and are arranged on the separator plate so that the periphery of the MEA and each manifold hole can be isolated as shown in FIG. The outer diameter of the stretchable tube when not pressurized was 0.5 mm and the wall thickness was 0.1 mm. All of these elastic tubes are connected. The tube was fixed to the separator plate with a butyl rubber adhesive layer having a thickness of 25 μm. The dimensions corresponding to the electrodes were such that the clearance from the electrode portion was 0.5 mm on one side from the center of the stretchable tube.
Next, an MEA having an electrode area of 100 cm ² was sandwiched between separator plates to which these stretchable tubes were joined, thereby constituting a single battery as shown in FIG. Between the adjacent single cells, a cooling unit for flowing cooling water, which is formed of an anode side separator plate and a cathode side separator plate, was provided. Then, an O-ring is interposed between the anode side separator plate and the cathode side separator plate to prevent leakage of cooling water.

The procedure for assembling the cell stack will be described below.
Place an assembly jig with a guide pin up, and place a separator plate with a stretchable tube on it. Next, the MEA is set along the guide pins. At that time, the gas diffusion layer of the MEA was carefully assembled so as not to protrude from the electrode set region surrounded by the elastic tube. After setting the MEA, the other separator plate is assembled. Since the separator plate is opaque, it cannot be visually observed that the gas diffusion layer of the MEA and the stretchable tube are in contact with each other.
After 50 cells were stacked as described above, they were fastened with a fastening load of 600 kgf with a stainless steel end plate and a fastening rod via a current collector plate and an insulating plate. Next, as shown in FIG. 3, nitrogen gas was supplied to the pressurizing manifold of the stretchable tube at a pressure of 1.0 kgf / cm ² to perform sealing. At this time, as a result of checking the contact between the MEA and the separator plate with the pressure sensitive paper, the surface pressure applied to the MEA was 10 kgf / cm ² .

A leak check was performed on the laminated battery thus manufactured. There were no leaks on the cathode side, the anode side, and the cooling water side, and it was confirmed that there was no problem in the fluid sealability as a laminated battery. In this case, the leak check was performed by closing the outlet side manifold of the flow path, allowing He gas to flow from the inlet side manifold at a pressure of 0.5 kgf / cm ² , and evaluating the pressure change after sealing.

<< Comparative Example 1 >>
A conventional gasket having a flat cross section was used for the seal.
FIG. 9 is a front view of an anode separator plate on which a gasket is set, and FIG. 10 is a cross-sectional view of an essential part thereof. The gasket 60 has a flat plate shape in which the central portion in which the anode of the MEA is to be set and the manifold hole portions of the fuel gas, the oxidant gas, and the cooling water are cut out. The gasket attached to the cathode side separator plate has the same configuration. The other configuration is the same as that of the first embodiment. The dimensions corresponding to the electrodes were such that the clearance with the electrode portion was 0.2 mm on one side from the end of the planar gasket. The cell stack was assembled in the same manner as in Example 1 using an assembly jig.
After stacking 50 cells, a leak check was performed in the same manner. Since the fastening load was 4000 kgf and the surface pressure applied to the MEA was 10 kgf / cm ² , the fastening was performed at 4000 kgf. As a result, in some cells, gas external leakage, gas cross leakage from the cathode side to the anode side, or both occurred, resulting in poor sealing. The leak check conditions are the same as those in the first embodiment.

<< Comparative Example 2 >>
Here, an example in which a conventional gasket having a flat cross section is used for the seal and the clearance between the electrode and the gas diffusion layer is increased will be described. The configuration is the same as that of Comparative Example 1 except that the clearance between the gasket and the electrode is 0.5 mm on one side. The cell stack was assembled in the same manner using an assembly jig. After stacking 50 unit batteries, a leak check was performed in the same manner. Since the fastening load was 4000 kgf and the surface pressure applied to the MEA was 10 kgf / cm ² , the fastening was performed at 4000 kgf. As a result, there was no leakage on the cathode side, the anode side, and the cooling water side, and it was confirmed that there was no problem in the fluid sealability as a laminated battery. The leak check conditions are the same as those in the first embodiment.

  When the batteries of Example 1 and Comparative Examples 1 and 2 were checked for leaks and disassembled, the MEA anode-side gas diffusion layer was assembled with a slight shift from the center of the anode-side gasket for all batteries. However, in the batteries of Example 1 and Comparative Example 2, since the part to be sealed is on the outside with a sufficient margin than the gas diffusion layer, sealing performance can be secured in the range of deviation of the gas diffusion layer during assembly. It was. On the other hand, in the battery of Comparative Example 1, the gas diffusion layer and the gasket were similarly deviated. However, in the gasket having a flat cross section, when even part of the gas diffusion layer rides on the gasket, the sealing performance is impaired, resulting in poor sealing. I understood that it would invite.

In assembling the cell, after setting the MEA, the other separator plate is assembled. At this time, it is desirable that the gas diffusion layer of the MEA is set at the center of the gasket. However, misalignment occurs due to accumulation of jig clearance, MEA dimensional error, and separator plate dimensional error. If the state of contact between the gas diffusion layer of the MEA and the gasket can be visually observed, stable assembly is possible. However, since the separator plate is opaque, the portion cannot be visually observed, and is assembled according to the guide pins.
In the case of a gasket having a conventional flat cross section, the gas diffusion layer rides on the gasket near the upper limit of the assumed positional deviation, and the sealing performance cannot be ensured. If the clearance is increased in order to improve the assemblability, the gas passes through the clearance and is no longer supplied to the electrode, so that the power generation performance is lowered.

On the other hand, when the gasket made of the stretchable tube of the present invention is used, even if the gas diffusion layer is displaced due to dimensional deviation, there is sufficient clearance between the gasket and the gas diffusion layer, so that sealing performance can be ensured. Furthermore, the clearance that was taken at the time of assembly can be reduced by injecting gas into the elastic tube from the pressurized gas manifold after fastening the cell stack and expanding it. become.
Furthermore, since the sealing parts are arranged in the vertical direction, no shear force or bending moment acts on the electrolyte membrane or the separator plate when the sealing material is fastened. Therefore, there is no stress on the separator plate or the like as well as the electrolyte membrane and the sealing material itself, and the risk of material damage can be eliminated.

Next, the polymer electrolyte fuel cells of Example 1 and Comparative Example 2 were maintained at 75 ° C., and hydrogen gas that had been humidified and heated to a dew point of 70 ° C. on the anode side was added to the cathode side at 60 ° C. Air that was humidified and warmed to the dew point was supplied. As a result, a battery open voltage of 50 V was obtained at the time of no load when both batteries did not output current. It was confirmed that there were no problems such as cross leak and short circuit.
The above battery has a fuel utilization rate of 80%, a current density of 0.3 A / cm ² , a fuel gas humidification with a dew point of 70 ° C., an oxidant gas side humidification of 65 ° C., and an oxidant gas utilization rate of 20% to 5%. Power generation was started under conditions that changed in increments, and power generation was performed for 12 hours under each condition. The battery voltage at that time and the minimum and maximum voltages during 12 hours of power generation are shown in FIG. 12 with error bars. As a result, in the laminated battery of Comparative Example 2, the output voltage became unstable under conditions where the oxidant gas utilization rate was 40% or more, and a decrease in output voltage was confirmed at 50% oxidant gas utilization rate. In contrast, the battery of Example 1 was confirmed to have a stable output voltage up to an oxidant gas utilization rate of 65%.

  Therefore, in the clearance between the gas diffusion layer on the cathode side and the gasket as in the battery of Comparative Example 2, the reaction gas bypasses the clearance and an amount of the reaction gas necessary for maintaining the battery performance is supplied to the electrode. It was confirmed that the product could not be supplied to the department. On the other hand, in the gasket configuration of Example 1, the clearance between the gas diffusion layer and the gasket at the time of assembly is large, but as described above, the elastic tube is deformed by gas injection and the clearance between the gas diffusion layer and the gasket is increased. Therefore, it is possible to reduce the bypass of the reaction gas and prevent the battery performance from being lowered.

Example 2
A laminated battery similar to that of Example 1 was produced except that two stretchable tubes were disposed as shown in FIG. The two stretchable tubes were made of fluororubber having different rubber hardness, and the tubes disposed on the outer side had higher rubber hardness than the inner tubes.
As in Example 1, the cell stack was fastened with a fastening load of 600 kgf. Next, sealing was performed by supplying nitrogen gas to the pressurizing manifold of the stretchable tube at a pressure of 0.5 to 1.0 kgf / cm ² . At this time, as a result of checking the contact between the MEA and the separator plate with the pressure sensitive paper, the surface pressure applied to the MEA was 10 kgf / cm ² .

The laminated battery thus manufactured was subjected to the same leak check as above in the range of gas pressure 0.5 to 1.0 kgf / cm ^{2 in} the elastic tube. At the same time, the laminated battery of Example 1 was subjected to a leak test in the same gas pressure range. The results are shown in Table 1. In the first embodiment, the seal gas pressure leak occurs in the range of 0.5~0.7kgf / cm ^2, no leakage from Example 2, 0.5 kgf / cm ^2, showed good sealability . This is due to the double seal structure and the hardness of the outer elastic tube is higher than that of the inner one, so the deformation of the inner elastic tube is a deformation facing the MEA side as shown in FIG. It is an effect limited to. The power generation characteristics of the laminated battery were the same as those in Example 1.

Example 3
As shown in FIG. 5, a laminated battery similar to that of Example 1 was produced except that a protrusion was provided on the outer peripheral edge of the separator plate. The edge portion of the protrusion that is in contact with the expanding tube was chamfered so as to be a curved surface with a radius of curvature R = 0.5 mm.
The cell stack was fastened with a fastening load of 600 kgf as in Example 1. Next, sealing was performed by supplying nitrogen gas to the pressurizing manifold of the stretchable tube at a pressure of 0.5 to 1.0 kgf / cm ² . At this time, as a result of checking the contact between the MEA and the separator plate with the pressure sensitive paper, the surface pressure applied to the MEA was 10 kgf / cm ² .

The laminated battery thus manufactured was subjected to the same leak check as above in the range of gas pressure 0.5 to 1.0 kgf / cm ^{2 in} the elastic tube. The results are shown in Table 1. As in the case of Example 2, there was no leakage from 0.5 kgf / cm ² , and good sealing performance was shown. This is the effect that the protrusion on the outer peripheral edge of the separator plate functions in the same manner as the outer peripheral seal of Example 2, and the deformation of the elastic tube is limited to the deformation facing the MEA side as shown in FIG. . The power generation characteristics of the laminated battery were the same as those in Example 1.

Example 4
As described in the fourth embodiment, the outer periphery of the electrode is sealed by an elastic tube, and each manifold hole for fuel gas, cooling water, oxidant gas, and pressurized gas is sealed by an O-ring. A laminated battery similar to that of Example 1 was produced except that.
The cell stack was fastened in the same manner as in Example 1 with a fastening load of 600 kgf. Next, sealing was performed by supplying nitrogen gas to the pressurizing manifold of the stretchable tube at a pressure of 0.5 to 1.0 kgf / cm ² . At this time, as a result of checking the contact between the MEA and the separator plate with the pressure sensitive paper, the surface pressure applied to the MEA was 10 kgf / cm ² .

A leak check similar to the above was performed on the laminated battery thus manufactured. There were no leaks on the cathode side, the anode side, and the cooling water side, and it was confirmed that there was no problem in the fluid sealability as a laminated battery. The power generation characteristics of the laminated battery were the same as those in Example 1.
Thus, even when the seal structure that pressurizes the elastic tube is applied only to the outer peripheral portion of the electrode that requires clearance accuracy, the same sealing performance as in Example 1 could be secured. Since the structure can be simplified by arranging the stretchable tube only on the outer periphery of the electrode, it is more effective in assembling reliability and cost reduction.

Although the present invention has been specifically described with reference to Examples and Comparative Examples, the present invention is not limited to them.
In addition to fluororubber, members used for gaskets including elastic tubes include polyisobrene, butyl rubber, ethylene propylene rubber, silicone rubber, nitrile rubber, thermoplastic elastomer, liquid crystal polymer, polyimide resin, polyether ether ketone resin, poly Ether imide resin, polyphenylene sulfide resin, terephthalamide resin, polyether sulfone resin, polysulfone resin, syndiotactic polystyrene resin, polymethylpentene resin, modified polyphenylene ether resin, polyacetal resin, polypropylene resin, fluorine resin, polyethylene terephthalate resin, Or those composite materials are used. As the pressure-sensitive adhesive for bonding the stretchable tube to the separator plate, a copolymer of styrene and ethylene butylene, polyisobutylene, ethylene propylene rubber, butyl rubber, a composite product thereof, or the like is used.

In the above embodiment, the stretchable tube is fixed to the separator plate with an adhesive, but the same effect can be obtained even if it is fixed to the separator plate directly by baking or the like. Further, as a method for pressurizing the stretchable tube, in the embodiment, the pressurization is performed by nitrogen. However, any fluid or gas can be used as long as the fluid can be pressurized. For example, air pressurized by a compressor, fuel gas supplied under pressure, cooling water, or the like can be used.
The sealing with an elastic tube does not require a groove to fill the O-ring unlike the sealing method using an O-ring, so the thickness of the separator plate can be reduced by that amount, and the laminated battery can be made compact. Needless to say. Furthermore, according to the present invention, the fastening force of the cell stack can be greatly reduced, so that the stack fastening structure itself can be simplified, and a resin can be used for the material of the end plate. Cost can be reduced.

  According to the present invention, it is possible to greatly reduce the clearance required at the time of assembly, improve the reliability of the seal, and significantly reduce the cost by improving the yield during mass production. Useful for molecular electrolyte fuel cells.

3 is a front view of an anode separator plate according to Embodiment 1. FIG. FIG. 2 is a cross-sectional view of the cell stack according to Embodiment 1 cut along the line II-II in FIG. 1. FIG. 2 is a cross-sectional view of the cell stack according to Embodiment 1 cut along the line II-II in FIG. FIG. 4 is a cross-sectional view of the cell stack according to the first embodiment cut along line IV-IV in FIG. 1. FIG. 6 is a cross-sectional view of a main part of a battery according to a second embodiment. It is sectional drawing of the principal part of the battery concerning Embodiment 2, and shows the state which inject | poured pressurized gas into the elastic tube. FIG. 6 is a cross-sectional view of a main part of a battery according to a third embodiment. It is sectional drawing of the principal part of the battery concerning Embodiment 3, and the state which injected the pressurized gas into the elastic tube is shown. FIG. 10 is a front view of an anode separator plate in a fourth embodiment. It is a front view of the anode side separator board in a comparative example. It is principal part sectional drawing of the cell stack in a comparative example. It is a graph which shows the relationship between the oxidizing agent utilization factor and battery voltage of the battery of Example 1 and Comparative Example 2.

Explanation of symbols

10 MEA
11 Polymer Electrolyte Membrane 12 Anode 13 Cathode 14, 15 Catalyst Layer 16, 17 Gas Diffusion Layer 20 Anode Side Separator Plate 30 Cathode Side Separator Plate 22 Fuel Gas Manifold Hole 23 Cooling Water Manifold Hole 24, 35 Gas Flow Path 25 Oxidant Manifold hole 27, 37 Cooling water flow path 28, 38 Pressurized gas manifold hole 40, 50 Stretchable tube 41, 51 Adhesive layer

Claims (6)

  Polymer electrolyte membrane, anode and cathode sandwiching the polymer electrolyte membrane, anode side separator plate having a gas channel for supplying fuel gas to the anode, and cathode side separator having a gas channel for supplying oxidant gas to the cathode And a pair of sealing means for maintaining airtightness between the anode and the anode side separator plate and airtightness between the cathode and the cathode side separator plate, and at least one of the sealing means has a gas inlet for pressurization. A fuel cell comprising at least one stretchable tube disposed on the surface of the separator plate.   2. The fuel cell according to claim 1, wherein the stretchable tube comprises two stretchable tubes surrounding the sealed portion, and the hardness of the outer stretchable tube is higher than that of the inner stretchable tube and the stretchability is small.   The fuel cell according to claim 1 or 2, wherein at least a part of a seal portion of the stretchable tube is fixed to the separator plate.   The fuel cell according to any one of claims 1 to 3, wherein the separator plate has a protrusion on the outside of the seal portion that prevents the expansion tube from bulging outward.   The fuel cell according to claim 4, wherein an edge portion of the protrusion that contacts the stretchable tube is curved, and the curvature radius of the edge portion is not less than 0.5 mm and not more than 2 mm.   5. The cell stack according to claim 1, wherein the cell stack includes a pressurized gas manifold hole, and gas is injected from the manifold hole into a pressurized gas suction port of the stretchable tube. Fuel cell.

Images