JP2009163907A - Polymer electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte fuel cell capable of exhibiting superior sealing properties and adding an appropriate fastening force, through alleviation of an uneven in-face contact pressure distribution between a membrane electrode assembly and a separator. <P>SOLUTION: As to end plates used in a fastening structure, a face at a unit cell module side is to be of a recessed shape, in which a site fastened with a fastening member is the thinnest and a site farthest from the fastening member is the thickest, while, it is flattened after fastening, so that a load is to be uniformly added on a whole face of the unit cell module. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell used for a portable power source, an electric vehicle power source, a domestic cogeneration system, and the like, and more particularly, to a polymer electrolyte fuel cell using a polymer electrolyte.

A fuel cell using a polymer electrolyte generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air. This fuel cell basically includes a polymer electrolyte membrane that selectively transports hydrogen ions and a pair of electrodes formed on both sides of the polymer electrolyte membrane, that is, an anode and a cathode. These electrodes are mainly composed of carbon powder supporting a platinum group metal catalyst, and have both a gas permeability and an electronic conductivity disposed on the outer surface of the catalyst layer formed on the surface of the polymer electrolyte membrane and the catalyst layer. It has a gas diffusion layer. An assembly in which the polymer electrolyte membrane and the electrode (including the gas diffusion layer) are integrally joined together is called an electrolyte membrane electrode assembly (hereinafter referred to as “MEA”).

  Further, on both sides of the MEA, conductive separators for mechanically sandwiching and fixing the MEAs and electrically connecting adjacent MEAs to each other in series are disposed. Gas separators are formed in portions of the separator that come into contact with the MEA to supply reaction gas such as fuel gas and oxidant gas to the respective electrodes and carry away generated water and surplus gas. Such a gas flow path can be provided separately from the separator, but a system in which a groove is provided on the surface of the separator to form a gas flow path is common. Note that the structure in which the MEA is sandwiched between the pair of separators is referred to as a unit cell module.

  The supply of the reaction gas to the gas flow path formed between the separator and the MEA and the discharge of the reaction gas and product water from the gas flow path are performed by providing a through hole called a manifold hole at the edge of the separator. The reaction is performed by distributing the reaction gas from the manifold hole to each gas flow path by connecting the inlet / outlet of the flow path to the manifold hole.

  In addition, the portion where the electrode in the MEA is formed, that is, the outer periphery of the power generation region, so that the fuel gas and the oxidant gas supplied to the gas flow channel do not leak to the outside or the two kinds of gases are mixed with each other. Between the pair of separators, a gas seal material or a gasket is disposed as a seal member so as to surround the pair. These gas seals and gaskets also seal around the manifold holes.

  Since the fuel cell generates heat during operation, it is necessary to cool the fuel cell with cooling water or the like in order to maintain the battery in a favorable temperature state. Usually, a cooling unit for flowing cooling water is provided for every 1 to 3 cells. After alternately stacking these MEAs, separators, and cooling units and laminating 10 to 200 cells, end plates are arranged on both ends of the laminate via current collector plates and insulating plates, It is the structure of a general laminated battery (fuel cell stack) that sandwiches this laminated body and is fixed from both ends with fastening bolts and rods.

  In such a stacked battery, a plurality of unit cell modules including a cooling unit are stacked in one direction, a pair of end plates are arranged at both ends, and each end plate is fixed with a fastening bolt and a rod, A tightening method for tightening the cell module is employed. As such a fastening method, from the viewpoint of mechanical strength, a metal material such as stainless steel is usually used for the end plate and fastening bolt, and an insulating plate is provided between these end plate and fastening bolt and the laminated battery. Therefore, a structure is employed in which the current is electrically insulated and current does not leak outside through the end plate. In addition, an end plate that is integrated with an insulating plate and molded or processed an insulator is also used. As for fastening bolts, a method of passing through a through-hole formed in the edge of the separator and a method of fastening the entire laminated battery with a metal belt over an end plate are common.

  In a laminated battery employing such a fastening method, it is important that the single cell module is fastened with a uniform fastening force in a plane (in a plane orthogonal to the stacking direction). With this uniform fastening force, it is possible to prevent leakage of air, hydrogen, cooling water, etc., and to prevent damage to the unit cell module, thereby further improving power generation efficiency and extending battery life. Because it becomes. From the viewpoint of uniform fastening force and cost reduction in such a tightening method, for example, in Patent Document 1, a bolster composed of a header and a low-rigid plate is bent and deformed convexly with respect to the stack before fastening, There has been proposed a method of reducing parts such as springs and bellows by tightening to a stack with a rod.

  Specifically, as shown in FIG. 16, a header 802 sandwiching the fuel cell stack 801 and a bolster 803 made of a low-rigid plate are provided, and the bolster 803 is elastically drawn toward the header 802. The bolster 803 is preliminarily stacked by a fixing portion provided at both ends of the surface opposite to the stack 801 and a tension rod 805 spanned between the fixing portions and tightened by a tension adjusting nut. Since the surface of the bolster 803 is pressed against the stack 801 when the rod 804 is temporarily bent and deformed toward the surface 801 and then drawn toward the stack 801 by the rod 804 to become a flat surface, A uniform load is applied to the surface.

Japanese Patent No. 3605937 (4th page, FIG. 1)

  By the way, when a plurality of unit cell modules are stacked in one direction, a pair of end plates are disposed at both ends thereof, and the end plates are fixed by fastening bolts and rods, the end plates are greatly deformed by the fastening bolts and rods. Sometimes. Therefore, due to the deformation of the end plate generated by fastening with the fastening bolt and the rod, a uniform fastening force cannot be applied to the single cell module, and a non-uniform in-plane contact pressure distribution is generated in the MEA contact pressure. Such a non-uniform in-plane contact pressure distribution has a non-uniform in-plane contact resistance distribution, which causes a problem of reducing power generation performance in the fuel cell. In order to suppress the deterioration of the power generation performance due to such non-uniform distribution of the contact resistance, a measure for applying a load more than necessary as the fastening force may be employed. In that case, there is a problem that the mechanical strength of the MEA or gasket is accelerated and the life of the fuel cell is shortened.

  Furthermore, in the method as disclosed in Patent Document 1, the degree of bending deformation of the bolster 803, which is an end plate, that can make the fastening force uniform is not defined. In addition, since the bolster 803 is curved and deformed in a convex manner with respect to the stack 801, a sufficient load is applied to the MEA, but the MEA and the outer periphery of the manifold, that is, the outer periphery of the bolster 803 are arranged. The gas sealing material and the gasket do not have a sufficient fastening load, resulting in a problem that the sealing performance is insufficient.

  Accordingly, an object of the present invention is to solve the above-described problem, and in a polymer electrolyte fuel cell, it is possible to reduce the occurrence of non-uniform in-plane contact pressure distribution between the membrane electrode assembly and the separator. Another object of the present invention is to provide a polymer electrolyte fuel cell in which a fastening end plate having an optimum shape that can sufficiently exhibit a sealing property and can add an appropriate fastening force is used.

  In order to achieve the above object, the present invention is configured as follows.

According to the first aspect of the present invention, a plurality of unit cell modules having a membrane electrode assembly and a pair of separators sandwiching the membrane electrode assembly are laminated to form a laminate, and ends are formed at both ends of the laminate. In a polymer electrolyte fuel cell comprising a fuel cell stack that is assembled by sandwiching and fastening the laminate with the pair of end plates by a plurality of fastening members, each of which is arranged with a plate,
Each of the end plates is configured such that the rigidity of the non-clamping portion away from the clamping portion is higher than that of the clamping portion to be clamped by the fastening member, and the surface of each end plate on the laminate side in the fastening state The present invention provides a polymer electrolyte fuel cell characterized by flattening.

  With this configuration, a uniform fastening force can be applied to the single cell module without increasing the number of parts, and the non-uniform in-plane contact pressure distribution of the MEA can be reduced while exhibiting sealing performance.

  According to the second aspect of the present invention, in each of the end plates, the surface of the cell side before fastening is thicker at the non-clamping part away from the clamping part than at the clamping part. After the fastening, due to the fastening force by the fastening member, the surface on the cell side of each end plate becomes a flat surface, and the shape of the surface on the opposite side to the cell side of each end plate is The non-clamping part is elastically deformed so that the thickness of the non-clamping part away from the clamping part is larger than that of the clamping part, so that the rigidity of the non-clamping part becomes higher than that of the clamping part. A polymer electrolyte fuel cell according to claim 1 is provided.

  According to the third aspect of the present invention, each end plate has a Young's modulus of the material of the tightening portion smaller than a Young's modulus of the material of the non-tightening portion separated from the tightening portion. The polymer electrolyte fuel cell according to the first aspect, which is configured so that the rigidity of the non-tightened portion is higher than that of the tightened portion.

  As described above, according to the polymer electrolyte fuel cell of the present invention, each end plate is configured so that the rigidity of the part away from each fastening member is higher than the part fastened by the fastening member. The laminate is sandwiched between the pair of end plates, and the plurality of single cell modules are fastened by the plurality of fastening members. For this reason, the rigidity of the end plate itself is increased with respect to a portion away from each fastening member (a portion to which the fastening force by the fastening member is difficult to be applied), while a portion to be tightened with the fastening member (tightening with the fastening member). Since the rigidity of the end plate itself is low for the portion to which a force is easily applied, the tightening force by the fastening member tends to be uniform as a whole, and a plurality of units are easily viewed from the end plate side. A uniform fastening force can be applied to the battery module, and the fastening load can be reduced while sufficiently maintaining the sealing performance. Therefore, the durability of the fuel cell can be improved.

  Embodiments according to the present invention will be described below in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view schematically showing a part of a structure of a fuel cell stack 101 as an example of a polymer electrolyte fuel cell (PEFC) according to a first embodiment of the present invention.

  As shown in FIG. 1, a substantially rectangular parallelepiped fuel cell stack 101 includes a plurality of unit cell modules (cells) 1 stacked to form a stacked body 100, and the stacked body including the plurality of cells 1. Current collector plate 2 and end plate 3 are attached to the outermost layers at both ends of 100, respectively, and laminated body 100 is sandwiched and assembled by a pair of end plates 3 by a plurality of fastening members. Each of the fastening members includes a fastening bolt 7 and a nut 8. The laminated body 100 composed of the plurality of cells 1 includes, from one end plate 3 side, one end plate 3, current collector plate 2, each cell 1 of the laminate 100, current collector plate 2, and the other end plate 3. The fastening bolts 7 are respectively inserted through the bolt through holes 6 of the end plate 3, and the nut 8 is screwed into the threaded portion of the fastening bolt 7 on the outside of the other end plate 3 and fastened. A large number of inner springs 4 as an example of an elastic body are attached to the inner surface of the end plate 3, that is, the recess 3 g on the current collector plate side, and between the head 7 a of the fastening bolt 7 and the end plate 3. The outer springs 5 are respectively attached.

  In the first embodiment, as an example, 60 cells 1 are stacked to form a stacked body 100, and the end plate 3 at the end of the stacked body 100 has a square planar shape. At the center position, the four fastening bolts 7 inserted through the four bolt through holes 6 and the four nuts 8 are fastened, for example, with a fastening force of 10 kN.

  The cell 1 is formed by sandwiching an electrolyte membrane electrode assembly (MEA) 9 having gaskets on both peripheral edges between a pair of conductive separators 10 (specifically, an anode side separator 10A and a cathode side separator 10C). It is configured. As a result, the gas diffusion layer disposed on the outermost side of the electrode layer of the main body portion 9a of the MEA 9 contacts the anode side or cathode side separator 10A or 10C, and the fuel gas flow channel groove 12A of the anode side separator 10A. The gas diffusion layer contact portion of the MEA 9 and the gas diffusion layer contact portion of the oxidant gas flow path 12C of the cathode separator 10C are covered by the gas diffusion layer of each surface of the MEA 9. In other words, the gas diffusion layer of the anode separator 10A is exposed to the fuel gas flowing through the gas diffusion layer contact portion on one side of the MEA 9, and the oxidant flowing through the gas diffusion layer contact portion on the other surface of the MEA 9 The gas diffusion layer on the cathode separator 10C side is exposed to the gas, and an electrochemical reaction of PEFC can be caused. Further, in the stacked cells 1, the main body portions 9a of the adjacent MEAs 9 are electrically connected to each other in series and in some cases in parallel.

  A pair of through-holes through which fuel gas and oxidant gas circulate, that is, a pair of fuel gas manifold holes 11A and a pair of oxidant gas manifold holes 11C, pass through the periphery of the separator 10 and the periphery 9b of the MEA 9, that is, the gasket. Each is worn. In a state in which the cells 1 are stacked to form the stacked body 100, these through holes 11A and 11C are connected to each other to form a fuel gas manifold and an oxidant gas manifold.

  Further, similarly to the fuel gas manifold hole 11A and the oxidant gas manifold hole 11C, the back surface (fuel gas flow channel groove) of the anode side separator 10A and the cathode side separator 10C is formed in the peripheral part of the separator 10 and the peripheral part 9b of the MEA 9, respectively. Cooling water manifold holes 11W that form two pairs of manifolds that communicate with the cooling water flow channel groove 12W on the surface 12A or the surface where the oxidant gas flow channel 12C is not formed and through which the cooling water flows are respectively formed. As a result, in a state where the cells 1 are stacked to form the stacked body 100, the manifold holes 11W are connected and coupled to each other to form two pairs of cooling water manifolds.

  The main body 9a of the MEA 9 includes a polymer electrolyte membrane that selectively transports hydrogen ions, and a pair of electrode layers (that is, anode and cathode electrodes) formed on both sides of the polymer electrolyte membrane from the periphery. Layer). The electrode layer has a laminated structure having a gas diffusion layer and a catalyst layer disposed between the gas diffusion layer and the polymer electrolyte membrane. The catalyst layer is usually composed of carbon powder carrying a platinum group metal catalyst as a main component, and is formed on the surface of the polymer electrolyte membrane. The gas diffusion layer is formed on the outer surface of the catalyst layer, and has both air permeability and electronic conductivity.

  The anode-side separator 10A and the cathode-side separator 10C constituting the separator 10 have a flat plate shape, and the surface on the side in contact with the MEA 9, that is, the inner surface corresponds to the shape of the MEA 9 and the gasket. Here, as an example, glassy carbon (thickness 3 mm) manufactured by Tokai Carbon Co., Ltd. is used as the anode separator 10A and the cathode separator 10C. In the anode-side separator 10A and the cathode-side separator 10C, various manifold holes 11A, 11C, 11W and bolt through-holes 6 respectively penetrate the anode-side separator 10A and the cathode-side separator 10C in the thickness direction. Further, a fuel gas channel groove 12A or an oxidant gas channel groove 12C is formed on the inner surfaces of the anode side separator 10A and the cathode side separator 10C, and a cooling water channel is formed on the back surface of the anode side separator 10A and the cathode side separator 10C. A groove 12W is formed. The various manifold holes 11A, 11C, 11W, the bolt through holes 6, the fuel gas passage groove 12A, the oxidant gas passage groove 12C, the cooling water passage groove 12W, and the like are formed by cutting or molding.

  Here, the cooling water channel groove 12W is formed so as to connect the two pairs of cooling water manifold holes 11W. That is, the cooling water branches from one manifold 11W, that is, the cooling water manifold 11W on the cooling water supply side, to the cooling water passage groove 12W, respectively, and the other cooling water manifold 11W, that is, the cooling water on the cooling water discharge side. It is configured to flow through the manifold 11W. Thereby, the cell 1 can be maintained at a predetermined temperature suitable for the electrochemical reaction by the heat transfer capability of water. Note that, similarly to the fuel gas and the oxidant gas, the cooling water supply / discharge passage may be formed in an external manifold structure without forming the cooling water manifold hole 11W in the peripheral edge portion of the separator 10 and the peripheral edge portion 9b of the MEA 9. Furthermore, without forming the cooling water channel groove 12W on the back surface of the anode side separator 10A and the cathode side separator 10C, a cooling unit in which cooling water circulates is inserted between the adjacent cells 1 to connect the cells 1 to each other. You may comprise so that it may laminate | stack via a cooling unit.

  The gasket is made of an elastic body, and is deformed according to the shape of the anode side separator 10A or the cathode side separator 10C by pressing the MEA 9 and the anode side separator 10A or the cathode side separator 10C. And the periphery of the cooling water manifold hole 11W is sealed. Similarly, in the fuel gas manifold hole 11A and the oxidant manifold hole 11C, the periphery of the manifold holes 11A and 11C is sealed by the gasket.

  General sealing members such as gaskets made of a heat-resistant material are disposed around the various manifold holes 11A, 11C, and 11W on the back surfaces of the anode side separator 10A and the cathode side separator 10C. As a result, leakage of fuel gas, oxidant gas and cooling water from the connecting portion between the cells 1 of the various manifold holes 11A, 11C, 11W is prevented between adjacent cells 1.

  The current collector plate 2 is disposed outside the cell stack 100 and, as an example, uses a copper plate plated with gold so that the generated electricity can be efficiently collected. For example, the current collector plate 2 may be made of a metal material having good electrical conductivity, such as iron, stainless steel, or aluminum. In addition, as an example, the surface treatment of the current collector plate 2 may be performed by tin plating or nickel plating. An insulating plate for insulating electricity is usually disposed outside the current collecting plate 2. In the first embodiment, as an example, the end plate 3 using an electrically insulating material serves as its role. Is also used.

  Here, as an example, the end plate 3 is manufactured by injection molding using polyphenylene sulfide resin. The pipe integrated with the end plate 3 is configured to be pressed against the manifold of the cell stack 100 via a gasket. The shape of the inner surface of the end plate 3 on the side of the current collector plate 2 before fastening is configured such that the rigidity of the parts separated from the fastening bolts 7 and the nuts 8 is higher than the parts fastened by the fastening bolts 7 and the nuts 8. is doing. As a specific example, as shown in FIG. 2A, a portion of the end plate 3 around the bolt through hole 6 of the fastening bolt 7, that is, a portion around the bolt through hole (intermediate portion of each side) (an example of a tightening portion) 3b The thickness of the outer peripheral portion (corner) (an example of the non-tightened portion) 3a that is the farthest from each fastening bolt 7 is the thickest, and the thickest corner from the bolt through-hole surrounding portion 3b The structure is such that up to 3a are connected by a gentle curved surface. In the first embodiment, an inner spring 4 that applies a load to the cell 1 is further provided on the inner side of the end plate 3 in a region facing the projection portion (main body portion 9a) of the MEA 9, that is, the inner portion of the cell 1. The urging force of the inner spring 4 is managed with a tightening dimension such that an 8.4 kN load is applied to the laminated body 100 with the end plates 3 being fastened to the laminated body 100 in a concentrated manner. The outer spring 5 is configured to fasten the entire fuel cell stack 101 at, for example, 10 kN so that the variation of the tightening force by the tightening bolt 7 can be adjusted when the tightening bolt 7 and the nut 8 are assembled.

  2A shows the shape of the end plate 3 before the cell 1, that is, the laminated body 100 is tightened, while FIG. 2B shows the shape of the end plate 3 after the laminated body 100 is tightened.

  That is, as described above, in FIG. 2A before the laminate 100 is fastened by the pair of end plates 3, the shape of the inner surface of each end plate 3 on the current collecting plate 2 side is the periphery of the bolt through hole 6 of the fastening bolt 7. (Between each side) 3b is thin, and the outermost part (corner) 3a farthest from each fastening bolt 7 is thickest.

  On the other hand, as shown in FIG. 2B, after the laminate 100 is fastened with the pair of end plates 3, the shape of the inner surface of each end plate 3 on the side of the current collecting plate 2 becomes flat. The shape of the outer surface of each end plate 3 on the side opposite to the inner surface on the 2 side is such that the thickness of the portion (intermediate portion of each side) 3b around the bolt through-hole 6 of each fastening bolt 7 is small. The thickness of the outer peripheral portion (corner) 3a farthest from the center is the thickest. This is because when the laminated body 100 is sandwiched between a pair of end plates 3 and a load is applied with four fastening bolts 7 and four nuts 8, each end plate 3 is affected by the tightening force and each end plate 3 is affected. This is because the plate 3 itself is deformed, and the current collecting plate side of each end plate 3, that is, the surface of the single cell module 1 side is flat, and the current collecting plate 2 and the laminate 100 are tightened with a substantially uniform force. is there. Since each end plate 3 is made of synthetic resin, the end plate 3 itself can be easily deformed. Thus, each end plate 3 becomes a flat surface with respect to the laminated body 100 and gives a tightening force. Therefore, a load can be applied uniformly to the surface of the unit cell module 1, and the anode of the laminated body 100 can be applied. The deformation of the side separator 10A or the cathode side separator 10C can be suppressed, the MEA 9 and the gasket on the outer periphery thereof can be evenly loaded, the sealing performance can be sufficiently maintained, and the in-plane contact pressure difference of the MEA 9 is also increased. Can be reduced. Thereby, the durability of the fuel cell stack 1 can be improved.

  In other words, each end plate 3 is configured such that the portion separated from each fastening bolt 7 or nut 8 has higher rigidity than the portion fastened by the fastening bolt 7 and nut 8. The laminated body 100 is sandwiched between the end plates 3, and the plurality of unit cell modules 1 are fastened by the plurality of fastening bolts 7 and nuts 8. For this reason, the rigidity of the end plate itself is increased for the portion where the fastening force by the fastening bolt 7 and the nut 8 is difficult to be applied, whereas the portion where the fastening force by the fastening bolt 7 and the nut 8 is easily applied. Since the rigidity of the end plate itself is low, the fastening force by the fastening bolt 7 and the nut 8 tends to be uniform as a whole, and a uniform fastening force is applied to the plurality of unit cell modules 1. Thus, the fastening load can be reduced while sufficiently maintaining the sealing performance, and the durability of the fuel cell can be improved. Moreover, according to the said structure, while the electrolyte membrane electrode assembly (MEA) 9 can be pressed uniformly by the inner side spring 4, the sealing member with small reaction force can be firmly pushed off by the outer side spring 5. FIG.

  The present invention is not limited to the end plate 3 with a spring, but can be applied to an end plate 3A without a spring.

  FIG. 3B shows an explanatory view including a perspective view, an end view, and a cross-sectional view taken along line AA of the end plate 3A without a spring instead of the end plate 3 with a spring. Only the recess 3g for disposing the inner spring 4 is unnecessary. Thus, when using the end plate 3A without a spring, there exists an advantage that a structure is simplified rather than the end plate 3 with a spring.

  FIG. 5 is a perspective view schematically showing a part of the structure of a fuel cell stack 101 as an example of a polymer electrolyte fuel cell (PEFC) using the end plate 3A without a spring. Since the structure other than the end plate 3A is the same as that of the end plate 3, the description thereof is omitted. Even with the end plate 3A without a spring, the same effect as the end plate 3 with a spring can be obtained except for the effect of the spring.

  FIG. 6 is a bottom view showing the surface on the side of the current collector plate of the square spring-less end plate 3A in which the bolt through holes 6 are formed through the middle portions of the respective sides.

  (A1), (B1), and (C1) in FIG. 7 are respectively an end view along the line AA in FIG. 6 (corresponding to a side view of the end plate 3A) and a line BB in the end plate 3A. Sectional view (corresponding to a sectional view along the line connecting the intermediate portions of the opposite sides of the end plate 3A) and CC sectional view (corresponding to a sectional view along the diagonal connecting the opposing corners of the end plate 3A) It is explanatory drawing including. (A2) to (A6), (B2) to (B6), and (C2) to (C6) in FIG. 7 are respectively along the line AA in FIG. It is explanatory drawing containing an end face figure, BB sectional drawing, and CC sectional view. Note that the end plate 3 with a spring also has a recess 3e, and the basic shape of the portion other than the recess 3e is the same as the end plate 3A without a spring.

  In the first embodiment, as described above, the outer peripheral portion (square corner) 3a farthest from the fastening bolts 7 on the surface of the end plate 3A on the side of the current collector plate (the lower surface in FIG. 7). From the surface of the end plate 3A on the side of the current collector plate (the lower surface in FIG. 7) is gently curved so that the portion around the bolt through hole 6 (intermediate portion of each side) 3b and the central portion 3f are the bottom. It has a shape connected by curved concave surfaces. Accordingly, in the end view (A1) of FIG. 7, the current collector plate side surface of the end plate 3A from the corner 3a on both sides of the surface of the end plate 3A on the current collector plate side (lower surface in FIG. 7) with respect to one fastening bolt 7 is shown. It has a shape connected by a gently curved concave surface with the intermediate portion 3b of each side as the bottom toward the intermediate portion 3b of each side of (the lower surface in FIG. 7). In the sectional view taken along line B-B in FIG. 7 (B1), the intermediate portion 3b of each side, the central portion 3f of the surface on the current collecting plate side of the end plate 3A (the lower surface in FIG. 7), and the intermediate portion 3b of each side. The connecting portion has a constant thickness, and the central portion 3f has the same thickness as the intermediate portion 3b of each side. In the sectional view taken along line CC in FIG. 7 (C1), a shape connected by a gently curved concave surface with the central portion 3f as the bottom from the corner 3a of the end plate 3A at both ends toward the central portion 3f. Presents. As a result of this configuration, the corner 3a is thicker than the intermediate portion 3b and the central portion 3f of each side and has a large rigidity, while the intermediate portion 3b and the central portion 3f of each side are thin and has a small rigidity. . According to such a configuration, it is possible to further increase the uniformity by adjusting the degree of curvature of the curved surface as compared with other modified examples.

  The present invention is not limited to such a shape, and may have various shapes as in the following modifications. In addition, also in the following modified examples, basically, the operational effects of the first embodiment can be obtained in substantially the same manner.

(First Modification of First Embodiment)
As a first modification of the first embodiment, the surface of the end plate 3A on the side of the current collecting plate is arranged such that the middle portion 3b and the central portion of each side of the end plate 3A with respect to the corner 3a of the four end plates 3A You may make it comprise in the bent plane which makes 3f each a bottom. In other words, the plane connecting the corner 3a and the central portion 3f may be a mountain fold line, and the line connecting the intermediate portion 3b and the central portion 3f of each side may be a valley fold line. Therefore, as shown in the end view (A2) of FIG. 7, the two adjacent corners 3a have a bent inverted V shape with the middle portion 3b of each middle side as a vertex. In the cross-sectional view (B2) taken along the line BB of FIG. 7, the thickness is constant at the portion connecting the intermediate portion 3b, the central portion 3f of each side, and the intermediate portion 3b of each side, and the intermediate portion 3b of each side. The central portion 3f has the same thickness. In the sectional view taken along line CC in FIG. 7 (C2), the corner 3a of the end plates 3A at both ends has a bent inverted V shape with the central portion 3f in the middle as a vertex. As a result of this configuration, the corner 3a is thicker than the intermediate portion 3b and the central portion 3f of each side and has a large rigidity, while the intermediate portion 3b and the central portion 3f of each side are thin and has a small rigidity. .

  With such a shape, it is easy to process and easy to manufacture.

(Second modification of the first embodiment)
As a second modification of the first embodiment, in addition to the first modification of the first embodiment, a plane portion 3d is formed in each of the intermediate portion 3b and the central portion 3f of each side to form each other. You may make it connect. That is, a shape in which the cross-shaped flat portion 3d is formed in the first modification may be used. Therefore, as shown in the end view (A3) of FIG. 7, the two adjacent corners 3a have a trapezoidal shape in which a flat portion 3d appears in the intermediate portion 3b of each intermediate side. In the cross-sectional view (B3) taken along the line BB in FIG. 7, the thickness is constant at the portion connecting the intermediate portion 3b, the central portion 3f of each side, and the intermediate portion 3b of each side, and the intermediate portion 3b of each side. The central portion 3f has the same thickness. In the sectional view taken along the line C-C in FIG. 7 (C3), the corner 3a of the end plates 3A at both ends has a trapezoidal shape with a flat portion 3d appearing at the middle portion 3f. The width of the flat portion 3d is in the range of (L / 6) to (L / 3), where L is the length of one side of the square of the end plate 3A in the end view (A3) of FIG. preferable. As a result of this configuration, the corner 3a is thicker than the intermediate portion 3b and the central portion 3f of each side and has a large rigidity, while the intermediate portion 3b and the central portion 3f of each side are thin and has a small rigidity. .

  With such a shape, processing can be made relatively easy and easy to manufacture.

  The reason why the width of the planar portion 3d is in the range of (L / 6) to (L / 3) is as follows. That is, if the width of the flat portion 3d is less than (L / 6), the central portion is too narrow and the center rigidity is too large. This is because when the width of the flat surface portion 3d exceeds (L / 3), the corner portion becomes small and the rigidity becomes small, so that the pressing force cannot be sufficiently applied to the laminate.

(Third Modification of First Embodiment)
The third modification of the first embodiment is similar to the second modification of the first embodiment, and is configured as an end plate 3A having the same thickness as the corner 3a as a whole. You may make it form the recessed part 3e in the part corresponding to each flat part 3d of the intermediate part 3b and the center part 3f of each edge | side of a modification. That is, the other portion is a thick plate so that the cross-shaped flat portion 3d of the second modification is the bottom surface of the recess 3e. Therefore, as shown in the end view (A4) of FIG. 7, the vicinity of the two adjacent corners 3a is a thick plate material, and has a shape in which the concave portion 3e appears only in the intermediate portion 3b of each intermediate side. . In the BB line sectional view (B4) of FIG. 7, the thickness is constant at the portion connecting the intermediate portion 3b, the central portion 3f of each side, and the intermediate portion 3b of each side, and the intermediate portion 3b of each side. The central portion 3f has the same thickness. In the CC sectional view (C4) of FIG. 7, the vicinity of the corner 3a of the end plates 3A at both ends is a thick plate material, and the concave portion 3e appears only at the middle portion 3f. The width of the recess 3e is the same as the width of the flat portion 3d of the second modification. In the end view (A4) of FIG. 7, when the length of one side of the end plate 3A is L, (L / 6) to (L / 3) is preferable. As a result of this configuration, the corner 3a is thicker than the intermediate portion 3b and the central portion 3f of each side and has a large rigidity, while the intermediate portion 3b and the central portion 3f of each side are thin and has a small rigidity. .

  With such a shape, there are no curved surfaces and inclined surfaces, and the processing is simple and easy to manufacture.

  The reason why the length of one side of the end plate 3A is in the range of (L / 6) to (L / 3) is as follows. That is, if the length of one side of the square of the end plate 3A is less than (L / 6), the central portion is too narrow and the center rigidity is too large. This is because when the length of one side of the end plate 3A exceeds (L / 3), the corner portion becomes small and the rigidity becomes small, so that the pressing force cannot be sufficiently applied to the laminate.

(Fourth modification of the first embodiment)
As a fourth modification of the first embodiment, similar to the third modification of the first embodiment, instead of integrally forming the end plate 3A with a single material, a plurality of materials are combined. It is to be formed. That is, the thin base plate 3E ₁ having the same thickness as the intermediate portion 3b and the central portion 3f of each side, the intermediate plate 3E ₁ on each side of the base plate 3E ₁ except for the intermediate portion 3b and the central portion 3f, and the corner 3a may be from thick to more structure and the reinforcing member 3E ₂ having a thickness of a thickness obtained by subtracting the base plate 3E _1. Here, the Young's modulus of the material _{E 1} of the base plate 3E ₁ is assumed to be smaller than the Young's modulus _{E 2} of the reinforcing member 3E ₂ material. As a result, the base plate 3E ₁ and the reinforcing member 3E _2, together with the third modified example similar to the recess 3e is formed, while the corner 3a has a greater rigidity by the reinforcing member 3E _2, an intermediate portion of each side the 3b and the central section 3f, is to have a small rigidity because there is no reinforcing member 3E _2. Therefore, as shown in the end view of FIG. 7 (A5), near the two adjacent corners. 3a, the base plate 3E ₁ and the reinforcing member 3E _2, it becomes a portion having a large constant thickness, each of the intermediate intermediate portion 3b of the sides has a shape formed recess 3e of only the base plate 3E ₁ is. In line B-B sectional view of FIG. 7 (B5), in the intermediate portion 3b and the central portion 3f and a portion connecting the intermediate portion 3b of each side of each side, and only a thickness of the base plate 3E ₁ is constant, The middle part 3b and the central part 3f of each side have the same thickness. In sectional view taken along line C-C in FIG. 7 (C5), near the corner 3a of the end plate 3A at both ends by a base plate 3E ₁ and the reinforcing member 3E _2, becomes a portion having a large constant thickness, the center of the intermediate portion 3f has a shape which recess 3e of only the base plate 3E ₁ is formed. The width of the concave portion 3e is the same as the width of the flat portion 3d of the second modified example. In the end view (A5) of FIG. 7, when the length of one side of the end plate 3A is L, (L / 6) to (L / 3) is preferable.

With such a configuration, by using different materials in the base plate 3E ₁ and the reinforcing member 3E _2, to be able to select materials appropriate, it is possible to adjust the rigidity easily.

  The reason why the length of one side of the end plate 3A is in the range of (L / 6) to (L / 3) is as follows. That is, if the length of one side of the square of the end plate 3A is less than (L / 6), the central portion is too narrow and the center rigidity is too large. This is because when the length of one side of the end plate 3A exceeds (L / 3), the corner portion becomes small and the rigidity becomes small, so that the pressing force cannot be sufficiently applied to the laminate.

Examples of the material of the base plate 3E _1, may be used polyphenylene sulfide resin. As examples of the material of the reinforcing member 3E _2, than the material of the base plate 3E ₁ can use large resin rigidity (Young's modulus).

(Fifth Modification of First Embodiment)
As a fifth modification of the first embodiment, a base plate 3E ₃ having the same thickness as the corner 3a of the fourth modification of the first embodiment over the entire surface of the end plate 3A is provided, and only near the corner 3a, it may be built in reinforcing member 3E ₄ different materials. Here, Young's modulus _{E 3} of the base plate 3E ₃ is assumed to be smaller than the Young's modulus _{E 4} of the material of the reinforcing member 3E _4. As a result, the vicinity of the corners 3a, due a base plate 3E ₃ and the reinforcing member 3E _4, while having a large stiffness, a small rigidity so the intermediate portion 3b and the central portion 3f of each side, there is no reinforcing member 3E ₄ To have. Therefore, as shown in the end view (A6) of FIG. 7, although the base plate 3E ₃ has the same thickness as a whole, the vicinity of two adjacent corners 3a is a reinforcing member as shown by dotted lines in the drawing. 3E ₄ forms a portion having high rigidity, and the intermediate portion 3b on each intermediate side is configured so as not to have the reinforcing member 3E _{4 and} is configured as a portion having small rigidity. In line B-B sectional view of FIG. 7 (B6), in the portion connecting the intermediate portion 3b of the intermediate portion 3b and the central portion 3f and each side of each side, the reinforcing member 3E ₄ without, only the base plate 3E ₃ The thickness is constant, and the intermediate portion 3b and the central portion 3f of each side have the same thickness. In sectional view taken along line C-C in FIG. 7 (C6), although the base plate 3E ₃ identical thickness as a whole, around the corner 3a of the end plate 3A of the two ends, as shown by a dotted line in the drawing, the reinforcing the member 3E _4, becomes a portion having a large rigidity, and constitutes a portion having a small rigidity is configured so as not reinforcing member 3E ₄ in the central portion 3f of the intermediate.

With such a configuration, by using different materials in the base plate 3E ₃ and the reinforcing member 3E _4, on which it is possible to adjust the rigidity easily, the collector plate side surface of the end plate 3A There is no unevenness on the surface, making it easy to handle. That is, since both end plates 3A are flat, it is easy to assemble and fasten.

Examples of the material of the base plate 3E _3, it is possible to use polyphenylene sulfide resin. As examples of the material of the reinforcing member 3E _4, than the material of the base plate 3E ₃ can use large resin rigidity (Young's modulus).

(Second Embodiment)
In previous 1st Embodiment, although the fastening bolt 7 was arrange | positioned in the intermediate part (for example, center position of each edge | side) of each edge | side of the square of the end plate 3A, it is not restricted to this, For example, the fastening bolts 7 may be arranged at each corner of the end plate 3A.

  A fuel cell stack 101 that is an example of a polymer electrolyte fuel cell (PEFC) according to the second embodiment of the present invention having the end plate 3B having such a structure will be described below.

  FIG. 8A shows the shape of the end plate 3B before fastening the laminate 100 (corresponding to FIG. 2A of the first embodiment). In this state, the shape of the inner surface of the end plate 3B on the current collecting plate 2 side is such that the portion (corner portion) (an example of a tightening portion) 3i around the bolt through hole 6 of the fastening bolt 7 is thin, The outermost part (the middle part of each side) that is farthest from the fastening bolt 7 (an example of an unfastened part) 3h is the thickest.

In contrast, as shown in FIG.
After the laminated body 100 is fastened by the pair of end plates 3B, the shape of the inner surface of each end plate 3B on the current collecting plate 2 side becomes flat, while each end plate on the side opposite to the inner surface on the current collecting plate 2 side. The shape of the outer surface of 3B is the outer peripheral part (the middle part of each side) farthest from each fastening bolt 7 with the thickness of the part (corner part) 3i around the bolt through hole 6 of each fastening bolt 7 being thin. The thickness of 3h is the thickest. This is because when the laminate 100 is sandwiched between a pair of end plates 3B and a load is applied with the four fastening bolts 7 and the four nuts 8, each end plate 3B is affected by the tightening force and each end plate 3B is affected. The plate 3B itself is deformed so that the current collecting plate side of each end plate 3B, that is, the surface of the single cell module 1 is flat, and the current collecting plate 2 and the laminate 100 are tightened with a substantially uniform force. is there. Since each end plate 3B is made of a synthetic resin, the end plate 3B itself can be easily deformed. In this way, each end plate 3B becomes a flat surface with respect to the stacked body 100 and applies a tightening force, so that a load can be applied uniformly in the plane of the unit cell module 1, and the anode of the stacked body 100 can be applied. The deformation of the side separator 10A or the cathode side separator 10C can be suppressed, the MEA 9 and the gasket on the outer periphery thereof can be evenly loaded, the sealing performance can be sufficiently maintained, and the in-plane contact pressure difference of the MEA 9 is also increased. Can be reduced. Thereby, the durability of the fuel cell stack 1 can be improved.

  In other words, each end plate 3B is configured so that the rigidity of the portion away from each fastening bolt 7 or nut 8 is higher than the portion fastened by the fastening bolt 7 and nut 8, so The laminated body 100 is sandwiched between the end plates 3B, and the plurality of unit cell modules 1 are fastened by the plurality of fastening bolts 7 and nuts 8. For this reason, the rigidity of the end plate itself is increased for the portion where the fastening force by the fastening bolt 7 and the nut 8 is difficult to be applied, whereas the portion where the fastening force by the fastening bolt 7 and the nut 8 is easily applied. Since the rigidity of the end plate itself is low, the fastening force by the fastening bolt 7 and the nut 8 tends to be uniform as a whole, and a uniform fastening force is applied to the plurality of unit cell modules 1. Thus, the fastening load can be reduced while sufficiently maintaining the sealing performance, and the durability of the fuel cell can be improved.

  FIG. 9 is a bottom view showing a surface on the current collecting plate side of a square spring-less end plate 3B in which bolt through holes 6 are formed through each corner.

  (A1), (B1), and (C1) in FIG. 10 are respectively an end view along the line AA in FIG. 9 (corresponding to a side view of the end plate 3B) and a line BB in the end plate 3B. Sectional view (corresponding to a sectional view along the line connecting the middle portions of the opposite sides of the end plate 3B), and CC sectional view (corresponding to a sectional view along the diagonal connecting the opposing corners of the end plate 3B) It is explanatory drawing including. (A2) to (A6), (B2) to (B6), and (C2) to (C6) in FIG. 10 are respectively along the line AA in FIG. 9 in the end plate 3B according to the five types of modifications. It is explanatory drawing containing an end face figure, BB sectional drawing, and CC sectional view.

  In the second embodiment, as described above, the end plate 3B is formed from the portion (corner portion of each side) 3h around the bolt through hole 6 on the surface (the lower surface in FIG. 10) of the end plate 3B on the current collector plate side. A gentle curve such that the outermost part (square intermediate part) 3i and the central part 3f that are farthest from each fastening bolt 7 on the surface on the current collector plate side of 3B (the lower surface in FIG. 10) are the apexes. It has a shape connected by curved convex surfaces. Therefore, in the end view (A1) of FIG. 10, the current collecting plate side of the end plate 3B from the corner 3i of the two fastening bolts 7 adjacent to the current collecting plate side surface (the lower surface in FIG. 10) of the end plate 3B. The shape is connected by a gently curved convex surface with the middle portion 3h of each side as a vertex toward the middle portion 3h of each side of the surface (lower surface in FIG. 10). In the BB line sectional view (B1) of FIG. 10, the intermediate portion 3h of each side, the central portion 3f of the surface on the current collecting plate side of the end plate 3B (the lower surface in FIG. 10), and the intermediate portion 3h of each side. The connecting portion has a constant thickness, and the central portion 3f has the same thickness as the intermediate portion 3h of each side. In the sectional view taken along the line C-C (C1) of FIG. 10, the shape is connected by a gently curved convex surface having the central portion 3f as the apex from the corner 3i of the end plate 3B at both ends toward the central portion 3f. Presents. As a result of such a configuration, the intermediate portion 3h and the central portion 3f are thicker than the corner portions 3i of each side and have a high rigidity, while the corner portions 3h of each side are thin and have a small rigidity. In addition, the uniformity can be further improved by adjusting the degree of curvature of the curved surface as compared with other modified examples.

  The present invention is not limited to such a shape, and may have various shapes as in the following modifications.

(First Modification of Second Embodiment)
As a first modified example of the second embodiment, the surface of the end plate 3B on the side of the current collector plate is arranged such that the middle portion 3h and the center of each side of the end plate 3B with respect to the corner 3i of the end plate 3B at the four corners. You may make it comprise in the bent plane which makes each part 3f a vertex. In other words, the plane connecting the corner 3i and the central portion 3f may be a valley fold line, and the line connecting the intermediate portion 3h and the central portion 3f of each side may be a mountain fold line. Therefore, as shown in the end view (A2) of FIG. 10, the two adjacent corners 3i have a bent V-shape with the middle portion 3h of each intermediate side as a vertex. In the BB line sectional view (B2) of FIG. 10, the thickness is constant at the portion connecting the intermediate portion 3h, the central portion 3f of each side, and the intermediate portion 3h of each side, and the intermediate portion 3h of each side. The central portion 3f has the same thickness. In the cross-sectional view (C2) taken along the line CC in FIG. 10, the corner 3i of the end plate 3B at both ends has a bent V shape with the center portion 3f in the middle as the apex. As a result of this configuration, the corner portion 3i is thinner than the intermediate portion 3h and the central portion 3f of each side and thus has a small rigidity, while the intermediate portion 3h and the central portion 3f of each side are thick and have a large rigidity. .

  With such a shape, it is easy to process and easy to manufacture.

(Second Modification of Second Embodiment)
As a second modification example of the second embodiment, in addition to the first modification example of the second embodiment, a plane part 3k may be formed at the corner part 3i of each side. That is, it is good also as a shape where the plane part 3k was formed in the corner | angular part 3i of each side of a 1st modification. Therefore, as shown in the end view (A3) of FIG. 10, each of the two adjacent corner portions 3i has a shape in which the planar portion 3k appears. In the cross-sectional view (B3) taken along the line BB in FIG. 10, the thickness is constant at the portion connecting the intermediate portion 3h, the central portion 3f of each side, and the intermediate portion 3h of each side, and the intermediate portion 3h of each side. The central portion 3f has the same thickness. In the sectional view taken along the line C-C (C3) in FIG. 10, the planar portions 3k appear in the corner portions 3i of the end plates 3B at both ends. The width of the flat portion 3k is {L- (L / 3)} to {L- (L / 6) when the length of one side of the end plate 3B is L in the end view (A3) of FIG. )} / 2 = (L / 3) to (5L / 12) is preferable. As a result of this configuration, the corner portion 3i is thinner than the intermediate portion 3h and the central portion 3f of each side and thus has a small rigidity, while the intermediate portion 3h and the central portion 3f of each side are thick and have a large rigidity. .

  With such a shape, processing can be made relatively easy and easy to manufacture.

  The reason why the length of one side of the end plate 3B is in the range of (L / 3) to (5L / 12) is as follows. That is, if the length of one side of the end plate 3B is less than (L / 3), the center convex portion is large and the center rigidity becomes too large. This is because when the length of one side of the end plate 3B exceeds (5L / 12), the corner portion becomes small and the rigidity becomes small, so that the laminated body cannot be sufficiently pressed.

(Third Modification of Second Embodiment)
The third modification of the second embodiment is similar to the second modification of the second embodiment, and is configured as an end plate 3B having the same thickness as the intermediate portion 3i as a whole. You may make it form the recessed part 3j in the part corresponding to the plane part 3k of the corner | angular part 3i of each side of the modification. That is, the other portions are thick plate members so that the four corner plane portions 3k of the second modification are the bottom surfaces of the recesses 3j. Therefore, as shown in the end view (A4) of FIG. 10, the intermediate portion 3h is a thick plate, and has a shape in which the recess 3j appears only in the vicinity of the two adjacent corner portions 3i. In the BB line sectional view (B4) of FIG. 10, the thickness is constant at the portion connecting the intermediate portion 3h, the central portion 3f of each side, and the intermediate portion 3h of each side, and the intermediate portion 3h of each side. The central portion 3f has the same thickness. In the sectional view taken along the line CC of FIG. 10 (C4), the central portion 3f is a thick plate material and has a shape in which the concave portion 3j appears only in the vicinity of the two adjacent corner portions 3i. The width of the recess 3j is the same as the width of the flat portion 3k of the second modification. In the end view (A4) of FIG. 10, when the length of one side of the end plate 3B is L, {L− (L / 3)} to {L− (L / 6)} / 2 = (L / 3) to (5L / 12) is preferable. As a result of this configuration, the corner portion 3i is thinner than the intermediate portion 3h and the central portion 3f of each side and thus has a small rigidity, while the intermediate portion 3h and the central portion 3f of each side are thick and have a large rigidity. .

  With such a shape, there are no curved surfaces and inclined surfaces, and the processing is simple and easy to manufacture.

  The reason why the length of one side of the end plate 3B is in the range of (L / 3) to (5L / 12) is as follows. That is, if the length of one side of the end plate 3B is less than (L / 3), the center convex portion is large and the center rigidity becomes too large. This is because when the length of one side of the end plate 3B exceeds (5L / 12), the corner portion becomes small and the rigidity becomes small, so that the laminated body cannot be sufficiently pressed.

(Fourth modification of the second embodiment)
The fourth modification of the second embodiment is similar to the third modification of the second embodiment, and instead of integrally forming the end plate 3B from a single material, a plurality of materials are combined. It is to be formed. That is, the thin base plate 3E ₅ having the same thickness as the corner 3i of each side, and the portions of the base plate 3E ₅ except for the corner 3i of each side, and the thickness of the intermediate portion 3h and the central portion 3f. it may be more structure and the reinforcing member 3E ₆ having a thickness obtained by subtracting the thickness of the base plate 3E ₅ from. Here, the Young's modulus _{E 5} of the material of the base plate 3E ₅ is assumed to be smaller than the Young's modulus _{E 6} of the material of the reinforcing member 3E _6. As a result, the base plate material 3E ₅ and the reinforcing member 3E ₆ form a recess 3j similar to that of the third modified example, and the intermediate portion 3h and the central portion 3f are more rigid than the reinforcing member 3E _6. , the corner portions 3i of each side, and to have a small rigidity because there is no reinforcing member 3E _6. Therefore, as shown in the end view of FIG. 10 (A5), near the two adjacent corners 3i, the recess 3j of the base plate 3E ₅ only is formed, the intermediate portion 3h of each side of the intermediate base The plate member 3E ₅ and the reinforcing member 3E ₆ have a shape that is a portion having a large constant thickness. In line B-B sectional view of FIG. 10 (B5), in the portion connecting the intermediate portion 3h of the intermediate portion 3h and the central portion 3f and the sides of each side are only a thickness of the base plate 3E ₅ is constant, The middle part 3h and the central part 3f of each side have the same thickness. In line C-C sectional view of FIG. 10 (C5), near the corners 3i end plate 3B on both ends, recesses 3j of the base plate 3E ₅ only is formed, the central portion 3f of the intermediate base plate 3E the ₅ and the reinforcing member 3E _6, and has a portion with became shape having a large constant thickness. The width of the recess 3j is the same as the width of the flat portion 3k of the second modification. In the end view (A5) of FIG. 10, when the length of one side of the square of the end plate 3B is L, (L / It is preferable to set it as the range of 3)-(5L / 12).

With such a configuration, by using different materials for the base plate material 3E ₅ and the reinforcing member 3E ₆ , the material can be appropriately selected, and the rigidity can be easily adjusted.

  The reason why the length of one side of the end plate 3B is in the range of (L / 3) to (5L / 12) is as follows. That is, if the length of one side of the end plate 3B is less than (L / 3), the center convex portion is large and the center rigidity becomes too large. This is because when the length of one side of the end plate 3B exceeds (5L / 12), the corner portion becomes small and the rigidity becomes small, so that the laminated body cannot be sufficiently pressed.

As an example of the material of the base plate 3E ₅ , polyphenylene sulfide resin can be used. Further, as an example of the material of the reinforcing member 3E _6, a resin having higher rigidity (Young's modulus) than that of the material of the base plate 3E ₅ can be used.

(Fifth Modification of Second Embodiment)
As a fifth modification of the second embodiment, the same thickness as that of the middle part 3h and the central part 3f of each side of the fourth modification of the second embodiment is constant over the entire surface of the end plate 3B. The base plate 3E ₇ may be used, and reinforcing members 3E ₈ made of different materials may be incorporated only in the vicinity of the intermediate portion 3h and the central portion 3f. Here, the Young's modulus _{E 7} of the material of the base plate 3E ₇ is assumed to be smaller than the Young's modulus _{E 8} of the material of the reinforcing member 3E _8. As a result, the vicinity of the corner portion 3i, while having a small rigidity because there is no reinforcing member 3E _8, intermediate portion 3h and the central portion 3f of each side, by a base plate 3E ₇ and the reinforcing member 3E _8, the greater rigidity To have. Therefore, as shown in the end view of FIG. 10 (A6), although the base plate 3E ₇ having the same thickness as a whole, around two adjacent corners 3i is configured so that there is no reinforcing member 3E ₈ It becomes part having a small rigidity Te, the intermediate portion 3h of each side of the middle, as indicated by a dotted line in the drawing, the reinforcing member 3E _8, is configured as a portion having a greater rigidity. In line B-B sectional view of FIG. 10 (B6), the intermediate portion 3h and the central portion 3f and a portion connecting the intermediate portion 3h of each side of each side, the reinforcing member 3E ₈ is built, appearance is The base plate 3E ₇ has a constant thickness, and the middle portion 3h and the central portion 3f of each side have the same thickness. In line C-C sectional view of FIG. 10 (C6), although the base plate 3E ₇ having the same thickness as a whole, around corners 3i end plate 3B on both ends, constructed so as not reinforcing member 3E ₈ to become a part having a small rigidity, the central portion 3f of the intermediate, as indicated by a dotted line in the drawing, the reinforcing member 3E _8, is configured as a portion having a greater rigidity.

With such a configuration, by using different materials for the base plate material 3E ₇ and the reinforcing member 3E ₈ , the rigidity can be easily adjusted, and the surface of the end plate 3B on the side of the current collector plate There is no unevenness on the surface, making it easy to handle. Moreover, since both end plates 3A are flat, it is easy to assemble and fasten.

Examples of the material of the base plate 3E _7, it is possible to use polyphenylene sulfide resin. As examples of the material of the reinforcing member 3E _8, than the material of the base plate 3E ₇ can be used a large resin rigidity (Young's modulus).

(Third embodiment)
In the previous first and second embodiments, the end plate is square, and the fastening bolts 7 are arranged at the four corners of the end plates 3, 3A, 3B or the center positions of the respective sides. It is not limited. For example, the end plate 3C may be rectangular, and the fastening bolts 7, in other words, the bolt through holes 6 may be arranged at the center positions of the four corners and long sides of the end plate 3C. This example is shown in FIGS. 11-12 as the end plate 3C of 3rd Embodiment of this invention. FIG. 11 is an explanatory view including a bottom view of the end plate 3C and a cross-sectional view taken along line AA in the bottom view. FIG. 12 is a cross-sectional view taken along line BB in the bottom view of the end plate 3C. The AA line sectional view of FIG. 11 is along a line connecting three bolt through holes 6 along the long side, that is, a pair of adjacent corner bolt through holes 6 and a bolt through hole 6 at an intermediate position. In the cross-sectional view, the thickness is constant. On the other hand, the cross-sectional view along the line BB in FIG. 12 is a cross-sectional view along a line connecting a pair of bolt through holes 6 along the opposing short sides, and is the thickest with the center position along the short sides as a vertex. The shape is such that a curved convex surface is formed so that is increased. This also has the same shape in a sectional view along a line connecting a pair of bolt through holes 6 along a short side at a pair of opposite corners on the left end side and the right end side of the bottom view of FIG.

  In the end plate 3C of the third embodiment, the portion 3n around the bolt through-hole 6 is the portion with the smallest thickness and the smallest rigidity, but the short side away from the portion 3n around the bolt through-hole 6 A portion 3m along the line connecting the center positions of the two is the portion having the largest thickness and the largest rigidity.

  According to the third embodiment, the bolt through holes 6 are respectively arranged at the center positions of the four corners and the long side of the rectangular end plate 3C, and the portion having low rigidity is arranged, so that the outer peripheral portion of the rectangular end plate 3C is arranged. While it is possible to arrange portions with low rigidity at equal intervals, portions with high rigidity are arranged only in the portion 3m along the line connecting the center positions of the short sides of the rectangular end plate 3C. Generally, a rectangular end plate is more likely to have a variation in tightening force than a square end plate, and it is difficult to tighten with a uniform tightening force. Even with a rectangular end plate, it is possible to suppress the occurrence of variations in the tightening force as much as possible, and it is possible to easily tighten with a uniform tightening force, and there are almost the same effects as the previous embodiment. Can do.

(Fourth embodiment)
As another aspect of the third embodiment, the end plate 3D has a rectangular shape, and one end of a pair of opposing corners of the end plate 3D (upper left in the bottom view of FIG. 13). Two fastening bolts 7, in other words, two bolt through holes 6, may be arranged in the vicinity of the right corner and the lower right corner). This example is shown in FIG. 13 as an end plate 3D of the fourth embodiment of the present invention. FIG. 13 is an explanatory diagram including a bottom view of the end plate 3D, a cross-sectional view taken along line CC in the bottom view, and a cross-sectional view taken along line DD in the bottom view. 13 is a cross-sectional view of a line along the long side passing through the lower bolt through hole 6 of the pair of bolt through holes 6 in the vicinity of the lower right corner, A portion around the bolt through hole 6 is a portion having a small thickness and a small rigidity. On the other hand, in the sectional view taken along the line C-C, the portion near the corner opposite to the bolt through hole 6 is a portion having a large thickness and a large rigidity. 13 is a cross-sectional view of the line along the long side passing through the upper bolt through-hole 6 of the pair of bolt through-holes 6 in the vicinity of the lower right corner. A portion around the through hole 6 is a portion having a small thickness and a small rigidity. On the other hand, in the sectional view taken along the line DD, the vicinity of the corner opposite to the bolt through hole 6 is a portion having a large thickness and a large rigidity.

  In the end plate 3D of the fourth embodiment, the portion 3q around the bolt through-hole 6 is the portion having the smallest thickness and the smallest rigidity, but on the opposite side to the corner portion where the bolt through-hole 6 is disposed. The corner portion (corner portion where the bolt through-hole 6 is not disposed) 3p is the portion having the largest thickness and the largest rigidity.

  According to the fourth embodiment, one set of corners of a pair of opposing corners of the rectangular end plate 3D (in the bottom view of FIG. 13, the upper left corner and the lower right corner). ) While two bolt through holes 6 are arranged in the vicinity, the bolt through holes 6 are formed in the vicinity of the remaining pair of corners (the bottom left corner and the upper right corner in the bottom view of FIG. 13). Therefore, manifold holes and the like can be arranged, and the degree of freedom in the arrangement design of the manifold holes can be increased while considering the improvement in the uniformity of the tightening force. In the fourth embodiment, substantially the same operational effects as in the previous embodiment can be obtained.

(Other)
In addition, this invention is not limited to the said embodiment, It can implement with another various aspect.

  For example, in the first embodiment, as an example of a portion having a large rigidity of the end plate 3, the outermost peripheral portion farthest from the fastening bolt 7 is the corner 3 a, but is not limited to the corner 3 a. For example, as shown in the modification, it may be a portion near the corner 3a or a portion excluding the intermediate portion 3b and the central portion 3f of each side. In short, the portion having a small rigidity refers to a portion where the end plate 3 is fastened by the tightening bolt 7, while the portion having a large rigidity means that the tightening force is most effective when the end plate 3 is tightened by the tightening bolt 7. This is a portion where the difference between the tightening force and the tightening force at the portion where the end plate 3 is tightened by the tightening bolt 7 is the largest.

  In one end plate 3, 3 </ b> A, 3 </ b> B of the above-described embodiments and modifications, the thickness h at the thinst portion, for example, the thinnest portion, and the thickness at the thickest portion, for example, the thickest portion The difference Ty from (h + Ty) (see FIG. 7) is practically 0.2 mm to 0.4 mm. The reason is that when it is less than 0.2 mm, there is not much difference in the magnitude of rigidity, and the effect of the present invention cannot be expected clearly, whereas when it exceeds 0.4 mm, the difference in rigidity becomes too large, This is because it may take time to adjust the uniformity.

  In addition, in one end plate 3, 3A, 3B such as each of the above embodiments and modifications, when there are, for example, four portions with low rigidity, the rigidity is substantially the same in all of these portions, and the portion with high rigidity For example, when there are four locations, the rigidity is substantially the same in all of these portions so that the uniformity of the tightening force can be easily maintained.

  The fastening structure using the end plate 3 according to the above embodiment of the present invention is different from the conventional example in that the uniformity of the load distribution is greatly improved. Here, some examples according to the above-described embodiment will be referred to, and simulation results of the load distribution will be described.

(Configuration common to the embodiments)
First, the specific forming material and manufacturing method of the single cell module 1 common to each Example demonstrated below are demonstrated. A catalyst on the cathode side was prepared by supporting 25% by weight of platinum particles having an average particle diameter of about 30 mm on acetylene black carbon powder (trade name “DENKABLACKFX-35” manufactured by Electrochemical Co., Ltd.). Further, 25 particles of platinum-ruthenium alloy (Pt: Ru = 1: 1 (weight ratio)) having an average particle diameter of about 30 mm are added to acetylene black carbon powder (trade name “DENKABLACKFX-35” manufactured by Electrochemical Co., Ltd.). The catalyst supported by weight% was used as the catalyst on the anode side. After each of these catalyst powders was dispersed in an isopropanol dispersion, an ethyl alcohol dispersion of perfluorocarbon sulfonic acid powder (trade name “FlemionFSS-1” manufactured by Asahi Glass Co., Ltd.) was mixed with each of these isopropanol dispersions. Each was made into a paste. After that, using these pastes as raw materials, an electrode catalyst layer is formed on one surface of a carbon nonwoven fabric (trade name “TGP-H-090” manufactured by Toray Industries, Inc.) each having a thickness of 250 μm using a screen printing method. did. Amount of platinum contained in the catalyst layer of each of the electrodes of the thus formed a cathode side and the anode ^side, 0.3mg / cm 2, the amount of perfluorocarbon sulfonic acid was 1.2 mg / cm ^2.

  In these electrodes, the structure other than the catalyst material is the same for both the cathode and the anode. The printed catalyst layer is in contact with the electrolyte membrane side on both sides of the central portion of a proton conductive polymer electrolyte membrane (trade name “NAFiON122” manufactured by DuPont, USA) having an area slightly larger than the electrode. Thus, it joined by hot press processing. In addition, the peripheral part of the polymer electrolyte membrane exposed on the outer peripheral part of each electrode is sandwiched between gaskets made of a sheet of fluorine rubber (trade name “Aphras” (registered trademark) manufactured by Asahi Glass Co., Ltd.) having a thickness of 250 μm. The peripheral part of the polymer electrolyte membrane and the gasket were joined and integrated by hot pressing. Thus, an electrolyte membrane electrode assembly (MEA) was produced. As the proton conductive polymer electrolyte membrane, a perfluorocarbon sulfonic acid thinned to a thickness of 30 μm was used.

In addition, a conductive separator was formed by forming a gas channel and a manifold hole by machining on an isotropic graphite plate having a thickness of 3 mm. The groove width of the gas flow path is 2 mm, the depth is 1 mm, and the width between the flow paths is 1 mm, and each has a flow path configuration of two paths (however, for simplification, one path is shown). The cooling water channel has a groove depth of 0.5 mm, and the other configuration of the cooling water channel is the same as that of the gas channel. The rated operating conditions of this battery are a fuel utilization rate of 75%, an oxygen utilization rate of 40%, and a current density of 0.3 A / cm ² .

  50 cells of the unit cell module 1 in which the MEA 9 was sandwiched between the cathode side separator 10C and the anode side separator 10A as described above were stacked. Between adjacent cells, a flow path of cooling water is formed by both separators 10C and 10A. The cell laminate 100 is sandwiched between a 5 mm copper current collector plate 2 plated with gold on the surface and an end plate 3 made of polyphenylene sulfide resin, and both end plates 3 are 1000 kgf with four fastening bolts 7 and four nuts 8. It was fastened with a load of.

Example 1
Here, FIGS. 1 and 2B show an example of a specific fastening structure of the fuel cell stack 101 according to the first embodiment as Example 1. FIG. The fastening bolt 7 in this fastening shape has a shape located at the center of one side of the square end plate 3. The inner surface (surface on the side of the current collector plate) of the end plate 3 used for the fastening structure is the thinnest portion (intermediate portion of each side) 3b to be fastened with the fastening bolt 7 in a state before fastening. It is made into the concave shape with respect to the cell module 1 so that the edge part (corner) 3a of the farthest end plate 3 may become the thickest. Thus, the fastening structure of the fuel cell stack 101 configured as shown in FIGS. 1 and 2B has an end plate structure that can absorb the deformation of the end plate 3 when a load is applied by the fastening bolt 7 and the nut 8. Therefore, as a result, the deformation of the separators 10C and 10A can be suppressed, a load can be applied evenly to the MEA 9 and the outer peripheral gasket, and the sealing performance can be sufficiently maintained.

  FIG. 3A shows the end plate 3 in the first embodiment. About the concave (curved surface) shape of the end plate 3, the thickest portion (corner) as the load P applied to one of the fastening bolts 7, the Young's modulus E of the material of the end plate 3, and the dimensions of each portion of the end plate 3 The distance x from 3a, the thickness direction distance y from the thickest point (corner) 3a, the length L of one side of the square end plate 3, and the recess 3g for arranging the inner spring of the end plate 3 Using the width w and the thickness h of the thinnest portion (the portion around the bolt through hole, in other words, the middle portion of each side) 3b of the end plate 3, it can be expressed as follows. The unit is a Si unit system. Also, w = (L / 2) to (L / 10). Here, the reason why the width w is in this range is that when the width w is less than (L / 2), the width is too small and the difference in rigidity is not so great, and the effect of the present invention is clearly expected. On the other hand, when the width w exceeds (L / 10), the width becomes too large, the area of the recess 3g for arranging the inner spring becomes smaller, and the uniformity adjustment by the inner spring 4 becomes difficult. is there.

  The difference Ty between the thinnest part and the thickest part of the end plate 3 used in this example is about 0.3 mm. As an example of the end plate 3, when x = L / 2, y = Ty = 0.3 mm and h = about 10 mm.

  Since the hole of the piping for manifolds is also processed in the outer peripheral part other than the part where the fastening bolt 7 or the nut 8 contacts the end plate 3, the strength is weakened. For this reason, the concave end plate having a thin periphery of the fastening bolt 7 or the nut 8 and a thick other portion has a strong strength with respect to the deformation by the fastening bolt 7 or the nut 8 and a shape with a small deformation. After the cell module 1 is fastened with the fastening bolt 7 and the nut 8, the end plate 3 having this curved shape becomes a flat surface with respect to the separators 10 </ b> A and 10 </ b> C, so that a uniform load is applied to the surface of the cell module 1. It came to be able to. As a result, the sealing performance was sufficiently maintained and the in-plane contact pressure difference of the MEA 9 could be reduced, so that the durability of the fuel cell stack 1 could be improved.

  Conventionally, at locations where the surface pressure is high, carbon fibers in the gas diffusion layer are excessively pressed against the electrolyte membrane, and the electrolyte membrane is pierced by the carbon fibers, resulting in an electrical short and a voltage drop. It was. Further, due to current concentration, local heat generation may occur and the film may be damaged. Therefore, conventionally, a hole was opened in the electrolyte membrane in about 5000 hours, and power generation was impossible.

  On the other hand, in the case of the present example, the surface pressure is uniformly generated without causing the carbon fiber piercing of the gas diffusion layer to the electrolyte membrane, so that the electrolyte membrane is damaged. No local voltage drop occurs in the plane. Therefore, durability of the electrolyte membrane could be ensured, and power generation for 40000 hours could be confirmed. Further, in the case of the embodiment, since the load can be made uniform only by the end plate 3, the fuel cell stack 1 can be reduced in size, and the fastening structure and assembly method of the fuel cell stack 1 can be simplified. Became possible.

  In this embodiment, the end plate 3 is manufactured by injection molding of synthetic resin. However, an end plate molded or machined using an electrically insulating material is also used. May be. Further, an end plate using a metal material such as stainless steel may be used together with the insulating plate.

  Further, in order to confirm the degree of uniformity of the pressure distribution in the electrode arrangement region in the MEA 9, a 1/4 model is used by using a structure analysis software (ABAQUS Version 6.4, a general-purpose nonlinear finite element analysis program of Dassault Systems Simula Corp.). A simulation was performed. FIG. 4 shows a simulation calculation result of the contact pressure generated in the electrode arrangement region (main body portion 9a) of the MEA 9 in the fastening structure of Example 1 obtained by performing the simulation of the fuel cell stack 1. FIG. 4 shows the degree of uniformity of the contact pressure in MEA 9 or the degree of uniformity of the in-plane contact pressure distribution. In the case where the illustrated change in density is small or the interval is wide, in-plane contact is shown. It is a graph which shows that the uniformity of a pressure distribution is low, and the contrary, in the reverse case, the uniformity of a contact pressure distribution is high. From FIG. 4, although there is in-plane contact pressure distribution from the center position of the end plate to the position of the corner end, the contact pressure difference is suppressed to be small. Moreover, in order to confirm this simulation result, in the single cell module 1 of Example 1, pressure sensitive paper (pressure sensitive paper made by Fuji Film) was sandwiched between the MEA 9 and the separator 10, and the contact pressure was confirmed. However, similar results to the simulation were obtained. Therefore, it was proved that the fuel cell stack 101 having the end plate of Example 1 has a small contact surface pressure difference of the MEA 9 and can equalize the load.

  FIG. 14 shows the fastening structure of the comparative example, and FIG. 15 shows the simulation calculation result of the contact pressure distribution. As shown in FIG. 14, in the comparative example, it fastens using the parallel end plate 203 made from a synthetic resin. Therefore, when the fastening bolt 207 and the nut 208 are fastened, the end plate 203 is deformed, and it is difficult to apply a load uniformly compared to the first embodiment. As a result of performing the simulation in the same manner as described above, the in-plane contact pressure distribution is large from the center position of the MEA of the cell 201 to the corner end position, and the contact pressure difference is about eight times that of the first embodiment.

(Example 2)
Next, an example of a specific fastening structure of the fuel cell stack 101 according to the second embodiment of the present invention is shown as Example 2. As Example 2, a fastening structure in which fastening bolts 7 or nuts 8 are arranged at both ends (in other words, corners) of one side of the end plate 3B is shown in FIGS. 8A and 8B. The end plate 3B used for the fastening structure has the thinnest corner portion 3i fastened by the fastening bolt 7 and the nut 8, and the middle portion of one side of the end plate 3B farthest from the fastening bolt 7 or the nut 8 (here, each It is convex with respect to the unit cell module 1 so that the center position of the side) 3h is the thickest. In the fastening structure of the fuel cell stack 1 configured as shown in FIGS. 8A and 8B, as in the first embodiment, the end that can absorb the deformation of the end plate 3B when a load is applied with the fastening bolt 7 and the nut 8. Since it has a plate structure, as a result, the deformation of the separators 10A and 10C can be suppressed, the sealing performance is sufficiently maintained, and a load can be applied to the MEA 9 evenly. The difference between the thinnest part and the thickest part of the end plate 3B used in the second embodiment is about 0.3 mm as in the first embodiment. In addition, as a result of the simulation of the contact pressure distribution, the pressure distribution as shown in FIG. 4 was obtained as in Example 1, and it was found that the contact pressure distribution difference was small and the uniformity was high.

  It is to be noted that, by appropriately combining arbitrary embodiments of the various embodiments described above, the effects possessed by them can be produced.

The polymer electrolyte fuel cell of the present invention is useful as a fuel cell for use in portable power supplies, electric vehicle power supplies, domestic cogeneration systems, and the like.

1 is an exploded perspective view of a fuel cell stack according to a first embodiment of the present invention. The schematic diagram which shows the fastening structure of a fuel cell stack in the state before the fastening of the fuel cell stack of 1st Embodiment of this invention. The schematic diagram which shows the fastening structure of a fuel cell stack in the state after the fastening of the fuel cell stack of 1st Embodiment of this invention. The perspective view of the end plate with a spring concerning the fuel cell stack of 1st Embodiment of this invention. The perspective view of the end plate without a spring concerning the fuel cell stack of 1st Embodiment of this invention. Graph of simulation result of contact pressure distribution in fastening structure of FIG. 2A 1 is a perspective view schematically showing a part of a structure of a fuel cell stack which is an example of a polymer electrolyte fuel cell (PEFC) using an end plate without a spring in a first embodiment of the present invention. Bottom view of the end plate of FIG. It is explanatory drawing of the end plate concerning 1st Embodiment, and the end plate concerning 5 types of modifications of 1st Embodiment, and, in detail, (A1)-(A6), (B1)-(B6), (C1 ) To (C6) are respectively an end view taken along the line AA in FIG. 6 and a line BB in the end plate according to the first embodiment and the end plate according to the five types of modifications of the first embodiment. Explanatory drawing including a sectional view and a CC sectional view The schematic diagram which shows the fastening structure of a fuel cell stack in the state before the fastening of the fuel cell stack of 2nd Embodiment of this invention. The schematic diagram which shows the fastening structure of a fuel cell stack in the state after the fastening of the fuel cell stack of 2nd Embodiment of this invention. The bottom view of the end plate of 2nd Embodiment of this invention It is explanatory drawing of the end plate concerning 2nd Embodiment, and the end plate concerning 5 types of modifications of 2nd Embodiment, and is (A1)-(A6), (B1)-(B6), (C1 in detail) ) To (C6) are respectively an end view taken along the line AA in FIG. 9 and a line BB in the end plate according to the second embodiment and the end plate according to five types of modifications of the second embodiment. Explanatory drawing including a sectional view and a CC sectional view It is explanatory drawing of the end plate of 3rd Embodiment of this invention, Specifically, explanatory drawing containing the AA line sectional drawing in the bottom view and bottom view of 3 C of end plates. BB sectional drawing in the bottom view of the end plate of 3rd Embodiment of this invention of FIG. It is explanatory drawing of the end plate of 4th Embodiment of this invention, and, in detail, the bottom view of the end plate of 4th Embodiment of this invention, CC sectional view taken on the line in the bottom view, D- in the bottom view Explanatory drawing including D line cross section Schematic diagram showing the fastening structure of the comparative example Graph of simulation result of contact pressure distribution in fastening structure of comparative example Schematic diagram showing the fastening structure of the background art

Explanation of symbols

1 Single battery module (cell)
Second collector plate 3 end plate 3A of the spring, the end plate 3E ₁ without 3B spring, _{3E 3,} 3E 5, _3E 7, the base plate _{3E 2, 3E 4, 3E 6} , 3E 8, the reinforcing member 3a fastening bolt The farthest outer periphery (corner)
3b Bolt through hole surrounding part (bolt through hole surrounding part) (intermediate part of each side)
3d Plane part 3e Concave part 3f Central part 3g Concave part for inner spring arrangement 3h Outermost part part (intermediate part of each side) farthest from fastening bolt
3i Bolt through hole (corner)
4 Inner Spring 5 Outer Spring 6 Bolt Through Hole 7 Fastening Bolt 8 Nut 9 MEA
9a Body portion 9b Peripheral portion 10 Separator 10A Anode side separator 10C Cathode side separator 11A Fuel gas manifold hole 11C Oxidant gas manifold hole 11W Cooling water manifold hole 12A Fuel gas channel groove 12C Oxidant gas channel groove 12W Cooling water channel groove 100, 100A Laminate 101, 101A Fuel cell stack 801 Fuel cell stack 802 Header 803 Bolster 804 Rod 805 Tension bar

Claims (3)

A plurality of unit cell modules having a membrane electrode assembly and a pair of separators sandwiching the membrane electrode assembly are laminated to form a laminate, and end plates are respectively disposed at both ends of the laminate, and a plurality of fastening members In a polymer electrolyte fuel cell comprising a fuel cell stack assembled by sandwiching and fastening the laminate with the pair of end plates,
Each of the end plates is configured such that the rigidity of the non-clamping portion away from the clamping portion is higher than that of the clamping portion to be clamped by the fastening member, and the surface of each end plate on the laminate side in the fastening state A polymer electrolyte fuel cell characterized by flattening.   Each of the end plates has a shape such that the cell side surface before fastening is thicker than the fastening portion so that the thickness of the non-tightening portion away from the fastening portion is larger than the fastening portion. Due to the fastening force of the fastening member, the surface on the cell side of each end plate is flat and the shape of the surface on the opposite side to the cell side of each end plate is more than the tightening portion. The elastic deformation of the non-clamping part that is separated from the attached part increases the thickness of the non-clamped part so that the rigidity of the non-clamped part is higher than that of the clamped part. Polymer electrolyte fuel cell.   Each of the end plates has a lower Young's modulus than that of the tightening portion because the Young's modulus of the material of the tightening portion is smaller than the Young's modulus of the material of the non-tightening portion apart from the tightening portion. The polymer electrolyte fuel cell according to claim 1, wherein the portion is configured to have high rigidity.

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