Fuel cell stack

Abstract

To perform positioning of a plurality of fuel battery cells by arranging a cooling water seal with a shape that fits a recess formed in the plurality of fuel battery cells adjacent in the stacking direction of a fuel cell stack.SOLUTION: A fuel cell stack includes: a plurality of fuel battery cells; and a cooling water seal sealing a cooling water passage formed in a region where, in the plurality of fuel battery cells, one fuel battery cell and another fuel battery cell adjacent to the one fuel battery cell in a stacking direction are arranged to face each other. The fuel cell stack has a fitting structure in which the cooling water seal, and the one fuel battery cell and the other fuel battery cell are fit together to perform positioning of the one fuel battery cell and the other fuel battery cell.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fuel cell stack formed by stacking a plurality of fuel cells. [Background technology]

[0002] The fuel cell cells installed in fuel-cell vehicles (Fuel-Cell Vehicles) are composed of polymer electrolyte fuel cells (PEFC: Polymer Electrolyte (Membrane) Fuel Cells). A fuel cell has an anode-side gas diffusion layer (GDL: Gas Diffusion Layer) and a cathode-side gas diffusion layer on both sides of a membrane electrode assembly (MEA: Membrane Electrode Assembly). One membrane electrode assembly (MEA) and two gas diffusion layers (GDL) that make up a fuel cell are sandwiched between an anode-side separator and a cathode-side separator. The anode-side separator and cathode-side separator have unevenness formed in the width direction, with the concave and convex portions extending in the lengthwise direction. A hydrogen flow path is formed between the anode-side separator and the anode-side gas diffusion layer to supply hydrogen gas. An air flow path is formed between the cathode-side separator and the cathode-side gas diffusion layer to supply oxygen-containing air.

[0003] A polymer electrolyte fuel cell generates electricity and water (water vapor) through an electrochemical reaction between hydrogen and oxygen using a catalyst such as platinum. The reaction temperature of a polymer electrolyte fuel cell is approximately 80 to 100°C. When multiple fuel cell cells are stacked, a cooling water flow path is formed between the separator on the cathode side of one fuel cell and the separator on the anode side of the adjacent fuel cell to circulate cooling water. The separator on the anode side (hydrogen side) and the GDL on the anode side are called the anode electrode, and the separator on the cathode side (oxygen side) and the GDL on the cathode side are called the cathode electrode.

[0004] Various techniques have been developed for stacking and positioning multiple fuel cell cells. Patent Document 1 discloses a fuel cell that employs an intervening layer made of an impact-resistant material on the inner circumferential surface of the stack case that houses the fuel cell stack in order to suppress the effects of external shocks and vibrations on the cell stack (a stack of multiple fuel cell cells). In other words, the intervening layer (constraining material) provided on the case that houses the fuel cell comes into direct contact with the fuel cell body to support the fuel cell body, thereby preventing displacement of the fuel cell cells. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-44070 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, a restraining material (intervening layer) is placed in direct contact with the fuel cell to prevent the fuel cell from shifting position. However, the restraining material in direct contact with the fuel cell may cause an electrical short circuit due to condensation or the adhesion of foreign matter.

[0007] The provision of a separate restraining material to the fuel cell increases the number of parts and processes, which increases manufacturing costs. In addition, the fuel cell and the outer case are fitted and supported by an insulating member, which increases the number of parts and processes, which increases manufacturing costs.

[0008] The contact points of the restraining members must be strong enough to prevent deformation of the fuel cells, and the attachment points of the fuel cell support members must be strong enough.

[0009] The technology of Patent Document 1 uses an intervening layer (constraining material) to prevent displacement of fuel cells, but there are problems with increased manufacturing costs due to the constraining material and the occurrence of short circuits due to condensation and adhesion of foreign matter.

[0010] In order to solve the above-mentioned problems, the present invention aims to provide a fuel cell stack in which the positioning of fuel cell cells can be performed by placing a cooling water seal along the recess of the separator arranged opposite to the fuel cell cells adjacent to each other in the stacking direction of the fuel cell cells. [Means for solving the problem]

[0011] A fuel cell stack according to the present invention includes a plurality of fuel cell units and a cooling water seal that seals a cooling water flow path formed in a region of the plurality of fuel cell units where one fuel cell unit faces another fuel cell unit adjacent to the one fuel cell unit in the stacking direction. The fuel cell stack has a fitting structure that positions the one fuel cell unit and the other fuel cell unit by fitting the cooling water seal and the one fuel cell unit and the other fuel cell unit together. [Effects of the Invention]

[0012] According to the present invention, the fuel cells can be positioned by arranging the cooling water seal along the recess of the separator that is arranged facing between the fuel cells adjacent in the stacking direction of the plurality of fuel cells. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1A is an exploded perspective view showing the overall configuration of a fuel cell stack, FIG. 1B is an exploded perspective view showing the structure of a fuel cell unit that constitutes the fuel cell stack, and FIG. 1C is a perspective view showing the appearance of a fuel cell unit. [Figure 2] 1A is a cross-sectional view of a fuel cell that constitutes a fuel cell stack according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view showing a stack structure of a plurality of fuel cells. [Figure 3] FIG. 10 is a cross-sectional view showing a stack structure of a plurality of fuel cells according to a modified example of the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of a fuel cell stack according to the present invention will be described with reference to the accompanying drawings. In the fuel cell stack according to this embodiment, a plurality of fuel cells are stacked by pressing. The fuel cells are stacked by heat pressing.

[0015] FIG. 1(A) is an exploded perspective view of a fuel cell stack 1 formed by stacking multiple fuel cell cells FC (FC1 to FCn) between two end plates EPa and EPb. The end plates EPa and EPb are provided with inlets and outlets for hydrogen, air, and cooling water. The overall structure of the fuel cell stack 1 shown in FIG. 1(A) is a typical structure for a polymer electrolyte fuel cell (PEFC). This embodiment is characterized by the inclusion of a fitting structure that positions and fits multiple fuel cell cells together using a cooling water seal that seals off the cooling water flow path formed between opposing regions of the multiple fuel cell cells.

[0016] Fig. 1(B) is an exploded perspective view of a fuel cell FC that constitutes the fuel cell stack 1. Fig. 1(C) is a perspective view showing the appearance of the fuel cell FC. Fig. 1(C) is a perspective view of the fuel cell FC as seen from the anode side. Fig. 1(B) is an exploded perspective view of the AA cross section of Fig. 1(C).

[0017] The fuel cell FC comprises a cooling water seal S, an anode-side separator SPa, an anode-side thermoplastic sheet BDa, an anode-side gas diffusion layer (GDL), a membrane electrode assembly (MEA), a cathode-side gas diffusion layer (GDL), a cathode-side thermoplastic sheet BDc, and a cathode-side separator SPc. Note that both sides of the MEA are sandwiched between the anode-side GDL and the cathode-side GDL.

[0018] As shown in Figure 1(B), the anode-side separator SPa has irregularities for the hydrogen flow path and irregularities for the cooling water flow path. As shown in Figure 1(C), the irregularities of the separator SPa extend in the longitudinal direction and are formed in a continuous, serpentine shape. Three holes are formed at both ends of the separator SPa in the longitudinal direction, for the inflow and outflow of fuel (hydrogen), air (oxygen), and cooling water. The cathode-side separator SPc has irregularities for the air flow path and irregularities for the cooling water flow path. The cathode-side separator SPc has the same configuration as the anode-side separator SPa.

[0019] The cooling water seal S is made of an elastic material such as rubber and is shaped to fit along the outer periphery of the opposing separators SPa and SPc. For this reason, the cooling water seal S is formed in a rectangular shape in a plan view, with holes formed in each corner. The cooling water seal S prevents the cooling water from leaking outside the cooling water flow path. Note that Figures 1(A), (B), and (C) are examples and do not limit the number or shape of the irregularities formed on the separators SPa and SPc.

[0020] Before describing this embodiment in detail, the stack structure of the multiple fuel cells FC included in the fuel cell stack 1 will be described.

[0021] The fuel cell stack 1 is formed by stacking (pressing) multiple fuel cells FC. A three-layer thermoplastic sheet BDa is provided between the membrane electrode assembly (MEA) and separator SPa at the anode-side periphery of each fuel cell FC. Similarly, a three-layer thermoplastic sheet BDc is provided between the membrane electrode assembly (MEA) and separator SPc at the cathode-side periphery of each fuel cell FC. The thermoplastic sheets BDa and BDc are formed by sandwiching both sides of a substrate (BM) between two adhesive layers (thermoplastic resin) (AD). The thermoplastic sheets BDa and BDc are located at the outermost periphery of the fuel cell, and the adhesive layers on their surfaces bond and fix the separators SPa and SPc to the membrane electrode assembly (MEA). The thermoplastic sheets BDa and BDc seal the hydrogen supplied to the anode and the air (oxygen) supplied to the cathode to prevent leakage outside the fuel cell FC. Note that Figure 1(B) shows the hardened shapes of the thermoplastic sheets BDa and BDc.

[0022] As will be described later, the separators SPa and SPc have recesses formed in positions where they contact the thermoplastic sheets BDa and BDc. For this reason, the adhesive layer adjacent to the separators SPa and SPc is made thicker, and the adhesive layer (thermoplastic resin) that melts during bonding fills the area around the recesses in the separators SPa and SPc. The recesses in the separators SPa and SPc are used to accommodate cooling water seals S made of an elastic material such as rubber to prevent cooling water supplied between two adjacent fuel cell cells FC in the stacking direction from leaking out when the fuel cell cells are stacked, and are sealed by the cooling water seals S when the stack is compressed. The separators SPa and SPc are made of thin plates of metal or carbon, and the cooling water seals S are made of an elastic material such as rubber.

[0023] It is also possible to prevent leakage of cooling water by arranging a flat (plate-shaped) cooling water seal S in the horizontal direction (perpendicular to the stacking direction) on the periphery of the separators SPa and SPc that abut against the thermoplastic sheets BDa and BDc. The cooling water seal S is a necessary component for constructing the fuel cell FC.

[0024] However, there is a possibility that the fuel cells FC may become misaligned when an external impact is applied to the fuel cell stack 1. In the case of the planar cooling water seal S arranged along the periphery of the separators SPa and SPc, there is a possibility that the cooling water seal S may become misaligned along with the separators SPa and SPc due to an external impact.

[0025] This embodiment is characterized by the adoption of a fitting structure in which recesses in separators SPa, SPc fit together via cooling water seals S between multiple fuel cell units FC adjacent to each other in the stacking direction of the fuel cell stack 1. This allows the multiple fuel cell units FC to be positioned with high precision without using additional parts such as restraining materials used in conventional technology, and prevents the separators SPa, SPc and cooling water seals S from shifting position due to external impact.

[0026] Next, the cross-sectional structure of the fuel cell FC that constitutes the fuel cell stack 1 according to the embodiment of the present invention will be described in detail with reference to FIGS. 2(A) and 2(B).

[0027] Fig. 2(A) is a cross-sectional view of a fuel cell FC that constitutes a fuel cell stack 1 according to this embodiment. In Fig. 2(A), the same parts as in Fig. 1(B) are assigned the same reference numerals. In Fig. 2(A), thermoplastic sheets BDa and BDc are formed on both sides of the periphery of the membrane electrode assembly (MEA) of the fuel cell stack 1. The thermoplastic sheets BDa and BDc have a three-layer structure and are composed of an adhesive layer (thermoplastic resin) AD, a substrate BM, and an adhesive layer (thermoplastic resin) AD.

[0028] The anode-side separator SPa has longitudinally extending irregularities formed in the region facing the anode-side GDL. A recess ra is formed in the periphery of the separator SPa, which faces the thermoplastic sheet BDa. The recess ra is recessed toward the adhesive layer AD of the thermoplastic sheet BDa, and has a shape that is wider in the horizontal direction than the recess of the separator SPa (for example, a trapezoidal shape in cross section). The recess ra extends in the longitudinal direction of the separator SPa.

[0029] The cathode-side separator SPc has longitudinally extending irregularities formed in the region facing the cathode-side GDL. Furthermore, a recess rc is formed in the periphery of the separator SPc, which faces the thermoplastic sheet BDc. The recess rc is recessed toward the adhesive layer AD of the thermoplastic sheet BDc, and has a shape that is wider in the horizontal direction than the recess of the separator SPc (for example, a trapezoidal shape in cross section). The recess rc extends in the longitudinal direction of the separator SPc.

[0030] Fig. 2(B) is a cross-sectional view showing the stacked structure of two fuel cell units FC. In this embodiment, a recess ra is formed in the anode-side separator SPa, a recess rc is formed in the cathode-side separator SPc, and a cooling water seal S is placed between the recesses ra and rc to form a fitting structure for multiple fuel cell units FC. In Fig. 2(B), the structure of the upper fuel cell unit FC10 is given the reference numeral "10," and the structure of the lower fuel cell unit FC20 is given the reference numeral "20."

[0031] The fuel cell FC10 comprises an anode-side separator SPa10 having a recess ra10, a cathode-side separator SPc10 having a recess rc10, an anode-side thermoplastic sheet BDa10, and a cathode-side thermoplastic sheet BDc10. The fuel cell FC20 comprises an anode-side separator SPa20 having a recess ra20, a cathode-side separator SPc20 having a recess rc20, an anode-side thermoplastic sheet BDa20, and a cathode-side thermoplastic sheet BDc20. The recesses ra10, rc10, ra20, and rc20 are trapezoidal in cross section.

[0032] In the stacked structure shown in Figure 2(B), two fuel cells FC10 and FC20 are stacked by heat pressing, so that the depression ra10 of the separator SPa10 of the fuel cell FC10 is embedded in the adhesive layer AD of the thermoplastic sheet BDa10. Also, the depression rc10 of the separator SPc10 of the fuel cell FC10 is embedded in the adhesive layer AD of the thermoplastic sheet BDc10. Similarly, the depression ra20 of the separator SPa20 of the fuel cell FC20 is embedded in the adhesive layer AD of the thermoplastic sheet BDa20. Also, the depression rc20 of the separator SPc20 of the fuel cell FC20 is embedded in the adhesive layer AD of the thermoplastic sheet BDc20.

[0033] In the fuel cell FC10, multiple hydrogen flow paths HC10 are formed between the convex portions of the separator SPa10 on the anode side and the gas diffusion layer (GDL). Hydrogen (fuel) supplied from the outside is supplied to the GDL and MEA on the anode side via the hydrogen flow paths HC10. Multiple air flow paths AC10 are formed between the convex portions of the separator SPc10 on the cathode side and the gas diffusion layer (GDL). Air (oxygen) supplied from the outside is supplied to the GDL and MEA via the air flow paths AC10.

[0034] Similarly, in the fuel cell FC20, a plurality of hydrogen flow paths HC20 are formed between the protrusions of the anode-side separator SPa20 and the gas diffusion layer (GDL), and a plurality of air flow paths AC20 are formed between the protrusions of the cathode-side separator SPc20 and the gas diffusion layer (GDL).

[0035] Furthermore, the separator SPc10 on the cathode side of the fuel cell FC10 and the separator SPa20 on the anode side of the fuel cell FC20 are arranged opposite each other. A space extending in the longitudinal direction is formed between the separator SPc10 and the separator SPa20, and this space forms a coolant flow path WC. The coolant flow path WC allows coolant to flow between the fuel cells FC10 and FC20, and uses the coolant to cool the heat generated by the electrochemical reaction between hydrogen and oxygen.

[0036] In FIG. 2(B), cooling water seals S (S10 to S30) are provided that are hexagonal in cross section so as to fit into the recesses ra (ra10, ra20) of the anode-side separator SPa (SPa10, SPa20) and the recesses rc (rc10, rc20) of the cathode-side separator SPc (SPc10, SPc20). The "hexagonal shape" is a combination of two trapezoidal shapes facing opposite each other, with two slopes on the side. These slopes disperse external forces. Note that the cross-sectional shape of the cooling water seals S (S11 to S13) is not limited to a hexagon, and may be a polygonal or annular shape.

[0037] Specifically, the cooling water seal S10 fits into the recess ra10 of the separator SPa10 and the recess (rc) of another separator (not shown, a separator on the cathode side of another fuel cell FC arranged opposite the separator SPa10). The cooling water seal S20 fits into the recess rc10 of the separator SPc10 and the recess ra20 of the separator SPa20. When the separator SPc10 and the separator SPa20 are brought into contact with each other facing each other, a space that is hexagonal in cross section (a shape formed by combining two trapezoidal shapes facing oppositely) is formed between the recess rc10 and the recess ra20, and the cooling water seal S20 fits to seal this space. The cooling water seal S30 fits into the recess rc20 of the separator SPc20 and the recess (ra) of another separator (not shown, a separator on the anode side of another fuel cell FC arranged opposite the separator SPc20). By fitting the cooling water seals S (S10 to S30) into the recesses ra and rc of the two opposing separators SPa and SPc, it is possible to prevent displacement between the fuel cell FC and the separator SP due to external impact.

[0038] The cooling water seal S is used in combination with separators SPa and SPc, which are made of thin metal or carbon plates. Generally, metal separators for fuel cells used in vehicles are press-molded, making it difficult to manufacture separators with right-angled depressions. For this reason, in consideration of the manufacturing process for separators SPa and SPc, the depressions ra and rc have a trapezoidal cross-sectional shape that narrows toward the bottom (the part that bites into the adhesive layer AD of the thermoplastic sheets BDa and BDc). The cross-sectional shape of the cooling water seal S is hexagonal so as to fit the hexagonal cross-sectional shape formed by the depressions ra and rc of the two opposing separators SPa and SPc.

[0039] If the cross-sectional shape of the cooling water seal S were made rectangular (quadrilateral), an external force applied to the side of the fuel cell FC (external force in the horizontal direction in Figure 2(B)) would be applied in the lateral direction of the cooling water seal S. In this case, the external force acting in the lateral direction of the cooling water seal S would not be dispersed, and would act to displace the two separators SPa and SPc, which have recesses ra and rc into which the cooling water seal S fits, in an in-plane direction (horizontal direction in Figure 2(B)), which could cause misalignment of the fuel cell cells FC that face each other.

[0040] On the other hand, if the cooling water seal S has a hexagonal cross section, even if an external force is applied to the side of the fuel cell FC, the external force will be dispersed in the in-plane and out-of-plane directions of the separators SPa and SPc by two slopes on the side of the cooling water seal S, and part of the external force dispersed in the out-of-plane direction will act in the stacking direction of the fuel cell FC (the vertical direction in Figure 2(B)). The ends of the fuel cell FC in the stacking direction in the fuel cell stack 1 are sandwiched and tightened by plate members with a certain strength. Therefore, if the load in the stacking direction of the fuel cell stack 1 increases, the force pressing the fuel cell cells FC against each other will increase, and the frictional force will also increase. As a result, the effect of preventing the fuel cell FC from shifting position when an external force is applied to the side of the fuel cell stack 1 is improved.

[0041] In this embodiment shown in Figures 2(A) and 2(B), a relatively thick three-layer thermoplastic sheet BD (BDa, BDc) is used between the membrane electrode assembly (MEA) and separators SP (SPa, SPc) of the fuel cell FC. Therefore, the cooling water seal S of a predetermined shape (e.g., hexagonal cross-sectional shape) ensures shock resistance by preventing the cooling water seal S and separator SP from shifting position due to external force. In other words, multiple fuel cell cells FC are integrally constructed by combining the separator SP, the cooling water seal S of a predetermined shape that fits into the recess of the separator SP, and the three-layer thermoplastic sheet BD. This makes it possible to maintain the predetermined structure even in the event of an accident such as an external impact, allowing the fuel cell stack 1 to be manufactured with a safe structure.

[0042] Next, a stacking structure of a plurality of fuel cells FC according to a modified example of this embodiment will be described. In the stacking structure of fuel cells FC shown in Fig. 2(B), a space of a predetermined shape is formed by the recesses ra, rc of the separators SPa, SPc in order to arrange a cooling water seal S of a predetermined shape, but this is not limited to this. In other words, it is sufficient if the combination of the separators SPa, SPc and the cooling water seal S can prevent displacement of the fuel cells FC due to external impacts, etc. For this reason, it is assumed that the recesses ra, rc of two separators SPa, SPc facing each other will be fitted together to sandwich and tightly sandwich the cooling water seal S, without forming a space for arranging the cooling water seal S using the recesses ra, rc of the separators SPa, SPc.

[0043] Fig. 3 is a cross-sectional view showing a stacked structure of a plurality of fuel cells FC according to a modified example of this embodiment. The modified example shown in Fig. 3 is characterized in that the orientation of the recess ra in the anode-side separator SPa is adjusted to match the orientation of the recess rc in the cathode-side separator SPc, and the cooling water seal S is sandwiched between them. In Fig. 3, the same parts as in Figs. 2(A) and (B) are given the same reference numerals, and detailed description thereof will be omitted.

[0044] In Figure 3, the recesses rc10 and rc20 of the separators SPc10 and SPc20 on the cathode side of the fuel cells FC10 and FC20 are the same as those in Figure 2(B). In the fuel cell FC10, a recess (or protrusion) ra10' is formed in the region of the separator SPa10 on the anode side that is close to the thermoplastic sheet BDa10. In the fuel cell FC20, a recess (or protrusion) ra20' is formed in the region of the separator SPa20 on the anode side that is close to the thermoplastic sheet BDa20. In addition, a recess (or protrusion) ra30' is also formed in the separator SPa30 of another fuel cell (not shown) that is adjacent below the fuel cell FC20. The anode-side recesses ra10', ra20', and ra30' are trapezoidal in cross section so as to fit into the recesses rc10 and rc20 on the cathode side. In Figure 3, the cathode-side recess rc is embedded in the adhesive layer AD of the thermoplastic sheet BDc, while the anode-side recess ra protrudes above the adhesive layer AD of the thermoplastic sheet BDa. For this reason, the anode-side recess ra may also be referred to as a "protrusion."

[0045] The separator SPc10 of the fuel cell FC10 and the separator SPa20 of the fuel cell FC20 are arranged opposite to each other, and the recess rc10 of the separator SPc10 and the recess (protrusion) ra20' of the separator SPa20 are fitted together. Similarly, the separator SPc20 of the fuel cell FC20 and the separator SPa30 of another fuel cell (not shown) are arranged opposite to each other, and the recess rc20 of the separator SPc20 and the recess (protrusion) ra30' of the separator SPa30 are fitted together.

[0046] In FIG. 3, when fuel cells FC10 and FC20 are stacked by heat pressing, the adhesive layer AD of the thermoplastic sheet BDa10 of the fuel cell FC10 deforms so as to fill the recess (protrusion) ra10' of the separator SPa10.

[0047] Similarly, the adhesive layer AD of the thermoplastic sheet BDa20 of the fuel cell FC20 deforms to fill the recess (protrusion) ra20' of the separator SPa20. The recess (protrusion) ra20' of the separator SPa20 fits into the recess rc10 of the separator SPc10.

[0048] The recess (protrusion) ra30' of the separator SPa30 on the anode side of another adjacent fuel cell (not shown) below the fuel cell FC20 fits into the recess rc20 of the separator SPc20 on the cathode side of the fuel cell FC20.

[0049] A cooling water seal S40 is arranged around the anode-side separator SPa10 of the fuel cell FC10 so as to contact the recess (protrusion) ra10'. Therefore, the cooling water seal S40 is partially deformed along the outer shape of the recess ra10' (trapezoidal outer shape in cross section).

[0050] A cooling water seal S50 is arranged around the periphery of the separator SPa20 on the anode side of the fuel cell FC20 so as to contact the recess (protrusion) ra20'. For this reason, the cooling water seal S50 is partially deformed along the outer shape of the recess ra20' (trapezoidal outer shape in cross section). Furthermore, the recess rc10 of the separator SPc10 on the cathode side of the fuel cell FC10 and the recess (protrusion) ra20' of the separator SPa20 on the anode side of the fuel cell FC20 are fitted together, with the cooling water seal S50 arranged between them. In other words, the cooling water seal S50 is deformed to fill the gap between the recess rc10 of the separator SPc10 and the recess ra20' of the separator SPa20, which fit together.

[0051] Similarly, a cooling water seal S60 is arranged around the anode-side separator SPa30 of another adjacent fuel cell (not shown) below the fuel cell FC20 so as to contact the recess (protrusion) ra30'. Therefore, the cooling water seal S60 is partially deformed along the outer shape of the recess ra30' (trapezoidal outer shape in cross section). Furthermore, the recess rc20 of the cathode-side separator SPc20 of the fuel cell FC20 and the recess (protrusion) ra30' of the anode-side separator SPa30 of the other fuel cell (not shown) are fitted together, with the cooling water seal S60 arranged between them. In other words, the cooling water seal S60 is deformed to fill the gap between the recess rc20 of the separator SPc20 and the recess (protrusion) ra30' of the separator SPa30, which fit together.

[0052] In the stacked structure of fuel cell cells FC10, FC20 relating to a modified example of this embodiment, there is no need to form the cooling water seals S40, S50, S60 into a predetermined shape, for example, a trapezoidal cross-sectional shape. Simply arranging a simple plate-shaped rubber seal so that it is partially deformed can prevent misalignment when multiple fuel cell cells FC10, FC20 are stacked, and can also prevent misalignment due to external impact acting on the side of the fuel cell stack 1.

[0053] In the above, the molten adhesive layer (thermoplastic resin) AD of the thermoplastic sheets BDa and BDc has a thickness that allows it to fill the recesses (protrusions) ra of the separator SPa. The cooling water seals S (S40, S50, S60) placed in the recesses ra and rc of the separators SPa and SPc are deformed into a shape that fits between the recesses ra and rc of the mutually mating separators SPa and SPc.

[0054] The adhesive layers AD of the three-layered thermoplastic sheets BDa and BDc on the membrane electrode assembly (MEA) side may be made of a material other than thermoplastic resin, provided that the adhesive layers AD of the thermoplastic sheets BDa and BDc are made of an adhesive material that can be deformed to fit the shapes of the recesses ra and rc in the separators SPa and SPc.

[0055] The cross-sectional shape of the cooling water seal S is preferably polygonal (for example, trapezoidal) so as to fit into the recesses ra and rc of the separators SPa and SPc. This is to distribute the force acting on the side surface of the cooling water seal S in the stacking direction of the fuel cell FC when an external force is applied to the side surface of the fuel cell stack 1. However, the cross-sectional shape of the cooling water seal S may be a circle or a rhombus having diagonals pointing in the stacking direction and in a direction intersecting the stacking direction, other than a trapezoidal shape.

[0056] In addition, since a predetermined rigidity can be ensured at the fitting portions between the separators SPa, SPc and the fuel cell FC or the thermoplastic sheets BDa, BDc, the cooling water seals S may be made of a material other than rubber.

[0057] Next, the effects of the fuel cell stack according to this embodiment will be described. The fuel cell stack 1 according to this embodiment is characterized by the placement of a cooling water seal S shaped to fit the recesses ra and rc provided in the separators SPa and SPc. This prevents an increase in the manufacturing cost of the fuel cell stack 1 and makes it possible to position the fuel cell units FC while suppressing the occurrence of electrical short circuits between the multiple fuel cell units FC.

[0058] Specifically, the recesses of the separators SPa and SPc of the fuel cell FC are filled with the adhesive layers (thermoplastic resin) AD of the thermoplastic sheets BDa and BDc, improving the rigidity of the recesses ra and rc of the separators SPa and SPc. The cooling water seals S fit into the recesses ra and rc of the separators SPa and SPc, maintaining the relative positions of the multiple fuel cell units FC and preventing displacement of the multiple fuel cell units FC due to impacts from external forces, etc.

[0059] When stacking multiple fuel cells FC, accurate positioning is possible by fitting the cooling water seal S into the recesses ra, rc of the separators SPa, SPc. The cooling water seal S is a necessary component for preventing leakage of the cooling water flowing between multiple fuel cells FC. Therefore, in the fuel cell stack 1 according to this embodiment, the cooling water seal S is shaped to fit into the recesses ra, rc of the separators SPa, SPc without introducing additional members (such as restraining materials), thereby preventing misalignment of the multiple fuel cells FC.

[0060] The fuel cell stack 1 according to this embodiment does not have additional members such as restraining members, so adjacent fuel cells FC do not come into contact with each other via the restraining members. Therefore, in this embodiment, it is possible to prevent the positional deviation of the fuel cells FC while suppressing electrical short circuits between the fuel cells FC.

[0061] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0062] 1. Fuel cell stack AC10, AC20 air flow path BDa10, BDc10, BDa20, BDc20 thermoplastic sheet FC, FC10, FC20 fuel cell HC10, HC20 hydrogen flow path ra10, rc10, ra20, rc20, ra10´, ra20´, ra30´ recess S10, S20, S30, S40, S50, S60 Cooling water seal SPa10, SPc10, SPa20, SPc20, SPa30 separator WC cooling water flow path

Claims

1. a plurality of fuel cell units; a cooling water seal that seals a cooling water flow path formed in a region where one fuel cell and another fuel cell adjacent to the one fuel cell in the stacking direction are arranged opposite each other among the plurality of fuel cell units, A fuel cell stack characterized by having a fitting structure that positions the one fuel cell cell and the other fuel cell cell by fitting the cooling water seal, the one fuel cell cell, and the other fuel cell cell together.

2. 2. The fuel cell stack according to claim 1, wherein the fitting structure includes a recess in each of the one fuel cell unit and the other fuel cell unit adjacent in the stacking direction to sandwich the cooling water seal.

3. 3. The fuel cell stack according to claim 2, wherein a first recess is formed in the one fuel cell and a second recess is formed in the other fuel cell, and when the one fuel cell and the other fuel cell adjacent to each other in the stacking direction are fitted together using the fitting structure, the cooling water seal fits between the first recess and the second recess.

4. 4. The fuel cell stack according to claim 3, wherein the first recess and the second recess are trapezoidal in cross section, and the cooling water seal has a cross-sectional shape that fits into the first recess and the second recess.

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