Separator for fuel cell and fuel cell stack

Abstract

To suppress deflection and deformation of a separator to be incorporated into a fuel cell stack.SOLUTION: A fuel cell stack separator 3 includes a pair of plates joined with each other to form a cooling flow path PAw through which a cooling medium flows between the pair of plates. Each of the pair of plates includes: a bead portion 32, 35 provided with a protrusion so as to block a communication between a through hole of the separator 3 and front / rear gas flow paths of the separator 3; a tunnel portion 52, 54 provided to cross the bead portion 32, 35, and provided with a protrusion so as to form a communication flow path PA21 communicating between the through hole and the cooling flow path PAw; and a rib portion 55 connected to the tunnel portion 52, 54 to form a connecting flow path PA22.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a fuel cell separator and a fuel cell stack. Regarding. [Background technology]

[0002] In recent years, technological developments have been made on fuel cells that contribute to energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. This type of fuel cell has a fuel cell stack that is configured by alternately stacking a structure including an assembly of an electrolyte membrane and electrodes and separators, and as a separator to be incorporated in such a fuel cell stack, a separator that is configured by joining a pair of metal plates and has a cooling medium flow path formed between the pair of metal plates through which a cooling medium flows has been known (for example, see Patent Document 1).

[0003] In Patent Document 1, a separator is provided with a communication hole for a coolant inlet and a communication hole for a coolant outlet on either side of a coolant flow path, and metal bead seals are provided around each of these communication holes. Furthermore, the separator is provided with tunnels that intersect with each of the metal bead seals, and the coolant flow path and the communication holes communicate with each other through the tunnels. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7038692 Summary of the Invention [Problem to be solved by the invention]

[0005] The separator described in Patent Document 1 has a pair of metal plates that are substantially flat in the region between the central region of the coolant flow path and the tunnel, which results in low rigidity of the pair of metal plates and makes the separator prone to bending and deformation. [Means for solving the problem]

[0006] One aspect of the present invention is a fuel cell separator that is alternately stacked with a structure including an assembly of an electrolyte membrane and an electrode to form a fuel cell stack together with the structure, the separator comprising a pair of metal plates each having inner faces facing each other and an outer face opposite the inner faces, each provided with communication holes that form a supply flow path and a discharge flow path for a coolant, and joined to each other to form a coolant flow path between the pair of inner faces through which the coolant flows. The separator includes a first region facing the assembly, a second region around the communication holes, and a third region between the first and second regions. Each of the pair of plates has a first flow passage forming portion with a concave-convex shape provided in the first region and forming a gas flow passage in the space between the bonded body and the outer surface, a sealing portion provided in the second region and protruding toward the structure so as to block communication between the communication hole and the space, a tunnel portion provided intersecting the sealing portion and protruding toward the structure so as to form a communicating flow passage connecting the communication hole and the coolant flow passage, and a second flow passage forming portion with a concave-convex shape provided in the third region and connected to the tunnel portion and forming a connecting flow passage that is part of the coolant flow passage.

[0007] A fuel cell stack according to another aspect of the present invention includes a plurality of structures including an assembly of an electrolyte membrane and an electrode, and a plurality of fuel cell separators as described above that are stacked alternately with the plurality of structures. Effect of the Invention

[0008] According to the present invention, the rigidity of the separator is increased, and bending and deformation of the separator can be suppressed. [Brief description of the drawings]

[0009] [Figure 1]1 is a perspective view showing a schematic overall configuration of a fuel cell stack according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 2 is a perspective view showing a schematic configuration of an electrode assembly included in the fuel cell stack of FIG. [Figure 4A] FIG. 2 is a rear view of a fuel cell separator according to an embodiment of the present invention. [Figure 4B] 1 is a front view of a fuel cell separator according to an embodiment of the present invention; [Diagram 5] FIG. 4C is a cross-sectional view of a main portion of the separator shown in FIGS. 4A and 4B. [Figure 6A] 4B is a cross-sectional view taken along line AA in FIG. 4A. [Figure 6B] FIG. 4C is a cross-sectional view taken along line BB in FIG. 4B. [Figure 7] Enlarged view of part VII in FIG. 4A. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. [Figure 9] FIG. 8 is a cross-sectional view taken along line VII-VII in FIG. [Figure 10] FIG. 8 is a diagram showing a modification of FIG. 7. [Figure 11] FIG. 8 is a diagram showing another modified example of FIG. 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to Figs. 1 to 11. A fuel cell stack according to an embodiment of the present invention is a main component of a fuel cell and is included in the fuel cell. The fuel cell is mounted on a vehicle, for example, and generates power for driving the vehicle. The fuel cell can also be mounted on moving objects other than vehicles, such as aircraft and ships, robots, and various industrial machines.

[0011] First, the overall configuration of the fuel cell stack will be described. FIG. 1 is a perspective view showing the overall configuration of a fuel cell stack 100 according to an embodiment of the present invention. In the following, for convenience, three axial directions perpendicular to each other as shown in the figure are defined as the front-rear direction, the left-right direction, and the up-down direction, and the configuration of each part will be described according to these definitions. These directions do not necessarily coincide with the front-rear direction, the left-right direction, and the up-down direction of the vehicle. For example, the front-rear direction in FIG. 1 may be the front-rear direction, the left-right direction, or the up-down direction of the vehicle.

[0012] As shown in FIG. 1, a fuel cell stack 100 has a cell stack 101 formed by stacking a plurality of power generating cells 1 in the front-rear direction, and end units 102 arranged at both front and rear ends of the cell stack 101, and has a generally rectangular parallelepiped shape as a whole. The length of the cell stack 101 in the left-right direction is longer than its length in the up-down direction. For convenience, FIG. 1 shows a single power generating cell 1. The power generating cell 1 has an electrode assembly 2 having an assembly including an electrolyte membrane and an electrode, and separators 3, 3 arranged on both the front and rear sides of the electrode assembly 2. The electrode assemblies 2 and the separators 3 are arranged alternately in the front-rear direction.

[0013] FIG. 2 is a cross-sectional view of a main part of the cell stack 101 in the left-right direction (a cross-sectional view taken along line II-II in FIG. 1). As shown in FIG. 2, the separator 3 has a front plate 3F and a rear plate 3R, which are a pair of front and rear metallic thin plates having a corrugated cross section. The front plate 3F extends in the up-down and left-right directions and has a front surface 3Fa facing forward and a rear surface 3Fb facing rearward. The rear plate 3R extends in the up-down and left-right directions and has a front surface 3Ra facing forward and a rear surface 3Rb facing rearward. The rear surface 3Fb of the front plate 3F and the front surface 3Ra of the rear plate 3R, which face each other, are joined at their outer peripheries by welding or the like. As a result, the front plate 3F and the rear plate 3R are integrally joined to form the separator 3. The separator 3 is made of a conductive material having excellent corrosion resistance, such as stainless steel, titanium, or a titanium alloy.

[0014] A cooling flow path PAw through which a cooling medium flows is formed inside the separator 3 surrounded by the front plate 3F and the rear plate 3R, that is, between the rear surface 3Fb of the front plate 3F and the front surface 3Ra of the rear plate 3R. The power generation surface of the power generation cell 1 is cooled by the flow of the cooling medium. Water, for example, can be used as the cooling medium. The surface (front surface 3Fa and rear surface 3Rb) of the separator 3 facing the electrode assembly 2 is formed unevenly by press molding or the like so as to form a gas flow path between the separator 3 and the electrode assembly 2. More specifically, the separator 3 has a pair of front and rear rib portions 3A protruding toward the electrode assembly 2, and a pair of front and rear recesses 3B formed in a concave shape and connected to the pair of front and rear rib portions 3A.

[0015] The pair of front and rear rib portions 3A abut against the front surface 2a and rear surface 2b of the electrode assembly 2. A compressive load F is applied to the cell stack 101 in the front-rear direction when the fuel cell stack 100 is assembled, and this compressive load F is maintained after the assembly of the fuel cell stack 100 is completed. As a result, a predetermined surface pressure due to the compressive load F acts on the electrode assembly 2 in the front-rear direction via the rib portions 3A.

[0016] Between the front surface 2a of the electrode assembly 2 and the rear plate 3R of the separator 3 facing the front surface 2a, an anode flow passage PAa through which a fuel gas flows is formed by the recess 3B. Between the rear surface 2b of the electrode assembly 2 and the front plate 3F of the separator 3 facing the rear surface 2b, a cathode flow passage PAc through which an oxidizer gas flows is formed by the recess 3B. For example, hydrogen gas can be used as the fuel gas, and for example, air can be used as the oxidizer gas. The fuel gas and the oxidizer gas are sometimes referred to as reactant gases without distinction between them.

[0017] Fig. 3 is a perspective view showing a schematic configuration of an electrode assembly 2 serving as a membrane electrode assembly (so-called MEA; Membrane Electrode Assembly). As shown in Fig. 3, the electrode assembly 2 has a substantially rectangular assembly 20 and a frame 21 supporting the assembly 20. As shown in the detailed view of part A in Fig. 2, the assembly 20 has an electrolyte membrane 23, an anode electrode 24 provided on a front surface 231 of the electrolyte membrane 23, and a cathode electrode 25 provided on a rear surface 232 of the electrolyte membrane 23.

[0018] The electrolyte membrane 23 is, for example, a solid polymer electrolyte membrane, and a thin film of a perfluorosulfonic acid polymer containing water can be used. The electrolyte membrane 23 is not limited to a fluorine-based electrolyte membrane, and a hydrocarbon-based electrolyte membrane can also be used.

[0019] The anode electrode 24 is formed on the front surface 231 of the electrolyte membrane 23 and has an electrode catalyst layer 241 which serves as a reaction field for the electrode reaction, and a gas diffusion layer 242 which is provided on the front surface of the electrode catalyst layer 241 and diffuses and supplies a fuel gas. An intermediate layer (underlayer) may be provided between the electrode catalyst layer 241 and the gas diffusion layer 242. The cathode electrode 25 is formed on the rear surface 232 of the electrolyte membrane 23 and has an electrode catalyst layer 251 which serves as a reaction field for the electrode reaction, and a gas diffusion layer 252 which is provided on the rear surface of the electrode catalyst layer 251 and diffuses and supplies an oxidant gas. An intermediate layer (underlayer) may be provided between the electrode catalyst layer 251 and the gas diffusion layer 252.

[0020] The electrode catalyst layers 241, 251 contain a catalytic metal that promotes an electrochemical reaction between hydrogen contained in the fuel gas and oxygen contained in the oxidant gas, an electrolyte (such as an ionomer) having proton conductivity, and carbon particles having electronic conductivity. The gas diffusion layers 242, 252 are made of a conductive material having gas permeability, such as a carbon porous body. The gas diffusion layers 242, 252 have a water-repellent function because they are mainly composed of carbon and fluorine.

[0021] At the anode electrode 24, the fuel gas (hydrogen) supplied via the anode flow path PAa is ionized by the action of a catalyst and passes through the electrolyte membrane 23 to move to the cathode electrode side. The electrons generated at this time pass through an external circuit and are extracted as electrical energy. At the cathode electrode 25, the oxidant gas (oxygen) supplied via the cathode flow path PAc reacts with the hydrogen ions introduced from the anode electrode 24 and the electrons that have moved from the anode electrode 24 to generate water. The generated water provides an appropriate humidity to the electrolyte membrane 23, and excess water is discharged to the outside of the electrode assembly 2 along the gas flow.

[0022] The frame 21 in Fig. 3 is a thin plate having a substantially rectangular shape, and is made of insulating resin, rubber, or the like. A substantially rectangular opening 21a is provided in the center of the frame 21. The joint body 20 is provided so as to cover the entire opening 21a, and the peripheral portion of the joint body 20 is supported by the frame 21. On the left side of the opening 21a of the frame 21, three through holes 211 to 213 penetrating the frame 21 in the front-rear direction are opened in a line in the vertical direction, and on the right side of the opening 21a, three through holes 214 to 216 penetrating the frame 21 in the front-rear direction are opened in a line in the vertical direction.

[0023] As shown in FIG. 1, the separators 3 at the front and rear of the electrode assembly 2 are provided with through holes 301-306 that penetrate the separators 3 in the front-rear direction at positions corresponding to the through holes 211-216 of the frame 21. The through holes 301-306 are connected to the through holes 211-216 of the frame 21, respectively. A collection of the through holes 211-216 and 301-306 that are connected to each other forms flow paths PA1-PA6 (indicated by arrows for convenience) that penetrate the cell stack 101 and extend in the front-rear direction. The flow paths PA1-PA6 are sometimes called manifolds. The flow paths PA1-PA6 are connected to a manifold external to the fuel cell stack 100.

[0024] A flow path PA1 (indicated by a solid arrow) extending forward via the through holes 211, 301 is a fuel gas supply flow path. A flow path PA6 (indicated by a solid arrow) extending rearward via the through holes 216, 306 is a fuel gas discharge flow path. The fuel gas supply flow path PA1 and the fuel gas discharge flow path PA6 are connected to an anode flow path PAa (FIG. 2) provided opposite to the front surface of the joined body 20, and as indicated by the solid arrow, fuel gas flows in the left-right direction through the anode flow path PAa via the fuel gas supply flow path PA1 and the fuel gas discharge flow path PA6. The communication between the anode flow path PAa and the other flow paths PA2 to PA5 is blocked via a bead portion, which will be described later.

[0025] A flow path PA4 (dotted arrow) extending forward through the through holes 214, 304 is an oxidant gas supply flow path. A flow path PA3 (dotted arrow) extending rearward through the through holes 213, 303 is an oxidant gas discharge flow path. The oxidant gas supply flow path PA4 and the oxidant gas discharge flow path PA3 communicate with a cathode flow path PAc ( FIG. 2 ) provided opposite to the rear surface of the joined body 20, and as indicated by the dotted arrow, the oxidant gas flows in the left-right direction through the cathode flow path PAc via the oxidant gas supply flow path PA4 and the oxidant gas discharge flow path PA3. The communication between the cathode flow path PAc and the other flow paths PA1, PA2, PA5, and PA6 is blocked via a bead portion described later.

[0026] A flow path PA5 (indicated by a dashed line arrow) extending forward through the through holes 215 and 305 is a cooling medium supply flow path. A flow path PA2 (indicated by a dashed line arrow) extending rearward through the through holes 212 and 302 is a cooling medium discharge flow path. The cooling medium supply flow path PA5 and the cooling medium discharge flow path PA2 communicate with a cooling medium flow path PAw (FIG. 2) provided inside the separator 3, and the cooling medium flows through the cooling medium flow path PAw via the cooling medium supply flow path PA5 and the cooling medium discharge flow path PA2. Communication between the cooling medium flow path PAw and the other flow paths PA1, PA3, PA4, and PA6 is blocked via a bead portion described later.

[0027] The end units 102 arranged on both the front and rear sides of the cell stack 101 each have a terminal plate 4, an insulating plate 5, and an end plate 6. The terminal plate 4 is a substantially rectangular plate-like member made of metal, and has a terminal portion for extracting power generated by an electrochemical reaction in the cell stack 101. The insulating plate 5 is a substantially rectangular plate-like member made of non-conductive resin or rubber, and electrically insulates the terminal plate 4 and the end plate 6.

[0028] The end plates 6 are plate-shaped members made of metal or high-strength resin. For example, a connecting member elongated in the front-rear direction is fixed to the end plates 6 with a bolt, and the front and rear end plates 6, 6 are connected to each other via the connecting member. The fuel cell stack 100 is held in a state in which it is pressed in the front-rear direction by the end plates 6, 6 via the connecting member. As a result, a compressive load F (FIG. 2) acts on the electrode assembly 2 and the separators 3 in the front-rear direction. A case surrounding the cell stack 101 may be used as the connecting member, and the end plates 6, 6 may be fixed to the front and rear end faces of the case, respectively.

[0029] The rear end unit 102 has a plurality of through holes 102a-102f penetrating the end unit 102 in the front-rear direction. The through hole 102a is opened on an extension of the fuel gas supply passage PA1 and communicates with the fuel gas supply passage PA1. The through hole 102b is opened on an extension of the cooling medium discharge passage PA2 and communicates with the cooling medium discharge passage PA2. The through hole 102c is opened on an extension of the oxidizing gas discharge passage PA3 and communicates with the oxidizing gas discharge passage PA3. The through hole 102d is opened on an extension of the oxidizing gas supply passage PA4 and communicates with the oxidizing gas supply passage PA4. The through hole 102e is opened on an extension of the cooling medium supply passage PA5 and communicates with the cooling medium supply passage PA5. The through hole 102f is opened on an extension of the fuel gas discharge passage PA6 and communicates with the fuel gas discharge passage PA6.

[0030] More specifically, a fuel gas tank storing high-pressure fuel gas is connected to the through-hole 102a via an ejector, an injector, etc., and the fuel gas is supplied to the fuel cell stack 100 via the through-hole 102a. The fuel gas is discharged from the through-hole 102f. A compressor for supplying oxidizing gas is connected to the through-hole 102d, and the oxidizing gas compressed by the compressor is supplied to the fuel cell stack 100 via the through-hole 102d. The oxidizing gas is discharged from the through-hole 102c. A pump for supplying a cooling medium is connected to the through-hole 102e, and the cooling medium is supplied to the fuel cell stack 100 via the through-hole 102e. The cooling medium is discharged from the through-hole 102b. The discharged cooling medium is cooled by heat exchange in the radiator, and is again supplied to the fuel cell stack 100 via the through-hole 102e.

[0031] The above is a schematic configuration of the fuel cell stack 100. The fuel cell stack 100 is housed in a substantially box-shaped case and mounted on a vehicle. The fuel cell stack 100 according to this embodiment is characterized by the configuration of the separator 3 incorporated in the fuel cell stack 100. The configuration of the separator 3 will be described in more detail below.

[0032] Fig. 4A is a rear view (viewed from the rear) of the separator 3, and Fig. 4B is a front view (viewed from the front) of the separator 3. In other words, Fig. 4A is a view showing the rear surface 3Rb of the rear plate 3R facing the anode electrode 24 on the front surface 2a of the electrode assembly 2, and Fig. 4B is a view showing the front surface 3Fa of the front plate 3F facing the cathode electrode 25 on the rear surface 2b of the electrode assembly 2. Both Fig. 4A and Fig. 4B are views of the separator 3 as seen from the front.

[0033] Hereinafter, the region of separator 3 facing the bonded body 20 of the electrode assembly 2 in a front view, i.e., the region AR1 facing the power generation surface, will be referred to as the active region of separator 3, and the rest will be referred to as the inactive region. Since active region AR1 is located in the center of separator 3 in the left-right direction, active region AR1 will also be referred to as the central region of separator 3.

[0034] Of the non-active areas, the areas at the left and right ends where the through holes 301-306 are provided are called end areas AR2 of the separator 3. The end areas AR2 include flow paths PA1-PA6 for supplying and discharging reactant gas and cooling medium. Of the non-active areas, areas on the left and right inside of the end areas AR2 are called connection areas AR3 of the separator 3. The connection areas AR3 are located between the active area AR1 and the left and right end areas AR2.

[0035] As shown in FIG. 4A, in the active region AR1 of the rear plate 3R, a plurality of convex portions 307 are provided at equal intervals in the vertical direction over almost the entire area, although some are omitted from the illustration. The plurality of convex portions 307 extend in the horizontal direction, and a concave portion 308 is provided between the convex portions 307, 307 adjacent to each other in the vertical direction. The anode flow path PAa (FIG. 2) is formed between the plurality of concave portions 308 and the front surface of the bonded body 20. On the rear surface 3Rb of the rear plate 3R, a plurality of embossed portions 371 are provided at equal intervals in the vertical direction on the right and left sides of the convex portions 307 and the concave portion 308, respectively. More specifically, a plurality of substantially cylindrical embossed portions 371 are provided at the inlet region and the outlet region of the anode flow path PAa from the rear surface 3Rb of the rear plate 3R toward the rear. Although FIG. 4A shows a row of embossed portions 371 in the vertical direction, a plurality of rows of embossed portions 371 may be provided. The embossed portion 371 may be omitted.

[0036] As shown in FIG. 4B, in the active region AR1 of the front plate 3F, a plurality of convex portions 309 are provided at equal intervals in the up-down direction over almost the entire region, although some of the convex portions 309 are not shown. The plurality of convex portions 309 extend in the left-right direction, and a concave portion 310 is provided between the convex portions 309, 309 adjacent to each other in the up-down direction. A cathode flow path PAc (FIG. 2) is formed between the plurality of concave portions 310 and the rear surface of the bonded body 20. A plurality of embossed portions 372 are provided at equal intervals in the up-down direction on the right and left sides of the convex portions 309 and the concave portions 310 on the front surface 3Fa of the front plate 3F. More specifically, a plurality of substantially cylindrical embossed portions 372 are provided at the inlet region and the outlet region of the cathode flow path PAc to protrude forward from the front surface 3Fa of the front plate 3F. Although FIG. 4B shows a row of embossed portions 372 in the up-down direction, a plurality of rows of embossed portions 372 may be provided. The embossed portion 372 may be omitted.

[0037] 4A, a rear surface 3Rb of the rear plate 3R is provided with a plurality of bead portions for sealing, i.e., metal bead seals, which protrude rearward toward the frame 21. The plurality of bead portions include an outer bead portion 31, an inner bead portion 32, and an end bead portion 33, which are formed by pressing the rear plate 3R.

[0038] In a front view of the separator 3, the outer bead portion 31 extends along the periphery of the rear plate 3R so as to surround all of the through holes 301-306, and has a generally rectangular shape. The end bead portions 33 are provided in the number of the through holes 301-306. Each of the end bead portions 33 has a generally rectangular shape, and surrounds each of the through holes 301-306 individually. The inner bead portion 32 is provided inside the outer bead portion 31. More specifically, the inner bead portion 32 extends in a zigzag shape, passing through the left-right outer side of the end bead portions 33 around the through holes 301, 303, 304, 306, and passing through the left-right inner side of the end bead portions 33 around the through holes 302, 305. The end bead portion 33 around the through holes 302 and 305 is located between the outer bead portion 31 and the inner bead portion 32 .

[0039] 4B, a front surface 3Fa of the front plate 3F is provided with a plurality of sealing bead portions that protrude forward toward the frame 21. The plurality of bead portions include an outer bead portion 34, an inner bead portion 35, and an end bead portion 36, which are formed by pressing the front plate 3F.

[0040] In a front view of the separator 3, the outer bead portion 34 extends along the periphery of the front plate 3F so as to surround all of the through holes 301-306, and has a generally rectangular shape. The end bead portions 36 are provided in the number of the through holes 301-306. Each of the end bead portions 36 has a generally rectangular shape and surrounds each of the through holes 301-306. The inner bead portion 35 is provided inside the outer bead portion 34. More specifically, the inner bead portion 35 extends in a zigzag shape, passing through the outer side in the left-right direction of the end bead portions 36 around the through holes 301, 303, 304, 306, and passing through the inner side in the left-right direction of the end bead portions 36 around the through holes 302, 305. The end bead portions 36 around the through holes 302 and 305 are located between the outer bead portion 34 and the inner bead portion 35 .

[0041] Fig. 5 is a cross-sectional view of a main part of the separator 3, in which the bead portions 31-36 are cut vertically. As shown in Fig. 5, the bead portions 31-36 have a substantially rectangular cross section, more specifically, a substantially trapezoidal cross section. The multiple bead portions 31-33 of the rear plate 3R and the multiple bead portions 34-36 of the front plate 3F are provided at the same positions as each other in the vertical and horizontal directions when viewed from the front. Therefore, a substantially rectangular space SP0 is provided between the bead portions 31-33 and the bead portions 34-36.

[0042] A seal material 40 is fixed to the rear surfaces of the bead portions 31-33 and the front surfaces of the bead portions 34-36. The seal material 40 is made of a structural material having elasticity, such as rubber or resin. The front seal material 40 is pressed against the rear surface 2b of the frame 21 (FIG. 2) of the electrode assembly 2, and the rear seal material 40 is pressed against the front surface 2a of the frame 21. This closes the gaps between the bead portions 31-36 and the frame 21, and a sealed anode flow path PAa and a cathode flow path PAc can be formed between the electrode assembly 2 and the separator 3. The seal material 40 may be omitted, and the tips of the bead portions 31-36 may be directly abutted against the frame 21.

[0043] The anode flow path PAa and the cathode flow path PAc are provided inside the inner bead portions 32 and 35 in a front view of the separator 3. A plurality of through holes 301, 303, 304, and 306 are arranged inside the inner bead portions 32 and 35. However, communication between the anode flow path PAa and the through holes 301, 303, 304, and 306 is blocked by the end bead portion 33, and communication between the cathode flow path PAc and the through holes 301, 303, 304, and 306 is blocked by the end bead portion 36. In this embodiment, the separator 3 is provided with a plurality of tunnel portions that perpendicularly intersect (transverse) the end bead portion 33 so that the anode flow path PAa communicates with the through holes 301 and 306 and the cathode flow path PAc communicates with the through holes 303 and 304, respectively.

[0044] More specifically, as shown in FIG. 4A, three tunnel portions 41 are provided parallel to each other and at equal intervals in the vertical direction for the end bead portion 33 around the through hole 301 of the rear plate 3R, crossing the right end bead portion 33 extending in the vertical direction in the left-right direction. Three tunnel portions 42 are provided parallel to each other and at equal intervals in the vertical direction for the end bead portion 33 around the through hole 303, crossing the right end bead portion 33 extending in the vertical direction in the left-right direction. Three tunnel portions 43 are provided parallel to each other and at equal intervals in the vertical direction for the end bead portion 33 around the through hole 304, crossing the left end bead portion 33 extending in the vertical direction in the left-right direction. Three tunnel portions 44 are provided parallel to each other and at equal intervals in the vertical direction for the end bead portion 33 around the through hole 306, crossing the left end bead portion 33 extending in the vertical direction in the left-right direction.

[0045] Similarly, as shown in FIG. 4B, for the end bead portion 36 around the through hole 301 of the front plate 3F, three tunnel portions 45 are provided parallel to each other and at equal intervals in the vertical direction, crossing the right end bead portion 36 extending in the vertical direction in the left-right direction. For the end bead portion 36 around the through hole 303, three tunnel portions 46 are provided parallel to each other and at equal intervals in the vertical direction, crossing the right end bead portion 36 extending in the vertical direction in the left-right direction. For the end bead portion 36 around the through hole 304, three tunnel portions 47 are provided parallel to each other and at equal intervals in the vertical direction, crossing the left end bead portion 36 extending in the vertical direction in the left-right direction. For the end bead portion 36 around the through hole 306, three tunnel portions 48 are provided parallel to each other and at equal intervals in the vertical direction, crossing the left end bead portion 36 extending in the vertical direction in the left-right direction.

[0046] The number of the tunnel portions 41-48 described above is an example, and the number of each of the tunnel portions 41-48 may be more or less than three. The tunnel portions 41-44 of the rear plate 3R and the tunnel portions 45-48 of the front plate 3F are provided at the same positions as each other when viewed from the front of the separator 3. The tunnel portions 41-48 each extend approximately linearly in the left-right direction, and their protrusion amounts in the front-rear direction, widths in the up-down direction, and lengths in the left-right direction are equal to each other. The tunnel portions 41-48 are formed by press-molding the front plate 3F and the rear plate 3R.

[0047] Fig. 6A is a cross-sectional view (cross-sectional view taken along line AA in Fig. 4A) showing the configuration of the tunnel portions 41, 45 in the vicinity of the through-hole 301. As shown in Fig. 6A, the tunnel portion 45 of the front plate 3F is provided so as to protrude forward, and the tunnel portion 41 of the rear plate 3R is provided so as to protrude backward. The amount of protrusion of the tunnel portions 41, 45 in the front-rear direction is smaller than the amount of protrusion of the bead portions 33, 36. Although not shown in the drawings, the tunnel portions 41, 45 have a substantially rectangular or trapezoidal cross section, and a communication flow path PA11 is formed between the front and rear tunnel portions 41, 45.

[0048] Of the tunnel portions 41, 45, the left side of the bead portions 33, 36 (the through hole 301 side) is called the outer tunnel portion 411, 451, and the right side of the bead portions 33, 36 (the anode flow path PAa side) is called the inner tunnel portion 412, 452. The left ends of the outer tunnel portions 411, 451 are located on the periphery of the through hole 301, and the left ends of the communication flow paths PA11 are open facing the through hole 301. The right ends of the outer tunnel portions 411, 451 penetrate the bead portions 33, 36 and communicate with the internal spaces of the bead portions 33, 36.

[0049] The left ends of the inner tunnels 412, 452 penetrate the bead portions 33, 36 and communicate with the internal spaces of the bead portions 33, 36. The right ends of the inner tunnels 412, 452 are provided with tapered portions 412a, 452a whose protruding amount gradually decreases toward the right. At the right ends of the tunnels 41, 45, the protruding amount in the front-rear direction becomes zero, and the communication flow path PA11 is blocked. The tapered portion 412a of the tunnel 41 has a fuel gas outlet 410 opened therein. This allows the through hole 301 to communicate with the anode flow path PAa at the rear of the rear plate 3R via the communication flow path PA11 and the outlet 410. Therefore, the fuel gas flowing through the through hole 301 can be supplied to the anode flow path PAa via the communication flow path PA11 and the outlet 410, as shown by the arrow in FIG. 6A.

[0050] Although not shown, the tunnels 44, 48 near the through hole 306 are configured similarly to the tunnels 41, 45 in FIG. 6A. That is, the tunnels 41, 45 and the tunnels 44, 48 have a symmetrical shape with respect to an axis extending in the vertical direction. Therefore, a fuel gas inlet 440 (FIG. 4A) is opened in the tapered portion at the left end of the tunnel 44. As a result, the fuel gas that has flowed through the anode flow path PAa is guided to the through hole 306 via the inlet 440 and the communication flow path PA11 inside the tunnels 44, 48.

[0051] Fig. 6B is a cross-sectional view (cross-sectional view taken along line BB in Fig. 4B) showing the configuration of the tunnel portions 43, 47 in the vicinity of the through-hole 304. As shown in Fig. 6B, the tunnel portion 47 of the front plate 3F is provided so as to protrude forward, and the tunnel portion 43 of the rear plate 3R is provided so as to protrude rearward. The amount of protrusion of the tunnel portions 43, 47 in the front-rear direction is smaller than the amount of protrusion of the bead portions 33, 36. Although not shown in the drawings, the tunnel portions 43, 47 have a substantially rectangular or trapezoidal cross section, and a communication flow path PA12 is formed between the front and rear tunnel portions 43, 47.

[0052] Of the tunnel portions 43, 47, the right side of the bead portions 33, 36 (the through hole 304 side) is called the outer tunnel portion 431, 471, and the left side of the bead portions 33, 36 (the cathode flow path PAc side) is called the inner tunnel portion 432, 472. The right ends of the outer tunnel portions 431, 471 are located on the periphery of the through hole 304, and the right ends of the communication flow paths PA12 are open facing the through hole 304. The left ends of the outer tunnel portions 431, 471 penetrate the bead portions 33, 36 and communicate with the internal spaces of the bead portions 33, 36.

[0053] The right ends of the inner tunnels 432, 472 penetrate the bead portions 33, 36 and communicate with the internal spaces of the bead portions 33, 36. The left ends of the inner tunnels 432, 472 are provided with tapered portions 432a, 472a whose protruding amount gradually decreases toward the left. At the left ends of the tunnels 43, 47, the protruding amount in the front-rear direction becomes zero, and the communication flow path PA12 is blocked. The tapered portion 472a of the tunnel 47 is provided with an outlet 470 for the oxidizer gas. This allows the through hole 304 to communicate with the cathode flow path PAc in front of the front plate 3F via the communication flow path PA12 and the outlet 470. Therefore, the oxidizer gas flowing through the through hole 304 can be supplied to the cathode flow path PAc via the communication flow path PA12 and the outlet 470, as shown by the arrow in FIG. 6B.

[0054] Although not shown, the tunnels 42 and 46 near the through hole 303 are configured similarly to the tunnels 43 and 47 in FIG. 6B. That is, the tunnels 43 and 47 and the tunnels 42 and 46 have a symmetrical shape with respect to an axis extending in the vertical direction. Therefore, an inlet 460 (FIG. 4B) for the oxidizer gas is opened in the tapered portion at the right end of the tunnel 46. As a result, the oxidizer gas that has flowed through the cathode flow path PAc is guided to the through hole 303 via the inlet 460 and the communication flow path PA12 inside the tunnels 42 and 46.

[0055] As shown in Fig. 4A and Fig. 4B, the front plate 3F and the rear plate 3R are provided with a plurality of tunnel portions 51-54 in the vicinity of the through holes 302 and 305, intersecting with the bead portions 32, 33, 35, and 36. More specifically, as shown in Fig. 4A, the rear plate 3R is provided with three tunnel portions 51, which are parallel to each other and equally spaced in the vertical direction, to the right of the through hole 302, intersecting (perpendicular to) the right end bead portion 33 extending in the vertical direction and the inner bead portion 32 extending in the vertical direction. In addition, to the left of the through hole 305, three tunnel portions 52 are provided with parallel to each other and equally spaced in the vertical direction, intersecting (perpendicular to) the left end bead portion 33 extending in the vertical direction and the inner bead portion 32 extending in the vertical direction.

[0056] 4B, on the front plate 3F, three tunnel portions 53 are provided parallel to each other and equally spaced apart in the vertical direction to the right of the through hole 302, intersecting (perpendicular to) the right end bead portion 36 extending in the vertical direction and the inner bead portion 35 extending in the vertical direction. Also, three tunnel portions 54 are provided parallel to each other and equally spaced apart in the vertical direction to the left of the through hole 305, intersecting (perpendicular to) the left end bead portion 36 extending in the vertical direction and the inner bead portion 35 extending in the vertical direction.

[0057] The number of the tunnel portions 51 to 54 described above is an example, and the number of the tunnel portions 51 to 54 may be more or less than three. The tunnel portions 51, 52 of the rear plate 3R and the tunnel portions 53, 54 of the front plate 3F are provided at the same positions as each other when viewed from the front of the separator 3. The tunnel portions 51 to 54 each extend linearly in the left-right direction, and their protrusion amounts in the front-rear direction, widths in the up-down direction, and lengths in the left-right direction are equal to each other.

[0058] 4A and 4B, the front plate 3F and the rear plate 3R are provided with a plurality of generally cylindrical embossed portions 373, 374 at equal intervals in the up-down direction on the left-right outer sides of the embossed portions 371, 372. The protruding direction of the embossed portions 373, 374 is opposite to the protruding direction of the embossed portions 371, 372. That is, the embossed portion 373 protrudes forward (toward the cooling flow path) from the front surface 3Ra of the rear plate 3R, and the embossed portion 374 protrudes rearward (toward the cooling flow path) from the rear surface 3Fb of the front plate 3F.

[0059] The embossed portions 373, 374 may be arranged inside the embossed portions 371, 372 in the left-right direction. Although a single row of the embossed portions 373, 374 is shown in Figs. 4A and 4B in the up-down direction, multiple rows of the embossed portions 373, 374 may be provided. In this case, the embossed portions 371, 372 and the embossed portions 373, 374 may be arranged alternately in the left-right direction. The embossed portions 373, 374 may be omitted.

[0060] FIG. 7 is an enlarged view (enlarged view of part VII) of FIG. 4A including the tunnel portion 52, and FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. For convenience, FIG. 7 also shows the reference numerals of the parts of the front plate 3F corresponding to the parts of the rear plate 3R (for example, the tunnel portion 54 corresponding to the tunnel portion 52). As shown in FIG. 8, the tunnel portion 54 of the front plate 3F is provided in a convex shape toward the front, and the tunnel portion 52 of the rear plate 3R is provided in a convex shape toward the rear. The protruding amount of the tunnel portions 52, 54 in the front-rear direction is smaller than the protruding amount of the end bead portions 33, 36 and the inner bead portions 32, 35. Although not shown, the tunnel portions 52, 54 have a substantially rectangular or trapezoidal cross section, and a communication flow path PA21 is formed between the front and rear tunnel portions 52, 54.

[0061] Of the tunnel portions 52, 54, the right side (through hole 305 side) of the end bead portion 33, 36 is called the outer tunnel portion 521, 541, and the left side (cooling flow passage PAw side) of the inner bead portion 32, 35 is called the inner tunnel portion 522, 542. The area between the end bead portion 33, 36 and the inner bead portion 32, 35 is called the middle tunnel portion 523, 543. The right end of the outer tunnel portion 521, 541 is located on the periphery of the through hole 305, and the right end of the communication flow passage PA21 is open facing the through hole 305. The left end of the outer tunnel portion 521, 541 penetrates the end bead portion 33, 36 and communicates with the internal space of the end bead portion 33, 36.

[0062] The right end of the intermediate tunnel portion 523, 543 penetrates the end bead portion 33, 36 and communicates with the internal space of the end bead portion 33, 36. The left end of the intermediate tunnel portion 523, 543 penetrates the inner bead portion 32, 35 and communicates with the internal space of the inner bead portion 32, 35. The right end of the inner tunnel portion 522, 542 penetrates the inner bead portion 32, 35 and communicates with the internal space of the inner bead portion 32, 35. The left end of the inner tunnel portion 522, 542 is provided with a tapered portion 522a, 542a whose protruding amount gradually decreases toward the left. The left ends of the inner tunnel portion 522, 542 are separated from each other with a predetermined amount of gap SP1 in the front-rear direction, and in this state, the front plate 3F and the rear plate 3R extend to the left.

[0063] As a result, the through hole 305 and the cooling flow passage PAw on the left side of the tunnel portions 52 and 54 are communicated with each other through the communication flow passage PA21 and the gap SP1. Therefore, the cooling medium flowing through the through hole 305 can be supplied to the cooling flow passage PAw through the communication flow passage PA21 and the gap SP1 as shown by the arrow in FIG. 8. As shown in FIG. 7, the tunnel portions 52 and 54 are provided such that the outer tunnel portions 521 and 541, the middle tunnel portions 523 and 543, and the inner tunnel portions 522 and 542 are aligned in a straight line. As a result, the pressure loss of the communication flow passage PA21 is small, and the cooling medium flowing through the through hole 305 can be smoothly guided to the cooling flow passage PAw.

[0064] Although not shown, the tunnels 51 and 53 near the through hole 302 are configured similarly to the tunnels 52 and 54 in FIG. 8. That is, the tunnels 51 and 53 and the tunnels 52 and 54 have a symmetrical shape with respect to an axis extending in the up-down direction through the left-right middle part of the separator 3. Therefore, a gap SP1 in the front-rear direction through which the cooling medium flows is provided at the right end of the tunnels 51 and 53. As a result, the cooling medium that has flowed through the cooling flow passage PAw is guided to the through hole 302 via the gap SP1 at the right end of the tunnels 51 and 53 and the communication flow passage PA21 inside the tunnels 51 and 53.

[0065] 4A and 4B, the cooling flow passage PAw is an area including the active area AR1, and is provided from the connection area AR3 on the left side of the tunnel sections 52, 54 to the connection area AR3 on the right side of the tunnel sections 51, 53. As shown in FIG. 7, in the connection area AR3, the rear plate 3R and the front plate 3F are provided with a plurality of rib portions 55 for regulating the flow direction of the cooling medium. The positions of the rib portions 55 of the rear plate 3R in the up, down, left, and right directions are the same as those of the rib portions 55 of the front plate 3F in the up, down, left, and right directions. The plurality of rib portions 55 have the same shape when viewed from the front of the separator 3, and their protrusion amounts in the front-rear direction and their widths in the up-down direction are equal to each other.

[0066] Fig. 9 is a cross-sectional view taken along line IX-IX in Fig. 7. As shown in Fig. 9, the rib portion 55 of the rear plate 3R protrudes forward from the front surface 3Ra of the rear plate 3R, and the rib portion 55 of the front plate 3F protrudes rearward from the rear surface 3Fb of the front plate 3F. That is, the rib portion 55 protrudes in the opposite direction to the bead portions 32, 33, 35, 36 and the tunnel portions 52, 54 in Fig. 8. The rib portion 55 has a substantially rectangular cross section, more specifically, a substantially trapezoidal cross section.

[0067] The front end surface of the rib portion 55 of the rear plate 3R and the rear end surface of the rib portion 55 of the front plate 3F are brought into contact with each other, and a flow path (called a connection flow path) PA22 for the cooling medium is formed between the vertically aligned rib portions 55, 55. At this time, the rib portion 55 constitutes a side wall or a partition wall of the connection flow path PA22, and the cooling medium flows along the rib portion 55.

[0068] 7, in a front view of the separator 3, the rib portions 55 are provided between the tunnel portions 52, 54 lined up in the vertical direction, above the uppermost tunnel portion 52, 54, and below the lowermost tunnel portion 52, 54. The multiple rib portions 55 are arranged parallel to each other and extend in the left-right direction. The multiple rib portions 55 have the same left-right length and are also at the same left-right positions.

[0069] The right end of the rib portion 55 is located a predetermined distance to the left of the left ends of the tunnel portions 52 and 54. The left end of the rib portion 55 is located a predetermined distance to the right of the embossed portions 373 and 374 (FIGS. 4A and 4B) or the right ends of the gas flow paths PAa and PAc. The distance from the right end of the rib portion 55 to the end region AR2 is shorter than the distance from the left end of the rib portion 55 to the active region AR1, and the rib portion 55 is provided on the right side (tunnel portion side) in the connection region AR3. The distance from the right end of the rib portion 55 to the end region AR2 and the distance from the left end of the rib portion 55 to the active region AR1 may be equal to each other. The embossed portions 373 and 374 may be omitted, and the rib portion 55 may be provided over the entire left-right area of ​​the connection region AR3.

[0070] By providing the rib portion 55 in this manner, the connection flow passage PA22 is located on an extension of the communication flow passage PA21 inside the tunnel portions 52, 54. In other words, the communication flow passage AR21 and the connection flow passage AR22 are located on the same straight line. As a result, as shown by the dotted arrow in Fig. 7, the cooling medium that has flowed through the communication flow passage PA21 flows through the connection flow passage PA22 without changing its flow direction. Therefore, the flow of the cooling medium in the connection area AR3 is smooth, and the cooling effect due to the flow of the cooling medium can be improved.

[0071] Although detailed illustration is omitted, a rib portion 55 is also provided to the right of the tunnel portions 51 and 53. That is, the rib portion 55 on the right of the tunnel portions 51 and 53 and the rib portion 55 on the left of the tunnel portions 52 and 54 have a bilaterally symmetrical shape with respect to an axis extending in the vertical direction through the left-right middle portion of the separator 3. Therefore, on the right of the tunnel portions 51 and 53, a connection flow path PA22 is provided between the vertically adjacent rib portions 55, 55 that are arranged at equal intervals in the vertical direction. As a result, the cooling medium that has flowed through the cooling flow path PAw is guided to the through hole 302 via the connection flow path PA22 and the communication flow path PA21.

[0072] As described above, the rear end surface of the rib portion 55 of the front plate 3F and the front end surface of the rib portion 55 of the rear plate 3R abut against each other (FIG. 9). This increases the rigidity of the separator 3 in the connection area AR3, making it possible to suppress bending and deformation of the separator 3. Specifically, it is possible to prevent the separator 3 from bending due to the compressive load F in the front-rear direction during assembly of the fuel cell stack 100. As a result, it is possible to ensure sealing performance at the abutting portion between the separator 3 and the frame 21.

[0073] According to this embodiment, the following advantageous effects can be obtained. (1) The separator 3 according to this embodiment is a fuel cell separator that is alternately stacked with electrode assemblies 2 including an assembly 20 of an electrolyte membrane 23, an anode electrode 24, and a cathode electrode 25, and that constitutes a fuel cell stack 100 together with the electrode assemblies 2 (FIGS. 1 and 2). The separator 3 has a pair of metal plates, a front plate 3F and a rear plate 3R, that are joined together (FIG. 2). The front plate 3F has a rear surface 3Fb that faces the rear plate 3R and a front surface 3Fa on the opposite side, and the rear plate 3R has a front surface 3Ra that faces the front plate 3F and a rear surface 3Rb on the opposite side (FIG. 2). The front plate 3F and the rear plate 3R are each provided with a through hole 305 that forms a supply flow path for the cooling medium and a through hole 302 that forms a discharge flow path, and a cooling flow path PAw through which the cooling medium flows is formed between the rear surface 3Fb of the front plate 3F and the front surface 3Ra of the rear plate 3R that face each other (FIG. 2). The separator 3 includes an active area (first area) AR1 facing the bonded body 20, an edge area (second area) AR2 around the through holes 302, 305, and a connection area (third area) AR3 between the active area AR1 and the edge area AR2 (Figures 4A and 4B).

[0074] The front plate 3F has a convex portion 309 and a concave portion 310 provided in the active region AR1 and forming a cathode flow path PAc in the space between the bonded body 20 and its front surface 3Fa, bead portions 35, 36 provided in the end region AR2 and protruding toward the frame 21 of the electrode assembly 2 so as to block communication between the through holes 302, 305 and the cathode flow path PAc, tunnel portions 53, 54 provided intersecting the bead portions 35, 36 and protruding toward the frame 21 to form a communication flow path PA21 that connects the through holes 302, 305 and the cooling flow path PAw, and a rib portion 55 provided in the connection region AR3 so as to be connected to the tunnel portions 53, 54 and form a connection flow path PA22 that is a part of the cooling flow path PAw (Figures 4B, 7, and 8). The rear plate 3R has a convex portion 307 and a concave portion 308 provided in the active region AR1 and forming an anode flow path PAa in the space between the bonded body 20 and its rear surface 3Rb, bead portions 32, 33 provided in the end region AR2 and protruding toward the frame 21 of the electrode assembly 2 so as to block communication between the through holes 302, 305 and the anode flow path PAa, tunnel portions 51, 52 provided intersecting the bead portions 32, 33 and protruding toward the frame 21 to form a communicating flow path PA21 that connects the through holes 302, 305 and the cooling flow path PAw, and a rib portion 55 provided in the connection region AR3 so as to be connected to the tunnel portions 51, 52 and form a connecting flow path PA22 that is a part of the cooling flow path PAw (Figures 4A, 7, and 8).

[0075] Providing the rib portion 55 on the separator 3 in this manner increases the rigidity of the separator 3, and makes it possible to suppress bending and deformation of the separator 3. As a result, it is possible to ensure the sealing performance at the contact portion between the separator 3 and the frame 21. In contrast, if the front plate 3F and the rear plate 3R are simply flat plates in the connection region AR3, bending and deformation may occur in the separator 3 when a compressive load F is applied in the front-rear direction, for example, and sufficient sealing performance may not be ensured.

[0076] (2) The rib portion 55 is provided so that the connection passage PA22 extends along the extension line of the communication passage PA21 (FIG. 7). This allows the cooling medium that has flowed through the communication passage PA21 to flow smoothly through the connection passage PA22, and the cooling medium that has flowed through the connection passage PA22 to flow smoothly through the communication passage PA21. This reduces pressure loss in the flow of the cooling medium, and improves the cooling effect.

[0077] (3) The rib portion 55 of the front plate 3F and the rib portion 55 of the rear plate 3R protrude from the rear face 3Fb and the front face 3Ra, respectively, to form the side walls (side walls or partition walls) of the connecting flow passage PA22, and abut against each other (FIG. 9). By abutting the rib portions 55 against each other in this manner, the rigidity of the connection region AR3 of the separator 3 against the compressive load F in the front-rear direction is further increased.

[0078] (4) The tunnel portions 51-54 are provided so that the communication flow path PA21 extends in a substantially straight line from one end to the other end (FIGS. 4A, 4B, and 7). This allows the cooling medium to flow smoothly through the communication flow path PA21 and efficiently guide the cooling medium from the through hole 305 to the connection area AR3 and from the connection area AR3 to the through hole 302.

[0079] (5) The rib portion 55 is provided so that the connection flow passage PA22 is connected to the communication flow passage PA21 and extends in a substantially straight line (FIG. 7). With this configuration, the cooling medium flows straight from the through hole 305 to the left end of the right-side connection flow passage PA22, and from the right end of the left-side connection flow passage PA22 to the through hole 302. This makes it possible to minimize loss of the cooling medium flow from the through hole 305 to the through hole 302.

[0080] (6) The fuel cell stack 100 includes an electrode assembly 2 including an assembly 20 of an electrolyte membrane 23 with an anode electrode 24 and a cathode electrode 25, and a plurality of the above-mentioned separators 3 that are stacked alternately with the plurality of electrode assemblies 2 (FIG. 1). A compressive load F is applied to the fuel cell stack 100 in the front-rear direction during assembly. However, by providing the separator 3 with a rib portion 55, the rigidity of the separator 3 is increased, and deflection or deformation of the separator 3 can be suppressed.

[0081] The above embodiment can be modified in various ways. Some modified examples will be described below. In the above embodiment, the rib portion 55 is provided as the second flow path forming portion in the connection region AR3 of the separator 3 to form the flow path of the cooling medium (connection flow path PA22), but a flow path of the reactant gas may be formed by further providing an uneven flow path forming portion. FIG. 10 is a diagram showing an example of the configuration of the rib portion 55 around the through hole 302 in that case. In FIG. 10, an uneven flow path PA23 through which the fuel gas flows is formed from the through hole 301 toward the anode flow path PAa. The flow path PA23 crosses the right side of the rib portion 55, and the area in which the flow path PA23 is provided expands downward. The rib portion 55 is formed to be gradually longer downward so as not to interfere with the flow path PA23. In this way, the lengths of the multiple rib portions 55 do not have to be the same. It should be noted that the lengths of the multiple rib portions 55 may be different from each other regardless of whether the flow path PA23 is provided or not.

[0082] In the above embodiment, the through holes 301-306 of the separator 3 are configured to have a substantially rectangular shape, but the through holes 301-306 may have various shapes, such as other polygonal shapes, circular shapes, shapes in which straight lines and curved lines are mixed, and the like. The number and arrangement of the through holes 301-306 are not limited to those described above. In the above embodiment, the multiple rib portions 55 are provided parallel to each other, but they may not be parallel. FIG. 11 is a diagram showing an example of the rib portion 55 around the through hole 302 configured in this manner. In FIG. 11, a part of the periphery of the through hole 302 has a curved shape in a front view, and the tunnel portion 51 and the rib portion 55 extend perpendicular to this periphery. Therefore, the multiple rib portions 55 are not in a parallel relationship. Note that the multiple rib portions 55 do not have to be parallel, regardless of whether the periphery of the through hole 302 has a curved shape or not. The direction in which the rib portion 55 extends does not have to be perpendicular to the periphery of the through hole 302. In the above embodiment, the multiple rib portions 55 are provided at equal intervals, but they do not have to be at equal intervals.

[0083] In the above embodiment, the width of the communication flow passage PA21 and the width of the connection flow passage PA22 are constant over the entire length of the flow passages PA21 and PA22, but they may be changed along the length of the flow passages PA21 and PA22. For example, the rib portion 55 may be inclined in the vertical direction when viewed from the front of the separator 3 so that the width of the connection flow passage PA22 on the upstream side of the cooling flow passage PAw gradually increases toward the downstream side in the flow direction of the cooling medium. The rib portion 55 may be inclined in the vertical direction when viewed from the front of the separator 3 so that the width of the connection flow passage PA22 on the downstream side of the cooling flow passage PAw gradually decreases toward the downstream side in the flow direction of the cooling medium. In the above embodiment, the tunnel portions 51 to 54 extend from one side of the rectangular periphery of the through holes 302 and 305, but the tunnel portions may extend from multiple sides (for example, two intersecting sides). In this case, the directions in which the tunnel portions extend from each side may be different from each other or may be the same.

[0084] In the above embodiment, the connection flow passage PA22 is formed in a straight line, but a part or all of it may be formed in a curved line. In the above embodiment, the communication flow passage PA21 inside the tunnel parts 51 to 54 and the connection flow passage PA22 on the left-right inner side thereof are communicated through the gap SP between the pair of plates, but as in Figs. 6A and 6B, through holes may be opened in the plates 3F and 3R to communicate the communication flow passage PA21 and the connection flow passage PA22. In the above embodiment, the separator 3 has a pair of rib parts 55 (convex parts) that protrude from the inner surfaces (rear surface 3Fb, front surface 3Ra) of the pair of plates 3F and 3R facing each other and abut against each other, and the pair of rib parts 55 form the side wall part of the connection flow passage PA22, but the pair of rib parts do not have to abut against each other, and the configuration of the second flow passage forming part is not limited to the above.

[0085] In the above embodiment, the active area AR1 of the plates 3F, 3R is formed in an uneven shape to form the gas flow paths PAa, PAc between the bonded body 20 and the outer surfaces (front surface 3Fa, rear surface 3Rb) of the plates 3F, 3R, but the configuration of the first flow path forming portion is not limited to the above. In the above embodiment, the bead portions 32, 33, 35, 36 are protruded toward the electrode assembly 2 (structure) so as to block communication between the through holes 302, 305 (communication holes) and the cooling flow path PAw (cooling medium flow path), but the configuration of the seal portion is not limited to the above. In the above embodiment, the connection flow path PA22 extends along the extension line of the communication flow path PA21, but the connection flow path may be shifted from the extension line of the communication flow path.

[0086] In the above embodiment, the electrode assembly 2, which is a structure including an assembly 20 of an electrolyte membrane 20a and electrodes 20b, 20c, and the separators 3 are alternately stacked in the front-to-rear direction to form the cell stack 101, but the stacking direction may be other than the front-to-rear direction (for example, the up-to-down direction).

[0087] The above description is merely an example, and the present invention is not limited to the above-mentioned embodiment and modifications, as long as the features of the present invention are not impaired. The above-mentioned embodiment and one or more modifications can be arbitrarily combined, and modifications can be combined with each other.

[0088] 2 electrode assembly, 3 separator, 3F front plate, 3Fa front surface, 3Fb rear surface, 3Ra front surface, 3Rb rear surface, 20 joint body, 23 electrolyte membrane, 24 anode electrode, 25 cathode electrode, 21 frame, 32, 33, 35, 36 bead portion, 51 to 54 tunnel portion, 55 rib portion, 100 fuel cell stack, 302, 305 through hole, 307, 309 convex portion, 308, 310 concave portion, PAa anode flow path, PAc cathode flow path, PAw cooling flow path, PA21 communication flow path, PA22 connection flow path, AR1 active area, AR2 end area, AR3 connection area

Claims

1. A fuel cell separator that is laminated alternately with a structure including an electrolyte membrane and an electrode assembly and that constitutes a fuel cell stack together with the structure, comprising: a pair of metal plates each having an inner surface facing each other and an outer surface opposite the inner surface, each provided with communication holes forming a coolant supply flow path and a coolant discharge flow path, and joined together to form a coolant flow path between the pair of inner surfaces through which the coolant flows; the separator includes a first region facing the bonded body, a second region around the communication hole, and a third region between the first region and the second region, Each of the pair of plates is a first flow passage forming portion having an uneven shape that is provided in the first region and forms a gas flow passage in a space between the bonded body and the outer surface; a seal portion provided in the second region and protruding toward the structure so as to block communication between the communication hole and the space; a tunnel portion that is provided to intersect with the seal portion and that protrudes toward the structure to form a communication flow path that communicates the communication hole and the coolant flow path; a second flow passage forming portion having an uneven shape that is provided in the third region so as to be connected to the tunnel portion and that forms a connecting flow passage that is a part of the coolant flow passage.

2. 2. The fuel cell separator according to claim 1, 2. A fuel cell separator, comprising: a second flow passage forming portion provided such that the connecting flow passage extends along an extension line of the communication flow passage.

3. 3. The fuel cell separator according to claim 1, a second flow passage forming portion of each of the pair of plates having protrusions that protrude from the inner surface so as to form side walls of the connecting flow passages and abut against each other;

4. 3. The fuel cell separator according to claim 1, The tunnel portion is provided so that the communication flow passage extends in a substantially straight line from one end to the other end of the tunnel portion.

5. The fuel cell separator according to claim 4, 2. A fuel cell separator, comprising: a first passageway formed between the first and second passageways, the first passageway being connected to the second passageway and extending substantially linearly.

6. A plurality of structures including an electrolyte membrane / electrode assembly; A fuel cell stack comprising: a plurality of fuel cell separators according to claim 1 or 2, stacked alternately with the plurality of structures.

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