POWER GENERATION CELL

Abstract

Power generation cell (12), which includes: a plate-shaped membrane electrode arrangement (28a); and metal separators (30, 32) arranged on one surface and another surface of the membrane electrode arrangement (28a), wherein the membrane electrode arrangement (28a) and the metal separators (30, 32) are stacked together in a horizontal direction, each of the metal separators (30, 32) has: a reaction gas flow field (48, 58) configured to allow a reaction gas to flow along an electrode surface of the membrane electrode arrangement (28a); characterized in that each of the metal separators (30, 32) further comprises: a reaction gas channel (34a, 34b, 38a, 38b) which is connected to the reaction gas flow field (48, 58), is positioned in the horizontal direction outside the reaction gas flow field (48, 58), and passes through the metal separator (30, 32) in a separator thickness direction; a channel bead (53, 63) for sealing, which surrounds the reaction gas channel (34a, 34b, 38a, 38b) and projects in the separator thickness direction; a bridge (80, 82, 90, 92) configured to connect an inside of the channel bulge (53, 63) to its outside; wherein a lower section of the channel rim (53, 63) contains a recessed section, and the width of the recessed section decreases downwards in the horizontal direction perpendicular to the direction in which the membrane electrode arrangement (28a) and the metal separators (30, 32) are stacked together; and wherein a water drainage channel (70, 72, 98, 100) is arranged separately from the bridge (80, 82, 90, 92) at a lowest section of the recessed section of the channel bulge (53, 63), which is configured to connect an interior of the channel bulge (53, 63) with the reaction gas channel (34a, 34b, 38a, 38b).

Description

BACKGROUND OF THE INVENTION: Field of invention:

[0001] The present invention relates to a power generation cell which includes a bead seal. Description of the related technique:

[0002] In general, a solid polymer electrolyte fuel cell uses a solid polymer electrolyte membrane. The solid polymer electrolyte membrane is a polymer ion exchange membrane. The fuel cell contains a membrane electrode assembly (MEA). The MEA is formed by placing an anode on one surface of the solid polymer electrolyte membrane and a cathode on the other surface of the solid polymer electrolyte membrane.

[0003] The membrane electrode array is layered between separators (bipolar plates) to form a power generation cell (cell unit). In use, a predetermined number of power generation cells are stacked together to form, for example, a fuel cell stack installed in a vehicle.

[0004] In the fuel cell stacks, a fuel gas flow field is formed between the MEA and one of the separators, representing one of the reaction gas flow fields, and an oxygen-containing gas flow field is formed between the MEA and the other separator, representing the other of the reaction gas flow fields. Furthermore, a plurality of reaction gas channels extend through the fuel cell stack in the stacking direction. These reaction gas channels include a fuel gas supply channel for supplying fuel gas to the fuel gas flow field, a fuel gas discharge channel for removing fuel gas from the fuel gas flow field, an oxygen-containing gas supply channel for supplying oxygen-containing gas to the oxygen-containing gas flow field, and an oxygen-containing gas discharge channel for removing oxygen-containing gas from the oxygen-containing gas flow field (see, for example, Japanese Patent Publication JP 2007 - 141 543 A).

[0005] The publication DE 20 2015 104 973 U1 discloses a separator of a power generation cell according to the preamble of claim 1. Reference is also made to the publication US 2007 / 0 111 083 A1. SUMMARY OF THE INVENTION

[0006] Water is produced in the power generation cell as a result of the power generation reaction. Furthermore, the water vapor in the reaction gases condenses, producing condensate. If the generated water remains standing at the bottom of the reaction gas channel, rust could form, or a liquid bridge could develop due to the stagnant water.

[0007] The present invention has been made with regard to the above problem, and the object of the present invention is to provide a power generation cell with a simple structure which is able to suppress the accumulation of generated water at the bottom of a reaction gas channel.

[0008] To solve the above problem, the present invention provides a power generation cell according to claim 1.

[0009] Furthermore, the metal separator includes a bridge configured to connect an inside of the channel bulge to its outside; the water drainage channel being connected to the bridge through the interior of the channel bulge.

[0010] Furthermore, the lower section of the channel bulge contains a recessed section, the width of which decreases downwards in a horizontal direction perpendicular to the direction in which the membrane electrode assembly and the metal separators are stacked; and the water drainage channel is arranged at a lowest section of the recessed section.

[0011] Preferably, the water drainage channel includes a hole that opens on a side wall of the channel bulge, as well as a water drainage tunnel that is connected to the hole and projects upwards towards the reaction gas channel.

[0012] Preferably, the water drainage tunnel extends in a vertical direction.

[0013] Preferably, a lower section of the reaction gas channel includes a recessed section, wherein the width of the recessed section decreases downwards in a horizontal direction perpendicular to the direction in which the membrane electrode arrangement and the metal separators are stacked together; and an upper end of the water drainage tunnel is arranged at a lowest section of the recessed section of the reaction gas channel.

[0014] In the power generation cell of the present invention, it is possible with a simple structure to suppress the accumulation of generated water at the bottom of the reaction gas channel.

[0015] The above and other objectives, features and advantages of the present invention will become more apparent from the following description in conjunction with the accompanying drawings, in which preferred embodiments of the present invention are shown as an illustrative example. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective view showing a stack of fuel cells; Fig. Figure 2 is an exploded view showing a power generation cell according to an embodiment of the present invention of a fuel cell stack; Fig. Figure 3 is a cross-sectional view that schematically shows the power generation cell; Fig. Figure 4 is a front view showing a first metal separator; Fig. Figure 5 is a partially magnified view showing an area in the vicinity of an oxygen-containing gas supply channel of the first metal separator; Fig. Figure 6 is a cross-sectional view showing the first metal separator along line VI-VI in Fig. 5 shows; Fig. Figure 7 is a cross-sectional view along line VII-VII in Fig. 5; Fig. Figure 8 is a front view showing a second metal separator; Fig. Figure 9 is a front view showing a first metal separator according to a modified design; Fig. Figure 10 is a cross-sectional view showing the first metal separator along line XX in Fig. 9 shows; and Fig. Figure 11 is a front view showing a second metal separator according to the modified design. DESCRIPTION OF THE PREFERRED VERSION

[0016] Preferred embodiments of a power generation cell according to the present invention are described below with reference to the accompanying drawings.

[0017] As in Fig. As shown in Figure 1, a fuel cell stack 10 includes a stack body 14 formed by stacking a plurality of power generating cells 12 (cell units) in the horizontal direction indicated by arrow A. For example, the fuel cell stack 10 is installed in a fuel cell vehicle, such as an electric fuel cell car (not shown).

[0018] At one end of the stacking body 14, in the stacking direction indicated by arrow A, a connection plate 16a is arranged. An insulator 18a is arranged outside the connection plate 16a, and an end plate 20a is arranged outside the insulator 18a. At the other end of the stacking body 14, in the stacking direction, a connection plate 16b is arranged. An insulator 18b is arranged outside the connection plate 16b, and an end plate 20b is arranged outside the insulator 18b. Coupling rods 24 are arranged between the sides of the end plates 20a and 20b, respectively.

[0019] Each of the end plates 20a, 20b has a laterally elongated (or longitudinally elongated) rectangular shape. The coupling rods 24 are arranged between the sides of the end plates 20a, 20b. Both ends of the coupling rods 24 are fastened to inner surfaces of the end plates 20a, 20b by means of bolts 26 to apply a tightening tensile load to a plurality of the stacked power generation cells 12 in the stacking direction indicated by arrow A. It should be noted that the fuel cell stack 10 may have a housing containing the end plates 20a, 20b, and the stack body 14 may be arranged in the housing.

[0020] As in Fig. As shown in Figure 2, the power generation cell 12 includes a membrane electrode assembly (plastic film MEA) 28 equipped with a plastic film, a first metal separator 30 arranged on one surface of the plastic film MEA 28, and a second metal separator 32 arranged on the other surface of the plastic film MEA 28.

[0021] Each of the first metal separator 30 and the second metal separator 32 is formed by press forming a thin metal sheet with a corrugated cross-section. For example, the metal sheet could be a steel sheet, a stainless steel sheet, an aluminum sheet, a galvanized steel sheet, or a metal sheet with an anti-corrosion treatment. When the first metal separator 30 faces one of the adjacent power generating cells 12 and the second metal separator 32 faces the other of the adjacent power generating cells 12, the outer edges of the first metal separator 30 and the second metal separator 32 are joined together by welding, soldering, crimping, etc., to form a connected separator 33.

[0022] At one end of the power generation cell 12 in the longitudinal direction indicated by arrow B (i.e., one end in the horizontal direction indicated by arrow B1), an oxygen-containing gas supply channel 34a, a coolant supply channel 36a, and a fuel gas discharge channel 38b are arranged. The oxygen-containing gas supply channel 34a, the coolant supply channel 36a, and the fuel gas discharge channel 38b extend through the power generation cell 12 in the stacking direction indicated by arrow A. The oxygen-containing gas supply channel 34a, the coolant supply channel 36a, and the fuel gas discharge channel 38b are arranged in the vertical direction indicated by arrow C. Oxygen-containing gas is supplied through the oxygen-containing gas supply channel 34a. A coolant, such as water, is supplied through the coolant supply channel 36a. Fuel gas, such as hydrogen-containing gas, is discharged through the fuel gas discharge channel 38b.

[0023] At the opposite end of the power generation cell 12 in the longitudinal direction (i.e., at the opposite end in the direction indicated by arrow B2) are arranged a fuel gas supply channel 38a, a coolant discharge channel 36b, and an oxygen-containing gas discharge channel 34b. The fuel gas supply channel 38a, the coolant discharge channel 36b, and the oxygen-containing gas discharge channel 34b extend through the power generation cell 12 in the stacking direction. The fuel gas supply channel 38a, the coolant discharge channel 36b, and the oxygen-containing gas discharge channel 34b are arranged in the vertical direction. The fuel gas is supplied through the fuel gas supply channel 38a. The coolant is discharged through the coolant discharge channel 36b. The oxygen-containing gas is discharged through the oxygen-containing gas discharge channel 34b.The layout of the oxygen-containing gas supply channel 34a, the oxygen-containing gas discharge channel 34b, the fuel gas supply channel 38a and the fuel gas discharge channel 38b are not limited to the embodiment of the present invention and should be suitably designed according to the required specifications.

[0024] As in Fig. As shown in Figure 3, the plastic film MEA 28 comprises a membrane electrode assembly 28a and a frame-shaped plastic film 46, which is arranged on the outer circumferential section of the membrane electrode assembly 28a. The membrane electrode assembly 28a comprises an electrolyte membrane 40, as well as an anode 42 and a cathode 44, between which the electrolyte membrane 40 is layered.

[0025] For example, electrolyte membrane 40 contains a solid polymer electrolyte membrane (cation exchange membrane). For example, the solid polymer electrolyte membrane is a thin membrane made of hydrated perfluorosulfonic acid. Electrolyte membrane 40 is layered between anode 42 and cathode 44. A fluorine-based electrolyte can be used as electrolyte membrane 40. Alternatively, a hydrocarbon-based electrolyte can be used as electrolyte membrane 40.

[0026] The cathode 44 contains a first electrode catalyst layer 44a, which is connected to one surface of the electrolyte membrane 40, and a first gas diffusion layer 44b, which is stacked on top of the first electrode catalyst layer 44a. The anode 42 contains a second electrode catalyst layer 42a, which is connected to the other surface of the electrolyte membrane 40, and a second gas diffusion layer 42b, which is stacked on top of the second electrode catalyst layer 42a.

[0027] The inner surface of the plastic film 46 is arranged such that it is adjacent to, overlaps with, or in contact with (abuts against) the outer end surface of the electrolyte membrane 40. As shown in Fig. As shown in Figure 2, at one end of the plastic film 46, the oxygen-containing gas supply channel 34a, the coolant supply channel 36a, and the fuel gas discharge channel 38b are arranged in the direction indicated by arrow B1. At the other end of the plastic film 46, in the direction indicated by arrow B2, the fuel gas supply channel 38a, the coolant discharge channel 36b, and the oxygen-containing gas discharge channel 34b are arranged.

[0028] For example, the plastic film 46 is made of PPS (polyphenylene sulfide), PPA (polyphthalamide), PEN (polyethylene naphthalate), PES (polyethersulfone), LCP (liquid crystal polymer), PVDF (polyvinylidene fluoride), silicone resin, fluorocarbon resin, m-PPE (modified polyphenylene ether), PET (polyethylene terephthalate), PBT (polybutylene terephthalate), or modified polyolefin. It should be noted that the electrolyte membrane 40 can be designed to project outwards without using the plastic film 46. Alternatively, a frame-shaped film can be arranged on both sides of the outwardly projecting electrolyte membrane 40.

[0029] As in Fig. As shown in Figure 2, an oxygen-containing gas flow field 48 is arranged on a surface 30a of the first metal separator 30, which faces the plastic film MEA 28 (hereinafter referred to as "surface 30a"). For example, the oxygen-containing gas flow field 48 extends in the direction indicated by arrow B. As shown in Fig. As shown in Figure 4, the oxygen-containing gas flow field 48 is fluidically connected to the oxygen-containing gas supply channel 34a and the oxygen-containing gas discharge channel 34b. The oxygen-containing gas flow field 48 contains straight flow grooves 48b between a plurality of ribs 48a extending in the direction indicated by arrow B. Instead of the plurality of straight flow grooves 48b, a plurality of corrugated flow grooves can also be provided.

[0030] An inlet buffer 50A is arranged on a surface 30a of the first metal separator 30 between the oxygen-containing gas supply channel 34a and the oxygen-containing gas flow field 48. The inlet buffer 50A contains a plurality of hub rows, each of which contains a plurality of hubs 50a arranged in the direction indicated by arrow C. Furthermore, an outlet buffer 50B is arranged on the surface 30a of the first metal separator 30 between the oxygen-containing gas discharge channel 34b and the oxygen-containing gas flow field 48. The outlet buffer 50B contains a plurality of hub rows, each of which contains a plurality of hubs 50b arranged in the direction indicated by arrow C.

[0031] On the other surface 30b of the first metal separator 30, which is the back side of the oxygen-containing gas flow field 48, rows of hubs, each containing a plurality of hubs 67a arranged in the direction indicated by arrow C, are arranged between the rows of hubs of the inlet buffer 50A, and rows of hubs, each containing a plurality of hubs 67b arranged in the direction indicated by arrow C, are arranged between the rows of hubs of the outlet buffer 50B. The hubs 67a, 67b form buffers on the coolant surface.

[0032] A first sealing line 51 is formed on the surface 30a of the first metal separator 30 by compression molding. The first sealing line 51 is located in front of the plastic film MEA 28 ( Fig. 2) As in Fig. As shown in Figure 3, plastic material 56 is attached to the projecting front surfaces of the first sealing line 51 by printing, coating, etc. For example, polyester fiber is used as the plastic material 56. The plastic material 56 can be arranged on the plastic film 46. The plastic material 56 is not essential and can also be omitted.

[0033] As in Fig. As shown in Figure 4, the first sealing line 51 includes a bead seal 51a (hereinafter referred to as the "inner bead 51a") surrounding the oxygen-containing gas flow field 48, the inlet buffer 50A, and the outlet buffer 50B; a bead seal 52 (hereinafter referred to as the "outer bead 52") located outside the inner bead 51a along the outer circumference of the first metal separator 30; and a plurality of bead seals 53 (hereinafter referred to as "channel beads 53"), each surrounding a plurality of fluid channels (oxygen-containing gas supply channel 34a, etc.). The outer bead 52 projects from the surface 30a of the first metal separator 30 toward the plastic film MEA 28 and extends around the outer circumferential edge of its surface 30a.

[0034] The multiple channel ridges 53 project from the surface 30a of the first metal separator 30 to the plastic film MEA 28. The channel ridges 53 each surround the oxygen-containing gas supply channel 34a, the oxygen-containing gas discharge channel 34b, the fuel gas supply channel 30, the fuel gas discharge channel 38b, the coolant supply channel 36a and the coolant discharge channel 36b.

[0035] Hereinafter, of the several channel bulges 53, a channel bulge surrounding the oxygen-containing gas supply channel 34a is referred to as "channel bulge 53a", and a channel bulge surrounding the oxygen-containing gas discharge channel 34b is referred to as "channel bulge 53b". The first metal separator 30 has bridges 80, 82 which connect the inner side (the side of the fluid channels 34a, 34b) with the outer side (the side of the oxygen-containing gas flow field 48) of the channel bulges 53a, 53b.

[0036] As described above, the channel bulge 53a surrounds the oxygen-containing gas supply channel 34a, and the bridge 80 is arranged on a side section of the channel bulge 53a that is closer to the oxygen-containing gas flow field 48. A water drainage channel 70 is arranged on a lower section 53a1 (bottom section) of the channel bulge 53a. The water drainage channel 70 connects an interior 53d ( Fig. 6) of the channel bulge 53a with the oxygen-containing gas supply channel 34a.

[0037] As described above, the channel bulge 53b surrounds the oxygen-containing gas discharge channel 34b, and the bridge 82 is arranged on a side section of the channel bulge 53b that is closer to the oxygen-containing gas flow field 48. A water drainage channel 72 is arranged on a lower section 53b1 of the channel bulge 53b in the direction of gravity. The water drainage channel 72 connects an interior of the channel bulge 53b to the oxygen-containing gas discharge channel 34b.

[0038] The first metal separator 30 and the second metal separator 32 of the connected separator 33 are joined together by welding along laser welding lines 33a to 33e. The laser welding line 33a surrounds the oxygen-containing gas supply channel 34a and the bridge 80. The laser welding line 33b surrounds the fuel gas discharge channel 38b and a bridge 92 described later. The laser welding line 33c surrounds the fuel gas supply channel 38a and a bridge 90 described later. The laser welding line 33d surrounds the oxygen-containing gas discharge channel 34b and the bridge 82. The laser welding line 33e is formed along the outer circumference of the connected separator 33 such that it surrounds the oxygen-containing gas flow field 48, the oxygen-containing gas supply channel 34a, the oxygen-containing gas discharge channel 34b, the fuel gas supply channel 38a, the fuel gas discharge channel 38b, the coolant supply channel 38a, and the coolant discharge channel 36b.

[0039] Channel bulge 53a and channel bulge 53b have the same structure. Furthermore, bridge 80 adjacent to oxygen-containing gas supply channel 34a and bridge 82 adjacent to oxygen-containing gas discharge channel 34b have the same structure. Additionally, water drainage channel 70 and water drainage channel 72 have the same structure. Therefore, as a representative example, only the configurations of channel bulge 53a, bridge 80, and water drainage channel 70 are described in detail below, while the detailed descriptions of the configurations of channel bulge 53b, bridge 82, and water drainage channel 72 are omitted.

[0040] As in Fig. As shown in Figure 5, the bridge 80 contains a plurality of inner bridges 80A arranged at intervals on the inside of the channel bead 53a, and a plurality of outer bridges 80B arranged at intervals on the outside of the channel bead 53a.

[0041] Each of the inner bridges 80A contains a through-hole 84a, which is arranged on one side of the apex of the channel bead 53a (side wall 53aw on the inside of the channel bead 53a), and an inner tunnel 86A, which is connected to the through-hole 84a. The inner tunnel 86A is formed by compression molding. The inner tunnel 86A projects from the side wall 53aw of the channel bead 53a to the oxygen-containing gas supply channel 34a. One end of the inner tunnel 86A, opposite the side connected to the channel bead 53a, opens to the oxygen-containing gas supply channel 34a.

[0042] Each of the outer bridges 80B contains a through-hole 84b located on the opposite side of the apex of the channel bulge 53a (side wall 53aw on the outside of the channel bulge 53a), as well as an outer tunnel 86B connected to the through-hole 84b. The outer tunnel 86B is formed by compression molding. The outer tunnel 86B projects from the side wall 53aw of the channel bulge 53a to the oxygen-containing gas flow field 48.

[0043] In the embodiment of the present invention, the majority of inner bridges 80A and the majority of outer bridges 80B are arranged in a staggered (zigzag) pattern along the channel bulge 53a. It should be noted that the majority of inner bridges 80A and the majority of outer bridges 80B can also be arranged opposite each other across the channel bulge 53a.

[0044] As in Fig. As shown in Figure 7, the first metal separator 30 has a recess 53c on the rear side of the ribbed channel bead 53a. The recess 53c forms an interior space 53d of the channel bead 53a. The through-holes 84a, 84b connect the interior space 53d of the channel bead 53a to the exterior. The recess 53c of the first metal separator 30 and the recess 63c of the second metal separator 32 on the rear side of the channel bead 63 face each other. Therefore, the interior space 53d of the channel bead 53a of the first metal separator 30 is connected to the interior space 63d of the channel bead 63 of the second metal separator 32.

[0045] Each of the inner tunnel 86A and the outer tunnel 86B has a rib shape that projects from the surface 30a of the first metal separator 30 towards MEA 28. The inner tunnel 86A and the outer tunnel 86B each contain tunnel channels 86a, 86b, which are connected to the interior 53d of the channel bulge 53a by the through-holes 84a, 84b. The inner tunnel 86A connects the oxygen-containing gas supply channel 34a to the interior 53d. The outer tunnel 86B connects the interior 53d to the oxygen-containing gas flow field 48 ( Fig. 4) The outer tunnel 86B has an opening 86c at one end opposite a section connected to the channel bulge 53a. The opening 86c allows the inner and outer sides of the outer tunnel 86B to communicate with each other.

[0046] As in Fig. As shown in Figure 5, a bottom 34a1 of the oxygen-containing gas supply channel 34a includes a recessed section 34a2 with a width in the horizontal direction (i.e., in the direction indicated by arrow B) perpendicular to the stacking direction (hereinafter referred to as the horizontal direction), wherein the horizontal width of the recessed section 34a2 decreases downwards. In the embodiment of the present invention, the recessed section 34a is V-shaped. Alternatively, the recessed section 34a2 can be arcuate. As in the case of the bottom 34a1 of the oxygen-containing gas supply channel 34a, each of the bottoms of the other fluid channels 34b, 36a, 36b, 38a, 38b includes a recessed section with a horizontal width (in the direction indicated by arrow B) that decreases downwards.

[0047] A lower section 53a1 (bottom section) of the channel bulge 53a in the direction of gravity contains a recessed section 53a2 with a horizontal width in the direction perpendicular to the stacking direction, the horizontal width of the recessed section 53a2 decreasing downwards. In the present embodiment, the recessed section 53a2 is V-shaped. Alternatively, the recessed section 53a2 can also be arc-shaped.

[0048] The water drainage channel 70 is arranged on the recessed section 53a2 of the channel bead 53a. In the embodiment of the present invention, the water drainage channel 70 includes a hole 94 formed in the side wall 53aw on the inside of the channel bead 53a, and a water drainage tunnel 96 connected to the hole 94. The water drainage tunnel 96 is formed by compression molding. The water drainage tunnel 96 projects in the same direction (stacking direction) as the channel bead 53a.

[0049] As in the Fig. 5 and Fig. As shown in Figure 6, the water drainage tunnel 96 projects upwards from the lower section 53a1 of the channel bulge 53a and connects the oxygen-containing gas supply channel 34a to the interior 53d of the channel bulge 53a. An upper end of the water drainage tunnel 96 opens to the oxygen-containing gas supply channel 34a. The upper end of the water drainage tunnel 96 is located at the lowest section 34a3 of the base 34a1 of the oxygen-containing gas supply channel 34a. A lower end of the water drainage tunnel 96 is connected to the lowest section 53a3 of the channel bulge 53a. Therefore, the water drainage tunnel 96 extends vertically. It should be noted that the water drainage tunnel 96 can also extend obliquely to the vertical direction.

[0050] As in Fig. As shown in Figure 5, the water drainage tunnel 70 is connected to bridge 80 through the interior 53d of the channel bulge 53a. Therefore, the opening 94 of the water drainage channel 70 is connected to the oxygenated gas flow field 48 through the interior 53d of the channel bulge 53a and the outer bridges 80B. Among the multiple outer bridges 80B, an outer bridge 80B1, located at the lowest position, is positioned closest to the water drainage channel 70. The outer bridge 80B1 at the lowest position is located below the lowest section of the oxygenated gas supply channel 34a and above the lowest section 53a3 of the channel bulge 53a.

[0051] The outer bridge 80B1 at the lowest position can be arranged at the same height as the lowest section 53a3 of the channel bulge 53a or below its lowest section 53a3. The outer bridge 80B1 can be inclined downwards with respect to the horizontal direction towards the oxygen-containing gas flow field 48.

[0052] As in Fig. As shown in Figure 2, the second metal separator 32 has a fuel gas flow field 58 on its surface 32a (hereinafter referred to as "surface 32a") facing the plastic film MEA 28. For example, the fuel gas flow field 58 extends in the direction indicated by arrow B. As shown in Fig. As shown in Figure 8, the fuel gas flow field 58 is fluidically connected to the fuel gas supply channel 38a and the fuel gas discharge channel 38b. The fuel gas flow field 58 contains straight flow grooves 58b between a plurality of ribs 58a, which extend in the direction indicated by arrow B. Instead of the plurality of straight flow grooves 58b, a plurality of corrugated flow grooves can also be provided.

[0053] An inlet buffer 60A is arranged on the surface 32a of the second metal separator 32 between the fuel gas supply channel 38a and the fuel gas flow field 58. The inlet buffer 60A contains a plurality of hub rows, each containing a plurality of hubs 60a arranged in the direction indicated by arrow C. Furthermore, an outlet buffer 60B is arranged on the surface 32a of the second metal separator 32 between the fuel gas discharge channel 38b and the fuel gas flow field 58. The outlet buffer 60B contains a plurality of hub rows, each containing a plurality of hubs 60b.

[0054] On another surface 32b of the second metal separator 32, which is the back side of the fuel gas flow field 58, rows of hubs, each containing a plurality of hubs 69a arranged in the direction indicated by arrow C, are arranged between the rows of hubs of the inlet buffer 60A, and other rows of hubs, each containing a plurality of hubs 69b arranged in the direction indicated by arrow C, are arranged between the rows of hubs of the outlet buffer 60B. The hubs 69a, 69b form buffers on the coolant surface.

[0055] A second sealing line 61 is formed on the surface 32a of the second metal separator 32 by compression molding. The second sealing line 61 projects towards the plastic film MEA 28. As in Fig. As shown in Figure 3, plastic material 56 is attached to the projecting front surfaces of the second sealing line 69 by printing, coating, etc. For example, polyester fiber is used as the plastic material 56. The plastic material 56 can be arranged on the plastic film 46. The plastic material 56 is not essential and can also be omitted.

[0056] As in Fig. As shown in Figure 8, the second sealing line 61 includes a bead seal 61a (hereinafter referred to as the "inner bead 61a") surrounding the fuel gas flow field 58, the inlet buffer 60A, and the outlet buffer 60B; a bead seal 62 (hereinafter referred to as the "outer bead 62") located outside the inner bead 61a along the outer circumference of the second metal separator 32; and a plurality of bead seals 63 (hereinafter referred to as "channel beads 63"), each surrounding the plurality of fluid channels (fluid channel 38a, etc.). The outer bead 62 projects from the surface 32a of the second metal separator 32 and extends around the outer circumferential edge of its surface 32a.

[0057] The multiple channel ridges 63 project from the surface 32a of the second metal separator 32. The channel ridges 63 each surround the oxygen-containing gas supply channel 34a, the oxygen-containing gas discharge channel 34b, the fuel gas supply channel 38a, the fuel gas discharge channel 38b, the coolant supply channel 36a and the coolant discharge channel 36b.

[0058] The second metal separator 32 has bridges 90, 92, which connect the inside (the side of the fluid channels 38a, 38b) with the outside (the side of the fuel gas flow field 58) of the channel bulges 63a, 63b, which each surround the fuel gas supply channel 38a and the fuel gas discharge channel 38b.

[0059] As described above, the channel bulge 63a surrounds the fuel gas supply channel 38a, and the bridge 90 is arranged on a side section of the channel bulge 63a that is closer to the fuel gas flow field 58. A water drainage channel 98 is arranged on a lower section 63a1 (bottom section) of the channel bulge 63a in the direction of gravity. The water drainage channel 98 connects the interior 63d of the channel bulge 63a to the fuel gas supply channel 38a.

[0060] As described above, the channel bulge 63b surrounds the fuel gas discharge channel 38b, and the bridge 92 is arranged on a side section of the channel bulge 63b that is closer to the fuel gas flow field 58. The bridge 92 includes outer and inner bridges arranged at intervals. A water drainage channel 100 is arranged on a lower section 63b1 (bottom section) of the channel bulge 63b in the direction of gravity. The water drainage channel 100 connects an interior space of the channel bulge 63b to the fuel gas discharge channel 38b.

[0061] These bridges 90, 92 of the second metal separator 32 have the same structure as the bridges 80, 82 above ( Fig. 4) of the first metal separator 30. The channel ridges 63a, 63b have the same structure and layout as the channel ridges 53a, 53b described above ( Fig. 4) Water drainage channels 98 and 100 have the same structure and layout as water drainage channels 70 and 72 described above ( Fig. 4).

[0062] As in Fig. As shown in Figure 2, a coolant flow field 66 is formed between the surface 30b of the first metal separator 30 and the surface 32b of the second metal separator 32, which are connected to each other. The coolant flow field 66 is connected (fluidically) to the coolant supply channel 36a and the coolant discharge channel 36b. The coolant flow field 66 is formed by stacking a back side of the first metal separator 30, which is provided with the oxygen-containing gas flow field 48, onto a back side of the second metal separator 32, which is provided with the fuel gas flow field 58. The first metal separator 30 and the second metal separator 32 are connected to each other by welding their outer circumferences and areas around the fluid channels. The first metal separator 30 and the second metal separator 32 can also be joined to each other by brazing instead of welding.

[0063] The operation of the fuel cell stack 10 with the above structure is described below.

[0064] First, as in Fig. Figure 1 shows an oxygen-containing gas, such as air, being supplied to the oxygen-containing gas supply channel 34a of the end plate 20a. A fuel gas, such as hydrogen-containing gas, is supplied to the fuel gas supply channel 38a of the end plate 20a. A coolant, such as pure water, ethylene glycol, or oil, is supplied to the coolant supply channel 36a of the end plate 20a.

[0065] As in Fig. As shown in Figure 2, the oxygen-containing gas flows from the oxygen-containing gas supply channel 34a through the bridge 80 into the oxygen-containing gas flow field 48 of the first metal separator 30 (see Figure 2). Fig. 4) Here, as in Fig. Figure 7 shows that the oxygen-containing gas first flows from the oxygen-containing gas supply channel 34a to the surface 30b of the first metal separator 30 (between the first metal separator 30 and the second metal separator 32), and then the oxygen-containing gas flows into the inner tunnel 86A (tunnel channel 86a), into the channel bulge 53a (interior 53d), and into the outer tunnel 86B (tunnel channel 86b). Afterward, the oxygen-containing gas flows out of the opening 86c to the surface 30a of the first metal separator 30. As shown in Fig. As shown in Figure 2, the oxygen-containing gas flows along the oxygen-containing gas flow field 48 in the direction indicated by arrow B, and the oxygen-containing gas is supplied to the cathode 44 of the membrane electrode arrangement 28a.

[0066] Meanwhile, the fuel gas flows from the fuel gas supply channel 38a through the bridge 90 into the fuel gas flow field 58 of the second metal separator 32 ( Fig. 8) The fuel gas flows along the fuel gas flow field 58 in the direction indicated by arrow B, and the fuel gas is supplied to the anode 42 of the membrane electrode arrangement 28a.

[0067] Thus, in each of the membrane electrode arrangements 28a, the oxygen-containing gas supplied to the cathode 44 and the fuel gas supplied to the anode 42 are consumed in the electrochemical reactions of the first electrode catalyst layer 44a and the second electrode catalyst layer 42a in order to generate electricity.

[0068] After the oxygen-containing gas supplied to the cathode 44 has been consumed at the cathode 44, the oxygen-containing gas flows from the oxygen-containing gas flow field 48 through the bridge 82 to the oxygen-containing gas discharge channel 34b, and then the oxygen-containing gas is discharged along the oxygen-containing gas discharge channel 34 in the direction indicated by arrow B. Similarly, after the fuel gas supplied to the anode 42 has been consumed at the anode 42, the fuel gas flows from the fuel gas flow field 58 through the bridge 92 ( Fig. 8) to the fuel gas discharge channel 38b, and then the fuel gas is discharged along the fuel gas discharge channel 38b in the direction indicated by arrow A.

[0069] Furthermore, the coolant supplied to the coolant supply channel 36a flows into the coolant flow field 66, which is formed between the first metal separator 30 and the second metal separator 32, and then flows in the direction indicated by arrow B. After the coolant has cooled the membrane electrode assembly 28a, the coolant is discharged by the coolant discharge channel 36b.

[0070] In this case, the power generation cell 12 of the present embodiment of the invention offers the following advantageous effects.

[0071] In power generation cell 12, the water drainage channels 70, 72, 98, 100 are arranged at the lower sections (bottom sections) of the channel bulges 53a, 53b, 63a, 63b, which surround the reaction gas channels (the oxygen-containing gas supply channel 34a, the oxygen-containing gas discharge channel 34b, the fuel gas supply channel 38a and the fuel gas discharge channel 38b). The water drainage channels 70, 72, 98, 100 are connected to the interiors of the channel bulges 53a, 53b, 63a, 63b. After the generated water W has flowed to the lower sections of the channel bulges 53a, 53b, 63a, 63b in the structure, the generated water W flows into the interiors of the channel bulges 53a, 53b, 63a, 63b through the water drainage channels 70, 72, 98, 100, and then the generated water W is discharged by the reaction gas channels.

[0072] As a representative example, the following is described in Fig. The water drainage channel 70 shown in Figure 5 is described. The generated water W flows from the oxygen-containing gas supply channel 34a into the interior 53d of the channel bulge 53a through the water drainage channel 70 and flows within the interior 53d. The generated water W is then discharged through the outer bridge 80B1 at the lowest position to the oxygen-containing gas flow field 48. Therefore, it is possible to prevent the generated water W from accumulating at the bottom of the reaction gas channel. Furthermore, it is possible to prevent disturbances in the flow distribution of the reaction gas.

[0073] If, contrary to the present invention, the water drainage channels 70, 72, 98, 100 are not provided, as for example in Fig. As indicated by a dashed line in Figure 5, the generated water W tends to remain in the reaction gas channel. If the generated water W remains stagnant, rust or a liquid bridge could form. Furthermore, if a large amount of the generated water is retained in the reaction gas channel, the flow distribution of the reaction gas could be disrupted. According to the invention, it is possible to solve this problem.

[0074] Bridges 80 and 82 are formed on the first metal separator 30. Bridges 80 and 82 connect the inner surface of channel bulges 53a and 53b to their outer surface. Water drainage channels 70 and 72 are connected to bridges 80 and 82 through the interiors of channel bulges 53a and 53b. Bridges 90 and 92 are formed on the second metal separator 32. Bridges 90 and 92 connect the inner surface of channel bulges 63a and 63b to their outer surface. Water drainage channels 98 and 100 are connected to bridges 90 and 92 through the interiors of channel bulges 63a and 63b. In this structure, the generated water W, which is carried from the reaction gas channels into the interiors of the channel ridges 53a, 53b, 63a, 63b, is discharged into the reaction gas flow field via the bridges 80, 82, 90, 92. This allows for improved discharge of the generated water W from the reaction gas channels.

[0075] The lower sections 53a1, 53b1, 63a1, 63b1 of the channel ridges 53a, 53b, 63a, 63b have recessed shapes (recessed section 53a2, etc.) with a horizontal width perpendicular to the stacking direction, the horizontal width gradually decreasing downwards. The water drainage channels 70, 72, 98, 100 are located at the lowest section of the recessed sections. Since the generated water W is effectively directed to the water drainage channels 70, 72, 98, 100 within the structure, the discharge of the generated water W is significantly improved.

[0076] Although the structure containing the water drainage channels 70, 72, 98, 100 with the water drainage tunnel 96 has been described above, the present invention is not limited thereto. As in the Fig. 9 and Fig. As shown in Figure 10, water drainage channels 102, 104, which do not have water drainage tunnels, can be provided at the first metal separator 30, and as shown in Fig. As shown in Figure 11, water drainage channels 106, 108, which do not have a water drainage tunnel, can be provided at the second metal separator 32.

[0077] As in the Fig. 9 and Fig. As shown in Figure 10, the water drainage channel 102 adjacent to the oxygen-containing gas supply channel 34a is formed by a hole 94 located on the lower section 53a1 of the channel bead 52a, and the water drainage channel 104 adjacent to the oxygen-containing gas discharge channel 34b is formed by a hole 94 located on the lower section 53b1 of the channel bead 53b.

[0078] In Fig. 11 the water drainage channel 106 adjacent to the fuel gas supply channel 38a is formed by a hole 94 which is arranged on the lower section 63a1 of the channel bead 62a, and the water drainage channel 108 of the fuel gas discharge channel 38b is formed by a hole 94 which is arranged on the lower section 63b1 of the channel bead 63b.

[0079] A first metal separator (30) of a power generation cell (12) comprises an oxygen-containing gas flow field (48) extending along an electrode surface of a membrane electrode assembly (28a), an oxygen-containing gas supply channel (34a) connected to the oxygen-containing gas flow field (48) and extending through the first metal separator (30) in a separator thickness direction, and a channel bead (53) surrounding the oxygen-containing gas supply channel (34a) and projecting in the separator thickness direction. A water drainage channel (70) for connecting an interior (53d) of the channel bead (53) to the oxygen-containing gas supply channel (34a) is arranged at a lower section of the channel bead (53).

Claims

[1] Power generation cell (12) which includes: a plate-shaped membrane electrode arrangement (28a); and metal separators (30, 32) arranged on one surface and another surface of the membrane electrode arrangement (28a), wherein the membrane electrode arrangement (28a) and the metal separators (30, 32) are stacked together in a horizontal direction, each of the metal separators (30, 32) has: a reaction gas flow field (48, 58) configured to allow a reaction gas to flow along an electrode surface of the membrane electrode arrangement (28a); characterized by , that each of the metal separators (30, 32) further exhibits: a reaction gas channel (34a, 34b, 38a, 38b) which is connected to the reaction gas flow field (48, 58), is positioned in the horizontal direction outside the reaction gas flow field (48, 58), and passes through the metal separator (30, 32) in a separator thickness direction; a channel bead (53, 63) for sealing, which surrounds the reaction gas channel (34a, 34b, 38a, 38b) and projects in the separator thickness direction; a bridge (80, 82, 90, 92) configured to connect an inside of the channel bulge (53, 63) to its outside; wherein a lower section of the channel rim (53, 63) contains a recessed section, and the width of the recessed section decreases downwards in the horizontal direction perpendicular to the direction in which the membrane electrode arrangement (28a) and the metal separators (30, 32) are stacked together; and wherein a water drainage channel (70, 72, 98, 100) is arranged separately from the bridge (80, 82, 90, 92) at a lowest section of the recessed section of the channel bulge (53, 63), which is configured to connect an interior of the channel bulge (53, 63) with the reaction gas channel (34a, 34b, 38a, 38b). [2] The power generation cell (12) according to claim 1, wherein the water drainage channel (70, 72, 98, 100) is connected to the bridge (80, 82, 90, 92) through the interior of the channel bulge (53, 63). [3] The power generation cell (12) according to claim 1 or 2, wherein the water drainage channel (70, 72, 98, 100) includes a hole (94) opening on a side wall of the channel bulge (53, 63) and a water drainage tunnel (96) connected to the hole (94) and projecting upwards towards the reaction gas channel (34a, 34b, 38a, 38b). [4] The power generation cell (12) according to claim 3, wherein the water drainage tunnel (96) extends in a vertical direction. [5] The power generation cell (12) according to claim 3 or 4, wherein a lower section of the reaction gas channel (34a, 34b, 38a, 38b) includes a recessed section, and the width of the recessed section decreases downwards in a horizontal direction perpendicular to a direction in which the membrane electrode arrangement (28a) and the metal separators (30, 32) are stacked together; and an upper end of the water drainage tunnel (96) is arranged at a lowest section of the recessed section of the reaction gas channel (34a, 34b, 38a, 38b). [6] The power generation cell (12) according to claim 2, wherein the bridge (80, 82, 90, 92) comprises a plurality of outer bridges in the form of tunnels, the outer bridges projecting from an outside of the channel bulge (53, 63); and of the multiple outer bridges, one outer bridge located at a lowest position is arranged in a position closest to the water drainage channel (70, 72, 98, 100). [7] The power generation cell (12) according to claim 2, wherein the bridge (80, 82, 90, 92) comprises a plurality of outer bridges in the form of tunnels, the outer bridges projecting from an outside of the channel bulge (53, 63); and of the multiple outer bridges, one outer bridge provided at a lowest position is arranged under a lowest section of the reaction gas channel (34a, 34b, 38a, 38b). [8] The power generation cell (12) according to claim 7, wherein of the several outer bridges the outer bridge provided at the lowest position is arranged over a lowest section of the channel bulge (53, 63). [9] The power generation cell (12) according to claim 7, wherein the channel bulge (53, 63) includes a section inclined with respect to the horizontal direction; and of the several outer bridges, the outer bridge provided at the lowest position is connected to the inclined section. [10] The power generation cell (12) according to claim 7, wherein of the several outer bridges the outer bridge provided at the lowest position is arranged closer to the reaction gas flow field (48, 58) than the water drainage channel (70, 72, 98, 100).

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