Fuel cell stack

Abstract

This invention provides a fuel cell stack. A flow path is formed between a first plate portion and a second plate portion constituting the fuel cell stack. The flow path includes a power generation region flow path, a supply flow path, a bypass flow path, and a connecting flow path. The power generation region flow path supplies cooling medium that flows along the power generation region of the plate. The supply flow path guides cooling medium supplied through a supply hole penetrating the plate into the power generation region flow path. The bypass flow path guides air bubbles contained in the cooling medium supplied through the supply hole downstream of the power generation region flow path. The connecting flow path connects the supply flow path and the bypass flow path. Downstream of the connection point for the connecting flow path, the supply flow path has a first throttling section and a second throttling section, the first throttling section being configured to have a greater flow resistance than the second throttling section. This allows for a substantial reduction in the amount of air bubbles supplied to the power generation section.

Description

Technical Field

[0001] This invention relates to a fuel cell stack. Background Technology

[0002] In recent years, research and development on fuel cells that help improve energy efficiency have been underway to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. As a technology related to such fuel cells, one known prior art involves discharging air bubbles that flow into a connecting hole for supplying a cooling medium via a bypass flow path that bypasses the power generation unit (for example, see Patent Document 1). In the fuel cell stack described in Patent Document 1, the upper end of the connecting hole for supplying the cooling medium is connected to the bypass flow path via a air bubble discharge flow path.

[0003] Existing technical documents Patent documents

[0004] Patent Document 1: Japanese Patent Publication No. 7297805 Summary of the Invention

[0005] The technical problem that the invention aims to solve

[0006] However, as described in Patent Document 1 above, it is difficult to sufficiently reduce the amount of bubbles supplied to the power generation unit by simply providing a bypass flow path that bypasses the power generation unit.

[0007] Technical solutions for solving technical problems

[0008] As one aspect of the present invention, a fuel cell stack is constructed by alternately stacking membrane electrode structures and separators in a predetermined direction. The membrane electrode structure has a membrane electrode assembly and a frame member, wherein the membrane electrode assembly has an electrolyte membrane and an electrode; the frame member supports the periphery of the membrane electrode assembly; the separator has a first plate portion and a second plate portion, wherein the first plate portion is concave-convex and convex, facing a first surface of the membrane electrode structure, and forming a first gas flow path for a first gas to flow between it and the membrane electrode structure; the second plate portion is concave-convex and convex, facing a second surface of the membrane electrode structure, and forming a second gas flow path for a second gas to flow between it and the membrane electrode structure. The first and second plates have flow path forming sections that form a flow path for cooling medium to flow between them. The flow path includes a power generation region flow path, a supply flow path, a bypass flow path, and a connecting flow path. The power generation region flow path allows the cooling medium to flow along the power generation region of a partition facing the membrane electrode assembly. The supply flow path guides the cooling medium supplied through a supply hole in the partition to the power generation region flow path. The bypass flow path guides air bubbles contained in the cooling medium supplied through the supply hole to bypass the power generation region flow path and guide them downstream. The connecting flow path connects the supply flow path and the bypass flow path. Downstream of the connection point for the connecting flow path, the supply flow path has multiple throttling sections that shorten the height of the gap between the first and second plates. Each throttling section has a first throttling section and a second throttling section located downstream of the first throttling section. The first throttling section is configured to have a greater flow path resistance than the second throttling section.

[0009] Invention Effects

[0010] According to the present invention, the amount of bubbles supplied to the power generation unit can be significantly reduced. Attached Figure Description

[0011] Figure 1 This is a perspective view that schematically represents the overall structure of the fuel cell stack according to an embodiment of the present invention.

[0012] Figure 2 yes Figure 1 Sectional view II-II in the middle.

[0013] Figure 3 It means Figure 1 A three-dimensional diagram showing the schematic structure of the integrated electrode assembly included in the fuel cell stack.

[0014] Figure 4 yes Figure 1 The front view of the diaphragms contained in the fuel cell stack.

[0015] Figure 5 It is Figure 4 The figure shows a pair of overlapping guide sections at the ends of the partition.

[0016] Figure 6 yes Figure 4 Sectional view VI-VI in the middle.

[0017] Figure 7 yes Figure 4 An enlarged view of part VII.

[0018] Figure 8 yes Figure 7 Sectional view VIII-VIII in the middle. Detailed Implementation

[0019] Below, refer to Figures 1 to 8 Embodiments of the present invention will be described. The fuel cell stack involved in the embodiments of the present invention is one of the main components of a fuel cell. The fuel cell, for example, is mounted in a vehicle and can generate electricity to drive the vehicle. First, the overall structure of the fuel cell stack will be described in general terms.

[0020] Figure 1 This is a perspective view that schematically represents the overall structure of the fuel cell stack 100 according to this embodiment. For convenience, as shown in the figure, the three orthogonal axes are defined as the front-back direction, the left-right direction, and the up-down direction, and the structure of each part will be described according to this definition. The down direction in the up-down direction corresponds to or approximately corresponds to the direction of gravity. The front-back direction corresponds to the stacking direction of the fuel cell stack 100. The front-back and left-right directions are not limited to being the same as the front-back and left-right directions of a vehicle.

[0021] like Figure 1 As shown, the fuel cell stack 100 is generally rectangular in shape, having a unit stack 101 and end units 102. The unit stack 101 is constructed by stacking multiple power generation units 1 in the front-to-back direction; the end units 102 are disposed at both ends of the unit stack 101 in the front-to-back direction. Although not shown in the figure, the unit stack 101 is surrounded by a shell of approximately rectangular shape. The length of the unit stack 101 in the left-to-right direction is longer than its length in the top-to-bottom direction. Figure 1 For convenience, only a single power generation unit 1 is shown in the image.

[0022] The power generation unit 1 includes: a unified electrode assembly (hereinafter referred to as UEA) 2, which has a junction including an electrolyte membrane and electrodes; and separators 3, 3, which are disposed on both sides of UEA 2 in the front-rear direction and clamp UEA 2. UEA 2 and separators 3 are alternately arranged in the front-rear direction. UEA 2 can also be referred to as a membrane electrode structure or membrane electrode component.

[0023] Figure 2This is a cross-sectional view of an important part of the power generation area in the center of the left-right direction of the unit stack 101. Figure 1 (See section II-II in the diagram). Figure 2 As shown, the partition 3 has a front plate 3F and a rear plate 3R, which are a pair of thin metal plates with a corrugated cross-section. The front plate 3F extends in the vertical and horizontal directions and has a front surface 3Fa and a rear surface 3Fb. The rear plate 3R extends in the vertical and horizontal directions and has a front surface 3Ra and a rear surface 3Rb. The outer periphery of the rear surface 3Fb of the front plate 3F and the front surface 3Ra of the rear plate 3R are joined together by welding or the like. Accordingly, the front plate 3F and the rear plate 3R are integrally joined. The partition 3 uses a conductive material with excellent corrosion resistance, such as stainless steel, titanium, or titanium alloy.

[0024] Inside the partition 3 formed by the front plate 3F and the rear plate 3R, specifically between the rear surface 3Fb of the front plate 3F and the front surface 3Ra of the rear plate 3R, a cooling flow path PAw for the flow of cooling medium is formed. Through the flow of the cooling medium, the power generation surface of the power generation unit 1 is cooled. Water can be used as the cooling medium, for example. The surfaces of the partition 3 facing UEA2 (front surface 3Fa and rear surface 3Rb) are formed into an uneven shape by stamping or the like to form a gas flow path between them and UEA2. More specifically, the partition 3 has a pair of front and rear protrusions 31 protruding towards UEA2, and a pair of front and rear recesses 32 connected to the pair of front and rear protrusions 31 and formed into a concave shape.

[0025] A pair of protrusions 31 abut against the rear surface 2b and the front surface 2a of UEA2, respectively. During the assembly of the fuel cell stack 100, a compressive load F in the front-rear direction is applied to the unit stack 101, and this compressive load F is maintained after the fuel cell stack 100 is assembled. Therefore, a predetermined surface pressure generated by the compressive load F acts on UEA2 in the front-rear direction via the protrusions 31.

[0026] An anode flow path PAa for fuel gas flow is formed through a recess 32 between the front surface 2a of UEA2 and the rear plate 3R of the partition 3 facing the front surface 2a. A cathode flow path PAc for oxidant gas flow is formed through a recess 32 between the rear surface 2b of UEA2 and the front plate 3F of the partition 3 facing the rear surface 2b. The fuel gas is a hydrogen-containing gas; for example, hydrogen gas can be used. The oxidant gas is an oxygen-containing gas; for example, air can be used. Sometimes, fuel gas and oxidant gas are not distinguished and are referred to as reactant gases.

[0027] Figure 3 This is a three-dimensional diagram representing the approximate structure of UEA2. For example... Figure 3As shown, UEA2 has a generally rectangular membrane electrode assembly (MEA) 20 and a frame 21 for supporting MEA20. MEA20 has an electrolyte membrane, an anode electrode disposed on the front surface of the electrolyte membrane, and a cathode electrode disposed on the rear surface of the electrolyte membrane.

[0028] The electrolyte membrane can be, for example, a solid polymer electrolyte membrane, such as a perfluorosulfonic acid polymer film containing water. It is not limited to fluorine-based electrolyte membranes; hydrocarbon-based electrolyte membranes can also be used. The anode electrode has an electrode catalyst layer and a gas diffusion layer, wherein the electrode catalyst layer is formed on the front surface of the electrolyte membrane, serving as the reaction field for the electrode reaction; the gas diffusion layer is disposed on the front surface of the electrode catalyst layer, diffusing and supplying fuel gas. The cathode electrode has: an electrode catalyst layer formed on the rear surface of the electrolyte membrane, serving as the reaction field for the electrode reaction; and a gas diffusion layer disposed on the rear surface of the electrode catalyst layer, diffusing and supplying oxidant gas.

[0029] In the anode electrode, via Figure 2 The fuel gas (hydrogen) supplied by the anolyte PAa is ionized by the catalyst and moves across the electrolyte membrane to the cathode electrode side. The electrons generated at this time flow through the external circuit and are extracted as electrical energy. In the cathode electrode, via… Figure 2 The oxidant gas (oxygen) supplied to the cathode flow path PAc reacts with hydrogen ions introduced from the anode electrode and electrons moving from the anode electrode to produce water. The produced water (called generated water) provides appropriate humidity to the electrolyte membrane, and excess water is discharged to the outside of UEA2 with the gas flow.

[0030] like Figure 3 As shown, the frame 21 is a roughly rectangular frame component made of insulating resin, rubber, or the like. A roughly rectangular opening 21a is provided in the center of the frame 21. The MEA 20 is positioned to cover the entire opening 21a, and its periphery is supported by the frame 21.

[0031] On the left side of the opening 21a of the frame 21, three through holes 211-213 are arranged vertically, and these three through holes 211-213 penetrate the frame 21 in the front-to-back direction. On the right side of the opening 21a, three through holes 214-216 are arranged vertically, and these three through holes 214-216 penetrate the frame 21 in the front-to-back direction. For convenience, the through holes 211-216 are shown as approximately rectangular in shape, but the shape and arrangement of the through holes 211-216 are not limited to this.

[0032] like Figure 1As shown, on the partition plates 3 before and after UEA2, through holes 301 to 306 are respectively provided at positions corresponding to the through holes 211 to 216 of the frame 21, penetrating the partition plates 3 in the front-back direction. Through holes 301 to 306 are connected to the through holes 211 to 216 of the frame 21. Through these interconnected through holes 211 to 216 and 301 to 306, flow paths PA1 to PA6 (indicated by arrows for convenience) are formed, penetrating the unit stack 101 and extending in the front-back direction. Flow paths PA1 to PA6 are sometimes also referred to as manifolds. Flow paths PA1 to PA6 are connected to manifolds outside the fuel cell stack 100.

[0033] Although the illustration is omitted, the end units 102 at the front and rear of the unit stack 101 each have multiple plates arranged overlapping in the front-rear direction. That is, the end unit 102 has a terminal plate, an insulating plate, and an end plate, wherein the terminal plate is arranged adjacent to the unit stack 101; the insulating plate is arranged outside the terminal plate in the front-rear direction; and the end plate is arranged outside the insulating plate in the front-rear direction.

[0034] On the rear end unit 102, at positions corresponding to the through holes 211-216 and 301-306 of the unit stack 101, a plurality of through holes 102a-102f are provided, extending through the end unit 102 in the front-rear direction. For convenience, the through holes 102a-102f are shown as approximately rectangular in shape, but the position and shape of the through holes 102a-102f are not limited to this.

[0035] Through-hole 102a is the fuel gas supply port, through which fuel gas is supplied to the fuel cell stack 100. The fuel gas is introduced into the anode flow path PAa between UEA2 and the rear plate 3R of the separator 3 via through-holes 211 and 301. After flowing through the anode flow path PAa, the fuel gas flows backward through through-holes 216 and 306 and is discharged from through-hole 102f.

[0036] Through-hole 102d is the oxidant gas supply port, through which oxidant gas is supplied to the fuel cell stack 100. This oxidant gas is introduced into the cathode flow path PAc between UEA2 and the front plate 3F of the separator 3 via through-holes 214 and 304. After flowing through the cathode flow path PAc, the oxidant gas flows rearward through through-holes 213 and 303 and is discharged from through-hole 102c.

[0037] Through-hole 102e is the supply port for the cooling medium, through which the cooling medium is supplied to the fuel cell stack 100. This cooling medium is introduced through through-holes 215 and 305 into the cooling flow path PAw between the front plate 3F and the rear plate 3R of the partition 3. After flowing through the cooling flow path PAw, the cooling medium flows rearward through through-holes 212 and 302 and is discharged from through-hole 102b. The above is a schematic structure of the fuel cell stack 100.

[0038] The structure of partition 3 will be described in more detail. Figure 4 This is the front view of partition 3 (viewed from the front), relative to... Figure 1 Reverse the left and right directions. That is, Figure 4 This refers to the front surface 3Fa of the partition 3 facing the cathode electrode of the rear surface 2b of UEA2. Figure 2 (The image is in...) Figure 4 In the middle, the shape and arrangement of through holes 301 to 306 are relative to Figure 1 Slight modifications have been made. Specifically, the through holes 302 and 305 for the cooling medium are positioned laterally than the through holes 301 and 306 for the fuel gas and 303 and 304 for the oxidizer gas. A positioning part (e.g., a locking recess) for positioning the partition 3 is provided at its periphery, but... Figure 4 Its illustration is omitted. Figure 4 The left-right and up-down directions in the middle correspond to the long side and short side directions of partition 3, respectively.

[0039] exist Figure 4 In the diagram, the area in the center of the left-right direction, facing MEA20 of UEA2, i.e., the double-dotted area AR1 facing the power generation surface, is called the active area of ​​partition 3. The area AR2 outside the active area AR1 in the left-right direction is called the inactive area. The inactive area AR2 of partition 3 faces the frame 21 of UEA2. The active area AR1 is equivalent to the power generation area where power generation takes place.

[0040] like Figure 2 , Figure 4 As shown, in the active region AR1 of the partition 3, although a portion is omitted from the diagram, multiple protrusions 31 are provided at equal intervals along the vertical direction, protruding forward over approximately the entire region. These protrusions 31 extend horizontally, and recesses 32 are provided between adjacent protrusions 31 in the vertical direction. A cathode flow path PAc is formed between the multiple recesses 32 and the rear surface of the MEA20. Figure 4 As indicated by arrow Ca, in the cathode flow path PAc, the oxidant gas flows from right to left.

[0041] like Figure 4As shown, on the front surface 3Fa of the partition 3 (front panel 3F), multiple ribs protruding forward toward the frame 21 are provided for sealing, i.e., metal bead seals. The multiple ribs include outer ribs 331 and multiple individual ribs 332. The forward protrusion of the multiple ribs is the same for each other. The multiple ribs extend with a specified width. For convenience, in... Figure 4 The raised ribs are indicated by thick lines. Although the illustration is omitted, the rear panel 3R, like the front panel 3F, also has multiple raised ribs.

[0042] Multiple independent ribs 332 extend along the periphery of multiple through holes 301 to 306, and independently surround each of the multiple through holes 301 to 306. The outer ribs 331 extend in the left and right directions above and below the active area AR1, along the upper and lower edges of the partition 3, and extend outward in the left and right directions through the independent ribs 332 around the through holes 301, 303, 304, and 306 and inward in the left and right directions through the independent ribs 332 around the through holes 302 and 305.

[0043] In the inactive area AR2 of the partition 3 (front plate 3F), a plurality of guide portions 333 are provided protruding from the front frame 21 in the vertical direction from the through hole 304 to the right end inlet of the cathode flow path PAc, and in the vertical direction from the left end outlet of the cathode flow path PAc to the through hole 303. The plurality of guide portions 333 extend at equal intervals and are substantially parallel to each other.

[0044] Between the through hole 304 and the guide portion 333, and between the through hole 303 and the guide portion 333, multiple channel portions 41 are provided protruding forward, each passing through an independent rib portion 332. The forward protrusion of the channel portions 41 is less than the forward protrusion of the independent rib portions 332. Although not shown in the figure, the rear plate 3R also has channel portions 41 provided in a symmetrical manner with the front plate 3F in the front-rear direction.

[0045] One end of the channel portion 41 communicates with through holes 303 and 304. The other end of the channel portion 41 communicates with the space in front of the partition 3 (front plate 3F) (the space between the partition 3 and the frame 21 on its front side). In the inactive region AR2 on the right, a cathode supply flow path PA11 is formed between adjacent guide portions 333 and 333 in the vertical direction. In the inactive region AR2 on the left, a cathode discharge flow path PA12 is formed between adjacent guide portions 333 and 333 in the vertical direction. Accordingly, through holes 304 and cathode supply flow path PA11, and through holes 303 and cathode discharge flow path PA12 are respectively connected via the channel portion 41.

[0046] On the partition 3, there are also channel portions 42 extending from through holes 301 and 306, and channel portions 43 extending from through holes 302 and 305. One end of the channel portion 42 communicates with through holes 301 and 306, and the other end communicates with the space behind the partition 3 (rear plate 3R). One end of the channel portion 43 communicates with through holes 302 and 305, and the other end communicates with the space between the front plate 3F and the rear plate 3R (see reference). Figure 6 ).

[0047] The oxidant gas supplied through the through-hole 304 flows through the channel 41 to the cathode supply flow path PA11 on the inlet side of the guide 333. Then, the oxidant gas flows to the left or slightly downward along the guide 333 and is guided to the cathode flow path PAc. The oxidant gas flowing through the cathode flow path PAc flows to the cathode discharge flow path PA12 on the inlet side of the guide 333. Then, the oxidant gas flows to the left or slightly downward along the guide 333, flows through the channel 41, and flows into the through-hole 303.

[0048] By providing the guide portion 333, the oxidant gas can be uniformly guided to the entire vertical region of the cathode flow path PAc. Alternatively, the guide portion 333 can be replaced, or multiple protruding, approximately cylindrical protrusions can be provided on the basis of the guide portion 333. The metal flange seal (outer rib portion 331, independent rib portion 332), the guide portion 333, and the channel portions 41 to 43 are formed by stamping the front plate 3F.

[0049] Although the illustration is omitted, the rear surface 3Rb of the partition plate 3 (rear plate 3R) is also formed by stamping the rear plate 3R, resulting in multiple protrusions 31 and recesses 32, metal rib seals (outer rib portion 331, independent rib portion 332), guide portions 333, and channels 41-43. Accordingly, fuel gas is guided from the through hole 301 through the channel portions 42 and the guide portions 333 to the anode flow path PAa. The fuel gas flowing through the anode flow path PAa is discharged from the through hole 306 through the guide portions 333 and the channel portions 42.

[0050] Figure 5 This diagram shows the guide portion 333 (solid line) of the front plate 3F and the guide portion 333 (dashed line) of the rear plate 3R overlapping on the right side of the partition 3 (left side in the diagram). Figure 5 In the diagram, the solid arrow Ca represents the flow direction of the oxidant gas in the cathode flow path PAc, and the dashed arrow An represents the flow direction of the fuel gas in the anode flow path PAa.

[0051] like Figure 5As shown, in the inactive region AR2 of the partition 3 (rear plate 3R), a plurality of guide portions 333 are provided protruding from the rear frame 21 in the entire area from the right end outlet of the anode flow path PAa to the through hole 306. The plurality of guide portions 333 extend at equal intervals and are substantially parallel to each other. Therefore, the guide portions 333 of the rear plate 3R (dashed lines) and the guide portions 333 of the front plate 3F (solid lines) extend in an intersecting manner.

[0052] The flow of the cooling medium is described. Figure 6 yes Figure 4 The VI-VI sectional view shows the structure of the channel portion 43 connected to the through hole 305. Figure 6 The frame 21, positioned before and after the partition 3, is also shown in the diagram. Figure 6 As shown, the front end face of the independent rib portion 332 and the front end face of the outer rib portion 331, which protrude forward from the front plate 3F of the partition 3, respectively abut against the rear surface of the frame 21 through sealing material 334. The rear end face of the independent rib portion 332 and the rear end face of the outer rib portion 331, which protrude rearward from the rear plate 3R of the partition 3, respectively abut against the front surface of the frame 21 through sealing material 334.

[0053] The channel portion 43 extends to the right from the through hole 305, passing over the independent rib portion 332 and the outer rib portion 331. The channel portion 43 has a front channel portion 431 bulging forward from the front plate 3F and a rear channel portion 432 bulging rearward from the rear plate 3R. A cooling medium supply flow path PA13 is formed between the front channel portion 431 and the rear channel portion 432. Figure 6 As shown by the middle arrow, the cooling medium flows from right to left through the cooling medium supply path PA13.

[0054] The cooling medium supply path PA13 includes an inner space SP12 of the independent rib 332 and an inner space SP11 of the outer rib 331. The inner space SP12 extends along the independent rib 332 in the vertical and horizontal directions, and the inner space SP11 extends along the outer rib 331 in a generally vertical direction (see reference). Figure 5 Although the diagram is omitted, the cross-sectional shape of the channel section 43 perpendicular to the cooling medium supply flow path PA13 is shown. Figure 6 The cross-sectional shape of the channel portion 43 after removing the ribs 331 and 332 is approximately polygonal (e.g., approximately rectangular), approximately elliptical, or approximately oblong.

[0055] exist Figure 4 Multiple channel portions 43 are shown, but the structures of the multiple channel portions 43 are the same or substantially the same. For example... Figure 4As shown by the dashed arrow A1, the cooling medium that has flowed through multiple channel sections 43 flows past the back side (rear side) of the guide section 333 and then flows to the right, flowing into the cooling flow path PAw in the active region AR1. Figure 2 Furthermore, the cooling medium flows along the cooling path PAw ( Figure 2 After flowing to the right, as shown by the dashed arrow A2, it flows past the back side (rear side) of the guide section 333 and then flows to the right again, reaching the through hole 302 via the channel section 43.

[0056] Figure 7 yes Figure 4 An enlarged view of part VII. (See image below.) Figure 7 As shown, at the upper edge of the through hole 305 for supplying cooling medium, one end (lower end) of the upper channel portion 44 is connected. The upper channel portion 44 extends across the independent protruding rib portion 332 surrounding the through hole 305, and its other end (upper end) is connected to the outer protruding rib portion 331. Accordingly, the inner space SP11 between the through hole 305 and the outer protruding rib portion 331 ( Figure 6 Connect.

[0057] like Figure 4 As shown, an upper channel portion 45 is connected to the upper end of the through hole 302 for discharging the cooling medium. The upper channel portion 45 extends across the independent rib portion 332 surrounding the through hole 302, and its other end is connected to the outer rib portion 331. Accordingly, the inner space SP11 between the through hole 302 and the outer rib portion 331 ( Figure 6 Connect.

[0058] Additionally, after the fuel cell stack 100 is assembled, it is accessed via through-hole 102e ( Figure 1 Cooling medium is injected into the interior of the fuel cell stack 100. At this time, the air in the cooling flow path PAw moves upward and flows along the cooling flow path PAw and flow paths PA5 and PA2 together with the cooling medium. In addition, if air is mixed in with the cooling medium supplied through the through hole 102e, the air also flows along the cooling flow path PAw and flow paths PA5 and PA2 together with the cooling medium.

[0059] When the cooling medium supplied to the through-hole 305 contains air (bubbles), such as Figure 7 As indicated by arrow A3, bubble B1 moves upward and enters the inner space SP13 of the upper channel portion 44. Bubble B1 passes through the inner space SP13 and then, as indicated by arrow A4, enters the inner space SP11 of the outer rib portion 331. Figure 4As shown by arrows A5 and A6, the bubbles in the inner space SP11 pass through the inner space SP11 of the outer rib portion 331 above the active area AR1, and are then guided to the through hole 302 through the inner space of the upper channel portion 45, as shown by arrow A7, and discharged to the outside through the through hole 302.

[0060] Thus, the inner space SP13 of the upper channel portion 44, the inner space SP11 of the outer rib portion 331, and the inner space of the upper channel portion 45 constitute a bypass flow path PAb. This bypass flow path PAb bypasses the active region AR1 and reaches the through hole 302 from the through hole 305. Accordingly, bubbles in the through hole 305 will flow around the cooling flow path PAw via the bypass flow path PAb. Therefore, it is possible to suppress bubbles B1 from flowing through the cooling medium supply flow path PA13 ( Figure 6 The refrigerant flows into the cooling flow path PAw, thereby enhancing the cooling effect in the active region AR1 caused by the flow of the cooling medium. Furthermore, the bypass flow path PAb allows not only air bubbles to flow but also refrigerant to pass through.

[0061] In this fuel cell stack 100, not all bubbles contained in the cooling medium supplied to the through-hole 305 are directed into the bypass flow path PAb; a portion is directed into the cooling medium supply flow path PA13. Since the bubbles flowing to the active region AR1 via the cooling medium supply flow path PA13 flow upwards towards the active region AR1, the cooling efficiency at the top may decrease. Therefore, to improve the cooling efficiency originating from the cooling medium flow, it is preferable to reduce the amount and size of bubbles directed into the active region AR1 via the cooling medium supply flow path PA13. With this in mind, this embodiment configures the fuel cell stack 100 as follows.

[0062] Figure 8 yes Figure 7 The VIII-VIII sectional view in the diagram is a sectional view of the cooling medium supply flow path PA13, cut along the flow direction of the cooling medium. For example... Figure 7 , Figure 8 As shown, on the front plate 3F of the partition 3, a plurality of guide portions 333 are provided protruding forward and are generally parallel to each other. Recesses 335 are provided between adjacent guide portions 333 in the left-right direction. At the front of the front plate 3F, the plurality of recesses 335 form a passage from the channel portion 41 to the active region AR1 (…). Figure 4 The cathode supply flow path PA11 () Figure 4 On the rear plate 3R of partition 3, no guide portion 333 is provided in this area, and the rear plate 3R is constructed flat (see reference). Figure 5 ).

[0063] The plurality of recesses 335 include a plurality of recesses 335a having a predetermined width W1, and a single wide recess 335b having a predetermined width W2. The width W2 is greater than the width W1, for example, the width W2 is more than twice the width W1. The wide recess 335b is located upstream of the plurality of recesses 335a in the flow direction of the cooling medium. For example, the first or second recess 335 after the passage portion 43 is a wide recess 335b.

[0064] The upper channel portion 44 and the channel portion 43 are connected outside the through hole 305 via an outer rib portion 331. The outer rib portion 331 between the upper channel portion 44 and the channel portion 43 is referred to as the connecting flow path portion 331a. One end (lower end) of the connecting flow path portion 331a is connected to the channel portion 43, and the other end (upper end) is connected to the connecting portion 338, wherein the connecting portion 338 is the part where the upper channel portion 44 and the outer rib portion 331 are connected. The cooling medium supply flow path PA13 branches at the channel portion 43 and communicates with the bypass flow path PAb via the connecting flow path PAs inside the connecting flow path portion 331a.

[0065] like Figure 8 As shown, regarding the height of the cooling medium supply flow path PA13, i.e., the distance between the rear surface 3Fb of the front plate 3F and the front surface 3Ra of the rear plate 3R, the height H1 of the wide recess 335b is the same as the height of the plurality of recesses 335a. Furthermore, the height H1 is lower than the height H2 of the guide portion 333. For example, the height H1 is less than half the height H2. Also, the height H1 is lower than the height of the bypass flow path PAb, for example, less than half the height of the bypass flow path PAb. The flow area of ​​the cooling medium supply flow path PA13 is narrowed at the recess 335. Therefore, the recess 335 constitutes a throttling portion. Hereinafter, the back side (rear side) of the recess 335a in the cooling medium supply flow path PA13 will be referred to as the throttling portion 336a, and the back side (rear side) of the wide recess 335b will be referred to as the wide throttling portion 336b.

[0066] like Figure 7 As shown, a welding portion 337 extending in the left-right direction is provided below the channel portion 41, and the front plate 3F and the rear plate 3R are welded together through the welding portion 337. Therefore, the opening at the upper end of the wide recess 335b is closed by the welding portion 337. Figure 4 As shown, the lower end of the wide recess 335b is located near the lower end of the active region AR1. Therefore, the wide recess 335b extends throughout the cooling medium supply path PA13 upstream of the active region AR1. Figure 4 The entire area extends from arrow A1 in the diagram.

[0067] In this fuel cell stack 100 structure, when the cooling medium is supplied via the through-hole 305, the bubbles contained in the cooling medium are miniaturized as they pass through the wide throttling section 336b. In particular, since the length of the wide throttling section 336b is longer than that of the throttling section 336a, miniaturization is promoted in the wide throttling section 336b. The miniaturized bubbles dissolve due to the flow of the refrigerant, and the bubble size gradually decreases. Accordingly, the amount and size of bubbles flowing into the active region AR1 via the cooling medium supply path PA13 can be reduced.

[0068] The flow resistance at the wide throttling section 336b of the cooling medium supply flow path PA13 is greater than that at the throttling section 336a. Therefore, bubbles that cannot pass through the wide throttling section 336b easily flow through the connecting flow paths PAs to the bypass flow path PAb. This promotes bubble flow in the bypass flow path PAb and inhibits bubble flow towards the active region AR1. Conversely, assuming there is no wide throttling section 336b, the number of bubbles passing through the throttling section 336a would increase, and the number of bubbles flowing towards the active region AR1 would also increase.

[0069] The wide-width throttling section 336b extends throughout the entire area of ​​the cooling medium supply flow path PA13. Therefore, all the cooling medium flowing towards the active region AR1 passes through the wide-width throttling section 336b. This effectively prevents bubbles from bypassing the wide-width throttling section 336b and flowing towards the active region AR1. Furthermore, since the cross-sectional area of ​​the wide-width recess 335b is large, the flow rate of the oxidant gas flowing in the wide-width recess 335b is increased. Therefore, sufficient oxidant gas can be supplied via the wide-width recess 335b to the inlet at the lowest part of the cathode flow path PAc, which is furthest from the through-hole 304.

[0070] According to this embodiment, the following effects can be achieved.

[0071] (1) The fuel cell stack 100 is constructed by alternately stacking the UEA2, which serves as the membrane electrode structure, and the separator 3 in the front-to-back direction (a predetermined direction). Figure 1 UEA2 has an MEA20 and a frame 21, wherein the MEA20 has an electrolyte membrane, an anode electrode, and a cathode electrode; the frame 21 supports the periphery of the MEA20. Figure 3 The partition 3 has a rear plate 3R and a front plate 3F, wherein the rear plate 3R is concave-convex and faces the front surface 2a of the UEA2, forming an anode flow path PAa for fuel gas flow between it and the UEA2; the front plate 3F is concave-convex and faces the rear surface 2b of the UEA2, forming a cathode flow path PAc for oxidant gas flow between it and the UEA2. Figure 2The rear plate 3R and the front plate 3F have flow path forming portions such as channel portion 43, recess portion 32, and outer rib portion 331, which are used to form a flow path between the rear plate 3R and the front plate 3F. Figure 4 , Figure 5 The flow path includes a cooling flow path PAw, a cooling medium supply flow path PA13, a bypass flow path PAb, and a connecting flow path PAs. The cooling flow path PAw supplies cooling medium to flow along the active region AR1 of the partition 3 facing the MEA20. The cooling medium supply flow path PA13 guides the cooling medium supplied through the through-hole 305 of the partition 3 to the cooling flow path PAw. The bypass flow path PAb allows air bubbles contained in the cooling medium supplied through the through-hole 305 to bypass the cooling flow path PAw and be directed downstream of it. The connecting flow path PAs connects the cooling medium supply flow path PA13 and the bypass flow path PAb. Figure 4 , Figure 7 The cooling medium supply path PA13 has multiple throttling sections 336a and 336b downstream of the channel 43 connected to the connecting path Pas. These multiple throttling sections 336a and 336b shorten the height of the gap between the rear plate 3R and the front plate 3F. Figure 7 Multiple throttling sections include a wide-range throttling section 336b and a throttling section 336a located downstream of the wide-range throttling section 336b. Figure 7 , Figure 8 The wide-range throttling section 336b is configured such that its flow resistance is greater than that of the throttling section 336a. Figure 8 ).

[0072] With this structure, when the cooling medium supplied through the through-hole 305 contains bubbles, the wide-width throttling section 336b can be used to refine the bubbles. The refined bubbles dissolve due to the flow of refrigerant, and the size of the bubbles gradually decreases. Accordingly, the amount of bubbles supplied to the active region AR1 through the cooling medium supply path PA13 can be significantly reduced. In contrast, if there were no wide-width throttling section 336b, the bubbles would easily pass through the throttling section 336a and flow to the active region AR1.

[0073] (2) The length (width W2) of the wide throttling section 336b along the flow direction of the cooling medium is longer than the length (width W1) of the throttling section 336a. Figure 7 , Figure 8 In this way, by increasing the length of the wide-width throttling section 336b, the flow resistance increases, thereby making it easier to miniaturize the bubble block.

[0074] (3) The size (height H1) of the gap in the wide throttling section 336b is smaller than the size of the gap in the connecting flow path PAs. Figure 8Accordingly, bubbles that cannot pass through the wide-width throttling section 336b can easily flow to the bypass flow path PAb via the upstream connecting flow path Pas of the wide-width throttling section 336b. Accordingly, bubble flow in the bypass flow path PAb is promoted, and bubble flow to the active region AR1 can be suppressed.

[0075] (4) The wide-width throttling section 336b extends over the entire area of ​​the cooling medium supply path PA13 in the direction intersecting with the flow direction of the cooling medium. Figure 4 , Figure 7 Accordingly, the cooling medium flowing to the active region AR1 will all flow through the wide throttling section 336b, thereby effectively preventing bubbles from bypassing the wide throttling section 336b and flowing to the active region AR1.

[0076] The above-described embodiments can be modified in various forms. Several modifications will be described below. In the above-described embodiments, the rear plate 3R of the partition 3, which is the first plate portion, is arranged facing the front surface 2a (first surface) of the UEA2, which is the membrane electrode structure, and is configured in an uneven shape to form an anode flow path PAa (first gas flow path) for the flow of fuel gas (first gas) between the partition 3 and the UEA2. The front plate 3F of the partition 3, which is the second plate portion, is arranged facing the rear surface 2b (second surface) of the UEA2, and is configured in an uneven shape to form a cathode flow path PAc (second gas flow path) for the flow of oxidant gas (second gas) between the partition 3 and the UEA2. However, the structures of the first plate portion and the second plate portion are not limited to the structures described above.

[0077] In the above embodiment, a flow path for the cooling medium and the air bubbles contained in the cooling medium to flow is formed between the rear plate 3R and the front plate 3F via a flow path forming section. Specifically, a cooling flow path PAw (power generation area flow path) is formed along the power generation area of ​​the partition 3 facing MEA20 via the recess 32; a cooling medium supply flow path PA13 (supply flow path) is formed by the channel section 43, the throttling sections 336a and 336b; a bypass flow path PAb is formed by the upper channel section 44 and the outer rib section 331, which allows the air bubbles contained in the cooling medium supplied through the through hole 305 to bypass the cooling flow path PAw and be guided downstream of the cooling flow path PAw; and a connecting flow path PAs is formed by the outer rib section 331, which connects the cooling medium supply flow path PA13 and the bypass flow path PAb. However, the structure of the flow path forming section is not limited to the above structure.

[0078] In the above embodiment, the length (width W2) of the wide throttling section 336b, which serves as the first throttling section, is set to be longer than the length (width W1) of the throttling section 336a, which serves as the second throttling section. However, as long as the flow path resistance of the first throttling section is greater than that of the second throttling section, the structure of the first and second throttling sections is not limited to the above structure. For example, the throttling capacity of the first throttling section may be less than that of the second throttling section. The lengths of the first and second throttling sections in the width direction are also not limited to the above lengths. In the above embodiment, the connecting flow path PAs is connected to the channel section 43, but the connection position of the connecting flow path PAs to the cooling medium supply flow path PA13 is not limited to this.

[0079] In the above embodiments, an example of applying the fuel cell stack 100 to a vehicle has been described, but the fuel cell stack with the power generation unit of the present invention can also be applied to mobile bodies other than vehicles such as aircraft and ships, robots and other types of industrial machinery.

[0080] The above description is merely an example, and the present invention is not limited to the above embodiments and modifications as long as it does not affect the features of the invention. The above embodiments and one or more modifications can be arbitrarily combined, or modifications can be combined with each other.

[0081] Explanation of reference numerals in the attached figures

[0082] 1: Power generation unit; 2: Integrated electrode assembly; 2a: Front surface; 2b: Rear surface; 3: Separator; 3F: Front plate; 3R: Rear plate; 20: Membrane electrode assembly; 21: Frame; 31: Protrusion; 32: Recess; 43: Channel section; 44: Upper channel section; 305: Through hole; 336a: Throttling section; 336b: Wide throttling section; 100: Fuel cell stack; PAa: Anode flow path; PAc: Cathode flow path; PAw: Cooling flow path; PA13: Cooling medium supply flow path; PAb: Bypass flow path; PAs: Connecting flow path; AR1: Active region; W1, W2: Width; H1: Height.

Claims

1. A fuel cell stack, characterized in that, is constructed by alternately stacking membrane electrode structures and separators along a predetermined direction, The membrane electrode structure includes a membrane electrode assembly and a frame component, wherein the membrane electrode assembly includes an electrolyte membrane and an electrode; the frame component supports the periphery of the membrane electrode assembly. The partition has a first plate portion and a second plate portion, wherein the first plate portion is concave-convex and is disposed facing the first surface of the membrane electrode structure, forming a first gas flow path for the first gas to flow between it and the membrane electrode structure; the second plate portion is concave-convex and is disposed facing the second surface of the membrane electrode structure, forming a second gas flow path for the second gas to flow between it and the membrane electrode structure. The first plate portion and the second plate portion have flow path forming portions that form flow paths between the first plate portion and the second plate portion. The flow path includes a power generation area flow path, a supply flow path, a bypass flow path, and a connecting flow path, wherein, The cooling medium flows along the power generation region of the partition facing the membrane electrode assembly. The supply flow path guides the cooling medium supplied through the supply hole penetrating the partition to the power generation area flow path; The bypass flow path will allow air bubbles contained in the cooling medium supplied via the supply hole to bypass the power generation area flow path and be directed downstream of the power generation area flow path; The connecting flow path connects the supply flow path and the bypass flow path. The supply flow path has multiple throttling sections downstream of the connection point for the connecting flow path, which shorten the height of the gap between the first plate and the second plate. The plurality of throttling sections have a first throttling section and a second throttling section located downstream of the first throttling section. The first throttling section is configured such that its flow resistance is greater than that of the second throttling section.

2. The fuel cell stack according to claim 1, characterized in that, The length of the first throttling section along the flow direction of the cooling medium is longer than the length of the second throttling section.

3. The fuel cell stack according to claim 2, characterized in that, The size of the gap in the first throttling section is smaller than the size of the gap in the connecting flow path.

4. The fuel cell stack according to any one of claims 1 to 3, characterized in that, The first throttling section extends over the entire area of ​​the supply flow path in the width direction, intersecting the flow direction of the cooling medium.

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