Fuel cell stack and method for manufacturing the housing

Abstract

To configure a fuel cell stack inexpensively.SOLUTION: A fuel cell stack 100 includes: a cell stacked body that is configured to stack alternately a membrane electrode assembly and a separator in a predetermined direction and that has a substantially rectangular parallelepiped shape; and a case 30 that has an upper wall 31, a right wall 32, a lower wall 33 and a left wall 34 facing four side surfaces of the cell stack body, respectively, extending in the predetermined direction and that forms an accommodation space SP0 accommodating the cell stacked body 10. Each of the upper wall 31, the right wall 32, the lower wall 33 and the left wall 34 is configured by a substantially plate-shaped member having a substantially rectangular shape. The case 30 includes joint portions joined by friction stir welding on connection surfaces between the upper wall 31 and the right wall 32, between the right wall 32 and the lower wall 33, between the lower wall 33 and the left wall 34, and between the left wall 34 and the upper wall 31, respectively, and further includes machined guide support portions 35 provided on inner surfaces 30a of side walls 300 facing the accommodation space SP0.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a fuel cell stack and a method for manufacturing a housing for use in a fuel cell stack or the like. [Background technology]

[0002] In recent years, research and development has been conducted on fuel cells that contribute to energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. As a fuel cell stack used in this type of fuel cell, a technology has been known in which a case for accommodating a cell stack of a fuel cell stack is manufactured by joining a first case and a second case, each of which has a roughly U-shaped cross section, by friction stir welding (see, for example, Patent Document 1). In Patent Document 1, the first case and the second case are each manufactured by casting, and then the two are joined by friction stir welding to manufacture a case having an accommodation space for accommodating the cell stack. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6388004 Summary of the Invention [Problem to be solved by the invention]

[0004] In some cases, this type of case requires some machining on the inner wall of the case facing the storage space, but machining the inner wall of the case requires a special tool, which increases costs. [Means for solving the problem]

[0005] A fuel cell stack according to one embodiment of the present invention comprises a cell stack having a generally rectangular parallelepiped shape formed by alternately stacking, in a predetermined direction, a membrane electrode structure including an electrolyte membrane and an electrode and separators, and a housing having a first side wall facing each of four sides of the cell stack extending in the predetermined direction, a second side wall connected to the first side wall, a third side wall connected to the second side wall, and a fourth side wall connected to the third side wall and the first side wall, the housing forming a storage space for accommodating the cell stack; a plate member attached to an end of the housing in a predetermined direction; The first side wall, the second side wall, the third side wall and the fourth side wall are each formed of a substantially rectangular plate-like member. The housing has friction members on a connection surface between the first side wall and the second side wall, a connection surface between the second side wall and the third side wall, a connection surface between the third side wall and the fourth side wall, and a connection surface between the fourth side wall and the first side wall. Mixing Having a joint by bonding , collection At least the first side wall facing the storage space has a machined portion on its inner surface. The first side wall, the second side wall, the third side wall and the fourth side wall have flanges at their ends in a predetermined direction, protruding toward the outside of the storage space and having holes for mounting the plate member. do.

[0006] A method for manufacturing a housing according to another aspect of the present invention includes a step of machining a surface of at least the first side wall among a first side wall, a second side wall, a third side wall, and a fourth side wall each extending in a substantially rectangular shape and configured in a substantially plate shape, and a step of pressing a substantially cylindrical joining tool while rotating along a connection surface between the first side wall and the second side wall, a connection surface between the second side wall and the third side wall, a connection surface between the third side wall and the fourth side wall, and a connection surface between the fourth side wall and the first side wall, which are arranged substantially perpendicular to one another, to frictionally join these connection surfaces. Mixing Joint to form a storage space And a process of a step of drilling holes for mounting the plate member in flanges provided in advance on ends of the first side wall, the second side wall, the third side wall, and the fourth side wall toward the outside of the accommodation space; Friction Mixing The joining step includes disposing a jig for receiving a pressing load of the joining tool in a space surrounded by the first side wall, the second side wall, the third side wall and the fourth side wall. Effect of the Invention

[0007] The present invention allows inexpensive machining of the interior of the fuel cell stack housing. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view showing a schematic overall configuration of a fuel cell stack according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] 2A to 2C are diagrams showing an example of a joining process for a case included in the fuel cell stack of FIG. 1. [Figure 4] FIG. 13 is a diagram showing an example of a connection surface of side walls joined to each other. [Figure 5A] 5A to 5C are diagrams illustrating an example of a side wall manufacturing step in the manufacturing method for the housing according to the embodiment of the present invention. [Figure 5B] FIG. 5B is a diagram showing an example of a pre-processing step subsequent to FIG. 5A. [Figure 5C] FIG. 5C is a diagram showing an example of a bonding step subsequent to FIG. 5B, which is different from FIG. 3; [Figure 5D] FIG. 5D is a diagram showing an example of a post-processing step following FIG. 5C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to Figs. 1 to 5D. A fuel cell stack according to an embodiment of the present invention constitutes a main element of a fuel cell. The fuel cell is mounted, for example, in a vehicle and can generate electric power for driving the vehicle. The fuel cell can also be mounted in moving bodies other than vehicles, such as aircraft and ships, robots, and various industrial machines.

[0010] First, the overall configuration of the fuel cell stack will be described. FIG. 1 is a perspective view showing a schematic overall configuration of a fuel cell stack 100 according to an embodiment of the present invention. In the following, for convenience, three axial directions perpendicular to each other as shown in the figure are defined as the front-rear direction, the left-right direction, and the up-down direction, and the configuration of each part will be described according to these definitions. These directions are not necessarily the same as the front-rear direction, the left-right direction, and the up-down direction of a vehicle. For example, the front-rear direction in FIG. 1 may be the front-rear direction, the left-right direction, or the up-down direction of a vehicle.

[0011] As shown in FIG. 1, the fuel cell stack 100 has a cell stack 10, end units 20 arranged at both the front and rear ends of the cell stack 10, and a case 30 surrounding the cell stack 10, and has an overall roughly rectangular parallelepiped shape.

[0012] The case 30 has four generally rectangular side walls 300 respectively facing the top, right, bottom, and left sides of the cell stack 10. These four side walls 300 form a generally box-shaped storage space SP0 with an open front and rear. The case 30 is made of a metal such as aluminum or iron. The end unit 20 includes a metal end plate 21, and the front and rear of the case 30 are covered by the end unit 20.

[0013] Guide members 50 (FIG. 2) are interposed between the cell stack 10 and each side wall 300 of the case 30. The guide members 50 are rod- or plate-shaped members extending in the front-rear direction, and are attached to the inner surfaces of the side walls 300 in advance.

[0014] 1 shows a cutaway view of a portion of a side wall 300 of the case 30. As shown in part A of Fig. 1, the cell stack 10 is formed by stacking a plurality of power generating cells 1 (for convenience, only a single cell 1 is shown) in the front-rear direction while being guided by a guide member 50.

[0015] The power generating cell 1 has an electrode assembly 2 having an assembly including an electrolyte membrane and electrodes, and separators 3 arranged on both the front and rear sides of the electrode assembly 2 to sandwich the electrode assembly 2. The electrode assemblies 2 and the separators 3 are arranged alternately in the front-rear direction.

[0016] Separator 3 has a pair of front and rear metallic thin plates with a corrugated cross section, and is integrally formed by joining the outer peripheries of the pair of thin plates. Separator 3 is made of a conductive material with excellent corrosion resistance, such as titanium, titanium alloy, stainless steel, etc. The pair of thin plates are formed into an uneven shape by press molding or the like so as to form cooling channels inside separator 3 through which a cooling medium (e.g., water) flows, and the power generation surface of power generation cell 1 is cooled by the flow of the cooling medium.

[0017] The separator 3 on the front side of the electrode assembly 2 is, for example, an anode side separator (anode separator), and an anode flow path through which a fuel gas containing hydrogen flows is formed between the anode separator 3 and the electrode assembly 2. The separator 3 on the rear side of the electrode assembly 2 is, for example, a cathode side separator (cathode separator), and a cathode flow path through which an oxidant gas containing oxygen flows is formed between the cathode separator 3 and the electrode assembly 2.

[0018] The electrode assembly 2 has a membrane electrode assembly (MEA) and a resin frame that supports the periphery of the membrane electrode assembly. The membrane electrode assembly has an electrolyte membrane, an anode electrode provided on the front surface of the electrolyte membrane, and a cathode electrode provided on the rear surface of the electrolyte membrane. The membrane electrode assembly is sometimes called a membrane electrode structure. The electrolyte membrane is, for example, a solid polymer electrolyte membrane. The anode electrode is an electrode catalyst layer formed on the front surface of the electrolyte membrane and serves as a reaction field for electrode reactions, and a gas diffusion layer that diffuses and supplies a fuel gas is provided on the front surface of the electrode catalyst layer. The cathode electrode is an electrode catalyst layer formed on the rear surface of the electrolyte membrane and serves as a reaction field for electrode reactions, and a gas diffusion layer that diffuses and supplies an oxidant gas is provided on the rear surface of the electrode catalyst layer.

[0019] At the anode electrode, the fuel gas (hydrogen) supplied via the anode flow path and gas diffusion layer is ionized by the action of a catalyst and passes through the electrolyte membrane to move to the cathode electrode. The electrons generated at this time pass through an external circuit and are extracted as electrical energy. At the cathode electrode, the oxidant gas (oxygen) supplied via the cathode flow path and gas diffusion layer reacts with the hydrogen ions guided from the anode electrode and the electrons that have moved from the anode electrode to produce water. The produced water provides an appropriate humidity to the electrolyte membrane, and excess water is discharged outside the electrode assembly 2.

[0020] Through holes 211 to 216 are opened in the front end plate 21. The through hole 211 is a through hole for supplying fuel gas to the inside of the cell stack 10. The through hole 212 is a through hole for discharging a cooling medium from the cell stack 10 to the outside. The through hole 213 is a through hole for discharging an oxidizing gas from the cell stack 10 to the outside. The through hole 214 is a through hole for supplying an oxidizing gas to the inside of the cell stack 10. The through hole 215 is a through hole for supplying a cooling medium to the inside of the cell stack 10. The through hole 216 is a through hole for discharging a fuel gas from the cell stack 10 to the outside.

[0021] At both left and right ends of the cell stack 10, a plurality of flow paths (manifolds) are formed extending in the front-rear direction so as to communicate with the through holes 211 to 216. A fuel gas supplied through the through hole 211 is guided to the anode flow path inside the cell stack 10, and an oxidant gas supplied through the through hole 214 is guided to the cathode flow path. This causes power generation in the power generation cell 1. The supplied fuel gas and oxidant gas are discharged from the cell stack 10 through the through holes 216 and 213, respectively. A cooling medium supplied through the through hole 215 is guided to the cell stack 10, thereby cooling the power generation surface. The cooling medium that has passed through the cell stack 10 is discharged through the through hole 212.

[0022] The fuel cell stack 100 according to this embodiment is particularly characterized by the configuration of the case 30. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. As shown in Fig. 2, a side wall 300 of the case 30 includes an upper wall 31, a right wall 32, a lower wall 33 and a left wall 34 which face the upper, right, lower and left faces of the cell stack 10, respectively. Hereinafter, the center side of the storage space SP0 in the case will be referred to as the inside of the case.

[0023] Guide support parts 35 for supporting guide members 50 are provided on the inner surface 30a of the side wall 300 facing the storage space SP0, i.e., the lower surface of the upper wall 31, the left surface of the right wall 32, the upper surface of the lower wall 33, and the right surface of the left wall 34. The guide support parts 35 protrude from the inner surface 30a of the side wall 300 toward the inside of the case and extend in the longitudinal direction (front-rear direction) of the side wall 300. The guide support parts 35 have recesses 35a, for example, in a portion facing the storage space SP0. The guide member 50 fits into the recesses 35a.

[0024] The guide support part 35 can be provided on the side wall 300 itself, for example, by machining the inner surface 30a of the side wall 300. The guide support part 35 can also be provided separately from the side wall 300 and fixed to the side wall 300 with bolts or the like. Even when the guide support part 35 is a separate part, it is necessary to machine the inner surface 30a of the side wall 300 to provide a seat surface, bolt holes, and the like for attaching the guide support part 35.

[0025] The guide member 50 is an elongated resin member extending in the front-rear direction, and is formed, for example, by extrusion molding. The cross-sectional shape of the guide member 50 is uniform along the longitudinal direction (front-rear direction). The guide member 50 has, for example, recesses 51 facing toward the inside of the case. The front-rear and left-right edges of the cell stack 10 are fitted into the recesses 51.

[0026] Specifically, protrusions 11 are provided on the front, rear, left and right edges of the separators 3 of the cell stack 10 in correspondence with the guide members 50, and the separators 3 are stacked while the protrusions 11 fit into the recesses 51. In this case, by previously forming a set of unit cells by joining a single electrode assembly 2 to a single separator 3 by welding, adhesive or the like, the electrode assembly 2 can be stacked at the same time as stacking the separators 3. Also, by stacking the separators 3 via the guide members 50, the cell stack 10 can be constructed while the separators 3 are accurately positioned relative to the case 30.

[0027] The case 30 is formed by joining the ends of the side walls 300 together after the machining of the guide support parts 35 of the side walls 300 is completed. Specifically, the upper end face of the right wall 32 and the upper end face of the left wall 34 are joined to the right end and left end of the inner surface 30a of the upper wall 31, respectively. The lower end faces of the right wall 32 and the lower end faces of the left wall 34 are joined to the right end and left end of the inner surface 30a of the lower wall 33, respectively. This joining is performed using a friction Mixing A joint is used.

[0028] FIG. 3 is a diagram showing an example of a joining process of the right wall 32 and the upper wall 31, and the right wall 32 and the lower wall 33. In the joining process of FIG. 3, first, the left wall 34 is placed on the base 200. Furthermore, the upper wall 31 and the lower wall 33 are erected on the base 200 with the upper wall 31 and the lower wall 33 abutting against both end faces of the left wall 34. At this time, both sides of the upper wall 31 and the lower wall 33 are held down by blocks 201 so that the upper wall 31 and the lower wall 33 do not fall outward. Next, a jig 202 of a predetermined length is placed on the upper surface of the left wall 34, and the right wall 32 is mounted on the upper surface of the jig 202. That is, the jig 202 is placed in the space SP1 surrounded by the upper wall 31, the right wall 32, the lower wall 33, and the left wall 34.

[0029] At this time, the height of the jig 202 is set so that both end faces of the right wall 32 are located at the end of the upper wall 31 and the end of the lower wall 33. This allows the right wall 32 to be held by the jig 202 against a downward load from above, with the upper wall 31 and the lower wall 33 abutting against both end faces of the right wall 32. Note that the state before joining of the side walls 300 is sometimes called a work. Therefore, Fig. 3 shows the joining process of the work.

[0030] In this state, while rotating a tool 210 having a generally cylindrical probe 210a at its tip, the tool 210 is pressed from above against a connection surface SF1 between the end surface of the right wall 32 and the upper wall 31 and a connection surface SF2 between the end surface of the right wall 32 and the lower wall 33. This causes friction between the connection surfaces SF1 and SF2. Mixing Next, the entire work is turned upside down, and the connection surface SF4 between the end surface of the left wall 34 and the upper wall 31 and the connection surface SF3 between the end surface of the left wall 34 and the lower wall 33 are similarly friction-welded. Mixing In this manner, the case 30 is manufactured.

[0031] After friction stir welding, the connection surfaces SF1 to SF4 do not exist, and the connection surfaces SF1 to SF4 become the welds SW1 to SW4, respectively. The size of the welds SW1 to SW4 is determined by the diameter of the tool tip, and the welds SW1 to SW4 exist in a predetermined region centered on the connection surfaces SF1 to SF4.

[0032] In this way, friction Mixing Since the side walls 300 are joined together by bonding, the bonding strength is high and there is little deformation or distortion due to bonding. Therefore, the guide member 50 can be easily fitted into the guide support portion 35 provided in advance on the inner surface 30a of the case 30. In addition, in the example of FIG. 3, the right wall 32 has connection surfaces SF1 and SF2 on both end surfaces. Therefore, the tool 210 can be brought close from the same direction without changing the posture of the workpiece, and the two connection surfaces SF1 and SF2 can be bonded. This reduces the number of times the posture of the workpiece needs to be changed, enabling efficient bonding.

[0033] 2, a voltage control unit (VCU) 205 for controlling power generation of the fuel cell stack 100 is mounted on the upper surface of the case 30 (upper wall 31). The upper surface of the upper wall 31 does not have any joints between the side walls 300, and the upper surface is formed flat without any irregularities. Therefore, the voltage control unit 205 can be favorably mounted on the upper surface of the upper wall 31 without any rattling.

[0034] In Fig. 3, each of the connection surfaces SF1 to SF4 of the side wall 300 is formed by a single plane, but they may be formed by a plurality of planes perpendicular to each other. Fig. 4 shows one example of this, showing another example of the connection surface SF1 between the top wall 31 and the right wall 32.

[0035] 4, the connection surface SF1 is composed of a plurality of surfaces SF11, SF12, and SF13. That is, the connection surface SF1 has an outer connection surface SF11 provided on an end surface of the right wall 32 and extending perpendicularly to the outer surface 30b by a predetermined length t1 from the outer surface 30b to the inner surface 30a of the side wall 300 (right wall 32), an inner connection surface SF12 extending perpendicularly to the inner surface 30a by a predetermined length t2 from the inner surface 30a to the outer surface 30b, and an intermediate connection surface SF13 that is perpendicular to the outer connection surface SF11 and the inner connection surface SF12 and connects the outer connection surface SF11 and the inner connection surface SF12.

[0036] In other words, the connection surface SF1 has a pair of connection surfaces (outer connection surface SF11, inner connection surface SF12) offset from each other in a direction perpendicular to the axis CL1 which is the rotation center of the tool 210, and a connection surface (middle connection surface SF13) connected to each of the connection surfaces SF11, SF12 in an L-shape. Therefore, the end surfaces of the upper wall 31 and the right wall 32 which face each other are each configured to have a stepped shape.

[0037] The offset amount W of the pair of connection surfaces SF11, SF12 (the length of connection surface SF13) is set to a value smaller than the diameter D of the probe 210a at the tip of the tool. The connection surfaces SF11, SF12 are provided equidistantly across the axis CL1. The length t1 of the outer connection surface SF11 is set to be equal to or less than the length L1 of the probe 210a. The length t2 of the inner connection surface SF12 is the value obtained by subtracting the length t1 from the plate thickness t0 of the side wall 300. Although not shown, the other connection surfaces SF2 to SF4 are configured in the same manner as in FIG. 4.

[0038] The tool 210 is pressed vertically against the outer surface 30b with the axis CL1 aligned with the center of the connection surfaces SF11 and SF12, and is moved until the tip of the probe 210a reaches the inner surface 30a. At this time, the intermediate connection surface SF13 receives the pressing load of the tool 210, so that the position of the right wall 32 with respect to the upper wall 31 is Gas This prevents the friction from being broken and ensures accurate Mixing The jig 202 may be unnecessary.

[0039] The manufacturing method of the case 30 as a housing can be summarized as follows. First, as shown in Fig. 5A, four side walls 300 made of substantially plate-like metal, that is, the upper wall 31, the right wall 32, the lower wall 33, and the left wall 34, are manufactured. These side walls 300 are manufactured by, for example, forging, casting, or extrusion (side wall manufacturing process). In the side wall manufacturing process, flange portions 301 for attaching end plates 21 (Fig. 1) are provided on the end faces of the side walls 300.

[0040] 5B, the side wall 300 is set on a processing table (not shown) and necessary machining is performed on the side wall 300 (pre-processing step). For example, a through hole 302 is machined so that a cable connected to a sensor can pass through. before In the processing step, the guide support portion 35 is also provided on the inner surface 30a of the side wall 300. At this stage, since the inner surface 30a is exposed, various processing steps can be easily performed on the side wall 300. Note that, after the guide support portion 35 is provided on the side wall 300 in the side wall manufacturing step, beforeIn the processing step, processing (cutting, drilling, etc.) may be performed on the guide support portion 35.

[0041] Next, as shown in FIG. 3, the connection surfaces SF1 to SF4 of the side walls 300 are joined using a jig 202 (joining process). That is, the tool 210 is rotated while being pressed against the connection surfaces SF1 to SF4 from above, thereby friction stir welding the connection surfaces SF1 to SF4. Instead of FIG. 3, the joining process may be performed as shown in FIG. 5C. In FIG. 5C, a substantially cross-shaped jig 206 is placed in a space SP1 surrounded by the side walls 300. The upper end, lower end, right end, and left end of the jig 206 are fitted into the guide support portion 35 of the inner surface 30a of the side walls 300, respectively. This allows the jig 206 to be easily held by utilizing the guide support portion 35 for supporting the guide member 50.

[0042] 5D, bolt holes 301a are machined in flange portion 301 of case 30 (post-processing step). Because flange portion 301 is provided at the end of case 30, machining of flange portion 301 can be easily performed even when case 30 is in an assembled state. This completes the manufacture of case 30.

[0043] Thereafter, when assembling the fuel cell stack 100, the guide member 50 is fitted into the guide support portion 35 (recess 35a) of the case 30 as shown in FIG. 2. Then, a predetermined number of separators 3 are stacked together with the electrode assemblies 2 along the guide member 50 to form the cell stack 10. Furthermore, a pressing force is applied to both ends of the cell stack 101 via the end units 20 by a pressurizer, compressing the cell stack 101 to a predetermined length. Then, in this state, the flange portions 301 of the case 30 are fastened to the end plates 21 using bolts.

[0044] According to this embodiment, the following advantageous effects can be obtained. (1) A fuel cell stack 100 includes a cell stack 10 having a generally rectangular parallelepiped shape formed by alternately stacking electrode assemblies 2, each including an electrolyte membrane and an electrode, and separators 3 in the front-rear direction, and a case 30 having four side walls 300 facing the four side surfaces of the cell stack 10 extending in the front-rear direction, i.e., an upper wall 31, a right wall 32 connected to the upper wall 31, a lower wall 33 connected to the right wall 32, and a left wall 34 connected to the lower wall 33 and the upper wall 31, and forming an accommodation space SP0 for accommodating the cell stack 10 (FIGS. 1 and 2). The upper wall 31, the right wall 32, the lower wall 33, and the left wall 34 are each formed of a generally rectangular plate-like member (FIG. 1). The case 30 has friction members at a connection surface SF1 between the upper wall 31 and the right wall 32, a connection surface SF2 between the right wall 32 and the lower wall 33, a connection surface SF3 between the lower wall 33 and the left wall 34, and a connection surface SF4 between the left wall 34 and the upper wall 31. Mixing The case 30 has joints SW1 to SW4 joined by welding (FIG. 3). Furthermore, the case 30 has a machined guide support portion 35 on at least the inner surface 30a of the upper wall 31 facing the accommodation space SP0 (FIG. 2).

[0045] In this way, the case 30 is constructed by joining the four side walls 300 by friction stir welding, which causes little distortion during joining, so that various types of machining can be performed on the inner surface 30a and the outer surface 30b of the side walls 300 before joining the side walls 300, that is, when the side walls 300 are still in a single body. Therefore, when machining is required to provide the guide support portion 35 on the inner surface 30a of the upper wall 31, for example, the machining can be easily performed. That is, when machining the inner surface 30a of the case 30 in an assembled state, a dedicated tool or the like is required, but according to this embodiment, a dedicated tool or the like is not required, and the case 30 of the fuel cell stack 100 can be constructed easily and inexpensively.

[0046] (2) The connection surface SF1 between the upper wall 31 and the right wall 32 is the connection surface between the inner surface 30a of the upper wall 31 and the upper end surface of the right wall 32, the connection surface SF2 between the right wall 32 and the lower wall 33 is the connection surface between the inner surface 30a of the lower wall 33 and the lower end surface of the right wall 32, the connection surface SF3 between the lower wall 33 and the left wall 34 is the connection surface between the inner surface 30a of the lower wall 33 and the lower end surface of the left wall 34, and the connection surface SF4 between the left wall 34 and the upper wall 31 is the connection surface between the inner surface 30a of the upper wall 31 and the upper end surface of the left wall 34 (FIGS. 2 and 3). As a result, the joint is not exposed on the upper surface of the upper wall 31, and the upper surface can be made flat without any irregularities. Therefore, devices such as the voltage control unit 205 can be stably mounted on the upper surface of the upper wall 31. Also, the joint is not exposed on the lower surface of the lower wall 33, and the lower surface can be made flat without any irregularities. Therefore, the fuel cell stack 100 can be stably mounted on the vehicle body. Furthermore, since connection surfaces SF1, SF2, SF3, SF4 are provided on both end faces of the right wall 32 and both end faces of the left wall 34, respectively, the tool 210 can be pressed against the multiple connection surfaces SF1, SF2, SF3, SF4 from the same direction. This reduces the number of times the position of the workpiece needs to be changed, enabling efficient joining of the side walls 300.

[0047] (3) The fuel cell stack 100 further includes guide members 50 that extend in the front-rear direction and are respectively interposed between the upper wall 31 and the cell stack 10, between the right wall 32 and the cell stack 10, between the lower wall 33 and the cell stack 10, and between the left wall 34 and the cell stack 10 (FIG. 2). The upper wall 31, the right wall 32, the lower wall 33, and the left wall 34 each have a guide support portion 35 that supports the guide member 50 on its inner surface 30a (FIG. 2). The guide support portion 35 is formed by machining. This allows the guide member 50 to be easily and accurately attached to the inner surface 30a of the side wall 300, and allows the multiple power generating cells 1 to be well stacked along the guide members 50.

[0048] (4) A manufacturing method of the housing (case 30) used in the fuel cell stack 100 includes a process (pre-processing process) of machining the surfaces of the upper wall 31, right wall 32, lower wall 33, and left wall 34, each of which extends in a substantially rectangular shape and is configured in a substantially plate-like shape, and a process of pressing a substantially cylindrical tool (joining tool) 210 while rotating along a connection surface SF1 between the upper wall 31 and the right wall 32, a connection surface SF2 between the right wall 32 and the lower wall 33, a connection surface SF3 between the lower wall 33 and the left wall 34, and a connection surface SF4 between the left wall 34 and the upper wall 31, which are arranged substantially perpendicular to one another, to frictionally bond these connection surfaces SF1 to SF4. Mixing and a joining step (joining step) (FIGS. 3, 5B, and 5C). The joining step includes arranging jigs 202 and 206 that receive the pressing load of tool 210 in space SP1 surrounded by upper wall 31, right wall 32, lower wall 33, and left wall 34 (FIGS. 3 and 5C). With this configuration, even if machining is required inside case 30, case 30 can be manufactured easily and inexpensively without using dedicated tools.

[0049] (5) The connection surface SF1 between the upper wall 31 and the right wall 32 may include an outer connection surface SF11 extending a predetermined length t1 from a predetermined position on the outer surface 30b of the right wall 32 in the thickness direction of the right wall 32, an inner connection surface SF12 extending a predetermined length t2 in the thickness direction of the right wall 32 from a position offset by a predetermined amount W from a predetermined position on the inner surface 30a of the right wall 32, and an intermediate connection surface SF13 extending perpendicular to the thickness direction of the right wall 32 and connecting the outer connection surface SF11 and the inner connection surface SF12 (FIG. 4). This makes it possible to prevent the right wall 32 from shifting in position relative to the upper wall 31 at the connection surface SF1 when a pressing load is applied from the tool 210 in the joining process, and to easily and accurately join at the connection surface SF1.

[0050] (6) The pre-processing step includes a step of processing the guide members 50 extending approximately parallel to the connection surfaces SF1 to SF4 on the inner surfaces 30a (sides facing the space SP1) of the upper wall 31, the right wall 32, the lower wall 33, and the left wall 34, respectively, i.e., the guide support parts 35 that support the guide members 50 for guiding and accommodating the separators 3 in the space SP1. The joining step includes supporting the jig 206 with the guide support parts 35 (FIG. 5C). Since the jig 206 is supported via the guide support parts 35 in this manner, the jig 206 for resisting the pressing load of the tool 210 can be stably held within the case.

[0051] The above embodiment can be modified in various ways. In the above embodiment, the four side walls 300 are each provided with a guide support portion 35 as a machined portion, but the configuration of the machined portion is not limited to this. The guide member 50 and the guide support portion 35 may be omitted. As long as a machined portion is provided on at least the inner surface of the first side wall, the second side wall, the third side wall, and the fourth side wall do not need to be provided with a machined portion. Here, the first side wall is any one of the upper wall 31, the right wall 32, the lower wall 33, and the left wall 34, the second side wall is a side wall that continues to the first side wall, the third side wall is a side wall that continues to the second side wall, and the fourth side wall is a side wall that continues to the third side wall and the first side wall.

[0052] In the above embodiment, the electrode assemblies 2 and the separators 3 as the membrane electrode assemblies including the electrolyte membrane and the electrodes are alternately stacked in the front-rear direction (a predetermined direction) to form the stack (cell stack 10), but the stacking direction is not limited to the front-rear direction and may be the up-down direction. In the above embodiment, the four side walls 300 are each formed in a substantially plate shape so that the side walls 300 do not include a bent portion at their end, but any of the four side walls 300 may include a bent portion bent at 90° at their end. In the above embodiment, the pair of connecting surfaces SF1, SF2 and the pair of connecting surfaces SF3, SF4 are each configured to extend in the same direction (the up-down direction in FIG. 3), but they may extend in different directions.

[0053] In the above embodiment (Figure 4), the upper wall 31 is the first side wall, the right wall 32 is the second side wall, and the connection surface SF1 is configured to include an outer connection surface SF11 (first connection surface) extending a predetermined length t1 (first length) in the thickness direction of the right wall 32 from a predetermined position on the outer surface 30b, which is the surface on one side of the right wall 32, an inner connection surface SF12 (second connection surface) extending a predetermined length t2 (second length) in the thickness direction of the right wall 32 from a position offset by a predetermined amount W from a predetermined position on the inner surface 30a, which is the surface on the other side of the right wall 32, and an intermediate connection surface SF13 (third connection surface) extending perpendicular to the thickness direction of the right wall 32 and connecting the outer connection surface SF11 and the inner connection surface SF12, but the configuration of the first side wall and the second side wall is not limited to this. The first side wall may be any wall other than the upper wall 31, i.e., the right wall 32, the lower wall 33, or the left wall , and the second side wall may be any wall other than the right wall 32, i.e., the upper wall 31, the lower wall 33, or the left wall .

[0054] Although an example has been described above in which the cell stack 10 is housed in the case 30 of the fuel cell stack 100, the housing of the present invention can also be used as a housing for something other than a fuel cell stack. Therefore, the contents housed in the housing are not limited to the cell stack.

[0055] The above description is merely an example, and the present invention is not limited to the above-mentioned embodiment and modifications, as long as the features of the present invention are not impaired. The above-mentioned embodiment and one or more modifications can be arbitrarily combined, and modifications can be combined with each other.

[0056] 2 electrode assembly, 3 separator, 10 cell stack, 30 case, 31 upper wall, 32 right wall, 33 lower wall, 34 left wall, 35 guide support portion, 50 guide member, 100 fuel cell stack, 202, 206 jig, 210 tool, SF1 to SF4 connection surfaces, SF11 outer connection surface, SF12 inner connection surface, SF13 intermediate connection surface, SW1 to SW4 joints

Claims

1. a cell stack having a substantially rectangular parallelepiped shape formed by alternately stacking a membrane electrode assembly including an electrolyte membrane and an electrode and a separator in a predetermined direction; a housing having first side walls facing four side surfaces of the cell stack extending in the predetermined direction, a second side wall connected to the first side wall, a third side wall connected to the second side wall, and a fourth side wall connected to the third side wall and the first side wall, and forming an accommodation space for accommodating the cell stack; a plate member attached to an end portion of the housing in the predetermined direction, the first side wall, the second side wall, the third side wall, and the fourth side wall are each formed of a substantially rectangular plate-like member, The housing has a joint portion formed by friction stir welding on a connection surface between the first side wall and the second side wall, a connection surface between the second side wall and the third side wall, a connection surface between the third side wall and the fourth side wall, and a connection surface between the fourth side wall and the first side wall, a machined portion is provided on at least an inner surface of the first side wall facing the storage space; a fuel cell stack characterized in that the first side wall, the second side wall, the third side wall and the fourth side wall have a flange portion at the end in the specified direction protruding toward the outside of the storage space and having a hole for mounting the plate member.

2. 2. The fuel cell stack according to claim 1, a connection surface between the first side wall and the second side wall is a connection surface between an inner surface of the first side wall and one end surface of the second side wall, a connection surface between the second side wall and the third side wall is a connection surface between an inner surface of the third side wall and the other end surface of the second side wall, a connection surface between the third side wall and the fourth side wall is a connection surface between an inner surface of the third side wall and one end surface of the fourth side wall, a connection surface between the fourth side wall and the first side wall is a connection surface between an inner surface of the first side wall and the other end surface of the fourth side wall, The fuel cell stack further comprises a device mounted on an upper surface of the first side wall.

3. 3. The fuel cell stack according to claim 1, The cell stack further includes guide members respectively interposed between the first side wall and the cell stack, between the second side wall and the cell stack, between the third side wall and the cell stack, and between the fourth side wall and the cell stack, and extending in the predetermined direction; the first side wall, the second side wall, the third side wall and the fourth side wall each have a guide support portion on an inner surface thereof for supporting the guide member; The fuel cell stack, wherein the guide support portion is the processed portion.

4. a step of machining a surface of at least the first side wall among a first side wall, a second side wall, a third side wall, and a fourth side wall each extending in a substantially rectangular shape and configured in a substantially plate shape; a step of pressing a substantially cylindrical joining tool while rotating along a connection surface between the first side wall and the second side wall, a connection surface between the second side wall and the third side wall, a connection surface between the third side wall and the fourth side wall, and a connection surface between the fourth side wall and the first side wall, which are arranged substantially perpendicular to each other, to frictionally stir join these connection surfaces to form an accommodation space; and forming holes for mounting a plate member in flange portions provided at ends of the first side wall, the second side wall, the third side wall, and the fourth side wall in advance and protruding toward the outside of the accommodation space, A method for manufacturing a housing, characterized in that the friction stir welding process includes placing a jig in a space surrounded by the first side wall, the second side wall, the third side wall, and the fourth side wall, the jig receiving the pressing load of the welding tool.

5. The method for manufacturing a housing according to claim 4, A connection surface between the first side wall and the second side wall is a first connection surface extending a first length from a predetermined position on one surface of the second side wall in a plate thickness direction of the second side wall; a second connection surface extending a second length in a plate thickness direction of the second side wall from a position offset by a predetermined amount from the predetermined position on the surface on the other side of the second side wall; A method for manufacturing a housing, comprising: a third connection surface extending perpendicular to a thickness direction of the second side wall and connecting the first connection surface and the second connection surface.

6. The method for manufacturing a housing according to claim 4 or 5, the machining step includes a step of machining a guide support portion on each of the inner surfaces of the first side wall, the second side wall, the third side wall, and the fourth side wall, the guide member extending approximately parallel to the connection surface, the guide support portion supporting the guide member for guiding and storing an item in the space, The method for manufacturing a housing, wherein the friction stir welding step includes supporting the jig with the guide support portion.

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