fuel cell stack

Abstract

To inexpensively constitute a fuel cell stack.SOLUTION: A fuel cell laminate comprises: a cell laminate constituted by laminating a power generation cell; a guide member 50 protruding from an inner wall of a case 30 toward the cell laminate; and positioning parts PT21 and PT22 provided on an upper surface 101 and a lower surface 102 of the power generation cell according to the guide member 50 and positioning the power generation cell with respect to the case 30. Each of the positioning parts PT21 and PT22 has a convex part 331 and a convex part 332 protruding from an upper side surface 101 and a lower side surface 102 of the power generation cell facing the inner wall of the case 30 toward the inner wall. The guide member 50 includes the upper guide member 50 provided on a right side of the convex part 331 and the lower guide member 50 provided on a left side of the convex part 332.SELECTED DRAWING: Figure 4A

Description

[Technical Field]

[0001] The present invention relates to a fuel cell stack including a stack of multiple power generating cells. [Background technology]

[0002] In recent years, technological 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. A known technology for fuel cell stacks used in this type of fuel cell involves providing a guide bar upright on a mounting base, and stacking power-generating cells on the mounting base while engaging recesses provided on the edges of the power-generating cells with the guide bar to form a stack (see, for example, Patent Document 1). In the stack described in Patent Document 1, a coating layer is provided on the surface of the guide bar to reduce frictional resistance between the power-generating cells and the guide bar when the power-generating cells are stacked. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-132847 Summary of the Invention [Problem to be solved by the invention]

[0004] However, providing a coating layer on the surface of the guide bar as described in Patent Document 1 increases the number of steps in assembling the fuel cell stack, resulting in increased costs. [Means for solving the problem]

[0005] A fuel cell stack according to one embodiment of the present invention includes a cell stack formed by stacking power-generating cells, each having a membrane electrode assembly including an electrolyte membrane and electrodes and separators, a housing surrounding the cell stack, a guide portion protruding from an inner wall of the housing toward the cell stack and extending along the stacking direction of the cell stack, and a positioning portion provided on an edge of the power-generating cell corresponding to the guide portion and positioning the power-generating cell relative to the housing. The positioning portion has a protrusion protruding from the edge of the power-generating cell toward the inner wall, and the protrusion includes a first protrusion and a second protrusion protruding toward the inner wall from a first edge of the power-generating cell facing the inner wall of the housing and a second edge opposite the first edge, respectively, and the first protrusion and the second protrusion each have a first end face extending substantially perpendicularly from the first edge and a second end face extending substantially perpendicularly from the second edge. a direction in which the first edge and the second edge extend, and When the opposite directions in a plane perpendicular to the stacking direction are defined as the first direction and the second direction, the guide portion includes a first guide portion provided on one side of the first convex portion in either the first direction or the second direction and having a first abutment surface that abuts against the first end face, and a second guide portion provided on the other side of the second convex portion in either the first direction or the second direction and having a second abutment surface that abuts against the second end face. [Effects of the Invention]

[0006] According to the present invention, the power generating cells can be stacked while being positioned without providing a coating layer on the guide members, and a fuel cell stack can be constructed inexpensively. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a perspective view schematically showing the overall configuration of a fuel cell stack according to an embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional view of a main part of the cell stack of FIG. 1. [Figure 3] FIG. 2 is a cross-sectional view of a main part of FIG. 1 showing the configuration of an electrode assembly. [Figure 4A] FIG. 2 is a cross-sectional view of a main part of FIG. 1, showing the configuration of a first separator. [Figure 4B] FIG. 2 is a cross-sectional view of a main part of FIG. 1, showing the configuration of a second separator. [Figure 5A] 3A to 3C are diagrams showing an example of a procedure for assembling a fuel cell stack according to an embodiment of the present invention. [Figure 5B] FIG. 5B is a diagram showing an example of a procedure following FIG. 5A. [Figure 5C] FIG. 5C is a diagram showing an example of a procedure following FIG. 5B. [Figure 5D] FIG. 5B is a diagram showing an example of a procedure following FIG. 5C. [Figure 5E] FIG. 5B is a diagram showing an example of the procedure following FIG. 5D. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to Figures 1 to 5E. A fuel cell stack according to an embodiment of the present invention is a main component of a fuel cell and is included in the fuel cell. The fuel cell is mounted, for example, in a vehicle and can generate power for driving the vehicle. The fuel cell can also be mounted in moving objects other than vehicles, such as aircraft and ships, robots, and various industrial machines.

[0009] First, the overall configuration of the fuel cell stack will be described briefly. FIG. 1 is a perspective view showing the overall configuration of a fuel cell stack 100 according to an embodiment of the present invention. Hereinafter, for convenience, three mutually orthogonal axial directions 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. The front-rear direction in FIG. 1 is the stacking direction of the fuel cell stack 100, and when assembling the fuel cell stack 100, the stacking direction is aligned with the direction of gravity.

[0010] As shown in FIG. 1, the fuel cell stack 100 has a cell stack 10, end units 40 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.

[0011] The case 30 has four generally rectangular side walls 300 that face 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 that is open on the front and back. The case 30 is made of a metal such as aluminum or iron.

[0012] Although not shown, the end unit 40 has multiple plates stacked in the front-rear direction. More specifically, the end unit 40 has a terminal plate arranged on the inside in the front-rear direction, an insulating plate arranged on the outside in the front-rear direction of the terminal plate, and an end plate arranged on the outside in the front-rear direction of the insulating plate.

[0013] The terminal plate is a generally rectangular metal plate-like member that has a terminal portion for extracting the power generated by the electrochemical reaction in the cell stack 10. The insulating plate is a generally rectangular non-conductive resin or rubber plate-like member that electrically insulates the terminal plate from the end plates. The end plates are metal or high-strength resin plate-like members.

[0014] Guide members 50 (FIG. 3) 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-to-rear direction. The guide members 50 are attached in advance to the inner surfaces of the four side walls 300 (the inner walls of the case 30), respectively, and the cell stack 10 is assembled in this state.

[0015] Part A of Fig. 1 shows a cutaway view of a side wall 300 of the case 30. As shown in part A of Fig. 1, the cell stack 10 is a stack having a plurality of power generating cells 1 (for convenience, only a single cell 1 is shown). The cell stack 10 is configured by being stacked in the front-to-rear direction while being guided by a guide member 50.

[0016] The power-generating cell 1 has an electrode assembly 2 and separators 3 that are arranged on both the front and rear sides of the electrode assembly 2 and sandwich the electrode assembly 2. The electrode assemblies 2 and separators 3 are arranged alternately in the front-to-rear direction. The separator 3 that faces the front surface of the electrode assembly 2 is sometimes called the first separator 31, and the separator 3 that faces the rear surface is sometimes called the second separator 32. Depending on which electrode assembly 2 is used as the reference, the same separator 3 can be the first separator 31 or the second separator 32.

[0017] FIG. 2 is a cross-sectional view of a main portion of the cell stack 10. As shown in FIG. 2, the separator 3 has a front plate 3F and a rear plate 3R, which are a pair of front and rear metal thin 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 opposing rear surface 3Fb of the front plate 3F and the front surface 3Ra of the rear plate 3R are joined at their outer peripheries by welding or the like. This integrally bonds the front plate 3F and the rear plate 3R to form the separator 3. The separator 3 is made of a conductive material with excellent corrosion resistance, such as stainless steel, titanium, or a titanium alloy.

[0018] A cooling flow path PAw through which a coolant flows is formed inside the separator 3 surrounded by the front plate 3F and the rear plate 3R, that is, between the rear surface 3Fb of the front plate 3F and the front surface 3Ra of the rear plate 3R. The flow of the coolant cools the power generation surface of the power generation cell 1. Water, for example, can be used as the coolant. The surface of the separator 3 facing the electrode assembly 2 (the front surface 3Fa and the rear surface 3Rb) is formed unevenly by press molding or the like to form a gas flow path between the separator 3 and the electrode assembly 2. More specifically, the separator 3 has a pair of front and rear rib portions 3A that protrude toward the electrode assembly 2, and a pair of front and rear recesses 3B that are connected to the pair of front and rear rib portions 3A and are formed in a concave shape.

[0019] The pair of front and rear rib portions 3A abut against the front surface 2a and rear surface 2b of the electrode assembly 2. A compressive load F is applied to the cell stack 10 in the front-to-rear direction during assembly of the fuel cell stack 100, and this compressive load F is maintained after assembly of the fuel cell stack 100 is complete. As a result, a predetermined surface pressure due to the compressive load F acts on the electrode assembly 2 in the front-to-rear direction via the rib portions 3A.

[0020] Between the front surface 2a of the electrode assembly 2 and the rear plate 3R of the separator 3 facing this front surface 2a, an anode flow path PAa is formed by the recess 3B, through which a fuel gas containing hydrogen flows. Between the rear surface 2b of the electrode assembly 2 and the front plate 3F of the separator 3 facing this rear surface 2b, a cathode flow path PAc is formed by the recess 3B, through which an oxidizer gas containing oxygen flows. For example, hydrogen gas can be used as the fuel gas, and for example, air can be used as the oxidizer gas. Sometimes, the fuel gas and the oxidizer gas are referred to as reactant gases without distinction between them.

[0021] FIG. 3 is a cross-sectional view (cross-sectional view along line III-III) of a main part of FIG. 1 showing a schematic configuration of an electrode assembly 2 (so-called UEA; Unitized Electrode Assembly). The electrode assembly 2 is sometimes called a membrane electrode structure or a membrane electrode member. As shown in FIG. 3, the electrode assembly 2 has a substantially rectangular assembly 20 serving as a membrane electrode assembly (so-called MEA; Membrane Electrode Assembly) and a frame 21 that supports the assembly 20. As shown in the detailed view of part A in FIG. 2, the assembly 20 has an electrolyte membrane 23, an anode electrode 24 provided on a front surface 231 of the electrolyte membrane 23, and a cathode electrode 25 provided on a rear surface 232 of the electrolyte membrane 23.

[0022] The electrolyte membrane 23 is, for example, a solid polymer electrolyte membrane, and a thin film of a perfluorosulfonic acid polymer containing water can be used. The electrolyte membrane 23 is not limited to a fluorine-based electrolyte membrane, and a hydrocarbon-based electrolyte membrane can also be used.

[0023] The anode 24 is formed on the front surface 231 of the electrolyte membrane 23 and includes an electrode catalyst layer 241 that serves as a reaction field for the electrode reaction, and a gas diffusion layer 242 that is provided on the front surface of the electrode catalyst layer 241 and diffuses and supplies a fuel gas. An intermediate layer (base layer) may be provided between the electrode catalyst layer 241 and the gas diffusion layer 242. The cathode 25 is formed on the rear surface 232 of the electrolyte membrane 23 and includes an electrode catalyst layer 251 that serves as a reaction field for the electrode reaction, and a gas diffusion layer 252 that is provided on the rear surface of the electrode catalyst layer 251 and diffuses and supplies an oxidant gas. An intermediate layer (base layer) may be provided between the electrode catalyst layer 251 and the gas diffusion layer 252.

[0024] The electrode catalyst layers 241, 251 contain a catalytic metal that promotes an electrochemical reaction between hydrogen contained in the fuel gas and oxygen contained in the oxidant gas, a proton-conductive electrolyte (e.g., ionomer), and electron-conductive carbon particles, etc. The gas diffusion layers 242, 252 are made of a gas-permeable conductive material, such as a porous carbon material.

[0025] At the anode electrode 24, the fuel gas (hydrogen) supplied via the anode flow path PAa is ionized by the action of a catalyst and moves through the electrolyte membrane 23 toward the cathode electrode. The electrons generated at this time pass through an external circuit and are extracted as electrical energy. At the cathode electrode 25, the oxidant gas (oxygen) supplied via the cathode flow path PAc reacts with the hydrogen ions introduced from the anode electrode 24 and the electrons that have moved from the anode electrode 24, producing water. The produced water provides an appropriate humidity to the electrolyte membrane 23, and excess water is discharged to the outside of the electrode assembly 2 along the gas flow.

[0026] As shown in FIG. 3, the frame 21 is a thin plate having a substantially rectangular shape and is made of insulating resin, rubber, or the like. A substantially rectangular opening 21a is provided in the center of the frame 21. The assembly 20 is provided to cover the entire opening 21a, and the peripheral edge of the assembly 20 is supported by the frame 21. On the left side of the opening 21a of the frame 21, three through holes 211 to 213 are opened in a vertically aligned manner, penetrating the frame 21 in the front-to-rear direction. On the right side of the opening 21a, three through holes 214 to 216 are opened in a vertically aligned manner, penetrating the frame 21 in the front-to-rear direction. For convenience, the through holes 211 to 216 are all shown as having a substantially rectangular shape, but the shape of the through holes 211 to 216 is not limited thereto. Point P in FIG. 3 is the midpoint in the vertical direction and the midpoint in the horizontal direction of the cell stack 10 and is referred to as the center point.

[0027] 4A is a cross-sectional view of a main portion of FIG. 1 showing the configuration of the rear surface (rear surface 3Rb of the rear plate 3R) of the first separator 31 arranged in front of the electrode assembly 2, and FIG. 4B is a cross-sectional view of a main portion of FIG. 1 showing the configuration of the rear surface (rear surface 3Rb of the rear plate 3R) of the second separator 32 arranged in the rear of the electrode assembly 2. Although not shown in part, a plurality of vertical rib portions 3A are provided at the center in the left-right direction of the rear surface 3Rb, extending in the left-right direction and facing the joined body 20 of the electrode assembly 2. Although not shown in detail, the rib portions 3A extend in a meandering manner in the left-right direction.

[0028] As shown in FIGS. 4A and 4B , the separators 3 (first separator 31 and second separator 32) have through-holes 311 to 316 that penetrate the separators 3 in the front-rear direction at positions corresponding to the through-holes 211 to 216 ( FIG. 3 ) of the frame 21. For convenience, the through-holes 311 to 316 are shown as being substantially rectangular, but the shape of the through-holes 311 to 316 is not limited thereto. The through-holes 311 to 316 are connected to the through-holes 211 to 216 of the frame 21, respectively. A plurality of flow paths that penetrate the cell stack 10 and extend in the front-rear direction are formed by a collection of these mutually connected through-holes 211 to 216 and 311 to 316. Although not shown, a plurality of sealing beads, i.e., metal bead seals, that protrude toward the frame 21 are provided around the through-holes 311 to 316 of the separators 3 and on the peripheral edge of the separators 3.

[0029] 1, the rear end unit 40 has a plurality of through holes 401-406 that penetrate the end unit 40 in the front-to-rear direction at positions corresponding to the through holes 211-216 and 311-316. The front end unit 40 does not have the through holes 401-406. The front end unit 40 may be referred to as the dry-side end unit, and the rear end unit 40 may be referred to as the wet-side end unit. For convenience, the through holes 401-406 are shown as being substantially rectangular, but the shape of the through holes 401-406 is not limited to this.

[0030] A fuel gas tank storing high-pressure fuel gas is connected to through-hole 401 via an ejector, injector, etc., and the fuel gas is supplied to fuel cell stack 100 via through-hole 401 as shown by the solid arrow. This fuel gas is guided via through-holes 211 and 311 to an anode flow path PAa between electrode assembly 2 and rear plate 3R of separator 3. After passing through anode flow path PAa, the fuel gas (fuel exhaust gas) passes through through-holes 216 and 316 and is discharged from through-hole 406 as shown by the solid arrow.

[0031] An oxidant gas supply compressor is connected to the through-hole 404, and as indicated by the dotted arrow, the oxidant gas compressed by the compressor is supplied to the fuel cell stack 100 via the through-hole 404. This oxidant gas is guided via the through-holes 214 and 314 to the cathode flow path PAc between the electrode assembly 2 and the front plate 3F of the separator 3. After passing through the cathode flow path PAc, the oxidant gas (oxidant exhaust gas) passes through the through-holes 213 and 313 and is discharged from the through-hole 403 as indicated by the dotted arrow.

[0032] through hole 405 A pump for supplying cooling medium is connected to the through hole as shown by the dashed arrow. 405 A cooling medium is supplied to the fuel cell stack 100 through the through holes 215 and 315. This cooling medium is guided to the cooling flow path PAw between the front plate 3F and the rear plate 3R of the separator 3 through the through holes 215 and 315. After passing through the cooling flow path PAw, the cooling medium passes through the through holes 212 and 312 and is discharged from the through hole 402 as shown by the dashed-dotted arrow. The discharged cooling medium is cooled by heat exchange in the radiator and is supplied again to the fuel cell stack 100 through the through hole 405.

[0033] The above is a schematic configuration of the fuel cell stack 100. The fuel cell stack 100 according to this embodiment is characterized by the support structure of the cell stack 10, which is supported by the inner wall of the case 30. The cell stack 10 is constructed by stacking the power generating cells 1 (electrode assemblies 2, separators 3) while positioning them in the storage space SP0 within the case 30 via guide members 50. For this reason, the fuel cell stack 100 needs to be configured not only to accurately position the power generating cells 1, but also to facilitate stacking of the power generating cells 1. Taking this into consideration, the fuel cell stack 100 of this embodiment is configured as follows.

[0034] 3, 4A, and 4B are views of the cell stack 10 as viewed from the stacking direction. As shown in Figures 3, 4A, and 4B, guide members 50 of the same shape are interposed between the four side walls 300 of the case 30 and the four side surfaces (upper side surface 101, lower side surface 102, left side surface 103, and right side surface 104) of the cell stack 10. The cell stack 10 has a generally rectangular shape with the upper side surface 101 and lower side surface 102 as long sides and the left side surface 103 and right side surface 104 as short sides.

[0035] The guide member 50 has an elongated base 51 extending along the side wall 300 and a protruding portion 52 protruding substantially perpendicularly from the base 51, and the entire guide member 50 has a substantially T-shaped cross section. More specifically, the protruding portion 52 protrudes not from the center of the base 51 but from a position shifted from the center toward one end. The four guide members 50 do not have to have the same shape, but may have different shapes. For example, the upper and lower guide members 50 may have the same shape, while the right and left guide members 50 may have different shapes.

[0036] The guide member 50 is formed by extrusion molding using, for example, a resin as a constituent material, and has a constant cross-sectional shape in the front-to-rear direction. The guide member 50 extends over the entire length of the fuel cell stack 100 in the front-to-rear direction. The front end of the guide member 50 is supported by the front end unit 40 in FIG. 1 , and the rear end is supported by the rear end unit 40. For example, the end unit 40 may be provided with a recess or through-hole, and the front and rear ends of the guide member 50 may be fitted or inserted into this recess or through-hole to support the guide member 50.

[0037] A support portion 301 is provided on each of the four side walls 300 of the case 30, facing the storage space SP0. The support portion 301 has an engagement groove 302 that extends approximately parallel to each of the side surfaces 101 to 104 of the cell stack 10, and an entrance portion 303 that is the entrance of the engagement groove 302. If the direction extending along the side surfaces 101 to 104 when viewed from the stacking direction is defined as the length direction and the direction perpendicular to the length direction is defined as the width direction, the entrance portion 303 has a pair of protrusions 303a that protrude inward beyond both ends of the engagement groove 302 in the length direction so as to narrow the entrance of the engagement groove 302.

[0038] The length and width of the engagement groove 302 are the same or approximately the same as the length and width of the base 51 of the guide member 50, and the base 51 is fitted into the engagement groove 302. As a result, the position of the base 51 is restrained by the protrusion 303a, and the base 51 is supported integrally with the side wall 300. At this time, the tip of the protrusion 52 protrudes beyond the inlet 303 toward the center point P.

[0039] As shown in FIGS. 4A and 4B , the protrusion 52 has a pair of end faces 50 a, 50 b extending toward the center point P. When the guide member 50 is supported by the support portion 301, the protrusion 52 of the upper guide member 50 facing the upper surface 101 of the cell stack 10 is located to the right of the center point P, and the protrusion 52 of the lower guide member 50 facing the lower surface 102 is located to the left of the center point P. More specifically, the upper protrusion 52 and the lower protrusion 52 are located symmetrically with respect to the center point P. Therefore, the distance from the center point P to the left end face 50 a of the upper protrusion 52 is the same as the distance from the center point P to the right end face 50 a of the lower protrusion 52. Furthermore, the distance from the center point P to the right end face 50 b of the upper protrusion 52 is the same as the distance from the center point P to the left end face 50 b of the lower protrusion 52.

[0040] With the guide members 50 supported by the support portions 301, the protrusion 52 of the left-side guide member 50 facing the left side surface 103 of the cell stack 10 is located above the center point P, and the protrusion 52 of the right-side guide member 50 facing the right side surface 104 is located below the center point P. More specifically, the left-side protrusion 52 and the right-side protrusion 52 are located symmetrically with respect to the center point P. Therefore, the distance from the center point P to the upper end face 50b of the left-side protrusion 52 is the same as the distance from the center point P to the lower end face 50b of the right-side protrusion 52. Furthermore, the distance from the center point P to the lower end face 50a of the left-side protrusion 52 is the same as the distance from the center point P to the upper end face 50a of the right-side protrusion 52.

[0041] Positioning portions PT11 to PT14, PT21 to PT24, and PT31 to PT34 are provided on the upper surface 101, lower surface 102, left surface 103, and right surface 104 of the electrode assembly 2, first separator 31, and second separator 32, respectively, in correspondence with the guide member 50. The electrode assembly 2, first separator 31, and second separator 32 are positioned relative to the case 30 via the guide member 50 and the positioning portions PT11 to PT14, PT21 to 24, and PT31 to 34.

[0042] 4A, a recess 101a is provided in the left-right center of the upper surface 101 of the first separator 31. A substantially rectangular protrusion 331 that protrudes upward is provided in the center of the recess 101a and serves as a positioning portion PT21. The vertical position of the upper end surface of the protrusion 331 is substantially the same as the vertical position of the upper surface 101 on both the left and right sides of the recess 101a. A right end surface 331a of the protrusion 331 extends vertically, i.e., perpendicular to the upper surface 101, so as to abut against the end surface 50a of the guide member 50.

[0043] Similarly, a recess 102a is provided in the center of the lower surface 102 of the first separator 31 in the left-right direction. A substantially rectangular protrusion 332 that protrudes downward is provided in the center of the recess 102a and serves as a positioning portion PT22. The vertical position of the lower end surface of the protrusion 332 is substantially the same as the vertical position of the lower surface 102 on both the left and right sides of the recess 102a. The left end surface 332a of the protrusion 332 extends in the vertical direction, i.e., perpendicular to the lower surface 102, so as to abut against the end surface 50a of the guide member 50.

[0044] The protrusions 331 and 332 are provided symmetrically with respect to the center point P. Therefore, the distance from the center point P to the right end face 331a of the protrusion 331 and the distance from the center point P to the left end face 332a of the protrusion 332 are equal to each other.

[0045] The left side surface 103 and the right side surface 104 of the first separator 31 are provided with generally rectangular recesses 341 and 342 as positioning portions PT23 and PT24, respectively. The width (vertical length) of the recesses 341 and 342 is wider than the width of the protrusion 52 of the guide member 50. The protrusion 52 of the left guide member 50 is inserted into the recess 341, and the protrusion 52 of the right guide member 50 is inserted into the recess 342. The recesses 341 and 342 are provided symmetrically with respect to the center point P.

[0046] More specifically, the left recess 341 is provided such that an upper end surface 341a abuts against the end surface 50b of the guide member 50 above the center point P, and a lower end surface 341b is spaced apart from the end surface 50a of the guide member 50. The right recess 342 is provided such that a lower end surface 342b abuts against the end surface 50b of the guide member 50 below the center point P, and a upper end surface 342a is spaced apart from the end surface 50a of the guide member 50.

[0047] As described above, in this embodiment, the right end surface 331a of the upper convex portion 331 and the left end surface 332a of the lower convex portion 332 of the first separator 31 abut against the left end surface 50a of the upper guide member 50 and the right end surface 50a of the lower guide member 50, respectively, thereby preventing left-right movement of the first separator 31. Furthermore, the upper end surface 341a of the left recess 341 and the lower end surface 342b of the right recess 342 of the first separator 31 abut against the upper end surface 50b of the left guide member 50 and the lower end surface 50b of the right guide member 50, respectively, thereby preventing up-down movement of the first separator 31.

[0048] Furthermore, since right end surface 331a of protrusion 331 and left end surface 332a of protrusion 332 each abut against guide member 50, clockwise rotation (direction of arrow R1) of first separator 31 is prevented about center point P. Furthermore, since upper end surface 341a of recess 341 and lower end surface 342b of recess 342 each abut against guide member 50, counterclockwise rotation (direction of arrow R2) of first separator 31 is prevented about center point P. As a result, movement and rotation of first separator 31 relative to case 30 are prevented, and first separator 31 can be accurately positioned and held in storage space SP0 of case 30 while being spaced apart from the inner wall (side wall 300) of case 30.

[0049] 4B, a recess 101b is provided in the center of the upper surface 101 of the second separator 32 in the left-right direction. A substantially rectangular protrusion 351 that protrudes upward is provided in the center of the recess 101b and serves as a positioning portion PT31. The vertical position of the upper end surface of the protrusion 351 is substantially the same as the vertical position of the upper surface 101 on both the left and right sides of the recess 101b. A left end surface 351a of the protrusion 351 extends vertically, i.e., perpendicular to the upper surface 101, so as to abut against the end surface 50b of the guide member 50.

[0050] Similarly, a recess 102b is provided in the center of the lower surface 102 of the second separator 32 in the left-right direction. A substantially rectangular protrusion 352 that protrudes downward is provided in the center of the recess 102b and serves as a positioning portion PT32. The vertical position of the lower end surface of the protrusion 352 is substantially the same as the vertical position of the lower surface 102 on both the left and right sides of the recess 102b. A right end surface 352a of the protrusion 352 extends in the vertical direction, i.e., perpendicular to the lower surface 102, so as to abut against the end surface 50b of the guide member 50.

[0051] The protrusions 351 and 352 are provided symmetrically with respect to the center point P. Therefore, the distance from the center point P to the left end face 351a of the protrusion 351 and the distance from the center point P to the right end face 352a of the protrusion 352 are equal to each other.

[0052] No. 2Separator 32 The left side surface 103 and the right side surface 104 of the guide member 50 are provided with generally rectangular recesses 361 and 362 as positioning portions PT33 and PT34, respectively. The width (vertical length) of the recesses 361 and 362 is wider than the width of the protrusion 52 of the guide member 50. The protrusion 52 of the left guide member 50 is inserted into the recess 361, and the protrusion 52 of the right guide member 50 is inserted into the recess 362. The recesses 361 and 362 are provided symmetrically with respect to the center point P.

[0053] More specifically, the left recess 361 is provided such that a lower end surface 361b abuts against the end surface 50a of the guide member 50 above the center point P, and the upper end surface 361a and the end surface 50b of the guide member 50 are spaced apart. The right recess 362 is provided such that an upper end surface 362a abuts against the end surface 50a of the guide member 50 below the center point P, and the lower end surface 362b and the end surface 50b of the guide member 50 are spaced apart.

[0054] As described above, in this embodiment, the left end surface 351a of the upper convex portion 351 and the right end surface 352a of the lower convex portion 352 of the second separator 32 abut against the right end surface 50b of the upper guide member 50 and the left end surface 50b of the lower guide member 50, respectively, thereby preventing left-right movement of the second separator 32. Furthermore, the lower end surface 361b of the left recess 361 and the upper end surface 362a of the right recess 362 of the second separator 32 abut against the lower end surface 50a of the left guide member 50 and the lower end surface 50a of the right guide member 50, respectively, thereby preventing up-down movement of the second separator 32.

[0055] Furthermore, because left end surface 351a of protrusion 351 and right end surface 352a of protrusion 352 each abut against guide member 50, counterclockwise rotation (direction of arrow R2) of second separator 32 about center point P is prevented. Furthermore, because lower end surface 361b of recess 361 and upper end surface 362a of recess 362 each abut against guide member 50, clockwise rotation (direction of arrow R1) of second separator 32 about center point P is prevented. As a result, movement and rotation of second separator 32 relative to case 30 are prevented, and second separator 32 can be accurately positioned and held in storage space SP0 of case 30 while being spaced apart from the inner wall (side wall 300) of case 30.

[0056] 4A and 4B, the protrusions 331, 332 of the first separator 31 and the protrusions 351, 352 of the second separator 32 are disposed on opposite sides of the guide member 50 in the left-right direction. Therefore, the protrusions 331, 332 of the first separator 31 and the protrusions 351, 352 of the second separator 32 are shifted in the left-right direction without overlapping each other when viewed from the stacking direction (front-rear direction). That is, the right end surface 331a of the protrusion 331 is located to the left of the left end surface 351a of the protrusion 351, and the left end surface 332a of the protrusion 332 is located to the right of the right end surface 352a of the protrusion 352. This increases the insulation distance between the protrusions 331, 332 and the protrusions 351, 352.

[0057] As shown in FIG. 3, a recess 101c is provided in the left-right center of the upper side surface 101 of the frame 21 of the electrode assembly 2. A substantially rectangular protrusion 261 that protrudes upward is provided in the center of the recess 101c. The vertical position of the upper end surface of the protrusion 261 is substantially the same as the vertical position of the upper side surface 101 on both the left and right sides of the recess 101c. Similarly, a recess 102c is provided in the left-right center of the lower side surface 102 of the frame 21 of the electrode assembly 2. A substantially rectangular protrusion 262 that protrudes downward is provided in the center of the recess 102c. The vertical position of the lower end surface of the protrusion 262 is substantially the same as the vertical position of the lower side surface 102 on both the left and right sides of the recess 102c.

[0058] The protrusion 261 is provided to the right of the protrusion 262. Roughly rectangular recesses 271 and 272 are provided as positioning portions PT11 and PT12 at the left-right center of the protrusion 261 and the left-right center of the protrusion 262, respectively. The recesses 271 and 272 are provided symmetrically with respect to the center point P. The width (left-right length) of the recesses 271 and 272 is approximately the same as the width of the protrusion 52 of the guide member 50. The protrusion 52 of the upper guide member 50 is fitted into the recess 271, and the protrusion 52 of the lower guide member 50 is fitted into the recess 272. This makes it possible to prevent the electrode assembly 2 from moving in the left-right direction.

[0059] Approximately rectangular recesses 273, 274 are provided on the left side surface 103 and the right side surface 104 of the frame 21 of the electrode assembly 2 as positioning portions PT13, PT14, respectively. The recesses 273 and 274 are provided symmetrically with respect to the center point P. The width (vertical length) of the recesses 273, 274 is approximately the same as the width of the protrusion 52 of the guide member 50. The protrusion 52 of the left guide member 50 is fitted into the recess 273, and the protrusion 52 of the right guide member 50 is fitted into the recess 274. This makes it possible to prevent the electrode assembly 2 from moving in the vertical direction.

[0060] While the separator 3 is made of metal, the frame 21 is made of resin or rubber. Therefore, the frame 21 has lower rigidity than the separator 3 and is easily deformed. Therefore, the protrusion 52 can be easily fitted into the recesses 271-274. Instead of providing the recesses 271-274 on the frame 21, a recess wider than the protrusion or recesses 271-274 may be provided as in the separator 3 of FIGS. 4A and 4B, so that only one end surface of the protrusion 52 abuts against one end surface of the protrusion or wider recess.

[0061] The protrusions 261, 262 of the frame 21 are interposed between the protrusions 331, 332 of the first separator 31 and the protrusions 351, 352 of the second separator 32. Furthermore, because the widths of the recesses 273, 274 of the frame 21 are narrow, the frame 21 is interposed between the recesses 341, 342 of the first separator 31 and the recesses 361, 362 of the second separator 32. This allows the separators to be well insulated from each other.

[0062] Although not shown in the drawings, in this embodiment, the vertical and horizontal lengths of the electrode assembly 2 are longer than the vertical and horizontal lengths of the separator 3. Therefore, when viewed from the stacking direction, the entire separator is covered by the electrode assembly 2. Therefore, the upper and lower ends of the frame 21 are located above and below the upper and lower ends of the separator 3, and the left and right ends of the frame 21 are located to the left and right of the left and right ends of the separator 3. This ensures that the separators are insulated from each other.

[0063] A method for assembling the fuel cell stack 100 according to this embodiment will now be described. FIGS. 5A to 5E are diagrams showing an example of the procedure for assembling the fuel cell stack 100. When assembling the fuel cell stack 100, the guide members 50 are manufactured in advance by extrusion molding or the like, and guide members 50 of a predetermined length are prepared (preparation step). Next, as shown in FIG. 5A, the case 30 is fixed to the end plate 41 of the end unit 40 on the wet side (the front side in FIG. 1) using bolts (case attachment step). A recess 41a is provided on the upper surface of the end plate 41 in correspondence with the position of the guide member 50.

[0064] 5B, the guide member 50 is inserted from above the case 30 along the engagement groove 302 provided on the inner surface of the side wall 300 of the case 30. Then, the lower end of the guide member 50 is fitted into the recess 41a on the upper surface of the end plate 41 (guide insertion step). At this time, before or after fitting the guide member 50, an extension guide member 55 having the same cross-sectional shape as the guide member 50 is attached to the upper end surface of the guide member 50 (extension guide attachment step). For example, a pin is provided protruding from the lower end surface of the extension guide member 55, a bottomed recess is provided on the upper end surface of the guide member 50, and the pin is fitted into the bottomed recess, thereby detachably attaching the extension guide member 55 to the guide member 50.

[0065] Next, the wet-side insulating plate and terminal plate are inserted into the case 30 along the extended guide member 55 and guide member 50 and stacked in order. Furthermore, as shown in Fig. 5C, a predetermined number of electrode assemblies 2 and separators 3 are housed in the case 30 from above along the extended guide member 55 and guide member 50 and stacked (stacking process). This completes the cell stack 10.

[0066] In this case, end faces 50a and 50b of protrusion 52 of guide member 50 abut against end faces 331a, 332a, 351a, and 352a of convex portions 331, 332, 351, and 352 of separator 3, and end faces 50a and 50b of protrusion 52 of guide member 50 abut against end faces 341a, 342b, 361b, and 362a of concave portions 341, 342, 361, and 362 of separator 3, so that separator 3 is positioned relative to case 30 and stacked within case 30. Furthermore, protrusion 52 of guide member 50 fits into concave portions 271 to 274 of electrode assembly 2, so that electrode assembly 2 is stacked within case 30 while being positioned relative to case 30. This allows cell stack 10 to be configured with electrode assembly 2 and separator 3 accurately positioned.

[0067] In particular, only one of the pair of end faces 50a, 50b of the protruding portion 52 of the guide member 50 abuts against the convex portions 331, 332, 351, 352 and concave portions 341, 342, 361, 362 of the separator 3. Therefore, frictional resistance is small when the separator 3 is lowered along the guide member 50, and the separators 3 can be easily stacked. Note that a single electrode assembly 2 and a single separator 3 (e.g., the second separator 32) may be previously joined together to form a set of unit cells, and a predetermined number of these unit cells may be lowered within the case 30 along the extension guide member 55 and the guide member 50 to form the cell stack 10.

[0068] Next, the terminal plate and insulating plate on the dry side (rear side in FIG. 1 ) are lowered along the extension guide member 55 and stacked in order. Then, as shown in FIG. 5D , the dry-side end plate 41 is lowered along the extension guide member 55. More specifically, the dry-side end plate 41 has through-holes 41b at positions corresponding to the guide members 50. The end plate 41 is placed above the cell stack 10 (strictly speaking, the insulating plate) while the extension guide member 55 is inserted through the through-holes 41b (final stacking step). Then, a pressure is applied from above the end plate 41 using a press (not shown). While maintaining the dry-side end plate 41 at a predetermined height, the dry-side end plate 41 is fixed to the case 30 using bolts (fixing step). In this state, the extension guide member 55 protrudes upward from the dry-side end plate 41.

[0069] Next, as shown in Fig. 5E, the extension guide member 55 is pulled out of the guide member 50 via the through hole 41b (pulling out step). Finally, the through hole 41b of the end plate 41 is covered with a cover (not shown) via a sealing material to seal the through hole 41b (sealing step). The cover is fastened to the end plate 41 using, for example, bolts. This completes the assembly of the fuel cell stack 100.

[0070] According to this embodiment, the following effects can be achieved. (1) The fuel cell stack 100 includes a cell stack 10 constructed by stacking power generating cells 1 each having an electrode assembly 2 including an electrolyte membrane 23, an anode electrode 24, and a cathode electrode 25, and a separator 3; a case 30 surrounding the cell stack 10; a guide member 50 protruding from the inner wall of the case 30 toward the cell stack 10 and extending along the stacking direction of the cell stack 10; and positioning portions PT11-PT14, PT21-PT24, PT31-PT34 provided on the edges (upper side 101, lower side 102, left side 103, and right side 104) of the power generating cells 1 corresponding to the guide member 50 and positioning the power generating cells 1 relative to the case 30 (Figures 1-4B). The positioning portions PT21, PT22, PT31, and PT32 have convex portions (first convex portions) 331 and 351 and convex portions (second convex portions) 332 and 352 that protrude from the upper surface 101 and the lower surface 102 of the power generating cell 1, which face the inner wall of the case 30, respectively, toward the inner wall (FIGS. 4A and 4B). The convex portions 331 and 351 and the convex portions 332 and 352 have end faces 331a and 351a that extend substantially perpendicularly from the upper surface 101 and end faces 332a and 352a that extend substantially perpendicularly from the lower surface 102, respectively (FIGS. 4A and 4B). The guide member 50 includes an upper guide member 50 provided to the right of the protrusion 331 and to the left of the protrusion 351 and having end faces 50a, 50b abutting against the end faces 331a, 351a, and a lower guide member 50 provided to the left of the protrusion 332 and to the right of the protrusion 352 and having end faces 50a, 50b abutting against the end faces 332a, 352a (Figures 4A and 4B).

[0071] According to this configuration, only one of the left-right end faces 50a, 50b of the protrusion 52 of the guide member 50 abuts against the end faces 331a, 332a, 351a, 352a of the convex portions 331, 332, 351, 352 of the power-generating cells 1 (separators 3). This reduces frictional resistance between the power-generating cells 1 and the guide member 50 when the power-generating cells 1 are stacked. This allows the power-generating cells 1 to be easily stacked without providing a coating layer on the guide member 50, enabling the fuel cell stack 100 to be constructed inexpensively. Furthermore, the upper convex portions 331, 351 and the lower convex portions 332, 352 of the power-generating cells 1 abut against the guide member 50 at the end faces 331a, 332a and end faces 351a, 352a that are in different left-right directions. This allows the power-generating cells 1 to be stacked while being positioned within the case.

[0072] (2) The protrusions 331, 351 and the protrusions 332, 352 are provided symmetrically with respect to a center point P that is located in the center of the power generating cell 1 when viewed from the stacking direction (FIGS. 4A and 4B). As a result, the positioning portions PT21, PT22, PT31, and PT32 are provided symmetrically on the upper surface 101 and the lower surface 102 of the power generating cell 1, thereby enabling the power generating cell 1 to be positioned satisfactorily.

[0073] (3) The case 30 has a plurality of inner wall surfaces that face the upper surface 101, lower surface 102, left side surface 103, and right side surface 104 of the power generating cell 1 (FIGS. 4A and 4B). Guide members 50 are provided on each of the inner wall surfaces, and positioning portions PT11 to PT14, PT21 to PT24, and PT31 to PT34 are provided on the upper surface 101, lower surface 102, left side surface 103, and right side surface 104 of the power generating cell 1, respectively. This allows the power generating cell 1 to be positioned accurately in the left-right and up-down directions.

[0074] (4) The separator 3 has a first separator 31 arranged facing the front surface 2a (first surface) of the electrode assembly 2 and a second separator 32 arranged facing the rear surface 2b (second surface) of the electrode assembly 2 (FIG. 1). The convex portion (first convex portion) 331 and the convex portion (second convex portion) 332 of the first separator 31 are arranged to be located on the left side (first direction side) of the upper guide member 50 and the right side (second direction side) of the lower guide member 50, respectively (FIG. 4A). The convex portion (first convex portion) 351 and the convex portion (second convex portion) 352 of the second separator 32 are arranged to be located on the right side (second direction side) of the upper guide member 50 and the left side (first direction side) of the lower guide member 50, respectively (FIG. 4B). As a result, the guide member 50 is sandwiched between the protrusions 331, 332 of the first separator 31 and the protrusions 351, 352 of the second separator 32, so that the pair of separators 31, 32 can be firmly positioned and held relative to the guide member 50.

[0075] (5) The power generating cell 1 has four sides (first and second sides, and third and fourth sides) that each constitute an edge and face each other, i.e., an upper side surface 101 and a lower side surface 102 that face each other, and a left side surface 103 and a right side surface 104 that face each other (FIGS. 4A and 4B). The convex portions (first convex portions) 331, 351 and the convex portions (second convex portions) 332, 352 are provided on the upper side surface 101 and the lower side surface 102, respectively (FIGS. 4A and 4B). As a result, the convex portions 331, 351 and the convex portions 332, 352 are provided on the upper side surface 101 and the lower side surface 102 that face each other, so that the power generating cell 1 can be properly positioned in the left-right direction.

[0076] (6) The power generating cell 1 has through holes 211-216, 311-316 through which gas and cooling medium flow near the left side surface 103 and the right side surface 104 (FIGS. 3, 4A, 4B). The positioning portions PT23, PT24, PT33, PT34 have recesses (first recesses) 341, 361 and recesses (second recesses) 342, 362 provided in the left side surface 103 and the right side surface 104, respectively (FIGS. 4A, 4B). The guide members 50 further include a left guide member 50 that is inserted into the recesses 341, 361 and has end faces 50a, 50b that abut against the upper end face 341a of the recess 341 and the lower end face 361b of the recess 361, and a right guide member 50 that is inserted into the recesses 342, 362 and has end faces 50a, 50b that abut against the lower end face 342b of the recess 342 and the upper end face 362a of the recess 362 ( FIGS. 4A and 4B ). As a result, the recesses 341, 361 and the recesses 342, 362 are provided on the opposing left side face 103 and right side face 104, so that the power generating cell 1 can be properly positioned in the up-down direction as well. The left side surface 103 and the right side surface 104 are provided with recesses 341, 361, 342, 362 instead of protrusions as positioning portions PT23, PT24, PT33, PT34, so that the power generating cell 1 can be prevented from becoming large in the left-right direction.

[0077] (7) The recesses 341, 361 and the recesses 342, 362 are provided symmetrically with respect to the center point P located at the center of the power generating cell 1 when viewed from the stacking direction (FIGS. 4A and 4B). As a result, the positioning portions PT23, PT24, PT33, and PT34 are provided symmetrically on the left side surface 103 and the right side surface 104 of the power generating cell 1, thereby enabling the power generating cell 1 to be positioned properly.

[0078] (8) The electrode assembly 2 includes an assembly 20 including an electrolyte membrane 23, an anode electrode 24, and a cathode electrode 25, and a frame 21 having an opening 21a in which the assembly 20 is disposed (FIG. 3). The protrusions 331, 332, 351, and 352 are provided on the upper and lower surfaces 101 and 102 of the separator 3 (FIGS. 4A and 4B). The frame 21 includes recesses 271-274 on the upper, lower, left, and right surfaces 103 and 104, respectively, with which the guide member 50 engages (FIG. 3). This allows the electrode assembly 2 to be properly positioned relative to the case 30, forming the cell stack 10. The frame 21, as a frame member, is less rigid and more easily deformed than the separators 3, allowing the guide member 50 to easily engage with the recesses 271-274 when the power-generating cells 1 are stacked.

[0079] (9) The size (left-right length and up-down length) of the frame 21 in a plane perpendicular to the stacking direction is larger than the size (left-right length and up-down length) of the separator 3. As a result, the frame 21 is interposed between the protrusions 331, 332 of the first separator 31 and the protrusions 351, 352 of the second separator 32, thereby ensuring sufficient insulation between the first separator 31 and the second separator 32.

[0080] The above embodiment can be modified in various ways. Several modifications will be described below. In the above embodiment, the cell stack 10 is surrounded by the case 30 having a substantially rectangular parallelepiped shape, but the configuration of the housing is not limited to that described above. In the above embodiment, a guide member 50 separate from the case 30 is provided as a guide portion that protrudes from the inner wall of the case 30 toward the cell stack 10. However, the guide portion may be formed on the inner wall of the case 30. In the above embodiment, the first protrusions 331, 351 and the second protrusions 332, 352 are provided on the upper surface 101 (first edge portion) and the lower surface 102 (second edge portion) of the power generating cell 1. However, these protrusions may also be provided on the left side surface 103 or the right side surface 104.

[0081] In the above embodiment, the end faces 50a, 50b (first abutment surfaces) of the upper guide member 50 (first guide portion) abut against the end faces 331a, 351a (first end faces) of the upper convex portions 331, 351 of the power generation cell 1, and the end faces 50a, 50b (second abutment surfaces) of the lower guide member 50 (second guide portion) abut against the end faces 332a, 352a (second end faces) of the lower convex portions 332, 352 of the power generation cell 1. In addition, the end faces 50a, 50b (third abutment surfaces) of the left guide member 50 (third guide portion) abut against the end faces 341a, 361b (third end faces) of the left recesses 341, 361 (first recesses) of the power generation cell 1, and the end faces 50a, 50b (fourth abutment surfaces) of the right guide member 50 (fourth guide portion) abut against the end faces 342b, 362a (fourth end faces) of the right recesses 342, 362 (second recesses) of the power generation cell 1. The first and second end faces are provided on one side (first direction side) and the other side (second direction side) of the protrusions 331, 351 and the protrusions 332, 352 in the left-right direction, respectively. The third and fourth end faces are provided on one side (third direction side) and the other side (fourth direction side) of the recesses 341, 361 and the recesses 342, 362 in the up-down direction, respectively. However, the power generation cell may have any configuration as long as it has first and second protrusions having first and second end faces facing opposite directions at least on the first edge portion and the second protrusion opposite thereto. The recesses 341, 361 and the recesses 342, 362 on the third and fourth side faces may be omitted. Protrusions may be provided on the third and fourth side faces, similar to the first and second side faces.

[0082] The above description is merely an example, and the present invention is not limited to the above-described embodiment and modifications as long as the features of the present invention are not impaired. One or more of the above-described embodiment and modifications can be arbitrarily combined, and modifications can also be combined with each other.

[0083] 1 power generating cell, 2 electrode assembly, 3 separator, 10 cell stack, 20 bonded body, 21 frame, 23 electrolyte membrane, 24 anode electrode, 25 cathode electrode, 30 case, 31 first separator, 32 second separator, 50 guide member, 50a, 50b end surface, 100 fuel cell stack, 101 upper surface, 102 lower surface, 103 left side surface, 104 right side surface, 211 to 216 through holes, 271 to 274 recesses, 311 to 316 through holes, 331, 332, 351, 352 convex portions, 331a, 332a, 351a, 352a end surface, 341, 342, 361, 362 recesses, 341a, 342b, 361b, 362a End face, PT11~PT14, PT21~PT24, PT31~PT34 positioning part, P center point

Claims

1. a cell stack formed by stacking power generation cells each having a membrane electrode assembly including an electrolyte membrane and an electrode, and a separator; a housing that surrounds the cell stack; a guide portion that protrudes from an inner wall of the housing toward the cell stack and extends along the stacking direction of the cell stack; a positioning portion provided on an edge of the power generating cell corresponding to the guide portion and positioning the power generating cell relative to the housing, the positioning portion has a protrusion that protrudes from an edge of the power generation cell toward the inner wall, the protrusions include a first protrusion and a second protrusion that protrude from a first edge portion of the power generation cell that faces the inner wall and a second edge portion that is opposite the first edge portion toward the inner wall, respectively; the first protrusion and the second protrusion each have a first end surface extending substantially perpendicularly from the first edge and a second end surface extending substantially perpendicularly from the second edge; When the directions in which the first edge portion and the second edge portion extend and which are opposite to each other in a plane perpendicular to the stacking direction are defined as a first direction and a second direction, the guide portion: a first guide portion provided on one side of the first protrusion in the first direction or the second direction and having a first contact surface that contacts the first end surface; a second guide portion provided on the other side of the second protrusion in either the first direction or the second direction, and having a second abutment surface that abuts the second end surface.

2. 2. The fuel cell stack according to claim 1, a fuel cell stack characterized in that the first convex portion and the second convex portion are arranged symmetrically with respect to a center point located in the center of the power generation cell when viewed from the stacking direction.

3. 2. The fuel cell stack according to claim 1, the housing has a plurality of inner wall surfaces facing a plurality of edge portions of the power generating cell, The fuel cell stack, wherein the guide portion is provided on each of the plurality of inner wall surfaces, and the positioning portion is provided on each of the plurality of edge portions.

4. The fuel cell stack according to any one of claims 1 to 3, the separator includes a first separator disposed facing a first surface of the membrane electrode assembly, and a second separator disposed facing a second surface of the membrane electrode assembly opposite to the first surface, the first convex portion and the second convex portion of the first separator are provided to be located on the first direction side of the first guide portion and on the second direction side of the second guide portion, respectively; a first convex portion and a second convex portion of the second separator arranged to be located on the second direction side of the first guide portion and the first direction side of the second guide portion, respectively.

5. 2. The fuel cell stack according to claim 1, The power generating cells each constitute the edge portion and have a first side and a second side opposed to each other, and a third side and a fourth side opposed to each other, The fuel cell stack, wherein the first protrusion and the second protrusion are provided on the first side and the second side, respectively.

6. 6. The fuel cell stack according to claim 5, the power generating cell is provided with through holes near the third side and the fourth side through which gas and a cooling medium flow; the positioning portion has a first recess and a second recess provided on the third side and the fourth side, respectively; When directions that are opposite to each other in a plane perpendicular to the stacking direction and that are orthogonal to the first direction and the second direction are defined as a third direction and a fourth direction, the guide portion: a third guide portion that is inserted into the first recess and has a third abutment surface that abuts on a third end surface of the first recess on one side in either the third direction or the fourth direction; a fourth guide portion that is inserted into the inside of the second recess and has a fourth abutment surface that abuts on a fourth end surface of the second recess on the other side of either the third direction or the fourth direction.

7. 7. The fuel cell stack according to claim 6, A fuel cell stack characterized in that the first recess and the second recess are arranged symmetrically with respect to a center point located in the center of the power generation cell when viewed from the stacking direction.

8. 2. The fuel cell stack according to claim 1, the membrane electrode structure includes a membrane electrode assembly including the electrolyte membrane and the electrodes, and a frame member having an opening in which the membrane electrode assembly is disposed, the protrusion is provided on an edge of the separator, The frame member has a recess in an edge portion thereof with which the guide portion engages.

9. 9. The fuel cell stack according to claim 8, A fuel cell stack, wherein the size of the frame member in a plane perpendicular to the stacking direction is larger than the size of the separator.

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