Fuel cell stack

Abstract

This fuel cell stack is provided with: a pair of first end units respectively disposed adjacent to one end surface and the other end surface of a cell laminate; a pair of second end units disposed on the outside of the pair of first end units so as to face the pair of first end units; a case having one end and the other end respectively fixed to the pair of second end units, and forming a housing space for housing the cell laminate; and elastic members interposed between the pair of first end units and the corresponding pair of second end units disposed opposite thereto, and having a sealing function in which the amount of contraction changes with relative movement of the pair of first end units and the cell laminate relative to the case in the laminate direction.

Description

fuel cell stack

[0001] The present invention relates to a fuel cell stack.

[0002] In recent years, technological developments related to fuel cells that contribute to energy efficiency have been underway to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. One known example of this type of fuel cell technology is a fuel cell stack configured to protect a cell stack arranged between a pair of end units against the input of impact loads (see, for example, Patent Document 1). In the fuel cell stack described in Patent Document 1, a load-receiving member is provided on the outside of the cell stack so as to span between the pair of end plates. The load-receiving member has one end fixed to one end unit and the other end movably fixed to the other end unit.

[0003] Patent No. 5144087

[0004] However, in a configuration in which a load-receiving member is provided on the outside of the cell stack, as in the fuel cell stack described in Patent Document 1, it is necessary to add large components, which increases the size of the fuel cell stack and the cost.

[0005] A fuel cell stack according to one aspect of the present invention comprises a cell stack formed by stacking in a predetermined direction a plurality of power generation cells, each having a membrane electrode assembly including an electrolyte membrane and an electrode, and a separator; a pair of first end units arranged adjacent to one end face and the other end face of the cell stack in the predetermined direction, a pair of second end units arranged opposite the pair of first end units and outside the pair of first end units; a case having one end and the other end fixed to the pair of second end units so that the cell stack is held in a state in which a predetermined compressive load is applied in the predetermined direction, and forming a storage space to house the cell stack; and an elastic member interposed between at least one of the pair of first end units and at least one of the pair of second end units facing each other, and having a sealing function whose amount of contraction changes in accordance with the relative movement of at least one of the pair of first end units and the cell stack in the predetermined body direction relative to the case.

[0006] According to the present invention, a fuel cell stack with excellent impact resistance can be constructed without requiring the addition of large components.

[0007] Fig. 1 is a perspective view schematically showing the overall configuration of a fuel cell stack according to an embodiment of the present invention. Fig. 2 is a cross-sectional view schematically showing the configuration of a main part of a cell laminate included in the fuel cell stack of Fig. 1. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 1. Fig. 4 is a cross-sectional view showing the configuration of a main part of a fuel cell stack according to an embodiment of the present invention. Fig. 5 is a cross-sectional view showing the configuration of a main part of a fuel cell stack as a reference example.

[0008] Hereinafter, an embodiment of the present invention will be described with reference to Figures 1 to 5. A fuel cell stack according to an embodiment of the present invention is a main component included in a fuel cell. The fuel cell is mounted, for example, in a vehicle and can generate power to drive the vehicle. The fuel cell can also be mounted in mobile 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. Figure 1 is a perspective view that shows a schematic overall configuration of a fuel cell stack 100 according to an embodiment of the present invention. For convenience, the three mutually orthogonal axial directions shown in the figure will be 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.

[0010] 1, the fuel cell stack 100 has a cell stack 10, end units 40 arranged on both the front and rear sides of the cell stack 10, and a case 30 that surrounds the cell stack 10, and has a generally rectangular parallelepiped shape as a whole. The length of the fuel cell stack 100 in the left-right direction is longer than the length in the up-down direction.

[0011] The end unit 40 has an end plate 41 at the outermost position in the front-to-rear direction. The case 30 has four generally rectangular side walls 300 that face the top, right, bottom, and left sides of the cell stack 10, respectively. These four side walls 300 form a generally box-shaped storage space SP0 with open front and rear sides. The case 30 is made of a metal such as aluminum or iron. The end plate 41 is also made of metal. The front and rear sides of the case 30 are covered with the end plate 41.

[0012] 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 made of resin that extend in the front-to-rear direction, and are attached in advance to the inner surfaces of the side walls 300, respectively.

[0013] 1 shows a cutaway view of a side wall 300 of the case 30. As shown in portion 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-to-rear direction while being guided by a guide member 50. Therefore, the front-to-rear direction corresponds to the stacking direction of the cell stack 10.

[0014] The power-generating cell 1 has a unitized electrode assembly 2 (hereinafter referred to as UEA) having a membrane electrode assembly including an electrolyte membrane and electrodes, and separators 3 arranged on both the front and rear sides of the UEA 2 to sandwich the UEA 2. The UEA 2 and the separators 3 are arranged alternately in the front-to-rear direction. The UEA 2 can also be called a membrane electrode structure.

[0015] 2 is a cross-sectional view showing a schematic configuration of the main components of the cell stack 10, i.e., a cross-sectional view showing a schematic configuration of a power generation area AR1 at the center in the vertical and horizontal directions and a non-power generation area AR2 outside the power generation area AR1. For convenience, FIG. 2 shows a single separator 3 and a pair of UEAs 2 on both the front and rear sides of the separator 3. The inside of FIG. 2 refers to the center side of the power generation cell 1 in the vertical and horizontal directions, and the outside refers to the outer edge side of the power generation cell 1. 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.

[0016] 2, the separator 3 has a pair of front and rear thin metal plates (a front plate 3F and a rear plate 3R) with a corrugated cross section, and is integrally formed by joining the outer peripheral edges of the front plate 3F and the rear plate 3R. The separator 3 is made of a conductive material with excellent corrosion resistance, such as titanium, a titanium alloy, or stainless steel. The separator 3 is formed into an uneven shape by press molding or the like so as to form a gas flow path between the separator 3 and the UEA2 (membrane electrode assembly 20) in the power generation region AR1.

[0017] More specifically, the rear plate 3R is an anode-side separator (anode separator), and an anode flow path PAa through which a fuel gas containing hydrogen flows is formed between the anode separator 3 and the UEA 2. The front plate 3F is, for example, a cathode-side separator (cathode separator), and a cathode flow path PAc through which an oxidant gas containing oxygen flows is formed between the cathode separator 3 and the UEA 2. The fuel gas and the oxidant gas are sometimes referred to as reactant gases without distinction between them.

[0018] The UEA 2 includes a membrane electrode assembly (MEA) 20 and a resin frame 21 that supports the entire outer periphery of the MEA 20. The MEA 20 includes 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 electrolyte membrane is, for example, a solid polymer electrolyte membrane. The anode electrode includes an electrode catalyst layer formed on the front surface of the electrolyte membrane and serving as a reaction field for electrode reactions, and a gas diffusion layer provided on the front surface of the electrode catalyst layer and diffusing and supplying fuel gas. The cathode electrode includes an electrode catalyst layer formed on the rear surface of the electrolyte membrane and serving as a reaction field for electrode reactions, and a gas diffusion layer provided on the rear surface of the electrode catalyst layer and diffusing and supplying oxidant gas.

[0019] At the anode electrode, fuel gas (hydrogen) supplied via the anode flow channel PAa and gas diffusion layer is ionized by the action of a catalyst and moves through the electrolyte membrane to the cathode electrode side. The electrons generated at this time pass through an external circuit and are extracted as electrical energy. At the cathode electrode, oxidant gas (oxygen) supplied via the cathode flow channel PAc and gas diffusion layer reacts with hydrogen ions introduced from the anode electrode and electrons transferred from the anode electrode to generate water. The generated water provides an appropriate humidity to the electrolyte membrane, and excess water is discharged outside the UEA2.

[0020] As shown in FIG. 1 , through holes 411 to 416 are opened in the front end unit 40. The through hole 411 is a through hole for supplying fuel gas into the inside of the cell stack 10. The through hole 412 is a through hole for discharging a coolant from the cell stack 10 to the outside. The through hole 413 is a through hole for discharging an oxidant gas from the cell stack 10 to the outside. The through hole 414 is a through hole for supplying an oxidant gas into the inside of the cell stack 10. The through hole 415 is a through hole for supplying a coolant into the inside of the cell stack 10. The through hole 416 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, multiple flow paths (internal manifolds) are formed extending in the front-rear direction so as to communicate with the through-holes 411 to 416. Fuel gas supplied via the through-hole 411 is guided to the anode flow path PAa inside the cell stack 10, and oxidant gas supplied via the through-hole 414 is guided to the cathode flow path PAc. This allows power generation in the power generation cell 1. After supplying the fuel gas and oxidant gas, they are discharged from the cell stack 10 via the through-holes 416 and 413, respectively. A cooling medium supplied via the through-hole 415 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 via the through-hole 412.

[0022] As shown in FIG. 2 , in the non-power generation area AR2, through holes 301, 201 that form internal manifolds are formed in the separator 3 and the frame 21 of the UEA2. The through holes 301, 201 in FIG. 2 are either through holes that form internal manifolds for supplying or discharging fuel gas or oxidant gas. A bead portion 31 that surrounds the entire periphery of the through hole 301 in the separator 3 protrudes in the front-to-rear direction. A thin-film sealing material 32 made of rubber, resin, or the like is fixed to the front end surface of the front bead portion 31 and the rear end surface of the rear bead portion 31. The bead portion 31 and the frame 21 are pressed together in a sealed state via the sealing material 32 under the action of a compressive load F.

[0023] Further outboard of the bead portion 31 of the separator 3, an outer bead portion 33 is provided that protrudes in the front-to-rear direction and surrounds the entire power generation region AR1 and the through-hole 301. As with the bead portion 31, a sealant 32 is fixed to the front end face of the front outer bead portion 33 and the rear end face of the rear outer bead portion 33. The outer bead portion 33 and the frame 21 are pressed together in a sealed state via the sealant 32 under the action of a compressive load F. At least one of the bead portion 31 and the frame 21 and the outer bead portion 33 and the frame 21 can also be pressed together in a sealed state without the sealant 32.

[0024] Fig. 3 is a cross-sectional view taken along line III-III in Fig. 1. For convenience, Fig. 3 shows only the shape of the outer edge of the cell stack 10. As shown in Fig. 3, side walls 300 of the case 30 are disposed opposite the top, right, bottom, and left sides of the cell stack 10. Each of these side walls 300 has an inner surface 30a facing the storage space SP0 and an outer surface 30b opposite the storage space SP0.

[0025] Guide support portions 35 that support the guide members 50 are provided on the inner surface 30a of the side wall 300 facing the storage space SP0. The guide support portions 35 protrude from the inner surface 30a of the side wall 300 toward the center of the case 30 and extend in the longitudinal direction (front-rear direction) of the side wall 300. The guide support portions 35 have, for example, recesses 35a in the portions facing the storage space SP0. The guide members 50 fit into the recesses 35a. The guide members 50 are elongated members made of resin that extend in the front-rear direction, and their cross-sectional shape is constant throughout the longitudinal direction (front-rear direction). The guide members 50 have, for example, recesses 51 on the surface facing the center of the case 30. The edges of the top, left, bottom, and right surfaces of the cell stack 10 fit into the recesses 51.

[0026] Specifically, convex portions 11 corresponding to the guide members 50 are provided on the top, left, bottom, and right surfaces of the separators 3 of the cell stack 10, and the separators 3 are stacked while the convex portions 11 fit into the concave portions 51. 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 guide member 50 also functions as a shock absorbing member that absorbs an external shock when it acts on the fuel cell stack 100. By interposing the guide member 50 between the cell stack 10 and the side wall 300 of the case 30, it is possible to prevent the cell stack 10 from coming into contact with the side wall 300 and being damaged when an impact acts on the fuel cell stack 100 in the vertical or horizontal direction. A shock absorbing member can also be provided separately from the guide member 50. For example, the shock absorbing member can be provided at the corners of the cell stack 10 in the vertical and horizontal directions.

[0028] Incidentally, when an external impact acts on the fuel cell stack 100 in the front-to-rear direction (stacking direction), the cell stack 10 moves in the front-to-rear direction relative to the case 30. As a result, a gap may be formed between the cell stack 10 and the end unit 40, which may result in leakage of reactant gases, etc. In this embodiment, to prevent such leakage, the end unit 40 is configured as follows.

[0029] 4 is a cross-sectional view showing a schematic configuration of a fuel cell stack 100 according to an embodiment of the present invention. As shown in FIG. 4, the end unit 40 has a pair of terminal plates 43 arranged on the outer sides of the cell stack 10 in the front-rear direction, a pair of insulating plates 42 arranged on the outer sides of the pair of terminal plates 43 in the front-rear direction, and a pair of end plates 41 arranged on the outer sides of the pair of insulating plates 42 in the front-rear direction.

[0030] The terminal plate 43 is a generally rectangular metal plate-like member and has a terminal portion for extracting the power generated by the electrochemical reaction in the cell stack 10. The insulating plate 42 is a generally rectangular non-conductive resin or rubber plate-like member that electrically insulates the terminal plate 43 from the end plate 41. The end plate 41 is a generally rectangular metal plate-like member made of metal or high-strength resin. The end plate 41 is sometimes referred to as the outer end unit 401, and the insulating plate 42 and terminal plate 43 are sometimes referred to as the inner end unit 402.

[0031] The outer end unit 401 is disposed in contact with the front and rear end faces of the case 30. Bolts 403 are inserted into the outer end unit 401. The bolts 403 are threaded into threaded holes 310 provided in the front and rear end faces of the case 30, thereby fastening the outer end unit 401 to the case 30. The outer dimensions of the inner end unit 402 are smaller than the outer dimensions of the inner wall surface of the case 30 when viewed in the stacking direction. Therefore, the inner end unit 402 is disposed in the storage space SP0 inside the case 30.

[0032] The cell stack 10 in the storage space SP0 is restricted from moving up and down and left and right by the guide members 50 (FIG. 3). Meanwhile, when the outer end unit 401 is fastened to the case 30, a compressive load F (FIG. 2) is applied to the cell stack 10 in the front-to-rear direction via the inner end unit 402. This restricts the movement of the cell stack 10 in the front-to-rear direction.

[0033] Seal members 44 made of rubber or other material are interposed between the fastening surfaces between the front and rear end faces of the case 30 and the outer end unit 401. This seals the fastening surfaces, forming a sealed storage space SP0 inside the outer end unit 401 and the case 30. Furthermore, seal members 45 made of rubber or other material are interposed between the pair of front and rear outer end units 401 and inner end unit 402. In particular, the seal member 45 between the rear outer end unit 401 and inner end unit 402 is provided so as to surround the through holes 411-416 ( FIG. 1 ) for supplying and discharging reactant gas and coolant. This seals the gap between the outer end unit 401 and inner end unit 402, preventing reactant gas and other gases from leaking into the case through the gap.

[0034] The seal member 45 may be, for example, an O-ring made of rubber and having a circular cross section. The seal member 45 is thicker than the seal material 32 (FIG. 2) attached to the end face of the bead portion 31, and it shrinks more. If the thickness of the seal member 45 before compression is d and the thickness after compression is h, the crushing ratio α of the seal member 45 is (d-h) / d×100 (percent). A range of the crushing ratio α is set for the seal member 45 to satisfy the required sealing performance. For example, the range is 10 to 30 percent.

[0035] Even if the amount of shrinkage of the seal member 45 changes, the sealing performance can be maintained as long as the crushing ratio α is within the usable range. For example, if the initial crushing ratio α is 30 percent, the sealing performance can be maintained even if the crushing ratio α changes to 10 percent. In this embodiment, the initial crushing ratio α is set so that the sealed state can be maintained even if the rear inner end unit 402 moves forward a predetermined amount relative to the case 30.

[0036] In the initial state, a minute gap is generated between the outer end unit 401 and the inner end unit 402. That is, a pressing force acts on the inner end unit 402 toward the outer end unit 401 due to the repulsive force of the cell stack 10 against the compressive load F during stacking, but the presence of the sealing member 45 maintains the minute gap against the pressing force. In the initial state, the gap between the outer end unit 401 and the inner end unit 402 may be zero.

[0037] From this state, if a rearward impact acts on the case 30, for example, the case 30 moves rearward relative to the cell stack 10, increasing the gap between the rear outer end unit 401 and the inner end unit 402. Alternatively, when the gap is initially set to 0, a gap occurs between the rear outer end unit 401 and the inner end unit 402. At this time, the amount of contraction of the rear seal member 45 decreases, reducing the crushing rate α, but the crushing rate α after the reduction is within the usable range. This makes it possible to prevent reactant gases and the like from leaking from the gap between the outer end unit 401 and the inner end unit 402, even when an impact acts on the case 30.

[0038] When a rearward impact acts on the case 30, the cell stack 10 presses the front end unit 40 forward due to inertial force. This increases the amount of contraction of the front seal member 45, allowing the seal member 45 to absorb the impact. In other words, the seal member 45 can function as an elastic body for absorbing impact. Although not shown in the figure, the seal member 45 is also provided inside the inner end unit 402. In other words, it is also interposed between the terminal plate 43 and the insulating plate 42.

[0039] Figure 5 is a diagram showing the reference example of Figure 4. The configuration of the end unit 40 differs between Figures 4 and 5. That is, in the reference example of Figure 5, the outer end unit 401 (end plate 41) and the inner end unit 402 (insulating plate 42, terminal plate 43) have the same outer dimensions when viewed in the stacking direction. Therefore, the inner end unit 402 abuts against the front and rear end surfaces of the case 30, and the outer end unit 401 abuts against the outside of the inner end unit 402.

[0040] Bolts 403 are inserted through the outer end unit 401 and the inner end unit 402 and screwed into threaded holes 310 in the case 30, thereby fastening the outer end unit 401 and the inner end unit 402 to the case 30. Identical seal members 44 are interposed between the fastening surfaces where the outer end unit 401 and the inner end unit 402 come into contact and between the fastening surfaces where the inner end unit 402 and the case 30 come into contact.

[0041] In this configuration, when a rearward impact is applied to the case 30, the case 30 moves rearward relative to the cell stack 10. As a result, a gap is formed between the rear inner end unit 402 and the cell stack 10, and there is a risk of reactant gas or the like leaking from this gap. In this regard, in the present embodiment, the inner end unit 402 is arranged so as to be movable in the front-to-rear direction within the case 30 via the seal member 45. As a result, when a rearward impact is applied to the case 30, the seal member 45 functions to prevent a gap from being formed between the rear inner end unit 402 and the cell stack 10.

[0042] The present embodiment can achieve the following advantageous effects: (1) The fuel cell stack 100 includes a cell stack 10 configured by stacking, in the front-to-rear direction, a plurality of power-generating cells 1, each of which has a UEA 2 including an electrolyte membrane and electrodes and separators 3, a pair of inner end units 402 disposed adjacent to the front and rear end faces of the cell stack 10, a pair of outer end units 401 disposed opposite the pair of inner end units 402 and outboard of the pair of inner end units 402 in the front-to-rear direction, a case 30 having a front end and a rear end fixed to the pair of outer end units 401 so as to hold the cell stack 10 in a state in which a predetermined compressive load F is applied in the front-to-rear direction, and forming an accommodation space SP0 for accommodating the cell stack 10, and a sealing member 45 interposed between the pair of opposing inner end units 402 and the pair of outer end units 401, and having a sealing function whose amount of contraction changes as the pair of inner end units 402 and the cell stack 10 move in the front-to-rear direction relative to the case 30 ( FIGS. 1 and 4 ).

[0043] With this configuration, when an impact is applied to the case 30 fixed to the vehicle and the cell stack 10 moves relatively forward and backward within the case, the amount of contraction of the sealing member 45 changes, thereby maintaining the sealing performance of the sealing member 45. Therefore, it is possible to configure a fuel cell stack 100 that has excellent impact resistance and sealing performance without requiring the addition of large components.

[0044] (2) The pair of inner end units 402 includes a pair of terminal plates 43 disposed adjacent to the front and rear end surfaces of the cell stack 10, and a pair of insulating plates 42 respectively interposed between the pair of terminal plates 43 and the pair of outer end units 401 (end plates 41) ( FIG. 4 ). The sealing member 45 is interposed between the pair of insulating plates 42 and the pair of end plates 41 ( FIG. 4 ). With this configuration, when a longitudinal impact is applied to the case 30, the gap between the insulating plate 42 and the end plate 41 changes. In this case, by interposing the sealing member 45 between the insulating plate 42 and the end plate 41, it is possible to prevent reactant gases and the like from leaking from the contact surfaces between the insulating plate 42 and the end plate 41.

[0045] (3) Of the pair of inner end units 402 and the pair of outer end units 401, the rear inner end unit 402 and the rear outer end unit 401 are provided with through-holes 411 to 416 for supplying and discharging reactant gases and cooling medium ( FIG. 1 ). A seal member 45 is interposed between the rear inner end unit 402 and the rear outer end unit 401 ( FIG. 4 ). This makes it possible to prevent leakage of reactant gases and the like through the through-holes 411 to 416.

[0046] Because the through-holes 411 to 416 for supplying and discharging reactant gases and cooling medium are not opened to the front end unit 40, the front seal member 45 is not necessary from the viewpoint of preventing leaks. However, in this embodiment, seal members 45 are provided not only on the rear side but also on the front side. As a result, when an impact acts on the case 30 in the front-to-rear direction, the impact can be well absorbed by the front and rear seal members 45.

[0047] (4) The separator 3 includes a rear plate 3R that faces each other and defines an anode flow path PAa through which fuel gas flows, and a front plate 3F that defines a cathode flow path PAc through which oxidizer gas flows ( FIG. 2 ). The rear plate 3R and the front plate 3F have bead portions 31 and sealing materials 32 that serve as convex sealing portions that abut against each other ( FIG. 2 ). The sealing materials 32 provided in the bead portions 31 make it difficult to prevent leakage from the gap between the outer end unit 401 and the inner end unit 402, and also make it difficult to absorb impacts in the front-to-rear direction. On the other hand, if a sealing member 45 is interposed between the outer end unit 401 and the inner end unit 402, leakage from the gap between the outer end unit 401 and the inner end unit 402 can be effectively prevented and impacts can be effectively absorbed in the front-to-rear direction.

[0048] The above embodiment can be modified in various ways. Several modifications will be described below. In the above embodiment, a pair of inner end units 402 are arranged as a pair of first end units adjacent to one end surface and the other end surface of the cell stack 10 in the front-rear direction, respectively. However, the configuration of the pair of first end units is not limited to the above. In the above embodiment, a pair of outer end units 401 are arranged as a pair of second end units facing the pair of inner end units 402 and outside the pair of inner end units 402. However, the configuration of the pair of second end units is not limited to the above. The stacking direction (predetermined direction) of the cell stack 10 is not limited to the front-rear direction, but may also be the left-right direction or the up-down direction.

[0049] In the above embodiment, the sealing members 45 are interposed between a pair of opposing inner end units 402 and a pair of opposing outer end units 401 as elastic members having a sealing function whose amount of contraction changes with relative movement in the front-to-rear direction of the pair of inner end units 402 and the cell stack 10 relative to the case 30. That is, although the sealing members 45 are provided on the front and rear end units 40, an elastic member may be provided on either one of the front and rear end units 40. The configuration of the elastic member is not limited to the sealing member 45 described above, as long as it has a sealing function.

[0050] In the above embodiment, the inner end unit 402 is formed by the terminal plate 43 as a current collecting member and the insulating plate 42 as an insulating member, and the seal member 45 is interposed between the insulating plate 42 and the outer end unit 401 (end plate 41). However, the configuration of the current collecting member and the insulating member is not limited to the above. In the above embodiment, the separator 3 includes the rear plate 3R (first plate) that forms the anode flow path PAa as a gas flow path through which the fuel gas (first reactant gas) flows and the front plate 3F (second plate) that forms the cathode flow path PAc as a gas flow path through which the oxidizer gas (second reactant gas) flows, and the rear plate 3R and the front plate 3F have the bead portion 31 and the seal material 32 as convex seal portions that abut against each other. However, the configuration of the separator 3 is not limited to the above.

[0051] 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.

[0052] REFERENCE SIGNS LIST 1 power generating cell, 2 integrated electrode assembly, 3 separator, 3F front plate, 3R rear plate, 10 cell stack, 30 case, 31 bead portion, 32 sealing material, 40 end unit, 41 end plate, 42 insulating plate, 43 terminal plate, 45 sealing member, 100 fuel cell stack, 401 outer end unit, 402 inner end unit, SP0 storage space, PAa anode flow path, PAc cathode flow path

Claims

1. A fuel cell stack comprising: a cell stack formed by stacking in a predetermined direction a plurality of power generation cells, each having a membrane electrode assembly including an electrolyte membrane and an electrode, and a separator; a pair of first end units arranged adjacent to one end face and the other end face of the cell stack in the predetermined direction, respectively; a pair of second end units arranged opposite the pair of first end units and outside the pair of first end units; a case having one end and the other end fixed to the pair of second end units, respectively, so that the cell stack is held in a state where a predetermined compressive load is applied in the predetermined direction, and forming a storage space to store the cell stack; and an elastic member interposed between at least one of the pair of first end units and at least one of the pair of second end units facing each other, and having a sealing function whose amount of contraction changes in accordance with relative movement of at least one of the pair of first end units and the cell stack in the predetermined direction relative to the case.

2. A fuel cell stack as described in claim 1, wherein the pair of first end units have a pair of current collecting members arranged adjacent to the one end face and the other end face of the cell stack, and a pair of insulating members respectively interposed between the pair of current collecting members and the pair of second end units, and the elastic member is interposed between at least one of the pair of insulating members and at least one of the pair of second end units.

3. A fuel cell stack as claimed in claim 1 or 2, wherein one of the pair of first end units and one of the pair of second end units have through holes for supplying and discharging reactant gases and cooling medium, and the elastic member is interposed between the one of the pair of first end units and the one of the pair of second end units.

4. A fuel cell stack according to claim 1 or 2, wherein the separators are arranged opposite each other and have a first plate forming a gas flow path through which a first reactant gas flows and a second plate forming a gas flow path through which a second reactant gas flows, and the first plate and the second plate have convex sealing portions that abut against each other.

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