JP4435466B2 - Assembly method of fuel cell stack - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention comprises an electrolyte membrane / electrode structure in which a solid polymer electrolyte membrane is sandwiched between carbon members with an electrode catalyst layer interposed therebetween, and separators that are alternately stacked with the electrolyte membrane / electrode structure. The present invention relates to a method for assembling a fuel cell stack.
[0002]
[Prior art]
Generally, a polymer electrolyte fuel cell has an electrolyte membrane / electrode structure in which an anode side electrode and a cathode side electrode are respectively provided on both sides of an electrolyte membrane made of a polymer ion exchange membrane (cation exchange membrane). , And is sandwiched between separators. This type of fuel cell is usually used as a fuel cell stack by alternately stacking a predetermined number of electrolyte membrane / electrode structures and separators.
[0003]
In this fuel cell, a fuel gas supplied to the anode side electrode, for example, a gas mainly containing hydrogen (hereinafter, also referred to as a hydrogen-containing gas) is ionized on the electrode catalyst, and the cathode side passes through the electrolyte. Move to the electrode side. Electrons generated in the meantime are taken out to an external circuit and used as direct current electric energy. The cathode side electrode is supplied with an oxidant gas, for example, a gas mainly containing oxygen or air (hereinafter also referred to as an oxygen-containing gas). And oxygen react to produce water.
[0004]
In this case, for example, in an in-vehicle fuel cell stack, it is necessary to greatly improve the impact resistance so that it can withstand changes in operating conditions such as sudden start and sudden stop. However, in general, the diffusion layer constituting the electrolyte membrane / electrode structure is formed of carbon fiber, and the surface pressure strength (restorability after compression, flexibility for bending, etc.) may not be sufficiently ensured. is there.
[0005]
For this reason, when a tightening load in consideration of impact resistance is applied to the fuel cell stack, an excessive surface pressure acts on the diffusion layer, and the diffusion layer is likely to be plastically deformed by compression. It becomes necessary and the entire work is considerably complicated. Therefore, there is a demand for a structure that does not apply a surface pressure to the diffusion layer such that the diffusion layer is plastically deformed by compression.
[0006]
[Problems to be solved by the invention]
However, if a configuration in which a disc spring, a stopper structure, or the like is disposed at the end of the fuel cell stack in response to the above request, the entire fuel cell stack is increased in size and weight. For this reason, an increase in the surface pressure is anticipated in advance, and the set surface pressure is reduced. However, it has been pointed out that the contact resistance increases as the surface pressure decreases, causing a voltage loss. In particular, the management of the desired contact resistance and the surface pressure for protecting the diffusion layer is extremely difficult.
[0007]
An object of the present invention is to solve this type of problem, and to provide a method for assembling a fuel cell stack capable of efficiently assembling the fuel cell stack and reliably maintaining desired power generation performance. To do.
[0008]
[Means for Solving the Problems]
In the on- vehicle fuel cell stack assembling method according to claim 1 of the present invention, after an electrolyte membrane / electrode structure and a separator are alternately stacked to obtain a fuel cell stack, a preload is applied to the fuel cell stack. Is granted. This preliminary load sets the maximum surface pressure that acts in the stacking direction of the porous carbon gas diffusion layer (hereinafter also referred to as carbon member) when the fuel cell stack is actually operated, and corresponds to this maximum surface pressure. It is set to a value lower than the maximum load to be applied and higher than the tightening load of the fuel cell stack.
[0009]
Next, the preliminary load is released, the thickness fluctuation amount of the gas diffusion layer before and after the provision of the preliminary load is detected, and the thickness fluctuation amount of the gas diffusion layer is required for the gas diffusion layer. After being within a preset allowable range for obtaining the pressure strength , the fuel cell stack is fastened and fixed with a desired fastening load in the stacking direction.
[0010]
Therefore, the surface pressure strength of the carbon member can be improved by a simple process, and a desired tightening load can be reliably applied to the fuel cell stack in a short time. For this reason, the assembly operation of the fuel cell stack can be performed efficiently and with high accuracy. In addition, since the surface pressure strength of the carbon member provided with the preload is further improved, the carbon member can be maintained in a good state even when the maximum surface pressure acts on the carbon member.
[0011]
Furthermore, since a preload is applied to the entire fuel cell stack, it is possible to effectively improve the surface pressure strength of all the carbon members laminated in a single pressing step. Thus, the preloading operation of the carbon member can be performed easily and quickly, and the surface pressure strength of only the necessary portion of the carbon member can be reliably improved. In addition, since a relatively high preliminary load is applied to the fuel cell stack, the surface pressure strength of the carbon member can be reliably improved in a short time.
[0012]
In the method for assembling the fuel cell stack according to claim 2 of the present invention, it is preferable to repeat the application and release of the preload until the thickness fluctuation amount of the gas diffusion layer falls within the allowable range .
[0013]
Furthermore, in the method for assembling the fuel cell stack according to claim 3 of the present invention, one carbon member has a larger surface area than the other carbon member, and protrudes outward from the outer peripheral portion of the other carbon member. A seal is interposed between the outer peripheral edge of the one carbon member and the separator disposed on the other carbon member side.
[0014]
Therefore, when a compressive load is applied to the fuel cell stack, the carbon member does not cause compressive deformation due to the seal load. For this reason, the sealing performance of the fuel cell stack is effectively improved, and no sag or the like occurs in the carbon member, so that a desired sealing function can be reliably maintained.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic perspective view of a fuel cell stack 10 according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view of a main part of the fuel cell stack 10.
[0016]
The fuel cell stack 10 includes a stacked body 18 in which a plurality of electrolyte membrane / electrode structures 12 are stacked with first and second separators 14 and 16 formed of, for example, a metal plate. As shown in FIG. 1, a negative electrode side current collector 20a, a positive electrode side current collector 20b, and end plates 22a and 22b are provided at both ends in the stacking direction (arrow A direction) of the stacked body 18 via insulating plates 24a and 24b. Arranged. A predetermined tightening load is applied between the end plates 22 a and 22 b via a plurality of tie rods 25.
[0017]
One end edge of the electrolyte membrane / electrode structure 12 and the first and second separators 14 and 16 in the direction of arrow B (the horizontal direction in FIG. 2) communicates with each other in the direction of arrow A, which is the stacking direction. An oxidizing gas supply passage 30a for supplying an agent gas, for example, an oxygen-containing gas, a cooling medium discharge passage 32b for discharging a cooling medium, and a fuel for discharging a fuel gas, for example, a hydrogen-containing gas Gas discharge communication holes 34b are arranged in the direction of arrow C (vertical direction).
[0018]
A fuel gas supply communication hole for supplying fuel gas to the other end edge of the electrolyte membrane / electrode structure 12 and the first and second separators 14 and 16 in the direction of arrow B and communicating with each other in the direction of arrow A 34a, a cooling medium supply communication hole 32a for supplying the cooling medium, and an oxidant gas discharge communication hole 30b for discharging the oxidant gas are arranged in the direction of arrow C.
[0019]
The electrolyte membrane / electrode structure 12 includes, for example, a solid polymer electrolyte membrane 36 in which a perfluorosulfonic acid thin film is impregnated with water, and an anode side electrode 38 and a cathode side electrode that sandwich the solid polymer electrolyte membrane 36. 40.
[0020]
As shown in FIG. 3, the anode side electrode 38 and the cathode side electrode 40 have gas diffusion layers (carbon members) 42a and 42b made of a porous carbon member, for example, carbon paper, and a platinum alloy supported on the surface. Porous carbon particles have electrode catalyst layers 44a and 44b formed by uniformly applying the surfaces of the gas diffusion layers 42a and 42b, respectively. The electrode catalyst layers 44a and 44b are bonded to both surfaces of the solid polymer electrolyte membrane 36 so as to face each other with the solid polymer electrolyte membrane 36 interposed therebetween.
[0021]
The anode side electrode 38 has a larger surface area than the cathode side electrode 40. The gas diffusion layer 42a constituting the anode side electrode 38 is provided with an outer peripheral edge portion 45 protruding outward by a distance H from the outer periphery of the gas diffusion layer 42b constituting the cathode side electrode 40.
[0022]
Between the first and second separators 14 and 16, for example, a first seal 47a such as a silicon O-ring is interposed, and the surface 14a of the first separator 14 and the solid polymer electrolyte membrane 36 are disposed. A second seal 47b such as an O-ring is interposed between the gaps (positions corresponding to the outer peripheral edge 45) around the cathode side electrode 40.
[0023]
The gas diffusion layers 42a and 42b have gas diffusibility and current collecting properties, and are made of carbon and metal (for example, iron, aluminum, nickel, copper, or stainless steel). Gas diffusion layers 42a, 42b, for example, have been used TGP-H manufactured by Toray Industries, Inc., specific resistance ^{0.2 × 10 -6 Ωcm~50 × 10 -6} Ωcm, more preferably, 0.3 in ^{× 10 -6 Ωcm~10 × 10 -6 Ωcm} , bulk density ^{0.2g / cm 3 ~0.6g / cm 3} , more preferably, at ^{0.3g / cm 3 ~0.5g / cm 3} , The gas permeability is 10 mmAq / mm to 100 mmAq / mm, more preferably 20 mmAq / mm to 50 mmAq / mm.
[0024]
As shown in FIG. 2, for example, an oxidant gas flow path 46 including a plurality of grooves extending in the direction of arrow B is provided on the surface 14 a on the electrolyte membrane / electrode structure 12 side of the first separator 14. At the same time, the oxidant gas passage 46 communicates with the oxidant gas supply communication hole 30a and the oxidant gas discharge communication hole 30b.
[0025]
A fuel gas passage 48 communicating with the fuel gas supply communication hole 34a and the fuel gas discharge communication hole 34b is formed on the surface 16a of the second separator 16 on the electrolyte membrane / electrode structure 12 side. The fuel gas channel 48 includes a plurality of grooves extending in the arrow B direction. A cooling medium flow path 50 that communicates with the cooling medium supply communication hole 32 a and the cooling medium discharge communication hole 32 b is formed on the surface 16 b of the second separator 16. The cooling medium flow path 50 includes a plurality of grooves extending in the direction of arrow B.
[0026]
As shown in FIG. 1, an oxidant gas supply communication hole 30a, a cooling medium discharge communication hole 32b, and a fuel gas discharge communication hole 34b are provided at one end edge of the long side (arrow B direction side) of the end plate 22a. It is done. A fuel gas supply communication hole 34a, a coolant supply communication hole 32a, and an oxidant gas discharge communication hole 30b are provided at the other end edge of the long side (arrow B direction side) of the end plate 22a.
[0027]
The operation of the fuel cell stack 10 configured as described above will be described below in relation to the assembling method according to the present embodiment.
[0028]
First, a unit cell is configured by sandwiching the electrolyte membrane / electrode structure 12 between the first and second separators 14, 16, and a predetermined number of unit cells are stacked in the direction of arrow A to form a stacked body 18. Is obtained. A negative electrode side current collector 20a, a positive electrode side current collector 20b, and end plates 22a and 22b are disposed at both ends in the stacking direction of the stacked body 18 via insulating plates 24a and 24b.
[0029]
Further, a plurality of tie rods 25 are disposed between the end plates 22 a and 22 b, and a temporary fastening load is applied to the end plates 22 a and 22 b, that is, the fuel cell stack 10 via the tie rods 25. This temporary fastening load is set to a value smaller than a predetermined fastening load.
[0030]
Next, as shown in FIG. 4, a preliminary load is applied to the fuel cell stack 10 via a press machine 60. The press machine 60 includes a lower mold 62 that is a fixed mold and an upper mold 64 that is a movable mold. The lower mold 62 and the upper mold 64 are pressed against the entire fuel cell stack 10 in the stacking direction. Is set to a shape that avoids the tie rod 25.
[0031]
In the present embodiment, the maximum surface pressure acting on the gas diffusion layers 42a and 42b when the fuel cell stack 10 is actually operated is set, and is lower than the maximum load corresponding to the maximum surface pressure, and the fuel cell stack. A preload higher than a tightening load of 10 is set. For example, when the fuel cell stack 10 is mounted on a vehicle, the maximum surface pressure is the surface pressure when the maximum impact force is applied to the fuel cell stack 10 due to a change in operating conditions such as sudden start and stop. Say.
[0032]
On the other hand, the tightening load includes a diffusion layer load corresponding to the surface pressure strength (compression limit surface pressure) of the gas diffusion layers 42a and 42b necessary for the entire fuel cell stack 10 to maintain a desired contact resistance, and a desired seal. And a seal load corresponding to the seal surface pressure interposed between the separators such as the first and second seals 47a and 47b, which are necessary for maintaining the performance, are set.
[0033]
FIG. 5 shows the relationship between the surface pressure for compressing the gas diffusion layers 42a and 42b and the thickness of the gas diffusion layers 42a and 42b. Therefore, the thickness tg of the gas diffusion layers 42a and 42b when the required surface pressure pg is applied to the gas diffusion layers 42a and 42b is obtained based on FIG.
[0034]
When the thickness tg of the gas diffusion layers 42a and 42b is set, the heights of the first and second seals 47a and 47b are determined based on the thickness tg. At that time, the surface pressure (seal surface pressure) p for compressing the first and second seals 47a and 47b and the height (seal height) ts of the first and second seals 47a and 47b are shown in FIG. It has the relationship shown.
[0035]
Therefore, when a desired tightening load is applied to the fuel cell stack 10 and the first and second seals 47a and 47b have a height dimension corresponding to the thickness tg of the gas diffusion layers 42a and 42b, a predetermined value is obtained. The initial seal heights of the first and second seals 47a and 47b are determined so that the seal surface pressure can be secured.
[0036]
The diffusion layer load Pg of the gas diffusion layers 42a and 42b and the seal load Ps of the first and second seals 47a and 47b have the relationship shown in FIG. Thereby, the diffusion layer load and the seal load become shared loads, and a value obtained by adding these is set as the tightening load of the entire fuel cell stack 10. As the shared load, the diffusion layer load of the gas diffusion layers 42a and 42b is considerably larger than the seal load of the first and second seals 47a and 47b.
[0037]
Therefore, as shown in FIG. 4, in the fuel cell stack 10, the upper die 64 is lowered while the end plate 22 b (or 22 a) is placed on the press surface of the lower die 62. Therefore, in the fuel cell stack 10, the end plate 22b (or 22a) is placed on the press surface of the lower die 62, and the end plate 22a (or 22b) is pressed against the press surface of the upper die 64, so that the fuel A predetermined preliminary load is applied to the battery stack 10 in the stacking direction. For example, the fuel cell stack 10 is held at about 120 ° C. for 5 minutes to 10 minutes, preferably 3 minutes to 7 minutes, with this preliminary load applied. The holding time can be shortened by applying a preliminary load at a high temperature.
[0038]
This preliminary load is set corresponding to a surface pressure that is 2 MPa lower than the maximum surface pressure acting on the gas diffusion layers 42a and 42b. That is, when a preload is applied to the gas diffusion layers 42a and 42b, as shown in FIG. 8, the surface pressure strength of the gas diffusion layers 42a and 42b is 2 MPa higher than the applied surface pressure (preliminary load). Is obtained.
[0039]
Therefore, by setting the preliminary load corresponding to a surface pressure that is 2 MPa lower than the maximum surface pressure, the surface pressure strength of the gas diffusion layers 42a and 42b is equal to the maximum surface pressure acting on the gas diffusion layers 42a and 42b. It becomes. As a result, even if the maximum surface pressure acts on the gas diffusion layers 42a and 42b, it is possible to prevent the gas diffusion layers 42a and 42b from being sag and damaged as much as possible.
[0040]
Next, when the upper die 64 constituting the press machine 60 is raised and the press load is removed from the fuel cell stack 10, the thickness fluctuation amount of the gas diffusion layers 42a and 42b before and after the press load is applied is detected. The In this case, when the thickness fluctuation amount at the time of removing the preload is not within the predetermined range from the thickness at the time of applying the preload of the gas diffusion layers 42a and 42b, the preloading operation by the press machine 60 is performed again. Is called.
[0041]
When the thickness fluctuation amount of the gas diffusion layers 42a and 42b falls within a predetermined range, a desired tightening load is applied to the fuel cell stack 10 via the press machine 60 or the like. In this state, a predetermined fastening force is applied between the end plates 22a and 22b via the tie rod 25, and the fuel cell stack 10 is fastened and fixed.
[0042]
Here, when the preliminary load was a load corresponding to a surface pressure of 6 MPa and the allowable range of thickness variation was set to 5 μm, the result shown in FIG. 9 was obtained. That is, when a preliminary load (press load) was applied once to the fuel cell stack 10 via the press machine 60, the amount of fluctuation of the gas diffusion layers 42a and 42b slightly exceeded 5 μm. Therefore, when the preliminary load was applied to the fuel cell stack 10 twice or more, the fluctuation amount was within 5 μm. Therefore, the gas diffusion layers 42a and 42b having the desired surface pressure strength were reliably obtained by applying the preload twice or more.
[0043]
When a tightening load was applied to the fuel cell stack 10 to which no preliminary load was applied, the thickness variation (thickness difference) of the gas diffusion layers 42a and 42b was 30 μm or more. For this reason, in the fuel cell stack 10 to which no preload is applied, the gas diffusion layers 42a and 42b are compressed and deformed through the seal load of the second seal 47b, and a desired sealability cannot be ensured.
[0044]
In contrast, in the present embodiment, a preload is applied to the entire fuel cell stack 10 after the fuel cell stack 10 is stacked, so that the second seal 47b is applied to the outer peripheral edge 45 of the gas diffusion layer 42a. A preliminary load is applied corresponding to the contact surface, and the surface pressure strength of the outer peripheral edge 45 is greatly improved. Therefore, as shown in FIG. 3, the outer peripheral edge 45 of the gas diffusion layer 42a has a thickness variation amount with respect to the seal load by the second seal 47b in a predetermined range in a state where a tightening load is applied to the fuel cell stack 10. Maintained within.
[0045]
Thereby, in the present embodiment, the sealing performance of the entire fuel cell stack 10 is effectively improved, and a desired sealing function is ensured without causing a sag or the like on the outer peripheral edge 45 of the gas diffusion layer 42a. The effect that it becomes possible to maintain at this is acquired.
[0046]
Further, a preliminary load is applied to the entire fuel cell stack 10. For this reason, it is possible to effectively improve the surface pressure strength of all the laminated gas diffusion layers 42a and 42b in a single pressing process by the press machine 60. Accordingly, there is an advantage that the preloading operation of the gas diffusion layers 42a and 42b can be performed easily and quickly, and the productivity can be improved.
[0047]
In addition, since a preload is applied to the entire fuel cell stack 10, the strength of only the necessary portions of the gas diffusion layers 42a and 42b is improved. Therefore, for example, the gas diffusion layers 42a and 42b are not crushed corresponding to the groove portions of the oxidant gas flow path 46 and the fuel gas flow path 48, and the oxidant gas and the fuel gas are smoothly circulated. be able to. Further, since a relatively high preliminary load is applied to the fuel cell stack 10, the surface pressure strength of the gas diffusion layers 42a and 42b can be reliably improved in a short time.
[0048]
When the fuel cell stack 10 is operated, as shown in FIG. 1, a fuel gas such as a hydrogen-containing gas is supplied to the fuel gas supply communication hole 34a, and an oxygen-containing gas is supplied to the oxidant gas supply communication hole 30a. An oxidant gas such as is supplied. Further, a coolant such as pure water, ethylene glycol, or oil is supplied to the coolant supply passage 32a.
[0049]
For this reason, as shown in FIG. 2, the oxidant gas is introduced into the oxidant gas flow path 46 of the first separator 14 from the oxidant gas supply communication hole 30a to form the electrolyte membrane / electrode structure 12 on the cathode side. It moves along the electrode 40. On the other hand, the fuel gas is introduced into the fuel gas passage 48 of the second separator 16 from the fuel gas supply communication hole 34 a and moves along the anode side electrode 38 constituting the electrolyte membrane / electrode structure 12.
[0050]
Therefore, in each electrolyte membrane / electrode structure 12, the oxidant gas supplied to the cathode side electrode 40 and the fuel gas supplied to the anode side electrode 38 are consumed by an electrochemical reaction in the electrode catalyst layer, Power generation is performed.
[0051]
Next, the fuel gas consumed by being supplied to the anode side electrode 38 is discharged in the direction of arrow A along the fuel gas discharge communication hole 34b. Similarly, the oxidant gas consumed by being supplied to the cathode side electrode 40 is discharged in the direction of arrow A along the oxidant gas discharge communication hole 30b.
[0052]
In addition, the cooling medium supplied to the cooling medium supply communication hole 32a is introduced into the cooling medium flow path 50 of the second separator 16, and then circulates in the direction of the arrow B. This cooling medium is discharged from the cooling medium discharge communication hole 32b after the electrolyte membrane / electrode structure 12 is cooled.
[0053]
In the present embodiment, the first seal 47a such as an O-ring is used. However, the present invention is not limited to this, and other seal structures such as a gasket may be employed.
[0054]
【The invention's effect】
In the method for assembling the fuel cell stack according to the present invention, the surface pressure strength of the carbon member can be improved by a simple process, and a desired tightening load can be reliably applied to the fuel cell stack in a short time. it can. For this reason, the assembly operation of the fuel cell stack can be performed efficiently and with high accuracy. Moreover, since the surface pressure strength of the carbon member provided with the preload is further improved, the carbon member can be well maintained even when the maximum surface pressure acts on the carbon member.
[0055]
Furthermore, since a preload is applied to the entire fuel cell stack, it is possible to effectively improve the surface pressure strength of all the carbon members in a single pressing step. Thereby, the preloading operation of the carbon member can be performed easily and quickly, and the surface pressure strength of only the necessary portion of the carbon member can be reliably improved. In addition, since a relatively high preliminary load is applied to the fuel cell stack, the surface pressure strength of the carbon member can be reliably improved in a short time.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a fuel cell stack according to an embodiment of the present invention.
FIG. 2 is an exploded perspective view of a main part of the fuel cell stack.
FIG. 3 is an explanatory cross-sectional view of a main part of the fuel cell stack.
FIG. 4 is an explanatory diagram of a press machine that applies a preload to the fuel cell stack.
FIG. 5 is an explanatory diagram showing a relationship between a diffusion layer surface pressure and a diffusion layer thickness;
FIG. 6 is an explanatory diagram showing a relationship between seal surface pressure and seal height.
FIG. 7 is an explanatory diagram showing a shared load between a diffusion layer load and a seal load in a tightening load.
FIG. 8 is an explanatory diagram showing an improvement in surface pressure strength of the gas diffusion layer after applying a preload.
FIG. 9 is an explanatory diagram showing the relationship between the presence / absence of a preload on the gas diffusion layer and the number of times of application and the thickness variation.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Fuel cell stack 12 ... Electrolyte membrane electrode assembly 14, 16 ... Separator 30a ... Oxidant gas supply communication hole 30b ... Oxidant gas discharge communication hole 32a ... Cooling medium supply communication hole 32b ... Cooling medium discharge communication hole 34a ... Fuel gas supply communication hole 34b ... Fuel gas discharge communication hole 36 ... Solid polymer electrolyte membrane 38 ... Anode side electrode 40 ... Cathode side electrode 42a, 42b ... Gas diffusion layer 44a, 44b ... Electrode catalyst layer 45 ... Outer peripheral edge 46 ... Oxidant gas flow paths 47a, 47b ... seal 48 ... fuel gas flow path 50 ... cooling medium flow path 60 ... press machine 62 ... lower mold 64 ... upper mold

Claims (3)

Consists of an electrolyte membrane / electrode structure in which a solid polymer electrolyte membrane is sandwiched by a porous carbon gas diffusion layer with an electrode catalyst layer interposed therebetween, and separators stacked alternately with the electrolyte membrane / electrode structure An in- vehicle fuel cell stack assembly method comprising:
Alternately stacking the electrolyte membrane / electrode structure and the separator to obtain a fuel cell stack;
Setting a maximum surface pressure acting in the stacking direction of the gas diffusion layer when the fuel cell stack is actually operated; lower than a maximum load corresponding to the maximum surface pressure; and from a tightening load of the fuel cell stack A process of setting a high preload,
Applying the preliminary load along the stacking direction to the fuel cell stack;
The step of detecting the thickness variation of the gas diffusion layer before and after the application of the preliminary load, while the preliminary load is released;
After the amount of variation in the thickness of the gas diffusion layer falls within a preset allowable range for obtaining the surface pressure strength required for the gas diffusion layer , the fuel cell stack is fastened and fixed with the tightening load. And a process of
A method for assembling a fuel cell stack, comprising: 2. The method of assembling a fuel cell stack according to claim 1, wherein the application and release of the preliminary load are repeated until the thickness fluctuation amount of the gas diffusion layer falls within the allowable range .   3. The assembly method according to claim 1, wherein one of the carbon members has a surface area larger than that of the other carbon member, and the outer surface of the one carbon member protrudes outward from an outer peripheral portion of the other carbon member. A fuel cell stack assembling method, wherein a seal is interposed between a peripheral portion and the separator disposed on the other carbon member side.

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