JP7615885B2 - Frame - Google Patents

Description

The present invention relates to a frame that supports a membrane electrode assembly of a fuel cell.

Conventionally, a fuel cell such as that shown in Patent Document 1 is known. A plurality of such fuel cells are stacked to form, for example, a fuel cell stack for use in a vehicle. The fuel cell comprises a resin frame member that supports a stepped electrolyte membrane/electrode structure, and a first separator and a second separator that sandwich the stepped electrolyte membrane/electrode structure. The stepped electrolyte membrane/electrode structure comprises a solid polymer electrolyte membrane, and an anode electrode and a cathode electrode that sandwich the solid polymer electrolyte membrane.

The resin frame member has an inner peripheral protrusion that is formed thinner than the outermost peripheral portion via a step and protrudes inward. The stepped electrolyte membrane/electrode structure has a step on the outer peripheral edge. Then, an adhesive is applied to the inner flat surface of the inner peripheral protrusion of the resin frame member, and the stepped electrolyte membrane/electrode structure is bonded to the resin frame member by overlapping the stepped portion of the stepped electrolyte membrane/electrode structure on the stepped portion of the resin frame member.

JP 2014-137936 A

However, in the resin frame member described above, the angle between the inner flat surface of the inner peripheral protrusion to which the adhesive is applied and the step portion is a right angle. Therefore, when applying adhesive to the inner flat surface of the inner peripheral protrusion by screen printing, it is difficult to align the printing plate with the resin frame member. This makes it difficult to apply adhesive to the inner flat surface of the inner peripheral protrusion of the resin frame member by screen printing. In other words, there is a problem in that adhesive cannot be applied with high precision to the inner flat surface of the inner peripheral protrusion of the resin frame member by screen printing.

The means for solving the above problems and their effects will be described below.
The frame that solves the above problem is a frame made of synthetic resin that supports the periphery of a rectangular plate-shaped membrane electrode assembly of a fuel cell, and comprises a rectangular opening formed in the center, a rectangular annular adhesive portion that forms the periphery of the opening and is capable of adhering the periphery of the membrane electrode assembly, and a rectangular annular outer periphery that is positioned closer to the outer periphery than the adhesive portion, is sandwiched between a pair of separators, and is formed to be thicker than the adhesive portion, and at least one of the four sides that form the adhesive portion is provided with an inclined portion that is thicker toward the outer periphery.

With this configuration, when applying adhesive to the adhesive portion by screen printing, the screen plate can be easily aligned with the frame body. This allows the adhesive to be applied to the adhesive portion with high precision by screen printing.

FIG. 2 is an exploded perspective view of a fuel cell according to an embodiment. FIG. 2 is an exploded perspective view showing a power generation unit of the fuel cell shown in FIG. 1 . FIG. 2 is a schematic plan view of the fuel cell shown in FIG. 1 . 4 is a cross-sectional view taken along line 4-4 in FIG. 3 . 1A is a schematic cross-sectional view showing the contact state of the screen plate with the frame body when adhesive is applied by screen printing to the adhesive portion of the frame body of the embodiment, and FIG. 1B is a schematic cross-sectional view showing the contact state of the screen plate with the frame body of the comparative example when adhesive is applied by screen printing to the adhesive portion of the frame body of the comparative example.

An embodiment of the frame will now be described with reference to the drawings.
1, the fuel cell 11 has a rectangular plate shape, and a plurality of fuel cells 11 are stacked to form a fuel cell stack. In the following description, the long side direction of the fuel cell 11 is defined as the X direction, the short side direction of the fuel cell 11 is defined as the Y direction, and the thickness direction of the fuel cell 11 is defined as the Z direction. The X direction, Y direction, and Z direction are perpendicular to each other.

The fuel cell 11 includes a rectangular plate-shaped power generation unit 12, a pair of rectangular plate-shaped gas diffusion layers 13 that sandwich the power generation unit 12, and a pair of rectangular plate-shaped metal separators 14 that sandwich the power generation unit 12 and the pair of gas diffusion layers 13. In other words, the fuel cell 11 has a structure in which the pair of gas diffusion layers 13, the power generation unit 12, and the pair of separators 14 are stacked.

Of the pair of gas diffusion layers 13, one (cathode side) is a first gas diffusion layer 15, and the other (anode side) is a second gas diffusion layer 16. Of the pair of separators 14, one (cathode side) is a first separator 17, and the other (anode side) is a second separator 18.

As shown in Figures 1 and 2, the power generation unit 12 includes a rectangular plate-shaped synthetic resin frame 19 and a rectangular plate-shaped membrane electrode assembly 20 (MEA: Membrane Electrode Assembly) supported by the frame 19. A rectangular (quadrangular) opening 22 is formed in the center of the frame 19.

A rectangular annular (quadratic annular) adhesive portion 23 is formed on the periphery of the opening 22 on the surface of the frame 19 facing the first gas diffusion layer 15, and is thinner than other portions so that it can be bonded while supporting the periphery of the membrane electrode assembly 20. In other words, the adhesive portion 23 constitutes the periphery of the opening 22 and supports the periphery of the membrane electrode assembly 20.

The frame body 19 has a rectangular ring-shaped outer peripheral portion 21 that is thicker than the adhesive portion 23 and is located on the outer periphery side of the adhesive portion 23. In other words, the outer peripheral portion 21 is located on the outer periphery side of the adhesive portion 23 of the frame body 19 and is sandwiched between a pair of separators 14.

As shown in Figures 1 to 4, the first gas diffusion layer 15 is slightly longer in the X and Y directions than the opening 22. The second gas diffusion layer 16 is the same length in the X and Y directions as the opening 22. The pair of separators 14 sandwich the power generation unit 12 in the Z direction from the outside of the pair of gas diffusion layers 13.

The fuel cell 11 is supplied with an oxidant gas, which is an example of a power generation gas containing oxygen, to one side (cathode side) of the membrane electrode assembly 20 in the Z direction, and a fuel gas containing hydrogen is supplied to the other side (anode side) of the membrane electrode assembly 20 in the Z direction. As a result, the fuel cell 11 generates electricity based on an electrochemical reaction between the oxidant gas and the fuel gas in the membrane electrode assembly 20.

At both ends of the fuel cell 11 in the Y direction, i.e., at both ends sandwiching the openings 22 in the frame 19 and the pair of separators 14 in the Y direction, two oxidant gas holes 26 are formed side by side in the X direction, penetrating the fuel cell 11. Of the two ends of the fuel cell 11 in the Y direction, the oxidant gas hole 26 formed at one end is an oxidant gas supply hole 27, and the oxidant gas hole 26 formed at the other end is an oxidant gas discharge hole 28.

Between the power generation unit 12 and the first separator 17, an oxidant gas flow path 29 is formed, which allows the oxidant gas supplied from the oxidant gas supply hole 27 to pass through the opening 22 and flow to the oxidant gas discharge hole 28. The oxidant gas flow path 29 through which the oxidant gas flows extends in the Y direction. That is, the flow direction of the oxidant gas in the oxidant gas flow path 29 is from the oxidant gas supply hole 27 to the oxidant gas discharge hole 28 in the Y direction.

At both ends of the fuel cell 11 in the X direction, i.e., at both ends sandwiching the opening 22 in the frame 19 and the pair of separators 14 in the X direction, a fuel gas hole 30 and a cooling medium hole 31 are formed side by side in the Y direction and penetrate the fuel cell 11. In other words, of both ends sandwiching the opening 22 in the fuel cell 11 in the X direction, one end has one fuel gas hole 30 and one cooling medium hole 31 formed side by side in the Y direction, and the other end has one fuel gas hole 30 and one cooling medium hole 31 formed side by side in the Y direction.

At both ends of the fuel cell 11 sandwiching the opening 22 in the X direction, the arrangement order of the fuel gas holes 30 and the cooling medium holes 31 in the Y direction is reversed. Of the two ends of the fuel cell 11 in the X direction, the fuel gas holes 30 and the cooling medium holes 31 formed at one end are respectively fuel gas supply holes 32 and cooling medium supply holes 33, and the fuel gas holes 30 and the cooling medium holes 31 formed at the other end are respectively fuel gas exhaust holes 34 and cooling medium exhaust holes 35.

Between the power generation unit 12 and the second separator 18, a fuel gas flow path 36 is formed, which allows the fuel gas supplied from the fuel gas supply hole 32 to pass through the opening 22 and flow to the fuel gas discharge hole 34. When multiple fuel cells 11 are stacked, a cooling medium flow path (not shown) is formed between the first separator 17 and the second separator 18, which allows the cooling medium supplied from the cooling medium supply hole 33 to flow to the cooling medium discharge hole 35. The oxidant gas hole 26, the fuel gas hole 30, and the cooling medium hole 31 in the frame 19 are all formed in the outer periphery 21.

As shown in Figures 2 to 4, the adhesive portion 23 of the frame 19 has a rectangular ring shape and is therefore composed of four sides. These four sides are a first side 37, a second side 38, a third side 39, and a fourth side 40. The first side 37 is located on the oxidant gas supply hole 27 side and extends in the X direction. The second side 38 is located on the oxidant gas exhaust hole 28 side and extends in the X direction.

The third side 39 is located on the fuel gas supply hole 32 and the cooling medium supply hole 33 side and extends in the Y direction. The fourth side 40 is located on the fuel gas exhaust hole 34 and the cooling medium exhaust hole 35 side and extends in the Y direction. The first side 37 and the second side 38 form a pair and face each other in the Y direction with the opening 22 in between. The third side 39 and the fourth side 40 form a pair and face each other in the X direction with the opening 22 in between.

The adhesive portion 23 is therefore composed of two pairs of sides that face each other in different directions. In this embodiment, the Y direction in which the first side portion 37 and the second side portion 38 face each other is the flow direction of the oxidant gas. The first side portion 37 and the second side portion 38 each have an inclined portion 41 that is thicker as it approaches the outer periphery 21.

That is, the inclined portion 41 is provided at the end portion on the outer periphery 21 side of each of the first side portion 37 and the second side portion 38. That is, the inclined portion 41 is disposed between the first side portion 37 and the outer periphery 21, and between the second side portion 38 and the outer periphery 21. The inclined portion 41 has an inclined surface 42 whose height from the adhesive portion 23 increases toward the outer periphery 21 side.

The angle A between the first side portion 37 and the inclined surface 42 is an obtuse angle. The angle between the second side portion 38 and the inclined surface 42 is also the same as angle A. In this embodiment, angle A is set to approximately 135°, as an example. The third side portion 39 and the fourth side portion 40 do not have an inclined portion 41.

The periphery of the membrane electrode assembly 20 is supported by the first side portion 37, the second side portion 38, the third side portion 39, and the fourth side portion 40, and is bonded to the first side portion 37 and the second side portion 38 by adhesive S. In this case, the adhesive S is applied to the first side portion 37 and the second side portion 38 by screen printing.

Next, the action when applying the adhesive S to the first side portion 37 and the second side portion 38 by screen printing will be described.
5A, when applying the adhesive S to the first side portion 37 and the second side portion 38 by screen printing, a screen plate 43 is placed facing the frame body 19 in a state where it is stretched directly above the frame body 19. The screen plate 43 is made of, for example, synthetic resin thread woven into a mesh shape. The mesh of the screen plate 43 is closed except for the areas corresponding to the first side portion 37 and the second side portion 38.

After supplying adhesive S to the top surface of the screen plate 43, a squeegee (spatula) is moved while being pressed against the top surface of the screen plate 43. Then, the adhesive S passes only through the mesh in the areas of the screen plate 43 that correspond to the first side portion 37 and the second side portion 38, so that the adhesive S is applied only to the first side portion 37 and the second side portion 38.

At this time, as shown in FIG. 5(a), the first side 37 and the second side 38 of the frame 19 of the above-mentioned embodiment (present embodiment) are each provided with an inclined portion 41. Therefore, when the squeegee (spatula) is moved while being pressed against the upper surface of the screen plate 43, the screen plate 43 follows the respective shapes of the first side 37, the second side 38, the inclined portion 41, and the outer periphery 21.

Therefore, the adhesive S is applied reliably and accurately to the first side portion 37 and the second side portion 38 of the frame body 19. As a result, in the frame body 19 of the embodiment, sufficient sealing is ensured between the first side portion 37 and the second side portion 38 and the periphery of the membrane electrode assembly 20 when the periphery of the membrane electrode assembly 20 is joined to the first side portion 37 and the second side portion 38 with the adhesive S.

Incidentally, in the frame of the comparative example, which is configured by omitting the inclined portion 41 from the frame 19 of the example (present embodiment), as shown in FIG. 5(b), since the inclined portion 41 does not exist, a right-angle step 44 is formed between each of the first and second sides 37 and 38 and the outer periphery 21. Therefore, even if adhesive S is applied to the first and second sides 37 and 38 of the frame of the comparative example by screen printing in the same manner as the frame 19 of the example described above, the presence of the right-angle step 44 prevents the screen plate 43 from following the first and second sides 37 and 38.

Therefore, in the frame of the comparative example, it is difficult to apply adhesive S to the first side portion 37 and the second side portion 38 by screen printing. As a result, in the frame of the comparative example, when the periphery of the membrane electrode assembly 20 is joined to the first side portion 37 and the second side portion 38 with adhesive S, sufficient sealing is not ensured between the first side portion 37 and the second side portion 38 and the periphery of the membrane electrode assembly 20.

Next, the operation of the fuel cell 11 will be described.
As shown in FIGS. 1 to 4, when power is generated by the fuel cell 11 , an oxidant gas is supplied from the oxidant gas supply hole 27 and a fuel gas is supplied from the fuel gas supply hole 32 .

When oxidant gas is supplied from the oxidant gas supply hole 27 in the fuel cell 11, the oxidant gas is supplied to the cathode side surface of the membrane electrode assembly 20 while being diffused by the first gas diffusion layer 15 as it flows through the oxidant gas flow path 29 to the oxidant gas discharge hole 28. At this time, the third side portion 39 and the fourth side portion 40 of the frame 19 are not provided with the inclined portion 41.

As a result, no gaps are formed between the outer periphery 21 and both sides (both left and right ends in FIG. 3) of the membrane electrode assembly 20 in the direction of oxidant gas flow (from top to bottom in FIG. 3). As a result, the oxidant gas flowing through the oxidant gas flow passage 29 does not flow beside the membrane electrode assembly 20. In other words, the oxidant gas flowing through the oxidant gas flow passage 29 flows toward the oxidant gas exhaust hole 28 without flowing through an area where the membrane electrode assembly 20 does not exist.

On the other hand, when fuel gas is supplied from the fuel gas supply hole 32 in the fuel cell 11, the fuel gas is supplied to the anode side surface of the membrane electrode assembly 20 while being diffused by the second gas diffusion layer 16 as it flows through the fuel gas flow passage 36 to the fuel gas exhaust hole 34.

The fuel cell 11 generates electricity based on an electrochemical reaction in the membrane electrode assembly 20 between the oxidant gas supplied to the cathode side of the membrane electrode assembly 20 and the fuel gas supplied to the anode side of the membrane electrode assembly 20. In this case, as described above, the oxidant gas flowing through the oxidant gas flow passage 29 does not flow outside the membrane electrode assembly 20, so that the fuel cell 11 generates electricity efficiently.

Incidentally, if the inclined portions 41 are provided on the third side 39 and the fourth side 40 of the frame 19, the following occurs. That is, gaps are created between both sides (both left and right ends in FIG. 3) of the membrane electrode assembly 20 in the flow direction of the oxidant gas (the direction from top to bottom in FIG. 3) and the inclined portions 41 (inclined surfaces 42) provided on the third side 39 and the fourth side 40.

As a result, some of the oxidant gas flowing through the oxidant gas flow passage 29 flows through the gap where the membrane electrode assembly 20 is not present. Since the oxidant gas flowing through the gap does not contribute to the power generation of the fuel cell 11, the power generation efficiency of the fuel cell 11 decreases.

According to the embodiment described above in detail, the following effects are achieved.
(1) The frame 19 supports the periphery of the membrane electrode assembly 20 of the fuel cell 11, which is a rectangular plate. The frame 19 has a rectangular opening 22 formed in the center, a rectangular annular adhesive portion 23 that constitutes the periphery of the opening 22 and can adhere the periphery of the membrane electrode assembly 20, and a rectangular annular outer periphery 21. The outer periphery 21 is disposed on the outer periphery side of the adhesive portion 23, is sandwiched between a pair of separators 14, and is formed to be thicker than the adhesive portion 23. At least one of the first side portion 37, the second side portion 38, the third side portion 39, and the fourth side portion 40 that constitute the adhesive portion 23 has an inclined portion 41 that is formed to be thicker toward the outer periphery 21.

With this configuration, when applying adhesive S to the adhesive portion 23 by screen printing, the screen plate 43 can be easily aligned with the frame body 19. Therefore, adhesive S can be applied to the adhesive portion 23 with high precision by screen printing.

(2) When the Y direction in which the first side portion 37 and the second side portion 38 of the frame body 19 face each other is the flow direction of the oxidant gas in the fuel cell 11, the frame body 19 does not have an inclined portion 41 on the third side portion 39 and the fourth side portion 40 that face each other in the X direction.

With this configuration, no gaps are formed between the inclined portion 41 and both sides (both ends in the X direction) of the membrane electrode assembly 20 in the oxidant gas flow direction, so that the oxidant gas can be prevented from flowing beside the membrane electrode assembly 20. This makes it possible to prevent a decrease in the power generation efficiency of the fuel cell 11 caused by the oxidant gas flowing beside the membrane electrode assembly 20.

(3) In the frame 19 , the inclined portions 41 are provided on the first side portion 37 and the second side portion 38 that face each other.
According to this configuration, the adhesive S can be applied with high precision to each of the first side portion 37 and the second side portion 38 by screen printing, so that the membrane electrode assembly 20 can be joined to the adhesive portion 23 in a well-balanced manner.

(Example of change)
The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other as long as they are not technically inconsistent.

The inclined portion 41 does not necessarily have to be provided on one of two pairs of sides that face each other in different directions on the four sides that make up the adhesive portion 23. In other words, the inclined portion 41 may be provided on two adjacent sides that do not face each other. For example, the inclined portion 41 may be provided on each of the first side 37 and the fourth side 40, or on each of the second side 38 and the third side 39.

- When the Y direction in which the first side portion 37 and the second side portion 38 face each other is the flow direction of the oxidant gas in the fuel cell 11, the third side portion 39 and the fourth side portion 40 that face each other in the X direction may be provided with an inclined portion 41. Alternatively, for example, when the X direction in which the third side portion 39 and the fourth side portion 40 face each other is the flow direction of the oxidant gas in the fuel cell 11, the first side portion 37 and the second side portion 38 that face each other in the Y direction may be provided with an inclined portion 41.

The inclined portions 41 may be provided on the third side portion 39 and the fourth side portion 40 instead of on the first side portion 37 and the second side portion 38 .
The inclined portion 41 may be provided on all, any three, any two, or any one of the first side portion 37, the second side portion 38, the third side portion 39, and the fourth side portion 40.

REFERENCE SIGNS LIST 11 fuel cell 12 power generation unit 13 gas diffusion layer 14 separator 15 first gas diffusion layer 16 second gas diffusion layer 17 first separator 18 second separator 19 frame 20 membrane electrode assembly 21 outer periphery 22 opening 23 adhesive portion 26 oxidant gas hole 27 oxidant gas supply hole 28 oxidant gas exhaust hole 29 oxidant gas flow path 30 fuel gas hole 31 cooling medium hole 32 fuel gas supply hole 33 cooling medium supply hole 34 fuel gas exhaust hole 35 cooling medium exhaust hole 36 fuel gas flow path 37 first side 38 second side 39 third side 40 fourth side 41 inclined portion 42 inclined surface 43 screen plate 44 step A angle S adhesive

Claims (1)

A frame made of synthetic resin that supports the periphery of a rectangular plate-shaped membrane electrode assembly of a fuel cell,
A rectangular opening formed in the center;
a rectangular annular adhesive portion that constitutes a peripheral portion of the opening and that is capable of adhering a peripheral portion of the membrane electrode assembly;
a rectangular ring-shaped outer periphery that is disposed on the outer periphery side of the adhesive portion, is sandwiched between a pair of separators, and is formed to be thicker than the adhesive portion;
At least one of the four sides constituting the adhesive portion is provided with an inclined portion that is thicker toward the outer periphery ,
A frame body characterized in that, when the direction in which one pair of sides of two pairs of sides that face each other in different directions among the four sides faces each other is the flow direction of oxidant gas in the fuel cell, the inclined portion is not provided on the other pair of sides .