JP7762437B2 - fuel cell - Google Patents

Description

This disclosure relates to fuel cell cells.

Patent Document 1 discloses a fuel cell that can alleviate stress on the electrolyte membrane by providing a porous carbon body and a porous metal body as intermediate layers.

JP 2013-196884 A

However, in the above-mentioned configuration, there is a problem in that the frame-shaped sheet in the gas diffusion section can deform and block the flow path due to factors such as the generation of a pressure difference between the anode and cathode. While deformation can be prevented by making the frame-shaped sheet thicker or supporting it with a metal plate, such a structure leads to an increase in the thickness of the fuel cell, which in turn leads to an increase in the size of the fuel cell.

The objective of this disclosure is to provide a fuel cell that can suppress blockage of the flow path in the diffusion section while keeping the thickness small.

A fuel cell according to one embodiment of the present disclosure includes:
A core sheet and
A separator is provided on the outside of the core sheet,
The core sheet includes an MEA having an electrolyte membrane and an electrode layer provided on the outside of the electrolyte membrane;
a resin frame sheet that supports the MEA,
The separator has an inlet portion and an outlet portion,
the inlet portion has a first inlet portion through which a first gas is introduced and a second inlet portion through which a second gas is introduced,
the outlet portion has a first outlet portion through which the first gas is discharged and a second outlet portion through which the second gas is discharged,
At least one of the first inlet portion, the second inlet portion, the first outlet portion, and the second outlet portion has a plurality of protrusions that protrude toward the frame-shaped sheet and support the frame-shaped sheet,
The protrusions abut against the frame-shaped sheet to suppress displacement of the frame-shaped sheet in the surface direction.

As a result of the above, it is possible to provide a fuel cell that can suppress blockage of the flow path in the diffusion section while keeping the thickness small.

FIG. 1 is a perspective view of a fuel cell using a fuel cell according to the present disclosure. FIG. 2 is an exploded perspective view of the fuel cell according to this embodiment. FIG. 3 is a front view of the separator according to this embodiment. FIG. 4 is a front view showing separators according to the present disclosure stacked together. FIG. 5 is a diagram showing how gas flows in the fuel cell according to this embodiment. FIG. 6A is an enlarged view of the circled portion A in FIG. FIG. 6B is a cross-sectional view of the diffusion portion taken along the line BB in FIG. 6A. FIG. 7 is a cross-sectional view of a portion of a fuel cell where the first inlet-side diffusion section of the anode-side separator and the second outlet-side collection section of the cathode-side separator overlap in a planar projection view.

[Details of the embodiment of the present disclosure]
Specific examples of the fuel cell 10 according to the embodiment of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Note that U, D, F, B, R, and L shown in Figure 1 etc. indicate directions in the fuel cell 10, with U being up, D being down, F being forward, B being rearward, R being right, and L being left. In the following explanation, when referring to right and left without distinction, they may simply be referred to as "side."

FIG. 1 is a perspective view of a fuel cell 1 using a fuel cell 10 according to the present disclosure.
As shown in Figure 1, a fuel cell 1 is constructed by stacking one or more fuel cell units 10. The fuel cell 1 has end plates provided at both ends of the stacked fuel cell units 10, electrodes for extracting electricity generated in the fuel cell units, and a case shown by the dashed line in Figure 1. In the following description, the fuel cell unit 10 may be simply referred to as a "cell."
One side of the end plate is provided with inlets and outlets for each fluid to enter and exit the stack, which are a first gas inlet 2, a first gas outlet 3, a second gas inlet 4, a second gas outlet 5, a cooling water inlet 6, and a cooling water outlet 7, respectively.

The configuration of the fuel cell 10 will be described using Figures 2 to 4. Figure 2 is an exploded perspective view of the fuel cell 10 according to this embodiment. As shown in Figure 2, the fuel cell 10 has a separator 20 and a core sheet 22. The fuel cell 10 is constructed with two separators 20 sandwiching the core sheet 22. The fuel cell 10 allows gas to flow between the separator 20 and the core sheet 22. Two types of gas, a first gas and a second gas, flow between the separator 20 and the core sheet 22 via different flow paths.

2, the core sheet 22 is a member having a substantially rectangular shape in a side view. The core sheet 22 has a frame-shaped sheet 23 and an MEA (Membrane Electrode Assembly) 24. The MEA 24 has a pair of electrode layers 24b (including a catalyst layer and a gas diffusion layer) and an electrolyte membrane 24a sandwiched between the pair of electrode layers 24b. The MEA 24 can generate electricity by reacting a first gas and a second gas flowing between the separator 20 and the core sheet 22 with each other via the electrolyte membrane 24a and the electrode layers 24b.
The frame-shaped sheet 23 is a thin, frame-shaped sheet made of resin that supports the MEA 24. The two frame-shaped sheets 23 support the MEA 24 by sandwiching the outer peripheral edge of the MEA 24. The MEA 24 is exposed from an opening in the center of the frame-shaped sheet 23.

The separator 20 is a thin plate-like member made of carbon material, metal material, or the like. The separator 20 has an anode-side separator 20a and a cathode-side separator 20b. In the following description, the anode-side separator 20a and the cathode-side separator 20b may be collectively referred to as "separator 20." A first gas is introduced between the anode-side separator 20a and the core sheet 22. A second gas is introduced between the cathode-side separator 20b and the core sheet. Cooling water passes through flow paths formed between adjacent fuel cell cells 10.

As shown in FIG. 2 , the separator 20 has a gas flow channel groove 21, an inlet portion 50, and an outlet portion 60. The separator 20 forms a gas flow channel between the separator 20 and the core sheet 22, through which gas can flow. The gas flow channel groove 21 is formed from the inlet portion 50 to the outlet portion 60. In this embodiment, the gas flow channel groove 21 is formed on the surface of the separator 20 and has a wavy uneven shape extending from the inlet portion 50 to the outlet portion 60. The gas flow channel groove 21 forms a plurality of fine flow channels between the separator 20 and the core sheet 22. Note that while FIG. 2 illustrates the gas flow channel groove 21 on a portion of the separator 20, in reality, it is provided on the entire surface of the separator 20 facing the electrode layer 24b.
The inlet portion 50 allows gas to be introduced between the separator 20 and the core sheet 22. A space serving as the inlet portion 50 is formed between the separator 20 and the core sheet 22.
The outlet portion 60 can discharge gas introduced between the separator 20 and the core sheet 22. The inlet portion 50 and the outlet portion 60 are provided at the end of the separator 20 in the direction in which the gas flow channel groove 21 extends.

In this embodiment, the anode-side separator 20a is provided with a first gas flow channel groove 21a as the gas flow channel groove 21. The anode-side separator 20a is also provided with a first inlet portion 50a and a first outlet portion 60a as the inlet portion 50 and the outlet portion 60.
In this embodiment, the cathode-side separator 20b is provided with a second gas flow channel groove 21b as the gas flow channel groove 21. The cathode-side separator 20b is also provided with a second inlet portion 50b and a second outlet portion 60b as the inlet portion 50 and the outlet portion 60. It should be noted that this embodiment employs a crossflow system in which the first gas and the second gas flow into the fuel cell 10 from opposite directions, and therefore the positions of the inlet portion 50 and the outlet portion 60 are different between the anode-side separator 20a and the cathode-side separator 20b.

Figure 3 is a front view (viewed from side F) of the anode side separator 20a and the cathode side separator 20b according to this embodiment. In this figure, the first gas flows between the back surface (opposite side of the page) of the anode side separator 20a and a core sheet (not shown). The second gas flows between the front surface of the cathode side separator 20b and a core sheet (not shown). As shown in Figure 3, the inlet section 50 has an inlet hole 51 and a diffusion section 52.

The inlet hole 51 is a hole for introducing gas taken in through the first gas inlet 2 and the second gas inlet 4 shown in FIG. 1 into the cell, and the gas is introduced into the cell from the inlet hole 51. The gas introduced from the inlet hole 51 is diffused in the diffusion section 52, and is guided to the gas flow channel 21 by the gas pressure acting within the diffusion section 52. The outlet section 60 has an outlet hole 61 and a collection section 62. The outlet hole 61 is provided to discharge the gas introduced between the separator 20 and the core sheet 22. The gas flowing out from the gas flow channel 21 is collected in the collection section 62 toward the outlet hole 61 and is discharged from the cell to the outside through the outlet hole 61.
In this embodiment, the inlet hole 51 and the outlet hole 61 are provided at diagonally opposite corners of the separator 20 .
In the following description, the inlet hole 51 and the outlet hole 61 may be collectively referred to as the "hole portion." Furthermore, in the following description, the diffusion portion 52 and the collection portion 62 may be collectively referred to as the "diffusion collection portion."
Although not shown in the present embodiment, a seal structure is provided between the separator 20 and the core sheet 22 to enclose the inlet hole 51, diffusion section 52, gas flow channel groove 21, collection section 62, and outlet hole 61 through which the gases pass. The cooling water flow channels formed between the fuel cell cells 10 also have a similar seal structure, so that the fluids can flow without mixing with each other.

Fig. 4 is a front view of a fuel cell 10 according to the present disclosure. The anode-side separator 20a is located on the front side of the paper in Fig. 4, and the cathode-side separator 20b is located on the back side of the paper in Fig. 4. Fig. 4 shows the anode-side separator 20a and the cathode-side separator 20b as seen perspectively from the F side.
In this embodiment, the anode-side separator 20a has a first flow path that is composed of a first gas inlet hole 51a, a first gas diffusion portion 52a, a first gas flow path groove 21a, a first gas outlet hole 61a, and a first gas collection portion 62a.
The cathode separator 20b also has a second flow path that is composed of a second gas inlet hole 51b, a second gas diffusion portion 52b, a second gas flow path groove 21b, a second gas outlet hole 61b, and a second gas collection portion 62b.
4, in a single fuel cell 10 according to this embodiment, the inlet and outlet sections do not overlap when viewed perspectively from the side of the fuel cell 10. Furthermore, when a single fuel cell 10 according to this embodiment is viewed perspectively from the side, the first gas diffusion section 52a overlaps with the second gas collection section 62b, and the first gas collection section 62a overlaps with the second gas diffusion section 52b.

Next, the manner in which gas flows between the separators 20 will be explained using Figure 5. Figure 5 is a diagram showing how gas flows in the fuel cell 10 according to this embodiment. Figure 5(a) is a diagram illustrating the first flow path formed between the anode side separator 20a and the core sheet 22 when the fuel cell 10 is viewed from the F side. Figure 5(b) is a diagram illustrating the second flow path formed between the cathode side separator 20b and the core sheet 22 when the fuel cell 10 is viewed from the F side.

As shown in FIGS. 5( a) and 5(b), in this embodiment, the first gas is introduced between the anode-side separator 20a and the core sheet 22 through the first gas inlet hole 51a. After being introduced through the first gas inlet hole 51a, the first gas is diffused in the vertical direction of the first gas flow channel 21a by the first gas diffusion section 52a and then flows in the direction R where the first gas outlet hole 61a is provided. The second gas flows between the cathode-side separator 20b and the core sheet 22 in the same direction as the first gas, but in a different direction from the first gas. In other words, when the first gas and the second gas are introduced into the fuel cell 10, the first gas and the second gas flow in directions that intersect with each other across the core sheet 22. In this embodiment, the first gas is hydrogen gas, and the second gas is air.
In this embodiment, a cross-flow (counter-flow) type fuel cell 10 in which the first gas and the second gas flow in different directions is described, but the present disclosure is not limited to this. For example, a parallel-flow type fuel cell in which the first gas and the second gas flow in the same direction may also be used.

Next, the diffusion collection section will be described in detail using Figures 6A and 6B. Figure 6A is an enlarged view of portion VI in Figure 5(b). Figure 6B is a cross-sectional view of the collection section taken along the line B-B in Figure 6A. In the following explanation, the second gas collection section 62b of the cathode-side separator 20b will be described in detail, but diffusion collection sections other than the second gas collection section 62b may also have a similar configuration.

6A , the diffusion collection section has a protrusion 100 and a base 101. The base 101 is a portion configured to be flush with the base surface of, for example, the cathode-side separator 20b. The protrusion 100 is a convex portion processed from the base 101 so as to abut against the frame-shaped sheet 23. More specifically, the protrusion 100 protrudes toward the frame-shaped sheet 23 sandwiched between the anode-side separator 20a and the cathode-side separator 20b.
6B , the protrusions 100 have flat portions 102 at their tips. The flat portions 102 are configured to be able to come into surface contact with the frame-shaped sheet 23. A gas conduction path R is formed by a pair of adjacent protrusions 100, the frame-shaped sheet 23, and the base portion 101.

As shown in FIG. 6A, the separation distance between the protrusions 100 provided on the second gas collection section 62b varies depending on the distance from the first gas inlet hole 51a. As shown in FIG. 6A, the separation distance S1 between the protrusions 100a and 100b is smaller than the separation distance S2 between the protrusions 100c and 100d, which are located farther from the first gas inlet hole 51a than the protrusions 100a and 100b. Near the first gas inlet hole 51a, the first gas pressure is greatest on the opposing sides of the frame-shaped sheet 23, whereas the second gas collection section 62b is located downstream in the gas flow path, resulting in a large pressure drop. As a result, the pressure difference between the first and second gases is greatest near the first gas inlet hole 51a. Therefore, to prevent deformation of the frame-shaped sheet 23 due to the pressure difference, the support interval between the protrusions 100 supporting the frame-shaped sheet 23 near the first gas inlet hole 51a is smaller than in other locations.

Next, the function of the convex portion 100 in this disclosure will be described in detail using Figure 7. Figure 7 is a cross-sectional view showing the portion where the frame-shaped sheet 23 is sandwiched between the first gas diffusion portion 52a of the anode-side separator 20a and the second gas collection portion 62b of the cathode-side separator 20b. In Figure 7, the anode-side separator 20a is located at the top of the page, and the cathode-side separator 20b is located at the bottom of the page.

As described above, in the first gas diffusion section 52a, the protrusion 100e forms a gas conduction channel R1 between the frame-shaped sheet 23 and the anode-side separator 20a. In the second gas collection section 62b, the protrusion 100f forms a gas conduction channel R2 between the frame-shaped sheet 23 and the cathode-side separator 20b. In this embodiment, hydrogen gas flows as the first gas through the gas conduction channel R1. Air flows as the second gas through the gas conduction channel R2.

When gas is introduced into the gas conduits R1 and R2, pressure from both the first gas and the second gas is applied to the frame-shaped sheet 23. In this situation, if the frame-shaped sheet 23 is deformed by the pressure, it may block the gas conduits R1 and R2.
More specifically, due to pressure loss within the flow path, the pressure of the gas flowing through the gas conduction passage R is highest near the inlet hole 51 and lowest near the outlet hole 61. For this reason, the pressure within the gas conduction passage R1 of the first gas diffusion section 52a is likely to be higher than the pressure within the gas conduction passage R2 of the second gas collection section 62b. Particularly in the case where the first gas is hydrogen gas and the second gas is air, as in this embodiment, the pressure loss of air is higher than that of hydrogen gas, so the pressure within the gas conduction passage R1 of the first gas diffusion section 52a is higher than the pressure within the gas conduction passage R2 of the second gas collection section 62b.
The gas conduction channel R1 and the gas conduction channel R2 are separated by a deformable resin frame-shaped sheet 23. The frame-shaped sheet 23 separating the gas conduction channel R1 and the gas conduction channel R2 may be deformed due to the pressure difference between the pressures in the gas conduction channel R1 and the gas conduction channel R2. Specifically, the frame-shaped sheet 23 may bulge convexly toward the base portion 101f of the cathode separator 20b, blocking the gas conduction channel R2.
The amount of deformation of the frame-shaped sheet 23 due to the pressure difference is determined by the magnitude of the pressure difference, the bending rigidity of the frame-shaped sheet 23, and the distance between the protrusions 100 that support the frame-shaped sheet 23. According to the fuel cell 10 according to the present disclosure, even if the frame-shaped sheet 23 has a thin plate thickness and low bending rigidity, by reducing the distance between the protrusions 100 that support the frame-shaped sheet 23 in accordance with the rigidity of the frame-shaped sheet 23, it is possible to suppress deformation of the frame-shaped sheet 23 due to the pressure difference to a level that does not block the flow path while keeping the thickness of the frame-shaped sheet 23 small.

Specifically, the maximum deflection δ when a differential pressure P is applied to the frame-shaped sheet 23 that deflects between any pair of adjacent protrusions 100 can be approximately calculated as the maximum displacement when a distributed load is applied to a doubly supported beam that is restrained and supported at both ends. That is, if the differential pressure between the first gas and the second gas is P, the thickness of the frame-shaped sheet 23 is h, the elastic modulus of the frame-shaped sheet 23 is E, the height of the protrusions 100 is D, and the distance between the contact portions 200 of the frame-shaped sheet 23 and the adjacent protrusions 100 is L, the maximum deflection δ can be expressed by the following equation:

From the above formula, it can be seen that even when the thickness h of the frame-shaped sheet 23 is thin, the value of the deflection amount δ can be kept small by reducing the distance L between the contact portions 200 of the convex portions 100 and the frame-shaped sheet 23.
One guideline for preventing the maximum deflection amount δ from blocking the flow path is that the deflection amount δ of the frame-shaped sheet 23 does not exceed the height D of the convex portion, i.e., 1/3 of the flow path height. Expressed mathematically, this is given by the following equation.

By configuring the fuel cell 10 so as to satisfy the above formula, it is possible to prevent blockage of the gas conduction passage R due to deformation of the frame-shaped sheet 23. For example, it can be used as an indicator for the height of the convex portion 100 to avoid blocking the gas conduction passage R, depending on the thickness h and elastic modulus E of the frame-shaped sheet 23. It can also be used as an indicator for determining the thickness h and elastic modulus E of the frame-shaped sheet 23, depending on the height D of the convex portion 100.
7, the height D of the protrusion 100f is the distance from the base portion 101f to the contact portion 200 where the flat portion 102f is in contact with the frame-shaped sheet 23. The distance L between adjacent protrusions 100 is the distance between the contact portions 200 where the adjacent protrusions 100 are in contact with the frame-shaped sheet 23.

In the embodiment shown in Figure 7, convex portions 100e and 100f provided on the diffusion section abut against the frame-shaped sheet 23, suppressing displacement of the frame-shaped sheet 23 in the planar direction. Furthermore, convex portion 100e has a flat portion 102e, and convex portion 100f has a flat portion 102f. Flat portion 102e and flat portion 102f are capable of surface contact with the frame-shaped sheet 23, dispersing the surface pressure acting on the frame-shaped sheet 23.

The pressure exerted on the frame-shaped sheet 23 by the gas flowing through the gas conduction passage R is highest near the inlet hole 51 and lowest near the outlet hole 61. Therefore, in the diffusion section near the inlet hole 51 and outlet hole 61, there is a large difference (differential pressure) between the pressure exerted on the frame-shaped sheet 23 by the anode-side gas conduction passage R and the pressure exerted on the frame-shaped sheet 23 by the cathode-side gas conduction passage R. Therefore, the areas near the inlet hole 51 and outlet hole 61 create an environment in which the frame-shaped sheet 23 is particularly susceptible to deformation.

In the fuel cell according to the present disclosure, the distance between the protruding portions 100 at the inlet portion 50 becomes smaller the closer they are to the inlet hole 51, and the distance between the protruding portions 100 at the outlet portion 60 becomes smaller the closer they are to the outlet hole 61. This allows the protruding portions 100 to effectively support areas of the frame-shaped sheet 23 where the differential pressure is high, and makes it possible to provide a fuel cell 10 that can suppress deformation of the frame-shaped sheet 23.
Furthermore, in this embodiment, the distance between the protrusions 100 is changed depending on the distance from the inlet hole and the outlet hole, but instead of changing the distance between the protrusions 100, the bending rigidity of the frame-shaped sheet 23 may be changed. That is, by increasing the bending rigidity of the frame-shaped sheet 23 (for example, by increasing the plate thickness) the closer it is to the inlet hole and the outlet hole, it is possible to suppress deformation of the frame-shaped sheet in areas where the differential pressure is greater.

Furthermore, in the fuel cell 10 according to the present disclosure, the protrusions 100 may be dimples that protrude toward the frame-shaped sheet 23. This configuration makes it easier to increase the flow path area of the gas conduction passage R.

The above describes an embodiment of the present disclosure, but it goes without saying that the technical scope of the present disclosure should not be interpreted as being limited by the description of this embodiment. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications to the embodiment are possible within the scope of the invention described in the claims. The technical scope of the present disclosure should be determined based on the scope of the invention described in the claims and their equivalents.

REFERENCE SIGNS LIST 1 fuel cell 2 first gas inlet 3 first gas outlet 4 second gas inlet 5 second gas outlet 6 cooling water inlet 7 cooling water outlet 10 fuel cell 20 separator 20a anode side separator 20b cathode side separator 21 gas flow channel groove 21a first gas flow channel groove 21b second gas flow channel groove 22 core sheet 23 frame-shaped sheet 24 MEA
24a Electrolyte membrane 24b Electrode layer 50 Inlet portion 50a First inlet portion 50b Second inlet portion 51 Inlet hole 51a First gas inlet hole 51b Second gas inlet hole 52 Diffusion portion 52a First gas diffusion portion 52b Second gas diffusion portion 60 Outlet portion 60a First outlet portion 60b Second outlet portion 61 Outlet hole 61a First gas outlet hole 61b Second gas outlet hole 62 Collection portion 62a First gas collection portion 62b Second gas collection portion 100, 100a, 100b, 100c, 100d, 100e, 100f Convex portions 101, 101e, 101f Base portion 102, 102e, 102f Flat portion 200 Contact portions R, R1, R2 Gas conduction path

Claims (8)

A core sheet and
A separator is provided on the outside of the core sheet,
The core sheet includes an MEA having an electrolyte membrane and an electrode layer provided on the outside of the electrolyte membrane;
a resin frame sheet that supports the MEA,
The separator has an inlet portion and an outlet portion,
the inlet portion has a first inlet portion through which a first gas is introduced and a second inlet portion through which a second gas is introduced,
the outlet portion has a first outlet portion through which the first gas is discharged and a second outlet portion through which the second gas is discharged,
At least one of the first inlet portion, the second inlet portion, the first outlet portion, and the second outlet portion has a plurality of protrusions that protrude toward the frame-shaped sheet and support the frame-shaped sheet,
the protrusions abut against the frame-shaped sheet to suppress displacement of the frame-shaped sheet in a surface direction,
the inlet portion has an inlet hole;
the outlet portion has an outlet hole;
a distance between the plurality of protrusions in the inlet portion is smaller as the protrusions are closer to the inlet hole in terms of concentric distance from the inlet hole,
A fuel cell , wherein the distance between the plurality of protrusions in the outlet portion decreases as the protrusions become closer to the outlet hole in terms of concentric distance from the outlet hole . The fuel cell according to claim 1, wherein the protrusions are dimples that protrude toward the frame-shaped sheet. The fuel cell according to claim 1 or 2, wherein the convex portion has a flat portion that abuts against the frame-shaped sheet, and the flat portion and the frame-shaped sheet are in surface contact. The fuel cell according to claim 1 or 2, wherein the first gas is hydrogen gas and the second gas is air. The first gas and the second gas are configured to flow in opposite directions to each other,
The fuel cell according to claim 1 or 2, wherein the protrusion is provided at least at the outlet portion. 3. The fuel cell according to claim 1, wherein the bending rigidity of the frame-shaped sheet increases as the frame-shaped sheet approaches the inlet hole in a concentric distance from the inlet hole , and the bending rigidity of the frame-shaped sheet at the outlet portion increases as the frame-shaped sheet approaches the outlet hole in a concentric distance from the outlet hole . Regarding the maximum deflection amount δ of the frame-shaped sheet deflected between any pair of adjacent convex portions,
The differential pressure between the first gas and the second gas is P,
The thickness of the frame-shaped sheet is h, the elastic modulus of the frame-shaped sheet is E,
The height of the convex portion is D,
3 . The fuel cell according to claim 1 , wherein the following formula is satisfied when the distance between the contact portions of adjacent protrusions and the frame-shaped sheet is L:
A fuel cell using the fuel cell according to claim 1 or 2.