JP7790198B2 - fuel cell stack - Google Patents

Description

The present invention relates to a fuel cell stack.

Patent Document 1 discloses a fuel cell stack. This fuel cell stack includes multiple stacked unit cells. Each unit cell includes two separators. Between the two separators, there is a membrane electrode assembly and two gas diffusion layers that sandwich the membrane electrode assembly in the stacking direction of the unit cells.

The surface of each separator facing the gas diffusion layer is provided with a groove-like flow path for guiding the reaction medium. The surface of each separator opposite the facing surface is provided with a groove-like flow path that forms a cavity for guiding the cooling medium between the separators of adjacent single cells.

Furthermore, the opposing surfaces of the separators are provided with convex beads and recesses formed between the beads and the flow paths.
The beads are provided all around the periphery of the flow path.

The bottom walls of the recesses formed in the separators are in contact with each other (see FIG. 6A of Patent Document 1).
In a fuel cell stack including such a separator, the cooling medium flowing through the cavity is prevented from flowing toward the beads, that is, from flowing by the recesses that are in contact with each other.

Patent Document 2 also discloses a molding method for forming fuel cell separators from metal sheet material. In this molding method, a continuous protrusion, i.e., a separator flow path, is formed in the metal sheet material between the recess and protrusion of the fixed die and the protrusion and recess of the movable punch. The recesses of the die and punch have bottoms that are convexly curved in the center. As a result, the center of the formed protrusion is curved concavely.

Special Publication No. 2020-522089 Japanese Patent Application Laid-Open No. 2018-89679

However, when applying the molding method described in Patent Document 2, for example, to form the separators for the fuel cell described in Patent Document 1, the following problem occurs. Specifically, the central portions of the opposing surfaces of the bottom walls of the recesses are curved in a concave shape. As a result, gaps are formed between the bottom walls of the recesses of each separator. As a result, the cooling medium that has flowed sideways from the cavity leaks out through the gaps, reducing the effectiveness of the recesses in suppressing sideways flow. This may result in a decrease in the cooling efficiency of the cooling medium, and ultimately in a decrease in the power generation efficiency of the fuel cell.

However, this problem is not limited to applications of the molding method described in Patent Document 2. For example, it can occur in any product that has a depression in the bottom wall of the recess due to molding shrinkage or the like.

The object of the present invention is to provide a fuel cell stack that can suppress side flow of the cooling medium.

A fuel cell stack for achieving the above-mentioned object is formed by stacking a plurality of unit cells in a first direction, each unit cell including a power generation unit and a first separator and a second separator sandwiching the power generation unit, and each of the first separator and the second separator has a plurality of groove flow paths extending in a second direction and arranged side by side on the surface opposite to the surface facing the power generation unit, through which a coolant flows, and the first separator has a first protrusion that protrudes toward the second separator of another unit cell adjacent to the first separator in the first direction and abuts against the second separator, and The first convex portion is provided outside the groove flow path located at the outermost position in a third direction intersecting both the first direction and the second direction, and multiple first convex portions are provided side by side in the second direction. The second separator has multiple second convex portions that each protrude toward the first convex portion in the first direction and abut against the first convex portions. A recessed portion extending in the third direction is provided in the center of the tip of each second convex portion in the second direction, the length of the recessed portion in the second direction is greater than the length of the first convex portion in the second direction, and the tip of each first convex portion is located within the recessed portion.

With this configuration, the first and second convex portions abut with the tip of the first convex portion positioned within the recess of the second convex portion. Therefore, the gap formed between the first convex portion and the recess of the second convex portion is smaller than when the length of the first convex portion in the second direction is the same as the length of the second convex portion in the second direction. This makes it more difficult for the cooling medium to flow through the gap to the outside of the first and second convex portions. Therefore, sideways flow of the cooling medium can be suppressed.

The fuel cell stack for achieving the above-mentioned object is formed by stacking a plurality of unit cells in a first direction, each unit cell including a power generation unit and a first separator and a second separator sandwiching the power generation unit. The first separator and the second separator each have a surface opposite to the surface facing the power generation unit, on which a plurality of groove channels extending in a second direction and through which a coolant flows are arranged side by side. The first separator has a first convex portion that protrudes toward the second separator of another unit cell adjacent to the first separator in the first direction and abuts against the second separator. The first convex portion is located outside the groove channel located at the outermost position in a third direction intersecting both the first direction and the second direction. The second separator is provided with a plurality of second protrusions arranged side by side in the second direction, each protruding toward the first protrusion in the first direction and abutting the first protrusion, and the tip of the first protrusion is provided with a first recessed portion located in the center in the second direction and extending in the third direction, and a pair of first bulges located on both sides of the first recessed portion in the second direction, and the tip of the second protrusion is provided with a second recessed portion located in the center in the second direction and extending in the third direction, and a pair of second bulges located on both sides of the second recessed portion in the second direction, and only one of the pair of second bulges is located within the first recessed portion.

With this configuration, the first and second protrusions come into contact with each other when one of the pair of second bulges of the second protrusion is located within the first recess of the first protrusion, and one of the pair of first bulges of the first protrusion is located within the second recess of the second protrusion. Therefore, when the first and second protrusions come into contact, the gap formed by the first and second recesses becomes smaller. This makes it more difficult for the cooling medium to flow through the gap to the outside of the first and second protrusions. Therefore, sideways flow of the cooling medium can be suppressed.

FIG. 1 is an exploded perspective view showing a unit cell of a fuel cell stack according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing the fuel cell stack of the embodiment. FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. FIG. 4 is a cross-sectional view corresponding to FIG. 3, showing a second embodiment of the fuel cell stack.

Each embodiment of a fuel cell stack will be described below with reference to Figures 1 to 4. Note that in each drawing, some components are exaggerated or simplified for ease of explanation, and the dimensional proportions of each component may differ from the actual proportions. Furthermore, in the following description, "orthogonal" does not necessarily mean strictly perpendicular, but also includes cases where the components intersect at approximately right angles within the range that achieves the effects of each embodiment.

First Embodiment
First, a first embodiment of a fuel cell stack will be described with reference to FIGS.
As shown in FIGS. 1 and 2, the fuel cell stack is formed by stacking a plurality of unit cells 90, each of which has a rectangular plate shape as a whole.

In the following description, the stacking direction of the unit cells 90 will be referred to as the first direction X. Furthermore, among the directions perpendicular to the first direction X, the longitudinal direction of the unit cells 90 will be referred to as the second direction Y. Furthermore, the direction perpendicular to both the first direction X and the second direction Y will be referred to as the third direction Z.

The unit cell 90 has inlet-side manifolds 91, 93, and 95 for introducing a reactant gas or a coolant into the unit cell 90, and outlet-side manifolds 92, 94, and 96 for discharging the reactant gas and coolant from the unit cell 90 to the outside. In this embodiment, the inlet-side manifold 91 and the outlet-side manifold 92 are manifolds through which a fuel gas flows. The fuel gas is, for example, hydrogen gas. The inlet-side manifold 93 and the outlet-side manifold 94 are manifolds through which a coolant flows. The coolant is, for example, cooling water. The inlet-side manifold 95 and the outlet-side manifold 96 are manifolds through which an oxidizer gas flows. The oxidizer gas is, for example, air.

The inlet side manifolds 91, 93, 95 and the outlet side manifolds 92, 94, 96 are rectangular in plan view and penetrate the unit cell 90 in the first direction X.
The inlet-side manifold 91 and the outlet-side manifolds 94, 96 are provided at an end of one side (the left side in the left-right direction in FIG. 1 ) of the unit cell 90 in the second direction Y. The inlet-side manifold 91 and the outlet-side manifolds 94, 96 are lined up in order from one side (the far side of the paper in FIG. 1 ) to the other side (the near side of the paper in FIG. 1 ) in the third direction Z.

The outlet side manifold 92 and the inlet side manifolds 93, 95 are provided at the end of the unit cell 90 on the other side in the second direction Y (the right side in Figure 1). The outlet side manifold 92 and the inlet side manifolds 93, 95 are lined up in order from the other side in the third direction Z (the front side of the paper in Figure 1) to one side (the back side of the paper in Figure 1).

The unit cell 90 has a membrane electrode assembly (hereinafter referred to as MEA 10), a frame member 20 that holds the MEA 10, and a first separator 30 and a second separator 40 that sandwich the MEA 10 and frame member 20.

Each component will be described in detail below.
<MEA10>
1 , the MEA 10 includes a solid polymer electrolyte membrane (hereinafter referred to as the electrolyte membrane) (not shown) and electrodes 11, 12 provided on both sides of the electrolyte membrane. In this embodiment, the electrode bonded to one side of the electrolyte membrane in the first direction X (the upper side in the vertical direction in FIG. 1 ) is the cathode electrode 11. The electrode bonded to the other side of the electrolyte membrane in the first direction X (the lower side in FIG. 1 ) is the anode electrode 12.

Each of the electrodes 11 and 12 has a catalyst layer bonded to the electrolyte membrane and a gas diffusion layer bonded to the catalyst layer (both not shown).
The MEA 10 corresponds to the power generating section of the fuel cell according to the present invention.

<Frame member 20>
As shown in FIGS. 1 and 2, the frame member 20 has a rectangular frame shape that is long in the second direction Y, and is made of, for example, a synthetic resin material.

The frame member 20 has through holes 21, 22, 23, 24, 25, and 26 that form the manifolds 91, 92, 93, 94, 95, and 96, respectively.
The frame member 20 has an opening 27 in the center. The MEA 10 is joined to the periphery of the opening 27 from one side in the first direction X (the upper side in FIG. 1 ).

<First separator 30>
As shown in FIGS. 1 and 2, the first separator 30 is formed by press-forming a metal plate made of, for example, titanium or stainless steel, which has a rectangular shape in plan view.

The first separator 30 has through holes 31 , 32 , 33 , 34 , 35 , and 36 that form the manifolds 91 , 92 , 93 , 94 , 95 , and 96 , respectively.
The first separator 30 has a first surface 30A having a facing surface 30a that faces the anode electrode 12 of the MEA 10 in the first direction X, and a second surface 30B having a surface 30b opposite to the facing surface 30a.

The first surface 30A is provided with a plurality of groove channels 37A through which fuel gas flows and a pair of connection portions 37B. Note that Figure 1 shows the groove channels 37A and connection portions 37B in a simplified form.

A plurality of groove channels 37A are provided on the opposing surface 30a. Each of the plurality of groove channels 37A extends linearly in the second direction Y (see Figure 1). Each of the plurality of groove channels 37A is arranged at intervals in the third direction Z (see Figure 2).

As shown in FIG. 1, a pair of connection portions 37B extend from both sides of the multiple groove flow paths 37A in the second direction Y toward each of the through holes 31 and 32. Fuel gas is introduced from the inlet manifold 91 into the multiple groove flow paths 37A via one of the connection portions 37B. Furthermore, the fuel gas flowing through the multiple groove flow paths 37A is discharged to the outlet manifold 92 via the other connection portion 37B.

As shown in Figures 1 and 2, the second surface 30B is provided with a plurality of groove channels 38A through which the cooling medium flows, a pair of connecting portions 38B, and a first protrusion 50. Note that Figure 1 shows the groove channels 38A and connecting portions 38B in a simplified form.

A plurality of groove channels 38A are provided on the surface 30b. Each of the plurality of groove channels 38A extends linearly in the second direction Y (see Figure 1). Each of the plurality of groove channels 38A is arranged at intervals in the third direction Z (see Figure 2).

As shown in FIG. 2, groove flow path 37A is formed by the backside of the convex portion located between adjacent groove flow paths 38A in the third direction Z. Also, groove flow path 38A is formed by the backside of the convex portion located between adjacent groove flow paths 37A in the third direction Z.

A pair of connection portions 38B, shown by dashed lines in FIG. 1, extend from both sides of the multiple groove flow paths 38A in the second direction Y toward each of the through holes 33, 34. The cooling medium is introduced from the inlet manifold 93 into the multiple groove flow paths 38A via one of the connection portions 38B. The cooling medium flowing through the multiple groove flow paths 38A is discharged to the outlet manifold 94 via the other connection portion 38B.

<First protrusion 50>
1 and 2, the first convex portions 50 are provided on the outside of a pair of outer grooves 38a that are located outermost in the third direction Z among the plurality of grooves 38A. In this embodiment, the first convex portions 50 are provided on the outside of both of the pair of outer grooves 38a (see FIG. 1). Here, "outside" in the third direction Z refers to the side away from the center of the unit cell 90 in the third direction Z. Note that FIG. 2 illustrates the outer grooves 38a that are located on one side of the pair of outer grooves 38a in the third direction Z (the farthest side in the plane of FIG. 1) and the first convex portions 50 that are located on the outside of the outer grooves 38a.

The first protrusion 50 protrudes toward the second separator 40 of another unit cell 90 adjacent to the unit cell 90 in the first direction X (see FIG. 2).
The first protrusion 50 extends in the third direction Z.

As shown in FIG. 1, multiple first protrusions 50 are arranged at intervals in the second direction Y. The multiple first protrusions 50 are provided over the entire area in the second direction Y where the outer groove flow path 38a is formed.

As shown in FIG. 3 , a first recess 52 and a pair of first bulges 53 are provided at the tip 51 of each first protrusion 50 .
The first recess 52 is located in the center of the tip 51 in the second direction Y.

As shown in FIG. 2, the first recess 52 extends in the third direction Z.
As shown in FIG. 3, the first recessed portion 52 is curved with respect to an imaginary line (not shown) extending in the second direction Y in a cross-sectional view.

The pair of first bulges 53 are located on both sides of the first recess 52 in the second direction Y.
In this embodiment, the height H1 of the first convex portion 50 in the first direction X is set within a range of 0.2 mm or more and 0.8 mm or less.

In this embodiment, the length of the tip portion 51 in the second direction Y (hereinafter referred to as width W1) is set to 1 mm. Note that width W1 corresponds to the length of the first convex portion in the second direction Y according to the present invention.

In this embodiment, the depth D1 of the first recess 52 in the first direction X is set to be in the range of 10 μm or more and 50 μm or less.
<Second separator 40>
As shown in FIGS. 1 and 2, the second separator 40 is formed by press-forming a metal plate made of, for example, titanium or stainless steel, which has a rectangular shape in plan view.

The second separator 40 has through holes 41 , 42 , 43 , 44 , 45 , and 46 that form the manifolds 91 , 92 , 93 , 94 , 95 , and 96 , respectively.
The second separator 40 has a first surface 40A having a facing surface 40a that faces the cathode electrode 11 of the MEA 10 in the first direction X, and a second surface 40B having a surface 40b opposite to the facing surface 40a.

The first surface 40A is provided with a plurality of groove channels 47A through which oxidant gas flows and a pair of connection portions 47B. Note that Figure 1 shows the groove channels 47A and connection portions 47B in a simplified form.

A plurality of groove channels 47A are provided on the opposing surface 40a. Each of the plurality of groove channels 47A extends linearly in the second direction Y (see Figure 1). Each of the plurality of groove channels 47A is arranged at intervals in the third direction Z (see Figure 2).

A pair of connection portions 47B, shown by dashed lines in FIG. 1, extend from both sides of the multiple groove flow paths 47A in the second direction Y toward each of the through holes 45, 46. Oxidant gas is introduced from the inlet side manifold 95 into the multiple groove flow paths 47A via one of the connection portions 47B. Furthermore, the oxidant gas flowing through the multiple groove flow paths 47A is discharged to the outlet side manifold 96 via the other connection portion 47B.

As shown in Figures 1 and 2, the second surface 40B is provided with a plurality of groove channels 48A through which the cooling medium flows, a pair of connecting portions 48B, and a second protrusion 60. Note that Figure 1 shows the groove channels 48A and connecting portions 48B in a simplified form.

A plurality of groove channels 48A are provided on the surface 40b. Each of the plurality of groove channels 48A extends linearly in the second direction Y (see Figure 1). Each of the plurality of groove channels 48A is arranged at intervals in the third direction Z (see Figure 2).

As shown in FIG. 2, groove flow path 47A is formed by the backside of the convex portion located between adjacent groove flow paths 48A in the third direction Z. Also, groove flow path 48A is formed by the backside of the convex portion located between adjacent groove flow paths 47A in the third direction Z.

As shown in FIG. 1, a pair of connection portions 48B extend from both sides of the multiple groove flow paths 48A in the second direction Y toward each of the through holes 43, 44. The cooling medium is introduced from the inlet side manifold 93 into the multiple groove flow paths 48A via one of the connection portions 48B. The cooling medium flowing through the multiple groove flow paths 48A is discharged to the outlet side manifold 94 via the other connection portion 48B.

<Second protrusion 60>
1 and 2, the second convex portions 60 are provided on the outer sides of a pair of outer groove channels 48a that are located outermost in the third direction Z among the plurality of groove channels 48A. In this embodiment, the second convex portions 60 are provided on the outer sides of both of the pair of outer groove channels 48a (see FIG. 1). Note that FIG. 2 illustrates the outer groove channel 48a that is located on one side of the pair of outer groove channels 48a in the third direction Z, and the second convex portions 60 that are located on the outer sides of the outer groove channels 48a.

The second protrusion 60 protrudes toward the first protrusion 50 in the first direction X (see FIG. 2).
The second protrusion 60 extends in the third direction Z.

As shown in FIG. 1 , the second protrusions 60 are arranged at intervals in the second direction Y. The second protrusions 60 are provided over the entire area in the second direction Y where the outer groove flow passage 48a is formed. In this embodiment, one second protrusion 60 is provided at a position corresponding to each of the first protrusions 50 in the first direction X.

As shown in FIG. 3 , a tip portion 61 of each second protrusion 60 is provided with a second recessed portion 62 and a pair of second bulged portions 63 .
The second recess 62 is located in the center of the tip 61 in the second direction Y.

As shown in FIG. 2, the second recessed portion 62 extends in the third direction Z.
As shown in FIG. 3, the second recessed portion 62 is curved with respect to an imaginary line (not shown) extending in the second direction Y in a cross-sectional view.

The pair of second bulges 63 are located on both sides of the second recess 62 in the second direction Y.
In this embodiment, the height H2 of the second convex portion 60 in the first direction X is set within a range of 0.2 mm or more and 0.8 mm or less.

The length of the tip portion 61 in the second direction Y (hereinafter referred to as width W2) is greater than the width W1 of the first protrusion 50 (width W2>width W1). In this embodiment, the width W2 is set to 2 mm.
In this embodiment, the depth D2 of the second recessed portion 62 in the first direction X is set within a range of 10 μm or more and 50 μm or less.

The length L of the second recessed portion 62 in the second direction Y is greater than the width W1 of the first protrusion 50 (length L>width W1).
The tip end 51 of the first protrusion 50 is located within the second recess 62 of the second protrusion 60. The pair of first bulges 53 are in contact with the second recess 62.

As shown in FIGS. 2 and 3 , a gap G<b>1 surrounded by the first recess 52 and the second recess 62 is formed between the first protrusion 50 and the second protrusion 60 .
2 , a gasket 70 is provided outside the first convex portions 50 and the second convex portions 60 in the third direction Z to seal between the separator 30 of the unit cell 90 and the second separator 40 of another unit cell 90 adjacent to the unit cell 90 in the first direction X. The multiple first convex portions 50 and the multiple second convex portions 60 are configured to partially fill the space S formed between the gasket 70 and the outer groove flow paths 38 a, 48 a in the third direction Z.

Next, the operation of the first embodiment will be described.
The first protrusion 50 and the second protrusion 60 come into contact with each other with the tip 51 of the first protrusion 50 positioned within the second recess 62 of the second protrusion 60. Therefore, the gap G1 formed by the first recess 52 of the first protrusion 50 and the second recess 62 of the second protrusion 60 is smaller than when the width W1 of the first protrusion 50 is the same as the width W2 of the second protrusion 60. This makes it difficult for the coolant to flow to the outside of the first protrusion 50 and the second protrusion 60 through the gap G1.

Next, the effects of the first embodiment will be described.
(1-1) The first separator 30 has a first protrusion 50 that protrudes toward the second separator 40 of another unit cell 90 adjacent to the unit cell 90 in the first direction X and abuts against the second separator 40. The first protrusion 50 is provided outside the outer groove 38a that is located outermost in the third direction Z. A plurality of first protrusions 50 are provided side by side in the second direction Y. The second separator 40 has a plurality of second protrusions 60 that protrude toward the first protrusions 50 in the first direction X and abut against the first protrusions 50. A second recess 62 extending in the third direction Z is provided at the center of the tip 61 of each second protrusion 60 in the second direction Y. The length L of the second recess 62 is greater than the width W1 of the first protrusion 50. The tip 51 of the first protrusion 50 is located within the second recess 62.

This configuration provides the above-mentioned effects, and therefore, the side flow of the cooling medium can be suppressed.
(1-2) The first protrusions 50 are provided over the entire area in which the outer groove passage 38a is formed in the second direction Y. The second protrusions 60 are provided over the entire area in which the outer groove passage 48a is formed in the second direction Y.

With this configuration, the above effect is achieved throughout the entire area in which the outer groove flow paths 38a, 48a are formed in the second direction Y. This further reduces sideways flow of the cooling medium.

(1-3) The first separator 30 and the second separator 40 are made of metal plates.
When the separators 30, 40 are made of a metal plate, recesses 52, 62 are likely to be formed at the tip ends 51, 61 of the protrusions 50, 60 during molding.

In this regard, with the above-described configuration, sideways flow of the cooling medium caused by the recesses 52 and 62 can be suppressed.
Second Embodiment
The second embodiment of the fuel cell stack will be described below, focusing on the differences from the first embodiment, with reference to Figure 4. Note that the same components of the fuel cell stack of the second embodiment as those of the fuel cell stack of the first embodiment are designated by the same reference numerals, and redundant explanations will be omitted. Furthermore, the components of the fuel cell stack of the second embodiment that correspond to those of the fuel cell stack of the first embodiment are designated by the reference numeral "1**," which is obtained by adding "100" to the reference numeral "**" of the first embodiment, and redundant explanations will be omitted.

<First protrusion 150>
As shown in FIG. 4, a plurality of first protrusions 150 are provided on the second surface 30B of the first separator 30.

A tip end 151 of each first protrusion 150 is provided with a first recess 152 and a pair of first bulges 153A and 153B.
In this embodiment, the height H3 of the first convex portion 150 in the first direction X is set within a range of 0.2 mm or more and 0.8 mm or less.

In this embodiment, the length of the tip portion 151 in the second direction Y (hereinafter referred to as width W3) is set to 2 mm.
In this embodiment, the depth D3 of the first recess 152 in the first direction X is set within a range of 10 μm or more and 50 μm or less.

<Second protrusion 160>
As shown in FIG. 4, a plurality of second protrusions 160 are provided on the second surface 40B of the second separator 40.

A tip end 161 of each second protrusion 160 is provided with a second recess 162 and a pair of second bulges 163A, 163B.
The second protrusion 160 has the same shape as the first protrusion 150. That is, the height H4 of the second protrusion 160 in the first direction X is the same as the height H3. The length of the tip 161 in the second direction Y (hereinafter referred to as the width W4) is the same as the width W3. The depth D4 of the second recess 162 in the first direction X is the same as the depth D3.

Of the pair of second bulges 163A, 163B, the second bulge 163A located on one side in the second direction Y (the left side in the left-right direction in Figure 4) is located within the first recess 152 and abuts against the first recess 152. On the other hand, of the pair of second bulges 163A, 163B, the second bulge 163B located on the other side in the second direction Y (the right side in Figure 4) is located on the other side of the tip 151 of the first convex portion 150.

Furthermore, of the pair of first bulging portions 153A, 153B, the first bulging portion 153B located on the other side in the second direction Y (right side in Figure 4) is located within the second recessed portion 162 and abuts against the second recessed portion 162. On the other hand, of the pair of first bulging portions 153A, 153B, the first bulging portion 153A located on one side in the second direction Y (left side in Figure 4) is located to one side of the tip portion 161 of the second convex portion 160.

A gap G2 surrounded by the first recess 152 and the second recess 162 is formed between the first protrusion 150 and the second protrusion 160 .
Next, the operation of the second embodiment will be described.

The first protrusion 150 and the second protrusion 160 come into contact with each other when only the second bulge 163A of the second protrusion 160 is located within the first recess 152 of the first protrusion 150 and only the pair of first bulge portions 153B of the first protrusion 150 are located within the second recess 162 of the second protrusion 160. Therefore, when the first protrusion 150 and the second protrusion 160 come into contact with each other, the gap G2 formed by the first recess 152 and the second recess 162 becomes smaller. This makes it more difficult for the coolant to flow to the outside of the first protrusion 150 and the second protrusion 160 through the gap G2.

Next, the effects of the second embodiment will be described.
(2-1) The tip 151 of the first protrusion 150 is provided with a first recess 152 located in the center in the second direction Y and extending in the third direction Z, and a pair of first bulges 153A, 153B located on both sides of the first recess 152 in the second direction Y. The tip 161 of the second protrusion 160 is provided with a second recess 162 located in the center in the second direction Y and extending in the third direction Z, and a pair of second bulges 163A, 163B located on both sides of the second recess 162 in the second direction Y. Of the pair of second bulges 163A, 163B, only the second bulge 163A is located within the first recess 152.

This configuration provides the above-mentioned effects, and therefore, the side flow of the cooling medium can be suppressed.
<Example of change>
The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

- The shapes of the inlet side manifolds 91, 93, 95 and the outlet side manifolds 92, 94, 96 are not limited to the rectangular shape in plan view as exemplified in the above embodiment, and may be, for example, an oval shape in plan view.

The flow of the reactant gas and coolant in the manifolds 91, 92, 93, 94, 95, and 96 is not limited to that exemplified in the above embodiment. For example, manifold 96 may be an inlet manifold for the oxidant gas, and manifold 95 may be an outlet manifold for the oxidant gas. Additionally, manifold 94 may be an inlet manifold for the coolant, and manifold 93 may be an outlet manifold for the coolant. In other words, the oxidant gas flowing through groove flow passage 47A and the coolant flowing through groove flow passages 38A and 48A may flow in the same direction as the fuel gas flowing through groove flow passage 37A.

- The groove flow path 37A (38A) is not limited to extending linearly in the second direction Y, as illustrated in the above embodiment. For example, the groove flow path 37A (38A) may extend in a wavy manner in the surface direction of the opposing surface 30a (surface 30b).

- The groove flow path 47A (48A) is not limited to extending linearly in the second direction Y, as illustrated in the above embodiment. For example, the groove flow path 47A (48A) may extend in a wavy manner in the planar direction of the opposing surface 40a (surface 40b).

The shapes of the first protrusion 50 and the second protrusion 60 are not limited to the shapes exemplified in the first embodiment. For example, the width W1 of the first protrusion 50 may be smaller than 1 mm or larger than 1 mm. The width W2 of the second protrusion 60 is not limited to 2 mm either, and can be changed as appropriate as long as the length L of the second recess 62 is greater than the width W1. The height H1 of the first protrusion 50 may be smaller than 0.2 mm or larger than 0.8 mm. In this case, the height H2 of the second protrusion 60 is not limited to the range of 0.2 mm or more and 0.8 mm or less, and can be changed as appropriate to match the height H1 of the first protrusion 50.

- The second convex portion 160 is not limited to a pair of second bulging portions 163A, 163B, in which only the second bulging portion 163A is located within the first recessed portion 152, as illustrated in the second embodiment. In other words, the second convex portion 160 may be a pair of second bulging portions 163A, 163B, in which only one of the pair of second bulging portions 163A, 163B is located within the first recessed portion 152.

The shapes of the first protrusion 150 and the second protrusion 160 are not limited to the shapes exemplified in the second embodiment. For example, the width W3 of the first protrusion 150 and the width W4 of the second protrusion 160 may each be less than 2 mm or greater than 2 mm. Furthermore, the shapes of the first protrusion 150 and the second protrusion 160 do not have to be identical. As long as only one of the pair of second bulges 163A, 163B is located within the first recess 152, the shapes of each can be modified as appropriate. For example, the width W3 may be less than or greater than the width W4. Furthermore, the height H3 may be less than 0.2 mm or greater than 0.8 mm. In this case, the height H4 is not limited to the range of 0.2 mm or more and 0.8 mm or less, and may be modified as appropriate to match the height H3 of the first protrusion 150.

The first recessed portion 52 (152) and the second recessed portion 62 (162) are not limited to being curved relative to an imaginary line extending in the second direction Y in a cross-sectional view, as illustrated in the above embodiment. For example, the first recessed portion 52 (152) may have a flat bottom surface extending in the planar direction of the second surface 30B. Similar modifications can also be made to the second recessed portion 62 (162).

- The first protrusion 50 is not limited to having a first recess 52 and a pair of first bulges 53. For example, the tip 51 of the first protrusion 50 may have a flat shape extending in the planar direction of the second surface 30B. Even in this case, it is sufficient that the length L of the second recess 62 is greater than the width W1 of the first protrusion 50.

- The first convex portion 50 (150) is not limited to being provided on the outside of both of the pair of outer groove flow paths 38a, as exemplified in the above embodiment. The first convex portion 50 (150) may be provided on the outside of only one of the pair of outer groove flow paths 38a. In this case, the second convex portion 60 (160) is not limited to being provided on the outside of both of the pair of outer groove flow paths 48a, and its arrangement may be changed appropriately to match the first convex portion 50 (150).

The fuel cell stack is not limited to the configuration illustrated in the above embodiment, in which one second protrusion 60 (160) is provided at a position corresponding to each of the multiple first protrusions 50 (150) in the first direction X, and some of the second protrusions 60 (160) may be omitted. In this case, the separator 30 includes first protrusions 50 (150) that do not face the second protrusions 60 (160) in the first direction X. Note that the first protrusions 50 (150) that do not face the second protrusions 60 (160) may be in contact with the second surface 40B of the separator 40.

The separators 30 and 40 are not limited to those formed by press-forming a metal plate material, but may be formed by, for example, cutting or etching.
The material of the separators 30 and 40 is not limited to titanium or stainless steel, but may also be aluminum or carbon.

- The first separator according to the present invention is not limited to being an anode-side separator as illustrated in the above embodiment, but can also be used as a cathode-side separator. In this case, the second separator according to the present invention can be used as an anode-side separator.

D1, D2, D3, D4...depth G1, G2...gap H1, H2, H3, H4...height L...length S...space W1, W2, W3, W4...width X...first direction Y...second direction Z...third direction 10...MEA
DESCRIPTION OF SYMBOLS 11...Anode electrode 12...Cathode electrode 20...Frame member 21...Through hole 22...Through hole 23...Through hole 24...Through hole 25...Through hole 26...Through hole 27...Opening 30...First separator 30A...First surface 30a...Opposite surface 30B...Second surface 30b...Surface 31...Through hole 32...Through hole 33...Through hole 34...Through hole 35...Through hole 36...Through hole 37A...Groove flow path 37B...Connecting portion 38A...Groove flow path 38a...Outer groove flow path 38B...Connecting portion 40...Second separator 40A...First surface 40a...Opposite surface 40B...Second surface 40b...Surface 41...Through hole 42...Through hole 43...Through hole 44...Through hole 45...Through hole 46...Through hole 47A...Groove flow path 47B...Connecting portion 48A...Groove flow path 48a...Outer groove flow path 48B...Connecting portion 50, 150...First convex portion 51, 151...Tip portion 52, 152...First recessed portion 53, 153A, 153B...First bulged portion 60, 160...Second convex portion 61, 161...Tip portion 62, 162...Second recessed portion 63, 163A, 163B...Second bulged portion 70...Gasket 90...Single cell 91...Inlet side manifold 92...Outlet side manifold 93...Inlet side manifold 94...Outlet side manifold 95...Inlet side manifold 96...Outlet side manifold

Claims (5)

A fuel cell stack is formed by stacking a plurality of unit cells in a first direction, each unit cell including a power generation section and a first separator and a second separator sandwiching the power generation section, and each of the first separator and the second separator has a surface opposite to a surface facing the power generation section, the surface of each of the first separator and the second separator having a plurality of grooves extending in a second direction and through which a coolant flows,
the first separator has a first protrusion that protrudes toward the second separator of another unit cell adjacent to the unit cell in the first direction and abuts against the second separator,
the first convex portion is provided outside the groove flow path that is located outermost in a third direction that intersects both the first direction and the second direction, and a plurality of the first convex portions are provided side by side in the second direction,
the second separator has a plurality of second protrusions that protrude toward the first protrusions in the first direction and abut against the first protrusions,
a recessed portion extending in the third direction is provided in a central portion in the second direction of a tip end portion of the second protrusion,
the recessed portion is curved with respect to an imaginary line extending in the second direction over the entirety of the second direction,
a length of the recessed portion in the second direction is greater than a length of the first protrusion in the second direction;
a tip end of the first protrusion is located within the recess;
Fuel cell stack. When the recessed portion is a second recessed portion,
a first recessed portion located at a center portion in the second direction and extending in the third direction, and a pair of bulging portions located on both sides of the first recessed portion in the second direction, at a tip end of the first protrusion;
The fuel cell stack of claim 1 . A fuel cell stack is formed by stacking a plurality of unit cells in a first direction, each unit cell including a power generation section and a first separator and a second separator sandwiching the power generation section, and each of the first separator and the second separator has a surface opposite to a surface facing the power generation section, the surface of each of the first separator and the second separator having a plurality of grooves extending in a second direction and through which a coolant flows,
the first separator has a first protrusion that protrudes toward the second separator of another unit cell adjacent to the unit cell in the first direction and abuts against the second separator,
the first convex portion is provided outside the groove flow path that is located outermost in a third direction that intersects both the first direction and the second direction, and a plurality of the first convex portions are provided side by side in the second direction,
the second separator has a plurality of second protrusions that protrude toward the first protrusions in the first direction and abut against the first protrusions,
a first recessed portion located at a center of the first protrusion in the second direction and extending in the third direction, and a pair of first bulging portions located on both sides of the first recessed portion in the second direction,
a second recessed portion located at a center portion in the second direction and extending in the third direction, and a pair of second bulging portions located on both sides of the second recessed portion in the second direction, are provided at a tip end of the second protrusion;
Only one of the pair of second bulging portions is located within the first recessed portion.
Fuel cell stack. the plurality of first convex portions and the plurality of second convex portions are provided over an entire range in which the groove flow passage is formed in the second direction;
The fuel cell stack according to any one of claims 1 to 3. The first separator and the second separator are made of metal plates.
The fuel cell stack according to any one of claims 1 to 4 .