JP7757221B2 - Complex - Google Patents

Description

The technology disclosed in this specification relates to composites.

One type of fuel cell that generates electricity using the electrochemical reaction between hydrogen and oxygen is the solid oxide fuel cell (hereinafter referred to as "SOFC"), which has an electrolyte layer containing solid oxide. A single fuel cell (hereinafter simply referred to as a "single cell"), which is the constituent unit of an SOFC, includes an electrolyte layer and an air electrode and a fuel electrode that face each other in a specific direction (hereinafter referred to as the "first direction") across the electrolyte layer.

SOFCs are generally used in the form of a fuel cell stack, which includes a power generation block in which multiple power generation units, each having a single cell, are arranged in a first direction, and a manifold is formed that communicates with a gas chamber facing a specific electrode, either the fuel electrode or the air electrode. The fuel cell stack also includes an end member, a gas passage member, and a joining member. The end member is disposed on one side of the power generation block in the first direction. The end member has an end through-hole that penetrates in the first direction and communicates with the manifold. The gas passage member is disposed on the one side of the end member in the first direction (the side opposite the power generation block). The gas passage member is a cylindrical body that penetrates in the first direction and has a gas through-hole that communicates with the end through-hole. The joining member is disposed between the power generation block and the end member (see, for example, Patent Document 1).

JP 2017-10804 A

In a fuel cell stack in which a joining member is disposed between the power generation block and the end member in this manner, if the power generation block and the end member are displaced apart, tensile stress is generated in the joining member, which may damage the joint formed by the joining member.

Note that these issues are also common to electrolysis cell stacks comprising multiple electrolysis cell units, each of which includes a single electrolysis cell, a constituent unit of a solid oxide electrolysis cell (hereinafter referred to as "SOEC") that generates hydrogen using the electrolysis reaction of water. In this specification, a single fuel cell cell and a single electrolysis cell are collectively referred to as a single electrochemical reaction cell, a fuel cell power generation unit and an electrolysis cell unit are collectively referred to as an electrochemical reaction unit, and a fuel cell stack and an electrolysis cell stack are collectively referred to as an electrochemical reaction cell stack. Furthermore, these issues are not limited to SOFCs and SOECs, but are also common to other types of fuel cells and electrolysis cells. Furthermore, these issues are not limited to electrochemical reaction cell stacks, but are also common to composites comprising a first member, a second member located on one side of the first member, and a joining member disposed between the first and second members.

This specification discloses technology that can solve the above-mentioned problems.

The technology disclosed in this specification can be realized, for example, in the following forms:

(1) The composite disclosed in this specification comprises a first member and a second member located on one side of the first member in a first direction, the composite also comprising: a stress relief portion disposed between the first member and the second member, the stress relief portion being joined to the first member by at least one of welding and brazing and having a displacement portion configured to be displaceable in the first direction relative to the first member in a region different from the joint with the first member; and a joining member disposed between the second member and the stress relief portion, joining at least the displacement portion of the stress relief portion to the second member.

In this composite, the joining member is joined to the first member and the second member via a stress relief portion. The stress relief portion is joined to the first member by at least one of welding and brazing, and is configured to have a displacement portion that is displaceable relative to the first member in a first direction (the direction in which the first member and the second member face each other). Therefore, even if the first member and the second member are displaced apart, the stress relief portion displaces to follow that displacement, thereby suppressing the generation of stress in the joining member. As a result, this composite can suppress damage to the joint points of the joining member caused by the displacement of the first member and the second member away from each other.

(2) In the above composite, the rigidity of the stress relief portion in the first direction may be lower than the rigidity of the first member in the first direction. This composite can reduce the ability of the stress relief portion to follow the displacement of the first member when the first member and the second member are displaced apart. Therefore, for example, compared to a configuration in which the rigidity of the stress relief portion is equal to or greater than the rigidity of the first member, the stress generated in the joining member due to the displacement is reduced. This allows the composite to effectively prevent damage to the joints formed by the joining members.

(3) In the above composite, the joining member may be configured to be joined only to a region of the stress relief section that is different from the joint section. With this composite, the stress generated in the joining member due to separation displacement is reduced compared to, for example, a configuration in which the joining member is joined to the displaced portion of the stress relief section as well as to a region that overlaps the joint section. As a result, with this composite, damage to the joint area caused by the joining member can be effectively suppressed.

(4) In the above composite, the first member and the second member may face a flow path extending in the first direction, and the joint portion of the stress relief portion may be disposed on the opposite side of the flow path from the joining member when viewed in the first direction. According to this composite, when the separation displacement between the first member and the second member on the flow path side is relatively large, the portion of the stress relief portion on the flow path side is significantly displaced, thereby effectively preventing damage to the joint portion formed by the joining member.

(5) In the above-described composite, one of the first and second members may be configured to have a standing portion formed thereon that protrudes toward the other side in the first direction. According to this composite, one of the first and second members has a standing portion. Therefore, when force is applied to this standing portion, the first and second members are likely to be displaced apart. Even in such a configuration, by applying the present invention, damage to the joints formed by the joining members can be suppressed.

(6) The composite may be an electrochemical reaction cell stack comprising a plurality of electrochemical reaction units arranged in the first direction, each of which has an electrochemical reaction unit including an electrolyte layer and an air electrode and an anode facing each other in the first direction with the electrolyte layer sandwiched therebetween, and in which a flow path is formed for gas exchange between a specific electrode, which is at least one of the air electrode and the anode, in each of the electrochemical reaction units. The first member and the second member may be members that face the flow path and are aligned in the first direction to constitute the electrochemical reaction cell stack. This composite can prevent damage to the joint formed by the joining member located between the two members facing the flow path.

The technology disclosed in this specification can be realized in various forms, such as an electrochemical reaction cell stack (fuel cell stack or electrolysis cell stack) comprising multiple electrochemical reaction units or electrochemical reaction cells, the above-mentioned composite, a manufacturing method thereof, etc.

FIG. 1 is a perspective view showing the external configuration of a fuel cell stack 100 according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 100 taken along the line II-II in FIG. 1. FIG. 2 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 100 taken along the line III-III in FIG. 1. FIG. 4 is an explanatory diagram showing the YZ cross-sectional structure of the fuel cell stack 100 taken along the line IV-IV in FIG. FIG. 3 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generating units 102 at the same position as the cross-section shown in FIG. 2 . FIG. 4 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generating units 102 at the same position as the cross-section shown in FIG. 3 . FIG. 5 is an explanatory diagram showing the YZ cross-sectional configuration of two adjacent power generating units 102 at the same position as the cross-section shown in FIG. FIG. 8 is an explanatory diagram showing the XY cross-sectional structure of the power generating unit 102 at the position VIII-VIII in FIG. 5. FIG. 6 is an explanatory diagram showing the XY cross-sectional structure of the power generating unit 102 at the position IX-IX in FIG. 5. FIG. 10 is an explanatory diagram showing an enlarged view of the joining structure between the lower end plate 106 and the lower terminal plate 420. FIG. 11 is an explanatory diagram showing the XY plane configuration of the glass seal member 197 and the like at the position XI-XI in FIG. 10A and 10B are explanatory diagrams showing the states before and after the lower end plate 106 and the lower terminal plate 420 are displaced apart from each other; FIG. 10 is an explanatory diagram illustrating an enlarged view of a joint structure between a lower end plate 106 and a lower terminal plate 420 in a first modified example of the embodiment. FIG. 10 is an explanatory diagram showing an enlarged view of the joint structure between the lower end plate 106 and the fuel electrode side frame 140 in a second modified example of the embodiment.

A. Embodiments:
A-1. composition:
(Configuration of fuel cell stack 100)
FIG. 1 is a perspective view showing the exterior configuration of a fuel cell stack 100 according to this embodiment. FIG. 2 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 100 taken along line II-II in FIG. 1 . FIG. 3 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 100 taken along line III-III in FIG. 1 . FIG. 4 is an explanatory diagram showing the YZ cross-sectional configuration of the fuel cell stack 100 taken along line IV-IV in FIG. 1 . Each figure shows orthogonal X, Y, and Z axes for identifying directions. For convenience, the positive Z-axis direction will be referred to as the upward direction and the negative Z-axis direction will be referred to as the downward direction in this specification. However, the fuel cell stack 100 may actually be installed in an orientation different from these orientations. The same applies to FIG. 5 and subsequent figures. The fuel cell stack 100 is an example of a composite as defined in the claims, and the vertical direction (Z-axis direction) is an example of a first direction as defined in the claims.

The fuel cell stack 100 includes a plurality of (seven in this embodiment) fuel cell power generation units (hereinafter simply referred to as "power generation units") 102, an end separator 210, an upper end plate 220, a lower end plate 189, a pair of terminal plates 410, 420, an insulating section 200, and a pair of end plates 104, 106. The seven power generation units 102 are arranged in a predetermined arrangement direction (vertical direction in this embodiment). One of the pair of terminal plates 410, 420 (hereinafter referred to as the "upper terminal plate 410") is located above the assembly (hereinafter referred to as the "power generation block 103") consisting of the seven power generation units 102, and the other of the pair of terminal plates 410, 420 (hereinafter referred to as the "lower terminal plate 420") is located below the power generation block 103. The terminal separator 210 is disposed above the upper terminal plate 410, and the lower end plate 189 is disposed below the lower terminal plate 420. The insulating section 200 is disposed above the terminal separator 210. One of the pair of end plates 104, 106 (hereinafter referred to as the "upper end plate 104") is disposed above the insulating section 200, and the other of the pair of end plates 104, 106 (hereinafter referred to as the "lower end plate 106") is disposed below the lower end plate 189. The pair of end plates 104, 106 are disposed to sandwich the power generation block 103, the terminal separator 210, the lower end plate 189, the pair of terminal plates 410, 420, and the insulating section 200 from above and below. The power generation unit 102 is an example of an electrochemical reaction unit as defined in the claims.

As shown in Figures 1 and 4, holes that penetrate each layer in the vertical direction are formed near the four corners of the outer periphery around the Z-axis of each layer (power generation block 103, terminal separator 210, lower end plate 189, pair of terminal plates 410, 420, and insulating section 200) that make up the fuel cell stack 100. Holes (screw holes) are formed near the four corners of the outer periphery around the Z-axis of the upper end plate 104, and holes (screw holes) are formed near the four corners of the outer periphery around the Z-axis of the lower end plate 106. Corresponding holes formed in these layers communicate with each other in the vertical direction to form bolt holes 109 that extend in the vertical direction. In the following description, the holes formed in each layer of the fuel cell stack 100 to form bolt holes 109 may also be referred to as bolt holes 109.

A bolt 22 is inserted into each bolt hole 109. The upper end of each bolt 22 is threaded into a threaded hole in a nut 24 through a hole in the upper end plate 104, and the lower end of each bolt 22 is threaded into a threaded hole in a nut 24 through a hole in the lower end plate 106. The bolts 22 and nuts 24 configured in this way fasten the layers of the fuel cell stack 100 together.

As shown in Figures 1 to 3, four holes that penetrate each layer in the vertical direction are formed around the Z-axis peripheral edge of each layer (each power generating unit 102, lower terminal plate 420, lower end plate 189, and lower end plate 106) that make up the fuel cell stack 100. Corresponding holes formed in each layer are vertically connected to form communication holes 108 that extend vertically from the uppermost power generating unit 102 to the lower end plate 106. In the following description, the holes formed in each layer of the fuel cell stack 100 to form the communication holes 108 may also be referred to as communication holes 108. Note that, of the communication holes 108, the holes formed in the lower end plate 106 will hereinafter be referred to specifically as end through-holes 107.

1 and 2 , one communication hole 108 located near one side (the side on the positive X-axis of the two sides parallel to the Y-axis) that constitutes the outer periphery of the fuel cell stack 100 around the Z-axis functions as an oxidant gas supply manifold 161, which is a gas flow path through which oxidant gas OG is introduced from outside the fuel cell stack 100 and supplied to the air chamber 166 (described later) of each power generation unit 102. Another communication hole 108 located near the opposite side (the side on the negative X-axis of the two sides parallel to the Y-axis) functions as an oxidant gas discharge manifold 162, which is a gas flow path through which oxidant off-gas OOG, which is gas discharged from the air chamber 166 of each power generation unit 102, is discharged to the outside of the fuel cell stack 100. The oxidant gas supply manifold 161 and the oxidant gas discharge manifold 162 are gas flow paths that exchange gas with the air electrode 114 (described later) of each power generation unit 102. The oxidant gas OG may be, for example, air.

1 and 3, among the sides constituting the outer periphery of the fuel cell stack 100 around the Z-axis direction, another communication hole 108 located near the side closest to the communication hole 108 functioning as the oxidant gas exhaust manifold 162 described above functions as a fuel gas supply manifold 171, which is a gas flow path through which fuel gas FG is introduced from outside the fuel cell stack 100 and supplied to the fuel chamber 176 (described later) of each power generation unit 102. Another communication hole 108 located near the side closest to the communication hole 108 functioning as the oxidant gas supply manifold 161 described above functions as a fuel gas exhaust manifold 172, which is a gas flow path through which fuel off-gas FOG, which is gas exhausted from the fuel chamber 176 of each power generation unit 102, is exhausted to the outside of the fuel cell stack 100. The fuel gas supply manifold 171 and the fuel gas exhaust manifold 172 are gas flow paths that exchange gas with the anode 116 (described later) of each power generation unit 102. The fuel gas FG is, for example, hydrogen-rich gas obtained by reforming city gas.

As shown in Figures 1 to 3, the fuel cell stack 100 is provided with four gas passage members 27. Each gas passage member 27 is formed of a conductive material (metal material), such as ferritic stainless steel containing aluminum, and includes a hollow cylindrical main body 28 and a flange 29. A gas through hole 26 is formed in the main body 28, penetrating it in the vertical direction. One end (upper end) of the main body 28 is connected to an end through-hole 107 formed in the lower end plate 106. Specifically, the upper end of the main body 28 is inserted into the end through-hole 107 and joined thereto, for example, by welding. The outer and inner diameters of the upper end of the main body 28 are smaller than the outer and inner diameters of the other end (lower end) of the main body 28. The plate thickness (difference between the outer and inner diameters) of the main body 28 can be, for example, 0.6 mm or more and 1.0 mm or less. The flange portion 29 is provided so as to protrude from the lower end side of the main body portion 28 in a plane direction (a direction parallel to the XY plane) perpendicular to the vertical direction (Z-axis direction). The flange portion 29 has a substantially rectangular shape when viewed from the vertical direction, and a bolt hole 29A (see FIG. 1) is formed at each of the four corners. A bolt (not shown) is inserted into each bolt hole 29A to connect the fuel cell stack 100 to an external device.

As shown in FIG. 2, the gas through holes 26 of the gas passage member 27 arranged at the position of the oxidant gas supply manifold 161 are connected to the oxidant gas supply manifold 161, and the gas through holes 26 of the gas passage member 27 arranged at the position of the oxidant gas exhaust manifold 162 are connected to the oxidant gas exhaust manifold 162. Also, as shown in FIG. 3, the gas through holes 26 of the gas passage member 27 arranged at the position of the fuel gas supply manifold 171 are connected to the fuel gas supply manifold 171, and the gas through holes 26 of the gas passage member 27 arranged at the position of the fuel gas exhaust manifold 172 are connected to the fuel gas exhaust manifold 172.

(Configuration of end plates 104, 106)
The pair of end plates 104, 106 are flat, plate-shaped members with a generally rectangular outer shape as viewed in the Z-axis direction. They are made of a conductive material (metal material), such as ferritic stainless steel, with an alumina oxide coating formed on the surface. Holes 32, 34 are formed near the center of each of the pair of end plates 104, 106, respectively, penetrating in the Z-axis direction. As viewed in the Z-axis direction, the inner circumferential lines of the holes 32, 34 formed in each of the pair of end plates 104, 106 encompass at least a portion of each unit cell 110, described below. The compressive force in the Z-axis direction generated by fastening the bolts 22 and nuts 24 acts primarily on the periphery of each power generating unit 102 (the portion outer than each unit cell 110, described below). Each of the end plates 104, 106 is formed by pressing (bending) a single plate-shaped member. The thickness of the end plates 104 and 106 may be, for example, 1 mm or more and 3 mm or less, and may be the same as or thinner than the thickness of the main body 28 of the gas passage member 27 .

As shown in Figures 2 to 4, the upper end plate 104 includes a planar portion 310 and a convex portion 320. The planar portion 310 is a flat portion along a surface direction perpendicular to the Z-axis direction (a direction parallel to the XY plane). Specifically, the planar portion 310 has an overall rectangular frame shape when viewed in the Z-axis direction. Note that the holes that form the bolt holes 109 described above are formed on the peripheral edge of the planar portion 310 around the Z-axis direction. The convex portion 320 is a rib that protrudes upward from the planar portion 310. The convex portion 320 has an outer convex portion 322 and an inner convex portion 324. The outer convex portion 322 protrudes upward from the outer periphery of the planar portion 310. The outer convex portion 322 is formed around the entire outer periphery of the planar portion 310. The inner convex portion 324 protrudes upward from the inner periphery of the planar portion 310. The inner convex portion 324 is formed around the entire inner periphery of the flat portion 310.

In this embodiment, the shape of the outer convex portion 322 when viewed in the Z-axis direction is rectangular overall. Specifically, the shape of the outer convex portion 322 has four straight sides 322A that form each side of the rectangle and four arc-shaped corners 322B that connect adjacent sides 322A. The shape of the inner convex portion 324 when viewed in the Z-axis direction is also rectangular overall. Specifically, the shape of the inner convex portion 324 has four straight sides 324A that form each side of the rectangle and four arc-shaped corners 324B that connect adjacent sides 324A. In this way, because the convex portion 320 has a straight or curved shape without any angular portions, it is possible to prevent stress from concentrating at specific locations on the convex portion 320 when the end plate 104 deforms.

Furthermore, the outer peripheral surface of at least one side 322A of the upper end plate 104 is formed with multiple protrusions 326 (two in Figure 1) aligned in the longitudinal direction of the side 322A. The lower end plate 106 is also shaped similarly to the upper end plate 104. For example, the fuel cell stack 100 is placed on a predetermined floor surface with the surface of the fuel cell stack 100 facing the positive Y-axis direction downward. In this case, the multiple protrusions 326 formed on each of the upper end plate 104 and the lower end plate 106 come into contact with the floor surface, separating the power generation block 103 from the floor surface. This prevents the power generation block 103 from interfering with the floor surface, etc.

The lower end plate 106 also includes a planar portion 510 and a convex portion 520. The planar portion 510 is a flat portion along a surface direction perpendicular to the Z-axis direction (a direction parallel to the XY plane). Specifically, the planar portion 510 has an overall rectangular frame shape when viewed in the Z-axis direction. The holes that form the bolt holes 109 described above are formed on the peripheral edge of the planar portion 510 around the Z-axis direction. The convex portion 520 is a rib that protrudes downward from the planar portion 510. The convex portion 520 has an outer convex portion 522 and an inner convex portion 524. The outer convex portion 522 protrudes downward from the outer periphery of the planar portion 510. The outer convex portion 522 is formed around the entire outer periphery of the planar portion 510. The inner convex portion 524 protrudes downward from the inner periphery of the planar portion 510. The inner convex portion 524 is formed around the entire inner periphery of the flat portion 510.

2 and 3, a reinforcing member 600 is fixed to the lower end plate 106. The reinforcing member 600 has a flat portion 610 and a tubular portion 620. The flat portion 610 is a flat portion parallel to the planar portion 510 of the lower end plate 106. The flat portion 610 has a generally rectangular shape when viewed from the top to bottom. The flat portion 610 is positioned below and spaced apart from the planar portion 510 of the lower end plate 106. One longitudinal edge of the flat portion 610 contacts the inner wall surface of the outer convex portion 522 and is joined thereto, for example, by welding, and the other longitudinal edge of the flat portion 610 contacts the inner wall surface of the inner convex portion 524 and is joined thereto, for example, by welding. A through hole 612 is formed in the flat portion 610, into which the main body 28 of the gas passage member 27 can be inserted. The tubular portion 620 is a cylindrical portion having a through hole 622 that communicates with the through hole 612 in the flat plate portion 610. The tubular portion 620 is formed to protrude downward from the periphery of the through hole 612 in the flat plate portion 610. The inner wall surfaces that define the through hole 612 in the flat plate portion 610 and the through hole 622 in the tubular portion 620 contact the outer peripheral surface of the main body 28 of the gas passage member 27 and are joined by, for example, welding. The flat plate portion 610 and the tubular portion 620 are integrally formed. The reinforcing member 600 is preferably formed from a heat-resistant material or the same material as the lower end plate 106, the gas passage member 27, etc., or a material with the same thermal expansion coefficient, such as a metal (such as ferritic stainless steel).

(Configuration of terminal plates 410, 420)
The pair of terminal plates 410, 420 are flat members with a substantially rectangular outer shape as viewed in the Z-axis direction, and are formed of a conductive material such as ferritic stainless steel with an alumina oxide coating formed on the surface. A hole 412 is formed near the center of the upper terminal plate 410, penetrating in the Z-axis direction. As viewed in the Z-axis direction, the inner periphery of the hole 412 formed in the upper terminal plate 410 encompasses each of the unit cells 110 (described later). As viewed in the Z-axis direction, one end of each of the pair of terminal plates 410, 420 (the positive X-axis direction) protrudes laterally from the power generation block 103. In this embodiment, the protruding portion of the upper terminal plate 410 functions as a positive output terminal for the fuel cell stack 100, and the protruding portion of the lower terminal plate 420 functions as a negative output terminal for the fuel cell stack 100.

(Configuration of the upper end plate 220)
The upper end plate 220 is a flat member having a substantially rectangular outer shape when viewed in the Z-axis direction, and is made of a conductive material such as stainless steel. The upper end plate 220 is disposed above the power generation block 103, and is electrically connected to an interconnector 190 (described below) located at the upper end of the power generation block 103. In this embodiment, the upper end plate 220 and the interconnector 190 are electrically connected via a connecting member having the same structure as the fuel electrode side current collecting member 144 (described below).

(Configuration of Terminal Separator 210)
The terminal separator 210 is a frame-shaped member formed of, for example, metal, with a substantially rectangular through-hole 211 formed near the center and penetrating in the vertical direction. The portion of the terminal separator 210 surrounding the through-hole 211 (hereinafter referred to as the "through-hole surrounding portion") is joined, for example by welding, to the upper surface of the peripheral portion of the upper end plate 220. The terminal separator 210 separates the space between the upper end plate 220 and the power generation block 103 from the space outside the fuel cell stack 100.

The terminal separator 210 includes an inner portion 216 that includes the area surrounding the through-hole of the terminal separator 210, an outer portion 217 that is located radially outward of the inner portion 216, and a connecting portion 218 that connects the inner portion 216 and the outer portion 217. In this embodiment, the inner portion 216 and the outer portion 217 are generally flat plates that extend in a direction generally perpendicular to the Z-axis direction. The connecting portion 218 is curved so that it protrudes downward relative to both the inner portion 216 and the outer portion 217. The lower portion of the connecting portion 218 (toward the power generation block 103) is a convex portion, and the upper portion of the connecting portion 218 (toward the upper end plate 104) is a concave portion. Therefore, the connecting portion 218 includes a portion whose position in the Z-axis direction differs from that of the inner portion 216 and the outer portion 217.

(Configuration of the lower end plate 189)
The lower end plate 189 is a flat member having a substantially rectangular outer shape when viewed in the Z-axis direction, and is made of an insulating material such as mica. The peripheral edge of the lower end plate 189 is sandwiched between the lower terminal plate 420 and the lower end plate 106, thereby ensuring insulation between the lower terminal plate 420 and the lower end plate 106.

(Configuration of insulating section 200)
The insulating section 200 is a frame-shaped member with a substantially rectangular through-hole formed in the center in the vertical direction, and is made of an insulating material such as mica. The insulating section 200 is sandwiched between the upper end plate 104 and the terminal separator 210, thereby ensuring insulation between the upper end plate 104 and the terminal separator 210.

(Configuration of power generation unit 102)
Fig. 5 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generating units 102 at the same position as the cross-section shown in Fig. 2, Fig. 6 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generating units 102 at the same position as the cross-section shown in Fig. 3, and Fig. 7 is an explanatory diagram showing the YZ cross-sectional configuration of two adjacent power generating units 102 at the same position as the cross-section shown in Fig. 4. Also, Fig. 8 is an explanatory diagram showing the XY cross-sectional configuration of the power generating unit 102 at the position VIII-VIII in Fig. 5, and Fig. 9 is an explanatory diagram showing the XY cross-sectional configuration of the power generating unit 102 at the position IX-IX in Fig. 5.

As shown in Figures 5 to 7, the power generation unit 102 includes a single fuel cell (hereinafter referred to as a "single cell") 110, a single cell separator 120, an air electrode side frame 130, an anode side frame 140, an anode side current collecting member 144, a pair of interconnectors 190 and a pair of IC separators 180 that form the top and bottom layers of the power generation unit 102. Holes that form the communication holes 108 that function as the manifolds 161, 162, 171, and 172, and holes that form the bolt holes 109, are formed in the peripheral portions around the Z-axis direction of the single cell separator 120, the air electrode side frame 130, the anode side frame 140, and the IC separator 180.

The unit cell 110 comprises an electrolyte layer 112, an air electrode 114 disposed on one side (upper side) of the electrolyte layer 112 in the Z-axis direction, an anode 116 disposed on the other side (lower side) of the electrolyte layer 112 in the Z-axis direction, and a reaction prevention layer 118 disposed between the electrolyte layer 112 and the air electrode 114. The unit cell 110 of this embodiment is an anode-supported unit cell in which the anode 116 supports the other layers (electrolyte layer 112, air electrode 114, reaction prevention layer 118) that make up the unit cell 110. The unit cell 110 is an example of an electrochemical reaction unit cell as defined in the claims.

The electrolyte layer 112 is a substantially rectangular, flat-plate member when viewed in the Z-axis direction and is configured to contain a solid oxide (e.g., YSZ (yttria-stabilized zirconia)). That is, the unit cell 110 of this embodiment is a solid oxide fuel cell (SOFC) that uses a solid oxide as an electrolyte. The air electrode 114 is a substantially rectangular, flat-plate member that is smaller than the electrolyte layer 112 when viewed in the Z-axis direction and is configured to contain, for example, a perovskite-type oxide (e.g., LSCF (lanthanum strontium cobalt iron oxide)). The anode 116 is a substantially rectangular, flat-plate member that is substantially the same size as the electrolyte layer 112 when viewed in the Z-axis direction and is formed of, for example, Ni (nickel), a cermet made of Ni and ceramic particles, a Ni-based alloy, or the like. The reaction prevention layer 118 is a substantially rectangular, flat-plate member that is substantially the same size as the air electrode 114 when viewed in the Z-axis direction and is configured to contain, for example, GDC (gadolinium-doped ceria). The reaction prevention layer 118 has the function of suppressing the generation of a highly resistive substance (e.g., SrZrO ₃ ) caused by the reaction of an element (e.g., Sr) diffused from the cathode 114 with an element (e.g., Zr) contained in the electrolyte layer 112. The cathode 114 and the anode 116 are examples of specific electrodes in the claims.

The single cell separator 120 is a frame-shaped component formed of, for example, metal, with a substantially rectangular through-hole 121 formed vertically near the center. The portion of the single cell separator 120 surrounding the through-hole 121 (hereinafter referred to as the "through-hole periphery") faces the upper surface of the peripheral edge of the single cell 110 (electrolyte layer 112). The single cell separator 120 is joined to the single cell 110 (electrolyte layer 112) by a joint 124 formed with brazing material (e.g., Ag brazing) placed in the opposing portion. The single cell separator 120 separates an air chamber 166 facing the air electrode 114 from a fuel chamber 176 facing the fuel electrode 116, thereby suppressing gas leakage (cross-leakage) from one electrode side to the other electrode side at the peripheral edge of the single cell 110.

The single-cell separator 120 includes an inner portion 126 that includes the area surrounding the through-holes of the single-cell separator 120, an outer portion 127 that is located radially outward of the inner portion 126, and a connecting portion 128 that connects the inner portion 126 and the outer portion 127. In this embodiment, the inner portion 126 and the outer portion 127 are generally flat plates that extend in a direction generally perpendicular to the Z-axis direction. The connecting portion 128 is curved so that it protrudes downward relative to both the inner portion 126 and the outer portion 127. The lower portion of the connecting portion 128 (facing the fuel chamber 176) is a convex portion, and the upper portion of the connecting portion 128 (facing the air chamber 166) is a concave portion. Therefore, the connecting portion 128 includes portions whose positions in the Z-axis direction differ from those of the inner portion 126 and the outer portion 127.

A glass seal portion 125 containing glass is disposed near the through-hole 121 in the single-cell separator 120. The glass seal portion 125 is located on the air chamber 166 side of the joint portion 124 and is formed so as to contact both the surface surrounding the through-hole in the single-cell separator 120 and the surface of the single cell 110 (electrolyte layer 112 in this embodiment). The glass seal portion 125 effectively prevents gas leakage (cross leakage) from one electrode side to the other electrode side at the periphery of the single cell 110.

The interconnector 190 is a conductive member having a substantially rectangular flat plate portion 150 and multiple substantially columnar air electrode-side current collecting portions 134 protruding from the flat plate portion 150 toward the air electrode 114. The interconnector 190 is made of metal (e.g., ferritic stainless steel). In this embodiment, a conductive coating layer 194, composed of, for example, a spinel-type oxide, is formed on the surface of the interconnector 190 (the surface facing the air chamber 166). Hereinafter, the interconnector 190 covered with the coating layer 194 will be simply referred to as the interconnector 190. The interconnector 190 (each of its air electrode-side current collecting portions 134) is bonded to the air electrode 114 of the single cell 110 via a conductive bonding material 196 composed of, for example, a spinel-type oxide, thereby electrically connecting the interconnector 190 to the air electrode 114 of the single cell 110. The interconnector 190 ensures electrical conductivity between the power generation units 102 and suppresses mixing of reactant gases between the power generation units 102. In this embodiment, when two power generating units 102 are arranged adjacent to each other, one interconnector 190 is shared by the two adjacent power generating units 102. That is, the upper interconnector 190 of one power generating unit 102 is made of the same material as the lower interconnector 190 of the other power generating unit 102 adjacent to the upper side of that power generating unit 102. Furthermore, because the fuel cell stack 100 includes a lower terminal plate 420 and a lower end plate 189, the power generating unit 102 located at the bottom of the fuel cell stack 100 does not include a lower interconnector 190 (see Figures 2 to 4).

The IC separator 180 is a frame-shaped member formed with a substantially rectangular through-hole 181 penetrating vertically near the center, and is made of, for example, metal. The portion of the IC separator 180 surrounding the through-hole 181 (hereinafter referred to as the "through-hole surrounding portion") is joined, for example by welding, to the upper surface of the peripheral portion of the flat portion 150 of the interconnector 190. Of a pair of IC separators 180 included in a certain power generating unit 102, the upper IC separator 180 separates the air chamber 166 of that power generating unit 102 from the fuel chamber 176 of the other power generating unit 102 adjacent to that power generating unit 102 on the upper side. Furthermore, of the pair of IC separators 180 included in a certain power generating unit 102, the lower IC separator 180 separates the fuel chamber 176 of that power generating unit 102 from the air chamber 166 of the other power generating unit 102 adjacent to that power generating unit 102 on the lower side. In this way, the IC separator 180 suppresses gas leakage between the power generating units 102 at the periphery of the power generating units 102. The IC separator 180 joined to the upper interconnector 190 of the power generating unit 102 located at the top of the fuel cell stack 100 is electrically connected to the upper terminal plate 410.

The IC separator 180 includes an inner portion 186 that includes the area surrounding the through-hole of the IC separator 180, an outer portion 187 that is located radially outward of the inner portion 186, and a connecting portion 188 that connects the inner portion 186 and the outer portion 187. In this embodiment, the inner portion 186 and the outer portion 187 are generally flat plates that extend in a direction generally perpendicular to the Z-axis direction. The connecting portion 188 is curved so that it protrudes downward relative to both the inner portion 186 and the outer portion 187. The lower portion of the connecting portion 188 (toward the air chamber 166) is a convex portion, and the upper portion of the connecting portion 188 (toward the fuel chamber 176) is a concave portion. Therefore, the connecting portion 188 includes portions whose positions in the Z-axis direction differ from those of the inner portion 186 and the outer portion 187.

As shown in FIG. 8 , the air electrode side frame 130 is a frame-shaped member with a substantially rectangular hole 131 formed near the center that penetrates in the Z-axis direction, and is formed from an insulating material such as mica. The hole 131 in the air electrode side frame 130 forms an air chamber 166 facing the air electrode 114. The air electrode side frame 130 is in contact with the upper surface of the peripheral portion of the single cell separator 120 and the lower surface of the peripheral portion of the upper IC separator 180, and functions as a sealing member that ensures gas sealing between the two (i.e., gas sealing of the air chamber 166). The air electrode side frame 130 also electrically insulates a pair of IC separators 180 (i.e., a pair of interconnectors 190) included in the power generation unit 102. The air electrode side frame 130 is also formed with an oxidant gas supply passage 132 that connects the oxidant gas supply manifold 161 to the air chamber 166, and an oxidant gas discharge passage 133 that connects the air chamber 166 to the oxidant gas discharge manifold 162.

As shown in FIG. 9 , the fuel electrode side frame 140 is a frame-shaped member formed with a substantially rectangular hole 141 near the center that penetrates in the Z-axis direction, and is made of, for example, metal. The hole 141 in the fuel electrode side frame 140 forms a fuel chamber 176 that faces the fuel electrode 116. The fuel electrode side frame 140 is in contact with the lower surface of the peripheral portion of the single cell separator 120 and the upper surface of the peripheral portion of the lower IC separator 180. The fuel electrode side frame 140 also has a fuel gas supply communication hole 142 that connects the fuel gas supply manifold 171 with the fuel chamber 176, and a fuel gas discharge communication hole 143 that connects the fuel chamber 176 with the fuel gas discharge manifold 172.

As shown in Figures 5 to 7, the anode side current collecting member 144 is disposed within the fuel chamber 176. The anode side current collecting member 144 includes an interconnector facing portion 146, an electrode facing portion 145, and a connecting portion 147 connecting the electrode facing portion 145 and the interconnector facing portion 146, and is formed of, for example, nickel, a nickel alloy, stainless steel, or the like. The electrode facing portion 145 contacts the lower surface of the anode 116, and the interconnector facing portion 146 contacts the upper surface of the interconnector 190 (the flat portion 150 thereof). However, as described above, the power generating unit 102 located at the bottom of the fuel cell stack 100 does not include a lower interconnector 190, and therefore the interconnector facing portion 146 of the anode side current collecting member 144 in that power generating unit 102 contacts the lower terminal plate 420. The anode side current collecting member 144 has such a configuration, and electrically connects the anode 116 and the interconnector 190 (or the lower end plate 189). A spacer 149 made of, for example, mica is disposed between the electrode facing portion 145 and the interconnector facing portion 146 of the anode side current collecting member 144. This allows the anode side current collecting member 144 to follow deformation of the power generating unit 102 due to temperature cycles and reactant gas pressure fluctuations, and good electrical connection between the anode 116 and the interconnector 190 (or the lower terminal plate 420) via the anode side current collecting member 144 is maintained. The anode side current collecting member 144 is fabricated, for example, by making multiple rectangular cuts in a flat plate-like material (e.g., nickel foil having a thickness of 10 to 200 μm), placing a sheet-like anode side current collecting member 144 with multiple holes formed on the material, and bending and processing the multiple rectangular portions to sandwich the spacer 149. Each bent rectangular portion becomes the electrode facing portion 145, the flat portion with holes other than the bent portion becomes the interconnector facing portion 146, and the portion connecting the electrode facing portion 145 and the interconnector facing portion 146 becomes the connecting portion 147.

A-2. Operation of the fuel cell stack 100:
2 and 5, when oxidant gas OG is supplied through a gas pipe (not shown) connected to the main body 28 of the gas passage member 27 provided at the position of the oxidant gas supply manifold 161, the oxidant gas OG is supplied to the oxidant gas supply manifold 161 through the gas through hole 26 of the gas passage member 27, and then supplied from the oxidant gas supply manifold 161 to the air chamber 166 through the oxidant gas supply passage 132 of each power generating unit 102. Also, as shown in FIGS. 3 and 6, when fuel gas FG is supplied through a gas pipe (not shown) connected to the main body 28 of the gas passage member 27 provided at the position of the fuel gas supply manifold 171, the fuel gas FG is supplied to the fuel gas supply manifold 171 through the gas through hole 26 of the gas passage member 27, and then supplied from the fuel gas supply manifold 171 to the fuel chamber 176 through the fuel gas supply passage 142 of each power generating unit 102.

When oxidant gas OG is supplied to the air chamber 166 of each power generating unit 102 and fuel gas FG is supplied to the fuel chamber 176, power is generated in the unit cell 110 through an electrochemical reaction between the oxidant gas OG and the fuel gas FG. This power generation reaction is exothermic. In each power generating unit 102, the air electrode 114 of the unit cell 110 is electrically connected to the upper interconnector 190, and the anode 116 is electrically connected to the lower interconnector 190 (or the lower terminal plate 420) via the anode-side current collecting member 144. In other words, the multiple power generating units 102 included in the fuel cell stack 100 are electrically connected in series. The upper interconnector 190 and IC separator 180 of the uppermost power generating unit 102 are electrically connected to the upper terminal plate 410, and the anode-side current collecting member 144 of the lowermost power generating unit 102 is electrically connected to the lower terminal plate 420. Therefore, electrical energy generated in each power generation unit 102 is extracted from terminal plates 410, 420, which function as output terminals of the fuel cell stack 100. Note that, because SOFCs generate electricity at relatively high temperatures (e.g., 600°C to 1000°C), after startup, the fuel cell stack 100 may be heated by a heater (not shown) until the heat generated by power generation can maintain the high temperature.

As shown in FIGS. 2 and 5, the oxidant off-gas OOG discharged from the air chamber 166 of each power generation unit 102 through the oxidant gas discharge passage 133 to the oxidant gas discharge manifold 162 passes through the gas through-hole 26 in the main body 28 of the gas passage member 27 located at the position of the oxidant gas discharge manifold 162 and is discharged to the outside of the fuel cell stack 100 through a gas piping (not shown) connected to the main body 28. Also, as shown in FIGS. 3 and 6, the fuel off-gas FOG discharged from the fuel chamber 176 of each power generation unit 102 through the fuel gas discharge passage 143 to the fuel gas discharge manifold 172 passes through the gas through-hole 26 in the main body 28 of the gas passage member 27 located at the position of the fuel gas discharge manifold 172 and is discharged to the outside of the fuel cell stack 100 through a gas piping (not shown) connected to the main body 28.

The fuel cell stack 100 of this embodiment is a counterflow type SOFC in which, in each power generation unit 102, the main flow direction of the oxidant gas OG in the air chamber 166 (direction from the positive X-axis direction to the negative X-axis direction) and the main flow direction of the fuel gas FG in the fuel chamber 176 (direction from the negative X-axis direction to the positive X-axis direction) are substantially opposite directions (opposing each other).

A-3. Joint structure between the lower end plate 106 and the lower terminal plate 420:
Next, the joining structure between the lower end plate 106 and the lower terminal plate 420 in the fuel cell stack 100 of this embodiment will be described. Fig. 10 is an explanatory diagram showing an enlarged view of the joining structure between the lower end plate 106 and the lower terminal plate 420, and Fig. 11 is an explanatory diagram showing the XY plane configuration of the glass seal member 197 and other components at position XI-XI in Fig. 10. Fig. 11 illustrates the glass seal member 197 that communicates with the oxidant gas supply manifold 161. The lower end plate 106 is an example of a first member in the claims, and the lower terminal plate 420 is an example of a second member in the claims.

As shown in Figures 2 to 4, four erected portions 530 are formed on the lower end plate 106 of this embodiment. As shown in Figure 10, the erected portions 530 protrude downward (toward the negative Z-axis direction) from the flat portion 510 of the lower end plate 106 and are cylindrical in shape surrounding the end through-hole 107 of the lower end plate 106 when viewed in the up-down direction. The erected portions 530 are formed integrally with the flat portion 510.

The gas passage member 27 is connected to the upright portion 530 of the lower end plate 106, and the gas flow path of the gas passage member 27 communicates with the end through-hole 107 of the lower end plate 106. Specifically, the tip portion 28a of the gas passage member 27 is inserted into the inner periphery of the upright portion 530, and the tip portion 28a of the gas passage member 27 and the upright portion 530 are joined, for example, by welding.

A stress relief portion 700 and a glass seal member 197 made of glass are arranged between the lower end plate 106 and the lower terminal plate 420. The glass seal member 197 is an example of a joining member within the scope of the claims.

As shown in Figures 10 and 11, the stress relief portion 700 is, for example, an elastically deformable flat member, and has a hole 708 formed therethrough that communicates with the gas through hole 26 of the gas passage member 27. The shape of the hole 708 when viewed from the top and bottom is an elongated hole that corresponds to the shape of the oxidant gas supply manifold 161.

The stress relief portion 700 has a joint portion 702, a displacement portion 704, and a support portion 706. The joint portion 702 is the portion of the stress relief portion 700 that is joined to the lower end plate 106 (flat portion 510) by at least one of welding and brazing. The joint portion 702 is formed in an annular shape so as to surround the entire circumference of the hole 708 (gas through hole 26). Figures 10 and 11 show an example of a configuration in which the stress relief portion 700 is joined to the lower end plate 106 by laser welding. It is preferable that the shape of the joint portion 702 when viewed from the top to bottom is a substantially circular ring with rounded corners.

The displacement portion 704 is a portion of the stress relief portion 700 that is located inside the joint portion 702 (on the gas through hole 26 side) and defines the hole 708. The displacement portion 704 is an annular portion formed to surround the entire circumference of the hole 708. As described above, the stress relief portion 700 is formed from an elastically deformable material, and therefore the displacement portion 704 is configured to be displaceable in the vertical direction relative to the lower end plate 106. In this embodiment, the portion of the displacement portion 704 on the gas through hole 26 side can be moved vertically away from the lower end plate 106, starting from the portion of the displacement portion 704 on the joint portion 702 side.

The support portion 706 is a portion of the stress relief section 700 located outside the joint portion 702 (on the opposite side from the gas through hole 26). The support portion 706 is formed to surround the entire periphery of the joint portion 702. The support portion 706 is also configured to be displaceable in the vertical direction relative to the lower end plate 106. However, the support portion 706 may also be joined to the lower end plate 106 so that it cannot be displaced.

The vertical rigidity of the stress relief portion 700 is lower than the vertical rigidity of the lower end plate 106. Specifically, in this embodiment, for example, the stress relief portion 700 and the lower end plate 106 are formed from the same material, and the vertical thickness of the stress relief portion 700 is thinner than the vertical thickness of the lower end plate 106. The vertical thickness of the stress relief portion 700 is preferably 0.5 mm or less, and can be, for example, 0.5 mm, 0.3 mm, 0.1 mm, or 0.05 mm.

The glass seal member 197 is disposed between the lower terminal plate 420 and the stress relief portion 700. The glass seal member 197 joins the lower terminal plate 420 to at least the displacement portion 704 of the stress relief portion 700. In this embodiment, the glass seal member 197 is joined only to an area of the stress relief portion 700 that is different from the joint portion 702.

Specifically, as shown in FIG. 11 , the glass seal member 197 is formed on the displacement portion 704 of the stress relief portion 700. More specifically, the glass seal member 197 is formed in a region outside the hole 708 of the stress relief portion 700 and inside the joint portion 702. In other words, the glass seal member 197 is formed at a position spaced apart from the joint portion 702. Furthermore, the glass seal member 197 is formed at a position spaced apart from the end of the displacement portion 704 opposite the joint portion 702. This prevents damage to the joint portion due to deformation that may occur at the end portion of the displacement portion 704 being transmitted to the glass seal member 197. The glass seal member 197 is annular and surrounds the entire circumference of the gas through hole 26 (hole 708). The thickness of the glass seal member 197 can be, for example, 1.0 mm or more and 1.5 mm or less.

As described above, the joint portion 702 is located on the opposite side of the glass seal member 197 from the gas through hole 26 when viewed from the top-bottom direction (see Figures 10 and 11). The gas through hole 26 is an example of a flow path within the scope of the claims.

A-4. Effects of this embodiment:
As described above, in the fuel cell stack 100 of this embodiment, the glass seal member 197 is joined to the lower end plate 106 and to the lower terminal plate 420 via the stress absorbing portion 700 (see FIG. 10 ). The stress absorbing portion 700 is joined to the lower end plate 106 by at least one of welding and brazing. The stress absorbing portion 700 also has a displacement portion 704 that is vertically displaceable relative to the lower end plate 106. Therefore, even if the lower end plate 106 and the lower terminal plate 420 are displaced apart, the displacement portion 704 of the stress absorbing portion 700 displaces accordingly, thereby suppressing stress generation in the glass seal member 197. As a result, this embodiment can suppress damage to the joint of the glass seal member 197 caused by the displacement of the lower end plate 106 and the lower terminal plate 420 away from each other.

Figure 12 is an explanatory diagram showing the state before and after the lower end plate 106 and the lower terminal plate 420 are displaced apart. Figure 12(A) shows the state before the displacement, and Figure 12(B) shows the state after the displacement. As described above, the lower end plate 106 has an upright portion 530, to which the gas passage member 27 is connected. For example, when a downward pulling force (see Figure 12(A)) or an external force from the left or right is applied to the gas passage member 27, the lower end plate 106 deforms so that the lower end plate 106 and the lower terminal plate 420 are displaced apart. Specifically, the flat portion 510 is tilted so that the upright portion 530 is positioned downward (see Figure 12(B)).

Here, if the stress absorbing portion 700 were not provided and the lower end plate 106 and the lower terminal plate 420 were directly joined by the glass seal member 197, tensile stress corresponding to the displacement of the lower end plate 106 and the lower terminal plate 420 would be directly applied to the glass seal member 197. This could damage the joint formed by the glass seal member 197 and reduce the bond strength between the lower end plate 106 and the lower terminal plate 420. Furthermore, in this embodiment, the sealability between the lower end plate 106 and the lower terminal plate 420 would be reduced, potentially resulting in gas leakage.

In contrast, in this embodiment, as described above, the glass seal member 197 is bonded to the lower end plate 106 via the stress absorbing portion 700, and is also bonded to the lower terminal plate 420. The displacement portion 704 of the stress absorbing portion 700 is displaceable in the vertical direction relative to the lower end plate 106. Therefore, the stress absorbing portion 700 does not follow the displacement of the lower end plate 106, but instead attempts to maintain the state before the lower end plate 106 and the lower terminal plate 420 were separated (see FIG. 12(B)). In other words, the amount of change in the distance between the lower terminal plate 420 and the stress absorbing portion 700 is smaller than the amount of separation displacement between the lower end plate 106 and the lower terminal plate 420. This suppresses stress generation in the glass seal member 197 and prevents damage to the joint of the glass seal member 197 due to the separation displacement between the lower end plate 106 and the lower terminal plate 420.

In this embodiment, the vertical rigidity of the stress absorbing portion 700 is lower than the vertical rigidity of the lower end plate 106. This reduces the ability of the stress absorbing portion 700 to follow the displacement of the lower end plate 106 when the lower end plate 106 and the lower terminal plate 420 are displaced apart (see FIG. 12(B)). Therefore, compared to a configuration in which the rigidity of the stress absorbing portion 700 is equal to or greater than the rigidity of the lower end plate 106, for example, the stress generated in the glass seal member 197 due to the displacement is reduced. As a result, this embodiment effectively prevents damage to the joint formed by the glass seal member 197.

In this embodiment, the glass seal member 197 is bonded only to an area of the stress relief section 700 that is different from the bonding section 702 (see Figures 10 to 12). Therefore, compared to a configuration in which the glass seal member 197 is bonded to the displaced portion 704 of the stress relief section 700 as well as to an area that overlaps the bonding section 702, the stress generated in the glass seal member 197 due to the separation displacement is reduced. As a result, this embodiment can effectively prevent damage to the bonding section caused by the glass seal member 197.

In this embodiment, the joint portion 702 is positioned on the opposite side of the glass seal member 197 from the gas through hole 26 when viewed from the top-bottom direction (see Figures 10 and 11). Therefore, even if the separation displacement between the lower end plate 106 and the lower terminal plate 420 on the gas through hole 26 side is relatively large (see Figure 12 (B)), the portion of the stress relief portion 700 on the gas through hole 26 side is largely displaced, effectively preventing damage to the joint portion formed by the glass seal member 197.

A-5. Modification 1 of this embodiment:
13 is an explanatory diagram showing an enlarged view of the joining structure between the lower end plate 106 and the lower terminal plate 420 in Modification 1 of the embodiment. In the following, among the configurations of Modification 1, the same components as those of the fuel cell stack 100 of the above-described embodiment are denoted by the same reference numerals and descriptions thereof will be omitted as appropriate.

In the above embodiment, the stress relief portion 700 was joined to the lower end plate 106, but in this first modification, the stress relief portion 700a is joined to the lower terminal plate 420. Specifically, the stress relief portion 700a is, for example, an elastically deformable flat member, and has a hole 708a formed therethrough that communicates with the gas through hole 26 of the gas passage member 27. The lower terminal plate 420 is an example of a first member in the claims, and the lower end plate 106 is an example of a second member in the claims.

The stress relief portion 700a has a joint portion 702a and a displacement portion 704a. The joint portion 702a is the portion of the stress relief portion 700a that is joined to the lower terminal plate 420 by at least one of welding and brazing. The displacement portion 704a is the portion of the stress relief portion 700a that is located outside the joint portion 702a (on the opposite side from the gas through hole 26). The displacement portion 704a is configured to be displaceable in the vertical direction relative to the lower terminal plate 420. The glass seal member 197a joins the lower end plate 106 to at least the displacement portion 704a of the stress relief portion 700a. The glass seal member 197a is an example of a joining member within the scope of the claims.

For example, when a downward pulling force is applied to the gas passage member 27 (tip portion 28a of the main body portion 28), the upright portion 530 of the lower end plate 106 is displaced downward, causing the glass seal member 197a to be displaced downward. However, the displaced portion 704a of the stress absorbing portion 700a is displaced downward and away from the lower terminal plate 420 in response to the displacement of the glass seal member 197a, thereby suppressing the generation of stress in the glass seal member 197a. As a result, according to this first variation, damage to the joint formed by the glass seal member 197a due to the displacement of the lower end plate 106 and the lower terminal plate 420 can be suppressed.

A-6. Modification 2 of this embodiment:
14 is an explanatory diagram showing an enlarged view of the joining structure between the lower end plate 106 and the fuel electrode side frame 140 in Modification 2 of the embodiment. In the following, among the configurations of Modification 2, the same configurations as those of the fuel cell stack 100 of the above-described embodiment are denoted by the same reference numerals and descriptions thereof will be omitted as appropriate.

In this second variant, a stress relief portion 700b and a glass seal member 197b are arranged between the lower end plate 106 and the lower terminal plate 420, and a stress relief portion 700c and a glass seal member 197c are arranged between the lower terminal plate 420 and the fuel electrode side frame 140 (power generation block 103).

The stress relief portion 700b has a joint portion 702b and a displacement portion 704b. The joint portion 702b is the portion of the stress relief portion 700b that is joined to the lower terminal plate 420 by at least one of welding and brazing. The displacement portion 704b is the portion of the stress relief portion 700b that is located more inward (toward the gas through hole 26) than the joint portion 702b. The displacement portion 704b is configured to be displaceable in the vertical direction relative to the lower terminal plate 420. The glass seal member 197b joins the lower end plate 106 to at least the displacement portion 704b of the stress relief portion 700b.

The stress relief portion 700c has a joint portion 702c and a displacement portion 704c. The joint portion 702c is the portion of the stress relief portion 700c that is joined to the lower terminal plate 420 by at least one of welding and brazing. The joint portion 702c is located more inward (on the gas through hole 26 side) than the joint portion 702b. The displacement portion 704c is the portion of the stress relief portion 700c that is located more outward (on the opposite side from the gas through hole 26) than the joint portion 702c. The displacement portion 704c is configured to be displaceable in the vertical direction relative to the lower terminal plate 420. The glass seal member 197c joins the fuel electrode side frame 140 to at least the displacement portion 704c of the stress relief portion 700c. The lower terminal plate 420 is an example of a first member in the claims, and the lower end plate 106 and the fuel electrode side frame 140 are an example of a second member in the claims. The glass seal members 197b and 197c are an example of a joining member in the claims.

For example, when a downward pulling force is applied to the gas passage member 27 (main body portion 28), the upright portion 530 of the lower end plate 106 is displaced downward, causing the glass seal member 197b to be displaced downward. However, in response to the displacement of the glass seal member 197b, the displaced portion 704b of the stress mitigation portion 700b is displaced downward and away from the lower terminal plate 420. This reduces stress on the glass seal member 197b. At this time, the lower terminal plate 420 is also displaced downward, causing the joint portion 702c of the stress mitigation portion 700c to be displaced downward. However, in response to the displacement of the lower terminal plate 420, the displaced portion 704c of the stress mitigation portion 700c is displaced downward. This reduces stress on the glass seal member 197c. As a result, according to this second modification, it is possible to prevent damage not only to the joints formed by glass seal member 197b, but also to the joints formed by glass seal member 197c.

B. Variations:
The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified in various forms without departing from the spirit thereof, for example, the following modifications are also possible.

The configurations of the fuel cell stack 100 and power generation unit 102 in the above embodiment are merely examples and can be modified in various ways. For example, in the above embodiment, the erected portion 530 of the lower end plate 106 may be inserted into the tip portion 28a of the gas passage member 27, or the lower end surface of the erected portion 530 may be butted against and joined to the upper end surface of the gas passage member 27.

In the above embodiment, glass sealing members 197, 197a, 197b, and 197c made of glass were used as examples of joining members. However, members having joining functions may be formed from materials other than glass (e.g., metal or resin). Furthermore, in the above embodiment, glass sealing members 197, 197a, 197b, and 197c were formed to surround the periphery of gas through hole 26 when viewed from the top and bottom (see FIG. 11) and functioned as sealing members to suppress gas leakage. However, this is not limited thereto. For example, glass sealing members 197, 197a, 197b, and 197c may be formed only partially around gas through hole 26. Furthermore, stress relief portions 700, 700a, 700b, and 700c may also be formed only partially around gas through hole 26.

In the above embodiment, examples have been described in which the present invention is applied to the joining structure between the lower end plate 106 and the lower terminal plate 420, and the joining structure between the lower terminal plate 420 and the fuel electrode side frame 140. However, this is not limited to this, and the present invention may also be applied to, for example, the joining structure between the upper end plate 104 and the terminal separator 210, or the joining structure between the IC separator 180 and the single cell separator 120. The present invention may also be applied to other manifolds 162, 171, 172, or to joining structures between two members arranged along the gas through holes 26 connected to other manifolds 162, 171, 172.

In the above embodiment, for example, by employing at least one of the following elements, the vertical rigidity of the stress relaxation portion 700 may be made lower than the vertical rigidity of the lower end plate 106.
(a) The stress relief portion 700 is made of a material softer than the material of the lower end plate 106 .
(b) By providing a reinforcing member or rib to the lower end plate 106 , the rigidity of the lower end plate 106 is made higher than that of the stress relaxation portion 700 .
Furthermore, it is sufficient that the rigidity of at least the displacement portion 704 of the stress relief portion 700 is lower than the rigidity of the lower end plate 106. Furthermore, in the above embodiment, the rigidity of the stress relief portion 700 in the vertical direction may be the same as or higher than the rigidity of the lower end plate 106 in the vertical direction.

In the above embodiment, the glass seal member 197 may be bonded not only to the displacement portion 704 of the stress relief portion 700, but also to, for example, the joint portion 702 or the support portion 706. In the above embodiment, the joint portion 702 may be located on the gas through hole 26 side of the glass seal member 197 when viewed from the top-bottom direction.

In the above embodiment, holes 32, 34 are formed in the pair of end plates 104, 106, but the holes 32, 34 do not have to be formed in at least one of the pair of end plates 104, 106. Also, in the above embodiment, the fuel cell stack 100 is provided with a pair of terminal plates 410, 420, but other components (e.g., the pair of end plates 104, 106) may also function as terminal plates, and the terminal plates 410, 420 as dedicated components may be omitted.

In the above embodiment, the unit cell separator 120 has a connecting portion 128 that is curved so as to protrude downward relative to both the inner portion 126 and the outer portion 127, but the shape of the connecting portion 128 may be other shapes. Furthermore, the unit cell separator 120 does not necessarily have to have a connecting portion 128. The same applies to the connecting portion 188 in the IC separator 180.

In the above embodiment, the glass seal portion 125 is disposed near the through-hole 121 in the single cell separator 120, but the glass seal portion 125 may be omitted.

In the above embodiment, the interconnector 190 includes a conductive coating layer 194, but the interconnector 190 does not necessarily have to include the coating layer 194. Also, in the above embodiment, the single cell 110 includes a reaction prevention layer 118, but the single cell 110 does not necessarily have to include the reaction prevention layer 118.

In the above embodiment, the unit cell 110 is an anode-supported unit cell, but it may be another type of unit cell, such as an electrolyte-supported or metal-supported unit cell. Also, in the above embodiment, the fuel cell stack 100 is a counterflow type fuel cell, but the fuel cell stack 100 may be another type of fuel cell, such as a coflow type.

In the above embodiment, the number of unit cells 110 (number of power generation units 102) included in the fuel cell stack 100 is merely an example, and the number of unit cells 110 is determined appropriately depending on the output voltage required for the fuel cell stack 100, etc. Furthermore, the materials constituting each component in the above embodiment are merely examples, and each component may be made of other materials.

While the above-described embodiment focuses on an SOFC that generates electricity using an electrochemical reaction between hydrogen contained in a fuel gas and oxygen contained in an oxidant gas, the technology disclosed herein is similarly applicable to electrolysis cell units, which are constituent elements of solid oxide electrolysis cells (SOECs) that generate hydrogen using the electrolysis reaction of water, and to electrolysis cell stacks comprising multiple electrolysis cell units. The configurations of the electrolysis cell units and electrolysis cell stacks are publicly known, as described in, for example, Japanese Patent Application Laid-Open No. 2016-81813, and will not be described in detail here. However, they are generally similar in configuration to the power generation unit 102 and fuel cell stack 100 in the above-described embodiment. That is, the fuel cell stack 100 in the above-described embodiment may be read as an electrolysis cell stack, the power generation unit 102 as an electrolysis cell unit, and the single cell 110 as an electrolysis single cell. However, during operation of the electrolysis cell stack, a voltage is applied between the air electrode 114 (positive electrode) and the fuel electrode 116 (negative electrode), and water vapor is supplied as a raw material gas via a manifold. This causes a water electrolysis reaction in each electrolysis cell unit, generating hydrogen gas in the fuel chamber 176, which is then extracted to the outside of the electrolysis cell stack via the manifold. Even in an electrolysis cell stack with this configuration, if a configuration similar to that of the above embodiment is adopted, damage to the joints of the joining members due to the separation displacement of the two components can be suppressed.

In the above embodiment, a so-called flat-plate type fuel cell stack has been used as an example, but the technology disclosed in this specification is not limited to flat-plate type, and can be similarly applied to other types of fuel cell stacks (so-called cylindrical flat-plate type and cylindrical type), as explained below.

In the above embodiment, a solid oxide fuel cell (SOFC) has been described as an example, but the technology disclosed in this specification can also be applied to other types of fuel cells (or electrolytic cells), such as polymer electrolyte fuel cells (PEFCs), phosphoric acid fuel cells (PAFCs), and molten carbonate fuel cells (MCFCs). Furthermore, the technology disclosed in this specification is not limited to electrochemical reaction cell stacks, but can also be applied to composites comprising a first member, a second member located on one side of the first member, and a joining member disposed between the first and second members.

22: Bolt 24: Nut 26: Gas through-hole 27: Gas passage member 28: Main body 28a: Tip portion 29: Flange portion 32, 34, 131, 141, 412, 708, 708a: Hole 100: Fuel cell stack 102: Power generation unit 103: Power generation block 104: Upper end plate 106: Lower end plate 107: End through-hole 108: Communication hole 109: Bolt hole 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Anode 118: Reaction prevention layer 120: Single cell separator 121, 181, 211, 612, 622: Through-hole 124: Joint 125: Glass seal portion 126, 186, 216: Inner portion 127, 187, 217: Outer portion 128, 188, 218: Connecting portion 130: Air electrode side frame 132: Oxidant gas supply passage 133: Oxidant gas discharge passage 134: Air electrode side current collecting portion 140: Anode side frame 142: Fuel gas supply passage 143: Fuel gas discharge passage 144: Anode side current collecting member 145: Electrode opposing portion 146: Interconnector opposing portion 147: Connecting portion 149: Spacer 150: Flat plate portion 161: Oxidant gas supply manifold 162: Oxidant gas discharge manifold 166: Air chamber 171: Fuel gas supply manifold 172: Fuel gas discharge manifold 176: Fuel chamber 180: IC separator 189: Lower end plate 190: Interconnector 194: Coating layer 196: Conductive bonding material 197, 197a, 197b, 197c: Glass seal member 200: Insulating portion 210: Terminal separator 220: Upper end plate 310, 510: Flat portion 320, 520: Convex portion 322, 522: Outer convex portion 322A, 324A: Side portion 322B, 324B: Corner portion 324: Inner convex portion 326: Protrusion 410: Upper terminal plate 420: Lower terminal plate 524: Inner convex portion 530: Standing portion 600: Reinforcing member 610: Flat portion 620: Cylindrical portion 700, 700a, 700b, 700c: Stress relaxation portion 702, 702a, 702b, 702c: Joint portion 704, 704a, 704b, 704c: Displacement portion 706: Support portion

Claims (5)

A first member;
a second member located on one side of the first member in a first direction,
a stress relaxation portion disposed between the first member and the second member, the stress relaxation portion being joined to the first member by at least one of welding and brazing, and having a displacement portion configured to be displaceable in the first direction relative to the first member in a region different from a joint portion with the first member;
a joining member disposed between the second member and the stress relaxation portion, joining at least the displacement portion of the stress relaxation portion to the second member,
the joint portion of the stress relaxation portion extends in the first direction with respect to the joint member, and is disposed on an opposite side to a gas flow path that penetrates the first member and the second member, when viewed in the first direction.
A complex characterized by: 2. The composite of claim 1 ,
The rigidity of the stress relaxation portion in the first direction is lower than the rigidity of the first member in the first direction.
A complex characterized by: In the complex according to claim 1 or claim 2,
The joining member is joined only to a region of the stress relaxation portion that is different from the joining portion.
A complex characterized by: The composite according to any one of claims 1 to 3,
One of the first member and the second member has a standing portion formed thereon that protrudes toward the other side in the first direction.
A complex characterized by: 5. The composite of claim 1, wherein
The complex is
a plurality of electrochemical reaction units arranged side by side in the first direction, each of the electrochemical reaction units having an electrochemical reaction unit cell including an electrolyte layer and an air electrode and an anode facing each other in the first direction with the electrolyte layer interposed therebetween;
an electrochemical reaction cell stack in which a flow path is formed to exchange gas between a specific electrode, which is at least one of the air electrode and the fuel electrode, in each of the electrochemical reaction units;
the first member and the second member are members that face the flow path and are aligned with each other in the first direction to constitute the electrochemical reaction cell stack;
A complex characterized by: