Complex

Abstract

To suppress damage to a joint portion by a joining member due to separation displacement between a first member and a second member.SOLUTION: A complex includes a first member, and a second member located on one side in the first direction with respect to the first member. The complex includes: a stress relaxation portion arranged between the first member and the second member, and including a displacement portion that is joined to the first member by at least one of welding and brazing and is configured to be displaceable in a first direction with respect 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 relaxation portion and joining at least the displacement portion of the stress relaxation portion and the second member.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The technology disclosed herein relates to a composite. [Background technology]

[0002] Solid oxide fuel cells (hereinafter referred to as "SOFCs"), which have an electrolyte layer containing solid oxide, are known as one type of fuel cell that generates electricity using the electrochemical reaction between hydrogen and oxygen. A fuel cell unit (hereinafter simply referred to as a "unit cell"), which is a constituent unit of an SOFC, includes an electrolyte layer and an air electrode and an anode that face each other in a specific direction (hereinafter referred to as the "first direction") across the electrolyte layer.

[0003] SOFCs are generally used in the form of a fuel cell stack, which includes a power generation block in which a plurality of 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, which is one of the anode and cathode. The fuel cell stack further 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). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-10804 Summary of the Invention [Problem to be solved by the invention]

[0005] In a fuel cell stack in which a joining member is arranged between the power generation block and the end member in this manner, there is a problem in that if the power generation block and the end member are displaced apart, tensile stress will be generated in the joining member, which may damage the joint created by the joining member.

[0006] Note that this issue is also common to electrolysis cell stacks that include multiple electrolysis cell units, each of which includes a single electrolysis cell, which is 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, this issue is not limited to SOFCs and SOECs, but is also common to other types of fuel cells and electrolysis cells. Furthermore, this issue is not limited to electrochemical reaction cell stacks, but is also common to composites that include a first member, a second member located on one side of the first member, and a joining member disposed between the first member and the second member.

[0007] This specification discloses a technique that can solve the above-mentioned problems. [Means for solving the problem]

[0008] The technology disclosed in this specification can be realized, for example, in the following forms.

[0009] (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 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.

[0010] In this composite, the joining member is joined to a first member and a 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 the displacement, thereby suppressing stress generation in the joining member. As a result, this composite can suppress damage to the joint portion of the joining member caused by the displacement of the first member and the second member away from each other.

[0011] (2) In the above composite, the rigidity of the stress relief portion in the first direction may be configured to be lower than the rigidity of the first member in the first direction. According to this composite, when the first member and the second member are displaced apart, the ability of the stress relief portion to follow the displacement of the first member can be reduced. 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, stress generated in the joining member due to the displacement is reduced. As a result, according to this composite, damage to the joint portion formed by the joining member can be effectively suppressed.

[0012] (3) In the above composite, the joining member may be joined only to a region of the stress relief portion that is different from the joint portion. With this composite, the stress generated in the joining member due to the 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 portion as well as to a region that overlaps the joint portion. As a result, with this composite, damage to the joint portion due to the joining member can be effectively suppressed.

[0013] (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 relaxation portion may be disposed on the opposite side of the flow path with respect to the joint 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 relaxation portion on the flow path side is largely displaced, thereby effectively preventing damage to the joint portion formed by the joint member.

[0014] (5) In the above composite, one of the first and second members may 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 a force is applied to this standing portion, the first and second members are likely to be displaced apart. Even in such a configuration, applying the present invention can prevent damage to the joints formed by the joining members.

[0015] (6) The composite may be an electrochemical reaction cell stack including a plurality of electrochemical reaction units arranged 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 sandwiched therebetween, and 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.

[0016] The technology disclosed in this specification can be realized in various forms, for example, an electrochemical reaction cell stack (fuel cell stack or electrolysis cell stack) having a plurality of electrochemical reaction unit cells or electrochemical reaction units, the above-mentioned composite, a manufacturing method thereof, etc. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view showing the external configuration of a fuel cell stack 100 according to an embodiment of the present invention. [Figure 2] 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. [Figure 3] 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. [Figure 4] FIG. 4 is an explanatory diagram showing the YZ cross-sectional configuration of the fuel cell stack 100 taken along the line IV-IV in FIG. 1. [Figure 5] 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. [Figure 6] 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. [Figure 7]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. 4. [Figure 8] 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. [Figure 9] FIG. 6 is an explanatory diagram showing the XY cross-sectional configuration of the power generating unit 102 at the position IX-IX in FIG. 5. [Figure 10] FIG. 1 is an explanatory diagram showing an enlarged view of the joint structure between the lower end plate 106 and the lower terminal plate 420. [Figure 11] 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. 10. [Figure 12] 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; [Figure 13] 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 in the first modified example of the embodiment. [Figure 14] 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 the second modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] A. Implementation: A-1.Configuration: (Configuration of fuel cell stack 100) FIG. 1 is a perspective view showing the external configuration of a fuel cell stack 100 according to this embodiment. FIG. 2 is an explanatory diagram showing an 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 an 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 a YZ cross-sectional configuration of the fuel cell stack 100 taken along line IV-IV in FIG. 1 . Each figure shows mutually 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.

[0019] 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 side by side 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 arranged on the upper side of an assembly (hereinafter referred to as the "power generation block 103") made up 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 arranged on the lower side of 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 so as 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 defined in the claims.

[0020] As shown in FIGS. 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 of the layers that make up the fuel cell stack 100 (the power generation block 103, the terminal separator 210, the lower end plate 189, the pair of terminal plates 410, 420, and the insulating part 200). Holes (screw holes) are formed through the upper end plate 104 near the four corners of the outer periphery around the Z-axis, and holes (screw holes) are formed through the lower end plate 106 near the four corners of the outer periphery around the Z-axis. 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 the bolt holes 109 may also be referred to as bolt holes 109.

[0021] 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.

[0022] 1 to 3, four holes that vertically penetrate each layer are formed in the peripheral portion around the Z axis direction 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, and corresponding holes formed in each layer are vertically connected to each other 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.

[0023] 1 and 2 , one communication hole 108 located near one side (the side on the positive X-axis side of 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 an oxidant gas OG is introduced from outside the fuel cell stack 100 and supplied to an 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 side of two sides parallel to the Y-axis) functions as an oxidant gas discharge manifold 162, which is a gas flow path through which an oxidant off-gas OOG, which is a 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 an air electrode 114 (described later) of each power generation unit 102. As the oxidizing gas OG, for example, air is used.

[0024] 1 and 3 , among the sides constituting the outer periphery of the fuel cell stack 100 around the Z axis, another communication hole 108 located near the side closest to the communication hole 108 functioning as the oxidant gas discharge 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 a fuel chamber 176 (described later) of each power generating unit 102, and 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 discharge manifold 172, which is a gas flow path through which fuel off-gas FOG, which is gas discharged from the fuel chamber 176 of each power generating unit 102, is discharged to the outside of the fuel cell stack 100. The fuel gas supply manifold 171 and the fuel gas discharge manifold 172 are gas flow paths that exchange gas with an anode 116 (described later) of each power generating unit 102. As the fuel gas FG, for example, hydrogen-rich gas obtained by reforming city gas is used.

[0025] As shown in FIGS. 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 a lower end plate 106. Specifically, the upper end of the main body 28 is inserted into the end through-hole 107 and joined thereto by, for example, 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 up-down direction (Z-axis direction). The flange portion 29 has a substantially rectangular shape when viewed from the up-down direction, and a bolt hole 29A (see FIG. 1) is formed at each of the four corners. A bolt (not shown) for connecting the fuel cell stack 100 to an external device is inserted into each bolt hole 29A.

[0026] 2, gas through holes 26 of gas passage member 27 arranged at the position of oxidizing gas supply manifold 161 communicate with oxidizing gas supply manifold 161, and gas through holes 26 of gas passage member 27 arranged at the position of oxidizing gas discharge manifold 162 communicate with oxidizing gas discharge manifold 162. Also, as shown in FIG. 3, gas through holes 26 of gas passage member 27 arranged at the position of fuel gas supply manifold 171 communicate with fuel gas supply manifold 171, and gas through holes 26 of gas passage member 27 arranged at the position of fuel gas discharge manifold 172 communicate with fuel gas discharge manifold 172.

[0027] (Configuration of end plates 104 and 106) The pair of end plates 104, 106 are flat, plate-like members with a substantially rectangular outer shape as viewed in the Z-axis direction, and are formed from a conductive material (metal material) such as ferritic stainless steel that forms an alumina oxide coating on its surface. Holes 32, 34 are formed near the center 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, which will be described later. 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, which will be described later). Each of the end plates 104, 106 is formed by pressing (bending) a single plate-like member. The thickness of the end plates 104, 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.

[0028] As shown in FIGS. 2 to 4 , the upper end plate 104 includes a flat portion 310 and a protruding portion 320. The flat 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 overall shape of the flat portion 310 when viewed in the Z-axis direction is a rectangular frame. Note that the holes that form the bolt holes 109 described above are formed on the peripheral portion of the flat portion 310 around the Z-axis direction. The protruding portion 320 is a rib that protrudes upward from the flat portion 310. The protruding portion 320 has an outer protruding portion 322 and an inner protruding portion 324. The outer protruding portion 322 protrudes upward from the outer periphery of the flat portion 310. The outer protruding portion 322 is formed around the entire outer periphery of the flat portion 310. The inner protruding portion 324 protrudes upward from the inner periphery of the flat portion 310. The inner convex portion 324 is formed around the entire inner periphery of the flat portion 310 .

[0029] In this embodiment, the shape of the outer convex portion 322 as viewed in the Z-axis direction is rectangular overall. Specifically, the shape of the outer convex portion 322 has four linear 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 as viewed in the Z-axis direction is also rectangular overall. Specifically, the shape of the inner convex portion 324 has four linear sides 324A that form each side of the rectangle and four arc-shaped corners 324B that connect adjacent sides 324A. In this way, the convex portion 320 has a straight or curved shape without any angular portions, which can prevent stress from concentrating at a specific location on the convex portion 320 when the end plate 104 deforms.

[0030] Furthermore, the outer peripheral surface of at least one side 322A of the upper end plate 104 is formed with a plurality of protrusions 326 (two in FIG. 1 ) aligned in the longitudinal direction of the side 322A. The lower end plate 106 has a shape similar to that of 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 facing downward. In this case, the plurality of 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.

[0031] The lower end plate 106 also includes a flat portion 510 and a protruding portion 520. The flat 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 overall shape of the flat portion 510 when viewed in the Z-axis direction is a rectangular frame. The holes that form the bolt holes 109 described above are formed on the periphery of the flat portion 510 around the Z-axis direction. The protruding portion 520 is a rib that protrudes downward from the flat portion 510. The protruding portion 520 has an outer protruding portion 522 and an inner protruding portion 524. The outer protruding portion 522 protrudes downward from the outer periphery of the flat portion 510. The outer protruding portion 522 is formed around the entire outer periphery of the flat portion 510. The inner protruding portion 524 protrudes downward from the inner periphery of the flat portion 510. The inner convex portion 524 is formed around the entire inner periphery of the flat portion 510 .

[0032] As shown in FIGS. 2 and 3 , a reinforcing member 600 is fixed to the lower end plate 106. The reinforcing member 600 has a flat plate portion 610 and a tubular portion 620. The flat plate portion 610 is a flat portion parallel to the planar portion 510 of the lower end plate 106. The flat plate portion 610 has a substantially rectangular shape when viewed in the vertical direction. The flat plate portion 610 is disposed at a position spaced downward from the planar portion 510 of the lower end plate 106. One longitudinal edge of the flat plate portion 610 contacts the inner wall surface of the outer convex portion 522 and is joined thereto by, for example, welding, and the other longitudinal edge of the flat plate portion 610 contacts the inner wall surface of the inner convex portion 524 and is joined thereto by, for example, welding. A through hole 612 is formed in the flat plate 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 form 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 (ferritic stainless steel, etc.).

[0033] (Configuration of terminal plates 410 and 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 penetrating in the Z-axis direction is formed near the center of the upper terminal plate 410. As viewed in the Z-axis direction, the inner periphery of the hole 412 formed in the upper terminal plate 410 encloses each of the unit cells 110 described below. As viewed in the Z-axis direction, one end of each of the pair of terminal plates 410, 420 (the X-axis positive direction side) 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 of the fuel cell stack 100, and the protruding portion of the lower terminal plate 420 functions as a negative output terminal of the fuel cell stack 100.

[0034] (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).

[0035] (Configuration of Terminal Separator 210) The terminal separator 210 is a frame-like member having a substantially rectangular through-hole 211 formed near the center in the vertical direction, and is made of, for example, metal. A portion of the terminal separator 210 surrounding the through-hole 211 (hereinafter referred to as the "through-hole surrounding portion") is joined to the upper surface of the peripheral portion of the upper end plate 220 by, for example, welding. 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.

[0036] The terminal separator 210 includes an inner portion 216 including the area surrounding the through-hole of the terminal separator 210, an outer portion 217 located radially outward of the inner portion 216, and a connecting portion 218 connecting the inner portion 216 and the outer portion 217. In this embodiment, the inner portion 216 and the outer portion 217 are generally flat plate-shaped extending in a direction generally perpendicular to the Z-axis direction. The connecting portion 218 is curved so as to protrude 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.

[0037] (Configuration of bottom plate 189) 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 lower end plate 189 is sandwiched between lower terminal plate 420 and lower end plate 106, thereby ensuring insulation between lower terminal plate 420 and lower end plate 106.

[0038] (Configuration of insulating part 200) Insulating section 200 is a frame-shaped member with a substantially rectangular through-hole formed in the center that penetrates vertically, and is made of an insulating material such as mica. Insulating section 200 is sandwiched between upper end plate 104 and terminal separator 210, thereby ensuring insulation between upper end plate 104 and terminal separator 210.

[0039] (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.

[0040] 5 to 7, the power generating 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, and a pair of interconnectors 190 and a pair of IC separators 180 that form the uppermost and lowermost layers of the power generating 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.

[0041] The unit cell 110 includes 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, and reaction prevention layer 118) that constitute the unit cell 110. The unit cell 110 is an example of an electrochemical reaction unit cell as defined in the claims.

[0042] 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 fuel electrode 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 preventing an element (e.g., Sr) diffused from the air electrode 114 from reacting with an element (e.g., Zr) contained in the electrolyte layer 112 to produce a highly resistive substance (e.g., SrZrO3). The air electrode 114 and the fuel electrode 116 are examples of specific electrodes in the claims.

[0043] The single cell separator 120 is a frame-like member having a substantially rectangular through-hole 121 formed near the center and penetrating in the vertical direction, and is made of, for example, metal. The portion of the single cell separator 120 surrounding the through-hole 121 (hereinafter referred to as the "through-hole surrounding portion") faces the upper surface of the peripheral portion 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 joining portion 124 formed of a brazing material (e.g., Ag brazing) placed in the facing portion. The single cell separator 120 defines an air chamber 166 facing the air electrode 114 and 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 portion of the single cell 110.

[0044] The single cell separator 120 includes an inner portion 126 including the through-hole periphery of the single cell separator 120, an outer portion 127 located radially outward of the inner portion 126, and a connecting portion 128 connecting the inner portion 126 and the outer portion 127. In this embodiment, the inner portion 126 and the outer portion 127 are generally flat plate-shaped extending in a direction generally perpendicular to the Z-axis direction. The connecting portion 128 is curved so as to protrude downward relative to both the inner portion 126 and the outer portion 127. A lower portion of the connecting portion 128 (on the fuel chamber 176 side) is a convex portion, and an upper portion of the connecting portion 128 (on the air chamber 166 side) is a concave portion. Therefore, the connecting portion 128 includes a portion whose position in the Z-axis direction differs from that of the inner portion 126 and the outer portion 127.

[0045] A glass seal portion 125 containing glass is disposed near the through-hole 121 in the unit 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 be in contact with both the surface of the unit cell separator 120 around the through-hole and the surface of the unit 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 unit cell 110.

[0046] The interconnector 190 is a conductive member having a flat plate portion 150 in the shape of a substantially rectangular plate and a plurality of substantially columnar air electrode-side current collecting portions 134 protruding from the flat plate portion 150 toward the air electrode 114, and is made of metal (e.g., ferritic stainless steel). In this embodiment, a conductive coating layer 194 made 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 the air electrode-side current collecting portions 134) is bonded to the air electrode 114 of the unit cell 110 via a conductive bonding material 196 made of, for example, a spinel-type oxide, and is thereby electrically connected to the air electrode 114 of the unit 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 in one power generating unit 102 is the same material as the lower interconnector 190 in another power generating unit 102 adjacent to and above that power generating unit 102. Furthermore, since 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).

[0047] The IC separator 180 is a frame-like member having a substantially rectangular through-hole 181 formed in the center thereof in the vertical direction, 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 the first power generating unit 102 on the upper side. Furthermore, of a 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 the first 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 uppermost position in the fuel cell stack 100 is electrically connected to the upper terminal plate 410.

[0048] The IC separator 180 includes an inner portion 186 including the periphery of the through-hole of the IC separator 180, an outer portion 187 located radially outward of the inner portion 186, and a connecting portion 188 connecting the inner portion 186 and the outer portion 187. In this embodiment, the inner portion 186 and the outer portion 187 are generally flat plate-shaped extending in a direction generally perpendicular to the Z-axis direction. The connecting portion 188 has a curved shape so as to protrude downward relative to both the inner portion 186 and the outer portion 187. The lower portion of the connecting portion 188 (on the air chamber 166 side) is a convex portion, and the upper portion of the connecting portion 188 (on the fuel chamber 176 side) is a concave portion. Therefore, the connecting portion 188 includes a portion whose position in the Z-axis direction differs from that of the inner portion 186 and the outer portion 187.

[0049] 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 of an insulator such as mica. The hole 131 in the air electrode side frame 130 forms an air chamber 166 that faces 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 them (i.e., gas sealing of the air chamber 166). The air electrode side frame 130 also electrically insulates a pair of IC separators 180 included in the power generating unit 102 (i.e., a pair of interconnectors 190). In addition, the air electrode side frame 130 is formed with an oxidant gas supply communication hole 132 that connects the oxidant gas supply manifold 161 to the air chamber 166, and an oxidant gas discharge communication hole 133 that connects the air chamber 166 to the oxidant gas discharge manifold 162.

[0050] 9, the fuel electrode side frame 140 is a frame-shaped member having a substantially rectangular hole 141 formed near the center and penetrating 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 facing 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 passage 142 that connects the fuel gas supply manifold 171 and the fuel chamber 176, and a fuel gas discharge passage 143 that connects the fuel chamber 176 and the fuel gas discharge manifold 172.

[0051] 5 to 7, the anode side current collecting member 144 is disposed in 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 is in contact with the lower surface of the anode 116, and the interconnector facing portion 146 is in contact with the upper surface of (the flat portion 150 of) the interconnector 190. 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 of this power generating unit 102 is in contact with 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 with 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 an electrode facing portion 145, the flat portion with holes other than the bent portions becomes an interconnector facing portion 146, and the portion connecting the electrode facing portion 145 and the interconnector facing portion 146 becomes a connecting portion 147.

[0052] A-2. Operation of 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.

[0053] When an oxidant gas OG is supplied to the air chamber 166 of each power generating unit 102 and a fuel gas FG is supplied to the fuel chamber 176, power is generated in the unit cell 110 by 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. That is, the multiple power generating units 102 included in the fuel cell stack 100 are electrically connected in series. Furthermore, 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 generating unit 102 is extracted from terminal plates 410, 420 which function as output terminals of the fuel cell stack 100. Since SOFCs generate electricity at relatively high temperatures (e.g., 600°C to 1000°C), the fuel cell stack 100 may be heated by a heater (not shown) after startup until the high temperature can be maintained using the heat generated by power generation.

[0054] 2 and 5, the oxidant off-gas OOG discharged from the air chamber 166 of each power generating 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 provided at the position of the oxidant gas discharge manifold 162, and is then 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 generating 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 provided at the position of the fuel gas discharge manifold 172, and is then discharged to the outside of the fuel cell stack 100 through a gas piping (not shown) connected to the main body 28.

[0055] 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 approximately opposite directions (opposing to each other).

[0056] A-3. Joint structure between lower end plate 106 and 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 the 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.

[0057] 2 to 4, four standing portions 530 are formed on the lower end plate 106 of this embodiment. As shown in Fig. 10, the standing portions 530 are cylindrical and protrude downward (toward the negative Z-axis direction) from the flat portion 510 of the lower end plate 106, and surround the end through-hole 107 of the lower end plate 106 when viewed in the up-down direction. The standing portions 530 are formed integrally with the flat portion 510.

[0058] Gas passage member 27 is connected to standing portion 530 of lower end plate 106, and the gas flow path of gas passage member 27 communicates with end through-hole 107 of lower end plate 106. Specifically, tip portion 28a of gas passage member 27 is inserted into the inner periphery of standing portion 530, and tip portion 28a of gas passage member 27 and standing portion 530 are joined by, for example, welding.

[0059] A stress relief portion 700 and a glass seal member 197 made of glass are disposed between the lower end plate 106 and the lower terminal plate 420. The glass seal member 197 is an example of a joining member in the claims.

[0060] 10 and 11 , the stress relief portion 700 is, for example, an elastically deformable flat member, and has holes 708 formed therethrough that communicate with the gas through holes 26 of the gas passage member 27. The shape of the holes 708 when viewed from the top and bottom is an elongated hole that corresponds to the shape of the oxidant gas supply manifold 161.

[0061] The stress relief portion 700 has a joint portion 702, a displacement portion 704, and a support portion 706. The joint portion 702 is a 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 periphery of the hole 708 (gas through hole 26). FIGS. 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. Note that the shape of the joint portion 702 when viewed in the vertical direction is preferably a substantially circular ring shape with rounded corners.

[0062] 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 of an elastically deformable member, 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 away from the lower end plate 106 in the vertical direction, starting from the portion of the displacement portion 704 on the joint portion 702 side.

[0063] The support portion 706 is a portion of the stress relaxation portion 700 that is located outside the joint portion 702 (on the opposite side from the gas through holes 26). The support portion 706 is formed so as to surround the entire periphery of the joint portion 702. The support portion 706 is also configured so as to be displaceable in the up and down direction relative to the lower end plate 106. However, the support portion 706 may also be joined to the lower end plate 106 so as not to be displaceable.

[0064] The vertical rigidity of the stress absorbing portion 700 is lower than the vertical rigidity of the lower end plate 106. Specifically, in this embodiment, for example, the stress absorbing portion 700 and the lower end plate 106 are formed from the same material, and the vertical thickness of the stress absorbing portion 700 is thinner than the vertical thickness of the lower end plate 106. The vertical thickness of the stress absorbing 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.

[0065] 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 a region of the stress relief portion 700 that is different from the joining portion 702.

[0066] Specifically, as shown in FIG. 11 , the glass seal member 197 is formed on the displacement portion 704 of the stress relaxation portion 700. More specifically, the glass seal member 197 is formed in a region that is outside the hole 708 of the stress relaxation 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. The glass seal member 197 is also 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.

[0067] As described above, the joint portion 702 is disposed on the opposite side of the glass seal member 197 from the gas through hole 26 when viewed in the up-down direction (see FIGS. 10 and 11). The gas through hole 26 is an example of a flow path in the claims.

[0068] A-4. Advantages 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 has a displacement portion 704 that is displaceable in the vertical direction 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 to follow the displacement, thereby suppressing stress generation in the glass seal member 197. As a result, this embodiment can suppress damage to the joint portion 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.

[0069] 12A and 12B are explanatory diagrams showing the states before and after the separation displacement of lower end plate 106 and lower terminal plate 420. FIG. 12A shows the state before the separation displacement, and FIG. 12B shows the state after the separation displacement. As described above, lower end plate 106 has standing portion 530 formed therein, and gas passage member 27 is connected to standing portion 530. For example, when gas passage member 27 is subjected to a downward pulling force (see FIG. 12A) or an external force from the left or right, lower end plate 106 is deformed so that lower end plate 106 and lower terminal plate 420 are separated. Specifically, flat portion 510 is tilted so that standing portion 530 is positioned downward (see FIG. 12B).

[0070] Here, if the configuration does not include stress absorbing portion 700 and lower end plate 106 and lower terminal plate 420 are directly joined by glass seal member 197, tensile stress corresponding to the displacement of lower end plate 106 and lower terminal plate 420 apart would be applied directly to glass seal member 197. This could damage the joint formed by glass seal member 197 and reduce the bonding strength between lower end plate 106 and lower terminal plate 420. Furthermore, in this embodiment, the sealing performance between lower end plate 106 and lower terminal plate 420 could be reduced, resulting in gas leakage.

[0071] In contrast, in this embodiment, as described above, the glass seal member 197 is joined to the lower end plate 106 via the stress absorbing portion 700, and is also joined to the lower terminal plate 420. The displaceable 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 attempts to maintain the state before the lower end plate 106 and the lower terminal plate 420 are 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 portion of the glass seal member 197 caused by the separation displacement between the lower end plate 106 and the lower terminal plate 420.

[0072] In this embodiment, the vertical rigidity of stress absorbing portion 700 is lower than the vertical rigidity of lower end plate 106. This reduces the ability of stress absorbing portion 700 to follow the displacement of lower end plate 106 when lower end plate 106 and lower terminal plate 420 are displaced apart (see FIG. 12(B)). Therefore, compared to a configuration in which the rigidity of stress absorbing portion 700 is equal to or greater than the rigidity of lower end plate 106, for example, stress generated in glass seal member 197 due to the displacement is reduced. As a result, this embodiment can effectively prevent damage to the joint formed by glass seal member 197.

[0073] In this embodiment, the glass seal member 197 is bonded only to a region of the stress relief section 700 that is different from the bonding section 702 (see FIGS. 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 a region that overlaps with 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 portion caused by the glass seal member 197.

[0074] In this embodiment, bonding portion 702 is disposed on the opposite side of glass seal member 197 from gas through hole 26 when viewed in the vertical direction (see FIGS. 10 and 11). Therefore, even if the separation displacement between lower end plate 106 and lower terminal plate 420 on the gas through hole 26 side is relatively large (see FIG. 12(B)), the portion of stress relaxation portion 700 on the gas through hole 26 side is largely displaced, so that damage to the bonding portion formed by glass seal member 197 can be effectively prevented.

[0075] 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 configurations as those of the fuel cell stack 100 of the above-described embodiment are denoted by the same reference numerals and the description thereof will be omitted as appropriate.

[0076] In the above embodiment, stress relief portion 700 is joined to lower end plate 106, but in this first modification, stress relief portion 700a is joined to lower terminal plate 420. Specifically, stress relief portion 700a is, for example, an elastically deformable flat plate-like member, and has holes 708a formed therethrough that communicate with gas through holes 26 of gas passage member 27. Lower terminal plate 420 is an example of a first member in the claims, and lower end plate 106 is an example of a second member in the claims.

[0077] The stress mitigation portion 700a has a joint portion 702a and a displacement portion 704a. The joint portion 702a is a portion of the stress mitigation portion 700a that is joined to the lower terminal plate 420 by at least one of welding and brazing. The displacement portion 704a is a portion of the stress mitigation 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 up and down 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 mitigation portion 700a. The glass seal member 197a is an example of a joining member defined in the claims.

[0078] For example, when a downward pulling force is applied to gas passage member 27 (tip portion 28a of main body portion 28), upright portion 530 of lower end plate 106 is displaced downward, causing glass seal member 197a to be displaced downward. However, displaced portion 704a of stress absorbing portion 700a is displaced downward and away from lower terminal plate 420 in response to the displacement of glass seal member 197a, thereby suppressing stress generation in glass seal member 197a. As a result, according to the first modification, damage to the joint formed by glass seal member 197a due to the displacement away from lower end plate 106 and lower terminal plate 420 can be suppressed.

[0079] 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 the description thereof will be omitted as appropriate.

[0080] In this modified example 2, 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 further, 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).

[0081] The stress relief portion 700b has a joint portion 702b and a displacement portion 704b. The joint portion 702b is a 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 a portion of the stress relief portion 700b that is located more inward (on the gas through hole 26 side) than the joint portion 702b. The displacement portion 704b is configured to be displaceable in the up and down 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.

[0082] The stress relief portion 700c has a joint portion 702c and a displacement portion 704c. The joint portion 702c is a 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 a 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 examples of a second member in the claims. The glass seal members 197b and 197c are an example of the joining member defined in the claims.

[0083] For example, when a downward tensile 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, and accordingly, the glass seal member 197b is displaced downward. However, to follow 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 suppresses the generation of stress in the glass seal member 197b. At this time, the lower terminal plate 420 is also displaced downward, and accordingly, the joint portion 702c of the stress mitigation portion 700c is displaced downward. However, to not follow the displacement of the lower terminal plate 420, the displaced portion 704c of the stress mitigation portion 700c is displaced downward. This suppresses the generation of stress in the glass seal member 197c. As a result, according to the second modification, it is possible to prevent damage not only to the joint portion formed by the glass seal member 197b but also to the joint portion formed by the glass seal member 197c.

[0084] 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.

[0085] The configurations of the fuel cell stack 100 and the power generating 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 the upper end surface of the gas passage member 27 and joined.

[0086] In the above embodiment, the glass seal members 197, 197a, 197b, and 197c made of glass are used as the joining members. However, any member having a joining function may be formed of a material other than glass (for example, metal or resin). In the above embodiment, the glass seal members 197, 197a, 197b, and 197c are formed so as to surround the periphery of the gas through hole 26 when viewed from the top and bottom (see FIG. 11 ) and function as a sealing member to suppress gas leakage. However, the present invention is not limited to this. For example, the glass seal members 197, 197a, 197b, and 197c may be formed only on a portion of the periphery of the gas through hole 26. In addition, the stress relaxation portions 700, 700a, 700b, and 700c may also be formed only on a portion of the periphery of the gas through hole 26.

[0087] In the above embodiment, an example has 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, the present invention is not limited to this, and may 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 unit 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 the other manifolds 162, 171, 172.

[0088] In the above embodiment, for example, by employing at least one of the following elements, the stiffness of the stress relaxation portion 700 in the vertical direction may be made lower than the stiffness of the lower end plate 106 in the vertical direction. (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 or the like to the lower end plate 106, the rigidity of the lower end plate 106 is made higher than the rigidity 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.

[0089] In the above embodiment, the glass seal member 197 may be bonded not only to the displacement portion 704 of the stress relaxation 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 disposed on the gas through hole 26 side of the glass seal member 197 when viewed in the up-down direction.

[0090] In the above embodiment, the 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 includes a pair of terminal plates 410, 420, but other members (for example, the pair of end plates 104, 106) may also function as terminal plates, and the terminal plates 410, 420 as dedicated members may be omitted.

[0091] In the above embodiment, the unit cell separator 120 has the 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. Also, the unit cell separator 120 does not have to have the connecting portion 128. The same applies to the connecting portion 188 in the IC separator 180.

[0092] 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.

[0093] In the above embodiment, the interconnector 190 includes the conductive coating layer 194, but the interconnector 190 may not include the coating layer 194. Also, in the above embodiment, the unit cell 110 has the reaction prevention layer 118, but the unit cell 110 may not have the reaction prevention layer 118.

[0094] 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 type or a metal-supported type. 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.

[0095] In the above embodiment, the number of unit cells 110 (the number of power generating 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 member in the above embodiment are merely examples, and each member may be made of other materials.

[0096] While the above-described embodiment focuses on an SOFC that generates electricity by utilizing an electrochemical reaction between hydrogen contained in a fuel gas and oxygen contained in an oxidant gas, the technology disclosed herein can also be applied to an electrolysis cell unit, which is a constituent unit of a solid oxide electrolysis cell (SOEC) that generates hydrogen by utilizing the electrolysis reaction of water, and an electrolysis cell stack including a plurality of electrolysis cell units. The configurations of the electrolysis cell unit and the electrolysis cell stack 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 can 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. As a result, a water electrolysis reaction occurs in each electrolysis cell unit, hydrogen gas is generated in the fuel chamber 176, and the hydrogen is extracted to the outside of the electrolysis cell stack via the manifold. In an electrolysis cell stack having such a configuration, if a configuration similar to that of the above embodiment is adopted, damage to the joints of the joining members due to displacement of the two members apart can be suppressed.

[0097] 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 the 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 will be explained below.

[0098] 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 a polymer electrolyte fuel cell (PEFC), a phosphoric acid fuel cell (PAFC), and a molten carbonate fuel cell (MCFC). Furthermore, the technology disclosed in this specification is not limited to electrochemical reaction cell stacks, but can also be applied to a composite including a first member, a second member located on one side of the first member, and a joining member disposed between the first member and the second member. [Explanation of symbols]

[0099] 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: Fuel electrode 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: fuel electrode side frame 142: fuel gas supply passage 143: fuel gas discharge passage 144: fuel electrode side current collecting member 145: electrode facing portion 146: interconnector facing 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 parts 706: support part

Claims

1. 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 is disposed on an opposite side of the gas flow path that extends in the first direction and penetrates the first member and the second member with respect to the joint member when viewed in the first direction. A complex characterized by:

2. 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:

3. 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:

4. 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. 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:

Images