stack

Abstract

We provide a stack that can reduce the occurrence of electrical failures. [Solution] The stack comprises a block in which cells are connected in series via an interconnect, including cells, separators fixed to the cells and extending outwards from the outer circumference of the cells, interconnects arranged in the thickness direction of the cells, and frames arranged in the thickness direction of the separators; an end plate positioned outside the block in the thickness direction and having an opening in the portion obtained by projecting the cells in the thickness direction; a cover positioned between the end plate and the block; a pressing member that presses the separator, frame, end plate and cover against each other in the thickness direction; and a limiting member coupled to the end plate and including an overhang that extends outwards from the opening of the end plate, wherein the overhang is located within the range obtained by projecting the cells in the thickness direction and limits the outward displacement of the cover in the thickness direction. The space between the cover and the overhang is not energized.

Description

[Technical Field]

[0001] This invention relates to a stack comprising multiple cells in which electrochemical reactions occur. [Background technology]

[0002] A stack is a device that converts fuel gas into electrical energy or synthesizes energy carriers by electrolysis through electrochemical reactions. The stack disclosed in Patent Document 1, etc., consists of reaction units arranged in the thickness direction, each including a cell containing an electrolyte that isolates electrodes in the thickness direction, a separator fixed to the cell, an interconnector positioned in the thickness direction of the cell, and a frame positioned in the thickness direction of the separator. A pressurizing member presses the separator and the frame together in the thickness direction to reduce gas leakage from between the separator and the frame, and the interconnector is pressed against the electrodes of the cell to connect the cell and the interconnector in series. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-80457 [Overview of the project] [Problems that the invention aims to solve]

[0004] In a stack, the internal pressure increases due to the gas supplied to the cells and the energy carriers generated in the cells, causing the separators to deform and bulge, displace the cells and interconnects, and potentially leading to electrical failures such as poor contact between the cells and interconnects or electrode detachment.

[0005] This invention was made to solve this problem and aims to provide a stack that can reduce the occurrence of electrical failures. [Means for solving the problem]

[0006] A first embodiment for achieving this objective is a stack comprising a block in which a plurality of reaction units are arranged in the thickness direction, each unit including a cell containing an electrolyte that separates a fuel electrode and an air electrode in the thickness direction, a separator fixed to the cell and extending outward from the outer circumference of the cell, an interconnector positioned in the thickness direction of the cell, and a frame positioned in the thickness direction of the separator, and the cells are connected in series via the interconnector; an end plate positioned on the outside of the block in the thickness direction and having an opening in the portion obtained by projecting the cell in the thickness direction; a cover positioned between the end plate and the block; a pressing member that presses the separator, frame, end plate and cover against each other in the thickness direction; and a limiting member coupled to the end plate and including an overhang extending outward from the opening of the end plate, wherein the overhang is located in the area obtained by projecting the cell in the thickness direction and limits the outward displacement of the cover in the thickness direction. The space between the cover and the overhang is not energized.

[0007] In the second embodiment, in the first embodiment, there is a gap between the protruding portion and the cover before the stack is in operation.

[0008] A third embodiment is the first or second embodiment, wherein the cover includes a thickness-curved stress buffer located between the range obtained by projecting the cells in the thickness direction and the range obtained by projecting the frame in the thickness direction, and the overhang is located in the range obtained by projecting the stress buffer in the thickness direction.

[0009] The fourth aspect is that, in any of the first to third aspects, the type of gas present on the cover side with the limiting member in between is the same as the type of gas present on the opposite side of the cover with the limiting member in between. [Effects of the Invention]

[0010] According to the present invention, a limiting member is connected to the end plate, and the protruding portion of the limiting member extends into the opening of the end plate and is located within the range projected in the thickness direction of the cell. The limiting member restricts the outward displacement of the cover in the thickness direction and limits the bulging of the separator, thereby reducing the occurrence of electrical failures such as poor contact between the cell and the interconnector or electrode peeling. Furthermore, since there is no current flow between the cover and the protruding portion, it is possible to prevent electrical malfunctions caused by current flow between the cover and the protruding portion. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view of the stack in the first embodiment. [Figure 2] This is a cross-sectional view of the stack at line II-II. [Figure 3] This is a cross-sectional view of the stack in the second embodiment. [Modes for carrying out the invention]

[0012] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Figure 1 is a perspective view of the stack 10 in the first embodiment. The stack 10 includes a block 12 formed by stacking a plurality of reaction units 11 in the thickness direction (vertical direction in Figure 1), metal frame-shaped end plates 13 and 14 arranged on the outside of the block 12 in the thickness direction, and covers 15 and 16 arranged between the end plates 13 and 14 and the block 12. The block 12 is made up of, for example, 10 to 30 reaction units 11 stacked on top of each other.

[0013] The cover 15 includes a terminal board 17 on which terminals for connecting electrical circuits are provided. An insulator 18 is placed between the cover 15 and the end plate 13. The insulator 18 electrically insulates the cover 15 from the end plate 13.

[0014] Cover 16 includes a terminal block 19 provided with terminals for connecting an electric circuit and a support plate 20. The support plate 20 is disposed between the terminal block 19 and the end plate 14. An insulator 21 is disposed between the support plate 20 and the end plate 14. The insulator 21 electrically insulates the cover 16 and the end plate 14. The materials of the terminal blocks 17, 19 and the support plate 20 are exemplified by stainless steel.

[0015] A pressing member 22 for pressing the end plates 13, 14, the covers 15, 16 and the block 12 against each other in the thickness direction is disposed on the periphery of the stack 10. In the present embodiment, the pressing member 22 includes a metal bolt that penetrates the end plates 13, 14, the covers 15, 16 and the block 12 in the thickness direction. A nut (not shown) into which the bolt fits is disposed on the end plate 14, and the end plates 13, 14, the covers 15, 16 and the block 12 are pressed by tightening the nut.

[0016] Four spaces that penetrate the periphery of the stack 10 in the thickness direction function as a passage 23 for supplying fuel gas from outside the stack 10 to a fuel chamber 38 (described later) of the reaction unit 11, a passage 24 for discharging gas from the fuel chamber 38 to the outside of the stack 10, a passage 25 for supplying oxidant gas from outside the stack 10 to an air chamber 39 (described later) of the reaction unit 11, and a passage 26 for discharging gas from the air chamber 39 to the outside of the stack 10, respectively.

[0017] FIG. 2 is a cross-sectional view of the stack 10 cut along the line II-II of FIG. 1 passing through the passages 23, 24, and the thicknesses of the respective parts are exaggerated in the drawing. In FIG. 2, the illustration of the middle in the thickness direction of the block 12 is omitted.

[0018] As shown in Fig. 2, the reaction unit 11 includes, in order in the thickness direction (the vertical direction in Fig. 2), a fuel electrode frame 27, a first separator 28, an air electrode frame 29, and a second separator 30. Holes (passages 23-26) penetrate through the fuel electrode frame 27, the first separator 28, the air electrode frame 29, and the second separator 30. Inside the fuel electrode frame 27, the first separator 28, the air electrode frame 29, and the second separator 30, cells 31 and interconnects 35 are arranged.

[0019] The cell 31 includes an electrolyte 32, a fuel electrode 33, and an air electrode 34 that are separated in the thickness direction by the electrolyte 32. In this embodiment, a flat plate-shaped cell 31 is described, but it is not limited thereto. The cell 31 may be a metal-supported type (metal-supported flat plate type) that supports the electrodes and the electrolyte with a porous body of a metal such as an Fe-Cr system. The cell 31 may be an electrode-supported type or an electrolyte-supported type.

[0020] The material of the electrolyte 32 is a solid oxide, and examples thereof include a solid solution of one or more selected from stabilized zirconia, ceria-based solid solutions, stabilized zirconia and ceria-based solid solutions, and alumina. Examples of the stabilizer for stabilized zirconia are CaO, MgO, Y2O3, Sc2O3, and Yb2O3. Examples of the elements that dissolve in ceria in the ceria-based solid solution are Gd, Sm, and Y.

[0021] Examples of the material of the fuel electrode 33 include those containing a catalyst containing Ni and zirconia in which Y is dissolved, and those containing a catalyst containing Ni and ceria in which Gd is dissolved. Examples of the catalyst are cermets that are composites (sintered bodies) of Ni, Ni-based alloys, and NiO and oxides (solid electrolytes).

[0022] The material of the air electrode 34 is a perovskite-type oxide La 1-X Sr X [[ID=X]]MnO 3-δ , La 1-X Sr X CoO 3-δ , La 1-X Sr X Co 1-Y Fe Y O3-δ ,Pr 1-X Sr X MnO 3-δ Examples are given.

[0023] The interconnector 35 is positioned between adjacent cells 31 in the thickness direction and electrically connects the cells 31 to each other. The interconnector 35 comprises a plate-shaped support portion 36 and a current collector portion 37 positioned on the support portion 36. Stainless steel is an example of the material of the support portion 36. The support portion 36 is provided with a groove (not shown) through which gas flows.

[0024] The current collector 37 is exemplified by including a bent conductor and a spacer such as mica placed within the conductor. Examples of conductor materials include nickel, nickel-based alloys, and stainless steel. The current collectors 37 are arranged at intervals from each other. Gas flows through the gaps between the current collectors 37.

[0025] The fuel electrode frame 27 is positioned between the second separator 30 and the first separator 28 and is a frame-shaped member that surrounds the cell 31 and the current collector 37. Stainless steel is an example of a material used for the fuel electrode frame 27.

[0026] The first separator 28 is a frame-shaped member that is airtightly joined to the electrolyte 32 by brazing material or the like, avoiding the air electrode 34. Stainless steel is an example of a material for the first separator 28.

[0027] The air electrode frame 29 is a frame-shaped member positioned between the first separator 28 and the second separator 30, surrounding the support portion 36. An example of the material for the air electrode frame 29 is an insulator such as mica.

[0028] The second separator 30 is a frame-shaped member and is airtightly joined to the support part 36 by brazing material or the like. Stainless steel is an example of a material for the second separator 30.

[0029] A fuel chamber 38 is provided inside the fuel electrode frame 27, and an air chamber 39 is provided inside the air electrode frame 29. The fuel chamber 38 is connected to passage 23 through a slit 40 and to passage 24 through a slit 41. The air chamber 39 is connected to passages 25 and 26 (see Figure 1) through a slit (not shown).

[0030] Fittings (not shown) connected to passages 23-26 are provided on the end plate 14. A gas pipe supplying fuel gas to passage 23, a gas pipe exhausting gas coming out of passage 24, a gas pipe supplying oxidizer gas to passage 25, and a gas pipe exhausting gas coming out of passage 26 (none of which are shown) are connected to the fittings, respectively. The first separator 28 and the second separator 30 separate the fuel chamber 38 and the air chamber 39, preventing the fuel gas in the fuel chamber 38 from mixing with the oxidizer gas in the air chamber 39.

[0031] If stack 10 is a fuel cell, examples of fuel gases include hydrogen, carbon monoxide, and hydrocarbons, and examples of oxidizer gases include oxygen and air. If stack 10 is an electrolytic device (cell 31 is an electrolytic cell that has the function of electrolyzing the fuel gas), examples of fuel gases include water vapor, carbon dioxide, and mixtures thereof, and examples of oxidizer gases include oxygen and air. Stack 10 also includes configurations that allow for reversible operation as both a fuel cell and an electrolytic device.

[0032] The cover 15 is provided between the block 12 and the end plate 13. The cover 15 includes a support portion 36 that contacts the air electrode 34 of the cell 31, a frame-shaped second separator 30 hermetically bonded to the support portion 36, a conductive plate 42 arranged in overlapping directions in the thickness direction of the support portion 36, and a current collector portion 37 sandwiched between the conductive plate 42 and the support portion 36. One side of the second separator 30 is in contact with the terminal plate 17 all around, and the other side of the second separator 30 is in contact with the air electrode frame 29 all around, except for a slit (not shown). The cover 15 electrically connects the terminals of the terminal plate 17 to the block 12 and partitions the air chamber 39 of the cell 31 located in the block 12 closest to the end plate 13.

[0033] A frame-shaped third separator 43 is hermetically bonded to the conductive plate 42. The rigidity of the conductive plate 42 is greater than that of the third separator 43. Stainless steel is an example of a material used for the conductive plate 42 and the third separator 43. One side of the third separator 43 is in contact with the terminal board 17 all around, and the other side of the third separator 43 is in contact with the insulator 18 all around. Because the block 12 and the terminal board 17 are connected by two conductive paths, the second separator 30 and the third separator 43, the electrical resistance near the terminal board 17 can be reduced compared to the case where there is only one conductive path.

[0034] In this embodiment, the third separator 43 has a stress buffer portion 44 that curves in an arc shape toward the second separator 30, extending around its entire circumference. The second separator 30 has a stress buffer portion 45 that curves in an arc shape toward the air chamber 39, located at a position corresponding to the stress buffer portion 44, extending around its entire circumference. The first separator 28 has a stress buffer portion 46 that curves in an arc shape toward the fuel chamber 38, located at a position corresponding to the stress buffer portion 45, extending around its entire circumference.

[0035] The cover 16 is provided between the block 12 and the end plate 14. The cover 16 includes a conductive plate 47 that is arranged in overlapping directions in the thickness direction of the support portion 36 and in contact with the support portion 36, and a frame-shaped third separator 48 that is hermetically bonded to the conductive plate 47. The rigidity of the conductive plate 47 is greater than the rigidity of the third separator 48. One side of the third separator 48 is in contact with the terminal plate 19 all around, and the other side of the third separator 48 is in contact with the air electrode frame 29 all around, except for a slit (not shown). The cover 16 electrically connects the terminals of the terminal plate 19 to the block 12.

[0036] The cover 16 includes a support plate 20, a support portion 36 positioned between the support plate 20 and the conductive plate 47, and a current collector 37 sandwiched between the support plate 20 and the support portion 36. A frame-shaped third separator 49 is hermetically bonded to the support portion 36. Stainless steel is an example of the material for the conductive plate 47 and the third separators 48 and 49. The rigidity of the support plate 20 is greater than that of the conductive plates 42 and 47 and the separators 28, 30, 43, 47, and 49.

[0037] One side of the third separator 49 is in contact with the terminal board 19 all around. Since the block 12 and the terminal board 19 are connected by the two conductive paths of the third separators 48 and 49, the electrical resistance near the terminal board 19 can be reduced compared to the case where there is only one conductive path.

[0038] In this embodiment, the third separator 48 has a stress buffer portion 50 that curves in an arc shape toward the third separator 49, located at a position corresponding to the stress buffer portion 46, extending around its entire circumference. The third separator 49 has a stress buffer portion 51 that curves in an arc shape toward the support plate 20, located at a position corresponding to the stress buffer portion 50, extending around its entire circumference.

[0039] The stress buffer sections 44, 45, 46, 50, and 51 are located between the area projected from the cell 31 in the thickness direction and the area projected from the fuel electrode frame 27 and the air electrode frame 29 in the thickness direction. Because the stress buffer sections 44, 45, 46, 50, and 51 are bent, they are more easily deformed than the parts of the first separator 28, second separator 30, and third separator 43, 48, and 49 other than the stress buffer sections 44, 45, 46, 50, and 51. As a result, when assembling the airtight stack 10, if a compressive force in the thickness direction is applied to the fuel electrode frame 27, first separator 28, and air electrode frame 29 by the pressurizing member 22 (see Figure 1), the stress buffer sections 44, 45, 46, 50, and 51 deform, reducing the bending stress on the cell 31. This reduces damage to the cell 31 during the assembly of the stack 10.

[0040] Multiple cells 31 are electrically connected in series between terminal plates 17 and 19 via an interconnector 35, a conductive plate 47, a second separator 30, and a third separator 48. When the stack 10 is an electrolytic device, electrons flow out toward the fuel electrode 33 of the cell 31 when the positive electrode of a power supply (not shown) is connected to terminal plate 17 and the negative electrode of the power supply is connected to terminal plate 19. The fuel gas that enters the fuel chamber 38 is reduced by the fuel electrode 33. Electrons are removed at the air electrode 34, so oxide ions that have moved to the air electrode 34 via the electrolyte 32 are oxidized at the air electrode 34. This generates energy carriers such as hydrogen and hydrocarbons in the fuel chamber 38.

[0041] If the stack 10 is a fuel cell, when fuel gas is flowed into the fuel chamber 38 and oxidant gas is flowed into the air chamber 39, gaseous oxygen reacts with electrons at the air electrode 34 of the cell 31 to generate oxide ions. These oxide ions move through the electrolyte 32 and react with the fuel gas at the fuel electrode 33 to generate electrons. This causes current to flow to the load (not shown) connected to terminal boards 17 and 19.

[0042] When the stack 10 operates, the gas supplied to the cell 31 and the energy carriers generated in the cell 31 increase the pressure in the fuel chamber 38 and the air chamber 39. As the pressure in the fuel chamber 38 and the air chamber 39 increases, the first separator 28 and the second separator 30 deform, and consequently, the airtight third separators 43, 48, and 49 also deform.

[0043] If the pressure inside the stack 10 increases or the separators 28, 30, 43, 48, 49 deform, causing displacement of the cell 31, interconnect 35, and conductive plates 42, 47, there is a risk of electrical failures occurring due to poor contact between the cell 31 and interconnect 35 or delamination of electrodes (fuel electrode 33 and air electrode 34). In particular, if stress buffer sections 44, 45, 46, 50, 51 are provided in the first separator 28, the second separator 30, and the third separators 43, 48, 49, the separators 28, 30, 43, 48, 49 become more susceptible to deformation, which in turn increases the likelihood of electrical failures.

[0044] Because the rigidity of cover 15 is less than that of cover 16 including support plate 20, when the internal pressure of stack 10 increases, bulging occurs on cover 15. Stack 10 has a limiting member 52 that restricts the bulging of cover 15, which is connected to the end plate 13. The limiting member 52 is attached to the end plate 13 by welding, screw joining, crimping, etc.

[0045] The limiting member 52 is provided with an overhang 53 that extends into the opening 13a located in the center of the end plate 13. The overhang 53 is located within the range where the cell 31 is projected in the thickness direction (vertical direction in Figure 2), and limits the displacement of the cover 15 in the thickness direction. By limiting the displacement of the cover 15 within the range where the cell 31 is projected in the thickness direction, the overhang 53 can reduce the occurrence of poor contact between the cell 31 and the interconnector 35, and the separation of the fuel electrode 33 from the electrolyte 32. This reduces the occurrence of electrical failures in the stack 10.

[0046] The protruding portion 53 only needs to be present in a portion of the area projected in the thickness direction of the cell 31. This is because the rigidity of the area of ​​the cover 15 projected in the thickness direction of the cell 31 is greater than the rigidity of the rest of the cover 15, so reducing the displacement of a portion of the area projected in the thickness direction of the cell 31 can reduce the occurrence of poor contact between the cell 31 and the interconnector 35. However, it is more preferable if the protruding portion 53 is present over the entire area projected in the thickness direction of the cell 31.

[0047] Furthermore, it is more preferable if the protruding portion 53 exists in the area obtained by projecting the stress buffer portion 44 in the thickness direction, as this can limit the deformation of the stress buffer portion 44. The protruding portion 53 only needs to exist in a part of the area obtained by projecting the stress buffer portion 44 in the thickness direction. It is even more preferable if the protruding portion 53 exists over the entire area obtained by projecting the stress buffer portion 44 in the thickness direction.

[0048] The space between the cover 15 and the protruding portion 53 is not electrically conductive. This means that no current flows between the cover 15 and the protruding portion 53, whether there is a gap 55 between the cover 15 and the protruding portion 53 or when the cover 15 and the protruding portion 53 are in contact. In this embodiment, an electrical insulator 54 is provided on the surface of the protruding portion 53 that faces the cover 15, so that the electrical insulator 54 comes into contact with the cover 15 when the cover 15 is deformed. Examples of electrical insulators 54 include solid insulators such as mica, heat-resistant cement, heat-resistant fiber, and glass or ceramic cloth or plates.

[0049] Since there is no current flow between the cover 15 and the protruding portion 53, current can be prevented from flowing through the cover 15 including the terminal plate 17, the limiting member 52 including the protruding portion 53, the end plate 13, the pressurizing member 22, the end plate 14, and the joint (not shown) attached to the end plate 14 to the gas pipe (not shown) connected to the joint. This prevents electrical malfunctions such as electric shock caused by contact of a part of the body with the gas pipe.

[0050] Before the stack 10 operates (before the fuel gas is converted into electrical energy or energy carriers are synthesized by electrolysis), in this embodiment, there is a gap 55 between the electrical insulator 54 of the protruding portion 53 and the cover 15. The size of the gap 55 is set such that when the cover 15 deforms and comes into contact with the protruding portion 53, and the deformation of the cover 15 is restricted, poor contact between the cell 31 and the interconnector 35 does not occur. Because there is a gap 55 before the stack 10 operates, the pressure exerted between the cover 15 and the protruding portion 53 is reduced compared to when there is no gap 55 before the stack 10 operates, and furthermore, in-plane pressure variation can be reduced. This reduces malfunctions in the cover 15 caused by pressure variation.

[0051] The type of gas present on the cover 15 side of the limiting member 52 (the type of gas present in the gap 55) is the same as the type of gas present on the opposite side of the cover 15 of the limiting member 52 (the type of gas present around the stack 10). Since there is no need to create an airtight structure between the cover 15 and the limiting member 52, the structure of the stack 10 equipped with the limiting member 52 can be simplified.

[0052] By limiting the deformation of the cover 15 with the limiting member 52, the deformation of the block 12, which is the cause of the deformation of the cover 15, can be limited. The deformation of the block 12 tends to increase as the number of reaction units 11 placed in the block 12 increases, but since the deformation of the block 12 can be limited by the limiting member 52, the number of reaction units 11 placed in the block 12 can be increased. This makes it possible to increase the amount of electrical energy and energy carriers generated in the stack 10.

[0053] A second embodiment will be described with reference to Figure 3. In the first embodiment, a stack 10 in which the limiting member 52 is arranged on one side was described. In the second embodiment, a case in which the limiting members 52 and 67 are arranged on both sides of the stack 60 will be described. In the second embodiment, the same reference numerals as in the first embodiment are used for the same parts as in the first embodiment, and some of the following descriptions will be omitted.

[0054] Figure 3 is a cross-sectional view of the stack 60 in the second embodiment. Similar to Figure 2, Figure 3 is a cross-sectional view of the stack 60 cut along the line II-II (see Figure 1) passing through passages 23 and 24, and the thickness of each part is exaggerated in the illustration. Figure 3 omits the illustration of the middle part of the thickness direction of block 61.

[0055] The stack 60 includes a block 61 formed by stacking multiple reaction units 11 in the thickness direction (vertical direction in Figure 3), metal frame-shaped end plates 13 and 14 positioned on the outside of the block 61 in the thickness direction, and covers 15 and 62 positioned between the end plates 13 and 14 and the block 61, respectively.

[0056] Block 61 consists of approximately 10-30 stacked reaction units 11 and includes an interconnector 63 that connects the reaction units 11. The rigidity of the interconnector 63 is greater than that of the interconnector 35. The periphery of the interconnector 63 overlaps with the fuel electrode frame 27 and the air electrode frame 29, and passages 23-26 (see Figure 1) and a pressurizing member 22 pass through it. The interconnector 63 is provided with a groove (not shown) through which an oxidizing gas flows between the air electrode 34 and the interconnector 63.

[0057] The cover 62 includes a conductive plate 47 that is arranged in overlapping directions in the thickness direction of the support portion 36 and in contact with the support portion 36, and a frame-shaped third separator 48 that is hermetically bonded to the conductive plate 47. One side of the third separator 48 is in contact with the terminal plate 19 all around, and the other side of the third separator 48 is in contact with the air electrode frame 29 all around. The cover 62 electrically connects the terminals of the terminal plate 19 to the block 61.

[0058] The cover 62 includes a conductive plate 64 arranged in overlapping directions in the thickness direction of the conductive plate 47, a frame-shaped third separator 65 hermetically bonded to the conductive plate 64, and a current collector 37 sandwiched between the conductive plate 64 and the conductive plate 47. The rigidity of the conductive plate 64 is greater than that of the third separator 65. One side of the third separator 65 is in contact with the terminal plate 19 all around, and the other side of the third separator 65 is in contact with the insulator 21 all around.

[0059] The stack 60 has a limiting member 52 that restricts the bulging of the cover 15, which is connected to the end plate 13. Before the stack 60 is in operation, there is a gap between the protruding portion 53 and the cover 15. The limiting member 52 is attached to the end plate 13 via an electrical insulator 66 by screw joining, crimping, etc. This makes it possible to de-energize the space between the cover 15 and the protruding portion 53.

[0060] The stack 60 has a limiting member 67 that restricts the bulging of the cover 62, which is connected to the end plate 14. The limiting member 67 has an overhang 68 that extends into an opening 14a provided in the center of the end plate 14. The limiting member 67 is attached to the end plate 14 via an electrical insulator 69 by screw joining, crimping, or the like. This makes it possible to keep the area between the cover 62 and the overhang 68 non-electrical.

[0061] The protruding portion 68 is located in the area projected from the cell 31 in the thickness direction, and restricts the displacement of the cover 62 in the thickness direction. By restricting the displacement of the cover 62 in the area projected from the cell 31 in the thickness direction, the protruding portion 68 can reduce the occurrence of poor contact between the cell 31 and the interconnector 35, and the separation of the fuel electrode 33 from the electrolyte 32. This reduces the occurrence of electrical failures in the stack 60.

[0062] The interconnector 63 is positioned approximately in the center of the thickness direction of block 61. The periphery of the interconnector 63 is sandwiched between end plates 13 and 14, and since the rigidity of the interconnector 63 is greater than that of the interconnector 35, when the limiting member 52 restricts the deformation of the cover 15 and the limiting member 67 restricts the deformation of the cover 62, the force applied to the portion of block 61 between the interconnector 63 and the cover 15 and the force applied to the portion of block 61 between the interconnector 63 and the cover 62 can be made approximately the same. Since the variation in stress in the thickness direction of block 61 can be reduced, the occurrence of failures caused by excessive stress can be reduced.

[0063] Although the present invention has been described above based on embodiments, it can be easily inferred that the present invention is not limited in any way to the above embodiments, and that various improvements and modifications are possible without departing from the spirit of the present invention.

[0064] The structures of covers 15, 16, and 62 in the embodiment are examples and are not limited to the structures of the embodiment. A cover is a layer that does not include the cell 31 and has an airtight structure that reduces leakage of fuel gas and oxidizer gas, or a layer that does not include the cell 31 and has a structure that includes terminals to which external electrical circuits are connected.

[0065] In the embodiment, a case in which stress buffer portions 44, 45, 46, 50, and 51 are provided in the first separator 28, the second separator 30, and the third separators 43, 48, 49, and 65 has been described, but it is not necessarily limited to this. It is of course possible to omit all or some of the stress buffer portions of the first separator 28, the second separator 30, and the third separators 43, 48, 49, and 65.

[0066] In this embodiment, the terminal board 17 is electrically connected to the blocks 12 and 61 via the conductive plate 42 and the third separator 43, but this is not necessarily the only possible configuration. It is certainly possible to omit the conductive plate 42 and the third separator 43 and make the terminal board 17 from a single flexible metal plate. Similarly, it is certainly possible to omit the conductive plate 47 and the third separator 48 and make the terminal board 19 from a single flexible metal plate.

[0067] In this embodiment, the case in which the terminal board 17 and blocks 12 and 61 are electrically connected by two conductive paths, the second separator 30 and the third separator 43, has been described, but this is not necessarily the only case. It is of course possible to omit one of the conductive paths. Similarly, it is of course possible to omit one of the third separators 48 and 49 or one of the third separators 48 and 65, and connect blocks 12 and 61 and the terminal board 19 by a single conductive path.

[0068] In this embodiment, we have described a case where the passage 23-26 passes through the terminal board 19 and a joint (not shown) to which the gas pipe is connected is provided on the end plate 14, but this is not necessarily the only option. Conversely, it is certainly possible to provide a terminal board 17 through which the passage 23-26 passes and a joint (not shown) to which the gas pipe is connected is provided on the end plate 13.

[0069] In the embodiment, a case was described in which electrical insulators 54, 66, and 69 are provided on a part of the limiting members 52 and 67, but this is not necessarily the only case. It is of course possible to make the entire limiting members 52 and 67 out of electrical insulators. In this case as well, it is possible to make the space between the covers 15 and 62 and the protruding parts 53 and 68 non-conductive.

[0070] In the embodiment, a case was described in which there is a gap between the protruding parts 53, 68 and the covers 15, 62 before the stacks 10, 60 are in operation, but this is not necessarily the only case. It is certainly possible to provide limiting members 52, 67 on the stacks 10, 60 so that the protruding parts 53, 68 and the covers 15, 62 are in contact before the stacks 10, 60 are in operation (when the stacks 10, 60 are assembled).

[0071] In the embodiment, the case where the shape of cell 31 is a rectangle was described, but it is not necessarily limited to this. The shape of cell 31 may be a circle or an ellipse, or it may be a polygon other than a rectangle, such as a triangle or a pentagon.

[0072] In the embodiment, the case in which the gas passages 23-26 are built into the stacks 10,60 has been described, but it is not necessarily limited to this. It is of course possible to connect the manifold as passage 23-26 to the cell and provide it outside the cell. Examples of manifold materials include ceramics with high high-temperature strength.

[0073] In the embodiment, a stack 10 including a solid oxide type cell 31 has been described, but it is not necessarily limited to this. It is certainly possible to apply the techniques of the embodiment to stacks including other types of cells, such as molten carbonate type cells.

[0074] In the second embodiment, a stack 60 was described in which a block 61 containing an interconnector 63 is placed between the covers 15 and 62. However, it is certainly possible to place the block 12 from the first embodiment between the covers 15 and 62 instead of the block 61. [Explanation of symbols]

[0075] 10,60 stacks 11 reaction units 12,61 blocks 13, 14 End Plates 13a,14a opening 15,16,62 cover 22 Pressurizing member 27 Fuel pole frame (frame) 28. First separator (separator) 29. Air pole frame (frame) 30. Second separator (separator) 31 cells 32 Electrolytes 33 Fuel electrode 34 Air pole 35,63 Interconnectors 43, 48, 49, 65 Third separator (separator) 44, 45, 46, 50, 51 Stress buffer section 52,67 Restricting members 53,68 Overhang 55 gaps

Claims

1. A cell containing an electrolyte that separates the fuel electrode and the air electrode in the thickness direction, A separator fixed to the cell and extending outwards from the outer circumference of the cell, Interconnectors arranged in the thickness direction of the cell, A block comprising a frame arranged in the thickness direction of the separator, a plurality of reaction units arranged in the thickness direction, and the cells connected in series via the interconnector, An end plate is positioned on the outside of the block in the thickness direction and has an opening in the portion obtained by projecting the cell in the thickness direction, A cover positioned between the end plate and the block, A stack comprising the separator, the frame, the end plate, and the cover, and a pressing member that presses them together in the thickness direction, The limiting member includes a portion that is connected to the end plate and extends outwards into the opening, The protruding portion is located within the range obtained by projecting the cell in the thickness direction, and restricts the outward displacement of the cover in the thickness direction. The stack between the cover and the protruding portion is not energized.

2. The stack according to claim 1, wherein there is a gap between the protruding portion and the cover before the stack is in operation.

3. The cover includes a stress buffer portion that is curved in the thickness direction and located between the area obtained by projecting the cell in the thickness direction and the area obtained by projecting the frame in the thickness direction. The stack according to claim 1 or 2, wherein the protruding portion is located in a range obtained by projecting the stress buffer portion in the thickness direction.

4. The stack according to claim 1 or 2, wherein the type of gas present on the cover side with the limiting member in between is the same as the type of gas present on the opposite side of the cover with the limiting member in between.

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