JP6902511B2 - Electrochemical reaction cell stack - Google Patents

Description

The techniques disclosed herein relate to electrochemical reaction cell stacks.

A solid oxide fuel cell (hereinafter referred to as "SOFC") having an electrolyte layer containing a solid oxide is known as one of the types of fuel cells that generate electricity by utilizing an electrochemical reaction between hydrogen and oxygen. Has been done. A fuel cell single cell (hereinafter, simply referred to as “single cell”), which is a constituent unit of SOFC, has an electrolyte layer and air that faces each other in a predetermined direction (hereinafter, referred to as “first direction”) across the electrolyte layer. Includes poles and fuel poles.

SOFCs generally consist of a structure in which a plurality of single cells are arranged side by side in the first direction (hereinafter referred to as "power generation block") and a pair of conductors facing each other in the first direction with an electrochemical reaction block interposed therebetween. Terminal members, a pair of insulating members that face each other in a first direction with a pair of terminal members sandwiched between them, and a pair of conductive end members that face each other in a first direction with a pair of insulating members sandwiched between them. It is used in the form of a fuel cell stack. The fuel cell stack is further inserted into a through hole formed in the pair of terminal members and a through hole formed in the pair of insulating members, and a conductive fastening member that engages with at least one of the pair of end members. Be prepared. In a fuel cell stack including such members, the inner peripheral surface of the through hole formed in one terminal member is the inner peripheral surface of the through hole formed in the insulating member arranged facing the terminal member. (See, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2017-11185

In a conventional fuel cell stack, for example, when a high voltage is generated, a discharge occurs between the above-mentioned one terminal member and an end member arranged facing an insulating member arranged facing the terminal member. May cause a short circuit between the terminal member and the end member.

It should be noted that such a problem is also common to the electrolytic cell stack, which is a form of a solid oxide type electrolytic cell (hereinafter referred to as “SOEC”) that generates hydrogen by utilizing the electrolysis reaction of water. Is. In the present specification, the fuel cell stack and the electrolytic cell stack are collectively referred to as an "electrochemical reaction cell stack", and the fuel cell single cell and the electrolytic single cell are collectively referred to as an "electrochemical reaction single cell". The power generation block and the electrolytic block are collectively called an "electrochemical reaction block". Further, such a problem is common not only to the solid oxide fuel cell but also to other types of electrochemical reaction cell stacks.

This specification discloses a technique capable of solving the above-mentioned problems.

The techniques disclosed herein can be realized, for example, in the following forms.

(1) The electrochemical reaction cell stack disclosed in the present specification is an electrochemical reaction block including a plurality of electrochemical reaction single cells arranged in the first direction, and each of the electrochemical reaction single cells is An electrochemical reaction block comprising an electrolyte layer and an air electrode and a fuel electrode facing each other in the first direction with the electrolyte layer interposed therebetween, and an electrochemical reaction block in the first direction with respect to the electrochemical reaction block. A terminal member arranged on one side, a conductive terminal member having a first through hole penetrating in the first direction and electrically connected to the electrochemical reaction block, and the above. An insulating member arranged on one side of the terminal member in the first direction, and a second through hole that communicates with the first through hole and penetrates in the first direction is formed. An insulating insulating member, a conductive end member arranged on the one side of the insulating member in the first direction, and a first through hole and a second through hole. In the electrochemical reaction cell stack, which comprises a conductive fastening member inserted into and engaged with the end member and fastened by the fastening member, in the first directional view, the terminal member. The inner peripheral edge of the first through hole formed in the above surrounds the inner peripheral edge of the second through hole formed in the insulating member, and in the first directional view, the second through hole in the insulating member. The inner peripheral edge of the through hole is separated from the fastening member.

In the present electrochemical reaction cell stack, in the first directional view, the inner peripheral edge of the first through hole formed in the terminal member surrounds the inner peripheral edge of the second through hole formed in the insulating member. That is, in the present electrochemical reaction cell stack, in a cross section that passes through the center of the fastening member in the first direction and is parallel to the first direction, the inner peripheral surface of the second through hole in the insulating member is a terminal. It protrudes toward the fastening member as compared with the inner peripheral surface of the first through hole in the member. Therefore, in the insulating member from the terminal member to the end member, as compared with the configuration in which the inner peripheral surface of the second through hole in the insulating member coincides with the inner peripheral surface of the first through hole in the terminal member. The creepage distance can be increased. Therefore, according to the present electrochemical reaction cell stack, it is possible to suppress the occurrence of a short circuit between the terminal member and the end member.

In the present electrochemical reaction cell stack, in the first directional view, the inner peripheral edge of the second through hole in the insulating member is separated from the fastening member. That is, a space is formed between the insulating member and the fastening member. Therefore, according to the present electrochemical reaction cell stack, it is possible to suppress the occurrence of a short circuit between the terminal member and the fastening member.

Therefore, according to the present electrochemical reaction cell stack, it is possible to suppress the occurrence of a short circuit between the terminal member and the fastening member and also suppress the occurrence of a short circuit between the terminal member and the end member.

(2) In the electrochemical reaction cell stack, the second through hole in the insulating member passes through the center of the fastening member in the first direction and is parallel to the first direction. The arbitrary point on the first line with respect to a first distance in a second direction orthogonal to the first direction between an arbitrary point on the first line corresponding to the inner peripheral surface and the fastening member. The ratio of the second distance along the first line between the point and the end point on one side of the first line in the first direction is the relative permittivity of the material forming the insulating member. The configuration may be less than the value of.

In the present electrochemical reaction cell stack, the ratio of the second distance to the first distance is insulated in a cross section that passes through the center of the fastening member in the first direction and is parallel to the first direction. It is less than the value of the relative permittivity of the material forming the member. Here, as the protrusion distance of the insulating member from the terminal member increases, the creepage distance of the insulating member from the terminal member to the end member increases, which improves the withstand voltage of the electrochemical reaction cell stack. However, if the protruding distance of the insulating member from the terminal member becomes too large, the first distance, that is, the distance between the insulating member and the fastening member cannot be sufficiently secured. As a result, in the electrochemical reaction cell stack, in the configuration in which the first distance, that is, the distance between the insulating member and the fastening member is not sufficiently secured, the space between the insulating member and the fastening member is sufficient. A short circuit occurs between the terminal member and the fastening member through the air (relative permittivity 1.0) that is not secured in the space. Specifically, in a configuration in which the ratio of the second distance to the first distance is equal to or greater than the value of the relative permittivity of the material forming the insulating member, a short circuit occurs between the terminal member and the fastening member. To do. On the other hand, in the present electrochemical reaction cell stack, the ratio of the second distance to the first distance is less than the value of the relative permittivity of the material forming the insulating member. That is, in the present electrochemical reaction cell stack, the first distance, that is, the distance between the insulating member and the fastening member is sufficiently secured. Therefore, a short circuit between the terminal member and the fastening member is more effectively suppressed by passing air (relative permittivity 1.0) filled in the space between the insulating member and the fastening member. can do.

Therefore, according to the present electrochemical reaction cell stack, it is possible to suppress the occurrence of a short circuit between the terminal member and the end member, and more effectively suppress the occurrence of a short circuit between the terminal member and the fastening member. can do.

(3) In the electrochemical reaction cell stack, the insulating member may be formed of mica. Since mica is easily and inexpensively available on the market and tends to have excellent molding processability, the electrochemical reaction cell stack can be efficiently produced according to the present electrochemical reaction cell stack.

(4) In the electrochemical reaction cell stack, an insulating tubular member that surrounds the outer circumference around the axis of the fastening member is arranged in the first through hole formed in the terminal member. May be good. According to the present electrochemical reaction cell stack, since the electrochemical reaction cell stack is provided with a protective tube, it is possible that the first through hole formed in the terminal member, which is a conductive member, and the fastening member are short-circuited. It can be effectively suppressed.

The techniques disclosed in the present specification can be realized in various forms, for example, in the form of an electrochemical reaction cell stack (fuel cell stack or electrolytic cell stack), a method for producing them, and the like. It is possible to do.

It is a perspective view which shows the appearance structure of the fuel cell stack 100 in this embodiment. It is explanatory drawing which shows the XZ cross-sectional structure of the fuel cell stack 100 at the position of II-II of FIG. 1 and FIG. It is explanatory drawing which shows the XZ cross-sectional structure of the fuel cell stack 100 at the position of III-III of FIG. 1 and FIG. It is explanatory drawing which shows the XZ cross-sectional structure of the fuel cell stack 100 at the position IV-IV of FIG. 1 and FIG. It is explanatory drawing which shows the XZ cross section configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. It is explanatory drawing which shows the YZ cross-sectional structure of two power generation units 102 adjacent to each other at the position of VI-VI of FIG. 1 and FIG. It is explanatory drawing which shows the XY cross-sectional structure of the lower terminal plate 420 at the position of VII-VII of FIG. In the cross-sectional view of the position of IV-IV of FIGS. 1 and 7, it is an XZ cross-sectional view partially showing the X1 part of the cross section shown in FIG. FIG. 5 is an XZ cross-sectional view partially showing the X1 portion of the cross section shown in FIG. 4 in a modified example. It is explanatory drawing which shows the performance evaluation result.

A. First Embodiment:
A-1. Device configuration:
(Structure of fuel cell stack 100)
FIG. 1 is a perspective view showing an external configuration of the fuel cell stack 100 in the present embodiment, and FIG. 2 is an XZ cross-sectional configuration of the fuel cell stack 100 at the position II-II in FIG. 1 (and FIG. 7 described later). 3 is an explanatory view showing the XZ cross-sectional configuration of the fuel cell stack 100 at the position III-III of FIG. 1 (and FIG. 7 described later), and FIG. 4 is an explanatory view showing the XZ cross-sectional configuration of FIG. 1 (and FIG. 7 described later). It is explanatory drawing which shows the XZ cross section structure of the fuel cell stack 100 at the position of IV-IV of FIG. 7) described later. Each figure shows XYZ axes that are orthogonal to each other to identify the direction. In the present specification, for convenience, the Z-axis positive direction is referred to as an upward direction, and the Z-axis negative direction is referred to as a downward direction, but the fuel cell stack 100 is actually in a direction different from such an orientation. It may be installed. The same applies to FIGS. 5 and later. Further, in the present specification, the direction orthogonal to the Z-axis direction is referred to as a plane direction.

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, a pair of terminal plates 410, 420, and a pair of insulating sheets 510, 520. , 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 the present embodiment). The pair of terminal plates 410 and 420 are arranged so as to sandwich an aggregate (hereinafter, referred to as "power generation block 103") composed of a plurality of power generation units 102 from above and below. The pair of insulating sheets 510 and 520 are arranged so as to sandwich the pair of terminal plates 410 and 420 from above and below. Further, the pair of end plates 104 and 106 are arranged so as to sandwich the pair of insulating sheets 510 and 520 from above and below.

As shown in FIGS. 1 and 4, each layer (upper end plate 104, each power generation unit 102, each terminal plate 410, 420, and each insulating sheet 510, 520) constituting the fuel cell stack 100 is oriented in the Z-axis direction. Around the four corners of the outer periphery, holes are formed that penetrate each layer in the vertical direction and are substantially circular in the Z-axis direction. Further, a hole (screw hole) into which the lower end portion of the bolt 22, which will be described later, is screwed into the upper surface around the four corners of the outer periphery of the lower end plate 106 constituting the fuel cell stack 100 in the Z-axis direction. ) Is formed. Holes formed in each power generation unit 102, each terminal plate 410, 420, each insulating sheet 510, 520, and each end plate 104, 106 communicate with each other in the vertical direction, and are inward from the upper end plate 104. It constitutes a bolt hole 109 extending in the vertical direction over the end plate 106 of the above. In the following description, the holes formed in each layer for forming the bolt holes 109 may also be referred to as bolt holes 109.

Each bolt 22 is a substantially cylindrical conductive member inserted into each bolt hole 109 extending in the vertical direction. At the lower end of each bolt 22, around the four corners of the outer circumference of the lower end plate 106 around the Z axis so that each bolt 22 can engage the lower end plate 106. A screw portion that can be screwed is formed in the above-mentioned hole (screw hole) formed on the upper surface. As described above, in the fuel cell stack 100 of the present embodiment, each power generation unit 102 and each end plate 104, 106 are integrally fastened by the head of each bolt 22 and the lower end plate 106. Here, "each bolt 22 is engaged with the lower end plate 106" means that each bolt 22 is directly or via another member (for example, a nut) of the lower end plate 106. It means that it is attached to.

Further, as shown in FIGS. 1 to 3, the vicinity of the outer periphery around the Z-axis direction of each layer (each power generation unit 102, lower terminal plate 420, and lower insulating sheet 520) constituting the fuel cell stack 100. Is formed with holes that penetrate each power generation unit 102 and the lower terminal plate 420 in the vertical direction, and a plurality of holes formed in each power generation unit 102 and corresponding to each other communicate with each other in the vertical direction. A communication hole 108 extending in the vertical direction is formed over the power generation unit 102 of the above. In the following description, the holes formed in each layer to form the communication holes 108 may also be referred to as the communication holes 108.

As shown in FIGS. 1 and 2, the fuel cell stack 100 is located near one side (the side on the positive side of the X-axis of the two sides parallel to the Y-axis) on the outer circumference of the fuel cell stack 100 around the Z-axis direction. The communication hole 108 is a gas flow path in which the oxidant gas OG is introduced from the outside of the fuel cell stack 100 and the oxidant gas OG is supplied to the air chamber 166 described later in each power generation unit 102. The communication hole 108 located near the side opposite to the side (the side on the negative side of the X-axis of the two sides parallel to the Y-axis) is from the air chamber 166 of each power generation unit 102. It functions as an oxidant gas discharge manifold 162, which is a gas flow path for discharging the oxidant off gas OOG, which is the discharged gas, to the outside of the fuel cell stack 100. As the oxidant gas OG, for example, air is used.

Further, as shown in FIGS. 1 and 3, among the sides constituting the outer periphery of the fuel cell stack 100 in the Z-axis direction, the vicinity of the side closest to the communication hole 108 functioning as the above-mentioned oxidant gas discharge manifold 162. In the other communication hole 108 located in, the fuel gas FG is introduced from the outside of the fuel cell stack 100, and the fuel gas FG is introduced into the fuel gas flow path which is a gas flow path for supplying the fuel gas FG to the fuel chamber 176 described later in each power generation unit 102. The other communication holes 108 located near the side closest to the communication holes 108 that function as the manifold 171 and function as the oxidant gas introduction manifold 161 described above are the gases discharged from the fuel cell 176 of each power generation unit 102. It functions as a fuel gas discharge manifold 172, which is a gas flow path for discharging a certain fuel off-gas FOG to the outside of the fuel cell stack 100. As the fuel gas FG, for example, a hydrogen-rich gas obtained by reforming city gas is used.

(Structure of terminal plates 410, 420, insulating sheets 510, 520 and end plates 104, 106)
The pair of terminal plates 410 and 420 are substantially rectangular flat plate-shaped conductive members, and are made of, for example, stainless steel. The thickness (plate thickness) of each of the terminal plates 410 and 420 in the Z-axis direction is 0.2 mm or more and 3 mm or less. The upper terminal plate 410 is arranged on the upper side of the power generation block 103 composed of a plurality of power generation units 102, and the lower terminal plate 420 is arranged on the lower side of the power generation block 103. That is, the upper terminal plate 410 is arranged on the upper side of the power generation unit 102 including the single cell 110 located on the uppermost side in the Z-axis direction among the plurality of single cells 110. Further, the lower terminal plate 420 is arranged on the lower side of the power generation unit 102 including the single cell 110 located on the lowermost side in the Z-axis direction among the plurality of single cells 110. As shown in FIGS. 2 to 4, four bolt holes 109 are formed in the upper terminal plate 410. Further, four communication holes 108 and four bolt holes 109 are formed in the lower terminal plate 420. The upper terminal plate 410 functions as a positive output terminal of the fuel cell stack 100, and the lower terminal plate 420 functions as a negative output terminal of the fuel cell stack 100. The configuration of the lower terminal plate 420 will be described in detail later.

The pair of insulating sheets 510 and 520 are substantially rectangular sheet-shaped insulating members. The insulating sheets 510 and 520 are made of, for example, mica, alumina, silicon nitride, zirconia, or the like. The thickness (sheet thickness) T1 of each of the insulating sheets 510 and 520 in the Z-axis direction is 0.1 mm or more and 5 mm or less, preferably 1 mm or more and 5 mm or less. The upper insulating sheet 510 is arranged on the upper side of the upper terminal plate 410, and the lower insulating sheet 520 is arranged on the lower side of the lower terminal plate 420. As shown in FIGS. 2 to 4, four bolt holes 109 are formed in the upper insulating sheet 510. Further, four communication holes 108 and four bolt holes 109 are formed in the lower insulating sheet 520. The configuration of the lower insulating sheet 520 will be described in detail later. In the present specification, the "conductive member" means a member having an electrical resistivity of 100 μΩ · m or less, and the “insulating member” means a member having an electric resistivity of 10 MΩ · m or more. doing.

The pair of end plates 104 and 106 are substantially rectangular flat plate-shaped conductive members, and are made of, for example, stainless steel. The thickness (plate thickness) of each of the end plates 104 and 106 in the Z-axis direction is 1 mm or more and 15 mm or less. The upper end plate 104 is arranged on the upper side of the upper insulating sheet 510, and the lower end plate 106 is arranged on the lower side of the lower insulating sheet 520. A pair of insulating sheets 510, 520, a pair of terminal plates 410, 420, and a plurality of power generation units 102 are sandwiched by a pair of end plates 104, 106 in a pressed state. As shown in FIGS. 2 to 4, four bolt holes 109 are formed in the upper end plate 104. Further, the lower end plate 106 is formed with four through holes 107 for flow paths and four bolt holes 109. The four flow path through holes 107 communicate with the oxidant gas introduction manifold 161, the oxidant gas discharge manifold 162, the fuel gas introduction manifold 171 and the fuel gas discharge manifold 172, respectively.

(Structure of gas passage member 27, etc.)
As shown in FIGS. 2 and 3, the fuel cell stack 100 further has four gas passages arranged on the opposite side (that is, the lower side) of the plurality of power generation units 102 with respect to the lower end plate 106. A member 27 is provided. The four gas passage members 27 are arranged at positions overlapping with the oxidant gas introduction manifold 161, the oxidant gas discharge manifold 162, the fuel gas introduction manifold 171 and the fuel gas discharge manifold 172, respectively. Each gas passage member 27 has a main body portion 28 in which a hole communicating with the flow path through hole 107 of the lower end plate 106 is formed, and a tubular branch portion 29 branched from the side surface of the main body portion 28. doing. The hole of the branch portion 29 communicates with the hole of the main body portion 28. A gas pipe (not shown) is connected to the branch portion 29 of each gas passage member 27. An insulating sheet 26 is arranged between the main body 28 of each gas passage member 27 and the end plate 106. The insulating sheet 26 is made of, for example, a mica sheet, a ceramic fiber sheet, a ceramic dust sheet, a glass sheet, a glass-ceramic composite material, or the like.

(Structure of power generation unit 102)
FIG. 5 is an explanatory view showing an XZ cross-sectional configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. 2, and FIG. 6 is a VI-VI of FIG. 1 (and FIG. 7 described later). It is explanatory drawing which shows the YZ cross-sectional structure of two power generation units 102 adjacent to each other at the position of. As shown in FIGS. 5 and 6, the power generation unit 102, which is the minimum unit of power generation, includes a fuel cell single cell (hereinafter, simply referred to as “single cell”) 110, a separator 120, an air electrode side frame 130, and air. It includes a pole-side current collecting member 134, a fuel pole-side frame 140, a fuel pole-side current collecting member 144, and a pair of interconnectors 150 that form the uppermost layer and the lowest layer of the power generation unit 102. On the outer periphery of the separator 120, the air pole side frame 130, the fuel pole side frame 140, and the interconnector 150 around the Z axis direction, holes forming each communication hole 108 functioning as each of the above-mentioned manifolds 161, 162, 171 and 172 are formed. And holes forming each bolt hole 109 are formed. Since the power generation unit 102 includes a single cell 110, the power generation block 103 described above can also be expressed as a structure in which a plurality of single cells 110 are arranged side by side in the vertical direction.

The pair of interconnectors 150 are substantially rectangular flat plate-shaped conductive members larger than the single cell 110 in the Z-axis direction, and are formed of, for example, ferritic stainless steel. The interconnector 150 ensures electrical continuity between the power generation units 102 and prevents mixing of reaction gases between the power generation units 102. Further, in the present embodiment, when two power generation units 102 are arranged adjacent to each other, one interconnector 150 is shared by two adjacent power generation units 102. That is, the upper interconnector 150 in a certain power generation unit 102 is the same member as the lower interconnector 150 in another power generation unit 102 adjacent to the upper side of the power generation unit 102. Further, since the fuel cell stack 100 includes a pair of terminal plates 410 and 420, the power generation unit 102 located at the top of the fuel cell stack 100 does not have the upper interconnector 150 and is located at the bottom. The power generation unit 102 does not include the lower interconnector 150 (see FIGS. 2 to 4).

The single cell 110 includes an electrolyte layer 112, an air electrode (cathode) 114 and a fuel electrode (anode) 116 facing each other in the vertical direction (arrangement direction in which the power generation units 102 are arranged) with the electrolyte layer 112 interposed therebetween. The single cell 110 of the present embodiment is a fuel pole support type single cell in which the fuel pole 116 supports the electrolyte layer 112 and the air pole 114.

The electrolyte layer 112 is a flat plate-shaped member that is substantially rectangular in the Z-axis direction, and is a dense layer. The electrolyte layer 112 is formed of, for example, a solid oxide such as YSZ (yttria-stabilized zirconia), ScSZ (scandia-stabilized zirconia), SDC (samarium-doped ceria), GDC (gadrinium-doped ceria), and perovskite-type oxide. There is. The air electrode 114 is a substantially rectangular flat plate-shaped member smaller than the electrolyte layer 112 in the Z-axis direction, and is a porous layer. The air electrode 114 is formed of, for example, a perovskite type oxide (for example, LSCF (lanternstrontium cobalt iron oxide), LSM (lanternstrontium manganese oxide), LNF (lantern nickel iron)). The fuel electrode 116 is a substantially rectangular flat plate-shaped member having substantially the same size as the electrolyte layer 112 in the Z-axis direction, and is a porous layer. The fuel electrode 116 is formed of, for example, Ni (nickel), a cermet composed of Ni and ceramic particles, a Ni-based alloy, or the like. As described above, the single cell 110 (power generation unit 102) of the present embodiment is a solid oxide fuel cell (SOFC) that uses a solid oxide as an electrolyte.

The separator 120 is a frame-shaped member in which a substantially rectangular hole 121 penetrating in the vertical direction is formed near the center, and is formed of, for example, a metal material such as stainless steel. The peripheral portion of the hole 121 in the separator 120 faces the peripheral edge of the surface of the electrolyte layer 112 on the side of the air electrode 114. The separator 120 is bonded to the electrolyte layer 112 (single cell 110) by a bonding portion 124 formed of a brazing material (for example, Ag wax) arranged at the opposite portion thereof. The separator 120 partitions the air chamber 166 facing the air electrode 114 and the fuel chamber 176 facing the fuel electrode 116, and a gas leak from one electrode side to the other electrode side at the peripheral edge of the single cell 110. It is suppressed. A seal member (for example, a glass seal member) that seals between the air chamber 166 and the fuel chamber 176 may be further provided near the joint between the single cell 110 and the separator 120.

The air electrode side frame 130 is a frame-shaped member in which a substantially rectangular air chamber hole 131 penetrating in the vertical direction is formed near the center, and is formed of, for example, an insulator such as mica. The air electrode side frame 130 is in contact with the peripheral edge of the surface of the separator 120 opposite to the side facing the electrolyte layer 112 and the peripheral edge of the surface of the interconnector 150 facing the air electrode 114. .. The air chamber holes 131 formed in the air pole side frame 130 form an air chamber 166 facing the air pole 114. Further, the air electrode side frame 130 electrically insulates between the pair of interconnectors 150 included in the power generation unit 102. Further, the air electrode side frame 130 has an oxidant gas supply communication flow path 132 that communicates the oxidant gas introduction manifold 161 and the air chamber 166, and an oxidant that communicates the air chamber 166 and the oxidant gas discharge manifold 162. A gas discharge communication flow path 133 is formed.

The fuel electrode side frame 140 is a frame-shaped member in which a substantially rectangular fuel chamber hole 141 penetrating in the vertical direction is formed near the center, and is formed of, for example, metal. The fuel electrode side frame 140 is in contact with the peripheral edge of the surface of the separator 120 facing the electrolyte layer 112 and the peripheral edge of the surface of the interconnector 150 facing the fuel electrode 116. The fuel chamber holes 141 formed in the fuel pole side frame 140 form a fuel chamber 176 facing the fuel pole 116. Further, in the fuel electrode side frame 140, a fuel gas supply communication flow path 142 that communicates the fuel gas introduction manifold 171 and the fuel chamber 176, and a fuel gas discharge communication flow that communicates the fuel chamber 176 and the fuel gas discharge manifold 172. A road 143 is formed.

The fuel electrode side current collector 144 is arranged in the fuel chamber 176. The fuel electrode 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. For example, nickel or nickel alloy. , Stainless steel, etc. The electrode facing portion 145 is in contact with the surface of the fuel pole 116 opposite to the side facing the electrolyte layer 112, and the interconnector facing portion 146 is on the surface of the interconnector 150 facing the fuel pole 116. Are in contact. Since the fuel electrode side current collecting member 144 has such a configuration, the fuel electrode 116 and the interconnector 150 are electrically connected to each other. A spacer 149 formed of, for example, mica is arranged between the electrode facing portion 145 and the interconnector facing portion 146. Therefore, the fuel pole side current collecting member 144 follows the deformation of the power generation unit 102 due to the temperature cycle and the reaction gas pressure fluctuation, and the electrical connection between the fuel pole 116 and the interconnector 150 via the fuel pole side current collecting member 144 is established. Well maintained.

The air pole side current collecting member 134 is arranged in the air chamber 166. The air electrode side current collecting member 134 is composed of a plurality of substantially square columnar current collecting member elements 135, and is made of, for example, ferritic stainless steel. The air pole side current collecting member 134 is in contact with the surface of the air pole 114 on the side opposite to the side facing the electrolyte layer 112 and the surface of the interconnector 150 on the side facing the air pole 114. Since the air electrode side current collecting member 134 has such a configuration, the air electrode 114 and the interconnector 150 are electrically connected to each other. In this embodiment, the air electrode side current collecting member 134 and the interconnector 150 are formed as an integral member. That is, the flat plate-shaped portion of the integrated member that is orthogonal to the vertical direction (Z-axis direction) functions as the interconnector 150, and is formed so as to project from the flat plate-shaped portion toward the air electrode 114. The current collecting member element 135, which is a plurality of convex portions, functions as the air electrode side current collecting member 134. Further, the integrated member of the air electrode side current collecting member 134 and the interconnector 150 may be covered with a conductive coat, and both are placed between the air electrode 114 and the air electrode side current collecting member 134. A conductive bonding layer to be bonded may be interposed. In each power generation unit 102, the air electrode side current collecting member 134 and the upper interconnector 150 may be separate members.

A-2. Operation of fuel cell stack 100:
As shown in FIG. 2, when the oxidant gas OG is supplied via a gas pipe (not shown) connected to the branch portion 29 of the gas passage member 27 provided at the position of the oxidant gas introduction manifold 161. , Oxidizing agent gas OG includes the branch portion 29 of the gas passage member 27, the main body portion 28, the through hole 107 for the flow path of the lower end plate 106, the communication hole 108 of the lower insulating sheet 520, and the lower terminal plate. It is supplied to the oxidant gas introduction manifold 161 through the communication hole 108 of 420, and is supplied from the oxidant gas introduction manifold 161 to the air chamber 166 via the oxidizer gas supply communication flow path 132 of each power generation unit 102. Further, as shown in FIG. 3, when the fuel gas FG is supplied via a gas pipe (not shown) connected to the branch portion 29 of the gas passage member 27 provided at the position of the fuel gas introduction manifold 171. , The fuel gas FG includes a branch portion 29 of the gas passage member 27, a main body portion 28, a through hole 107 for a flow path of the lower end plate 106, a communication hole 108 of the lower insulating sheet 520, and a lower terminal plate 420. It is supplied to the fuel gas introduction manifold 171 through the communication hole 108 of the above, and is supplied from the fuel gas introduction manifold 171 to the fuel chamber 176 via the fuel gas supply communication flow path 142 of each power generation unit 102.

When the oxidant gas OG is supplied to the air chamber 166 of each power generation unit 102 and the fuel gas FG is supplied to the fuel chamber 176, oxygen contained in the oxidant gas OG and hydrogen contained in the fuel gas FG in the single cell 110 are supplied. Power is generated by the electrochemical reaction with. This power generation reaction is an exothermic reaction. In each power generation unit 102, the air pole 114 of the single cell 110 is electrically connected to one of the interconnectors 150 (or the upper terminal plate 410) via the air pole side current collector 134, and the fuel pole 116 is the fuel pole. It is electrically connected to the other interconnector 150 (or the lower terminal plate 420) via the side current collector 144. Further, the plurality of power generation units 102 included in the fuel cell stack 100 are electrically connected in series. Therefore, the electric energy generated in each power generation unit 102 is extracted from the terminal plates 410 and 420 that function as the output terminals of the fuel cell stack 100. Since the SOFC generates electricity at a relatively high temperature (for example, 700 ° C. to 1000 ° C.), the fuel cell stack 100 is a heater (for example, after the start-up, until the high temperature can be maintained by the heat generated by the power generation. It may be heated by (not shown).

As shown in FIG. 2, the oxidant off-gas OOG discharged from the air chamber 166 to the oxidant gas discharge manifold 162 via the oxidant gas discharge communication flow path 133 of each power generation unit 102 is a terminal plate 420 on the lower side. The communication hole 108, the communication hole 108 of the lower insulating sheet 520, the through hole 107 for the flow path of the lower end plate 106, the main body 28 of the gas passage member 27 provided at the position of the oxidant gas discharge manifold 162, and It is discharged to the outside of the fuel cell stack 100 via the branch portion 29 and a gas pipe (not shown) connected to the branch portion 29. Further, as shown in FIG. 3, the fuel off-gas FOG discharged from the fuel chamber 176 to the fuel gas discharge manifold 172 via the fuel gas discharge communication flow path 143 of each power generation unit 102 communicates with the lower terminal plate 420. The main body 28 and the branch portion of the gas passage member 27 provided at the positions of the hole 108, the communication hole 108 of the lower insulating sheet 520, the through hole 107 for the flow path of the lower end plate 106, and the fuel gas discharge manifold 172. After passing through 29, the fuel is discharged to the outside of the fuel cell stack 100 via a gas pipe (not shown) connected to the branch portion 29.

In each power generation unit 102 constituting the fuel cell stack 100 of the present embodiment, the main flow direction of the oxidant gas OG in the air chamber 166 and the main flow direction of the fuel gas FG in the fuel chamber 176 are substantially opposite directions ( The directions are opposite to each other). That is, the power generation unit 102 (fuel cell stack 100) of the present embodiment is a counterflow type SOFC.

A-3. Detailed configuration of the lower terminal plate 420 and the lower insulating sheet 520:
FIG. 7 is an explanatory view showing an XY cross-sectional configuration of the lower terminal plate 420 at the position of VII-VII in FIG. Note that, for convenience, FIG. 7 also shows a lower insulating sheet 520 existing in an XY cross section at a position different from the XY cross section of the lower terminal plate 420 at the position of VII-VII in FIG. 4 in the Z-axis direction. ing. FIG. 8 is an explanatory view partially showing the XZ cross-sectional configuration of the fuel cell stack 100. FIG. 8 is a partially enlarged view of the X1 portion of the cross section shown in FIG. 4, that is, a partially enlarged view of the cross section of the positions IV-IV of FIGS. 1 and 7. Specifically, FIG. 8 shows a configuration of an XZ cross section that passes through the center point PO of the bolt 22 in the Z-axis direction and is parallel to the Z-axis direction.

As described above, the lower terminal plate 420 is a substantially rectangular flat plate-shaped conductive member, and is made of, for example, stainless steel (see FIG. 7). Further, the lower terminal plate 420 is formed with communication holes 108 constituting an oxidant gas introduction manifold 161, an oxidant gas discharge manifold 162, a fuel gas introduction manifold 171 and a fuel gas discharge manifold 172. There is. The lower terminal plate 420 is further formed with bolt holes 109 around four corners on the outer circumference in the Z-axis direction. Further, in the Y-axis direction view, the inner peripheral surface Si of the insulating sheet through hole 522 in the lower insulating sheet 520 is a substantially straight line parallel to the Z-axis direction. In other words, in the Y-axis direction, the inner peripheral surface Si of the insulating sheet through hole 522 is orthogonal to the upper surface of the lower insulating sheet 520.

As shown in the partially enlarged view in FIG. 7, the bolt 22 is arranged at substantially the center of the bolt hole 109 in the Z-axis direction. The center point of the bolt hole 109 in the Z-axis direction is substantially the same position as the center point PO of the bolt 22. The hole diameter D2 of the bolt hole 109 (hereinafter, also referred to as “terminal plate through hole 422”) formed in the lower terminal plate 420 forming a part of the bolt hole 109 is the outer diameter (hereinafter, also referred to as “terminal plate through hole 422”) in the shaft portion of the bolt 22. Maximum outer diameter) Larger than D1. Further, the hole diameter D3 of the bolt hole 109 (hereinafter, also referred to as “insulating sheet through hole 522”) formed in the lower insulating sheet 520, which constitutes a part of the bolt hole 109, is outside the shaft portion of the bolt 22. It is larger than the diameter (maximum outer diameter) D1 and smaller than the hole diameter D2 of the terminal plate through hole 422. Further, in the Z-axis direction view, the shaft portion of the bolt 22, the terminal plate through hole 422, and the insulating sheet through hole 522 are substantially concentric. That is, in the Z-axis direction, the inner peripheral edge Et of the terminal plate through hole 422 formed in the lower terminal plate 420 surrounds the inner peripheral edge Ei of the insulating sheet through hole 522 formed in the lower insulating sheet 520. I'm out. Here, the "inner peripheral edge Et of the terminal plate through hole 422" is an edge including a point P1 where the inner peripheral surface St of the terminal plate through hole 422 and the upper surface of the lower insulating sheet 520 are in contact with each other. Further, "in the Z-axis direction, the inner peripheral edge Et of the terminal plate through hole 422 formed in the lower terminal plate 420 is the inner peripheral edge Ei of the insulating sheet through hole 522 formed in the lower insulating sheet 520. "Surrounding" means that the inner peripheral edge Et of the terminal plate through hole 422 is located outside the inner peripheral edge Ei of the insulating sheet through hole 522 over the entire circumference of the inner peripheral edge Et in the Z-axis direction. It does not mean that the inner peripheral edge Et and the inner peripheral edge Ei match. In other words, in the Y-axis direction, the inner peripheral surface Si of the lower insulating sheet through hole 522 projects from the inner peripheral surface St of the lower terminal plate through hole 422 toward the bolt 22 side.

In the Z-axis direction, the inner peripheral edge Et of the terminal plate through hole 422 in the lower terminal plate 420 and the inner peripheral edge Ei of the insulating sheet through hole 522 in the lower insulating sheet 520 are all the entire shaft portion of the bolt 22. Separated over the circumference. The inner peripheral surface St of the lower terminal plate 420 described above is the surface of the lower terminal plate 420 facing the bolt 22, and is the inner peripheral surface of the lower insulating sheet 520 described later. Si is the surface of the lower insulating sheet 520 facing the bolt 22. The inner peripheral surface St of the terminal plate through hole 422 in the lower terminal plate 420 and the inner peripheral surface Si of the insulating sheet through hole 522 in the lower insulating sheet 520 are separated from the bolt 22 in all of them. ing. Further, the space between the lower terminal plate 420 and the bolt 22 is air (specific dielectric constant 1.0) without any other member intervening between the lower terminal plate 420 and the bolt 22. Is filled with. In other words, the value of the volume of air occupied in the bolt hole 109 is equivalent to the value obtained by subtracting the volume of the bolt 22 from the volume of the bolt hole 109.

As shown in FIG. 8, in the Y-axis direction orthogonal to the Z-axis direction, the inner peripheral surface St of the terminal plate through hole 422 of the lower terminal plate 420 and the lower insulating sheet 520 are in contact with each other at the point P1. ing. In the Y-axis direction view, the inner peripheral surface Si of the insulating sheet through hole 522 of the lower insulating sheet 520 and the lower end plate 106 are in contact with each other at the end point P3. In the Y-axis direction, the point P2 on the upper surface of the lower insulating sheet 520 is the point closest to the bolt 22 and the bending point on the surface of the lower insulating sheet 520. The line L1 is a line corresponding to the inner peripheral surface Si of the insulating sheet through hole 522 in the lower insulating sheet 520 in the Y-axis direction. The spatial distance Da is the shortest distance in the X-axis direction between an arbitrary point Pa on the line L1 and the bolt 22. The distance Db is a distance along the line L1 between an arbitrary point Pa on the line L1 and an end point P3 on the downward side of the line L1 in the Z-axis direction. In FIG. 8, the dotted line shown in the bolt hole 109 is a dotted line shown for convenience to indicate the space in the terminal plate through hole 422 and the space in the insulating sheet through hole 522.

In the fuel cell stack 100 of the present embodiment, the ratio (Db / Da) of the distance Db to the space distance Da is less than the value of the relative permittivity of the material forming the lower insulating sheet 520. In the present embodiment, when the material forming the lower insulating sheet 520 is mica and the relative permittivity of mica is 7.0, the ratio (Db / Da) is less than 7.0. The space formed by the insulating sheet through hole 522 in the lower insulating sheet 520 is filled with air (relative permittivity 1.0). When the materials forming the lower insulating sheet 520 are alumina, silicon nitride, and zirconia, their relative permittivity is 8.5 to 10.0 for alumina and 8.3 to 9 for silicon nitride. 6.6, 28-33 for zirconia. The relative permittivity of the material forming the lower insulating sheet 520 can be measured according to, for example, JIS C2141. The fuel cell stack 100 of the present embodiment has the same configuration not only in the XZ cross section shown in FIG. 8 but also in any cross section passing through the center point PO of the bolt 22 in the Z-axis direction.

In the fuel cell stack 100 of the present embodiment, the outer diameter D1 of the shaft portion (specifically, the threaded portion of the shaft portion) of each bolt 22 is 4 mm or more and 14 mm or less, preferably 8 mm or more and 11 mm or less. Is. The hole diameter D2 of the terminal plate through hole 422 formed in the lower terminal plate 420 is 6 mm or more and 16 mm or less, preferably 10 mm or more and 13 mm or less. The hole diameter D3 of the insulating sheet through hole 522 formed in the lower insulating sheet 520 is 5 mm or more and 15 mm or less, preferably 9 mm or more and 12 mm or less. Further, the ratio of the protrusion distance from the lower terminal plate 420 of the lower insulating sheet 520 to the gap between the bolt 22 and the lower terminal plate through hole 422 is 5% or more, preferably 5% or more. It is 20% or more, more preferably 50% or more. Here, the gap between the bolt 22 in the lower terminal plate through hole 422 is the distance between the inner peripheral edge Et of the terminal plate through hole 422 and the outer diameter D1 of the bolt 22 ((D2-D1) / 2). ), And the protrusion distance from the lower terminal plate 420 of the lower insulating sheet 520 is the distance between the inner peripheral edge Et of the terminal plate through hole 422 and the inner peripheral edge Ei of the insulating sheet through hole 522 ((D2). -D3) / 2).

The Z-axis direction (arrangement direction or vertical direction) corresponds to the first direction in the claims. The power generation block 103 corresponds to an electrochemical reaction block within the scope of the claims. The single cell 110 corresponds to an electrochemical reaction single cell in the claims. The lower terminal plate 420 corresponds to a terminal member within the scope of the claims. The terminal plate through hole 422 corresponds to the first through hole in the claims. The lower insulating sheet 520 corresponds to an insulating member within the scope of the claims. The insulating sheet through hole 522 corresponds to the second through hole in the claims. The lower end plate 106 corresponds to an end member in the claims. The bolt 22 corresponds to a fastening member within the scope of claims. The spatial distance Da corresponds to the first distance in the claims. The distance Db corresponds to the second distance in the claims.

A-4. Performance evaluation:
The performance evaluation performed using the samples of the plurality of fuel cell stacks 100 will be described below. FIG. 10 is an explanatory diagram showing the result of performance evaluation (evaluation of withstand voltage value). The vertical axis of FIG. 10 is the ratio of withstand voltage values, and the horizontal axis is the space distance Da (mm) between the lower insulating sheet 520 and the bolt 22 constituting the fuel cell stack 100.

(Evaluation method)
In this performance evaluation, a fuel cell stack 100 having the following configuration was used.
・ Bolt 22
Material: Stainless steel, lower terminal plate 420
Material: Stainless Steel Thickness T1: 1mm
-Lower insulation sheet 520
Material: Mica (relative permittivity 7.0)
Thickness T1: 1.5mm
-Lower end plate 106
Material: Stainless steel Thickness T1: 8mm
-Space distance Da between the lower insulating sheet 520 and the bolt 22:
0mm, 0.15mm, 0.3mm, 0.5mm, 1mm, 1.5mm, 1.8mm, 2mm

(Evaluation results)
In FIG. 10, the vertical axis “ratio of withstand voltage value” is the above space distance Da when the measured value of the withstand voltage of the fuel cell stack 100 having a configuration in which the space distance Da is 2 mm is 1. It is the ratio of the measured value of the withstand voltage of the fuel cell stack 100 having the structure which is each distance (0 mm to 1.8 mm). The “configuration in which the spatial distance Da is 2 mm” means a configuration in which the hole diameter D2 of the terminal plate through hole 422 and the hole diameter D3 of the insulating sheet through hole 522 have the same value. Further, in the fuel cell stack 100 used for the performance evaluation, the inner peripheral surface Si of the insulating sheet through hole 522 is orthogonal to the upper surface of the lower insulating sheet 520 in the Y-axis direction. Therefore, the spatial distance Da has the same value at any point Pa on the line L1 corresponding to the inner peripheral surface Si of the insulating sheet through hole 522 in the lower insulating sheet 520 in the Y-axis direction. is there. Further, since the thickness T1 of the lower insulating sheet 520 is 1.5 mm, the distance Db is 1.5 mm at the maximum.

In this performance evaluation, the ratio of the withstand voltage value increased as the space distance Da decreased from the point of 2 mm as the base point, and showed the maximum value at the point where the space distance Da was 0.3 mm. This is because, in the fuel cell stack 100 having a configuration in which the space distance Da is 0.3 mm to 1.8 mm, the ratio (Db / Da) of the distance Db to the space distance Da is the lower insulating sheet 520. It is probable that the relative permittivity of mica, which is the material to be formed, was less than 7.0. On the other hand, the ratio of the withstand voltage value at the point where the space distance Da is 0.15 mm shows a significantly lower value than the ratio of the withstand voltage value at the point where the space distance Da is 0.3 mm. This is a material in which the ratio (Db / Da) of the distance Db to the space distance Da in the fuel cell stack 100 having a configuration in which the space distance Da is 0.15 mm forms the lower insulating sheet 520. It is probable that the relative dielectric constant of a certain mica exceeded 7.0.

Since the dielectric constant of the air in the space between the lower insulating sheet 520 and the bolt 22 is smaller than the dielectric constant of mica, which is the material forming the lower insulating sheet 520, the discharge occurs along the distance Db. It is thought that it is likely to occur. On the other hand, when the ratio (Db / Da) is equal to or greater than the relative permittivity of mica, it is considered that discharge is likely to occur at the space distance Da.

A-5. Effect of this embodiment:
As described above, the fuel cell stack 100 of the present embodiment includes a power generation block 103, a lower terminal plate 420, a lower insulating sheet 520, a lower end plate 106, and a bolt 22. .. The power generation block 103 includes a plurality of single cells 110 arranged in the Z-axis direction. Each single cell 110 includes an electrolyte layer 112, and air poles 114 and fuel poles 116 that face each other in the Z-axis direction with the electrolyte layer 112 in between. The lower terminal plate 420 is arranged on the lower side in the Z-axis direction with respect to the power generation block 103. The lower terminal plate 420 is formed with a terminal plate through hole 422 penetrating in the Z-axis direction. The lower terminal plate 420 is a conductive member that is electrically connected to the power generation block 103. The lower insulating sheet 520 is an insulating member arranged on the lower side in the Z-axis direction with respect to the lower terminal plate 420. The lower insulating sheet 520 is formed with an insulating sheet through hole 522 that communicates with the terminal plate through hole 422 and penetrates in the Z-axis direction. The lower end plate 106 is a conductive member arranged on the lower side in the Z-axis direction with respect to the lower insulating sheet 520. The bolt 22 is a conductive member that is inserted into the terminal plate through hole 422 and the insulating sheet through hole 522 and is engaged with the lower end plate 106. Further, in the fuel cell stack 100 of the present embodiment, in the Z-axis direction, the inner peripheral edge Et of the terminal plate through hole 422 formed in the lower terminal plate 420 is insulated formed in the lower insulating sheet 520. It surrounds the inner peripheral edge Ei of the sheet through hole 522. In the Z-axis direction view, the inner peripheral edge Ei of the insulating sheet through hole 522 in the lower insulating sheet 520 is separated from the bolt 22.

In the fuel cell stack 100 of the present embodiment, in the Z-axis direction, the inner peripheral edge Et of the terminal plate through hole 422 formed in the lower terminal plate 420 penetrates the insulating sheet formed in the lower insulating sheet 520. It surrounds the inner peripheral edge Ei of the hole 522. That is, in the fuel cell stack 100 of the present embodiment, the insulating sheet through hole 522 in the lower insulating sheet 520 passes through the center point PO of the bolt 22 in the Z-axis direction and is parallel to the Z-axis direction. The inner peripheral surface Si projects toward the bolt 22 side as compared with the inner peripheral surface St of the terminal plate through hole 422 in the lower terminal plate 420. Therefore, compared with the configuration in which the inner peripheral surface Si of the insulating sheet through hole 522 in the lower insulating sheet 520 coincides with the inner peripheral surface St of the terminal plate through hole 422 in the lower terminal plate 420, the lower side The creepage distance of the lower insulating sheet 520 from the terminal plate 420 to the lower end plate 106 can be increased. Therefore, according to the fuel cell stack 100 of the present embodiment, it is possible to suppress the occurrence of a short circuit between the lower terminal plate 420 and the lower end plate 106.

In the fuel cell stack 100 of the present embodiment, the inner peripheral edge Ei of the insulating sheet through hole 522 in the insulating sheet 520 is separated from the bolt 22 in the Z direction view. That is, a space is formed between the insulating sheet 520 and the bolt 22. Therefore, according to the fuel cell stack 100 of the present embodiment, it is possible to suppress the occurrence of a short circuit between the lower terminal plate 420 and the bolt 22.

Therefore, according to the fuel cell stack 100 of the present embodiment, the occurrence of a short circuit between the lower terminal plate 420 and the bolt 22 is suppressed, and the lower terminal plate 420 and the lower end plate 106 are combined. It is possible to suppress the occurrence of a short circuit between them.

A simulation of the electric field strength was performed for the fuel cell stack 100 having a configuration in which the spatial distance Da is 2 mm and 1.5 mm used in the performance evaluation. As a result, the space distance Da is 1.5 mm, that is, from the inner peripheral surface St of the terminal plate through hole 422 of the lower terminal plate 420 to the inside of the insulating sheet through hole 522 of the lower insulating sheet 520. In the configuration in which the peripheral surface Si protrudes toward the bolt 22 side (hereinafter, also referred to as “protruding configuration”), the electric field strength at the point P1 where the inner peripheral surface St and the lower insulating sheet 520 contact is 0.640e7. .. On the other hand, the above-mentioned spatial distance Da is 2 mm, that is, the inner peripheral surface St of the terminal plate through hole 422 of the lower terminal plate 420 and the inner peripheral surface Si of the insulating sheet through hole 522 of the lower insulating sheet 520. In the configuration in which is flush with each other (hereinafter, also referred to as “plane configuration”), the electric field strength at the point P1 where the inner peripheral surface St and the lower insulating sheet 520 are in contact with each other is 0.229e7. That is, it was shown that the electric field strength at the point P1 in the protruding configuration is larger than the electric field strength at the point P1 in the flush configuration. As a result, it is considered that the protruding configuration is more likely to cause a short circuit between the lower terminal plate 420 and the lower end plate 106 as compared with the flush configuration. However, as shown in the results of the performance evaluation, the configuration of the fuel cell stack 100 of the present embodiment, that is, the lower insulation from the lower terminal plate 420 to the lower end plate 106. It is considered that the withstand voltage value is increased by increasing the creepage distance of the seat 520, and as a result, a short circuit between the lower terminal plate 420 and the lower end plate 106 is less likely to occur. Be done.

(Simulation conditions)
The conditions of the simulation regarding the electric field strength are as follows.
・ Bolt 22
Material: Stainless steel (relative permittivity 1e6)
・ Lower terminal plate 420
Material: Stainless steel (relative permittivity 1e6)
Thickness T1: 1mm
-Lower insulation sheet 520
Material: Mica (relative permittivity 7.0)
Thickness T1: 1.5mm
-Lower end plate 106
Material: Stainless steel (relative permittivity 1e6)
Thickness T1: 8mm
-Space distance Da between the lower insulating sheet 520 and the bolt 22:
1.5mm, 2mm
・ Potential bolt 22: 0V in each member
Lower terminal plate 420: 1000V
Lower end plate 106: 0V

In the fuel cell stack 100 of the present embodiment, in the XZ cross section that passes through the center point PO of the bolt 22 in the Z-axis direction and is parallel to the Z-axis direction, the inside of the insulating sheet through hole 522 in the lower insulating sheet 520. In the Z-axis direction of the point Pa on the line L1 and the line L1 with respect to the space distance Da in the X-axis direction orthogonal to the Z-axis direction between the arbitrary point Pa on the line L1 corresponding to the peripheral surface Si and the bolt 22. The ratio of the distance Db (Db / Da) along the line L1 to the lower end point P3 is less than the value of the relative dielectric constant of the material forming the lower insulating sheet 520.

In the fuel cell stack 100 of the present embodiment, the ratio of the distance Db to the space distance Da (Db / Da) in the XZ cross section that passes through the center point PO of the bolt 22 in the Z-axis direction and is parallel to the Z-axis direction. ) Is less than the value of the relative permittivity of the material forming the lower insulating sheet 520. Here, as the protrusion distance of the lower insulating sheet 520 from the lower terminal plate 420 increases, the creepage distance of the lower insulating sheet 520 from the lower terminal plate 420 to the lower end plate 106 Increases, which improves the withstand voltage of the fuel cell stack 100. However, if the protrusion distance of the lower insulating sheet 520 from the lower terminal plate 420 becomes too large, the space distance Da between the lower insulating sheet 520 and the bolt 22 cannot be sufficiently secured. As a result, in the fuel cell stack 100, in the configuration in which the space distance Da between the lower insulating sheet 520 and the bolt 22 is not sufficiently secured, the space between the lower insulating sheet 520 and the bolt 22 is not sufficiently secured. A short circuit occurs between the lower terminal plate 420 and the bolt 22 through the air (relative permittivity 1.0) that is not sufficiently secured and fills the space. Specifically, in a configuration in which the ratio (Db / Da) of the distance Db to the space distance Da is equal to or greater than the value of the relative permittivity of the material forming the lower insulating sheet 520, the lower terminal plate 420 A short circuit occurs between the bolt 22 and the bolt 22. On the other hand, in the fuel cell stack 100 of the present embodiment, the ratio (Db / Da) of the distance Db to the space distance Da is less than the value of the relative permittivity of the material forming the lower insulating sheet 520. To do. That is, in the fuel cell stack 100 of the present embodiment, a sufficient space distance Da between the lower insulating sheet 520 and the bolt 22 is secured. Therefore, a short circuit occurs between the lower terminal plate 420 and the bolt 22 through the air (relative permittivity 1.0) filled in the space between the lower insulating sheet 520 and the bolt 22. Can be suppressed more effectively.

Therefore, according to the fuel cell stack 100 of the present embodiment, it is possible to suppress the occurrence of a short circuit between the lower terminal plate 420 and the lower end plate 106, and the lower terminal plate 420 and the bolt. The occurrence of a short circuit with 22 can be suppressed more effectively.

In the fuel cell stack 100 of the present embodiment, the lower insulating sheet 520 is formed of mica. Since mica is easily and inexpensively available on the market and tends to be excellent in molding processability, the fuel cell stack 100 can be efficiently manufactured.

B. Modification Examples The techniques disclosed in the present specification are not limited to the above-described embodiments, and can be transformed into various forms without departing from the gist thereof. For example, the following modifications are also possible. ..

As shown in FIG. 9, in the fuel cell stack 100 of the above embodiment, the lower terminal plate 420 may be formed with a defective space 425 facing the lower insulating sheet 520. The defective space 425 is, for example, one of the welded portions generated when the lower terminal plate 420 and the fuel electrode side frame 140 in the power generation unit 102 facing the lower terminal plate 420 are joined by welding. Formed to accommodate the bead. In this way, in the configuration in which the defective space 425 is formed in the lower terminal plate 420, the inner peripheral edge Et of the terminal plate through hole 422 of the lower terminal plate 420 is the inner peripheral surface St of the terminal plate through hole 422. The edge including the point P4 where the lower surface of the insulating sheet 520 is in contact with the upper surface of the lower insulating sheet 520. This is because in such a configuration, the current is considered to flow from the point P4 on the lower terminal plate 420 through the point P2 to the lower end plate 106. That is, even in the configuration in which the defective space 425 is formed in the lower terminal plate 420, the inner peripheral edge Et including the point P4 in the terminal plate through hole 422 formed in the lower terminal plate 420 in the Z-axis direction. Surrounds the inner peripheral edge Ei of the insulating sheet through hole 522 formed in the lower insulating sheet 520, and the inner peripheral edge Ei of the insulating sheet through hole 522 in the lower insulating sheet 520 is separated from the bolt 22. With the configuration, it is possible to suppress the occurrence of a short circuit between the lower terminal plate 420 and the lower end plate 106. In FIG. 9, the dotted line shown in the bolt hole 109 is a dotted line shown for convenience to show the space in the terminal plate through hole 422 and the space in the insulating sheet through hole 522.

In the above embodiment, the fuel cell stack 100 may include a protective tube which is a substantially cylindrical insulating member. Specifically, the protective tube is arranged between the inner peripheral surface of the bolt hole 109 shown in FIGS. 4 and 8 and the bolt 22. The protective tube is formed of an insulating material such as alumina, zirconia, and silicon nitride. More specifically, the protective tube surrounds the outer circumference of the shaft portion of the bolt 22 around the entire circumference, and extends from the upper end plate 104 to the lower terminal plate 420 in the Z-axis direction to protect the bolt 22. The lower end face of the pipe is in contact with the upper surface of the lower insulating sheet 520. The thickness of the protective tube is preferably substantially uniform over the entire circumference of the protective tube around the axis. Further, the thickness of the protective tube is preferably substantially uniform over the entire length of the protective tube. Further, the thickness of the protective tube is preferably 1/3 or more, more preferably 1/2 or more, with respect to the distance in the surface direction between the bolt 22 and the inner peripheral surface of the bolt hole 109. preferable. The protective tube corresponds to a tubular member within the scope of the claims. As described above, when the fuel cell stack 100 is provided with the protective tube, the terminal plates 410 and 420, the separator 120, the fuel electrode side frame 140, and the bolt holes 109 and the bolts 22 formed in the interconnector 10 are provided as conductive members. Can be suppressed from short-circuiting. The protective tube is not limited to a substantially cylindrical shape, and may be a tubular shape such as a substantially square tubular shape.

In the fuel cell stack 100 of the above embodiment, the shaft portion of the bolt 22, the terminal plate through hole 422, and the insulating sheet through hole 522 are substantially concentric in the Z-axis direction, but the configuration is limited to this. Not done. That is, in the Z-axis direction, the inner peripheral edge Et of the terminal plate through hole 422 formed in the lower terminal plate 420 surrounds the inner peripheral edge Ei of the insulating sheet through hole 522 formed in the lower insulating sheet 520. If the inner peripheral edge Ei of the insulating sheet through hole 522 in the lower insulating sheet 520 is separated from the bolt 22, the shaft portion of the bolt 22, the terminal plate through hole 422, and the insulating sheet through hole 522 However, the configuration may not be substantially concentric in the Z-axis direction.

In the fuel cell stack 100 of the above embodiment, the lower end portion of the shaft portion of the bolt 22 penetrates the lower end plate 106 and protrudes downward, and a nut is formed on the screw portion formed at the protruding lower end portion. It may be a screwed configuration. Further, in the above embodiment, a screw is formed on the outer peripheral surface of the upper end portion of the shaft portion of the bolt 22, and a female screw is formed on the inner peripheral surface of the through hole formed in the upper end plate 104. The upper end portion of the shaft portion of the bolt 22 may be screwed into the through hole formed in the upper end plate 104.

In the fuel cell stack 100 of the above embodiment, the inner peripheral surface Si of the insulating sheet through hole 522 in the lower insulating sheet 520 may not be a substantially straight line parallel to the Z-axis direction in the Y-axis direction. .. Specifically, in the Y-axis direction view, the inner peripheral surface Si of the insulating sheet through hole 522 has a configuration in which the distance between the inner peripheral surface Si and the bolt 22 becomes smaller toward the downward side. Good.

In the fuel cell stack 100 of the above embodiment, the portion of the lower insulating sheet 520 including the point P2 may have an R shape in the Y-axis direction. However, from the viewpoint of ensuring a good withstand voltage in the fuel cell stack 100, it is preferable that the portion of the lower insulating sheet 520 including the point P2 has a right-angled shape as in the above embodiment. Even if the creepage distance of the lower insulating sheet 520 from the lower terminal plate 420 to the lower end plate 106 is the same, the portion of the lower insulating sheet 520 including the point P2 is at a right angle. This is because the withstand voltage tends to be improved more effectively when the shape is formed, that is, when the portion is bent at the point P2.

In the above embodiment, the inner peripheral edge Ei of the insulating sheet through hole 522 of the lower insulating sheet 520 is an edge of the inner peripheral surface Si including the point closest to the bolt 22 side in the Z-axis direction.

In the fuel cell stack 100 of the above embodiment, the configuration of the upper terminal plate 410 and the upper insulating sheet 510 may be the same as that of the lower terminal plate 420 and the lower insulating sheet 520.

The material forming each member in the fuel cell stack 100 of the above embodiment is merely an example, and each member may be formed of another material.

In the above embodiment, the SOFC that generates power by utilizing the electrochemical reaction between hydrogen contained in the fuel gas and oxygen contained in the oxidizing agent gas is targeted, but the present invention utilizes the electrolysis reaction of water. It is also applicable to an electrolytic single cell, which is a constituent unit of a solid oxide fuel cell (SOEC) that generates hydrogen, and an electrolytic cell stack including a plurality of electrolytic single cells. The configuration of the electrolytic cell stack is not described in detail here because it is known as described in, for example, Japanese Patent Application Laid-Open No. 2016-81813, but is generally the same as the fuel cell stack 100 in the above-described embodiment. It is the composition of. That is, the fuel cell stack 100 in the above-described embodiment may be read as an electrolytic cell stack, the power generation unit 102 may be read as an electrolytic cell unit, and the single cell 110 may be read as an electrolytic single cell. However, during the operation of the electrolytic cell stack, a voltage is applied between both electrodes so that the air electrode 114 is positive (anode) and the fuel electrode 116 is negative (cathode), and the voltage is applied through the communication hole 108. Water vapor as a raw material gas is supplied. As a result, an electrolysis reaction of water occurs in each electrolytic cell, hydrogen gas is generated in the fuel chamber 176, and hydrogen is taken out of the electrolytic cell stack through the communication hole 108. The above effect can be obtained by applying the present invention even in an electrolytic single cell having such a configuration.

10: Interconnector 22: Bolt 26: Insulation sheet 27: Gas passage member 28: Main body 29: Branch 100: Fuel cell stack 102: Fuel cell power generation unit (power generation unit) 103: Power generation block 104: Upper end plate 106 : Lower end plate 107: Through hole for flow path 108: Communication hole 109: Bolt hole 110: Fuel cell single cell (single cell) 112: Electrolyte layer 114: Air electrode (cathode) 116: Fuel electrode (anode) 120 : Separator 121: Hole 124: Joint 130: Air pole side frame 131: Air chamber hole 132: Oxidizing agent gas supply communication flow path 133: Oxidizing agent gas discharge communication flow path 134: Air pole side current collecting member 135: Collection Electrical member element 140: Fuel pole side frame 141: Fuel chamber hole 142: Fuel gas supply communication flow path 143: Fuel gas discharge communication flow path 144: Fuel pole side current collector 145: Electrode facing part 146: Interconnector facing part 147: Connecting part 149: Spacer 150: Interconnector 161: Oxidizing agent gas introduction manifold 162: Oxidizing agent gas discharge manifold 166: Air chamber 171: Fuel gas introduction manifold 172: Fuel gas discharge manifold 176: Fuel chamber 410: Upper terminal Plate 420: Lower terminal plate 422: Terminal plate through hole 425: Defect space 510: Upper insulation sheet 520: Lower insulation sheet 522: Insulation sheet through hole D1: Outer diameter D2: Hole diameter D3: Hole diameter Da: Space Distance Db: Distance Ei: Inner peripheral edge Et: Inner peripheral edge FG: Fuel gas FOG: Fuel off gas L1: Line OG: Oxidizing agent gas OOG: Oxidizing agent off gas P1: Point P2: Point P3: End point P4: Point PO: Center point Pa : Point Si: Inner peripheral surface St: Inner peripheral surface T1: Thickness

Claims (4)

It is an electrochemical reaction block including a plurality of electrochemical reaction single cells arranged in the first direction, and each of the electrochemical reaction single cells is oriented in the first direction with the electrolyte layer and the electrolyte layer interposed therebetween. An electrochemical reaction block, including an air electrode and a fuel electrode facing each other,
A terminal member arranged on one side of the first direction with respect to the electrochemical reaction block, the first through hole penetrating in the first direction is formed, and the electrochemical reaction block has a first through hole. With electrically connected conductive terminal members
An insulating member arranged on one side of the terminal member in the first direction, which communicates with the first through hole and has a second through hole penetrating in the first direction. The formed insulating insulating member and
A conductive end member arranged on one side of the insulating member in the first direction,
A conductive fastening member inserted into the first through hole and the second through hole and engaged with the end member.
In an electrochemical reaction cell stack fastened by the fastening member.
In the first directional view, the inner peripheral edge of the first through hole formed in the terminal member surrounds the inner peripheral edge of the second through hole formed in the insulating member.
In the first directional view, the inner peripheral edge of the second through hole in the insulating member is separated from the fastening member.
On a first line corresponding to the inner peripheral surface of the second through hole in the insulating member in a cross section that passes through the center of the fastening member in the first directional view and is parallel to the first direction. The first of the first line and the arbitrary point on the first line with respect to a first distance in a second direction orthogonal to the first direction between the arbitrary point and the fastening member. The ratio of the second distance along the first line to the one-sided endpoint in the direction of is less than the relative permittivity of the material forming the insulating member.
It is characterized by an electrochemical reaction cell stack. It is an electrochemical reaction block including a plurality of electrochemical reaction single cells arranged in the first direction, and each of the electrochemical reaction single cells is oriented in the first direction with the electrolyte layer and the electrolyte layer interposed therebetween. An electrochemical reaction block, including an air electrode and a fuel electrode facing each other,
A terminal member arranged on one side of the first direction with respect to the electrochemical reaction block, the first through hole penetrating in the first direction is formed, and the electrochemical reaction block has a first through hole. With electrically connected conductive terminal members
An insulating member arranged on one side of the terminal member in the first direction, which communicates with the first through hole and has a second through hole penetrating in the first direction. The formed insulating insulating member and
A conductive end member arranged on one side of the insulating member in the first direction,
A conductive fastening member inserted into the first through hole and the second through hole and engaged with the end member.
In an electrochemical reaction cell stack fastened by the fastening member.
In the first directional view, the inner peripheral edge of the first through hole formed in the terminal member surrounds the inner peripheral edge of the second through hole formed in the insulating member.
In the first directional view, the inner peripheral edge of the second through hole in the insulating member is separated from the fastening member.
On a first line corresponding to the inner peripheral surface of the second through hole in the insulating member in a cross section that passes through the center of the fastening member in the first directional view and is parallel to the first direction. The first of the first line and the arbitrary point on the first line with respect to a first distance in a second direction orthogonal to the first direction between the arbitrary point and the fastening member. The ratio of the second distance along the first line to the one end point in the direction of is less than the relative permittivity value of the material forming the insulating member.
The insulating member is formed of mica.
It is characterized by an electrochemical reaction cell stack. In the electrochemical reaction cell stack according to claim 1 or 2.
In the first through hole formed in the terminal member, an insulating tubular member surrounding the outer circumference around the axis of the fastening member is arranged.
It is characterized by an electrochemical reaction cell stack. In the electrochemical reaction cell stack according to any one of claims 1 to 3.
The electrochemical reaction single cell is a fuel cell single cell.
It is characterized by an electrochemical reaction cell stack.

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