JP6907081B2 - Stack connector - Google Patents

Description

The techniques disclosed herein relate to stack connections.

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 are sometimes used in the form of fuel cell systems with multiple fuel cell stacks to enable high voltage power supply. Each fuel cell stack has 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 one side of the power generation block in the first direction. A positive pole member that is electrically connected to the pole, a positive side conductive member that is arranged on the opposite side of the positive pole member from the power generation block and has conductivity, and a positive pole member and the positive side conductivity. It is provided with a positive-side insulating member which is arranged between the members and has an insulating property. Further, each fuel cell stack is arranged on the other side of the power generation block in the first direction, and is a negative pole member electrically connected to the fuel pole, and the power generation block with respect to the negative pole member. A negative conductive member arranged on the opposite side, having conductivity, and electrically connected to the positive conductive member, and arranged between the negative electrode member and the negative conductive member to insulate. It is provided with a negative side insulating member having a property. Then, a plurality of power generation blocks provided in each of the plurality of fuel cell stacks are electrically connected in series, and a minus-side conductive member provided in each of the plurality of fuel cell stacks is electrically connected to each other. Will be done.

In a fuel cell system capable of supplying high voltage power in this way, since a plurality of power generation blocks are electrically connected in series, the potential of the positive electrode member provided in the fuel cell stack having the highest potential and the maximum potential are obtained. The potential difference between the positive-side conductive member provided in the potential fuel cell stack (hereinafter referred to as “maximum potential difference”) becomes large, and a short circuit is likely to occur between the positive-side conductive member and the positive-side conductive member. .. Therefore, conventionally, there is an attempt to reduce the maximum potential difference of a fuel cell system by individually providing an insulation mechanism for each of a plurality of fuel cell stacks (see Patent Document 1 below).

Japanese Unexamined Patent Publication No. 2009-87863

In the above-mentioned conventional fuel cell system, since it is necessary to individually provide an insulation mechanism for each of a plurality of fuel cell stacks, problems such as complicated configuration of the fuel cell system may occur. There was room.

In addition, such a problem is an electrolytic cell including a plurality of electrolytic cell stacks, which is a form of a solid oxide type electrolytic cell (hereinafter referred to as “SOEC”) that generates hydrogen by utilizing an electrolysis reaction of water. This is a common issue for systems. In this specification, the fuel cell system and the electrolytic cell system are collectively referred to as a "stack connection".

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 stack connection disclosed in the present specification is a stack connection including a plurality of electrochemical reaction cell stacks, and each of the electrochemical reaction cell stacks has an electrolyte layer, an air electrode, and a fuel electrode. A plurality of single cells containing each are arranged side by side in the first direction, and a plus that is arranged on one side of the first direction with respect to the cell block and is electrically connected to the air electrode. The pole member is arranged on the side opposite to the cell block with respect to the positive pole member, and is arranged between the positive side conductive member having conductivity and the positive pole member and the positive side conductive member. The positive side insulating member having an insulating property, the negative pole member arranged on the other side in the first direction and electrically connected to the fuel pole, and the cell block with respect to the negative pole member The negative side conductive member, which is arranged on the opposite side and has conductivity and is electrically connected to the positive side conductive member, is arranged between the negative electrode member and the negative side conductive member. A cell block that includes a negative-side insulating member having an insulating property and is electrically connected in series with a plurality of the cell blocks provided in each of the plurality of electrochemical reaction cell stacks is electrically in series. In a stack connection in which the negative conductive members provided in each of the plurality of electrochemical reaction cell stacks are electrically connected to each other, among the plurality of electrochemical reaction cell stacks, The specific negative electrode member, which is the negative electrode member provided in the first electrochemical reaction cell stack, and the positive electrode member, which is provided in the second electrochemical reaction cell stack and is electrically connected to the specific negative electrode member. By holding the specific positive pole member, which is a polar member, at a specific potential via a conductor, a potential obtained by adding the potential difference between the positive pole member and the specific negative pole member, which has the highest potential, to the specific potential is obtained. , The potential of the positive pole member having the highest potential, and the potential obtained by subtracting the potential difference between the specific positive pole member and the negative pole member having the lowest potential from the specific potential is the potential of the negative pole member having the lowest potential. It is defined as a potential, and the absolute value of the difference between the potential of the positive pole member having the highest potential and the potential of the positive conductive member is the total voltage of the plurality of electrochemical reaction cell stacks and the positive conductivity. The potential of the negative pole member and the potential of the negative conductive member, which are smaller than the absolute value of the difference from the electric potential of the member and have the lowest potential. The absolute value of the difference between the two is smaller than the absolute value of the difference between the total voltage of the plurality of electrochemical reaction cell stacks and the potential of the negative conductive member. According to this stack connector, a specific negative pole member which is a negative pole member provided in the first electrochemical reaction cell stack and a specific negative pole member provided in the second electrochemical reaction cell stack are electrically provided to the specific negative pole member. The positive electrode member connected to is held at a specific potential via a conductor. Here, the potential of the positive pole member having the highest potential, the potential of the positive side conductive member, the potential of the negative pole member having the lowest potential, and the potential of the negative side conductive member are related to the following relational expression (1). The condition shown in (2) is satisfied.
｜ "Potential of positive electrode member with maximum potential"-"Potential of positive conductive member" ｜ ＜ ｜ "Total voltage of multiple electrochemical reaction cell stacks"-"Potential of positive conductive member" | (1)
｜ "Potential of negative electrode member with lowest potential"-"Potential of negative conductive member" ｜ ＜ ｜ "Total voltage of multiple electrochemical reaction cell stacks"-"Potential of negative conductive member" | (2)
The positive side conductive member and the negative side conductive member are electrically connected, and their potentials are substantially the same.
| "Potential of the positive pole member with the highest potential"-"Potential of the positive side conductive member" | is the absolute difference between the potential of the positive pole member with the highest potential and the potential of the positive side conductive member in this stack connection. The value (hereinafter referred to as "the maximum potential difference of this stack connection") is shown. In addition, | "total voltage of a plurality of electrochemical reaction cell stacks"-"potential of the positive side conductive member" | is the positive potential of the maximum potential when the specific negative pole member and the specific positive pole member are not held at the specific potential. The absolute value of the difference between the potential of the polar member and the potential of the positive conductive member (hereinafter referred to as “maximum potential difference when not connected”) is shown. That is, the relational expression (1) means that the maximum potential difference of this stack connection is smaller than the maximum potential difference when not connected.
Next, | "potential of the negative pole member of the lowest potential"-"potential of the negative side conductive member" | is the potential of the lowest potential negative pole member and the potential of the negative side conductive member in this stack connection. The absolute value of the difference (hereinafter referred to as "minimum potential difference of this stack connection") is shown. That is, the relational expression (2) means that the minimum potential difference of this stack connector is smaller than the maximum potential difference when not connected. According to this stack connection, the positive electrode member provided in the electrochemical reaction cell stack having the highest potential and the positive electrode member, as compared with the case where the specific negative electrode member and the specific positive electrode member are not held at the specific potential. It is possible to reduce the potential difference (hereinafter, referred to as “maximum potential difference”) between the positive side conductive member provided in the electrochemical reaction cell stack having the highest potential. Moreover, the potential difference between the negative electrode member provided in the lowest potential electrochemical reaction cell stack and the negative conductive member provided in the lowest potential electrochemical reaction cell stack (hereinafter referred to as "minimum potential difference"). ) Can be suppressed from increasing.

(2) The stack connection is further provided with a conductive tube connected to each electrochemical reaction cell stack, and the specific negative pole member and the specific positive pole member are connected to the specific negative pole member via the conductor. It may be configured to be held at the specific potential by being electrically connected to the tube. According to this stack connector, the specific negative pole member and the specific positive pole member are held at a specific potential by being electrically connected to a conductive tube connected to each electrochemical reaction cell stack. .. Therefore, the maximum potential of the stack connection can be lowered without separately requiring a special configuration for holding the specific negative pole member and the specific positive pole member at a specific potential.

(3) In the stack connecting body, the stack connecting body further includes a conductive housing for accommodating at least one of the plurality of electrochemical reaction cell stacks, and the specific negative pole member and the specific positive pole. The member may be configured to be held at the specific potential by being electrically connected to the housing via the conductor. According to the stack connector, the specific negative pole member and the specific positive pole member are identified by being electrically connected to a conductive housing accommodating at least one of a plurality of electrochemical reaction cell stacks. It is held at the potential. Therefore, the maximum potential of the stack connection can be lowered without separately requiring a special configuration for holding the specific negative pole member and the specific positive pole member at a specific potential.

(4) In the stack connection, the total number of the plurality of electrochemical reaction cell stacks is 6 or more, and the order in which the cell blocks are connected in series among the plurality of electrochemical reaction cell stacks is as follows. A plurality of the electrochemical reaction cell stacks containing one or two of the electrochemical reaction cell stacks located in the center and having a continuous arrangement order of 1/3 or less of the total number are referred to as a specific cell stack group. At that time, the first electrochemical reaction cell stack and the second electrochemical reaction cell stack may be included in the specific cell stack group. According to this stack connector, the highest stack connector is compared with the case where the first electrochemical reaction cell stack and the second electrochemical reaction cell stack held at a specific potential are not included in the specific cell stack group. While lowering the potential, it is possible to prevent the lowest potential of the stack connector (the potential of the negative electrode member of the electrochemical reaction cell stack at the lowest potential) from becoming too low.

(5) In the stack connection, when the total number of the plurality of electrochemical reaction cell stacks is an even number of 4 or more, the first electrochemical reaction cell stack and the second electrochemical reaction cell stack When the pair of electrochemical reaction cell stacks located in the middle in the order of the cell blocks connected in series and the total number of the plurality of electrochemical reaction cell stacks is an odd number of 5 or more, the first The electrochemical reaction cell stack and the second electrochemical reaction cell stack are arranged in series, with one electrochemical reaction cell stack located in the middle and front or back of the one electrochemical reaction cell stack. It may be configured to be in the order of other electrochemical reaction cell stacks. According to this stack connector, the first electrochemical reaction cell stack and the second electrochemical reaction cell stack held at a specific potential are two electrochemical cells located approximately in the middle in the order in which they are connected in series. Since it is a stack, two electrochemical cells that are not located in the center of the stack. Compared to a stack configuration, the maximum potential of the stack connection is lowered, and the minimum potential of the stack connection (the lowest potential electrochemical reaction cell). It is possible to effectively prevent the potential of the negative electrode member of the stack from becoming too low.

The technique disclosed in the present specification can be realized in various forms, for example, a method for manufacturing a stack connector including a plurality of electrochemical reaction cell stacks. Is.

It is explanatory drawing which shows the whole structure of the fuel cell system 10 in 1st Embodiment. It is a perspective view which shows the appearance structure of the fuel cell stack 100 in 1st Embodiment. 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. It is explanatory drawing which shows the YZ cross-sectional structure of the fuel cell stack 100 at the position IV-IV of 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 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 whole structure of the fuel cell system 10X in the comparative example. It is explanatory drawing which shows the whole structure of the fuel cell system 10Y in 2nd Embodiment. It is explanatory drawing which shows the whole structure of the fuel cell system 10Z in the modification of 2nd Embodiment.

A. First Embodiment:
A-1. Constitution:
(Configuration of fuel cell system 10)
FIG. 1 is an explanatory diagram showing an overall configuration of the fuel cell system 10 according to the present embodiment. In the figure, the gas passage member 27 and the like, which will be described later, are omitted. The 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 system 10 and the fuel cell stack 100 described below are actually such. It may be installed in a direction different from the normal direction. The same applies to FIGS. 2 and later.

As shown in FIG. 1, the fuel cell system 10 includes a plurality of (four in this embodiment) fuel cell stacks 100, and a plurality of power generation blocks 103 (described later) provided in each of the four fuel cell stacks 100. Are electrically connected in series. Since the fuel cell system 10 has a form in which a plurality of power generation blocks 103 (described later) are electrically connected in series in this way, it is possible to supply high voltage power, for example, as a fuel cell for business or industrial use. It will be used. Hereinafter, assuming that the output voltages of the four fuel cell stacks 100 are substantially the same, the output voltage of one fuel cell stack 100 (for example, 20 (V)) is referred to as "stack voltage VS", and the entire fuel cell system 10 is used. The output voltage of (= VS × 4, for example 80 (V)) is referred to as “system voltage VA”. The electrical connection relationship in the fuel cell system 10 will be described in detail later. The fuel cell system 10 corresponds to a stack connector in the claims, and the fuel cell stack 100 corresponds to an electrochemical reaction cell stack in the claims.

(Structure of each fuel cell stack 100)
FIG. 2 is a perspective view showing an external configuration of the fuel cell stack 100 according to the present embodiment, and FIG. 3 is an explanatory view showing an XZ cross-sectional configuration of the fuel cell stack 100 at the position III-III of FIG. FIG. 4 is an explanatory view showing a YZ cross-sectional configuration of the fuel cell stack 100 at the position of IV-IV-IV-IV of FIG.

As shown in FIGS. 2 to 4, the fuel cell stack 100 includes a plurality of power generation units 102 (seven in this embodiment), a first end plate 104, a second end plate 106, and a current collector plate. It is provided with 18. The plurality of power generation units 102 included in the fuel cell stack 100 are arranged side by side in a predetermined arrangement direction (vertical direction in the present embodiment). The first end plate 104 and the second end plate 106 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. A current collector plate 18 is arranged between the power generation block 103 and the second end plate 106. The arrangement direction (vertical direction) corresponds to the first direction in the claims, and the power generation block 103 corresponds to the cell block in the claims.

A plurality of layers (power generation unit 102, first and second end plates 104, 106, current collector plate 18) constituting the fuel cell stack 100 are provided with a plurality of layers penetrating in the vertical direction (this embodiment). In the form, eight holes are formed, and the through holes 108 formed in each layer and corresponding to each other communicate with each other in the vertical direction and extend in the vertical direction from the first end plate 104 to the second end plate 106. Consists of. In the following description, the holes formed in each layer of the fuel cell stack 100 to form the through holes 108 may also be referred to as through holes 108.

A bolt 22 extending in the vertical direction is inserted into each through hole 108, and the fuel cell stack 100 is fastened by the bolt 22 and the nuts 24 fitted on both sides of the bolt 22.

The outer diameter of the shaft portion of each bolt 22 is smaller than the inner diameter of each through hole 108. Therefore, a space is secured between the outer peripheral surface of the shaft portion of each bolt 22 and the inner peripheral surface of each through hole 108. As shown in FIGS. 2 and 3, the position is near the midpoint of one side (the side on the positive side of the X axis among the two sides parallel to the Y axis) on the outer circumference of the fuel cell stack 100 around the Z direction. In the space formed by the bolt 22 (bolt 22A) and the through hole 108 into which the bolt 22A is inserted, the oxidant gas OG is introduced from the outside of the fuel cell stack 100, and the oxidant gas OG is generated for each power generation. It functions as an oxidizer gas introduction manifold 161 that is a gas flow path supplied to the unit 102, and is the midpoint of the side opposite to the side (the side on the negative side of the X axis among the two sides parallel to the Y axis). The space formed by the bolt 22 (bolt 22B) located in the vicinity and the through hole 108 into which the bolt 22B is inserted provides the oxidizer off-gas OOG, which is the gas discharged from the air chamber 166 of each power generation unit 102. It functions as an oxidant gas discharge manifold 162 that discharges to the outside of the fuel cell stack 100. In this embodiment, for example, air is used as the oxidant gas OG.

Further, as shown in FIGS. 2 and 4, the vicinity of the midpoint of one side (the side on the positive side of the Y axis among the two sides parallel to the X axis) on the outer circumference of the fuel cell stack 100 around the Z direction. In the space formed by the bolt 22 (bolt 22D) located in the above and the through hole 108 into which the bolt 22D is inserted, the fuel gas FG is introduced from the outside of the fuel cell stack 100, and the fuel gas FG is generated by each power generation. A bolt 22 that functions as a fuel gas introduction manifold 171 to be supplied to the unit 102 and is located near the midpoint of the opposite side (the side on the negative side of the Y axis of the two sides parallel to the X axis). The space formed by (bolt 22E) and the through hole 108 into which the bolt 22E is inserted sends the fuel-off gas FOG, which is the gas discharged from the fuel chamber 176 of each power generation unit 102, to the outside of the fuel cell stack 100. It functions as a fuel gas discharge manifold 172 to be discharged. In the present embodiment, for example, a hydrogen-rich gas obtained by reforming city gas is used as the fuel gas FG.

The fuel cell stack 100 is provided with four gas passage members 27. Each gas passage member 27 is made of metal and has a hollow tubular main body 28 and a hollow tubular branch 29 branched from the side surface of the main body 28. The hole of the branch portion 29 communicates with the hole of the main body portion 28. Gas pipes (for example, the fuel gas introduction pipe 60 and the fuel off gas discharge pipe 70 shown in FIG. 1) are connected to the branch portion 29 of each gas passage member 27. Further, as shown in FIG. 3, the hole of the main body 28 of the gas passage member 27 arranged at the position of the bolt 22A forming the oxidant gas introduction manifold 161 communicates with the oxidant gas introduction manifold 161. The hole of the main body 28 of the gas passage member 27 arranged at the position of the bolt 22B forming the oxidant gas discharge manifold 162 communicates with the oxidant gas discharge manifold 162. Further, as shown in FIG. 4, the hole of the main body 28 of the gas passage member 27 arranged at the position of the bolt 22D forming the fuel gas introduction manifold 171 communicates with the fuel gas introduction manifold 171 and fuel gas. The hole of the main body 28 of the gas passage member 27 arranged at the position of the bolt 22E forming the discharge manifold 172 communicates with the fuel gas discharge manifold 172.

As shown in FIGS. 3 and 4, between the nut 24 fitted on one side (upper side) of the bolt 22 and the upper surface of the first end plate 104 constituting the upper end of the fuel cell stack 100. A sealing material 52 formed of mica is interposed. The sealing material 52 is formed with holes communicating with each of the above-mentioned through holes 108. The sealing material 52 electrically insulates the upper nut 24 and the first end plate 104 that are adjacent to each other in the arrangement direction with the sealing material 52 in between, and the upper nut 24 and the first end plate 104. The gas sealability between them is ensured. Further, between the nut 24 fitted on the other side (lower side) of the bolt 22 and the gas passage member 27, and the lower surface of the second end plate 106 forming the lower end of the fuel cell stack 100 and the gas. A conductive sealing material 53 is interposed between the passage members 27, respectively. The sealing material 53 is formed with holes communicating with each of the above-mentioned through holes 108. The sealing material 53 ensures the gas sealing property between the second end plate 106, the gas passage member 27, and the lower nut 24. Further, the upper nut 24 and the second end plate 106 are electrically connected via the bolt 22, the lower nut 24, and the gas passage member 27, and are held at substantially the same potential. Further, as described above, by connecting the fuel gas introduction pipe 60 or the like to the branch portion 29 of each gas passage member 27, the upper nut 24 and the second end plate 106 are held at substantially zero (V). Has been done.

(Structure of end plates 104 and 106)
The first and second end plates 104 and 106 are substantially rectangular flat plate-shaped conductive members, and are made of, for example, stainless steel. The first end plate 104 includes a first protruding portion 14 that projects in a direction substantially orthogonal to the arrangement direction (for example, a negative direction on the X-axis). The first protrusion 14 of the first end plate 104 functions as a positive output terminal of the fuel cell stack 100.

(Structure of current collector plate 18)
The current collector plate 18 is a substantially rectangular flat plate-shaped conductive member, and is made of, for example, stainless steel. The current collector plate 18 includes a second protruding portion 16 that protrudes in a direction substantially orthogonal to the arrangement direction (for example, in the positive direction of the X-axis). The protruding portion 16 of the current collector plate 18 functions as an output terminal on the negative side of the fuel cell stack 100.

An insulating material 57 such as mica is interposed between the current collector plate 18 and the second end plate 106. The current collector plate 18 and the second end plate 106, which are two conductive members adjacent to each other in the arrangement direction with the insulating material 57 interposed therebetween, are electrically insulated from each other, and the current collector plate 18 and the second end are electrically insulated from each other. Gas sealability with the plate 106 is ensured.

(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. 3, and FIG. 6 is an explanatory view showing the XZ cross-sectional configuration of the 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.

As shown in FIGS. 5 and 6, the power generation unit 102, which is the minimum unit of power generation, includes a single cell 110, a separator 120, an air pole side frame 130, an air pole side current collector 134, and a fuel pole side frame. It includes 140, a fuel electrode side current collector 144, and a pair of interconnectors 150 that form the uppermost layer and the lowermost layer of the power generation unit 102. Holes corresponding to the through holes 108 into which the bolts 22 described above are inserted are formed in the peripheral edges of the separator 120, the air pole side frame 130, the fuel pole side frame 140, and the interconnector 150 in the Z direction.

The interconnector 150 is a substantially rectangular flat plate-shaped conductive member, and is made 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. 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 end plates 104 and 106, 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.

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 substantially rectangular flat plate-shaped member and contains at least Zr, and solid oxides such as YSZ (yttria-stabilized zirconia), ScSZ (scandia-stabilized zirconia), and CaSZ (calcia-stabilized zirconia). It is formed by objects. The air electrode 114 is a substantially rectangular flat plate-shaped member, and is formed of, for example, a perovskite-type oxide (for example, LSCF (lanternstrontium cobalt iron oxide), LSM (lanternstrontium manganese oxide), LNF (lantern nickel iron)). Has been done. The fuel electrode 116 is a substantially rectangular flat plate-shaped member, and 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, metal. 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 joined to the single cell 110 by a joining portion formed of a brazing material (for example, Ag brazing) 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.

The air electrode side frame 130 is a frame-shaped member in which a substantially rectangular hole 131 penetrating in the vertical direction is formed near the center, and is formed of, for example, an insulator such as mica. The hole 131 of the air electrode side frame 130 constitutes an air chamber 166 facing the air electrode 114. 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 single cell 110 and the peripheral edge of the surface of the interconnector 150 facing the air electrode 114. .. The air electrode side frame 130 electrically insulates between the pair of interconnectors 150 included in the power generation unit 102. As shown in FIG. 5, the air electrode side frame 130 includes an oxidant gas supply communication hole 132 that communicates the oxidant gas introduction manifold 161 and the air chamber 166, and an air chamber 166 and the oxidant gas discharge manifold 162. An oxidant gas discharge communication hole 133 that communicates with the oxidant gas is formed.

The fuel pole side frame 140 is a frame-shaped member in which a substantially rectangular hole 141 penetrating in the vertical direction is formed near the center, and is formed of, for example, metal. Hole 141 of the fuel electrode side frame 140 constitutes a fuel chamber 176 facing the fuel electrode 116. The fuel pole side frame 140 is in contact with the peripheral edge of the surface of the separator 120 facing the single cell 110 and the peripheral edge of the surface of the interconnector 150 facing the fuel pole 116. As shown in FIG. 6, in the fuel electrode side frame 140, the fuel gas supply communication hole 142 that communicates the fuel gas introduction manifold 171 and the fuel chamber 176, and the fuel that communicates the fuel chamber 176 and the fuel gas discharge manifold 172. A gas discharge communication hole 143 is formed.

The fuel electrode side current collector 144 is arranged in the fuel chamber 176. The fuel electrode side current collector 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. However, as described above, since the power generation unit 102 located at the bottom of the fuel cell stack 100 does not have the lower interconnector 150, the interconnector facing portion 146 in the power generation unit 102 is the current collector plate 18. It is in contact with the surface. Since the fuel pole side current collector 144 has such a configuration, the fuel pole 116 and the interconnector 150 (or the current collector plate 18) are electrically connected. 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 electrode side current collector 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 electrode 116 and the interconnector 150 via the fuel electrode side current collector 144 is established. Well maintained. However, as described above, a current collector plate 18 is arranged instead of the interconnector 150 on the lower side of the power generation unit 102 located at the bottom of the fuel cell stack 100 (power generation block 103). 18 is electrically connected to the fuel pole 116 via the fuel pole side current collector 144. Therefore, the current collector plate 18 corresponds to a negative electrode member in the claims. Further, the second end plate 106 corresponds to the negative side conductive member in the claims. Further, the insulating material 57 arranged between the current collector plate 18 and the second end plate 106 corresponds to the negative side insulating member in the claims.

The air pole side current collector 134 is arranged in the air chamber 166. The air electrode side current collector 134 is composed of a plurality of substantially square columnar current collector elements 135, and is formed of, for example, ferritic stainless steel. The air electrode side current collector 134 is in contact with the surface of the air electrode 114 opposite to the side facing the electrolyte layer 112 and the surface of the interconnector 150 on the side facing the air electrode 114. However, as described above, since the power generation unit 102 located at the top of the fuel cell stack 100 does not have the upper interconnector 150, the air electrode side current collector 134 of the power generation unit 102 has a first end. It is in contact with the surface of the plate 104. In this way, the air electrode side current collector 134 electrically connects the air electrode 114 and the interconnector 150 (or the first end plate 104). However, as described above, the first end plate 104 is arranged in place of the interconnector 150 on the upper side of the power generation unit 102 located at the top of the fuel cell stack 100 (power generation block 103), and the first end plate 104 is arranged. The end plate 104 of the above is electrically connected to the air electrode 114 via the air electrode side current collector 134. Therefore, the first end plate 104 corresponds to a positive electrode member in the claims. Further, the nut 24 fitted to one side (upper side) of the bolt 22 corresponds to the positive side conductive member in the claims. Further, the sealing material 52 arranged between the first end plate 104 and the upper nut 24 corresponds to the positive side insulating member in the claims.

A-2. Operation of each fuel cell stack 100:
As shown in FIGS. 3 and 5, the oxidant gas is passed through an oxidant gas introduction pipe (not shown) connected to a branch portion 29 of the gas passage member 27 provided at the position of the oxidant gas introduction manifold 161. When the OG is supplied, the oxidant gas OG is supplied to the oxidant gas introduction manifold 161 through the holes of the branch portion 29 and the main body portion 28 of the gas passage member 27, and each power generation unit is supplied from the oxidizer gas introduction manifold 161. It is supplied to the air chamber 166 through the oxidant gas supply communication hole 132 of 102. Further, as shown in FIGS. 4 and 6, the fuel gas is passed through the fuel gas introduction pipe 60 (see FIG. 1) connected to the branch portion 29 of the gas passage member 27 provided at the position of the fuel gas introduction manifold 171. When the FG is supplied, the fuel gas FG is supplied to the fuel gas introduction manifold 171 through the holes of the branch portion 29 and the main body portion 28 of the gas passage member 27, and the fuel of each power generation unit 102 is supplied from the fuel gas introduction manifold 171. It is supplied to the fuel chamber 176 via the gas supply communication hole 142.

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, power is generated by the electrochemical reaction of the oxidant gas OG and the fuel gas FG in the single cell 110. Will be. 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 via the air pole side current collector 134, and the fuel pole 116 is via the fuel pole side current collector 144. It is electrically connected to the other interconnector 150. 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 first protruding portion 14 of the first end plate 104 and the second protruding portion 16 of the current collector plate 18 that function as output terminals. 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 FIGS. 3 and 5, the oxidant off-gas OOG discharged from the air chamber 166 of each power generation unit 102 is discharged to the oxidant gas discharge manifold 162 through the oxidant gas discharge communication hole 133, and further oxidized. Oxidizing agent gas discharge pipe (not shown) connected to the branch portion 29 through the holes of the main body portion 28 and the branch portion 29 of the gas passage member 27 provided at the position of the agent gas discharge manifold 162 (not shown). ) To the outside of the fuel cell stack 100. Further, as shown in FIGS. 4 and 6, the fuel off-gas FOG discharged from the fuel chamber 176 of each power generation unit 102 is discharged to the fuel gas discharge manifold 172 through the fuel gas discharge communication hole 143, and further, the fuel gas. The fuel cell stack is passed through the holes of the main body 28 and the branch 29 of the gas passage member 27 provided at the position of the discharge manifold 172, and the fuel off gas discharge pipe 70 (see FIG. 1) connected to the branch 29. It is discharged to the outside of 100.

A-3. Electrical connection relationship in fuel cell system 10:
Hereinafter, for each of the four fuel cell stacks 100, in order from the one having the highest potential, "first fuel cell stack 100A", "second fuel cell stack 100B", "third fuel cell stack 100C", It is called "fourth fuel cell stack 100D".

As shown in FIG. 1, the current collector plate 18 of the first fuel cell stack 100A and the first end plate 104 of the second fuel cell stack 100B are electrically connected via the first conductor L1. The current collector plate 18 of the second fuel cell stack 100B and the first end plate 104 of the third fuel cell stack 100C are electrically connected to each other via the second conductor L2. The current collector plate 18 of the fuel cell stack 100C of No. 3 and the first end plate 104 of the fourth fuel cell stack 100D are electrically connected via the third conductor L3. As a result, the four power generation blocks 103 provided in each of the first fuel cell stack 100A, the second fuel cell stack 100B, the third fuel cell stack 100C, and the fourth fuel cell stack 100D are in this order. They are electrically connected in series. Of the four fuel cell stacks 100, the first protruding portion 14 of the first end plate 104 included in the first fuel cell stack 100A having the highest potential functions as a positive output terminal of the fuel cell system 10. Further, the second protruding portion 16 of the current collector plate 18 included in the fourth fuel cell stack 100D having the lowest potential functions as an output terminal on the negative side of the fuel cell system 10.

The fuel gas introduction pipe 60 is a pipe for introducing the fuel gas FG into the fuel gas introduction manifold 171 of each fuel cell stack 100, and is made of a conductive material such as stainless steel. Specifically, as shown in FIG. 1, the fuel gas introduction pipe 60 includes, for example, a hollow tubular common portion 62 extending along the arrangement direction (X-axis direction) of the fuel cell stack 100, and the common portion 62. Includes a plurality of hollow tubular branching portions 64 branched from the side surface. The holes of each branch portion 64 communicate with the holes of the common portion 62. The tip of each branch 64 on the fuel cell stack 100 side is connected to a gas passage member 27 communicating with the fuel gas introduction manifold 171 of each fuel cell stack 100.

The fuel off-gas discharge pipe 70 is a pipe for discharging the fuel off-gas FOG discharged from the fuel gas introduction manifold 171 of each fuel cell stack 100 to the outside, and is made of a conductive material such as stainless steel. Specifically, as shown in FIG. 1, the fuel off-gas discharge pipe 70 includes, for example, a hollow tubular common portion 72 extending along the arrangement direction (X-axis direction) of the fuel cell stack 100, and the common portion 72. It includes a plurality of hollow tubular branch portions 74 branched from the side surface. The holes of each branch portion 74 communicate with the holes of the common portion 72. The tip of each branch 74 on the fuel cell stack 100 side is connected to a gas passage member 27 communicating with the fuel gas discharge manifold 172 of each fuel cell stack 100.

In the present embodiment, the current collector plate 18 of the second fuel cell stack 100B (hereinafter, referred to as “specific current collector plate 18T”) and the first end plate 104 of the third fuel cell stack 100C (hereinafter, “specification”). The second conductor L2 connected to the end plate 104T) is connected to the fuel gas introduction pipe 60 via the connection line L4, and the fuel gas introduction pipe 60 is grounded. .. For example, the area of the cross section orthogonal to the axial direction of the connecting line L4 is smaller than the area of the cross section orthogonal to the axial direction of the second conductor L2, so that the specific resistance value of the connecting line L4 becomes the second conductor. It is larger than the intrinsic resistance value of L2. Therefore, during normal operation of the fuel cell system 10, almost no current flows through the connection line L4. As a result, the specific current collector plate 18T and the specific end plate 104T are held at substantially zero (V) via the second conductor L2 and the fuel gas introduction pipe 60. Further, the connection line L4 is provided with a resistance element 500. The resistance value of the resistance element 500 (about 100 kΩ to 1 MΩ) is larger than the natural resistance value of the second conductor L2 and the connecting wire L4. Thereby, for example, when the first conductor L1 or the third conductor L3 comes into contact with the fuel gas introduction pipe 60 and is short-circuited, it is possible to suppress a large current from flowing through the fuel cell stack 100. The specific end plate 104T corresponds to a specific positive pole member in the claims, and the specific current collector plate 18T corresponds to a specific negative pole member in the claims.

A-4. Conditions for reducing the maximum potential difference of the fuel cell system 10:
Hereinafter, the potential at which the specific current collector plate 18T and the specific end plate 104T are held is referred to as “specific potential V1”. Further, the first end plate 104 having the highest potential among the potentials of the first end plate 104 provided in each of the four fuel cell stacks 100 (the first end provided in the first fuel cell stack 100A). The potential of the plate 104) is hereinafter referred to as "the highest potential VH of the fuel cell system 10", and the lowest potential current collector plate 18 among the four current collector plates 18 provided in each of the four fuel cell stacks 100 The potential of (the current collector plate 18 provided in the fourth fuel cell stack 100D) is hereinafter referred to as "the lowest potential VL of the fuel cell system 10". Further, the potentials of the upper nut 24 and the second end plate 106 are hereinafter referred to as "reference potential VG". Further, the total number of fuel cell stacks 100 in the entire fuel cell system 10 is k, the number of fuel cell stacks 100 located between the maximum potential VH and the specific potential V1 is h, and the specific potential V1 and the minimum potential VL are defined. Let m be the number of fuel cell stacks 100 located between and. In the present embodiment, as described above, the upper nut 24 and the second end plate 106 are electrically connected to the fuel gas introduction pipe 60 and the like, so that the reference potential VG is set to zero (V). It is held.

In 100 of this embodiment, the conditions shown in the following relational expressions (1) and (2) are satisfied.
| "Maximum potential VH (= V1 + h · VS) of fuel cell system 10"-"Reference potential VG" | <| "System voltage VA (= k · VS)"-"Reference potential VG" |
| "Minimum potential VL (= V1-m · VS) of fuel cell system 10"-"Reference potential VG" | <| "System voltage VA"-"Reference potential VG" |
The "system voltage VA" in the relational expressions (1) and (2) means the maximum potential VH of the fuel cell system 10 when not connected. The maximum potential VH of the fuel cell system 10 corresponds to the potential of the positive pole member having the highest potential in the claims, and the minimum potential VL of the fuel cell system 10 corresponds to the potential of the negative pole member having the lowest potential in the claims. Corresponds to. Further, the reference potential VG corresponds to the potential of the positive side conductive member and the potential of the negative side conductive member in the claims. The system voltage VA corresponds to the total voltage of the plurality of electrochemical reaction cell stacks in the claims.

The relational expression (1) is a potential difference between the first end plate 104 provided in the first fuel cell stack 100A having the highest potential and the upper nut 24 provided in the first fuel cell stack 100A. The conditions regarding (hereinafter referred to as "maximum potential difference") are shown. That is, | "maximum potential VH of the fuel cell system 10"-"reference potential VG" | means the maximum potential difference in the fuel cell system 10. | "System voltage VA"-"reference potential VG" | refers to the maximum potential difference (hereinafter referred to as "maximum potential difference when not connected") when the specific current collector plate 18T and the specific end plate 104T are not held at the specific potential V1. means. Therefore, the relational expression (1) means that the maximum potential difference in the fuel cell system 10 is smaller than the maximum potential difference when not connected.

Next, the relational expression (2) is a combination of the current collector plate 18 provided in the fourth fuel cell stack 100D having the lowest potential and the second end plate 106 provided in the fourth fuel cell stack 100D. The conditions regarding the potential difference between them (hereinafter referred to as "minimum potential difference") are shown. That is, | "minimum potential VL of the fuel cell system 10"-"reference potential VG" | means the minimum potential difference in the fuel cell system 10. Therefore, the relational expression (2) means that the minimum potential difference in the fuel cell system 10 is smaller than the maximum potential difference when not connected.
The second fuel cell stack 100B corresponds to the first electrochemical reaction cell stack in the claims, and the third fuel cell stack 100C corresponds to the second electrochemical reaction cell stack in the claims. Corresponds to. Further, the fuel gas introduction pipe 60 corresponds to a pipe in the claims, and the second conductor L2 and the connecting line L4 correspond to the conductors in the claims.

FIG. 7 is an explanatory diagram showing the overall configuration of the fuel cell system 10X in the comparative example. As shown in FIG. 7, in the fuel cell system 10X of the comparative example, none of the first to third conductors L1 to L3 is held at a predetermined potential, and the minimum potential VL of the fuel cell system 10 is zero ( It is assumed that it is held at V) and the reference potential VG is held at zero (V). In the fuel cell system 10X of the comparative example, the specific potential V1 = +2 · VS (V) (specifically +40 (V)), and the maximum potential VH of the fuel cell system 10X of the comparative example is +4 · VS (V). ) (Specifically, +80 (V)). Therefore, the maximum potential difference in the fuel cell system 10X of the comparative example is 4.VS (V), which is the same as the maximum potential difference (4.VS (V)) when not connected, and satisfies the above relational expression (1). do not have. The minimum potential difference in the fuel cell system 10X of the comparative example is zero (V) and satisfies the above relational expression (2).

On the other hand, as shown in FIG. 1, in the present embodiment, the specific potential V1 = the potential V2 of the specific end plate 104T = approximately 0 (V), and the maximum potential VH of the fuel cell system 10 is +2 · VS (V). (Specifically, it is +40 (V)). Therefore, the maximum potential difference in the fuel cell system 10 is 2.VS (V), which is smaller than the maximum potential difference (4.VS (V)) when not connected, and therefore satisfies the above relational expression (1). Further, the minimum potential difference in the fuel cell system 10 is also 2.VS (V), which satisfies the above relational expression (2). That is, according to the fuel cell system 10 of the present embodiment, the maximum potential difference is smaller than that of the fuel cell system 10X of the comparative example, and the minimum potential difference is suppressed to be larger than the maximum potential difference when not connected. Has been done. In the example of FIG. 1, if the specific potential V1 is larger than −40 (V) and smaller than +40 (V), both of the above relational expressions (1) and (2) are satisfied. Therefore, the reference potential VG and the specific potential V1 may be held at different potentials from each other. For example, the reference potential VG may be held at zero (V) and the specific potential V1 may be held at +30 (V).

A-5. Effect of this embodiment:
In the fuel cell system 10 of the present embodiment, the specific current collecting plate 18T provided in the second fuel cell stack 100B and the specific end plate 104T provided in the third fuel cell stack 100C are second conductive. It is held at a specific potential V1 via the body L2 or the like. Then, in the fuel cell system 10 of the present embodiment, as described above, the above relational expression (1) is satisfied. Therefore, the potentials of the specific current collector plate 18T and the specific end plate 104T are zero as compared with the configuration in which the specific current collector plate 18T and the specific end plate 104T are not held at the specific potential V1 (fuel cell system 10X in the above comparative example). Since it is close to (V), the maximum potential VH of the fuel cell system 10 can be lowered. Further, since the maximum potential VH of the fuel cell system 10 is low, the sealing material 52 is damaged due to the large potential difference between the first end plate 104 and the upper nut 24 in the fuel cell stack 100A. Is suppressed, and short-circuiting between the first end plate 104 and the upper nut 24 is suppressed.

Further, according to the fuel cell system 10 of the present embodiment, the specific current collector plate 18T and the specific end plate 104T are electrically connected to the conductive fuel gas introduction pipe 60 connected to each fuel cell stack 100. By doing so, it is held at a specific potential V1. Therefore, the maximum potential VH of the fuel cell system 10X can be lowered without separately requiring a dedicated configuration for holding the specific current collector plate 18T and the specific end plate 104T at the specific potential V1.

Further, according to the fuel cell system 10 of the present embodiment, the two fuel cell stacks 100 held at the specific potential V1 are substantially in the middle of the four fuel cell stacks 100 in the order in which the power generation blocks 103 are connected in series. The second fuel cell stack 100B and the third fuel cell stack 100C are located. Therefore, the two fuel cell stacks 100 held at the specific potential V1 are, for example, the first fuel cell stack 100A and the second fuel cell stack 100B, or the third fuel cell stack 100C and the fourth. It is possible to effectively suppress that the minimum potential VL of the fuel cell system 10 becomes too low while lowering the maximum potential VH of the fuel cell system 10 as compared with the configuration of the fuel cell stack 100D of the above. ..

B. Second embodiment:
FIG. 8 is an explanatory diagram showing the overall configuration of the fuel cell system 10Y according to the second embodiment. The fuel cell system 10Y of the second embodiment has a different configuration for holding the specific current collector plate 18T and the specific end plate 104T at the specific potential V1 from the fuel cell system 10 of the first embodiment described above. In the following, among the configurations of the fuel cell system 10Y of the second embodiment, the same configurations as those of the fuel cell system 10 of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

B-1. Constitution:
As shown in FIG. 8, the fuel cell system 10Y of the second embodiment includes a first fuel cell stack 100A and a second fuel cell stack 100B. The current collector plate 18 of the first fuel cell stack 100A (hereinafter referred to as “specific current collector plate 18T”) and the first end plate 104 of the second fuel cell stack 100B (hereinafter referred to as “specific end plate 104T”). ) Are electrically connected via the first conductor L1Y. As a result, the two power generation blocks 103 provided in the first fuel cell stack 100A and the second fuel cell stack 100B are electrically connected in series in this order. Further, in the fuel cell system 10Y, the first fuel cell stack 100A and the second fuel cell stack 100B are collectively housed in one heat insulating container 12Y. The heat insulating container 12Y has a structure in which a heat insulating material is provided on the inner side surface of a housing made of, for example, stainless steel, and the conductive housing is grounded.

The first conductor L1Y connected between the specific current collector plate 18T and the specific end plate 104T is electrically connected to the housing of the heat insulating container 12Y via the connection line L2Y. For example, the area of the cross section orthogonal to the axial direction of the connecting line L2Y is smaller than the area of the cross section orthogonal to the axial direction of the first conductor L1Y, so that the specific resistance value of the connecting line L2Y becomes the first conductor. It is larger than the intrinsic resistance value of L1Y. Therefore, during normal operation of the fuel cell system 10Y, almost no current flows through the connection line L2Y. Therefore, the specific potential V1 of the specific current collector plate 18T and the specific end plate 104T is held at substantially zero (V) via the housing of the connecting line L2Y and the heat insulating container 12Y. The first conductor L1Y and the connecting wire L2Y correspond to the conductors in the claims.

B-2. Effect of this embodiment:
In the fuel cell system 10Y of the present embodiment, the specific potential V1 = the potential V2 of the specific end plate 104T = approximately 0 (V), and the maximum potential difference is 2.VS (V) (specifically, 20 (V)). be. Therefore, for the fuel cell system 10Y, the relational expression (1) in the above-described first embodiment is satisfied. Specifically, the maximum potential VH of the fuel cell system 10Y (the potential of the first end plate 104 included in the first fuel cell stack 100A having the maximum potential) is + VS (V) (specifically, +20 (V)). ), And the lowest potential VL of the fuel cell system 10Y (the potential of the current collector plate 18 provided in the second fuel cell stack 100B of the lowest potential) is -VS (V) (specifically, -20 (V). )). Therefore, the potentials of the specific current collector plate 18T and the specific end plate 104T are closer to zero (V) as compared with the configuration in which the specific current collector plate 18T and the specific end plate 104T are not held at the specific potential V1, so that the fuel cell The maximum potential VH of the system 10Y can be lowered, and the maximum potential difference can be reduced.

Further, according to the fuel cell system 10Y, the specific current collector plate 18T and the specific end plate 104T are electrically connected to a conductive housing for accommodating the first fuel cell stack 100A and the second fuel cell stack 100B. By being connected to, it is held at a specific potential V1. Therefore, the maximum potential VH of the fuel cell system 10Y can be lowered without separately requiring a dedicated configuration for holding the specific current collector plate 18T and the specific end plate 104T at the specific potential V1.

B-3. Modification example of the second embodiment:
FIG. 9 is an explanatory diagram showing the overall configuration of the fuel cell system 10Z in the modified example of the second embodiment. In the fuel cell system 10Z of the present modification, the first fuel cell stack 100A is housed in the first heat insulating container 12Z, and the second fuel cell stack 100B is housed in the second heat insulating container 14Z. The first heat insulating container 12Z and the second heat insulating container 14Z have a configuration in which a heat insulating material is provided on the inner surface of a housing made of, for example, stainless steel, and the conductive housing is grounded.

The first conductor L1Y connected between the specific current collector plate 18T and the specific end plate 104T is electrically connected to the housing of the first heat insulating container 12Z via the connection line L2Z. For example, the area of the cross section orthogonal to the axial direction of the connecting line L2Z is smaller than the area of the cross section orthogonal to the axial direction of the first conductor L1Y, so that the specific resistance value of the connecting line L2Z becomes the first conductor. It is larger than the intrinsic resistance value of L1Y. Therefore, during normal operation of the fuel cell system 10Z, almost no current flows through the connection line L2Z. Therefore, the specific potential V1 of the specific current collector plate 18T and the specific end plate 104T is held at substantially zero (V) via the connection line L2Z and the housing of the heat insulating container 12Y. The first conductor L1Y and the connecting wire L2Z correspond to the conductors in the claims. The first conductor L1Y connected between the specific current collector plate 18T and the specific end plate 104T may be electrically connected to the housing of the second heat insulating container 14Z.

According to the fuel cell system 10Z of the present modification, as in the fuel cell system 10Y described above, the specific current collector plate 18T and the specific end plate 104T are not held at the specific potential V1 as compared with the specific current collector plate 18T and the specific end plate 104T. Since the potential of the specific end plate 104T is close to zero (V), the maximum potential VH of the fuel cell system 10Z can be lowered. Further, the maximum potential VH of the fuel cell system 10Z can be lowered without separately requiring a special configuration for holding the specific current collector plate 18T and the specific end plate 104T at the specific potential V1.

C. Modification example:
The technique disclosed in the present specification is not limited to the above-described embodiment, and can be transformed into various forms without departing from the gist thereof. For example, the following modifications are also possible.

In the first embodiment, the number of fuel cell stacks 100 provided in the fuel cell system 10 is four, but it may be two, three, or five or more. When the number of fuel cell stacks 100 is 6 or more, the two fuel cell stacks 100 (first electrochemical reaction cell stack and second electrochemical reaction cell stack) held at a specific potential are specified cell stacks. It is preferably included in the group. In the specific cell stack group, for example, when the number of fuel cell stacks 100 is 6, one or two fuels located in the center of the six fuel cell stacks 100 in the order in which the power generation blocks 103 are connected in series. The fuel cell stacks 100 include the battery stacks 100, and the order of arrangement is continuous, for the number (2) of the total number (1/3) or less. As a result, the maximum potential VH of the fuel cell system 10 is lowered and the minimum potential VL of the fuel cell system 10 is lowered as compared with the case where the two fuel cell stacks 100 held at the specific potentials are not included in the specific cell stack group. Can be suppressed from becoming too low.

In the first embodiment, when the number of the fuel cell stacks 100 is an odd number (five or more), the two fuel cell stacks 100 (the first electrochemical reaction cell stack and the second electrochemical reaction cell stack) are held at a specific potential. The electrochemical reaction cell stack) is composed of one fuel cell stack 100 located in the center and another fuel cell stack 100 which is arranged in front of or behind the one fuel cell stack 100 in the order in which they are connected in series. It is preferable to have. As a result, the minimum potential VL of the fuel cell system 10 is lower while lowering the maximum potential VH of the fuel cell system 10 as compared with the configuration in which the two fuel cell stacks 100 held at the specific potentials are not located substantially in the center. It is possible to prevent it from becoming too much.

In the first embodiment, the specific current collector plate 18T and the specific end are provided by a conductor different from the second conductor L2 that connects the second fuel cell stack 100B and the third fuel cell stack 100C in series. The plate 104T may be connected to the fuel gas introduction pipe 60. Further, in the first embodiment, it is assumed that the fuel gas introduction pipe 60 is grounded, but the fuel gas introduction pipe 60 may not be grounded as long as the above relational expression (1) is satisfied. Further, it is said that the current collector plate 18 and the first end plate 104 provided in each of the four fuel cell stacks are connected via the conductors L1 to L3, but the current collector plate 18 and the first end plate 104 The end plate 104 may be electrically connected by being directly connected by a fastening member or the like (not shown). Further, also in the second embodiment, the heat insulating container 12Y and the first heat insulating container 12Z may not be grounded as long as the above relational expression (1) is satisfied.

Further, in the first embodiment, the second conductor L2 is connected to the fuel gas introduction pipe 60 via the connecting line L4, but the second conductor L2 is connected to the fuel gas introduction pipe 60 via the connecting line L4. Instead, it may be connected to the fuel gas introduction pipe 60. Further, instead of the second conductor L2, the first conductor L1 or the third conductor L3 may be held at the specific potential V1 by being connected to the fuel gas introduction pipe 60 or the like. Further, in the first embodiment, the resistance element 500 may not be provided on the connection line L4.

In the first embodiment, the specific current collector plate 18T and the specific end plate 104T are not limited to the fuel gas introduction pipe 60, but are electrically connected to the fuel off gas discharge pipe 70, the oxidant gas introduction pipe, and the oxidant off gas discharge pipe. By being connected, it may be held at a specific potential V1. In short, the specific current collector plate 18T and the specific end plate 104T are connected to a gas pipe communicating with either the air chamber 166 facing the air electrode 114 or the fuel chamber 176 facing the fuel electrode 116 in the fuel cell stack 100. It suffices if they are connected to each other. Further, the specific current collector plate 18T and the specific end plate 104T may be connected not only to the above gas pipe but also to a conductive pipe other than the gas pipe.

In the above embodiment, the specific potential V1 and the reference potential VG are assumed to be substantially zero (V), but as long as the above relational expressions (1) and (2) are satisfied, they may not be substantially zero (V). .. For example, in the fuel cell system 10X of the comparative example shown in FIG. 7, the reference potential VG is assumed to be +30 (V). Then, the maximum potential VH is +80 (V), and the upper nut 24 (positive side conductive member) electrically connected to the second end plate 106 is approximately +30 (V), and the maximum potential difference is Is 50 (V), which is the same as the maximum potential difference when not connected, and does not satisfy the above relational expression (1). On the other hand, in the fuel cell system 10 of the present embodiment shown in FIG. 1, the reference potential VG is assumed to be +30 (V). Then, the specific potential V1 is also +30 (V), and the maximum potential VH is +70 (V). As a result, the maximum potential difference in the fuel cell system 10 is 40 (V), which is smaller than the maximum potential difference when not connected, and therefore satisfies the above relational expression (1). Further, the minimum potential difference in the fuel cell system 10 is 10 (V), which satisfies the above relational expression (2). That is, according to the fuel cell system 10 of the present modification, the maximum potential difference is smaller than that of the fuel cell system 10X of the comparative example, and the minimum potential difference is suppressed to be larger than the maximum potential difference when not connected. Has been done. In this modification, if the specific potential V1 is larger than +20 (V) and smaller than +40 (V), both the above relational expressions (1) and (2) are satisfied.

In the fuel cell system 10 of the first embodiment, the two fuel cell stacks 100 held at the specific potential V1 are the first fuel cell stack 100A and the second fuel cell stack 100B, or a third fuel cell stack 100B. The fuel cell stack 100C and the fourth fuel cell stack 100D may be configured. Even with these configurations, the maximum potential VH of the fuel cell system 10 can be lowered.

In the first embodiment, in each fuel cell stack 100, the fuel gas introduction pipe 60 is electrically connected to the second end plate 106, and the gas passage member 27, the lower nut 24, and the bolt 22 are connected. It may be configured to be electrically connected to the upper nut 24 via the structure. In such a configuration, the specific current collector plate 18T and the specific end plate 104T are attached to the second end plate 106 provided in the second fuel cell stack 100B via a conductor such as the fuel gas introduction pipe 60. It is electrically connected. As a result, the second fuel cell is compared with a configuration in which the specific current collector plate 18T and the specific end plate 104T are not electrically connected to the second end plate 106 provided in the second fuel cell stack 100B. In the stack 100B, since the potential difference between the current collector plate 18 and the second end plate 106 becomes smaller, it is possible to prevent the current collector plate 18 and the second end plate 106 from short-circuiting. Further, the specific current collector plate 18T and the specific end plate 104T are electrically connected to the upper nut 24 provided in the third fuel cell stack 100C via a conductor such as a fuel gas introduction pipe 60. There is. As a result, the third fuel cell stack 100C is compared with the configuration in which the specific current collector plate 18T and the specific end plate 104T are not electrically connected to the upper nut 24 provided in the third fuel cell stack 100C. Since the potential difference between the first end plate 104 and the upper nut 24 becomes smaller, it is possible to prevent the first end plate 104 and the upper nut 24 from short-circuiting.

In the present specification, "output voltage is substantially the same" and "substantially the same potential" are not limited to the case where the voltage or potential is not necessarily completely the same, but ± 5% (when the average is 20 (V), ± It also includes cases where there is an error of 1 (V) or less).

In the above embodiment, in each fuel cell stack 100, the first end plate 104 and the upper nut 24 are insulated via the sealing material 52, but the power generation block 103 and the first end plate 104 A terminal plate may be separately provided between the first end plate 104 and the glass may be arranged between the first end plate 104 and the terminal plate. Even in a fuel cell system having such a configuration, the maximum potential of the fuel cell system can be lowered by applying the present invention. Further, since the maximum potential of the fuel cell system is low, it is possible to prevent the insulating member from being damaged due to the large potential difference between the first end plate 104 and the terminal plate, and the first end plate. The short circuit between the 104 and the terminal plate is suppressed.

Further, in the above embodiment, the fuel cell stack 100 has a configuration in which a plurality of flat plate-shaped single cells 110 are laminated, but the present invention is described in another configuration, for example, International Publication No. 2012/1655409. As described above, the same applies to a configuration in which a plurality of substantially cylindrical fuel cell single cells are connected in series.

Further, 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 comprises an 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 uses it to generate 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 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 through 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 through hole 108. By applying the present invention, the maximum potential of the stack connector can be lowered even in an electrolytic single cell having such a configuration.

Further, in the above embodiment, the solid oxide fuel cell (SOFC) has been described as an example, but the present invention also applies to other types of fuel cells (or electrolytic cells) such as the molten carbonate fuel cell (MCFC). Applicable.

10, 10X, 10Y, 10Z: Fuel cell system 12Y: Insulation container 12Z: First insulation container 14: First protrusion 14Z: Second insulation container 16: Second protrusion 18: Current collector plate 18T: Specified current collector 22: Bolt 24: Nut 27: Gas passage member 28: Main body 29: Branch 52: Sealing material 53: Sealing material 57: Insulating material 60: Fuel gas introduction pipe 62: Common part 64: Branching part 70 : Fuel off gas discharge pipe 72: Common part 74: Branch part 100, 100A, 100B, 100C, 100D: Fuel cell stack 102: Power generation unit 103: Power generation block 104, 106: End plate 104T: Specific end plate 108: Through hole 110 : Single cell 112: Electrolyte layer 114: Air pole 116: Fuel pole 120: Separator 121: Hole 130: Air pole side frame 131: Hole 132: Oxidizing agent gas supply communication hole 133: Oxidizing agent gas discharge communication hole 134: Air electrode Side current collector 135: Current collector element 140: Fuel pole side frame 141: Hole 142: Fuel gas supply communication hole 143: Fuel gas discharge communication hole 144: Fuel pole side current collector 145: Electrode facing part 146: Interconnector Opposing 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 500: Resistance Element FG: Fuel gas FOG: Fuel off gas L1, L1Y: First conductor L2: Second conductor L2Y, L2Z, L4: Connection line L3: Third conductor OG: Oxidizing agent gas OOG: Oxidizing agent off gas V1: Specific potential V2: Potential VA: System voltage VG: Reference potential VH: Maximum potential VL: Minimum potential VS: Stack voltage

Claims (5)

A stack connector with multiple electrochemical reaction cell stacks
Each of the electrochemical reaction cell stacks
A cell block in which a plurality of single cells including an electrolyte layer, an air electrode, and a fuel electrode are arranged side by side in the first direction, and
A positive pole member arranged on one side of the first direction with respect to the cell block and electrically connected to the air pole.
A positive-side conductive member arranged on the opposite side of the positive pole member from the cell block and having conductivity, and a positive-side conductive member.
A positive insulating member arranged between the positive electrode member and the positive conductive member and having an insulating property,
A negative pole member arranged on the other side of the first direction and electrically connected to the fuel pole,
A negative conductive member which is arranged on the opposite side of the cell block with respect to the negative electrode member, has conductivity, and is electrically connected to the positive conductive member.
A negative-side insulating member arranged between the negative-pole member and the negative-side conductive member and having an insulating property,
Is equipped with
A plurality of the cell blocks provided in each of the plurality of electrochemical reaction cell stacks are electrically connected in series, and the negative side conductive member provided in each of the plurality of electrochemical reaction cell stacks. In stack connections where are electrically connected to each other
Among the plurality of electrochemical reaction cell stacks, the specific negative electrode member which is the negative electrode member provided in the first electrochemical reaction cell stack and the specific negative electrode member provided in the second electrochemical reaction cell stack are provided. By holding the specific positive pole member, which is the positive pole member electrically connected to the pole member, at a specific potential via a conductor,
The potential obtained by adding the potential difference between the positive pole member and the specific negative pole member at the highest potential to the specific potential is defined as the potential of the positive pole member at the highest potential.
The potential obtained by subtracting the potential difference between the specific positive pole member and the negative pole member having the lowest potential from the specific potential is defined as the potential of the negative pole member having the lowest potential.
The absolute value of the difference between the potential of the positive electrode member and the potential of the positive conductive member having the highest potential is the difference between the total voltage of the plurality of electrochemical reaction cell stacks and the potential of the positive conductive member. Less than the absolute value of
The absolute value of the difference between the potential of the negative pole member and the potential of the negative conductive member at the lowest potential is the total voltage of the plurality of electrochemical reaction cell stacks and the potential of the negative conductive member. A stack connector characterized by being less than the absolute value of the difference between. In the stack connector according to claim 1, further
A conductive tube connected to each of the electrochemical reaction cell stacks is provided.
A stack connection body characterized in that the specific negative pole member and the specific positive pole member are held at the specific potential by being electrically connected to the tube via the conductor. In the stack connector according to claim 1 or 2.
The stack connector further
It comprises a conductive housing that houses at least one of the plurality of electrochemical reaction cell stacks.
A stack connection body characterized in that the specific negative pole member and the specific positive pole member are held at the specific potential by being electrically connected to the housing via the conductor. In the stack connection according to any one of claims 1 to 3,
The total number of the plurality of electrochemical reaction cell stacks is 6 or more.
Among the plurality of electrochemical reaction cell stacks, the order in which the cell blocks are connected in series includes one or two the electrochemical reaction cell stacks located in the middle, and the order is continuous. When a plurality of the electrochemical reaction cell stacks of 1/3 or less of the number are used as a specific cell stack group,
A stack connector, wherein the first electrochemical reaction cell stack and the second electrochemical reaction cell stack are included in the specific cell stack group. In the stack connection according to any one of claims 1 to 3,
When the total number of the plurality of electrochemical reaction cell stacks is an even number of 4 or more, the first electrochemical reaction cell stack and the second electrochemical reaction cell stack are arranged in series connection of the cell blocks. In order, a pair of electrochemical reaction cell stacks located in the middle,
When the total number of the plurality of electrochemical reaction cell stacks is an odd number of 5 or more, the first electrochemical reaction cell stack and the second electrochemical reaction cell stack are in the middle in the order in which they are connected in series. A stack connector, characterized in that it is one electrochemical reaction cell stack located in, and another electrochemical reaction cell stack in the order of front or back of the one electrochemical reaction cell stack.

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