Fuel cell stack

Abstract

A fuel cell stack disclosed in the present specification has a plurality of sub-units stacked. Each sub-unit has a pair of pressurizing plates, a plurality of single cells stacked between the pair of pressurizing plates, and a link member that pressurizes the plurality of single cells in a stacking direction and links the pair of pressurizing plates. A hydrogen flow path through which hydrogen used for reaction in the single cells passes and an oxygen flow path through which oxygen passes are provided in each pressurizing plate. Two adjacent sub-units are connected to each other, and the hydrogen flow paths of the two adjacent sub-units are connected to each other and the oxygen flow paths are connected to each other. Since each sub-unit pressurizes the single cells, a housing that pressurizes the entire FC stack is not needed.

Description

Technical Field

[0001] The technology disclosed in this specification relates to fuel cell stacks. Background Technology

[0002] Fuel cell stacks have a structure consisting of multiple stacked individual cells. In a fuel cell stack, a stack of multiple individual cells is placed in a housing and held under pressure along the stacking direction (e.g., Japanese Patent Application Laid-Open No. 2005-056814, Japanese Patent Application Laid-Open No. 2012-059712). Alternatively, sometimes a frame holds the stack of multiple individual cells instead of a housing (e.g., Japanese Patent Application Laid-Open No. 2023-134285). The frame holds the stack under pressure in the stacking direction.

[0003] User requirements related to the output of fuel cells vary widely. The output of a fuel cell is determined by the number of stacked individual cells. That is, the number of stacked individual cells needs to be varied according to user requirements. Manufacturing the casing or frame according to the number of stacked cells increases the cost. This specification provides a technology for achieving a fuel cell stack with an output (number of stacked individual cells) corresponding to user requirements at low cost. Summary of the Invention

[0004] The fuel cell stack disclosed in this specification comprises multiple stacked sub-units. Each sub-unit includes: a pair of pressure plates; multiple individual cells stacked between the pair of pressure plates; and connecting components that pressurize the multiple individual cells in the stacking direction and connect them to the pair of pressure plates. Each pressure plate is provided with a hydrogen flow path for hydrogen used in the reaction within the individual cells and an oxygen flow path for oxygen. Adjacent sub-units are interconnected, and the hydrogen flow paths and oxygen flow paths of adjacent sub-units are interconnected.

[0005] In the fuel cell stack disclosed in this specification, the output (number of individual cells) can be changed by altering the number of connected sub-units. Multiple individual cells are pressurized through the sub-units. Therefore, only adjacent sub-units need to be connected; there is no need to pressurize the stack of multiple sub-units. That is, there is no need for a housing or frame that pressurizes the stack of sub-units. Therefore, a fuel cell stack that provides the user's desired output can be achieved at a low cost.

[0006] The detailed description of the technology disclosed in this specification and further improvements are described in the following "Detailed Description". Attached Figure Description

[0007] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals denote the same elements, wherein,

[0008] Figure 1This is a perspective view of the fuel cell stack in an embodiment.

[0009] Figure 2 This is a 3D diagram of a subunit.

[0010] Figure 3 This is a three-dimensional view of a subunit of the first modified example.

[0011] Figure 4 This is a three-dimensional view of a subunit of the second variation. Detailed Implementation

[0012] The fuel cell stack 2 of the embodiment will be described with reference to the accompanying drawings. Figure 1 This is a 3D view of fuel cell stack 2. For ease of explanation, the term "fuel cell stack" will be referred to as "FC stack" below. "FC" is short for "Fuel Cell".

[0013] FC group 2 comprises multiple sub-units 10a, 10b, 10c, 10d, and 10e, and a pair of end plates 30 and 40. The multiple sub-units 10a, 10b, 10c, 10d, and 10e have identical construction. Hereinafter, without distinguishing which of the multiple sub-units 10a, 10b, 10c, 10d, and 10e is referred to as sub-unit 10. The multiple sub-units 10 are stacked, and the stack of sub-units 10 is held by a pair of end plates 30 and 40. The X-direction of the coordinate system in the attached figures is aligned with the stacking direction. Figure 1 In the first case, there are 5 sub-units 10 stacked, but in FC group 2, the number of sub-units 10 stacked can be any number.

[0014] Two adjacent subunits 10 are fixed to each other by bolts 51. At one end of subunit 10a, an end plate 40 is fixed by bolts 53. At the other end of subunit 10e, an end plate 30 is fixed by bolts 52.

[0015] Figure 2 This is a 3D diagram representing two subunits, 10a and 10b. Figure 2 In the diagram, sub-unit 10a is depicted to the left of the center line CL, and sub-unit 10b is depicted to the right. Note that in... Figure 2 In the diagram, the viewpoints differ to the right and left of the centerline CL. The right-hand diagram depicts sub-unit 10b from a viewpoint that rotates the coordinate system in the left-hand diagram by 90 degrees around the Z-axis.

[0016] A subunit 10 consists of multiple individual cells 11 of a fuel cell and a pair of pressure plates 12 and 13. The multiple individual cells 11 are stacked. The X-direction of the coordinate system in the figure is aligned with the stacking direction of the multiple individual cells 11. Each individual cell 11 is the power generation unit of the fuel cell. In the case of a solid polymer fuel cell, the membrane electrode assembly (MEA) is equivalent to an individual cell 11. One side of each individual cell in the stacking direction is the positive electrode, and the other side is the negative electrode. High output voltage and output current are obtained by stacking multiple individual cells 11. In the figures, each individual cell 11 is represented by a simple plate, and its detailed structure is omitted from the illustration.

[0017] A stack of multiple individual battery cells 11 is held by a pair of pressure plates 12 and 13. The pair of pressure plates 12 and 13 are connected by four connecting members 14 (one connecting member 14 is hidden within the individual battery cell 11 or pressure plates 12 and 13 and is not visible). When viewed along the X direction of the coordinate system in the attached figure, the four connecting members 14 are arranged to surround the individual battery cell 11. The four connecting members 14 pressurize the multiple individual battery cells 11 along the stacking direction and connect the pressure plates 12 and 13 on both sides of them.

[0018] In subunit 10, pressure plates 12 and 13 are respectively provided with an oxygen supply flow path 21 for supplying oxygen to individual cells 11, a hydrogen supply flow path 22 for supplying hydrogen, and a refrigerant supply flow path 23 for supplying refrigerant. Additionally, pressure plates 12 and 13 are respectively provided with an oxygen discharge flow path 24 for discharging oxygen not used in the reaction, a hydrogen discharge flow path 25 for discharging hydrogen and water not used in the reaction, and a refrigerant discharge flow path 26 for discharging refrigerant after cooling individual cells 11. Individual cells 11 are also provided with the same flow paths, with oxygen supplied through oxygen supply flow path 21 supplied to multiple individual cells 11. Unused oxygen in individual cells 11 is discharged outside subunit 10 through oxygen discharge flow path 24. The same applies to the other flow paths 22, 23, 25, and 26.

[0019] The oxygen supply path 21 of the pressure plate 12 has a protrusion 21a protruding from the outer side of the pressure plate 12 (the side opposite to the adjacent sub-unit 10b) toward the sub-unit 10b. Similarly, the hydrogen supply path 22 (refrigerant supply path 23) also has a protrusion 22a (23a) protruding from the outer side of the pressure plate 12 toward the sub-unit 10b. In addition, the oxygen supply path 21 of the pressure plate 13 of the sub-unit 10b has a recess 21b that engages with the protrusion 21a of the oxygen supply path 21 of the pressure plate 12 of the opposite sub-unit 10a. Similarly, the hydrogen supply path 22 of the pressure plate 13 of the sub-unit 10b has a recess 22b that engages with the protrusion 22a of the hydrogen supply path 22 of the pressure plate 12 of the opposite sub-unit 10a. The refrigerant supply path 23 of the pressure plate 13 of sub-unit 10b has a recess 23b that engages with the protrusion 23a of the refrigerant supply path 23 of the pressure plate 12 of the opposite sub-unit 10a.

[0020] The oxygen discharge path 24 of the pressure plate 13 of sub-unit 10b has a protrusion 24a protruding from the outer side of the pressure plate 13 (the side opposite to the adjacent sub-unit 10a) toward sub-unit 10a. Similarly, the hydrogen discharge path 25 (refrigerant discharge path 26) also has a protrusion 25a (26a) protruding from the outer side of the pressure plate 13 toward sub-unit 10a. In addition, the oxygen discharge path 24 of the pressure plate 12 of sub-unit 10a has a recess 24b that engages with the protrusion 24a of the oxygen discharge path 24 of the pressure plate 13 of the opposite sub-unit 10b. Similarly, the hydrogen discharge path 25 of the pressure plate 12 of sub-unit 10a has a recess 25b that engages with the protrusion 25a of the hydrogen discharge path 25 of the pressure plate 12 of the opposite sub-unit 10b. The refrigerant discharge path 26 of the pressure plate 12 of sub-unit 10a has a recess 26b that engages with the protrusion 26a of the refrigerant discharge path 26 of the pressure plate 13 of the opposite sub-unit 10b.

[0021] In FC group 2, two sub-units 10a and 10b are adjacent. The pressure plate 12 of sub-unit 10a is opposite to the pressure plate 13 of sub-unit 10b, and the two sub-units 10a and 10b are joined together. At this time, the protrusion 21a and the concave portion 21b are fitted together. Similarly, the protrusion 22a (23a) of the pressure plate 12 of sub-unit 10a is fitted together with the concave portion 22b (23b) of the pressure plate 13 of sub-unit 10b. In addition, a gasket (not shown) is provided around the protrusions 21a (22a, 23a), and when the concave portions 21b (22b, 23b) are fitted together, the two are sealed. Similarly, the protrusions 24a (25a, 26a) of sub-unit 10b are fitted together with the concave portions 24b (25b, 26b) of sub-unit 10a.

[0022] Furthermore, the pressure plate 12 of sub-unit 10a is provided with a positive terminal 27a and a negative terminal 28a of a stack of single-cell 11. Both the positive terminal 27a and the negative terminal 28a are convex in shape. The pressure plate 13 of sub-unit 10b is provided with a positive terminal 27b and a negative terminal 28b of a stack of single-cell 11. Both the positive terminal 27a and the negative terminal 28a are concave in shape from the surface of the pressure plate 13. If sub-units 10a and 10b are stacked, the convex positive terminal 27a of sub-unit 10a is fitted with the concave positive terminal 27b of sub-unit 10b. The convex negative terminal 28a of sub-unit 10a is fitted with the concave negative terminal 28b of sub-unit 10b.

[0023] If subunits 10a and 10b are stacked, the plurality of protrusions 21a, 22a, and 23a of subunit 10a engage with the plurality of recesses 21b, 22b, and 23b of subunit 10b. Similarly, the positive end 27a and negative end 28a of the protrusion of subunit 10a engage with the concave positive end 27b and negative end 28b of subunit 10b. Conversely, the plurality of protrusions 24a, 25a, and 26a of subunit 10b engage with the plurality of recesses 24b, 25b, and 26b of subunit 10a. In this way, adjacent subunits 10a and 10b are securely joined together without shifting. Furthermore, adjacent subunits 10a and 10b are connected to each other using bolts 51 through bolt holes 15.

[0024] In all sub-units 10, adjacent sub-units 10 are connected in the same manner. The end plate 30 is connected to the end sub-unit 10e of the FC group 2 via bolts 52. An oxygen supply port 31 connected to the oxygen supply flow path 21 of the sub-unit 10e is provided on the end plate 30. Additionally, a hydrogen supply port 32 (refrigerant supply port 33) connected to the hydrogen supply flow path 22 (refrigerant supply flow path 23) of the sub-unit 10e is provided on the end plate 30. Furthermore, an oxygen discharge port 34 (hydrogen discharge port 35 (refrigerant discharge port 36) connected to the oxygen discharge flow path 24 (hydrogen discharge flow path 25, refrigerant discharge flow path 26) of the sub-unit 10e is provided on the end plate 30. Although not shown in the figure, the end plate 40 connected to the sub-unit 10a has a U-shaped flow path connecting the oxygen supply flow path 21 and the oxygen discharge flow path 24 of the sub-unit 10a. Similarly, the end plate 40 also has a U-shaped flow path connecting other flow paths.

[0025] In the FC system, including FC group 2, oxygen (air) is supplied to oxygen supply port 31, hydrogen is supplied to hydrogen supply port 32, and refrigerant is supplied to refrigerant supply port 33. The oxygen (hydrogen, refrigerant) supplied to oxygen supply port 31 (hydrogen supply port 32, refrigerant supply port 33) is supplied to all individual cells 11 through oxygen supply flow path 21 (hydrogen supply flow path 22, refrigerant supply flow path 23) of each sub-unit 10. The remaining oxygen (hydrogen) used in the individual cells 11 is discharged through oxygen discharge flow path 24 (hydrogen discharge flow path 25) of each sub-unit 10, and finally exits from oxygen discharge port 34 (hydrogen discharge port 35) of end plate 30. Similarly, the refrigerant used in the individual cells 11 is discharged through refrigerant discharge flow path 26 of each sub-unit 10, and finally exits from refrigerant discharge port 36 of end plate 30.

[0026] Multiple individual cells 11 stacked in FC group 2 need to be kept pressurized along the stacking direction. In the FC group 2 of this embodiment, multiple individual cells 11 are kept pressurized in each sub-unit 10. Furthermore, the output of the FC group 2 of this embodiment can be changed by the number of stacked sub-units 10. The number of stacked sub-units 10 in FC group 2 can be changed according to the user's wishes. In this case, it is not necessary to pressurize the entire stack of multiple sub-units 10. Adjacent sub-units 10 can be connected without separation. In the case of the FC group 2 of this embodiment, two adjacent sub-units 10 are connected by bolts 51. The FC group 2 does not require pressurizing the entire stack of sub-units, and the number of stacked sub-units 10 can be easily changed. The FC group 2 of this embodiment can realize a fuel cell stack with an output (number of stacked individual cells) corresponding to the user's requirements at low cost.

[0027] Furthermore, a protrusion protruding towards the other is provided on one side of two adjacent sub-units 10, and a recess that engages with the protrusion is provided on the other side. This configuration allows two adjacent sub-units 10 to be stacked without offsetting each other. Moreover, flow paths are provided inside the protrusion and recess, connecting the flow paths of the two sub-units 10 through the engagement of the protrusion and recess. A sealing gasket is provided around the protrusion, which, when the recess engages, isolates (seales) the flow paths of both from the outside. This configuration also contributes to cost reduction for the FC assembly.

[0028] The end plate 30 has a positive terminal 37 connected to the positive terminal 27a of the adjacent sub-unit 10e, and a negative terminal 38 connected to the negative terminal 28a of the sub-unit 10e. Furthermore, as described above, the positive terminal 27a (negative terminal 28a) of one of the two adjacent sub-units 10 is connected to the positive terminal 27b (negative terminal 28b) of the other. The positive terminal 27a (negative terminal 28a) is convex, and the positive terminal 27b (negative terminal 28b) is concave. When adjacent sub-units 10 are joined together, the convex positive terminal 27a (negative terminal 28a) and the concave positive terminal 27b (negative terminal 28b) engage and are electrically connected. The convex positive terminal 27a (negative terminal 28a) and the concave positive terminal 27b (negative terminal 28b) also facilitate the joining of adjacent sub-units 10 without offset.

[0029] In FC group 2, the positive terminals of all sub-units 10 are connected to each other, and the negative terminals are connected to each other. That is, multiple sub-units 10 are electrically connected in parallel. By increasing the number of stacked sub-units 10, FC group 2 increases the capacitance that can be stored while maintaining the same output voltage.

[0030] Figure 3 Subunits 100a and 100b of the FC group in the first variant are represented. Figure 3 and Figure 2 Correspondingly, in sub-unit 100a, a convex positive terminal 27a is provided on the pressure plate 12 opposite to sub-unit 100b. On the other hand, in sub-unit 100b, a concave negative terminal 28b is provided on the pressure plate 13 opposite to sub-unit 100a. In sub-units 100a and 100b, the position of the concave negative terminal 28b is different from that of sub-unit 10 in the embodiment. The other structures of sub-units 100a and 100b are the same as those of sub-unit 10, therefore, in Figure 3 The reference numerals for several components have been omitted from the accompanying drawings.

[0031] In sub-unit 100, multiple individual cells 11 are electrically connected in series. The positive terminal 27a and the negative terminal 28b correspond to the positive and negative terminals of the series-connected individual cells 11, respectively. If multiple sub-units 100 are stacked, the positive terminal 27a of one sub-unit of two adjacent sub-units is connected to the negative terminal 28b of the other sub-unit. Adjacent sub-units are connected in series. Therefore, in the FC group of the first modified example, the output voltage can be changed by varying the number of stacked sub-units 100.

[0032] Figure 4 Subunits 200a and 200b of the FC group in the second variation are represented. Figure 4 and Figure 2Correspondingly, in sub-units 200a and 200b, a plurality of single-cell batteries 11 connected in series (positive terminal 227) are provided on the upper part of the pressure plate 12. Additionally, a plurality of single-cell batteries 11 connected in series (negative terminal 228) are provided on the upper part of the pressure plate 13. The construction of the positive and negative terminals in sub-units 200a and 200b differs from that of sub-unit 10 in this embodiment. The other constructions of sub-units 200a and 200b are the same as those of sub-unit 10, therefore... Figure 4 The reference numerals for several components have been omitted from the accompanying drawings.

[0033] In the second modified FC group, the positive terminals 227 (negative terminals 228) of each of the multiple sub-units 200 are neither connected to the positive terminals 227 of other sub-units 200 nor to the negative terminals 228 of other sub-units 200. In the second modified FC group, after the multiple sub-units 200 are stacked, the multiple positive terminals 227 are connected and the multiple negative terminals 228 are connected using other conductors. In this way, the multiple sub-units 200 are electrically connected in parallel.

[0034] Alternatively, in the FC group of the second modification, after stacking multiple sub-units 200, other conductors are used to connect the positive terminal 227 of one side of an adjacent sub-unit to the negative terminal 228 of the other side. In this way, the multiple sub-units 200 are electrically connected in series. In the FC group of the second modification, it is possible to select whether the sub-units are connected in series or in parallel.

[0035] Considerations related to the techniques described in the embodiments are described. The number of individual cells included in a sub-unit can also be arbitrary. Additionally, the number of sub-units included in an FC group can also be arbitrary.

[0036] The main features of FC Group 2 are as follows. Subunit 100 includes a pair of pressure plates 12 and 13, a plurality of single cells 11 stacked between the pair of pressure plates 12 and 13, and a connecting component 14. The connecting component 14 pressurizes the plurality of single cells 11 in the stacking direction (X direction in the coordinate system of the attached figure) and connects the pair of pressure plates 12 and 13. Pressure plates 12 and 13 are respectively provided with oxygen flow paths (oxygen supply flow path 21, oxygen discharge flow path 24) for oxygen used in the reaction within the single cells 11, and hydrogen flow paths (hydrogen supply flow path 22, hydrogen discharge flow path 25) for hydrogen. Furthermore, in FC Group 2, adjacent subunits 10 are interconnected, and the hydrogen flow paths and oxygen flow paths of adjacent subunits 10 are connected to each other.

[0037] In two adjacent sub-units 100, the oxygen flow path (oxygen supply flow path 21) of one sub-unit 100a has a protrusion 21a protruding toward the other sub-unit 100b, and the oxygen flow path (oxygen supply flow path 21) of the other sub-unit 100b has a recess 21b that engages with the protrusion 21a. The same applies to the hydrogen supply flow path 22 and the refrigerant supply flow path 23.

[0038] Furthermore, in FC group 2 of the embodiment, a pressure plate 12 has a convex positive terminal 27a and a negative terminal 28a, and the pressure plate 13 of the sub-unit 10b combined with the pressure plate 12 has a concave positive terminal 27b that fits into the positive terminal 27a and a concave negative terminal 28b that fits into the negative terminal 28a.

[0039] In one of the two adjacent subunits 100a and 100b, the pressure plate 12 of subunit 100a has protrusions 21a, 22a, 23a and recesses 24b, 25b, 26b. In the other subunit 200b, the pressure plate 13 (opposite to the pressure plate 12 of subunit 200a) has recesses 21b (22b, 23b) that engage with the protrusions 21a (22a, 23a) and protrusions 24a (25a, 26a) that engage with the recesses 24b (25b, 26b).

[0040] The specific examples of the present invention have been described in detail above, but these are merely illustrative and do not limit the technical solutions. The technology described in the technical solutions includes various modifications and variations of the specific examples described above. The technical elements described in this specification or drawings exert their technical usefulness individually or in various combinations, and are not limited to the combinations described in the technical solutions at the time of application. Furthermore, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful.

Claims

1. A fuel cell stack comprising multiple sub-units, characterized in that, Each of the said sub-units has: A pair of pressure plates; Multiple single cells are stacked between the pair of pressure plates; and The connecting component applies pressure to the plurality of said individual cells in the stacking direction and connects the pair of pressure plates. Each of the pressure plates is provided with a hydrogen flow path for hydrogen used in the reaction in the single cell and an oxygen flow path for oxygen. The two adjacent sub-units are connected to each other, and the hydrogen flow paths of the two adjacent sub-units are connected to each other, and the oxygen flow paths are connected to each other.

2. The fuel cell stack according to claim 1, characterized in that, The oxygen flow path of one of the two adjacent sub-units has a protrusion protruding toward the other sub-unit, and the oxygen flow path of the other sub-unit has a recess that engages with the protrusion.

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