Stack fastening structure

Abstract

To provide a stack fastening structure used for assembling a fuel battery stack, capable of applying an appropriate weight to a cell lamination body of the fuel battery stack and enabling miniaturization of a case constructing the fuel battery stack and a reduction in cost.SOLUTION: A stack fastening structure is fastened to a case of a fuel battery stack to apply a predetermined weight to a construction component of the fuel battery stack stored in the case. The stack fastening structure comprises: first weight application means fastened to the case from the outside of the case to apply a first depression weight to the construction component; and second weight application means fastened to the case from the outside of the case to apply a second depression weight that is different from the first depression weight to the construction component from a direction where the first depression weight is applied to the construction component.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a stack fastening structure used in assembling a fuel cell stack. [Background technology]

[0002] Fuel cell stacks (solid polymer fuel cells), which are being considered for use as a power source for automobiles and in home cogeneration systems, etc., are composed of a cell stack in which multiple unit cells are stacked and connected in series, with current collectors and end plates arranged on either side of the cell stack.

[0003] Each unit cell is composed of a pair of separators arranged on either side of a membrane electrode assembly (MEA), which consists of a polymer electrolyte membrane and a pair of catalytic electrodes (fuel electrode, air electrode) arranged on either side of the membrane.

[0004] In the cell stack of a fuel cell stack, a predetermined load is applied to the cell stack in order to reduce contact resistance between and within each unit cell, and to ensure sealing against reactant gases and water.

[0005] To maximize the performance of a fuel cell stack, it is necessary to apply a certain amount of load. However, if the load applied is too large, there is a risk that the membrane electrode assembly (MEA) and sealing materials will be damaged, resulting in reduced power generation efficiency.

[0006] Therefore, a structure is required that can apply an appropriate load to the cell laminate of the fuel cell stack, and can absorb the lamination tolerance of the laminate consisting of a plurality of stacked unit cells, current collector plates, end plates, etc.

[0007] Conventionally, there have been proposals for applying a predetermined load to the cell laminate of the fuel cell stack by employing an elastic body or a mechanism for absorbing stacking tolerances.

[0008] Patent document 1 proposes a cell pressing assembly that can be housed together with a cell stack in a case of fixed dimensions without applying excessive load to the cell stack, and that can apply a desired load to the cell stack, as well as a fuel cell stack having the cell pressing assembly.

[0009] Patent document 2 also proposes a fuel cell stack compression system that is a mechanical system for maintaining a compressive load on a fuel cell stack and has a compression assembly, at least a portion of which is positioned outside the case that constitutes the fuel cell stack. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2010-198861 A [Patent Document 2] Special Publication No. 2006-512730 Summary of the Invention [Problem to be solved by the invention]

[0011] The object of the present invention is to propose a stack fastening structure used in assembling a fuel cell stack, which is capable of applying an appropriate load to the cell laminate of the fuel cell stack, and which enables the case that constitutes the fuel cell stack to be made smaller, lighter, and less expensive. [Means for solving the problem]

[0012] The present invention, which solves the above-mentioned problems, can be exemplified as follows. [1] 1. A stack fastening structure for applying a predetermined load to a fuel cell stack component that is fastened to a case of the fuel cell stack and stored in the case, comprising: a first load applying means that is fastened to the case from the outside of the case and applies a first pressing load to the component; a second load applying means that is fastened to the case from the outside of the case and applies a second pressure load different from the first pressure load to the component from a direction in which the first pressure load is applied to the component; A stack fastening structure comprising:

[0013] [2] the second load applying means is fastened to the case from the outside of the first load applying means, The second pressing load on the component is applied directly to the component from the second load applying means.

[0014] [3] The second load applying means includes a pressing member extending toward the component, The stack fastening structure according to [2], wherein the pressing member extends toward the component through a through hole provided in the first load applying means.

[0015] [4] The stack fastening structure according to claim 1, wherein the first pressure load is equal to or greater than the load that generates the seal pressure required for the seal structure between each unit cell that constitutes a cell stack included in the component.

[0016] [5] a difference (X2-X1) between a cell compression amount X2, which is the amount by which a cell stack included in the component is compressed and displaced by the second pressing load applied to the component by the second load application means, and a cell compression amount X1, which is the amount by which a cell stack included in the component is compressed and displaced by the first pressing load applied to the component by the first load application means, is greater than a maximum expansion amount of the cell stack when the component is housed in the case and the fuel cell stack is in use [1].

[0017] [6] The second pressing load applied by the second load-applying means is generated by an elastic body provided in the second load-applying means, and the spring constant of the elastic body, that is, the elastic body spring constant, is set to a predetermined value or less. [1] A stack fastening structure.

[0018] [7] The predetermined value of the spring constant is an average value of a cell stack spring constant, which is a spring constant due to a cell stack structure of the cell stack included in the component [6].

[0019] [8] The predetermined value of the spring constant is a value obtained by dividing the difference between the load acting on the cell stack in a standard balanced state and the allowable cell load by the maximum cell displacement due to thermal expansion from the standard balanced state [6].

[0020] [9] The second pressing load by the second load applying means is generated by an elastic body provided in the second load applying means, and the elastic body is a disc spring.

[0021]

[10] The second pressing load by the second load applying means is generated by an elastic body provided in the second load applying means, and the elastic body is a coil spring.

[0022]

[11] the second load applying means includes a pressing member extending toward the component; The stack fastening structure according to

[10] , wherein the pressing member is constituted by the coil spring extending toward the component through a through hole provided in the cover member.

[0023]

[12] A stack fastening structure [3] in which a first fastening unit is fastened to the case, the first fastening unit being an integral combination of a plate-shaped second load-applying means cover member constituting the second load-applying means, an elastic body that generates the second pressing load to be applied to the component via the pressing member, and a second load-applying means fastening member that fastens the second load-applying means cover member to the case.

[0024]

[13] A stack fastening structure [3] in which a second fastening unit is fastened to the case, the second fastening unit being an integral combination of a plate-shaped second load applying means cover member constituting the second load applying means, a plurality of the pressing members, an elastic body that generates the second pressing load to be applied to the component via the pressing members, and a second load applying means fastening member that fastens the second load applying means cover member to the case.

[0025]

[14] a plate-shaped second load application means cover member constituting the second load application means, a plurality of the pressing members, an elastic body that generates the second pressing load to be applied to the component via the pressing members, and a second load application means fastening member that fastens the second load application means cover member to the case, a plate-shaped first load application means cover member constituting the first load application means, the plate-shaped first load application means cover member having a plurality of through holes through which the plurality of pressing members respectively pass; [3] A stack fastening structure in which a third fastening unit formed by integrally combining the above is fastened to the case. Effect of the Invention

[0026] According to the present invention, there can be provided a stack fastening structure used in assembling a fuel cell stack, which can apply an appropriate load to the cell laminate of the fuel cell stack, and which enables the case that constitutes the fuel cell stack to be made smaller, lighter, and less expensive. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a conceptual diagram illustrating an example of a stack fastening structure according to one embodiment of the present invention, in which a first load-applying means for applying a first compressive load to a fuel cell stack component, such as a cell stack housed in a case constituting a fuel cell stack, is fastened to the case from the outside of the case. [Diagram 2] FIG. 2 is a conceptual diagram illustrating an example of a state in which, following the state shown in FIG. 1, a second load applying means applies a second pressing load different from the first pressing load to a fuel cell stack component, such as a cell stack housed in a case constituting a fuel cell stack, from a direction in which the first pressing load is applied to the component, the second load applying means being fastened to the case from the outside of the case. [Diagram 3] FIG. 4 is a conceptual diagram illustrating an example of a state in which a first pressure load and a second pressure load are applied to components of the fuel cell stack, such as a cell stack housed in a case, by a first load application means and a second load application means fastened to the outside of the case constituting the fuel cell stack, following the state shown in FIG. 2. [Figure 4] FIG. 4 is a side view with some parts omitted, illustrating an example of the positional relationship in which the first load application means and the second load application means are fastened from the upper side of the case to the upper end of the case, when the state shown in FIG. 3 is viewed from the side of the case that constitutes the fuel cell stack. [Diagram 5] FIG. 1 is a conceptual diagram, with some parts omitted, illustrating one embodiment of a structure in which a pressing member provided in the second load application means extends toward a component part of a fuel cell stack housed in a case through a through hole provided in the first load application means. [Figure 6] A conceptual diagram with some parts omitted to explain another embodiment of a structure in which a pressing member provided in the second load application means extends toward a component part of a fuel cell stack housed in a case through a through hole provided in the first load application means. [Figure 7]A conceptual diagram with some parts omitted to explain yet another embodiment of a structure in which a pressing member provided in the second load application means extends toward a component of a fuel cell stack housed in a case through a through hole provided in the first load application means. [Figure 8] FIG. 8 is a partially omitted conceptual diagram illustrating a case in which the second load application means is an elastic mechanism having a simpler structure than the embodiment shown in FIGS. 3 and 5 to 7. [Figure 9] 1 is a graph illustrating the relationship between the seal pressure (seal load) required for the seal structure between each unit cell that constitutes a cell stack included in a component part of a fuel cell stack, and a first pressing load F1 and a second pressing load F2. [Figure 10] FIG. 1 is a diagram illustrating the relationship between a cell compression amount X1 due to a first pressure load F1 from a first load application means and a cell compression amount X2 due to a second pressure load F2 from a second load application means, where (a) is a partially omitted conceptual diagram illustrating a state before the first load application means is fastened to the case 1, and (b) is a state in which the first load application means is fastened to the case 1, and the first pressure load F1 is applied to a fuel cell stack component stored in the case 1, such as a cell stack 2, generating a cell compression amount X1 due to the first pressure load F1. 10(c) is a conceptual diagram, with some parts omitted, illustrating a state in which, subsequent to the state of FIG. 10(b), a second load-applying means is fastened to case 1, and a second pressing load F2 is applied to fuel cell stack components stored in case 1, such as cell stack 2, resulting in a cell compression amount X2 due to the second pressing load F2; and (d) is a graph showing an example of the relationship between the cell compression amount X1 due to the first pressing load F1 shown in FIGS. 10(b) and 10(c), and the cell compression amount X2 due to the second pressing load F2. [Figure 11]A graph showing an example of fluctuation in the average spring constant due to the cell stack structure, the spring constant due to the inter-cell gasket, the spring constant due to cell elements other than the gasket, and the spring constant of the elastic body provided in the second load-applying means consisting of an elastic body mechanism (= spring constant due to the elastic body), based on the relationship between the magnitude of the load applied to the cell stack and the amount by which the cell stack is compressed and displaced due to the load applied to the cell stack (cell compression amount). [Figure 12] A graph illustrating the case where the second pressure load is generated by an elastic body provided in the second load application means, in which the spring constant of the elastic body is set to a value equal to or less than the difference between the load acting on the cell stack in the standard balanced state and the cell allowable load divided by the maximum cell displacement due to thermal expansion from the standard balanced state. [Figure 13] 13(a) is a conceptual diagram with some parts omitted, illustrating the state in which part of the configuration of the second load-applying means fastened to the case and the fastening member that fastens the second load-applying means to the case are integrated into a unit; (b) is a conceptual diagram with some parts omitted, illustrating the stack fastening structure of the present invention, which is configured by fastening the unit shown in Figure 13(a) to the case. [Figure 14] (a) is a conceptual diagram, with some parts omitted, illustrating the state in which the second load-applying means fastened to the case and the fastening member that fastens the second load-applying means to the case are integrated into a unit, and (b) is a conceptual diagram, with some parts omitted, illustrating the stack fastening structure of the present invention, which is configured by fastening the unit shown in Figure 14(a) to the case. [Figure 15] 15(a) is a conceptual diagram with some parts omitted to illustrate the state in which the second load-applying means fastened to the case, the fastening member fastening the second load-applying means to the case, and a plate-shaped first load-applying means cover member having a plurality of through holes and constituting the first load-applying means are integrated into a unit, and (b) is a conceptual diagram with some parts omitted to illustrate the stack fastening structure of the present invention, which is formed by fastening the unit shown in Figure 15(a) to a case. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The stack fastening structure of this embodiment applies a predetermined load to components of the fuel cell stack that are fastened to a case constituting the fuel cell stack and stored within the case.

[0029] 1 to 4, a cell stack 2 is housed in a case 1. Although detailed illustration of the cell stack 2 is omitted, as is conventionally known, a plurality of unit cells are stacked in the vertical direction in Fig. 1 and connected in series. End plates 3a, 3b are arranged above and below the cell stack 2, respectively, with current collector plates (not shown) interposed therebetween.

[0030] The cell stack 2 is housed in the case 1 with a predetermined load being applied in the vertical direction in FIG.

[0031] In conventional fuel cell stacks, it is common for fuel cell stack components such as the cell stack 2, and pressing means for applying a predetermined load to the cell stack 2, to be housed in the case 1. In such a configuration, not only fuel cell stack components such as the cell stack 2 but also pressing means and the like are housed in the case 1. This increases the dimensions of the case 1, making the case larger and heavier, which in turn leads to problems such as increased manufacturing costs for the case 1 and the fuel cell stack.

[0032] In this embodiment, a stack fastening structure is configured in such a way that a pressing means for applying an appropriate load to the cell stack 2 of the fuel cell stack housed within the case 1 is arranged on the outside of the case 1, thereby making it possible to reduce the size and weight of the case 1 that constitutes the fuel cell stack, reduce the manufacturing costs of the case 1, and reduce the manufacturing costs of the fuel cell stack.

[0033] 1 to 4, a first load application means for applying a first pressure load to fuel cell stack components such as the cell stack 2 housed in the case 1 constituting the fuel cell stack 100 (FIG. 3) is fastened to the case 1 from the outside of the case 1. In addition, a second load application means for applying a second pressure load different from the first pressure load described above to the fuel cell stack components such as the cell stack 2 housed in the case 1 constituting the fuel cell stack from the direction in which the first pressure load described above is applied to the fuel cell stack components such as the cell stack 2 housed in the case 1 constituting the fuel cell stack is fastened to the case 1 from the outside of the case 1 (FIG. 3).

[0034] In the stack fastening structure shown in FIGS. 1 to 4, both the first load applying means and the second load applying means described above are fastened to the case 1 from above the case 1. In the stack fastening structure shown in FIGS.

[0035] In this embodiment, the case 1 constituting the fuel cell stack 100 (FIG. 3) only contains fuel cell stack components such as the cell stack 2, but does not contain pressing means for applying a predetermined load to the cell stack 2. This makes it possible to reduce the size and weight of the case 1 constituting the fuel cell stack, reduce the manufacturing costs of the case 1, and ultimately reduce the manufacturing costs of the fuel cell stack.

[0036] In the embodiment shown in Figure 1, a plate-shaped cover member 4 is fastened to the case 1 from the outside of the case 1 (the upper side of the case 1 in Figure 1), and a first compressive load is applied from the top to the bottom in Figure 1 to the components of the fuel cell stack consisting of the cell stack 2 and the like.

[0037] The left and right ends of the plate-shaped cover member 4, whose lower surface 4a abuts against the upper surface of the upper end plate 3a, are fastened to the upper ends of the left and right side walls 1a and 1b of the case 1 in FIG. 1 by fastening members 5a and 5b, respectively.

[0038] The plate-shaped cover member 4 has through holes 6a, 6b, and 6c at predetermined positions as shown in Fig. 1. A pressing member provided in a second load applying means described later passes through the through holes 6a, 6b, and 6c in the vertical direction in Fig. 1.

[0039] The fastening members 5a, 5b may be, for example, bolts. By appropriately adjusting the amount of fastening when fastening the cover member 4 to the upper ends of the side walls 1a, 1b on both the left and right sides of the case 1 in FIG. 1, such as by adjusting the amount of fastening of the bolts, it is possible to achieve a configuration in which a first pressing load of an appropriate magnitude is applied to the cell laminate 2 of the fuel cell stack.

[0040] In this embodiment, the plate-shaped cover member 4, whose lower surface 4a abuts against the upper surface of the upper end plate 3a, is fastened to the case 1 from the outside of the case 1 by fastening members 5a, 5b, thereby forming the above-mentioned first load-applying means.

[0041] Thus, in the stack fastening structure shown in Figures 1 to 4, a first load-applying means for applying a first compressive load to fuel cell stack components such as the cell stack 2 housed in the case 1 constituting the fuel cell stack 100 (Figure 3) is fastened to the case 1 from the outside of the case 1.

[0042] The above-mentioned second load applying means is also fastened to the case 1 from the outside of the case 1. The second load applying means applies a second pressure load, different from the above-mentioned first pressure load, to components of the fuel cell stack, such as the cell stack 2, from the direction in which the above-mentioned first pressure load is applied to the components of the fuel cell stack, such as the cell stack 2, i.e., from the direction from the top to the bottom of the drawings in Figures 1 to 3.

[0043] In the illustrated embodiment, the above-mentioned second load-applying means comprises a plate-shaped cover member 8 that is fastened to the case 1, and pressing members 7a, 7b, 7c that are arranged on the underside of the cover member 8 and extend toward the components of the fuel cell stack, such as the cell stack 2 (FIG. 2).

[0044] Plate-like cover member 8 is fastened to case 1 from the outside of case 1 (from above the first load applying means fastened to case 1 in Figs. 2 to 4).

[0045] In the illustrated embodiment, both left and right ends of the plate-shaped cover member 8 in Figures 2 and 3 are fastened to the upper ends of the left and right side walls 1a and 1b of the case 1 in Figures 2 and 3 by fastening members 9a and 9b, respectively.

[0046] Fig. 4 is a partially omitted side view of the state shown in Fig. 3, seen from the side of the case 1 that constitutes the fuel cell stack 100. The position at which the cover member 4 that constitutes the first load application means is fastened by fastening members 5b, 5c to the upper end of the side wall 1b of the case 1 extending in the left-right direction in Fig. 4 is different from the position at which the cover member 8 that constitutes the second load application means is fastened by fastening members 9b, 9c.

[0047] In this embodiment, by adopting such a configuration, a structure is achieved in which the second load applying means is fastened to the case 1 from the outside of the first load applying means. Although not shown in the figures, it is also possible to adopt another configuration in which the second load applying means is fastened to the case 1 from the outside of the first load applying means.

[0048] The fastening members 9a, 9b, and 9c may be, for example, bolts. By appropriately adjusting the amount of fastening when fastening the cover member 8 to the upper ends of the side walls 1a and 1b on both the left and right sides of the case 1 in FIG. 1, such as by adjusting the amount of fastening of the bolts, it is possible to make the load applied by the second load applying means to the cell laminate 2 of the fuel cell stack appropriate by means of an elastic body mechanism described later.

[0049] When the first load-applying means and the second load-applying means are fastened to the case 1 as described above, the pressing members 7a, 7b, 7c of the second load-applying means extend toward the components of the fuel cell stack, such as the cell stack 2, through the through holes 6a, 6b, 6c of the first load-applying means described above (Figure 3).

[0050] In this embodiment, by adopting the above-mentioned configuration, the second load-applying means is fastened to the case 1 from the outside of the case 1, i.e., from the outside of the first load-applying means fastened to the case 1, and applies a second pressing load different from the first pressing load directly to the components of the fuel cell stack such as the cell stack 2 from the direction in which the first pressing load is applied by the first load-applying means to the components of the fuel cell stack such as the cell stack 2.

[0051] As described above, when the first load-applying means and the second load-applying means are fastened to the case 1, the pressing members 7a, 7b, 7c of the second load-applying means extend toward the components of the fuel cell stack, such as the cell stack 2, through the through holes 6a, 6b, 6c of the first load-applying means, and their tips abut against the upper surface of the upper end plate 3a. As will be described below, various structures can be adopted for this structure.

[0052] The structure shown in FIG. 5 represents an example of an embodiment in which the first load applying means is provided with elastic members surrounding the pressing members 7a-7c passing through the through holes 6a-6c within the through holes 6a-6c.

[0053] 5, elastic members 12a, 12b, 12c surrounding the pressing members 7a-7c passing through the through holes 6a-6c, respectively, within the through holes 6a-6c, are provided on the cover member 4 constituting the first load applying means. As an embodiment in which the elastic members 12a, 12b, 12c are provided on the cover member 4 constituting the first load applying means, for example, a structure in which the elastic members 12a, 12b, 12c are provided in the through holes 6a, 6b, 6c of the cover member 4, respectively, can be adopted.

[0054] The structure shown in FIG. 6 represents an example of an embodiment in which the first load applying means includes an elastic member that is pressed by the tips of the pressing members 7a to 7c penetrating the through holes 6a to 6c and comes into contact with the member on the side of the above-mentioned component, and is interposed between the tips of the pressing members 7a to 7c and the member on the side of the above-mentioned component.

[0055] In Fig. 6, elastic members 13a, 13b, and 13c are pressed by the tips of pressing members 7a-7c penetrating through holes 6a-6c to abut against the upper side surface of upper end plate 3a, and are interposed between the tips of pressing members 7a-7c and end plate 3a, and are in contact with cover member 4 constituting the first load applying means, and are disposed in a manner surrounding through holes 6a, 6b, and 6c. Fig. 6 shows a state in which elastic members 13a, 13b, and 13c are interposed between the tips of pressing members 7a, 7b, and 7c and end plate 3a.

[0056] In the embodiment shown in FIG. 6, the upper end plate 3a is the member on the side of the fuel cell stack components such as the cell laminate 2, against which the tips of the pressing members 7a, 7b, 7c abut.

[0057] As an embodiment in which the elastic members 13a, 13b, 13c are provided on the cover member 4 constituting the first load-applying means, for example, a structure can be adopted in which the elastic members 13a, 13b, 13c are respectively provided on the lower sides of the through holes 6a, 6b, 6c of the cover member 4 so as to be detachable from the lower surface of the cover member 4.

[0058] The structure shown in FIG. 7 represents an example of an embodiment in which an elastic member surrounding the portion above the first load applying means of each of the pressing members 7a-7c passing through the through holes 6a-6c is provided on the first load applying means.

[0059] In Fig. 7, elastic members 14a, 14b, 14c surrounding the upper part of the first load applying means of the pressing members 7a, 7b, 7c penetrating the through holes 6a, 6b, 6c are provided on the cover member 4 constituting the first load applying means. Note that in Fig. 7, illustration of the case 1 and components of the fuel cell stack such as the cell stack 2 housed in the case 1 is omitted.

[0060] As an embodiment in which the elastic members 14a, 14b, 14c are provided on the cover member 4 constituting the first load-applying means, for example, a structure can be adopted in which cylindrical elastic members 14a, 14b, 14c are provided on the upper sides of the through holes 6a, 6b, 6c of the cover member 4, respectively.

[0061] As the cylindrical elastic members 14a, 14b, 14c, for example, bellows-shaped cylinders can be used. The elastic members 14a, 14b, 14c made of bellows-shaped cylinders are compressed in the vertical direction when the second load applying means is attached to the case 1 from above the first load applying means as shown in Fig. 7 and the pressing members 7a, 7b, 7c penetrate the through holes 6a, 6b, 6c downward in Fig. 7.

[0062] In the structure illustrated in Figures 5 to 7, when the above-mentioned elastic members 12a to 12c, 13a to 13c, and 14a to 14c are provided in the first load-applying means, it is advantageous because it can prevent contaminants such as dust from entering the fuel cell through gaps between the through holes 6a, 6b, and 6c and the pressing members 7a, 7b, and 7c.

[0063] The elastic members 12a-12c, 13a-13c, and 14a-14c used in the structures illustrated in Figures 5-7 are all members that deform in response to a pressing force when they receive the pressing force, and can exert a restoring force when the pressing force is released. In the structure illustrated in Figure 7, a bellows-shaped cylinder is illustrated as an example of the elastic members 14a-14c, but various materials and shapes can be used for the elastic members 12a-12c, 13a-13c, and 14a-14c as long as they have the above-mentioned characteristics. For example, the above-mentioned elastic members can be made of rubber or resin.

[0064] Although not shown, a configuration different from that described above and illustrated in Figures 1 to 7 can be adopted, in which the second load-applying means is fastened to case 1 from the outside of case 1 in the same manner as the first load-applying means, and a second pressing load different from the first pressing load is applied directly from the second load-applying means to components such as the cell stack 2 from the direction in which the first pressing load is applied by the first load-applying means to components of the fuel cell stack such as the cell stack 2.

[0065] 1 to 7 illustrating the above-mentioned embodiment, three through holes 6a, 6b, 6c are formed in the plate-shaped cover member 4, and pressing members 7a, 7b, 7c penetrate through the three through holes. As described above, the first pressing load is applied from the first load application means to the fuel cell stack components such as the cell stack 2 by the plate-shaped cover member 4 abutting its lower surface 4a against the upper flat surface of the upper end plate 3a. The second pressing load is applied from the second load application means to the fuel cell stack components such as the cell stack 2 by the pressing members 7a, 7b, 7c abutting their respective lower surfaces against the upper flat surface of the upper end plate 3a.

[0066] Taking into consideration the form of application of the first pressing load, the form of application of the second pressing load, the area where the lower surface 4a of the cover member 4 abuts against the upper flat surface of the upper end plate 3a, the area where the lower surfaces of the pressing members 7a, 7b, 7c abut against the upper flat surface of the upper end plate 3a, etc., the number of through holes to be formed in the cover member 4, their respective sizes, their formation positions, the areas of the lower surfaces of the pressing members 7a, 7b, 7c, etc. can be set.

[0067] The plate-shaped cover member 4 and the plate-shaped cover member 8 in the present embodiment described above serve as support bodies for a first pressure load and a second pressure load applied to components of the fuel cell stack, such as the cell stack 2 housed in the case 1 that constitutes the fuel cell stack 100 (Figure 3), respectively.

[0068] Therefore, the cover members 4 and 8 are required to have the necessary rigidity for this purpose, and the cover members 4 and 8 can be formed from various materials that satisfy this requirement.

[0069] In addition, since the pressing members 7a, 7b, and 7c are members that play a role in transmitting the second pressing load to the components, they are required to have the necessary rigidity for this purpose, and the pressing members 7a, 7b, and 7c can be formed from various materials that satisfy this requirement.

[0070] <Embodiment in which the second load applying means is an elastic mechanism> In the embodiment shown in Fig. 3, the second pressure load by the second load application means is generated by an elastic body provided in the second load application means. As the elastic body, a disc spring, a coil spring, or the like can be adopted.

[0071] In the embodiment shown in Fig. 3, disc springs 10a, 10b, and 10c stacked in series are used as the elastic bodies. As shown in Fig. 3, the disc springs 10a, 10b, and 10c are disposed on the second load applying means in such a manner that their upper ends are supported by the lower surface of the cover member 8 made of a plate-like body and their lower ends abut against the upper ends of the pressing members 7a, 7b, and 7c.

[0072] As shown in FIG. 3, the pressing members 7a, 7b, and 7c abut their tips (lower ends) against the upper surface of the upper end plate 3a, and apply a second pressing load based on the elastic force of an elastic body such as a disc spring or a coil spring to components of the fuel cell stack such as the cell stack 2.

[0073] Thus, the second load-applying means includes a configuration in which the second pressing load generated by the elastic body of the second load-applying means is applied to components of the fuel cell stack, such as the cell stack 2. This type of second load-applying means can also be called an elastic body mechanism, since it utilizes the elastic force of the elastic body.

[0074] As described above, the strength of the second pressing load can be made appropriate by setting the amount of fastening when fastening the plate-shaped cover member 8 constituting the second load-applying means to the upper ends of the side walls 1a, 1b of the case 1 with fastening members 9a, 9b such as bolts in consideration of the strength of the second pressing load based on the elastic force of an elastic body such as a disc spring or coil spring.

[0075] Fig. 8 illustrates another embodiment of the second load applying means made of an elastic body mechanism. Cylindrical coil springs 15a, 15b, 15c are used instead of the pressing members 7a, 7b, 7c in the embodiment shown in Figs. 1 to 7. As described above, the strength of the second pressing load can be made appropriate by setting the tightening amount when fastening the plate-like cover member 8 constituting the second load applying means to the upper ends of the side walls 1a, 1b of the case 1 by the fastening members 9a, 9b such as bolts in consideration of the strength of the second pressing load based on the elastic force of the coil springs 15a, 15b, 15c.

[0076] 1 to 7, elastic bodies such as disc springs and coil springs are provided between the pressing members 7a, 7b, 7c and the cover member 8, but in the embodiment shown in Fig. 8, the coil springs 15a, 15b, 15c also serve as the pressing members 7a, 7b, 7c. Therefore, the number of parts can be reduced compared to the embodiment shown in Fig. 1 to 7.

[0077] FIG. 8 shows an embodiment in which coil springs 15a, 15b, 15c are employed, however, as described above, various elastic bodies, such as a cylindrical elastic body made of a rubber material or the like, can be employed in place of coil springs 15a, 15b, 15c, so long as they can fulfill the role of pressing members 7a, 7b, 7c and can apply a second pressing load to components of the fuel cell stack, such as the cell stack 2, based on their elastic force when the cover member 8 is fastened to the upper ends of the side walls 1a, 1b of the case 1 with a predetermined fastening amount by fastening members 9a, 9b, such as bolts.

[0078] <Appropriate Magnitude of First Pressing Load by First Load Applying Means> As described above, the cover member 4 constituting the first load-applying means is fastened to the upper ends of the side walls 1a, 1b of the case 1 by fastening members 5a, 5b with its lower surface 4a abutting against the upper surface of the upper end plate 3a.

[0079] Therefore, as described above, by appropriately adjusting the amount of fastening when fastening the cover member 4 to the upper ends of the side walls 1a, 1b on both the left and right sides of the case 1 in Figure 1 using the fastening members 5a, 5b, it is possible to configure the case 1 to apply a first pressing load F1 of an appropriate magnitude to the cell stack 2 of the fuel cell stack.

[0080] This first pressing load F1 of appropriate magnitude can be made equal to or greater than the load generating the sealing pressure required for the sealing structure between each unit cell constituting the cell stack 2 included in the constituent parts of the fuel cell stack.

[0081] FIG. 9 is a graph illustrating the relationship between the sealing pressure (sealing load) required for the sealing structure between each unit cell constituting the cell stack 2 included in the constituent parts of the fuel cell stack, and the first pressing load F1 and the second pressing load F2.

[0082] In the stack fastening structure of this embodiment, as described above, a first pressing load F1 is applied by a first load-applying means to a component of the fuel cell stack, such as the cell stack 2, while a second pressing load F2 is applied by a second load-applying means to a component of the fuel cell stack, such as the cell stack 2.

[0083] As described above, the second load applying means may be an elastic body mechanism that applies the second pressure load F2 generated by an elastic body to a fuel cell stack component such as the cell stack 2. In this case, creep or damage to the elastic body may occur.

[0084] As described above, if the first pressure load F1 is set to a magnitude equal to or greater than the load that generates the sealing pressure required for the sealing structure between each unit cell that constitutes the cell stack 2 included in the constituent parts of the fuel cell stack, then, as described above, the sealing load can be secured even if the elastic body used in the second load-applying means creeps or breaks.

[0085] <Relationship between cell compression amount X1 due to first pressure load and cell compression amount X2 due to second pressure load> In the stack fastening structure of this embodiment, as described above, a first pressure load F1 is applied to components of the fuel cell stack stored in the case 1, such as the cell stack 2, by a first load-applying means fastened to the case 1 from the outside of the case 1, and a second pressure load F2 different from the first pressure load F1 is applied to the components from the direction in which the first pressure load F1 is applied by a second load-applying means fastened to the case 1 from the outside of the case 1 in the same manner as the first load-applying means.

[0086] A preferable relationship between the cell compression amount X1 due to the first pressure load F1 and the cell compression amount X2 due to the second pressure load F2 at this time will be described with reference to FIG.

[0087] As shown in FIG. 10(b), a cell compression amount is defined as X1, which is the amount by which the cell stack 2 included in the fuel cell stack component stored in the case 1, such as the cell stack 2, is compressed and displaced by a first pressure load F1 applied to the component by a first load-applying means consisting of a cover member 4 or the like.

[0088] Furthermore, as shown in FIG. 10(c), a cell compression amount is defined as X2, which is the amount by which the cell stack 2 included in the fuel cell stack components stored in the case 1, such as the cell stack 2, is compressed and displaced by a second pressure load F2 applied to the components by a second load-applying means consisting of a cover member 8 or the like.

[0089] In the stack fastening structure of this embodiment, it is desirable that the difference (X2-X1) between the cell compression amount X2 and the cell compression amount X1 is greater than the maximum expansion amount of the cell stack 2 when the fuel cell stack 100 is in use with fuel cell stack components such as the cell stack 2 housed in the case 1.

[0090] Such a relationship is desirable in order to avoid a sudden increase in thermal stress caused by the case bottoming out of the stacked cells at high temperatures.

[0091] <Spring constant of the elastic body of the second load applying means formed of the elastic body mechanism> As described above, the second load-applying means includes an elastic body mechanism that applies a second compressive load generated by an elastic body provided in the second load-applying means to a component of the fuel cell stack, such as the cell stack 2.

[0092] It is desirable that the spring constant of the elastic body provided in the second load applying means made of such an elastic body mechanism is set to a predetermined value or less. This will be explained with reference to FIG.

[0093] As described above, a first compressive load F1 is applied by a first load-applying means to the components of the fuel cell stack stored in the case 1, such as the cell stack 2, and further, a second compressive load F2 generated by an elastic body provided in the second load-applying means is applied from the direction in which the first compressive load F1 is applied.

[0094] In the cell stack 2 receiving such a first compression load F1 and a second compression load F2, it is necessary to take into account the spring constant due to the cell stack structure, which is caused by multiple unit cells being stacked, and the spring constant due to the inter-cell gasket, which is caused by the presence of a gasket, for example a rubber gasket, present between the stacked unit cells.

[0095] Figure 11 is a graph showing an example of fluctuation in the average spring constant due to the cell stack structure, the spring constant due to the inter-cell gasket, the spring constant due to cell elements other than the gasket, and the spring constant of the elastic body provided in the second load-applying means consisting of an elastic body mechanism (=spring constant due to the elastic body), with the magnitude of the load applied to the cell stack 2 on the vertical axis and the amount by which the cell stack 2 is compressed and displaced due to the load applied to the cell stack 2 (cell compression amount) on the horizontal axis.

[0096] Spring constant due to elastic body = If the spring constant of the elastic body provided in the second load-applying means consisting of the elastic body mechanism is too large, the load change with respect to the amount of compression becomes large, and the load stability against variations in temperature change, manufacturing tolerances, etc. decreases.

[0097] Therefore, as described above, it is desirable that the spring constant of the elastic body, which is the spring constant of the elastic body provided in the second load applying means consisting of the elastic body mechanism, is set to a predetermined value or less.

[0098] As an example, it is possible to set this predetermined value to the average value of the cell stack spring constant, which is the spring constant due to the cell stack structure of the cell stack 2 included in the fuel cell stack components housed in the fuel cell stack case 1, as shown in the graph of Figure 11. This setting makes the spring constant of the second load applying means substantially equal to or less than the spring constant of the first load applying means, thereby preventing a sudden change in the spring constant of the entire fastening structure.

[0099] The above-mentioned predetermined value can also be set to a value obtained by dividing the difference between the load acting on the cell in the standard balanced state and the cell allowable load by the maximum cell displacement due to thermal expansion from the standard balanced state.

[0100] An example of this is shown in Figure 12. The cell compression amount due to the first pressure load F1 is X1, and the cell compression amount when the second pressure load F2 is applied in addition to the first pressure load F1 is X2, and the applied loads and the cell compression amount X2 are in balance as shown in Figure 12.

[0101] From this, for example, assume that the maximum temperature change on the high temperature side causes the cell to expand and the compression amount decreases by Δx.

[0102] At this time, the elastic body of the second load applying means is further compressed by Δx from the balanced position, with the result that the load applied to the stacked cells increases (FIG. 12).

[0103] At this time, the spring constant k2 (slope of the straight line) of the second load applying means is the load F2 acting in the standard state and the cell allowable load F c If the difference between the load and the allowable cell load is smaller than the value obtained by dividing the load by Δx, the load will not reach the allowable cell load even if the load on the cell increases due to cell expansion. By adopting such a configuration, it is possible to prevent the cell from being damaged by the load during expansion.

[0104] <Unitized stack fastening structure> In the stack fastening structure of this embodiment, a first load application means applies a first pressing load to fuel cell stack components such as the cell stack 2 housed in case 1 constituting the fuel cell stack 100 (Figure 3), and a second load application means applies a second pressing load, different from the first pressing load described above, to the fuel cell stack components such as the cell stack 2 housed in case 1 constituting the fuel cell stack from the direction in which the first pressing load described above is applied to the fuel cell stack components such as the cell stack 2 housed in case 1 constituting the fuel cell stack. These are each fastened to case 1 from the outside of case 1 (Figures 1 to 4, Figure 8).

[0105] The process of fastening the stack fastening structure having the above-mentioned configuration to the case 1 constituting the fuel cell stack 100 can be simplified by using a unit described below.

[0106] <Embodiment 1 using the unit> The second load-applying means comprises a plate-shaped cover member 8 (hereinafter referred to as the "plate-shaped second load-applying means cover member 8") and elastic bodies 15a, 15b, 15c which generate a second pressing load on fuel cell stack components such as the cell stack 2 housed in the case 1 which constitutes the fuel cell stack 100 (Figures 13(a) and (b)).

[0107] The plate-shaped second load application means cover member 8 is configured to be fastened to the upper ends of the side walls 1a, 1b of the case 1 by fastening members 9a, 9b (hereinafter referred to as "second load application means fastening members 9a, 9b") (Figures 13(a) and (b)).

[0108] Figure 13(a) illustrates an embodiment in which the above-mentioned plate-shaped second load-applying means cover member 8, elastic bodies 15a, 15b, 15c, which are part of the components of the second load-applying means, and second load-applying means fastening members 9a, 9b that fasten the plate-shaped second load-applying means cover member 8 to the upper ends of the side walls 1a, 1b of the case 1 are integrated into a unit.

[0109] The stack fastening structure of this embodiment using the unit shown in FIG. 13(a) can be fastened to the case 1 constituting the fuel cell stack 100 in the following manner.

[0110] First, the first load-applying means is fastened to the case 1 by fastening a plate-shaped cover member 4 constituting the first load-applying means (hereinafter referred to as the "plate-shaped first load-applying means cover member 4") to the upper ends of side walls 1a, 1b of the case 1 constituting the fuel cell stack 100 via fastening members 5a, 5b.

[0111] Next, the elastic bodies 15a, 15b, 15c constituting the second load application means of the unit shown in FIG. 13(a) are inserted into the through holes 6a, 6b, 6c provided in the plate-shaped first load application means cover member 4.

[0112] Thereafter, the elastic bodies 15a, 15b, 15c of the unit shown in FIG. 13(a) abut against the upper end of the end plate 3a, and the plate-shaped second load-applying means cover member 8 of the unit shown in FIG. 13(a) is fastened to the upper ends of the side walls 1a, 1b of the case 1 constituting the fuel cell stack 100 via the second load-applying means fastening members 9a, 9b, thereby fastening the second load-applying means to the case 1 (FIG. 13(b)).

[0113] In this way, the stack fastening structure of this embodiment can be easily fastened to the case 1 constituting the fuel cell stack 100 (FIG. 3).

[0114] <Embodiment 2 using the unit> The unit shown in Fig. 14(a) is a unit in which the multiple elastic bodies 10a, 10b, 10c and pressing members 7a, 7b, 7c of the second load applying means are integrated with the unit shown in Fig. 3. The plate-shaped second load applying means cover member 8, pressing members 7a, 7b, 7c, elastic bodies 10a, 10b, 10c, which are components of the second load applying means, and second load applying means fastening members 9a, 9b for fastening the plate-shaped second load applying means cover member 8 to the upper ends of the side walls 1a, 1b of the case 1 are integrated into a unit.

[0115] The stack fastening structure of this embodiment using the unit shown in FIG. 14(a) can be fastened to the case 1 constituting the fuel cell stack 100 in the following manner.

[0116] First, the first load-applying means is fastened to the case 1 (not shown) by fastening a plate-shaped cover member 4 constituting the first load-applying means (hereinafter referred to as the "plate-shaped first load-applying means cover member 4") to the upper ends of side walls 1a, 1b of the case 1 constituting the fuel cell stack 100 via fastening members 5a, 5b.

[0117] Thereafter, the unit shown in FIG. 14(a) is mounted so that the pressing members 7a, 7b, 7c of the unit shown in FIG. 14(a) are inserted into the through holes 6a, 6b, 6c provided in the plate-shaped first load-applying means cover member 4, and the plate-shaped second load-applying means cover member 8 of the unit shown in FIG. 14(a) is fastened to the upper ends of the side walls 1a, 1b of the case 1 constituting the fuel cell stack 100 via the second load-applying means fastening members 9a, 9b, thereby fastening the second load-applying means to the case 1 (FIG. 14(b)).

[0118] In this manner, the stack fastening structure of this embodiment can be easily fastened to the case 1 constituting the fuel cell stack 100.

[0119] <Embodiment 3 using the unit> The unit shown in FIG. 15(a) is a unit in which a plate-shaped first load applying means cover member 4 of the first load applying means is also integrated in addition to the unit shown in FIG. 14(a). The plate-shaped second load applying means cover member 8, pressing members 7a, 7b, 7c, elastic bodies 10a, 10b, 10c, which are components of the second load applying means, the second load applying means fastening members 9a, 9b for fastening the plate-shaped second load applying means cover member 8 to the upper ends of the side walls 1a, 1b of the case 1, and the plate-shaped first load applying means cover member 4 constituting the first load applying means are integrated into a unit in a state in which the pressing members 7a, 7b, 7c of the second load applying means penetrate through the through holes 6a, 6b, 6c. The cover member 4 needs to be temporarily fixed or temporarily secured to the unit shown in FIG. 14(a) until it is fastened to the case 1 described later, but is not shown here.

[0120] The stack fastening structure of this embodiment using the unit shown in FIG. 15(a) can be fastened to the case 1 constituting the fuel cell stack 100 in the following manner.

[0121] First, the first load-applying means is fastened to the case 1 by fastening the plate-shaped first load-applying means cover member 4 of the first load-applying means to the upper ends of the side walls 1a, 1b of the case 1 constituting the fuel cell stack 100 via fastening members 5a, 5b.

[0122] Thereafter, the temporary fastening of the cover member 4 to the unit shown in Figure 14(a) is released, and then the plate-shaped second load-applying means cover member 8 of the unit shown in Figure 15(a) is fastened to the upper ends of the side walls 1a, 1b of the case 1 constituting the fuel cell stack 100 (Figure 3) via second load-applying means fastening members 9a, 9b, thereby fastening the second load-applying means to the case 1 (Figure 15(b)).

[0123] In this way, the stack fastening structure of this embodiment can be easily fastened to the case 1 constituting the fuel cell stack 100 (FIG. 15(b)).

[0124] Although an embodiment of the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiment and can be modified in various ways within the technical scope understood from the description of the claims.

Claims

1. 1. A stack fastening structure for applying a predetermined load to a fuel cell stack component that is fastened to a case of the fuel cell stack and stored in the case, comprising: a first load applying means fastened to the case from outside the case by a first load applying means fastening means for applying a first pressing load to the component, the magnitude of the first pressing load applied to the component by the first load applying means being adjusted by the first load applying means fastening means; a second load applying means that is fastened to the case by a second load applying means fastening means from outside the case and from outside the first load applying means in a direction in which the first pressing load is applied to the component, and applies a second pressing load different from the first pressing load to the component from the direction in which the first pressing load is applied to the component, the second load applying means being configured to adjust the magnitude of the second pressing load applied to the component by the second load applying means; Equipped with the second load applying means includes a pressing member extending toward the component through a through hole of the first load applying means, The second pressing load on the component is applied to the component via the pressing member. Stack fastening structure.

2. 2. The stack fastening structure according to claim 1, wherein the first pressure load is equal to or greater than a load that generates a seal pressure required for a seal structure between each unit cell that constitutes a cell stack included in the component.

3. 2. The stack fastening structure of claim 1, wherein a difference (X 2 -X 1 ) between a cell compression amount X 2 , which is the amount by which a cell stack included in the component is compressed and displaced by the second pressing load applied to the component by the second load application means, and a cell compression amount X 1 , which is the amount by which a cell stack included in the component is compressed and displaced by the first pressing load applied to the component by the first load application means, is greater than a maximum expansion amount of the cell stack when the component is housed in the case and the fuel cell stack is in use.

4. 2. A stack fastening structure as described in claim 1, wherein the second pressing load applied by the second load application means is generated by an elastic body provided in the second load application means, and the spring constant of the elastic body is set to a predetermined value or less.

5. 5. The stack fastening structure according to claim 4, wherein the predetermined value of the spring constant is an average value of a cell stack spring constant, which is a spring constant due to a cell stack structure of the cell stack included in the component.

6. 5. The stack fastening structure of claim 4, wherein the predetermined value of the spring constant is the difference between the load acting on the cell stack in a standard balanced state and the cell allowable load divided by the maximum cell displacement due to thermal expansion from the standard balanced state.

7. 2. The stack fastening structure according to claim 1, wherein the second pressing load applied by the second load applying means is generated by an elastic body provided in the second load applying means, the elastic body being a disc spring.

8. 2. The stack fastening structure according to claim 1, wherein the second pressing load applied by the second load applying means is generated by an elastic body provided in the second load applying means, the elastic body being a coil spring.

9. 2. The stack fastening structure according to claim 1, wherein the pressing member is formed of a coil spring.

10. 2. A stack fastening structure as described in claim 1, wherein a first fastening unit is fastened to the case, the first fastening unit being an integral combination of a plate-shaped second load applying means cover member constituting the second load applying means, an elastic body that generates the second pressing load to be applied to the component via the pressing member, and a second load applying means fastening member that fastens the second load applying means cover member to the case.

11. 2. A stack fastening structure as described in claim 1, wherein a second fastening unit is fastened to the case, the second fastening unit being an integral combination of a plate-shaped second load applying means cover member constituting the second load applying means, a plurality of the pressing members, an elastic body that generates the second pressing load to be applied to the component via the pressing members, and a second load applying means fastening member that fastens the second load applying means cover member to the case.

12. a plate-shaped second load application means cover member constituting the second load application means, a plurality of the pressing members, an elastic body that generates the second pressing load to be applied to the component via the pressing members, and a second load application means fastening member that fastens the second load application means cover member to the case, a plate-shaped first load application means cover member constituting the first load application means, the plate-shaped first load application means cover member having a plurality of through holes through which the plurality of pressing members respectively pass; 2. The stack fastening structure according to claim 1, wherein a third fastening unit having an integral combination of the above is fastened to the case.

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