Fuel cell stack

Abstract

The present invention provides a fuel cell stack in which a gap is not formed between the clamping member and the insulating member due to the elastic sealing member returning to its pre-compression shape, thereby preventing a decrease in sealing performance. [Solution] Each end structure of the fuel cell stack has an insulating member 202 and a clamping member. A housing groove 232 is formed in the clamping member or the insulating member 202, and an elastic sealing member 250 is housed in the housing groove 232. The clamping member and the insulating member 202 have a plurality of flow holes 22 through which fuel gas, oxidizer gas, or cooling medium flows, respectively. The elastic sealing member 250 surrounds the outer circumference of the plurality of flow holes 22. In addition, three or more connecting bolts are arranged around each of the plurality of flow holes 22.

Description

Technical Field

[0001] The present disclosure relates to a fuel cell stack.

Background Art

[0002] A fuel cell stack includes a cell stack in which unit cells are stacked, and end structures provided at both ends of the cell stack. Each of the end structures includes an end plate disposed outermost in the stacking direction of the cell stack, an insulating member positioned between the cell stack and the end plate, a terminal plate interposed between the cell stack and the insulating member, and the like.

[0003] In some cases, a seal is provided between two members that abut against each other among the above-described plurality of members to prevent leakage of a reaction gas or a cooling medium. As an example of the seal material, a liquid gasket (FIPG; Formed In Place Gasket) described in Japanese Patent Application Laid-Open No. 2017-62891 can be cited. As is well known, a liquid gasket exhibits sealing performance as it cures.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When a liquid gasket is used, there is a concern that the sealing performance may deteriorate over time. To eliminate this concern, it is conceivable to use an elastic seal member (elastic solid) such as an O-ring. However, in that case, the following disadvantages are assumed.

[0006] In other words, the elastic sealing member is compressed when the fuel cell stack is tightened during the assembly process of the fuel cell stack. The compressed elastic sealing member exhibits an elastic restoring force that returns it to its original shape. This elastic restoring force acts as a reaction force on the two members sandwiching the elastic sealing member. If a gap is formed between the two members due to this reaction force, the sealing performance between the two members will decrease.

[0007] The present invention aims to solve the problems described above. [Means for solving the problem]

[0008] An aspect of the present disclosure is a fuel cell stack comprising a cell stack in which a plurality of single cells are stacked, and end structures provided at both ends of the cell stack in the stacking direction, wherein each of the end structures has an end plate located at the outermost end in the stacking direction, an insulating member located between the cell stack and the end plate in the stacking direction, a clamping member interposed between the cell stack and the insulating member in the stacking direction, a housing groove formed in the clamping member or the insulating member, an elastic sealing member housed in the housing groove and sealing the space between the clamping member and the insulating member, and a plurality of connecting bolts for connecting the clamping member and the insulating member, wherein the clamping member extends along the stacking direction and has a plurality of flow holes through which fuel gas, oxidizer gas, or cooling medium supplied to the cell stack flows, respectively, the elastic sealing member surrounds the outer periphery of the plurality of flow holes, and three or more of the plurality of connecting bolts are arranged around each of the plurality of flow holes. [Effects of the Invention]

[0009] According to this disclosure, the formation of a gap between the clamping member and the insulating member due to the elastic sealing member returning to its pre-compression shape is avoided, thus preventing a decrease in the sealing performance between the clamping member and the insulating member. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic overall perspective view of a fuel cell stack according to an embodiment of the present invention. [Figure 2] Figure 2 is a partially exploded perspective view of the end structure. [Figure 3] Figure 3 is a schematic front view of a portion of the end structure as seen from the inside in the stacking direction, with the clamping members omitted. [Figure 4] Figure 4 is a schematic front view of another part of the end structure as seen from the inside in the stacking direction, with the clamping members omitted. [Figure 5] Figure 5 is a cross-sectional view of the VV line in Figure 3. [Figure 6] Figure 6 is a side cross-sectional view of the end structure, taken from the width direction. [Figure 7] Figures 7A and 7B are cross-sectional views of the elastic sealing member when cut in a direction perpendicular to the longitudinal direction. [Modes for carrying out the invention]

[0011] In the following, "stacking direction" refers to the direction in which the single cells 12 shown in Figure 1 are stacked, and refers to the longitudinal direction of the cell stack 14 (the axial direction of the fuel cell stack 10). "Vertical direction" is perpendicular to the stacking direction and connects the first side 11a and the second side 11b of the fuel cell stack 10. "Width direction" is perpendicular to the stacking direction and the vertical direction and connects the third side 11c and the fourth side 11d of the fuel cell stack 10. However, the vertical direction and width direction are convenient orientations for the purpose of simplifying the explanation and making it easier to understand, and do not necessarily refer to the direction in which the fuel cell stack 10 is actually used.

[0012] Furthermore, the "thickness" of the elastic sealing member 250, etc., shown in Figures 2 to 4 refers to the thickness in its natural state. "Natural state" means a condition in which no external force, such as compressive force, is applied to the elastic sealing member 250 or elastic gasket 260.

[0013] Figure 1 is a schematic overall perspective view of the fuel cell stack 10 according to this embodiment. The fuel cell stack 10 comprises a cell stack 14 in which a plurality of single cells 12 are stacked. Briefly describing the single cell 12, the single cell 12 has a membrane electrode assembly (MEA). The MEA has an electrolyte membrane and an anode electrode and a cathode electrode formed on both end faces of the electrolyte membrane, respectively. The single cell 12 is formed by sandwiching the MEA between a pair of separators 30 (see Figure 6). The configuration of the single cell 12 in the fuel cell stack 10 is well known, so illustration and detailed description are omitted.

[0014] The fuel cell stack 10 has a pair of end structures 20 provided at both ends in the stacking direction. Each of the pair of end structures 20 includes a pair of end plates 200 located at the outermost end in the stacking direction.

[0015] The cell laminate 14 has a plurality of flow holes 22. Each opening of the plurality of flow holes 22 is formed in one of the pair of end plates 200. In the illustrated example, the plurality of flow holes 22 have a fuel gas supply hole 24a, an oxygen-containing gas supply hole 26a, a first refrigerant supply hole 28a, and a second refrigerant supply hole 28b. The plurality of flow holes 22 also have a first fuel gas discharge hole 24b, a second fuel gas discharge hole 24c, a first oxygen-containing gas discharge hole 26b, a second oxygen-containing gas discharge hole 26c, a first refrigerant discharge hole 28c, and a second refrigerant discharge hole 28d. Note that the plurality of flow holes 22 may also have one refrigerant inlet. The plurality of flow holes 22 may also have one fuel gas discharge hole, one oxygen-containing gas discharge hole, or one refrigerant discharge hole.

[0016] In the illustrated example, at one end (the third side portion 11c) in the width direction of the fuel cell stack 10, from the bottom upward, the first oxygen-containing gas discharge hole 26b, the first refrigerant discharge hole 28c, the fuel gas supply hole 24a, the second refrigerant discharge hole 28d, and the second oxygen-containing gas discharge hole 26c are arranged in sequence. At the other end (the fourth side portion 11d) in the width direction of the fuel cell stack 10, from the bottom upward, the first fuel gas discharge hole 24b, the first refrigerant supply hole 28a, the oxygen-containing gas supply hole 26a, the second refrigerant supply hole 28b, and the second fuel gas discharge hole 24c are arranged in sequence. However, the above arrangement order is only an example.

[0017] The plurality of flow holes 22 extend along the stacking direction. In the fuel cell stack 10, the reaction gases (oxygen-containing gas and fuel gas) and the cooling medium flow along the stacking direction and are distributed to each of the plurality of single cells 12 through oxygen-containing gas flow paths, fuel gas flow paths, and refrigerant flow paths (not shown) formed in the pair of separators 30.

[0018] In the present embodiment, each of the pair of end structures 20 has an insulating member 202 and a sandwiching member 204. The insulating member 202 is located between the cell stack 14 and the end plate 200. The sandwiching member 204 is interposed between the cell stack 14 and the insulating member 202. The insulating member 202 is located outside the sandwiching member 204 in the stacking direction and abuts against the sandwiching member 204.

[0019] The insulating member 202 and the sandwiching member 204 have a plurality of flow holes 22, similar to the cell stack 14. That is, the insulating member 202 and the sandwiching member 204 have the fuel gas supply hole 24a, the oxygen-containing gas supply hole 26a, the first refrigerant supply hole 28a, the second refrigerant supply hole 28b, the first fuel gas discharge hole 24b, the second fuel gas discharge hole 24c, the first oxygen-containing gas discharge hole 26b, the second oxygen-containing gas discharge hole 26c, the first refrigerant discharge hole 28c, and the second refrigerant discharge hole 28d. However, in the insulating member 202, the fuel gas supply hole 24a, the oxygen-containing gas supply hole 26a, the first fuel gas discharge hole 24b, the second fuel gas discharge hole 24c, the first oxygen-containing gas discharge hole 26b, and the second oxygen-containing gas discharge hole 26c may be blocked.

[0020] In the aspect shown in FIG. 2, the sandwiching member 204 has an opening 206 penetrating along the stacking direction. Therefore, the sandwiching member 204 is a rectangular (annular) member. The material of the sandwiching member 204 is, for example, stainless steel.

[0021] The sandwiching member 204 has an inner edge portion 208 around the opening 206 and an outer edge portion 210 around the outer periphery of the first to fourth side portions 11a to 11d. A plurality of bolt insertion holes 212 are respectively formed in the inner edge portion 208 and the outer edge portion 210. Hereinafter, the plurality of bolt insertion holes 212 formed in the inner edge portion 208 may be referred to as inner insertion holes 212a, and the plurality of bolt insertion holes 212 formed in the outer edge portion 210 may be referred to as outer insertion holes 212b.

[0022] A current collecting member 224 made of a conductor is inserted into the opening 206. The current collecting member 224 overlaps the MEA of the single cell 12 at the rear of the stacking. Note that the current collecting member 224 and the sandwiching member 204 are electrically insulated from each other. Therefore, no current flows from the current collecting member 224 to the sandwiching member 204, and no current flows from the sandwiching member 204 to the current collecting member 224.

[0023] As shown in FIGS. 3 and 4, the insulating member 202 has an engaging opening 220. Therefore, the insulating member 202 is a rectangular (annular) member. A terminal plate 222 is held in the engaging opening 220. The terminal plate 222 is electrically connected to the current collecting member 224. The electric power obtained in the cell stack 14 is supplied to an external load via the current collecting member 224 and the terminal plate 222.

[0024] As described above, in the aspect of the illustrated example, the sandwiching member 204, the current collecting member 224, and the terminal plate 222 are separate members. However, the sandwiching member 204, the current collecting member 224, and the terminal plate 222 may be integrated to form a terminal member. In this case, the sandwiching member 204 (terminal member) does not need to have the opening 206. Also, the insulating member 202 does not need to have the engaging opening 220.

[0025] A suitable example of the material for the insulating member 202 is resin. In this case, the insulating member 202 is manufactured, for example, by injection molding using molten resin as the raw material. This makes it possible to mass-produce insulating members 202, which have multiple bolt holes 230 and receiving grooves 232, etc., formed therein, at low cost and easily. However, the material for the insulating member 202 is not limited to resin.

[0026] The insulating member 202 has a plurality of bolt holes 230. The positions of the plurality of bolt holes 230 correspond to the positions of the plurality of bolt insertion holes 212. Hereinafter, the bolt holes 230 corresponding to the inner insertion holes 212a will be referred to as inner holes 230a. The inner holes 230a are located inside the circumferential groove 240 (described later) in the width direction. The bolt holes 230 corresponding to the outer insertion holes 212b will be referred to as outer holes 230b. The outer holes 230b are located outside the circumferential groove 240 in the width direction or in the vertical direction.

[0027] The end structure 20 has a receiving groove 232 and an elastic sealing member 250. The receiving groove 232 is formed on the end face of the insulating member 202 facing the clamping member 204. The receiving groove 232 may also be formed on the end face of the clamping member 204 facing the insulating member 202.

[0028] The accommodating groove 232 has a first groove 232a and a second groove 232b. As shown in Figure 3, the first groove 232a has a first annular groove portion 233a, a second annular groove portion 233b, a third annular groove portion 233c, a fourth annular groove portion 233d, and a fifth annular groove portion 233e. The first annular groove portion 233a surrounds the outer circumference of the first oxygen-containing gas discharge hole 26b, and the second annular groove portion 233b surrounds the outer circumference of the first refrigerant discharge hole 28c. The third annular groove portion 233c, the fourth annular groove portion 233d, and the fifth annular groove portion 233e surround the fuel gas supply hole 24a, the second refrigerant discharge hole 28d, and the second oxygen-containing gas discharge hole 26c, respectively.

[0029] The first groove 232a further comprises a first straight groove 234a, a second straight groove 234b, a third straight groove 234c, and a fourth straight groove 234d. The first straight groove 234a connects the first annular groove 233a and the second annular groove 233b. The second straight groove 234b connects the second annular groove 233b and the third annular groove 233c, and the third straight groove 234c connects the third annular groove 233c and the fourth annular groove 233d. The fourth straight groove 234d connects the fourth annular groove 233d and the fifth annular groove 233e.

[0030] As shown in Figure 4, the second groove 232b has a sixth annular groove 233f, a seventh annular groove 233g, an eighth annular groove 233h, a ninth annular groove 233i, and a tenth annular groove 233j. The sixth annular groove 233f surrounds the outer circumference of the first fuel gas discharge hole 24b, and the seventh annular groove 233g surrounds the outer circumference of the first refrigerant supply hole 28a. The eighth annular groove 233h, the ninth annular groove 233i, and the tenth annular groove 233j surround the oxygen-containing gas supply hole 26a, the second refrigerant supply hole 28b, and the second fuel gas discharge hole 24c, respectively.

[0031] The second groove 232b further includes a fifth straight groove 234e, a sixth straight groove 234f, a seventh straight groove 234g, and an eighth straight groove 234h. The fifth straight groove 234e connects the sixth annular groove 233f and the seventh annular groove 233g. The sixth straight groove 234f connects the seventh annular groove 233g and the eighth annular groove 233h, and the seventh straight groove 234g connects the eighth annular groove 233h and the ninth annular groove 233i. The eighth straight groove 234h connects the ninth annular groove 233i and the tenth annular groove 233j.

[0032] On the other hand, the elastic sealing member 250 has a first sealing body 250a (see Figures 2 and 3) and a second sealing body 250b (see Figures 2 and 4). The first sealing body 250a is housed in the first groove 232a, and the second sealing body 250b is housed in the second groove 232b.

[0033] As shown in Figure 3, the first seal body 250a has a plurality of ring portions 252 and a plurality of connecting portions 254. The plurality of ring portions 252 have a first ring portion 252a, a second ring portion 252b, a third ring portion 252c, a fourth ring portion 252d, and a fifth ring portion 252e. The plurality of connecting portions 254 have a first connecting portion 254a, a second connecting portion 254b, a third connecting portion 254c, and a fourth connecting portion 254d. The first connecting portion 254a connects the first ring portion 252a and the second ring portion 252b. The second connecting portion 254b connects the second ring portion 252b and the third ring portion 252c, and the third connecting portion 254c connects the third ring portion 252c and the fourth ring portion 252d. The fourth connecting section 254d connects the fourth ring section 252d and the fifth ring section 252e.

[0034] The first ring portion 252a to the fifth ring portion 252e are housed in the first annular groove portion 233a to the fifth annular groove portion 233e, respectively. The first connecting portion 254a to the fourth connecting portion 254d are housed in the first straight groove portion 234a to the fourth straight groove portion 234d, respectively.

[0035] Figure 5 is a cross-sectional view along the VV line in Figure 3. As can be seen from Figure 5, the depth direction of the first groove 232a and the second groove 232b (multiple accommodating grooves 232) coincides with the stacking direction. Also, the thickness T2 along the stacking direction in the second connecting portion 254b is smaller than the thickness T1 along the stacking direction in the second ring portion 252b and the third ring portion 252c. Note that the thickness T1 of the multiple ring portions 252 are approximately equal to each other. Similarly, the thickness T2 of the multiple connecting portions 254 are also approximately equal to each other. Furthermore, the depth D of the first groove 232a is approximately constant.

[0036] Furthermore, the thickness T1 of the second annular portion 252b and the third annular portion 252c is slightly larger than the depth D of the second annular groove portion 233b and the third annular groove portion 233c. For this reason, before the insulating member 202 and the clamping member 204 come into contact, the second annular portion 252b and the third annular portion 252c are slightly exposed from the openings of the second annular groove portion 233b and the third annular groove portion 233c. The same applies to the first annular portion 252a, the fourth annular portion 252d and the fifth annular portion 252e.

[0037] In contrast, the thickness T2 of the second connection portion 254b is slightly smaller than the depth D of the second straight groove portion 234b. Therefore, before the insulating member 202 and the clamping member 204 come into contact, the entire second connection portion 254b is housed in the second straight groove portion 234b. The same applies to the first connection portion 254a, the third connection portion 254c, and the fourth connection portion 254d. Alternatively, before the insulating member 202 and the clamping member 204 come into contact, a portion of the multiple connection portions 254 may be exposed from the first groove 232a. Or, the position of the end of each of the multiple connection portions 254 in the stacking direction may be the same as the position of the end face of the insulating member 202.

[0038] Figure 6 is a side cross-sectional view of the main part of the end structure 20 as seen from the width direction. As shown in Figure 6, in the stacking direction, it is preferable that the first ring portion 252a to the fifth ring portion 252e overlap with the bead seal 32 of the separator 30.

[0039] The same relationship applies to the second groove 232b and the second seal body 250b.

[0040] In the embodiments shown in Figures 2 to 4, each end structure 20 further has a circumferential groove 240 formed in the insulating member 202. The circumferential groove 240 is located between two accommodating grooves 232 (first groove 232a and second groove 232b) and surrounds the outer circumference of the engagement opening 220. The depth direction of the circumferential groove 240 coincides with the stacking direction. Note that the circumferential groove 240 does not need to be formed in insulating members 202 where the engagement opening 220 is not formed. Also, the circumferential groove 240 may be formed in the clamping member 204.

[0041] Each of the end structures 20 further includes an annular elastic gasket 260 housed in a circumferential groove 240. The elastic gasket 260 seals the outer circumference of the engagement opening 220 in an annular manner. The thickness of the elastic gasket 260 along the lamination direction is slightly greater than the depth of the circumferential groove 240. Therefore, before the insulating member 202 and the clamping member 204 come into contact, the elastic gasket 260 is slightly exposed from the opening of the circumferential groove 240.

[0042] Each end structure 20 further has a plurality of connecting bolts 268 for connecting the clamping member 204 and the insulating member 202. The plurality of connecting bolts 268 have inner edge bolts 280 and outer edge bolts 270. The inner edge bolts 280 are passed through the inner insertion hole 212a of the clamping member 204 and screwed into the inner hole 230a of the insulating member 202. The outer edge bolts 270 are passed through the outer insertion hole 212b of the clamping member 204 and screwed into the outer hole 230b of the insulating member 202. The inner edge bolts 280 are located inside the circumferential groove 240 and the elastic gasket 260 in the width direction. Conversely, the outer edge bolts 270 are located outside the circumferential groove 240 and the elastic gasket 260 in the width direction.

[0043] Specific examples of the elastic sealing member 250 and elastic gasket 260 include O-rings made of rubber or elastomer. As illustrated in Figure 7A, when the elastic sealing member 250 is an O-ring, the cross-section in the diametrical direction is approximately circular. In the elastic sealing member 250 and elastic gasket 260, the shape of the cross-section along the depth direction of the housing groove 232 does not have to be circular. Examples of shapes other than circular include an elliptical shape or the approximately barrel shape shown in Figure 7B. Figure 7B is an example of an elastic sealing member 250A in which the cross-sectional shape along the depth direction of the housing groove 232 is approximately barrel-shaped.

[0044] In the above configuration, three or more of the multiple connecting bolts 268 are arranged around each of the multiple flow holes 22 (see Figures 3 and 4). Note that some of the connecting bolts 268 surrounding the outer circumference of one flow hole 22 may also serve as connecting bolts 268 surrounding the outer circumference of another flow hole 22. This point will be explained with reference to Figures 3 and 4.

[0045] As shown in Figure 3, the reference numerals for the outer edge bolts 270 located at the third side portion 11c are 271a, 271b, 271c, 271d, 271e, and 271f. The reference numerals for the inner edge bolts 280 located at the third side portion 11c are 281a, 281b, 281c, and 281d. The first oxygen-containing gas discharge hole 26b is surrounded by the outer edge bolts 271a, 271b, 271c, and 281a. The first refrigerant discharge hole 28c is surrounded by the outer edge bolts 271c, 271d, 281a, and 281b.

[0046] The fuel gas supply port 24a is surrounded by outer edge bolts 271d, inner edge bolts 281b and 281c. The second refrigerant discharge port 28d is surrounded by outer edge bolts 271d, outer edge bolts 271e, inner edge bolts 281c and 281d. The second oxygen-containing gas discharge port 26c is surrounded by outer edge bolts 271e, outer edge bolts 271f and 281d.

[0047] As shown in Figure 4, the reference numerals for the outer edge bolts 270 located on the fourth side portion 11d are 272a, 272b, 272c, 272d, 272e, 272f, and 272g. The reference numerals for the inner edge bolts 280 located on the fourth side portion 11d are 282a, 282b, 282c, and 282d. The first fuel gas discharge hole 24b is surrounded by the outer edge bolts 272a, 272b, and 282a. The first refrigerant supply hole 28a is surrounded by the outer edge bolts 272b, 272c, 282a, and 282b.

[0048] The oxygen-containing gas supply port 26a is surrounded by outer edge bolts 272c, 272d, 282b, and 282c. The second refrigerant supply port 28b is surrounded by outer edge bolts 272d, 272e, 282c, and 282d. The second fuel gas discharge port 24c is surrounded by outer edge bolts 272e, 272f, 272g, and 282d.

[0049] Note that the above combinations are just examples. Other combinations are also acceptable as long as three or more connecting bolts 268 are assigned to each of the multiple flow holes 22.

[0050] The outer edge bolt 270 has outer edge bolts 273a and 273b located on the first side portion 11a, and further has outer edge bolts 274a and 274b located on the second side portion 11b. The outer edge bolts 273a, 273b, 274a, and 274b are located near the outer circumference of the elastic gasket 260.

[0051] The assembly method for the fuel cell stack 10 configured as described above will be explained below.

[0052] As shown in Figure 1, the worker stacks multiple single cells 12. This results in a cell stack 14. Next, the worker provides end structures 20 at both ends of the cell stack 14. To do this, the worker places the first seal body 250a into the first groove 232a (see Figures 2 and 3) formed in the insulating member 202. If the first to fifth annular sections 252a to 252e are separate members, it is necessary to place the first to fifth annular sections 252a to 252e into the first to fifth annular grooves 233a to 233e, respectively. In this case, the work is complicated.

[0053] In contrast, in this embodiment, the first seal body 250a is a single component in which a plurality of ring portions 252 are integrated via a plurality of connecting portions 254. Therefore, the first seal body 250a can be accommodated in the first groove 232a by roughly positioning the first seal body 250a in the first annular groove portion 233a to the fifth annular groove portion 233e, and then pushing the first ring portions 252a to the fifth annular groove portion 252e into the first annular groove portion 233a to the fifth annular groove portion 233e, respectively. The same applies to the second seal body 250b. Therefore, the work is simplified. Furthermore, the work efficiency in assembling the fuel cell stack 10 is improved.

[0054] Furthermore, the worker places the elastic gasket 260 into the circumferential groove 240. This mounts the elastic sealing member 250 (first sealing body 250a and second sealing body 250b) and the elastic gasket 260 onto the insulating member 202. At this point, as shown in Figure 6, each ring portion 252 of the elastic sealing member 250 is exposed inward in the stacking direction from the opening of the housing groove 232. Similarly, a portion of the elastic gasket 260 is also exposed inward in the stacking direction from the opening of the circumferential groove 240. Each connecting portion 254 of the elastic sealing member 250 may or may not be exposed from the opening of the housing groove 232, but it is preferable that it not be exposed.

[0055] Next, the worker connects the clamping member 204 and the insulating member 202 to each other. That is, as shown in Figure 2, the end faces of the insulating member 202, which are fitted with the two elastic sealing members 250 and the elastic gasket 260, face the clamping member 204. In this state, each of the multiple connecting bolts 268 is inserted into the bolt hole 230 through the bolt insertion hole 212. Furthermore, each of the multiple connecting bolts 268 is rotated and screwed into the bolt hole 230.

[0056] As a result of this screwing, the end face of the clamping member 204 comes into close contact with the end face of the insulating member 202. Consequently, the portion of the elastic sealing member 250 that was exposed from the housing groove 232 is compressed. Similarly, the portion of the elastic gasket 260 that was exposed from the circumferential groove 240 is compressed. That is, at least each ring portion 252 of the elastic sealing member 250 is housed in the housing groove 232 in a contracted state, and the elastic gasket 260 is housed in the circumferential groove 240 in a contracted state. In this way, an assembly of the clamping member 204, the current collector member 224 inserted into the opening 206 of the clamping member 204, and the insulating member 202 is obtained.

[0057] Furthermore, if each connecting portion 254 of the elastic sealing member 250 is not exposed from the housing groove 232, a large load acting on each connecting portion 254 during the above-mentioned screwing process is avoided. In other words, the fracture of the connecting portion 254 due to the tightening of multiple connecting bolts 268 is avoided.

[0058] Next, the worker places the assembly in between and overlaps the end plate 200 onto the end of the cell stack 14. The clamping member 204 of the assembly faces the cell stack 14, and the insulating member 202 of the assembly faces the end plate 200. After providing the end structures 20 at both ends of the cell stack 14 in the stacking direction in this manner, the worker fastens the pair of end plates 200 together with a connecting bar 40 or the like. This causes the individual cells 12 to be in close contact with each other, and the cell stack 14 and the end structures 20 to be in close contact.

[0059] Next, we will explain how to operate the fuel cell stack 10.

[0060] When the fuel cell stack 10 is in operation, a fuel gas such as hydrogen gas is supplied to the fuel gas supply port 24a shown in Figure 1, and an oxygen-containing gas such as compressed air is supplied to the oxygen-containing gas supply port 26a. The fuel gas flows through the fuel gas flow path of each single cell 12 and comes into contact with the anode electrode. The oxygen-containing gas flows through the oxygen-containing gas flow path of each single cell 12 and comes into contact with the cathode electrode. As a result, each single cell 12 generates electricity. The electricity obtained is supplied to an external load via the current collector 224 and terminal plate 222 shown in Figure 2. Unreacted fuel gas is discharged from the first fuel gas discharge port 24b and the second fuel gas discharge port 24c, and unreacted oxygen-containing gas is discharged from the first oxygen-containing gas discharge port 26b and the second oxygen-containing gas discharge port 26c.

[0061] Each individual cell 12 generates heat during power generation. This heat is absorbed by the cooling medium supplied to the first refrigerant supply port 28a and the second refrigerant supply port 28b. The cooling medium flows through the refrigerant flow path of each individual cell 12 and is then discharged from the first refrigerant discharge port 28c and the second refrigerant discharge port 28d.

[0062] While the fuel cell stack 10 is in operation, the multiple ring portions 252 (see Figure 3) of the elastic sealing member 250 seal the space between the insulating member 202 and the clamping member 204 around the multiple flow holes 22. This prevents fuel gas from leaking into flows other than the fuel gas flow path. Similarly, it prevents oxygen-containing gas from leaking into flows other than the oxygen-containing gas flow path, and prevents cooling medium from leaking into flows other than the refrigerant flow path.

[0063] Furthermore, the elastic gasket 260 seals the space between the insulating member 202 and the clamping member 204 on the outer circumference of the terminal plate 222 and the current collector member 224. This prevents the fuel gas, oxygen-containing gas, and cooling medium from coming into contact with the terminal plate 222 and the current collector member 224. Consequently, corrosion of the terminal plate 222 and the current collector member 224 is prevented.

[0064] Each individual cell 12 undergoes thermal expansion as it heats up. In the elastic sealing member 250, three or more connecting bolts 268 are arranged around each of the first to fifth annular portions 252a to 252e. Therefore, the first to fifth annular portions 252a to 252e receive a large clamping force from the connecting bolts 268. Consequently, the first to fifth annular portions 252a to 252e maintain a compressed state (contracted state) in the first to fifth annular grooves 233a to 233e. In other words, the first to fifth annular portions 252a to 252e are prevented from returning to their pre-compression shape (expanding) based on the elastic restoring force between the clamping member 204 and the insulating member 202.

[0065] This prevents the formation of a gap between the clamping member 204 and the insulating member 202 due to the first ring portion 252a to the fifth ring portion 252e returning to their pre-compression shape. As a result, a decrease in the sealing performance between the clamping member 204 and the insulating member 202 is avoided.

[0066] When the thickness T2 of the first connection portion 254a to the fourth connection portion 254d is smaller than the depth D of the first straight groove portion 234a to the fourth straight portion, the first connection portion 254a to the fourth connection portion 254d are not compressed when the connecting bolt 268 is tightened. Therefore, the clamping member 204 and the insulating member 202 are prevented from being pressed by the elastic restoring force of the first connection portion 254a to the fourth connection portion 254d. Consequently, a decrease in the sealing performance between the clamping member 204 and the insulating member 202 due to pressure from the first connection portion 254a to the fourth connection portion 254d is avoided.

[0067] As described above, even when using an elastic sealing member 250 which is an elastic solid, the reaction force received from the elastic sealing member 250 prevents the formation of a gap between the clamping member 204 and the insulating part. Therefore, even if each single cell 12 (or cell laminate 14) undergoes thermal expansion, a decrease in the sealing performance between the clamping member 204 and the insulating member 202 is avoided.

[0068] Furthermore, the elastic gasket 260 is subjected to large clamping forces from the inner edge bolts 281a-281d, inner edge bolts 282a-282d, and outer edge bolts 273a, 273b, 274a, and 274b. Therefore, the elastic gasket 260 maintains a compressed state (contracted state) in the circumferential groove 240. In other words, the elastic gasket 260 is prevented from returning to its pre-compression shape (expanding) based on the elastic restoring force between the clamping member 204 and the insulating member 202. That is, the formation of a gap between the clamping member 204 and the insulating member 202 due to the elastic gasket 260 returning to its pre-compression shape is prevented. As a result, a decrease in the sealing performance between the clamping member 204 and the insulating member 202 is prevented.

[0069] This embodiment provides the following effects.

[0070] As shown in Figure 2, each end structure 20 of the fuel cell stack 10 has an insulating member 202 and a clamping member 204. A housing groove 232 is formed in the insulating member 202, and an elastic sealing member 250 is housed in the housing groove 232. The current collector member 224 and the insulating member 202 are connected by a plurality of connecting bolts 268. The clamping member 204 and the insulating member 202 have a plurality of flow holes 22. The elastic sealing member 250 has a plurality of ring portions 252 (first ring portion 252a to fifth ring portion 252e) that surround the outer circumference of each of the plurality of flow holes 22. As shown in Figure 3, in the above configuration, three or more of the plurality of connecting bolts 268 are arranged around each of the plurality of flow holes 22.

[0071] Since three or more connecting bolts 268 are arranged around each of the flow holes 22, the multiple ring portions 252 in the elastic sealing member 250 receive a large tightening force from the connecting bolts 268. Consequently, the elastic sealing member 250 maintains a contracted state in the housing groove 232. Therefore, for example, when the fuel cell stack 10 undergoes thermal expansion during operation, expansion of the multiple ring portions 252 between the clamping member 204 and the insulating member 202 based on elastic restoring force is prevented.

[0072] This prevents the formation of a gap between the clamping member 204 and the insulating member 202. As a result, a decrease in the sealing performance between the clamping member 204 and the insulating member 202 is avoided.

[0073] The clamping member 204 has an opening 206 that penetrates along the stacking direction. Each of the end structures 20 has an annular elastic gasket 260 located between the insulating member 202 and the clamping member 204, surrounding the outer circumference of the opening 206.

[0074] Since an annular, elastic solid elastic gasket 260 is located around the outer circumference of the opening 206, the reaction gas or cooling medium is prevented from flowing toward the opening 206. Consequently, the reaction gas or cooling medium is prevented from coming into contact with the current collector 224 located in the opening 206.

[0075] The multiple connecting bolts 268 have inner edge bolts 280 positioned on the inner edge (opening 206 side) of the clamping member 204 and outer edge bolts 270 positioned on the outer edge (outer circumference side) of the clamping member 204. Each of the multiple flow holes 22 is located between the inner edge bolts 280 and the outer edge bolts 270.

[0076] In this case, the tightening force from the inner edge bolt 280 and the tightening force from the outer edge bolt 270 are balanced. Therefore, expansion of some of the ring portions 252 due to an imbalance in tightening force is avoided. It is preferable that the inner edge bolt 280 is located on the inner circumference side of the elastic gasket 260. As a result, the elastic gasket 260 is subjected to the tightening force from both the inner edge bolt 280 and the outer edge bolt 270, so the elastic gasket 260 also remains in a contracted state. In other words, expansion of the elastic gasket 260 is avoided.

[0077] Some of the multiple (three or more) connecting bolts 268 surrounding the outer circumference of one flow hole 22 also serve as multiple (three or more) connecting bolts 268 surrounding the outer circumference of another flow hole 22 adjacent to that flow hole 22.

[0078] This reduces the number of connecting bolts 268. Consequently, the time required for tightening the connecting bolts 268 is shortened. In addition, the fuel cell stack 10 can be made lighter.

[0079] The elastic sealing member 250 has multiple connecting parts 254 (first connecting part 254a to fourth connecting part 254d) that connect two adjacent ring parts 252.

[0080] This configuration allows sealing members to be placed around multiple flow holes 22 in a single installation operation. This improves the efficiency of the assembly work of the fuel cell stack 10.

[0081] As shown in Figure 5, the thickness T2 along the stacking direction in each of the multiple connection portions 254 is smaller than the thickness T1 along the stacking direction in each of the multiple ring portions 252.

[0082] In this case, even if the multiple connection points 254 expand due to elastic restoring force, the reaction force received by the insulating member 202 and the clamping member 204 from the multiple connection points 254 is small. Therefore, the effect on the sealing performance between the insulating member 202 and the clamping member 204 is small.

[0083] In the embodiment shown in Figure 5, the thickness T2 of each of the multiple connection portions 254 is smaller than the depth D of the accommodating groove 232.

[0084] In this case, the multiple connecting parts 254 are not exposed from the housing groove 232. Therefore, for example, when tightening the connecting bolt 268, a large load is applied to the connecting parts 254, which can prevent them from breaking.

[0085] The insulating member 202 is made of resin, and the receiving groove 232 is formed in the insulating member 202.

[0086] The insulating member 202 is manufactured, for example, by injection molding using molten resin. When molding the insulating member 202 in this injection molding process, the receiving groove 232 can be easily formed.

[0087] The following additional information is disclosed regarding the above embodiments.

[0088] (Note 1) The fuel cell stack (10) of the present disclosure comprises a cell stack (14) in which a plurality of single cells (12) are stacked, and end structures (20) provided at both ends in the stacking direction of the cell stack, wherein each of the end structures comprises an end plate (200) located at the outermost position in the stacking direction, an insulating member (202) located between the cell stack and the end plate in the stacking direction, a clamping member (204) interposed between the cell stack and the insulating member in the stacking direction, and the clamping member or the insulating part The material has a receiving groove (232) formed in it, an elastic sealing member (250) housed in the receiving groove and sealing the space between the clamping member and the insulating member, and a plurality of connecting bolts (268) for connecting the clamping member and the insulating member. The clamping member extends along the stacking direction and has a plurality of flow holes (22) through which fuel gas, oxidizing gas, or cooling medium supplied to the cell stack flows, respectively. The elastic sealing member surrounds the outer periphery of the plurality of flow holes, and three or more of the plurality of connecting bolts are arranged around each of the plurality of flow holes.

[0089] Since three or more connecting bolts are arranged around each flow hole, the elastic sealing member receives a large tightening force from the connecting bolts. Therefore, the elastic sealing member is prevented from returning to its pre-compression shape (expanding) due to its elastic restoring force. As a result, the formation of a gap between the clamping member and the insulating member is prevented, and thus a decrease in the sealing performance between the clamping member and the insulating member is prevented.

[0090] (Note 2) In the fuel cell stack described in Appendix 1, the clamping member has an opening (206) that penetrates along the stacking direction, and each of the end structures may have an annular elastic gasket (260) located between the insulating member and the clamping member and surrounding the outer circumference of the opening.

[0091] Since an annular elastic gasket is positioned around the outer circumference of the opening, the reaction gas or cooling medium is prevented from flowing toward the opening. Therefore, for example, if a current collector is placed in the opening, contact between the reaction gas or cooling medium and the current collector is prevented.

[0092] (Note 3) In the fuel cell stack described in Appendix 2, the plurality of connecting bolts include inner edge bolts (280) positioned on the inner edge of the clamping member and outer edge bolts (270) positioned on the outer edge of the clamping member, and each of the plurality of flow holes may be located between the inner edge bolts and the outer edge bolts.

[0093] In this case, the tightening force from the inner edge bolts and the tightening force from the outer edge bolts are balanced. Therefore, expansion of a portion of the elastic sealing member due to an imbalance in tightening forces is avoided.

[0094] (Note 4) In the fuel cell stack described in any one of the appendices 1 to 3, some of the three or more connecting bolts surrounding the outer circumference of one of the multiple flow holes may also serve as three or more connecting bolts surrounding the outer circumference of another flow hole adjacent to the first flow hole.

[0095] This reduces the number of connecting bolts, thereby shortening the time required for tightening the connecting bolts. Furthermore, it allows for a lighter fuel cell stack.

[0096] (Note 5) In the fuel cell stack described in any one of the appendices 1 to 4, the elastic sealing member may have a plurality of ring portions (252) surrounding each of the plurality of flow holes, and a plurality of connecting portions (254) connecting two adjacent ring portions.

[0097] This configuration allows sealing members to be positioned around multiple flow holes in a single installation operation. This improves the efficiency of fuel cell stack assembly.

[0098] (Note 6) In the fuel cell stack described in Appendix 5, the natural thickness (T2) along the stacking direction at each of the plurality of connection portions may be smaller than the natural thickness (T1) along the stacking direction at each of the plurality of ring portions.

[0099] In this case, even if multiple connection points expand due to elastic restoring force, the impact on the sealing performance between the insulating member and the clamping member is small.

[0100] (Note 7) In the fuel cell stack described in Appendix 6, the natural thickness of each of the plurality of connection portions may be less than the depth (D) of the housing groove.

[0101] This configuration prevents the connection from being exposed through the opening of the housing groove even in its natural state. Therefore, for example, when tightening the connecting bolt, it prevents the connection from being subjected to a large load and breaking.

[0102] (Note 8) In the fuel cell stack described in any one of the appendices 1 to 7, the insulating member may be made of resin, and the housing groove may be formed in the insulating member.

[0103] In this case, the accommodating groove can be easily formed when molding the insulating member from the molten resin.

[0104] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the intent of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of symbols]

[0105] 10…Fuel cell stack 12…Single cell 14…Cell stack 20…End structure 22…Flow hole 200…End plate 202...Insulating material 204...Clamping material 206…Opening 208…Inner edge 210...Outer edge 212...Bolt insertion hole 222...Terminal board 232...Housing groove 233a~233j…Annular groove section 234a~234h…Straight groove section 240...Circumferential groove 250, 250A...Elastic sealing member 252... Ring section 254... Connection section 260...Elastic gasket 268...Connecting bolt 270...Outer edge bolt 280...Inner edge bolt

Claims

1. A fuel cell stack comprising a cell stack in which a plurality of single cells are stacked, and end structures provided at both ends of the cell stack in the stacking direction, Each of the end structures is, The outermost end plate in the aforementioned stacking direction, In the aforementioned stacking direction, an insulating member is located between the cell stack and the end plate, In the aforementioned stacking direction, a clamping member is interposed between the cell stack and the insulating member, A housing groove formed in the clamping member or the insulating member, An elastic sealing member is housed in the aforementioned groove and seals the space between the clamping member and the insulating member, A plurality of connecting bolts for connecting the clamping member and the insulating member, It has, The clamping member extends along the stacking direction and has a plurality of flow holes through which fuel gas, oxidizer gas, or cooling medium supplied to the cell stack flows, and the elastic sealing member surrounds the outer periphery of the plurality of flow holes. A fuel cell stack in which three or more of the multiple connecting bolts are arranged around each of the multiple flow holes.

2. In the fuel cell stack according to claim 1, the clamping member has an opening that penetrates along the stacking direction, A fuel cell stack, wherein each of the end structures is located between the insulating member and the clamping member and has an annular elastic gasket surrounding the outer circumference of the opening.

3. A fuel cell stack according to claim 2, wherein the plurality of connecting bolts have inner-edge bolts arranged on the inner edge of the clamping member and outer-edge bolts arranged on the outer edge of the clamping member, and each of the plurality of flow holes is located between the inner-edge bolts and the outer-edge bolts.

4. A fuel cell stack according to any one of claims 1 to 3, wherein some of the three or more connecting bolts surrounding the outer circumference of one of the plurality of flow holes also serve as three or more connecting bolts surrounding the outer circumference of another flow hole adjacent to the one flow hole.

5. A fuel cell stack according to any one of claims 1 to 3, wherein the elastic sealing member has a plurality of ring portions that surround a plurality of flow holes, and a plurality of connecting portions that connect two adjacent ring portions.

6. A fuel cell stack according to claim 5, wherein the thickness of each of the plurality of connection portions in the natural state along the stacking direction is smaller than the thickness of each of the plurality of ring portions in the natural state along the stacking direction.

7. A fuel cell stack according to claim 6, wherein the natural thickness of each of the plurality of connection portions is smaller than the depth of the housing groove.

8. A fuel cell stack according to any one of claims 1 to 3, wherein the insulating member is made of resin and the housing groove is formed in the insulating member.

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