Fuel cell stack

Abstract

This fuel cell stack includes: a cell stacked body configured by stacking a plurality of power generating cells in a predetermined direction; a housing surrounding the cell stacked body; and a plurality of partitioning members that extend in a predetermined direction so as to divide a space between an inner wall surface of the housing and an outer side surface of the cell stacked body into a plurality of spaces including a first space and a second space. The inner wall surface is configured with protrusions and recesses so as to form a communicating flow path that provides communication between the first space and the second space.

Description

Fuel cell stack

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

[0002] In recent years, in order to enable more people to access affordable, reliable, sustainable, and advanced energy, technological developments related to fuel cells that contribute to energy efficiency have been carried out. As a technology related to a fuel cell stack used in this type of fuel cell, conventionally, a technology for ventilating the inside of a case in which a fuel cell is housed is known (see, for example, Patent Document 1). The case described in Patent Document 1 is provided with an air intake and an air outlet, and the case is configured to take in air from the outside through the air intake, pass it through the inside of the case, and discharge it from the air outlet.

[0003] Japanese Unexamined Patent Application Publication No. 2006-302606

[0004] In this type of fuel cell stack, the inside of the case may be partitioned into a plurality of spaces. In that case, it is difficult to ventilate the entire inside of the case due to the flow of air taken into the case through the air intake.

[0005] A fuel cell stack according to an aspect of the present invention includes a cell stack body formed by stacking a plurality of power generation cells in a predetermined direction, a housing surrounding the cell stack body, and a plurality of partition members extending in a predetermined direction so as to divide a space between an inner wall surface of the housing and an outer surface of the cell stack body into a plurality of spaces including a first space and a second space. The inner wall surface of the housing is configured in a concavo-convex shape so as to form a communication flow path that communicates the first space and the second space.

[0006] According to the present invention, the entire inside of the housing of the fuel cell stack can be satisfactorily ventilated.

[0007] A schematic perspective view showing the overall configuration of a fuel cell stack according to an embodiment of the present invention. A cross-sectional view along line II-II in Figure 1. A perspective view showing the configuration of the inner wall surface at the lower left corner of the case in Figure 1. A perspective view showing the state in which a retaining bar is attached to the inner wall surface at the lower left corner of the case in Figure 1. A cross-sectional view along line IV-IV in Figure 3B. A view of arrow V in Figure 3B. A cross-sectional view along line VI-VI in Figure 4. A diagram schematically showing the gas flow in a fuel cell stack according to an embodiment of the present invention. A view of arrow VIII in Figure 5. A view of arrow IX in Figure 8. A cross-sectional view along line XX in Figure 9. An enlarged view of the main part of Figure 9. A diagram showing a modified example of Figure 9. A diagram showing another modified example of Figure 9.

[0008] Embodiments of the present invention will be described below with reference to Figures 1 to 7. The fuel cell stack according to the embodiment of the present invention is the main component of the fuel cell. The fuel cell can be mounted on a vehicle, for example, and can generate electricity for driving the vehicle. The fuel cell can also be mounted on mobile devices other than vehicles, such as aircraft and ships, as well as robots and various industrial machines.

[0009] Figure 1 is a schematic perspective view showing the overall configuration of a fuel cell stack 100 according to an embodiment of the present invention. For convenience, the three mutually orthogonal axial directions shown in the figure will be defined as the longitudinal direction, the left-right direction, and the vertical direction, and the configuration of each part will be described according to this definition. The downward direction in the vertical direction of Figure 1 corresponds to the direction of gravity. The longitudinal direction in Figure 1 corresponds to the stacking direction of the fuel cell stack 100. Note that the longitudinal and left-right directions in Figure 1 are not necessarily the same as the longitudinal and left-right directions of a vehicle.

[0010] As shown in Figure 1, the fuel cell stack 100 comprises a cell stack 10, end units 40 positioned at both ends of the cell stack 10 in the front-to-back direction, and a case 30 positioned around the cell stack 10 so as to surround it, and the overall shape is substantially rectangular. The length of the fuel cell stack 100 in the left-to-right direction is longer than its length in the up-to-down direction.

[0011] The case 30 has four roughly rectangular plate-shaped side walls 300, namely the top, bottom, left, and right sides of the case 30, and the fuel cell stack 100 as a whole has a roughly rectangular parallelepiped shape. The case 30 in Figure 1 can be configured as the lower case 30D, and the upper case 30U, shown by the dashed line, can be provided above the lower case 30D. In that case, the lower case 30D and the upper case 30U together constitute the case 30 of the fuel cell.

[0012] Part A of Figure 1 shows a section of the upper wall 31 of the case 30 that has been cut away. As shown in Part A of Figure 1, the cell stack 10 is constructed by stacking a plurality of power generation cells 1 (for convenience, only a single power generation cell 1 is shown) in the front-to-back direction, and the whole structure has a roughly rectangular parallelepiped shape. The power generation cell 1 has a unitized electrode assembly (UEA) 2 having a membrane electrode assembly that includes an electrolyte membrane and an electrode, and separators 3 arranged on both the front and rear sides of the UEA 2 and sandwiching the UEA 2. The UEA 2 and the separators 3 are arranged alternately in the front-to-back direction. The separator 3 has a pair of thin metal plates with a corrugated cross-section, and the outer periphery of these pairs of thin plates is joined together to form a single unit. Cooling channels are formed inside the pair of thin plates through which a cooling medium (e.g., water) flows, and the power generation surface of the power generation cell 1 is cooled by the flow of the cooling medium. The UEA 2 can also be called a membrane electrode structure.

[0013] The front separator 3 of the UEA2 is, for example, an anode separator, and an anode channel is formed between the anode separator 3 and the membrane electrode assembly of the UEA2 through which a hydrogen-containing fuel gas flows. The rear separator 3 of the UEA2 is, for example, a cathode separator, and a cathode channel is formed between the cathode separator 3 and the membrane electrode assembly of the UEA2 through which an oxygen-containing oxidizing gas flows.

[0014] The UEA2 comprises a membrane electrode assembly (MEA) and a resin frame supporting the MEA. The MEA includes an electrolyte membrane, an anode electrode provided on the front surface of the electrolyte membrane, and a cathode electrode provided on the rear surface of the electrolyte membrane. The electrolyte membrane is, for example, a solid polymer electrolyte membrane. The anode electrode has an electrode catalyst layer formed on the front surface of the electrolyte membrane, which serves as the reaction field for the electrode reaction, and a gas diffusion layer provided on the front surface of the electrode catalyst layer, which diffuses and supplies fuel gas. The cathode electrode has an electrode catalyst layer formed on the rear surface of the electrolyte membrane, which serves as the reaction field for the electrode reaction, and a gas diffusion layer provided on the rear surface of the electrode catalyst layer, which diffuses and supplies oxidizing gas.

[0015] At the anode electrode, fuel gas (hydrogen) supplied via the anode channel and gas diffusion layer is ionized by the action of a catalyst and moves to the cathode electrode side through the electrolyte membrane. The electrons generated at this time pass through an external circuit and are extracted as electrical energy. At the cathode electrode, oxidizing gas (oxygen) supplied via the cathode channel and gas diffusion layer reacts with hydrogen ions introduced from the anode electrode and electrons that have moved from the anode electrode to produce water. The generated water provides appropriate humidity to the electrolyte membrane, and excess water is discharged to the outside of UEA2.

[0016] The rear end unit (end plate, etc., not shown) 40 has through holes 401 to 406 that penetrate the end unit 40 in the front-to-back direction. Through holes 401 to 403 are positioned vertically offset near the left end of the end unit 40, and through holes 404 to 406 are positioned vertically offset near the right end of the end unit 40. The front end unit 40 does not have through holes 401 to 406, and the front surface of the fuel cell stack 100 is closed.

[0017] Figure 2 is a cross-sectional view along the line II-II in Figure 1. Figure 2 shows an example in which the case 30 is composed of a lower case 30D and an upper case 30U. As shown in Figure 2, the cell stack 10 (multiple power generation cells 1) has multiple through holes 101 to 106 opened at positions corresponding to the through holes 401 to 406 of the end unit 40. The through holes 101 to 106 include through holes provided in the UEA 2 and through holes provided in the separator 3.

[0018] Fuel gas is supplied to the cell stack 10 through through-holes 401 of the end unit 40. This fuel gas is guided through through-holes 101 of the cell stack 10 to the anode channels of the multiple power generation cells 1. After passing through the anode channels, the fuel gas is discharged through through-holes 106 of the end unit 40. Oxidizer gas is supplied to the cell stack 10 through through-holes 404 of the end unit 40. This oxidizer gas is guided through through-holes 104 of the cell stack 10 to the cathode channels of the multiple power generation cells 1. After passing through the cathode channels, the oxidizer gas is discharged through through-holes 103 of the end unit 40. Cooling medium is supplied to the cell stack 10 through through-holes 405 of the end unit 40. This cooling medium is guided through through-holes 105 of the cell stack 10 to the cooling channels of the multiple power generation cells 1. After passing through the cooling channel, the cooling medium is discharged from the through-hole 102 of the end unit 40 via the through-hole 102.

[0019] Case 30 (lower case 30D) has four side walls 300, namely an upper wall 311 and a lower wall 313 extending in a substantially horizontal direction, and a left wall 312 and a right wall 314 extending in a substantially vertical direction. The four side walls 300 are made of metal such as iron or aluminum and are formed, for example, by casting. The ends of four adjacent side walls 300 (311 to 314) are fastened together by bolts (not shown), forming the lower case 30D. A substantially box-shaped space SP1 is formed inside the lower case 30D.

[0020] The upper wall 311 constitutes a partition wall separating the lower case 30D and the upper case 30U. The upper case 30U is fixed to the upper surface of the upper wall 311. A roughly box-shaped space SP2 is formed inside the upper case 30U. A control unit (for example, a voltage control unit) that controls the operation of the fuel cell can be housed in space SP2. The upper wall 31 is provided with a communication opening 35 that penetrates the upper wall 31, and space SP1 in the lower case and space SP2 in the upper case are in communication through the communication opening 35.

[0021] A retaining bar 20 is interposed between the inner wall surface (case inner wall surface) 30a of the side wall 300 of case 30 (lower case 30D) and the outer surface 10a of the cell laminate 10 as an impact receiving member. Specifically, if the four sides of the cell laminate 10 (for example, separator 3) are defined as the top side 11, left side 12, bottom side 13, and right side 14, then a pair of retaining bars 20 are positioned between the top side 11 and the case inner wall surface 30a, between the left side 12 and the case inner wall surface 30a, between the bottom side 13 and the case inner wall surface 30a, and between the right side 14 and the case inner wall surface 30a. The pair of retaining bars 20 are provided near the corners of the cell laminate 10. In other words, a pair of retaining bars 20 are positioned near each of the four corners of the cell laminate 10, sandwiching each corner. The distance from the corners of the pair of retaining bars 20 is the same, and the pair of retaining bars 20 are arranged symmetrically across the corners.

[0022] To be positioned near the corners of the cell stack 10 means that the retaining bar 20 is positioned at least on the corner side of the midpoint of each side 11 to 14 of the cell stack 10 in the longitudinal direction, or within a predetermined distance from the angle of the cell stack 10. Alternatively, it means that the retaining bar 20 is positioned in the corner area when each side 11 to 14 of the cell stack 10 is divided into at least four equal parts.

[0023] The retaining bars 20 have a substantially rectangular cross-section and extend almost the entire length of the cell stack 10 in the front-to-back direction. Multiple retaining bars 20 have the same cross-sectional shape. The retaining bars 20 are made of an elastic material such as resin or rubber and are composed of an insulator. The retaining bars 20 are, for example, pre-attached to the inner wall surface 30a of the case and provided integrally with the case 30. By providing the retaining bars 20 near the corners of the cell stack 10, when an impact is applied to the case 30 in a direction perpendicular to the stacking direction of the cell stack 10, the area near the corners of the cell stack 10 will come into contact with the retaining bars 20 due to inertial force. This effectively suppresses displacement of the power generation cells 1.

[0024] A single UEA 2 and a single separator 3 are pre-welded together to form a unit cell. Multiple concave positioning portions 15 are provided on the periphery of the unit cell (e.g., separator 3). Multiple guide members 16 are arranged inside the case corresponding to the positioning portions 15. The guide members 16 have a consistent cross-sectional shape from their lower end to their upper end (from the rear end to the front end in Figure 1). Multiple guide members 16 are identical in shape to each other, and their cross-sectional shape is, for example, circular. The lower and upper ends of the multiple guide members 16 fit into recesses or through holes provided in the end unit 40, thereby holding the guide members 16 in predetermined positions inside the case.

[0025] Multiple unit cells are stacked while the positioning part 15 is fitted into the guide member 16. This positions the unit cells relative to the case 30, allowing the cell stack 10 to be constructed with high precision. The guide member 16 may have a cross-sectional shape other than a circular shape, such as a roughly L-shape or a roughly T-shape. The guide member 16 may be supported from the case 30 instead of the end unit 40. The guide member 16 may be provided at the corners of the cell stack 10, and the position and number of guide members 16 are not limited to those shown in Figure 2.

[0026] The roughly frame-shaped space (also called the excess space) SP1 between the cell stack 10 and the case 30 (lower case 30D) is divided into multiple circumferential spaces by the retaining bar 20. Specifically, it is divided into the space above the cell stack 10 (upper space SP11), the space to the left (left space SP12), the space below (lower space SP13), the space to the right (right space SP14), and the corner space (corner space SP15).

[0027] The retaining bar 20 has an outer end face 21 facing the inner wall surface 30a of the case and an inner end face 22 facing the outer surface 10a of the cell stack 10. The outer end face 21 abuts against the inner wall surface 30a of the case. On the other hand, there is a small gap between the inner end face 22 and the outer surface 10a of the cell stack 10. Therefore, communication between multiple spaces (for example, the left space SP12 and the lower space SP13) is blocked by the retaining bar 20. Consequently, there is no gas flow between the multiple spaces, or only a slight gas flow through the gap between the inner end face 22 of the retaining bar 20 and the outer surface 10a of the cell stack 10.

[0028] Incidentally, the gas channels (anode channel and cathode channel) of the cell stack 10 are sealed by a sealing member provided between the UEA 2 and the separator 3 so as to surround the gas channels. The sealing member is made of a flexible material such as rubber or resin, and ensures airtightness by adhering tightly to the surfaces of the UEA 2 and the separator 3. Some gas leaks from inside the cell stack 10 through such a sealing member. The leaked gas accumulates in the excess space SP1. As a result, there is a risk that the concentration of hydrogen gas contained in the fuel gas in the excess space SP1 will increase.

[0029] To suppress such an increase in fuel gas concentration, the fuel cell stack 100 of this embodiment is provided with a ventilation device. The ventilation device has a plurality of ventilation openings 301 that penetrate the side wall 300 of the case 30, and a filter unit 302 that is mounted facing the ventilation openings 301.

[0030] The filter unit 302 includes a cover attached to the side wall 300 from the outside of the side wall 300 by bolts or the like so as to cover the ventilation opening 301, and a filter fixed to the cover so as to shield the ventilation opening 301. The cover has a mesh portion or louver portion that covers the ventilation opening 301, preventing relatively large foreign objects from entering the case 30 and protecting the filter. The filter is an air filter, and by removing dust and other particles from the gas passing through the filter, especially from the air flowing into the case 30 from the outside, it prevents dust and other particles from entering the case 30 and protects the cell laminate 10.

[0031] If ventilation openings 301 and filter units 302 are provided facing each of the spaces SP11 to SP15 within the case, ventilation of multiple spaces SP11 to SP15 becomes possible. However, increasing the number of filter units 302 increases costs and complicates the surface configuration of the case 30, resulting in a larger fuel cell stack 100. For this reason, it is preferable to keep the number of ventilation openings 301 and filter units 302 as small as possible. However, if the number of ventilation openings 301 and filter units 302 is reduced, there will be spaces with ventilation openings (referred to as open spaces) and spaces without ventilation openings (referred to as closed spaces), making it difficult to adequately ventilate the closed spaces.

[0032] In this embodiment, a communication channel is provided to connect the open space and the closed space, thereby enabling the flow of gas from the closed space to the open space. For this reason, the ventilation openings 301 and the filter unit 302 are provided facing only some of the spaces SP11 to SP15. Specifically, ventilation openings 301 are provided on the left wall 312 and the right wall 314 of the lower case 30D, and on the right wall of the upper case 30U, facing spaces SP12, SP14, and SP2, respectively. The filter unit 302 is then provided facing these ventilation openings 301. The configurations of the multiple ventilation openings 301 and the multiple filter unit 302 are identical to each other.

[0033] When ventilation openings 301 are provided facing spaces SP12, SP14, and SP2 in this manner, the left space SP12, the right space SP14, and the upper space SP2 become open spaces, while the lower space SP13 and the corner space SP15 become closed spaces. The upper space SP11 is open because it communicates with space SP2 via the communication opening 35.

[0034] The configuration of the communication channel connecting the open space and the closed space will be described below. Figures 3A and 3B are perspective views (viewed from the right rear) showing the configuration of the inner wall surface 30a at the lower left corner of the rear end of case 30 where the left wall 312 and the lower wall 313 of case 30 intersect. Figure 3A shows the state before the retaining bar 20 is attached to the inner wall surface 30a of the case, and Figure 3B shows the state after the retaining bar 20 is attached. Figure 4 is a cross-sectional view of the main part of case 30 cut along the line IV-IV in Figure 3B. Although not shown, the configuration of the upper left, upper right, and lower right corners of case 30, and the configuration of the front end corner of case 30 are the same as those shown in Figures 3A, 3B, and 4.

[0035] In predetermined parts of the case 30, which is constructed by casting, machined surfaces (flange surfaces and seating surfaces) are provided, which are machined to be flat surfaces. For convenience, the machined surfaces are shown with hatching in Figure 3A. The machined surfaces include a rear end machined surface formed on the rear end surface 300b of the side wall 300. Multiple screw holes 315 are provided on the rear end surface 300b facing forward. Bolts (not shown) inserted through the through holes of the end unit 40 (Figure 1) are screwed into the screw holes 315, thereby fastening the end unit 40 to the rear end surface 300b of the side wall 300.

[0036] As shown in Figures 3A and 34, the lower wall 313 has a flat plate portion 41 of constant thickness extending in a substantially horizontal direction and a plurality of ribs 42 projecting upward from the upper surface 41a of the flat plate portion 41, and the inner wall surface 30a of the lower wall 313 is configured to be uneven overall. The ribs 42 have a plurality of vertical ribs 421 extending in the front-rear direction, a plurality of horizontal ribs 422 extending in the left-right direction, and intersecting ribs 423 extending in a direction that intersects the plurality of horizontal ribs 422 and connecting the horizontal ribs 422 to each other. The vertical ribs 421 are provided so as to coincide with the position of the screw holes 315.

[0037] On the inner wall surface 30a of the lower wall 313, an attachment area AR1 for the retaining bar 20 is provided between the left end of the lower wall 313 and the vertical rib 421 to its right. In both the attachment area AR1 and the non-attachment area AR3 to the right of the attachment area AR1, a plurality of transverse ribs 422 are provided at equal intervals in the front-rear direction. The number of transverse ribs 422 in the attachment area AR1 is greater than the number of transverse ribs 422 in the non-attachment area AR3, for example, twice the number of transverse ribs 422 in the non-attachment area AR3. The number of transverse ribs 422 in the attachment area AR1 may be the same as the number of transverse ribs 422 in the non-attachment area AR3. That is, the transverse ribs 422 of the non-attachment area AR3 may be provided on the extension line of each transverse rib 422 of the attachment area AR1.

[0038] In the mounting area AR1, a mounting surface SF1 for the retaining bar 20 is formed as a machined surface (hatching). Specifically, as shown in Figure 4, a high rib portion 425, which is higher than the other parts of the horizontal rib 422 and the intersecting rib 423, is formed in the casting process at the left-right center of the horizontal rib 422 in the mounting area AR1. Then, before the assembly of the case 30, that is, while the lower wall 313 is still a single unit, the upper surface of the high rib portion 425 is machined to form a mounting surface SF1 that extends in the front-rear direction and is on the same horizontal plane. The mounting surface SF1 is located higher than the upper surface of the intersecting rib 423.

[0039] As shown in Figures 3A and 34, the left wall 312 has a flat plate portion 43 of constant thickness extending substantially vertically, and a plurality of ribs 44 projecting to the right from the right surface 43a of the flat plate portion 43, and the inner wall surface 30a of the left wall 312 is configured to be uneven overall. The ribs 44 have a longitudinal rib 441 extending in the front-rear direction and a plurality of transverse ribs 442 extending in the up-down direction. The longitudinal rib 441 is provided so as to coincide with the position of the screw hole 315. In Figure 3A, a single longitudinal rib 441 is provided on the left wall 312, but it is not limited to this, and a plurality of longitudinal ribs 441 may be provided at equal intervals in the up-down direction. Intersecting ribs may be provided on the inner wall surface 30a of the left wall 312 so as to intersect with the transverse ribs 442, similar to the lower wall 313.

[0040] On the inner wall surface 30a of the left wall 312, a mounting area AR2 for the retaining bar 20 is provided between the lower end of the left wall 312 and the vertical rib 441 above it. Multiple horizontal ribs 442 are present in the mounting area AR2. These horizontal ribs 442 are provided at the same position in the front-rear direction as the horizontal ribs 422 of the lower wall 313. Therefore, the number of horizontal ribs 442 and horizontal ribs 422 are the same. The horizontal ribs 442 may be provided with a position offset from the horizontal ribs 422 in the front-rear direction, and the number of horizontal ribs 442 and horizontal ribs 422 may be different.

[0041] In the mounting area AR2, a mounting surface SF2 for the retaining bar 20 is formed as a machined surface (hatching). Specifically, as shown in Figure 4, a high rib portion 445, which is higher than other parts of the horizontal rib 442, is formed in the casting process at the vertical center or lower part of the horizontal rib 442 in the mounting area AR2. Then, before the assembly of the case 30, that is, while the left wall 312 is in a standalone state, the upper surface of the high rib portion 445 is machined to form a mounting surface SF2 that extends in the front-rear direction and is on the same plane.

[0042] As shown in Figures 3B and 34, the retaining bar 20 is fixed to the lower wall 313 with its outer end face 21 in contact with the mounting surface SF1 of the transverse rib 422. The retaining bar 20 is fixed to the left wall 312 with its outer end face 21 in contact with the mounting surface SF2 of the transverse rib 442. In this embodiment, multiple retaining bars 20 are used, but the configuration of the multiple retaining bars 20 is the same as that of the others.

[0043] Figure 5 is a plan view (viewpoint V in Figure 3B) showing the configuration of the retaining bar 20, which is provided on the left side of the lower wall 313. As shown in Figure 5, the retaining bar 20 has a roughly rectangular parallelepiped shape overall, and has an upper outer end face 21 and a lower inner end face 22, as well as a front end face 23 and a rear end face 24, and a pair of side faces 25 and 26. Of the pair of side faces 25 and 26, the side face 25 on the side where the lower wall 313 and the left wall 312 intersect, that is, the left side face 25 that is close to the corner of the case 30, is called the corner side face, and the opposite side face 26 is called the central side face.

[0044] From the front end face 23 and the rear end face 24 of the holding bar 20, tabs 27 project forward and backward, respectively. From the corner side faces 25 of the holding bar 20, a plurality of tabs 28 project leftward. The bottom surfaces of the tabs 27 and 28 extend, for example, on the same plane as the outer end face 21. The bottom surfaces of the tabs 27 and 28 may not be on the same plane as the outer end face 21. Through holes 27a and 28a are opened at the central portions of the tabs 27 and 28, respectively.

[0045] As shown in FIG. 3A, on the inner wall surface 30a of the lower wall 313, a plurality of bosses 316 project corresponding to the positions of the tabs 27 and 28 when the holding bar 20 is mounted. That is, as shown by the two-dot chain line in FIG. 5, bosses 316 are provided in front of, behind, and to the left of the mounting region AR1, respectively. On the end face (upper face) of the boss 316, a substantially horizontal seating surface SF3 is formed as a machined surface. On the inner wall surface 30a of the left wall 312, bosses 316 also project corresponding to the positions of the tabs 27 and 28 when the holding bar 20 is mounted. That is, bosses 316 are provided in front of, behind, and below the mounting region AR2, respectively, and a substantially vertical seating surface SF4 is formed on the end face of the boss 316 as a machined surface. Threaded holes are provided at the central portions of the seating surfaces SF3 and SF4.

[0046] As shown in FIG. 3B, above the lower wall 313, bolts 29 passing through the tabs 27 and 28 are screwed into the threaded holes of the seating surface SF3 of the lower wall 313, whereby the holding bar 20 is fixed to the lower wall 313. Similarly, on the right side of the left wall 312, bolts 29 passing through the tabs 27 and 28 are screwed into the threaded holes of the seating surface SF4 of the left wall 312, whereby the holding bar 20 is fixed to the left wall 312. The holding bar 20 of the left wall 312 is mounted in a reversed front-rear direction with respect to the holding bar 20 of the lower wall 313 (FIG. 5). For this reason, the tab 28 of the holding bar 20 of the left wall 312 projects downward.

[0047] As shown in FIG. 5, three tabs 28 project from the corner side surface 25 of the holding bar 20. The distance D1 from the rear end surface 24 of the holding bar 20 to the left tab 28 is longer (or shorter) than the distance D2 from the front end surface 23 to the right tab 28. The central tab 28 is provided at a position shifted forward (or backward) from the central position in the front-rear direction of the holding bar 20. As a result, as shown in FIG. 3B, the tab 28 of the holding bar 20 on the lower wall 313 and the tab 28 of the holding bar 20 on the left wall 312 are arranged shifted in the front-rear direction. Therefore, the tab 28 of the holding bar 20 on the lower wall 313 and the tab 28 of the holding bar 20 on the left wall 312 can be arranged close to each other without interference. For this reason, the pair of holding bars 20 can be easily arranged near the corner of the cell laminate 10.

[0048] FIG. 6 is a cross-sectional view taken along the line VI-VI of FIG. 4. FIG. 6 also shows the gap Δd between the outer surface 10a of the cell laminate 10 and the inner end surface 22 of the holding bar 20. As shown in FIG. 6, the outer end surface 21 of the holding bar 20 abuts against the mounting surface SF1 at the upper ends of a plurality of horizontal ribs 422 in the front-rear direction of the lower wall 313. At this time, there is a gap between the outer end surface 21 and the flat plate portion 41 and the intersecting ribs 423 of the lower wall 313, and a plurality of communication flow paths PA0 in the front-rear direction partitioned by the horizontal ribs 422 are formed between the outer end surface 21 and the flat plate portion 41. The height of the communication flow path PA0 (the height of the horizontal rib 422) is sufficiently larger than the gap Δd between the cell laminate 10 and the holding bar 20. The communication flow path PA0 communicates the space on the right side of the holding bar 20 (the lower space SP13 in FIG. 1) and the space on the left side (the corner space SP15 in FIG. 1). Since the plurality of communication flow paths PA0 are provided over substantially the entire length in the front-rear direction of the lower wall 313, a sufficient flow passage area of the communication flow path PA0 can be obtained.

[0049] Although not shown in the diagram, multiple communication channels PA0 in the front-rear direction are also formed between the outer end face 21 of the retaining bar 20, which is in contact with the transverse rib 442 of the left wall 312, and the flat plate portion 43 of the left wall 312 by the transverse rib 442. These communication channels PA0 connect the space above the retaining bar 20 (the left space SP12 in Figure 1) and the space below it (the corner space SP15 in Figure 1). As a result, the lower space SP13 and the left space SP12 are connected via the communication channels PA0 provided between the transverse ribs 422, 422 of the lower wall 313 and the communication channels PA0 provided between the transverse ribs 442, 442 of the left wall 312, that is, the closed space and the open space are connected.

[0050] The main operation of the fuel cell stack 100 according to this embodiment will now be described. Figure 7 is a schematic cross-sectional view of the main part of the fuel cell stack 100 showing the flow of gas (air and fuel gas) in spaces SP1 and SP2. As shown by arrow A in Figure 7, air flows into the excess space SP1 between the case 30 (lower case 30D) and the cell stack 10 through ventilation openings 301 provided in the left wall 312 and the right wall 314. In some cases, fuel gas accumulated in the excess space SP1 may flow out without air flowing in through the ventilation openings 301.

[0051] Within the excess space SP1, as shown by arrow B in Figure 7, gas flow occurs through the communication channel PA0 between the holding bar 20 and the inner wall surface 30a of the case. Specifically, gas flow occurs between the left space SP12 and the lower space SP13, between the left space SP12 and the upper space SP11, between the right space SP14 and the lower space SP13, and between the right space SP14 and the upper space SP11. Since the communication channel PA0 is provided along almost the entire length of the case 30 in the front-to-back direction, gas flow can be generated throughout the entire area of ​​the excess space SP1.

[0052] The gas flowing through the communication channel PA0 contains fuel gas (hydrogen gas), which has a lower specific gravity than air. Therefore, it rises within the excess space SP1 and flows into the upper space SP2 through the communication port 35 in the upper wall 311. The gas in space SP2 is discharged to the outside through a ventilation port 301 provided in the side wall (right wall) of the upper case 30U. A ventilation port for gas discharge may also be provided in the upper wall of the upper case 30U. As a result, the entire area inside the case can be ventilated, and the hydrogen concentration in spaces SP1 and SP2 can be kept below a predetermined value.

[0053] According to this embodiment, the following effects can be achieved. (1) The fuel cell stack 100 comprises a cell stack 10 formed by stacking a plurality of power generation cells 1 in the front-rear direction, a case 30 and an end unit 40 surrounding the cell stack 10, and a plurality of retaining bars 20 extending in the front-rear direction so as to divide the excess space SP1 between the inner wall surface 30a of the case and the outer surface 10a of the cell stack 10 into a plurality of spaces SP11 to SP15, including the left space SP12 and the lower space SP13 (Figures 1, 2, 3B). The case 30 has an inner wall surface 30a facing the retaining bars 20. The inner wall surface 30a of the case is configured to be uneven so as to form a communication channel PA0 that connects the left space SP12 and the lower space SP13 (Figures 3A, 6).

[0054] This configuration allows the open space facing the ventilation opening 301 and the closed space not facing the ventilation opening 301 to be connected via the communication channel PA0. Therefore, when the excess space SP1 inside the case 30 is divided into multiple spaces SP11 to SP15 by the retaining bar 20, gas can flow through the spaces via the communication channel PA0 facing the retaining bar 20. As a result, the entire excess space SP1 inside the case can be efficiently ventilated, and the hydrogen gas accumulated in the excess space SP1 can be effectively discharged to the outside.

[0055] (2) The retaining bar 20 has an outer end face 21 facing the inner wall surface 30a of the case and an inner end face 22 facing the outer surface 10a of the cell laminate 10 (Figure 2). The inner wall surface 30a of the case has substantially plate-shaped flat portions 41, 43 and a plurality of ribs 42, 44, in particular transverse ribs 422, 442, that protrude from the flat portions 41, 43 so as to intersect with the outer end face 21 of the retaining bar 20 (Figure 3A). The communication channels PA0 are provided between the plurality of transverse ribs 422, 422 and between transverse ribs 442, 442 (Figure 4). This makes it possible to form good communication channels PA0 on the inner wall surface 30a of the case without increasing the size of the case 30, while ensuring the strength of the case 30 with the rib structure.

[0056] (3) The retaining bar 20 is an impact receiving member (restraining member) that receives impacts acting on the fuel cell stack 100 (cell stack 10) and restrains the position of the cell stack 10. The fuel cell stack 100 is further provided with bolts 29 that fix the retaining bar 20 to the inner wall surface 30a of the case 30 with the outer end surface 21 of the retaining bar 20 in contact with the end surfaces (mounting surfaces SF1, SF2) of the transverse ribs 422, 442 (Figure 3B). By configuring the inner wall surface 30a of the case to be uneven, it is not necessary to process the retaining bar 20 as an impact receiving member to provide a flow path, so the retaining bar 20 can be easily constructed. In addition, the strength of the retaining bar 20 can be ensured, and it can perform its function as an impact receiving member to a sufficient degree.

[0057] (4) The case 30 has a roughly box shape (Figure 1). The retaining bars 20 are positioned near the corners of the cell stack 10 (Figure 2). By positioning the retaining bars 20 near the highly rigid corners in this way, the cell stack 10 can be firmly held, and displacement of the power generation cells 1 can be effectively suppressed.

[0058] (5) The retaining bars 20 are positioned on both sides of the corners of the cell stack 10 so as to sandwich the corners of the cell stack 10 (Figure 2). This allows the cell stack 10 to be held more firmly by the retaining bars 20.

[0059] (6) The retaining bar 20 is provided such that there is a predetermined gap Δd between the outer surface 10a of the cell laminate 10 and the inner end surface 22 of the retaining bar 20, and the height of the transverse ribs 442, 442 is greater than the predetermined distance (Figure 6). This makes the area of ​​the communication channel PA0 sufficiently large compared to the area of ​​the gap Δd, and allows for easy ventilation of gas through the communication channel PA0.

[0060] Figure 8 is a view VIII of the arrow in Figure 5. As shown in Figure 8, in this embodiment, a long resin retaining bar 20 is used in the fuel cell stack 100 in the front-rear direction. The retaining bar 20 functions as an impact receiving member (restraining member). Therefore, in order to ensure the strength of the retaining bar 20, the retaining bar 20 needs to have a thickness of a predetermined amount or more (vertical length in Figure 8). When molding such a long and thick retaining bar 20, deformation due to shrinkage of the resin may occur, and it may warp in a curved shape as shown by the dashed line L1 in Figure 8. As a result, it becomes difficult to provide a predetermined gap Δd (Figure 6) between the retaining bar 20 and the outer surface 10a of the cell stack 10 along the entire length of the retaining bar 20, and there is a risk that a part of the retaining bar 20 may come into contact with the cell stack 10 when assembling the fuel cell stack 100. The configuration of the retaining bar 20 to prevent such contact will be described below.

[0061] Figure 9 is a bottom view of the retaining bar 20 attached to the left side of the lower wall 313 (viewed via arrow IX in Figure 8), and Figure 10 is a cross-sectional view along line XX in Figure 9. In Figure 9, the front-to-back direction is reversed compared to Figure 5. As shown in Figures 9 and 10, the outer end face 21 of the retaining bar 20 is provided with a plurality of recesses 210. More specifically, the recesses 210 have a plurality of corner recesses 211 provided on the corner side surface 25 and a plurality of central recesses 212 provided on the central side surface 26. The shapes (width and depth) of the recesses 211 and 212 are equal to each other and have an elongated, roughly rectangular shape along the longitudinal direction. However, at the front-to-back ends, the recesses 211 and 212 have a roughly square shape.

[0062] The front edge 211f and rear edge 211r of the corner recess 211 and the front edge 212f and rear edge 212r of the central recess 212 are at the same position in the front-rear direction. Therefore, with reference to the bottom surface 210a of the recess 210 (211, 212), the outer end face 21 of the retaining bar 20 has a plurality of ribs 213 (referred to as short ribs) that protrude downward from the corner side surface 25 to the central side surface 26, between the front edges 211f, 212f and the rear edges 211r, 212r of the recesses 211, 212. The plurality of short ribs 213 are provided at equal intervals in the front-rear direction along the entire length of the retaining bar 20. The widths (front-rear lengths) of the plurality of short ribs 213 are equal to each other.

[0063] The left edge 211L and right edge 211R of the multiple corner recesses 211 are located on virtual straight lines (partially shown) L11 and L12, respectively, that extend in the front-rear direction. The left edge 212L and right edge 212R of the multiple central recesses 212 are located on virtual straight lines (partially shown) L13 and L14, respectively, that extend in the front-rear direction. Therefore, with reference to the bottom surface 210a of the recesses 210 (211, 212), the outer end face 21 of the retaining bar 20 is provided with multiple (3) ribs (referred to as long ribs) 214 that protrude downward from the front end face 23 to the rear end face 24, between the corner side surface 25 and the left edge 211L of the corner recess 211, between the right edge 211R of the corner recess 211 and the left edge 212L of the central recess 212, and between the right edge 212R of the central recess 212 and the central side surface 26. The widths (lengths in the left-right direction) of the multiple long ribs 214 are equal to each other.

[0064] By providing multiple recesses 210 on the bottom surface (outer end surface 21) of the retaining bar 20 in this manner, the formability of the retaining bar 20 is improved and warping can be prevented. In addition, the weight of the retaining bar 20 can be reduced, thereby lowering material costs. Furthermore, since the retaining bar 20 has a rib structure with multiple ribs 213 and 214 protruding from the bottom surface 210a, sufficient strength can be ensured. Note that, considering the formability of the retaining bar 20, some of the recesses 210 may be omitted or the shape of some of the recesses 210 may be changed.

[0065] Figure 11 is an enlarged view of the main part of Figure 9, specifically an enlarged view of the front portion of the outer end face 21 of the retaining bar 20. For convenience, the positions of the mounting surface SF1 and the seating surface SF3 of the lower wall 313 to which the retaining bar 20 is attached (see Figure 3A) are shown in Figure 11 with hatching. As shown in Figure 11, the outer end face 21 of the retaining bar 20 includes the end faces (rib faces SF5) of the ribs 213 and 214 and the bottom faces SF6 of the tabs 27 and 28.

[0066] Multiple short ribs 213 are provided so as to coincide with the mounting surfaces SF1 of multiple transverse ribs 422 arranged in the front-rear direction. As a result, when the retaining bar 20 is installed, the mounting surfaces SF1 of the transverse ribs 422 of the case 30 and the rib surfaces SF5 of the short ribs 213 of the retaining bar 20 come into contact. Consequently, deformation of the retaining bar 20 can be effectively suppressed when impact loads are applied to the fuel cell stack 100 in the vertical, horizontal, or lateral directions.

[0067] The long rib 214 extends continuously along the entire length of the retaining bar 20 in the front-rear direction. This effectively suppresses deformation of the retaining bar 20 when a bending load F (Figure 8) due to a combustion impact load acts on the retaining bar 20, thereby suppressing displacement of the power generation cell 1.

[0068] Unlike Figure 3A, in Figure 11, the transverse ribs 422 and bosses 316 of the case 30 are provided in a continuous manner, thereby providing the mounting surface SF1 and the seating surface SF3 in a continuous manner without being separated. As a result, the entire bottom surface of the retaining bar 20 from the short rib 213 to the tab 28 abuts against the entire area of ​​the case 30 from the mounting surface SF1 to the seating surface SF3. This reduces the stress generated in the case 30 and retaining bar 20 when an impact load is applied (such as the stress generated at the base of the thin-walled tab 28). The front and central bosses 316 may also be formed in a continuous manner with the transverse ribs 422, similar to the rear boss 316, and the short ribs 213 and tabs 28 may be provided on the retaining bar 20 accordingly.

[0069] The shape of the recess 210 of the retaining bar 20 is not limited to that shown in Figure 9. Figures 12A and 12B show modified examples of Figure 9, respectively. In the figures, the position of the mounting surface SF1 and the position of a part of the seating surface SF3 of the case 30 (lower wall 313) to which the retaining bar 20 is attached are shown by dotted lines for convenience.

[0070] In the example shown in Figure 12A, the corner recesses 211 and the central recess 212 are extended in the front-to-back direction compared to those in Figure 9, and furthermore, the corner recesses 211 and the central recess 212 are offset from each other in the front-to-back direction. That is, the corner recesses 211 and the central recess 212 are arranged alternately in the front-to-back direction, i.e., in a staggered pattern. This makes the recesses 210 larger, allowing the retaining bar 20 to be made lighter. In this case, the length (length in the left-to-right direction) of the short ribs 213 that abut the case 30 is shorter than that in Figure 9, but it is sufficient to ensure the strength of the retaining bar 20.

[0071] In the example of Figure 12B, the lengths of the corner recesses 211 and the central recess 212 in the front-to-back direction (especially the length of the front side) are shorter than those in Figure 9. Furthermore, a recess 215 is added adjacent to the short rib 213 in the shortened portion of the recesses 211 and 212. Therefore, in the example of Figure 12B, the number of recesses 210 (211, 212, 215) increases. The recess 215 extends in an elongated shape in the left-to-right direction. In other words, in the example of Figure 12B, horizontally elongated recesses 211 and 212 and vertically elongated recess 215 are alternately provided along the longitudinal direction of the retaining bar 20. In both examples of Figures 12A and 12B, a long rib 214 is provided along the entire length of the retaining bar 20. Therefore, sufficient strength of the retaining bar 20 against bending load F (Figure 8) can be ensured.

[0072] This embodiment can further provide the following effects: (1) The fuel cell stack 100 comprises a cell stack 10 formed by stacking a plurality of power generation cells 1 in the front-rear direction, a case 30 and an end unit 40 surrounding the cell stack 10, and a resin retaining bar 20 that is arranged in the surplus space SP1 between the inner wall surface 30a of the case and the outer surface 10a of the cell stack 10, and has an outer end surface 21 facing the inner wall surface 30a of the case, and extends in the front-rear direction (Figures 1 and 2). The inner wall surface 30a of the case has transverse ribs 422 projecting toward the outer end surface 21 (Figure 3A). The outer end surface 21 has ribs 213 and 214 projecting toward the inner wall surface 30a of the case (Figures 9, 12A, and 12B). The ribs of the outer end surface 21 include short ribs 213 that are provided to abut against the end surface (mounting surface SF1) of the transverse ribs 422 of the case 30 (Figure 11).

[0073] Since the retaining bar 20 is long and thick, it is prone to deformation such as warping due to shrinkage during resin molding. However, the above configuration improves the moldability of the retaining bar 20 and suppresses warping. The short ribs 213 abut against the transverse ribs 422 of the case 30, so they can firmly support the rib structure of the retaining bar 20 without obstructing the gas flow through the communication channel PA0 between the transverse ribs 422.

[0074] (2) The inner wall surface 30a of the case has a plurality of transverse ribs 422 (Figure 3A). The outer end surface 21 of the retaining bar 20 has a plurality of short ribs 213 provided corresponding to the plurality of transverse ribs 422, and recesses 210 provided between the plurality of short ribs 213 (Figures 9, 12A, 12B). As a result the retaining bar 20 has a weight-reducing structure, the retaining bar 20 can be made lighter, and material costs can be reduced.

[0075] (3) The ribs of the retaining bar 20 include a long rib 214 extending in the front-rear direction and a plurality of short ribs 213 extending in a direction intersecting the long rib 214 (left-right direction) (Figures 9, 12A, 12B). By using such a rib structure, the retaining bar 20 can be made strong while being lightweight.

[0076] (4) The long rib 214 extends along the entire length of the retaining bar 20 in the front-rear direction (Figures 9, 12A, 12B). This effectively suppresses deformation of the retaining bar 20 when a bending load F due to an impact load is applied to the retaining bar 20, thereby suppressing displacement of the power generation cell 1.

[0077] (5) Multiple short ribs 213 are provided at equal intervals in the front-rear direction (Figures 9, 12A, 12B). This ensures that the retaining bar 20 is evenly supported by the case 30 over its entire area, preventing large localized loads from acting on the retaining bar 20.

[0078] (6) The inner wall surface 30a of the case has a seat surface SF3 for fixing the retaining bar 20, which is connected to the mounting surface SF1 of the transverse rib 422 of the case 30 (Figure 11). The outer end surface 21 of the retaining bar 20 further has a bottom surface SF6 of a tab 28 that abuts against the seat surface SF3 of the transverse rib 422 (Figure 11). The bottom surface SF6 of the tab 28 is connected to the end surface (rib surface SF5) of the short rib 213 (Figure 11). This makes it possible to reduce the stress generated in the case 30 and the retaining bar 20 when an impact load is applied.

[0079] The above embodiment can be modified into various forms. Several modifications are described below. In the above embodiment, the case 30 as an enclosure is constructed from the lower case 30D and the upper case 30U, but the case 30 may be constructed from the lower case 30D alone. In the above embodiment, the case 30 is formed in a substantially box shape, but the shape of the enclosure is not limited to that described above. In the above embodiment, a ventilation opening 301 is provided in the side wall 300 of the case 30, but the ventilation opening 301 may be connected to a blower and cooling air may be blown into the case via the blower. In the above embodiment, a ventilation opening 301 is provided in the left wall 312 and right wall 314 of the lower case 30D and in the side wall of the upper case 30U, but the position where the ventilation opening is provided is not limited to that described above.

[0080] In the above embodiment, the excess space SP1 between the inner wall surface 30a of the case 30 and the outer surface 10a of the cell stack 10 is divided into a plurality of spaces SP11 to SP15 via a retaining bar 20 (partition member). However, the number of partition members is not limited to those described above, as long as the space is divided into at least two spaces (first space, second space). Here, it is preferable that the space facing the ventilation opening be designated as the first space, and the space not facing the ventilation opening be designated as the second space. In the above embodiment, the retaining bar 20 extending in the stacking direction of the power generation cells 1 is configured with a substantially rectangular cross-section. However, the configuration of the partition member extending in a predetermined direction is not limited to those described above. Therefore, the configuration of the outer end surface 21 (first end surface) facing the inner wall surface 30a of the case and the inner end surface 22 (second end surface) facing the outer surface 10a of the cell stack 10 is also not limited to those described above.

[0081] In the above embodiment, the retaining bars 20 are positioned to sandwich the corners of the cell stack 10, but the position in which the retaining bars 20 are positioned is not limited to that described above. A single partition member may be positioned corresponding to the corners of the cell stack 10. In the above embodiment, the retaining bars 20 are fixed to the inner wall surface 30a of the case using bolts 55 as fixing parts, but the partition member may be fixed to the inner wall surface of the housing using fixing parts other than bolts. In the above embodiment, the inner wall surface 30a of the case has substantially plate-shaped flat parts 41, 43 and a plurality of transverse ribs 422, 442 (rib parts) protruding from the flat parts 41, 43 so as to intersect with the outer end faces 21 of the retaining bars 20, but the configuration of the rib parts is not limited to that described above.

[0082] The above description is merely an example, and the present invention is not limited by the embodiments and modifications described above, as long as the features of the present invention are not impaired. It is also possible to arbitrarily combine one or more of the above embodiments and modifications, and to combine modifications with each other.

[0083] 1 Power generation cell, 10 Cell stack, 20 Holding bar, 21 Outer end face, 22 Inner end face, 30 Case, 30a Inner wall surface, 29 Bolt, 30D Lower case, 30U Upper case, 40 End unit, 41, 43 Flat plate section, 100 Fuel cell stack, 422, 442 Transverse rib, SP0 Excess space, SP11-SP15 Space, PA0 Communication channel

Claims

1. A fuel cell stack comprising: a cell stack formed by stacking a plurality of power generation cells in a predetermined direction; a housing surrounding the cell stack; and a plurality of partition members extending in the predetermined direction such as to divide the space between the inner wall surface of the housing and the outer surface of the cell stack into a plurality of spaces including a first space and a second space, wherein the inner wall surface is configured to be uneven in order to form a communication channel connecting the first space and the second space.

2. A fuel cell stack according to claim 1, wherein the partition member has a first end face facing the inner wall surface and a second end face facing the outer surface of the cell stack, the inner wall surface has a substantially plate-shaped flat portion and a plurality of rib portions projecting from the flat portion so as to intersect with the first end face of the partition member, and the communication channel is provided between the plurality of rib portions.

3. A fuel cell stack according to claim 2, wherein the partition member is an impact receiving member that receives impacts acting on the cell stack, and further comprises a fixing portion that fixes the partition member to the inner wall surface with the first end face in contact with the rib portion.

4. A fuel cell stack according to claim 3, characterized in that the housing has a substantially box shape, and the partition member is arranged near the corner of the cell stack.

5. A fuel cell stack according to claim 4, characterized in that the partition members are arranged on both sides of the corner of the cell stack so as to sandwich the corner of the cell stack.

6. A fuel cell stack according to any one of claims 2 to 5, wherein the partition member is provided such that there is a gap of a predetermined distance between the outer surface of the cell stack and the second end face of the partition member, and the height of the rib portion is greater than the predetermined distance.

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