Fuel cell stack

Abstract

To properly dispose an air vent tube in a cooling medium discharge flow path.SOLUTION: A fuel cell stack includes: a cell stacked body; a pair of end units arranged on both ends of the cell stacked body; a cooling medium discharge flow path provided to penetrate through the cell stacked body in a predetermined direction so as to discharge a cooling medium led to a plurality of power generation cells; and a tube with a substantially cylindrical shape which is arranged in the cooling medium discharge flow path and in which a first opening and a second opening in communication respectively with an upstream side and a downstream side of the cooling medium discharge flow path are provided in one end portion and a lower end portion, respectively. In one end unit of the pair of end units, a through hole in communication with the second opening of the tube to penetrate through the one end unit is opened. The end units includes a first support portion and a second support portion, respectively, the first and second support portions supporting a peripheral portion of a first end portion of the tube and a peripheral portion of a second end portion of the tube, respectively, and the second support portion includes a tapered portion formed, on a peripheral surface of the through hole, so as to gradually narrow toward the exit of the through hole about an axis.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] In recent years, technological development has been conducted on fuel cells that contribute to energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. A known technology for this type of fuel cell involves arranging a resin air vent passage inside a refrigerant discharge manifold and discharging air bubbles inside the refrigerant discharge manifold to the outside through the air vent passage (see, for example, FIG. 8 of Patent Document 1). Patent Document 1 states that the air vent passage is bonded or fixed to the inner surface of the refrigerant discharge manifold inside the refrigerant discharge manifold. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-079779 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it is difficult to stably support the air vent passage within the coolant discharge manifold through which the coolant flows without interfering with components such as the end unit. [Means for solving the problem]

[0005] A fuel cell stack according to one embodiment of the present invention includes a cell stack formed by stacking a plurality of power-generating cells, each having a membrane electrode assembly and a separator, in a predetermined direction, a first end unit and a second end unit disposed at one end and the other end of the cell stack in the predetermined direction, a coolant discharge flow path extending through the cell stack in the predetermined direction to discharge a coolant guided to the power-generating cells, and a substantially cylindrical tubular body disposed in the coolant discharge flow path, the tubular body having a first opening and a second opening at one end and a lower end, respectively, which communicate with the upstream and downstream sides of the coolant discharge flow path. The second end unit has a through hole extending through the second end unit and communicating with the second opening in the tubular body. The first end unit and the second end unit have a first support portion and a second support portion supporting a peripheral edge of the first end and a peripheral edge of the second end of the tubular body, respectively. The second support portion has a tapered portion formed on the circumferential surface of the through hole so as to taper toward the outlet of the through hole about an axis extending substantially parallel to the predetermined direction. [Effects of the Invention]

[0006] According to the present invention, the air bleeding pipe can be stably supported in the coolant discharge flow path without interfering with components such as the end unit. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a perspective view schematically showing the overall configuration of a fuel cell stack according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view showing a schematic configuration of an integrated electrode assembly included in the fuel cell stack of FIG. 1. [Figure 3] FIG. 2 is a rear view of the fuel cell stack of FIG. 1. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3 . [Figure 5] Enlarged view of part V in Figure 4. [Figure 6] FIG. 5B is a cross-sectional view taken along line VI-VI in FIG. 5A. [Figure 7] Enlarged view of part VII in Figure 4. [Figure 8]10A and 10B are views showing another example of a rear support portion that supports the rear end portion of the communication pipe. [Figure 9] Arrow IX view of Figure 8. [Figure 10] FIG. 10 is a diagram showing a modification of FIG. 9; DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to Figs. 1 to 10. A fuel cell stack according to an embodiment of the present invention is a main component of a fuel cell. The fuel cell is mounted on, for example, a vehicle and can generate electric power for driving the vehicle. First, the overall configuration of the fuel cell stack will be described in brief.

[0009] FIG. 1 is a perspective view showing a schematic view of the overall configuration of a fuel cell stack 100 according to this embodiment. For convenience, the three mutually orthogonal axial directions shown in the figure are defined as the front-rear direction, the left-right direction, and the up-down direction, and the configuration of each part will be described in accordance with these definitions. The downward direction in the up-down direction corresponds to the direction of gravity or approximately the direction of gravity. The front-rear direction corresponds to the stacking direction of the fuel cell stack 100. The front-rear direction and the left-right direction are not necessarily the same as the front-rear direction and the left-right direction of a vehicle.

[0010] As shown in Fig. 1, the fuel cell stack 100 has a cell stack 101 formed by stacking a plurality of power-generating cells 1 in the front-to-rear direction, and end units 102 arranged at both front and rear ends of the cell stack 101, and has a generally rectangular parallelepiped shape as a whole. Although not shown in the figure, the cell stack 101 is surrounded by a generally rectangular parallelepiped case. The length of the cell stack 101 in the left-to-right direction is longer than the length in the up-to-down direction. For convenience, only a single power-generating cell 1 is shown in Fig. 1.

[0011] The power-generating cell 1 has a unitized electrode assembly 2 (UEA) having an assembly including an electrolyte membrane and electrodes, and separators 3, 3 arranged on both the front and rear sides of the unitized electrode assembly 2 to sandwich the unitized electrode assembly 2. The unitized electrode assemblies 2 and the separators 3 are arranged alternately in the front-to-rear direction. The unitized electrode assembly 2 can also be called a membrane electrode structure or membrane electrode member.

[0012] The separator 3 has a pair of front and rear thin metal plates with a corrugated cross section, which are joined together at their outer edges. The separator 3 is made of a conductive material with excellent corrosion resistance, such as titanium, titanium alloy, or stainless steel. A cooling flow path through which a coolant flows is formed inside the separator 3 (between the pair of thin plates), and the flow of the coolant cools the power generation surface of the power generation cell 1. For example, water can be used as the coolant. The surfaces (front and rear surfaces) of the separator 3 facing the integrated electrode assembly 2 are formed unevenly by press molding or the like to form gas flow paths between them and the integrated electrode assembly 2 assembly.

[0013] The separator 3 on the front side of the integrated electrode assembly 2 is, for example, an anode side separator (anode separator), and an anode flow path through which a fuel gas flows is formed between the anode separator 3 and the assembled integrated electrode assembly 2. The separator 3 on the rear side of the integrated electrode assembly 2 is, for example, a cathode side separator (cathode separator), and a cathode flow path through which an oxidant gas flows is formed between the cathode separator 3 and the assembled integrated electrode assembly 2. For example, hydrogen gas can be used as the fuel gas, and for example, air can be used as the oxidant gas. Sometimes, the fuel gas and the oxidant gas are referred to as reactant gases without any distinction being made between them.

[0014] Fig. 2 is a perspective view showing a schematic configuration of the integrated electrode assembly 2. As shown in Fig. 2, the integrated electrode assembly 2 has a substantially rectangular assembly 20 and a frame 21 that supports the assembly 20. The assembly 20 is a membrane electrode assembly (MEA) that has 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.

[0015] The electrolyte membrane is, for example, a solid polymer electrolyte membrane, and a thin film of perfluorosulfonic acid containing water can be used. The electrolyte is not limited to a fluorine-based electrolyte, and a hydrocarbon-based electrolyte can also be used.

[0016] The anode electrode is formed on the front surface of the electrolyte membrane and has an electrode catalyst layer that serves as a reaction field for the electrode reaction, and a gas diffusion layer that is provided on the front surface of the electrode catalyst layer and diffuses and supplies the reactant gas. The cathode electrode is formed on the rear surface of the electrolyte membrane and has an electrode catalyst layer that serves as a reaction field for the electrode reaction, and a gas diffusion layer that is provided on the rear surface of the electrode catalyst layer and diffuses and supplies the reactant gas. The electrode catalyst layer contains a catalytic metal that promotes the electrochemical reaction between hydrogen contained in the fuel gas and oxygen contained in the oxidant gas, a proton-conductive electrolyte, and electron-conductive carbon particles. The gas diffusion layer is made of a gas-permeable conductive material, such as a porous carbon material.

[0017] At the anode electrode, fuel gas (hydrogen) supplied via the anode flow channel and gas diffusion layer is ionized by the action of a catalyst and moves through the electrolyte membrane to the cathode electrode. The electrons generated at this time pass through an external circuit and are extracted as electrical energy. At the cathode electrode, oxidant gas (oxygen) supplied via the cathode flow channel and gas diffusion layer reacts with hydrogen ions introduced from the anode electrode and electrons transferred from the anode electrode, producing water. The produced water provides an appropriate humidity to the electrolyte membrane, and excess water is discharged outside the electrode assembly 2.

[0018] The frame 21 is a film-like member having a substantially rectangular shape and is made of insulating resin, rubber, or the like. A substantially rectangular opening 21a is provided in the center of the frame 21. The joining body 20 is disposed so as to cover the entire opening 21a and is supported by the peripheral edge of the opening 21a. Three through-holes 211 to 213 that penetrate the frame 21 in the front-to-rear direction are opened in a vertically aligned manner on the left side of the opening 21a of the frame 21, and three through-holes 214 to 216 that penetrate the frame 21 in the front-to-rear direction are opened in a vertically aligned manner on the right side of the opening 21a.

[0019] As shown in FIG. 1, the front and rear separators 3 of the integrated electrode assembly 2 are provided with through holes 311 to 316 that penetrate the separators 3 in the front-rear direction at positions corresponding to the through holes 211 to 216 of the frame 21. The through holes 311 to 316 are connected to the through holes 211 to 216 of the frame 21, respectively. A collection of these mutually communicating through holes 211 to 216 and 311 to 316 form flow paths PA1 to PA6 (indicated by arrows for convenience) that penetrate the cell stack 101 and extend in the front-rear direction. The flow paths PA1 to PA6 are sometimes called manifolds. The flow paths PA1 to PA6 are connected to a manifold external to the fuel cell stack 100.

[0020] Flow path PA1 (solid arrow) extending forward via through holes 211 and 311 is a fuel gas supply flow path. Flow path PA6 (solid arrow) extending rearward via through holes 216 and 316 is a fuel gas discharge flow path. The fuel gas supply flow path PA1 and the fuel gas discharge flow path PA6 communicate with an anode flow path provided opposite to the front surface of the joined body 20, and as shown by the solid arrows, fuel gas flows from left to right through the anode flow path via the fuel gas supply flow path PA1 and the fuel gas discharge flow path PA6. Communication between the anode flow path and the other flow paths PA2 to PA5 is blocked via a seal portion (not shown).

[0021] A flow path PA4 (dotted arrow) extending forward through the through-holes 214 and 314 is an oxidant gas supply flow path. A flow path PA3 (dotted arrow) extending rearward through the through-holes 213 and 313 is an oxidant gas discharge flow path. The oxidant gas supply flow path PA4 and the oxidant gas discharge flow path PA3 communicate with a cathode flow path provided opposite to the rear surface of the joined body 20, and as shown by the dotted arrows, the oxidant gas flows from right to left through the cathode flow path via the oxidant gas supply flow path PA4 and the oxidant gas discharge flow path PA3. Communication between the cathode flow path and the other flow paths PA1, PA2, PA5, and PA6 is blocked by a seal (not shown).

[0022] A flow path PA5 (indicated by a dashed-dotted arrow) extending forward through through-holes 215 and 315 is a cooling medium supply flow path. A flow path PA2 (indicated by a dashed-dotted arrow) extending rearward through through-holes 212 and 312 is a cooling medium discharge flow path. The cooling medium supply flow path PA5 and the cooling medium discharge flow path PA2 are connected to the cooling flow path inside the separator 3, and the cooling medium flows from right to left through the cooling flow path via the cooling medium supply flow path PA5 and the cooling medium discharge flow path PA2. Communication between the cooling flow path and the other flow paths PA1, PA3, PA4, and PA6 is blocked by a seal (not shown).

[0023] The end units 102, arranged on both the front and rear sides of the cell stack 101, each have a terminal plate 4, an insulating plate 5, and an end plate 6. The front end unit 102 is sometimes called the dry-side end unit, and the rear end unit 102 is sometimes called the wet-side end unit. The pair of front and rear terminal plates 4, 4 are arranged on both the front and rear sides of the cell stack 101, sandwiching the cell stack 101 between them. The pair of front and rear insulating plates 5, 5 are arranged on both the front and rear sides of the terminal plates 4, 4, sandwiching them between them. The pair of front and rear end plates 6, 6 are arranged on both the front and rear sides of the insulating plates 5, 5, sandwiching them between them.

[0024] The terminal plate 4 is a metal, generally rectangular plate-like member that has a terminal portion for extracting the electric power generated by the electrochemical reaction in the cell stack 101. The insulating plate 5 is a non-conductive, generally rectangular plate-like member made of resin or rubber that electrically insulates the terminal plate 4 from the end plates 6. The end plates 6 are metal or high-strength resin plate-like members. A compressive load is applied to the cell stack 101 in the front-to-rear direction during assembly of the fuel cell stack 100, and in this state, the case surrounding the cell stack 101 is fastened to the front and rear end units 102. Therefore, the compressive load on the fuel cell stack 100 is maintained after assembly of the fuel cell stack 100 is complete.

[0025] The rear end unit 102 has a plurality of through holes 102a to 102f that penetrate the end unit 102 in the front-to-rear direction. The through holes 102a to 102f include a through hole that penetrates the terminal plate 4, a through hole that penetrates the insulating plate 5, and a through hole that penetrates the end plate 6, but for convenience, these are collectively shown as through holes 102a to 102f in FIG.

[0026] The through-hole 102a is opened on an extension of the fuel gas supply passage PA1 and communicates with the fuel gas supply passage PA1. The through-hole 102b is opened on an extension of the coolant discharge passage PA2 and communicates with the coolant discharge passage PA2. The through-hole 102c is opened on an extension of the oxidant gas discharge passage PA3 and communicates with the oxidant gas discharge passage PA3. The through-hole 102d is opened on an extension of the oxidant gas supply passage PA4 and communicates with the oxidant gas supply passage PA4. The through-hole 102e is opened on an extension of the coolant supply passage PA5 and communicates with the coolant supply passage PA5. The through-hole 102f is opened on an extension of the fuel gas discharge passage PA6 and communicates with the fuel gas discharge passage PA6.

[0027] Of these through holes 102a to 102f, a pump for supplying a cooling medium is connected to through hole 102e in particular, and the cooling medium is supplied to the fuel cell stack 100 through through hole 102e. The cooling medium is discharged from through hole 102b. The discharged cooling medium is cooled by heat exchange in the radiator and is supplied again to the fuel cell stack 100 through through hole 102e.

[0028] The above is a schematic configuration of the fuel cell stack 100. The fuel cell stack 100 is housed in a substantially box-shaped case and mounted on a vehicle.

[0029] In such a fuel cell stack 100, after the fuel cell stack 100 is assembled, a cooling medium is injected into the interior of the fuel cell stack 100 through the through-hole 102e. At this time, the air in the cooling channel moves upward and moves along with the flow of the cooling medium to the cooling medium discharge channel PA2. Furthermore, if air is mixed in the cooling medium supplied through the through-hole 102e, this air also moves along with the flow of the cooling medium to the cooling medium discharge channel PA2. For this reason, air (air bubbles) tend to accumulate in the upper region of the cooling medium discharge channel PA2, and it is necessary to discharge the accumulated air from the cooling medium discharge channel PA2. This embodiment is characterized by a configuration for discharging air accumulated in the cooling medium discharge channel PA2. This point will be described below.

[0030] Fig. 3 is a rear view of the fuel cell stack 100, and Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3. Fig. 3 more specifically shows the shape of the rear surface of the wet-side end plate 6 (such as the arrangement of the through-holes 102a to 102f). Fig. 4 does not show the individual power-generating cells 1 of the cell stack 101. In Figs. 3 and 4, in order to distinguish between the configurations of the front and rear end units 102, the front (dry-side) end unit 102 is represented by a terminal plate 40, an insulating plate 50, and an end plate 60, and the rear (wet-side) end unit 102 is represented by a terminal plate 41, an insulating plate 51, and an end plate 61.

[0031] 4, the coolant discharge channel PA2 extends in the front-to-rear direction via the through-hole 102b of the front end unit 102, the through-holes 212 and 312 of the cell stack 101, and the through-hole 102b of the rear end unit 102. The through-hole 102b of the front end unit 102 includes the through-hole 40b of the terminal plate 40 and the through-hole 50b of the insulating plate 50. The front end of the coolant discharge channel PA2 is closed by the end plate 60.

[0032] The through hole 102b of the rear end unit 102 includes the through hole 41a of the terminal plate 41, the through hole 51a of the insulating plate 51, and the through hole 61a of the end plate 61. More specifically, the insulating plate 51 is provided with a protruding portion 510 that protrudes rearward, and the protruding portion 510 is fitted into the through hole 61a of the end plate 61. Therefore, the through hole 51a is provided inside the through hole 61a.

[0033] Fig. 3 shows pipe mounting portions 103a to 104f to which external pipes communicating with the through holes 102a to 102f of the rear end unit 102 are attached. As shown in Fig. 3, pipe mounting portions 103b and 103e for supplying and discharging the coolant are positioned outside in the left-right direction of pipe mounting portions 103a and 103d for supplying fuel gas and oxidizing gas, respectively, and are also positioned outside in the left-right direction of pipe mounting portions 103f and 103c for discharging fuel gas and oxidizing gas.

[0034] An air discharge through-hole 102g is formed in the end unit 102 diagonally above and to the left of the coolant discharge through-hole 102b. A piping attachment part 103g is attached to the through-hole 102g. The through-hole 102g communicates with an external piping for air discharge via the piping attachment part 103g. In FIG. 3, the coolant discharge flow path PA2 of the cell stack 101 is indicated by a dotted line. Both the through-holes 102b and 102g are provided inside the coolant discharge flow path PA2. More specifically, the through-hole 102b is located at the bottom of the coolant discharge flow path PA2, and the through-hole 102g is located at the top of the coolant discharge flow path PA2.

[0035] 4, through-hole 102b and through-hole 102g branch off from coolant discharge flow path PA2 and are provided in insulating plate 51. The periphery of through-hole 102b has a tapered surface 511 that is tapered so that the opening area gradually decreases toward the rear, and a cylindrical surface 512 that extends rearward from the rear end of tapered surface 511 to the outlet at the rear end of through-hole 102b. Through-hole 102g extends rearward from tapered surface 511 and penetrates insulating plate 51 in the front-to-rear direction. Through-hole 102g has a smaller diameter than cylindrical surface 512.

[0036] A communicating pipe 7 is installed in the coolant discharge flow path PA2 along the upper surface of the flow path. The communicating pipe 7 is an elongated pipe member with a generally cylindrical cross section and openings (front end opening 71a and rear end opening 72a) at a front end face 71 and a rear end face 72, respectively. The communicating pipe 7 extends linearly in the front-to-rear direction along the coolant discharge flow path PA2. The front and rear ends of the communicating pipe 7 protrude forward and rearward beyond the cell stack 101.

[0037] The communicating pipe 7 is made of resin, rubber, glass, or the like. However, considering that vibrations and temperature changes may occur in the fuel cell stack 100, the communicating pipe 7 is preferably made of flexible resin or rubber. Air (air bubbles) accumulated above the coolant discharge flow path PA2 passes through the inside of the communicating pipe 7. The cross-sectional area of ​​the communicating pipe 7 is sufficiently smaller than the cross-sectional area of ​​the coolant discharge flow path PA2.

[0038] The front end opening 71a of the communicating pipe 7 is located in the internal space SP1 of the through hole 102a of the front end unit 102. More specifically, the through hole 40a of the terminal plate 40 and the through hole 50a of the insulating plate 50 have substantially the same shape as the coolant discharge flow path PA2 when viewed from the front-rear direction, and the front end opening 71a passes through the through hole 40a and is located inside the through hole 50a. As a result, the front end opening 71a communicates with the coolant discharge flow path PA2 via the internal space SP1. Note that instead of the through hole 50a, a recess may be provided in the rear surface of the insulating plate 50, with the front end opening 71a located inside the recess and communicating with the coolant discharge flow path PA2 via the internal space of the recess.

[0039] The rear end of the communicating pipe 7 is fitted into the through-hole 102g of the insulating plate 51, and the rear end opening 72a communicates with the through-hole 102g. Therefore, the internal space SP1 of the front end unit 102 and the through-hole 102g of the rear end unit 102 communicate with each other via the communicating pipe 7.

[0040] The internal space SP1 is an upstream space of the coolant discharge flow path PA2, and the pressure in the internal space SP1, which is upstream of the coolant flow, is greater than the pressure in the through-hole 102g. As a result, a pressure difference occurs between the front end opening 71a and the rear end opening 72a of the communicating pipe 7, and bubbles move within the communicating pipe 7 from the front end opening 71a to the rear end opening 72a in response to the pressure difference. By providing the long communicating pipe 7 in the coolant discharge flow path PA2, which extends from the front end unit 102 to the rear end unit 102 in this way, the pressure difference between the two ends of the communicating pipe 7 becomes greater, thereby facilitating the movement of bubbles.

[0041] The front end of the communicating pipe 7 is supported by a front support portion 201 provided on the front end unit 102, and the rear end of the communicating pipe 7 is supported by a rear support portion 202 provided on the rear end unit 102. FIG. 5 is an enlarged view of a main portion of FIG. 4 (an enlarged view of portion V in FIG. 4) showing the configuration of the rear support portion 202, and FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 4. As shown in FIGS. 5 and 6, the terminal plate 41 has a protrusion 411 that protrudes into the through hole 41a at the upper left corner of the periphery of the through hole 41a. A substantially circular through hole 411a is opened in the protrusion 411, and the rear end of the communicating pipe 7 is inserted through the through hole 411a.

[0042] Through hole 102g is centered on axis CL1 extending in the front-to-rear direction. Through hole 102g has tapered portion 521 formed in a tapered shape around axis CL1 so that the opening area gradually decreases toward the rear, small-diameter portion 522 of a generally cylindrical shape centered on axis CL1, connected to rear end 521a of tapered portion 521 and having a smaller opening area than rear end 521a, and large-diameter portion 523 of a generally cylindrical shape connected to small-diameter portion 522 and having a larger opening area than small-diameter portion 522. Small-diameter portion 522 and tapered portion 521 are connected in a stepped manner, and small-diameter portion 522 and large-diameter portion 523 are connected in a stepped manner.

[0043] An external pipe is connected to the large diameter portion 523 via the pipe mounting portion 103b (FIG. 3). For example, the tip of the external pipe is fitted into the large diameter portion 523, and the external pipe is mounted to the pipe mounting portion 103b in an axially sealed state. The opening area of ​​the large diameter portion 523 is larger than the opening area of ​​521a at the rear end portion of the tapered portion 521. Note that, to avoid interference between the external pipes, the center of the large diameter portion 523 (the center of the pipe mounting portion 103b) is offset from the axis CL1 (see FIG. 9). If there is no risk of interference between the external pipes, the center of the large diameter portion 523 may be aligned with the axis CL1.

[0044] The entire circumference of rear end surface 72 of communicating pipe 7, more specifically the outer periphery of rear end surface 72, abuts against tapered portion 521. For example, it abuts against tapered portion 521 forward of rear end portion 521a of the tapered portion. This causes axis CL1 of through hole 102g and center line CL2 of communicating pipe 7 to coincide, and the position of rear end opening 72a of communicating pipe 7 can be determined with high precision.

[0045] FIG. 7 is an enlarged view (enlarged view of part VII) of FIG. 4 showing the configuration of the front support part 201. As shown in FIG. 7, the front support part 201 is configured similarly to the rear support part 202. That is, the terminal plate 40 has a protrusion 410 that protrudes into the through hole 40a. A substantially circular through hole 410a is formed in the protrusion 410, and the front end of the communicating pipe 7 is inserted through the through hole 410a. A substantially cylindrical holder 505 is provided at the upper end of the periphery of the through hole 50a of the insulating plate 50, and its center is on an axis CL3 that is located on an extension of the axis CL1 (FIG. 5). The outer peripheral surface of the front end of the communicating pipe 7 is supported by the holder 505.

[0046] A substantially circular opening 505a is provided in the front wall of holder 505, and front end opening 71a and internal space SP1 communicate with each other through opening 505a. A cutout may be provided in the lower part of holder 505, and front end opening 71a and internal space SP1 may communicate with each other through the cutout. The inner peripheral surface of holder 505 may be tapered, similar to rear support part 202, instead of being cylindrical.

[0047] As described above, in this embodiment, the rear end and front end of the communicating pipe 7 are supported via the rear support part 202 of the end unit 102, which has a tapered portion 521 tapering toward the rear, and the front support part 201 of the end unit 102, which has a substantially cylindrical holder 505. This allows the communicating pipe 7 to be stably held at a predetermined position at the upper end of the coolant discharge flow path PA2. As a result, the position of the front end opening 71a relative to the opening 505a is regulated, allowing air bubbles to be efficiently introduced into the communicating pipe 7 through the opening 505a. Furthermore, the position of the rear end opening 72a relative to the through-hole 102g is regulated, allowing air bubbles that have passed through the communicating pipe 7 to be efficiently discharged to the outside through the through-hole 102g.

[0048] In the configuration shown in FIG. 5, the outer peripheral edge of the rear end of the communicating pipe 7 abuts against the circumferential surface of the tapered portion 521 over the entire circumference at abutment position Pa. Therefore, there is no gap between the through hole 102g and the communicating pipe 7 at abutment position Pa. Therefore, if bubbles are generated around the rear end of the communicating pipe 7 (for example, inside the through hole 102b) along the flow of the coolant, it is difficult to discharge the bubbles to the outside through the communicating pipe 7 because the distance from the bubbles to the front end opening 71a of the communicating pipe 7 is long. In consideration of this, it is preferable to configure the rear support part 202 as shown in FIG. 8. FIG. 8 is an enlarged view of a main part of FIG. 4 showing another example of the rear support part 202, and FIG. 9 is a view taken along arrow IX of FIG. 8.

[0049] 8 differs from FIG. 5 in the configuration of the through-hole 102g, particularly the configuration of the tapered portion 521. That is, as shown in FIGS. 8 and 9, slit-shaped grooves 525, 526 are provided at the upper and lower ends of the tapered portion 521, penetrating a part of the small diameter portion 522 and extending in the front-rear direction substantially parallel to the axis CL1. The bottom surface (upper end surface) of groove 525 is located below the upper end surface of the large diameter portion 523. The bottom surface (lower end surface) of groove 526 is located above the lower end surface of the large diameter portion 523.

[0050] Grooves 525, 526 have a predetermined width in the left-right direction and extend from tapered surface 511 to front end surface 523a of large diameter portion 523, beyond the abutment position Pa of the rear end of communicating pipe 7. The positions of the bottoms of grooves 525, 526, i.e., the positions of the upper end surface of groove 525 and the lower end surface of groove 526, are constant in the front-rear direction. The cross-sectional shape of through hole 102g in the range from tapered surface 511 to front end surface 523a of large diameter portion 523 is, for example, elliptical, as shown in FIG. 9. Therefore, both left-right ends of the rear end of communicating pipe 7 abut against tapered portion 521, and both upper and lower ends expose rear end surfaces 72 (shown hatched for convenience).

[0051] This creates a gap between the communicating pipe 7 and through-hole 102g, from through-hole 102b on the front side of tapered surface 511 to the inner space of large-diameter portion 523 at the rear of the communicating pipe 7. This allows air to flow as shown by the arrows in FIG. 8, and air bubbles can be moved rearward via the gap (grooves 525, 526). As a result, even if air bubbles are generated around the rear end of communicating pipe 7 along the flow of the cooling medium, the air bubbles can be efficiently discharged to the outside of fuel cell stack 100 via through-hole 102g.

[0052] The cross-sectional shape of the through-hole 102g is not limited to an oval shape, but may be an ellipse elongated in the vertical direction. Bubbles accumulate above the coolant discharge flow path PA2. Therefore, instead of providing grooves 525, 526 at the upper and lower ends of the tapered portion 521, a groove 527 may be provided only at the upper end, as shown in FIG. 10, for example. In FIG. 10, the width of the groove 527 is smaller than the diameter of the small diameter portion 522. The width of the groove 527 may be the same as or larger than the width of the small diameter portion 522.

[0053] According to this embodiment, the following effects can be achieved. (1) A fuel cell stack 100 includes a cell stack 101 formed by stacking a plurality of power-generating cells 1, each having an integrated electrode assembly 2 and a separator 3, in the front-to-rear direction, front and rear end units 102, 102 disposed at the front and rear ends of the cell stack 101, a coolant discharge passage PA2 extending through the cell stack 101 in the front-to-rear direction to discharge a coolant introduced to the plurality of power-generating cells 1, and a substantially cylindrical communicating pipe 7 disposed in the coolant discharge passage PA2 and having a front end opening 71 a and a rear end opening 72 a at the front and rear ends, respectively, that communicate with the upstream and downstream sides of the coolant discharge passage PA2 ( FIGS. 1, 2, and 4 ). The rear end unit 102 is provided with a through-hole 102 g that passes through the rear end unit 102 and is in communication with the rear end opening 72 a of the communicating pipe 7 ( FIG. 4 ). The front and rear end units 102, 102 have a front support portion 201 and a rear support portion 202 that respectively support the peripheral edge portion of the front end portion and the peripheral edge portion of the rear end portion of the communicating pipe 7. The rear support portion 202 has a tapered portion 521 formed on the circumferential surface of the through hole 102g so as to taper toward the outlet of the through hole 102g around an axis CL1 that extends substantially parallel to the front-to-rear direction (FIG. 5).

[0054] In this way, the front end of the communicating pipe 7 ahead of the cell stack 101 and the rear end of the communicating pipe 7 behind the cell stack 101 are supported via the front support portion 201 provided on the front end unit 102 and the rear support portion 202 provided on the rear end unit 102, and the front end is further supported via the tapered portion 521, so that the communicating pipe 7 can be accurately positioned and held within the coolant discharge flow path PA2. As a result, when a compressive load is applied in the stacking direction of the power-generating cells 1 to compress the cell stack 101 during assembly of the fuel cell stack 100, the end units 102 and the communicating pipe 7 do not interfere with each other, and the communicating pipe 7 can be stably held at the upper end of the coolant discharge flow path PA2 where the coolant flows.

[0055] (2) The tapered portion 521 has grooves 525-527 extending substantially parallel to the axis CL1 beyond the contact position Pa where the rear end of the communicating pipe 7 contacts (FIGS. 8-10). When the rear end of the communicating pipe 7 contacts the tapered portion 521, the gap between the communicating pipe 7 and the through-hole 102g is blocked, which may cause air bubbles to accumulate around the rear end of the communicating pipe 7. In this regard, by providing the grooves 525-527 in the tapered portion 521, air can flow rearward through the grooves 525-527, past the contact position Pa. This allows air bubbles accumulated in the coolant discharge flow path PA2 to be efficiently discharged.

[0056] (3) The communicating pipe 7 extends in a substantially horizontal direction (FIG. 4). The grooves 525, 527 are provided in the upper part of the tapered portion 521 (FIGS. 9 and 10). Bubbles tend to accumulate above the coolant discharge flow path PA2, but by providing the grooves 525, 527 in the upper part, only the bubbles can be efficiently discharged through the grooves 525, 527.

[0057] (4) The rear end unit 102 has a terminal plate 41 arranged adjacent to the cell stack 101, an insulating plate 51 arranged adjacent to the terminal plate 41, and an end plate 61 arranged adjacent to the insulating plate 51 (FIG. 4). A tapered portion 521 is provided on the insulating plate 51 (FIGS. 5 and 8). This makes it possible to easily form the tapered portion 521 together with the grooves 525 to 527.

[0058] The above embodiment can be modified in various ways. Some modifications will be described below. In the above embodiment, the dry-side end unit 102 (first end unit) is configured by the terminal plate 40 (current collector plate), the insulating plate 50 (insulating plate), and the end plate 60 (end plate), and the wet-side end unit 102 (second end unit) is configured by the terminal plate 41 (current collector plate), the insulating plate 51 (insulating plate), and the end plate 61 (end plate). However, the configurations of the first end unit and the second end unit are not limited to those described above. The tapered portion 521 may be provided on a member other than the terminal plate 41.

[0059] In the above embodiment, the communicating pipe 7, which has a front end opening 71a (first opening) and a rear end opening 72a (second opening) at its front end (one end) and rear end (other end) that communicate with the upstream side and downstream side of the coolant discharge flow path PA2, respectively, is disposed at the top of the coolant discharge flow path PA2, but the configuration of the substantially cylindrical pipe body is not limited to that described above. In the above embodiment, the communicating pipe 7 is disposed so as to extend in a substantially horizontal direction, i.e., in a substantially horizontal position, but the position of the pipe body is not limited to a substantially horizontal position. In the above embodiment, the cell stack 101 is formed by stacking multiple power generating cells 1 in the front-to-rear direction (a predetermined direction), but the predetermined direction may be other than the front-to-rear direction.

[0060] In the above embodiment, the front support portion 201 (first support portion) and the rear support portion 202 (second support portion) support the periphery of the front end portion (periphery of the first end portion) of the communicating pipe 7 in front of the cell stack 101 and the periphery of the rear end portion (periphery of the second end portion) of the communicating pipe 7 in the rear of the cell stack 101. However, the configuration of the first support portion is not limited to the above. Furthermore, the second support portion may have any configuration as long as it has a tapered portion formed so as to taper toward the outlet of the through hole 102g, centered on the axis CL1 extending in the stacking direction of the power-generating cells 1. In the above embodiment, the grooves 525, 526 are formed continuous with the upper and lower ends of the small diameter portion 522 of the through hole 102g. However, the grooves may have any configuration as long as they extend substantially parallel to the axis CL1 beyond the abutment position Pa where the tip of the communicating pipe 7 abuts.

[0061] The above description is merely an example, and the present invention is not limited to the above-described embodiment and modifications as long as the features of the present invention are not impaired. One or more of the above-described embodiment and modifications can be arbitrarily combined, and modifications can also be combined with each other. [Explanation of symbols]

[0062] 1 power generating cell, 2 integrated electrode assembly, 3 separator, 7 communicating pipe, 41 terminal plate, 51 insulating plate, 61 end plate, 71a front end opening, 72a rear end opening, 100 fuel cell stack, 101 cell stack, 102 end unit, 102g through hole, 201 front support portion, 202 rear support portion, 521 tapered portion, 525-527 groove portion, PA2 coolant discharge flow path, Pa abutment position, CL1 axis

Claims

1. a cell stack formed by stacking a plurality of power generation cells, each having a membrane electrode assembly and a separator, in a predetermined direction; a first end unit and a second end unit disposed at one end and the other end of the cell stack in the predetermined direction; a coolant discharge flow path provided to penetrate the cell stack in the predetermined direction so as to discharge the coolant guided to the plurality of power generating cells; a substantially cylindrical pipe body that is disposed in the coolant discharge flow path and has a first opening and a second opening at one end and the other end of the pipe body that communicate with the upstream side and the downstream side of the coolant discharge flow path, respectively; a through-hole that passes through the second end unit and communicates with the second opening of the pipe; the first end unit and the second end unit have a first support portion and a second support portion that support a peripheral edge portion of the one end portion and a peripheral edge portion of the other end portion of the pipe body, respectively; a second support portion having a tapered portion formed on the circumferential surface of the through hole so as to taper toward the outlet of the through hole around an axis extending approximately parallel to the predetermined direction.

2. 2. The fuel cell stack according to claim 1, The fuel cell stack according to claim 1, wherein the tapered portion has a groove extending substantially parallel to the axis beyond a contact position where the tip of the pipe contacts.

3. 3. The fuel cell stack according to claim 2, The pipe extends in a substantially horizontal direction, The fuel cell stack is characterized in that the groove portion is provided on an upper portion of the tapered portion.

4. 4. The fuel cell stack according to claim 1, the second end unit has a current collector plate disposed adjacent to the cell stack, an insulating plate disposed adjacent to the current collector plate, and an end plate disposed adjacent to the insulating plate, The fuel cell stack, wherein the tapered portion is provided on the insulating plate.

Images