Fuel cell stack

Abstract

To satisfactorily discharge liquid water without passing through a power generation cell while ensuring a smooth flow of reaction gas.SOLUTION: A fuel cell stack includes a cell stacked body 101 having a plurality of power generation cells 1, end units 102 arranged on both the front and rear sides of the cell stacked body 101, and a communication pipe 7 arranged in the gas supply flow path of the cell stacked body 101, extending in the front-to-rear direction and having a rear end opening 72a and a front end opening 71a at its front end on the downstream side and its rear end on the upstream side of the gas flow, respectively. The downstream end unit 102 is provided with a water discharge passage PA10 that guides liquid water flowing out from the front end opening 71a to a gas discharge flow path.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] In recent years, in order to enable more people to access affordable, reliable, sustainable, and advanced energy, technological development related to fuel cells that contribute to energy efficiency has been carried out. As a technology related to this type of fuel cell, conventionally, a fuel cell system has been known in which a stirring mixer for swirling the fuel gas is provided in the flow path for supplying the fuel gas to the fuel cell stack to suppress the concentration of impurities such as water near the inlet of the fuel cell cell (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when a stirring mixer is provided in the flow path for supplying the fuel gas to the fuel cell stack as in the fuel cell system described in Patent Document 1 above, the pressure loss in the flow path increases, and the smooth flow of the fuel gas is hindered.

Means for Solving the Problems

[0005] A fuel cell stack according to one aspect of the present invention has a plurality of power generation cells stacked in a predetermined direction, and a gas supply flow path through which a reaction gas is supplied and a gas discharge flow path through which the reaction gas is discharged extend along the predetermined direction, respectively. A cell stack body is provided with a gas flow path communicating the gas supply flow path and the gas discharge flow path. A first end unit is disposed on one side in the predetermined direction of the cell stack body and is provided with a supply port communicating with the gas supply flow path and a discharge port communicating with the gas discharge flow path. A second end unit is disposed on the other side in the predetermined direction of the cell stack body. A pipe body is disposed in the gas supply flow path and extends in the predetermined direction, and a first opening communicating with the upstream side of the gas supply flow path and a second opening communicating with the downstream side are provided at one end side in one direction of the predetermined direction and the other end side in the other direction of the predetermined direction, respectively. A drainage passage for guiding the liquid water flowing out from the second opening to the gas discharge flow path is provided in a non-power generation region on the other side in the predetermined direction than the power generation region of the cell stack body where the plurality of power generation cells are disposed.

Advantages of the Invention

[0006] According to the present invention, while ensuring a smooth flow of the reaction gas, the liquid water can be discharged well without passing through the power generation cells.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5A

Figure 5B

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 9. The fuel cell stack according to the embodiment of the present invention is a main component of the fuel cell. The fuel cell can be mounted on a vehicle, for example, and generate electric power for driving the vehicle. First, the overall configuration of the fuel cell stack will be schematically described.

[0009] FIG. 1 is a perspective view schematically showing the overall configuration of a fuel cell stack 100 according to the present embodiment. Hereinafter, for convenience, three axial directions orthogonal to each other as 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 according to this definition. The lower side in the up-down direction corresponds to, for example, 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 the vehicle. For example, the front-rear direction in FIG. 1 may be the front-rear direction of the vehicle or the left-right direction.

[0010] As shown in FIG. 1, the fuel cell stack 100 includes a cell stack 101 formed by stacking a plurality of power generation cells 1 in the front-rear direction, and end units 102 disposed at both front and rear ends of the cell stack 101, and has an overall substantially rectangular parallelepiped shape. Although not shown, the periphery of the cell stack 101 is covered by a substantially rectangular parallelepiped case. The length of the cell stack 101 in the left-right direction is longer than the length in the up-down direction. For convenience, a single power generation cell 1 is shown in FIG. 1.

[0011] The power generation cell 1 has an electrode assembly 2 (UEA; Unitized Electrode Assembly) having a joined body including an electrolyte membrane and electrodes, and separators 3, 3 disposed on both the front and rear sides of the electrode assembly 2 to sandwich the electrode assembly 2. The electrode assembly 2 and the separators 3 are alternately arranged in the front-rear direction. The electrode assembly 2 can also be referred to as a membrane electrode structure or a membrane electrode member.

[0012] The separator 3 has a pair of front and rear thin metal plates with a corrugated cross-section (see Fig. 3), and the outer peripheral edges of these thin plates are joined together to form an integral structure. A conductive material with excellent corrosion resistance is used for the separator 3, and for example, stainless steel, titanium, titanium alloy, etc. can be used. Inside the separator 3 (between the pair of thin plates), a cooling flow path through which a cooling medium flows is formed, and the power generation surface of the power generation cell 1 is cooled by the flow of the cooling medium. For example, water can be used as the cooling medium. The surfaces (front surface and rear surface) of the separator 3 facing the electrode assembly 2 are configured in a concavo-convex shape by press molding or the like so as to form a gas flow path between the joined body of the electrode assembly 2.

[0013] The separator 3 on the front side of the 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 joined body of the electrode assembly 2. The separator 3 on the rear side of the 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 joined body of the electrode assembly 2. The fuel gas is a gas containing hydrogen, and for example, hydrogen gas can be used. The oxidant gas is a gas containing oxygen, and for example, air can be used. Sometimes, without distinguishing between the fuel gas and the oxidant gas, these are called reaction gases.

[0014] Figure 2 is a perspective view showing the schematic configuration of the electrode assembly 2. As shown in Figure 2, the electrode assembly 2 has a substantially rectangular joined body 20 and a frame 21 that supports the joined body 20. The joined body 20 is a membrane electrode assembly (MEA), and 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 moisture can be used. Not limited to fluorine-based electrolytes, hydrocarbon-based electrolytes 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 provided on the front surface of the electrode catalyst layer that diffuses and supplies the fuel 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 provided on the rear surface of the electrode catalyst layer that diffuses and supplies the oxidant gas. The electrode catalyst layer contains a catalyst metal that promotes the electrochemical reaction between hydrogen contained in the fuel gas and oxygen contained in the oxidant gas, an electrolyte having proton conductivity, and carbon particles having electron conductivity, etc. The gas diffusion layer is composed of a conductive member having gas permeability, for example, a carbon porous body.

[0017] In the anode electrode, the fuel gas (hydrogen) supplied through the anode flow path is ionized by the action of the catalyst, passes through the electrolyte membrane, and moves to the cathode electrode side. The electrons generated at this time pass through the external circuit and are taken out as electrical energy. In the cathode electrode, the oxidant gas (oxygen) supplied through the cathode flow path reacts with the hydrogen ions led from the anode electrode and the electrons that have moved from the anode electrode, and water is generated. The generated water (referred to as generated water) gives an appropriate humidity to the electrolyte membrane, and the excess water is discharged to the outside of the electrode assembly 2 along the gas flow. The generated water on the cathode side also flows to the anode side by reverse diffusion through the electrolyte membrane. Therefore, generated water exists in both the anode flow path and the cathode flow path.

[0018] The frame 21 is a thin plate having a substantially rectangular shape and is made of a resin, rubber, or the like having insulating properties. A substantially rectangular opening 21a is provided in the central portion of the frame 21. The joining body 20 is provided so as to cover the entire opening 21a, and the peripheral portion of the joining body 20 is supported by the frame 21. On the left side of the opening 21a of the frame 21, three through-holes 211 to 213 penetrating the frame 21 in the front-rear direction are opened side by side in the vertical direction. On the right side of the opening 21a, three through-holes 214 to 216 penetrating the frame 21 in the front-rear direction are opened side by side in the vertical direction. The through-holes 211 to 216 are all shown as substantially rectangular shapes for the sake of convenience, but the shapes and arrangements of the through-holes 211 to 216 are not limited to this.

[0019] As shown in FIG. 1, in the separators 3 before and after the electrode assembly 2, through-holes 311 to 316 penetrating the separator 3 in the front-rear direction are respectively opened at positions corresponding to the through-holes 211 to 216 of the frame 21. The through-holes 311 to 316 communicate with the through-holes 211 to 216 of the frame 21 respectively. By the set of these mutually communicating through-holes 211 to 216 and 311 to 316, flow paths PA1 to PA6 (shown by arrows for convenience) extending in the front-rear direction through the cell laminate 101 are formed. The flow paths PA1 to PA6 may also be called a manifold (internal manifold). The flow paths PA1 to PA6 are connected to a manifold outside the fuel cell stack 100.

[0020] The flow path PA1 (solid arrow) extending forward through the through holes 211 and 311 is a fuel gas supply flow path. The flow path PA6 (solid arrow) extending rearward through the 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 facing the front surface of the joined body 20. As shown by the solid arrow, fuel gas flows through the fuel gas supply flow path PA1 and the fuel gas discharge flow path PA6 from the left (upper left) to the right (lower right) in the anode flow path. The communication between the anode flow path and the other flow paths PA2 to PA5 is blocked via a seal portion (not shown). The fuel gas flowing through the fuel gas discharge flow path PA6 is the fuel gas after a part of it has been used at the anode electrode, and this may be referred to as fuel exhaust gas.

[0021] The flow path PA4 (dotted arrow) extending forward through the through holes 214 and 314 is an oxidant gas supply flow path. The 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 facing the rear surface of the joined body 20. As shown by the dotted arrow, oxidant gas flows through the oxidant gas supply flow path PA4 and the oxidant gas discharge flow path PA3 from the right (upper right) to the left (lower left) in the cathode flow path. The communication between the cathode flow path and the other flow paths PA1, PA2, PA5, PA6 is blocked via a seal portion (not shown). The oxidant gas flowing through the oxidant gas discharge flow path PA3 is the oxidant gas after a part of it has been used at the cathode electrode, and this may be referred to as oxidant exhaust gas. Sometimes, without distinguishing between the fuel exhaust gas and the oxidant exhaust gas, these are collectively referred to as reaction exhaust gas.

[0022] The flow path PA5 (dashed arrow) extending forward through the through holes 215 and 315 is a cooling medium supply flow path. The flow path PA2 (dashed arrow) extending rearward through the 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 communicate with the cooling flow path inside the separator 3, and the cooling medium flows through the cooling flow path via the cooling medium supply flow path PA5 and the cooling medium discharge flow path PA2. The communication between the cooling flow path and the other flow paths PA1, PA3, PA4, PA6 is blocked via a seal portion (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 may be referred to as the dry side end unit, and the rear end unit 102 may be referred to as the wet side end unit. A pair of front and rear terminal plates 4, 4 are arranged on both the front and rear sides of the cell stack 101 with the cell stack 101 interposed therebetween. A pair of front and rear insulating plates 5, 5 are arranged on both the front and rear sides of the terminal plates 4, 4 with the terminal plates 4, 4 interposed therebetween. A pair of front and rear end plates 6, 6 are arranged on both the front and rear sides of the insulating plates 5, 5 with the insulating plates 5, 5 interposed therebetween.

[0024] The terminal plate 4 is a substantially rectangular plate-shaped member made of metal and 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 substantially rectangular plate-shaped member made of resin or rubber having non-conductivity and electrically insulates the terminal plate 4 and the end plate 6. The end plate 6 is a plate-shaped member made of metal or resin configured with high strength. The front and rear end plates 6, 6 are fixed by bolts to the front end portion and the rear end portion of, for example, a case surrounding the cell stack 101 in a state where a predetermined compressive load is applied in the front-rear direction. The fuel cell stack 100 is held in a state of being pressed in the front-rear direction via the case.

[0025] In the rear end unit 102, a plurality of through-holes 102a to 102f penetrating the end unit 102 in the front-rear direction are opened. The through-holes 102a to 102f each include a through-hole penetrating the terminal plate 4, a through-hole penetrating the insulating plate 5, and a through-hole penetrating the end plate 6. In FIG. 1, for the sake of convenience, these are collectively shown as through-holes 102a to 102f. The through-hole 102a is opened on the extension line of the fuel gas supply flow path PA1 and communicates with the fuel gas supply flow path PA1. The through-hole 102b is opened on the extension line of the cooling medium discharge flow path PA2 and communicates with the cooling medium discharge flow path PA2. The through-hole 102c is opened on the extension line of the oxidant gas discharge flow path PA3 and communicates with the oxidant gas discharge flow path PA3. The through-hole 102d is opened on the extension line of the oxidant gas supply flow path PA4 and communicates with the oxidant gas supply flow path PA4. The through-hole 102e is opened on the extension line of the cooling medium supply flow path PA5 and communicates with the cooling medium supply flow path PA5. The through-hole 102f is opened on the extension line of the fuel gas discharge flow path PA6 and communicates with the fuel gas discharge flow path PA6.

[0026] More specifically, a fuel gas tank storing high-pressure fuel gas is connected to the through-hole 102a via an ejector, an injector, etc., and the fuel gas in the fuel gas tank is supplied to the fuel cell stack 100 through the through-hole 102a. A gas-liquid separator is connected to the through-hole 102f, and the fuel gas (fuel exhaust gas) discharged through the through-hole 102f is separated into fuel gas and water by the gas-liquid separator. The separated fuel gas is sucked in through the ejector and supplied again to the fuel cell stack 100 through the through-hole 102a. The separated water is discharged to the outside through the drain flow path.

[0027] A compressor for supplying an oxidant gas is connected to the through-hole 102d, and the oxidant gas compressed by the compressor is supplied to the fuel cell stack 100 through the through-hole 102d. The oxidant gas (oxidant exhaust gas) flows out to the outside from the through-hole 102c. A pump for supplying a cooling medium is connected to the through-hole 102e, and the cooling medium is supplied to the fuel cell stack 100 through the through-hole 102e. The cooling medium is discharged from the through-hole 102b. The discharged cooling medium is cooled by heat exchange in a radiator and supplied again to the fuel cell stack 100 through the through-hole 102e.

[0028] The above is the 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] By the way, generated water is produced on the anode electrode due to diffusion from the cathode electrode side through the electrolyte membrane. This generated water flows through the anode flow path into the fuel gas discharge flow path PA6 and is discharged together with the fuel exhaust gas. However, when the fuel gas is recirculated, it may flow into the fuel gas supply flow path PA1 together with the fuel gas. Condensed water is generated inside the fuel cell stack 100 and in the pipes constituting the external manifold, and this condensed water may also flow into the fuel gas supply flow path PA1 together with the fuel gas. Hereinafter, the generated water and the condensed water are collectively referred to as liquid water. The liquid water flows not only into the fuel gas supply flow path PA1 but also into the oxidant gas supply flow path PA4.

[0030] When liquid water flows into the supply flow paths (gas supply flow paths) PA1 and PA4 of the reaction gas in this way, the liquid water is guided to the power generation surface of the power generation cell 1, which may cause unstable power generation and a decrease in power generation performance. In order to avoid such inflow of liquid water, if a stirring mixer or the like is arranged in the external manifold upstream of the gas supply flow paths PA1 and PA4, the pressure loss increases, making it difficult to obtain the desired power generation performance. Therefore, in order to suppress the decrease in power generation performance due to the liquid water flowing into the gas supply flow paths PA1 and PA4, the fuel cell stack 100 is configured as follows in this embodiment.

[0031] The configurations of the fuel gas supply passage PA1 and the oxidant gas supply passage PA4 are substantially the same. Therefore, hereinafter, the configurations of the gas supply passages PA1 and PA4 will be described by focusing on the fuel gas supply passage PA1. FIG. 3 is a cross-sectional view showing the main part configuration of the fuel cell stack 100 along the fuel gas supply passage PA1.

[0032] In FIG. 3, in order to distinguish the configurations of the front and rear end units 102, the front end unit 102 is represented by the terminal plate 40, the insulating plate 50, and the end plate 60, and the rear end unit 102 is represented by the terminal plate 41, the insulating plate 51, and the end plate 61. As shown in FIG. 3, the fuel gas supply passage PA1 extends in the front-rear direction through the through-hole 102a of the rear end unit 102, the through-holes 211 and 311 of the cell stack 101, and the through-hole 102a of the front end unit 102. Therefore, the end unit 102 and the cell stack 101 form the fuel gas supply passage PA1 and constitute the flow path forming portion.

[0033] The through-hole 102a of the front end unit 102 includes the through-hole 40a of the terminal plate 40 and the through-hole 50a of the insulating plate 50. The front end of the fuel gas supply passage PA1 is blocked by the end plate 60. The through-hole 102a 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.

[0034] The cell stack 101 has a plurality of power generation cells 1 that are power generation bodies and dummy cells 1d that are non-power generation bodies. The dummy cells 1d are interposed between the last power generation cell 1 and the rear terminal plate 41 and between the foremost power generation cell 1 and the front terminal plate 40. More specifically, two sets of dummy cells 1d are interposed between the power generation cell 1 and the terminal plates 40 and 41, respectively.

[0035] The dummy cell 1d has a pair of separators 3 with the same configuration as the power generation cell 1 before and after, and a dummy assembly 2d interposed between the separators 3, 3. The dummy assembly 2d has a frame 21 with the same configuration as the power generation cell 1 and a dummy junction 20d. That is, the dummy cell 1d is different from the power generation cell 1 in that it has a dummy junction 20d instead of the junction 20.

[0036] The dummy junction 20d is a junction of a conductive plate and an electrode provided to cover the opening 21a (Fig. 2) of the frame 21. Therefore, the dummy cell 1d does not have an electrolyte membrane 23, and power generation does not occur in the dummy cell 1d. By arranging the dummy cells 1d adjacent to both ends in the front-rear direction of the power generation cell 1 in this way, the dummy cells 1d can function as a heat insulating layer and suppress the temperature drop of the power generation cell 1. In Fig. 3, two sets of dummy cells 1d are arranged between the power generation cell 1 and the terminal plates 40, 41, respectively, but one set or three or more sets of dummy cells 1d may be arranged. It is also possible to omit the dummy cells 1d on one or both of the front side and the rear side.

[0037] In the fuel gas supply flow path PA1, a communication pipe 7 is installed along the flow path PA1 on the upper surface of the flow path. Although detailed illustration is omitted, around the through hole 311 of the separator 3 constituting the flow path PA1, a communication port 3b that communicates the flow path PA1 and the anode flow path is opened in a region from the lower surface to the right surface of the through hole 311. The communication pipe 7 is installed in a region (upper surface) different from the region (lower surface to right surface) where the communication port 3b is provided among the inner wall surfaces of the flow path PA1. The communication port 3b is constituted by, for example, a tunnel portion that traverses a rib-shaped seal portion (metal bead seal 3c) in the vertical direction.

[0038] The communication pipe 7 is an elongated pipe member with a substantially ring-shaped cross-section, having openings (front-end opening 71a and rear-end opening 72a) provided at the front-end portion 71 and the rear-end portion 72 respectively, and extends linearly in the front-rear direction through the cell stack 101. The front-end opening 71a of the communication pipe 7 is located inside the internal space SP1 of the through-hole 102a of the front-end unit 102 on the front side, more specifically, inside the through-hole 50a of the insulating plate 50. The rear-end opening 72a of the communication pipe 7 is located inside the internal space SP2 of the through-hole 102a of the rear-end unit 102 on the rear side, more specifically, inside the through-hole 51a of the insulating plate 51. Therefore, the internal space SP1 of the front-end unit 102 on the front side and the internal space SP2 of the rear-end unit 102 on the rear side communicate with each other through the communication pipe 7.

[0039] The communication pipe 7 is formed using materials such as resin, rubber, and glass as constituent materials. However, considering that vibrations and temperature changes occur in the fuel cell stack 100, the communication pipe 7 is preferably composed of a flexible resin or rubber. The pressure in the internal space SP2, which is the upstream side of the fuel gas supply flow path PA1, is higher than the pressure in the internal space SP1, which is the downstream side. Water flows from the rear-end opening 72a to the front-end opening 71a in the communication pipe 7 according to the pressure difference between the internal spaces SP1 and SP2. Therefore, although the cross-sectional area of the communication pipe 7 is sufficiently smaller than the cross-sectional area of the fuel gas supply flow path PA1, it is set to allow a flow of water of a predetermined amount or more. In other words, the communication pipe 7 forms a constricted region in the flow path PA1 with a significantly smaller cross-sectional area compared to the flow path PA1.

[0040] The front-end portion of the communication pipe 7 is supported by the front support portion 201 provided in the front-end unit 102 on the front side. The rear-end portion of the communication pipe 7 is supported by the rear support portion 202 provided in the rear-end unit 102 on the rear side.

[0041] FIG. 4A is an enlarged view of the main part of FIG. 3 showing the configuration of the front support portion 201, and FIG. 4B is a view taken along arrow IVB in FIG. 4A (a view seen from the front). As shown in FIGS. 4A and 4B, on the upper surface of the through hole 50a of the insulating plate 50, a bulging portion 52 that bulges downward is provided from the rear end portion to the middle portion in the front-rear direction. In FIG. 4A, the bulging portion 52 has a protruding portion 52a that protrudes rearward, and the protruding portion 52a is located inside the through hole 40a of the terminal plate 40. For this reason, a part of the insulating plate 50 is configured to be long in the front-rear direction, and the front end portion of the communication pipe 7 is supported by this long portion.

[0042] In the bulging portion 52, a through hole 520 having a circular cross-section is opened around an axis CL0 extending in the front-rear direction from the front end face 525 to the rear end face 526. The through hole 520 includes a tapered portion 521 behind the boundary surface 527 and a straight portion 522 in front of the boundary surface 527 with the boundary surface 527 extending vertically with respect to the axis CL0 as a boundary. The tapered portion 521 is formed in a tapered shape such that the cross-sectional area gradually decreases from the rear end face 526 of the bulging portion 52 to the boundary surface 527. That is, it is formed to have a frustum-shaped space inside. The straight portion 522 is formed linearly with a constant or substantially constant cross-sectional area from the front end face 525 of the bulging portion 52 to the boundary surface 527. The cross-sectional area of the straight portion 522 is smaller than the cross-sectional area at the front end of the tapered portion 521. The angle formed by the tapered portion 521 with respect to the axis CL0 is about several degrees (for example, 2 to 3° or 4 to 5°), and the length of the tapered portion 521 in the front-rear direction is longer than the length of the straight portion 522 in the front-rear direction.

[0043] The diameter of the outer peripheral surface of the communication pipe 7 is larger than the diameter of the front end surface (boundary surface 527) of the tapered portion 521 and smaller than the diameter of the rear end surface 526 of the tapered portion 521. The diameter of the inner peripheral surface of the communication pipe 7 is the same as or smaller than the diameter of the straight portion 522. Thus, when the communication pipe 7 is inserted into the through hole 520 from the rear of the bulging portion 52, the outer peripheral corner portion at the front end of the communication pipe 7 abuts against the peripheral surface of the tapered portion 521, and the center line CL1 of the communication pipe 7 coincides with the axis CL0. As a result, with the front end portion of the communication pipe 7 positioned by the tapered portion 521, the front end portion of the communication pipe 7 can be supported from the insulating plate 50. Since the movement of the communication pipe 7 is restricted by the tapered portion 521, displacement of the communication pipe 7 can also be prevented. In a state where the communication pipe 7 is supported by the front support portion 201, the front end opening 71a of the communication pipe 7 communicates with the internal space SP1 of the end unit 102, more specifically, the internal space SP1 in front of the bulging portion 52, through the through hole 520.

[0044] FIG. 5A is an enlarged view of the main part of FIG. 3 showing the configuration of the rear support portion 202, and FIG. 5B is a view taken in the direction of arrow VB in FIG. 5A (a view seen from the rear). As shown in FIGS. 5A and 5B, on the upper surface of the through hole 51a of the insulating plate 51, a bulging portion 53 that bulges downward is provided from the front end portion to the middle portion in the front-rear direction. In FIG. 5A, the bulging portion 53 has a protruding portion 53a that protrudes forward, and the protruding portion 53a is located inside the through hole 41a of the terminal plate 41. For this reason, a part of the insulating plate 51 is configured to be long in the front-rear direction, and the rear end portion of the communication pipe 7 is supported by this long portion.

[0045] In the bulging portion 53, a through hole 530 having a circular cross-section is opened from the rear end surface 535 to the front end surface 536 around an axis CL0 extending in the front-rear direction. The through hole 530 includes a tapered portion 531 in front of the boundary surface 537 and a straight portion 532 behind the boundary surface 537 with the boundary surface 537 extending vertically with respect to the axis CL0. The tapered portion 531 is formed in a tapered shape such that the cross-sectional area gradually decreases from the front end surface 536 of the bulging portion 53 to the boundary surface 537. That is, it is formed to have a frustum-shaped space inside. The straight portion 532 is formed linearly with a constant or substantially constant cross-sectional area from the rear end surface 535 of the bulging portion 53 to the boundary surface 537. The cross-sectional area of the straight portion 532 is smaller than the cross-sectional area at the front end of the tapered portion 531. The angle formed by the tapered portion 531 with respect to the axis CL0 is about several degrees (for example, 2 to 3° or 4 to 5°), and the front-rear direction length of the tapered portion 531 is longer than the front-rear direction length of the straight portion 532.

[0046] The diameter of the outer peripheral surface of the communication pipe 7 is larger than the diameter of the rear end surface (boundary surface 537) of the tapered portion 531 and smaller than the diameter of the front end surface 536 of the tapered portion 531. The diameter of the inner peripheral surface of the communication pipe 7 is the same as or smaller than the diameter of the straight portion 532. Thus, when the communication pipe 7 is inserted into the through hole 530 from the front of the bulging portion 53, the outer peripheral corner portion at the rear end of the communication pipe 7 abuts against the peripheral surface of the tapered portion 531, and the center line CL1 of the communication pipe 7 coincides with the axis CL0. As a result, the rear end portion of the communication pipe 7 can be supported from the insulating plate 51 in a state where the rear end portion of the communication pipe 7 is positioned by the tapered portion 531. Since the movement of the communication pipe 7 is restricted by the tapered portion 531, displacement of the communication pipe 7 can also be prevented. In a state where the communication pipe 7 is supported by the rear support portion 202, the rear end opening 72a of the communication pipe 7 communicates with the internal space SP2 of the end unit 102, more specifically, the internal space SP2 behind the bulging portion 53, through the through hole 530.

[0047] In addition to supporting the communication pipe 7 by the support portions 201 and 202 of the front and rear end units 102, the communication pipe 7 may also be supported by the frame 21 of the electrode assembly 2 included in the cell stack 101. That is, an intermediate support portion for supporting the intermediate portion in the front-rear direction of the communication pipe 7 may be provided. FIG. 6 is a front view (viewed from the rear) showing the configuration of the through hole 211 (FIG. 2) of the frame 21 for fuel gas supply provided with the intermediate support portion 203. As shown in FIG. 6, a pair of left and right protrusions 217 and 218 protruding downward are provided on the upper surface of the through hole 211 of the frame 21. The protrusions 217 and 218 are formed in a substantially arc shape so as to form a substantially cylindrical space SP3 along the upper surface of the through hole 211.

[0048] The communication pipe 7 is inserted into the space SP3 from the front or rear of the cell stack 101. The diameter of the space SP3 is slightly larger than the outer diameter of the communication pipe 7 so that the communication pipe 7 can be easily inserted. Thereby, the intermediate portion in the front-rear direction of the communication pipe 7 is positioned by the protrusions 217 and 218, and the communication pipe 7 can be stably supported. However, since both the front and rear end portions of the communication pipe 7 are positioned by the tapered portions 521 and 531, the protrusions 217 and 218 are provided so as to perform a gentle positioning that does not impair the positioning by the tapered portions 521 and 531. Therefore, it is not necessary to increase the accuracy of the protrusions 217 and 218 so much.

[0049] The protrusions 217 and 218 constitute an intermediate support portion 203 for supporting the intermediate portion of the communication pipe 7. The intermediate support portion 203 may be provided on all the frames 21 included in the cell stack 101, or may be provided on some of the frames 21. The tip portions of the protrusions 217 and 218 may be connected to each other to provide a single protrusion, and an opening having a substantially circular shape in a front view may be provided in this protrusion to form the intermediate support portion 203. Depending on the material of the communication pipe 7, if the rigidity of the communication pipe 7 is high and the communication pipe 7 can be firmly supported by the front support portion 201 and the rear support portion 202, the intermediate support portion 203 may be omitted. The front support portion 201 and the rear support portion 202 may be configured to regulate only the position of the communication pipe 7 in the front-rear direction, and the intermediate support portion 203 may regulate the position of the communication pipe 7 in the vertical and horizontal directions.

[0050]

[0050] As shown in FIGS. 3 and 5A, the peripheral surface of the through hole 51a of the insulating plate 51, particularly the innermost peripheral surface at the uppermost part, is configured as a flat surface 51b that is flat in the front-rear direction. The innermost peripheral surface at the uppermost part of the straight portion 532 is located on an extension surface obtained by extending the flat surface 51b forward, and the peripheral surface of the through hole 51a is connected to the inner peripheral surface of the straight portion 532 without a step.

[0051] As shown in FIG. 3, the upper end portion 81 of the substantially L-shaped pipe 8 is attached to the through hole 61a of the rear end plate 61. The pipe 8 extends downward via a bent portion 8a, and the lower end portion 82 of the pipe 8 opens downward. For example, an ejector is connected to the lower end portion 82 of the pipe 8. The pipe 8 forms an external flow path PA15 having an opening surface 82a at the lower end, and fuel gas is supplied into the pipe 8 from below as indicated by the arrow. The supplied fuel gas flows upward and collides with the inner peripheral surface of the upper end portion (bent portion 8a) of the pipe 8, and then changes its flow direction forward and flows into the fuel gas supply flow path PA1 inside the cell stack 101.

[0052] A communication hole 55 for communicating the fuel gas supply flow path PA1 and the fuel gas discharge flow path PA6 is provided in the front insulating plate 50. The opening 55a of the communication hole 55 on the fuel gas supply flow path PA1 side is located on the bottom surface of the through hole 50a. The opening 55a is provided at the same position or substantially the same position in the front-rear direction as the front end surface 525 (FIG. 4A) of the bulging portion 52, or in front of the front end surface 525. The communication hole 55 forms a drainage passage PA10 for guiding liquid water to the fuel gas discharge flow path.

[0053]

[0051] The main operation of the fuel cell stack 100 configured as described above will be described. FIG. 7 is a diagram schematically showing the flow of fuel gas and liquid water in the fuel gas supply flow path PA1. Although illustration is omitted, since the fuel gas supply flow path PA1 and the oxidant gas supply flow path PA4 have substantially the same configuration, the flow of oxidant gas and liquid water in the oxidant gas supply flow path PA4 is also the same as that in FIG. 7. As shown by the arrow A1 in FIG. 7, the fuel gas that flows into the pipe 8 through the opening surface 82a and flows upward from below in the external flow path PA15 changes its flow direction to the right and flows into the fuel gas supply flow path PA1.

[0054] In the fuel gas supply passage PA1, the fuel gas flows forward while dispersing as shown by arrow A2, and flows into the anode passage facing the power generation surface of the fuel cell 1 through the communication port 3b as shown by arrow A3. Thereby, power generation is performed in the fuel cell 1. Due to such a flow of the fuel gas, the pressure in the passage PA1 gradually decreases forward. For this reason, in the fuel gas supply passage PA1, the pressure P2 in the internal space SP2 near the rear end opening 72a of the communication pipe 7 is the maximum, the pressure P1 in the internal space SP1 near the front end opening 71a of the communication pipe 7 is the minimum, and the pressure difference (P2 - P1) between the internal spaces SP1 and SP2 is relatively large.

[0055] Since the pipe 8 has a bent portion 8a near the attachment portion to the end unit 102, the fuel gas containing liquid water (mainly generated water) collides with the inner peripheral surface of the pipe 8 near the bent portion 8a, and the liquid water w easily adheres to the inner peripheral surface (upper surface) near the bent portion 8a. The surface of the bent portion 8a faces the atmosphere and the temperature easily drops, so liquid water (condensed water in this case) also easily adheres at this point. The liquid water w adhering to the inner peripheral surface of the bent portion 8a moves forward as shown by arrow B1 along with the flow of the fuel gas, and further moves forward in the communication pipe 7 due to the pressure difference between the internal spaces SP1 and SP2 as shown by arrow B2. At this time, the liquid water w flows toward the communication pipe 7 along the flat surface 51b on the upper surface of the through hole 51a. Therefore, the liquid water w can be easily guided into the interior of the communication pipe 7.

[0056] The liquid water w that has flowed through the communication pipe 7 flows out from the front end opening 71a of the communication pipe 7, and then flows into the drainage passage PA10 through the opening 55a below the front end opening 71a as shown by arrow B3. Further, the liquid water w flows into the fuel gas discharge passage PA6 through the drainage passage PA10 and is discharged from the fuel cell stack 100 along with the flow of the fuel exhaust gas. Thereby, it is possible to suppress the liquid water w in the gas supply passages PA1 and PA4 from being guided to the power generation surface, and stable power generation performance can be obtained.

[0057] In the above description, the drain passage PA10 is provided in the front end unit 102. However, as long as it is an area different from the power generation area where the power generation cell 1 is installed (non-power generation area), a drain passage may be provided other than the end unit 102. For example, a drain passage can also be provided in the front dummy cell 1d. FIG. 8 is a diagram schematically showing the flow of fuel gas and liquid water in the fuel gas supply passage PA1 in that case, and is a diagram showing a modification of FIG. 7. Although illustration is omitted, the oxidant gas supply passage PA4 is also configured in the same manner as the fuel gas supply passage PA1.

[0058] As shown in FIG. 8, a drain passage PA11 that communicates the fuel gas supply passage PA1 and the fuel gas discharge passage PA6 is provided in the front dummy cell 1d. The drain passage PA11 is constituted by a gas passage (corresponding to the anode passage of the power generation cell 1) provided between the dummy assembly 2d of the dummy cell 1d and the separator 3. Therefore, the drain passage PA11 can be configured without performing new processing on the dummy cell 1d.

[0059] An opening 71b is provided at the bottom surface of the communication pipe 7 at the same position in the front-rear direction as the front dummy cell 1d. At this time, the front end opening 71a of the communication pipe 7 is closed. As a result, the liquid water w flows through the inside of the communication pipe 7 according to the pressure difference between the internal space SP1 and the space in the passage PA1 near the opening 71b (the space near the internal space SP1), and the liquid water w flows out from the opening 71b. This liquid water w further flows through the drain passage PA11 as shown by the arrow B4, is guided to the fuel gas discharge passage PA6, and is discharged from the fuel cell stack 100. The opening 71b of the communication pipe 7 may be provided in front of the dummy cell 1d. Instead of providing the opening 71b at the bottom surface of the communication pipe 7, the front end opening 71a may be opened, the liquid water w may be made to flow out from the front end opening 71a, and the discharged liquid water w may be guided to the drain passage PA11 of the dummy cell 1d.

[0060] According to the present embodiment, the following operational effects can be achieved. (1) The fuel cell stack 100 has a plurality of power generation cells 1 stacked in the front-rear direction, and gas supply channels PA1, PA4 through which reaction gas is supplied and gas discharge channels PA3, PA6 through which reaction gas is discharged extend along the front-rear direction respectively. A cell stack 101 is provided with gas channels (anode channel, cathode channel) that communicate the gas supply channels PA1, PA4 and the gas discharge channels PA3, PA6. A rear end unit 102 is disposed on the rear end side of the cell stack 101 and is provided with through holes 102a, 102d (supply ports) that communicate with the gas supply channels PA1, PA4 and through holes 102c, 102f (discharge ports) that communicate with the gas discharge channels PA3, PA6. A front end unit 102 is disposed on the front end side of the cell stack 101. A communication pipe 7 is disposed in the gas supply channels PA1, PA4 and extends in the front-rear direction, and a rear end opening 72a and a front end opening 71a that communicate with the upstream internal space SP2 and the downstream internal space SP1 of the gas supply channels PA1, PA4 are provided at the front end portion and the rear end portion respectively (FIGS. 1 to 3). Drainage channels PA10, PA11 are provided in the non-power generation region in front of the power generation region of the cell stack 101 where the plurality of power generation cells 1 are disposed to guide the liquid water flowing out from the front end opening 71a to the gas discharge channels PA3, PA6 (FIGS. 3 and 8).

[0061] With this configuration, the liquid water flowing into the gas supply channels PA1, PA4 is guided through the communication pipe 7 beyond the power generation cell 1 to the downstream side of the channels PA1, PA4, so that it is possible to suppress the liquid water from flowing from the channels PA1, PA4 to the power generation surface. That is, the liquid water flowing into the gas supply channels PA1, PA4 flows into the gas discharge channels PA3, PA6 without passing through the anode channel and the cathode channel. As a result, stable power generation performance can be obtained and a decrease in power generation performance can be suppressed. In addition, since there is no need to arrange a stirring mixer or the like on the upstream side of the channels PA1, PA4, an increase in cost can be suppressed, the pressure loss of the channels can be suppressed, and a smooth flow of the reaction gas can be realized. That is, while ensuring a smooth flow of the reaction gas, the liquid water can be discharged well without passing through the power generation cell 1.

[0062] (2) The drain passage PA10 is provided in the front end unit 102 (Figs. 3 and 7). As a result, the longitudinal distance from the power generation cell 1 to the drain passage PA10 can be increased, and it is possible to preferably suppress the mixing of liquid water into the power generation cell 1. Also, the pressure difference between the front and rear of the communication pipe 7 becomes large, and liquid water easily flows inside the communication pipe 7.

[0063] (3) The cell stack 101 has dummy cells 1d, which are non-power generation bodies, between the plurality of power generation cells 1 and the front end unit 102 (Fig. 3). The drain passage PA11 is provided in the dummy cell 1d (Fig. 8). As a result, since it is not necessary to form the drain passage P10 in the end unit 102, the fuel cell stack 100 can be configured at low cost.

[0064] (4) The communication pipe 7 is provided so as to form a narrow region in a part of the gas supply channels PA1 and PA4 (Figs. 3 and 6). As a result, a part of the gas supply channels PA1 and PA4 is used as a flow path for liquid water. For this reason, the configuration of the fuel cell stack 100 is easier than the case where a passage for the flow of liquid water is provided in a space different from the gas supply channels PA1 and PA4.

[0065] (5) In a predetermined circumferential region (first region) of the inner wall surface of the flow path along the longitudinal direction of the cell stack 101 that forms the gas supply channels PA1 and PA4, that is, in the region from the right surface to the lower surface in the fuel gas supply channel PA1 and in the region from the left surface to the lower surface in the oxidant gas supply channel PA4, communication ports 3b communicating with the anode flow path and the cathode flow path are provided, respectively (Fig. 3). The communication pipe 7 is arranged in a region different from the region where the communication port 3b is provided (second region), that is, on the upper surface of the inner wall surface of the flow path (Fig. 6). As a result, it is possible to prevent the gas flow passing through the communication port 3b from being obstructed by the provision of the communication pipe 7.

[0066] (6) An external flow path PA15 that communicates with the gas supply flow paths PA1 and PA4 is formed from the lower end portion 82 to the upper end portion 81, and a pipe 8 connected to the end unit 102 is further provided so that the upper end portion 81 communicates with the through holes 102a and 102d of the rear end unit 102 (FIG. 3). The pipe 8 is configured such that an opening surface 82a is provided facing downward at the lower end portion 82 (FIG. 3). When the reaction gas is supplied through such a pipe 8, the reaction gas collides with the inner peripheral surface of the bent portion 8a of the pipe 8, and liquid water is likely to adhere to the vicinity of the bent portion 8a. In the present embodiment, since the communication pipe 7 is arranged so as to be continuous with the bent portion 8a, the liquid water can be easily guided to the communication pipe 7, and the drainage performance of discharging the liquid water from the flow paths PA1 and PA4 is improved.

[0067] (7) The peripheral surfaces of the through holes 102a and 102d of the rear end unit 102 have flat surfaces 51b that extend flat in the front-rear direction up to the rear end opening 72a of the communication pipe 7 (FIG. 3). Thereby, the liquid water is smoothly guided to the communication pipe 7 along the flat surface 51b, and the drainage performance is improved.

[0068] (8) The rear end unit 102 has a rear support portion 202 that supports the rear end portion 72 of the communication pipe 7, and the front end unit 102 has a front support portion 201 that supports the front end portion 71 of the communication pipe 7 (FIG. 3). Thereby, the positions of both the front and rear end portions of the communication pipe 7 can be regulated to support the communication pipe 7 well.

[0069] The above-described embodiment can be modified into various forms. Hereinafter, some modification examples will be described. In the above-described embodiment, the communication pipe as the pipe body is arranged on the upper surfaces of the gas supply channels PA1 and PA4, but it may be arranged on other surfaces than the upper surface. For example, it may be arranged on the lower surface (bottom surface) of the gas supply channels PA1 and PA4, or on the right surface or the left surface. FIG. 9 is an example thereof, and is a diagram schematically showing an example installed on the bottom surface. In FIG. 9, the peripheral surfaces of the through holes 102a and 102d of the end unit 102 communicating with the gas supply channels PA1 and PA4 further have inclined surfaces 102g that incline downward in a forward direction. Thereby, the liquid water w near the through holes 102a and 102d can flow along the inclined surface 102g and easily flow into the inside of the communication pipe 7 through the rear end opening 72a of the communication pipe 7. As a result, the flow of the liquid water w through the communication pipe 7 can be promoted.

[0070] In the above-described embodiment, the drainage channels PA10 and PA11 are provided in the front end unit 102 or the front dummy cell 1d, but if they are provided in the non-power generation region on the downstream side of the power generation region of the cell stack in which a plurality of power generation cells are arranged, any configuration of the drainage channels may be used. When providing a drainage channel other than the dummy cell 1d, the dummy cell 1d may be omitted. In the above-described embodiment, a plurality of power generation cells 1 are stacked in the front-rear direction (predetermined direction), and an end unit 102 (first end unit) is arranged behind the power generation cell 1 which is one of the predetermined directions, and an end unit 102 (second end unit) is arranged in front of the power generation cell 1 which is the other of the predetermined directions, but the stacking direction may be other than the front-rear direction. In this case, the stacking direction is preferably a substantially horizontal direction.

[0071] In the above-described embodiment, the communication pipe 7 as the tubular body is arranged along the upper surfaces (second regions) of the gas supply channels PA1 and PA4. However, as long as it is a region different from the circumferential region (first region) where the communication ports 3b of the gas supply channels PA1 and PA4 are provided, the communication pipe 7 may be arranged in other regions. In the above-described embodiment, the communication pipe 7 is provided with a rear end opening 72a as the first opening on the upstream side and a front end opening 71a as the second opening on the downstream side of the gas supply channels PA1 and PA4. However, the first opening and the second opening may be provided at positions other than the rear end and the front end of the communication pipe. In the above-described embodiment, the front and rear end portions of the communication pipe 7 are supported by the rear support portion 202 as the first support portion and the front support portion 201 as the second support portion. However, the configurations of the first support portion and the second support portion are not limited to those described above.

[0072] In the above-described embodiment, the gas supply channels PA1 and PA4 are configured to have a constant opening area in the front-rear direction. However, the opening area may be changed in the front-rear direction. For example, the opening areas of the gas supply channels PA1 and PA4 may be configured so as to obtain a Venturi effect. Thereby, the difference between the pressure P1 in the internal space SP1 facing the front end opening 71a of the communication pipe 7 and the pressure P2 in the internal space SP2 facing the rear end opening 72a can be increased, and the flow of liquid water inside the communication pipe 7 can be promoted.

[0073] The above description is merely an example, and the present invention is not limited to the above-described embodiments and modified examples 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-described embodiments and modified examples, and it is also possible to combine the modified examples with each other.

Explanation of Reference Numerals

[0074] 1 Power generation cell, 1d dummy cell, 3 separator, 3b communication port, 7 communication pipe, 8 pipe, 51b flat surface, 71a front end opening, 72a rear end opening, 82a opening, 100 fuel cell stack, 101 cell laminate, 102 end unit, 201 front support portion, 202 rear support portion, PA1, PA4 gas supply channels, PA3, PA6 gas discharge channels, PA10, PA11 drainage passages, PA15 external flow path

Claims

1. A fuel cell stack having a plurality of power generation cells stacked in a predetermined direction, a gas supply passage through which a reaction gas is supplied and a gas discharge passage through which the reaction gas is discharged extending along the predetermined direction, respectively, and a gas passage communicating the gas supply passage and the gas discharge passage; A first end unit disposed on one side of the cell stack in the predetermined direction, having a supply port communicating with the gas supply passage and a discharge port communicating with the gas discharge passage; A second end unit disposed on the other side of the cell stack in the predetermined direction; A pipe body disposed in the gas supply passage, extending in the predetermined direction, and having a first opening communicating with the upstream side and a second opening communicating with the downstream side of the gas supply passage provided at one end side in one direction of the predetermined direction and the other end side in the other direction of the predetermined direction, respectively; and A drain passage for guiding the liquid water flowing out from the second opening to the gas discharge passage is provided in a non-power generation region on the other side of the predetermined direction than the power generation region of the cell stack in which the plurality of power generation cells are disposed.

2. In the fuel cell stack according to Claim 1, The drain passage is provided in the second end unit.

3. In the fuel cell stack according to Claim 1, The cell stack has a dummy cell, which is a non-power generation body, between the plurality of power generation cells and the second end unit, The drain passage is provided in the dummy cell.

4. In the fuel cell stack according to any one of Claims 1 to 3, The pipe body is provided so as to form a narrowed region in a part of the gas supply passage.

5. In the fuel cell stack according to any one of Claims 1 to 3, A communication port communicating with the gas passage is provided in a first region in the circumferential direction of the inner wall surface of the flow passage along the predetermined direction of the cell stack forming the gas supply passage, The pipe body is disposed in a second region in the circumferential direction of the inner wall surface of the flow passage different from the first region.

6. In the fuel cell stack according to any one of Claims 1 to 3, A pipe is further provided which forms an external flow path communicating with the gas supply flow path from one end portion to the other end portion, and is connected to the first end unit such that the other end portion communicates with the supply port of the first end unit. The fuel cell stack is characterized in that the pipe is configured such that an opening is provided at one end portion facing in a direction orthogonal to the predetermined direction. **Claim 7** In the fuel cell stack according to any one of claims 1 to 3, the fuel cell stack is characterized in that the peripheral surface of the supply port has a flat surface that extends flat in the predetermined direction toward the first opening of the tubular body. **Claim 8** In the fuel cell stack according to any one of claims 1 to 3, the first end unit has a first support portion that supports one end portion of the tubular body in the predetermined direction, the fuel cell stack is characterized in that the second end unit has a second support portion that supports the other end portion of the tubular body in the predetermined direction.

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