Fuel cell stack

Abstract

This fuel cell stack comprises: a cell stack body having a plurality of power generation cells and a dummy cell disposed adjacent to the power generation cell at an end; and an end unit that is disposed adjacent to the dummy cell and is provided with a gas supply port and a gas discharge port which are in communication with a gas supply flow path and a gas discharge flow path of the cell stack body, respectively. The gas supply flow path is configured by a through-hole penetrating through each of the power generation cells and the dummy cell in a predetermined direction. A gas flow path includes: a central flow path provided in a central region of each of the power generation cells and the dummy cell; and an end flow path providing communication between the central flow path and the through-hole. The area of a first flow regulation portion for regulating a flow rate in the end flow path of the dummy cell is larger than the area of a second flow regulation portion for regulating a flow rate in the end flow path of the power generation cells.

Description

fuel cell stack

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

[0002] In recent years, technological developments have been made in 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 example of this type of fuel cell technology is a fuel cell stack in which a dummy cell is arranged on the dry side of the fuel cell stack, and liquid water contained in reactant gases supplied through a gas supply passage is separated from the reactant gases downstream of the dummy cell (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2022-165808

[0004] However, in the fuel cell stack described in Patent Document 1, liquid water contained in the reactant gas flows into the power generation cells before reaching the dummy cells on the dry side, which may cause unstable power generation performance.

[0005] a cell stack including a plurality of power-generating cells stacked in a predetermined direction as power generating bodies and a dummy cell as a non-power-generating body arranged adjacent to an end power-generating cell located at one end of the plurality of power-generating cells in the predetermined direction, the cell stack including a gas supply passage for supplying a reactant gas and a gas exhaust passage for exhausting the reactant gas, each extending along the predetermined direction, and a gas passage communicating between the gas supply passage and the gas exhaust passage; and an end unit arranged adjacent to the dummy cell and provided with a gas supply port communicating with the gas supply passage and a gas exhaust port communicating with the gas exhaust passage. The gas supply passage is formed by through-holes passing through the power-generating cells and the dummy cell in the predetermined direction, and the gas passage includes a central passage provided in a central region of each of the power-generating cells and the dummy cell, and an end passage communicating between the central passage and the through-hole, and a first flow restriction portion restricting a flow rate in the end passage of the dummy cell is larger in area than a second flow restriction portion restricting a flow rate in the end passage of the power-generating cell.

[0006] According to the present invention, it is possible to prevent liquid water contained in the reactant gas supplied through the gas supply port from flowing into the power generation cell, thereby achieving stable power generation performance.

[0007] 1 is a perspective view schematically showing the overall configuration of a fuel cell stack according to an embodiment of the present invention. A cross-sectional view taken along line II-II in FIG. 1. A perspective view showing the schematic configuration of an integrated electrode assembly included in the fuel cell stack of FIG. 1. A front view of the separator of FIG. 1. An enlarged view of a main portion of FIG. 4. A view showing a modified example of FIG. 5A. A cross-sectional view taken along line VI-VI in FIG. 5A. A cross-sectional view taken along line VII-VII in FIG. 1. A view taken along arrow VIII in FIG. 7. An enlarged view showing the configuration around a through-hole in a dummy separator constituting a fuel cell stack according to an embodiment of the present invention.

[0008] Hereinafter, an embodiment of the present invention will be described with reference to Figures 1 to 9. A fuel cell stack according to an embodiment of the present invention is one of the main components of a fuel cell. The fuel cell is mounted, for example, in a vehicle and can generate electric power to drive 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-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, the cell stack 101 is surrounded by a generally 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, only a single power-generating cell 1 is shown in Fig. 1.

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

[0012] FIG. 2 is a cross-sectional view (a cross-sectional view taken along line II-II in FIG. 1 ) of a main portion of the power generation region at the center in the left-right direction of the cell stack 101. As shown in FIG. 2 , the separator 3 includes a front plate 3F and a rear plate 3R, which are a pair of front and rear metal thin plates with a corrugated cross section. The front plate 3F extends vertically and horizontally and has a front surface 3Fa and a rear surface 3Fb. The rear plate 3R extends vertically and horizontally and has a front surface 3Ra and a rear surface 3Rb. The opposing rear surface 3Fb of the front plate 3F and the front surface 3Ra of the rear plate 3R are joined at their outer peripheries by welding or the like. This integrally bonds the front plate 3F and the rear plate 3R. The separator 3 is made of a conductive material with excellent corrosion resistance, such as stainless steel, titanium, or a titanium alloy.

[0013] A cooling flow path PAw through which a coolant flows is formed inside the separator 3 surrounded by the front plate 3F and the rear plate 3R, i.e., between the rear surface 3Fb of the front plate 3F and the front surface 3Ra of the rear plate 3R. The flow of the coolant cools the power generation surface of the power generation cell 1. Water, for example, can be used as the coolant. The surface of the separator 3 facing the UEA 2 (the front surface 3Fa and the rear surface 3Rb) is formed unevenly by press molding or the like to form a gas flow path between the separator 3 and the UEA 2. More specifically, the separator 3 has a pair of front and rear protrusions 31 protruding toward the UEA 2 and a pair of front and rear recesses 32 formed concavely and connected to the pair of front and rear protrusions 31.

[0014] The pair of front and rear protrusions 31 abut against the front surface 2a and rear surface 2b of the UEA 2. A compressive load F is applied to the cell stack 101 in the front-to-rear direction during assembly of the fuel cell stack 100, and this compressive load F is maintained after assembly of the fuel cell stack 100 is complete. Therefore, a predetermined surface pressure due to the compressive load F acts on the UEA 2 in the front-to-rear direction via the protrusions 31.

[0015] Between the front surface 2a of the UEA 2 and the rear plate 3R of the separator 3 facing this front surface 2a, an anode flow path PAa through which fuel gas flows is formed by a recess 32. Between the rear surface 2b of the UEA 2 and the front plate 3F of the separator 3 facing this rear surface 2b, a cathode flow path PAc through which oxidizer gas flows is formed by a recess 32. The fuel gas is a gas containing hydrogen, and hydrogen gas can be used, for example. The oxidizer gas is a gas containing oxygen, and air can be used, for example. The fuel gas and the oxidizer gas are sometimes referred to as reactant gases without distinction between them.

[0016] Fig. 3 is a perspective view showing a schematic configuration of the UEA 2. As shown in Fig. 3, the UEA 2 has a substantially rectangular membrane electrode assembly (hereinafter referred to as MEA) 20 and a frame (also referred to as frame) 21 that supports the MEA 20. The MEA 20 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.

[0017] The electrolyte membrane is, for example, a solid polymer electrolyte membrane, and a thin film of a perfluorosulfonic acid polymer containing water can be used. The electrolyte membrane is not limited to a fluorine-based electrolyte membrane, and a hydrocarbon-based electrolyte membrane can also be used.

[0018] 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 electrode reactions, and a gas diffusion layer that is provided on the front surface of the electrode catalyst layer and diffuses and supplies a 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 electrode reactions, and a gas diffusion layer that is provided on the rear surface of the electrode catalyst layer and diffuses and supplies an oxidant gas.

[0019] At the anode electrode, fuel gas (hydrogen) supplied through the anode flow path PAa (FIG. 2) 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 through the cathode flow path PAc (FIG. 2) reacts with hydrogen ions introduced from the anode electrode and electrons transferred from the anode electrode to generate water. The generated water (referred to as "generated water") provides an appropriate humidity to the electrolyte membrane, and excess water is discharged to the outside of the UEA2 along the gas flow. The generated water on the cathode side also flows to the anode side by back diffusion through the electrolyte membrane 23. Therefore, generated water exists in both the anode flow path PAa and the cathode flow path PAc.

[0020] 3, the frame 21 has a generally rectangular shape and is made of insulating resin, rubber, or the like. A generally rectangular opening 21a is provided in the center of the frame 21. The MEA 20 is provided so as to cover the entire opening 21a, and the peripheral edge of the MEA 20 is supported by the frame 21. Because the frame 21 is thin, it can also be called a film.

[0021] Three through holes 211 to 213 are aligned vertically and penetrate the frame 21 in the front-to-rear direction on the left side of the opening 21a of the frame 21. Three through holes 214 to 216 are aligned vertically and penetrate the frame 21 in the front-to-rear direction on the right side of the opening 21a. For convenience, the through holes 211 to 216 are shown as being substantially rectangular, but the shape and arrangement of the through holes 211 to 216 are not limited to this.

[0022] As shown in FIG. 1 , the front and rear separators 3 of the UEA 2 are provided with through-holes 301-306 that penetrate the separators 3 in the front-rear direction at positions corresponding to the through-holes 211-216 of the frame 21. The through-holes 301-306 are connected to the through-holes 211-216 of the frame 21, respectively. The interconnected through-holes 211-216 and 301-306 collectively form flow paths PA1-PA6 (indicated by arrows for convenience) that penetrate the cell stack 101 and extend in the front-rear direction. The flow paths PA1-PA6 are sometimes called manifolds. The flow paths PA1-PA6 are connected to a manifold external to the fuel cell stack 100.

[0023] Although not shown in the figure, the front and rear end units 102 of the cell stack 101 each have a plurality of plates stacked in the front-to-rear direction. That is, the end unit 102 has a terminal plate arranged adjacent to the cell stack 101, an insulating plate arranged on the outer side of the terminal plate in the front-to-rear direction, and an end plate arranged on the outer side of the insulating plate in the front-to-rear direction.

[0024] The rear end unit 102 is a wet-side end unit through which the reactant gas and the cooling medium pass, and the front end unit 102 is a dry-side end unit through which the reactant gas and the cooling medium do not pass. The rear end unit 102 has a plurality of through-holes 102a-102f that penetrate the end unit 102 in the front-rear direction at positions corresponding to the through-holes 211-216, 301-306 of the cell stack 101. For convenience, the through-holes 102a-102f are shown as being substantially rectangular, but the shape of the through-holes 102a-102f is not limited to this.

[0025] The through-hole 102a is a fuel gas supply port, and the fuel gas is supplied to the fuel cell stack 100 through the through-hole 102a. This fuel gas is guided to the anode flow path PAa between the UEA 2 and the rear plate 3R of the separator 3 through the through-holes 211 and 301. After passing through the anode flow path PAa, the fuel gas is discharged from the through-hole 102f via the through-holes 216 and 306.

[0026] The through-hole 102d is an oxidant gas supply port, and the oxidant gas is supplied to the fuel cell stack 100 through the through-hole 102d. This oxidant gas is guided to the cathode flow path PAc between the UEA 2 and the front plate 3F of the separator 3 through the through-holes 214 and 304. After passing through the cathode flow path PAc, the oxidant gas is discharged from the through-hole 102c through the through-holes 213 and 303.

[0027] The through-hole 102e is a supply port for the cooling medium, and the cooling medium is supplied to the fuel cell stack 100 through the through-hole 102e. This cooling medium is guided to the cooling flow path PAw between the front plate 3F and the rear plate 3R of the separator 3 through the through-holes 215 and 305. After passing through the cooling flow path PAw, the cooling medium is discharged from the through-hole 102b via the through-holes 212 and 302. The above is a schematic configuration of the fuel cell stack 100.

[0028] The structure of the separator 3 will be described in more detail. FIG. 4 is a front view (viewed from the front) of the separator 3. That is, FIG. 4 is a view showing the front surface 3Fa (FIG. 2) of the separator 3 facing the cathode electrode on the rear surface 2b of the UEA 2, with the left-right direction determined relative to FIG. 1. Point P in the figure is the midpoint of the separator 3 in the left-right direction and the midpoint in the up-down direction, and is referred to as the center point. Hereinafter, the side toward the center point P will be referred to as the inside, and the side away from the center point P will be referred to as the outside. The left-right direction and the up-down direction in FIG. 4 correspond to the longitudinal and lateral directions of the separator 3, respectively.

[0029] In Fig. 4, the region AR1 of the UEA 2 facing the MEA 20, i.e., the region facing the power generation surface, is called the active region of the separator 3, and the region AR2 on the left and right outer side of the active region AR1 is called the inactive region. As shown in Figs. 2 and 4, the active region AR1 of the separator 3 has a plurality of protrusions 31 (Fig. 2) protruding forward at equal intervals in the vertical direction over almost the entire area, although some of these are not shown. Each of the plurality of protrusions 31 extends in the horizontal direction, and a recess 32 (Fig. 2) is provided between adjacent protrusions 31 in the vertical direction. A cathode flow path PAc is formed between the plurality of recesses 32 and the rear surface 2c of the MEA 20.

[0030] 4 , a plurality of bead portions for sealing, i.e., metal bead seals, are provided on the front surface 3Fa in the inactive area AR2 of the separator 3 (front plate 3F), protruding forward toward the frame 21. The plurality of bead portions include an outer bead portion 331 and a plurality of individual bead portions 332.

[0031] The individual bead portions 332 each have a substantially rectangular shape and individually surround the through holes 301 to 306. The outer bead portions 331 extend in the left-right direction above and below the active region AR1 along the upper and lower edges of the separator 3, and also extend in a zigzag pattern, passing on the outside in the left-right direction of the individual bead portions 332 around the through holes 301, 303, 304, and 306, and on the inside in the left-right direction of the individual bead portions 332 around the through holes 302 and 305.

[0032] In the inactive region AR2 on the left-right outer side of the active region AR1 of the separator 3 (front plate 3F), a guide portion 333 is provided to protrude forward from the through hole 304 over the entire area of ​​the inlet at the right end of the cathode flow channel PAc and from the entire area of ​​the outlet at the left end of the cathode flow channel PAc to the through hole 303. A plurality of tunnel portions 40 that cross the individual bead portions 332 are provided between the through hole 304 and the guide portion 333 and between the through hole 303 and the guide portion 333.

[0033] The oxidant gas supplied through the through-hole 304 passes through the tunnel 40 and flows to the inlet at the right end of the right-side guide 333. The oxidant gas then flows leftward along the guide 333 and is guided to the cathode flow path PAc. The oxidant gas that has flowed through the cathode flow path PAc flows to the inlet at the right end of the left-side guide 333. The oxidant gas then flows leftward along the guide 333, passes through the tunnel 40, and flows into the through-hole 303.

[0034] The provision of the guide portion 333 allows the oxidant gas to flow evenly throughout the entire cathode flow channel PAc. A generally cylindrical embossed portion protruding forward may be provided instead of or in addition to the guide portion 333. The protrusions 31, recesses 32, metal bead seals (outer bead portion 331, individual bead portion 332), guide portion 333, and tunnel portion 40 are formed by press working the front plate 3F.

[0035] Although not shown, a plurality of protrusions 31 and recesses 32, metal bead seals (outer bead portions 331 and individual bead portions 332), guide portions 333, tunnel portions 40, and the like are similarly formed on the rear surface 3Rb of the separator 3 (rear plate 3R) by press working the rear plate 3R. As a result, fuel gas is supplied from the through hole 301 to the anode flow channel PAa via the tunnel portion 40 and guide portion 333. The fuel gas that has flowed through the anode flow channel PAa is discharged from the through hole 306 via the guide portion 333 and tunnel portion 40.

[0036] 5A is an enlarged view showing the configuration around the through hole 304 of the separator 3 in FIG. 4. As shown in FIG. 5A, one ends of multiple tunnel portions 40 are connected to the periphery of the through hole 304, particularly the left and lower peripheries. These tunnel portions 40 extend leftward and downward, i.e., toward the inside (center point P in FIG. 4). More specifically, each of the multiple tunnel portions 40 extends perpendicular to the periphery of the through hole 304, crossing the individual bead portions 332. The other ends of the multiple tunnel portions 40 are connected to elongated protrusions 41. The elongated protrusions 41 extend along the individual bead portions 332, forming a single communication space SP1 therein.

[0037] The cathode flow channel PAc and the anode flow channel PAa are both provided in the active region AR1 at the center in the left-right direction of the separator 3. For this reason, these flow channels PAc and PAa are sometimes referred to as central flow channels. On the other hand, flow channels (such as the tunnel section 40) connecting the through-holes 303 and 304 to the cathode flow channel PAc and flow channels (such as the tunnel section 40) connecting the through-holes 301 and 306 to the anode flow channel PAa are provided in the inactive region AR2 on the left-right end side of the separator 3. For this reason, these are sometimes referred to as edge flow channels. The central flow channel and the edge flow channels collectively constitute a gas flow channel (separator surface flow channel) through which the reactant gas flows along the surface of the separator 3.

[0038] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5A , showing the configuration of the tunnel portion 40. As shown in FIG. 6 , the front plate 3F is provided with a tunnel portion 40 that protrudes forward, and the rear plate 3R is provided with a tunnel portion 40 that protrudes rearward. The tunnel portion 40 protrudes less in the front-to-rear direction than the individual bead portion 332. Although not shown, the tunnel portion 40 has a generally rectangular or trapezoidal cross section, and a communication flow path PA11 is formed between the front and rear tunnel portions 40, 40. Sealants 334 are fixed to the front and rear end surfaces of the individual bead portion 332. The individual bead portion 332 abuts against the individual bead portion 332 of the separator 3 adjacent in the front-to-rear direction via the sealants 334 and the frame 21. The sealants 334 may be omitted.

[0039] The outer end face (the right end in FIG. 6 ) of the tunnel portion 40 is located on the periphery of the through-hole 304, and the communication flow path PA11 communicates with the through-hole 304. The inner end face (the left end in FIG. 6 ) of the tunnel portion 40 is connected to the elongated protrusion 41. The elongated protrusion 41 is formed by protruding the front plate 3F and the rear plate 3R forward and rearward, respectively, and a communication space SP1 that communicates with the communication flow path PA11 is formed between the front and rear elongated protrusions 41. The protrusion amount of the elongated protrusion 41 in the front-to-rear direction is greater than the protrusion amount of the tunnel portion 40 but less than the protrusion amount of the individual bead portion 332. The protrusion amount of the elongated protrusion 41 may be equal to the protrusion amount of the tunnel portion 40.

[0040] The inner end (left end in FIG. 6 ) of the elongated protrusion 41 is provided with a tapered surface 411 whose protrusion amount gradually decreases toward the left, and the protrusion amount in the front-to-rear direction becomes zero at the left end of the elongated protrusion 41. An oxidizer gas outlet 412 is opened in the tapered surface 411 of the front plate 3F. This allows the through hole 304 to communicate with the cathode flow channel PAc in front of the front plate 3F via the communicating flow channel PA11 and the outlet 412, more specifically, via the communicating flow channel PA11, the communicating space SP1, and the outlet 412. Therefore, the oxidizer gas flowing through the through hole 304 can be supplied to the cathode flow channel PAc via the communicating flow channel PA11, the communicating space SP1, and the outlet 412, as shown by the arrows in FIG. 6 .

[0041] 5A , the elongated convex portion 41 is provided with a plurality of outlets 412 corresponding to the plurality of tunnel portions 40. The outlets 412 corresponding to the tunnel portions 40 refer to a single or a plurality of outlets 412 located near the outlet of each tunnel portion 40 (the connection portion between the tunnel portion 40 and the elongated convex portion 41). For example, a pair of outlets 412a, 412b corresponds to a tunnel portion 40a (referred to as a corner tunnel portion) that is connected to the vicinity of the lower left corner of the through-hole 304 and extends downward. Hereinafter, the flow path of the communication flow path PA11 that leads to the outlets 412a, 412b via the corner tunnel portion 40a will be referred to as a corner communication flow path 414 for convenience.

[0042] 5A , the outlet 412 is not located on an extension of the tunnel portion 40, but is located offset from the tunnel portion 40. Therefore, the oxidant gas that has passed through the communication flow path PA11 changes its flow direction in the communication space SP1 before flowing out from the outlet 412. This allows the oxidant gas to be supplied evenly from the multiple outlets 412.

[0043] Fig. 5B is a diagram showing a modified example of Fig. 5A. In the example of Fig. 5B, the elongated protrusion 41 is omitted. That is, an outlet 412 is provided at each end of a plurality of tunnels 40, one end of which is connected to the edge of the through-hole 304. In the example of Fig. 5B, a single outlet 412 corresponds to each tunnel 40.

[0044] Although not shown, a tunnel portion 40 is also provided around the through-hole 301 of the separator 3, similar to Fig. 5A or 5B. However, unlike Figs. 5A and 5B, the outlet 412 is provided on the tapered surface 411 of the rear plate 3R. This allows the fuel gas flowing through the through-hole 301 to flow out of the outlet 412 via the communication flow path PA11 and the communication space SP1, similar to Fig. 5A, or via the communication flow path PA11, similar to Fig. 5B, and be guided to the anode flow path PAa.

[0045] FIG. 7 is a cross-sectional view (a cross-sectional view taken along line VII-VII in FIG. 1 ) of a main portion of the rear end portion of the fuel cell stack 100 including the oxidant gas supply flow path PA4 shown in FIG. 1 . For convenience, the elongated protrusions 41 are omitted from FIG. 7 . As shown in FIG. 7 , the cell stack 101 has a plurality of power-generating cells 1 that are power generating elements and dummy cells 10 that are non-power generating elements. The dummy cells 10 are interposed between the rearmost power-generating cell 1 (referred to as end power-generating cell 1a for convenience) and the rear end unit 102. A dummy cell 10 can also be interposed between the frontmost power-generating cell 1 and the front end unit 102.

[0046] The dummy cell 10 has a dummy assembly 25 corresponding to the UEA2, and dummy separators 35 arranged on both the front and rear sides of the dummy assembly 25. The configuration of the dummy separator 35 is the same as that of the separator 3 of the power-generating cell 1, except for the configuration of the outlet 412, as will be described later. Therefore, the dummy separator 35 has through-holes 301 to 306 that are the same as those of the separator 3, and is also formed with uneven flow paths PAa, PAc, a tunnel portion 40, etc.

[0047] The dummy assembly 25 has a dummy frame 210 and a dummy joined body 200. The dummy frame 210 is configured similarly to the frame 21 of the power-generating cell 1, except for the configuration (size) of the through holes 211, 214 for supplying reactant gases. Therefore, the dummy frame 210 has through holes similar to the through holes 211 to 216 and opening 21a of the frame 21. Figure 7 shows the through hole 214a of the dummy frame 210 that corresponds to the through hole 214 of the frame 21. Because the dummy frame 210 is thin, the dummy frame can also be called a dummy film.

[0048] The dummy assembly 200 is an assembly of a conductive plate and an electrode, provided so as to cover the opening 21a (FIG. 3) of the dummy frame 210. The dummy cell 10 differs from the power-generating cell 1 in that it does not have an electrolyte membrane, and therefore does not generate electricity. By arranging the dummy cell 10 adjacent to the end unit 102 in this manner, the dummy cell 10 functions as a heat insulating layer, thereby suppressing a decrease in temperature of the power-generating cell 1. Instead of providing the dummy frame 210 and the dummy assembly 200 separately, the plate of the dummy assembly 200 may be enlarged so that the plate of the dummy assembly 200 functions as the dummy frame 210. Although a single dummy cell 10 is arranged between the power-generating cell 1 and the end unit 102 in FIG. 7, multiple dummy cells 10 may be arranged.

[0049] Similar to the separator 3, the front plate 3F and rear plate 3R of the dummy separator 35 are also provided with individual sealing bead portions 332, and sealing materials 334 made of an elastic component material such as rubber or resin are fixed to the surfaces of the individual bead portions 332. A compressive load F (FIG. 2) is applied to the separator 3 and the dummy separator 35 in the front-to-rear direction, thereby sealing the contact surfaces between the separator 3 and the frame 21, and the contact surfaces between the dummy separator 35 and the dummy frame 210 and the end unit 102.

[0050] Fig. 7 shows an axis CL1 that extends in the front-rear direction and passes through the center of the through-hole 214 of the frame 21 and the through-hole 214a of the dummy frame 210 in the up-down and left-right directions. Fig. 8 is a view taken along arrow VIII in Fig. 7 , showing the shapes of the through-holes 214, 214a, and 304 of the frame 21, the dummy frame 210, and the separator 3. As shown in Figs. 7 and 8 , the through-holes 214, 214a of the frame 21 and the dummy frame 210 are smaller than the through-hole 304 of the separator 3 and the dummy separator 35 over their entire periphery. For this reason, a protrusion 217 that protrudes inward (toward the axis CL1) from the separator 3 and the dummy separator 35 is provided on the periphery of the through-holes 214, 214a of the frame 21 and the dummy frame 210.

[0051] Furthermore, a portion of the periphery of through-hole 214a in dummy frame 210, specifically, lower left corner 214b, is located more inward (toward axis CL1) than corner 214b (dotted line) of the periphery of through-hole 214 in frame 21. For this reason, a protrusion 218 that protrudes more inward than frame 21 is provided on the lower periphery of through-hole 214a in dummy frame 210.

[0052] Liquid water (produced water or condensed water) may flow into the cell stack 101 together with the oxidant gas through the through-holes 102d of the end units 102. In particular, condensed water is likely to occur in the fuel cell stack 100 because the oxidant gas, which has been humidified by passing through a humidifier (not shown), is supplied to the fuel cell stack 100 through the through-holes 102d via external piping. If the liquid water that has flowed into the cell stack 101 then jumps over the through-holes of the dummy cells 10 (through-holes 214a of the dummy frames 210) and reaches the power-generating cells 1, the following problems may occur.

[0053] That is, the liquid water that reaches the power-generating cell 1 is guided along the flow of the oxidant gas via the communication flow path PA11 ( FIG. 6 ) inside the tunnel section 40 to the cathode flow path PAc facing the power-generating surface of the UEA2. As a result, the electrochemical reaction on the power-generating surface is inhibited, which may cause unstable power generation performance and a decline in power generation performance. This problem is not limited to the flow path PA4 for supplying oxidant gas, but is also applicable to the flow path PA1 ( FIG. 1 ) for supplying fuel gas. That is, the liquid water in the flow path PA1 is guided along the flow of the fuel gas via the communication flow path PA11 inside the tunnel section 40 to the anode flow path PAa facing the power-generating surface of the UEA2, which may cause unstable power generation performance and a decline in power generation performance.

[0054] In this regard, in this embodiment, protrusions 217, 218 are provided on the periphery of the through-hole 214a of the dummy frame 210, so that liquid water that flows in through the through-hole 102d collides with the protrusions 217, 218. More specifically, because liquid water tends to flow downward due to gravity, most of the liquid water that passes through the through-hole 102d collides with the lower protrusions 217, 218. Therefore, as shown by hatching in FIG. 8 , the flow of liquid water is blocked by the protrusions 217, 218.

[0055] The blocked liquid water flows downward along the communication flow path PA11 (FIG. 6) of the dummy separator 35 and the rear surface of the dummy assembly 25. It is then discharged to the outside of the cell stack 101 via the flow path PA3 (FIG. 1) for discharging oxidant gas. This prevents the liquid water in the flow path PA1 from passing over the through-hole 214a of the dummy frame 210 and being guided to the cathode flow path PAc of the power generating cell 1, thereby achieving stable power generation performance.

[0056] Liquid water flowing in through the through hole 102d of the end unit 102 concentrates, for example, at the lower left corner 214b of the dummy frame 210. Taking this into consideration, a protrusion 218 is provided at the lower left corner 214b in FIG. 8. The location where the flow of liquid water concentrates is determined by the shape of the external piping, etc. If liquid water concentrates at the lower right corner, the protrusion 218 can be provided at the lower right corner, and if liquid water is dispersed throughout the entire lower area, the protrusion 218 can be provided over the entire lower area. A protrusion may also be provided on the frame 21 in a similar manner. That is, the shape of the through hole 214a of the dummy frame 210 may be the same as the shape of the through hole 214 of the frame 21.

[0057] Incidentally, when liquid water is blocked by dummy frame 210, the flow rate of liquid water increases through communication flow path PA11 in tunnel portion 40 of dummy separator 35. In particular, as described above, liquid water concentrates at lower left corner 214b on the periphery of through hole 214a, and therefore the flow rate of liquid water increases through corner communication flow path 414 on the inside of corner tunnel portion 40a among the multiple tunnel portions 40 in FIG.

[0058] The flow of liquid water passing through the corner communicating flow passages 414 is restricted by the outlets 412a and 412b. Therefore, the liquid water blocked by the dummy frame 210 cannot pass through the outlets 412 smoothly and without stagnation, and there is a risk that the liquid water will overflow the dummy frame 210 and reach the power generating cell 1. Therefore, in this embodiment, the dummy separator 35 is configured as follows so that the liquid water can pass through the inside of the tunnel portion 40 smoothly.

[0059] Figure 9 is an enlarged view showing the configuration around the through-hole 304 of the dummy separator 35 constituting the fuel cell stack 100 according to this embodiment. Compared to the separator 3 in Figure 5A, the configuration of the outlet 412 of the elongated protrusion 41 is different. That is, as shown in Figure 9, the elongated protrusion 41 is provided with an outlet 412c with a large opening area corresponding to the corner tunnel 40a. Hereinafter, for convenience, the flow path leading to the outlet 412c via the corner tunnel 40a will be referred to as the corner communicating flow path 415.

[0060] The outlet 412c is configured as a single outlet including a pair of outlets 412a, 412b (FIG. 5A) provided in the separator 3. Therefore, the outlet 412c and the outlets 412a, 412b are located on the same imaginary line CL2 extending in the front-rear direction, as shown in FIG. 7, for example. In other words, the outlet 412c and the outlets 412a, 412b are located at the same positions in the up-down and left-right directions.

[0061] The outlet 412c can be formed by removing the portion between the outlets 412a and 412b so as to connect the outlets 412a and 412b. Unlike the other outlets 412, the outlet 412c is located on an extension of the tunnel portion 40. On the other hand, the outlet 412d corresponding to the uppermost tunnel portion 40b (referred to as the upper tunnel portion) is located offset from the upper tunnel portion 40b. To distinguish it from the corner communicating flow path 415, the flow path leading to the outlet 412d via the upper tunnel portion 40b is conveniently referred to as the upper communicating flow path 416. The outlet 412c may be extended outward in the left-right direction relative to the outlets 412a and 412b, thereby further increasing the area of ​​the outlet 412c.

[0062] Increasing the area of ​​the outlet 412c corresponding to the corner communication flow path 415 in this way prevents the flow of liquid water from being obstructed by the outlet 412c. This allows liquid water to flow smoothly inside the corner tunnel 40a in the direction of gravity, as shown by the arrow in Figure 9. As a result, even if the flow of liquid water concentrates in one area (the lower left corner), liquid water that has flowed into the cell stack 101 through the through-hole 102d of the end unit 102 can be prevented from passing over the dummy frame 210 and reaching the power-generating cell 1, thereby achieving stable power generation performance.

[0063] In the example shown in Fig. 5B that does not have the elongated convex portion 41, the corner tunnel portion 40a may be enlarged to increase the area (e.g., width in the left-right direction) of the communication flow path PA11, and the area of ​​the outlet 412a corresponding to the corner tunnel portion 40a may also be increased. Similarly, in Fig. 9, not only may the area of ​​the outlet 412c be enlarged, but the area of ​​the communication flow path PA11 may also be increased by enlarging the corner tunnel portion 40a. Although not shown, the configuration around the through hole 301 of the dummy separator 35 for fuel gas supply is also similar to that shown in Fig. 9.

[0064] The present embodiment can achieve the following advantageous effects: (1) The fuel cell stack 100 includes a plurality of power-generating cells 1 that are power-generating bodies stacked in the front-rear direction, and a dummy cell 10 that is a non-power-generating body and is arranged adjacent to an end power-generating cell 1a that is located at the rear end of the plurality of power-generating cells 1, and includes a cell stack 101 in which gas supply flow paths PA1 and PA4 to which reactant gases are supplied and a gas discharge flow path from which the reactant gases are discharged extend along the predetermined direction, and in which separator surface flow paths (gas flow paths) are provided that respectively connect the flow path PA1 to the flow path PA6 and the flow path PA4 to the flow path PA3, and an end unit 102 that is arranged adjacent to the dummy cell 10 and that is provided with gas supply ports (through-holes 102a and 102d) that communicate with the gas supply flow paths PA1 and PA4 and gas discharge ports (through-holes 102f and 102c) that communicate with the gas discharge flow paths PA6 and PA3 ( FIGS. 1 and 7 ). The gas supply channels PA1 and PA4 are formed by through-holes 211, 214, 214a, 301, and 304 that penetrate the power-generating cell 1 and the dummy cell 10 in the front-rear direction, respectively ( FIG. 7 ). The separator surface channels include central channels (cathode channel PAc and anode channel PAa) provided in the left-right central regions of the power-generating cell 1 and the dummy cell 10, respectively, and end channels (e.g., communication channel PA11) that connect the cathode channel PAc to the through-holes 303 and 304 and the anode channel PAa to the through-holes 301 and 306. The area of ​​the outlet 412c that regulates the flow rate in the end channel of the dummy cell 10 is larger than the area of ​​the outlets 412a and 412b that regulate the flow rate in the end channel of the power-generating cell 1 ( FIGS. 5A and 9 ).

[0065] With this configuration, liquid water (produced water and condensed water) that flows into the gas supply flow paths PA1 and PA4 together with the reactant gas can flow through the inside of the dummy cell 10 to the gas discharge flow paths PA3 and PA6 before reaching the power generation cell 1. In other words, because the area of ​​the outlet 412c is large, the flow of liquid water through the dummy cell 10 is promoted, and it becomes possible to discharge a larger amount of liquid water without the flow of liquid water being stagnated in the dummy cell 10. As a result, it is possible to suppress the supply of liquid water to the power generation cell 1, and stable power generation performance can be obtained.

[0066] (2) The outlet 412c and the outlets 412a, 412b are located on the same imaginary line CL2 that extends in the front-rear direction (FIG. 7). This allows the dummy separator 35 to be easily configured by simply changing the outlets 412a, 412b of the separator 3 to the outlet 412c without changing their positions.

[0067] (3) The power-generating cell 1 includes a UEA 2 and a separator 3 disposed opposite the UEA 2, and the dummy cell 10 includes a substantially plate-shaped dummy assembly 25 and a dummy separator 35 disposed opposite the dummy assembly 25 ( FIG. 7 ). The dummy separator 35 is configured to form a plurality of communication channels PA11 included in the end channel between the dummy assembly 25 and the dummy assembly 25 ( FIG. 9 ). The separator 3 is configured to form a plurality of communication channels PA11 included in the end channel between the dummy assembly 25 and the separator 3 ( FIG. 5A ). The outlet 412c is one of the plurality of outlets 412 corresponding to the plurality of communication channels PA11, and corresponds to the corner communication channel 415 on the inside of the corner tunnel portion 10a ( FIG. 9 ). Outlets 412a and 412b are outlets corresponding to corner communication flow path 414 on the inside of corner tunnel portion 10a, among the multiple outlets 412 corresponding to the multiple communication flow paths PA11 ( FIG. 5A ). With this configuration, the only difference between separator 3 and dummy separator 35 is the shape of outlets 412a and 412b corresponding to corner communication flow path 414 and outlet 412c corresponding to corner communication flow path 415, among the multiple outlets 412. Therefore, by performing additional processing on a portion of separator 3, dummy separator 35 can be constructed easily and inexpensively.

[0068] (4) The plurality of communication channels PA11 includes a corner communication channel 415 (target communication channel) that communicates with the through hole 304 at the lower left corner 214b (first position) along the edge of the through hole 304, and an upper communication channel 416 (non-target communication channel) that communicates with the through hole 304 at the edge of the through hole 304 that is higher than the corner 214b (second position) ( FIG. 9 ). The area of ​​the outlet 412c corresponding to the corner communication channel 415 is larger than the area of ​​the outlet 412d corresponding to the upper communication channel 416 ( FIG. 9 ). As a result, the area of ​​the outlet 412c corresponding to the lower communication channel (corner communication channel 415) where liquid water is likely to concentrate is larger among the plurality of communication channels PA11. Therefore, the liquid water captured by the dummy assembly 25 can be efficiently discharged to the gas discharge channels PA3 and PA6 via the dummy cell 10.

[0069] (5) The edge of the through hole 214a in the dummy frame 210 protrudes further toward the center (toward the axis CL1) of the through holes 214a, 304 than the edge of the through hole 304 in the separator 3 that constitutes the end power-generating cell 1a ( FIG. 8 ). In other words, protrusions 217, 218 are provided on the periphery of the dummy frame 210. This allows the dummy assembly 25 in front of the end power-generating cell 1a to capture liquid water, preventing the liquid water from jumping over the dummy cell 10 and reaching the power-generating cell 1.

[0070] The above embodiment can be modified in various ways. Some modifications are described below. In the above embodiment, the outlet 412c (first flow restriction portion) of the dummy separator 35 is formed by connecting the outlets 412a and 412b (second flow restriction portion) of the separator 3. However, the configurations of the first flow restriction portion and the second flow restriction portion are not limited to those described above, as long as the area of ​​the first flow restriction portion is larger than the area of ​​the second flow restriction portion. That is, the flow rate in the end flow path of the dummy cell 10 may be restricted at another portion of the dummy separator 35 (other than the outlet 412c in FIG. 9 ), or the flow rate in the end flow path of the power-generating cell 1 may be restricted at another portion of the separator 3 (other than the outlets 412a and 412b in FIG. 5A ).

[0071] In the above embodiment, the portions (outlet 412c and outlets 412a, 412b) that regulate the flow rate in the end flow passages are set at the same positions in the vertical and horizontal directions, but they may be set at different positions. Therefore, the first flow regulation portion and the second flow regulation portion do not have to be on the same imaginary line CL2 ( FIG. 7 ) that extends in the front-rear direction (predetermined direction). In the above embodiment, the first flow regulation portion and the second flow regulation portion are set at the outlet 412, which is the flow passage outlet of the communication flow passage PA11. However, they may be set at the middle of the communication flow passage rather than at the flow passage outlet. In the above embodiment, the dummy cell 10 is configured by the approximately plate-shaped dummy assembly 25 (dummy plate) and the dummy separator 35. However, the dummy plate does not have to be an assembly composed of multiple members.

[0072] In the above embodiment, a plurality of communication channels PA11 are formed between the dummy assembly 25 and the dummy separator 35 via the tunnel portion 40 ( FIG. 9 ). However, the configuration of the plurality of first communication channels is not limited to the above. In the above embodiment, a plurality of communication channels PA11 are formed between the UEA2 (membrane electrode assembly) and the separator 3 via the tunnel portion 40 ( FIG. 5A ). However, the configuration of the plurality of second communication channels is not limited to the above. In the above embodiment, the plurality of communication channels PA11 of the dummy separator 35 include a corner communication channel 415 (target communication channel) and an upper communication channel 416 (non-target communication channel) ( FIG. 9 ). That is, the target communication channel includes a channel outlet (outlet 412) with an area larger than that of the non-target communication channel. However, the target communication channel may extend from a location other than the corner of the through-holes 301 and 304, and the first position is not limited to the above. The asymmetrical communication flow paths may extend from a position of the through holes 301, 304 other than those described above, as long as they extend from a second position that is higher than the first position.

[0073] In the above embodiment, the edge of the through hole 214a in the dummy frame 210 (dummy plate) protrudes toward the center of the through hole 214a (toward the axis CL1) beyond the edge of the through hole 304 in the dummy separator 35 disposed between the dummy frame 210 and the end unit 102 around the entire circumference of the through hole 214a ( FIG. 8 ). However, it is also possible for only a portion (for example, a corner of the through hole 214a) to protrude rather than the entire circumference. In the above embodiment, the cell stack 101 is formed by stacking multiple power generating cells 1 in the front-to-rear direction. However, the cell stack may also be formed by stacking multiple power generating cells in a predetermined direction other than the front-to-rear direction. In this case, the stacking direction is preferably approximately horizontal.

[0074] In the above embodiment, the dummy separator 35 adjacent to the end unit 102 is configured by joining a front plate 3F and a rear plate 3R, similar to the separator 3, but it may be configured by a single plate (for example, the front plate 3F), and the configuration of the dummy cell 10 is not limited to that described above. In the above embodiment, the end unit 102 is provided with through-holes 102a and 102d (gas supply ports) so as to communicate with the gas supply flow paths PA1 and PA4 (gas supply flow paths), and the end unit 102 is provided with through-holes 102c and 102f (gas exhaust ports) so as to communicate with the gas exhaust flow paths PA3 and PA6 (gas exhaust flow paths), but the configurations of these gas supply ports and gas exhaust ports are not limited to that described above.

[0075] In the above embodiment, the area of ​​the outlet 412c of the communication flow path PA11 is increased, which promotes the flow of liquid water in the dummy cells 10 and makes it possible to suppress the flow of liquid water beyond the dummy cells 10 and reaching the power-generating cells 1 even without the protrusions 217, 218. Therefore, the protrusions 217, 218 provided on the periphery of the through-hole 214a of the dummy frame 210 can be omitted.

[0076] 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.

[0077] 1 Power generating cell, 1a End power generating cell, 2 Integrated electrode assembly, 3 Separator, 10 Dummy cell, 21 Frame, 100 Fuel cell stack, 101 Cell stack, 102 End unit, 102a, 102c, 102d, 102f Through hole, 210 Dummy frame, 211, 213, 214, 216 Through hole, 214a Through hole, 217, 218 Protrusion, 301, 303, 304, 306 Through hole, 412, 412a, 412b, 412c Outlet, 414, 415 Corner communication channel, 416 Upper communication channel, CL2 Axis, PA1, PA4 Gas supply channel, PA3, PA6 Gas discharge channel, PAa Anode channel, PAc Cathode channel, PA11 Communication channel

Claims

1. A cell stack comprising: a plurality of power generating cells which are power generating bodies stacked in a predetermined direction; and dummy cells which are non-power generating bodies arranged adjacent to end power generating cells which are located at one end of the plurality of power generating cells in the predetermined direction, wherein a gas supply flow path for supplying a reactant gas and a gas exhaust flow path for exhausting the reactant gas each extend along the predetermined direction, and a gas flow path is provided which connects the gas supply flow path with the gas exhaust flow path; and an end unit arranged adjacent to the dummy cell and provided with a gas supply port which connects to the gas supply flow path and a gas exhaust port which connects to the gas exhaust flow path, wherein the gas supply flow path is constituted by a through hole which penetrates the power generating cells and the dummy cell in the predetermined direction, and the gas flow path includes a central flow path provided in a central region of each of the power generating cells and the dummy cell, and an end flow path which connects the central flow path with the through hole, a first flow restriction portion that restricts the flow rate in the end flow path of the dummy cell having a larger area than a second flow restriction portion that restricts the flow rate in the end flow path of the power generation cell; 2. A fuel cell stack according to claim 1, wherein the first flow regulating portion and the second flow regulating portion are located on the same imaginary straight line extending in the predetermined direction.

3. A fuel cell stack as claimed in claim 2, wherein the power generation cell has a membrane electrode assembly and a separator arranged opposite the membrane electrode assembly, the dummy cell has a substantially plate-shaped dummy plate and a dummy separator arranged opposite the dummy plate, the dummy separator is configured to form a plurality of first communication flow paths included in the end flow path between itself and the dummy plate, the separator is configured to form a plurality of second communication flow paths included in the end flow path between itself and the membrane electrode assembly, the first flow regulation portion is one of a plurality of flow path outlets corresponding to the plurality of first communication flow paths, and the second flow regulation portion is one of a plurality of flow path outlets corresponding to the plurality of second communication flow paths.

4. A fuel cell stack as described in claim 3, wherein the plurality of first communication flow paths include a target communication flow path that communicates with the through hole at a first position along the edge of the through hole, and a non-target communication flow path that communicates with the through hole at a second position higher than the first position, and the area of ​​the flow path outlet corresponding to the target communication flow path is larger than the area of ​​the flow path outlet corresponding to the non-target communication flow path.

5. A fuel cell stack as claimed in claim 3 or 4, characterized in that the edge of the through hole in the dummy plate protrudes towards the centre of the through hole beyond the edge of the through hole in the separator constituting the end power generation cell.

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