Separator and fuel cell provided with said separator

Abstract

The present invention provides: a separator which is capable of suppressing stagnation of liquid water under a partition wall (rib) that defines flow paths through which a reaction gas or a refrigerant flows; and a fuel cell. A separator of a fuel cell according to one embodiment of the present disclosure comprises at least three flow paths that are arranged in a transverse direction that is perpendicular to a flow path direction in which a cathode gas of the fuel cell flows, wherein: (i) the three flow paths each have, in the flow path direction, a medium path part in which the cross-sectional area of the flow path is of medium size, a narrow path part which has a smaller cross-sectional area than the medium path part, and a wide path part which has a larger cross-sectional area than the medium path part; and (ii) in at least a part of the flow paths, the medium path part is sandwiched between the wide path parts adjacent to the medium path part, or the medium path part is sandwiched between the narrow path parts adjacent to the medium path part in the flow path direction.

Description

Separator and fuel cell equipped with the separator

[0001] The present disclosure relates to a separator and a fuel cell including the separator.

[0002] In a system using a fuel cell, hydrogen gas is supplied to one electrode (fuel electrode) and oxygen gas is supplied to the other electrode (air electrode), and electrical energy is obtained by the reaction between these. Such a system can be mounted on, for example, a mobile object, such as a fuel cell vehicle.

[0003] Fuel cell vehicles are equipped with a fuel cell stack made up of several hundred individual cells (fuel cell units) separated by separators, for example. These separators are formed with flow paths through which fluids such as reactant gases (anode gas and cathode gas) and refrigerant supplied to the fuel cell flow. For example, the separator flow paths disclosed in Patent Document 1 include wide and narrow portions with partially wide groove widths to prevent increased refrigerant pressure loss and a resulting decrease in the cooling performance of the fuel cell stack.

[0004] JP 2019-139929 A JP 2017-228482 A

[0005] Indeed, as exemplified in Patent Document 1, by employing a separator flow path structure having the wide and narrow portions described above, it is possible to suppress an increase in pressure loss of the refrigerant flowing through the flow paths. However, as also disclosed in Patent Document 2, when a reactant gas flows through a separator flow path, a phenomenon called "submersion" (hereinafter, in this disclosure, this submersion phenomenon is also referred to as "underground flow"), in which the reactant gas diffuses from the flow path into the gas diffusion layer due to a change in cross-sectional area at the narrow portion described above, can occur.

[0006] However, it was found that the separator flow path structure disclosed in Patent Document 1 reduces the pressure difference between adjacent flow paths, particularly when wide and narrow portions are adjacent in the direction across the flow path, making the above-mentioned underflow less likely to occur. Liquid water generated by the fuel cell reaction flows out into the gas diffusion layer and separator flow paths, but in Patent Document 1, liquid water tends to accumulate under the partition walls (ribs) between the wide and narrow portions, where the above-mentioned underflow is less likely to occur. Narrow portions with small flow path cross-sectional areas are at high risk of clogging due to liquid water intrusion, and are areas where liquid water accumulation in the surrounding area should be avoided. However, Patent Document 1 has the problem that the accumulated liquid water eventually clogs the flow path, causing increased pressure loss and resulting in performance degradation and cell damage.

[0007] The present disclosure has been made in consideration of the above-mentioned problems as an example, and aims to provide a separator that can prevent liquid water from accumulating under partition walls (ribs) that separate flow paths through which reactant gases and refrigerants flow, and a fuel cell equipped with this separator.

[0008] In order to solve the above problems, a separator in one embodiment of the present disclosure is a separator including at least three flow paths aligned in a transverse direction perpendicular to the flow path direction in which the cathode gas of the fuel cell flows, wherein (i) the three flow paths each have, along the flow path direction, a parallel path section in which the cross-sectional area of ​​the flow path is medium, a narrow path section in which the cross-sectional area is smaller than that of the parallel path section, and a wide path section in which the cross-sectional area is larger than that of the parallel path section, and (ii) at least a portion of the flow paths are characterized in that, in the flow path direction, the parallel path section is sandwiched between the wide path section adjacent to the parallel path section, or the parallel path section is sandwiched between the narrow path section adjacent to the parallel path section.

[0009] In order to solve the above problems, a fuel cell according to another aspect of the present disclosure includes the separator of the present disclosure.

[0010] According to the present disclosure, by appropriately applying a differential pressure between the flow paths in the transverse direction across the flow paths, it is possible to promote the convection of the reaction gas into the gas diffusion layer and prevent liquid water from accumulating under the partition walls (ribs).

[0011] 4 is a functional block diagram of a fuel cell stack formed by stacking fuel cell cells according to a first embodiment, and a fuel cell vehicle (an example of a mobile body) equipped with this fuel cell stack. FIG. 5 is a schematic diagram showing components (one example) of a fuel cell cell according to the first embodiment. FIG. 6 is a schematic diagram showing a partial cross-sectional view of a fuel cell cell according to the first embodiment. FIG. 7 is a top view schematically showing a cathode separator of a fuel cell cell according to the first embodiment. FIG. 8 is an enlarged view of portion α in FIG. 4, showing a schematic diagram of a flow path structure of a cathode separator according to the first embodiment. FIG. 9 is a schematic diagram showing a layout of parallel path sections, narrow path sections, and wide path sections in four flow paths adjacent in the transverse direction in the flow path structure of a cathode separator according to the first embodiment. FIG. 10 is a graph showing a pressure difference between four flow paths adjacent in the transverse direction in the flow path structure of a cathode separator according to the first embodiment. FIG. 11 is a graph showing a comparison (one example) of current density between a conventional structure and the fuel cell stack according to the first embodiment. FIG. 12 is a schematic diagram showing a flow path structure of a cathode separator according to a second embodiment. 10 is a schematic diagram showing the layout of parallel passage sections, narrow passage sections, and wide passage sections in three passages adjacent in the transverse direction in the passage structure of the cathode separator according to the second embodiment. 11 is a graph showing the pressure difference between two passages adjacent in the transverse direction in the passage structure of the cathode separator according to the second embodiment.

[0012] Next, preferred embodiments of the present disclosure will be described. Furthermore, configurations other than those described in detail can be implemented by appropriately supplementing elemental technologies and configurations related to known fuel cells, fuel cell stacks, and fuel cell systems, including the driving thereof, including those described in the above-mentioned patent documents.

[0013] First Embodiment <Fuel Cell Vehicle 300> First, the configuration of a fuel cell vehicle 300 as an example of a mobile body in the present disclosure will be described with reference to FIG. 1. As shown in FIG. 1, the fuel cell vehicle 300 in this embodiment may be configured to include a fuel cell stack 200, an inverter 210, a load 220, and a control device 230. In the fuel cell vehicle 300, under the control of the control device 230, electric power generated in the fuel cell stack 200 is supplied to the load 220 via the well-known inverter 210. Note that the fuel cell vehicle 300 in this embodiment is configured to include various well-known devices (not shown) that are mounted on fuel cell vehicles, such as a hydrogen tank, a gas supply mechanism (anode gas supply device, cathode gas supply device), a refrigerant supply device, and a DC / DC converter.

[0014] The fuel cell stack 200 is constructed by stacking, for example, several tens to several hundreds of fuel cell units 100, which serve as unit cells (described later), in the stacking direction. Each fuel cell unit 100 has the function of generating electricity by reacting an anode gas AG (also called a fuel gas or hydrogen gas) and a cathode gas CG (oxygen in the air, also called an oxidant gas) as reactant gases. The fuel cell stack 200 is equipped with a known voltage sensor SR that can measure the voltage applied to the fuel cell stack and the voltage of each individual fuel cell unit 100. １ and a known current sensor SR capable of measuring the current flowing through the fuel cell 100. ２ The fuel cell 100 is not particularly limited as long as it does not deviate from the spirit of the present disclosure, and a known PEFC (polymer electrolyte fuel cell) or the like is suitable, for example.

[0015] The inverter 210 is configured to have the function of converting DC power obtained by boosting the voltage using, for example, a DC / DC converter (not shown) into AC power suitable for driving an electric motor, which is the downstream load 220. There are no particular limitations on the inverter 210 as long as it can perform the above function, and various known inverters including, for example, a three-phase bridge circuit can be used.

[0016] The load 220 is configured to include, for example, a known electric motor capable of outputting power for driving drive wheels (not shown) of the fuel cell vehicle 300. Note that in this embodiment, an electric motor that generates the power required for the drive wheels is used as an example of the load 220, but the load 220 may also be other electrical equipment mounted on the fuel cell vehicle 300. Furthermore, one example of the electric motor is a known three-phase AC electric motor.

[0017] The control device 230 is a known ECU (Electronic Control Unit) mounted on the electric vehicle, and is configured to include a known CPU which is an arithmetic processing device, a known ROM which is a memory element that stores programs used by the CPU, calculation parameters, etc., and a known RAM which is a memory element that temporarily stores various information. The control device 230 may also be configured to include a known BMU (Battery Management Unit) that monitors and controls the state of the battery. The control device 230 may be configured to be able to communicate with other known EUCs and various sensors (not shown) mounted on the fuel cell vehicle 300.

[0018] While the following description uses a fuel cell vehicle as an example of a moving body, the present disclosure can be applied to various known moving bodies that can move using a fuel cell system as a driving source, such as ships, aircraft, trains, etc. In other words, the fuel cell stack of the present disclosure can be applied not only to fuel cell vehicles but also to other moving bodies such as ships and aircraft.

[0019] <Fuel Cell 100> Next, the configuration of the fuel cell 100 in the first embodiment will be described with appropriate reference to Figures 2 to 8. As shown in Figure 2 and other figures, the fuel cell 100 in this embodiment has a structure in which a known MEA gasket 20 that holds a known membrane electrode assembly (MEA 10) is sandwiched between an anode separator 30 and a cathode separator 40. The anode separator 30 and the cathode separator 40 can be, for example, known metal separators made of aluminum or stainless steel, or carbon separators made of known carbon-based materials.

[0020] 3, the MEA 10 includes a catalyst coated membrane in which a known electrolyte layer 11 is sandwiched between a known anode catalyst layer 12 and a known cathode catalyst layer 13. The MEA 10 of this embodiment has a structure in which this CCM is sandwiched between a known anode gas diffusion layer 14 and a known cathode gas diffusion layer 15.

[0021] As shown in Fig. 3, the anode separator 30 is in close contact with the anode gas diffusion layer 14. The anode separator 30 is provided with flow channel grooves (anode gas flow channel grooves 31 and refrigerant flow channel grooves 32) through which a fluid (gas or liquid) can flow. Therefore, anode gas AG (hydrogen gas) as a reactant gas can flow through the anode gas flow channel grooves 31 on the MEA 10 side of the anode separator 30. Furthermore, cooling water CL as a known refrigerant can flow through the refrigerant flow channel grooves 32 on the opposite side of the anode separator 30 from the MEA 10.

[0022] The cathode separator 40 is in close contact with the cathode gas diffusion layer 15. The cathode separator 40 is provided with flow paths (a cathode gas flow path 44 and a refrigerant flow path 48, described below) through which a fluid (gas or liquid) can flow. Therefore, a cathode gas (air) as a reactant gas can flow on the MEA 10 side of the cathode separator 40. Furthermore, the above-mentioned cooling water CL can flow through the refrigerant flow path 48 on the side of the cathode separator 40 opposite the MEA 10.

[0023] <Flow Channel Structure of Cathode Separator> Next, the flow channel structure of the cathode separator 40 included in the fuel cell 100 of this embodiment will be described in detail with reference to Figures 4 to 7. First, as shown in Figure 4, the cathode separator 40 of this embodiment has first through holes 41 which constitute an anode manifold 41 through which the anode gas AG as a reactant gas is supplied to the fuel cell. ｉｎ The second through-hole 41 constitutes the anode manifold 41 through which the anode off-gas flows after the reaction in the fuel cell. ｏｕｔ It has.

[0024] The cathode separator 40 of this embodiment also has a third through-hole 42 that constitutes a coolant manifold 42 through which a known coolant, such as cooling water, for cooling the fuel cell stack is supplied. ｉｎ The fourth through-hole 42 constitutes a refrigerant manifold 42 through which the refrigerant flows after passing through the fuel cell. ｏｕｔ It has.

[0025] Furthermore, the cathode separator 40 of this embodiment has a fifth through-hole 43 which constitutes a cathode manifold 43 through which the cathode gas CG as a reactant gas is supplied to the fuel cell. ｉｎ The sixth through-hole 43 constitutes the cathode manifold 43 through which the cathode off-gas flows after the reaction in the fuel cell. ｏｕｔ It has.

[0026] The cathode separator 40 has a corrugated cross-sectional shape as viewed from the main gas flow direction (Y direction), with multiple concaves and convexes arranged in the transverse direction (X direction). More specifically, as shown in Figures 2 and 3, the cathode separator 40 of this embodiment has a cathode gas flow path 44 formed on the surface facing the MEA 10. The cathode gas flow path 44 is partitioned by a flow path forming rib RB, which will be described later. As shown in Figure 4, the cathode gas flow path 44 is formed by a fifth through-hole 43 constituting the cathode manifold 43. ｉｎ a cathode gas main flow path 46 that communicates with the cathode gas main flow path 46 and at least a portion of which faces the power generation region of the MEA 10; and a sixth through-hole 43 that communicates with the cathode gas main flow path 46 and through which the cathode off-gas flows and that constitutes the cathode manifold 43. ｏｕｔ and a cathode off-gas discharge flow path 47 communicating with the cathode off-gas discharge flow path 47 .

[0027] Furthermore, a refrigerant flow path 48 through which the above-mentioned refrigerant (cooling water) flows is formed on the rear surface of the cathode separator 40 of this embodiment, opposite to the surface facing the MEA 10. As can be seen from FIGS. 3 and 4 , the refrigerant flow path 48 of this embodiment is formed by the third through-holes 42 constituting the refrigerant manifold 42. ｉｎa refrigerant main flow path 50 that communicates with the refrigerant introduction flow path 49 and corresponds to the rear side of the cathode gas main flow path 46; and a fourth through-hole 42 that constitutes the refrigerant main flow path 50 and the refrigerant manifold 42. ｏｕｔ and a refrigerant discharge flow path 51 that communicates with the refrigerant main flow path 50 and through which the refrigerant that has flowed through the refrigerant main flow path 50 is discharged.

[0028] As for the specific structure of the main refrigerant flow channel 50, the channel may be formed by utilizing the uneven shape constituting the main cathode gas flow channel 46 on the opposite surface, or the channel may be formed with a structure different from the uneven structure of the main cathode gas flow channel 46. The specific shape of the refrigerant flow channel 48 may be of various structures as long as it does not deviate from the spirit of the present disclosure, and known refrigerant flow channels that can be formed in a separator may also be used.

[0029] Next, a detailed description will be given of the structure of the cathode gas main channel 46 of the cathode separator 40 of this embodiment, at least a portion of which faces the power generation region of the MEA 10. Fig. 5 shows an enlarged schematic diagram of a portion (portion α) of the cathode gas main channel 46 of the cathode separator 40 of Fig. 4 .

[0030] The cathode separator 40 of the present embodiment is a separator including at least three flow path units (first to third flow paths in FIG. 5 ) arranged in a transverse direction (X direction in FIGS. 4 and 5 ) perpendicular to the macro flow path direction (Y direction in FIGS. 4 and 5 ) in which the above-described cathode gas flows, and has a structure that satisfies the following two conditions (i) and (ii):

[0031] (i) Each of the three flow paths has, along the flow path direction (Y direction), a parallel path section 46A having a medium cross-sectional area of ​​the flow path, a narrow path section 46N having a smaller cross-sectional area than the parallel path section 46A, and a wide path section 46W having a larger cross-sectional area than the parallel path section 46A.

[0032] (ii) At least a portion of the flow path constituting the cathode separator 40 is an area in the flow path direction (Y direction) where a wide path portion 46W adjacent to a parallel path portion 46A sandwiches the parallel path portion 46A (see box P in Figure 6), or where a narrow path portion 46N adjacent to a parallel path portion 46A sandwiches the parallel path portion 46A (see box Q in Figure 6).

[0033] Here, the "flow path direction" refers to the direction in which the cathode gas flows macroscopically (as a large overall flow) in the cathode gas main flow path 46 of the cathode separator 40, and is defined as the Y direction in Figures 4 and 5, for example. The "transverse direction" refers to the direction perpendicular to the flow path direction and crossing the flow paths that constitute the cathode gas main flow path 46, and is defined as the X direction in Figures 4 and 5, for example.

[0034] In the present disclosure, the "cross-sectional area of ​​a flow path" can be adjusted by varying the width (length in the transverse direction) of each flow path and the depth (length in the Z direction) of each flow path. That is, as shown in the figure, each flow path in the cathode separator 40 is partitioned by a rib RB (partition wall), and the cross-sectional area of ​​the flow path can be adjusted as desired by adjusting at least one of the width and depth of the flow path formed by this rib RB.

[0035] As an example, in this embodiment, as shown in FIG. 3, the above-mentioned "parallel path section 46A," "narrow path section 46N," and "wide path section 46W" are set by adjusting the magnitude of both the flow path width W (in this example, width W1 and W2 narrower than W1) and the depth D (in this example, depth D1 and D2 shallower than D1). However, the present invention is not limited to this form, and the narrow path section 46N and the wide path section 46W may be set by keeping one (for example, depth) constant and varying the other (for example, flow path width).

[0036] 6, the cathode separator 40 of this embodiment may further have a structure that satisfies the following condition (iii): (iii) Three flow paths (flow paths 1, 2, and 3 in FIGS. 5 and 6) adjacent to each other in the transverse direction (X direction) are grouped into a first basic flow path group BFG. １ In this case, in the flow path other than the parallel path portion 46A, two wide path portions 46W are adjacent to each other in succession along the transverse direction, or two narrow path portions 46N are adjacent to each other in succession.

[0037] That is, in the flow path configuration of a portion (within frame A) of flow paths 1 and 2 shown in FIG. 6, two wide path portions 46W are adjacent to each other in the transverse direction. Furthermore, in the flow path configuration of another portion (within frame B) of flow paths 1 and 2 shown in FIG. 6, two narrow path portions 46N are adjacent to each other in the transverse direction. Similarly, in the flow path configuration of a portion (within frame C) of flow paths 2 and 3 shown in FIG. 6, two narrow path portions 46N are adjacent to each other in the transverse direction. Furthermore, in the flow path configuration of a portion (within frame D) of flow paths 3 and 4 shown in FIG. 6, two wide path portions 46W are adjacent to each other in the transverse direction.

[0038] In the parallel path section 46A constituting a part of the cathode gas main flow channel 46, the opposing ribs RB extend parallel to each other along the flow channel direction so that the width of the opposing ribs RB in the transverse direction is uniform. On the other hand, in the wide path section 46W constituting another part of the cathode gas main flow channel 46, for example, at least one of the opposing ribs RB may have a shape that widens in the transverse direction with respect to the flow channel width. Also, in the narrow path section 46N constituting another part of the cathode gas main flow channel 46, for example, at least one of the opposing ribs RB may have a shape that narrows in the transverse direction with respect to the flow channel width.

[0039] As an example, in the narrow path portion 46N of this embodiment, as shown in FIG. 5 and the like, one of the partition walls (ribs RB) forming the flow path through which the cathode gas flows narrows in the transverse direction, and the other of the partition walls has a linear wall structure along the flow path. Also, as an example, in the wide path portion 46W of this embodiment, as shown in the same figure, one of the partition walls (ribs RB) forming the flow path through which the cathode gas flows bulges in the transverse direction, and the other of the partition walls has a linear wall structure along the flow path. In other words, the cathode separator 40 of this embodiment may include a region where one of the partition walls forming the flow path through which the cathode gas flows bulges or narrows in the transverse direction, and the other of the partition walls has a linear wall structure along the flow path.

[0040] Furthermore, as can be seen from FIGS. 5 and 6, the cathode separator 40 of this embodiment has the first basic flow path group BFG in which at least the width of the flow paths is varied along the transverse direction (X direction). １ The four flow paths, including the three flow paths constituting the first flow path and one flow path (flow path 4 in FIGS. 5 and 6) adjacent to the three flow paths, are referred to as a second unit flow path group BFG. ２ The cathode separator 40 of this embodiment includes the above-mentioned second unit flow path group BFG. ２ may be arranged repeatedly in the transverse direction (X direction).

[0041] As shown in FIG. 5 and other figures, the second unit flow path group BFG ２ It is preferable that the flow passage comprises a first flow path having a right-side bulging portion RW where the right side wall bulges in the transverse direction, a second flow path adjacent to the first flow path having a left-side bulging portion LW where the left side wall bulges in the transverse direction, a third flow path adjacent to the second flow path having a right-side narrowing portion RN where the right side wall narrows in the transverse direction, and a fourth flow path adjacent to the third flow path having a left-side narrowing portion LN where the left side wall narrows in the transverse direction.

[0042] <Operational Effects of the Cathode Separator of the Present Embodiment Compared to a Conventional Structure> Next, operational effects of the cathode separator of the present embodiment compared to a conventional structure will be described with further reference to FIGS. 7 and 8. FIG.

[0043] As described above, by providing a constriction section (narrow path section 46N) or a bulge section (wide path section 46W) that changes the cross-sectional area of ​​the flow path through which the reactant gas (cathode gas in this example) flows in the separator, a subsurface flow in which the reactant gas diffuses from this flow path into the gas diffusion layer can occur due to, for example, a change in fluid pressure in the narrow path section 46N described above.

[0044] In each fuel cell 100, liquid water is generated as a reaction product after a chemical reaction occurs when reactant gases are supplied. The liquid water generated by this reaction can be removed by, for example, the cathode off-gas passing through the gas diffusion layer and reaching the flow path of the cathode separator 40. However, in areas where the underflow does not occur efficiently, there is a concern that the liquid water may accumulate in areas of the gas diffusion layer that come into contact with the partition walls (ribs RB) of the cathode separator 40 (also referred to as under the ribs).

[0045] In order to generate the underflow and effectively remove the liquid water generated by power generation in the fuel cell, it is important to determine how to generate a pressure difference between adjacent flow paths in the transverse direction. In other words, since the cathode gas main flow path 46 of the cathode separator 40 has multiple flow paths aligned in the transverse direction, the arrangement of the constrictions and bulges along the flow path direction differs between adjacent flow paths, as shown in Figure 5 and other figures. After extensive research, the inventors have concluded that a separator having a structure that satisfies at least the two conditions (i) and (ii) above can maintain a pressure difference between adjacent flow paths in the transverse direction and effectively generate the underflow.

[0046] More specifically, the inventors conducted simulations and found that, for example, the narrow width portion disclosed in Patent Document 1 eliminates the pressure difference between adjacent flow paths, making it difficult for underflow to occur in the middle of the flow path, resulting in liquid water stagnation, particularly under the adjacent ribs near the middle of the flow path. On the other hand, as shown in FIG. 7 (see, for example, section 6-7), the cathode separator 40 of this embodiment can maintain a constant pressure difference between adjacent narrow path portions 46N, for example, and this pressure difference can efficiently generate underflow. Applying a pressure difference between the flow paths to at least one side in the transverse direction of the flow path in this way promotes the convection of reactant gases into the gas diffusion layer, thereby preventing liquid water from stagnating under the partition walls (ribs) and clogging the flow path.

[0047] Furthermore, in areas of the gas diffusion layer where underflows through which reactant gases diffuse do not occur, not only are liquid water likely to accumulate as described above, but the current density may also be low due to an insufficient supply of reactant gas from the gas diffusion layer to the MEA 10. In contrast, the cathode separator 40 of this embodiment can improve current density by promoting the supply of reactant gas in conjunction with the improvement in liquid water retention described above. As a result, as shown in FIG. 8 as an example, a fuel cell equipped with the cathode separator 40 of this embodiment can obtain a higher current density than a fuel cell with a conventional structure.

[0048] 9 to 11, a preferred second embodiment of the present disclosure will be described. In the narrow path section 46N of the cathode separator 40 of the first embodiment described above, one of the partition walls forming the flow path narrows in the transverse direction, and the other of the partition walls has a linear wall structure along the flow path. In the wide path section 46W of the cathode separator 40 of the first embodiment, one of the partition walls forming the flow path bulges in the transverse direction, and the other of the partition walls has a linear wall structure along the flow path.

[0049] In contrast, in the cathode separator 40 of the second embodiment, both of the partition walls forming the flow paths at the narrow path portion 46N narrow in the transverse direction, and both of the partition walls forming the flow paths at the wide path portion 46W bulge in the transverse direction. Even with this flow path structure, it is possible to achieve the same effects as in the first embodiment. The following description will mainly focus on differences from the first embodiment, and the same reference numerals will be used to designate components with the same functions as those already described, and their description will be omitted where appropriate.

[0050] As shown in FIGS. 9 and 10 , the cathode separator 40 of the second embodiment is a separator in which three flow path units (the fifth to seventh flow paths in FIG. 9 ) aligned in the transverse direction are repeated along the transverse direction, and has a structure that satisfies conditions (i) and (ii) in the same manner as the first embodiment described above.

[0051] (i) Each of the three flow paths has, along the flow path direction (Y direction), a parallel path section 46A having a medium cross-sectional area of ​​the flow path, a narrow path section 46N having a smaller cross-sectional area than the parallel path section 46A, and a wide path section 46W having a larger cross-sectional area than the parallel path section 46A.

[0052] (ii) At least a portion of the flow path constituting the cathode separator 40 is an area in the flow path direction (Y direction) where a wide path portion 46W adjacent to a parallel path portion 46A sandwiches the parallel path portion 46A (see box P in Figure 10), or where a narrow path portion 46N adjacent to a parallel path portion 46A sandwiches the parallel path portion 46A (see box Q in Figure 10).

[0053] As can be seen from the figure, the cathode separator 40 of the second embodiment may further have a structure that satisfies the following condition (iv): (iv) Three flow path units (flow paths 5, 6, and 7 in FIGS. 9 and 10) adjacent to each other in the transverse direction (X direction) are grouped into a first basic flow path group BFG. １ In this case, in the flow paths other than the parallel path portion 46A, two wide path portions 46W sandwich a narrow path portion 46N, or two narrow path portions 46N sandwich a wide path portion 46W, along the transverse direction.

[0054] That is, in the flow path configuration of a portion (within frame E) of the flow paths 5 to 7 shown in Figures 9 and 10, two wide path portions 46W sandwich a narrow path portion 46N along the transverse direction. Also, in the flow path configuration of another portion (within frame F) of the flow paths 5 to 7 shown in Figures 9 and 10, two narrow path portions 46N sandwich a wide path portion 46W along the transverse direction.

[0055] 11 (see, for example, section 6-7), the cathode separator 40 of this embodiment can also maintain a constant pressure difference between, for example, two adjacent flow paths (for example, flow paths 5 and 6 shown in the figure), and this pressure difference can cause the above-mentioned underflow. Therefore, the cathode separator 40 of this embodiment also promotes the convection of the reactant gas into the gas diffusion layer, preventing liquid water from accumulating below the partition walls (ribs), and can obtain a higher current density than conventional structures.

[0056] Although the preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art of the present disclosure may attempt further modifications to these embodiments and variations within the scope of the technical ideas set forth in the claims, and it is understood that these modifications also fall within the technical scope of the present disclosure.

[0057] For example, in the above embodiment, the cathode separator 40 has the parallel path portion, narrow path portion, and wide path portion described above, but the above structures may also be applied to the anode separator 30 .

[0058] REFERENCE SIGNS LIST 100 Fuel cell 10 MEA 20 MEA gasket 30 Anode separator 40 Cathode separator 50 Main refrigerant channel 200 Fuel cell stack 210 Inverter 220 Load 230 Control device 300 Fuel cell vehicle (mobile body)

Claims

1. A separator comprising at least three flow paths aligned in a transverse direction perpendicular to the flow path direction in which a cathode gas flows, wherein: (i) the three flow paths each have, along the flow path direction, a parallel path section having a medium cross-sectional area, a narrow path section having a cross-sectional area smaller than that of the parallel path section, and a wide path section having a cross-sectional area larger than that of the parallel path section; and (ii) in at least some of the flow paths, in the flow path direction, the parallel path section is sandwiched between the wide path section adjacent to the parallel path section, or the parallel path section is sandwiched between the narrow path section adjacent to the parallel path section.

2. A separator as described in claim 1, wherein (iii) when the three adjacent flow paths are considered as a basic flow path group, in flow paths other than the parallel path portion, two of the wide path portions are adjacent to each other in succession along the transverse direction, or two of the narrow path portions are adjacent to each other in succession.

3. The separator according to claim 2, wherein one of the partition walls forming the flow path through which the cathode gas flows bulges or narrows in the transverse direction, and the other of the partition walls has a straight wall structure along the flow path.

4. A separator as claimed in claim 3, wherein when a unit flow path group is made up of four flow paths, including the three flow paths lined up along the transverse direction with at least varying flow path widths and one flow path adjacent to the three flow paths, the unit flow path group comprises: a first flow path having a right-side bulging portion where its right side wall bulges in the transverse direction; a second flow path adjacent to the first flow path and having a left-side bulging portion where its left side wall bulges in the transverse direction; a third flow path adjacent to the second flow path and having a right-side narrowing portion where its right side wall narrows in the transverse direction; and a fourth flow path adjacent to the third flow path and having a left-side narrowing portion where its left side wall narrows in the transverse direction.

5. A fuel cell comprising the separator according to claim 1.

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