Fuel Cell Stack

Abstract

To provide a fuel cell stack in which stagnation of a cooling medium can be suppressed.SOLUTION: A cathode-side cooling medium flow passage includes a cathode-side termination groove which is branched, extends in a first direction and is terminated and a cathode-side fold-back groove which is folded back around the cathode-side termination groove. An anode-side cooling medium flow passage includes an anode-side termination groove which is branched, extends in the first direction and is terminated and an anode-side fold-back groove which is folded back around the anode-side termination groove. The cathode-side termination groove is opposed to the anode-side fold-back groove, and the anode-side termination groove is opposed to the cathode-side fold-back groove.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE The present invention relates to a fuel cell stack. [Background technology]

[0002] An oxidant gas flow path that supplies gas to the cathode electrode is formed in the cathode separator of the fuel cell stack, and a fuel gas flow path that supplies gas to the anode electrode is formed in the anode separator. The cathode separator and the anode separator are adjacent to each other, and a cooling water flow path is formed between the cathode separator and the anode separator.

[0003] The oxidant gas flow channel is composed of a plurality of flow grooves. These flow grooves are formed in a concave shape on the surface adjacent to the cathode electrode. A cathode-side convex portion is formed between adjacent flow grooves, protruding toward the cathode electrode and adjacent to the cathode electrode. A flow groove constituting a cooling water flow channel is formed in a concave shape on the back side of the cathode-side convex portion. Similarly, the fuel gas flow channel is composed of a plurality of flow grooves. These flow grooves are formed in a concave shape on the surface adjacent to the anode electrode. A anode-side convex portion is formed between adjacent flow grooves, protruding toward the anode electrode and adjacent to the anode electrode. A flow groove constituting a cooling water flow channel is formed in a concave shape on the back side of the anode-side convex portion. The cooling water flow channel groove formed in the cathode-side separator and the cooling water flow channel groove formed in the anode-side separator face each other.

[0004] A serpentine flow channel structure may be adopted for the oxidant gas flow channel and the fuel gas flow channel in order to increase the flow channel length and pressure loss in the flow channel. This makes it possible to make the gas flow uniform. The serpentine flow channel structure is a structure that includes a turn-back flow channel portion in which the flow channel groove turns back.

[0005] All of the flow grooves constituting the oxidant gas flow path are formed to turn back at the turn-back flow path section, and the oxidant gas flows in parallel through each groove. However, the cooling water flow path formed in the cathode-side separator has a shape that is inverted from the oxidant gas flow path. Therefore, the cooling water flow path includes a terminal groove that branches off and terminates midway. There is a possibility that the cooling water will stagnate in the terminal groove, increasing the amount of impurities such as ions contained in the cooling water. In this case, a potential difference will occur locally in the cathode-side separator, and the phenomenon of a local battery may occur. If the cathode-side separator is formed of metal, local corrosion may occur.

[0006] As in the cathode-side separator, the anode-side separator also has a cooling water flow passage that includes a terminal groove, and similar problems may occur. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5077620 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in consideration of the above points, and has an object to provide a fuel cell stack that can prevent the cooling medium from stagnating. [Means for solving the problem]

[0009] A fuel cell stack according to an embodiment includes a plurality of fuel cells stacked on one another. The fuel cell includes a membrane electrode assembly including a cathode electrode and an anode electrode, a cathode separator adjacent to the cathode electrode, and an anode separator adjacent to the anode electrode. The cathode separator includes an oxidant gas flow path facing the cathode electrode, and a cathode cooling medium flow path facing the anode separator. The cathode cooling medium flow path includes a first cathode flow groove and a second cathode flow groove arranged in parallel, and a cathode turn-back flow path portion provided at a position overlapping the cathode electrode. In the cathode turn-back flow path portion, the first cathode flow groove includes a cathode terminal groove that branches and extends in a first direction and terminates, and the second cathode flow groove includes a cathode turn-back groove that turns back around the cathode terminal groove. The anode-side separator includes a fuel gas flow path facing the anode electrode, and an anode-side coolant flow path facing the cathode-side separator. The anode-side coolant flow path includes a first anode-side flow groove and a second anode-side flow groove arranged in parallel, and an anode-side turn-back flow path section provided at a position overlapping the anode electrode. In the anode-side turn-back flow path section, the first anode-side flow groove includes an anode-side terminal groove that branches off and extends in a first direction and terminates, and the second anode-side flow groove includes an anode-side turn-back groove that turns back around the anode-side terminal groove. The cathode-side terminal groove faces the anode-side turn-back groove, and the anode-side terminal groove faces the cathode-side turn-back groove. Effect of the Invention

[0010] According to the present invention, it is possible to suppress stagnation of the cooling medium. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a partial cross-sectional view showing a fuel cell stack according to the present embodiment. [Diagram 2] FIG. 2 is a plan view showing the electrode structure of FIG. [Diagram 3]FIG. 3 is a plan view showing the cathode side cooling water flow path of the cathode side separator of FIG. [Figure 4] 4 is a plan view showing the anode side cooling water flow path of the anode side separator of FIG. [Diagram 5] FIG. 5 is a plan view showing the overlap of the cathode side cooling water flow passage and the anode side cooling water flow passage. [Figure 6] FIG. 6 is a perspective view of the cathode side separator and the anode side separator, including a cross section taken along line AA in FIG. [Figure 7] FIG. 7 is a diagram showing the results of a computational fluid analysis of the cooling water flow path in this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A fuel cell stack according to an embodiment of the present invention will now be described with reference to the drawings. Note that in the drawings, the scale and aspect ratios have been appropriately altered and exaggerated from those of the actual objects for ease of understanding.

[0013] First, a fuel cell stack according to the present embodiment will be described with reference to Fig. 1. In the present embodiment, a fuel cell stack 2 constituting a fuel cell 1, an example of which is a polymer electrolyte fuel cell, will be described as an example. The fuel cell 1 is configured to generate power using an oxidant gas and a fuel gas.

[0014] 1, the fuel cell 1 includes a fuel cell stack 2, and an oxidant gas manifold, a fuel gas manifold, and a cooling water manifold (not shown) attached to the fuel cell stack 2. The oxidant gas manifold supplies and exhausts oxidant gas to and from an oxidant gas flow path 30 (described below). The fuel gas manifold supplies and exhausts fuel gas to and from a fuel gas flow path 60 (described below). The cooling water manifold supplies and exhausts cooling water to and from a cathode side cooling water flow path 40 and an anode side cooling water flow path 70 (described below).

[0015] The fuel cell stack 2 includes a plurality of fuel cells 3 stacked on top of one another. Each fuel cell 3 includes an electrode assembly 10, a cathode side separator 20, and an anode side separator 50.

[0016] The electrode structure 10 may include a membrane electrode assembly (MEA) 11 and an electrode frame 15 (see FIG. 2).

[0017] The membrane electrode assembly 11 includes a cathode electrode 12, an anode electrode 13, and an electrolyte membrane 14. The cathode electrode 12 is also called an oxidizer electrode. The anode electrode 13 is also called a fuel electrode. The electrolyte membrane 14 is interposed between the cathode electrode 12 and the anode electrode 13. The membrane electrode assembly 11 may be formed in a thin plate shape.

[0018] An oxidant gas is supplied to the cathode electrode 12 from an oxidant gas flow channel 30 described later. The oxidant gas is a gas containing oxygen, and may be, for example, air. A fuel gas is supplied to the anode electrode 13 from a fuel gas flow channel 60 described later. The fuel gas may be, for example, a gas containing hydrogen. When the oxidant gas and the fuel gas are supplied, an electrochemical reaction occurs in the membrane electrode assembly 11 as shown below. As a result, electrical energy can be extracted. Anode reaction: H 2 → 2H + + 2e - Oxidant electrode reaction: 2H + +2e - + (1 / 2)O 2 → H 2 O

[0019] The electrode frame 15 may be provided around the membrane electrode assembly 11 when viewed in the stacking direction of the fuel cell 3 (the Z-axis direction shown in FIG. 1) as shown in Fig. 2. The membrane electrode assembly 11 is fixed to the electrode frame 15. The electrode frame 15 may be formed in a thin plate shape. The electrode frame 15 may be impermeable to the oxidant gas and the fuel gas.

[0020] As shown in FIG. 2, the electrode frame 15 is provided with an oxidant gas supply port 15a, a fuel gas supply port 15b, a cooling water supply port 15c, an oxidant gas discharge port 15d, a fuel gas discharge port 15e, and a cooling water discharge port 15f. These supply ports 15a to 15c and discharge ports 15d to 15f penetrate the electrode frame 15. Each of the supply ports 15a to 15c is located on one side of the membrane electrode assembly 11, and each of the discharge ports 15d to 15f is located on the other side of the membrane electrode assembly 11. When the X-axis and the Y-axis are defined as shown in FIG. 2, each of the supply ports 15a to 15c is located on the negative side of the X-axis of the membrane electrode assembly 11, and each of the discharge ports 15d to 15f is located on the positive side of the X-axis of the membrane electrode assembly 11. In other words, the membrane electrode assembly 11 is located between each of the supply ports 15a to 15c and each of the discharge ports 15d to 15f in the X-axis direction. The supply ports 15a to 15c and the discharge ports 15d to 15f may have the same planar shape.

[0021] Next, the cathode-side separator 20 will be described with reference to Fig. 1 and Fig. 3. Fig. 3 shows the cathode-side cooling water flow path 40 when viewed from above in the stacked state shown in Fig. 1. When a cathode-side cooling water flow path surface 22 described below is viewed, the cathode-side separator 20 including the cathode-side cooling water flow path 40 has a shape that is upside down or left-right inverted. In Fig. 3, for convenience, the flow path groove is indicated by a single thick line.

[0022] 1, the cathode-side separator 20 includes an oxidant gas flow path 30 facing the cathode electrode 12, and a cathode-side cooling water flow path 40 facing the anode-side separator 50. Cooling water is an example of a cooling medium. The cathode-side separator 20 may be impermeable to the oxidant gas and the cooling water.

[0023] The oxidant gas flow channel 30 is provided on the oxidant gas flow channel surface 21 adjacent to the cathode electrode 12. The oxidant gas flowing through the oxidant gas flow channel 30 is supplied to the cathode electrode 12. The oxidant gas flow channel 30 includes a plurality of oxidant gas flow grooves 31 arranged in parallel at a predetermined pitch. The oxidant gas flow grooves 31 may be arranged at equal intervals. The oxidant gas flow grooves 31 are formed in a concave shape on the oxidant gas flow channel surface 21. The oxidant gas flow channel 30 has a serpentine flow channel structure, and each oxidant gas flow groove 31 is formed so as to turn back. The oxidant gas flow channel grooves 31 are formed so as to turn back at a portion facing the cathode electrode 12.

[0024] The cathode side cooling water flow path 40 is provided on the cathode side cooling water flow path surface 22 adjacent to the anode side separator 50. The cathode side cooling water flow path surface 22 is located on the opposite side to the oxidant gas flow path surface .

[0025] As shown in FIG. 3, the cathode separator 20 is provided with an oxidant gas supply port 25a, a fuel gas supply port 25b, a cooling water supply port 25c, an oxidant gas discharge port 25d, a fuel gas discharge port 25e, and a cooling water discharge port 25f. These supply ports 25a to 25c and discharge ports 25d to 25f penetrate the cathode separator 20. Each of the supply ports 25a to 25c is located on one side of the cathode cooling water flow path 40, and each of the discharge ports 25d to 25f is located on the other side of the cathode cooling water flow path 40. More specifically, as shown in FIG. 3, each of the supply ports 25a to 25c is located on the negative side of the X-axis of the cathode cooling water flow path 40, and each of the discharge ports 25d to 25f is located on the positive side of the X-axis of the cathode cooling water flow path 40. In other words, in the X-axis direction (a second direction perpendicular to a first direction described later), the cathode side cooling water flow path 40 is located between each of the supply ports 25a to 25c and each of the discharge ports 25d to 25f. Each of the supply ports 25a to 25c and each of the discharge ports 25d to 25f may have the same planar shape.

[0026] The oxidant gas supply port 25a overlaps with and communicates with the oxidant gas supply port 15a of the electrode frame 15. The fuel gas supply port 25b overlaps with and communicates with the fuel gas supply port 15b of the electrode frame 15. The cooling water supply port 25c overlaps with and communicates with the cooling water supply port 15c of the electrode frame 15. The oxidant gas exhaust port 25d overlaps with and communicates with the oxidant gas exhaust port 15d of the electrode frame 15. The fuel gas exhaust port 25e overlaps with and communicates with the fuel gas exhaust port 15e of the electrode frame 15. The cooling water exhaust port 25f overlaps with and communicates with the cooling water exhaust port 15f of the electrode frame 15.

[0027] The cathode-side cooling water flow path 40 includes a cathode-side electrode flow path section 41 overlapping the cathode electrode 12, a supply-side flow path section 42, and a discharge-side flow path section 43. The supply-side flow path section 42 is located between the cooling water supply port 25c and the cathode-side electrode flow path section 41, and cooling water is supplied from the cooling water supply port 25c through the supply-side flow path section 42 to the cathode-side electrode flow path section 41. The discharge-side flow path section 43 is located between the cathode-side electrode flow path section 41 and the cooling water discharge port 25f, and cooling water is discharged from the cathode-side electrode flow path section 41 through the discharge-side flow path section 43 to the cooling water discharge port 25f.

[0028] The cathode electrode flow passage section 41 includes a cathode side turn-back flow passage section 44. The cathode side turn-back flow passage section 44 is located at a position overlapping the cathode electrode 12. In the cathode side turn-back flow passage section 44, the cathode side flow passage groove constituting the cathode side cooling water flow passage 40 is formed so as to turn back. The oxidant gas flow passage 30 has a serpentine flow passage structure, thereby forming the cathode side turn-back flow passage section 44.

[0029] The cathode-side cooling water flow passage 40 includes a first cathode-side flow groove 45 and a second cathode-side flow groove 46. The first cathode-side flow groove 45 and the second cathode-side flow groove 46 are arranged in parallel at a predetermined arrangement pitch T. The cathode-side cooling water flow passage 40 may include a cathode-side flow groove other than the first cathode-side flow groove 45 and the second cathode-side flow groove 46. All the cathode-side flow grooves including the first cathode-side flow groove 45 and the second cathode-side flow groove 46 may be arranged in parallel at a predetermined arrangement pitch T. This arrangement pitch T may be the same as the pitch of the oxidant gas flow groove 31 described above. The number of cathode-side flow grooves including the first cathode-side flow groove 45 and the second cathode-side flow groove 46 is arbitrary as long as it is two or more. The cathode side flow passage grooves constituting the cathode side cooling water flow passage 40 are formed in a concave shape on the cathode side cooling water flow passage surface 22 .

[0030] In the cathode-side turnback flow passage section 44, the first cathode-side flow passage groove 45 includes a cathode-side terminal groove 45a that branches off, extends in the first direction, and terminates. As shown in Fig. 3, the cathode-side terminal groove 45a extends in the Y-axis direction.

[0031] The first cathode side flow channel 45 includes a cathode side base end groove 45b extending in the X-axis direction. The cathode side terminal groove 45a branches off and is connected to the cathode side base end groove 45b. The first cathode side flow channel 45 is formed in a T-shape in the cathode side folded flow channel section 44. The cathode side base end groove 45b communicates with the cooling water supply port 25c via the supply side flow channel section 42, and communicates with the cooling water discharge port 25f via the discharge side flow channel section 43.

[0032] In the cathode-side folded flow passage section 44, the second cathode-side flow passage groove 46 includes a cathode-side folded groove 46a that folds back around the cathode-side terminal groove 45a. As shown in Fig. 3, the cathode-side folded groove 46a is formed in a rectangular U-shape so as to fold back in the Y-axis direction along the cathode-side terminal groove 45a. The portion of the cathode-side folded groove 46a that extends in the Y-axis direction is parallel to the cathode-side terminal groove 45a.

[0033] In the present embodiment, the first cathode side flow channel 45 and the second cathode side flow channel 46 are adjacent to each other. Around the outer periphery of the cathode side turn-back groove 46a, turn-back grooves constituting other cathode side flow channel may be formed.

[0034] The cathode-side cooling water flow passage 40 may include a plurality of cathode-side turn-back flow passage sections 44. Although an example in which three cathode-side turn-back flow passage sections 44 are formed is shown in Fig. 3, the number of the cathode-side turn-back flow passage sections 44 is arbitrary. In the example shown in Fig. 3, the cathode-side cooling water flow passage 40 includes two first cathode-side flow passage grooves 45 and two second cathode-side flow passage grooves 46.

[0035] As shown in FIG. 3, in the cathode side turn-back flow passage sections 44 located on both sides (left and right sides) in the X-axis direction, the first cathode side flow passage groove 45 constituting the cathode side terminal groove 45a is located on the most positive side of the Y-axis. In the cathode side turn-back flow passage section 44 located in the center in the X-axis direction, the first cathode side flow passage groove 45 constituting the cathode side terminal groove 45a is located on the most negative side of the Y-axis. The cathode side turn-back groove 46a of the second cathode side flow passage groove 46 is formed around this cathode side terminal groove 45a. Another cathode side flow passage groove may be arranged in parallel with the arrangement pitch T between the two second cathode side flow passage grooves 46. Alternatively, the two second cathode side flow passage grooves 46 may be formed of one common cathode side flow passage groove. In this case, the cathode side cooling water flow passage 40 may be formed of three cathode side flow passage grooves.

[0036] The cathode-side separator 20 in this embodiment may be produced by pressing a metal plate, injection molding of a carbon material, etc. As a result, the cathode-side separator 20 has a generally wavy cross section as shown in FIG.

[0037] More specifically, as described above, the oxidant gas flow grooves 31 are formed in a concave shape in the oxidant gas flow surface 21. Between adjacent oxidant gas flow grooves 31, a cathode-side protrusion 32 is formed protruding toward the cathode electrode 12 and adjacent to the cathode electrode 12. The cathode-side flow grooves including the first cathode-side flow groove 45 and the second cathode-side flow groove 46 are each formed in a concave shape on the back side of the cathode-side protrusion 32.

[0038] Next, the anode side separator 50 will be described with reference to Fig. 1 and Fig. 4. Fig. 4 shows the anode side cooling water flow path 70 when looking at the anode side cooling water flow path surface 52. In Fig. 4, for convenience, the flow path groove is indicated by a single thick line.

[0039] 1, the anode side separator 50 includes a fuel gas flow path 60 facing the anode electrode 13, and an anode side cooling water flow path 70 facing the cathode side separator 20. The anode side separator 50 may be impermeable to the fuel gas and the cooling water.

[0040] The fuel gas flow passage 60 is provided on the fuel gas flow passage surface 51 adjacent to the anode electrode 13. The fuel gas flowing through the fuel gas flow passage 60 is supplied to the anode electrode 13. The fuel gas flow passage 60 includes a plurality of fuel gas flow passage grooves 61 arranged in parallel at a predetermined pitch. This pitch may be the same as the pitch of the oxidant gas flow passage grooves 31 described above. The fuel gas flow passage grooves 61 may be arranged at equal intervals. The fuel gas flow passage grooves 61 are formed in a concave shape on the fuel gas flow passage surface 51. The fuel gas flow passage 60 has a serpentine flow passage structure, and each fuel gas flow passage groove 61 is formed so as to fold back. The fuel gas flow passage grooves 61 are formed so as to fold back at a portion facing the anode electrode 13.

[0041] The anode side cooling water flow path 70 is provided on the anode side cooling water flow path surface 52 adjacent to the cathode side separator 20. The anode side cooling water flow path surface 52 is located on the opposite side to the fuel gas flow path surface 51.

[0042] As shown in FIG. 4, the anode-side separator 50 is provided with an oxidant gas supply port 55a, a fuel gas supply port 55b, a cooling water supply port 55c, an oxidant gas discharge port 55d, a fuel gas discharge port 55e, and a cooling water discharge port 55f. These supply ports 55a to 55c and discharge ports 55d to 55f penetrate the anode-side separator 50. Each of the supply ports 55a to 55c is located on one side of the anode-side cooling water flow path 70, and each of the discharge ports 55d to 55f is located on the other side of the anode-side cooling water flow path 70. More specifically, as shown in FIG. 4, each of the supply ports 55a to 55c is located on the negative side of the anode-side cooling water flow path 70 along the X-axis, and each of the discharge ports 55d to 55f is located on the positive side of the anode-side cooling water flow path 70 along the X-axis. In other words, in the X-axis direction (second direction), the anode side cooling water flow path 70 is located between each of the supply ports 55a to 55c and each of the discharge ports 55d to 55f. Each of the supply ports 55a to 55c and each of the discharge ports 55d to 55f may have the same planar shape.

[0043] The oxidant gas supply port 55a overlaps with and communicates with the oxidant gas supply port 15a of the electrode frame 15. The fuel gas supply port 55b overlaps with and communicates with the fuel gas supply port 15b of the electrode frame 15. The cooling water supply port 55c overlaps with and communicates with the cooling water supply port 15c of the electrode frame 15. The oxidant gas exhaust port 55d overlaps with and communicates with the oxidant gas exhaust port 15d of the electrode frame 15. The fuel gas exhaust port 55e overlaps with and communicates with the fuel gas exhaust port 15e of the electrode frame 15. The cooling water exhaust port 55f overlaps with and communicates with the cooling water exhaust port 15f of the electrode frame 15.

[0044] The anode-side cooling water flow path 70 includes an anode-side electrode flow path section 71 overlapping the anode electrode 13, a supply-side flow path section 72, and a discharge-side flow path section 73. The supply-side flow path section 72 is located between the cooling water supply port 55c and the anode-side electrode flow path section 71, and cooling water is supplied from the cooling water supply port 55c through the supply-side flow path section 72 to the anode-side electrode flow path section 71. The discharge-side flow path section 73 is located between the anode-side electrode flow path section 71 and the cooling water discharge port 55f, and cooling water is discharged from the anode-side electrode flow path section 71 through the discharge-side flow path section 73 to the cooling water discharge port 55f.

[0045] The anode-side electrode flow passage section 71 includes an anode-side turn-back flow passage section 74. The anode-side turn-back flow passage section 74 is located at a position overlapping the anode electrode 13. In the anode-side turn-back flow passage section 74, the anode-side flow passage groove constituting the anode-side cooling water flow passage 70 is formed so as to turn back. The anode-side turn-back flow passage section 74 is formed by the fuel gas flow passage 60 having a serpentine flow passage structure.

[0046] The anode-side cooling water flow passage 70 includes a first anode-side flow groove 75 and a second anode-side flow groove 76. The first anode-side flow groove 75 and the second anode-side flow groove 76 are arranged in parallel at a predetermined arrangement pitch T. The anode-side cooling water flow passage 70 may include an anode-side flow groove other than the first anode-side flow groove 75 and the second anode-side flow groove 76. All the anode-side flow grooves including the first anode-side flow groove 75 and the second anode-side flow groove 76 may be arranged in parallel at a predetermined arrangement pitch T. This arrangement pitch T may be the same as the pitch of the fuel gas flow groove 61 described above. The number of anode-side flow grooves including the first anode-side flow groove 75 and the second anode-side flow groove 76 is arbitrary as long as it is two or more. The anode-side flow grooves constituting the anode-side cooling water flow passage 70 are formed in a concave shape on the anode-side cooling water flow passage surface 52.

[0047] In the anode-side turn-back flow passage section 74, the first anode-side flow passage groove 75 includes an anode-side terminal groove 75a that branches off, extends in the first direction, and terminates. As shown in Fig. 4, the anode-side terminal groove 75a extends in the Y-axis direction.

[0048] The first anode side flow channel 75 includes an anode side base end groove 75b extending in the X-axis direction. The anode side terminal groove 75a branches off and is connected to the anode side base end groove 75b. The first anode side flow channel 75 is formed in a T-shape in the anode side folded back flow channel section 74. The anode side base end groove 75b communicates with the cooling water supply port 55c via the supply side flow channel section 72, and communicates with the cooling water discharge port 55f via the discharge side flow channel section 73.

[0049] In the anode-side folded flow passage section 74, the second anode-side flow passage groove 76 includes an anode-side folded groove 76a that folds back around the anode-side terminal groove 75a. As shown in Fig. 4, the anode-side folded groove 76a is formed into a rectangular U-shape so as to fold back in the Y-axis direction along the anode-side terminal groove 75a. The portion of the anode-side folded groove 76a that extends in the Y-axis direction is parallel to the anode-side terminal groove 75a.

[0050] In the present embodiment, the first anode side flow groove 75 and the second anode side flow groove 76 are adjacent to each other. Around the outer periphery of the anode side turn-back groove 76a, turn-back grooves constituting other anode side flow grooves may be formed.

[0051] The anode-side cooling water flow path 70 may include a plurality of anode-side turn-back flow path sections 74. Although Fig. 4 shows an example in which three anode-side turn-back flow path sections 74 are formed, the number of anode-side turn-back flow path sections 74 is arbitrary. In the example shown in Fig. 4, the anode-side cooling water flow path 70 includes two first anode-side flow path grooves 75 and two second anode-side flow path grooves 76.

[0052] As shown in FIG. 4, in the anode side turn-back flow passage sections 74 located on both sides (left and right sides) in the X-axis direction, the first anode side flow passage groove 75 constituting the anode side end groove 75a is located furthest on the Y-axis positive side. In the anode side turn-back flow passage section 74 located in the center in the X-axis direction, the first anode side flow passage groove 75 constituting the anode side end groove 75a is located furthest on the Y-axis negative side. The anode side turn-back groove 76a of the second anode side flow passage groove 76 is formed around this anode side end groove 75a. Another anode side flow passage groove may be arranged in parallel with the arrangement pitch T between the two second anode side flow passage grooves 76. Alternatively, the two second anode side flow passage grooves 76 may be formed of a common anode side flow passage groove. In this case, the anode side cooling water flow passage 70 may be formed of three anode side flow passage grooves.

[0053] The anode-side separator 50 in this embodiment may be produced by pressing a metal plate, injection molding of a carbon material, etc. As a result, the anode-side separator 50 has a generally wavy cross section as shown in FIG.

[0054] More specifically, as described above, the fuel gas flow grooves 61 are formed in a concave shape in the fuel gas flow surface 51. Between adjacent fuel gas flow grooves 61, an anode side protrusion 62 is formed protruding toward the anode electrode 13 and adjacent to the anode electrode 13. The anode side flow grooves including the first anode side flow groove 75 and the second anode side flow groove 76 are each formed in a concave shape on the back side of the anode side protrusion 62.

[0055] When viewed in the stacking direction of the fuel cell 3 (the Z-axis direction shown in FIG. 1), in the second direction (the X-axis direction), each anode side turn-back flow passage section 74 is shifted by the arrangement pitch T from the corresponding cathode side turn-back flow passage section 44. In the example shown in FIG. 3 and FIG. 4, each anode side turn-back flow passage section 74 is shifted by the arrangement pitch T on the negative side of the X-axis from the corresponding cathode side turn-back flow passage section 44. As shown in FIG. 3, when the distance between the leftmost cathode side terminal groove 45a and the cooling water supply port 25c is C1 and the distance between the rightmost cathode side terminal groove 45a and the cooling water discharge port 25f is C2, C1>C2. The difference between C1 and C2 is half the arrangement pitch T described above. 4, when the distance between the leftmost anode side terminal groove 75a and the cooling water supply port 55c is A1 and the distance between the rightmost anode side terminal groove 75a and the cooling water discharge port 55f is A2, A2>A1. The difference between A2 and A1 is half the arrangement pitch T described above.

[0056] The planar shape of the anode-side cooling water flow path 70 is the same as the planar shape of the cathode-side cooling water flow path 40. The cross-sectional shape of each flow path groove of the anode-side cooling water flow path 70 is also the same as the cross-sectional shape of each flow path groove of the cathode-side cooling water flow path 40. The anode-side cooling water flow path 70 shown in FIG. 4 is obtained by inverting the cathode-side cooling water flow path 40 shown in FIG. 3 in the X-axis direction. That is, in this embodiment, the shape of the cathode-side separator 20 and the shape of the anode-side separator 50 are the same.

[0057] Next, the configuration of the cooling water flow path will be described in more detail with reference to Fig. 5. The cooling water flow path is composed of a cathode side cooling water flow path 40 and an anode side cooling water flow path 70. In Fig. 5, the cathode side cooling water flow path 40 is shown by a solid line, and the anode side cooling water flow path 70 is shown by a dashed line. The cathode side cooling water flow path 40 and the anode side cooling water flow path 70 may overlap in many parts, but in Fig. 5, they are shown shifted in the X-axis direction and the Y-axis direction for convenience. In addition, the cathode side cooling water flow path surface 22 is hatched to clarify the drawing.

[0058] As described above, the anode side turn-back flow passage section 74 is shifted by the arrangement pitch T from the cathode side turn-back flow passage section 44. Therefore, as shown in FIG. 5 and FIG. 6, the cathode side end groove 45a of the first cathode side flow passage groove 45 faces the anode side turn-back groove 76a of the second anode side flow passage groove 76 at the facing position P1. As a result, the cathode side end groove 45a and the anode side turn-back groove 76a communicate with each other, and the cooling water can flow between the cathode side end groove 45a and the anode side turn-back groove 76a. Therefore, it is possible to prevent the cooling water from stagnation in the cathode side end groove 45a. In this embodiment, the cathode side end groove 45a and the anode side end groove 75a do not face each other.

[0059] Each cathode side flow channel of the cathode side cooling water flow channel 40 faces and communicates with each anode side flow channel of the anode side cooling water flow channel 70. For example, the cathode side turn-back groove 46a of the second cathode side flow channel 46 faces the anode side turn-back groove 76a of the second anode side flow channel 76 at the facing position P2. This allows the cathode side turn-back groove 46a and the anode side turn-back groove 76a to communicate with each other, allowing cooling water to flow between the cathode side turn-back groove 46a and the anode side turn-back groove 76a.

[0060] The cathode side flow groove includes a cathode side opposing portion 47 that faces an anode side cooling water flow surface 52 located between the anode side flow grooves. The flow cross-sectional area of ​​the cathode side opposing portion 47 is approximately half the flow cross-sectional area of ​​the portion where the cathode side flow groove and the anode side flow groove face each other. However, since the cathode side flow grooves are formed continuously, the cooling water can flow smoothly through each flow groove.

[0061] 5, the anode side terminal groove 75a of the first anode side flow groove 75 faces the cathode side turn-back groove 46a of the second cathode side flow groove 46 at the facing position P3. This allows the anode side terminal groove 75a and the cathode side turn-back groove 46a to communicate with each other, allowing the cooling water to flow between the anode side terminal groove 75a and the cathode side turn-back groove 46a. This makes it possible to prevent the cooling water from stagnation in the anode side terminal groove 75a.

[0062] Each flow groove of the anode side cooling water flow path 70 faces and communicates with each flow groove of the cathode side cooling water flow path 40. For example, the anode side turn groove 76a of the second anode side flow path groove 76 faces the cathode side turn groove 46a of the second cathode side flow path groove 46 at the facing position P2. This allows the anode side turn groove 76a and the cathode side turn groove 46a to communicate with each other, allowing cooling water to flow between the anode side turn groove 76a and the cathode side turn groove 46a.

[0063] 5 and 6, the anode-side flow groove includes an anode-side opposing portion 77 that faces the cathode-side cooling water flow surface 22 located between the cathode-side flow grooves. The flow cross-sectional area of ​​the anode-side opposing portion 77 is approximately half the flow cross-sectional area of ​​the portion where the anode-side flow groove and the cathode-side flow groove face each other. However, since the anode-side flow grooves are formed continuously, the cooling water can flow smoothly through each flow groove.

[0064] A result of a computational fluid analysis of the flow of cooling water in the cooling water flow passage configured as described above is shown in Fig. 7. Fig. 7 representatively shows a result of a computational fluid analysis of the anode side cooling water flow passage.

[0065] As shown in FIG. 7, the cooling water in the anode end groove 75a has a flow velocity. This confirms that the cooling water flows in the anode end groove 75a and does not stagnate. It can be said that the cooling water in the cathode end groove 45a also has a flow velocity. In FIG. 7, a low cooling water flow velocity means a flow velocity that is a certain value other than zero, and means that the flow velocity is relatively low.

[0066] It is also shown that cooling water flows throughout the anode-side cooling water flow passage 70. This confirms that the anode electrode 13 can be effectively cooled. It can also be said that cooling water can flow throughout the cathode-side cooling water flow passage 40.

[0067] Thus, according to this embodiment, the cathode side end groove 45a of the cathode side cooling water flow passage 40 faces the anode side return groove 76a of the anode side cooling water flow passage 70. This allows the cathode side end groove 45a to communicate with the anode side return groove 76a, and allows cooling water to flow between the cathode side end groove 45a and the anode side return groove 76a. This prevents the cooling water from stagnating in the cathode side end groove 45a. In this case, it is possible to prevent a local potential difference from occurring locally in the cathode side separator 20, thereby preventing the local battery phenomenon from occurring. As a result, it is possible to prevent local corrosion from occurring, and improve quality.

[0068] In addition, according to this embodiment, the anode side end groove 75a of the anode side cooling water flow passage 70 faces the cathode side return groove 46a of the cathode side cooling water flow passage 40. This allows the anode side end groove 75a to communicate with the cathode side return groove 46a, and allows the cooling water to flow between the anode side end groove 75a and the cathode side return groove 46a. This prevents the cooling water from stagnating in the anode side end groove 75a. In this case, it is possible to prevent a local potential difference from occurring locally in the anode side separator 50, thereby preventing the local cell phenomenon from occurring. As a result, it is possible to prevent local corrosion from occurring, and improve the quality of the fuel cell stack 2.

[0069] According to the present embodiment, the first cathode side flow groove 45 including the cathode side terminal groove 45a and the second cathode side flow groove 46 including the cathode side turn-back groove 46a are adjacent to each other. The first anode side flow groove 75 including the anode side terminal groove 75a and the second anode side flow groove 76 including the anode side turn-back groove 76a are adjacent to each other. In this case, the anode side turn-back flow section 74 is shifted from the cathode side turn-back flow section 44 by the arrangement pitch T. This can reduce the amount of shift between the cathode side turn-back flow section 44 and the anode side turn-back flow section 74. Therefore, the oxidant gas flow path 30 can be prevented from being shifted from the cathode electrode 12, and the supply of the oxidant gas to the cathode electrode 12 can be made uniform. Similarly, the fuel gas flow path 60 can be prevented from being shifted from the anode electrode 13, and the supply of the fuel gas to the anode electrode 13 can be made uniform. As a result, the quality of the fuel cell stack 2 can be improved.

[0070] Furthermore, according to this embodiment, the planar shape of the cathode-side cooling water flow path 40 is the same as the planar shape of the anode-side cooling water flow path 70. This allows the shape of the cathode-side separator 20 and the anode-side separator 50 to be the same, allowing the separators to be standardized. This makes it possible to reduce the number of types of parts. Furthermore, when the separators are produced by press working, the cathode-side separator 20 and the anode-side separator 50 can be produced using a common die, allowing the production costs to be reduced.

[0071] Furthermore, according to the present embodiment, the cathode-side protrusions 32 that protrude toward the cathode electrode 12 and are adjacent to the cathode electrode 12 are formed between adjacent oxidant gas flow grooves 31, and the first cathode-side flow groove 45 and the second cathode-side flow groove 46 are each formed in a concave shape on the back side of the cathode-side protrusions 32. This allows the cathode-side separator 20 to be produced by press working, and the production cost of the cathode-side separator 20 can be reduced.

[0072] Furthermore, according to the present embodiment, an anode-side protrusion 62 is formed between adjacent fuel gas flow grooves 61 so as to protrude toward the anode 13 and be adjacent to the anode 13, and the first anode-side flow groove 75 and the second anode-side flow groove 76 are each formed in a concave shape on the back side of the anode-side protrusion 62. This allows the anode-side separator 50 to be produced by press working, thereby reducing the production cost of the anode-side separator 50.

[0073] In the above-described embodiment, an example has been described in which the first cathode side flow groove 45 and the second cathode side flow groove 46 are adjacent to each other, and the first anode side flow groove 75 and the second anode side flow groove 76 are adjacent to each other. In this case, the anode side turn-back flow groove 74 is shifted from the cathode side turn-back flow groove 44 by the arrangement pitch T. However, this is not limited to this. For example, the amount of shift between the anode side turn-back flow groove 74 and the cathode side turn-back flow groove 44 may be an integer multiple of twice or more the arrangement pitch T. In this case, one or more other cathode flow grooves may be interposed between the first cathode side flow groove 45 and the second cathode side flow groove 46, and one or more other anode side flow grooves may be interposed between the first anode side flow groove 75 and the second anode side flow groove 76.

[0074] According to the embodiment described above, it is possible to prevent the cooling medium from stagnating.

[0075] Although the embodiments and some modifications of the present invention have been described, these embodiments and modifications are presented as examples and are not intended to limit the scope of the invention. These new embodiments and modifications can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims. In addition, it is of course possible to combine these embodiments and modifications in part as appropriate within the gist of the present invention. [Explanation of symbols]

[0076] 1: fuel cell, 2: fuel cell stack, 3: fuel cell unit, 11: membrane electrode assembly, 12: cathode electrode, 13: anode electrode, 20: cathode side separator, 30: oxidant gas flow path, 31: oxidant gas flow path groove, 32: cathode side protrusion, 40: cathode side cooling water flow path, 44: cathode side turn-back flow path portion, 45: first cathode side flow path groove, 45a: cathode side terminal groove, 46: second cathode side flow path groove, 46a: cathode side turn-back groove, 50: anode side separator, 60: fuel gas flow path, 61: fuel gas flow path groove, 62: anode side protrusion, 70: anode side cooling water flow path, 74: anode side turn-back flow path portion, 75: first anode side flow path groove, 75a: anode side terminal groove, 76: second anode side flow path groove, 76a: anode side turn-back groove

Claims

1. A fuel cell system includes a plurality of fuel cells stacked on top of one another, The fuel cell is a membrane electrode assembly including a cathode electrode and an anode electrode; a cathode-side separator adjacent to the cathode electrode; an anode-side separator adjacent to the anode electrode; the cathode-side separator includes an oxidant gas flow path facing the cathode electrode and a cathode-side coolant flow path facing the anode-side separator, the cathode-side coolant flow field includes a first cathode-side flow groove and a second cathode-side flow groove arranged in parallel, and a cathode-side turn-back flow field provided at a position overlapping the cathode electrode, In the cathode-side turn-back flow passage section, the first cathode-side flow passage groove includes a cathode-side terminal groove that branches off and extends in a first direction and terminates, and the second cathode-side flow passage groove includes a cathode-side turn-back groove that turns back around the cathode-side terminal groove, the anode-side separator includes a fuel gas flow field facing the anode electrode and an anode-side coolant flow field facing the cathode-side separator, the anode-side coolant flow field includes a first anode-side flow groove and a second anode-side flow groove arranged in parallel, and an anode-side turn-back flow field portion provided at a position overlapping the anode electrode, in the anode-side turn-back flow channel section, the first anode-side flow channel includes an anode-side terminal groove that branches off to extend in the first direction and terminate, and the second anode-side flow channel includes an anode-side turn-back groove that turns back around the anode-side terminal groove, The cathode side end groove faces the anode side fold groove, and the anode side end groove faces the cathode side fold groove.

2. the first cathode side flow groove and the second cathode side flow groove are adjacent to each other, 2. The fuel cell stack according to claim 1, wherein the first anode side flow groove and the second anode side flow groove are adjacent to each other.

3. 3. The fuel cell stack according to claim 1, wherein a planar shape of the anode side coolant flow field is the same as a planar shape of the cathode side coolant flow field.

4. the oxidant gas flow field includes a plurality of oxidant gas flow field grooves, a cathode-side protrusion protruding toward the cathode electrode and adjacent to the cathode electrode is formed between the adjacent oxygen-containing gas flow grooves; 4. The fuel cell stack according to claim 1, wherein the first cathode side flow groove and the second cathode side flow groove are each formed in a concave shape on a rear side of the cathode side protrusion.

5. the fuel gas flow field includes a plurality of fuel gas flow field grooves, an anode-side protrusion protruding toward the anode electrode and adjacent to the anode electrode is formed between the adjacent fuel gas flow grooves; 4. The fuel cell stack according to claim 1, wherein the first anode side flow groove and the second anode side flow groove are each formed in a concave shape on a rear side of the anode side protrusion.

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