Method for manufacturing fuel cell

Abstract

To adhere a separator to a resin member with high adhesive strength.SOLUTION: A manufacturing method of a fuel cell includes a laser irradiation step and an adhesion step. In the laser irradiation step, by irradiating a carbon film covering the surface of a metal plate of a separator having the metal plate and the carbon film with laser, the carbon film is removed within the irradiation range of the laser to expose the metal plate. In the adhesion step, the separator is adhered to a resin member in a range including at least a part of the range where the metal plate is exposed.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a method for manufacturing a fuel cell.

[0002] The fuel cell disclosed in Patent Document 1 has a structure in which a resin frame (also called a resin sheet) is sandwiched and fixed between a pair of separators. Each separator is bonded to the resin frame. The resin frame has through holes that are covered by the pair of separators. A membrane / electrode assembly is disposed in the through holes. In addition, a gasket is bonded to the back surface of one of the separators (the surface opposite to the surface bonded to the resin frame). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-129213 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the fuel cell of Cited Document 1, the surface of the separator is covered with a carbon film. That is, the separator is composed of a metal plate and a carbon film covering the surface of the metal plate. For this reason, the carbon film is bonded to a resin member such as a resin frame or a gasket. When bonding a resin member to a carbon film, it is difficult to bond the resin member with a high adhesive strength.

[0005] The separator may also have a structure in which the metal plate is exposed on the surface (i.e., a structure in which the surface is not covered with a carbon film). In this type of separator, dirt (e.g., lubricating oil used when processing the metal plate) may be attached to the surface of the separator. The dirt on the surface of the metal plate can be removed by irradiating the separator with a laser, and the separator can then be bonded to a resin member. However, because the separator (i.e., the metal plate) has a glossy surface, the laser is easily reflected by the separator surface, and the laser is difficult to absorb by the separator. This makes it difficult to thoroughly remove dirt from the surface of the separator, and therefore difficult to bond the separator to the resin member with high adhesive strength.

[0006] As described above, in conventional fuel cells, it is difficult to bond the separator to the resin member with high strength. Therefore, there is a problem that the adhesive portion between the separator and the resin member is easily peeled off due to the pressure (pressure of various gases and pressure of refrigerant) generated in the fuel cell. In this specification, a manufacturing method of a fuel cell capable of bonding the separator to the resin member with high adhesive strength is proposed. [Means for solving the problem]

[0007] The method for manufacturing a fuel cell disclosed in this specification includes a laser irradiation step and a bonding step. In the laser irradiation step, a carbon film of a separator having a metal plate and a carbon film covering a surface of the metal plate is irradiated with a laser to remove the carbon film within the laser irradiation area to expose the metal plate, and in the bonding step, the separator is bonded to a resin member within an area including at least a part of the area where the metal plate is exposed.

[0008] The carbon film may be any film containing elemental carbon.

[0009] In the laser irradiation process, the carbon film within the laser irradiation range is removed. Carbon films easily absorb lasers. Therefore, in the laser irradiation process, the temperature of the carbon film within the irradiation range easily rises, and the carbon film can be easily removed. In addition, since the carbon film easily rises in temperature, if dirt is present on the surface of the metal plate, the dirt is removed along with the carbon film. Therefore, the metal plate can be exposed with little dirt. Therefore, in the bonding process, the exposed area of ​​the metal plate can be bonded to the resin member with high adhesive strength. In this way, according to this manufacturing method, the separator can be bonded to the resin member with high adhesive strength. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a fuel cell stack. [Diagram 2] FIG. [Diagram 3] FIG. 7 is a cross-sectional view of a fuel cell (a cross-sectional view taken along line III-III in FIGS. 4 to 6). [Figure 4] FIG. 4 is a plan view of a surface 40b of the separator 40. [Diagram 5] FIG. 4 is a plan view of a surface 50a of a separator 50. [Figure 6] FIG. 4 is a plan view of a surface 40a of a separator 40. [Figure 7] FIG. 3 is a cross-sectional view of stacked fuel cells. [Figure 8] FIG. 4 is an explanatory diagram of a process for forming a carbon film. [Figure 9] FIG. [Figure 10] FIG. [Figure 11] FIG. [Figure 12] 1 is a graph showing the difference in peel strength between the presence and absence of a carbon film. [Figure 13] FIG. 11 is an explanatory diagram of a resin frame bonding step in Example 2. [Figure 14] FIG. 11 is an explanatory diagram of a resin frame bonding step in Example 2. [Figure 15] 1 is a graph showing the difference in peel strength depending on whether or not offset is performed. [Figure 16] Cross-sectional view when the widths of the ranges 40s and 50s are enlarged. [Figure 17] FIG. 11 is an explanatory diagram of a laser irradiation step in the third embodiment. [Figure 18] 1 is a diagram illustrating the relationship between contact angle and hydrophilicity. [Figure 19] FIG. 1 is a diagram illustrating the relationship between laser fluence and contact angle. [Figure 20] 13 is a graph showing the effect of the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The technical elements of the electric vehicle disclosed in this specification are listed below. Note that each of the technical elements below is useful independently.

[0012] In one example of the manufacturing method disclosed in the present specification, the resin member may be a resin frame having a through hole. The manufacturing method may further include a step of arranging a membrane / electrode assembly in the through hole. In the bonding step, the separator may be bonded to the resin frame so that the through hole is blocked by the separator. The step of arranging the membrane / electrode assembly in the through hole of the separator may be performed before the bonding step, after the bonding step, or simultaneously with the bonding step.

[0013] According to this configuration, the separator can be adhered to the resin frame with high adhesive strength.

[0014] In one example of the manufacturing method disclosed in the present specification, a gas flow path may be formed at an interface between the separator and the resin frame when the separator is bonded to the resin frame. The laser irradiation step and the bonding step may be performed to satisfy the following conditions: an irradiation area of ​​the laser is disposed away from the gas flow path and extends along the gas flow path, an adhesion area for bonding the separator to the resin frame is disposed away from the gas flow path and extends along the gas flow path, and a central axis of the irradiation area is disposed closer to the gas flow path than a central axis of the adhesion area.

[0015] According to this configuration, even if the width of the laser irradiation range is narrowed, high adhesive strength can be imparted to the bonding portion. In addition, by narrowing the width of the laser irradiation range, the laser irradiation process can be completed in a short time.

[0016] In one example of the manufacturing method disclosed in the present specification, when the separator is bonded to the resin frame, a gas flow path may be formed at the interface between the separator and the resin frame. In the bonding step, the separator may be bonded to the resin frame within the pressurized range by heating the pressurized range while pressing the separator toward the resin frame with a mold. The laser irradiation step and the bonding step may be performed to satisfy the following conditions: the laser irradiation range is disposed away from the gas flow path and extends along the gas flow path, the pressurized range is disposed away from the gas flow path and extends along the gas flow path, and the central axis of the irradiation range is disposed closer to the gas flow path than the central axis of the pressurized range.

[0017] According to this configuration, even if the width of the laser irradiation range is narrowed, high adhesive strength can be imparted to the bonding portion. In addition, by narrowing the width of the laser irradiation range, the laser irradiation process can be completed in a short time.

[0018] In one example of the manufacturing method disclosed in the present specification, the resin member may be a gasket. The separator may have a first surface covered with the carbon film and a second surface located on the opposite side of the first surface. The laser irradiation step may irradiate the first surface with the laser. The bonding step may bond the first surface to the gasket. The manufacturing method may further include a step of arranging a membrane / electrode assembly in a through hole of a resin frame having a through hole, and a step of bonding the second surface to the resin frame so that the through hole is blocked by the separator.

[0019] The step of placing the membrane / electrode assembly in the through-hole and the step of adhering the second surface to the resin frame may be performed before the laser irradiation step, after the laser irradiation step, or after the adhering step.

[0020] According to this configuration, the separator can be bonded to the gasket with high adhesive strength.

[0021] In the example manufacturing method disclosed in the present specification, a laser fluence in the laser irradiation step may be 100 mJ / mm2 or less. In the bonding step, the separator may be bonded to the resin member after an adhesion curing agent or an adhesion promoter is applied to the surface of the metal plate within the irradiation area.

[0022] By setting the laser fluence in the laser irradiation step to 100 mJ / mm2 or less, a porous structure can be formed on the surface of the metal plate within the irradiation range (i.e., the exposed surface). Therefore, when an adhesive hardener or an adhesion promoter is applied to the surface of the metal plate within the irradiation range, the adhesive hardener or adhesion promoter can be permeated into the porous structure. Therefore, in the bonding step, migration of the adhesive hardener or adhesion promoter from the surface of the metal plate to the resin member can be suppressed, and the metal plate can be bonded more appropriately.

[0023] In one example of the manufacturing method disclosed in the present specification, in the laser irradiation step, after performing a first laser irradiation for removing the carbon film, a laser beam having a larger intensity than that of the first laser irradiation is applied to a part or all of the region where the first laser irradiation has been performed. centre A second laser irradiation with a lower luminance may be performed.

[0024] According to this configuration, it is possible to reduce the hydrophilicity (i.e., improve the water repellency) of the surface of the metal plate within the second laser irradiation range (i.e., the exposed surface), thereby suppressing the decrease in adhesive strength caused by water generated in each fuel cell.

[0025] In one example of the manufacturing method disclosed in the present specification, the laser of the second laser irradiation centre Luens is 10-20mJ / mm 2 may be also possible.

[0026] According to this configuration, it is possible to more effectively prevent the adhesive strength from decreasing due to water.

[0027] The fuel cell stack 10 shown in FIG. 1 is composed of a stack of a plurality of fuel cell cells 12. In each of the drawings including FIG. 1, the direction in which the plurality of fuel cell cells 12 are stacked is indicated as the z direction, one direction perpendicular to the z direction is indicated as the x direction, and a direction perpendicular to the x direction and the z direction is indicated as the y direction. The fuel cell stack 10 is provided with flow paths 71-76. Each of the flow paths 71-76 extends in the z direction from an end face of the fuel cell stack 10. The flow path 71 is an oxidizing gas supply flow path, and the flow path 76 is an oxidizing gas discharge flow path. An oxidizing gas (oxygen (O2) in this embodiment) is supplied to each fuel cell cell 12 via the oxidizing gas supply flow path 71. The oxidizing gas that has passed through each fuel cell cell 12 is discharged to the outside of the fuel cell stack 10 via the oxidizing gas discharge flow path 76. The flow path 74 is a fuel gas supply flow path, and the flow path 73 is a fuel gas discharge flow path. A fuel gas (hydrogen (H2) in this embodiment) is supplied to each fuel cell cell 12 via the fuel gas supply flow path 74. The fuel gas that has passed through each fuel cell 12 is discharged to the outside of the fuel cell stack 10 via a fuel gas discharge flow path 73. By supplying fuel gas and oxidant gas to each fuel cell, power is generated in each fuel cell 12. Flow path 75 is a refrigerant supply flow path, and flow path 72 is a refrigerant discharge flow path. A refrigerant is supplied to each fuel cell 12 via the refrigerant supply flow path 75. The refrigerant that has passed through each fuel cell 12 is discharged to the outside of the fuel cell stack 10 via the refrigerant discharge flow path 72. Each fuel cell 12 is cooled by the refrigerant flowing inside the fuel cell stack 10.

[0028] FIG. 2 is an exploded perspective view of one fuel cell 12. As shown in FIG. 2, the fuel cell 12 has a membrane electrode assembly (hereinafter referred to as MEA (membrane electrode assembly)) 20, a resin frame 30, a separator 40, and a separator 50. The resin frame 30, the separator 40, and the separator 50 each have a plate shape and are stacked in the z direction. In the following, the surface of the resin frame 30 closer to the separator 40 is referred to as surface 30a, and the surface of the resin frame 30 on the opposite side is referred to as surface 30b. In the following, the surface of the separator 40 closer to the resin frame 30 is referred to as surface 40b, and the surface of the separator 40 on the opposite side is referred to as surface 40a. In the following, the surface of the separator 50 closer to the resin frame 30 is referred to as surface 50a, and the surface of the separator 50 on the opposite side is referred to as surface 50b. A through hole 36 is provided in the center of the resin frame 30, penetrating the resin frame 30 in the z direction. The MEA 20 is disposed in the through-hole 36. The surface 40b of the separator 40 is bonded to the surface 30a of the resin frame 30. The through-hole 36 is covered by the separator 40. The surface 50a of the separator 50 is bonded to the surface 30b of the resin frame 30. The through-hole 36 is covered by the separator 50. In this manner, the resin frame 30 is sandwiched between the separator 40 and the separator 50.

[0029] The resin frame 30, the separator 40, and the separator 50 are each provided with a through hole 71a corresponding to the flow path 71, a through hole 72a corresponding to the flow path 72, a through hole 73a corresponding to the flow path 73, a through hole 74a corresponding to the flow path 74, a through hole 75a corresponding to the flow path 75, and a through hole 76a corresponding to the flow path 76. When the fuel cell 12 is viewed in a plan view along the z direction, the through hole 36 (i.e., the MEA 20) is disposed between the through holes 71a, 72a, 73a and the through holes 74a, 75a, 76a.

[0030] The resin frame 30 is an insulating member. As shown in FIG. 3, the resin frame 30 has resin layers 31, 32, and 33 laminated in the z direction. The resin layers 31, 32, and 33 are all made of insulating resin (e.g., acid-modified polypropylene, etc.). The resin layer 31 has high rigidity. The resin layers 32 and 33 have thermoplasticity and exhibit high adhesion when softened. The resin layer 31 is sandwiched between the resin layer 32 and the resin layer 33. As will be described in detail later, the resin layer 32 is bonded to the separator 40, and the resin layer 33 is bonded to the separator 50.

[0031] The MEA 20 has an electrolyte membrane 21, an anode layer 22, and a cathode layer 23. The electrolyte membrane 21 is made of a solid polymer material. The anode layer 22 and the cathode layer 23 are made of a material in which conductive particles containing a catalyst such as platinum are dispersed in an electrolyte. The anode layer 22 covers the surface of the electrolyte membrane 21 closer to the separator 40. The cathode layer 23 covers the surface of the electrolyte membrane 21 closer to the separator 50.

[0032] The separator 40 is a conductive member. The separator 40 has a metal plate 41 and carbon films 42 and 43. The metal plate 41 is made of titanium (Ti) or a titanium alloy. The carbon film 42 covers the surface of the metal plate 41 on the side closer to the resin frame 30 and the MEA 20. The carbon film 43 covers the surface of the metal plate 41 located on the opposite side to the carbon film 42.

[0033] A part of the separator 40 is bent, and this forms a groove 44 on the surface 40b of the separator 40. As shown in FIG. 4, the groove 44 extends from the through hole 74a to the through hole 73a. A range 60 in FIG. 4 indicates a range in which the separator 40 faces the MEA 20 (a range in which the separator 40 overlaps with the MEA 20 when viewed along the z direction). The groove 44 extends in a serpentine manner within the range 60. As shown in FIG. 3, the surface 40b of the separator 40 contacts the resin frame 30 and the MEA 20 in a portion other than the groove 44. More specifically, the surface 40b contacts the resin layer 32 of the resin frame 30 and the anode layer 22 of the MEA 20 in a portion other than the groove 44. A fuel gas flow path 77 is formed by a space surrounded by the groove 44, the resin frame 30, and the MEA 20. The fuel gas flow path 77 extends along the interface between the separator 40 and the resin frame 30 and the interface between the separator 40 and the MEA 20. The fuel gas flowing in the fuel gas supply flow path 74 (through hole 74a) flows into the fuel gas flow path 77. The fuel gas flows from the upstream end to the downstream end in the fuel gas flow path 77, and then is discharged to the fuel gas discharge flow path 73 (through hole 73a).

[0034] As shown in FIG. 3, the carbon film 43 is not provided in a region 40s, which is a part of the surface 40b. The separator 40 is bonded to the resin layer 32 of the resin frame 30 in the region 40s. That is, the metal plate 41 in the region 40s is bonded to the resin layer 32 of the resin frame 30. As shown in FIG. 4, the region 40s where the carbon film 43 is not provided is provided along the outer periphery of the separator 40 on the surface 40b. Moreover, the region 40s is provided on the surface 40b so as to surround the through holes 71a, 72a, 75a, and 76a. The separator 40 is bonded to the resin frame 30 in the region 40s shown in FIG. 4.

[0035] The separator 50 is a conductive member. As shown in Fig. 3, the separator 50 has a metal plate 51 and carbon films 52 and 53. The metal plate 51 is made of titanium (Ti) or a titanium alloy. The carbon film 52 covers the surface of the metal plate 51 on the side closer to the resin frame 30 and the MEA 20. The carbon film 53 covers the surface of the metal plate 51 located on the opposite side to the carbon film 52.

[0036] As shown in FIG. 3, a part of the separator 50 is bent, and thus a groove 54 is provided on the surface 50a of the separator 50. As shown in FIG. 5, the groove 54 extends from the through hole 71a to the through hole 76a. A range 62 in FIG. 5 indicates a range where the separator 50 faces the MEA 20 (a range where the separator 50 overlaps with the MEA 20 when viewed along the z direction). The groove 54 extends in a meandering manner within the range 62. As shown in FIG. 3, the surface 50a of the separator 50 contacts the resin frame 30 and the MEA 20 in a portion other than the groove 54. More specifically, the surface 50a contacts the resin layer 33 of the resin frame 30 and the cathode layer 23 of the MEA 20 in a portion other than the groove 54. The space surrounded by the groove 54, the resin frame 30, and the MEA 20 constitutes an oxidant gas flow path 78. The oxidant gas flow path 78 extends along the interface between the separator 50 and the resin frame 30 and the interface between the separator 50 and the MEA 20. The oxidant gas flowing in the oxidant gas supply flow path 71 (through hole 71a) flows into the oxidant gas flow path 78. The oxidant gas flows from the upstream end to the downstream end in the oxidant gas flow path 78, and then is discharged to the oxidant gas discharge flow path 76 (through hole 76a).

[0037] As shown in FIG. 3, the carbon film 52 is not provided in a region 50s, which is a part of the surface 50a. The separator 50 is bonded to the resin layer 33 of the resin frame 30 in the region 50s. That is, the metal plate 51 in the region 50s is bonded to the resin layer 33 of the resin frame 30. As shown in FIG. 5, the region 50s in which the carbon film 52 is not provided is provided along the outer periphery of the separator 50 on the surface 50a. Moreover, the region 50s is provided on the surface 50a so as to surround the through holes 72a, 73a, 74a, and 75a. The separator 50 is bonded to the resin frame 30 in the region 50s shown in FIG. 5.

[0038] As shown in FIG. 3, the carbon film 42 is not provided in a region 40t that is a part of the surface 40a of the separator 40. A gasket 46 is bonded to the separator 40 (i.e., the metal plate 41) in the region 40t. As shown in FIG. 6, the region 40t where the carbon film 42 is not provided is provided so as to surround the through holes 71a, 73a, 74a, and 76a on the surface 40a. The region 40t is also provided so as to surround a region including the through holes 72a and 75a and the region 60 (a region overlapping with the MEA 20) on the surface 40a. The gasket 46 is provided along the region 40t. Hereinafter, the portion of the gasket 46 that is provided so as to surround the region including the through holes 72a and 75a and the region 60 is referred to as the gasket 46a. FIG. 7 shows a state where a plurality of fuel cells 12a and 12b are stacked in the z direction. When the fuel cells 12a, 12b are stacked, the gasket 46 of the fuel cell 12b comes into contact with the separator 50 of the fuel cell 12a. This forms a refrigerant flow path 80 surrounded by the gasket 46a and the separators 40 and 50. As shown in Fig. 6, the refrigerant flow path 80 is connected to the refrigerant supply flow path 75 and the refrigerant discharge flow path 72. The refrigerant flows from the refrigerant supply flow path 75 into the refrigerant flow path 80. The refrigerant that has flowed through the refrigerant flow path 80 from the upstream end to the downstream end is discharged into the refrigerant discharge flow path 72.

[0039] When the fuel cell 12 is operated, fuel gas is passed through the fuel gas flow passage 77, and oxidant gas is passed through the oxidant gas flow passage 78. As a result, fuel gas and oxidant gas are supplied to the MEA 20, and power is generated in the MEA 20. The power generated in the MEA 20 is taken out by the separators 40 and 50. That is, the separators 40 and 50 function as wiring. Since the surfaces of the separators 40 and 50 are covered with a carbon film, the separators 40 and 50 have high electrical conductivity. Therefore, power is supplied from the MEA 20 to the outside with little loss. In addition, when the fuel cell 12 is operated, a coolant is passed through the coolant flow passage 80. As a result, the MEA 20 is cooled. EXAMPLES

[0040] Next, a manufacturing method of the fuel cell 12 of Example 1 will be described. First, the through holes 71a-76a and the grooves 44 are formed in the metal plate 41 by pressing or the like. Similarly, the through holes 71a-76a and the grooves 54 are formed in the metal plate 51 by pressing or the like. Next, as shown in Fig. 8, the carbon films 42, 43 are formed so as to cover the entire surface of the metal plate 41. Similarly, the carbon films 52, 53 are formed so as to cover the entire surface of the metal plate 51. Here, the carbon films 42, 43, 52, 53 are formed to a thickness of 10 nm to 100 nm.

[0041] (Laser irradiation process) Next, as shown in FIG. 9, a part of the surface 40b of the separator 40 is irradiated with a laser L (e.g., a YAG laser) to remove the carbon film 43 within the laser irradiation range. As a result, a range 40s where the carbon film 43 has been removed is formed. Here, the range 40s is formed by moving the laser spot. As shown in FIG. 4, the range 40s is formed at a position away from the groove 44 (i.e., the flow path 77). In a part of the surface 40b (e.g., the range where the III-III line is located), the range 40s is formed so as to extend along the groove 44 (i.e., the flow path 77). The width of the laser irradiation range (i.e., the width of the range 40s) can be 1 to 10 mm. Since the carbon film 43 easily absorbs the laser, the separator 40 is heated to a high temperature within the laser irradiation range. As a result, the carbon film 43 is evaporated and removed. In addition, if dirt (e.g., lubricant residue) is attached to the surface of the metal plate 41, the dirt is evaporated along with the carbon film 43. Therefore, the metal plate 41 is exposed with almost no dirt present within the range 40s. Similarly, the carbon film 42 within the irradiated range is removed by irradiating a part of the surface 40a of the separator 40 with a laser, and a range 40t from which the carbon film 42 has been removed is formed as shown in Figs. 3 and 6. Similarly, the carbon film 52 within the irradiated range is removed by irradiating a part of the surface 50a of the separator 50 with a laser, and a range 50s from which the carbon film has been removed is formed as shown in Figs. 3 and 5. As shown in Fig. 5, the range 50s is formed at a position away from the groove 54 (i.e., the flow path 78). In a part of the range of the surface 50a (for example, the range where the III-III line is located), the range 50s is formed to extend along the groove 54 (i.e., the flow path 78).

[0042] (Separator bonding process) Next, as shown in FIG. 10, in a state where the MEA 20 is arranged in the through-hole 36 of the resin frame 30, the resin frame 30 is sandwiched between the separator 40 and the separator 50. Here, the surface 40b of the separator 40 is brought into contact with the resin frame 30 and the MEA 20, and the surface 50a of the separator 50 is brought into contact with the resin frame 30 and the MEA 20. In this manner, in a state where the through-hole 36 of the resin frame 30 is blocked by the separators 40 and 50, the separators 40 and 50 are bonded to the resin frame 30. That is, first, as shown in FIG. 10, a part of the laminate of the separator 40, the resin frame 30, and the separator 50 is sandwiched between the molds 90 and 92. Here, a part of the laminate including the ranges 40s and 50s is sandwiched between the molds 90 and 92. Next, while pressing the laminate with the molds 90 and 92, the pressed portion (i.e., the portion including the ranges 40s and 50s) is heated to 150 to 180°C through the molds 90 and 92. Then, the resin layers 32 and 33 soften in the vicinity of the molds 90 and 92. Then, when the laminate is cooled, the softened resin layers 32 and 33 harden. As a result, as shown in FIG. 11, the resin layer 32 is bonded to the separator 40 within the bonding area 40u, and the resin layer 33 is bonded to the separator 50 within the bonding area 50u. The bonding areas 40u and 50u are pressurized areas pressed by the molds 90 and 92. The bonding area 40u is formed at a position away from the flow path 77. The bonding area 40u is formed along the area 40s. Therefore, similar to the area 40s shown in FIG. 4, the adhesive area 40u is formed to extend along the flow path 77 in a portion of the surface 40b (for example, the area where the III-III line is located). As shown in FIG. 11, the adhesive area 50u is formed at a position away from the flow path 78. The adhesive area 50u is formed along the area 50s. Thus, similar to the area 50s shown in FIG. 5, the adhesive area 50u is formed to extend along the flow path 78 in a portion of the surface 50a (for example, the area where the III-III line is located). Here, as shown in FIG. 11, the resin layer 32 is adhered to the separator 40 within the adhesive area 40u which is wider than the area 40s. Therefore, the resin layer 32 is adhered to the metal plate 41 throughout the entire area 40s.Since the dirt has been removed from the surface of the metal plate 41 within the range 40s by the laser irradiation, the resin layer 32 is adhered to the metal plate 41 with high adhesive strength. Furthermore, the resin layer 33 is adhered to the separator 50 within an adhesion range 50u that is wider than the range 50s. Therefore, the resin layer 33 is adhered to the metal plate 51 throughout the entire range 50s. Since the dirt has been removed from the surface of the metal plate 51 within the range 50s by the laser irradiation, the resin layer 33 is adhered to the metal plate 51 with high adhesive strength.

[0043] (Gasket bonding process) Next, as shown in Fig. 3, a gasket 46 is adhered to a range 40t on the surface 40a of the separator 40. The gasket 46 may be adhered with an adhesive, or the gasket 46 may be adhered to the separator 40 when the gasket 46 is hardened. Because dirt has been removed from the surface of the metal plate 41 within the range 40t by the laser irradiation, the gasket 46 is adhered to the metal plate 41 with high adhesive strength. By adhering the gasket 46, the fuel cell 12 shown in Fig. 3 is completed.

[0044] As described above, according to the manufacturing method of Example 1, the separators 40, 50 can be bonded to the resin frame 30 with high adhesive strength, and the gasket 46 can be bonded to the separator 40 with high adhesive strength. FIG. 12 shows the peel strength of the bonded portion by the method of Example 1 and the bonded portion by the method of the comparative example. In the bonded portion by the method of Example 1, the separator 40 is bonded to the resin frame 30 in the range 40s where the carbon film 43 has been removed. In the bonded portion of the comparative example, the separator 40 is bonded to the resin frame 30 without removing the carbon film 43 (i.e., the carbon film 43 is bonded to the resin frame 30). As is clear from FIG. 12, according to the method of Example 1, a high peel strength can be obtained.

[0045] In Example 1, the resin member was bonded to the metal plate over substantially the entire area where the carbon film was removed. However, as long as at least a portion of the area where the carbon film was removed is included in the bonding area, bonding may be performed in any manner. For example, bonding may be performed only in a portion of the area where the carbon film was removed. EXAMPLES

[0046] Next, a manufacturing method of Example 2 will be described. The manufacturing method of Example 2 differs from Example 1 in that the areas 40s and 50s from which the carbon films 43 and 52 are removed are offset with respect to the adhesion areas 40u and 50u. In other respects, Example 2 is the same as Example 1.

[0047] FIG. 13 shows a separator bonding process of Example 2. As shown in FIG. 13, in Example 2, the central axes C2 and C3 of the ranges 40s and 50s are shifted in a direction closer to the gas flow channels 77 and 78 than the central axis C1 of the pressurized range in which the laminate is sandwiched between the dies 90 and 92. The pressurized range in which the laminate is sandwiched between the dies 90 and 92 partially overlaps with the ranges 40s and 50s from which the carbon films 43 and 52 have been removed. According to this method, as shown in FIG. 14, a configuration is obtained in which the ranges 40s and 50s are offset in a direction closer to the gas flow channels 77 and 78 than the bonding ranges 40u and 50u. That is, a configuration is obtained in which the central axes C2 and C3 of the ranges 40s and 50s are offset in a direction closer to the gas flow channels 77 and 78 than the central axis C1 of the bonding ranges 40u and 50u.

[0048] In the manufacturing method of the second embodiment, the resin frame 30 is bonded to the separators 40 and 50 in the ranges 40s and 50s from which the carbon films 43 and 52 have been removed, so that a high adhesive strength can be obtained. In addition, when the ranges 40s and 50s are offset in a direction closer to the gas flow paths 77 and 78 with respect to the bonding ranges 40u and 50u in this way, a higher adhesive strength can be obtained compared to the case where there is no offset (as in FIG. 11). FIG. 15 shows the results of measuring the peel strength of the bonding range 40u when the pressure in the fuel gas flow path 77 increases in the case where the range 40s is offset toward the fuel gas flow path 77 side with respect to the bonding range 40u (with offset) and the case where it is not offset (without offset). As shown in FIG. 15, a higher peel strength was obtained with the offset than without the offset. In this way, a higher adhesive strength can be obtained by offsetting the ranges from which the carbon films have been removed to the side closer to the gas flow path with respect to the bonding range. In addition, by widening the widths of the ranges 40s and 50s as shown in FIG. 16, an adhesive strength as high as that obtained when the offset is used can be obtained. However, when the width of the ranges 40s and 50s is increased, it is necessary to irradiate a wide range with the laser, and the laser irradiation process takes a long time. In contrast, in the configuration using offset as in FIG. 14, although the width of the ranges 40s and 50s (i.e., the width of the laser irradiation range) is narrow, an adhesive strength equivalent to that of the configuration in FIG. 16 can be obtained. Therefore, the laser irradiation process can be performed in a short time, and the fuel cell can be manufactured more efficiently. In this way, according to the manufacturing method of Example 2, a fuel cell having high adhesive strength can be manufactured in a short time. EXAMPLES

[0049] In the manufacturing method of Example 3, the laser fluence is controlled to 100 mJ / mm2 or less in the laser irradiation step, and an adhesion hardener or adhesion promoter is applied to the surface of the metal plate in the separator bonding step.

[0050] In the laser irradiation step of Example 3, the laser fluence is controlled to 100 mJ / mm2 or less. By controlling the laser fluence in this manner, as shown in FIG. 17, a porous structure 41p made of TiOx (titanium oxide) is formed on the surface of the metal plate 41 within the range 40s irradiated with the laser. Similarly, a porous structure is also formed on the surface of the metal plate within the ranges 50s and 40t. Here, a porous structure with a thickness of about 10 nm to 1000 nm is formed.

[0051] In the separator bonding process of Example 3, an adhesive hardener or an adhesion promoter is applied to the surface of the metal plates 41, 51 in the ranges 40s, 50s. Then, the adhesive hardener or the adhesion promoter permeates the porous structure. Thereafter, the part including the ranges 40s, 50s is heated while being pressurized by the molds 90, 92 as in Example 1 or 2. Since the viscosity of the adhesive hardener and the adhesion promoter is low, the adhesive hardener and the adhesion promoter are easily pushed out by the pressure of the molds 90, 92 and move outside the ranges 40s, 50s. However, if a porous structure is formed in the ranges 40s, 50s as in Example 3, the adhesive hardener or the adhesion promoter permeates the porous structure, so that the adhesive hardener or the adhesion promoter is easily retained in the ranges 40s, 50s. Therefore, bonding can be performed with a higher adhesive force in the ranges 40s, 50s.

[0052] In the gasket bonding process of Example 3, an adhesion hardener or adhesion promoter is applied to the surface of the metal plate 41 within the area 40t. The adhesion hardener or adhesion promoter then permeates the porous structure. Then, the gasket 46 is bonded within the area 40t in the same manner as in Examples 1 or 2. According to this method, the adhesion hardener or adhesion promoter is likely to remain within the area 40t, so that bonding can be performed with higher adhesive strength within the area 40t.

[0053] In the above-mentioned Examples 1 and 2, the adhesive hardener or the adhesion promoter was applied in the range of 40s, 5 May be applied within 0s and 40t. EXAMPLES

[0054] Example 4 differs from Examples 1 to 3 in the laser irradiation step. In other respects, Example 4 is the same as any one of Examples 1 to 3.

[0055] In the manufacturing method of Example 4, in the laser irradiation step, after performing a first laser irradiation for removing the carbon film, a part or all of the region where the first laser irradiation was performed is irradiated with a laser beam that is larger than the first laser irradiation. centre The second laser irradiation is performed with a smaller luminance. The types of lasers irradiated in the first laser irradiation and the second laser irradiation may be different. The second laser irradiation may be performed after the first laser irradiation is completed on the entire target area (for example, a range of 40s), or the second laser irradiation may be started on the part irradiated with the first laser while the first laser irradiation is being performed on the target area.

[0056] In the laser irradiation step of Example 4, first, the laser centre Luens 100mJ / mm 2 After performing the first laser irradiation at about 100 nm, the first laser irradiation is performed on a part or the whole of the region where the first laser irradiation is performed. centre Luens 10~20mJ / mm 2 The second laser irradiation is performed at about 1000 nm. centre The fluence is 10-20mJ / mm for the second laser irradiation. 2 However, this is not necessarily the case as long as the metal plate 41 is not significantly evaporated. centre Luence is 100mJ / mm 2 For example, in the fourth embodiment, a Yb fiber laser with a wavelength λ=1060 nm is assumed for the second laser irradiation, but in the case of a laser with a different absorption efficiency, a laser in which evaporation does not occur may be used. centre The range of luence is also different.

[0057] As described above in the first embodiment, the carbon film 43 absorbs the laser by the first laser irradiation, and the separator 40 is heated to a high temperature within the laser irradiation range. This causes the carbon film 43 to evaporate and be removed, and if there is dirt (e.g., lubricant residue) on the surface of the metal plate 41, the dirt evaporates along with the carbon film 43. Therefore, the metal plate 41 is exposed with almost no dirt present within the range 40s. At this time, the laser centre If the fluence is high, the components of the metal plate 41 may also evaporate, and oxides of the components of the metal plate 41 may re-adhere.

[0058] Due to the re-adhesion of the oxide, the part of the metal plate 41 where the oxide is attached within the range 40s becomes more hydrophilic. Hydrophilicity is also called wettability, and is evaluated using the contact angle. As shown in Figures 18(a) and 18(b), the contact angle is the angle between the wall surface and the tangent of the sphere passing through the edge of the droplet when the edge of the droplet attached to the wall surface is considered as a sphere. If the contact angle is high, it becomes small as shown by α in Figure 18(a), and conversely, if the hydrophilicity is low, it becomes large as shown by β in Figure 18(b). The property of low hydrophilicity is also called high water repellency. Since the molecular structure of oxides has polarity, they become highly hydrophilic. In other words, the contact angle becomes small. If the hydrophilicity becomes extremely high (contact angle is about 10° or less), water easily penetrates the interface where the resin layer 32 and the separator 40 are bonded in the bonding range 40u, and the peel strength decreases. A similar phenomenon occurs in the ranges 50s and 40t. Since water is generated inside each fuel cell 12 by the reaction of the oxidant gas (oxygen (O2) in Example 4) and the fuel gas (hydrogen (H2) in Example 4), it is preferable to take measures against the re-adhesion of oxides, which causes high hydrophilicity.

[0059] In the fourth embodiment, the laser centre Luens 100mJ / mm 2 After performing the first laser irradiation at about 100 nm, the laser is applied to at least a part of the region where the first laser irradiation is performed. centre Luens 10~20mJ / mm 2 By irradiating the metal plate 41 with the second laser beam at about the same intensity, the metal plate 41 does not evaporate but only melts, and redeposits on the surface are removed.

[0060] The data on the effects of Example 4 will be described with reference to FIGS.

[0061] FIG. 19 shows the contact angle of the region 40s (50s, 40t) of the metal plate 41 after laser irradiation and the laser irradiation. centre FIG. 1 shows the relationship between the laser power and the radiance. centre Luens 10~20mJ / mm 2 On the other hand, the contact angle is 20° or more, which is low in hydrophilicity. centre Luence is 20mJ / mm 2 When the contact angle is larger than 10°, it can be seen that the surface is highly hydrophilic. centre Luence is 10mJ / mm 2 If the laser power is further reduced, the output tends to become unstable. centre Luence is 10-20mJ / mm 2 is preferred.

[0062] FIG. 20 shows the laser beam intensity distribution of the first laser irradiation when only the first laser irradiation is performed and when the second laser irradiation is performed after the first laser irradiation in a situation where the region 40s (the same applies to 50s and 40t) of the metal plate 41 is reproduced. centre The horizontal axis shows the relationship between the luminance of the first laser irradiation and the contact angle of the region 40s. centre The vertical axis shows the contact angle, and the vertical axis shows the laser irradiation time of the second laser. centre Luence is 10mJ / mm 2 According to this figure, the laser irradiation is larger than the second laser irradiation. centre When the first laser irradiation was performed at 100 nm, the effect of reducing the hydrophilicity due to the second laser irradiation was not small.

[0063] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings achieves multiple objectives simultaneously, and achieving one of the objectives itself has technical utility. [Explanation of symbols]

[0064] Fuel cell stack: 10 Fuel cell: 12 MEA:20 Electrolyte membrane: 21 Anode layers: 22 Cathode layer: 23 Plastic frame: 30 Resin layer: 31-33 Separator:40 Metal plate: 41 Carbon film: 42~43 Gasket: 46 Separator:50 Metal plate: 51 Carbon film: 52~53 Fuel gas flow path 77 Oxidant gas flow path 78 Coolant flow path 80

Claims

1. A method for manufacturing a fuel cell, comprising the steps of: a laser irradiation step of irradiating a carbon film of a separator having a metal plate and a carbon film covering a surface of the metal plate with a laser to remove the carbon film within an irradiation area of ​​the laser to expose the metal plate; and a bonding step of bonding the separator to a resin member in an area including at least a part of the area where the metal plate is exposed, The laser irradiation step includes performing a first laser irradiation for removing the carbon film, A second laser irradiation having a smaller laser fluence than the first laser irradiation is performed on a part or all of the region that has been irradiated with the first laser; The laser fluence of the second laser irradiation is 10 to 20 mJ / mm 2 ; A manufacturing method comprising the steps of:

2. the resin member is a resin frame having a through hole, The method further comprises the step of disposing a membrane / electrode assembly in the through-hole, In the bonding step, the separator is bonded to the resin frame so that the through-hole is blocked by the separator. The method of claim 1.

3. When the separator is bonded to the resin frame, a gas flow path is formed at the interface between the separator and the resin frame, The laser irradiation step and the bonding step, The laser irradiation area is disposed away from the gas flow path and extends along the gas flow path; The adhesive area for adhering the separator to the resin frame is disposed away from the gas flow path and extends along the gas flow path. The central axis of the irradiation area is located closer to the gas flow path than the central axis of the bonding area. Execute it so as to satisfy the condition The method of claim 2.

4. When the separator is bonded to the resin frame, a gas flow path is formed at the interface between the separator and the resin frame, In the bonding step, the separator is bonded to the resin frame within the pressurized area by heating the pressurized area while pressing the separator toward the resin frame with a mold; The laser irradiation step and the bonding step, The laser irradiation area is disposed away from the gas flow path and extends along the gas flow path; the pressurized area is located away from and extends along the gas flow path; The central axis of the irradiation area is located closer to the gas flow path than the central axis of the pressurization area. Execute it so as to satisfy the condition The method of claim 3.

5. The resin member is a gasket, the separator has a first surface covered with the carbon membrane and a second surface located on the opposite side to the first surface, In the laser irradiation step, the first surface is irradiated with the laser, The bonding step includes bonding the first surface to the gasket; a step of disposing a membrane / electrode assembly in a through-hole of a resin frame having the through-hole; a step of adhering the second surface to the resin frame so that the through hole is blocked by the separator; Further comprising The method of claim 1.

6. The laser fluence of the first laser irradiation in the laser irradiation step is 100 mJ / mm ２ is as follows: In the bonding step, an adhesive curing agent or an adhesion promoter is applied to the surface of the metal plate within the irradiated area, and then the separator is bonded to the resin member. The method according to any one of claims 1 to 5.

7. The manufacturing method according to claim 6 , wherein in the laser irradiation step, a porous structure is formed on the surface of the metal plate within the irradiated area.

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