JP5418988B2 - Fuel cell stack - Google Patents

Description

  The present invention relates to an improvement in a fuel cell stack having a structure in which a plurality of fuel cells as power generation elements are stacked.

  As a fuel cell, for example, a reaction gas circulation space is provided between a membrane electrode structure (MEA) in which an electrolyte layer is sandwiched between a fuel electrode layer and an air electrode layer, and the membrane electrode structure. One having two separators to be formed is well known, and a fuel cell stack is configured by stacking a plurality of separators.

  An example of this type of fuel cell or fuel cell stack is described in Patent Document 1. The cell for a fuel cell described in Patent Document 1 includes a gas diffusion layer on both surfaces of a membrane electrode structure, and a protrusion having a through hole is provided on the outer periphery of the electrolyte layer, and a gasket is integrally formed on the outer periphery of the cell. It is. The gasket is fixed to the electrolyte layer by filling a part of the molding material of the gasket into the through hole.

JP 2007-188757 A

  By the way, in a fuel cell, a seal for preventing leakage of fuel gas, water vapor generated during power generation, and a cooling medium is indispensable. For example, when water vapor leaks to the outside, it condenses and causes leakage and corrosion.

  However, in the seal structure described in Patent Document 1, although the end surface (side surface) of the membrane electrode structure is sealed with a gasket, sealing to the end surface (side surface) of the separator is not taken into consideration, so that it still remains as described above. Problems may occur.

  The present invention has been made by paying attention to the above-mentioned conventional problems, and in particular, to provide a fuel cell stack having a sufficient sealing function of fluid flowing inside the end face (side face) of the separator. It is aimed.

  The fuel cell stack of the present invention includes a fuel cell having a structure in which a membrane electrode structure is sandwiched between two separators, and a plurality of the fuel cells stacked therein. The membrane electrode structure and each separator However, the outer periphery of each has a joining peripheral part, and the outer periphery of each laminated fuel cell is integrally covered with a resin member. The peripheral edge for bonding may be provided as a dedicated component for the membrane electrode structure and the separator, or the existing peripheral edge itself may be used.

  In the fuel cell stack, the resin member includes a gap seal portion interposed between at least the membrane electrode structure and the separator peripheral portions of the peripheral peripheral portions adjacent to each other in the stacking direction, and each joint. The outer peripheral seal portion in a range from the distal end of the peripheral portion to the outer peripheral surface of the resin member is provided, and the above configuration is used as a means for solving the conventional problems.

  The fuel cell stack of the present invention is provided with a sufficient sealing function of the fluid flowing inside, particularly on the end surface (side surface) of the separator, by employing the resin member having the gap seal portion and the outer periphery seal portion.

It is a disassembled perspective view explaining one Embodiment of the fuel cell stack of this invention. It is a top view explaining the fuel cell which comprises a fuel cell stack. It is sectional drawing explaining the temporary compression state (A) and main compression state (B) of a fuel cell stack. It is a side view explaining the temporary compression state (A) and this compression state (B) of a fuel cell stack. It is a flowchart explaining the manufacturing method of a fuel cell stack. It is sectional drawing explaining other embodiment of the fuel cell stack of this invention. It is sectional drawing explaining further another embodiment of the fuel cell stack of this invention. It is sectional drawing explaining further another embodiment of the fuel cell stack of this invention.

Hereinafter, an embodiment of a fuel cell stack of the present invention will be described based on the drawings.
The fuel cell stack FS shown in FIG. 1 has a structure in which a plurality of fuel cells C are stacked. As shown in FIG. 2, the fuel cell C of this embodiment includes a membrane electrode structure 2 having a frame 1 around it and two separators 3 and 3 sandwiching the frame 1 and the membrane electrode structure 2. I have. The reaction gas is circulated between the frame 1 and the separators 3 and 3.

  The membrane electrode structure 2 is generally called an MEA (Membrane Electrode Assembly). As shown in an enlarged view in FIG. 3A, for example, an electrolyte layer 21 made of a solid polymer is used as a fuel electrode layer (anode). ) 22 and the air electrode layer (cathode) 23. In the membrane electrode structure 2, a fuel gas (hydrogen) that is one reaction gas is supplied to the fuel electrode layer 22, and an oxidant gas (air) that is the other reaction gas is supplied to the air electrode layer 23. It is supplied and generates electricity by electrochemical reaction.

   The membrane electrode structure 2 shown in FIGS. 3A and 3B has gas diffusion layers 24 and 25 made of carbon paper or a porous body on the surfaces of the fuel electrode layer 22 and the air electrode layer 23. However, the membrane electrode structure includes an electrolyte layer, a fuel electrode layer, and an air electrode layer.

  The frame 1 is integrated with the membrane electrode structure 2 by resin molding (for example, injection molding). In this embodiment, the frame 1 has a rectangular shape with the membrane electrode structure 2 at the center. The frame 1 has three manifold holes H1 to H6 arranged at both ends, and a region from each manifold hole group to the membrane electrode structure 2 serves as a reaction gas flow region. Each of the frame 1 and the separators 3 and 3 has a rectangular shape having substantially the same vertical and horizontal dimensions.

  Each separator 3 is formed by press-molding a metal plate such as stainless steel, and a central portion corresponding to the membrane electrode structure 2 is formed in a wave shape in a cross section in the short side direction. This wave shape forms a reaction gas flow path continuously in the long side direction. Each separator 3 has manifold holes H1 to H6 that are equivalent to the manifold holes H1 to H6 of the frame 1 at both ends, and the region from each manifold hole group to the cross-sectional corrugated portion is made of reaction gas. It becomes a distribution area.

  The frame 1 and the membrane electrode structure 2 and the separators 3 and 3 are overlapped to constitute the fuel cell C. At this time, the fuel cell C includes a power generation unit that is an area of the membrane electrode structure 2 in the center, a manifold unit that supplies and discharges the reaction gas on both sides of the power generation unit, and power generation from each manifold unit. The diffuser part leading to the part is provided.

  The manifold holes H1 to H3 shown on the left side in FIG. 2 are for fuel gas supply (H1), cooling fluid supply (H2), and oxidant gas supply (H3). Form. The manifold holes H4 to H6 shown on the right side in FIG. 2 are for fuel gas discharge (H4), cooling fluid discharge (H5), and oxidant gas discharge (H6). Form. The supply and discharge may be partially or entirely reversed in positional relationship.

  In the fuel cell stack FS, a plurality of fuel cells C having the above-described configuration are stacked. At this time, as shown in FIGS. 1 and 3, the elastic member 4 is interposed between the separators 3 and 3 adjacent to each other in the stacking direction. Is inserted. The elastic member 4 is a plate member having a corrugated cross section, and applies an elastic force in the stacking direction between the separators 3 and 3, and the flow path of the cooling fluid in the continuous direction of the corrugation (long side direction of the cell). 31 is formed. The elastic member 4 absorbs the displacement in the stacking direction of the fuel cell stack FS when the electrolyte layer 21 expands and contracts due to power generation. In the fuel cell stack FS, the fuel cell C and the elastic member 4 shown in FIG.

  Further, the fuel cell stack FS shown in FIG. 1 has end plates 5A and 5B and current collecting plates 6A and 6B for pressurizing the fuel cells C in the stacking direction on both sides of the stacked fuel cells C in the stacking direction. Are attached respectively. Thereby, a predetermined lamination load is applied. Further, the fuel cell stack FS is finally accommodated in a case composed of two fastening plates 7A and 7B and reinforcing plates 8A and 8B.

  Here, in the fuel cell stack FS, as shown in FIGS. 2 and 3, the membrane electrode structure 2 and the separators 3 have bonding peripheral portions 1F and 3F on their outer circumferences. In this embodiment, since the membrane electrode structure 2 includes the frame 1, the peripheral portion of the frame 1 is used as the joining peripheral portion 1 </ b> F of the membrane electrode structure 2. These joining peripheral portions 1F and 3F may be provided as dedicated components for the frame 1 or the membrane electrode structure 2 and the separator 3, or the existing peripheral portions themselves may be used.

  In addition, as shown in FIG. 3, the fuel cell stack FS integrally covers the outer periphery of each stacked fuel cell C with a resin member R. The resin member R includes a gap seal portion S1 interposed between at least the membrane electrode structure 2 and the joining peripheral portions 1F and 3F of the separator 3 among the joining peripheral portions adjacent in the stacking direction, and each joining. An outer peripheral seal portion S2 is provided in a range from the distal ends of the peripheral edge portions 1F and 3F to the outer peripheral surface of the resin member R.

  Further, in the embodiment shown in FIG. 3, the resin member R has a gap seal portion S <b> 1 interposed between the joining peripheral portions 3 </ b> F and 3 </ b> F of the separators 3 and 3 adjacent in the stacking direction. The resin member R integrally covers not only the outer periphery of each fuel battery cell C but also the outer periphery of the end plates 5A and 5B and the current collector plates 6A and 6B.

  The end portions of the separators 3 and 3 are provided with appropriate irregularities to prevent the fuel gas and the cooling fluid from flowing unevenly, or a resin material intrusion prevention member 9 is interposed. In the case of the illustrated example, the intrusion prevention member 9 has an apparently large interval between the bonding peripheral portions 3F and 3F of the separators 3 and 3 in the interval between the bonding peripheral portions, and when the resin member R is molded, Since the resin material easily enters, the resin material is prevented from entering.

  Further, in the fuel cell stack FS, the gap seal portions S1 are interposed in a compressed state in the stacking direction between the joining peripheral portions adjacent in the stacking direction. Such a fuel cell stack FS is manufactured by the following method.

  That is, as shown in FIG. 4A, a plurality of fuel cells C are stacked to form a fuel cell group Cc, and a final stack is formed on the fuel cell group Cc using jigs J1 and J2. The load is applied or a lamination load less than that is applied. Thereafter, the resin member R is molded on the outer periphery of the fuel cell group Cc. Then, after molding or curing of the resin member R, as shown in FIG. 4B, a final stacking load is applied to the fuel cell group Cc. Thereby, each gap seal portion S1 is compressed in the stacking direction.

  More specifically, as shown in FIG. 5, in step S101, a plurality of fuel cells C (Cc) and current collector plates 6A and 6B are set in jigs J1 and J2. The jigs J1 and J2 are preferably those that apply loads from both sides of the fuel cell group Cc so as not to obstruct the application of the resin material.

  Next, in step S102, a resin material that becomes the resin member R is applied to the outer periphery of the fuel cell group Cc. At this time, the wettability between the component parts and the resin material and the resin depending on the interval between the peripheral edges for bonding so that an appropriate amount of the resin material that becomes the gap seal portion S1 is filled between the peripheral edges for bonding. Control each parameter such as material viscosity. Thereby, finally, sufficient sealing performance by the gap seal portion S1 can be ensured.

  Next, in step S103, the resin material is cured. As the curing treatment, charging into a high-temperature tank, application of warm air or infrared rays, and the like are performed. When the resin material is cured, predetermined parts such as end plates 5A and 5B are set in step S104. Thereafter, in step S105, a set load is applied, that is, an original stacking load is applied, and in step S106, the fuel cell stack FS is taken out from the jigs J1 and J2.

  In this manner, the fuel cell stack FS changes from the temporarily compressed state shown in FIG. 3A to the fully compressed state shown in FIG. Thereby, each gap seal part S1 is compressed in the stacking direction and functions as a compression seal.

  In the flowchart of FIG. 5, the case where the resin member R is formed by application of a resin material has been described. However, the resin member R may be at least one of injection molding, extrusion molding, blow molding, application, coating, and laminating. By adopting a means or a combination of a plurality of means, it is possible to mold efficiently.

  The above fuel cell stack FS is provided with a sufficient sealing function of the fluid flowing inside, particularly in the end face (side face) of the separator 3 by the resin member R having the gap seal part S1 and the outer peripheral seal part S2. It is possible to reliably prevent leakage of fluids such as fuel gas, water vapor generated by power generation, and cooling fluid.

  That is, since the outer periphery of the fuel cell stack FS is covered with the resin member R having the gap seal portion S1 and the outer periphery seal portion S2, and the gap seal portion S1 is in a compressed state, the adhesive strength of the resin member R is utilized. However, it also has a function of a compression seal, and higher sealing performance can be obtained.

  Further, in the fuel cell stack FS, since the resin member R integrally covers not only each fuel cell C but also the outer peripheries of the end plates 5A and 5B and the current collector plates 6A and 6B. Is further enhanced.

  The fuel cell stack FS and the method for manufacturing the fuel cell stack FS are formed in a state where the fuel cells C and the like are laminated, and the resin member R is molded on the outer periphery thereof. In addition, since a seal structure can be formed, an improvement in production efficiency and a reduction in cost can be realized. Further, since the resin member R can also ensure electrical insulation from the outside, for example, there is no need to provide an insulating member between the fastening plates 7A and 7B and the reinforcing plates 8A and 8B constituting the case. The case can be abolished, which can contribute to further reduction in size and weight of the fuel cell.

  In the fuel cell stack FS of the present invention, examples of the resin material used for the resin member R include those having elasticity such as silicone resin and those having no elasticity (or relatively low elasticity) such as epoxy resin. It is done. Similarly, the intrusion preventing member 9 described above can be selectively used either having elasticity or not having elasticity.

  When a resin material having elasticity is used for the resin member R, the elastic member 4 between the separators 3 and 3 when the expansion and contraction of the fuel cell stack FS occurs along with the expansion and contraction of the electrolyte layer 21 during power generation. Thus, the displacement is absorbed, and the resin member R follows the displacement, so that the stacking load in the plane of the fuel cell C can be maintained almost evenly.

  On the other hand, when a resin material having no elasticity is used for the resin member R, the outer peripheral portion is fixed, so that the center of the power generation portion swells due to the expansion of the electrolyte layer 21, and the stacking load in the plane is increased. Variations may occur. However, when the stacking load is above a certain level, there is little change in contact resistance due to an increase in surface pressure, and the sensitivity of variation in surface pressure may be small depending on the shape and size of the fuel cell C. Those having elasticity and those having no elasticity can be properly used, and in addition, these resin materials can be properly used in the stacking direction or in-plane direction of the fuel cell C.

  In the fuel cell stack FS of the present invention, as a more preferred embodiment, the resin member R can be made of a plurality of different materials. Specifically, for each gap seal portion S1 and the outer peripheral seal portion S2. Resin materials having different characteristics can be selectively used.

  That is, the resin material can be selected in accordance with the purpose such as gas sealing property, water vapor sealing property and insulating property and the constituent parts. In particular, the end plates 5A and 5B and the current collector plates 6A and 6B are mainly required to have insulating properties. Considering elasticity, sealing properties and resistance to embrittlement at low temperatures, for example, a resin material such as a silicone resin is desirable, and considering the assembly property at the time of lamination, a resin material having self-bonding properties is also effective. The self-bonding resin material prevents self-bonding until the final stacking load is applied, thereby improving the assemblability.

  In addition, the fuel cell stack FS of the present invention has a more preferable embodiment in which the membrane electrode structure 2 and the air electrode side separator 3 are joined between the peripheral edges 1F and 3F for bonding of the membrane electrode structure 2 and the fuel electrode side separator 3. The size of the gap seal portion S1 and the outer periphery seal portion S2 in the stack inner / outer direction between the bonding peripheral portions 1F and 3F and between the bonding peripheral portions 3F and 3F of the separator 3 adjacent in the stacking direction. The ratio of thickness can be selectively varied.

  That is, the functional inclination of the resin member R is provided in consideration of the shielding properties against the fuel gas, the water vapor, and the cooling fluid. Specifically, as shown in FIG. 3B, the water vapor shielding property between the membrane electrode structure 2 and the peripheral edge portions 1F and 3F for bonding on the air electrode side (lower side in the figure) separator 3 is the same. Therefore, the size of the outer peripheral seal portion S2 in the stack inner / outer direction is set to be equal to or larger than the size of the gap seal portion S1 (S1 ≦ S2). That is, the resin member R is thickened.

  Further, between the membrane electrode structure 2 and the fuel electrode side (upper side in the figure) separator peripheral edges 1F and 3F and between the separator peripheral edge joints 3F and 3F, fuel gas and cooling Since the shielding property of the working fluid is required, the size of the outer peripheral seal portion S2 in the stack inner / outer direction is set to be equal to or smaller than the size of the gap seal portion S1 (S1 ≧ S2). That is, the resin member R is thinned. It should be noted that the thickness of the outer peripheral seal portion S2 in the inner and outer directions of the stack is made as small as possible to reduce the thickness of the resin material R in portions where there is no permeation of water vapor, such as the end plates 5A and 5B and the current collector plates 6A and 6B. Also good.

  Furthermore, as a more preferred embodiment, the fuel cell stack FS of the present invention can be made of a resin material including an adhesive in which at least the outer peripheral seal portion S2 of the resin member R is peeled off by energization. Of course, an equivalent resin material may be used for the gap seal portion S1.

  As a result, the fuel cell stack FS can easily peel and remove the outer peripheral seal portion S2 and the gap seal portion S1 by applying a predetermined voltage to the resin member R. Very convenient to.

  Furthermore, as a more preferred embodiment, the fuel cell stack FS of the present invention has a plurality of layers in which the outer peripheral seal portion S2 of the resin member R has a plurality of layers in the stack inner and outer directions as shown in FIG. At least one of the layers is an electromagnetic wave shielding layer SL containing a metal filler. As the metal filler, for example, metal powder such as nickel, aluminum, copper and stainless steel, or powder of ferrite or carbon can be used.

  The fuel cell stack FS can suppress electromagnetic wave noise generated from the stack by the electromagnetic wave shielding layer SL. Thereby, it becomes more suitable as a power supply mounted in an electric vehicle.

   FIG. 7 is a view for explaining still another embodiment (approximately one pitch) of the fuel cell stack of the present invention. The illustrated fuel cell stack FS has no elastic member (see reference numeral 4 in FIG. 3), and the separators 3 and 3 have an uneven shape. In the stacked state of the fuel cells C, each separator 3 forms a cooling fluid flow path 31 therebetween, and the fuel gas flow path 32 and the oxidant between the separator 3 and the membrane electrode structure 2. A gas flow path 33 is formed.

  The fuel cell stack FS of the present invention can be applied to a structure using the corrugated separator 3 as described above, and the production efficiency is ensured by ensuring a sufficient sealing property by the resin member R covering the outside. Improvement, cost reduction, and insulation from the outside can be obtained.

   FIG. 8 is a view for explaining still another embodiment (for one pitch) of the fuel cell stack of the present invention. The illustrated fuel cell stack FS has the same basic configuration as that of the embodiment shown in FIG. 3, but the joining peripheral portions 3F and 3F of the separators 3 and 3 adjacent in the stacking direction are joined by welding (W). . And it has the structure which coat | covered each edge part 1F and 3F for joining also with the resin material R also including the peripheral edge part 3F for welding.

  In the fuel cell stack FS, the welded portion and the outer peripheral seal portion S2 perform a sealing function for the cooling fluid, and the resin member R, that is, the gap seal portion S1 and the outer peripheral seal for the fuel gas and water vapor. The part S2 performs a sealing function.

  In the fuel cell stack of the present invention, the resin member R is a gap interposed between at least the membrane electrode structure 2 and the joining peripheral portions 1F and 3F of the separator 3 among the joining peripheral portions adjacent in the stacking direction. A seal portion S1 and an outer peripheral seal portion S2 are provided. Therefore, a structure in which the joining peripheral portions 3F and 3F of the separators 3 and 3 are welded (W) as described above is also included. In this case as well, the same operations and effects as those of the previous embodiments can be obtained. .

  The configuration of the fuel cell stack of the present invention is not limited to each of the above embodiments, and details such as the shape, number, and material of the constituent members are appropriately changed without departing from the gist of the present invention. It is possible.

1F Joining peripheral part 2 Membrane electrode structure 3 Separator 3F Joining peripheral part
C fuel cell FS fuel cell stack R resin member S1 gap seal part S2 outer periphery seal part 31 flow path of cooling fluid SL electromagnetic wave shield layer

Claims (10)

A fuel cell stack comprising a fuel cell having a structure in which a membrane electrode structure is sandwiched between two separators, and a plurality of the fuel cells stacked.
Each membrane electrode structure and each separator has a peripheral edge for bonding on each outer periphery,
While integrally covering the outer periphery of each stacked fuel cell with a resin member,
The resin member has a gap seal portion interposed between at least the membrane electrode structure and the separator peripheral portions of the peripheral peripheral portions adjacent to each other in the stacking direction, and the tip of each peripheral edge portion. A fuel cell stack comprising an outer peripheral seal portion in a range reaching an outer peripheral surface of a resin member.   2. A cooling fluid passage is provided between separators adjacent to each other in the stacking direction, and a gap seal portion is interposed between joining peripheral portions of both separators. The fuel cell stack described.   3. The fuel cell stack according to claim 1, wherein a gap seal portion is interposed in a compressed state in the stacking direction between the joining peripheral portions adjacent to each other in the stacking direction.   4. The fuel cell stack according to claim 2, wherein a resin material having different characteristics is selectively used for each gap seal portion and the outer periphery seal portion.   Between the joining peripheral portions of the membrane electrode structure and the fuel electrode side separator, between the joining peripheral portions of the membrane electrode structure and the air electrode side separator, and between the joining peripheral portions of the separators adjacent in the stacking direction. 4. The fuel cell stack according to claim 2, wherein the ratio of the size of the gap seal portion and the outer peripheral seal portion in the stack inner and outer directions is selectively varied with respect to the gap.   An end plate and a current collecting plate for pressurizing each fuel cell in the stacking direction are attached to both sides in the stacking direction of each stacked fuel cell, and a resin member is attached to each fuel cell, end plate and current collecting plate. The fuel cell stack according to claim 1, wherein an outer periphery of the fuel cell stack is integrally covered.   The fuel cell stack according to any one of claims 1 to 6, wherein at least an outer peripheral seal portion of the resin member is made of a resin material containing an adhesive that is peeled off when energized.   The outer peripheral seal portion of the resin member has a plurality of layers in the stack inside and outside directions, and at least one of the plurality of layers is an electromagnetic wave shielding layer containing a metal filler. 2. The fuel cell stack according to item 1.   When manufacturing the fuel cell stack according to any one of claims 1 to 8, a plurality of fuel cells are stacked to form a fuel cell group, and a final stack load or The resin member is molded on the outer periphery of the fuel cell group with the following stacking load applied, and the final stacking load is applied to the fuel cell group after molding or curing of the resin member. A method of manufacturing a fuel cell stack characterized by the above.   The method for producing a fuel cell stack according to claim 9, wherein the resin member is molded by at least one of injection molding, extrusion molding, blow molding, coating, coating, and laminating.

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