JP4738979B2 - Polymer electrolyte fuel cell stack - Google Patents

Description

  The present invention relates to a polymer electrolyte fuel cell stack having an electromotive portion formed by repetition of a membrane electrode assembly in which a solid polymer electrolyte membrane is sandwiched between gas diffusion electrodes and a separator in which a gas flow passage is formed. In particular, the present invention relates to a technique for uniformly humidifying a solid polymer electrolyte membrane.

  The fuel cell system is a system for generating power by supplying a fuel gas containing hydrogen to a fuel electrode and supplying an oxidant gas containing oxygen to an oxidant electrode. Among fuel cell systems, in a fuel cell system using a solid polymer electrolyte membrane having proton conductivity as an electrolyte, the electromotive part of the fuel cell stack is a gas that uses the solid polymer electrolyte membrane as a fuel electrode and an oxidizer electrode. The membrane electrode assembly is sandwiched between diffusion electrodes and a separator having a gas flow passage is repeatedly formed.

  In this case, the fuel gas and the oxidant gas are supplied to the fuel electrode and the oxidant electrode of the membrane electrode assembly from the vertical direction along the gas flow passage provided on the surface of the flat plate of the conductive material. The gas flow passage communicates with a gas supply manifold and a gas discharge manifold arranged on the side surface of the electromotive portion, and fuel gas and oxidant gas are supplied to the gas flow passage of the electromotive portion through the gas supply manifold. After flowing from upstream to downstream of the gas flow passage, the gas is discharged from the gas discharge manifold to the outside.

  On the other hand, the solid polymer electrolyte membrane has a characteristic that the moisture content of the membrane changes due to the equilibrium water vapor pressure, and the resistance of the electrolyte membrane changes. For this reason, in order to reduce the resistance of the electrolyte membrane and obtain sufficient power generation performance, it is necessary to add moisture to the solid polymer electrolyte membrane, that is, humidification. As a method for humidifying the solid polymer electrolyte membrane, there are an external humidification method in which water vapor is previously added to a fuel gas and an oxidant gas, and an internal humidification method in which water is directly added via a separator.

  Moreover, in order to maintain the battery temperature within an appropriate range, it is necessary to remove the heat generated by the battery reaction and cool the battery. There are a cooling plate system that is inserted and cooled by flowing water or air through the cooling plate, and an internal humidification / latent heat cooling system that cools by evaporation latent heat of water supplied by internal humidification.

  There is a close relationship between the humidification method and the cooling method as described above. For example, in the external humidification method, a cooling water flow passage is inserted every several cells according to the heat generation state of the operating conditions. In this external humidification system, a dense conductive material is used for the separator to form a fuel gas flow path, an oxidant gas flow path and a cooling water flow path, and to prevent leakage. When the flow paths are provided on both sides of the separator, the number of separators is 1 to 2 per cell.

  In the internal humidification / latent heat cooling system, humidified water provided on the same separator surface as the gas flow passage is directly supplied to the gas flow passage, and cooling is performed by the latent heat of vaporization of the humidified water. In this internal humidification / latent heat cooling system, a dense conductive material is used for the separator to prevent leakage. In this system, the cooling plate can be omitted, and the number of separators is one per cell.

  By the way, in any of the above external humidification method and internal humidification / latent heat cooling method, the water produced by the reaction is recovered as water vapor and discharged together with the unreacted gas. In order to keep the resistance of the electrolyte membrane small, the water vapor pressure in the gas flow passage becomes high, and a dense material is used as the separator, so that moisture condensation occurs and the gas diffusion layer in the fuel electrode / oxidant electrode is blocked. Gas diffusion is hindered. This phenomenon is called “flooding” and is one of the factors that degrade the performance of polymer electrolyte fuel cells.

  As described above, in the conventional humidification / cooling method, although the number of separators can be reduced to 1 to 2 per cell, there is a problem that flooding is easy.

On the other hand, in Patent Document 1, a conductive porous plate having micropores is used as a separator, and a cooling water flow passage is provided in each cell, whereby cooling water is supplied to the gas flow passage through the conductive porous plate. And a humidifying / cooling method for removing generated water and condensed water through a conductive porous plate. In this humidification / cooling method, the pressure of the fuel gas and the oxidant gas is made higher than the pressure of the cooling water to prevent gas leakage and to achieve uniform humidification and cooling in the reaction surface of the cell. .
Special table flat 11-508726

  However, in the humidification / cooling method according to Patent Document 1, one cooling water flow passage is required for each cell in order to humidify / cool all the cells. As a result, two separators are required for each cell, which increases the cost.

  The present invention has been made to solve the above-described problems, and its purpose is to achieve uniform humidification and cooling in the reaction surface of the cell and to reduce the cost of the separator. It is to provide a molecular fuel cell stack.

  In order to achieve the above object, the present invention arranges a cooling water manifold so that the cooling water contacts the side surface of the separator, and flows the cooling water flowing through the cooling water manifold from the side surface of the separator to the inside. By supplying the membrane electrode assembly from the main surface of the separator and humidifying the solid polymer electrolyte membrane, uniform humidification and cooling within the reaction surface of the cell can be achieved while using only one separator per cell. It has been realized.

  That is, the polymer electrolyte fuel cell stack according to the present invention includes a membrane electrode composite in which a solid polymer electrolyte membrane is sandwiched between two gas diffusion electrodes, and a gas diffusion electrode on the opposing main surface of the conductive porous plate. In a polymer electrolyte fuel cell stack having an electromotive unit composed of a repetition of basic components composed of a fuel gas flow passage and a separator each having an oxidant gas flow passage formed in contact with each other, A side cooling water manifold is arranged so that the cooling water is brought into contact with the side surface, and the humidification means is constituted by the side cooling water manifold and the separator. Here, the humidifying means is means for flowing the cooling water flowing through the side surface cooling water manifold into the inside of the separator from the side surface of the separator and supplying the membrane electrode assembly from the main surface of the separator to humidify the solid polymer electrolyte membrane.

  In such a polymer electrolyte fuel cell stack of the present invention, the cooling water flowing through the side cooling water manifold flows into the separator from the side of the separator, evaporates on the main surface of the separator, and is supplied to the gas diffusion electrode. The molecular electrolyte membrane is uniformly humidified. In addition, the reaction heat generated in the membrane electrode composite is transferred from the main surface of the membrane electrode composite to the separator main surface, conducted to the side of the separator, and then transferred from the side of the separator to the cooling water. The composite can be cooled uniformly. Further, since one separator provides a cooling water flow passage in addition to the fuel gas flow passage and the oxidant gas flow passage, the number of separators can be only one per cell.

  According to the present invention, it is possible to provide a polymer electrolyte fuel cell stack that can realize uniform humidification and cooling in the reaction surface of the cell and can reduce the cost of the separator.

  Hereinafter, a plurality of embodiments of a polymer electrolyte fuel cell stack according to the present invention will be specifically described with reference to the drawings. In the following description and drawings, the polymer electrolyte fuel cell stack is abbreviated as “fuel cell stack” as appropriate.

[First Embodiment]
[Constitution]
FIG. 1 is an exploded perspective view showing a configuration of a polymer electrolyte fuel cell stack 100 according to a first embodiment of the present invention. As shown in FIG. 1, the fuel cell stack 100 includes an electromotive unit 100 a that performs a cell reaction in the center, and first and second gas manifolds 110 and 120 and upper and lower side surface cooling water manifolds around the electromotive unit 100 a. 130 and 140, and first and second end plates 150 and 160 are arranged. Here, the electromotive unit 100a is disposed so that the stacking direction is horizontal as indicated by the arrows in the drawing, and the first and second end plates 150, It is tightened by 160.

  In this case, the shape of the reaction surface (a plane orthogonal to the stacking direction, a plane parallel to the end plate) of the electromotive unit 100a is a rectangle including a pair of long sides and a pair of short sides, and the electromotive unit 100a. First and second gas manifolds 110 and 120 are arranged along the side surfaces forming the short side of the reaction surface. Here, the first gas manifold 110 includes a fuel inlet manifold 171 disposed at a lower portion and an air inlet manifold 181 disposed at an upper portion, and the second gas manifold 120 is a fuel disposed at an upper portion. It consists of an outlet manifold 172 and an air outlet manifold 182 disposed in the lower part. In the figure, reference numerals 171a and 172a denote a fuel inlet and a fuel outlet, and reference numerals 181a and 182a denote an air inlet and an air outlet.

  Further, an upper side cooling water manifold 130 and a lower side cooling water manifold 140 are arranged along the upper and lower side surfaces of the electromotive unit 100a, which are the side surfaces forming the long side of the electromotive unit 100a reaction surface. . In the figure, reference numerals 201 and 202 denote a cooling water inlet and a cooling water outlet. The cooling water supplied from the cooling water inlet 201 passes through the upper side cooling water manifold 130 and the first and second end plates 150. , 160, and flows vertically from the upper end to the lower end of these end plates 150, 160, and then is discharged from the cooling water outlet 202 via the lower side cooling water manifold 140. .

  FIG. 2 is a schematic diagram showing a gas flow in the fuel cell stack 100 shown in FIG. As shown in FIG. 2, the first and second gas manifolds 110 and 120 communicate with the gas flow passage of the electromotive unit 100a. Further, since the fuel inlet manifold 171 and the air inlet manifold 181 are on the same side (first gas manifold 110) and the fuel outlet manifold 172 and the air outlet manifold 182 are on the same side (second gas manifold 120), the fuel Gas and air flow in the same direction from the first gas manifold 110 to the second gas manifold 120.

  That is, the fuel inlet manifold 171 and the air inlet manifold 181 of the first gas manifold 110 communicate with the fuel gas flow path and the oxidant gas flow path indicated by the dotted line and the broken line of the electromotive unit 100a, respectively. Fuel gas is supplied to the flow passage and air is supplied to the oxidant gas flow passage. The fuel outlet manifold 172 and the air outlet manifold 182 of the second gas manifold 120 communicate with the fuel gas flow path and the oxidant gas flow path of the electromotive unit 100a, respectively, and are unreacted in the electromotive unit 100a. Fuel gas and air are discharged respectively.

  FIG. 3 is a schematic view partially showing an A-A ′ cross section of the fuel cell stack 100 shown in FIG. 2. As shown in FIG. 3, the electromotive unit 100 a is composed of a plurality of unit batteries (cells) 101 that are stacked. Each unit cell 101 includes a membrane electrode assembly (MEA) 105 in which a solid polymer electrolyte membrane 102 is sandwiched between an anode gas diffusion electrode (anode) 103 and a cathode gas diffusion electrode (cathode) 104, and the membrane electrode assembly ( The fuel gas flow passage 103c and the oxidant gas flow passage 104c in contact with the (MEA) 105 are respectively formed of separators 106.

  In this case, since one separator 106 with a gas flow passage is sandwiched between adjacent membrane electrode assemblies (MEAs) 105, each unit cell 101 is substantially shown by a broken line in FIG. As shown, the membrane electrode assembly (MEA) 105 and the halves of the separators 106 on both sides thereof are constituted.

  An anode catalyst layer 103a and a cathode catalyst layer 104a are provided on the sandwiching surfaces of the solid polymer electrolyte membrane 102 in the anode gas diffusion electrode 103 and the cathode gas diffusion electrode 104 of the membrane electrode assembly (MEA) 105, respectively. With this configuration, the membrane electrode assembly (MEA) 105 generates electricity by causing an electrochemical reaction between hydrogen in the fuel gas and oxygen in the oxidant gas.

  On the other hand, the separator 106 is a member having a channel groove on the opposing main surface of the conductive porous carbon plate, and is disposed in contact with the gas diffusion electrodes 103 and 104 so that the channel grooves on the main surfaces on both sides are disposed. However, the fuel gas flow passage 103c and the oxidant gas flow passage 104c are respectively formed.

  Here, as described above, the shape of the reaction surface of the electromotive unit 100a is a rectangle including a pair of long sides and a pair of short sides, and each side surface forming the long side of the electromotive unit 100a, that is, the electromotive unit 100a. The upper side cooling water manifold 130 and the lower side cooling water manifold 140 are respectively arranged along the upper and lower side surfaces. Therefore, the main surface shape of the separator 106 constituting the electromotive unit 100a is also a rectangle composed of a pair of long sides and a pair of short sides, and the side surfaces of the separators forming the long sides are the upper and lower side surface cooling water manifolds 130. , 140 is in contact with the cooling water flow passage 107c formed in the cooling water flow passage 107c.

  That is, the upper and lower side surface cooling water manifolds 130 and 140 and the separator 106 supply the cooling water flowing through the upper and lower side surface cooling water manifolds 130 and 140 to the membrane electrode assembly (MEA) 105 from the side surface of the separator 106, A humidifying means for humidifying the molecular electrolyte membrane 102 is configured.

[Action]
Hereinafter, the flow of heat and water in the polymer electrolyte fuel cell stack 100 of the first embodiment will be described with reference to the arrows in FIG.

  First, the reaction heat generated in the membrane electrode assembly (MEA) 105 is transferred from the main surfaces of the gas diffusion electrodes 103 and 104 to the main surface of the separator 106 as shown by the black arrows in FIG. After conducting toward the side surface, heat is transferred from the side surface of the separator 106 to the cooling water flowing through the cooling water flow passage 107c. In this case, the reaction heat of the membrane electrode assembly (MEA) 105 is continuously and uniformly transferred from the main surface to the separator 106 main surface, and the heat transfer from the side surface of the separator 106 to the cooling water is As the cooling water flows in the upper and lower side surface cooling water manifolds 130 and 140, the operation is continuously and efficiently performed. Therefore, the membrane electrode assembly (MEA) 105 can be cooled uniformly.

  On the other hand, the cooling water flowing through the upper and lower side surface cooling water manifolds 130 and 140 flows from the side surface of the separator 106, flows inside the separator 106, and then uniformly evaporates on the main surface of the separator 106 and is supplied to the gas diffusion electrodes 103 and 104. Then, the solid polymer electrolyte membrane 102 is uniformly humidified. That is, since the cooling water continuously flows and flows continuously from the side surface of the separator 106, the pores of the separator 106 made of the conductive porous carbon plate are always filled with the cooling water. As a result, the cooling water is uniformly evaporated on the main surface of the separator 106 and supplied uniformly to the main surfaces of the gas diffusion electrodes 103 and 104, and the solid polymer electrolyte membrane 102 is uniformly humidified through these diffusion electrodes 103 and 104. .

  In this case, the water consumed by humidification is continuously replenished via the side surface of the separator 106. However, by keeping the cooling water pressure lower than the pressures of the fuel gas and the oxidant gas, It is possible to prevent a problem that water in the hole oozes out and closes the gas flow passages 103c and 104c. Further, by setting the pore diameter of the separator 106 within a range in which water in the pore is retained by capillary force, leakage of the fuel gas and the oxidant gas can be prevented.

[effect]
According to the first embodiment as described above, by arranging the side surface cooling water manifold for bringing the cooling water into contact with the side surface of the separator, these side surface cooling water manifold and the separator can function as humidifying means. Cooling water flowing through the side cooling water manifold flows into the separator from the side of the separator, evaporates on the main surface of the separator and is supplied to the membrane electrode assembly, so that the solid polymer electrolyte membrane can be uniformly humidified.

  In addition, the reaction heat generated in the membrane electrode composite is transferred from the main surface of the membrane electrode composite to the separator main surface, conducted to the side of the separator, and then transferred from the side of the separator to the cooling water. The composite can be cooled uniformly.

  Further, since one separator provides a cooling water flow passage in addition to the fuel gas flow passage and the oxidant gas flow passage, the number of separators can be only one per cell. Therefore, the cost of the separator for each fuel cell stack can be reduced.

[Example]
As an example for verifying the effects of the first embodiment as described above, a fuel cell stack was manufactured by stacking 100 unit cells (effective area 100 cm ² ) shown in FIG. The fuel cell stack was supplied with a dry gas containing hydrogen as a fuel and dry air as an oxidant, and a power generation test was conducted by supplying cooling water having a pressure 40 kPa lower than the pressure of the fuel and air. It was confirmed that stable power generation was possible up to a current density of 0.3 A / cm ² (30 A).

[Second Embodiment]
[Constitution]
FIG. 4 is a schematic diagram showing a gas flow in the polymer electrolyte fuel cell stack 100 according to the second embodiment of the present invention. As shown in FIG. 4, in the present embodiment, the first and second gas manifolds 110 and 120 are in communication with the gas flow path of the electromotive unit 100a, as in the first embodiment. However, the flow direction of the fuel gas and air is opposite to each other.

  That is, the first gas manifold 110 includes a fuel outlet manifold 172 disposed at the lower portion and an air inlet manifold 181 disposed at the upper portion, and the second gas manifold 120 is a fuel inlet disposed at the upper portion. It consists of a manifold 171 and an air outlet manifold 182 disposed at the lower part. With this configuration, air flows from the first gas manifold 110 toward the second gas manifold 120 as in the first embodiment, but the fuel gas flows in the opposite direction to the second gas manifold. It flows in the direction from 120 to the first gas manifold 110.

  The configuration of the first and second gas manifolds 110 and 120 as described above and the portions other than the gas flow direction thereby are configured in the same manner as in the first embodiment. That is, the configuration of the cross section A-A ′ of the electromotive unit 100 a in FIG. 4 is as shown in FIG. 3.

[Action]
In the second embodiment as described above, the flow of heat and water in the AA ′ cross section of the polymer electrolyte fuel cell stack 100 is the same as that in the first embodiment, but in this embodiment, Further, the following effects can be obtained.

  That is, in this embodiment, the flow direction of the fuel gas and the air is opposite to each other, so that as shown in FIG. A substantial amount of water movement in and out of the main plane is suppressed. In FIG. 5, the substantial amount of water movement inside and outside the separator is shown as the amount of water movement to the separator (= absorption amount−evaporation amount).

  As shown in FIG. 5, in the vicinity of the fuel upstream side (fuel inlet manifold 171 side) end portion and the air upstream side (air inlet manifold 181 side) end portion of the separator 106, the membrane electrode assembly (MEA) 105 to the separator 106. The amount of water transferred to the water becomes negative, that is, the amount of evaporation from the separator to the MEA increases, but water is stably absorbed by the separator 106 from the membrane electrode assembly (MEA) 105 in the central portion. I understand.

  That is, in the vicinity of the upstream end of the fuel in the separator 106, the water transfer amount from the anode to the separator is negative, as indicated by the broken line in the figure, and from the separator 106 to the anode 103 side of the membrane electrode assembly (MEA) 105. Water evaporates. On the other hand, in the vicinity of the end of the downstream side of the air (on the side of the air outlet manifold 182) that overlaps with the vicinity of the end of the upstream side of the fuel in the stacking direction of the separator 106, as shown by the dotted line in the figure, Is positive, and the amount of water absorbed from the cathode 104 to the separator 106 side is larger than the amount of water evaporated from the separator 106 to the cathode 104 side of the membrane electrode assembly (MEA) 105. Yes.

  For this reason, the balance (absorption amount and evaporation amount) of the amount of water movement inside and outside the separator 106 in the vicinity of the fuel upstream end and the air downstream end of the separator 106 cancels each other, as shown by the solid line in the figure. In addition, the substantial amount of water movement inside and outside the separator in this portion (the difference between the absorption amount and the evaporation amount) is suppressed.

  Further, in the vicinity of the air upstream end portion of the separator 106, the amount of water movement from the cathode to the separator is negative, and water evaporates from the separator 106 to the cathode 104 of the membrane electrode assembly (MEA) 105. On the other hand, the amount of water movement from the anode to the separator is negative in the vicinity of the fuel downstream side (fuel outlet manifold 172 side) end portion that overlaps with the vicinity of the air upstream end portion in the stacking direction of the separator 106. The amount of water evaporated from the anode 103 to the anode 103 side of the membrane electrode assembly (MEA) 105 is substantially equal to the amount of water absorbed from the anode 103 to the separator 106 side.

  For this reason, the balance (absorption amount and evaporation amount) of the total amount of water movement in and around the stacking direction of the separator 106 near the upstream end of the separator 106 and the downstream end of the fuel cancels each other, and is shown by a solid line in the figure. As shown, the substantial amount of water movement inside and outside the separator (the difference between the absorption amount and the evaporation amount) in this portion is suppressed.

[effect]
According to the second embodiment as described above, the following effects can be obtained in addition to the effects of the first embodiment. That is, the balance of the amount of water movement (absorption amount and evaporation amount) inside and outside the separator in the stacking direction cancels out at the end of the separator in the gas flow direction. Since the local consumption of water in the separator can be suppressed by suppressing the amount (difference between absorption and evaporation), the amount of water replenished from the side of the separator can be reduced and the fuel cell stack can be operated stably. Is possible.

[Third Embodiment]
[Constitution]
FIG. 6 is an exploded perspective view showing the configuration of the polymer electrolyte fuel cell stack 100 according to the third embodiment of the present invention. FIG. 7 is a perspective view showing a cooling water flow passage in the fuel cell stack 100 of FIG.

  As shown in FIGS. 6 and 7, the fuel cell stack 100 includes an electromotive unit 100a, first and second gas manifolds 110 and 120, upper and lower side surface cooling water manifolds 130 and 140, first and first. The two end plates 150 and 160 and the positional relationship between the fuel inlet / outlet manifolds 171 and 172 and the air inlet / outlet manifolds 181 and 182 are the same as those in the first embodiment.

  In the present embodiment, the difference from the first embodiment is that the upper and lower side surface cooling water manifolds 130 and 140 and the first and second end plates 150 and 160 each have a plurality of cooling water flow passages, As shown in FIG. 7, each flow passage is sequentially communicated to form a spiral flow passage 200 in which cooling water flows spirally around the electromotive unit 100 a.

  First, as shown in FIG. 6, the upper side cooling water manifold 130 is provided with a plurality of cooling water flow passages 211, 212,..., 21 n extending in parallel with the first gas manifold 110. They are sequentially arranged from the manifold 110 to the second gas manifold 120, that is, in the air flow direction. Among these, the cooling water flow passage 211 at the first gas manifold 110 side end portion communicates with the cooling water inlet 201.

  Further, the second end plate 160 is provided with a plurality of cooling water flow passages 221, 222,..., 22n extending in the vertical direction, and they are sequentially arranged in the air flow direction. As shown in FIG. 7, these cooling water flow passages 221, 222,..., 22n communicate with one ends of the cooling water flow passages 211, 212,. .

  The lower side cooling water manifold 140 is provided with a plurality of cooling water flow passages 231, 232,..., 23 n facing the plurality of cooling water flow passages 211, 212,. These cooling water flow passages 231, 232,..., 23 n communicate with the lower ends of the cooling water flow passages 221, 222,. Yes. Further, the cooling water flow passage 23 n at the end portion on the second gas manifold 120 side communicates with the cooling water outlet 202.

  In addition, the first end plate 150 is provided with a plurality of cooling water flow passages 241, 242,..., 24n-1 extending in an obliquely vertical direction, and these cooling water flow passages 241, 242,. As shown in FIG. 7, the lower end communicates with one end of the cooling water flow passages 231, 232,..., 23 n-1 of the lower side cooling water manifold 140 and the upper side cooling water manifold 130 at the upper end. , 21n-1 are respectively communicated with one end of the cooling water flow passages 211, 212, ..., 21n-1.

  As described above, the cooling water flow passages 211, 212,..., 21 n of the upper side cooling water manifold 130, the cooling water flow passages 221, 222,. The cooling water flow passages 231, 232,..., 23n and the cooling water flow passages 241, 242,..., 24n-1 of the first end plate 150 are sequentially communicated according to the arrangement order of the respective flow passages. A spiral flow passage 200 reaching the cooling water outlet 202 is formed.

  In this case, as indicated by a large arrow in FIG. 7, the direction of cooling water flowing in the spiral flow passage 200 (in the direction of the central axis of the spiral) with respect to the electromotive unit 100 a and the oxidizing agent in the electromotive unit 100 a The air flows in the gas flow passage 104c in the same direction.

[Action]
In the third embodiment as described above, the heat flow in the AA ′ cross section of the polymer electrolyte fuel cell stack 100 is the same as that in the first embodiment, but in this embodiment, FIG. As shown, the water flow is different.

  That is, as shown in FIG. 7, since the spiral flow passage 200 in which the cooling water flows spirally around the electromotive unit 100a, the second end plate 160 is the same as that of the first embodiment. Similarly, the cooling water flows from the top to the bottom, but in the first end plate 150, the cooling water flows from the bottom to the top. In addition, the cooling water flowing through the upper and lower side surface cooling water manifolds 130 and 140 flows into the individual separators 106 from the side surfaces thereof, flows through the inside of the separators 106, and is supplied to the membrane electrode assembly (MEA) 105. The point of humidifying the electrolyte membrane 102 is the same as in the first embodiment.

  In the present embodiment, in particular, the direction of cooling water flowing in the spiral flow passage 200 around the electromotive unit 100a (in the direction of the central axis of the spiral) and the oxidant gas flow passage 104c in the electromotive unit 100a Since the flowing direction is the same direction, the temperature of the cooling water flowing through the spiral flow passage 200 increases toward the downstream of the spiral flow passage 200 due to reaction heat transferred from the separator 106 of the electromotive unit 100a. Will do.

  Therefore, in the separator 106, the temperature of the cooling water increases toward the downstream side of the oxidant gas flow passage, that is, the downstream side of the air. As a result, as shown in FIG. The amount of water absorbed by the separator is reduced, and the substantial amount of water movement inside and outside the separator (the difference between the amount of absorption and the amount of evaporation) at this portion is suppressed.

  In FIG. 8, the total water movement amount to the separator in the present embodiment is indicated by a solid curve, and the total water movement amount to the separator in the second embodiment (the same data as FIG. 5) is indicated by a broken line. It is shown by the curve. As is clear from the comparison of these two curves, in this embodiment, the substantial amount of water movement inside and outside the separator (difference between the absorption amount and the evaporation amount) from the air downstream portion to the central portion is the second amount. It is further suppressed compared to the embodiment.

[effect]
According to the third embodiment as described above, the following effects can be obtained in addition to the effects of the first embodiment. That is, in the separator, the temperature of the cooling water rises toward the downstream side of the air, and as a result, a substantial amount of water movement inside and outside the separator (difference between absorption amount and evaporation amount) near the downstream portion of the air is suppressed. Since local water consumption can be suppressed, the amount of water replenished from the side of the separator can be reduced, and the fuel cell stack can be stably operated.

[Fourth Embodiment]
[Constitution]
FIG. 9 is a schematic diagram showing a dimensional relationship in cross section of the separator 106 of the polymer electrolyte fuel cell stack 100 according to the fourth embodiment of the present invention.

  As shown in FIG. 9, the separator 106 of this embodiment includes a total thickness L1 of the separator 106, a fuel gas flow passage 103 c and an oxidant gas flow passage formed on the main surfaces on both sides of the separator. The ratio of the remaining thickness L2 / total thickness L1 to the thickness (remaining thickness) L2 of the remaining portion 106a excluding the depth of 104c is 50% or more, that is, L2 / L1 ≧ 50% Yes. The fuel cell stack 100 of the present embodiment is configured in the same manner as in the first embodiment, except for the limitation of the dimensional relationship in the cross section of the separator 106.

[Action / Effect]
In the fourth embodiment as described above, the relationship between the total thickness L1 and the remaining thickness L2 of the separator 106 is such that the remaining thickness / total thickness ratio is 50% or more, that is, L2 / L1 ≧ 50%. By limiting, heat conduction and water flow in the separator 106 can be set appropriately. As a result, the maximum temperature of the central portion in the electromotive unit 100a can be suppressed to be equal to or lower than the upper limit temperature of the polymer electrolyte fuel cell, and the side surfaces of the separator 106 that are in contact with the upper and lower side cooling water manifolds 130 and 140 A sufficient amount of water permeation at the portion can be secured, and water generated by the cell reaction can be appropriately treated, so that the fuel cell stack 100 can be stably operated.

[Example]
As an example for verifying the effects of the fourth embodiment as described above, as shown in Table 1 below, the remaining thickness / total thickness ratios are 49%, 66%, and 75%, respectively. Three types of fuel cell stacks were manufactured by stacking 100 unit cells (effective area 100 cm ² ) shown in FIG. 3 using different types of separators, and differing only in the dimensions of each part of the separators. That is, Examples 1 and 2 are examples using a separator that satisfies the condition “L2 / L1 ≧ 50%” according to the present embodiment, and Comparative Example 1 satisfies the same condition unlike the present embodiment. This is an example using a separator that does not.

  And about these comparative examples 1 and Examples 1 and 2, when the temperature distribution in the fuel cell stack and the water permeation amount on the side surface of the separator were measured, the results shown in FIGS. 10 and 11 were obtained.

  Among these, FIG. 10 shows the relationship between the distance from the electrode center to the side surface coolant manifold and the separator temperature in the separator main surface direction (horizontal direction) of the fuel cell stack. As shown in FIG. 10, the temperature at the center of the electrode is the highest, and the temperature gradually decreases toward the side cooling water manifold. The reason for this is as shown by the black arrows in FIG. This is because the reaction heat of the fuel cell is cooled by heat conduction from the center to the side surface in the separator.

Here, assuming that the temperature of the cooling water is 60 ° C. and the current density of the fuel cell stack is 0.3 A / cm ² (30 A), in the comparative example in which the remaining thickness / total thickness ratio of the separator is 49%, The central maximum temperature exceeds 90 ° C., and thus exceeds 80 ° C., which is the upper limit of operation of the polymer electrolyte fuel cell. On the other hand, in Example 1 where the remaining thickness / total thickness ratio of the separator is 66%, the maximum temperature is 78 ° C., and the remaining thickness / total thickness ratio of the separator is 75%. In this case, the maximum temperature is 72 ° C., and both can be suppressed to 80 ° C. or less which is the upper limit of operation.

  Moreover, FIG. 11 shows the water permeation amount on the side surface of the separator in contact with the side surface cooling water manifold. As shown in FIG. 11, since the cross-sectional area through which water permeates increases as the remaining thickness / total thickness ratio of the separator increases, the amount of water permeation increases. Here, in the comparative example of the remaining thickness / total thickness ratio of the separator: 49%, the amount of water permeation is 0.44, which is less than the amount of water produced by the reaction (0.5). It cannot be secured. On the other hand, in Example 1 where the remaining thickness / total thickness ratio of the separator was 66%, the water permeation amount was 0.89, and the remaining thickness / total thickness ratio of the separator was 75%. In Example 2, the water permeation amount is 1.33, and both exceed the reaction product water amount, so that the product water can be appropriately treated.

[Other Embodiments]
It should be noted that the present invention is not limited to the above-described embodiments, and various other variations can be implemented within the scope of the present invention. First, the configuration of the fuel cell stack and the size and shape of each part shown in the embodiment are merely examples, and the specific configuration and size and shape of each part can be selected as appropriate. For example, the specific dimensions and shape of the gas manifold and the cooling water manifold, the number of unit cells stacked, and the like can be freely selected according to the rating and application of the fuel cell stack.

  That is, according to the present invention, a cooling water manifold is arranged so that the cooling water contacts the side surface of the separator, and the cooling water flowing through the cooling water manifold is poured into the inside from the side surface of the separator, and from the main surface of the separator to the membrane electrode assembly. As long as it supplies and humidifies a solid polymer electrolyte membrane, the specific embodiment can be freely selected.

1 is an exploded perspective view showing a configuration of a polymer electrolyte fuel cell stack according to a first embodiment of the present invention. The schematic diagram which shows the flow of the gas in the fuel cell stack which concerns on 1st Embodiment. The schematic diagram which shows the A-A 'cross section of FIG. 2 partially. The schematic diagram which shows the flow of the gas in the polymer electrolyte fuel cell stack concerning the 2nd Embodiment of this invention. The fuel cell stack which concerns on 2nd Embodiment, The graph which shows the amount of water movement to the separator in each part of the gas flow direction. The disassembled perspective view which shows the structure of the polymer electrolyte fuel cell stack concerning the 3rd Embodiment of this invention. The perspective view which shows the cooling water flow path in the fuel cell stack which concerns on 3rd Embodiment. The graph which shows the water movement amount to the separator in each part of the gas flow direction in the fuel cell stack according to the third embodiment in comparison with the second embodiment. The schematic diagram which shows the dimensional relationship in the cross section of the separator of the polymer electrolyte fuel cell stack which concerns on the 4th Embodiment of this invention. The graph which shows the relationship between the distance from the electrode center to a side surface cooling water manifold, and separator temperature about the Example and comparative example of the fuel cell stack which concern on 3rd Embodiment. The graph which shows the water permeation amount of the separator side surface which contacts a side surface cooling water manifold about the Example and comparative example of the fuel cell stack which concern on 3rd Embodiment.

Explanation of symbols

100: Solid polymer fuel cell stack (fuel cell stack)
DESCRIPTION OF SYMBOLS 100a ... Electromotive part 101 ... Unit battery 102 ... Solid polymer electrolyte membrane 103 ... Anode gas diffusion electrode (anode)
103c ... Fuel gas flow passage 104 ... Cathode gas diffusion electrode (cathode)
104c ... Oxidant gas flow passage 105 ... Membrane electrode assembly (MEA)
106 ... Separator 107c ... cooling water flow passage 110 ... first gas manifold 120 ... second gas manifold 130 ... upper side cooling water manifold 140 ... lower side cooling water manifold 150 ... first end plate 160 ... second end plate 171 ... Fuel inlet manifold 171a ... Fuel inlet 172 ... Fuel outlet manifold 172a ... Fuel outlet 181 ... Air inlet manifold 181a ... Air inlet 182 ... Air outlet manifold 182a ... Air outlet 200 ... Spiral flow passage 201 ... Cooling water inlet 202 ... Cooling Water outlets 211 to 21n ... Cooling water flow passages 221 to 22n of the upper side cooling water manifold ... Cooling water flow passages 231 to 23n of the second end plate ... Cooling water flow passages 241 to 24n-1 of the lower side cooling water manifold ... End plate cooling water Passage

Claims (6)

A membrane electrode assembly in which a solid polymer electrolyte membrane is sandwiched between two gas diffusion electrodes, and a fuel gas flow path and an oxidant gas disposed on the opposing main surface of the conductive porous plate in contact with the gas diffusion electrode In the polymer electrolyte fuel cell stack provided with an electromotive unit composed of repetition of basic components composed of separators each having a flow path formed therein,
A side cooling water manifold is disposed so that the cooling water contacts the side surface of the separator, and the cooling water flowing through the side cooling water manifold is caused to flow into the separator from the side of the separator by the side cooling water manifold and the separator. A solid polymer fuel cell stack comprising a humidifying means for supplying the membrane electrode assembly from the surface to humidify the solid polymer electrolyte membrane. The shape of the main surface of the separator is a rectangle composed of a pair of long sides and a pair of short sides, the side cooling water manifold is disposed along each long side of the separator, and a gas is formed along each short side of the separator. 2. The polymer electrolyte fuel cell stack according to claim 1, further comprising a manifold. 3. The solid according to claim 1, wherein the fuel gas flow path and the oxidant gas flow path are arranged so that a flow direction of the fuel gas and a flow direction of the oxidant gas are opposed to each other. Polymer fuel cell stack. The side cooling water manifold includes a plurality of flow passages arranged in a horizontal direction, and the plurality of flow passages are communicated in series so that the cooling water flows in an order corresponding to the arrangement order of the respective flow passages,
2. The structure according to claim 1, wherein the forward flow direction of the cooling water flows through the plurality of flow passages and the flow direction of the oxidant gas through the oxidant gas flow passages are the same direction. Item 4. The polymer electrolyte fuel cell stack according to any one of items 3 to 4. The electromotive unit is disposed such that the stacking direction is a horizontal direction, and a pair of end plates are provided to clamp the electromotive unit from both end surfaces in the stacking direction. A plurality of flow passages arranged in a horizontal direction through which the cooling water flows in the direction,
The upper and lower side surface cooling water manifolds are respectively disposed on the upper and lower side surfaces of the electromotive unit opposed to each other, and each of the upper and lower side surface cooling water manifolds has a plurality of horizontal passages arranged in the horizontal direction. With a flow path,
The flow passages of the upper and lower side cooling water manifolds and the flow passages of the pair of end plates are sequentially communicated according to the arrangement order of the respective flow passages, so that the cooling water flows spirally around the electromotive unit. A flow path is formed,
5. The solid polymer according to claim 4, wherein the direction in which the cooling water flows in the spiral flow path is the same as the direction in which the oxidant gas flows in the oxidant gas flow path. Type fuel cell stack. In the separator, the thickness of the remaining portion excluding the depth of the fuel gas flow path and the oxidant gas flow path formed on the pair of main surfaces is 50% or more of the total thickness of the separator. 6. The polymer electrolyte fuel cell stack according to any one of claims 1 to 5, wherein:

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