JP2009026476A - Unit cell of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance power generation performance and reduce unevenness of temperature and power generation performance in the gas flow direction in a unit cell of a fuel cell. <P>SOLUTION: Two or more groove parts 60 are formed in an oxidizing gas side porous body 32 interposed between a separator and a cathode of a membrane-electrode assembly in the gas flow direction. Each groove part 60 is formed in a triangular pyramid shape, and its cross section is gradually decreased from the upstream side toward the downstream side of the oxidizing gas. Thereby, the oxidizing gas side porous body 32 has a shape more reducing pressure loss of gas on the upstream side of the gas than the downstream side of the gas. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell including a power generation body, a separator, and a porous body that is disposed between the power generation body and the separator and allows reaction gas to flow therethrough.

  Conventionally, various proposals have been made on fuel cells. A fuel cell is generally configured by laminating a plurality of fuel cells, and each fuel cell is a power generator, and is composed of a pair of separators disposed on both sides of a membrane-electrode assembly (MEA) via gas flow paths. Become. In such a fuel fuel cell, it is important to devise a gas flow path in order to efficiently send the reaction gas, which is an oxidizing gas such as air or hydrogen gas, to the membrane-electrode assembly side. Regarding the configuration of the flow path, for example, there are proposals of Patent Document 1 and Patent Document 2.

  In Patent Document 1, as shown in FIG. 21, a cross-sectional view of the main part of the fuel cell is described. The fuel cell sandwiches the electrolyte membrane / electrode structure 10 and the electrolyte membrane / electrode structure 10. Individual separators 12. A seal member (not shown) is interposed between the two separators 12 so as to cover the outer periphery of the electrode surface. The electrolyte membrane / electrode structure 10 includes an anode side electrode 16 and a cathode side electrode 18 that sandwich the electrolyte membrane 14. Each electrode 16, 18 has a gas diffusion layer 20 and an electrode catalyst layer 22. The gas diffusion layer 20 is formed of a foam made of a metal material, and a flow path wall is formed in the foam. A gas flow path is formed in the gas diffusion layer 20. The oxidant gas supplied to the cathode side electrode 18 and the fuel gas supplied to the anode side electrode 16 are consumed by an electrochemical reaction in the electrode catalyst layer 22 to generate power.

  Patent Document 2 describes a fuel cell stack configured using a separator. The fuel cell stack is configured by laminating a plurality of single cells including two separators, a frame disposed between the separators, and a membrane-electrode assembly. The separator is composed of a separator body and a collector that collects gas diffusion and generated electricity. The collector is formed from a thin metal plate in which a large number of through holes are formed in a mesh shape by applying a lath process to a stainless steel plate.

JP 2004-87318 A JP 2007-87768 A

  In the fuel cell described in Patent Document 1, when another gas diffusion layer having a larger gas flow resistance than the gas diffusion layer 20 is provided between the gas diffusion layer 20 having a foam and the electrode catalyst layer 22, the gas The gas in the gas diffusion layer 20 corresponding to the porous body is compared with the case where the diffusion layer 20 is a groove flow path forming member having a constant cross-sectional area in the gas flow direction and having a groove flow path extending over the entire length of the gas flow direction. Increased distribution resistance. That is, the pressure loss with respect to the gas of the gas diffusion layer 20 becomes high. For this reason, a large amount of gas flows relatively in another gas diffusion layer on the electrode catalyst layer 22 side. For example, when the gas is air, the gas downstream side of another gas diffusion layer is not easily affected by a decrease in oxygen concentration, and flooding in the vicinity of the electrolyte membrane 14, that is, water is less likely to accumulate. There is a possibility that the power generation output of the fuel cell can be made higher than when the flow path forming member is provided.

  FIG. 22 is a diagram showing an example of the relationship between the stoichiometric ratio of the reaction gas supplied to the cathode side electrode, that is, the air stoichiometric ratio, which is the cathode stoichiometric ratio, and the fuel cell voltage. As shown in FIG. 22, when the cathode stoichiometric ratio becomes smaller than a certain value, the fuel cell voltage rapidly decreases. From this, it can be seen that it is preferable to increase the cathode stoichiometric ratio to a certain level or more from the aspect of increasing the generated voltage. As described above, in the configuration in which another gas diffusion layer is provided closer to the electrode catalyst layer 22 than the gas diffusion layer 20, when the gas diffusion layer 20 is configured to have a foam, for example, the reaction gas is air. In some cases, the cathode stoichiometric ratio of the air supplied to the electrode catalyst layer 22 on the cathode side can be increased to some extent, and the power generation output can be increased to some extent.

  However, in the case of the configuration in which the gas diffusion layer 20 having the foam is provided as described above, the pressure loss with respect to the gas of the gas diffusion layer 20 tends to increase. For example, although it depends on the specification of the foam, the pressure loss may be about 5 to 30 times higher than in the case of using a groove flow path forming member instead of the foam. When the pressure loss increases, it is necessary to increase the power for driving a supply device that supplies gas, for example, an air compressor. Further, it is conceivable to reduce the pressure loss by increasing the thickness of the gas diffusion layer 20, but in this case, the size of the fuel cell becomes large. Such an inconvenience may also occur in the case where the fuel cell stack described in Patent Document 2 is provided with a structure in which a lath-like metal thin plate is provided. Therefore, it is desired to realize a configuration in which the pressure loss with respect to the gas in the fuel cell is reduced and the power generation performance is increased without increasing the size of the fuel cell.

[Description of Prior Invention]
On the other hand, the applicant of the present application provides a power generation body, a porous body that is disposed on the power generation body and in which a reaction gas flows, a separator that is disposed on the porous body, and drainage formed in the porous body. An application was filed for an invention relating to a fuel cell comprising a part (Japanese Patent Application No. 2007-25402). Next, the fuel cell according to the invention of the present invention will be described. In the fuel cell of the prior invention, a membrane electrode assembly is provided between two separators, and a porous body made of carbon or foam metal is provided between the membrane electrode assembly and the separator. The membrane / electrode assembly includes an electrolyte layer, an electrode layer, and a gas diffusion layer. Moreover, the groove part as a drainage part is formed in the separator side of the porous body. Thereby, the generated water generated in the membrane electrode assembly flows through the groove, and the generated water can be quickly conveyed in the gas downstream direction and discharged to the outside of the fuel cell. Further, when the groove is formed in the porous body in this way, there is a possibility that the pressure loss with respect to the gas in the fuel cell can be reduced and the power generation performance can be improved without increasing the size of the fuel cell.

  However, in the case of such a prior invention, the gas upstream side of the fuel cell has a large gas stoichiometric ratio and is easy to generate power, whereas the gas downstream side has a small gas stoichiometric ratio and tends to be difficult to generate power. . For this reason, it cannot be said that there is no possibility that the non-uniformity between the power generation performance and the temperature will increase in the gas flow direction of the fuel cell. When the temperature of a part of the fuel cell is high, a cooling device for a fuel cell such as a radiator needs to determine the cooling performance corresponding to this high temperature, so that there is no possibility that the cooling device will become large. Absent. For this reason, it is required to reduce the nonuniformity of the temperature of the fuel cell.

  An object of the present invention is to increase power generation performance and reduce nonuniformity of temperature and power generation performance with respect to a gas flow direction in a fuel cell.

  A fuel battery cell according to the present invention is a fuel battery cell including a power generator, a separator, and a porous body that is disposed between the power generator and the separator and allows a reaction gas to flow therethrough. The fuel battery cell is characterized in that the pressure loss to the gas is lower on the side than on the gas downstream side.

  Preferably, the cross-sectional area of the porous body with respect to a virtual plane orthogonal to the gas flow direction is made smaller on the gas upstream side than on the gas downstream side.

  More preferably, a groove having a cross-sectional area larger on the gas upstream side than on the gas downstream side is formed in the porous body.

  More preferably, the groove is formed on the separator side of the porous power generator and the separator.

  Further, in the configuration in which the groove portion having a cross-sectional area larger on the gas upstream side than on the gas downstream side is formed in the porous body, more preferably, the width of the groove portion formed in the porous body in a direction parallel to the side surface of the power generation body. The gas upstream side is larger than the gas downstream side.

  Further, in the configuration in which the groove portion having a larger cross-sectional area at the gas upstream side than at the gas downstream side is formed in the porous body, more preferably, the depth of the groove portion formed in the porous body in the direction orthogonal to the side surface of the power generation body. This is made larger on the gas upstream side than on the gas downstream side.

  Further, in the configuration in which the cross-sectional area of the porous body in the direction orthogonal to the gas flow direction is smaller on the gas upstream side than on the gas downstream side, more preferably, a plurality of groove portions are formed in the porous body, and the groove portions Is increased on the gas upstream side than on the gas downstream side.

  In the configuration in which the cross-sectional area of the porous body in the direction orthogonal to the gas flow direction is smaller on the gas upstream side than on the gas downstream side, more preferably, the porous body has a plurality of pieces extending from the gas upstream end. While forming a groove part, the length of at least one part groove part is varied.

  Further, in the configuration in which the cross-sectional area of the porous body related to the virtual plane orthogonal to the gas flow direction is smaller on the gas upstream side than the gas downstream side, more preferably, the direction of the porous body orthogonal to the gas flow direction The cross-sectional area of the gas is changed stepwise with respect to the gas flow direction.

  More preferably, the size of the porous body such as the porosity or the diameter of the pores is changed with respect to the gas flow direction.

  More preferably, the number of pores of the porous body is made larger on the gas upstream side than on the gas downstream side.

  In the fuel cell stack according to the present invention, preferably, a gas diffusion layer having a larger gas flow resistance than the porous body is provided between the power generation body and the porous body.

  More preferably, the porosity of the gas diffusion layer or the diameter of the pores is made smaller on the gas upstream side than on the gas downstream side.

  More preferably, the porous body is made of expanded metal.

  According to the fuel cell of the present invention, the porous battery is provided between the power generator and the separator, and has a porous body having a shape in which the pressure loss with respect to the gas is lower on the gas upstream side than on the gas downstream side. Compared to the case where the cross-sectional area is constant with respect to the flow direction of the reaction gas and the groove flow path forming member is formed with a groove flow path extending over the entire length of the gas flow direction, the gas flow resistance of the porous body can be increased and the power generator side relatively Since a large amount of reaction gas can be supplied to the battery, power generation performance can be improved. In addition, since the pressure loss of the gas is larger on the gas downstream side of the porous body than on the gas upstream side, the power generation performance on the gas upstream side, which tends to increase the power generation performance, can be suppressed, while the power generation performance decreases. The power generation performance on the downstream side of the gas can be improved. For this reason, the nonuniformity regarding the distribution direction of gas of temperature and power generation performance can be made small.

  In addition, according to the configuration in which the groove portion having a cross-sectional area larger on the gas upstream side than on the gas downstream side is formed in the porous body, the pressure loss with respect to the gas in the fuel cell is reduced without increasing the size of the fuel cell. In addition, the power generation performance can be improved.

  Moreover, according to the structure which forms a groove part in the separator side among the power generation bodies and separators of a porous body, unlike the case where a groove part is formed in the power generation body side of a porous body, the generated water accompanying power generation accumulates in the vicinity of a power generation body. Can be made difficult to occur. At the same time, it is possible to prevent the contact pressure between the power generation body or the gas diffusion layer provided on the power generation body side and the porous body from becoming significantly uneven in the surface direction or the length direction of the porous body. For this reason, the nonuniformity of the electric power generation performance regarding the surface direction or length direction of a porous body can be made small.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 8 show a first embodiment according to the present invention. FIG. 1 is a schematic perspective view of a fuel cell stack configured by stacking a plurality of fuel cells according to the present embodiment. FIG. 2 is a front view of FIG. FIG. 3 is a view showing a part of the AA cross section of FIG. FIG. 4 is a partial perspective view showing an example in the case where the oxidizing gas side porous body is made of expanded metal. 5 is a cross-sectional view of the oxidizing gas side porous body of FIG. 3 taken along the line BB. 6A is a cross-sectional view taken along the line CC in FIG. 5, FIG. 6B is a cross-sectional view taken along the line DD in FIG. 5, and FIG. 6C is a cross-sectional view taken along the line EE in FIG. FIG. 7A shows a groove portion, a porous body main body, and an oxidizing gas diffusion layer at each cross-sectional portion between the gas upstream side and the gas downstream side in the oxidizing gas side porous body and the oxidizing gas diffusion layer. FIG. 5B is a diagram showing an example of the flow rate ratio of the oxidizing gas, and FIG. 5B is a diagram showing a change in pressure loss with respect to the gas flow direction of the oxidizing gas side porous body. FIG. 8 is a diagram showing the oxygen concentration in each cross section orthogonal to the gas flow direction of the oxidizing gas side porous body and the entire oxidizing gas diffusion layer.

  As shown in FIGS. 1 and 2, the fuel cell stack 24 is configured by stacking a plurality of fuel cells 26 and sandwiching them by a pair of end plates (not shown) from both sides. As shown in FIG. 3, each fuel cell 26 is provided with a pair of separators 30 on both sides of a membrane-electrode assembly (MEA) 28 that is a power generation body. In the membrane-electrode assembly 28, an anode side electrode is disposed on one surface (lower surface in FIG. 3) of an electrolyte membrane made of a polymer ion exchange membrane, and a cathode side electrode is disposed on the other surface (upper surface in FIG. 3). ing. The membrane-electrode assembly 28 includes a catalyst, such as platinum. Further, an oxidizing gas side porous body 32 for allowing an oxidizing gas as a reaction gas to flow therethrough and an oxidizing gas diffusion layer 34 are provided between the separator 30 and the cathode side electrode in order from the separator 30 side. In addition, a fuel gas side porous body 36 for allowing a fuel gas, which is a reactive gas to flow, and a fuel gas diffusion layer 38 are provided between the separator 30 and the anode side electrode in order from the separator 30 side. A plurality of such fuel battery cells 26 are stacked via the intermediate separator 40, and are further sandwiched between current collector plates, insulating plates and end plates (not shown), and tightened with tension rods and nuts (not shown). A fuel cell stack 24 (FIGS. 1 and 2) that generates a voltage is configured. The oxidizing gas is air, for example. The fuel gas is a hydrogen-containing gas such as hydrogen gas.

  As shown in FIGS. 1 and 2, each separator 30 is made of a flat metal, and has a fuel gas supply manifold hole 42, a fuel gas discharge manifold hole 44, an oxidizing gas supply manifold hole 46, and an oxidizing gas discharge at the outer periphery. A manifold hole 48, a refrigerant supply manifold hole 50, and a refrigerant discharge manifold hole 52 are provided. In a state where the plurality of fuel cells 26 are stacked, the plurality of manifold holes 42, 44, 46, 48, 50, 52 facing each other in the stacking direction of the fuel cells 26 communicate with each other, and the fuel gas supply manifold 43, the fuel A gas discharge manifold 45, an oxidizing gas supply manifold 47, an oxidizing gas discharge manifold 49, a refrigerant supply manifold 51, and a refrigerant discharge manifold 53 are configured. These manifolds 43, 45, 47, 49, 51, 53 are each provided with a fuel gas inlet, a fuel gas outlet, an oxidizing gas inlet, an oxidizing gas outlet provided on an end plate (not shown) at one end of the fuel cell stack 24 in the stacking direction. The refrigerant is connected to the refrigerant inlet and the refrigerant outlet, respectively. Each manifold 43, 45, 47, 49, 51, 53 is provided in the stacking direction of the plurality of stacked fuel cells 26.

  The fuel gas supply manifold 43, the fuel gas discharge manifold 45, the oxidant gas supply manifold 47, and the oxidant gas discharge manifold 49 correspond to the fuel cells 26, respectively, through internal channels (not shown) branched in different directions. The porous bodies 32 and 36 (FIG. 3) and the gas diffusion layers 34 and 38 (FIG. 3) are communicated.

  2, the membrane-electrode assembly 28, the porous bodies 32 and 36, and the gas diffusion layers 34 and 38 are disposed at a substantially central portion between the adjacent separators 30. . The membrane-electrode assembly 28, the porous bodies 32 and 36, and the gas diffusion layers 34 and 38 are formed by a sealing member 55 (FIG. 3) having insulating properties such as a resin disposed between the outer peripheral portions of the adjacent separators 30. And is sealed from the outside. Further, as shown in FIG. 3, a refrigerant flow path for arranging an intermediate separator 40 between two separators 30 constituting adjacent fuel battery cells 26 and causing a coolant as a refrigerant to flow through the intermediate separator 40. 54 is formed. The refrigerant flow path 54 communicates with the refrigerant supply manifold 51 and the refrigerant discharge manifold 53.

  Each gas diffusion layer 34 and 38 shown in FIG. 3 is comprised by the member which has electroconductivity and gas permeability. As the gas diffusion layers 34 and 38, for example, a carbon porous body such as carbon paper, a woven fabric formed of a conductive material, or the like can be used.

  Further, the porous bodies 32 and 36 shown in FIG. 3 are made of a conductive material such as a carbon porous body or a foamed metal body, and are provided with a large number of pores. Moreover, each porous body 32 and 36 can also be comprised with an expanded metal. For example, as shown in FIG. 4, by bending and shearing a thin metal plate such as stainless steel using a processing device having a blade shape, etc., it corresponds to pores in multiple staircases in discrete steps. An expanded metal 58 having an opening 56 to be formed can be formed. The opening 56 can have various shapes such as a substantially hexagonal shape and a substantially diamond shape.

  Each of the porous bodies 32 and 36 has a function of guiding the reaction gas to the membrane-electrode assembly 28 side in a direction orthogonal to the direction parallel to the membrane-electrode assembly 28, that is, a direction orthogonal to the gas flow direction. Have The porosity in the cross section regarding the virtual plane orthogonal to the gas flow direction of each porous body 32, 36 is substantially constant with respect to the gas flow direction.

  In addition, as shown in FIG. 5, a plurality (three in the illustrated example) of groove portions (slits) 60 are formed in each oxidizing gas side porous body 32 in the gas flow direction. Each groove part 60 has a triangular pyramid shape. That is, as shown in FIG. 5, the cross-sectional shape of each groove 60 when each oxidizing gas side porous body 32 is viewed in the BB cross section of FIG. 3 parallel to the side surface of the membrane-electrode assembly 28 (FIG. 3). Is a triangle having one end opened at the upstream end face (left end face in FIG. 5) of the oxidizing gas and the top (back) as the other end at the downstream side (right side in FIG. 5) of the oxidizing gas. Each groove part 60 does not reach the gas downstream side end face (the right end face in FIG. 5) of each oxidizing gas side porous body 32.

  FIGS. 6A, 6B, and 6C show the CC cross section, the DD cross section, and the EE cross section of FIG. 5, respectively. As shown in FIGS. 6 (a) and 6 (b), each fuel cell 26 (FIG. 3) is crossed perpendicularly to the side surface of the membrane-electrode assembly 28, taken along the lines CC, DD, EE of FIG. When viewed in cross section, the cross-sectional shape of each groove 60 is such that one end opens on the side facing the separator 30 (FIG. 3) (the left side in FIGS. 6A and 6B) and the membrane-electrode assembly 28 side ( It is set as the triangle which has the top part (back part) which is the other end in Fig.6 (a) (right side). That is, the groove part 60 is formed in the separator 30 side among the membrane-electrode assembly 28 and the separator 30 of each oxidizing gas side porous body 32. Further, as shown in FIGS. 6A, 6B, and 6C, the cross-sectional shape of each groove portion 60 with respect to a virtual plane orthogonal to the side surface of the membrane-electrode assembly 28 increases from the gas upstream side toward the downstream side. It is small. That is, the groove 30 formed in each oxidant gas side porous body 32 has an opening end on the separator 30 side in a direction parallel to the side surface of the membrane-electrode assembly 28 (vertical direction in FIGS. 6A, 6B, and 6C). The width W (FIG. 6A) is made larger on the gas upstream side than on the gas downstream side, and the depth H of each groove 60 in the direction orthogonal to the side surface of the membrane-electrode assembly 28 (FIG. 6A )) Is larger on the gas upstream side than on the gas downstream side.

  In this way, the groove portions 60 having a cross-sectional area larger on the upstream side of the gas than on the downstream side of the gas are formed in each oxidizing gas side porous body 32, and the cross-sectional area of each groove portion 60 is increased on the upstream side of the oxidizing gas. The gas is made smaller toward the gas downstream side. When compared in terms of unit cross-sectional areas, the gas flow resistance increases in the order of the groove 60, the oxidizing gas side porous body 32, and the oxidizing gas diffusion layer 34. That is, the gas flow resistance is highest in the oxidizing gas diffusion layer 34, and the gas flow resistance is lowest in the groove 60. Since it comprises in this way, the oxidizing gas side porous body 32 will have a shape where the pressure loss of gas becomes lower on the gas upstream side than on the gas downstream side. Moreover, the cross-sectional area regarding the virtual plane orthogonal to the gas flow direction of the porous body main body 62 that is the portion excluding the groove 60 of the oxidizing gas side porous body 32 is smaller on the gas upstream side than on the gas downstream side. .

  In such a fuel cell stack 24 (FIG. 1), for example, hydrogen gas as a fuel gas is fed into the fuel gas supply manifold 43 in the direction indicated by the arrow α in FIG. Fuel gas is fed into the corresponding fuel gas side porous body 36 (FIG. 3) and fuel gas diffusion layer 38 (FIG. 3). Then, the fuel gas is discharged to the outside through the fuel gas discharge manifold 45 in the direction indicated by the arrow β in FIG. Further, by sending air, which is an oxidizing gas, into the oxidizing gas supply manifold 47 in the direction indicated by an arrow γ in the same figure, the oxidizing gas side porous body 32 (FIG. 3) corresponding to the oxidizing gas flow path on the cathode side and Oxidizing gas is fed into the oxidizing gas diffusion layer 34 (FIG. 3). Then, the oxidizing gas is discharged to the outside through the oxidizing gas discharge manifold 49 in the direction indicated by the arrow δ in FIG. Fuel gas and oxidizing gas are subjected to an electrochemical reaction at membrane-electrode assembly 28 (FIG. 3). Then, the generated power is obtained between the cathode side electrode and the anode side electrode, and the battery output is obtained from both ends of the fuel cell stack 24 (FIG. 1) including a plurality of stacked fuel cell units 26.

  According to the fuel cell 26 constituting the fuel cell stack 24 as described above, the pressure loss to the gas is lower on the gas upstream side than on the gas downstream side, which is disposed between the membrane-electrode assembly 28 and the separator 30. Therefore, the oxidizing gas side porous body 32 is a groove channel forming member having a constant cross-sectional area with respect to the flowing direction of the oxidizing gas and having a groove channel extending over the entire length of the gas flowing direction. Compared to the case, the gas flow resistance of the oxidizing gas side porous body 32 can be increased, and a relatively large amount of oxidizing gas can be supplied to the membrane-electrode assembly 28 side, so that the power generation performance can be improved.

  In addition, since the pressure loss of the gas is larger on the gas downstream side of the oxidizing gas side porous body 32 than on the gas upstream side, the power generation performance on the gas upstream side that tends to increase the power generation performance can be suppressed, while the power generation The power generation performance on the gas downstream side where the performance tends to be low can be increased. For this reason, the nonuniformity regarding the flow direction of gas of the temperature of the fuel cell 26 and the fuel cell stack 24 and the power generation performance can be reduced.

  That is, in the fuel cell stack 24, the oxygen concentration is usually high in the gas upstream portion of the oxidizing gas diffusion layer 34, and the existing water tends to remain as water vapor, so that flooding in the vicinity of the electrolyte membrane hardly occurs. For this reason, it is not necessary to flow a large amount of oxidizing gas in the upstream portion of the oxidizing gas diffusion layer 34. In the present embodiment, due to such circumstances, most of the oxidizing gas flowing in the gas upstream side portion of the oxidizing gas side porous body 32 is caused to flow into the groove portion 60 to reduce the pressure loss in the gas upstream side portion. For this reason, the power generation performance on the gas upstream side is suppressed, and the amount of heat generated by power generation can be reduced. On the other hand, since the oxygen concentration is low in the gas upstream portion of the oxidizing gas diffusion layer 34 and flooding tends to occur, the cross-sectional area of the groove 60 formed in the oxidizing gas side porous body 32 is reduced to the gas. The amount of oxidizing gas flowing in the gas downstream portion of the oxidizing gas diffusion layer 34 is increased by decreasing gradually toward the downstream side to increase the pressure loss in the gas downstream portion of the oxidizing gas side porous body 32. Can be increased. Therefore, the power generation performance on the gas downstream side can be improved, and the amount of heat generated by power generation can be increased. As a result, the nonuniformity of the temperature and power generation performance of the fuel cell 26 and the fuel cell stack 24 in the gas flow direction can be reduced. In particular, during power generation operation under high temperature conditions, it is possible to effectively suppress the temperature at the upstream side of the oxidizing gas of the fuel battery cell 26 from becoming excessively high.

  FIG. 7A shows a groove 60 (range indicated by P in the figure) at each cross-sectional portion between the gas upstream side and the gas downstream side in the oxidizing gas side porous body 32 and the oxidizing gas diffusion layer 34. The flow rate ratio of the oxidizing gas between the porous body main body 62 (the range indicated by Q in the figure) other than the groove 60 of the oxidizing gas side porous body 32 and the oxidizing gas diffusion layer 34 (the range indicated by R in the figure). It is a figure which shows one example of. In the description of FIGS. 7 and 8, the symbols used in FIGS. 1 to 6 are used. In FIG. 7A, CC, DD, and EE correspond to the CC, DD, and EE sections of FIG. 5, respectively. As shown in FIG. 7A, a large amount of oxidizing gas flows in the groove 60 on the gas upstream side where the groove 60 is formed with respect to the flow path of the oxidizing gas.

  FIG. 7B shows the change in pressure loss related to the gas flow direction of the oxidizing gas side porous body 32 at each cross-section between the gas upstream side and the gas downstream side, corresponding to FIG. Show. In FIG. 7B, the solid line S represents the case of the present embodiment, and the broken line T represents the case of the comparative example in which the groove 60 is omitted from the oxidizing gas side porous body 32 in the same configuration as the present embodiment. , Respectively. As shown in FIG. 7B, in the present embodiment, since the groove portion 60 is formed, the fuel battery cell 26 is shown by the oblique lattice shown in FIG. 7 in comparison with the comparative example in which the groove portion 60 is not formed. And the pressure loss with respect to the gas of the fuel cell stack 24 can be reduced.

  FIG. 8 shows that the present embodiment is orthogonal to the gas flow direction of the entire oxidizing gas side porous body 32 and the oxidizing gas diffusion layer 34 between the oxidizing gas upstream side and the oxidizing gas downstream side of the fuel cell 26. It is a diagram which shows the oxygen concentration in each cross section. In the figure, the solid line La represents the case of the present embodiment, and the broken line Lb represents the case of a comparative example in which the groove portion 60 is not formed in the oxidizing gas side porous body 32 in the same configuration as the present embodiment. . As shown in FIG. 8, in any case, the oxygen concentration decreases as a result of power generation from the gas upstream side toward the gas downstream side. However, in the present embodiment, the oxidizing gas side porosity is provided by the groove 60 on the gas upstream side. Since the pressure loss of the body 32 is reduced, the degree of decrease in oxygen concentration is reduced compared to the comparative example because it is difficult to generate power. On the other hand, since the groove portion 60 is eliminated or the cross section of the groove portion 60 is reduced on the gas downstream side, the pressure loss of the oxidizing gas side porous body 32 is increased, so that a large amount of oxygen is supplied to the membrane-electrode assembly 28 side. Provided. For this reason, on the gas downstream side, the degree of decrease in oxygen concentration is greater than in the comparative example. As a result, compared with the comparative example in which the groove portion 60 is not formed, the oxygen concentration gradient with respect to the oxidizing gas flow direction can be moderated. Therefore, the nonuniformity of the temperature and power generation performance of the fuel cell 26 and the fuel cell stack 24 with respect to the gas flow direction can be reduced.

  Further, in the present embodiment, the groove portion 60 having a larger cross-sectional area at the gas upstream side than at the gas downstream side is formed in the oxidizing gas side porous body 32, so that the fuel cell stack 24 is not enlarged and the fuel cell stack 24 is not enlarged. The pressure loss with respect to the gas in the battery stack 24 can be reduced, and the power generation performance can be improved.

  Moreover, in order to form the groove part 60 on the separator 30 side among the membrane-electrode assembly 28 and the separator 30 of the oxidizing gas side porous body 32, the groove part 60 is formed on the membrane-electrode assembly 28 side of the oxidizing gas side porous body 32. Unlike the case, so-called flooding, in which generated water associated with power generation accumulates in the vicinity of the membrane-electrode assembly 28, can be made difficult to occur. At the same time, the contact pressure between the oxidizing gas diffusion layer 34 provided on the membrane-electrode assembly 28 side and the oxidizing gas side porous body 32 is greatly non-uniform in the surface direction or length direction of the side surface of the oxidizing gas side porous body 32. Can be prevented. For this reason, the nonuniformity of the electric power generation performance regarding the surface direction or length direction of the side surface of the oxidizing gas side porous body 32 can be reduced.

  In addition, as a method of forming the groove portion 60 in the oxidizing gas side porous body 32, for example, when the oxidizing gas side porous body 32 is configured by sintering a set of metal particles, that is, a metal powder, For example, a nested mold may be arranged at a position corresponding to a part of the groove portions 60. In the case where the oxidizing gas side porous body 32 is made of expanded metal, when the groove portion 60 is formed, a slit or the like is cut into the expanded metal to widen the cut or a portion corresponding to the groove portion 60 is formed. The groove 60 can be formed by drilling or the like. Moreover, the groove part 60 can also be formed by giving a press process to an expanded metal and crushing the groove part 60 part. In the case where the oxidizing gas side porous body 32 is made of expanded metal, the oxidizing gas side porous body 32 can also be formed by stacking a plurality of expanded metals. In this case, for example, the oxidizing gas side porous body 32 can be configured by forming the groove portion 60 in a part of the expanded metal and laminating the remaining expanded metal that does not form the groove portion 60.

[Second Embodiment]
FIG. 9 and FIG. 10 are diagrams corresponding to FIG. 5 and FIG. 6 of the first embodiment, respectively, in the second embodiment of the present invention. In the present embodiment, as shown in FIGS. 10A, 10 </ b> B, and 10 </ b> C, each oxidizing gas side porous body 32 is viewed in a cross section regarding a virtual plane orthogonal to the side surface of the membrane-electrode assembly 28. The cross-sectional shape of each groove 60a is rectangular. In each oxidizing gas side porous body 32, the end portion of the groove 60a on the separator 30 side (FIGS. 10A, 10B, and 10C) is opened on the side surface of each oxidizing gas side porous body 32.

  Further, the depth H (FIG. 10A) of each groove 60a when the fuel battery cell 26 (see FIG. 3) is viewed in a cross-section with respect to a virtual plane orthogonal to the side surface of the membrane-electrode assembly 28 is shown in FIG. It gradually decreases from the side toward the downstream side. Since other configurations and operations are the same as those in the first embodiment, the same reference numerals are given to the equivalent parts, and overlapping illustrations and descriptions are omitted. In addition, when each oxidizing gas side porous body 32 is viewed in a section related to a virtual plane orthogonal to the side surface of the membrane-electrode assembly 28, the cross-sectional shape of each groove 60a can be a shape other than a rectangle or a triangle. .

[Third Embodiment]
FIG. 11 is a diagram corresponding to FIG. 10 of the second embodiment shown in FIGS. 9 and 10 in the third embodiment of the present invention. In the present embodiment, the cross-sectional shape of each groove portion 60b when the fuel battery cell 26 (see FIG. 3) is viewed in a cross section related to a virtual plane orthogonal to the side surface of the membrane-electrode assembly 28 is rectangular, The depth H of the groove 60b is constant with respect to the gas flow direction. Other configurations and operations are the same as those of the second embodiment shown in FIG. 9 and FIG.

[Fourth Embodiment]
FIGS. 12 and 13 are diagrams corresponding to FIGS. 5 and 6 of the first embodiment shown in FIGS. 1 to 8, respectively, in the fourth embodiment of the present invention. In the present embodiment, as shown in FIG. 12, the cross-sectional shape of the groove 60 c when each oxidizing gas side porous body 32 is viewed in a cross section related to a virtual plane parallel to the side surface of the membrane-electrode assembly 28 is A rectangle in which the left end in FIG. 12 is open at the gas upstream end face of the oxidizing gas side porous body 32 and the other end (right end in FIG. 12) is not open at the gas downstream end face of the oxidizing gas side porous body 32. It is said.

  Further, as shown in FIG. 13, when the fuel cell 26 (see FIG. 3) is seen in a cross section regarding a virtual plane orthogonal to the side surface of the membrane-electrode assembly 28, the cross-sectional shape of each groove 60 c is rectangular. . In the present embodiment, the depth H of each groove 60c when the fuel battery cell 26 is viewed in a cross-section with respect to a virtual plane orthogonal to the side surface of the membrane-electrode assembly 28, and the bottom surface of the groove 60c as an inclined surface. For example, the sectional area of the groove 60c is gradually reduced from the gas upstream side to the downstream side by gradually reducing the gas upstream side toward the downstream side. In the present embodiment, the width W of the groove 60c is not changed with respect to the gas flow direction. Since other configurations and operations are the same as those of the first embodiment shown in FIGS. 1 to 8 described above, the same parts are denoted by the same reference numerals, and overlapping illustrations and descriptions are omitted.

[Fifth Embodiment]
FIGS. 14 and 15 are diagrams corresponding to FIGS. 5 and 6 of the first embodiment shown in FIGS. 1 to 8, respectively, in the fifth embodiment of the present invention. In the present embodiment, as shown in FIG. 14, in each oxidizing gas side porous body 32, a plurality of groove portions 60d are formed in the gas flow direction, and the number of groove portions 60d is maximized on the gas upstream side, The number is intermediate in the center of the gas flow direction, and the number is the smallest on the gas downstream side. For this purpose, all the one ends of the plurality of groove portions 60d are opened at the gas upstream end surface (left end surface in FIG. 14) of each oxidizing gas side porous body 32, and some of the groove portions 60d are formed on the oxidizing gas side porous body. 32 is the shortest length that does not reach the center in the length direction. Further, a part of the remaining groove part 60d has the longest length reaching the gas downstream end portion of the oxidizing gas side porous body 32, and the remaining part of the remaining groove part 60d has an intermediate length. As described above, a plurality of groove portions 60d extending from the gas upstream end are formed in the oxidizing gas side porous body 32, the lengths of some of the groove portions 60d are made different from each other, and the number of the groove portions 60d is changed to gas. It is also possible to increase the amount on the upstream side than on the gas downstream side.

  In the case of this embodiment as well, the cross section of the porous body main body 62 of the oxidizing gas side porous body 32 with respect to the virtual plane orthogonal to the gas flow direction, that is, the cross section orthogonal to the gas flow direction is seen. The cross-sectional area in this case is smaller on the gas upstream side than on the gas downstream side. Since other configurations and operations are the same as those of the first embodiment shown in FIGS. 1 to 8 described above, the same parts are denoted by the same reference numerals, and overlapping illustrations and descriptions are omitted.

[Sixth Embodiment]
FIG. 16 is a diagram corresponding to the third embodiment shown in FIG. 11 in the sixth embodiment of the present invention. In the present embodiment, the end of the groove 60 e formed in the oxidizing gas side porous body 32 on the membrane-electrode assembly 28 side (the right side of FIGS. 16A, 16 B, and 16 C) is the oxidation gas side porous body 32. The end surface of the membrane-electrode assembly 28 is reached. According to this embodiment, the processing and manufacturing work of each oxidizing gas side porous body 32 can be easily performed. Other configurations and operations are the same as those of the third embodiment shown in FIG.

[Seventh Embodiment of the Invention]
FIG. 17A is a diagram corresponding to FIG. 5 of the first embodiment shown in FIGS. 1 to 8 in the seventh embodiment of the present invention, and FIG. It is FF sectional drawing of Fig.17 (a). In the present embodiment, in the fourth embodiment shown in FIGS. 12 to 13, the depth of the groove 60f formed in each oxidizing gas side porous body 32 is set to be a stepped shape on the bottom surface of the groove 60f. Thus, the gas is gradually changed from the gas upstream side to the gas downstream side, and is reduced in stages. Other configurations and operations are the same as those in the fourth embodiment shown in FIGS. 12 to 13 described above, and thus redundant description is omitted.

[Eighth Embodiment]
FIG. 18A is a diagram corresponding to FIG. 5 of the first embodiment shown in FIGS. 1 to 8 in the eighth embodiment of the present invention, and FIG. FIG. 18C is a diagram showing a change in porosity of the oxidizing gas side porous body 32 in the gas flow direction, and FIG. 18C is a diagram showing a change in pressure loss of the oxidizing gas side porous body 32 in the gas flow direction. is there. In the present embodiment, unlike each of the above embodiments, no groove is formed in each oxidizing gas side porous body 32. Instead, the porosity of each oxidizing gas side porous body 32, that is, the number of pores per unit area, is changed with respect to the gas flow direction. That is, as shown in FIG. 18B, the porosity of each oxidizing gas side porous body 32 is gradually reduced at a constant rate from the gas upstream side toward the downstream side. That is, the number of pores of each oxidizing gas side porous body 32 is made larger on the gas upstream side than on the gas downstream side. Accordingly, as shown in FIG. 18C, the pressure loss of each oxidizing gas side porous body 32 gradually increases at a constant rate from the gas upstream side toward the downstream side. That is, each oxidizing gas side porous body 32 has a shape in which the pressure loss to the gas is lower on the gas upstream side than on the downstream side.

  According to such a case of the present embodiment, since the oxidizing gas side porous body 32 having a shape in which the pressure loss to the gas is lower on the gas upstream side than on the downstream side is provided, the oxidizing gas side porous body 32 is oxidized. Compared to the case where the groove flow passage forming member has a constant cross-sectional area with respect to the gas flow direction and has a groove flow passage extending over the entire length of the gas flow direction, the gas flow resistance of the oxidizing gas side porous body 32 can be increased. In addition, since a large amount of oxidizing gas can be supplied to the membrane-electrode assembly 28 (see FIG. 3) side, power generation performance can be improved. Moreover, since the pressure loss with respect to the gas is larger on the gas downstream side of the oxidizing gas side porous body 32 than on the upstream side, the power generation performance on the gas upstream side where the power generation performance tends to be high can be suppressed. The power generation performance on the downstream side of the gas, which tends to be low, can be improved. For this reason, the nonuniformity regarding the flow direction of the gas of the temperature of the fuel cell 26 (refer FIG. 3) and the fuel cell stack 24 (refer FIG. 1) and power generation performance can be made small. Other configurations and operations are the same as those in the first embodiment shown in FIGS. 1 to 8 described above, and thus redundant illustration and description are omitted.

  In FIG. 18B of the present embodiment, the porosity of the oxidizing gas side porous body 32 may be replaced with the pore diameter (pore diameter) that is the size of the pores of the oxidizing gas side porous body 32. it can. In this case, in the oxidizing gas side porous body 32, even if the porosity in the gas flow direction is constant, the size of the pores is larger on the gas upstream side than on the downstream side. For this reason, as in the present embodiment, the pressure loss for the gas is smaller on the gas upstream side than on the downstream side. Further, in the oxidizing gas side porous body 32, the porosity or the pore diameter can be changed stepwise as it goes from the upstream side to the downstream side of the gas, that is, it can be reduced stepwise. For example, by combining a plurality of porous elements having a porosity and a pore diameter that are substantially constant with respect to the gas flow direction, and a plurality of porous elements having different porosity or pore diameters with respect to the gas flow direction. 32 can also be configured.

  Further, in the present embodiment, when each oxidizing gas side porous body 32 is made of an expanded metal, in order to change the porosity or the pore diameter of the oxidizing gas side porous body 32, pores, that is, openings 56 (see FIG. 4). ) The shape of the blade mold used for forming or the pitch for moving the blade mold can be changed stepwise in the middle.

[Ninth Embodiment]
FIGS. 19 and 20 are diagrams corresponding to FIGS. 5 and 6 of the first embodiment shown in FIGS. 1 to 8, respectively, in the ninth embodiment of the present invention. In the present embodiment, a plurality of through holes 64 penetrating in a direction perpendicular to the side surface of the membrane-electrode assembly 28 (see FIG. 3) are formed in each of the oxidizing gas side porous bodies 32 that are substantially homogeneous with respect to the pores. . The number of through holes 64 is gradually reduced from the upstream side to the downstream side of the oxidizing gas. Thereby, each oxidizing gas side porous body 32 is assumed to have a shape in which the pressure loss to the gas is lower on the gas upstream side than on the downstream side.

  In the case of this embodiment as well, since the oxidizing gas side porous body 32 having a shape in which the pressure loss with respect to the gas is lower on the gas upstream side than on the downstream side, the fuel cell 26 (see FIG. 3) The power generation performance can be increased, and the non-uniformity of the temperature and the power generation performance with respect to the gas flow direction can be reduced. Other configurations and operations are the same as those in the first embodiment shown in FIGS. 1 to 8 described above, and thus redundant illustration and description are omitted.

  In addition, in the eighth to ninth embodiments shown in FIGS. 18 to 20, the gas upstream side when the gas flow resistance of the oxidizing gas side porous body 32 is anisotropic. The direction is regulated so that the gas flow resistance of the oxidant gas side porous body 32 becomes smaller at the portion while the gas flow resistance of the oxidant gas side porous body 32 becomes larger at the gas downstream side portion, and the fuel cell 26 ( (See FIG. 3).

  In each of the embodiments described above, the porosity or pore diameter of the oxidizing gas diffusion layer 34 (see FIGS. 3 and 6) is made smaller on the gas upstream side than on the gas downstream side, so that the oxidizing gas diffusion layer 34 It is also possible to reduce the pressure loss on the gas downstream side. In each of the above embodiments, when the gas flow resistance of the oxidizing gas diffusion layer 34 has anisotropy, the gas flow resistance of the gas diffusion layer 34 becomes larger at the gas upstream side portion, while the gas downstream resistance. The direction can be regulated so that the gas flow resistance of the gas diffusion layer becomes smaller at the side portion, and the gas diffusion layer can be assembled to the fuel cell 26 (see FIG. 3).

  Further, in each of the above embodiments, the anode side fuel gas side porous body 36 (see FIGS. 3 and 6) and the fuel gas diffusion layer 38 (see FIGS. 3 and 6) are combined with the cathode side oxidizing gas side porous body. The body 32 and the oxidizing gas diffusion layer 34 can also have the same structure. The oxidizing gas side porous body 32 and the oxidizing gas diffusion layer 34 are shaped so that the pressure loss does not change in the gas flow direction, and the fuel gas The side porous body 36 and the fuel gas diffusion layer 38 may be shaped so that the pressure loss changes with respect to the gas flow direction. For example, the fuel gas side porous body 36 may be formed with a groove portion having a cross-sectional area that decreases in the direction from the upstream side to the downstream side of the fuel gas, similar to that formed in the oxidizing gas side porous body 32. In each of the above embodiments, the gas diffusion layer is provided between the porous body and the membrane-electrode assembly. However, the gas diffusion layer may be omitted and the porous body may have the function of the gas diffusion layer. it can. In each of the above embodiments, the gas diffusion layer may be a collector that constitutes a separator together with a plate-like separator body.

1 is a schematic perspective view of a fuel cell stack configured by stacking a plurality of fuel cells according to a first embodiment of the present invention. It is a front view of FIG. It is a figure which shows a part of AA cross section of FIG. It is a fragmentary perspective view which shows an example in the case of comprising an oxidizing gas side porous body with an expanded metal. It is BB sectional drawing of the oxidizing gas side porous body of FIG. (A) is a CC cross section of FIG. 5, (b) is a DD cross section of FIG. 5, (c) is a figure which shows the EE cross section of FIG. (A) In the oxidizing gas side porous body and the oxidizing gas diffusion layer, the oxidation of the groove, the porous body main body, and the oxidizing gas diffusion layer at each cross-sectional portion between the gas upstream side and the gas downstream side It is a figure which shows one example of the flow ratio of gas, (b) is a figure which shows the change of the pressure loss regarding the distribution direction of the gas of an oxidizing gas side porous body. It is a diagram which shows the oxygen concentration in each cross section orthogonal to the gas distribution direction of the oxidizing gas side porous body and the entire oxidizing gas diffusion layer. In the 2nd Embodiment of this invention, it is a figure corresponding to FIG. It is a figure corresponding to FIG. 6 similarly. In the 3rd Embodiment of this invention, it is a figure corresponding to FIG. In the 4th Embodiment of this invention, it is a figure corresponding to FIG. It is a figure corresponding to FIG. 6 similarly. In the 5th Embodiment of this invention, it is a figure corresponding to FIG. It is a figure corresponding to FIG. 6 similarly. In the 6th Embodiment of this invention, it is a figure corresponding to FIG. (A) is a figure corresponding to Drawing 5 in a 7th embodiment of the present invention, and (b) is an FF sectional view of (a). (A) is a figure corresponding to Drawing 5 in an 8th embodiment of the present invention, and (b) is a figure showing change of the porosity about the gas distribution direction of an oxidizing gas side porous body. (C) is a figure which shows the change of the pressure loss regarding the gas distribution direction of an oxidizing gas side porous body. FIG. 10 is a diagram corresponding to FIG. 5 in the ninth embodiment of the present invention. It is a figure corresponding to FIG. 6 similarly. It is principal part sectional drawing of one example of the fuel cell known conventionally. It is a diagram which shows one example of the relationship between the stoichiometric ratio of the reactive gas supplied to a cathode side electrode, and a fuel cell voltage.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Electrolyte membrane / electrode structure, 12 Separator, 14 Electrolyte membrane, 16 Anode side electrode, 18 Cathode side electrode, 20 Gas diffusion layer, 22 Electrode catalyst layer, 24 Fuel cell stack, 26 Fuel cell, 28 Membrane-electrode assembly (MEA), 30 separator, 32 oxidizing gas side porous body, 34 oxidizing gas diffusion layer, 36 fuel gas side porous body, 38 fuel gas diffusion layer, 40 intermediate separator, 42 fuel gas supply manifold hole, 43 fuel gas supply manifold, 44 Fuel gas discharge manifold hole, 45 Fuel gas discharge manifold, 46 Oxidation gas supply manifold hole, 47 Oxidation gas supply manifold, 48 Oxidation gas discharge manifold hole, 49 Oxidation gas discharge manifold, 50 Refrigerant supply manifold hole, 51 Refrigerant supply manifold, 52 cold Discharge manifold hole, 53 the coolant discharge manifold, 54 a refrigerant flow passage, 55 seal member, 56 opening, 58 expanded metal, 60,60a, 60b, 60c, 60d, 60e, 60f groove 62 porous body portion 64 through hole.

Claims (14)

A power generator,
A separator;
A porous body disposed between a power generation body and a separator and allowing a reaction gas to flow therethrough,
The porous battery has a shape in which the pressure loss with respect to the gas is lower on the gas upstream side than on the gas downstream side. The fuel cell according to claim 1,
A fuel cell, wherein a cross-sectional area of a porous body related to a virtual plane orthogonal to a gas flow direction is smaller on the gas upstream side than on the gas downstream side. The fuel cell according to claim 1 or 2,
A fuel cell, wherein a groove portion having a cross-sectional area larger on the gas upstream side than on the gas downstream side is formed in the porous body. The fuel cell according to claim 3, wherein
A fuel cell comprising a porous power generation body and a separator, wherein a groove is formed on the separator side. The fuel cell according to claim 3, wherein
A fuel cell, wherein a width of a groove formed in a porous body in a direction parallel to a side surface of a power generation body is larger on a gas upstream side than on a gas downstream side. The fuel cell according to claim 3, wherein
A fuel cell, wherein a depth of a groove formed in a porous body in a direction orthogonal to a side surface of a power generation body is made larger on a gas upstream side than on a gas downstream side. The fuel cell according to claim 2,
A fuel cell, wherein a plurality of groove portions are formed in a porous body, and the number of groove portions is greater on the gas upstream side than on the gas downstream side. The fuel cell according to claim 2,
A fuel cell, wherein a plurality of grooves extending from a gas upstream end are formed in a porous body, and at least some of the grooves are different in length. The fuel cell according to any one of claims 2 to 8,
A fuel cell, wherein a cross-sectional area of a porous body with respect to a virtual plane orthogonal to a gas flow direction is changed stepwise with respect to a gas flow direction. The fuel cell according to claim 1,
A fuel cell, wherein a porosity or a pore size of a porous body is changed with respect to a gas flow direction. The fuel cell according to claim 10, wherein
A fuel cell, wherein the number of pores in the porous body is greater on the gas upstream side than on the gas downstream side. The fuel cell according to any one of claims 1 to 11, wherein
A fuel battery cell, wherein a gas diffusion layer having a greater gas flow resistance than a porous body is provided between the power generation body and the porous body. The fuel cell according to claim 12, wherein
A fuel cell comprising a gas diffusion layer having a porosity or a pore diameter smaller on the gas upstream side than on the gas downstream side. The fuel cell according to any one of claims 1 to 13,
A fuel cell comprising a porous body made of expanded metal.

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