JP2005158435A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell capable of enhancing seal reliability of a porous separator. <P>SOLUTION: An anode gas passage 5 is provided on a face 1a sandwiching a MEA 3 composed of an electrolyte membrane and a pair of electrodes, and a porous anode separator 1 having a pure water passage 7 is provided on its rear face 1b. In addition, the separator thickness h from the bottom face of the anode gas passage 5 to the bottom face of the pure water passage 7 is made thicker than those in the other portion in the upstream region of the anode gas passage 5. The depth H of the pure water passage 7 in a region B overlapping the upstream side of the anode gas passage 5 is set so as to make it smaller when comparing it with that of the other region C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell. In particular, the present invention relates to a structure for water management that effectively humidifies gas and absorbs condensed water in a polymer electrolyte fuel cell using a porous separator.

  A fuel cell using a porous separator has a function of humidifying a reaction gas introduced into the cell while blocking the reaction gas with a plate previously holding water. Further, it has a function of suppressing flooding phenomenon by absorbing water generated by an electrochemical reaction, particularly condensed water, into the plate. Therefore, the need for humidification from the outside of the cell is extremely small, and a fuel cell that performs stable power generation can be realized.

Since the medium on both sides of the plate is blocked by the water held inside the porous separator, it is necessary to always hold the water in the plate when the battery is operating. It is necessary to control the pores so that the surface tension of water in the body exceeds. Therefore, a water seal is realized by setting appropriate conditions according to the temperature at the time of battery operation, the differential pressure generated on the front and back of the plate, the pore diameter in the porous body, the contact angle of water, etc. 1).
US Pat. No. 5,503,944

  On the other hand, during the power generation operation of the fuel cell, a relatively dry reaction gas is supplied to the reaction gas flow path, and a large amount of water evaporates from the surface of the porous plate, particularly at the gas inlet. Therefore, in a certain range from the gas inlet, the equilibrium state is reached with the gas-liquid interface entering from the plate surface to the inside.

  In particular, when the thickness of the separator is reduced in order to reduce the volume of the fuel cell stack, the portion of the plate that expresses the water seal described above becomes smaller. The seal may be broken and a gas leak may occur.

  In addition, since the porous separator controls the pores so that the surface tension of water in the porous body exceeds the surface tension, it is desirable to have uniform pores. is there. Therefore, it is conceivable that gas leaks from that portion, and the thinner the porous separator, the higher the possibility of leakage due to the presence of different pore diameters.

  In view of the above problems, an object of the present invention is to provide a fuel cell that can improve the sealing reliability of a porous separator.

  The present invention comprises a porous separator having a reactive gas flow path on a surface sandwiching a power generation layer composed of an electrolyte membrane and a pair of electrodes, and a pure water flow path on the back surface thereof, and further from the bottom surface of the reactive gas flow path. The separator thickness up to the bottom surface of the pure water channel is made thicker than other parts in the upstream region of the reaction gas channel.

  In this way, by making the separator thickness from the bottom of the reaction gas flow path to the bottom of the pure water flow path thicker than other parts in the upstream region of the reaction gas flow path, the gas-liquid interface easily moves into the plate due to the evaporation phenomenon. In the upstream region, many portions that exhibit a water seal can be left, so that reliability can be improved.

  A first embodiment will be described. The structure of the unit cell 100 which comprises a fuel cell is shown in FIG. The fuel cell may be composed of one unit cell 100 or a stack formed by stacking a plurality of unit cells 100.

  A membrane electrode assembly (MEA) 3 in which an electrode composed of an electrolyte membrane, a catalyst layer, and a gas diffusion layer is integrally formed is used. An anode separator 1 having an anode gas flow path 5 between the MEA 3 and the MEA 3 is provided on one side of the MEA 3. Further, a cathode separator 2 having a cathode gas flow path 6 between the MEA 3 and the MEA 3 is provided on the other side surface of the MEA 3. Here, the anode gas flow path 5 and the cathode gas flow path 6 are configured by grooves formed on the respective surfaces 1 a and 2 a that are in contact with the MEA 3 of the anode separator 1 and the cathode separator 2.

  The anode separator 1 and the cathode separator 2 are each made of a porous material. For example, as a porous plate constituting the anode separator 1 and the cathode separator 2, a composite material composed mainly of a resin and carbon powder is molded and fired. Both the anode separator 1 and the cathode separator 2 are not necessarily porous, and one of them may be formed of a dense material. In this case, the pure water flow path 7 to be described later is formed only for the separator formed of a porous material. In addition, as the dense material constituting the separator, for example, a material obtained by impregnating graphite with a resin to improve airtightness is used.

  Further, a pure water channel 7 is formed on the back surface 1b of the surface 1a on which the anode gas channel 5 of the anode separator 1 is formed. Similarly, a pure water channel 7 is formed on the back surface 2b of the surface 2a on which the cathode gas channel 6 of the cathode separator 2 is formed. Here, the pure water flow path 7 is constituted by grooves 70 formed on the back surfaces 1b and 2b of the anode separator 1 and the cathode separator 2, respectively.

  By allowing pure water to flow through the pure water flow path 7, pure water is contained in the anode separator 1 and the cathode separator 2 constituted by the porous base material, and flows through the anode gas flow path 5 and the cathode gas flow path 6. The reaction gas is sealed. Further, the reaction gas is humidified by the pure water that has moved from the pure water channel 7 to the anode gas channel 5 and the cathode gas channel 6 through the anode separator 1 and the cathode separator 2. Further, the condensed water generated in the MEA 3 or the anode gas flow path 5 and the cathode gas flow path 6 is absorbed by the anode separator 5 and the cathode separator 6 and collected in the pure water flow path 7, so that the MEA 3 and the anode gas flow path 5. Flooding generated in the cathode gas flow path 6 is suppressed.

  A cooling plate 4 adjacent to the anode separator 1 and the cathode separator 2 is also provided. Since one unit cell 100 is shown in FIG. 1, the cooling plate 4 is in contact with only the cathode separator 2, but by stacking a plurality of unit cells 100, the cooling plate 4 is adjacent to the back surface 1 b of the anode separator 1. A cooling plate 4 is arranged. The cooling plate 4 constitutes a refrigerant flow path for cooling the unit cell 100. Here, the cooling plate 4 is composed of two dense plates 4a and 4b, and an LLC flow path 8 which is a refrigerant flow path is formed between the cooling plates 4a and 4b. For example, by providing a groove on the surface of the cooling plate 4a adjacent to the cathode separator 2 on the side opposite to the contact surface with the cathode separator 2, and covering with the cooling plate 4b adjacent to the anode separator 1, the LLC flow path 8 is configured. Note that LLC is used as the refrigerant. Thereby, for example, even when the fuel cell is mounted on a moving body such as a vehicle, the refrigerant for adjusting the temperature of the fuel cell can be circulated regardless of the environmental temperature. As the cooling plate 4, for example, glassy carbon having excellent long-term LLC resistance and no problem even under fuel cell operation conditions is used.

  By disposing the cooling plate 4 made of a dense material adjacent to the anode separator 1, the pure water flow path 7 formed on the back surface 1 b of the anode separator 1 is covered. Similarly, the pure water channel 7 formed on the back surface 2 b of the cathode separator 2 is covered by disposing the cooling plate 4 made of a dense material adjacent to the cathode separator 2. That is, the pure water supplied to the unit cell 100 through the pure water flow path 7 does not move between the adjacent unit cells 100 but moves only within the unit cell 100.

  Further, a gasket (not shown) is provided between the anode separator 1 and the cathode separator 2 along the outer edge of the laminated surface, and the reaction gas supplied to the unit cell 100 is sealed in each electrode.

  Next, the configuration of the anode separator 1 will be described in detail. The configuration of the laminated surface of the anode separator 1 is shown in FIG. 2A shows a plan view of the surface 1a in contact with the MEA 3, and FIG. 2B shows a plan view of the back surface 1b.

  As shown in FIG. 2A, an anode gas flow path 5 through which a fuel gas, for example, hydrogen gas flows, is formed on the surface facing the MEA 3. Here, the anode gas flow path 5 is configured by providing a plurality of parallel folded grooves on the surface 1a. The anode gas flow path 5 can have various shapes such as a straight shape, a meandering shape, and an interdigitated shape.

  Further, a hydrogen gas inlet manifold 21 that penetrates the fuel cell in the stacking direction and communicates with the inlet side of the anode gas channel 5 in each unit cell 100, and a hydrogen gas outlet manifold 22 that communicates with the outlet of the anode gas channel 5. Is provided. The hydrogen gas flowing through the hydrogen gas inlet manifold 21 in the stacking direction is distributed to the anode gas flow path 5 of each unit cell 100 and used for the power generation reaction in the reaction region, and then recovered through the hydrogen gas outlet manifold 22. The

  Further, an oxidant gas that circulates in the cathode gas passage 6 configured in the cathode separator 2 shown in FIG. 1, for example, an air inlet manifold 23 that circulates air, and an air outlet manifold 24 that collects air from the cathode gas passage 6 are provided. Prepare. Both the air inlet manifold 23 and the air outlet manifold 24 penetrate the fuel cell in the stacking direction and communicate with the cathode gas flow path 6.

  A pure water flow path 7 is provided on the back surface 1b of the surface 1a facing the MEA 3 of the anode separator 1 as shown in FIG. The pure water flow path 7 is constituted by a groove 70 formed in the back surface 1 b of the anode separator 1. The pure water channel 7 is constituted by a plurality of parallel channels. Here, although the pure water flow path 7 is configured by a flow path configured in a straight shape along the reaction region, this is not restrictive. For example, it may be a folded shape or a meandering shape. Further, the pure water flow path 7 is configured to be substantially parallel to the anode gas flow path 5, but this is not restrictive.

  Further, a pure water inlet manifold 26 that penetrates the fuel cell in the stacking direction and communicates with the inlet side of the pure water passage 7, and a distribution portion that distributes the pure water from the pure water inlet manifold 26 to the plurality of parallel pure water passages 7. 27. Furthermore, a pure water outlet manifold 25 that penetrates the fuel cell in the stacking direction and communicates with the outlet side of the pure water flow path 7, and a recovery unit that collects pure water from each pure water flow path 7 and discharges it to the pure water outlet manifold 25 28.

  Pure water is introduced into each unit cell 100 through the pure water inlet manifold 26 and is distributed to each pure water flow path 7 in the distribution unit 27. When flowing through the pure water flow path 7, a part of the flowing pure water permeates into the anode separator 1, and a part of the pure water is recovered from the anode separator 1. The pure water flowing through the pure water flow path 7 is collected in the pure water outlet manifold 25 via the recovery unit 28 and discharged from the fuel cell.

  Next, the detail of the shape of the pure water flow path 7 which comprises the anode separator 1 is demonstrated using FIG. 3A shows a plan view of the back surface 1b of the anode separator 1, as in FIG. 2B, and FIG. 3B shows a cross section taken along the line AA of the anode separator 1. FIG. 3A is a region overlapping the upstream region of the anode gas flow path 5 formed on the opposite surface 1a, and the region C is a region overlapping the downstream region of the anode gas flow path 5. Here, the region B is defined as a region that overlaps from the inlet of the anode gas flow channel 5 to the folded portion, and the region C is defined as a region that overlaps from the folded portion of the anode gas flow channel 5 to the outlet.

  The depth Hb of the pure water channel 7 configured in the region B overlapping the upstream region of the anode gas channel 5 was made smaller than the depth Hc of the pure water channel 7 configured in the region overlapping the region C overlapping the downstream region. Here, for example, the depth Hb of the pure water passage 7 in the region B is set to about half of the depth Hc of the pure water passage 7 in the region C. Thereby, the thickness hb of the thin portion of the plate constituting the anode separator 1 in the region B is set larger than the thickness hc in the region C.

  The change of the depth of the pure water flow path 7 also depends on a change in pressure loss of the pure water circulation due to a decrease in the cross-sectional area of the flow path, a necessary supply amount, and the like. In addition to this, the average radius of the pores present in the porous plate constituting the anode separator 1, that is, the pores having a size that develops a water seal under the battery operating conditions is the bottom surface of the pure water channel 7 and the anode gas. It is set so that at least one of the thin-walled portions of the plate between the bottom surfaces of the flow paths 5 is stochastically included. As a result, even when water is evaporated in the porous plate due to the hydrogen gas introduced from the hydrogen gas inlet manifold 21 and the gas-liquid interface moves, the anode gas flow path 5 side and the pure water flow path 7 The reliability of the water seal that can withstand the differential pressure on the side can be improved.

  In the present embodiment, the depth of the pure water passage 7 is halved in the region B overlapping the upstream region of the anode gas passage 5, so that the pure water introduced from the pure water inlet manifold 26 is evenly arranged in parallel. It is difficult to distribute to the pure water flow path 7. In view of this, it is preferable to perform distribution adjustment using appropriate means in the distribution unit 27 formed in the middle of the pure water inlet manifold 26 and the pure water flow path 7.

  For example, by changing the depth of the distribution unit 27, substantially the same amount of pure water is supplied to all of the pure water flow paths 7 having two different depths. That is, the distribution unit 27 communicating with the pure water inlet manifold 26 is configured to be deeper than the region E communicating with the pure water channel 7 configured in the region C in the region D communicating with the pure water channel 7 configured in the region B. .

  There is a possibility that the distribution of pure water is affected by the temperature distribution in the cell, etc., but it is basically supplied with pure water that exceeds the amount consumed by humidification minus the amount of condensed water recovered. It is important to Therefore, it is desirable to configure the distribution unit 27 so that pure water is preferentially supplied to the pure water flow path 7 formed in the region B where evaporation is actively performed.

  In addition, although the pure water flow path 7 comprised in the anode separator 1 was demonstrated here, the pure water flow path 7 comprised in the cathode separator 2 can also be made into the same shape.

  Next, the effect of this embodiment will be described.

  A porous surface having an anode gas channel 5 (cathode gas channel 6) on the surface 1a (2a) sandwiching the MEA 3 composed of an electrolyte membrane and a pair of electrodes, and a pure water channel 7 on the back surface 1b (2b). An anode separator 1 (cathode separator 2) is provided. Further, the separator thickness h from the bottom surface of the anode gas flow channel 5 (cathode gas flow channel 6) to the bottom surface of the pure water flow channel 7 is made thicker than other portions in the upstream region of the anode gas flow channel 5 (cathode gas flow channel 6). . As a result, in the upstream region where the evaporation of water from the surface of the anode gas channel 5 (cathode gas channel 6) is active, a water seal is developed even when the gas-liquid interface moves into the plate due to the evaporation phenomenon of water. Since many parts remain, the reliability of water sealability can be improved.

  Here, the depth H of the pure water channel 7 is made shallower than other portions in the region B overlapping the upstream region of the anode gas channel 5 (cathode gas channel 6). Thereby, it is possible to increase the thickness from the bottom of the anode gas channel 5 (cathode gas channel 6) to the bottom of the pure water channel 7 in the upstream region without changing the performance of the battery.

  Next, a second embodiment will be described. The unit cell 100 is configured similarly to the first embodiment. Details of the pure water flow path 7 configured in the anode separator 1 will be described with reference to FIG. Hereinafter, a description will be given centering on differences from the first embodiment.

  Similar to the first embodiment, a relatively shallow pure water flow path 7 is formed in a region B overlapping the upstream region of the anode gas flow channel 5. Here, the depth Hb of the pure water channel 7 formed in the region B is configured to be half the depth Hc of the pure water channel 7 formed in the region C.

  Further, in order to equalize the amount of pure water flowing along the region B and the amount of pure water flowing along the region C, the density of the pure water flow path 7 in the region B is increased compared to the region C. . Here, since the areas of the region B and the region C are the same, more pure water channels 7 are configured in the region B than the pure water channels 7 configured in the region C.

  Thereby, the total cross-sectional area of the pure water flow path 7 configured in the area B and the total cross-sectional area of the pure water flow path 7 configured in the area C are equalized. In particular, in each of the regions B and C, it is preferable that the size of the cross-sectional area of the pure water channel 7 configured per unit area is equal. For example, when the depth is set to Hb: Hc = 1: 2, it is preferable that the number of the pure water flow paths 7 is configured to be approximately double in the region B with respect to the region C. As a result, in the region B, it is possible to suppress an increase in the pressure loss of pure water due to a decrease in the cross section of the flow path caused by reducing the depth of the pure water flow path 7, and it is possible to equalize the amount of pure water that circulates. .

  Next, the effect of this embodiment will be described. Only the effects different from those of the first embodiment will be described below.

  In the region B overlapping the upstream region of the anode gas flow channel 5 (cathode gas flow channel 6), the density of the pure water flow channel 7 is configured to be higher than that of other portions. Thus, the original total channel cross-sectional area can be made constant by increasing the number of the pure water channels 7 corresponding to the decrease in the channel depth H. As a result, a large amount of pure water can be circulated along the region B, and gas leakage due to insufficient supply of pure water can be prevented.

   Particularly, in the region B that overlaps the upstream region of the anode gas channel 5 (cathode gas channel 6) and the other region C, the ratio of the cross-sectional area of the pure water channel 7 is configured to be substantially equal. Thereby, pure water can be circulated all over the plate surface, and it is possible to suppress the shortage of pure water particularly in the upstream region where water supply is required.

  Next, a third embodiment will be described. The unit cell 100 is configured similarly to the first embodiment. Details of the pure water flow path 7 configured in the anode separator 1 will be described with reference to FIG. Hereinafter, a description will be given centering on differences from the first embodiment.

  An inclination is provided in the depth of the pure water channel 7 formed in the region B overlapping the upstream region of the anode gas channel 5. A region overlapping the vicinity of the inlet of the anode gas channel 5, that is, the deepest depth Hb in the uppermost stream portion in the vicinity of the distributor 27, and the groove depth H gradually increases along the pure water flow direction. . The depth H of the pure water flow path 7 is configured to be the same depth Hc as the area C in the downstream end of the upstream area of the anode gas flow path 5, here in the area overlapping the folded portion. In addition, the area | region which overlaps with a return part here becomes the collection | recovery part 28 vicinity.

  In addition, since the humidification of the reaction gas introduced into the anode gas flow path 5 is completed to some extent from the entrance to several centimeters, the plate thin wall constituting the anode separator 1 is made shallower by reducing the flow path depth H. The thickness h of the portion may be increased only in this range. In other words, the operating conditions such as the humidity and supply amount of the reaction gas introduced into the fuel cell are set in advance, and in that case, the section where the water evaporates violently is confirmed by elemental experiments, etc. An inclination of 7 depth H can be set.

  FIG. 5 shows a continuous inclination from the entrance, but this is not a limitation. For example, it may be configured such that only a portion overlapping the most upstream region where evaporation is intense as described above has a constant depth Hb, and thereafter, the channel depth H is inclined in the increasing direction.

   In the present embodiment as well, the pure water flow is equalized by changing the depth of the distribution unit 27 as in the first embodiment, or the pure water flow in the region B as in the second embodiment. By increasing the path 7, the pure water distribution may be equalized by equalizing the channel cross section.

  Next, the effect of this embodiment will be described. Hereinafter, only effects different from those of the first embodiment liquid will be described.

  The depth H of the pure water channel 7 is continuously changed. Thereby, the plate thickness h can be ensured according to the intensity of evaporation. At this time, setting the depth H of the pure water channel 7 to be smaller than necessary can be suppressed, so that an increase in pressure loss due to a reduction in the cross section of the pure water channel 7 can be suppressed.

  For example, the plate thickness h is set to be small for the region where evaporation is intense, and the depth H is gradually increased for the region overlapping the downstream side of the anode gas flow path 5. Thereby, gas leak can be prevented and the reliability of the sealing performance can be improved, and an increase in pressure loss of the pure water passage 7 in the region B can be suppressed.

  Next, a fourth embodiment will be described. Hereinafter, a description will be given centering on differences from the first embodiment.

  The configuration of the unit cell 100 is shown in FIG. Similar to the first to third embodiments, in the region B, the depth Hb of the pure water flow path 7 is configured to be shallower than the depth Hc of other portions. In the region B in which the depth is reduced, the surface of the cooling plate 4 made of a dense material disposed adjacent to the surface 1b of the anode separator 1 on which the pure water flow path 7 is formed is positioned opposite the pure water flow path 7. A groove 71 is provided. That is, in the region B in which the cross-sectional area of the groove 70 constituting the pure water flow path 7 formed on the surface of the anode separator 1 is small, the groove 71 that supplements the cross-sectional area is formed at a position facing the groove 70. Thereby, the cross-sectional area of the pure water channel 7 in the region C where the groove 70 is configured to have a relatively large depth Hc and the pure water channel 7 in the region B where the groove 70 is configured to have a relatively small depth Hb. Can be made uniform in cross-sectional area.

  Here, the cooling plate 4 constituting the LLC flow path 8 that circulates the LLC has a limit to the depth of the groove 71 formed in the dense material in order to suppress the thickness to 2 mm or less per sheet. For this reason, it is preferable to increase the number of the pure water flow paths 7 in the region B as in the second embodiment, or to reduce the depth of only necessary portions as in the third embodiment.

  By configuring in this way, as shown in FIG. 7, in the region B where the evaporation is intense and the gas-liquid equilibrium interface is easily formed inside the anode separator 1, the thickness of the plate that performs the sealing function is increased. The sealability can be maintained regardless of the pore variation in the plate.

  In particular, in the uppermost stream region of the anode gas passage 5 where the evaporation of water is intense due to humidification of the reaction gas, the portion where the pure water and the porous plate are in contact may be increased as much as possible. For example, as shown in FIG. 6B, the width of the groove 71 formed in the cooling plate 4 is made larger than the width of the groove 70 formed in the porous plate constituting the anode separator 1. As a result, part of the water comes into contact with the ribs 72 formed between the grooves 70 at the openings of the grooves 71, so that the penetration of pure water into the porous plate becomes smooth. As a result, it is possible to suppress the occurrence of gas leak due to the delay in movement of pure water to the porous plate. Further, by increasing the width of the groove 71 that constitutes the pure water flow path 7, it is possible to increase the flow rate of the pure water that is circulated, and to avoid the shortage of pure water.

  Next, the effect of this embodiment will be described. Only the effects different from those of the first embodiment will be described below.

  A cooling plate 4 is provided adjacent to the back surface 1b (2b) of the surface 1a (2a) on which the anode gas flow path 5 (cathode gas scale 6) of the anode separator 1 (cathode separator 2) is formed. The pure water flow path 7 is formed between the anode separator 1 (cathode separator 2) and the adjacent cooling plate 4, and in the region B that overlaps the upstream area of the anode gas flow path 5 (cathode gas flow path 6), The water flow path 7 is configured by combining a groove 70 formed in the anode separator 1 (cathode separator 2) and a groove 71 formed in the cooling plate 4. Thereby, in the area | region B where the depth H of the groove | channel 70 was reduced, since the cross-sectional area of the pure water flow path 7 can be supplemented, the circulation of pure water can be performed appropriately.

  At this time, the ratio of the cross-sectional area of the pure water channel 7 is configured to be approximately equal in the region B overlapping the upstream region of the anode gas channel 5 (cathode gas channel 6) and the other region C. Thereby, it can suppress that the pure water which distribute | circulates the area | region B reduces, while supplying the water required for gas humidification, it can suppress that the gas leak by water shortage arises.

  Note that the present invention is not limited to the best mode for carrying out the invention, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

  The present invention can be applied to a polymer electrolyte fuel cell using a porous plate. In particular, an appropriate effect can be obtained by applying to a fuel cell for a mobile body that is desired to be downsized.

It is a block diagram of the unit cell of the fuel cell used for 1st Embodiment. It is a top view of the anode separator used for 1st Embodiment. It is a figure which shows the shape of the pure water flow path used for 1st Embodiment. It is a figure which shows the shape of the pure water flow path used for 2nd Embodiment. It is a figure which shows the shape of the pure water flow path used for 3rd Embodiment. It is a block diagram of the unit cell of the fuel cell used for 4th Embodiment. It is a figure explaining the state of the pure water in 4th Embodiment.

Explanation of symbols

1 Anode separator (separator)
2 Cathode separator (separator)
3 Membrane electrode assembly (MEA) (power generation layer)
4 Cooling plate (adjacent plate)
5 Anode gas channel (reactive gas channel)
6 Cathode gas channel (reactive gas channel)
7 Pure water flow path 8 LLC flow path 27 Distributing section Area B: Area overlapping the upstream area of the gas flow path Area C: Area overlapping the downstream area of the gas flow path H: Depth of the pure water flow path h ... Thickness of thin part of porous plate

Claims (6)

Provided with a porous separator having a reactive gas flow path on the surface sandwiching a power generation layer composed of an electrolyte membrane and a pair of electrodes, and a pure water flow path on the back surface thereof,
Further, the fuel cell is characterized in that the separator thickness from the bottom surface of the reaction gas channel to the bottom surface of the pure water channel is made thicker than other parts in the upstream region of the reaction gas channel.   2. The fuel cell according to claim 1, wherein the depth of the pure water passage is shallower than other portions in a region overlapping the upstream region of the reaction gas passage.   The fuel cell according to claim 2, wherein the depth of the pure water channel is continuously changed.   4. The fuel cell according to claim 2, wherein the density of the pure water channel is higher in a region overlapping the upstream region of the reaction gas channel than in other portions. A plate adjacent to the back surface of the surface on which the reaction gas flow path of the separator is formed;
Forming the pure water flow path between the separator and the adjacent plate;
5. The pure water flow path according to claim 1, wherein the pure water flow path is configured by combining a groove formed in the separator and a groove formed in the plate in a region overlapping the upstream region of the reaction gas flow channel. Fuel cell.   6. The fuel cell according to claim 4, wherein the ratio of the cross-sectional area of the pure water channel is substantially equal in a region overlapping the upstream region of the reaction gas channel and the other region.

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