JP2005093244A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell capable of suitably managing water corresponding to various reaction gases. <P>SOLUTION: The fuel cell has an anode gas diffusion layer 3a and a cathode gas diffusion layer 3c arranged at an anode 2a and a cathode 2c as a pair of electrodes 2 interposing an electrolyte film 1, and a separator 8 interposing the anode gas diffusion layer 3a and the cathode gas diffusion layer 3c. An anode gas flow passage 5a is arranged on a face 18a of the separator 8 contacting the anode gas diffusion layer 3a. Furthermore, a hollow part 20 is formed on the surface of the flow passage at the upper stream area A<SB>2</SB>of the anode gas flow passage 5, and a thin groove 30 is formed on the surface of the flow passage at the downstream area B<SB>2</SB>having larger proportion of area then the upper stream area A<SB>2</SB>. A cathode gas flow passage 5c is arranged on a face 18a of the separator 8 contacting the cathode gas diffusion layer 3c, and the thin groove 30 is formed on the surface of the flow passage at the downstream area B<SB>1</SB>of the cathode gas flow passage 5c, and the hollow part 20 is formed on the surface of the flow passage at the upper area A<SB>1</SB>having larger proportion of area then the downstream area B<SB>1</SB>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell. In particular, the present invention relates to a configuration for improving a water management function in a polymer electrolyte fuel cell.

  In a polymer electrolyte fuel cell, in order to generate a power generation reaction, the polymer membrane needs to contain moisture. This is because the polymer film has good conductivity when it is hydrated. Giving moisture is referred to as humidification, but this humidification means is a very important technique for realizing efficient power generation in a polymer electrolyte fuel cell.

In order to humidify the polymer membrane, as one method for keeping the anode gas and cathode gas in a wet state, an invention has been made in which a water reservoir is formed in the gas flow path. In the rib portion provided in a lattice shape, the cathode gas is humidified by providing a water reservoir in the cathode gas flow path. (For example, see Patent Document 1)
JP-A-11-204118

  However, in the fuel cell, since a water generation reaction occurs at the cathode, the condensed water obtained by condensing the generated water or water vapor accumulates in the gas flow channel particularly in the downstream of the gas flow channel. Therefore, when the water reservoir is provided as shown in the background art above, the water reservoir particularly downstream is immediately saturated with liquid water, so that no more water can be stored. In addition, since the downstream reaction gas has a relative humidity of 100%, the water does not evaporate further into the reaction gas, resulting in the problem that the downstream water reservoir does not perform its function. .

  Further, the anode gas has a relatively small flow rate, and reaches a saturated state relatively upstream of the anode gas flow path. On the other hand, the cathode gas has a relatively large flow rate, and the polymer film may be dried and deteriorated to a relatively downstream side of the cathode gas flow path.

  In view of the above problems, an object of the present invention is to provide a fuel cell capable of performing appropriate water management according to each reaction gas.

  The present invention relates to an anode gas diffusion layer and a cathode gas diffusion layer disposed on both sides of an anode and a cathode, which are a pair of electrodes that sandwich an electrolyte membrane, and a separator that sandwiches the anode gas diffusion layer and the cathode gas diffusion layer And comprising. Moreover, an anode gas flow path is provided in the surface which contacts the said anode gas diffusion layer among the said separators. Further, water holding means is provided on the surface of the upstream area of the anode gas flow path, and water discharge means having a larger area ratio than the water holding means is provided on the surface of the downstream area of the flow path.

  Further, an anode gas diffusion layer and a cathode gas diffusion layer disposed on both sides of the anode and the cathode which are a pair of electrodes sandwiching the electrolyte membrane, a separator sandwiching the anode gas diffusion layer and the cathode gas diffusion layer, Is provided. Moreover, a cathode gas flow path is provided in the surface which contacts the said cathode gas diffusion layer among the said separators. Furthermore, a water discharge means is provided on the flow path surface in the downstream area of the cathode gas flow path, and a water holding means having a larger area ratio than the water discharge means is provided on the flow path surface in the upstream area.

  Water holding means is provided on the flow path surface in the upstream region of the anode gas flow path, and water discharge means having a larger area ratio than the water holding means is provided on the flow path surface in the downstream region. This makes it easy to humidify the gas holding water in the upstream portion of the gas where the relative humidity of the gas is less than 100%, and discharges water in the downstream portion of the gas where the relative humidity of the gas is 100%. It becomes easy to do. In addition, on the anode gas side where the gas flow rate is relatively small and condensation is likely to occur, the existence ratio is increased with respect to the water holding means in order to promote the effect of the water discharging means. As a result, the gas distribution can be made uniform.

  Further, water discharge means is provided on the flow path surface in the downstream area of the cathode gas flow path, and water holding means having a larger area ratio than the water discharge means is provided on the flow path surface in the upstream area. This makes it possible to hold the water in the upstream portion of the gas where the relative humidity of the gas is less than 100% to facilitate humidification of the gas, and to supply water in the downstream portion of the gas where the relative humidity of the gas is 100%. It becomes easy to discharge. In addition to this, on the cathode gas side where the unsaturated region near the gas upstream increases, in order to promote the effect of the water holding means, the existence ratio is increased with respect to the water discharging means. In addition, the wettability to the polymer film is improved, and the deterioration of the polymer film and the membrane electrode assembly due to drying can be suppressed.

  A first embodiment will be described. A schematic configuration of the fuel cell 11 is shown in FIG. Here, the fuel cell 11 is configured by stacking a plurality of unit cells 10, but the fuel cell 11 may be configured by one unit cell 10.

  The unit cell 10 constituting the fuel cell 11 is configured by arranging separators 8 on both sides of the membrane electrode assembly 4. The unit cell 10 is constituted by sandwiching the membrane electrode assembly 4 between the anode side separator 8a and the cathode side separator 8c.

  The membrane electrode assembly 4 includes an electrolyte membrane 1, an electrode 2 (anode 2a and cathode 2b) sandwiching the electrolyte membrane 1, and a gas diffusion layer 3 (anode gas diffusion layer 3a and cathode gas diffusion layer 3c) sandwiching the membrane 2 ) And. A reactive gas is diffused into each gas diffusion layer 3 from a reactive gas flow path 5 described later, and an electromotive force is generated by performing an electrochemical reaction in the electrode 2 using the reactive gas.

  Further, a groove-like reaction gas flow path 5 is formed on the surface of the separator 8 that contacts the membrane electrode assembly 4, here the surface 18 that contacts the gas diffusion layer 3. An anode gas flow path 5a is formed in the anode side separator 8a in contact with the anode gas diffusion layer 3a, and a cathode gas flow path 5c is formed in the cathode side separator 8c in contact with the cathode gas diffusion layer 3c. Here, as shown in FIGS. 2 and 6, a plurality of reaction gas flow paths 5 are formed in parallel in the laminated surface 18 of the separator 8. The shape of the reaction gas channel 5 will be described in detail later.

  Although not shown in FIG. 1, the fuel cell 11 includes a cathode gas supply manifold 12 i that penetrates the fuel cell 11 in the stacking direction and distributes the cathode gas to each unit cell 10, and the cathode gas from each unit cell 10. Is provided with a cathode gas discharge manifold 12o. Similarly, an anode gas supply manifold 13 i that penetrates the fuel cell 11 in the stacking direction and distributes the anode gas to each unit cell 10 and an anode gas supply manifold 13 o that collects the anode gas from each unit cell 10 are provided. Each manifold 12 and 13 is comprised by the through-hole formed in the lamination | stacking surface 18 as shown in FIG. 2, FIG.

  Further, as shown in FIG. 1, the fuel cell 11 includes a gasket 9 between the electrolyte membrane 1 and the separator 8 in order to prevent leakage of anode gas and cathode gas. The gasket 9 seals the anode gas diffusion layer 3a including the anode 2a and the cathode gas diffusion layer 3c including the cathode 2c.

  Next, the configuration of the surface 18c of the cathode separator 8c that contacts the cathode gas diffusion layer 3c will be described with reference to FIG. The cathode side separator 8c is formed of a dense carbon material.

  A plurality of meandering cathode gas flow paths 5c are arranged in parallel on the laminated surface 18c of the cathode separator 8c. One end of each cathode gas flow path 5c communicates with the cathode gas supply manifold 12i, and the other end communicates with the cathode gas discharge manifold 12o. A partition wall 7c that separates the flow paths is formed between the adjacent cathode gas flow paths 5 in the stacked surface 18c. Here, a plurality of cathode gas flow paths 5c are provided, but a single flow path may be used. Moreover, although it has a meandering shape, it may be a linear shape or a comb shape.

A water holding means is provided in the upstream region A ₁ of the cathode gas flow path 5c formed in this way. Here, in the upstream region A ₁ , the water retaining means is formed by providing a plurality of depressions 20 on the surface of the groove forming the cathode gas flow path 5c. Figure 3 shows an enlarged view of the upstream region A ₁ of the cathode gas passage 5c provided with recess 20. FIG. 4 shows a cross section of the recess 20 in the direction of the flow path axis (X ₁ -X ₁ cross section of FIG. 3).

  The depression 20 is provided in the bottom surface 51c of each cathode gas flow path 5c. The depressions 20 are configured at equal intervals along the flow path axis. The recess 20 is formed in a conical shape with the apex 20a positioned inside the cathode separator 8c. That is, the cross section of the recess 20 in the flow path axis direction is V-shaped. The cathode gas is circulated along the cathode gas flow path 5c provided with such a depression 20.

  Due to changes in operating conditions, mist or condensed water may flow into the cathode gas flow path 5c together with the cathode gas. In such a case, as shown in FIG. 4, liquid water accumulates in the recess 20 and is used as water holding means. Further, when the dried cathode gas is supplied to the cathode gas flow path 5c due to a change in operating conditions or the like, the cathode water is humidified by evaporating the liquid water stored in the recess 20. As described above, by providing the recess 20, liquid water mixed in the cathode gas can be removed, and drying of the cathode gas and thus drying of the electrolyte membrane 1 can be suppressed. Can be suppressed.

The depression 20 only needs to be present in the upstream region A ₁ of the cathode gas flow path 5c, and the specification of the depression 20 in the upstream region A ₁ is not limited to this.

On the other hand, in the downstream region B ₁ of the cathode gas channel 5c, it comprises a water discharge means as shown in FIG. The cathode gas passage 5c bottom 52c of the groove forming the downstream region B _1, forming the water discharge means by providing the narrow grooves 30. The narrow groove 30 is formed in parallel to the gas flow direction in the cathode gas flow path 5c. Further, one end of the narrow groove 30 is formed so as to communicate with the cathode gas discharge manifold 12o. Here, although the cross section of the narrow groove 30 is configured in a V shape, this is not restrictive.

In the downstream region B ₁ of the cathode gas channel 5c, the cathode gas reaches a saturated state. On the downstream side of the time when the cathode gas reaches the saturated state, the water generated as the oxygen is consumed exists in a liquid state, or the water contained in the cathode gas is condensed. Therefore, by providing the narrow groove 30 in the downstream region B ₁ , such liquid water is selectively collected in the narrow groove 30. Within the narrow groove 30, the liquid water is moved in the downstream direction under the influence of the cathode gas flow, and is discharged from the cathode gas discharge manifold 12o. For this reason, clogging of water in the downstream region B ₁ can be suppressed, and a reduction in power generation efficiency due to the cathode gas flow path 5c being blocked can be suppressed.

Usually, air or the like is used as the cathode gas. Therefore, the cathode gas has a relatively high flow rate and a high flow rate. As a result, the cathode gas tends to exist in a dry state in a wide range on the upstream side in the cathode gas flow path 5c. Further, since the flow rate is large, the cathode gas is saturated at a relatively downstream side, so that the possibility of water clogging is a narrow range on the downstream side. Therefore, when comparing the area of the upstream region A ₁ provided with the water holding means and the area of the downstream region B ₁ provided with the water discharge means in the cathode gas flow path 5c, the area of the upstream region A ₁ is larger. Configure to be That is, the upstream region A ₁ is configured such that the ratio of the upstream region A ₁ and the downstream region B ₁ to the total cathode gas flow path 5c is larger in the upstream region A ₁ . In this way, by configuring the cathode gas channel 5c as a channel that places importance on water retention, it is possible to suppress the cathode gas from being supplied in a dry state, and perform water management according to the cathode gas. be able to.

  Next, the configuration of the anode gas channel 5a will be described. FIG. 6 shows the configuration of the surface 18a that contacts the anode gas diffusion layer 3a of the anode separator 8a. The anode side separator 8a is formed of a dense carbon material.

  A plurality of meandering anode gas flow paths 5a are formed in parallel on a surface 18a of the anode separator 8a that contacts the anode gas diffusion layer 3a. The anode gas flowing through the anode gas flow path 5a and the cathode gas flowing through the cathode gas flow path 5c are configured to flow substantially in parallel. One end of each anode gas flow path 5a communicates with the anode gas supply manifold 13i, and the other end communicates with the anode gas discharge manifold 13o. A partition wall 7a is formed between adjacent anode gas flow paths 5a in the laminated surface 18a to separate the flow paths. Here, a plurality of anode gas flow paths 5a are used, but a single flow path may be used. Moreover, although it has a meandering shape, it may be a linear shape or a comb shape.

The upstream region A ₂ of the thus-formed anode gas passage 5a comprises water holding means. Similarly to the cathode gas channel 5c, a water retaining means is formed by providing a recess 20 as shown in FIGS. 3 and 4 on the bottom surface 51a of the groove forming the anode gas channel 5a. When mist or condensed water is mixed in the anode gas due to a change in operating conditions or the like, liquid water can be selectively collected and stored in the recess 20. In addition, when the dried anode gas is supplied due to changes in operating conditions, the water stored in the recess 20 evaporates, and the anode gas can be humidified. Thus, by providing the water holding means (20) on the upstream side and the water discharge means (30) on the downstream side, it is possible to suppress the introduction of excess liquid water into the anode gas flow path 5a. Moreover, it can suppress that anode gas is supplied in the dry state.

Also comprises water discharge means downstream region B ₂ in the anode gas flow channel 5a. Similarly to the cathode gas flow path 5c, a water discharge means is configured by providing a narrow groove 30 as shown in FIG. 5 on the bottom surface 52a of the groove. When the anode gas is saturated while flowing through the anode gas flow path 5a, the water vapor is condensed on the downstream side with the consumption of hydrogen, and condensed water is generated. By providing the narrow groove 30, the liquid water is selectively collected in the narrow groove 30. The recovered liquid water moves downstream in the narrow groove 30 due to the influence of the flow of the anode gas, and is discharged to the anode gas discharge manifold 13o. This suppresses that the liquid water in the downstream region B ₂ of the anode gas passage 5a is present, it is possible to turn suppress the water clogging in the anode gas flow channel 5a.

Usually, hydrogen gas or the like is used as the anode gas. Therefore, the anode gas has a relatively small flow rate and a low flow rate. As a result, the anode gas is easily humidified, and it is possible to be in a dry state in a narrow range on the upstream side. Further, since the saturated state is reached at a relatively early stage, liquid water may be generated in a wide range on the downstream side. Therefore, the anode gas passage 5a, and the area of the upstream region A ₂ having a water holding means, when comparing the area of the downstream region B ₂ having a water discharge means, larger in the area of the downstream region B ₂ Configure to be That is, the downstream area B ₂ is configured such that the ratio of the upstream area A ₂ and the downstream area B ₂ to the total anode gas flow path 5a is larger in the downstream area B ₂ . In this way, by configuring the anode gas channel 5a as a channel that places importance on water discharge, it is possible to prevent the anode gas from becoming difficult to be locally supplied due to clogging, and water corresponding to the anode gas can be avoided. Management can be performed.

  Next, the effect of this embodiment will be described.

The anode gas diffusion layer 3a and the cathode gas diffusion layer 3c disposed on both sides of the anode 2a and the cathode 2c, which are a pair of electrodes 2 sandwiching the electrolyte membrane 1, and the anode gas diffusion layer 3a and the cathode gas diffusion layer 3c are narrowed. And a separator 8 to be held. Moreover, the anode gas flow path 5a is provided in the surface 18a which contacts the anode gas diffusion layer 3a among the separators 8. FIG. Furthermore, the water retaining means (20) installed in a flow path surface of the upstream region A ₂ of the anode gas passage 5, and a large water discharge area ratio than water holding means (20) in the flow path surface of the downstream region B ₂ Means (30) were provided. Thereby, in the upstream region A ₂ of the gas where the relative humidity of the reaction gas is less than 100%, the gas holding water can be easily humidified, and the downstream region B _{2 of the} gas whose relative humidity of the gas is 100%. Then, it becomes easy to discharge water. In addition, on the anode gas side where the gas flow rate is relatively small and condensation is likely to occur, the existence ratio is increased with respect to the water holding means in order to promote the effect of the water discharging means. Water discharge becomes good, water clogging can be suppressed, and gas distribution can be made uniform.

The anode gas diffusion layer 3a and the cathode gas diffusion layer 3c disposed on both sides of the anode 2a and the cathode 2c, which are a pair of electrodes 2 sandwiching the electrolyte membrane 1, and the anode gas diffusion layer 3a and the cathode gas diffusion layer 3c are narrowed. And a separator 8 to be held. Further, among the separator 8, the surface 18c in contact with the cathode gas diffusion layer 3c comprising a cathode gas passage 5c, further downstream region B ₁ of the flow path surface of the cathode gas passage 5c water discharge means (30) provided, and provided upstream region a ₁ of the flow path of water discharge means to the surface (30) area ratio greater water retaining means 20 from. As a result, in the upstream region A ₁ of the gas where the relative humidity of the gas is less than 100%, the water can be retained and the gas can be easily humidified, and the downstream region B of the gas whose relative humidity of the gas is 100%. ₁ can make it easy to drain water. In addition to this, on the cathode gas side where the unsaturated region near the gas upstream increases, the existence ratio is increased with respect to the water discharge means (30) in order to promote the effect of the water holding means (20). . Therefore, in the cathode gas, the wettability to the electrolyte membrane 1 is improved, and deterioration of the electrolyte membrane 1 and the membrane electrode assembly 4 due to drying can be suppressed.

  The water holding means is constituted by a large number of depressions 20 provided in the flow path bottom 51. Thereby, the mist and the condensed water in the reaction gas flowing in contact with the depression 20 can be held in the depression 20. Thereby, since the reaction gas supplied in the dry state can be humidified, it is possible to suppress a decrease in power generation efficiency due to insufficient humidification.

Further, the water discharge means is constituted by the narrow groove 30 provided in the flow path bottom 52. As a result, the liquid water generated in the downstream regions B ₁ and B ₂ moves downstream in the narrow groove 30 due to the influence of the flow of the reaction gas, so that the liquid water can be easily discharged, and the reaction gas flow Water clogging in the path 5 can be suppressed.

  Next, a second embodiment will be described. FIG. 7 shows the configuration of the fuel cell 11. Here, the fuel cell 11 is configured by stacking a plurality of unit cells 10, but the fuel cell 11 may be configured by a single unit cell 10. Hereinafter, a description will be given centering on differences from the first embodiment.

  The anode separator 8a disposed adjacent to the membrane electrode assembly 4 is made of a dense carbon material, and the anode gas flow path 5a is formed in the same manner as in the first embodiment. On the other hand, the cathode separator 8c is formed of a carbon-based porous material. As in the first embodiment, the cathode gas flow path 5c is provided on the surface 18c of the cathode separator 8c that contacts the membrane electrode assembly 4, and the groove-like cooling water flow path is provided on the opposite surface 19c. 6 is formed.

  A cooling water channel forming member 15 made of a dense material is disposed adjacent to the surface 19c of the cathode separator 8c where the cooling water channel 6 is formed. Pure water is circulated through the cooling water flow path 6 so that heat generated by power generation can be removed, and at the same time, the cathode gas flowing through the cathode gas flow path 5c is passed through the cathode side separator 8c made of a porous material. It can be humidified.

A configuration diagram of the flat surface 18c of the cathode-side separator 8c is shown in FIG. 2 as in the first embodiment. The upstream area A ₁ is provided with a recess 20 that is a water holding means, and the downstream area B ₁ is provided with a narrow groove 30 that is a water discharge means.

Next, the state of water in the cathode gas passage 5c in the fuel cell 11 as described above will be described. The cross-section of the cathode-side recess 20 is provided in the upstream region A ₁ of the separator 8c shown in FIG.

  Since the cathode side separator 8c is made of a porous material, pure water flowing through the cooling water flow path 6 is included in the cathode side separator 8c. The pore diameter of the porous material is within an appropriate range, and the cathode gas does not enter the pores of the porous material within the range of the used gas pressure and the used pure water pressure.

In the upstream region A ₁ , a plurality of depressions 20 are provided at equal intervals along the channel axis in the bottom surface 51 c of the cathode gas channel 5 c. On the surface of the recess 20 provided in the cathode-side separator 8c, a part of the pure water in the cooling water flow path 6 flowing on the back surface moves through the inside of the porous material and is stored. The driving force for movement is a capillary force generated in the recess 20 having a V-shaped cross section. That is, by making the cathode-side separator 8c porous, pure water always accumulates on the surface of the depression 20, so that water is always retained in the depression 20 in addition to mist and condensed water mixed with changes in operating conditions. be able to.

As described above, normally, the cathode gas having a relatively large flow rate can be reliably humidified in the upstream region A ₁ of the cathode gas flow path 5c, so that the stably moistened cathode gas can be supplied. Drying of the film 1 can be prevented.

  Moreover, since the liquid water adhering to the surface of the groove constituting the cathode gas flow path 5c can be collected in the cathode-side separator 8c by using the porous material, the occurrence of water clogging can be suppressed. it can.

  The anode side separator 8a may be formed of a porous material. In this case, the cooling water channel 6 is configured to contact the back surface 19a of the surface 18a on which the anode gas channel 5a of the anode separator 8a is formed.

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

  The separator 8 is made of a porous material. Here, the cathode-side separator 8c is made of a porous material. Thereby, since water can be held in the separator 8 (c), the water holding means (20) can always be supplemented with water from the inside of the separator 8 (c). Moreover, it becomes possible to collect | recover water in the separator 8 (c) as a water discharge means.

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

The cathode side separator 8c is formed of a dense carbon material as in the first embodiment. Further, as shown in FIG. 2, a depression 21 as water holding means is formed in the upstream region A ₁ of the cathode gas flow path 5c, and a narrow groove 30 as water discharging means is formed in the downstream region B ₁ .

FIG. 9 shows an enlarged view of the upstream region A ₁ of the cathode gas flow path 5c. A plurality of depressions 21 are configured at equal intervals along the flow path axis. However, the shape of the recess 21 is a substantially oblique cone shape. The recess 21 is formed by tilting the axis of the recess 21 toward the downstream side. That is, the depression 21 is formed so that the oblique cone-shaped apex 21a is inclined to the downstream side. When the depression 21 is formed in this way, the water storage state in the depression 21 is as shown in FIG. FIG. 10 shows an X ₃ -X ₃ cross section along the flow path axis of the recess 21.

  The cross section of the recess 21 is formed in a triangular shape in which the apex 21a is biased to the downstream side of the cathode gas flow path 5c. Thereby, it can suppress that the water collected in the hollow 21 is discharged | emitted with the flow of cathode gas.

Although not shown here, for the water retention means provided in the upstream region A ₂ of the anode gas passage 5a of the anode side separator 8a, like the water holding means provided in the cathode gas passage 5a, oblique conical It is good also as the hollow 21 of. In addition, the separator 8 is made of a dense material, but may be made of a porous material as in the second embodiment.

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

  The depression 21 is formed in an oblique cone shape with the apex 21a inclined toward the downstream side of the gas flow. Thus, by making the cross-sectional shape of the depression 21 an oblique conical shape, it becomes difficult to carry water by the flow of the reaction gas, so that it becomes easy to hold water.

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

The cathode side separator 8c is formed of a carbon-based porous material. In FIG. 11, the block diagram of the plane 18c of the cathode side separator 8c is shown. Here, in the upstream region A ₁ of the cathode gas flow path 5 c, a narrow groove 22 partitioned into a line segment shape is formed instead of the recess 20 as water holding means.

An enlarged view of the upstream region A ₁ of the cathode gas channel 5c shown in FIG. 12.

A plurality of narrow grooves 22 divided into line segments are formed at equal intervals on the bottom surface 51c of each cathode gas channel 5c. The cross-sectional shape of the narrow groove 22 in the direction perpendicular to the flow path axis is a V shape. FIG. 13 shows an X ₄ -X ₄ cross section in the direction along the flow path axis of the narrow groove 22. The cross-sectional shape along the channel axis of the narrow groove 22 is a U-shape that opens toward the inside of the cathode gas channel 5c. On the surface of the narrow groove 22, water flowing through the cooling water flow path 6 formed on the back surface passes through the cathode side separator 8 c and is stored. By using the line-shaped narrow groove 22 as the water holding means as described above, water is easily held at the end 22a of the narrow groove 22 as shown in FIG. It is difficult for the water accumulated in the water to be discharged.

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

The water holding means is constituted by a plurality of line-shaped narrow grooves 22 provided at the bottom 51 of the reaction gas channel 5. Thereby, it becomes easy for water to condense and hold | maintain in the fine groove 22 divided | segmented into the line segment shape. Here in particular, providing a narrow groove 22 as a water holding means provided in the upstream region A ₁ of the cathode gas channel 5c. Since the cathode gas has a large flow rate, the water stored in the water holding means is easily discharged due to the influence of the gas flow, but the function of holding the water can be improved by using the narrow groove 22.

Here, the cathode separator 8c is made of a porous material, but a line-shaped fine groove 22 may be provided on a separator made of a dense material as in the first embodiment. It may also be applied to the narrow groove 22 in the water holding means constituting the upstream region A ₂ of the anode gas passage 5a.

  Thus, 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 fuel cell, particularly a polymer electrolyte fuel cell that requires water management.

It is a schematic block diagram of the fuel cell used for 1st Embodiment. It is a top view of the cathode side separator used for a 1st embodiment. It is the schematic of the water holding means used for 1st Embodiment. It is sectional drawing of the water holding means used for 1st Embodiment. It is the schematic of the water discharge means used for 1st Embodiment. It is a top view of the anode side separator used for 1st Embodiment. It is a schematic block diagram of the fuel cell used for 2nd Embodiment. It is sectional drawing of the water holding means used for 2nd Embodiment. It is the schematic of the water holding means used for 3rd Embodiment. It is sectional drawing of the water holding means used for 3rd Embodiment. It is a top view of the cathode side separator used for 4th Embodiment. It is the schematic of the water holding means used for 4th Embodiment. It is sectional drawing of the water holding means used for 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolyte membrane 2 Electrode 2a Anode 2c Cathode 3 Gas diffusion layer 3a Anode gas diffusion layer 3c Cathode gas diffusion layer 5 Reaction gas flow path 5a Anode gas flow path 5b Cathode gas flow path 6 Cooling water flow path 8 Separator 11 Fuel cell 20 Depression 21 Hollow 21a apex 22 narrow groove 30 narrow groove

Claims (7)

An anode gas diffusion layer and a cathode gas diffusion layer disposed on both sides of the anode and the cathode as a pair of electrodes sandwiching the electrolyte membrane;
A separator sandwiching the anode gas diffusion layer and the cathode gas diffusion layer, and
Of the separator, provided with an anode gas flow path on the surface in contact with the anode gas diffusion layer,
Further, water holding means is provided on the upstream flow path surface of the anode gas flow path, and water discharge means having a larger area ratio than the arrangement area of the water holding means is provided on the downstream flow path surface. A fuel cell. An anode gas diffusion layer and a cathode gas diffusion layer disposed on both sides of the anode and the cathode as a pair of electrodes sandwiching the electrolyte membrane;
A separator sandwiching the anode gas diffusion layer and the cathode gas diffusion layer, and
A cathode gas flow path is provided on a surface of the separator that contacts the cathode gas diffusion layer,
Further, water discharge means is provided on the downstream surface of the cathode gas flow path, and water holding means having a larger area ratio than the area where the water discharge means is provided on the upstream flow path surface. A fuel cell.   The fuel cell according to claim 1, wherein the separator is made of a porous material.   The fuel cell according to any one of claims 1 to 3, wherein the water holding means is a plurality of depressions provided at a flow path bottom.   The fuel cell according to claim 4, wherein the depression is formed in an oblique cone shape whose apex is inclined toward the downstream side of the gas flow.   4. The fuel cell according to claim 1, wherein the water holding means is a plurality of line-shaped narrow grooves provided at the bottom of the gas flow path.   The fuel cell according to any one of claims 1 to 3, wherein the water discharging means is a narrow groove provided at a bottom of the flow path.

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