JP2009110838A - Separator for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance power generation efficiency of a fuel cell by decreasing concentration polarization. <P>SOLUTION: A separator 100 for a fuel cell has a gas passage 111 on the contact surface with a membrane electrode assembly, the gas passage 111 is formed in a plurality of independent gas passage regions 110 installed in parallel from the upstream side to the downstream side of gas flow. the gas passage 111 of each gas passage region 110 includes a plurality of parallel upstream passages 111a into which reaction gas flows from the upstream side and whose downstream ends are closed and a plurality of parallel downstream passages 111b formed between the upstream passages 11a and whose upstream ends are closed and exhausting the reaction gas to the down stream side, and reaction gas flowing through the upstream passages 111a is passed through a gas diffusion layer of the membrane electrode assembly coming in contact with the upstream passages 111a and flows in the downstream passages 111b adjoined to the upstream passages 111a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell separator.

The conventional fuel cell separator separates the gas supply flow path and the gas discharge flow path so that all the reaction gas in the gas supply flow path passes through the gas diffusion layer and the catalyst layer before being discharged. It was discharged into the work channel. Thereby, the reaction gas can be uniformly distributed to the electrode reaction surface, and the power generation efficiency of the fuel cell can be improved (for example, see Patent Document 1).
JP-A-11-16591

  However, the conventional fuel cell separator described above has a slow flow rate of the gas diffusing from the gas supply channel to the gas discharge channel, and the concentration polarization increases particularly in the downstream portion where the reaction gas concentration becomes thin, thereby generating power. There was a problem that efficiency decreased.

  The present invention has been made paying attention to such conventional problems, and an object of the present invention is to reduce the concentration polarization and improve the power generation efficiency of the fuel cell.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention provides a fuel cell separator (100) in which a gas flow path (111) is formed on a contact surface with a membrane electrode assembly (12), wherein the gas flow path (111) It is formed in a plurality of independent gas flow path regions (110) provided side by side from the upstream side to the downstream side, and the gas flow path (111) of each gas flow path region (110) is a reaction gas from the upstream side. And a plurality of parallel upstream flow paths (111a) whose downstream ends are closed, and a plurality of upstream flow paths (111a) whose upstream ends are closed and a reaction gas is discharged downstream. The reaction gas flowing in the upstream flow path (111a) includes a parallel downstream flow path (111b), and the gas diffusion layer (17) of the membrane electrode assembly (12) in contact with the upstream flow path (111a). ) Through the downstream adjacent to the upstream flow path (111a) Wherein the flow into the road (111b).

  A plurality of upstream flow paths in which the reaction gas flows and the downstream ends are blocked; and a downstream flow path formed between the upstream flow paths, and the reaction gas that has flowed through the upstream flow path flows through the gas diffusion layer under the ribs. , A plurality of gas flow path regions are provided side by side from the upstream side to the downstream side in the reaction gas flow direction. As a result, the channel length of each gas channel region is shorter than that of a gas channel region configured by a single long gas channel. As a result, the flow rate of the reaction gas flowing from the upstream flow path to the downstream flow path is increased also on the downstream side, so that concentration polarization can be reduced and power generation efficiency can be improved in the downstream portion where the reaction gas concentration decreases.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
In a fuel cell, an electrolyte membrane is sandwiched between an anode electrode (fuel electrode) and a cathode electrode (oxidant electrode), an anode gas containing hydrogen in the anode electrode (fuel gas), and a cathode gas containing oxygen in the cathode electrode (oxidant) Electricity is generated by supplying gas. The electrode reaction that proceeds in both the anode electrode and the cathode electrode is as follows.

Anode electrode: 2H ₂ → 4H ⁺ + 4e ⁻ (1)
Cathode electrode: 4H ⁺ + 4e ⁻ + O ₂ → 2H ₂ O (2)
The fuel cell generates an electromotive force of about 1 volt by the electrode reactions (1) and (2).

  When such a fuel cell is used as a power source for automobiles, a large amount of electric power is required, so that it is used as a fuel cell stack in which several hundred fuel cells are stacked. Then, a fuel cell system that supplies anode gas and cathode gas to the fuel cell stack is configured, and electric power for driving the vehicle is taken out.

  FIG. 1 is a schematic configuration diagram of a fuel cell system 1 according to a first embodiment of the present invention.

  The fuel cell system 1 includes a fuel cell stack 10, an anode gas path 20, and a cathode gas path 30.

  The fuel cell stack 10 is configured by stacking a plurality of single cells in which separators are arranged on both surfaces of a membrane electrode assembly (hereinafter referred to as “MEA”) including an anode electrode and a cathode electrode. Details of the single cell will be described later with reference to FIG.

  The anode gas path 20 includes a fuel tank 21 and a pressure regulating valve 22 on the upstream side of the fuel cell stack 10, and a circulation pump 23 and a purge valve 24 on the downstream side of the fuel cell stack 10.

  The fuel tank 21 stores the anode gas supplied to the fuel cell stack 10 in a high pressure state.

  The pressure regulating valve 22 reduces the pressure of the fuel tank 11 to an appropriate pressure.

  The circulation pump 23 circulates the anode gas. A circulation channel 25 is provided downstream of the circulation pump 23 to supply unreacted reaction gas discharged from the fuel cell stack 10 to the fuel cell stack 10 again.

  The purge valve 24 purges impure gas such as nitrogen and liquid water existing in the anode gas path out of the system.

  The cathode gas path 30 includes a compressor 31 on the upstream side of the fuel cell stack 10 and a pressure adjustment valve 32 on the downstream side of the fuel cell stack.

  The compressor 31 pumps and supplies air (cathode gas) to the fuel cell stack 10.

  The pressure adjustment valve 32 adjusts the supply pressure of air (cathode gas) supplied to the fuel cell stack 10.

  Below, with reference to FIG. 2, the single cell 11 which comprises the fuel cell stack 10 is demonstrated in detail.

  FIG. 2 is a diagram showing a part of a cross section of the single cell 11.

  The single cell 11 is configured by arranging separators 100 on both front and back surfaces of a membrane electrode assembly (hereinafter referred to as “MEA”) 12.

  The MEA 12 includes a solid polymer electrolyte membrane 13, an anode electrode 14, and a cathode electrode 15. The MEA 12 has an anode electrode 14 on one surface of the solid polymer electrolyte membrane 13 and a cathode electrode 15 on the other surface.

  The solid polymer electrolyte membrane 13 is a proton-conductive ion exchange membrane formed of a fluorine-based resin. The solid polymer electrolyte membrane 13 exhibits good electrical conductivity in a wet state.

  The anode electrode 14 includes a catalyst layer 16 and a gas diffusion layer 17.

  The catalyst layer 16 is in contact with the solid polymer electrolyte membrane 13. The catalyst layer 16 is formed from carbon black particles on which platinum or platinum is supported.

  The gas diffusion layer 17 is provided on the outer side of the catalyst layer 16 (opposite side of the electrolyte membrane 13) and is in contact with the separator 100. The gas diffusion layer 17 is formed of a member having sufficient gas diffusibility and conductivity, and is formed of, for example, a carbon cloth woven with yarns made of carbon fibers. In the following description, the gas diffusion layer 17 that is in direct contact with the ribs (partition walls) 112 of the separator 100, which will be described later with reference to FIG. 3, is referred to as “under-rib gas diffusion layer 17a”. On the other hand, the gas diffusion layer 17 in contact with the gas flow path 111 of the separator 100, which will be described later with reference to FIG.

  Similarly to the anode electrode 14, the cathode electrode 15 includes a catalyst layer 16 and a gas diffusion layer 17.

  The separator 100 is in contact with the gas diffusion layer 17. The separator 100 has a plurality of gas flow paths 111 for supplying reaction gas to the anode electrode 14 and the cathode electrode 113 on the side in contact with the gas diffusion layer 17. The gas flow path 111 is a flow path formed between the ribs 112 that are in direct contact with the gas diffusion layer 17. The separator 100 is made of a dense carbon material or the like so that the anode gas flowing through the gas flow path 111 does not pass through the adjacent gas flow path 111. Similarly, the cathode separator is made of a dense carbon material.

  Next, in order to facilitate understanding of the present invention, before describing the separator 100 according to the present embodiment, first, the separator 200 according to the conventional example and its problems will be described with reference to FIGS. 9 to 11.

  FIG. 9 is a plan view of a separator 200 according to a conventional example. FIG. 10 is a diagram showing a part of a cross section of a single cell 11 using a separator 200 according to a conventional example.

  As shown in FIG. 9, the separator 200 according to the conventional example alternately closes the ends of the gas flow paths 204. Thus, the separator 200 according to the conventional example separates the gas flow path 204 into the gas supply flow path 204a that communicates with the gas inlet hole 202a and the gas discharge flow path 204b that communicates with the gas outlet hole 202b by the rib 211. It was.

  Thus, as shown in FIG. 10, the reaction gas is diffused from the gas supply channel 204a to the gas discharge channel 204b by forcibly passing through the under-rib gas diffusion layer 17a. As a result, the reaction gas is forcibly supplied also to the catalyst layer under the rib where the reaction gas concentration tends to decrease, thereby suppressing the occurrence of concentration polarization due to the decrease in the reaction gas concentration. In addition, the arrow in the figure of FIG. 10 is an arrow which shows the flow of the reactive gas which diffuses from the gas supply flow path 204a to the gas discharge flow path 204b through the gas diffusion layer 17a under rib.

  However, the flow rate (flow rate) of the reaction gas that diffuses from the gas supply flow path 204a to the gas discharge flow path 204b through the under-rib gas diffusion layer 17a has not been considered at all.

  FIG. 11 shows the flow rate of the reaction gas diffused in the gas flow direction and the vertical direction from the gas supply channel 204a to the gas discharge channel 204b through the sub-rib gas diffusion layer 17a and the current density at a predetermined cell voltage. It is the figure which showed the relationship. Here, the flow rate of the reaction gas is a gas flow rate that passes through the under-rib gas diffusion layer 17a of unit length per unit time, and the gas flow rate from the gas supply channel 204a to the gas discharge channel 204b increases as the gas flow rate increases. The flow rate of the reaction gas that diffuses increases.

  As shown by a solid line in FIG. 11, when the concentration of the reaction gas that diffuses from the gas supply channel 204a to the gas discharge channel 204b through the gas diffusion layer 17a under the rib is high, the flow rate of the reaction gas is small. However, the decrease in current density is small.

  However, as shown by a broken line in FIG. 11, when the concentration of the reaction gas that diffuses from the gas supply channel 204a to the gas discharge channel 204b through the gas diffusion layer 17a under the rib is low, the flow rate of the reaction gas is If it is less, the current density will be extremely lowered.

  As described above, the inventors have a low flow rate of the diffusing reaction gas when the concentration of the reaction gas diffusing from the gas supply passage 204a to the gas discharge passage 204b through the under-rib gas diffusion layer 17a is low. It was found that the concentration polarization is remarkably increased and the performance of the fuel cell is lowered.

  The reaction gas flowing through the gas supply flow path 204a is consumed by the electrode reaction as it goes downstream, the flow rate decreases, and the concentration also decreases. Therefore, the separator 200 according to the conventional example has a problem in that concentration polarization increases in the downstream portion where the flow rate and concentration of the reaction gas decrease.

  Therefore, in the separator 100 according to the present embodiment, the gas flow path is divided into three flow paths from the first flow path portion to the third flow path portion. As a result, the flow rate of the reaction gas passing through the sub-rib gas diffusion layer was made faster than that of the separator 200 according to the conventional example. Hereinafter, the separator 100 according to the present embodiment will be described in detail with reference to FIG.

  FIG. 3 is a plan view of the separator 100 according to the present embodiment as viewed from the electrode side.

  As shown in FIG. 3, at one end (left side in the figure) of the separator 100, in order from the top, a second reactive gas (anode gas) outlet hole 103b, a cooling water outlet hole 101b, and a first reactive gas (cathode gas) inlet. A hole 102a is formed. On the other hand, a first reactive gas outlet hole 102b, a cooling water inlet hole 101a, and a second reactive gas inlet hole 103a are formed in order from the top at the other end (right side in the figure) of the separator 100.

  A strip-shaped sealing material 104 is provided on the outer periphery of the separator 100, the periphery of the cooling water inlet hole 101a and the outlet hole 101b, and the periphery of the second reactive gas inlet hole 103a and the outlet hole 103b. The sealing material 104 prevents leakage of the reaction gas to the outside and mixing of the reaction gas and cooling water.

  Three independent gas flow channel regions 110 in which a plurality of groove-shaped gas flow channels 111 are formed are formed on the surface of the separator 100 from the upstream side to the downstream side along the gas flow direction. Hereinafter, when it is necessary to particularly distinguish each of the gas flow path regions 110 formed at these three locations, the first gas flow path region 110a, the second gas flow path region 110b, The third gas flow path region 110c is used.

  The gas channel 111 formed in each gas channel region 110 is a channel formed between a plurality of ribs 112 parallel to the gas flow direction. The rib 112 protrudes from the bottom surface of the gas flow path 111 to the MEA side and is in contact with the MEA 12.

  The gas flow path 111 includes a gas supply flow path 111a whose downstream end is closed by a rib 113 that is formed in the width direction of the separator 100 and closes the downstream end, and a rib 114 that similarly closes the upstream end. The gas discharge channel 111b is closed at the upstream end. The gas supply channel 111a and the gas discharge channel 111b are alternately arranged in parallel. Similarly to the rib 112, the ribs 113 and 114 protrude from the bottom surface of the gas flow path 111 toward the MEA and are in contact with the MEA 12.

  A gas diffusion region 120 is formed between the first reactive gas inlet hole 102a and the first gas flow channel region 110a. The gas diffusion region 120 diffuses the reaction gas supplied from the first reaction gas inlet hole 102a and uniformly distributes the reaction gas to each gas supply channel 111a of the first gas channel region 110a.

  A gas junction 130 is formed between the gas flow channel regions 110. The gas merger 130 merges the reaction gas that has flowed through the gas discharge channel 111b of the upstream gas flow channel region 110 and supplies it to the gas supply flow channel 111a of the downstream gas flow channel region 110.

  A gas convergence region 140 is formed between the third gas flow channel region 110c and the first reactive gas outlet hole 102b. The gas converging region 140 converges the reaction gas flowing through the gas discharge passage 111b of the third gas passage region 110c, and discharges the reaction gas from the first reaction gas outlet hole 102b.

  Each gas flow channel region 110 is formed such that the length in the gas flow direction (= the length of the ribs 112) W becomes longer as it goes upstream. That is, if the lengths of the gas flow direction of the first gas flow channel region 110a, the second gas flow channel region 110b, and the third gas flow channel region 110c are W1, W2, and W3, respectively, W1> W2> It is formed to be W3.

  Since the separator 100 is a separator having a constant width direction, and the number of flow paths in each gas flow path region 110 is the same, the total length of the ribs 113 and the ribs 114 formed in the width direction is equal. Therefore, the length L (hereinafter referred to as “total extension of the ribs”) L of the rib 112 formed in the gas flow direction and the ribs 113 and 114 formed in the width direction in each gas flow channel region 110 is: The longer the length W in the gas flow direction, the longer. That is, if the total extension of the ribs of the gas flow channel regions of the first gas flow channel region 110a, the second gas flow channel region 110b, and the third gas flow channel region 110c is L1, L2, and L3, respectively, L1> L2> L3 It becomes.

  Next, operations and effects of the separator 100 will be described with reference to FIGS. 2 and 4.

  FIG. 4A is a diagram illustrating a gas flow state of the separator 100. FIG. 4B shows the reaction gas diffused by flowing in the gas flow direction and the vertical direction from the gas supply flow path 111a to the gas discharge flow path 111b through the under-rib gas diffusion layer 17a of the rib 112 of the separator 100. It is the figure which showed the flow rate.

  As shown in FIG. 4A, the reaction gas supplied from the first reaction gas inlet hole 102a diffuses in the gas diffusion region 120 and flows into each gas supply channel 111a of the first gas channel region 110a. . The reactive gas diffuses into the gas diffusion layer 17b under the channel facing the gas supply channel 111a while flowing downstream through the gas supply channel 111a of the first gas channel region 110a. The downstream end of the gas supply channel 111 a is closed by a rib 113. Accordingly, the reaction gas that has diffused into the gas diffusion layer 17b under the flow path and was not used for the electrode reaction diffuses into the adjacent gas discharge flow path 111b through the gas diffusion layer 17a under the rib.

  The reaction gas diffused to the gas discharge flow path 111b in the first gas flow path region 110a is diffused to the gas diffusion layer 17b below the flow path while flowing downstream through the gas discharge flow path 111b. Used for electrode reaction. Then, the remaining reaction gas flows into the gas merge region 130 formed between the first gas flow channel region 110a and the second gas flow channel region 110b.

  The reactive gas that has flowed into the gas merge region 130 formed between the first gas flow channel region 110a and the second gas flow channel region 110b flows into the gas supply flow channel 111a of the second gas flow channel region 110b. This reaction gas passes through the gas diffusion layer 17a under the ribs and flows out of the gas in the second gas flow channel region 110b in the same manner as the reaction gas that flows into the gas supply flow channel 111a of the first gas flow channel region 110a. It diffuses into the path 111b. Thereafter, the gas flows into the gas merge region 130 formed between the second gas flow channel region 110b and the third gas flow channel region 110c. Then, the gas flows from the first reaction gas outlet hole 102 b through the gas supply flow path 111 a in the third gas flow path region → the under-rib gas diffusion layer 17 a → the gas discharge flow path 111 b → the gas convergence region 140.

  Here, the flow rate of the reaction gas passing through the under-rib gas diffusion layer 17a increases as the cross-sectional area of the under-rib gas diffusion layer 17a serving as the reaction gas flow path decreases. The cross-sectional area of the under-rib gas diffusion layer 17a is obtained by multiplying the length of the rib 112 formed in the gas flow direction (= the length W of the gas flow path region) by the thickness of the gas diffusion layer. is there. In the present embodiment, the thickness of the gas diffusion layer 17 is constant in the gas flow direction. Therefore, as the length of the rib 112 is shortened, the cross-sectional area of the under-rib gas diffusion layer 17a is reduced, and the flow rate of the reaction gas passing through the under-rib gas diffusion layer 17a is increased.

  Therefore, as shown in FIG. 4B, the flow velocity of the reaction gas passing through the gas diffusion layer 17a in the third flow path region in which the length of the rib 112 is the shortest becomes the fastest. On the other hand, the flow velocity of the reaction gas passing through the gas diffusion layer 17a in the first flow path region where the length of the rib 112 is the longest becomes the slowest.

  Thus, according to the separator 100 according to the present embodiment, the flow rate of the reaction gas passing through the downstream gas diffusion layer in the downstream portion where the flow rate is reduced and the concentration is reduced due to the electrode reaction is set to the upstream flow rate. Can be faster. Therefore, it is possible to suppress the occurrence of concentration polarization due to a decrease in the reaction gas concentration that is likely to occur in the downstream portion.

  In addition, the length of the rib 112 is a reaction that passes through the under-rib gas diffusion layer 17a necessary for obtaining a predetermined current density according to the concentration of the reaction gas flowing through the gas flow path 111 of each gas flow path region 110. The gas flow rate is obtained in advance and determined by the following equation.

  According to the present embodiment described above, the independent gas flow channel region 110 in which the plurality of groove-shaped gas flow channels 111 are formed is divided into a plurality from the upstream side to the downstream side along the gas flow direction. Formed.

  Thereby, the flow velocity of the reaction gas passing through the sub-rib gas diffusion layer can be adjusted by adjusting the length of each gas flow channel region in the gas flow direction according to the gas supply amount.

  That is, the length of the rib 112 of the first gas flow channel region 110a is adjusted according to the amount of the reaction gas supplied from the first reaction gas inlet hole 102a, and the first gas flow region 110a is adjusted according to the amount of the reaction gas flowing into the junction 130. 2. Adjust the length of the rib 112 of the third gas flow path regions 110b and 110c. Thereby, since the fall of the flow velocity of the reactive gas which passes the gas diffusion layer 17a of the downstream part can be suppressed, generation | occurrence | production of concentration polarization by the fall of reactive gas concentration can be suppressed. Therefore, the current density on the electrode reaction surface can be made uniform from the upstream portion to the downstream portion, and the output of the single cell 11 can be improved.

  Further, in the present embodiment, the length of the rib 112 in the gas flow path region formed in the downstream is particularly shortened. Therefore, the catalyst under the rib in the downstream portion in which the reaction gas concentration tends to decrease. Sufficient reaction gas can be supplied to the layer. Therefore, the occurrence of concentration polarization due to a decrease in the reaction gas concentration can be further suppressed.

  Moreover, since the condensed water produced | generated by electric power generation can be rapidly discharged | emitted from the inside of a gas diffusion layer by making the flow rate of the reactive gas which passes a gas diffusion layer under a rib fast, flooding can be prevented.

  Furthermore, since the gas flow rate is determined according to the reaction gas concentration, the flow rate can be reduced (= pressure loss is reduced and concentration polarization is also small) in a portion where the reaction gas concentration is high. On the other hand, the flow rate can be increased (= pressure loss is increased, but concentration polarization can be greatly reduced) in the portion where the reaction gas concentration is low. As a result, the power generation efficiency can be improved without increasing the power consumption of the excessive compressor 31.

(Second Embodiment)
Next, a separator 100 according to a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, the lengths W1, W2, and W3 in the gas flow direction of the gas flow channel regions 110a, 110b, and 110c are all the same, and the number of the gas flow channels 111 is reduced as the gas flow channel region is formed downstream. This is different from the first embodiment. Hereinafter, the difference will be mainly described. In each of the following embodiments, the same reference numerals are used for portions that perform the same functions as those of the first embodiment described above, and repeated descriptions are omitted as appropriate.

  FIG. 5 is a plan view of the separator 100 according to the present embodiment as viewed from the electrode side.

  As shown in FIG. 5, in the separator 100 according to the present embodiment, the gas flow path 111 has the same flow path width, but the width of the rib 112 in the gas flow path region formed downstream is the gas flow formed upstream. It is wider than the rib 112 in the road area. As a result, the number n of the gas flow paths 111 is reduced in the downstream gas flow path region. That is, the number n2 of the gas flow paths 111 in the second gas flow path area 110b downstream of the first gas flow path area 110a is smaller than the number n1 of the gas flow paths 111 in the first gas flow path area 110a. I did it. Then, the number n3 of gas channels 111 in the third gas channel region 110c downstream of the second gas channel region 110b is smaller than the number n2 of gas channels 111 in the second gas channel region 110b. I did it.

  Since the separator 100 is formed so that the lengths W1, W2, and W3 in the gas flow direction of the gas flow channel regions 110a, 110b, and 110c are substantially the same, the smaller the number n of the gas flow channels 104, the more the ribs. The total length L is shortened. Therefore, when the gas channel regions 110a, 110b, and 110c total rib extensions L1, L2, and L3 are compared, the number n of the gas channels 111 has a relationship of n1> n2> n3, and thus L1> L2> L3. .

  As a result, as in the first embodiment, the flow rate of the reaction gas passing through the under-rib gas diffusion layer 17a of the gas flow channel region 110c formed in the downstream portion is set to be the same as that of the gas flow channel region 110a formed in the upstream portion. This can be faster than the flow rate of the reaction gas passing through the under-rib gas diffusion layer 17a. Therefore, also in this embodiment, the same effect as the first embodiment can be obtained.

(Third embodiment)
Next, a separator 100 according to a third embodiment of the present invention will be described with reference to FIG. This embodiment is different from the first embodiment in that the shape of the separator 100 is changed and the lengths W1, W2, and W3 in the gas flow direction of the gas flow channel regions 110a, 110b, and 110c are all the same. . Hereinafter, the difference will be mainly described.

  FIG. 6 is a plan view of the separator 100 according to the present embodiment as viewed from the electrode side.

  As shown in FIG. 6, the separator 100 is formed such that the entire width gradually decreases from the first reaction gas inlet hole 102a to the first reaction gas outlet hole 102b. Further, the lengths W1, W2, and W3 in the gas flow direction of the gas flow channel regions 110a, 110b, and 110c are formed to be substantially the same.

  Then, since the flow channel width of the gas flow channel 111 and the width of the rib 112 of each gas flow channel region 110a, 110b, 110c are formed to be substantially the same, the gas flow channel region is more downstream. The number n of 111 is reduced. Therefore, when the total rib lengths L1, L2, and L3 of the gas flow channel regions 110a, 110b, and 110c are compared, the number n of the gas flow channels 111 has a relationship of n1> n2> n3, and therefore L1> L2> L3. Become.

  As a result, as in the first embodiment, the flow rate of the reaction gas passing through the under-rib gas diffusion layer 17a of the gas flow channel region 110c formed in the downstream portion is set to be the same as that of the gas flow channel region 110a formed in the upstream portion. This can be faster than the flow rate of the reaction gas passing through the under-rib gas diffusion layer 17a. Therefore, also in this embodiment, the same effect as the first embodiment can be obtained.

(Fourth embodiment)
Next, with reference to FIG. 7, the separator 100 by 4th Embodiment of this invention is demonstrated. This embodiment is different from the first embodiment in that the gas flow path 104 is folded halfway. Hereinafter, the difference will be mainly described.

  FIG. 7 is a plan view of the separator 100 according to the present embodiment as viewed from the electrode side.

  As shown in FIG. 7, at one end (left side in the figure) of the separator 100, a cooling water outlet hole 101b, a first reactive gas inlet hole 102a, and a first reactive gas outlet hole 102b are formed in order from the top. On the other hand, a cooling water inlet hole 101a, a second reactive gas inlet hole 103a, and a second reactive gas outlet hole 103b are formed in order from the top at the other end (right side in the figure) of the separator 100.

  As described above, in the separator 100 according to the present embodiment, the first reactive gas inlet hole 102 a and the outlet hole 102 b are formed at the end portion on the same side of the separator 100. A gas diffusion region 120, a first gas flow channel region 110a, and a gas junction 130 are formed in series with the first reaction gas inlet hole 102a from the left to the right in the drawing. Further, the second gas flow path region 110b and the gas converging region 140 are formed in series with the first reaction gas outlet hole 102b from the right to the left in the figure so as to be folded at the gas junction 130. The first gas flow channel region 110a and the second gas flow channel region 110b are partitioned vertically in the figure by a sealing material 104a extending in parallel with the gas flow channel 111.

  As a result, the reaction gas supplied from the first reaction gas inlet hole 102a and flowing through the first gas flow path region 110a from the left to the right in the figure makes a U-turn at the gas junction 130, and this time in the opposite direction. It flows through the second gas flow path region 110b and is discharged from the first reaction gas outlet hole 102b.

  Here, the number n1 of the gas flow paths 111 in the first gas flow path area 110a on the upstream side of the gas junction 130 is greater than the number n2 of the gas flow paths 111 in the second gas flow path area 110b on the downstream side. It is formed as follows. In other words, the width of the first gas flow path region 111a is formed to be wider than the width of the second gas flow path region 110b. Since the first gas flow channel region 110a and the second gas flow channel region 110b have the same flow channel length (= the length of the ribs 112) in the gas flow direction, the total length L of the ribs is compared. The total rib extension L1 of the first gas flow channel region 110a having a large number 111 is longer than the total rib extension L2 of the second gas flow channel region 110b. That is, L1> L2.

  Therefore, as in the first embodiment, the flow rate of the reactive gas passing through the gas diffusion layer 17a below the rib of the gas flow channel region 110c formed in the downstream portion is set to the rib of the gas flow channel region 110a formed in the upstream portion. This can be faster than the flow rate of the reaction gas passing through the lower gas diffusion layer 17a. Therefore, also in this embodiment, the same effect as the first embodiment can be obtained.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  For example, in the first embodiment, three gas flow path regions 110 are formed, but at least two gas flow channel regions 110 may be provided.

  In the fourth embodiment, the gas convergence region 140 is formed immediately behind the second gas flow channel region 110b. However, as shown in FIG. The gas convergence region 140 may be formed after forming the third gas diffusion region 110c.

1 is a schematic configuration diagram of a fuel cell system according to a first embodiment of the present invention. It is a figure which shows a part of cross section of a single cell. It is the top view which looked at the separator by 1st Embodiment of this invention from the electrode side. It is the figure which showed the flow velocity of the reactive gas which passes the gas diffusion layer under a rib of the separator by 1st Embodiment of this invention. It is the top view which looked at the separator by 2nd Embodiment of this invention from the electrode side. It is the top view which looked at the separator by 3rd Embodiment of this invention from the electrode side. It is the top view which looked at the separator by 4th Embodiment of this invention from the electrode side. It is the top view which looked at the separator by other embodiment of this invention from the electrode side. It is a top view of the separator by a prior art example. It is a figure which shows a part of cross section of the single cell using the separator by a prior art example. It is the figure which showed the relationship between the flow volume of the reactive gas which passes a gas diffusion layer under a rib, and the current density in a predetermined cell voltage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Fuel cell 12 Membrane electrode assembly 100 Separator 110 Gas flow path area | region 111 Gas flow path 111a Gas supply flow path (upstream flow path)
111b Gas discharge channel (downstream channel)
112 rib (first partition)
113 rib (second partition)
114 rib (third partition)

Claims (6)

A fuel cell separator in which a gas flow path is formed on a contact surface with a membrane electrode assembly,
The gas flow path is formed in a plurality of independent gas flow path regions provided side by side from the upstream side to the downstream side of the gas flow,
The gas channel of each gas channel region is
A plurality of parallel upstream flow paths in which the reaction gas flows from the upstream side and the downstream end is blocked;
A plurality of parallel downstream flow paths formed by closing the upstream end between the upstream flow paths and discharging the reaction gas downstream,
The reaction gas flowing in the upstream flow path flows from the upstream flow path to the adjacent downstream flow path through the gas diffusion layer of the membrane electrode assembly in contact with the upstream flow path. Separator for use. Each gas flow channel region is
A first partition formed in parallel with a gas flow direction separating the upstream flow path and the downstream flow path;
A second partition wall closing the downstream end of the upstream flow path;
A third partition wall closing the upstream end of the downstream flow path,
2. The total extension of the partition walls obtained by adding the lengths of the first partition wall, the second partition wall, and the third partition wall is shorter for the gas flow channel region formed on the downstream side. Fuel cell separator. The length of the upstream flow path and the downstream flow path is made shorter for the gas flow path area formed on the downstream side, and the length of the gas flow path area for which the total extension of the partition wall is formed on the downstream side. The fuel cell separator according to claim 2, wherein the fuel cell separator is shortened. The number of the upstream flow channel and the downstream flow channel is decreased as the gas flow channel region formed on the downstream side, and the total extension of the partition wall is shorter as the gas flow channel region formed on the downstream side. The fuel cell separator according to claim 2 or 3, wherein the fuel cell separator is configured as follows. The width of the first partition wall is made wider for the gas flow channel region formed on the downstream side, and the number of the upstream flow channel and the downstream flow channel in the gas flow channel region formed on the downstream side is reduced. The fuel cell separator according to claim 4, wherein the separator is a fuel cell separator. The total width of the gas flow path area is narrower as that of the gas flow path area formed on the downstream side, and the number of upstream and downstream flow paths in the gas flow path area formed on the downstream side is reduced. The fuel cell separator according to claim 4 or 5.

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