JP2006066257A - Fuel battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress dry-up in an upstream part and flooding in a downstream part of both sides of an oxidizer gas flow passage and a fuel gas flow passage without causing a gap of a fuel battery single cell without any possibility of damage of a membrane electrode assembly due to a pressure difference of the fuel gas and the oxidizer gas. <P>SOLUTION: The fuel battery single cell 2 in which a first separator 5 and a second separator 6 with their thickness gradually getting thinner from an outer side toward an inner side and with groove depths of the fuel gas passage 8 and the oxidizer gas passage 12 made gradually thinner from an entrance side to an exit side, are arranged at the both faces of and pinching the membrane electrode assembly 4 to generate power by reaction of the fuel gas and the oxidizer gas, are lapped in plurality and made cylindrical-shaped, and a cylindrical laminated body is fastened and fixed by a fastening member. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell, and more particularly, to a fuel cell that can prevent misalignment when a single fuel cell is stacked and can suppress flooding.

  For example, at the time of power generation of a polymer electrolyte fuel cell, a reaction for generating water from oxygen, hydrogen ions, and electrons proceeds on the oxidant electrode side. An excess of the generated water is called flooding. This flooding is likely to occur in the downstream portion of the oxidant gas flow path, and reduces the diffusion of the oxidant gas to the electrode.

  Some of the water generated on the oxidant electrode side moves to the fuel electrode side due to the reverse diffusion phenomenon, but if flooding occurs on the oxidant electrode side, the amount of water transferred to the fuel electrode side due to the reverse diffusion As a result, flooding is likely to occur at the downstream side of the fuel gas flow path where the gas flow velocity is reduced, particularly on the fuel electrode side.

  When oxidant gas and fuel gas are supplied without humidification or low humidification, flooding can be suppressed, but on the other hand, the electrolyte membrane tends to dry (dry up) at the upstream of the gas flow path, and hydrogen ions in the electrolyte membrane Movement is suppressed. Therefore, if these phenomena occur when operating the fuel cell at a constant voltage, the current obtained by power generation is reduced.

  In addition, when these phenomena occur when operating the fuel cell at a constant current, not only will the voltage drop, but a part of the electrode will not be used, so current will flow in the part being used. There is a risk that the deterioration of the electrode and the electrolyte membrane due to the heat generated during power generation is accelerated.

  Therefore, in the separator having a certain thickness, the groove depth of the fuel gas passage formed in the separator is gradually shallowed from the inlet to the outlet, thereby preventing a decrease in the flow velocity in the downstream portion of the fuel gas passage, A fuel cell in which flooding in the fuel gas channel is suppressed has been proposed (see, for example, Patent Document 1).

  However, in this case, since the groove depth is changed only on the fuel gas channel side, there is no effect on flooding on the oxidant electrode side. Also, since the separator thickness is determined at the deepest position of the groove depth, the separator thickness becomes thicker on the entire cell surface, and at the shallow groove position, the separator thickness is wasted, resulting in stack stacking. The direction length becomes large and the stack weight also increases.

  Therefore, conventionally, the flow directions of the fuel gas and the oxidant gas are opposite to each other, and both the fuel gas channel groove depth and the oxidant gas channel groove depth formed in the separator are gradually shallow from the inlet to the outlet. However, by making the sum of the fuel gas channel groove depth and the oxidant gas channel groove depth constant, a fuel cell having a structure in which the separator thickness is not wasted and the stack is made compact and lightweight has been proposed. (For example, refer to Patent Document 2).

In the fuel cell described in Patent Document 2, since the gas flow rate not only in the downstream portion of the fuel gas flow path but also in the downstream portion of the oxidant gas flow path can be increased, flooding on the oxidant gas side can also be suppressed. Furthermore, when the flow of the refrigerant is in the same direction as the oxidant gas, the temperature of the upstream part of the oxidant gas flow path decreases, so that dry-up in this part is suppressed, while the downstream part of the oxidant gas flow path is suppressed. Since the temperature rises, flooding in this portion is suppressed.
Japanese Patent Laid-Open No. 11-16590 (pages 2 to 4, FIG. 1) JP 2003-132911 A (pages 3 and 4 and FIG. 3)

  However, in the fuel cell described in Patent Document 2, since the cross-sectional shape of the fuel cell single cell is a parallelogram, the force applied in the stacking direction from both ends of the stack becomes a shear force when stacked, and each fuel cell single cell Misalignment may occur.

  Further, in the fuel cell described in Patent Document 2, since the flow directions of the fuel gas and the oxidant gas are opposite to each other, a membrane electrode assembly (MEA: membrane electrode) at a position where the fuel gas pressure in the fuel gas channel is high. The oxidant gas pressure is low in the oxidant gas flow path on the opposite side across the assembly). On the other hand, the fuel gas pressure is low in the fuel gas passage on the opposite side across the membrane electrode assembly at a position where the oxidant gas pressure in the oxidant gas passage is high.

  For this reason, in the fuel cell described in Patent Document 2, the pressure difference between the fuel gas and the oxidant gas particularly at both ends becomes large, stress is applied to the membrane electrode assembly, and in the worst case, the membrane electrode assembly is damaged. There is a possibility. When the membrane electrode assembly is damaged, the fuel gas and the oxidant gas are directly mixed and burned, which not only prevents power generation from being continued but also causes a serious safety problem.

  In addition, when the flow of the refrigerant is in the same direction as the oxidant gas, the temperature of the upstream part of the oxidant gas flow path decreases, so that dry-up in this part is suppressed, and the temperature of the downstream part of the oxidant gas flow path increases. For this reason, flooding in this portion is suppressed, but conversely, the temperature in the upstream portion of the fuel gas flow path increases, so that dry-up in this portion is promoted, while the temperature in the downstream portion of the fuel gas decreases. Therefore, flooding in this part is promoted.

  Accordingly, the present invention has been made to solve the above problems, and does not cause waste of separator thickness or displacement of a single fuel cell, and a membrane electrode assembly due to a pressure difference between fuel gas and oxidant gas. It is an object of the present invention to provide a fuel cell that can suppress dry-up in the upstream portion of both sides of the oxidant gas passage and the fuel gas passage and flooding in the downstream portion.

  In the fuel cell of the present invention, the membrane electrode assembly that generates power by the reaction of the fuel gas and the oxidant gas, the first separator in which the fuel gas flow path through which the fuel gas flows is formed from both sides, and the oxidant gas flow A plurality of fuel cell single cells sandwiched between second separators in which an oxidant gas flow path was formed were stacked into a cylindrical shape, and the cylindrical laminate was fastened and fixed with a fastening member.

  In the fuel cell of the present invention, the thickness of the first separator and the second separator is gradually reduced from the outside to the inside, and the groove depths of the fuel gas channel and the oxidant gas channel are further reduced. Is formed so as to gradually become shallower from the inlet side toward the outlet side.

  According to the present invention, the thicknesses of the first separator and the second separator are gradually reduced from the outside to the inside, and the groove depths of the fuel gas channel and the oxidant gas channel are set from the inlet side to the outlet side. Since the fuel cell gradually becomes shallower toward the side, a fuel cell is formed when a plurality of fuel cell single cells each having a membrane electrode assembly sandwiched between the first and second separators are stacked to form a cylindrical laminate. Single cells do not become parallelograms, and stacking can prevent misalignment between the single fuel cell units.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

"Fuel cell configuration"
1 is a perspective view of a fuel cell according to the present embodiment, FIG. 2 is an enlarged perspective view of a single fuel cell, FIG. 3 is a cross-sectional view taken along line AA in FIG. 2, and FIG. FIG. 4B is a plan view of the second separator formed with the oxidant gas flow path, FIG. 4C is a plan view of the cooling plate, and FIG. 5A is an enlarged perspective view showing a gas refrigerant discharge manifold, FIG. 5B is an enlarged perspective view showing a gas refrigerant supply manifold, and FIG. 6 is a stack provided between the gas refrigerant discharge manifold and the gas refrigerant supply manifold. It is a figure which shows a pressure adjustment means.

  As shown in FIG. 1, the fuel cell 1 of the present embodiment is configured by stacking a plurality of fuel cell single cells 2 into a cylindrical shape, and fastening and fixing the cylindrical stack with a fastening member 3. Has been.

  As shown in FIGS. 2 and 3, the fuel cell single cell 2 includes a membrane electrode assembly 4, a first separator 5 that is an anode separator through which fuel gas flows, and a second cathode separator through which oxidant gas flows. And a cooling plate 7 provided in contact with at least one of the first separator 5 and the second separator 6.

  In addition, the cooling plate 7 may be installed in all the fuel cell single cells 2, or may be installed only in some fuel cell single cells 2. The cooling plate 7 is not necessarily provided in contact with either the first separator 5 or the second separator 6, and is provided according to whether or not the fuel cell single cell 2 needs to be cooled.

  The membrane electrode assembly 4 is configured, for example, by disposing a fuel electrode and an oxidant electrode on both sides of a solid polymer electrolyte membrane, and if necessary, gas diffusion layers are provided on both sides of the fuel electrode and the oxidant electrode. Be placed. In this membrane electrode assembly 4, power is generated by the reaction between the fuel gas (for example, hydrogen) supplied to the fuel electrodes arranged on both sides of the membrane electrode assembly 4 and the oxidant gas (for example, oxygen) supplied to the oxidant electrode. Made.

  As shown in FIGS. 3 and 4A, the first separator 5 is disposed on one surface 4a of the membrane electrode assembly 4, that is, the side surface on which the fuel electrode is provided. The first separator 5 has a so-called fan shape in which the joint surface with the membrane electrode assembly 4 has a substantially rectangular shape in plan view and the thickness is gradually reduced from the outside to the inside of the laminate. ing.

  In the first separator 5, a fuel gas flow path 8 for supplying fuel gas to the fuel electrode is formed on the surface of the membrane electrode assembly 4 facing the fuel electrode. When the fuel gas flow path 8 is indicated by an arrow in FIG. 3, the groove depth of the fuel gas flow path 8 is gradually decreased from the inlet side toward the outlet side. That is, the flow rate of the fuel gas is high on the inlet side of the fuel gas flow path 8, and the flow rate of the fuel gas gradually decreases toward the outlet side.

  In the first separator 5, a fuel gas inlet internal manifold 9 </ b> A and a fuel gas outlet internal manifold 9 </ b> B formed as opening holes communicating with the fuel gas flow path 8 are formed at diagonal corners. Further, the first separator 5 communicates with an oxidant gas flow path, which will be described later, at a corner on the diagonal opposite to the diagonal where the fuel gas inlet internal manifold 9A and the fuel gas outlet internal manifold 9B are provided. An oxidant gas inlet internal manifold 10A and an oxidant gas outlet internal manifold 10B that are formed as opening holes are formed.

  Further, the first separator 5 is formed with a refrigerant inlet internal manifold 11A and a refrigerant outlet internal manifold 11B which are formed as opening holes communicating with a refrigerant flow path to be described later. The refrigerant inlet internal manifold 11A is provided between the fuel gas inlet internal manifold 9A and the oxidant gas inlet internal manifold 10A, and the refrigerant outlet internal manifold 11B includes the fuel gas outlet internal manifold 9B and the oxidant gas outlet internal manifold 10B. Between.

  As shown in FIGS. 3 and 4B, the second separator 6 is disposed on the other surface 4b, that is, the side surface on which the oxidant electrode is provided, with the membrane electrode assembly 4 interposed therebetween. Similar to the first separator 5, the second separator 6 has a substantially rectangular shape in plan view when joined to the membrane electrode assembly 4, and its thickness gradually decreases from the outside to the inside of the laminate. The so-called fan shape.

  In the second separator 6, an oxidant gas flow path 12 for supplying an oxidant gas to the oxidant electrode is formed on the surface of the membrane electrode assembly 4 that faces the oxidant electrode. When the direction in which the oxidant gas flows is indicated by an arrow in FIG. 3, the oxidant gas flow path 12 has a groove depth that gradually decreases from the inlet side toward the outlet side. The flow rate of the oxidant gas gradually decreases toward the flow and outlet side.

  The second separator 6 includes an oxidant gas inlet internal manifold 10A and an oxidant gas outlet internal manifold 10B communicating with the oxidant gas flow path 12, and a fuel gas penetrating in the thickness direction (stacking direction). An inlet internal manifold 9A, a fuel gas outlet internal manifold 9B, a refrigerant inlet internal manifold 11A, and a refrigerant outlet internal manifold 11B are formed.

  As shown in FIG. 3 and FIG. 4C, the cooling plate 7 is provided in contact with the second separator 6, and the joint surface with the second separator 6 has a substantially rectangular shape in plan view. Unlike the first separator 5 and the second separator 6, the cooling plate 7 has a constant thickness. As shown by arrows in FIG. 3, the cooling plate 7 is formed with a refrigerant flow path 13 through which a refrigerant (for example, cooling water) flows toward the center of the cylindrical laminated body.

  The cooling plate 7 includes a refrigerant inlet internal manifold 11A and a refrigerant outlet internal manifold 11B communicating with the refrigerant flow path 13, a fuel gas inlet internal manifold 9A and a fuel gas outlet internal manifold 9B penetrating in the thickness direction, and oxidation. An agent gas inlet internal manifold 10A and an oxidant gas outlet internal minor hold 10B are formed.

  As shown in FIG. 1, the fuel cell single cell 2 configured as described above forms a cylindrical stacked body by stacking a plurality of fuel cell single cells 2 in close contact with each other. The laminated body having a cylindrical shape is fixed by fastening the outer peripheral surface of the laminated body in the center direction with a fastening member 3 such as a band or a belt excellent in heat resistance so as to withstand heat during power generation.

  As shown in FIGS. 5 and 6, gas supply manifolds 14 for supplying fuel gas, oxidant gas and refrigerant to each fuel cell single cell 2, and each fuel are provided at both ends of the laminate. A gas discharge manifold 15 is provided for discharging fuel gas, oxidant gas, and refrigerant from the battery unit cell 2 to the outside.

  Similarly to the first and second separators 5 and 6, the gas supply manifold 14 has a fan shape. The gas supply manifold 14 is provided with a fuel gas supply port 16 for supplying fuel gas to the fuel gas passage 8 formed in the first separator 5 of each fuel cell single cell 2. On one surface 14a of the gas supply manifold 14, a fuel gas supply opening window 17 is provided for supplying the fuel gas supplied from the fuel gas supply port 16 to the fuel gas inlet internal manifold 9A. Is formed.

  Further, the gas supply manifold 14 is provided with an oxidant gas supply port 18 for supplying an oxidant gas to the oxidant gas flow path 12 formed in the second separator 6 of each fuel cell single cell 2. ing. Similarly, on one surface 14a of the gas supply manifold 14, an oxidant gas for supplying the oxidant gas supplied from the oxidant gas supply port 18 to the oxidant gas inlet internal manifold 10A is provided. A supply opening window 19 is formed.

  Further, the gas supply manifold 14 is provided with a refrigerant supply port 20 for supplying the refrigerant to the refrigerant flow path 13 formed in the cooling plate 7. The one surface 14a of the gas supply manifold 14 is formed with a refrigerant supply opening window 21 for supplying the refrigerant supplied from the refrigerant supply port 20 to the refrigerant inlet internal manifold 11A. Yes.

  On the other hand, the gas discharge manifold 15 has a fan shape like the gas supply manifold 14, a fuel gas discharge port 22 for discharging the fuel gas from the single fuel cell 2 to the outside, and an oxidant gas to the outside. It has an oxidant gas outlet 23 for discharging and a refrigerant outlet 24 for discharging the refrigerant to the outside. Further, on one surface 15a of the gas discharge manifold 15, a fuel gas discharge opening window 25 connected to the fuel gas outlet internal manifold 9B and an oxidant gas discharge connected to the oxidant gas outlet internal minor hold 10B are provided. An opening window 26 and a refrigerant discharge opening window 27 connected to the refrigerant outlet internal manifold 11B are formed.

  Further, between the gas supply manifold 14 and the fuel cell single cell 2, a current collecting plate 28 for taking out the current obtained by generating power in the single fuel cell 2, and the current collecting plate 28 An insulating plate 29 that insulates between the gas supply manifolds 14 is provided. Similarly, a current collecting plate 28 and an insulating plate 29 are provided between the gas discharge manifold 15 and the single fuel cell 2.

  Moreover, as shown in FIG. 6, the opposing distance between the gas supply manifold 14 and the gas discharge manifold 15 is varied at both ends of the stacked body to adjust the pressure applied in the stacking direction of each fuel cell single cell 2. Laminating pressure adjusting means is provided. The lamination pressure adjusting means includes a full screw bolt 30 and a nut 31 screwed into the full screw bolt 30.

  The entire screw bolt 30 has one end screwed to the gas supply manifold 14 and the other end screwed to the gas discharge manifold 15, so that the gas supply manifold 14 and the gas discharge manifold 15 are screwed together. 15 are connected. The nut 31 is attached to the entire screw bolt 30 and is used to maintain a facing distance between the gas supply manifold 14 and the gas discharge manifold 15. That is, the surface of the membrane electrode assembly 4 and the first and second separators 5 and 6 is rotated by turning the entire screw bolt 30 so that the gas supply manifold 14 and the gas discharge manifold 15 move away from each other. When the pressure is made uniform in the plane, the nut 31 is fixed to maintain the state.

"Action / Effect"
According to the fuel cell configured as described above, the cross-sectional shape of the fuel cell single cell 2 is not a parallelogram, one surface is a horizontal plane, and each fuel cell single cell 2 is laminated in a cylindrical shape. Since the peripheral surface is fastened with the fastening member 3, the positional deviation of the single fuel cell 2 can be suppressed.

  Further, in the fuel cell of the present embodiment, the groove depths of the fuel gas channel 8 and the oxidant gas channel 12 are deep on the upstream side of the gas flow of the first separator 5 and the second separator 6, and the gas flow downstream. Since the groove depth is shallow on the side, the flow rates of the fuel gas and the oxidant gas increase toward the downstream. As a result, flooding can be suppressed by blowing off condensed water on the gas downstream side where flooding is likely to occur.

  In the fuel cell according to the present embodiment, the flow of the fuel gas and the oxidant gas is directed to the center of the cylindrical laminate and is in the same direction. There is no part which becomes large, and the breakage of the membrane electrode assembly 4 can be suppressed. Furthermore, since the flow of the refrigerant is in the same direction as the fuel gas and oxidant gas, the temperature near the gas inlet where dry-up is likely to occur decreases, so that the saturated vapor pressure decreases, and condensing is likely to occur. Can be suppressed. Further, the temperature in the vicinity of the gas outlet where flooding is likely to occur increases, so that the saturated vapor pressure rises and it becomes difficult to condense, and flooding can be suppressed.

  Further, according to the fuel cell of the present embodiment, the stack for adjusting the pressure applied in the stacking direction of each fuel cell single cell 2 by changing the facing distance between the gas supply manifold 14 and the gas discharge manifold 15. Since the pressure adjusting means is provided, the separators 5 and 6 are adjusted without adjusting the number of cells even when the stacked body does not become a complete cylinder due to the sum of the dimensional tolerances generated when the fuel cell single cells 2 are stacked in a cylindrical shape. In addition, the surface pressure applied to the membrane electrode assembly 4 can be made uniform in the surface.

It is a perspective view of the fuel cell in this Embodiment. It is an expansion perspective view of a fuel cell single cell. It is the sectional view on the AA line of FIG. 4A is a plan view showing the first separator in which the fuel gas flow path is formed, FIG. 4B is a plan view of the second separator in which the oxidant gas flow path is formed, and FIG. ) Is a plan view of a cooling plate in which a refrigerant channel is formed. FIG. 5A is an enlarged perspective view showing a gas refrigerant discharge manifold, and FIG. 5B is an enlarged perspective view showing a gas refrigerant supply manifold. It is a figure which shows the lamination pressure adjustment means provided between the manifold for gas refrigerant discharge, and the manifold for gas refrigerant supply.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell 2 ... Fuel cell single cell 3 ... Fastening member 4 ... Membrane electrode assembly 5 ... 1st separator 6 ... 2nd separator 7 ... Cooling plate 8 ... Fuel gas flow path 12 ... Oxidant gas flow path 13 ... Refrigerant flow path 14 ... Gas supply manifold 15 ... Gas discharge manifold 28 ... Current collector plate 29 ... Insulating plate 30 ... Full screw bolt (lamination pressure adjusting means)
31 ... Nut (lamination pressure adjusting means)

Claims (4)

A membrane electrode assembly that generates electric power by the reaction of fuel gas and oxidant gas;
The membrane electrode assembly is disposed on one side of the membrane electrode assembly, the thickness thereof is gradually reduced from the outside to the inside, and the groove depth of the fuel gas passage through which the fuel gas flows is gradually reduced from the inlet side to the outlet side. A first separator;
It is arranged on the other surface across the membrane electrode assembly, the thickness of the oxidant gas passage gradually decreases from the outside to the inside, and the groove depth of the oxidant gas flow path through which the oxidant gas flows gradually from the inlet side toward the outlet side. A shallow second separator;
A plurality of fuel cell single cells formed by sandwiching the membrane electrode assembly between the first separator and the second separator to form a cylindrical shape, and a fastening member for fastening and fixing the cylindrical laminate. A fuel cell characterized by the above. The fuel cell according to claim 1, wherein
The fuel gas, wherein the fuel gas and the oxidant gas flow toward the center of the cylindrical laminate. The fuel cell according to claim 1 or 2,
A cooling plate having a refrigerant flow path through which the refrigerant flows toward the center of the cylindrical laminate, and the cooling plate is disposed in contact with either the first or second separator; The fuel cell characterized by the above-mentioned. The fuel cell according to claim 1, wherein
A gas supply manifold that supplies at least the fuel gas and the oxidant gas to the first and second separators; and a gas discharge manifold that discharges at least the fuel gas and the oxidant gas from the stacked body to the outside. A stacking pressure adjusting means for adjusting the pressure applied in the stacking direction of each fuel cell single cell by changing the facing distance between the gas supply manifold and the gas discharge manifold is provided between the gas supply manifold and the gas discharge manifold. A fuel cell characterized by the above.

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