JP2006127948A - Fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell stack in which a sealing effect can be obtained by precisely crushing a sealing member even if warpage is generated in a separator, and in which occurrence of gas leakage can be prevented. <P>SOLUTION: Because a recessed part 26 is formed in the separator 15 composed of a metal plate in which a fuel gas flow passage and an oxidizer gas flow passage are press-molded by alternately forming a recessed stripe part and a convex stripe part as a retaining means to retain an apex part shape of the sealing member 25 installed between the separators 15, 15 of a fuel cell single cell, even if there is the warpage in the separator 15, the sealing member 25 can be crushed precisely. Because the sealing member 25 can be crushed precisely, the separators 15, 15 can be adhered airtightly without a gap therebetween, and the gas leakage between these can be prevented securely. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell stack, and more particularly to a gas leakage prevention technique using a seal.

  For example, in a fuel cell in which hydrogen and oxygen are supplied to both surfaces of a polymer electrolyte membrane to generate electromotive force, a metal thin plate is pressed to form a gas flow path in order to further increase the electromotive force per unit volume. A so-called thin metal separator that forms a thin film has been developed.

  However, when an uneven gas flow path is formed in the central portion of the metal plate by pressing, warpage occurs in the entire separator due to a difference in local elongation (residual stress) between the front and back of the separator.

  When the separator is warped, the contact resistance is increased due to poor contact with the polymer electrolyte membrane, and the power generation performance is lowered. Moreover, the gas sealing performance near the manifold of each separator is reduced.

  Therefore, after press forming a gas flow path having a concavo-convex shape on a metal plate, minute rhombus indentations are formed on the flat portion of the concavo-convex portion, or protrusions for forming indentations are formed on the upper and lower surfaces of the mold, respectively. A technique has been disclosed that prevents the occurrence of warpage by forming an indentation at the same time as forming a gas flow path (see, for example, Patent Document 1).

Moreover, after press-molding a vertically elongated gas channel in the center part of the metal plate, by applying a tensile force in the same direction as the rolling direction by pressing only to the peripheral part orthogonal to the longitudinal direction of the gas channel, There is disclosed a technique for correcting distortion caused by restricting the extension of the center portion rolled by the formation of the gas flow path at the non-rolled peripheral portion orthogonal to the longitudinal direction of the gas flow path (for example, Patent Document 2).
JP 2000-138065 (pages 5 to 8, FIGS. 2 and 3) JP 2003-249241 A (2nd and 3rd pages, FIGS. 4 to 6)

  By the way, a fuel cell stack is configured by stacking a plurality of fuel cell single cells each having a polymer electrolyte membrane sandwiched between the separators from both sides via a seal member.

  However, when a resin seal formed by injection molding is used as the seal member, the shape of the seal member is a precise shape, and a sealing effect cannot be obtained unless it is accurately crushed. In particular, if the separator is deformed, there is a possibility that the seal member cannot be crushed accurately.

  In order to eliminate the warpage of the separator, the technique described in Patent Document 1 prevents the warpage of the separator by forming a minute indentation in the mold. In the technique described in Patent Document 2, the tensile force is formed after the gas flow path is formed. Although the step of imparting is added to prevent the warpage of the separator, the use of these techniques inevitably increases the cost of the mold and increases the number of steps.

  Accordingly, an object of the present invention is to provide a fuel cell stack that can obtain a sealing effect by accurately crushing a sealing member even when the separator is warped and can prevent the occurrence of gas leakage. To do.

  The fuel cell stack according to the present invention includes a plurality of fuel cell single cells in which separators made of a metal plate obtained by pressing a flow path having a concavo-convex shape in a region contributing to power generation are arranged on both sides of a polymer electrolyte membrane. This is a fuel cell stack in which individual pieces are stacked.

  And in the present invention, a seal member is provided between the separators of at least adjacent fuel cell single cells among the laminate in which a plurality of the fuel cell single cells are stacked, and holding means for holding the top shape of the seal member, The separator is provided.

  According to the present invention, since the holding means for holding the top shape of the sealing member is provided in the separator, the sealing member is crushed because the top shape of the sealing member can be held by the holding means even if the separator itself is warped. The deformation at the time can be suppressed, and the seal member can be crushed as specified. Therefore, according to the present invention, it is possible to prevent gas leakage by sealing between the separators without any gap.

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

  First, the overall configuration of the fuel cell stack will be briefly described. 1 is a perspective view showing the overall configuration of the fuel cell stack, FIG. 2 is an enlarged cross-sectional view of a main part showing a part of the laminated structure of the fuel cell stack, FIG. 3 is a perspective view of a separator, and FIG. 4 is shown in FIG. It is a BB line sectional view of a separator. 2 is an enlarged cross-sectional view of the main part at the position of the line AA in FIG.

  As shown in FIG. 1, the fuel cell stack 1 is a laminated body 3 in which a predetermined number of fuel cell single cells 2 as unit cells that generate an electromotive force by the reaction of fuel gas and oxidant gas are laminated. Current collector plate 4, insulating plate 5, and end plate 6 are arranged at both ends of 3, and a tie rod 7 is passed through a through-hole (not shown) penetrating through the laminated body 3. And a nut (not shown) are screwed together.

  In this fuel cell stack 1, a fuel gas introduction port 8 for allowing fuel gas, oxidant gas, and cooling water to flow through channel grooves formed in the separators (not shown) of each fuel cell single cell 2. A fuel gas discharge port 9, an oxidant gas introduction port 10, an oxidant gas discharge port 11, a cooling water introduction port 12 and a cooling water discharge port 13 are formed in one end plate 6.

  The fuel gas is introduced from the fuel gas introduction port 8, flows through a fuel gas supply channel groove formed in the separator, and is discharged from the fuel gas discharge port 9. The oxidant gas is introduced from the oxidant gas introduction port 10, flows through the oxidant gas supply channel groove formed in the separator, and is discharged from the oxidant gas discharge port 11. The cooling water is introduced from the cooling water introduction port 12, flows through the cooling water supply channel groove formed in the separator, and is discharged from the cooling water discharge port 13.

  As shown in FIG. 2, the fuel cell single cell 2 includes a membrane electrode assembly (MEA) 14 and separators 15 disposed on both surfaces of the membrane electrode assembly 14.

  The membrane electrode assembly 14 includes, for example, a solid polymer electrolyte membrane that is a polymer electrolyte membrane that passes hydrogen ions, an anode electrode that includes an anode catalyst and a gas diffusion layer, and a cathode electrode that includes a cathode catalyst and a gas diffusion layer (both are (Illustration is omitted). The membrane electrode assembly 14 has a laminated structure in which a solid polymer electrolyte membrane is sandwiched from both sides by an anode electrode and a cathode electrode.

  The separator 15 is formed by forming a thin metal plate into a predetermined shape using a mold. As shown in FIG. 3 and FIG. 4, the separator 15 has the recess 16 and the protrusion 17 alternately formed in the active region that contributes to power generation (region of the central portion in contact with the membrane electrode assembly 14). An uneven shape (so-called corrugated shape) is formed.

  The concave portion 16 disposed in contact with the anode side of the membrane electrode assembly 14 forms a fuel gas flow path for allowing the fuel gas (hydrogen H) to flow between the concave portion 16 and the membrane electrode assembly 14. On the other hand, the recessed strip portion 16 disposed in contact with the cathode side of the membrane electrode assembly 14 forms an oxidant gas flow path through which the oxidant gas (oxygen O) flows. And the space part enclosed by the protruding strip parts 17 and 17 with which separators 15 and 15 were joined forms the coolant flow path which distribute | circulates cooling water (LLC).

  The separator 15 communicates with the fuel gas inlet 8, fuel gas outlet 9, oxidant gas inlet 10, oxidant gas outlet 11, cooling water inlet 12, and cooling water outlet 13. The manifolds 18, 19, 20, 21, 22, and 23 are formed. For example, a fuel gas introduction manifold 18, a cooling water introduction manifold 19, and an oxidant introduction manifold 20 are sequentially formed from the left side to the right side of the separator 15 shown in FIG. 3. Further, an oxidant discharge manifold 21, a coolant discharge manifold 22, and a fuel gas discharge manifold 23 are sequentially arranged from left to right before the separator 15. Furthermore, a stacking hole 24 through which the tie rod 7 passes is formed in the separator 15.

  Further, the separator 15 holds the top shape of the seal member 25 disposed between at least the separators 15 and 15 of the adjacent fuel cell single cells 2 in the stacked body in which a plurality of the single fuel cell cells 2 are stacked. A recess 26 is formed as a means. The concave portion 26 is arranged so as to surround the flow passage formed of the concave strip portion 16 and the convex strip portion 17 and the manifolds 18 to 23 formed in the central portion of the separator 15, and is rectangularly disposed in the vicinity of the outer periphery of the separator 15. It is formed as a groove having a shape.

  As shown in FIG. 5, the shape of the concave portion 26 is formed as a dent for fitting the top portion of the seal member 25 formed by injection molding of resin. For example, the recess 26 is formed as an indentation having a mountain shape with a width W of 0.4 mm and a depth H of about 0.2 mm. The seal member 25 is formed in a cross-sectional shape having a flat portion 25A having a flat side provided on one separator 15 and a mountain-shaped portion 25B protruding from the center of the flat portion 25A. The seal member 25 is formed in a precise size and shape by injection molding a resin made of a sealant. The top portion 25 </ b> C of the seal member 25 is shaped to fit into the recess 26.

  The fuel cell single cell 2 composed of the membrane electrode assembly 14 and the separator 15 thus configured is laminated so that the membrane electrode assembly 14 is sandwiched between the pair of separators 15 and 15 from both sides thereof. The upper and lower separators 15 and 15 are joined and integrated through a seal member 25 provided in the vicinity of the outer peripheral edge of the joined body 14. In addition, an outer frame member (frame) 27 for appropriately compressing the gas diffusion layer is provided between the membrane electrode assembly 14 and the separator 15 along their outer peripheral edge portions.

  As shown in FIG. 2, the fuel cell single cell 2 having such a configuration is configured such that the separators 15 and 15 are stacked in close contact with each other, and a seal member 25 is interposed between the stacked separators 15 and 15. The top portion 25C of the seal member 25 is fitted and brought into close contact with the concave portion 26 formed in the separator 15. And the fuel cell stack 1 as a laminated body is comprised by the several lamination | stacking of this fuel cell single cell 2. As shown in FIG. The outer frame member 27 is also interposed between the fuel cell single cells 2.

  According to the present embodiment, as shown in FIG. 6, even when the separator 15 that has been warped by pressing is pressed against the seal member 25, the recess 26 formed in the separator 15 is formed on the top portion 25 </ b> C of the seal member 25. Because of the fitting, the seal member 25 can be crushed accurately (specified value). Therefore, the separators 15 and 15 can be closely bonded to each other without any gap, and gas leakage can be prevented.

  On the other hand, as shown in FIG. 7, when the concave portion 26 is not formed in the separator 15, when the separator 15 having a warp is pressed against the seal member 25, the seal member 25 is moved outward by the warped portion of the separator 15. And the crushing of the seal member 25 is not accurate (specified value). For this reason, even if a specified amount of crushing is applied to the seal member 25, the seal member 25 is deformed, so that it is impossible to closely contact the separators 15 and 15, and gas leakage between them cannot be prevented. .

  In addition, according to the present embodiment, since the concave portion 26 is formed along the vicinity of the outer periphery of the separator 15, the concave portion 26 can improve the rigidity of the separator 15 itself and suppress deformation of the separator 15. . When the concave portion 26 is not formed along the outer peripheral portion of the separator 15, as shown in FIG. 8, when the concave portion 16 and the convex portion 17 are pressed, local elongation (residual stress) is obtained. ) Causes wrinkles on the side surface of the separator 15 and deformation. However, if the recessed part 26 as an annular groove is formed in the outer peripheral edge part of the separator 15 like this Embodiment, the deformation | transformation of the said separator 15 can be suppressed. If a plurality of fuel cell single cells 2 manufactured using the separator 15 without deformation are stacked and stacked, all components can be accurately stacked.

  Further, according to the present embodiment, since the concave portion 26 in which a part of the separator 15 is recessed and the top portion 25C of the seal member 25 is fitted is used as the holding means, the concave portion 16 and the convex portion 17 are provided. The concave portion 26 can be processed together at the time of pressing, so that it is not necessary to use a dedicated mold for forming the concave portion 26 and the manufacturing process is not increased.

  The specific embodiment to which the present invention is applied has been described above, but the present embodiment is not limited to the above-described embodiment, and various modifications can be made.

  In the above-described embodiment, the present invention is applied to the portion that seals between the separators 15 and 15 of the stacked fuel cell single cells 2, but the membrane electrode assembly 14 and the separator 15 that constitute the fuel cell single cell 2. The present invention may be applied between them. If it does so, the sealing performance between the membrane electrode assembly 14 and the separator 15 can be improved further.

  Moreover, the shape of the separator 15 used in the description of the above-described embodiment is an example, and is not limited to the present embodiment.

It is a perspective view which shows the whole structure of a fuel cell stack. It is a principal part expanded sectional view which shows a part of laminated structure of a fuel cell stack. It is a perspective view of a separator. FIG. 4 is a cross-sectional view of the separator shown in FIG. It is a principal part expanded sectional view which shows the state before making the separator which formed the recessed part which fits the top part of a seal member closely_contact | adhere to a seal member. It is a principal part expanded sectional view which shows the state which crushed the sealing member with the separator, after mounting the separator which formed the recessed part which fits the top part of a sealing member on a sealing member. It is a principal part expanded sectional view which shows sequentially the process of crushing a sealing member with a separator, after mounting the separator which did not have a recessed part on the sealing member. It is a perspective view of the separator which wrinkles generate | occur | produced because the recessed part was not formed in the outer periphery part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell stack 2 ... Fuel cell single cell 14 ... Membrane electrode assembly 15 ... Separator 16 ... Concave part 17 ... Convex part 25 ... Seal member 25C ... Top part 26 ... Concave part (holding means)

Claims (3)

This is a fuel cell stack in which a plurality of fuel cell single cells are formed by laminating separators made of metal plates, which are formed by pressing a flow path having an uneven shape in a region contributing to power generation, on both sides of the polymer electrolyte membrane. And
A sealing member is provided between the separators of at least adjacent fuel cell single cells in the laminate in which a plurality of the fuel cell single cells are stacked, and holding means for holding the top shape of the sealing member is provided in the separator. A fuel cell stack characterized by The fuel cell stack according to claim 1, wherein
The fuel cell stack according to claim 1, wherein the holding means is a concave portion in which a part of the separator is recessed and the top of the seal member is fitted. The fuel cell stack according to claim 2, wherein
The fuel cell stack, wherein the recess is formed along the vicinity of the outer periphery of the separator.

Images