JP2009252470A - Separator, and solid polymer electrolyte fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a flow path pattern to be changeable without reducing the cross section area of a low-profile separator. <P>SOLUTION: A flow path communication part is formed so that the cross section area of the flow path of the flow path communication part provided near a manifold is almost the same as the cross section area of a flow path facing an electrode, the groove width of the flow path communication part is greater than a groove width facing the electrode, and the groove depth of the flow path communication part is smaller than a groove depth facing the electrode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a separator, and more particularly to a separator effective for a compact polymer electrolyte fuel cell.

  A polymer electrolyte fuel cell (hereinafter referred to as PEFC) has characteristics such as a high output density, a high power generation efficiency, and a low operating temperature (about 70 to 80 ° C.), so that the startup time is short. For this reason, a wide range of uses such as power sources for electric vehicles, distributed power sources for business use and home use are expected.

  Among these applications, a distributed power source (for example, a cogeneration power generation system) equipped with a PEFC takes out electricity from the PEFC, and at the same time, recovers heat generated from the battery during power generation as hot water, thereby effectively using energy. It is a system to be used.

  Such a distributed power source is required to have a long life of 50,000 to 100,000 hours, and the improvement of the membrane-electrode assembly (hereinafter abbreviated as MEA), cell configuration, power generation conditions, etc. is progressing. It has been.

  In addition, when this fuel cell is used as a power source for moving objects, downsizing of the battery is emphasized.

  On the other hand, a direct methanol fuel cell (hereinafter referred to as DMFC) that uses methanol as a fuel has a cell voltage lower than that of PEFC, but it has attracted attention as a mobile application and a portable power source in terms of fuel portability and ease of handling. Has been.

  In the case of a fuel cell using such a liquid fuel, since the battery is frequently carried, the size of the battery is very important.

  For the needs as described above, the thickness of the separator constituting the fuel cell is a main factor determining the cell size. That is, the number of separators is determined according to the number of cells, and the product of the number of separators and the thickness of the separator mainly determines the battery length. The total thickness of the separator includes the minimum wall thickness defined by the distance between the fuel and oxidant flow path bottoms formed on the front and back sides, in addition to the fuel and oxidant flow path depths. Wall thickness is also an important parameter.

  Therefore, development of thin separators using various materials such as graphite and metal in order to reduce the battery size is underway, and separators with a minimum thickness of 0.2 mm to less than 0.1 mm are being realized.

  However, if the minimum wall thickness of the separator is made as small as possible, the flow paths through which the fuel and oxidant flow become integrated, and there is a restriction that the flow path pattern formed on each surface cannot be freely changed, causing the following problems Bring points.

  First, the fact that the flow path pattern is integral with each other means that the fuel and oxidant flow paths face each other through the MEA in the same pattern. If the flow direction of fuel and oxidant in the facing channel is the same, reactants such as fuel will have a high concentration in the supply manifold and the reaction rate will be large, and the concentration will gradually decrease along the channel, and the discharge manifold This means that the reaction rate decreases with the lowest concentration.

  Under such circumstances, considering the current flowing through the MEA electrodes divided into small sizes, the current is large at the high concentration of the reactant, and the current decreases as it goes downstream along the flow path. At low concentrations of reactants, the current is minimal. Such non-uniform current distribution results in an increase in reaction resistance in the entire cell, and the output of the battery decreases. This is the first problem.

  As a second problem, the fact that the front and back flow paths are not separated has a problem in the cell structure that the fuel and the oxidant cannot be taken out to separate manifolds.

  For example, when considering a bipolar separator that oxidizes fuel on one side of the separator and reduces oxidant on the other side, the flow direction of one channel follows the channel on the back, so both Paths are connected to the same manifold. This means mixing of the reaction gas, and power generation becomes impossible.

  Therefore, a structure that allows the flow path pattern on the front and back sides of the separator to be freely changed is an important technique along with a reduction in the minimum thickness of the separator.

  According to the conventional technology (Patent Documents 1 to 3), in a separator having a corrugated channel shape with a small wall thickness, a technology is disclosed in which the reaction gas is separated on the front and back sides and an optimum channel pattern is formed in the separator surface. ing.

  According to the invention described in these documents, a structure in which a nozzle plate and a flow path are joined (Patent Document 1), a structure in which a gas introduction part is formed by a frame (Patent Document 2), or an island-shaped convex part With the structure combining the frames (Patent Document 3), the flow path pattern of the thin separator is changed, or the reaction gas is communicated to separate manifolds.

  Further, Patent Documents 4, 5, and 6 disclose that the flow path pattern on the front and back of the separator is changed and the cross-sectional area of the flow path is changed in the separator surface.

JP 2004-171887 A JP 2005-129343 A JP 2007-157667 A JP 2001-043868 A JP 2004-192985 A JP 2005-268110 A

  In such a conventional technique, even if the separator is thinned, additional parts are required, and adverse effects such as an increase in parts cost and a complicated manufacturing process cannot be avoided (Patent Documents 1 to 3).

  In addition, the conventional technology simply indicates that the flow path cross-sectional area can be changed, and the flow pattern on the front and back sides can be changed independently, suggesting that the reaction gas is separated into separate manifolds. It is not (Patent Documents 4 to 6).

  Accordingly, an object of the present invention is to realize a separator structure in which a flow path pattern on the front and back sides can be freely changed without increasing the total thickness of the separator in a separator having a reduced minimum wall thickness. This is to solve the conventional problems.

  An object of the present invention is to provide a structure in which the flow path patterns on the front and back of a thin separator can be freely changed and each flow path on the front and back is connected to a separate manifold. By using the separator of the present invention, not only the power generating cell but also the cell intended for cooling the battery is miniaturized and the whole fuel cell is aimed to be compact.

  Furthermore, it is providing the fuel cells, such as PEFC and DMFC, to which such a separator is applied, and a power generation system equipped with them.

  The separator of the present invention is a separator having a flow channel in a flow channel connecting portion provided in the vicinity of a manifold and a flow channel that communicates the flow channel and faces the electrode, and has a flow channel width of the flow channel connecting portion. However, the present invention is characterized in that a flow passage connecting portion that is larger than the flow passage width facing the electrode and in which the flow passage depth of the flow passage connecting portion is smaller than the flow passage depth facing the electrode is provided. .

  Moreover, it is preferable that the cross-sectional area (cross-sectional area perpendicular to the flow direction) of the flow path and the flow path facing the electrode in the flow path connecting portion is substantially equal.

  Moreover, you may form the flow-path separation part which consists of a convex-shaped rib in the said flow-path connection part.

  Moreover, you may provide the confluence | merging part which connects the some flow path formed in a flow path to the said flow-path connection part in at least one surface of a surface or a back surface.

  Moreover, it is preferable to have the flow path bending part which changes the direction of a gas flow path in the middle of the flow path which faces an electrode.

  Further, in the flow channel connecting portion, an island-shaped convex portion may be provided between the flow channels.

  These separators are suitable for fuel cells in general using fuel and an oxidant (regardless of whether or not a refrigerant is used), particularly PEFC and DMFC.

  In addition, one surface of the separator is used as a surface having a flow path facing the electrode, and the other surface is provided with two cooling water manifolds provided at positions different from the manifolds for fuel and oxidant via the flow path connecting portion. A solid polymer fuel cell having a cooling cell formed by opposing two cooling water flow channel surfaces using the two separators having the cooling water flow channel surfaces, which are used as cooling water flow channel surfaces communicated with each other. You can also.

  In addition, a solid polymer fuel cell can be formed by having a cooling cell in which one separator having such a structure and a flat plate face each other.

  Thus, in the present invention, a method for allowing the flow path pattern on the front and back of the separator to be freely changed is presented. That is, the present invention changes the dimensions of the flow path. The “flow path pattern” used in the present specification includes the meaning of the traveling direction in which fuel and oxidant flow along the flow path.

  According to the present invention, it is possible to freely change the flow path pattern on the front and back of the thin separator, and to provide a structure for connecting the flow paths on the front and back to separate manifolds.

  A single cell structure of this embodiment is shown in FIG.

  In FIG. 1, the thin separator 101 of this embodiment has a fuel flow path 110. The fuel flow path 110 is on the lower surface of the separator 101 and is in contact with the anode 103 composed of a catalyst layer and a gas diffusion layer. Here, the catalyst layer is included in the anode 103 and adhered to the surface of the electrolyte membrane 102. The catalyst layer supports platinum fine particles on graphite powder, or supports fine particles made of platinum alloyed with a promoter such as lutite that has the function of oxidizing and removing carbon monoxide generated during the process of fuel oxidation. And further bonded with an electrolyte binder. Other catalysts may be used. A gas diffusion layer is provided on the catalyst layer. In the following, “channel” and “groove” are used synonymously.

The electrolyte membrane 102 serves as a medium for transporting hydrogen ions (H ⁺ ) generated at the anode 103 to the cathode 104.

  When hydrogen ions are generated from fuel such as hydrogen or methanol, electrons are also extracted. The electrons are transferred to the separator 101, transmitted to the separator 107 after passing through an external circuit, and the same number of electrons finally generated at the anode 103 are sent to the cathode 104.

  An oxidant flow path 111 is formed in the separator 107, and the flow path 111 is in contact with the cathode 104. The oxidant (oxygen) is supplied from the flow path 111 to the cathode 104 and reacts with hydrogen ions that have permeated the electrolyte membrane 102 to generate generated water.

  The cathode 104 includes a catalyst layer and a gas diffusion layer. The catalyst layer is included in the cathode 104 and is fixed to the surface of the electrolyte membrane 102. The catalyst layer is generally one in which platinum fine particles are supported on graphite powder, but other catalysts may be used. A gas diffusion layer is provided on the catalyst layer.

  In this embodiment, a structure in which the anode 103 and the cathode 104 are bonded to both surfaces of the electrolyte membrane 102 is referred to as a membrane-electrode assembly (hereinafter referred to as MEA). A material having a gas diffusion function, for example, a gas diffusion layer is included in the anode 103 and the cathode 104.

  Thus, in the power generation reaction by PEFC, one oxygen molecule reacts with every two hydrogen molecules to produce two water molecules. In the case of DMFC, 1.5 molecules of oxygen react with one molecule of methanol to generate one molecule of carbon dioxide and two molecules of water.

  In this embodiment, the minimum unit of power generation shown in FIG. 1 is defined as a single cell. When a plurality of single cells are connected in series, the voltage increases and the necessary output can be obtained. Such a single cell stacked in series is referred to as a cell stack.

  The fuel and the oxidizer are separated by the MEA and the separator so that no direct chemical reaction occurs. Further, these reactants are prevented from leaking to the outside by the gaskets 105, 112, and 113.

  In order to supply fuel to each single cell, a fuel supply manifold 108 is provided so as to penetrate a part of the separators 101 and 107. After being supplied from the manifold 108 to each single cell and oxidized at the anode 103, it is discharged to the outside of the battery via the fuel discharge manifold 109. The gaskets 105, 112, and 113 are inserted between the separators 101 and 107 and the electrolyte membrane 102 to prevent leakage of fuel, oxidant, or cooling water.

  A passage communicating from the fuel supply manifold 108 to the flow path 110 is formed in the plane of the separator 101. However, when it is shown in a plan view, it appears to overlap with a part of the gasket 112 on the left side of FIG.

  In addition, the flow path from the flow path 110 to the fuel discharge manifold 109 is also formed in the plane of the separator 101, but it looks like it overlaps with a part of the gasket 113 when drawn in a plan view. Omitted.

  The cathode supply manifold and the discharge manifold, and the cooling water supply manifold and the discharge manifold are omitted because they overlap with the anode manifolds 108 and 109 in the single cell cross section of FIG. The arrangement of the cathode manifold and the cooling water manifold will be described with reference to FIG.

  Next, the flow path structure of the thin separators 101 and 107 of this embodiment will be described in detail.

  FIG. 2 is a top view of the separator 201 having an anode channel surface. This drawing corresponds to the separator 101 in FIG. 1, and FIG. 1 shows a cross section viewed from the negative direction of the Y axis in FIG. 2 in the positive direction. Also, the fuel manifolds 208 and 209 in FIG. 2 correspond to the manifolds 108 and 109 in FIG. 1, respectively.

  Comparing the positional relationship of the surrounding ribs and flow paths with reference to the positions of these manifolds, it can be seen that the flow paths are asymmetric both left and right and up and down. For example, when paying attention to the fuel supply manifold 208, the flow path 203 of the flow path connecting portion 202 or the flow path 219 of the power generation surface 218 located near the outer edge of the separator 201 coincides with the outer edge of this manifold. On the other hand, the flow passage connecting portion 216 in the vicinity of the fuel discharge manifold 209 is displaced inward by approximately one groove width with reference to the outer edge position of the flow passage. Such an asymmetric structure ensures the MEA performance while maintaining the same cross-sectional area of the front and back channels, and reducing the flow rate variation of the reactants between cells (hereinafter referred to as flow distribution) as small as possible. It is to do. The reason will be explained below.

  When overlapping with other separators adjacent via the MEA, it is necessary to align the vertical and horizontal positions of the separator so that the ribs of the flow path 219 face each other. That is, if the separator ribs 206 do not face each other so as to sandwich the MEA in the flow path formed between the two separators, it is impossible to apply an appropriate pressure to the MEA, resulting in power generation failure. It is.

  For example, when the rib 206 of one separator faces the flow path 219 on the power generation surface of the other separator, the portion where the rib 206 and the flow path 219 are engaged increases, and the pressure applied to the MEA decreases. As a result, the contact resistance between the MEA and the separator increases, and the battery output decreases.

  However, it is not necessary that all the rib positions of the facing separators coincide with each other, and some of the ribs may not coincide. This is because even if some ribs do not face each other via the MEA, the cell voltage may not be substantially affected. Especially when the gas is supplied uniformly to supply the reactants at high pressure (several hundreds of kilopascals) or when the contact resistance between the ribs and the MEA is negligible due to the low current density power generation. Even if some of the ribs do not face each other, the current distribution is uniform throughout the MEA, so that the cell voltage is not substantially affected.

  Therefore, a separator having a concavo-convex structure symmetrical to the manifold (concave means groove, convex means rib) and the ribs are opposed to each other through the MEA, but the front and back flow path patterns do not have to be exactly the same. .

  For the above reasons, the present invention can be applied even to an asymmetric separator. Therefore, in order to clarify the positional relationship when incorporated in the cell stack, the X-axis and Y-axis are indicated on the separator of the present invention (FIG. 2). In the following description, it is assumed that the separator is incorporated in the battery with the Y-axis facing the gravity (the opposite direction of gravity), the X-axis being the side surface direction of the battery, and the flow path surface being upright.

  However, the flow path surface of the separator may be a vertical (gravity) direction, a horizontal direction (perpendicular to gravity), and even in an arbitrary direction, it has an essential influence on the effect obtained by the present invention. Absent.

  The fuel is supplied from the anode supply manifold 208 and passes through the flow path connecting portion 202 surrounded by a dotted line. The flow passage connecting portion 202 is formed with two wide flow passages 203 and one convex portion (referred to as a flow passage separation portion 204). The separator has an outer peripheral portion (flat portion) 205 in the same plane. Here, since the wide flow path 203 is communicated with the flow path 219 that is later divided into a plurality of grooves, it is referred to as a merging portion of the flow paths.

  After passing through the two flow paths 203, the fuel is guided to the flow path 219 divided by the rib 206 and moves in the internal direction of the separator (the negative direction of the X axis). The fuel flow is reversed at the bent portion 214. In the bent portion 214, only the flow path separation portion 204 is extended, and the ribs on both sides are eliminated. The rib width of the flow path separation portion can be set in a range that does not substantially reduce the cross-sectional area of the flow path of the bent portion 214.

  In the flow path separation part 202 and the bent part 214 shown in FIG. 2, the number of grooves is reduced from 4 to 2, so that the flow path cross-sectional area is not significantly reduced.

  After the fuel flow direction is reversed, the fuel flows upward (in the positive direction of the X axis) in FIG. 2 and reaches the bent portion 215. Similarly, the flow direction of the fuel is reversed at the bent portion 215 and flows toward the discharge manifold 209. In the vicinity of the fuel discharge manifold 209, a flow passage connecting portion 216 having the same shape as the flow passage connecting portion 202 is provided. Also on the fuel outlet side, the fuel that has passed through the flow path 219 merges in a wide flow path 220 (referred to as a merging portion).

  In the flow path folding portion, the central rib width is smaller than the width of the rib 206 of the power generation surface 218. In the channel turning portion, the groove depth becomes shallower as in the channel connecting portion 202 (detailed in FIG. 7). Therefore, it is necessary not to make the flow path cross-sectional area substantially small at the flow path folded portion. The center rib width is preferably in the range of ¼ to ¾ of the width of the rib 206 in order to compensate for an increase in pressure loss accompanying a change in the fuel flow direction. When graphite or a material having electrical conductivity equivalent thereto is used, the central rib width may be set to a small range from 1/4 to 1/2 of the width of the rib 206. Further, when there is a margin in the channel cross-sectional area of the channel bending portion, the rib 206 on the power generation surface is extended as it is, and after passing through the channel bending portion 214, the rib 206 (see FIG. 2 may be connected to a rib located at the center of 2). Also in this case, if the width is narrowed in the same manner as the central rib, the flow paths 219 of the two power generation surfaces having different flow directions can be connected without substantially reducing the flow path cross-sectional area.

  In addition, since the reactant decreases in accordance with the traveling direction of the flow path, the flow path connecting portion 216 downstream of the flow path is allowed to substantially reduce the cross-sectional area of the flow path without changing the number of grooves. There is a case. In particular, in the case of a fuel cell using a reformed gas containing pure hydrogen (concentration 100%) or high concentration hydrogen of 70% or more as the fuel, the fuel utilization rate is set to a high value of 70% or more. However, the amount of gas downstream of the flow path is significantly reduced. For this reason, in the flow path connecting part 216, the sum of the cross-sectional areas of the flow paths may be smaller than the sum of the cross-sectional areas of the power generation surface 216.

  That is, it is necessary to reduce the groove depth of the downstream flow passage connecting portion 216 so that the direction of the flow passage on the front surface can be changed regardless of the flow passage pattern on the back surface (detailed in FIG. 7). ), The groove can be extended to the flow passage connecting portion 216 without reducing the number of grooves on the power generation surface 218. In this way, the ribs are continuously extended to the vicinity of the manifold 209 at the flow passage connecting portion 216, so that the island-like protrusions 217 can be omitted and the load on the MEA and the gasket is made uniform. It is advantageous in that it can.

  The oxidizing agent is supplied from the supply manifold 210 to the flow path on the back surface (FIG. 5 described later), and is guided to the discharge manifold 211 arranged in the diagonal direction. The cooling water is supplied from the supply manifold 212, passes through a cooling water passage (FIG. 12 described later), and is then discharged to the discharge manifold 213.

  The island-shaped protrusions 217 are provided in the vicinity of the manifolds 208 and 209 in the region of the flow passage connecting portions 202 and 216. The cross-sectional structure cut out at right angles to the flow direction of the flow path 203 of the flow passage connecting portion including this island-shaped protrusion 217 will be described with reference to FIG. 7, but here, only the function of the island-shaped protrusion 217 will be described. To do.

  The island-shaped protrusion 217 has a gasket mounted thereon, and further has an electrolyte membrane thereon. Since there is also a gasket on the flat portion of the other separator facing the separator 201, the island-shaped protrusion 217 has a structure of island-shaped portion / gasket / electrolyte membrane / gasket / flat portion (the other separator). Become. In this way, a stacked structure (sandwich structure) of a gasket and an electrolyte membrane is provided between two separators so that a reactant such as fuel moves inside the cell (referred to as an internal leak described later). Can be prevented.

  The island-shaped protrusion 217 may be connected to the rib 206 of the power generation surface 218 so as to have a continuous convex shape, and the convex portion may be extended to substantially the same length as the rib 204. In this case, the width of the convex portion of the flow passage connecting portion 202 is narrowed from 1/4 to 3/4 of the width of the rib 206, and the sum of the groove cross-sectional areas of the flow passage connecting portion 202 is determined as It is possible not to reduce the pressure loss of the separator substantially without reducing the sum of the cross-sectional areas, or to suppress the pressure loss range in which a fuel or an oxidant pump can supply fuel or the like to the separator. When such a continuous convex part is provided in the flow path connecting part 202 or the flow path connecting part 216, the effect of suppressing the sagging of the gas diffusion layer and preventing internal leakage can be obtained. Below, the continuous convex part which provided in the above-mentioned flow-path connection part or flow-path folding | returning part and connected with the rib of the electric power generation surface is described as a thin rib.

  The mechanism for suppressing the internal leak is estimated as follows. When the laminated structure (sandwich structure) has a low bending strength and is easy to bend, when the island-like protrusions 217 or the thin ribs are omitted, the gasket or the electrolyte membrane hangs down toward the channel 203 of the channel connecting unit. There is. When such deformation occurs, the fuel leaks to the oxidant flow path side. Conversely, power generation failure occurs due to a phenomenon (internal leakage) in which the oxidant leaks to the fuel flow path side. Alternatively, the cross-sectional area of the flow path 203 of the flow path connecting portion may be reduced due to sagging of a gasket or the like, thereby obstructing the flow of fuel or oxidant and causing loss of auxiliary power.

  Therefore, in the channels 203 and 216 of the channel connecting portion, the use of the island-shaped protrusions 217 or the thin ribs for the purpose of supporting the gasket from the channel toward the electrolyte membrane can avoid the above-described problems. it can.

  The island-shaped protrusions 217 or the thin ribs do not excessively reduce the cross-sectional area of the flow path connecting portions 202 and 216. That is, the cross-sectional area of the protrusion cut out so as to cross the island-shaped protrusion 217 perpendicular to the fuel flow direction is 50% or less, preferably 30% or less with respect to the cross-sectional area when the island-shaped portion is not provided. (Figure 7 below). In this way, it is possible to prevent a large pressure loss without disturbing the flow of the fluid in the flow path connecting portion.

  When the amount of reduction in the channel cross-sectional area due to the installation of the island-shaped protrusions is large, the pressure loss can be reduced by shortening the length of the island-shaped protrusions. On the contrary, when the amount of decrease is relatively small, the length of the island-shaped protrusion can be increased, which is advantageous in improving the adhesion to the gasket. When thin ribs are used, the pressure loss can be substantially reduced by narrowing the rib width.

  In any case, depending on the flow path parameters such as the groove shape, cross-sectional area and length, or the utilization rate of the reactant (in other words, the remaining amount of the reactant downstream of the channel) You can choose.

  It is desirable to omit the island-shaped protrusion 217 if it is not necessary. For example, if a resin frame part is inserted into a portion where the MEA electrolyte membrane and the gasket are pressure-bonded to prevent the electrolyte membrane and the like from sagging, the island-shaped protrusion 217 is unnecessary. The presence or absence of island-shaped protrusions 217 is determined according to the structure and strength of the MEA and gasket.

  As described above, if the above-described island-shaped protrusion 217 is replaced with a thin rib, the fuel can flow to the discharge manifold 209 through the flow passage connecting portion 216 without changing the number of grooves on the power generation surface 218. It becomes possible. At this time, in consideration of the fuel consumption, the shape of the thin rib is selected so that the pressure of the fuel passing through the flow passage connecting portion 216 does not increase.

  Furthermore, island-shaped protrusions or thin ribs may be provided in the grooves of the flow path bent portions 214 and 215. In this case, the island-shaped protrusions have a function of further reducing the contact resistance between the MEA and the separator. In addition, the two power generation surfaces on the front and rear sides of the channel bent portion may be connected to the ribs of the power generation surface and the thin ribs to substitute for the island-shaped protrusions. This method is effective in improving the battery output because the MEA can be supported by a continuous rib and an equal pressure can be applied.

  Next, the assembled state of the separator and MEA of FIG. 2 will be described (FIG. 3). The anode of the MEA is installed on the separator 301 so as to be in contact with the flow path surface of the separator of FIG. 1 (FIG. 3). Here, the separator 301 means the same surface as the separator 201 of FIG. That is, FIG. 3 shows the fuel flow path surface. Protrusions 317 corresponding to the island-like protrusions 217 of FIG. 2 are shown, but these are for sandwiching a gasket and an electrolyte membrane between facing separators to form a sandwich structure.

  Further, in FIG. 3, the outer edge of the electrode 302 is indicated by a broken line so that the positional relationship between the outer edge of the electrode 302 and the flow path of the separator 301 can be understood. Although the electrolyte membrane is omitted in FIG. 3, it is the same as the outer dimensions of the separator 301, and through holes are formed at the same positions and sizes as the manifolds 308, 309, 310, 311, 312, 313. Is.

  As shown in the cross-sectional structure diagram of FIG. 1, an electrolyte membrane is present on the electrode 302, and a cathode (corresponding to the cathode 104 in FIG. 1) is further present thereon. The oxidant flow path surface (the flow path 111 in FIG. 1) of another separator is opposed to the cathode. In addition, it is a part of flow-path connection part (part corresponding to 202,216 of FIG. 2), Comprising: MEA exists also in the upper part. Electrons exchanged during power generation are transmitted via the flow path separation unit. Therefore, power generation occurs even in a part of the flow passage connecting portion. Hereinafter, the region of the separator where the flow path in contact with either the anode or the cathode exists is referred to as a power generation surface.

  Further, a fuel flow path is formed on the back surface of the oxidant flow path surface in this other separator. Furthermore, the separator which has MEA and an oxidizing agent flow path surface is laminated | stacked one after another. Thus, a cell stack having a plurality of cells can be assembled by alternately laminating separators and MEAs.

  The flow path structure of the separator (power generation surface) of the present invention has a corrugated shape. FIG. 4 shows a corrugated shape in the CC section of FIG. In FIG. 4, the fuel flows in a groove that opens upward and is recessed downward. On the back surface, the oxidant flows into the groove that opens downward and is recessed upward.

  In this way, the zigzag structure in which the flow of the fuel and the oxidant is separated by the separator material and the respective flow paths enter the opposite surfaces is advantageous in reducing the thickness of the entire separator.

  A separator 501 corresponding to the back surface of FIG. 2 and having a flow path 519 through which an oxidizing agent flows is shown in FIG. The channel cross-sectional shape is as shown in FIG.

  In the separator structure of the present embodiment, the upper side of the separator (the direction opposite to the gravity) is reversed to the left side to form the back surface of FIG. The oxidant supply manifold 510 and the oxidant discharge manifold 511 in this drawing correspond to the manifolds 210 and 211 in FIG. 2, respectively.

  The cooling water supply manifold 512 and the discharge manifold 513 correspond to the cooling water supply manifold 212 and the discharge manifold 13 shown in FIG. Further, the fuel supply manifold 508 and the discharge manifold 509 are the same as the supply manifold 208 and the discharge manifold 209 in FIG. 2, respectively.

  Since the flow path is corrugated as shown in FIG. 4, the position of the flow path relative to the manifold is shifted by one groove width from FIG. The AA, BB, and CC cross-sections that indicate the cross-sectional position of the separator are also moved to the opposite left and right positions of FIG.

  The oxidant is supplied from the supply manifold 510 and flows to the flow path 519 of the power generation surface 518 via the flow path 503 of the flow path connecting unit 502. Thereafter, after passing through the two bent portions 514 and 515 and the flow passage connecting portion 516, the oxidant after the reaction is discharged from the oxidant discharge manifold 511.

  The channel connecting portions 502 and 516 were provided with island-like projections 517 in the same manner as the fuel channel surface (see FIG. 2).

  The flow path structure relating to power generation can be seen by looking at the CC cross section, and its shape is as shown in the perspective view of FIG. FIG. 6 shows the detailed structure.

  A flow path through which fuel flows is formed on the upper surface of FIG. 6, and the shape is defined by the groove opening width 602 and the groove bottom width 603. The lower surface has an oxidant channel, and the shape is defined by the groove opening width 605 and the groove bottom width 606. The thickness of the separator is shown at 601.

  6 is a trapezoidal shape, it may be a semicircular shape, a square shape, or other shapes.

  The width of the flow path 519 of the power generation surface 518 has an appropriate range according to the type of gas diffusion layer used for the MEA. Usually, it is common to provide grooves and protrusions (ribs) with a width of several millimeters (0.5 to 5 mm). In the case of a fuel cell that operates at normal pressure, if the groove width and rib width are provided in the range of 1 to 2 mm, the electronic resistance can be reduced while the reactants are easily circulated at a low pressure. As a result, a high output battery can be obtained.

  In addition, if the paper-like hard material is relatively strongly dependent on the bending strength of the gas diffusion layer, the groove cross section is difficult to close, so the groove width can be increased to 2 mm or more. On the other hand, in the case of a cloth-like flexible material, the gas diffusion layer is likely to sag on the groove side, so a device for narrowing the groove width is necessary. That is, the range of 0.5 to 2 mm, particularly 1.0 to 1.5 mm is preferable. From the viewpoint of improving the battery output, the result that the fine rib is more desirable than the island-shaped protrusion is obtained. This is because the fine ribs have a continuous convex shape, so that a more uniform current density can be obtained by applying a uniform pressure to the MEA. By adding finer ribs and island-like protrusions to the grooves between the thin ribs and subdividing the grooves to prevent the gas diffusion layer from sagging, the pressure loss of the flow path is reduced and further desirable performance is obtained. .

  Next, the cross-sectional structure of the flow passage connecting portions 202 and 216 in FIG. 2 will be described in detail. The back surface has the shape shown in FIG. The channel connecting portions 502 and 516 in the oxidant channel follow the same design guidelines.

  The BB cross section (same as the BB cross section of FIG. 5) in the flow-path connection part 202 of FIG. 2 was shown in FIG. The right direction in FIG. 7 is matched with the positive direction (the direction of gravity) of the Y axis in FIG. The upper side is the fuel flow path surface of FIG. 2, and the lower is the oxidant flow path surface of FIG. The flow path 203 of the flow path connecting portion 202 in FIG. 2 is the fuel flow path 703 shown in FIG. The channel separation unit 204 is the channel separation unit 704 in FIG. The oxidant flow path 706 in FIG. 7 corresponds to the flow path of the flow path bent portion 515 in FIG.

  With the structure of FIG. 7, the upper and lower groove bottoms do not interfere with each other on the basis of the center separation line (indicated by a one-dot broken line) in the separator cross section. As a result, the directions of the front and back flow paths can be freely turned. In the CC cross section of FIG. 6, if the direction of the fuel flow path is changed, the oxidant flow path on the back surface also follows, so the flow path directions on the front and back sides cannot be changed independently. From this, the effectiveness of the flow passage connecting portion having the structure of FIG. 7 is clear.

  If the flow channel connecting portion of the present invention is applied to the part where the front and back flow channels are to be turned in any direction, a compact separator that does not change the thickness of the entire separator and does not substantially increase the pressure loss is provided. can do. The same method can also be applied to the channel bent part (for example, the channel bent part 214 in FIG. 2 and the channel bent part 514 in FIG. 5).

  The AA cross section of FIG. 2 is a cross section that passes through the island-shaped protrusion 217 of the flow channel connecting portion 202 and is cut out perpendicular to the traveling direction of the flow channel 203 of the flow channel connecting portion. The structure is shown in FIG. The island-shaped portion 817 in FIG. 8 is the island-shaped protrusion 217 in FIG. 2 correspond to the flow path separation unit 804, the flow path 803, and the flat portion 805 of FIG. 8, respectively. Since the oxidant flow path is not formed on the back surface, the thickness of the lower half separator is larger than the center separation line of the separator (shown by a one-dot broken line).

  The cross-sectional area of the channel in the channel connecting part or the channel bending part of this embodiment can be estimated from the dimensions of the cross-sectional structure in FIG. 7 or FIG. Further, the cross-sectional area of the power generation region can be calculated from the cross-sectional structure of FIG.

  Focusing on FIG. 7 and FIG. 6, a method for securing the flow passage cross-sectional area by applying the flow passage connecting portion of the present invention will be described. The cross-sectional area of the fuel flow path 703 in the flow path connection section (BB cross section in FIG. 2) in the flow path connection section of FIG. 7 is obtained by connecting the upper surfaces of the three convex portions 705, 704, and 705 with virtual lines. And the total area of the region surrounded by the side and bottom surfaces of the two fuel flow paths 703. The cross-sectional area of the flow path in the power generation area in FIG. 6 is also the area of the area surrounded by the line, the side surface of the groove, and the bottom width 603 of the fuel flow path (groove). . From the area of this region, the cross-sectional area of five flow paths 219 on the power generation surface 218 in FIG. 2 is integrated.

  Then, if the cross-sectional area of the flow path of the flow path connecting portion (FIG. 7) and the cross-sectional area of the power generation surface (FIG. 6) are substantially the same, the pressure required for the flow of the reactant is substantially the same. can do. In order to satisfy such requirements, the width and depth of the fuel flow path 703 and the width and depth of the flow path separation section 704 in the flow path connecting section (BB cross section in FIG. 2) of FIG. To be decided.

  First, it is desirable that the cross-sectional area of the groove is usually equal to or greater than the former (the cross-sectional area of the flow passage connecting portion) with respect to the latter (the cross-sectional area of the power generation surface). However, since the thickness of the separator (601 in FIG. 6) is limited, the former is often smaller than the latter.

  Therefore, focusing on the fact that the former channel length is significantly shorter than the latter channel length, the former channel cross-sectional area is set to 50% or more of the latter. This can suppress an increase in pressure loss of 5 kPa or less, or a substantial increase in pressure loss, when the former is 20 times or more of the latter.

  In order to suppress the pressure increase in the flow channel connecting portion to a small pressure increase range of less than 10 kilopascals, it is desirable that the former flow channel cross-sectional area be 70% or more of the latter. As a system that needs to substantially suppress an increase in pressure, there is a system that supplies gas at normal pressure (such as a home cogeneration system or a portable methanol fuel cell).

  If the BB cross section of the flow passage connecting portion 202 of FIG. 2 can be made the structure shown in FIG. 7, the upper flow passage connecting portion is based on the center separation line (shown by a one-dot broken line) of the separator. The fuel flow path 703 and the lower flow path 706 in (B-B cross section in FIG. 2) can be freely rotated. As a result, the bent portions 515 and 514 of FIG. 5 can be formed on the back surfaces of the flow passage connecting portions 202 and 216 of FIG.

  Flow channel connecting portions 502 and 516 of FIG. 5 are formed on the back surfaces of the flow channel bent portions 214 and 215 of FIG. Similarly, when the structure of the present invention is applied, the front and back flow paths can be turned in any direction, and it is possible to connect between the two power generation flow paths or between the power generation flow path and the manifold. Furthermore, if each channel | path connection part is made into the structure of FIG. 7, it can approximate to the sum of the channel cross-sectional area in an electric power generation area | region, without substantially reducing the sum of a channel cross-sectional area. As a result, the pressure loss of the fuel flow path and the oxidant flow path is not substantially increased.

  FIG. 9 is an example of a separator 901 having an oxidant channel surface facing the fuel channel surface of FIG. 2 having an oxidant channel surface facing the fuel channel surface of FIG. The position of the flow path 903 of the flow path connecting portion with respect to the oxidant supply manifold 910 is moved in the positive direction of the Y axis by an amount corresponding to the groove width. Similarly, the position of the flow path with respect to the oxidant discharge manifold 911 is also moved by an amount corresponding to the groove width in the positive direction of the Y axis. Compared with FIG. 5, it can be seen that the groove position is shifted by an amount corresponding to the groove width.

  When the MEA is inserted between the two separators having the flow path surfaces of FIG. 2 and FIG. 9 and facing each other so that the Y-axis of each separator is aligned, the rib 206 of FIG. 2 and the rib 906 of FIG. Even pressure can be applied.

  FIG. 10 shows a separator in which a fuel flow path surface is formed so as to face the oxidant path surface of FIG. Compared to FIG. 2, the position of the flow path 1003 relative to the fuel supply manifold 1008 moves by an amount corresponding to the groove width in the negative direction of the Y axis. Similarly, the flow path for the fuel discharge manifold 1009 has also moved in the same direction by an amount corresponding to the groove width. Compared with FIG. 2, it can be seen that the entire fuel flow path is shifted by an amount corresponding to the groove width.

  When the shape of the flow path in the power generation region (power generation surface) is the structure shown in FIG. 6, FIG. 9 and FIG.

  When the corrugated flow path of FIG. 6 described above is employed, two types of bipolar separators having the flow path shapes of FIGS. 2 and 5 and FIGS. 9 and 10 are obtained. Also, any separator can be selected according to the arrangement relationship of a plurality of single cells.

  However, in FIG. 2, if the channel shape is point-symmetric with respect to the center of the separator, the number of grooves on both sides differs by one, but a single cell can be configured with one type of separator. In this case, single cells having only one flow channel and small single cells are alternately stacked. In the case of a fuel cell that supplies fuel at high pressure or a fuel cell that generates power close to 100%, it is less affected by the number of flow paths, so it is point-symmetric with respect to such special fuel cells. These separators can be used. As a result, an advantage of reducing the number of parts can be obtained.

  FIG. 11 shows the structure of the cooling water flow path surface formed on the back surface of FIG. This flow path structure can be combined with the back surface that is one groove width down in the negative direction of the Y-axis as the back surface. The cooling water is supplied from the supply manifold 1112, and is discharged to the discharge manifold 1113 through the flow passage connecting portion 1102, the flow passage bent portions 1114, 1115, and the flow passage connecting portion 1116. On the back surface between the manifold 1112 and the flow passage connecting portion 1102 and the flow passage connecting portion 1116 to the manifold 1113, the flow passage bent portion 1015 and the flow passage connecting portion 1002 or the flow passage bent portion 1014 and the flow passage connecting portion of FIG. 1016 are respectively formed. Thus, the front and back flow paths can be turned in any direction.

  FIG. 12 is a cooling water flow path surface formed on the back surface of FIG. Compared to FIG. 11, the difference is that the groove moves by one width in the negative direction of the Y-axis. The cooling water is supplied from the supply manifold 1212, and after passing through a wide groove on the way, passes through the flow passage connecting portion 1202, the flow passage bent portions 1214, 1215, and the flow passage connecting portion 1216 to the discharge manifold 1213. Discharged.

  When the two cooling water flow paths face each other so that the rib positions of the flow paths coincide with the cooling water flow path of FIG. 12, the cooling water flow path in which the groove depth of the cooling water flow path of FIG. (Expansion channel) can be formed. FIG. 13 shows a cooling water flow path that can be opposed to FIG. This is a structure in which the relationship between the front and back of the separator displayed in FIG. 12 is reversed. To clarify this, the direction of the Y axis was reversed.

  In the case of using a cooling water channel formed in this way as a cooling cell, there is either a fuel channel or an oxidant channel on the opposite side of the surface on which the cooling water channel is formed. This is particularly effective when a cooling cell is inserted between the single cells. That is, if this cooling cell is used, a large cooling water flow rate can be ensured without increasing the length of the battery. The flow path of FIG. 2 or FIG. 9 can be formed on the back surface of the separator of FIG.

  Further, when the cooling water flow path surface of FIG. 11, FIG. 12, FIG. 13 or FIG. 14 is made to face a flat plate made of graphite or metal, a cooling cell having the same depth as the groove depth shown in each drawing is formed. can do. The material of the flat plate facing the cooling water flow path surface is not limited to the above material as long as it is conductive. Since the flow path cross-sectional area of the cooling cell having such a configuration is ½ of the above-described expansion channel, the flow rate is reduced to ½. Since the flat plate can be used so as to contact the current collector plate of the fuel cell, this cooling cell is installed at a position adjacent to the current collector plate, particularly when the end cell is not cooled too much. It is valid.

  FIG. 14 shows a structure when the cooling water channel surface is formed on the back surface of the oxidant channel of FIG. Compared to FIG. 13, there is a shift corresponding to one groove in the positive direction of the Y-axis. When this flow path surface faces the flow path of FIG. 11, a cooling water flow path (expansion channel) in which the cooling water flow path is doubled can be formed.

  Finally, another variation will be described with respect to the structure (FIG. 7) of the flow path connecting portions 202 and 216 in FIG. FIG. 15 and FIG. 16 are examples.

  FIG. 15 differs from FIG. 7 in the positions of the central flow path separation sections 1504 and 1507. That is, the center positions of the flow path separation portions 704 and 707 in FIG. 7 coincide in the horizontal direction (the in-plane direction of the separator), but the centers of the flow path separation portions 1504 and 1507 in FIG. . Even with such a structure, the flow paths on the front and back sides are separated on the basis of the center separation line (shown by a one-dot broken line) of the separator cross section, so that the respective flow paths can be freely rotated.

  The structure shown in FIG. 15 is effective in suppressing an increase in pressure loss as compared with FIG. In FIG. 7, the grooves at the end of the plurality of grooves in the same plane are completely moved under the terminal groove at the other face, and the ends of the front and back grooves are aligned. However, in FIG. 15, it is not moved to below the end channel on the other surface. As described above, since the movement of the groove is partially omitted in FIG. 15, the bent portion of the groove can be reduced, and an increase in pressure at the flow path connecting portion can be suppressed.

  As described above, the rib position at the center of the flow path bending portion can also be shifted on the front and back sides. As a result, the same pressure loss reducing effect as that of the flow path connecting portion can be obtained. Further, when applied to the flow path bent portions 214 and 215 shown in FIG. 2, the same effect can be obtained.

  The upper diagram of FIG. 16 shows a structural example in which the flow path separation portions 1604 and 1607 and the convex portions 1605 and 1606 at the flow path end portions are formed in an S shape. Such a structure is effective for a thin base material, for example, a metal separator obtained by pressing a metal plate with a die. When a thin base material is pressed, it is extremely difficult to swell (form convex protrusions) in the thickness direction on both sides of the separator, as in the flow path separation portions 704, 707, 1504, and 1507 in FIGS. Have difficulty. In such a case, if the structure shown in FIG. 16 is used, the flow path separation portions 1604 and 1607 can be formed on the front and back sides. From this state, only the S-shaped protrusions on the front and back sides move separately from each other, so that the direction of the front and back grooves can be arbitrarily turned (lower diagram in FIG. 16).

  The surface flow path 1603 is formed by an S-shaped convex portion 1605 and a flow path separation portion 1604. Similarly, the channel 1608 on the back surface is formed by a convex portion 1606 and a channel separation portion 1607. These flow paths are divided by a central flow path separation unit 1604 and 1607. The end portion forms a portion 1605 or 1606 processed into a convex shape. When the convex parts 1605 and 1606 are sandwiched between the gaskets and pressed against the other separator, the reactants do not leak out of the flow path, and the sealing property is secured.

  If the separator structure of this form is adopted, it is possible to change the direction of the front and back channels even if the separator channels are wavy, and the reactants flowing through the front and back channels are connected to separate manifolds. It becomes possible to make it. As a result, a thin fuel cell can be provided with a thin separator.

  As a typical embodiment of the present invention, FIG. 17 shows a cell stack using the power generating cell separator 1704 and the cooling cells 1708 and 1722 of the present invention.

As the power generation separator 1704, a bipolar separator that mainly forms a fuel flow path on one side (left side in FIG. 17) and an oxidant flow path on the opposite side (right side in FIG. 17) was mainly used.
This bipolar separator has a fuel flow channel surface shown in FIG. 2 and a separator having the oxidant flow channel surface of FIG. 5 on its back surface (hereinafter referred to as “alpha type”), a fuel flow channel surface of FIG. Two types of separators (hereinafter referred to as “beta type”) having nine oxidant flow path surfaces were prepared. The cross sections of the front and back flow paths have the trapezoidal corrugated shape shown in FIG.

  The reason why the two types of separators are prepared in this way is to allow the ribs of the separators constituting the single cell to face each other via the MEA even if the interval between the cooling cells is freely changed. . In addition, when inserting one cooling cell for every two single cells, as described later, either the alpha type or the beta type is sufficient for the bipolar separator, and only the beta type is used in this embodiment. It was.

  The raw materials for producing the separator were expanded graphite and a phenol resin thermosetting binder, and the separator was formed by a mold of a mixture thereof. The binder content was 20% by weight with respect to the graphite weight.

  Further, in the cross-sectional shape of FIG. 6, when the upper side is the fuel flow path surface and the lower side is the oxidant flow path surface, the fuel flow path opening width 602 is 1 mm, the fuel flow path (groove) bottom width 603 is 0.8 mm, and the groove depth. The length 604 was set to 0.6 mm. The opening width 605 of the oxidant channel was 1 mm, the bottom width 606 was 0.8 mm, and the groove depth 607 was 0.6 mm. The wall thickness 601 was set to 0.3 mm over the entire surface. Therefore, the total thickness of the separator is the sum of the groove depth (0.6 mm) and the wall thickness (0.3 mm), that is, 0.9 mm.

  In the cross-sectional shape of FIG. 6, if the opening width and bottom width of the groove are fixed, the groove depths on the front and back sides are the same unless the thickness of the groove bottom is changed. In this example, the groove bottom wall thickness was the same for both the front and back surfaces (that is, both the groove bottom wall thickness in the fuel and oxidant flow paths), so the groove depth was also the same.

  Thus, since the flow path shape of the separator (which means a dimension composed of groove width, depth, etc.) is symmetric in the thickness direction, and the manifold position is symmetric in the separator plane, the alpha separator When the channel surface (for example, FIG. 2) is rotated by 180 °, it coincides with the channel surface of FIG. 9 of the beta separator. Although FIG. 9 is originally used as an oxidant flow path surface, since the flow path shape is symmetrical in the thickness direction, it can also be used as a fuel flow path surface. Therefore, the rib position of the facing separator can be aligned by rotating the separator, and the cell stack can be assembled with a few types of bipolar separators. If the flow path shape or the manifold position is not symmetrical, rib alignment by rotation cannot be performed, so it is necessary to prepare a plurality of bipolar separators.

  Therefore, in this embodiment, only the beta type is used, and the ribs (convex parts) on the flow path surface are faced through the MEA. Between the two separators, a membrane-electrode assembly (MEA) 1702 and a gasket 1705 made of ethylene / propylene rubber were installed on the outer edge of the separator, and a single cell 1701 was assembled. Next, the cooling water channel surface (FIG. 14) + oxidant channel surface (FIG. 5) / MEA / fuel channel surface (FIG. 10) + oxidant channel surface (FIG. 9) / MEA / fuel channel surface (FIG. 2) + cooling water flow Two cells consisting of the road surface (FIG. 12) are defined as a basic unit U1. Here, “/” means facing each other, and “+” represents a separator having a channel formed on the front and back. That is, in the above arrangement, “cooling water channel surface (FIG. 14) + oxidant channel surface (FIG. 5)” is a separator in which the channels of FIG. 14 and FIG. “+ Oxidant flow path surface (FIG. 9)” corresponds to a beta separator, and “fuel flow path surface (FIG. 2) + cooling water flow path surface (FIG. 12)” corresponds to a separator obtained by combining FIG. 2 and FIG.

  Here, in order to connect the next basic unit to the right side of the cooling water flow path surface (FIG. 12) at the right end of U1, a unit U2 in which U1 is turned upside down is prepared. If it does in this way, it will be in the state where the up-down direction of the cooling water flow-path surface (FIG. 14) in the left end of the basic unit U2 was reversed, and it becomes the same surface as FIG. This surface can face FIG. 12 to form a cooling water flow path (extended channel). Accordingly, the cooling water flow path (FIG. 12) at the right end of U2 also has the same plane as FIG. 11 because the Y-axis direction of FIG. 12 at the right end of U1 is reversed. This surface can directly connect the cooling water flow path surface of U1 (FIG. 14) without reversing the positive / negative of the Y axis. Similarly, U1 and U2 were alternately connected to produce a laminate other than the cooling cell adjacent to the current collector plate.

  The cooling cell adjacent to the current collecting plate 1713 at the left end of FIG. 17 bonds a graphite flat plate forming a manifold of gas and cooling water so as to face the cooling water flow path surface (FIG. 14) at the left end of the laminate. Then, the flat plate side was brought into close contact with the current collector plate 1713. The bonded resin seal 1706 is provided around the outer edge of the separator and the cooling water manifold to prevent cooling water leakage. The cooling cell adjacent to the current collector plate 1714 on the opposite side is bonded to a graphite flat plate on the cooling water flow path surface (FIG. 12 or a view obtained by rotating it 180 °) at the right end of the laminate (the adhesive portion is sealed with resin). 1706), and the flat plate side was pressure-bonded to the current collector plate 1714. Thereby, since it cools with a small amount of water, without extending a cooling water flow path, it can avoid overcooling and can stabilize the cell voltage of an edge part.

  For the resin seal 1706, a water-resistant epoxy resin was used as an adhesive. An elastic body such as silicon rubber, fluorine rubber, or ethylene / propylene rubber may be used.

  In the cells other than the end portions, a cooling water flow path (expansion channel) having a depth twice as large as that in each drawing is formed by the repeating structure of the basic units U1 and U2. By this method, the cells inside the battery can be cooled efficiently by double the cooling water flow rate, and the entire battery including the cooling state of the end cell is maintained at a uniform temperature. It becomes possible to do.

  A cooling cell was placed in every two of the single cells described above. The single cell interval for inserting the cooling cells may be 1 to 3 cells. If the current density flowing through the MEA is small, the amount of heat generated per single cell is small, so the interval between single cells into which cooling cells are inserted can be increased, and the number of cooling cells can be reduced.

  With such a component structure, a 40-cell stack in which one single cooling cell was inserted into two single cells was manufactured. This fuel cell is referred to as CS1.

  The fuel is supplied from a supply connector 1710 provided on the end plate 1709 shown in FIG. 17, passes through each single cell 1701, and is provided on the opposite end plate 1709 after the fuel is oxidized on the anode of the MEA. The fuel gas pipe connector 1722 is discharged. Here, pure hydrogen or hydrogen obtained by reforming fossil fuel such as natural gas or kerosene can be used as the fuel. Further, it is possible to use liquid fuel such as methanol or methanol aqueous solution.

  Similarly, the oxidant is supplied from an oxidant gas pipe connector 1711 provided on the left end plate 1709 and discharged from the oxidant gas pipe connector 1723 of the right end plate 1709. Air was supplied from a commercial air blower.

  The cooling water is supplied from the connector 1712, and after passing through the cooling cell 1708, the cooling water is discharged from an end plate connector 1724 provided on the right side.

  As shown in FIG. 17, a plurality of unit cells 1701 are connected in series to form a stacked body. Current collector plates 1713 and 1714 were provided on the outside, and sandwiched between end plates 1709 and insulating plates 1707 via insulating plates 1707. Both end plates held the laminate in a state where a predetermined load was applied using bolts 1716, springs 1717, and nuts 1718. The gas seal 1705 was installed between the two separators constituting both the fuel gas channel surface and the oxidant gas channel surface and the cooling water cell.

Pure hydrogen was supplied as fuel to such a cell stack, and air was supplied as an oxidant. After confirming that the voltage in the open circuit reached 0.9 to 1 V, power generation was started at a current density of 0.3 A / cm ² , and a continuous power generation test for 8 hours was performed. A stable voltage was obtained in the range of 0.68 to 0.70V. The air pressure at the battery inlet during this test was 9 ± 0.3 kPa. The fuel utilization rate was 80%, and the oxidant utilization rate was 60%. The dew point of the gas was 60 ° C. for both the fuel gas and the oxidant gas.

  Next, in order to compare the size with the cell stack in the present embodiment, the fuel flow path is formed on the front and back of the boundary surface without using the corrugated separator of FIG. 6 with reference to the boundary surface passing through the thickness center of the separator. And a separator (thick separator) provided with an oxidant channel. That is, as shown in FIG. 6, the flow paths on the front and back sides are not meshed, and the fuel flow path (depth 0.6 mm) and the oxidant flow path (depth 0.6 mm) are made of graphite flat plates (thickness of 0.2 mm). 3 mm) was separated at the boundary, and the separator was formed as a whole. The thickness of such a separator is the sum of the wall thickness and the groove depth on the front and back sides, and the total thickness of the separator reaches 1.5 mm.

  Components other than the separator (end plate 1709, current collecting plates 1713 and 1714, insulating plate 1707, etc.) were the same as those used in the cell stack described above, and a cell stack consisting of 40 cells was manufactured. This fuel cell is referred to as CS2.

  When comparing the lengths of the fuel cell CS1 of this example and the fuel cell CS2 using the conventional separator, the size could be reduced by 35%.

  That is, referring to FIG. 6, the fuel and oxidant channel depths of the present example were 0.6 mm in common, and the wall thickness was 0.3 mm. Therefore, the separator thickness is 0.9 mm. Since the thickness of the MEA including the thickness of the gasket is 0.5 mm, the thickness of the single cell of CS1 is (0.9 × 2 + 0.5) ÷ 2 = 1.15 mm. In addition, in the formula, the reason for assigning by 2 is to exclude the separator thickness corresponding to the flow path not facing the MEA because the flow paths are provided on both sides.

  On the other hand, when the conventional thick separator is used, the thickness of the separator itself reaches 1.5 mm even if the minimum thickness is 0.3 mm. As a result, the thickness equivalent to a single cell when using a conventional separator is (1.5 × 2 + 0.5) ÷ 2 = 1.75 mm. In addition, 0.5 in a formula means the thickness (0.5 mm) of MEA.

  Therefore, when the separator of the present invention is used, the size of the single cell can be reduced by about 35% compared to the case where the conventional separator is used.

  In the first embodiment, the cross-sectional areas of the front and back channels are the same. One means for changing the cross-sectional area of the front and back channels is to change the groove pitch between the front and back sides by adjusting the opening width and groove width of the grooves. According to this method, it is possible to change the channel cross-sectional area of the front and back sides without making the wall thickness constant in all regions, that is, without making the thicknesses of the groove bottoms on the front and back sides different.

Therefore, as a second embodiment, a separator was manufactured with the same composition as the first embodiment, and the groove shape was changed. In the cross-sectional shape of FIG. 6, the upper side is the fuel flow path surface, the lower side is the oxidant flow path surface, the fuel flow path opening width 602 is 1 mm, the fuel flow path (groove) bottom width 603 is 0.8 mm, and the groove depth 604 is The thickness was 0.6 mm. The opening width 605 of the oxidant flow path was 1.3 mm, the bottom width 606 was 1.1 mm, and the groove depth 607 was 0.6 mm. The wall thickness 601 was set to 0.3 mm over the entire surface. With such a flow path shape, the cross-sectional area per fuel flow path is 0.54 mm ^{2 in} a trapezoidal approximation, and the cross-sectional area per oxidant flow path is 0.72 mm ² . The road cross-sectional area can be increased by 30% or more with respect to the fuel side. As a result, in an operation with a low oxidant utilization rate, it is possible to suppress an increase in pressure in the flow path and reduce power loss of the auxiliary equipment.

  The second embodiment is particularly effective when the gas supply condition is such that the flow rate of the oxidant gas is larger than the fuel gas flow rate, or when the gas condition uses almost 100% hydrogen using pure hydrogen. . Thereby, the pressure loss of the oxidizing agent can be reduced.

The cooling water flow path was the same as in the first embodiment, and all the parts other than the separator such as the MEA, gasket, and current collector plate were the same, and a cell stack was manufactured. Pure hydrogen was supplied to the cell stack as a fuel, and air was supplied as an oxidant. After confirming that the voltage in the open circuit reached 0.9 to 1 V, power generation was started at a current density of 0.3 A / cm ² , and a continuous power generation test for 8 hours was performed. A stable voltage was obtained in the range of 0.68 to 0.70V. The battery voltage and output were almost the same and no difference was observed, but the air pressure at the battery inlet decreased from 9 ± 0.3 kPa to 6 ± 0.2 kPa. As a result, the power of the blower supplying air was reduced. It could be reduced by 20%.

  In this example, the fuel utilization rate was 80% and the oxidant utilization rate was 60%. The dew point of the gas was 60 ° C. for both the fuel gas and the oxidant gas.

  Furthermore, as another embodiment, when the thickness of the groove bottom of the oxidant flow path is smaller than the thickness of the groove bottom of the fuel flow path, the cross-sectional area of the oxidant flow path is relatively greater than the cross-sectional area of the fuel flow path. Also expanded. In this way, since the cross-sectional area is enlarged in the oxidant flow path, the pressure loss can be reduced, and as a result, the power loss of air supply equipment such as a blower and other auxiliary equipment can be reduced. It becomes possible.

  On the other hand, if the cross-sectional area of the fuel flow path is made relatively small from the opposite viewpoint, it is disadvantageous in terms of loss of auxiliary power, but the gas linear velocity increases and drainage performance is improved. In the case of power generation conditions in which the fuel utilization rate is increased, the gas flow rate is reduced on the outlet side of the flow path. In such a case, if the cross-sectional area of the fuel flow path is reduced, drainage can be improved while avoiding an increase in pressure loss.

  The separator of the present invention can be used for a compact polymer electrolyte fuel cell.

The cross-sectional structure of the single cell of this invention is shown. The separator structure which has the fuel flow-path surface of this invention is shown. The state which the electrode and MEA were laminated | stacked on the separator of this invention is shown. The perspective view of the electric power generation flow path surface in the separator of this invention is shown. The separator structure which has the oxidizing agent channel surface of the present invention is shown. The cross section of the electric power generation flow path surface in the separator of this invention is shown. The cross section of the flow-path connection part in the separator of this invention is shown. The cross section of the flow-path connection part in the separator of this invention is shown. The separator structure which has the oxidizing agent channel surface of the present invention is shown. The separator structure which has the fuel flow-path surface of this invention is shown. The separator structure which has the cooling water flow-path surface of this invention is shown. The separator structure which has the cooling water flow-path surface of this invention is shown. The separator structure which has the cooling water flow-path surface of this invention is shown. The separator structure which has the cooling water flow-path surface of this invention is shown. The cross section of the flow-path connection part in the separator of this invention is shown. The cross section of the flow-path connection part in the separator of this invention is shown. The cell stack using the separator of this invention is shown.

Explanation of symbols

101, 301 Separator 102 having fuel flow path Electrolyte membrane 103 Electrode (anode)
104 electrode (cathode)
105, 112, 113 Gasket (seal material)
107, 501 Separators 108, 208, 308, 508, 908, 1008, 1108, 1208, 1308, 1408 having oxidant flow path surfaces Fuel supply manifolds 109, 209, 309, 509, 909, 1009, 1109, 1209, 1309, 1409 Fuel discharge manifold 110 Fuel flow path 111 Oxidant flow path 201 Separator 202, 216, 220, 502, 516, 902, 916, 1002, 1016, 1102, 1106, 1202, 1206, 1302, 1306 having a fuel flow path surface 1402, 1406 Flow path connecting portion 203, 503, 903, 1003 Flow path (merging portion) of flow path connecting portion
204, 504, 904, 1004, 1504, 1507, 1604, 1607 Channel separation part 205, 505, 905, 1005, 1505, 1506 Formed on the separator flat part 206, 506, 906, 1006 on the power generation surface Ribs 210, 310, 510, 910, 1010, 1110, 1210, 1310, 1410 Oxidant supply manifold 211, 311, 511, 911, 1011, 1111, 1211, 1311, 1411 Oxidant discharge manifolds 212, 312, 512, 912 , 1012, 1112, 1212, 1312, 1412 Cooling water supply manifolds 213, 313, 513, 913, 1013, 1113, 1213, 1313, 1413 Cooling water discharge manifolds 214, 215, 514, 515, 914, 915, 1014, 1015, 1104, 1105, 1204, 1205, 1304, 1305, 1404, 1405 Channel bent portions 217, 517, 917, 1017 Island-like projections 218, 518, 918, 1018 Part 219 of the power generation surface, 519, 919, 1019 Channel 302 electrodes on the power generation surface (shown in a projected state)
601 Wave type separator thickness 602 Fuel channel (groove) opening width 603 Fuel channel (groove) bottom width 604 Fuel channel (groove) groove depth 605 Oxidant channel (groove) opening width 606 Bottom width 607 of oxidant flow path (groove) Groove depth 703 of oxidant flow path (groove) Fuel flow paths 704, 707, and 804 in flow path communication section (cross section BB in FIG. 2) Flow path separators 705 and 805 in the BB cross section in FIG. 2 Flat portion 706 in the flow path connecting section (BB cross section in FIG. 2) Oxidant flow in the flow path connecting section (BB cross section in FIG. 2) Road 803 Fuel flow path 817 in the flow passage connecting portion (C-C cross section in FIG. 2) Island-like protrusion 901 in the flow passage connecting portion (BB cross section in FIG. 2) Oxidant facing the fuel flow passage surface in FIG. Separator 1001 having a channel surface Separator having a fuel channel surface facing the oxidant channel surface of FIG. 1101, 1201, 1301, 1401 Separators 1503 and 1603 having cooling water flow paths Fuel flow paths 1508 and 1608 in the flow passage connecting portions Oxidant flow paths 1605 and 1606 in the flow passage connecting portions Corresponding convex part 1701 Single cell 1702 Membrane-electrode assembly (MEA)
1703 Flat plate component 1704 facing cooling water flow path Separator of the present invention (for single cell)
1705 Gasket (seal)
1706 Resin seal (adhesive)
1707 Insulating plate 1708 Cooling cell having expansion channel (right side is oxidant flow path surface, left side is fuel flow path surface)
1709 End plate 1710, 1722 Fuel gas piping connector 1711, 1723 Oxidant gas piping connector 1712, 1724 Cooling water piping connector 1713, 1714 Current collector plate 1716 Bolt 1717 Spring 1718 Nut 1719 External power line 1720 DC-DC converter or inverter 1721 Load 1722 installed outside Cooling cell comprising cooling water flow path and flat plate parts

Claims (8)

A separator having a fuel or oxidant manifold, a flow passage connecting portion provided in the vicinity of the manifold, and a flow passage communicating with the flow passage connecting portion and facing the electrode,
The width of the flow channel of the flow channel connecting portion is larger than the width of the flow channel facing the electrode, and the depth of the flow channel of the flow channel connecting portion is smaller than the depth of the flow channel facing the electrode. A separator characterized by having a flow passage connecting portion.   The separator according to claim 1, wherein a cross-sectional area (a cross-sectional area perpendicular to the flow direction) of the flow path and the flow path facing the electrode in the flow path connecting portion is substantially equal.   The separator according to claim 1, wherein a flow path separating portion including a convex rib is formed in the flow path connecting portion.   2. The separator according to claim 1, wherein a joining portion that connects a plurality of flow paths formed on at least one of a front surface and a back surface of the separator is provided in the flow path connecting portion.   The separator according to claim 1, further comprising a channel bent portion that changes the direction of the gas channel in the middle of the channel facing the electrode.   The separator according to claim 4, wherein an island-shaped convex portion is provided at a junction portion of the flow passage connecting portion.   One surface of the separator having the structure according to claim 1 is used as a surface having a flow path facing the electrode, and the other surface is supplied with two cooling water manifolds provided at positions different from the manifold according to claim 1. 2. A cooling cell, which is used as a cooling water flow path surface communicated via a road connecting portion and has two separators having the cooling water flow path surface formed by facing each other of the cooling water flow path surfaces, is provided. The solid polymer fuel cell as described.   A solid polymer fuel cell comprising a cooling cell formed by facing one separator having a structure according to claim 7 and a flat plate.

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