JP5068896B2 - Polymer electrolyte fuel cell - Google Patents

Description

  The present invention relates to a polymer electrolyte fuel cell including a manifold separately from a single cell through which a refrigerant for recovering heat from a plurality of single cells flows.

  Conventionally, a polymer electrolyte fuel cell (hereinafter referred to as a “fuel cell”) has an electrochemical reaction between a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air, Electric power and heat are generated simultaneously. Note that the fuel gas and the oxidant gas are sometimes referred to as reaction gases.

  The fuel cell is configured by stacking a plurality of single cells (cells). The unit cell is mainly composed of a polymer electrolyte membrane made of a cation exchange resin that selectively transports hydrogen ions and a carbon powder carrying a platinum-based metal catalyst, and is formed on both sides of the polymer electrolyte membrane. And a diffusion layer made of, for example, carbon paper, carbon cloth, etc., which allows the reaction gas to flow and has electronic conductivity, and is formed on the catalyst reaction layer. The catalytic reaction layer and the diffusion layer constitute an electrode. The electrode supplied with the fuel gas is called an anode (fuel electrode), and the electrode supplied with the oxidant gas is called a cathode (oxygen electrode). Moreover, the structure which consists of a polymer electrolyte membrane and an electrode is called MEA (electrode electrolyte membrane assembly).

  Furthermore, the unit cell has a conductive separator made of a carbon material or a metal material. The separator is formed with a reaction gas channel for supplying a reaction gas to the electrode. The separator is also formed with a refrigerant flow path through which a refrigerant that recovers heat generated from the unit cell flows. Such a flow path is generally constituted by a groove formed on the surface of the separator.

  In order to supply the reaction gas and the refrigerant to the reaction gas channel and the refrigerant channel of each unit cell of the fuel cell, a manifold that is fluidly connected to the channel is provided.

  For example, in the case of the fuel cell described in Patent Document 1, as shown in FIG. 11, a manifold 102 is attached to a side surface (a surface parallel to the stacking direction) of a unit cell stack (stack) 100. The side surface of the stack 100 is provided with a plurality of openings 104 communicating with the reaction gas flow path and the refrigerant flow path of each unit cell, and the manifold 102 has a corresponding flow path through the corresponding opening 104 for the reaction gas and the refrigerant. To supply. Although not shown, a sealing member for fluidly fluidly connecting the flow path of each unit cell and the manifold 102, that is, preventing leakage of reaction gas or refrigerant to the outside, and reaction gas and A seal member for preventing mixing with the refrigerant is disposed. Thus, the manifold 102 provided separately from the unit cell (stack 100) is called an external manifold.

  Unlike such an external manifold, there is what is called an internal manifold. The internal manifold is formed in a stack of unit cells like the fuel cells described in Patent Documents 2 and 3, for example. For example, each unit cell is formed with a through hole communicating with the refrigerant flow path, and the through holes of each unit cell are fluid-tightly connected when the unit cells are stacked. Thereby, the flow path of the refrigerant | coolant which penetrates several cell, ie, the internal manifold for refrigerant gas, is formed. The internal manifold for the reaction gas is formed in the same manner.

  For example, as shown in FIG. 12, one separator 200 is provided with a through hole 202 for refrigerant, a through hole 204 for oxidant gas, and a through hole 206 for fuel gas. The separator 200 is formed with a flow path (groove) 208 through which the refrigerant flows, and the flow path 208 communicates with the through hole 202 for the refrigerant. The refrigerant through-hole 202 and the flow path 208 are arranged so that the refrigerant does not leak to the outside and the oxidant gas and fuel gas from the oxidant gas through-hole 204 and the fuel gas through-hole 206 do not flow in. A sealing member 210 is provided to surround. Similarly, a sealing member is provided for the oxidant gas and the fuel gas.

JP 2001-093563 A JP 2004-139788 A Special table 2010-532085 gazette

  However, in the case of the fuel cell described in Patent Document 1, since the external manifold 102 is attached to the side surface of the unit cell stack (stack 100) via the seal member, the seal member is formed by the unevenness on the side surface of the stack 100. There is a possibility that the reaction gas or the refrigerant leaks from between the stack 100. Specifically, since the stack 100 has a structure in which a plurality of plate-shaped members such as separators including dimensional errors are stacked, the side surface of the stack 100 is unlikely to be a flat surface with high adhesion to the seal member. In addition, since plate-shaped members such as a plurality of separators have different thermal expansions, a gap may be generated between some separators and the seal member. Therefore, the reliability of the fluid-tight fluid connection between the cell flow path and the external manifold 102 is low.

  In the case of the external manifold 102 as described above, when exchanging a specific unit cell (for example, a defective unit cell) from among a plurality of unit cells, it is necessary to remove the external manifold 102 and the seal member from the stack 100. . That is, every time a specific unit cell is replaced, it is necessary to release the fluid connection between the flow paths of all the unit cells and the external manifold 102. In addition, since the fluid-tight fluid connection between the flow path of each unit cell and the external manifold is performed at the same time, there is a poor connection between the flow path of one unit cell and the external manifold. When it happens, everything is considered bad. As a result, the maintenance time of the fuel cell such as replacement of the unit cell becomes longer, or the manufacturing time of the fuel cell becomes longer.

  Therefore, when the flow path of each unit cell and the external manifold are fluid-tightly connected (via a seal member), it takes time to make a good fluid-tight fluid connection between each unit cell and the external manifold. There is such a problem.

  On the other hand, in the case of the internal manifold of the fuel cell described in Patent Documents 2 and 3, when a specific unit cell is replaced, the fluid connection between the flow path of the other unit cell and the manifold is not released. However, when an internal manifold for refrigerant is provided, the separator of the unit cell may be corroded by the refrigerant in the internal manifold. Specifically, a short circuit occurs between two unit cells separated by one or more unit cells via the refrigerant in the internal manifold, and the separator of the unit cell on the high potential side is corroded by current. .

  When the current corrosion of the separator progresses, a hole opens in the separator, and the fuel gas and the oxidant gas may be mixed through the hole. As a result, the electrochemical reaction is inhibited, the ionic conductivity is lowered, and the output of the battery is lowered. As countermeasures for this, it is conceivable to keep the electrical conductivity of the refrigerant low by using an ion exchanger or to coat the separator with an insulator, but naturally the manufacturing cost and the maintenance cost of the fuel cell increase.

  Further, when current corrosion progresses in the portion of the separator that comes into contact with the seal member, the sealing performance between the separator and the sealing member is lowered, and the refrigerant may leak out from the portion where the sealing performance is lowered. As a result, cooling by the refrigerant is insufficient, the battery temperature rises, and the battery output decreases. As a countermeasure, it is conceivable to increase the distance between the through hole for coolant provided in the separator and the seal member. In this case, however, the separator is enlarged, that is, the fuel cell is enlarged.

  In particular, when the separator is made of a metal material, metal ions are eluted from the separator into the refrigerant, so that the electric conductivity of the refrigerant is increased, thereby accelerating current corrosion of the separator.

  Therefore, when an internal manifold for refrigerant is provided, the life of the fuel cell may be shortened.

  Therefore, in view of the above-mentioned problems, the present invention can connect the refrigerant flow path and the refrigerant manifold of each unit cell in a short time with good fluid tightness, and also reduce the life due to the refrigerant in the refrigerant manifold. It is an object of the present invention to provide a polymer electrolyte fuel cell having a structure capable of suppressing the above.

  In order to achieve the above object, the present invention is configured as follows.

  According to an aspect of the present invention, an ion conductive polymer electrolyte membrane, an anode disposed on one side of the polymer electrolyte membrane, a cathode disposed on the other side of the polymer electrolyte membrane, and a refrigerant flow path A polymer electrolyte fuel cell in which a plurality of unit cells each having a conductive separator formed thereon are stacked, each having a plurality of refrigerant manifolds detachably provided on each unit cell, The refrigerant manifold can be connected to the refrigerant manifold of another unit cell, and fluidly connects the refrigerant manifold connected to one side and the refrigerant manifold connected to the other side in the stacking direction of the unit cells. There is provided a polymer electrolyte fuel cell comprising an extended main channel and a sub-channel that fluidly connects the main channel and the refrigerant channel of the separator.

  According to the present invention, since a plurality of refrigerant manifolds are detachably provided in each unit cell, and the refrigerant manifolds provided in each unit cell are connectable, one unit cell is defective. However, it is not necessary to release the fluid connection between the refrigerant flow path of the other unit cell and the corresponding refrigerant manifold. Therefore, the refrigerant flow path of each unit cell and the corresponding refrigerant manifold can be fluid-tightly connected in a short time. In addition, since the manifold can be attached to and detached from the unit cell (that is, a separate body), the refrigerant manifold has an inner manifold penetrating the separator as compared with the case where the refrigerant manifold is provided in the unit cell. The current corrosion of the separator due to the refrigerant can be suppressed, and the life of the polymer electrolyte fuel cell is extended.

These aspects and features of the present invention will become apparent from the following description taken in conjunction with the preferred embodiments with reference to the accompanying drawings. In this drawing,
1 is a top view of a unit cell of a polymer electrolyte fuel cell according to an embodiment of the present invention. Sectional view along the AA line shown in FIG. Top view of the separator showing the surface of the separator disposed on the cathode side facing the cathode The top view of this separator which shows the surface on the opposite side to the surface facing this anode of the separator arrange | positioned at the anode side Partial sectional view of a single cell with the refrigerant manifold removed Sectional drawing which shows a part of unit cell of the state which removed the manifold for refrigerant | coolants based on another embodiment Partial sectional view of a polymer electrolyte fuel cell of a comparative example in which the manifold for refrigerant is an internal manifold The figure which shows distribution of the corrosion current in the refrigerant | coolant manifold of an Example and a comparative example The figure which shows the corrosion current density value of an Example and a comparative example Sectional drawing which shows a part of unit cell of the state which removed the manifold for refrigerant | coolants which concerns on another embodiment Figure showing a conventional polymer electrolyte fuel cell with an external manifold structure A top view of a separator of a unit cell of a conventional polymer electrolyte fuel cell with an internal manifold structure

  Hereinafter, a polymer electrolyte fuel cell (hereinafter referred to as “fuel cell”) according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a top view of a unit cell (cell) constituting a polymer electrolyte fuel cell according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the unit cell taken along the line AA in FIG.

  A fuel cell according to an embodiment of the present invention includes a unit cell stack formed by stacking a plurality of unit cells 10 shown in FIGS. 1 and 2.

Briefly, the fuel cell has a current collector plate made of a conductive metal material on the outer side in the stacking direction of a stack of 10 to 200 single cells, and each of the current collector plates And an end plate made of a metal material having excellent mechanical strength on the outside of each of the insulating plates. A fuel cell is formed by fastening a stack of unit cells, a current collector plate, and an insulating plate in the stacking direction with fastening bolts while sandwiching the stack of unit cells by the end plates. In order to reduce the contact resistance between the polymer electrolyte membrane and the separator, which will be described later, and to provide a good seal between the polymer electrolyte membrane and the separator and the seal member, the fastening force in the stacking direction by the fastening bolt is Generally, it is set to 10 to 20 kgf / cm ² . In some cases, a necessary fastening force may be obtained using a spring.

  As shown in FIG. 2, the unit cell 10 includes a frame-shaped MEA support 18 that supports an MEA (electrode electrolyte membrane assembly) including a polymer electrolyte membrane 12, an electrode (anode) 14, and an electrode (cathode) 16. And two conductive separators 20 and 22 are laminated.

  The polymer electrolyte membrane 12 of the unit cell 10 is made of a cation exchange resin that selectively transports hydrogen ions.

  Each of the anode 14 and the cathode 16 is mainly composed of carbon powder supporting a platinum-based metal catalyst and has a catalytic reaction layer formed on both surfaces of the polymer electrolyte membrane 12 and vents the reaction gas and has electronic conductivity. It comprises, for example, carbon paper, carbon cloth, etc., and a diffusion layer formed on the catalytic reaction layer. The anode 14 is a side to which fuel gas is supplied, and the cathode is a side to which oxidant gas is supplied.

  The separator 20 is made of a material such as carbon or a metal material that has high gas tightness with respect to the reaction gas, excellent conductivity, and acid resistance against the oxidation-reduction reaction. The separator 20 also includes an oxidant gas flow path 24 through which the oxidant gas flows on the surface facing the cathode 16 in order to supply the oxidant gas to the cathode 16. The oxidant gas flow path 24 is produced by cutting or pressing.

  A manifold that supplies the oxidant gas to the oxidant gas flow path 24 and a manifold that collects the oxidant gas from the oxidant gas flow path 24 are configured in a stack of the unit cells 10. In addition, the “manifold” referred to in the present specification refers to what constitutes a flow path for dividing one flow into a plurality of flows, or for joining a plurality of flows into one flow.

  Specifically, the manifold for supplying the oxidant gas to the oxidant gas flow path 24 is a top view of the through hole 26a formed in the MEA support 18 and the separator 20 as shown in FIG. As shown in FIG. 3, the through hole 28a formed in the separator 20 and the through hole 30a formed in the separator 22 as shown in FIG. That is, it is configured by overlapping in the stacking direction of the unit cells 10.

  In addition, a manifold that collects oxidant gas (oxidant gas remaining without being used in the reaction) from the oxidant gas flow path 24 is formed in the separator 20 and the through hole 26 b formed in the MEA support 18. The through hole 28b and the through hole 30b formed in the separator 22 are fluid-tightly fluidly connected (that is, overlapped in the stacking direction of the unit cells 10).

  As shown in FIG. 3, the oxidant gas flow path 24 of the separator 20 meanders from a through hole 28a constituting a part of the reaction gas supply manifold to a through hole 28b constituting a part of the reaction gas recovery manifold. While extending.

  The MEA support 18 is provided with a ring-shaped seal 32a that prevents leakage of oxidant gas from the oxidant gas supply manifold to the outside or prevents inflow of fuel gas or refrigerant into the oxidant gas supply manifold. , Provided so as to surround the through hole 26a. The seal 32 a seals between the MEA support 18 and the separator 22 by being sandwiched between the MEA support 18 and the separator 22. The seal 32a may be integrally formed on the surface of the MEA support 18 as a seal layer, or may be press-fitted into a groove formed in the MEA support 18.

  In connection with the oxidant gas supply manifold, a seal 34 surrounding the through holes 28a and 28b and the oxidant gas flow path 24 is provided in the separator 20 as shown in FIG. As shown, a seal 36 a surrounding the through hole 30 a is provided on the separator 22. Similarly, in relation to the oxidant gas recovery manifold, a seal 32b surrounding the through hole 26b is provided in the MEA support 18 as shown in FIG. 1, and a seal surrounding the through hole 30b as shown in FIG. 36 b is provided in the separator 22.

  The separator 22 is made of the same material as the separator 20, for example, carbon or a metal material. As shown in FIG. 2, the separator 20 also includes a fuel gas passage 40 through which the fuel gas flows on the surface facing the anode 14 in order to supply the fuel gas to the anode 14. Note that the fuel gas channel 40 is also produced by cutting or pressing, like the oxidant gas channel 24.

  As shown in FIG. 1, the manifold for supplying fuel gas to the fuel gas flow path 40 includes a through hole 42a formed in the MEA support 18 and a through hole 44a formed in the separator 20 as shown in FIG. 4 and a through hole 46a formed in the separator 22 as shown in FIG. 4 is fluid-tightly connected (that is, overlapped in the stacking direction of the unit cells 10).

  A manifold that collects fuel gas (fuel gas that remains without being used in the reaction) from the fuel gas flow path 40 includes a through hole 42b formed in the MEA support 18 and a through hole 44b formed in the separator 20. And a through hole 46b formed in the separator 22 is fluid-tightly connected (that is, overlapped in the stacking direction of the unit cells 10).

  Although not shown, the fuel gas flow path 40 of the separator 22 meanders from a through hole 46a constituting a part of the reaction gas supply manifold to a through hole 46b constituting a part of the reaction gas recovery manifold. It extends.

  In connection with the fuel gas supply manifold, a seal 48 surrounding the through holes 42a and 42b and the anode 14 is provided in the MEA support 18 as shown in FIG. 1, and surrounds the through hole 44a as shown in FIG. A seal 50a is provided on the separator 20, and a seal 52a surrounding the through hole 46a is provided on the separator 22 as shown in FIG. Similarly, in connection with the fuel gas recovery manifold, a seal 50b surrounding the through hole 44b is provided in the separator 20 as shown in FIG. 3, and a seal 52b surrounding the through hole 46b is provided in the separator 22 as shown in FIG. Provided.

  As shown in FIGS. 2 and 4, the separator 22 also includes a refrigerant flow path 60 through which a refrigerant that recovers heat generated from the unit cell 10 flows, on the surface facing the separator 20.

  However, unlike the manifold for oxidant gas and fuel gas, the refrigerant manifold is not configured inside the unit cell 10 and is configured to be detachable from the unit cell 10.

  As shown in FIG. 1 and FIG. 2, the refrigerant manifold 62 is different from a manifold provided for a single cell stack (stack) such as the conventional fuel cell shown in FIG. Is provided against. Each unit cell 10 is provided with two refrigerant manifolds 62 for supplying refrigerant and collecting refrigerant.

  As shown in FIG. 2, the refrigerant manifold 62 is a main flow path (mainstream) that fluidly connects the refrigerant manifold 62 connected to one side to the refrigerant manifold 62 connected to the other side as a flow path through which the refrigerant passes. Path) 62c, and a sub-channel (sub-channel) 62d that fluidly connects the main channel 62c and the refrigerant channel 60 of the separator 22.

  The refrigerant manifold 62 is also configured to be detachable from the unit cell 10. Specifically, the refrigerant manifold 62 has a quadrangular shape when viewed in the stacking direction of the single cells 10 as shown in FIG. 1 and a direction orthogonal to the stacking direction as shown in FIG. When viewed in a specific direction, the block is formed of an “L” -shaped block. Specifically, the refrigerant manifold 62 forms a main flow path 62c, a main flow path portion 62h having a thickness (thickness in the stacking direction of the single cells 10) substantially the same as the thickness of the single cell 10, and a sub flow path 62d. , And the sub-flow passage portion 62i is smaller than the thickness of the unit cell 10.

  The unit cell 10 includes a space for accommodating the “L” -shaped refrigerant manifold 62 constituted by the main flow path portion 62h and the sub flow path portion 62i. The MEA support 18, the separator 20, and the separator 22 of the unit cell 10 include notches 64, 66, and 68 having shapes corresponding to the refrigerant manifold 62. Specifically, as shown in FIG. 2, the sub-flow passage 62 i of the refrigerant manifold 62 is sandwiched between the unit cells 10, and the refrigerant manifold 62 is arranged in the outline of the unit cell 10 as shown in FIG. 1. Notches 64, 66, and 68 are formed so that they can be accommodated without protruding. Thereby, the unit cell 10 to which the refrigerant manifold 62 is attached has a substantially rectangular parallelepiped shape. As shown in FIG. 2, the refrigerant manifold 62 is sandwiched between the stacked unit cells 10, so that the refrigerant manifold 62 is prevented from dropping from the corresponding unit cell 10.

  Moreover, as shown in FIG. 5 which shows a part of the unit cell 10 with the refrigerant manifold 62 removed, the refrigerant manifold 62 is detachably positioned and fixed with respect to the separator 20 of the unit cell 10. Specifically, as shown in FIG. 3, the separator 20 is formed with a seal surface 20 a for fluid connection with the refrigerant manifold 62. The sealing surface 20 a is configured by a plane orthogonal to the stacking direction of the unit cells 10. Further, two positioning holes 20b are formed in the sealing surface 20a as positioning portions for positioning. A seal surface 62a of the refrigerant manifold 62 that is fluid-tightly engaged with the seal surface 20a of the separator 20 is formed in the sub-flow channel portion 62i. Further, a protrusion 62b to be inserted into the positioning hole 20b is formed on the seal surface 62a. The seal surface 62a is formed by a plane orthogonal to the stacking direction of the unit cells 10, and when the refrigerant manifold 62 is accommodated in the unit cell 10, the MEA side surface of the separator 20 and the separator 22 side are arranged. Located between the faces.

  Further, the refrigerant manifold 62 is configured to be detachably connected to other refrigerant manifolds 62. As shown in FIG. 2, the refrigerant manifold 62 attached to one of the two unit cells 10 is aligned with the refrigerant manifold 62 attached to the other unit cell 10 in the stacking direction of the unit cells 10. It is comprised so that it may connect.

  As shown in FIG. 5, the refrigerant manifold 62 also includes a seal surface 62g for fluidly connecting the refrigerant manifolds 62 to each other. The sealing surfaces 62g are formed at both ends in the stacking direction of the unit cells 10 of the main flow path portion 62h. The sealing surface 62g is configured by a plane orthogonal to the stacking direction of the unit cells 10.

  As described above, the unit cell 10 includes the seal surface 62g formed in the main flow path portion 62h of the refrigerant manifold 62, the seal surface 20a formed in the unit cell 10, and the seal surface 62a formed in the sub channel unit 62i. It is comprised by the plane orthogonal to the lamination direction. Therefore, by fastening the unit cells 10 in the stacking direction, the seal surface 62g of the refrigerant manifold 62 and the seal surface 20a of the unit cell 10 can be fluid-tightly engaged, and the seal surface of the refrigerant manifold 62 can be engaged. 62g can be fluid-tightly engaged with each other. Therefore, as in the conventional example shown in FIG. 11, compared to the case where one refrigerant manifold is attached to the cell stack in a direction orthogonal to the cell stack direction, the cell stack misalignment (orthogonal to the stack direction). Misalignment) is less likely to occur.

  The sealing surfaces 62a and 62g of the refrigerant manifold 62 and the sealing surface 20a of the unit cell 10 are not limited to a plane orthogonal to the stacking direction of the unit cells 10, but may be a plane intersecting the stacking direction. Preferably, as shown in FIG. 10, the seal surface 62 ′ of the refrigerant manifold 62 is an inclined surface that is inclined downward from the main flow path portion 62 h side. Further, the sealing surface 20 a ′ of the unit cell 10 is also configured with an inclined surface that fluidly engages with the sealing surface 62 a ′ of the refrigerant manifold 62. As a result, the refrigerant manifold 62 sandwiched between the two unit cells 10 is more difficult to drop off from the corresponding unit cells 10.

  Note that the clearance between the refrigerant manifold 62 and at least one of the notch 64 of the MEA support 18, the notch 66 of the separator 20, or the notch 68 of the separator 22 is reduced, so that the refrigerant manifold 62 is replaced by the unit cell 10. You may make it the structure fitted by. In this case, the positioning hole 20b and the protrusion 62b can be omitted.

  As shown in FIGS. 2 and 5, the main flow path 62 c of the refrigerant manifold 62 extends in the stacking direction of the cells 10 (the connection direction of the refrigerant manifold 62), and the main flow of the adjacent refrigerant manifold 62. A fluid-tight connection is established through the passage 62c and the sealing surface 62g. In order to fluid-tightly connect the main flow paths 62c, a ring-shaped seal 70 surrounding the opening of the main flow path 62c is provided on the seal surface 62g as shown in FIG. Similarly to the other seals, the seal 70 may be formed integrally with the refrigerant manifold 62 as a seal layer, or a ring-shaped seal 70 ′ may be formed on the refrigerant manifold 62 as shown in FIG. You may press-fit in the groove | channel 62e.

  As shown in FIGS. 2 and 5, the sub flow path 62d of the refrigerant manifold 62 is connected to the seal surface 62a from the main flow path 62c (the opening of the sub flow path 62d is formed in the seal surface 62a). ). A flow path 20c is formed in the separator 20 in fluid-tight connection with the sub flow path 62d. In order to fluidly connect the sub-channel 62d and the channel 20c in a fluid-tight manner, as shown in FIG. 5, a ring-shaped seal 72 surrounding the opening of the sub-channel 62d is provided on the seal surface 20a. Similarly to the seal 70, the seal 72 may be formed integrally with the refrigerant manifold 62 as a seal layer, or a groove formed with a ring-shaped seal 72 ′ in the refrigerant manifold 62 as shown in FIG. 6. You may press-fit to 62f.

  As shown in FIG. 2, the refrigerant manifold 62 is fluidly connected to a refrigerant flow path 60 formed in the separator 22 via a flow path 20 c formed in the separator 20. However, the unit cell 10 can be configured such that the refrigerant manifold 62 and the refrigerant flow path 60 formed in the separator 22 are directly fluidly connected without using the separator 20. It will be apparent to those skilled in the art, and such a configuration is also included in the scope of the present invention.

  With such a configuration, both ends of the refrigerant flow path 60 of the separators 20 and 22 can be pressed in the stacking direction of the unit cells 10 by the refrigerant manifold 62, and refrigerant leakage can be suppressed. That is, it is not necessary to apply more pressure than necessary to the MEA portion.

  Further, it is preferable that the seal 70 of the main flow path 62c of the refrigerant manifold 62 is made of a material (low elasticity material) having a smaller repulsive force than the seal 72 of the sub flow path 62d. Since the seal 70 is visible from the outside, if it can be visually confirmed that the seal 70 is well sealed, it can be considered that the seal 72 having a larger repulsive force than the seal 70 is also well sealed.

  Although details will be described later, in order to suppress current corrosion of the separators 20 and 22 due to the refrigerant flowing through the refrigerant manifold 62, the cross-sectional area of the sub-channel 62d (area of the cross section orthogonal to the refrigerant flow direction). Is preferably smaller than the channel cross-sectional area of the main channel 62c. In addition, the sub flow path 62 d is preferably fluidly connected to the refrigerant flow path 60 of the separator 22 in the stacking direction of the unit cells 10. Thereby, as shown in FIG. 2, the sub flow path 62 d includes a bent shape, and compared to the case where the sub flow path 62 d is fluidly connected to the refrigerant flow path 60 of the separator 22 in a direction perpendicular to the stacking direction of the unit cells 10. The flow path length becomes long. In other words, the sub-channel 62d can be lengthened without increasing the size of the entire fuel cell. Thus, by comprising the sub flow path 62d, the electrical resistance of a refrigerant | coolant becomes high and the electric current corrosion of the separators 20 and 22 can be suppressed.

Further, when the sub flow path 62d is fluidly connected to the refrigerant flow path 60 of the separator 22 in the stacking direction of the unit cells 10, there is a secondary effect. That is, since a fastening force (for example, 10 to ²⁰ kgf / cm ² ) for laminating and fastening a plurality of unit cells 10 acts in the stacking direction of the unit cells 10, this fastening force is used as a seal for the refrigerant manifold 62. It can be used for fluid-tight engagement between the surface 62a and the seal surface 20a of the separator 20. That is, it is not necessary to separately provide a means for maintaining fluid-tight (via the seal member 72) fluid connection between the refrigerant manifold 62 and the unit cell 10.

  In addition, the refrigerant manifold 62 is preferably made of a non-conductive material such as a resin when the refrigerant is a fluid having conductivity such as water. When the refrigerant is conductive, a short circuit occurs through the refrigerant between two unit cells 10 that are separated by at least one unit cell 10 interposed therebetween. At this time, when the refrigerant manifold 62 is made of a metal material, the refrigerant manifold 62 is corroded by current. Therefore, in order to suppress current corrosion, the refrigerant manifold 62 is made of a non-conductive material such as polyphenylene sulfide (PPS), modified polyphenylene ether (PPE), glass-filled polypropylene resin (PPG), or phenol resin. It is preferable to be made from

  When the refrigerant manifold 62 is made of a metal material, as a measure against current corrosion, the current corrosion may occur at a position in the refrigerant flow path where an insulator is coated or the manifold function is hardly affected. Protrusions and other metal members that occur in a concentrated manner may be provided.

  In addition, in connection with current corrosion via the refrigerant, the seals 70 and 72 are also preferably non-conductive materials. Since the seals 70 and 72 also require elasticity, it is preferable that the seals 70 and 72 are made of a material such as a polyisobutylene resin, an epoxy resin, a silicone resin, an acrylic resin, a fluororesin, or an elastomer.

  When the seals 70 and 72 are integrally provided on the refrigerant manifold 62, it is necessary to select a material in consideration of bondability. For example, when the refrigerant manifold 62 is made of glass-filled polypropylene resin (PPG), an elastomer material is suitable for the seals 70 and 72.

  As shown in FIG. 11, instead of providing one refrigerant manifold for the fuel cell (unit cell stack), each unit cell 10 constituting the stack is provided with the refrigerant manifold 62 and the refrigerant. For example, when one unit cell 10 is replaced due to a failure or a defect by making the unit manifold 62 detachable from the unit cell 10, the refrigerant manifold 62 corresponding to the coolant channel 60 of the other unit cell 10 is used. There is no need to release the fluid connection between the two.

  For example, a plurality of unit cells 10 (stacks of unit cells 10) located on both sides of the unit cell 10 to be replaced can be maintained without removing the refrigerant manifold 62 connected to each other while maintaining the stacked state. Remove from the unit cell 10 to be replaced. Thereby, the unit cell 10 to be exchanged with the refrigerant manifold 62 attached thereto can be removed from the fuel cell. In addition, the refrigerant manifold 62 attached to the replacement target cell 10 can be attached to a new cell 10.

  Furthermore, since the fluid connection between the refrigerant flow path 60 of the fuel cell 10 other than the replacement target and the corresponding refrigerant manifold 62 is maintained, a good fluid-tight fluid connection (via the seal member 72) between them. Is secured. As a result, even if one unit cell 10 is replaced from among the plurality of unit cells 10, a good fluid-tight fluid connection between the refrigerant flow path 60 of each unit cell 10 and the corresponding refrigerant manifold 62 is obtained. It takes a short time.

  Further, the refrigerant manifold 62 is detachably provided to each unit cell 10, that is, separated from the unit cell 10, so that the refrigerant manifold is an internal manifold penetrating the separator of the unit cell. The life of the fuel cell is extended. This will be described in comparison with a fuel cell shown in FIG. 7 in which the refrigerant manifold is an internal manifold penetrating a single cell separator.

  The fuel cell 300 of the comparative example shown in FIG. 7 has a plurality of single cells 302. Each unit cell 302 has an MEA support 304 and separators 306 and 308. The separator 308 is formed with a refrigerant flow path 310 through which the refrigerant flows. The fuel cell 300 also includes a refrigerant manifold 312 that is an internal manifold that passes through the separators 306 and 308 of the single cell 302 and supplies the refrigerant to the refrigerant flow path 310 of each single cell 302.

  FIG. 8A shows the distribution of the corrosion current in the refrigerant in the refrigerant manifold 62 which is the external manifold according to the embodiment. FIG. 8B shows the distribution of the corrosion current in the refrigerant in the refrigerant manifold 312 which is an internal manifold as a comparative example. 8A and 8B, the length of the arrow indicates the magnitude of the corrosion current, and the direction of the arrow indicates the direction of the corrosion current.

  The corrosion current distribution shown in FIG. 8A and FIG. 8B was calculated using an electromagnetic field analysis module “ANSYS Emag” of ANSYS finite element method software “ANSYS”. This module is capable of simulating magnetic fields with currents or permanent magnets, as well as low frequency electrical circuits and electric fields of the system including conductors and capacitors. It also has a comprehensive set of tools for static, transient, and harmonic analysis of low-frequency electromagnetic fields, allowing simulation of electrostatic, static, electromagnetic, electrical, and current conduction, and electrostatic and static magnetic fields. You can also perform charged particle tracing simulations.

  The analysis condition was that 21 unit cells were stacked in series, and the conductivity of the refrigerant was 10 μS. In order to simplify the drawing, FIG. 8 shows the corrosion current distribution in six cells in the example (FIG. 8A) and five cells in the comparative example (FIG. 8B). ing.

  An area A1 shown in FIG. 8A indicates a connection area between the main flow path 62c and the sub flow path 62d of the refrigerant manifold 62, and A2 indicates a connection area between the sub flow path 62d and the separator 20. A region A3 illustrated in FIG. 8B indicates a connection region between the internal manifold 312 and the separator 308. Although the shape of the sub-channel 62d shown in FIG. 8A is different from the shape of the sub-channel 62d shown in FIG. 2, the channel length and the channel cross-sectional area are the same.

  As shown in FIG. 8A, in the case of the example, in the single cell on the high potential side and the low potential side, the density of the corrosion current in the connection region A2 between the sub flow path 62d of the refrigerant manifold 62 and the separator 20 is obtained. However, the density of the corrosion current is low in the medium potential cell. The reason why the corrosion current density is high in the connection region A1 is that the flow passage cross-sectional area of the sub flow passage 62d is smaller than that of the main flow passage 62c.

  On the other hand, as shown in FIG. 8B, in the case of the comparative example, the density of the corrosion current is high in the connection region A3 between the internal manifold 312 and the separator 308 regardless of the electric potential of the unit cell.

  The specific value of the corrosion current density in each unit cell is shown in FIG. In FIG. 9, the solid line (square dot) indicates the corrosion current density value in the connection region A2 between the sub flow path 62d of the refrigerant manifold 62 and the separator 20 in each of the 21 single cells. On the other hand, dotted lines (triangular dots) indicate the corrosion current density values in the connection area A3 of the internal manifold 312 and the separator 308 in each of the 21 single cells. The 0th cell has the lowest potential, the potential increases in order, and the 20th cell has the highest potential.

In the case of the example (solid line), the higher the cell is, the lower the potential, the higher the corrosion current density, and the corrosion current density in the 0th and 20th cells (ie, the lowest and highest potential cells) is About 0.35 A / m ² . Further, the corrosion current density of the tenth unit cell is almost zero. As the potential increases or decreases with respect to the potential of the tenth unit cell, the corrosion current density increases.

On the other hand, in the case of the comparative example (dotted line), the corrosion current density in the zeroth and twentieth unit cells (that is, the unit cells having the lowest potential and the highest potential) is about 0.91 A / m ² . Further, the corrosion current density in the third to seventeenth cells is about 0.7 A / m ² . Furthermore, the corrosion current density in all the single cells is higher than in the examples.

  Accordingly, when the embodiment and the comparative example are compared, the refrigerant manifold shown in FIG. 7 is obtained by making the refrigerant manifold an external manifold 62 that can be attached to and detached from the unit cell (that is, separate) as shown in FIG. It can be seen that the density of the corrosion current generated between the refrigerant and the separator is reduced, that is, the corrosion of the separator can be suppressed, as compared with the case where the manifold for use is the internal manifold 312 penetrating the single cell separator.

  Further, as shown in FIG. 8 (A), in the refrigerant manifold 62, the sub flow path 62d has a smaller flow path cross-sectional area than the main flow path 62c, and further bends the flow path. If the flow path length from the path 62c to the separator 20 is increased, the electrical resistance of the refrigerant between the main flow path 62c and the separator 20 can be increased. As a result, the corrosion current density value in the connection region A2 between the sub flow path 62d of the refrigerant manifold 62 and the separator 20 can be further reduced.

  As described above, according to the present embodiment, the plurality of refrigerant manifolds 62 are detachably provided in each unit cell 10, and the refrigerant manifolds 62 provided in each unit cell 10 can be connected to each other. Even if one unit cell 10 is defective, it is not necessary to release the fluid connection between the refrigerant flow path 60 of the other unit cell 10 and the corresponding refrigerant manifold 62. Therefore, the refrigerant flow path 60 of each unit cell 10 and the corresponding refrigerant manifold 62 can be fluid-tightly connected in a short time. Further, since the refrigerant manifold 62 can be attached to and detached from the single cell 10 (that is, a separate body), the refrigerant manifold 62 can be used as an internal manifold penetrating the separator as compared with the case where the refrigerant manifold is provided in the single cell. The current corrosion of the separator due to the refrigerant in the manifold can be suppressed, and the life of the polymer electrolyte fuel cell is extended.

  Although the present invention has been described with reference to the above-described embodiment, the present invention is not limited to the above-described embodiment.

  For example, in the case of the above-described embodiment, as shown in FIGS. 1 and 2, there are two refrigerant manifolds 62 provided in each unit cell 10, one of which supplies the refrigerant to the refrigerant flow path 60. The refrigerant supply is for refrigerant supply and the other is for refrigerant recovery from the refrigerant flow path 60, but the present invention is not limited to this. For example, it is possible to realize one refrigerant manifold including a main flow channel and a sub flow channel for supplying refrigerant, and a main flow channel and a sub flow channel for refrigerant recovery. In this case, the refrigerant flow path needs to be shaped so as to extend from one end of the separator to which the refrigerant manifold is attached toward the other end, and bend at the other end and extend to one end.

  The polymer electrolyte fuel cell according to the present invention can be used as a fuel cell used for a portable power source, an electric vehicle power source, a domestic cogeneration system, and the like.

DESCRIPTION OF SYMBOLS 10 Cell 12 Polymer electrolyte membrane 14 Anode 16 Cathode 22 Separator 60 Flow path (refrigerant flow path)
62 Manifold (Manifold for refrigerant)
62c Main channel (main channel)
62d Sub channel (sub channel)

Claims (8)

An ion conductive polymer electrolyte membrane, an anode disposed on one side of the polymer electrolyte membrane, a cathode disposed on the other side of the polymer electrolyte membrane, and a conductive separator formed with a refrigerant flow path A polymer electrolyte fuel cell in which a plurality of unit cells including:
It has a plurality of refrigerant manifolds that are detachably attached to each unit cell,
A refrigerant manifold of each unit cell is connectable to a refrigerant manifold of another unit cell, and fluidly connects a refrigerant manifold connected to one side and a refrigerant manifold connected to the other side. A polymer electrolyte fuel cell comprising: a main channel extending in the stacking direction; and a sub-channel that fluidly connects the main channel and the refrigerant channel of the separator. The refrigerant manifold is composed of a main flow path portion that forms a main flow path, and a sub flow path portion that forms a sub flow path and has a smaller thickness in the stacking direction of the cells than the main flow path portion,
The polymer according to claim 1, wherein a space for accommodating the sub-flow channel portion of the refrigerant manifold is formed in the single cell so that the single cells stacked with the sub-flow channel portion of the refrigerant manifold can be sandwiched. Electrolytic fuel cell.   The sub-channel is bent in the sub-channel section so that the sub-channel of the refrigerant manifold and the refrigerant channel of the unit cell are fluidly connected in the cell stacking direction. Polymer electrolyte fuel cell.   The polymer electrolyte fuel cell according to claim 3, wherein the seal surface of the main flow path and the seal surface of the sub flow path of the refrigerant manifold are configured by a plane orthogonal to the stacking direction of the single cells.   4. The polymer electrolyte fuel according to claim 3, wherein the seal surface of the sub-flow path of the manifold for refrigerant intersects the stacking direction of the unit cells and is inclined with respect to the main flow path side. battery.   The polymer electrolyte fuel cell according to any one of claims 1 to 5, wherein the refrigerant manifold is made of an insulating material.   The polymer electrolyte according to any one of claims 1 to 6, wherein the refrigerant manifold and the single cell are provided with positioning portions that engage with each other for positioning and fixing the refrigerant manifold with respect to the separator. Type fuel cell. A main flow path seal provided on the main flow path seal surface and a sub flow path seal provided on the sub flow path seal surface;
The polymer electrolyte fuel cell according to any one of claims 1 to 7, wherein the main channel seal is made of a material having a smaller repulsive force than the sub channel seal.

Images