JP6780950B2 - Fuel cells, fuel cell stacks, fuel cell systems, and bipolar plates - Google Patents

Description

The present invention relates to fuel cells, fuel cell stacks, fuel cell systems, and bipolar plates.

In a fuel cell provided with a cell for generating power and a separator, a plurality of heating elements are provided on a surface of the separator opposite to the surface on which the flow path is formed, from the center to the outside in the surface direction of the separator. Is known (see, for example, Patent Document 1). In this fuel cell, the maximum heat generation temperature of the heating element is configured to gradually increase from the center to the outside in the surface direction of the separator.

Japanese Patent No. 5764000

In the above fuel cell, it is not possible to eliminate the non-uniformity of the in-plane temperature of the cell caused by the heat transfer (heat diffusion) upward in the vertical direction. Therefore, in the plane of the cell, the lower region in the vertical direction becomes relatively low temperature, which makes it difficult for the power generation reaction to occur, and as a result, there is a problem that the output of the fuel cell is difficult to stabilize.

An object to be solved by the present invention is to provide a fuel cell, a fuel cell stack, a fuel cell system, and a bipolar plate capable of stabilizing the output.

[1] The fuel cell according to the present invention includes a membrane electrode assembly and a pair of bipolar plates sandwiching the membrane electrode assembly, and the membrane in the stacking direction of the membrane electrode assembly and the bipolar plate. The electrode assembly and the bipolar plate overlap each other in an overlapping region, the fuel cell further includes a heating element provided on at least one of the pair of bipolar plates, and the heating element includes the overlapping region. The fuel cell is arranged so as to overlap at least the lower region of the region divided into two in the vertical direction.

[2] In the above invention, the heating element may be a PTC heater.

[3] In the above invention, the bipolar plate constitutes a first communication hole forming a first manifold connected to the inlet of the electrode of the fuel cell and a second manifold connected to the outlet of the electrode of the fuel cell. The fuel cell may further include a first communication hole and a sealing portion for sealing between the second communication hole and the heating element. Good.

[4] In the above invention, the heating element has a rectangular shape or an upper side and a lower side located vertically with respect to the vertical direction, and has a side side orthogonal to the upper side and the lower side. It may have a shape having a recess near the center of the upper side.

[5] In the above invention, the heating element has a first terminal extending from one of the side sides of the heating element and a second terminal extending from the other side of the heating element. You may be doing it.

[6] The fuel cell stack according to the present invention includes a plurality of the fuel cells, and the plurality of fuel cells have the first terminals overlapping each other and the second terminals overlapping each other in the stacking direction. Stacked so as to overlap each other, the fuel cell stack extends linearly and extends linearly with a first conductor wire electrically connected to the plurality of first terminals. , A fuel cell stack comprising a plurality of second conductor wires electrically connected to the second terminal.

[7] In the fuel cell system according to the present invention, the fuel cell or the fuel cell stack, a first supply means for supplying fuel to the anode of the fuel cell, and an oxidizing agent are applied to the cathode of the fuel cell. It is a fuel cell system including a second supply means for supplying.

[8] The bipolar plate according to the present invention is a bipolar plate used in a fuel cell and arranged to face the membrane electrode assembly, and the membrane is in a state where the membrane electrode assembly and the bipolar plate are laminated. In the stacking direction of the electrode assembly and the bipolar plate, the membrane electrode assembly and the bipolar plate overlap each other in an overlapping region, and the lower side of the region obtained by dividing the overlapping region into two in the vertical direction. It is a bipolar plate in which the heating element is arranged so as to overlap the region of.

According to the present invention, by arranging the heating element so as to overlap the lower region of the region in which the overlapping region is divided into two in the vertical direction, the temperature is relatively high in the plane of the membrane electrode assembly. Areas with low temperature can be partially heated. As a result, the non-uniformity of the in-plane temperature of the membrane electrode assembly can be suppressed, and the output of the fuel cell can be stabilized.

FIG. 1 is a perspective view showing a fuel cell stack according to an embodiment of the present invention. FIG. 2A is a cross-sectional view taken along the line IIA-IIA of FIG. 1, and FIG. 2B is a cross-sectional view taken along the line IIB-IIB of FIG. FIG. 3 is an exploded perspective view showing a fuel cell according to an embodiment of the present invention. FIG. 4 is a cross-sectional view of the membrane electrode assembly according to the embodiment of the present invention as viewed from the width direction. FIG. 5 (A) is a plan view of the first main surface of the first bipolar plate according to the embodiment of the present invention as viewed from the stacking direction, and FIG. 5 (B) is an embodiment of the present invention. It is a top view which looked at the 1st main surface of the 2nd bipolar plate which concerns on the embodiment as seen from the stacking direction. FIG. 6 (A) is a plan view of the second main surface of the first bipolar plate according to the embodiment of the present invention as viewed from the stacking direction, and FIG. 6 (B) is an embodiment of the present invention. It is a top view which viewed from the stacking direction the heating element and the conductor part which concerns on the form of. FIG. 7 is a cross-sectional view taken along the line VII-VII of FIG. 6 (B). FIG. 8 is a top view showing a fuel cell stack according to an embodiment of the present invention. FIG. 9 is a block diagram showing a fuel cell system according to an embodiment of the present invention. FIG. 10A is a view for explaining the fuel cell according to another embodiment of the present invention, and is a plan view of the second main surface of the first bipolar plate as viewed from the stacking direction. FIG. 10B is a plan view of the heating element and the conductor portion according to another embodiment of the present invention as viewed from the stacking direction. FIG. 11 is a cross-sectional view of the bipolar plate according to another embodiment of the present invention as viewed from the width direction.

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

1 is a perspective view showing a fuel cell stack according to an embodiment of the present invention, FIG. 2A is a sectional view taken along the line IIA-IIA of FIG. 1, and FIG. 2B is IIB- of FIG. A sectional view taken along line IIB, FIG. 3 is an exploded perspective view showing a fuel cell according to an embodiment of the present invention, and FIG. 4 is a view of a membrane electrode joint according to an embodiment of the present invention from the width direction. A cross-sectional view, FIG. 5 (A) is a plan view of the first main surface of the first bipolar plate according to the embodiment of the present invention as viewed from the stacking direction, and FIG. 5 (B) is an embodiment of the present invention. A plan view of the first main surface of the second bipolar plate according to the embodiment as viewed from the stacking direction, FIG. 6A shows the second main surface of the first bipolar plate according to the embodiment of the present invention. A plan view seen from the stacking direction, FIG. 6B is a plan view of the heating element and the conductor portion according to the embodiment of the present invention as viewed from the stacking direction, and FIG. 7 is a line VII-VII of FIG. 6B. FIG. 8 is a top view showing a fuel cell stack according to an embodiment of the present invention.

The fuel cell stack 10 of the present embodiment is used, for example, as a power source for a notebook computer, a mobile phone, a small video camera, an automobile, or the like. As shown in FIGS. 1 and 2, the fuel cell stack 10 includes a plurality of direct methanol type fuel cells 11, end plates 75, 76, and first and second conductor wires 77, 78. There is. The plurality of fuel cells 11 are stacked so that their surface directions and stacking directions (described later) substantially coincide with each other. By stacking a plurality of fuel cells 11 and electrically connecting them in series, it is possible to obtain high output power according to the number of stacks. The fuel cell 11 will be described in detail later. The "fuel cell stack 10" in the present embodiment corresponds to an example of the "fuel cell stack" in the present invention, and the "fuel cell 11" in the present embodiment corresponds to an example of the "fuel cell" in the present invention. The "first conductor wire 77" in the embodiment corresponds to an example of the "first conductor wire" in the present invention, and the "second conductor wire 78" in the present embodiment is the "second conductor wire" in the present invention. Corresponds to one example.

The pair of end plates 75, 76 are arranged at both ends of the plurality of stacked fuel cells 11. The end plates 75 and 76 are connected to each other by a plurality of fastening bolts (not shown). By tightening the fastening bolts, a tightening load is applied between the pair of end plates 75 and 76, and a plurality of stacked fuel cells 11 can be held.

The end plate 75 has a fuel supply port 751, a fuel discharge port 752, an air supply port 753, and an air discharge port 754. The fuel supply port 751 receives fuel (aqueous methanol solution) supplied from the outside of the fuel cell stack 10 to the anode of the fuel cell 11. The fuel supply port 751 communicates with the fuel supply side manifold 2 of the fuel cell stack 10. The fuel supply side manifold 2 is configured by connecting fuel supply communication holes 251, 301, 351 (all described later) in the stacking direction. The fuel supply side manifold 2 is connected to the inlet 121 of the anode of each fuel cell 11.

The air supply port 753 receives air (oxidizer) supplied from the outside of the fuel cell stack 10 to the cathode of the fuel cell 11. The air supply port 753 communicates with the air supply side manifold 4 of the fuel cell stack 10. The air supply side manifold 4 is configured by connecting air supply communication holes 253, 303, 353 (all described later) in the stacking direction. The air supply side manifold 4 is connected to the inlet 131 of the cathode of each fuel cell 11.

And those the anode product of unreacted of fuel sent to the anode of the fuel cell 11, through the fuel discharge side manifold 3 connected with the anode of the outlet 122, the fuel discharge side manifold 3 and the fuel discharge port communicating with It is discharged from 752 to the outside of the fuel cell stack 10. The fuel discharge side manifold 3 is configured by connecting fuel discharge communication holes 252, 302, and 352 (all of which will be described later) in the stacking direction.

On the other hand, the air sent to the cathode of the fuel cell 11 and the product of the cathode pass through the air discharge side manifold 5 connected to the outlet 132 of the cathode, and the fuel cell from the air discharge port 754 communicating with the air discharge side manifold 5. It is discharged to the outside of the stack 10. The air discharge side manifold 5 is configured by connecting air discharge communication holes 254, 304, 354 (all of which will be described later) in the stacking direction.

The fuel supply side manifold 2 and the fuel discharge side manifold 3 are arranged side by side in the vertical direction with the membrane electrode assembly 20 (described later) interposed therebetween. In the present embodiment, the fuel supply side manifold 2 is located above the fuel discharge side manifold 3 in the vertical direction. The air supply side manifold 4 and the air discharge side manifold 5 are arranged side by side in the width direction of the fuel cell stack 10 with the membrane electrode assembly 20 interposed therebetween. The vertical direction refers to the + Z direction with respect to FIG. Therefore, for example, if there is something that exists in the + Z direction with respect to FIG. 1 from a certain point, it is assumed that the existing thing exists above the above-mentioned point in the vertical direction. If there is something that exists in the -Z direction with respect to FIG. 1 from the point, it is assumed that the thing that exists exists below the above-mentioned point in the vertical direction. The "fuel supply side manifold 2" and "air supply side manifold 4" in the present embodiment correspond to an example of the "first manifold" in the present invention, and the "fuel discharge side manifold 3" and "air discharge" in the present embodiment. The "side manifold 5" corresponds to an example of the "second manifold" in the present invention. Further, the "fuel cell 11 anode inlet 121" and "fuel cell 11 cathode inlet 131" in the present embodiment correspond to an example of the "fuel cell electrode inlet" in the present invention, and the "fuel cell electrode inlet 121" in the present embodiment corresponds to the "inlet". The "outlet 122 of the anode of the fuel cell 11" and the "outlet 132 of the cathode of the fuel cell 11" correspond to an example of the "outlet of the electrode of the fuel cell" in the present invention.

Two legs 755 and 755 are provided on the lower surface of the end plate 75 with respect to the + Z direction in FIG. Further, two legs 765 and 765 are provided on the lower surface of the end plate 76 with respect to the + Z direction in FIG. The legs 755,755,765,765 are placed on a horizontal plane to install the fuel cell stack 10. In this case, in the fuel cell stack 10, the fuel cell 11 is in a standing state (a state in which the stacking direction and the vertical direction intersect). In the fuel cell stack 10 of the present embodiment, a current collector (not shown) incorporated in the end plate 76 electrically connected to the cathode of the fuel cell 11 serves as a positive electrode and is electrically connected to the anode of the fuel cell 11. A current collector (not shown) incorporated in the end plate 75 serves as a negative electrode. By connecting these electrodes to an external load, electric power is supplied from the fuel cell stack 10 to the external load.

As shown in FIG. 3, the fuel cell 11 includes a membrane electrode assembly (MEA), a first bipolar plate 30, a second bipolar plate 35, a heating element 40, and an insulating portion 51. , 52, a conductor portion 55, and first to third sealing portions 60, 65, 70. In the fuel cell 11, the second bipolar plate 35, the membrane electrode assembly 20, the first bipolar plate 30, the insulating portion 51, the heating element 40 and the conductor portion 55, and the insulating portion 52 are shown in FIG. 3 in the stacking direction. It is sequentially laminated in the + Y direction in. The stacking direction of the plurality of fuel cells 11 in the fuel cell stack 10 and the stacking direction of the components of the fuel cell 11 in the fuel cell 11 are substantially the same. In the following description, each case is simply referred to as a stacking direction. The "membrane electrode assembly 20" in the present embodiment corresponds to an example of the "membrane electrode assembly" in the present invention, and the "first bipolar plate 30" and "second bipolar plate 35" in the present embodiment are the present. It corresponds to an example of the "bipolar plate" in the present invention, the "heating body 40" in the present embodiment corresponds to an example of the "heating body" in the present invention, and the "third sealing portion 70" in the present embodiment is the present. It corresponds to an example of the "sealing part" in the invention.

As shown in FIG. 4, the membrane electrode assembly 20 includes a polymer electrolyte membrane 21 having hydrogen ion (cation) conductivity, an anode catalyst layer 221, a cathode catalyst layer 231 and an anode gas diffusion layer 222. It includes a cathode gas diffusion layer 232. The anode catalyst layer 221 and the anode gas diffusion layer 222 form the anode of the fuel cell 11, and the cathode catalyst layer 231 and the cathode gas diffusion layer 232 form the cathode of the fuel cell 11.

The polymer electrolyte membrane 21, the anode catalyst layer 221 and the cathode catalyst layer 231 laminated on the front surface and the back surface thereof, and the anode gas diffusion layer 222 and the cathode gas diffusion layer 232 laminated on the front surface and the back surface thereof, respectively, The shape is appropriate according to the external shape of the direct methanol type fuel cell 1, such as a rectangular shape, a circular shape, an elliptical shape, and a polygonal shape.

The polymer electrolyte membrane 21 is not particularly limited, and a polymer electrolyte membrane such as a solid polymer electrolyte membrane mounted on a normal polymer electrolyte fuel cell can be used.

The anode catalyst layer 221 and the cathode catalyst layer 231 include an electrode catalyst such as a metal catalyst (platinum-based catalyst) made of platinum or a platinum alloy, and a carbon material having conductive pores that supports the electrode catalyst, for example. It is composed of the conductive carbon particles of the above and a polymer electrolyte having hydrogen ion conductivity. Since the anode catalyst layer 221 has a problem that carbon monoxide, which is an intermediate product, poisons the platinum-based catalyst, it is desirable that the anode catalyst layer 221 contains ruthenium or the like having carbon monoxide toxicity resistance.

The polymer electrolyte contained in the anode catalyst layer 221 and the cathode catalyst layer 231 and having the hydrogen ion conductivity to be attached to the catalyst-supporting particles is the same polymer electrolyte as that constituting the polymer electrolyte film 21, for example. Ionomers can be used. The polymer electrolytes constituting the anode catalyst layer 221 and the cathode catalyst layer 231 and the polymer electrolyte membrane 21 may be of the same type or different types.

The anode gas diffusion layer 222 is not particularly limited as long as it has a function and conductivity for efficiently guiding the fuel flowing from the anode flow path 311 (described later) of the first bipolar plate 30 to the anode catalyst layer 221. Similarly, the cathode gas diffusion layer 232 is not particularly limited as long as it has a function and conductivity of efficiently guiding the air flowing from the cathode flow path of the second bipolar plate 35 to the cathode catalyst layer 231. As the anode gas diffusion layer 222 and the cathode gas diffusion layer 232, various known gas diffusion layers can be used.

As the base material constituting the anode gas diffusion layer 222 and the cathode gas diffusion layer 232, a conductive porous base material having gas permeability and electron conductivity can be used. The same gas diffusion layer may be used on the cathode side and the anode side, or different gas diffusion layers may be used.

The membrane electrode assembly 20 is held by the frame 25. The frame 25 has corrosion resistance and electrical insulation against fuel, and is made of, for example, a known thermosetting resin such as a phenol resin or a known thermoplastic resin having heat resistance. The frame 25 is formed in a frame shape so as to surround the side surface of the membrane electrode assembly 20, and the membrane electrode assembly is joined to the opening corresponding to the shape of the membrane electrode assembly 20 formed in the center of the frame 25. The body 20 is arranged.

The frame 25 is formed with a fuel supply communication hole 251, a fuel discharge communication hole 252, an air supply communication hole 253, and an air discharge communication hole 254 around the opening formed in the center. These communication holes 251,252,253,254 have a substantially rectangular shape when viewed from the stacking direction, and penetrate the frame 25 along the stacking direction. The frame 25 is not an indispensable configuration, and the frame 25 may be omitted by forming the above-mentioned communication holes in a part of the widely formed membrane electrode assembly 20.

As shown in FIGS. 2 and 3, the first bipolar plate 30 has a function of guiding electrons generated in the membrane electrode assembly 20 while isolating the adjacent membrane electrode assemblies 20 and 20 from each other. As the material constituting such a first bipolar plate 30, for example, a metal material, graphite, or the like can be used. Among these, a metal material is preferable from the viewpoint of ease of processing. Further, from the viewpoint of preventing corrosion by fuel, the surface of the first bipolar plate 30 may be plated with gold or the like.

The first bipolar plate 30 is arranged so as to face the anode of the membrane electrode assembly 20. The main surface of the first bipolar plate 30 facing the membrane electrode assembly 20 (hereinafter, referred to as "first main surface 31") corresponds to the anode gas diffusion layer 222 of the membrane electrode assembly 20. I'm in contact. As a result, the first bipolar plate 30 can receive the electrons generated at the anode of the fuel cell 11.

As shown in FIGS. 3 and 5A, the first bipolar plate 30 has a fuel supply communication hole 301, a fuel discharge communication hole 302, an air supply communication hole 303, and an air discharge communication hole 304. Have. These communication holes 301, 302, 303, 304 have a substantially rectangular shape when viewed from the stacking direction, and penetrate the first bipolar plate 30 along the stacking direction. The "fuel supply communication hole 301" and the "air supply communication hole 303" in the present embodiment correspond to an example of the "first communication hole" in the present invention, and the "fuel discharge communication hole 302" and "air" in the present embodiment. The “discharge communication hole 304” corresponds to an example of the “second communication hole” in the present invention.

As shown in FIG. 5A, a plurality of anode flow paths 311 which are grooves opened on the first main surface 31 are formed on the first main surface 31. The anode flow path 311 is formed at least in a region where the membrane electrode assembly 20 and the first bipolar plate 30 overlap each other (hereinafter, also referred to as “overlapping region Z ₁ ”) in the stacking direction. The "overlapping region Z ₁ " in the present embodiment corresponds to an example of the "overlapping region" in the present invention.

One end of the anode flow path 311 is connected to the fuel supply communication hole 301. On the other hand, the other end of the anode flow path 311 is connected to the fuel discharge communication hole 302. The anode flow path 311 is formed linearly along the vertical direction between the fuel supply communication hole 301 and the fuel discharge communication hole 302. The anode flow path 311 is not particularly limited to the above, and is composed of, for example, a plurality of linear grooves and a plurality of turn-shaped grooves connecting adjacent linear grooves, although not particularly shown. It may have a serpentine shape.

A first sealing portion 60 is provided on the first main surface 31 of the first bipolar plate 30. The first sealing portion 60 is interposed between the frame 25 and the first bipolar plate 30. The first sealing portion 60 is deformed by applying a tightening load by a fastening bolt, and is brought into close contact with the frame 25 and the first bipolar plate 30, so that the frame 25 and the first bipolar plate 30 are brought into close contact with each other. The space is sealed. As such a first sealing portion 60, one known in the art such as rubber can be used.

A part of the first sealing portion 60 is provided so as to collectively surround the fuel supply communication hole 301, the fuel discharge communication hole 302, and the anode flow path 311 when viewed from the stacking direction. It is allowed that the fuel supply side manifold 2 and the fuel discharge side manifold 3 are connected to each other through the anode flow path 311. Further, a part of the first sealing portion 60 surrounds the air supply communication hole 303 when viewed from the stacking direction in order to prevent air from flowing out from the air supply side manifold 4. Similarly, a part of the first sealing portion 60 surrounds the air discharge communication hole 304 when viewed from the stacking direction in order to prevent the air and cathode products from flowing out from the air discharge side manifold 5. There is.

As shown in FIGS. 2 and 3, the second bipolar plate 35 is generated in the membrane electrode assembly 20 while isolating the adjacent membrane electrode assemblies 20 and 20 from each other, similarly to the first bipolar plate 30. It has the function of guiding the electrons. The second bipolar plate 35 is arranged so as to face the cathode of the membrane electrode assembly 20. The membrane electrode assembly 20 is sandwiched between the first and second bipolar plates 30 and 35, and is gripped by these bipolar plates 30 and 35 by the action of a tightening load by the fastening bolts. As the material constituting such a second bipolar plate 35, the same material as the material constituting the first bipolar plate 30 described above can be used.

The main surface of the second bipolar plate 30 on the side facing the membrane electrode assembly 20 (hereinafter, referred to as "first main surface 36") corresponds to the cathode gas diffusion layer 232 of the membrane electrode assembly 20. I'm in contact. As a result, a movement path is formed in which the electrons generated at the anode of the fuel cell 11 move to the cathode side.

As shown in FIGS. 3 and 5B, the second bipolar plate 35 has a fuel supply communication hole 351, a fuel discharge communication hole 352, an air supply communication hole 353, and an air discharge communication hole 354. Have. These communication holes 351, 352, 353, 354 have a substantially rectangular shape when viewed from the stacking direction, and penetrate the second bipolar plate 35 along the stacking direction.

As shown in FIG. 5B, a plurality of cathode flow paths 361, which are grooves opened on the first main surface 36, are formed on the first main surface 36. The cathode channel 361 in the stacking direction, are formed at least in the overlapping region Z _1. One end of the cathode flow path 361 is connected to the air supply communication hole 353. On the other hand, the other end of the cathode flow path 361 is connected to the air discharge communication hole 354. The cathode flow path 361 is formed linearly along the width direction between the air supply communication hole 353 and the air discharge communication hole 354. The cathode flow path 361 may have a serpentine shape like the anode flow path 311.

A second sealing portion 65 is provided on the first main surface 36. The second sealing portion 65 is interposed between the frame 25 and the second bipolar plate 35. The second sealing portion 65 is deformed by applying a tightening load by a fastening bolt, and is brought into close contact with the frame 25 and the second bipolar plate 35, whereby the frame 25 and the second bipolar plate 35 are brought into close contact with each other. The space is sealed. As the material forming the second sealing portion 65, the same material as the material forming the first sealing portion 60 can be used.

A part of the second sealing portion 65 is provided so as to collectively surround the air supply communication hole 353, the air discharge communication hole 354, and the cathode flow path 361 when viewed from the stacking direction. It is allowed that the air supply side manifold 4 and the air discharge side manifold 5 are connected to each other through the cathode flow path 361. A part of the second sealing portion 65 surrounds the fuel supply communication hole 351 when viewed from the stacking direction in order to prevent fuel from flowing out from the fuel supply side manifold 2. Similarly, a part of the second sealing portion 65 surrounds the fuel discharge communication hole 352 when viewed from the stacking direction in order to prevent fuel and anode products from flowing out from the fuel discharge side manifold 3. There is.

As shown in FIGS. 2 and 3, in the first bipolar plate 30 of the present embodiment, on the main surface (hereinafter, referred to as “second main surface 32”) opposite to the first main surface 31. Is provided with a heating element 40, a conductor portion 55, and a third sealing portion 70.

The heating element 40 is provided to prevent the in-plane temperature of the membrane electrode assembly 20 from becoming non-uniform due to the heat generated by the power generation of the fuel cell 11. The heating element 40 of the present embodiment heats the membrane electrode assembly 20 from the anode side of the membrane electrode assembly 20 via the first bipolar plate 30.

As shown in FIG. 3, the heating element 40 has a main body 41 and first and second terminals 42 and 43. The main body 41 has a PTC (Positive Temperature Coefficient) characteristic in which the electric resistance value of the main body 41 increases with a positive coefficient as the temperature rises. A PTC heater can be used as such a main body 41. Examples of PTC heaters include conductors such as carbon particles that generate heat when energized (specifically, Joule heat is generated according to the resistance of the conductor when energized) and heat that expands and contracts according to temperature. Examples thereof include those formed by blending with responsive insulating (non-conductive) particles. In such a PTC heater, when energized, the conductor generates heat, which heats and expands the heat-responsive insulating particles. Thermal response When the insulating particles expand, the conductors separate from each other, making it difficult for current to flow, and the heat generated by the conductors subsides. As described above, the PTC heater has a temperature self-control function that changes the ease of current flow according to the temperature and stabilizes at a predetermined temperature. The main body 41 is not particularly limited to the PTC heater. For example, it may be a general heating element using nichrome wire or carbon fiber.

As shown in FIGS. 6 (A) and 6 (B), the main body 41 of the present embodiment is viewed from the vertical direction among the regions in which the overlapping region Z ₁ is divided into two with respect to the vertical direction when viewed from the stacking direction. It is located in the lower area when viewed. Here, when the membrane electrode assembly 20 generates heat with the power generation of the fuel cell 11, heat is transferred toward the upper side in the vertical direction due to the influence of heat diffusion. Therefore, in the plane of the membrane electrode assembly 20, the upper region in the vertical direction has a relatively high temperature, and the lower region has a relatively low temperature, resulting in non-uniform temperature. In the present embodiment, on the basis of non-uniform in-plane temperature of the above-described membrane electrode assembly 20, of the sides of the rectangular overlap region Z1, overlap region Z ₁ extending in the + Z direction shown in FIG. 6 (A) as 2 divides the sides with respect to the vertical direction, are divided into two overlapping regions Z ₁ with respect to the vertical direction. In the present specification, when the structure having legs is placed on a horizontal plane as shown in FIG. 1, the upper region of the region in which the overlapping region Z ₁ is divided into two in the vertical direction is referred to as the high temperature region Z ₂ . It referred, called the lower region and low temperature region Z _3.

The method of dividing the high temperature region Z ₂ and the low temperature region Z ₃ in the overlapping region Z ₁ differs depending on the performance of the fuel cell 11 to be used and the usage environment of the fuel cell 11. In the present embodiment, the high temperature region Z ₂ passes through the center of the overlapping region Z ₁ and extends above the virtual straight line L ₁ extending in the width direction of the fuel cell 11, and the temperature region Z ₂ is located above the virtual straight line L _{1 with} respect to FIG. It has a lower low temperature region Z _3. In this case, the widths of the high temperature region Z ₂ and the low temperature region Z ₃ (the length in the width direction of the fuel cell 11) are substantially the same as the width of the membrane electrode assembly 20. On the other hand, the height (length in the vertical direction) of the high temperature region Z ₂ and the low temperature region Z _{3 is about half} the height of the membrane electrode assembly 20.

In the present embodiment, from the viewpoint of uniformly heating the entire low temperature region Z ₃ , the main body 41 is arranged so as to overlap the entire low temperature region Z _{3 when} viewed from the stacking direction. The form of arrangement of the main body 41 is not particularly limited as long as at least a part of the main body 41 is arranged in the lower region of the region obtained by dividing the overlapping region Z ₁ into two in the vertical direction. For example, the main body 41 may be arranged so as to overlap a part of the low temperature region Z _{3 when} viewed from the stacking direction. Further, a portion of the body portion 41 may be disposed protrudes from the low temperature region Z ₃ when viewed from the laminating direction. Further, the outer shape of the main body portion may be larger than the outer shape of the low temperature region Z ₃ when viewed from the stacking direction may be smaller.

As shown in FIG. 6B, the main body 41 of the present embodiment is an elongated plate-shaped member. The main body 41 has a rectangular planar shape when viewed from the stacking direction, and has parallel opposite sides including short sides 411 and 412 and long sides 413 and 414. In the main body 41 of the present embodiment, the short sides 411 and 412 extend substantially parallel to the vertical direction, and the long sides 413 and 414 extend substantially parallel to the width direction. The "short sides 411,412" in the present embodiment correspond to an example of the "side sides" in the present invention.

The first and second terminals 42 and 43 are band-shaped members and are provided to supply electric power to the main body 41. From the short side 411 of the main body 41, the first terminal 42 is on the side away from the center of the main body 41 and extends in the horizontal direction with respect to the long sides 413 and 414 of the main body 41. The first terminal 42 is arranged so as not to overlap the plurality of communication holes 301, 302, 303, 304 formed in the first bipolar plate 30 when viewed from the stacking direction.

As shown in FIG. 7, the first terminal 42 is arranged apart from the first bipolar plate 30 in order to prevent a short circuit with the first bipolar plate 30. The tip of the first terminal 42 projects outward from the outer edge of the first bipolar plate 30. A through hole 421 that penetrates the first terminal 42 along the stacking direction is formed at the tip of the first terminal 42. The "first terminal 42" in the present embodiment corresponds to an example of the "first terminal" in the present invention.

As shown in FIG. 6B, from the short side 412 of the main body 41, the second terminal 43 is on the side away from the center of the main body 41 with respect to the long sides 413 and 414 of the main body 41. It extends in the horizontal direction. The second terminal 43 is arranged so as not to overlap the plurality of communication holes 301, 302, 303, 304 formed in the first bipolar plate 30 when viewed from the stacking direction.

As shown in FIG. 7, the second terminal 43 is arranged apart from the first bipolar plate 30 in order to prevent a short circuit with the first bipolar plate 30. The tip of the second terminal 43 projects outward from the outer edge of the first bipolar plate. A through hole 431 that penetrates the second terminal 43 along the stacking direction is formed at the tip of the second terminal 43. The "second terminal 43" in the present embodiment corresponds to an example of the "second terminal" in the present invention.

As shown in FIGS. 2 and 3, in the present embodiment, an insulating portion 51 having electrical insulation is interposed between the first bipolar plate 30 and the heating element 40. If the PTC heater as a heating element and the bipolar plate are in direct contact with each other, the contacting portion becomes a short-circuit path through which the current generated by the power generation of the fuel cell flows, and the heating element may malfunction. is there. In addition, the heating element consumes the electric power output from the fuel cell, which may deteriorate the power generation characteristics of the fuel cell. The insulating portion 51 of the present embodiment electrically insulates between the first bipolar plate 30 and the heating element 40, so that the above-described heating element malfunctions and the power generation characteristics of the fuel cell 11 deteriorate. Preventing problems.

The insulating portion 52 is interposed between the heating element 40 and the second bipolar plate 35 constituting another fuel cell 11 adjacent to the above-mentioned fuel cell 11 in the stacking direction, and electrically insulates them. doing.

From the viewpoint of ensuring electrical insulation between the heating element 40 and the first and second bipolar plates 30 and 35, the insulating portions 51 and 52 are at least the entire main body portion 41 when viewed from the stacking direction. It is preferable that it is formed so as to overlap with. As such insulating portions 51 and 52, it is preferable to use a material that does not deteriorate or deform up to about 90 ° C. For example, a sheet made of a thermosetting resin such as a polyimide resin or a fluororesin, a resin material such as a known thermoplastic resin having heat resistance (for example, Super Empra), or a rubber material such as silicone rubber or EP rubber. Can be used. The insulating portion is not particularly limited to the above, and only one insulating portion may be provided so as to surround the entire heating element 40.

Conductor 55, as shown in FIG. 6 (A) and 6 (B), when viewed from the laminating direction, are provided so as to overlap with the high-temperature region Z _2. The conductor portion 55 electrically connects the first bipolar plate 30 and the second bipolar plate 35 constituting another fuel cell 11 adjacent to the above-mentioned fuel cell 11 in the stacking direction. The heating element 40 and the conductor portion 55 are arranged apart from each other and electrically insulated. The material constituting such a conductor portion 55 may be any material having heat resistance and conductivity. For example, a metal material or a material obtained by dispersing a conductive material in a heat-resistant resin material may be used. Can be used. The material constituting the conductor portion 55 preferably has corrosion resistance to fuel.

As shown in FIG. 2, in the fuel cell stack 10, from the viewpoint of evenly applying the tightening load by the fastening bolt to the in-plane of the fuel cell 11, the thickness of the conductor portion 55 and the heating element 40 are formed in the stacking direction. It is preferable that the thicknesses are substantially the same. Specifically, as shown in FIG. 3, the thickness of the conductor portion 55, the thickness of the main body portion 41, the thickness of the insulating portion 51, and the thickness of the insulating portion 52 It is preferable that the sum of the sums is substantially equal.

As shown in FIG. 6A, the third sealing portion 70 is interposed between the first bipolar plate 30 and the second bipolar plate 35 constituting the adjacent fuel cell 11. The third sealing portion 70 is deformed by applying a tightening load by a fastening bolt, and is brought into close contact with the first and second bipolar plates 30 and 35, whereby the first and second bipolar plates are brought into close contact with each other. The space between the plates 30 and 35 is sealed. As the material constituting the third sealing portion 70, the same material as the material constituting the first sealing portion 60 can be used.

The third sealing portion 70 includes a first annular portion 701, a second annular portion 702, a third annular portion 703, a fourth annular portion 704, and a fifth annular portion 705. Have. The first annular portion 701 is formed so as to collectively surround the main body portion 41 and the conductor portion 55 when viewed from the stacking direction. The first annular portion 701 is formed on a plurality of first bipolar plates 30 for the purpose of suppressing deterioration of the heating element 40 due to the fuel flowing out from the manifolds 2, 3, 4, and 5. The communication holes 301, 302, 303, 304 and the heating element 40 are sealed and provided. In this case, the first and second terminals 42 and 43 of the heating element 40 are provided across the first annular portion 701, penetrate the first annular portion 701, and the first annular portion. It extends from the inside to the outside of the 701. The mode in which the first and second terminals 42 and 43 cross the first annular portion 701 is not particularly limited to the above. For example, the main of the second bipolar plate 35 in which the sealing portion is provided on the second main surface 32 of the first bipolar plate 30 and constitutes another fuel cell 11 adjacent to the stacking direction of the fuel cell 11 described above. A sealing portion may be provided on the main surface of the surface facing the second main surface 32, and the first and second terminals 42 and 43 may cross between the two sealing portions. Further, the main of the second bipolar plate 35 which is provided with a sealing portion on the second main surface 32 of the first bipolar plate 30 and constitutes another fuel cell 11 adjacent to the above-mentioned fuel cell 11 in the stacking direction. The first and second terminals 42 and 43 may be provided between the second main surface 32 and the sealing portion of the surface.

The second annular portion 702 surrounds the fuel supply communication hole 301 when viewed from the stacking direction in order to prevent fuel from flowing out from the fuel supply side manifold 2. The third annular portion 703 surrounds the fuel discharge communication hole 302 when viewed from the stacking direction in order to prevent the fuel and the products of the anode from flowing out from the fuel discharge side manifold 3. The fourth annular portion 704 surrounds the air supply communication hole 303 when viewed from the stacking direction in order to prevent air from flowing out from the air supply side manifold 4. The fifth annular portion 705 surrounds the air discharge communication hole 304 when viewed from the stacking direction in order to prevent the air and cathode products from flowing out from the air discharge side manifold 5.

When the third sealing portion 70 is formed on the second main surface 32 of the first bipolar plate 30 as in the present embodiment, the first and second terminals 42 and 43 of the heating element 40 are formed. Is arranged so as not to overlap with the second to fifth annular portions 702, 703, 704, 705 of the third sealing portion 70 when viewed from the stacking direction.

As shown in FIGS. 1 and 8, in the fuel cell stack 10 of the present embodiment, the plurality of fuel cells 11 are arranged so that the first terminals 42 overlap each other in the stacking direction. The plurality of first terminals 42 are arranged at equal intervals with each other in the stacking direction. The through holes 421 of the plurality of first terminals 42 are arranged substantially coaxially along the stacking direction.

Further, the plurality of fuel cells 11 are arranged so that the second terminals 43 overlap each other in the stacking direction. The plurality of second terminals 43 are arranged at equal intervals with each other in the stacking direction. The through holes 431 of the plurality of second terminals 43 are arranged substantially coaxially along the stacking direction.

The first conductor wire 77 has a function of electrically connecting a plurality of first terminals 42 to an external power source (not shown) at once. The first conductor wire 77 is inserted into the through hole 421 of each of the first terminals 42, and extends linearly on the axis shared by the plurality of through holes 421. One end of the first conductor wire 77 is fixed to a first terminal 42 constituting one of the fuel cells 11 located at both ends of the plurality of stacked fuel cells 11. The other end of the first conductor wire 77 is electrically connected to an external power source (not shown).

The second conductor wire 78 has a function of electrically connecting a plurality of second terminals 43 to an external power source (not shown) at once. The second conductor wire 78 is inserted into the through hole 431 of each of the second terminals 43, and extends linearly on the axis shared by the plurality of through holes 431. One end of the second conductor wire 78 is fixed to a second terminal 43 constituting one of the fuel cells 11 located at both ends of the plurality of stacked fuel cells 11. The other end of the second conductor wire 78 is electrically connected to an external power source (not shown). The first and second conductor wires 77 and 78 are made of a metal material having high conductivity such as copper.

The operation of the fuel cell stack 10 of the present embodiment will be described below.

The fuel cell stack 10 of the present embodiment operates as follows. First, as shown in FIG. 2A, fuel is supplied to the fuel supply side manifold 2 from the fuel supply port 751 of the end plate 75. The fuel supply side manifold 2 distributes and supplies fuel to the anodes of the plurality of fuel cells 11. Then, fuel is introduced into the anode flow path 311 of the first bipolar plate 30 (see the arrow in FIG. 2A). On the other hand, as shown in FIG. 2B, air is supplied to the air supply side manifold 4 from the air supply port 753 of the end plate 75. The air supply side manifold 4 distributes and supplies air to the cathodes of the plurality of fuel cells 11. Then, air is introduced into the cathode flow path 361 of the second bipolar plate 35 (see the arrow in FIG. 2B).

As a result, at the anode of each fuel cell 11,
[Number 1] CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻
Oxidation reaction occurs, and at the cathode of each fuel cell 11,
[Number ^{_{2] 3 / 2O 2 + 6H}} + + 6e - → 3H 2 O
The reduction reaction occurs. This causes a current to flow between the anode and the cathode.

Due to the chemical reaction (power generation reaction) shown above, the membrane electrode assembly 20 generates heat and the temperature rises. The generated heat moves in the plane of the membrane electrode assembly 20 due to the influence of heat diffusion. Specifically, heat is transferred upward in the vertical direction in the plane of the membrane electrode assembly 20. Therefore, the upper region of the in-plane of the membrane electrode assembly 20 divided into two in the vertical direction tends to have a relatively high temperature, and the lower region tends to have a relatively low temperature.

In a conventional fuel cell, the in-plane temperature of the membrane electrode assembly may become non-uniform in the vertical direction due to heat transfer (heat diffusion) toward the upper side in the vertical direction. Further, in general, in a fuel cell, the higher the temperature of the membrane electrode assembly, the more likely the power generation reaction occurs, and the lower the temperature of the membrane electrode assembly, the less likely the power generation reaction occurs. Therefore, the power generation reaction is less likely to occur in the lower region in the vertical direction in the plane of the membrane electrode assembly, which has a relatively low temperature. In this case, since the power generation reaction does not occur in the entire in-plane of the membrane electrode assembly, the fuel utilization efficiency in the fuel cell is lowered, and the expected output of the fuel cell is obtained from the reaction area of the membrane electrode assembly. There is a problem that it may not be possible. The fuel utilization efficiency can be expressed by the following equation (1).
A = (BC) / B ... (1)
However, in the above equation (1), A is the fuel utilization efficiency, B is the fuel supply amount, and C is the permeated fuel crossover amount and the amount of fuel that has not permeated through the cathode and has not been discharged to the anode discharge port. It is the total value with the fuel emission of the reaction.

Further, since the upper region in the vertical direction in the plane of the membrane electrode assembly becomes relatively hot, a local power generation reaction occurs, and local deterioration of the catalyst occurs in the upper region. There is a risk that it will end up. In this case, as a result of continuing the operation of the fuel cell, there is a problem that the power generation reaction may be delayed even in a region of the membrane electrode assembly where the temperature is relatively high, and the output of the fuel cell may decrease. There is.

In addition, a power generation reaction occurs locally in a region of the membrane electrode assembly where the temperature is relatively high, so that the membrane electrode assembly generates heat locally. Therefore, the non-uniformity of the in-plane temperature of the membrane electrode assembly further increases. When the temperature of the membrane electrode assembly exceeds a certain temperature, the fuel supplied to the anode of the fuel cell passes through the polymer electrolyte membrane without reacting and reaches the cathode of the fuel cell (so-called). , Crossover phenomenon) is likely to occur. In this case, there is a problem that the efficiency of fuel utilization in the fuel cell is further lowered, and the output of the fuel cell may be lowered.

As described above, in the conventional fuel cell, the in-plane temperature of the membrane electrode assembly is non-uniform in the vertical direction, which causes the above-mentioned problems in a complex manner, and as a result, the output of the fuel cell is increased. There was a problem that it was difficult to stabilize.

In contrast, the fuel cell 11 of the present embodiment, the lower region (low temperature region of the heat generating element 40 provided in the first bipolar plate 30, and divided into two overlapping regions Z ₁ with respect to the vertical direction region It is arranged so as to overlap with Z ₃ ). Therefore, since a region having a relatively low temperature can be partially heated in the in-plane of the membrane electrode assembly 20, non-uniformity of the in-plane temperature of the membrane electrode assembly 20 can be suppressed.

As a result, a power generation reaction occurs in the entire in-plane of the membrane electrode assembly 20, so that the fuel utilization efficiency in the fuel cell 11 can be improved. Further, since the power generation reaction occurs in the entire in-plane of the membrane electrode assembly 20, local deterioration of the catalyst is less likely to occur. Further, since the entire in-plane of the membrane electrode assembly 20 generates heat, it is possible to prevent the non-uniformity of the in-plane temperature of the membrane electrode assembly 20 from expanding, and it is possible to suppress the occurrence of fuel crossover. As a result, in the present embodiment, the output of the fuel cell 11 can be stabilized.

Further, since the heating element 40 is only arranged so as to overlap the low temperature region Z ₃ and is not arranged in the entire overlapping region Z ₁ , the manufacturing cost of the fuel cell 11 can be reduced.

When the temperature of the membrane electrode assembly 20 is excessively raised, the amount of air introduced into the cathode of the fuel cell 11 from the outside is increased to cool the entire in-plane of the membrane electrode assembly 20. However, in this case, since the non-uniformity of the in-plane temperature of the membrane electrode assembly 20 is suppressed, only the temperature of the entire in-plane of the membrane electrode assembly 20 is uniformly lowered. , Appropriate temperature control of the membrane electrode assembly 20 can be performed.

Further, in the present embodiment, a PTC heater is used as the heating element 40. Here, the output of the fuel cell stack 10 (fuel cell 11) and the fuel utilization efficiency increase as the temperature of the fuel cell stack 10 (fuel cell 11) rises, but above a predetermined temperature, the fuel crosses. Due to the effect of overshooting, the output of the fuel cell stack 10 (fuel cell 11) and the efficiency of fuel utilization decrease as the temperature rises. On the other hand, the PTC heater used in the present embodiment contains a conductor and heat-responsive insulating particles, and when the conductor is energized, heat is generated, which heats and expands the heat-responsive insulating particles. .. Thermal response When the insulating particles expand, the conductors separate from each other, making it difficult for current to flow, and the heat generated by the conductors subsides. In this way, the PTC heater has a temperature self-control function that changes the ease of current flow according to the temperature and stabilizes at a predetermined temperature, and is set so as not to exceed the predetermined temperature. The temperature of the membrane electrode assembly 20 can be stabilized at a predetermined temperature, and the output of the fuel cell stack 10 (fuel cell 11) and the fuel utilization efficiency can be stabilized in a high state.

Further, in the present embodiment, the manifolds 2, 3 and 3 are provided by providing a third sealing portion for sealing between the communication holes 301 and 302 formed in the first bipolar plate 30 and the heating element 40. The deterioration of the heating element 40 is suppressed by the fuel flowing out from the 4th and 5th.

Further, in the present embodiment, the heating element 40 is formed in a rectangular shape. In this case, the main body portion 41 as viewed from the lamination direction, since it is arranged so as to overlap the entire cold zone Z _3, evenly relatively entire regions of low temperatures in the plane of the membrane electrode assembly 20 Can be heated. As a result, the non-uniformity of the in-plane temperature of the membrane electrode assembly 20 can be further suppressed.

Further, in the present embodiment, the side away from the center of the main body 41 from the short side 411 of the rectangular heating element 40 when viewed from the stacking direction, and horizontally with respect to the long sides 413 and 414 of the main body 41. The first terminal 42 extends toward the center of the main body 41 from the short side 412 opposite to the short side 411 when viewed from the stacking direction, and extends to the long sides 413 and 414 of the main body 41. On the other hand, the second terminal 43 extends in the horizontal direction. Therefore, since electricity can be applied to substantially the entire heating element 40, the entire heating element 40 can be uniformly heated.

Further, in the fuel cell stack 10 of the present embodiment, a plurality of fuel cells 11 are laminated so that the first terminals 42 overlap each other and the second terminals 43 overlap each other in the stacking direction. There is. Then, these plurality of first terminals 42 are electrically connected to the first conductor wire 77 extending linearly, and the plurality of second terminals 43 are linearly extending second. It is electrically connected to the conductor wire 78. As a result, the plurality of first terminals 42 can be collectively electrically connected to the external power source, and the plurality of second terminals 43 can be collectively electrically connected to the external power source. The fuel cell stack 10 can be easily handled and the second conductor wires 77 and 78 can be miniaturized.

The fuel cell system 1 including the fuel cell stack 10 described above will be described with reference to FIG. FIG. 9 is a block diagram showing a fuel cell system according to an embodiment of the present invention.

As shown in FIG. 9, the fuel cell system 1 of the present embodiment includes a fuel cell stack 10 electrically connected to an external load, a fuel tank 80, a pump 81, a blower 82, a water tank 83, and the like. It includes a pump 84, a methanol tank 85, and a pump 86. The "fuel tank 80" and "pump 81" in the present embodiment correspond to an example of the "first supply means" in the present invention, and the "blower 82" in the present embodiment is the "second supply means" in the present invention. Corresponds to one example.

The fuel tank 80 stores a fuel (liquid fuel) in which a high-concentration methanol aqueous solution or methanol stock solution supplied from the methanol tank 85 and water supplied from the water tank 83 are mixed.

Pump 81, the fuel supply port 751 of the fuel cell stack 10 via the piping _{F 1,} for supplying fuel from the fuel tank 80. The fuel product (carbon dioxide) and unreacted discharged from the anode of the fuel cell 11 is returned to the fuel tank 80 via a pipe F ₂ connected to the fuel discharge port 752 of the fuel cell stack 10.

Blower 82, the air supply port 753 of the fuel cell stack 10 via the piping _{F 3,} for supplying air. An air filter (not shown) for removing dust and the like contained in the sucked air is provided on the suction side of the blower 82. The products (water, water vapor, carbon dioxide, etc.) discharged from the cathode of the fuel cell 11, the unreacted air, and the unreacted methanol that has permeated the membrane electrode assembly 20 are the air discharge port 754 of the fuel cell stack 10. It sent to the discharge facilities through pipes F ₄ connected to. In the discharge facility, the gas phase component such as carbon dioxide is separated from the liquid phase component such as water, and the gas phase component is discharged to the outside.

Stored in the water tank 83 water by a pump 84 and sent to the fuel tank 80 via a pipe F _5. Further, an aqueous methanol solution or methanol stock solution of high concentration stored in the methanol tank 85, a pump 86 and sent to the fuel tank 80 via a pipe F _6.

FIG. 10A is a view for explaining the fuel cell according to another embodiment of the present invention, and is a plan view of the second main surface of the first bipolar plate viewed from the stacking direction, FIG. 10 (A). B) is a plan view of the heating element and the conductor portion according to another embodiment of the present invention as viewed from the stacking direction. The same reference numerals are given to the same configurations as those in the above-described embodiment, the repeated description is omitted, and the description in the above-described embodiment is incorporated.

In the embodiment described below, since the heat diffuses in a circular shape, the heat distribution that can actually be generated is near the center of the membrane electrode assembly 20 where the heat does not easily escape, as shown in FIG. 10 (B). It was noted that the high temperature region Z ₂₁ having the arc-shaped region Z ₂₁₂ is often formed. Therefore, the fuel cell stack 11 will be described when the heat distribution is as shown in FIG. 10B.

As shown in FIG. 10A, in the present embodiment, the high temperature region Z ₂₁ and the low temperature region Z ₃₁ are set as follows in the overlapping region Z ₁ . That is, the high-temperature region _{Z 21} is combined with the upper area _{Z 211} to the virtual straight line _{L 1,} and the arcuate region _{Z 212} projecting downward in the vicinity of the center of the lower long side of the region _{Z 211} Area. On the other hand, the low temperature region Z ₃₁ is a region below the virtual straight line L ₁ that does not overlap with the region Z ₂₁₂ .

Since the vicinity of the outer edge of the membrane electrode assembly 20 is close to the outside of the fuel cell 11, heat is relatively easy to escape. On the other hand, since the vicinity of the center of the membrane electrode assembly 20 is far from the outside of the fuel cell 11, heat is relatively difficult to escape. Therefore, the vicinity of the center of the membrane electrode assembly 20 tends to be relatively hot, and the vicinity of the outer edge of the membrane electrode assembly 20 tends to be relatively low. That is, in the present embodiment, the heat transfer upward in the vertical direction in the plane of the membrane electrode assembly 20 and the heat from the center to the outer edge of the membrane electrode assembly 20 in the plane of the membrane electrode assembly 20. has set a high-temperature region _Z21 and the low temperature area Z ₃₁ based movement and the. Therefore, even in the area below the imaginary straight line L _1, a region overlapping with the center area of the membrane electrode assembly 20 (region Z ₂₁₂₎ is excluded from the low temperature region Z _31.

As shown in FIG. 10B, the main body 41B of the heating element 40B has a shape corresponding to the above-mentioned low temperature region Z ₃₁ when viewed from the stacking direction. That is, the main body 41B has long sides 413B and 414 located vertically with respect to the vertical direction, and has short sides 411 and 412 orthogonal to the long sides 413B and 414, and has long sides 413B. It has a shape having a recess 415 near the center. Here, as shown in FIG. 10B, the recess 415 is provided so as to open upward with respect to the vertical direction. The width of the recess 415 in the + X direction in FIG. 10B is preferably 1/4 to 1/8 of the width of the main body 41B in the + X direction in FIG. 10B, and is particularly 1/2. Is more preferable. Further, the depth of the recess 415 in the + Z direction of FIG. 10B is preferably 1/4 to 1/8 of the height of the main body 41B in the + Z direction of FIG. 10B, particularly 2 minutes. It is more preferable that it is 1. The conductor portion 55B has a shape corresponding to the high temperature region Z ₂₁ . That is, the conductor portion 55B has long sides located vertically in the vertical direction, has side sides orthogonal to the long sides, and is on the lower side of the conductor portion with respect to FIG. 10B. It has a shape having an arc-shaped convex portion protruding downward near the center of the long side. The "long side 413B" in the present embodiment corresponds to an example of the "upper side" in the present invention, the "long side 414" in the present embodiment corresponds to an example of the "lower side" in the present invention, and the "short side" in the present embodiment. "Sides 411,412" correspond to an example of "sides" in the present invention.

In the present embodiment, the heating element 40B is formed so as not to overlap with the vicinity of the center of the membrane electrode assembly 20 which tends to be relatively hot when viewed from the stacking direction. As a result, the vicinity of the center of the membrane electrode assembly generates heat, and further, the heating by the heating element prevents the vicinity of the center of the membrane electrode assembly from being overheated. As a result, the non-uniformity of the in-plane temperature of the membrane electrode assembly 20 can be further suppressed, and the output of the fuel cell 11 can be further stabilized.

FIG. 11 is a cross-sectional view of the bipolar plate according to another embodiment of the present invention as viewed from the width direction.

The bipolar plate 30B of the present embodiment is interposed between the membrane electrode assemblies 20 and 20 constituting the adjacent fuel cells 11 and 11 in the fuel cell stack 10. The first main surface 31 of the bipolar plate 30B faces the anode of one membrane electrode assembly 20 and is in contact with the anode gas diffusion layer 222 of the membrane electrode assembly 20. The second main surface 32B opposite to the first main surface 31 of the bipolar plate 30B faces the cathode of the other membrane electrode assembly 20, and meets the cathode gas diffusion layer 232 of the membrane electrode assembly 20. It is in contact.

In the bipolar plate 30B shown in FIG. 11, the anode flow path 311 is formed on the first main surface 31 facing the anode of the membrane electrode assembly 20, and the second main surface 32B facing the cathode of the membrane electrode assembly 20. A cathode flow path 321 is formed in the surface. Since the cathode flow path 321 has the same shape as the cathode flow path 361 in the above-described embodiment, the repeated description is omitted, and the description in the above-described embodiment is incorporated.

The heating element 40C is embedded inside the bipolar plate 30B. That is, the heating element 40C of the present embodiment is located on the −Y direction side of the first main surface 31 of the bipolar plate 30B with respect to FIG. 11, and is in the + Y direction of the second main surface 32B. Located on the side.

In order to prevent the bipolar plate 30B and the heating element 40C from being short-circuited, the entire main body 41 of the heating element 40C is covered with an insulating portion 51B having electrical insulation. Although not particularly shown, in order to prevent the bipolar plate 30B and the heating element 40C from short-circuiting, the portion of the first and second terminals of the heating element 40C that is embedded in the bipolar plate 30B is also insulated with electrical insulation. It is covered with a layer.

When the bipolar plate 30B of the present embodiment is used, since the first and second bipolar plates 30 and 35 are not required, the number of parts in the fuel cell 11 can be reduced, and the manufacturing cost of the fuel cell 11 can be reduced. it can.

It should be noted that the embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

For example, in the present embodiment, the heating element 40 is provided on the second main surface 32 of the first bipolar plate 30, but the heating element 40 is not particularly limited thereto, and the second bipolar plate 30 is replaced with the second heating element 40. Using the bipolar plate 35, a heating element is provided on the second main surface of the second bipolar plate 35 (the main surface of the second bipolar plate 35 opposite to the main surface facing the membrane electrode assembly 20). You may. In this case, similarly to the above embodiment, an insulating portion, a conductor portion, and a third sealing portion are also provided on the second main surface of the second bipolar plate 35.

1 ... Fuel cell system 2 ... Fuel supply side manifold 3 ... Fuel discharge side manifold 4 ... Air supply side manifold 5 ... Air discharge side manifold 10 ... Fuel cell stack 11 ... Fuel cell Z ₁ ... Overlapping area
Z ₂ , Z ₂₁ ... High temperature region
Z ₂₁₁ , Z ₂₁₂ ... Area
Z ₃ , Z ₃₁ ... Low temperature region 121 ... Anode inlet 122 ... Anode outlet 131 ... Cathode inlet 132 ... Cathode outlet 20 ... Membrane electrode assembly (MEA)
21 ... Polymer electrolyte membrane 221 ... Anode catalyst layer 222 ... Anode gas diffusion layer 231 ... Cathode gas diffusion layer 232 ... Cathode gas diffusion layer 25 ... Frame 251 ... Fuel supply communication hole 252 ... Fuel discharge communication hole 253 ... Air supply communication hole 254 … Air exhaust communication holes 30, 30B… First bipolar plate
301 ... Fuel supply communication hole
302 ... Fuel discharge communication hole
303 ... Air supply communication hole
304 ... Air discharge communication hole 31 ... First main surface
311 ... Anode flow path 32, 32B ... Second main surface
321 ... Cathode flow path 35 ... Second bipolar plate
351 ... Fuel supply communication hole
352 ... Fuel discharge communication hole
353 ... Air supply communication hole
354 ... Air discharge communication hole 36 ... First main surface
361 ... Cathode flow path 37 ... Second main surface 40, 40B, 40C ... Heating element 41, 41B, 41C ... Main body
411,412 ... Short side
413,414 ... Top
415 ... Recesses 42, 43 ... First and second terminals
421, 431 ... Through holes 51, 52 ... Insulation part 55 ... Conductor part 60 ... First sealing part 65 ... Second sealing part 70 ... Third sealing part 701 ... First annular part 702 ... First 2 annular part 703 ... 3rd annular part 704 ... 4th annular part 705 ... 5th annular part 75 ... End plate 751 ... Fuel supply port 752 ... Fuel discharge port 753 ... Air supply port 754 ... Air discharge port 755 ... Leg 76 ... End plate 765 ... Leg 77, 78 ... First and second conductor wires 80 ... Fuel tank 81 ... Pump 82 ... Blower 83 ... Water tank 84 ... Pump 85 ... Methanol tank 86 ... Pump F ₁ ~ F ₆ ... Piping

Claims (7)

A fuel cell comprising a membrane electrode assembly and a pair of bipolar plates sandwiching the membrane electrode assembly.
In the stacking direction of the membrane electrode assembly and the bipolar plate, the membrane electrode assembly and the bipolar plate overlap each other in an overlapping region.
The fuel cell further comprises a heating element provided on at least one of the pair of bipolar plates.
The heating element has an upper side and a lower side located vertically with respect to the vertical direction, has a side side orthogonal to the upper side and the lower side, and has a recess in the vicinity of the center of the upper side. fuel cell are disposed so as to overlap only an area of the overlapping region of two divided areas sac Chi lower with respect to the vertical direction. The fuel cell according to claim 1.
The heating element is a fuel cell which is a PTC heater. The fuel cell according to claim 1 or 2.
The bipolar plate is
The first communication hole constituting the first manifold connected to the inlet of the electrode of the fuel cell, and
It has a second communication hole that constitutes a second manifold that connects to the outlet of the electrode of the fuel cell.
The fuel cell is a fuel cell further comprising a sealing portion for sealing between the first communication hole and the second communication hole and the heating element. The fuel cell according to any one of claims 1 to 3 .
The heating element is
A first terminal extending from one of the side surfaces of the heating element and
A fuel cell having a second terminal extending from the other side of the heating element. A fuel cell stack including a plurality of fuel cells according to claim 4 .
The plurality of fuel cells are laminated so that the first terminals overlap each other and the second terminals overlap each other in the stacking direction.
The fuel cell stack
A first conductor wire extending linearly and electrically connected to the plurality of the first terminals,
A fuel cell stack comprising a second conductor wire extending linearly and electrically connected to the plurality of said second terminals.
The fuel cell according to any one of claims 1 to 4 , or the fuel cell stack according to claim 5.
A first supply means for supplying fuel to the anode of the fuel cell,
A fuel cell system comprising a second supply means for supplying an oxidizing agent to the cathode of the fuel cell. A bipolar plate used in fuel cells and placed opposite a membrane electrode assembly.
In a state where the membrane electrode assembly and the bipolar plate are laminated, the membrane electrode assembly and the bipolar plate overlap each other in an overlapping region in the stacking direction of the membrane electrode assembly and the bipolar plate. ,
The heating element is arranged so as to overlap only the lower region of the region obtained by dividing the overlapping region into two in the vertical direction .
The heating element has an upper side and a lower side located vertically with respect to the vertical direction, has a side side orthogonal to the upper side and the lower side, and has a concave portion near the center of the upper side. plate.

Images