JP4776788B2 - Fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell having an insulating structure on an outer peripheral portion.
[0002]
[Prior art]
As shown in FIG. 7, in the fuel cell 87, an electrode membrane structure 84 composed of a solid polymer electrolyte membrane 81 and anode electrodes 82 and cathode electrodes 83 on both sides thereof is sandwiched between a pair of separators 85 and 86. There is something configured as. A plurality of fuel cells 87 are stacked to constitute a fuel cell stack. In this fuel cell 87, a flow path 88 of fuel gas (for example, hydrogen) is provided on the surface of the separator 85 disposed opposite to the anode electrode 82, and an oxidant gas (on the surface of the separator 86 disposed opposite to the cathode electrode 83). For example, a flow path 89 of oxygen-containing air) is provided, and a cooling medium flow path 90 is provided between the adjacent separators 85 and 86.
[0003]
In the fuel cell 87, when fuel gas is supplied to the reaction surface of the anode electrode 82, hydrogen is ionized here and moves to the cathode electrode 83 side through the solid polymer electrolyte membrane 81. Electrons generated during this time are taken out to an external circuit and used as direct current electric energy. Since the oxidant gas is supplied to the cathode electrode 83, hydrogen ions, electrons, and oxygen react to generate water. Further, the power generation surface is cooled by the cooling medium flowing between the separators 85 and 86.
[0004]
Since the reaction gas and the cooling medium need to pass through independent flow paths, the flow paths are partitioned by a seal member 91.
The sealing part includes a periphery of a communication hole formed through the separators 85 and 86 to distribute and supply the reaction gas and the cooling medium to each fuel cell 87 of the fuel cell stack, the outer periphery of the electrode film structure 84, the separators 85 and 86. And the outer periphery of the front and back surfaces of the separators 85 and 86.
[0005]
By the way, the separators 85 and 86 are generally made of a conductive material (for example, carbon or metal), and the outer periphery of the separators 85 and 86 is exposed at the outer periphery of the fuel cell, so that the conductive portion is exposed. .
In the fuel cell configured as described above, if a foreign substance having conductivity such as condensed water or iron powder adheres to the outer periphery of the separators 85 and 86, there is a possibility of a short circuit. In addition, there is a possibility that an operator accidentally contacts the outer periphery of the separators 85 and 86 during maintenance of the fuel cell stack.
[0006]
[Problems to be solved by the invention]
In order to cope with this, as shown in FIG. 8, an insulating member 92 made of rubber or the like is provided on the outer periphery of each separator 85, 86.
However, in this case, since the insulating member 92 is attached to each of the separators 85 and 86, there are problems that the number of parts increases and the number of work steps increases.
[0007]
Moreover, although the insulation of the outer periphery of the separators 85 and 86 is ensured, since the outer periphery of the polymer membrane structure 84 is exposed and exposed to the outside air, the solid polymer electrolyte membrane 81 is dried, resulting in performance deterioration. There is a fear.
Furthermore, if the outer periphery of the polymer membrane structure 84 is exposed to the outside air, the solid polymer electrolyte membrane 81 is greatly affected by the swelling due to humidity, so that humidity management is required in the environment of the fuel cell stack assembly process. It was cumbersome.
[0008]
Here, if the thickness of the insulating member 92 is increased and the adjacent insulating members 92 are brought into contact with each other, the outer periphery of the polymer membrane structure 84 is not exposed, and the solid polymer electrolyte membrane is formed. It is possible to solve the problem of humidity management during the drying and assembly process of 81. However, in this case, in order to ensure the sealing performance, it is necessary to ensure the contact between the insulating members 92 and the contact between the separators 85 and 86 and the electrode film structure 84 at the same time. It becomes necessary to manage the thickness of 91 with high accuracy, resulting in inferior mass productivity.
[0009]
Japanese Patent Application Laid-Open No. 7-29592 discloses an insulating member provided on the outer periphery of each separator on both sides of the polymer membrane structure, and the outer periphery of the solid polymer electrolyte membrane is sandwiched between these insulating members. A fuel cell stack is disclosed in which an outer frame surrounding the outside of a solid polymer electrolyte membrane is provided and the outer frames are sequentially connected by a connecting member. In this way, it is possible to prevent the solid polymer electrolyte membrane from being dried, but humidity management is required until the fuel cell stack is completed by connecting the outer frames to each other. The problem of humidity management cannot be solved. In addition, this increases the number of parts.
[0010]
As an approximate technique, as disclosed in JP-A-5-101837, the outer periphery of the polymer membrane structure is surrounded by a seal member, and the polymer membrane structure and the separator are surrounded by the seal member. There is also a fuel cell in which the gap is sealed, but in this fuel cell, since the outer periphery of the separator is exposed, the above-mentioned problem due to the exposure of the conductive portion cannot be solved.
Accordingly, the present invention provides a fuel cell that can ensure insulation at the outer periphery of the fuel cell, can prevent the solid polymer electrolyte membrane from drying, and is excellent in assemblability.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the invention according to claim 1, the solid polymer electrolyte membrane (e.g., a solid polymer electrolyte membrane 12 in the embodiment described below) the anode electrode (e.g., in the embodiment described below Fuel sandwiched between an anode electrode 13) and a cathode electrode (for example, cathode electrode 14 in an embodiment described later), and the outside thereof is sandwiched between a pair of separators (for example, separators 16 and 17 in an embodiment described later). In a battery (for example, the fuel cell 15 in an embodiment described later), the outer periphery of the pair of separators has a substantially U-shaped cross section, and the outer peripheral edge of the pair of separators (for example, the thin portion 16a in the embodiment described later). mounted so as to straddle the 17a) insulating cover around the periphery of said pair of separators (e.g., below The insulation cover 30) in the form of facilities provided, the insulating cover between the fuel cell adjacent when stacking the fuel cells to each other, characterized in that sealing between the fuel cell and pressure.
With this configuration, only one insulating cover is required for the pair of separators, and the number of parts can be reduced. Further, it becomes possible to insulate the entire outer periphery of the fuel cell. Furthermore, the outer periphery of the solid polymer electrolyte membrane is not exposed and is not exposed to the outside air.
According to a second aspect of the present invention, in the first aspect of the invention, the insulating cover has a semi-circular pressure contact surface projecting outward on an outer surface disposed on one separator side, and the other The outer surface disposed on the separator side has a flat pressure contact surface, and when the two fuel cells are stacked, the pressure contact surface having a semicircular cross section in the insulation cover of one fuel cell and the insulation cover of the other fuel cell The flat pressure contact surface in FIG. 2 is in pressure contact with each other to seal between the fuel cells.
With this configuration, it is possible to reliably seal between the two fuel cells.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a fuel cell according to the present invention will be described below with reference to the drawings of FIGS.
FIG. 1 is a longitudinal sectional view of an in-vehicle fuel cell stack 11, which has a solid polymer electrolyte membrane 12 sandwiched between an anode electrode 13 and a cathode electrode 14, and a pair of separators on the outside. A plurality of fuel cells 15 sandwiched between 16 and 17 are stacked in the horizontal direction.
[0013]
Between the anode electrode 13 and the separator 16 adjacent to the anode electrode 13, a fuel gas flow path 18 through which fuel gas (for example, hydrogen gas) flows is formed. Further, an oxidant gas flow path 19 through which an oxidant gas (for example, oxygen-containing gas or air) flows is formed between the cathode electrode 14 and the separator 17 adjacent thereto.
[0014]
Further, a coolant flow path 20 is formed between the back surfaces of the separators 16 and 17 for circulating a coolant (pure water, ethylene glycol, oil, etc.) for cooling the fuel cell 15.
[0015]
And in order to supply the said hydrogen gas, air, and a cooling fluid to each flow path 18,19,20, the solid polymer electrolyte membrane 12 of each fuel cell 15, and the separators 16 and 17 are penetrated, and communication hole 25a, 25b, 26a, 26b, 27a, 27b are formed respectively. Each communication hole 25a, 25b, 26a, 26b, 27a, 27b will be described in detail below. The stacked fuel cells 15 are fastened by stud bolts (not shown).
[0016]
Next, a specific shape of the separator 17 adjacent to the cathode electrode 14 will be described with reference to FIG.
The separator 17 is made of carbon, and the surface facing the cathode electrode 14 and the opposite surface are set in a rectangular shape. For example, the long side is oriented in the horizontal direction and the short side is oriented in the direction of gravity. Has been.
[0017]
On the lower side of both edge portions on the short side of the separator 17, there are communication holes 25a on the oxidant gas supply side for allowing the oxidant gas to pass therethrough, and communication holes 26a on the fuel gas supply side for allowing the fuel gas to pass through. However, the separator 17 has a communication hole 25b on the short side and a communication hole 25b on the oxidant gas discharge side and a fuel gas discharge side. The communication hole 26b is provided with a long shape in the vertical direction so as to be diagonal to the communication holes 25a and 26a.
[0018]
The upper end edge on the long side of the separator 17 is provided with two coolant supply side communication holes 27a, 27a that are long in the longitudinal direction (left and right in FIG. 4), and the lower end edge on the long side. Similarly, there are provided two communication holes 27b, 27b on the coolant discharge side that are long in the longitudinal direction.
The coolant is supplied to the communication holes 27a and 27a on the coolant supply side.
[0019]
On the surface of the separator 17 that faces the cathode electrode 14, an oxidant gas flow channel 19 a that connects the oxidant gas supply side communication hole 25 a and the oxidant gas discharge side communication hole 25 b meanders in the horizontal direction. However, it is provided in the direction of gravity.
The oxidant gas flow channel 19 is formed by closing the opening of the oxidant gas flow channel groove 19 a with the cathode electrode 14.
[0020]
The oxidant gas flows into the oxidant gas passage groove 19a from the communication hole 25a on the oxidant gas supply side, flows meandering in the direction of gravity, and flows out from the communication hole 25b on the oxidant gas discharge side. . In addition, the groove | channel is not formed in the surface facing the separator 16 in the separator 17, but it is a flat surface.
[0021]
Next, a specific shape of the separator 16 adjacent to the anode electrode 13 will be described with reference to FIG.
The separator 16 is also made of carbon and has the same shape as the separator 17. Like the separator 17, the separator 16 has a communication hole 25 a on the oxidant gas supply side, a communication hole 25 b on the oxidant gas discharge side, and a fuel gas. A communication hole 26a on the fuel gas supply side for passing through, a communication hole 26b on the fuel gas discharge side, communication holes 27a and 27a on the coolant supply side, and communication holes 27b and 27b on the coolant discharge side are provided. Yes.
[0022]
Although not shown in the surface of the separator 16 facing the anode electrode 13, a fuel gas flow channel configured similarly to the oxidant gas flow channel groove 19 a formed on the surface of the separator 17 facing the cathode electrode 14. A groove is formed, and the fuel gas channel 18 is formed by closing the opening of the fuel gas channel groove with the anode electrode 13. The fuel gas flows out from the communication hole 26b on the fuel gas discharge side through the fuel gas flow channel groove from the communication hole 26a on the fuel gas supply side.
[0023]
On the other hand, on the surface of the separator 16 facing the separator 17, as shown in FIG. 5, the communication holes 27 a and 27 a on the coolant supply side and the communication holes 27 b and 27 b on the coolant discharge side are provided in the direction of gravity (in FIG. 5). A large number of coolant channel grooves 20a communicating linearly along the vertical direction are formed, and the coolant channel grooves 20a are closed by the separator 17 so that the coolant channel 20 It is formed.
The coolant flows into the coolant channel 20a from the coolant supply side communication hole 27a, flows in the direction of gravity through the coolant channel 20a, and flows out of the coolant discharge side communication hole 27b.
[0024]
Further, in order to allow the fuel gas, the oxidant gas, and the coolant to flow through independent flow paths, the periphery of each communication hole 25a, 25b, 26a, 26b, 27a, 27b, and the outer circumferences of the solid polymer electrolyte membrane 12 A seal member is disposed on the outer periphery of the opposing surface of the separators 16 and 17 on the coolant flow path 20 side.
[0025]
For example, the seal member will be described by taking the periphery of the communication hole 27a on the coolant supply side shown in FIG. 1 as an example. The seal is provided between the solid polymer electrolyte membrane 12 and the separators 16 and 17 so as to surround the communication hole 27a. A material 21 is disposed, and a seal material 22 is disposed between the separator 16 and the separator 17 so as to surround the outer periphery of the communication hole 27 a and the coolant flow path 20.
[0026]
Each fuel cell 15 is unitized by an insulating cover 30 provided so as to go around the outer circumferences of the separators 16 and 17. As shown in the partially enlarged view of FIG. 2, the outer peripheral edge portions of the separators 16 and 17 are formed with thin portions 16a and 17a in which the surfaces on the sides that do not face each other are recessed, and the thin portions 16a and 17a On the base side, concave grooves 16b and 17b are provided so as to make a round around the outer periphery of the separators 16 and 17.
[0027]
The insulating cover 30 is made of an insulating material such as rubber, is formed in an annular shape with a substantially U-shaped cross section, and is attached so as to straddle the thin portion 16 a of the separator 16 and the thin portion 17 a of the separator 17. The end portion 31 disposed on the separator 16 side of the insulating cover 30 is formed in a circular cross section, and the semicircular portion inside the end portion 31 engages with the concave groove 16b in the thin portion 16a of the separator 16 and A part of the semicircular portion protrudes outward from the outer surface of the separator 16. Further, the end portion 32 disposed on the separator 17 side of the insulating cover 30 has an inner surface formed in a semi-circular cross section and an outer surface formed in a flat surface, and a semicircular portion on the inner surface side of the end portion 32 is formed. The flat surface on the outside engages with the concave groove 17 b in the thin portion 17 a of the separator 17, and is located on the inner side of the outer surface of the separator 17.
[0028]
Then, the insulating cover 30 having the end portions 31 and 32 engaged with the concave grooves 16b and 17b of the separators 16 and 17 is attached so as to surround the entire outer periphery of the separators 16 and 17 by surrounding the outer periphery. The polymer electrolyte membrane 12, the anode electrode 13, the cathode electrode 14, and the separators 16 and 17 are integrated and unitized for each fuel cell 15.
[0029]
However, the insulating cover 30 does not dominate the compressive force of the seal materials such as the seal materials 21 and 22, and the compressive force of these seal materials is set by tightening a stud bolt (not shown) after the fuel cells 15 are stacked. .
[0030]
When the fuel cell 15 is stacked and the stud bolt is tightened, as shown in FIG. 1, the outer semicircular portion of the end portion 31 of the insulating cover 30 is elastically compressed to insulate the adjacent fuel cell 15. The cover 30 is in pressure contact with the flat surface of the end portion 32. Thereby, the fuel cells 15 are sealed by the insulating cover 30. Here, since the outer surface side of the end portion 32 of the insulating cover 30 is formed as a flat surface, even if the positioning is slightly loose when the fuel cells 15 are stacked, the semicircular portion outside the end portion 31 is The flat surface on the outer surface side of the end portion 32 can be reliably brought into close contact with and can be reliably sealed. On the other hand, when the end portion 32 has a circular cross section similar to the end portion 31, the semicircular portion outside the end portion 31 and the semicircular portion outside the end portion 32 when the fuel cells 15 are stacked. If it is not arranged so as to face each other, it is difficult to ensure sealing performance, and therefore accurate positioning is required.
[0031]
Further, as shown in FIGS. 2 and 3, a rectangular attachment for attaching a cell voltage measuring terminal 40 as shown in FIG. 6 is provided at a predetermined portion of the insulating cover 30 of each fuel cell 15 covering the separator 16. A hole 33 is formed. A terminal cover 34 having a cell voltage measuring terminal 40 as shown in FIG. 6 is detachably attached to the attachment hole 33. The terminal cover 34 is made of the same material as the insulating cover 30 and has a shape and size that fits exactly into the mounting hole 33, and a seal protrusion 35 is annularly provided on the bottom surface of the terminal cover 34.
[0032]
When the tip of the cell voltage terminal 40 penetrating the terminal cover 34 is inserted into the cell terminal connection hole 16c provided on the end face of the separator 16 and the terminal cover 34 is pushed into the attachment hole 33, the outer periphery of the terminal cover 34 is attached to the attachment hole. In addition to being in close contact with the inner periphery of 33, the seal protrusion 35 is in close contact with the end face of the separator 16 so as to ensure insulation and sealing properties. In addition, the shape of the terminal cover 34 is not restricted to the shape shown in FIG. 6, A various shape is employable.
[0033]
In the fuel cell stack 11 configured as described above, the entire outer periphery of the fuel cell 15 is insulated and sealed by the insulating cover 30, whereby the entire outer periphery of the fuel cell stack 11 is insulated. Because it is insulated and sealed by this, it is possible to prevent short circuit due to adhesion of conductive foreign matter such as dew condensation water and iron powder, and to ensure safety even when an operator accidentally contacts during maintenance. it can.
[0034]
Further, since the insulating cover 30 is attached and unitized for each fuel cell 15, it becomes extremely easy to handle when the fuel cell stack 11 is assembled by stacking the fuel cells 15.
Further, since one insulating cover 30 is mounted across the separators 16 and 17, only one insulating cover 30 is required for one fuel cell 15, and the outer periphery of the fuel cell 15 can be reduced in the number of parts and man-hours. It becomes possible to insulate and seal.
[0035]
In the unitized fuel cell 15, the solid polymer electrolyte membrane 12 is surrounded by separators 16 and 17 on both sides and the outer periphery thereof is surrounded by an insulating cover 30, so that the solid polymer electrolyte membrane 12 is Since it is not exposed to the outside air, it is possible to prevent the solid polymer electrolyte membrane 12 from drying, and as a result, it is possible to prevent the performance degradation of the solid polymer electrolyte membrane 12 and to improve the durability of the fuel cell. improves.
[0036]
Further, since the solid polymer electrolyte membrane 12 is not exposed to the outside air in the unitized fuel cell 15, the humidity management in the assembly environment of the fuel cell stack 11 becomes unnecessary, and the equipment related thereto becomes unnecessary. Cost can be reduced.
[0037]
[Other Embodiments]
The present invention is not limited to the embodiment described above.
For example, in the embodiment described above, the insulating cover 30 is made of rubber, but it can be made of various insulating materials other than rubber.
Further, in this embodiment, the insulating cover 30 is formed in an annular shape to be an integral object, but it may be configured by being divided (for example, divided into two) in the circumferential direction. When the insulating cover 30 is divided in this way, the assemblability is improved. In this case, the insulating cover 30 is fixed to the separators 16 and 17 with an adhesive or the like so that the insulating cover 30 is not removed.
[0038]
Further, in the above-described embodiment, the fuel gas flow path 18 of the separator 16 and the oxidant gas flow path 19 of the separator 17 are formed in a meandering shape, but these flow paths 18 and 19 are arranged in the longitudinal direction of the separators 16 and 17. It may be formed as a horizontal linear channel extending horizontally from one short side to the other short side.
Furthermore, in embodiment mentioned above, although separators 16 and 17 are comprised with carbon, it is also possible to comprise with metal materials, such as stainless steel.
[0039]
【The invention's effect】
As described above, according to the first aspect of the present invention, since only one insulating cover is sufficient for a pair of separators, the number of parts can be reduced and the number of assembly steps can be reduced.
[0040]
In addition, since it is possible to insulate the entire outer periphery of the fuel cell, it is possible to prevent a short circuit due to adhesion of conductive foreign matters such as condensed water and iron powder, and to improve safety during maintenance.
[0041]
Furthermore, since the outer periphery of the solid polymer electrolyte membrane is not exposed and is not exposed to the outside air, the performance degradation of the solid polymer electrolyte membrane can be prevented, and the durability of the fuel cell is improved. In addition, the fuel cell can be unitized at the stage where the insulating cover is provided, and the solid polymer electrolyte membrane is not exposed to the outside air at that stage, so when assembling a fuel cell stack by laminating many fuel cells It is not necessary to perform humidity management, and the equipment cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an embodiment of a fuel cell according to the present invention.
FIG. 2 is an enlarged longitudinal sectional view showing a main part of the fuel cell.
FIG. 3 is a plan view of a main part of the fuel cell.
FIG. 4 is a plan view of one separator constituting the fuel cell.
FIG. 5 is a plan view of the other separator constituting the fuel cell.
FIG. 6 is a cross-sectional view of a terminal cover and a cell voltage measurement terminal of the fuel cell.
FIG. 7 is a longitudinal sectional view of a conventional fuel cell.
FIG. 8 is a longitudinal sectional view of another conventional fuel cell.
[Explanation of symbols]
12 Solid polymer electrolyte membrane 13 Anode electrode 14 Cathode electrode 15 Fuel cell 16, 17 Separator 30 Insulation cover

Claims (2)

The solid polymer electrolyte membrane is sandwiched between the anode electrode and the cathode electrode, in yet pinched fuel cell to the outside by a pair of separators,
An outer periphery of the pair of separators is provided with an insulating cover that is attached so as to straddle the outer peripheral edge of the pair of separators and has a substantially U-shaped cross section ,
The fuel cells, wherein when the fuel cells are stacked, the insulating covers of the adjacent fuel cells are in pressure contact with each other to seal between the fuel cells. The insulating cover has a pressure contact surface with a semicircular cross section projecting outward on an outer surface disposed on one separator side, and has a flat pressure contact surface on an outer surface disposed on the other separator side. When the fuel cells are stacked, the pressure contact surface having a semicircular cross section in the insulation cover of one fuel cell and the flat pressure contact surface in the insulation cover of the other fuel cell are in pressure contact to seal between the fuel cells. The fuel cell according to claim 1.

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