JP2001006715A - Fuel cell stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a stack by forming a through hole in each member of a stack and an endplate provided at its both ends to insert a fastener to fasten them, and by making a supply hole formed in the endplate to supply a hydrogen gas or an oxygen gas communicate with the through hole. SOLUTION: Four through holes (41a and the like) to insert a bolt 43 passing through an end plate are formed, and a plurality of supply holes (41e and the like) to supply a hydrogen gas or an oxygen gas to corresponding through holes are formed. A plurality of recesses 50 communicating with the through holes and the supply holes respectively are formed on the inner wall of the endplate. A through hole 48a corresponding to each through hole of the endplate is formed at the four corners of a first and second gaskets 48, 49. An insulating plate 47 is superimposed between the endplate and a fuel cell, and is partitioned by the first gasket 48 and the second gasket 49. The through hole is also used for a gas introducing path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell stack formed by stacking fuel cells, and more particularly to a structure for introducing gas supplied to a fuel cell.

[0002]

2. Description of the Related Art In recent years, fuel cells have been developed for the purpose of application to batteries of motors for electric vehicles. In a fuel cell, after hydrogen as a negative electrode active material is brought into contact with a catalyst such as platinum (platinum) to dissociate it into electrons and protons, water is obtained by reacting the protons with oxygen as a positive electrode active material. Based on reaction mechanism.
That is, in the fuel cell, an electron emitted from hydrogen moves on the negative electrode side and reaches the positive electrode side to induce an electromotive force.

[0003] Based on such a principle, a fuel cell is
Since the chemical energy change can be directly converted into electric energy, the energy conversion efficiency is extremely high as compared with other power generation methods. Therefore, the fuel cell has less energy loss than an internal combustion engine based on the Carnot cycle, and is useful as a battery of a motor for an electric vehicle, which is an alternative to the internal combustion engine.

In a fuel cell, exhaust gas is mainly water vapor and does not emit harmful gases such as nitrogen compounds, hydrocarbons or hydrogen monoxide unlike an internal combustion engine. Practical use of electric vehicles using batteries as batteries has been desired.

FIG. 2 is a diagram showing an example of a fuel cell stack in which a fuel cell is housed when the fuel cell is applied to an electric vehicle. The fuel cell stack 4 has a configuration in which a plurality of fuel cells 40 are stacked in series in order to obtain a required voltage, and a separator 4 is provided between the fuel cells 40.
6 are interposed. Each fuel cell 40 is sandwiched between end plates 41 by bolting. More specifically, the fuel cell stack 4 has a through hole (not shown) formed in a plurality of members constituting the end plate 41 and the fuel cell 40, and a bolt 4 inserted through the through hole.
3 and a nut 44 screwed thereto.

The end plates 41 and the members constituting the fuel cell 40 have supply holes 41 e to 41 h for supplying hydrogen gas and oxygen gas to the fuel cell 40.
Are formed. By supplying hydrogen gas and oxygen gas to each fuel cell 40 from the supply holes 41e to 41h, the fuel cell 40 functions as a battery in a region sandwiched between the separators 48.

As described above, each of the members constituting the end plate 41 and the fuel cell 40 has a through hole for bolting for stacking the fuel cells 40, and hydrogen gas and oxygen gas are supplied to each fuel cell 40. Supply hole 41 for supply
e to h are independently formed. The inventor of the present application focused on the fact that a plurality of these holes exist in the end plate 41 and the like, and thought that if these holes could be shared, the fuel cell stack could have a more compact configuration.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been conceived under the circumstances described above, and has as its object to provide a fuel cell stack that can be reduced in size.

In order to solve the above problems, the present invention takes the following technical measures. That is, according to the present invention, a fuel cell stack in which a plurality of members constituting a fuel cell and end plates provided at both ends thereof are clamped and clamped by a clamping body,
A through hole through which the fastener is inserted is formed in each of the members and the end plate, a supply hole for supplying hydrogen gas or oxygen gas is formed in the end plate, and the supply hole is communicated with the through hole. A fuel cell stack is provided.

According to the above invention, the supply hole for supplying the hydrogen gas or the oxygen gas is connected to the through hole through which the fastening body for holding the fuel cell is inserted. The hydrogen gas or oxygen gas is guided to the through hole and introduced into the fuel cell through the through hole. Therefore, the through hole for inserting the fastening body can be shared as an introduction path for introducing hydrogen gas or oxygen gas,
The size of the fuel cell stack can be further reduced. In addition, a bolt, a spring washer, or the like is preferably used as the fastening body, but a spring or the like may be used instead.

According to a preferred embodiment, the size of the cross section of the through hole is larger than that of the fastening body, and the fuel cell is formed by utilizing a gap formed between the through hole and the fastening body. Hydrogen gas or oxygen gas is introduced. With this configuration,
Hydrogen gas or oxygen gas can be reliably introduced into the fuel cell and perform their functions well.

According to another preferred embodiment,
A tube is provided in the gap for electrically insulating the fastening body and the plurality of members. With this configuration, the fastening body and the plurality of members can be electrically insulated, and each member of the fuel cell can be reliably protected.

Further, according to another preferred embodiment, a sealing member for preventing leakage of hydrogen gas or oxygen gas to the outside is provided in the through hole of the end plate. With this configuration, the hydrogen gas or oxygen gas introduced from the supply hole does not leak from the end plate side when guided to the through hole. As the seal member, for example, an O-ring is preferably used.

[0014] Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG.
1 is a schematic configuration diagram illustrating an example of a fuel cell system to which a fuel cell stack according to the present invention is applied. The fuel cell system 1 includes a reformer 2 for reforming ethanol to obtain a hydrogen-rich fuel gas, a reformer 3 for converting carbon monoxide gas contained in the fuel gas into carbon dioxide gas, A fuel cell 40 for obtaining a desired electromotive force by reacting a gas and an oxygen gas is provided with a fuel cell stack 4 in which the fuel cells 40 are assembled in series.

The reformer 2 reforms ethanol into a hydrogen-rich fuel gas by, for example, a steam reforming method, and comprises a reformer 20 filled with a catalyst for reforming ethanol, and a reformer 20. And a heater 21 for heating the inside of the container 20 to a temperature suitable for reforming ethanol. The ethanol and steam supplied to the reformer 20 and heated by the heater 21 react by the action of a catalyst to generate carbon monoxide and hydrogen. When a boiler is used as the heater 21, part of the raw material ethanol and hydrogen gas not consumed in the fuel cell stack 4 are used as boiler fuel.

The shift unit 3 selectively oxidizes only carbon monoxide of the carbon monoxide and hydrogen supplied from the reforming unit 2 to shift to carbon dioxide. That is, the mixed gas containing a trace amount of carbon monoxide obtained in the reformer 2 is supplied to the shift converter 3 together with the air,
By the action of the catalyst (photocatalyst), the carbon monoxide gas is air-oxidized (converted) into carbon dioxide gas and supplied to the fuel cell stack 4.

FIG. 2 is a perspective view of the fuel cell stack 4 shown in FIG. FIG. 3 is an exploded perspective view of an end of the fuel cell stack 4, and FIG. 4 is an exploded perspective view of the fuel cell. FIG. 5 is a cross-sectional view of a main part at an end of the fuel cell stack 4. The fuel cell stack 4 has a configuration in which a plurality of fuel cells 40 are stacked in series between end plates 41 and sandwiched by a plurality of bolts 43, nuts 44, and washers 45. Each fuel cell 40
The fuel cell 40 is separated from the adjacent fuel cell 40 by a separator 46.

As shown in FIG. 3, an insulating plate 47 is provided between the end plate 41 and the fuel cell 40 so as to insulate them from each other. A gasket 48 and a second gasket 49 are arranged.

The end plate 41 is entirely made of a metal conductor such as titanium and has a plate shape having a predetermined thickness. The first to fourth through holes 41 a to 41, which penetrate the end plate 41 in the thickness direction and through which the bolts 43 are inserted, are provided.
1d is formed. In addition, the end plate 41 has a through hole 41a near each through hole 41a to 41d.
A plurality of supply holes 41e to 41h for supplying hydrogen gas or oxygen gas into the fuel cell 40 are formed corresponding to .about.41d. Further, as will be described in detail later, a plurality of recesses 50 are formed on the inner wall surface of the end plate 41 to communicate with the through holes 41a to 41d and the supply holes 41e to 41h, respectively (see FIG. 5).

The first and second gaskets 48, 49
This is for enhancing the sealing state between adjacent members, and is disposed between the insulating plate 47 and the end plate 41 or the separator 46. An end plate 4 is provided at each of the four corners of the first and second gaskets 48, 49.
Substantially square-shaped through holes 48a to 48d and 49a to 49d are formed at portions corresponding to the respective through holes 41a to 41d.

The insulating plate 47 is formed of a resin having a characteristic of electrically insulating the end plate 41 and the separator 46 from each other.
Substantially square-shaped through-holes 47a to 47d are formed at portions corresponding to the respective through-holes 41a to 41d.

As shown in FIG. 4, the fuel cell 40 includes a plurality of separators 46, an ion exchange membrane 51 interposed between the separators 46, and an ion exchange membrane 51 interposed between the separators 46. Positive electrode current collector 52 and negative electrode current collector 53, and positive electrode current collector 52 and negative electrode current collector 5
The third gasket 54 and the fourth gasket 55 are arranged so as to surround the third outer frame.

The entire separator 46 is made of a metal conductor such as titanium, stainless steel, or a titanium alloy, and is formed in a plate shape. The separator 46 is provided to secure a region functioning as a battery between the separator 46 and another separator 46, and is used when hydrogen gas or oxygen gas is supplied. At each of the four corners of the separator 46, substantially square first to fourth through holes 46 a to 46 d are formed at portions corresponding to the through holes 41 a to 41 d of the end plate 41.
d is formed.

The first side 46A of the separator 46 is provided with a first
A plurality of grooves 56 formed by etching by, for example, photo etching or the like so as to communicate with each other so as to connect the through-hole 46a and the second through-hole 46b so as not to cross each other.
Are formed. Also, the other side 46 of the separator 46
B (see FIG. 5) is formed with a plurality of grooves 56 communicating with each other so as to connect the third through-hole 46c and the fourth through-hole 46d, similarly to the one surface side 46A. Each separator 46
The groove 56 formed on the one surface 46A serves as a flow path for hydrogen gas, and the groove 56 formed on the other surface 46B serves as a flow passage for oxygen gas. Therefore, in this fuel cell 40,
Adjacent fuel cells 40 can share one separator 46.

Note that, on one surface of each of the separators 46 located at both ends of the separators 46, no grooves are formed because they are not opposed to the current collectors 52 and 53.
That is, the groove portion of one surface 46A of the separator 46 located on one end plate 41 side and the other surface side 46 of the separator 46 located on the other end plate 41 side
B grooves are not formed.

The through hole 41a of the end plate 41
The first and second through holes 41a and 41b, which are diagonally located, communicate with the groove 56 formed on the other surface side 46B of each separator 46, and the third and fourth through holes 41 c and 41 d communicate with grooves 56 formed on one surface 46 A of each separator 46, respectively.

The ion-exchange membrane 51 has four substantially square through-holes 51a to 51d at four corners corresponding to the through-holes 41a to 41d of the end plate 41, respectively.
The ion exchange membrane 51 has proton conductivity, and selectively allows hydrogen ions to pass therethrough. A positive electrode catalyst section 51A is provided on each of both sides of the ion exchange membrane 51.
And a negative electrode catalyst portion 51B.

The cathode catalyst portion 51A is a porous layer composed of catalyst particles in which platinum and rhodium coexist and are supported on the surfaces of carbon particles, for example, so that oxygen molecules can pass therethrough. In the cathode catalyst section 51A, oxygen gas is
Water reacts with hydrogen ions and electrons to produce water. On the other hand, the anode catalyst part 51B is a porous layer made of catalyst particles having platinum supported on the surface of carbon particles, for example, and is capable of passing hydrogen molecules and hydrogen ions.
In the negative electrode catalyst section 51B, the supplied hydrogen gas is dissociated into hydrogen ions and electrons.

The positive electrode current collector 52 is formed of, for example, a carbon-based material and is formed in a substantially cross shape as a porous body. The positive electrode current collector 52 receives electrons from the outside and supplies the electrons to the positive electrode catalyst portion 51A. The oxygen gas is passed so that the oxygen gas reaches the cathode catalyst unit 51A. on the other hand,
Like the positive electrode current collector 52, the negative electrode current collector 53 is formed of, for example, a carbon-based material in a substantially cross shape as a porous body, and collects electrons dissociated from hydrogen gas in the negative electrode catalyst portion 51 </ b> B to form So that they can be taken out,
The hydrogen gas is passed so that the supplied hydrogen gas reaches the negative electrode catalyst unit 51B.

The third and fourth gaskets 54, 55
This is for improving the sealing state between the ion exchange membrane 51 and each separator 46, that is, between the adjacent separators 46. The third and fourth gaskets 54, 55 have a shape in which substantially cross-shaped openings 54A, 55A larger than the area of the current collectors 52, 53 are provided in the center thereof, and when the fuel cell 40 is configured. , Gaskets 54, 55
Are configured to surround the current collectors 52 and 53.

The fuel cell stack 4 is assembled by the members described above. Next, referring to FIG. 5, the structure for introducing hydrogen gas or oxygen gas, which is a feature of this embodiment, will be described in detail. explain. FIG.
Is a diagram showing a structure near the through hole 41a, but the other through holes 41b to 41d have the same structure.

According to FIG. 3, a concave portion 50 is formed on the inner wall surface of the end plate 41 for communicating the through hole 41a and the supply hole 41e. More specifically, the recess 50 is a space formed between the end plate 41 and the first gasket 48 when the fuel cell stack 4 is configured. The hole 41e is connected. That is, the through hole 4
1a is formed so as to extend in the thickness direction of the end plate 41, and is connected to the recess 50 by the time it reaches the other side 41B of the end plate 41. Similarly to the through hole 41a, the supply hole 41e is formed to extend in the thickness direction of the end plate 41, and is connected to the concave portion 50 until reaching the other surface 41B of the end plate 41.

First and second gaskets 48, 49,
Insulating plate 47, separator 46, third and fourth gaskets 54, 55, and through holes 48a, 49, 47a, 46a, 54 formed in respective members of ion exchange membrane 51.
a, 55a, and 51a (hereinafter, collectively referred to as “through holes 4a”) are disposed so as to be coaxially connected to the through holes 41a of the end plate 41, respectively. Therefore, the concave portion 50 is connected to the through hole 4a of each member, and the supply hole 41e is
The communication with the through-hole 4a of each member is performed through the concave portion 50.

A substantially cylindrical tube 57 made of a fluororesin such as Teflon is inserted into the through hole 4a. The tube 57 is provided for easier insertion of the bolt 43 and for insulating the bolt 43 from each member. The outer diameter of the tube 57 is smaller than the cross-sectional size of the through hole 4 a and slightly larger than the outer diameter of the bolt 43. The length of the tube 57 is set at a position where both ends of the tube 57 project from the end plate 41 in a state where the fuel cell stack 4 is configured. More specifically, the height is the same as the height of a notch 58 formed on the inner surface of the bottom of the washer 45 described later.

A bolt 43 having a length greater than the length of the tube 57 is inserted into a tube 57 inserted into the through hole 4 a of each member. A washer 45 is fitted into both ends of the bolt 43, and a screw is screwed by a nut 44. Be worn. The washer 45 is formed in a substantially cylindrical shape having a through hole 45a at the center, and a substantially tapered notch 5 is formed on the inner surface at the bottom of the through hole 45a.
8 are provided. A rubber O-ring 60 that is in tight contact with the peripheral surface of the tube 57 is arranged in the cutout 58 in a stacked state.

The through-hole 41a of the end plate 41
An annular concave portion 61 is formed on the inner wall surface along the peripheral surface, and a rubber O-ring 62 is fitted into the concave portion 61. The inner diameter of the O-ring 62 is substantially the same as or slightly smaller than the outer diameter of the tube 57, so that the O-ring 62 comes into sealing contact with the peripheral surface of the tube 57 in a stacked state. These multiple O
The through holes 41 a and the tubes 57 are formed by the rings 60 and 62.
Is sealed at a plurality of locations to prevent gas from leaking to the outside.

In such a configuration, for example, when oxygen gas is supplied from the supply hole 41e, as shown by the white arrow in FIG. It is guided to the gap between the through hole 4a of the member and the groove 46 on the other side 46B of the separator 46.

In this case, since the cross-sectional size of the through-hole 4a of each member is slightly larger than the outer diameter of the tube 57, oxygen gas flows through the tube 57 and the through-hole 4a of each member.
The gap is formed between the grooves 46a and the groove 46 of the separator 46.

Further, according to the above configuration, the oxygen gas supplied from the supply hole 41e tries to be discharged to the outside through the through hole 41a of the end plate 41.
Oxygen gas does not leak to the outside because its progress is blocked by 0,62. Moreover, the O-ring 60,
Since 62 is provided at a plurality of locations, it is possible to more reliably seal and enhance the sealing effect.

In this way, the through holes 4a for the bolts 43 formed in each member can be shared as a passage for introducing hydrogen gas or oxygen gas. Therefore, on one surface side 46A and the other surface side 46B of the separator 46, the area where the groove portion 56 can be formed is wider than when the through holes for bolts and the supply holes for gas introduction are provided independently. Become. That is, since the number of the grooves 56 can be increased or the length of one groove 56 can be increased, the area where the hydrogen gas or the oxygen gas contacts the current collectors 52 and 53 can be increased. Therefore, the reaction of hydrogen gas or oxygen gas can be promoted, and as a result,
It is possible to contribute to improvement of the output of the electromotive force in the fuel cell.

The fact that the area in which the groove portions 56 of the separator 46 are arranged is widened means that, when the same amount of electromotive force is output, the area of the groove portions 56 can be narrowed. For example, when the fuel cell stack 4 is mounted on an automobile, the space can be saved.

In this fuel cell stack 4, if oxygen gas is supplied from one or both of the first and second supply holes 41 e and f with one end plate 41 as an inlet, all of the separators are provided. Oxygen gas is passed through the groove 56 on the other side 46B of the 46. The oxygen gas is usually supplied in an air state.

When the hydrogen gas is supplied from one or both of the third and fourth supply holes 41g and 41h, the hydrogen gas is passed through the grooves 56 on the one surface 46A of all the separators 46. Then, excess hydrogen gas is discharged from the other end plate 41 side, and this hydrogen gas is supplied as fuel for the heater 21 of the reformer 2 as shown in FIG.

In each fuel cell 40, for example, a part of the hydrogen gas passing through the third through hole 46g of the separator 46 is supplied to a groove 56 formed on one surface 46A of the separator 46, and this hydrogen gas is It passes through the current collector 53. The hydrogen gas that has passed through the negative electrode current collector 53 is dissociated into hydrogen ions and electrons in the negative electrode catalyst unit 51B.

The electrons generated during this reaction are collected in the negative electrode current collector 53, and the electrons are supplied to the positive electrode current collector 52 of the adjacent fuel cell 40 sharing the separator 46 via the separator 46. Is done.

On the other hand, hydrogen ions generated during the reaction in the anode catalyst unit 51B pass through the ion exchange membrane 51 and move to the cathode catalyst unit 51A. Electrons are further supplied to the cathode catalyst unit 51A from the anode current collector 53 of the adjacent fuel cell 40 sharing the separator 46, and the air (oxygen gas) passing through the second through hole 46b of the separator 46 is also discharged. A part is supplied through a groove 56 formed on the other surface side 46B of the separator 46 and the positive electrode current collector 52. In this way, in the cathode catalyst unit 51A to which the oxygen gas, the electrons, and the hydrogen ions are supplied, they react to generate water.

As described above, in the fuel cell stack 4, 1
The electrons collected in the negative electrode current collector 53 of the fuel cell 40 of
It is supplied to the positive electrode current collector 52 of the adjacent fuel cell 40. Then, the electrons collected in the negative electrode current collector 53 of the fuel cell 40 located at the most downstream in the electron flow direction pass through an external circuit, and the positive electrode of the fuel cell 40 located at the most upstream in the electron flow direction is passed through the external circuit. The power is supplied to the current collector 52. That is, in the fuel cell stack 4, electrons flow in a certain direction as a whole, and electrons are circulated from the most downstream fuel cell 40 to the most upstream fuel cell 40 via an external circuit. . Then, energy is taken out and used in an external circuit.

Of course, the scope of the present invention is not limited to the above embodiment. In the above embodiment,
Although an O-ring is used for the seal member, the present invention is not limited to this, and another seal member may be used.

The shape of the through-hole formed in each member constituting the fuel cell is not limited to a substantially square shape. In short, it is only necessary that the cross section be larger than the sectional shape of the bolt or tube.

[0051]

As described above, according to the fuel cell stack of the present invention, the supply holes for supplying the hydrogen gas or the oxygen gas have the through holes through which the fastening members for holding the fuel cell are inserted. Since the gas is communicated with the holes, the hydrogen gas or oxygen gas supplied from the supply holes is guided to the through holes and introduced into the fuel cell through the through holes. Therefore, the through hole for inserting the fastening body can be shared as an introduction path for introducing hydrogen gas or oxygen gas, and the size of the fuel cell stack can be reduced by effectively utilizing the space of the separator. Can be

Further, since the cross section of the through hole is larger than that of the above-mentioned fastening body, the hydrogen gas or the oxygen gas can be surely introduced into the fuel cell, and these functions can be performed well. it can.

Further, since a tube for electrically insulating the fastening body and the plurality of members is provided in a gap formed between the through hole and the fastening body, each member of the fuel cell is reliably protected. can do.

Further, since a sealing member for preventing leakage of hydrogen gas or oxygen gas to the outside is provided in the through hole of the end plate, the hydrogen gas or oxygen gas introduced from the supply hole does not penetrate. When guided into the holes, the sealing properties can be improved without leaking from the end plate side.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram to which a fuel cell stack according to the present invention is applied.

FIG. 2 is a perspective view of the fuel cell stack shown in FIG.

FIG. 3 is an exploded perspective view of an end of the fuel cell stack.

FIG. 4 is an exploded perspective view of the fuel cell.

FIG. 5 is a sectional view of a main part at an end of the fuel cell stack.

[Explanation of symbols]

 Reference Signs List 4 fuel cell stack 40 fuel cell 41 end plate 41a to 41d through hole 41e to 41h supply hole 43 bolt 44 nut 46 separator 56 groove 60, 62 O-ring

Claims (4)

[Claims] 1. A fuel cell stack in which a plurality of members constituting a fuel cell and end plates provided at both ends thereof are fastened and clamped by a fastening body. A through hole through which the fastening body is inserted is formed, a supply hole for supplying hydrogen gas or oxygen gas is formed in the end plate, and the supply hole is communicated with the through hole. Yes, the fuel cell stack. 2. A cross-sectional size of the through-hole is larger than that of the fastening body, and a hydrogen gas is supplied to the fuel cell by utilizing a gap formed between the through-hole and the fastening body. The fuel cell stack according to claim 1, wherein oxygen gas is introduced. 3. The fuel cell stack according to claim 2, wherein a tube is provided in the gap to electrically insulate the fastening body and the plurality of members. 4. The fuel cell stack according to claim 1, wherein a seal member for preventing hydrogen gas or oxygen gas from leaking outside is provided in the through hole of the end plate.