JP2005259409A - Fuel cell and electrical apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently pressurize a stack formed by stacking unit cells and to miniaturize a fuel cell. <P>SOLUTION: At least two end plates 7 interposing the stack 9 formed by stacking unit cells 2 generating electric power with fuel are installed and a fastening member 10 generating force in the direction approaching the end plates is installed between the end plates 7 to fasten the stack 9. Sufficient pressure to the stack 9 is realized and the fuel cell is miniaturized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell and an electric device.

  From the viewpoint of environmental problems represented by greenhouse gases, fuel cells as clean energy sources are being developed at a rapid pace. In particular, solid electrolyte fuel cells are being actively researched and developed because of their low-temperature operation, small size, and high power density. When installing fuel cells in electrical equipment, stacks (power generation elements) in which the required number of fuel cells (single cells) are stacked are tightly narrowed to prevent fuel leakage and increase current collection efficiency. It is necessary to have. Therefore, as shown in FIG. 8, a laminated body 101 in which single cells 100 made of an electrode / electrolyte membrane assembly (MEA), a separator, and the like are laminated is sandwiched between two end plates 102, and the end plates 102 are arranged. It is common to perform tightening with a metal rod 103 and a bolt 104 that connect the two. At this time, in many cases, the laminated body 101 is fixed by tightening the four corners of the two end plates 102 so that the in-plane of the joined body (MEA) is uniformly pressed.

  On the other hand, as a means for reducing the size and weight of a fuel cell and a means for applying pressure to a single cell (stacked body) of a fuel cell, techniques such as Patent Document 1 and Patent Document 2 have been proposed. In Patent Document 1, the laminate is accommodated in a box and is held between leaf springs. In Patent Document 2, two end plates are connected by a shaft, and a surface pressure is applied to the laminated body by a spring force of a disc spring (elastic body) disposed between the two end plates.

JP 2003-151611 A JP 2000-195529 A

  However, when the bolt and the metal rod are tightened as shown in FIG. 8, the bolt and the metal rod jump out on the outer surface of the end plate (the side opposite to the power generation element). Further, a space for tightening the bolt is required outside the end plate. Therefore, the fuel cell and the apparatus including the fuel cell are increased in size, which causes an increase in volume and weight. In particular, when designing a fuel cell, there is an unnecessary space that does not contribute to power generation, which is a factor for lowering the volume energy density and weight energy density of the fuel cell. The end plate is tightly tightened to obtain a gas seal. However, it is necessary to adjust the center of the plate so that it does not bend, and the pressure on the electrode surface, which is the power generation part, is adjusted to be uniform. Because it is necessary to do, it takes time to tighten.

  On the other hand, in the technique of Patent Document 1, since a space for the leaf spring is necessary, the fuel cell is increased in size and its weight is also increased. Furthermore, in order to apply a sufficient pressure to the single cell of the fuel cell, the box body needs to be strong. Therefore, the member which comprises a box will become thick and the weight of a fuel cell will become heavy. Moreover, in the technique of patent document 2, since the space of a disc spring is required, a fuel cell will enlarge and the weight will also increase.

  An object of the present invention is to realize sufficient pressurization to a laminate in which single cells are laminated and miniaturization of a fuel cell. In addition, the weight of the fuel cell can be reduced.

  A fuel cell according to a first aspect of the present invention includes a laminate in which single cells that generate electricity with fuel supplied with an electrolyte and an electrode that sandwiches the electrolyte are laminated, and two ends that sandwich the laminate. A plate, and a fastening member that is provided between the two end plates and tightens the laminate by generating a force in a direction in which the two end plates approach each other.

  According to a second aspect of the present invention, in the fuel cell according to the first aspect, the tightening member includes a first support rod provided on one of the end plates and a second support provided on the other end plate. It comprises a support bar, and a rotating part that connects the first support bar and the second support bar and makes them approach by rotating.

  According to a third aspect of the present invention, in the fuel cell according to the first aspect, the fastening member is provided on a first support bar provided on one of the end plates and on the other end plate, and the first A second support rod into which the support rod is slidably inserted, and an elastic member which is attached to the first support rod and the second support rod and tightens the laminate by a contraction force. It is configured.

  According to a fourth aspect of the present invention, in the fuel cell according to the first, second, or third aspect, the fastening member is provided at two positions facing each other with the stacked body interposed therebetween.

  According to a fifth aspect of the present invention, in the fuel cell according to the first or third aspect, the fastening member is provided so as to penetrate the laminated body.

  The invention according to claim 6 is the fuel cell according to claim 5, wherein the stacked body and the two end plates are provided with their centers aligned, and the fastening member includes the stacked body and It is provided in the range of 1/2 or less of the distance from the center of the end plate to the outer periphery.

  A seventh aspect of the present invention is the fuel cell according to the sixth aspect, wherein the fastening member is provided at the center of the laminate and the end plate.

  The invention according to claim 8 is the fuel cell according to claim 7, wherein the end plate is a circular plate.

  According to a ninth aspect of the present invention, in the fuel cell according to any one of the first to eighth aspects, the clamping member has the center of gravity of the stacked body and the two end plates so that their centers of gravity coincide with each other. The laminate is tightened.

  The invention according to claim 10 is the fuel cell according to any one of claims 1 to 9, wherein the fuel is a fuel containing alcohol.

  According to an eleventh aspect of the present invention, in the fuel cell according to the tenth aspect, the alcohol is ethanol.

  An electronic device according to a twelfth aspect includes the fuel cell according to any one of the first to eleventh aspects.

  According to the first aspect of the present invention, it is possible to realize sufficient pressurization to the stacked body in which the single cells are stacked, and to further reduce the size of the fuel cell.

  According to invention of Claim 2, sufficient pressurization to the laminated body by which the single cell was laminated | stacked by simple structure is implement | achieved, and also a fuel cell can be reduced in size.

  According to invention of Claim 3, sufficient pressurization to the laminated body by which the single cell was laminated | stacked is implement | achieved by simple structure, Furthermore, a fuel cell can be reduced in size.

  According to the invention described in claim 4, a uniform pressure can be applied to the fuel cell.

  According to the invention described in claim 5, the fuel cell can be reduced in size and weight.

  According to the invention described in claim 6, it is possible to apply a uniform pressure to the fuel cell while maintaining the energy density.

  According to the seventh aspect of the invention, a more uniform pressure can be applied to the fuel cell.

  According to the eighth aspect of the invention, more uniform pressure can be applied to the fuel cell, the surface pressure of the electrode portion becomes uniform, and stable power generation characteristics can be obtained.

  According to the ninth aspect of the invention, a more uniform pressure can be applied to the fuel cell.

  According to the invention of claim 10, the driving time of the fuel cell can be improved by using the fuel having a high energy density.

  According to the eleventh aspect of the present invention, it is possible to supply fuel with high environmental conservation and safety.

  According to invention of Claim 12, there exists an effect as described in any one of Claim 1 thru | or 11.

  A first embodiment of the present invention will be described with reference to FIGS.

  First, a power generation concept of a fuel cell using a proton conducting solid polymer electrolyte will be described as an example with reference to FIG. FIG. 1 is an explanatory diagram for explaining a power generation concept of a fuel cell.

  The fuel cell 1 (single cell 2) is provided with an electrolyte 3 (here, for example, proton conductor) as an ionic conductor at the center as basic components, and an anode 4a and a cathode as electrodes 4 on both sides thereof. 4b is arranged. The anode 4 a and the cathode 4 b are connected via an external circuit (load) 5. The anode 4a and the cathode 4b are provided with separators 6 each having a fuel flow path 6a for supplying fuel to each. The two separators 6 sandwich the electrolyte 3 and the electrode 4 opposed thereto.

Here, when the proton conductive electrolyte 3 is used, a fuel (hydrogen (H ₂ ), alcohol, or the like) serving as a proton source is supplied to the anode 4a side, and hydrogen is generated from the fuel by the catalytic action in the anode 4a. Ions (H ⁺ ) are generated. At this time, the generated electrons (e ⁻ ) flow to the external circuit 5. The generated hydrogen ions propagate through the electrolyte 3 and reach the cathode 4b. By supplying an oxidizing agent (air, oxygen (O ₂ ), etc.) to the cathode 4b side, hydrogen ions, oxygen, and electrons flowing through the external circuit 5 react to generate water (H ₂ O). The This is the concept of power generation, which can be expressed as the following reaction equation.

Anode reaction: H ₂ → 2H ⁺ + 2e ⁻ (in the case of hydrogen fuel)
Cathode reaction: 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O
Total reaction: H ₂ + 1 / 2O ₂ → H ₂ O
Here, the power generation element requires the anode 4a, the cathode 4b, and the electrolyte 3, and among the other elements necessary for the fuel cell to generate power, such as the separator 6, between the two end plates 7 shown below. Points to an existing element. Among the power generation elements of the fuel cell 1, the joined body of the membrane electrolyte membrane 3 a and the electrode 4 (anode 4 a and cathode 4 b) is called a membrane electrode assembly (MEA) 8. The MEA 8 is used to improve the interface characteristics between the catalyst and the electrolyte 3, or to reduce the electrical resistance of the electrode 4 and the separator 6, in order to improve the sealing performance of substances necessary for (and associated with) the reaction. It is firmly held by the two end plates 7.

  FIG. 2 schematically shows the fuel cell 1 of the present embodiment, where (a) is a front view, (b) is a side view, and FIG. 3 is a longitudinal side view schematically showing an exploded view of a single cell 2. .

  As shown in FIG. 2, the fuel cell 1 according to the present embodiment includes a laminated body 9 in which three single cells 2 are laminated, two end plates 7 that sandwich the laminated body 9, and these end plates 7 on the inside. The fastening member 10 is fastened in a direction (a direction in which the end plate 7 approaches).

As shown in FIG. 3, the single cell 2 is configured by sandwiching an MEA 8, which is a joined body of an electrolyte membrane 3 a and an electrode 4, with a separator 6. The electrolyte membrane 3 a is sandwiched between the electrodes 4. On the outer periphery of the electrode 4, a gas seal member 11 is provided along the outer periphery to prevent leakage of fuel and generated substances. Here, for example, the electrode 4, the solid electrolyte membrane 3a, the separator 6 and the end plate 7 are formed in a square shape. The electrode 4 is 5 cm ² , the electrolyte membrane 3 a is 90 cm ² , the separator 6 is 90 cm ² , and the end plate 7 is 182 cm ² .

  The end plate 7 is provided with four fastening members 10. The four fastening members 10 are respectively positioned at the four corners of the end plate 7. That is, the two fastening members 10 are provided at two positions facing each other with the laminated body 9 interposed therebetween. Thereby, a uniform pressure can be applied to the laminate 9. Such a fastening member 10 has a structure that generates a force that pulls the two end plates 7 inward (in a direction in which the end plates 7 approach each other) by rotating.

  The fastening member 10 includes two support bars 12 provided on the two end plates 7, and a rotating unit 13 that connects the support bars 12. Here, the two support rods 12 are a first support rod and a second support rod, respectively. The two support rods 12 and the rotating portion 13 are connected with the supporting rod 12 as a male screw and the rotating portion 13 as a female screw. In addition, a thread groove (not shown) is cut into the rotating portion 13 so that the two support rods 12 approach or separate from each other depending on the rotation direction.

  In such a configuration, the laminated body 9 is pressed and fixed by the end plate 7 by rotating the rotating portions 13 of the four fastening members 10 in the direction in which the end plate 7 approaches. At this time, since the fastening member 10 does not protrude to the outer surface of the end plate 7 (the surface opposite to the laminated body 9), the fuel cell 1 can be reduced in size, and the simple structure can be used. Sufficient pressurization to the laminated body 9 in which the cells 2 are laminated can be realized.

  In the present embodiment, the fastening member 10 is configured to pull the end plate 7 inward by the rotating portion 13, but is not limited thereto, and for example, a spring such as a screw or a coil spring is used. Then, the end plate 7 may be configured to be pulled inward (in a direction in which the end plate approaches).

  A second embodiment of the present invention will be described with reference to FIGS. FIG. 4 schematically shows a fuel cell 1A of the present embodiment, where (a) is a front view, (b) is a side view, and FIG. 5 is a longitudinal side view schematically showing an exploded view of a single cell 2A. 6 is a perspective view schematically showing the structure of the fastening member 10A. Note that the same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is also omitted.

  In the first embodiment of the present invention, a space is required on the outer periphery of the laminate 9 for holding. Further, as the area of the MEA 8 increases, it is necessary to use a thicker and thicker plate so that the centers of the separator 6 and the end plate 7 do not bend (the pressure at the center does not differ from the outer peripheral portion). That is, the larger the MEA 8, the more difficult it is to reduce the size of the fuel cell 1. Further, when a hole is formed in the end plate 7 and the support rod 12 is provided in the hole, it is necessary to process a plurality of holes in the thick end plate 7 with high accuracy, and the surface is made uniform in a uniform assembly. Tightening is also difficult. Therefore, in the present embodiment, the size of the fuel cell 1A is reduced by providing the fastening member 10 in the vicinity of the center of the MEA 8 in the plane.

  As shown in FIG. 4, the fuel cell 1A includes a laminated body 9 in which three single cells 2A are laminated, two end plates 7 sandwiching the laminated body 9, and the end plates 7 inward (end plate 7 The fastening member 10 is fastened in the direction in which the two are approached.

  As shown in FIG. 5, the single cell 2 </ b> A is configured by a MEA 8, which is a joined body of an electrolyte membrane 3 a and an electrode 4 </ b> A, sandwiched between separators 6. The electrolyte membrane 3a is sandwiched between the electrodes 4A. A through hole 21 is provided at the center of the electrode 4A. Thereby, the electrode 4A is not provided in the central part of the electrolyte membrane 3a. A gas seal member 11 is provided along the outer periphery of the electrode 4A.

  As shown in FIG. 4, near the center of the fuel cell 1 </ b> A, three through holes 22 that penetrate from the end plate 7 at one end to the end plate 7 through the stacked body 9 are formed. These through-holes 22 pass through the vicinity of the center of the end plate 7 and the vicinity of the center of the laminated body 9, and pass through the through-hole 21 of the electrode 4A. A fastening member 10A is inserted and provided in each of the three through holes 22.

  As shown in FIG. 6, the fastening member 10 includes two support bars 23 a and 23 b provided on the two end plates 7, and a coil spring 24 that is an elastic member attached to the support bars 23 a and 23 b. It is configured. Both ends of the coil spring 24 are fixed to the end portions on the end plate 7 side of the two support rods 23a and 23b, respectively. The support bar 23a is formed slightly smaller than the support bar 23b, and is inserted into the support bar 23b. The support bar 23a is a mechanism that can slide inside the support bar 23b. That is, the support bar 23a is slidably inserted into the support bar 23b. Further, the fastening member 10A is a mechanism capable of changing the length of the support bar 23b. Here, the support bar 23a is a first support bar, and the support bar 23b is a second support bar. In addition, in the fastening member 10 before clamping the laminated body 9, the coil spring 24 and the support rods 23a and 23b are in the shortest state in the length direction. In this state, when the laminated body 9 is inserted between the end plates 7, the coil spring 24 generates a force that pulls the end plate 7 inward (in a direction in which the end plate 7 approaches).

  Therefore, the fastening member 10 fastens the two end plates 7 inward by the coil spring 24. By tightening the center portion of the end plate 7, there is no center deflection, and it becomes easy to uniformly adjust the in-plane pressure. Further, since the contact surface on which the end plate 7 and the laminate 9 abut is formed with the same size, the fuel cell 1 can be further reduced in size and weight as compared with the fuel cell 1 of the first embodiment. can do.

  In the present embodiment, the coil spring 24 is used as the elastic member. However, the present invention is not limited to this, and for example, a rubber-like member may be used.

  In the present embodiment, the fastening member 10 is used for fastening at three points (see FIG. 4B). However, the present invention is not limited to this. For example, two or four points may be used. As long as the required tightening strength is obtained, one point may be used.

  Here, as a tightening position, when a plurality of positions are tightened, the tightening member 10A is disposed in the vicinity of the center of the electrode 4A, particularly in the range of 1/2 of the distance from the center of the end plate 7 required for the stack to the outer periphery. Good. Thereby, it can clamp | tighten equally with respect to the center and outer periphery of the end plate 7, there is no fuel leakage, and since contact resistance can also be made small uniformly, current collection efficiency is good. Further, when the fastening member 10A is installed in the vicinity of the center, the area necessary for fastening can be concentrated as shown in FIG. 4B, and the area of the electrode 4A can be provided efficiently (largely). it can. The arrangement is not particularly limited. In the case where the center of gravity of the fastening member 10 is located at the center of the electrode 4A, it is possible to hold the electrode 4A so that the electrode 4A is uniformly pressed by adjusting all the fastening forces to be constant. it can. That is, it is possible to obtain the fuel cell 1A with high accuracy in tightening pressure.

  In order to tighten the vicinity of the center of the end plate 7 and to uniformly hold the laminate 9 by the end plate 7, it is desirable that the end plate 7 has a symmetrical shape from the center. However, even if the end plate 7 has a polygonal shape, it is possible to obtain a fuel cell 1A that achieves miniaturization. However, in order to make the surface pressure of the end plate 7 uniform with high accuracy by the center tightening force, the end plate 7 is preferably circular, and a laminated layer having a separator 6, a MEA 8, etc. sandwiched between them. The body 9 is also preferably circular. This is because when the tightening member 10 is tightened so that the center of gravity of the end plate 7 and the laminated body 9 is at the center, the surface pressure of the electrode 4A becomes uniform and stable power generation characteristics are obtained. . When the tightening position is set to one point, it is desirable to tighten the center of the circular end plate 7 in order to easily obtain accuracy in performing uniform tightening.

  Therefore, a modification of the present embodiment will be described with reference to FIG. FIG. 7 schematically shows a fuel cell 1B according to a modification of the present embodiment, where (a) is a front view and (b) is a side view. As shown in FIG. 7, in the fuel cell 1B, the end plate 7 is circular, and the laminated body 9 including the separator 6, the MEA 8 and the like sandwiched between the end plates 7 is also circular, and a fastening member is provided at the center of the circular end plate 7. It is configured by providing only one 10A. The fastening member 10 </ b> A fastens the laminate 9 so that the centers of gravity of the laminate 9 and the two end plates 7 coincide with each other. Thereby, more uniform pressure can be applied to the laminated body 9, the surface pressure of an electrode part becomes uniform, and the stable electric power generation characteristic can be acquired.

  The fuel used in each embodiment is appropriately set in accordance with the fuel cells 1, 1A, 1B, but basically any fuel can be used. However, it is preferable to use a fuel excellent in volume and weight energy density. In particular, a fuel excellent in volume energy density is preferable.

Therefore, gaseous fuel is not preferable because it is inferior in volumetric energy density, and liquid fuel is preferable. This is because, for example, the number of electrons that can be extracted by oxidation reaction of one molecule is 2 if hydrogen, 6 if methanol, and 12 if ethanol, so the amount of Coulomb that can be extracted from 1 mol of each molecule is theoretical. The values are 96500 × 2C, 96500 × 6C, and 96500 × 12C. Considering density and molecular weight of each, 1 cm ³ per coulomb amount converted to the about 9C / cm ³ with hydrogen, approximately methanol 14400C / cm ^3, the energy density of 15200C / cm ³ with ethanol. Hydrogen as a normal pressure gas has a significantly low energy density per unit volume. Methanol and ethanol require one molecule and three molecules of water for the oxidation reaction (see the following formula), but it is clear that liquid fuel is excellent even when this is taken into account.

CH ₃ OH + H ₂ O → 6H ⁺ + 6e ⁻ + CO ₂
C ₂ H ₅ OH + 3H ₂ O → 12H ⁺ + 12e ⁻ + 2CO ₂
Although it is possible to use high-pressure hydrogen or liquid hydrogen, it is necessary to make the container robust, and considering the energy density of the container, liquid or solid fuel at room temperature and normal pressure is excellent. Yes. Specifically, hydrogen stored in the hydrogen storage alloy, solid fuel such as gasoline, liquid hydrocarbon, liquid alcohol, or liquid fuel can be used, but the main fuel cell can be downsized, volume energy From the viewpoint of excellent density, it is preferable to use an alcohol fuel. By using alcohol fuel, portable fuel cells 1, 1A, 1B with improved driving time can be formed. Among these, it is preferable to use an alcohol having 4 or less carbon atoms, and it is particularly preferable to use ethanol from the viewpoint of high safety and biosynthesis (environmental aspect).

  In addition, the fuel cells 1, 1A, 1B obtained by the respective embodiments are smaller and lighter than conventional fuel cells, but by using a fuel having excellent volumetric energy density such as liquid fuel. Further, it is possible to further reduce the size including the space for storing the fuel and peripheral devices. For this reason, when the fuel cells 1, 1 </ b> A, and 1 </ b> B of the embodiments are applied to electronic devices, particularly portable electronic devices, small and light electronic devices can be obtained.

It is explanatory drawing for demonstrating the electric power generation concept of a fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS The fuel cell of the 1st Embodiment of this invention is shown schematically, (a) is a front view, (b) is a side view. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal side view schematically showing an exploded view of a single cell constituting a fuel cell according to a first embodiment of the present invention. The fuel cell of the 2nd Embodiment of this invention is shown schematically, (a) is a front view, (b) is a side view. It is a vertical side view which decomposes | disassembles and shows schematically the single cell which comprises the fuel cell of the 2nd Embodiment of this invention. It is a perspective view which shows roughly the structure of the clamping member of the 2nd Embodiment of this invention. The fuel cell of the modification of the 2nd Embodiment of this invention is shown schematically, (a) is a front view, (b) is a side view. The conventional fuel cell is shown schematically, (a) is a front view, (b) is a side view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 1A Fuel cell 1B Fuel cell 2 Single cell 2A Single cell 3 (3a) Electrolyte (electrolyte membrane)
4 electrode 4A electrode 7 end plate 9 laminate 10 clamping member 10A clamping member 12 first support rod 12 second support rod 13 rotating part 23a first support rod 23b second support rod 24 telescopic member (coil spring)

Claims (12)

A laminate in which single cells that generate electricity with fuel supplied with an electrolyte and electrodes sandwiching the electrolyte are laminated;
Two end plates sandwiching the laminate,
A tightening member that is provided between the two end plates and tightens the laminate by generating a force in a direction in which the two end plates approach each other;
A fuel cell comprising: The fastening member is
A first support bar provided on one of the end plates;
A second support bar provided on the other end plate;
A rotating part that connects the first support bar and the second support bar and makes them approach by rotating; and
The fuel cell according to claim 1, comprising: The fastening member is
A first support bar provided on one of the end plates;
A second support bar which is provided on the other end plate and into which the first support bar is slidably inserted;
An elastic member that is attached to the first support bar and the second support bar and clamps the laminate by a contraction force;
The fuel cell according to claim 1, comprising:   4. The fuel cell according to claim 1, wherein the fastening member is provided at each of two positions facing each other through the stacked body.   The fuel cell according to claim 1, wherein the fastening member is provided so as to penetrate the laminated body. The laminate and the two end plates are provided with their centers aligned,
The fuel cell according to claim 5, wherein the fastening member is provided in a range of ½ or less of a distance from a center to an outer periphery of the stacked body and the end plate.   The fuel cell according to claim 6, wherein the fastening member is provided at a center of the laminated body and the end plate.   The fuel cell according to claim 7, wherein the end plate is a circular plate.   The fuel cell according to any one of claims 1 to 8, wherein the fastening member fastens the laminated body so that the center of gravity of the laminated body and the two end plates coincide with each other.   The fuel cell according to any one of claims 1 to 9, wherein the fuel is a fuel containing alcohol.   The fuel cell according to claim 10, wherein the alcohol is ethanol.   An electronic device comprising the fuel cell according to any one of claims 1 to 11.

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