JP2007173110A - Fuel cell and power source system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell and a power source system in which a fuel transmission to a cathode is prevented, while a power generation is not in operation. <P>SOLUTION: The fuel cell includes a cathode 2, an anode 3 and a fuel chamber 5 in which a liquid fuel is contained, a gas liquid separation layer 7 which transmits selectively steam of the above liquid fuel in the above fuel chamber 5 and a squeezing mechanism 8 which is arranged between the gas liquid separation layer 7 and the anode and controls a transmission amount of the steam of the liquid fuel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell and a power supply system including the fuel cell.

  In recent years, various electronic devices such as personal computers and mobile phones have been miniaturized with the development of semiconductor technology, and attempts have been made to use fuel cells as power sources for these small devices. Fuel cells have the advantage that they can generate electricity simply by supplying fuel and oxidant, and can continuously generate electricity by replenishing and replacing only the fuel. It can be said that the system is extremely advantageous for operation. In particular, direct methanol fuel cells (DMFCs) use methanol with high energy density as fuel and can directly extract current from methanol on the electrode catalyst, so a reformer is not required and the size can be reduced. It is possible and the fuel is easier to handle than hydrogen gas fuel, so it is promising as a power source for small equipment.

  DMFC fuel supply methods include a gas supply type DMFC in which liquid fuel is vaporized and then fed into the fuel cell by a blower or the like, and a liquid supply type DMFC in which liquid fuel is directly fed into the fuel cell by a pump or the like. However, in these fuel supply methods, the pump for supplying methanol and the blower for supplying air are required as auxiliary devices as described above, and the system has a complicated form and has a drawback that it is difficult to reduce the size.

  On the other hand, an internal vaporization type DMFC as shown in Patent Document 1 is known as another fuel supply method. This internal vaporization type DMFC includes a fuel permeation layer for holding liquid fuel, and a fuel vaporization layer for diffusing a vaporized component of the liquid fuel held in the fuel permeation layer. Supplied from the fuel vaporization layer to the anode. In Patent Document 1, a methanol aqueous solution in which methanol and water are mixed at a molar ratio of 1: 1 is used as a liquid fuel, and both methanol and water are supplied to the anode in the form of vaporized gas.

However, in the internal vaporization type DMFC shown in Patent Document 1, since fuel is supplied by a vaporization reaction, it is difficult to control the amount of fuel supply, and there is a problem in suppressing methanol crossover when power generation is stopped.
Japanese Patent Publication No. 3413111

  The objective of this invention is providing the fuel cell and power supply system which can suppress the fuel permeation to the cathode at the time of an electric power generation stop.

A fuel cell according to the present invention comprises a cathode,
An anode,
A fuel chamber containing liquid fuel;
A gas-liquid separation layer that selectively permeates the vapor of the liquid fuel in the fuel chamber;
A throttle mechanism is provided between the gas-liquid separation layer and the anode, and controls a permeation amount of the vapor of the liquid fuel.

The power supply system according to the present invention includes a charge storage mechanism, a fuel cell that supplies charges to the charge storage mechanism, and a control that controls the operation of the throttle mechanism of the fuel cell in accordance with a residual charge amount of the charge storage mechanism. A mechanism,
The fuel cell includes a cathode, an anode, a fuel chamber in which liquid fuel is accommodated, a gas-liquid separation layer that selectively transmits vapor of the liquid fuel in the fuel chamber, the gas-liquid separation layer, and the anode. And a throttle mechanism that controls the permeation amount of the vapor of the liquid fuel.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell and power supply system which can suppress the fuel permeation | transmission to the cathode at the time of an electric power generation stop can be provided.

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

(First embodiment)
FIG. 1 is a cross-sectional view schematically showing a state in which the throttle mechanism of the direct methanol fuel cell according to the first embodiment of the present invention is opened, and FIG. 2 shows the direct methanol fuel cell of FIG. FIG. 3 is a cross-sectional view schematically showing a state where the aperture mechanism is closed, and FIG. 3 is a schematic diagram showing a positional relationship between the aperture mechanism and the anode.

  As shown in FIG. 1, a membrane electrode assembly (MEA) 1 includes a cathode 2 (for example, an oxidizer electrode), an anode 3 (for example, a fuel electrode), and a solid electrolyte membrane disposed between the cathode 2 and the anode 3. 4. The cathode 2 includes a cathode gas diffusion layer 2a and a cathode catalyst layer 2b laminated on the cathode gas diffusion layer 2a. On the other hand, the anode 3 includes an anode gas diffusion layer 3a and an anode catalyst layer 3b laminated on the anode gas diffusion layer 3a.

  The cathode gas diffusion layer 2a plays a role of uniformly supplying an oxidizing agent to the cathode catalyst layer 2b, but also serves as a current collector for the cathode catalyst layer 2b. Further, the cathode gas diffusion layer 3a serves to uniformly supply fuel to the anode catalyst layer 3b, and also serves as a current collector for the anode catalyst layer 3b. Examples of the cathode gas diffusion layer 2a and the cathode gas diffusion layer 3a include carbon paper.

  Examples of the catalyst contained in the cathode catalyst layer 2b and the anode catalyst layer 3b include platinum group element simple metals (Pt, Ru, Rh, Ir, Os, Pd, etc.), alloys containing platinum group elements, and the like. be able to. It is desirable to use Pt—Ru, which is highly resistant to liquid fuels such as methanol and carbon monoxide, as the anode catalyst, and platinum as the cathode catalyst, but it is not limited to this. Further, a supported catalyst using a conductive support such as a carbon material may be used, or an unsupported catalyst may be used.

  Examples of the proton conductive material contained in the solid electrolyte membrane 4 include a fluorine-based resin having a sulfonic acid group (for example, perfluorosulfonic acid polymer) and a hydrocarbon-based resin having a sulfonic acid group (for example, sulfonic acid). Group, polyether ketone having a group, sulfonated polyether ether ketone), and inorganic substances such as tungstic acid and phosphotungstic acid, but are not limited thereto.

  A liquid fuel tank 5 is disposed below the membrane electrode assembly 1 as a fuel chamber. A liquid fuel 6 is accommodated in the liquid fuel tank 5. Examples of the liquid fuel 6 include pure methanol and aqueous methanol solution. The methanol concentration of the liquid fuel is preferably 64% by weight or more and 100% by weight or less. A more preferable range of the methanol concentration is 65% by weight or more and 100% by weight or less. Note that the liquid fuel stored in the liquid fuel tank 5 is not necessarily limited to methanol fuel, and may be ethanol fuel such as an aqueous ethanol solution or pure ethanol, dimethyl ether, formic acid, or other liquid fuel. In any case, liquid fuel corresponding to the fuel cell is accommodated.

  Above the opening of the liquid fuel tank 5, a gas-liquid separation membrane 7 as a gas-liquid separation layer is disposed. The gas-liquid separation membrane 7 has a function of separating the vapor of the liquid fuel and the liquid component by selectively transmitting the vapor of the liquid fuel. Examples of the gas-liquid separation membrane 7 include a silicone rubber sheet.

  The throttle mechanism 8 is disposed between the gas-liquid separation membrane 7 and the anode 3. The throttle mechanism 8 is for controlling the amount of liquid fuel vapor supplied to the anode, and includes a movable plate 9 disposed opposite to the gas-liquid separation film 7 and a fixed plate 10 stacked on the movable plate 9. Is. The size of the fixing plate 10 is larger than the reaction area of the anode 3 as shown in FIG. Further, the fixed plate 10 has a plurality of rectangular fuel permeation holes 11. In FIG. 3, although the shape of the fuel permeation hole 11 is rectangular, it is not limited to this, and for example, it can be a polygonal shape (for example, a triangle, a hexagon, etc.) other than a rectangle, a circle, an ellipse, or the like. However, in order to increase the opening area of the fuel permeation hole 11, a rectangular shape is advantageous. The opening area of the fuel permeation hole 11 is desirably 50% or less. If the opening area exceeds 50%, the moving distance of the movable plate 9 necessary for closing the fuel permeation hole 11 may increase, or it may be difficult to close the fuel permeation hole 11 in the non-opening region of the movable plate 9. There is sex. The size of the fuel permeation hole 11 can be about 1 to 2 mm × 3 to 10 mm. Further, it is desirable that the pitch interval of the fuel permeation holes 11 is about several millimeters.

  The rectangular frame-shaped sealing member 12 is disposed between the lower surface periphery of the solid electrolyte membrane 4 and the upper surface periphery of the gas-liquid separation membrane 7, and seals between the solid electrolyte membrane 4 and the gas-liquid separation membrane 7. . The gas vent hole 12a is opened at a position above the throttle mechanism 8 of the seal member 12, and exhaust gas such as carbon dioxide generated by power generation is exhausted therefrom.

  The fixing plate 10 is fixed to a rectangular frame-shaped sealing member 12 so as to face the anode gas diffusion layer 3a. An opening 13 is formed in the movable plate 9 at a position facing the fuel transmission hole 11 of the fixed plate 10. The shape of the opening 13 may be different from that of the fuel permeation hole 11, but is preferably substantially the same. The movable plate 9 is disposed immediately below the fixed plate 10. From the side surface of the movable plate 9, a resin support rod 14 extends in the horizontal direction. The support bar 14 is inserted into the horizontal hole of the seal member 12 so as to be horizontally movable, and the vicinity of the tip is drawn out to the outside. For example, the magnetic block 15 formed of iron is fixed to the tip of the support bar 14. The electromagnet 16 is disposed at a desired distance from the magnetic block 15. The spring support plate 17 is fixed to the lower peripheral surface of the support bar 14. One end of the spring 18 is fixed to the spring support plate 17 and the other end is in a free state.

  The operation of the direct methanol fuel cell configured as described above will be described. At the time of power generation, as shown in FIG. 1, the current supply to the electromagnet 16 is stopped, and the support plate 17 is pressurized in the horizontal direction by the spring 18, thereby moving the movable plate 9 horizontally in the direction away from the electromagnet 16. The position of the opening 13 of the plate 9 is matched with the position of the fuel permeation hole 11 of the fixed plate 10. Thereby, the fuel permeation hole 11 of the fixed plate 10 is opened. The open state is maintained by pressurizing the support plate 17 with a constant pressure by the spring 18.

  The vapor of the liquid fuel that has diffused through the gas-liquid separation membrane 7 passes through the opening 13 of the movable plate 9 and the fuel permeation hole 11 of the fixed plate 10, and then diffuses through the anode gas diffusion layer 3a to the anode catalyst layer 3b. Supplied. The steam supplied to the anode catalyst layer 3b reacts with an oxidant (for example, air) supplied to the cathode catalyst layer 2b to generate a power generation reaction.

  When power generation is stopped, as shown in FIG. 2, the electromagnet 16 is energized and the magnetic block 15 is attracted to the electromagnet 16. Thereby, since the movable plate 9 moves horizontally in a direction approaching the electromagnet 16, the position of the opening 13 of the movable plate 9 is shifted from the position of the fuel transmission hole 11 of the fixed plate 10, and the fuel transmission hole 11 of the fixed plate 10 is moved. The movable plate 9 is blocked by a non-opening region. As a result, the supply of fuel to the anode 3 is stopped, so that power generation is interrupted and fuel permeation (methanol crossover) to the cathode 2 during power generation stoppage can be suppressed, thereby reducing fuel waste. it can. In addition, since the aperture mechanism 8 is opened and closed by the horizontal movement of the movable plate 9, it is less likely to prevent miniaturization of the fuel cell.

(Second Embodiment)
FIG. 4 is a cross-sectional view schematically showing a state in which the throttle mechanism of the direct methanol fuel cell according to the second embodiment of the present invention is opened, and FIG. 5 shows the direct methanol fuel cell of FIG. It is sectional drawing which showed typically the state by which the aperture mechanism is obstruct | occluded.

  4 and 5, members similar to those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  The fuel cell according to the second embodiment is an example in which the drive unit of the aperture mechanism 8 is changed. As shown in FIG. 4, a resin movable rod 19 extends in the horizontal direction from the side surface of the movable plate 9. The movable rod 19 is inserted into the horizontal hole of the sealing material 12 in a state where it can freely move horizontally, and the vicinity of the tip is drawn out to the outside. Teeth 20 are provided in the vicinity of the tip of the movable bar 19. A gear 21 meshed with the teeth 20 of the movable bar 19 is attached to a rotating shaft 22 of a motor (not shown). When the gear 21 is rotated by the rotation of the motor, the movable bar 19 in which the gear 21 and the teeth 20 are engaged moves in the horizontal direction. Thereby, the movable plate 9 moves in the horizontal direction, and the fuel permeation hole 11 of the fixed plate 10 is opened and closed.

  According to the fuel cell having such a configuration, during power generation, the movable rod 19 is horizontally moved leftward by rotating the motor counterclockwise (in the direction of the arrow in FIG. 4). As the movable bar 19 moves, the movable plate 9 also moves horizontally in the left direction, so that the position of the opening 13 of the movable plate 9 can be adjusted to the position of the fuel transmission hole 11 of the fixed plate 10. Thereby, the fuel permeation hole 11 of the fixed plate 10 is opened.

  The vapor of the liquid fuel that has diffused through the gas-liquid separation membrane 7 passes through the opening 13 of the movable plate 9 and the fuel permeation hole 11 of the fixed plate 10, and then diffuses through the anode gas diffusion layer 3a to the anode catalyst layer 3b. Supplied. The steam supplied to the anode catalyst layer 3b reacts with an oxidant (for example, air) supplied to the cathode catalyst layer 2b to generate a power generation reaction.

  When stopping power generation, as shown in FIG. 5, the movable rod 19 is moved horizontally in the right direction by rotating the motor clockwise (in the direction of the arrow in FIG. 5). As the movable rod 19 moves, the movable plate 9 also moves horizontally in the right direction. Therefore, the position of the opening 13 of the movable plate 9 deviates from the position of the fuel transmission hole 11 of the fixed plate 10, and the fuel transmission hole of the fixed plate 10. 11 is blocked by the non-opening region of the movable plate 9. As a result, the supply of fuel to the anode 3 is stopped, so that power generation is interrupted and fuel permeation (methanol crossover) to the cathode 2 during power generation stoppage can be suppressed, thereby reducing fuel waste. it can. In addition, since the aperture mechanism 8 is opened and closed by the horizontal movement of the movable plate 9, it is less likely to prevent miniaturization of the fuel cell.

  In the first and second embodiments described above, the movable plate 9 is opposed to the gas-liquid separation film 7, but the arrangement of the movable plate 9 and the fixed plate 10 can be reversed, and the fixed plate 10 is replaced with the gas-liquid separation. It may be opposed to the separation membrane 7.

  The movable plate 9, the fixed plate 10, the support rod 14, and the movable rod 19 are preferably formed from a resin that is stable against methanol.

(Third embodiment)
The third embodiment is a power supply system including the fuel cell according to the first embodiment or the second embodiment.

  FIG. 6 is a block diagram of a power supply system according to the third embodiment. The charge storage mechanism 31 plays a role of supplying power to an external load. For the charge storage mechanism 31, a capacitor and a secondary battery (for example, an alkaline secondary battery such as a nickel hydride secondary battery or a nonaqueous electrolyte secondary battery such as a lithium secondary battery) are used. The fuel cell 32 plays a role of supplying charges to the charge storage mechanism 31. As the fuel cell 32, the fuel cell according to the first embodiment or the second embodiment is used. The control mechanism 33 monitors the remaining electricity amount (remaining charge amount) of the charge storage mechanism 31 and transmits a control signal to the fuel cell 32 according to the remaining electricity amount of the charge storage mechanism 31.

  When the remaining electricity amount of the charge storage mechanism 31 is equal to or less than the set value, the control mechanism 33 transmits a signal to the fuel cell 32 so as to open the throttle mechanism 8. As a result, the throttle mechanism 8 is opened and fuel is supplied to the anode 3, so that the fuel cell generates power and charges are supplied to the charge storage mechanism 31.

  When the remaining amount of electricity in the charge storage mechanism 31 exceeds the set value, the control mechanism 33 transmits a signal to the fuel cell 32 so as to close the throttle mechanism 8. As a result, the throttle mechanism 8 is closed, and the fuel supply to the anode 3 is stopped. Therefore, the power generation of the fuel cell is stopped, and the charge supply to the charge storage mechanism 31 is stopped.

  Thus, since the fuel supply to the anode 3 can be controlled in accordance with the charge supply to the charge storage mechanism 31, the fuel loss can be reduced and the efficiency of the power supply system can be increased.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The sectional view showing typically the state where the diaphragm mechanism of the direct type methanol fuel cell concerning a first embodiment of the present invention is opened. FIG. 2 is a cross-sectional view schematically showing a state in which a throttle mechanism of the direct methanol fuel cell in FIG. 1 is closed. The schematic diagram which showed the positional relationship of an aperture mechanism and an anode. Sectional drawing which showed typically the state by which the aperture mechanism of the direct methanol fuel cell which concerns on 2nd embodiment of this invention is open | released. FIG. 5 is a cross-sectional view schematically showing a state in which a throttle mechanism of the direct methanol fuel cell in FIG. 4 is closed. The block diagram of the power supply system which concerns on 3rd embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Membrane electrode assembly (MEA), 2 ... Cathode, 2a ... Cathode gas diffusion layer, 2b ... Cathode catalyst layer, 3 ... Anode, 3a ... Anode gas diffusion layer, 3b ... Anode catalyst layer, 4 ... Solid electrolyte membrane, DESCRIPTION OF SYMBOLS 5 ... Liquid fuel tank, 6 ... Liquid fuel, 7 ... Gas-liquid separation layer, 8 ... Throttle mechanism, 9 ... Movable plate, 10 ... Fixed plate, 11 ... Fuel permeation hole, 12 ... Sealing material, 13 ... Opening part, 14 DESCRIPTION OF SYMBOLS ... Support rod, 15 ... Magnetic block, 16 ... Electromagnet, 17 ... Spring support plate, 18 ... Spring, 19 ... Movable rod, 20 ... Teeth, 21 ... Gear, 22 ... Motor rotating shaft, 31 ... Charge storage mechanism, 32 ... Fuel cell, 33 ... Control mechanism.

Claims (8)

A cathode,
An anode,
A fuel chamber containing liquid fuel;
A gas-liquid separation layer that selectively permeates the vapor of the liquid fuel in the fuel chamber;
A fuel cell comprising: a throttle mechanism that is disposed between the gas-liquid separation layer and the anode and controls a permeation amount of the vapor of the liquid fuel.   The throttle mechanism includes a fixed plate having a fuel permeation hole and an opening formed at a position facing the fuel permeation hole. The throttle mechanism moves in parallel with the fixed plate to reduce an opening area of the fuel permeation hole. The fuel cell according to claim 1, further comprising a movable plate to be controlled.   The fuel cell according to claim 1 or 2, wherein an opening area of the fuel permeation hole of the fixing plate is 50% or less.   The fuel cell according to any one of claims 1 to 3, wherein the driving means for the movable plate includes a magnetic body formed on the movable plate and an electromagnet facing the magnetic body.   The movable plate driving means includes a motor, a gear disposed on a shaft of the motor, and a movable rod formed on the movable plate and having teeth engaged with the gear. Item 4. The fuel cell according to any one of Items 1 to 3. A charge storage mechanism;
The fuel cell according to any one of claims 1 to 5, wherein charge is supplied to the charge storage mechanism;
A power supply system comprising: a control mechanism that controls the operation of the throttle mechanism of the fuel cell in accordance with a remaining charge amount of the charge storage mechanism.   The power supply system according to claim 6, wherein the charge storage mechanism is a secondary battery.   The control mechanism outputs a control signal for opening the throttle mechanism when a residual charge amount of the charge storage mechanism is equal to or less than a set value, and closing the throttle mechanism when the residual charge amount exceeds the set value. The power supply system according to claim 6 or 7, wherein the power supply system transmits to a battery.

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