JP2010027467A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell can control supply of fuel without depending on electric power, and reduce power consumption of a control device or the like. <P>SOLUTION: The fuel cell is provided with a membrane electrode assembly having a fuel electrode 113, an air electrode 116, and an electrolyte membrane 117 pinched by the fuel electrode 113 and the air electrode 116, a fuel supply part 2 connected to the fuel electrode 113 through a passage, and a shape memory alloy 5 of which a part is fixed to a heat generating part of the membrane electrode assembly and adjusts the fuel supply amount to the membrane electrode assembly by deforming by receiving heat. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell using liquid fuel.

  The use of small fuel cells is attracting attention as a power source for mobile devices such as notebook computers and mobile phones. Conventional secondary batteries need to be connected to an outlet for charging for a certain period of time, but fuel cells can be used simply by replenishing the fuel for supply, making them extremely suitable as power sources for mobile devices. Yes.

  As such a fuel cell for mobile devices, a direct methanol fuel cell (DMFC) is particularly promising. As a DMFC liquid fuel supply system, there is an active system in which fuel supply is controlled by a pump or a valve in addition to a passive system such as an internal vaporization type. When a fuel cell is put into practical use as a power source for a mobile device, it is important to reduce the size and improve the safety.

  In the DMFC, when methanol as a fuel is excessively supplied to the power generation unit, there is a risk that the power generation unit, particularly the cathode, abnormally generates heat. In order to prevent heat generation due to such an excessive supply of fuel, a fuel cell including a device that detects the temperature of the power generation unit and controls the amount of fuel supply has been manufactured. However, it is conceivable that such a control device may break down. Therefore, even if such a device is provided, it cannot be said that safety is ensured.

  The control device always controls the supply amount according to the temperature even during normal power generation. Therefore, power from the power generation unit or power from an independent external power source is consumed. There is also a need to reduce the power consumption of such a control device in order to increase the output and size of the fuel cell.

Patent Document 1 describes a valve or the like for shutting off the supply of fuel. However, Patent Document 1 uses a valve or the like that operates by heating due to the reaction between the fuel and the oxidant to solve the problem due to fuel leakage, and does not prevent abnormal heat generation when the fuel is excessively supplied. .
JP 2006-19102 A

  An object of the present invention is to provide a fuel cell that can control the supply of fuel without depending on electric power and can reduce power consumption of a control device or the like.

  According to one aspect of the present invention, a fuel electrode, an air electrode, a membrane electrode assembly having an electrolyte membrane sandwiched between the fuel electrode and the air electrode, and a fuel connected to the fuel electrode via a flow path A shape memory alloy that adjusts the amount of fuel supplied from the fuel supply unit to the membrane electrode assembly by being deformed by receiving a heat and being partly fixed to the heat generating unit of the membrane electrode assembly A fuel cell comprising:

  According to the present invention, it is possible to provide a fuel cell capable of controlling the supply of fuel without depending on electric power and reducing power consumption of a control device or the like.

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

  FIG. 1 shows a configuration of a fuel cell according to an embodiment of the present invention. The fuel cell includes a power generation unit 1, a fuel supply unit 2, a pump 3, a fuel cutoff unit 4, and a shape memory alloy 5.

  The fuel cell in FIG. 1 is a type of fuel cell called a semi-passive that uses a pump or the like for part of the fuel supply. In the semi-passive type fuel cell, the fuel supplied from the fuel supply unit 2 to the power generation unit 1 is used for a power generation reaction and is not circulated thereafter and returned to the fuel supply unit 2. The semi-passive type fuel cell is different from the conventional active method because it does not circulate the fuel, and does not impair the downsizing of the device. In addition, the fuel cell uses a pump for supplying fuel, and is different from a pure passive system such as a conventional internal vaporization type. For this reason, the fuel cell is referred to as a semi-passive method as described above.

  The power generation unit 1 includes a fuel battery cell 11 and a fuel distribution mechanism 12.

  The fuel cell 11 includes an anode (fuel electrode) 113 having an anode catalyst layer 111 and an anode gas diffusion layer 112, and a cathode (air electrode or oxidant electrode) 116 having a cathode catalyst layer 114 and a cathode gas diffusion layer 115. And a membrane electrode assembly (MEA) composed of a proton (hydrogen ion) conductive electrolyte membrane 117 sandwiched between the anode catalyst layer 114 and the cathode catalyst layer 115. The fuel cell 11 preferably includes a cover plate 118, an O-ring 119, and a power generation unit porous body 120.

  Examples of the catalyst contained in the anode catalyst layer 111 and the cathode catalyst layer 114 include simple elements of platinum group elements such as Pt, Ru, Rh, Ir, Os, and Pd, and alloys containing these platinum group elements. For the anode catalyst layer 111, it is preferable to use a Pt—Ru alloy or a Pt—Mo alloy having strong resistance to methanol, carbon monoxide and the like. Pt or Pt—Ni alloy is preferably used for the cathode catalyst layer 114. However, the anode catalyst layer 111 and the cathode catalyst layer 114 are not limited to these catalysts, and various substances having catalytic activity can be used. As the catalyst, a supported catalyst using a conductive support such as a carbon material, or an unsupported catalyst may be used.

  As the proton conductive material constituting the electrolyte membrane 117, for example, a fluororesin such as a perfluorosulfonic acid polymer having a sulfonic acid group (trade name Nafion (manufactured by DuPont) or trade name Flemion (manufactured by Asahi Glass Co., Ltd.)) or An organic material such as a hydrocarbon-based resin having a sulfonic acid group, or an inorganic material such as tungstic acid or phosphotungstic acid is used. However, the material of the electrolyte membrane 117 is not limited to these.

  The anode gas diffusion layer 112 uniformly supplies fuel to the anode catalyst layer 111 and serves as a current collector for the anode catalyst layer 111. Further, the cathode gas diffusion layer 115 uniformly supplies an oxidant to the cathode catalyst layer 114 and plays a role as a current collector of the cathode catalyst layer 114. The anode gas diffusion layer 112 and the cathode gas diffusion layer 115 are made of a porous substrate.

  The conductive layer is laminated on the anode gas diffusion layer 112 and the cathode gas diffusion layer 115 as necessary (not shown in FIG. 1). As the conductive layer, for example, a porous body (for example, a mesh), a foil body or a thin film made of a conductive metal material such as Au or Ni, or a conductive metal material such as stainless steel (SUS) or a good material such as gold. A composite material coated with a conductive metal is used. Further, rubber O-rings 119 are sandwiched between the electrolyte membrane 117 and the fuel distribution mechanism 12 and between the cover plate 118 and the electrolyte membrane 117, respectively, and these leak fuel from the power generation unit 1. And prevent oxidant leakage. The cover plate 118 can be provided with an opening for taking in air as an oxidant. A moisture retaining layer (not shown) and / or a surface layer (not shown) can be provided between the cover plate 118 and the cathode 116 as necessary. The moisturizing layer is impregnated with a part of the water generated in the cathode catalyst layer 114 to suppress the transpiration of water and promote uniform diffusion of air to the cathode catalyst layer 114. The surface layer adjusts the amount of air taken in, and has a plurality of air inlets whose number, size, etc. are adjusted according to the amount of air taken in.

  The fuel distribution mechanism 12 is provided on the anode (fuel electrode) 113 side of the fuel battery cell 11. The fuel distribution mechanism 12 is connected to the fuel supply unit 2 via a liquid fuel flow path 13. Liquid fuel is supplied from the fuel supply unit 2 to the fuel distribution mechanism 12 via the flow path 13. When the fuel distribution mechanism 12 and the fuel supply unit 2 are stacked and integrated, the flow path 13 may be a liquid fuel flow path 13 that connects the fuel distribution mechanism 12 and the fuel supply unit 2. As long as it is connected to the fuel supply unit 2 via the other structure, other structures can be adopted. However, in any case, the pump 3 and the fuel shut-off unit 4 described later need to be disposed in the flow path 13.

  As shown in FIG. 1, the fuel distribution mechanism 12 includes at least one fuel inlet 121 through which liquid fuel flows, and a plurality of fuel outlets 122 through which liquid fuel and vaporized components thereof are discharged to the fuel cell 11. It has the fuel distribution plate 123 which has. Inside the fuel distribution plate 123, as shown in FIG. 1, a thin tube 124 serving as a passage for the liquid fuel led from the fuel inlet 121 is provided. The thin tube 124 is preferably a through hole having an inner diameter of 0.05 to 5 mm, for example. The plurality of fuel discharge ports 122 are directly connected to narrow tubes 124 that function as fuel passages. The liquid fuel introduced into the fuel distribution mechanism 12 from the fuel inlet 121 enters the thin tubes 124 and is guided to the plurality of fuel discharge ports 122 via the thin tubes 124 functioning as fuel passages. For example, a gas separator (not shown) that transmits only the vaporized component of the liquid fuel and does not transmit the liquid component may be disposed in the plurality of fuel discharge ports 122. Thus, only the vaporized component of the liquid fuel is supplied to the anode (fuel electrode) 113 of the fuel battery cell 11. The gas / liquid separator may be installed as a gas / liquid separation membrane or the like between the fuel distribution mechanism 12 and the anode 113. The vaporized component of the liquid fuel is discharged from a plurality of fuel discharge ports 122 toward a plurality of locations on the anode 113.

  Further, it is effective to insert the power generation unit porous body 120 between the fuel distribution mechanism 12 and the anode (fuel electrode) 113. Various resins are used as the constituent material of the power generation unit porous body 120, and a resin film or the like in a porous state is used as the power generation unit porous body 120. By disposing such a power generation unit porous body 120, the fuel supply to the fuel electrode 113 can be further averaged. That is, the liquid fuel ejected from the fuel discharge port 122 of the fuel distribution mechanism 12 is once absorbed by the power generation unit porous body 120 and diffuses in the in-plane direction inside the power generation unit porous body 120. Thereafter, the fuel is supplied from the power generation unit porous body 120 to the fuel electrode 113, so that the fuel supply can be further averaged.

The fuel released from the fuel distribution mechanism 12 is supplied to the anode (fuel electrode) 113 of the fuel cell 11 as described above. In the fuel battery cell 11, the fuel is diffused in the anode gas diffusion layer 112 and supplied to the anode catalyst layer 111. When methanol fuel is used as the liquid fuel, an internal reforming reaction of methanol represented by the following formula (1) occurs in the anode catalyst layer 111.
CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ (1).

  When pure methanol is used, water generated in the cathode catalyst layer 114 and / or water in the electrolyte membrane 117 is reacted with methanol to cause an internal reforming reaction of the formula (1). Alternatively, the internal reforming reaction is caused by another reaction mechanism that does not require water.

Electrons (e ⁻ ) generated by this reaction are guided to the outside via a current collector, and are operated to a cathode (air electrode) 116 after operating a portable electronic device or the like as so-called electricity. In addition, protons (H ⁺ ) generated by the internal reforming reaction of the formula (1) are guided to the cathode 116 through the electrolyte membrane 117. Air is supplied to the cathode 116 as an oxidant. The electrons (e ⁻ ) and protons (H ⁺ ) that have reached the cathode 116 react with oxygen in the air in accordance with the following formula (2) in the cathode catalyst layer 114, and water is generated along with this reaction.
6e ⁻ + 6H ⁺ + (3/2) O ₂ → 3H ₂ O (2).

  The fuel cell 11 has a cover plate 118, and one end of the wire-shaped shape memory alloy 5 is fixed to one point on one side of the cover plate 118. It arrange | positions so that it may extend in the direction of a side. In order to efficiently transfer the heat of the cover plate 118, the contact portion can be appropriately devised. For example, the shape memory alloy 5 can be fixed so as to meander on the surface of the cover plate 118, and the contact area can be increased. As a material of the cover plate 118, a resin such as polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE) can be used. It is preferable to form the metal material.

  The fuel supply unit 2 stores liquid fuel corresponding to the fuel battery cell 11. The fuel supply unit 2 may be in the form of a tank and can be replenished with liquid fuel from the outside, or may be in the form of a cartridge and the fuel supply unit 2 itself is already filled with fuel. It can be exchanged for. A known fuel supply unit 2 can be used. As the material for the fuel supply unit 2, it is preferable to use a material having methanol resistance. For example, a metal material can be used as a raw material if measures are taken by surface treatment or the like in order to prevent elution of metal ions into PPS (polyphenylene sulfide), COC (cycloolefin copolymer) or fuel. In particular, it is preferable to use PPS (polyphenylene sulfide).

  As the liquid fuel, methanol fuels such as methanol aqueous solutions of various concentrations or pure methanol can be used as described above. However, it is also possible to use other fuels, for example, ethanol fuel such as ethanol aqueous solution or pure ethanol, propanol fuel such as propanol aqueous solution or pure propanol, glycol fuel such as glycol aqueous solution or pure glycol, dimethyl ether, formic acid, Other fuels can be used. In any case, the fuel supply unit 2 stores liquid fuel corresponding to the fuel battery cell 11.

  The pump 3 is provided in a flow path 13 that connects the fuel supply unit 2 and the power generation unit 1 in order to send the liquid fuel of the fuel supply unit 2 to the power generation unit 1. As the pump 3, a diaphragm pump, a rotary vane pump, an electroosmotic flow pump, a squeezing pump, or the like can be used. However, the present invention is not limited to these, and any pump used in the art can be used. Preferably, the flow rate of the pump 3 is appropriately adjusted by the control device (CTR) 6. The control device (CTR) 6 is connected to the anode 113 and the cathode 116 and can be operated by electric power supplied from the fuel cell 11.

  The fuel shut-off unit 4 is provided in a flow path that connects the fuel supply unit 2 and the pump 3. The fuel blocking unit 4 adjusts the flow of the liquid fuel from the fuel supply unit 2 by blocking or opening the flow path. In particular, when the power generation unit 1 abnormally generates heat, further heat generation can be suppressed by blocking or reducing the liquid fuel supply by blocking the flow path.

  The structure of the fuel cutoff part 4 will be described. The fuel cutoff unit 4 can include a cutoff valve 41 and an actuator 42. In this case, the actuator 42 is operated to adjust the opening and closing of the shutoff valve 41. The actuator 42 can be controlled by a control device (CTR) as described above. Further, a shape memory alloy 5 is connected to the fuel cutoff portion 2, and the flow path cutoff is also adjusted by the shape memory alloy 5.

  A known valve can be used as the shutoff valve 41. An example of the shut-off valve 41 is shown with reference to FIGS. As shown in FIGS. 2A and 2B, the cutoff valve 41 has a cutoff valve unit 41U. The shutoff valve unit 41U has a valve chamber 411 into which fuel is injected from the fuel supply unit 2, a convex portion 413 projecting from the wall surface of the valve chamber 411, and a narrow portion 412 surrounded by the convex portion 413. The wall surface of the valve chamber 411 has a fuel injection port MIN through which fuel flows from the fuel supply unit 2, and the narrow portion 412 is provided with an exhaust port MOUT serving as an outlet for the fuel flowing into the shutoff valve.

  Further, the shutoff valve 41 has a columnar rod LOD1 disposed over the valve chamber 411 and the narrow portion 412. The rod LOD1 has a columnar part A and a valve head B that protrudes from the columnar part A and exists in the valve chamber 411. A surface of the valve chamber 411 opposite to the convex portion 413 is enclosed by the movable film FLM. The movable film FLM is fixed between the holder HL and the wall surface of the valve chamber 411. For this reason, the inflow and outflow of fuel is limited to only those that pass through the fuel inlet MIN and the outlet MOUT. In the rod LOD1, one end of the columnar portion A is in contact with the movable film FLM. The rod LOD1 is supported by the movable film FLM, the wall surface of the valve chamber 411 in contact with the valve rod B, and the wall surface of the narrow portion 412 in contact with the opposite side portion of the columnar part A to the movable film FLM. However, the valve head B and the wall surface of the valve chamber 411 and between the columnar part A and the wall surface of the narrow part 412 are not completely in contact with each other, and there is a gap that allows liquid fuel to flow in. ing. In addition, an O-ring RNG is disposed between the convex portion 413 and the valve head B so as to surround the columnar portion A. Further, the rod LOD1 has a recess at the end opposite to the surface in contact with the movable film FLM, and a spring SPR is provided between the recess and the recess provided on the wall surface of the narrow portion 412. .

  The holder HL is provided with an opening, through which the slider columnar portion SLD2 of the slider SLD is inserted and is in contact with the movable film FLM. The slider columnar portion SLD2 is in contact with the rod LOD1 through the movable film FLM. 1 is arranged in contact with the outer surface of the slider head SLD1 of the slider SLD, the other end of the shape memory alloy 5 being a holder. It is fixed at one point on the outer surface of the HL. Further, the movable rod LOD2 of the actuator 42 is in contact with the slider head SLD1.

  Next, the mechanism of the fuel cutoff unit 4 will be described. When the shut-off valve is opened, the liquid fuel that has flowed from the fuel inlet MIN passes through the valve chamber 411 and the narrow portion 412 and is discharged from the outlet MOUT (FIG. 2A). On the other hand, when the shutoff valve is shut off, the liquid fuel that has flowed from the fuel inlet MIN stays in the valve chamber 411 and is not discharged from the outlet MOUT (FIG. 2B). When each state is specifically described, at the time of opening (a), the rod LOD1 is pushed in the direction of the movable film FLM by the force of the extension of the spring SPR, and the O-ring RNG and the convex portion 413 are opened. . Therefore, the liquid fuel does not stay in the valve chamber 411 but passes through the narrow portion 412 and is discharged from the discharge port MOUT. On the other hand, at the time of blocking (b), the slider SLD slides into the blocking valve 41 by the operation of the actuator 42 and / or the shape memory alloy 5 and further moves the rod LOD1 through the movable film FLM. Slide in the direction of the narrow portion 412. By this slide, the O-ring RNG approaches or comes into contact with the convex portion 413, the communication between the valve chamber 411 and the narrow portion 412 is blocked, and the liquid fuel remains in the valve chamber 411. Here, the operation of the actuator 42 is a movement of moving the movable rod 2 so as to push the slider SLD in the direction of the shutoff valve. Further, here, the operation of the shape memory alloy 5 is a movement of the movable rod 2 to be deformed by receiving the heat of the cover plate 118 and to push the slider SLD in the direction of the shutoff valve. The force that pushes the slider SLD of the actuator 42 and the shape memory alloy 5 is a force that exceeds the sum of the force that the spring SPR extends and the force that pushes back the slider of the movable film FLM. Further, the extending force of the spring SPR is a force that exceeds the pressure with which the liquid fuel pushes the valve head B, and is a force that pushes back the rod LOD1 in a state where the actuator 42 and / or the shape memory alloy 5 do not operate. .

  The movable film FLM has a central portion FLM1 and a ring-shaped end portion FLM2 surrounding the periphery thereof. The movable film FLM is fixed to the holder HL by the end portion FLM2. The movable film FLM is formed of, for example, EPDM (ethylene-propylene-diene rubber) having methanol resistance. However, the material of the movable film is not limited to EPDM, and VMQ (silicone rubber), FVMQ (fluorosilicone rubber), FKM (fluororubber), NBR (nitrile rubber), and HNBR (hydrogenated nitrile rubber) are preferably used. Further, the materials listed above are preferably used for the end portion FLM2, and for the central portion FLM1, a resin having methanol resistance, such as PEI (polyetherimide), PI (polyimide), PEEK (polyetheretherketone), PPS. It is good also as a structure which uses films, such as (polyphenylene sulfide), and formed the edge part FLM2 of the lip shape on the film. As shown in FIGS. 2A and 2B, the end FLM2 has a circular cross section, and the diameter thereof can be made larger than the thickness of the central portion FLM1. Further, the cross section of the end portion FLM2 is not limited to a circular shape, and may have a substantially rhombus shape in order to increase the seal surface pressure.

  Since the spring SPR is arranged in the fuel flow path and comes into contact with the fuel, it is preferable to use a spring-treated one. Specifically, a stainless steel spring that has been passivated to enhance corrosion resistance is preferable. The surface treatment is not limited to the passivation treatment, and a precious metal plating such as gold or a resin coating such as a fluorine-based resin is preferably used. Also, a spring using carbon as a material can be used.

  As the actuator 42, an electric drive capable of controlling its operation with an electric signal can be used. For example, a stepping motor can be used. However, the configuration is not limited to that of electric drive, and the movable rod LOD2 can be manually operated, or can be configured to be operated by both electric drive and manual operation.

  The shape memory alloy 5 is preferably a wire-shaped one, but other shapes can also be used. For example, in order to efficiently absorb the heat generated from the cover plate 118, the contact surface with the cover plate 118 can be made flat to increase the contact area. The member with which the shape memory alloy 5 is brought into contact is not limited to the cover plate 118 and may be any member as long as it is a heat generating portion of the membrane electrode assembly. As a material of the shape memory alloy 5, titanium-nickel alloy, iron-manganese-silicon alloy, copper-zinc-aluminum alloy, titanium-nickel-iron alloy, titanium-nickel-copper alloy and the like can be used. The temperature at which the shape memory alloy 5 is deformed is preferably set as appropriate in accordance with the design of the fuel cell and the position where the shape memory alloy is disposed. Such a preferred temperature is between 45 ° C. and 70 ° C., in particular the use of shape memory alloy 5 which deforms at a temperature between 60 ° C. and 65 ° C. is preferred. Further, the mechanism by which the shape memory alloy 5 pushes the slider SLD is not limited to the mechanism shown in FIG. Any mechanism may be used as long as the shape memory alloy 5 is deformed by receiving heat from the cover plate 118 and the slider SLD is pushed in by the deforming force. Therefore, a mechanism in which a wire such as a resin is fixed to the slider SLD and the wire such as a resin is pulled by a force that deforms the shape memory alloy 5 and the slider SLD is pushed in may be used.

  Further, the movable film FLM is not limited to a planar disk shape as shown in FIGS. 2 (a) and 2 (b). For example, as shown in FIGS. 3A and 3B, the center portion FLM1 having a curved surface recessed toward the valve chamber 411 can be used. In this case, even when the slider SLD is not pressing the movable film FLM, the movable film FLM is recessed toward the valve chamber 411 side. When the slider SLD protrudes, the rod LOD1 is pressed to the narrow portion 412 side via the movable film FLM. At this time, the movable film FLM is recessed in advance to the valve chamber 411 side, so that the slider SLD is movable. The load for pressing the membrane FLM toward the valve chamber 411 is reduced. Further, as shown in FIGS. 4A and 4B, a bellows-shaped central portion FLM1 can be used. In this case, the central portion FLM1 of the movable film FLM has a first portion F1 that is in contact with the slider SLD and a second portion F2 that connects the first portion F1 and the end portion FLM2. Further, the second portion F2 is bent outward at the central portion in the axial direction of the rod LOD1. Since the movable film FLM has such a bellows shape, the movable film FLM is easily deformed when pressed by the movement of the slider SLD, and the load on the slider SLD can be reduced. .

  FIG. 5 is a cross-sectional view showing a fuel cell according to an embodiment of the present invention. As in the embodiment according to FIG. 1, the power generation unit 1, the fuel supply unit 2, the pump 3, and the fuel cutoff unit 4 have the shape memory alloy 5 extending from the cover plate 118 of the power generation unit 1. Are directly fixed to the flow path 13 between them.

  The power generation unit 1, the fuel supply unit 2, the pump 3, and the optionally provided control device CTR in the embodiment according to FIG. 5 are the same as the respective units described in the embodiment according to FIG. The shape memory alloy 5 is not connected to the fuel cutoff part 4. That is, the fuel cutoff part in which the shape memory alloy 5 is removed from the fuel cutoff part 4 shown in FIGS. Further, the slider SLD is excluded from these, and a fuel cutoff part in which the movable rod LOD2 of the actuator 42 is in direct contact with the movable film FLM can be used. However, it is not limited to the fuel shut-off portion as shown in FIGS. 2, 3 and 4, and a valve known in the art can be used.

  As shown in FIG. 5, one end of the wire-shaped shape memory alloy 5 is wound around the flow path, and it can be blocked by detecting heat and deforming to narrow the flow path. The flow path can be made of a soft material so that the flow of fuel is blocked by the deformation force of the shape memory alloy 5. For example, it can be made of rubber or silicon. In particular, it is preferable to use EPDM (ethylene-propylene-diene rubber) as a raw material. The inner diameter of the channel can be 1 mm and the outer diameter can be 1.5 to 2.0 mm. As used herein, the term “blocking” includes not only completely blocking the opening, but also reducing the amount of liquid fuel that passes by narrowing the opening.

  Further, the shape memory alloy 5 extending from the cover plate 118 is connected to both the flow passage blocking unit 6 and the flow channel 13, and the fuel supply amount adjustment by the shape memory alloy 5 is adjusted to both the fuel blocking unit 4 and the flow channel 13. It is also possible to adopt a configuration to be performed.

  According to the fuel cell of the present invention, the shape memory alloy 5 adjusts the flow rate of the liquid fuel in response to the heat generated in the power generation unit 1. Specifically, when the temperature exceeds a certain temperature, the shape memory alloy 5 is deformed, and the valve of the fuel shut-off unit 4 is shut off or the flow path 13 is narrowed to stop or reduce the fuel supply. With such a function, the shape memory alloy 5 functions as an emergency stop safety device that stops the supply of fuel when the power generation unit 1 abnormally generates heat, or during normal power generation, the control device CTR 6 and the actuator 42 It functions to assist operation and reduce power consumption. The former function works even when the control device CTR6 fails, and can effectively prevent abnormal heat generation of the power generation unit 1. For the latter function, it is effective to set the set temperature of the control device CTR for determining the temperature at which the shut-off operation command is sent and the change temperature of the shape memory alloy 5 in consideration of each other. . For example, by setting the change temperature of the shape memory alloy 5 to be lower than the temperature at which the control device CTR6 sends the command, the shape memory alloy 5 operates in preference to the control device CTR6, whereby the control device CTR6 and the actuator The operation of 42 can be reduced, leading to a reduction in power consumption. Also, by setting the temperature at the time of change of the shape memory alloy 5 high, it does not operate in the temperature range during normal power generation, and operates only to shut off when the temperature range greatly exceeds the temperature range and an emergency stop is required. You can also. According to the present invention, it is possible to provide a fuel cell that includes a fuel control safety device that does not depend on electric power, and that can further suppress power consumption by the control device CTR and the like.

  Below, the effect of this invention is demonstrated based on an Example.

  It was confirmed that the power consumption by the control device CTR6 and the actuator 42 can be reduced by the fuel cell according to the present invention.

[Example]
The fuel cell of the embodiment according to FIG. 1 and the fuel cell of the embodiment according to FIG. 5 were prepared. In particular, the fuel shut-off unit 4 uses the shut-off valve shown in FIG. 2 and a stepping motor as the actuator 42. The controller CTR6 that controls the stepping motor monitors the temperature near the surface of the cathode 116 of the power generation unit 1 with a thermistor, and shuts off the shutoff valve 41 when the temperature exceeds 70 ° C. during steady operation, and shuts off when the temperature falls below 65 ° C. The valve 41 was set to be opened. The shape memory alloy 5 used was deformed at 60 ° C. or higher.

[Comparative example]
Moreover, the thing similar to the fuel cell of an Example was prepared except not having the shape memory alloy 5 as a comparative example.

[Experiment]
The fuel cells of the above examples and comparative examples were operated for 24 hours, and the power consumption of the control device CTR6 and the stepping motor at that time was measured.

[result]
The power consumption in the comparative example was about 50 mW, whereas the power consumption in the example was about 5 mW.

  In the fuel cell according to the example, it was confirmed that the shape memory alloy 5 was operated before the temperature of the cathode 116 reached 70 ° C. As a result, the fuel supply amount was adjusted, and the number of times the stepping motor was operated was smaller than that of the comparative example. As a result, it is considered that the power consumption of the fuel cell according to the example was reduced to about 1/10 of the comparative example.

  It has been confirmed that the fuel cell according to the present invention surely reduces the power consumption of the control device CTR6 and the actuator.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements 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 components 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.

  Further, the liquid fuel supplied to the power generation unit may be supplied entirely with vapor of liquid fuel, but the present invention can be applied even when a part of the liquid fuel is supplied in a liquid state.

The figure which shows the structure of the fuel cell based on one Embodiment of this invention. Sectional drawing which shows an example of the fuel cutoff part in the fuel cell of this invention. Sectional drawing which shows an example of the fuel cutoff part in the fuel cell of this invention. Sectional drawing which shows an example of the fuel cutoff part in the fuel cell of this invention. The figure which shows the structure of the fuel cell based on one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Power generation part, 11 ... Fuel cell, 111 ... Anode catalyst layer, 112 ... Anode gas diffusion layer, 113 ... Anode (fuel electrode), 114 ... Cathode catalyst layer, 115 ... Cathode gas diffusion layer, 116 ... Cathode (air) Poles or oxidizer poles), 117 ... electrolyte membrane, 118 ... cover plate, 119 ... O-ring, 120 ... power generation part porous body, 13 ... flow path, 2 ... fuel supply part, 3 ... pump, 4 ... fuel cutoff part, 41 ... Shut-off valve, 41U ... Shut-off valve unit, 411 ... Valve chamber, 412 ... Narrow part, 413 ... Convex part, 42 ... Actuator, MIN ... Injection port, MOUT ... Discharge port, FLM ... Movable membrane, FLM1 ... Central part, FLM2 ... end, LOD1 ... rod, A ... columnar part, B ... valve head, RNG ... O-ring, SPR ... spring, LOD2 ... movable rod, HL ... holder , HL2 ... second holder, 5 ... shape memory alloy, 6 ... control device (CTR).

Claims (7)

A membrane electrode assembly having a fuel electrode, an air electrode, and an electrolyte membrane sandwiched between the fuel electrode and the air electrode;
A fuel supply unit connected to the fuel electrode via a flow path;
A shape memory alloy that adjusts the amount of fuel supplied from the fuel supply unit to the membrane electrode assembly by being partially fixed to the heat generating part of the membrane electrode assembly and deformed by receiving heat. A fuel cell characterized by the above. A pump located in the flow path and for feeding fuel from the fuel supply unit to the fuel electrode;
A fuel cutoff part located in a flow path between the fuel supply part and the pump;
The fuel cell according to claim 1, further comprising:   The fuel cell according to claim 1, wherein the shape memory alloy has a wire shape.   The fuel cell according to claim 2, wherein a part of the shape memory alloy is fixed to the fuel cutoff part.   2. The fuel cell according to claim 1, wherein a part of the shape memory alloy is fixed to the flow path.   The fuel cell according to claim 5, wherein the shape memory alloy is wound around and fixed to the flow path.   The fuel cell according to claim 1, wherein the fuel is methanol or a methanol aqueous solution.

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