JP2010108614A - Fuel cell - Google Patents

Abstract

A fuel supply amount and a fuel supply time for each part of an electromotive part of a fuel cell are equalized by improving the structure of a curved part of a flow path that inhibits the flow of liquid fuel.
A fuel cell includes an electromotive unit including a membrane electrode assembly and a fuel storage unit that stores liquid fuel. The fuel electrode of the membrane electrode assembly includes a plurality of fuel discharge ports connected to the fuel injection port via a fuel flow channel composed of a fuel injection port connected to the fuel storage portion, a straight portion, and a curved portion. Fuel is supplied from a fuel supply unit having In the curved portion 27 of the fuel flow path, a section 29 including at least a portion connected to the straight portion 25 is constituted by a clothoid curve.
[Selection] Figure 5

Description

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

  A direct methanol fuel cell (DMFC) is promising as a power source and a charger for portable electronic devices because it can be miniaturized and can easily handle fuel. As the liquid fuel supply method in the DMFC, there are known an active method such as a gas supply type and a liquid supply type, and a passive method such as an internal vaporization type in which the liquid fuel in the fuel container is vaporized inside the cell and supplied to the fuel electrode. It has been.

  In the passive DMFC, for example, a structure is adopted in which an electromotive unit including a membrane electrode assembly (MEA) having a fuel electrode, an electrolyte membrane, and an air electrode is disposed on the fuel storage unit. In such a structure, it is difficult to improve the controllability of the battery output. Therefore, the electromotive part of the DMFC and the fuel storage part are connected via a flow path, or liquid fuel is pumped from the fuel storage part to the flow path. Has been proposed (see Patent Documents 1 and 2). When fuel is supplied from the fuel storage part to the electromotive part via the flow path, it is required to supply the fuel evenly to the entire surface of the electromotive part.

  Therefore, it has been studied to use a flow path plate in which a fuel inlet and a plurality of fuel outlets are connected by a flow path (pipe). In order to supply the fuel evenly to the entire surface of the electromotive unit, the piping in the flow path plate is branched into a plurality of parts on the way, and a fuel discharge port is provided at each end of the piping. By equalizing the distance from the fuel inlets of the flow path plate to the multiple fuel outlets and increasing the number of fuel outlets, the fuel can be evenly supplied to the electromotive section (equal supply amount and supply time). Increase). However, since the flow path must be set within a limited area, it is necessary to configure the flow path (pipe) by combining not only a straight line but also a curve.

However, the curved portion of the flow path (pipe) becomes a factor that hinders the flow of liquid fuel. In particular, when the flow path plate is applied to a small DMFC, the pipe diameter of the internal piping itself needs to be reduced, so that the flow of the liquid fuel tends to stagnate at the curved portion. Further, in order to shorten the fuel supply time, it is necessary to increase the supply speed of the liquid fuel. In such a case, the speed control of the liquid fuel tends to occur at the curved portion of the piping. As described above, when the flow of the liquid fuel is inhibited, the uniform supply of fuel to the entire surface of the electromotive portion (fuel electrode) is hindered.
JP 2005-518646 A JP 2006-089552 A

  An object of the present invention is to improve the structure of the curved portion of the flow path that obstructs the flow of liquid fuel, thereby equalizing the fuel supply amount and fuel supply time for each part of the electromotive unit, and generating power over the entire electromotive unit. It is an object of the present invention to provide a fuel cell with improved reaction efficiency.

  A fuel cell according to an aspect of the present invention contains a fuel electrode, an air electrode, an electromotive unit including a membrane electrode assembly having an electrolyte membrane sandwiched between the fuel electrode and the air electrode, and a liquid fuel And a plurality of fuel discharge ports connected to the fuel injection port via a fuel flow path constituted by a straight portion and a curved portion. And a fuel supply part that supplies fuel to the fuel electrode, and a flow path shape of a section including a portion connected to at least the linear part of the curved part is configured by a clothoid curve. It is said.

  In the fuel cell according to the aspect of the present invention, since the clothoid curve is applied to the flow path shape of the curved portion of the fuel flow path, the fuel can flow smoothly at the curved portion. Therefore, the fuel supply amount and fuel supply time for each part of the electromotive unit are made uniform, and a power generation reaction can be efficiently generated in the entire electromotive unit. As a result, the output characteristics of the fuel cell can be improved.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of a fuel cell according to an embodiment of the present invention. A fuel cell 1 shown in FIG. 1 accommodates a liquid fuel by an electromotive unit 2 including a membrane electrode assembly (MEA), a fuel supply mechanism 4 including a fuel supply unit 3 for supplying fuel to the electromotive unit 2. It is mainly composed of the fuel storage portion 5.

  The electromotive unit 2 includes an anode (fuel electrode) 8 having an anode catalyst layer 6 and an anode gas diffusion layer 7, and a cathode (air electrode / oxidant electrode) 11 having a cathode catalyst layer 9 and a cathode gas diffusion layer 10. And a membrane electrode assembly (MEA) 13 comprising a proton (hydrogen ion) conductive electrolyte membrane 12 sandwiched between an anode catalyst layer 6 and a cathode catalyst layer 9.

  Examples of the catalyst contained in the anode catalyst layer 6 and the cathode catalyst layer 9 include a simple substance of a platinum group element such as Pt, Ru, Rh, Ir, Os, and Pd, and an alloy containing the platinum group element. The anode catalyst layer 6 is preferably made of Pt—Ru, Pt—Mo, or the like that has strong resistance to methanol, carbon monoxide, or the like. It is preferable to use Pt, Pt—Ni or the like for the cathode catalyst layer 9. However, the catalyst is not limited to these, and various substances having catalytic activity can be used. The catalyst may be either a supported catalyst using a conductive support such as a carbon material or an unsupported catalyst.

  The anode gas diffusion layer 7 laminated on the anode catalyst layer 6 has a current collecting function of the anode catalyst layer 6 at the same time as supplying fuel to the anode catalyst layer 6 uniformly. The cathode gas diffusion layer 10 laminated on the cathode catalyst layer 9 has a current collecting function of the cathode catalyst layer 9 while supplying the oxidant uniformly to the cathode catalyst layer 9. The anode gas diffusion layer 7 and the cathode gas diffusion layer 10 are made of a conductive porous substrate capable of circulating fuel and air, for example, a carbon porous substrate such as carbon paper or carbon cloth.

  The electrolyte membrane 12 is made of a proton conductive material. Examples of the proton conductive material constituting the electrolyte membrane 12 include fluorine-based resins such as perfluorosulfonic acid polymer having a sulfonic acid group (Nafion (trade name, manufactured by DuPont) and Flemion (trade name, manufactured by Asahi Glass Co., Ltd.). Etc.), organic materials such as hydrocarbon resins having sulfonic acid groups, or inorganic materials such as tungstic acid and phosphotungstic acid. However, the proton conductive electrolyte membrane 11 is not limited to these materials.

  The electromotive unit 2 is configured by sandwiching the MEA 13 between an anode current collector 14 and a cathode current collector 15. The anode current collector 14 is laminated with the anode gas diffusion layer 7, and the cathode current collector 15 is laminated with the cathode gas diffusion layer 10. The current collectors 14 and 15 have through holes through which fuel and air flow. The current collectors 14 and 15 are covered with a porous layer (for example, a mesh) made of a conductive metal material such as Au or Ni, a foil, or a conductive metal material such as stainless steel with a good conductive metal such as Au. The composite material etc. which were made are used. The electromotive unit 2 is sealed by a sealing member 16 such as an O-ring, and fuel leakage and oxidant leakage from the MEA 13 are prevented.

  The electromotive unit 2 is disposed on the fuel supply unit 3. The fuel supply unit 3 is disposed on the anode 8 side of the MEA 13 constituting the electromotive unit 2. The fuel supply unit 3 supplies the fuel while dispersing and diffusing the fuel in the surface direction of the anode 8, that is, distributing and supplying the fuel to the entire surface of the anode 8. The fuel supply unit 3 is connected to the fuel storage unit 5 via a fuel pipe 17. Liquid fuel is introduced into the fuel supply unit 3 from the fuel storage unit 5 through the fuel pipe 17. The connection body between the fuel supply unit 3 and the fuel storage unit 5 is not limited to an independent pipe. For example, a connection flow path in the case where the fuel supply unit 3 and the fuel storage unit 5 are stacked may be used. Good.

  As shown in FIGS. 2 and 3, the fuel supply unit 3 discharges at least one fuel inlet 18 through which liquid fuel flows from the fuel storage unit 5 through the fuel pipe 17, and discharges the liquid fuel and its vaporized components. A fuel distribution plate (flow path plate) 20 having a plurality of fuel discharge ports 19 is formed. Inside the fuel distribution plate 20, a thin tube 21 that functions as a fuel flow path (pipe) is provided. A fuel injection port 18 is provided at one end (starting end) of the thin tube 21. The narrow tube 21 is branched into a plurality of portions along the way, and a fuel discharge port 19 is provided at each end portion of the branched thin tube 21.

  The liquid fuel introduced into the fuel distribution plate 20 from the fuel inlet 18 is guided to a plurality of fuel outlets 19 through a plurality of thin tubes 21, and the vaporized component (fuel) is supplied to the anode 8 of the MEA 13. The A fuel diffusion chamber (fuel diffusion space) may be provided between the MEA 13 and the fuel distribution plate 20. It is also effective to dispose a fuel diffusion porous body or the like between the MEA 13 and the fuel distribution plate 20 instead of the fuel diffusion chamber. Various resins are used as the constituent material of the porous body for diffusion, and porous resin sheets (such as foamed polyethylene sheets and foamed polyurethane sheets), resin nonwoven fabrics, and resin woven fabrics can be used.

A plurality of fuel discharge ports 19 are provided on the surface of the fuel distribution plate 20 in contact with the anode 8 so as to uniformly supply fuel to the entire electromotive unit 2 (MEA 13). The number of the fuel discharge ports 19 may be plural. However, in order to equalize the fuel supply amount to each part in the plane of the MEA 13, the fuel discharge ports 19 of 0.1 to 10 pieces / cm ² seem to exist. It is preferable to form. If the number of the fuel discharge ports 19 is less than 0.1 / cm ² , the fuel supply amount to the entire surface of the MEA 13 may not be sufficiently equalized. Even if the number of the fuel discharge ports 19 exceeds 10 / cm ² , not only the effect is not obtained, but also the flow path design by the thin tube 21 is complicated, and the flow of the liquid fuel is impaired. There is a fear.

  The thin tube 21 is preferably a through hole formed inside the fuel distribution plate 20, and the inner diameter thereof is preferably in the range of 0.05 to 5 mm. If the inner diameter of the narrow tube 21 is less than 0.05 mm, the flow of liquid fuel may be hindered. Although the thin tube 21 having a large inner diameter is effective for smoothing the flow of the liquid fuel, the formation area of the flow path is increased accordingly, so that the flow from the fuel inlet 18 to the plurality of fuel outlets 19 is increased. It may be difficult to adjust (uniformize) the road length. The inner diameter of the thin tube 21 is preferably 5 mm or less.

  The narrow tube 21 provided inside the fuel distribution plate 20 has a branch portion, and is branched in order from the fuel inlet 18 toward the plurality of fuel outlets 19 at the branch portion. The branch portion of the thin tube 21 is preferably set so that the cross-sectional area after branching is equal to or smaller than the cross-sectional area before branching so as to suppress pressure loss. The narrow tube 21 connected to the fuel inlet 18 is branched into four at the first branch, for example, and is further branched at a plurality of branches to be connected to the fuel outlet 19. The number of branches of the narrow tube 21 is appropriately set according to the number of fuel discharge ports 19 and the area of the fuel distribution plate 20.

  The branch of the narrow tube 21 is performed in order to connect the plurality of fuel discharge ports 19 to the fuel injection port 18 and to equalize the distance from the fuel injection port 18 to the plurality of fuel discharge ports 19. Furthermore, the narrow tube 21 is required to have a flow channel shape that allows liquid fuel to flow smoothly. In satisfying such conditions, the flow path shape by the narrow tube 21 is configured by combining a straight portion and a curved portion. In particular, it is preferable that the curved portion of the thin tube 21 has a flow channel shape that allows the liquid fuel to flow smoothly, that is, a flow channel shape that does not cause rate control of the liquid fuel at the connecting portion between the straight portion and the curved portion. A specific flow path shape of the thin tube 21 will be described in detail later.

  By applying the fuel distribution plate 20 having such a thin tube 21 as the fuel supply unit 3, it is possible to equalize the amount of fuel supplied, the supply time, and the like to the plurality of fuel discharge ports 19. Therefore, it is possible to supply fuel evenly over the entire surface of the MEA 13 and efficiently generate a power generation reaction in the entire MEA 13. Thereby, the output characteristics of the fuel cell 1 can be improved. The fuel supply unit 3 may be composed of a flow path plate having a fuel flow groove functioning as a fuel flow path and a diffusion plate arranged so as to cover the opening of the fuel flow groove. In this case, the diffusion plate is provided with a through hole serving as a fuel discharge port.

  Then, the electromotive unit 2 and the moisturizing layer 22 are laminated on the fuel supply unit 3, and a metal (for example, stainless steel) cover plate 23 is placed thereon to hold the whole so that a fuel cell (DMFC) One power generation unit is configured. The moisturizing layer 22 is impregnated with a part of the water generated in the cathode catalyst layer 9 to suppress the transpiration of water and promote uniform diffusion of air to the cathode catalyst layer 9. The moisture retention layer 22 is made of a porous member having moisture retention, and for example, a resin porous plate made of polyethylene, polypropylene, polyurethane or the like is used. The cover plate 23 has an opening 23a for introducing air.

  The fuel supply unit 3 is connected to the fuel storage unit 5 through the fuel pipe 17 as described above. Liquid fuel corresponding to the MEA 13 is stored in the fuel storage unit 5. Examples of the liquid fuel include methanol fuels such as aqueous methanol solutions of various concentrations and pure methanol. Liquid fuel is not limited to this, but ethanol fuel such as ethanol aqueous solution and pure ethanol, propanol fuel such as propanol aqueous solution and pure propanol, glycol fuel such as glycol aqueous solution and pure glycol, dimethyl ether, formic acid, and other liquid fuels There may be.

  A pump 24 is interposed in the flow path 17. The pump 24 is not a circulation pump that circulates fuel, but is a fuel supply pump that sends liquid fuel from the fuel storage unit 5 to the fuel supply unit 3 to the last. The fuel supplied from the fuel supply unit 3 to the MEA 13 is used for the power generation reaction, and is not circulated thereafter and returned to the fuel storage unit 5. Since the fuel cell 1 does not circulate fuel, it is different from the conventional active method. Further, the pump 24 is used to supply the liquid fuel, which is different from a pure passive system such as a conventional internal vaporization type. The fuel cell 1 of this embodiment applies a system called a semi-passive type.

  The type of the pump 24 is not particularly limited, but a rotary vane pump, an electroosmotic flow pump, a diaphragm pump, from the viewpoint that a small amount of liquid fuel can be sent with good controllability and can be reduced in size and weight. It is preferable to use an ironing pump or the like. In the fuel cell 1, liquid fuel is intermittently sent from the fuel storage unit 5 to the fuel supply unit 3 using the pump 24. The operation of the pump 24 is controlled based on, for example, the output of the fuel cell 1, temperature information, operation information of an electronic device that is a power supply destination, and the like.

  Since the main target of the fuel cell 1 is a small electronic device, the liquid feeding capacity of the pump 24 is preferably in the range of 10 μL / min to 1 mL / min. When the liquid feeding capacity exceeds 1 mL / min, the amount of liquid fuel fed at one time becomes too large, and the stop time of the pump 24 in the entire operation period becomes long. For this reason, the fluctuation in the amount of fuel supplied to the MEA 13 increases, and as a result, the fluctuation in output increases. If the liquid feeding capacity of the pump 24 is less than 10 μL / min, there is a risk of insufficient supply capacity when the amount of fuel consumption increases, such as when the apparatus is started up (at startup). The pumping capacity of the pump 31 is more preferably in the range of 10 to 200 μL / min.

By sending liquid fuel from the fuel storage unit 5 to the fuel supply unit 3, the fuel is discharged from the plurality of fuel discharge ports 19 of the fuel distribution plate 20. The fuel released from the fuel supply unit 3 is supplied to the anode (fuel electrode) 8 of the MEA 13. In the MEA 13, the fuel diffuses through the anode gas diffusion layer 7 and is supplied to the anode catalyst layer 6. 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 6. When pure methanol is used as the methanol fuel, the water produced in the cathode catalyst layer 9 or the water in the electrolyte membrane 12 is reacted with methanol to cause the internal reforming reaction of the formula (1).
_{CH 3 OH + H 2 O →} CO 2 + 6H + + 6e - ... (1)

The electrons (e ⁻ ) generated by this reaction are guided to the outside via the current collector 14, and after operating a portable electronic device or the like as so-called electricity, the cathode (air electrode) via the current collector 15. ) 11. Protons (H ⁺ ) generated by the internal reforming reaction of the formula (1) are guided to the cathode 11 through the electrolyte membrane 12. Air is supplied to the cathode 11 as an oxidant. Electrons (e ⁻ ) and protons (H ⁺ ) reaching the cathode 11 react with oxygen in the air in the cathode catalyst layer 9 according to the following formula (2), and water is generated along with this reaction.
6e ⁻ + 6H ⁺ + (3/2) O ₂ → 3H ₂ O (2)

  In the fuel cell 1 of this embodiment, in order to make use of the performance of the electromotive unit 2, it is necessary to supply fuel evenly to the entire surface of the electromotive unit 2 (MEA 13). For this purpose, the liquid fuel introduced into the fuel inlet 18 of the fuel distribution plate 20 needs to flow evenly and smoothly to the plurality of fuel outlets 19. Therefore, in the fuel cell 1, each fuel discharge from the fuel inlet 18 is made by connecting the straight flow paths (straight portions) with curved flow paths (curved portions) while branching the thin tubes 21 in the fuel distribution plate 20. The distance to the outlet 19 is made uniform.

  FIG. 4 is an enlarged view of a portion A in FIG. 3 and shows a part of a thin tube (fuel flow path) 21 composed of a straight portion and a curved portion. The straight portion 25A of the thin tube 21 is branched into two at the branch portion 26A, and is connected to the straight portions 25B and 25C via the curved portions 27A and 27B, respectively. Further, the straight portion 25B is branched into two at the branch portion 26B and connected to the straight portions 25D and 25E via the curved portions 27C and 27D, respectively. The straight portion 25C is the same, and after being branched into two at the branch portion 26C, it is connected to the straight portions 25F and 25G via the curved portions 27E and 27F. The straight portions 25D to 25G are connected to the fuel discharge ports 19A to 19D, respectively.

  When the pipe having such a channel shape is configured, the straight portions are usually connected by a curved portion (single arc-shaped curved portion) having a constant curvature radius. When the radius of curvature in the curved portion of the pipe is large or the pipe diameter of the pipe is large, the flow of the liquid fuel is not hindered by the curved portion. However, if the curved part of the pipe cannot be formed with a large radius of curvature, and if the pipe diameter of the pipe cannot be made sufficiently large, the joint between the straight part and the curved part is the flow of liquid fuel. This prevents the liquid fuel from flowing smoothly into the pipe (narrow tube 21).

  That is, when a curved portion having a constant radius of curvature (R) is applied, the curvature of the straight line portion (zero) is instantaneously changed from the curvature of the straight line portion (zero) at the joint portion. For example, if the liquid fuel flowing in the pipe is likened to a car, the angle of the handle necessary to run the curved part needs to be adjusted (cut the handle) instantly at the joint between the straight part and the curved part. Will occur. In this case, the angle of the handle corresponds to the curvature of the curved portion. For this reason, when a curved portion having a constant curvature radius is applied, the speed control of the liquid fuel flowing in the pipe is generated at the joint portion, and the liquid fuel cannot be flowed smoothly.

Particularly, in order to form the fuel discharge ports 19 densely in the fuel distribution plate 20 (for example, the formation density of the fuel discharge ports 19 is 2 / cm ² or more), the thin tube (pipe) 21 is branched many times (for example, When the radius of curvature of the curved portion 27 of the narrow tube 21 can only be 1.5 mm or less due to the area limitation of the fuel distribution plate 20, or when the tube diameter is 0.5 mm or less In addition, the curved portion 27 tends to hinder the flow of liquid fuel. In addition, when the liquid fuel is forcibly sent into the fuel distribution plate 20 using the pump 24 and the flow rate (supply rate) of the liquid fuel is increased (the flow rate is 50 μL / min or more), the curved portion 27 of the narrow tube 21 is used. As a result, the rate control of the liquid fuel tends to occur. Speed control is more likely to occur as the flow rate increases.

  Therefore, in the fuel cell 1 of this embodiment, the clothoid curve is applied to the flow path shape of the curved portion 26 of the thin tube 21 provided in the fuel distribution plate 20. The flow path shape to which the clothoid curve is applied is applied to a section including a portion (joint portion) connected to at least the straight portion 25 of the curved portion 26. Moreover, it is preferable to apply the shape of the flow path composed of clothoid curves to all the curved portions 26. For example, the curved portion 27 that can have a radius of curvature exceeding 10 mm has a constant curvature radius (single curve). Arc). The flow path shape to which the clothoid curve is applied is applied to at least a part of the curved portion 26.

  In the clothoid curve, the radius of curvature of the curved portion 26 is gradually reduced from the joint portion with the straight portion 25 (the radius of curvature is infinite), and finally the desired radius of curvature is obtained. That is, when the radius of curvature of the curved portion 26 is R, the length of the curved portion 26 is L, and the final radius of curvature is R1, the curved portion 26 to which the clothoid curve is applied is connected to the straight portion 25. From the curvature (0) of the eye portion to the final curvature (1 / R1), gradually change according to the curvature of the clothoid curve (1 / R = C · L (C is an arbitrary constant in the range of 0 to 1)). Since the curvature of the curved portion 26 gradually increases from zero, the rate control of the liquid fuel at the joint portion between the straight portion 25 and the curved portion 26 is relaxed. Flows smoothly.

  FIG. 5 shows an example of a thin tube 21 in which a clothoid curve is applied to the curved portion 26. The thin tube 21 has a flow channel shape in which two straight portions 251 and 252 are connected by a curved portion 27. The curved portion 27 has a single circular arc section (curved section having a constant radius of curvature R1) 28 near the center thereof. The sections between the single circular arc section 28 and the straight sections 251 and 252 of the curved portion 27 are each a clothoid curve section (a curve in which the curvature gradually changes based on a clothoid curve section (cursoid curve (curvature 1 / R = C · L)). Section) 29a, 29b.

  The flow path shapes of the clothoid curve sections 29a and 29b of the curved portion 27 will be described with reference to FIGS. FIG. 6 shows the relationship between the curvature 1 / R and the curve length L of the curved portion 27 having a single arc section 28 and clothoid curve sections 29a and 29b. In addition, the broken line in FIG. 5 has shown the thin tube shape at the time of connecting the two linear parts 251 and 252 with the curved part (single circular arc-shaped curved part) with a curvature radius R1. FIG. 7 shows the relationship between the curvature 1 / R1 and the curve length L of the curved portion 30 having a constant radius of curvature R1.

  As shown in FIGS. 5 and 6, the clothoid curve section 29a extends from the joint portion P1 (curvature = 0) to the straight portion 251 to the joint portion P2 (curvature = 1 / R1) to the single arc section 28. The curvature (1 / R) changes according to the curvature C · L (L = 0 to 1 / CR = 1 / R1) of the clothoid curve. Here, C is an arbitrary constant that changes continuously (or intermittently). The curvature 1 / R of the clothoid curve section 29a gradually increases from the curvature (0) of the joint portion P1, and finally reaches the curvature (1 / R1) of the joint portion P2. Similarly, the curvature 1 / R of the clothoid curve section 29b gradually decreases from the curvature (1 / R1) of the joint portion P3 with the single arc section 28, and finally the joint portion P4 with the straight line portion 252. The curvature (0) is reached.

  Thus, by providing clothoid curve sections 29a and 29b between the two straight sections 251 and 252 and the single arc section 28 of the curved section 27, the joint between the straight sections 251 and 252 and the curved section 27 is provided. The rate control of the liquid fuel in the portions P1 and P4 is relaxed. For this reason, the liquid fuel can flow smoothly also in the curved portion 27. This means that the liquid fuel flows smoothly through the thin tubes 21 connected to the plurality of fuel discharge ports 19 while repeating branching. Accordingly, it is possible to equalize the fuel release properties from the plurality of fuel discharge ports 19 and, in turn, the amount of fuel supplied to the entire MEA 13 and the supply time.

  On the other hand, as shown in the broken line in FIG. 5 and FIG. 7, when the two straight portions 251 and 252 are connected by the curved portion 30 having a constant radius of curvature R1, the curvature is instantaneously generated at the joint portions P1 and P4. Since it changes, it turns out that the rate control of liquid fuel is easy to generate in this part. Furthermore, when the tube diameter of the thin tube 21 is small, there is a possibility that clogging may occur even with a small amount of impurities based on the rate-limiting at the joint portion. These are factors that hinder the uniform supply of fuel to the entire MEA 13. The curve portion 27 having the clothoid curve sections 29a and 29b eliminates such a factor that hinders the uniform supply of fuel to the entire MEA 13.

  The curve portion 27 having the clothoid curve sections 29a and 29b described above is branched many times (for example, the number of branches is 50 or more), the curvature radius of the curve portion 27 is 1.5 mm or less, and the tube diameter is 0. It is effective for a thin tube 21 of 5 mm or less. Furthermore, even when the flow rate (supply speed) of the liquid fuel is 50 μL / min or more, the curved portion 27 having the clothoid curve sections 29a and 29b acts effectively. In the fuel cell 1 of this embodiment, the fuel distribution plate 20 has the narrow tube 21 having the above-described conditions.

  In the fuel cell 1 of this embodiment, since the clothoid curve is applied to at least a part of the curved portion 27 of the thin tube (fuel flow path) 21 in the fuel distribution plate 20, the entire thin tube 21 including the curved portion 27 is applied. It becomes possible to maintain the flow of the liquid fuel well. Therefore, the fuel supply amount and supply time to the entire MEA 13 are equalized, and the power generation reaction occurs efficiently in the entire MEA 13, so that the output characteristics of the fuel cell 1 can be improved. That is, it becomes possible to provide the fuel cell 1 that is excellent in output characteristics and its stability.

  Next, specific examples of the fuel cell of the present invention and evaluation results thereof will be described.

Example 1
Here, a fuel cell (DMFC) having an outer dimension of 50 × 90 mm is manufactured. In such a fuel cell, about 120 fuel outlets of the fuel distribution plate and about 250 curved portions of the thin tubes are required. Further, the minimum diameter of the thin tube in the fuel distribution plate is 0.05 mm, and the minimum radius of curvature of the curved portion is 0.8 mm. Such a fuel distribution plate (thickness t = 1.8 mm) was produced by applying a clothoid curve to the curved portion of the thin tube (minimum diameter d = 0.05 mm). Using this fuel distribution plate, a DMFC power generation unit was manufactured, and methanol was intermittently supplied as a liquid fuel with a pump to perform a power generation test.

  As a result of the power generation test described above, it was confirmed that in the DMFC of Example 1, fuel was evenly supplied to the entire fuel electrode. Furthermore, it was confirmed that the fuel tube was not rate-controlled or clogged with the narrow tube of the fuel distribution plate. As a result, improvement in output characteristics of DMFC was recognized. The outer dimensions of the fuel distribution plate are within the above-described area A (50 × 90 mm) of the DMFC, and the thickness of the fuel distribution plate satisfies t (1.8 mm).

(Comparative Example 1)
A fuel distribution plate was produced in the same manner as in Example 1 except that a single arc curve (single R curve) having a constant curvature radius was applied to the curved portion of the thin tube. The radius of curvature R of the single arc curve was set to 0.8 mm so as to satisfy the above-described outer dimensions (area A) of the DMFC, the minimum diameter d of the narrow tube, and the thickness t of the fuel distribution plate. A DMFC power generation unit was manufactured using such a fuel distribution plate, and a power generation test was performed by intermittently supplying methanol as a liquid fuel with a pump.

  As a result of the power generation test described above, in the DMFC of Comparative Example 1, the fuel was uniformly supplied to the entire fuel electrode at the beginning of operation. However, as the amount of fuel supplied increased, the fuel speed was controlled at the curved portion of the narrow tube. It was confirmed that no fuel was supplied from some fuel outlets. As a result, a decrease in output characteristics of DMFC was observed.

(Comparative Example 2)
In addition to applying a single arc curve (single R curve) with a constant radius of curvature to the curved portion of the capillary, the minimum diameter of the capillary is set to 0.2 mm in order to prevent fuel speed control and clogging. A fuel distribution plate was produced in the same manner as in Example 1. In order to satisfy the number of fuel discharge ports (about 120) with the fuel distribution plate having such a configuration, the outer dimensions cannot be accommodated within the outer dimensions (area A) of the DMFC, and the fuel distribution plate The thickness could not be within t.

(Comparative Example 3)
In addition to applying a single arc curve (single R curve) with a constant radius of curvature to the curved portion of the capillary, the minimum diameter of the capillary is set to 0.2 mm in order to prevent fuel speed control and clogging. A fuel distribution plate was produced in the same manner as in Example 1. In order to keep the outer dimensions of the fuel distribution plate having such a configuration within the outer dimensions (area A) of the DMFC, it was necessary to reduce the number of fuel discharge ports to 60. As a result, in the power generation test, the fuel could not be evenly supplied to the entire fuel electrode, and a decrease in the output characteristics of DMFC was observed. The thickness of the fuel distribution plate also exceeded t.

(Comparative Example 4)
In addition to applying a single arc curve (single R curve) with a constant radius of curvature to the curved portion of the thin tube, and setting the minimum R of the curved portion to 2 mm in order to prevent fuel speed control and clogging, A fuel distribution plate was produced in the same manner as in Example 1. In order to satisfy the number of fuel discharge ports (about 120) with the fuel distribution plate having such a configuration, the external dimensions cannot be accommodated within the external dimensions (area A) of the DMFC.

(Comparative Example 5)
A single arc curve (single R curve) with a constant radius of curvature is applied to the curved portion of the thin tube, and the minimum R of the curved portion is set to 2 mm in order to prevent fuel speed control and clogging. A fuel distribution plate was produced in the same manner as in Example 1 except that the minimum diameter of the fuel was set to 0.2 mm. In order to satisfy the number of fuel discharge ports (about 120) with the fuel distribution plate having such a configuration, the outer dimensions cannot be accommodated within the outer dimensions (area A) of the DMFC, and the fuel distribution plate The thickness could not be within t.

(Comparative Example 6)
A single arc curve (single R curve) with a constant radius of curvature is applied to the curved portion of the thin tube, and the minimum R of the curved portion is set to 2 mm in order to prevent fuel speed control and clogging. A fuel distribution plate was produced in the same manner as in Example 1 except that the minimum diameter of the fuel was set to 0.2 mm. In order to keep the outer dimensions of the fuel distribution plate having such a configuration within the outer dimensions (area A) of the DMFC, it was necessary to reduce the number of fuel discharge ports to 60. As a result, in the power generation test, the fuel could not be evenly supplied to the entire fuel electrode, and a decrease in the output characteristics of DMFC was observed. The thickness of the fuel distribution plate could not be within t.

  Tables 1 and 2 collectively show the configurations, dimensions, and power generation test results of the fuel cells (fuel distribution plates) of Example 1 and Comparative Examples 1 to 6 described above.

  The present invention can be applied to various fuel cells using liquid fuel. In addition, the specific configuration of the fuel cell, the supply state of the fuel, and the like are not particularly limited, and all of the fuel supplied to the MEA is liquid fuel vapor, all is liquid fuel, or part is liquid state. The present invention can be applied to various forms such as a vapor of supplied liquid fuel. In the implementation stage, the constituent elements can be modified and embodied without departing from the technical idea of the present invention. Furthermore, various modifications are possible, such as appropriately combining a plurality of constituent elements shown in the above embodiments, or deleting some constituent elements from all the constituent elements shown in the embodiments.

It is sectional drawing which shows the structure of the fuel cell by embodiment of this invention. It is a perspective view which shows an example of the fuel supply part of the fuel cell shown in FIG. FIG. 10 is a plan view of the fuel supply unit shown in FIG. 9. It is a figure which expands and shows the A section of FIG. It is a figure which shows an example of a structure of the curve part of the thin tube shown in FIG. It is a figure which shows the relationship between the curvature and curve length in the curve part of the thin tube shown in FIG. It is a figure which shows the relationship between a curvature at the time of applying a single circular arc curve (single R curve) to the curve part of the thin tube as a comparison with this invention, and curve length.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 2 ... Electromotive part, 3 ... Fuel supply part, 4 ... Fuel supply mechanism, 5 ... Fuel accommodating part, 6 ... Anode catalyst layer, 7 ... Anode gas diffusion layer, 8 ... Anode (fuel electrode), DESCRIPTION OF SYMBOLS 9 ... Cathode catalyst layer, 10 ... Cathode gas diffusion layer, 11 ... Cathode (air electrode), 12 ... Electrolyte membrane, 13 ... MEA, 14, 15 ... Current collector, 17 ... Fuel piping, 18 ... Fuel inlet, 19 DESCRIPTION OF SYMBOLS ... Fuel discharge port, 20 ... Fuel distribution plate, 21 ... Narrow tube, 25 ... Straight part, 26 ... Branch part, 27 ... Curve part, 28 ... Single arc section, 29 ... Clothoid curve section.

Claims (5)

An electromotive part comprising 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 storage section for storing liquid fuel;
A fuel injection port connected to the fuel storage unit, and a plurality of fuel discharge ports connected to the fuel injection port via a fuel flow path constituted by a straight part and a curved part, and the fuel electrode A fuel supply unit for supplying fuel to
A fuel cell, wherein a flow path shape of a section including at least a portion connected to the straight portion of the curved portion is constituted by a clothoid curve. The fuel cell according to claim 1, wherein
The curved portion has a clothoid curve section including a portion connected to the straight section and a single arc section having a constant curvature radius, where R is a curvature radius of the clothoid curve section, and L is a curve length. The clothoid curve section has a curvature (1 / R) of C · L from the curvature of the connection portion with the straight line portion to the curvature of the single arc section (where C is an arbitrary constant in the range of 0 to 1). ) Based on the fuel cell. The fuel cell according to claim 1 or 2,
The fuel cell further comprises a fuel supply pump interposed between the fuel storage part and the fuel supply part. The fuel cell according to any one of claims 1 to 3, wherein
The fuel supply unit includes a fuel distribution plate having the fuel injection port and the plurality of fuel discharge ports, and the fuel distribution plate has a narrow tube provided therein as the fuel flow path. battery. The fuel cell according to claim 4, wherein
The thin tube has a branch portion, and is branched in order at the branch portion from the fuel inlet toward the plurality of fuel outlets.

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