JP2009021209A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of keeping the water content held in a cathode catalyst layer or a cathode gas diffusion layer composing a membrane electrode assembly in an optimum range, and keeping stable output for a long time. <P>SOLUTION: The fuel cell system 1 is equipped with a fuel cell 2 having a cathode conductive layer 19 and a heating means 50. A current shutoff means 102 shutting off current flowing to the fuel cell 2 is installed in output wiring 100, 101 outputting power from the fuel cell 2, and a voltage detecting means 103 detecting voltage generating in a unit cell 10 of the fuel cell is installed between the output wiring 100 and the output wiring 101. A control means 110 electrically connected to the heating means 50, the current shutoff means 102, and the voltage detecting means 103 is installed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  In recent years, attempts have been made to use a fuel cell as a power source for portable electronic devices such as notebook computers and mobile phones so that they can be used for a long time without being charged. The fuel cell has a feature that it can generate electric power simply by supplying fuel and air, and can generate electric power continuously for a long time if fuel is replenished. For this reason, if the fuel cell can be reduced in size, it becomes a very advantageous system as a power source for portable electronic devices.

  The direct methanol fuel cell (DMFC) is promising as a power source for portable electronic devices because it can be miniaturized and the fuel can be easily handled. 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.

  Among these, a passive system such as an internal vaporization type is particularly advantageous for downsizing of the DMFC. In the passive type DMFC, for example, a structure in which a membrane electrode assembly (fuel cell) having an anode (fuel electrode), an electrolyte membrane, and a cathode (air electrode) is disposed on a fuel housing portion made of a resin box-like container. Has been proposed (see, for example, Patent Document 1). When the fuel vaporized from the fuel container is directly supplied to the fuel cell, it is important to improve the output controllability of the fuel cell, but the current passive DMFC does not always have sufficient output controllability. .

  On the other hand, it has been studied to connect a fuel cell of DMFC and a fuel storage part via a flow path (see, for example, Patent Documents 2-4). By supplying the liquid fuel supplied from the fuel storage unit to the fuel cell via the flow path, the supply amount of the liquid fuel can be adjusted based on the shape and diameter of the flow path. Patent Document 3 describes a fuel cell that supplies liquid fuel by a pump from a fuel storage portion to a flow path, and Patent Document 4 describes a fuel cell that supplies liquid fuel or the like using an electroosmotic flow pump. ing.

Conventionally, a heating unit such as a heater is provided in the fuel cell to adjust the output of the fuel cell. For example, a heating unit that heats the fuel cell is provided in the fuel cell. For example, when the required power is larger than the suppliable power that is the power that can be supplied by the power supply, the technology that limits the power used to heat the heating unit (For example, refer to Patent Document 5).
International Publication No. 2005/112172 Pamphlet JP 2005-518646 A JP 2006-089552 A US Patent Publication No. 2006/0029851 JP 2006-114364 A

  When power is generated by operating the fuel cell, water is generated in the cathode catalyst layer as a result of the power generation reaction. In conventional fuel cells, the water necessary for the reaction in the cathode catalyst layer may not be sufficiently supplied by holding the water in the cathode catalyst layer or the cathode gas diffusion layer more than necessary. In addition, if water is retained more than necessary in the cathode catalyst layer or the cathode gas diffusion layer, at least part of the members constituting the membrane electrode assembly may be accelerated, and the output of the fuel cell may be reduced. there were. In addition, the conventional fuel cell provided with a heating unit such as a heater has not been configured to solve these problems in the cathode.

  Therefore, the present invention has been made to solve the above problems, and it is possible to maintain the amount of water retained in the cathode catalyst layer and cathode gas diffusion layer constituting the membrane electrode assembly within an appropriate range. An object of the present invention is to provide a fuel cell system that can maintain a stable output over a long period of time.

  According to one aspect of the present invention, a membrane electrode assembly having a fuel electrode, an air electrode, and an electrolyte membrane sandwiched between the fuel electrode and the air electrode, and the fuel electrode side of the membrane electrode assembly And a fuel supply mechanism for supplying fuel to the fuel electrode, a heating means provided so as to heat the air electrode, and a control means for controlling the heating means. A fuel cell system is provided.

  Moreover, according to one aspect of the present invention, a membrane electrode assembly having a fuel electrode, an air electrode, and an electrolyte membrane sandwiched between the fuel electrode and the air electrode, and the fuel of the membrane electrode assembly A fuel supply mechanism that is disposed on the pole side and has a fuel supply means for supplying fuel to the fuel electrode; and a current control means that cuts off a current flowing through the membrane electrode assembly or controls the current value to be a predetermined value or less. The voltage detection means for detecting the voltage generated in the membrane electrode assembly and the current control means are controlled, the current flowing through the membrane electrode assembly is cut off or set to a current value below a predetermined value, and the voltage detection means There is provided a fuel cell system comprising: a control means for controlling the fuel supply means based on the detected voltage value to adjust the amount of fuel supplied to the fuel electrode.

  According to the fuel cell system of the present invention, the amount of water retained in the cathode catalyst layer and the cathode gas diffusion layer constituting the membrane electrode assembly can be maintained in an appropriate range and stable over a long period of time. Output can be maintained.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view showing a configuration of a fuel cell system 1 according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a configuration of the fuel cell system 1 when the fuel cell according to the first embodiment of the present invention includes the pump 80.

  As shown in FIG. 1, a fuel cell system 1 includes a fuel cell 10 constituting an electromotive unit, and anodes provided on the anode (fuel electrode) side and the cathode (air electrode) side of the fuel cell 10 respectively. A conductive layer 18, a cathode conductive layer 19, a fuel distribution layer 30 having a plurality of openings 31 provided to face the anode conductive layer 18, and a side of the fuel distribution layer 30 different from the fuel cell 10 side The fuel supply mechanism 40 for supplying the liquid fuel F to the fuel distribution layer 30, the heating means 50 laminated on the cathode conductive layer 19, the moisture retention layer 60 laminated on the heating means 50, and the moisture retention layer A fuel cell 2 having a surface cover 62 having a plurality of air inlets 61 stacked on 60 is provided. Further, a temperature detecting means 70 for measuring the temperature of the cathode gas diffusion layer 15 is provided at a predetermined position of the cathode gas diffusion layer 15 of the cathode (air electrode) 16.

  The fuel cell system 1 includes output wirings 100 and 101 that output power from the fuel cell 2 and are connected to the anode conductive layer 18 and the cathode conductive layer 19, respectively. Further, the output wiring 100 is provided with a current interrupting means 102 that interrupts the current flowing through the fuel cell 2. The fuel cell 2 is connected to an external load (not shown) via these output wirings 100 and 101. Furthermore, the fuel cell system 1 includes voltage detection means 103 that is provided between the output wirings 100 and 101 and detects a voltage generated in the fuel cell 10. The fuel cell system 1 further includes a control unit 110 electrically connected to the heating unit 50, the temperature detection unit 70, the current interruption unit 102, and the voltage detection unit 103. In the drawing, the wiring for electrically connecting the control means 110 and each means is omitted.

  The fuel cell 10 is a so-called membrane electrode assembly (MEA), and includes an anode (fuel electrode) 13 having an anode catalyst layer 11 and an anode gas diffusion layer 12, a cathode catalyst layer 14, and a cathode gas diffusion. A cathode (air electrode) 16 having a layer 15 and an electrolyte membrane 17 having proton (hydrogen ion) conductivity sandwiched between the anode catalyst layer 11 and the cathode catalyst layer 14.

  Examples of the catalyst contained in the anode catalyst layer 11 and the cathode catalyst layer 14 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. As the anode catalyst layer 11, for example, Pt—Ru, Pt—Mo, or the like having strong resistance to methanol, carbon monoxide, or the like is preferably used. As the cathode catalyst layer 14, for example, Pt, Pt—Ni, Pt—Co or the like is preferably used. 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.

  Examples of the proton conductive material constituting the electrolyte membrane 17 include fluorine-based resins (Nafion (trade name, manufactured by DuPont) and Flemion (trade name, manufactured by Asahi Glass Co., Ltd.) such as a perfluorosulfonic acid polymer having a sulfonic acid group. 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 17 is not limited to these.

  The anode gas diffusion layer 12 laminated on the anode catalyst layer 11 serves to uniformly supply fuel to the anode catalyst layer 11 and also serves as a current collector for the anode catalyst layer 11. The cathode gas diffusion layer 15 laminated on the cathode catalyst layer 14 serves to uniformly supply the oxidant to the cathode catalyst layer 14 and also serves as a current collector for the cathode catalyst layer 14. The anode gas diffusion layer 12 and the cathode gas diffusion layer 15 are porous bodies or meshes made of a porous carbonaceous material such as carbon paper, carbon cloth, or carbon silk, or a metal material such as titanium, titanium alloy, stainless steel, or gold. Etc.

  The anode conductive layer 18 laminated on the surface of the anode gas diffusion layer 12 and the cathode conductive layer 19 laminated on the surface of the cathode gas diffusion layer 15 are, for example, a mesh or a porous film made of a conductive metal material such as Au. Etc. Among these, the anode conductive layer 18 and the cathode conductive layer 19 are preferably formed of a thin film having a plurality of openings opened corresponding to the fuel cell 10, and the fuel cell is formed through the openings. The fuel from the opening 31 of the fuel distribution layer 30 provided facing the cell 10 is guided to the fuel cell 10. The anode conductive layer 18 and the cathode conductive layer 19 are configured so that fuel and oxidant do not leak from their peripheral edges. Also, rubber O-rings 20 are interposed between the electrolyte membrane 17 and the anode conductive layer 18 and the cathode conductive layer 19, respectively, thereby preventing fuel leakage and oxidant leakage from the fuel cell 10. is doing. Here, the fuel cell 2 including the anode conductive layer 18 and the cathode conductive layer 19 is shown, but the anode gas diffusion layer 12 and the anode conductive layer 18 and the cathode conductive layer 19 are not provided as described above. The cathode gas diffusion layer 15 may function as a diffusion layer and may function as a conductive layer.

  The heating means 50 is laminated so as to be in contact with the surface of the cathode conductive layer 19 while allowing passage of air, fuel, and the like through the cathode conductive layer 19. The installation position of the heating means 50 is not limited to this position. For example, even if the cathode gas diffusion layer 15 is embedded in the cathode gas diffusion layer 15 so as to directly heat the cathode gas diffusion layer 15, for example, It may be provided in contact with the surface of the diffusion layer 15. In other words, the heating means 50 may be arranged so that the cathode 16, particularly the cathode gas diffusion layer 15, can be directly or indirectly heated. The heating unit 50 is activated or stopped, temperature-controlled, and the like under the control of the control unit 110. The heating means 50 is configured by an electric heater or the like, and specifically, preferably configured by an element that generates heat when a current flows, such as a nichrome wire, a rubber heater, or a ceramic heater.

  The temperature detection means 70 is provided, for example, at a predetermined position on the surface or inside of the cathode gas diffusion layer 15 and detects the temperature of the cathode gas diffusion layer 15. This temperature detection means 70 is, for example, at the center of the cathode gas diffusion layer 15 (for example, the intersection of the diagonal lines if the cathode gas diffusion layer has a rectangular outer shape) or the vicinity of the cathode gas diffusion layer 15 where the temperature may be highest. It is preferably installed on the surface or inside of the cathode gas diffusion layer 15. Further, the temperature detecting means 70 may be provided on the surface or inside of the cathode conductive layer 19 facing the center of the cathode gas diffusion layer 15 or the vicinity thereof. If there is a position where the temperature is likely to be the highest other than the center of the cathode gas diffusion layer 15 due to the outer shape or configuration of the fuel cell 2, the cathode gas diffusion at or near that position is likely to be present. It is preferable to provide the temperature detection means 70 on the surface or inside of the cathode conductive layer 19 facing the layer 15 or the center of the cathode gas diffusion layer 15 or the vicinity thereof. In the case where the temperature detection means 70 is provided inside the cathode gas diffusion layer 15 or the cathode conductive layer 19, for example, holes or recesses that do not penetrate are formed, and the temperature detection means 70 is installed in the holes or recesses. It is preferable.

  As the temperature detection means 70, for example, a thermocouple, a resistance thermometer, a thermistor, a Peltier element, or other elements that output an electrical signal according to temperature can be used. Further, the output from the temperature detection means 70 is input to the control means 110.

  The moisturizing layer 60 is impregnated with a part of the water generated in the cathode catalyst layer 14 to suppress the transpiration of water and promote uniform diffusion of air to the cathode catalyst layer 14. The moisturizing layer 60 is composed of a flat plate made of, for example, a polyethylene porous film. Note that the fuel cell 2 may be configured without providing the moisture retention layer 60.

  The front cover 62 is for adjusting the amount of air taken in, and the adjustment is performed by changing the number and size of the air inlets 61. For example, the front cover 62 can be made of a metal such as SUS304, but is not limited thereto.

  The fuel supply mechanism 40 mainly includes a fuel storage part 41, a fuel supply part 42, and a flow path 43.

  The fuel storage unit 41 stores liquid fuel F corresponding to the fuel battery cell 10. Examples of the liquid fuel F include methanol fuels such as methanol aqueous solutions having various concentrations and pure methanol. The liquid fuel F is not necessarily limited to methanol fuel. The liquid fuel F may be, for example, an ethanol fuel such as an ethanol aqueous solution or pure ethanol, a propanol fuel such as a propanol aqueous solution or pure propanol, a glycol fuel such as a glycol aqueous solution or pure glycol, dimethyl ether, formic acid, or other liquid fuel. In any case, liquid fuel corresponding to the fuel cell 10 is stored in the fuel storage portion 41.

  The fuel supply unit 42 is connected to the fuel storage unit 41 via a flow path 43 of the liquid fuel F configured by piping or the like. Liquid fuel F is introduced into the fuel supply unit 42 from the fuel storage unit 41 via the flow path 43, and the introduced liquid fuel F and / or the vaporized component of the liquid fuel F vaporized are the fuel distribution layer 30 and The fuel cell 10 is supplied via the anode conductive layer 18. The flow path 43 is not limited to piping independent of the fuel supply unit 42 and the fuel storage unit 41. For example, when the fuel supply unit 42 and the fuel storage unit 41 are stacked and integrated, a flow path of the liquid fuel F that connects them may be used. That is, the fuel supply unit 42 only needs to communicate with the fuel storage unit 41 through a flow path or the like.

  The liquid fuel F accommodated in the fuel accommodating part 41 can be dropped and sent to the fuel supply part 42 via the flow path 43 using gravity. Alternatively, the flow path 43 may be filled with a porous body or the like, and the liquid fuel F stored in the fuel storage section 41 may be fed to the fuel supply section 42 by capillary action. Further, as shown in FIG. 2, a pump 80 functioning as a fuel supply means is interposed in a part of the flow path 43 to force the liquid fuel F stored in the fuel storage unit 41 to the fuel supply unit 42. You may send liquid.

  The pump 80 functions as a supply pump that simply supplies the liquid fuel F from the fuel storage unit 41 to the fuel supply unit 42, and is a circulation pump that circulates excess liquid fuel F supplied to the fuel cells 10. It does not have the function as. Since the fuel cell 2 provided with the pump 80 does not circulate fuel, the fuel cell 2 is called a so-called semi-passive type, which has a different configuration from a conventional active method and a different configuration from a pure passive method such as a conventional internal vaporization type. Applicable to the method. The type of the pump 80 that functions as the fuel supply means is not particularly limited, but from the viewpoint that a small amount of the liquid fuel F can be fed with good controllability and that further reduction in size and weight can be achieved. It is preferable to use a vane pump, an electroosmotic flow pump, a diaphragm pump, a squeezing pump, or the like. The rotary vane pump feeds liquid by rotating wings with a motor. The electroosmotic flow pump uses a sintered porous body such as silica that causes an electroosmotic flow phenomenon. A diaphragm pump drives a diaphragm with an electromagnet or piezoelectric ceramics to send liquid. The squeezing pump presses a part of a flexible fuel flow path and squeezes the fuel. Among these, it is more preferable to use an electroosmotic pump or a diaphragm pump having piezoelectric ceramics from the viewpoint of driving power, size, and the like. When the pump 80 is provided as described above, the pump 80 is electrically connected to the control unit 110, and the supply amount of the liquid fuel F supplied to the fuel supply unit 42 is controlled by the control unit 110.

  In addition, if the fuel is supplied from the fuel supply unit 42 to the fuel cells 10, a fuel control valve may be arranged as a fuel supply means instead of the pump 80. This fuel control valve is provided to control the supply of the liquid fuel F through the flow path 43. In addition, the fuel control valve is electrically connected to the control means 110 in the same manner as the pump 80, the opening degree of the fuel control valve is adjusted by the control means 110, and the liquid fuel F supplied to the fuel supply unit 42 is adjusted. The supply amount is controlled.

  The fuel distribution layer 30 is configured by, for example, a flat plate in which a plurality of openings 31 are formed, and is sandwiched between the anode gas diffusion layer 12 and the fuel supply unit 42. The fuel distribution layer 30 is made of a material that does not allow the vaporized component of the liquid fuel F or the liquid fuel F to permeate. Specifically, for example, a polyethylene terephthalate (PET) resin, a polyethylene naphthalate (PEN) resin, or a polyimide resin. Etc. Further, the fuel distribution layer 30 may be constituted by, for example, a gas-liquid separation membrane that separates the vaporized component of the liquid fuel F and the liquid fuel F and permeates the vaporized component to the fuel cell unit 10 side. Examples of the gas-liquid separation membrane include silicone rubber, low density polyethylene (LDPE) thin film, polyvinyl chloride (PVC) thin film, polyethylene terephthalate (PET) thin film, fluororesin (for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene). -Perfluoroalkyl vinyl ether copolymer (PFA) etc.) A microporous film etc. are used.

  The voltage detection unit 103 detects a voltage generated in the fuel battery cell 10 and is provided between the output wirings 100 and 101. As the voltage detection means 103, for example, a digital voltmeter using an electronic circuit can be used. Further, the output from the voltage detection means 103 is input to the control means 110.

  The control means 110 mainly includes, for example, an arithmetic unit (CPU), a read-only memory (ROM), a random access memory (RAM), a built-in timer, and other storage means such as a semiconductor memory that keeps information as necessary. The CPU is configured to execute various arithmetic processes using programs and data stored in the storage means such as the ROM and RAM. The control unit 110 controls input / output of signals to / from each of the heating unit 50, the temperature detection unit 70, the current interruption unit 102, and the voltage detection unit 103.

  Here, the program stored in the storage means such as the ROM or RAM includes a program for determining the suitability of the amount of water held in the cathode 16, which will be described later. In accordance with the program, it is determined whether or not the amount of water held in the cathode 16 is appropriate.

  Here, the fuel cell system 1 is not limited to the above-described configuration. For example, the fuel cell 2 includes a plurality of fuel cells 10 and the fuel cells 10 are connected in series, in parallel, or a combination thereof. The present invention can be applied even in the case of being electrically connected with.

  3A and 3B are diagrams schematically showing an example of the fuel cell system 1 when a plurality of fuel cells 10 are connected in series.

  As shown in FIG. 3A and FIG. 3B, the current interrupting means 102 may be provided for at least one fuel cell 10 among the plurality of fuel cells 10 so that the current can be interrupted. In this case, as shown in FIG. 3A, normally, a plurality of fuel cells 10 are connected in series, and the output of each fuel cell 10 is supplied to an external load. When determining whether or not the amount of water held in the cathode 16 is appropriate, the control means 110 controls the current interrupting means 102 to supply a current to one fuel cell 10 as shown in FIG. 3B. The voltage detection means 103 detects the voltage generated in the fuel cell 10. Based on the voltage of the fuel cell 10, the control unit 110 determines whether or not the amount of water held in the cathode 16 is appropriate, and controls the heating unit 50 of each fuel cell 10. Then, after the above determination, the control means 110 controls the current interrupting means 102 so that the plurality of fuel cells 10 shown in FIG. 3A are connected in series and returned to the wiring state.

  Thus, by using one fuel cell 10 among the plurality of fuel cells 10 to determine the suitability of the amount of water held in the cathode 16, the output of the other fuel cells 10 is Supplied to external load. As a result, when determining the appropriateness of the amount of water held in the cathode 16, it is possible to minimize a decrease in output as the fuel cell system 1.

  Next, the operation of the fuel cell 2 described above will be described.

The liquid fuel F supplied from the fuel storage unit 41 to the fuel supply unit 42 via the flow path 43 remains as a liquid fuel, or in a state where liquid fuel and vaporized fuel vaporized from the liquid fuel are mixed. And supplied to the anode gas diffusion layer 12 of the fuel cell 10 through the anode conductive layer 18. The fuel supplied to the anode gas diffusion layer 12 is diffused in the anode gas diffusion layer 12 and supplied to the anode catalyst layer 11. 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 11.
CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ Formula (1)

  When pure methanol is used as the methanol fuel, is methanol reformed by water generated in the cathode catalyst layer 14 or water in the electrolyte membrane 17 and the internal reforming reaction of the above formula (1)? Or other reaction mechanisms that do not require water.

Electrons (e ⁻ ) generated by this reaction are guided to the outside through a current collector, and are guided to the cathode 16 after operating a portable electronic device or the like as so-called electricity. Proton (H ⁺ ) generated by the internal reforming reaction of the formula (1) is guided to the cathode 16 through the electrolyte membrane 17. Air is supplied to the cathode 16 as an oxidant. The electrons (e ⁻ ) and protons (H ⁺ ) that have reached the cathode 16 cause a reaction shown in the following equation (2) with oxygen in the air at the cathode catalyst layer 14, and water is generated along with this power generation reaction. .
(3/2) O ₂ + 6e ⁻ + 6H ⁺ → 3H ₂ O Formula (2)

  The internal reforming reaction described above is performed smoothly, and a high output and a stable output can be obtained in the fuel cell 2.

Further, in the fuel cell system 1 according to the present invention, the following 20mA the current flowing through the area of 1cm per ^second fuel cell 2 (cut-off state, that is, the current value including 0) in a state set to the cathode constituting the cathode 16 The suitability of the amount of water retained in the catalyst layer and the cathode gas diffusion layer is determined. When it is determined that the amount of water held in the cathode 16 is large and impedes the output of the fuel cell 2, the cathode 16, particularly the cathode gas diffusion layer 15 is heated, and the water held in the cathode 16 is discharged. By evaporating, the amount of water retained in the cathode 16 is maintained within an appropriate range.

Here, the reason why it is preferable to determine the suitability of the amount of water held in the cathode 16 in a state where the current flowing per 1 cm ² area of the fuel cell (membrane electrode assembly) is set to 20 mA or less. explain.

As a method for determining that water is held more than necessary in the cathode 16, the inventors, as a result of research, cut off the current flowing through the fuel cell 10, or a current value smaller than that during normal power generation (area 1 cm). ^{When the} current flowing per ² is controlled to 20 mA or less), it has been found that by measuring the voltage generated in the fuel cell 10, the suitability of the amount of water retained in the cathode 16 can be easily and reliably determined. .

FIG. 4 is a diagram showing the relationship between the current flowing per 1 cm ² area of the fuel cell (membrane electrode assembly) and the voltage generated in the fuel cell at that time. FIG. 4 shows that (A) when the amount of water held in the cathode is optimal, (B) the amount of water held in the cathode is optimal, but the voltage during normal power generation due to other causes. When the current value decreases in value, (C) the relationship between the current and voltage is shown for the case where the amount of water retained in the cathode is excessive and inappropriate.

  As shown in FIG. 4, the change curve of the voltage with respect to the current in the case of (C), that is, when the amount of water retained in the cathode is excessive and inappropriate, is retained in the case of (A), that is, in the cathode. The voltage change curve with respect to the current in the case where the amount of water is optimal shows a shape close to a state in which the voltage is reduced in parallel. In the case of (C), the current value at the voltage value during normal power generation (when the voltage is controlled to be constant during normal power generation) is smaller than in the case of (A). However, in the case of (C), in the case of (B), that is, the amount of water retained in the cathode is optimal, but the current value decreases in the voltage value during normal power generation due to other causes. Since the current value at the voltage value during normal power generation is approximately the same, it is determined from the current value at the voltage value during normal power generation whether the case is (B) or (C). I can't do it.

  On the other hand, under the condition where the current is interrupted or 20 mA or less, the difference between the voltage value in the case of (B) and the voltage value in the case of (C) becomes large. Therefore, when this current is cut off or 20 mA or less, the voltage value in the case of (C) is used as a boundary value, and when the voltage value is smaller than this boundary value, the amount of water retained in the cathode Can be determined to be excessive and inappropriate.

The current flowing per 1 cm ² area of the fuel cell (membrane electrode assembly), which is more preferably determined as to whether or not the amount of water held in the cathode is appropriate, is the voltage value in the case of (B) and (C). In this case, the difference from the voltage value is 10 mA or less.

  Immediately after the current is cut off or set to 20 mA or less, the voltage generated in the fuel cell rises and then gradually decreases to a predetermined value. Therefore, since the predetermined voltage value is not obtained immediately after the current control, the voltage value is preferably evaluated after a predetermined time after the current control. On the other hand, while the current is cut off or controlled to a condition of 20 mA or less, the output value of the fuel cell is “0” or smaller than that during normal power generation, so the fuel cell is used as a power source for other devices. In some cases, the shorter the time for controlling the current, the better. Therefore, in consideration of the fact that the voltage value is almost stable and the deterioration of the function as a power source is minimized, the voltage value can be evaluated within a range of 1 second to 10 minutes after current control. preferable. More preferably, it is 1 minute or more and 5 minutes or less.

  Next, the operation of the fuel cell system 1 will be described with reference to FIG.

FIG. 5 is a flowchart showing the operation of the fuel cell system 1.
First, for example, based on the operation of the fuel cell system 1, the control unit 110 sets the current time t1 of the built-in timer to “0” and counts the elapsed time thereafter (step S210).

  Subsequently, the control unit 110 compares the current time t1 in the timer with a preset time t2 stored in a storage unit such as a ROM or a RAM (step S211). Here, the preset time t2 is the time from the start of operation until the start of determination of the suitability of the amount of water held in the cathode 16, and can be set as appropriate.

  If it is determined in step S211 that the current time t1 is smaller than the preset time t2, that is, the preset time t2 has not been reached (“t1 <t2” in step S211), the control means 110 again executes the processing from step S211.

  When it is determined in step S211 that the current time t1 is equal to or greater than the preset time t2, that is, the preset time t2 (“t1 ≧ t2” in step S211), the control unit 110 The current interrupting means 102 and the like are controlled for a predetermined time, and the current flowing through the fuel cell 2 is 20 mA or less (in the interrupted state, that is, the current value includes 0). That is, the current value is set to 0 (step S212).

  Here, the interruption of the current flowing through the fuel cell 2 can be realized by controlling the current interruption means 102 to be in the interruption state. When the current flowing through the fuel cell 2 is set to be larger than 0 and 20 mA or less, the DC / DC converter connected between the fuel cell and the external load is controlled at a constant current, and the controlled current This value can be realized by setting the above value to the above set value. At this time, the predetermined time for controlling the current flowing through the fuel cell 2 is not less than 1 second and not more than 10 minutes, more preferably not less than 1 minute and not more than 5 minutes.

  Subsequently, the control unit 110 specifies the voltage V1 generated in the fuel cell 2 based on the output from the voltage detection unit 103, and is stored in a storage unit such as a ROM or a RAM, for example. Compare with V2 (step S213). Here, the preset voltage V2 is the water held in the cathode 16 in the state where the current flowing through the fuel cell 2 is set to 20 mA or less (cut-off state, that is, the current value includes 0). This is a voltage value when the amount is excessive and inappropriate (in the case of FIG. 4C). That is, the voltage V2 is a value set in advance corresponding to a current value of 20 mA or less flowing through the fuel cell 2. The voltage V1 is a value measured within a predetermined time range for controlling the above-described current.

  If it is determined in step S213 that the specified voltage V1 is equal to or higher than the preset voltage V2 (“V1 ≧ V2” in step S213), the process returns and the process from the start is executed.

  On the other hand, when it is determined in step S213 that the specified voltage V1 is smaller than the preset voltage V2 (“V1 <V2” in step S213), the control unit 110 subsequently detects the temperature. Based on the output from the means 70, the temperature T1 of the cathode gas diffusion layer 15 is specified, and the specified temperature T1 is stored in a storage means such as ROM or RAM and compared with a preset temperature T2 (step). S214).

  If it is determined in step S214 that the identified temperature T1 is higher than the preset temperature T2 (“T1> T2” in step S214), the processing from step S210 is executed again.

  On the other hand, when it is determined in step S214 that the specified temperature T1 is equal to or lower than the preset temperature T2 (“T1 ≦ T2” in step S214), the control unit 110 operates the heating unit 50. (Step S215). Thus, the heat generated by the heating means 50 is conducted to the cathode gas diffusion layer 15 through the cathode conductive layer 19 and heats the cathode gas diffusion layer 15.

  Subsequently, the control unit 110 sets the current time t1 of the built-in timer to “0”, and counts the elapsed time after the heating unit 50 is activated (step S216).

  Subsequently, the control unit 110 compares the current time t1 in the timer with a preset time t3 stored in a storage unit such as a ROM or a RAM (step S217). Here, the preset time t3 is the time from when the heating means 50 is operated until the determination of the suitability of the amount of water held in the cathode 16 is started, and can be set as appropriate.

  If it is determined in step S217 that the current time t1 is smaller than the preset time t3, that is, has not reached the preset time t3 (“t1 <t3” in step S217), the control means 110 again executes the processing from step S217.

  When it is determined in step S217 that the current time t1 is equal to or greater than the preset time t3, that is, the preset time t3 (“t1 ≧ t3” in step S217), the control unit 110 The current interrupting means 102 and the like are controlled for a predetermined time, and the current flowing through the fuel cell 2 is 20 mA or less (in the interrupted state, that is, the current value includes 0). That is, the current value is set to 0 (step S218).

  Here, the interruption of the current flowing through the fuel cell 2 can be realized by controlling the current interruption means 102 to be in the interruption state. When the current flowing through the fuel cell 2 is set to be larger than 0 and 20 mA or less, the DC / DC converter connected between the fuel cell and the external load is controlled at a constant current, and the controlled current This value can be realized by setting the above value to the above set value. At this time, the predetermined time for controlling the current flowing through the fuel cell 2 is not less than 1 second and not more than 10 minutes, more preferably not less than 1 minute and not more than 5 minutes.

  Subsequently, the control unit 110 specifies the voltage V1 generated in the fuel cell 2 based on the output from the voltage detection unit 103, and is stored in a storage unit such as a ROM or a RAM, for example. Compare with V2 (step S219). Here, the preset voltage V2 is the water held in the cathode 16 in the state where the current flowing through the fuel cell 2 is set to 20 mA or less (cut-off state, that is, the current value includes 0). This is a voltage value when the amount is excessive and inappropriate (in the case of FIG. 4C). That is, the voltage V2 is a value set in advance corresponding to a current value of 20 mA or less flowing through the fuel cell 2. The voltage V1 is a value measured within a predetermined time range for controlling the above-described current.

  If it is determined in step S219 that the specified voltage V1 is smaller than the preset voltage V2 (“V1 <V2” in step S219), the processing from step S216 is executed again.

  On the other hand, when it is determined in step S219 that the specified voltage V1 is equal to or higher than the preset voltage V2 (“V1 ≧ V2” in step S219), the control unit 110 stops the heating unit 50. (Step S220). Then, the process returns and the process from the start is executed.

  Here, as described above, the cathode gas diffusion layer 15 may be heated by using the pump 80 or the fuel control valve functioning as the fuel supply means instead of using the heating means 50. In this case, in step S 215, the control unit 110 controls the pump 80 and the fuel control valve to increase the amount of fuel supplied to the fuel cell 10. In step S220, the control unit 110 controls the pump 80 and the fuel control valve to return the amount of fuel supplied to the fuel cell 10 to a normal amount.

  Thus, when the amount of fuel supplied to the fuel cell 10 is increased by the pump 80 or the fuel control valve, the amount of fuel that passes through the electrolyte membrane 17 and permeates to the cathode side increases. That is, fuel crossover is promoted. The fuel permeated to the cathode side causes an exothermic reaction with oxygen on the cathode side. The cathode gas diffusion layer 15 is heated using the heat generated by this reaction. Here, the amount of fuel to be permeated to the cathode side is preferably set such that, for example, the amount of heat generated by an exothermic reaction on the cathode side is equal to the amount of heat generated by the heating means 50. Specifically, for example, it is preferable to increase the fuel supply amount until the temperature of the cathode gas diffusion layer 15 reaches the above-described preset temperature T2.

  Further, in the fuel cell system 1, the fuel cell system may be operated without providing or operating the temperature detecting means 70. In this case, the process of step S214 is not performed, the process of step S215 is performed after the process of step S213, and the heating unit 50 is activated.

  According to the fuel cell system 1 of the first embodiment of the present invention described above, the current flowing through the fuel cell 10 is controlled to be cut off or smaller than the current during normal power generation and detected by the voltage detection means 103. When the measured voltage value falls below a preset value, it is determined that the amount of water retained in the cathode 16 is excessive, and at least a part of the cathode 16, particularly the cathode gas diffusion layer 15, can be heated. it can. As a result, the water in the cathode 16 evaporates and the amount of water retained in the cathode 16 can be reduced, and a decrease in the output of the fuel cell 2 due to the retention of excess water in the cathode 16 is suppressed. be able to.

(Other embodiments)
The fuel cell system 1 according to the first embodiment includes a temperature detection unit 70, a current interruption unit 102, a voltage detection unit 103, and the like, and interrupts the current flowing through the fuel cell 10 or is smaller than the current during normal power generation. The system that heats the cathode gas diffusion layer 15 when the voltage value detected by the voltage detection means 103 falls below a preset value has been described. However, the system that heats the cathode gas diffusion layer 15 is described below. The configuration is not limited to this.

  FIG. 6 is a cross-sectional view showing a configuration of a fuel cell system 1 according to another embodiment of the present invention. FIG. 7 is a diagram illustrating an example of control of the fuel cell system 1 including the heating unit 50 and the control unit 110. For example, as shown in FIG. 6, the fuel cell system 1 may be configured to include the heating unit 50 and the control unit 110 without including the temperature detection unit 70, the current interruption unit 102, and the voltage detection unit 103. In this configuration, as shown in FIG. 7, the heating means 50 is operated for a predetermined time every predetermined time to heat the cathode gas diffusion layer 15. Further, as shown in FIG. 7, the heating time interval is preferably set in correspondence with the time when the temperature of the surface of the cathode gas diffusion layer 15 of the fuel cell 10 rapidly decreases. It should be noted that the time during which the temperature of the fuel cell 10 rapidly decreases can be grasped based on the results obtained in advance through tests or the like. For example, the heating means 50 is turned off for 50 minutes (non-heated state) and then turned on for 10 minutes (heated state). Here, the control means 110 only needs to be able to control the heating means 50 to operate for a predetermined time every predetermined time, and may be constituted by, for example, a timer. Further, the upper limit value of the temperature of the cathode gas diffusion layer 15 when the heating unit 50 is operated minimizes deterioration and deformation of each member constituting the fuel cell 10 due to heat, and the present invention relates to the present invention. From a safety point of view of minimizing the risk that a user of a portable device equipped with a fuel cell may cause a burn (including low temperature burn) when touching the surface of the portable device, the temperature is 60 to 80 ° C. It is preferable to do. 6 shows the configuration of the fuel cell system 1 that is not provided with a pump, the pump 80 may be provided similarly to the fuel cell system 1 shown in FIG.

  Further, the heating unit 50 is not limited to the above-described electric heater or the like, or the pump 80 or the fuel control valve functioning as the fuel supply unit instead of using the heating unit 50. For example, the current interrupting means 102 may be provided in the same manner as the case shown in FIG. 1, and the current interrupting means 102 may function as a heating means. That is, the cathode gas diffusion layer 15 may be heated by cutting off the current flowing through the fuel cell 2. Specifically, when the current flowing through the fuel cell 2 is interrupted, the fuel permeates the cathode catalyst layer without reacting with the anode catalyst layer 11. The fuel that has permeated the cathode catalyst layer side generates an oxidation reaction on the cathode catalyst layer side to generate heat. The cathode gas diffusion layer 15 is heated by the heat. FIG. 8 is a diagram illustrating an example of control of the fuel cell system 1 when the current interrupting unit 102 is caused to function as a heating unit. As shown in FIG. 8, the current interrupting means 102 interrupts the current flowing through the fuel cell 10 for a predetermined time every predetermined time, and the cathode gas diffusion layer 15 is heated. Further, as shown in FIG. 8, the heating time interval is set corresponding to the time during which the temperature of the surface of the cathode gas diffusion layer 15 of the fuel cell 10 is lowered to a predetermined temperature (for example, 30 to 50 ° C.). It is preferable. The time for which the temperature of the fuel cell 10 is lowered to the predetermined temperature can be grasped based on the result obtained in advance through a test or the like. For example, a current is supplied for 50 minutes (non-heated state), and then the current is interrupted (heated state) for 10 minutes. Further, in this case, if the current is kept interrupted, the temperature does not continue to rise, and the temperature of the fuel cell 10 decreases as the interrupting time becomes longer. Further, when the current is cut off, the fuel battery cell 10 is in a state where it does not generate power. Therefore, it is preferable to minimize the time for cutting off the current.

  Further, as still another embodiment, in the fuel cell system 1 of the other embodiment shown in FIG. 6, as in the fuel cell system 1 shown in FIG. You may provide the temperature detection means 70 in a position. FIG. 9 is a diagram illustrating an example of control of the fuel cell system 1 further including the temperature detection means 70 in the fuel cell system 1 of the other embodiment illustrated in FIG. 6. In this configuration, as shown in FIG. 9, when the control unit 110 determines that the temperature of the cathode gas diffusion layer 15 is lower than a preset temperature based on information from the temperature detection unit 70, The heating means 50 is operated to heat the cathode gas diffusion layer 15. When the control means 110 determines that the temperature of the cathode gas diffusion layer 15 exceeds a preset temperature based on the information from the temperature detection means 70, the control means 110 stops the heating means 50. For example, when the control unit 110 determines that the temperature of the cathode gas diffusion layer 15 is lower than 50 ° C., which is a preset temperature, based on information from the temperature detection unit 70, the control unit 110 switches the heating unit 50. When it is determined that the temperature exceeds 50 ° C., the heating means 50 is stopped. Also in this case, as described above, for example, the current interrupting means 102 is provided in the same manner as in the case of FIG. 1, and the current interrupting means 102 functions as a heating means to heat the cathode gas diffusion layer 15. May be.

  FIG. 10 is a diagram showing an example of control different from the control of the fuel cell system 1 shown in FIG. As shown in FIG. 10, when the control unit 110 determines that the temperature of the cathode gas diffusion layer 15 is lower than a preset lower limit value based on the information from the temperature detection unit 70, the heating unit 50. And the cathode gas diffusion layer 15 is heated to a preset upper limit value based on information from the temperature detection means 70. When the control unit 110 determines that the temperature of the cathode gas diffusion layer 15 exceeds a preset upper limit value based on the information from the temperature detection unit 70, the control unit 110 stops the heating unit 50. For example, when the control unit 110 determines that the temperature of the cathode gas diffusion layer 15 is lower than a preset lower limit value of 50 ° C. based on the information from the temperature detection unit 70, the heating unit 50. If it is determined that the temperature is higher than the preset upper limit of 60 ° C., the heating means 50 is stopped. Further, the upper limit value of the temperature of the cathode gas diffusion layer 15 set in advance when the heating means 50 is operated minimizes deterioration or deformation of each member constituting the fuel cell 10 due to heat, and From the viewpoint of safety, a user of a portable device equipped with the fuel cell according to the present invention minimizes the risk of causing burns (including low temperature burns) when touching the surface of the portable device. It is preferable to set it to -80 degreeC. Also in this case, as described above, for example, the current interrupting means 102 is provided in the same manner as in the case of FIG. 1, and the current interrupting means 102 functions as a heating means to heat the cathode gas diffusion layer 15. May be.

  Further, in the heating process, the above example shows an example in which the heating means 50 is continuously operated, but the present invention is not limited to this. FIG. 11 is a diagram illustrating an example of control of the fuel cell system 1 when the heating unit 50 is intermittently operated in the heating process. As shown in FIG. 11, when the control unit 110 determines that the temperature of the cathode gas diffusion layer 15 is lower than a preset temperature based on the information from the temperature detection unit 70, the control unit 110 switches the heating unit 50. The cathode gas diffusion layer 15 is heated by operating intermittently. When the control means 110 determines that the temperature of the cathode gas diffusion layer 15 exceeds a preset temperature based on the information from the temperature detection means 70, the control means 110 stops the heating means 50. For example, when the control unit 110 determines that the temperature of the cathode gas diffusion layer 15 is lower than 50 ° C., which is a preset temperature, based on information from the temperature detection unit 70, the control unit 110 switches the heating unit 50. When it is determined that the temperature exceeds 50 ° C., the heating unit 50 is stopped. The on / off interval and the like can be appropriately set according to the use conditions.

  Also in this case, as described above, for example, the current interrupting means 102 is provided in the same manner as in the case of FIG. 1, and the current interrupting means 102 functions as a heating means to heat the cathode gas diffusion layer 15. May be. FIG. 12 is a diagram illustrating an example of the control of the fuel cell system 1 when the heating unit 50 is intermittently operated when the current interrupting unit 102 functions as the heating unit. As shown in FIG. 12, when the control unit 110 determines that the temperature of the cathode gas diffusion layer 15 is lower than a preset temperature based on information from the temperature detection unit 70, the current interruption unit 102. Is intermittently operated, and the cathode gas diffusion layer 15 is heated by intermittently turning on (non-heating state) / off (heating state) the current flowing through the fuel cell 10. When the control means 110 determines that the temperature of the cathode gas diffusion layer 15 exceeds a preset temperature based on the information from the temperature detection means 70, the control means 110 controls the current interrupting means 102 to control the fuel cell. A current is allowed to flow continuously through the cell 10. For example, when the control unit 110 determines that the temperature of the cathode gas diffusion layer 15 is lower than a preset temperature of 50 ° C. based on the information from the temperature detection unit 70, the current interruption unit 102. Is controlled at intervals of 1 minute, and the current flowing through the fuel cell 10 is turned on / off at intervals of 1 minute. When it is determined that the temperature has exceeded 50 ° C., the current is continuously supplied to the fuel cell 2.

  Moreover, the preset temperature used as the reference | standard which starts heating is not restricted to constant temperature, You may set so that it may become different temperature for every fixed time. FIG. 13 is a diagram illustrating an example of control of the fuel cell system 1 when a preset temperature that is a reference for starting heating is set to be different at regular time intervals. In addition, the preset temperature used as the reference | standard which starts a heating can also become a reference | standard temperature which stops a heating. Here, a case where two different values of the first set temperature and the second set temperature are set as the preset temperature as a reference for starting heating will be described as an example. Note that three or more different values may be set as the preset temperature.

  As shown in FIG. 13, the control means 110 is based on the information from the temperature detection means 70 for a predetermined time with the first set temperature as a preset temperature as a set value. When it is determined that the temperature is lower than the first set temperature, the heating means 50 is intermittently operated to heat the cathode gas diffusion layer 15. When the control unit 110 determines that the temperature of the cathode gas diffusion layer 15 has exceeded the first set temperature based on the information from the temperature detection unit 70, the control unit 110 stops the heating unit 50. On the other hand, the control means 110 determines that the temperature of the cathode gas diffusion layer 15 is the second temperature based on the information from the temperature detection means 70 for a predetermined time in which the second preset temperature is set as a preset temperature. When it is determined that the temperature is lower than the set temperature, the heating means 50 is intermittently operated to heat the cathode gas diffusion layer 15. When the control means 110 determines that the temperature of the cathode gas diffusion layer 15 exceeds the second set temperature based on the information from the temperature detection means 70, the control means 110 stops the heating means 50. For example, the first set temperature is 50 ° C. for 10 hours, and the second set temperature is 60 ° C. for 1 hour. It should be noted that the predetermined time using the first and second set temperatures as set values, the on / off interval of the heating means 50, and the like can be appropriately set according to the use conditions. Also in this case, as described above, for example, the current interrupting means 102 is provided in the same manner as in the case of FIG. 1, and the current interrupting means 102 functions as a heating means to heat the cathode gas diffusion layer 15. May be.

  In the above-described fuel cell system 1 according to another embodiment of the present invention, the same effects as those of the fuel cell system 1 according to the first embodiment can be obtained, and the optimum according to the use conditions can be obtained. Control of a fuel cell system is possible.

  Next, it will be described based on Examples 1 to 5 and Comparative Example 1 that the fuel cell system according to the present invention has excellent output characteristics.

Example 1
The fuel cell system used in Example 1 has the same configuration as that of the fuel cell system 1 shown in FIG. 1, and will be described with reference to FIG.

  First, a method for producing the fuel battery cell 10 will be described.

  To the carbon black supporting the anode catalyst particles (Pt: Ru = 1: 1), a perfluorocarbon sulfonic acid solution as a proton conductive resin and water and methoxypropanol as a dispersion medium were added to support the anode catalyst particles. A paste was prepared by dispersing carbon black. The obtained paste was applied to porous carbon paper (40 mm × 30 mm rectangle) as the anode gas diffusion layer 12 to obtain an anode catalyst layer 11 having a thickness of 100 μm.

  To the carbon black carrying the cathode catalyst particles (Pt), a perfluorocarbon sulfonic acid solution as a proton conductive resin and water and methoxypropanol as a dispersion medium are added to disperse the carbon black carrying the cathode catalyst particles. A paste was prepared. The obtained paste was applied to porous carbon paper as the cathode gas diffusion layer 15 to obtain a cathode catalyst layer 14 having a thickness of 100 μm. The anode gas diffusion layer 12 and the cathode gas diffusion layer 15 have the same shape and size, and the anode catalyst layer 11 and the cathode catalyst layer 14 applied to these gas diffusion layers have the same shape and size.

  A perfluorocarbon sulfonic acid membrane (trade name: nafion membrane) having a thickness of 30 μm and a water content of 10 to 20% by weight as the electrolyte membrane 17 between the anode catalyst layer 11 and the cathode catalyst layer 14 produced as described above. The fuel cell 10 was obtained by performing hot pressing in a state where the anode catalyst layer 11 and the cathode catalyst layer 14 face each other.

  Subsequently, the fuel battery cell 10 was sandwiched between gold foils having a plurality of openings to form an anode conductive layer 18 and a cathode conductive layer 19. A rubber O-ring 20 was sandwiched between the electrolyte membrane 17 and the anode conductive layer 18 and between the electrolyte membrane 17 and the cathode conductive layer 19 for sealing.

Further, as the moisture retaining layer 60, the thickness is 500 μm, the air permeability is 2 seconds / 100 cm ³ (according to the measurement method specified in JIS P-8117), and the moisture permeability is 4000 g / (m ² · 24 h) (JIS L -1099 A-1 polyethylene porous film (by the measurement method specified in A-1) was used.

  A stainless steel plate (SUS304) having a thickness of 1 mm on which an air introduction port 61 (circular diameter of 3.6 mm, number of units: 35) for air intake is formed is disposed on the moisturizing layer 60 and the surface cover 62 is arranged. It was.

  An electric heater was installed as the heating means 50 so as to contact the surface of the cathode conductive layer 19, and a thermocouple was installed as the temperature detection means 70 on the surface of the cathode gas diffusion layer 15. Further, output wirings 100 and 101 for outputting electric power from the fuel cell 2 were connected to the anode conductive layer 18 and the cathode conductive layer 19, respectively. The fuel cell 2 was connected to an external load (not shown) via these output wirings 100 and 101. The output wiring 100 is provided with current interrupting means 102 that interrupts the current flowing through the fuel cell 2. Further, a digital voltmeter using an electronic circuit is provided between the output wirings 100 and 101 as the voltage detecting means 103 for detecting the voltage generated in the fuel cell 10. The heating means 50, the temperature detection means 70, the current interruption means 102, and the voltage detection means 103 are electrically connected to the control means 110 and can be controlled by the control means 110.

  The fuel cell system was operated based on the operation of the fuel cell system described above (see FIG. 5). Here, the preset time t2 is set to 60 minutes, and the time for cutting off the current in steps S212 and S218 is set to 1 minute. Further, the preset voltage V2 to be compared with the voltage V1 detected in step S213 and step S219 is set to 0.6V. In addition, a preset temperature T2 to be compared with the temperature T1 detected in step S214 was set to 45 ° C. Further, when it is determined in step S214 that the specified temperature T1 is equal to or lower than the preset temperature T2, the amount of heat generated by the heating means 50 is generated when the power generation of the fuel cell 2 is started. The value was equivalent to 10% of the electric power. That is, for example, when the electric power generated at the start of power generation in the fuel cell 2 is 1 W, the resistance value and the flowing current value of the heating unit 50 are set so that the amount of heat generated by the heating unit 50 is 0.1 W. did.

  Further, the amount of fuel supplied to the fuel cell 2 is set to the amount of fuel required to cause an electrochemical reaction for current to flow through the fuel cell 2 (the amount of methanol supplied 3 per minute per current 1A). .3 mg) and set to be always constant.

  Then, pure methanol having a purity of 99.9% by weight was supplied to the above-described fuel cell 2 under the environment where the temperature was 25 ° C. and the relative humidity was 50% so as to satisfy the above supply amount. A constant voltage power source as an external load was connected, and the current flowing through the fuel cell 2 was controlled so that the output voltage of the fuel cell 2 was constant at 0.3V.

Under the above conditions, the output density P1 of the fuel cell 2 after 1000 hours of power generation and the output density P0 of the fuel cell 2 when the power generation was started were measured. Then, a ratio (P1 / P0) of the output density P1 to the output density P0 was calculated. Here, the output density (mW / cm ² ) of the fuel cell 2 refers to the current density flowing through the fuel cell 2 (current value per 1 cm ² area (mA / cm ² ) of the power generation unit) and the output voltage of the fuel cell 2. Multiplied by. Further, the area of the power generation unit is the area of the portion where the anode catalyst layer 11 and the cathode catalyst layer 14 face each other. In this embodiment, since the anode catalyst layer 11 and the cathode catalyst layer 14 have the same area and are completely opposed to each other, the area of the power generation unit is equal to the area of these catalyst layers. The ratio (P1 / P0) of the calculated output density P1 to the output density P0 was 0.81 (81%).

(Example 2)
In the second embodiment, a fuel control valve for controlling the amount of fuel supplied to the fuel cell 2 is provided in place of the heating means 50 of the fuel cell 2 used in the first embodiment. The fuel control valve is electrically connected to the control means 110 and can be controlled by the control means 110. Further, in the present embodiment, the temperature detecting means 70 is not provided, that is, the above-described processing in step S214 is not executed, and the processing in step S215 is executed after the processing in step S213, and the heating means 50 is operated.

  The amount of fuel supplied to the fuel cell 2 is controlled by the opening of the fuel control valve, and when the voltage V2 detected by the voltage detection means 103 is greater than the preset voltage V1, the fuel supply The amount was set to 1.4 times the fuel supply amount necessary to cause an electrochemical reaction for the current to flow through the fuel cell 2. This supply amount was set as a normal fuel supply amount.

  When the voltage V2 detected by the voltage detection means 103 is equal to or lower than the preset voltage V1, the fuel control valve is controlled so that the fuel supply amount is 1.2 times the normal fuel supply amount, that is, the fuel cell. 2 is 1.68 times the fuel supply amount necessary to cause an electrochemical reaction for current to flow.

  Other configurations and set values are the same as those of the fuel cell system used in the first embodiment. The measurement method and measurement conditions of the output density P1 of the fuel cell 2 after 1000 hours of power generation and the output density P0 of the fuel cell 2 when power generation is started are the same as the measurement method and measurement conditions in the first embodiment. It is.

  The ratio (P1 / P0) of the output density P1 to the output density P0 calculated based on the measurement result was 0.77 (77%).

(Example 3)
In Example 3, the fuel cell provided with the temperature detection means 70 was used for the fuel cell 2 used in Example 2. That is, in the present embodiment, the above-described process of step S214 is executed. A preset temperature T2 to be compared with the temperature T1 detected in step S214 was set to 45 ° C.

  In step S214, when the determined temperature T1 is determined to be higher than the preset temperature T2, the amount of fuel supplied is the normal fuel supply amount of the second embodiment, that is, the current flows through the fuel cell 2. Therefore, the amount of fuel supply necessary to cause an electrochemical reaction was 1.4 times. On the other hand, when it is determined in step S214 that the specified temperature T1 is equal to or lower than the preset temperature T2, the fuel supply amount is controlled by controlling the fuel control valve to control the fuel supply amount in the second embodiment. The amount is 1.5 times the amount, that is, 2.1 times the fuel supply amount necessary for causing an electrochemical reaction for the current to flow through the fuel cell 2.

  Other configurations and set values are the same as those of the fuel cell system used in the second embodiment. The measurement method and measurement conditions of the output density P1 of the fuel cell 2 after 1000 hours of power generation and the output density P0 of the fuel cell 2 when power generation is started are the same as the measurement method and measurement conditions in the first embodiment. It is.

  The ratio (P1 / P0) of the output density P1 to the output density P0 calculated based on the measurement result was 0.83 (83%).

Example 4
In Example 4, instead of the heating means 50 of the fuel cell 2 used in Example 1, a pump 80 for controlling the amount of fuel supplied to the fuel cell 2 was provided as shown in FIG. The pump 80 is electrically connected to the control means 110 and can be controlled by the control means 110. Further, in the present embodiment, the temperature detecting means 70 is not provided, that is, the above-described process of step S214 is not performed, the process of step S213 is performed after the process of step S213, and the pump 80 is operated.

  The amount of fuel supplied to the fuel cell 2 is controlled by the pump 80, specifically, by the rotational speed of the pump 80, and the voltage V2 detected by the voltage detecting means 103 is greater than the preset voltage V1. Is larger than that, the fuel supply amount is set to 1.4 times the fuel supply amount necessary for causing an electrochemical reaction for current to flow through the fuel cell 2. This supply amount was set as a normal fuel supply amount.

  When the voltage V2 detected by the voltage detection means 103 is equal to or lower than the preset voltage V1, the pump 80 is controlled so that the fuel supply amount is 1.2 times the normal fuel supply amount, that is, the fuel cell 2 1.68 times the fuel supply amount necessary to cause an electrochemical reaction for current to flow through.

  Other configurations and set values are the same as those of the fuel cell system used in the first embodiment. The measurement method and measurement conditions of the output density P1 of the fuel cell 2 after 1000 hours of power generation and the output density P0 of the fuel cell 2 when power generation is started are the same as the measurement method and measurement conditions in the first embodiment. It is.

  The ratio (P1 / P0) of the output density P1 to the output density P0 calculated based on the measurement result was 0.78 (78%).

(Example 5)
In Example 5, the fuel cell provided with the temperature detection means 70 was used for the fuel cell 2 used in Example 4. That is, in the present embodiment, the above-described process of step S214 is executed. A preset temperature T2 to be compared with the temperature T1 detected in step S214 was set to 45 ° C.

  In step S214, when the determined temperature T1 is determined to be higher than the preset temperature T2, the fuel supply amount is the normal fuel supply amount of the fourth embodiment, that is, the current flows through the fuel cell 2. Therefore, the amount of fuel supply necessary to cause an electrochemical reaction was 1.4 times. On the other hand, when it is determined in step S214 that the specified temperature T1 is equal to or lower than the preset temperature T2, the fuel supply amount is controlled by the pump 80 to control the normal fuel supply amount of the fourth embodiment. Of the fuel supply amount required to cause an electrochemical reaction for causing a current to flow through the fuel cell 2 is 2.1 times the fuel supply amount.

  Other configurations and set values are the same as those of the fuel cell system used in the fourth embodiment. The measurement method and measurement conditions of the output density P1 of the fuel cell 2 after 1000 hours of power generation and the output density P0 of the fuel cell 2 when power generation is started are the same as the measurement method and measurement conditions in the first embodiment. It is.

  The ratio (P1 / P0) of the output density P1 to the output density P0 calculated based on the measurement result was 0.82 (82%).

(Comparative Example 1)
In Comparative Example 1, the fuel cell 2 used in Example 1 was used, and this fuel cell 2 was simply connected to an external load via an output wiring. That is, Comparative Example 1 does not include the same system as that of Examples 1 to 5 including the heating unit 50, the temperature detection unit 70, the current interruption unit 102, the voltage detection unit 103, and the control unit 110, but simply from the fuel cell 2. Output to an external load. In addition, the amount of fuel supplied to the fuel cell used in this comparative example was set to 1.4 times the amount of fuel necessary to cause an electrochemical reaction for current to flow through the fuel cell. And this supply amount was always maintained.

  Further, the fuel cell output density P1 after 1000 hours of power generation and the measurement method and measurement conditions of the fuel cell output density P0 when power generation is started are the same as the measurement method and measurement conditions in the first embodiment. .

  The ratio (P1 / P0) of the output density P1 to the output density P0 calculated based on the measurement result was 0.6 (60%).

(Summary of Examples 1 to 5 and Comparative Example 1)
Table 1 shows the ratio (P1 / P0) of the output density P1 to the output density P0 in Examples 1 to 5 and Comparative Example 1.

  As shown in Table 1, it was found that the ratio of the output density P1 to the output density P0 (P1 / P0) was higher in Examples 1 to 5 than in Comparative Example 1. That is, the current flowing through the fuel cell 2 is cut off or controlled to a current smaller than the current during normal power generation, and when the voltage value detected by the voltage detection means 103 falls below a preset value, It was clarified that excellent output characteristics can be obtained by determining that the amount of water retained is excessive and heating at least a part of the cathode 16, particularly the cathode gas diffusion layer 15.

  In the first to fifth embodiments, when the temperature detection unit 70 is provided and the process of step S214 described above is performed, the temperature detection unit 70 is not included, and the process of step S213 is performed after the process of step S213. It was found that the ratio (P1 / P0) of the output density P1 to the output density P0 is higher than that obtained. This is because the temperature detection means 70 is provided, and the above-described processing of step S214 is executed, thereby suppressing an increase in the temperature of the fuel cell 2 more than necessary and suppressing a decrease in the output of the fuel cell 2 due to the temperature increase. it is conceivable that.

  The present invention can be applied to various fuel cells using liquid fuel. Further, the specific configuration of the fuel cell, the supply state of the fuel, etc. are not particularly limited, and all the fuel supplied to the fuel cell is liquid fuel vapor, all is liquid fuel, or part is liquid. The present invention can be applied to various forms such as liquid fuel vapor supplied in a state. 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 components shown in the above embodiment, or deleting some components from all the components shown in the embodiment. Embodiments of the present invention can be expanded or modified within the scope of the technical idea of the present invention, and these expanded and modified embodiments are also included in the technical scope of the present invention.

1 is a cross-sectional view showing a configuration of a fuel cell system according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows the structure of the fuel cell system at the time of providing the pump in the fuel cell of one Embodiment which concerns on this invention. The figure which shows typically an example of the fuel cell system in case a some fuel cell is connected in series. The figure which shows typically an example of the fuel cell system in case a some fuel cell is connected in series. The figure which showed the relationship between the electric current which flows per 1 cm < ² > area of a fuel cell (membrane electrode assembly), and the voltage which generate | occur | produces in a fuel cell at that time. The flowchart which shows operation | movement of a fuel cell system. Sectional drawing which shows the structure of the fuel cell system of other embodiment which concerns on this invention. The figure which shows an example of control of a fuel cell system provided with a heating means and a control means. The figure which shows an example of control of a fuel cell system at the time of making an electric current interruption means function as a heating means. The figure which shows an example of control of the fuel cell system further provided with the temperature detection means in the fuel cell system of other embodiment shown in FIG. The figure which shows an example of control different from control of the fuel cell system shown in FIG. The figure which showed an example of control of the fuel cell system when a heating means is intermittently operated in a heating process. The figure which showed an example of control of a fuel cell system in the case of making a heating means operate | move intermittently when an electric current interruption means is made to function as a heating means. The figure which showed an example of control of the fuel cell system in case the preset temperature used as the reference | standard which starts a heating is set so that it may become a different temperature for every fixed time.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 10 ... Fuel cell, 11 ... Anode catalyst layer, 12 ... Anode gas diffusion layer, 13 ... Anode (fuel electrode), 14 ... Cathode catalyst layer, 15 ... Cathode gas diffusion layer, 16 ... Cathode ( Air electrode), 17 ... electrolyte membrane, 18 ... anode conductive layer, 19 ... cathode conductive layer, 20 ... O-ring, 30 ... fuel distribution layer, 31 ... opening, 40 ... fuel supply mechanism, 41 ... fuel storage portion, 42 DESCRIPTION OF SYMBOLS ... Fuel supply part, 43 ... Flow path, 50 ... Heating means, 60 ... Moisturizing layer, 61 ... Air inlet, 62 ... Surface cover, 70 ... Temperature detection means, 100, 101 ... Output wiring, 102 ... Current interruption means, 103: Voltage detection means, 110: Control means.

Claims (10)

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 mechanism disposed on the fuel electrode side of the membrane electrode assembly for supplying fuel to the fuel electrode;
Heating means provided to be able to heat the air electrode;
And a control means for controlling the heating means. Further comprising temperature detecting means for detecting the temperature of the air electrode;
2. The fuel cell system according to claim 1, wherein the control unit controls the heating unit based on information detected by the temperature detection unit.   3. The fuel cell system according to claim 1, wherein the heating unit includes a current interruption mechanism that interrupts a current flowing through the membrane electrode assembly. 4. A current control means for cutting off or controlling the current flowing through the membrane electrode assembly to a current value of a predetermined value or less;
Voltage detecting means for detecting a voltage generated in the membrane electrode assembly, and
The control means controls the current control means, cuts off the current flowing through the membrane electrode assembly or sets the current value to a value equal to or less than a predetermined value, and controls the heating means based on the voltage value detected by the voltage detection means. The fuel cell system according to claim 1, wherein the fuel cell system is controlled.   5. The fuel cell system according to claim 1, wherein the heating means is a heating element that generates heat by energy from the outside.   6. The fuel cell system according to claim 1, wherein when the heating unit is operated, the heating unit is intermittently operated by the control unit. 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 mechanism disposed on the fuel electrode side of the membrane electrode assembly and having a fuel supply means for supplying fuel to the fuel electrode;
A current control means for cutting off or controlling the current flowing through the membrane electrode assembly to a current value of a predetermined value or less;
Voltage detecting means for detecting a voltage generated in the membrane electrode assembly;
Controlling the current control means, cutting off the current flowing through the membrane electrode assembly or setting the current value to a predetermined value or less, and controlling the fuel supply means based on the voltage value detected by the voltage detection means to And a control means for adjusting a fuel supply amount to the fuel electrode.   8. The fuel cell system according to claim 7, wherein the fuel supply means is a pump.   8. The fuel cell system according to claim 7, wherein the fuel supply means is a fuel control valve.   The fuel cell system according to any one of claims 1 to 9, wherein the fuel is an aqueous methanol solution or pure methanol.

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