JP2007134213A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a fuel cell system to supply stable power without being affected by load changes by efficiently carrying out the removal of water produced in the vicinity of electrodes in accordance with cell characteristics. <P>SOLUTION: The fuel cell system is provided with a membrane electrode conjugant having an anode diffusion electrode, a cathode diffusion electrode, and an electrolyte film pinched between them, and a pair of separators pinching the membrane electrode conjugant and forming a fuel flow channel for making fuel pass through between one of them and the anode diffusion electrode and a gas flow channel for making gas pass through between the other and the cathode diffusion electrode. The fuel cell system is also provided with a fuel cell body supplying power to an outside load, a gas supply means for supplying gas containing oxygen at the upstream of the gas flow channel, a flow channel switching means for opening and closing the gas flow channel at its downstream, and an exhaust control means opening and closing the flow channel switching means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell device.

  Portable electronic devices such as cellular phones, portable information terminals, notebook personal computers, portable audio devices, and portable visual devices are spreading. Conventionally, such portable electronic devices are driven by a primary battery or a secondary battery. In particular, as the secondary battery, a nickel cadmium battery or a lithium ion battery is used, and a battery having a small size and a high energy density has been developed. However, since a secondary battery needs to be charged for a certain period of time using a charging device after using a certain amount of power, a battery that can be continuously driven for a long time with a short charging time is desired.

  In order to meet this demand, fuel cells that do not require charging have been proposed. A fuel cell is a generator that electrochemically converts chemical energy of fuel into energy. As an example of such a fuel cell, a polymer electrolyte fuel cell (Polymer Electrolyte) is used, in which hydrogen gas is reduced at the anode electrode using a perfluorocarbon sulfonic acid-based electrolyte, and oxygen is reduced at the cathode electrode to generate power. Fuel Cell (hereinafter referred to as PEFC) is known. Such a PEFC has a feature that it is a battery with a high output density, and its development is underway.

Here, the reaction formula performed in PEFC is shown below.
Anode: H ₂ → 2H ⁺ + 2e ⁻
Cathode: 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O
Hydrogen gas used as fuel in such PEFC has a low volumetric energy density, and it is necessary to increase the volume of the fuel tank, and supply fuel gas and oxidizing gas (such as air) to the fuel cell body (power generation unit) And an auxiliary device such as a humidifying device is required to stabilize the battery performance, and the fuel cell system becomes large, so it is not suitable as a power source for portable electronic devices.

  On the other hand, a direct methanol fuel cell (hereinafter referred to as DMFC), which generates electricity by directly extracting protons from methanol as a fuel, has a disadvantage that its output is smaller than that of the PEFC. However, the volume energy density of the fuel can be increased, and the configuration of the fuel cell main body becomes simple, so that the size can be reduced. For this reason, it attracts attention as a power source for portable devices, and some proposals have been made.

Here, the reaction formula performed in DMFC is shown below.
Anode: CH ₃ OH + H ₂ O → CO ₂ + 6e ⁻ + 6H ^{+
_{Cathode: 1.5O 2 + 6H + + 6e}} - → 3H 2 O
As shown in any of the above reaction formulas of PEFC and DMFC, water is generated on the cathode side by generating electricity using a fuel cell.

  In order to perform these reactions continuously, it is necessary to continuously supply the reactants to the electrode and to remove the product from the vicinity of the electrode. In both of the fuel cells described above, it is necessary to continuously supply oxygen and remove water as a product substance at the cathode. This is because if the product water is not removed, water stays in the vicinity of the electrode, clogs the pores of the electrode substrate, lowers the operating efficiency, and in some cases stops the reaction.

  Several methods are known as methods for removing the water, which is the product.

  For example, when the output voltage and impedance of a fuel cell are measured and the output voltage and impedance are out of a predetermined range, respectively, (1) a method of increasing the oxygen gas flow rate to increase the flow rate of oxygen gas, 2) A method of reducing the humidity by supplying a more dry oxygen gas, and (3) a method of increasing the flow rate of the oxygen gas by increasing the opening of the regulating valve of the oxygen gas discharge section by operating the fuel cell. This is a method of quickly removing excess water generated near the electrodes (see Patent Document 1).

  Further, there is a method in which gas suction means for sucking supply gas is provided on the downstream side of air supply of the fuel cell, and pressure control means for controlling the pressure of the supply gas is provided upstream of the fuel cell (see Patent Document 2).

Furthermore, a fuel cell is mounted on a mechanical vibration table, and an end plate of the fuel cell is provided with an ultrasonic vibrator, and a gas cylinder is attached to a gas pipe for supplying anode gas and cathode gas. There is a method of releasing (see Patent Document 3).
JP 7-235324 A JP 2002-33110 A JP 2002-305018 A

  However, the conventional technique described in Patent Document 1 has a problem that the output voltage fluctuates because a series of operations for recovering the output voltage is entered only when the output voltage is equal to or lower than a predetermined value. . In addition, since a complicated and large-scale mechanism such as a voltmeter, impedance meter, oxygen gas flow rate control valve and control unit for controlling these is required, the power loss for operating this mechanism is large, and the fuel cell It is also difficult to reduce the size of the apparatus.

  Further, in the prior art described in Patent Document 2, there is a problem that the output voltage fluctuates because a series of operations for recovering the output voltage is started only after the output voltage exceeds the lower limit value as described above. Further, since the gas suction means is always operated and the pressure of the supply gas is always in a negative pressure state, oxygen that is originally necessary is also sucked, resulting in a decrease in gas concentration and utilization efficiency. When this system is applied to a DMFC, the membrane permeation of fuel on the anode electrode side is promoted, and the catalyst may be deteriorated by an oxidation reaction at the cathode electrode.

  Furthermore, Patent Document 3 discloses only suppressing reduction in battery performance due to water generated by continuous operation under certain operating conditions, and discharge corresponding to the amount of water generated according to the operating state of the battery. The method is not shown.

  The present invention has been made in view of these problems, and the object of the present invention is to efficiently remove water generated in the vicinity of the electrode along with the operation of the fuel cell according to the cell characteristics. It is an object of the present invention to provide a fuel cell device capable of supplying stable power without being affected by load fluctuations.

  Said subject is solved by the following structures.

1. An anode diffusion electrode, a cathode diffusion electrode, a membrane electrode assembly having an electrolyte membrane sandwiched between the anode diffusion electrode and the cathode diffusion electrode, and the membrane electrode assembly, and the anode diffusion electrode A fuel cell body for supplying electric power to an external load, comprising a pair of separators forming a fuel flow path through which fuel passes and a gas flow path through which a gas containing oxygen passes between the cathode diffusion electrode ,
Gas supply means for supplying the gas containing oxygen upstream of the gas flow path;
Channel opening and closing means for opening and closing the gas channel downstream of the gas channel;
And a discharge control means for opening and closing the flow path opening and closing means.

  2. 2. The fuel cell device according to 1, wherein the discharge control means is configured to control the flow path opening / closing means at an opening / closing cycle determined based on at least the magnitude of the load.

  3. 3. The fuel cell device according to claim 1, wherein the discharge control unit is configured to control the flow path opening / closing unit at an opening / closing cycle determined based on at least the change of the load.

4). A gas flow rate adjusting means for adjusting a supply amount for supplying the gas containing oxygen to the gas flow path;
The discharge control means includes at least an opening / closing cycle determined based on the magnitude of the load, and at least a gas supply amount determined based on the magnitude of the load. 2. The fuel cell device according to 1, wherein the fuel cell device has a configuration for controlling the flow rate adjusting means.

5. A gas flow rate adjusting means for adjusting a supply amount for supplying the gas containing oxygen to the gas flow path;
The discharge control means includes at least an opening / closing cycle determined based on a change in the load, and at least a gas supply amount determined based on the change in the load. 5. The fuel cell device according to 1 or 4, further comprising a configuration for controlling the means.

6). Fuel supply means for supplying the fuel to the fuel flow path using the first piezoelectric element as an actuator is provided adjacent to the separator,
In a state where the flow path opening / closing means opens the gas flow path, the first piezoelectric element is driven at a frequency A within a range in which the fuel can be supplied,
6. The device according to claim 1, wherein the first piezoelectric element is driven at a frequency higher than the frequency A in a state where the flow channel opening / closing means closes the gas flow channel. Fuel cell device.

7). A liquid recovery means for recovering the liquid in the gas flow path;
The fuel cell apparatus according to any one of claims 1 to 6, wherein the liquid recovery means is stopped when the flow path opening / closing means closes the gas flow path.

8). A liquid recovery means for recovering the liquid in the gas flow path using the second piezoelectric element as an actuator is provided adjacent to the separator,
In a state where the flow path opening / closing means opens the gas flow path, the second piezoelectric element is driven at a frequency B in a range in which the liquid in the gas flow path can be collected,
7. The device according to claim 1, wherein the second piezoelectric element is driven at a frequency higher than the frequency B in a state where the flow channel opening / closing means closes the gas flow channel. Fuel cell device.

  According to the first aspect of the present invention, the gas supply means supplies the gas, and the discharge control means closes the gas flow path using the flow path opening / closing means so that the pressure of the gas in the gas flow path The gas is sent into the cathode diffusion electrode by increasing the gas flow rate, and then the gas in the cathode diffusion electrode is jetted into the gas flow channel by opening the gas flow channel and reducing the gas pressure in the gas flow channel. Thus, the water generated in the vicinity of the cathode diffusion electrode with the gas ejection can be discharged into the gas flow path. Further, the opening / closing operation of the flow path opening / closing means controlled by the discharge control means can be set in accordance with the time when the magnitude of the load changes, and at a period corresponding to the magnitude of the load. Therefore, it is possible to remove the water whose amount of generation changes in the vicinity of the cathode diffusion electrode according to the size of the load according to the size of the load and without delaying the change in the size of the load.

  Accordingly, there is provided a fuel cell device that can efficiently remove water generated in the vicinity of an electrode in accordance with the operation of the fuel cell in accordance with battery characteristics and can supply stable power without being affected by load fluctuations. I can do it.

  FIG. 1 shows the configuration of an example fuel cell apparatus according to an embodiment of the present invention. A fuel cell apparatus A shown in FIG. 1A employs a direct methanol (DMFC) fuel cell as a fuel cell. The fuel cell 1 is supplied with fuel liquid from a fuel liquid supply section F to generate power. Can do. FIG. 1B is a diagram schematically showing an enlarged internal structure of the fuel cell 1.

  As shown in FIG. 1 (B), the fuel cell 1 includes an MEA (an anode diffusion electrode (hereinafter referred to as an anode) 12 and a cathode diffusion electrode (hereinafter referred to as a cathode) 13 bonded to both surfaces of an electrolyte membrane 11. The fuel passage 140 is formed by bonding the separator A14 to the anode 12 and the separator B15 is also bonded to the cathode 13 to form the air flow path 150 that is a gas flow path. Yes.

Here, the anode 12 is composed of a catalyst layer in contact with the electrolyte membrane 11 (for example, platinum black or a platinum alloy supported on carbon black) and a diffusion electrode such as carbon paper laminated thereon, and the cathode 13 is also composed of the electrolyte membrane 11. And a similar diffusion electrode laminated on the catalyst layer.

  The separator A14 has a fuel flow path 140 that leads to the fuel liquid supply port 141 and the surplus fuel liquid recovery port 142, and the fuel liquid supplied from the fuel liquid supply unit F to the fuel supply port 141 is supplied to the fuel flow path 140. It has the function of being distributed and supplied to the entire anode 12 by passing through.

  The separator B15 has an air flow path 150. An air supply port 152 is provided upstream of the separator B15, and a discharge port 151 is provided downstream. The air supply port supplies air supplied from an air pump AP serving as gas supply means. By supplying to 152, it has the function to distribute and supply to the whole cathode 13. Further, the separator B15 is water generated in the vicinity of the cathode 13 by an electrochemical reaction in the presence of a catalyst between oxygen contained in air and protons supplied from the anode 12 side, and the electrolyte membrane 11 from the anode 12 side. The liquid that may move to the cathode 13 side through the gas and the unreacted gas in the supplied air also have a function of recovering from the entire cathode 13 through the air flow path 150. The recovered gas or liquid is discharged out of the separator B15 from the discharge port 151 located downstream of the air flow path 150.

  The air pump AP is provided so as to suck air outside the separator B15 and supply it to the air supply port 152, and is not particularly limited as long as it can suck and send air.

The fuel liquid supply unit F includes a high-concentration fuel liquid supply path L1 connected to a fuel liquid container C1 that contains a high-concentration fuel liquid (in this example, approximately 100% concentration methanol), and a diluent (in this example, water Or a diluent supply path L2 connected to a container C2 containing a liquid mainly composed of water.

  A pump MP1 for sending out the high-concentration fuel liquid in the fuel liquid container C1 is connected to the high-concentration fuel liquid supply path L1, and the dilute-liquid supply path L2 is connected to the inside of the container C2 in the middle. A pump MP2 for feeding out the diluted solution is connected.

  The supply paths L1 and L2 merge at a junction L3, and the junction L3 is connected to the fuel supply port 141 of the fuel channel 14 via a gas-liquid separator F2.

  The gas-liquid separator F2 prevents gas generated by dilution mixing from being supplied to the separator A14 and prevents gas generated on the anode 12 side from entering the mixing channel L4 from the fuel supply port 141. The gas-liquid is separated here and released to the outside.

  The surplus fuel liquid recovery port 142 of the separator A14 of the fuel cell 1 communicates with the diluent storage container C2 through the liquid recovery path L5. The liquid recovery path L5 is used on the anode 12 side, and guides excess liquid such as fuel liquid having a reduced methanol concentration to the container C2.

  Further, a gas-liquid separator F1 for separating gas from the liquid flowing out from the surplus fuel liquid recovery port 142 and releasing it to the outside is connected between the surplus fuel liquid recovery port 142 and the diluent storage container C2. Yes.

  The discharge port 151 of the separator B15 of the fuel cell 1 is connected to the diluent storage container C2 in the liquid recovery path L6 via the valve B1 which is a flow path opening / closing means capable of opening and closing the flow path leading to the separator B3 and the gas-liquid separator F3. The pump MP3 which is a liquid recovery means is connected in the middle. The gas-liquid separator F3 is for separating and discharging the gas out of the liquid and the gas discharged from the discharge port 151. The valve B1 will be described later.

  The fuel cell apparatus A of FIG. 1 includes pumps MP1, MP2, and MP3, an air pump AP, a drive circuit for the valve B1, and a control unit 2 that controls these drive circuits. The pump drive circuit drives each pump under the instruction of the control unit 2 so that the high-concentration fuel liquid is sent from the fuel liquid container C1 to the merging part L3 by the pump MP1 and from the diluent storage container C2 by the pump MP2. The diluting liquid is sent to the merging portion L3, these liquids are subsequently mixed in the mixing flow path L4, and the obtained diluted fuel liquid (for example, about 3% methanol aqueous solution) is supplied to the fuel cell 1 for power generation, Electric power is supplied to the load LD.

The water produced on the cathode 13 side by the electrochemical reaction in the fuel cell 1 and the anode 1
The liquid that may pass through the electrolyte membrane 11 from the second side and arrive at the cathode 13 side is the pump M
By driving P3, it is recovered from the separator B15 to the diluent container C2. At the beginning of use of the fuel cell device A, initial water may be stored in the diluent storage container C2. Further, the control unit 2 includes a discharge control unit 2a that is a discharge control unit that controls the valve B1 and the pump AP in accordance with a preset control procedure in response to the load change timing and magnitude from the load LD. Yes. The discharge control unit 2a may be constituted by, for example, a microcomputer controlled by a program.

  Here, the valve B1 will be described. The valve B1 only needs to have a function capable of instantaneously closing or opening the flow path leading to the discharge port 151 according to an instruction from the discharge control unit 2a. In this embodiment, an electromagnetic valve is used. In the fuel cell device A, when the operation is continued with the valve B1 opened, the reactants such as fuel and oxygen are sufficiently supplied, and the output voltage is lowered although there is no change in the load state. This is because water generated in the vicinity of the cathode 13 by the electrochemical reaction stays in the vicinity of the cathode 13 and closes the pores (diffusion layer) of the electrode base material of the cathode 13, so that the electrochemical reaction becomes increasingly difficult. It is to become. Therefore, in order to stabilize the output voltage when the fuel cell apparatus A is continuously operated, it is necessary to remove water that closes the pores of the electrode base material.

  In the fuel cell apparatus A in which the output voltage is lowered by continuing the operation by the inventor's experiment, when the valve B1 is once closed and then opened, water is discharged from the valve B1 and the output which has been reduced so far. It was found that the voltage recovered temporarily.

  This is because air is supplied with pressure to the air flow path 150 of the separator B15 by the air pump AP, and the air pressure in the air flow path 150 increases abruptly when the valve B1 is instantaneously closed. Air is pushed into the pores of the electrode base material of the cathode 13 by this air pressure, and thereafter, the air that has been pushed up to the pores by instantaneously opening the valve B1 is lowered at once. This is considered to be because the water is discharged into the air flow path 150 together with water and finally discharged from the discharge port 151 located downstream of the air flow path 150.

  The inventor pays attention to this phenomenon and applies a method of continuously opening and closing the valve B1 when operating the fuel cell device A, so that it is continuously generated and the electrode base material is thinned. The output voltage was prevented from decreasing by removing the water blocking the holes intermittently and continuously.

  FIG. 2 is a diagram schematically showing the relationship between the opening and closing of the valve B1 and the pressure in the air flow path 150 and time. As shown in FIG. 2A, when the valve B1 is closed at T1, the pressure P in the air flow path 150 increases due to the air pressure supplied from the air pump AP as shown in FIG. In parallel with this, water that has blocked the pores of the electrode base material of the cathode 13 is pushed into the pores. At this time, the pressure P in the air flow path 150 needs to be higher than the pressure in a state where the valve B1 is not closed. However, if the pressure P is too high, the life of the fuel cell device may be reduced due to deterioration of the electrolyte membrane 11. Therefore, it may be appropriately determined by setting the closing period Ta (= T2−T1) of the valve B1 from the capacity of the air pump AP, the capacity of the air flow path 150, the structure thereof, and the like. In the present embodiment, this period Ta is 1 second.

  When the valve B1 is suddenly opened at the time T2 when the pressure in the air flow path 150 rises to an appropriate value, the air that has been pushed into the pores due to a sudden drop in air pressure enters the air flow path 150 with water. It is discharged and finally discharged from the discharge port 151.

  FIG. 3 is a diagram schematically showing the relationship between the current density generated by the fuel cell device A and the amount of water generated in the vicinity of the cathode 13. As shown in FIG. 3, the amount of water generated increases as the power generation amount of the fuel cell device A increases. Therefore, when the load to which the fuel cell device A supplies power increases, more water is generated, and the pores of the electrode base material of the cathode 13 are blocked in a shorter time, leading to a decrease in output voltage. Become.

  In order to cope with this, the opening / closing cycle Tc (= T3-T1) of the valve B1 shown in FIG. 2A is indicated by the solid line 4-1 in FIG. When the load is short and the load is small, the open / close cycle Tc may be increased according to the load. Therefore, for example, the opening / closing cycle Tc of the valve B1 is shortened as the load increases, and the output voltage decreases by efficiently discharging water whose amount generated as the load increases to the outside of the air flow path 150. Stable power can be supplied without doing so. The opening / closing cycle Tc may be determined as appropriate according to the period Ta during which the valve B1 is closed, the capacity of the fuel cell, the magnitude of the load, the fluctuation range of the load, and the like. In the present embodiment, the variable range of the opening / closing cycle Tc is 1.5 seconds to 10 seconds. Further, when the opening / closing cycle Tc of the valve B1 is determined according to the magnitude of the load, the opening / closing cycle may be continuously changed according to the change in the load to which the fuel cell device A supplies power. However, the magnitude of the load may be classified into several, and the switching cycle may be changed discretely. An example in which the magnitude of the load is classified into three and the opening / closing cycle Tc of the valve B1 is set in three stages is shown by a broken line 4-2 in FIG.

  Here, the control unit 2 includes a discharge control unit 2a that controls the valve B1 based on the change timing and magnitude of the change load received from the load that the fuel cell apparatus A supplies power. When the discharge control unit 2a uses a microcomputer, for example, to obtain the time when the load changes from the load and the magnitude of the load after the change, the discharge control unit 2a determines in advance from the characteristics of the fuel cell 1 obtained in advance through experiments or the like. An opening / closing cycle Tc is calculated from a closing period Ta and the magnitude of the load, or a reference table or the like, and the opening / closing control of the valve B1 is performed according to the closing period Ta and the opening / closing cycle Tc.

  For example, in the fuel cell as shown in Patent Document 1, when attention is paid to the output voltage, as shown by the broken line in FIG. 5, the fluctuation of the load at the time Tf, for example, the water generated in the vicinity of the cathode when the load becomes large is shown. The output voltage decreases due to the increase, and the water generated for the first time from the time Ts when the output voltage value reaches the output voltage value Vc, which is reduced by a certain amount, is detected by, for example, a voltmeter provided at the output of the fuel cell. Since the discharge has started, the output voltage fluctuates.

  In the present embodiment, the discharge control in consideration of the amount of water generated according to the magnitude of the load is started in accordance with the time Tf when the load fluctuates by the discharge control unit 2a. As indicated by the solid line, stable power can be supplied without causing output voltage fluctuations due to load fluctuations.

  In the method for removing water that has blocked the pores of the electrode base material of the cathode 13 described above, the amount of air supplied from the air supply pump AP is constant as shown in FIG. Although the opening / closing cycle is controlled, the flow control of the air pump AP as a gas flow rate adjusting means is added to the control of the opening / closing of the valve B1 in the discharge control unit 2a as shown in FIGS. 6B and 6C. Although the number of objects increases, the variable width of the opening / closing cycle of the valve B1 can be made relatively narrow, and the width of the gas flow path adjustment need not be widened. Therefore, control of the valve B1 and the air pump AP can be facilitated, and deterioration of the electrolyte membrane 11 is preferably suppressed by suppressing the pressure in the air flow path 150 to be low.

  In the control example shown in FIG. 6 (B), the load range is classified into three, the air flow rate is made variable in three stages accordingly, and the opening / closing cycle of the valve B1 is the load range within the three divided load ranges. This is a method of continuously varying according to the amount of change.

  In addition, in the control example shown in FIG. 6C, the load ranges are classified into three categories as described above, and the opening / closing cycle of the valve B1 is made variable in three stages accordingly, and the air flow rate is within the load range divided into three. This is a method of continuously varying the load according to the amount of change in load. Even if any method is used, the effect of removing the water blocking the pores of the electrode base material of the cathode 13 is the same, so the combination and load range described above according to the characteristics of the fuel cell device 1 and the load LD. What is necessary is just to select suitably the division | segmentation number of this, whether it shall be continuously variable or discretely variable.

  As a method for removing the clogged water, it is conceivable to greatly increase the gas flow rate, but in addition to the deterioration of the electrolyte membrane described above, an increase in the capacity of the air pump for increasing the air supply pressure, This is not preferable because problems such as an increase in the size of the apparatus due to an increase in the mechanical strength of the fuel cell body such as a separator occur.

  Further, the pump MP1, the pump MP2, and the cathode-side pump MP3 in the fuel supply unit F are only required to be able to send liquids. For example, a diaphragm type micro pump driven by a piezoelectric element (Japanese Patent Laid-Open No. 2001-322099) Can be used. When a micropump using this piezoelectric element is used, it is preferable to provide this pump on the outer wall or the like near the separator of the fuel cell.

  In the state where the valve B1 is open, these pumps function as a pump for feeding normal fuel or diluent and collecting the liquid to stably supply power to the fuel cell device A. In the closed state, it functions as a high-frequency vibration source, and the removal of water blocking the pores of the cathode electrode substrate is applied to the pressurization in the air flow path 150 to cause high-frequency vibrations by these piezoelectric elements. This can be done more effectively by adding it to the fuel cell main body 1, particularly the separator B15. The frequency applied to the piezoelectric elements of these micropumps is preferably set to, for example, a range of about 3 kHz to 10 kHz when functioning as a pump, and 20 kHz or more when functioning as a high frequency vibration source.

  Further, according to the method for removing generated water according to the present embodiment, since the water is discharged from the discharge port 151 for a while immediately after the opening of the valve B1, the pump MP3 for recovering the discharged liquid. Does not need to be operated continuously, and may be operated within a period during which the valve B1 is open. By doing so, the power consumption of the fuel cell device A can be suppressed by reducing the operation time of the pump MP3.

Example 1
In the same fuel cell apparatus A as shown in FIG. 1, the pump MP1 and the pump MP2, which are fuel and diluent supply pumps, continue to supply constant fuel under an initial load of 50 mA / cm ^2. During this time, the air supply from the air pump AP was also kept constant, and the operation was continued. At this time, the closing period Ta of the valve B1 was 1 second, and the opening / closing cycle Tc was 6 seconds. With the fuel cell device stably supplying power, the load was increased to 100 mA / cm ² at time P1 shown in FIG. The fuel cell apparatus A receives the change timing and magnitude of the load from the load by the discharge control section 2a of the control section 2, and opens / closes the valve B1 based on the relationship between the preset load magnitude and the opening / closing cycle Tc of the valve B1. The period Tc was changed from the initial 6 seconds to 3 seconds. The resulting change in output voltage is shown by the solid line in FIG. As shown by this result, the fuel cell apparatus A was kept almost constant without fluctuation of the output voltage despite the change in the load.

As a reference example, using the same fuel cell device A, even though the load was switched from 50 mA / cm ² to 100 mA / cm ^2, the load information (changing the timing and magnitude of the load) is discharge control unit 2a The discharge control unit 2a receives the information that the load is switched at the time point P2 after about 7 minutes, and the operation is continued with the opening / closing cycle Tc of the valve B1 being initially maintained at 6 seconds. The change in the output voltage is shown by the broken line in FIG. As shown in this result, the output voltage starts to decrease at the time point P1 when the load increases, and the output voltage starts to recover at the time point P2 when the information that the load is switched is received, and is in a stable state after the recovery. I understand that.

  Therefore, the discharge control unit 2a receives the time when the load changes and the magnitude of the changed load in response to the load fluctuation, and controls the opening / closing cycle Tc of the valve B1, so that the fuel cell device A can supply stable power. It was confirmed that it could be supplied.

It is a figure which shows the structure of an example of a fuel cell apparatus. It is the figure which showed typically the relationship between valve opening and closing and the pressure in an air flow path. It is the figure which showed typically the relationship between the current density which a fuel cell apparatus generate | occur | produces, and the amount of water produced | generated in the cathode vicinity. It is a figure which shows the relationship between the magnitude | size of load, and the opening-and-closing period of valve | bulb B1. It is a figure explaining the example regarding stability of the output voltage of a fuel cell apparatus. It is a figure explaining the example of the removal method of the water produced | generated in the cathode vicinity shown in this embodiment. It is a figure which shows the state of the output voltage of the fuel cell apparatus in an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Control part 2a Emission control part 11 Electrolyte membrane 12 Anode diffusion electrode (anode)
13 Cathode diffusion electrode (cathode)
14 Separator A (forms fuel flow path)
15 Separator B (forms gas flow path)
140 Fuel flow path 141 Fuel liquid supply port 142 Excess fuel liquid recovery port 150 Gas flow path 151 Discharge port 152 Air supply port A Fuel cell device B1 Valve C1 Fuel liquid container C2 Diluent container MP1, MP2, MP3 Micropump AP Air Pump F Fuel liquid supply section F1, F2, F3 Gas-liquid separator L1 Fuel liquid supply path L2 Diluent supply path L3 Merging section L4 Mixing flow path L5, L6 Liquid recovery path LD Load

Claims (8)

An anode diffusion electrode, a cathode diffusion electrode, a membrane electrode assembly having an electrolyte membrane sandwiched between the anode diffusion electrode and the cathode diffusion electrode, and the membrane electrode assembly, and the anode diffusion electrode A fuel cell body for supplying electric power to an external load, comprising a pair of separators forming a fuel flow path through which fuel passes and a gas flow path through which a gas containing oxygen passes between the cathode diffusion electrode ,
Gas supply means for supplying the gas containing oxygen upstream of the gas flow path;
Channel opening and closing means for opening and closing the gas channel downstream of the gas channel;
And a discharge control means for opening and closing the flow path opening and closing means. The fuel cell apparatus according to claim 1, wherein the discharge control means is configured to control the flow path opening / closing means at an opening / closing cycle determined based on at least the size of the load. 3. The fuel cell device according to claim 1, wherein the discharge control means is configured to control the flow path opening / closing means at least with an opening / closing cycle determined based on a change in the load. 4. A gas flow rate adjusting means for adjusting a supply amount for supplying the gas containing oxygen to the gas flow path;
The discharge control means includes at least an opening / closing cycle determined based on the magnitude of the load, and at least a gas supply amount determined based on the magnitude of the load. 2. The fuel cell device according to claim 1, further comprising a configuration for controlling the flow rate adjusting means. A gas flow rate adjusting means for adjusting a supply amount for supplying the gas containing oxygen to the gas flow path;
The discharge control means includes at least an opening / closing cycle determined based on a change in the load, and at least a gas supply amount determined based on the change in the load. 5. The fuel cell device according to claim 1, further comprising a configuration for controlling the means. Fuel supply means for supplying the fuel to the fuel flow path using the first piezoelectric element as an actuator is provided adjacent to the separator,
In a state where the flow path opening / closing means opens the gas flow path, the first piezoelectric element is driven at a frequency A within a range in which the fuel can be supplied,
6. The device according to claim 1, wherein the first piezoelectric element is driven at a frequency higher than the frequency A in a state in which the flow path opening / closing means closes the gas flow path. The fuel cell device according to the description. A liquid recovery means for recovering the liquid in the gas flow path;
The fuel cell apparatus according to any one of claims 1 to 6, wherein the liquid recovery means is stopped when the flow path opening / closing means closes the gas flow path. A liquid recovery means for recovering the liquid in the gas flow path using the second piezoelectric element as an actuator is provided adjacent to the separator,
In a state where the flow path opening / closing means opens the gas flow path, the second piezoelectric element is driven at a frequency B in a range in which the liquid in the gas flow path can be collected,
7. The device according to claim 1, wherein the second piezoelectric element is driven at a frequency higher than the frequency B in a state where the flow channel opening / closing means closes the gas flow channel. The fuel cell device according to the description.

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