JP2006278130A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of quickly removing water or the like generated at inside or surface of a catalyst layer of an oxygen electrode of a fuel cell and bi-product of battery reaction generated at inside or surface of a catalyst layer, smoothly supplying air (oxygen) to the catalyst layer, smoothing a reaction at the oxygen electrode, capable of improving power generating efficiency only by the above. <P>SOLUTION: The fuel cell system A uses a fuel cell 1 provided with a cathode chamber (liquid collection chamber) 15 installed adjacent to the oxygen electrode 13, provided with a liquid lead-out port 151 and an air supply vent hole 152; an exhaust part 15E exhausting gas in the cathode chamber 15; a liquid feeding pump MP4 connected to the liquid lead-out port 151; and a liquid reservoir 154. The pump MP4 can suck and lead out the liquid in the chamber 15 from the lead-out port 151 at forward operation, and push the liquid into the chamber 15 from the lead-out port 151 at reversed operation. Air supply from the vent hole 152 to the chamber 15, and exhaustion from the exhaust part 15E are carried out in accordance with the forward and reversed operation of the pump MP4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention uses a battery body having an electrolyte membrane sandwiched between a fuel electrode and an oxygen electrode, and a fuel cell provided adjacent to the oxygen electrode of the battery body and having a liquid recovery chamber having a liquid outlet and an air supply vent. The present invention relates to a fuel cell system using a fuel cell using a fuel solution obtained by diluting a high-concentration fuel solution with a diluent such as water, such as a direct methanol fuel cell (DMFC). .

  With the start of the ubiquitous society, demands for longer battery life are increasing. Conventional lithium batteries are approaching their theoretical limits and no further significant performance improvement can be expected. In the meantime, a fuel cell that can greatly extend the life of a conventional battery is attracting attention because of its high energy density per weight (volume).

  Among fuel cells, in particular, (1) simple structure, (2) easy to obtain fuel without requiring large-scale infrastructure development such as a hydrogen station, (3) from which point can operate at low cost and low temperature For example, direct methanol fuel cells (DMFC), which can be said to be suitable as fuel cells for portable devices (notebook personal computers, mobile phones, various personal digital assistants (PDA) devices, etc.), are attracting attention and are actively researched. Has been.

  Fuel cell systems employing DMFC type fuel cells are classified into two types according to the fuel supply method. One is called an active type, which is a type that supplies fuel to the battery by a pump, and the other is a type that is called a passive type, which supplies fuel by capillary force or the like without using a pump. .

Here, the reaction formula of DMFC is shown.
Reaction on the fuel electrode (anode) side: CH ₃ OH + H ₂ O → CO ₂ + 6e ⁻ + 6H ⁺
Reaction on the oxygen electrode (cathode) side: (3/2) O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O
Total reaction: CH ₃ OH + (3/2) O ₂ → CO ₂ + 2H ₂ O

According to this reaction formula, methanol and water react equimolarly at the fuel electrode to produce CO ₂ , six electrons and protons, CO ₂ is discharged to the outside, and the electrons pass through an external circuit and the oxygen electrode ( Protons are sent to the oxygen electrode (air electrode) through the electrolyte layer to the oxygen electrode (air electrode), and react with each other to generate three water molecules. The total reaction produces CO ₂ and 2 molecules of H ₂ O.
Such DMFC is described in, for example, Japanese Patent Application Laid-Open No. 2003-132924.

  Further, according to the above reaction formula, methanol and water react at an equimolar ratio at the fuel electrode, but the fuel solution actually supplied to the fuel electrode is usually a methanol aqueous solution having a low concentration of 3 to 5%. Used. The reason is to prevent the phenomenon of crossover, in which methanol passes through the electrolyte membrane without reaching the above reaction at the fuel electrode and reaches the air electrode. The crossover phenomenon is more likely to occur as the methanol concentration in the fuel increases. When such a close-over phenomenon occurs, the methanol reaction that should occur at the fuel electrode of the two DMFC poles (fuel electrode and oxygen electrode) also occurs at the oxygen electrode, resulting in a battery due to waste of fuel and potential drop on the oxygen electrode side. A significant reduction in efficiency occurs. Therefore, the above-mentioned low-concentration aqueous methanol solution diluted with water is usually used.

  As described above, a low-concentration fuel liquid obtained by diluting a high-concentration fuel liquid with a diluent is adopted as the fuel liquid supplied to the fuel cell that employs alcohol as the fuel. The solution diluted to the concentration can be stored in the fuel liquid storage container and supplied to the fuel cell using a pump.However, since it is necessary to always supply the fuel liquid during power generation, the fuel liquid is consumed immediately. The fuel liquid storage container must be frequently replaced or the fuel liquid must be supplied to the container.

If the fuel liquid storage container is made larger, the frequency of container replacement and the frequency of fuel liquid supply to the container will decrease, but it is not suitable for a portable fuel cell system for the purpose of downsizing.
In this regard, for example, the above-mentioned JP-A-2003-132924 and JP-A-2004-152561 collect water generated from the oxygen electrode, mix it with high-concentration alcohol, dilute the alcohol concentration, A method for supplying batteries is proposed.

  In addition to DMFC type fuel cells, in general, in fuel cells, as described above, water is generated on the oxygen electrode side by the electrochemical reaction of the cell, and in DMFC, water is generated on the oxygen electrode side. In some cases, the liquid may move from the fuel electrode side to the oxygen electrode side through the electrolyte membrane.

In any case, unless a liquid such as water is quickly removed from the oxygen electrode, sufficient air (oxygen) cannot be supplied to the oxygen electrode, and the power generation state deteriorates.
In this regard, Japanese Patent Application Laid-Open No. 2001-185181 discloses that in a fuel cell using hydrogen as a fuel, air (oxygen) is supplied to the oxygen electrode, and a chamber adjacent to the oxygen electrode is exhausted by a blower to generate a negative pressure. It is disclosed that a blower for sucking air from the outside into the room by the negative pressure and evaporating and discharging the liquid in the room or supplying air to the room is also provided.

JP 2003-132924 A JP 2004-152561 A JP 2001-185181 A

However, the fuel cell system still has the following problems.
That is, taking the fuel cell system using the DMFC as an example, water is generated as described above by the electrochemical reaction in the battery. Further, the liquid may move from the fuel electrode side through the electrolyte membrane to the oxygen electrode side.

  These liquids are received in a liquid recovery chamber (cathode chamber) adjacent to the oxygen electrode and having a vent for taking in air (oxygen), and discarded from the recovery chamber, or a high-concentration fuel liquid is diluted. However, some of the liquid in the liquid recovery chamber may adhere to and stay on the surface or the inside of the catalyst tank in the oxygen electrode, making it difficult to separate. Liquid such as water adhering or staying on the surface or inside of the catalyst tank reduces the reaction efficiency of the battery.

  In addition, impurities in the liquid and by-products due to the reaction may adhere to the catalyst layer of the oxygen electrode and inhibit a normal reaction. In the DMFC, a gas such as air dissolved in a liquid that may move from the fuel electrode side to the oxygen electrode side through the electrolyte membrane precipitates and stays on the surface of the catalyst layer of the oxygen electrode. May interfere with the normal response.

  As described in JP-A-2001-185181, the liquid such as water, impurities, by-products, etc. adhering to the inside or the surface of the catalyst layer are merely set to a negative pressure in the liquid recovery chamber. In some cases, it cannot be removed sufficiently.

  Accordingly, the present invention provides a fuel cell comprising a battery body having an electrolyte membrane sandwiched between a fuel electrode and an oxygen electrode, and a liquid recovery chamber provided adjacent to the oxygen electrode of the battery body and having a liquid outlet and an air supply vent. The fuel cell system used is a liquid such as water or the like that adheres to or adheres to the inside or surface of the catalyst layer of the battery oxygen electrode, or further adheres to or attempts to adhere to the inside or surface of the catalyst layer. By-products etc. of the battery reaction can be quickly removed from the catalyst layer and air (oxygen) can be smoothly supplied to the catalyst layer of the oxygen electrode, thereby facilitating the reaction at the battery oxygen electrode and generating power accordingly. It is an object to provide a fuel cell system capable of improving efficiency.

In order to solve the above problems, the present invention
A fuel cell system using a fuel cell including a battery body having an electrolyte membrane sandwiched between a fuel electrode and an oxygen electrode, and a liquid recovery chamber provided adjacent to the oxygen electrode of the battery body and having a liquid outlet and an air supply vent An exhaust part for discharging the gas in the liquid recovery chamber from the liquid recovery chamber, and a liquid feed pump and a liquid reservoir connected to the liquid outlet, the liquid feed pump And the liquid reservoir are connected to the liquid outlet in this order, and the liquid feed pump can suck out the liquid in the liquid recovery chamber from the liquid outlet through a normal operation, and The liquid can be pushed into the liquid recovery chamber from the liquid outlet, and the air supply from the air supply vent to the liquid recovery chamber and the exhaust section as the liquid feed pump is operated in the forward and reverse directions. Provided is a fuel cell system in which exhaust is performed.

  According to the fuel cell system of the present invention, the liquid collection chamber liquid is sucked from the liquid discharge port by normal operation of the liquid feed pump connected to the liquid discharge port of the liquid recovery chamber adjacent to the oxygen electrode of the fuel cell. The liquid can be led out, and the liquid can be pushed into the liquid recovery chamber from the liquid outlet by performing the reverse operation. Thus, it is possible to generate a normal liquid flow toward the liquid outlet and a reverse liquid flow toward the back side of the liquid recovery chamber in the liquid recovery chamber, and adhere to the inside and the surface of the catalyst layer of the oxygen electrode by the normal and reverse flow of the liquid. Or by-product that may be generated by the battery reaction, is shaken and placed in a liquid flow, and they may stay inside or on the surface of the catalyst layer. It is suppressed.

  The gas to be replaced may adhere to the surface of the catalyst layer of the oxygen electrode, the interior thereof, the stepped portion in the liquid recovery chamber, other recesses, or the inner wall surface. Due to the backflow, it is shaken, or due to the pressure fluctuations in the liquid recovery chamber due to the forward and backward flow of the liquid, the bubbles caused by the gas are repeatedly compressed and expanded, so that the bubbles are easily detached from the site and smoothly discharged. It can be removed outside.

Further, as the liquid feed pump is operated forward and reverse, air supply from the air supply vent into the liquid recovery chamber and exhaust from the exhaust section are performed, so that sufficient air ( Oxygen) can be supplied.
As a result, the liquid adhering or adhering to the inside or surface of the catalyst layer of the battery oxygen electrode, or the by-product of the cell reaction adhering or adhering to the inside or surface of the catalyst layer, etc. It can be quickly removed from the catalyst layer and air (oxygen) can be smoothly supplied to the catalyst layer of the oxygen electrode, thereby facilitating the reaction at the battery oxygen electrode and improving the power generation efficiency accordingly.

More specific examples of the fuel cell system according to the present invention will be listed below.
<First Example Fuel Cell System>
In the fuel cell system,
A valve for opening and closing the air supply vent is provided, and the exhaust part includes an exhaust hole provided in the liquid recovery chamber wall and a valve for opening and closing the exhaust hole. When the liquid in the liquid recovery chamber is sucked and led out from the liquid outlet through a normal operation, the negative pressure generated in the liquid recovery chamber opens the valve for opening and closing the air supply vent, while exhausting the exhaust section When the liquid is pushed into the liquid recovery chamber by the reverse operation of the liquid feed pump, the valve for opening and closing the air supply vent is closed by the positive pressure generated in the liquid recovery chamber. On the other hand, a fuel cell system in which a valve for opening and closing the exhaust hole of the exhaust unit is opened.

<Fuel Cell System of Second Example>
In the fuel cell system,
The exhaust part is a gas-liquid separator connected between the liquid feed pump and the liquid outlet, and the liquid in the liquid recovery chamber is sucked out from the liquid outlet by the normal operation of the liquid pump. When the air is sucked into the liquid recovery chamber from the air supply vent due to the negative pressure generated in the liquid recovery chamber, the liquid is sucked out from the liquid outlet in the gas-liquid separator. A fuel cell system in which gas is discharged from the air supply vent when gas is separated and discharged and liquid is pushed into the liquid recovery chamber by reverse operation of the liquid feed pump.

<Fuel cell system of third example>
In the fuel cell system,
An air pump is connected to the air supply vent hole, and the exhaust part is a gas-liquid separator connected between the liquid feed pump and the liquid outlet port. When the liquid in the liquid recovery chamber is sucked and led out from the liquid outlet, gas is separated and discharged from the liquid sucked and led out from the liquid outlet in the gas-liquid separator. Air is supplied from the air pump to a portion of the liquid recovery chamber that becomes a space when the liquid recovery chamber liquid is sucked and led out from the liquid outlet, and the liquid is supplied into the liquid recovery chamber by reverse operation of the liquid feed pump. A fuel cell system in which the gas in the liquid recovery chamber is discharged through the air pump when pushed.

In any of the fuel cell systems described above, in order to suppress liquid adhesion and stagnation, and in order to suppress leakage of liquid in the liquid recovery chamber from the hole portion where ventilation is performed between the outside and the liquid recovery chamber, The surface of the liquid recovery chamber may be subjected to water repellent treatment.
Such water repellency treatment is desirably performed on at least a liquid recovery chamber inner surface portion having a hole portion through which air is ventilated between the liquid recovery chamber exterior and outer surfaces.

  Examples of the fuel cell include a battery using a fuel solution obtained by diluting a high-concentration fuel solution with a diluent as the fuel. When this type of fuel cell is employed, the liquid sucked out from the liquid recovery chamber may be recovered into the diluent storage container by the normal operation of the liquid feed pump.

  A representative example of such a fuel cell is DMFC. In this case, examples of the “high concentration fuel liquid” include methanol and a high concentration methanol aqueous solution, and examples of the diluent include water and a liquid containing water as a main component. be able to. For this diluted solution, water generated on the oxygen electrode (in other words, air electrode or cathode) side of DMFC can be used.

In addition, each pump is recommended to be a micropump in order to reduce the size and size of the system, but is not limited thereto.
The micropump may be formed integrally with the fuel cell in order to reduce the size and size of the system.

  The micro pump includes a first throttle channel, a second throttle channel shorter than the first throttle channel, a pump chamber between the first and second throttle channels, and a diaphragm facing the pump chamber whose pump chamber volume can be varied. And a drive actuator installed in the diaphragm, and applying a pulse voltage to the drive actuator allows liquid to flow from the first throttle channel (or second throttle channel) to the pump chamber in accordance with the pulse voltage waveform. An example is a pump that is sucked and the liquid in the pump chamber is discharged from the second throttle channel (or the first throttle channel).

  As described above, according to the present invention, the battery body having the electrolyte membrane sandwiched between the fuel electrode and the oxygen electrode, and the liquid recovery chamber having the liquid outlet and the air supply vent are provided adjacent to the oxygen electrode of the battery body. A fuel cell system using a provided fuel cell, which is attached to or inside a catalyst layer of a battery oxygen electrode or a liquid such as water to be attached, or further attached to the inside or surface of the catalyst layer Alternatively, by-products or the like of the battery reaction to be attached can be quickly removed from the catalyst layer and air (oxygen) can be smoothly supplied to the catalyst layer of the oxygen electrode, thereby facilitating the reaction at the battery oxygen electrode. Therefore, it is possible to provide a fuel cell system that can improve the power generation efficiency.

<Fuel cell system shown in FIG. 1>
The fuel cell system A shown in FIG. 1 employs a direct methanol fuel cell (DMFC) 1 as a fuel cell, and the fuel liquid can be supplied to the battery 1 from the fuel liquid supply unit F to generate electric power.

  The battery 1 has an MEA (Membrane Electrode Assembly) structure in which an anode (fuel electrode) 12 and a cathode (in other words, an oxygen electrode or an air electrode) 13 are joined to both surfaces of an electrolyte membrane 11. An anode chamber (fuel supply chamber) 14 is formed by bonding, and a separator is also bonded to the cathode 13 to form a cathode chamber (liquid recovery chamber) 15.

  Here, the anode 12 includes a catalyst layer in contact with the electrolyte membrane 11 (for example, platinum black or a platinum alloy supported on carbon black) and an electrode such as carbon paper laminated thereon, and the cathode 13 is also formed on the electrolyte membrane 11. It consists of a similar catalyst layer in contact and a similar electrode laminated thereon. The anode chamber 14 has a fuel liquid supply port 141 and a fuel liquid recovery port 142.

  The anode chamber 14 further has a vent hole 143 for releasing carbon dioxide gas generated on the anode 12 side by the electrochemical reaction of the battery 1 to the outside on the chamber wall. The vent hole 143 allows the passage of gas from the inside of the room to the outside, but has been subjected to a water repellent treatment with, for example, a fluorine-based resin (for example, PTFE) so as to prevent the passage of liquid from the inside of the room.

  The cathode chamber 15 collects from the entire cathode 13 a liquid (water) generated on the cathode side by an electrochemical reaction and a liquid that may move from the anode side to the cathode side through the electrolyte membrane 11. It has a passage and a liquid lead-out port 151 through which the liquid is led out from the liquid passage. Further, air supply air holes 152 for taking in air (oxygen) from the outside to the cathode 13 and the gas in the cathode chamber 15 are provided. It also has an exhaust part 15E for discharging to the outside.

  In the cathode chamber 15, as shown in an enlarged view in FIG. 5, each of the air supply air holes 152 is provided with a valve v <b> 1 for opening and closing the hole. The exhaust part 15E is provided on the end wall opposite to the liquid outlet 151. The exhaust part 15E includes an exhaust hole 153 formed in the end wall and a valve v2 for opening and closing the exhaust hole 153. The inner surface of the cathode chamber 15 includes the inner peripheral surfaces of the valve v1 and the vent hole 152, and further includes the inner peripheral surfaces of the valve v2 and the exhaust hole 153 of the exhaust section so as to prevent the passage of liquid from the inside to the outside. Further, for example, a water repellent treatment f is performed with a fluorine-based resin (for example, PTFE).

  The fuel liquid supply unit F includes a high-concentration fuel liquid supply path L1 connected to a container C1 that stores a high-concentration fuel liquid (in this example, approximately 100% concentration methanol) and a diluent (this example). Then, a diluent supply path L2 connected to a container C2 for containing water or a liquid containing water as a main component) is included.

A pump MP1 for sending out the high-concentration fuel liquid in the container C1 is connected to the high-concentration fuel liquid supply path L1, and the dilution in the container C2 is connected to the dilution liquid supply path L2 in the middle. A pump MP2 for feeding out the liquid is connected.
The supply paths L1 and L2 merge at the junction L3, and the mixing channel L4 extends from the junction L3 to the fuel supply port 141 of the anode chamber 14, and the fuel supply chamber 14 passes through the gas-liquid separator F2. The fuel supply port 141 is connected.

The gas-liquid separator F2 is for preventing gas generated on the anode side from entering the mixing flow path L4 from the fuel supply port 141. Here, the gas-liquid separator F2 is separated to release the gas to the outside. .
The liquid recovery port 142 of the anode chamber 14 communicates with the diluent storage container C2 through the recovery path L5. The recovery path 5 is used on the anode side, and guides a surplus liquid such as a fuel liquid having a reduced methanol concentration to the container C2, and a pump MP3 is connected in the middle thereof.
Further, a gas-liquid separator F1 for separating gas from the liquid flowing out from the liquid recovery port 142 and releasing it to the outside is connected between the liquid recovery port 142 and the pump MP3.

A liquid outlet 151 of the cathode chamber 15 of the fuel cell 1 is connected to a diluent storage container C2 through a gas recovery unit L3 through a gas / liquid separator F3, and a pump MP4 and a liquid reservoir 154 are provided in the middle thereof. They are connected in this order. The gas-liquid separator F3 is for separating and discharging gas from the liquid coming out from the liquid outlet 151.
The pump MP4 and the like form a liquid recovery unit RE that recovers the liquid into the container C2 so that the liquid in the cathode chamber 15 can be used as a diluent.

The gas-liquid separators F1, F2, and F3 may be any one that can separate gas-liquid and release the gas to the outside. For example, gas-liquid separation using a gas-liquid separation membrane known per se Can be used.
The fuel cell system A of FIG. 1 further includes a drive circuit D for the pumps MP1, MP2, MP3, and MP4 and a controller Cont that controls the pump drive circuit D.

  The pump MP1, the pump MP2, the pump MP3, and the cathode-side pump MP4 in the fuel supply unit F may be any pumps that can send liquid, but here, the basic configuration is shown in FIGS. 2 (A) and 2 (B). This is a micropump (collectively referred to as “MC” in FIG. 2) that performs a liquid feeding operation by applying the drive waveform signal shown in FIG. 2C or FIG. 2D.

  First, the configuration will be described. The micropump MC includes a pump chamber PC set in the liquid passage L1, L2, L5, or L6, a throttle flow formed between the upstream liquid flow path portion Li and the pump chamber PC. An example of a path f1, a throttle flow path f2 formed between the downstream liquid flow path portion Lo and the pump chamber PC, a diaphragm DF provided adjacent to the pump chamber PC, and an actuator attached to the diaphragm DF A certain piezoelectric element PZT is included. The throttle channels f1 and f2 have substantially the same cross-sectional area, but the downstream channel f2 is longer than the upstream channel f1.

  The pump MC applies a pulse voltage to the piezoelectric element PZT to vibrate the pump chamber wall (diaphragm) DF, thereby contracting and expanding the pump chamber PC according to the applied pulse voltage waveform, and the first throttle channel f1 (or The liquid can be sucked into the pump chamber PC from the second throttle channel f2), and the pump chamber liquid can be discharged from the second throttle channel f2 (or the first throttle channel f1).

  More specifically, as a pulse voltage for driving the piezoelectric element PZT, a pulse voltage waveform showing a steep rise and a gradual fall as shown in FIG. When the diaphragm DF is suddenly deformed by the piezoelectric element at the time of steep rise and the pump chamber PC is rapidly contracted, the liquid flows in a laminar flow due to the flow resistance in the long flow path f2, whereas the liquid flows in the short flow path f1. It becomes a turbulent flow and the outflow of the liquid from the flow path f1 is suppressed. Thereby, the pump chamber liquid can be discharged from the flow path f2.

Further, when the diaphragm DF is gently returned by the piezoelectric element when the applied voltage gradually falls, and the pump chamber PC is gently expanded, the liquid flows into the pump chamber PC from the short flow path f1. When the flow path f1 is larger than the flow path f1, the liquid discharge from the long flow path f2 is suppressed. Thereby, the liquid can be sucked from the flow path f1 into the pump chamber PC.
Each of the pumps MP1, MP2, MP3, and MP4 has such a basic structure, and performs liquid feeding according to such an operating principle.

Therefore, in the fuel cell system A of FIG. 1, in each of the pumps MP1 and MP2, by arranging the flow path f1 on the upstream side (containers C1 and C2 side) and the flow path f2 on the downstream side (battery 1 side), The diluted fuel liquid can be supplied to the anode chamber 14 of the battery 1 in a forward flow (positive flow) by driving the pumps MP1 and MP2 alternately or simultaneously.
In addition, with respect to the pump MP3, the flow path f1 is arranged on the upstream side (battery 1 side) and the flow path f2 is arranged on the downstream side (container C2 side), so that the pump MP3 is driven and the spent fuel liquid is supplied from the anode chamber 14. Can be collected in the container C2.
Further, with respect to the pump MP4, the flow path f1 is disposed on the upstream side (battery 1 side) and the flow path f2 is disposed on the downstream side (container C2 side), so that the pump MP4 is driven and the container C2 from the cathode chamber 15 of the battery. Capable of liquid recovery.

FIG. 3 illustrates a state in which the micropumps MP1 and MP2 are alternately driven to alternately send the high concentration fuel liquid and the dilution liquid to the mixing flow path L4. The liquid diffuses and mixes with each other while proceeding through the mixing flow path to become a diluted fuel liquid, which is supplied to the cathode chamber 14.
Even if the micropumps MP1 and MP2 are driven simultaneously and sent to the mixing flow path L4 simultaneously with the high-concentration fuel liquid and the diluting liquid, both liquids are mixed while traveling through the mixing flow path to obtain a diluted fuel liquid.

When a pulse voltage indicating a gradual rise and a steep fall shown in FIG. 2D is applied from the drive circuit D, the liquid is sucked into the pump chamber PC from the flow path f2, and the pump chamber liquid is flowed from the flow path f1. Can be discharged. Thus, each of the pumps MP1, MP2, MP3, and MP4 can be driven to generate a reverse flow, thereby generating a reverse flow in the anode chamber 14 or the cathode chamber 15 as necessary. You can also.
The micropump may be formed integrally with the anode chamber 14 and the cathode chamber 15 in order to make the system compact.

  According to this fuel cell system A, the pump drive circuit D inputs a drive signal to the piezoelectric element of each pump under the instruction of the controller Cont, so that the high-concentration fuel liquid is merged from the container C1 by the pump MP1. And the liquid for dilution is sent from the container C2 to the merging section L3 by the pump MP2, and these liquids are continuously mixed in the mixing flow path L4. The diluted fuel liquid thus obtained (for example, about 3% aqueous methanol solution) Can be supplied to the fuel cell 1 for power generation and power can be supplied to the load LD.

Further, the spent fuel liquid in the anode chamber 14 can be recovered into the container C2 by the action of the pump MP3.
Further, the water generated on the cathode 13 side by the electrochemical reaction in the fuel cell 1 and the liquid that may arrive at the cathode 13 side through the electrolyte membrane 11 from the anode 12 side are brought into the cathode chamber by the action of the pump MP4. 15 to the container C2. At the beginning of use of the fuel cell system, initial water may be stored in the container C2.

  The fuel cell system A shown in FIG. 1 can basically generate electric power as described above, but in the carbon dioxide gas or fuel liquid generated on the anode (fuel electrode) 12 side by the electrochemical reaction in the battery 1. In order to smoothly remove impurities, by-products associated with the reaction, etc., and increase power generation efficiency, the control unit is configured so that the pumps MP1 to MP3 operate as in the following [Example 1] or [Example 2], for example. Let Cont control the pump drive circuit D. In [Example 1] and [Example 2], the pumps MP1 and MP2 are alternately driven to supply the fuel liquid.

[Example 1]
As shown in FIG. 4A, the pump groups MP1 and MP2 and the pump MP3 are alternately operated in the positive direction. When the pumps MP1 and MP2 are alternately operated in the positive direction, the inside of the anode chamber 14 is pressurized with respect to the atmospheric pressure. When the pump groups MP1 and MP2 are stopped and the pump MP3 is operated positively, the anode chamber 14 is in a reduced pressure (negative pressure) state with respect to the atmospheric pressure.
Although the pump MP3 has the throttle channels f1 and f2 as in the pump structure described above, the liquid can be circulated when the pump MP3 is not driven by the piezoelectric element PZT. However, at the level of the liquid circulation, when the pumps MP1 and MP2 are alternately operated in the positive direction, the inside of the anode chamber 14 is pressurized with respect to the atmospheric pressure.

By repeating the pressurization and decompression in the anode chamber 14, the carbon dioxide gas is compressed and expanded to facilitate movement while supplying the fuel liquid to the anode 14, and is discharged from the vent hole 143. Carbon dioxide mixed with liquid flowing out from the liquid recovery port 142 is removed by the gas-liquid separator F1, and carbon dioxide mixed with liquid that may flow backward from the fuel supply port 141 is removed by the gas-liquid separator F2. The In addition, impurities in the fuel liquid and by-products accompanying the reaction also easily move and are smoothly discharged out of the anode chamber.
As described above, the fuel liquid is supplied while efficiently discharging the carbon dioxide gas.

[Example 2]
As shown in FIG. 4B, the pumps MP1 and MP2 are alternately arranged between them, but when viewed as the pump groups MP1 and MP2, the pump MP3 is operated while continuously operating the pump groups. Reverse operation intermittently. During the reverse operation of the pump MP3, the internal pressure of the anode chamber 14 can be increased, and when the pump MP3 is stopped, the internal pressure of the anode chamber 14 can be relatively reduced.

By pressurizing and depressurizing the anode chamber 14, the fuel gas is supplied to the anode 14, and the carbon dioxide gas is compressed and expanded to be easily moved and discharged from the vent hole 143. Carbon dioxide mixed with liquid flowing out from the liquid recovery port 142 is removed by the gas-liquid separator F1, and carbon dioxide mixed with liquid that may flow out from the fuel supply port 141 is removed by the gas-liquid separator F2. The In addition, impurities in the fuel liquid and by-products accompanying the reaction also easily move and are smoothly discharged out of the cathode chamber.
As described above, the fuel liquid is supplied while efficiently discharging the carbon dioxide gas.

  Further, in the fuel cell system A shown in FIG. 1, water generated on the cathode (oxygen electrode) 13 side due to the electrochemical reaction in the battery 1 or moves from the anode 12 side through the electrolyte membrane 11 to the cathode 13 side. In some cases, liquids or by-products generated by battery reactions adhere to and stay inside or on the surface of the catalyst layer of the cathode 13, so that the supply of air (oxygen) to the catalyst layer does not become insufficient. In addition, the controller Cont controls the pump drive circuit D so that the pump MP4 operates as follows, for example.

  As shown in FIG. 6, by causing the pump MP4 to repeat the forward / reverse operation in a predetermined period Ta, the forward liquid flow toward the liquid outlet 151 in the cathode chamber 15 and the reverse toward the back side of the cathode chamber 15 are performed. By alternately generating a liquid flow, the liquid flowing forward and backward shakes the liquid adhering to or adhering to the inside or the surface of the catalyst layer of the cathode 13, or a by-product that may be generated by a cell reaction. The liquid flow suppresses them from staying inside or on the surface of the catalyst layer.

  Furthermore, even if the gas to be replaced in the cathode chamber 15 may adhere to the surface of the catalyst layer of the oxygen electrode, the inside thereof, the stepped portion in the liquid recovery chamber or other recesses or the inner wall surface, it will also adhere. However, the liquid is shaken by the forward / reverse flow of the liquid, or the air bubbles in the cathode chamber 15 are fluctuated by repeated compression / expansion due to the pressure fluctuation in the cathode chamber 15 due to the normal / reverse flow of the liquid. Can be easily detached from the battery and smoothly removed from the battery.

  Further, during the positive operation of the pump MP4, the liquid in the cathode chamber 15 is sucked and led out from the liquid outlet 151, so that the atmospheric pressure in the cathode chamber 15 becomes negative with respect to the atmospheric pressure. The valve v1 for opening and closing the valve is opened and air is sucked and supplied from the outside into the cathode chamber 15, while the valve v2 for opening and closing the exhaust hole 153 is closed in the exhaust part 15E.

  During the reverse operation of the pump MP4, the liquid in the flow path between the liquid outlet 151 and the pump MP4, the liquid that may remain in the pump MP4, or further the liquid in the liquid reservoir 154 is liquid outlet 151. The valve v1 that opens and closes the vent hole 152 is closed by the positive atmospheric pressure generated in the cathode chamber 15 and thus the valve v2 that opens and closes the exhaust hole 153 is opened. The gas having a reduced oxygen concentration is discharged to the outside. In this way, as the pump MP4 is operated in the forward and reverse directions, air is supplied from the vent hole 152 into the cathode chamber 15 and exhausted from the exhaust part 15E, so that sufficient air (oxygen) is supplied to the catalyst layer of the cathode 13. Can be supplied smoothly.

  As a result, the liquid adhering or adhering to the inside or the surface of the catalyst layer of the cathode 13 or the by-product of the cell reaction adhering to or adhering to the inside or the surface of the catalyst layer can be quickly obtained. In addition, it can be removed from the catalyst layer and air (oxygen) can be smoothly supplied to the catalyst layer of the cathode 13, thereby facilitating the reaction on the cathode 13 side and improving the power generation efficiency accordingly.

In the period Tb next to the period Ta, the pump MP4 is continuously operated in the positive direction to recover the liquid from the cathode chamber 15 to the container C2. Further, in the next period Tc (<Tb), the liquid in the liquid reservoir 154 is used to supply the liquid into the cathode chamber 15, and then the pump MP4 is operated in the forward and reverse directions again as in the period Ta. .
The above operation is repeated.

  FIG. 7 shows another example of the cathode chamber 15. In the cathode chamber 15 shown in FIG. 7, a plurality of air supply vent holes 152 ′ are formed in the cathode chamber wall. Unlike the vent hole 152 in the cathode chamber 15 of FIG. 5, each vent hole 152 ′ is not provided with a valve v <b> 1, and has a small diameter that allows gas to pass but prevents liquid from passing. The inner surface of the cathode chamber 15 is subjected to a water repellent treatment f by using, for example, a fluorine resin (for example, PTFE).

  Also in the case of the cathode chamber 15, a liquid such as water attached or about to adhere to the inside or surface of the catalyst layer of the cathode 13, or a battery attached to or about to attach to the inside or surface of the catalyst layer. In order to quickly remove reaction by-products and the like from the catalyst layer and to smoothly supply air (oxygen) to the catalyst layer of the cathode 13, the control unit Cont is operated so that the pump MP4 operates, for example, as follows. The pump drive circuit D is controlled.

  That is, as shown in FIG. 8, by causing the pump MP4 to repeat the forward / reverse operation in a predetermined period Ta ′, a normal liquid flow and a reverse liquid flow are alternately generated in the cathode chamber 15, By the forward and backward flow, the liquid adhering to or adhering to the inside or the surface of the catalyst layer of the cathode 13 or the by-product that may be generated by the cell reaction is shaken and placed in the liquid flow. Is prevented from staying inside or on the surface of the catalyst layer.

  Furthermore, even if the gas to be replaced in the cathode chamber 15 may adhere to the surface of the catalyst layer of the oxygen electrode, the inside thereof, the stepped portion in the liquid recovery chamber or other recesses or the inner wall surface, it will also adhere. However, the liquid is shaken by the forward / reverse flow of the liquid, or the air bubbles in the cathode chamber 15 are fluctuated by repeated compression / expansion due to the pressure fluctuation in the cathode chamber 15 due to the normal / reverse flow of the liquid. Can be easily detached from the battery and smoothly removed from the battery.

  Further, during the positive operation of the pump MP4, the liquid in the cathode chamber 15 is sucked and led out from the liquid outlet 151, so that the atmospheric pressure in the cathode chamber 15 becomes negative with respect to the atmospheric pressure. From the air, the air in the cathode chamber 15 is sucked and supplied, while the gas in the liquid sucked and led out from the liquid outlet 151 is separated and discharged in the gas-liquid separator F3. Here, the gas-liquid separator F3 functions as an exhaust part.

  During the reverse operation of the pump MP4, the liquid in the flow path between the liquid outlet 151 and the pump MP4, the liquid that may remain in the pump MP4, or the liquid in the liquid reservoir 154 is further removed from the liquid outlet 151. The gas having a reduced oxygen concentration in the cathode chamber 15 is discharged from the vent hole 152 to the outside due to the positive pressure generated in the cathode chamber 15.

  As a result, the liquid adhering or adhering to the inside or the surface of the catalyst layer of the cathode 13 or the by-product of the cell reaction adhering to or adhering to the inside or the surface of the catalyst layer can be quickly obtained. In addition, the air can be removed from the catalyst layer and air (oxygen) can be smoothly supplied to the catalyst layer of the cathode 13, thereby facilitating the reaction at the cathode 13 and improving the power generation efficiency accordingly.

In the period Tb ′ next to the period Ta ′, the pump MP4 is continuously operated in the positive direction to recover the liquid from the cathode chamber 15 to the container C2. Further, in the next period Tc ′ (<Tb ′), the liquid in the liquid reservoir 154 is used to supply the liquid into the cathode chamber 15, and then the pump MP4 is again set in the same manner as in the period Ta ′. Reverse drive.
The above operation is repeated.

  FIG. 9A shows still another example of the cathode chamber 15. In the cathode chamber 15 shown in FIG. 9, a vent hole 153 ′ that also serves as an exhaust hole is formed in the cathode chamber wall at the end opposite to the liquid outlet port 151 as an air supply vent hole. 2 is connected. A water repellent treatment f is applied to the inner surface of the cathode chamber.

  As shown in FIG. 9B, the air pump 2 is a diaphragm pump, and a diaphragm 22 is stretched on the case with respect to the pump chamber 20 in the case 21, and this is a piezoelectric that is an example of an actuator. The volume of the pump chamber 20 can be increased or decreased by vibrating with the element 23.

The case 21 is formed with an intake hole 24 and a discharge hole 26 communicating with the pump chamber 20. A valve 25 is provided for the intake hole 24, and a valve 27 is provided for the discharge hole 26.
When the diaphragm 22 is deformed to reduce the volume of the pump chamber 20, the valve 25 contacts the valve seat S 1, while the valve 27 is opened to discharge the pump chamber air, and the cathode chamber 15 is vented from the vent hole 153 ′ of the cathode chamber 15. 15 can be supplied with air.

When the diaphragm 22 is deformed to the opposite side and the volume of the pump chamber 20 is increased, the valve 27 is brought into contact with the valve seat S2, while the valve 25 is opened so that air can be sucked into the pump chamber 20.
As the volume of the pump chamber 20 increases or decreases with the deformation of the diaphragm 22, air is sucked into the pump chamber 20, and the sucked air is supplied into the cathode chamber 15.

The valves 25 and 27 of the pump 2 open and close as the diaphragm 22 is driven by the piezoelectric element 23. When the diaphragm 22 is not driven, the valves 25 and 27 are separated from the valve seats S1 and S2 and between the pump chambers 24 and 26. Ventilation is free.
The pump 2 is also driven by the drive circuit D under the instruction of the control unit Cont.

  Also in the case of the cathode chamber 15, a liquid such as water attached or about to adhere to the inside or surface of the catalyst layer of the cathode 13, or a battery attached to or about to attach to the inside or surface of the catalyst layer. Control is performed so that the pump MP4 and the pump 2 operate, for example, as follows so that reaction by-products and the like can be quickly removed from the catalyst layer and air (oxygen) can be smoothly supplied to the catalyst layer of the cathode 13. The part Cont controls the pump drive circuit D.

  That is, as shown in FIG. 10, in the period T1, the pump 2 is turned off and the pump MP4 is normally operated. At that time, the liquid in the cathode chamber 15 is led out from the liquid outlet 151 and collected in the container C2. The gas in the liquid is separated and discharged in the gas-liquid separator F3. Here, the gas-liquid separator F3 functions as an exhaust part. In addition, in the period T1 in which the pump 2 is turned off and the pump MP4 is operated positively, the cathode chamber 15 has a negative pressure, so that air flows into the cathode chamber 15 from the vent hole 153 ′ through the pump 2 in the off state. Sucked.

  In the next period T2, the pump MP4 is turned off and the pump 2 is normally operated. At this time, air is forcibly supplied into the cathode chamber 15 by the pump 2, and the air filled in the cathode chamber 15 reaches the gas-liquid separator F <b> 3 from the liquid outlet 151, from which excess air is discharged. The However, in the air supply into the cathode chamber 15, liquid such as water on the surface of the cathode 13 is pushed out to the vicinity of the liquid outlet 151 by the air flow, and water stays around the liquid outlet (in an extreme case, The liquid outlet may be closed), and water may not reach the gas-liquid separator.

  Therefore, in the next period T3 (<T1), the pump 2 is turned off, the pump MP4 is operated in reverse, and the liquid is supplied to the liquid outlet 151 and its surroundings using the liquid in the liquid reservoir 154, Water around the liquid outlet is drawn in and the pump MP4 is switched to normal operation from that state. The above pump operation is repeated.

  Thus, the liquid adhering or adhering to the inside or the surface of the catalyst layer of the cathode 13 or the by-product of the cell reaction adhering to or adhering to the inside or the surface of the catalyst layer can be promptly obtained. It can be removed from the catalyst layer and air (oxygen) can be smoothly supplied to the catalyst layer of the cathode 13, thereby facilitating the reaction at the cathode 13 and improving the power generation efficiency accordingly.

  In a fuel cell system using a fuel cell, the present invention smoothly removes water and the like generated on the oxygen electrode side of the fuel cell from the oxygen electrode side and smoothly supplies air (oxygen) to the oxygen electrode to generate power. Can be used to improve

It is a figure which shows one example of the fuel cell system which concerns on this invention. 2A is a cross-sectional view of an example of a micropump that can be used in a fuel cell system, FIG. 2B is a plan view of the micropump, and FIG. 2C is when the micropump is normally operated. (D) shows an example of a drive signal waveform when the micropump is operated in reverse. It is a figure which shows the example which supplies a high concentration fuel liquid and a dilution liquid alternately with two micropumps, and supplies the diluted fuel liquid to a battery. 4 (A) and 4 (B) are timing charts showing an example of the operation of the anode pump by the fuel cell system of FIG. It is a figure which expands and shows the fuel cell structure in the fuel cell system shown in FIG. 2 is a timing chart showing an operation example of a cathode side pump and a valve by the fuel cell system of FIG. 1. It is a figure which shows the other example of a cathode chamber. It is a timing chart which shows the operation example of the cathode side pump in the case of employ | adopting the cathode chamber of the structure shown in FIG. It is a figure which shows the further another example of a cathode chamber. FIG. 10 is a timing chart showing an operation example of the cathode side pump when the cathode chamber having the structure shown in FIG. 9 is employed.

Explanation of symbols

A Fuel cell system 1 Fuel cell 11 Electrolyte membrane 12 Anode (fuel electrode)
13 Cathode (oxygen electrode)
14 Anode chamber (fuel supply chamber)
141 Fuel liquid supply port 142 Fuel liquid recovery port 143 Vent hole 15 Cathode chamber (liquid recovery chamber)
151 Liquid outlet port 152 Air supply vent v1 Valve 15E of vent 152 152 Exhaust part 153 Exhaust hole v2 Valve 154 of exhaust hole 153 Liquid reservoir f Water repellent treatment part 152'Air supply vent hole / exhaust hole 153 ' Pore / exhaust hole 2 Air pump 20 Pump chamber 21 Pump case 22 Diaphragm 23 Piezoelectric element 24 Intake hole 25 Valve S1 Valve seat 26 Discharge hole 27 Valve S2 Valve seat F Fuel liquid supply part C1 High concentration fuel liquid container C2 Diluted liquid container Container L1 High-concentration fuel liquid supply path L2 Diluent liquid supply path L3 Junction section L4 Mixing flow path L5 Liquid recovery path L6 Liquid recovery paths MP1 to MP4, MC Micropump PC Pump chamber f1, f2 Restriction flow path Li Upstream path Lo Downstream Side passage DF Diaphragm PZT Piezoelectric elements F1, F2, F3 Gas-liquid separator D Pump drive circuit Cont Control unit LD Load

Claims (6)

  A fuel cell system using a fuel cell including a battery body having an electrolyte membrane sandwiched between a fuel electrode and an oxygen electrode, and a liquid recovery chamber provided adjacent to the oxygen electrode of the battery body and having a liquid outlet and an air supply vent An exhaust part for discharging the gas in the liquid recovery chamber from the liquid recovery chamber, and a liquid feed pump and a liquid reservoir connected to the liquid outlet, the liquid feed pump And the liquid reservoir are connected to the liquid outlet in this order, and the liquid feed pump can suck out the liquid in the liquid recovery chamber from the liquid outlet through a normal operation, and The liquid can be pushed into the liquid recovery chamber from the liquid outlet, and the air supply from the air supply vent to the liquid recovery chamber and the exhaust section as the liquid feed pump is operated in the forward and reverse directions. A fuel cell system, wherein exhaust is performed.   A valve for opening and closing the air supply vent is provided, and the exhaust part includes an exhaust hole provided in the liquid recovery chamber wall and a valve for opening and closing the exhaust hole. When the liquid in the liquid recovery chamber is sucked and led out from the liquid outlet through a normal operation, the negative pressure generated in the liquid recovery chamber opens the valve for opening and closing the air supply vent, while exhausting the exhaust section When the liquid is pushed into the liquid recovery chamber by the reverse operation of the liquid feed pump, the valve for opening and closing the air supply vent is closed by the positive pressure generated in the liquid recovery chamber. The fuel cell system according to claim 1, wherein a valve for opening and closing the exhaust hole of the exhaust unit is opened.   The exhaust part is a gas-liquid separator connected between the liquid feed pump and the liquid outlet, and the liquid in the liquid recovery chamber is sucked out from the liquid outlet by the normal operation of the liquid pump. When the air is sucked into the liquid recovery chamber from the air supply vent due to the negative pressure generated in the liquid recovery chamber, the liquid is sucked out from the liquid outlet in the gas-liquid separator. 2. The fuel cell according to claim 1, wherein when the gas is separated and discharged and the liquid is pushed into the liquid recovery chamber by the reverse operation of the liquid feed pump, the gas in the liquid recovery chamber is discharged from the air supply vent. system.   An air pump is connected to the air supply vent hole, and the exhaust part is a gas-liquid separator connected between the liquid feed pump and the liquid outlet port. When the liquid in the liquid recovery chamber is sucked and led out from the liquid outlet, gas is separated and discharged from the liquid sucked and led out from the liquid outlet in the gas-liquid separator. Air is supplied from the air pump to a portion of the liquid recovery chamber that becomes a space when the liquid recovery chamber liquid is sucked and led out from the liquid outlet, and the liquid is supplied into the liquid recovery chamber by reverse operation of the liquid feed pump. The fuel cell system according to claim 1, wherein when being pushed in, the gas in the liquid recovery chamber is discharged through the air pump.   The fuel cell system according to any one of claims 1 to 4, wherein a water-repellent treatment is performed on a surface of the liquid recovery chamber. The fuel cell is a battery that uses a fuel liquid obtained by diluting a high-concentration fuel liquid with a diluent as a fuel, and recovers the liquid sucked and led out from the liquid recovery chamber by a normal operation of the liquid feed pump into the diluent storage container. 6. The fuel cell system according to claim 1, wherein the fuel cell system is enabled.