JP2007095424A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system in which wasteful consumption of a fuel liquid can be suppressed at stopping of the fuel cell system, and in which a battery lifetime can be improved by keeping an electrolyte film in a wet state even at a system stop over a long-term. <P>SOLUTION: This is the fuel cell system A in which the fuel is supplied from a fuel supply room 14 to a fuel electrode 12 of the cell main body pinching the electrolyte film 11 between the fuel electrode 12 and an oxygen electrode 13, and in which the fuel cell to generate electricity by supplying air to the oxygen electrode 13 is comprised. The system A includes a fuel supplying means (supply passages L1, L2 including containers C1, C2, pumps P1, P2, and a mixing flow passage L3) in order to supply a fuel liquid to the room 14, a fuel recovery means (recovery passage L5 or the like including pump P4) to recover residual fuel of the room 14, and a supplying means to start supplying a moisturizing liquid of the electrolyte film 11 to the fuel supplying room 14, accompanying fuel recovery by the fuel recovery means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a fuel cell that supplies fuel to the fuel electrode of a battery main body sandwiching an electrolyte membrane between a fuel electrode and an oxygen electrode, and generates air by supplying air to the oxygen electrode.

  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 (PDAs), etc.) have attracted attention and have been actively studied. ing.

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.

  According to this electrochemical reaction, protons take a hydrated state when moving from the fuel electrode toward the oxygen electrode (air electrode) in the electrolyte membrane, so that the ionic conductivity decreases when the electrolyte membrane is dried. And energy conversion efficiency falls. Moreover, once the electrolyte membrane is dried, even if it tries to absorb water, it will not readily absorb water in a short time, and battery characteristics cannot be maintained. Therefore, in order to maintain good ion conduction, it is required to supply moisture to the solid electrolyte membrane, and it is also required to keep the electrolyte membrane hydrated while the fuel cell is stopped.

  The above is the case of DMFC using methanol as the fuel. However, even in the fuel cell using fuel gas (usually hydrogen gas) as the fuel, the proton is transferred from the fuel electrode to the oxygen electrode (air electrode) according to the electrochemical reaction in the cell. In order to assume a hydration state when moving in the electrolyte membrane toward the surface, similarly, it is required that the electrolyte membrane is hydrated while the fuel cell is stopped.

  In this regard, in the case of a battery such as a DMFC that directly supplies liquid fuel, even when the fuel supply system is stopped, the fuel liquid for the volume of the fuel supply chamber generally located at the fuel electrode remains, The residual fuel solution temporarily keeps the electrolyte membrane wet.

Japanese Patent Laid-Open No. 2002-15760 discloses that in a PEM type fuel cell having a fuel electrode and an air electrode, water is supplied to the air electrode, for example, in the form of a mist, and the water is preferentially deprived of latent heat. The publication describes that the evaporation of moisture from the electrolyte membrane is suppressed, thereby keeping the electrolyte membrane in a wet state.
JP 2002-15760 A

  However, in the case of a battery such as a DMFC that directly supplies liquid fuel, even when the fuel supply system is stopped as described above, the fuel liquid for the volume of the fuel supply chamber generally located on the fuel electrode remains. However, although the electrolyte membrane is kept moist by the remaining fuel liquid, the chemical reaction proceeds due to the remaining fuel liquid, and the remaining fuel in the fuel supply chamber is wasted. In addition, maintaining the wetness of the electrolyte membrane by the residual fuel liquid is only temporary while the residual fuel liquid is present. If the battery is stopped for a long period of time, the electrolyte membrane will eventually dry. To do.

  Even in fuel cells that use fuel gas as fuel, even if the fuel supply system is stopped, the fuel gas for the volume of the fuel supply chamber generally located at the fuel electrode remains, and the remaining fuel gas is consumed wastefully. Will be.

  Even if fuel liquid is used as fuel or fuel gas is used, even if water is supplied to the oxygen electrode (air electrode) in accordance with the water supply described in Japanese Patent Application Laid-Open No. 2002-15760, the battery However, in the case where the water is stopped for a long period of time, such water supply is not always continued. In any case, the water contained in the electrolyte membrane is volatilized and the electrolyte membrane is dried.

  Therefore, the present invention supplies fuel to the fuel electrode of the battery body sandwiching the electrolyte membrane between the fuel electrode and the oxygen electrode from the fuel supply chamber adjacent to the fuel electrode, and supplies air to the oxygen electrode. A fuel cell system that includes a fuel cell that generates power and can suppress wasteful consumption of fuel when the system is stopped (when power generation is stopped) and keep the electrolyte membrane moist even during long-term system shutdown. It is an object to provide a fuel cell system capable of improving the battery life.

The present invention
A fuel cell in which fuel is supplied to a fuel electrode of a battery body sandwiching an electrolyte membrane between a fuel electrode and an oxygen electrode from a fuel supply chamber adjacent to the fuel electrode, and air is supplied to the oxygen electrode to generate power A fuel cell system including
Fuel supply means for supplying fuel to the fuel supply chamber;
Fuel recovery means for recovering the remaining fuel in the fuel supply chamber when the fuel supply operation of the fuel supply means is stopped;
A fuel cell system is provided that includes a wetting liquid supply means that starts supplying the wetting liquid for the electrolyte membrane to the fuel supply chamber as the fuel is recovered by the fuel recovery means.

  According to the fuel cell system of the present invention, when the fuel supply operation by the fuel supply unit is stopped (in other words, when the fuel cell system according to the present invention is stopped), the fuel recovery unit supplies the fuel with the stop. Collect the remaining fuel from the chamber. Therefore, wasteful consumption of fuel when the system is stopped is suppressed accordingly.

  Further, as the fuel is recovered by the fuel recovery means, the wetting liquid supply means starts to supply the wetting liquid for the electrolyte membrane to the fuel supply chamber, so that the electrolyte membrane of the battery body is wetted by the supply of the wetting liquid. The state is maintained for a long time, and the battery life can be improved accordingly.

  Examples of the wetting liquid supply means include those having a wetting liquid storage section connected to the fuel supply chamber.

  The wetting liquid supply means may be any means as long as it can supply the wetting liquid for the electrolyte membrane to the fuel supply chamber in accordance with the recovery of the fuel liquid by the fuel recovery means. A liquid storage section is connected in communication with the fuel supply chamber, and the wetting liquid in the wetting liquid storage section is generated by capillary force according to a negative pressure generated in the fuel supply chamber by the fuel recovery by the fuel recovery means. The thing flowing into the fuel supply chamber can be exemplified.

The fuel cell may be either one using liquid fuel or one using gas fuel.
In the case of using liquid fuel, the fuel liquid supply means may supply a high-concentration fuel liquid as it is to the fuel supply chamber. For example, a high-concentration fuel liquid storage section and a dilution liquid storage section are provided. A high-concentration fuel liquid is taken out from the high-concentration fuel liquid storage section, and the dilution liquid is taken out from the dilution liquid storage section, and the high-concentration fuel liquid and the diluted liquid are mixed to obtain the diluted fuel liquid into the fuel supply chamber. Mention what is supplied.

  When adopting the fuel supply means for supplying the diluted fuel liquid in this way, the dilution liquid storage section may also serve as the wetting liquid storage section in the wetting liquid supply section in order to simplify the system. . In this case, the diluent can be used as a wetting liquid.

  Further, when the fuel cell uses liquid fuel, the liquid generated at the oxygen electrode, that is, the water generated on the oxygen electrode side by the electrochemical reaction of the fuel cell, or the liquid moving from the fuel electrode side to the oxygen electrode side. An oxygen electrode side liquid recovery means for recovery may be provided. In that case, the oxygen electrode side liquid recovery means may include a recovery liquid storage section. Further, when the diluted fuel liquid as described above is employed as the fuel liquid, the diluted liquid storage section in the fuel supply means also serves as the recovered liquid storage section, and the wetting liquid storage section in the wetting liquid supply means It may be combined.

When the fuel cell uses gas fuel, the fuel supply means may supply fuel gas to the fuel supply chamber.
Also in this case, oxygen electrode side liquid recovery means for recovering the liquid generated at the oxygen electrode may be provided. Such oxygen electrode side liquid recovery means may include a recovery liquid storage section. The recovery liquid storage section may also serve as a wetting liquid storage section in the wetting liquid supply means.

  In any case, the fuel recovered from the fuel supply chamber by the fuel recovery means can be reused, but for the reuse, the fuel recovery means uses the fuel recovered from the fuel supply chamber as the fuel supply. In the fuel supply operation of the means, a means for circulating to the fuel supply chamber (during the fuel supply operation) may be included.

  A representative example of the fuel cell is a direct methanol fuel cell (DMFC) that uses methanol, high-concentration methanol, or diluted methanol as a fuel liquid.

  As described above, according to the present invention, fuel is supplied to the fuel electrode of the battery body between which the electrolyte membrane is sandwiched between the fuel electrode and the oxygen electrode from the fuel supply chamber adjacent to the fuel electrode, and the oxygen electrode A fuel cell system that includes a fuel cell that generates air by supplying air to the fuel cell, and can reduce wasteful consumption of fuel when the system is shut down. It is possible to provide a fuel cell system capable of improving the efficiency.

Embodiments of the present invention will be described below with reference to the drawings.
(1) Fuel cell system A shown in FIGS. 1, 2 and 3
The fuel cell system A has a fuel cell 1.
The main body of the battery 1 is a direct methanol fuel cell (DMFC), and an MEA (Membrane) in which a fuel electrode (anode) 12 and an oxygen electrode, in other words, an air electrode (cathode) 13 are joined to both surfaces of an electrolyte membrane 11. Electrode Assembly) structure. A plate-shaped fuel supply chamber 14 is laminated and bonded to the fuel electrode 12, and a plate-shaped air supply chamber 15 is bonded to the oxygen electrode 13.

  The electrolyte membrane 11 is an electrolyte polymer membrane (for example, Nafion (perfluorosulfonic acid membrane) manufactured by DuPont). The fuel electrode 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 oxygen electrode 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 fuel supply chamber 14 has a fuel inlet 141. In addition, a fuel supply passage 142 in the form of a groove that communicates with the fuel inlet 141 and is open toward the fuel electrode 12 is provided. As shown in FIG. 2A, the fuel supply path 142 is formed in a zigzag serpentine shape and communicates with the fuel recovery port 143. The fuel supply chamber 14 also has a gas discharge hole 144 that communicates with the fuel supply path 142. In addition, a wetting liquid inlet 145 communicating with the fuel supply path 142 is also provided in the vicinity of the fuel inlet 141.

  The air supply chamber 15 has an air inlet 151 for introducing external air. Furthermore, it has a groove-shaped air supply path 152 that communicates with the air inlet 151 and is open toward the oxygen electrode 13. As shown in FIG. 2B, the air supply path 152 is formed in a zigzag serpentine shape. The air supply chamber 15 also has a liquid recovery port 153 for recovering the liquid accumulated therein.

The fuel cell system A further includes
A container C1 containing a high-concentration fuel liquid (here, a high-concentration methanol aqueous solution);
A high concentration fuel liquid supply path L1 including a pump P1 for supplying a high concentration fuel liquid from the container C1,
A container C2 for storing a diluent (in this case, water or a diluent mainly composed of water),
A diluent supply path L2 including a pump P2 for supplying the diluent from the container C2,
A mixing flow path L3 that mixes the high-concentration fuel liquid supplied from the supply path L1 and the dilution liquid supplied from the supply path L2 and leads the mixture to the fuel inlet 141 of the fuel supply chamber 14 as a diluted fuel liquid;
A liquid recovery path L4 including a pump P3 for recovering the liquid accumulated in the air supply chamber 15 from the liquid recovery port 153 of the air supply chamber to the container C2,
A fuel recovery path L5 having a pump P4 for recovering the fuel liquid from the fuel recovery port 143 of the fuel supply chamber 14 to the container C2, and the liquid in the container C2 to the wetting liquid inlet 145 of the fuel supply chamber 14 A leading wetting liquid supply path L6.

A gas-liquid separator 4 may be provided in the liquid recovery path L4 as necessary.
As shown in FIG. 3, each of the pumps P1 to P4 is on / off controlled under the instruction of the pump control unit Cont. Furthermore, the pump control unit Cont receives a battery on / off signal (a power generation signal / a power generation stop signal) from a device (for example, various portable devices) where the fuel cell system A is used or mounted. When the battery on signal is input, the pumps P1 and P2 are operated to supply the diluted fuel liquid to the fuel supply chamber 14, and the pump P3 is operated to accumulate in the air supply chamber 15. The liquid is collected in the diluent storage container C2. On the other hand, the pump P4 is stopped.

  When a battery off signal is input to the pump control unit Cont, the pumps P1 to P3 are stopped, and the remaining fuel in the fuel supply chamber 14 is recovered to the container C2 by the operation of the pump P4, and after the fuel recovery (preliminary) The pump P4 is stopped after elapse of the time required for fuel recovery determined by experiments or the like.

As described above, the high-concentration fuel liquid storage container C1, the dilution liquid storage container C2, the high-concentration fuel liquid supply path L1 including the pump P1, the pump P2 through the dilution liquid supply path L2, and the mixing flow path L3 to the fuel supply chamber 14. An example of fuel supply means for supplying fuel is configured.
The liquid recovery path L4 including the diluent storage container C2 and the pump P3 constitutes one example of the oxygen electrode side liquid recovery means.

The fuel recovery path L5 having the diluent container C2 and the pump P4 constitutes an example of the fuel recovery means.
The wetting liquid supply path L6 that guides the liquid in the diluent container C2 and the liquid in the container C2 to the wetting liquid inlet 145 of the fuel supply chamber 14 constitutes an example of the wetting liquid supply means.

  As can be seen from this, in this system A, the diluent storage container C2 also serves as a wetting liquid storage section in the wetting liquid supply means and a recovery liquid storage section in the oxygen electrode side liquid recovery means. It also serves as a recovered fuel storage part in the recovery means.

  According to the fuel cell system A, the high-concentration fuel liquid from the container C1 and the diluted liquid from the container C2 are mixed and diluted in the mixing flow path L3 by the operation of the pumps P1 and P2 instructed by the pump control unit Cont. Liquid is produced, flows through the fuel inlet 141 of the fuel supply chamber 14 and flows into the fuel supply path 142 in the chamber, is supplied to the fuel electrode 12, and is used for power generation.

On the other hand, on the oxygen electrode side, external air flowing in from the air inlet 151 of the air supply chamber 15 flows into the air supply path 152 in the chamber 15 and is supplied to the oxygen electrode 13 for power generation.
Thus, the load LD connected to the fuel electrode 12 and the oxygen electrode 13 can be energized.

The gas generated on the fuel electrode 12 side is discharged to the outside from a gas discharge hole 144 (see FIG. 2A) formed in the fuel supply chamber 14.
The water that is generated at the oxygen electrode 13 by the electrochemical reaction in the fuel cell main body and the liquid that may arrive from the fuel electrode 12 side to the oxygen electrode 13 side through the electrolyte membrane 11 is the air supply path 152 of the air supply chamber 15. However, these liquids are collected in the diluent container C2 through the liquid collection path L4 by the operation of the pump P3.

  Although external air can be sucked into the air supply chamber 15 by the suction operation of the pump P3, for example, an air supply pump may be provided in an air passage leading to the air inlet 151 as necessary. Further, a gas-liquid separator 4 may be provided in the liquid recovery path L4 as necessary.

  According to the fuel cell system A, when a battery off signal is input to the pump control unit Cont, as described above, the control unit Cont stops the pumps P1 and P2 and stops the fuel supply to the fuel supply chamber 14. In addition, the pump P3 is stopped. On the other hand, instead of stopping the pump, the pump P4 in the fuel recovery path L5 is started, whereby the remaining fuel liquid in the fuel supply chamber 14 is recovered into the container C2 and can be reused together with the diluent.

  As described above, when the power generation of the fuel cell system A is stopped, the remaining fuel in the fuel supply chamber 14 can be recovered and reused. Compared with the case where it is continued in vain, wasteful consumption of fuel is suppressed, and fuel can be saved.

  Further, with the recovery of the remaining fuel from the fuel supply chamber 14, the pressure in the chamber becomes negative, so that the diluting liquid from the diluting liquid storage container C2 becomes the wetting liquid by the action of capillary force. The liquid is supplied to the wetting liquid inlet 145 of the fuel supply chamber 14 through the supply path L 6 and further supplied into the fuel supply path 142. Thereby, the electrolyte membrane 11 of the battery body 1 is maintained in a wet state from the fuel electrode side. When power generation is stopped for a long period of time, the dilution liquid (wetting liquid) in the fuel supply chamber 14 decreases, but the decrease is compensated for by replenishment of the dilution liquid by the capillary force from the container C2.

  Thus, even when the system is stopped for a long period of time, the battery life can be improved by keeping the electrolyte membrane 11 in a wet state.

(2) Fuel cell system B shown in FIGS. 4 and 5
4 and 5 show another example B of the fuel cell system according to the present invention.
In the fuel cell system B, similarly to the system A, the fuel supply chamber 11 and the air supply chamber 15 are provided on the DMFC main body of the MEA structure including the electrolyte membrane 11 and the fuel electrode 12 and the oxygen electrode 13 bonded to each other. It includes a fuel cell 1, a high-concentration fuel liquid container C1, and a diluent container C2.

In the system A, the pumps P1 to P4 are employed, but here, instead, the plate-like pump unit 16 provided in the fuel supply chamber 14 and the plate-type pump unit provided in the air supply chamber 15 are provided. 17 is adopted.
Components, parts, etc. that are substantially the same as parts, parts, etc. in system A are given the same reference numerals as in system A.

  As shown in FIG. 5A, the pump unit 16 includes a high concentration fuel liquid supply path 161 including a micropump MP1, a diluent supply path 162 including a micropump MP2, and a high concentration supplied from the supply path 161. It has a mixing flow path 163 that mixes the fuel liquid and the dilution liquid supplied from the supply path 162 to obtain a diluted fuel liquid, and supplies this to the fuel inlet 141 of the fuel supply chamber 14. The supply paths 161 and 162 and the mixing flow path 163 are formed in a groove shape opened toward the fuel supply chamber 14.

  A container C1 containing a high-concentration fuel liquid is connected to the inlet 161a of the supply path 161, and a diluent storage container C2 is connected to the inlet 162a of the supply path 162.

  The pump unit 16 also has a fuel recovery path 164 including the micro pump MP4 (see FIG. 5A), and the inlet thereof communicates with the fuel recovery port 143 of the fuel supply chamber 14. The outlet 143a is connected to a diluent container C2 that also serves as a recovered fuel container. The fuel recovery path 164 is also formed in a groove shape opened toward the fuel supply chamber 14.

  As shown in FIG. 5B, the pump unit 17 on the air supply chamber side has a liquid recovery path 171 including a micropump MP3. On the other hand, the liquid recovery path 171 is a liquid in the air supply chamber 15. It communicates with the recovery port 153, and on the other hand, communicates with the container C <b> 2 via a through hole h, that is, a hole h that penetrates the air supply chamber 15, the battery body, the fuel supply chamber 14, and the pump unit 16.

A hole 165 in the pump unit 16 shown in FIG. 5A is a hole that forms a part of the through hole h.
Also, the hole 170 in the pump unit 17 shown in FIG. 5B is a through hole for introducing external air that communicates with the air inlet 151 of the air supply chamber 15.

  Note that PZT1, PZT2, and PZT4 in FIG. 5A are piezoelectric elements that are actuators of the micropumps MP1, MP2, and MP4, and PZT3 in FIG. 5B is a piezoelectric element of the micropump MP3. The micro pump will be described in detail later.

  Each of the pumps MP1 to MP4 is operated by a pump drive unit (not shown), and the pump drive unit is controlled to be turned on / off under the instruction of a pump control unit (not shown). Furthermore, the pump control unit receives a battery on / off signal from a device (for example, various portable devices) in which the fuel cell system B is used or mounted. When the signal is input, the pumps MP1 and MP2 are operated to supply the diluted fuel liquid to the fuel supply chamber 14, and the pump MP3 is operated to recover the liquid accumulated in the air supply chamber 15 to the diluent storage container C2. Let On the other hand, the pump MP4 is stopped.

  When the battery off signal is input, the pumps MP1 to MP3 are stopped, while the fuel in the fuel supply chamber 14 is recovered to the container C2 by the operation of the pump MP4, and after the fuel recovery (preliminarily obtained through experiments or the like). After the time required for fuel recovery has elapsed), the pump MP4 is stopped.

  According to the fuel cell system B, the high concentration fuel liquid from the container C1 and the diluted liquid from the container C2 are mixed in the mixing channel 163 by the operation of the pumps MP1 and MP2, and the diluted fuel liquid is produced. The fuel liquid flows through the fuel inlet 141 of the fuel supply chamber 14 to the fuel supply path 142 in the fuel supply chamber 14, is supplied to the fuel electrode 12, and is used for power generation.

On the other hand, in the air supply chamber 15, the external air flows from the hole 170 of the pump unit 17 and the air inlet 151 of the air supply chamber 15 into the air supply path 152 in the air supply unit, and the external air is supplied to the oxygen electrode 13. And used for power generation.
Thus, the load LD connected to the fuel electrode 12 and the oxygen electrode 13 can be energized.

The gas generated on the fuel electrode 12 side is discharged to the outside through the same gas discharge hole formed in the fuel supply chamber 14 as in the system A.
The water generated at the oxygen electrode 13 by the electrochemical reaction in the fuel cell body and the liquid that may arrive from the fuel electrode 12 side to the oxygen electrode 13 side through the electrolyte membrane 11 are received by the air supply chamber 15 and are pumped. It is recovered into the container C2 by the operation of MP3.
Although external air can be introduced into the air supply chamber 15 by the operation of the micropump MP3, an air supply pump may be provided in a portion that communicates with the air inlet 151 of the air supply chamber 15.

  Also in the fuel cell system B, when a battery off signal (power generation stop instruction signal) is input to a pump control unit (not shown), power supply to the piezoelectric elements PZT1 and PZT2 is stopped under the instruction of the pump control unit. Then, the pumps MP1 and MP2 are stopped, and the fuel supply to the fuel supply chamber 14 is stopped. Also, the power supply to the piezoelectric element PZT3 is cut off and the M pump P3 is also stopped. On the other hand, instead of stopping the pump, the piezoelectric element PZT4 is driven to start the pump MP4, whereby the remaining fuel liquid in the fuel supply chamber 14 is collected into the container C2 and can be reused together with the diluent.

  As described above, also in the fuel cell system B, when power generation is stopped, the remaining fuel in the fuel supply chamber 14 can be recovered and reused. Compared with the case where the fuel consumption is continued further in vain, the wasteful consumption of fuel is suppressed and the fuel can be saved.

  In addition, as the remaining fuel is recovered from the fuel supply chamber 14, the pressure in the chamber becomes negative, so that the diluent as a wetting liquid from the diluent storage container C2 becomes a fuel supply chamber by the action of capillary force. 14 is supplied to the hole 145 ′ (see FIG. 5A) of the pump unit 16 leading to the wetting liquid inlet 145 through the wetting liquid supply path L ′, and is further supplied into the fuel supply path 142. The Thereby, the electrolyte membrane 11 of the battery body 1 is maintained in a wet state from the fuel electrode side. When power generation is stopped for a long period of time, the dilution liquid (wetting liquid) in the fuel supply chamber 14 decreases, but the decrease is compensated for by replenishment of the dilution liquid by the capillary force from the container C2.

  Thus, even when the system is stopped for a long period of time, the battery life can be improved by keeping the electrolyte membrane 11 in a wet state.

  Further, since the system B employs the pump unit 16 including the micro pumps MP1, MP2, and MP4 and the pump unit 17 including the micro pump MP3, the entire system is reduced in size and size.

  A groove-like fuel supply passage 142 of the fuel supply chamber 14 is formed on one surface of one plate, and liquid passages 161, 162, 163, 164 in the pump unit 16 are formed on the opposite side of the same plate. By closing the flow path with a thin plate or film, the fuel supply chamber 14 and the pump unit 16 may be integrated, so that the system can be made more compact. The air supply chamber 15 and the pump unit 17 can also be integrated in the same manner, so that the system can be made more compact.

The micro pumps MP1, MP2, MP3, and MP4 all have the basic structure shown in FIG.
That is, the first throttle channel f1 for sucking liquid, the second throttle channel f2 for discharging liquid, the pump chamber PC between the first and second throttle channels f1, f2, and the pump chamber PC This is a pump including a piezoelectric element PZT installed on a flexible wall (diaphragm) DF.

  By applying a pulse voltage as a drive signal from a pump drive unit (not shown) to the piezoelectric element PZT, the pump chamber wall (diaphragm) DF is vibrated, thereby changing the volume of the pump chamber PC and from the first throttle channel f1. The liquid can be sucked into the pump chamber PC, and the pump chamber liquid can be discharged from the second throttle channel f2.

  More specifically, the first and second throttle channels f1 and f2 have the same or substantially the same cross-sectional area, but the channel f2 is formed longer than the channel f1. As a pulse voltage for driving the piezoelectric element PZT, as shown in FIG. 6C, a pulse voltage showing a steep rise and a gradual fall is used.

  As shown in FIG. 6A, when the diaphragm DF is suddenly deformed by the piezoelectric element and the pump chamber PC is abruptly contracted at the steep rise of the applied voltage, the liquid is layered by the channel resistance in the long channel f2. On the other hand, the liquid flows turbulently in the short flow path f1, 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.

  As shown in FIG. 6B, 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 short passage f1 causes the inside of the pump chamber PC. While the liquid flows into the liquid, the liquid discharge from the long channel f2 having a larger channel resistance than the channel f1 is suppressed at this time. Thereby, the liquid can be sucked from the flow path f1 into the pump chamber PC.

  Therefore, liquid flow is possible in the desired direction by disposing the flow path f1 on the upstream side and the flow path f2 on the downstream side in the desired liquid supply direction. Each of the pumps MP1, MP2, MP3, and MP4 has such a basic structure, and performs liquid feeding according to such an operating principle.

  The pumping capacity of each of the pumps MP1, MP2, MP3, and MP4 is one of the pump chamber volume, the performance of the piezoelectric element, the cross-sectional area and / or the length of the first and second throttle channels in each pump. Alternatively, it can be made desired by appropriately selecting and determining two or more.

  Note that, as shown in FIG. 6F, the micropump whose basic structure is shown in FIG. 6 applies a pulse voltage indicating a gradual rise and a steep fall to the piezoelectric element PZT, so that FIG. The liquid in the pump chamber can be discharged from the flow path f1 as shown in FIG. 6 and the liquid can be sucked from the flow path f2 as shown in FIG. 6E. Here, the drive waveform shown in FIG. Yes.

  In the fuel cell systems A and B, when recovering the remaining fuel liquid from the fuel supply chamber 14, a drain valve is provided at the fuel recovery port 143, and this is opened to discharge the remaining fuel liquid to a fuel recovery container or the like. It may be. Regardless of whether the drain valve is opened or discharged, the recovered fuel liquid is stored in an appropriate container, and is discharged from the container C1 at an appropriate timing, regardless of whether it is recovered by the pump P4 or the micropump MP4 as described above. It may be reused by mixing it with a highly concentrated fuel solution.

(3) Fuel cell system C shown in FIG.
The fuel cell system C uses hydrogen gas as fuel.
In the system C, a fuel supply chamber 14 ′ is provided on the fuel electrode 12 ′ of the fuel cell main body in which the fuel electrode 12 ′ and the oxygen electrode 13 ′ are bonded to the electrolyte membrane 11 ′. The fuel cell 1 ′ is provided with the same air supply chamber 15 as in the case.

System C also has
Hydrogen gas cylinder C3,
A fuel gas supply path L1 ′ including a pump P1 ′ for supplying hydrogen gas from the hydrogen gas cylinder C3 to the fuel inlet of the fuel supply chamber 14 ′;
A liquid recovery path L4 including a pump P3 for recovering the liquid accumulated in the air supply chamber 15 from the air supply chamber to the recovery liquid storage container C4;
A fuel recovery path L5 ′ having a pump P4 ′ for recovering the fuel gas from the fuel recovery port of the fuel supply chamber 14 ′ to the recovery gas container C5, and the liquid in the container C4 as the wetting liquid in the fuel supply chamber 14 ′ A wetting liquid supply path L6 leading to the introduction port is included.
A gas-liquid separator 4 may be provided in the liquid recovery path L4.

  Each of the pumps P <b> 1 ′, P <b> 3, and P <b> 4 ′ is on / off controlled under the instruction of a pump control unit (not shown). Furthermore, the pump control unit receives a battery on / off signal from a device (for example, various portable devices) in which the fuel cell system C is used or mounted. When the signal is input, the pump P1 ′ is operated to supply hydrogen gas to the fuel supply chamber 14 ′, and the pump P3 is operated to recover the liquid accumulated in the air supply chamber 15 to the recovery liquid storage container C4. . On the other hand, the pump P4 'is stopped.

  When the battery off signal is input, the pumps P1 ′ and P3 are stopped, and the fuel gas in the fuel supply chamber 14 ′ is recovered to the container C5 by the operation of the pump P4 ′. The pump P4 'is stopped after the elapse of the time required for fuel recovery determined in (1).

According to the fuel cell system C, hydrogen gas is supplied from the container C3 to the fuel supply chamber 14 ′ and further to the fuel electrode 12 ′ by the operation of the pump P1 ′ according to an instruction of a pump control unit (not shown), and is used for power generation.
On the other hand, on the oxygen electrode side, external air flowing in from the air inlet 151 of the air supply chamber 15 flows into the air supply path in the chamber 15 and is supplied to the oxygen electrode 13 ′ for power generation.
Thus, the load LD connected to the fuel electrode 12 ′ and the oxygen electrode 13 ′ can be energized.

  Water or the like generated at the oxygen electrode 13 'by an electrochemical reaction in the fuel cell main body is recovered into the container C4 by operating the pump P3.

  According to the fuel cell system C, when a battery off signal is input to the pump control unit, the control unit stops the pump P1 ′ to stop the fuel supply to the fuel supply chamber 14 ′, and also stops the pump P3. Let On the other hand, instead of stopping the pump, the pump P4 'in the fuel recovery path L5' is started, thereby recovering the remaining fuel gas in the fuel supply chamber 14 'to the container C5. The gas recovered in the container C5 can be reused by mixing it with hydrogen gas from the cylinder C3 at an appropriate timing during power generation.

  Thus, when the power generation of the fuel cell system C is stopped, the remaining fuel in the fuel supply chamber 14 ′ can be recovered and reused. In other words, compared to the case where the fuel is not recovered, in other words, power generation for the remaining fuel is generated. Furthermore, compared with the case where it continues vainly, the wasteful consumption of fuel is suppressed and the fuel can be saved.

  Further, with the recovery of the remaining fuel from the fuel supply chamber 14 ', the pressure in the chamber becomes negative, so that the recovery liquid from the recovery liquid storage container C4 becomes a wetting liquid due to the action of capillary force. The fuel is supplied to the fuel supply chamber 14 ′ through the liquid supply path L6. Thereby, the electrolyte membrane 11 'of the battery body is maintained in a wet state from the fuel electrode side. When the power generation is stopped for a long period of time, the wetting liquid in the fuel supply chamber 14 ′ decreases, but the decrease is compensated by the replenishment of the liquid by the capillary force from the container C 4.

  Thus, even when the system is shut down for a long period of time, the battery life can be improved by keeping the electrolyte membrane 11 'in a wet state.

  The present invention is a fuel cell system including a fuel cell that supplies fuel to the fuel electrode of a battery body sandwiching an electrolyte membrane between a fuel electrode and an oxygen electrode and generates air by supplying air to the oxygen electrode, It can be used to improve the battery life by suppressing wasteful fuel consumption when power generation is stopped and maintaining the electrolyte membrane in a wet state.

It is a figure which shows one example of the fuel cell system which concerns on this invention. 2A is a view of the fuel supply chamber in the fuel cell system of FIG. 1 as viewed from the left side in FIG. 1, and FIG. 2B is a view of the air supply chamber in the system as viewed from the right side in FIG. FIG. It is a block diagram which shows the outline of a pump control circuit. It is a figure which shows the other example of the fuel cell system which concerns on this invention. 5A is a view of the pump unit on the fuel supply chamber side in the fuel cell system of FIG. 4 as viewed from the left side in FIG. 4, and FIG. 5B is an air supply in the fuel cell system of FIG. It is the figure which looked at the chamber side pump unit from the right side in FIG. FIG. 6A is a diagram showing a liquid discharge operation, FIG. 6B is a diagram showing a liquid suction operation, and FIG. 6C is a diagram of such a liquid. It is a figure which shows the voltage waveform applied to the piezoelectric element for discharge operation | movement and attraction | suction operation | movement. 6D is a diagram showing a liquid ejection operation in the opposite direction to FIG. 6A, FIG. 6E is a diagram showing a liquid suction operation in the opposite direction to FIG. 6B, and FIG. F) is a diagram showing a waveform of a voltage applied to the piezoelectric element for the opposite operation. It is a figure which shows the further another example of the fuel cell system which concerns on this invention.

Explanation of symbols

A Fuel cell system 1 Fuel cell 11 Electrolyte membrane 12 Fuel electrode (anode)
13 Oxygen electrode, in other words, air electrode (cathode)
14 Fuel supply chamber 141 Fuel introduction port 142 Fuel supply passage 143 Fuel recovery port 144 Gas discharge hole 145 Wetting liquid introduction port 15 Air supply chamber 151 Air introduction port 152 Air supply passage 153 Liquid collection port C1 High concentration fuel liquid container C2 Diluent container L1 High-concentration fuel liquid supply path L2 Diluted liquid supply path L3 Mixing flow path L4 Liquid recovery path L5 Fuel recovery path L6 Wetting liquid supply paths P1 to P4 Pump 4 Gas-liquid separator LD Load

B Fuel cell system 16, 17 Pump unit MP1 to MP4 Micro pump PZT1 to PZT4 Piezoelectric element 161 High concentration fuel liquid supply path 161a Supply path 161 inlet 162 Diluted liquid supply path 162a Supply path 162 inlet 163 Mixing path 164 Fuel recovery Path 145 ′, 165 hole 171 liquid recovery path h through hole 170 hole

C Fuel cell system 1 'Fuel cell 11' Electrolyte membrane 12 'Fuel electrode (anode)
13 'oxygen electrode, in other words, air electrode (cathode)
14 'Fuel supply chamber C3 Hydrogen gas cylinder C4 Recovery liquid storage container C5 Recovery gas container P1', P4 'Pump L1' Fuel gas supply path L5 'Fuel recovery path

Claims (7)

A fuel cell in which fuel is supplied to a fuel electrode of a battery body sandwiching an electrolyte membrane between a fuel electrode and an oxygen electrode from a fuel supply chamber adjacent to the fuel electrode, and air is supplied to the oxygen electrode to generate power A fuel cell system including
Fuel supply means for supplying fuel to the fuel supply chamber;
Fuel recovery means for recovering the remaining fuel in the fuel supply chamber when the fuel supply operation of the fuel supply means is stopped;
A fuel cell system comprising: a wetting liquid supply means for supplying a wetting liquid for the electrolyte membrane to the fuel supply chamber as the fuel is recovered by the fuel recovery means.   2. The fuel cell system according to claim 1, wherein the wetting liquid supply means has a wetting liquid storage section connected to the fuel supply chamber.   The wetting liquid storage section is connected in communication with the fuel supply chamber, and the wetting liquid in the wetting liquid storage section corresponds to a negative pressure generated in the fuel supply chamber by the fuel recovery by the fuel recovery means. The fuel cell system according to claim 2, wherein the fuel cell system flows into the fuel supply chamber by capillary force.   The fuel supply means includes a high-concentration fuel liquid storage part and a dilution liquid storage part, takes out the high-concentration fuel liquid from the high-concentration fuel liquid storage part and takes out the dilution liquid from the dilution liquid storage part, The high-concentration fuel liquid and the diluting liquid that have been taken out are mixed and supplied to the fuel supply chamber as a diluting fuel liquid, and the diluting liquid storage section also serves as a wetting liquid storage section in the wetting liquid supply means The fuel cell system according to claim 2 or 3.   An oxygen electrode side liquid recovery means for recovering a liquid generated at the oxygen electrode, the oxygen electrode side liquid recovery means including a recovery liquid storage portion, and the diluent storage portion in the fuel supply means includes the recovery liquid storage portion; 5. The fuel cell system according to claim 4, wherein the fuel cell system also serves as a liquid storage section and also serves as a wetting liquid storage section in the wetting liquid supply means.   An oxygen electrode side liquid recovery means for recovering a liquid generated at the oxygen electrode is provided, the fuel supply means supplies fuel gas to the fuel supply chamber, and the oxygen electrode side liquid recovery means is a recovery liquid. 4. The fuel cell system according to claim 2, further comprising a storage portion, wherein the recovered liquid storage portion also serves as a wetting liquid storage portion in the wetting liquid supply means.   7. The fuel cell according to claim 1, wherein the fuel recovery means includes means for circulating the fuel recovered from the fuel supply chamber to the fuel supply chamber in the fuel supply operation of the fuel supply means. system.