JP5248286B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system including a fuel cell to which liquid fuel is supplied.

  Conventionally, as a fuel cell to which liquid fuel is supplied, for example, a direct methanol fuel cell (DMFC), a direct dimethyl ether fuel cell (DDFC), and the like are known.

  Since the liquid fuel type fuel cell does not require a reformer for generating hydrogen gas, simplification of the structure as a system is expected.

  As a system including a liquid fuel type fuel cell, for example, a tank for storing liquid fuel, a fuel cell to which liquid fuel is supplied, and a pump capable of sucking the liquid fuel stored in the tank and supplying it to the fuel cell And a first flow path for supplying liquid fuel from the tank to the fuel cell, and a second flow path for returning the used waste liquid discharged from the fuel cell into the tank. (For example, refer to Patent Document 1).

  In such a fuel cell system, liquid fuel is supplied to the anode of the fuel cell by driving the pump, and air is supplied to the cathode of the fuel cell. And when a fuel cell is an anion exchange type fuel cell which has an electrolyte layer which can move an anion component, and a liquid fuel is methanol, in a fuel cell, an electrochemical reaction shown by the following formulas (1) and (2) And an electromotive force is generated.

(1) CH ₃ OH + 6OH ⁻ → CO ₂ + 5H ₂ O + 6e ⁻ (reaction at the anode)
(2) O ₂ + H ₂ O + 4e ⁻ → 4OH ⁻ (reaction at the cathode)
JP-A-2005-203269

  However, in the fuel cell system described above, water is generated on the anode side, so that the concentration of methanol decreases with the progress of operation of the fuel cell. As a result, there is a problem that methanol cannot be used efficiently and the operating efficiency of the fuel cell is lowered.

  As a measure against this problem, it is conceivable to provide a drainage tank separately and discharge the water generated in the anode to the drainage tank. However, the installation of the drainage tank causes another problem that the entire system becomes larger and more complicated. Further, it is considered that the fuel tank is partitioned into a fuel storage unit for storing methanol and a drainage storage unit for storing generated water, and the generated water is discharged to the drainage storage unit. However, every time the drainage storage is full, the fuel tank must be replaced, which is very laborious.

  On the other hand, when the fuel cell is continuously operated at a high load, there is a problem that a so-called dry-up occurs in which the moisture content of the cell on the cathode side decreases (drys).

  An object of the present invention is to provide a fuel cell system that can easily suppress a decrease in concentration of liquid fuel on the anode side and dry-up on the cathode side.

  In order to achieve the above object, a fuel cell system of the present invention includes an electrolyte layer in which an anion component can move, an anode disposed on one side of the electrolyte layer, and supplied with liquid fuel, and the other of the electrolyte layer. An anion exchange type fuel cell disposed on the side and having a cathode to which oxygen is supplied; water amount detection means for detecting the amount of water contained in the liquid fuel in the anode; and the anode and the cathode A differential pressure generating means for generating a differential pressure in between, and a control means for operating the differential pressure generating means based on the detection of the water amount detecting means.

  According to this configuration, when the water amount detecting means detects that the amount of water contained in the liquid fuel in the anode is greater than or equal to the predetermined amount, the difference between the anode and the cathode is caused by the operation of the differential pressure generating means. Pressure is generated. With this differential pressure, a pressure flow from the anode side to the cathode side can be generated. Therefore, the water generated at the anode can be moved to the cathode, the water on the anode side can be reduced, and the water on the cathode side can be increased. As described above, the water on the anode side can be reduced and the water on the cathode side can be increased by controlling the pressure difference between the anode and the cathode without separately providing a facility such as a drainage tank. As a result, it is possible to easily suppress the decrease in the concentration of the liquid fuel on the anode side and the dry-up on the cathode side.

  In the fuel cell system of the present invention, the liquid fuel discharged from the anode is recirculated to the anode, and the gas that is interposed in the recirculation path and separates the gas contained in the liquid fuel. A gas separation valve, wherein the differential pressure generating means is provided in the gas-liquid separation section, and is a gas discharge valve for discharging the gas in the gas-liquid separation section, and the control means is the gas discharge valve It is preferable that the gas pressure in the gas-liquid separator is increased by closing the pressure to generate a differential pressure between the anode and the cathode.

  In this configuration, since the return path is provided, the liquid fuel circulates in the system closed by the anode and the return path. And the gas pressure in a gas-liquid separation part is raised by closing the gas exhaust valve for exhausting the gas in the gas-liquid separation part interposed in the reflux path. Since the pressure in the closed system can be increased by increasing the gas pressure in the gas-liquid separation unit, a differential pressure can be generated between the anode and the cathode. That is, a differential pressure can be generated between the anode and the cathode by a simple control of opening / closing the gas discharge valve.

  According to the fuel cell system of the present invention, the water on the anode side can be reduced and the water on the cathode side can be reduced by controlling the differential pressure between the anode and the cathode without separately providing facilities such as a drainage tank. Can be increased. As a result, it is possible to easily suppress the decrease in the concentration of the liquid fuel on the anode side and the dry-up on the cathode side.

1. Overall Configuration of Fuel Cell System FIG. 1 is a schematic configuration diagram of an electric vehicle equipped with a fuel cell system according to an embodiment of the present invention.

  The electric vehicle 1 is a vehicle that uses a fuel cell as a power source, and is equipped with a fuel cell system 2.

The fuel cell system 2 includes a fuel cell 3, a fuel supply / exhaust unit 4, an air supply / exhaust unit 5, a control unit 6 as control means, and a power unit 7.
(1) Fuel Cell The fuel cell 3 is an anion exchange type fuel cell to which liquid fuel is directly supplied, and is disposed at the lower center of the electric vehicle 1.

  Examples of the liquid fuel supplied to the fuel cell 3 include methanol, dimethyl ether, hydrazine (including hydrated hydrazine, anhydrous hydrazine, and the like).

  Further, the output voltage Vfc of the fuel cell 3 is 0.2 to 1.5 V, for example, and the output current Ifc is 10 to 400 A, for example. These outputs are outputs per unit cell described later.

  The fuel cell 3 includes a fuel cell (unit cell) having an electrolyte layer 8, an anode 9 disposed on one side of the electrolyte layer 8, and a cathode 10 disposed on the other side of the electrolyte layer 8, and an insulating material. It is formed in a stack structure in which a plurality of layers are stacked via separators (not shown). That is, a plurality of unit cells in which the anode 9 and the cathode 10 are arranged to face each other with the electrolyte layer 8 interposed therebetween are stacked. In FIG. 1, only one of the plurality of unit cells is represented as the fuel cell 3, and the other unit cells are omitted.

  The electrolyte layer 8 is a layer in which an anion component can move, and is formed using, for example, an anion exchange membrane.

The anion exchange membrane is not particularly limited as long as it is a medium in which an anion component (for example, hydroxide ion (OH ⁻ )) can move, and for example, an anion exchange group such as a quaternary ammonium group or a pyridinium group can be used. And a solid polymer membrane (anion exchange resin).

  The anode 9 includes an anode electrode 11 and a fuel supply member 12 for supplying liquid fuel to the anode electrode 11.

  The anode electrode 11 is formed on one surface of the electrolyte layer 8. Examples of the electrode material of the anode electrode 11 include a porous support (catalyst-supported porous support) on which a catalyst is supported.

  Examples of the porous carrier include water-repellent carriers such as carbon.

  Examples of the catalyst include 8th to 10th (VIII) group elements of the periodic table such as platinum group elements (Ru, Rh, Pd, Os, Ir, Pt), iron group elements (Fe, Co, Ni), and the like. Examples include Group 11 (IB) elements of the periodic table such as Cu, Ag, and Au.

  The anode electrode 11 is prepared, for example, by preparing an electrode ink of the above electrode material, applying the electrode ink to one surface of the electrolyte layer 8 by a known method (for example, spray method, die coater method, etc.), and drying at a predetermined temperature. By doing so, it is joined to one surface of the electrolyte layer 8 as a thin electrode film.

  The fuel supply member 12 is made of a gas impermeable conductive member. The fuel supply member 12 is formed with a distorted groove recessed from the surface thereof. The surface of the fuel supply member 12 in which the groove is formed is opposed to the anode electrode 11. As a result, a fuel supply path 13 is formed between the one surface of the anode electrode 11 and the other surface (the surface on which the groove is formed) of the fuel supply member 12 so that liquid fuel contacts the entire anode electrode 11. The

  In the fuel supply path 13, a fuel supply port 15 for allowing the liquid fuel to flow into the anode 9 is formed on one end side (lower side), and a fuel discharge port 14 for discharging the liquid fuel from the anode 9 is the other end. It is formed on the side (upper side).

  The cathode 10 includes a cathode electrode 16 and an air supply member 17 for supplying air to the cathode electrode 16.

  The cathode electrode 16 is formed on the other surface of the electrolyte layer 8.

  Examples of the electrode material of the cathode electrode 16 include a catalyst-supporting porous carrier exemplified as the electrode material of the anode electrode 11.

  The cathode electrode 16 is bonded to the other surface of the electrolyte layer 8 as a thin film electrode film by, for example, the same method as the anode electrode 11. Thus, the electrolyte layer 8, the anode electrode 11, and the cathode electrode 16 have the thin film anode electrode 11 bonded to one surface of the electrolyte layer 8 and the thin film cathode electrode 16 bonded to the other surface of the electrolyte layer 8. A membrane / electrode assembly is formed.

  The air supply member 17 is made of a gas impermeable conductive member. The air supply member 17 is formed with a twisted groove recessed from the surface thereof. The air supply member 17 has a grooved surface in contact with the cathode electrode 16. As a result, an air supply path 18 is formed between the other surface of the cathode electrode 16 and one surface of the air supply member 17 (the surface on which the grooves are formed) so that air contacts the entire cathode electrode 16. .

In the air supply path 18, an air supply port 19 for allowing air to flow into the cathode 10 is formed on one end side, and an air discharge port 20 for discharging air from the cathode 10 is formed on the other end side. .
(2) Fuel Supply / Discharge Unit The fuel supply / discharge unit 4 supplies a fuel tank 21 for storing liquid fuel and liquid fuel supplied from the fuel tank 21 to the anode 9 and liquid discharged from the anode 9. And a reflux pipe 22 as a reflux path for returning the fuel to the anode 9.

  The fuel tank 21 is disposed behind the fuel cell 3 and behind the electric vehicle 1. For example, methanol, dimethyl ether, hydrazine, or the like is stored in the fuel tank 21 as a liquid fuel.

  One end side (lower side) of the reflux pipe 22 is connected to the fuel supply port 15 via a sealing material (such as a gasket), and the other end side (upper side) thereof is connected to the fuel discharge port 14 via a sealing material (such as a gasket). It is connected to the. By being connected via the sealing material, the reflux pipe 22 is tightly fitted to the fuel discharge port 14 and the fuel supply port 15. Thereby, both ends (the fuel discharge port 14 and the fuel supply port 15) of the fuel supply path 13 communicate with each other in a sealed state via the reflux pipe 22 provided outside the fuel cell 3. Therefore, between the fuel cell 3 and the fuel supply / discharge section 4, liquid fuel discharged from the fuel discharge port 14 (upstream side) flows to the fuel supply port 15 (downstream side) via the reflux pipe 22, By returning to the fuel discharge port 14 again through the fuel supply path 13, a closed line (closed flow path) that circulates through the anode 9 is formed.

  In the middle of the reflux pipe 22, a gas-liquid separator 23 as a gas-liquid separator is interposed. The gas-liquid separator 23 is composed of, for example, a hollow container, and a pair of bottom portion circulation ports 24 through which the inside and outside of the gas-liquid separator 23 are circulated is formed at the bottom portion.

  In addition, one upper circulation port 25 through which the inside and outside of the gas-liquid separator 23 circulates is formed at the upper part of the gas-liquid separator 23. The upper flow port 25 and the pair of bottom flow ports 24 can flow with each other through a hollow portion.

  The gas-liquid separator 23 is interposed in the reflux pipe 22 by connecting a pair of bottom flow ports 24 to the reflux pipe 22 in the upper rear side of the fuel cell 3.

  The pair of bottom flow ports 24 and the reflux pipe 22 are connected via a sealing material (such as a gasket). Thereby, the reflux pipe 22 is tightly fitted to each of the pair of bottom circulation ports 24, and the upstream reflux pipe 22 tightly fitted to one (upstream side) bottom circulation port 24 and the other (downstream side). ) And the downstream reflux pipe 22 tightly fitted to the bottom circulation port 24 through the hollow portion of the gas-liquid separator 23. That is, the hollow part of the gas-liquid separator 23 forms a part of the closed line.

  A gas discharge pipe 26 for discharging the gas (gas) separated by the gas-liquid separator 23 is connected to the upper circulation port 25. The gas discharge pipe 26 is connected to the upper circulation port 25 via a sealing material (gasket). Thereby, the gas discharge pipe 26 is tightly fitted to the upper circulation port 25. Further, a gas discharge valve 27 as a differential pressure generating means is provided in the middle of the gas discharge pipe 26.

  The gas discharge valve 27 is a valve for opening and closing the gas discharge pipe 26. For example, a known open / close valve such as an electromagnetic valve is used. The gas discharge valve 27 is electrically connected to the control unit 6 (see the broken line in FIG. 1). As a result, a control signal from the control unit 6 can be input to the gas discharge valve 27.

  A fuel supply pump 29 is interposed in the reflux pipe 22 downstream of the gas-liquid separator 23 and in the middle of the upstream side of the anode 9 (that is, the downstream reflux pipe 22).

  As the fuel supply pump 29, for example, a known liquid feed pump such as a rotary pump such as a rotary pump or a gear pump, a reciprocating pump such as a piston pump, or a diaphragm pump is used. The fuel supply pump 29 is electrically connected to the control unit 6 (see the broken line in FIG. 1). Thereby, a control signal from the control unit 6 can be input to the fuel supply pump 29.

  Between the gas-liquid separator 23 and the fuel supply pump 29 in the reflux pipe 22 (that is, upstream of the fuel supply pump 29 in the downstream reflux pipe 22), the liquid fuel stored in the fuel tank 21 is returned to the reflux pipe. A fuel supply pipe 30 for supplying the fuel to 22 is connected. A fuel supply valve 31 is provided in the middle of the fuel supply pipe 30. The fuel supply pipe 30 and the fuel tank 21 are connected via a sealing material (such as a gasket).

The fuel supply valve 31 is a valve for opening and closing the fuel supply pipe 30. For example, a known on-off valve such as an electromagnetic valve is used. The fuel supply valve 31 is electrically connected to the control unit 6 (see the broken line in FIG. 1). As a result, a control signal from the control unit 6 can be input to the fuel supply valve 31.
(3) Air Supply / Discharge Unit The air supply / discharge unit 5 includes an air supply pipe 32 for supplying air to the cathode 10 and an air discharge pipe 33 for discharging the air discharged from the cathode 10 to the outside. ing.

  One end side (upstream side) of the air supply pipe 32 is opened to the atmosphere, and the other end side (downstream side) is connected to the air supply port 19. An air supply pump 34 is interposed in the middle of the air supply pipe 32.

  As the air supply pump 34, for example, a known air supply pump such as an air compressor is used. The air supply pump 34 is electrically connected to the control unit 6 (see the broken line in FIG. 1). Thereby, a control signal from the control unit 6 can be input to the air supply pump 34.

  An air supply valve 35 is provided downstream of the air supply pump 34 in the air supply pipe 32.

  The air supply valve 35 is a valve for opening and closing the air supply pipe 32. For example, a known on-off valve such as an electromagnetic valve is used. The air supply valve 35 is electrically connected to the control unit 6 (see the broken line in FIG. 1). Thereby, a control signal from the control unit 6 can be input to the air supply valve 35.

One end side (upstream side) of the air discharge pipe 33 is connected to the air discharge port 20, and the other end side (downstream side) is a drain.
(4) Control Unit The control unit 6 is a unit (for example, ECU: Electronic Control Unit) that performs electrical control in the electric vehicle 1 and is configured by a microcomputer including a CPU, a ROM, a RAM, and the like. The ROM of the control unit 6 serving as a water amount detecting means includes an input signal (measured value by the ammeter 41) from an ammeter 41 described later and the amount of water generated in the liquid fuel by the power generation of the fuel cell 3. A control map showing the relationship is stored.

In the control map, for example, it is recorded that 0.01 to 3 cc of water per minute is generated at the anode 9 by power generation of 10 to 400 A by the fuel cell 3. The control unit 6 includes a timer 36.
(5) Power unit The power unit 7 supplies electric power to the motor 37 for converting the electrical energy output from the fuel cell 3 into mechanical energy as the driving force of the electric vehicle 1 and the electrical equipment of the electric vehicle 1. The battery 38 is provided.

  The motor 37 is disposed in front of the fuel cell 3 and on the front side of the electric vehicle 1. Examples of the motor 37 include known three-phase motors such as a three-phase induction motor and a three-phase synchronous motor.

  Examples of the battery 38 include known secondary batteries such as lead storage batteries. In addition, examples of the power supply target from the battery 38 include general electric equipment mounted on a vehicle such as a headlight, a car audio, and an air conditioner.

  The power unit 7 includes a DC / DC converter 39. The DC / DC converter 39 has a switching function for distributing input power to a plurality of devices connected thereto, and a step-down function for stepping down the input voltage.

  A positive electrode wiring 40 connected to the cathode 10 is connected to the positive input terminal of the DC / DC converter 39. On the other hand, a negative electrode wiring 42 connected to the anode 9 is connected to the negative input terminal of the DC / DC converter 39.

  An ammeter 41 is connected in series to a pair of wires composed of a positive electrode wire 40 and a negative electrode wire 42. The ammeter 41 is electrically connected to the control unit 6 (see the broken line in FIG. 1). As a result, the value of the current flowing from the fuel cell 3 to the DC / DC converter 39 is measured, and the electric signal can be input to the control unit 6.

  The DC / DC converter 39 is electrically connected to the control unit 6 (see the broken line in FIG. 1). Thereby, the control signal from the control unit 6 can be input to the DC / DC converter 39.

  In addition, although illustration is abbreviate | omitted, the above-mentioned electrical equipment may be directly connected to the DC / DC converter 39 not via the battery 38.

  The motor 37 and the battery 38 are electrically connected to the DC / DC converter 39 in parallel. Thus, the electromotive force generated in the fuel cell 3 can be supplied to the motor 37 or the battery 38 or to the motor 37 and the battery 38 simultaneously by the switching function of the DC / DC converter 39.

An inverter 43 is connected in series between the motor 37 and the DC / DC converter 39. The inverter 43 is not particularly limited as long as it is a device capable of converting DC power to AC power, and includes, for example, a power conversion device in which a known inverter circuit is incorporated. As a result, power from the DC / DC converter 39 to the motor 37 is converted from DC power to three-phase AC power in the inverter 43 and supplied to the motor 37 as three-phase AC power.
2. Power Generation by the Fuel Cell System In the fuel cell system 2 described above, the fuel supply valve 31 is opened and the fuel supply pump 29 is driven, whereby liquid fuel is supplied to the anode 9 via the reflux pipe 22. On the other hand, when the air supply valve 35 is opened and the air supply pump 34 is driven, air is supplied to the cathode 10 via the air supply pipe 32. The fuel supply valve 31 is closed after a predetermined amount of liquid fuel is supplied.

  In the anode 9, the liquid fuel passes through the fuel supply path 13 while being in contact with the anode electrode 11. On the other hand, in the cathode 10, air passes through the air supply path 18 while being in contact with the cathode electrode 16.

  Then, an electrochemical reaction occurs in each electrode (the anode electrode 11 and the cathode electrode 16), and an electromotive force is generated. For example, when the liquid fuel is methanol, the following formulas (1) to (3) are obtained.

(1) CH ₃ OH + 6OH ⁻ → CO ₂ + 5H ₂ O + 6e ⁻ (reaction at anode electrode 11)
(2) O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (reaction at cathode electrode 16)
(3) CH ₃ OH + 3 / 2O ₂ → CO ₂ + 2H ₂ O (reaction in the entire fuel cell 3)
That is, at the anode electrode 11 supplied with methanol, methanol (CH ₃ OH) reacts with hydroxide ions (OH ⁻ ) generated by the reaction at the cathode electrode 16 to react with carbon dioxide (CO ₂ ) and water. (H ₂ O) is generated and electrons (e ⁻ ) are generated (see the above formula (1)).

Electrons (e ⁻ ) generated at the anode electrode 11 reach the cathode electrode 16 via an external circuit (not shown). That is, electrons (e ⁻ ) passing through the external circuit become current.

On the other hand, in the cathode electrode 16, electrons (e ⁻ ), water (H ₂ O) generated by external supply or reaction in the fuel cell 3, and oxygen (O ₂ ) in the air flowing through the air supply path 18. React with each other to produce hydroxide ions (OH ⁻ ) (see the above formula (2)).

And the produced | generated hydroxide ion (OH < ^- >) passes the electrolyte layer 8, reaches the anode electrode 11, and a reaction similar to the above (refer said formula (1)) arises.

  When the electrochemical reaction at the anode electrode 11 and the cathode electrode 16 is continuously generated, the reaction expressed by the above formula (3) occurs in the fuel cell 3 as a whole, and an electromotive force is generated in the fuel cell 3. To do.

  In the power unit 7, the generated electromotive force is transmitted to the DC / DC converter 39 via the positive electrode wiring 40 and the negative electrode wiring 42, and is supplied to the motor 37 and / or the battery 38 by the switching operation of the DC / DC converter 39. Power is transmitted. In the motor 37, the electric energy converted into the three-phase AC power by the inverter 43 is converted into mechanical energy that drives the wheels of the electric vehicle 1. On the other hand, the battery 38 is charged with the received power.

  In the fuel supply / discharge section 4, the used and unreacted liquid fuel discharged from the anode 9 flows into the upstream reflux pipe 22 by the driving force of the fuel supply pump 29, and the upstream reflux pipe 22. And flows into the gas-liquid separator 23 from the bottom side circulation port 24 on the upstream side. In the gas-liquid separator 23, a liquid fuel liquid reservoir 44 whose liquid level is held at a position below the upper flow port 25 is generated in the hollow portion of the gas-liquid separator 23, and a gas ( Gas) is separated into the space above the liquid reservoir 44. On the other hand, a part of the liquid reservoir 44 flows out from the downstream bottom circulation port 24 to the downstream reflux pipe 22. The liquid fuel flowing out to the downstream reflux pipe 22 passes through the downstream reflux pipe 22 and flows into the fuel supply path 13 again. In this way, the liquid fuel circulates through the closed line (the reflux pipe 22, the gas-liquid separator 23, and the fuel supply path 13). The gas separated by the gas-liquid separator 23 is discharged to the outside through the gas discharge pipe 26 when the gas discharge valve 27 is opened.

  For example, when the liquid fuel is hydrazine, the following formulas (4) to (6) are obtained.

(4) N ₂ H ₄ + 4OH ⁻ → N ₂ + 4H ₂ O + 4e ⁻ (reaction at anode electrode 11)
(5) O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (reaction at cathode electrode 16)
(6) N ₂ H ₄ + O ₂ → N ₂ + 2H ₂ O (reaction in the entire fuel cell 3)
In the above power generation, water is generated in the anode electrode 11, so that the concentration of the liquid fuel circulating through the anode 9 may decrease as the operation of the fuel cell 3 proceeds.

The fuel cell system 2 has a differential pressure generation mode in which a differential pressure is generated between the anode 9 and the cathode 10 as a control mode for suppressing this decrease in concentration.
3. FIG. 2 is a flowchart showing the flow of control processing executed in the control unit 6 of FIG.

  When a predetermined instruction signal (for example, an ignition on signal) is input to the control unit 6, a start command signal is input to the fuel cell 3. Thereby, the operation of the fuel cell 3 is started.

  After starting the operation, for example, first, it is determined whether or not the operating state of the fuel cell 3 is a steady operation. The steady operation is an operation state in which the current value measured by the ammeter 41 is stable for a predetermined time, for example, an operation state in which the current value is stable at 10 to 100 A for 10 to 30 seconds. The current value stabilization time is measured by the timer 36 of the control unit 6.

  When the operation state of the fuel cell 3 reaches the steady operation, that is, when the control unit 6 determines that the operation is steady based on the measurement value of the ammeter 41 and the measurement time of the timer 36, this determination time is used as a reference. Thus, the timer 36 is activated.

  During steady operation, the measurement time of the timer 36 is constantly processed by the control unit 6, and the control unit 6 calculates (detects) the total amount of water generated at the anode 9 based on the processing signal and the stored control map.

  When the increase amount of water at the anode 9 (the amount of water generated at the anode electrode 11) exceeds Qcc (for example, 100 to 1000 cc) in total (YES in step S1), the differential pressure generation mode is started. (Step S2).

  In the differential pressure generation mode, for example, first, it is determined whether or not the output current Ifc of the fuel cell 3 is larger than a target current value Io (for example, 100 to 400 A) in the differential pressure generation mode, and the output current Ifc is the target current. When the value is equal to or less than the value Io (No in step S3), a current command value Iref signal for making the output current Ifc larger than the target current value Io is input to the fuel cell 3 (step S4).

  When the output current Ifc exceeds the target current value Io (YES in step S3), the closing time of the gas discharge valve 27 is calculated (step S5).

  In the differential pressure generation mode, the gas discharge valve 27 is closed and opened in this order, and each execution time has a valve closing time Tcl of, for example, 0.1 to 3600 seconds. Top is, for example, 0.1 to 10 seconds.

  After calculating the closing time, the gas discharge valve 27 is closed (step S6). As a result, the gas discharge pipe 26 communicating from the gas-liquid separator 23 to the outside is shut off, so that the closed line (the reflux pipe 22, the gas-liquid separator 23 and the fuel supply path 13) is in a sealed state, and the gas-liquid separator The gas pressure in 23 is increased.

  After the gas discharge valve 27 is closed, the valve closing time is measured by the timer 36. When Tcl has elapsed (YES in step S7), the gas discharge valve 27 is opened (step S8). As a result, the gas pressure in the gas-liquid separator 23 temporarily increased is released, and the pressure on the anode 9 side and the pressure on the cathode 10 side are approximately the same.

  After the gas exhaust valve 27 is opened, the valve opening time is measured by the timer 36, and when Top is elapsed (YES in step S9), the gas exhaust valve 27 is closed again (step S10).

Thereafter, the same control process as described above is continued during the steady operation of the fuel cell 3.
4). As described above, according to the fuel cell system 2, the amount of water generated in the anode electrode 11 exceeds a predetermined amount Qcc (for example, 100 to 1000 cc) based on the measurement time of the timer 36 and the record information of the control map. When this is detected by the control unit 6, the differential pressure generation mode is executed.

  In the differential pressure generation mode, the gas discharge valve 27 is closed for Tcl (for example, 0.1 to 3600 seconds) while maintaining the output current Ifc of the fuel cell 3 in a range exceeding the target current value Io. Thereby, the gas pressure in the gas-liquid separator 23 is increased. By increasing the gas pressure in the gas-liquid separator 23 constituting a part of the closed line (the reflux pipe 22, the gas-liquid separator 23 and the fuel supply path 13), the pressure in the closed line system in the sealed state is reduced. Can be increased. Thereby, since the pressure on the anode 9 side becomes larger than the pressure on the cathode 10 side, a differential pressure can be generated between the anode 9 and the cathode 10.

  With this differential pressure, a pressure flow from the anode 9 side toward the cathode 10 side can be generated. Therefore, the water generated at the anode electrode 11 can be moved to the cathode electrode 16 through the electrolyte layer 8. Therefore, the water contained in the liquid fuel circulating through the anode 9 can be reduced, and the water contained in the cathode electrode 16 can be increased.

  As described above, the water contained in the liquid fuel circulating through the anode 9 can be reduced by controlling the differential pressure between the anode 9 and the cathode 10 without separately providing a facility such as a drainage tank, and the cathode electrode. The moisture contained in 16 can be increased. As a result, the decrease in the concentration of the liquid fuel circulating through the anode 9 and the dry-up of the cathode electrode 16 can be easily suppressed.

  Furthermore, in the fuel cell system 2, since the differential pressure control between the anode 9 and the cathode 10 is executed by the open / close control of the gas discharge valve 27, the control can be prevented from becoming complicated.

  As mentioned above, although embodiment of this invention was described, embodiment of this invention is not limited to this, A design can be suitably changed in the range which does not change the summary of this invention.

  For example, the amount of water generated in the anode 9 can be detected by providing a water meter in the reflux pipe 22.

  Further, the differential pressure between the anode 9 and the cathode 10 can also be generated by lowering the pressure on the cathode 10 side by controlling the air supply valve 35 to open and close.

  Furthermore, as a use of the fuel cell system of the present invention, there are a railway, a ship, an aircraft and the like in addition to the electric vehicle shown in the above embodiment.

1 is a schematic configuration diagram of an electric vehicle equipped with a fuel cell system according to an embodiment of the present invention. It is a flowchart showing the flow of the control processing performed in the control unit of FIG.

Explanation of symbols

2 Fuel Cell System 3 Fuel Cell 6 Control Unit 8 Electrolyte Layer 9 Anode 10 Cathode 22 Reflux Pipe 23 Gas-Liquid Separator 27 Gas Discharge Valve

Claims (1)

Anion exchange having an electrolyte layer to which an anion component can move, an anode disposed on one side of the electrolyte layer and supplied with liquid fuel, and a cathode disposed on the other side of the electrolyte layer and supplied with oxygen Type fuel cell,
Water amount detection means for detecting the amount of water contained in the liquid fuel in the anode;
Differential pressure generating means for generating a differential pressure between the anode and the cathode;
Control means for operating the differential pressure generating means based on the detection of the water amount detecting means ,
A reflux path for refluxing the liquid fuel discharged from the anode to the anode;
A gas-liquid separation part interposed in the reflux path for separating the gas contained in the liquid fuel,
The differential pressure generating means is a gas discharge valve provided in the gas-liquid separator, for discharging the gas in the gas-liquid separator;
The fuel cell system according to claim 1, wherein the control means raises a gas pressure in the gas-liquid separation unit by closing the gas discharge valve to generate a differential pressure between the anode and the cathode .

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