JP2002324564A - Fuel cell device and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a high performance for a long period in such operation condition that start and stop are repeated, with no catalyst eluting when a fuel cell device is stopped, no carbon carrying the catalyst eroding, no catalyst sintering, or no effective area of the catalyst decreasing. SOLUTION: There are provided a fuel cell 11, a fuel supply pipe line 21 connected to a fuel chamber 48, an air guide device provided to the fuel supply pipe line 21, a fuel discharge pipe line connected to the fuel chamber 48, and a forced fuel discharging device provided to the fuel discharge pipe line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell device and a control method for the fuel cell device.

[0002]

2. Description of the Related Art Conventionally, fuel cells have a high power generation efficiency and do not emit harmful substances. Therefore, fuel cells have been put to practical use as power sources for industrial and domestic use, or as power sources for artificial satellites and spacecraft. In recent years, development as a power source for vehicles such as passenger cars, buses, and trucks has been advanced.

FIG. 2 shows a conventional fuel cell device.

In FIG. 1, reference numeral 101 denotes a fuel cell, which may be an alkaline aqueous solution type, a phosphoric acid type, a molten carbonate type, a solid oxide type, a direct type methanol, or the like. Is common.

In this case, the solid polymer electrolyte membrane is sandwiched between two gas diffusion electrodes, integrated and joined. When one of the gas diffusion electrodes is used as an anode electrode and hydrogen gas is supplied as a fuel gas to the surface thereof, hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions pass through the solid polymer electrolyte membrane. When the other of the gas diffusion electrodes is used as a cathode and air is supplied as an oxidant to the surface of the cathode, oxygen in the air is combined with the hydrogen ions and electrons to generate water. An electromotive force is generated by such an electrochemical reaction.

Reference numeral 102 denotes a condenser, which is a fuel cell 1
The water contained in the oxidant discharge port No. 01 is condensed and removed from the discharged air, and flows into a water tank (not shown) through the drain pipe 108.

Reference numeral 103 denotes a fuel storage means such as a hydrogen storage alloy or a hydrogen gas cylinder in which hydrogen gas as fuel is stored. The hydrogen gas passes through the fuel supply pipe 111 from the fuel storage means 103 and passes through the fuel supply pipe 111. The fuel is supplied to the fuel cell 101. Numeral 112 denotes a fuel filling line for filling the fuel storage means 103 with hydrogen gas from the outside, and is connected to the fuel supply line 111. here,
The fuel supply line 111 has a fuel pressure regulating valve 120 for adjusting the pressure of the supplied hydrogen gas, a pressure sensor 119 for measuring the pressure of the supplied hydrogen gas, and opens and closes the fuel supply line 111. A fuel supply solenoid valve 115 is provided.

Reference numeral 113 denotes a fuel discharge pipe for discharging hydrogen gas discharged from the fuel cell 101 to the atmosphere. A check valve 116 for preventing backflow of hydrogen gas and a fuel discharge solenoid valve 117 for opening and closing the fuel discharge line 113 are provided in the fuel discharge line 113.

On the other hand, reference numeral 105 denotes an air supply fan provided as an oxidant supply source disposed in the oxidant supply pipe 107, and supplies air to the air manifold 104 of the fuel cell 101. 106 is the air manifold 10
4 is a water supply nozzle for spraying water into the air electrode 4 to maintain the air electrode, which is the cathode electrode of the fuel cell 101, in a wet state.

In the fuel cell device having the above-described structure, the pressure sensor 119 controls the pressure in the fuel supply pipe 111 so that the pressure of the hydrogen gas supplied to the fuel cell 101 is maintained at a predetermined constant pressure. While monitoring the hydrogen gas pressure, adjust the fuel pressure adjustment valve 120,
Hydrogen gas is supplied from the fuel storage means 103. After adjusting the fuel pressure adjusting valve 120 so that the pressure of the hydrogen gas in the fuel supply pipe 111 becomes a predetermined constant pressure, the fuel pressure adjusting valve 120 is adjusted during the operation of the fuel cell 101. And the state is maintained as it is.

The air supply fan 105 operates to supply a sufficient amount of air to the air electrode of the fuel cell 101 according to the required amount. In this case, the amount of air supplied is
The amount is sufficiently larger than the amount of air necessary for the output of the fuel cell 101 to be maximum.

As described above, in the fuel cell device, a necessary and sufficient amount of hydrogen gas is always supplied to the fuel cell 101.
The components of the fuel cell 101 are not burned out, the output of the fuel cell 101 is stabilized,
The fuel efficiency is good, and the cost of the fuel cell device can be reduced.

[0013]

However, in the above-mentioned conventional fuel cell device, when the fuel cell system is repeatedly started and stopped, a long period of time elapses.
No. 1 catalyst is eluted, carbon supporting the catalyst is corroded, or the catalyst sinters, the effective area of the catalyst is reduced, and the output voltage of the fuel cell 101 is reduced.

FIG. 3 is a flowchart showing the operation of stopping the conventional fuel cell device.

Conventionally, when stopping the fuel cell device, first, when the air supply fan 105 is stopped, the air supply fan 105 is operated (step S1). When the air supply fan 105 is operating, the operation is continued.

Next, the fuel supply solenoid valve 115 is closed to shut off the supply of hydrogen gas to the fuel cell 101 (step S2). Then, the fuel discharge solenoid valve 117 is opened, and hydrogen gas in the fuel cell 101 is discharged from the fuel discharge line 113 to the atmosphere (step S3).

In this state, the process waits until the hydrogen gas in the fuel cell 101 becomes lower than a predetermined pressure (for example, 1.1 [Pa]) (step S4). Subsequently, the fuel discharge solenoid valve 117 is closed (step S5), and the air supply fan 105 is stopped (step S6).

As a result, the hydrogen gas in the fuel cell 101 falls to the atmospheric pressure level, and the above-described electrochemical reaction of the fuel cell 101 stops.

In this case, it takes time for the hydrogen gas in the fuel cell 101 to drop to the atmospheric pressure level.
In addition, the hydrogen gas is not completely discharged from the fuel cell 101, but remains in the flow channel and the catalyst layer, albeit slightly.

When the hydrogen gas remains on the hydrogen electrode serving as the anode of the fuel cell 101 and the air containing oxygen remains on the oxygen electrode serving as the cathode, when the electrical connection to the external load is interrupted. Then, a potential difference occurs between the hydrogen electrode and the oxygen electrode. Then, the catalyst is eluted by the potential difference, carbon supporting the catalyst is corroded, and the catalyst sinters, so that the effective area of the catalyst is reduced.

Since the hydrogen electrode and the oxygen electrode are only separated by an extremely thin solid polymer electrolyte membrane, the hydrogen gas remaining at the hydrogen electrode passes through the electrolyte and moves to the oxygen electrode, and There is a danger of explosion if mixed with residual oxygen in the air.

Therefore, when stopping the fuel cell device, it is necessary to quickly and reliably discharge hydrogen gas from the fuel cell 101.

For this reason, after the fuel cell device is stopped, an inert gas is introduced into the reaction gas passages of the hydrogen electrode and the oxygen electrode in the fuel cell, and the reactive gas is purged, whereby the hydrogen electrode and the oxygen electrode are purged. A method has been proposed in which the poles are made to have an inert atmosphere (see JP-A-2-33866).

However, even if an inert gas is introduced as in the above-described method, the potential difference generated between the hydrogen electrode and the oxygen electrode does not decrease rapidly. This is considered to be because hydrogen and oxygen attached to the catalyst of the fuel cell are not immediately purged even when the inert gas is introduced. Further, in the case of a fuel cell device for a vehicle, it is necessary to store a tank or a cylinder for storing an inert gas in the vehicle. However, it is difficult to store the tank or the cylinder in the vehicle from the viewpoint of space and cost. is there.

Further, after stopping the fuel cell device, cooling water is introduced into the reaction gas passage of the hydrogen electrode in the fuel cell,
An apparatus has been proposed which reduces the potential difference between a hydrogen electrode and an oxygen electrode by introducing air into the reaction gas passage after purging hydrogen gas (Japanese Patent Laid-Open No. 7-2727).
No. 37).

However, in the case of a fuel cell device for a vehicle, the arrangement of pipes and control valves for introducing cooling water becomes complicated, resulting in an increase in cost. In addition, since the cooling water for vehicles usually contains impurities such as antifreeze which affect the components of the fuel cell, there is a risk that the components of the fuel cell may be deteriorated.

The present invention solves the above-mentioned conventional problems,
When stopping the fuel cell device, the hydrogen gas remaining on the hydrogen electrode side is quickly discharged, and air is introduced into the hydrogen electrode side, thereby rapidly reducing the potential difference generated between the hydrogen electrode and the oxygen electrode. The catalyst does not elute, the carbon carrying the catalyst does not corrode, or the catalyst does not sinter, so that the effective area of the catalyst does not decrease, and even in an operation state where starting and stopping are repeated, the It is an object of the present invention to provide a fuel cell device and a control method of the fuel cell device which can maintain high performance over a long period of time.

[0028]

For this purpose, in a fuel cell device according to the present invention, there is provided a fuel cell including a fuel chamber in contact with a fuel electrode, an oxygen chamber in contact with an oxygen electrode, and a fuel cell connected to the fuel chamber. A fuel supply line for supplying fuel to the fuel chamber;
An air introduction device disposed in the fuel supply line; a fuel discharge line connected to the fuel supply line through the fuel chamber to discharge fuel in the fuel chamber; and a fuel discharge line. And a forced fuel discharge device arranged.

In another fuel cell device according to the present invention, the position of the forcible fuel discharge device is higher than the lowest position of the fuel discharge pipe.

In still another fuel cell device according to the present invention, after the fuel in the fuel cell is discharged by operating the fuel forcible discharge device, the air introduction device is operated to allow the fuel cell to enter the fuel cell. It has control means for introducing air.

In still another fuel cell apparatus according to the present invention, when the control means receives an instruction to stop the output of the fuel cell, the control means activates the fuel forcible discharge device to operate the fuel cell. After discharging the fuel, the air introducing device is operated to introduce air into the fuel cell.

In the control method for a fuel cell device according to the present invention, a fuel cell including a fuel chamber in contact with a fuel electrode and an oxygen chamber in contact with an oxygen electrode is connected to the fuel chamber, and fuel is supplied to the fuel chamber. A fuel supply line to be supplied, an air introduction device disposed in the fuel supply line, and a fuel discharge line connected to the fuel supply line via the fuel chamber to discharge fuel from the fuel chamber And, after the fuel in the fuel chamber is discharged by operating the fuel forcible discharge device of the fuel cell device having the fuel forcible discharge device disposed in the fuel discharge line, the air introduction device is operated. Air is introduced into the fuel chamber.

In another control method of the fuel cell device according to the present invention, when an instruction to stop the output of the fuel cell is received, the fuel forcible discharge device is operated to discharge the fuel in the fuel chamber. Activating the air introduction device to introduce air into the fuel chamber.

[0034]

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

FIG. 1 is a conceptual diagram of a fuel cell device according to an embodiment of the present invention, and FIG. 4 is a cross-sectional view showing a configuration of a unit unit of the fuel cell according to the embodiment of the present invention.

In FIG. 1, reference numeral 11 denotes a fuel cell (FC), which is used as a power source for vehicles such as cars, buses and trucks. Here, the vehicle is provided with a large number of auxiliary devices that consume electricity, such as lighting devices, radios, and power windows, which are used even when the vehicle is stopped. Since the output range is very wide, it is desirable to use the fuel cell 11 as a power source together with a secondary battery (not shown) as power storage means.

The fuel cell 11 is of an alkaline aqueous solution type (AFC), a phosphoric acid type (PAFC), a molten carbonate type (MCFC), a solid oxide type (SOFC), a direct type methanol (DMFC), or the like. Although it may be present, a polymer electrolyte fuel cell (PEMFC) is preferable.

More preferably, PEMFC (prot) using hydrogen gas as a fuel and oxygen or air as an oxidant is used.
on exchange membrane fue
lcell) type fuel cell or PEM (proton)
This is called an exchange membrane type fuel cell. Here, the PEM fuel cell generally has a stack in which a plurality of cells (fuel cells) in which a catalyst, an electrode, and a separator are combined on both sides of a solid polymer electrolyte membrane that transmits ions such as protons are connected in series. (Japanese Patent Laid-Open No. 11-31)
No. 7235).

In the present embodiment, the cell 40 corresponds to FIG.
As shown in (2), the solid polymer electrolyte membrane 45 is sandwiched between two gas diffusion electrodes 43 and 44, sandwiched between separators 46 and 47 made of carbon black or the like, and joined. Also, one of the separators 46 has a plurality of fuel chambers 48.
Are formed so as to extend in the direction perpendicular to the plane of the paper in the figure, and the other 47 of the separator has a plurality of oxygen chambers 49.
Are formed to extend in the vertical direction in the figure.
One surface of the fuel chamber 48 and one surface of the oxygen chamber 49 are in contact with the gas diffusion electrodes 43 and 44. When one of the gas diffusion electrodes 43 is used as a fuel electrode (anode electrode) and hydrogen gas is supplied as a fuel gas into the fuel chamber 48, the hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions are converted into solids. The light passes through the polymer electrolyte membrane 45. When the other of the gas diffusion electrodes 44 is used as an oxygen electrode (cathode electrode) and air is supplied as an oxidizing gas into the oxygen chamber 49, oxygen in the air is combined with the hydrogen ions and electrons to form water. Generated. An electromotive force is generated by such an electrochemical reaction.

For example, in the present embodiment, a PEM fuel cell is used as an example, and a stack in which 400 cells are connected in series is used. In this case, the total electrode area is 300 [cm ² ], and the open terminal voltage is about 350
[V], the output is about 50 [kW]. The temperature during the steady operation is about 50 to 90 [° C.].

It should be noted that hydrogen gas, which is a fuel obtained by reforming methanol, gasoline or the like by a reformer (not shown), can be directly supplied to the fuel cell 11.
In order to stably supply a sufficient amount of hydrogen even during high-load operation of a vehicle, a hydrogen storage alloy,
It is desirable to supply the hydrogen gas stored in the fuel storage means 13 such as a hydrogen gas cylinder. As a result, the hydrogen gas is always sufficiently supplied at a substantially constant pressure, so that the fuel cell 11 can supply a necessary current without delaying the fluctuation of the load of the vehicle.

In this case, the output impedance of the fuel cell 11 is extremely low and can be approximated to zero.

FIG. 1 shows an apparatus for supplying a fuel cell 11 with hydrogen gas as fuel and air as an oxidant. Hydrogen gas is supplied from a fuel storage means 13 such as a hydrogen storage alloy or a hydrogen gas cylinder through a fuel supply line 21,
The fuel is supplied to a fuel chamber 48 (FIG. 4) of the fuel cell 11. Reference numeral 22 denotes a fuel filling line for filling the fuel storage means 13 with hydrogen gas from the outside.
Connected to. A fuel pressure adjusting valve 25, a fuel supply solenoid valve 26, a check valve 24, and a pressure sensor 27 are provided in the fuel supply pipe 21. The fuel storage means 13 has a sufficiently large capacity and always has a capability of supplying hydrogen gas at a sufficiently high pressure.

The hydrogen gas discharged from the fuel chamber 48 of the fuel cell 11 is discharged to the atmosphere through the fuel discharge pipe 31. The hydrogen gas may not be directly discharged to the atmosphere, but may be discharged after being combined with oxygen to form water. A filter 33, a fuel discharge solenoid valve 34 and a check valve 35 are provided in the fuel discharge line 31.
And a bypass line 32 that bypasses the fuel discharge solenoid valve 34 is connected. The bypass pipe 32 is provided with a pressure reducing pump 36 as a fuel forcible discharge device and a leakage prevention electromagnetic valve 37.

The position of the pressure reducing pump 36 is the lowest position of the fuel discharge pipe 31, that is, the fuel discharge pipe 3.
1 is located at a position higher than the position connected to the outlet of the fuel chamber 48. This prevents water generated at the fuel electrode (anode electrode) 43 from entering the decompression pump 36 and causing water clogging even when the vehicle is tilted while traveling.

Here, the fuel pressure regulating valve 25 is a butterfly valve, a regulator valve, a diaphragm valve, a mass flow controller, a sequence valve, or the like. Any type can be used as long as the pressure can be adjusted to a preset pressure. The pressure may be adjusted manually, but is desirably adjusted by an actuator such as an electric motor, a pulse motor, or an electromagnet.

The fuel supply solenoid valve 26, the fuel discharge solenoid valve 34 and the leakage prevention solenoid valve 37 are so-called on-off solenoid valves, and are operated by actuators such as electric motors, pulse motors, electromagnets and the like. .
The check valves 24 and 35 have a normal structure. Further, the decompression pump 36 may be of any type as long as it is a pump capable of forcibly discharging hydrogen gas and bringing the inside of the fuel chamber 48 into a negative pressure state.

The pressure sensor 27 is communicably connected to control means of the fuel cell device described later, and transmits a pressure detection signal of hydrogen gas flowing in the fuel supply pipe 21 to the control means. The pressure sensor 27 is
It may be provided in the fuel chamber 48, the fuel discharge line 31, or the like.
In this case, the fuel supply line 2 which is a path through which hydrogen gas flows
1. In the fuel chamber 48 and the fuel discharge line 31, if the range is from the fuel supply solenoid valve 26 to the fuel discharge solenoid valve 34 or the pressure reducing pump 36, the hydrogen gas pressure may be considered to be the same. it can.

The fuel supply pipe 21 is provided with an air introduction solenoid valve 28 as an air introduction device. The air introduction solenoid valve 28 basically includes the fuel supply solenoid valve 2.
6. It has the same configuration as the fuel discharge solenoid valve 34 and the leakage prevention solenoid valve 37. One end is connected to the fuel supply pipe 21 and the other end is opened to the atmosphere via the filter 29. The filters 29 and 33 have basically the same configuration, and remove dust (dust), impurities, harmful gases and the like contained in air.

On the other hand, air as an oxidizing agent is supplied from an oxidizing agent supply source 15 such as an air supply fan, an air cylinder, an air tank, etc., through an oxidizing agent supply line 17 and a manifold 14 to an oxygen chamber of the fuel cell 11. 49 (FIG. 4).
Note that oxygen can be used instead of air as the oxidizing agent. And the air discharged from the oxygen chamber 49 is
It is discharged to the atmosphere through the oxidant discharge line 18. Also, water is sprayed into the manifold 14,
A water supply nozzle 16 for keeping the oxygen electrode (cathode electrode) 44 of the fuel cell 11 wet is provided. Further, a condenser 12 for condensing and removing water contained in the discharged air is disposed on the oxidant discharge pipe 18 side of the fuel cell 11, and the water passes through a drain pipe 19. It is collected in a water tank (not shown).

The secondary battery as the power storage means is as follows:
It is a so-called battery (storage battery), which is generally a lead storage battery, a nickel cadmium battery, a nickel hydrogen battery, a lithium ion battery, a sodium sulfur battery, or the like. , A sodium-sulfur battery, a nickel-metal hydride battery, and the like.

For example, in the present embodiment, a high performance lead storage battery is used as an example. In this case, the open terminal voltage is about 210 [V], and the capacity is such that a current of about 10 [kW] can be supplied for about 5 to 20 minutes.

The storage means may not necessarily be a battery, but may be a capacitor (capacitor) such as an electric double layer capacitor, a flywheel, a superconducting coil,
Any form may be used as long as it has a function of electrically storing and releasing energy, such as an accumulator. Further, any of these may be used alone, or a plurality of them may be used in combination.

The fuel cell 11 is connected to a load (not shown) and supplies the generated current to the load. Here, the load is generally an inverter device that is a drive control device, and converts a direct current from the fuel cell 11 or the battery into an alternating current to supply the load to a drive motor that rotates wheels of the vehicle. I do. Here, the drive motor also functions as a generator, and generates a so-called regenerative current during deceleration operation of the vehicle. In this case, since the drive motor is rotated by the wheels to generate power, the wheels are braked, that is, function as a vehicle braking device (brake). Then, the regenerative current is supplied to the battery to charge the battery.

In the present embodiment, the fuel cell device has control means (not shown). The control means is C
A pressure sensor 2 provided with arithmetic means such as PU and MPU, storage means such as a semiconductor memory, an input / output interface, etc.
7. oxidant supply source 15, fuel pressure adjustment by detecting the flow rate, temperature, output voltage, etc. of hydrogen, oxygen, air, etc. supplied to fuel chamber 48 and oxygen chamber 49 of fuel cell 11 from other sensors. The operation of the valve 25, the fuel supply solenoid valve 26, the air introduction solenoid valve 28, the fuel discharge solenoid valve 34, the pressure reducing pump 36, and the leakage prevention solenoid valve 37 is controlled. Further, the control means comprehensively controls the operation of the device for supplying fuel and oxidant to the fuel cell 11 in cooperation with another sensor and another control device.

Next, the operation of the fuel cell device having the above configuration will be described.

FIG. 5 is a diagram showing the characteristics of the fuel cell when the output of the fuel cell according to the present embodiment is stopped in comparison with the conventional example. FIG. 6 is a graph showing the change over time of the output of the fuel cell according to the present embodiment. FIG. 7 is a diagram showing a comparison with the conventional example, FIG. 7 is a first flowchart showing the operation of the fuel cell device according to the present embodiment, and FIG. 8 is a second flowchart showing the operation of the fuel cell device according to the present embodiment. .

In the fuel cell device according to the present embodiment,
After adjusting the pressure of the hydrogen gas flowing out from the outlet of the fuel pressure control valve 25 to a predetermined constant pressure, the fuel pressure control valve 25 is not adjusted during the operation of the vehicle, and the state is maintained as it is. Is done.

The oxidant supply source 15 operates so as to always supply a constant amount of air to the oxygen chamber 49 of the fuel cell 11. In this case, the amount of supplied air is sufficiently larger than the amount of air necessary for the output of the fuel cell 11 to be maximized.

When the driver stops the vehicle and turns off the power source of the vehicle, an instruction to stop the output of the fuel cell 11 is issued from the control device of the vehicle, and the control means of the fuel cell device is controlled. Sent to. Then, the control means operates the air supply fan which is the oxidant supply source 15, that is, turns on the air supply fan (step S11). When the air supply fan is already operating, the operation is continued.

Thus, even if hydrogen gas is diffused from the fuel electrode (anode) 43 through the solid polymer electrolyte membrane 45, it is discharged together with the air without staying at the oxygen electrode (cathode) 44. Therefore, the hydrogen gas diffused from the fuel chamber 48 does not locally stay at the air electrode and does not explode due to combustion.

Subsequently, spraying of water from the water supply nozzle 16 is started (step S12). As a result, the fuel electrode 43 is also cooled, so that even if the hydrogen gas remaining in the fuel chamber 48 reacts with oxygen in the air and burns, it is possible to prevent the fuel electrode 43 from deteriorating due to heat generated by combustion. .

Next, the control means controls the fuel supply solenoid valve 2.
6, the supply of hydrogen gas to the fuel chamber 48 is shut off (step S13). Then, the fuel discharge solenoid valve 34 is opened, and the hydrogen gas in the fuel chamber 48 is discharged from the fuel discharge pipe 31 to the atmosphere (step S14). Note that the hydrogen gas discharged into the atmosphere may be combined with oxygen to form water and then discharged.

In this state, the process waits until the pressure of the hydrogen gas in the fuel chamber 48 becomes a predetermined pressure, for example, 1.1 [Pa] or less, or until a predetermined time, for example, 3 [seconds] elapses. (Step S15). However, the fuel chamber 48
The pressure of the hydrogen gas in the inside should not be negative. Here, the pressure of the hydrogen gas in the fuel chamber 48 is detected by the pressure sensor 27. In this case, the pressure of the hydrogen gas can be considered to be the same in the range from the fuel supply solenoid valve 26 to the fuel discharge solenoid valve 34 or the pressure reducing pump 36 in the flow path of the hydrogen gas. , The pressure detected by the pressure sensor 27 is equal to the pressure of the fuel chamber 48 of the fuel cell 11.

The predetermined time is a time required until the pressure of the hydrogen gas in the fuel chamber 48 reaches the predetermined pressure, and is obtained in advance by an experiment.

When the pressure of the hydrogen gas in the fuel chamber 48 becomes equal to or lower than the predetermined pressure or when the predetermined time elapses, the control means closes the fuel discharge electromagnetic valve 34 and closes the fuel discharge line 31. Is shut off (step S16), and the pressure reducing pump 36 is operated (step S17).
The leakage prevention electromagnetic valve 37 is opened (step S18).

Thus, the bypass pipe 32 is opened, and the hydrogen gas in the fuel chamber 48 is sucked by the pressure reducing pump 36 and is forcibly discharged into the atmosphere via the bypass pipe 32. In this case, since the inside of the fuel chamber 48 has a negative pressure, hydrogen gas is reliably and promptly removed from the fuel chamber 48 and discharged.

Subsequently, in this state, the pressure of the hydrogen gas in the fuel chamber 48 becomes a predetermined pressure, for example, 0.1 [MPa] or less, or a predetermined time, which is a time until the pressure becomes the predetermined pressure, for example, It waits until 40 [seconds] elapses or until the output of the fuel cell reaches a predetermined voltage, for example, 30 [V] (step S19). In this case, since the predetermined pressure is a considerable negative pressure, there is substantially no hydrogen gas remaining in the fuel passage in the fuel chamber 48.

The predetermined time is a time required until the pressure of the hydrogen gas in the fuel chamber 48 reaches the predetermined pressure.
The predetermined voltage is an output voltage of the fuel cell 11 when the pressure of the hydrogen gas is at the predetermined pressure. The predetermined time and the predetermined voltage are obtained in advance by experiments.

When the pressure of the hydrogen gas in the fuel chamber 48 becomes equal to or lower than the predetermined pressure or when the predetermined time elapses, the control means opens the air introduction solenoid valve 28,
Air is introduced into the fuel chamber 48 (step S20). In this case, since the fuel supply solenoid valve 26 is in the closed state,
The introduced air does not flow toward the fuel storage means 13. Thus, the fuel chamber 48 is filled with air. Since the air is filtered through the filter 29, it does not include dust, impurities, harmful gases, etc. existing in the atmosphere. Therefore, members such as the catalyst in the fuel chamber 48 are not contaminated or deteriorated by the dust, impurities, harmful gas and the like.

Further, by introducing air, residual hydrogen reacts with oxygen in the air on the catalyst and burns. Therefore, the potential difference disappears, and the output voltage of the fuel cell 11 decreases. At this time, heat is temporarily generated by combustion, but since the heat capacity of the fuel cell 11 is sufficiently large and water is sprayed from the water supply nozzle 16 into the oxygen chamber 49, a rapid rise in temperature is suppressed. can do.

Subsequently, in this state, the output of the fuel cell 11 becomes equal to or lower than a predetermined voltage, for example, 5 [V], or a predetermined time which is a time until the output becomes the predetermined voltage, for example, 10 [sec]. , Waits (step S
21). Here, the predetermined voltage is such that no hydrogen gas remains in the fuel chamber 48, the air is
This is an output voltage corresponding to a state in which substantially no potential difference occurs between the oxygen electrode 44 and the oxygen electrode 44.

Then, when the output of the fuel cell 11 falls below the predetermined voltage or when the predetermined time has elapsed,
The water spray from the water supply nozzle 16 is stopped (step S22), the control means stops the pressure reducing pump 36 (step S23), closes the air introduction solenoid valve 28 (step S24), and the leakage prevention solenoid valve 37 Is closed (step S25), and finally the oxidant supply source 15 is stopped (step S26).

Thus, the output of the fuel cell 11 is stopped.

In this case, when an instruction to stop the output of the fuel cell 11 is issued, the output of the fuel cell 11 rapidly decreases.

In FIG. 5, reference numeral 41 denotes a line indicating a change in the output voltage of one cell 40 out of a number of cells 40 constituting the fuel cell 11 in the fuel cell device of the present embodiment, and reference numeral 42 denotes a line. It is a line which shows a change of output voltage of one cell among many cells which constitute fuel cell 101 in a conventional fuel cell device explained in "prior art".

As shown in the figure, in the fuel cell device of the present embodiment, the output of the fuel cell 11 is instructed to stop, and the output voltage of the cell drops without elapse of 20 [seconds]. start. On the other hand, the output voltage of the cell of the fuel cell 101 in the conventional fuel cell device starts to decrease 40 minutes after the instruction is issued, that is, when 2400 [seconds] have elapsed. Further, even after the output voltage of the cell starts to decrease, the output voltage decreases rapidly in the fuel cell device of the present embodiment, but decreases slowly in the conventional fuel cell device.

For this reason, in the conventional fuel cell device, every time the output of the fuel cell 101 is stopped, the electrical connection to the external load is cut off, and then hydrogen gas remains in the fuel chamber and oxygen gas remains. The state where air containing oxygen remains in the chamber and a potential difference occurs between the fuel electrode and the oxygen electrode continues for a long time. And, depending on the potential difference, the catalyst elutes,
Since the carbon carrying the catalyst corrodes or sinters the catalyst, the effective area of the catalyst decreases. Therefore, when starting and stopping of the fuel cell device are repeated,
The performance of the fuel cell 101 deteriorates, and the output voltage decreases.

On the other hand, in the fuel cell device of the present embodiment, when the output of the fuel cell 11 is stopped, the electric connection with the external load is cut off, and then the hydrogen gas is supplied to the fuel chamber 48. The state in which air containing oxygen remains and oxygen-containing air remains in the oxygen chamber 49 and a potential difference occurs between the fuel electrode 43 and the oxygen electrode 44 is completed in an extremely short time. Therefore, the catalyst does not elute, the carbon supporting the catalyst does not corrode, or the catalyst does not sinter due to the potential difference, so that the effective area of the catalyst does not decrease. Therefore, even if the start and stop of the fuel cell device are repeated, the performance of the fuel cell 11 does not deteriorate and the output voltage does not decrease.

In FIG. 6, reference numeral 51 denotes a line indicating a change in the average output voltage of a large number of cells 40 constituting the fuel cell 11 in the fuel cell device of the present embodiment, and 52 denotes a line.
7 is a line showing a change in average output voltage of a large number of cells constituting a fuel cell 101 in the conventional fuel cell device described in “Prior Art”.

As shown in the figure, the average output voltage of the cells of the fuel cell 101 in the conventional fuel cell device decreases as the number of stops increases, whereas the average output voltage of the fuel cell of the present embodiment increases. It can be seen that in the device, the average output voltage of the fuel cell 11 is maintained substantially constant even when the number of stops increases.

When the fuel cell 11 is started, first, the fuel discharge solenoid valve 34 is opened and the fuel chamber 48 is opened.
The inside air is discharged through the fuel discharge line 31. Subsequently, the fuel supply solenoid valve 26 is turned on so that the hydrogen gas from the fuel storage means 13 is supplied to the fuel chamber 48 through the fuel supply pipe 21. At this time, since the fuel discharge solenoid valve 34 is open, the pressure in the fuel chamber 48 does not rise suddenly, and there is no possibility of damaging the electrolyte membrane and the like. Further, the air remaining in the fuel chamber 48 is purged by the supplied hydrogen gas (Japanese Patent Laid-Open No.
317235).

Thereafter, when the fuel cell 11 enters a steady operation, the fuel discharge solenoid valve 34 intermittently turns on and off. For example, a cycle of turning on for 2 seconds and then turning off for 58 seconds is repeated. On the other hand, the fuel supply solenoid valve 26 is kept on.

As described above, in the present embodiment, when an instruction to stop the fuel cell 11 is issued, the pressure reducing pump 36 is operated to suck the hydrogen gas in the fuel chamber 48 to cause the fuel discharge line 31 Forcibly discharged from Thereafter, the air introduction solenoid valve 28 is opened, and air is introduced from the fuel supply pipe 21 into the fuel chamber 48.

Therefore, when the output of the fuel cell 11 is stopped, after the electrical connection to the external load is cut off, hydrogen gas remains in the fuel chamber 48 and air containing oxygen remains in the oxygen chamber 49. Then, the state in which a potential difference occurs between the fuel electrode 43 and the oxygen electrode 44 is completed in a very short time. for that reason,
The potential difference does not elute the catalyst, corrode the carbon supporting the catalyst, or sinter the catalyst, so that the effective area of the catalyst does not decrease. Therefore,
Even if the start and stop of the fuel cell device are repeated, the performance of the fuel cell 11 does not deteriorate, the output voltage does not decrease, and high performance can be maintained for a long period of time.

In this embodiment, the fuel chamber 4
In order to suck the hydrogen gas inside the fuel discharge line 8 and forcibly discharge the hydrogen gas from the fuel discharge line 31, the pressure reducing pump 3
6 and a bypass line 3 provided with a leakage prevention solenoid valve 37
2 and the air introduction solenoid valve 28 is merely connected to the fuel supply line 21 in order to introduce air from the fuel supply line 21 into the fuel chamber 48.

Therefore, the arrangement of pipes and valves is simple,
Manufacturing costs and maintenance costs can be reduced.

Further, the air introduced into the fuel chamber 48 is
Since the air is filtered through the filter 29, it does not contain dust, impurities, harmful gases and the like existing in the atmosphere.

Therefore, members such as the catalyst in the fuel chamber 48 are not contaminated or deteriorated by the dust, impurities, harmful gas and the like.

The present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0091]

As described above in detail, according to the present invention, in a fuel cell device, a fuel cell including a fuel chamber in contact with a fuel electrode, an oxygen chamber in contact with an oxygen electrode, and the fuel chamber A fuel supply line connected to and supplying fuel to the fuel chamber, and an air introduction device disposed in the fuel supply line,
The fuel supply system includes a fuel discharge pipe connected to the fuel supply pipe via the fuel chamber to discharge fuel from the fuel chamber, and a fuel forcible discharge device disposed in the fuel discharge pipe.

In the control method of the fuel cell device, the fuel cell includes a fuel chamber in contact with the fuel electrode, an oxygen chamber in contact with the oxygen electrode, and a fuel cell connected to the fuel chamber and supplying fuel to the fuel chamber. A supply pipe, an air introduction device disposed in the fuel supply pipe, a fuel discharge pipe connected to the fuel supply pipe via the fuel chamber, and discharging fuel in the fuel chamber; After the fuel in the fuel chamber is discharged by operating the fuel forcible discharging device of the fuel cell device having a fuel forcibly discharging device disposed in a fuel discharge line, the air introducing device is operated to cause the fuel in the fuel chamber. Introduce air into the

In this case, when the fuel cell device is stopped, the hydrogen gas remaining in the fuel chamber is quickly discharged and air is introduced into the fuel chamber, so that the potential difference between the fuel electrode and the oxygen electrode is reduced. Can be reduced rapidly.
Therefore, the catalyst does not elute, the carbon carrying the catalyst does not corrode, or the catalyst does not sinter, and the effective area of the catalyst does not decrease. High performance can be maintained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a fuel cell device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional fuel cell device.

FIG. 3 is a flowchart illustrating an operation of stopping a conventional fuel cell device.

FIG. 4 is a sectional view showing a configuration of a unit unit of the fuel cell according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating characteristics of the fuel cell when the output of the fuel cell according to the present embodiment is stopped, in comparison with a conventional example.

FIG. 6 is a diagram showing a change over time of the output of the fuel cell in the present embodiment in comparison with a conventional example.

FIG. 7 is a second flowchart showing the operation of the fuel cell device according to the present embodiment.

FIG. 8 is a second flowchart showing the operation of the fuel cell device according to the present embodiment.

[Explanation of symbols]

 Reference Signs List 11 fuel cell 21 fuel supply line 28 air introduction electromagnetic source 36 fuel discharge pump

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masataka Ueno 2--19-12 Sotokanda, Chiyoda-ku, Tokyo F-term in Equos Research Co., Ltd. 5H026 AA06 5H027 AA06 BA01 BA13 BA14 DD03 MM01 MM08

Claims (6)

[Claims] 1. A fuel cell having a fuel chamber in contact with a fuel electrode, an oxygen chamber in contact with an oxygen electrode, connected to the fuel chamber,
A fuel supply pipe for supplying fuel to the fuel chamber, an air introduction device provided in the fuel supply pipe, and the fuel supply pipe connected to the fuel supply pipe via the fuel chamber; A fuel cell device comprising: a fuel discharge pipe to be discharged; and a fuel forcible discharge device disposed in the fuel discharge pipe. 2. The fuel cell device according to claim 1, wherein the position of the forcible fuel discharge device is higher than the lowest position of the fuel discharge pipe. 3. The fuel cell system according to claim 1, further comprising: control means for activating said fuel forcible discharge device to discharge the fuel in said fuel cell and thereafter activating said air introduction device to introduce air into said fuel cell. 3. The fuel cell device according to 2. 4. When the control means receives an instruction to stop the output of the fuel cell, the control means activates the fuel forcible discharge device to discharge the fuel in the fuel cell, and then activates the air introduction device. 4. The fuel cell device according to claim 3, wherein air is introduced into the fuel cell. 5. A fuel cell having a fuel chamber in contact with a fuel electrode, an oxygen chamber in contact with an oxygen electrode, and a fuel cell connected to the fuel chamber;
A fuel supply pipe for supplying fuel to the fuel chamber, an air introduction device provided in the fuel supply pipe, and the fuel supply pipe connected to the fuel supply pipe via the fuel chamber; After operating the fuel forcible discharge device of the fuel cell device having a fuel discharge line to be discharged and a fuel forcible discharge device disposed in the fuel discharge line to discharge the fuel in the fuel chamber,
A method for controlling a fuel cell device, comprising: activating the air introduction device to introduce air into the fuel chamber. 6. When receiving an instruction to stop the output of the fuel cell, the fuel forcible discharge device is operated to discharge the fuel in the fuel chamber, and the air introduction device is operated to cause air to enter the fuel chamber. The method for controlling a fuel cell device according to claim 5, wherein: