JPH07272738A - Fuel cell system - Google Patents

Abstract

PURPOSE:To provide a fuel cell system wherein a pressure between anode/ cathode electrodes and between each of these electrodes and a fuel cell vessel is set to a permissible pressure difference or less, even when changed gas volume by generating each part temperature difference at the time of storing the fuel cell system stopped. CONSTITUTION:In an anode electrode side gas supply path and in an anode electrode side discharge gas flow path, of a fuel cell 1, valves 11, 12 are provided, and on the other hand, in a cathode electrode side gas supply path and in a cathode electrode side discharge gas flow path, of the fuel cell 1, valves 13, 14 are provided. Accordingly, when the valves 11, 12 and the valves 13, 14 are closed, an anode electrode closed path 40 and a cathode electrode closed path 41 are formed. Further, a flow path between the anode electrode closed path and the cathode electrode closed path 41. is connected by a connecting path 44, and in this connecting path 44, a pair of check valves 20, 21, set to a prescribed cracking pressure, are parallelly provided so as to make a flow direction opposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell system, and more particularly to a space between the anode electrode and the cathode electrode, and between each of these electrodes and the fuel cell, even if the gas volume changes due to the temperature difference at each part when the fuel cell system is stopped and stored. The present invention relates to a fuel cell system in which the pressure difference between the container and the container is not more than an allowable pressure difference.

[0002]

2. Description of the Related Art A fuel cell using a power generation system by an electrochemical reaction has high efficiency and excellent environmental characteristics.
Recently, it has been spotlighted as a small output battery. The principle of the fuel cell utilizes the reverse reaction of electrolysis of water, that is, electric energy generated when hydrogen and oxygen combine to generate water. An actual fuel cell power generation system is mainly composed of a fuel cell main body for power generation, and includes a reformer for supplying hydrogen-rich gas to the fuel cell main body and peripheral devices such as a humidifier for adding water to the hydrogen-rich gas. Has been done.

As the fuel cell, there are a phosphoric acid type fuel cell using phosphoric acid which is an inorganic acid as an electrolyte, and a molten carbonate type fuel cell using an electrolyte plate impregnated with a mixed carbonate of lithium carbonate and potassium carbonate. Instead of liquid materials such as phosphoric acid aqueous solution and molten carbonate, solid stabilized zirconia having oxygen ion conductivity is used as an electrolyte at an operating temperature of 1000.
° C solid electrolyte fuel cell, alkaline fuel cell using potassium hydroxide aqueous solution as electrolyte, hydrogen ion conductive fluororesin ion exchange membrane (for example, Nafion (Na
There is a polymer electrolyte fuel cell having fion DuPont (registered trademark) as an electrolyte and an operating temperature of 80 to 90 ° C.

In recent years, a polymer electrolyte fuel cell has been attracting attention because it has no problems such as electrolyte dissipation and retention, and has advantages such as starting at room temperature and extremely short starting time. This polymer electrolyte fuel cell (PEFC: Polymer Electrolyte
Fuel Cells) is an ion-exchange membrane fuel cell (IEMFC: Ion
Exchange Membrane Fuel Cells (PEMFC: Proton Exchange Membrane Fuel Cell)
s), polymer electrolyte fuel cell (SPEFC: Solid Polymer
r Electrolyte Fuel Cells) and its structure is shown in Fig. 7. Note that FIG. 7 shows the structure of a single cell fuel cell.

That is, an anode electrode 62 and a cathode electrode 63, which are made of porous carbon paper or carbon cloth having gas diffusing ability, are arranged on both side surfaces of the solid polymer electrolyte membrane 61, and further on the outer side surfaces of both electrodes. The dense carbon plate 64 on the anode side and the dense carbon plate 65 on the cathode side are arranged so as to sandwich the solid polymer electrolyte membrane 61. Further, current collectors 66 and 67 made of a highly conductive metal such as copper are arranged on the outer contours of the anode pole side dense carbon plate 64 and the cathode pole side dense carbon plate 65, respectively. And each member is arrange | positioned and mutually joined. Further, an anode electrode side gas flow channel 68 consisting of a plurality of rib-shaped grooves is formed on the side of the anode electrode side dense carbon plate 64 which is in contact with the anode electrode 62, and the reforming is performed in the anode electrode side gas flow channel 68. A reformed gas, which is a hydrogen-rich gas supplied as a fuel gas for an electrochemical reaction, flows from the reactor. On the other hand, on the side of the cathode electrode side dense carbon plate 65 that is in contact with the cathode electrode 63, a cathode electrode side gas flow passage 69 is formed which is composed of a plurality of rib-shaped grooves. Oxygen gas or air supplied as the fuel gas for the reaction flows.

Then, at the anode electrode 62, a hydrogen oxidation reaction of the following formula occurs.

H ₂ → 2H ⁺ + 2e ^{− The} generated hydrogen ions H ⁺ pass through the solid polymer electrolyte 1 and move to the cathode 63. On the other hand, the cathode 63
Then, the supplied oxygen or air reacts with hydrogen ions H ⁺ as in the following equation.

1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O Due to these electrochemical reactions, the polymer electrolyte fuel cell exhibits an electromotive force.

Usually, in order to secure a desired output voltage,
The fuel cell has a plurality of single cells stacked. In FIG.
A structure of a so-called three-cell stack, which is an assembly of fuel cells in which three single cells are electrically stacked in series, is shown. Unlike the above-mentioned FIG. 7, the 3-cell stack as shown in FIG. 8 is partitioned between the cells by ribbed separators 74 that allow different combustion gases to flow on both sides. Further, at both ends of the stack, a cooling water flow path 70 for absorbing heat generated by power generation and maintaining the fuel cell at a predetermined reaction temperature, current collectors 66 and 67 in its outer shell, and insulators (insulators) in its outer shell.
71 and an end plate 72 are arranged, and each member is closely joined by a tightening bolt 73.

When the above-mentioned solid polymer fuel cell is mounted in, for example, an automobile, the solid polymer fuel cell is frequently operated / stopped, that is, intermittent operation is performed according to the operation / stop of the automobile. When the polymer electrolyte fuel cell is stopped, the fuel cell main body is cooled by the purge gas for making the inside of the fuel cell an inert atmosphere and the cooling water. As the fuel cell body cools, the gas temperature inside the fuel cell decreases. On the other hand, water vapor is present in the anode-side gas flow path and the cathode-side gas flow path, and the residual water vapor amount may differ. Here, as the gas temperature decreases due to the stop of the fuel cell, the water vapor on the anode side and the cathode side aggregate to become water. Further, when mounted on a vehicle, the fuel cell main body is closed after purging in order to suppress consumption of purge gas. Therefore, the internal pressure of the closed space of the fuel cell is reduced, and the pressures in the cathode closed passage and the anode closed passage having different residual water vapor amounts are also decreased, and a pressure difference is generated between the closed passages.

Due to the pressure difference between the anode pole closed path and the cathode pole closed path, for example, the bonded body of the solid electrolyte membrane and the electrode is applied with pressure from one direction. For this reason, the bonded body of the solid electrolyte membrane and the electrodes may be pressed against the corners of the rib-shaped grooves provided on the opposing separators, and may be deformed or cut in some cases. In such cases, usually 0.2 to 3 mm
The solid polymer electrolyte membrane, which is thin and weak in strength, is easily affected.

Furthermore, when the pressurized fuel gas is introduced into the fuel cell whose internal pressure has dropped due to the stoppage at the time of the next start, a rapid pressure change occurs, so that a large amount of fuel gas flows in at one time. As a result, the solid polymer electrolyte membrane and each part of the solid polymer fuel cell may be damaged.

When such a problem occurs, there is a possibility that the durability of the fuel cell cannot be sufficiently ensured.

Therefore, in the "method for balancing the pressure difference in the fuel cell" of Japanese Patent Laid-Open No. 397064/1993, in order to always balance the pressure between the anode side, the cathode side and the cell storage container. The method of installing the bellows type balancer is described.

[0015]

However, the above-mentioned Japanese Unexamined Patent Application Publication No.
In the configuration of Japanese Patent No. 297064, it is necessary as a bellows type balancer to have an internal capacity enough to absorb and balance the gas according to the pressure difference between the two to be controlled.
And this bellows balancer is like a giant accordion.

Therefore, for example, assuming a solid polymer fuel cell having an output of 10 kW, the internal volume required for this bellows type balancer will be 10 liters or more from the space volume inside the pipe, and the solid polymer fuel cell It is necessary to install a huge bellows type balancer that is comparable to the size of the fuel cell body. That is, when the output scale of the polymer electrolyte fuel cell is increased, the bellows type balancer must be increased in proportion thereto, which makes it difficult to mount the fuel cell in a limited space like an automobile. .

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to reduce the size of the anode and the anode even if the gas volume changes due to the temperature difference between parts when the fuel cell system is stopped and stored. It is an object of the present invention to provide a fuel cell system in which the pressure difference between the cathode electrodes and between each of these electrodes and the fuel cell container is kept below the allowable pressure difference.

[0018]

In order to achieve the above object, the fuel cell system according to the present invention is characterized by the following.

(1) In the fuel cell system in which the fuel cell is replaced with an inert atmosphere by a purge gas after the fuel cell system is stopped and then the fuel cell body is sealed, the gas passage on the anode electrode side is hermetically sealed. The anode closed passage, the cathode closed passage formed by closing the cathode side gas passage, the connecting passage connecting between the anode closed passage and the cathode closed passage, A pair of check valves, which are arranged in parallel in the connection path with the gas flow directions opposite to each other and set to a predetermined cracking pressure, and which have a closed anode path and a cathode of the fuel cell body when the fuel cell system is stopped and stored. The pressure difference between the pole closed path is kept constant.

(2) In the fuel cell system according to the above (1), further, a purge gas supply passage for supplying a purge gas to a fuel cell closed passage consisting of the anode closed passage and the cathode closed passage, and the fuel cell closed passage. A check valve which is provided in the passage and is set to a predetermined cracking pressure so that the purge gas flows toward the closed passage of the fuel cell, and the fuel to the fuel cell when the fuel cell system is stopped and stored. The pressure difference between the gas supply passage and the fuel cell closed passage is kept constant.

(3) In the fuel cell system according to (2) above, further, a fuel cell main container for accommodating the fuel cell, and a second purge gas supply passage for supplying a purge gas to the fuel cell container. A second connecting path that connects the fuel cell storage container to either the anode pole closed path or the cathode pole closed path, and a predetermined cracking lined up in the second connection path with their flow directions opposite to each other. A pair of check valves set to pressure, and a predetermined cracking pressure provided in the second purge gas supply passage, and one of the fuel cell storage container and the anode seal passage or the cathode seal passage. And a check valve installed so that the purge gas flows toward the fuel cell system. Holding the pressure differential constant.

[0022]

According to the above structure of the fuel cell system, the connecting passage for connecting the flow passages of the anode closed passage and the cathode closed passage and the connection passage are arranged in parallel with the gas flow directions opposite to each other. Since it has a pair of check valves set to the cracking pressure of the fuel cell, the pressure difference between the anode electrode side and the cathode electrode side of the fuel cell, which is caused by cooling during the stop and storage of the fuel cell, is constant, and the predetermined cracking pressure is maintained. Can be held at.

Further, in addition to the above structure, a purge gas supply passage for supplying a purge gas to a fuel cell closed passage consisting of an anode closed passage and a cathode closed passage, and a predetermined cracking pressure provided in the fuel cell closed passage are set. And having a check valve installed so that the purge gas flows toward the fuel cell closed path, depending on the decrease in the internal pressure of the fuel cell caused by cooling during the stopped storage of the fuel cell, By supplying the purge gas to the fuel cell closed passage, the pressure difference between the fuel gas supply passage and the fuel cell closed passage can be kept constant. Therefore, it is possible to prevent the fuel gas from rapidly flowing into the fuel cell at the next startup.

Further, in the above structure, when the fuel cell is further housed in the fuel cell main container, the second purge gas supply passage for supplying the purge gas to the fuel cell container, the fuel cell container and the fuel cell closed passage. A second connecting path for connecting to the second connecting path, a pair of check valves installed in parallel in the second connecting path with flow directions opposite to each other and set to a predetermined cracking pressure, and the second purge gas supply path. A check valve that is provided and is set to a predetermined cracking pressure, and is installed so that the purge gas flows toward the fuel cell closed passage.
Therefore, when the internal pressure of the fuel cell decreases during the stop and storage of the fuel cell system, the purge gas is supplied from the inside of the fuel cell storage container to the closed passage of the fuel cell to quickly maintain the internal pressure drop within the fuel cell at a constant pressure. be able to. Further, since the purge gas is also supplied to the fuel cell container in which the pressure has dropped, as a result, the pressure difference between the fuel cell closed passage and the fuel cell container can be kept constant.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 shows a block diagram for balancing the pressure difference between the anode electrode side and the cathode electrode side of the fuel cell, which is caused by cooling during the stopped storage of the fuel cell. .

As shown in FIG. 1, an anode-side gas supply for supplying a reformed gas, which is a hydrogen-rich gas, to an anode-side inlet 2 of a polymer electrolyte fuel cell 1 (hereinafter abbreviated as "fuel cell 1"). On the other hand, the cathode side inlet 4 of the fuel cell 1 is provided with a cathode electrode side gas supply passage for supplying oxygen gas or air. Further, the anode side outlet 3 of the fuel cell 1 is provided with an anode side exhaust gas flow path for discharging the exhaust gas consumed in the fuel cell 1, while the cathode side outlet 5 of the fuel cell 1 is provided with a fuel cell. The exhaust gas passage on the cathode side is provided for discharging water vapor including oxygen or air consumed in 1. Then, valves 11, 13, 12, and 14 are provided respectively.

Therefore, when the valves 11 and 12 are closed, the anode closed passage 40 is formed, and when the valves 13 and 14 are closed, the cathode closed passage 41 is formed.

Further, the flow paths of the anode pole closed path 40 and the cathode pole closed path 41 are connected by a connection path 44. A pair of check valves 20 and 21 set to a predetermined cracking pressure are arranged in parallel in the connecting path 44 so that the flow directions thereof are opposite to each other. The arrow indicates the allowable flow direction of gas. Further, the connecting path 44 is provided with a valve 19 for opening and closing the flow path of the connecting path 44.

In this embodiment, the valves 11, 1
Reference numerals 2, 13, 14, and 19 are solenoid valves, which are latched and driven by electric signals from a control unit (not shown).

Next, the operation of the fuel cell system of this embodiment will be described.

During operation of the fuel cell 1, the valve 11 on the anode side and the valve 13 on the cathode side are opened, and fuel gas is supplied to the fuel cell 1 to generate electricity. At this time, the valve 19 is closed to close the flow path of the connecting path 44.

On the other hand, when the fuel cell 1 is stopped, in order to replace the inside of the fuel cell with an inert atmosphere, the valve 11 on the anode side and the valve 13 on the cathode side are closed, and a purge tank (not shown) is attached to the fuel cell 1. ) Supply the purge gas. Also at this time, the valve 19 is closed.

When the purging is completed, the valves 12 and 14 are closed and the valve 19 is opened. In this state, a fuel cell closed passage including the anode closed passage 40 and the cathode closed passage 41 is formed. Then, as the fuel cell 1 cools,
Gas pressure of anode closed passage 40 and cathode closed passage 4
1, the pressure difference from the gas pressure of a certain value or more, namely, the check valve 20,
When the cracking pressure becomes equal to or higher than 21, the check valve 20 or the check valve 21 opens, and gas flows from the higher pressure side to the lower pressure side. Further, since the pair of check valves 20 and 21 are arranged in parallel so as to face each other, the check valves are opened regardless of which pressure is higher on the anode side or the cathode side or which pressure is lower. , The pressure difference becomes constant. In particular,
During operation, the cathode side is generally pressurized (for example, 2 atm pressure) as compared with the anode side, and if the cracking pressure is set to this amount (for example, 2 atm), it can be used during operation and when stopped and stored. The solid polymer electrolyte membrane of the solid polymer electrolyte fuel cell is always held at the same pressure from the same direction, and the solid polymer electrolyte membrane does not sway due to the pressure difference at the time of startup. Therefore, the solid polymer electrolyte membrane is deformed,
No damage such as cutting.

Since the anode side and the cathode side have already been purged with the purge gas, the check valves 20, 21 are opened and the gas flowing into each other is the purge gas (nitrogen or argon). Therefore, the fuel gas (hydrogen in the anode system, oxygen or air in the cathode system) does not flow into each other.

The check valve 2 is provided on the inlet side of the fuel cell 1.
Even if 0 and 21 are provided, the same effect can be obtained.

Second Embodiment FIG. 2 shows that the purge gas is supplied to the fuel cell closed passage to the fuel cell in response to the decrease in the internal pressure of the fuel cell caused by the cooling during the stopped storage of the fuel cell. 2 is a block configuration diagram for maintaining a constant pressure difference between the fuel gas supply passage and the fuel cell closed passage. The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

The feature of this embodiment is that the purge gas tank 80 is further connected to the anode closed passage 40 and the cathode closed passage 4.
1 is provided with a purge gas supply path for supplying a purge gas, and the purge supply path is the anode side purge gas supply path 50.
And a cathode side purge gas supply path 52. A predetermined cracking pressure is set in each of the anode-side purge gas supply passage 50 and the cathode-side purge gas supply passage 52, and the purge gas tank 80 and the fuel cell 1 are connected to each other.
The anode check valve 18 and the cathode check valve 22 are installed so that the purge gas flows. Further, a valve 60 is installed upstream of the purge gas supply passage. The valve 60 is a solenoid valve in this embodiment.

Next, the operation of the fuel cell system of this embodiment will be described. The operation during operation of the fuel cell 1 is
It is similar to the embodiment of.

In the present embodiment, it is possible to prevent the fuel cell closed passage composed of the anode closed passage 40 and the cathode closed passage 41 from having a certain pressure or less as the fuel cell is cooled. That is, the valve 60 is left open even after the replacement of the purge gas is completed. Next, valve 1
2, 14 are closed and valve 19 is opened. In this state, a fuel cell closed passage including the anode closed passage 40 and the cathode closed passage 41 is formed. Then, when the gas pressure in the anode closed passage 40 and the gas pressure in the cathode closed passage 41 become equal to or higher than the cracking pressure of the check valves 20 and 21 as the fuel cell 1 is cooled, the check valve 20 or the check valve. 21 opens, the gas flows from the higher pressure side to the lower pressure side, and the pressure difference becomes constant.

Further, the cracking pressures of the anode side check valve 18 and the cathode side check valve 22 are set to the gas pressures of the anode side gas supply path and the cathode side gas supply path for supplying the fuel gas, for example. In other words, the purge gas is supplied to the fuel cell closed passage in accordance with the decrease in pressure of the fuel cell closed passage.

With this, it is possible to prevent the sudden inflow of the fuel gas into the fuel cell at the next startup and the abrupt fluctuation of the pressure accompanied therewith. Furthermore, since it does not unnecessarily increase the overall pressure drop of both electrodes, it is possible to prevent the outside air from entering the fuel cell, and to suppress the damage of the seal part and the components due to the pressure difference between the inside and the outside, which is stable. Can be kept in a good storage state.

In this embodiment, the check valves 20 and 21 may be provided on the inlet side of the fuel cell 1 and the purge gas supply passage may be provided on the outlet side. Further, the check valves 20 and 21 and the purge gas supply passage may be provided. The same effect can be obtained even if they are provided on the same side.

Third Embodiment FIG. 3 is a block diagram showing a constant pressure difference between the fuel cell closed passage and the fuel cell container when the fuel cell system is stopped and stored. The same components as those in the first and second embodiments are designated by the same reference numerals, and the description thereof will be omitted.

In the present embodiment, the fuel cell 1 is further housed in a fuel cell container 6, and this fuel cell container 6 contains:
Purge gas is supplied through the purge gas supply path 51. Further, the fuel cell container 6 and the anode closed passage 40
And are connected by a second connecting path 46. In addition, a pair of check valves 25 and 26, which are set to a predetermined cracking pressure, are arranged in parallel in the second connecting passage 46 with the flow directions thereof being opposite to each other, and the valve 2 which opens and closes the second connecting passage 46 is further provided.
4 are provided. Further, in the purge gas supply passage 51, the check valve 23 set to a predetermined cracking pressure and installed so that the purge gas flows toward the fuel cell storage container 6, and the second purge gas supply passage 51 are opened and closed. And a valve 61.

Next, the operation of the fuel cell system of this embodiment will be described. The operation during operation of the fuel cell 1 is
It is similar to the embodiment of.

In the present embodiment, it is prevented that the fuel cell closed passage composed of the anode closed passage 40 and the cathode closed passage 41 and the fuel cell storage container become below a certain pressure as the fuel cell is cooled. can do. That is, the valves 60 and 61 are left open even after the replacement of the purge gas is completed. Next, the valves 12 and 14 are closed. In this state, a fuel cell closed passage including the anode closed passage 40 and the cathode closed passage 41 is formed. Next, valve 1
Open 9, 24. Then, as the fuel cell 1 cools,
Gas pressure of anode closed passage 40 and cathode closed passage 4
When the gas pressure of 1 becomes equal to or higher than the cracking pressure of the check valves 20 and 21, the check valve 20 or the check valve 21 opens, the gas flows from the higher pressure side to the lower pressure side, and the anode pole closed passage 40 When the gas pressure and the gas pressure in the fuel cell storage container 6 become equal to or higher than the cracking pressure of the check valves 25 and 26, the check valve 25 or the check valve 26 opens, and the gas flows from the higher pressure side to the lower pressure side. Further, when the purge gas flows out from the fuel cell storage container 6 and the pressure drops, the purge gas is supplied to the fuel cell storage container 6 via the purge gas supply passage 51. As a result, the pressure difference between the fuel cell closed path and the fuel cell container 6 is kept constant, and the fuel cell body is not damaged.

Further, similarly to the second embodiment, the cracking pressures of the anode side check valve 18 and the cathode side check valve 22 are
For example, if the gas pressure between the anode electrode side gas supply passage and the cathode electrode side gas supply passage for supplying the fuel gas is set, the pressure difference between the fuel cell closed passage and the fuel gas supply passage can be made constant. Therefore, it is possible to prevent the rapid inflow of the fuel gas into the fuel cell at the time of the next startup and the abrupt fluctuation of the pressure accompanying it. Furthermore, since it does not unnecessarily increase the overall pressure drop of both electrodes, it is possible to prevent the outside air from entering the fuel cell, and to suppress the damage of the seal part and the components due to the pressure difference between the inside and the outside, which is stable. Can be kept in a good storage state.

In this embodiment, the check valves 20, 21, 25 and 26 may be provided on the inlet side of the fuel cell 1, and two purge gas supply passages may be provided on the outlet side. , 21, 25, and 26 are provided on the same side, the same effect can be obtained.

Fourth Embodiment FIG. 4 shows, in addition to the third embodiment, a block diagram for maintaining the cooling water system of the polymer electrolyte fuel cell at a constant pressure difference. The same components as those in the first, second and third embodiments are designated by the same reference numerals and the description thereof will be omitted.

In the case of the present embodiment, a cooling pipe is further provided which comprises a cooling water supply passage 48 for supplying cooling water to the fuel cell 1 and a cooling water discharge passage 49 for letting the cooling water out of the fuel cell 1. . Further, the purge gas supply passage 5 is joined to the cooling water supply passage 48 and supplies the purge gas to the cooling water supply passage 48.
3 is provided. The purge gas supply passage 53 is provided to prevent oxygen dissolved in the cooling water from corroding the cooling water pipe.

Next, the operation of the fuel cell system of this embodiment will be described. The operation during operation of the fuel cell 1 is
It is similar to the embodiment of.

In this embodiment, it is possible to prevent the pressure in the fuel cell closed passage and the cooling system from becoming lower than a certain pressure as the fuel cell 1 is cooled. That is, even after the replacement of the purge gas is completed, the supply path for the purge gas is left open. Next, the valves 12 and 14 are closed. In this state, a fuel cell closed passage including the anode closed passage 40 and the cathode closed passage 41 is formed. Next, valve 1
Open 9, 24 and 30. Then, when the gas pressure in the anode closed passage 40 and the gas pressure in the cathode closed passage 41 become equal to or higher than the cracking pressure of the check valves 20 and 21 as the fuel cell 1 is cooled, the check valve 20 or the check valve. 21 opens, gas flows from the higher pressure side to the lower pressure side, and when the gas pressure of the anode closed passage 40 and the gas pressure of the fuel cell storage container 6 becomes equal to or higher than the cracking pressure of the check valves 25 and 26, the reverse pressure is generated. The stop valve 25 or the check valve 26 opens, and gas flows from the higher pressure side to the lower pressure side. Further, when the gas pressure in the cathode pole closed passage 41 and the gas pressure in the cooling water discharge passage 49 become equal to or higher than the cracking pressure of the check valves 31 and 32, the check valve 31 or the check valve 32 opens, and the one with the higher pressure is used. Gas flows downward from the Further, when the purge gas flows out from the fuel cell storage container 6 and the pressure in the cooling pipe decreases, the purge gas is supplied to the fuel cell storage container 6 and the cooling pipe via the purge gas supply paths 51 and 53. As a result, the pressure difference between the fuel cell closed passage and the fuel cell storage container 6 and between the fuel cell closed passage and the cooling pipe is kept constant, and the fuel cell main body is not damaged. Further, since the pressure difference between the cooling system and the reaction electrode side or the inside of the container is suppressed, it is possible to prevent the electrode or the membrane from being pressed and damaged by the deformation of the cooling plate. Since the cooling system is configured close to the reaction system in order to improve the cooling efficiency, it has a great influence.

Fifth Embodiment FIG. 5 is a block diagram of a fuel cell system for keeping the pressure difference between the reformer and the fuel cell closed passage constant. The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 5, the humidifier 7 is the fuel cell 1
To the fuel gas (the fuel gas here is anode gas (H ₂ ) and cathode gas (O ₂ or air))
It includes both). By humidifying, the movement of hydrogen ions H ⁺ in the solid polymer electrolyte membrane is promoted, the cell resistance of the fuel cell is lowered, and more output current can be taken out. In the fuel gas supply path for supplying the fuel gas to the fuel cell 1 via the humidifier 7,
Valves 9, 10, 11 are provided. A heater 8 is provided in a pipe connecting the humidifier 7 and the fuel cell 1 so that the humidified fuel gas is maintained at a predetermined temperature. The humidifier 7 is also replaced by the purge gas when the fuel cell is stopped. Therefore, the purge gas is also supplied to the humidifier 7 via the purge gas supply path 54. The purge gas supply passage 54 is provided with a valve 15 that opens and closes the purge gas supply passage 54. Further, the purge gas supply path 54
Branch and supply purge gas between the humidifier 7 and the heater 8 and between the heater 8 and the fuel cell 1, respectively. Check valves 16, 17, and 18 are provided in the respective branched purge gas supply paths. Usually, a large amount of water is stored in the humidifier 7 for humidification. Furthermore, the cooling rate of the humidifier 7 is slower than that of other metal pipe parts, and therefore the pressure inside the humidifier 7 is
The relative pressure is apparently higher than the pressure in the compartments before and after it, and when the valves 9, 10 and 11 are next opened to start the fuel cell 1, the pressure difference causes the internal pressure of the humidifier 7 to rise. Water may flow into the next compartment or back into the previous compartment. In addition, the pressure inside the humidifier has the lowest pressure relationship with other devices at the time when all the devices reach normal temperature.

The operation of the system according to this embodiment will be described with reference to FIG. 5 by way of example.

An example will be described in which the gas pressure during operation of the fuel cell 1 is 2 atm, the cracking pressure of the check valves 16, 17, 18 is 0.5 atm, and the purge gas pressure is 2 atm. . When the fuel cell 1 is stopped, 2
Return from atmospheric pressure to normal pressure.

First, during normal operation, the valve 1
5 is closed to shut off the purge gas supply passage 54. Then, the valves 9, 10 and 11 are opened, and the valve 12 is adjusted so that the gas pressure becomes 2 atm to maintain the internal pressure in the system.

Next, when the operation of the fuel cell 1 is stopped, the heater 8 is stopped with the valve 15 kept closed.
At this time, leave the valves 10 and 11 open and leave the valve 12
Is fully opened to lower the system, and the gas pressure is set to normal pressure (1 atm).

Thereafter, the valve 9 is closed and the valves 10, 1
Leave 1 and 12 open. Next, the valve 15 is opened and an inactive purge gas is supplied into the system through the purge gas supply path 54. The purge gas at this time is injected at a gas pressure of 2 atm.

After purging, the valves 9, 10, 1
The valves 1 and 12 are closed, and only the valve 15 is continuously supplied from the purge gas supply path 54 to continuously inject the barge gas at a gas pressure of 2 atm. As a result, "2 atm (purge gas pressure)-
The pressure in the system can be increased to 1.5 atm by "0.5 atm (cracking pressure) = 1.5 atm (system internal pressure)".

In this state, for example, when the internal pressure of the humidifier 7 drops to 1.2 atm, the purge gas flows in from the check valve 16 and the internal pressure of the humidifier 7 becomes 1.5 atm.
The purge gas pressure is not limited to 2 atm,
It suffices that the purge gas pressure has a relationship larger than the sum of the cracking pressure of the check valves 16, 17, and 18 and the atmospheric pressure. With such a pressure, it is not necessary to change the purge gas pressure midway.

Sixth Embodiment FIG. 6 shows a system configuration in which gas is released to the outside of the system when the internal pressure of the humidifier increases due to the difference in cooling rate from the surrounding metal pipes when stopped. There is. In addition,
The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 6, the humidifier 7 is the fuel cell 1
It humidifies the fuel gas supplied to. The humidification promotes the movement of hydrogen ions H ⁺ in the solid polymer electrolyte membrane and promotes the efficiency of the fuel cell.
Valves 9, 10 and 11 are provided in the fuel gas supply path for supplying the fuel gas to the fuel cell 1 via the humidifier 7. Further, a heater 8 is provided between the humidifier 7 and the fuel cell 1 so that the humidified fuel gas is kept at a predetermined temperature. Further, when the humidifier 7 or the fuel cell is stopped, the humidifier 7 is also replaced by the purge gas. Therefore, the purge gas is also supplied to the humidifier 7 via the purge gas supply path 54. The purge gas supply passage 54 is provided with a valve 15 that opens and closes the purge gas supply passage 54. Further, the purge gas supply path 54 is branched to supply the purge gas downstream of the humidifier 7, between the valve 10 and the heater 8, and between the heater 8 and the fuel cell 1. Check valves 33, 17, and 18 are provided in the respective branched purge gas supply paths. Also, the check valve 33
The branch purge gas supply path having a branch is further branched to join the gas vent passage 100 branched from between the valve 9 and the humidifier 7. A valve 99 is provided in the branch purge gas supply passage, and a check valve 34 is provided downstream of the confluence point of the gas vent passage 100. The check valve 34 is provided so that the flow direction thereof is opposite to that of the check valve 33.

The operation of the system of this embodiment will be described by way of an example with reference to FIG.

An example will be described in which the gas pressure during operation of the fuel cell 1 is 2 atm, the cracking pressure of the check valves 33, 17 and 18 is 0.5 atm, and the purge gas pressure is 2 atm. . When the fuel cell 1 is stopped, 2
Return from atmospheric pressure to normal pressure.

First, in normal operation, the valve 1
5 is closed to shut off the purge gas supply passage 54. Then, the valves 9, 10, 11, 99 are opened, the valve 12 is adjusted so that the gas pressure becomes 2 atm, and the internal pressure in the system is maintained.

Next, when the operation of the fuel cell 1 is stopped, the heater 8 is stopped while the valve 99 is closed and the valve 15 is closed. At this time, with the valves 10 and 11 still open, the valve 12 is fully opened to lower the inside of the system to bring the gas pressure to normal pressure (1 atm).

Thereafter, the valve 9 is closed and the valves 10 and 1 are
Leave 1 and 12 open. Next, the valve 15 is opened and an inactive purge gas is supplied into the system through the purge gas supply path 54. The purge gas at this time is injected at a gas pressure of 2 atm.

After purging, the valves 9, 10, 1
1, 12, 99 are closed, and only the valve 15 is continuously supplied from the purge gas supply passage 54 to continuously inject the barge gas at a gas pressure of 2 atm. As a result, the pressure in the system can be increased to 1.5 atm by "2 atm (purge gas pressure) -0.5 atm (cracking pressure) = 1.5 atm (system internal pressure)".
In this state, for example, the internal pressure of the humidifier 7 decreases,
When the pressure reaches 1.2 atm, the purge gas flows in from the check valve 16 and the inside of the humidifier 7 becomes 1.5 atm. As described above, the purge gas pressure is not limited to 2 atm, and the purge gas pressure may be greater than the sum of the cracking pressures of the check valves 33, 17, and 18 and the atmospheric pressure. It is not necessary to change the purge gas pressure on the way if the pressure is set to a proper value.

The feature of this embodiment is that the purge gas is also introduced from the inlet of the humidifier 7 via the valve 99. For example, if the purge gas is injected only into the outlet of the humidifier 7 and the valve 9 is kept closed, the internal pressure of the humidifier 7 rises, and along with this, water overflows from the inlet of the humidifier 7. As in this embodiment, if the inlet of the humidifier 7 is opened and the purge gas is allowed to flow in, there is no risk of water overflowing from the humidifier 7.

Further, the feature of this embodiment is that a check valve 34 for venting gas is provided. When the internal pressure of the humidifier 7 becomes higher than the internal pressure of the system after the predetermined purge (1.5 atm in the above example), the check valve 34 promptly sets the internal pressure of the humidifier 7 to the predetermined value. Can be pressure. Further, the check valve 34 is arranged as shown in FIG. 6 so that the check valve 34 is discharged to the outside, so that, for example, when the internal pressure of the humidifier 7 is rapidly increased and the humidifier 7 overflows with water. Also, the overflowed water can be promptly discharged to the outside without flowing out to the pipe toward the fuel cell 1.

In the present invention, although the details of the material gas supply source on the anode side of the polymer electrolyte fuel cell are not shown for the sake of simple explanation, the supply by a high-pressure hydrogen gas cylinder and the methanol reforming method are not shown. It can be applied to any method used as a method for supplying a material gas on the anode side of a polymer electrolyte fuel cell, such as supply from a hydrogen generator, supply from a hydrogen storage alloy, supply from a liquid hydrogen tank, etc. it can.

Similarly, in the material gas supply source on the cathode side, solid polymer fuel such as high pressure oxygen (or air) gas cylinder supply, pressurized air supply by a compressor, liquid oxygen (or air) tank supply, etc. It can be applied to any method used as a method of supplying the material gas on the cathode side of the battery.

In FIGS. 5 and 6, the humidification of the material gas of the polymer electrolyte fuel cell is shown only as a humidifier, and its details are not described in order to explain the contents in a simple manner. Here, not only the humidifier by the bubbling method generally shown, but also a method in which water is atomized directly in a gas stream or gaseous water as described in JP-A-3-239958 is passed. With a porous membrane that does not allow liquid water to pass through, it can be applied to any humidifying method such as a method of vaporizing.

When a reformer (methanol reformer or methane reformer) is used on the anode side, generally, the reforming reaction is carried out by adding a water amount more than that required for the reforming reaction. Since this is done, the reformed gas obtained from the reformer already contains a certain amount of steam. Therefore, the humidifier may be provided only when the water vapor content is insufficient.

Although only "fuel gas" is shown in FIGS. 5 and 6, this may be either the anode side material gas or the cathode side material gas. Therefore, although FIG. 5 and FIG. 6 show only the piping system of either the anode or the cathode, the present invention can be similarly applied to another material gas system not shown.

In the above-mentioned embodiment, one fuel cell system may be composed of one fuel cell stack in order to explain the contents in a simple manner. At this time, these stacks are electrically connected to each other. They are connected in series or in parallel (and combinations thereof). However, in such a case, the material gas and the cooling water are generally supplied by connecting the stacks in parallel. The present invention can be applied as it is to a system including a plurality of fuel cell stacks. As a matter of course, each stack may have a structure described in the embodiment, "having a check valve which is arranged in parallel in the gas connecting passage in the direction opposite to the gas flow direction and set to a predetermined cracking pressure", or the fuel cell. The configuration may be such that only one place is provided "there is a check valve that is arranged in parallel in the gas connecting path in the direction opposite to the gas flow direction and has a predetermined cracking pressure". If the pipes between the stacks are long and it is predicted that the pressure fluctuations in these pipes may affect the fuel cell, it is better to install each stack.

In the above-mentioned embodiment, the means for heating the material gas was not specified for the sake of simplicity of explanation, but the polymer electrolyte fuel cell is operated at 80 to 100 ° C. Is the gas the same as the polymer electrolyte fuel cell,
Alternatively, heating to a slightly higher temperature is desirable. However, when the reformed gas from the reformer is used as the anode-side material gas, the operating temperature of the reformer is 200 ° C. or higher, and thus it is not necessary to provide a separate heating means.

[0080]

As described above, according to the fuel cell system of the present invention, the connecting passage connecting the passages of the anode closed passage and the cathode closed passage, and the gas flow in the connecting passage. Since it has a pair of check valves arranged in parallel in opposite directions and set to a predetermined cracking pressure, the anode electrode side and the cathode electrode side of the fuel cell, which are generated by cooling during the stopped storage of the fuel cell, are formed. The pressure difference can be kept constant, for example at the cracking pressure.

In addition to the above structure, a purge gas supply passage for supplying a purge gas to a fuel cell closed passage consisting of an anode closed passage and a cathode closed passage, and a predetermined cracking pressure provided in the fuel cell closed passage are set. And having a check valve installed so that the purge gas flows toward the fuel cell closed path, depending on the decrease in the internal pressure of the fuel cell caused by cooling during the stopped storage of the fuel cell, By supplying the purge gas to the fuel cell closed passage, the pressure difference between the fuel gas supply passage and the fuel cell closed passage can be kept constant. Therefore, it is possible to prevent the fuel gas from rapidly flowing into the fuel cell at the next startup.

Further, in the above structure, when the fuel cell is housed in the fuel cell main container, the second purge gas supply passage for supplying the purge gas to the fuel cell container, the fuel cell container and the fuel cell closed passage. A second connecting path for connecting to the second connecting path, a pair of check valves installed in parallel in the second connecting path with flow directions opposite to each other and set to a predetermined cracking pressure, and the second purge gas supply path. A check valve that is provided and is set to a predetermined cracking pressure, and is installed so that the purge gas flows toward the fuel cell closed passage.
Therefore, when the internal pressure of the fuel cell decreases during the stop and storage of the fuel cell system, the purge gas is supplied from the inside of the fuel cell storage container to the closed passage of the fuel cell to quickly maintain the internal pressure drop within the fuel cell at a constant pressure. be able to. Further, since the purge gas is also supplied to the fuel cell container in which the pressure has dropped, as a result, the pressure difference between the fuel cell closed passage and the fuel cell container can be kept constant.

When the fuel cell system of the present invention is applied to a fuel cell, for example, the following effects are obtained.

That is, high reliability can be ensured even in applications such as a polymer electrolyte fuel cell mounted on an automobile, which is repeatedly operated, stopped and operated.

Further, as compared with the prior art, it can be realized easily and at low cost, and has excellent durability performance.

Further, even if the polymer electrolyte fuel cell to which the present invention is applied becomes large in size, the size of the portion where the pressure should be controlled to be constant, that is, the check valve, is of a size corresponding to the purge gas pipe diameter. If the size (output scale) of the polymer electrolyte fuel cell, which the conventional technology has, is increased, the bellows type balancer must be increased in proportion thereto. Or, the pressure cannot be controlled beyond the internal volume of the bellows type balancer, and in order to control the pressure in any case, a bellows type balancer with a sufficient margin, that is, a huge bellows type balancer must be prepared. . Such problems can be solved.

It is possible to prevent a long-term deterioration of the performance of the polymer electrolyte fuel cell (cell body and piping forming the system) and provide a polymer electrolyte fuel cell having a long life.

[Brief description of drawings]

FIG. 1 is a block diagram of a fuel cell system according to a first embodiment of the present invention.

FIG. 2 is a block configuration diagram of a fuel cell system according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a fuel cell system according to a third embodiment of the present invention.

FIG. 4 is a block diagram of a fuel cell system according to a fourth embodiment of the present invention.

FIG. 5 is a block configuration diagram of a fuel cell system according to a fifth embodiment of the present invention.

FIG. 6 is a block configuration diagram of a fuel cell system according to a sixth embodiment of the present invention.

FIG. 7 is a cross-sectional view showing the structure of a single cell fuel cell.

FIG. 8 is a cross-sectional view showing the structure of a 3-cell stack.

[Explanation of symbols]

 1 Fuel cell 2 Anode side inlet 3 Anode side outlet 4 Cathode side inlet 5 Cathode side outlet 11, 13, 12, 14, 19 Valve 20, 21 Check valve 40 Anode sealed passage 41 Cathode sealed passage 44 Connection passage

Claims (3)

[Claims] 1. A fuel cell system in which a fuel cell system is replaced with an inert atmosphere by a purge gas after the fuel cell system is stopped, and then the fuel cell body is hermetically sealed, in which an anode side gas flow passage is hermetically sealed. An anode closed passage, a cathode closed passage formed by closing a gas passage on the cathode side, a connecting passage connecting the anode closed passage and the cathode closed passage, and the connection A pair of check valves, which are installed in parallel with the gas flow directions opposite to each other and are set to a predetermined cracking pressure, and the anode electrode closed passage and the cathode electrode of the fuel cell main body when the fuel cell system is stopped and stored. A fuel cell system characterized in that the pressure difference between the fuel cell system and the closed passage is kept constant. 2. The fuel cell system according to claim 1, further comprising: a purge gas supply passage for supplying a purge gas to a fuel cell closed passage formed of the anode closed passage and the cathode closed passage, and the fuel cell closed passage. A check valve which is provided and set to a predetermined cracking pressure and is installed so that the purge gas flows toward the fuel cell closed passage, and the fuel cell closed passage and the fuel gas when the fuel cell system is stopped and stored. A fuel cell system characterized in that the pressure difference between the fuel cell system and the supply channel is kept constant. 3. The fuel cell system according to claim 1, further comprising: a fuel cell main container for accommodating the fuel cell; a second purge gas supply passage for supplying a purge gas to the fuel cell accommodating container; A second connecting path for connecting the battery container and one of the anode pole closed path and the cathode pole closed path, and the second connection path are arranged in parallel with the flow directions being opposite to each other to a predetermined cracking pressure. A pair of check valves that are set, a predetermined cracking pressure that is provided in the second purge gas supply passage, and is directed to either the fuel cell container and the anode closed passage or the cathode closed passage. And a check valve installed so that the purge gas can flow through the fuel cell system.The check valve is installed between the anode and cathode closed passages and the fuel cell container when the fuel cell system is stopped and stored. A fuel cell system characterized by maintaining a constant pressure difference.