JP3066736B2 - Fuel cell stack - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a highly stacked fuel cell stack, and more particularly to a stack split tightening for reducing a difference in tightening pressure between cells located above and below the stack due to the weight of a battery module. With an attached structure,
The present invention relates to a fuel cell stack that ensures stack safety by stably installing a battery module.

[0002]

2. Description of the Related Art A cell composed of an electrolyte plate, anode and cathode electrodes sandwiching the electrolyte plate, and a separator provided outside each electrode has a clamping pressure in order to ensure gas sealing. And the components must be kept in close contact. FIG. 2 shows a basic structure of a cell which is a minimum unit constituting a stack of a molten carbonate type fuel cell. In this cell, the anode is supplied with fuel gas through one separator and the cathode is supplied with oxidant gas through another separator, and both gases undergo an electrochemical reaction in the electrolyte, generating power.

The gas supplied to each electrode is separated by a separator, and the outside periphery of the separator is gas-sealed by a molten liquid electrolyte by a method called wet sealing. An appropriate tightening pressure is applied to a stacked cell in which a plurality of cells are stacked to ensure gas sealing. If the tightening pressure is too small, the gas sealing performance will be poor.

Further, each electrode and electrolyte plate have a pore structure in order to cause an electrochemical reaction in the reaction gas, and an appropriate structure such as the shape and size of the pores and the pore surface area exists. I have. If the tightening pressure is too large, the pore structure of the electrode or the porous ceramic of the electrolyte plate will be deformed or damaged, and the battery performance will not be maintained.

In a high-stack (large-capacity) fuel cell stack which aims to increase the capacity by stacking a large number of cells, a structure in which a plurality of cells are stacked simply as shown in FIG. The more cells that are located at the bottom of the stack, the greater the weight of the cells above them, so the difference between the tightening pressures of the cells at the top and bottom of the stack increases, and the deviation from the appropriate value is reduced. Too big. Here, the battery module has a configuration including a stacked cell and gas headers provided above and below the stacked cell. The smaller the deviation from the appropriate tightening pressure value, the better. This is because if the surface pressure is small, the gas sealing property is deteriorated, the gas flow required for the power generation reaction in the cell cannot be secured, and the cell performance (cell voltage) decreases. This is because members such as the electrolyte plate and the electrode are deformed or cracked or damaged, and the cell performance is also lowered.

In order to reduce the difference in the tightening pressure, a method has been considered in which a highly stacked fuel cell stack is divided in the stacking direction and tightened for each divided unit. For example,
As shown in FIG. 4, the fuel cell stack is divided into two in the stacking direction, and the upper cell module group 1 (cell module 1a,
1b, 1c) and the lower battery module group 2 (battery module 2
a, 2b, and 2c) are divided into upper and lower stages, and a pressure applying device is provided for each stage. An intermediate fastening plate 4 is provided between the module groups 1 and 2.

The upper battery module group 1 includes an upper tightening bellows 6 as a pressure applying device installed thereon, an upper tightening plate 3 disposed on the upper tightening bellows 6, and a lower module group 1. And a tightening means including a tightening bolt 8a for connecting the respective tightening plates 3 and 4 to each other. On the other hand, the lower battery module group 2 includes a lower tightening bellows 7 installed thereunder, a lower tightening plate 5 arranged below the lower tightening bellows 7, and the above-described module located on the module group 2. It has a tightening means including a middle tightening plate 4 and a tightening bolt 8b connecting the respective tightening plates 4 and 5. The upper tightening bellows 6 applies a tightening force to the module group 1 between the middle tightening plate 4 and the upper tightening plate 3, and the lower tightening bellows 7 controls the middle tightening plate 4 and the lower tightening plate 5. A tightening force is applied to the module group 2 during the period. In particular, the lower tightening bellows 7 pushes up the lower battery module group 2 from below and presses it against the middle tightening plate 4 to apply a tightening force. Since the weight of all the members stacked on the lower battery module group 2 acts on the lower battery module group 2, the lower tightening bellows 7 has the tightening force due to the weight of the stacked member and the tightening force required by the cell itself. A predetermined tightening surface pressure can be obtained by adding a tightening force of the difference of the above. By thus reducing the difference in the tightening surface pressure of the divided units, the tightening surface pressure difference in the entire stack is reduced. be able to.

[0008]

The structure shown in FIG. 4 has the following problem. That is, as shown in FIG. 5, in a case where the lower tightening bellows 7 for applying a surface pressure to the lower battery module group 2 is broken and the pushing-up force is released, the lower tightening bellows 7 is attached to the lower battery module group. The module group 2 loses the tightening force applied thereto and contracts due to the weight of the module group 2. At this time, the lower battery module group 2 directly laminated on the upper surface of the lower tightening bellows 7 continues to descend until the lower tightening bellows 7 contracts, and the upper battery module group 1 includes only the tightening bolt 8b. Supported by
Since the upper battery module group 1 is supported in an unstable state, there is a risk of collapse of the upper battery module group 1, and in that case, not only the battery modules but also the entire fuel cell stack including the storage device and the pressure applying device is greatly damaged. Will be given.

In the event of an earthquake or the like, the lower battery module group 2 is directly stacked on the elastic tightening bellows 7, so that the lower battery module group 2 becomes unstable against shaking due to an earthquake, and may fall. Will be higher.

In the structure in which the battery module is directly stacked on a pressure applying device such as a tightening bellows to transmit a load upward from the pressure applying device as described above, when the pressure applying device loses a compressive force or when an earthquake occurs. There are no danger avoidance measures against shaking due to.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is a highly stacked battery module having a stack divisional tightening structure for reducing a difference in tightening pressure between cells located above and below a stack. It is an object of the present invention to provide a fuel cell stack that can secure the safety of the stack by stably installing the fuel cell stack.

[0012]

In order to achieve the above object, a fuel cell stack according to the present invention comprises a plurality of cells having a positive electrode on one side of an electrolyte plate and a negative electrode on the other side of the cell, with a separator interposed therebetween. A stack in which a plurality of battery modules each including a stacked cell formed by stacking vertically and gas headers provided above and below the stacked cell are stacked, and the plurality of battery modules are placed on an upper surface , and Legs on the foundation
A frame fixed through the upper module group, an intermediate fastening plate inserted between an upper module group and a lower module group in which a plurality of battery modules are divided into upper and lower parts, and a pressure A first pressure applying device for adding or removing the pressure, an upper tightening plate attached to the upper part of the first pressure applying device, and a lower hanging around the upper module group, connecting the upper tightening plate and the intermediate tightening plate. A connecting member, a second pressure applying device installed on the lower surface of the gantry and applying or removing pressure by expansion and contraction, a lower tightening plate attached to a lower end of the second pressure applying device, a lower module group , A connection member is provided which hangs around the gantry and the legs and connects the intermediate fastening plate and the lower fastening plate.

Preferably, the first and second pressure applying devices are bellows which expand and contract with compressed gas.

According to the above configuration, the compressive load for applying the necessary surface pressure to the lower module group is the compressive force of the second pressure applying device that pulls the connecting member connected to the intermediate tightening plate downward, that is, the second compressive load. It is obtained by the compressive load generated when the pressure applying device is extended. Therefore, the second pressure applying device can apply a required load to the lower module group, which sufficiently satisfies the functions to be provided by the conventional pressure applying device. In addition, according to the configuration of the present invention, even if the second pressure applying device cannot generate a compressive force for some reason, the position of the lower module group is moved because the lower module group is mounted on the gantry. Without
Only the phenomenon that the compressive load on the lower module group is insufficient occurs. The fact that the position of the lower module group does not move means that all the members stacked on the upper surface of the lower module group do not move. That is, according to the configuration of the present invention, even if the function of applying a compressive force to the second pressure applying device located below the gantry is lost, the entire stacked battery module group is moved in the height direction and the horizontal direction. There is no displacement and can always be put in a static state. Therefore, it is possible to avoid a crisis such as collapse of the entire fuel cell stack, and to obtain a safer and more reliable fuel cell stack.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. FIG. 1 is a diagram showing the overall structure of the fuel cell stack according to the present embodiment.

In this fuel cell stack, as shown in FIG.
The battery modules 21a, 21b, 2
1c, and a lower battery module group 22 composed of battery modules 22a, 22b, 22c. Each battery module is composed of a stacked cell 18 and gas headers 19 and 20 disposed above and below the stacked cell 18. Some battery modules have gas headers at upper, middle and lower positions of the stacked cell 18, respectively. Is treated similarly.

An upper tightening bellows 23 is provided on the upper battery module group 21 as a first pressure applying device. The bellows 23 and the module group 21 are mounted on the upper tightening bellows 23. Plate 25 and module group 21
Is sandwiched by the middle fastening plate 26 disposed under the center.
Then, the upper tightening plate 25 and the middle tightening plate 26 are suspended around the upper tightening bellows 23 and the upper battery module group 21.
The upper and lower ends of the bolt 28 are attached to the fastening plates 25 and 26 by nuts 34a and 34b. On the other hand, the lower battery module group 22 is mounted on the upper surface of the support base 30 fixed to the base base 33 via the legs 31, and the above-mentioned middle fastening plate 26 is located on the module group 22. Support stand 3
Bottom tightening bellows 2 as a second pressure applying device
4 is installed with its upper surface attached, and a lower fastening plate 27 is attached to the lower surface of the lower fastening bellows 24. The middle tightening plate 26 and the lower tightening plate 27 are connected by four long bolts 29 (connecting members) hanging around the lower battery module group 22, the support base 30 and the lower tightening bellows 24. The upper and lower ends of the bolt 29 are nuts 34c and 34
It is attached to the fastening plates 26 and 27 by d. In the fuel cell stack configured as described above, all the battery modules are supported by the support cradle, and the weight of all the battery modules is applied to the support cradle.

The fuel cell stack shown in FIG. 1 is housed in a pressure vessel 32. This is because, as is well known, the performance is improved by placing the cell module under a pressurized atmosphere when operating the fuel cell. However, a pressure vessel is not necessary. The legs 31 of the support gantry 30 extend through the bottom plate of the pressure vessel 32 to the base 33. The legs 31 are H-shaped steel of structural steel material SS400 and the like, and the lower tightening bellows 24, the support base 30, and the lower tightening plate 27 are welded structures made of SS400 and the like. The intermediate fastening plate 26 is a welded structure made of a material such as stainless steel SUS304.

Upper tightening bellows 23 and lower tightening bellows 2
4 is a stacked battery module group 21 generated during battery operation,
22 has a function of applying a constant compressive force to the stacked battery module groups 21 and 22 while absorbing their respective contractions and thermal expansions.

Upper tightening bellows 23 and lower tightening bellows 2
Numeral 4 expands or contracts by injecting nitrogen gas or the like from an external device. The upper tightening bellows 23 expands to generate a compressive load between the upper tightening plate 25 and the middle tightening plate 26 to apply a predetermined tightening load necessary for the upper battery module group 21.

When the lower tightening bellows 24 expands,
Since the upper surface of the lower tightening bellows 24 is held down by the support frame 30, the lower surface of the lower tightening bellows 24 extends downward, and the lower tightening plate 27 is pushed down, thereby lowering the lower tightening plate 2.
7, a downward tensile load is applied to the middle tightening plate 26 by the lower tightening bolt 29, and a predetermined tightening required for the lower battery module group 22 between the middle tightening plate 26 and the support base 30. Load is applied. Although the bellows is used as the pressure applying device in the present embodiment, for example, a hydraulic cylinder may be used instead.

According to the above configuration, the lower battery module group 22 includes the weight of the members stacked on the upper surface of the module group 22, that is, the middle fastening plate 26, the upper battery module group 2
1, upper tightening bellows 23, upper tightening plate 25, upper tightening bolt 28, nuts 34a to 34d and lower tightening bolt 29,
A load acts on the total weight of the lower tightening bellows 24 and the lower tightening plate 27. Surface pressure caused by these weights,
The sum of the surface pressure applied by the lower tightening bellows 24 and
Lower tightening bellows 24 so that the surface pressure required for the fuel cell is attained.
Adjust pressure.

On the other hand, in the upper battery module group 21, the total of the surface pressure generated by the total weight of the upper tightening plate 25 and the upper tightening bellows 23 and the surface pressure applied by the upper tightening bellows 23 is applied to the fuel cell. The pressure of the upper tightening bellows 23 is adjusted so that a necessary surface pressure is obtained.

As described above, since a plurality of fuel cell modules to be stacked are divided into upper and lower cell module groups 21 and 22 and fastened, the maximum surface pressure difference generated in the entire fuel cell module group is The surface pressure difference caused by the weight of the stacked battery module group unit is reduced. In the case of a large-capacity fuel cell in which the number of fuel cells is increased,
If the surface pressure difference when tightening without dividing exceeds the allowable range, the surface pressure difference can be reduced by dividing the laminated fuel cell module into two parts.

In the fuel cell stack in which the stacked battery module group which keeps the surface pressure difference within the allowable range as described above is divided into two and the tightening bellows are arranged on the upper and lower sides, the upper battery module group 21 has the middle tightening plate 26 interposed therebetween. The lower battery module group 22 is fixed on the support base 30, the support base 30 is fixed to the legs 31, and the legs 31 are fixed to the base base 33. After the lower battery module group 22 is installed on the support base 30, the upper and lower stacked battery module groups 21, 22
Does not move up and down due to actions other than thermal expansion and cell shrinkage. For example, even if the lower tightening bellows 24 expands and fails while applying the surface pressure to the lower battery module group 22 to lose the expansion force, and the lower tightening bellows 24 contracts, the upper and lower stacked battery modules The groups 21 and 22 do not change in position.

[0026]

According to the present invention, a plurality of stacked battery modules are divided into upper and lower parts, and a pressure applying device is provided in each module group to reduce a difference in tightening pressure between cells located above and below the stack. In a high-stack fuel cell stack, all the battery modules are placed on a gantry fixed to a base, and the divided upper module group is placed in the upper module.
The first pressure application device installed on the group is tightened, and the divided lower module group is configured to be tightened by the second pressure application device installed on the lower surface of the gantry. If the function of applying a predetermined compressive force to each module group is lost, especially when the lower second pressure applying device fails, all batteries are supported by the base fixed to the base base. It can prevent large damage such as collapse of modules,
It is possible to suppress the damage to a minimum, which is only a shortage of the surface pressure borne by the pressure applying device, and to improve the safety of the fuel cell stack.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a fuel cell stack according to an embodiment of the present invention.

FIG. 2 is a diagram showing a basic configuration of a battery cell.

FIG. 3 is a diagram illustrating a conventional example of a fastening structure for a highly stacked fuel cell stack.

FIG. 4 is a view showing a conventional example having a tightening structure for reducing a surface pressure difference applied to cells above and below a stack in a high-stack fuel cell stack.

FIG. 5 is a view for explaining a problem in the fastening structure shown in FIG. 4;

[Explanation of symbols]

 18 Stacked cell 19, 20 Gas header 21 Upper battery module group 21a, 21b, 21c Battery module 22 Lower battery module group 22a, 22b, 22c Battery module 23 Upper tightening bellows 24 Lower tightening bellows 25 Upper tightening plate 26 Medium tightening Plate 27 Lower tightening plate 28 Upper tightening bolt 29 Lower tightening bolt 30 Support base 31 Leg 32 Pressure vessel 33 Base base 34a, 34b, 34c, 34d Nut

────────────────────────────────────────────────── ─── Continued on the front page (56) References JP-A-6-60902 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 8/00-8/24

Claims (2)

(57) [Claims] 1. A laminated cell formed by vertically laminating a plurality of cells having a positive electrode on one surface of an electrolyte plate and a negative electrode on the other surface with a separator interposed therebetween, and provided above and below the laminated cell. In a fuel cell stack in which a plurality of battery modules each including a gas header are stacked, the plurality of battery modules are mounted on an upper surface , and the lower base is interposed via legs.
The fixed base and the plurality of battery modules are vertically
An intermediate fastening plate inserted between the divided upper module group and the lower module group, a first pressure application device installed on the upper module group to apply or remove pressure by expansion and contraction; An upper tightening plate attached to an upper portion of the pressure applying device, a connecting member hanging down around the upper module group and connecting the upper tightening plate and the intermediate tightening plate, and installed on a lower surface of the gantry; A second pressure applying device for applying or removing pressure by expansion and contraction, a lower tightening plate attached to a lower end of the second pressure applying device, and a hanging around the lower module group , the gantry and the legs. A fuel cell stack, comprising: a connecting member that connects the intermediate tightening plate and the lower tightening plate. 2. The fuel cell stack according to claim 1, wherein the first and second pressure applying devices are bellows that expand and contract with compressed gas.