KR100710274B1 - Fastening Structure of Fuel Cell Stack - Google Patents

Abstract

The present invention relates to a fastening structure of a fuel cell stack, and more particularly to a fastening structure of a fuel cell stack for fastening a fuel cell stack in which a plurality of membrane-electrode assemblies are stacked between a plurality of separator plates.

In the conventional fuel cell stack, the squeezing structure cannot maintain uniform surface pressure because local pressure is applied at a specific position of the end plate, resulting in breakage of the separator plate and damage of the membrane-electrode assembly, and each nut is individually There was an inconvenience to be assembled.

The present invention has been made to solve this problem, the center gear as a drive gear in the center of the end plate, and designed the fastening structure to function as a driven gear by engaging the connection screw which is a nut with the center gear. . Therefore, by rotating only the center gear, the remaining screw gears engaged with and engaged with each other also rotate together to maintain a uniform surface pressure.

Fuel Cell, MEA, Separator, Surface Pressure, Uniform, Gear, Bolt, Nut

Description

Fastening structure of fuel cell stack {FASTENING STRUCTURE OF A FUEL CELL STACK}

1 is a perspective view showing an example of a fastening structure of a conventional fuel cell stack.

2 is a view showing a cross section of an example of a fastening structure of a conventional fuel cell stack.

3 (a) and 3 (b) are diagrams showing an arrangement example of nuts provided on the end plate of the conventional fuel cell stack.

4 is a view schematically showing an example of the configuration of the center gear and the screw gear on the end plate according to the present invention.

5 is a perspective view of FIG. 4.

6 (a) to 6 (c) are diagrams showing an example of connecting the center gear and the screw gear of the present invention.

<Description of the symbols for the main parts of the drawings>

1: end plate

2, 3: through hole

4: Bolt

5: End Plate Cavity

6: Nut, Screw Gear

7: separator

8: membrane-electrode assembly

10: center gear

11: wrench connection

100: fuel cell stack

※ The accompanying drawings reveal that they are illustrated as a reference to enhance the understanding of the technical idea of the present invention, and adds that the scope of the present invention is not limited to the specific shape of the drawings.

The present invention relates to a fastening structure of a fuel cell stack, and more particularly to a fastening structure of a fuel cell stack for fastening a fuel cell stack in which a plurality of membrane-electrode assemblies are stacked between a plurality of separator plates.

Fuel cell is a high-efficiency, pollution-free and noise-free advanced power generation technology that directly converts chemical fuels such as methanol and hydrogen into electrical energy, and has more than 1.5 times more energy conversion efficiency than existing internal combustion engines. It has the advantage of not emitting at all. In particular, the polymer electrolyte fuel cell is a high output fuel cell having a higher current density than other types of fuel cells. The polymer electrolyte fuel cell operates at a temperature of less than 100 ° C., and has a simple structure and is suitable as a power source of a vehicle. It has fast start-up and response characteristics and excellent durability, and has the advantage of being easy to transport and store fuel as it can use methanol or natural gas in addition to hydrogen.

The fuel cell is composed of an anode in which hydrogen ions and electrons are generated by the oxidation of hydrogen, a cathode in which water is generated by the reduction of air, and an electrolyte in which hydrogen ions generated from the hydrogen electrode are delivered to the cathode. The type of the electrolyte layer disposed between the anode and the cathode is called a membrane-electrode assembly (MEA), and the membrane-electrode assembly is disposed between the separator and the separator to form a unit cell.

The theoretical voltage of one MEA is about 1.2V and in actual operation it is less than 1V. Therefore, to produce power enough to be used as a vehicle or mobile power source, a plurality of MEAs must be stacked to form a fuel cell stack (STACK). Typically, 10, 20, 50 or 100 or more MEAs are stacked in one fuel cell stack.

The separation plate (bipolar plate) is mainly made of graphite-polymer composite material, and is engraved with the gas flow path for chemical reaction in the electrode, through which the gas flows and moves to the gas diffusion layer of the electrode, An electrochemical reaction occurs in the catalyst layer of.

When the membrane-electrode assembly is stacked between the separator and the separator, the gap is sealed using a gasket to prevent the supply gas from leaking out. The electric current generated by the electrochemical reaction flows through the separator, which is an electrical conductor, and finally, electricity is extracted from the separator and used. In addition, the water produced by the electrochemical reaction is discharged to the outside through the gas flow path of the separator plate, but some of it is also used to help the electrochemical reaction.

In such a fuel cell, there are various factors that improve efficiency, such as a catalyst, ionomer, carbon support, electrolyte, and separator used for the electrode, but the fuel cell stack is separated because a plurality of MEAs are stacked. Uniform surface pressure between plate and separator is considered to be a very important factor.

If the surface pressure is too small, the contact resistance between the separator and the electrode support and the contact resistance between the membrane and the electrolyte increase, which hinders the flow of current. On the contrary, if the surface pressure is too high, it may be damaged due to the characteristics of the graphite-polymer composite, which is the material of the separator, and the gas diffusion layer of the electrode may be compressed so that the fuel does not move, thereby reducing the efficiency in the material transfer region of the fuel cell. do. Moreover, when stacking multiple separators and membrane-electrode assemblies, as the number of stacks increases, the internal resistance increases and fatal damage to the separator and membrane-electrode assemblies reduces the performance of the entire fuel cell stack. In severe cases, this can lead to stack breakage and fuel leakage.

Therefore, finding the optimum surface pressure that can maximize the efficiency of the fuel cell contributes to the improvement of performance, and it is possible to prevent damage to the separator and the membrane-electrode assembly by fastening at a uniform surface pressure.

1 illustrates an example of a structure of a fuel cell stack 100 which has been generally used. A plurality of separation plates and a collection of MEAs are stacked between end plates 1 positioned at both ends of the fuel cell stack 100, and bolts 4 having a predetermined length pass through the plurality of pre-prepared through holes 2. Both ends of the bolt 4 are tightly fastened by the nut 6 in the through hole 3 of the cavity 5 of the end plate 1. These bolts 4 serve to apply a constant surface pressure to the fuel cell stack 100.

2 shows a cross section of the conventional fuel cell stack 100 as described above. The membrane-electrode assembly (MEA) 8 of the fuel cell stack 100 is stacked between the separators 7 as a portion where the electrochemical reaction of the fuel cell occurs. The separation plate (bipolar plate) 7 is provided with a flow path (gas flow path) (not shown) for collecting current generated in the MEA, fuel on one side, and air on the other side. Through this flow path, fuel (H ₂ ) is used as an anode on one side of the separator plate 7. Gas), and air flows as the reducing electrode on the other side. The end plates 1 are configured at both ends of the stack to maintain a specific surface pressure of the stack in which the separator 7 and the membrane-electrode assembly 8 are stacked. The surface pressure exerted by both endplates 1 on the stack 100 is achieved by elongated bolts 4 placed between both endplates 1 and serving as supports, which bolts 4 comprise both endplates 1. ) Is tightened by the nut 6 prepared in advance. Through this, the surface pressures of both end plates 1 of the stacked fuel cell stack 100 are maintained.

3 shows an arrangement example of the nut 6 on the end plate. For example, four nuts may be provided or eight nuts may be provided. Although not shown, three, five, six, seven, or more may be used. Since the nuts 6 are engaged with the bolts 4, the number of the nuts 6 is equal to the bolts 4 penetrating the stack.

The fastening structure of the conventional fuel cell stack 100 as described above has a problem in that a non-uniform force acts on the separating plate and the MEA at the same time by tightening a plurality of bolts 4 sequentially. In other words, if a plurality of bolts are tightened separately, the force is applied only to the tightening part, which increases the risk of damage to the MEA. Damage to the MEA causes the gas diffusion layer of the electrode constituting the MEA to collapse, resulting in poor fuel delivery and reduced battery performance. In addition, if each bolt is tightened separately, the force is applied only at the joining part, thereby causing damage to the separator.

On the other hand, if the stack fastening force is not uniform, there is a serious problem that can create a gap between the separator and the MEA resulting in an explosion due to the leakage of fuel. Furthermore, there is a problem that the stack assembly process is complicated and takes a long time because each bolt is tightened.

The present invention is to provide a unique fastening structure for solving the above problems.

An object of the present invention is to provide a means capable of applying a uniform surface pressure from the end plate to the fuel cell stack. Through this, the efficiency of the fuel cell is to be improved.

In addition, while applying a uniform surface pressure, there is another object of the present invention to increase the stability in the stack fastening process and to simplify the fastening assembly process.

Further objects and advantages of the present invention will be described below, which are further described by means of the disclosure in the claims and the disclosure of the embodiments thereof, as well as means and combinations within the range that can be easily deduced therefrom. It will be covered in a wide range.

In order to achieve the above object, the present invention is a unit cell comprising a membrane-electrode assembly and a separator plate or a fuel cell stack in which at least two unit cells are stacked, a pair of end plates is the unit cell Or by applying surface pressure to both ends of the fuel cell stack,

A plurality of connecting bolts at both ends of which are fixed at the pair of end plates to fasten the pair of end plates to attract the pair of end plates; A plurality of screw gears on the end plate for accommodating the ends of the connecting bolts and fixing the connecting bolts to the end plates by rotational force; And

The connecting bolts are provided on an end plate and are connected to the screw gears in contact with each other, and are connected to an external torque wrench to rotate the force evenly to the plurality of screw gears when rotating by the action of the torque wrench. It characterized in that it comprises a; a center gear to be automatically engaged with the screw gear forming a.

In the fastening structure of the fuel cell stack of the present invention, the center gear is located in the center portion of the end plate,

At least three screw gears may be provided, and each of the screw gears may have a structure in which the screw gears rotate in engagement with the center gear.

In addition, it can be understood that the center gear is fixed on the end plate or located on the end plate only when the screw gear and the connecting bolt are fastened.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, it is already known to those skilled in the art, such as known functions or known configurations, such as the principle of electrochemical reaction of fuel cells, the specific functions of each component of the fuel cell stack, and the mechanical principle of gear driving. If it is determined that the gist of the present invention may be unnecessarily obscured, the detailed description thereof will be omitted.

4 schematically illustrates the basic concept of the fuel cell stack fastening structure of the present invention. The end plate is provided with a plurality of screw gears 6 for fastening the fuel cell stack, and the screw gears 6 are coupled with connecting bolts that pull and fix both end plates.

In the fuel cell stack fastening structure of the present invention, the screw gears 6 also rotate together by the rotation of the gear in the center, and at this time, the connecting bolt is driven by the rotational force acting on the screw gears 6. It is to be coupled to the screw gear (6) for receiving. To this end, after the center gear 10 is positioned as a driving gear in the center portion of the end plate, a plurality of screw gears 6 (for example, 3 to 10) are connected to the center gear 10.

On the other hand, a torque wrench (not shown) for transmitting a rotational driving force to the external center gear 10 is connected via the wrench connection portion 11 of the center gear 10. The rotational driving force is applied to the center gear 10 through the torque wrench, and the rotational force of the center gear 10 generated at this time is transmitted to the screw gear 6 which is connected to be engaged. At this time, by maintaining the diameter of the plurality of screw gear (6) as the driven gear evenly, and by maintaining the physical contact of the portion engaged with the center gear evenly, the screw gear (6) applied by the rotation of the center gear (10) Since the rotational torque of these can be maintained evenly, it is possible to apply uniform pressure to the connecting bolts that eventually engage with the screw gears 6. This produces a uniform surface pressure between the pair of end plates facing each other.

Of course, the center gear 10 as the driving gear and the screw gear 6 as the driven gear form only the contacts, so that the rotational force is difficult to be transmitted, and the connecting bolt cannot be firmly fastened to the screw gear 6. It is necessary to study how to ensure that all connecting bolts can be firmly tightened to the screw gear at once, while maintaining the surface pressure applied to the stack uniformly. To this end, a drive gear is provided in the center of the end plate, and all the screw gears are brought into contact with the drive gear, so that when the drive gear rotates, the screw gears in contact with the drive gear can rotate in conjunction with each other.

To this end, screw gears should act as driven gears, preferably with teeth (like teeth) made on the heads of the screw gears.

4 and 5 present such a specific solution. The outer circumferential surface of the circular center gear 10 located on the end plate is provided with teeth in an uneven shape. The outer circumferential surface of the screw gear 6, which is the driven gear, is also provided with teeth of irregularities. The screw gear (6) is present in a plurality around the center gear 10 is all meshed with the outer peripheral surface of the center gear (10).

Meanwhile, the number of screw gears means the number of connecting bolts. In order to maintain a stable stack stack of a plurality of separators and membrane-electrode assemblies, connecting bolts are provided to pull and support a pair of end plates, and two or three connecting bolts are provided. It is preferable. In the case of a small fuel cell stack, even if two connecting bolts are provided, proper surface pressure may be maintained and stability may be secured. However, at least three or more fuel cell stacks may be destroyed because the number of stacked fuel cells increases and the size thereof increases. A connection bolt will be required. Of course, four or more connecting bolts are preferable to most stably support the stack of fuel cells and to apply a uniform surface pressure above a certain pressure.

6 shows various embodiments of the screw gear 6 connected with the center gear 10. 6 (a) shows eight screw gears (6), FIG. 6 (b) shows four screw gears (6), and FIG. 6 (c) shows six screw gears (6) with a center gear (10). Connected by gears. The screw gears 6 of FIG. 6 are fastened to 8, 4, and 6 connecting bolts, respectively, by rotation of the center gear 10.

In the above embodiment, the center gear 10 is mounted on the end plate, and when the fuel cell stack is made, an external torque wrench is connected to the wrench connecting portion 11 of the center gear 10 to rotate the center gear 10. , Screw gear (6) is to be securely fastened to the connecting bolt. In this case, the center gear 10 is fixed on the end plate. However, in another embodiment, the center gear 10 is configured detachably. For example, the center gear 10 is positioned and mounted on the end plate only when the screw gear and the connection bolt are fastened, and then the center gear 10 is connected to the torque wrench to rotate. Through this, the screw gears and the connecting bolts are fastened by a uniform rotational torque, and then separate the center gear 10 from the end plate.

The fuel cell stack fastening structure of the present invention is generally applied to a stack of fuel cells in which a plurality of unit cells are stacked to form a stack. However, even in a unit cell having one MEA, it is a fact that uniform surface pressure must be maintained by the end plates at both ends. Therefore, the configuration of the present invention described above is applied to the fastening structure of the unit cell as well as the conventional fuel cell stack.

It is noted that the above embodiments are only for illustrating the present invention, and the protection scope of the present invention is not limited by these examples. In particular, the scope of protection of the present invention is limited to the size, rotation speed, quantitative force data applied to the gears, the internal configuration and performance of the fuel cell stack itself, and the dimensions, shapes and numbers of the other components. It should be noted that the scope of protection of the present invention cannot be limited by obvious changes or substitutions in the technical field to which the present invention belongs.

According to the present invention described above,

Rotating the center gear located in the center of the end plate has the advantage that the screw gear connected to it to rotate at the same time to tighten the stack. Through this, it is possible to reduce the damage of the separator plate or the damage of the MEA caused by the local pressure non-uniformity caused by tightening separately before. This effect prevents the fuel cell from degrading and contributes to its efficiency.

In addition, the process of tightening each of the plurality of bolts and nuts separately, according to the present invention, since only one of the center gear is now required to turn, there is an effect that can simplify the assembly process for fastening the stack.

Claims (3)

In a unit cell comprising a membrane-electrode assembly and a separator or a stack of two or more unit cells, a pair of end plates are subjected to surface pressure at both ends of the unit cell or the fuel cell stack. , A plurality of connecting bolts whose ends are fixed at the pair of end plates to fasten the pair of end plates to draw; A plurality of screw gears on the end plate for accommodating the ends of the connecting bolts and fixing the connecting bolts to the end plates by rotational force; And It is provided on the end plate, and located in the center of the screw gears and all the mesh gears in contact with each other, when connected to the external torque wrench and rotated by the action of the torque wrench, evenly the rotational force to the plurality of the screw gear And a center gear for automatically coupling the connecting bolts to the pair of screw gears. The method of claim 1, The center gear is located in the central portion of the end plate, The screw gear is provided with at least three, the fastening structure of the fuel cell stack, characterized in that having a structure to rotate in engagement with each of the center gear around the center gear. The method of claim 1, The center gear is fastened on the end plate or the fastening structure of the fuel cell stack, characterized in that located on the end plate to rotate the screw gear only when fastening the screw gear and the connecting bolt.

Images