KR101272588B1 - Separator gasket for fuel cell - Google Patents

Abstract

The present invention relates to a fuel cell metal separator gasket having an improved molding structure applied to the metal separator plate of a fuel cell.

The present invention can improve the molding precision of the gasket by improving the structure of the gasket formed on the metal separator plate, and can prevent the short-circuit between cells of the metal separator stack and insulation with the stack case. To provide.

The metal separator plate gasket structure of the fuel cell provided in the present invention has a structure in which the outer edge portion of the metal separator plate has a structure in which both sides of the reaction / cooling surface are wrapped and an unwound form is repeated, thereby improving molding precision of the gasket, and The short circuit between cells of the separator stack can be prevented, and insulation from the stack case can be realized.

Fuel Cell, Metal Separator, Gasket, Airtight

Description

Separator gasket for fuel cell

The present invention relates to a metal separator plate gasket for a fuel cell, and more particularly, to a metal separator plate gasket for a fuel cell having an improved forming structure of a gasket applied to a metal separator plate of a fuel cell.

In general, the operation mechanism of a fuel cell begins by oxidizing fuels such as hydrogen, natural gas, methanol, and the like at the anode to generate electrons and hydrogen ions (protons).

Hydrogen ions produced at the anode move to the cathode through the electrolyte membrane, and electrons generated at the anode are supplied to an external circuit through a conductive wire.

The hydrogen ions that reach the cathode are electrons that reach the cathode through an external circuit and

Water is combined with oxygen supplied from the outside.

Fuel cells are in the spotlight as next generation energy conversion devices with high power generation efficiency and environmental friendliness.

The fuel cell may be classified into a polymer electrolyte membrane fuel cell (PEMFC), a phosphoric acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), and a solid oxide fuel cell (SOFC) according to the type of electrolyte used.

Depending on the type of fuel cell, the operating temperature, the material of the component, and the like vary.

Among them, the PEMFC can be operated at about 80 to 120 ° C., which is a relatively low temperature as the operating temperature of the fuel cell, and can be applied as a power source for automobiles or homes because it can have a very high power density.

In the PEMFC, one of the important components that need to be improved in order to obtain a small, light and inexpensive PEMFC is a bipolar plate.

Main components of PEMFC include bipolar plates, membrane electrode assemblies (MEAs), and the like.

The MEA includes an anode where the oxidation of the fuel occurs, a cathode where the reduction of the oxidant occurs, and an electrolyte membrane located between the anode and the cathode.

The electrolyte membrane has ion conductivity to transfer hydrogen ions generated at the anode to the cathode, and has electronic insulation to electrically insulate the anode and the cathode.

As is well known in the art, a bipolar plate has a channel through which fuel and air flow, and serves as an electron conductor for electron transfer between MEAs.

Therefore, bipolar plates must be non-porous to allow fuel and oxygen to separate, must have good electrical conductivity, have sufficient thermal conductivity for temperature control of the fuel cell, and withstand the forces of clamping the fuel cell. In addition to having sufficient mechanical strength to a degree, it must have corrosion resistance against hydrogen ions.

Graphite plate is mainly used as a material of the bipolar plate of the conventional PEMFC, wherein the fuel and air flow paths are mainly formed by milling.

Graphite plate has the advantage of good electrical conductivity and poor corrosion, but the price of the graphite plate itself and the milling processing cost is a major factor in the high price of the bipolar plate.

In addition, graphite plates are fragile and therefore difficult to process to a thickness of 2 mm to 3 mm or less.

Due to the thickness of the graphite-based bipolar plate has a difficulty in reducing the size of the fuel cell stack (stack) consisting of tens to hundreds of unit cells (unit cell).

As one of the alternatives to reduce the processing cost and thickness of the bipolar plate, the material of the bipolar plate is replaced by metal.

As is well known in the art, a metal separator is a plate having a flow path for fuel or an oxidant formed on one side thereof and a flow path for cooling fluid formed on the other side thereof.

On the other hand, the fuel cell stack (Stack) is configured by stacking the membrane electrode assembly, the gas diffusion layer and the separator plate as necessary capacity, the unit cell is an assembly that is united without slipping or slipping through the device that provides the appropriate pressure from the outside It is.

Upper and lower portions of the membrane electrode assembly and the separator are formed with a plurality of manifolds for supplying or discharging hydrogen and air required for the reaction and cooling water for cooling the reaction heat, respectively. The pipe is supplied to the electrode through a gas flow path formed in the separator plate of each unit cell through the manifold of the separator plate.

In this case, sealing means for preventing the leakage of hydrogen, air and cooling water from each reaction manifold and a reaction zone in which hydrogen and air react. A fuel cell is frequently operated and stopped repeatedly due to its characteristics. Since heat is generated by chemical reactions, expansion and contraction occur frequently.

Therefore, the sealing structure for fuel cell must maintain its sealing even in the case of frequent expansion and contraction, and stress distribution in each component of the fuel cell should be as uniform as possible in the expansion and contraction process to prevent breakage due to fatigue. Should be

For this purpose a gasket is arranged around the electrode and manifold.

The gasket mainly uses a rubber material having elasticity as a silicone-based, fluorine-based or olefin-based material having excellent elastic restoring force and soft properties.

The gasket manufacturing method of the rubber material includes a method of making an O-ring using a mold and a method of manufacturing using a dispenser.

The metal separation plate is manufactured by a molding method such as stamping using a metal thin plate having a thickness of 0.1 to 0.2 mm, and the sealing cannot be maintained due to local deformation unless the uniform surface pressure is maintained during lamination.

To prevent this, a complicated sealing structure is intended to improve stack stackability.

Unlike graphite, gaskets applied to metal separators cannot be grooved for positioning gaskets, and since it is difficult to bond solid rubber materials to metal surfaces, liquid rubber materials are applied and injected to harden on metal separator surfaces. The method of / gluing is generally applied.

Here, the gasket 10 positioned at the outer edge of the metal separator plate may be formed independently of the reaction surface / cooling surface (a), or the reaction surface / of the separator plate 11, as shown in FIG. 3. The form (a) etc. which wrap the cooling surface together are used (Japanese Patent Laid-Open No. 07-065847, Korean Registered Room No. 0383221, Japanese Laid-Open Patent No. 2002-231264).

The shape of (a) has a sharp outer edge of the thin metal material, which may injure the worker, and when the stack is stacked, the outer edge of the stack is densely present in the state of metal lamination, and there is a risk of short circuit between cells due to metal fragments. Very large.

In addition, unlike the graphite separator, the edge of the metal separator may be deformed due to a small impact when handled, and thus a high risk of short circuit between cells may be obtained.

Form (b) can be used to compensate for the above disadvantages.

However, the gasket forming die 12 cannot hold the left and right metal surfaces of the gasket as in the case of forming the gasket of (c), but only one side thereof (d).

In general, it is difficult to completely eliminate the distortion caused by the spring-back phenomenon during the press molding of a large-area metal separator plate in which a complicated flow path is formed (deformation may be present on the edge part), and the handling of the metal separator plate is intended for the outer edge part due to the impact. (B) If the gasket is formed in an unformed form, the gasket height of the reaction / cooling surface of the metal separator plate may be different from the design value when the gasket is formed (e), and the compression length of the gasket may be different, thereby preventing the stack from being sealed. (Typically, the gasket shrinkage height is very small, less than 0.1 mm from the original height, when fastening the fuel cell stack).

In addition, deformation of the separator may occur due to the injection pressure of the liquid rubber.

Accordingly, the present invention has been made in view of the above, and it is possible to improve the molding precision of the gasket by improving the structure of the gasket formed on the metal separator plate, and to prevent the short circuit between cells of the metal separator stack and the stack case and An object of the present invention is to provide a metal separator gasket for a fuel cell capable of realizing the isolation of the fuel cell.

Metal separator plate gasket according to an embodiment of the present invention for achieving the above object is in the form of surrounding the reaction surface / cooling surface of the outer edge portion of the metal separator plate rubber gaskets applied for airtightness in the metal separator stack While bonding, the exposed portion of each surface may be repeatedly formed without enclosing the reaction surface / cooling surface along the edge portion.

Here, the length ratio of the portion surrounding the edge portion and the portion not wrapped by the rubber gasket may be the same, or the portion that the wrapping portion is long, or the portion that does not wrap the long form.

On the other hand, the metal separator plate gasket according to another embodiment of the present invention for achieving the above object is the metal separator plate gasket is a rubber gasket for applying the airtight in the metal separator stack or the manifold portion of the inner region of the metal separator plate The edge portion of the flow path portion is bonded in the form of wrapping the reaction surface / cooling surface together, it may be made in the form that the exposed portion of each surface repeatedly appears without wrapping the reaction surface / cooling surface along the edge portion.

Here, it is preferable that the length ratio of the portion surrounding the edge portion and the portion not wrapped with the rubber gasket is the same, or the length of the portion wrapped is long, or the portion not wrapped is long.

As described above, the present invention has the following effects.

First, the molding precision of the fuel cell metal separator gasket can be improved.

Usually, the metal separation plate is formed by molding a thin plate having a thickness of about 0.1 to 0.2 mm, and when stacking a vehicle, 400 or more metal separation plates should be stacked.

When injection molding a liquid rubber gasket on the outer edge of the metal separator plate, the mold can be partially introduced to stably support the right and left sides of the gasket section, thereby improving the gasket molding precision.

Second, it is possible to realize a short circuit prevention between the cells of the fuel cell metal separator stack and insulation with the stack enclosure.

By partially introducing a structure that surrounds the outer edge of the metal separator plate with a gasket to keep the cell gap of the stack constant, short-circuit between cells due to local deformation of the unintentional separator plate can be prevented.

In addition, since the outer surface of the stack is covered with a rubber material, it is possible to insulate from the stack case, so that no additional insulation structure is introduced outside the stack or inside the stack case.

Hereinafter, the structure of the metal separator gasket according to various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view showing a configuration of a metal separator stack module to which a metal separator gasket according to an embodiment of the present invention is applied, and FIG. 2 is a plan view illustrating a metal separator gasket according to an embodiment of the present invention.

As shown in FIG. 1, the stacking order of the module and the metal separator 11 of the stack to which the metal separator 11 is applied is shown.

The fuel cell stack is formed by stacking a thin metal separator plate 11, a gasket 10, a MEA 14, a gas diffusion layer, and the like, and the metal separator plates 11 stacked as such to form an assembly form. The gasket 10, the MEA 14, and the like are finished by double-sided end plates 15 to complete one fuel cell stack unit.

As shown in FIG. 2, the shape and the gasket structure of the metal separator 11 are shown here.

The metal separator 11 includes manifolds that serve as reaction hydrogen, air, and cooling water inlet and outlet passages, and the airtightness between the cell separator and anode separator / cathode separator (coolant passage) based on MEA. A gasket 10 for holding is attached (adhered) to both sides of the outer edge portion of the metal separation plate 11.

Since there are many difficulties in bonding a solid gasket to a metal surface, an injection gasket mainly using a liquid rubber material is applied to the metal separator 11 at this time.

In this case, the cross-sectional shape of the gasket of the outer edge portion of the metal separator plate may be formed to surround both sides of the metal separator plate.

In particular, the rubber gasket applied to maintain the airtightness in the metal separator stack is based on the form of the both sides of the reaction surface / cooling surface of the outer edge of the metal separator plate, and the form in which the reaction surface / cooling surface remains as it is without wrapping. It may be formed into a structure represented by.

As described above, the structure of the gasket can take advantage of preventing the short circuit between the cells and the stack case, while taking advantage of the gasket forming mold to stably hold the left and right metal surfaces with the gasket forming mold. Do it.

To this end, the metal separator plate gasket is partially wrapped around the outer edge of the metal separator plate, and the portion is not wrapped.

That is, when bonding the outer edge reaction surface / cooling surface of the metal separator plate 11 in the form of wrapping the rubber gasket together, some of the entire sections that are covered do not cover the reaction surface / cooling surface, but the exposed portion of each surface For example, the thin plate exposed portion 13 may be formed.

At this time, the unwrapped form, that is, the thin plate exposed portion 13 may repeatedly appear at regular intervals along the rim, and the unwrapped portion becomes the support of the gasket forming mold.

Accordingly, while having the advantage of protecting the edges of the metal separator plate, it is possible to increase the gasket molding precision by securing the molding die support.

In addition, the portion wrapped with the rubber gasket and the portion not wrapped may be set at a predetermined ratio in consideration of the possibility of deformation or structural safety.

That is, the length and ratio of the portion (m) and the portion (n) surrounding the outer edge of the metal separator plate are the overall length of the metal separator plate, the possibility of deformation and structural stability according to the thickness of the metal separator plate (gasket mold support) It should be decided by considering.

It is ideal to repeat the length of the wrapped portion (m) and the unwrapped portion (n) shortly, but since it is difficult to manufacture a gasket mold and may impair the flowability of the liquid rubber, it is preferable to select and set it appropriately for each condition. .

At this time, the selection may be made by equalizing the length ratio between the portion surrounding the edge portion and the portion not wrapped, lengthening the portion wrapped, or lengthening the portion not wrapped.

Herein, when m <n, gasket molding dimensional precision is improved, and when m> n, short circuit prevention and insulation are improved.

On the other hand, the gasket structure as described above, that is, the structure is repeated in the wrapped portion and the unwrapped portion can be applied to the gasket shape of the hydrogen, air, cooling water flow path in addition to the outer edge of the metal separator plate.

For example, a rubber gasket may be basically bonded together to cover the rim of the manifold portion or the flow path portion of the inner side of the metal separator plate or the flow side of the flow path portion. It may include a form in which the exposed portion of each side repeatedly appears without wrapping.

1 is a perspective view showing a configuration of a metal separator stack module to which a metal separator gasket is applied according to an embodiment of the present invention;

Figure 2 is a plan view showing a metal separator gasket according to an embodiment of the present invention

3 is a schematic view showing a conventional metal separator gasket structure

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

10: gasket 11: metal separator

12: mold 13: thin plate exposed portion

14: MEA 15: end plate

Claims (8)

A rubber gasket applied for airtightness in the metal separator stack is bonded in the form of wrapping the outer edge reaction surface / cooling surface of the metal separator plate together with each other without enclosing the reaction surface / cooling surface along the edge portion. A metal separator plate gasket for a fuel cell, characterized in that the exposed portion is made repeatedly appear. The method of claim 1, wherein the length ratio of the portion surrounding the edge portion and the non-wrapped portion of the rubber gasket, the metal separator plate gasket for a fuel cell. The method of claim 1, wherein the length ratio of the portion surrounding the rim portion and the non-wrapped portion of the rubber gasket, the portion of the fuel cell metal separator plate gasket characterized in that the long. The method of claim 1, wherein the ratio of the length portion of the portion surrounding the rim portion and the non-wrapped portion of the rubber gasket, the portion of the fuel cell metal separator plate gasket characterized in that the long. The metal separator gasket is bonded to a rubber gasket applied for airtightness in the metal separator stack in such a manner as to enclose the edge reaction surface / cooling surface of the manifold portion or the flow path portion of the inner region of the metal separator plate, A metal separator plate gasket for a fuel cell, characterized in that the exposed portion of each surface is repeatedly formed without enclosing the reaction surface / cooling surface. The method of claim 5, wherein the ratio of the length of the portion surrounding the rim portion and the non-wrapped portion of the rubber gasket, the metal separator plate gasket for a fuel cell. The metal separator plate gasket of claim 5, wherein a length ratio between the portion surrounding the edge portion and the portion not wrapping the rubber gasket is long. The method of claim 5, wherein the ratio of the length ratio of the portion surrounding the edge portion and the non-wrapped portion of the rubber gasket, the portion that does not wrap the fuel cell metal separator plate gasket.

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