JP7685396B2 - Manufacturing method of gasket - Google Patents

Description

The present invention relates to a method for manufacturing a gasket.

Conventionally, a method is known in which a gasket with a flat surface is manufactured by screen printing on a substrate such as a separator provided in a fuel cell. It is known that in screen printing, a phenomenon occurs in which the thickness is thin in the center in the short direction and thick near both sides in the width direction (called the saddle phenomenon). When this phenomenon occurs, there is a risk of a decrease in sealing performance.

Japanese Patent Application Publication No. 6-349663 Japanese Patent Application Publication No. 8-264374 JP 2020-138514 A JP 2021-32372 A

The object of the present invention is to provide a method for manufacturing a gasket that can make the gasket thickness uniform.

The present invention employs the following measures to solve the above problems.

That is, the method for producing a gasket of the present invention is as follows:
a first step of forming a first thin film layer on the substrate by screen printing using a first screen plate having a first support portion in contact with a surface of the substrate and disposed along both sides of a region where a gasket is to be formed, and a first screen supported on the first support portion;
a second step of heating the first thin film layer to promote crosslinking after the first step;
a third step of forming a second thin film layer on the substrate by screen printing so as to cover the first thin film layer using a second screen plate having a second support portion arranged along both sides of the first thin film layer and in contact with the substrate surface, and a second screen supported on the second support portion, after the second step;
The thickness of the second support portion is less than or equal to the thickness of the thickest portion near both sides of the first thin film layer in the width direction, and the width between opposing surfaces of the second support portion provided on both sides of the first thin film layer is greater than or equal to the width of the first thin film layer.

According to the present invention, the first thin film layer has a phenomenon in which the thickness is thin in the center in the short direction and thick near both sides in the width direction. However, after the shape of the first thin film layer is stabilized in the second process, a second thin film layer is formed in the third process so as to cover the first thin film layer using the second screen plate configured as described above. As a result, the thin part in the center in the short direction of the first thin film layer and both sides of the thick part near both sides in the width direction are covered by the second thin film layer.

In the second step, the crosslinking of the first thin film layer should be allowed to proceed to a degree that does not completely harden the first thin film layer and does not lose its shape.

The thickness of the second support portion should be set to be at least 0.01 mm thinner than the thickest portions near both sides of the first thin film layer in the width direction.

The width between the opposing surfaces of the second support parts provided on both sides of the first thin film layer should be set to be at least 0.05 mm wider than the width of the first thin film layer.

The above configurations may be combined as much as possible.

As explained above, the present invention makes it possible to make the gasket thickness uniform.

FIG. 1 is a cross-sectional view of a sealing structure according to an embodiment of the present invention. FIG. 2 is a plan view of a gasket according to an embodiment of the present invention. FIG. 3 is a process diagram of the method for producing a gasket according to an embodiment of the present invention. FIG. 4 is a manufacturing process diagram of the method for manufacturing a gasket according to the embodiment of the present invention.

The following describes in detail the embodiments of the present invention with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, and relative positions of the components described in the embodiments are not intended to limit the scope of the present invention.

(Example)
A method for manufacturing a gasket according to an embodiment of the present invention will be described with reference to Figures 1 to 4. In this embodiment, a case in which a gasket is provided on a separator serving as a base material in a fuel cell will be described.

<Sealed structure>
The sealing structure according to the present embodiment will be described with reference to FIG. 1. FIG. 1 is a cross-sectional view of the sealing structure according to the embodiment of the present invention, and more specifically, shows a part of the cross-sectional view of a fuel cell. The fuel cell 10 is configured as a cell stack consisting of a plurality of unit cells. The unit cell is configured of an MEA (Membrane Electrode Assembly) 100 and a pair of separators 200 provided on both sides of the MEA 100. The MEA 100 includes an electrolyte membrane 110 and a pair of gas diffusion layers 120 provided on both sides of the electrolyte membrane 110. The separator 200 as a substrate is a plate-shaped member made of a metal, a carbon material, or the like. A flow path 201 through which a fuel gas, an oxidizing gas, or the like flows is formed in the separator 200.

The single cell is provided with a gasket 210 made of a rubber-like elastic material to prevent the fuel gas, oxidant gas, etc. from leaking to the outside. Suitable examples of the material for the gasket 210 include silicone rubber (VMQ), fluororubber (FKM), EPDM, and butyl rubber. The gasket 210 seals the gap between the separator 200 and the electrolyte membrane 110.

<Gasket>
The gasket 210 will be described in more detail with reference to Figures 1 and 2. Figure 2 is a plan view of the gasket 210 provided on the separator 200 according to the embodiment of the present invention. The cross-sectional view of the separator 200 and the gasket 210 in Figure 1 corresponds to the cross-sectional view taken along line AA in Figure 2.

The separator 200 has a flow path 201 formed on the surface of the separator 200 and a number of manifolds 202. The manifolds 202 are provided to distribute fuel gas, oxidizer gas, coolant, etc. to each cell.

To prevent the fuel gas and the like from leaking to the outside, gaskets 210 are provided integrally with the separator 200 around the area where the flow passage 201 is formed and around the manifold 202. That is, the gaskets 210 are provided integrally with the separator 200 so as to surround the areas to be sealed (the areas where the flow passage 201 is formed and the area where the manifold 202 is provided). In FIG. 2, the areas where the gaskets 210 are provided are indicated by thick lines. In this embodiment, the gaskets 210 are provided on both sides of the separator 200.

<Manufacturing method of gasket>
In particular, the manufacturing method of the gasket 210 according to this embodiment will be described with reference to Figures 3 and 4. Figures 3 and 4 are manufacturing process diagrams of the manufacturing method of the gasket according to the embodiment of the present invention, and each member is shown in a cross-sectional view.

The gasket 210 according to this embodiment is formed on the surface of the separator 200 by screen printing. The manufacturing method according to this embodiment includes a printing process (first process) using a first screen print, a heating process (second process), and a printing process (third process) using a second screen print. The steps are explained below in order.

<<First step>>
3 is an explanatory diagram of the first step. In the first step, screen printing is performed using a first screen plate 510. The first screen plate 510 includes a first support portion (mask) 512 arranged so as to be in contact with the surface of the separator 200, which is a base material, and a mesh-like first screen 511 supported on the first support portion 512. The first support portion 512 is provided so as to be along both sides of the region in which the gasket 210 is to be formed, which is indicated by a thick line in FIG. 2. The first support portion 512 is also made of an emulsion (hardened emulsion).

Using the first screen plate 510 configured in this manner, the first thin film layer 211 is formed on the surface of the separator 200 by screen printing. In screen printing, the first screen plate 510 is first placed on the separator 200 so that the first support portion 512 is in contact with the surface of the separator 200. In this state, the gasket material 250 is supplied to the surface side of the first screen plate 510 (the surface side of the first screen 511) (see FIG. 3(a)). Then, the squeegee 600 moves so as to slide on the surface of the first screen 511 while being pressed against the separator 200 (moves to the right in the figure).

As a result, a portion of the gasket material 250 pushed in by the squeegee 600 passes through the mesh-like first screen 511 and is pushed out onto the surface of the separator 200 (see FIG. 3(b)). The tip of the squeegee 600 moves from one side to the other side of the first support parts 512 provided on both sides of the region where the gasket 210 is to be formed, so that the gasket material 250 is embedded in the entire region between the opposing surfaces of the first support part 512 on one side and the first support part 512 on the other side. The first screen plate 510 is then removed, and the first thin film layer 211 is formed on the surface of the separator 200 (see FIG. 3(c)).

The first thin film layer 211 formed as described above has a thin thickness in the center in the short side direction (width direction) and a thick thickness near both sides in the width direction due to the so-called saddle phenomenon. For convenience, the thickness of the thickest part near both sides in the width direction of the first thin film layer 211 is defined as H11, and the thickness of the flat part in the center of the first thin film layer 211 is defined as H12. In addition, the maximum width of the first thin film layer 211 (the width of the part in contact with the surface of the separator 200) is defined as W1.

<<Second process>>
After the first thin film layer 211 is formed in the first step, the first thin film layer 211 is heated. Various known techniques can be used as the heating method. This heating causes crosslinking of the first thin film layer 211 to proceed. However, in this heating step, it is preferable not to completely harden the first thin film layer 211, but to cause crosslinking of the first thin film layer to proceed to an extent that the shape of the first thin film layer is not distorted. This stabilizes the shape of the first thin film layer 211.

<<Third step>>
4 is an explanatory diagram of the third step. In the third step, screen printing is performed using a second screen plate 520. The second screen plate 520 includes a second support portion (mask) 522 arranged along both sides of the first thin film layer 211 and in contact with the surface of the separator 200, and a mesh-like second screen 521 supported on the second support portion 522. The second support portion 522 is also provided along both sides of the region where the gasket 210 is to be formed, which is indicated by a thick line in FIG. 2. The second support portion 522 is also made of an emulsion (hardened emulsion).

Using the second screen plate 520 configured in this manner, the second thin film layer 212 is formed on the surface of the separator 200 by screen printing so as to cover the first thin film layer 211. In screen printing, the second screen plate 520 is first placed on the separator 200 so that the second support parts 522 are in contact with the surface of the separator 200 on both sides of the first thin film layer 211. In this state, the gasket material 250 is supplied to the surface side of the second screen plate 520 (the surface side of the second screen 521) (see FIG. 4(a)). Then, the squeegee 600 moves so as to slide on the surface of the second screen 521 while being pressed against the separator 200 (moves to the right in the figure).

As a result, a portion of the gasket material 250 pushed in by the squeegee 600 passes through the mesh-like second screen 521 and is pushed out toward the surface of the first thin film layer 211 (see FIG. 4(b)). As the tip of the squeegee 600 moves from one side to the other side of the second support parts 522 provided on both sides of the first thin film layer 211, the gasket material 250 is embedded in the area between the opposing surfaces of the second support part 522 on one side and the second support part 522 on the other side, excluding the first thin film layer 211. Thereafter, the second screen plate 520 is removed, and the second thin film layer 212 is formed to cover the first thin film layer 211 (see FIG. 4(c)).

Here, the thickness H20 of the second support portion 522 in the second screen plate 520 is set to be equal to or less than the thickness H11 described above near both sides of the first thin film layer 211 in the width direction. In addition, the width W2 between the opposing surfaces of the second support portion 522 provided on both sides of the first thin film layer 211 is set to be equal to or greater than the width W1 of the first thin film layer 211.

The second screen plate 520 configured as described above is used to form the second thin film layer 212 so as to cover the first thin film layer 211. As a result, the second thin film layer 212 covers the thin central portion in the short direction of the first thin film layer 211 and both sides of the thick portions near both sides in the width direction.

After the second thin film layer 212 is formed in the third step, the first thin film layer 211 and the second thin film layer 212 are heated. Various known techniques can be used for the heating method. The first thin film layer 211 and the second thin film layer 212 are hardened by crosslinking due to this heating. In this heating step, the first thin film layer 211 and the second thin film layer 212 are heated for a time longer than the heating time in the second step so that the crosslinking of the first thin film layer 211 and the second thin film layer 212 progresses and the layer is completely hardened.

<Advantages of the gasket manufacturing method according to the present embodiment>
According to the manufacturing method of the gasket 210 of this embodiment, the first thin film layer 211 has a phenomenon that the thickness is thin at the center in the short direction and thick near both sides in the width direction. However, after the shape of the first thin film layer 211 is stabilized in the second step, the second thin film layer 212 is formed in the third step using the second screen plate 520 so as to cover the first thin film layer 211. The thickness H20 of the second support portion 522 in the second screen plate 520 is set to be equal to or less than the thickness H11 near both sides in the width direction of the first thin film layer 211. In addition, the width W2 between the opposing surfaces of the second support portions 522 provided on both sides of the first thin film layer 211 is set to be equal to or greater than the width W1 of the first thin film layer 211.

Therefore, the second thin film layer 212 is provided so as to cover the thin portion in the center in the short direction of the first thin film layer 211. More specifically, the second thin film layer 212 is provided so as to fill the region between a pair of thick portions near both sides in the width direction of the first thin film layer 211. As described above, since H20≦H11 is satisfied, the tips of the thick portions near both sides in the width direction of the first thin film layer 211 are inserted into the mesh-like second screen 521 during screen printing. As a result, the amount of gasket material 250 supplied to this vicinity is small, and the amount of gasket material 250 supplied to the center is large.

In addition, by satisfying W2≧W1, both sides of the thicker portions near both sides in the width direction of the first thin film layer 211 are covered by the second thin film layer 212. As described above, by satisfying H20≦H11, it is possible to prevent the thickness H31 near both sides in the width direction of the second thin film layer 212 from becoming thicker than H11.

As a result, it is possible to make the thickness of the gasket 210, which is composed of the first thin film layer 211 and the second thin film layer 212, uniform. As shown in FIG. 4(c), the thickness of the thickest portion near both sides of the gasket 210 in the width direction is H31, and the thickness of the flat portion in the center of the gasket 210 is H32.

Here, we will explain the results of comparing a gasket with a width of 5 mm and a thickness of 0.1 mm manufactured using silicone rubber (VMQ) by one screen printing as in the conventional method with a gasket manufactured by two screen printings as in this embodiment. In the comparison test, the thickness H20 of the second support portion 522 in the second screen plate 520 used in the second screen printing was set to be 0.01 mm thinner than the thickest portion near both ends of the first thin film layer 211. In other words, it was set to H20 = H11 - 0.01 mm. In addition, the width W2 between the opposing surfaces of the pair of second support portions 522 was set to be 0.2 mm wider than the width W11 of the first thin film layer 211. In other words, it was set to W2 = W1 + 0.2 mm.

As a result, the difference in thickness between the thickest part and the center in the short direction of a gasket manufactured by a conventional manufacturing method (corresponding to (H11-H12) in FIG. 3(c)) of the gasket 210 obtained by the manufacturing method of this embodiment (corresponding to (H31-H32) in FIG. 4(c)) can be reduced to about 20%. In the above comparison test, H20 = H11-0.01 mm and W2 = W1 + 0.2 mm are set. However, in the present invention, the dimensions of H20 and W2 are not particularly limited. For example, it is preferable to set H20 to be 0.01 mm or more thinner than H11, and W2 to be 0.05 mm or more wider than W1.

(others)
In the above embodiment, a gasket is provided on a separator of a fuel cell. However, the gasket according to the present invention is not limited to such an application. For example, the present invention can be applied to a metal gasket in which a gasket made of a rubber-like elastic material is provided on the surface of the metal gasket body.

10 Fuel Cell 100 MEA
REFERENCE SIGNS LIST 110 Electrolyte membrane 120 Gas diffusion layer 200 Separator 201 Flow path 202 Manifold 210 Gasket 250 Gasket material 510 First screen plate 511 First screen 512 First support portion 520 Second screen plate 521 Second screen 522 Second support portion 600 Squeegee

Claims (4)

a first step of forming a first thin film layer on the substrate by screen printing using a first screen plate having a first support portion in contact with a surface of the substrate and disposed along both sides of a region where a gasket is to be formed, and a first screen supported on the first support portion;
a second step of heating the first thin film layer to promote crosslinking after the first step;
a third step of forming a second thin film layer on the substrate by screen printing so as to cover the first thin film layer using a second screen plate having a second support portion arranged along both sides of the first thin film layer and in contact with the substrate surface, and a second screen supported on the second support portion, after the second step;
A method for manufacturing a gasket, characterized in that the thickness of the second support portion is less than or equal to the thickness of the thickest portion near both sides of the first thin film layer in the width direction, and the width between opposing surfaces of the second support portions provided on both sides of the first thin film layer is greater than or equal to the width of the first thin film layer. The method for manufacturing a gasket according to claim 1, characterized in that in the second step, the crosslinking of the first thin film layer is advanced to a degree that the first thin film layer is not completely hardened and the shape of the first thin film layer is not distorted. The method for manufacturing a gasket according to claim 1 or 2, characterized in that the thickness of the second support portion is set to be at least 0.01 mm thinner than the thickest portions near both sides of the first thin film layer in the width direction. The method for manufacturing a gasket according to claim 1, 2 or 3, characterized in that the width between the opposing surfaces of the second support parts provided on both sides of the first thin film layer is set to be at least 0.05 mm wider than the width of the first thin film layer.

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