Gasket manufacturing method

Abstract

A gasket manufacturing method is provided. The gasket has a base material with a bead and an elastomeric gasket body disposed in a top portion of the bead. The method includes sequentially forming the bead on one part of a plane of the base material and applying a molding material of the gasket body to the top of the bead. When forming the bead on the one part of the plane, a protrusion is formed in each end in the width direction in the top of the bead. The protrusions are utilized as a coating width defining means of the molding material when applying the molding material to the top of the bead.

Claims

1. A gasket manufacturing method, the gasket comprising a base material provided with a bead portion on one part of a plane and a gasket body formed of a rubber-like elastic body disposed in a top portion of the bead portion, the method comprising: sequentially performing a process of forming the bead portion on the one part of the plane of the base material, and a process of applying a molding material of the gasket body to the top portion of the bead portion, wherein the bead portion includes pair upwardly extending inclined surface portions that each terminate at a projection portion defined by a planar surface that extends in a direction parallel with a plane defined by the base material, the planar surface of each projection portion terminating at a downwardly extending inclined surface portion that each terminate at a planar recessed portion that is located between each of the downwardly extending inclined surface portions, the protrusion portions are utilized to define a coating width of the molding material when the molding material is applied to the planar recessed portion that is located between each of the downwardly extending inclined surface portions, a length of the upwardly extending inclined surface portions being greater than a length of the downwardly extending inclined surface portions, and a length of the planar surface of the projection portion being less than a length of the planar recessed portion.

2. The gasket manufacturing method according to claim 1, wherein the base material is a fuel cell separator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a plan view of a gasket according to an embodiment of the present invention.

(2) FIG. 2 is a cross-sectional view of a principal portion illustrating an example of the cross-sectional shape of the gasket and is an enlarged cross-sectional view along the A-A line of FIG. 1.

(3) FIG. 3 is a cross-sectional view of a principal portion illustrating another example of the cross-sectional shape of the gasket and is an enlarged cross-sectional view along the A-A line of FIG. 1.

(4) FIG. 4 is a cross-sectional view of a principal portion of a gasket according to a prior-art embodiment.

(5) FIG. 5 is a plan view of the gasket.

(6) FIG. 6 is an explanatory view illustrating a molding defect in the gasket.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) (1) The present invention relates to a fuel cell gasket or a metal gasket.

(8) (2) As the fuel cell gasket, a bead is formed in a separator, and then rubber is applied onto the bead and molded, whereby a cost reduction is expected. In this case, a flat shape is adopted for the bead surface. However, when a gasket is formed using a liquid rubber material by liquid application, such as a screen printing system, the coating cross-sectional shape cannot be controlled due to the surface tension between the rubber material and a base material, and thus the sealability is problematic (Variations in the coating width and height of rubber occur.).

(9) (3) Then, the present invention stabilizes the coating shape of the liquid rubber material by forming end portions of a bead shape formed in the separator into a protrusion shape. The seal shape can be controlled, and therefore an improvement of the sealability quality can be achieved. A fuel cell gasket has a feature that the separator bead cross-sectional end portions are formed into the protrusion shape. The variation in the rubber height can be prevented without being affected by the surface tension between the base material and the rubber material.

(10) Hereinafter, an embodiment of the present invention is described according to the drawings.

(11) FIG. 1 illustrates a plane of an entire gasket 11 manufactured by a manufacturing method according to an embodiment of the present invention. The gasket 11 is used as a fuel cell gasket. The gasket 11 has a fuel cell reaction surface 22 and a plurality of manifold holes 23 on a plane of a fuel cell separator 21 containing a metal plate as a base material, and therefore seal lines S are set on the peripheries thereof.

(12) As illustrated in the enlarged cross section of FIG. 2, a bead portion 24 having a solid shape is integrally provided in the seal line S. The bead portion 24 is formed into a full bead shape having a cross section of a substantially trapezoid shape, i.e., a shape in which a top portion 26 is provided between a pair of inclined surface portions 25 in the width direction. The bead portion 24 is provided over the entire length of the seal line S. The bead portion 24 projects in one direction (upward in the figure) in the thickness direction of the separator 21.

(13) A protrusion portion 27 is integrally provided in each end portion in the width direction in the top portion 26 of the bead portion 24. The protrusion portions 27 are provided over the entire length of the bead portion 24. The protrusion portions 27 project in one direction (upward in the figure) in the thickness direction of the separator 21. The protrusion portion 27 is provided in each end portion in the width direction of the top portion 26, and therefore a center portion in the width direction of the top portion 26 is relatively formed into a recessed portion 28. The recessed portion 28 is also provided over the entire length of the bead portion 24.

(14) A gasket body 31 containing a rubber-like elastic body is provided in the recessed portion 28, i.e., upper surface of the top portion 26 and between the pair of protrusion portions 27 in the width direction. The gasket body 31 is molded by applying a molding material by a means, such as a dispenser method. The gasket body 31 is provided over the entire length of the seal lines S.

(15) In manufacturing the above-described gasket 11, the bead portion 24 is formed on the one part of the plane of the separator 21 by press processing or the like, and the protrusion portions 27 are simultaneously formed at this time.

(16) Subsequently, the molding material (liquid rubber or the like) of the gasket body 31 is applied to the upper surface of the top portion 26 of the bead portion 24 by a means, such as the dispenser method, and a coating process is performed utilizing the protrusion portions 27 as the coating width defining means of the molding material at this time.

(17) Therefore, according to this method, the protrusion portions 27 block the flow (spread in the width direction) of the molding material and define the coating width in the coating process of the molding material described above. Therefore, the coating width is made constant or substantially constant and, when the coating width is made constant or substantially constant, the coating thickness is also made constant or substantially constant because the coating amount is a fixed amount. Accordingly, the cross-sectional shape of the gasket body 31 is made constant or substantially constant, and therefore the sealability by the gasket body 31 can be stabilized and the occurrence of a molding defect by the bulging-out of the molding material can be prevented.

(18) In FIG. 2, although the cross-sectional shape of the protrusion portions 27 is formed into an arc shape and the cross-sectional shape (cross-sectional shape of the bottom surface of the recessed portion 28) of the top portion 26 is also formed into an arc shape, the cross-sectional shapes thereof may be linear shapes or may contain a combination of a plurality of straight lines.

(19) As an example in this case, the cross-sectional shape of the protrusion portions 27 is formed into a trapezoid shape and the cross-sectional shape (cross-sectional shape of the bottom surface of the recessed portion 28) of the top portion 26 is formed into a flat and linear shape in FIG. 3.

(20) As a matter common to the example of FIG. 2 and the example of FIG. 3, it is preferable that the height of the protrusion portion 27 is smaller than the thickness of the gasket body 31, and thus the gasket body 31 can be certainly brought into contact with the mating surface in assembling a fuel cell stack.