Patent Description:
A technique for fuel cell applications in which separators are provided with beads and gaskets made of elastic material are integrally formed on the beads has hitherto been known (see PTL <NUM>). According to this technique, the beads provide a predetermined reaction force, which allows the gaskets made of elastic material to conform to and make tight contact with even minute irregularities on a surface with which the gaskets are to be close contact so that the sealing performance can be enhanced.

The beads have a contour in plan view that includes linear portions and curved portions. The reaction force of the beads tends to be higher in the curved portions than in the linear portions. The reaction force also tends to be higher in portions with a smaller radius of curvature. The applicants of the present invention have previously proposed a technique for making the reaction force of the beads uniform by designing the beads to be wider in their short direction in curved portions than in linear portions, and to be wider proportionally in portions with smaller radii of curvature (see PTL <NUM>).

It was found out that, with this technique, in the case where the gasket was integrally provided to the separator body by a conventional method, the gasket thickness was not uniform because of a tendency of the gasket having a smaller thickness in portions of the beads that are wide in the short direction, when compared to narrow portions. This leaves a scope of improvement because unevenness in the thickness of the gasket leads to inconsistent sealing performance. Similar issues could conceivably arise not only with separator-integrated gaskets but in the case with common metal gaskets.

<CIT> discloses a gasket manufacturing method comprising the steps of:.

An object of the present invention is to provide a gasket manufacturing method that enables an improvement in sealing performance by making the thickness of the gasket formed on beads on a base member more uniform.

The present invention is defined by claim <NUM> and adopts the following means to achieve the object discussed above.

The gasket manufacturing method of the present invention includes the steps of:.

This way, the gasket material is dispensed at a moving speed in accordance with the width in the short direction of the bead, so that the thickness of the gasket can be adjusted suitably.

Compared to the moving speed in a narrow portion of the bead having a small width in the short direction, the moving speed may be slower in a wide portion having a larger width than the narrow portion.

The wider the bead is in the short direction thereof, the smaller the gasket thickness tends to be, as the gasket material being dispensed easily spreads widthwise. Such a reduction in thickness can be prevented by slowing down the moving speed of the dispensing apparatus relative to the separator.

The bead includes a portion that is linear in plan view and a portion that is curved in plan view, the curved portion being wider than the linear portion.

The curved portion is provided with portions with different radii of curvature, and, compared to the width in a first portion having a large radius of curvature, the width is larger in a second portion having a smaller radius of curvature than the first portion.

The configurations described above can be adopted in any possible combinations.

As described above, according to the present invention, the thickness of the gasket formed on a bead provided on a base member can be made uniform, whereby the sealing performance can be enhanced.

Hereinafter, modes for carrying out this disclosure will be illustratively described in detail based on a specific embodiment with reference to the drawings. It should be noted that, unless otherwise particularly specified, the sizes, materials, shapes, and relative arrangement or the like of constituent components described in the embodiment are not intended to limit the scope of this disclosure.

A gasket manufacturing method according to the embodiment of the present invention will be described with reference to <FIG>. In this embodiment, a manufacturing method for a separator-integrated gasket will be described as one example of the gasket manufacturing method.

A fuel cell provided with the separator-integrated gasket <NUM> according to the embodiment will be described with reference to <FIG>. Generally, a fuel cell is configured as a cell stack composed of a plurality of single cells. <FIG> illustrates a cross-sectional view of a single cell <NUM>. The single cell <NUM> includes a pair of separator-integrated gaskets <NUM> and an MEA (Membrane Electrode Assembly) provided between the pair of separator-integrated gaskets <NUM>. The MEA includes an electrolyte membrane <NUM> and a pair of gas diffusion layers <NUM> on both sides of the electrolyte membrane <NUM>.

The separator-integrated gasket <NUM> provided in the fuel cell (single cell <NUM>) will now be described in more detail with reference to <FIG> and <FIG> is a plan view of a separator body according to the embodiment of the present invention. <FIG> shows a schematic plan view of the separator body <NUM> before the gasket <NUM> is provided thereto.

The separator-integrated gasket <NUM> includes a separator body (base member) <NUM> designed for fuel cells, and a gasket <NUM> made of an elastic material and integrally formed to the separator body <NUM>. The separator body <NUM> is formed by a plate-like member made of metal, for example. Carbon materials, resin materials and the like can also be adopted as the material of the separator body <NUM>. While it is common to provide a plurality of manifolds to the separator body <NUM>, and flow channels on the surface of the separator body <NUM>, the drawings omit illustration of these elements. Manifolds are provided to distribute the fuel gas, oxidant gas, cooling liquid and the like to each of the cells. The flow channels formed on the surface of the separator body <NUM> are used for the fuel gas, oxidant gas and the like to flow through.

The gasket <NUM> made of an elastic material described above is integrally formed to the separator body <NUM> around each manifold and around each region where flow channels are formed to prevent leakage of the fuel gas and others mentioned above to the outside. In this embodiment, to improve the sealing performance, a bead <NUM> is provided to the separator body <NUM> and the gasket <NUM> is formed on this bead <NUM>. This configuration is adopted so that a predetermined reaction force is provided by the bead <NUM>, which allows the gasket <NUM> made of elastic material to conform to and make tight contact with even minute irregularities on a surface with which the gaskets <NUM> are to be close contact so that the sealing performance can be enhanced.

The separator body <NUM> is formed with the bead <NUM> around each manifold and around each region with flow channels, with the gasket <NUM> made of elastic material formed on each of these beads <NUM>. Namely, the separator body <NUM> is formed with beads in several locations, although, for brevity, <FIG> shows a simplified illustration of the bead <NUM> in only one location.

Examples of favorable materials for the gasket <NUM> include silicone rubber, fluoride rubber, EPDM, butyl rubber, and so on. The gasket <NUM> seals the gap between the separator body <NUM> and the electrolyte membrane <NUM>.

The separator body <NUM> according to this embodiment will be described in more detail with reference particularly to <FIG> and <FIG> shows cross-sectional views of the separator-integrated gasket <NUM> according to the embodiment of the present invention. <FIG> respectively show cross sections of the separator body taken along A-A, B-B and C-C in <FIG>.

Beads <NUM> provided to the separator body <NUM> according to this embodiment include linear portions and curved portions in plan view. The curved portions include portions with different radii of curvature. For the convenience of explanation, hereinafter where applicable, a portion of the bead <NUM> that is linear in plan view shall be called a "linear portion," and a portion that is curved in plan view shall be called a "curved portion. " Where applicable, a portion with a large radius of curvature in a curved portion shall be called a "first portion," and a portion with a smaller radius of curvature than that of the "first portion" shall be called a "second portion.

The A-A cross section shown in <FIG> is the cross section of a linear portion 111a of the bead <NUM>. The B-B cross section shown in <FIG> is the cross section of a first portion 111b of the bead <NUM>. The C-C cross section shown in <FIG> is the cross section of a second portion 111c of the bead <NUM>.

In this embodiment, the bead <NUM> is designed to be wider in the short direction of the bead <NUM> in the curved portions (first portion 111b and second portion 111c) than in the linear portion 111a. Therefore, the linear portion 111a can be called a "narrow portion. " The curved portion can be called a "wide portion," since it is wider in the short direction of the bead <NUM> than the linear portion 111a. More specifically, as illustrated in <FIG>, the linear portion, first portion, and second portion satisfy W1 < W2 and W1 < W3, where W1 represents the width in the short direction of the linear portion 111a, W2 represents the width in the short direction of the first portion 111b, and W3 represents the width in the short direction of the second portion 111c. The bead <NUM> is designed also such that the second portion 111c with a smaller radius of curvature than that of the first portion 111b has a larger width in the short direction than the width in the short direction of the first portion 111b having a large radius of curvature. Namely, W2 < W3 is satisfied. When the first portion 111b and second portion 111c are compared, the latter is wider in the short direction, and therefore the first portion 111b can be called a "narrow portion" and the second portion 111c can be called a "wide portion. " As shown above, the "narrow portion" and "wide portion" are defined in relation to another portion they are compared to.

The bead <NUM> is configured to have a height H1 that is equal over the entire length. The gasket <NUM> formed on the bead <NUM> is also configured to have a thickness H2 that is equal over the entire length. The thickness H2 of the gasket <NUM> should preferably be set in a range from <NUM> to <NUM> inclusive. The width in the short direction of the gasket <NUM> should preferably be set in a range from <NUM> to <NUM> inclusive.

A manufacturing method of the separator-integrated gasket according to this embodiment will be described with reference particularly to <FIG> and <FIG>. <FIG> is a diagram illustrating a process of manufacturing the separator-integrated gasket according to the embodiment of the present invention. <FIG> is a graph showing a relationship between the moving speed of a dispensing apparatus relative to the separator and the thickness of the gasket material.

The manufacturing method of the separator-integrated gasket according to this embodiment includes a dispensing step wherein a dispensing apparatus <NUM> dispenses a gasket material 120X (such as liquid rubber) on a bead <NUM> of a separator body <NUM>, and a curing step of curing the dispensed gasket material 120X. <FIG> shows a simplified illustration of a state in the dispensing step. In <FIG>, the separator body <NUM> is shown only partly in a cross section cut along the bead <NUM>.

In the case of using a dispensing apparatus <NUM> to dispense the gasket material 120X on the bead <NUM> of the separator body <NUM>, any one of a configuration where the dispensing apparatus <NUM> is moved while the separator body <NUM> is fixed, a configuration where the separator body <NUM> is moved while the dispensing apparatus <NUM> is fixed, and a configuration where both the dispensing apparatus <NUM> and separator body <NUM> are moved, may be adopted. <FIG> shows a state in which a dispensing apparatus <NUM> is dispensing a gasket material 120X while moving from left to right in the drawing relative to the separator body <NUM>. The mechanisms that move the dispensing apparatus and separator body, controllers that control the movements, etc., are known techniques and therefore description thereof will be omitted. Various known techniques such as dispensers and inkjet apparatuses may be adopted as the dispensing apparatus <NUM>.

A thermosetting rubber material can be applied as the gasket material 120X of this embodiment. In this case, the separator body <NUM> on which the gasket material 120X has been applied is heated by a heater (not shown) in the curing step so that the gasket material 120X cures and is fixed to the separator body <NUM>. The gasket <NUM> can thus be formed integrally to the separator body <NUM>.

As described above, the bead <NUM> according to this embodiment has a plurality of portions having different widths in the short direction. In the dispensing step, the moving speed of the dispensing apparatus <NUM> relative to the separator body <NUM> (hereinafter, the speed will be referred to as "relative speed") is set different in respective portions of the bead <NUM> having different widths in the short direction. <FIG> shows a relationship between the relative speed and the thickness of the applied gasket material 120X in each of the portions of the bead <NUM> having different widths in the short direction. Graphs W1, W2, and W3 respectively correspond to the portions with widths W1, W2, and W3 in the short direction of the bead <NUM>.

As is seen from this graph, the thickness of the gasket material 120X becomes thinner as the relative speed is increased irrespective of the width in the short direction of the bead <NUM>. It can also be seen that the wider the bead <NUM> is in the short direction, the thinner the thickness of the gasket material 120X becomes. It thus follows that, to achieve a desired thickness t in respective portions, the relative speed should be V1 in the portion with width W1, the relative speed should be V2 in the portion with width W2, and the relative speed should be V3 in the portion with width W3 (V1 > V2 > V3).

As described above, in this embodiment, the relative speeds V2 and V3 in wide portions having a larger width in the short direction of the bead <NUM> than the linear portion 111a are set slower than the relative speed V1 in the linear portion 111a that is narrower in the short direction of the bead <NUM>. The relative speed V3 in the second portion 111c that is wider in the short direction of the bead <NUM> is set slower than the relative speed V2 in the first portion 111b. This way, the thickness of the gasket material 120X can be made constant (to a desired thickness t) in any of the linear portion 111a, first portion 111b, and second portion 111c. Thus the gasket <NUM> after it has cured can have a constant thickness in all the portions.

In the separator-integrated gasket <NUM> according to this embodiment, the bead <NUM> on the separator body <NUM> employs a configuration in which the width in the short direction of the bead <NUM> varies depending on whether the portion is linear or curved in plan view, and depending on the radius of curvature when the portion is curved in plan view. Thus the reaction force of the bead <NUM> is made uniform.

In the manufacturing method of the separator-integrated gasket <NUM> according to this embodiment, the relative speed is changed in accordance with the width in the short direction of the bead <NUM> in the dispensing step. The thickness of the gasket <NUM> formed on the bead <NUM> can thus be made uniform, whereby the sealing performance can be enhanced.

While the bead <NUM> has three locations with different widths in the short direction in the embodiment described above, it should be understood that the thickness of the gasket <NUM> can be made uniform by setting the relative speed similarly in other cases where the width varies in two locations, or four or more locations.

In a portion shaped such that the width in the short direction of the bead <NUM> changes continuously, the relative speed may be changed continuously. For such a portion where the width in the short direction of the bead <NUM> changes continuously, it is also possible to make the thickness of the gasket <NUM> uniform to some degree by changing the relative speed stepwise.

Claim 1:
A gasket manufacturing method comprising the steps of:
dispensing a gasket material (120X) along a bead (<NUM>) provided to a base member (<NUM>) by moving a dispensing apparatus (<NUM>) that dispenses the gasket material (120X) relative to the base member (<NUM>); and
curing the gasket material (120x) dispensed on the bead (<NUM>); wherein
the bead (<NUM>) includes a plurality of portions each having a different width (W1, W2, W3) in a short direction thereof, and
the dispensing apparatus (<NUM>) operates in different moving speeds (V1, V2, V3) relative to the base member (<NUM>) at each of the plurality of portions, characterized in that
the bead (<NUM>) includes a portion (111a) that is linear in plan view and a portion (111b, 111c) that is curved in plan view, the curved portion (111b, 111c) being wider than the linear portion, and
the curved portion (111b, 111c) is provided with portions with different radius of curvature, and, compared to the width in a first portion (111b) having a large radius of curvature, the width is larger in a second portion (111c) having a smaller radius of curvature than the first portion.