WO2024147282A1

WO2024147282A1 - Airbag with reinforced tether fabric sewn part

Info

Publication number: WO2024147282A1
Application number: PCT/JP2023/045477
Authority: WO
Inventors: 史章伊勢; 拓海壁谷
Original assignee: 旭化成株式会社
Priority date: 2023-01-04
Filing date: 2023-12-19
Publication date: 2024-07-11

Abstract

Provided is an airbag such as a pedestrian airbag that has a comparatively large size so as to cover the entire vehicle width and that regulates an inflation thickness with a tether connecting opposing panels, the airbag thinning the panels and being lightweight and small capacity for storage, while suppressing breakage during airbag deployment at a sewn part between the panels and the tether. The present invention relates to an airbag having a bag body in which a pair of base fabric panels are sewn at the outer peripheral edge thereof, and a tether fabric that is sewn on the pair of base fabric panels inside the bag body so as to make it possible to regulate the distance between the pair of base fabric panels during inflation of the bag body, the airbag being characterized in that the base fabric panels and the tether fabric are sewn together with a reinforcing fabric on the outside of the bag body, and the reinforcing fabric and the base fabric panels are in a laminated form fixed by an adhesive layer having an adhesive agent. The airbag is preferably a pedestrian airbag.

Description

Airbag with reinforced tether fabric seams

The present invention relates to an airbag used in an airbag device mounted on a vehicle. More specifically, the present invention relates to an airbag in which opposing base fabric panels are sewn together with a tether fabric to maintain a predetermined thickness of the airbag when inflated, and the sewn portions of the tether fabric are reinforced to prevent breakage.

An airbag system mounted on a vehicle comprises an airbag module (device), a sensor, and an operation control device. The airbag module comprises an airbag container, an inflator of a gas generator, and an airbag bag (cushion). Here, the airbag bag (cushion) is simply referred to as an airbag. Conventionally, when the thickness of an airbag at the time of completion of inflation is specified, an airbag is configured such that a tether connecting opposing panels determines the distance between the opposing panels. The following Patent Document 1 discloses a pedestrian airbag in which the tether between the opposing panels is relatively wide, and the tether supports the inflation and deployment structure of the airbag that widely covers the automobile hood cover (bonnet).
However, Patent Document 1 does not specifically describe the type of stitching between the panel and the tether, much less the strength of the stitching. In addition, in the airbag described in Patent Document 1, the thickness of the airbag is restricted by the tether when gas inflates, so that excessive force acts on the tether stitching, which may cause the bag to tear near the stitching.

The following Patent Document 2 proposes that, in order to reinforce the base fabric near the seams, a reinforcing fabric is overlapped on the outer surface of the base fabric and sewn to the base fabric with a seam (single stitching), while one end of a connecting fabric is sewn to both the reinforcing fabric and the base fabric with a seam (co-stitching) (see Figure 3 of the same document).
However, although Patent Document 2 teaches that the stress generated in the joint stitching part when the airbag part inflates is distributed between the reinforcing fabric and the base fabric, the reinforcing fabric is fixed to the base fabric by sewing, and problems arise due to the stitching being too steep. In addition, there is no description at all about the relationship between the strength of the independently sewn seams and the joint stitching.

In the following Patent Document 3, in order to provide a pedestrian protection airbag in which the tether is less likely to break, it is proposed to sew the base fabric and the tether by folding the upper end of the tether along the base fabric to form a horizontal folded portion and sewing the tether (see Figures 5 and 6 of the same document).
However, Patent Document 3 does not disclose sewing a reinforcing fabric to the base fabric when sewing the tether to the base fabric, or using an adhesive layer to fix the reinforcing fabric to the base fabric, much less teaches adding a reinforcing fabric to bear the stress of the sewn area together with the base fabric and strengthen the sewn area.

JP 2019-172170 A JP 2011-148365 A JP 2019-34618 A

For example, pedestrian protection airbags must be large enough to cover the entire width of the vehicle and must be rapidly inflated to protect the human body. If gas is supplied from a single location, the cushion bag of the airbag will be subjected to a large load when it inflates, and depending on the shape design, there is a risk of the bag rupturing.
Furthermore, when attempts are made to make the airbag lighter to further improve the energy efficiency of the vehicle and to reduce the storage volume by using thinner fabric panels for the airbag, the airbag may tear when inflated in conventional airbag configurations.
Under these circumstances, the problem that the present invention aims to solve is to provide an airbag that is relatively large, such as a pedestrian protection airbag that covers the entire width of a vehicle and whose inflation thickness is regulated by a tether connecting opposing panels, by making the panels thinner, making the airbag lightweight and requiring a small storage capacity, while suppressing damage to the seams between the panels and the tethers when the airbag is deployed.

That is, the original idea is as follows:
[1] An airbag having a bag body in which a pair of base fabric panels are sewn together at their outer periphery, and a tether cloth sewn to the pair of base fabric panels inside the bag body so as to regulate the distance between the pair of base fabric panels when the bag body is inflated,
The base fabric panel and the tether fabric are sewn together with a reinforcing fabric on the outside of the bag body,
The airbag is characterized in that the reinforcing fabric and the base fabric panel are fixed to each other by an adhesive layer to form a laminate.
[2] The airbag according to [1], wherein the adhesive layer between the reinforcing fabric and the base fabric panel is a single layer or an intermittent pattern layer.
[3] The airbag according to [2], wherein the coverage area rate of the adhesive in the adhesive layer between the reinforcing fabric and the base fabric panel is 3% or more and 100% or less.
[4] The airbag according to [2] or [3], wherein at least a part of the intermittent pattern layer of the adhesive layer has a dot pattern or a stripe pattern.
[5] The airbag according to any one of [1] to [3], wherein the adhesive of the adhesive layer is a tacky resin, a hot melt resin, or a curable resin.
[6] The airbag according to any one of [1] to [5], wherein the adhesive layer is missing at a sewing line portion where the base fabric panel, the tether fabric, and the reinforcing fabric are sewn together.
[7] The airbag according to any one of [1] to [6], wherein the reinforcing fabric and the base fabric panel are both plain weave fabrics, and the reinforcing fabric is biased and fixed to the base fabric panel in the warp and weft directions.
[8] The airbag described in any of [1] to [7], wherein the reinforcing fabric is sewn to the base fabric panel via the adhesive outside the seam allowance of the tether fabric with a seam strength lower than the seam strength between the reinforcing fabric, the base fabric panel, and the tether fabric.
[9] The airbag described in [8], wherein the lower stitching strength than the stitching strength between the reinforcing fabric, the base fabric panel, and the tether fabric is achieved by reducing the strength of the stitching thread, the fineness of the stitching thread, or the number of stitches used in stitching.
[10] The airbag according to any one of [1] to [9], wherein the weave fineness of the reinforcing fabric (the value obtained by multiplying the weave fineness (dtex) by the weave density (threads/2.54 cm) and adding the results in the warp and weft directions) is 1.1 to 1.6 times the weave fineness of the base fabric panel.
[11] The airbag according to any one of [1] to [10], wherein the weave fineness of the tether fabric (the value obtained by multiplying the weave fineness (dtex) by the weave density (threads/2.54 cm) and adding the results in the warp and weft directions) is 1.1 to 1.6 times the weave fineness of the base fabric panel.
[12] The airbag according to any one of [1] to [11], wherein the base fabric panel and the tether fabric are sewn together with a reinforcing fabric fixed to the base fabric panel by adhesive on the outside of the bag body, and a tether reinforcing fabric arranged on the outside of the seam allowance of the tether fabric on the inside of the bag body.
[13] The airbag according to [12], wherein the seam of the tether cloth and the tether reinforcing cloth are fixed with an adhesive.
[14] The airbag according to any one of [1] to [13], wherein the seam allowance of the tether cloth is folded back and sewn.
[15] The airbag according to any one of [1] to [14], wherein the fineness of the yarn constituting the base fabric panel is 200 dtex or more and 400 dtex or less.
[16] The airbag according to any one of [1] to [15], wherein the airbag is a pedestrian protection airbag.

The airbag of the present invention can provide an airbag that is relatively large, such as a pedestrian protection airbag that covers the entire width of a vehicle and whose inflation thickness is regulated by a tether connecting opposing panels, by making the panels thinner, resulting in a lightweight airbag with a small storage capacity, while suppressing damage to the seams between the panels and the tethers when the airbag is deployed.

FIG. 1 is a cross-sectional view of aspect 1 of an embodiment of the present invention. FIG. 2 is a cross-sectional view of aspect 2 of an embodiment of the present invention. FIG. 3 is a cross-sectional view of aspect 3 of an embodiment of the present invention. FIG. 4 is a cross-sectional view of aspect 4 of an embodiment of the present invention. FIG. 5 is a cross-sectional view of aspect 5 of an embodiment of the present invention. FIG. 6 is a cross-sectional view of an aspect 6 of an embodiment of the present invention. FIG. 11 is a cross-sectional view of aspect 7 of an embodiment of the present invention. FIG. 11 is a cross-sectional view of aspect 8 of an embodiment of the present invention. FIG. 2 is an explanatory diagram showing an outline of a sample shape (before sewing) in the examples and comparative examples. FIG. 1 is an explanatory diagram showing an outline of a sample shape (after sewing) in an example and a comparative example. FIG. 2 is an explanatory diagram showing an outline of a method for measuring sewing strength in Examples and Comparative Examples. FIG. 13 is an explanatory diagram showing an outline of a sample shape (after sewing) in Comparative Example 6.

Hereinafter, an embodiment of the present invention will be described in detail.
One embodiment of the present invention is an airbag having a bag body in which a pair of base fabric panels are sewn together at the outer peripheral edge of an inflation chamber in the bag body, and a tether cloth sewn to the pair of base fabric panels inside the bag body so as to regulate the distance between the pair of base fabric panels when the bag body is inflated, wherein the base fabric panels and the tether cloth are sewn together with a reinforcing cloth on the outside of the bag body, and the reinforcing cloth and the base fabric panels are in a laminated form fixed together with an adhesive layer.

In the prior art, for example, a reinforcing cloth for panel reinforcement is sewn (stitched) to a (base fabric) panel, and a tether is sewn to the reinforced portion (see FIG. 2 of Patent Document 2). In contrast to this, in this embodiment, a reinforcing cloth for reinforcement is attached to the base fabric panel with adhesive (from the outside of the base fabric panel) and a tether (cloth) is sewn to the reinforced portion (see FIG. 1). By attaching a reinforcing cloth for panel reinforcement to the panel and sewing a tether to the reinforced portion, it is possible to avoid an increase in the amount of sewing around the reinforced portion or a concentration of sewing, improving the workability of the process of attaching the reinforcing cloth, making it easier to fold and store, and eliminating the obstruction of deployment due to rough and hard stitching, and rather enhancing the reinforcing effect. In this embodiment, by eliminating the area of the reinforcing cloth that was required as a seam allowance in the prior art when using a reinforcing cloth, it is possible to reduce the amount of reinforcing cloth used itself.

For example, in the case of a pedestrian protection airbag, tension is applied to the base fabric panel and tether fabric by gas pressure when the airbag is inflated and deployed. When the airbag expands from a folded state, breaks the airbag case cover (container), deploys, and is in a properly inflated state to protect pedestrians, there is a risk of the bag breaking. The breakage occurs at the seam where the tether fabric is attached. In particular, when the fabric of the panel is made thinner to reduce weight, the tether fabric attachment part may become the starting point of the breakage, causing damage to the base fabric panel.
In this embodiment, when sewing the tether cloth to the base cloth panel, the reinforcing cloth is attached to the base cloth panel from the outside (fixed with adhesive) and then sewn together. Therefore, even if the fabric of the base cloth panel is made thinner to reduce weight, the reinforcing part consisting of the base cloth panel and the reinforcing cloth can receive the stress concentration at the sewn part, so that the bag can be prevented from breaking. As a whole, the airbag is lighter, but the gas pressure breakage of the bag is avoided, and it reaches a high ultimate pressure, so that it can fulfill its function of protecting the human body. In addition, the process of attaching the reinforcing cloth to the base cloth panel by attaching it is easy to work with. Since there is less sewing, it is easier to fold and store, the sewn part does not hinder deployment, and the reinforcing effect is rather enhanced due to the unity of the base cloth panel and the reinforcing cloth.
It is advisable to arrange the reinforcing fabric on the opposite side to where the tether fabric is sewn to the base fabric panel. In other words, the reinforcing fabric on the outermost side of the airbag can support the stress concentration at the seam due to gas pressure.

The adhesive constituting the adhesive layer used to attach and fix the reinforcing fabric to the base fabric panel is not particularly limited, and various adhesive resins and adhesive resins (adhesives) can be used. When assembling an airbag, the assembly work is also made easier by disposing an adhesive resin or adhesive resin on the reinforcing fabric and attaching and fixing the panel and the reinforcing fabric.
If an adhesive resin is used, the base fabric panel and the reinforcing fabric can be attached simply by pressing them together. The adhesive resin is a resin that has adhesiveness at room temperature (around 20°C), and examples of the adhesive include acrylic adhesives, urethane adhesives, and silicone adhesives. The main raw material for acrylic adhesives is butyl acrylate, but ethyl acrylate and 2-hexyl acrylate are also included.

The adhesive resin may be a hot melt resin that is a solid resin at room temperature and has thermal melting properties, or a hardening resin that hardens when heated or the like.
The hot melt resin may be a thermoplastic resin having a melting point of 80 to 200° C. Examples of the hot melt resin include polyamide, polyurethane, polyester, polypropylene, polyethylene, and modified ethylene vinyl acetate copolymer.
Among the curable resins, examples of the thermally crosslinkable resin include those in which an epoxy-based crosslinking agent is added to acrylic or polyurethane, and those containing N-methylolacrylamide are particularly preferred.

The adhesive (laminating resin) may be applied in a thin layer to the base fabric panel and/or the reinforcing fabric.
The adhesive layer may be a substantially uniform single layer (coverage area ratio 100%) or a layer with an intermittent pattern. The intermittent pattern may be, for example, a dot pattern or a stripe pattern. When the adhesive layer has an intermittent pattern, the coverage area ratio of the intermittent pattern of the adhesive layer to the reinforcing fabric may be 3% or more and 100% or less. In particular, in order to obtain the effect of reinforcing the sewn parts, the coverage area ratio is preferably 5% or more, while in terms of ease of folding and flexibility of the sewn parts, the coverage area ratio is preferably 60% or less.

It is also preferable that the intermittent pattern layer is arranged in a dot pattern (point pattern). The dot diameter can be, for example, 100 μm or more and 1500 μm or less. The number of dots can be, for example, 9 (pieces/(25.4×25.4 ^{mm 2} )) or more and 2500 (pieces/(25.4×25.4 mm ² )) or less. If the adhesive is arranged in a dot pattern, the adhesive part is less likely to become rough and hard, and the foldability of the airbag is not hindered. In addition, the laminating resin may be arranged in a line pattern (linear pattern) to form a stripe pattern. In this case, for example, lines having a width of 0.5 mm to 3 mm may be arranged at intervals of 0.5 mm to 3 mm. If the adhesive is arranged in a stripe pattern, the adhesive part is less likely to become rough and hard, and the foldability of the airbag is not hindered. In particular, if the line direction matches the folding line, the airbag can be folded flexibly. Furthermore, by applying adhesive in a manner that avoids the areas where the tether cloth, base cloth panel, and reinforcing cloth are sewn together, it is possible to avoid deterioration of workability due to dirt on the sewing machine needle during the sewing process (see FIG. 2).

When the laminating resin is arranged in a dot or stripe pattern, the resin coverage is 3% to 90%, preferably 5% to 60%, of the area of the reinforcing fabric, and the amount of the laminating resin is 5 (g/ ^m2 ) to 35 (g/ ^m2 ), preferably 10 (g/ ^m2 ) to 30 (g/ ^m2 ).
The laminating resin can be applied to the base panel and/or reinforcing fabric by gravure coating or screen coating, or the laminating resin can be transferred onto the base panel and/or reinforcing fabric by using a release paper.
When the reinforcing fabric is attached to the base fabric panel in an intermittent pattern such as a dot pattern or stripe pattern, or partially attached only at specific locations, the folding workability is improved. Also, by attaching the reinforcing fabric to the base fabric panel using a thermoplastic material and fixing the reinforcing fabric to the panel at a relatively low temperature before sewing, the airbag sewing can be completed without impairing the physical properties of the panel. Furthermore, by attaching the reinforcing fabric to the base fabric panel in an intermittent pattern such as a dot pattern, the folding of the integral part of the panel and the reinforcing fabric remains flexible, and the foldability is not impaired. If the attachment and fixing portion is arranged to avoid the sewing line, the adhesive does not soil the sewing needle, and there is no variation in the sewing needle resistance, so the sewing process is stable. Interference with folding and storage is avoided, and there is less interference with unfolding due to rough sewing portions.

When bonding the base fabric panel and the reinforcing fabric, if the reinforcing fabric and the base fabric panel are both plain weave fabrics, the reinforcing fabric can be biased and fixed to the base fabric panel in the warp and weft directions (not shown). "Biased" means that the warp threads of the reinforcing fabric and the warp or weft threads of the base fabric panel are not parallel, but are inclined at approximately 45 degrees. This allows the reinforcing fabric and the base fabric panel to mutually absorb the force applied to the seam when the airbag is deployed, increasing the strength of the co-stitched seams.

When bonding a base fabric panel and a reinforcing fabric together, both the base fabric panel and the reinforcing fabric can be single-sided coated fabrics, but to ensure flexibility and adhesive strength at the bonded area, it is preferable to bond the non-coated surfaces together (not shown).

As described above, by attaching reinforcing fabric to the base fabric panel and then sewing tethers to the reinforced areas, the process of attaching the reinforcing fabric becomes easier, the bag becomes easier to fold and store, and the bag is no longer hindered from unfolding by rough stitching, and the reinforcing effect is actually enhanced.
On the other hand, a minimum amount of stitching (sewing) may be performed to fix the reinforcing cloth (see FIG. 3). A reinforcing cloth for reinforcement may be attached to the base fabric panel, and then the outer periphery of the reinforcing cloth may be sewn, and then a tether may be sewn to the reinforced portion to finish. This is because the sewing process may be stable if the reinforcing cloth is sewn to the panel at approximately its outer periphery. The sewing of the reinforcing cloth to the base fabric panel at such an outer periphery is different from the sewing of the reinforcing cloth and the tether cloth, and is preferably weaker than this. The sewing strength at such an outer periphery that is lower than the sewing strength of the sewing between the reinforcing cloth, the base fabric panel, and the tether cloth can be due to the strength of the sewing thread, the fineness of the sewing thread, or a reduced number of stitches in the sewing. The sewing of the reinforcing cloth to the base fabric panel at such an outer periphery can prevent the sewing of the sewing thread from becoming the starting point of the destruction of the airbag by breaking the sewing thread when a force is applied during deployment and inflation. Furthermore, the sewing of the outer periphery facilitates folding and storage, and reduces the hindrance to deployment of the airbag that would otherwise be caused by rough stitching.
By sewing almost the entire periphery of the reinforcing fabric to the base fabric panel, the process up to the sewing step becomes more stable. The sewing between the reinforcing fabric and the base fabric panel at the periphery is performed with a weaker stitch than the sewing between the reinforcing fabric, the base fabric panel, and the tether fabric. The thread breaks in the former first, which prevents the airbag from breaking in the latter. This also prevents the airbag from being hindered when folded and stored, and reduces the obstruction to deployment caused by rough stitching.

The reinforcing fabric is intended to compensate for the lack of strength of the base fabric panel (woven fabric), and preferably compensates for the thickness of the base fabric (woven fabric) (see Figure 4). The weave fineness of the reinforcing fabric (dtex/2.54 cm) is preferably 0.65 to 1.6 times the weave fineness of the base fabric panel, more preferably 0.9 to 1.6 times, and even more preferably 1.1 to 1.6 times. If the weave fineness of the reinforcing fabric (dtex/2.54 cm) is 1.6 times or less the weave fineness of the base fabric panel, storability and weight reduction are not impaired. Here, the weave fineness is the value obtained by multiplying the fineness (dtex) by the weave density (threads/2.54 cm) in the woven fabric that constitutes the base fabric panel or tether cloth, and adding them in the warp and weft directions. If the weave fineness is large, the thickness of the fabric is large and the weight per unit area is large. By making the weave fineness of the reinforcing fabric greater than that of the base fabric panel (1.1 times or more), damage to the base fabric panel at the seam can be effectively prevented. When the base fabric panel is inflated with gas, the thickness of the airbag is regulated by the tether fabric, so a large force acts on the seam of the tether fabric. However, when a force acts on the base fabric panel via the sewing thread, the reinforcing fabric helps to withstand the force.

In particular, when the base fabric panel is made thinner by reducing the fineness of its constituent woven yarns, the part that bears the force when the airbag inflates and deploys is mainly the reinforcing fabric rather than the base fabric panel, and this allows the seam to withstand destruction. From the standpoint of mechanical properties and packability, the fineness of the constituent yarns of the thin base fabric panel is preferably 200 dtex or more and 400 dtex or less, and more preferably 200 dtex or more and 300 dtex or less.

The tensile breaking strength (N/cm) of the reinforcing fabric is preferably at least 0.9 times the tensile breaking strength of the panel, and more preferably at least 1.1 times. If it is 1.6 times or less, it is easily available as a woven fabric (not shown).

As shown in FIG. 5, the weave fineness of the tether fabric (dtex/2.54 cm) is preferably larger than the weave fineness of the base fabric panel, and is preferably 1.1 times or more, more preferably 1.2 times or more, and even more preferably 1.4 times or more. On the other hand, if the weave fineness of the tether fabric (dtex/2.54 cm) is 1.6 times or less than the weave fineness of the base fabric panel, storage ability and weight reduction are not impaired.

As shown in FIG. 6, when the tether cloth is sewn to the panel, it is also preferable to attach and sew a tether reinforcing cloth. The weave fineness (dtex/2.54 cm) of the tether reinforcing cloth is preferably larger than the weave fineness of the base cloth panel. The tether reinforcing cloth is preferably attached so as to cover the seam allowance of the tether cloth from above. In this case, as shown in FIG. 7, the tether cloth and the tether reinforcing cloth can be fixed with an adhesive in the same manner as the reinforcing cloth and base cloth panel described above.

As shown in Figure 8, it is also preferable for the tether fabric to be folded and sewn to the base fabric panel, as this strengthens the seams.

This embodiment is an airbag that is configured using tethers that regulate the thickness of the base fabric panel, and is particularly suitable for use as a pedestrian protection airbag.

The present invention will be specifically described below with reference to examples and comparative examples.
First, the materials used in the examples and comparative examples, and the methods for measuring the physical properties will be described.

[Base fabric panel]
The fabric used was a plain weave fabric woven using nylon 66 multifilament fibers as warp and weft yarns and coated with silicone resin. The total fineness of the weaving yarn constituting the base fabric used was 235 dtex, the number of filaments was 72, the weaving density of the base fabric panel was 72/inch (2.54 cm), the weaving fineness was 33,840 (dtex/2.54 cm), and the amount of silicone resin coated was 17 g/ ^m2 .

[Tether fabric]
The fabric was a plain weave fabric made of warp and weft yarns of nylon 66 multifilament fiber, coated with silicone resin. The total fineness of the yarn constituting the base fabric was 470 dtex, the number of filaments was 136, the weave density of the tether fabric was 49/inch (2.54 cm), and the weave fineness was 46,060 (dtex/2.54 cm). The amount of silicone resin coated was 25 g/ ^m2 .

[Reinforcing fabric]
The fabric used was a plain weave fabric woven with nylon 66 multifilament fibers as warp and weft, coated with silicone resin. The total fineness of the weaving yarn constituting the base fabric was 235 dtex, the number of filaments was 72, the weaving density of the reinforcing fabric was 72/inch, the weaving fineness was 33,840 (dtex/2.54 cm), and the amount of silicone resin coated was 17 g/ ^m2 .

[Heat melting film]
A 20 μm thick film was formed using CoPA1 (glass transition temperature Tg = 47 ° C., melting point Tm = 128 ° C.) described in International Patent Application No. 2020/032032 as the adhesive (laminating resin) constituting the adhesive layer, and the adhesive layer was formed using this.

[Adhesive]
An acrylic adhesive described in JP 2008-254269 A was used as the adhesive (adhesive resin) to form an intermittent pattern layer as an adhesive layer on the reinforcing fabric using a gravure roll coater. The intermittent pattern layer had a dot pattern with a dot thickness of 30 μm, a dot diameter of 100 μm, a dot interval of 150 μm, and an adhesive (coated) area ratio of 25%. Alternatively, the intermittent pattern layer had a stripe pattern with a stripe width of 2.0 mm, a stripe interval of 0.8 mm, a stripe thickness of 40 μm, and an adhesive (coated) area ratio of 40%.

[Sutures]
Airbag sewing thread manufactured by Gunze Ltd. (total fineness 1880 dtex, nylon 66 multifilament fiber 940 dtex two-ply twist) was used for the upper and lower threads.

[sewing machine]
The tether fabric and the base fabric panel were sewn together using LU-2210W-7 manufactured by JUKI Corporation.

[Preparation of test specimens]
As shown in the <sample shape> of Figure 9, the tether base fabric and the base fabric panel were cut into strips along the grain of the base fabric so that they were 320 mm in warp and 500 mm in weft. The reinforcing fabric (also called a patch) was cut along the grain of the base fabric so that they were 300 mm in warp and 30 mm in weft. First, the reinforcing fabric was layered on the base fabric panel with the non-coated side facing each other, and they were glued or sewn together within the range of the fixing point (4b). Then, as shown in the <sample shape (after tether sewing)> of Figure 9, three layers were layered in the order of tether fabric → panel base fabric → reinforcing fabric, and sewn together.
The co-sewing was performed by using the sewing machine to sew a straight line (4a: tether sewing) at 50 stitches/10 cm with the sewing thread in a range of 270 mm from the center in the width direction, with a sewing allowance of 15 mm for the tether cloth. Note that three backstitches were performed at the beginning and end of sewing. Next, as shown in <Sample shape (after sewing of tether overlapping part)> in Figure 10, in order to evaluate the mechanical properties of the sewn part, the ends of the base fabric panels in the length direction were overlapped, the rectangular shape was made into a loop, and the overlapping part was sewn in three rows of straight lines in the base fabric warp direction at 35 stitches/10 cm (7a: sewing of overlapping part of base fabric panel). The loop length was 320 mm in circumference. The end of the tether cloth far from the straight stitch (4a) was folded back, and the tether cloths were sewn together in the intermediate portion between the straight stitch (4a) and the folded back portion with three rows of straight stitches (7b: sewing of the overlapping portion of the tether cloth) in the base fabric warp direction with a stitch count of 35 stitches/10 cm. The length from the folded back portion to the straight stitch (4a) was 200 mm. Finally, it was confirmed that the overlapping portions of the base fabric panels and the tether cloths were not tilted, and that the straight stitches (4a) and the sewing of the overlapping portions (7a, 7b) were aligned along the base fabric warp direction. It was confirmed that these were not misaligned so that the stress applied to the sewing portion during measurement would not be biased, causing measurement errors.

(1) Measurement of sewing strength (N/cm) As shown in the <jig shape> of Figure 11, a jig that holds a test specimen by passing it through the loops of the base fabric panel and the tether fabric was attached to a Tensilon universal material testing machine manufactured by A&D Co., Ltd. As shown in the <sample attachment state> of Figure 11, when the test specimen is attached to the testing machine, the tether fabric was adjusted so that it was perpendicular to the base fabric panel (forming a T-shape) when viewed from the side (the direction in which the thickness of the test specimen can be confirmed). At this time, the stroke was adjusted so that the tether fabric was stretched parallel to the tensile direction, and the stroke (the distance from the straight stitch (4a: tether stitch) to the fixing point (folded back part) of the lower part of the tether fabric to the jig) was 200 to 400 mm. Measurement was performed at a pulling speed of 300 mm/min, and the maximum strength at the time of break was calculated as the sewing strength (N), and the value divided by the length of the straight stitch was calculated as the sewing strength (N/cm).

(2) Measurement of tether part folded thickness (mm) For the test piece prepared as described above, the base fabric panel and tether fabric were cut to match the size of the protective fabric to obtain a sample piece of 300 mm x 30 mm. The cut sample piece was folded in half perpendicular to the straight stitch (4a), and then folded in half again perpendicular to the crease to prepare a four-fold sample. The crease of the sample was sandwiched under a 150 mm x 15 mm plate, and a load was applied for 30 seconds so that the total weight of the sample and the plate was 1 kg. After that, the sample thickness at the four corners of the plate was measured with a vernier caliper, and the average of the measurements at the four points was taken as the value of the bending thickness of the sewn part.

(3) Flatness after four-fold pressing A load of 5 kg in total was applied to the sample prepared in the same manner as in the measurement of the four-fold thickness (mm) of the tether portion for 30 seconds. After that, it was confirmed whether any marks other than the folds remained on the base fabric of the sample.

(4) Reinforcing fabric utilization rate (N/cm ² )
The sewing strength (N) of the test pieces was divided by the area (cm ² ) of the reinforcing fabric of each test piece to obtain the reinforcing fabric utilization rate (N/cm ² ).

(5) Sewing time The sewing time was compared from the time required to cut the sample pieces from the sample fabric to the time required to sew the evaluation samples. The time required to finish three test pieces for each sewing strength evaluation was measured for three workers. The average of the obtained results was taken as the sewing time, and was expressed as an index with Comparative Example 3 as the standard of 100. However, in Examples 1 to 4, the heat-melting film of the reinforcing fabric was prepared by cutting it into the required shape in advance. Also, in Examples 5 and 6, the adhesive of the reinforcing fabric was prepared by cutting into the required shape a raw fabric on which the required pattern had been arranged in advance by a coater on the raw fabric of the reinforcing fabric.

[Examples 1 to 6, Comparative Examples 1 to 6]
Test pieces were prepared having the reinforcing fabric and its fixing method and location shown in Table 1. The fixing locations shown in Table 1 indicate the positions of sewing and/or bonding performed in the range of the fixing location (4b) in Fig. 9 in each Example or Comparative Example, with the solid line indicating the outer edge of the reinforcing fabric, the gray hatching indicating the bonding range, and the dashed line indicating the sewing location.
In Examples 1 to 4 and Comparative Example 6, when the reinforcing fabric was overlaid on the base fabric panel with the non-coated surfaces aligned and shifted by 100 mm in the weft direction, a hot melt film was inserted between the reinforcing fabric and the base fabric panel and the reinforcing fabric were bonded by heat pressing at 190°C for 5 seconds. The positions where the hot melt film was inserted are shown by gray hatching at the fixing points in Table 1. Examples 2 to 4 are in a form where partial bonding is performed at a part of the inner periphery of the reinforcing fabric. The base fabric panel with the reinforcing fabric bonded thereto was overlaid on the tether fabric with a shift of 100 mm in the weft direction, and the positions were arranged so that the end of the tether fabric and the end of the reinforcing fabric were aligned, resulting in a three-layer structure in the order of tether fabric → base fabric panel → reinforcing fabric.

In Examples 5 and 6, the reinforcing fabric with adhesive attached was attached to the uncoated surface of the base fabric panel. The adhesive attachment position is shown by gray hatching at the fixing point in Table 1. The base fabric panel with the reinforcing fabric attached was placed on top of the tether fabric, shifted by 100 mm in the weft direction, and arranged so that the ends of the tether fabric and the reinforcing fabric were aligned, resulting in a three-ply structure in the order of tether fabric → base fabric panel → reinforcing fabric.

In Comparative Example 1, no reinforcing fabric was used, and two layers were layered together in the order of tether fabric and base fabric panel and sewn together.
In Comparative Example 2, no adhesive was used, and three layers were sewn together in the order of tether fabric, base fabric panel, and reinforcing fabric.
In Comparative Example 3, the reinforcing fabric size was 320 mm x 50 mm, and no adhesive was used. The base fabric panel and reinforcing fabric were fixed together by sewing along the outer edge of the reinforcing fabric with a seam allowance of 10 mm. Three layers were then layered in the order of tether fabric → base fabric panel → reinforcing fabric, and the tether fabric was sewn together with a seam allowance of 25 mm.
In Comparative Example 4, no adhesive was used, and sewing was performed to secure the base fabric panel and reinforcing fabric along the outer edge of the reinforcing fabric with a seam allowance of 3 mm, and then the three layers were sewn together in the order of tether fabric → base fabric panel → reinforcing fabric.
In Comparative Example 5, no adhesive was used, and sewing was performed to secure the base fabric panel and reinforcing fabric along the outer edge of the reinforcing fabric with a seam allowance of 10 mm, after which the three layers were sewn together in the order of tether fabric → base fabric panel → reinforcing fabric.
In Comparative Example 6, as shown in Fig. 12, the size of the tether cloth was 270 mm in warp and 500 mm in weft, and instead of sewing to fix the base fabric panel and the reinforcing cloth, a 270 mm long slit (4c) was made in the base fabric panel, and the tether cloth was inserted into the slit. The length of the tether cloth inserted into the slit was 15 mm, and the end of the tether cloth inserted into the base fabric panel was arranged so as to be in close contact with the opposite half of the base fabric panel without folding, and the reinforcing cloth was layered and bonded on top of it with the non-coated sides facing each other, resulting in a three-layer structure in the order of tether cloth → base fabric panel → reinforcing cloth.

The above-mentioned sewing strength (N/cm), the thickness (mm) of the tether part folded in four, the flatness after pressing in four, the reinforcing cloth utilization rate (N/cm ² ), and the sewing operation time were measured and evaluated. The results are shown in Table 1 below.

The airbag according to the present invention can provide an airbag that is relatively large, such as a pedestrian airbag that covers the entire width of a vehicle and whose inflation thickness is regulated by a tether connecting opposing panels, by making the panels thinner, resulting in a lightweight airbag with a small storage capacity, while suppressing damage to the seams between the panels and the tethers when the airbag is deployed. Therefore, the airbag according to the present invention can be widely used in airbag devices for vehicles, including aircraft, ships, and automobiles.

1 Tether cloth 2 Base cloth panel 3 Reinforcement cloth 4 Adhesive (between the reinforcing cloth and the base cloth panel)
5. Suturing (co-stitching)
5' stitching (auxiliary stitching, between reinforcing fabric and base fabric panel)
6 Tether reinforcing cloth 7 Adhesive (between the tether reinforcing cloth and the base cloth panel)
4a Tether sewing (see Figures 9 to 12)
4b Fixing points of base fabric panel and reinforcing fabric (see Figures 9 to 11)
4c: Cutout of base fabric panel (insertion part for tether fabric, see FIG. 12)
7a Sewing overlapping parts of base fabric panels (see Figures 9 to 12)
7b Sewing overlapping parts of tether fabric (see Figures 9 to 12)
8 Stroke (see Figure 11)

Claims

An airbag having a bag body in which a pair of base fabric panels are sewn together at their outer periphery, and a tether cloth sewn to the pair of base fabric panels inside the bag body so as to regulate the distance between the pair of base fabric panels when the bag body is inflated,
The base fabric panel and the tether fabric are sewn together with a reinforcing fabric on the outside of the bag body,
The airbag is characterized in that the reinforcing fabric and the base fabric panel are fixed to each other by an adhesive layer to form a laminate.
The airbag of claim 1, wherein the adhesive layer between the reinforcing fabric and the base fabric panel is a single layer or an intermittent pattern layer.
The airbag according to claim 2, wherein the adhesive coverage area in the adhesive layer between the reinforcing fabric and the base fabric panel is 3% or more and 100% or less.
The airbag according to claim 2 or 3, wherein at least a portion of the intermittent pattern layer of the adhesive layer has a dot pattern or a stripe pattern.
The airbag according to claim 1 or 2, wherein the adhesive of the adhesive layer is a tacky resin, a hot melt resin, or a curable resin.
The airbag according to claim 1 or 2, wherein the adhesive layer is missing at the seam where the base fabric panel, the tether fabric, and the reinforcing fabric are sewn together.
The airbag according to claim 1 or 2, wherein the reinforcing fabric and the base fabric panel are both plain weave fabrics, and the reinforcing fabric is biased and fixed to the base fabric panel in the warp and weft directions.
The airbag according to claim 1 or 2, wherein the reinforcing fabric is sewn to the base fabric panel via the adhesive outside the seam allowance of the tether fabric with a seam strength lower than the seam strength between the reinforcing fabric, the base fabric panel, and the tether fabric.
The airbag of claim 8, wherein the lower stitching strength than the stitching strength between the reinforcing fabric, the base fabric panel, and the tether fabric is achieved by reducing the strength of the stitching thread, the fineness of the stitching thread, or the number of stitches used in stitching.
The airbag according to claim 1 or 2, wherein the weave fineness of the reinforcing fabric (the value obtained by multiplying the weave fineness (dtex) by the weave density (threads/2.54 cm) and adding the result in the warp and weft directions) is 1.1 to 1.6 times the weave fineness of the base fabric panel.
The airbag according to claim 1 or 2, wherein the weave fineness of the tether fabric (the value obtained by multiplying the weave fineness (dtex) by the weave density (threads/2.54 cm) and adding the result in the warp and weft directions) is 1.1 to 1.6 times the weave fineness of the base fabric panel.
The airbag according to claim 1 or 2, wherein the base fabric panel and the tether fabric are sewn together with a reinforcing fabric fixed to the base fabric panel by adhesive on the outside of the bag body, and a tether reinforcing fabric arranged on the outside of the seam allowance of the tether fabric on the inside of the bag body.
The airbag according to claim 12, wherein the seam of the tether fabric and the tether reinforcing fabric are fixed with an adhesive.
The airbag according to claim 1 or 2, in which the seam allowance of the tether cloth is folded back and sewn.
The airbag according to claim 1 or 2, wherein the fineness of the yarn constituting the base fabric panel is 200 dtex or more and 400 dtex or less.
The airbag according to claim 1 or 2, wherein the airbag is a pedestrian protection airbag.