WO2024117134A1

WO2024117134A1 - Air bag with increased ability to maintain internal pressure

Info

Publication number: WO2024117134A1
Application number: PCT/JP2023/042578
Authority: WO
Inventors: 拓海壁谷; 祐介佐藤; 達夫田中
Original assignee: 旭化成株式会社
Priority date: 2022-11-29
Filing date: 2023-11-28
Publication date: 2024-06-06

Abstract

Provided is an air bag that has a high ability to maintain internal pressure and also has excellent compactness. This air bag is formed by stitching together at least a pair of ground fabric panels at the outer peripheral edges thereof, wherein: outer surfaces at both ends of a band-shaped non-air-permeable protective material that has been folded in half are bonded to respective internal surfaces of the pair of ground fabric panels in bonding regions that have a prescribed width, that follow the stitching and, from the vicinity of the stitching toward the interior of a bag body, that have a distal end and a proximal end; and, when tensile strength is applied to the pair of ground fabric panels during deployment of the air bag, the distance between the distal ends along the non-air-permeable protective material that has been folded in half is greater than or equal to the distance between the distal ends along the pair of ground fabric panels.

Description

Airbag with improved internal pressure retention

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 having improved internal pressure retention performance, in which the outer edges of a pair of base fabric panels are sewn together.

Conventionally, airbags used in airbag devices mounted on vehicles are made by sewing (stitching) the outer edges of a pair of base fabric panels together to form a bag-like shape, into which gas is instantly injected to inflate and deploy. However, because the sewing (stitching) is usually done using sewing thread, gas leakage between the pair of base fabric panels and through the holes in the sewing needle is unavoidable.

Today, various types of airbags are used depending on where they are installed in a vehicle, such as PAB (Passenger Airbag), DAB (Driver Airbag), SAB (Side Airbag), KAB (Knee Airbag), CAB (Curtain Airbag), and pedestrian airbag. Airbags absorb impacts on the human body by retaining injected gas. In particular, DABs meet performance requirements if they can handle instantaneous impacts (first impacts). However, for example, CABs need to maintain the inflated state of the airbag even while the vehicle is rolling over after the first impact, and are required to maintain a constant pressure (e.g., 30 kPa) or higher (i.e., internal pressure maintenance) within the airbag for a long period of time (e.g., six seconds). In addition, pedestrian airbags need to maintain internal pressure for a longer period of time than DABs, because the timing at which a pedestrian lands on the bonnet and hits the vehicle body (e.g., the pillar section) varies.

In order to meet the requirement of maintaining the internal pressure, the following methods have been considered.
One method is to bond the outer edges of a pair of base fabric panels with only an adhesive instead of sewing. Although this method can prevent gas leakage, there is a risk that the adhesive will not be able to withstand the strength required for the airbag to deploy because there is no sewing.

Another method is to manufacture a pair of base fabric panels using the One Piece Woven method and then coat the outside of the base fabric. With this method, there are no stitching and the coating means there is no problem with airtightness, and there is no problem with strength either, but it is difficult to create complex shapes, the coating needs to be applied relatively thickly, and the airbag tends to be heavy and expensive.

Another method is to bond the outer edges of a pair of base fabric panels with a silicone adhesive and then sew the bonded portion. This method can ensure strength while suppressing gas leakage, but it has problems such as low productivity, thick bonded portions, and poor folding and storage properties of the airbag. In addition, the weight of the silicone adhesive increases the weight of the airbag.
As illustrated in FIG. 2, in this method, the silicone adhesive stretches during airbag deployment, preventing gas from accessing the stitching.
Generally, silicone adhesives are suitable for such applications because of their high adhesive strength with base fabric panels, but the adhesive takes half a day to about a day to harden, resulting in low productivity, and for example, under certain conditions, the folded thickness of a pair of base fabric panels at the location where there is no adhesive (location where internal pressure does not need to be maintained) is 2.2 mm, while the folded thickness at the location where there is adhesive and sewing is 5.2 mm (corresponding to Comparative Example 4 in the present specification), resulting in a lack of compactness (foldability, storability). Furthermore, silicone adhesives must be separated from the airbag fabric when recycled, and they emit a relatively large amount of GHG (Green House Gas) during production, so they are not environmentally friendly in the manufacture and disposal of airbags.

The following Patent Document 1 describes an airbag device having a protective cloth sewn along a seam where a pair of opposing portions of a base fabric are sewn together, at a position away from the seam so as to cover the seam from the inside where gas from the inflator is introduced (see Figures 2 and 7 of the same document). Patent Document 1 discloses a protective material for the seam, but this protective material is fixed to the base fabric by sewing, not by adhesion. The purpose of this protective material is to prevent the seam from being directly exposed to the high-pressure gas from the inflator and being destroyed, and to distribute tension in the protective material's seam to prevent damage to the seam of the pair of base fabrics, but is not intended to maintain internal pressure without damaging the seam.

Patent Document 2 listed below discloses an airbag having walls including a laminate material, the laminate material including a backing layer having a breathable sheet-like structure made of a woven or knitted fabric, at least two layers of coextruded polymer film, a first polymer layer having a predetermined glass transition temperature on the backing layer side, and a second polymer layer having a predetermined storage modulus on the opposite side to the backing layer, the airbag having walls bonded together such that the second polymer layer is bonded at the edge of the airbag, and a manufacturing method for bonding the first polymer layer and the second polymer layer by applying different thermal energies to them.
The object of the invention described in US Pat. No. 5,399,633 is to provide an airbag which can be produced at low cost and which is easy and reliable to seal (see Figs. 1-3 of the same document).
Patent Document 2 does not disclose any protective material for the seams of the airbag, and the manufacturing method therefor is primarily intended to increase productivity, not to maintain internal pressure.

The following Patent Document 3 describes an airbag in which panels are joined together at joints, the panels having a woven fabric and a synthetic resin film bonded to the woven fabric via an adhesive, the panels are joined together by pressurizing and heating with a hot melt adhesive sheet interposed between the panels, and the synthetic resin film is disposed on the outside of the airbag. The object of the invention described in Patent Document 3 is to provide an airbag in which the strength of the seams between the panels is high, the durability is excellent, gas leakage is prevented, and handling is easy (see Figures 3 and 4).
In the invention described in Patent Document 3, panels are bonded together with a bonding layer made of hot melt adhesive, thereby increasing the strength of the joints between the panels, reducing the thread density of the woven fabric, and a synthetic resin film is placed on the outside of the panel to prevent the woven fabric from coming into direct contact with the inside of the vehicle body, thereby increasing durability. In addition, the stitching of the woven fabric is impregnated with hot melt adhesive to prevent gas leaks from pinholes and stitching threads from coming loose.
Patent Document 3 does not describe a method for preventing gas leakage from stitching holes due to stress being applied to the joints between the panels when the adhesive surface around the outer periphery of the airbag is stressed during deployment, which may cause the adhesive to break.Furthermore, there is no mention of the technical idea of adhering a protective material for the stitching to the base fabric at a location separate from the stitching, and maintaining the adhesion between the protective material and the base fabric to maintain the internal pressure.

As such, in light of the state of the art, an airbag that has excellent internal pressure retention performance when inflated and deployed, as well as excellent compactness, has not yet been provided.

International Publication No. 2010/122852 US Patent Application Publication No. 2010/0320736 JP 2018-177122 A

The problem that the present invention aims to solve under such conventional technology is to provide an airbag having at least one pair of base fabric panels sewn together at their outer periphery, in which an airtight structure is formed by bonding the outer surfaces of both ends of a half-folded, strip-shaped, non-breathable protective material to the inner surface of each of the pair of base fabric panels in a bonding region of a predetermined width along the stitching from near the stitching toward the inside of the bag body, the bonding region having a proximal end and a distal end, and which is maintained even when the airbag is deployed, thereby improving the internal pressure retention performance and providing an airbag that is also highly compact.

The inventors of the present application conducted intensive research and repeated experiments in order to solve the above-mentioned problems, and unexpectedly discovered that the above-mentioned problems could be solved by using a non-breathable protective material having the structure defined below, which led to the completion of the present invention.
That is, the present invention is as follows.

[1] An airbag comprising at least one pair of base fabric panels sewn together at their outer periphery,
An airbag in which both end outer surfaces of a folded, strip-shaped non-breathable protective material are bonded to the inner surface of each of the pair of base fabric panels in bonding regions of a predetermined width along the seams from near the seams toward the inside of the bag, and when a tensile force is applied to the pair of base fabric panels during deployment of the airbag, the length between the distal ends along the folded, strip-shaped non-breathable protective material is greater than or equal to the length between the distal ends along the pair of base fabric panels.
[2] The airbag according to [1], wherein the folded band-shaped non-breathable protective material is a single resin film folded in half.
[3] The airbag according to [1] or [2], wherein, when the airbag is not deployed, stored or folded, 1/2 of the length between the distal ends along the half-folded non-breathable protective material (inter-adhesive distance a) and 1/2 of the length between the distal ends along the pair of base fabric panels (inter-adhesive distance b) satisfy the relationship 0.5<a/b<10.
[4] The airbag according to any one of [1] to [3], wherein the adhesion in the adhesive region is by welding.
[5] The airbag according to any one of [1] to [4], wherein when the airbag is not deployed, stored or folded, 1/2 of the length between the distal ends along the half-folded non-breathable protective material (adhesive distance a) is 0.1 cm or more and 10.0 cm or less.
[6] The airbag according to any one of [1] to [5], wherein when the airbag is not deployed, stored or folded, the predetermined width w of the adhesive region is 0.1 cm or more and 5.0 cm or less.
[7] The airbag according to any one of [1] to [6], wherein when the airbag is not deployed, stored or folded, the effective adhesive width, which is the smaller of 1/2 the length between the distal ends along the pair of base fabric panels (the adhesive distance b) and the specified width w of the adhesive region, is 0.1 cm or more.
[8] The airbag according to any one of [1] to [7], wherein when the airbag is not deployed, stored or folded, the ratio w/b of 1/2 of the length between the distal ends along the pair of base fabric panels (inter-bonding distance b) to the predetermined width w of the bonded region satisfies the relationship 0.2<w/b<5.0.
[9] The airbag according to any one of [1] to [8], wherein the inner surface of the base fabric panel is an uncoated surface.
[10] The airbag according to any one of [1] to [9], wherein the inner surface of the base fabric panel is film laminated.
[11] The airbag according to any one of [1] to [10], wherein the thickness of the non-breathable protective material is 0.001 mm or more and 0.5 mm or less.
[12] The airbag according to any one of the above [1] to [11], wherein the tensile modulus of the half-folded band-shaped non-breathable protective material is 100 to 800 MPa.
[13] The airbag according to any one of [1] to [12], wherein the adhesive strength in the adhesive region is 1 N/cm or more.
[14] The airbag according to any one of [1] to [13], wherein the airbag has an R portion in the adhesive region with a curvature radius of 300 mm or less.
[15] The airbag according to any one of [1] to [14], wherein the airbag has an inverse R portion in the adhesive region, the radius of curvature of which is 300 mm or less.
[16] The airbag according to [14] or [15], wherein the surface step (peak-to-valley difference) of the R portion is 400 μm or less.
[17] The airbag according to any one of [14] to [16], wherein a ratio (R portion/straight portion) of a surface step (peak-valley difference) of the R portion to a surface step (peak-valley difference) of a substantially straight portion excluding the R portion is 0.6 to 2.0.
[18] The airbag according to any one of [14] to [17], wherein the adhesive strength at the R portion is 1 N/cm or more.
[19] The airbag according to any one of [14] to [18], wherein a ratio of an adhesive strength in the R portion to an adhesive strength of a substantially straight portion excluding the R portion (R portion/substantially straight portion) is 0.5 to 2.5.
[20] The airbag according to any one of [1] to [19], wherein the airbag includes an isolated sewn portion in a closed space.

The airbag of the present invention has both end outer surfaces of a folded, strip-shaped, non-breathable protective material adhered to the inner surface of each of at least a pair of base fabric panels in adhesive regions of a predetermined width along the seams, the adhesive regions having proximal and distal ends from near the seams toward the inside of the bag, and when a tensile force is applied to the pair of base fabric panels when the airbag is deployed, substantially no tensile force is applied to the adhesive regions, resulting in an airbag with high internal pressure retention performance and excellent compactness.
Therefore, the airbag according to the present invention can be suitably used for automobile airbags, in particular for CABs and pedestrian airbags, which require high internal pressure retention performance.

1 is a plan view of an airbag according to an embodiment of the present invention in which a pair of base fabric panels are sewn together at their outer periphery to form a bag body. 2 is an explanatory diagram of the state of an airbag when deployed, in a location corresponding to the cross section AA in FIG. 1, in which a portion bonded with a silicone adhesive is sewn. FIG. 4 is an explanatory diagram of a state of a non-breathable protective material in the airbag of the present embodiment when the airbag is deployed. FIG. 4(a) is a first pattern, and FIG. 4(b) is a second pattern (loop outside, film folded back for storage) showing a state in which, when a tensile force is applied between the pair of fabric panels in the airbag of the present embodiment during deployment of the airbag, the length between the distal ends of the folded non-breathable protective material is greater than or equal to the length between the distal ends of the pair of fabric panels, thereby maintaining an airtight structure in the adhesive region. This is an explanatory diagram of the relationship between the specified width of the adhesive region, the adhesive distance b (1/2 the length between the distal ends along the base fabric panel), the adhesive distance a (1/2 the length between the distal ends along the half-folded non-breathable film-like protective material), and the seam allowance s of the base fabric panel. This is an explanatory diagram of a state in which a non-breathable film-like protective material that is folded in half is a laminated resin film of two or more layers including a first surface layer and a second surface layer, and the first surface layer is welded to the base fabric panel, but the second surface layers are not bonded to each other, thereby maintaining an airtight structure in the adhesive area. This is an explanatory diagram of a state in which the half-folded non-breathable film-like protective material is a laminated resin film of two or more layers including a first surface layer and a second surface layer, and the first surface layer is welded to the base fabric panel, while the second surface layers are bonded together.However, when a tensile force is applied to the pair of base fabric panels when the airbag is deployed, the second surface layer peels off, thereby maintaining an airtight structure in the adhesive area. 1 is an explanatory diagram showing the relationship between the resin constituting the first surface layer and the resin constituting the second surface layer of a laminated resin film which is a non-breathable film-like protective material folded in half. FIG. FIG. 2 is an explanatory diagram of an example of a method for producing a half-folded non-breathable film-like protective material (winding up a half-folded film). FIG. 13 is an explanatory diagram of a state in which a wound, half-folded non-breathable film-like protective material is supplied to a heat welding location. This is a diagram explaining the supply state of a half-folded film in a welding process in which a half-folded, strip-shaped non-air-permeable film-like protective material consisting of a single-layer resin film with a release paper of a predetermined width sandwiched between the inner surfaces of a pair of base fabric panels, or a laminated resin film of two or more layers including a first surface layer and a second surface layer, is continuously sandwiched along the straight or curved outer peripheral edge of the pair of base fabric panels while applying tension, and heat or ultrasound from the outside of the pair of base fabric panels to weld the surface of the single-layer resin film or the first surface layer to the inner surface of the base fabric panels. This is an explanatory diagram of a case where a non-breathable protective material is produced and bonded by laminating two protective materials cut into the base fabric panel shape (horseshoe shape) shown in Figure 1. Two pieces of resin film, coated fabric, or laminated base fabric cut into a desired shape are used, and the outer layers of one end (inner edge side) of a multilayer film (for example, in the case of a multilayer film, part of the second surface layer is peeled off and the first surface layers are laminated together) or the non-coated surfaces of the base fabrics are laminated together, and the length from the outer edge is a predetermined length, and the two are laminated together by welding or adhesive along the inner edge. FIG. 1 is an explanatory diagram of a method for winding a multi-layer film in a two-ply state around a 3-inch paper tube by an inflation method using a multi-layer circular die. FIG. 1 is an explanatory diagram of a method for producing a laminated (base) fabric by using a laminator to bond a multilayer film to a silicone rubber roll so that the multilayer film is in contact with the silicone rubber roll. 1 is an explanatory diagram of an example of an airbag (cushion) including an isolated sewn portion (in the center) of a closed space. 10 is an explanatory diagram of one method of adhering a folded film to an isolated sewn portion of a closed space. FIG. FIG. 17 is an explanatory diagram of the sealing state according to the method 1 shown in FIG. 16 . 13A and 13B are explanatory diagrams of another method for adhering a folded film to an isolated sewn portion of a closed space and a sealed state. FIG. 2 is an explanatory diagram of the layer structure of a folded film in terms of the melting point difference (left side) and the interlayer SP value difference (right side).

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
One embodiment of the present invention is an airbag comprising at least one pair of base fabric panels sewn together at their outer periphery,
The airbag has both end outer surfaces of a folded, strip-shaped non-breathable protective material bonded to the inner surface of each of the pair of base fabric panels at bonding regions of a predetermined width along the seams from near the seams toward the inside of the bag, and when a tensile force is applied to the pair of base fabric panels during deployment of the airbag, the length between the distal ends along the folded, strip-shaped non-breathable protective material is greater than or equal to the length between the distal ends along the pair of base fabric panels.

[Base fabric panel (panel fabric, main panel)]
The pair of base fabric panels is not particularly limited and may be a plain weave fabric of polyamide or polyester that is normally used as a base fabric for airbags. The fineness of the fibers constituting the base fabric used in this embodiment is preferably 150 to 900 dtex. A fineness of 150 dtex or more can provide the strength required for an airbag, and a fineness of 900 dtex or less can provide a soft base fabric for an airbag.
It is preferable to use a multifilament as the fiber constituting the base fabric used in this embodiment, and the single yarn fineness of the fiber is preferably 0.1 to 10 dtex. When the fiber is in this range, the base fabric for an airbag is flexible and has a high deployment speed.
In addition, the weaving density of the base fabric used in this embodiment is preferably 30 to 90 threads/inch for both warp and weft, and the cover factor is preferably 1500 to 2500. Within this range, when used as a base fabric for an airbag, it is flexible and can obtain strength sufficient to withstand deployment. However, the cover factor is a value calculated by the following formula.
CF = (number of warp threads per 2.54 cm) × √ (total warp thread size (dtex)) + (number of weft threads per 2.54 cm) × √ (total weft thread size (dtex))

In order to reduce the breathability of the base fabric panel, it is preferable that the base fabric panel is coated with a resin on one or both sides thereof or laminated with a single-layer or multi-layer film. In this case, the resin used for the resin coating may be a silicone-based or polyurethane-based coating, or a method of thermal lamination using a flame-retardant thermoplastic resin film, etc. may be adopted.
When coating with a resin, the coating amount is preferably 5 to 50 g/m ^2. When laminating a film on a base fabric, the thickness of the film is preferably 0.001 mm or more and 0.5 mm or less. Within this range, a base fabric that is flexible and has excellent airtightness when used as a base fabric for an airbag can be obtained.

The airbag according to this embodiment can be one in which a pair of base fabric panels are sewn together at their outer periphery to form a bag, as shown in FIG. 1. In FIG. 1, reference numeral 2 indicates the sewn (stitched) portion of the main panel, and reference numeral 4' indicates the position of the inner edge (top of the loop) of a half-folded non-breathable protective material, which is on the back side of the front base fabric panel and which will be described below. As shown in FIG. 1, an inner tube (reference numeral 23) made into a cylindrical shape from base panels of the same material can be inserted into the opening, and when the airbag inflates and deploys, gas is instantly injected into the airbag from inside the inner tube.

[suture]
The stitching is not particularly limited as long as it is not broken when the airbag is inflated and deployed, but it is preferably machine-sewn with sewing thread made of multifilament fiber of the same material as the base fabric panel. As described above, in order to maintain the internal pressure, it is required that the stitching does not break when the airbag is deployed and that there is substantially no gas leakage.
The sewing thread may be a single twisted fiber or a multiple twisted fiber having two or more single twisted fibers twisted together, and the total fineness of the twisted fibers is preferably 700 to 2000 dtex.
The sewing method may be a lock stitch, a chain stitch, etc. The number of stitches (stitch pitch) is preferably 30 to 60 stitches/10 cm.

[Semi-folded non-breathable protective material]
Fig. 2 is an enlarged view of the area corresponding to the A-A cross section in Fig. 1 to prevent gas leakage at the seams, and explains the state of an airbag when it is deployed if it is sewn to the area bonded with silicone adhesive in the conventional technology. When silicone adhesive is used, the silicone adhesive deforms and stretches during deployment to seal in the gas, improving the internal pressure retention, but the thickness of the silicone adhesive after curing increases the thickness of the airbag after folding (when stored), making it difficult to store, and it takes a long time, from half a day to about a day, to cure, reducing the productivity of the airbag.

In the airbag of this embodiment, instead of using such silicone adhesive, the outer surfaces of both ends of a folded, strip-shaped non-breathable protective material are bonded to the inner surface of each of a pair of base fabric panels in an adhesive region of a predetermined width along the seam from near the seam toward the inside of the bag, the adhesive region having a proximal end and a distal end, and the length between the distal ends along the folded, strip-shaped non-breathable protective material is greater than or equal to the length between the distal ends along the pair of base fabric panels when a tensile force is applied to the pair of base fabric panels when the airbag is deployed.
The structure having such a feature may be used in the entire outer periphery of the airbag, or in a part of the airbag. Here, a part means, for example, 50% or more. When the structure having such a feature is used in a part of the airbag, for example, a silicone adhesive may be used in the stitching part of the airbag where other gas leakage may occur, in order to obtain airtightness of the entire airbag. Moreover, the structure having such a feature may be applied in the vicinity of the stitching of any two (a pair) of the base fabric panels of the airbag composed of at least two or more base fabric panels. The pair of base fabric panels do not necessarily have to have the same shape, and may be three-dimensionally sewn in which the shapes of the stitching lines between the pair of base fabric panels are different, as long as the airtightness of the adhesive region is not impaired.

In this specification, the term "an airbag formed by sewing at least one pair of fabric panels together at their outer periphery" refers to an airbag in which the fabric panels are sewn together to form an inflation chamber of the airbag, and in which two or more fabric panels are sewn together at the outer periphery of the chamber. Therefore, the airbag is not limited to an airbag composed of only two fabric panels, which are made by overlapping two fabric panels of the same shape, as shown in Figures 1 and 15, and there is no limit to the number of fabric panels that make up the airbag or the overall structure of the airbag, as long as there is a portion where two or more fabric panels are joined together at the outer periphery of the chamber. Here, there is at least one pair of fabric panels to be sewn together, that is, at least two, and these sewn fabric panels may be made of the same fabric or different fabrics. For example, this broadly includes a single, line-symmetrical base fabric panel that is folded along the line of symmetry and the overlapping portions sewn together, a single, strip-shaped base fabric panel that is rolled into a tube and the overlapping portions sewn together, and three or more base fabric panels that are sewn together, that is, as long as the partial structure has a non-breathable protective material covering the sewn portions of the base fabric panels.

In this specification, the term "non-breathable" refers to the surface property of a protective material that suppresses ventilation to a degree that does not significantly impair the airtightness of the airbag. When a differential pressure of 500 Pa is applied between the front and back of the protective material, the amount of gas passing through the surface is preferably 0.5 L/ ^dm2 /min or less, more preferably 0.1 L/ ^dm2 /min or less, and even more preferably 0.05 L/ ^dm2 /min or less.

Fig. 3 illustrates the state of the semi-folded non-breathable protective material when the airbag is deployed. As can be seen from Fig. 3, the semi-folded non-breathable protective material presents a loop shape toward the inside of the airbag and forms an airtight structure in the bonded area with the base fabric panel, thereby exhibiting internal pressure retention.
In the airbag of this embodiment, the length between the distal ends along the folded non-breathable protective material is greater than or equal to the length between the distal ends along a pair of fabric panels when the airbag is deployed, thereby maintaining an airtight structure in the adhesive region. That is, as shown in Figures 4(a) and 4(b), the loop-shaped protective material has a sufficient length, so that when the airbag is deployed and pulled horizontally from the seam, substantially no force is applied to the adhesive region between the protective material and the fabric panel, and there is no peeling or destruction in the adhesive region, so that airtightness is maintained. Note that, when the non-breathable protective material has high extensibility, even if the length of the loop of the protective material before the airbag is deployed (when the airbag is housed) is approximately the same as or shorter than the adhesive distance along the fabric panels, the non-breathable protective material is stretched by the tensile force applied when the airbag is deployed, and the seam is destroyed first, substantially no force is applied to the adhesive region, resulting in the same result.
The state of the airbag when it is deployed can be simulated by, for example, using the following method. First, the stored airbag is taken out, a part of the protective material and the base fabric panel are cut, and the pair of base fabric panels are spread 180° as shown in the deployed state in Figures 4(a) and (b). When each base fabric panel is grasped and pulled in a direction parallel to the base fabric panel, it is confirmed whether the seam is broken before the protective material. At this time, attention is paid to arranging the seam so that it is approximately perpendicular to the pulling direction. As described above, Figure 4(a) is the first pattern, and Figure 4(b) is the second pattern (loop outside, film folded back and stored). In either pattern, in the state when the airbag is deployed, the length between the distal ends along the half-folded non-breathable protective material is greater than or equal to the length between the distal ends along the pair of base fabric panels, thereby maintaining an airtight structure in the adhesive region.

In this specification, the term "half-folded (film-like) non-breathable protective material" refers not only to a material that is in a half-folded state when housed in an airbag, as shown in the upper part of Figures 4(a) and (b), i.e., a material in which a strip-shaped single-layer or multi-layer resin film or laminate base fabric is half-folded, but also to a material that is folded multiple times, such as into an accordion-like shape, or to a material in which two strip-shaped (including curved) single-layer or multi-layer resin films or laminate base fabrics are overlapped and one end is bonded or welded with an adhesive (i.e., a material produced by laminating two sheets together). Such a band-shaped non-breathable protective material may be adhered to the base fabric in a straight or curved line along the seam, or may be prepared by using two pieces of resin film, coated fabric, or laminated base fabric cut into a desired shape, and overlapping the outer layers of one end (inner edge side) of the multilayer film (for example, in the case of a PE (second surface layer)-PA6/12 (first surface layer) multilayer film, a part of the second surface layer is peeled off and the first surface layers are overlapped) or the non-coated surfaces of the base fabric, and welding them together along the inner edge so that the length from the outer edge is a predetermined length, for example, at a width of 5 mm, or by bonding them together with, for example, a cyanoacrylate-based instant adhesive (manufactured by Konishi Co., Ltd.), and thoroughly drying (i.e., not in a band shape, but for example, by bonding two pieces of protective material cut into the base fabric panel shape (horseshoe shape) shown in FIG. 1) (see FIG. 12).
However, it is more preferable to manufacture the protective material by continuously supplying a band-shaped resin film folded in half and heat welding it while applying tension as shown in Figs. 9 to 11, rather than by manufacturing it by the two-sheet lamination method. This is because, while the two-sheet lamination method requires cutting out the resin film along the sewing shape of the airbag, by using a band-shaped resin film folded in half, the utilization efficiency of the film can be maximized, and the productivity can be increased because there is no process of bonding the films together. That is, since the film is cut into strips, there is little loss when cutting out the film, and there is no process of bonding the films together, so the productivity is high. Furthermore, since an actual airbag is deployed instantly from a folded state, a part of the airbag may be exposed to a very fast inflator gas flow velocity at the beginning of deployment, etc., but by using a single resin film, the adhesive space between the resin films is not required, and the adhesive space can be prevented from being exposed to the gas flow velocity and being destroyed. Furthermore, since there is no need to bond resin films together, there is little change in thickness or hardness of the loop-shaped resin film between the distal ends along the half-folded band-shaped resin film, and even if the airbag is exposed to a high gas flow rate when it is deployed, stress concentration occurs at the location where the thickness or hardness changes at the adhesive interface between the resin films, etc., and the loop structure is prevented from being destroyed. In addition, by using a single resin film, it is possible to prevent the film from becoming hard due to adhesion between the films, compared to the method of bonding two films together, and since there is no need for an adhesive between the films, the airbag can be made lighter and the storability of the airbag can be improved.
When a resin film is used as the half-folded non-breathable protective material, by using a manufacturing method in which the resin film is continuously supplied and thermally welded while applying tension, as described below, even if the material is a single sheet of non-breathable protective material, it is possible to weld even curved portions (including R portions and reverse R portions) without wrinkles, and to produce an airbag with excellent airtightness.

As mentioned above, the band-shaped non-breathable protective material folded in half is preferably "a single resin film folded in half," but in this specification, the term "a single resin film folded in half" means that the film is continuously manufactured as shown in Figures 13 and 14, folded in half to form a roll as shown in Figure 9, and integrated at the point where it can be unwound and supplied for bonding to the base fabric panel, making it a single piece, regardless of whether such a single piece is a multilayer resin film or whether it has been cut to a specified length. In addition, the term "a single resin film folded in half" does not include those made by the two-sheet lamination method, as mentioned above.

　There are no particular limitations on the non-breathable protective material as long as it is not destroyed when the airbag is inflated or deployed, and single-layer or multi-layer resin films, woven fabrics, knitted fabrics, nonwoven fabrics, etc. can be used. When using a substrate such as woven fabric, knitted fabric, or nonwoven fabric, it is preferable to coat both or one side of the substrate with resin or laminate a single-layer or multi-layer film to obtain the internal pressure retention of the airbag. However, from the viewpoint of the weight reduction and compactness (foldability, storability) of the airbag, it is more preferable to use a single-layer or multi-layer resin film as the non-breathable protective material rather than a coated fabric or laminated base fabric. When using a single-layer or multi-layer resin film as the non-breathable protective material, or a substrate laminated with a single-layer or multi-layer film, the adhesive strength can be increased and the internal pressure retention of the airbag can be improved by bonding the substrate panel laminated with the same type of single-layer or multi-layer resin film. Furthermore, by using the same type of single-layer or multi-layer resin film (and substrate) used for the non-breathable protective material and the base fabric panel, recyclability can be improved.

In this specification, the term "bonding" includes bonding with an adhesive and welding with ultrasonic waves or heat. As explained in the section on the manufacturing method of the airbag below, if the material of the base fabric panel and the material of the outer layer of the semi-folded non-breathable protective material are the same, the base fabric panel and the protective material can be bonded by welding using heat or ultrasonic waves to form a bonded area that will not peel off even when the airbag is deployed and can maintain airtightness. Welding without using adhesives is preferable from the standpoint of thickness after folding, productivity, recycling, etc.

As shown in Figures 4(a) and 4(b), the term "bonding region (5, 5')" has a proximal end (6, 6') and a distal end (7, 7') with respect to the seam (2). As shown in Figures 4(a), 4(b) and 5, the proximal end (6, 6') may be located on the inside of the airbag from the seam (2) (see the upper part of Figures 4(a) and 4(b) and the lower part of Figure 5) or on the outside of the airbag (see the upper part of Figure 5). In the latter case, the bonding region will extend to the seam allowance s.
Also, as shown in Fig. 4(b), the loop structure of the half-folded non-breathable protective material in the adhesive region may be arranged to face the outer edge of the airbag (the outside of the airbag). When the airbag is deployed, the half-folded non-breathable protective material assumes a loop shape toward the inside of the airbag, and the length between the distal ends along the half-folded non-breathable protective material becomes larger than the length between the distal ends along a pair of base fabric panels, so that an airtight structure can be formed in the adhesive region with the base fabric panels in the same manner as in the case of Fig. 4(a).
The "bonded region" need only be bonded in such a way that it will not be destroyed or peeled off when the airbag inflates and deploys, and that it maintains airtightness and internal pressure retention.

5 illustrates the relationship between the seam allowance s, the predetermined width w of the bonded region, the bonded distance a, which is 1/2 the length between the distal ends along the folded non-breathable protective material, and the bonded distance b, which is 1/2 the length between the distal ends along a pair of base fabric panels. That is, the distal end is the reference point for the bonded distance a from the seam to the distal end (1/2 the length between the distal ends along a pair of base fabric panels) and the bonded distance b (1/2 the length between the distal ends along the folded non-breathable protective material).
In the airbag of this embodiment, when the airbag is not deployed, stored, or folded, 1/2 of the length between the distal ends along the folded non-breathable protective material (adhesive distance a) and 1/2 of the length between the distal ends along the pair of base fabric panels (adhesive distance b) are preferably in the relationship of 0.5<a/b<10, more preferably 1.0<a/b<2.0, and even more preferably 1.1<a/b<1.8. When the airbag is deployed, the adhesive region must not break and airtightness must be maintained, but the value of a/b can be appropriately adjusted taking into account the elasticity of the base fabric panel and the protective material. As mentioned above, in the range of 0.5<a/b≦1.0, it is assumed that the protective material has extensibility and stretchability.
In the airbag of this embodiment, when the airbag is not deployed, stored or folded, half of the length between the distal ends along the folded non-breathable protective material (adhesive distance a) is preferably 0.1 cm or more and 10.0 cm or less, and more preferably 0.5 cm or more and 4.0 cm or less, from the viewpoints of airtightness and folded thickness.

In the airbag of this embodiment, when the airbag is not deployed, stored, or folded, the predetermined width w of the adhesive region is preferably 0.1 cm or more and 5.0 cm or less, and more preferably 0.5 cm or more and 3.0 cm or less, from the viewpoints of airtightness and folded thickness.

In the airbag of this embodiment, when the airbag is not deployed, stored or folded, the effective adhesive width, which is the smaller of 1/2 the length between the distal ends along the pair of base fabric panels (adhesive distance b) and the specified width w of the adhesive region, is preferably 0.1 cm or more, and more preferably 0.5 cm or more, from the standpoint of airtightness and folded thickness.

In the airbag of this embodiment, when the airbag is not deployed, stored or folded, the ratio w/b of 1/2 of the length between the distal ends along the pair of base fabric panels (bonding distance b) to the predetermined width w of the bonded area is preferably in the range of 0.2<w/b<5.0, and more preferably 0.5<w/b<2.0, from the standpoint of airtightness and folded thickness.

In the airbag of this embodiment, the thickness of the non-breathable protective material is preferably 0.001 mm or more and 0.5 mm or less, and more preferably 0.001 mm or more and 0.1 mm or less, from the viewpoint of the folded thickness.

In the airbag of this embodiment, the adhesive strength (peel strength) in the adhesive region between the base fabric panel and the non-breathable protective material is preferably 1 N/cm or more, and more preferably 3 N/cm or more, from the viewpoint of airtightness. If the adhesive strength is 3 N/cm or more, the occurrence of leaks caused by the film peeling off from the panel base fabric due to the wind pressure of the gas when the airbag is deployed is significantly reduced.

The airbag (cushion) of this embodiment may include an isolated sewn portion (in the center) of a closed space as shown in FIG. 15. A method for manufacturing an airbag having an isolated sewn portion of a closed space will be described later.

The tensile modulus of the half-folded band-shaped non-breathable protective material is preferably 100 to 800 MPa in both MD (machine direction) and TD (transverse direction), more preferably 150 to 600 MPa, and even more preferably 200 to 500 MPa. However, the tensile modulus of the film referred to here is the measurement result when the band-shaped non-breathable film-like protective material is opened from the half-folded state and pulled. When tension is applied to the band-shaped non-breathable film-like protective material to deform it to fit the curved outer edge, the above tensile modulus (flexibility) makes it easy to form a curved structure to fit the curved parts (including R parts and reverse R parts) that are usually used in the main fabric of an airbag. By setting the tensile modulus to 100 to 800 MPa, the film has moderate flexibility and good handleability (balance between ease of deformation at curved parts and handling of the film). In addition, in terms of the durability required for the film, the tensile breaking strength of the film is preferably 10 to 100 MPa in both MD and TD from the viewpoint of durability, more preferably 15 to 80 MPa, and even more preferably 20 to 60 MPa. By setting the tensile breaking strength to 100 MPa or less, the rigidity is suppressed and the film has good handling properties. Furthermore, when the band-shaped non-permeable and breathable film-like protective material is deformed to follow the curved outer peripheral edge by applying tension, it is preferable to use a thermoplastic resin film, since the film can be easily stretched by applying heat.

The airbag of this embodiment may have an R portion with a radius of curvature of 300 mm or less and/or an inverse R portion with a radius of curvature of 300 mm or less in the adhesive region, as shown in Figs. 1 and 15. Here, the R portion is a portion of the seam line along the outer periphery of the base fabric panel that has a curved shape that is convex toward the side other than the inflatable portion (chamber) of the airbag. For example, the X portion in Fig. 1 corresponds to this. On the other hand, the inverse R portion is a portion of the seam line along the outer periphery of the base fabric panel that has a curved shape that is convex toward the inflatable portion (chamber) of the airbag. For example, the Y portion in Fig. 1 corresponds to this. In curved seams including such R portions and inverse R portions, wrinkles are more likely to occur when the non-breathable protective material is adhered along the seam line than in straight seams, and tension is more likely to be applied to the sewn portion when the airbag is deployed. The degree of wrinkles when the non-breathable protective material is adhered can be confirmed by measuring the step (peak-valley difference) between the wrinkled portion and the normal portion. The step (peak-valley difference) between the wrinkled portion and the normal portion of the R portion is preferably 400 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, and even more preferably 100 μm or less. By making the surface step (peak-valley difference) of the R portion 400 μm or less, the step between the wrinkled portion and the normal portion can be reduced to prevent stress concentration, gas leakage from the adhesive portion can be suppressed, and an airbag with excellent storage capacity can be obtained.
In addition, the ratio (R portion/straight portion) of the step (peak-valley difference) between the wrinkled portion and the normal portion of the R portion to the step (peak-valley difference) between the wrinkled portion and the normal portion of the approximately straight portion excluding the R portion is preferably 0.6 to 2.0, and more preferably 0.8 to 1.5.
The wrinkle step measurement was performed using a surface roughness measuring instrument (SURFTEST EXTREME SV-3000CNC) manufactured by Mitutoyo Corporation, and the wrinkled area and the surrounding normal area were measured in three-dimensional mode under the following measurement conditions. An arbitrary cross-section extraction function was used in the obtained three-dimensional image to extract a cross-section that included the largest step area, and a baseline was drawn on the extracted cross-section (two-dimensional) connecting the start point and end point of the wrinkled area (step), and the maximum height from the baseline was determined.
(Surface roughness measurement conditions)
Measurement length: 10 mm
Measurement width: 5 mm
Measurement speed: 5 mm/sec
Sampling pitch: 1 μm
Sampling interval: 50 μm
Stylus: radius = 10 μm (Code No. 12AAB415)
(Image processing)
-Trend correction is only performed on the "plane"

In addition, the adhesive strength (peel strength) in the adhesive region between the base fabric panel and the non-breathable protective material in the R portion is preferably 1 N/cm or more, more preferably 2 N/cm or more, and even more preferably 3 N/cm or more. If the adhesive strength is 3 N/cm or more, the occurrence of leakage caused by the film peeling off from the panel base fabric due to the wind pressure of the gas when the airbag is deployed is significantly reduced. However, the adhesive strength (peel strength) in the adhesive region between the base fabric panel and the non-breathable protective material in the R portion referred to here is calculated based on the tensile strength of a test piece obtained by cutting the airbag into a 100 x 30 strip shape perpendicular to the line connecting the two points, as described below in the measurement method of the adhesive strength (peel strength) (N/cm) between the protective material and the panel fabric in the R portion, and the sample is taken from the R portion with a curvature radius of 300 mm or less.
In addition, the ratio of the adhesive strength at the R portion to the adhesive strength of the substantially straight portion excluding the R portion (R portion/substantially straight portion) is preferably 0.5 to 2.5, more preferably 0.7 to 2.0, and even more preferably 0.8 to 1.5. By setting the adhesive strength ratio within the above range, there are no portions in the entire airbag with extremely low adhesive strength, and therefore the occurrence of leaks caused by the film peeling off from the panel base fabric due to the wind pressure of gas when the airbag is deployed is significantly reduced.

[Airbag manufacturing method]
The method for manufacturing the airbag of the present embodiment is not particularly limited. For example, the method for manufacturing the airbag may include the following steps:
a step of sandwiching a non-breathable film-like protective material having a predetermined width and made of a laminated resin film having two or more layers including a first surface layer and a second surface layer, between the inner surfaces of the pair of base fabric panels along the outer periphery of the pair of base fabric panels, the non-breathable film-like protective material having a shape conforming to the shape of the base fabric panels and being in a half-folded strip shape;
a welding step of applying heat or ultrasonic waves from the outside of the pair of fabric panels to weld the first surface layer to the inner surface of the pair of fabric panels, wherein the second surface layers are not welded to each other by thermal welding or ultrasonic welding, or are welded to each other by thermal welding or ultrasonic welding, but the second surface layers peel off when a tensile force is applied to the pair of fabric panels when the airbag is deployed;
a sewing step of sewing the pair of fabric panels together adjacent the area of the resulting weld, either before, after, or simultaneously with said welding;
The manufacturing method may include the steps of:

As shown in Figures 6, 7 and 8, when a single-layer resin film is used as the protective material for heat welding between the base fabric panel and the protective material by heating, if a release paper is inserted inside the loop, it is possible to bond a protective material of a sufficient loop length to maintain airtightness in the bonding area, but if a multi-layer resin film is used as the half-folded belt-shaped protective material and no release paper is used, the second surface layers on the inside of the loop are not bonded to each other, or are welded by heat welding or ultrasonic welding, but when a tensile strength is applied to the pair of base fabric panels when the airbag is deployed, the productivity of the airbag is improved by configuring the second surface layers to peel off. Furthermore, with such a configuration, even if it is difficult to remove the release paper from the sewn curved or circular shape due to the sewing shape of the airbag, the release paper does not remain in the airbag, so that the weight of the airbag does not increase and the storability does not deteriorate, and the release paper can be prevented from affecting the deployment speed and deployment behavior of the airbag.
Such a configuration can be achieved, for example, by setting the melting point of the resin constituting the first surface layer of the laminated resin film, which is a non-breathable film-like protective material that is folded in half, to be 50°C to 160°C lower than the melting point of the resin constituting the second surface layer, so that the second surface layers on the inside of the loop are not welded to each other, or by setting the difference in SP value of the resin constituting the first surface layer and the resin constituting the second surface layer of the laminated resin film, which is a non-breathable film-like protective material that is folded in half, between adjacent layers to be 2.0 [cal/ ^cm3 ) ^1/2 ] or more, so that delamination of the first surface layer occurs or the second surface layer peels off from the first surface layer. That is, in a multilayer film including a first surface layer and a second surface layer of the laminated resin film which is the half-folded non-breathable film-like protective material, the difference in SP value between any adjacent layers is preferably 2.0 [cal/ ^cm3 ) ^1/2 ] or more, more preferably 2.5 [cal/ ^cm3 ) ^1/2 ] or more, even more preferably 3.0 [cal/ ^cm3 ) ^1/2 ] or more, and even more preferably 4.0 [cal/ ^cm3 ) ^1/2 ] or more.

Hereinafter, such a configuration will be described with reference to FIG.
For example, the melting point of PA6/12 is 128°C, the melting point of TPEE is 216°C, the melting point of PA6/66 is 194°C, the melting point of PA12 elastomer is 176°C, the melting point of PO (acid-modified polyethylene) is 120°C, and the melting point of PE (LDPE) is 110°C. Therefore, if a TPEE (second surface layer)-PA6/12 (first surface layer) multilayer film, a TPEE-PO-PA6/12 multilayer film, or a PA6/66-PO-PA6/12 multilayer film is used as a protective material, the difference between the melting point of the resin constituting the first surface layer and the melting point of the resin constituting the second surface layer can be made 50°C or more. The preferred range of the melting point difference is 50°C to 160°C, more preferably 60°C to 160°C, and even more preferably 80°C to 160°C. By making the melting point difference 50°C or more, the adhesive strength with the base fabric panel can be increased and fusion between the second surfaces can be made less likely to occur. Furthermore, by making the melting point difference 160° C. or less, when a film is produced by, for example, inflation molding, flow irregularities and melt tension are appropriately maintained, improving the stability of film production.
The melting point of the resin constituting the protective material is preferably 90° C. or higher, more preferably 100° C. or higher, and even more preferably 110° C. or higher. By making the melting point 90° C. or higher, sufficient adhesive strength can be maintained even when the temperature inside the vehicle becomes high.

For example, the SP value of PE is 8.1 [cal/cm ³ ) ^1/2 ], the SP value of PA6/66 is 13.6 [cal/cm ³ ) ^1/2 ], the SP value of PA6/12 is 13.6 [cal/cm ³ ) ^1/2 ] and the SP value of PET is 10.7 [cal/cm ³ ) ^1/2 ], so if PE (second surface layer)-PA6/66 (first surface layer) or PE (second surface layer)-PET (first surface layer) is used as the protective material, the difference in SP value with the PA base fabric or PET base fabric, respectively, can be made 2.0 [cal/cm ³ ) ^1/2 ] or more.

For example, in the case of the diagram on the right side of Fig. 19 (SP value difference), the first surface layer (fabric panel side) can be considered to be composed of an adhesive layer (PA6/12), while the second surface layer (inside the loop) can be considered to be composed of four layers including a release layer (PE), an intermediate layer (acid-modified PE), and a high melting point layer (PA6/66). It should be noted that the release effect can be achieved not only when the SP value difference between the high melting point layer (PA6/66) and the release layer (PE) is greater than or equal to 2.0 [cal/cm3)1/2], but also when the SP value difference between any of the adjacent layers constituting the first surface layer, the adhesive layer (PA6/12), the X layer (e.g., the intermediate layer (acid-modified PE)), and the high melting point layer (PA6/66), is greater than or equal to 2.0 [cal/ ^cm3 ) ^1/2 .

The above-mentioned configuration based on the SP value difference is preferable to the above-mentioned configuration based on the melting point difference. The reason for this is that the fusion (processing) temperature can be raised above the melting point of the film, making it possible to strengthen the adhesion between the base fabric panel and the film, and by increasing the processing speed, productivity can be improved.

The SP value (Hildebrand solubility parameter) is a physical property defined as the square root of the cohesive energy density, and indicates the solubility behavior of a solvent. Therefore, the inventors of this application used combinations with large differences in SP value as an index for selecting the release layer. The SP values of various resins are listed, for example, in "Guide to Various Standards and Usage: Plastic Material Test Methods, Comparisons, Evaluations, and Results" p. 32 (2nd edition, May 10, 2011) by Sangyo Gijutsu Center Co., Ltd., and a reference for calculating the SP value is "Practical Polymers for Engineers" by Kodansha, August 1, 1989.

In addition to the SP value, the Hansen solubility parameter (HSP) is also a commonly used parameter. The HSP value is also shown in the examples, but the peeling effect can be achieved by making the HSP value difference 1.0 (cal/ ^cm3 ) ^1/2 or more.
Here, HSP is a predicted value by Winmostar (V9.3.0) manufactured by CrossAbility Co., Ltd., and is calculated by the dispersion term (δD), polarization term (δP), and hydrogen bond term (δH) between certain substances. In addition, the HSP calculation for the copolymer composition is a value obtained by calculating the HSP of each homopolymer and multiplying it by the composition ratio (volume ratio) to obtain a total value.

In addition, in order to avoid tacking in a high-temperature environment and ensure internal pressure retention after aging, the glass transition temperature (Tg) of the second surface layer (inside of the loop) is preferably 0°C or higher, more preferably 20°C or higher, and even more preferably 30°C or higher. On the other hand, in terms of flexibility, the upper limit of the glass transition temperature is 80°C or lower, more preferably 70°C or lower, and even more preferably 60°C or lower.

By using the above-described manufacturing method, in an airbag in which a pair of base fabric panels are sewn together at their outer periphery to form a bag body,
An airbag can be provided with high productivity in which both end outer surfaces of a folded, band-like, non-breathable film-like protective material are bonded to the inner surface of each of the pair of base fabric panels in an adhesive region of a predetermined width along the seam from near the seam toward the inside of the bag body, the outer surfaces being bonded in a straight or curved line, the folded, non-breathable film-like protective material being a laminated resin film of two or more layers including a first surface layer and a second surface layer, the first surface layer being welded to the base fabric panel, and the second surface layers being not bonded to each other, or being bonded to each other but causing the second surface layer to peel off when a tensile force is applied to the pair of base fabric panels when the airbag is deployed.

The airbag of the present embodiment can also be manufactured (provided) with high productivity by using the manufacturing method described below.
[Tensioning and clamping method]
A method for manufacturing an airbag in which a pair of base fabric panels are sewn together at their outer periphery to form a bag, the method comprising the steps of:
a welding step of continuously sandwiching a semi-folded, band-shaped non-breathable film-like protective material, which is made of a single-layer resin film having a predetermined width and a release paper sandwiched therebetween or a laminated resin film having two or more layers including a first surface layer and a second surface layer, between the inner surfaces of the pair of base fabric panels along the straight or curved outer periphery of the pair of base fabric panels while applying tension thereto, and welding a surface of the single-layer resin film or the first surface layer to the inner surface of the base fabric panel by applying heat or ultrasonic waves from the outside of the pair of base fabric panels, wherein although the surfaces of the single-layer resin film on the release paper side are not welded to each other due to the presence of the release paper, or the second surface layers of the laminated resin film are not welded to each other by heat welding or ultrasonic welding, or are welded to each other by heat welding or ultrasonic welding, the second surface layer peels off when a tensile force is applied to the pair of base fabric panels when the airbag is deployed;
a sewing step of sewing the pair of fabric panels together adjacent the area of the resulting weld, either before, after, or simultaneously with said bonding;
The manufacturing method comprising the steps of:
In the above manufacturing method, for the workability (R processability, reverse R processability) of welding the film into a curved shape, the tensile modulus of the film is preferably 100 to 800 MPa in both MD (machine direction) and TD (transverse direction), more preferably 150 to 600 MPa, and even more preferably 200 to 500 MPa. However, the tensile modulus of the film referred to here is a measurement result when the band-shaped non-permeable and breathable film-like protective material is opened from a half-folded state and pulled. When the band-shaped non-permeable and breathable film-like protective material is deformed to follow the curved outer periphery by applying tension, the above tensile modulus (flexibility) makes it easy to form a curved structure along the curved part that is usually used in the main fabric of an airbag. By setting the tensile modulus to 100 to 800 MPa, the film has a good handleability (balance between ease of deformation at the curved part and handling of the film) due to moderate flexibility. In terms of the durability required for the film, the tensile breaking strength of the film is preferably 10 to 100 MPa in both MD and TD, more preferably 15 to 80 MPa, and even more preferably 20 to 60 MPa. By setting the tensile breaking strength to 100 MPa or less, the rigidity is suppressed, resulting in a film with good handleability.

In the above manufacturing method, methods for sandwiching a strip-shaped non-air-permeable, breathable film-like protective material along the straight or curved outer peripheral edges of a pair of base fabric panels include a method of preparing a roll of half-folded film in advance and sending the strip-shaped non-air-permeable film-like protective material from the roll to the welding point by heat welding or ultrasonic welding, as exemplified in Figures 9 to 11, a method of preparing a roll of the strip-shaped non-air-permeable film-like protective material in an unfolded state in advance and folding the strip-shaped non-air-permeable film-like protective material in half during the process of sending it from the roll to the welding point by heat welding or ultrasonic welding, and then sending it to the welding point, and a method of folding a strip-shaped non-air-permeable film-like protective material that has been cut in advance to the length of the straight or curved outer peripheral edges of a pair of base fabric panels in half and sending it to the welding point by heat welding or ultrasonic welding, and the first method is preferred. By winding the film that has already been folded in half onto a roll, the pleats in the folded portion can be firmly fixed, and by continuously feeding the film from the wound roll, the folded portion of the film is less likely to shift, and warping of the folded film is suppressed (as the film structure is symmetrical between the top and bottom), which is expected to have the further effect of suppressing the occurrence of wrinkles (improving quality).

In this manufacturing method, the method of applying tension to the half-folded film (tape) is not particularly limited, but for example, a method can be used in which the tape is pulled while adjusting the tension applied to the tape so as to conform to the shape of the outer peripheral edge of the airbag while holding the tape with one hand and the base fabric with the other hand, as shown in Fig. 11. Alternatively, a roll of the half-folded film may be prepared in advance, and a tension control mechanism may be provided in the process of feeding the band-shaped non-breathable film-like protective material from the roll to the welding location by thermal welding or ultrasonic welding.
Also, for example, as shown in Fig. 11, the base fabric is sandwiched between upper and lower conveyor belts at the welding location, and while the base fabric is transported by the conveyor belt, it is sandwiched between upper and lower hot plates and heat is applied, so that continuous welding can be performed. In the vicinity of the welding location, the tape (sandwiched between the base fabrics) is in a heated state, and the tape is stretched to fit the shape of the outer periphery of the airbag by applying tension, so that the non-air-permeable and breathable film-like protective material can be bonded without wrinkles even in curved parts including R parts and reverse R parts. Furthermore, before welding by heat welding or ultrasonic welding, a part or the whole of the non-air-permeable and breathable film-like protective material can be preheated by a method such as a hot plate or hot air, so that the tape can be easily stretched to fit the shape of the outer periphery of the airbag.
As shown in Fig. 11, a cooling section using a cooling plate may be provided immediately after welding. By providing a cooling section, the adhesiveness of the non-permeable, breathable film-like protective material is improved. In addition, by intermittently applying and releasing the pressure of the hot plate and the cooling plate, the welding workability of the curved portion can be improved.

However, the method of continuously sandwiching the half-folded film (tape) along the straight or curved outer periphery of the pair of base fabric panels while applying tension to the film and applying heat or ultrasonic waves from the outside of the pair of base fabric panels to bond the panels together may lead to misalignment of the base fabrics, as the upper and lower base fabrics are bonded together continuously and simultaneously. Also, in the final stages of bonding or depending on the sewing shape of the airbag, there may be a small space, which may make it difficult to insert the tape under the upper base fabric.

Instead of the above-mentioned tensioning and clamping method, the following two-step method may be used, in which, rather than clamping the tape between a pair of base fabric panels, one side of the tape is adhered to the first piece of base fabric (1st step), and then a second piece of base fabric is placed on top of the tape and compressed (2nd step).

[2-Step Method]
a welding step of applying tension to a semi-folded band-shaped non-breathable film-like protective material of a predetermined width, which is made of a laminated resin film of two or more layers including a first surface layer and a second surface layer, on one base fabric panel, while continuously applying heat or ultrasonic waves to the band-shaped non-breathable film-like protective material along a straight or curved outer periphery of the one base fabric panel from below the one base fabric panel, thereby welding the first surface layer to an upper surface of the one base fabric panel;
a welding step of overlapping another base fabric panel on the welded film-like protective material and applying heat or ultrasonic waves from the upper side of the overlapped base fabric panel to weld the first surface layer to the lower surface of the overlapped base fabric panel, wherein the second surface layers of the laminated resin film are not welded to each other by thermal welding or ultrasonic welding, or are welded to each other by thermal welding or ultrasonic welding, but the second surface layer peels off when a tensile force is applied to the base fabric panels when the airbag is deployed;
a sewing step of sewing the fabric panels together adjacent the areas of the resulting welds after said bonding;
The manufacturing method comprising the steps of:

In the 2-step method, instead of sandwiching the tape between a pair of base fabric panels, the tape is first fed onto one base fabric panel while applying tension, and then the tape is welded onto the first base fabric by heating from below, thereby fixing the tape onto one base fabric panel without wrinkles (1st step). Then, a second base fabric is placed on top of the tape, and pressure-bonded by heating by thermal welding or ultrasonic welding (2nd step). This eliminates the need to simultaneously operate the upper and lower base fabrics as described above, and only one base fabric is operated. Also, since the tape is not sandwiched between the base fabrics, a situation in which the space becomes narrow at the final stage of bonding does not occur.
In this manufacturing method, the method of applying tension to the tape is not particularly limited, and a method of pulling the tape while adjusting the tension applied to it so as to follow the shape of the outer periphery of the airbag, while holding the tape with one hand and the base fabric with the other hand, can be used, similar to the above-mentioned tension application and sandwiching method. Alternatively, a roll of a half-folded film may be prepared in advance, and a tension control mechanism may be provided in the process of feeding a strip-shaped non-breathable film-like protective material from the roll to a welding location by thermal welding or ultrasonic welding. In this manufacturing method, since the tape is not sandwiched between the base fabrics, there is an advantage that the operation of continuously welding the tape while automatically inserting it into the hot plate part of the welding machine (belt thermocompression machine) is easy to perform. By automatically inserting the tape into the heating part, the occurrence of processing defects due to the positional deviation of the tape caused by manual work is reduced. In addition, when the tape is automatically inserted into the belt thermocompression machine, tension can be indirectly applied to the tape by changing the direction when feeding the base fabric side, and the tape can be stretched in the vicinity of the welding location so as to follow the shape of the outer periphery of the airbag. In this manufacturing method, like the above-mentioned tension application and clamping method, it is possible to preheat a part or the whole of the tape, provide a cooling section, and apply/release the pressure of the hot plate and the cold plate intermittently. In preheating the tape, for example, while the tape is welded onto the first base fabric by the hot plate from below the belt thermocompression machine, the tape can be assisted in stretching the R and reverse R portions by heating with the upper hot plate.
In this manufacturing method, the method for placing the second base fabric on the tape and heating by thermal welding or ultrasonic welding is not particularly limited, and may be continuously welded using a belt heat pressing machine as in the first step, or may be welded at once using a heat press machine that can heat the welded parts simultaneously, but from the viewpoint of productivity, it is preferable to use a heat press machine that can heat the welded parts simultaneously. In this manufacturing method, since the welded parts are heated twice, the first step is expected to have the secondary effect of improving the processing speed by temporarily fixing the welded parts.

[Method of manufacturing an airbag including an isolated sewn portion in a closed space]
In order to ensure the internal pressure of the airbag by applying tension and sandwiching in an isolated sewn part in a closed space as shown in Fig. 15, it is necessary to fabricate the half-folded strip-shaped non-breathable protective material so that the ends (both the start and end points) are not open. For this purpose, the following two methods can be adopted.
In one method, as shown in Fig. 16, a band-shaped non-breathable protective material is cut to a certain length with a margin, and both ends are sealed in advance (a) (for example, after peeling off the LDPE film of the inner layer, heat-pressing is performed for a sufficient time). Then, one end is left and sandwiched between the base fabric to start adhesion (thermal welding) (b), and finally the other end is overlapped and both ends are adhered to each other (c), and then sewn (d). The sealed state after sewing is shown in Fig. 17 (reference number 2: seam, reference number 5: adhesive area).
In the second method, as shown in Fig. 18, instead of sealing both ends of the folded strip of non-breathable protective material in advance, one end is sandwiched between the base fabric and straddles the dotted line to the right of where the sewing part should be (see the left side of Fig. 18), and adhesion (thermal welding) is started, and finally the other end is overlapped, also straddles the dotted line to the right of where the sewing part should be, and both ends are adhered to each other, and then sewn. As shown in the right side of Fig. 18, it can be seen that the airbag is sealed by the adhesive area in both A-A'section and C-C'section (reference number 2: seam, reference number 5: adhesive area).
As shown in Fig. 17 and Fig. 18, the half-folded band-shaped non-breathable protective material is adhered to the inner surface of each of the pair of base fabric panels in an overlapping manner, and the end of the non-breathable protective material may be sealed. Here, the non-breathable protective material is "adhered to the overlapping manner" means that a plurality of the non-breathable protective materials are arranged in an overlapping manner, the non-breathable protective materials are adhered to each other, and the non-breathable protective material closest to the base fabric panel is adhered to the inner surface of each of the pair of base fabric panels. For example, as shown in Fig. 17 and Fig. 18, the non-breathable protective materials may be overlapped at the same sewing portion and adhered to each other, or in a sewing shape having a branch point, a half-folded band-shaped non-breathable protective material arranged near one sewing line and a half-folded band-shaped non-breathable protective material arranged near the other sewing line may be partially overlapped and adhered near the sewing branch point. In either case, the multiple non-breathable protective materials are united to form a loop-shaped structure bonded to the inner surface of each of the base fabric panels, and when a tensile force is applied between the pair of base fabric panels, a state can be formed in which the length between the distal ends along the folded non-breathable protective materials is greater than or equal to the length between the distal ends along the pair of base fabric panels.
The term "sealed end portions" of the non-breathable protective materials refers to a state in which the end portions of the plurality of non-breathable protective materials are not open to the inflatable portion (chamber) of the airbag. The method for sealing the end portions of the non-breathable protective materials is not particularly limited, and may be adhesion with an adhesive, heat welding, ultrasonic welding, or folding the non-breathable protective materials. Also, as shown in FIG. 18, a structure in which the end portions are exposed to the outside of the inflatable portion (chamber) may be used.
This manufacturing method can be used as a method for intentionally providing a joint portion of a band-shaped non-breathable protective material folded in half when welding a band-shaped non-breathable protective material folded in half near a sewing shape having a branch point or a bent sewing shape, when the airbag size is large and the process is divided from the viewpoint of workability, etc. Moreover, regardless of the tension application or clamping method, it can be widely applied to the 2-step method, the two-sheet bonding method, etc.

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.

[(Si) coated (base) fabric]
The Si-coated fabric used as the base fabric panel and/or protective material was a plain weave fabric woven using nylon 66 multifilament fibers as the warp and weft, with one side coated with silicone resin. The total fineness of the weaving yarn constituting the base fabric was 470 dtex, the number of filaments was 136, the weaving density of the coated fabric was 49/inch (2.54 cm), and the amount of silicone resin coated was 25 g/ ^m2 .

[Laminate (base) fabric]
The multilayer film was laminated on one side of a plain weave fabric woven using nylon 66 multifilament fibers as the warp and weft. The total fineness of the weaving yarn constituting the base fabric was 470 dtex, the number of filaments was 136, and the weaving density of the coated fabric was 49/inch (2.54 cm).
The multilayer film used was a three-kind, three-layer film with a layer structure of "adhesive layer/middle layer/outer layer". PA6/12 was used for the adhesive layer, m-PE for the middle layer, and PA6/66 for the outer layer. The film was extruded from a multilayer circular die and an inflation method was used to obtain a three-kind, three-layer film with a thickness of 20 μm. The adhesive layer was used as the surface to be laminated to the plain weave base fabric.
The multilayer film and the nylon 66 base fabric were overlapped and bonded using a laminator (see FIG. 14) so that the multilayer film was in contact with the silicone rubber roll. The lamination conditions were as follows:
Temperature: 160°C
Roll speed: 0.3 m/min Linear pressure: 2.3 kg/cm

[film]
(Film Preparation Method)
The film used as the protective material was produced as follows. As shown in FIG. 13, a multi-layer circular die was used to wind the desired multi-layer film in a two-ply state around a 3-inch paper tube by the inflation method. At this time, the film was formed so that the inner surface side 1b of the tubular film was the adhesive layer and the outer surface side 1a was the outer layer. The film formation conditions were as follows.
Die temperature setting: 210°C
Circular die: Lip outer diameter = 95 mm, lip clearance = 3 mm
Blow-up ratio: 1.1 times Air ring temperature: 22℃
Film surface temperature just before pinch rolling: 32°C
Distance between circular die and pinch roll: 2.4 m
Take-off speed: 12 m/min

(Film raw material)
The following materials were used for the film:
(Resin A)
PE: LDPE (manufactured by Asahi Kasei): Trade name "Suntech LD F1920" (MFR = 2.0, Tm = 110°C, SP value = 8.1 (cal/ ^cm3 ) ^1/2 ), HSP value = 18.0 (cal/ ^cm3 ) ^1/2 )
(Resin B)
PA6/12: Product name "Ube Nylon 7128B" (manufactured by Ube Industries) polyamide 6/12 copolymer (Tg = 47°C, Tm = 128°C, SP value = 13.6 (cal/ ^cm3 ) ^1/2 ), HSP value = 20.7 (cal/ ^cm3 ) ^1/2 )
(Resin C)
PA6/66: Product name "Ube Nylon NAV503X10" (manufactured by Ube Industries, Ltd.) Polyamide 6/66 copolymer (Tg = 43°C, Tm = 194°C, SP value = 13.6 (cal/ ^cm3 ) ^1/2 ), HSP value = 22.8 (cal/ ^cm3 ) ^1/2 )
(Resin D)
m-PE: Product name "Admer NF528" (manufactured by Mitsui Chemicals) acid-modified polyethylene (Tm = 120°C)
(Resin E)
PO elastomer: Product name "Engage EG8100" (Dow Chemical, Japan) (Tm = 60°C, melt index = 1.0g/10min (190°C/2.16kg)

(Film Composition)
The films used in Examples 1-3, 5, 7, 9-15, 17, 19-22 and Comparative Examples 2 and 5 were 4-type, 4-layer multilayer films with a thickness of 20 μm consisting of "adhesive layer/intermediate/resin layer 1/resin layer 2". The adhesive layer was made of PA6/12, the intermediate layer was made of m-PE, the resin layer 1 was made of PA6/66, and the resin layer 2 was made of PE (LDPE). The films were extruded from a multilayer circular die and obtained by the inflation method. The layer thickness ratio was adhesive layer/intermediate/resin layer 1/resin layer 2 = 10%/70%/10%/10%. The tensile modulus in the MD direction was 210 MPa, and the tensile modulus in the TD direction was 200 MPa. The tensile elongation at break in the MD direction was 420%, and the tensile elongation at break in the TD direction was 350%.

The film (low modulus) used in Examples 8 and 18 was a 20 μm thick multilayer film of 5 types and 6 layers consisting of "adhesive layer/intermediate/resin layer 1/intermediate/resin layer 2/resin layer 3". The adhesive layer was made of PA6/12, the intermediate layer was made of m-PE, the resin layer 1 was made of PO elastomer, the resin layer 2 was made of PA6/66, and the resin layer 3 was made of PE (LDPE). The film was extruded from a multilayer circular die and obtained by the inflation method. The layer thickness ratio was adhesive layer/intermediate/resin layer 1/intermediate/resin layer 2/resin layer 3 = 10%/10%/50%/10%/10%/10%. The tensile modulus in the MD direction was 160 MPa, and the tensile modulus in the TD direction was 150 MPa. The tensile elongation at break in the MD direction was 500%, and the tensile elongation at break in the TD direction was 440%.

(Film Tensile Modulus)
The tensile modulus of the film was measured using an Autograph AG-IS (manufactured by Shimadzu Corporation) in an atmosphere of 23°C and 50% RH. In accordance with the method described in ASTM-D-882, a sample cut from the film in the MD or TD direction was displaced from 0.05% to 0.25% under the conditions of a tensile speed of 5 mm/min (strain speed of 5%/min) and a chuck distance of 100 mm, and the tensile modulus was calculated from the stress when the sample was displaced from 0.05% to 0.25%. However, the tensile modulus of the film is the measurement result when a band-shaped non-permeable and breathable film-like protective material is opened from a half-folded state and pulled, and if the length of the measurement sample is short and the chuck distance cannot be satisfied, the chuck distance may be narrowed. In this case, a tensile speed at which the strain rate is 5%/min is selected.

(Tensile elongation at break of film)
The tensile elongation at break of the film was measured in accordance with ASTM D-882. The measurement was performed in an atmosphere of 23°C and 50% RH. The tensile elongation at break in the MD and TD directions was measured using an autograph AG-IS (manufactured by Shimadzu Corporation). The width of the sample film was 10 mm, the chuck distance was 50 mm, and the tensile speed was 50 mm/min (strain rate = 100%/min). The tensile elongation at break of a sample cut into a length of 150 mm and a width of 10 mm in the MD or TD direction was measured. However, the tensile elongation at break of the film is the measurement result when a band-shaped non-permeable and breathable film-like protective material is opened from a half-folded state and pulled. If the length of the measurement sample is short and the chuck distance cannot be satisfied, the chuck distance may be narrowed. In this case, a tensile speed at which the strain rate is 100%/min is selected.

(Film Melting Point (Tm))
A film prepared by the inflation method according to the above-mentioned "Film Preparation Method" was measured in accordance with JIS K 7121.

(Glass Transition Temperature (Tg) of Film)
A film prepared by the inflation method according to the above-mentioned "Film Preparation Method" was measured in accordance with JIS K 7121.

(Glass Transition Temperature (Tg) of Second Surface Layer of Film)
A film prepared by the inflation method according to the above-mentioned "Film Preparation Method" was measured in accordance with JIS K 7244-2.
・Normal force: -0.3N
Swing angle: 0.1%
Frequency: 1Hz
Heating rate: 1.5°C/min

[Silicone adhesive]
The adhesive used for bonding the sewn portion between the protective material and the main panel was TCS 7770XL/C manufactured by Elkem Japan Co., Ltd. The cartridge was a Mixpack with a capacity of 200cc:200cc. It was loaded into a manual gun DM400-01 manufactured by Tomita Engineering Co., Ltd., and was made to be capable of being injected using a static mixer MC13-12.

[Sewing thread]
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]
Each part of the airbag was sewn using LU-2210W-7 manufactured by JUKI Corporation.

[Welding machine (belt heat pressing machine)]
The protective material and the main panel were welded using a continuous feed type small hot plate device LHP-PP1 manufactured by Quinlite Electronics Co., Ltd. The upper heater temperature was 230°C, the lower heater temperature was 190°C, and the feed speed was 0.3 m/min, and the main panel was sandwiched from above and below. As shown in Figure 11, by using such a device, efficient heat conduction is possible through the upper and lower (heating) plates and cooling plates, and by temperature control, it is possible to form a bonded part with sufficient strength while applying heat to the bonded part while avoiding melting damage to the panel base fabric.

[Creating protective material (2-sheet bonding method)]
In Examples 1 to 12 and Comparative Examples 1, 2, and 5, two pieces of the film, coated fabric, or laminated base fabric cut into the shape shown in FIG. 12 were used, and the outer layers of the film or the uncoated surfaces of the base fabric were overlapped with each other so that they faced each other on the inside. A 10 mm wide PE layer was peeled off from the inner edge of the film so that the length from the outer edge was a predetermined length, and the PA resins were attached to each other along the inner edge at a width of 5 mm with a cyanoacrylate instant adhesive (manufactured by Konishi), and then thoroughly dried.

[Preparation of protective material (heat tension method)]
In Examples 13 to 22, as shown in Figures 9 to 11, a single piece of the resin film or laminate base fabric was folded in half in advance and wound up on a roll, and then continuously fed from the wound roll.

[Preparation of protective material (room temperature fixing method)]
In Examples 23 and 24, the coated fabric or laminated base fabric previously folded in half was wound into a roll, and then cut to the same length as the sewing length of the outer edge of the airbag.

[Making the main (base fabric) panel]
Two sheets of base fabric cut into the shape shown in Fig. 1 were stacked together to form the bag-shaped inflatable portion (main panel) of the airbag. After inserting a protective material (described later) and/or applying or welding an adhesive, the outer periphery was sewn with the sewing machine using the sewing thread and the sewing number of 50 stitches/10 cm so that the seam allowance was 10 mm. Note that three backstitches were applied at the beginning and end of the stitching.

[Preparation of inner tube]
To form an inner tube for insertion into the gas inlet of an airbag, two pieces of the Si-coated fabric cut into the shape shown in Fig. 1 were used, overlapped with the coated surfaces facing each other, and both ends were sewn together with the sewing machine using the sewing thread at a stitch count of 50 stitches/10 cm with a seam allowance of 10 mm. Note that three backstitches were used at the beginning and end of the stitching.

(1) Adhesion strength (peel strength) between protective material and panel cloth (N/cm)
As shown in A of FIG. 1, the airbag was cut into 100×10 strips perpendicular to the seam. Of the adhesive regions along the seam of a given width having a proximal end and a distal end from the vicinity of the seam of the cut strip sample toward the inside of the bag body, the protective material and the main panel extending from the proximal end of the adhesive region on one side were cut along the proximal end. Furthermore, the main panels extending from the distal ends of the adhesive regions on both sides were cut along their distal ends, respectively. Through the above operations, a test sample was prepared in which the (strip-shaped) main panel on one side and the (strip-shaped) protective material were bonded in the adhesive region on one side.
The main panel and protective material of the test sample were each held in the chuck (chuck width 25 mm) of a Tensilon universal material testing machine manufactured by A&D Co., Ltd., and pulled at an initial length of 100 mm and a pulling speed of 50 mm/min, and the maximum strength generated when the main panel and protective material were peeled off was recorded. Three samples were prepared, and the average value of the three measurements was recorded as the adhesive strength (peel strength) between the protective material and the panel fabric.

(2) First breaking point of panel grip tensile test As shown in Fig. 1A, the airbag was cut into 100 x 10 strips perpendicular to the stitching. In this way, test samples were prepared in which one side of the main panel (in the form of a strip) was bonded to the protective material (in the form of a strip) at each bonding region.
Each main panel of the test sample was held in the chuck of a Tensilon universal material testing machine manufactured by A&D Co., Ltd., and pulled at an initial length of 100 mm and a pulling speed of 50 mm/min, and the location where the first break occurred was recorded. For example, when the break of the protective material was observed first after the start of the tensile test, and then the break of the base fabric of the sewn part was observed, the first break point was determined to be the protective material. Three test samples were prepared, and the part where breakage was observed in a total of three measurements was determined to be the first break point of the panel part gripping tensile test.
Although it is difficult to accurately measure the state of the airbag at the moment of deployment, this can be roughly substituted by observing the first breaking point in the panel grip tensile test.

(3) Internal pressure retention rate after 6 seconds (%)
An inner tube was inserted through the mounting opening of the main panel sewn to each of the specifications described below, and the relative positions of the main panel and the inner tube were adjusted to prepare an airbag for evaluation. The airbag was filled with room temperature helium in a 0.22 liter tank so that the internal pressure was 8800 kPa, and the tank was connected to the tip of the tank via a metal pipe (inner diameter 21.3 mm). An electromagnetic valve attached near the tip of the tank was instantly opened and closed, and then the change in the internal pressure of the airbag over time was examined using a pressure sensor (PGMC-A-1 MPa, manufactured by Kyowa Electric Industry Co., Ltd.) attached near the connection between the pipe and the airbag.
The internal pressure of the airbag 6 seconds after the solenoid valve was opened was divided by the maximum internal pressure of the airbag after the solenoid valve was opened, and the value was recorded. The test was performed once for each of the three airbags, and the average of the three measurements was calculated as the internal pressure retention rate after 6 seconds, expressed as a percentage.
In addition, to evaluate a situation assuming that the airbag instantly deploys from a folded state and the stitching is exposed to an extremely fast inflator gas flow rate, a measurement was conducted in the same manner as the above-mentioned method for measuring the internal pressure retention after 6 seconds, except that a 0.22 liter tank was filled with room temperature helium so that the internal pressure was 11,000 kPa, and the average of all three measurement results was calculated as the internal pressure retention after 6 seconds (high output) as a percentage.

(4) Thickness of the sewn part after folding (mm)
The straight stitched portion (part B in FIG. 1) of the main panel sewn according to each specification described below was cut to obtain a 60 mm x 30 mm sample piece for thickness evaluation. The cut sample piece was folded in half perpendicular to the straight stitching to produce a folded sample of 30 mm x 30 mm. Using a digital caliper (ABS Digimatic Caliper CD-20APX) manufactured by Mitutoyo Corporation, the measurement part of the caliper was used to pinch the stitched portion 10 mm from the fold and press it with a force of 300 gf, and the value was recorded. The test was performed once for each of the three airbags, and the average value of the three measurements was taken as the thickness after folding.

(5) Weight of the reference bag (g)
Three main panels were prepared according to each of the specifications described below, and their weights were measured. In each of the Examples and Comparative Examples, main panels of the same shape and size as shown in Figure 1 were used. The average weight of the three panels was taken as the weight (g) of the reference bag.

(6) Manufacturing time per bag The time required from the process of cutting the sample pieces from the sample fabric to the production of three bags sewn according to each specification described below was divided by 3 to obtain the manufacturing time per bag, which was expressed as an index with Example 1 being the standard of 100. However, the process of producing the protective material was carried out and prepared in advance. The time from application of the adhesive until it completely hardened was also included.

(7) Surface step (peak-valley difference) in the protective material adhesion area
At the R portion of the airbag (for example, the X portion in FIG. 1), a sample with a width of 10 cm and a depth of 5 cm was cut from the end portion. Scissors were inserted inside the half-folded protective material of the sample to cut along the folded portion of the protective material, and the sewing thread of the sewing portion with the base fabric panel was untied to separate the pair of base fabric panels and the protective material. The adhesive area between the base fabric panel and the protective material in the separated sample (having one base fabric panel and the protective material cut with scissors) was visually observed to identify the wrinkled portion to be measured. If the wrinkled portion could not be visually confirmed, an arbitrary measurement point was selected. A measurement sample of 2 cm x 2 cm was cut out so that the identified wrinkled portion or measurement point was approximately centered.
The measurement sample was placed on a glass plate with the protective material surface facing upward, and the four sides of the measurement sample were fixed with commercially available adhesive tape (product name: Cellotape/manufactured by Nichiban Co., Ltd.) so that the measurement sample did not generally float from the glass plate. The measurement sample was set on the measurement table of a surface roughness measuring instrument (SURFTEST EXTREME SV-3000CNC) manufactured by Mitutoyo Corporation, and the specified wrinkled portion or measurement point was measured in three-dimensional mode according to the following measurement conditions. The obtained three-dimensional measurement data was imported into image analysis software (FORMTRACEPAK PRO) to create a three-dimensional mapping image with "plane" correction processing added, and the largest step portion was extracted using an arbitrary cross-section extraction function, and a baseline connecting the start point and end point of the highest peak in the extracted cross-section (two dimensions) was drawn, and the maximum height from the baseline was determined.
(Surface roughness measurement conditions)
Measurement length: 10 mm
Measurement width: 5 mm
Measurement speed: 5 mm/sec
Sampling pitch: 1 μm
Sampling interval: 50 μm
Stylus: radius = 10 μm (Code No. 12AAB415)

(8) Adhesion strength (peel strength) between protective material of R portion and panel cloth (N/cm)
As shown in FIG. 1C, two points were taken on the sewn curved portion (R portion) with a shortest distance between the two points of 30 mm, and the airbag was cut into a 100 x 30 strip shape so as to be perpendicular to the line segment connecting the two points. Of the adhesive region along the seam of a predetermined width having a proximal end and a distal end from the vicinity of the seam of the cut strip-shaped sample toward the inside of the bag body, the protective material and the main panel extending from the proximal end of the adhesive region on one side were cut along the proximal end. Furthermore, the main panels extending from the distal ends of the adhesive regions on both sides were cut along the distal ends, respectively. Through the above operations, a test sample was prepared in which the (strip-shaped) main panel on one side and the (strip-shaped) protective material were bonded in the adhesive region on one side. The radius of curvature of the sewn curved portion (R portion) of the obtained sample was 200 mm.
The main panel and protective material of the test sample were each held in the chuck (chuck width 25 mm) of a Tensilon universal material testing machine manufactured by A&D Co., Ltd., and pulled at an initial length of 100 mm and a pulling speed of 50 mm/min, and the maximum strength generated when the main panel and protective material were peeled off was recorded. Three samples were prepared, and the average value of the three measurements was recorded as the adhesive strength (peel strength) between the protective material and the panel fabric in the R section.

[Comparative Examples 1 to 5, Examples 1 to 12]
Airbag test pieces having the main panels and protective materials shown in Tables 1 and 2 below were prepared.

In Comparative Example 1, a silicon-coated fabric was used as the protective material, and the loop was formed on the inside of the airbag by sandwiching it between the stitches of the panel fabric, and no adhesive was used between the protective material and the panel fabric. Because there was no adhesive area, the internal pressure retention rate after 6 seconds was low.

In Comparative Example 2, an airbag was produced in the same manner as in Comparative Example 1, except that the protective material was replaced with a film. As in Comparative Example 1, there was no adhesive area, so the internal pressure retention rate after 6 seconds was low.

In Comparative Example 3, no protective material was used, and laminated fabric was used as the main panel. The laminated surfaces were bonded together by heat welding, and the main panels were not sewn together. Because there was no sewing, the airbag was unable to withstand the deployment pressure when it was deployed and was destroyed, and the internal pressure retention rate after 6 seconds was also low. Because there was no sewing, the first breaking point in the panel grip tensile test was the adhesive part.

In Comparative Example 4, a Si-coated cloth was used as the panel cloth, and a silicone-based adhesive was applied to the sewing points with the Si-coated side facing inward so that the width was approximately 10 mm and the thickness was approximately 2 mm. Another piece of panel cloth was then attached from above with the Si-coated side facing inward, and allowed to dry thoroughly. At this time, the amount of silicone-based adhesive applied per 1 cm of the length of the sewn part of the airbag was 0.15 to 0.25 g. After drying, the part attached with the silicone-based adhesive was sewn. The obtained airbag was thick after folding, the weight of the standard bag was also large, and the manufacturing time per bag was long.

In Comparative Example 5, a film was used as the protective material, and two panels of cloth were sandwiched together with their Si-coated surfaces facing outward so that a loop was formed on the inside of the airbag. The protective material and the panel cloth were then heat-sealed and then sewn together. Because the protective material had been cut in advance to the shape shown in Figure 12, the heat-sealing was performed without applying tension. Because the adhesive distance a of the protective material was shorter than the adhesive distance b of the panels, the heat-sealed portion was partially destroyed when the airbag was deployed, and the internal pressure retention rate after 6 seconds was also low.

In Example 1, a Si-coated cloth was used as the panel cloth with the Si-coated side facing outward, a film was used as the protective material, and the two panels of cloth were sandwiched together so that a loop was formed on the inside of the airbag. The protective material and the uncoated side of the panel cloth were then bonded by heat welding, and the panel cloths were then sewn together. Because the protective material had been cut in advance to the shape shown in Figure 12, the heat welding was performed without applying tension. The resulting airbag had good physical properties and effects.

In Example 2, as shown in FIG. 4(b), an airbag was produced in the same manner as in Example 1, except that the loops of protective material were formed on the outside of the airbag. The production time per bag was slightly longer.

In Example 3, a Si-coated cloth was used as the panel cloth with the Si-coated surface facing inward, a film was used as the protective material, and the two panels were sandwiched together so that a loop was formed on the inside of the airbag. The protective material and the Si-coated surface of the panel cloth were then bonded together with a silicone adhesive, and the panel cloths were then sewn together. Because the protective material had been cut in advance to the shape shown in Figure 12, the heat welding was performed without applying tension. The resulting airbag was inferior in terms of thickness after folding, weight of the reference bag, and manufacturing time per bag.

In Example 4, an airbag was produced in the same manner as in Example 3, except that a Si-coated cloth was used as the protective material. The resulting airbag was inferior in terms of thickness after folding, weight of the reference bag, and manufacturing time per bag.

In Example 5, a laminated cloth was used as the panel cloth with the laminated surface facing inward, a film was used as the protective material, and the two panels of cloth were sandwiched together so that a loop was formed on the inside of the airbag. The protective material and the laminated surface of the panel cloth were then heat-sealed, and the panel cloths were then sewn together. When heat-sealing, the protective material was previously cut into the shape shown in Figure 12, so the adhesion was performed without applying tension. The resulting airbag had good physical properties and effects.

In Example 6, an airbag was produced in the same manner as in Example 5, except that a laminated fabric was used as the protective material. The resulting airbag was inferior in terms of thickness after folding and weight compared to the reference bag.

In Example 7, an airbag was produced in the same manner as in Example 1, except that the protective material and the Si-coated surface of the panel cloth were bonded by thermal welding. The resulting airbag had a reduced internal pressure retention rate after 6 seconds due to a decrease in the adhesive strength between the protective material and the panel cloth.

In Example 8, an airbag was produced in the same manner as in Example 1, except that a thicker film (low modulus of elasticity) was used as the protective material and the a/b ratio was lowered. The resulting airbag had a worsened thickness after folding and a lower internal pressure retention rate after 6 seconds.

In Example 9, an airbag was produced in the same manner as in Example 1, except that the a/b ratio was lowered. The resulting airbag had a lower internal pressure retention rate after 6 seconds.

In Example 10, an airbag was produced in the same manner as in Example 1, except that the a/b ratio was increased. The resulting airbag had a worsened thickness after folding.

In Example 11, an airbag was produced in the same manner as in Example 1, except that the effective bonding width (the smaller of b or W) was increased. The resulting airbag had a worsened thickness after folding.

In Example 12, an airbag was produced in the same manner as in Example 1, except that the effective bonding width (the smaller of b or W) was reduced. The internal pressure retention rate of the resulting airbag after 6 seconds was reduced.

In Example 13, a Si-coated cloth was used as the panel cloth with the Si-coated surface facing outward, a film was used as the protective material, and the two panels were sandwiched together so that a loop was formed on the inside of the airbag. The protective material and the uncoated surface of the panel cloth were then bonded by heat welding, and the panel cloths were then sewn together. During heat welding, the protective material was continuously fed from a wound roll and was attached while applying tension by hand so that it would conform to the shape shown in Figure 12. The obtained airbag had good physical properties and effects, and had an excellent internal pressure retention rate (high output) after 6 seconds.

In Example 14, an airbag was produced in the same manner as in Example 13, except that the protective material loops were formed on the outside of the airbag. The production time per bag was slightly longer.

In Example 15, a laminated cloth was used as the panel cloth with the laminated surface facing inward, a film was used as the protective material, and the two panels were sandwiched together so that a loop was formed on the inside of the airbag. The protective material and the laminated surface of the panel cloth were heat-sealed, and the panel cloths were then sewn together. During heat welding, the protective material was continuously fed from a wound roll and attached while applying tension by hand so that it would conform to the shape shown in Figure 12. The obtained airbag had good physical properties and effects, and had an excellent internal pressure retention rate (high output) after 6 seconds.

In Example 16, an airbag was produced in the same manner as in Example 15, except that a laminated fabric was used as the protective material. The resulting airbag was inferior in thickness after folding and weight to the reference bag.

In Example 17, an airbag was produced in the same manner as in Example 13, except that the protective material and the Si-coated surface of the panel cloth were bonded by thermal welding. The resulting airbag had a reduced internal pressure retention rate after 6 seconds due to a decrease in the adhesive strength between the protective material and the panel cloth.

In Example 18, an airbag was produced in the same manner as in Example 13, except that a thicker film (low modulus of elasticity) was used as the protective material and the a/b ratio was lowered. The resulting airbag had a worsened thickness after folding and a lower internal pressure retention rate after 6 seconds.

In Example 19, an airbag was produced in the same manner as in Example 13, except that the a/b ratio was lowered. The internal pressure retention rate of the resulting airbag after 6 seconds was reduced.

In Example 20, an airbag was produced in the same manner as in Example 13, except that the a/b ratio was increased. The resulting airbag had a worsened thickness after folding.

In Example 21, an airbag was produced in the same manner as in Example 13, except that the effective bonding width (the smaller of b or W) was increased. The resulting airbag had a worsened thickness after folding.

In Example 22, an airbag was produced in the same manner as in Example 13, except that the effective bonding width (the smaller of b or W) was reduced. The internal pressure retention rate of the resulting airbag after 6 seconds was reduced.

In Example 23, a Si-coated cloth was used as the panel cloth with the Si-coated surface facing inward, and a Si-coated cloth was used as the protective material. The two panels were sandwiched together so that a loop was formed on the inside of the airbag, and the panel cloths were then sewn together. The protective material and the Si-coated surface of the panel cloth were then bonded together on the inside of the stitching with a silicone adhesive. The protective material was fixed in place by the stitching, so the bonding was performed without applying tension to the protective material.

In Example 24, a laminated fabric was used as the panel fabric with the laminated surface facing inward, a film was used as the protective material, and the two panels were sandwiched together so that a loop was formed on the inside of the airbag. The panel fabrics were then sewn together, and the protective material and the laminated surface of the panel fabric were heat welded on the inside of the stitching. During bonding, the protective material was fixed in place by the stitching, so the bonding was performed without applying tension to the protective material.

The results for Examples 13-24 are shown in Table 3 below.

The airbag according to the present invention has both outer surfaces of a folded, band-like, non-breathable protective material bonded to the inner surface of each of a pair of base fabric panels in a bonding region of a predetermined width along the seam, with a proximal end and a distal end from near the seam toward the inside of the bag, resulting in an airbag with high internal pressure retention and excellent compactness. Therefore, the airbag according to the present invention can be suitably used for automobile airbags, particularly CAB and pedestrian airbags, which require high internal pressure retention.

1. Base fabric panel (panel fabric, main panel)
1' Base fabric panel (panel fabric, main panel)
2: stitched (sewn) portion 2': isolated stitched (sewn) portion 3: silicone adhesive 4: non-breathable (film-like) protective material 4': inner edge of non-breathable (film-like) protective material 4": half-folded strip-shaped non-breathable (film-like) protective material 5: adhesive region 5': adhesive region 6: proximal end of adhesive region 6': proximal end of adhesive region 7: distal end of adhesive region 7': distal end of adhesive region 8: terminal (sealed) portion of non-breathable (film-like) protective material 8': terminal (sealed) portion of non-breathable (film-like) protective material 10: bag-shaped airbag with outer edge sewn A-A: cross section w: predetermined width of adhesive region (adhesive width)
b Bonding distance b (1/2 the length between the distal ends along the base panel)
a Adhesive distance a (1/2 the length between the distal ends along the half-folded non-breathable protective material)
s Seam allowance of base fabric panel 11 Multilayer film 11a Multilayer film (outer layer)
11b Multilayer film (adhesive layer)
12 Multi-layer die 13 Air ring 14 Deflator (free roll)
15 First pinch drive roll 16 Guide roll (free roll)
17 Second pinch drive roll 18 Touch roll (free roll)
19 Winding drive roll 20 Nylon 66 base fabric 21 Pressure roll (silicon rubber lining)
22 Heating roll (chrome plated)
23 Inner tube 24 Sewing part of inner tube

Claims

An airbag comprising at least one pair of base fabric panels sewn together at their outer periphery,
An airbag in which both end outer surfaces of a folded, strip-shaped non-breathable protective material are bonded to the inner surface of each of the pair of base fabric panels in bonding regions of a predetermined width along the seams from near the seams toward the inside of the bag, and when a tensile force is applied to the pair of base fabric panels during deployment of the airbag, the length between the distal ends along the folded, strip-shaped non-breathable protective material is greater than or equal to the length between the distal ends along the pair of base fabric panels.
The airbag according to claim 1, wherein the folded band-shaped non-breathable protective material is a single resin film folded in half.
The airbag according to claim 1 or 2, wherein when the airbag is not deployed, stored or folded, 1/2 of the length between the distal ends along the folded non-breathable protective material (glue distance a) and 1/2 of the length between the distal ends along the pair of base fabric panels (glue distance b) satisfy the relationship 0.5<a/b<10.
The airbag according to claim 1 or 2, wherein the adhesion in the adhesive region is achieved by welding.
The airbag according to claim 1 or 2, wherein when the airbag is not deployed, stored or folded, 1/2 of the length between the distal ends along the folded non-breathable protective material (adhesive distance a) is 0.1 cm or more and 10.0 cm or less.
The airbag according to claim 1 or 2, wherein the predetermined width w of the adhesive region is 0.1 cm or more and 5.0 cm or less when the airbag is not deployed, stored, or folded.
The airbag according to claim 1 or 2, in which, when the airbag is not deployed, stored or folded, the effective adhesive width, which is the smaller of 1/2 the length between the distal ends along the pair of base fabric panels (adhesive distance b) and the predetermined width w of the adhesive region, is 0.1 cm or more.
The airbag according to claim 1 or 2, wherein when the airbag is not deployed, stored or folded, the ratio w/b of 1/2 of the length between the distal ends along the pair of base fabric panels (the bonded distance b) to the predetermined width w of the bonded region satisfies the relationship 0.2<w/b<5.0.
The airbag according to claim 1 or 2, wherein the inner surface of the base fabric panel is an uncoated surface.
The airbag according to claim 1 or 2, wherein the inner surface of the base fabric panel is film laminated.
The airbag according to claim 1 or 2, wherein the thickness of the non-breathable protective material is 0.001 mm or more and 0.5 mm or less.
The airbag according to claim 1 or 2, wherein the tensile modulus of the semi-folded band-shaped non-breathable protective material is 100 to 800 MPa.
The airbag according to claim 1 or 2, wherein the adhesive strength in the adhesive region is 1 N/cm or more.
The airbag according to claim 1 or 2, wherein the airbag has an R portion in the adhesive region with a curvature radius of 300 mm or less.
The airbag according to claim 1 or 2, wherein the airbag has a reverse R portion in the adhesive region with a curvature radius of 300 mm or less.
The airbag according to claim 14, wherein the surface step (peak-to-valley difference) of the R portion is 400 μm or less.
The airbag according to claim 16, wherein the ratio (R/Straight section) of the surface step (peak-valley difference) of the R section to the surface step (peak-valley difference) of the substantially straight section excluding the R section is 0.6 to 2.0.
The airbag according to claim 14, wherein the adhesive strength at the R portion is 1 N/cm or more.
The airbag according to claim 16, in which the ratio of the adhesive strength at the R portion to the adhesive strength of the substantially straight portion excluding the R portion (R portion/substantially straight portion) is 0.5 to 2.5.
The airbag according to claim 1 or 2, wherein the airbag includes an isolated sewn portion in a closed space.