Airbag

Abstract

Provided is an airbag formed by sewing opposing base fabric panels to each other with a broad tethering fabric for maintaining a predetermined thickness, wherein tearing of the sewn areas is reduced. This airbag is characterized: in that stitching between the base fabric panels and the tethering fabric includes a plurality of discrete rectilinear stitches along a virtual line extending in the width direction of the tethering fabric, and the ends of the rectilinear stitches have bends that bend by a prescribed angle and to a predetermined length from the virtual line toward a seam-allowance edge of the tethering fabric; or in that stitching between the base fabric panels and the tethering fabric includes a plurality of individual curved stitches that form protrusions on the opposite side from the seam-allowance edge of the tethering fabric, and the vertices of the plurality of individual curved stitches are on a virtual line extending in the width direction of the tethering fabric.

Description

Technical Field

[0001] The present invention relates to an airbag used in an airbag device mounted on a vehicle. More specifically, the present invention relates to an airbag in which opposing base fabric panels are sewn together with a wide tether fabric for maintaining a predetermined thickness during inflation, and in which tearing of the sewing portion is reduced.

[0002] The present invention relates to an airbag used in an airbag device mounted on a vehicle. More specifically, the present invention relates to an airbag in which opposing base fabric panels are sewn together with a wide tether fabric for maintaining a predetermined thickness during inflation, and in which tearing of the sewing portion is reduced.

Background Art

[0003] Conventionally, as an airbag of an airbag device mounted on a vehicle, when defining the thickness at the completion of inflation, a tether for connecting opposing panels is configured to determine the distance between the opposing panels. Patent Document 1 below is a pedestrian airbag, and the tether between the opposing panels is a wide tether having a length reaching about one-half to one-third of the vehicle width. It supports the inflation and deployment structure of an airbag that widely covers a wide hood cover (bonnet) of a vehicle by means of the tether. However, Patent Document 1 does not specifically describe what the stitching between the panel and the tether (a split body consisting of stitching together of the tethers) is like, let alone the strength of the stitching.

[0004] In Patent Document 2 below, in order to provide a bag structure for an airbag device that has a small inertial mass of the bag and can also reduce the number of parts and manufacturing costs, a gas inflow opening side half portion 21a in which a gas inflow opening is formed and a collision side half portion 21b are sewn together to form a bag 21. Inside this bag 21, a cloth string body 23 (corresponding to a tether) is arranged such that one end is locked to the gas inflow opening side half portion 21a and the other end is sewn to the inside of the collision side half portion 21b. In the airbag device that regulates the shape of the bag 21 during inflation and deployment with this string body 23, the string body 23 is arranged (biased arrangement) such that the extending direction of the weft or warp is oblique to the longitudinal direction of the string body 23, and the other end of this string body 23 is sewn to the inner surface of the collision side half portion 21b with non-sewn portions δ of a predetermined width set on both sides in the width direction. Patent Document 2 discloses that those sewn to the test piece at a portion exceeding the total width of the tether and those sewn at a portion substantially equal to the total width of the tether are more likely to break than those sewn with non-sewn portions of a predetermined width set on both sides of the tether (see Table 1 of the same document). Also, Patent Document 2 states that by forming the sewn portion into a substantially rectangular shape, chamfering (angle α) is applied to both corners of the end portion, the area gradually increases in the longitudinal direction, sewing is performed in a substantially elliptical shape, and the areas at both ends in the longitudinal direction are gently changed, even when an impact force acts on the tether during inflation and deployment of the bag, no stress concentration behavior occurs in the sewing portion, and inconveniences such as peeling can be prevented (see FIGS. 4b, 5, and 6 of the same document). It is an airbag for the driver's seat, and a thin string-like tether defines the inflation and deployment structure. However, the tether described in Patent Document 2 has a relatively narrow overall width compared to the comparative example, and the panel and the tether are connected by a single continuous stitch.

[0005] The following Patent Document 3 relates to a crash protection device for passengers in a vehicle, particularly a motor vehicle, and comprises a cushion or cover plate, an airbag, fixing components, an electronic or mechanical device, and a gas generator. The airbag consists of a covered or uncovered fabric, a stock (2) having a gas inlet opening to which a flame prevention device may be attached, an upper part (1), and one or more layers of safety stop bands (corresponding to tethers) (3). The ends of the safety stop bands are fixed by a substantially circular or rectangular seam (4) inside the ends of the safety stop bands together with the upper part, the lower part, other components, or one or more of them (see FIGS. 1 to 4 of the same document). Patent Document 3 states that in the case of a load, the resulting force must be transmitted to the connecting components (the upper and lower parts) through the shape and connection points of the safety stop bands in a sufficiently safe manner. If the force is transmitted too abruptly, there is a risk of damage to the connecting parts and similar components. When a force is applied to the safety stop band, a particularly strong force is generated in the direction X (the side facing the force), while in the direction Y (the side not facing the force) (see FIG. 1 of the same document), no force acts and it is the smallest. Therefore, as a useful shape of sewing for the safety stop band under stress to dissipate the force, a closed double sewing that is approximately oval in shape but has a rounder shape on the side facing the force than on the side not facing the force, a closed circular single sewing where the entire seam system is provided on the side facing the impact, and a double seam that is open on the side where no force is applied have been proposed (see FIGS. 2a, 2b, and 3 of the same document). It is an airbag for the driver's seat, and a thin string-like tether defines the inflation deployment structure. However, the tether described in Patent Document 3 has a relatively narrow overall width, and the panel and the tether are connected by a continuous single stitching.

[0006] Conventionally, as the airbag of an airbag device mounted on a vehicle, when defining the thickness at the completion of inflation, the tether connecting the opposing panels was configured to determine the distance between the opposing panels.

[0007] The following Patent Document 1 is a pedestrian airbag, and the tether between the opposing panels is a wide tether reaching a length of about one-half to one-third of the vehicle width. The tether supports the inflation and deployment structure of the airbag that widely covers the wide hood cover (bonnet) of the vehicle. However, Patent Document 1 does not specifically describe what the stitching between the panel and the tether (which consists of the joining of divided bodies) is like, let alone describe the strength of the stitching.

[0008] The following Patent Document 2 provides a bag structure of an airbag device that has a small inertial mass of the bag and can also reduce the number of parts and manufacturing costs. The gas inflow opening side half part 21a and the impact side half part 21b in which a gas inflow opening is formed are stitched to form a bag 21. Inside this bag 21, a cloth string body 23 (corresponding to a tether) is arranged such that one end is locked to the gas inflow opening side half part 21a and the other end is sewn into the inner eye of the impact side half part 21b. In the airbag device that regulates the shape of the bag 21 during inflation and deployment with this string body 23, the string body 23 is arranged (biased arrangement) such that the extending direction of the weft or warp is oblique to the longitudinal direction of the string body 23. Also disclosed is a structure in which the other end of this string body 23 is sewn to the inner surface of the impact side half part 21b while setting non-sewn parts δ of a predetermined width on both sides in the width direction. Patent Document 2 describes that those stitched to the test piece at a portion exceeding the entire width of the tether and those stitched at a portion substantially equal to the entire width of the tether are more likely to break than those stitched while setting non-sewn parts of a predetermined width on both sides of the tether (see Table 1 of the same document). Also, Patent Document 2 describes that by forming the sewing part into a substantially rectangular shape, chamfering (angle α) both corners of the end, gradually increasing the area in the longitudinal direction, sewing it into a substantially elliptical shape, and gently changing the area at both ends in the longitudinal direction, even when an impact force acts on the tether during inflation and deployment of the bag, stress concentration behavior does not occur in the sewing part, and inconveniences such as peeling can be prevented (see FIGS. 4b, 5, and 6 of the same document). It is a driver's seat airbag, and a thin string-like tether defines the inflation and deployment structure. Geometric sewing lines such as a substantially elliptical shape have been proposed for the stitching of the tether. However, the tether described in Patent Document 2 has a relatively narrow overall width, and the panel and the tether are connected by a single continuous stitch.

[0009] The following Patent Document 3 relates to a collision protection device for passengers in a vehicle, particularly an automobile, and comprises a cushion or cover plate, an airbag, fixing components, an electronic or mechanical device, and a gas generator. The airbag consists of a covered or uncovered fabric, a stock (2) having a gas inlet opening to which a flame prevention device may be attached, an upper part (1), and one or more safety stop bands (corresponding to tethers) (3). The ends of the safety stop bands are fixed by a substantially circular or rectangular stitch (4) inside the ends of the safety stop bands together with the upper part, the lower part, other components, or one or more of them (see FIGS. 1 to 4 of the same document). Patent Document 3 states that in the case of a load, the resulting force must be transmitted safely enough through the shape and connection points of the safety stop bands to the connection components (the upper and lower parts). If the force is transmitted too abruptly, there is a risk of damage to the connection part and similar components. When a force is applied to the safety stop band, a particularly strong force is generated in the direction X (the side facing the force), while in the direction Y (the side not facing the force) (see FIG. 1 of the same document), no force acts and it is the smallest. Therefore, as a useful shape of stitching for the safety stop band under stress to dissipate the force, a closed double stitch that is approximately oval in shape but has a rounder shape on the side facing the force than on the side not facing the force, a closed circular single stitch where the entire seam system is provided on the side facing the impact, and a double seam that is open on the side where no force is applied have been proposed (see FIGS. 2a, 2b, and 3 of the same document). It is an airbag for the driver's seat, and a thin string-like tether defines the inflation deployment structure. It is proposed to use a geometric stitching line such as a substantially elliptical shape for the stitching of the tether, and the tether also has a curved shape along the stitching line. However, the tether described in Patent Document 3 has a relatively narrow overall width, and the panel and the tether are connected by a single continuous stitch.

Prior Art Documents

Patent Documents

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-172170 [Patent Document 2] Japanese Utility Model Application Laid-Open No. 05-046615 [Patent Document 3] Japanese Patent Application Laid-Open No. 11-501269 [Summary of the Invention] [Problems to be Solved by the Invention]

[0011] With the weight reduction and compactification of airbags, a thinner base fabric is required. However, usually, when the base fabric becomes thinner, its strength decreases, so the risk of breakage starting from the sewing part increases. Therefore, it is important to reduce breakage by sewing (sewing form). As shown in FIG. 1, for example, the inventors of the present application focused on the sewing between the wide decorative fabric described in Patent Document 1 and the base fabric panel base, and noticed that due to stress concentration during inflation and deployment, the edge of the sewing part easily becomes a breakage starting point and leads to damage to the sewing part. Such damage to the sewing part must be avoided for maintaining the internal pressure of the airbag and thus protecting the human body (pedestrian). In addition, since a wide tether has higher strength than a narrow tether, it can be applied to parts and designs where stress is applied during the inflation and deployment of an airbag. On the other hand, since the possibility of breakage starting from the sewing part due to stress concentration also increases, its reduction is important. Under such circumstances, the problems to be solved by the present invention are to provide an airbag in which the breakage of the sewing part is reduced in an airbag in which opposing base fabric panels are sewn together with a wide tether fabric for maintaining a predetermined thickness during inflation, and to provide a method for manufacturing the airbag using a high-strength sewing form.

[0012] With the reduction in weight and size of airbags, the base fabric is required to be thinner. However, usually, when the base fabric becomes thinner, its strength decreases, so the risk of tearing starting from the sewing part increases. Therefore, it is important to reduce tearing by sewing (sewing pattern). As shown in FIG. 1, for example, the inventors of the present application focused on the fact that in the sewing between the wide decorative fabric described in Patent Document 1 and the base fabric panel, the edge of the sewing part is likely to become a starting point of tearing due to stress concentration during inflation and expansion, leading to damage to the sewing part. Such damage to the sewing part must be avoided for maintaining the internal pressure of the airbag and thus protecting the human body (pedestrian). In addition, since a wide tether has higher strength than a narrow tether, it can be applied to parts and designs where stress is applied during the inflation and expansion of the airbag. On the other hand, since the possibility of tearing starting from the sewing part due to stress concentration also increases, its reduction is important. Under such circumstances, the problems to be solved by the present invention are to provide an airbag in which the tearing of the sewing part is reduced in an airbag formed by sewing a wide tether fabric for maintaining a predetermined thickness between opposing base fabric panels during inflation, and to provide a method for manufacturing the airbag using a high-strength sewing pattern.

Means for Solving the Problems

[0013] As a result of intensive studies and repeated experiments to solve the above problems, the inventors of the present application unexpectedly found that the above problems can be solved by a sewing (sewing pattern) of a specific shape defined below, and thus completed the present invention. That is, the present invention is as follows.

[0014] [1] In an airbag having a bag body in which a pair of base fabric panels are sewn at the outer peripheral edge, and a tether fabric of a predetermined width sewn to each of the pair of base fabric panels inside the bag body so as to regulate the distance between the pair of base fabric panels when the bag body expands, The stitching between the base fabric panel and the tether fabric includes a plurality of discrete linear stitches arranged along a virtual line extending in the width direction of the tether fabric, and the ends of the linear stitches have bent portions that bend at a predetermined angle and a predetermined length from the virtual line toward the edge of the tether fabric. The airbag is characterized by this. [2] The airbag according to [1] above, wherein a predetermined width of the tether fabric is 50 mm or more and 500 mm or less. [3] The airbag according to [1] or [2] above, wherein the length of the linear stitch is 5 mm or more and 100 mm or less. [4] The airbag according to any one of [1] to [3] above, wherein the interval between the linear stitches arranged along the virtual line is 5 mm or more and 50 mm or less. [5] The airbag according to any one of [1] to [4] above, wherein the ratio of the interval between the linear stitches to the length of the linear stitch (interval between linear stitches / length of linear stitch) is 0.2 or more and 1.5 or less. [6] The airbag according to any one of [1] to [5] above, wherein the bending angle of the end of the linear stitch is 60° or more and 120° or less. [7] The airbag according to any one of [1] to [6] above, wherein the length of the bent portion at the end of the linear stitch is 3 mm or more and 50 mm or less. [8] The airbag according to any one of [1] to [7] above, wherein the plurality of discrete linear stitches arranged along the virtual line are present 2 or more and 20 or less per 10 cm of the length of the virtual line. [9] The airbag according to any one of [1] to [8] above, wherein the linear stitch is a polygon or a semi - circle that shares one side with the virtual line or a part thereof.

[10] The airbag according to any one of [1] to [9] above, wherein the linear stitches are each part of a different stitch.

[11] The airbag according to any one of [1] to

[10] above, wherein the linear stitch is part of a continuous rectangular wave on the virtual line.

[12] The airbag according to any one of [1] to

[11] above, wherein the airbag is a pedestrian airbag.

[13] A method for manufacturing an airbag having a bag body in which a pair of base fabric panels are stitched at the outer peripheral edge, and a tether fabric having a predetermined width stitched to each of the pair of base fabric panels inside the bag body so as to regulate the distance between the pair of base fabric panels when the bag body expands, the method comprising the following steps: Stitching the base fabric panel and the tether fabric by stitches including a plurality of discrete linear stitches arranged along a virtual line extending in the width direction of the tether fabric, and having bent portions where the ends of the linear stitches are bent at a predetermined angle and a predetermined length toward the stitch allowance end of the tether fabric from the virtual line; The manufacturing method including the above.

[14] The method for manufacturing an airbag according to the above

[13] , wherein the linear stitches are part of continuous stitches and include a step of continuously stitching.

[0015] As a result of intensive studies and repeated experiments to solve the above problems, the inventors of the present application unexpectedly found that the above problems can be solved by stitches of a specific shape (specific sewing form) defined below, and thus completed the present invention. That is, the present invention is as follows.

[0016]

[15] In an airbag having a bag body in which a pair of base fabric panels are stitched at the outer peripheral edge, and a tether fabric having a predetermined width stitched to each of the pair of base fabric panels inside the bag body so as to regulate the distance between the pair of base fabric panels when the bag body expands, The stitches between the base fabric panel and the tether fabric include a plurality of curved stitches convex on the opposite side of the stitch allowance end of the tether fabric, and the apexes of the convex portions of the plurality of curved stitches are on a virtual line extending in the width direction of the tether fabric. An airbag characterized by this.

[16] The airbag according to the above

[15] , wherein the predetermined width of the tether fabric is 100 mm or more and 500 mm or less.

[17] Among the plurality of curved stitches arranged along the virtual line, the distance between the portion farthest from the virtual line and the virtual line is 1 mm or more and 100 mm or less. The airbag according to the above

[15] or

[16] .

[18] When the length in the direction parallel to the virtual line of the stitching of a plurality of curves arranged along the virtual line is defined as the width of the curve stitching, the width of the curve stitching is 5 mm or more and 100 mm or less, the airbag according to any one of

[15] to

[17] above.

[19] The value calculated by (distance between the portion farthest from the virtual line and the virtual line) / (width of the curve stitching) is 0.1 or more and 2.0 or less, the airbag according to any one of

[15] to

[18] above.

[20] The interval between the convex vertices of the stitching of adjacent curves is 5 mm or more and 100 mm or less, the airbag according to any one of

[15] to

[19] above.

[21] The value obtained by subtracting the width of the curve stitching from the interval between the convex vertices of the stitching of adjacent curves is 0 mm or more and 50 mm or less, the airbag according to any one of

[15] to

[20] above.

[22] The value calculated by (interval between the convex vertices of the curve stitching - width of the stitching on the arc) / (width of the curve stitching) is 0 or more and 1.5 or less, the airbag according to any one of

[15] to

[21] above.

[23] The stitching of the curves arranged along the virtual line exists 2 or more and 20 or less per 10 cm of the virtual line, the airbag according to any one of

[15] to

[22] above.

[24] The shape of the curve stitching is a part of a circle or an ellipse, the airbag according to any one of

[15] to

[23] above.

[25] The stitching of a plurality of curves arranged along the virtual line is a part of a different stitching and is discrete, the airbag according to any one of

[15] to

[24] above.

[26] The curve stitching is a part of a continuous stitching, the airbag according to any one of

[15] to

[25] above.

[27] The curve stitching is a part of a continuous sine curve parallel to the virtual line, the airbag according to any one of

[15] to

[26] above.

[28] The airbag is a pedestrian airbag, the airbag according to any one of

[15] to

[27] above.

[29] A method for manufacturing an airbag having a bag body formed by sewing a pair of base fabric panels at their outer peripheral edges, and a tether fabric of a predetermined width sewn to each of the pair of base fabric panels inside the bag body so as to regulate the distance between the pair of base fabric panels when the bag body expands, the method comprising the following steps: Sewing the base fabric panel and the tether fabric by a stitching including a plurality of curved stitches that are convex on the side opposite to the hemming end of the tether fabric, and the apexes of the convexities of the plurality of curved stitches being on a virtual line extending in the width direction of the tether fabric; The manufacturing method including the above.

[30] The stitching of the curve is a continuous stitch or a part thereof, and the method for manufacturing an airbag according to the above

[29] , including the step of continuously stitching.

Advantages of the Invention

[0017] The airbag according to the present invention is an airbag in which opposing base fabric panels are sewn with a wide tether fabric to maintain a predetermined thickness during inflation, and the tearing of the sewing part is reduced due to the stitching in a specific sewing form. In the specific sewing form, linear stitches are discrete, and there are bent portions at the ends of each stitch toward the hemming end (depth direction) of the tether fabric. Therefore, compared with simple linear stitches, the amount of stitching increases, and when stress is applied, the stress is dispersed in the depth direction, resulting in higher strength. Furthermore, in the specific sewing form, a large number of linear stitches are discrete and the number of ends of the stitches is also large. Therefore, compared with a single simple linear stitch having two ends, the number of locations where stress is likely to concentrate increases. As a result, the stress per end portion is reduced, and there is no tearing from the end portion. Therefore, the airbag according to the invention can be suitably used as an airbag for automobiles, particularly an airbag for pedestrians.

[0018] The airbag according to the present invention is an airbag in which opposing base fabric panels, which have reduced tearing at the sewing part due to sewing in a specific sewing form, are sewn with a wide tether fabric to maintain a predetermined thickness during inflation, and a method for manufacturing the same. In the specific sewing form, a plurality of curved stitches that protrude on the side opposite to the sewing margin end (depth direction) of the tether fabric (the side where stress is applied) preferably exist discretely, and there is a bent portion (a part of the curve) toward the sewing margin end of the tether fabric. Therefore, compared to simple linear stitching, the amount of stitching increases, and when stress is applied, the stress is dispersed in the depth direction, resulting in higher strength. Furthermore, in the specific sewing form, when the stitches of the plurality of curves are discrete, the number of the bent portions (parts of the curves) also becomes large. Therefore, although the number of locations where stress is likely to concentrate increases compared to a single simple linear stitch having two ends, the stress per end portion is rather reduced, and there is no tearing from the end portions. Therefore, the airbag according to the invention can be suitably used as an airbag for automobiles, particularly an airbag for pedestrians.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0020]

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be described in detail. One embodiment of the present invention is an airbag having a bag body in which a pair of base fabric panels are stitched at the outer peripheral edge, and a tether fabric having a predetermined width stitched to each of the pair of base fabric panels inside the bag body so as to regulate the distance between the pair of base fabric panels when the bag body is inflated. The stitching between the base fabric panel and the tether fabric includes a plurality of discrete linear stitches arranged along a virtual line extending in the width direction of the tether fabric, and the ends of the linear stitches have bent portions that bend at a predetermined angle and a predetermined length from the virtual line toward the edge of the tether fabric where the seam allowance ends. The airbag is characterized by this.

[0022] The stitching between the base fabric panel and the tether fabric can be, for example, the stitching represented by 66a(41a) in (B) in the pedestrian airbag described in Patent Document 1 shown in FIG. 1. The inventors of the present application found that stress concentrates at the ends of such stitching and it is likely to become a starting point of tearing. Paying attention to this, they found a stitching in a specific sewing form that can further reduce the occurrence of tearing. In this specification, as described above, the "specific sewing form" means a sewing form in which the stitching between the base fabric panel and the tether fabric includes a plurality of discrete linear stitches arranged along a virtual line extending in the width direction of the tether fabric, and the ends of the linear stitches have bent portions that bend at a predetermined angle and a predetermined length from the virtual line toward the edge of the tether fabric where the seam allowance ends.

[0023] In this specification, the term "virtual line" refers to the shape in which the folded portion of the tether fabric thin plate is superimposed on the thin plate of the base fabric panel in the state where the base fabric panel and the tether fabric are stitched, and this folding line. This is because the tether that regulates the interval between a pair of base fabric panels when the airbag expands generally corresponds to the part (line) that becomes the action point receiving the expansion pressure. Alternatively, the "virtual line" can be a straight or curved sewing design line through which the sewing machine needle passes when sewing the panel base fabric and the tether fabric together.

[0024] As an example of the specific sewing form, FIG. 2 shows stitches in which inverted triangles are arranged along the virtual line at regular intervals. In the schematic representation of the sewing form in FIG. 2, the "virtual line" corresponds to the upper line (4) of the seam allowance of the tether fabric. In this example, one side of a plurality of inverted triangles is arranged on the virtual line, and the total length of these sides ensures the total length of the sewn part of the stressed part required for the wide tether. Since the sewing interval is too wide, the amount of sewing simply does not decrease and the strength does not decrease. Also, in this example, the linear stitches, which are one side of the inverted triangle, are discrete, and at the end of each stitch, there is a bent part (the other two sides of the inverted triangle) toward the folded edge end of the tether cloth (5 in FIG. 2). Therefore, compared with a simple linear stitch, the amount of sewing increases, and when stress is applied, the stress is dispersed in the direction of the folded edge end (downward in the right side view of FIG. 2), resulting in higher strength (see the right side of FIG. 3). At this time, wrinkles are generated in the panel base fabric, and the state of stress dispersion can be observed. Further, in this example, since a large number of linear stitches are discrete and the number of stitch ends (the vertices of the inverted triangles on the virtual line) is also large, compared with a single simple linear stitch with two ends, the number of locations where stress is likely to concentrate increases. As a result, the stress per end decreases and there is no breakage from the ends (compare the left and right sides of FIG. 3). FIG. 4 shows other examples of specific correction forms in the following Examples 1-1 to 1-4, 1-6, and 1-7. It can be seen that any of these examples is the specific sewing form. Furthermore, as in Examples 1-1 to 1-5, when the linear stitches on the virtual line are each part of a different stitch, when folding and storing the airbag, it can be folded at the part without sewing thread. Therefore, the bending thickness of the sewing part when folding in the direction perpendicular to the virtual line can be reduced, and the storage performance of the airbag can be improved.

[0025] The predetermined width of the tether cloth is preferably 50 mm or more and 500 mm or less, more preferably 100 mm or more and 500 mm or less, even more preferably 100 mm or more and 400 mm or less, and particularly preferably 200 mm or more and 400 mm or less. The specific sewing form described above has a strength capable of withstanding the stress of a wide tether having this range.

[0026] It is preferable that a plurality of discrete and arranged linear suture lengths along a virtual line extending in the width direction of the tether cloth be 5 mm or more and 100 mm or less, and more preferably 10 mm or more and 50 mm or less. Within this range, a sufficient total amount of sutures of a length capable of withstanding the stress during inflation deployment and a sufficient number of suture ends can be ensured. That is, if this length is insufficient, the amount of sewing under stress will decrease.

[0027] The interval between the linear sutures arranged along the virtual line is preferably 5 mm or more and 50 mm or less, and more preferably 7 mm or more and 20 mm or less. Within this range, a sufficient total amount of sutures of a length capable of withstanding the stress during inflation deployment and a sufficient number of suture ends can be ensured. If this interval is too wide, the amount of sewing under stress will decrease, and if it is too narrow, the stress will be difficult to disperse.

[0028] The ratio of the interval of the linear suture to the length of the linear suture ((interval of the linear suture / length of the linear suture)) is preferably 0.2 or more and 1.5 or less, and more preferably 0.3 or more and 1.0 or less. Within this range, a sufficient total amount of sutures of a length capable of withstanding the stress during inflation deployment and a sufficient number of suture ends can be ensured.

[0029] The bending angle of the end of the linear suture is preferably 60° or more and 120° or less, and more preferably 70° or more and 110° or less. If the bending angle is less than 60° or more than 120°, the sewing form approaches a dotted line shape, so when stress is applied, the stress is difficult to disperse in the depth direction (downward in FIG. 2), and the strength decreases. That is, if the bending angle is too acute, the end becomes close to a straight line, and on the other hand, if it is too obtuse, the end also becomes close to a straight line.

[0030] The length of the bent portion at the end of the linear suture is preferably 3 mm or more and 50 mm or less, more preferably 5 mm or more and 30 mm or less. If this length is less than 3 mm, when stress is applied, it is difficult for the stress to be dispersed in the depth direction (downward in Fig. 2), resulting in a decrease in strength. On the other hand, if it exceeds 50 mm, although the pressure dispersion is good, the amount of suturing increases, leading to a decrease in productivity. That is, if this length is too short, the end becomes closer to a straight line, and the portion receiving stress decreases.

[0031] It is preferable that a plurality of linearly arranged sutures are discretely arranged along the virtual line at 2 or more and 20 or less per 10 cm of the length of the virtual line, more preferably 2 or more and 10 or less, even more preferably 3 or more and 10 or less, and particularly preferably 4 or more and 7 or less. Incidentally, the length of the virtual line is the distance between the two outermost ends among the ends of the linearly arranged sutures discretely arranged in plurality. Within this range, it is possible to ensure a sufficient total amount of sutures with a length sufficient to withstand the stress during expansion and deployment, and a sufficient number of suture ends.

[0032] The linear suture can be a polygon or a semi-circle or a part thereof that shares one side with the virtual line as long as it meets the requirements of a specific sewing form. Also, the linear suture can be a part of a continuous rectangular wave on the virtual line. As described above, the sewing forms shown in Fig. 4 and the following Examples 1-1 to 1-4, 1-6, and 1-7 are an example of a specific correction form. Incidentally, the bent portion may be only at one end, but bending both ends has a higher effect on stress dispersion. Also, in the rectangular wave, when the amplitude is small, it becomes closer to a straight line, and the portion receiving stress decreases. Also, as long as stress is dispersed to each of the plurality of linearly arranged sutures along the virtual line, they do not all have to completely coincide with the virtual line, and some may be arranged before and after the virtual line. Also, the specific sewing shape may be, for example, a series of the same inverted triangles spaced apart, or a series of inverted triangles and quadrilaterals arranged alternately. The stitching of the base fabric panel including the linear stitching and the tether fabric may be stitched to the test piece at a portion exceeding the entire width of the tether, at a portion substantially equal to the entire width of the tether, or may be stitched with a non-sewn portion of a predetermined width provided on both sides of the tether. By stitching the base fabric panel and the tether fabric at a portion exceeding the entire width of the tether or at a portion substantially equal to the entire width of the tether, the inflation and deployment structure of the airbag can be supported by the entire width of the tether, and the utilization efficiency of the material is good. On the other hand, by providing a non-sewn portion of a predetermined width on both sides of the tether and stitching, the occurrence of extreme stress concentration at the ends of the tether can be prevented, a base fabric with a lower fineness can be selected as the tether fabric, and it contributes to the storage property of the airbag.

[0033] The airbag according to the present invention is preferably an airbag for pedestrians.

[0034] Another aspect of the present invention is a method for manufacturing an airbag having a bag body in which a pair of base fabric panels are stitched at an outer peripheral edge, and a tether fabric having a predetermined width stitched to each of the pair of base fabric panels inside the bag body so as to be able to regulate the distance between the pair of base fabric panels when the bag body is inflated, the following steps: A step of stitching the base fabric panel and the tether fabric with a stitch including a plurality of discrete linear stitches arranged along a virtual line extending in the width direction of the tether fabric, and having a bent portion in which an end portion of the linear stitch is bent at a predetermined angle and a predetermined length from the virtual line toward the stitched end of the tether fabric; The manufacturing method including the above.

[0035] The stitching method is not particularly limited. For example, the tether fabric and the base fabric panel can be overlapped in a planar shape and stitched by planar sewing to obtain a specific sewing form, and since the sewing work is not time-consuming, the productivity is not significantly reduced. The stitching means is also not particularly limited. For example, it can be stitched manually according to a sewing line previously drawn on the base fabric using a JUKI LU-2210 series, or can be obtained by programming the sewing form using an industrial sewing machine such as a JUKI AMS-221EN series. If a plurality of discrete linear stitches arranged along the virtual line are part of a continuous stitch, productivity can be improved by performing a continuous stitching process. In addition, by reducing the number of starting and ending stitches, it is possible to contribute to the reduction of sewing defects.

[0036] The tether fabric is not particularly limited. For example, it can be a plain weave fabric with a weave density of 49 threads / inch woven using nylon 66 multifilament fibers with a total fineness of 470 dtex and 136 filaments for the warp and weft. A coating can be applied to the tether fabric to impart heat resistance. For example, 25 g / m of silicone resin can be 2 applied.

[0037] The panel base fabric is also not particularly limited. For example, it can be a plain weave fabric with a weave density of 72 threads / inch woven using nylon 66 multifilament fibers with a total fineness of 235 dtex and 72 filaments for the warp and weft. A coating can be applied to the tether fabric to impart heat resistance and internal pressure retention. For example, 17 g / m of silicone resin can be 2 applied.

[0038] The sewing thread that constitutes a specific sewing form is also not particularly limited. For example, nylon 66 or polyester thread can be used as the sewing thread of a sewing machine. There is also no particular limitation on the fineness of the sewing thread, but from the perspective of achieving both strength and storability, 400 dtex or more and 2000 dtex or less are preferable. It is preferable that the sewing thread is twisted from the perspective of sewing workability. It can be a single twist or a twisted combination of multiple raw yarns such as a three-ply twist. Also, the upper thread and the lower thread can be the same or different.

[0039] Hereinafter, embodiments of the present invention will be described in detail. One embodiment of the present invention is an airbag having a bag body in which a pair of base fabric panels are sewn together at the outer peripheral edge, and a tether fabric with a predetermined width sewn to each of the pair of base fabric panels inside the bag body so as to regulate the distance between the pair of base fabric panels when the bag body expands. The stitching between the base fabric panel and the tether fabric includes stitching of a plurality of curves that bulge on the side opposite to the stitched edge of the tether fabric, and the vertices of the stitching of the plurality of curves are on a virtual line extending in the width direction of the tether fabric. The airbag is characterized by this.

[0040] The stitching between the base fabric panel and the tether fabric can be, for example, the stitching represented by 66a(41a) in part B of FIG. 6 in the pedestrian airbag described in Patent Document 1 shown in FIG. 6. The inventors of the present application found that stress concentrates at the ends of such stitching and it is likely to become a starting point of tearing. Paying attention to this, they found a stitching of a specific sewing form that can further reduce the occurrence of tearing. In this specification, as described above, the "specific sewing form" means a sewing form in which the stitching between the base fabric panel and the tether fabric includes stitching of a plurality of curves that bulge on the side opposite to the stitched edge of the tether fabric, and the vertices of the stitching of the plurality of curves are on a virtual line extending in the width direction of the tether fabric.

[0041] In this specification, the term "virtual line" refers to a shape in which the folded portion of the tether fabric thin plate is overlapped with respect to the thin plate of the base fabric panel in a state where the base fabric panel and the tether fabric are stitched, and this folding line. This is because the tether that regulates the interval between a pair of base fabric panels when the airbag expands corresponds approximately to the part (line) that becomes the action point receiving the expansion pressure. Alternatively, the "virtual line" can be a straight or curved sewing design line through which the sewing machine needle is to pass when sewing by overlapping the panel base fabric and the tether fabric.

[0042] As an example of the specific sewing form, FIG. 7 shows stitching in which circles are arranged along the virtual line at regular intervals. In the schematic representation of the sewing form in FIG. 7, the "virtual line" corresponds to the upper line (4) of the stitched edge of the tether fabric. In this example, a plurality of circles are arranged on the virtual line, and the total length of the convex portions on the opposite side of the seam edge of the tether cloth ensures the total length of the sewing of the stress-applied portion required for the wide tether. Since the sewing interval is too wide, the sewing amount does not simply decrease and the strength does not decrease. Also, in this example, the sewing of the curves arranged along the virtual line is discrete, and each sewing has two bent portions (a part of the curve) toward the seam edge of the tether cloth (5 in FIG. 7). Therefore, compared with a simple straight sewing, the sewing amount increases, and when stress is applied, the stress is dispersed in the direction of the seam edge (downward in the right figure of FIG. 7), resulting in higher strength (see the right side of FIG. 8). At this time, wrinkles are generated in the panel base cloth, and the state of stress dispersion can be observed. Furthermore, in this example, a large number of circular sewings are discrete and the number of bent portions (a part of the curve) of the sewing is also large. Therefore, compared with a single simple straight sewing with two ends, the number of locations where stress is likely to concentrate increases, the stress received by each such location decreases, and there is no breakage from such location (compare the left and right sides of FIG. 8). FIG. 9 shows examples of specific correction forms in the following Examples 2-1 to 2-7. It can be seen that any of these examples is the specific sewing form described above. Furthermore, as in Examples 2-1, 2-3 to 2-5, when the sewing of the curves arranged along the virtual line is a part of different sewings and is discrete, when folding and storing the airbag, it can be folded at the part without sewing thread. Therefore, the bending thickness of the sewing part when folding in the direction perpendicular to the virtual line can be reduced, and the storage property of the airbag can be improved.

[0043] The predetermined width of the tether cloth is preferably 50 mm or more and 500 mm or less, more preferably 100 mm or more and 500 mm or less, and even more preferably 200 mm or more and 400 mm or less. The specific sewing form described above has a strength capable of withstanding the stress of a wide tether having this range.

[0044] Among the sewings of a plurality of curves arranged along a virtual line extending in the width direction of the tether cloth, the distance between the portion farthest from the virtual line and the virtual line is 1 mm or more and 100mm or less It is preferably in the range of 5 mm or more and 50 mm or less, more preferably 10 mm or more and 20 mm or less. Within this range, it does not affect productivity and a bent portion (a part of the curve) with a sufficient length can be ensured. In addition, when a plurality of curves that bulge on the side opposite to the hem edge of the tether cloth are part of a circle, an ellipse, and a sine curve, as shown in FIG. 7, the boundary between the portion that bulges on the side opposite to the hem edge of the tether cloth and the portion that bulges on the hem edge side of the tether cloth is set to be the portion farthest from the virtual line among the stitches of the plurality of curves that bulge on the side opposite to the hem edge of the tether cloth. In other words, the stitches of the plurality of curves that bulge on the side opposite to the hem edge of the tether cloth refer to the upper portion when the convex shape is divided by the boundary in the upward and downward directions in the example of the circle or sine curve in FIG. 7.

[0045] When the length in the direction parallel to the virtual line of the stitches of a plurality of curves arranged along the virtual line extending in the width direction of the tether cloth is defined as the width (straight line) of the stitches of the curve, the width of the stitches of the curve is preferably 5 mm or more and 100 mm or less, more preferably 10 mm or more and 100 mm or less, still more preferably 10 mm or more and 50 mm or less, and particularly preferably 20 mm or more and 50 mm or less. Within this range, a stitch with a sufficient length that can withstand the stress during inflation and deployment can be ensured. In addition, when a plurality of curves are part of a circle, an ellipse, and a sine curve, as shown in FIG. 7, the length in the direction parallel to the virtual line of the portion that bulges on the side opposite to the hem edge of the tether cloth is defined as the width of the stitches of the curve, and the boundary between the portion that bulges on the side opposite to the hem edge of the tether cloth and the portion that bulges on the hem edge side of the tether cloth is set as the start or end of the width of the stitches of the curve.

[0046] The value calculated by (the distance between the portion farthest from the virtual line and the virtual line of the stitches of the curve) / (the width of the stitches of the curve) is preferably 0.1 or more and 2.0 or less, and more preferably 0.5 or more and 1.0 or less. Within this range, a stitch with a sufficient length that can withstand the stress during inflation and deployment and a bent portion (a part of the curve) with a sufficient length can be ensured.

[0047] The distance between the convex vertices of the curved sutures arranged along the suture line is preferably 5 mm or more and 100 mm or less, more preferably 10 mm or more and 100 mm or less, still more preferably 15 mm or more and 100 mm or less, and particularly preferably 20 mm or more and 50 mm or less. Within this range, the total amount of sutures of sufficient length to withstand the stress during inflation and deployment can be ensured, and a sufficient number of bent portions (parts of the curve) can be secured. If this distance is too wide, the amount of sewing under stress will decrease, and if it is too narrow, it will be difficult for the stress to concentrate at a particular location, and as a result, the stress borne by each location will increase. When a plurality of curved sutures are part of a circle, ellipse, or sine curve, as shown in FIG. 7, the point farthest from the suture edge of the tether cloth is taken as the convex vertex of the curved suture. Also, when the curved suture has a portion that is substantially linear on the virtual line, the midpoint of that portion is taken as the vertex of the curved suture.

[0048] The value obtained by subtracting the width of the curved suture from the distance between the convex vertices of the curved sutures arranged along the virtual line (corresponding to the distance between the ends of the curved suture) is preferably 0 mm or more and 50 mm or less, and more preferably 3 mm or more and 30 mm or less. Within this range, the total amount of sutures of sufficient length to withstand the stress during inflation and deployment can be ensured.

[0049] The value calculated by (distance between the convex vertices of the curved suture - width of the curved suture) / (width of the curved suture) of the curved suture is preferably 0 or more and 1.5 or less, and more preferably 0 or more and 1.0 or less. Within this range, the total amount of sutures of sufficient length to withstand the stress during inflation and deployment can be ensured.

[0050] It is preferable that the stitches of the curves arranged along the virtual line are present in a number of 2 or more and 20 or less per 10 cm of the virtual line, more preferably 2 or more and 10 or less, still more preferably 3 or more and 10 or less, and particularly preferably 4 or more and 7 or less. Note that the length of the virtual line is the distance between the outermost two ends of the stitches among the ends of the stitches of the plurality of curves. Within this range, it is possible to ensure a total amount of stitches of a sufficient length that can withstand the stress during expansion deployment and a sufficient number of bent portions (parts of the curves).

[0051] The stitches of the curves can be a circle, an ellipse, or a part thereof that shares a part with the virtual line as long as they meet the requirements of a specific sewing form. Also, the stitches of the curves may be continuous without being discrete or a part of a continuous sine curve parallel to the virtual line. As described above, the sewing forms shown in FIG. 9 and the following Examples 2-1 to 2-7 are an example of a specific correction form. Note that in the case of a thin circle or arc, it becomes linear and the portion for relieving stress decreases. The same applies when the amplitude is small in the sine curve. Also, as long as the stress is dispersed in each of the stitches of the curves, not all the convex vertices need to be arranged completely coincident with the virtual line, and a part may be arranged before and after the virtual line. Also, the specific sewing shape may be, for example, one in which the same curves are arranged at intervals or one in which curves and polygons are arranged alternately. The stitching of the base fabric panel including the stitching of the curve and the tether fabric may be stitched to the test piece at a portion exceeding the entire width of the tether, stitched at a portion substantially equal to the entire width of the tether, or stitched with a non-sewn portion of a predetermined width provided on both sides of the tether. By stitching the base fabric panel and the tether fabric at a portion exceeding the entire width of the tether or at a portion substantially equal to the entire width of the tether, the inflation and deployment structure of the airbag can be supported by the entire width of the tether, and the utilization efficiency of the material is good. On the other hand, by setting a non-sewn portion of a predetermined width on both sides of the tether and stitching it, the occurrence of extreme stress concentration at the ends of the tether can be prevented, a base fabric with a lower fineness can be selected as the tether fabric, and it contributes to the storage property of the airbag.

[0052] The airbag according to the present invention is preferably an airbag for pedestrians.

[0053] Another aspect of the present invention is a method for manufacturing an airbag having a bag body in which a pair of base fabric panels are stitched at the outer peripheral edge, and a tether fabric of a predetermined width stitched to each of the pair of base fabric panels inside the bag body so as to regulate the distance between the pair of base fabric panels when the bag body expands, the following steps: Stitching the base fabric panel and the tether fabric by a stitching including stitching of a plurality of curves convex on the opposite side of the sewing margin end of the tether fabric, and the vertices of the stitching of the plurality of curves being on a virtual line extending in the width direction of the tether fabric; The manufacturing method including the above.

[0054] The stitching method is not particularly limited. For example, the tether fabric and the base fabric panel can be overlapped in a planar shape and stitched by planar sewing to form a specific sewing form, and since it does not take time for the sewing operation, the productivity is not significantly reduced. The sewing means is also not particularly limited. For example, it can be stitched manually according to the sewing line previously drawn on the base fabric using the LU-2210 series manufactured by JUKI, or obtained by programming the sewing form using an industrial sewing machine such as the AMS-221EN series manufactured by JUKI. Suturing a plurality of curves arranged along the provisional virtual line as continuous suturing or a part thereof, and performing continuous suturing can improve productivity. Also, by reducing the number of starting and ending stitches, it can contribute to reducing sewing defects.

[0055] The tether cloth is not particularly limited. For example, it can be a plain weave fabric with a weaving density of 49 threads / inch woven using nylon 66 multifilament fibers with a total fineness of 470 dtex and 136 filaments for the warp and weft. A coating can be applied to the tether cloth to impart heat resistance. For example, 25 g / m of silicone resin 2 can be applied.

[0056] The panel base is not particularly limited. For example, it can be a plain weave fabric with a weaving density of 72 threads / inch woven using nylon 66 multifilament fibers with a total fineness of 235 dtex and 72 filaments for the warp and weft. A coating can be applied to the tether cloth to impart heat resistance and internal pressure retention. For example, 17 g / m of silicone resin 2 can be applied.

[0057] The sewing thread constituting the specific sewing form is not particularly limited, and nylon 66 or polyester thread can be used as the sewing thread of the sewing machine. There is no particular limitation on the fineness of the sewing thread, but from the viewpoint of achieving both strength and storability, 400 dtex or more and 2000 dtex or less are preferable. It is preferable that the sewing thread is twisted from the viewpoint of sewing workability, and it can be a single twist or a twisted combination of a plurality of raw yarns such as a three-ply twist. Also, the upper thread and the lower thread can be the same or different.

Examples

[0058] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. First, the materials used in the Examples and Comparative Examples, the measurement methods of physical properties, etc. will be described.

[0059] [Panel base fabric] A plain weave fabric woven using nylon 66 multifilament fibers as warp and weft and coated with a silicone resin was used. The total fineness of the base fabric used was 235 dtex, the number of filaments was 72, the weaving density was 72 threads / inch, and the silicone resin coating amount was 17 g / m 2 It was.

[0060] [Tether fabric] A plain weave fabric woven using nylon 66 multifilament fibers as warp and weft and coated with a silicone resin was used. The total fineness of the base fabric used was 470 dtex, the number of filaments was 136, the weaving density was 49 threads / inch, and the silicone resin coating amount was 25 g / m 2 It was.

[0061] [Sewing thread] Mitsubishi airbag sewing thread (total fineness 1880 dtex, nylon 66 multifilament fiber 940 dtex 2-ply twist) made by Gunze was used for the upper and lower threads.

[0062] [Sewing machine] For sewing in a specific sewing form, JUKI LU-2210W-7 was used.

[0063] [Preparation of test piece] As shown in the <sample shape> of Fig. 5, the panel base fabric and the tether fabric were each cut into strips along the base fabric pattern so that the warp was 300 mm and the weft was 500 mm. Next, the tether fabric was shifted 100 mm in the weft direction and overlapped on the main base fabric. With a sewing allowance of 15 mm for the tether fabric, in the range of 270 mm in the center of the width direction, the sewing machine was used with the sewing thread to sew in a specific sewing pattern at a stitch density of 50 stitches / 10 cm. In addition, 3 stitches of backstitching (or double stitching) were performed at the start and end of sewing. Subsequently, the ends in the length direction of the main base fabric were overlapped so that the strip shape became a loop, and the overlapping part was sewn with 3 rows of straight stitching (7a) in the warp direction of the base fabric at a stitch density of 35 stitches / 10 cm. The length of the loop was 320 mm for one round. The tether fabric was folded back at the end farther from the specific sewing pattern, and in the middle part between the specific sewing pattern and the folded-back part, the tether fabrics were sewn together with 3 rows of straight stitching (7b) in the warp direction of the base fabric at a stitch density of 35 stitches / 10 cm. The length from the folded-back part to the virtual line of the specific sewing pattern was 200 mm. Finally, it was confirmed that the overlapping parts of the main fabrics and the tether fabrics were not tilted, and that the sewing on the virtual line and the sewing of the overlapping part were along the warp direction of the base fabric. If these are misaligned, the stress applied to the sewing part during measurement may be biased, resulting in measurement errors.

[0064] (1) Measurement of the sewing strength (N / cm) per 1 cm of the virtual line As shown in the <fixture shape> of Fig. 5, a fixture for holding a test piece by passing it through the loops of the main base fabric and the tether fabric was attached to a tensilon universal material testing machine manufactured by A&D Company, Limited. As shown in the <sample attachment state> of Fig. 5, when the test piece was viewed from the lateral direction (the direction in which the thickness of the test piece could be confirmed) in the state of being attached to the testing machine, the tether fabric was adjusted to be perpendicular to the main base fabric (forming a T shape). At this time, the stroke was adjusted so that the tether fabric was stretched parallel to the tensile direction, and the stroke (the distance from the virtual line to the fixed point of the tether fabric) was 200 to 400 mm. The measurement was carried out at a tensile speed of 300 mm / min, and the maximum strength at break was divided by the length of the virtual line to obtain the sewing strength per 1 cm of the length of the virtual line. Those with a sewing strength (N / cm) per 1 cm of the virtual line less than 350 N / cm were judged as "×", those with 350 N / cm or more and less than 450 N / cm were judged as "△", and those with 450 N / cm or more were judged as "〇".

[0065] (2) Measurement of the bending thickness (mm) (perpendicular to the virtual line) of the sewing part For the test piece prepared as described above, it was bent perpendicular to the virtual line, the folded part of the sample was sandwiched under a 3 cm × 6 cm plate, and a load was applied for 30 seconds so that the total weight became 1 kg together with the plate. Then, the measuring head of a thickness gauge (FFA-10 manufactured by Ozaki Seisakusho) was set so that the center of the fold came to the center line of the measuring head, and the value after 1 minute was measured. The position of the fold was set so that the number of sewing lines passing through the fold was minimized, and the average of the measured values at three locations was taken as the value of the bending thickness of the sewing part. Those with such a bending thickness of 3.5 mm or less were judged as "〇", and those exceeding 3.5 were judged as "×".

[0066] [Examples 1-1 to 1-7, Comparative Examples 1-1, 1-2] Test pieces having the sewing forms shown in Table 1 below were prepared, and the sewing strength (N / cm) per 1 cm of the virtual line and the bending thickness (mm) of the sewing part (perpendicular to the virtual line) described above were measured. The results are shown in Table 1 below.

[0067]

Table 1

[0068] In the comparison of Examples 1-1 to 1-3, it can be seen that when the ratio of the linear stitching interval is outside the range of 0.2 to 1.5, the stitching strength per 1 cm of the virtual line decreases. From Example 1-4, it can be seen that when the length of the linear stitching is less than 5 mm, the stitching strength per 1 cm of the virtual line decreases. From Example 1-5, it can be seen that when the bending angle is less than 60°, the stitching strength per 1 cm of the virtual line decreases. From Example 1-6, it can be seen that when the stitching is part of a rectangular wave, the stitching strength per 1 cm of the virtual line does not decrease, but the bending thickness (mm) of the sewing part increases. From Example 1-7, it can be seen that when the stitching is part of a rectangular wave and the length of the bent part is less than 3 mm, the stitching strength per 1 cm of the virtual line decreases, and furthermore, the bending thickness (mm) of the sewing part increases. In Comparative Example 1-1, since there is no interval and no bent part, it can be seen that the stitching strength per 1 cm of the virtual line further decreases, and furthermore, the bending thickness (mm) of the sewing part increases. In Comparative Example 1-2, although there is an interval, since there is no bent part, it can be seen that the total amount of stitching decreases and the stitching strength per 1 cm of the virtual line further decreases.

[0069] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. First, the materials used in the Examples and Comparative Examples, the measurement methods of physical properties, etc. will be described.

[0070] [Panel base fabric] A plain weave fabric woven using nylon 66 multifilament fibers as warp and weft and coated with a silicone resin was used. The total fineness of the base fabric used was 235 dtex, the number of filaments was 72, the weaving density was 72 threads / inch, and the silicone resin coating amount was 17 g / m 2 was.

[0071] [Tether fabric] A plain weave fabric woven using Iron 66 multifilament fibers as warp and weft and coated with a silicone resin was used. The total fineness of the base fabric used was 470 dtex, the number of filaments was 136, the weaving density was 49 threads / inch, and the silicone resin coating amount was 25 g / m 2 It was.

[0072] [Sewing thread] Mitsubishi sewing thread for airbags (total fineness 1880 dtex, 2-ply twist of nylon 66 multifilament fiber 940 dtex) was used for the upper and lower threads.

[0073] [Sewing machine] For sewing in a specific sewing pattern, JUKI LU-2210W-7 was used.

[0074] [Preparation of test piece] As shown in the <sample shape> of Figure 5, the panel base fabric and the tether fabric were each cut into strips along the base fabric pattern so that the warp was 300 mm and the weft was 500 mm. Next, the tether fabric was overlapped with a 100 mm shift in the weft direction on the main base fabric, and with a sewing allowance of 15 mm for the tether fabric, in the range of 270 mm in the center of the width direction, the sewing machine was used with the sewing thread to sew in a specific sewing pattern at a stitch density of 50 stitches / 10 cm. In addition, 3 backstitches (or double stitches) were made at the start and end of sewing. Subsequently, the ends in the length direction of the main base fabric were overlapped so that the strip shape became a loop, and the overlapping part was sewn in 3 rows of straight stitches (7a) in the warp direction of the base fabric at a stitch density of 35 stitches / 10 cm. The length of the loop was set to 320 mm for one round. On the other hand, for the tether fabric, the end far from the specific sewing pattern was folded back, and in the middle part between the specific sewing pattern and the folded-back part, the tether fabrics were sewn together in 3 rows of straight stitches (7b) in the warp direction of the base fabric at a stitch density of 35 stitches / 10 cm. The length from the folded-back part to the virtual line of the specific sewing pattern was set to 200 mm. Finally, it was confirmed that the overlapping parts of the main fabrics and the tether fabrics were not tilted, and that the sewing on the virtual line and the sewing of the overlapping part were along the warp direction of the base fabric. If these are misaligned, the stress applied to the sewing part during measurement may be uneven, resulting in measurement errors.

[0075] (1) Measurement of the stitching strength (N / cm) per 1 cm of the virtual line As shown in the <fixture shape> of Fig. 10, a fixture for holding the test piece by passing it through the loops of the main base fabric and the tether fabric was attached to a tensilon universal material testing machine manufactured by A&D Company, Limited. As shown in the <sample attachment state> of Fig. 10, when the test piece was viewed from the lateral direction (the direction in which the thickness of the test piece could be confirmed) in the state of being attached to the testing machine, the tether fabric was adjusted to be perpendicular to the main base fabric (forming a T shape). At this time, the stroke was adjusted so that the tether fabric was stretched parallel to the tensile direction, and the stroke (the distance from the virtual line to the fixed point of the tether fabric) was 200 to 400 mm. The measurement was performed at a tensile speed of 300 mm / min, and the maximum strength at break was divided by the length of the virtual line to obtain the stitching strength per 1 cm of the virtual line. Those with a stitching strength (N / cm) per 1 cm of the virtual line less than 330 N / cm were judged as "×", those with a stitching strength of 330 N / cm or more and less than 440 N / cm were judged as "△", and those with a stitching strength of 440 N / cm or more were judged as "〇".

[0076] (2) Measurement of the bending thickness (mm) (perpendicular to the virtual line) of the sewing part Regarding the test piece prepared as described above, it was bent perpendicular to the virtual line, the folded part of the sample was sandwiched under a 3 cm × 6 cm plate, and a load was applied for 30 seconds so that the total weight became 1 kg together with the plate. Then, the measuring head of a thickness gauge (FFA-10 manufactured by Ozaki Seisakusho) was set so that the center of the fold came to the center line of the measuring head, and the value after 1 minute was measured. The position of the fold was set so that the number of sewing lines passing through the fold was minimized, and the average of the measured values at three locations was used as the value of the bending thickness of the sewing part. Those with such a bending thickness of 3.5 mm or less were judged as "〇", and those exceeding 3.5 mm were judged as "×".

[0077] [Examples 2-1 to 2-3, 2-4, 2-4b, 2-5 to 2-7, Comparative Examples 2-1, 2-2] Test pieces with the stitching of the sewing forms shown in Table 2 below were prepared, and the stitching strength (N / cm) per 1 cm of the above-mentioned virtual line and the bending thickness (mm) of the stitched part (perpendicular to the virtual line) were measured. The results are shown in Table 2 below.

[0078]

Table 2

[0079] In the comparison of Examples 2-1 to 2-3, it can be seen that if the interval of the circular stitching is too narrow or too wide, the stitching strength per 1 cm of the virtual line will decrease. Also, if it is too narrow, the bending thickness of the stitched part will deteriorate. From Examples 2-4 and 2-4b, it can be seen that if the width (straight line) of the curved stitching is less than 10 mm, the stitching strength per 1 cm of the virtual line will decrease. From Example 2-5, it can be seen that if the circular stitching is too thin, the stitching strength per 1 cm of the virtual line will decrease. From Example 2-6, it can be seen that when the curved stitching is continuous, the stitching strength per 1 cm of the virtual line does not decrease much, but the bending thickness (mm) of the stitched part deteriorates. From Example 2-7, it can be seen that if it is a sine curve, the stitching strength per 1 cm of the virtual line does not decrease, but the bending thickness (mm) of the stitched part deteriorates. In Comparative Example 2-1, since there is no interval and no bent part, it can be seen that the stitching strength per 1 cm of the virtual line further decreases, and furthermore, the bending thickness (mm) of the stitched part also deteriorates. In Comparative Example 2-2, although there is an interval, since there is no bent part (a part of the curve), it can be seen that the total amount of stitching decreases and the stitching strength per 1 cm of the virtual line further decreases.

Industrial Applicability

[0080] The airbag according to the present invention is an airbag in which opposing base fabric panels, which have reduced tearing at the sewing part due to sewing in a specific sewing form, are sewn with a wide tether fabric to maintain a predetermined thickness during inflation, and a method for manufacturing the same. In the specific sewing form, the total amount of the sewing length of the portion where stress is applied, which is required for the wide tether, is ensured (that is, since the sewing interval is too wide, the sewing amount is not simply reduced and the strength is not lowered). Further, in the specific sewing form, the linear stitches are discrete, and there are bent portions toward the end of the sewing allowance (depth direction) of the tether fabric at the ends of each stitch. Therefore, compared with simple linear stitches, the sewing amount increases, and when stress is applied, the stress is dispersed in the depth direction, resulting in higher strength. Furthermore, in the specific sewing form, since a large number of linear stitches are discrete and the number of ends of the stitches is also large, compared with a single simple linear stitch having two ends, the number of locations where stress is likely to concentrate increases. As a result, the stress per end portion is reduced, and there is no tearing from the end portion. Therefore, the airbag according to the invention can be suitably used as an airbag for automobiles, particularly an airbag for pedestrians.

[0081] The airbag according to the present invention is an airbag formed by sewing a wide tether cloth for maintaining a predetermined thickness when inflated between opposing base cloth panels, in which the breakage of the sewing part is reduced due to a specific sewing form, and a method for manufacturing the same. In the specific sewing form, the total amount of the sewing length of the portion where stress is applied, which is required for the wide tether, is ensured (that is, since the sewing interval is too wide, the sewing amount is not simply reduced and the strength is not lowered). Further, in the specific sewing form, a plurality of curved stitches that protrude on the side opposite to the sewing margin end (depth direction) of the tether cloth (the side where stress is applied) preferably exist discretely, and there is a bent portion (a part of the curve) toward the sewing margin end (depth direction) of the tether cloth. Therefore, compared with a simple linear stitch, the sewing amount increases, and when stress is applied, the stress is dispersed in the depth direction, causing wrinkles in the panel base cloth, so the strength becomes higher. Furthermore, in the specific sewing form, when a plurality of curved stitches are discrete, the number of the bent portions (a part of the curves) also becomes large. Therefore, although the number of portions where stress is likely to concentrate increases compared to a single simple linear stitch having two ends, the stress per end portion rather decreases, and there is no breakage from the end portion. Therefore, the airbag according to the invention can be suitably used as an airbag for automobiles, particularly an airbag for pedestrians.

Explanation of Reference Numerals

[0082] (Hereinafter, FIGS. 1 to 5) 1 Panel base cloth 2 Tether cloth 3 Specific sewing form 4 Virtual line 5 Sewing margin end of tether cloth 6 Sewing allowance of tether cloth 7a Three - row straight sewing 7b Three - row straight sewing (Note) The above reference numerals relate to the drawings except FIGS. 1(A) and 1(B).

[0083] (Hereinafter, FIGS. 6 to 10) 1 Panel base cloth 2 Tether cloth 3 Specific sewing form 3a Stitching of the curve (the part that bulges on the side opposite to the hem edge of the tether cloth) 3b Stitching of the curve and the continuous stitching part 4 Virtual line 5 Hem edge of the tether cloth 6 Sewing allowance of the tether cloth 7 Width of the curve stitching 8 Interval between the vertices of the curve stitching 9 Distance between the part of the curve stitching that is farthest from the virtual line and the virtual line (Note) The above symbols relate to the drawings except for FIGS. 6(A) and 6(B).

Claims

Claim 1 An airbag having a bag body formed by stitching a pair of base fabric panels at their outer peripheral edges, and a tether fabric of a predetermined width stitched to each of the pair of base fabric panels inside the bag body so as to regulate the distance between the pair of base fabric panels when the bag body expands, wherein the stitching between the base fabric panel and the tether fabric includes a plurality of discrete linear stitches arranged along a virtual line extending in the width direction of the tether fabric, and the ends of the linear stitches have bent portions that bend at a predetermined angle and for a predetermined length from the virtual line toward the edge of the stitching allowance of the tether fabric, and the linear stitches are part of a continuous rectangular wave on the virtual line. The airbag is characterized by this.

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