Air bag and manufacturing method of air bag

Abstract

To prevent extension gas from being leaked from a gap formed by a stitching hole spacing being reduced by force applied for separating a base fabric stitched on a seam when an air bag is extended by the extension gas.SOLUTION: An air bag is configured so as to prevent a gap of a base fabric between stitching holes formed by a stitching hole spacing being reduced at the air bag is extended from being enlarged by having two or more rows of seams of the sewing thread of the air bag and by shifting the phase difference of the stitching hole positions between the seams (at 360 degrees for one stitching hole) and to reduce leakage of the extension gas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an airbag having seams that reduce leakage of inflation gas, and a method for manufacturing the airbag. [Background technology]

[0002] Following seat belts as a safety device in automobiles, SRS airbags (airbags as a supplementary device to seat belts; hereafter referred to as airbags) began to be installed as an optional feature in Japan in 1987. Initially, they were installed in the driver's seat. As time passed, airbags became standard equipment in the driver's seat (steering wheel), and then in the passenger seat as well. When a car collision is detected by an acceleration sensor, gas is injected into the airbag in 0.01 seconds, causing it to expand and inflate, and once it is fully expanded and deployed, the gas is released and the airbag deflates.

[0003] Through this series of actions, the airbag assists the seatbelt in preventing collisions between the driver and the steering wheel, or the front passenger and the dashboard, and reduces the impact of the human body on the interior structures of the vehicle. In addition to the airbags mentioned above, many other types of airbags have been developed and put into practical use, such as those that extend between the side window and the head to reduce impact, and those that extend from the side of the seatback to the sides and front of the occupant's body to protect the abdomen and chest.

[0004] When a car collides with an obstacle, the body of the car suddenly decelerates, but the occupants continue to move forward due to inertia, so even if the driver is wearing a seat belt, there is a risk that their chest or head will hit the steering wheel. For this reason, airbags are installed in the steering wheel as mentioned above. After detecting a car collision, the airbag fully inflates in about 0.03 seconds, catches the driver, absorbs energy, and then deflates.

[0005] It takes approximately 0.2 seconds for an airbag to expand and contract after a vehicle collision. If the airbag were to inflate too slowly, the driver would crash into the steering wheel. In order to inflate the airbag quickly, it is important not only to determine the method of generating the inflation gas, but also to ensure that the airbag is fully inflated during the inflation process by preventing more than a predetermined amount of inflation gas from leaking from unwanted locations.

[0006] Patent Document 1 discloses a technology that can make the seams highly pressure-resistant, since, in response to the demand for smaller and lighter airbag modules, using thinner bag fabric and thinner sewing thread than conventional fabrics can easily cause the seams to slip and gas leak from the seams, as the bag fabric is thinner than conventional woven fabrics.The technology describes specifying the fineness and strength of the bag fabric, the thickness and number of stitches of the sewing thread, and using two rows of seams. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2005-138704 Summary of the Invention [Problem to be solved by the invention]

[0008] Patent Document 1 specifies the stitch spacing, number of stitches, and type of thread for the two rows of stitches, and also mentions the application of a gas leakage prevention agent such as a resin coating to the sewn area. However, it does not disclose the phase relationship between the two rows of stitches. When an airbag deploys, a force is applied that pulls apart the fabric sewn together at the seams. The thread is pulled, drawing the stitch holes connected to the thread toward each other, creating a tunnel-like shape between the fabric and the stitch holes. If the two parallel rows of stitches are in phase (the stitch holes are adjacent), a tunnel-like structure will form in the same position in both rows of stitches, making it more likely that expansion gas will leak.

[0009] Therefore, the present invention provides an airbag in which the phase of multiple seams (seam lines in Patent Document 1) is adjusted to prevent tunnel portions, which tend to occur at seams during stretching as described above, from occurring in the same place at different seams, and a method for manufacturing such an airbag. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides the following. As a first invention, A sheet-like first base fabric and a sheet-like second base fabric arranged in accordance with the first base fabric, a sewing thread for sewing the first base fabric and the second base fabric together; An airbag comprising: The stitches formed by the suture thread are at least two or more rows of approximately parallel stitches, To provide an airbag in which stitches of two or more rows of sewing threads are formed so that the pitch of stitched holes on a base fabric constituting any one row of stitches is the same as the pitch of stitched holes on the base fabric constituting any other row of stitches, and the phases of the stitched hole positions formed along the stitches on the base fabric are different between the first row and the other row of stitches.

[0011] A second invention provides an airbag based on the first invention, in which the amount of phase difference between adjacent seams is 180 degrees.

[0012] As a third invention, based on the first invention, there is provided an airbag in which the amount of phase difference is 120 degrees between two adjacent stitches among three adjacent stitches when the stitches are in a row that is a multiple of three.

[0013] As a fourth invention, based on the second invention, there is provided an airbag in which the sewing hole positions between adjacent seams are arranged so that neighboring sewing hole positions form an equilateral triangle.

[0014] As a fifth invention, a first base fabric and a second base fabric arranged in accordance with the first base fabric, a sewing thread for sewing the first base fabric and the second base fabric together; A method for manufacturing an airbag comprising: The stitches formed by the suture thread are at least two or more rows of approximately parallel stitches, To provide a method for manufacturing an airbag in which stitching of two or more rows of stitching threads is configured such that the stitching hole pitch on the base fabric constituting any one row of stitching is the same as the stitching hole pitch on the base fabric constituting any other row of stitching, and the phases of the stitching hole positions configured along the stitching on the base fabric are different between the first row and the other row of stitching.

[0015] The sixth invention is based on the fifth invention. The method for manufacturing an airbag is provided, wherein the amount of phase difference between adjacent seams is 180 degrees.

[0016] The seventh invention is based on the fifth invention. The method for manufacturing an airbag is provided such that, when the stitches are arranged in a row that is a multiple of three, the phase difference is 120 degrees between two adjacent stitches between three adjacent stitches.

[0017] The eighth invention is based on the sixth invention. To provide a method for manufacturing an airbag in which sewing hole positions between adjacent seams are arranged so that neighboring sewing hole positions form an equilateral triangle. [Effects of the Invention]

[0018] The present invention having the above-described configuration can provide an airbag in which inflation gas is less likely to leak from the seams when the airbag is inflated, and can also provide a method for manufacturing such an airbag. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a plan view of a seam of an airbag according to a first embodiment of the present invention; [Figure 2] 1 is a schematic diagram of a longitudinal section of a seam portion of an airbag according to a first embodiment of the present invention; [Figure 3]FIG. 1 is a plan view showing the cross-sectional position of a seam portion of the first embodiment of the present invention when the airbag is expanded. [Figure 4] 1 is a schematic diagram of a cross section of a seam portion of an airbag according to a first embodiment of the present invention when the airbag is expanded. [Figure 5] Schematic plan view of a seam of an airbag according to a second embodiment of the present invention. [Figure 6] 10 is a plan view of a seam of an airbag according to a third embodiment of the present invention; [Figure 7] 10 is a schematic plan view of a seam of an airbag according to a fourth embodiment of the present invention; [Figure 8] Schematic diagram showing an example of the structure of the suture of the present invention. [Figure 9] Schematic diagram showing an example of the cross-sectional structure of the suture of the present invention. [Figure 10] Illustration of common types of passenger car airbags [Figure 11] Schematic diagram showing hardening of the binder in the present invention [Figure 12] FIG. 1 is a schematic diagram showing an example of applying a binder to the suture of the present invention in advance. [Figure 13] Schematic plan view of the outer appearance of the upper thread side of the double-row stitch of the present invention (when thread tension is correct) [Figure 14] Schematic plan view of the appearance of the bobbin thread side of the double-row stitch (when thread tension is correct) of the present invention [Figure 15] Schematic plan view of the appearance of the upper thread side of the double-row stitching of the present invention (when the bobbin thread is strong) [Figure 16] Schematic plan view of the appearance of the double-row stitching of the present invention (when the bobbin thread is strong) on ​​the bobbin thread side [Figure 17] Vertical cross-sectional view of a sewn hole when the bobbin thread is strong [Figure 18] Cross-sectional view of the sewn hole when the bobbin thread is strong [Figure 19] Schematic diagram showing the propagation of expansion gas when an airbag is inflated in a double-row seam in the prior art [Figure 20] Schematic diagram showing the propagation of expansion gas when the airbag is expanded in the double-row seam of the present invention. [Figure 21] Schematic diagram of needle tip movement illustrating the stitch phase shift of the present invention. [Figure 22]Schematic plan view illustrating needle position when the stitch phase is shifted by 180 degrees according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Examples of the present invention will be described below. However, the present invention should not be limited to these examples and can be implemented in various forms without departing from the spirit of the present invention. The symbols in the explanation of the configuration of the invention and in the explanatory diagrams of the configuration in this specification are expressed as four-digit numbers, with the first two digits representing the drawing number and the last two digits representing a number uniquely assigned to each part. Depending on the symbol, a lowercase English letter (a, b, etc.) may be added to the last two digits as an auxiliary.

[0021] <Airbag: Structure> An airbag consists of an inflator (mostly an inflator that burns gunpowder) that generates gas to expand the bag, an acceleration sensor to detect a collision, a control circuit, the bag, and a rotating connector (driver's seat only). In this specification, the bag of an airbag will be referred to as an airbag in the narrow sense.

[0022] <Airbag: Types> Airbags are used in a variety of vehicles, but the most familiar airbags are those used in passenger cars. Figure 10 shows an example of an airbag installed in the passenger compartment of an automobile.

[0023] Various types of airbags are installed in the vehicle cabin, including a driver's airbag (1020) stored in the steering wheel of the driver's seat to protect the head and chest of the driver in the driver's seat in the event of a frontal collision, a passenger airbag (1021) stored in the dashboard on the passenger side to protect the head and chest of the passenger in the front seat in the event of a frontal collision, a curtain shield airbag (1022) attached to the top of the door opening and deployed to cover the window to protect the head and neck of the driver and passenger or rear seat passenger in the event of a side collision or vehicle rollover, side airbags (1023) stored on the left and right sides of the seat to protect the chest and abdomen of the driver and passenger or rear seat passenger in the event of a side collision, and a knee airbag (1024) to protect the legs of the passengers and reduce the impact on the knees.

[0024] Among these, the driver's airbag (1020) and passenger's airbag (1021) have a large volume when inflated, and since passengers are likely to be hit by them in the event of an accident, if they remain inflated, the passengers will collide with the airbag and be damaged. Therefore, they inflate to absorb and reduce the forward inertia of the passenger, and then immediately release the expansion gas and deflate, so they are equipped with a gas release valve. Other airbags, especially curtain airbags (1023), inflate between the passenger and the window, and to prevent the passenger from coming into contact with the window when the passenger sways sideways, it is better for them to remain inflated for a longer period of time than the driver's and passenger's airbags.

[0025] Therefore, it is preferable that the expansion gas does not easily escape from an airbag such as a curtain airbag (1023) which is thin and has a small volume when expanded, and is an airbag suitable for applying the airbag or the manufacturing method thereof of the present invention.

[0026] <Embodiment 1> <Outline of Embodiment 1> Mainly claims 1 and 5

[0027] The airbag of this embodiment is configured such that the stitch pitch between any two or more rows of approximately parallel stitches is the same but the stitches are out of phase with each other.

[0028] <Configuration of Embodiment 1> Fig. 1 is a schematic plan view showing stitching holes (white circles) in two rows of parallel seams (thick solid lines) on an airbag as an example of embodiment 1. In Fig. 1, the positions of the stitching holes shown by the white circles are shifted (out of phase) between adjacent parallel-running seams 1 and 2 with the same stitch pitch. Fig. 2 is a schematic diagram of a vertical cross section of the stitching holes along the seams of the airbag in Fig. 1.

[0029] The seam of the bag body (0200) is made up of a first base fabric (0201), a second base fabric (0202), fibers (0203) constituting the sewing thread, and a sewing thread (0204) formed by bundling a plurality of fibers (0203). The fibers (0203) in the sewing thread (0204) are not shown. After sewing, a binder made of a resin such as silicone resin, polyvinyl chloride resin, urethane resin, polyurethane resin, or other elastomers can be applied to the seam and allowed to dry and harden, thereby further reducing gas leakage from the seam when the airbag is inflated.

[0030] The binder may be applied to one side or both sides as appropriate. In the present invention, the phases of two or more adjacent parallel rows of seams are shifted at least in areas such as the vicinity of the inflator, in the direction in which the inflator releases inflation gas, and in areas where the airbag structure is particularly susceptible to stress.

[0031] <Embodiment 1: First base fabric (0201) and second base fabric (0202)> The "first base fabric" (0201) and the "second base fabric" (0202) are in the form of sheets, and the first base fabric (0201) and the second base fabric (0202) are sewn together to form a gas injection space.

[0032] The first base fabric "first base fabric" and the second base fabric "second base fabric" are each configured in a sheet-like shape. The base fabrics may be woven fabrics made by weaving threads, knitted fabrics, nonwoven fabrics, or sheets made by stretching synthetic resins into thin films, and can be selected appropriately depending on the desired performance.

[0033] <Embodiment 1 First base fabric / second base fabric: base fabric material> The airbag bag, formed by sewing together the first and second base fabrics, is stretched and inflated by the gas produced by the inflator burning gunpowder. Therefore, the first and second base fabrics that make up the airbag must be made of a material that is as soft as possible, while being strong enough to withstand the sudden stretching caused by the instantaneous high temperature and high pressure of the gas and not break when the occupant comes into contact with them, and also needs to support the occupant's body.

[0034] If both base fabrics of the airbag are woven, they may be made of fabrics known for use in airbags, such as nylon, polyethylene terephthalate, or polyester. When the base fabric is woven, it is possible to use a coated fabric with a surface coated with a silicone resin, urethane resin, or the like (often coated on one side), or an uncoated fabric. The presence or absence of a coating on the woven fabric and the thread density of the fabric affect how the inflation gas escapes from the inflated airbag, and therefore can be selected appropriately depending on the type of airbag to be used and the required specifications.

[0035] The first and second base fabrics may be coated or uncoated, or may have different fabric densities or may be made of different materials, depending on the design of how the airbag expands and collapses.

[0036] <Embodiment 1: First base fabric / second base fabric: base fabrics constituting airbag> In the description herein, the first and second base fabrics are illustrated as being made up of one piece each, but each may be made up of multiple pieces (for example, a long, thin tape-like piece of fabric is placed near the seam and then sewn together to reinforce it). Alternatively, one of the pieces may be a single piece of fabric and the other may be made up of multiple pieces of fabric. The first or second base fabric may each be a single piece of sheet-like fabric, or may be formed by joining multiple sheet-like fabrics together. When made up of joined sheets, the sheet-like fabrics may be made of different materials rather than the same material.

[0037] Furthermore, the airbag bag body may be configured to have a three-dimensional shape formed by sewing together different shaped base fabrics, rather than by overlapping and sewing together first and second base fabrics of approximately the same shape. The shape may be suitable for the purpose of installing the airbag, and may be a cylindrical shape consisting of a top, bottom, and side surfaces, or a mushroom cap shape (hamburger bun shape) formed by sewing together different shaped fabrics. The seam basically sews together two types of base fabric, a sheet-like first base fabric and a sheet-like second base fabric, but the scope of the present invention may also include cases where more than two types of sheet-like base fabric are sewn together due to the structural design of the airbag.

[0038] <Embodiment 1 Suture (0204)> The sewing thread (0204) that sews the first and second base fabrics together and receives the expansion gas to inflate the airbag is made by twisting and bundling a plurality of fibers (0203). In addition, at least some of the fibers of the sewing thread are bound together with a binder so that the tension generated in the sewing thread tightens the twist and prevents gaps from forming between the sewing thread and the base fabrics at the sewn hole.

[0039] Figure 8 is a schematic diagram showing an example of the structure of a suture. The suture (0804) shown in the schematic diagram of Figure 8 is shown with the twist gradually decreasing towards the top to make the structure easier to understand. The suture (0804) in the example of Figure 8 is a large diameter twisted suture (0804) made by twisting three small diameter twisted yarns, each made by twisting a single fiber (0803) in an S twist, together with two strands of the small diameter twisted yarn, which are then twisted in a Z twist.

[0040] However, this twisting process is only one example, and any twisted material falls within the scope of the suture of the present invention. As shown in Figure 8, the binder (0805), shown in gray in the figure, permeates the suture (0804) in various places, and at least some of the single fibers (0803) are bound together by the binder. The binder not only binds the single fibers (0803), but also binds at least some of the three small diameter twisted yarns formed by twisting single fibers together (0805), making it difficult for the three small diameter twisted yarns to unravel. Figure 9 is a schematic diagram showing a cross section of the d-d' section in Figure 8. The small circles represent the short fibers (0903).

[0041] The small diameter twisted yarn is a yarn in which multiple fibers are divided into three groups, and the circular dotted lines surrounding the three small diameter twisted yarns indicate the large diameter twisted yarn, suture (0904). The fibers (0903) and the small diameter twisted yarns are at least partially bound together by a binder (0905). Note that Figure 2 does not show the binder permeating between at least some of the fibers (0203) of the suture (0204). Unless otherwise specified in the figures in this specification, it is assumed that at least some of the fibers constituting the suture are bound together by the binder permeating between them, even if not shown.

[0042] <Embodiment 1: Effect of suture (0204): binder> In Figure 9, the binder (0905) between these fibers (0903) applies tension to the suture thread (0904) when the airbag is extended in addition to the tension during sewing, and even if this causes the twist to tighten, the binder secures the fibers (0903) or the small diameter twisted yarns together, so the distance between adjacent fibers (0903) or adjacent small diameter twisted yarns does not decrease, and the diameter of the suture thread does not become thinner. This will be explained using the table in Figure 11.

[0043] In Figure 11, the left column shows sutures without binder penetration, and the right column shows sutures in which the binder has penetrated at least some of the fibers that make up the suture. The top row shows the state of the suture before the tension applied when the airbag is expanded, and the bottom row shows the state immediately after the tension is applied. The left column of each column is a simplified outline of the outer shape of the suture, showing the change in diameter. The right column is a cross-sectional view of an excerpt of the fibers that make up the suture. The distance between the fibers that make up the suture and the diameter of the suture before the tension applied when the airbag is expanded are almost the same in both the cases with and without binder penetration. The twisted fibers cross the cross section diagonally, giving the fiber cross section an elliptical shape. In the case of binder-impregnated sutures, the fibers are bonded together by the binder.

[0044] After tension is applied, the suture thread in the lower left column, which was not permeated with a binder, has its fibers pulled, reducing the gaps between the fibers. The angle of the fibers crossing the cross section tends to become more vertical, and the shape approaches a circle rather than an ellipse. These effects reduce the diameter of the suture thread. In the lower right column, under conditions where tension is applied to the suture thread at least partially permeated with a binder, the fibers bound by the binder do not move and the distance between the fibers does not change, so the cross section of the fibers crossing the cross section remains roughly the same ellipse as before tension was applied. These effects ensure that the thickness of the suture thread remains roughly the same as before tension was applied. Therefore, no gaps are created between the suture thread and the base fabric at the sewn holes, preventing leakage of the expansion gas when the airbag is expanded.

[0045] Without the binder, as in the conditions in the lower left column of Figure 11 (no binder, sewing thread after tension application), the diameter of the sewing thread would narrow when tension is applied during airbag expansion, creating a gap between the sewing thread and the base fabric at the sewn hole, which would allow expansion gas to leak when the airbag expands. By impregnating the sewing thread with a binder and binding at least a portion of the fibers that make up the sewing thread, it is possible to prevent such gas leakage during airbag expansion.

[0046] <Embodiment 1: Suture: Binder: Material and Properties> The binder material can be selected from resins such as silicone resin, polyvinyl chloride resin, urethane resin, polyurethane resin, or other elastomers. When the airbag is stored in a predetermined position inside the automobile, such as in the steering wheel, seat, pillar, or above the side window, the stitched portion to which the binder is applied is also folded, so the binder must be a material that remains flexible even after drying.

[0047] The hardness after curing, measured using a durometer type E or A specified in JIS K6253-3, is preferably between 0 and 30, more preferably between 5 and 20, and most preferably between 5 and 15. If the first backing fabric and / or the second backing fabric is a coated fabric, a binder made of the same material as the coating material on the surface of the backing fabric is preferred, as this is expected to increase the adhesive strength.

[0048] For example, in the case of a base fabric coated with silicone rubber, the silicone rubber itself can be made flame-retardant by blending a known flame retardant into the silicone rubber. Therefore, when using a base fabric constructed in this way, it is preferable to use a silicone rubber-based binder that also blends a flame retardant. In addition, when the coating agent for the base fabric is a urethane resin-based coating, it is preferable to use a urethane resin-based binder, and when a polyvinyl chloride resin is used as the coating agent, it is preferable to use a polyvinyl chloride-based material as the binder.

[0049] In order for the binder to penetrate the fibers of the suture and bind the fibers together, it must have good adhesion to the fibers. Nylon is more difficult to bond to than polyester, so a binder material that can bond to nylon, such as a silicone resin or urethane resin, must be selected. A binder material that can bond to nylon is selected depending on the type of material (e.g., fiber, coating material, sheet material, etc.) that makes up the suture and / or base fabric.

[0050] <Embodiment 1 Suture (0204): Penetration of Binder> Before being used to sew a base fabric, at least some of the fibers of the suture thread may be bound together with a binder (described later). As shown in Figure 12, during the production of the suture thread, while the suture thread is being wound onto a reel (1210) or the like, the binder (1205) is intermittently applied to the suture thread (1204) by, for example, intermittently discharging the binder from a discharge nozzle (1211) to coat the suture thread over a length equivalent to 1 mm, leaving a gap of 0.5 mm without coating, and repeating this process.

[0051] The applied binder is allowed to penetrate at least some of the spaces between the fibers that make up the suture thread, and the suture is then wound up after being heated with an infrared lamp heater (1212) or other suitable curing and drying conditions for the binder, thereby producing a suture thread in which at least some of the fibers have already been bound together with the binder. Alternatively, when sewing base fabrics using a sewing machine or other similar device, the binder may be allowed to penetrate the suture thread just before it is unwound and threaded through the base fabric. However, since sewing the first and second base fabrics together applies sewing tension (tension generated between the suture threads and tension based on the pressure applied by the base fabrics) to the free suture thread, it is preferable to bind the suture threads with the binder after the sewing tension has been applied.

[0052] It takes a certain amount of time for these tensions to become constant after sewing, so it is preferable to apply the binder after the tension has become constant. The time required for the tension to become constant is at least one second and approximately five minutes. This time length varies depending on the type of suture thread and the material of the base fabric.

[0053] <Embodiment 1 Binder: Application after suturing> In addition to applying the binder beforehand as described above, one example of a method for allowing the binder to penetrate between the fibers of the suture thread is to sew together the first base fabric (0201) and the second base fabric (0202) with the suture thread (0204), and then apply the binder to the seam using a dispenser or syringe, silk screen printing, inkjet printing, or brush printing. For example, the binder can be applied to the seam from the first base fabric side, dried, and then applied to the seam from the opposite side, the second base fabric side. The binder penetrates between the fibers of the suture thread exposed on the surface of the base fabrics.

[0054] Furthermore, in the seams, the binder penetrates through the holes in the seams, along the suture thread (0204), and into the spaces between the fibers (0203) that make up the suture thread (0204). As a result, by binding at least some of the fibers (0203) that make up the suture thread (0204) with the binder, the fibers (0203) are less likely to shift or separate. The binder also fills the gaps between the base fabric and the suture thread (0204) in the seams. As explained above in the effect of the binder in the explanation of the suture thread, even when tension is applied when the airbag is expanded, the diameter of the suture thread (0204) does not narrow, and it is possible to prevent gaps from forming between the suture thread and the base fabric at the seam holes.

[0055] <Embodiment 1 Suture (0204): Material> The fiber (0203) can be any fiber that constitutes a known thread for sewing airbags, such as polyamide fiber, polyester fiber, or bio-polyester fiber. Bio-polyester fiber in particular is expected to be increasingly adopted in response to the growing consumer awareness of environmental issues and interest in the SDGs in recent years.

[0056] <Embodiment 1 Suture (0204): Thickness, Fineness> The diameter of the fibers can be selected appropriately depending on the specifications required for the thread that constitutes the stitches. If the diameter of the fibers that constitute the thread is large without changing the diameter of the thread itself, the number of fibers that make up the thread will be small, resulting in a thread that is highly rigid and difficult to sew. Examples of specifications for suture threads include a single fiber fineness of 10 dtex or less and a total fineness of 200 to 3100 dtex, and more preferably 900 to 1800 dtex (130 to 210 fibers), which can be selected appropriately. While suture threads can be made from single fibers like nylon fishing line, multiple thin fibers twisted together are more flexible, easier to handle during sewing, and less likely to break due to scratches, etc.

[0057] An example of a suture thread is one in which 20 to 50 nylon monofilaments with a diameter of 0.02 to 0.04 mm are twisted together to form three small-diameter twisted threads with a diameter of approximately 0.1 to 0.3 mm, which are then twisted together to form a large-diameter twisted thread (diameter approximately 0.5 mm), i.e., a suture thread (approximately 1000 dtex). However, the number of small-diameter twisted threads is not limited to three, and it is preferable to use multiple small-diameter twisted threads. This is because using multiple small-diameter twisted threads creates a permeation path for the binder, making it easier for the binder to penetrate to the center of the suture thread. The number of small-diameter twisted threads is preferably around 2 to 7. Alternatively, a single thread may be made by twisting together 130 to 210 monofilaments without creating a small-diameter twisted thread.

[0058] <Embodiment 1 Suture (0204): Stitch> When sewing using suture thread, multiple rows of stitches are preferable to a single row, as they are more likely to withstand the force applied when the airbag expands. Increasing the number of rows increases manufacturing costs, increases the size of the airbag itself (increasing the seam allowance), and can have side effects such as making it difficult to fold. Two rows are preferred to minimize side effects while maintaining strength. The schematic diagrams in Figures 13 and 14 show examples of the appearance of the present invention when two rows of stitches are used and the tension of the upper and lower threads is matched.

[0059] Figure 13 shows the appearance of the upper thread (1304a) side during sewing, and Figure 14 shows the appearance of the bobbin thread (1404b) side during sewing. The base fabric edge is on the left side of the figure, and the base fabric area is to the right of the base fabric edge. As an example of a seam, seam 1 (pitch d = 2 mm) is located 10 mm inside the base fabric edge, and seam 2 (pitch d = 2 mm) is located 5 mm inside that. The stitching phases of seam 1 and seam 2 are 180 degrees out of phase, with the stitching hole of seam 2 located in the center between the stitching holes of seam 1. As shown in Figure 2, the upper and bobbin threads cross each other at the stitching hole area and are pulled into the base fabrics up to the boundary between the first and second base fabrics, so the threads at the stitching hole area are not visible from the outside and the seam has a dotted line appearance. Figures 15 and 16 are schematic diagrams showing the case where the tension of one of the threads (thread tension during sewing) is strong, using the case where the bobbin thread is strong as an example. FIG. 15 shows the appearance as seen from the upper thread (1504a) side, and FIG. 16 shows the appearance as seen from the lower thread (1604b) side.

[0060] The positional relationship between the base fabric edge and the stitches, and the pitch and phase difference between stitches 1 and 2 are the same as those in Figures 13 and 14, which have been explained above. As shown in the schematic diagrams of the longitudinal and transverse sections of the stitched hole in Figures 17 and 18, under conditions where the bobbin thread is strong, in Figure 15 the upper thread (1504a) is pulled toward the bobbin thread (1504b) at the stitched hole, so the appearance of the base fabric on the upper thread (1504a) side is the same as in Figure 13, but in the appearance of the bobbin thread (1604b) side shown in Figure 16, part of the upper thread (1604a) is visible at the stitched hole. In Figure 16, the parts where the stitches are thicker in places indicate stitched holes where the upper thread (1604a) is pulled toward the bobbin thread (1604b) and is visible. The same applies to stitches with more than two rows.

[0061] <Embodiment 1 Suture: Machine Suture> When sewing using a sewing machine, two types of thread are used: an upper thread and a lower thread. However, different threads of different materials and strengths may be used depending on the purpose. In the case of asymmetrical stitching, in which the upper or lower thread is strong and the opposite sewing thread is visible at the seam, it is preferable to make the shear strength of the thread on the side that receives tension during the airbag expansion process higher than that of the other sewing thread. In the case of a sewing method in which the lower thread is strong, the upper thread that is pulled into the seam will receive higher tension during the airbag expansion process, so it is preferable to make the shear strength of the upper thread sewing thread on that side higher than that of the lower thread sewing thread. To distinguish between the first and second backing fabrics and the upper and lower threads, it is recommended to use different colors for the upper and lower threads, such as blue and red. While only straight stitching is illustrated in the figures in this specification, other sewing methods may also be used.

[0062] <Embodiment 1 Suture (0204): Stitch Pitch> The stitch pitch is preferably 2 to 8 stitch holes per cm, more preferably 3 to 7 stitch holes, and most preferably 4 to 6 stitch holes per cm.

[0063] <Embodiment 1 Suture (0204): Stitch Pitch> When sewing the vicinity of the edge of the base fabric, the position of the seam closest to the edge of the base fabric from the edge of the base fabric is preferably 5 to 20 mm, more preferably 5 to 15 mm, and most preferably 7 to 12 mm.

[0064] <Embodiment 1 Suture (0204): Stitch Spacing> The stitch spacing between two or more rows of approximately parallel stitches is (√3) / 2 or more times the stitch hole pitch within the stitches, and is preferably 10 mm or less, more preferably 7 mm or less, and most preferably 5 mm or less.

[0065] <Embodiment 1 Suture (0204): Pitch of multiple stitches> The "stitch" is formed with the sewing thread (0204) and consists of at least two or more rows of stitches that are approximately parallel, and the pitch of the stitched holes on the base fabric that make up any one row of stitches is the same as the pitch of the stitched holes on the base fabric that make up any other row of stitches, and the stitches of the two or more rows of sewing thread are configured so that the phase of the stitched hole positions formed along the stitches on the base fabric is different between the first row and the other rows.

[0066] <Embodiment 1 Suture: Example 1 of phase shift of multiple rows of stitches> The stitches consist of two or more rows of approximately parallel stitches with the same pitch width. When any one row of stitches is configured to be out of phase with any other row, it simply means that the phases of all the rows of stitches are different. For two rows of stitches, the rows can be configured to be shifted by 180 degrees, and for three rows, the rows can be configured to be shifted by 120 degrees each. For four rows, the rows can be shifted by 90 degrees each. It is not necessary to be limited to an equal distribution, and three rows of stitches can also be configured to be shifted by 90 degrees each.

[0067] <Embodiment 1 Suture: Phase shift example 2 of multiple rows of stitches> In another example, multiple rows of stitches are classified into multiple phase groups, and other stitches adjacent to one stitch belong to a phase group different from the phase group to which the first stitch belongs. In the latter example, when there are three or more rows of stitches, the phases of adjacent stitches may be shifted by 180 degrees. For example, when four rows of stitches positioned in the order A, B, C, and D from the end are run in parallel, A and C may be arranged at the same pitch, B and D may be arranged at the same pitch, and there may be a 180-degree phase shift between AC and BD.

[0068] <Embodiment 1 Suture (0204): Effect of phase shift of stitches> Figure 3 is a plan view of a seam consisting of two rows of stitches, and Figure 4 shows a cross section taken along line C-C' in Figure 3, showing the situation when the airbag inflation gas acts on the seams in Figure 3 to separate the first and second base fabrics. The first and second base fabrics are sewn together with two rows of stitches, and a binder is applied to each seam on both the first and second base fabric sides. The right side of Figure 4 shows the inside of the airbag, with the upper first base fabric attempting to spread upward and the lower second base fabric attempting to spread downward in the direction of the arrows, exerting force on the seams, particularly the inner seams.

[0069] Because the two base fabrics are fixed together by the stitching thread at the stitching holes of the seam, when the airbag is inflated by the expansion gas and a force is applied that separates the two base fabrics, the seam behaves in such a way that the distance between the stitching holes decreases. When the distance between the stitching holes decreases, the first and second base fabrics separate between the stitching holes, and the expansion gas leaks through the resulting gap. Figure 19 is a plan view of a conventional two-row seam that runs parallel at the same pitch and in the same phase. The edge of the base fabric is at the top of the figure, and the area below the edge of the base fabric is the base fabric region.

[0070] Stretching gas advances from between the stitched holes in seam 2 in concentric circles as shown by the dotted lines. The advancing stretching gas reaches outer seam 1. Because outer seam 1 is in phase with seam 2, the stretching gas advances directly to between the stitched holes in seam 1. Figure 20 shows a plan view of two rows of parallel, out-of-phase stitches according to the present invention. Stretching gas advancing from between the stitched holes in inner seam 2 collides with the stitched holes in outer seam 1 and encounters resistance. Even if the distance between the stitched holes in inner seam 2 decreases as described above and a gap is about to form between the two base fabrics when the airbag is inflated, because the stitched holes in outer seam 1 secure the two base fabrics together, the gap does not reach the edge of the airbag, and the gap in the seam does not increase in size, thereby reducing leakage of stretching gas.

[0071] <Embodiment 1 Suture (0204): Phase shift at curved part of stitch> When two or more rows of stitches run parallel to form a curve, the pitch of the outer or inner stitches relative to the center of the approximate arc for three adjacent stitch holes on one stitch may be adjusted by increasing or decreasing only the curved portion. This is because, with the same pitch for the curved portion, the difference in the radius of curvature of the inner and outer seams will prevent the phase from shifting as specified relative to the center of the approximate arc that makes up the curved portion. However, it is not prohibited to run the stitches parallel to each other at the same pitch in the curved portion without adjusting the pitch between the stitches.

[0072] <Embodiment 1 Manufacturing Method> <Embodiment 1 Manufacturing Method: Preparation of Base Fabric> First and second base fabrics are prepared. They may be cut to the final airbag shape, or they may be cut larger and then cut to the final shape after sewing and before applying the binder, or after applying the binder. Alternatively, a cutting blade or laser may be equipped on the sewing machine and the fabric may be cut simultaneously with sewing. If the base fabrics are to be coated with a resin or the like, they should be coated before sewing, or pre-coated fabrics may be purchased and used. If the binder is applied to the seams after sewing, there is a risk that the binder will spread onto the base fabrics immediately after application and spill over from the edge of the base fabric onto the manufacturing equipment stage, resulting in the binder adhering to the fabric.

[0073] If the binder adheres to the stage, it may adhere to other unnecessary parts of the base fabric or to the bag body of another sewn airbag, which may cause problems when folding it to make the product. Alternatively, if it adheres to the stage and hardens, it may act as a protrusion, lifting the sewn base fabric when applying the binder, changing the distance between the application dispenser and the base fabric, which may cause the binder to spread more than expected. To prevent these problems, if the base fabric is cut before sewing, cut it larger, or if it is not cut before sewing, sew a larger size base fabric.

[0074] <Embodiment 1: Manufacturing Method: Suturing> When sewing, the base fabric is set in a predetermined position on the base fabric support stage of the sewing machine. If the binder is to be applied subsequently, the first and second base fabrics are set up and placed on the support table in a top-down position that is convenient for applying the binder. If the binder is to be applied from above first on the first base fabric side, the second base fabric is placed underneath and the first base fabric is placed on top of it when setting them up.

[0075] <Embodiment 1: Manufacturing method, sewing, means for creating multiple stitches> When creating multiple rows of stitches, there are several methods, such as using one needle to sew repeatedly for the number of rows of stitches, using needles for the number of stitches to be sewn separately, or using a needle that combines multiple needles (for example, a forked or trident needle).From the perspective of the time and cost required for sewing, it is desirable to sew multiple stitches at once using needles for the number of stitches to be sewn.

[0076] It is most preferable to move the needles independently, but this would complicate the structure of the sewing machine and increase the equipment costs. Therefore, a forked needle can be moved at an angle equivalent to the phase difference relative to the stitch direction to create a stitch with a phase difference. When sewing with multiple needles moved simultaneously, the sewing machine has the function of simultaneously driving at least multiple upper threads and corresponding multiple bobbin threads to sew.

[0077] <Embodiment 1: Manufacturing Method, Sewing, Sewing Multiple Stitches at Once Using Multiple Needles> Figure 21 is a diagram explaining the up and down movement of needles when sewing by simultaneously moving multiple needles, at least the needles for adjacent stitches independently. The horizontal axis represents the phase when the distance between stitched holes is 360 degrees (not the horizontal movement distance of the base fabric), and the vertical axis shows shifted graphs indicating the needle tip positions at the reference phase, phase difference of +90 degrees, phase difference of +120 degrees, and phase difference of +180 degrees.

[0078] The maximum and minimum points on each graph represent when the needle tip is at its highest and lowest point, and are labeled "top" and "bottom" in the diagram. Where the base fabric is located in the up and down stroke of the needle's movement varies depending on the sewing machine's specifications, but in Figure 21, the explanation will be given assuming that the center of the up and down stroke indicates the position of the base fabric. In the reference graph, at a phase of 180 degrees (hereafter, "phase" will be omitted), the needle penetrates the base fabric from above and the needle tip exits the bottom of the fabric. At 270 degrees, the needle tip descends to the bottom and begins to rise, and the lower thread entangles with the upper thread, which has loosened from the needle tip, via the bobbin on the lower thread side. The needle tip rises, exits the sewing hole it was in at 360 degrees, and moves above the base fabric, reaching its highest point at 450 degrees.

[0079] Between 360 degrees and 540 degrees after the needle has left the base fabric, the base fabric is fed to the next needle hole position (the position where the needle will next pierce the base fabric from above). This process is repeated to create one stitch. When the phase difference between stitch holes is 90 degrees, the needle will pierce the base fabric at a position shifted by 1 / 4 of the stitch pitch, when the phase difference is 120 degrees it will be 1 / 3 of the stitch pitch, and when the phase difference is 180 degrees it will be pierced by the needle with the corresponding phase difference.

[0080] Figure 22 is a schematic diagram showing the stitch pitch and needle positional relationship when sewing with a two-needle sewing machine with a 180-degree phase difference. To sew simultaneously with a phase difference between the stitches, one of the two needles is positioned offset in the direction of base fabric travel or opposite the direction of base fabric travel by a length equivalent to half the stitching hole pitch, as shown in Figure 22 (the corresponding bobbin thread is also positioned offset in the same way). By matching the up and down movements of the two needles, the base fabric can be fed in the same way as with a single needle, and a 180-degree phase difference can be achieved between the two rows of stitches. The same applies when driving three or more needles.

[0081] <Embodiment 1: Manufacturing Method: Application of Binder> The base fabric is transferred from the support table of the sewing machine used for sewing to a base fabric support table for applying the binder (which does not have to be integrated with the base fabric support table of the sewing machine), and the binder is applied to the seams along the seams using a dispenser or syringe. As mentioned above, the binder can be selected appropriately from silicone resin, urethane resin, etc. In addition to the above, the binder can also be applied by known methods such as silk screen printing, inkjet printing, and brush painting.

[0082] Although application can be done from just one side, applying it to one side and then the other side is more effective in preventing leakage from the stitching holes, preventing the suture thread from shifting when the airbag is expanded, and preventing gas leakage during expansion. The binder may be impregnated into the suture thread before sewing, or it may be impregnated as the thread is unwound during sewing. It may also be applied separately to multiple seams (multiple seams may be applied simultaneously), or it may be applied all at once to cover multiple seams, including the spaces between them. After application of the binder, it is cured and dried. Depending on the specifications of the binder, it may be naturally dried, heated in a constant temperature bath, or exposed to ultraviolet light. The inflator and other components are then attached to complete the airbag.

[0083] In the present invention, by shifting the phase of the stitched holes between two or more rows of approximately parallel stitches, it is possible to reduce gaps between the base fabrics that occur when the airbag is inflated, thereby reducing leakage of inflation gas.

[0084] <Embodiment 2> <Outline of Embodiment 2> Mainly claims 2 and 6 In the second embodiment, which is based on the first embodiment, the phase difference between adjacent stitches is 180 degrees. As a reference for the phase value, the distance between one stitch hole and the adjacent stitch hole in one stitch is expressed as 360 degrees.

[0085] <Configuration of Embodiment 2> The seams of the second embodiment, which are based on the first embodiment, will be described with reference to Fig. 5. Fig. 5 is a schematic plan view of the seam portion of the airbag of the second embodiment of the present invention. Differences from the first embodiment will be described.

[0086] <Embodiment 2: Seams> The stitches of the second embodiment are configured so that the phase difference between the stitching hole positions of the substantially parallel stitches is 180 degrees between adjacent stitches. Other than the phase difference, the configuration is the same as that of the first embodiment.

[0087] As shown in Figure 5, in stitches 1 and 2, where the stitching hole pitch is the same as d, the interval between stitching holes A and B in stitch 2 is d, and stitching hole C on stitch 1 is arranged in a phase such that the lengths of stitching holes AC and BC are the same. If the length of stitching holes AB is a phase of 360 degrees, then stitching hole C in stitch 1 is exactly at the midpoint, resulting in a phase difference of 360 / 2 = 180 degrees.

[0088] Let's say seam 2 is on the inside of the airbag and seam 1 is on the end face side of the airbag. If the phase difference between adjacent seams is 180 degrees, even if a gap is about to form between the first and second base fabrics between seams AB when the airbag expands, the two base fabrics will be fixed together by stitching hole C in seam 1, which is located in the middle of stitching hole AB in seam 2, so the gap will be more effectively prevented from expanding and leakage of expansion gas will be reduced compared to other phase differences.

[0089] <Embodiment 2 Manufacturing Method> The manufacturing method of this embodiment 2 is the same as that of embodiment 1. Sewing is performed so that the phase difference between adjacent stitches is 180 degrees. When sewing with one needle for the number of stitches, the start and end points of sewing are shifted horizontally by a distance equivalent to the phase difference of 180 degrees relative to adjacent stitches that have already been sewn. When sewing using multiple needles at once, the needle positions are adjusted and positioned so that there is a distance equivalent to the phase difference and the stitch spacing before sewing. When sewing using forked needles, the needles are moved and tilted by an angle corresponding to the phase difference with respect to the stitch direction, as shown in the positions of needles 1 and 2 in Figure 22, so that there is a phase difference equivalent to 180 degrees, and sewing is performed.

[0090] In the present invention, by setting the phase difference between adjacent seams to 180 degrees, leakage of gas for expanding the airbag through the seams can be further reduced or prevented.

[0091] <Embodiment 3> <Outline of Embodiment 3> Mainly claims 3 and 7 In a third embodiment based on the first embodiment, when the number of stitches (i.e., two or more rows of approximately parallel stitches) is a multiple of 3, the phase of the stitching hole positions of the approximately parallel stitches is 120 degrees between any two adjacent stitches among three adjacent stitches. As a basis for the phase value, the distance between one stitching hole and the adjacent stitching hole in one stitch is expressed as 360 degrees.

[0092] <Configuration of Embodiment 3> The seams of embodiment 3, which are based on embodiment 1, will be described with reference to Fig. 6. Fig. 6 is a schematic plan view of the seam portion of the airbag of embodiment 3 of the present invention. Differences from embodiment 1 will be described.

[0093] <Embodiment 3: Seams> The stitches in this embodiment are arranged in rows of multiples of three, and the phase difference between the stitching holes of the approximately parallel stitches is 120 degrees between any two adjacent stitches among three adjacent stitches. Other than the phase difference, the configuration is the same as that of the first embodiment.

[0094] Three adjacent stitches are three rows of stitches that run almost parallel to one another, and no other stitches exist in the stitching area of ​​the three rows (see Figure 6). Among these, the space between two adjacent stitches refers to adjacent stitches that run parallel to one another, such as stitches 1 and 2, or stitches 2 and 3, as shown in Figure 6.

[0095] As shown in Figure 6, in seams 1, 2 and 3, which have the same stitching hole pitch as d, the stitching hole of seam 2 is shifted by d / 3 (a phase difference of 120 degrees) from seam 1, and the stitching hole of seam 3 is shifted by d / 3 (a phase difference of 120 degrees) from seam 2. The stitching hole of seam 3 is shifted by 2d / 3 (or -d / 3) from the stitching hole of seam 1. By shifting adjacent stitching threads (stitches) by 120 degrees in this way, in the case of seams formed in rows that are multiples of three, it is possible to more effectively prevent the gaps between the stitching holes on one seam from widening when the airbag inflates.

[0096] <Embodiment 3 Manufacturing Method> The manufacturing method of this embodiment 3 is the same as that of embodiment 1. Sewing is performed so that the phase difference between adjacent stitches is 120 degrees. When sewing with one needle for the number of stitches, the start and end points of sewing are separated horizontally from adjacent stitches that have already been sewn by a distance corresponding to the phase difference of 120 degrees. When sewing at once using multiple needles, sewing is performed by adjusting and arranging the needle positions so that they are separated by a distance corresponding to the phase difference and the stitch spacing. When sewing using forked needles, the needles are moved and tilted by an angle corresponding to the phase difference with respect to the stitch direction so that a phase difference equivalent to 120 degrees is achieved, as in the positions of needles 1 and 2 in Figure 22, although the phase difference value is different.

[0097] In the present invention, when the stitches are arranged in rows that are multiples of three, the phase difference between adjacent stitches is set to 120 degrees, thereby further reducing and preventing leakage of gas for inflating the airbag from the stitches.

[0098] <Embodiment 4> Mainly claims 4 and 8 <Outline of Embodiment 4> Embodiment 4 is an airbag based on either embodiment 1 or 2, in which the sewing hole positions of adjacent stitching threads are arranged so that neighboring sewing hole positions form an equilateral triangle.

[0099] <Configuration of Embodiment 4> The seams of embodiment 4, which are based on either embodiment 1 or 2, will be described using Fig. 7. Fig. 7 is a schematic plan view of the seam portion of the airbag of embodiment 4, which is based on embodiment 2. Differences from embodiment 2 will be described. Similar effects can be obtained even when embodiment 1 is used as a base.

[0100] <Embodiment 4: Seams> In the stitches of this embodiment 4, when the phase of the sewing hole positions of adjacent stitches is 180 degrees between the stitches, the sewing hole positions of adjacent sutures are arranged so that the nearby sewing hole positions form an equilateral triangle. Other than the sewing hole positions, the configuration is the same as that of embodiment 2.

[0101] As shown in Figure 7, in stitches 1 and 2, where the stitch hole pitch is the same as d, the distance between stitch hole A and stitch hole B in stitch 2 is d, and stitch hole C on stitch 1 is arranged in a phase such that the length between stitch holes AC and BC is the same as the length d of stitch hole AB. As a result of this arrangement, triangle ABC becomes an equilateral triangle. If the length of stitch hole AB is a phase of 360 degrees, stitch hole C in stitch 1 is exactly at the midpoint, so there is a phase difference of 360 / 2 = 180 degrees.

[0102] Assuming that seam 2 is on the inside of the airbag and seam 1 is on the end face side of the airbag, by shifting the phase difference between adjacent seams by 180 degrees and arranging nearby stitching holes to form an equilateral triangle, if a gap were to form between the first and second base fabrics between seams A and B when the airbag expands, the two base fabrics would open up and create a gap, but stitching hole C, which is equidistant from stitching holes A and B and also has the same distance as the distance between stitching holes AB, will fix the two base fabrics together, thereby more effectively preventing the gap from widening and reducing leakage of expansion gas than in embodiment 2.

[0103] <Embodiment 4 Manufacturing Method> The manufacturing method of this embodiment 4 is the same as that of embodiment 1. When sewing, adjacent stitches are sewn so that the phase difference between them is 180 degrees and the positions of adjacent stitching holes form an equilateral triangle. When sewn with one needle for the number of stitches, the start and end points of the stitching are separated by a distance corresponding to a phase difference of 180 degrees from the adjacent stitches that have already been sewn, and sewing is performed with a stitch spacing such that the positions of adjacent stitching holes form an equilateral triangle. When sewn using multiple needles at once, the needle positions are adjusted and arranged so that the positions of adjacent stitching holes form an equilateral triangle.

[0104] When suturing using a forked needle, the needle is tilted by an angle corresponding to the phase difference relative to the stitch direction so that there is a phase difference equivalent to 180 degrees, as shown by needles 1 and 2 in Figure 22 (although in Figure 22 the positions of nearby sewing holes are not in a relationship that forms an equilateral triangle), and the needle is moved at a pitch adjusted so that the positions of nearby sewing holes form an equilateral triangle.

[0105] In the present invention, the positions of adjacent stitching holes for the stitching threads are arranged so that the positions of adjacent stitching holes form an equilateral triangle, thereby further reducing and preventing leakage of gas for inflating the airbag from the seams.

[0106] <Effects> By stitching the airbag in two or more rows and staggering the positions of the stitching holes between the rows, it is possible to reduce leakage of inflation gas when the airbag is inflated. [Explanation of symbols]

[0107] First base cloth...0201 Second base fabric...0202 Fiber··0203 Sutures··0204

Claims

1. A sheet-like first base fabric and a sheet-like second base fabric arranged in accordance with the first base fabric, a sewing thread for sewing the first base fabric and the second base fabric together; An airbag comprising: The stitches formed by the suture thread are at least two or more rows of approximately parallel stitches, The airbag has two or more rows of stitching formed by sewing thread such that the pitch of stitched holes on the base fabric forming any one row of stitching is the same as the pitch of stitched holes on the base fabric forming any other row of stitching, and the phases of the stitched hole positions formed along the stitching on the base fabric are different between the first row and the other rows.

2. 2. The airbag of claim 1, wherein the amount of phase difference is 180 degrees between adjacent seams.

3. 2. The airbag according to claim 1, wherein the phase difference is 120 degrees between two adjacent stitches between three adjacent stitches when the stitches are arranged in a row that is a multiple of three.

4. 3. The airbag according to claim 1, wherein the positions of the stitching holes between adjacent stitches are arranged so that the adjacent stitching holes form an equilateral triangle.

5. A first base fabric and a second base fabric arranged in accordance with the first base fabric, a sewing thread for sewing the first base fabric and the second base fabric together; A method for manufacturing an airbag comprising: The stitches formed by the suture thread are at least two or more rows of approximately parallel stitches, A method for manufacturing an airbag in which two or more rows of stitching are formed such that the pitch of stitched holes on the base fabric forming any one row of stitching is the same as the pitch of stitched holes on the base fabric forming any other row of stitching, and the phases of the stitched hole positions formed along the stitching on the base fabric are different between the first row and the other row of stitching.

6. The method for manufacturing an airbag according to claim 5, wherein the amount of phase difference between adjacent seams is 180 degrees.

7. The method for manufacturing an airbag according to claim 5, wherein the phase difference is 120 degrees between two adjacent stitches between adjacent three stitches when the stitches are arranged in a row that is a multiple of three.

8. The method for manufacturing an airbag according to claim 6, wherein the sewing hole positions between adjacent seams are arranged so that the neighboring sewing hole positions form an equilateral triangle.

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