GB2527824A - Airbag assembly - Google Patents

Abstract

A side airbag assembly for a vehicle seat (10) in which a tear seam joins the edges (120, 125) of the first and second portions (60, 65) of the seat trim cover (35) to at least one edge of a seat airbag guide (100) which can generally be tubular in shape, and which guides the airbag towards the tear stitch, the guide edge being sewn to an edge of only one seat trim cover portion. This configuration allows for the attachment of the trim cover portions and guide portions to be performed in a single sewing operation. The method of construction consists of aligning the seat trim cover edges to the airbag guide edges and sewing them such that the guide edges are attached to only one of the seat trim cover portions.

Description

Airbag Assembly

Field of the Invention

The present invention relates to a side airbag for a vehicle seat assembly. In particular the invention relates to a method of assembling a side airbag assembly.

Background of the Invention

Side airbags in vehicles provide improved side impact protection for occupants. Side airbags will inflate when, for example, the vehicle is hit from the side.

Side airbags are typically installed in front seats, and inflate between the seat occupant and the door. The airbag deploys through the seat upholstery to occupy the space between the occupant and vehicle structures (e.g. door, A-panel, etc).

One problem with side airbags is controlling the deployment path of the airbag, especially through the seat upholstery. The path of the airbag through the seat may be affected by variables in seat construction. The airbag can end up deployed in an incorrect position, which lowers or even negates the effectiveness of the side airbag. For example, the airbag may be blocked by the cushion material in the seat, or the seat trim does not rupture uniformly.

This can cause the airbag to be diverted in the wrong direction.

Many airbag assemblies comprise an airbag module fixed inside a cavity in the seat assembly. The airbag module has the airbag and airbag inflating mechanism plus assorted fixing components. A weakened seam, known as a tear seam, is provided in the seat cover trim such that the inflating airbag will rupture the tear seam and exit the seat assembly. To aid deployment, a airbag guide or chute is included to guide the inflating airbag through to the tear seam. See for example GB2293355. It is known to sew the ends of the airbag guide in the region of the tear seam. For example, EP096331 0 discloses using weak seams to help the airbag rupture through the seat trim.

Figures 4A-4E show a conventional prior art side airbag construction process.

A conventional guide 500 comprises two sheets of material 505, 510.

Each sheet is fitted into place over a corresponding sheets 515, 520 of seat trim cover material. Each pair of sheets 505, 515 and 510, 520 are sewn 0 together along edges as shown, producing two pairs of sheets 505, 515 and 510, 520. This step is require to provide good alignment of material edges. If the edges are badly aligned, then there is an increased risk of the final stitching being non-uniform along the length of tear seam. This increase the risk of the tear seam rupturing in a non-uniform manner, and the airbag not correctly deploying.

The resulting pair of sheets 505, 515 and 510, 520 of the guide material and trim cover material are then sewn together (Fig SC). This produces a trim cover part 540 with a with tear seam 545. The remaining edges of the guide 500 are then sewn together at another seam 550 to give the conventional sleeve configuration for the guide 500. The guide material can be fitted around the airbag module and fixed in place in the seat assembly 555.

Although this structure overcomes the problems mentioned above regarding deployment of the airbag, there are number of separate alignment and sewing and assembly stages involved. It can be difficult to assemble the seat and side airbag assembly. This increases manufacturing times and costs as it can be time consuming and awkward to sew the numerous different seams together.

It is desirable to direct the airbag to the tear seam, and for the tear seam to open reliably and uniformly. Additionally, it is desirable be able to simply and reliably manufacture seats with side airbags to the above specifications while minimising manufacturing expense.

Accordingly, it is an object of the invention to provide a side airbag assembly that can be easily manufactured and will provide safe, simple and effective deployment through the seat.

Summary of the Invention

According to a first embodiment of the invention there is provided a side airbag assembly and method of assembling the same, as claimed in the 0 appended claims.

The advantage of the claimed assembly and method is that the seat trim with tear stitch can be fitted with a side airbag guide, so that a side airbag assembly with the guide can be reliably and rapidly assembled using as few steps as possible.

Using a construction that sews the guide and trim cover in single step has the advantage that the number of steps, and hence time and expense, of assembling and fitting the side airbag assembly to the seat assembly can be reduced. The guide is a single piece of suitable fabric. As the guide is sewn on the same side of the seam then a one piece bag is possible, advantageously reducing costs and manufacturing effort. Additionally, using a guide made form a single sheet of material reduces the possible points of failure (e.g. extra stitching holding the guide together) of the guide, improving reliability.

The different edges of the side airbag assembly (edges of trim material, edges of guide material) are aligned using a tacking stitch. This preliminary step increase edge alignment accuracy and reliability.

Brief description of the drawings

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a seat assembly for a vehicle accordance with an embodiment of the invention; Figure 2 shows a cross section of a seat assembly with side airbag as depicted in figure 1; Figure 3 shows a detail of the seam and tear stitch for a side airbag in accordance with the invention; Figures 4A to 4E show a known method of stitching and constructing a side airbag assembly; Figures 5A to 5C show a method of stitching a and constructing a side airbag assembly according to the invention; and

Detailed description of the embodiments

Figure 1 is a seat assembly 10 for vehicle, the seat assembly containing a side airbag 15. This example shows the side airbag 15 in a deployed state.

The side airbag 15 has been inflated, breaking through the seat upholstery.

The seat assembly comprises lower cushion assembly 20 and upwardly extending seat back cushion assembly 25. The seat back cushion assembly further comprises left and right side bolsters 30.

The side airbag shown is mounted in a side bolster 30. It is also possible to mount the side airbag in the seat back cushion assembly 25.

The seat assembly is covered by a seat trim cover 35, made from sheets of leather, vinyl, or other suitable material. The sheets of the seat trim cover are joined by seams, for example side bolster seams. In this case the bolster seam indicated is used as a tear seam 40. Tear seam 40 is designed to rupture when the airbag is inflated, so that the airbag deploys through the seat trim cover as shown in figure 1.

Figure 2 is a cross section of a seat assembly with a side airbag. This shows the external parts of the seat assembly: side bolster 30, seat trim cover 35 and tear seam 40. The trim cover 35 comprises separate sheets of material 60, 65, which are joined together at seams, in particular tear seam 40.

The seat back cushion assembly 25 includes seat back frame 50. The frame 0 provides support for the seat back cushion 25. The frame 50 supports the cushion material 55 for the seat back cushion 25 and bolster 30. The cushion material 55 in turn is covered by the seat trim cover 35. The cushion material may be a foam pad of any suitable material known in the ad.

The side airbag 15 is part of the side airbag module 70. The side airbag module 70 comprises: Side airbag module mounting means 75, which attaches the module 70 to the frame 50 by any suitable means such as a threaded stud and nut. The module 70 includes housing 80. The housing 80 houses the folded (undeployed) side airbag 15 itself, and side airbag inflator (not shown). The inflator is triggered by a crash sensor, and inflates the side airbag 15. The module 70 is fitted in a cavity 90 in the cushion material 55.

This may be, for example, a hollowed-out or moulded space in the material or the space between separate pieces of cushion material.

The side airbag guide 100 surrounds the side airbag module 70. This is a sleeve or "chute" of material that guides the expanding side airbag through the seat cushion material 55 towards tear seam 40. The side airbag ruptures the seam and deploys outside the seat assembly in the correct position to protect the seat occupant.

Figure 2 also shows trim cover sheets 60, 65 that are joined at seam 40 by seam tear stitch 105. The tear stitch 105 also joins the side airbag guide 100 to trim cover on one side of the seam 40.

In operation, the airbag 15 is inflated by an airbag inflator (not shown). The airbag 15 inflates and follows a path through the upholstery, through the cushion material 55, guided by guide 100. The guide directs a the airbag towards the tear seam 40, breaking the tear stitch 105. The airbag exits the seat assembly 10 to assume the deployed configuration shown in Figure 1.

The guide 100 is folded from a single sheet of material to form a generally cylindrical structure or sleeve or pouch like structure that surrounds the airbag module and contain the side airbag as it inflates. The guide is attached to the 0 trim cover by tear stitch 105 forming tear seam 40.

The guide 100 directs the force of the inflating airbag to the tear seam 40, and the airbag 15 ruptures the tear stitch 105.

The guide 100 extends from the airbag module 70 to the seam 40. The inflating airbag 15 is contained within the guide 40 until it breaks the tear stitch in seam 40 to deploy outside the seat assembly 10 in the correct position.

The guide 100 comprises a single sheet of material having tensile strength sufficient to withstand the force of the inflating bag 15 without tearing, splitting or otherwise compromising the correct path through the cushion material 55 and to the seam 40. The tear stitch 105 is designed to fail through choice of stitch design and thread strength before the material sheets 60, 65 fail. This means that the tear 40 will rupture before the seat trim cover material ensuring deployment in the correct direction. A single sheet construction reduces the number of possible points of failure in the guide while inflating.

For example, a guide made from two sheets of material has an additional seam which could fail, causing the guide to steer the inflating airbag in the wrong direction.

Figure 3 shows the detail of the seam 40 and seam tear stitch 105 for side airbag 15.

As can be seen, the tear stitch 105 attaches the guide to one sheet 60 of seat trim cover 35, i.e. it is attached to only one side of the tear seam.

Edges 120, 125 of the guide material are brought together and tacked into place on one of the sheets 60 of the trim cover material. The guide 100 and sheet 60 are brought together with trim cover sheet 65 and sewn with seam tear stitch 105 to produce the tear seam 40.

In this example, a further tear stitch 135 also secures the seam allowance of the trim mover material sheet 55 and the seam allowance of the guide material edges 120, 125. The second tear stitch 135 may secure one, both or 0 none of the seam allowances of the guide edges.

A third stitch 145 may be made on the opposing sheet 60. this can be used to secure the seam allowance of sheet 65.

The single sheet guide, trim cover, and stitch configuration reduces the number of steps in manufacturing the airbag assembly. The resulting airbag assembly with airbag guide is simpler to construct and fit into the seat assembly.

The method of stitching the airbag assembly will now be described with reference to Figures 5A, SB, and SC.

The operation of incorporating the guide 100 into the seat trim cover 35 is a two step operation.

The first step is illustrated in Figure 6A, where a single sheet of material making up the guide 100 is folded and edges 120, 125 are tacked (605) to a single trim sheet 60. Tacking the sheets together ensures that the guide is accurately aligned with the tear seam 40 when fitted in the seat assembly.

This preliminary tacking step increase the accuracy of aligning the different edges for the sewing step, increasing reliability of the final stitch and seam.

Second trim cover sheet 65 is brought together edge to edge as shown with sheet 60 and the two sheets sewn together using tear stitch 105 to produce a single trim cover piece with tear seam 40.

After the initial alignment, only a single sewing operation is needed to accurately join all the edges together, reducing the number of sewing stages for assembly, and reducing the possibility of misaligning of the different pieces of the guide and seat trim material.

0 In a separate operation the seam allowances of sheet 60, 65 and guide 100 can be sewn together using a tear stitch.

This sequence of operations produces a combined seat trim cover and guide, which can be fitted over the airbag module 70, the airbag module 70 having S been attached to the seat assembly as shown if figure 2, to produce the finished seat with a side airbag fitted.

Figure 6C shows the seam tear stitch in detail, showing the two trim cover sheets 60, 65 joined at tear seam 40 by seam tear stitch. The seam tear stitch comprises a top stitch 150 and bottom stitch 155. The bottom stitch 155 is typically a weak thread. Thus the when the airbag inflates the weaker stitch will be break first, producing an even break along seam 40, allowing the inflating airbag 15 to deploy outside the seat assembly 10. The order of strong and weak stitches can of course be reversed, with the weaker stitch being the topstitch.

Claims (10)

1. Claims 1. A side airbag assembly for a vehicle seat assembly (10) comprising a seat trim cover and a side airbag guide, and side airbag module (70), wherein the seat trim cover has a tear seam (40) joining first and second edges (120, 125) of first and second portions (60, 65) of the seat trim cover (35), and further joining at least one edge of a seat airbag guide (100) to one edge of one portion of the seat trim cover, the seat airbag guide configured to 0 guide a side airbag (15) towards the tear seam (40), and where the at least one of the side airbag guide edges are sewn only to one side of a portion of the seat trim cover material (35); and the side airbag guide edges (120, 125), first and second portions (60, 65) of the seat trim cover material are sewn together in a single operation.
2. 2. The side airbag assembly of any preceding claim wherein the side airbag guide is a single sheet of material.
3. 3. The side airbag assembly of any preceding claim wherein the side airbag guide is generally tubular in shape.
4. 4.The side airbag assembly of any preceding claim where the tear seam is sewn together using a tear stitch.
5. 5. The side airbag assembly of any preceding claim wherein the tear stitch comprises a top stitch and a bottom stitch, and the breaking strength of the top stitch is different from the breaking strength of the bottom stitch.
6. 6. The side airbag assembly of claim 5 wherein breaking strength of the bottom stitch is less than the breaking strength of the top stitch.
7. 7. A tear seam for a side airbag assembly comprising a first and second seat trim cover portions, and a side airbag guide, wherein a single tear stitch joins a first and second seat trim cover portions, and a side airbag guide together; the guide being stitched onto only the first portion (60) of the trim cover material.
8. 8. A method of constructing a side air assembly comprising the steps of: aligning first and second edges of an airbag guide with first edge of a first sheet of a vehicle seat trim cover, aligning an edge of a second sheet of a O vehicle seat trim cover with said airbag guide edges and first edge of a first sheet, then sewing the edges together, and where the edges of the airbag guide are sewn only to the first sheet of the vehicle seat trim cover.
9. 9. A method as claimed in claim 8 wherein said aligning further includes S tacking the first and second edges of an airbag guide with the first edge of a first sheet of a vehicle seat trim cover,
10. 10. A side airbag assembly substantially as hereinbefore described, with reference to or as illustrated in the accompanying drawings.