GB2391840A

GB2391840A - Side curtain airbag

Info

Publication number: GB2391840A
Application number: GB0218597A
Authority: GB
Inventors: Markus Richter; Marko Morhard; Volker Hofmann; Stefan Florsheimer
Original assignee: Breed Automotive Technology Inc
Current assignee: Breed Automotive Technology Inc
Priority date: 2001-08-23
Filing date: 2002-08-12
Publication date: 2004-02-18
Also published as: GB0218597D0; DE10141437A1; ITMI20021841A1

Abstract

A side curtain airbag for a vehicle comprises at least two essentially parallel outer fabric layers 2,4 connected to each other at their outer peripheries and internally by a gas permeable fabric layer 10 extending perpendicularly between the outer layers 2,4. Internal connection between the outer layers 2,4 may also be provided by at least one connecting strip (16, fig 4). The gas permeable layer 10, such as a net, preferably lies horizontally and determines the distance between the outer layers 2,4, thus limiting the airbag's volume whilst enabling gas to flow rapidly between the airbag's internal chambers on inflation. As an alternative to the gas permeable layer, a plurality of connecting strips (16) may be used to form an airbag with a quilted appearance (see fig 6). The strips (16) may be secured by welding points (22, fig 6), gluing, sewing and/or by washers (20, fig 5) which may be held by a thickened or knotted strip end portion (18, fig 5).

Description

SIDE CURTAIN AIRBAG

The invention relates to a side curtain airbag.

Many airbags encounter the problem that the airbag exhibits too large a volume. A large volume of the airbag on the one hand requires a correspondingly large gas generator, on the other hand the inflation time required to inflate the airbag with gas in order sufficiently to protect a vehicle occupant, is extended. These types of problems arise in particular with side curtain airbag modules. These consist of airbag modules in which an airbag extends downwards from a lateral roof region or roof beam. The airbag in this case extends preferably laterally over the entire length of the vehicle, to provide lateral protection from injuries to a front passenger as well as a rear seat occupant. Up to now, tucks have often been foreseen in the airbags of such side curtain airbag modules, directly connecting the two outer fabric layers, which form the airbag.

A diagrammatic view of a known airbag of this type is shown in Fig.1.

The airbag has two essentially parallel fabric layers 2, 4, which are connected to each other at their outer circumference to form a closed airbag. In the upper region of the airbag, a fastening web 6 is located, via which the airbag is fastened to a lateral roof beam of a vehicle. The two fabric layers 2, 4 are directly connected to each other in predetermined positions by tucks 8, i.e. the two fabric layers 2, enter into contact with each other in the region of the tucks. In the region of the tucks 8, dead spaces are created, which extend in a funnel-shaped manner. In this region there is not sufficient gas volume to enable satisfactory protection of a vehicle occupant. If the head of the vehicle occupant hits the airbag exactly in the region of the tucks 8 and strikes the body parts of the car lying positioned behind the airbag without any cushioning. In addition, side airbags are known from the prior art, comprising fabric

layers that divide the airbag into several chambers. In these fabric layers, overflow openings are provided, which enable a specific inflation of the

individual chambers successively. In this case the fabric layers with the overflow openings present a significant gas flow resistance, so that a rapid inflation of the entire airbag is rendered difficult. This is a problem in particular with large airbags, such as side curtain airbags. I The side curtain airbag according to the invention comprises two i essentially parallel extending outer fabric layers. The two fabric layers are connected to each other at their outer circumference to form a closed airbag.

In this case at a suitable position, at least one gas entry opening is foreseen, which is connected to a gas generator. The connection of the two fabric I layers can be carried out in a known manner by welding, sewing, gluing or by a single-pieced design of the two fabric layers. The two fabric layers i preferably consist of a gas impermeable fabric, but can also consist of other I suitable materials such as for instance a foil, or if necessary be gas! permeable at least in sections. Inside the airbag the two fabric layers are connected to each other by at least one gas permeable fabric layer or a connecting strip, that extend(s) essentially perpendicular to the outer fabric layers. The connecting strip or the gas permeable fabric layer in the direction perpendicular to the outer fabric layers, exhibits a specific length, so that the two outer fabric layers can be held at a predetermined distance from each other. During the inflation of the airbag, the connecting strip or the gas E permeable fabric layer prevents the airbag from completely inflating and therefore assuming an essentially round cross sectional form. On the i contrary, the connecting strip or the gas permeable fabric layer keeps the two outer fabric layers at a predetermined distance from each other, so that the i inflated airbag assumes an essentially flat "air-mattress" shape. Inside the airbag, several connecting strips or gas permeable fabric layers can also be, provided, so that over the entire surface of the airbag a predetermined depth (thickness) can be set. The connecting strips or gas permeable fabric layers can be designed with varying lengths in the direction perpendicular to the outer fabric layers, so that the airbag exhibits varying depths in various regions The gas permeable fabric and the connecting strips form only an extremely low flow resistance inside the airbag, or essentially no flow

l resistance. A rapid and complete inflation of the airbag with gas is not impaired by the gas permeable fabric layers and/or connecting strips, so that in the event of a crash the airbag according to the invention can provide complete protection in a sufficiently rapid manner.

The airbag preferably has an airbag for a side curtain airbag module.

The application of the present invention with this type of airbag is particularly advantageous since with an airbag module it is necessary to design a large-

surface airbag with an essentially constant depth. It is at the same time necessary to minimise the gas volume in the airbag, to enable the use of a I small gas generator and a rapid inflation of the airbag with gas. The invention enables a very rapid inflation of the airbag with gas during the ignition of the i gas generator, so that the most rapid possible optimal protection can be I achieved for a vehicle occupant.

It is preferable that the gas permeable fabric layer extends in essentially the longitudinal direction of the airbag, preferably in an essentially horizontal manner. In a side curtain airbag module, the inflated airbag extends essentially parallel to the vehicle longitudinal direction along a vehicle inner side. The airbag forms an air cushion between the vehicle occupants and the vehicle outer side, i.e. in particular the vehicle side windowpanes. In this type of airbag, the gas permeable fabric layer extends in essentially the longitudinal direction of the airbag, i.e. also in the longitudinal direction of the vehicle. If such an airbag of a side curtain airbag module is installed in a vehicle, the gas permeable fabric layer in the deployed airbag extends preferably in an essentially horizontal manner.

The gas permeable fabric layer preferably is a net. This net-shaped fabric layer enables a sufficiently strong connection of the two outer fabric layers. The strength should be such that the forces operating in the airbag due to the gas pressure can be safely accommodated. Alternatively, set breaking points can be foreseen in the gas permeable fabric layer or the connecting strip, which enable a rupture when a predetermined internal i pressure is reached in the airbag. The design of the gas permeable fabric

layer as a net has the further advantage that the gas can penetrate through the net almost unimpeded.

The at least one connecting strip preferably extends through the outer fabric layers and is fastened to the latter's outer sides, i.e. the outer sides of the airbag. This arrangement enables an easy and secure fastening of the connecting strip to the outer fabric layers. It is possible to fasten the connecting strip to the outer fabric layers such that the fastening points between the fastening strip and fabric layers are pressure-loaded, rather than tension-loaded, so that a greater strength of the connecting points can be I achieved. It is preferred that plain washers are located at the outer sides of the i outer fabric layers, through which the connecting strip extends and to which I the connecting strip is fastened. The plain washers enable a large-surface force transmission onto the outer fabric layers, so that a secure force transmission can be achieved between the connecting strip and the outer fabric layers. The plain washers can be designed such that they simultaneously seal the entry opening, through which the connecting strip penetrates through the outer fabric layer. This can take place in that in the inflated state of the airbag the outer fabric layer is extensively pushed against the plain washer due to the gas pressure inside. This way a sealing contact is achieved between the fabric layer in the peripheral region of the entry opening and the plain washer. This means that additional sealing means can be omitted. The connecting strip is preferably secured to the outer sides of the outer fabric layers and/or plain washers by welding, gluing and/or sewing.

The connecting processes can be chosen in dependence on the materials used. When synthetic materials are being used, the welding process is particularly suitable for achieving a connection, since it is a very simple and cost-efficient connecting process.

Alternatively or additionally, the connecting strip engages behind the outer sides of the outer fabric layers and/or the plain washers with a

thickening (thickened part). In the simplest case, this type of thickening can consist of a knot. The thickening can, however, be achieved by recasting a connecting strip out of synthetic material, for instance. Alternatively, thickening elements can be provided to the connecting strip by welding, gluing or clamping. In all cases, the thickening ensures an interlocking of the connecting strip and the outer fabric layer or plain washer, to guarantee a secure force transmission between these elements.

In the process according to the invention for the manufacture of an airbag for an airbag module, initially an airbag is designed with two essentially parallel outer fabric layers. This takes place in the known manner. The two fabric layers can be connected or woven to each other in one piece.

Alternatively, the two outer fabric layers can be connected to each other along their outer periphery, for instance by welding, gluing or sewing. At a suitable point in the airbag, at least one gas entry opening is provided. Then a connecting strip is inserted through the two fabric layers, preferably superimposed in a parallel manner. This can be carried out with a needle, for instance, which penetrates the two fabric layers. Alternatively, the connecting strip can be pulled through pre-designed entry openings in the fabric layers.

Subsequently the connecting strip is secured to the outer sides of the two outer fabric layers, whereby the part of the connecting strip extending between the fabric layers exhibits a predetermined length. The two opposite ends of the connecting strip are preferably in each case secured to an outer side of the two fabric layers. The connecting strip in this case exhibits a predetermined length, so that a predetermined length of the connecting strip is arranged between the two fabric layers. In this way the connecting strip can hold the two fabric layers at a predetermined distance from each other, when the airbag is inflated with a gas.

Plain washers, through which the connecting strip is inserted, are preferably arranged on the outer sides of the outer fabric layers. The connecting strip is subsequently secured with its ends to or behind the plain washers, so that the force flow from the outer fabric layers to the connecting strip is carried out via the plain washer. The plain washers in this case

provide a large force transmission surface, so that a secure force transmission is enabled. In addition, the plain washer can also serve, as described above, to seal an entry opening in the outer fabric layer, through which the connecting strip penetrates. Alternatively, the sealing can also be carried out by gluing or welding or by additional sealing elements.

Advantageously, the connecting strip is secured to the plain washers.

The connecting strip can for instance be welded to the washers. Alternatively, a connection between the connecting strip and the plain washer is possible by gluing or an interlocking or non-interlocking contact fit connection. For instance, clamping means can be designed on the plain washer, in which the connecting strip is clamped.

Thickenings, for instance knots, which engage behind the outer fabric layers or plain washers, are preferably located on the connecting strip. In this way a very simple interlocking between the connecting strip and the outer fabric layer can be achieved. For instance, a connecting strip can initially be provided at its first end with a thickening, for instance a knot, before being pulled through a first plain washer, and subsequently inserted through the two fabric layers, for instance by a needle. Subsequently, the free second end of the connecting strip is inserted through a second plain washer and at the second end a further thickening, preferably a knot, is located. In this state, the connecting strip with its knots at its free ends and the plain washers engages behind the two outer sides of the two outer fabric layers, so that these are arranged between the thickenings or the plain washers, preferably freely movable on the connecting strip. If the airbag is now inflated with gas, the two outer fabric layers are pushed apart by the gas pressure and pushed against the plain washers or thickenings in the connecting strip. The connecting strip now holds the two outer fabric layers at a predetermined distance against the gas pressure. The distance between the two fabric layers can be adjusted easily by the length of the connecting strip. Preferably, several connecting strips are distributed over the surface of the airbag and arranged in the latter, in order to be able to set a predetermined thickness of the airbag. The individual connecting strips can in this case exhibit varying

lengths, so that the airbag displays varying degrees of thickness in different regions. For instance, the airbag can be particularly thick in the region in which the head of the vehicle occupant is positioned.

Alternatively or additionally, the connecting strip can be secured to the outer fabric layers or plain washers by welding, gluing and/or sewing. I n the case where the connecting strip as well as the outer fabric layers or, if necessary, the plain washers are made of synthetic material, welding is suitable, since in this manner a particularly simple and cost- effective connection can be achieved.

The invention will be described in more detail by means of examples with reference to the figures, in which: Fig.1 is a diagrammatic sectional view of an airbag according to the prior art;

Fig.2 is a diagrammatic sectional view of the airbag according to the invention in accordance with a first embodiment; Fig.3 is a perspective, partly sectional view of the airbag according to the invention in accordance with the first embodiment; Fig.4 is a diagrammatic sectional view of the airbag according to the invention in accordance with a second embodiment; Fig.5 is a detailed view of a connecting strip, and Fig.6 is a diagrammatic top view of the airbag according to Fig.4.

Fig. 2 is a diagrammatic sectional view of an airbag for a side curtain airbag module in accordance with a first embodiment of the invention. It is a sectional view of the airbag, essentially transverse to its extension direction, i.e. transverse to the longitudinal direction of a vehicle. The airbag has two fabric layers 2, 4, which are connected to each other alongside their outer circumferences by sewing, welding or gluing. Alternatively, the fabric layers 2, 4, at least in part of their periphery, can consist of one piece, i.e. for instance be woven together as one piece. Inside the airbag, the two fabric layers 2, 4 are connected to each other by a gas permeable fabric layer 10 and in the

inflated state of the airbag they are held at a distance from each other. The gas permeable fabric layer 10 in this case preferably extends over the entire length of the airbag and exhibits a predetermined width, which defines the distance between the two fabric layers 2, 4. The gas permeable fabric layer 10 in this case holds the fabric layers 2, 4 together such that when the airbag is inflated with gas, a flat airbag of a predetermined thickness, i.e. with a predetermined distance between the fabric layers 2, 4, is created. In Fig.2 merely one gas permeable fabric layer 10 is shown; several of these fabric I layers, however, can be arranged inside the airbag. The gas permeable fabric layer 10 is preferably a net, which enables the greatest possible gas permeability. Such a net 10 essentially does not impede a gas flow entering the airbag, so that the inflation the airbag with gas is not obstructed or delayed. Fig.3 is a perspective view of an airbag for a side curtain airbag module in accordance with the embodiment of Fig.2. In Fig.3 the end regions of the airbag are cut off from view and two gas permeable fabric layers or nets 10 are arranged inside the airbag. The two fabric layers 2, 4 are connected to each other along their edges such that a fastening web 6 is created. In the latter, holes 13 are arranged, with which the airbag can be secured to the vehicle structure. On the opposite lower surface 14 of the two outer fabric layers 2, 4, the latter are connected to each other in a known manner, as in the other not shown peripheral regions, for instance by welding, sewing or gluing. Inside the airbag, two gas permeable fabric layers or nets 10 are arranged. The nets 10 extend essentially perpendicularly to the two fabric layers 2, 4 and parallel to the latter's longitudinal edges 6, 14. This arrangement in the installed state of the airbag for a side curtain airbag module corresponds essentially to a horizontal arrangement. Due to the arrangement of the two nets, the two fabric layers 2, 4 are held at a I predetermined distance to each other in the inflated states of the airbag,: against the gas pressure. The gas permeable fabric layers 10, which are preferably nets, are gas permeable in the sense that they essentially do not

present any flow resistance to a gas flowing into the airbag, so that the i inflation of the airbag is not obstructed or delayed. In this way, optimal protection for a vehicle occupant can be achieved due to the airbag.

Fig.4 is a sectional view of an airbag in accordance with a second embodiment of the invention. This airbag also has an airbag that is foreseen particularly for a side curtain airbag module. As for the airbags shown in Fig.1 to 3, the airbag has two outer fabric layers 2, 4 which are connected to each other along their periphery, as is shown in the section of the lower edge 14 1 and the upper edge 6. The upper edge 6 in this case is preferably a fastening web. The connection is shown as a sewn connection in Fig.4, but can also be achieved by gluing or welding. Inside the airbag connecting strips 16 are arranged between the two outer fabric layers 2, 4. The connecting strip 16 extends essentially perpendicular to the outer fabric layers 2, 4 and connect these two with each other. The connecting strips 16 exhibit a predetermined length, so that the outer fabric layers 2, 4 are held at a predetermined distance to each other in the inflated state of the airbag. In this way an airbag can be created with a defined thickness and a flat shape. In Fig.4 two connecting strips 16 are shown. It is possible, however, to arrange only one single connecting strip 16 or a larger number of connecting strips 16 inside the airbag.

Fig.5 is a detailed view of the structure of a connecting strip 16. The connecting strip 16 exhibits a predetermined length. The connecting strip 16 is connected at its two opposite ends 18 with plain washers 20. In alternative; embodiments, the plain washers 20 can be omitted. In the shown example, the connection between the plain washer 20 and the connecting strip 16 is achieved by welding points 22. Alternatively, it is possible to knot the connecting strip 16 so that the knot holds the plain washer 20, or to secure the connecting strip 16 to the plain washer 20 in a different suitable manner.

To install the connecting strip 16 in the airbag, preferably initially a l plain washer 20 is secured to one end 18 of the connecting strip 16 with a: welding point 22. Subsequently, the connecting strip 16 is pulled with the

other, free end 18 through the superimposed fabric layers 2, 4, for instance by a needle or through pre-designed entry openings. Subsequently, the connecting strip 16 is pulled through a second plain washer 20 and with its still free end 18 secured to the second plain washer 20 through a second welding point 22. If the connecting strip 16 is arranged in this manner, the fabric layers 2, 4 are held between the two plain washers 20 at an essentially predetermined distance, which corresponds to the length of the connecting strip 16.

Fig.6 is a top view of the fabric layer 4 of the airbag according to the invention. In the airbag, several connecting strips 16 are arranged at a distance to each other, as is shown in Fig.6 by the representation of the plain washers 22 or corresponding fastening points on the fabric layer 4. Due to the arrangement of a multitude of connecting strip 16, a stitched "quilted" shape of the airbag is achieved, whereby the fabric layers 2, 4 in the inflated state are held at a distance from each other such that they do not enter into direct contact with each other apart from at their periphery. In this way, in contrast to the prior art, dead spaces in which no sufficient air cushion is

provided are avoided. With the arrangement of a multitude of connecting strips 16, these can all exhibit the same length, so that an airbag with an essentially constant thickness is achieved. It is also possible, however, to design the connecting strips 16 with varying lengths, so that in the airbag areas of varying thickness can be created. It is conceivable to design the connecting strips 16 or a part of the connecting strips 16 such that they tear off or through at a set internal pressure in the airbag. In this way set breaking points can be created, which enable the further unfolding or inflation process of the airbag to be specifically controlled.

lo

Claims

CLAIMS:

1. A side curtain airbag comprising at least two essentially parallel extending outer fabric layers (2, 4) each having an outer periphery, the fabric layers being connected to one another in the region of their outer peripheries, whereby the two outer fabric layers are connected to each other by at least one gas permeable fabric layer (10) that extends essentially perpendicular to the outer fabric layers (2, 4).

2. The side curtain airbag of claim 1 wherein the gas permeable fabric layer (10) extends in essentially the longitudinal direction of the airbag, preferably in essentially perpendicular to the two outer fabric layers.

3. The side curtain airbag of either of claims 1 or 2 at least one gas permeable fabric layer (10) is a net.

4. The side curtain airbag of claim 1 wherein at least one connecting strip (16) extends through the outer fabric layers and is secured to an exterior side of each of the outer fabric layers (2, 4).

5. The side curtain airbag of any claims 2 to 4 wherein at least one connecting strip (16) extends through the outer fabric layers (2, 4) and is secured to an exterior side of each of the outer fabric layers.

6. The side curtain airbag of claim 5 wherein the connecting strip (16) is secured to the exterior sides of the outer fabric layers (2, 4) by a securing means selected from the group consisting of welding, gluing, sewing, and a thickened portion of the connecting strip.

r

7. The side curtain airbag of claim 5 wherein at the exterior sides of the outer fabric layers (2, 4), plain washers (20) are located through which the connecting strip extends and to which the connecting strip (16) is secured.

8. The side curtain airbag of claim 7 wherein the connecting strip (16) is secured to the plain washers (20) by a securing means selected from the group consisting of welding, gluing, sewing, clamping and a thickened portion of the connecting strip.