GB2339736A

GB2339736A - Airbag assembly with retractable cover

Info

Publication number: GB2339736A
Application number: GB9915002A
Authority: GB
Inventors: Homayoun Karimi
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1998-07-10
Filing date: 1999-06-29
Publication date: 2000-02-09
Also published as: GB9915002D0

Description

2339736 AN AIRBAG ASSEMB The present invention relates to an airbag

assembly and more particularly to an airbag assembly used within a motor vehicle in order to protect an occupant from injury as a result of a traffic accident.

Use of airbags within motor vehicles has become common place.

Essentially, the airbag provides, almost instantaneously, an energy absorption cushion to protect and diminish injury to vehicle occupants. Unfortunately, it will be appreciated that in order to achieve as near an instantaneous deployment as possible, relatively aggressive propulsion of the airbag must be provided. Such aggressive and rapid deployment of the airbag can itself injure a vehicle occupant.

The present invention is particularly concerned with regard to the possibility of occupant injury due to an airbag storage cover being propelled - toward a vehicle occupant during an airbag deployment. It will be understood that an airbag assembly generally comprises an airbag housing within which the airbag is stowed. This housing includes a cover member which must be displaced in order to allow the airbag to be propelled towards the occupant. Thus, these airbag housing covers, even when made from relatively soft plastic materials can still approach the vehicle - o'ccupant with significant percussive force and so injure that occupant.

2- It is an object of the present invention to provide an airbag assembly in which the airbag housing cover is less likely to injure the vehicle occupant on deployment of the airbag.

In accordance with the present invention, there is provided an airbag assembly for a vehicle, the assembly comprising a housing to accommodate an airbag therein, said housing having a cover displaceable upon deployment of the airbag, the assembly characterised in that the cover includes at least one rupture propagation zone coupled to retraction means operative upon airbag deployment to cleave the cover into cover petals and retract those petals substantially inwardly behind the airbag as it inflates upon deployment.

Preferably, the rupture propagation zones are lines of weakness produced within the housing and/or the cover. Typically, two, four or more zones of rupture propagation will be provided in opposed pairs to create effectively quarter petals of the cover.

Preferably, the retraction means comprises a wire coupled to a respective rupture propagation zone and to propulsive displacement elements. These propulsive displacement elements may have a pyrotechnic or gas cylinder mechanism for fast pull retraction in use. Furthermore, the 3, retraction means may be confined and facilitated through appropriate guide or pulley elements secured about the housing and/or the cover.

Preferably, the cover will be hinged about an edge of the housing to further facilitate retraction of the cover upon deployment of the airbag.

The retraction means may cut or sever or cleave the cover itself through a combination of the of the violence of retraction and explosive punching of the cover by the-airbag inflation mechanism therebeneath.

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:

Figure 1 is a pictorial representation of a first embodiment of an airbag assembly; Figure 2 is a pictorial representation of a second embodiment of an airbag assembly; and Figure 3 is a pictorial perspective representation of the first embodiment as deployed; and Figure 4 is a pictorial plan of the fairst embodiment as deployed.

As indicated above, an airbag assembly comprises a housing to accommodate an airbag and means for rapid deployment of that airbag upon detection of an accident. Thus, as illustrated in Figure 1, an airbag assembly comprising a housing I coupled to a gas inflation mechanism 2 and having a cover 3 secured to provide a container within which an airbag is stored. Briefly, and normally upon deployment of the airbag, the gas inflation mechanism inflates the airbag stowed within the housing 1 and such inflation "punches" the cover 3 in order to deploy the airbag as shown with broken line D.

Figure la illustrates a front perspective view of an airbag assembly.

Figure lb shows a plan view, whilst Figure 1c shows a rear perspective view.

As indicated previously, it is the "pushing out" of the cover 3 which can precipitate itself injury upon an occupant through impact. If the cover 3 becomes detached from the housing 1, it will be appreciated that it is free to fly under the inflationary pressure presented by the inflation mechanism 2 toward the occupant.

In accordance with the present invention, the cover 3 is segmented into petals upon deployment. Furthermore, these segments or petals of the cover 3 are retracted or pulled inwardly behind the inflating airbag and so away 5- from any possibility of contact with an occupant. Such deployment is depicted in Figures 3 and 4. Thus, the petals of cover 3 are behind a deployed airbag 50 which develops from an injection nozzle 51.

Rupture propagation zones 4 are provided in the cover 3. These zones 4 5 are coupled to cover retraction mechanisms preferably through wire retraction members 5. Thus, upon deployment of the airbag from the housing 1, the retraction mechanism pulls upon the wire members 5 such that the rupture propagation zones divide the cover 3 into appropriate petals through which the inflating airbag can pass for deployment.

Wire members 5 are preferred in that through choice of high tensile socalled cheese wire, it will be appreciated that, the cover 5, particularly if made from a suitable plastics material can be cut and easily cleaved or divided into the petals and these petals then hinged to one side of the - housing 1 by the force of the inflating airbag.

The rupture propagation zones 4 typically will provide slits or at least lines of relative weakness in the cover 3 such that rupture or cleavage of the cover 3 is easily nucleated by the coupled retraction mechanism/member 5 along with the inflating airbag therebeneath.

Clearly, the retraction mechanism must achieve rapid pull retraction in use. Thus, the wire members 5 are coupled to retraction cylinders 6 through pistons 7. Thus, when a pyrotechnic or other pressurised gas is injected into the cylinder 6, the pistons 7 are driven in the direction of arrowhead R to pull the retraction wire members 5. As the members 5 are secured to the rupture propagation zones 4 it will be appreciated that rupture or cleavage of the cover 3 is precipitated. Furthermore, it will be appreciated that the cover member 3 is being punched by the underlying airbag and its inflation mechanism 2. Thus, as the wire member 5 is taut and if the cover member 3 is a relatively soft material, this wire member 5 will cut or cleave the cover member 3 into further petaling.

It will be appreciated that the wire member 5 will typically be secured through guide members or pulleys 8 for appropriate presentation. Thus, in Figure 1, it will be seen that pulley members 8 are located around the edges of the housing 1. Those skilled in the art will therefore appreciate that either the cover 3 alone may be split into petals by the retraction mechanism about the top edges 9 or the cover 3 and side walls 10 of the housing 1 split into petals about the lower edges 11. It will therefore be appreciated that the cover 3 alone could be made from a soft material easily cleaved by the wire member 5 with the rest of the housing 1 made from relatively robust material or the whole housing 1 including cover 3 made from material which may be cut or cleaved by the wire member 5 upon retraction by the retraction mechanism, ie. cylinder 6 and piston 7.

It will be understood that the inflationary gas from the airbag deployment mechanism 2 could be utilised in the retraction mechanism 5 cylinder 6 and piston 7.

As indicated above, it is not essential to have the retraction mechanism cut or cleave the cover 3 but rather that the rupture propagation zones 4, under retraction tension, split the cover 3 at least into two petals through which the airbag may be deployed. It is preferred that the cover 3 is hinged about the upper edges 9 to ensure detachment of the cover 3 does not occur during airbag deployment. However, it will be appreciated that essentially the petals of the cover 3 produced are secured by the wire members 5 and so hinging about edges 9 is advantageous but not essential. Furthermore, due - - to such robust retention of the cover 3 by the members 5 it will be appreciated that even when preferred hinging about the edge 9 is utilised that such hinging can be relatively free and of low strength due to the reassurance of retention by the members 5 of all the parts of the cover 3 upon deployment of the airbag behind that airbag and so away from an occupant.

Normally, the cover 3 and/or the side walls 10 of the housing 1 will include auxiliary lines or areas of weakness in order to further precipitate easy petal formation upon airbag deployment and under pull retraction against the rupture propagation zones 4.

The first embodiment depicted in Figure 1 will essentially divide the cover 3 and, where required, the housing 1 into two parts through which the airbag will be deployed. It will be appreciated, that such two part openings may be restrictive in terms of speed and necessary pull retraction propulsion strength required to achieve adequate speed. Thus, in Figure 2 a second embodiment of the present invention is illustrated in which a cover member 23 is divided into four petals radiating from a central area of that cover 23.

The air bag assembly illustrated in Figure 2 is similar to that depicted in Figure 1 in that a housing 21 is arranged to accommodate an airbag (not shown) and is associated with an airbag deployment mechanism 22 such that, as required, the stowed airbag within the housing 21 is inflated and the cover 23 is punched outwardly to allow such airbag deployment.

However, in accordance with the present invention, the cover 23 includes rupture propagation zones 24 in respective opposed pairs. Thus, upon airbag deployment, the retraction members 25 coupled to the zones 24, pull the cover 23 in opposite directions such that rupture or cleavage of the cover 23 is achieved in order to divide that cover 23 such that the inflating air bag may pass through it.

Those skilled in the art will appreciate that care must be taken with regard to positioning the rupture propagation zones 24 such that the central section between these zones 24 does not itself become detached and projected with force in the direction of airbag inflation, ie. at a vehicle occupant.

I As indicated previously with regard to Figure 1, it is preferred that retraction members 25 take the form of high tensile wire such that the cover 23, and possibly the side walls of the housing 21, are cut by the wire under pull retraction as the airbag is deployed to further precipitate radial petal displacement.

- The retraction mechanism used to pull the retraction members 25 is similar to that described with regard to Figure 1 in that the members 25 are secured to pistons 27 within cylinders 26. Thus, for retraction, the or each piston 27 is driven violently by gas pressure or a pyrotechnic device in the direction of arrow head P in order to pull the member 25 and so the cover 23 against the rupture propagation zones 24..

Gas pressure can be provided by the existing airbag propulsion mechanism 22. Prior to airbag deployment, the deployment mechanism 22 provides pressure to piston 27 to move it in the direction "P". Once the end of piston 27 travel has been reached, any excess rise in gas pressure will 5 open a valve into the airbag and so deploy that bag.

As with the first embodiment depicted in Figure 1, it will be appreciated that it is preferred for the cover 23 to be hinged about edges of the housing 21 in order to provide further assurance that the cover 23 will not be propelled towards a vehicle occupant by the airbag deployment sequence. Furthermore, the cover 23 along with the side walls of the housing 21 can include auxiliary lines or areas of weakness to further facilitate petal formation and radial expansion in order to allow the airbag to pass towards the occupant through or passed the cover 23 upon deployment.

It win be appreciated that presentation of the retraction members 5, 25 is important in accordance with the present invention. Thus, guides or pulleys 8, 28 must ensure appropriate presentation of the members 5, 25 to precipitate rapid rupture of the cover 23 along with, where designed, cutting of the cover 23 and side walls of the housing 1, 21. In such circumstances, it will be appreciated that simple rollers or nylon channels may be used to appropriately present wire retraction members 5, 25.

It will be appreciated that, the cover petals created by cover rupture about the rupture propagation -zones and through retraction member 5 cleavage, in themselves may present jagged edges unacceptable in a motor vehicle particularly during a traffic accident. Thus, it will be appreciated that the cover petals created in accordance with the present invention are substantially hidden behind the expansive cushion or pillow of the inflated airbag after deployment. In such circumstances, the jagged or angular edges of the cover petals are isolated from contact with a vehicle occupant. Furthermore, the airbag as it bellows will increasingly provide propulsive force to rotate the cover petals about the edges of the housing 1 and so away from an occupant located in front of the housing. Thus, this rotation of the petals augments the retraction mechanism particularly as the strength of pull retraction diminishes as piston 7, 27 displacement increases in the cylinders 6, 26.

-15 It will be appreciated that a single rupture propagation zone could be used with retraction members either side. However, in such circumstances, the strength of pull retraction necessary will be significantly greater than that required for multiple rupture propagation zone arrangements of the present invention.

Claims

- 12CIAIMS 1. An airbag assembly for a vehicle, the assembly comprising a housing to accommodate an airbag therein and said housing having a cover displaceable upon deployment of the airbag, the assembly characterised in that the cover includes at least one rupture propagation zone coupled to retraction means operative upon airbag deployment to cleave the cover into cover petals and retract those petals substantially behind said airbag as it inflates upon deployment.

1

2. An assembly as claimed in Claim 1, wherein the rupture propagation zone comprises a line of weakness within the cover.

3. An assembly as claimed in Claim I or Claim 2, wherein there are two opposed rupture propagation zones coupled to respective members of the retraction means operative to retract in opposed directions therefrom.

4. As assembly as claimed in Claim 1 or Claim 2, wherein there are four opposed rupture propagation zones arranged in opposed pairs with respective members of the retraction means operative to retract in opposite directions therefrom with respect to each pair of opposed rupture propagation zones.

13-

5. An airbag assembly as claimed in any preceding claim, wherein the retraction means comprises a wire member coupled to each respective said rupture propagation zone and to propulsive displacement means in order to retract, in use, such wire members.

6. An airbag assembly as claimed in Claim 5, wherein the propulsive displacement means comprises a pyrotechnic device or gas piston and cvlinder svstem.

1

7. An assembly as claimed in Claim 5 or Claim 6, wherein the wire members are configured about the housing and the cover through respective guides or pulleys secured to edges thereof

8. An assembly as claimed in any of Claims 5, 6 or 7, wherein the wire members are arranged to cut through and so cleave the cover when the retraction means is operative in order to further facilitate cleavature into the cover petals.

9. An airbag assembly as claimed in any preceding claim, wherein the cover is substantially hinged about edges of the housing to facilitate retention about that housing in use.

10. An assembly as claimed in any preceding claim, wherein auxiliary lines of weakness are provided within the cover and/or the housing in order to further facilitate cover petal retraction in use.

11. An airbag assembly substantially as hereinbefore described with reference to Figure 1.

12. An airbag assembly substantially as hereinbefore described with reference to Figure 2.

1

13. A motor vehicle including an airbag assembly as claimed in any preceding claim.