GB2339558A

GB2339558A - A vehicle airbag assembly

Info

Publication number: GB2339558A
Application number: GB9915004A
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: 2000-02-02
Also published as: GB9915004D0

Description

2339558 A VEHICLE AIRBAG ASSEMBLY The present invention relates to a

vehicle airbag assembly and more particularly to an airbag assembly inflated by a pyrotechnic gas inflation mechanism.

Over recent years there has been an increasing use of airbags within motor vehicles in order to protect occupants during colhsions. Typically, these airbags comprise a fabric bag which is inflated rapidly through a pyrotechnic gas generating inflation mechanism. Such mechanisms typically used ignitable solid propellants. Unfortunately, such gas inflation precipitates relatively large volumes of hot inflated gas which can be 10 directed directly towards a vehicle occupant.

Clearly, if such hot inflation gas were directed towards an occupant's skin there is a reasonable prospect of burn injury even through the fabric of the airbag. It will also be understood that the airbag should present a transitory cushion to protect a motor vehicle occupant during a collision but 15 the occupant should not be injured by -inflation of the airbag itself. Furthermore, the airbag, on inflation, should include pressure regulation in order to prevent rupture of the airbag through over inflation. The airbag after deployment should also deflate to allow emergency personnel access to a vehicle occupant for speedy extraction of that occupant from the vehicle 20 after a traffic accident.

It is an object of the present invention to provide a vehicle airbag assembly where the prospect of aggressive direct contact between hot inflation gas and the occupant is inhibited and preferably prevented.

In accordance with the present invention there is provided a vehicle airbag assembly comprising an airbag coupled through a coupling portion to an inflation stem with inflation means to inflate said airbag as required, said airbag including vent means adjacent said coupling portion between the airbag and the inflation stem, said vent means being configured to direct any surplus inflation gas from the inflation means away from an abutment surface of the airbag.

Preferably, the vent means comprises flaps or orifices or perforations or open tubes through which the inflation gas can be directed and dispersed.

The vent means may be created through rupture or tear of the airbag or fold displacement or rip tie or hatch displacement or simple weakening of the airbag adjacent the coupling portion between the airbag and the inflation stem.

The vent means may provide chutes transiently inflated in order to more appropriately direct surplus inflation gas. Furthermore, the portions of the airbag between the vent means may be similarly transiently inflated by inflation surplus inflation gas in order to create presentational and/or rigidity in the airbag for disbursement of the surplus inflation gas.

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

Figure 1 is a pictorial side representation of a vehicle airbag assembly; Figure 2 is a part plan pictorial representation in the direction X-X in Figure 1 of a first vent arrangement; Figure 3 is a part plan pictorial representation in the direction X-X in Figure 1 of a second vent arrangement; Figure 4 is a part pictorial side representation of a third vent arrangement between a stowed and a deployed configuration; Figure 5 is a part pictorial side representation of a fourth vent arrangement between a stowed and a deployed configuration; Figure 6 is a part pictorial side representation of a fifth vent arrangement between a stowed and a deployed configuration; Figure 7 is a part pictorial side representation of a portion of an airbag between vent sections of a vent arrangement; and, Figure 8 is a part pictorial side representation of a portion of an airbag between vent sections of a vent arrangement.

In Figure 1, a schematic pictorial representation of an airbag upon deployment is illustrated in accordance with the present invention. Thus, an airbag 1 is coupled to an airbag housing including an inflation stem 2 which also includes a pyrotechnic gas inflation device to inflate the airbag 1.

In such circumstances, a rapid deployment of hot gas is projected in the direction of arrow head G in order to push in particular an abutment surface 3 of the airbag 1 towards an occupant of a motor vehicle. In effect, the airbag provides a transient cushion to absorb the occupant's kinetic energy during a vehicle collision.

As indicated above, the hot inflation gas from the inflation stem 2 will be detrimental if it came into direction contact with the occupant. For example, the gas will be at relatively high temperature and may include particles of incompletely combusted solid propellant with the result that an occupant's skin may be burnt and exceptionally clothing set alight.

In accordance with the present invention, the inflation gas, either upon contact between the abutment surface 3 and an occupant or after a predetermined level of airbag 1 inflation, gas is directed away from the abutment surface 3, and so a vehicle occupant, in the direction of arrow heads A. In such circumstances, it will be appreciated that the possibility of direct aggressive contact between the hot inflation gas and an occupant is significantly reduced.

Direction of the hot inflation gas is through vents 4 appropriately located adjacent and about a coupling 5 between the airbag 1 and the inflation stem 2. Typically, the vents 4 in the arrangement win comprise discontinuous segments of the airbag 1 in order to create flaps or orifices or perforations or open tubes connecting the interior of the airbag 1 with the outside environment of the airbag assembly.

In Figure 1 the flap arrangement of vents 4 provides a guide surface to direct the inflation gas in the direction of arrow heads A. Direction of the inflation gas is important to ensure the prospect of direct contact between the hot gas and the occupant is diminished. It will be appreciated that, once cooled, i.e. through dilution with environmental air about the airbag assembly, such contact with the occupant is not so potentially detrimental.

It will also be understood that, at least transiently, the anchoring base between the airbag 1 and the inflation stem 2 or airbag holder is broadened from simply the width of the stem/holder 2 to the width between the flap arrangement vents 4 stiffened and stabilised by relatively rapid ejected gas flow therethrough. Such broader transient anchoring may provide additional stability for the abutment surface 3 during those critical 5 microseconds before contact with an occupant during a collision.

It will be appreciated that the actual vent arrangement used in the vehicle airbag assembly in accordance with the present invention can take a wide range of forms. As indicated above, the vent arrangement could comprise flaps or orifices or perforations or tube members which extend a gas passage between the interior of the airbag 1 and the exterior about the assembly. Clearly, in order to achieve the most effective deployment of the airbag 1 for occupant energy dissipation, actual early stage inflation of the airbag 1 should be in a conventional manner. Thus, the vent arrangement will be deployed or created at a predetermined time or inflation condition of the airbag 1. For example, the vent arrangement could be created upon contact between the abutment surface 3 and the occupant or after a certain degree of airbag 1 inflation. - In Figures 2 and 3 a first and a second vent arrangement are illustrated respectively.

In Figure 2 a view in the direction X-X of Figure 1 is illustrated in part plan pictorial view. Thus, the airbag 1 has extended from the airbag holder or stem 2 into its deployed state. The arrangement of vents 4 comprises three flaps 7, 8, 9 which radiate about the inflation stem or airbag holder 2 such that vent apertures 10, 11, 12 provide direct access from the airbag 1 interior to the exterior about the airbag 1 adjacent the coupling between that airbag 1 and the stem 2. Thus, hot inflation gas can pass through these apertures 10, 11, 12. The flaps 7, 8, 9 hang downward in order to direct such hot inflation gas flow similarly downward and therefore away from the abutment surface 3 (not shown) above.

As indicated previously, creation of the flaps 7, 8, 9 is typically through rupture of respective seams in the airbag adjacent the coupling to the stem 2. Thus, for example with regard to flap 8, a base seam 14 along with side seams 15, 16 rupture under inflation gas pressure in order to deploy the flap 8 and so relieve surplus inflation gas pressure as described. Similar deployment of flaps 7, 9 is achieved through respective base seams and side seams.

In Figure 3 an airbag 31 is coupled to an inflation stem or airbag holder 32. The airbag 31 is shown in a deployed condition, such that an abutment surface (not shown) is located above the inflation stem or airbag holder 32.

About and adjacent the holder 32 there is located a plurality of orifices 33 which act to direct surplus inflation gas downwardly and therefore away from the abutment surface (not shown).

In order to further precipitate inflation gas direction through the orifices or apertures 33, it will be appreciated that the material thickness of the airbag 31 in the location of these apertures or orifices 33 could be thickened in order to provide a longer guide tube through which the inflation gas must pass.

Deployment of the apertures 33 could be through rupture displacement of each aperture 33 upon a predetermined gas pressure within the airbag 31. In such circumstances, each aperture 32 would in effect be plugged with an element which would be forced out under inflation gas pressure. Alternatively, the apertures or orifices 33 will be permanent within the airbag 31 but only achieving a gas dispersion effect upon full inflation, or to the desired partial inflation of the airbag 31before gas dispersal.

Those skilled in the art will appreciate that the vent arrangement in accordance with the present invention may be permanent within the airbag 1 such that it is only effective upon full or desired partial deployment or, alternatively, the vent arrangement is precipitated by some active response within the airbag 1 at a desired airbag inflation condition.

In Figures 4 to 6 three further approaches to providing a vent arrangement through active response of the airbag during inflation are illustrated in pictorial side elevation.

In Figure 4 a hatch type vent arrangement is illustrated. An airbag 41 5 comprises a first section 42 secured to an airbag housing or inflation stem (not shown) and a second portion 43 extending away from that airbag housing. Between the portions 42 and 43 of the airbag 41 there is a line of weakness 44 and secured either to the first portion 40 or the second portion 43 there is a hatch element 45. This hatch element 45 effectively covers the line of weakness 44 such that upon deployment of the airbag 41, the stresses induced in the airbag 41 rupture the line of weakness 44 and the portions 41 and 42 separate. The purpose of the hatch 45 is to effectively cover the aperture between the portions 42, 43 until the desired level of airbag 41 inflation is achieved whereupon a passage 46 is created between either side of the airbag 41 in order to guide inflation gas out of the containment of the airbag 41 in the direction away from the vehicle occupant. The airbag 41 is pulled in the direction of arrow head B between the stowed configuration (Figure 4a) and the deployed configuration (Figure 4b).

In Figure 5 a fold embodiment of a vent arrangement is illustrated in pictorial side elevation. Thus, as illustrated in Figure 5a, an airbag 51 in a stowed configuration includes a first portion 52 and a second portion 53 including a fold section 54. This fold section 54 effectively seals an opening 55 between the sections 52, 53 of the airbag 51. Typically, the fold section 54 will be adhered through a contact area 56 between the first section 52 and that fold 54. Upon deployment of the airbag 51, the airbag will be pulled in the direction of arrow head C such that the fold 54 is released in order to create an aperture 57 through which inflation gas can be directed in accordance with the present invention away from direct contact with an occupant of a motor vehicle. The purpose of the fold 54 is again to delay or limit deployment of the vent arrangement until the airbag 51 is sufficiently inflated by providing 'slack' which must be tightened before revealing the vent aperture 57 for inflation gas dispersal.

Figure 6 illustrates a guide tube embodiment of the vent arrangement in accordance with the present invention in pictorial side elevation. Thus, in a stowed configuration an airbag 61 comprises a first section 62 and a second section 63 secured together through a contact area 64. In effect, the sections 62, 63 are in a staggered relationship such that upon deployment of the airbag 61 with the resultant pulling in the direction of arrow head D, any bonding between the sections 62, 63 in the contact area 64 is ruptured and creates a guide passage 65 between opposed surfaces of each settion 62, 63. This guide passage 65 can direct hot inflation gas away from the airbag 61 abutment surface in accordance with the present invention.

Those skilled in the art will appreciate that presentation of the vent arrangement in accordance with the present invention is highly important in ensuring that the inflation gas is appropriately guided away from direct contact with an occupant during deployment of the airbag assembly. Such presentation of the vent arrangement can be inhibited by the inherent flexible and limp nature of the materials from which airbags are typically made. Thus, in accordance with the present invention, it will be appreciated that the vent arrangement itself or sections of the air bag between, vents of the vent arrangement can at least be transiently inflated in order to create some presentational rigidity within the airbag for appropriate guiding of the inflation gases. In effect, chute or tube structures within the airbag are inflated in order to create transient sturdy components. These chutes or tubes can be open ended or closed at one end as required. Those skilled in the art will appreciate that a tube, whether open ended or closed at one end, when inflated under pressure, assumes a mechanical strength significantly greater than the fabric tube alone.

By way of example, Figure 7 illustrates in pictorial part side elevation, an airbag section 72 between vents of a vent arrangement in accordance with the present invention. In Figure 7a, an airbag 71 is illustrated in its stowed configuration. Thus, a section 72 of the airbag 71 between vents of the vent arrangement is substantially continuous between its coupling to the airbag housing and abutment surface. Secured to this section 72 is a displaceable section 73. In such circumstances, upon inflation of the airbag 71, the displaceable section 73 is displaced away from the section 72 'in order to create a chute or reinforcing channel 74 between opposed surfaces of these sections 72, 73. Typically, such displacement of section 73 is achieved through inflation gas pressure acting against the adhesion between the sections 72, 73 in a contact area 75. Such rupture of the adhesion in the contact area 75 may be facilitated by provision of a scoop end 76 to the section 73 such that inflation gas presented in the direction of arrow head E acts to lift and separate the sections 72, 73.

It will be appreciated that the rapid movement of inflation gas through the passage 74 creates a transient stability in the section 72 about the opposed section 73 which can be utilised in order to ensure appropriate presentation of the vent arrangement either side of the section 72 of the airbag 71.

Those skilled in the art will appreciate that a similar reinforcing and presentational effect can be achieved with the vent arrangement depicted in Figure 6 in the overlapping stagger between sections 62, 63.

It will be appreciated that in order to further enhance guidance of the inflation gas an open ended sock extension for flaps or apertures could be provided which extend from those flaps or apertures in the direction required. Thus, as illustrated in Figure 8, an airbag 81 could include a vent aperture 82 with an open ended sock 83 extending therefrom. This sock 83 essentially guides inflation gas in the direction of arrow head S which in accordance with the present invention is away from an occupant of a 5 vehicle.

Within the sock 83 a tube element 84 can be provided in order to achieve substantially concentric gas flows which can further enhance the control and directionality of guiding to inflation gas evacuation in the I direction required.

As indicated previously, the vent arrangement in accordance with the present invention may be passive in that the vent is permanently open with the airbag assembly in its stowed state or active, i.e. opened upon suitable deployment of the airbag arrangement. Such active deployment of the vent arrangement could be through rupturable sections about a fold or a hatched cover or a staggered configuration or through use of a rip tie or cord as required.

Claims

- 14CLAIMS 1. A vehicle airbag assembly comprising an airbag coupled through a coupling portion to an inflation stem which includes inflation means to inflate said airbag as required, said airbag including vent means adjacent said coupling portion between said airbag and the inflation stem, said vent means being configured to direct any surplus inflation gas from the inflation means away from an abutment surface of the airbag.

1

2. An assembly as claimed in Claim 1, wherein the vent means comprises flaps or orifices or perforations or open tubes in order to direct said surplus inflation gas as required.

3. An assembly as claimed in Claim 1 or Claim 2, wherein the vent means is permanently open during storage of the airbag prior to inflation via the inflation means.

4. An assembly as claimed in Claim 1 or Claim 2, wherein the vent means is closed during storage of the airbag prior to inflation and is only activated upon deployment of the airbag assembly as desired.

5. An assembly as claimed in Claim 4, wherein the vent means is configured for rupture or tear within the airbag as it is deployed in 15- order to define the vent means in use to direct any surplus inflation gas away from the abutment surface.

6. An airbag assembly as claimed in Claim 4, wherein the vent means is defined by unfolding a fold within the airbag as it is deployed.

7. An airbag assembly as claimed in Claim 4, wherein the vent means is defined through inflation displacement from the airbag in order to rupture a line of weakness therein and said rupture of the airbag is closed by a hatch element until the desired extent of airbag deployment is achieved whereupon the vent means is configured to direct any surplus inflation gas away from the abutment surface.

8. An airbag assembly as claimed in any preceding claim, wherein the vent means includes chutes or tubes or open ended socks in order to extend the vent means and so the degree of inflation gas direction guiding achieved by that vent means.

9. A vehicle airbag assembly as claimed in any preceding claim, wherein the vent means includes transiently inflated chutes or tubes, either open ended or closed at one end, in order to provide presentational rigidity to the vent means to facilitate appropriate inflation gas direction guiding away from the abutment surface of that airbag.

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10. An airbag assembly substantially as hereinbefore described with reference to Figure 1 and Figure 2 or Figure 3 or Figure 4 or Figure 5 or Figure 6 or Figure 7 or Figure 8.

11. A motor vehicle including an airbag assembly in accordance with any preceding claim.