GB2340452A - An air bag arrangement - Google Patents

Abstract

An airbag arrangement for a motor vehicle comprising an airbag (1) coupled to inflation means (4) where, during a vehicle impact the inflation means (4) inflates the airbag (1) with a volume of gas which is less in volume, at atmospheric pressure than the volume of the airbag (1) such that the airbag (1) remains flexible. An occupant (2) then coming into contact with the airbag (1) has less possibility of deployment induced injury from the airbag (1) than if the airbag (1) were inflated to a greater pressure.

Description

2340452 - 1 An Airbag Arrangement The present invention relates to an

airbag arrangement and more particularly to an airbag arrangement used within a motor vehicle to protect occupants in frontal impacts.

The use of airbags in motor vehicles over recent years has become relatively common place in order to meet a continuous quest to improve vehicle safety. Thus, airbags are provided to present a 'cushion' to a vehicle occupant or, where externally mounted, to a pedestrian during an impact. Clearly, in order to provide adequate protection, it is necessary for the air bag to be deployed sufficiently quickly in order to present the airbag to the occupant or pedestrian before they come into contact with a hard surface. Such rapid deployment requires powerful inflation gas injection and typically,at least, transient over-pressure within the airbag.

Such powerful inflation and over-pressure can lead to injury itself. Thus, motor vehicle manufacturers have tended to include relatively expensive vent means and inflation control in order to reduce the potential for airbag induced injury. Unfortunately, as airbag deployment is a relatively rare event and when deployed it is of paramount importance that the airbag provides adequate protection there is an inherent limit to the degree of occupant sympathetic deployment that can be achieved by such an approach.

It is an objective of the present invention to provide an airbag arrangement that can substantially overcome the above mentioned problems.

In accordance with the present invention there is provided an airbag arrangement for a motor vehicle, the arrangement including an airbag deployed upon determination of a vehicle impact from inflation means such that the inflation means only partially inflates the airbag with an inflation gas volume and such that the inflation gas volume when substantially combined with an engagement front volume constitutes at least the airbag's notional volume, and therefore atmospheric gas pressure of the airbag to achieve restraint engagement by the airbag with an occupant of a vehicle.

Preferably, the inflation gas volume constitutes at least seventy percent of the air bag volume at expected atmospheric pressure.

The engagement front volume will typically comprise a vehicle occupant or pedestrian along with associated seating or facia or bumper etc. incident in the airbag deployment direction.

The inflation means may provide single or multiple point gas inflation to the airbag. Furthermore, normally the inflation gas will be provided by pyrotechnic propellant suitable associated with the airbag arrangement.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawing depicting, in pictorial schematic cross-sectiOn, a deployed airbag arrangement.

Deployment of an airbag in accordance with the present invention is similar to previous arrangements in regard to determination of an impact, or potential for such an impact, necessitating provision of an airbag cushion' to protect a vehicle occupant or pedestrian. Thus, upon determination that deployment is required, an appropriate gas inflation mechanism is activated and the airbag inflated. However, in accordance with the present invention, this inflation is limited to avoid airbag induced injury but nevertheless sufficiently rapidly to provide effective protection to an occupant or pedestrian.

In the present invention, the airbag of the arrangement has an enclosed free space without vents to limit over-pressure but coupled to gas inflation means which will only provide an inflation volume of gas less than that of the airbag at normal atmospheric pressure. Thus, the airbag will be relatively relaxed until it encounters an engagement front typically constituted by a vehicle occupant and associated seating and facia etc.

Upon such engagement between the airbag and the engagement front it will be appreciated that the scope for airbag development is curtailed and so further inflation gas will simply pressurise the airbag. However, within limits such pressurisation will more firmly engage the occupant and augment the protection provided thereto.

In the drawing, a pictorial schematic cross-section of an airbag arrangement in a deployed configuration is depicted. Thus, an airbag 1 is presented to an occupant 2 such that the airbag 1 at least partially envelopes the occupant 2. In such circumstances, the occupant 2 is engaged by the airbag 1 through an engagement front surface 3 (shown in broken line). Clearly, it will be appreciated that in previous systems, the natural tendency under over-pressure and inflation is for the airbag to assume as spherical a configuration as possible to provide the lowest surface area to volume.ratio This tendency M previous arrangements leads to a sustained compressive pressure upon the occupant 2 in the direction of arrowheads A after the initial percussive shock of the powerful inflation gas jetted toward that occupant 2. The combination of these factors can result in the potential for injuries previously described.

In the present invention the airbag 1 is only partially inflated by gas inflation means 4 such that there is no over-pressure and so no need for vents to limit that over-pressure upon deployment to expected or reasonable levels. However, the airbag 1 does achieve some pressure upon engagement with the occupant 2 and any surfaces adjacent or associated with the occupant 2.

Essentially, the inflation volume of gas provided by the inflation means only partially inflates the airbagl and the volume of the engagement front constituted by the occupant 2 and associated surfaces enveloped by the airbag 1 combine to exceed the notional volume of the airbag 1 and so pressurise it. In such circumstances, it will be appreciate that the designer of that airbag arrangement must, at least, predict the expected occupant size and distance from the inflation means 4 in order to determine the notional airbag volume and degree of inflation to achieve an acceptable level of pressurisation under engagement with the occupant 2 and other surfaces roundabout Thus, each airbag arrangement will be specific for a particular vehicle interior cabin configuration and will be based upon an averaging of expected occupant size, orientation and distance between the occupant and is the inflation means 4.

Although the airbag 1 is only partially inflated it will be understood that it is still as important, if not more so, than previous arrangements that the airbag 1 should be rapidly inflated to its inflation volume. Thus, a single or multiple gas injection strategy using preferably a pyrotechnic device will be used. It will be appreciated with a partially inflated airbag as in the present invention the 'window' of protection to the occupant 2 is only available when the airbag 1 is nearly full deployed with all the inflation volume but that the impact excursion presented to that occupant is still over the same time scale as previous arrangements where there is the luxury of in-built over capacity from over-pressure and high powered inflation means 5 specification.

With pyrotechnically generated gas inflation it will be understood that that the volume of gas produced is dependent upon combustion of a normally solid propellant. Thus, in accordance with the present invention, the inflation gas volume is determined by the weight of such pyrotechnic material provided whilst that pyrotechnic material is configured and arranged with an appropriate oxidant le. air to combust sufficiently quickly to inflate the airbag 1 in time to provide adequate protection. Alternatively, and provided the inflation gas volume can be provide quickly enough and the container is not an explosion risk, then the inflation means may comprise a gas bottle or similar container.

Normally, the airbag 1 will be inflated by the inflation means 4 to at least seventy percent of its notional volume at normal environmental/atmospheric pressures. Thus, the remaining airbag 1 volume to full, atmospheric, inflation pressure will be taken up by the occupant 2 and any other surfaces or objects the airbag 1 should contact, collectively referred to as the engagement front volume. Once, the combined inflation volume and the engagement front volume exceed the notional airbag I volume it will be appreciated that the airbag 1 is pressurised.

Ideally, the inflation volume and the expected engagement front volume should just exceed the notional volume of the airbag 1 so that there is compressive engagement with the occupant. Thus, this compressive engagement gently progressively builds upon the occupant 2 and any further pressurisation, due for example to the occupant 2 and inflation means coming closer together as a vehicle body structures crumple, will also progressively increase to further engage the occupant. It win therefore be understood that the present invention presents the compressive engagement force necessary to protect the occupant 2 more progressively and so sympathetically than previous arrangements where the inflation pressure is aggressively presented in the airbag and so to the occupant. The degree and rate of airbag 2 pressure progression is a design choice made by the of the air bag arrangement in a particular vehicle geometry and as outlined above. Typically, the inflation gas and the engagement front volume win exceed the notional airbag 1 volume by at least ten percent to provide a minimum pressurisation for compressive engagement.

It will be understood that several airbags in accordance with the present invention could be configured into an arrangement for presentation to an occupant of a vehicle. Thus, it may be possible to more accurately control both the volume and rate of deployment of these airbags due to the reduced individual volume of each airbag rather than a larger single volume of a single airbag arrangement described above. These airbags could be of varying size or shape dependent upon their respective position in the engagement front to the occupant. Furthermore, these airbags could be free and sprouting from the inflation means as petals or, these airbags could be located within a cover bag or net to maintain a greater level of consistency of association and so presentation to the occupant of a vehicle.

Although the invention has been principally described with reference to 10 airbag presentation to an occupant of a motor vehicle, it will be understood that the present airbag arrangement could be use with regard to pedestrian impact scenarios. Thus, the repellent nature of previous airbag arrangement with regard to unsupported or restrained articles i.e. pedestrians is attenuated by the reactive pressurisation of the airbag rather than the previous proactive over-inflation of conventional airbag arrangements. In such circumstances, the airbag arrangement of the present invention would be mounted in an external panel or bumper and react to deploy the airbag upon deformation loading of the panel or bumper such that an energy absorbing cushion depth is provided to protect the pedestrian under impact.

Claims (8)

-9CIAIMS

1. An airbag arrangement for a motor vehicle, the arrangement including an airbag deployed upon determination of a vehicle impact from inflation means such that the inflation means only partially inflates the airbag with an inflation gas volume and such that the inflation gas volume when substantially combined with an engagement front volume constitutes at least the airbag's notional volume, and therefore atmospheric gas pressure of the airbag to achieve restraint engagement by the airbag with an occupant of a vehicle

2. An arrangement as claimed in claim 1 wherein the inflation gas 10 volume constitutes at least seventy percent of the airbag volume.

3. An arrangement as claimed in claim lor claim 2 wherein engagement front volume comprises, in use, a vehicle occupant and associated seating and facia within a motor vehicle interior cabin in the airbag deployment direction.

4. An arrangement as claimed in claim 1 or claim2 wherein engagement front volume comprises, in use, a pedestrian and external bumper andlor panels of a motor vehicle which impact that pedestrian in the airbag deployment direction.

5. An arrangement as claimed in any proceeding claim wherein the arrangement includes a plurality of airbags individually coupled to the inflation means.

6. An arrangement as claimed in any proceeding claim wherein the substantially combined volume of the inflation gas volume and the engagement front volume constitutes up to ten percent more volume than the notional volume of the airbag at atmospheric pressure.

7. An air bag arrangement substantially as hereinbefore described with reference to the accompanying drawing.

8. A motor vehicle including an airbag arrangement as claimed in any proceeding claim.