WO2000003898A1

WO2000003898A1 - An airbag

Info

Publication number: WO2000003898A1
Application number: PCT/GB1999/002051
Authority: WO
Inventors: Homayoun Karimi
Original assignee: Bayerische Motoren Werke Aktiengesellschaft
Priority date: 1998-07-14
Filing date: 1999-06-30
Publication date: 2000-01-27
Also published as: GB9815115D0

Abstract

An airbag (1) is provided which comprises a plurality of airbag compartments (3, 9, 11) coupled together with vents (8, 10) such that these airbag compartments (3, 9, 11) are sequentially inflated upon deployment. A first airbag compartment (3) is inflated angularly but under the control of a control member (5) to define an engagement front for contact with a vehicle occupant (6). The first airbag compartment (3) in association with the control member (5) defines a deployment cone within which the other airbag compartments (9, 11) are sequentially inflated to progressively engage the occupant (6) in a less aggressive manner than previous airbag configurations. Typically, the vents (8, 10) are arranged such that there is indirect inflation of the airbag compartments (9, 11) and so further regulation of airbag (1) deployment.

Description

AN AIRBAG

The present invention relates to an airbag and more particularly to an

airbag for a motor vehicle in order to protect an occupant of that vehicle

from injury in a traffic accident.

The use of airbags within motor vehicles in order to provide for vehicle

occupant protection during road traffic accidents has become relatively

commonplace. It will be appreciated that airbags must be rapidly deployed

in order, to be effective and therefore relatively aggressive inflation of the

airbag must be precipitated upon detection of an accident. Unfortunately, a

consequence of such relatively violent deployment of air bags is that an

occupant may be injured by the airbag itself due to unexpected occupant

positioning.

In view of the above, considerable effort has been made with regard to

diminishing the aggressive nature of airbag deployment. However, and

inherently, reduction in aggressive inflation will reduce deployment speed

and therefore may render the airbag, either fully or partially, ineffective.

It is an object of the present invention to provide an airbag which is

more adaptable to vehicle occupant unexpected positioning without

diminishing deployment speed. In accordance with the present invention there is provided an airbag for

a vehicle, the airbag comprising a plurality of bag compartments

sequentially coupled with valve vents therebetween to inflate, in use, in

succession a first bag compartment coupled to airbag inflation means in

order to deploy away from that inflation means with a control member

extending from radial portions of that first compartment to define a

deployment cone within which the other bag compartments are inflated

sequentially upon attainment of a predetermined gas pressure or volume in

previous, bag compartments in the succession.

Preferably, the control member is a fabric cover or net or tie straps

extending across the radial dimensions of the first bag compartment as it is

deployed under inflation. Furthermore, the control member may be

elastomeric or non-elastomeric or loose about the first bag compartment.

The control member may be secured to the first bag compartment or include

a shaped lip or overhang to contain the first bag compartment under

deployment.

Sequential deployment of respective bag compartments may be

dependent upon attainment of the predetermined gas pressure or volume in

the immediate previous bag compartment in the succession or all the

previous bag compartments in the succession. The valve vents between bag compartments may comprise one-way

pressure relief valves of a diaphragm type. Furthermore, the valve vents

may be located in walls of the bag compartment to provide indirect gas

pathways and so regulate deployment inflation or deflation to achieve

desired airbag deployment and/or inflation retention.

Typically, the first compartment will present a ring or doughnut under

inflation with the control member extending from the leading radial edge of

that ring or doughnut in order to define the deployment cone therebeneath.

The other bag compartments, i.e. not the first bag compartment may be

arranged in a stack along a common axis which extends from the inflation

means. Preferably, at least two such bag compartments will be located

within the deployment cone of the airbag in use.

An embodiment 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 cross-section of an airbag at a first stage with a

first airbag compartment inflated;

Figure 2 is a pictorial plan view of the airbag depicted in Figure 1; Figure 3 is a pictorial cross-section of an airbag in a second stage of

airbag deployment;

Figure 4 is a plan view of the airbag depicted in Figure 3;

Figure 5 is a pictorial cross-section of a fully deployed airbag; and

Figure 6 is a plan view of the airbag depicted in Figure 5.

An airbag is generally deployed from its airbag housing built into a

motor vehicle interior in a forward direction towards an occupant. However,

the airbag must present a relatively broad contact surface in order to fully

protect and engage an occupant during a traffic accident. Clearly, such

broad engagement requires a relatively voluminous airbag, both in terms of

the width of engagement and depth of the airbag to facilitate good occupant

protection.

Unfortunately, inflation with sufficient rapidity of a large voluminous

airbag necessitates a relatively aggressive gas inflation mechanism. Such

aggressive deployment can be relatively intolerant to occupant

misalignment from the expected and to variation in occupant type. For

example, if the occupant should be leaning out of their seat at the time of

collision or if the seat is unusually close to the airbag housing or a large/small adult is the occupant. It will be appreciated that airbag design

is based upon average occupant requirements and so deviations from those

predicted averages can precipitate occupant injury during the airbag

deployment itself.

In accordance with the present invention a multi-compartment airbag

is provided. Thus, in the drawings, an airbag 1 is illustrated sprouting

under deployment from an airbag housing 2 which is normally located

within a vehicle interior. In Figures 1 and 2, a first stage of airbag 1

deployment is depicted during which only a first bag component 3 is inflated

by airbag deployment apparatus 4 in the housing 2. Typically, this airbag

deployment apparatus 4 will comprise a gas inflation arrangement in which

a pyrotechnic solid propellant is ignited to rapidly produce gas for inflation

of the airbag 1.

During this initial first stage of airbag 1 deployment, inflation gas is

only provided to the first airbag compartment 3 in order to create a ring or

doughnut-like configuration as depicted in Figure 2. This ring is defined by

a control member 5 which controls radial expansion of the first airbag

compartment 3. Typically, the control member 5 will comprise a fabric

cover or net or tie straps between the radially expanding edges of the

compartment 3. Thus, a relatively broad engagement front is provided by

the airbag 1 upon which an occupant of a vehicle can be engaged. It will be appreciated that in this initial airbag inflation stage, only the

first airbag compartment 3 is deployed and this provides a more angular

approach to a vehicle occupant 6. Thus, for comparison it will be

appreciated that previous airbag deployments have substantially presented

an aggressive inflation in the direction of arrow head A straight at the

occupant 6 whilst, the present airbag initially propels the airbag in the form

of the first airbag compartment 3 in the direction of arrow heads B. Thus,

the occupant 6 is subjected to less of a frontal "punch" or assault from the

airbag, but rather an encompassing embrace with the control member 5

enveloping the front of the occupant 6.

Within the ring or doughnut configuration of the inflated first

compartment 3 a deployment cone 7 is defined. Furthermore, it will be

understood that the combination of the first airbag compartment 3 and the

control member δ will generally be insufficient to absorb occupant 6 energy

or protect that occupant 6 during a traffic accident. Thus, in accordance

with the present invention, this deployment cone 7 is filled with further

airbag compartments in a consecutive and sequential manner in order to

appropriately engage the occupant 6.

The initial inflation gas of the apparatus 4 is propelled into the

compartment 3 in the direction of arrow heads G in order to appropriately

rapidly inflate this compartment 3. When the compartment 3 is sufficiently inflated or upon sufficient pressurisation due to engagement with the

occupant 6, the vent valves 8 are opened or exposed in order to allow

inflation and so deployment of a second airbag compartment 9 into the

deployment cone 7.

Figures 3 and 4 illustrate the airbag 1 during inflation of the second

airbag compartment 9. It will be appreciated that the occupant 6, although

depicted as still in a displaced position relative to the airbag 1, will

generally by this stage impinge upon the control member 5 and therefore be

partly enveloped by the airbag 1. The occupant 6 and control member 5 are

shown separated for clarity.

It will be noted that the airbag deployment inflation gas from the

apparatus 4 passes through the first compartment 3 into the second

compartment 9 via the vents 8. Thus, there is an indirect inflation to the

second airbag compartment 9 which in itself regulates the speed or time

delay with which the second airbag 9 is inflated within the airbag

deployment sequence. As the second airbag 9 is inflated, it would be

appreciated that it more gradually moves towards the occupant 6 in order to

engage that occupant 6 than the first compartment 3 previously.

As the second airbag compartment 9 must fill the deployment cone 9, it

will be appreciated that generally the volume of inflation gas to achieve the same displacement length towards the occupant 6 in comparison with the

first compartment 3 will be greater. Thus, the speed with which the second

airbag 9 approaches the occupant 6 will be lower than the deployment speed

of the first compartment 3. Such less aggressive engagement with the

occupant 6 will be more acceptable in terms of diminishing the possibility of

airbag induced injury to the occupant 6.

It will be appreciated that the second airbag 9 in the embodiment

depicted in the drawing, will act as the sturdy or substantial base of the

airbag 1 with the first airbag 3 projecting outwardly from that sturdy base

of the second airbag compartment 9 in order to provide an embracing front

to the occupant 6. In such circumstances, normally the occupant 6 will, in

accordance with an idealised scenario, have contacted the control member 5

and after inflation of the second airbag compartment 9 will be arranged

whereby the chest of the occupant 6 is engaged by the compartment 9

whilst the shoulders of the occupant 6 are engaged by the first compartment

3. Upon such engagement, a final valve 10 is opened or exposed in order to

inflate a third airbag compartment 11 which fills the remaining volume of

the deployment cone 7. This third airbag compartment 11 essentially

compresses the occupant 6 into a vehicle seat to resiliently hold that

occupant 6 during the violence of a vehicle collision.

Figures 5 and 6 illustrate the airbag 1 in full deployment. It will be noted that the inflation gas from the airbag deployment

apparatus 4 passes through the first airbag compartment 3 into the second

airbag compartment 9 via vents 8 and then subsequently into the third

airbag compartment 11 through vent 10. Thus, inflation of the airbag

compartments 3, 9, 11 is consecutive and successive and furthermore

indirect in order to regulate airbag inflation rate as required. The third

airbag compartment 11 fills the remainder of the deployment cone 7 in order

to fully engage the occupant 6 and so provide protection during a traffic

accident,

Those skilled in the art will also appreciate that due to the indirect

labyrinthine inflation gas pathway through vents 8, 10 that deflation of the

airbag 1 will be reduced such that the occupant 6 may be protected for a

longer period from secondary collisions in a vehicle accident as the airbag 1

will remain substantially inflated for a longer period of time.

The purpose of the third airbag compartment 11 as indicated previously

is to provide final engagement with the occupant 6. However, it will be

appreciated due to the indirect nature of inflation via vents 8 and 10, that

the force or aggression of inflation for the third compartment 11 will be

significantly less than that for previous compartments 3, 9 in the

succession. This less aggressive inflation of the third compartment 11 should diminish the percussive shock to the occupant 6 of airbag 1

deployment and so injury to that occupant 6.

Normally, the vent 10 is located centrally within the wall between the

second compartment 9 and the third compartment 11 in order to propel

inflation gas directly towards the occupant 6. Such direct propulsion of the

inflation gas towards the occupant 6 imitates previous single airbag

compartment constructions but in the present airbag 1, it will be

appreciated that the force of inflation gas propulsion is diminished by the

indirect inflation route through the first compartment 3 and the second

compartment 9.

As indicated previously, a pyrotechnic gas generation mechanism is

generally used with regard to the airbag deployment apparatus 4. Such

pyrotechnically generated inflation gas is typically very hot. Thus, it will be

appreciated, that the cooling effects of indirect inflation to the final third

airbag compartment 11, which is that substantially in relatively long term

contact with the occupant 6, will again reduce potential problems of direct

contact of hot inflation gas with the occupant 6 with the inherent possibility

of burn injuries to that occupant 6.

A control element 5 is necessary in order to confine the first airbag

compartment 3 under inflation within a desired engagement front. It will be appreciated, that the first airbag compartment 3 is substantially

angularly projected from the housing 2 and so could easily be deflected over

a broader than desirable engagement front. The function of the control

member 5 is to limit and retain the engagement front presented to the

occupant 6. Typically, the control member 5, as indicated previously, could

comprise a fabric cover or net or straps extending from the peripheral

portions of the compartment 3. Furthermore, the control member 5 could be

elastic or fixed or loose as required. Thus, an elastic control member 5

would expand in accordance with its elastic limits to define the engagement

front. A fixed control member simply allows the compartment 3 to expand

until inhibited by the control member 5. A loose control member 5 would

simply act through friction in order to slow radial expansion until the airbag

1 engages the occupant 6 whereupon inflation of the second compartment 9

will begin with the inherent reduction in inflation gas to the first

compartment and so restrain broader engagement front development

through inflation gas lost by diversion to that compartment 9. It will also

be understood that the control member 5 could comprise a loose cover with

overhanging valence or shaped lips into which the first compartment 3

expands.

Normally, the vents 8, 10 will comprises one-way pressure relief valves

normally of a simple diaphragm type. Although single sequential compartments 3, 9, 11 are illustrated in the

drawings, it will be appreciated by those skilled in the art that a cascade of

airbag compartments could be envisaged whereby a single airbag

compartment could through appropriate vent valves feed two or more

subsequent compartments in order to best engage an occupant. Thus, a

third compartment 11 could be split into two parallel compartments about

the centre of the airbag 1 such that the second compartment 9 feeds both

such airbag compartments through respective vents. In such circumstances,

it will e appreciated that occupant 6 mis-alignment may be adjusted

through natural pressure equalisation between these two parallel airbag

compartments.

Although development of the first airbag compartment has been

described as a cone, it will be appreciated that other hollow funnel like

configurations such as a pyramid or other shape which presents a polygon or

oval base front for presentation to an occupant which tapers or narrows to a

more focused vertex upon which it is secured to the inflation mechanism,

could be used. Thus, those skilled in the art will appreciate that the term

cone includes these other configurations of the first airbag compartment.

In order to further define the first compartment additional control

members may be located within and across the 'cone' of that first compartment provided these control members do not interfere with

deployment of subsequent airbag compartments in the succession.

Claims

1. An airbag (1) for a vehicle, the airbag (1) comprising a plurahty of bag

compartments (3, 9, 11), the airbag (1) characterised in that the bag

compartments (3, 9, 11) are consecutively coupled with vents (8, 10)

therebetween to inflate in succession, a first bag compartment (3)

coupled to airbag inflation means (4) to sprout from that inflation

means (4) with a control member (5) extending from peripheral portions

of that first compartment (3) to define a deployment cone within which

the other bag compartments (9, 11) are inflated sequentially upon

attainment of a predetermined inflation gas pressure or volume in

previous bag compartments (3, 9, 11) in the succession.

2. An airbag (1) as claimed in Claim 1, wherein the control member (5) is

a fabric cover or a net or a plurality of tie straps.

3. An airbag (1) as claimed in Claim 1 or Claim 2, wherein the control

member (5) is fixed or elastic or loose.

4. An airbag (1) as claimed in any of Claims 1, 2 or 3, wherein the vents

(8, 10) are configured to operate dependent upon inflation gas pressure

or volume in the immediate previous bag compartment (3, 9, 11) in the

succession.

5. An airbag (1) as claimed in any preceding claim, wherein the vents (8,

10) comprise one-way pressure relief valves.

6. An airbag (1) as claimed in any preceding claim, wherein the vents (8,

10) are arranged within the airbag compartment (3, 9, 11) walls in

order to provide an indirect inflation gas path and so regulate airbag (1)

inflation to ensure proper deployment and/or inflation retention.

7. An airbag (1) as claimed in any preceding claim, wherein the first

airbag compartment (3) provides upon inflation, a ring or doughnut

configuration with the control member (5) extending from radial

peripheral portions of that first compartment (3).

8. An airbag (1) as claimed in any preceding claim, wherein airbag

compartments (9, 11), other than the first airbag compartment (3) are

stacked about a common axis of the airbag (1) extending from the

airbag inflation means (4).

9. A motor vehicle including an airbag (1) as claimed in any preceding

claim.