WO2003093071A1

WO2003093071A1 - An air-bag and a method of deploying an air-bag

Info

Publication number: WO2003093071A1
Application number: PCT/SE2003/000627
Authority: WO
Inventors: Dick Eriksson; Mikael ENÄNGER; Yngve Håland
Original assignee: Autoliv Development Ab
Priority date: 2002-05-01
Filing date: 2003-04-17
Publication date: 2003-11-13
Also published as: DE10392576T5; GB2388081B; GB2388081A; GB0210005D0; AU2003230481A1

Abstract

An overhead air-bag (1) has a mounting element (5) secured to the air-bag by means of a tear-seam (6) which is adapted to break on inflation of the air-bag, there being a gas flow-duct extending from the inflator into the interior of the air-bag and being adapted to be withdrawn from the air-bag on inflation thereof.

Description

An air-bag and a method of deploying an air-bag.

THE PRESENT INVENTION relates to an air-bag and more particularly relates to an air-bag intended to be mounted in the roof of a motor vehicle and adapted to move to a position in front of an occupant of the vehicle when an accident occurs.

Whilst it is convenient to provide an air-bag which is mounted in the roof of a motor vehicle, with the intention that the air-bag will, on inflation thereof, move to a position in front of an occupant of the vehicle, difficulties can arise with such air-bags since there is a risk that as the torso and head of the occupant of the vehicle to be protected by the air-bag moves forwardly during an impact situation, the air-bag itself may impart an undesirable force to the head of the occupant, thus forcing the head backwards relative to the torso and causing neck injuries.

The present invention seeks to provide an improved air-bag arrangement.

According to this invention there is provided an air-bag adapted to be used as an overhead air-bag in a motor vehicle, the air-bag having at least one mounting element secured to the air-bag by means of a tear-seam which is adapted to break on inflation of the air-bag, the mounting element being adapted to co-operate with a mounting arrangement provided on the motor vehicle to mount the upper part of the air-bag in position, the air-bag being associated with an inflator arrangement, there being at least one gas flow duct for gas from the inflator arrangement, the gas flow duct extending into the interior of the air-bag and being adapted to be withdrawn from the air-bag on inflation thereof, subsequent to the breaking of the tear-seam.

Preferably the gas flow duct extends from the exterior of the air-bag to the interior of the air-bag through an aperture formed in the air-bag and has a free end within the air-bag, the duct thus being adapted to be completely withdrawn from the air-bag.

Conveniently the aperture is provided with a valve to at least partially seal the aperture when the duct is completely withdrawn from the air-bag.

Preferably the part of the air-bag which is to form the lowermost part of the air-bag on deployment thereof is provided with at least one lower tear-seam or strap adapted to initially restrict the degree of inflation of the lower part of the air-bag and adapted to break during inflation of the air-bag.

Conveniently the tear-seam connecting the mounting lug to the air-bag is adapted to break when a first relatively low pressure is reached within the interior of the air-bag and the lower tear-seams are adapted to break when a higher pressure is present within the air-bag.

Preferably the lower pressure is between 20-30 kPa and the higher pressure is between 40-50 kPa. Conveniently a central part of the air-bag is provided with stitching or strapping in order to minimise the dimension of that part of the air-bag on inflation thereof.

Advantageously the inflater arrangement is adapted to provide a relatively low flow rate of gas during an initial stage of inflation of the air-bag and a higher flow rate of gas during a subsequent stage of inflation of the air- bag.

The invention also relates to an air-bag as described above when in a folded condition, the lower part of the air-bag being rolled, and the upper part of the air-bag being zig-zag or concertina folded, the said gas supply duct having an opening within the concertina folded section of the air-bag.

The invention also relates to a method of deploying an air-bag, the air- bag having an upper part provided with a mounting element connected to the air-bag by means of a first tear-seam and which mounts the air-bag in position, the air-bag having a lower part provided with at least one lower tear-seam or strap to control the deployment of the air-bag, the method of deploying the air- bag comprising the steps of injecting gas into the air-bag such that a substantial proportion of the gas flows to the lower part of the air-bag and inflates the lower part of the air-bag without bursting the tear-seams, with the gas then flowing to the upper part of the air-bag to inflate the upper part of the air-bag and burst the tear-seam associated with the mounting element, the flow of gas then serving to increase pressure within the air-bag to burst the in each lower tear-seam or strap.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIGURE 1 is a perspective view of an air-bag in accordance with the invention prior to folding thereof,

FIGURE 2 is a diagrammatic front view of the air-bag of Figure 1 provided for explanatoiy purposes, illustrating gas flows within the air-bag on deployment thereof,

FIGURE 3 is a diagrammatic sectional view taken on the line A-A of Figure 2 illusfrating the bag in the stored condition before deployment,

FIGURE 4 is a view corresponding to Figure 3 illustrating the condition of the bag at an initial stage during deployment,

FIGURE 5 is a view corresponding to Figure 4 showing the bag at a subsequent stage in deployment,

FIGURE 6 is a view corresponding to Figure 5 showing the bag in a later stage of deployment,

FIGURE 7 is a view corresponding to Figure 6 illusfrating the bag in a final stage of deployment, and

FIGURE 8 is a diagrammatic view of a flap valve.

Referring initially to Figure 1 of the accompanying drawings, an air-bag 1 is formed from two superimposed layers of fabric defining a rear face 2 and a front face 3. The air-bag, as illustrated, is of generally rectangular form. The air-bag is an overhead air-bag. At the uppermost edge 4 of the air-bag, a mounting tab 5 is provided. The mounting tab 5 is a tab formed of fabric which is secured to the main body of the air-bag by means of tear-seams 6. The mounting tab 5 may be engaged with a mounting arrangement such as a hook or mounting bar provided in the roof of the motor vehicle, as will become clear from the following description, to mount the air-bag 1 in position witliin the vehicle. The tear-seams 6 are designed so that they will break when the pressure within the air-bag passes a first threshold, that threshold preferably being in the region of 20 to 25 kPa, or in the region of 20 to 30 kPa. The mounting tab 5 is then released from the hook or bar. Thus the mounting tab 5 forms a releasable mounting for the upper part of the air-bag which becomes released in response to inflation of the air-bag.

Provided near the upper edge 4 of the air-bag 1 are two gas inlet holes 7,

8. A respective gas supply duct 9, 10 is inserted through each of the holes 7, 8. The gas supply duct extends into the interior of the air-bag, and terminates with a free end located within the interior of the air-bag. The free end is the end of the duct within the air-bag, this end of the duct not being connected to the air- bag. It is desnable for the gas ducts 9, 10 to be foimed of a stiff but flexible material. The material utilised may thus be much stiffer than the material utilised for an ordinary air-bag, and indeed may be formed of material similar to that used in the fabrication of fire hoses. It is preferred that the material is such that the gas inlet ducts 9, 10 have a degree of rigidity, although the ducts should not be completely rigid but should be able to flex. Also the ducts 9, 10 should be capable of being folded so that the complete air-bag may be folded compactly to be stored in a housing. Within a central region of the air-bag 1 the rear fabric layer 2 and the front fabric layer 3 are interconnected by stitching or strapping 11. The stitching or strapping 11 is provided so that when the air-bag is inflated the central region of the air-bag has a thickness which is determined by the length of the stitching or strapping.

The lowermost part of the air-bag is provided with a re-entrant tuck or fold 12, resembling a gusset formed by the bottom of the air-bag, which effectively forms two "wings" at the lowermost part of the air-bag, these wings being interconnected by a tear-seam 13 at the very lowest part of the air-bag. A further tear-seam 14 is provided extending parallel with the lower part of the air-bag at a position above the re-entrant tuck or fold 12. The tear-seams 13 and 14 at the lowermost part of the air-bag are designed so that they initially restrict the degree of inflation of the lower part of the air-bag. However, the tear-seams 13 and 14 are such that they will break when the pressure within the bag passes a second threshold, which is higher than the first threshold, typically being in the region of 40 to 50 kPa. The lower part of the air-bag may then inflate fully.

Referring now to Figure 2, it is intended that the gas supply ducts 9, 10 should be comiected to a gas supply manifold 15 which contains or is associated with a gas generator or inflator 16. It is envisaged that, on inflation of the air-bag, initially gas will flow through the gas flow ducts 9, 10 and, because of the location of the gas flow ducts within the air-bag 1, after a preliminaiy stage during the inflation gas will be caused to flow downwardly past the strap area 11 towards the lowermost part of the air-bag. The lowermost part of the air-bag will inflate to a restricted degree. Gas will then flow upwardly during the next stage of inflation of the air-bag to inflate the upper part of the air-bag. As the upper part of the air-bag inflates so the tear- seam 6 which connects the mounting tab 5 to the main part of the air-bag will break. Thus the main part of the air-bag will then no longer be connected by the connecting tab 5 to the vehicle. As will be described below in greater detail, the pressure within the air-bag will continue to rise until the second threshold is reached and the tear-seams 13, 14 in the lower part of the air-bag break, enabling the lower part of the air-bag to inflate fully whilst simultaneously the main part of the air-bag may then move downwardly, with the gas supply ducts 9 and 10 being slidably withdrawn from the air-bag until it is completely withdrawn. The free end of each duct is no longer within the air- bag. Thus, in the described embodiment, the air-bag may become totally free and totally disconnected from the rest of the vehicle. When this happens there is no physical connection between the air-bag and the vehicle.

The precise pressure at which the tear-seams 13 and 14 break may be selected in dependence upon the desired inflation chaiacteristic of the air-bag. For example, the upper-most of these two seams, the seam 14, may break at a relatively low pressure so that the lower part of the air-bag may partially inflate to provide a certain degree of protection at a relatively early stage, the lowermost seam, seam 13, only breaking at a relatively high pressure.

Referring now to Figure 3 of the accompanying drawing, it is to be appreciated that when the air-bag 1 is mounted in position in a motor vehicle the air-bag is received within a recess or housing 20 provided within the roof 21 of a motor vehicle. The mounting tab 5 engages a hook or bar within the recess or housing 20. The lowermost part of the air-bag is rolled, and more particularly is rolled in a sense as if it was being rolled from the front of the vehicle, to form a rolled portion 22. The uppermost part of the air-bag is zigzag or concertina folded, to form a "concertina" section 23. The gas flow ducts 9, 10 either have their open ends within the concertina section 23 or, alternatively, have apertures in the side walls thereof which communicate with the concertina section 23.

It is to be appreciated that on actuation of the gas generator 16 within the gas supply manifold 15, gas will flow into the gas supply ducts 9 and 10. That gas will initially be injected into the concertina section 23 of the folded air-bag. The concertina section will immediately begin to expand, thus forcing the rolled section 22, still in a rolled condition, downwardly. The lowermost part of the housing 20, which is constituted by two doors 24, 25, bursts open and the rolled section 22 emerges from the roof of the vehicle to fall downwardly in front of the occupant to be protected by the air-bag as the concertina section 23 becomes inflated. After inflation of the concertina section 23 the rolled section 22 will begin to inflate, with the rolled section 22 umOlling, again as if towards the front of the vehicle. Gas then flows into the interior of the air-bag as described above with reference to Figure 2. The air- bag then reaches the condition as shown in Figure 5 in which the air-bag extends fully down from the recess or housing 20. The combination of the tear- seams 13, 14 provided at the lower part of the bag and the straps 11 ensure that the air-bag. as it moves downwardly, has a restricted "thickness" as measured axially of the vehicle. This helps ensure that the air-bag is deployed to an appropriate position in front of the occupant to be protected even if that occupant is leaning forward or "out of position".

When the rolled section 22 has become fully unrolled, pressure will begin to rise in the air-bag and when the pressure is in the region of 20 to 25 kPa or 20 to 30 kPa, the tear-seam 6 will break, thus discoimecting the mounting tab 5 from the main part of the air-bag 1. The air-bag 1 is itself now no longer connected to the vehicle, as the gas ducts 9, 10 merely extend through holes 7, 8 into the interior of the air-bag and do not provide a firm connection. At this stage the gas supply ducts 9, 10 still extend into the interior of the air-bag 1, but the gas ducts are only inserted through apertures in the air- bag 1, and so the air-bag 1 can move away from the housing 20 while the gas ducts 9, 10 are being withdrawn from the air-bag.

The pressure within the air-bag will rise, until a pressure in the region of 40 to 50 kPa is achieved, when the tear-seams 13, 14 in the lower part of the air-bag will break. The lower part of the air-bag then fully inflates.

In a modified embodiment the seam 14 may break at a pressure within the range of 15 to 30 kPa so that the lower part of the air-bag may inflate at an early stage.

As an occupant 26 to be protected by the air-bag moves forwardly and impinges with the air-bag, the occupant may impart a generally forward and generally downward force to the air-bag. If a generally downward force is applied to the air-bag the entire air-bag is free to move downwardly, with the gas supply ducts being completely withdrawn from the air-bag. Thus, as shown in Figure 7, the air-bag 1 may become totally disconnected from the rest of the vehicle. The air-bag will, of course, be located between the occupant of the vehicle and the structure of the vehicle located in front of that occupant. The structure may be the steering wheel, if the occupant is the driver, or the dashboard if the occupant is a front seat passenger. Alternatively, the structure may be the front seats of the vehicle if the occupant is a rear seat occupant.

The inflated air-bag forms a "cushion" between the occupant and the structure of the vehicle in front of the occupant. The apertures 7 and 8, from which the gas supply ducts 9 and 10 have been withdrawn, act as venting apertures although, if desired, non return or "flap" valves 27 as shown in Figure 8 may be provided within the air-bag which serve to seal, or at least reduce the flow of gas through, these apertures once the gas supply ducts 9 and 10 have been withdrawn from them. The flap valve 27 shown in Figure 8 is associated with the aperture 9. The flap is secured to the fabric of the air-bag 1 adjacent the aperture 9 and is configured so that when the gas duct 9 is withdrawn from the air-bag the flap valve 27 will move to a position in which it at least substantially seals the aperture 7.

In a preferred embodiment of the invention, the gas generator 16 may be adapted such that during the initial stage of deployment, during which the concertina section 23 is being inflated, the gas generator only provides a relatively low flow rate of gas, and during the subsequent stage of inflation, when the rolled region is being unrolled and inflated, a much higher flow of gas is provided. This may be achieved by using two gas generators which are actuated sequentially, the first gas generator being a relatively "gentle" gas generator and a second gas generator, which is actuated a predeteimined period of time after actuation of the first gas generator, being more aggressive.

Whilst the invention has been described with reference to an embodiment in which there is a single gas generator 16 and a gas supply manifold 15 supplying gas to the two gas supply ducts, a separate gas generating arrangement may be provided for each gas supply duct. In a further modified embodiment of the invention there is only one gas supply duct.

In certain embodiments the lower tear-seams 13, 14 may be replaced by internal tear straps which limit the initial degree of inflation of the lower part of the air-bag and which break when a predeterrnined internal pressure is achieved. In the present Specification "comprises" means "includes or consists of and "comprising" means "including or consisting of.

Claims

CLAIMS:

1. An air-bag adapted to be used as an overhead air-bag in a motor vehicle, the air-bag having at least one mounting element secured to the air-bag by means of a tear-seam which is adapted to break on inflation of the air-bag, the mounting element being adapted to co-operate with a mounting arrangement provided on the motor vehicle to mount the upper part of the air-bag in position, the aή-bag being associated with an inflator arrangement, there being at least one gas flow duct for gas from the inflator arrangement, the gas flow duct extending into the interior of the air-bag and being adapted to be withdrawn from the air-bag on inflation thereof, subsequent to the breaking of the tear-seam.

2. An air-bag according to Claim 1 wherein the gas flow duct extends from the exterior of the air-bag to the interior of the air-bag through an aperture foi ed in the air-bag and has a free end within the air-bag, the duct thus being adapted to be completely withdrawn from the air-bag.

3. A air-bag according to Claim 2, wherein the aperture is provided with a valve to at least partially seal the aperture when the duct is completely withdrawn from the air-bag.

4. An air-bag according to any one of the preceding Claims wherein the part of the air-bag which is to form the lowermost part of the air-bag on deployment thereof is provided with at least one lower tear-seam or strap adapted to initially restrict the degree of inflation of the lower part of the air- bag and adapted to break during inflation of the air-bag.

5. An air-bag according to any one of the preceding Claims wherein the tear-seam connecting the mounting lug to the air-bag is adapted to break when a first relatively low pressure is reached within the interior of the air-bag and the lower tear-seams are adapted to break when a higher pressure is present within the air-bag.

6. An air-bag according to Claim 5 wherein the lower pressure is between 20-30 kPa and the higher pressme is between 40-50 kPa.

7. An air-bag according to any one of the preceding Claims wherein a central part of the air-bag is provided with stitching or strapping in order to lrunimise the dimension of that part of the air-bag on inflation thereof.

8. An air-bag according to any one of the preceding Claims, wherein the inflator arrangement is adapted to provide a relatively low flow rate of gas during an initial stage of inflation of the air-bag and a higher flow rate of gas during a subsequent stage of inflation of the air-bag.

9. An air-bag according to any one of the preceding Claims when in a folded condition, the lower part of the air-bag being rolled, and the upper part of the air-bag being zig-zag or concertina folded, the said gas supply duct having an opening within the concertina folded section of the air-bag.

10. A method of deploying an air-bag, the air-bag having an upper part provided with a mounting element connected to the air-bag by means of a first tear-seam and which mounts the air-bag in position, the air-bag having a lower part provided with at least one lower tear-seam or strap to control the deployment of the air-bag, the method of deploying the air-bag comprising the steps of injecting gas into the air-bag such that a substantial proportion of the gas flows to the lower part of the air-bag and inflates the lower part of the air- bag without bursting the tear-seams, with the gas then flowing to the upper part of the air-bag to inflate the upper part of the air-bag and burst the tear-seam associated with the mounting element, the flow of gas then serving to increase pressure within the air-bag to burst the in each lower tear-seam or strap.