WO2008130286A1

WO2008130286A1 - An airbag module

Info

Publication number: WO2008130286A1
Application number: PCT/SE2007/000384
Authority: WO
Inventors: Andreas Freimüller; Thomas Wienecke
Original assignee: Autoliv Development Ab
Priority date: 2007-04-23
Filing date: 2007-04-23
Publication date: 2008-10-30
Also published as: DE112007003431T5; DE112007003431B4

Abstract

An airbag module comprising an airbag 21 and an inflator 8. The airbag 21 defining an inflator chamber 22 having an inlet aperture 23 arranged to receive inflating glass from the inflator 8 upon activation of the inflator 8. The module further comprising a retainer 24 positioned within the inflator chamber 22. A holding 15 is secured relative to the inflator 8 and configured to hold the retainer 24 relative to the inflator 8 during activation of the inflator 8.

Description

Title: An Airbag Module

Description of Invention

THIS INVENTION relates to an airbag module suitable for use as part of a safety device in a motor vehicle. A preferred embodiment of the invention relates to an airbag module in which the airbag is vacuum packed.

It is known to mount an airbag module in a motor vehicle, for example to the steering wheel of a motor vehicle, so that, in the event of a crash situation, the airbag may be inflated out from the airbag module to offer a level of protection to the driver or passenger of the motor vehicle.

In such airbag modules, an airbag is provided in an initially tightly packed configuration and in fluid communication with an inflator, such that the airbag is inflated when the inflator is activated upon receipt of a signal from a sensor, the signal being indicative of an actual or anticipated crash situation. Typically, the airbag and inflator are provided in a housing and the airbag is held in position, during activation of the inflator, by being clamped in the region of its gas inlet aperture, between a retainer ring and the housing. The retainer ring can take the form of a flange carried by the inflator, and is typically secured to a region of the housing by nuts and bolts or the like.

There is an increasing need for airbag modules, particularly those mounted in the steering wheel of a motor vehicle, to become smaller and smaller to meet the demands of car manufacturers wishing to introduce increasingly stylish and space efficient interior trims to the motor vehicles. It is conventional for airbag modules to incorporate an initially tightly packed airbag. A packed airbag of this type is often provided with a flexible wrapper that is useful to maintain the airbag in its tightly packed folding prior to the addition of a hard cover, and also to provide protection from external elements. These tightly packed folded airbags, however, provide airbag modules that are still relatively large and can be difficult to insert into the housing of a motor vehicle.

In order to provide even smaller airbag modules, methods of packaging the airbag using vacuum-packing have been proposed, such as that disclosed in US2002/0135160-A1. The vacuum-packing of the airbag further reduces the overall dimensions of the airbag package, thereby enabling even smaller airbag modules to be produced. The nature of a vacuum-packed airbag arrangement necessitates the use of a hermetically sealed wrapper around the airbag to maintain the pressure within the sealed wrapper below atmospheric pressure. Again, as with the folded airbag arrangements discussed above, the sealed wrapper provides additional protection to the airbag.

A problem that arises with vacuum-packed airbag modules is that, conventional clamping to secure the airbag to the inflator requires one or more retaining elements to pass through the sealed wrapper, making it difficult to maintain the hermetic seal. If the hermetic seal, and hence the vacuum-packing, cannot be maintained, there will be an undesirable increase in the spatial dimensions of the airbag module. This can also lead to undesirable contamination of the airbag by external elements/factors.

It is an object of the present invention to provide an improved an airbag module.

According to the present invention there is provided an airbag module comprising an airbag, and an inflator, the airbag defining an inflatable chamber having an inlet aperture arranged to receive inflating gas from the inflator upon activation of the inflator, the module further comprising a retainer positioned within the inflatable chamber, and a holder secured relative to the inflator and being configured to hold the retainer relative to the inflator during activation of the inflator.

Advantageously, the holder is positioned outside the inflatable chamber.

Preferably, the holder defines an aperture through which part of the airbag extends, but through which the retainer will not pass.

More preferably, the retainer is secured to the airbag.

Conveniently, the retainer is positioned around the periphery of the inlet aperture. Advantageously, the retainer is in the form of a ring.

Conveniently, the retainer is secured to the airbag by extending through loops and/or holes provided in the inflatable chamber.

Preferably, the airbag is packaged within a flexible wrapper.

More preferably, the wrapper is substantially hermetically sealed around the airbag.

Conveniently, the inflator and holder are positioned outside of the wrapper.

Advantageously, the airbag and wrapper are vacuum-packed such that the pressure within the sealed wrapper is below atmospheric pressure.

Preferably, the wrapper is plastic foil.

Advantageously, the holder is releasably secured relative to the inflator.

Conveniently, the airbag module further comprises a housing in which the holder and inflator are secured.

So that the invention may be more readily understood, and so that further features of the invention may be appreciated, an embodiment of the invention is described below, by way of example, with reference to the accompanying drawings, in which:

FIGURE 1 shows a schematic sectional view of an embodiment of an airbag module in accordance with the present invention, prior to activation,

FIGURE 2 shows a view generally similar to that of figure 1, during an early stage of activation, and FIGURE 3 shows a further view, generally similar to that of figures 1 and 2, during a subsequent stage of activation.

Figure 1 illustrates an airbag module 1 comprising a housing 2 configured to be mounted to part of the structure of a motor vehicle, for example the central hub of a steering wheel (not shown). The housing 2 can be metal or made from plastics material and has a substantially planar base 3 and an upwardly directed peripheral side wall 4. The base 3 has a central aperture 5 to accommodate part of an inflator, as will be described below. A plurality of fixing apertures 6 are formed through the base 3 at spaced-apart positions around the central aperture 5, to allow an inflator to be fixed to the base 3. A plurality of apertures 7 are also formed at spaced-apart positions through the side wall 4.

An inflator 8 is provided, preferably taking the form of a conventional gas generator for inflating airbags, having a generally cylindrical shape with a plurality of gas-outlet ports 9 provided at radially-spaced positions around the upper end 10 of the inflator 8. Substantially half way down the length of the inflator 8 is an outwardly directed peripheral flange 11. A plurality of fixing apertures 12 are formed at spaced apart positions around the flange 11. The fixing apertures 12 configured for alignment with respective fixing apertures 6 formed through the base 3 of the housing 2.

The lower part 13 of the inflator 8 is received through the aperture 5 of the housing 2, such that the flange 11 overlies and bears against the upper surface of the base 3. The inflator is rotationally positioned relative to the housing 2 such that the fixing apertures 12 are aligned with the fixing apertures 6 formed in the base 3. The inflator 8 is then secured to the housing 2 by way of a plurality of nut and bolt fasteners 14 passing through each pair of aligned apertures 6,12. When mounted, the gas outlet ports 9 are located within the housing 2 and above the base 3.

A holder 15 is provided, having a generally annular shape with an "L-" shaped radial cross-section. The "L" shaped cross section comprises a securing portion 16 in the form of a substantially vertical peripheral wall, and a holding portion 17 which is arranged so as to extend inwardly from the upper region of the securing portion 16. The external dimensions of the securing portion 16 are proportioned to be slightly smaller than the internal dimension of the housing 2, between the side walls 4. The securing portion 16 has a plurality of fixing apertures 18 positioned radially around the holder 15, these apertures being configured for alignment with respective apertures 7 formed through the side wall 4. The holder 15 is received within the housing 2 and secured thereto by aligning the apertures 7 in the side wall 4 of the housing 2 with the fixing apertures 18 in the securing portion 16 of the holder 15 and fixing a nut and bolt arrangement 19 through the apertures 7, 18. When secured in the housing 2, in the orientation of the airbag module illustrated in figure 1, the holding portion 17 is positioned in a generally horizontal plane. The holding portion 17 defines a relatively large central holding aperture 20 having a diameter d, through which the upper region 10 of the inflator extends.

The airbag module 1 further comprises an airbag 21 of generally conventional construction, most preferably made from a woven fabric material. The airbag 21 is folded to reduce the overall dimensions of the airbag 21. The airbag 21 defines an interior chamber 22 having a lower region that tapers to a throat, the lower part of which defines an inlet aperture 23. The throat of the airbag 21 is received through the holding aperture 20 and the inlet aperture 23 is generally positioned around the inflator 8, below the gas outlet ports 9.

A retainer 24 is provided within the inflatable chamber 22 of the airbag 21 and which, in the orientation of the airbag module illustrated in figure 1, is positioned immediately below the holder 15, between the holding aperture 20 and the base 3 of the housing 2. The retainer 24 shown in figure 1 is in the form of a ring positioned around the periphery of the inlet aperture 23 such that the retainer 24 is substantially below the gas outlet ports 9. The retainer 24 is secured to the airbag 21 by rivet, bolt or the like 25. The retainer 24 has a diameter D which is greater than the diameter, d, of the holding aperture 20, which prevents the passage of the retainer through the holding aperture so as to limit movement of the inlet aperture 23 away from the inflator 8 upon activation of the inflator 8, thereby effectively holding the retainer 24 (and inlet aperture 23) relative to the inflator. The folded airbag 21 is packaged in a flexible wrapper 27 that is substantially hermitically sealed around the airbag 21, such that the wrapper 27 passes through the holding aperture 20 and forms a recess 28 to accommodate the part of the inflator 8 located in the housing 2, which is substantially below the airbag 21. The airbag 21 and the wrapper 27 are vacuum-packed such that the pressure within the sealed wrapper is below atmospheric pressure. The wrapper 27 is preferably a plastic foil.

The airbag module 1 further comprises a cover 29 mounted to the housing 2. The cover 29 is configured to allow deployment of the air-bag 21 from within the housing 2. For example, the cover may be provided with one or more split lines (eg as shown at 30) which are configured to split upon inflation of the air- bag 21 so that an opening is provided in the cover 29 through which the air- bag 21 can inflate.

Figures 2 and 3 show an airbag, of the preferred embodiment of the invention illustrated in figure 1, during an early stage and subsequent stage of activation of the inflator upon receipt of a signal from a sensor indicative of an actual or anticipated crash situation.

As shown in figure 2, during the early stage of activation, inflating gas is released from the gas outlet ports 9 of the inflator 8, into the recess 28. The inflating gas may have an initial high temperature that melts the wrapper 27 present within the recess 28, or, alternatively, the substantial pressure of the inflating gas may simply burst the wrapper 27 in this region. This effectively breaks the seal of the wrapper 27, as shown in figure 2.

Once the seal of the wrapper has been broken, the inflating gas, which is released from the gas outlet ports 9 with a substantial pressure, is directed into the inflatable chamber 22 through the inlet aperture 23. As the airbag 21 is inflated, and the pressure within the airbag module 1 reaches a predetermined level, the split line 30 of the cover 29 splits to allow further inflation of the airbag 21 during which the upper region of the wrapper 27 is forcedly split open to allow substantially unrestricted inflation of the airbag 21, as illustrated schematically in figure 3 with the cover omitted for clarity. As describe above, the diameter D of the retainer 24, is greater than the diameter, d, of the holding aperture 20, which means that during activation of the inflator, the retainer 24 cannot pass through the holding aperture 20. This arrangement ensures that during activation, and despite the substantial pressure of the inflating gas, the inlet aperture 23 of airbag 21 maintains its position relative to the inflator 8. The arrangement also maintains the position of the airbag 21 and wrapper 27 prior to activation of the inflator 8, without breaking the seal of the wrapper.

Whilst the invention has been described above with reference to a specific embodiment, it is to be appreciated that modifications could be made without departing from the scope of the invention. For example, whilst in the preferred embodiment outlined above, the retainer 24 is secured to the airbag 21 by a rivet, bolt or the like 25, in other embodiments the retainer 24 could be secured to the airbag 21 by extending through loops and/or holes provided in the inflatable chamber 22. Such loops and/or holes may be provided in the fabric of the airbag 21 itself.

Whilst in the preferred embodiment outlined above, the holder 15 is secured to the housing 2 by a nut and bolt arrangement 14 through aligned apertures 6,12, in other embodiments the holder 15 could be releasably secured. For example, the holder 15 may be secured using a bayonet or hook-and-window fixation.

In other embodiments, the airbag 21 and sealed wrapper 27 may not necessarily be vacuum-packed. In alternative embodiments, the airbag 21 is packaged in an un-sealed wrapper. In further embodiments, the airbag 21 is not packaged in a wrapper.

In a further embodiment of the invention the airbag 21 may be a normal driver airbag with extra layers of fabric around the inlet aperture 23 for reinforcement. Moreover, the airbag 21 may be a passenger, knee or side airbag. When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. An airbag module comprising an airbag (21), and an inflator (8), the airbag (21) defining an inflatable chamber (22) having an inlet aperture (23) arranged to receive inflating gas from the inflator (8) upon activation of the inflator (8), the module further comprising a retainer (24) positioned within the inflatable chamber (22), and a holder (15) secured relative to the inflator (8) and being configured to hold the retainer (24) relative to the inflator (8) during activation of the inflator (8).

2. An airbag module according to Claim 1 wherein the holder (15) is positioned outside the inflatable chamber (22).

3. An airbag module according to Claim 2 wherein the holder (15) defines an aperture (20) through which part of the airbag (21) extends, but through which the retainer (24) will not pass.

4. An airbag module according to any preceding claim wherein the retainer (24) is secured to the airbag (21).

5. An airbag module according to any preceding claim wherein the retainer (24) is positioned around the periphery of the inlet aperture (23).

6. An airbag module according to any preceding claim wherein the retainer (24) is in the form of a ring.

7. An airbag module according to any one of Claims 4 to 6 wherein the retainer (24) is secured to the airbag (21) by extending through loops and/or holes provided in the inflatable chamber (22).

8. An airbag module according to any preceding claim wherein the airbag (21) is packaged within a flexible wrapper (27).

9. An airbag module according to Claim 8 wherein the wrapper (27) is substantially hermetically sealed around the airbag (21).

10. An airbag module according to Claim 9 wherein the inflator (8) and holder (15) are positioned outside of the wrapper (27).

11. An airbag module according to Claim 9 or 10 wherein the airbag (21) and wrapper (27) are vacuum-packed such that the pressure within the sealed wrapper (27) is below atmospheric pressure.

12. An airbag module according to any one of Claims 8 to 11 wherein the wrapper (27) is plastic foil.

13. An airbag module according to any preceding claim wherein the holder (15) is releasably secured relative to the inflator (8).

14. An airbag module according to the preceding claim further comprising a housing (2) in which the holder (15) and inflator (8) are secured.