WO2018007311A1

WO2018007311A1 - Airbag apparatus

Info

Publication number: WO2018007311A1
Application number: PCT/EP2017/066488
Authority: WO
Inventors: Richard Brown; Bill FENG; Gareth STOKES
Original assignee: Jaguar Land Rover Limited
Priority date: 2016-07-07
Filing date: 2017-07-03
Publication date: 2018-01-11
Also published as: GB201611855D0; GB2552146A; GB2552146B

Abstract

The present disclosure relates to an airbag assembly (4) for an airbag module (1) disposed 5 in a vehicle (2). The airbag assembly includes a primary bag (7) and a secondary bag (8) disposed on the primary bag (7). A primary surface (12) is formed by the primary bag (7); and an annular restraint (6) is formed by the secondary bag (7) and configured to control rotation of the vehicle occupant's head. The airbag assembly (4) is configured such that the annular restraint (6) projects relative to said primary surface (12) when the airbag assembly 10 (4) is inflated. The present disclosure also relates to an airbag module (1) incorporating an airbag assembly (4). The present disclosure also relates to a vehicle (2) incorporating an airbag assembly (4) and/or an airbag module (1).

Description

AIRBAG APPARATUS TECHNICAL FIELD

The present disclosure relates to an airbag apparatus. Particularly, but not exclusively, the present disclosure relates to an airbag assembly; to an airbag module comprising an airbag assembly; and to a vehicle comprising an airbag module.

BACKGROUND

During a frontal crash test of an automobile, the head of the anthropomorphic test device (ATD) (also referred to as a "crash test dummy") in the driver's seat can sometimes contact the driver airbag (DAB) in such a way that it moves laterally off the DAB, or may roll over the airbag surface. Both linear (straight-line) motion and rotational motion of the head are measured. The rotational motion may be about one or more of the three principal axes, namely: rotation about the head longitudinal X axis (referred to as "twisting"), rotation about the head transverse Y axis (referred to as "nodding"), and rotation about the head vertical Z axis (referred to as "shaking"). In the case of head rotation, the Br|C (Brain Rotational Injury Criterion) measures the rotation of the head of the ATD about said principal axes, and is influenced by the relationship between the head and the driver and curtain airbags. Known DABs conventionally present a smooth surface and resistance to sideways and rolling movement of the head of the ATD with respect to the DAB is dependent on friction. This may cause the head to rotate on the DAB (a shaking mode). Alternatively, or in addition, the head may slide off the DAB (a nodding motion). The head of the ATD may also contact a side curtain airbag (CAB) causing rotation either towards, or away from the DAB. Controlling this behaviour is complex, and involves many different elements of the vehicle restraint system design. The behaviour may occur in load cases that incorporate a sideways component of vehicle motion, including oblique and offset load cases, but can also occur in other crash laboratory tests carried out in all world markets. Key tests are found in the USNCAP (NCAP), EuroNCAP, FMVSS, European legal requirements, and other world legal and consumer test regimes.

It is against this backdrop that the present invention has been conceived. At least in certain embodiments the present invention seeks to overcome at least some of the shortcomings or problems associated with prior art airbags. SUMMARY OF THE INVENTION

Aspects of the present invention relate to an airbag assembly, an airbag module and a vehicle as claimed in the appended claims. According to a further aspect of the present invention there is provided an airbag assembly for a vehicle, the airbag assembly comprising:

a primary bag;

a secondary bag disposed on the primary bag;

a primary surface formed by the primary bag; and

an annular restraint formed by the secondary bag and configured to control rotation of a vehicle occupant's head;

wherein the airbag assembly is configured such that the annular restraint projects relative to said primary surface when the airbag assembly is inflated. In use, the primary surface is the surface of the airbag assembly adapted to be contacted by the vehicle occupant. When the airbag assembly is inflated the primary surface is deformable and may receive at least a portion of the vehicle occupant's head. The airbag assembly is operative to provide a cushion for the vehicle occupant, for example in the event of an impact or collision. The primary surface may decelerate the vehicle occupant. The primary surface is occupant- facing and the annular restraint is configured to project towards the vehicle occupant when the airbag assembly is inflated. The airbag assembly may be configured such that the annular restraint projects towards the vehicle occupant. When inflated, the annular restraint may establish a recess or depression in the airbag assembly suitable for receiving at least a portion of the vehicle occupant's head. The recess is effective to reduce rotation and/or lateral movement of the vehicle occupant's head. At least in certain embodiments the annular restraint may provide improved resistance to lateral and/or rolling motion. The effect is especially relevant for load cases containing a sideways component of motion. By providing an annular restraint on the airbag assembly, the airbag assembly can aid management of lateral and/or rolling movement of the vehicle occupant's head. The annular restraint may also control sliding of the vehicle occupant's head relative to the primary surface.

The airbag assembly may be arranged such that full deployment of the secondary bag occurs at substantially the same time a full deployment of the primary bag.

The airbag assembly may be arranged such that the secondary bag deflates at a slower rate than the primary bag. The airbag assembly may be mounted to a steering wheel of the vehicle. In this arrangement, the use of an annular restraint is advantageous since its function is independent of steering wheel rotation. The airbag assembly may comprise a primary bag and a secondary bag.

The primary surface is configured to face the vehicle occupant when the airbag assembly is deployed. In a conventional installation, the primary surface may face a rear of the vehicle.

The airbag assembly may comprise a primary bag. The airbag assembly may optionally also comprise a secondary bag. The primary surface may be formed by the primary bag; and the annular restraint may be formed by the secondary bag. The primary surface may form a portion of a front face of the primary bag. The secondary bag may be disposed on the primary bag. The secondary bag may be created by additional fabric, for example attached to a front face of the primary bag. The airbag assembly may be configured such that the primary bag and the secondary bag inflate substantially simultaneously when the airbag assembly is deployed.

The primary bag may comprise a first internal chamber and the secondary bag may comprise a second internal chamber. The first and second internal chambers may be in communication with each other via one or more vents. The secondary bag may be inflated by gas expelled from the primary bag. Each vent may be configured to permit the flow of gas from the primary bag into the secondary bag and to inhibit the flow of gas from the secondary bag into the primary bag. For example, each vent may comprise a one-way valve.

The airbag assembly may comprise one or more internal tether configured to form said annular restraint. The internal tether may be associated with the front face of the primary bag. For example, the one or more internal tether may be connected to an inside of the front face of the primary bag. The one or more internal tether may extend radially. The one or more internal tether may restrict radial expansion of an annular portion of the front face of the primary bag. When the airbag assembly is inflated, the annular portion of the front face may expand to form the annular restraint. Alternatively, or in addition, the internal tether may extend from a mount for the airbag assembly.

The annular restraint may have a circular profile. The annular restraint may have an inner sidewall and an outer sidewall. The inner sidewall and/or the outer sidewall may be cylindrical. The inner sidewall may be tapered outwardly, for example to form a conical sidewall that tapers inwardly towards or away from the primary surface. In alternate arrangements, the annular restraint may have a non-circular profile. For example, the annular restraint may have a polygonal or elliptical profile.

The annular restraint extends around the primary surface. Thus, the shape of the primary surface may vary depending on the profile of the annular restraint. In certain embodiments, the primary surface may be circular.

The annular restraint projects relative to said primary surface. The annular restraint may project relative to said primary surface by at least 40mm. The annular restraint may project relative to said primary surface by approximately 40mm, 60mm or 80mm.

The annular restraint may have an internal diameter of at least 200mm. The annular restraint may have an internal diameter of approximately 250mm or approximately 300mm. The internal diameter of the annular restraint may be less than or equal to 500mm.

The annular restrain may have an external diameter less than or equal to 600mm.

The annular restraint may have a width of approximately 80mm, 90mm or 100mm. According to a further aspect of the present invention there is provided an airbag module comprising an airbag assembly as described herein. The airbag module may comprise one or more inflator configured to inflate the airbag assembly.

In use, the airbag module described herein is deployed in dependence on an activation signal. The activation signal may, for example, be generated in dependence on a measured acceleration exceeding a predefined threshold. The deployment of the airbag module comprises inflating the airbag assembly. The inflated airbag assembly is suitable for absorbing and/or re-directing energy from a collision, thereby helping to protect the vehicle occupant. The airbag assembly is configured to undergo deformation in order to cushion the vehicle occupant. It will be understood that, unless specified otherwise or required by the circumstances, the airbag assembly is described herein following inflation but without application of external loads. The airbag assembly is therefore described in an inflated, un- deformed state. According to a further aspect of the present invention there is provided a vehicle comprising an airbag module as described herein. The airbag module may be mounted to a steering wheel of the vehicle. For example, the airbag module may be fixedly mounted to a centre section of the steering wheel. Alternatively, the airbag module may be mounted to a steering wheel column structure. The steering wheel and/or the steering wheel column structure may provide a reactive support surface for the airbag assembly. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which:

Figure 1 shows a schematic representation of a vehicle incorporating an airbag module in accordance with an embodiment of the present invention;

Figure 2A shows a perspective view of an airbag assembly deployed from the airbag module shown in Figure 1 in an inflated condition;

Figure 2B shows a plan view of the airbag assembly shown in Figure 2A;

Figure 3 shows a perspective view of a simulated anthropomorphic test device engaging an annular front portion of the airbag assembly shown in Figure 3;

Figure 4A shows a perspective view of a simulated anthropomorphic test device engaging a reference airbag assembly without an annular front portion during a simulated nearside oblique frontal impact;

Figure 4B shows a perspective view of a simulated anthropomorphic test device engaging an airbag assembly in accordance with an embodiment of the present invention during a simulated nearside oblique frontal impact;

Figures 5A, 5B and 5C show the simulated angular head velocities about the X, Y and Z axes respectively for the simulations shown in Figures 4A and 4B;

Figure 6A shows a perspective view of a simulated anthropomorphic test device engaging a reference airbag assembly without an annular front portion during a simulated farside oblique frontal impact; Figure 6B shows a perspective view of a simulated anthropomorphic test device engaging an airbag assembly in accordance with an embodiment of the present invention during a simulated farside oblique frontal impact;

Figures 7A, 7B and 7C show the simulated angular head velocities about the X, Y and Z axes respectively for the simulations shown in Figures 6A and 6B; and

Figure 8 shows a perspective view of an airbag module in accordance with a further embodiment of the present invention.

DETAILED DESCRIPTION

An airbag module 1 in accordance with an embodiment of the present invention will now be described with reference to the accompanying figures. The airbag module 1 in the present embodiment is a driver airbag module and is configured to deploy in the event of a collision to protect a driver of a vehicle 2. The vehicle 2 is an automobile in the present embodiment but it will be appreciated that the airbag module 1 may be used in other types of vehicle.

As shown schematically in Figure 1 , the airbag module 1 is implemented in a vehicle 2. The airbag module 1 is configured to be mounted to a steering wheel 3 of the vehicle 2. In particular, the airbag module 1 is mounted centrally in the steering wheel 3, for example under a steering wheel cover. With reference to Figures 2A and 2B, the airbag module 1 comprises an airbag assembly 4 and an inflator 5. The airbag module 1 comprises an annular restraint (denoted generally by the reference numeral 6) which is configured to control rotation of the driver's head. The airbag assembly 4 comprises a primary bag 7 and a secondary bag 8. The primary bag 7 and the secondary bag 8 are formed from a woven material or fabric. The secondary bag 8 is disposed on the primary bag 7 and is configured to form the annular restraint 6 of the airbag assembly 4. The inflator 5 is operable in dependence on an electrical activation signal to discharge gas to inflate the airbag assembly 4. The inflator 5 is disposed inside the primary bag 7 and is fixedly mounted to the steering wheel 3. The primary bag 7 and the secondary bag 8 are in fluid communication with each other via a plurality of vents 9. In the present embodiment, two diametrically opposed vents 9 establish fluid communication between the primary bag 7 and the secondary bag 8. The inflator 5 is operable to discharge gas into the primary bag 7, thereby inflating the primary bag 7. The discharged gas is expelled through the vents 9 and also inflates the secondary bag 8. The vents 9 may optionally be configured to inhibit or slow the subsequent release of air from the secondary bag 8 into the primary bag 7; this arrangement may delay deflation of the secondary bag 8 after deployment of the airbag module 1 . It will be understood that the gas in the primary bag 7 and the secondary bag 8 may vent to atmosphere over time, for example through the weave of the material and/or one or more separate vent (not shown).

The primary bag 7 is configured to provide a cushion for the driver. The primary bag 7 has a generally circular profile. The primary bag 7 comprises a front face 10 and a rear face 1 1 formed from separate pieces of fabric joined together, for example by stitching and/or bonding. When the airbag assembly 4 is inflated, the front face 10 is configured to face towards the driver and to define a primary surface 12. The rear face 1 1 of the primary bag 7 is configured to face away from the driver. In a conventional installation, the driver faces towards a front of the vehicle 2 and the front face of the primary bag 7 faces towards a rear of the vehicle 2. It will be understood, therefore, that the front face 10 of the airbag assembly 4 faces towards a rear of the vehicle 2. The vents 9 are formed in the front face 10 of the primary bag 7. When inflated, the primary bag 7 forms a first internal chamber which is in the form of an oblate spheroid.

The secondary bag 8 forms the annular restraint 6 and is configured to control rotation of the driver's head. At least in certain embodiments, the secondary bag 8 may reduce angular head velocities. The secondary bag 8 may also help to reduce lateral movement. As shown in Figure 2A, the secondary bag 8 has an annular profile and is disposed on the front surface 10 of the primary bag 7. The secondary bag 8 projects from said front face 10 towards the rear of the vehicle 2 when the airbag module 1 is deployed. A portion of the front surface 10 remains exposed and this forms the primary surface 12 of the primary bag 7. The secondary bag 8 may be stitched or woven onto the primary bag 7. The secondary bag 8 is composed of a fabric which may optionally be coated in silicone. The secondary bag 8 comprises an annular surface 13, an inner sidewall 14 and an outer sidewall 15 formed from separate pieces of fabric joined together, for example by stitching. The seams of the secondary bag 8 may optionally be sealed to reduce air leakage after deployment, thereby delaying deflation. The inner sidewall 14 and the outer sidewall 15 are joined to the front face 10 of the primary bag 7. The inner sidewall 14 in the present embodiment is generally circular such that the functionality of the airbag assembly 4 is substantially unaffected by changes in the angular position of the steering wheel 3. The outer sidewall 15 is also circular in the present embodiment. When inflated, the secondary bag 8 forms a second internal chamber which is in the form of a toroid. With reference to Figure 2B, the secondary bag 8 has an external diameter D_EXT which is approximately 480mm. The secondary bag 8 has an internal diameter D,_N which is approximately 300mm and a width of approximately 90mm. In the present embodiment, the inner and outer sidewalls 14, 15 have a depth of approximately 40mm. Thus, the annular restraint 6 projects from the front face 10 of the primary bag 7 towards the driver by a distance of approximately 40mm. In alternate embodiments, the depth of the inner and outer sidewalls 14, 15 may be increased, for example to 60mm or 80mm. The secondary bag 8 is described herein as having an annular profile which is circular, but other profiles could be used.

The airbag module 1 is deployed in dependence on an electrical activation signal. The electrical activation signal may, for example, be generated by an accelerometer upon detection of accelerations indicative of a collision. The electrical activation signal energizes the inflator 5 causing gas to be discharged into the airbag assembly 4. As described herein, the gas is introduced directly into the primary bag 7 and is expelled through the vents 9 into the secondary bag 8. The primary bag 7 and the secondary bag 8 are thereby inflated by the inflator 5. The secondary bag 8 forms a raised annulus projecting outwardly from the front face 10 of the primary bag 7. A substantially circular section 16 of the front face 10 is exposed in the centre of inflated airbag assembly 4. When deployed, the airbag assembly 4 forms a cushion to decelerate the torso and head of the driver. The secondary bag 8 provides improved head support and helps to reduce rotational (angular) head velocities. At least in certain embodiments, the inner sidewall 14 of the secondary bag 8 may control rotation of the driver's head, thereby helping to reduce angular head velocities. The annular restraint 6 of the airbag assembly 4 may also function to reduce lateral movement of the driver's head. The function of the secondary bag 8 is of particular significance if the vehicle 2 is involved in an oblique impact. The primary airbag 7 may be inflated as per a standard driver or passenger airbag, with one or more vents 9 between the primary airbag 7 and the, or each, secondary bags 8A, 8B allowing gas to flow from the primary airbag 7 to the secondary bags 8A, 8B. This results in the secondary bags 8A, 8B starting to inflate as soon as the inflator gases reach the vent holes 9. Full deployment of the secondary bags 8A, 8B may thus occur at substantially the same time as full deployment of the primary airbag 7.

Although in the illustrated examples one vent 9A. 9B has been illustrated between the primary airbag 7 and each of the secondary bags 8A, 8B, it will be appreciated that alternative numbers of vents 9 may be provided. For example, it is contemplated that two or four vents 9 may alternative be provided between the primary airbag 7 and each secondary bag 8A, 8B. The vents 9 may be implemented as valves, allowing gas to flow from the primary airbag 7 to the secondary bags 8A, 8B, whilst inhibiting gas flow back from the secondary bags 8A, 8B to the primary airbag 7. This results in the secondary bags 8A, 8B deflating at a slower rate than the primary airbag 7 for improved retention of the occupants head.

In order to further retain pressure in the secondary bags 8A, 8B, a silicone coated fabric of standard decitex may be used for secondary bags 8A, 8B. This will also help to ensure current packaging constraints are respected. The operation of the airbag module 1 will now be described with reference to a computer simulation of an anthropomorphic test device (ATD) in response to an impact on the vehicle 2. The ATD is denoted generally by the reference numeral 18 herein, and the head of the ATD 18 is denoted by the reference numeral 19. As shown in Figure 3, the secondary bag 8 helps to control rotation of the head 19 of the ATD 18.

The behaviour of the ATD 18 during a simulation of a nearside oblique frontal impact on the vehicle 2 (i.e. a frontal impact on a driver side of the vehicle 2) is illustrated in Figures 4A and 4B. A first image 32 shown in Figure 4A illustrates the movement of the ATD 18 during a first simulation comprising an airbag module without an annular restraint. A second image 33 shown in Figure 4B illustrates the movement of the ATD 18 during a second simulation comprising an airbag module 1 incorporating the annular restraint 6 in accordance with an embodiment of the present invention. The rotation and/or lateral movement of head 19 of the ATD 18 is restrained by the annular restraint 6. The computer simulation comprises modelling the angular velocities (rad/s) of the head 19 of the ATD 18 with reference to the principal axes, namely a head longitudinal X axis, a head transverse Y axis and a head vertical Z axis. The modelled angular head velocities (rad/s) about the X, Y and Z axes during said first and second simulations are shown in Figures 5A, 5B and 5C respectively. With reference to Figure 5A, a first graph 23 shows first and second plots 24, 25 corresponding to the angular head velocities (rad/s) about the X axis for the first and second simulations respectively. With reference to Figure 5B, a second graph 26 shows first and second plots 27, 28 corresponding to the angular head velocities (rad/s) about the Y axis for the first and second simulations respectively. With reference to Figure 5C, a third graph 29 shows first and second plots 30, 31 corresponding to the angular head velocities (rad/s) about the Z axis for the first and second simulations respectively. The secondary bag 8 provides improved head support and reduces rotational head velocities. The secondary bag 8 can help to reduce the magnitude of the angular velocities about each of the principal axes. The behaviour of the ATD 18 during a simulation of a farside oblique frontal impact on the vehicle 2 (i.e. a frontal impact on a side of the vehicle 2 opposite to the driver) is illustrated in Figures 6A and 6B. A third image 42 shown in Figure 6A illustrates the movement of the ATD 18 during a first simulation comprising an airbag module without an annular restraint. A fourth image 44 shown in Figure 6B illustrates the movement of the ATD 18 during a second simulation comprising an airbag module 1 incorporating the annular restraint 6 in accordance with an embodiment of the present invention. The modelled angular head velocities (rad/s) about the X, Y and Z axes during said first and second simulations are shown in Figures 7A, 7B and 7C respectively. With reference to Figure 7A, a first graph 34 shows first and second plots 35, 36 corresponding to the angular head velocities (rad/s) about the X axis for the first and second simulations respectively. With reference to Figure 7B, a second graph 37 shows first and second plots 38, 39 corresponding to the angular head velocities (rad/s) about the Y axis for the first and second simulations respectively. With reference to Figure 7C, a third graph 40 shows first and second plots 41 , 42 corresponding to the angular head velocities (rad/s) about the Z axis for the first and second simulations respectively. The secondary bag 8 provides improved head support and reduces rotational head velocities. It will be appreciated that the secondary bag 8 can help to reduce the magnitude of the angular velocities about each of the principal axes.

A further embodiment of the airbag module 1 in accordance with an aspect of the present invention will now be described with reference to Figure 8. Like reference numerals will be used for like features. The airbag module 1 according to the second embodiment is configured to be mounted to a steering wheel 3 of the vehicle 2. The airbag module 1 comprises an airbag assembly 4 and an inflator 5. The airbag assembly 4 comprises an annular restraint 6. In the present embodiment the airbag assembly 4 comprises a primary bag 7 which is sub-divided by a plurality of internal tethers 20 to form an annular supplementary volume 8 disposed on the front of the airbag assembly 4. The supplementary volume 8 forms the annular restraint 6 in the present embodiment. The inflator 5 is disposed inside the primary bag 7 and is operable in dependence on an electrical activation signal to discharge gas to inflate the airbag assembly 4. The primary bag 7 is configured to provide a cushion for the driver. The primary bag 7 comprises a front face 10 and a rear face 1 1 formed from separate pieces of fabric. The front face 10 is configured to face towards the driver; and the rear face 1 1 is configured to face away from the driver. The front surface 10 comprises a primary surface 12 and an annular surface 13. The internal tethers 20 are attached to an inside of the front face 10, for example by stitching or weaving, and extend radially within the airbag assembly 4. The internal tethers 20 gather (or bunch) the material forming the annular surface 13 to restrict radial expansion so as to form the supplementary volume 8 when the airbag assembly 4 is inflated. The internal tethers 20 each have an inner end 21 and an outer end 22. The inner end 21 of each internal tether 20 is attached to an inner portion of the front face 10 of the primary bag

7 in a ring configuration, thereby defining the annular surface 13. The outer end 22 of each internal tether 20 is attached to an outer portion of the front face 10, for example an outer edge of the front face 10.

It will be understood that the operation of the airbag module 1 according to the current embodiment is unchanged from the previous embodiment. An electrical activation signal energizes the inflator 5 causing gas to be discharged into the airbag assembly 4 causing the primary bag 7 to inflate. The internal tethers 20 limit radial expansion of the annular surface 13 of the front surface 10. The annular surface 13 expands out-of-plane, thereby forming the supplementary volume 8. When inflated, the primary bag 7 forms a first internal chamber which is in the form of an oblate spheroid. The supplementary volume 8 forms a second internal chamber which is in the form of a toroid. The first and second internal chambers are in fluid communication with each other. It will be understood that the supplementary volume

8 forms the annular restraint 6 in the present embodiment. The supplementary volume 8 is configured to control rotation of the driver's head. At least in certain embodiments the supplementary volume 8 may reduce angular head velocities. One or more longitudinal tether may optionally be provided to control displacement of a central region of the front surface 10 when the airbag assembly 4 is inflated. The one or more longitudinal tether may restrict longitudinal displacement of the central region of the front surface 10 such that the primary surface 12 is offset from the annular surface 13 of the supplementary volume 8. This may help further to recess the primary surface 12 relative to the annular surface 13 to form a central depression.

Other techniques may be used to form the annular constraint 6. For example, the internal tethers 20 could extend longitudinally from the front face 10 of the primary bag 7, for example to a mounting point on the steering wheel 3. The internal tethers 20 may be connected to the front face 10 in a ring configuration to form the annular restraint 6. Again, one or more longitudinal tether may optionally be provided to tether a central region of the front surface 10. It will be appreciated that various modifications may be made to the embodiment(s) described herein without departing from the scope of the appended claims. Rather than mounting the airbag module 1 to the steering wheel 3, the airbag module 1 could be mounted to a steering wheel column structure. This arrangement would be independent of the angular orientation of the steering wheel 3. The steering wheel 3 may provide a reactive support surface for the rear face 1 1 of the primary bag 7.

Claims

CLAIMS:

1 . An airbag assembly for a vehicle, the airbag assembly comprising:

a primary bag;

a secondary bag disposed on the primary bag;

a primary surface formed by the primary bag; and

wherein the airbag assembly is configured such that the annular restraint projects relative to said primary surface when the airbag assembly is inflated.

2. An airbag assembly as claimed in claim 1 , wherein the airbag assembly is arranged such that full deployment of the secondary bag occurs at substantially the same time as full deployment of the primary bag.

3. An airbag assembly as claimed in claim 1 or claim 2, wherein the airbag assembly is arranged such that the secondary bag deflates at a slower rate than the primary bag.

4. An airbag assembly as claimed in claim 2 or claim 3, wherein the primary bag comprises a first internal chamber and the secondary bag comprises a second internal chamber, the first and second internal chambers being in communication with each other via one or more vents.

5. An airbag assembly as claimed in claim 4, wherein the secondary bag is configured to be inflated by gas expelled from the primary bag.

6. An airbag assembly as claimed in claim 4 or claim 5, wherein each vent is configured to permit the flow of gas from the primary bag into the secondary bag and to inhibit the flow of gas from the secondary bag into the primary bag.

7. An airbag assembly as claimed in any one of the preceding claims comprising one or more internal tethers configured to form said annular restraint.

8. An airbag assembly as claimed in claim 7, wherein said one or more internal tethers extend radially.

9. An airbag assembly as claimed in any one of the preceding claims, wherein the annular restraint is circular.

10. An airbag assembly as claimed in any one of the preceding claims, wherein the annular restraint projects relative to said primary surface by at least 40mm.

1 1 . An airbag assembly as claimed in claim 10, wherein the annular restraint projects relative to said primary surface by approximately 40mm, 60mm or 80mm.

12. An airbag assembly as claimed in any one of the preceding claims, wherein the annular restraint has an internal diameter of approximately 250mm or approximately 300mm.

13. An airbag assembly as claimed in any one of the preceding claims, wherein the annular restraint has a width of approximately 90mm.

14. An airbag module comprising an airbag assembly as claimed in any one of the preceding claims; and one or more inflator for inflating the airbag assembly;

15. A vehicle comprising an airbag module as claimed in claim 14.

16. A vehicle as claimed in claim 15, wherein the airbag assembly is mounted to a steering wheel of the vehicle.

17. A vehicle as claimed in claim 15, wherein the airbag assembly is mounted to a steering wheel column structure.

18. An airbag assembly or an airbag module substantially as herein described with reference to the accompanying figures.

19. A vehicle substantially as herein described with reference to the accompanying figures.