The present disclosure relates to an airbag apparatus. Particularly, but not exclusively, the present disclosure relates to an airbag module; 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 for a vehicle, the airbag assembly comprising: a primary bag comprising a front face having a primary surface; and a lateral restraint formed by at least one secondary bag and configured to control rotation of the vehicle occupant's head;

wherein the lateral restraint is disposed on a lateral region of the front face, said lateral restraint being untethered. The airbag assembly does not include any internal tethers associated with the lateral restraint. Rather, it has been determined that, at least in certain embodiments, the inherent stability of the airbag assembly is sufficient to control the shape and/or stability of the lateral restraint. The airbag assembly may comprise one or more internal tether. The one or more internal tether may consist of one or more longitudinal tether configured to extend in a substantially longitudinal direction when the airbag assembly is inflated. In this arrangement, the airbag assembly is formed without any lateral tethers, i.e. without any tethers extending in a lateral direction.

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 comprising a front face having a primary surface; a lateral restraint formed by at least one secondary bag and configured to control rotation of the vehicle occupant's head, the lateral restraint being disposed on a lateral region of the front face; and

one or more internal tether;

wherein said one or more internal tether consist of one or more longitudinal tether configured to extend in a substantially longitudinal direction 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 lateral restraint is configured to project towards the vehicle occupant when the airbag assembly is inflated. When the airbag assembly is inflated, the lateral restraint may be disposed on at least one side of the primary surface. The lateral restraint may reduce rotation and/or lateral movement of the vehicle occupant's head. At least in certain embodiments the lateral 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 a lateral restraint on the airbag assembly, the airbag assembly can aid management of lateral and/or rolling movement of the vehicle occupant's head. The lateral restraint may also control sliding of the vehicle occupant's head relative to the primary surface. The one or more longitudinal tether may be connected to a central region of the front face of the primary bag.

The at least one longitudinal tether may be offset from the lateral region of the front face of the primary bag. There may be a horizontal and/or vertical offset between the lateral region and the connection of the longitudinal tether to the front face.

The one or more longitudinal tether may be fixedly mounted proximal to an inflator. The inflator may be centrally mounted in a transverse direction. The airbag assembly may be arranged such that full deployment of the lateral restraint occurs at substantially the same time as full deployment of the primary bag.

The airbag assembly may be arranged such that the lateral restraint deflates at a slower rate than the primary bag.

The lateral restraint may comprise an inboard secondary bag and/or an outboard secondary bag. The inboard secondary bag and/or the outboard secondary bag may be disposed on the front face of the primary bag. The inboard secondary bag may be elongated in a vertical direction; and/or the outboard secondary bag may be elongated in a vertical direction. The inboard secondary bag and the outboard secondary bag may be arranged substantially parallel to each other.

The primary bag may comprise a main internal chamber. The inboard secondary bag and/or the outboard secondary bag may each comprise an auxiliary internal chamber. The main internal chamber may be in communication with the auxiliary internal chamber(s) via one or more vents. 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.

The inboard secondary bag and/or the outboard secondary bag may be inflated by gas expelled from the primary bag. The lateral restraint may project relative to said primary surface by approximately 100mm. In alternate embodiments, the lateral restraint may project relative to said primary surface by approximately 60mm, 80mm, 120mm or 140mm.

The lateral restraint may have a width of approximately 125mm. In alternate embodiments, the lateral restraint may have a width of approximately 80mm, 100mm or 140mm.

The primary surface is occupant facing. The primary surface is the surface of the airbag assembly adapted to be contacted by the vehicle occupant. The primary surface may provide a cushion by decelerating the vehicle occupant. The orientation of the primary surface may depend on the orientation of the associated seat. If the associated seat is forward facing, the primary surface may face towards a rear of the vehicle. If the associated seat is rearward facing, the primary surface may face towards a front of the vehicle. The lateral restraint is configured to project from said primary surface when the airbag assembly is inflated. The airbag assembly may be configured such that the lateral restraint projects towards the vehicle occupant.

According to a further aspect of the present invention there is provided an airbag module comprising an airbag assembly described herein. The airbag module may comprise one or more inflator for inflating 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 is mounted to a dashboard of the vehicle. 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 the dimensions of a secondary bag of the airbag assembly shown in Figure 2A;

Figure 3A shows a plan elevation of the airbag assembly shown in Figure 2A;

Figure 3B shows a front elevation of the airbag assembly shown in Figure 2A;

Figure 4 shows a perspective view of a simulated anthropomorphic test device engaging a lateral front portion of the airbag assembly shown in Figure 4;

Figure 5A shows a perspective view of a simulated anthropomorphic test device engaging a reference airbag assembly in accordance with an embodiment of the present invention during a simulated passenger nearside oblique frontal impact;

Figure 5B shows a comparison of the movement of the anthropomorphic test device engaging an airbag assembly with and without a lateral restraint during a simulated passenger nearside oblique frontal impact;

Figures 6A, 6B and 6C show the simulated angular head velocities about the X, Y and Z axes respectively for the simulations shown in Figures 5A and 5B;

Figure 6D shows the BrIC values for the simulations shown in Figures 5A and 5B; Figure 7 shows a perspective view of a simulated anthropomorphic test device engaging a reference airbag assembly with and without a lateral restraint during a simulated passenger farside oblique frontal impact;

Figures 8A, 8B and 8C show the simulated angular head velocities about the X, Y and Z axes respectively for the simulations shown in Figure 7; and Figure 8D shows the BrIC values for the simulations shown in Figure 7;

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 passenger airbag module and is configured to deploy in the event of a collision to protect a passenger 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 dashboard 3 of the vehicle 2. The airbag module 1 is mounted under a removable panel (not shown) disposed on the dashboard 3. With reference to Figures 2A and 2B, the airbag module 1 comprises an airbag assembly 4 and an inf lator 5. The airbag module 1 comprises a lateral restraint (denoted generally by the reference numeral 6) which is configured to control rotation of the passenger's head. The airbag assembly 4 comprises a primary bag 7, an inboard secondary bag 8A, and an outboard secondary bag 8B. The inboard and outboard secondary bags 8A, 8B are mounted to the primary bag 7 and are configured to form the lateral restraint 6 of the airbag assembly 4. The inboard and outboard secondary bags 8A, 8B have a tubular structure in the present embodiment. The primary bag 7, the inboard secondary bag 8A and the outboard secondary bag 8B are formed from a woven material or fabric.

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 dashboard 3. The inflator 5 is centrally mounted in a transverse direction. The primary bag 7 is in fluid communication with the inboard and outboard secondary bags 8A, 8B via first and second vents 9A, 9B respectively. 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 first and second vents 9A, 9B and inflates the inboard and outboard secondary bags 8A, 8B. The first and second vents 9A, 9B may optionally be configured to inhibit or slow the subsequent release of air from the inboard and outboard secondary bags 8A, 8B 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 cushion the passenger in the event of a collision. The primary bag 7 comprises a front face 10 and a rear face 1 1 . When the airbag assembly 4 is inflated, the front face 10 is configured to face towards the passenger and to define a primary surface 12. The rear face 1 1 of the primary bag 7 is configured to face away from the passenger. In a conventional installation, the passenger faces towards a front of the vehicle 2 and the front face 10 of the primary bag 7 faces towards a rear of the vehicle 2. The vent 9 is formed in the front face 10 of the primary bag 7. When inflated, the primary bag 7 forms a first internal chamber.

The inboard and outboard secondary bags 8A, 8B form the lateral restraint 6 and are operative to control rotation of the passenger's head. At least in certain embodiments, the inboard and outboard secondary bags 8A, 8B may reduce angular head velocities. The inboard and outboard secondary bags 8A, 8B may also help to reduce lateral movement. As shown in Figure 2A, the inboard secondary bag 8A is disposed on a first lateral region 10A of the front face 10; and the outboard secondary bag 8B is disposed on a second lateral region 10B of the front face 10. The first lateral region 10A is disposed in an inboard position proximal to the central longitudinal axis XX of the vehicle 2. The first lateral region 10A is disposed in an outboard position distal from the central longitudinal axis XX of the vehicle 2. The first and second lateral regions 10A, 10B are untethered and do not include any internal tethers to provide lateral or longitudinal support. In the present embodiment the inboard and outboard secondary bags 8A, 8B are arranged such that the inflated airbag assembly 4 is substantially symmetrical about a vertical plane. The symmetrical arrangement of the airbag assembly 4 allows the airbag module 1 to be installed on either side of the vehicle 2 for left and right drive variants.

The inboard and outboard secondary bags 8A, 8B project from said front face 10 towards the rear of the vehicle 2 when the airbag module 1 is deployed. A central portion of the front face 10 remains exposed between said inboard and outboard secondary bags 8A, 8B and this forms the primary surface 12 of the primary bag 7. The inboard and outboard secondary bags 8A, 8B may be stitched or woven onto the primary bag 7. The inboard and outboard secondary bags 8A, 8B are composed of a fabric which may optionally be coated in silicone. The inboard and outboard secondary bags 8A, 8B each comprise an outer face 13, an inner sidewall 14 and an outer sidewall 15 formed from separate pieces of fabric joined together, for example by stitching. The inner sidewall 14 and the outer sidewall 15 are joined to the front face 10. The seams of the inboard and outboard secondary bags 8A, 8B may optionally be sealed to reduce air leakage after deployment, thereby prolonging inflation. When inflated, the inboard and outboard secondary bags 8A, 8B each form a second internal chamber.

With reference to Figure 2B, the inboard and outboard secondary bags 8A, 8B each have a width of approximately 125mm, a depth of approximately 100mm and a length of approximately 300mm. It will be appreciated that the dimensions of the inner and outer sidewalls 14, 15 may be varied to adjust the dimensions of the inboard and outboard secondary bags 8A, 8B, for example to change the depth thereof. It will be appreciated that the lateral restraint 6 projects from the front face 10 of the primary bag 7 towards the passenger by a distance of approximately 100mm. In alternate embodiments, the depth of the inner and outer sidewalls 14, 15 may be increased, for example to 120mm or 140mm; or may be reduced, for example to 60mm or 80mm.

With reference to Figures 3A and 3B, the airbag assembly 4 comprises a plurality of internal tethers 20. In the present embodiment, the airbag assembly 4 comprises two (2) internal tethers 20. The internal tethers 20 are arranged to limit the displacement of the front face 10 towards the passenger when the airbag assembly 4 inflates. The internal tethers 20 consist of longitudinal tethers extending longitudinally from the inflator 5 to the front face 10 of the primary bag 7. As shown in Figure 3A, the internal tethers 20 are fixedly mounted to the inflator 5. In use, the airbag module 1 is configured such that the longitudinal tethers 20 are disposed in a vertical plane extending substantially parallel to a central longitudinal axis X-X of the vehicle 2 (shown in Figure 1 ). The longitudinal tethers 20 are connected to a central region of the front face 10, as shown in Figure 3B. It will be understood that the airbag assembly 4 in the present embodiment is substantially symmetrical about a vertical plane. In alternate embodiments, the airbag assembly 4 may be formed without any internal tethers.

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 first and second vents 9A, 9B into the inboard and outboard secondary bags 8A, 8B. The primary bag 7, the inboard secondary bag 8A and the outboard secondary bag 8B are thereby inflated by the inflator 5. The inboard and outboard secondary bags 8A, 8B project from the front face 10 of the primary bag 7. When deployed, the airbag assembly 4 forms a cushion to decelerate the torso and head of the passenger. The inboard and outboard secondary bags 8A, 8B provide improved head support and help 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 passenger's head, thereby helping to reduce angular head velocities. The lateral restraint 6 of the airbag assembly 4 may also function to reduce lateral movement of the passenger'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 4, the inboard and outboard secondary bags 8A, 8B help to control rotation of the head 19 of the ATD 18. The behaviour of the ATD 18 during a simulation of a passenger nearside oblique frontal impact on the vehicle 2 (i.e. a frontal impact on a passenger side of the vehicle 2) is illustrated in Figure 4. A first computer simulation was performed for an airbag module 1 which does not include a lateral restraint 6. A second computer simulation was performed for an airbag module 1 incorporating the lateral restraint 6 in accordance with an embodiment of the present invention. A first image 21 shown in Figure 5A illustrates the movement of the ATD 18 during the second computer simulation. A second image 22 shown in Figure 5B shows a comparison of the movement of the ATD 18 during the first and second computer simulations. The movement of the head 19 of the ATD 18 for the first computer simulation is indicated by a prime (') in Figure 5B. The rotation and/or lateral movement of head 19 of the ATD 18 is restrained by the lateral restraint 6. The first and second computer simulations comprise 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 6A, 6B and 6C respectively. With reference to Figure 6A, a first graph 24 shows first and second plots 25, 26 corresponding to the angular head velocities (rad/s) about the X axis for the first and second simulations respectively. With reference to Figure 6B, a second graph 27 shows first and second plots 28, 29 corresponding to the angular head velocities (rad/s) about the Y axis for the first and second simulations respectively. With reference to Figure 6C, a third graph 30 shows first and second plots 31 , 32 corresponding to the angular head velocities (rad/s) about the Z axis for the first and second simulations respectively. A fourth graph 33 is shown in Figure 6D comprising first and second plots 34, 35 representing the calculated BrIC for the first and second computer simulations respectively. The inboard and outboard secondary bags 8A provide improved head support and reduce rotational head velocities. The inboard and outboard secondary bags 8A, 8B can also 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 passenger farside oblique frontal impact on the vehicle 2 (i.e. a frontal impact on a driver side of the vehicle 2) is illustrated in a third image 36 in Figure 7. A first computer simulation was performed for an airbag module 1 which does not include a lateral restraint 6. A second computer simulation was performed for an airbag module 1 incorporating the lateral restraint 6 in accordance with an embodiment of the present invention. The third image 36 illustrates the movement of the ATD 18 during the first and second computer simulations. The movement of the head 19 of the ATD 18 in the first computer simulation is indicated by a prime (') in Figure 7. The rotation and/or lateral movement of head 19 of the ATD 18 is restrained by the outboard lateral restraint 6. The first and second computer simulations comprise modelling the angular velocities (rad/s) of the head 19 of the ATD 18 with reference to the principal axes, namely a longitudinal X axis, a transverse Y axis and a 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 8A, 8B and 8C respectively. With reference to Figure 8A, a first graph 37 shows first and second plots 38, 39 corresponding to the angular head velocities (rad/s) about the X axis for the first and second simulations respectively. With reference to Figure 8B, a second graph 40 shows first and second plots 41 , 42 corresponding to the angular head velocities (rad/s) about the Y axis for the first and second simulations respectively. With reference to Figure 8C, a third graph 43 shows first and second plots 44, 45 corresponding to the angular head velocities (rad/s) about the Z axis for the first and second simulations respectively. A fourth graph 46 is shown in Figure 8D comprising first and second plots 47, 48 representing the calculated BrIC values for the first and second computer simulations respectively. The inboard and outboard secondary bags 8A provide improved head support and reduce rotational head velocities. The inboard and outboard secondary bags 8A, 8B can also help to reduce the magnitude of the angular velocities about each of the principal axes.

The airbag assembly 4 has been described herein as comprising inboard and outboard secondary bags 8A, 8B. It will be appreciated that the airbag assembly 4 may comprise only one secondary bag 8A, either the inboard secondary bag 8A or the outboard secondary bag 8B.

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. For example, the specific description herein describes the inboard and outboard secondary bags 8A, 8B as comprising an outer face 13, an inner sidewall 14 and an outer sidewall 15 which are formed from separate pieces of fabric. In a variant, the outer face 13, the inner sidewall 14 and the outer sidewall 15 may be formed integrally with the front surface 10 of the primary bag 7.