GB2520686A - A pedestrian airbag - Google Patents

Abstract

A pedestrian airbag 3 for a motor vehicle safety arrangement, the airbag having an inflatable chamber (16 fig.3) for the receipt of inflating gas defined between a front layer 1 and a rear layer 2, both of flexible material. The airbag includes at least one elongate internal shaping tether 6 formed of flexible material having first and second opposed edges 9, 10 extending between opposite ends 7, 8 of the tether and being connected to said front layer 1 along its first edge 9 and said rear layer 2 along said second edge 10 so as to extend between the layers and across the inflatable chamber (16) during inflation. The tether is shaped such that spacing between said first and second edges is greater in a central region of the tether than at each end of the tether. The first or/and second edge may have a convex and a concave region forming an s-shaped profile to direct airbag over windscreen wipers during deployment when airbag is fitted near upper region of bonnet.

Description

A PEDESTRIAN AIRBAG

The present invention relates to a pedestrian airbag, and more particularly relates to a pedestrian airbag for a motor vehicle safety device.

When a motor vehicle is involved in a frontal impact with a pedestrian, it is common for the body of the pedestrian to strike the windscreen of the vehicle which can result in serious injury to the pedestrian, and significant damage to the vehicle. In an attempt to alleviate this, it has been proposed to provide a motor vehicle with a so-called pedestrian airbag which, if vehicle sensors indicate that a collision with a pedestrian is occurring or is likely to occur, inflates to cover a central portion of the windscreen, and optionally also the left and right A-pillars of the vehicle. Typically, an airbag of this general type is provided in an initially tightly folded and/or rolled package and is stored beneath a rear part of the vehicle's hood or bonnet, or beneath a cowl which is provided between the base of the windscreen and the rear part of the hood or bonnet. The rear of the hood or bonnet may be lifted by a suitable air-bag, piston or other arrangement to allow sufficient space for the pedestrian airbag to inflate so that it deploys in a manner effective to cover at least part of the windscreen and/or A-pillars of the vehicle, thereby cushioning the impact of a pedestrian with these parts of the vehicle. Alternatively, it is also possible to configure the pedestrian airbag such that as it begins inflation it performs the hood-lifting function itself. Such an arrangement may incorporate a cell structure to the pedestrian airbag beneath the hood, or may comprise a structure adjacent the airbag to guide the airbag for inflation in a direction effective to lift the rear part of the hood or bonnet.

As will be appreciated, however, space beneath the rear part of a vehicle's hood or bonnet can be very limited which makes it difficult to conveniently package a sufficiently large airbag to ensure adequate protection for a pedestrian. Also, the larger the airbag which is successfully packaged in such an arrangement, then the larger the volume of gas required to inflate the airbag (which also necessitates a larger inflator). Relying on a large volume of gas to inflate a pedestrian airbag generally results in a slower deployment time which can reduce the effectiveness of the airbag in preventing or reducing injuries to a pedestrian. It is therefore considered advantageous to design pedestrian airbags with a sufficiently low inflatable volume to ensure that they can be tightly packaged prior to deployment and inflate sufficiently rapidly upon deployment, but to avoid the airbag offering insufficient cushioning effect in the region where it must protect a pedestrian in the event of deployment. It is therefore desirable to ensure that the airbag is configured to have a relatively low overall inflatable volume whilst also ensuring that it develops into a sufficiently thick form in regions behind the hood or bonnet of the vehicle when deployed in order to offer effective protection in these regions.

It is an object of the present invention to provide an improved pedestrian airbag. It is another object of the present invention to provide a motor vehicle with an improved pedestrian airbag.

According to the present invention, there is provided a pedestrian airbag for a motor vehicle safety arrangement, the airbag having an inflatable chamber for the receipt of inflating gas and which is defined between a front layer of flexible material and a rear layer of flexible material, wherein the airbag includes an elongate internal shaping tether formed of flexible material, the tether having first and second opposed edges extending between opposite ends of the tether and being connected to said front layer along its first edge and connected to said rear layer along said second edge so as to extend between the layers and across the inflatable chamber when the airbag is inflated, the airbag being characterised in that said tether is shaped such that the spacing between said first and second edges is greater in a central region of the tether than at each end of the tether.

Advantageously, said first edge has a convex region.

Conveniently, said convex region is located centrally between the ends of the tether.

Optionally, said first edge has a concave region.

Advantageously, said concave region is located adjacent one end of the tether.

Conveniently, said concave region is adjacent said convex region such that said first edge has an S-shaped profile.

Optionally, said second edge has a concave region.

Advantageously, said second edge has a convex region.

Conveniently, said concave region of the second edge is adjacent said convex region of the second edge such that said second edge has an S-shaped profile.

Optionally, the interconnection between said first edge and said front layer is of equal length to the interconnection between said second edge and said rear layer.

Advantageously, said first edge and said second edge of the tether are of equal length.

Conveniently, said tether has a pair of opposed end edges, each end edge extending between said first and second edges at respective ends of the tether and being unconnected to either layer of the airbag.

Optionally, the airbag has a plurality of said shaping tethers provided in spaced relation to one another.

According to another aspect of the present invention, there is provided a motor vehicle having a hood, a windscreen and a pedestrian airbag as defined above, the airbag being arranged to deploy upwardly from beneath a rear part of the hood and over the windscreen upon inflation to adopt an inflated configuration in which one end of the or at least one said tether is located beneath the rear edge of the hood, and said central region of the or at least one said tether is located in spaced relation to the rear edge of the hood.

Advantageously, the airbag is configured such that when in said inflated configuration the concave region of the first edge of the or at least one said tether is located beneath the rear is edge of the hood.

Conveniently, the motor vehicle, is further provided with at least one windscreen wiper having an inoperative position at the base of the windscreen adjacent the rear edge of the hood, and wherein is configured such that when in said inflated configuration the concave region of said second edge of the or at least one said tether is located above the inoperative position of the windscreen wiper.

Optionally, the airbag is configured such that when it is in said inflated configuration, the or at least one said tether extends generally parallel to a longitudinal axis of the vehicle.

So that the invention may be more readily understood, and so that further features thereof may be appreciated, embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a plan view showing an initial stage in the production of a pedestrian airbag embodying the present invention, illustrating two superimposed sheets of flexible material; Figure 2 is a plan view showing an additional sheet of fabric material, which is used to define a shaping tether in the airbag; Figure 3 is a view corresponding generally to that of figure 1, showing the superimposed sheets connected around their peripheral edges to define an inflatable chamber of the airbag, with a plurality of shaping tethers similar to that shown in figure 2 connected therebetween; Figure 4 is a plan view from above of the front part of a motor vehicle equipped with the airbag, the airbag being shown in a deployed, inflated, configuration across the lower region of the vehicle's windscreen; and Figure 5 is a longitudinal cross sectional view, taken along line V-V in figure 4.

Turning now to consider the drawings in more detail, figure 1 shows a pair of substantially ic identical primary sheets of flexible material 1, 2 from which an airbag 3 (shown in figure 3) is produced. The sheets 1, 2 are preferably formed from woven fabric material and in the embodiment illustrated are both elongate and somewhat arcuate. Furthermore, it will be noted from figure 1 that in the particular embodiment illustrated, the sheets 1, 2 each have a pair of spaced apart re-entrant recesses 4 provided along their uppermost edges in the is orientation illustrated. Because of the somewhat complex shape of the sheets 1, 2, it will thus be noted that their height (measured in the vertical direction as illustrated) varies across their width (as measured in the horizontal direction as illustrated). The sheets 1, 2 are shown in figure 1 in superimposed relation to one another. As will be noted, each sheet 1, 2 is shown provided with an outwardly projecting tab 4 at a generally central position along one of its sides.

Figure 2 shows a shaping tether 6 which is formed from a secondary sheet 6 of flexible material, and which is one of several such tethers having a generally similar configuration (though possibly slightly different dimensions) which may be used in the production of an airbag in accordance with the present invention. In preferred embodiments the tether is also formed from woven fabric material, which may be identical to the material of the two primary sheets 1,2.

The shaping tether 6 is generally elongate in form and has a pair of relatively short opposed end edges 7, 8 and a pair of relatively long opposed side edges 9, 10. The two end edges 7, 8 are generally straight and parallel to one another, but it will be noted that the side edges 9, 10 are curved.

More particularly, it will be noted that the first side edge 9 is shaped so as to have an outwardly convex region 11 and an outwardly concave region 12. The convex region 11 is located centrally between the two ends 7, 8 of the tether 6, and the concave region 12 is located adjacent the first end 7 of the tether, and is thus between the convex region 12 and the first end 7. As will be noted from figure 2, the first side edge 9 thus has a generally 5-shaped profile.

The second side edge 10 also has an outwardly convex region 13 and an outwardly concave region 14. In the case of the second side edge 10, the concave region 14 is located centrally between the two ends 7, 8 of the tether, and the convex region 13 is located adjacent the first end 7 of the tether, between the concave region 14 and the convex region 13. The second side edge 10 thus also has a generally S-shaped profile.

Furthermore, it is to be noted that the concave region 14 of the second side edge 10 is provided opposite the convex region 11 of the first side edge 9, whilst the convex region 13 of the second side edge 10 is provided opposite the concave region 12 of the first side edge 9. The profile of the tether 6 as a whole can thus also be said to be generally S-shaped.

However, it is important to note that the tether 6 is shaped such that the spacing between the first and second side edges 9, lOis greater in a central region (as indicated atW in figure 2) than at each end 7, 8 of the tether (as indicated at win figure 2).

It is considered advantageous for the first and second side edges 9, 10 of the tether to be of substantially equal length to one another, which can be achieved by careful adjustment of the curvature of their respective concave 12, 14 and convex regions 11, 13.

Turning now to consider figure 3 in more detail, the two superimposed primary sheets 1, 2 are interconnected along substantially the entire extent of their peripheral side edges by a peripheral seam 15 to define an inflatable chamber 16 between the sheets for the receipt of inflating gas. In this interconnected configuration the sheets 1, 2 define, respectively, a front layer and a rear layer of fabric forming the airbag 3.

Importantly, it is to be noted that a plurality of tethers 6 similar to the one illustrated in figure 2 are each connected to the front layer 1 of the airbag along their first side edges 9, and to the rear layer 2 of the airbag along their second side edges 10, in spaced relation to one another across the width of the airbag 3. The tethers 6 thus each extend between the two layers 1, 2 of the airbag and across the inflatable chamber 16, dividing the inflatable chamber up into a plurality of discrete inflatable cells 17 between neighbouring tethers 6. The tethers 6 will thus also serve as internal baffles inside the airbag 3.

The side edges 9, 10 of each tether 6 may be connected along substantially their entire length to the front and rear layers 1, 2 respectively. This interconnection can be via simple seams, such as stitched seams 18 provided between each side edge 9, 10 and the respective layer 1, 2 of the airbag. In this way, because the side edges 9, 10 are of equal length to one another for each individual tether, the interconnecting seam 18 between the front layer 1 and the first edge 9, and the interconnecting seam 18 between the rear layer 2 and the second edge 10 for each tether are also of equal length. However, it is to be noted that the side edges 9, 10 of each tether 6 do not have to be of equal length to one another, but in such an arrangement it is envisaged that the interconnecting seams 18 along each side edge will nevertheless be of equal length to one another, and thus not necessarily extending the full length of each side edge 9, 10 of the tether.

As will be noted from figure 3, each tether 6 is sized so as to extend across the airbag 3 between a point spaced from the lower edge 19 of the airbag to a point spaced from the upper edge 20 of the airbag 3. Because the height of the airbag 3 (in the vertical direction as illustrated in figure 3) varies across the width of the airbag, the tethers 6 are thus of varying lengths between their opposed ends 7, 8. More particularly, it is to be noted that the end edges 7, 8 of each tether 6 are spaced inwardly from the peripheral seam 15 and are not connected directly to the fabric of either the front layer 1 or the rear layer 2 of the airbag. In this way, a gas flow passage is defined between each end 7, 8 of each tether and the peripheral seam 15, which means that the discrete cells 17 defined between the tethers 6 are in fluid communication with one another around the ends of the tethers 6.

The tabs 5 of each primary sheet 1, 2 are aligned when the sheets 1, 2 are superimposed.

The peripheral seam 15 connecting the two primary sheets 1, 2 begins at one corner of the aligned tabs 5, runs around the periphery of the sheets 1, 2 and terminates at the opposite corner of the aligned tabs 5. The tabs 5 are thus unconnected along their aligned free edges 21 and so cooperate to form an open neck 22 to the airbag, the neck 22 defining a gas inlet aperture to the airbag 3. As illustrated, the neck 22 is arranged so as to be generally tangential to the central region of the airbag 3, and is intended to receive an inflator such as a gas generator in a known manner, such that upon actuation of the inflator a large volume of inflating gas will be directed into the inflatable chamber 16, thereby inflating the airbag 3.

Turning now to consider figure 4, the airbag 3 is shown in a deployed, and hence inflated, configuration on a motor vehicle 23. More particularly, it will be understood that figure 4 shows the airbag after it has been inflated from an initially packed configuration beneath the rear part 24 of the hood or bonnet 25 of the motor vehicle so as to extend over the lower part s of the windscreen 26, and the A-pillars 27 of the vehicle 23. It is envisaged that the rear pail of the hood or bonnet 25 will be lifted, for example via a separate lifting arrangement, in response to detection of an accident or likely accident requiring deployment of the airbag 3, in order to allow the airbag 3 to deploy from beneath the hood or bonnet 25 and into the position illustrated.

As will be noted, the recesses 4 along the upper edge of the airbag 3 are arranged to substantially coincide with the lateral positions of the driver's and passenger's front seats of the motor vehicle, and will therefore permit the driver substantially unrestricted view past the airbag 3 in the event that it should deploy, regardless of whether the vehicle is of a left-or right-hand drive configuration.

As will also be noted, the internal tethers 6 are each arranged to extend generally parallel to the longitudinal axis 28 of the motor vehicle 23 when the airbag 3 adopts its inflated and deployed configuration, such that the discrete cells 17 defined therebetween also extend generally parallel to the longitudinal axis 28 of the vehicle. However, the most important function of the tethers 6 can be seen more clearly in figure 5 which is discussed below.

The above-described shape of the tethers 6 is important in imparting a desired cross-sectional shape characteristic to the airbag 3 when it is inflated as illustrated in figure 5. As will be noted, because the tethers 6 are relatively narrow at their ends 7, 8 and relatively wide ( in their central regions, the same general characteristic is imparted to the cross-sectional shape of the airbag 3 when it is inflated. In particular, it will be noted that the narrow end region 7 of each tether 6 located below the rear edge region 24 of the hood or bonnet 25 makes the cross-sectional thickness of the airbag 3 itself in this region relatively narrow, which allows the airbag 3 to extend from beneath the hood or bonnet 25 even if the hood or bonnet 25 is only lifted a short distance. Also, it will be noted that the widest region W of the tethers 6 is located reaiwardly from the rear edge 29 of the hood or bonnet 25, in spaced relation thereto, and so in this position the airbag 3 has its maximum cross-sectional thickness when inflated 3. It is in this region that the airbag 3 is required to provide maximum cushioning effect to the head and/or torso of a pedestrian in the event of an accident and so the tethers 6 serve to shape the airbag 3 such that its maximum inflated thickness is positioned in this location to provide the best possible protection to the pedestrian. The uppermost edge of the airbag 3, in the region of the second ends 8 of each tether 6 is also relatively narrow on account of the shape of the tethers 6. By shaping the airbag 3 in this manner, such that its widest inflated cross-section is positioned between its upper and lower edges and spaced rearwardly from the rear edge 29 of the hood or bonnet 25, the airbag can be configured so as to have appropriate thickness where required, but without having unnecessary thickness, and hence volume requiring inflation, elsewhere.

Furthermore, it will be noted that the concave region 12 of the first edge 9 of each tether 6 is located beneath the rear edge 29 of the hood or bonnet 25 and thus imparts a corresponding concave shape to the inflated profile of the airbag 3 such that the airbag fits around the rear edge 29 of the hood or bonnet, and transitions smoothly to its widest region as defined by the convex regions 11 of the first edges 9 of the tethers 6.

Figure 5 also shows a windscreen wiper 30 of the motor vehicle, the windscreen wiper 30 being shown in a conventional inoperative position in which it is located at the base of the windscreen 26 adjacent the rear edge of the hood or bonnet. When the airbag 3 is inflated as shown in figure 3, the concave region 14 of the tethers 6 provided within the region of the airbag which lies over the windscreen wiper 30 become positioned above the inoperative position of the windscreen wiper 30. In this way, the rear surface of the airbag 3 is shaped so as to have a corresponding concavity and so fits around the windscreen wiper so as to reduce any likelihood of the windscreen wiper 30 interfering with the proper deployment of the airbag or urging it out of its intended deployed position.

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 integers.

The features disclosed in the foregoing description, or in the following claims, or in 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 obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

Claims (15)

1. CLAIMS1. A pedestrian airbag (3) for a motor vehicle safety arrangement, the airbag (3) having an inflatable chamber (16) for the receipt of inflating gas and which is defined between a front layer (1) of flexible material and a rear layer (2) of flexible material, wherein the airbag includes an elongate internal shaping tether (6) formed of flexible material, the tether (6) having first and second opposed edges (9, 10) extending between opposite ends (7, 8) of the tether and being connected to said front layer (1) along its first edge (9) and connected to said rear layer (2) along said second edge (10) so as to extend between the layers (1, 2) and across the inflatable chamber (16) when the airbag is inflated, the airbag (3) being characterised in that said tether (6) is shaped such that the spacing between said first and second edges (9, 10) is greater in a central region of the tether than at each end (7, 8) of the tether.
2. 2. A pedestrian airbag according to claim 1, wherein said first edge (9) has a convex region (11).is
3. 3. A pedestrian airbag according to claim 2, wherein said convex region (11) is located centrally between the ends (7, 8) of the tether (6).
4. 4. A pedestrian airbag according to any preceding claim, wherein said first edge (9) has a concave region (12).
5. 5. A pedestrian airbag according to claim 4, wherein said concave region (12) is located adjacent one end (7) of the tether (6).
6. 6. A pedestrian airbag according to claim 4 or claim 5, as dependent upon claim 2 or claim 3, wherein said concave region (12) is adjacent said convex region (11) such that said first edge (9) has an S-shaped profile.
7. 7. A pedestrian airbag according to any preceding claim, wherein said second edge (10) has a concave region (14).
8. 8. A pedestrian airbag according to any preceding claim, wherein said second edge (10) has a convex region (13).
9. 9. A pedestrian airbag according to claim 8 as dependent upon claim 7, wherein said concave region (14) of the second edge (10) is adjacent said convex region (13) of the second edge (10) such that said second edge (10) has an S-shaped profile.
10. 10. A pedestrian airbag according to any preceding claim, wherein the interconnection (18) between said first edge (9) and said front layer (1) is of equal length to the interconnection (18) between said second edge (10) and said rear layer (2).
11. 11. A pedestrian airbag according to claim 8, wherein said first edge (9) and said second edge (10) of the tether (6) are of equal length.
12. 12. A pedestrian airbag according to any preceding claim having a plurality of said shaping tethers (6) provided in spaced relation to one another.
13. 13. A motor vehicle (23) having a hood (25), a windscreen (26) and a pedestrian airbag (3) according to any preceding claim, the airbag (3) being arranged to deploy upwardly from beneath a rear part (24) of the hood (25) and over the windscreen (26) upon inflation to adopt an inflated configuration in which one end (7) of the or at least one said tether (6) is is located beneath the rear edge (29) of the hood, and said central region ( of the or at least one said tether (6) is located in spaced relation to the rear edge (29) of the hood (25).
14. 14. A motor vehicle according to claim 13, wherein the airbag (3) is in accordance with claim 4 or claim 5 and is configured such that when in said inflated configuration the concave region (12) of the first edge (9) of the or at least one said tether (6) is located beneath the rear edge (29) of the hood (25).
15. 15. A motor vehicle according to claim 13 or claim 14, further provided with at least one windscreen wiper (30) having an inoperative position at the base of the windscreen (26) adjacent the rear edge (29) of the hood (25), and wherein the airbag (3) is in accordance with claim 7 and is configured such that when in said inflated configuration the concave region (14) of said second edge (10) of the or at least one said tether (6) is located above the inoperative position of the windscreen wiper (30).