GB2386877A

GB2386877A - An air-bag safety device

Info

Publication number: GB2386877A
Application number: GB0306440A
Authority: GB
Inventors: Jose Maria Segura
Original assignee: Peguform GmbH
Current assignee: SMP Deutschland GmbH
Priority date: 2002-03-26
Filing date: 2003-03-21
Publication date: 2003-10-01
Anticipated expiration: 2023-03-21
Also published as: GB2386877B; DE10307964A1; GB0207087D0; GB0306440D0

Abstract

An air-bag safety device for a vehicle interior, comprises an air bag unit 3 attached to a vehicle structure and an air-bag cover 12 surrounded by a carrier layer 5 having attached lateral guides 8, 9 providing a path for an expanding air-bag 18, and connected to a supporting structure 4 by a flexible strap connection 10 having at least one curved section (25, Fig 4) with means to absorb pressure forces resulting from impacts from the interior passenger space of the vehicle. Preferably the flexible strap connection 10 is fastened by a screw 19 or bolt to a reinforcing structure 17 and is glued to the supporting structure 4 which supports a dashboard. Optionally a foam layer separates the carrier layer 5 and a decorative layer (not shown). Advantageously no injuries are caused to vehicle passengers by the air-bag cover 12 which remains linked at all times to the dashboard 1 and further as a result of the curved section 25 has the ability to sustain impacts stemming from the vehicle interior.

Description

Air ban cover assembly The invention relates to an air bag cover for use

in the interior of motor vehicles with a 5 carrier layer formed with desired break lines in a cover area. The air bag activation causes the expanding airbag to strike against the carrier layer in the cover area. The carrier layer in the cover area, the so called splinter protection part, breaks open along the break lines, so that the expanding air bag can enter the interior space of the vehicle. When air bag passes through the air bag cover, the air bag cover performs a 10 rotary movement while the air bag is guided laterally by guide structures defining a projectile path.

Air bag covers are known from the prior art, such as DE1 9958865A1. During assembly

the flexible strap connection needs to be fixed to a spar of the vehicle. This assembly Is requires considerable skill, as the spar is not easy to access after having assembled dashboard to the dashboard supporting structure.

Document DE101 04036A1 describes a possibility for the solution of the problem of the assembly of the reinforcement of the airbag covering by use of connecting elements.

These connecting elements are attached to a carrier structure or a metal sheet in the 20 trim part of a vehicle door and to a portion of the foam layer of said trim part. The major function of these connecting elements is to ensure primarily the presence of sufficient adhesive forces between the foam layer and the decorative layer, to avoid delaminations of the decorative layer and/or the foam layer. The problem of delaminations occurs primarily because it is impossible to predict the type of 25 deformation of the foam and decorative layers in the disclosed embodiment due to the absence of a stiff carrier layer. This solution is therefore suitable uniquely for application in a door side panel of a vehicle. For the application in an instrument panel of a vehicle, the presence of a stiff carrier layer is necessary.

Said carrier layer is usually partially weakened by introducing weakening structures in a 30 process step subsequent to the manufacture of the trim part. In the embodiment disclosed in document DE10104036A1 a subsequent weakening of the trim part is no longer possible as the connecting element, which is part of the foam layer will be at least partially destroyed, whereby the connecting element looses its function as such.

This invention concerns a safety device arrangement for a vehicle interior trim part, which includes an air bag unit. This airbag unit comprises an air bag and an air bag module together with an ignition device, which may be integrated into the air bag unit or arranged separately in the interior of a vehicle. The air bag unit is normally hidden from S the passengers view, because the trim part hiding the air bag unit extends between the interior space of the vehicle and the air bag unit itself. In order to ensure the function of such an air bag unit upon activation of the latter, the trim part is disposed with an air bag cover (12), comprising at least one carrier layer and optional decorative or filling layers. The air bag cover has weakening structures (15) applied onto the carrier layer 10 and at least part of the filling or decorative layers which separate at least the carrying layer and at least a part of the filling or decorative layers and thereby create an air bag cover, which becomes an almost completely distinct part of the trim part, such as an dashboard for a vehicle. For a controlled deployment of the air bag, the air bag cover ruptures precisely along the weakening structures (15). Lateral guides (8,9) attached to 15 the carrier layer (5) provide a path for the expanding airbag unit (3). Thereby it is ensured that the air bag fulfills its protecting function when activated to be inflated into the interior space of the vehicle and at the same time mitigating the effects of a sudden impact on the passenger due to a crash situation.

The airbag cover is attached to the vehicle structure in such a way, that the airbag 20 cover is neither connected to the airbag unit (3) nor to the supporting structure of the vehicle (13). The air bag cover comprises a fastening end (11) having one end (6) connected to a dashboard supporting structure (4).The fastening end (11) is attached on an opposite end (20) to the air bag cover (12) by a flexible strap connection (10).

The fastening end (11) is secured by a connecting means such as a screw connection 25 (19) to a reinforcing structure (17).

The assembly of an air bag cover (12) with a dashboard supporting structure (4) comprises the steps of molding a dashboard structure (1) integrally with a flexible strap connection (10), foreseeing weakening structures for said dashboard structure (1) to 30 provide an air bag cover (12) which will open along the designated weakening structures (15). The deployment of the air bag causes the sudden exertion of a pressure force onto the invisible side of the air bag cover (12), the so called impact side (9). Therefore the air bag cover will undergo a translational and rotary movement. The elasticity of the flexible strap connection (10) causes the translational movement, which 35 is necessary for the uniform deployment of the airbag in a first time period. It ensures that the pressure force acts uniformly on the cover so as to tear the cover open

simultaneously on all sides. The pressure force of the airbag introduces a tensile stress into the air bag cover materials, and especially into the weakening structures, with their reduced cross-section. The increasing air bag pressure released during deployment of said air bag (18) in a second time period causes a rotary movement of the cover so as 5 to give way for the deploying air bag. The flexible strap connection (10) provides the link of the air bag cover to the dashboard supporting structure (4) during the first and second dime periods and thereafter. By means of the flexible strap connection (10) the air bag cover remains linked at all times to the dashboard supporting structure, so that it will not cause injuries to passengers. For additional stability, the flexible strap 10 connection (10) is fixed to the dashboard supporting structure by a connecting means (19). The attachment of the flexible strap connection (10) may take place any time after the weakening structures have been applied to the trim part, such as a dashboard structure. Consequently there exists no limitation on the choice of the process of weakening the interior trim part, which allows for the application of any known 15 technology for the creation of weakening structures. The position of the carrying layer is now open to almost indefinite design variations, because the stiffness of said carrying layer is safeguarded by the choice of a stiff plastic material and the additional stiffening effect of the flexible strap connection.

20 An advantage of the invention is the possibility to assemble an air bag cover in a dashboard of a vehicle to the dashboard supporting structure, which is part of the trim part comprising the air bag cover and the dashboard. There is no more need to connect the air bag cover to a spar or another part of the vehicle frame. Therefore the dashboard or the instrument panel of the vehicle may be completely assembled with 25 the entire safety device in any location before reaching the final assembly line in the vehicle manufacturing plant. The dashboard may be mounted in one single step to the vehicle frame structure, which simplifies the final assembly of the vehicle.

A further advantage of the invention is the possibility to fix the dashboard to the 30 dashboard supporting structure by the flexible strap connection used to hold the air bag cover close to the dashboard during air bag deployment.

A further advantage of the invention is the positioning of the cover so that the weight of the cover structure itself will not lead to visibility of weakening structures even ff the 35 inventive cover is in operation for several years.

.,

As the airbag cover is composed of a carrying layer an optional decorative layer and one or more filling layers more or less in the same way as the remainder of the dashboard, consequently the stiffness of the airbag cover must be necessarily the same as the stiffness of the dashboard. The flexible strap connection is used as an 5 additional reinforcing member, which allows for compensation of the reduced stiffness due to the weakening structures. The flexible strap connection shows elastic properties if it opens due to the pressure force of the expanding air bag, but normally positions and support the air bag cover. Therefore the air bag cover, as disclosed in this invention, has the double function of ensuring as a first objective an controlled opening 10 behaviour of the air bag cover, whereby no delaminations of any layer occur nor the splintering of any particles due to the precise application of tearing forces in the weakening structures and ensuring as a second objective a support of the air bag cover during normal operation of the vehicle.

15 A further advantage of the invention is the controlled movement of the air bag cover in two steps. In a first time period, the air bag cover is pushed by the pressure of the air bag to a translational movement. In a second time period, the air bag cover is rotated away from the opening so as not to impede the deployment of the air bag. The air bag cover is shifted a certain distance into the vehicle interior space by the pressure of the 20 expanding air bag. The displacement due to said shifting movement is used to separate the materials along the weakening structures. The air bag cover is then separated with a clean separation line from the dashboard structure on all sides except in the area adjacent to the flexible strap connection. Due to the translational movement, tension and shearing stresses are introduced in said area adjacent to the flexible strap 25 connection and consequently the air bag cover is separated completely from the dashboard structure. Due to this translational movement, any delamination extending over a large surface of the decorative layer may be safely avoided.

As a subsequent step to said separation of air bag cover and dashboard structure, the air bag cover is subjected to a rotational movement. Due to the elastic properties of the 30 flexible strap connection, the air bag cover is pushed instantly out of the way of the expanding air bag and does not come into contact with the air bag anymore, whereby the function of said air bag is not impeded by any portion of the air bag cover..

A further advantage of the invention is the increased safety for the passenger. As the 35 air bag cover remains connected to the dashboard carrier, and does not disconnect

therefrom at any time whereby any danger of cover parts flying around in the passenger compartment is eliminated.

A further advantage of the invention is the ability of the air bag cover to sustain any 5 impacts resulting from forces stemming from the interior space of the vehicle. The flexible strap connection has at least one curved section (25) which fulfills the additional function of an impact absorbing element. Any misuse of the air bag cover is therefore safely prevented.

10 Fig. 1 shows in a sectioned side view a safety device, which is equipped with an air bag cover area opening into the interior of a motor vehicle Fig. 2 shows the rupture of the tear seams during the initial stage of air bag deployment of the embodiment of Fig.1 Fig. 3 shows the position of the air bag cover when the air bag is fully blown up of the embodiment of Fig.1 Fig. 4 shows an alternative embodiment of a safety device Fig. 1 shows an exemplary mode of performing the invention. The dashboard 1, shown in part as a sectional view, is equipped with an air bag assembly hidden from the..

passenger of the vehicle. The dashboard 1 consists of a carrier layer 5 and optionally of one or more filling or decorative layers (not shown). The carrier layer 5 is connected 25 to a dashboard support 4, which supports the entire carrier layer.

The air bag cover (12) is a part of the carrier layer (5) forming the dashboard (1). The carrier layer may be a single layer or a multilayer product consisting of a carrier layer and optional decorative or filling layers (not shown). Weakening structures (15), such as cuts or perforations are cut out of the carrier layer on the side of the cover, which is 30 invisible for the passenger. If applicable, the filling or decorative layers may also be partially weakened so as to provide a tear seam more or less following the geometry of the weakening structure. The carrier layer may have molded or welded lateral guides; (8,9) attached to the carrier layer (5) on the side of the dashboard facing the air bag for: providing a path for the expanding airbag unit (3). The air bag is attached to the vehicle, 35 structure such as a spar (13) or any other portion of the vehicle frame structure and

may be mounted any time before assembling the dashboard. The airbag cover is neither connected to the airbag unit (3) nor to the spar (13).

The air bag cover is connected to the dashboard supporting structure (4) by at least one connecting element, the flexible strap connection (10). Said flexible strap 5 connection is composed of elastic material, but shows sufficient strength and stiffness to absorb impacts resulting from the interior space of the vehicle without deformation of the air bag cover or creating a visible impression in the area of the air bag cover or resulting in any other defect stemming from incorrect use of the dashboard structure.

The flexible strap connection (10) has a fastening end (11) having one end (16) 10 connected to a dashboard supporting structure (4).The flexible strap connection (10) is attached on an opposite end (20) to the air bag cover (12). The fastening end (11) is secured by a connecting means such as a screw or bolt connection (19) to a reinforcing structure (17), which is part of the dashboard supporting structure (4).

If the space in the area of the air bag cover after the process of introduction of the

l 5 weakening structures (e.g. by perforation, laser technology) is accessible for a welding tool it is possible to foresee a welded connection between the hrst end of the fastening end and the reinforcement structure, which is substantially composed of the flexible strap connection.

On its second end (20), the flexible strap connection may be welded, glued or be 20 manufactured as a single injection molded piece of the air bag cover. The flexible strap connection (10) may be connected to the air bag cover also by a screw or bolt connection as shown in Fig. 4.

The choice of the type of connection is depending on the carrier layer, in particular its suitability for being processed in a standard injection molding process, the required 25 mounting space and the steps of assembly. In this embodiment, the flexible strap connection forms an integral part with the carrier layer of the air bag cover, the so called splinter protection part (6). The flexible strap connection may be composed from material having elastic properties, such as a polymeric material. This invention is not limited to the use of a single flexible strap connection (10). Two or more flexible strap 30 connections may be foreseen to ensure a controlled movement of the air bag cover. As an additional function, the flexible strap connection has to provide a reinforcement of the airbag cover against any impact resulting from the interior space of the vehicle. - -I; The flexible strap connection may be provided with at least one curved section (25)- -: which absorbs such pressure forces. If a passenger unintentionally uses the area of 35 the air bag cover as support, the resulting pressure force will be introduced into the curved section (25), whereby the pressure force is absorbed by the structure of the

curved section (25). Consequently the air bag cover is not displaced with respect to the interior trim part and no undue strain is exerted upon the weakening structures which would result in a visibility of said weakening structures or might even cause ruptures of the decorative layer. The flexible strap connection fulfils therefore a 5 protective function to ensure that the air bag cover is not damaged because of improper use. The curved section may assume the shape of a circle, a wavy line or a zig-zag line or any other shape resulting in an enhanced energy absorption behaviour.

If more than one curved section is provided, they may be connected amongst each other by use of lateral struts or ribs which increase the overall stiffness of this air cover 10 supporting device. Another alternative for increasing the stiffness of the flexible strap connection in its function as an air bag cover supporting device is the increase of the cross-section of the flexible strap connection in the area of the curved section. In another embodiment it may be foreseen to use a composite material, which comprises: a metal insert or a fibre-reinforced structure. Alternatively, a hybrid structure may be 15 employed, for reasons of assembly or space, the use of a steel sheet inlay structure, a fibre-reinforced structure or an impregnated cloth with metal or other reinforcements may be advantageous. It is possible to mold a grid-like structure of material improving the tensile strength of the flexible strap connection. This invention comprises also any combination of the shape and material properties for the flexible strap connection.

20 In Fig. 1, the splinter protection part is shown as a distinct part, differing from the carrier layer 5. The splinter protection part is preferably composed of the same or a similar material, such as a polymeric material in order to allow for a connection between carrier layer and splinter protection part by welding, gluing or application of heat to melt the materials whereby an adhesive effect between the two adjacent layers is 25 obtained. In an alternative embodiment, a hybrid structure may be foreseen which may result from other constraints, which may relate to the dimensional requirements for a dashboard structure or the necessity for the integration of other elements, such as air ducts, cables, storage areas and the like. The splinter protection part or the insert element forming part of the splinter protection part comprises a steel plate, a fibre 30 reinforced structure, an impregnated woven or non- woven material or similar reinforcement structures. In another embodiment, a grid-like material structure increasing the tensile strength of the flexible strap connection and the splinter protection part may be foreseen. Additionally to the possibilities for obtaining a tear -

resistant connection, fastening elements, which ensure a mechanical engagement of 35 the two layers, may be foreseen, the choice of connection depending essentially on the material properties of the carrier layer and the splinter protection part.

The assembly of an air bag cover (12) to a dashboard supporting structure (4) comprises the steps of molding a dashboard structure (1) integrally with a flexible strap connection (10) cutting weakening structures into the dashboard 1 to provide an air bag 5 cover (12) which will open along the designated weakening structures (15) upon the air bag pressure released during deployment of said air bag (18), connecting the dashboard to the dashboard supporting structure (4), fixing the flexible strap connection to the dashboard supporting structure by a fixing means (19). The fixing means may be a screw or a bolt.

10 Alternatively the end (16) of the fastening end (11) could be of arrowlike shape such as to fit into an opening in the dashboard supporting structure (4). The hooks of the end (16) are flexible enough to pass through the narrow opening in the dashboard supporting structure, but engage with the walls so as to be secured against release after assembly. This provides an easy-to-fit assembly possibility when the area behind 15 the dash board supporting structure is difficult to access during assembly. As there is normally no need to disassemble the parts at any time, there is no need to provide a possibility for disassembly.

Alternatively the first end (16) of the fastening end (11) may be welded to the dash board supporting structure. The fastening end (11) which is used as connecting end 20 (11) may have one or more corrugated sections (14) between the ends (16) and (20).

These corrugated sections increase the flexibility of the flexible strap connection (10).

Fig. 2 shows the initial stage of air bag deployment a few milliseconds after the ignition of the pressurized gas capsule. The pressure of the airbag (18) causes an almost simultaneous rupture along the tear seams on all sides. The function of the web 25 structure (7) on the impact side (9) is to guide the airbag to avoid that it expands laterally into the room between dashboard and spar (13) or supporting structure (4) instead gaining volume in the passenger compartment.

It may be possible to omit the web structure (7) if lateral guides for the air bag are provided on the dash board supporting structure (4). As the dashboard supporting 30 structure (4) - often referred to as carrier layer- is preferably a part manufactured by injection molding, it is possible to foresee such lateral guides (21) already during the injection molding process. On the side of the fastening end (11), the so-called impact side (9), the fastening end itself can be designed as a guiding structure for the air bag It is also possible to foresee two or more fastening ends on each side. The position of 35 the weakening structures (15) could be shmed in this case, so as to provide a single break line, positioned substantially centrally on the air bag cover- for an opening,

which could be compared to the opening of a fish-mouth. Alternatively, lateral break lines might be introduced. In a view from the opposite of the passenger side, these break lines would present themselves in the shape of the capital letter H. Fig. 3 shows a final stage of air bag deployment. The air bag cover is pushed back by 5 the air bag, but it is still attached to the reinforcing structure (17). Therefore it is avoided, that parts of the air bag cover are tom away and propagate into the passenger area. As the opening for the airbag can be relatively small, it can be excluded altogether, that passengers come into contact with the air bag cover (5) during any phase of the air bag deployment.

10 In the embodiment according to Fig. 4 the area of the air bag cover (12) comprises an insert part (26) instead of the splinter protection part of the previous embodiments providing a dimensional equilibration. Such an insert is disclosed in the German patent application DE10305545.2 of the applicant which is incorporated for reference. The ',rx' shape of the insert part (26) is such as to provide a constant distance between the air 15 bag module and the air bag cover. Therefore the expanding air bag comes into contact with the entire inner surface of the air bag cover contemporaneously. The carrier layer includes a lateral guide (21) and a reinforcing structure (17), which is used jointly as a lateral guide element and a fastening structure for a fastening (11)of a flexible strap connection (10). The shape of the reinforcing structure (17) adapts at least on the 20 surface adjacent to the flexible strap connection (22) to the structure of the curved section (25) of the reinforcing structure. This surface (22) ensures that upon deployment of the air bag, the part of the dashboard structure, which is different from the air bag cover, conserves substantially its original position. As the flexible strap connection (10) is subjected to strong tensile stress during the deployment of the air 25 bag, it is advantageous not to include sharp edges either in the flexible strap connection or the surface, as such sharp edges may cause cuts or grooves, which would result in an unintentional weakening of the flexible strap connection. This constructional detail ensures that the flexible strap connections does not get separated from the first end (16) of the fastening end (11).

30 Fig. 4 comprises an embodiment in which the carrier layer is disposed with a protrusion (23) in the area of the air bag cover (12) which engages the second end of the fastening end (20). The second end of the fastening end (20) may include an opening (24) into which a the protrusion (23) engages at least in part. Alternatively the engaging elements of the air bag cover (12) and the second end of the fastening end (20) may 35 be combined permanently by welding, a screw or bolt connection. -

-. v -............,.

Part list 1. dashboard 2. projectile path 5 3. air beg unit 4. dashboard supporting structure 5. carrier layer 6. splinter protection part 7. web 10 8. contour adapter 9. impact side 10. flexible strap connection 11. fastening end 12. air bag cover 15 13. spar 14. corrugated section (not shown) 15. tear seam (break line) 16. one end of the fastening end 17. reinforcing structure 20 18. air bag 19. fixing means (screw) 20. second end of the fastening end 21. lateral guide 22. surface adjacent to the curved section 25 23. protrusion 24. opening 25. curved section 26. insert part .. 35: :.

Claims

1. A safety device for the interior passenger space of a vehicle,

comprising an air bag cover (12) surrounded by at least a carrier layer having lateral guides (8,9) attached 5 to said carrier layer (5) so as to provide a path for the expanding airbag (18) and an airbag unit (3) attached to the vehicle structure characterized in that the airbag cover is connected to a supporting structure (4) by at least one flexible strap connection (10), which has means to absorb pressure forces resulting from impacts from the interior passenger space of the vehicle, comprising at least one curved 10 section (25).

2. A safety device according to claim 1, characterized in that the flexible strap connection (10) has at least one fastening end (11) having one end (16) connected to a supporting structure (4).

3. A safety device according to claim 1, characterized in that the supporting structure (4) is a dashboard supporting structure.

4. A safety device according to claim 2, characterized in that the fastening end (11) is 20 attached by a screw or bolt connection (19) to a reinforcing structure (17) or a to a protrusion (23).

5. A safety device according to claim 2, characterized in that the fastening end (11) is attached by a welded connection to a reinforcing structure (17).

6. A safety device according to claim 2, characterized in that the fastening end (11) is secured by gluing to the dashboard supporting structure (4).

7. A safety device according to claim 2, characterized in that the fastening end (11) is 30 secured by a hook fitting into an opening of the dashboard supporting structure (4).

8. A safety device according to claim 1, characterized in that the curved section (25) has substantially circular shape.

9. A safety device according to claim 1, characterized in that the curved section (25) has a cross-section which differs at least partially from the thickness of the carrier layer (5).

5

10. A safety device according to claim 1, characterized in that the curved section (25) comprises ribs.

11. A safety device according to claim 1, characterized in that the curved section (25) has a wave-like shape.

12. A safety device according to claim 1, characterized in that the curved section (25) has substantially zig-zag shape.

13. A safety device according to claim 1, characterized in that more than one curved 15 section (25) is provided.

14. A safety device according to claims 1 or 13, characterized in that at least some of the curved sections (25) are connected.

20

15. A safety device according to claim 1, characterized in that the carrier layer (5) is covered by a decorative layer.

16. A safety device according to claims 1 or 15, characterized in that at least one foam layer extends between carrier layer and decorative layer.