WO2009071306A1

WO2009071306A1 - Front airbag device, front airbag module and process for manufacture of a front airbag module

Info

Publication number: WO2009071306A1
Application number: PCT/EP2008/010313
Authority: WO
Inventors: Laurent Hellot
Original assignee: Autoliv Development Ab
Priority date: 2007-12-05
Filing date: 2008-12-04
Publication date: 2009-06-11
Also published as: EP2231443A1; DE102007058546B4; DE102007058546A1

Abstract

A front airbag device for a motor vehicle is described. This front airbag device comprises an airbag (22), a gas generator (20) for filling the airbag (22), a housing (10), into which airbag (22) is folded, and which exhibits an exit opening (18) for the airbag (22), a cover foil (30) spanning over the exit opening (18) and being connected with the housing (10) at at least two connection sections (32a, 32b) which basically lie opposite and parallel to one another, and a cover element with a door (42), which is basically located in front of the cover foil (30). In order to simplify the manufacture the cover foil (30) is isotropic in at least one direction being parallel to the connecting sections. An airbag module for the use in such a front airbag device and a method for its manufacture are also described.

Description

Front airbag device, front airbag module and process for manufacture of a front airbag module

Description

Technical field of the invention

The invention relates to a front airbag device according to the preamble of Claim 1 , a front airbag module according to Claim 9 and a process for manufacturing a front airbag module according to Claim 11.

Almost every modern passenger vehicle has a front airbag device, which protects the passenger in case of a frontal crash or a frontal crash which is offset to the side. Such a front airbag device exhibits a front airbag module consisting of a housing, an airbag and a gas generator. The airbag module is connected to the instrument panel on the side facing away from the passenger. The housing exhibits an exit opening through which the airbag is folded into the housing during manufacture, and through which it exits from the housing if the gas generator is triggered. The instrument panel has a door at the location of the exit opening of the housing, so that the airbag expands through the instrument panel into the interior of the vehicle when the gas generator is triggered. This means that the area of the instrument panel on which the front airbag module is held is a part of the front airbag device.

Prior art

In order to provide security during transport, and in order to prevent the airbag from jamming between the housing and the instrument panel during assembly, the exit opening is closed with a closing element which generally consists of a foil. Such a cover foil is mostly glued to or welded with the housing on the narrow sides of the exit opening, which is in most cases rectangular in shape. In order to make it possible for the airbag to exit, the cover foil exhibits set break lines in the form of perforations, whereby these perforations have to lie at precisely predefined locations.

Summary of the invention

The task of the present invention is to improve a front airbag device and a front airbag module respectively of the generic type in such a way that manufacture is made easier and therefore costs can be saved.

This task is fulfilled by a front airbag device with the characteristics of Claim 1 and a front airbag module with the characteristics of Claim 9. A preferred manufacturing method for the front airbag module is described in Claim 11.

As mentioned above, in the state of the art, perforated cover foils are used in order to close the exit opening. The perforation is two-dimensional and forms for example a double T. This makes it necessary first to make up the cover foils, namely to cut and perforate them and then to connect them to the housing. According to the invention, a foil is used, that is isotropic in at least one first direc- tion. In other words: The foil looks the same regardless of the length one looks at it. This first direction is generally parallel to sides of the exit opening to which the cover element is fixed.

In a first embodiment, the cover element has no set split line at all and is thus ho- mogenous. The foil forming the cover element can be directly wound off from a roll. The intermediate step of making up the foils is no longer needed, which makes production easier and correspondingly more cost effective.

As the cover foil now has no perforation or similar to form a set split line, other measures have to be taken which ensure that the airbag can exit from the housing through the exit opening when the gas generator is triggered. This is achieved in that the connection between the cover foil and the housing is in a first section such that the expanding airbag destroys the connection. This can easily be achieved, for example, if only a few weld points are present. As it is not desirable that the cover foil detaches completely from the housing upon exit of the airbag, means are provided in the second connection section which prevent the cover foil from detaching from the housing during expansion. This could be achieved, for example, in that the connection between cover foil and housing is formed to be considerably more robust in the second connection section than the connection in the first connection section. However, this is generally not to be preferred, as it would again somewhat increase manufacturing costs.

According to Claim 4 the second connection section is held in clamped fashion between a cover element, which spans over the front airbag module, and the housing. In the case of a passenger airbag, the cover element is a part of the instrument panel.

In a second embodiment one split line, in most cases a perforation, extends in one first direction across the entire length of the cover foil. Consequently, the foil forming the cover foil can also be rolled directly from a roll. As in the first embodiment, no making up of the cover foil is necessary. It is possible that the split line (perforation) is applied to the foil by the manufacturer of the foil so that the front section of the foil can by directly attached to the housing. This is the preferred possibility. Alternatively it would also be possible that the foil is supplied to the manufacturer without any split lines and that a continuous split line is applied to the foil after being rolled off but before being attached to the housing.

Further preferred embodiments result from the further subclaims and from the preferred embodiment now shown in more detail with reference to the drawings. The drawings are as follows:

Brief description of the drawings

Figure 1 A schematic representation of a front airbag module in cross-section, Figure 2 The front airbag module from Figure 1 in a view from direction A, - A -

Figure 3 The front airbag module from Figure 1 , which is connected with the instrument panel of the vehicle so that the front airbag device results,

Figure 4 The items shown in Figure 3 with deployed airbag, Figures 5-8 A schematic representation of the mounting of the cover foil on the housing of the airbag module from Figure 1 ,

Figure 9 A second embodiment of an airbag module in a representation according to figure 2,

Figure 10 The mounted airbag module of figure 9 in a representation according to figure 3 and

Figure 11 The items shown in Figure 10 with deployed airbag.

Detailed description of preferred embodiments

First embodiment

Figures 1 and 2 show a front airbag module for a front airbag device. Here, Figure 1 is a sectional view and Figure 2 is a view from Direction A from Figure 1. The front airbag module exhibits a housing 10 with a floor 12 and a circumferential sidewall 14, a gas generator 20, an airbag 22 folded into the housing and a cover foil 30. Floor 12 and side walls 14 surround an accommodation area of housing 10, which exhibits exit the opening 18 on the side lying opposite to the floor 12. Floor 12 is of basically rectangular shape, so that the exit opening is also rectangular and is framed by the front surfaces 16 of the side walls 14. The circumferen- tial side wall 14 has two short first sides 14a and two long second sides 14b. From the short first sides 14a, fixing flanges 19 with fixing holes 19a extend and flush with front surfaces 16.

Cover foil 30 is connected with front surface 16 of side wall 14 along two connec- tion sections 32a, 32b. The two connection sections 32 basically extend over the entire length of the front surface of short first sides 14a. Preferably, connection sections 32 are welded connections between cover foil 30 consisting of plastic and housing 10 consisting of plastic. However, glued connections are also possi- ble. The cover foil 30 is homogenous and in particular does not exhibit any perforation or similar weakened locations along which cover foil 30 could tear open during expansion of the airbag 22. In the preferred embodiment shown here, the connection sections 32 are equally made, so that they cannot withstand the force during expansion of airbag 32, so that cover foil 30 would completely detach from the housing during expansion of the airbag without further measures. However, complete detachment of the cover foil during expansion of the airbag is not desired, and therefore means are provided which have the function of preventing complete detachment.

In the embodiment shown here, this function is taken over by a cover element, which spans over the exit opening of the housing. As the embodiment shown here is a passenger front airbag module, the cover element is a part of the instrument panel. Figure 3 shows a complete front airbag device, which consists of the front airbag module just described and a section of the instrument panel 40. The front airbag module is connected with the inner side of instrument panel 40 by means of screws 50. A door 42 is located above the exit opening of the housing; this door is delineated by a basically U-shaped set break line 44 and a hinge 46. As can be seen from Figure 3, in the area of first connection section 32a, the cover foil is held in clamped fashion between the front surface 16 of housing 10 and the instrument panel 40 serving as cover element here, while the cover foil 30 lies open in relation to instrument panel 40 in the area of second connection section 32a.

If, as is shown in Figure 4, the gas generator is triggered, the airbag 20 enters into the interior space of the vehicle. In this process the airbag detaches the cover foil

30 from the housing 10 in the area of the second connection section 32b, while the cover foil 30 remains connected with the housing 10 in the area of the first connection section 32a because of the clamping between the instrument panel 40 and the housing 10. The door 42 flaps open along the hinge 46 after the break line 44 has been broken open.

Figures 5 to 8 show how cover foil 30 is preferably applied to the housing 10. A piece of foil is wound off from the foil roll 70, so that a front section 70a of this foil comes to lie on the housing 10 (see Figures 5 and 6). Then, this front section of the foil, which is still wound on, is connected with the housing 10 along the connection sections, for example welded in such a way as is indicated in Figure 7 in schematic form. Finally, the front section is separated off (Figure 8), so that the front section 70a forms the cover foil 30. It can be seen that it is not necessary to make up the foil in advance, and that the foil is utilised almost completely without wastage.

Second embodiment

The figures 9 to 11 show a second embodiment of the invention. Here, the cover foil 30 is not completely homogenous but isotropic in one direction, namely the longitudinal direction L of the foil. By the term "isotropic in one direction" the following fact is meant: The cover foil looks the same regardless the longitudinal po- sition. In Figure 9 two longitudinal positions U and b are marked with the first edge 34a of the cover foil 30 as reference point. One could define this property also as translation invariance.

Along the long edges (third and fourth edge 34c,34d), the cover foil 30 is attached - for example glued or welded - to the housing via connecting sections 32a ,32b. A perforation 35 serving as a split line extends from the first edge 34a of the cover foil 30 to the second edge 34b of the cover foil 30 lying opposite to the first edge 34a of the cover foil. This perforation extend parallel to the connecting sections 32a,32b and thus parallel to the third and fourth edge 34c,34d of the cover foil 30. Consequently this perforation can be a part of the supplied foil and does not need to be created during the manufacture of the airbag module. So, the process of manufacture is the same as described in the first embodiment (figures 5 to 8) with the exception that it is possible to create both connecting sections that strong that they can withstand the forces occurring during deployment of the airbag. Another difference to the manufacturing process described for the first embodiment is that the connecting sections extend parallel to the longitudinal direction of the foil but it needs to be emphasised that this would also be possible in the first embodiment. In the second embodiment it is essential that the connecting sections 32a, 32b extend parallel to the longitudinal direction of the foil and thus to the perforation 35 forming the split line.

The figures 10 and 11 show the airbag module of the second embodiment in a representation according to figures 3 and 4 of the first embodiment. The figure 10 shows a sectional view along plane B-B of the airbag module of figure 9 with the airbag module being mounted to an instrument panel 40. In figure 11, which shows the items of figure 10 during the deployment of the airbag, one can see that both connecting sections remain intact and that the cover foil is broken along the perforation. In the embodiment shown in Figure 10 there is no clamping of the cover foil 30 between the front surface 16 of housing 10 and the instrument panel

40 serving as the cover element. But since both connection sections 32a,32b should remain intact during deployment of the airbag, it would also be possible to clamp the third and/or the fourth edge of the cover foil 30 between the front sur- face 16 of the housing 10 and the instrument panel 40.

List of reference numbers

10 Housing

12 Floor

14 Side wall

14a First side

14b Second side

16 Front surface

18 Exit opening

20 Gas generator

22 Airbag

30 Cover foil

32a,b Connection section

34a first edge

34b second edge

34c third edge

34d fourth edge

35 perforation

40 Instrument panel

42 Door

44 break line

46 Hinge

70 Roll with foil

70a Front section of foil

Claims

Patent claims

1. Front airbag device with an airbag (22), a gas generator (20) for filling the airbag (22), a housing (10), into which airbag (22) is folded, and which ex- hibits an exit opening (18) for the airbag (22), a cover foil (30) spanning over the exit opening (18) and being connected with the housing (10) at at least two connection sections (32a,32b) which basically lie opposite and parallel to one another, and a cover element with a door (42), which is basically located in front of the cover foil (30), characterised in that the cover foil (30) is isotropic in at least one direction being parallel to the connecting sections.

2. Front airbag device according to claim 1 , characterised in that the cover foil (30) is homogenous and that the connection between the cover foil (30) and the housing in the second section (32b) is such that the expanding air- bag (22) destroys this connection and that in the area of the first section (32a) means are provided which prevent a complete detachment of the cover foil (30) from the housing (10) during expansion of the airbag (22).

3. Front airbag device according to Claim 2, characterised in that the first connection section (32a) is held in clamped fashion against the cover element, so that the cover element prevents a detachment of the cover foil (30) from the housing.

4. Front airbag device according to one of the preceding Claims, characterised in that it is a passenger airbag, whereby the cover element is a section of the instrument panel (40).

5. Front airbag device according to claim 1 , characterised in that the cover foil (30) comprises exactly one split line (perforation 35) being parallel to the connecting sections (32a, 32b) and extending from a first edge (34a) of the cover foil (30) to a second edge (34b) of the cover foil (30).

6. Front airbag device according to one of the preceding claims, characterised in that the cover foil (30) is welded to the housing (10) in the connection sections (32a,32b).

7. Front airbag device according to one of the preceding claims, characterised in that the cover foil (30) is glued to the housing (10) at the connection sections (32a, 32b).

8. Front airbag device according to one of the preceding claims, characterised in that the cover foil (30) is a plastic foil.

9. Front airbag module for use in a front airbag device according to one of Claims 1 to 7 consisting of a housing (10) exhibiting an exit opening (18), a gas generator (20) held on said housing (10), whose outflow area lies within the housing, an airbag (22) folded into the housing, and a cover foil

(30) covering the exit opening (18) and being connected with the housing (10) at at least two connection sections (32a, 32b) basically lying opposite to one another, said cover foil being isotropic at least in the direction being parallel to the connection sections.

10. Front airbag module according to claim 9, characterised in that it shows exactly two connection sections (32a, 32b).

11. Process for manufacture of a front airbag module according to Claim 9, whereby an end section (70a) of a foil located on a roll (70) is applied to the housing, fixed and then cut from the roll in order to attach the cover foil (30) to the housing.