WO2009049905A1

WO2009049905A1 - Airbag unit

Info

Publication number: WO2009049905A1
Application number: PCT/EP2008/008847
Authority: WO
Inventors: Jürgen MACKENSEN; Raimund Nebel
Original assignee: Autoliv Development Ab
Priority date: 2007-10-20
Filing date: 2008-10-18
Publication date: 2009-04-23
Also published as: DE102007050261A1; DE102007050261B4

Abstract

An airbag unit with a housing (10) exhibiting a housing floor (12), an airbag (50), a gas generator (20) exhibiting a fixing flange (22) for filling of the airbag (50), and a retaining ring (30), which is connected to the floor by means of bolts and which holds fixing flange (22) against housing floor (12) in clamped fashion is described. In order to prevent rattling noises, retaining ring (30) and/or housing floor (12) exhibits at least three deformable sections, which press on fixing flange (22).

Description

Airbag Unit

Description

Technical field of the invention

The invention relates to an airbag unit according to the preamble of Claim 1.

In the case of airbag units for motor vehicles, in particular in the case of driver airbag units which are intended for installation in a steering wheel, so-called pancake generators are often used. These exhibit a flat cylindrical form and generally also a fixing flange, which extends round the lateral area of the flat cylinder. Many possibilities are known of linking the gas generator, airbag and housing of such an airbag unit.

Prior art

In generic patent US 5 518 266, it is proposed that a retaining ring is provided which is screwed together with the housing floor by means of screws and which holds gas generator, airbag and housing floor together. Here, the retaining ring presses against a section of the airbag fabric along its entire circumference, which again presses on the fixing flange or on the housing floor.

The proposed solution in fact functions in a basically reliable fashion. However, rattling noises can occur because of manufacturing tolerances and/or assembly which is not one hundred per cent correct, in particular between the fixing flange and the housing floor, as here, metal lies directly against metal. Summarv of the invention

Starting from this point, the present invention sets itself the task of developing an airbag unit of the generic type in such a way that rattling noises are also reliably prevented if the components which are used exhibit relatively large manufacturing tolerances.

This task is solved by means of an airbag unit with the characteristics of claim 1.

According to the invention, the fixing flange is not held in clamped fashion between the retaining ring and the housing floor over its entire circumference, but is held in sections, for which purpose the retaining ring and/or the housing floor exhibits at least three deformable sections. The deformable nature of these sections is such that it exhibits at least an elastic portion. This has the following advan- tages: on the one hand, the force which exists between the components is concentrated in a very small area, which means that the press pressures are correspondingly increased. On the other hand, any manufacturing tolerances are compensated by selective deformation of the sections which are capable of deformation which are provided for the purpose.

For reasons of static the best results can be achieved if three fixing bolts and three deformable sections are present symmetrically.

Preferred embodiments of the invention result from the subclaims, and also from the embodiments described in more detail below with reference to the drawings.

The drawings are as follows:

Brief description of the drawings

Figure 1 A section through an airbag unit,

Figure 2 The retaining ring of the airbag unit from Figure 1 in a birds-eye view,

Figure 3 An alternative form of a retaining ring and Figure 4 An alternative form of the airbag unit in a view corresponding to Figure 1.

Detailed description of preferred embodiments

Figure 1 shows a cross-section through an airbag unit, whereby airbag 50 is in a state where it is not folded in. In addition to this airbag 50, the airbag unit exhibits a housing 10 with side walls 11 and a housing floor 12, a gas generator 20, a retaining ring 30 as well as screws 40 and corresponding nuts 42. The fixing flange extends around the lateral area of gas generator 20 and is fixed rigidly to the remainder of gas generator 20.

The retaining ring 30 is positioned inside the housing and serves to hold fixing flange 22 of gas generator 20 on housing floor 12 in clamped fashion and to fix airbag 50 in relation to housing floor 10. In the embodiment shown here (see also Figure 2, which shows retaining ring 30 with screws 40), three screws 40 are present, whereby each screw extends through corresponding through-holes in the retaining ring, airbag and housing floor. As can be seen, for example, in Figure 1 , clamping of the edge area of airbag 50 takes place along the entire circumference between the retaining ring 30 and the floor 12. This does not apply for the clamping of fixing flange 22 between housing floor 12 and retaining ring 30. It is rather the case that clamping of the fixing flange only takes place in three deformable sections which are separated from one another, which in the embodiment shown here are in the form of elastic tabs 34 of retaining ring 30. These elastic tabs 34 can be seen particularly clearly in Figure 2. Retaining ring 30 is a stamped and bent part of steel sheet which is formed in one piece and elastic tabs 34 are simply produced in that corresponding grooves are stamped in and the areas which are located between the grooves are pressed outwards by means of plastic deformation. As can particularly be seen in Figure 1 the inner edge of retaining ring 30 does not touch fixing flange 22 in the areas in which no elastic tabs are formed, for which purpose the inner edge of the retaining ring is in the form of a bulb 32 bent towards the outside. As can particularly be seen in Figure 1 , the bulb (or bead) 32 does not touch the flange 22 but overlaps it. When high forces act - A - when the gas generator is ignited, the tabs 34 may be strongly bent, but the presence of the bulb (or bead) 32 prevents the gas generator 20 from de-attaching from the housing floor 12. Since the bulb extends around the complete circumference (except the areas of the elastic tabs 14), it can withstand high forces so that it is ensured that the gas generator can not de-attach from the housing.

As can further seen from Figure 2, precisely three screws 40 and three tabs 34 are present, whereby screws 40 and elastic tabs 34 each form a triangle with equal sides and each elastic tabs 34 lies exactly in the centre between two screws 40 and vice versa.

The fact that the clamping of fixing flange 22 only takes places at the positions of elastic tabs 34 has the following advantages: on the one hand it is ensured that where housing floor 12, fixing flange 22 and retaining ring 30 touch, the contact is complete and relatively high pressure is exerted, so that movement of the touching sections of the components against each other, which can lead to noises, cannot occur. Furthermore, the force in these sections is decoupled from the pull forces in the screws 40, which prevents a local pressure load which is too high. By these means it is particularly prevented that any deformations of a component are transferred to the other component. In particular it is prevented that deformations of fixing flange 22 are transferred to housing 10.

Ideally, three screws 40 and three elastic tabs 34 are present, as shown in the first embodiment, as with this arrangement the system is fully defined from the statics point of view, but is not overdefined, which is particularly advantageous from the point of view that deformations of one component are not transferred to the other. However, the link between the components in accordance with the invention also functions if more than three elastic tabs 34 or more than three screws 40 are present, as shown for example in Figure 3, which shows a retaining ring 30 with four screws and four elastic tabs 34.

In Figure 1 the retaining ring 30 and the screw 40 is shown in a view corresponding to section A-A in Figure 2. Figure 4 shows a second embodiment of the airbag unit according to the invention in a view basically corresponding to Figure 1. In contrast to the first embodiment, the deformable sections are here not assigned to retaining ring 30, but to housing floor 12, for which purpose the floor exhibits three elastic tabs 14, which are basically formed in exactly the same way as the elastic tabs 34 of the retaining ring of the first embodiment. Here, retaining ring 30 and fixing flange 22 touch along the entire circumference, but fixing flange 22 and housing floor 12 only touch in the areas of elastic tabs 14, but overlaps it in the areas where no elastic tabs 14 are present. It would basically be possible to combine the two embodiments described above with one another, whereby both housing floor 12 and also retaining ring 30 exhibit deformable areas at the same positions, in particular in the form of elastic tabs.

It should be noted that in both embodiments described here, and this is generally to be preferred, airbag 50 is exclusively clamped between retaining ring 30 and housing floor 12, and in particular airbag 50 is not even clamped in part between retaining ring 30 and fixing flange 22 or between fixing flange 22 and housing floor 12.

It should additionally be noted, that instead of screws 40 and nuts 42, other fixing elements can be provided which exhibit a bolt, in particular fixing elements of the kind described, for example, in DE 10 2006 014 830 A1.

List of reference numbers

10 Housing

12 Housing floor 12a Through-hole

14 Elastic tab

20 Gas generator

22 Fixing flange

30 Retaining ring 32 Bulb

34 Elastic tab

34a Front edge

36 Through-hole

40 Screw 41 Screw head

42 Nut

50 Airbag

Claims

Patent claims

1. Airbag unit with a housing (10) exhibiting a housing floor (12), an airbag (50), a gas generator (20) exhibiting a fixing flange (22) for filling of the air- bag (50), and a retaining ring (30), which is connected to the floor by means of bolts and which holds the fixing flange (22) against housing floor (12) in clamped fashion, characterised in that the retaining ring (30) and/or the housing floor (12) exhibits at least three deformable sections which press on the fixing flange (22).

2. Airbag unit according to Claim 1 , characterised in that only the deformable sections press on the fixing flange (22).

3. Airbag unit characterised in that the airbag (50) is also held by the retaining ring (30).

4. Airbag unit according to Claim 3, characterised in that there is no airbag material between the deformable sections and the fixing flange (22).

5. Airbag unit according to one of the previous claims, characterised in that retaining ring (30) is a one-piece stamped and bent part of sheet metal.

6. Airbag unit according to one of the previous claims, characterised in that the deformable sections are elastic tabs (34).

7. Airbag unit according to 5 and 6, characterised in that the elastic tabs (34) are separated from the main body of the retaining ring (30) or housing floor by stamped out grooves.

8. Airbag unit according to claim 7, characterised in that the inner edge of the retaining ring (30) or the housing floor (12) is in the areas in which no elastic tabs are formed in the form of a bulb (32) bent to the outside.

9. Airbag unit according to one of the claims 7 or 8, characterised in that the inner edge of the retaining ring (30) or the housing floor (12) does not touch the fixing flange (22) in the areas in which no elastic tabs are formed, but overlaps it.

10. Airbag unit according to one of the previous claims, characterised in that exactly three deformable sections are present.

11. Airbag unit according to Claim 10, characterised in that exactly three bolts are present.

12. Airbag unit according to one of the previous claims, characterised in that each deformable section lies in a central position between two bolts.