WO2009124760A1

WO2009124760A1 - Side airbag and side airbag unit

Info

Publication number: WO2009124760A1
Application number: PCT/EP2009/002628
Authority: WO
Inventors: Frédéric CHARPENTIER; Emeric Dujardin; Damien Demulder
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 2008-04-11
Filing date: 2009-04-09
Publication date: 2009-10-15
Anticipated expiration: 2010-10-11

Abstract

A side airbag (20) for the protection of a vehicle occupant (I) in case of a side impact is described. This side airbag (20) exhibits an outer skin enclosing a gas chamber. In order so achieve optimum protection both, when the gas generator assigned to the airbag is triggered based on the signal of a proximity sensor as well as when the gas generator assigned to the airbag is triggered based on the signal of an impact sensor, the side airbag has a first and a second protective state. The gas chamber volume in the second protective state is larger than the gas chamber volume in the first protective state. The side airbag has a ventilation device which in the second protective state is throttled compared to the first protective state. The side airbag is for the use in a side airbag unit that comprises a proximity sensor as well as an impact sensor for the triggering of the side airbag's gas generator.

Description

Side airbag and side airbag unit

Description

Technical field of the invention

The invention relates to a side airbag according to the preamble of Claim 1 and a side airbag unit according to Claim 11.

Side airbags are known in automotive technology and serve to protect the occupants of a vehicle in case of a side impact. Such a side airbag is generally located in the side structure of the vehicle or in the backrest of a vehicle seat and expands between the internal structure and the vehicle occupant when the gas generator assigned to it ignites. One problem which generally exists in the case of side air- bags in comparison to front airbags is that as from the time of collision, there is much less time for unfolding and filling of the airbag than in the case of a front airbag.

Prior art

In generic patent WO 2007/003406, it is therefore proposed to provide a proximity sensor, so that the gas generator assigned to the side airbag is not ignited as late as an object impacts against the side wall, but already when an object approaches the side wall and an evaluation and triggering unit forecasts a side impact from this. Such a system, which ignites the gas generator already when an object approaches, must be set in such a way that "groundless" triggering of the gas generator is practically excluded, as such groundless triggering represents a considerable danger. In case of doubt, triggering, in particular of a side airbag assigned to the driver, must not occur. For this reason, and as work is still in progress in achieving absolute reliability of proximity sensors, an impact sensor is ad- ditionally present in the device of the WO 2007/003406, and the evaluation and triggering unit is set up in such a way that the gas generator for filling of the side airbag is triggered upon impact of an object on the side wall, in so far as this has not already occurred based on the proximity sensor which is also present. The impact sensor therefore serves as a "fallback" sensor. In the same way as practically all airbags, the proposed side airbag exhibits a ventilation device.

Summary of the invention

Starting from this, the present invention sets itself the problem to improve a side airbag of the generic type and a side airbag unit of the generic type in such a way that a protection level which is as high as possible is achieved for the occupants both when the gas generator is triggered based on a signal from the proximity sensor and when the gas generator is triggered based on a signal from the impact sensor.

This problem is solved by means of a side airbag with the characteristics of Claim 1 or by a side airbag unit with the characteristics of Claim 11.

When the gas generator is triggered based on the signal of the proximity sensor, there is a relatively large amount of space between the internal structure of the vehicle and the vehicle occupants and it is ideal to make use of the space available completely, in other words to provide an airbag which has a relatively large thickness. However, if the gas generator is not ignited until an object strikes the side wall, there is less space available, as at the time of complete expansion of the airbag the vehicle occupant has already moved in the direction of the internal structure and/or the structure was already pushed in the direction of the vehicle occupant by the intruding object. There is therefore less space available and the thickness of the side airbag should be less than in case of the ignition of the gas generator before the object strikes the vehicle. In this case, a too-thick airbag would have a negative influence on the protective effect, as it could lead to the vehicle occupant being pushed away too far into the interior of the vehicle, respectably the forces exerted on the vehicle occupant would be too large. Therefore a side airbag with a first protective state and a second protective state is provided whereby the second protective state exhibits an increased gas chamber volume and therefore a greater thickness than the first protective state. At least one tear-open connection is provided which tears open during the transition from the first protective state to the second protective state; in other words, there is a defined transition from the first to the second protective state. It is possible to allocate a precise gas chamber volume and a precise maximum thickness to each of the two protective states. This means that the suitable thickness of the side air- bag is provided for both situations. This thickness can be selected so as to be ideal in each case. This means in particular, that in the case of optimal protection, in other words if the side airbag is already triggered before an object has struck, no compromises have to be made in order to achieve acceptable values in a non- optimal situation, in other words if the side airbag is not triggered until an object impacts the side wall.

As, however, usually only a single gas generator is used, and this gas generator does not "know" whether it was ignited based on the proximity sensor or based on the impact sensor, and the airbag volume to be filled is of different sizes, further measures have to be taken in order to achieve the appropriate airbag hardness in every case. According to the invention, this is achieved in that the ventilation in the second protective state is throttled in comparison to the first protective state. In other words: at least one ventilation device is present, which has a free cross- section in every state, with the free cross-section in the first protective state being larger than in the second protective state, so that more gas can exhaust in the first protective state.

Further advantageous embodiments of the invention result from the subclaims, and also from the embodiment shown in more detail in relation to the figures. The figures show: Brief description of the drawings

Figure 1 A strongly schematised representation of the invention, whereby the gas generator of a side airbag was ignited based on the signal of a proximity sensor and the side airbag is in a pre-unfolding state,

Figure 2 The items shown in Figure 1 , whereby the side airbag is in its first protective state,

Figure 3 The items shown in Figure 2, whereby the side airbag is in a second protective state, Figure 4 The items shown in Figure 1 , whereby the gas generator was ignited based on the signal of an impact sensor and the side airbag is in its pre-unfolding state,

Figure 5 The items shown in Figure 4, where by the vehicle occupant is lying against the impact surface of the airbag and the latter is in its first protective state,

Figure 6a A perspective view of a side airbag in its pre-unfolding state,

Figure 6b The items shown in Figure 6a in a broken up view,

Figure 7a The items shown in Figure 6a, whereby the side airbag is in its first protective state, Figure 7b The items shown in Figure 7a, in a broken up view,

Figure 8a The items shown in Figure 7a, whereby the side airbag is in its second protective state,

Figure 8b The items shown in Figure 8a, in a broken up view,

Figure 9 A view of the side airbag from Figure 7a from Direction R, Figure 10 A view of the side airbag from Figure 8a from Direction R,

Figure 11a The principle of the outlet valve shown in Figures 9 and 10 in a further three-dimensional view in the state shown in Figure 9,

Figure 11b The items shown in Figure 11a in a sectional view,

Figure 12a The items shown in Figure 11a in a state corresponding to Figure 10,

Figure 12b The items shown in Figure 12a in a sectional view, Figure 13 A schematic representation of a second embodiment of the invention, whereby the side airbag is in its first protective state, Figure 14 The items shown in Figure 13, whereby the side airbag is in its second protective state,

Figure 15 A schematic representation of a ventilation device, as can be used in the second embodiment, in the first protective state of the side air- bag and

Figure 16 The items shown in Figure 15 in the second protective state of the side airbag.

Detailed description of preferred embodiments

Figure 1 shows a simplified principle view of a side airbag unit according to the invention. A side airbag 20 is held on the vehicle side wall F and can be inflated by a gas generator 16, which is located in the inside of the side airbag. Gas generator 16 is triggered by the evaluation and triggering unit 14 which in turn is con- nected to a proximity sensor 10 and an impact sensor 12. The evaluation and triggering unit 14 is programmed in such a way that it ignites the gas generator 16 when it interprets the signals of a proximity sensor 10 in such a way that striking of an object O against the vehicle side wall F is certain. If an object O strikes the vehicle side wall F without the gas generator 16 being ignited, this is registered by the impact sensor 12 upon whose signal the gas generator 16 is ignited by the evaluation and triggering unit 14. the impact sensor 12 therefore serves as a "fallback" sensor for the proximity sensor 10.

The side airbag 20 exhibits three unfolding states, namely a pre-unfolding state, as is shown in Figure 1 , a first protective state, as shown in Figure 2, and a second protective state, as is shown in Figure 3. In each of these unfolding states, the side airbag has a defined volume and a defined maximum thickness d_maxv. dm_axsi. d_maχ_S2- In order to reach these three unfolding states, the side airbag 20 is constructed as follows:

The side airbag exhibits an impact section 22 with an edge area 22a and a support section 24 lying opposite to the impact section 22 with an edge area 24a. Along at least a part of the edge areas 22a, 24a, impact section 22 and support section 24 are connected with each other in the passive state and in the pre- unfolding state by means of a first tear seam 30. This first tear seam 30 forms the first tear-open connection. Preferably, the first tear seam 30, as will be seen precisely later, extends over the upper, lower and front sections of the edge areas 22a and 24a. If the first tear seam 30 is closed, the pre-unfolding state results as is shown, for example, in Figure 1. In this pre-unfolding state, the impact section 22 and the support section 24 form the entire outer skin of the side airbag. Between the edge areas, in the embodiment shown in the upper, lower and front area of the same, a further skin section 26 is provided and connected both with the impact section and with support section 24. This further skin section 26 again exhibits a primary area 26a and a secondary area 26b. The secondary area 26b is, until the second protective state is reached, connected with itself by means of a tear seam field 32. In the passive state and in the pre-unfolding state the further skin section 26 is folded into the inside of the side airbag. The items described above will be explained again later in more detail in view to the Figures 6a to 8b.

As indicated schematically in Figures 2 and 3, a ventilation device is present, which is active at least in the two protective states. The ventilation device is throttled in the second protective state in comparison to the first protective state.

With reference to Figures 1 to 5, now the sense and the way of functioning of the several unfolding states and also the sense of the associated ventilation states will be explained.

Figure 1 shows the situation when the side airbag 20 is ignited because of the signal of the proximity sensor 10. In this connection, Figure 1 shows the side air- bag 20 in the pre-unfolding state, in which the first tear seam 30 is still closed. The presence of this first tear seam 30, which determines the existence of the pre- unfolding state, has the sense that the side airbag 20 is completely unfolded at a very early point in time, which is also a requirement for reliable functioning of the side airbag according to the shown embodiment of the invention. In order to achieve rapid unfolding into the pre-unfolding state, preferably no ventilation takes place in the first unfolding phase until the pre-unfolding state is reached. Following the completion of the pre-unfolding phase, as is shown in Figure 1 , the first tear seam 30 tears open, upon which the side airbag 20 unfolds up to its first protective state as is shown in Figure 2. It can be seen that in this state the pri- mary area 26a of the further skin section 26 forms a part of the outer skin of the side airbag 20. The ventilation device becomes active at the latest when the first protective state is reached, and exhibits a first free overall cross-section. If the gas generator 16 is ignited based on a signal of the proximity sensor 10, the first protective state is reached before the occupant I strikes the impact section 22 of the side airbag 20, which means that the side airbag 20 can expand further. This occurs in that the seams in the tear seam field 32 tear open and release the secondary area 26b of the further skin section 26.

Following the completion of this process, the second protective state shown in Figure 3 with the maximum gas chamber volume and maximum thickness d_maxs₂ of the airbag is reached. This is the optimum protective state. Because of the early unfolding, occupant I, as indicated in Figure 3, does not strike the impact section 22 until the second protective state is reached. As the volume that has to be filled by the gas generator is larger than in the first protective state, the whole effective cross-section of the ventilation device is selected so as to be smaller than in the first protective state, in which the volume to be filled is smaller.

Figures 4 and 5 show the items just described if the gas generator 16 is not ignited based on a signal of proximity sensor 10, but based on a signal of the im- pact sensor 12, in other words later. Here also, as is shown in Figure 4, first the pre-unfolding state is reached. However, at the latest following the completion of the first protective state, the impact section 2 is already lying against the occupant I, so the expansion of the side airbag 20 is correspondingly hindered and there is no longer sufficient force available in order to open the tear seams in the tear seam field 32, which means that the second protective state is not reached. The maximum gas chamber volume and the maximum thickness remain smaller than in the second protective state. As already mentioned, the ventilation device is then in a condition in which it is opened to a larger extend than in the second protective state (Fig. 5).

In relation to Figures 6a to 12, the construction of the side airbag will now be de- scribed again in more detail and in particular it will be explained by means of a possible embodiment how the different free cross-sections of the ventilation device are achieved in the two protective states.

Figure 6a shows a perspective view of the side airbag in a pre-unfolding state, The first tear seam 30 can be seen, which connects the two edge areas 22a, 24a of impact section 22 and support section 24 in an upper, a lower and front section. One can also see a valve tab 42, which encloses a part of the lower section of the edge area. This ventilation tab 42 is a part of the ventilation device.

In Figure 6b it can be seen how the further skin section 26 extends into the interior of the airbag in the pre-unfolding state. Here also, the primary area 26a and the secondary area 26b, in which the tear seam field 32 is located, can be recognised. The second ventilation opening 44 is located at the rear edge of the secondary area 26b, which is inactive in the pre-unfolding state and in the first protec- tive state. The secondary area 26b is preferably woven in one piece, so that the tear seam field 32 is an integral part of the further skin section 26 and the tear seams are woven threads. However it is also possible, though in general more time-consuming and costly, to sew the tear seams in tear seam field 32 separately.

After the first tear seam 30 has torn open, the side airbag 20 enters into the first protective state shown in Figures 7a and 7b. It can be seen that in this state the primary area 26a of the further skin section 26 forms a part of the outer skin of the side airbag. The side airbag has transformed from a 2-D structure into a 3-D structure. As can be seen in Figure 7a and Figure 9, which is a view from Direction R in Figure 7a, also in the first protection state, the valve tab 42 does not lie tightly against the side airbag. This means that gas can stream out through the two first ventilation openings 40, which are located in the primary area 26a of the further skin section 26, and which were released during the transition from the pre-unfolding state into the first protective state.

If the side airbag can continue to unfold freely, the tear seams in tear seam field 32 tear open, and the secondary area 26b of the further skin section 26 is released, which means that it also forms a part of the outer skin of the side airbag. Thus, the side airbag has a greater volume and a greater maximum thickness. Furthermore, the second ventilation opening 44 is released by these means and gas then streams out of the gas chamber through this second ventilation opening 44. At the same time, first ventilation openings 40 are closed because the ventilation tab 42 is pressed onto the first ventilation openings 40 because of the further thickening of the side airbag, as can be seen in Figures 8a and 10. The surface of the second ventilation opening 44 is smaller than the total surface of the first ventilation openings 40, so that the entire ventilation device is throttled in the second protective state in comparison to the first protective state.

The second ventilation opening 44 opens very late, namely when the second protective state is completely or almost completely reached. The side airbag can be adjusted in such a way that it is not ventilated during the transition from the first to the second protective state. This is possible as the side airbag unit can be set up in such a way that the second protective state is only reached when the gas generator is ignited based on a signal of proximity sensor 10, and it is then also sure that the occupant does not strike the side airbag until the completion of the second protective state. This means that it is possible to "save gas" during the transition from the first into the second protective state, which naturally also favours a rapid completion of the second protective state.

The functioning of the lower valve, which is closed during the transition from the first into the second protective state, is shown again in Figures 11a to 12b.

The side airbag therefore exhibits two partial ventilation devices, whereby the first partial ventilation device is formed of the first ventilation opening 40 and the ven- tilation tab 42 and the second partial ventilation device is formed of the second ventilation opening 44 and the tear seam field 32.

Figures 13 and 14 show a second embodiment of a side airbag 20 according to the invention in a schematic representation. The side airbag of this embodiment is comprised of only two cuttings 50, 52, whereby the impact surface 50a is a part of the first cutting 50 and the support surface 52a is a part of the second cutting 52. A further skin section 26 is not present. In contrast to the first embodiment, the side airbag 20 only exhibits a first and a second protective state. There is no de- fined pre-unfolding state. In the first protective state, the front areas of the first and the second cutting 52 are connected with each other by means of a tear seam field 32, so that an area which projects towards the inside is formed. The innermost point of this area which projects towards the inside is connected with a fixed point, for example with the gas generator 16 by means of a tether 54. If the impact surface 22a comes into contact with the vehicle occupant early, a further expansion is prevented, and the airbag remains in the first protective state shown in Figure 13 with reduced volume and reduced maximum thickness.

However, if the side airbag 20 can inflate unhindered, the tear seams in the tear seam field 32 tear after reaching the first protective state and the side airbag expands up to its second protective state shown in Figure 14, in which it exhibits a heart-shaped cross-section because of the relatively short tether.

In Figures 13 and 14 a ventilation device is shown in schematic form whose state is actively influenced. This vent device exhibits a ventilation opening 74, a valve element 72 which can be torn off the skin of the airbag (referred to as "tearable valve element 72"), a pull element 70 and an actuator, which can for example work pyrotechnically. This actuator can for example be flanged onto the gas generator. The tearable valve element 72 is sewn to the skin of the side airbag by means of a tear seam around the ventilation opening 74 and is connected with the actuator by means of the pull element 70. The tearable valve element 72 has a through-hole 72a, whose diameter is smaller than the diameter of the ventilation opening 74. The actuator is connected with the evaluation and triggering unit 14 by means of a signal line. If the ignition of the gas generator 16 is caused by the evaluation and triggering unit 14 based on a signal of the impact sensor 12, the actuator is also ignited and the tearable valve element 72 is torn off by the pull element 70, so that the side airbag 20 is ventilated via the entire ventilation open- ing 74 - Figure 13, first protective state. If₁ in contrast, the gas generator 16 is ignited based on a signal of the proximity sensor 10, the evaluation and triggering unit 14 does not trigger the actuator and the tearable valve element 72 remains in front of ventilation opening 74 and the ventilation device is throttled in the second protective state in comparison to the first protective state - Fig. 14.

However, because of the increased effort and cost involved, passive solutions are often to be preferred and are also possible in the case of a side airbag of the second embodiment, as shown in Figures 15 and 16:

Figures 15 and 16 show a possible passive ventilation device for the embodiment just shown (in so far as no active ventilation device is present). Here, the second cutting 52 exhibits a common ventilation opening 60 with a defined cross-section. A cover cutting 56 is provided, which is connected with the first and second cuttings 50, 52 by means of permanent seams 57a and 57b. In addition, a cover cut- ting 56 is connected with the second cutting 52 by means of a valve tear seam 58. The length of the cover cutting 56 is selected in such a way that a loop 56a is formed between the valve tear seam 58 and the permanent seam 57b. The cover cutting 56 has two openings 65 and 66, whereby the first opening 65 is located over the ventilation opening 60 of the second cutting 52 in the first protective state, whereby the two openings are basically of the same size. The second opening 66 is located in the area of the loop and has a smaller diameter.

If the tear seams in the tear seam field 32 tears, and if the thickness of the side airbag therefore increases, the valve tear seam 58 tears because of the pull forces and the cover cutting 56 is pulled over the ventilation opening. In the completely expanded second protective state, the second opening 62 comes to lie above the ventilation opening, so that the ventilation device is throttled in comparison to the first protective state. In view to the first and the second embodiment it can be seen, that the ventilation device of the side airbag according to the invention can consist of two partial ventilation devices which are completely separate from one another, in which a first partial ventilation device is open in the first protective state and is closed in the second protective state and in which a second partial ventilation device is closed in the first protective state and is open in the second protective state (first embodiment), or of a common ventilation device, which exhibits different effective cross-sections in the two protective states (second embodiment). Mixed forms of these could also be imagined.

List of reference numbers

10 proximity sensor

12 impact sensor

14 evaluation and triggering unit

16 gas generator

20 side airbag

22 impact section

22a edge area

24 support section

24a edge area

26 further skin section

26a primary area

26b secondary area

30 first tear seam

32 tear seam field

40 first ventilation opening

42 valve tab

44 second ventilation opening

50 first cutting

52 second cutting

54 tether

56 cover cutting

57a,b permanent seam

58 valve tear seam

60 common ventilation opening

65 first opening

66 second opening

70 pull element

72 tearable valve element

72a through-hole

74 ventilation opening

F vehicle side wall

I occupant

Claims

Patent claims

1. Side airbag (20) for protection of a vehicle occupant in case of a side im- pact, whereby the side airbag (20) exhibits an outside skin surrounding a gas chamber and a ventilation device, characterised in that the side airbag has a first protective state and a second protective state with a larger gas chamber volume compared to the first protective state, whereby at least one tear-open connection (tear seam field 32) is present which tears open at the transition from the first protective state to the second protective state, and whereby the ventilation device in the second protective state is throttled compared to the first protective state.

2. Side airbag (20) according to Claim 1 , characterised in that it further has a pre-unfolding state with a gas chamber volume which is smaller than the gas chamber volume of the first protective state, whereby at least one further tear-open connection (first tear seam 30) is present, which tears open at the transition from the pre-unfolding state into the first protective state.

3. Side airbag (20) according to Claim 2, characterised in that in the pre- unfolding state it has a 2D structure and in the first and second protective state it has a 3D structure.

4. Side airbag according to Claim 2 or Claim 3, characterised in that the ventilation device is closed in the pre-unfolding state.

5. Side airbag (20) according to Claim 1 , characterised in that it comprises a tether (54) which limits its length.

6. Side airbag (20) according to one of the previous Claims, characterised in that it comprises at least two partial ventilation devices, whereby a first partial ventilation device is open in the first protective state and closed in the second protective state and whereby a second partial ventilation device is closed in the first protective state and open in the second protective state.

7. Side airbag (20) according to one of the Claims 1 to 5, characterised in that s it comprises a common ventilation device, which in the first protective state exhibits a first effective cross-section and in the second protective state exhibits a second effective cross-section which is smaller than the first effective cross-section but larger than zero. o

8. Side airbag (20) according to Claim 7, characterised in that the common ventilation device exhibits a movable or tearable cover.

9. Side airbag (20) according to one of the previous Claims, characterised in that the change in state of the ventilation device occurs passively. 5

10. Side airbag (20) according to one of Claims 1 to 8, characterised in that the change of state of the ventilation device occurs actively.

11. Side airbag unit comprising a side airbag (20) according to one of the pre-0 vious Claims, a gas generator (16) for filling of the side airbag (20), an evaluation and triggering unit (14) for actuation of the gas generator (16), a proximity sensor (10) interacting with the evaluation and triggering unit (14) and an impact sensor (12) interacting with the evaluation and triggering unit (14), whereby the evaluation and triggering unit (14) ignites the gas gen-5 erator (16) upon a signal of the impact sensor (12), in so far as this has not yet occurred based on a signal of the proximity sensor (10).