Description

Technical field of the invention

The invention relates to a side airbag for protection of a vehicle occupant accord- ing to the preamble of claim 1 and to an airbag unit according to claim 11.

Airbags are generally well known in the vehicle industry and are provided in the vehicle for protection of vehicle occupants in a frontal, side or roll over crash of the vehicle. In case of sensing such a crash by a crash or pre-crash sensor one or several gas generators are triggered by a control device which fills the or each airbag with gas.

Side airbags are also well known and there are airbags used to protect occupants during a side impact or roll over accident. Those side airbags are usually mounted in the seat back of vehicle seats and inflate in position between the occupant and the side structure of the vehicle. Side airbags typically protect the head, thorax and/ or pelvic area of an occupant. It is also known to provide a so-called inflatable curtain airbag which is mounted in the roof rail portion of the vehicle and deploys downwards to cover the side windows.

Prior art

GB 2 404 623 discloses a generic side airbag which is provided in the seat back of a vehicle seat. The side airbag comprises an inner airbag as a first chamber which is provided with an inflator. Several openings are provided in the peripheral wall of the inner airbag in order to let gas flow from the inner airbag into an outer airbag which forms a second chamber. According to an embodiment the second chamber can be divided in several cells in order to protect different regions of an occupant.

The side airbag in GB 2 404 623 is considered to give an occupant good side protection, but it is complicate to assemble and rather heavy weight with two air- bags arranged inside each other.

Summary of the invention

Based on this the present invention sets itself the problem to improve a generic side airbag and a generic side airbag unit to that effect that the assembly is simplified, the weight and cost are reduced.

For a side airbag to protect the head and thorax regions of an occupant there is further a problem to get such airbag in position passing the shoulder region of the occupant. There is usually only little space between the side structure of the vehicle and the shoulder of an occupant.

For solving the above mentioned problems a side airbag is provided with a divid- ing wall which is formed as dividing seam and the gas overflow passage is located between a top portion of the first chamber and a top portion of the second chamber. Preferably the gas overflow passage is formed between a top end of the dividing seam and the periphery seam of the side airbag. There is provided only a single gas overflow passage between first and second chambers.

Using a seam to divide first and second chambers is simple to produce and does not create extra weight. The location of the overflow passage at the top portion of the airbag brings the advantage that the first chamber can be inflated swiftly and the second chamber is inflated subsequently after the first chamber. In case of a head-thorax side airbag such overflow passage is located above the shoulder region of an occupant. The second chamber can be positioned and is supported by the inflated first chamber. To protect the thorax region of an occupant the bottom portion of the first chamber has a generally wide shape extending from the front portion to the rear portion of the side airbag. The first chamber extends from the bottom portion to the top portion and has a tapered shape with a generally narrow top portion. The narrower top portion enables the first chamber to be inflated very swiftly. The first chamber is provided with an inflator interface portion and it is inflatable by gas from an in- flator.

In order to protect the head of an occupant the top portion of the second chamber has a generally wide shape extending from the front portion to the dividing seam. The second chamber extends from the top portion to the dividing seam and has a tapered shape with a generally narrow bottom portion. A vent opening can be formed in the bottom portion of the second chamber. Preferably the vent opening is located in the side airbag layer directing away from the occupant in the inflated condition of the side airbag in the vehicle. By doing this the occupant will not be treated with the hot exhaust gas from the vent opening.

During inflation of the side airbag the first chamber is inflated first in upward direction with gas from an inflator and subsequently the second chamber is inflated in downward direction with gas from the first chamber via the overflow passage.

Further preferred alternatives of the invention result from the subclaims and also from the embodiments which will now be described in more detail with reference to the figures. The drawings show:

Brief description of the drawings

Figure 1 A side view to a vehicle seat with an inflated side airbag,

Figure 2 a side view to the side airbag of figure 1 in a partly inflated condition,

Figure 3 a side view to the side airbag of figure 2 in fully inflated condition. Detailed description of preferred embodiments

Figure 1 shows a vehicle seat 1 with a seat back 2, a seat pad 3 and a head rest 4. An occupant or respectively a dummy 10 is shown sitting on the seat 1.

Figure 1 also shows a side airbag 20 in the inflated condition. The side airbag 20 has a first chamber 28 which is provided with an interface portion 21 to an inflator which is not shown in figure 1 in order to improve the clarity of the figure. An inlet opening 22 is located in the inflator interface portion 21 into which an inflator 25 (see figure 2) may be inserted into the first chamber 28 at least partly. The inflator 25 may then be secured to the seat frame via studs 27, wherein a first stud 27 can project through the stud opening 23 and a second stud 27 may project through the inlet opening 22. In order to protect the airbag material from the hot inflator gas a heat protection panel 24 is arranged in the inflator interface portion 21 at least covering the fabric material in the area of the outlet openings 26 of the inflator 25.

The first chamber 28 extends from the bottom portion 29 to the top portion 30 of the first chamber 28 which is actually the bottom and the top of the side airbag 20. The bottom portion 29 has a relatively wide extension from front to rear portions in order to provide protection of the thorax region 11 of the occupant 10. The bottom portion 29 extends from the front portion 37 to the rear portion 36 of the side air- bag 20. The first chamber 28 has a tapered shape from bottom to top and ends with a relatively narrow top portion 30.

Figure 2 shows a condition in which the first chamber 28 is inflated. After it has been inflated, gas will enter the gas overflow passage 35 between the top edge of the side airbag and the looped shaped top part 33 of the dividing seam 32 which extends substantially vertically through the side airbag 20 and divides the first chamber 28 from the second chamber 38. The top end 33 of the dividing seam 32 is formed as loop in order to create more robustness in the seam portion. Such loop 33 can better withstand the heat and force from the gas flow. Figure 3 shows the side airbag 20 in fully inflated condition. The second chamber 38 extends from the top portion 39 in a tapered shape down to the bottom portion 40, wherein the top portion 39 extends from the front portion 37 of the side airbag 20 to the dividing seam 32. The top portion 39 has a relatively wide shape from front to rear in order to provide protection for the head 13 of an occupant 10. The top portion 39 of the second chamber 38 receives gas from the gas overflow passage 35 and the second chamber 38 is inflated starting at the top portion 39 down to the bottom portion 40. It is to be understood that the gas overflow passage 35 must be at the top portions 30, 39 of both first and second chambers 28, 38 and there is only such gas overflow passage 35 arranged between both chambers 28, 38. However, the invention will also work, if the gas flow passage 35 would be split into several overflow channels all arranged in the top portions 30, 39 of both chambers 28, 38 above the shoulder region 12 of the occupant 10. Those split gas channels would be considered as a single overflow passage 35 according to the invention.

Due to this sequence of inflation the shoulder 12 of the occupant 10 is by-passed, in that the first chamber 28 inflates rearwards the shoulder 12 - as shown in figure 1 - and the gas overflow passage 35 is located above the shoulder 12 in the in- flated condition of the side airbag 20. The second chamber 38 inflates downwardly above and in front of the shoulder 12 - again as shown in figure 1. Therefore the shoulder 12 of the occupant 10 does not act as an obstacle for the deployment of the side airbag 20.

In the bottom portion 40 of the second chamber 38 a vent opening 42 is provided in order to release gas from the side airbag 20 during the contact between side airbag 20 and occupant 10 and to absorb energy. The vent 42 is located in the side wall away from the occupant 10 in order to avoid any contact of the occupant 10 with the hot gas.

In figure 3 there is shown an alternative type of inflator interface portion 21 with an inlet slit 45 to insert the inflator 25. The studs 27 can be exposed through stud holes 47 for attachment to the seat frame. A sealing panel 46 is provided to minimize any leakage through the inlet slit 45 during the inflation process.

The side airbag 20 of figure 3 is formed of a single so called "butterfly" fabric panel which is folded along an axis (not shown) extending along the rear portion 36 of the side airbag 20, so that a folded edge 48 is created at the rear portion. A periphery seam 31 arranged at the top, front and bottom portions of the side air- bag and connects the two fabric layers in order to close the side airbag 20.

List of reference numbers

1 Vehicle seat

2 Seat back

3 Seat pad

4 Head rest

10 Occupant

11 Thorax region of occupant

12 Shoulder region of occupant

13 Head of occupant

20 Side airbag

21 lnflator interface portion

22 Inlet opening

23 Stud opening

24 Heat protection panel

25 lnflator

26 Outlet openings

27 Studs

28 First chamber

29 Bottom portion (thorax protection)

30 Top portion

31 Periphery seam

32 Dividing seam

33 Loop

35 Overflow passage

36 Rear portion of side airbag

37 Front portion of side airbag

38 Second chamber

39 Top portion (head protection)

40 Bottom portion

42 Vent opening

45 Inlet slit Sealing panel Stud holes Folded edge