WO2006130059A1

WO2006130059A1 - Airbag inflator system

Info

Publication number: WO2006130059A1
Application number: PCT/SE2005/000844
Authority: WO
Inventors: Roland Schneider; Stefan SVEDJENÄS; Johan Lindqvist; Ulf Magnusson; Alf Holgers
Original assignee: Autoliv Development Ab
Priority date: 2005-06-03
Filing date: 2005-06-03
Publication date: 2006-12-07

Abstract

The invention relates to an airbag inflator (3, 3´, 3´´) comprising a first chamber (1, 1´, 1´´) with a first outlet (4, 4´, 4´´) through which a high velocity gas flow is released. The first outlet (4, 4´, 4´´) is encircled by a shroud orifice (5, 5´, 5´´) to direct a pressurized shrouding gas flow circumferentially around the high velocity gas, when released. Preferably, a second chamber (2, 2´) or a separate outlet (5´´) for instance a diffuser, is arranged for discharging the shrouding gas flow at a lower velocity level than the velocity of the high velocity gas flow in order to reduce high sound levels in the environment, due to the high velocity gas flow.

Description

AIRBAG INFLATOR SYSTEM

Technical area

The present invention relates to an airbag inflator comprising at least a first chamber having at least a first outlet through which a high velocity gas flow is released.

Technical background

Airbag inflators are well known in the art of motor vehicles for protecting the occupants of the vehicle in the case that an accident occurs. Generally the airbag is filled with a gas flow which is released at a high velocity from an inflator chamber via an outlet to a nozzle. The nozzle is arranged inside the airbag to distribute the gas flow uniformly and to quickly fill the airbag before the occupants collides with it.

The released high velocity gas flow from the inflator chamber and the outlet interacts with the ambient essentially stagnant air, wherein shearing forces are created which in turn leads to turbulence and high sound levels.

From DE 198 44 427 Al it is known to have an outlet arranged with a bypass conduit, to lead ambient stagnant air into the outlet before the mix of gas and air enters the airbag. By using the ambient atmospheric air, which is sucked or pumped from the interior of the vehicle, the sound levels can be reduced.

However, the described arrangement in DE 198 44 427 Al is difficult to control and exhibits difficulties in response time for quickly inflating the airbag. The need for regulated ports or pumps will be more complex and expensive than conventional airbag inflators. Summary of the invention

An object of the present invention is to provide an improved airbag inflator which eliminates at least some of the above problems . This and other objects are achieved in accordance with the teachings of the present invention, wherein the airbag inflator of the kind outlined in the introduction characterises in that; said first outlet is at least partly encircled by shroud orifice portions which are arranged to direct a pressurized shrouding gas flow circumferentially around the high velocity gas, when released, and wherein said inflator further comprises means for discharging the pressurized shrouding gas flow at a lower velocity level than the velocity of the high velocity gas flow in order to reduce high sound levels in the environment, due to the high velocity gas flow.

The present invention is based on the understanding that by using at least one shrouding gas flow at a gradually reduced velocity around the high velocity gas flow, the high sound levels can be reduced. Thus the peripheral gradual velocity reduction to the ambient air (at essentially zero or almost zero velocity) will lead to a smooth and moderate velocity difference which will facilitate the sound reduction. The smaller velocity difference the better sound reduction. Preferably the shrouding gas flow is formed as close to the sound source as possible, for instance adjacent the first chamber and its outlet.

The feature, said first outlet is at least partly encircled by shroud orifice portions denotes primarily that said first outlet is fully encircled. However a plurality of separate orifice portions may for instance be arranged peripherally of the first outlet to form the shrouding gas . The feature, a pressurized shrouding gas flow denotes a gas (a generated gas or a pressurized gas) which at least is pressurized when released, for instance by a burst disc.

The feature, means for discharging the pressurized gas flow denotes the mechanical characteristics of the shroud orifice portions, such as a constriction and/or the characteristics of the gas pressurization, such as an adapted propellant medium.

According to an embodiment of the invention, the airbag inflator further comprises at least a second chamber which is connected to said shroud orifice portions for separately discharging the shrouding gas flow from said high velocity gas flow. By providing at least a second chamber, the use of a different characteristic of the shrouding gas, then the one of the high velocity gas, is enabled. Thus, the velocity of the shrouding gas in relation to the inner high velocity gas can be more predictable, easier to control and adapt. It should be noted that a third chamber and additional chambers can be arranged for providing additional shrouding gas flows in accordance with the invention.

Preferably, the second chamber may be separated from said first chamber. By separating the chambers ensures for a predetermined and controllable inflator function. Further the second chamber is arranged to at least partly enclose said first chamber. Thus the first chamber can be arranged inside the second chamber. As mentioned above additional chambers may be arranged to enclose at least the first chamber for providing additional shrouding gas flows . In accordance with an embodiment the shroud orifice portions are arranged adjacent to said first outlet to form an ejector device. Such an ejector device will draw the shrouding gas out of the second chamber by means of the high velocity gas flow. The ejector device will ensure that the shrouding gas flows around the high velocity flow. Preferably the shroud orifice portions and the first outlet is at least partly arranged inside said second chamber. By arranging the shroud orifice portions and the first outlet in this way, before entering the boundary of the airbag cushion, the reduction of high sound levels can be achieved in a early stage. Thus the shrouding gas can be formed around the high velocity gas well before entering a nozzle or the like for distributing the gas in the airbag. Further, the first chamber and the second chamber can be provided with a common burst disc for in common use. This burst disc can be the separating element between the first and the second chamber when separated. By using, the same burst disc for both chambers an immediate chamber opening, is achieved. The burst disc arrangement enables that the shroud can be formed at the burst disc or at least downstreams in the vicinity of said burst disc. As mentioned above, apart from the two chambers, additional chambers may be arranged, preferably arranged as the layers as of an onion wherein a common burst disc also can be used.

The first chamber may be provided with a plurality of angularly spaced radially directed first outlets. By providing, several radial outlets, the gas distribution and safety, are improved. In order to adapt the inflation to a desired form of the airbag, the radial outlets may be unevenly distributed around the first chamber and consequently also the second chamber.

In addition, at least the first chamber may be provided with a propellant medium. For instance the gas (the high velocity gas) can be generated and pressurized with an ignited propellant medium which at least partly creates a sound source to be reduced, in accordance with the invention. Alternatively or additionally, at least the second chamber is provided with stored pressurized gas. It should be noted that combinations and alterations are possible for the contents of the first and second chambers (pressurized gas/propellant medium) .

In accordance with one embodiment of the present invention the high velocity gas as well as the shrouding gas emanates from the first chamber, as a common chamber. This enables to split up the gas from the first chamber by the shroud orifice portions and the first outlet.

Further, the shroud orifice portions may be separated from the first outlet. Also the shroud orifice portions can be provided with said means for discharging the shrouding gas flow, such as a diffuser. By providing such a shroud orifice portion, a required velocity difference can be achieved in relation to the high velocity gas and the shrouding gas. The shroud orifice portions and the first outlet may be at least partly arranged outside said first chamber. The external arrangement will ease the assembly of the airbag inflator. Alternatively the shroud orifice portions and the first outlet may be at least partly arranged inside said first chamber.

Preferably the first chamber is provided with stored pressurized gas. For instance the first outlet and the shroud orifice portions at the first chamber, in the case of an accident, may be open by, an opening mechanism (pyrotechnic or non-pyrotechnic) for releasing the pressurized gas.

Alternatively or additionally, the first chamber may be provided with a propellant medium. Such a medium can for instance be a part of an opening mechanism as described above.

Apart from the already mentioned, other objects and advantages will be apparent to those skilled in the art from the following detailed description taken in conjunction with the appended claims and drawings.

Brief description of the drawings The present invention will now be described in more detail with reference to the accompanying schematic drawings which show preferred embodiments of the invention and in which: Fig. Ia shows a perspective view of an airbag inflator according to a first embodiment of the invention;

Fig. Ib shows an enlarged view of a section of the airbag inflator in fig. Ia. Fig. 2 shows a longitude-sectional view and a cross- sectional view of an airbag inflator according to a second embodiment of the invention.

Fig. 3 shows a longitude-sectional view of an airbag inflator according to a third embodiment of the invention.

Detailed description of preferred embodiments

Preferred embodiments of the invention will be described in the following. The embodiments described should not be regarded as restricting, but merely as examples .

Fig. 1 shows an airbag inflator 3 according to a first embodiment of the invention, which inflator preferably is made of metal, has a first chamber 1 arranged internally of a second chamber 2. In this specific first embodiment the second chamber 2 is a storage chamber that is filled and pressurized with a compressed gas. Such compressed gases can be stored in gaseous or liquid form, or as a mixture of gas and liquid. The second chamber forms at least partly a shrouding gas, explained below in detail. The shrouding gas flow is indicated with an unfilled arrow.

The shown second chamber 2 is elongated and cylindrical, preferably in the form of a seamless tube. The first chamber 1 is preferably arranged inside the second chamber 2. In this specific first embodiment the first chamber 1 is a combustion chamber which contains a propellant medium in order to generate a gas. The generated gas forms at least partly a high velocity gas, indicated with a filled arrow in fig. Ia, b. The propellant medium can for instance be a selected gas generating reactant material, for example in the form of pellets, wafers or grains. The propellant medium is preferably ignited by a initiator device (not shown in the drawings) .

The first chamber 1 has a cylindrical main portion 8 which is connected to a tapered, essentially cone shaped portion 9. A sleeve shaped outlet portion 10, forming a first outlet 4, is arranged at the smaller end of the tapered portion 9. In fig 1, the longitudinal axis of the first chamber 1, in line with the first outlet 4, is essentially perpendicular to the longitudinal axis of the second chamber.

The outlet 4 is preferably covered by a burst disc 7 or alternatively a device with similar function. According to the first embodiment the burst disc 7 is attached to the wall of the second chamber 2 (storage chamber) . With reference to fig. Ib, the burst disc 7 exceeds the diameter of the outlet portion 10. Apart from the first outlet 4, the burst disc 7 preferably also covers an opening 11 in the second chamber, as a part of the second chamber wall, see fig. Ib.

The opening 11 with the burst disc 7 are adapted to the outlet 4 for forming shroud orifice portions 5 at the peripheral of the outlet portion 10. As will be appreciated by those skilled in the art, the adaptation of the shroud orifice portion 5 in relation to the outlet 4 can be selected to provide a desired particular inflation performance in a certain inflator installation. The adaptation for forming the shroud orifice portion is mainly achieved by adapting the burst disc. By selecting a specific burst disc an appropriate passage, is achieved. Other parameters that may be varied is the pressurization of the first chamber and/or second chamber .

A distribution means 12, such as one or several nozzles may be arranged downstream the burst disc 7. The nozzles 12 are arranged to distribute the gas evenly- inside an associated airbag cushion 14. As nozzles 12 and similar distribution means are well known in the art further explanation is omitted. The airbag cushion 14 is attached to the second chamber 2 by fastening means 13, such as a rivet or an adhesive.

Opposite the outlet end of the first chamber, the first chamber has an end portion 15 that is adapted to the inner wall of the second chamber 2. Thus the end portion 15 is curved with the cylindrical shape of the second chamber 2. The first chamber 1 may be fasten at the overlap between the first and second chamber. Said initiator device (not shown) for the propellant medium is preferably arranged at this overlap. The first chamber can also be provided with other fasting means such as bridge portions (not shown in the drawings) between the first and second chambers .

With reference to fig. 2 a second embodiment will be described. The description of similar components and features in fig. 2 will be omitted under reference to fig 1 and related description, wherein similar features are indicated with similar reference number. The second chamber 2^r is in principal similar to the second chamber 2. The first chamber 1' has a cylindrical main portion 8'. The longitudinal axis of the cylindrical first chamber 1 is essentially in line with the longitudinal axis of the tube shaped second chamber 2' . According to the second embodiment shown in fig 2 (the cross sectional view) , the first chamber 1' are coaxially arranged in the second chamber 2'. The first chamber 1' has three first outlets 4' which are evenly circumferentially spaced and radial outwardly directed of the cylindrical portion 8'. The first outlets 4' at the sleeve shaped outlet portion 10' are formed or appropriately joined with the cylindrical portion 8'. The second chamber 2' has three openings 11' with a respective burst disc 7' . The burst discs 7' are correspondingly arranged in a similar way as in the first embodiment. The opening 11' with the burst disc 7' are adapted to form, together with the outer peripheral of the outlet portion 10' and the cylindrical portion 8' the shroud orifice portions 5', as an adapted passage. The openings 11' arranged with said burst discs 7' are fluid connected to an airbag cushion or the airbag inflator is at least partly arranged inside the airbag cushion .

Nozzles or other distribution means (not shown in figure) may be arranged externally of said second chamber 2' for distributing the gas in the airbag cushion.

With reference to the cross sectional view of fig. 2 three bridge portions 16' are arranged between the first chamber 1' and second chamber 2', which bride portion 16' is circumferentially spaced on the first chamber 1' evenly distributed between the outlet portion 10' . At least one of said bridge portion 16 may be provided with an initiator device (not shown) .

In the following a typical function of an airbag inflator 3, 3' according to the first and second embodiment of the invention is described in more detail. Upon sensing a collision involving the vehicle, an electrical signal is sent from a sensor (not shown) and received by the initiator device. The initiator device ignites at least a part of the propellant medium wherein a gas is generated. At a predetermined pressure the burst disc rupture and breaks or otherwise opens.

The generated gas is released from the first chamber 1, 1' at a high velocity. However, as the burst disc 7, 7' also covers the opening to the second chamber 2, 2' also the stored gas is released from the second chamber. Both the high velocity gas and the shrouding gas are used for filling up the airbag cushion. The shroud orifice portions 5, 5' will direct the shrouding gas around the high velocity gas. By adapting, the gases chemically (different pressure or propellant medium) or mechanically (the form of the shroud orifice portion and first outlet) the velocity of the shrouding gas can be lower than high velocity gas wherein a sound reduction is achieved. Also the shrouding gas flow will be drawn into the flow of the high velocity gas, as an ejector device 6, 6' . Apart from pressurization of the chambers the function is mainly achieved by the adapted shroud orifice portion in relation to the adjacent arranged first outlet. Preferably, when the gases are released (in use) , the average velocity of the shrouding gas is preferably 20- 80% of the high velocity gas, more preferred 30-70% and most preferred 40-60% of the high velocity gas.

Fig. 3 shows a third embodiment of the invention. The first chamber 1' ' is preferably a storage chamber with pressurized gas, wherein reference is made to the storage chamber described above.

The first chamber 1' ' is on its lateral side provided with means for discharging the shrouding gas flow which in this case is a diffuser 17''. In fig. 3 the shrouding gas flow is indicated with an unfilled arrow.

The first outlet 4'' is essentially coaxially arranged in said diffuser 17''. Shroud orifice portions 5'' are arranged peripherally of the first outlet 4''. The passage trough the diffuser 17'' is varied from the storage chamber and out. Downstream the storage chamber 1'' a first constriction portion 18'' is arranged which is connected to an expansion portion 19''. Downstream the expansion portion 19' ' there is a second constriction portion 20' arranged. According to the third embodiment the outlet area of the first constriction portion 18'' is smaller than for the second portion 20' . The diffuser 17'' are adapted to perform a velocity reduction of a gas flow, in this case the shrouding gas in comparison to the high velocity gas in the first outlet 4'' . In fig. 3 the high velocity gas flow is indicated with a filled arrow. The velocity reduction of the gas flow through the shroud orifice portion 5'' may^¬ be achieved differently, for instance by a porous material arranged in the diffuser, for reducing the gas velocity. As an alternative the diffuser 17'' and the first outlet 4'' may be arranged at least partly internally of the first chamber 1''. The diffuser 17'' may have bridge portions (not shown) for attaching the first outlet 4'' . The gas in the storage chamber is released with a pyrotechnic opening device (not shown) which may be arranged at the diffuser 17'' and outlet 4' ' .

In the following a typical function of an airbag inflator 3'' according to the third embodiment of the invention is described in more detail. However reference is made to the function description above and mainly differing functions are described. The electrical signal (as described above) initiates the pyrotechnic opening device wherein the pressurized gas can be released. The gas pressure inside the storage chamber will force the gas to be discharged through the outlet 4'' and shroud orifice portions 5' respectively. Due to the elaboration of the diffuser the shrouding gas velocity will get a reduced velocity in comparison to the high velocity gas, as described above. Note that the adaptation of the diffuser and outlet also must consider, the fact that the gas from the storage chamber will primarily take the easiest way with less resistance. By providing the adapted diffuser, or the like, the shrouding gas can be formed around the high velocity gas at an early stage before entering the airbag cushion or entering a present nozzle or the like for distributing the gas in the airbag. It should be noted that different modifications of the embodiments of the invention described above are feasible within the scope of the invention, as it is defined by the following claims. For example other constructions for generating gas flows may be used, wherein a storage chamber used in a specific preferred may be changed to a propellant medium chamber or vice versa. Further a chamber with a combination of pressurized gas and a propellant medium may be used.

Claims

PATENT CLAIMS

1. An airbag inflator (3, 3', 3'') comprising at least a first chamber (1, 1', I¹') having at least a first outlet (4, 4', 4'') through which a high velocity gas flow is released, c h a r a c t e r i s e d i n that, said first outlet (4, 4' , 4' ' ) is at least partly encircled by shroud orifice portions (5, 5', 5'') which are arranged to direct a pressurized shrouding gas flow circumferentially around the high velocity gas, when released, wherein said inflator further comprises means for discharging the pressurized shrouding gas flow at a lower velocity level than the velocity of the high velocity gas flow in order to reduce high sound levels in the environment, due to the high velocity gas flow.

2. An airbag inflator (3, 3') according to claim 1, which further comprises at least a second chamber (2, 2') which is connected to said shroud orifice portions (5, 5') for separately discharging the shrouding gas flow from said high velocity gas flow.

3. An airbag inflator according to claim 2, wherein the second chamber (2, 2') is separated from said first chamber (1, 1' ) .

4. An airbag inflator according to any one of claims 2-3, wherein the second chamber (2, 2') is arranged to at least partly enclose said first chamber (1, 1').

5. An airbag inflator according to any one of claims 2-4, wherein the shroud orifice portions (5, 5') are arranged adjacent to said first outlet (4, 4' ) to form an ejector device (6, 6').

6. An airbag inflator according to any one of claims 2-5, wherein the shroud orifice portions (5, 5') and the first outlet (4, 4') is at least partly arranged inside said second chamber (2, 2') .

7. An airbag inflator according to any one of claims 2-5, wherein the first chamber (1, 1') and the second chamber (2, 2') is provided with a common burst disc (7, 7') for in common use.

8. An airbag inflator according to any one of claims 2-7, wherein the first chamber (1') is provided with a plurality of angularly spaced radially directed first outlets (4' ) .

9. An airbag inflator according to any one of claims 2-8, wherein at least the first chamber (1, 1' ) is provided with a propellant medium.

10. An airbag inflator according to any one of claims 2-8, wherein at least the second chamber (2, 2') is provided with stored pressurized gas.

11. An airbag inflator according to claim 1, wherein the high velocity gas as well as the shrouding gas emanates from the first chamber {!''), as a common chamber.

12. An airbag inflator according to claim 11, wherein the shroud orifice portions (5' ' ) is separated from the first outlet (4'').

13. An airbag inflator according to any one of claims 11-12, wherein said shroud orifice portions (5'') is provided with said means for discharging the shrouding gas flow, such as a diffuser.

14. An airbag inflator according to any one of claims 11-13, wherein the shroud orifice portions and the first outlet (4'') are at least partly arranged outside said first chamber (1'')-

15. An airbag inflator according to any one of claims 11-14, wherein the first chamber (1'') is provided with stored pressurized gas.

16. An airbag inflator according to any one of claims 11-15, wherein the first chamber {!' ' ) at least is provided with a propellant medium.