GB2443614A

GB2443614A - Airbag with secondary chamber opening door

Info

Publication number: GB2443614A
Application number: GB0622274A
Authority: GB
Inventors: Jeremy Angus Longland; Anthony Richard Bates; Richard Eric White; Mark David Croucher
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2006-11-09
Filing date: 2006-11-09
Publication date: 2008-05-14
Anticipated expiration: 2026-11-09
Also published as: GB0622274D0; GB2443614B

Abstract

An airbag assembly 10 for a motor vehicle includes an airbag unit 12 housed in a housing 11 located behind an airbag door 16 formed in a dashboard 15 of the vehicle. The airbag unit 12 has primary and secondary chambers 12a, 12b of differing volume. The smallest chamber is the secondary chamber 12b which is arranged to be inflated first so as to open the airbag door 16. The larger primary chamber 12a is then inflated to provide protection for an occupant of the motor vehicle. Because the airbag door 16 has already been opened by the secondary chamber 12b the primary chamber 12a is deployed with less force thereby reducing the risk of injury to an out of position occupant. The primary and secondary chambers 12a and 12b can be formed permanently by an internal wall within a single airbag 12 forming the airbag unit or can be formed temporarily by folding and securing of the airbag 12 so that when the airbag 12 is deployed, the means securing the airbag 12 into the primary and secondary chambers 12a and 12b is released to form a single chamber.

Description

An Airbag Assembly for a Motor Vehicle This invention relates to motor

vehicles and in particular to an airbag assembly for a motor vehicle to protect an occupant of the vehicle.

It is well known to provide a motor vehicle with an airbag to provide protection for a front seated passenger in which the airbag is stored in a dashboard or instrument panel of the vehicle. When the airbag is energised it inflates rapidly, forcing open an airbag door that normally conceals the airbag from view, and then expands rapidly towards the passenger to reduce the possibility of contact between the passenger and the instrument panel or windscreen of the vehicle. Examples of airbag assemblies having opening airbag doors and methods of producing such doors are shown in, for example and without limitation, US Patent 6,896,310 and GB Patent publications 2,342,898; 2,401,352 and 2,414,449.

A problem with such a prior art arrangement is that considerable energy is required to open the airbag door on a passenger airbag and this causes a build up of pressure in the airbag before the door is opened. This has the consequence that the airbag, when the door is eventually forced open, will deploy faster and with more force in its initial few milliseconds than is desirable, especially in the case of an out-of-position occupant. That is to say, if a passenger is out of position during inflation of the airbag, as can occur if the passenger is leaning forward or if the passenger is not wearing a safety belt, then the force of the rapidly inflating airbag can itself cause injury to the passenger.

It is further known from US-B-7,066,487 to produce an airbag that has two separate chambers in order to reduce the risk of injury to an out of position passenger.

It is an object of this invention to provide a motor vehicle providing improved protection for an occupant and in particular one that provides reduced risk to an out of position occupant.

According to the invention there is provided an airbag assembly for a motor vehicle comprising an airbag unit forming a primary chamber and a secondary chamber, a housing for stowing the airbag unit prior to deployment, an inflator to inflate the airbag unit during deployment and a hinged airbag door positioned close to a mouth of the housing through which the airbag unit is deployed, wherein at least a portion of the secondary chamber is stowed adjacent to the airbag door so that during deployment of the airbag unit the secondary chamber is operable to open the airbag door.

A flow control means may be provided to ensure that the secondary chamber is at least partially inflated with gas from the inflator during deployment before inflation of the primary chamber commences.

The secondary chamber may be fully inflated before inflation of the primary chamber commences.

The secondary chamber may have an inlet portion through which during deployment gas flows to inflate the secondary chamber and an inflatable portion which is inflated by the gas flowing through the inlet portion.

At least a portion of the secondary chamber may be stowed in a gap defined between the airbag door and a reaction surface on or fast with the housing.

The portion of the secondary chamber stowed in the gap defined between the airbag door and the reaction surface may be the inflatable portion.

The airbag door may be hingedly supported at a first edge and, prior to deployment of the airbag, is held closed by a securing means at a second edge opposite the first edge and the gap is defined between the reaction surface and a portion of the airbag door located near to the second edge of the airbag door.

The reaction surface may be formed on a flange located adjacent the mouth of the housing.

The flange may be formed as part of the housing.

The volume of the secondary chamber may be such that, even when fully inflated, the secondary chamber only extends a short distance through the airbag door.

The volume of the secondary chamber may be of a considerably smaller volume than the primary chamber.

The airbag unit may comprise of a single airbag having an internal dividing wall separating the airbag into the primary and secondary chambers.

The flow control means may include one of a gas flow director device to deflect the gas emitted from the inflator towards the secondary chamber, one or more pressure control means to control the flow of gas from the inflator and separate inflators for the primary and secondary chambers.

A single airbag may be folded and temporarily secured so as to form the primary and secondary chambers and during deployment of the airbag the secondary chamber may be filled with gas in order to open the airbag door.

When a predetermined pressure is reached in the secondary chamber, a force produced by the secondary chamber may be sufficient to release the means temporarily securing the airbag into two separate chambers so that the airbag becomes a single chamber that is filled with gas to provide protection to an occupant of the motor vehicle.

The flow control means may include a tear seam joining the primary and secondary chambers that is ruptured when the gas pressure in the secondary chamber reaches a predetermined level and a temporary securing means that prevents filling of the primary chamber until the secondary chamber is substantially fully inflated.

The airbag assembly may be a passenger airbag assembly in which the housing is arranged to be fastened to a rear side of a dashboard of the motor vehicle.

According to a second aspect of the invention there is provided motor vehicle having an airbag assembly in accordance with said first aspect of the invention.

The invention will now be described by way of example with reference to the accompanying drawings, of which:-Fig.l is a side view of an airbag assembly according to the invention showing an airbag unit having primary and secondary chambers in a stowed state; Fig.2 is a view similar to Fig.l but showing the secondary chamber of the airbag unit in a partially inflated state; Fig.3 is a view similar to Fig.2 but showing the secondary chamber of the airbag unit in an inflated state at the moment when inflation of the primary chamber of the airbag unit is commencing; Fig..4 is a plan view of the airbag assembly with the airbag unit removed so that an inflator for the airbag unit can be seen; and Fig.5 is a view similar to Fig.2 but showing an alternative embodiment in an inflated state.

With references to Figs. 1 to 4 there is shown an airbag assembly 10 having a housing or reaction can 11 fastened to a rear surface of a dashboard 15 of a motor vehicle by fastening means (not shown). The housing 11 defines a storage volume for an airbag unit 12 comprising a primary chamber 12a and a secondary chamber 12b.

The housing 11 has a mouth 9 through which the primary and secondary chambers 12a and 12b of the airbag unit 12 are deployed when they are inflated and has a flange 19 attached to or formed as an integral part of the housing 11 adjacent the mouth 9 of the housing 11. The flange 19 has a surface facing towards the direction of airbag deployment that forms a reaction surface 19a for the secondary chamber 12b as will be described later in greater detail. It will be appreciated that the reaction surface 19a could be a surface on any member have sufficient strength and need not be on a flange attached to the housing 11. It could, for example be formed on a flange depending from or attached to the dashboard 15.

A door 16 is formed in the dashboard 15 by, in this case, producing slots separated by small lands 17 so that three sides of the airbag door 16 are defined by a row of perforations. A fourth side of the airbag door 16 is formed by a weakened portion of the dashboard 15 that forms a living hinge 18 along one edge of the airbag door 16. The airbag door 16 is held closed prior to deployment of the airbag 12 by the lands 17 which form a securing means for the airbag door 16. A gap is formed between a portion of the airbag door 16 adjacent to the edge opposite the edge of the door 16 where it is hingedly connected to the dashboard by the living hinge 18 and the reaction surface 19a.

It will be appreciated that other forms of door Construction could be used and that the invention is not limited to this type of construction. For example, the entire periphery of the door could be perforated so that the door is forced off when the airbag 12 is deployed.

An inflator 13 is fastened to the housing 11 within the airbag unit 12. As is well known in the art, the inflator 13 includes a pyrotechnic material that produces a large volume of gas in a very short period of time when initiated by control means (not shown). The gas produced by the io inflator 13 is used to inflate the airbag unit 12 so as to deploy it when required. The inflator 13 includes outlet vents 20 and 22 from which the gas produced by the inflator 13 can flow into the two chambers 12a, 12b.

In Fig.2 only the vent 20 for the secondary chamber 12b is shown, whereas in Fig.3 the vent 20 for the secondary chamber l2b and the vent 22 for the primary chamber 12a are both shown. This is because in Fig.2 the vent 22 to the primary chamber 12a is closed off by a sealing member 23 as shown in Fig.4 and no gas is flowing to the primary chamber 12a while in Fig.3 the sealing member 23 has been blown off the inflator 13 and gas is flowing into the primary chamber 12a as well as into the secondary chamber 12b. The sealing member 23 is arranged to be blown off the inflator 13 when the pressure in the inflator 13 reaches a predetermined pressure so as to act as a pressure control means or pressure controlled valve.

The material forming the primary chamber 12a is folded and stowed in the housing 11 to one side of the inflator 13 and the material forming the secondary chamber 12b is folded and stowed in the housing on an opposite side of the inflator 13. The primary and secondary chambers 12a and 12b are separate volumes even though they are formed as a single airbag. The two chambers 12a, l2b are divided by a flange 14 connected to the inflator 13 to which the material forming the airbag unit 12 is permanently fastened.

The secondary chamber l2b comprises an inlet portion 12c through which during deployment gas flows to inflate the secondary chamber 12b and an inflatable portion 12d which is inflated by the gas flowing through the inlet portion l2c.

The inflatable portion 12d of the secondary chamber 12b is stowed in the gap defined between the airbag door 16 and the reaction surface 19a. The secondary chamber 12b is of a considerably smaller volume than the primary chamber 12a so that it can be inflated very rapidly by the gas from the inflator 13 to open the airbag door 16 as is described in greater detail hereinafter.

It will be appreciated that in the example shown the primary and secondary chambers are formed as a single airbag that is divided into the two chambers. However, the invention is not limited to such an arrangement and the term "airbag unit" as used herein is intended to cover the use of two separate airbags stowed in the housing, one of which forms the primary chamber and a second of which forms the secondary chamber.

Operation of the airbag assembly is as follows starting from the pre-deployment state shown in Fig.l. In this state the primary and secondary chambers 12a and 12b are both stowed in the housing 11 ready for deployment. When the inflator 13 is initiated to begin producing gas, the gas immediately flows through the vent 20 into the inlet portion 12c of the secondary chamber 12b so as to begin inflating the inflatable portion 12d but does not flow to the primary chamber 12a because the vent 22 is sealed by the sealing member 23.

The secondary chamber 12b or to be more precise the inflatable portion l2d of the secondary chamber 12b then rapidly inflates and, because the inflatable portion l2d is stowed between the reaction surface 19a and the door 16, the secondary chamber 12b applies a load to the door 16. As shown in F'ig.2, the load applied by the secondary chamber 12b will eventually cause the door 16 to be forced open when the force applied to the door 16 can no longer be resisted by the small lands 17 securing it closed.

As the secondary chamber 12b continues to inflate the door 16 swings further open about the living hinge 18 until the secondary chamber 12b is fully inflated. It will be appreciated that the volume of the secondary chamber l2b is such that, even when fully inflated, the secondary chamber 12b only extends a short distance through the door 16. This helps to ensure that the very rapidly inflating secondary chamber 12b cannot come into contact with an occupant of the motor vehicle. It will also be appreciated that because the secondary chamber is of a small volume it can be fully inflated very rapidly and its inflation is virtually instantaneous, taking only a matter of a few milliseconds.

As soon as the secondary chamber 12b is fully inflated the pressure within it and also within the inflator 13 will rise rapidly until, as shown in Fig.3, the pressure is such that the sealing member 23 is blown off the inflator 13 and gas can begin to flow into the primary chamber l2a so as to inflate the primary chamber l2a. Gas will continue to flow into the primary chamber 12a until it is fully inflated at which time the gas supply from the inflator 13 will be exhausted.

There will not be a build up of pressure in the primary chamber l2a before the door 16 is opened as is normally the case because the door 16 has already been opened by the secondary chamber 12b. That is to say, the primary chamber l2a can deploy freely out through the mouth 9 of the housing 11 and so the force that would be applied to an out of position occupant is far less.

It will be appreciated that as soon as the sealing member 23 is blown off the inflator 13 the pressure in the inflator 13 will drop due to the large volume of the primary chamber 12a to which it is now exposed.

Although the invention has been described with reference to an embodiment in which a flow control means used to phase the supply of gas to the primary and secondary chambers 12a and l2b is in the form of a pressure control means formed by the sealing member 23, it will be appreciated that other flow control means could be used.

For instance, the flow control means could include a gas flow director device to deflect the gas emitted from the inflator 13 towards the secondary chamber l2b, a tear seam joining the primary and secondary chambers 12a and 12b that is ruptured when the gas pressure in the secondary chamber 12b reaches a predetermined level, a folded portion of the primary chamber positioned so as to obscure the vent from the inflator until it is pushed out of the way by the gas pressure or separate inflators for the primary and secondary chambers 12a and 12b that are phased to inflate the primary and secondary chambers 12a and l2b such that the secondary chamber 12b is substantially fully inflated before commencing inflation of the primary chamber 12a.

It will, however, be appreciated that it is not essential for the secondary chamber 12b to be fully inflated before commencing inflation of the primary chamber 12a and it is only necessary for the secondary chamber 12b to have been inflated to a sufficient degree to have opened the airbag door 16 before the primary chamber 12a is inflated.

With reference to Fig.5 there is shown an alternative embodiment to that shown in Figs.l to 4. The same reference numerals are used for this embodiment as for that previously described with reference to Figs.1 to 3.

-10 -The only significant physical differences between the embodiment shown in Fig.5 and that shown in Figs.1 to 4 are that the primary and secondary chambers 12a and 12b are temporary rather than permanent, that there is no need for a pressure controlled vent and only one vent 20 is provided.

That is to say, in the previous embodiment, the primary and secondary chambers 12a and 12b are permanently fastened to the flange 14 so that they remain as separate chambers 12a, 12b at all times even though they are formed as a single airbag whereas in the embodiment shown in Fig.5 this is not the case and the portion of the airbag 12 folded over the flange 14 is only temporarily secured so that when the pressure in the secondary chamber 12b reaches a predetermined level the force of the secondary chamber 12b on the means securing the folded airbag 12 to the flange 14 is sufficient to release the securing means and the airbag 12 then continues to be inflated as a single chamber airbag 12. The term temporarily secured' means that the folding of the airbag is such as to keep that portion of the airbag in place on the flange 14 or that releasable fastening means are provided to temporarily hold the airbag on the flange.

Operation during the initial stages of deployment is much as before and the representations of Figs.l to 3 are also relevant to this alternative embodiment.

When the inflator 13 is initiated to begin producing gas, the gas immediately flows through the vent 20 into the inlet portion l2c of the secondary chamber l2b so as to begin inflating the inflatable portion l2d but cannot flow to the primary chamber 12a because the airbag 12 is sealed to the flange 14 so as to form the two chambers 12a, 12b.

As before, the inflatable portion 12d of the secondary chamber l2b rapidly inflates and, because the inflatable portion 12d is stowed between the reaction surface 19a and the door 16, the secondary chamber l2b applies a load to the -3_i -door 16. As shown in Fig.2, the load applied by the secondary chamber 12b will eventually cause the door 16 to be forced open when the force applied to the door 16 can no longer be resisted by the small lands 17 securing it closed.

As the secondary chamber l2b continues to inflate the door 16 swings further open about the living hinge 18 until the secondary chamber 12b is fully inflated. It will be appreciated that because the secondary chamber 12b is of a small volume it can be fully inflated very rapidly.

As soon as the secondary chamber 12b is fully inflated the pressure within it will produce a reaction force of sufficient magnitude to release the means securing the airbag 12 to the flange 14. The airbag 12 then becomes a single chamber airbag and gas begins to flow from the inflator 13 into the entire volume of the airbag 12 causing to inflate as shown in Fig.5. Gas will continue to flow into the airbag 12 until it is fully inflated at which time the gas supply from the inflator 13 will be exhausted.

As yet further alternatives, the airbag could be formed as a single airbag divided by an internal wall into two permanent chambers that are required to be separately filled or the airbag could be formed as a single airbag divided into two chambers by an internal wall having a tear seam that is intended to rupture when the pressure in one of the chambers reaches a predetermined pressure so that the airbag subsequently has only a single chamber.

Although the invention has been described with reference to a passenger airbag assembly fastened to a dashboard of a motor vehicle it will be appreciated that it could be applied to other airbag applications.

Claims

-12 - CLAIMS

1. An airbag assembly for a motor vehicle comprising an airbag unit forming a primary chamber and secondary chamber, a housing for stowing the airbag unit prior to deployment, an inflator to inflate the airbag unit during deployment and a hinged airbag door positioned close to a mouth of the housing through which the airbag unit is deployed, wherein at least a portion of the secondary chamber is stowed adjacent to the airbag door so that during deployment of the airbag unit the secondary chamber is operable to open the airbag door.

2. An airbag assembly as claimed in claim 1 wherein a flow control means is provided to ensure that the secondary chamber is at least partially inflated with gas from the inflator during deployment before inflation of the primary chamber commences.

3. An airbag assembly as claimed in claim 2 wherein the secondary chamber is fully inflated before inflation of the primary chamber commences.

4. An airbag assembly as claimed in any of claims 1 to 3 wherein the secondary chamber has an inlet portion through which during deployment gas flows to inflate the secondary chamber and an inflatable portion which is inflated by the gas flowing through the inlet portion.

5. An airbag assembly as claimed in any of claims 1 to 4 wherein at least a portion of the secondary chamber is stowed in a gap defined between the airbag door and a reaction surface on or fast with the housing.

6. An airbag assembly as claimed in claim 5 when dependent upon claim 4 wherein the portion of the secondary -13 -chamber stowed in the gap defined between the airbag door and the reaction surface is the inflatable portion.

7. An airbag assembly as claimed in claim 5 or in claim 6 wherein the airbag door is hingedly supported at a first edge and, prior to deployment of the airbag, is held closed by a securing means at a second edge opposite the first edge and the gap is defined between the reaction surface and a portion of the airbag door located near to the second edge of the airbag door.

8. An airbag assembly as claimed in any of claims 5 to 7 wherein the reaction surface is formed on a flange located adjacent the mouth of the housing.

9. An airbag assembly as claimed in claim 8 wherein the flange is formed as part of the housing.

10. An airbag assembly as claimed in any of claims 1 to 9 wherein the volume of the secondary chamber is such that, even when fully inflated, the secondary chamber only extends a short distance through the airbag door.

11. An airbag assembly as claimed in any of claims 1 to 10 wherein the volume of the secondary chamber is of a considerably smaller volume than the primary chamber.

12. An airbag assembly as claimed in any of claims 1 to 11 wherein the airbag unit comprises a single airbag having an internal dividing wall separating the airbag into the primary and secondary chambers.

13. An airbag assembly as claimed in claim 2 wherein the flow control means includes one of a gas flow director device to deflect the gas emitted from the inflator towards the secondary chamber, one or more pressure control means to -14 -control the flow of gas from the inflator and separate inflators for the primary and secondary chambers.

14. An airbag assembly as claimed in any of claims 1 to 11. wherein a single airbag is folded and temporarily secured so as to form the primary and secondary chambers and during deployment of the airbag the secondary chamber is filled with gas in order to open the airbag door.

15. An airbag assembly as claimed in claim 14 wherein, when a predetermined pressure is reached in the secondary chamber, a force produced by the secondary chamber is sufficient to release the means temporarily securing the airbag into two separate chambers so that the airbag becomes a single chamber that is filled with gas to provide protection to an occupant of the motor vehicle.

16. An airbag assembly as claimed in claim 14 or in claim 15 when claim 14 is dependent upon claim 2 wherein the flow control means includes a tear seam joining the primary and secondary chambers that is ruptured when the gas pressure in the secondary chamber reaches a predetermined level and a temporary securing means that prevents filling of the primary chamber until the secondary chamber is substantially fully inflated.

17. An airbag assembly as claimed in any of claims 1 to 16 wherein the airbag assembly is a passenger airbag assembly in which the housing is arranged to be fastened to a rear side of a dashboard of the motor vehicle.

18. A motor vehicle having an airbag assembly as claimed in any of claims 1 to 17.

19. An airbag assembly substantially as described herein with reference to the accompanying drawing.