Patent Description:
Inflatable occupant restraints or airbags are commonly included on motor vehicles to provide impact protection for occupants of the motor vehicle. In the event of an accident, one or more sensor within the vehicle measure abnormal deceleration, for example, and triggers inflation of the airbag within a few milliseconds with gas produced by a device commonly referred to as an "inflator". The inflated airbag cushions and protects the motor vehicle occupant from impact forces.

Various types of inflators have been disclosed in the art for the inflation of airbags. One known inflator devices is shown and described in commonly assigned <CIT> (the '<NUM> patent). The inflator of the '<NUM> patent is an adaptive pyrotechnic inflator, or dual stage inflator, having gas generant materials in two chambers. The gas generant materials are independently activated by two ignition devices. The gas generant material-containing chambers of such ignitors may be referred to as "combustion chambers" as the gas generant material therein is combusted or otherwise reacted to produce gas used to inflate an associated occupant restraint.

While known inflators for inflatable occupant restraints, including the inflator of <CIT>, have generally proven to be suitable for their intended uses, a continuous need for improvement in the relevant art remains. Finally, document <CIT> relates to a gas generator for a multi-stage airbag and an airbag device using the same.

It is a general object of the present teachings to provide a dual stage inflator with a combustion cup including a lid and having an increased volume for gas generant loading.

In accordance with one particular embodiment, the present teachings provide a dual stage inflator for an inflatable vehicle safety device including a housing defining a first chamber containing a first gas generant material. An ignitor cup is disposed in the first chamber and defines an interior containing an ignitor material. A first ignitor device extends into the interior of the ignitor cup. A combustion cup and a lid are disposed in the first chamber and cooperate to define a second chamber containing a second gas generant material. The combustion cup includes a cup sidewall extending between a first axial end and a second axial end. The first axial end is an open end. The lid is normally in a closed position relative to the combustion cup to close the open end of the combustion cup and is moveable away from the combustion cup in response to an increase of pressure within the combustion cup for venting combustion gas out of the combustion cup. A second ignitor device extends into the combustion cup and closes the second axial end of the combustion cup. The combustion cup includes a first axially extending portion adjacent the first axial end having a first outer diameter and a second axially extending portion adjacent the second axial end having a second outer diameter greater than the first outer diameter. The lid includes a lid sidewall extending in an axial direction and radially overlapping at least a portion of the combustion cup including the first outer diameter.

In accordance with another particular embodiment, the present teachings provide an inflator for an inflatable vehicle safety device including a cup having a cup sidewall and an open end. The cup sidewall extends between a first axial end and a second axial end. A lid cooperates with the cup sidewall to define a combustion chamber. The lid normally closes the combustion chamber and is movable away from the cup sidewall to vent combustion gas from the combustion chamber. A gas generant is disposed in the combustion chamber. An ignition device extends into the combustion chamber. The cup includes a first axially extending portion adjacent the first axial end having a first outer diameter and a second axially extending portion adjacent the second axial end having a greater second outer diameter. The lid includes an axially extending lid sidewall extending in an axial direction and radially overlapping at least a portion of the cup including the first outer diameter.

One or more example embodiments will now be described more fully with reference to the accompanying drawings. The one or more example embodiments are provided so that this disclosure will be thorough and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth, such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, and that the example embodiment should not be construed to limit the scope of the present disclosure. Well-known processes, well-known device structures, and well-known technologies are not described herein in detail.

The phrases "connected to", "coupled to" and "in communication with" refer to any form of interaction between two or more entities, including mechanical, electrical, magnetic, electromagnetic, fluid, and thermal interaction. Two components may be coupled to each other even though they are not in direct contact with each other. The term " adjacent" refers to items that are in close physical proximity with each other, although the items may not necessarily be in direct contact. "Exemplary" as used herein means serving as a typical or representative example or instance, and does not necessarily mean special or preferred.

With general reference to drawings, a dual stage inflator for an inflatable occupant protection device such as an airbag in accordance with the present teachings is illustrated and generally identified at reference character <NUM>. The inflator <NUM> shown in the drawings is a dual-stage inflator particularly adapted for a passenger side front airbag. It will be understood, however, that various aspects of the present teachings may be readily adapted for use with driver side front airbags and other airbags.

The inflator <NUM> is generally illustrated to have a cylindrical external outline and to include a housing <NUM> formed of two structural components, i.e., a first housing portion or base portion <NUM> and a second housing portion or diffuser cap portion <NUM>. As such, the housing <NUM> may have a generally circular cross section. The first and second housing portions <NUM> and <NUM> may be formed of aluminum or other suitable material and may be secured to one another by inertia welded, for example, and welding or otherwise suitably connected to one another. In the particular embodiment illustrated, the housing <NUM> may have a diameter of approximately <NUM> and a length L of approximately <NUM>.

As shown in the drawings, the second housing portion <NUM> may be considered an upper housing portion and the first housing portion <NUM> may be considered a lower housing portion. These descriptors (e.g., upper and lower) used with regard to the housing portions <NUM> and <NUM> and elsewhere herein with respect to other features or elements will be understood to merely provide an ease of reference to the drawings and will not be understood to be limiting. The second housing portion <NUM> is in the general shape of an inverted bowl and includes an end wall <NUM> and a cylindrical sidewall <NUM>. The sidewall <NUM> includes a plurality of spaced gas exit ports <NUM>.

The first housing portion <NUM> includes first and second mounting openings, designated by the reference numerals <NUM> and <NUM>, respectively, the use of which will be discussed in greater detail below. The first housing portion <NUM> may be integrally formed to include a peripheral mounting bracket <NUM> that extends radially outward from the housing <NUM>.

The housing <NUM> is configured to define a first chamber <NUM>. The first chamber may be a generally cylindrical cavity <NUM>. The first chamber <NUM> contains or houses a supply of a first gas generant material <NUM>, typically in the form of a pyrotechnic, such as known for use in airbag inflators. Surrounding the first gas generant material <NUM> is a filter <NUM>. The filter <NUM> may be formed of multiple layers or wraps of a metal screen. Surrounding the filter <NUM> and generally adjacent an inner surface of the sidewall <NUM> is an adhesive-backed foil seal <NUM>. The adhesive-backed foil seal <NUM> may hermetically seal the gas generant material <NUM> within the inflator <NUM>, thereby protecting the gas generant material from ambient conditions, such as moisture. The inflator <NUM> may also includes a retainer <NUM> to retain the inflator components in proper relative arrangement within the inflator <NUM>.

An ignitor cup <NUM> is disposed within the first chamber <NUM>. As illustrated, the first igniter cup <NUM> defines an ignition chamber <NUM> and may include a cylindrical sidewall <NUM>. An igniter material <NUM> is contained within the ignitor cup <NUM>. A first igniter device <NUM> is mounted to the housing <NUM> in a location within the first chamber <NUM> via the first mounting opening <NUM>. Insofar as the present teachings are concerned, it will be understood that the first igniter device <NUM> may take the form of a known pyrotechnic initiator device. As such the first igniter device <NUM> may include a squib <NUM>, a squib adapter or holder <NUM>, whereby the first igniter device <NUM>, and a squib seal <NUM>. The ignitor device <NUM> is conventionally mounted to or is mated with the housing <NUM> by the squib adapter or holder <NUM>. The squib seal <NUM> conventionally seals the squib <NUM> with the adapter <NUM>.

As shown, the igniter cup <NUM> may include an open upper end that is closed by a spacer member <NUM>. The spacer member <NUM> may be generally cylindrical in shape with a closed lower end. The spacer member or igniter tube lid <NUM> may function to prevent the ignitor generant <NUM> from getting out of the igniter cup <NUM>. This spacer member <NUM> has holes in the bottom that allow gases coming from the combustion to ignite the generant. Alternatively, the igniter cup <NUM> may be integrally formed to include a closed upper end.

The igniter cup <NUM> may be formed of a gas-impermeable material, such as metal, with the cylindrical sidewall <NUM> including a plurality of spaced, preferably, generally uniformly spaced gas exit orifices <NUM>. The gas exit orifices <NUM> may be normally (e.g., when the inflator is in a static or prior to actuation state) covered and the passage of material therethrough prevented by a pressure sensitive covering or barrier, such as by an adhesive-backed foil seal wrap or the like as is well known in the art. As is known, the covering may be selected to open or rupture upon the application of a predetermined pressure from the interior of the igniter cup <NUM>.

When actuated, ignition of the igniter material <NUM> results in an increase in pressure within an interior of the igniter cup <NUM> with the subsequent predetermined rupturing or opening of the covering to permit passage of ignition products produced by the combustion of the igniter material <NUM> through the exit orifices <NUM>, from the first igniter device <NUM> to the gas generant material <NUM> contained within the first chamber <NUM>. The resulting contact by or between the ignition products and the first gas generant material <NUM> results in the ignition and reaction of the first gas generant material <NUM>. The inflation gases produced pass through the filter <NUM>, rupture the foil seal <NUM> and pass through the gas exit ports <NUM> (as signified by the arrows A in <FIG>) and out of the inflator <NUM> into an associated airbag cushion (not shown).

The first chamber <NUM> also houses or contains a combustion cup <NUM> or second stage cup and a lid <NUM>. The combustion cup <NUM> and lid <NUM> cooperate to define a sub chamber or second chamber or combustion chamber <NUM>. The second chamber contains a second gas generant material <NUM>. The second gas generant material <NUM> may be in the form of a pyrotechnic material and may be either the same or different in composition, shape, size or form, as compared to the first gas generant material <NUM>.

The combustion cup <NUM> includes a cup sidewall <NUM>, a first axial end <NUM> and a second axial end <NUM>. The first axial end is an open end <NUM>. In the embodiment illustrated, the cup sidewall is a cylindrical sidewall <NUM>. The lid <NUM> is normally in a closed position relative to the cup sidewall <NUM> to close the open end <NUM> of the combustion cup <NUM>. As will be discussed further below, the lid <NUM> is moveable in an axial direction away from the cup sidewall <NUM> in response to an increase of pressure within the combustion cup <NUM> for venting combustion gas out of the combustion cup <NUM>. The axial direction will be understood to be up and down, as shown in the drawings. As with the ignitor cup <NUM>, the combustion cup <NUM> may be formed of a gas-impermeable material, such as metal.

In the embodiment illustrated, the combustion cup <NUM> is illustrated to include a first axially extending portion <NUM> adjacent the first end <NUM> and a second axially extending portion <NUM> adjacent the second end <NUM>. The first axially extending portion <NUM> has a first outer diameter D<NUM> and the second axially extending portion <NUM> has a second outer diameter D<NUM>. The first outer diameter D<NUM> is less than the second outer diameter D<NUM>. The cup sidewall <NUM> includes a tapered portion <NUM> between the first axially extending portion <NUM> and the second axially extending portion <NUM>. The tapered portion <NUM> tapers from the first outer diameter D<NUM> to the second outer diameter D<NUM>. In the particular embodiment illustrated, the first outer diameter D<NUM> is approximately <NUM> and the second outer diameter D<NUM> is approximately <NUM>.

The lid <NUM> includes an end portion <NUM> and a lid sidewall <NUM>. The lid sidewall <NUM> extends in the axial direction and radially overlaps with at least a portion of the first axial portion <NUM> of the combustion cup <NUM>. The lid sidewall <NUM> has a third outer diameter D<NUM>. In certain applications, the third outer diameter D<NUM> is no greater than the first outer diameter D<NUM>. In the embodiment illustrated, the third outer diameter D<NUM> is substantially equal to the first outer diameter D<NUM>. According to the invention, the lid sidewall <NUM> has a thickness in a radial direction, the second axially extending portion <NUM> of the combustion cup <NUM> is positioned closer to the filter <NUM> in the radial direction than the thickness of the lid sidewall <NUM>. In this manner, a volume within the combustion cup <NUM> may be effectively increased to hold a greater amount of the second gas generant material <NUM>. In the embodiment illustrated, the volume of the combustion chamber <NUM> cooperatively defined by the combustion cup <NUM> and lid <NUM>.

The second end <NUM> of the combustion cup <NUM> is closed by a second igniter device <NUM>. In the embodiment illustrated, the combustion cup <NUM> is shown to include an axially extending circumferential flange <NUM> at the second end <NUM>. An end wall <NUM> radially extending between the axially extending circumferential flange <NUM> and the second portion <NUM> of the combustion cup <NUM>. The axially extending circumferential flange <NUM> defines an opening <NUM> receiving the second ignitor device <NUM>. The opening <NUM> has a fourth diameter D<NUM> that is smaller than the first diameter D<NUM>. The axially extending circumferential flange <NUM> is shown to extend away from the second portion <NUM> of the combustion cup <NUM>. Alternatively, the axially extending circumferential flange <NUM> may extend into the second portion <NUM> of the combustion cup <NUM>. The second igniter device <NUM> is mounted to or mates with the housing <NUM> through a second squib adapter or holder <NUM>. A second squib seal <NUM> seals the second squib <NUM> with the adapter <NUM>.

At least one of the lid <NUM> and the cup sidewall <NUM> includes a venting geometry for venting combustion gas from the combustion cup <NUM>. According to the present teachings, at least one of the lid <NUM> and the cup sidewall <NUM> may include an axially elongated venting geometry that is gradually revealed in response to movement of the lid <NUM> away from the cup sidewall <NUM>. The axially elongated venting geometry may be in the form of at least one axially elongated hole <NUM>, at least two axially spaced apart holes <NUM>, and combinations thereof. In the embodiment illustrated, the axially elongated venting geometry is provided in the lid sidewall <NUM>.

With particular reference to the cross-sectional views of <FIG> and 3C and to <FIG>, the lid <NUM> is illustrated to include a plurality of axially elongated holes <NUM>. In the embodiment illustrated, the lid <NUM> includes six axially elongated holes <NUM> equally spaced circumferentially about the lid sidewall <NUM>. In this particular embodiment, the axially elongated holes <NUM> may be similarly shaped. It will be understood that the lid <NUM> may include a greater or lesser number of axially elongated holes <NUM> within the scope of the present teachings. It will also be understood that the holes <NUM> may be shaped differently or sized differently.

Turning to <FIG>, an alternative lid <NUM> in accordance with the present teachings is illustrated. Distinct from the lid <NUM>, the lid <NUM> includes an elongated venting geometry in the form of a plurality of axially spaced holes <NUM>. As shown, the holes <NUM> are circular. Alternatively, the holes <NUM> may be elongated or of any other shape. The holes <NUM> may be arranged in circumferentially extending rows. As illustrated, the sidewall <NUM> of the lid <NUM> includes three rows of holes. The circumferentially extending rows of holes may axially spaced from one another.

It will be appreciated that an inflator <NUM> in accordance with the present teachings can provide operation performance in accordance with selected operating conditions as may be required or desired for particular inflatable restraint system installations and applications. More specifically, an inflator <NUM> of the present teachings can be actuated in a manner such that either or both the quantity or rate of inflation gas production can be appropriately varied, such as at the time of a vehicle crash or collision incident, to take into account one or more conditions of occupant presence. Such inflator performance adaptability results is provided by the two discrete and ballistically isolated chambers of gas generant materials of the inflator <NUM> of the present teachings.

For example, such an inflator <NUM> may be operated to have a first stage discharge in which the igniter material <NUM> is ignited to produce combustion products which are passed to the first chamber <NUM> to combust the first gas generant material <NUM>. In this manner, inflation gas may be produced at a first output level without actuating or firing the second igniter device <NUM> or reacting or without activating the gas generant material <NUM> contained in the second chamber <NUM>. As will be appreciated, such operation may be desired to provide a minimized or reduced inflator output such as may be desired in an instance of a low speed collision, for example. Alternatively, an inflator <NUM> in accordance with the present teachings may be operated such that both the first and second igniter devices <NUM> and <NUM> are actuated.

As will be appreciated, such operation and ignition of both the first and second igniter devices <NUM> and <NUM> and first and second gas generant materials <NUM> and <NUM> may involve the simultaneous or near simultaneous actuation and firing of the first and second igniter devices <NUM> and <NUM>. Such simultaneous or near simultaneous actuation may be desired to provide a rapid inflation and deployment of an associated airbag cushion. For example, this rapid inflation and deployment may be desired in response to a high speed or severe vehicle collision. Alternatively, sequential actuation and firing of the first and second igniter devices <NUM> and <NUM> may be desired in response to detection of a moderately severe vehicle collision. Further, with such sequential actuation and firing, the time lag or delay between the actuation and firing of the first and second squibs and, in turn, the combustion of the first and second gas generant materials <NUM> and <NUM> may be tailored to meet the specific requirements for a particular inflatable restraint system installation, as will be appreciated by those skilled in the art. Thus, such inflator assemblies are particularly suited for application as adaptive output inflators in that they may be made generally dependent on one or more selected operating conditions such as ambient temperature, occupant presence, seat belt usage and rate of deceleration of the motor vehicle, for example.

With actuation of the second igniter device <NUM>, the second gas generant material <NUM> is combusted to produce reaction products, resulting in an increase in pressure within the cup interior <NUM>. The increase of pressure within the cup interior <NUM> displaces the lid <NUM> away from the combustion cup <NUM> to gradually reveal the elongated venting geometry in the lid sidewall <NUM>. As shown in the <FIG> plot of pressure within the combustion chamber <NUM> verses time, the gradual reveal of the elongated venting geometry functions to longer maintain the pressure within the combustion chamber <NUM>. As a result, the second gas generant material <NUM> may be more thoroughly combusted and associated effluents are reduced.

Accordingly, the present teachings provide a dual stage inflator <NUM> having a combustion cup <NUM> with a lid <NUM> that has an increased volume for gas generant loading as compared to a conventional combustion cup with a constant diameter. In the particular application described herein, the dual stage inflator <NUM> of the present teachings may realize an increase in volume of at least <NUM>%, preferably at least <NUM>% and more preferably at least <NUM>%. In one example, the present teachings provided an increase in volume of approximately <NUM>%.

Claim 1:
A dual stage inflator (<NUM>) for an inflatable vehicle safety device, the dual stage inflator (<NUM>) comprising:
a housing (<NUM>) defining a first chamber (<NUM>) containing a first gas generant material (<NUM>);
an ignitor cup (<NUM>) disposed in the first chamber (<NUM>) and defining an interior containing an ignitor material (<NUM>);
a first ignitor device (<NUM>) extending into the interior of the ignitor cup (<NUM>);
a combustion cup (<NUM>) and a lid (<NUM>) disposed in the first chamber (<NUM>) and cooperating to define a second chamber (<NUM>) containing a second gas generant material (<NUM>), the combustion cup (<NUM>) including a cup sidewall (<NUM>) extending between a first axial end (<NUM>) and a second axial end (<NUM>), the first axial end (<NUM>) being an open end, the lid (<NUM>) normally in a closed position relative to the combustion cup (<NUM>) to close the open end (<NUM>) of the combustion cup (<NUM>), the lid (<NUM>) moveable away from the combustion cup (<NUM>) in response to an increase of pressure within the combustion cup (<NUM>) for venting combustion gas out of the combustion cup (<NUM>); and
a second ignitor device (<NUM>) extending into the combustion cup (<NUM>) and closing the second axial end (<NUM>) of the combustion cup (<NUM>);
wherein:
the combustion cup (<NUM>) includes a first axially extending portion (<NUM>) adjacent the first axial end (<NUM>) having a first outer diameter and a second axially extending portion (<NUM>) adjacent the second axial end (<NUM>) having a second outer diameter, the first outer diameter being less than the second outer diameter, and
wherein the lid (<NUM>) includes a lid sidewall (<NUM>) extending in an axial direction and radially overlapping at least a portion of the combustion cup (<NUM>) including the first outer diameter,
wherein the dual stage inflator (<NUM>) comprises a filter (<NUM>) arranged radially between the cup sidewall (<NUM>) and the housing (<NUM>),
characterized in that the lid sidewall (<NUM>) has a thickness in a radial direction, the second axially extending portion (<NUM>) of the combustion cup (<NUM>) being positioned closer to the filter (<NUM>) in the radial direction than the thickness of the lid sidewall (<NUM>).