Patent Description:
The present disclosure generally concerns an inflator to provide inflation gases for a passive vehicle safety device, such as an inflatable airbag. More particularly, the present disclosure relates to an inflator for a passive vehicle safety device with an insulating member on a first axial side of a filter coupled to a separating member on a second, opposite axial side of the filter.

Inflatable occupant restraints or airbags are commonly included on motor vehicles. In the event of an accident, a sensor within the vehicle measures 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 the vehicle occupant from impact forces.

Inflators may commonly have one or more chambers containing gas generant materials. Adaptive pyrotechnic inflators having gas generant materials in two chambers, which are independently activated by two ignition devices commonly referred to as "dual stage" inflators. In practice, each such gas generant material-containing chamber may be referred to as a "combustion chamber" as the gas generant material therein is combusted or otherwise reacted to produce gas used to inflate an associated occupant restraint.

One known inflator is shown and described in commonly assigned <CIT>. The inflator is a dual stage inflator device including a housing defining first and second chambers each containing a quantity of gas generant combustible to produce inflation gases.

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. The document <CIT> discloses an inflator according to the preamble of claim <NUM>.

In accordance with one particular aspect, the present teachings provide an inflator for generating inflation gases for a safety device. The inflator includes a housing having an internal cavity including a combustion chamber and a filter chamber. A filter is disposed in the filter chamber. A separating member is disposed in the housing on a first axial side of the filter and separates the filter chamber from the combustion chamber. An insulating member is disposed in the filter chamber on a second axial side of the filter. The second axial side is opposite the first axial side. The separating member is coupled to the insulating member.

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. The phrase "fluid communication" refers to two features that are connected such that a fluid within one feature is able to pass into the other feature. "Exemplary" as used herein means serving as a typical or representative example or instance, and does not necessarily mean special or preferred.

With reference to drawings, an inflator for an inflatable occupant protection device in accordance with the present teachings is illustrated and generally identified at reference character <NUM>. The inflator <NUM> is part of an occupant restraint system of a motor vehicle that includes an inflatable airbag (not particularly shown). The inflator <NUM> shown in the drawings is a dual-stage inflator particularly adapted for a driver side front airbag. It will be understood, however, that various aspects of the present teachings may be readily adapted for use with passenger side front airbags and other airbags.

The inflator <NUM> is generally illustrated to include housing <NUM> having a first housing portion <NUM> and a second housing portion <NUM>. In the embodiment illustrated, the housing <NUM> has a generally circular cross section. The first housing portion <NUM> may be inertia welded or otherwise suitably attached to the second housing portion <NUM>. The first and second housing portions <NUM> and <NUM> cooperate to define an internal cavity <NUM> having a filter chamber <NUM> separated from a combustion chamber <NUM> by an internal wall <NUM>.

The combustion chamber <NUM> includes a first portion or first combustion chamber portion <NUM> containing a first gas generant material <NUM>. The combustion chamber <NUM> further includes a second portion or second combustion chamber portion <NUM> containing a second gas generant material <NUM>. Insofar as the present teachings are concerned, the first and second gas generant materials <NUM> and <NUM> may be the same material or may be different materials.

The internal wall may be a vented wall or gas generant retaining wall <NUM> for retaining the first and second gas generant materials <NUM> and <NUM> within the combustion chamber <NUM>. The gas generant retaining wall <NUM> includes a plurality of openings <NUM> for venting combustion gases from the combustion chamber <NUM> to the filter chamber <NUM>. A foam disc <NUM> may be disposed in the combustion chamber <NUM> adjacent to the gas generant retaining wall <NUM>. As will be understood by those skilled in the art, the foam disc conventionally functions to provide stability to the storage of the first and second gas generant materials <NUM> and <NUM> which may settle within the combustion chamber <NUM> over time. The foam disc may be consumed upon combustion of the first and second gas generant materials <NUM> and <NUM>.

A first stage ignition device <NUM> is disposed in the first portion <NUM> of the combustion chamber <NUM> for combusting the first gas generant material <NUM>. A second stage ignition device <NUM> is correspondingly disposed in the second portion <NUM> of the combustion chamber <NUM> for combusting the second gas generant material <NUM>. The first and second stage ignition devices <NUM> and <NUM> will be understood to be conventional in construction and operation insofar as the present teachings are concerned. The first and second stage ignition devices <NUM> and <NUM> may be conventional mounted to or mated with the housing <NUM>.

The second portion <NUM> of the combustion chamber <NUM> is defined by one or more sidewalls <NUM> and a lid <NUM>. In the embodiment illustrated, the one or more sidewalls includes a single, continuous wall or chamber wall <NUM>. The wall <NUM> may be oval, circular or of any other cross-sectional shape. At a first end (the lower end as shown in the drawings) of the chamber wall <NUM>, the chamber wall <NUM> receives the second stage ignition device <NUM> and a base <NUM> of the second stage ignition device <NUM> closes the first end. At a second or opposite end (the upper end as shown in the drawings) of the chamber wall <NUM>, the lid <NUM> normally (i.e., prior to activation of the inflator <NUM>) closes the second portion <NUM> of the combustion chamber <NUM>. The lid <NUM> may be oval in shape or otherwise cooperatively configured with the chamber wall <NUM> to close the second portion <NUM> of the combustion chamber <NUM>.

The lid <NUM> is movable in an axial direction from a first or closed position prior to combustion of the gas generant materials to a second or open position following combustion of the gas generant materials. The inflator <NUM> is shown prior to combustion of the gas generant materials <NUM> and <NUM> in <FIG> and after combustion of the gas generant materials <NUM> and <NUM> in <FIG>. Explaining further, prior to combustion of the second gas generant material <NUM> (as shown in the cross-sectional view of <FIG>), the lid <NUM> is axially spaced from the generant retaining wall <NUM>. As illustrated, the lid <NUM> may be spaced from the generant retaining wall <NUM> by the foam disk <NUM>. Upon combustion of the second gas generant material <NUM> (as shown in the cross-sectional view of <FIG>), the foam disk <NUM> is consumed by the heat of the reaction and the lid <NUM> is axially displaced (upward as shown in the drawings) to a position adjacent to the generant retaining wall <NUM> in response to an increase of pressure within the second portion <NUM> of the combustion chamber <NUM>.

An outer side <NUM> of the lid <NUM> and an adjacent side <NUM> of the generant retaining wall <NUM> may be cooperatively configured to allow an improved flow of combustion gas between the gas generant retaining wall <NUM> and the lid <NUM> when the lid abuts the gas generant retaining wall <NUM> in the open position. In this regard, at least one of the outer side <NUM> of the lid and the adjacent side <NUM> of the gas generant retaining wall <NUM> includes a planar portion <NUM> and a raised portion <NUM>. In the embodiment illustrated, the lid <NUM> includes the planar portion and the raised portion <NUM> and the adjacent side <NUM>. The raised portion may be stamped into the lid <NUM> or otherwise formed with or into the lid <NUM>, and may outwardly extend from the planar portion <NUM> in a direction away from the second portion <NUM> of the combustion chamber <NUM>.

The raised portion <NUM> of the lid <NUM> is configured to cooperate with the gas generant retaining wall <NUM> and maintain a generally parallel orientation between the gas generant retaining wall <NUM> and the planar portion <NUM> of the lid <NUM> when the lid <NUM> is in the open position and abutting the gas generant retaining wall <NUM>. To this end, the raised portion <NUM> includes at least three spaced apart points defining a plane perpendicular to an axial direction that abut the gas generant retaining wall <NUM> to maintain the generally parallel orientation. Perhaps more preferably, the raised portion <NUM> includes at least three legs <NUM> each outwardly extending from a common point <NUM> in a direction parallel to the gas generant retaining wall <NUM>. In the embodiment illustrated, the raised portion has a cruciform shape with four legs <NUM> each outwardly extending from the common point <NUM> in the direction parallel to the gas generant retaining wall <NUM>. Each of the legs <NUM> may have a generally convex shape. It will be appreciated that the legs <NUM> of the raised portion <NUM> may alternatively be spaced from each other (i.e., not connected to one another through a common point <NUM>).

At least one of the gas generant retaining wall <NUM> and the raised portion <NUM> of the lid <NUM> may be constructed of a material that partially deforms upon movement of the lid <NUM> from the first position to the second position under the heat and pressure of the reaction. This partial deformation may increase surface area contact between the lid <NUM> and the gas generant retaining wall <NUM> to avoiding tilting of the lid <NUM> while maintaining the combustion gas flow path therebetween. In one embodiment, the lid <NUM> may be constructed of carbon steel and the gas generant retaining wall may similarly be constructed of carbon steel.

A filter <NUM> is disposed in the filter chamber <NUM> for filtering combustion gases before the combustion gases are exhausted through radially extending ports <NUM> in the second portion <NUM> of the housing <NUM>. The second portion <NUM> of the housing <NUM> may be a diffuser cap portion. The filter <NUM> includes a main body <NUM> and an opening <NUM> that axially passes through the main body <NUM>. The opening <NUM> has a first end <NUM> at a first axial side <NUM> of the main body portion <NUM> and a second end <NUM> at a second axial side <NUM> of the main body portion <NUM>. The first end <NUM> of the opening <NUM> has a first diameter D<NUM>. The second end <NUM> has a second diameter D<NUM>. The second diameter D<NUM> is greater than the first diameter D<NUM>.

The opening <NUM> includes a first axially extending portion 68A inwardly extending into the main body portion <NUM> from the first axial side <NUM> and a second axially extending portion 68B inwardly extending into the main body portion <NUM> from the second axial side <NUM>. The first axially extending portion 68A may have a cylindrical shape. The second axially extending portion 68B may have a frustoconical shape. The frustoconical shape of the second axially extending portion 68B may outwardly taper from the first diameter D<NUM> adjacent the first axially extending portion 68A to the second diameter D<NUM> at the second end <NUM>. The second axially extending portion 68A may outwardly taper at an angle α.

In one particular application, the first axially extending portion 68A has a first height H<NUM> of approximately <NUM>, the second extending portion 68B has a second height H2 of approximately <NUM>, and the second axially extending portion 68A outwardly tapers at an angle between <NUM> degrees and <NUM> degrees, and more preferably at an angle of approximately <NUM> degrees. In this particular example, the first diameter D<NUM> of the first end <NUM> of the opening <NUM> is approximately <NUM> and the second diameter D2 of the second end <NUM> of the opening <NUM> is approximately <NUM>.

The opening <NUM> of the filter <NUM> may alternatively include a stepped shape. In this regard, the opening <NUM> may be alternatively defined by one or more cylindrical portions of different diameters. For example, the second axially extending portion 68B of the opening <NUM> may alternatively be cylindrically shaped with a stepped portion between the first and second axially extending portions 68A and 68B.

The filter <NUM> may include a first filter portion 62A radially surrounding the first axially extending portion 68A and a second filter portion 62B radially surrounding the second axially extending portion 68B. The first filter portion 62A may have a first radial density in a radial direction and the second filter portion may have a second radial density in the radial direction. The second radial density may be greater than the first radial density such that combustion gases more easily radially flow through the first filter portion 62A as compared to radially through the second filter portion 62B. The second filter portion 68B may have a variable density in the radial direction that increases from the first filter portion 62A to the second axial side <NUM> of the filter <NUM>. The variable density of the second filter portion 68B may linearly increase from adjacent the first filter portion 62A to the second axial side <NUM> of the filter <NUM>.

The filter <NUM> may be constructed of metal. More preferably, the filter may be a woven wire mesh filter. The frustoconical shape of the portion of the opening <NUM> passing through the second filter portion 62B may be defined by a correspondingly shaped mandrel. In this regard, a mandrel (not shown) used to create the frustoconical shape of the second axially extending portion 68B of the opening <NUM> may have a male frustoconical shape corresponding to the shape of the second axially extending portion 68B. The wire mesh filter <NUM> may be compressed from an initial, generally toroidal shape by the mandrel which is inserted into the opening <NUM>. Compression of the wire mesh of the filter <NUM> with the mandrel may simultaneously axially compress the wire mesh of the first and second filter portions 62A and 62B and radially compress the wire mesh of the second filter portion 62B. Insofar as the wire mesh of the first filter portion 62A is not radially compressed (or at least radially compressed to a lesser degree), the density of the second filter portion 62B is greater than the density of the first filter portion 62A.

A separating member <NUM> disposed in the housing <NUM> axially separates the filter chamber <NUM> and the combustion chamber <NUM>. The separating member <NUM> includes a plate portion 78A disposed adjacent the first axial side <NUM> of the filter <NUM>. The plate portion 72A and may include a weakened zone <NUM>. The weakened zone <NUM> may be adapted to open in response to an increase in pressure within the combustion chamber <NUM>. The weakened zone <NUM> is shown prior to opening in <FIG> and <FIG>. The weakened zone <NUM> is shown after opening in <FIG> and <FIG>. In the embodiment illustrated, the weakened zone <NUM> has a cruciform shape. As such, the weakened zone <NUM> opens to define four petals <NUM>. It will be understood, however, that alternately shaped weakened zones may be employed within the scope of the present teachings to define a greater or lesser number of petals <NUM>. After the weakened zone <NUM> opens, a plurality of petals <NUM> of the plate portion 78A axially extend into the filter chamber <NUM>. The first axially extending portion 68A of the filter <NUM> is sized and positioned to oppose radial movement of the plurality of petals <NUM> upon opening of the weakened zone <NUM>. The petals <NUM> of the plate portion 78A are radially spaced from the second diameter of the second axially extending portion 68B of the opening <NUM> upon opening of the weakened zone.

An insulating member <NUM> is axially disposed between the filter <NUM> and the second housing portion <NUM>. Combustion gases passing through the filter <NUM> elevate the temperature of the filter <NUM>. The insulating member <NUM> includes a plate portion <NUM> including a plurality of vent holes <NUM>. The insulating member <NUM> functions to protect the second housing portion <NUM> from these elevated filter temperatures. In the embodiment illustrated, the insulating member <NUM> is coupled to the separating member <NUM> such that the insulating member <NUM> is radially and axially captured by the separating member <NUM>.

The separating member <NUM> and the insulating member <NUM> are cooperatively configured to be coupled together. In this regard, the separating member includes a circumferential flange axially extending from the plate portion 78A in a direction away from the combustion chamber <NUM>. The insulating member <NUM> includes a plurality of engagement elements <NUM>. The engagement elements <NUM> may be hook shaped engagement elements sized and positioned to be press-fit to the separating member <NUM>. The hook shaped engagement elements <NUM> axially extend from a circumferential flange <NUM> that axially extends from the plate portion <NUM> of the insulating member <NUM>. In the embodiment illustrated, the insulting member <NUM> includes four (<NUM>) engagement elements <NUM> equally spaced circumferentially about the insulating member. While the hook shaped engagement elements <NUM> may be preferred for particular applications, it will be understood that other types of engagement elements may be incorporated within the scope of the present teachings. It will also be understood that the engagement elements <NUM> may be alternatively carried by the separating member <NUM>.

The filter <NUM> is axially captured between the insulating member <NUM> and the separating member <NUM> such that movement of the filter <NUM> within the filter chamber <NUM> is directly opposed in a first axial direction by the plate portion <NUM> of the insulating member <NUM> and directly opposed in a second, opposite axial direction by the plate portion 78A of the separating member <NUM>. The filter <NUM> is radially captured by at least one of the insulating member <NUM> and the separating member <NUM> such that movement in any radial direction is opposed. In the embodiment illustrated, radial movement of the filter <NUM> within the filter chamber <NUM> is directly opposed by the circumferential flange <NUM> of the insulating member <NUM>.

With particular reference to the cross-sectional views of <FIG> and <FIG>, operation of the inflator <NUM> of the present teachings will be described. Flow of combustion gases is represented in <FIG> with arrows. It will be understood, however, that the arrows included in <FIG> identify the primary flow of combustion gases through the inflator <NUM> in a simplified manner.

Upon activation of the inflator <NUM>, the first gas generant material <NUM> begins to ignite and produce inflation gases which pressurize the first portion <NUM> of the combustion chamber <NUM>. The increased pressure within the first portion <NUM> of the combustion chamber <NUM> open the weakened zone <NUM> of the plate portion 78A of the separating member <NUM> causing the petals <NUM> to extend into the filter chamber <NUM>. More specifically, the petals <NUM> of the plate portion 78A extend into the opening <NUM> of the filter <NUM>. As shown in <FIG>, the petals <NUM> continue to open until they are radially opposed by the first portion 62A of the filter <NUM> at the first axially extending portion 68A of the opening <NUM>. As such, the petals <NUM> are radially spaced from the second portion 62B of the filter <NUM> at the second axially extending portion 68B of the opening <NUM> for unimpeded flow of combustion gases in a radial direction. The combustion gases from the first gas generant material <NUM> pass radially through the filter <NUM> and are exhausted through the radially extending ports <NUM>. Given the lower density of the filter <NUM> at the first portion 62A, flow of the combustion gases radially passes not only through the second portion 62B of the filter <NUM> but also through the first portion 62A. It will be appreciated that the reduced diameter portion of the opening <NUM> of the filter <NUM> services to block movement of the petals <NUM> and thereby reduces variability in performance of the inflator <NUM>.

When the second ignition device <NUM> is activated, the second gas generant material <NUM> is activated to produce a second source of inflation gases. Upon activation of the second gas generant material <NUM>, the second source of combustion gases pressurize the second portion <NUM> of the combustion chamber <NUM>. The increased pressure within the second portion <NUM> of the combustion chamber <NUM> displaces the lid <NUM> from the closed position to the open position. A flow path is maintained between the lid <NUM> and the gas generant retaining wall <NUM>. Again, it will be understood that this flow path maintained between the lid <NUM> and the gas generant retaining wall <NUM> is not specifically represented by arrows in <FIG>. It will be further understood, however, that this flow path even further reduces variability in performance of the inflator <NUM>. The combustion gases from the second gas generant material <NUM> similarly pass through the openings <NUM> in the gas generant retaining wall, through the opening in the plate portion 78A of the separating member <NUM>, axially into the opening <NUM> of the filter <NUM>, radially through the filter <NUM> and out the ports <NUM>.

Claim 1:
An inflator (<NUM>) for generating inflation gases for a safety device, the inflator (<NUM>) comprising:
a housing (<NUM>) having an internal cavity including a combustion chamber (<NUM>) and a filter chamber (<NUM>);
a filter (<NUM>) disposed in the filter chamber (<NUM>);
a separating member (<NUM>) disposed in the housing (<NUM>) on a first axial side (<NUM>) of the filter (<NUM>) and separating the filter chamber (<NUM>) from the combustion chamber (<NUM>);
an insulating member (<NUM>) disposed in the filter chamber (<NUM>) on a second axial side (<NUM>) of the filter (<NUM>), the second axial side (<NUM>) being opposite the first axial side (<NUM>),
characterized in that the separating member (<NUM>) is coupled to the insulating member (<NUM>).