Inflators for passive vehicle safety systems.

Abstract

The two-stage inflator (10) includes a housing (12) defining an internal cavity including a combustion chamber (20). The combustion chamber (20) includes a first portion (28) having a first gas generant material (30) separated from a second portion (32) having a second gas generant material (34). A gas generant retaining wall (26) is disposed within the housing (12). A first-stage igniter (40) is disposed within the first portion (32) of the combustion chamber (20). A second-stage igniter (42) is disposed within the second portion (32) of the combustion chamber (20). A lid (46) typically closes the second portion (32) of the combustion chamber (20) and is spaced from the gas generant retaining wall (26). The lid (46) is movable to an open position in response to an increase in pressure in the second portion (32) of the combustion chamber (20) to open the second portion (32) of the combustion chamber (20) to release combustion gases and abut against the gas generant retaining wall (26). The exterior of the lid (46) and the adjacent side of the gas generant retaining wall (26) are cooperatively configured to permit the flow of combustion gases between the gas generant retaining wall (26) and the lid (46) when the lid (46) abuts against the gas generant retaining wall (26) in the open position.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent Application Publication No. 16 / 909,960, filed June 23, 2020, the entire disclosure of which is incorporated herein by reference.

[0002] FIELD OF THE DISCLOSURE This disclosure relates generally to inflators that provide inflation gas for passive vehicle safety devices, such as inflatable airbags. [Background technology]

[0003] This section provides background information related to the present disclosure, which is not necessarily prior art.

[0004] Inflatable passenger restraint devices, or airbags, are commonly included in automobiles. In the event of an accident, sensors within the vehicle measure, for example, abnormal deceleration and trigger inflation of the airbag within milliseconds by gas generated by a device commonly referred to as an "inflator." The inflated airbag protects the vehicle occupants from the forces of the impact.

[0005] An inflator may generally have one or more chambers that contain the gas generant material. Adaptive pyrotechnic inflators have gas generant material in two chambers and 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" because the gas generant material therein is combusted or otherwise reacted to produce the gas used to inflate the associated occupant restraint.

[0006] One known inflator is shown and described in commonly assigned U.S. Patent No. 7,950,693. The inflator is a dual stage inflator device including a housing defining first and second chambers each containing a quantity of combustible gas generant for producing inflation gas. U.S. Patent No. 7,950,693 is incorporated herein by reference as if fully set forth herein.

[0007] Although known inflators for inflatable passenger restraint systems, including the inflator of U.S. Pat. No. 7,950,693, have generally been found to be suitable for their intended uses, there is a continuing need for improvements in the related art. Summary of the Invention

[0008] This section provides an overview of the disclosure and is not a comprehensive disclosure of the entire scope or all of the features of the disclosure.

[0009] A general object of the present teachings is to provide a dual stage inflator with improved inflation gas flow.

[0010] According to one particular aspect, the present teachings provide a dual stage inflator including a housing defining an internal cavity including a combustion chamber. The combustion chamber includes a first portion having a first gas generant material separated from a second portion having a second gas generant material. A gas generant retaining wall is disposed within the housing. A first stage igniter is disposed within the first portion of the combustion chamber. A second stage igniter is disposed within the second portion of the combustion chamber. A lid normally closes the second portion of the combustion chamber and is spaced from the gas generant retaining wall. The lid is movable to an open position abutting the gas generant retaining wall in response to an increase in pressure within the second portion of the combustion chamber to open the second portion of the internal cavity to release combustion gases in response to an increase in pressure within the second portion of the combustion chamber. An exterior side of the lid and an adjacent side of the gas generant retaining wall are cooperatively configured to permit a flow of combustion gases between the gas generant retaining wall and the lid when the lid abuts the gas generant retaining wall in the open position.

[0011] In accordance with another specific aspect, the present teachings provide a method of supplying inflation gas to a safety device having a dual stage inflator, the method including actuating a second stage igniter and increasing pressure in a second portion of the interior cavity to move the lid to a second position abutting the gas generant retaining wall, the method further including maintaining a combustion gas flow path for combustion gas between the lid and the gas generant retaining wall by a raised portion of the lid.

[0012] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. [Brief description of the drawings]

[0013] The drawings described herein are only for purposes of illustrating selected embodiments rather than all possible implementations and are not intended to limit the scope of the present disclosure. [Figure 1] 1 is a cross-sectional view of an inflator for an inflatable passenger restraint system in accordance with the present teachings, the inflator shown in a pre-activation state; [Figure 1A] 2 is a cross-sectional view of an inflator of the present teachings similar to FIG. 1, showing the inflator in a state after activation. [Diagram 2] FIG. 2 is a perspective view of a lid of a second stage igniter in accordance with the present teachings. [Diagram 3] FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2. [Figure 4] 1 is a simplified perspective view of a filter of an inflator of the present teachings. [Diagram 5] FIG. 5 is a top view of the filter of FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line 6-6 in FIG. 5. [Figure 7A] FIG. 8 is a top view of the central portion of the plate of FIG. 7, showing the plate in a state prior to activation of the inflator. [Figure 7B] FIG. 8 is a top view similar to FIG. 7, showing the plate after activation of the inflator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] One or more exemplary embodiments will now be described more fully with reference to the accompanying drawings. One or more exemplary embodiments are provided to fully convey the scope of the present disclosure to those skilled in the art. Many specific details, such as examples of specific components, devices, and methods, are described to provide a thorough understanding of the embodiments of the present disclosure. It is apparent to those skilled in the art that specific details need not be employed, and that the exemplary embodiments 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 in detail herein.

[0015] The phrases "connected," "coupled," and "in communication with" refer to any form of interaction between two or more entities, including mechanical, electrical, magnetic, electromagnetic, fluid, and thermal interactions. Two components may be coupled to one another even if the two components are not in direct contact with one another. The term "adjacent" refers to things being in physical proximity to one another, but not necessarily in direct contact with one another. The phrase "fluid communication" refers to two features being connected such that fluid in one feature can pass into the other feature. As used herein, "exemplary" means serving as a typical or representative example or instance, and does not necessarily mean special or preferred.

[0016] Referring now to the drawings, an inflator for an inflatable passenger protection device in accordance with the present teachings is illustrated and generally identified by the reference numeral 10. The inflator 10 is part of an automobile passenger restraint system that includes an inflatable airbag (not specifically shown). The inflator 10 shown in the drawings is a dual stage inflator specifically adapted for a driver's side front airbag. However, it will be understood that various aspects of the present teachings may be readily adapted for use with passenger's side front airbags and other airbags.

[0017] The inflator 10 is generally shown to include a housing 12 having a first housing portion 14 and a second housing portion 16. In the illustrated embodiment, the housing 12 has a generally circular cross-section. The first housing portion 14 may be inertia welded or otherwise suitably attached to the second housing portion 16. The first and second housing portions 14 and 16 cooperate to define an interior cavity 20 having a filter chamber 22 separated from a combustion chamber 24 by an interior wall 26.

[0018] The combustion chamber 24 includes a first portion or first combustion chamber section 28 that includes a first gas generant material 30. The combustion chamber 24 further includes a second portion or second combustion chamber section 32 that includes a second gas generant material 34. As far as the present teachings are concerned, the first and second gas generant materials 30 and 34 may be the same material or may be different materials.

[0019] The inner wall may be a vent wall or gas generant retaining wall 26 for retaining the first and second gas generant materials 30 and 34 within the combustion chamber 24. The gas generant retaining wall 26 includes a plurality of openings 36 for venting combustion gases from the combustion chamber 24 to the filter chamber 22. A foam disk 38 may be disposed within the combustion chamber 24 adjacent the gas generant retaining wall 26. As will be appreciated by those skilled in the art, the foam disk functions to provide stability to the storage of the first and second gas generant materials 30 and 34 that may traditionally settle within the combustion chamber 24 over time. The foam disk may be consumed upon combustion of the first and second gas generant materials 30 and 34.

[0020] The first stage igniter 40 is disposed within the first portion 28 of the combustion chamber 24 for combusting the first gas generant material 30. The second stage igniter 42 is correspondingly disposed within the second portion 32 of the combustion chamber 24 for combusting the second gas generant material 34. It will be understood that the first stage igniter 40 and the second stage igniter 42 are conventional in construction and operation as far as the present teachings are concerned. The first stage igniter 40 and the second stage igniter 42 may be conventionally mounted to or coupled with the housing 12.

[0021] The second portion 32 of the combustion chamber 24 is defined by one or more side walls 44 and a lid 46. In the illustrated embodiment, the one or more side walls include a single continuous wall or chamber wall 44. The wall 44 may be elliptical, circular, or any other cross-sectional shape. At a first end of the chamber wall 44 (the lower end as shown in the drawings), the chamber wall 44 receives the second stage igniter 42, and a base 48 of the second stage igniter 42 closes the first end. At a second or opposite end of the chamber wall 44 (the upper end as shown in the drawings), a lid 46 normally (i.e., before activation of the inflator 10) closes the second portion 32 of the combustion chamber 24. The lid 46 may be elliptical or otherwise configured to cooperate with the chamber wall 44 to close the second portion 32 of the combustion chamber 24.

[0022] The lid 46 is axially movable from a first or closed position prior to combustion of the gas generant material to a second or open position following combustion of the gas generant material. The inflator 10 is shown in FIG. 1 prior to combustion of the gas generant materials 30 and 34 and after combustion of the gas generant materials 30 and 34. To further explain, the lid 46 is axially spaced from the generant retaining wall 26 prior to combustion of the second gas generant material 34 (as shown in cross-sectional view in FIG. 1). As shown, the lid 46 may be spaced from the generant retaining wall 26 by a foam disk 38. As the second gas generant material 34 combusts (as shown in cross-sectional view in FIG. 1A), the foam disk 38 is consumed by the heat of reaction and the lid 46 is displaced axially (upward as shown in the drawings) to a position adjacent the generant retaining wall 26 in response to an increase in pressure within the second portion 32 of the combustion chamber 24.

[0023] An exterior 50 of the lid 46 and an adjacent side 52 of the generant retaining wall 26 may be cooperatively configured to improve the flow of combustion gases between the gas generant retaining wall 26 and the lid 46 when the lid abuts the gas generant retaining wall 26 in the open position. In this regard, at least one of the exterior 50 of the lid and the adjacent side 52 of the gas generant retaining wall 26 includes a planar portion 54 and a raised portion 56. In the illustrated embodiment, the lid 46 includes a planar portion, a raised portion 56, and an adjacent side 52. The raised portion may be stamped or otherwise formed with or in the lid 46 and may extend outwardly from the planar portion 54 in a direction away from the second portion 32 of the combustion chamber 24.

[0024] The raised portion 56 of the lid 46 is configured to cooperate with the gas generant retaining wall 26 to maintain a generally parallel orientation between the gas generant retaining wall 26 and the planar portion 54 of the lid 46 when the lid 46 is in the open position and abutting the gas generant retaining wall 26. To this end, the raised portion 56 includes at least three spaced apart points defining an axially perpendicular plane that abuts the gas generant retaining wall 26 to maintain a generally parallel orientation. Perhaps more preferably, the raised portion includes at least three legs 58 each extending outwardly from a common point 60 in a direction parallel to the gas generant retaining wall 26. In the illustrated embodiment, the raised portion has a cross shape with four legs 58 each extending outwardly from the common point 60 in a direction parallel to the gas generant retaining wall 26. Each of the legs 58 may have a generally convex shape. It will be appreciated that the legs 58 of the raised portion 56 may alternatively be spaced apart from one another (ie, not connected to one another via the common point 60).

[0025] At least one of the gas generant retaining wall 26 and the raised portion 56 of the lid 46 may be constructed from a material that partially deforms as the lid 46 moves from a first position to a second position under the heat and pressure of the reaction. This partial deformation may increase the surface area contact between the lid 46 and the gas generant retaining wall 26 to avoid tilting of the lid 46 while maintaining a combustion gas flow path therebetween. In one embodiment, the lid 46 may be constructed from carbon steel and the gas generant retaining wall may likewise be constructed from carbon steel.

[0026] A filter 62 is disposed within the filter chamber 22 for filtering the combustion gases before they are discharged through a radially extending port 64 in the second portion 16 of the housing 12. The second portion 16 of the housing 12 may be a diffuser cap portion. The filter 62 includes a body 66 and an opening 68 axially extending through the body 66. The opening 68 has a first end 70 at a first axial side 72 of the body portion 66 and a second end 74 at a second axial side 76 of the body portion 66. The first end 70 of the opening 68 has a first diameter D1. The second end 74 has a second diameter D2. The second diameter D2 is greater than the first diameter D1.

[0027] The opening 68 includes a first axially extending portion 68A extending inwardly into the body portion 66 from a first axial side 72 and a second axially extending portion 68B extending inwardly into the body portion 66 from a second axial side 76. The first axially extending portion 68A may have a cylindrical shape. The second axially extending portion 68B may have a frusto-conical shape. The frusto-conical shape of the second axially extending portion 68B may taper outwardly from a first diameter D1 adjacent the first axially extending portion 68A to a second diameter D2 at the second end 74. The second axially extending portion 68A may taper outwardly at an angle α.

[0028] In one particular application, first axially extending portion 68A has a first height H1 of about 3.5 mm and second axially extending portion 68B has a second height H2 of about 7.2 mm, with second axially extending portion 68A tapering outwardly at an angle between 45 degrees and 70 degrees, more preferably about 60 degrees. In this particular example, first diameter D1 of first end 70 of opening 68 is about 19.5 mm and second diameter D2 of second end 74 of opening 68 is about 27.8 mm.

[0029] The opening 68 of the filter 62 may alternatively include a stepped shape. In this regard, the opening 68 may alternatively be defined by one or more cylindrical portions of different diameters. For example, the second axially extending portion 68B of the opening 68 may alternatively be cylindrical with a stepped portion between the first axially extending portion 68A and the second axially extending portion 68B.

[0030] The filter 62 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 a radial direction. The second radial density may be greater than the first radial density such that the combustion gas flows radially more easily through the first filter portion 62A compared to flowing radially through the second filter portion 62B. The second filter portion 68B may have a variable radial density that increases from the first filter portion 62A toward a second axial side 76 of the filter 62. The variable density of the second filter portion 68B may increase linearly from adjacent the first filter portion 62A to the second axial side 76 of the filter 62.

[0031] The filter 62 may be constructed of metal. More preferably, the filter may be a woven wire mesh filter. The frusto-conical shape of the portion of the aperture 68 passing through the second filter portion 62B may be defined by a mandrel of corresponding shape. In this regard, the mandrel (not shown) used to create the frusto-conical shape of the second axially extending portion 68B of the aperture 68 may have a male frusto-conical shape corresponding to the shape of the second axially extending portion 68B. The wire mesh filter 62 may be compressed from an initial approximately toroidal shape by the mandrel inserted into the aperture 68. Compression of the wire mesh of the filter 62 by 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. The density of second filter portion 62B is greater than the density of first filter portion 62A, insofar as the wire mesh of first filter portion 62A is not radially compressed (or at least radially compressed to a lesser extent).

[0032] A plate 78 disposed within the housing 12 axially separates the filter chamber 22 and the combustion chamber 24. The plate 78 may be disposed adjacent the first axial side 72 of the filter 62 and may include a weakened zone 80. The weakened zone 80 may be adapted to open in response to an increase in pressure within the combustion chamber 24. The weakened zone 80 is shown in FIGS. 1 and 7A prior to opening. The weakened zone 80 is shown in FIGS. 2 and 7B after opening. In the illustrated embodiment, the weakened zone 80 has a cross shape. Thus, the weakened zone 80 opens to define four petals 82. However, it will be understood that alternatively shaped weakened zones may be employed to define a greater or lesser number of petals 82 within the scope of the present teachings. After the weakened zone 80 opens, the multiple petals 82 of the plate 78 extend axially into the filter chamber 22. The first axially extending portion 68A of the filter 62 is sized and positioned to oppose radial movement of the plurality of petals 82 upon opening of the weakened zone 80. The petals 82 of the plate 78 are radially spaced from a second diameter of the second axially extending portion 68B of the opening 68 upon opening of the weakened zone.

[0033] An insulating plate 84 is axially disposed between the filter 62 and the second housing portion 16. Combustion gases passing through the filter 62 increase the temperature of the filter 62. The insulating plate 84 functions to protect the second housing portion 16 from these increased filter temperatures.

[0034] The operation of an inflator 10 of the present teachings will be described with particular reference to the cross-sectional views of Figures 1 and 2. The flow of combustion gases is indicated by arrows in Figure 1A. However, it will be understood that the arrows included in Figure 1A are a simplified representation of the primary flow of combustion gases through the inflator 10.

[0035] When the inflator 10 is actuated, the first gas generant material 30 begins to ignite and generates inflation gases that pressurize the first portion 28 of the combustion chamber 20. The increased pressure in the first portion 28 of the combustion chamber 20 opens the weakened zone 80 of the plate 78, causing the petal 82 to extend into the filter chamber 22. More specifically, the petal 82 of the plate 78 extends into the opening 68 of the filter 62. As shown in FIG. 1A, the petal 82 continues to open until it is radially opposed by the first portion 62A of the filter 62 at the first axially extending portion 68A of the opening 68. Thus, the petal 82 is radially spaced from the second portion 62B of the filter 62 at the second axially extending portion 68B of the opening 68 such that the combustion gases flow radially unimpeded. The combustion gases from the first gas generant material 30 pass radially through the filter 62 and are discharged through the radially extending ports 64. If the density of the filter 62 is low in the first portion 62A, the flow of combustion gases will pass radially through the first portion 62A as well as through the second portion 62B of the filter 62. It will be appreciated that the reduced diameter portion of the opening 68 in the filter 62 acts to inhibit movement of the petal 82, thereby reducing variability in the performance of the inflator 10.

[0036] Upon activation of the second igniter 42, the second gas generant material 34 is activated to generate a second source of inflation gas. Upon activation of the second gas generant material 34, the second source of combustion gas pressurizes the second portion 32 of the combustion chamber 20. The increased pressure in the second portion 32 of the combustion chamber 20 displaces the lid 46 from a closed position to an open position. A flow path is maintained between the lid 46 and the gas generant retaining wall 26. Again, it will be appreciated that this flow path maintained between the lid 46 and the gas generant retaining wall 26 is not specifically represented by arrows in FIG. 1A. However, it will be further appreciated that this flow path further reduces the variability in the performance of the inflator 10. Combustion gases from the second gas generant material 34 similarly pass through the openings 36 in the gas generant retaining wall, through the openings in the plate 78, axially into the openings 68 of the filter 62, radially through the filter 62, and out the port 64.

[0037] While specific embodiments and applications of the present disclosure have been illustrated and described, it will be understood that the invention is not limited to the precise configuration and components disclosed herein. Various modifications, changes and variations which will be apparent to those skilled in the art may be made in the arrangement, operation and details of the methods and systems of the present disclosure without departing from the spirit and scope of the present disclosure.

Claims

1. A two-stage inflator 10, a housing (12) defining an internal cavity including a combustion chamber (20), said combustion chamber (20) including a first portion (28) having a first gas generant material (30) separated from a second portion (32) having a second gas generant material (34); a gas generant retaining wall 26 disposed within the housing 12; a first stage ignition device 40 disposed within the first portion 28 of the combustion chamber 20; a second stage igniter 42 disposed within the second portion 32 of the combustion chamber 20; a lid 46 that normally closes the second portion 32 of the combustion chamber 20 and is spaced from the gas generant retaining wall 26, the lid 46 being movable to an open position against the gas generant retaining wall 26 in response to an increase in pressure within the second portion 32 of the combustion chamber 20 to open the second portion 32 of the combustion chamber 20 and release combustion gases; Equipped with an outer side of the lid 46 and an adjacent side of the gas generant retaining wall 26 are cooperatively configured to permit a flow of combustion gases between the gas generant retaining wall 26 and the lid 46 when the lid 46 abuts the gas generant retaining wall 26 in the open position; at least one of the outer side of the lid 46 and the adjacent side of the gas generant holding wall 26 includes a flat portion and a raised portion, and the raised portion abuts against the other of the outer side of the lid 46 and the adjacent side of the gas generant holding wall 26 when the lid 46 is in the open position to maintain a combustion gas flow path between the lid 46 and the gas generant holding wall 26. Two-stage inflator 10.

2. 2. The dual stage inflator (10) of claim 1, wherein said exterior of said lid (46) includes said planar portion and said raised portion.

3. 3. The dual stage inflator (10) of claim 2, wherein said raised portion extends outwardly from said planar portion in a direction away from said second portion (32) of said combustion chamber (20).

4. 4. The dual stage inflator (10) of claim 3, wherein said lid is stamped to define said raised portion.

5. 4. The dual stage inflator (10) of claim 3, wherein said raised portion of said lid (46) is configured to maintain a substantially parallel orientation between said gas generant retaining wall (26) and said planar portion of said lid (46) when said lid (46) is in said open position and abutting said gas generant retaining wall (26).

6. 6. A dual stage inflator (10) as defined in claim 5, wherein said raised portion of said lid (46) includes at least three spaced apart points which abut said gas generant retaining walls to maintain said generally parallel orientation.

7. 4. The dual stage inflator (10) of claim 3, wherein said raised portion includes at least three legs each extending outwardly from a common point in a direction parallel to said gas generant retaining wall (26), each of said at least three legs having a generally convex shape in the outward direction.

8. 4. The dual stage inflator (10) of claim 3, wherein said raised portion has a cross shape with four legs each extending outwardly from a common point in a direction parallel to said gas generant retaining wall (26).

9. 2. The dual stage inflator 10 of claim 1, wherein at least one of the gas generant retaining wall 26 and the raised portion of the lid 46 is constructed from a material that partially deforms upon movement of the lid 46 from a closed position to the open position so as to increase surface area contact between the lid 46 and the gas generant retaining wall 26 to avoid tilting of the lid 46 while maintaining the combustion gas flow path therebetween.

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