WO1992021534A1

WO1992021534A1 - Air bag assembly

Info

Publication number: WO1992021534A1
Application number: PCT/US1992/004496
Authority: WO
Inventors: William E. Rogerson; Sean P. Donovan; William D. Gaw, Jr.; John B. Sparhawk
Original assignee: Allied Signal Inc.
Priority date: 1991-05-31
Filing date: 1992-05-28
Publication date: 1992-12-10

Abstract

An air bag assembly (10) comprising: a housing (12) having a central first opening (14); an air bag (18) having a second opening (34), secured to the housing, for protecting an occupant of a vehicle upon inflation thereof; a gas generator (20) for generating gases to inflate an air bag, including a central portion (24) received within the first and second openings and a retaining ring (40), including a third opening (44) for securing the air bag to the housing. The retaining ring (40) is positioned interior to the air bag opposite the housing and includes no more than four fasteners extending from a generally flat portion through any of the air bag, housing and gas generator to provide the only fastener used to clamp the various components together. The second opening in the air bag is made smaller than the diameter of the cylindrical portion (24) of the gas generator (20) such that upon insertion of the gas generator into the housing (12) and air bag (18) the material defining the second opening is deflected inwardly to define a seal (58) against the gas generator.

Description

AIR BAG ASSEMBLY

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to an air bag assembly and more particularly to a driver side air bag assembly installed within a vehicle steering wheel for protecting an occupant in the event of a collision of the vehicle.

Various types of driver side air bag assemblies have been proposed for protecting an occupant against injury. Typically, the driver side air bag assembly comprises a housing, a gas generator, typically using a solid propellant such as sodium azide, and an air bag. The air bag is maintained in a folded configuration and secured in this configuration to the housing by a cover. The air bag which typically includes a central opening into which is positioned the gas generator. The air bag is secured to the housing by a retaining ring. The retaining ring is secured to the housing by a combination of bolts and rivets. These rivets extend through mating holes positioned about the central opening and through aligned holes within the housing. Use of these rivets increases the cost of manufacture as the assembly process also requires providing the through-holes in the retainer, housing, and air bag. The use of rivets does provide a benefit in that they tend to reinforce the interface between the retaining ring, housing and air bag. However, they provide a source of air leaks requiring compensation which may add to the cost and complexity of the overall assembly. In the typical air bag assembly as described above, the gas generator will pressurize the air bag to a significant degree. It is desirable to provide an air tight seal between the gas generator and housing to prevent the flow of pressurized gas. This type of seal is often constructed of an O-ring or gasket secured between the gas generator and housing. The use of this O-ring also increases the cost of the assembly and is eliminated by the present invention.

It is an object of the present invention to provide an air bag assembly which uses a rivetless retaining ring and one which provides a seal without the use of additional gasket material.

Accordingly, the invention comprises: an air bag assembly comprising a housing having a central first opening; an air bag, having a second opening, secured to the housing, for protecting an occupant of a vehicle; a gas generator for generating gases to inflate an air bag, including a central portion received within the first and second openings and a retaining ring, including a third opening for securing the air bag to the housing. The retaining ring is positioned interior to the air bag opposite the housing and includes generally two to six fasteners extending from a generally flat portion through any of the airbag, housing and gas generator components to provide the only means for clamping retainer, airbag and housing together. The second opening in the air bag being smaller than the diameter of the cylindrical portion of the gas generator such that upon insertion of the gas generator into the housing and air bag, the air bag material defining the second opening is deflected inwardly to define a seal against the gas generator.

Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIGURE 1 illustrates a cross-sectional view of. an air bag assembly incorporating the features of the present invention.

FIGURE 2 illustrates an isolated top plan view of a retaining ring for use in the present invention.

FIGURE 3 is a cross-sectional view of the retaining ring.

FIGURE 4 illustrates a detailed view of an air bag assembly using a tethered air bag. FIGURE 5 illustrates an alternate embodiment of the present invention.

FIGURES 6 and 7 show other alternate embodiments of the invention.

PETAILEP DESCRIPTION QF THE PRAWINSS

FIGURE 1 illustrates an air bag assembly 10 incorporating the features of the present invention. The assembly 10 includes a housing 12 defining a central opening 14. The edges 16 of the housing 12 may be arcuately shaped to prevent damaging the air bag 18 and facilitate attachment of a frangible cover (not shown) . The assembly additionally includes a gas generator shown as 20. The gas generator 20 may include a flange 22 mounted to the underside of the housing 12. In addition, the gas generator may include a thin cylindrical portion 24 which extends into the interior of the air bag through opening 14. The diameter of the cylindrical portion 24 is slightly smaller than the diameter of the housing opening 14 to permit easy entry. Typical of gas generators used in driver side air bag assemblies is the inclusion of a plurality of openings 26, which are circumferentially spaced about the cylindrical portion 24 to permit the generated gases to inflate same. Arrows 30 and 32 generally show the flow of generated gas from the gas generator 20.

The air bag 18 is constructed of a suitable soft, often woven material. If the density of the weave is relatively open, the air bag 18 may be coated on its interior side with a rubber or other suitable material to make the air bag essentially air tight with appropriate vent holes (not shown) as is known in the art. The air bag 18 includes a central opening 34 which is also shown in the phantom line as 34 in FIGURE 2. The diameter of this opening 34 is slightly smaller than the diameter of the housing opening 14 and cylindrical portion 24 of the gas generator.

The air bag 18 is secured to the housing 12 by a retaining ring generally shown as 40. This retaining ring is shown in both FIGURES 1 and 2. In the illustrated embodiment of the invention the retaining ring 40 is generally square shaped, but can be circular, oval, etc. A cut-out is provided in a central bottom portion 42 to define a circular opening 44. The diameter of this opening is generally slightly larger than the diameter of the opening 34 in the air bag 18. A typical diameter of this opening 44 is approximately 105 millimeters while a typical diameter of the air bag opening 34 is approximately 99 millimeters. The retainer ring includes bent up edges 46 about its four sides. These edges extend into the air bag 18 such that they intercept only a portion of the generated gases (see arrows 30 and 32) thereby deflecting this portion of the generated gases in the direction of the occupant . One goal of any air bag assembly of the type shown in FIGURE 1 is to generate inflation gases and to quickly and controllably communicate same to the air bag to provide for the rapid inflation of same. It can be appreciated that the length or height of the edges 46 can be such that they extend inwardly into the air bag beyond the openings 26 in the gas generator 20 such that the retainer 40 deflects the total stream of generated gases perpendicularly into the air bag. This type of an arrangement may provide for a too rapid inflation of the air bag and as such, one advantage presented by the present invention is that only a portion of the generated gas stream is so deflected, which will permit the more controlled inflation of the air bag 18. Typically the height, h, of these edges is sized to intercept 25 to 33 percent of the generator gas. Reference is made to FIGURES 2 and 3. FIGURE 2 illustrates a top plan view of a retaining ring 40. FIGURE 2 also shows, in phantom line, various elements of the air bag 18. As an example, the air bag material 50 which defines the opening 34 can be seen extending inwardly of the retainer opening 46. In addition, another element of the air bag generally shown as 52a and 52b is illustrative of a portion of the tethers which are often used in an air bag. As can be seen in FIGURE 1, the tethers 52a, b extend upwardly and are sewn along stitch lines such as 54 to the exterior portion 56 of .the air bag 18 at the top or dome portion. The retaining ring shown in FIGURES 2 and 3 also includes a plurality of bolts shown as 60 which are used to clamp the air bag 18, housing 12 and gas generator 20 together. A nut 62 secures the various components together.

FIGURE 3 illustrates a cross-sectional view taken through the section line 3-3. In addition, FIGURE 3 generally shows the clamping arrangement of an air bag such as 18 (the material comprising the tethers 52a, b is not shown) and the housing 12. The gas generator 20 is not shown in FIGURE 3, but is shown in FIGURE 1 where one of the bolts 60 and nuts 62 is shown in phantom line so that the general mounting relationship used in the present invention can be appreciated. All other bolts 60 have been eliminated from FIGURE 1 (as well as from FIGURE 3) for the purpose of clarity.

As can be seen from FIGURE 2, the individual corners such as 66 are curved to prevent damaging the bag. The bottom 68 of the retainer is generally flat to provide a sufficient clamping area between the housing. As can be seen from FIGURE 3, the bottom corner 70 of each side 46 is also curved. The retaining ring is designed to have an increased wall thickness and section modulus of approximately 37mm₃. This was achieved by insuring that the thickness t of the retaining ring be approximately 2 millimeters . It has been found that by using a steel such as 1010/1008, the retaining ring will be sufficiently stiff to provide the required clamping force and not warp or buckle so that the clamping force, is adequately distributed about the generally flat contact area on the bottom of the retaining ring.

During the assembly of the present invention, the gas generator 20 is inserted within the opening 14 of the housing. As the gas generator 20 is inserted further within the housing and into the air bag 18, it engages the flexible air bag material 50 defining the opening 34 and bends same inwardly such that upon secure ent of the gas generator 20 to the housing 12 this material 50 lies between the cylindrical portion 24 and the edge of the retaining ring 40 about the central opening 44 to define an airtight seal 58 between the gas generator 20. Upon generation of the inflation gases by the gas generator 20 and the pressurization of the air bag 18, this extending material 50 is squeezed against the gas generator 20 and housing 12 further enhancing its sealing qualities.

Reference is made to FIGURE 4 which illustrates in greater detail the construction of a typical air bag such as 18 which uses a tether or tethers such as 52a, b. More specifically, FIGURE 4 illustrates the housing 12,retainer 40 and gas generator 20 having the central cylindrical portion 24. In addition, an air bag 18 is shown having an outer portion or panel 56 and a tether 52. The inner portion of the tether may be constructed of at least two layers of air bag material such as 80a and 80b which are sewn at location 82 to a single piece of air bag fabric such as 52b. The reinforced portions of the tether 80a, b are clamped between the retaining ring 40 and housing 12. To protect the air bag 18 from burning or melting due the hot gases generated by the gas generator 20, it is desirable to line the interior of the outer panel 56 as well as the interior of the tether with an inner reinforcement panel 84 of air bag material. The outer panel 56 may also be reinforced by securing an additional layer of material to provide an outer reinforcement panel which is shown generally as 86. The panels 84 and 86 as well as the other portions of air bag material extend between the retaining ring 40 and housing 12 and may be sewn together at location 88. As can been seen in FIGURE 4, as the gas generator is inserted within the opening 14 of the housing 12 all of the various portions of air bag material extending into the opening of the retaining ring are bent upwardly forming the seal 58.

Reference is made to FIGURE 5 which illustrates an alternate embodiment of the retainer 40. In this alternate embodiment the cut-out in the bottom forming the opening 44 is such that a greater amount of the retainer material is removed to reduce its weigh . As shown, the opening 44 is defined by circular segments 90a-d resulting in a lighter weight retainer.

Reference is made to FIGURES 6 and 7 which illustrate another embodiment of the present invention in which the retaining ring 40 is provided with a plurality of integrally formed tabs such as 94. Four such tabs are shown, but any number (typically four to eight) may be used. The tabs are positioned about the circumference of the opening 44 and extend through openings in the air bag and housing as illustrated in FIGURE 7. As these integrally formed tabs 94 extend through the air bag material proximate its opening 34, less deformation of the air bag about its central opening 34 will occur during deployment .

Many changes and modifications in the above described embodiment of the invention can, of course, be carried out without departing from the scope thereof.

Accordingly, that scope is intended to be limited only by the scope of the appended claims .

Claims

IN THE CLAIMS

1. An air bag assembly comprising: a housing having a central first opening; an air bag, having a second opening, secured to the housing, for protecting an occupant of a vehicle upon inflation thereof; a gas generator for generating gases to inflate an air bag, including a central portion received within the first and second openings; a retaining ring, including a third opening for securing the air bag to the housing; the retaining ring positioned interior to the air bag opposite the housing and including a plurality of fasteners extending from a generally flat portion through the airbag, housing and gas generator to provide the only means for clamping at least the retainer, air bag and housing together.

2. The assembly as defined in Claim 1 wherein the retaining ring is of generally square exterior dimension and wherein the each of the fasteners is located proximate a corner of the retaining ring about the third opening.

3. The assembly as defined in Claim 2 wherein the third opening is circular.

4. The assembly as defined in Claim 2 wherein the second opening is defined by circular segments formed in the bottom of the retaining ring.

5. The assembly as defined in Claim 1 wherein the second opening in the air bag is smaller than the central portion of the gas generator such that as the gas generator is inserted into the air bag the material of the air bag defining the second opening stretches to permit entry of the gas generator and to provide an interference fit therebetween.

6. The assembly as defined in Claim 5 wherein the gas generator, air bag material proximate the second opening cooperate to define an air tight seal therebetween.

7. The assembly as defined in Claim 1 wherein the third opening of the retaining ring has a primary diameter slightly greater than the diameter of the central portion of the gas generator, and wherein the diameter of the second opening in the air bag is smaller than the diameters of the first and third openings, such that when the central portion of the gas generator is inserted in the first opening the gas generator engages air bag material defining the third opening, urging same inwardly and securing same between its central portion and an inner edge of of the retaining ring by its third opening to define an air tight seal seal therebetween to restrict the flow of generated gas.

8. The assembly as defined in Claim 1 wherein the gas generator includes first means for directing the generated gases in a direction generally perpendicular to the direction of expansion of the air bag and wherein the retaining ring includes a circumferentially raised edge sized to intercept only a portion of the generated gases and divert such portion, same upon contact with the retaining ring in the expansion direction.

9. The assembly as defined in Claim 1 wherein the recessed edge intercepts between 25% and 33% of the generated gases.