Integral steering wheel and airbag module

Abstract: A unitary moulded plastic body (22) with an unbroken outer surface contains a circumferential steering wheel rim armature (18) and radially extending spoke armatures (20) and has an internal cavity (26) closed by an integral door portion defined by tear lines (28, 30). Inner ends of the spoke armatures (20) are connected to a hub plate (10) by screws (32) which when removed permit removal of the body (22) allowing access to a folded airbag (40) a mouth of which is clamped between a mounting flange (36) of an inflator (38) and the hub plate (10) by bolts (34). A retainer ring with tabs which project through the airbag (40) may be interposed between the mounting flange (36) and the airbag (40). As the plastic body (22) serves as steering wheel body and accommodates airbag module components, assembly and maintenance is facilitated.

Description: This invention relates to the field of vehicular airbags. More particularly, it relates to a steering wheel and driver's side airbag module integrated into a single unit. Conventional driver's side airbag modules are separate units positioned in a recess in the front of the steering wheel. This creates a crack encircling the airbag module where it meets the remaining front surface of the steering wheel. This crack tends to collect dust and is aesthetically undesirable. It would be preferable for the steering wheel to present to the driver a substantially unbroken surface. One means of overcoming this problem is described in European Patent Publication No. EP 0 648 661 A1, published April 19, 1995. That publication discloses a steering wheel having an unseamed front surface on a body which is integral with the steering wheel rim. The rim portion is connected to elongated spokes which engage the steering wheel mounting hub. The airbag module is connected to the central body of the steering wheel and is also connected by screws to the elongated spokes. Accordingly, in order to service or replace the airbag module, it is necessary to remove the screws which interconnect the module with the spokes, then remove the screws which connect the rim and the central body to the spokes. This allows the main body of the steering wheel and the connected airbag module to be removed. It is then necessary to remove the module from the central body of the .steering wheel. This results in an undesirable amount of labor and resulting expense which it would be desirable to eliminate. EP-A-0700810 discloses a vehicle steering wheel having an upper body, a lower hub plate and an element in between. The hub plate has a radial flange surrounding a depressed central region with a bush beneath for connecting the hub plate to a steering column. The element has a mounting flange which extends radially around a depressed central region that fits inside the depressed region of the hub plate, the mounting flange being clamped in between the body and the hub plate. Seated in the element's depressed region is an inflator with a gas bag attached, the gas bag being contained by a cavity in the body above. The body also contains a number of spokes which extend from a radial flange. The body, the element and the hub plate are connected together by bolts which pass through the spoke radial flange, the element's mounting flange and the hub plate radial flange. EP-A-0728652 also discloses a vehicle steering wheel and was filed on 16 February 1996, claiming priority from JP 38744/95 and JP 38745/95 both filed on 27 February 1995, JP 105832/95 filed on 28 April 1995 and JP 122661/95 filed on 22 May 1995. EP-A-0728652 was published on 28 August 1996 and the Contracting States DE, FR and GB were designated. The steering wheel disclosed in EP-A-0728652 includes a hub plate with a depressed central region. A plastic body has an internal cavity containing an airbag and is adapted to be positioned over the hub plate. An inflator for the airbag has an encircling mounting flange which mounts the inflator on the hub plate so that it is received partially within the depressed central region, the inflator also being partially within the cavity. The airbag has a mouth which is positioned between the mounting flange and the hub plate and bolts are provided to releasably secure the mounting flange and the mouth to the hub plate. Accordingly, it is a primary object of the present invention to provide a steering wheel in the form of a molded body having an unbroken front surface which can be removed in one operation to expose the airbag module, the steering wheel being easier to assemble. Other objects, features, and advantages will become apparent from the following description and appended claims. The invention comprises an automotive steering wheel comprising: a hub plate having a depressed central region and a hub mounted on and extending downwardly from said depressed central region, said hub being connectable directly to a steering column and said hub plate extending substantially radially outwardly therefrom; a spoke armature having a first end and a second end, the second end adapted to be positioned radially outwardly from said hub plate in a plane spaced from said hub plate in a direction away from said steering column; a rim armature adapted to be in said spaced plane secured to the second end of said spoke armature; a one-piece plastic body integral with and enclosing said spoke and rim armatures and defining an internal cavity to be positioned over said hub plate; an airbag inflator adapted to be partially within said internal cavity of the body; a folded airbag adapted to be within said internal cavity, said airbag having a mouth positioned to receive inflating gas from the airbag inflator; and means for releasably securing said spoke armature first end to said hub plate, said inflator and airbag being fully exposed when said spoke armature is detached from said hub plate and said body is removed; characterised in that the airbag inflator is mounted on said hub plate and is partially within said depressed central region, the body is moulded, and the first end of the spoke armature is directly connectable to the hub plate and releasably secured by said releasable securing means. The invention will now be described, by way of example only, with reference to the accompanying Figures, in which: Fig. 1 is a front, or driver's side, view of a steering wheel and airbag module in accordance with the present invention; Fig. 2 is a cross-section taken substantially along the line 2-2 of Fig. 1; Fig. 3 is an enlarged partial cross-section illustrating one way of retaining the airbag within the steering wheel; Fig. 4 is a plan view of an airbag retainer ring usable in the present invention; and Fig. 5 is a view similar to Fig. 3 showing the manner of installing the retainer ring of Fig. 3. In accordance with the present invention, a hub plate 10 having a depressed central region 12 is mounted on a hub 14 which is secured to the end of a steering column 16 by conventional means. A steering wheel in the form of a rim amature 18 mounted to one end of one or more spoke armatures 20 molded integrally into a plastic body 22 provides an unbroken surface 24 as shown in FIG. 1. The body 22 is formed with an internal cavity 26. The front surface of the body 22 overlying the cavity 26 is thinned on the cavity side to form one or more tearlines 28, 30 which are designed to burst open in a conventional manner to release the airbag upon activation. The steering wheel is mounted to the hub plate 10 by fastening means such as screws 32 which extend through the hub plate 10 and into the spoke armatures 20. When so mounted, the spoke armatures 20 extend radially outward from the hub plate and the rim armature is located in a plane spaced from the hub plate 10 in a direction away from the steering column 16. Also releasably secured on the hub plate 10 by means of nuts and bolts 34 is an encircling mounting flange 36 of a conventional inflator 38. The inflator 38 also extends downwardly into the depressed central region 12 of the hub plate. The cavity 26 also encloses a folded airbag 40. Thus it will be seen that the disclosed integral steering wheel in and of itself becomes the airbag module. When the airbag or its inflator are to be serviced or replaced, it is merely necessary to remove the screws 32 thereby allowing the steering wheel to be removed and completely revealing the airbag and inflator. A shroud 42 which is often present at the back of the wheel may either be removed or provided with access openings for reaching the screws 32. As the airbag module of this invention does not have a separate housing apart from the steering wheel itself, it is possible to achieve a simplified construction in the manner of installing the airbag. The airbag 40 has a conventional round mouth 44 formed therein. The peripheral region surrounding this mouth may be mounted between the mounting flange 36 of the inflator and the hub plate 10. This is illustrated in the enlarged detail view of FIG. 3. As will be seen therein, the fabric of the airbag 40 which surrounds the mouth 44 is positioned between the flange 36 of the inflator and the hub plate 10. In this position it is pinched and retained by the nuts and bolts 34 which serve to simultaneously mount the airbag and the inflator on the hub plate, thus achieving an economy of parts and installation labor. If it is deemed necessary to increase the friction retaining the mouth of the airbag 40, a retainer ring 46 of the type shown in FIG. 4 and disclosed and claimed in U.S. Patent No. 5,443,284 may be employed. The illustrated ring has four mounting holes 48 for receiving the bolts 34 mounting the inflator 38 to the hub plate 10. It is also pierced by eight U-shaped cuts about its periphery. The material within each cut is bent downwardly to create eight tabs 50 depending from eight U-shaped openings 52. As illustrated in FIG. 5, the retaining ring is mounted atop the fabric of the airbag 40 surrounding its mouth 44. Suitable openings 54 are provided in the hub plate 10 to receive the tabs after they have pierced the fabric. If desired, the tabs may be longer and crimped below the hub plate for even more security. In addition to increasing retention force on the airbag, the retainer ring may be of a heat insulating material to help shield the airbag fabric from the intense heat generated by some inflator gas generants. It is believed that the many advantages of this invention will now be apparent to those skilled in the art. It will also be apparent that a number of variations and modifications may be made therein without departing from its scope. Accordingly, the foregoing description is to be construed as illustrative only, rather than limiting. This invention is limited only by the scope of the following claims.

Claims: An automotive steering wheel comprising: a hub plate (10) having a depressed central region (12) and a hub (14) mounted on and extending downwardly from said depressed central region, said hub (14) being connectable directly to a steering column (16) and said hub plate (10) extending substantially radially outwardly therefrom; a spoke armature (20) having a first end and a second end, the first end being directly connectable to the hub plate (10) and the second end adapted to be positioned radially outwardly from said hub plate (10) in a plane spaced from said hub plate (10) in a direction away from said steering column (16); a rim armature (18) adapted to be in said spaced plane secured to the second end of said spoke armature (20); a one-piece moulded plastic body (22) integral with and enclosing said spoke and rim armatures (18,20) and defining an internal cavity (26) to be positioned over said hub plate (10); an airbag inflator (38) adapted to be partially within said internal cavity (26) of the body and partially within said depressed central region (12), and said inflator has an encircling mounting flange (36) mounted on said hub plate; a folded airbag (40) adapted to be within said internal cavity (26), said airbag (40) having a mouth (44) positioned to receive inflating gas from the airbag inflator (38), the mouth (44) of said airbag (40) being positioned between said mounting flange (36) and said hub plate (10); means (32) for releasably securing said spoke armature first end to said hub plate (10), said inflator (38) and airbag (40) being fully exposed when said spoke armature (20) is detached from said hub plate (10) and said body (22) is removed; and means (34) for releasably securing said mounting flange (36) on said hub plate (10) and simultaneously securing the mouth (44) of said airbag (40) between said flange (36) and said hub plate (10), wherein said means comprises a retainer ring (46) surrounding the mouth (44) of said airbag (40) intermediate said hub plate (10) and said inflator flange (36), and means (50) extending from said retainer ring (46) for piercing the airbag (40) at spaced positions around said mouth (44). The steering wheel as claimed in claim 1, comprising a plurality of spoke armatures (20), each having a first end connectable to said hub plate (10) and a second end positioned radially outwardly from said hub plate (10), wherein said rim armature (18) is secured to the second end of each of said spoke armatures (20). The steering wheel as claimed in claim 1 or 2, wherein said piercing means (50) are received in aligned openings (54) in said hub plate (10).

Inventors: ADAMS GARY V, MANNINO JOSEPH J, RICKS MERLE K, VIGEANT PETER L, ADAMS, GARY V., MANNINO, JOSEPH J., RICKS, MERLE K., VIGEANT, PETER L.
Applicants: AUTOLIV ASP INC, TG NORTH AMERICA CORP, AUTOLIV ASP, INC., TG NORTH AMERICA CORPORATION
Application year: 1997
Main classification: B60R21
IPC codes: B62D1, B60R21