Abstract:
A steering wheel assembly including an inflator subassembly, a steering wheel armature, and a cushion subassembly. The inflator subassembly and the cushion subassembly are located on opposite sides of the steering wheel armature. The inflator subassembly comprises an inflator. The inflator subassembly has a lip, which fits into a circular channel on the bottom portion of the steering wheel armature. The cushion subassembly includes an airbag, a retainer, and an airbag cover. Upon detection of a crash from a crash sensor, the inflator begins to generate gas. The gas flows through the inflator subassembly and then is forced to flow through the hub portion of the steering wheel and into the cushion.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The invention generally relates to an air bag module and an associated steering wheel, which features a method providing a continuous electrical connection to the vehicle without the use of a contact coil. 
     A typical driver side air bag module comprises a housing, an inflator, a cushion and a cover. The housing is mounted at or near the steering wheel armature. The inflator and air bag are located within the housing and the cover (and housing) protects the air bag. When the airbag sensor senses a collision has occurred, an electrical signal is sent through a wiring harness, into a contact coil (also known in the art as “clockspring”), and into the inflator. A contact coil is used to provide a secure, reliable connection regardless of the orientation of the steering wheel. Upon receipt of this signal, the inflator begins to generate gas, which in turn inflates the cushion. As the cushion inflates, the cover is separated permitting the inflating cushion to expand toward the occupant. 
     If the inflator could remain fixed on (or become part of) the steering column, and the remaining airbag module components were allowed to rotate about it, the contact coil would be unnecessary. A method of doing this that is known in the art was described in U.S. Pat. No. 5,954,359. In this patent, Ross teaches that it is possible to place a tubular inflator within the steering shaft, and then vent the gas within this shaft and into-the airbag cushion. This is a valid solution; however, it requires not only a tubular style inflator but also a special, non-standard steering shaft. 
     In accordance with the present invention, a steering wheel assembly contains an inflator subassembly comprising a largely circular inflator of the type typically used in driver side airbag modules; the inflator subassembly also contains a flange that has been welded to the inflator before a gas deflector has been attached to the flange. The steering wheel assembly further contains a steering wheel armature containing a circular orifice for receiving gas from the flange and gas deflector; the steering wheel armature further containing features for attachment of the retaining ring to the steering wheel, and for the attachment of the steering wheel armature to the steering shaft. The steering wheel assembly further contains a; cushion subassembly comprising a cushion surrounding the retaining ring, and a cover surrounding the cushion. The steering.wheel assembly further contains a slip ring that serves to pass electrical signals into the steering wheel assembly for electronics such as the horn, cruise control, radio buttons, etc. As will be seen, the inflator, flange, and gas deflector are fixed to the steering column through the use of a bracket, while the steering wheel armature and the cushion subassembly are allowed to rotate about it, and with the aid of a slip ring, electrical signals can be sent-to the steering wheel for devices other then the inflator. As the inflator generates gas, the gas fills the flange and is forced by the gas deflector to flow through the steering wheel armature and into the cushion. The.cushion then expands, opening the cover, and allowing for restraint of the occupant during a collision. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its structure and manner of operation, may be understood by referring to the following detailed description, taken in accordance with the accompanying drawings. 
     FIG. 1 shows a perspective view of the steering wheel assembly in accordance with the present invention. 
     FIG. 2 shows a cross section view of the steering wheel assembly. 
     FIG. 3 shows an exploded view of the steering wheel assembly. 
     FIG. 4 shows a perspective view of an inflator subassembly including an inflator, a flange, and a gas deflector. 
     FIG. 5 shows a perspective view of a steering wheel armature along with the inflator subassembly. 
     FIG. 6 shows a steering wheel armature. 
     FIG. 7 shows a perspective view of a retainer ring attached to an airbag cover with the cushion folded therein. 
     FIG. 8 shows a view of the bottom of the attachment bracket. 
     FIG. 9 shows a view of the top of the attachment bracket. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a steering wheel assembly, which comprises a steering wheel armature  20 , an inflator subassembly  26 , and a cushion subassembly  27 . For the present invention, an inflator  18  is included as part of the inflator subassembly, which is disposed on one side of the steering wheel armature  20  while the cushion subassembly  27  is disposed on.the other side of the armature. The cushion subassembly is positioned on the side of the steering wheel armature  20  that is in closer proximity to the vehicle occupant. FIG. 2 is a cross sectional view of FIG. 1, which also shows that the cushion subassembly  27  and the inflator subassembly  26  are divided by the steering wheel armature  20 . 
     FIG. 3 depicts the various components for the steering wheel assembly. The steering wheel armature is secured to the steering wheel shaft  15  via a threaded fastener  22 . The fastener  22  engages corresponding threads within the steering shaft  15 . One skilled in the art appreciates that other fastening arrangements are suitable for the present invention. The entire steering wheel armature  20  is shown in FIG. 6 including the hub portion  34 , the spokes  35 , and the rim portion  36 . The rim portion  36  has an essentially circular shape with a substantially U-shaped cross sectional configuration and is connected to the hub portion  34  by the spokes  35 . The rim  36 , the spokes  35 , and the hub  34  are generally cast from aluminum or magnesium based alloy, but other materials can be utilized. 
     The hub portion has a steering shaft receptacle adapted to securely couple to the end of the steering shaft  15 . The steering shaft  15  is an integral part of the steering column (not shown) and extends therethrough. The steering wheel armature  20  is rotationally coupled to the steering shaft  15 , and the steering shaft is connected to a vehicle axis, thus a rotation of the steering wheel brings about a direction change for a vehicle. 
     As mentioned earlier, the threaded fastener connects the steering wheel armature  20  to the steering shaft  15 . This threaded fastener passes through an aperture in the inflator subassembly  26  whereby the rotation of the armature  20  does not cause the inflator subassembly  26  to rotate. Accordingly, the inflator subassembly  26  and the armature  20  are decoupled. 
     FIG. 4 shows a perspective view of the inflator subassembly  27 . The inflator subassembly comprises an inflator  18 , flange  17 , and gas deflector  19 . The inflator subassembly  27  is attached to the steering column by way of a bracket  60 . For the present invention, a pyrotechnic inflator is utilized, which generates gas by burning of a gas generant. The inflator having a largely round shape sits inside the pan  28  of the flange and can be secured to the flange  17  by welding, a strap, or other suitable means. On the underside portion of the pan  28 , there are one or more igniter apertures  14  for receiving electrical wiring for the inflator. 
     As can be seen from FIG. 4, a gas deflector  19  is secured to the outer portion of the flange  17  by an interlocking engagement. The aperture  30  of the inflator subassembly receives a steering shaft  15 . The diameter of the aperture  30  is greater than the diameter for the steering shaft  15  enabling the steering shaft  15  to rotate without causing the gas deflector  17  to rotate. 
     The inflator  18  is off set mounted as shown in FIG.  4 . The inflator  18  is situated on the pan  28  of the gas deflector  17  and does not overlie any portion of the aperture  30 . The position of the inflator can be described in relation to the steering shaft  15 . Illustrated in FIG. 3, the steering shaft has a longitudinal axis B, which travels through the aperture  30  of the gas deflector  17 . The inflator is mounted in a portion of the gas deflector  17  so that the longitudinal axis B of the steering shaft  15  does not pass through the inflator  18 , and the inflator  18  and that the inflator does not cover any portion of the aperture  30   
     A slip ring  16  could be installed in the aperture  30  of the deflector portion  29 . A slip ring  16  is part of a slip ring mechanism, which is a rotary electrical connector that is used to make an electrical connection between a vehicle electrical system and an electronic device of the cushion subassembly such as a horn, cruise control, radio buttons, etc. The slip ring mechanism  16  consists of a lower housing  54  that is fixed to the inflator flange  17  and an upper housing  50  that rotates with the steering shaft  15 . In between the housings are lower contacts  56  that are flat and are in constant contact With the upper contacts or brushes  58  which contact a slight bend to ensure a reliable electrical connection will exist. The brush is electrically connected to switches on the cushion subassembly  27 , and the slip ring is electrically connected to the horns and electrical systems. The slip ring  16  takes the place of the more expensive connector, the contact coil. The contact coil is a more reliable connector, but it is not necessary to use in conjunction with the present invention since the electrical signals for the inflator do not travel through this connector. The electrical wires for the inflator are connected directly to the inflator through the igniter apertures  14 . 
     The inflator subassembly  26  has an flexible lip  38  formed from contoured edges of flange  17  and the gas deflector  19 . The flexible lip  38  fits into a circular channel on the bottom portion of the steering wheel armature  20 . The diameter of the flexible lip  38  is less than the diameter of the hub portion  34 . This results in a small gap between the flexible lip  38  and the hub portion  34  to provide for easy assembly, and so that noise will not be generated as the steering wheel assembly is rotated or encounters vibration. However, during deployment sufficient pressure exists in the inflator flange  17  to cause the flexible lip  38  to flex and come into contact with the hub portion  34  in order to provide a tight seal. 
     The cushion subassembly  27  comprises a retainer ring  23 , an airbag  24 , and an airbag cover  25 . As mentioned earlier, the cushion subassembly  27  is arranged on the opposite side of the armature than the inflator subassembly  26 . 
     The airbag cover  25  and the retainer ring are shown in FIG.  7 . This cover is only diagrammatically illustrated as many different configurations of the cover can be used with the present invention. As is known in the art, the purpose of the airbag cover  25  is to provide a decorative fascia, which encloses and protects the airbag  24 . In the embodiment illustrated, the airbag cover is of a generally circular configuration, conforming to the shape of the retainer ring  23 . 
     The retainer ring has a circular configuration with a plurality of small tabs  42  and two brackets  41  extending therefrom. The retainer ring is placed into the airbag, and the small tabs  42  and brackets  41  fit through openings in the airbag (not shown). The airbag  24  is folded and the airbag with the retainer ring is placed in the airbag cover  25 . The airbag cover  25  has flaps  43  that wrap around the back of the airbag cover. The small tabs  42  from the retainer ring pass through the flaps to retain the, airbag cover, which is shown in FIG.  7 . 
     The cushion subassembly  27  is secured to the top of the steering wheel armature  20  by passing a bolt through the bracket  41  and into the side of the hub portion  34 . The cushion subassembly may contain various switches, which may be used to control a horn, radio, tape and/or compact disk player, cruise control, etc. The airbag cover  25  can also fact as a horn switch by the insertion of a membrane horn device (not shown) or a floating horn device (not shown) under the airbag cover  25  One skilled in the art appreciates that other types of horn devices can be utilized that will be actuated upon the application of force on the airbag cover  25 . The presence of switches or a horn device under the airbag cover will not interfere with the normal operation of the present invention. 
     Upon actuation of the inflator, the inflator provides inflation gas, which rapidly travels through the flange  17 . This rapid flow of gas causes the flexible lip  38  to flex or expand toward the outer wall of the channel of the hub portion  34 . The expansion of the flexible lip reduces the size of the gap thereby reducing inflation gas leakage during airbag deployment. The inflation gas then travels through the orifice of the hub portion  34  into the airbag cushion. The inflation gas causes the airbag  24  to deploy. 
     FIGS. 8 and 9 illustrate a bracket. 60  used to connect the inflator assembly  26  to the steering column. The bracket  60  is typically made from a soft plastic material, and contains a number of integrated rivets  62 . The top of these rivets  62  contain posts  64  so that as pressure is applied, they force the legs  66  apart so that it is compression fitted to the inflator flange  17 . Two of the rivets  68  are mounted in an opposite direction of the rivets  62  so that the bracket  60  can be riveted to the steering column, thus securing the airbag inflator assembly  26 . 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.