SNAP-IN DRIVER'S AIRBAG MODULE

Abstract: A steering wheel assembly comprising an armature for fastening an airbag module having a mounting plate with a plurality of snap-in attachment studs. The armature comprises a base portion (35) with holes (36, 37) and at least one retaining mechanism having an elastic serpentine retention wire (40). The serpentine retention wire has two locking portions (85, 86) for engaging the snap-in attachment studs and at least two disengaging lobe portions (74, 76) which can be actuated by a disassembly tool (38). The airbag module is fixed to the steering wheel armature by engagement of the serpentine retention wire with the snap-in attachment studs when the snap-in attachment studs are pushed into the base portion holes (36, 37).

Description: SNAP-IN DRIVER'S AIRBAG MODULE The present invention relates to a driver's airbag module with a housing for direct attachment to a vehicle's steering wheel. Commonly, driver's side airbag modules have a cover for enclosing a cushion and an mflator. Typically, the cushion mflator and cover are mounted to the housing using a number of fasteners to attach the airbag module to a vehicle's steering wheel. The housing functions as a stable surface for enclosing the cushion pack assembly and for the absorption of the deployment reaction forces. This housing is often used to couple the airbag module to the steering column. It is known that the housing can have a plurality of notched studs, which engage the airbag module to the steering wheel assembly. Other driver airbag systems currently available, including snap-m module systems, tend to be cumbersome and difficult to remove from the steering wheel. As such, a system which allows for the easy insertion and removal of the driver airbag module would significantly reduce the cost and increase the ease of manufacturing in the vehicle assembly plant and improve ease of serviceability. These advantages are provided by a steering wheel assembly of the current invention as set forth in claim 1. In accordance with the teachings of the present invention, the module has improved mounting hardware that allows utilizes a steering wheel's armature to secure the module and allows proper distribution of reaction forces. Brief Description of the Drawings Fig. 1 is an exploded view of the driver airoag module according to the current invention. Fig. 2 is an airbag module subassembly of the current invention. Fig. 3 is a cross section of the subassembly of Fig. 2. Fig. 4 is an exploded view of the steering wheel and retainer mechanism. Figs. 5-8 are views of the retention mecnanism. Figs. 9a and 9b show a snap-in stud. Detailed Description of the Invent-on Figs. 1 and 4 show the presert invention is comprised of eight primary components: an mflator 20, a cushion 22, a retainer ring 24, a cover 26, a mounting plate 31, a plurality of snap-in attachment studs 32, the steering wheel armature 30, and a pair of retaining mechanisms 34. An airbag module subassembly 29 is assembled by placing the retainer ring 24 withm the cushion 22 so that its threaded studs 28 pass through openings 21 lr the neck of the cushion. The threaded studs 28 on the retainer ring 24 are then passed tnrough corresponding holes 36 on the mflator 20. The studs can be secureα to the ring 24 or loosely received therethrough. The cushion 22 is then folded and placed onto the mounting plate 31 within the cover 26 as is shown in Figs. 2 and 3. As is known, an optional layer of TYVEK® or shrink-wrap polymer can oe wrapped around the cushion 22 after it is folded to prevent contaminants from entering the bag pack. The snap-in attachment studs 32, which are swaged into the mounting plate 31, serve to fix the airbag module subassembly 29 to the steering wheel armature 30. The airbag module subassembly 29 is designed so that the snap-m attachment studs 32 function to prevent movement of the mounting plate 31 with respect to the steering wheel armature 30 during a deployment. As best seen m Figs. 1 and 3, a tear seam 46 is placed through the entire center of the cover so allowing the cushion to deploy therethrough. With the module in the configuration shown m Fig. 2, it is ready for shipment to an automobile assembly plant. At the assembly plant, the steering wheel armature 30 is first fastened to the steering shaft. Then, the driver airbag module 29 of the current invention is connected to the steering wheel assembly by first making the required electrical connections and then snapping the airbag module subassembly 29 into the steering wheel armature 30. The retaining mechanisms 34 are disposed on the rear surface of the steering wheel armature 30. As best seen Figs. 5-8, each of the two retainer mechanisms 34 is defined by a base portion 35, which defines a pair of holes 36, 37, which accept a pair of the snap-m attachment studs 32. Incorporated into the retainer mechanism 34 is a serpentine retention wire 40 that latches into grooves or notches 48a, b in the snap-in attachment studs 32. The retention mechanism 34 further has a tubular alignment guide 39, which functions to guide in a disassembly tool 38 and allow disengagement of the serpentine retention wire 40 from the snap-m attachment studs 32. A tool 38 (shown in Fig. 5), which can be a flat head or Phillips head screw driver, is inserted with the tubular alignment guide 39 and forces the lobes 74, 76 of the wire 40 apart, which moves the locking portions 85, 86 out from a respective groove 48a, . The retention mechanisms 34 also include attachment tabs 88 that function to couple the retainer mechanism 34 to the steering wheel armature 30. The snap-in attachment tabs 88 hold the retaining mechanisms 34 onto the steering wheel armature 30 and ensure the serpentine retention wire 40 is kept in position. Additionally, the retention mechanism 34 has a retention slot 90 cut into a flange portion 92. When the snap-m attacnment stud 32 is pusheα into the base portion holes 36, 37, the angled ends of each stud move the serpentine retainer wire 40 perpendicular to the direction of insertion of the studs. The serpentine retainer wire 40 provides an increased overall free length. This increased length is an especially important advance over more straight retention wire attachmert mechanisms in as much as it significantly increases the ease with which the module can be snapped into the wheel armature 30 during installation. The configuration allows the serpentine retention wire 40 to move at the two apertures 74 but gives the serpentine retention wire 40 enough sprmgback to "capture" the engagement groove 48 of the snap-m attachment stud 32. In addition, the extending tab 93 m the flange portion 92 interacts with the retention wire loop 50 to prevent the wire from moving out of position during vibration. The tab 93 also prevents tne wire 40 from sliding out of the retaining mechanism 34 unless a mechanic inserts the disengagement tool 38 with sufficient force that the locking portions 84, 85 move out of the groove 48. The configuration and function of the serpentine retention wire 40 are clearly distinguishable from other more linear retention wire mechanisms. The serpentine retention wire 40 is defined by its numerous bends, each bend enhancing the overall functionality of the serpentine retaining wire 40. As best seen m Fig. 5, the wire has a pair of locking portions 85, 86, whicn function to engage the groove 48 in the snap-m attachments 32. The serpentine retention wire 40 is further characterized by a first large radius loop 50, which has an inner radius which is concave with respect to the disassembly tool 38. The first large radius functions as a spring, which brings the locking portic o s 85, 86 in contact with the groove 48. The serpentine retention wire 40 also defines first and second lobe portions 74, 76, which define a pair of disengagement surfaces 52. Tne first and second lobe portions are located close enough to each other so that the insertion of a single disengagement tool wι__ spread the disengagement surfaces 52 apart counteracting the spring force of the first large radius 50. The serpentine retention wire 40 also defines a second radius, which places the locking portions 85, 86 of the serpentine retention wire over the center of the holes 36, 37 in the base portion. The retaining mechanisms 34 receive the snap-m attachment stud 32 of the airbag module suoassembly 29 by initially displacing the ends or locking portions 85, 86 of the serpentine retention .-/ire 40 away from the center of the holes 36, 37 m the base portion. As the snap-m attachment studs 32 are pushed through the openings 35, 36 they slice past the locking portions 85, 86 of the serpentine retention wire 40 and the locking portions spread apart as the center loop 50 of the wire 40 is deformed. Once the groove 48 in the snap-m attachment stud 32 reaches the locking portions, the locking portions 85, 86 snap into a corresponding groove 48 to retain the airbag module subassembly 29. Should the module experience vibration following assembly, the configuration prevents both locking portions 85, 86 from moving out of position during vibration at the same time. When a module s to be removed from the steering wheel armature 30, an operator inserts a tool 38 such as a normal screwdriver into the alignment guide 39, engaging and displacing the lobe portions 74, 76. When the operator inserts the tool 38, the serpentine retention wire 40 αeforms at the retention wire loop 50 to cause disengagement of the locking portions 85, 86, and snap-m attachment stud groove 48. The steering wheel armature 30 has a recessed portion 81 which allows for incorporation of the nut which mounts the steering wheel assembly to the steering column shaft and allows clearance for the connector necessary to ensure the mflator is electrically connected to the rest of the vehicle. This reduces the overall profile of the module/steering wheel assembly. In addition, a hole 82 is provided to allow the mflator connector wire to be passed from the vehicle to the top of the steering wheel. In the preferred embodiment, the module is of the "floating horn" type, which allows for actuating the vehicle's horn by depressing the entire module toward the steering wheel armature 30. The module is normally biased away from the steering wheel armature 30 by a plurality of coil springs 23, one disposed about a corresponding snap-m stud 32. As shown m Fig. 9a, the groove 48a has sufficient length to allow the module to move toward and away from the wheel armature to actuate the horn. The coil springs 23 function to push the module subassembly 29 away from the horn contacts on the steering wheel armature 30. The retention mechanism 34 functions as an electrical insulator, which allows the module to function as a horn switch. As such, the base portion of tne retention mechanism 34 is formed of injection molded plastic such as nylon or polypropylene. The steering wheel armature 30 of the steering wheel is provided with a fiat surface 54 containing projections 55, which function as electrical contact points. The steering wheel armature 30 of tne wheel further contains a recessed hole 56 immediately behind the module to allow installation of the inflator. The flat top surface 54 is important for the functioning of the module as it functions as a reaction surface and ensures the cushion 22 will always deploy towards the occupant. Another benefit of this flat surface 54 is that if the surface were not flat, the cushion 22 would be forced along an uneven surface and could snag . Fig. 9b shows the snap-in attachment studs 32 of the current invention used in a non-floating module. This snap-in attachment stud 32 has a V-shaped groove 48b for engaging the serpentine wire 40 of the engagement mechanism 34. Tne shape of the groove is such that it locks the module into the wheel armature without letting it move relative to the wheel armature 30. In a non-floating module system, the retention mechanism 34 may be cast or formed integrally into the steering wheel armature.

Claims: CLAIMS 1. A steering wheel assembly comprising: an armature (30); a driver airbag module (29); an mflator (20 ) ; a cushion (22 ) ; a mounting plate (31); a cover (26) coupled to the mounting plate (31) having a plurality of snap-m attachment studs (32) ; at least one retaining mechanism { 3 ^ disposed on said armature (30) having a serpentine retention wire (40) having a spring portion (50) and at least two disengaging lobe portions (74, 76) whereby said serpentine retention wire (40) engages the snap-m attachment studs (32) to lock the cover in place . 2. The steering wheel assembly of Claim 1 wherein the retaining mechanism (34) has an a_ιgnment guide (39) for guiding a disassembly tool (38 . 3. The steering wheel assembly of Claim 2 further including at least one retention means (90) for regulating the amount of elastic deformation of the serpentine retention wire (40) . 4. The steering wheel assembly of Claim 1 wherein the retaining mechanism (34) has a serpentine retention wire (40) having a pair of locking portions (85, 86) and a set of disengaging portions (52) coupled to a disassembly tool (38). 5. The steering wheel assembly of Claim 4 wherein the engagement portions (52) of the serpentine retention wires (40) engage a groove (48) defined m the snap-m ad ustment nut (32)

Inventors: KURZ SCOTT, LEVINE AARON, KURZ, SCOTT, LEVINE, AARON
Applicants: BREED AUTOMOTIVE TECH, BREED AUTOMOTIVE TECHNOLOGY, INC.
Application year: 2001
Main classification: B60R21
IPC codes: B60R21