MXPA97002821A - Steering wheel assembly and airbag bag - Google Patents

Abstract

The present invention relates to an assembly of air bag and steering wheel, characterized in that it comprises: a rigid skeleton that includes a central hub, a lip surrounding the hub and

Description

ASSEMBLY OF STEERING WHEEL AND INTEGRAL AIR BAG FIELDS To IHVEN? IQN This invention relates to the field of steering wheels and more particularly to steering wheel and air bag assemblies and methods for manufacturing steering wheel and bag assemblies of air. AWTg? FiPEMTES pfi LA t.NVfiycT, QIT Inflatable supplementary restraints or airbags for the driver's side of the motor vehicle are typically mounted on the steering wheel of the motor vehicle. When the airbag deploys in a frontal impact, the airbag helps cushion the resulting forward movement of the driver towards the steering wheel. Typically, the air bag is mounted in its undeployed state on a skeleton of a steering wheel. The airbag has a plastic cover that is adjusted in color to match the color of the plastic steering wheel cover. A plurality of fasteners projecting from one of the 'Steering wheel skeleton and air bag module, are used to fix the two together. In order to maintain a perception of the overall quality of the vehicle, the color, surface grains and brightness levels of both the airbag cover and the steering wheel cover must not vary significantly from the rest of the steering wheel, and the position of the airbag module must be precisely controlled to present a central position on the steering wheel, with homogeneous or consistent spaces and / or ability to level between the tires. One method to desensitize the mounting to the relative position of the air bag with respect to the steering wheel has been to cause the air bag cover to overlap the quality or opening in the steering wheel that the air bag module receives. However, we still have the difficulty of matching the colors, grains and brightness levels. It is desired to provide a combined assembly of steering wheel and air bag, which is both insensitive to minor variations in position in the air bag module with respect to the steering wheel and does not vary in color, grain levels and brightness between steering wheels. direction and cover of the airbag. COMPENDIUM OF THE INVENTION A steering wheel assembly includes a rigid skeleton with a central hub, a lip surrounding the hub and a plurality of spokes disposed therebetween. An air bag module is mounted on the skeleton. A continuous plastic liner is disposed on the skeleton and the airbag module, presenting a continuous surface to an operator of the vehicle, when the steering wheel is mounted on the vehicle.

A method for forming an integral air bag and steering wheel assembly includes the step of forming a rigid skeleton having a central hub, a lip surrounding the hub and a plurality of spokes disposed therebetween. The method also includes the step of placing the air bag module inside the hub at a pre-determined site. A first plastic is injected around the air bag module, retaining the air bag module in a desired fixed position with respect to the skeleton. The airbag assembly and integral steering wheel described, is insensitive to less relative variations in air bag to the steering wheel placement and eliminates the need for adjustment of color grain level of brightness between the airbag the steering wheel of address as well as spaces or leveling capacity. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a steering wheel assembly and integral air bag according to this invention. Figure 2 is a perspective view of a steering wheel skeleton, with the configuration of a complete steering wheel assembly illustrated in dotted lines. Figure 3 is an exploded view of an integral air bag and steering wheel assembly.

Figure 4 is a sectional view of the integral air bag and steering wheel assembly taken from the bottom. Figure 5 is a sectional view of the integral steering-airbag assembly that is taken from the side. Figure 6 is an enlarged sectional view of the integral steering-airbag assembly of the circle portion 6 of Figure 4. Figure 7 is a first embodiment of a steering-to-arrow steering wheel connection. Figure 8 is a second embodiment of an arrow-to-arrow steering wheel connection. Figure 9 is a third embodiment of a steering wheel to arrow connection. Figure 10 is a fourth embodiment of a steering-to-arrow steering wheel connection. BRIEF DESCRIPTION OF A PREFERRED MODE An integral steering-airbag assembly 10 is illustrated as finished in Figure 1. A rigid skeleton 12, illustrated in Figure 2 and made in a preferred embodiment of aluminum, provides a structure of complete assembly support 10. Of course, other materials such as magnesium and steel can be used for the backbone.

An air bag module 14 is illustrated in Figure 3, as part of the assembly 10. An outer plastic cover 16 is molded onto the skeleton 12, providing a surface presented to vehicle occupants. A column locking collar 18 is disposed on a rear side of the skeleton 12 for coupling a steering arrow. Various embodiments of the collar 18 are illustrated in Figures 7 to 10. The skeleton 12 is a unitary die cast member including a hub 20, a lip 22 surrounding the hub 20 and three spokes 24 connecting the hub 20 and the lip 22. It will be appreciated of course that the skeleton 12 may have a different amount of spokes, such as 2 or 4, and may be a welded structure that is formed of several pieces. The air bag module 14 includes a steel mounting plate 26 with a pair of shoulder studs 28 for connecting the plate 26 to the skeleton 12. A nut 29 is placed on each side of the studs 28 to retain it on the skeleton 12. An inflator 30 is held against a lower side of the plate 26 and surrounded by a steel fusion ring 32 disposed on an upper side of the plate 26. Four bolts or rods 34 and four nuts 36, hold the plate 26 between the ring 32 and inflator 30. An air bag 38, or inflatable cushion illustrated in Figure 4 and Figure 5, is bent and aligned to inflator 30 to receive gas therefrom, when deployed. A plastic housing or cover 40, disposed on the air bag 38 and inflator 30, is fixed to the plate 26 by four self-deriving screws 41 which thread on each corner of the plate 26. The air bag module 14 is provided with a protective seal, such as a silicone seal strip around the openings, or shrink wrap film around the assembly to protect the module 14 against plastic intrusion during the molding process. The cover 40 has an outer tear seam 44 in the form of a sharp edge, better illustrated in Figure 6, on an upper surface of the cover 40. The outer seam 44 constitutes a U-shaped pattern open towards an upper side of the steering wheel. An inner tear seam 46 is formed on an inner surface as a V-shaped groove, and approximately aligns with the outer seam 44. The inner tear seam 46 is configured to facilitate tearing the cover 40 about its length when the air bag 38 is deployed. The inner tear seam 46 defines the door element 48 that swings or pivots opening on the side that has no tear seam. An outer strip 49 circumscribes an outer periphery of the cover 40. An electrical connector 50 extends from the inflator. An inner plastic 52 surrounds the module 14 attaching it to the skeleton 12. The inner plastic 52 is formed in the following manner. The airbag module 14 is loosely connected to the skeleton 12 by shoulder studs 28 and nuts 29 as illustrated in Figure 4. The skeleton of the steering wheel 12 and the air bag module 14 are placed in a first mold (not shown) that has a top surface, which in conjunction with the skeleton 12 circumscribes the air bag module 14. Four molding support pins 53 are inserted between the spokes 24 through the skeleton 12, and into receiving openings 39 in the cover 40. The pins 3 they are directed upwards until the outer strip 49 engages the mold. A plastic molding cycle is injected into the first mold, forming the inner plastic. The outer strip 49 serves as a dam, preventing the first or inner molding cycle from covering the door element 48 of the cover 40. The inner plastic 52 is preferably a type of plastic foam that is relatively light in weight and economical . An outer plastic 54 or plastic coating circumscribes the entire steering wheel skeleton and the air bag module 14. A metallic thin sheet membrane switch and mylar 55, which serves as the horn drive switch, is disposed between the cover 40 and exterior plastic 54. Membrane switch 55 has corrugations that maximize the surface area in contact with outer plastic 54 to increase the strength of the adhesive bond between switch 55 and exterior plastic 54. A portion of switch 55 wraps around an upper side of the cover 40, to serve as a hinge for the outer plastic portion 54 on the door element 48 after deployment of the air bag 38. The pins 53 are used to position the assembled skeleton 12 and the air bag module 14 in a second mold (not shown). A second cycle of plastic molding, preferably water-blown polyurethane, a thermoset plastic, is injected into the second mold, forming the outer plastic 54 which completely covers the skeleton and the air bag module, thereby providing an assembly air bag-steering wheel modular completely seamless 10. In alternate form, other thermoset plastic or thermoplastics such as vinyl can be used for the outer plastic. The selected material must be able to form a surface layer throughout the part and be resistant to wear, with superior characteristics of adhesion to paints and have superior performance characteristics at hot and cold temperatures. An additional advantage of this method, beyond the seamless formation, is that the outer tear seam 44 defines a relatively thin section of outer plastic 54, which facilitates tearing of the outer plastic 54 during deployment of the air bag, and also supports the outer plastic 54. The support provided by the outer tear seam 44, eliminates the "perceptible tear seam" effect, wherein a tear seam not supported on an inner surface of an outer plastic cover, It is visible due to material sinking inside the seam hole. Since the front side (the side facing the driver) of the hub 20 is completely inaccessible once the assembly 10 is completed, an alternate method will be required to connect the assembly 10 to the arrow of the steering column. The usual method is to place the steering wheel on a threaded end of the arrow of the steering column and run a nut down against the hub to fix the two together. Four alternate connection modes are illustrated in Figures 7, 8, 9 and 10. The embodiment illustrated in Figures 1 to 6 is shown in more detail in Figure 8. The steering column arrow 56 and a portion of reduced diameter 57 that define on shoulders. An interlocking sleeve 58, fixed to the hub 20, is slidably disposed on the reduced diameter portion 57 and abuts against the shoulder. A slot (not shown) or other feature is used to orient the integral steering-airbag assembly 10 on the steering column arrow 56. When properly aligned, the reduced diameter portion 57 and the sleeve 58 define a pair of pin openings 59. Both of these openings 59 have threaded ends and at least one of the openings tapers to receive a first portion 60 having corresponding taper and one end threaded As the first pin 60 is tightened in the opening 59, the taper eliminates any bumping between the sleeve 58 and arrow 556. The second pin 62 and its corresponding opening can already be tapered or of a constant diameter. The two pins 60 and 62 together hold the arrow 56 and sleeve 58 rotatably locked. The pins 60 and 62 also ensure correct alignment of the steering wheel to the steering arrow. An additional benefit of this configuration is that whenever the steepening of the steering column remains intact, only one of the pins 60 and 62 can be removed without having the ignition keys, making it impossible to access and remove more than one of the pins 60 and 62 and therefore impossible to steal the airbag assembly and steering wheel 10. In a first alternative embodiment illustrated in Figure 7, an arrow of steering column 64 is provided with a frustoconically tapered end 65. The column arrow of direction 64 is received by a locking sleeve 66 fixed to the hub 20. A wedge pin 68 passes transversely through aligned openings 67 and 69 in both the sleeve 66 and the arrow 64 respectively. A tapered side of the pin 68 engages a similarly tapered side of the opening in the arrow 64, while a flat opposite side of the pin 64 engages the sleeve 66, forcing the arrow deeper into the sleeve 66. A retaining nut 70 in one end of the wedge pin 68 directs the pin 68 within the opening 69 and holds it there. In a second alternative modality illustrated in Figure 9, an arrow of steering column 72 has a first annular lip 73 at one end. A rod arrow for steering wheel 74 is fixed to hub 20 and extends e there.

A second annular lip 75 surrounds one end of the short arrow (74 distal to the hub 20. A pair of alignment pins 76, one larger than the other, are placed at one end of one of the steering column arrow 72 and the short arrow The arrows 72 and 74 are then aligned so that the pins can pass into the aligned openings in the facing arrow, allowing the arrows to butt against each other in the desired alignment. Slides on the annular lips An open end 79 of the collar is stretched closed or almost closed by tightening a clamping clip 80, fixing the air bag assembly and steering wheel 10 to the steering column arrow 72. In a third alternative embodiment illustrated in Figure 10, an arrow of steering column 82, with a frustoconically tapered end 83 has an annular lip 84 formed therein, close to a larger diameter portion of the end 83 A threaded interlock collar 86 is retained on the arrow 82 by the lip 84. A hub bearing 88 fixed to the hub 20 has a tapered opening 89 complementary to the end 83. A threaded portion 90 of the sleeve 88 is engaged by the collar. Interlock 86. As the locking collar 86 is tightened in the sleeve 88, the tapered end 83 of the arrow 82 is directed upwardly into the opening 89. A mating groove 92 in the arrow 82 is for use with a tool of special displacement 94, illustrated in dotted lines. The displacement teeth 96 in the collar 86 are engaged by a displacement gear 98 mounted on the displacement tool 94. The displacement gear 98 is selectively rotated by an electric motor (not shown) that is connected to it. The displacement tool 94 has a collar portion 98 selectively disposed in the slot 92, which reacts against any thrust generated against the tool 94, when the collar 88 is tightened. The invention operates in the following manner. In an impact situation, a signal from the controller responding to pre-determined rates of acceleration, the inflator 30 acts. Gas from the inflator 30 moves toward the air bag 38, causing it to expand against the cover 40. When the air bag 38 deploys a sufficiently large pressure against the cover 40, the cover 40 breaks on the inner seal seam 46, where the cover 49 is thinner. As the seam 46 separates, the door 48 begins to open, the outer plastic portion 54 is divided over the outer tear seam 44. The door 48 and the outer plastic portion 54 disposed thereon, rapidly oscillate open with the outer plastic portion 54 retained by the switch 55 and the door 48 which remains connected on its hinge side. While specific embodiments have been described, it will be appreciated that many of the specific features described are merely exemplary, and that the actual scope of the invention is as described below in the claims. For example, the cover 40 may have its tear seams configured to provide two half doors instead of a large door through which the air pocket 38 can escape. The precise method for attaching the steering wheel assembly to the Steering column arrow can be changed.

Claims (9)

1. CLAIMS 1.- Assembly of air bag and steering wheel, characterized in that it comprises: a rigid skeleton that includes a central hub, a lip that surrounds the hub and a plurality of spokes arranged between them; an air bag module mounted on the skeleton; and a continuous plastic liner disposed on at least the skeleton hub and the air bag module having a continuous surface to a vehicle operator, when the steering wheel is mounted on a vehicle.
2. 2. Assembly of air bag and steering wheel as described in claim 1, characterized in that an amount of plastic filler other than the plastic coating surrounds the air bag module and fixes it with respect to the skeleton.
3. 3. Assembly of air bag and steering wheel as described in claim 1, characterized in that the air bag module includes a cover and an air bag on which the cover is disposed and the cover has a seam of interior tearing through an upper portion of the cover, to define a door through which a deployed airbag passes and the cover furthermore has an outer tear seam in the form of a sharp edge, essentially aligned with the seam of internal tearing and projecting from the cover in a direction opposite to the air bag and in engagement with the plastic coating.
4. 4. Assembly of air bag and steering wheel as described in claim 1, characterized in that a membrane type nozzle switch is arranged on the cover and the switch is wrapped on one side of the cover and the plastic coating it is attached to it, the membrane switch serves to retain a portion of the plastic coating after deployment of the air bag.
5. 5. A method for forming an assembly of air bag and integral steering wheel, characterized in that it comprises the steps of: forming a rigid skeleton having a central hub, a lip surrounding the hub and a plurality of spokes arranged between them; placing an air bag module on the skeleton in a pre-determined location; and injection molding a first plastic that completely covers the air bag module on one side of the air bag module opposite the skeleton.
6. 6. A method for forming an assembly of air bag and steering wheel as described in claim 5, characterized in that it also includes the step of injection molding a second plastic between the air bag module and the skeleton before molding the first plastic, wherein the second plastic retains the air bag module in a desired fixed portion with respect to the skeleton.
7. 7. - A method for forming an air bag and steering wheel assembly as described in claim 6, characterized in that it also includes the steps of passing a plurality of molding support pins through the skeleton and into reception openings in the cover and choose the airbag module away from the skeleton and in contact with a first mold, before injection molding the second plastic.
8. 8. A method for forming an air bag assembly and steering wheel as described in claim 7, characterized in that it also includes the step of placing the relatively fixed skeleton and the air bag module in a pre-determined portion. desired, with the molding support pins in a second mold after molding the second plastic and before molding the first plastic.
9. 9. A method for forming an assembly of air bag and steering wheel as described in claim 7, characterized in that it also includes the steps of providing a peripheral strip circumscribing a top surface of a housing of the module for air bag , which engages the first mold when the module or air bag is diverted away from the skeleton, wherein the peripheral strip acts as a dam to block the flow of the second plastic that reaches a top surface of the housing.