AIRBAG MODULE WITH HORN SWITCH

Abstract: A driver airbag module (22) has a cover (16), an airbag (12), an inflator (10), and a horn switch assembly (20). The horn switch assembly (20) is formed by a flat upper housing member (40) that is slideably coupled to a generally flat lower member (42). A pair of electrical contacts (43, 44) are disposed therein and is coupled to the generally flat lower member (42). The horn switch assembly (20) is coupled to an inflator (10) and incorporated into the airbag (12).

Description: AIRBAG MODULE WITH HORN SWITCH This invention generally relates a driver side airbag module having an integral horn switch. A driver side airbag module is typically mounted upon a motor vehicle's steering wheel. A typical module includes a mounting plate or housing attached to the hub of the steering wheel, an inflator mounted to the mounting plate, an airbag and a cover. The prior art teaches that horn switches can be placed within spokes of the steering wheel. The placement of this type of horn switch can be bothersome because it is difficult to install in the steering wheel, is not aesthetically pleasing, and it is often difficult for the driver of the vehicle to find and activate the horn. Several other designs have incorporated various horn mechanisms into the airbag module. One class of vehicle modules is floated on a spring assembly within a steering wheel assembly relative to a fixed, externally mounted horn switch, also mounted on the steering wheel. An electrical contact of the horn switch is placed on both the module and the wheel. To actuate the horn, the entire module is moved toward the steering wheel hub, closing the contacts and activating the horn. This method of horn switch design is expensive and requires a large gap between the module and the steering wheel so the module can float. Another problem with floating horns/modules is that they are susceptible to vibration because the weight of the module must be supported by the springs. As a result, large springs must be used to avoid inadvertent actuation during vibration, jolt, bounce, etc., which in turn leads to high forces and displacements to activate the horn. Another type of horn switch mounts a thin, flexible membrane switch on the back or inner surface of the airbag module cover. Membrane switches conventionally comprise two very thin non-conductive sheets having conductive coatings separated by thin spacers. Pressure on the switch moves the conductive surfaces together to close an electrical circuit and actuate the horn. The membrane switches are expensive and their installation is labor intensive. In the case of a malfunction of the horn switch, the entire cover must be replaced, as the membrane switch is an integral part of the cover. Membrane horns have adequate appearance and actuation properties, but they also have problems with inadvertent horn actuation. This is typically caused when the airbag is not folded properly, or expands over time, placing undo pressure on the membrane. In other instances, extreme hot or cold temperatures can cause the cover to expand or contract, which activates the switch causing the horn to actuate. Automotive horns contained in airbag modules have also proven extremely difficult to manufacture because of the stringent requirements placed on them. These include specific requirements on the force and displacement used to activate the horn, appearance, and resistance to inadvertent activation due to vibration. The present invention eliminates these concerns by providing an airbag module with a reliable horn switch, which allows for a module of reduced size. In the preferred embodiment, the horn switch comprises six components: a lower housing, upper housing, lower contact, upper contact, an optional wave spring, a wiring harness, and an adhesive disk. Activation of the horn occurs when the upper contact touches the lower contact, completing an electrical circuit. Brief Description of the Drawings FIG. 1 is an exploded view of the driver airbag module according to the invention. FIG. 2 is a cross section of the driver airbag module. FIG. 3 is an inflator and horn switch assembly. FIG. 4 is an inflator and a lower housing assembly of the horn switch. FIG. 5 is an exploded view of the horn switch assembly. FIG. 6 is a top view of an inflator with an alternative attachment feature. FIG. 7 is a top perspective view of the lower housing of the horn switch assembly. FIG. 8 is a bottom perspective view of the lower housing of the horn switch assembly. FIG. 9 is a bottom view of the upper housing. FIG. 9a is a cross-sectional view through section 9-9 of FIG. 9. FIG. 10 is a top view of the alternative horn mechanism set in place on top of the inflator. FIG. 11 is a top view of the horn mechanism rotated into the attached position with the horn switch upper housing removed for clarity. FIG. 12 is a cross-sectional view of the alternative horn design in the attached position. Detailed Description of the Invention In FIG. 1 the present invention comprises six primary components: an inflator 10, an airbag 12, a retaining ring 14, a cover 16, a mounting plate 18, and a horn switch assembly 20, which form an airbag module 22. The airbag module 22 is assembled by placing the retaining ring 14 within on opening 12a in the neck of the airbag 12. The airbag is only partially shown. The threaded studs 24 contained on the retaining ring 14 pass through its corresponding openings 12b. The horn switch assembly 20 is mechanically or adhesively bonded to an upper surface 26 of the inflator 10. A pair of wires 28 from the horn switch assembly 20 are passed through the opening 12a of the airbag. An optional aperture 30 can be provided in the airbag 12 for the wires. The wires will be passed through a slot 31 in the mounting plate 18 to electrically connect the horn switch assembly to a wiring harness. After the airbag 12, with the retaining ring therein, has been folded, the studs of the retaining ring are passed through openings in the mounting plate. These parts are mounted onto the cover 16 and then the inflator 10 and horn switch assembly 20 is fixedly attached to the mounting plate 18 by connecting it to the threaded studs 24 of the retaining ring 14. As known, an optional layer of Tyvek ® or shrink wrapped polymer can be wrapped around the airbag 12 after it is folded to prevent contaminants from entering the airbag. In FIG. 1 the cover 16 includes a tear-seam 32 located on the underside of the top of the center of cover 16 allowing the airbag 12 to deploy therethrough in a crash. FIG. 2 is a cross section of the module 22. The cover 16 is attached to the mounting plate 18 by snaps or rivets, as is known in the art. The horn switch assembly 20 of this embodiment is adhesively coupled to the upper surface 26 of the inflator 10. Disposed between the side surface 34 of the cover 16 and the upper surface 36 of the horn switch assembly 20 is the airbag 12. As shown in FIG. 2, it is preferred that a controllable amount of fabric be disposed between the upper surface 36 of the horn switch assembly 20 and the inner surface 34 of the cover 16. Although several layers of fabric from the airbag 12 can be tolerated, it is preferable to have as few layers as practical. The more layers of fabric there are, the less sensitive the horn is, and the greater the chance the folds will cause inadvertent actuation of the horn switch assembly 20. FIG. 3 shows the inflator 10 of FIG. 1 with the horn switch assembly 20 mounted thereon. The horn switch assembly 20 can be coupled to the inflator 10 by an adhesive pad 37. As shown in FIGS. 4 and 5, the assembly 20 has an upper 40 and lower 42 housing with upper and lower electrical contact components 43, 44 disposed therebetween. When the inflator 10 is installed in the module 22, and the horn with it, the problem of an irregularly folded airbag is less severe. This is because the horn switch assembly 20 is slightly smaller in diameter than the inflator 10, forcing the airbag material away from the horn switch assembly 20. The problem of vibration causing inadvertent horn actuation is also drastically reduced because of the way the horn is installed. This is because the weight of the few layers of fabric above the horn is negligible compared to the weight of the entire module that must be countered by a floating horn. The spring force for the horn can be minimized because a vibration needed to cause activation is much more severe than in a conventional floating horn. FIG. 5 is an exploded view of the horn switch assembly showing the upper housing member 40, lower housing member 42, and a double- sided adhesive pad 37 for mounting the horn switch assembly 20 to the inflator 10. Disposed between the upper 40 and lower 42 housings, are upper 43 and lower 44 contacts and, optionally, a biasing wave spring 46. The upper and lower contacts are secured to the lower housing 42. When used, the wave spring 46, which is seated on a first ridge member 48 formed onto the inner surface 50 of the lower housing 42, functions to additionally bias the underside 52 of the upper housing 40 away from the lower housing 42. The wave spring increases the force that must be applied to activate the horn, as may be required for some applications. In FIG. 7 the lower housing has a first annular wall 56, which can be segmented, and which supports an upper latching ring or shelf 57 above the base 42a of the lower housing 42. The upper latching shelf 57 has a plurality of notches 61 disposed therein for accepting a plurality of latching tab members 55 disposed on the undersurface of the upper housing. The latching shelf 57 functions to provide a location for, and to apply radial pressure to, the latching tab members 55 of the upper housing to snap onto so that the upper 40 and lower 42 housings are held together, as shown in FIGS. 9 and 9a. The upper 40 and lower 42 housings slideably engage each other to allow movement along a first axis 54. The wall tolerances of the latching tab members 55 and the notches 61 prevent the upper 40 and lower 42 housing from moving radially with respect to each other. Axial movement of the upper 40 and lower 42 housing with respect to each other causes the upper 43 and lower 44 contacts to engage and electrically close the circuit, activating the horn. In FIGS. 7 and 8, the lower housing 42 has a pair of walled structures or grooves 66, 106 for slideably receiving a wire of the wire harness. These grooves 66 function to hold the wire harness 62 in a fixed location with respect to the lower housing 42, allowing for the soldering of the wire 28, 62 to the upper and lower contacts 43, 44. The wire coupling portion has an integral strain relief 68 molded therein. The lower housing 42 assembly has disposed therein a first set of slots 100 and a second set of slots 102 for respectively receiving ends of the upper and lower electrical contacts. In FIGS. 5, 7 and 8, the lower contact 44 has four flexible legs 104. The ends of each leg form a tab portion 60 that is passed through one of the slots 102 and bent over. One of the tabs is captured between a walled structure 106 to facilitate attachment to one of the wires 28. Radially disposed about and above the lower contact 44 is the upper contact 43. The upper contact 43 includes a ring 110 and four, flexible upper contact members 64. Extending downwardly from the ring are four legs 112, an end of each leg forms a corresponding tab 58 that is assembled with the lower housing 42. Each of the tabs 58 is received through one of the slots 100 and bent over. One of the foldable tabs 58 is received within another walled structure 66, which functions as a connecting location with a second wire 62 of the wiring harness. The four upper contact members 64 are angled above the lower contact 44 and also function to apply spring bias forces on the upper housing 40 to separate the lower housing from the upper housing 40. When a force is applied to the surface 36 of the upper housing 40, the underside 52 of the upper housing 40 applies a force to the upper contact members 64. The upper contact members 64 are then elastically depressed into the lower contacting members 58, thus completing the electrical circuit. When the force on the upper surface 99 of the upper housing 40 is removed, the upper contact members 64 function as a leaf spring, separating the upper 43 and lower 44 contacts and upper 40 and lower 42 housings, thus disconnecting the upper 43 and lower 44 contacts. A wave spring 46 may be added to the assembly to increase the effective spring constant and assist in separating the upper 43 and lower 44 contacts and upper 40 and lower 42 housings. FIG. 9 is a bottom view of the upper 40 housing showing the plurality of latching tab members 55, also shown in FIG. 9a, which mate with the notches in the upper shelf 57 of the lower housing 42. Also shown is a support ring 70 with radiating flange members 72. These radiating flange members 72 serve to stiffen the upper housing 40. The support ring 70 is configured so as to not interfere with the coupling region of the wire harness in the lower housing 42 or with the upper shelf portion 57 of the lower housing 42. The stroke of the switch assembly is limited by length of the latching tab members 55, the boss 116 and by the upper shelf 57 of the lower housing 42. Upon full depression of the switch member, the support shelf 57 of the lower housing 42 engages the under side 52 of the upper housing 40. The underside 52 also includes a central extending boss 116, which engages the upper contact members 64. FIGS. 6 and 10-12 show an alternate embodiment in which the lower housing 42 lockably engages with inflator rather than using the adhesive as described above. The lower housing 42 engages the mechanical lock member 39 disposed on inflator 10. The locking member 39 has a plurality of inwardly directed teeth 38, which are used to engage the lower housing 42 of the horn switch assembly 20. The locking teeth 38, and slots, are indexed to allow for the proper orientation of the horn switch assembly 20 onto the inflator assembly 10. The slots on the lower housing 42 are aligned with a corresponding tooth and the lower housing forced down toward the inflator. The lower housing 42, that is the entire assembly 20, is rotated moving each slot out of alignment with a tooth 38 as shown in FIG. 11. FIG. 10 shows the horn assembly 20 in position on inflator 10. FIG. 12 shows a partial cross-sectional view of the assembly 20 in engagement with one of the teeth 38. A method for producing an airbag module 22 assembly includes the steps of: providing an airbag cover 16, mounting plate 18, retaining ring 14, inflator 10, airbag 12, and switch assembly 20. The switch assembly 20 is coupled to the surface of the inflator 10 by applying a layer of double-sided adhesive 37 or by a mechanical connection. A retaining ring 14 is placed within the airbag 12. The airbag 12 is coupled to a mounting plate.

Claims: CLAIMS 1. A driver side airbag module (22) comprising a cover (16), an airbag (12), an inflator (10), and a horn switch assembly (20), said horn switch assembly (20) comprising an upper housing member (40) and a lower housing member (42) disposed adjacent said upper housing member (40) and having a lower (44) and upper (43) electrical contact disposed thereon. 2. The driver side airbag module (22) of Claim 1 wherein the upper housing member has a plurality of snap attachment features (55), and said lower member (42) has a shelf (57) capable of engaging said snap features. 3. The driver side airbag module (22) of Claim 2 further comprising a wave spring (46) disposed between said upper (40) and lower (42) housing members. 4. The driver side airbag module (22) of Claim 2 wherein said horn switch assembly (20) is disposed on said inflator (10). 5. The driver side airbag module (22) of Claim 2 wherein said upper (43) and lower (44) contacts have a plurality of connecting flanges (58, 60) for mechanically coupling the upper (43) and lower (44) contacts to said lower housing member (42). 6. The driver side airbag module (22) of Claim 5 wherein the coupling flanges (58, 60) are capable of electrically coupling the upper and lower contacts (58, 60) to a wire harness (62) of the vehicle. 7. The driver side airbag module (22) of Claim 1 wherein the horn switch assembly (20) is located inside said airbag (12). 8. The driver side airbag module (22) of Claim 1 wherein said upper electrical contact (43) acts as a spring assembly disposed between said upper (40) and lower (42) housing members for biasing said upper (40) and lower (42) housing members apart. 9. The driver side airbag module (22) of Claim 2 wherein said upper electrical contact (43) acts as a spring assembly disposed between said upper (40) and lower (42) housing members for biasing said upper (40) and lower (42) housing members apart, and said shelf (57) is generally circular and said upper (43) and lower (44) contact members are disposed within said shelf member (57). 10. The driver side airbag module (22) of Claim 9 wherein said upper electrical contact (43) is enclosed within said shelf. ( 0

Inventors: FORD BRIAN, FORD, BRIAN
Applicants: BREED AUTOMOTIVE TECH, BREED AUTOMOTIVE TECHNOLOGY, INC.
Application year: 2001
Main classification: B60R21
IPC codes: B60Q5, B60R21