Air bag module construction and assembly technique

Abstract: The invention is an apparatus comprising an air bag/cover subassembly (34) adapted to be coupled to an inflator/reaction device subassembly (36) to form an air bag module (14). The air bag/cover subassembly (34) comprises: (a) a cover (24) defining an air bag cavity (37) and having an access opening (40) communicating with said air bag cavity (37), and an integral rim (42), formed in one piece with the remaining portions of said cover (24), surrounding said access opening (40); (b) a folded air bag (22) disposed in said air bag cavity (37), said air bag (22) having a border portion (48) defining a gas inlet opening (49), and (c) means (46, 50, 52) for connecting said portion (48) of said folded air bag (22) with said cover (24); and is characterised in that said means (46, 50, 52) for connecting said portion (48) of said folded air bag (22) with said cover (24) is adapted to connect said portion (48) of said air bag (22) with said rim (42) of said cover (24).

Description: Technical Field The present invention relates to an air bag module structure and to techniques for forming the air bag module structure. The air bag module comprises a pair of assemblies which are coupled together to form the module. One structure comprises a folded air bag/cover subassembly. The other structure comprises an inflator/reaction device subassembly. The subassemblies are separately formed, and then connected with each other to complete an air bag module. Background A vehicle air bag module is a complete air bag unit which is assembled apart from the vehicle and then coupled as a unit with the vehicle. Typically, an air bag module includes (i) a reaction device, (ii) a folded air bag connected to the reaction device, (iii) an inflator, or gas generator, connected to the reaction device, and (iv) a cover connected to the reaction device to complete an enclosure for the folded air bag. The module is generally coupled with a structural part of the vehicle via the reaction device. In the case of a passenger side air bag module, for example, the reaction device may be coupled with the support structure for the instrument panel of the vehicle. Alternatively, in the case of a driver side air bag module, the reaction device may be coupled with the steering wheel support structure. When coupled with a vehicle, an air bag module operates to deploy an air bag at the onset of a vehicle collision. Specifically, at the onset of a collision, a chemical mixture in the inflator that forms part of the module is ignited to generate large quantities of gas under relatively high pressure. The gas simultaneously (i) forces the air bag through the cover and (ii) inflates the air bag. As the air bag is being inflated, relatively high forces are applied to the various components of the air bag module. The reaction device transmits such forces to the vehicle structure to stabilize the air bag module during deployment of the air bag. Over the years, various techniques for forming air bag modules have been suggested. One well known technique comprises initially securing an air bag and an inflator with a reaction device, folding the air bag into a predetermined pattern relative to the inflator and the reaction device, and then attaching a cover to the reaction device. The reaction device is adapted to be coupled with a structural part of the vehicle, to couple the module with the vehicle. One example of such a technique is shown in U.S. Patent 4,146,503 which corresponds to the pre-characterising part of claim 1, wherein an air bag module comprises an inflator and an air bag secured to a reaction device or bracket arranged at a central part of a steering wheel and secured to a steering wheel spoke. The air bag is arranged to surround the inflator and is then received in a folded condition within a receiving case or cover. Another example of such a technique is shown in U.S. Patent No. 4,842,300, wherein an air bag module comprises an inflator and an air bag secured within a reaction device. The air bag is folded into a predetermined pattern within the reaction device, relative to the. inflator, and a cover is then attached to the reaction device to complete the module. Another known technique for forming an air bag module is to initially form a subassembly comprising a reaction device, a folded air bag and a cover, and to secure an inflator to the subassembly to complete the module. The subassembly is formed by folding the air bag into a predetermined configuration, and securing and closing the air bag within a covered reaction device to complete the subassembly. The inflator is then secured to the subassembly to complete the air bag module. This technique minimizes the handling of inflators in assembling the module. Also, it enables inflators to be transported separately from the subassembly. Thus, if the chemical mixture in the inflators is accidently ignited during transport, the subassemblies of the modules are not destroyed. An example of such a technique is shown in U.S. Patent No. 4,153,273. As seen from the foregoing discussion, the reaction device performs several important functions in an air bag module. The reaction device connects the module to a structural portion of the vehicle and, during air bag bag deployment, transmits forces from the air bag module to the vehicle. Further, the reaction device is the element of the module to which virtually all other components of the module (i.e., inflator, air bag and cover) are connected. Thus, the reaction device integrates the other air bag module components into a structural unit. In the air bag industry, new and useful techniques for forming air bag modules are becoming increasingly important. Air bag modules are currently being installed in large numbers of automobiles. The number of air bag modules installed in the future will continue to increase, as consumer demand and federal regulatory requirements for vehicle safety also continue to increase. To enable auto makers to meet this growing demand, there is a continuing need for simple and effective techniques which lend themselves to the mass production of air bag modules. Applicants believe there is a continuing need for air bag module structures and assembly techniques which allow inflators to be manufactured and transported separately from the remaining parts of the modules, and incorporated into the modules as the last step in the assembly process. This minimizes the risk of damage to the remaining parts of the modules, due to accidental ignition of an inflator. Summary of the Present Invention The present invention is an apparatus comprising an airbag/cover subassembly adapted to be coupled to an inflator/reaction device subassembly to form an air bag module, the air bag/cover subassembly comprising: (a) a cover defining an airbag cavity and having an access opening communicating with said air bag cavity, and a rim surrounding said access opening; (b) a folded airbag disposed in said airbag cavity, said airbag having a border portion defining a gas inlet opening, and (c) means for connecting said border portion of said folded airbag with said cover; characterised in that said rim is an integral rim, formed in one piece with the remaining portions of said cover and said means for connecting said border portion of said folded airbag with said cover is adapted to connect said border portion of said airbag with said rim of said cover. The airbag/cover assembly is formed by prefolding an airbag and then coupling the prefolded air bag with a cover. The cover defines an air bag cavity, and has an access opening with an integral peripheral rim. The prefolded airbag is inserted through the access opening and is located within the airbag cavity. The cover is flexible and can be flexed elastically, if necessary, to enable the prefolded airbag to be inserted through the access opening. The prefolded airbag has a gas inlet opening bordered by a portion of the air bag which is designed to be coupled with the rim of the cover, to couple the prefolded airbag with the cover. The border portion of the airbag and the rim on the cover each have attachment openings with are aligned with one another to enable the air bag to be attached to the cover, preferably by fasteners which extend through such aligned openings. The inflator/reaction device subassembly comprises an inflator housing which is adapted to contain a gas generating device connected with the outside of the inflator housing. Preferably, the inflator housing and the reaction device comprise a single, one-piece member, which is impact extruded from aluminum. The inflator housing has gas dispensing nozzles through which gas is directed when the gas generating device is ignited. The reaction device is formed with attachment openings which align with the aligned attachment openings in the border portion of the air bag and the rim of the cover in the air bag/cover subassembly. The air bag/cover subassembly can be readily coupled with the inflator/reaction device subassembly by coupling the aligned attachment openings, preferably by using some of the same fasteners which couple the air bag with the cover. When the air bag/cover subassembly is coupled with the inflator/reaction device subassembly, the gas dispensing nozzles in the inflator housing are disposed in fluid communication with the gas inlet opening of the air bag. Thus, when the gas generating compound within the inflator is ignited, gas is directed through the nozzles and into the gas inlet opening in the air bag to inflate the air bag. The air bag/cover subassembly and the inflator/reaction device subassembly are designed to be separately formed and transported, and then coupled together as the last step in the formation of the module. Thus, the dangers involved in the handling and transportation of live inflators are believed to be minimized. The resulting air bag module comprises the air bag/cover subassembly fastened to the inflator/reaction device subassembly. Moreover, the same fasteners which couple the subassemblies together to form the module can also be used to couple the air bag module to the vehicle. Thus, the installation of the air bag module within the vehicle is also simple and efficient. Applicants believe the air bag module and the techniques used to form the module components and subassemblies are particularly suited for efficient and effective mass production of air bag modules. Further features and advantages of the present invention will become further apparent from the following detailed description and the accompanying drawings. Brief Description of the Drawings Figure 1 is a schematic, three-dimensional illustration of a vehicle steering wheel (in phantom) to which an air bag module constructed according to the principles of the present invention is connected thereto; Figure 2 is a three-dimensional illustration of an air bag module constructed according to the principles of the present invention, taken at an angle from the rear side of the air bag module; Figure 3 is a fragmentary, sectional view of the air bag module of Figure 2, taken along the plane 3-3; Figure the 4 is a sectional view of the air bag module of Figure 2, taken along the plane 4-4; Figure 5 is an exploded perspective view of the air bag/cover and inflator/reaction device subassemblies of an air bag module constructed according to the principles of the present invention; Figure 6 is an exploded view of the elements forming the air bag/cover subassembly; Figure 7 is a perspective view of an alternate form of the air bag module constructed according to the principles of the present invention, taken at an angle from the rear side of the air bag module; Figures 8 and 9 are fragmentary, sectional views of the air bag module of Figure 7, taken along the planes 8-8 and 9-9, respectively; Figure 10 is an exploded view of the air bag/cover and inflator/reaction device subassemblies forming the air bag module of Figure 7; Figure 11 is an exploded view of the components forming the air bag/cover subassembly in the air bag module of Figure 7; Figure 12 is a side elevational view of a preferred version of an inflator/reaction device subassembly of an air bag module constructed according to the principles of the present invention; and Figure 13 is a sectional view of the inflator/reaction device subassembly of Figure 12, taken along the plane 13-13 of Figure 12. Detailed Description of the Preferred Embodiment Figure 1 schematically illustrates a driver side vehicle air bag system 10. The system is mounted on a vehicle steering wheel 12 and includes an air bag module 14, constructed according to the principles of the present invention. The steering wheel 12 has a central yoke 16 which is coupled with a steering column 18 by means (not shown) which are well known in the art. The air bag module 14 is located in the center of the yoke 16, and is secured to a structural portion of the steering wheel column 18. When located in the center of the yoke 16, the air bag module 14 is in position to deploy an air bag in a manner which will prevent a driver from striking the steering wheel of the vehicle in the event of a collision. The air bag module 14 is shown in Figures 2, 4 and 7. The air bag module 14 is a self-contained unit the primary components of which include a gas generator or inflator 20, a folded air bag 22, a reaction device 28, and a cover 24 which encloses the folded air bag and engages at least part of the reaction device 28. The inflator 20 includes an inflator housing 26 that is formed in one piece with reaction device 28. By forming the reaction device 28 in one piece with the inflator housing 26, the present invention further reduces the number of parts used in the air bag module and thereby additionally reduces module weight. The inflator housing 26 is preferably formed as a cup-like member whose construction is similar to that illustrated in U.S. Patent Application Serial No. 07/322,079, which is assigned to the assignee of the present application. The inflator housing 26 defines a central cylindrical cavity 27 which contains a gas generating composition or a sealed container of inert, pressurized gas. Gas dispensing nozzles 30 are formed in the housing 26 and are disposed in fluid communication with the interior of the air bag 22 when the air bag module is assembled. The gas generating composition can have any of several compositions which are well known to those of ordinary skill in the art, and thus require no further explanation. One such composition is described in U.S. Patent No. 4,817,828. In an emergency situation, the gas generating composition inside the inflator 20 is ignited by means of an ignition mechanism which forms no part of this invention. Alternatively, if a container of pressurized gas is used, the container is pierced or otherwise opened to release the gas in an emergency situation. The gas generated within the inflator is dispensed through the gas dispensing nozzles 30 into the interior of the air bag. The pressure of the gas on the air bag causes the air bag to expand and split the cover 24 to allow deployment of the air bag into the vehicle compartment in front of the steering wheel 10. The cover 24 has appropriate score lines 32, which are also well known in the art, to facilitate splitting of the cover 24 and deployment of the air bag 22 through the cover- 24 in the event of a collision. The reaction device 28 of the inflator housing 26 provides the force transmitting coupling between the module 14 and the structural portion S of the steering wheel column. Thus, forces transmitted during inflation of the air bag 22 are applied through the reaction device 28 to the structural portion S of the vehicle. The air bag module 14 is shown in one embodiment in Figures 1-6. and in a second, alternate embodiment in Figures 7-11. Where the illustrated components of the air bag module embodiments are the same, the same reference numerals are used to reference the components. The air bag module 14 is constructed of two sub-assemblies. One subassembly, the air bag/cover subassembly, generally referenced at 34, consists of the folded air bag 22, the cover 24 and fasteners 52, described more fully hereinafter, for connecting the air bag and the cover. The other subassembly, the inflator/reaction device subassembly, generally referenced at 36, consists of the inflator 20 and reaction device 28. The air bag/cover subassembly 34 of the first embodiment of the present invention is illustrated in Figure 6. The cover 24 includes a rectangular main body 44 with a closed end 38 which forms the front cover door that is presented to the passenger compartment of the vehicle. Opposite the end 38 is an access opening 40 surrounded by a peripheral flange or rim 42 joined to the main body 44. The rim 42 extends generally inward from the main body 44 of the cover, and has an inside surface 42a on the inside of the cover, and an outside surface 42b on the outside of the cover 24. Spaced around the rim 42 are attachment openings 46 for use in securing the air bag 22 to the cover 24. The cover 24 is hollow and defines an air bag cavity 37. The air bag 22, which may be made of porous, woven fabric or an impermeable material, such as plastic film, is formed with a gas inlet opening 49, through which gas generated by the inflator 20 passes during operation of the module 14. The portion 48 of the air bag 22 which borders the opening 49 is a continuous portion of the bag fabric and may be reinforced if desired. Spaced around the bag portion 48 are attachment openings 50, designed for alignment with the respective attachment openings 46 in the rim 42 of the cover 24. To form the air bag/cover subassembly 34 of the present invention, the air bag 22 is initially folded (i.e., prefolded) to a desired predetermined configuration outside the cover, as illustrated in Figure 6. The prefolded air bag is then inserted as a unit into the air bag cavity 37 defined within the cover 24 so that only the border 48 of the bag is exposed. The cover is made of a relatively flexible plastic, such as polyvinylchloride, which allows the cover to be resiliently and elastically deformed, if necessary, to accept the prefolded air bag to be inserted into the air bag cavity. Once the prefolded air bag 22 has been inserted into the cover 24, one surface 48b of the border portion 48 of the air bag is engaged with the outside surface 42b of the rim 42 of the cover so that the openings 50 in the air bag portion 48 are aligned with the openings 46 in the rim of the cover. Once the attachment openings 46, 50 in the air bag and cover, respectively, are aligned with one another, the air bag 22 is secured to the cover 24. As illustrated in Figure 4, at least two of the respective attachment openings 46, 50 are adapted to accept individual rivets 52, which function exclusively to connect the air bag with the cover. Retaining bolts 54, as illustrated in Figure 3, are inserted into the remaining aligned openings 46, 50 to secure the air bag to the cover and, as will be described hereinafter, the air bag/cover subassembly 34 to the inflator/reaction device subassembly 36. To form the air bag/cover subassembly 34 of the second embodiment of the present invention, as illustrated in Figure 7-11, a retaining ring 43 (see Fig. 11) is engaged with the one side 48b of the border portion 48 of the air bag. With the retaining ring 43 attached to the air bag, in a manner described hereinafter, the air bag is then prefolded and inserted into the air bag cavity 37 so that both the border portion 48 of the bag and the retaining ring are within the cavity. Since the retaining ring is a substantially rigid member, the flexible plastic cover 24 is elastically deformed to encompass the retaining ring and attached air bag. With the retaining ring and air bag positioned inside the cover, the side 48a of the border portion 48 opposite the side 48b is then engaged with the inside surface 42a of the rim 42 of the cover. The air bag is thus captured between the retaining ring 43 and the border rim 42. The attachment openings 47 in the retaining ring 43 are aligned with the openings 50 in the border portion 48 of the air bag and the openings 46 in the rim 42 of the cover 24. Once the attachment openings 47, 46, 50 in the retaining ring, air bag and cover, respectively, are aligned with one another, the air bag 22 is secured to the cover as described above in connection with the first embodiment of the air bag/cover subassembly. As illustrated in Figure 8, retaining bolts 54 are used to secure the retaining ring 43 and the air bag 22 to the cover 24 and the air bag/cover subassembly 34 to the inflator/reaction device subassembly 36. As illustrated in Figure 9, individual rivets 52 are inserted through certain aligned openings 46, 47 and 50 exclusively to connect the retaining ring and air bag with the cover. In the illustrated embodiments of the air bag module 14 in Figures 1-6 and 7-11, the retaining bolts 54 preferably serve the dual function of coupling the components of the air bag/cover subassembly 34 together, and of coupling the inflator/reaction device subassembly 36 with the air bag/cover subassembly. The same retaining bolts additionally serve to couple the module to the structural portion S of the vehicle as described below. By using the same retaining fasteners to perform multiple connecting functions, the air bag module uses a relatively small number of parts. The advantages obtained by reducing the number of parts used in the air bag module, include a reduction in overall module weight and cost.

Claims: Apparatus comprising an air bag/cover subassembly (34) adapted to be coupled to an inflator/reaction device subassembly (36) to form an air bag module (14), said air bag/cover subassembly (34) comprising: (a) a cover (24) defining an air bag cavity (37) and having an access opening (40) communicating with said air bag cavity (37), and a rim (42) surrounding said access opening (40); (b) a folded air bag (22) disposed in said air bag cavity (37), said air bag (22) having a border portion (48) defining a gas inlet opening (49), and (c) means (46, 50, 52) for connecting said border portion (48) of said folded air bag (22) with said cover (24); characterized in that said rim (42) is an integral rim (42), formed in one piece with the remaining portions of said cover (24), and said means (46, 50, 52) for connecting said border portion (48) of said folded air bag (22) with said cover (24) is adapted to connect said border portion (48) of said air bag (22) with said rim (42) of said cover (24). Apparatus according to claim 1, in which means (46. 50, 52) for connecting said border portion (48) of said folded air bag (22) with said cover (24) is also adapted to couple said air bag (22) and cover (24) to an inflator/reaction device subassembly (34).

Inventors: AUGUSTITUS JAMES A, LECZNAR MARK T, WIPASURAMONTON PONGDET, AUGUSTITUS, JAMES A., LECZNAR, MARK T., WIPASURAMONTON, PONGDET
Applicants: TRW VEHICLE SAFETY SYSTEMS, TRW VEHICLE SAFETY SYSTEMS INC.
Application year: 1991
Main classification: B60R21
IPC codes: B60R21