Airbag device

Abstract: An airbag device is provided which allows the required strength of a container to be reduced, thus lightening the weight of the container. A holding plate 18 is inserted into an airbag 20 through an opening 24 of the airbag 20. A flange 18b of the holding plate 18 is superposed on a peripheral portion of the opening 24 and stud bolts 22 are inserted through bolt-through holes formed in the peripheral portion of the airbag 20. The stud bolts 22 are further inserted through bolt-through holes 26 formed in the bottom of a container 10. After an inflator 16 is fitted into a housing portion 18a of the holding plate 18 through an opening 12 of the container 10, a mounting bracket 14 is superposed on the bottom of the container 10 and the stud bolts 22 are inserted through bolt-through holes of the mounting bracket 14. Then, nuts 30 are screwed up onto the bolts 22. After the airbag 20 is folded and accommodated in the container 10, a lid 32 is put on the container 10.

Description: BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT The present invention relates to an airbag device for protecting an occupant which is installed in a conveyance such as a vehicle and, more particularly, to an airbag device preferably used for a passenger's seat. In detail, the present invention relates to an airbag device which has an improved structure for fixing an airbag and an inflator to reduce the required strength of a container, thereby lightening the container. As well known in the art, an airbag device is designed for protecting an occupant by inflating an airbag with gas from an inflator. In case of an airbag device for a front passenger's seat, the airbag is folded and accommodated in a container. Japanese patent publications 6-72272A and 6-72266A disclose an airbag device for a passenger which has a container of synthetic resin to reduce weight of the device. In the passenger airbag device as described in these publications, since the airbag is connected to the inlet side of the container, the container is required to have high strength as a whole. When the airbag is inflated, large tensile force is exerted to the container from the airbag, so that the container is required to have enough strength for withstanding this tensile force. A mesh member is inserted in the synthetic resin to reinforce thereof whereby increasing weight of the container. In US 5,470,102 A, an airbag device according to the preamble of claim 1 is disclosed. In US 5,490,690 A, an airbag device is described wherein an inflator is fixed between a first portion and a second portion of a housing. This housing is in turn fixed to a container at an opening thereof. US 5,346,248 A discloses an airbag device with a housing covering an inflator, which is coupled to an airbag via a coupling device having a flange. Said housing may be made of resin, while a portion for fixing the airbag device to a vehicle may be made of metal. OBJECT AND SUMMARY OF THE INVENTION An object of the present invention is to provide an airbag device which allows a container to have lower strength and lower weight than conventional containers. This object is achieved by an airbag device as defined by claim 1. The dependent claims define preferred or advantageous embodiments of the present invention. An airbag device of the present invention comprises a container having a bottom and side walls; an airbag disposed inside the container; a lid covering the container; and an inflator which spouts gas for inflating the airbag. The airbag has an opening formed in a portion thereof confronting the bottom of the container. A holding plate for mounting the inflator and the airbag to the container is disposed inside the airbag. A mounting bracket for securing the airbag device to a structural member of a vehicle is disposed on an outer surface of the bottom of the container. A peripheral portion of the opening of the airbag and the container are clamped between the holding plate and the mounting bracket. The bottom of the container and the peripheral portion of the opening of the airbag are damped between the mounting bracket and the holding plate, whereby the airbag can be securely connected to the mounting bracket even when the container itself has lower strength. When the mounting bracket and the holding plates are made of high-strength material including metal (e.g. steel), the airbag can be securely held when inflated even though the container is made of light material such as a relatively thin steel plate or synthetic resin. The inflator is supported by the holding plate, thereby eliminating a special member for mounting the inflator. The container is provided with an opening formed in the bottom thereof. The opening in the bottom of the container lies between the inflator and the mounting bracket. The holding plate may comprise a housing portion covering the inflator and a flange portion projecting from the entire periphery of the housing portion and being superposed on a peripheral portion of the opening of the airbag, and the housing portion may be provided with gas holes for allowing gas spouted from the inflator to pass therethrough. The flange portion may have stud bolts fixed thereto, end portions of the stud bolts protrude outside through the airbag and the container, and nuts are screwed onto the end portions of the stud bolts outside the container, whereby the holding plate, the peripheral portion of the opening of the airbag, the inflator, the container, and the mounting bracket are integrated together. The container may be made of synthetic resin and the holding plate and the mounting bracket may be made of metal. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1a is a front view of an airbag device according to an embodiment, of which the left-hand side shows a section taken along a line Ia-Ia in Fig. 1b; Fig. 1b is a sectional view taken along a line Ib-Ib of Fig. 1a; Fig. 2 is an exploded perspective view of the airbag device; Fig. 3 is a bottom view of the airbag device; and Fig. 4 is a sectional view of another airbag device. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. A container 10 is a vessel-like member having a bottom and four side walls, further having an opening 12 formed in the bottom. Disposed beneath the bottom is a mounting bracket 14. Disposed above the bottom are an inflator 16, a holding plate 18, and an airbag 20. The holding plate 18 has an Ω-like section and comprises a housing portion 18a in which the inflator 16 is accommodated and a flange portion 18b projecting from the entire periphery of the housing portion 18a. The housing portion 18a is provided with gas holes 18c for allowing gas spouted out from the inflator 18 to pass therethrough. Stud bolts 22 are fixed to the flange portion 18b by welding or the like. The airbag 20 has an opening 24 which has substantially the same configuration and the same size as the opening 12. The holding plate 18 is inserted into the airbag 20 through the opening 24. The flange portion 18b is superposed on the peripheral portion of the opening 24 and the stud bolts 22 are inserted through bolt-through holes formed in the peripheral portion of the opening 24. The stud bolts 22 are further inserted into bolt-through holes 26 formed in the bottom of the container 10. After the inflator 16 is fitted into the housing portion 18a through the opening 12, the mounting bracket 14 is superposed on the bottom of the container 10. In this state, the stud bolts 22 are inserted through bolt-through holes 28 of the mounting bracket 14 and then nuts 30 are screwed onto the stud bolts 22. As a result of this, the holding plate 18, the airbag 20, the inflator 16, the container 10, and the mounting bracket 14 are all connected integrally. After that, the airbag 20 is folded and accommodated inside the container 10 and then a lid 32 is put on the container 10 and is fixed to the container 10 by, for example, rivets 34. The airbag device is secured to a vehicle by fixing the mounting bracket 14 to a structural member transversely extending inside an instrument panel of the vehicle. When the inflator 16 is actuated because of a vehicle collision, the airbag 20 is inflated and the lid 34 opens like doors toward a windshield so that the airbag 20 can be largely inflated into a compartment. Since the peripheral portion of the opening 24 of the airbag 20 is clamped between the holding plate 18 and the mounting bracket 14, impact during the inflation of the airbag 20 is transferred to the structural member of the vehicle through the holding plate 18, the mounting bracket 14, the bolts 22, and the nuts 30. No tensile force from the airbag 20 is exerted onto the container 10. This allows the container 10 to be made of synthetic resin which has lower strength as compared to steel, but has lighter weight. This also eliminates the requirement of a mesh member for reinforcing the synthetic resin. The opening 12 is formed in the container 10 so that the inflator 16 is in contact with the mounting bracket 14, not in contact with the container 10. Therefore, as for the heat generated during the actuation of the inflator 16, little is transferred to the container 10. As a result of this, a synthetic resin having poor heat resistance can be employed as the synthetic resin for the container 10. A container 10' without the opening 12 is shown in Fig. 4. The other structures of the airbag device of Fig. 4 are the same as those of the airbag of Fig. 1b. For assembling the airbag device of Fig. 4, the inflator 16 is previously fitted into the housing portion 18a of the holding plate 18 inside the airbag 20. After that, the holding plate 18 is mounted to the container 10' as well as the airbag 20, whereby the inflator 16 is mounted to the container 10'. Though the embodiments mentioned above relate to the airbag device for the passenger's seat, the present invention can be applied to an airbag device for a rear seat. Though the container is made of the synthetic resin in the aforementioned embodiments, the container may be made of synthetic resin impregnated paper or thin and lightweight metal including aluminum or an alloy thereof. As mentioned above, according to the present invention, the airbag, the inflator, the holding plate, and the mounting bracket can be connected together. A member made of lightweight material including synthetic resin may be employed as the container for the airbag device. In case where the container is made of synthetic resin, the container can be manufactured easily even when the container has a complex configuration. The reinforcement by a mesh member is not required even when the container is made of synthetic resin.

Claims: An airbag device comprising: a container (10) having a bottom and side walls; an airbag (20) being disposed inside said container (10) and having an opening (24) formed in a portion thereof confronting a bottom of said container (10), a lid (32) covering said container (10); and an inflator (16) which spouts gas for inflating said airbag (20); wherein a holding plate (18) is disposed inside said airbag, for mounting said inflator (16) and said airbag (20) to said container (10); wherein a mounting bracket (14) is disposed on an outer surface of the bottom of the container (10), for securing said airbag device to a structural member of a vehicle; and wherein a peripheral portion of said opening (24) of said airbag (20) and said container (10) are clamped between said holding plate (18) and said mounting bracket (14), characterized in that the opening (12) in the bottom of said container (10) lies between said inflator (16) and said mounting bracket (14). The airbag device as claimed in claim 1, wherein said holding plate (18) comprises a housing portion (18a) covering said inflator and a flange portion (18b) projecting from the entire periphery of said housing portion (18a) and being superposed on a peripheral portion of said opening (24) of said airbag (20), and the housing portion (18a) is provided with gas holes (18c) for allowing gas spouted from said inflator (16) to pass therethrough. The airbag device as claimed in claim 2, wherein said flange portion (18b) has stud bolts (22) fixed thereto, end portions of said stud bolts (22) protrude through the airbag (20) and the container (10) and nuts (30) are screwed onto the end portions of said stud bolts (22) outside said container (10), whereby the holding plate (18), the peripheral portion of the opening (24) of the airbag (20), the inflator (16), the container (10), and the mounting bracket (14) are integrated together. The airbag device as claimed in any one of claims 1 through 3, wherein said container (10) is made of synthetic resin and said holding plate (18) and said mounting bracket (14) are made of metal.

Inventors: IGAWA TADAHIRO, IGAWA, TADAHIRO
Applicants: TAKATA CORP, TAKATA CORPORATION
Application year: 1999
Main classification: B60R21
IPC codes: B60R21