Inflator and airbag device

Abstract: An inflator, which can inflate an airbag into a laterally symmetrical configuration as a whole, and an airbag device having the inflator are provided. The inflator 1 has a cylindrical casing 2, the inside of which is divided into two chambers, i.e. a first chamber and a second chamber, by a partition 3. The partition 3 defining the first chamber and the second chamber is positioned to be offset from the middle in the longitudinal direction of casing 2 to the left. The chambers are provided with gas spout holes 4, 5, respectively. As for the first chamber 11 positioned on the left side in the figure, a plurality of the holes 4 formed therein are located as close to the middle in the longitudinal direction of the container 8 as possible. As for the second chamber 12 positioned on the right side in the figure, a plurality of the holes 5 formed therein are positioned about the middle of the longitudinal direction of the container 8. Filled in the chambers are gas generant for generating gas, respectively. The chambers are provided with igniters 6, 7, respectively. Whether gas spouts from either of the first and second chambers, the gas spouting though the holes 4, 5 spouts out in the vicinity of the center of the airbag 9.

Description: BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT The present invention relates to an inflator for inflating an airbag which is installed in a vehicle including an automobile and, more particularly, to an inflator which generates gases in multiple stages. The present invention further relates to an airbag device having the inflator. An airbag device protects an occupant by an airbag which is inflated by gases generated by an inflator. Japanese patent publication 9-136604 discloses an inflator having a casing which is divided into two small combustion chambers, each of which is filled with gas generating agents. By igniting the two combustion chambers at different timings, the airbag is adjusted in its inflation speed and the inflation continuing time period. When a collision is made in small magnitude, only one of the combustion chambers is ignited. As clearly shown in the drawings of the publication 9-136604, the inflator has the first combustion chamber disposed at one end side and the second chamber disposed at the other end side of the casing, and gas spout holes are formed in the respective middle portions in the longitudinal direction of the combustion chambers. Therefore, when gas spouts only from the first chamber, gas is introduced only from the one end side of the casing into the airbag so that a one-end-side portion of the airbag is inflated quickly and largely as compared to the other-end-side portion of the airbag. In the same manner, when gas spouts only from the second chamber, gas is introduced only from the other end side of the casing into the airbag so that the other-end-side portion of the airbag is inflated quickly and largely as compared to the one-end-side portion of the airbag. From the FR 2 233 202 an inflator is known which corresponds to the preamble of claim 1 and 2 which comprises a casing which is divided into two chambers arranged in the longitudinal direction of the casing. The disclosed inflator comprises furthermore gas generant for generating gas filled in the chambers and gas spout holes formed in the casing, wherein the gas spout holes are disposed close to the middle in the longitudinal direction of the casing. Furthermore, the EP 0 792 776 discloses a hybrid inflator comprising two different sized chambers containing pressurized gas. The first chamber contains a gas generating material and an ignition device for a projectile for the rupture of a first burst disc closing an outlet of the first chamber. The second chamber only contains pressurized gas and a heating device and is closed by a second burst disc. The openings of both chambers lead to a common space between the two chambers which is surrounded by a cylinder connecting the two chambers and comprising gas outlets. This hybrid inflator has the disadvantage that the chambers have to be made of a strong material in order to keep the pressurized gas so that they have a high weight. Furthermore, there is the risk that in the case of a leakage the pressurized gas escapes rendering the inflator unusable. OBJECT AND SUMMARY OF THE INVENTION It is an object of the present invention to provide an inflator which inflates an airbag in bilateral symmetry as a whole and can be realized with a reduced weight and to provide an airbag device having the inflator. An inflator of the present invention has a cylindrical casing, at least one partition defining a plurality of chambers in the casing which are arranged in the longitudinal direction of the casing, gas generating agents filled in the chambers, and gas spout holes formed in the casing. The holes are disposed close to the middle in the longitudinal direction of the casing. An airbag device of the present invention has a container, an airbag folded and accommodated in the container, and the inflator of the present invention for inflating the airbag. In the airbag device having the inflator as mentioned above, whether gas spouts from either of the chambers, the gas spouts from substantially the middle or the vicinity of the middle in the longitudinal direction of the casing of the inflator whereby the airbag is inflated into a bilaterally symmetrical configuration as a whole. The inside of the casing is divided into two chambers by the partition. Furthermore, the partition is disposed to be offset from the middle in the longitudinal direction of the casing to one end side of the casing so that the casing has a first chamber on the one end side and a second chamber on the other end side, and that the holes formed in the first chamber are disposed close to the partition and the holes formed in the second chamber are disposed about the middle in the longitudinal direction of the casing. In the airbag device, the container has a configuration elongated in the longitudinal direction of the inflator, the partition of the inflator is disposed to be offset from the middle in the longitudinal direction of the container to one end side of the container, the holes formed in the first chamber on the one end side are disposed as close to the middle in the longitudinal direction of the container as possible, and that the holes formed in the second chamber on the other end side are disposed about the middle in the longitudinal direction of the container. Since the gas for inflating the airbag is generated by a gas generating agent, the casing need not to be very strong since the generated gas immediately can exit the chambers through a gas spout holes. Furthermore, the two chambers due to the different sizes have different inflating properties so that in case they are activated independently by increased number of different possibilities for controlling the inflating process of the airbag is obtained. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1a - 1c illustrate the structure of a container (a housing for accommodating an airbag of a passenger airbag device) to which an inflator according to an embodiment of the present invention is attached, Fig. 1a is a sectional view taken along a line A-A of Fig. 1b, Fig. 1b is a front view of the container, and Fig. 1c is a side view of the container; and Fig. 2 is a perspective view of the inflator. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. An inflator 1 has a cylindrical casing 2, the inside of which is divided into two chambers, i.e. a first chamber 11 and a second chamber 12, by a partition 3. The casing 2 may be composed of an integral material from the left end to the right end in Figs. 1a, 1b and may be provided with the partition 3 inside thereof to form the first chamber and the second chamber. Alternatively, the casing 2 may comprise a first casing for the first chamber and a second casing for the second chamber which are integrally connected to each other. The casing 2 is made of metal such as aluminum or aluminum alloy. The partition 3 defining the first chamber and the second chamber is positioned to be offset from the middle in the longitudinal direction of casing 2 to the left side of Figs. 1a, 1b so that the first chamber 11 is smaller than the second chamber 12. The casing 2 is provided with gas spout holes 4 for allowing gas to spout from the chamber 11 and gas spout holes 5 for allowing gas to spout from the chamber 12. As for the first chamber 11 positioned on the left side in the figure, a plurality of the holes 4 formed therein are located as close to the partition 3 as possible. As for the second chamber 12 positioned on the right side in the figure, a plurality of the holes 5 formed therein are located about the middle of the longitudinal direction of the casing 2. Filled in the chambers 11, 12 are gas generant 21, 22 for generating gas, respectively. The chambers 11, 12 is provided with igniters 6, 7. The inflator 1 is disposed in a lower or rear portion of a container 8 in which the folded airbag 9 is accommodated. The top or front face of the container 8 is covered by a hd 10 (shown by two-dot chain lines in Fig. 1c). The container 8 is formed in a vessel-like configuration elongated in the longitudinal direction of the inflator 1. The holes 5 formed in the second chamber of the inflator 1 are disposed about the middle in the longitudinal direction of the container 8. Particularly according to this embodiment, the holes 5 are disposed symmetrically about the center line C of the container 8. The airbag device having the inflator 1 structured as mentioned above, whether gas spouts from either of the first chamber 11 and the second chamber 12, the gas spouting through the holes 4, 5 spouts out about the center of the airbag 9 whereby the airbag 9 is inflated into a laterally symmetrical configuration in front of the occupant. As mentioned above, according to the present invention, in case of inflating an airbag by using an inflator having two chambers, the airbag can be inflated into a laterally symmetrical configuration in front of an occupant. Particularly, even in case where gas spouts only from one chamber, the airbag can be inflated into a laterally symmetrical configuration.

Claims: An inflator (1) comprising a cylindrical casing (2), one partition (3) defining two chambers (11, 12) in the casing (2) which are arranged in the longitudinal direction of the casing (2), gas generant (21, 22) for generating gas filled in the chambers (11, 12), and gas spout holes (4, 5) formed in the casing (2), wherein the holes (4, 5) are disposed dose to the middle in the longitudinal direction of the casing (2), and the inside of said casing (2) is divided into two chambers (11, 12), characterized in that said partition (3) is disposed to be offset from the middle in the longitudinal direction of the casing (2) to one end side of the casing (2) so that the casing (2) has a first chamber (11) on the one end side and a second chamber (12) on the other end side, and wherein the holes (4) formed in the first chamber (11) are disposed close to the partition (3) and the holes (5) formed in the second chamber (12) are disposed about the middle in the longitudinal direction of the casing (2). An airbag device including a container (8), an airbag (9) folded and accommodated in the container (8), and an inflator (1) for inflating the airbag (9), wherein the inflator (1) comprises a cylindrical casing (2), one partition (3) defining two chambers (11, 12) in the casing (2) which are arranged in the longitudinal direction of the casing (2), gas generant (21, 22) for generating gas filled in the chambers (11, 12), and gas spout holes (4, 5) formed in the casing (2) close to the middle in the longitudinal direction of the casing (2), wherein the inside of the casing (2) of the inflator (1) is divided into two chambers (11, 12): a first chamber (11) and a second chamber (12), characterzed in that the container (8) has a configuration elongated in the longitudinal direction of said inflator (1), the partition (3) of said inflator is disposed to be offset from the middle in the longitudinal direction of the container (2) to one end side of the container (2), the holes (4) formed in the first chamber (11) on the one end side are disposed close to the partition (3), and the holes (5) formed in the second chamber (12) on the other end side are disposed about the middle in the longitudinal direction of the container (2).

Inventors: NAKANO YOSHIYUKI, NAKANO, YOSHIYUKI
Applicants: TAKATA CORP, TAKATA CORPORATION
Application year: 1999
Main classification: B60R21
IPC codes: B60R21