Gas generating agent pack for air bag inflation gas generator

Abstract: In a gas generating agent pack for an air bag inflation gas generator of this invention, a plurality of gas generating agents (57) with a through hole (55) formed at the center is accommodated in the axial direction in the stacked state within a longitudinal cylindrical pack (73) whose both ends are tightly closed, and an energizing means (89) for energizing the gas generating agents (57) toward the end of the cylindrical pack (73) is disposed within the cylindrical pack (73), so that the plurality of gas generating agents (57) accommodated into the cylindrical pack (73) can be tightly contacted securely to one another.

Description: The invention relates to an air bag inflation gas generator. A prior shock absorber to protect a passenger car driver from shocks at collision accidents comprises an air bag and a gas generator to inflate the air bag with gas. At a collision accident of a passenger car, explosives or other gas generating agents having a similar composition thereto, which are charged in the gas generator, are ignited and burnt to produce gas. The air bag is instantaneously inflated by the resultant gas for protecting the driver against any collision shocks, thereby avoiding possible serious injury of the driver. Fig. 7 shows the air bag inflation gas generator disclosed in JP-A-5 138 005. This air bag inflation gas generator comprises a longitudinal outer cylindrical member 13 having a plurality of gas outlets 11 formed in the outer periphery, an inner cylindrical member 17 inserted in the outer cylindrical member 13 and having gas flow openings 15 formed in the outer periphery, a final filter 19 disposed between the outer cylindrical member 13 and the inner cylindrical member 17, a plurality of gas generating agents 23 with a through hole 21 formed at the center accommodated in the stacked state in the axial direction of the inner cylindrical member 17, and an igniter 25 and an ignition agent 27 disposed at one end of the inner cylindrical member 17, wherein the gas generating agents 23 and the ignition agent 27 are accommodated in a gas generating agent pack 29. With the above air bag inflation gas generator, volume of combustion gas from the gas generating agents 23 can be steeply increased and a large volume of combustion gas can be surely purified. But, the gas generating agent pack 29 for the above conventional air bag inflation gas generator has drawbacks that it is difficult to tightly stack the gas generating agents 23 without any gaps in the gas generating agent pack 29 and the gas generating agents 23 are mutually bumped by vibration, resulting in damages. More specifically, the aforementioned gas generating agents 23 are generally produced by dispersing a gas generating component into a binder, charging the resultant binder into a metal mold and molding under pressure. But, it is very difficult to produce them in a uniform thickness. Therefore, when many of such gas generating agents 23 are accommodated in the gas generating agent pack 29, errors in thickness are accumulated and, for example, when about 20 gas generating agents are stacked, about 3 mm gap is formed in the gas generating agent pack 29 in to worst case and the gas generating agents 23 are mutually bumped by vibration, possibly damaging them. Document WO 92/22 440 discloses an air bag inflation gas generator including a plurality of gas generating agents with a through hole formed at the center which agents are accommodated in the axial direction in the stacked state within a longitudinal cylindrical housing with both ends tightly closed, and a resilient means for pressing the gas generating agents towards an end face of said longitudinal cylindrical housing. A complete inner cylindrical pack as well as a separated, complete outer cylindrical member which are tightly closed by end faces or caps are not described in this document. The known longitudinal cylindrical pack of this document corresponds to the outer cylindrical member of the air bag inflation gas generator according to the present invention. US-A-5 178 547 discloses an air bag inflation gas generator which is provided with an annular cushion as a resilient means between the uppermost gas generating disk and the inside of a canister cover having a rather limited thickness. It is the object of the present invention to provide an air bag inflation gas generator by which a reliable ignition is achieved at any time. This object is solved by an air bag inflation gas generator comprising the features of claim 1. According to the present invention the cylindrical spacer as well as the first and second resilient means operate in such a manner that, on the one hand, the gas generating agents are pressed towards the one end face of the cylindrical pack, and that, on the other hand, also the spacer accommodating the ignition agent is pressed towards the same side of the cylindrical pack such that the space between the igniter disposed in a one end plate part of the outer cylindrical member and the ignition agent disposed at the center of the spacer is maintained at any time in order to improve the reliability of the gas generator as a whole. Further embodiments of the invention are mentioned in the subclaims. The present invention is described in detail with reference to the attached drawings wherein Fig. 1 is a longitudinal sectional view showing one embodiment of an air bag inflation gas generator; Fig. 2 is a transverse sectional view taken along the line 2-2 of Fig. 1; Fig. 3 is a sectional view showing the gas generating agent pack of Fig. 1; Fig. 4 is a sectional view showing the holder of Fig. 3; Fig. 5 is a sectional view showing the spacer of Fig. 3; Fig. 6 is a sectional view showing another embodiment of the air bag inflation gas generator; and Fig. 7 is a longitudinal sectional view showing the air bag inflation gas generator disclosed in JP-A-5 138 005. Fig. 1 and Fig. 2 show an air bag inflation gas generator provided with one embodiment of a gas generating agent pack of this invention. In the drawings, the reference numeral 35 represents a longitudinal outer cylindrical member whose both ends are tightly closed by end plate parts 37, 39. The outer cylindrical member 35 has a plurality of gas flow openings 41 formed in its outer periphery. And, the end plate part 39 is integrally formed with a part 43 to be mounted on a vehicle. The outer cylindrical member 35 has a cylindrical final filter 45 disposed therein. This final filter 45 is formed by winding, for example, fine-mesh woven metal wire, close-woven metal wire, etc. in layers. This filter has the functions that the combustion gas is cooled so that the air bag is not damaged, the combustion residue contained in the combustion gas is removed, and harmless nitrogen gas only is supplied into the air bag. Inside the final filter 45 is inserted an inner cylindrical member 47. The inner cylindrical member 47 has many gas flow openings 49 formed in the entire length of the outer periphery thereof. The inner cylindrical member 47 accommodates a gas generating agent pack 51 which is one embodiment of this invention. The gas generating agent pack 51 has a bottom-closed longitudinal cylindrical pack 53 which is made of aluminum as shown in Fig. 3. Within the cylindrical pack 53, many gas generating agents 57 having a through hole 55 formed in their center are accommodated in the stacked state in the axial direction. One end of the cylindrical pack 53 is sealed by one end face 59, and the other end is sealed by another end face 62 made of, for example, an aluminum cap 61. At one end face 59 of the cylindrical pack 53, a cylindrical spacer 63 is disposed. This spacer 63 is formed of, for example, aluminum and an ignition agent 64 is disposed at its center. The ignition agent 64 contains powder for auto-ignition which ignites at a low temperature of 180 C° and is accommodated in an ignition agent pack 65. On the other hand, the cap 61 disposed on the other end of the cylindrical pack 53 is tightly wound around its outer periphery by the cylindrical pack 53 to have a cylindrical fasten-folded section 67. And, at the center of the cap 61 is formed a projection 68 to accommodate an ignition agent 66. The ignition agent 66 contains powder for auto-ignition which ignites at a low temperature of 180 C° and is accommodated in an ignition agent pack 69. A space 71 is formed on the side of the cap 61 in the cylindrical pack 53. In the space 71, a holder 73 which is in contact with one of the gas generating agents 57 and another holder 75 which is in contact with the cap 61 are accommodated. Both ends of a coil spring 77 are supported by the holders 73, 75 to form a first resilient means 78. As shown in Fig. 1, the end plate part 37 which seals one end of the outer cylindrical member 35 is made of an end cap and caulked for fixing against the cylindrical pack 53 by an open end 79 of the outer cylindrical member 35. The above fixing by caulking is made by a step that with a mating section 81 of the end plate part 37 mated with the open end of the inner cylindrical member 47, the open end 79 of the outer cylindrical member 35 is bent toward the end plate part 37 by a press under a certain pressure to effect plastic deformation. A through hole 83 is formed at the center of the end plate part 37, and an igniter 85 is inserted into the through hole 83 and is fixed to the end plate part 37 by caulking. A packing 87 made of, for example, inflammable silicone rubber, is disposed between one end of the final filter 45 and the end plate part 37 and between the other end of the final filter 45 and the end plate part 39. XXX, In this embodiment, a second resilient means 89 made of, for example, a coil spring is disposed between the cap 61 forming the other end face 62 of the gas generating agent pack 51 and the other end plate part 39 of the outer cylindrical member 35. And, the leading end of the projection 68 is disposed with a certain gap L provided against the other end plate part 39. With this projection 68, a heat transmission member 91 which is pressed by the second resilient means 89 against the other end plate part 39 is mated by a mating load smaller than the resilient load of resilient means 89. Fig. 4 shows the details of a pair of holders 73, 75 which is disposed within the cylindrical pack 53 shown in Fig. 3. These holders 73, 75 are made of aluminum for example and have an annular flange 95 formed at one end of a cylinder 93. And, a rust-preventive film 97 is adhered to the outer face of the flange and the inner face of the cylinder 93. This rust-preventive film 97 prevents the holders 73, 75 from being corroded by azide contained in the gas generating agents 57. This film 97 is made of a nylon resin having a thickness of about 15 to 150 micrometers for example. Fig. 5 shows the details of the spacer 63 which is disposed within the cylindrical pack 53 shown in Fig. 3. This spacer 63 has the shape of a relatively thick cylinder. It has the ignition agent pack containing the ignition agent 64 therein disposed in its through hole 99. And, a sealing member 101 is adhered to both sides of the spacer 63 to shield the through hole 99. This sealing member 101 is made of a transparent polyester resin film for example. In the aforementioned air bag inflation gas generator, the ignition agent 64 burns when electricity is sent to the igniter 85, which in turn burns the gas generating agents 57, the cylindrical pack 53 of the gas generating agent pack 51 is broken at the gas flow openings 49 of the inner cylindrical member 47, the combustion gas flows into the final filter 45 through the gas flow openings 49 of the inner cylindrical member 47 and is purified by the final filter 45, then it is flown into the air bag through the gas flow openings 41 of the outer cylindrical member 35. And, in the above embodiment, when electricity is sent to the igniter 85 which is disposed at one end of the outer cylindrical member 35, the ignition agent 64 disposed at one end burns first and the gas generating agent 57 adjacent to the igniter 85 starts burning and, at the same time, the ignition agent 66 disposed at the other end burns, and the gas generating agent 57 next to it burns. In the gas generating agent pack of the air bag inflation gas generator configured as described above, since the first resilient means 78 which presses the gas generating agents 57 toward the one end face 59 of the cylindrical pack 53 is disposed within the cylindrical pack 53, a plurality of gas generating agents 57 accommodated into the cylindrical pack 53 can be closely contacted to one another. More specifically, with the aforementioned gas generating agent pack, when many gas generating agents 57 are accommodated in the cylindrical pack 53, errors in thickness are accumulated and, for example, when about 40 gas generating agents 57 are stacked, accumulation of errors will reach about 6-mm in the worst case. But, since the gas generating agents 57 are surely pressed against the one end face 59 of the cylindrical pack 53 by the first resilient means 78, a plurality of gas generating agents 57 can be tightly contacted to one another. As a result, the gas generating agents 57 are not mutually bumped by vibration, and a possibility of damaging the gas generating agents 57 can be extensively reduced as compared with prior art. And, since the coil spring 77 with high expansion and contraction properties is used as the first resilient means 78 in this embodiment, the gas generating agents 57 can be surely energized even if the accumulation of errors of the gas generating agents 57 is increased. Furthermore, in the above embodiment, since the holders 73, 75 are disposed at both sides of the coil spring 77 to support them, the gas generating agents 57 can be surely pressed by the coil spring 77. Besides, since the rust-preventive film 97 is adhered to the exterior of the holders 73, 75 in this embodiment, the holders 73, 75 are surely prevented from being corroded by azide contained in the gas generating agents 57. In addition, with the above gas generating agent pack, the spacer 63 which is disposed in contact with the one end face 59 of the cylindrical pack 53 is surely pressed against the one end face 59 by the first resilient means 78. Thus, a space can be surely retained between the igniter 85 and the ignition agent 64 and reliability of ignition by the igniter 85 can be improved. And, with the aforementioned gas generating agent pack, since the through hole 99 of the spacer 63 in which the ignition agent 64 is accommodated is shielded by the sealing member 101, the ignition agent 64 is prevented from being moistened by means of a simple structure. Furthermore, with the aforementioned gas generating agent pack, since the ignition agent 64 in which powder for automatic ignition which ignites at a low temperature of 180 C° for example is disposed within the spacer 63 made of aluminum having good heat conductivity, if a car catches fire, heat from the one end plate part 37 on the side of the igniter 85 is effectively transmitted to the spacer 63, igniting the powder for automatic ignition. Thus, potential destruction of the air bag inflation gas generator in case of a car fire can be surely prevented. Fig. 6 shows another embodiment of this invention. In this embodiment, a resilient means 78A which is made of expanded silicone and has a through hole 78a in the axial direction is disposed between the cap 61 and the gas generating agent 57. This resilient means 78A presses the gas generating agents 57 toward the one end face 59. This embodiment also provides an effect which is almost same with that obtained by the aforementioned embodiment. In the aforementioned embodiments, the coil spring 77 or the expanded silicone is used as the first resilient means 78 but this invention is not limited to the above embodiments. It is needless to say that a spring member such as leaf spring or a cushion member such as sponge can be used.

Claims: An air bag inflation gas generator comprising: a longitudinal outer cylindrical member (35) having its both ends sealed by one end plate part (37) and another end plate part (39), having an igniter (85) disposed in said one end plate part (37) and having a plurality of gas flow openings (41) formed in its outer periphery, a gas generating agent pack (51) which is accommodated in said outer cylindrical member (35), and which pack (51) comprises a plurality of gas generating agents (57) with a through hole (55) formed at the center, said agents (57) being accommodated in the axial direction in the stacked state within a longitudinal cylindrical pack (53) whose both ends are sealed by one end face (59) and another end face (62), a cylindrical spacer (63) disposed within the cylindrical pack (53) at one end face (59) thereof said spacer (63) accommodating an ignition agent (64) at its center, a first resilient means (78, 78A) disposed within said cylindrical pack (53) on the side of the other end face (62) thereof for pressing said gas generating agents (57) and the spacer (63) against the one end face (59) of said cylindrical pack (53), and a second resilient means (89) disposed outside of said cylindrical pack (53) between the other end face (62) and the other end plate part (39) of the outer cylindrical member (35) for pressing the cylindrical pack (53) with its one end face (59) against the one end plate part (37) of the outer cylindrical member (35). An air bag inflation gas generator according to claim 1, characterized in that the spacer (63) has the shape of a relatively thick cylinder comprising a through hole (99). An air bag inflation gas generator according to claim 1 or 2, characterized in that the ignition agent (64) contains powder for auto-ignition which ignites at a low temperature of 180 C and which is accommodated in an ignition agent pack (65). An air bag inflation gas generator according to one of the foregoing claims, characterized in that a sealing member (101) is adhered to both sides of the spacer (63), said sealing member (101) being preferably made of a transparent polyester resin film.

Inventors: KISHIMOTO JUNICHI, MINAMIZAWA TAKASHI, KISHIMOTO, JUNICHI, MINAMIZAWA, TAKASHI
Applicants: NIPPON KOKI KK, NIPPON KOKI CO., LTD.
Application year: 1993
Main classification: B60R21
IPC codes: B60R21