Air bag inflation gas generator

Abstract: This invention relates to an air bag inflation gas generator comprising an inner cylindrical member (47) with gas flow openings (49) formed in the outer periphery being inserted into a longitudinal bottom-closed outer cylindrical member (35) with gas outlets (41) formed in the outer periphery with a filter (45) disposed therebetween and gas generating agents (57) being accommodated in the inner cylindrical member (47), wherein mating sections (97) are disposed at the open end of the inner cylindrical member (47) so as to engage with other mating sections (93) formed at the bottom of the outer cylindrical member (35), so that the position of the gas flow openings (49) formed in the inner cylindrical member (47) and the position of the gas outlets (41) formed in the outer cylindrical member (35) can be easily and surely set in a predetermined positional relation.

Description: The invention relates to air bag inflation gas generator according to the preamble of claim 1. Such air bag inflation gas generators are used to feed combustion gas for inflation of air bags such as air bags for absorbing collision shocks, life jackets, rafts, and escape chutes. 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. An air bag inflation gas generator according to the preamble of claim 1 is known from JP-A-5 138 005 and shown in Fig. 9. 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, in the above conventional air bag inflation gas generator, since the end of the inner cylindrical member 17 is merely inserted into a hole 13b formed at a bottom 13a of the outer cylindrical member 13, it is difficult to set easily and surely the position of the gas flow openings 15 formed keeping certain positional relation in the inner cylindrical member 17 and the position of the gas outlets 11 formed keeping certain positional relation in the outer cylindrical member 13 in the predetermined positional relation. And, there is a problem that it is difficult to let the combustion gas from the gas generating agents 23 which are burnt inside the inner cylindrical member 17 out from the gas outlets 11 through an optimum route. More specifically, the combustion gas from the gas generating agents 23 which are burnt inside the inner cylindrical member 17 is flown into the final filter 19 through the gas flow openings 15 of the inner cylindrical member 17, purified in the final filter 19 and flown into an air bag through the gas outlets 11 of the outer cylindrical member 13. But, when the gas flow openings 15 and the gas outlets 11 are not in the predetermined positional relation, the flow-in position of the combustion gas into the final filter 19 and the flow-out position from the final filter 19 are deviated from the set position, and the purifying capacity of the final filter 19 is degraded. A further gas generator is disclosed in DE-U1-92 17 637. This gas generator is provided with an adjustable discharge geometry which may be adapted to the respective requirements. The position of the radial holes of both, the inner and the outer cylindrical member, may be changed with respect to each other. The circumferential movement of the inner and outer cylindrical members with respect to each other is limited by a nose positioned at the outer cylindrical member and a corresponding recess at a locking member. The limitation is constructed in such a manner that in one extremal position the holes of the inner and outer members are aligned to each other wherein in the other extremal position the holes are not in alignment with each other. Thus, in the last case, there exist only very small discharge openings. The respective elements (nose at the outer member and recess at the locking member) are shown in two figures of the drawings of said document. Since the engaging means are mounted on the outer member and on the locking member the known gas generator has the disadvantage that the alignment of the holes formed in the inner and the outer cylindrical member may unintentionally be changed for example by sustained vibrations of the vehicle into which the gas generator is inserted. It is an object of the present invention to provide an air bag inflation gas generator wherein the position of the gas outlets formed in the outer cylindrical member and the position of the gas flow openings formed in the inner cylindrical member can easily and surely be set in a predetermined positional relation. This object is solved by an air bag inflation gas generator comprising the features of claim 1. The first engaging mean comprising at least one projecting portion is provided at the bottom of the outer cylindrical member whereas the second engaging mean comprising at least one recess is disposed at the open end of the inner cylindrical member. Thus, when these engaging means mate with each other any rotational movement of the inner cylindrical member relative to the outer cylindrical member is surely avoided. Therefore, the reliability of the gas generator according to the present invention is amended since the positions of the gas outlets of the inner and the outer cylindrical member cannot change with respect to each other. Further embodiments of the invention are mentioned in the subclaims. In the following, a preferred embodiment of the present invention is described with respect to the drawings in which Fig. 1 is a longitudinal sectional view showing 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 outer cylindrical member of Fig. 1; Fig. 5 is a sectional view taken on the line 5-5 of Fig. 4; Fig. 6 is a sectional view showing the inner cylindrical member of Fig. 1; Fig. 7 is a front view of Fig. 6; Fig. 8 is an enlarged view showing the details of the concave part of Fig. 6; and Fig. 9 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 one embodiment of the air bag inflation gas generator 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 outlets 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. 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 an 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 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 which includes an auto-ignition powder igniting at a low temperature of, for example, 180 C° is disposed at its center. The ignition agent 64 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 form 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. As shown in Fig. 1, the end plate 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 fitting 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 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 37, and an igniter 85 is inserted into the through hole 83 and fixed to the end plate 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 37 and between the other end of the final filter 45 and the end plate 39. In this embodiment, a resilient member 89 made of, for example, a coil spring is disposed between the cap 61 forming the end face 62 of the gas generating agent pack 51 and the end plate 39 of the outer cylindrical member 35. And, the leading end of the projection 68 is disposed with a certain gap provided against the end plate 39. With this projection 68, a heat transmission member 91 which is pressed by the resilient member 89 against the end plate 39 is mated by a mating load smaller than the resilient load of the resilient member 89. In this embodiment, a hole 93 in which the end of the inner cylindrical member 47 is inserted is formed in the end plate 39 of the outer cylindrical member 35 as shown in Fig. 4 and Fig. 5. On the wall of the hole 93, a pair of rectangular first engaging means 95 comprising at least one projecting portion are integrally formed opposite to each other at an angle of 180 degrees. On the other hand, both open ends of the inner cylindrical member 47 have a pair of rectangular second engaging means 97 comprising at least one recess diagonally opposing each other at an angle of 180 degrees as shown in Fig. 6 and Fig. 7. At the entrance to the second engaging mean 97, a chamfer 99 is formed as shown in Fig. 8, so that the projecting portions 95 can be easily inserted into the recesses 97. 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, 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 outlets 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 air bag inflation gas generator configured as described above, since the second engaging means 97 which are engaged with the first engaging means 95 formed on the end plate 39 of the outer cylindrical member 35 are formed at the open end of the inner cylindrical member 47, the position of the gas flow openings 49 formed in the inner cylindrical member 47 and the position of the gas outlets 41 formed in the outer cylindrical member 35 can be easily and surely set in a predetermined positional relation. More specifically, in the aforementioned air bag inflation gas generator, when the inner cylindrical member 47 is inserted through the open end of the outer cylindrical member 35 and the second engaging means 97 formed at the open end of the inner cylindrical member 47 are engaged with the first engaging means 95 formed at the end plate 39 of the outer cylindrical member 35, the positional relation between the outer cylindrical member 35 and the inner cylindrical member 47 is defined, so that the position of the gas flow openings 49 formed in the inner cylindrical member 47 and the position of the gas outlets 41 formed in the outer cylindrical member 35 can be easily and surely set in a predetermined positional relation. And, in this embodiment, since the second engaging means 97 and the first engaging means 95 are disposed opposite to each other at an angle of 180 degrees on the inner cylindrical member 47 and the outer cylindrical member 35, respectively, and the gas flow openings 49 and the gas outlets 41 are symmetrically formed in the both members, it is possible to engage the second engaging means 97 with the first engaging means 95 by turning the inner cylindrical member 47 for at least 180 degrees and thus assembling property can be improved. Further, in this embodiment, since the second engaging means 97 are formed at both ends of the inner cylindrical member 47, the inner cylindrical member 47 can be inserted from either end thereof into the outer cylindrical member 35, improving assembling property. In the aforementioned embodiment, the second engaging means 97 are formed in the inner cylindrical member 47 and the first engaging means 95 are formed on the outer cylindrical member 35, but this invention is not limited to the above embodiment.

Claims: An air bag inflation gas generator, comprising: a longitudinal bottom-closed outer cylindrical member (35) with gas outlets (41) formed in the outer periphery, an inner cylindrical member (47) with gas flow openings (49) formed in the outer periphery, said inner cylindrical member (47) being inserted into the outer cylindrical member (35), a filter (45) disposed therebetween, gas generating agents (57) being accommodated in the inner cylindrical member (47), characterized in that first engaging means comprising at least one projecting portion (95) is formed at the bottom of the outer cylindrical member (35), and second engaging means comprising at least one recess (97, 99) is disposed at the open end of the inner cylindrical member (47), so as to mate with the first engaging means (95) when the inner cylindrical member (47) is inserted into the outer cylindrical member (35) in order to avoid any rotational movement of the inner cylindrical member (47) relative to the outer cylindrical member (35). Gas generator according to claim 1, characterized in that the recess (97) tightly accommodates the projecting portion (95) when the inner cylindrical member (47) is inserted into the outer cylindrical member (35). Gas generator according to claim 2, characterized in that the outer cylindrical member (35) is provided with two projecting portions (95) diagonally opposing each other, and the inner cylindrical member (47) is provided with two recesses (97) also diagonally opposing each other, such that the projecting portions (95) and the recesses (97) encompass an angle of 180 , respectively. Gas generator according to one of the foregoing claims, characterized in that the second engaging means (97) are formed at both ends of the inner cylindrical member (47). Gas generator according to one of the foregoing claims, characterized in that a hole (93) in which the end of the inner cylindrical member (47) is inserted, is formed in the bottom of the outer cylindrical member (35), each first engaging mean (95) is disposed on the wall of the hole (93) and that a chamfer (99) is formed at the entrance to each second engaging mean (97) so that each first engaging mean (95) can easily be inserted into each second engaging mean (97).

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, F42B3