Inflator

Abstract: An inflator (24) which generates gas and heat as the inflator is actuated. The inflator includes an identifying member. The identifying member (34) is provided on the inflator (24) so as to permit the identification of an unactuated state and an actuated state of the inflator (24) on the basis of heat generated during the actuation of the inflator (24).

Description: BACKGROUND OF THE INVENTION Field of the Invention: The present invention relates to an inflator for generating a gas and heat upon actuation thereof. Description of the Related Art: As a passive vehicle occupant restraint system, air bags, for instance, are in widespread use. An air bag of this type is provided with a sensor of a mechanical ignition type or an electric ignition type for detecting a state of collision. When the sensor detects the state of collision, the inflator is actuated to eject a high-temperature gas, thereby to inflate a bag. The structure of an inflator of this type is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 5-213149. To give a brief description, as shown in Fig. 4, an inflator 100 has an upper case 102 and a lower case 104 which are made of an aluminum alloy or the like and are formed integrally as their joining surfaces are welded together. A sensor 106 of the mechanical ignition type for detecting the state of collision is disposed in an axial portion of the inflator 100. Disposed immediately above the sensor 106 are a detonator 107, which is ignited by being pierced by an unillustrated firing pin, and a fire propagating agent 108 for propagating the flame from the detonator 107. A gas generating agent 110, which burns by the flame propagated by the fire propagating agent 108, is sealed in around the sensor 106. As the gas generating agent 110 is burned, a large amount of high-temperature gas is generated. There has been a demand to reutilize, for instance, the upper case 102 and the lower case 104 after the inflator 100 is actuated. Generally, however, a caution label is attached to the bottom surface or the like of the lower case 104 of the inflator 100 to call attention not to subject the inflator 100 to heating, electrical energization, or the like during removal of the air bag or repairing of a steering wheel. For this reason, if the inflator 100 of the air bag has been actuated, the inflator 100 could be removed and heated by ignoring the contents of the caution label, but since this caution label still exists even after its actuation, it is liable to be thought that the inflator 100 must not be subjected to melting or the like for the purpose of reutilization. That is, the caution label merely continues to remain in its intact form even after the actuation of the inflator 100, so that it is impossible to identify whether or not the inflator 100 was actuated, thereby constituting a factor hampering the reutilization of the inflator 100. Further information regarding the prior art can be found in EP-A-0 625 700, which describes a temperature sensitive fluid indicator comprising an envelope formed of two layers of transparent polymeric film material which are welded one to another in a matrix of welds to provide an array of cells each containing a temperature sensitive fluid. The fluid may be an emulsion and indicia in the form of a color, or a word such as "VOID", or a pattern may be reverse printed on an inner surface of one of the layers so as to be visible through the cells and through the other of the layers when the emulsion changes to a matrix phase. GB-A-2 074 975 describes a container for α-cyanoacrylate adhesives that is provided with an indicator that irreversibly indicates when a predetermined temperature has been exceeded, and hence makes it possible to check whether the recommended storage temperature has been observed. The indicator comprises a carrier bearing a dot of material that changes color at temperatures above the predetermined value. Alternatively, the indicator may be a temperature sensitive strip or label. GB-A-2 243 140 relates to a label or tag for an item of clothing that has an area thereon that changes color permanently if the item of clothing is washed above a recommended washing temperature. Then an item of clothing damaged because recommended washing instructions were ignored cannot be taken back to a retailer for replacement or refund on the ground of being faulty. Alternatively, the permanent change may be the appearance, disappearance or disintegration of a marking. JP-A-56 061468 discloses how to obtain a releasable adhesive that is easily released by losing its adhesiveness when heated and that is useful as masking tape, etc., by adding a specific amount of an expansible fine granule to a thermoplastic resin adhesive. In detail, a thermally expansible fine granule is obtained by microcapsulating a substance e.g., butane, isobutane, neopentane etc., capable of giving out a gas at a temperature below the softening point of a thermoplastic resin in the shell of a thermoplastic resin, e.g., an acrylonitrile-vinylidene chloride copolymer resin, an acrylonitrile-vinyl acetate copolymer resin etc., and then 30-100pts wt. thermally expansible fine granule thus obtained is compounded in 100pts.wt. adhesive component, e.g., a thermoplastic resin adhesive, etc., to obtain a releasable adhesive. When a label, etc., bonded by this adhesive is heated for releasing, the thermally expansible fine granule is expanded to make the releasing of the label easier by the loss of its adhesiveness. SUMMARY OF THE INVENTION In view of the above-described circumstances, it is an object of the present invention to provide an inflator which promotes reutilization by changing the appearance of the inflator by heat generated during the actuation of the inflator. In accordance with the invention, these objects are acheived by the pyrotechnic, passive vehicle occupant restraint system component as defined in independent claim 1. Further embodiments of the invention are defined in the dependent claims. In accordance with a first aspect of the present invention, there is provided an inflator for generating gas and heat as the inflator is actuated, the inflator comprising: an identifying means provided on the inflator and permitting the identification of an unactuated state and an actuated state of the inflator on the basis of heat generated during actuation. In accordance with a second aspect of the present invention, in the inflator for generating gas and heat as the inflator is actuated according to the first aspect of the invention, the identifying means has a shape changing member which undergoes a change in its shape on the basis of the heat generated during the actuation. In accordance with a third aspect of the present invention, in the inflator for generating gas and heat as the inflator is actuated according to the second aspect of the invention, the identifying means has a display member which, in conjunction with the change in the shape of the shape changing member, displays by means of at least one of characters and a symbol the fact that the inflator has been actuated. In accordance with the first aspect of the present invention, since the inflator is provided with the identifying means which permits the identification of the unactuated state and the actuated state of the inflator on the basis of heat generated during actuation, if the inflator is actuated, on the basis of the heat generated at that time it is possible to identify the fact that the inflator has been actuated. In accordance with the second aspect of the present invention, in the first aspect of the invention, when the inflator is actuated, the shape changing member undergoes a change in its shape on the basis of the heat generated at that time. As a result, it can be identified that the inflator has been actuated. In accordance with the third aspect of the present invention, in the second aspect of the invention, when the inflator is actuated, in conjunction with the change in the shape of the shape changing member the display member displays by means of at least one of characters and a symbol the fact that the inflator has been actuated. As a result, it can be identified that the inflator has been actuated. As described above, the inflator in accordance with the first aspect of the present invention is provided with the identifying means which permits the identification of the unactuated state and the actuated state of the inflator on the basis of heat generated during actuation. Hence, an outstanding advantage is obtained in that the reutilization of the inflator can be promoted. As for the inflator in accordance with the present invention, the identifying means is provided with the shape changing member which undergoes a change in its shape on the basis of the heat generated during the actuation. Further, since the arrangement provided is such that the shape is made to undergo a change on the basis of the heat generated during the actuation, an outstanding advantage is obtained in that the arrangement can be made simple. Furthermore in accordance with the present invention the inflator is provided with the display member which, in conjunction with the change in the shape of the shape changing member, displays by means of at least one of characters and a symbol the fact that the inflator has been actuated. Hence an outstanding advantage is obtained in that the reutilization of the inflator can be promoted. Further, since the fact that the inflator has been actuated is displayed directly by the display member by means of characters or the like, an outstanding advantage is obtained in that it is possible to reliably confirm whether or not the inflator has been actuated. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of an inflator illustrating the arrangement of an identifying means in accordance with a first embodiment; Fig. 2 is a perspective view, taken from the rear surface side, of an air bag provided with the inflator shown in Fig. 1; Fig. 3 is a perspective view of the air bag shown in Fig. 2 in a state in which the air bag is separated from a steering wheel; and Fig. 4 is a vertical cross-sectional view illustrating a conventional inflator of an air bag. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to Figs. 1 to 3, a description will be given of a first embodiment. It should be noted that this first embodiment corresponds to the embodiment of the present invention stated in the first to third aspects of the present invention. Fig. 3 shows a perspective view of a state in which an air bag 10 for a driver seat is separated from a steering wheel 12. Fig. 2 shows a perspective view of a reverse surface of the air bag 10. As shown in these drawings, a pair of brackets 14 each having a bolt insertion hole are attached to vicinities of a hub 12A of the steering wheel 1. Correspondingly, a pair of legs 18, each capable of abutting against the bracket 14 and having a bolt insertion hole, are provided on a base plate 16 of the air bag 10. In a state in which the brackets 14 respectively abut against the legs 18, and the respective bolt insertion holes are positioned coaxially, the air bag 10 is affixed to the steering wheel 12 by means of unillustrated bolts and nuts. As described above, the air bag 10 has the base plate 16 having a substantially box-shaped configuration. Attached to the base plate 16 is an air bag pad 22 which is fractured at a thin-walled portion 20 during a collision (during a sudden deceleration of a vehicle) and a pair of expanding portions 22A expand in directions away from each other. Incidentally, as for a method of attaching the air bag pad 22, among others there is a method in which the air bag pad 22 is attached to the base plate 16 via an unillustrated insert plate which is insert-molded in its interior. An unillustrated bag is accommodated between the air bag pad 22 and the base plate 16 in a folded state. In addition, a protruding portion 16A which is square as seen from the reverse side is formed in a central portion of the base plate 16. An inflator 24 is secured to the producing portion 16A by means of bolts 26. As shown in Fig. 1, the inflator 24 has an upper case 27, which is inserted in the protruding portion 16A of the base plate 16, and a lower case 28, which is fitted to the upper case 27 and is formed integrally by welding. A plurality of gas ejecting holes 29 are formed in a peripheral wall of the upper case 27. Meanwhile, a through hole 32 is formed in an axial portion of the lower case 28 of the inflator 24, and a squib (not shown) is disposed in this through hole 32. An unillustrated fire propagating agent is disposed immediately above the squib, and a gas generating agent, a coolant, a filter, and the like are accommodated around the squib. It should be noted that the case where the squib is used is the case of the electric ignition type, and an acceleration sensor is disposed in the case of the mechanical ignition type. Here, a substantially fan-shaped caution label 34 serving as an identifying means is bonded to the bottom surface of the lower case 28 of the above-described inflator 24. The caution label 34 has a two-layered structure comprising an upper label layer 36 serving as a shape-changing member and a lower label layer 38 serving as a display member. Usual handling precautions (i.e., instructions concerning the air bag 10 in an unactuated state, e.g., "DO NOT HEAT") are written on the upper label layer 36. This upper label layer 36 is made of a material which shrinks at about 100°C, e.g., a polystyrene-based film material. Meanwhile, the fact that the inflator 24 has been actuated and appropriate information for reutilization (e.g., "AIR BAG HAS BEEN ACTUATED" and the types of metal used, as useful information for reutilization) are written on the lower label layer 38. In addition, this lower label layer 38 is made of a material which allows the written notes to be readable even at about 180°C, e.g., a polyester-based film material. The upper label layer 36 and the lower label layer 38 are laminated by means of an adhesive. Incidentally, since the upper label layer 36 and the lower label layer 38 are fabricated separately, if a color indicating safety (e.g., a green color, a blue color, or the like) is provided on the lower label layer 38, and a color capable of calling attention (e.g., a yellow color, a red color, or the like) is provided on the upper label layer 36, it is possible to enhance the information-providing effect regarding the written contents. Next, a description will be given of the operation and effect of this embodiment. At the time of a collision, a predetermined electric current flows across the squib. Consequently, the fire propagating agent is ignited, and its flame is propagated to the gas generating agent. For this reason, the gas generating agent is burned, and a large amount of high-temperature gas is generated. Incidentally, the generated gas flows into the bag through the gas ejecting holes formed in the inflator 24, and inflates the bag. As a result, the air bag pad 22 ruptures along the thin-walled portion 20, and the bag projects toward the occupant seated in the driver seat while expanding the pair of expanding portions 22A. Here, as the high-temperature gas is ejected from the inflator 24, the temperature of the lower case 28 of the inflator 24 also rises. For this reason, when the temperature of the lower case 28 reaches about 100°C, the upper label layer 36 shrinks and in some cases falls off the lower case 28. Accordingly, the lower label layer 38 is exposed. Incidentally, although the temperature of the lower case 28 rises to 180°C or thereabouts, even if the temperature of the lower label layer 38 reaches this temperature level, the lower label layer 38 maintains its readable state. Since the aforementioned information is written on the lower label layer 38, an operator is capable of reading the information written on the lower label layer 38 so as to reutilize the inflator 24. Thus, the arrangement provided in this embodiment is such that the caution label 34 is formed as a two-layered structure comprising the upper label layer 36 and the lower label layer 38, and after the actuation of the inflator 24, the upper label layer 36 on which the usual precautions are written is caused to shrink and peel off due to the heat generated at that time, with the result that only the lower label layer 38 for identifying the actuation of the inflator 24 remains. Therefore, it is possible to promote the reutilization of the inflator 24. Further, in accordance with this embodiment, the lower label layer 38 is exposed in conjunction with a change in the shape of the upper label layer 36, and the fact that the inflator 24 has been actuated and the like are directly displayed by means of characters, it is possible to improve the identifiability as compared with a case where an indirect display is given. Incidentally, in this embodiment, the caution label 34 is formed as a two-layered structure comprising the upper label layer 36 and the lower label layer 38, and the shape of the upper label layer 36 is changed (shrunk and peeled off) by the heat during the actuation of the inflator 24, it is possible to adopt various arrangements as the shape changing member. Although in the foregoing embodiments the inflator 24 of the air bag 10 for a driver seat has been cited as an example, the present invention is not limited to the same, and the present invention is similarly applicable to the. inflator of the air bag 10 for a passenger seat and the inflator of the air bag 10 for side collision. As for the label used in the embodiments described above, it is essential that it changes due to the heat occurring during the actuation of the inflator 24, and it is also essential that its state after the change continues to remain. In other words, it must be made of a material having an irreversible characteristic. It goes without saying that insofar as such a material is used, it is possible to use a material other than the aforementioned materials. In addition, although in the foregoing embodiments the inflator 24 is used for the air bag 10, the present invention is not limited to the same, and if the shape and the like of the inflator are altered, the present invention is applicable to a pretensioner for retracting a buckle device during a collision or for rotating the takeup shaft of a webbing retractor at high speed in the taking-up direction.

Claims: A pyrotechnic, passive vehicle occupant restraint system component for generating gas and heat as said pyrotechnic component is actuated, said pyrotechnic component comprising: an identifying label provided on said pyrotechnic component and permitting the identification of a charged state and a discharged state of said pyrotechnic component on the basis of heat generated during actuation, wherein said identifying label has a two-layered structure comprising a shape changing member as an upper label and a display member as a lower label, and wherein said shape changing member undergoes a change in its shape on the basis of the heat generated during the actuation, and in conjunction with the change in the shape of said shape changing member said display member displays information indicating that said pyrotechnic component has been actuated. The pyrotechnic component of Claim 1, wherein said display member is formed of a polyester-based film material. The pyrotechnic component of any of Claims 1-2, wherein said shape changing member is formed of a material which shrinks due to the generated heat and falls off said pyrotechnic component. The pyrotechnic component of any of Claims 1-3, wherein said shape changing member is formed of a polystyrene-based film material. The pyrotechnic component of any of Claims 1-4, wherein said shape changing member displays information regarding usual handling precautions for said pyrotechnic component. The pyrotechnic component of any of Claims 1-5, wherein said display member displays information for reutilization of said pyrotechnic component. The pyrotechnic component of any of Claims 1-6, wherein said pyrotechnic component is an inflator for inflating an air bag. The pyrotechnic component of any of Claims 1-6, wherein said pyrotechnic component is employed in a seatbelt pretensioner.

Inventors: FUKAWATASE OSAMU, HAMADA MAKOTO, YAMADA RYUICHI, FUKAWATASE, OSAMU, HAMADA, MAKOTO, YAMADA, RYUICHI, Fukawatase, Osamu, c/o Toyota Jidosha K. K., Hamada, Makoto, c/o Toyota Jidosha K. K., Yamada, Ryuichi, c/o Toyota Jidosha K. K.
Applicants: TOYOTA MOTOR CO LTD, TOYOTA JIDOSHA KABUSHIKI KAISHA
Application year: 1996
Main classification: B60R21
IPC codes: F42D5, B60R21, G09F3, B01J7