Land vehicles – Wheeled – Attachment
Reexamination Certificate
2001-12-13
2004-01-20
Dickson, Paul N. (Department: 3616)
Land vehicles
Wheeled
Attachment
Reexamination Certificate
active
06679521
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gas generator for an air bag, and to an air bag system.
2. Description of the Related Art
An air bag system mounted on various vehicles such as automobiles has an object that, when the vehicle collides at a high speed, an air bag (bag body), which is rapidly inflated by gas, supports a vehicle occupant so as to prevent the occupant from being injured in colliding with hard portions of a vehicle interior such as a steering wheel and a windshield glass due to inertia of the occupant.
In general, such an air bag system comprises a gas generator which is operated by a collision of a vehicle to discharge gas, and an air bag to which the discharged gas is introduced to be inflated. Conventionally, as such a gas generator, there has been provided a gas generator having a structure that gas generating means is, burnt to generate combustion gas, is accommodated in the gas generator, and gas generated by the combustion of the gas generating means is discharged from the gas generator.
In the gas generator for an air bag which generates combustion gas by a combustion of the gas generating means, an operating time of the gas generator is an extremely short, that is, about 60 milliseconds. However, since a combustion gas generated by the combustion of the gas generating means has high temperature, the following case is considered after the gas generator has been operated; more specifically, a temperature of an outer container (housing) of the gas generator gradually increases due to conduction of heat generated by combustion of the gas generating means. In particular, in the case of a gas generator including coolant means in its outer container so that high temperature gas is not directly introduced into an air bag, the coolant means cools combustion gas and combustion residues by heat exchange. For this reason, the coolant means itself becomes hot, and then, heat of the coolant means is transferred to the outer container; as a result, the temperature of the outer container increases. The aforesaid gas generator is installed in a module case together with an air bag, and is mounted on various vehicles as an air bag system. In this case, considering safety after the gas generator has been operated, in the gas generator, it is desirable to prevent a temperature increase on a side where the air bag is inflated, that is, on the diffuser shell side, as much as possible. This is because the following problem is considered. An air bag quickly deflates after inflating due to a collision. When an occupant accidentally touches the diffuser shell, in the case where the surface temperature on the diffuser shell side is too high, the occupant may burn himself due to the increased temperature of the diffuser shell side.
However, there has not been provided a gas generator for an air bag, which effectively reduces or inhibits a temperature increase in an outer shell container on a diffuser side after the gas generator has been operated (in particular, a temperature increase by conduction of heat generated by combustion of the gas generating means).
Incidentally, in the past, International Publication No. W096/10495 discloses a gas generator having a structure in which a heat insulating member is provided above and/or below an outer chamber including a gas generating agent. In the aforesaid gas generator, the heat insulating member is disposed between the gas generating agent and the container (housing) in order not to affect a burning velocity of the gas generating agent by ambient temperature. In this case, the gas generator has an effect of preventing a temperature increase of a housing, where the heat insulating member is provided, after the gas generator is operated. However, the surface temperature under the heat insulating member is substantially high, and the heat insulating member peels from the outer container by gas jetting at a high speed. As a result, there is the case where no achievement of the purpose is made.
SUMMARY OF THE INVENTION
In view of the above problem in the prior art, it is therefore an object of the present invention to provide a gas generator for an air bag, which can restrict conduction of heat generated by combustion of gas generating means after the generator is operated to effectively reduce or inhibit a temperature increase of a diffuser side in an outer shell container, and thus, can reduce the maximum surface temperature of the diffuser.
According to the present invention, the diffuser is prevented from becoming too hot and the air bag can be used with safety.
To achieve the above object, the present invention provides a gas generator for an air bag comprising a housing which has a diffuser shell with at least one gas discharge port and a closure shell for forming an accommodating space together with the diffuser shell, and gas generating means, installed in the housing, to be ignited and burnt by igniting means and to generate a combustion gas, wherein the gas generator further includes heat transfer restricting means for making a conduction of heat generated by combustion of the gas generating means to the diffuser shell side less than that to the closure shell side. In the case that the coolant means for cooling the combustion gas generated by the combustion of the gas generating means is accommodated in the housing, it is desirable that the heat transfer restricting means reduces or inhibits heat conduction from the coolant means to the diffuser shell. In general, the coolant means is used so as not to directly introduce the combustion gas generated by the combustion of the gas generating means into the air bag. The conduction of heat generated by combustion of the gas generating means to the diffuser shell after the gas generator has been operated is mainly made from the coolant means. For this reason, the heat transfer restricting means is disposed between the coolant means and the diffuser shell, and thereby, it is possible to effectively reduce or inhibit heat conduction from the coolant means.
The gas generator of the present invention includes the heat transfer restricting means, and thereby, it is possible to make the maximum surface temperature of the diffuser shell (i.e., the highest temperature of a surface temperature range of the diffuser shell after the gas generating agent has been burnt) lower than that of the closure shell. The aforesaid heat transfer restricting means includes, for instance, a heat transfer suppressing member disposed between the diffuser shell and a member such as the coolant means for conducting a heat generated by the combustion of the gas generating means to the diffuser shell, or a space formed between both components. The heat transfer suppressing member reduces or inhibits conduction of heat generated by combustion of the gas generating means from the coolant means and the like to the diffuser shell, and must function so that at least heat generated by combustion of the gas generating means is not conducted to the diffuser shell. The aforesaid heat transfer suppressing member includes, for instance, a heat insulating member formed by using a proper heat insulating material, a space forming member for forming a heat insulating space or the like. Desirably, the heat insulating member is sufficiently durable to a combustion temperature of the gas generating means and exhibits a heat insulating effect. Preferably, a ceramic or ceramic fiber is used as the heat insulating member, in particular. Moreover, a space formed by the space forming member disposed between the coolant means and the diffuser shell serves to reduce or inhibit a heat conduction from the coolant means to the diffuser shell. Therefore, preferably, the space is a heat insulating space at least capable of reducing or inhibiting a heat conduction between the coolant means and the diffuser shell. In particular, the space forming member preferably has a structure where the heat insulating space can be formed. In addition, in the case of using the space formed between the coolan
Miyaji Katsuhito
Yamazaki Masayuki
Birch & Stewart Kolasch & Birch, LLP
Daicel Chemical Industries Ltd.
Draper Deanna
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