Land vehicles – Wheeled – Attachment
Reexamination Certificate
2002-01-07
2003-07-29
Dickson, Paul N. (Department: 3616)
Land vehicles
Wheeled
Attachment
C280S741000, C280S742000
Reexamination Certificate
active
06598901
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gas generator for an air bag and an air bag apparatus including two or more ignition means and two or more gas generating means for controlling discharge of gas or behavior of flow of the gas.
2. Description of Related Art
An air bag system which is mounted on various kinds of vehicles and the like including automobiles, aims to hold an occupant by means of an air bag (a bag body) rapidly inflated by a gas when the vehicle collides at a high speed to prevent the occupant from crashing into a hard portion inside the vehicle such as a steering wheel and a windscreen due to an inertia and being injured. This kind of air bag system generally comprises a gas generator actuated upon a collision of the vehicle and discharges gas, and the gas is introduced into an air bag to inflate the air bag.
It is desired that the air bag system of this type can safely restrain an occupant even when a frame of the occupant (for example, whether a sitting height of the occupant is long or short, whether the occupant is an adult or a child, and the like), a sitting attitude of the occupant (for example, an attitude of the occupant holding the steering wheel), and the like are different. Then, there has been conventionally suggested an air bag system which actuates while applying an impact as small as possible to the occupant at the initial stage of the actuation. Gas generators directed to such a system are disclosed in JP-A 8-207696, U.S. Pat. Nos. 4,998,751, and 4,950,458.
JP-A 8-207696 suggests a gas generator in which one igniter ignites two kinds of gas generating agent capsules to generate the gas in two stages. U.S. Pat. Nos. 4,998,751 and 4,950,458 suggest a gas generator in which two combustion chambers are provided for controlling actuation of the gas generator to generate gas in two stages due to an expanded flame of the gas generating agent.
However, these gas generators have drawbacks in that an internal structure thereof is complicated, a size of a container large, and a cost therefor is expensive.
Further, since the ratio between a surface area of gas generating agent, which burns at each of stages, and an area of a nozzle for controlling the combustion is not preferable over the entire stages, the internal pressure in the housing may be excessively low in the combustion of the first stage and excessively high in the combustion of the second stage, and therefore, it is not possible to control inflation of the air bag appropriately.
Further, in JP-A 9-183359 and DE-B 19620758, there is disclosed a gas generator in which two combustion chambers storing a gas generating agent are provided in a housing and an igniter is arranged in each combustion chamber, to adjust an activation timing of each of the igniters, thereby adjusting an output of the gas generator. However, in any of the gas generators, since the igniters arranged in the respective combustion chambers are independently arranged, it is difficult to assemble (manufacture), the structure itself of the gas generator becomes complicated and a volume thereof becomes large.
BRIEF SUMMARY OF THE INVENTION
Accordingly, the present invention provides a gas generator which actuates while applying as small an impact as possible to an occupant at the initial stage of an actuation, and can widely and optionally adjust an output and timing of an output increase of the gas generator to safely restrain an occupant even when a frame of the occupant (for example, whether a sitting height of the occupant is long or short, whether the occupant is an adult or a child, and the like), a sitting attitude of the occupant (for example, an attitude of the occupant holding the steering wheel) and the like are different, and also can stabilize a combustion performance as well as restricting the total size of a container, having a simple structure, and being easily manufactured and lightweight.
A gas generator for an air bag of the present invention includes two or more ignition units in a housing in combination of a gas discharge port or gas discharge ports formed in the housing, and a sealing unit such as a seal tape for closing the gas discharge port. When a plurality of combustion chambers are provided in the housing, respective gas generating agents accommodated in each combustion chamber are independently ignited and burnt simultaneously or at intervals by a different ignition unit. And by controlling a diameter of the opening (opening area) of the gas discharge port and/or a thickness of the seal tape which closes the gas discharge port, it is possible to equalize the pressure (hereinafter, referred as “combustion internal pressure”) in the housing when the gas generating means burns, and also to stabilize the combustion performance.
Namely, the present invention provides the gas generator for an air bag which comprises a housing forming an outer shell container and accommodating two or more ignition units to ignite upon an impact, and two or more gas generating agents which are respectively ignited and burnt by the ignition units to generate a combustion gas for inflating an air bag, and a plurality of gas discharge ports formed in the housing and closed by sealing means for maintaining an internal pressure of the housing to a given pressure, wherein a breaking pressure for breaking the sealing unit is adjusted at multiple stages by two or more gas discharge ports and/or two or more sealing units.
Preferably, a difference in the maximum internal pressures in the housing at the time of activation of the respective ignition unit is suppressed.
The breaking pressure can be adjusted by either one of an opening diameter, an opening area of the gas discharge port and the sealing units, or by a combination thereof. That is, the opening diameter can be changed between 1 and 8 mm, or 1.2 and 4 mm. With respect to the gas discharge ports being next to each other in breaking pressure for breaking the sealing units, a ratio of different breaking pressures thereof is 1.1/1 or greater, and more preferably, 4/1 to 1.1/1.
The opening area and the ratio of the opening area are changed in accordance with the amount of the gas generating agent or a surface area of the agent. The thickness of the sealing unit is changed in accordance with the ratio of the opening area or the amount of the gas generating agent or the surface area of the agent.
The amount and shape of the gas generating agent can be individually and optionally set for each of the plurality of combustion chambers. The amount of generated gas is largely varied by the number of ignitions and ignition timing. Therefore, in comparison with the generator having a single ignition unit, there exist a plurality of gas generating behavior, i.e., output characteristics, and any one of them can be selected. The combustion internal pressure depends on the ratio between the surface area of the gas generating agent and the opening area of the gas-discharge ports. When there are more than one kind of gas generating agents, the surface area of the gas generating agent, i.e., the combustion surface area is changed by the number of the ignitions and the igniting timing.
The breaking pressure is adjusted by arranging two or more kinds of opening diameters and/or opening areas of the gas discharge port. It is preferable that among two kinds or more of the gas discharge ports formed in the housing, with respect to two kinds of openings being next to each other in size of the opening diameter thereof, a ratio between the larger diameter gas discharge port and the smaller diameter gas discharge port is 4/1 to 1.1/1 and/or a ratio in opening area is 97/3 to 3/97.
Further, the breaking pressure is adjusted by arranging two or more kinds of thicknesses of the sealing unit. It is preferable that among sealing units having two kinds or more of thicknesses, with respect to the sealing units being next to each other in thickness, a thickness ratio between them is 1.1/1 to 12/1. The breaking pressure is adjusted by setting an area ratio of the two
Nakashima Yoshihiro
Ohji Nobuyuki
Birch & Stewart Kolasch & Birch, LLP
Daicel Chemical Industries Ltd.
Dickson Paul N.
Draper Deanna
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