JP3976155B2 - Inflator for airbag - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a cushioning effect by cooling a high-temperature gas containing solids generated by explosive combustion and filtering and feeding it into a bag in order to protect the passengers when the vehicle or the like decelerates rapidly. The present invention relates to an inflator for an airbag apparatus.
[0002]
[Prior art]
The airbag device detects a rapid change in acceleration due to a vehicle collision or a sudden stop, and inflates a bag incorporated in a front portion of a passenger with gas generated by combustion of a gas generating agent. The inflated bag is interposed between the passenger and the vehicle internal structure and serves as a cushion to protect the passenger. The bag that has cushioned by inflating is designed to shrink rapidly thereafter without disturbing the driver's view.
[0003]
At present, various types of airbag devices have been developed in preparation for side collisions as well as driver seats and passenger seats. For example, in an airbag device that is attached to a steering wheel of a driver's seat, a folded bag is disposed between a base plate attached to a hub of a steering wheel and a wheel pad (airbag cover), and sudden deceleration is detected. The airbag cover is broken, and the airbag is inflated toward the occupant side while the bag is deployed.
[0004]
There are several types of airbag expansion methods, but the most widely used method is a method using combustion gas generated by exploding explosives. An apparatus equipped with this type of gas generation mechanism is called an inflator. The inflator is a central mechanism of the airbag device.
[0005]
As a solid gas generating agent, those mainly composed of metal azide that generates non-toxic nitrogen gas are generally used, but this involves generation of decomposition residue and a large amount of reaction heat. Therefore, a metal net or the like is laminated and used for collecting the solid residue from the gas generating agent and for cooling the high-temperature nitrogen gas.
[0006]
A general inflator structure will be described. A sensor for detecting the vehicle sudden deceleration state is disposed at the shaft core portion of the inflator. When this sensor detects the vehicle sudden deceleration state, the ignition agent is ignited. There is also a type in which a sensor is installed in another part of the vehicle and a signal is transmitted to the inflator.
[0007]
Inside the inflator, a fire transfer agent and a gas generating agent are disposed around the ignition agent, and the gas generating agent burns through the fire transfer agent. When the gas generating agent burns, a large amount of gas is generated. This gas is mixed with high-temperature explosion residue dust consisting of vaporized and melted combustion particulates, etc., and if it flows into the airbag as it is, the airbag will break and the gas will be discharged into the vehicle, Therefore, the passenger is damaged.
[0008]
For this reason, the gas generated by explosive combustion is cooled by the coolant disposed in the inflator, then passes through the filter, and is ejected into the bag from the gas inflow hole formed in the peripheral wall of the inflator. Become.
[0009]
Usually, the device has both a coolant function and a filter function. A filter formed of a metal wire mesh serves as a filter that removes solid matter together with a cooling effect. Many filter structures contain wire screens, steel wool and / or ceramic materials to filter gases. Typically a combination of these materials is used. Since high heat resistance is required for filters, conventionally, metal wire (usually stainless steel wire) is flat-woven or twill-woven wire mesh is cut into strips of appropriate size, and this is wound in multiple tubes. We use what we did.
[0010]
A method for producing a filter using a metal wire mesh is described in JP-A-6-255440. After one end of a band-shaped wire mesh that becomes a filter is locked to the rotary winding jig, the rotary winding jig is rotated a predetermined number of times. As a result, the wire mesh is polymerized to form a ring and a filter is formed.
[0011]
The filter structure used for cooling and filtering the combustion gas in the inflator needs to be able to withstand the pressure of the explosion. In U.S. Pat. No. 4,846,368, the inflator is wrapped around a perforated tube with a cylindrical filter containing a substance that produces a large amount of flammable gas in the perforated tube. A cylindrical housing extends around and surrounds the gas generant, the perforated tube, and the filter.
[0012]
U.S. Pat. No. 4,902,036 discloses a gas generator for an air bag. This gas generator includes a plurality of filters. The filter has a first screen portion and removes reaction product particulates from the gas stream. The filter has a second mesh screen portion with a smaller mesh size. These first and second mesh screen portions are separated by a spacer pad formed of a ceramic fiber that is a mixture of aluminum oxide and silicon oxide.
[0013]
U.S. Pat. No. 4,878,690 also discloses a filter assembly for use in a gas generator that restrains a vehicle occupant. The filter assembly includes a plurality of stainless steel screen layers, a filter member for filtering generated gas particulates, and another stainless steel screen layer in the gas flow direction.
[0014]
An ordinary airbag is composed of an inflator including a bag, a cover for storing the bag, a gas generating agent, and an ignition device for igniting the gas generating agent. As such an inflator, in USP 4,380,346, as shown in FIG. 1, an ignition powder 3 is stored in a cylindrical container 2 thinner than the outer container in the center of the cylindrical outer container 1, and one end thereof is ignited. There has been proposed an inflator having a structure in which an apparatus is installed, a gas generating agent is further disposed around the apparatus, and a filter is disposed outside the apparatus. The gas generating agent at this time is in the form of pellets and is filled around the ignition powder container.
[0015]
In the conventional inflator as described above, the igniter is installed only on one side of the inflator, and has a structure in which the flame is transmitted in the axial direction of the container. The time to reach the maximum gas pressure is delayed, and therefore the shock absorption due to the expansion of the bag may not be fully achieved. In particular, since the passenger-side airbag needs to have a larger capacity than the vehicle structure, such a risk is further increased.
[0016]
U.S. Pat. Nos. 4,017,100 and 3,972,545 disclose two types of filters used to filter the gas that inflates an airbag. U.S. Pat. No. 4,017,100 discloses a gas filter for inflating an air bag, as shown in FIG. This filter 4 is arranged in the housing between the gas generating material 5 and the gas outlet of the housing. The filter includes filter material layers arranged in three adjacent groups. The first group of layers is a screen that forms the support for the other groups of layers. The second group of layers acts as a filter layer and is formed from glass fibers. The third group of layers serves as a filter layer and is formed from steel wool. A support screen is provided on each side of the third group of layers and a metal plate having openings separates the filter layer from the gas generating material.
[0017]
The problem is that the continuous filter material layer reduces porosity in the downstream direction of the gas flow through the filter. This is because it is designed to continuously remove particulate matter from the gas as it moves through the filter into a substantially straight path.
[0018]
Another type of gas filter is disclosed in US Pat. No. 3,972,545. FIG. 3 shows a cross-sectional view. This patent discloses an elongated cylindrical housing 6 that allows gas to flow from a gas generating material through a plurality of filter layers to a gas outlet. These filter layers 7 include a pair of apertured plates that support plastic bags containing PH neutralizing material and fine and coarse wire screens arranged alternately in the axial direction. A third apertured plate separates the screen from the gas exhaust aperture in the housing. The gas travels axially through a substantially straight path filter.
[0019]
[Problems to be solved by the invention]
Currently, a specific problem with airbag devices is to develop an effective and inexpensive filter device that filters solids contained in hot gases. The conventional filter has a small shape retaining strength, expands when subjected to gas pressure, and easily enters the gas passage hole of the inflator and breaks. If the filter breaks, there is a risk that the explosive explosive propellant dust will leak into the bag and damage the bag, impairing the function of the bag or causing occupants to burn.
[0020]
In addition, since the shape retention is small, a structure for reinforcement is required, and the structure of the inflator is complicated. The present invention solves the problem of the filter for an inflator of the conventional airbag system, and improves the trapping property of high-temperature fine particles and prevents the filter from being damaged when subjected to gas pressure. An object of the present invention is to provide an inflator having a filter with improved strength and high shape retention.
[0021]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides an inflator for an airbag provided with a filter for cooling and filtering a high-temperature gas flow generated by combustion, wherein the filter includes one or more metal wires in a multi-layer cylindrical network. A sintered network that is knitted and then integrated by heat treatment such as sintering or welding is used.
[0022]
As a material for the metal wire, an appropriate metal other than stainless steel can be used. Electrical welding is suitable for welding.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the apparatus of the present invention will be described with reference to examples. Note that this example is an example of the present invention and is not limited to this example. As an example of the metal wire used in the present invention, a round wire having a diameter of 0.5 mm or a flat wire having a width of 0.6 mm and a thickness of 0.3 mm is used. As the material of this metal wire, stainless steel wire (SUS304) or mild steel wire (SWRM) is used. Such a metal wire is wound about 400 to 500 layers to form a knitted tubular body 8 having an inner diameter of 45 mm, an outer diameter of 60 mm, and a length of 30 mm as shown in FIG. 4. The mesh winding angle is as shown in FIG. Furthermore, it is about 10 to 30 degrees. The cylindrical body thus made has a weight of 120 to 140 g.
[0024]
The heat treatment is preferably performed at 1200 to 1300 ° C. in the sintering process. Another resistance heat treatment is electrical resistance welding. The wire mesh produced in this way has a structure as shown in FIG. 6, and the explosive and burned gas passes through the wire mesh as shown in FIG.
[0025]
【The invention's effect】
In the apparatus of the present invention, since the entire filter is composed of one or several metal wires knitted, the metal wire has fewer cut portions than a conventional filter made by winding a wire mesh, and as a result, local The number of places where the strength falls is reduced. At the time of explosion, the pressure is dispersed and received by the entire filter with respect to the pressure of the expanded high-pressure gas flow, so the strength is high and accidents such as breakage of the filter are unlikely to occur.
[0026]
Further, since the integrity is high by sintering or welding and the property of maintaining the shape is great, there is no need for another reinforcing body, so that the structure of the inflator device can be simplified.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an example of a filter unit that filters inflation gas in a conventional airbag device.
FIG. 2 is a cross-sectional view of an example of a filter unit that filters inflation gas in a conventional airbag device.
FIG. 3 is a cross-sectional view of an example of a filter unit that filters inflation gas in a conventional airbag device.
FIG. 4 is a perspective view of the outer shape of a filter used in the apparatus of the present invention.
FIG. 5 is an explanatory view of a method for knitting a wire mesh of a filter used in the apparatus of the present invention.
FIG. 6 is an explanatory view of a method for knitting a wire mesh of a filter used in the apparatus of the present invention.
FIG. 7 is an explanatory diagram showing the state in which the expansion gas passes through the wire mesh of the filter used in the apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylindrical outer container 2 Cylindrical container 3 Igniter 4 Filter 5 Gas generating material 6 Cylindrical housing

Claims (1)

In an inflator for an air bag equipped with a filter for cooling and filtering a high-temperature gas flow containing solids generated by combustion, the filter sinters after one or several metal wires are knitted into a multi-layer cylindrical net An inflator for an air bag, characterized by being a net-like body that is integrated and has a large property of maintaining a shape.

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