JP2006168669A - Gas generator for airbag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas generator for an air bag with good occupant restraining performance.
SOLUTION: A combustion chamber 28 in which a gas generating agent molded body 6 serving as a gas source which is an inflation medium of an airbag is accommodated, and a gas connected to the combustion chamber and used for discharging gas into the airbag. A gas generator for an air bag having two ignition means 4, wherein the gas generant molded body is a mixture in which two types of molded bodies having different surface areas (surface areas per unit number of moles generated) are uniformly dispersed and mixed. The ratio (S ₁ : S ₂ ) between the total surface area S ₁ of the gas generant molded body having a large surface area and the total surface area S ₂ of the gas generant molded body having a small surface area is from 1.01 to 1.3. A gas generator for an air bag, which is 1:
[Selection] Figure 3

Description

  The present invention relates to a gas generator for an air bag.

  An airbag of an airbag system that protects an occupant from an impact is made by sewing one piece of cloth, so that the inflation gas discharged into the airbag may leak from the seam.

  The airbag for the driver's seat and the passenger's seat has a vent hole for venting to give cushioning when the occupant comes into contact with the airbag. The gas is exhausted excessively from the vent hole, and the bottomed state (the air bag is crushed by contact with the occupant and the performance of receiving the occupant cannot be sufficiently exerted, and the occupant hits the vehicle structure to which the air bag is attached In such a situation, the occupant's restraining performance may be reduced.

  Thus, when gas leaks from the seam or vent hole (when gas escapes), it is difficult to maintain sufficient restraint performance without replenishing the gas. Further, even when gas cannot escape, depending on the gas supply state, it may be difficult to obtain sufficient restraint performance for a passenger with a large physique.

Patent Document 1 discloses a gas generator that generates gas at different timings, and Patent Document 2 discloses a gas generator having a first explosive that generates gas in 50 msec and a second explosive that generates gas in several seconds. A gas generator is disclosed in which a solid gas 10 is burned quickly to generate gas and then a pressurized gas is gradually generated.
JP 2003-81050 A JP2003-220925A USP 6,237,950

  In patent documents 1-3, there is no indication about solving the problem resulting from the gas which leaks from the seam of an airbag, and the gas which leaked from the vent hole.

  An object of the present invention is to prevent a reduction in the restraining performance of an occupant due to gas leaking from an inflated airbag during operation of the airbag system.

As a means for solving the problems, the present invention
A gas generator for an air bag having a gas source that is an inflation medium of the air bag and one ignition means used for discharging the gas into the air bag;
When the output performance of the gas generator for an air bag is evaluated by a curve X (FIG. 1) showing changes in time (horizontal axis) and 60 L tank pressure (vertical axis) obtained by a 60 L tank test (20 ° C.),
The output performance of the gas generator for an air bag is the same or approximate angle from the start of the tank internal pressure rise (P ₀ ) until the maximum pressure (P _max ) from the start of the tank internal pressure rise (P ₀ ). For an airbag, which is indicated by a curve X that rises at a ₁ ) and reaches the maximum pressure after rising while gradually decreasing the angle (a 2, a 3, a 4, etc. in FIG. 1). A gas generator is provided.

  A curve X (tank pressure curve) obtained by the 60 L tank test also shows a change in the output of the gas generator, and is obtained according to Example 1 and Comparative Example 1.

When the tank pressure curve gradually rises at substantially the same angle (for example, b ₁ = b ₂ = b ₃ = b ₄ ) with respect to the horizontal line in the graph as shown by the curve Y in FIG. 1, the airbag is also constant. It will expand at a speed. However, if gas is generated at a constant rate until the maximum pressure (maximum output = P _max ) is reached, gas generation ends after the maximum pressure (maximum output). Supply cannot be expected.

However, in the operating state indicated by the curve X in FIG. 1, the tank pressure curve exhibits a certain output at an angle a ₁ that is the same or approximate from the start of operation (point A in FIG. 1), and the angle (a ₂ , a _3, raised while gradually reducing _{a 4,} etc.). For this reason, the internal pressure of the airbag is increased during the angles a _{1 to} a ₂ , and the airbag is ready to restrain the occupant. Thereafter, the gas is gradually supplied even after the gas leaks with the exhaust from the vent hole or the contact of the occupant (angles a _{4 to} P _max in FIG. 1). Therefore, since the gas leaked from the airbag can be supplemented, there is no bottomed state.

In addition, at the point A of FIG. 1, the maximum output is not exhibited. This is because, in order to provide a certain degree of cushioning even when the occupant comes into contact with the airbag at this point A, there is a margin in the output, and the occupant's protection performance is subsequently generated. It is maintained sufficiently by the addition of gas (angle a ₃ or later) that. That is, in the gas generator of the present invention, it is preferable that the inflection point indicated by the point A appears at a time earlier than the maximum value P _max of the output curve of the conventional gas generator.

The gas generator of the present invention can be used for an airbag system for a driver's seat and an airbag system for a passenger's seat. In the case of an airbag system for a driver's seat, the timing at which an occupant contacts the airbag is Since the current application to the igniter (at the horizontal axis 0 in FIG. 1) is about 40 msec, the inflection point A is preferably in the range of 20 to 50 msec, and is in the range of 30 to 45 msec. It is more preferable. And in the pressure curve in the tank shown in FIG. 1, it is preferable that the output after 40 msec from the current application to the igniter is 60 to 90% of the maximum output (P _max ).

On the other hand, in the case of an airbag system for a passenger seat, the occupant comes into contact with the airbag about 45 msec after the current is applied to the igniter. Therefore, the inflection point indicated by point A in FIG. It is preferably present at ˜60 msec, more preferably at 35-50 msec. And it is preferable that the output in 45 msec after an electric current application is 60 to 90% of the maximum output ( _Pmax ).

  If the airbag is fully inflated from the initial stage of deployment (when the occupant starts to contact the airbag), the bottomed state does not occur, but the occupant may be affected when the occupant contacts the airbag. There is a problem in that the reaction pressure received by the occupant may increase because the inflation pressure of the airbag is excessive.

  On the other hand, with the gas generating agent at a constant gas generation rate (curve Y in FIG. 1), if the occupant restraint posture is not adjusted at the initial stage of the airbag deployment, and the bottom of the airbag occurs, the state is improved. There is a problem that it is difficult to reset the pressure inside the airbag.

  In other words, the gas generator for an air bag according to the present invention is the greatest feature that the conventional gas generator does not have.

The present invention provides other means for solving the problems,
A combustion chamber in which a gas generant molded body serving as a gas source that is an inflation medium of the airbag is housed; and one ignition means connected to the combustion chamber and used to discharge gas into the airbag. A gas generator for an air bag,
The gas generant molded product is a mixture in which two types of molded products having different surface areas (surface area per unit generated mole number) are uniformly dispersed and mixed,
The ratio (S ₁ : S ₂ ) of the total surface area S ₁ of the gas generant molded body having a large surface area to the total surface area S ₂ of the gas generant molded body having a small surface area is from 1.01: 1 to 1.3: 1 is a gas generator for an air bag.

  In the present invention, when referring to the surface area of the gas generant molded article, all means "surface area per unit number of moles generated". “Surface area per unit number of moles generated” means the surface area of a gas generant molded product that generates 1 mole of gas.

  The gas generant molded body having a large surface area and the gas generant molded body having a small surface area are uniformly dispersed and mixed. Therefore, when the gas generator is operated, combustion is simultaneously started regardless of the difference in surface area.

  As the combustion proceeds, the gas generating agent molded body having a larger surface area completes the combustion earlier, and the gas generating agent molded body having the smaller surface area completes with a delay.

Since it is such a combustion state, at the time of a combustion start, all the gas generating agent molded objects start combustion simultaneously. This combustion process corresponds to the angles a _{1 to} a ₂ in the tank pressure curve of FIG.

  However, after that, there is a difference in the combustion state between the large and small gas generant compacts, and the combustion of the gas generant having a large surface area is completed quickly (a large amount of gas is generated). Combustion is completed late (small amount of gas generated). As combustion progresses in this way, the gas generant molded body with a large surface area burns out first, so the amount of gas generated as a whole decreases, and the gas generant molded body with a small surface area with a large amount of unburned parts becomes smaller. Only the amount of gas generated from the direction.

For this reason, in the one tank pressure curve in the figure, the influence of the gas generated by the combustion of the gas generating agent having a large surface area is large around the angles a _{2 to} a ₃ , and after the angles a _{3 to} a ₄ The influence of the gas generated by the combustion of the gas generating agent compact with a small surface area is large.

  In this way, by combining the gas generating agent compacts having a large surface area and a small surface area so as to have a specific total surface area, the amount of gas per unit time generated by combustion can be controlled, and the airbag can be controlled at a predetermined pressure. Since the gas leaked from the airbag can be replenished, the restraining performance of the occupant is enhanced.

  The present invention provides the airbag according to claim 2, wherein the gas generating agent molded body contains a guanidine compound as a fuel component and basic copper nitrate as an oxidant as another means for solving the problem. A gas generator is provided.

  The present invention provides, as another means for solving the problems, a gas generator for an air bag according to claim 2 or 3, wherein the gas generant molded article has a through hole.

  By providing a through-hole, it is easy to adjust the surface area without changing the overall size, and the combustion surface area is unlikely to change even when combustion progresses, so it is designed from the start to the end of combustion. The normal gas generation state can be maintained. There may be one through hole, or two or more.

  According to the gas generator for an air bag of the present invention, stable occupant restraint performance can be maintained regardless of the occupant's physique (weight).

  The airbag gas generator of the present invention is not particularly limited, and a known structure can be used, for example, the same as that shown in FIG. 1 of JP-A-10-95302 as shown in FIG. (However, the display of the gas generator molded bodies 6a and 6b is excluded) can be used.

  The combustion chamber 20 is filled with solid gas generating agents (gas generating agent molded bodies) 6a and 6b in a uniformly mixed and dispersed state. Each of the gas generant molded bodies 6a and 6b has one through-hole in the length direction, and has the same composition as each other, but has a different surface area per piece.

The ratio (S ₁ : S ₂ ) of the total surface area S _{1 of the} gas generating agent molded body 6a having a large surface area to the total surface area S ₂ of the gas generating agent molded body 6b having a small surface area is 1.01: 1-1. 3: 1.

  The composition of the gas generating agent molded bodies 6a and 6b is not particularly limited, and a known gas generating agent described in JP-A No. 2004-155645 can be used, but the guanidine compound is used as a fuel component in an amount of 5 to 60% by mass. It is preferable to contain 10 to 55% by mass, 95 to 40% by mass of basic copper nitrate as an oxidizing agent, and preferably 90 to 45% by mass.

  As the guanidine compound, guanidine nitrate (guanidine nitrate), aminoguanidine nitrate, nitroguanidine, triaminoguanidine nitrate and the like are preferable.

  The gas generant molded bodies 6a and 6b can contain known binders and various additives described in JP-A No. 2004-155645 as necessary, if necessary. As the composition and composition ratio at that time, those disclosed in the above publication can be used.

  The gas generating agent molded bodies 6a and 6b may have the same composition (containing component), composition ratio (content component ratio), filling amount (total mass), shape, etc., as long as the problems of the present invention can be solved. These may be different, but those having the same composition and the same composition ratio but different filling amounts and surface areas are preferred.

  Next, the operation of the airbag system incorporating the gas generator for an airbag according to the present invention will be described with reference to FIGS. FIG. 3 shows a gas generator for use in a driver airbag system, and FIG. 1 shows an output curve at that time.

  When the vehicle collides, the igniter 4 operates to ignite and burn the transfer charge 5. The flame generated by the ignition combustion of the charge transfer agent 5 breaks the aluminum tape 52 'and flows into the combustion chamber 20 from the through hole 54, and ignites and burns the gas generating agent molded bodies 6a and 6b.

  The gas generated by the ignition combustion of the gas generant molded bodies 6a and 6b is cooled by passing through the coolant / filter 7, and after the combustion residue is filtered, the aluminum tape 52 is broken and discharged from the gas discharge port 11. Inflate the airbag.

Since the gas generating agent molded body 6a (large surface area) and the gas generating agent molded body 6b (small surface area) are filled in a uniformly dispersed and mixed state, ignition combustion starts simultaneously and gas is generated. The tank pressure curve at this time is in the range of angles a _{1 to} a ₂ in FIG. 1, and the airbag is inflated and deployed.

If the combustion continues further, the gas generating agent molded body 6a (large surface area) is combusted earlier than the gas generating agent molded body 6b (small surface area), so in the tank pressure curve of FIG. until angle a ₂ to a ₃ around, the larger the influence of the gas generated by combustion of the gas generating agent molded body 6a (surface area is large).

Thereafter, if the combustion continues further, the gas generant molded body 6a (large surface area) will burn out first, but the gas generant molded body 6b (small surface area) with much unburned will continue to burn. in one of the tank curve, from the angle a ₃ to a ₄ and later to Pmax, the larger the influence of the gas generated by combustion of the gas generating agent molded article 6b (surface area small).

  Thus, as is apparent from the tank pressure curve of FIG. 1, after the tank pressure curve (inner pressure of the airbag) rises to point A due to the specific combustion state due to the difference in surface area of the gas generant molded bodies 6a and 6b. Also gradually increase while decreasing the angle. For this reason, in the event of a vehicle collision, after the air bag is inflated instantaneously to a predetermined inflating pressure, gas leaks from the seam of the air bag or excessive gas escapes from the vent hole due to contact with the passenger. However, since the gas is replenished, the predetermined inflation pressure can be maintained and the restraint performance of the occupant can be maintained.

Example 1
A well-known 60 L tank combustion test (for example, a test method disclosed in paragraph No. 98 of Japanese Patent Laid-Open No. 2001-97176) was performed using the gas generator of FIG. FIG. 2 shows a tank pressure curve.

(Structure of gas generator)
・ Gas outlet: Diameter 2mm × 21 ・ Coolant filter mass: Approximately 50g
・ Ignition device (igniting agent): ZPP (zirconium / potassium perchlorate) 150mg
・ Explosive: 1.45 g of boron nitrate
(Gas generant molded product)
-Gas generant molded product 6a (single-hole cylindrical shape)
Example 32 of JP-A No. 2004-155645 outer diameter 4.5 mm × inner diameter 1.2 mm × length 14 mm [29.6 g, total surface area (S ₁ ) 213.7 cm ² ]
-Gas generant molded product 6b (single-hole cylindrical shape)
Example 32 of JP-A-2004-155645 outer diameter 1.8 mm × inner diameter 0.7 mm × length 11.9 mm [12.5 g, total surface area (S ₂ ) 249.63 cm ² ]
-Surface area per unit number of moles of gas generant molded body 6a: Surface area per unit number of moles of gas generant molded body 6b = 1: 2.5
S ₁ : S ₂ = 1: 1.17
Comparative Example 1
Using the same gas generator as in Example 1, as a gas generant molded body, a single-hole cylindrical shape, outer diameter 4.5 mm × inner diameter 1.2 mm × length 14 mm (39.4 g, total surface area 313.5 cm ² ) A similar test was conducted using The results are shown in FIG.

  As is clear from FIG. 2, in the curve X (Example 1), the output up to 20 msec rose earlier than the curve Y (Comparative Example 1), and then gradually increased. This indicates that the gas is gradually discharged even after 30 msec. On the other hand, the curve Y (Comparative Example 1) showed a similar rising curve up to around 50 msec.

  Therefore, in the curve X (Example 1), even if the air bag is quickly inflated and gas is leaked due to contact between the occupant and the air bag after that, sufficient gas can be replenished. It does not drop and does not become bottomed. On the other hand, in curve Y (Comparative Example 1), there is little change in the gas supply rate to the airbag. Therefore, if the gas leaks when the occupant comes into contact with the airbag, the leaked gas is sufficiently replenished. Since it is not performed, it may become a bottomed state and may not be able to protect passengers.

The graph of the tank pressure curve which shows the output performance of the gas generator for airbags of this invention. The graph of the tank pressure curve which shows the output performance of the gas generator for airbags of Example 1 and Comparative Example 1. FIG. The axial sectional view of the gas generator for airbags.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diffuser shell 2 Closure shell 3 Housing 4 Igniter 5 Transfer agent 6 Solid gas generating agent 7 Coolant filter 8 Outer peripheral wall 9 Gap 10 Peripheral wall part 11 Gas exhaust port 12 Circular part 13 Protruding circular part 14 Axial bending part 15 Central hole 16 Central cylinder member 17 End face of one end side of central cylinder member 18 End face of bent part 19 Flange part 20 Flange part 21 Laser welding 22 Electron beam welding 23 Ignition means accommodating chamber 24 Holding member for igniter 25 Flange part 26 Cavity part 27 Caulking part 28 Combustion chamber 29 Outer layer 30 Circular portion 31 Inclined portion 32 Plate member 33 Plate member 34 Peripheral wall portion 35 Central hole 36 Circular portion 37 Inner surface of housing 38 Coolant / filter end surface 39 Central hole 40 Upper end opening 41 Inner peripheral surface of coolant / filter 42 Lower end opening 43 Opposite Opposite end face 44 Laser welding 47 Peripheral wall part 49 Step part 50 Circular part 51 Peripheral wall part 52, 52 'Aluminum tape 53 Transfer charge container 54 Through hole

Claims (4)

A gas generator for an air bag having a gas source that is an inflation medium of the air bag and one ignition means used for discharging the gas into the air bag;
When the output performance of the gas generator for an air bag is evaluated by a curve X (FIG. 1) showing changes in time (horizontal axis) and 60 L tank pressure (vertical axis) obtained by a 60 L tank test (20 ° C.),
The output performance of the gas generator for an air bag is the same or approximate angle from the start of the tank internal pressure rise (P ₀ ) until the maximum pressure (P _max ) from the start of the tank internal pressure rise (P ₀ ). For an airbag, which is indicated by a curve X that rises at a ₁ ) and reaches the maximum pressure after rising while gradually decreasing the angle (a 2, a 3, a 4, etc. in FIG. 1). Gas generator. A combustion chamber in which a gas generant molded body serving as a gas source that is an inflation medium of the airbag is housed; and one ignition means connected to the combustion chamber and used to discharge gas into the airbag. A gas generator for an air bag,
The gas generant molded product is a mixture in which two types of molded products having different surface areas (surface area per unit generated mole number) are uniformly dispersed and mixed,
The ratio (S ₁ : S ₂ ) of the total surface area S ₁ of the gas generant molded body having a large surface area to the total surface area S ₂ of the gas generant molded body having a small surface area is from 1.01: 1 to 1.3: 1 is a gas generator for an air bag.   The gas generator for an air bag according to claim 2, wherein the gas generant molded article contains a guanidine compound as a fuel component and basic copper nitrate as an oxidant. The gas generator for airbags of Claim 2 or 3 whose gas generating agent molded object has a through-hole.

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