JPH08230604A - Gas generator - Google Patents

Abstract

PURPOSE: To enable stable and safe use as a gas generator by setting the total volume of a free space in a combustion chamber surrounded by a combustion chamber wall in which a gas blowout hole is arranged in specific times the true volume of a solid gas generating agent before the gas generator is actuated. CONSTITUTION: A stub detonator 3 is thrust by a striking needle 4, and is ignited, and a solid gas generating agent 6 filled in a front combustion chamber 5 is ignited. Combustion gas generated by ignition of the solid gas generating agent 6 flows in a rear combustion chamber 8 after bursting a thin part 7 of the front combustion chamber 5 by its pressure. At this time, the front combustion chamber 5 and the rear combustion chamber 8 are connected to each other, and constitute an integral combustion chamber. The combustion gas is discharged outside through a gas blowout hole 10 bored in a combustion chamber wall 9, and expands a bag continuously connected to the blowout hole 10. A gas generator which can be put to practical use when the volume of a free space in the combustion chambers 5 and 8 is 3 to 20 times the true volume of the solid gas generating agent, can be constituted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a gas generator used for an emergency human body protection device for vehicles, ships, aircraft and leisure sports products, for example, an airbag.

[0002]

2. Description of the Related Art Among airbags mounted on vehicles such as vehicles, in a system utilizing a solid gas generating agent, the solid gas generating agent burns in a combustion chamber under high pressure, and the gas generated thereby burns. The gas is discharged to the outside of the combustion chamber to reduce the pressure by passing through the gas ejection holes provided in the chamber wall, and if necessary, it is guided to the bag after passing through a filter, a coolant or the like to inflate the bag.

In the above-mentioned flow of generated gas, the cross-sectional area of the gas ejection holes arranged at the outlet of the combustion chamber plays an important role in setting the pressure in the combustion chamber. The larger the area of the gas ejection hole, the smaller it becomes, and the larger the amount of gas generated from the solid gas generating agent, the higher it becomes. The gas generator is determined by the conditions on the gas ejection side and the conditions on the gas generation side. Combustion continues at a steady equilibrium pressure.

In the conventional gas generator, the pressure in the combustion chamber rises rapidly after the ignition of the gas generating agent, the gas is discharged while continuing the combustion at a substantially stable equilibrium pressure, and then the gas generating agent is burned. With the end, the pressure drops,
It is supposed to finish the function.

[0005]

However, in the prior art as described above, when a solid gas generating agent having high pressure sensitivity is used, the equilibrium pressure value becomes unstable, and a reproducible performance as a gas generator is exhibited. There is a problem that it becomes difficult to do.

For example, when a solid gas generating agent having high pressure sensitivity is used as the gas generating agent, the area of the ejection hole is narrowed due to combustion residue or the like, or the burning area of the solid gas generating agent is increased or decreased during the combustion of the solid gas generating agent. If there is a slight change, such as a change in the amount of gas generated due to the change in the amount of gas generated from the solid gas generating agent due to a change in the operating temperature, the pressure in the combustion chamber changes significantly As a result, it was difficult to exert stable and steady performance.

A pressure index is generally used to numerically express the pressure sensitivity of a solid gas generating agent such as explosive. This value has been used for a long time to evaluate the stability of the combustion chamber pressure in gas generators that have a mechanism for releasing combustion gas to the external low pressure region, such as solid rockets. When it is about 0.5 or less, it is almost stable, but when it is about 0.7, it becomes considerably unstable, and it is said that it is difficult to exert a substantially stable pressure with a solid gas generating agent of 0.9 or more.

Therefore, when a solid gas generating agent is conventionally used in the combustion chamber of a gas generator, a composition is such that a catalyst is added to the solid gas generating agent in order to minimize the pressure sensitivity of the solid gas generating agent. However, it is generally extremely difficult to reduce the pressure sensitivity because the pressure sensitivity has a property that has a unique value depending on the type of solid gas generating agent. There are many cases where you cannot do it.

In general, many solid gas generating agents such as explosives have high pressure sensitivity, and extremely inexpensive explosives which are often used in gun propellants and the like, and solid gas generating agents having excellent properties of harmlessness or nontoxicity. Even agents are often not available for gas generators due to their high pressure sensitivity.

The present invention has been devised in view of the above-mentioned circumstances. Even if a solid gas generating agent having high pressure sensitivity is used, the inside of the combustion chamber of the gas generator has a special structure. The purpose is to enable stable and safe use as a gas generator.

[0011]

DISCLOSURE OF THE INVENTION The present invention relates to a gas generator for an emergency human body protection apparatus, which uses a solid gas generating agent as a main gas generating source, and has a gas injection hole having a function of controlling a combustion pressure of the solid gas generating agent. The total volume of the free space in the combustion chamber (5, 8) surrounded by the combustion chamber wall (9) in which (10) is arranged is 3 times the true volume of the solid gas generating agent before the operation of the gas generator. The gas generator is characterized by being up to 20 times. In the present invention, the volume of the free space is preferably 3 to 20 times the true volume of the solid gas generating agent, and if it is less than 3 times, it becomes difficult to obtain stable combustion characteristics. Becomes difficult. The shape of the free space can be any shape as long as it is inside the combustion chamber. There is no particular limitation on the solid gas generating agent that can be used in the present invention, for example, smokeless explosives such as propellants or double base propellants, composite propellants using perchlorates, sodium azide-based gas generating agents, non-azide. Although a gas-based gas generating agent, a potassium perchlorate-based gas generating agent or the like can be used, a smokeless explosive having a relatively high pressure sensitivity, a potassium perchlorate-based gas generating agent or the like can be preferably used. The shape of the solid gas generating agent is not particularly limited, and a commonly used one such as a granular shape, a cylindrical shape with holes, a plate shape, or a pellet shape can be used.

[0012]

In the gas generator having the structure of the present invention,
The combustion gas generated by the ignition of the solid gas generating agent flows out of the combustion chamber through the gas ejection holes and inflates the airbag etc., but at the same time, it increases the pressure of the large free space existing inside the combustion chamber. Since it is used, the pressure in the combustion chamber does not rise sharply as compared with the conventional gas generator having a small free space, but gradually increases.

Here, in the present gas generator, by appropriately determining the conditions such as the size of the solid gas generating agent, the burning speed, and the cross-sectional area of the gas injection holes, the solid gas generating agent of the solid gas generating agent is reached before the equilibrium pressure is reached. When the combustion is terminated, the pressure in the combustion chamber has nothing to do with the equilibrium pressure, so that a stable function can be exhibited even if a solid gas generating agent having high pressure sensitivity is used.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. Example 1 FIG. 1 shows the structure of a gas generator according to the present invention, in which a stub detonator 3 held by an adapter 1 and a holder 2 is pierced by a firing pin 4 from the outside,
The detonator 3 is ignited, and further the solid gas generating agent 6 loaded inside the front combustion chamber 5 is ignited. Even if this ignition part is implemented by using another system such as an electric detonator, the effect is exactly the same.

The combustion gas generated by the ignition of the solid gas generating agent ruptures the thin portion 7 at the end of the front combustion chamber by the pressure thereof, and then flows into the rear combustion chamber 8. At this time, the front combustion chamber and the rear combustion chamber are connected to form an integral combustion chamber, in which the solid gas generating agent generates combustion gas to increase the pressure in the combustion chamber. On the other hand, the combustion gas is discharged to the outside through a gas ejection hole 10 formed in a part of the combustion chamber wall 9 to inflate a bag arranged in contact with the ejection hole. In this embodiment, the mesh filter 12 is attached to the inside of the combustion chamber wall in order to prevent the solid gas generating agent from being discharged to the outside through the gas ejection holes.

In this embodiment, in order to improve the ignitability of the solid gas generating agent, the solid gas generating agent is previously loaded only in the front combustion chamber having a small volume, and the front portion is ignited after the solid gas generating agent is ignited. I tried to connect the combustion chamber and the rear combustion chamber,
When there is no risk of a problem with the ignitability of the solid gas generating agent, it is possible to use an integral combustion chamber from the beginning.

Example 2 In order to confirm the effective range of the operation described above, the function of the gas generator was investigated using the experimental apparatus shown in FIG. In this device, the combustion chamber wall 9 is divided into three pieces 9a, 9b, and 9c so that the free space of the combustion chamber can be arbitrarily changed, and the length of the combustion chamber wall 9b is changed to confirm the performance. I was able to do it. In addition, in order to detect the pressure of the combustion chamber, a pressure sensor 13 was attached to the combustion chamber wall 9c for measurement.

In the present embodiment, as the solid gas generating agent 6, a granular smokeless explosive used for propellants such as guns was used. The pressure index of the smokeless powder was about 1, and the dose was 16 g.
In this case, the bulk specific gravity of the solid gas generating agent is about 0.8, but the true specific gravity is about 1.6, so the true volume of the solid gas generating agent is 10 cc. Further, since the internal volume of the front combustion chamber 5 is about 25 cc, the free space of only the front combustion chamber is the difference of 15 cc. The free space existing in the combustion chamber defined in the present invention is the free space of the combustion chamber including the front combustion chamber and the rear combustion chamber, and therefore 15
It corresponds to the volume of cc plus the volume of the rear combustion chamber.

The inner diameter of the rear combustion chamber 8 was 30 mm, and the free space volume of the entire combustion chamber was tested for 30, 40, 55, 90 and 180 cc by changing the chamber length. Under this condition, the pressure in the combustion chamber is 25
The area of the gas ejection holes was adjusted so as to be 0 to 350 kgf / cm ² . As a result, the area of the gas ejection hole is reduced to 1
When changing by 0%, the fluctuation rate of the maximum combustion chamber pressure is about 20, 15 for each value of the free space volume,
It was 8, 2, 1%.

From this example, it is understood that the larger the volume of the free space, the smaller the change in the maximum combustion chamber pressure with respect to the change in the area of the gas ejection holes and the more stable. Various fluctuation factors of the combustion chamber pressure are usually estimated to be within 5% at maximum when converted into changes in the cross-sectional area of the gas ejection holes. Therefore, if the free space volume is 30 cc or more, the fluctuation rate of the maximum combustion chamber pressure is high. Is within 10%, and can be said to have an acceptable level of stability as a product. In this case, since the true volume of the solid gas generating agent is 10 cc, the volume of the free space is three times the true volume of the solid gas generating agent.

Since the mechanism of the present invention is a correlation between the volume of gas generation and the volume of free space, if the volume of gas generation increases due to an increase in the amount of the solid gas generating agent, the volume of free space corresponding to the ratio. Also needs to be increased. Therefore, from this example, if the volume of the free space in the combustion chamber is about 3 to 20 times the true volume of the solid gas generating agent, a gas generator that can be put to practical use can be configured. In this embodiment, smokeless explosive was used as an example of the solid gas generating agent having high pressure sensitivity, but other solid gas generating agents or the like may be used. In carrying out the experiment of this example, an experiment similar to the above was used as a preliminary experiment in the case where the volume of the free space was 1 and 2 times the true volume of the solid gas generating agent. With double, the adapter part of the gas generator was blown away, and with double, the adapter part and its mounting part were greatly deformed. This shows the importance of choosing an appropriate free space volume.

Embodiment 3 FIG. 3 shows the shape of the front combustion chamber 5 in the embodiment of FIG.
It is arranged on the central axis of the combustion chamber in place of the inner cylinder 14 having 5, and the hole is closed with a film 16 made of metal or plastic. This membrane is installed to prevent moisture and improve ignitability of the solid gas generating agent.After the solid gas generating agent ignites, it is automatically destroyed by the increase in pressure, and the solid gas generating agent burns on the outer periphery. It burns in a combustion chamber including the chamber to generate combustion gas. Although this structure is different from the structure shown in FIG. 1 in a plurality of points, it has exactly the same functions in order to utilize the effect of the present invention.

Embodiments 4 and 5 FIGS. 4 and 5 are modifications of the structure of the rear combustion chamber in the embodiment of FIG. 4 shows the rear combustion chamber in FIG. 1 elongated and elongated, and FIG. 5 shows the rear combustion chamber in FIG. 1 elongated in the middle, further bent, and thickened at the tip.

The effects of the structure shown in FIGS. 4 and 5 are as follows. In the gas generator of the present invention, it is important that a free space having a certain size exists in the combustion chamber, and the free space may have any shape.
Therefore, in the case where the portion to which the airbag is attached does not have a sufficient volume margin, such as the handle portion, a portion of the free space is deformed as shown in FIGS. Can be placed in parts. Further, at this time, the position of the gas ejection hole can be freely changed, and a convenient arrangement for attaching the airbag can be taken.

[0025]

According to the gas generator of the present invention, a solid gas generating agent having a high pressure sensitivity can be stably and safely burned in the gas generator, so that it has a high pressure sensitivity and cannot be used conventionally. An inexpensive solid gas generating agent such as smokeless powder or a non-toxic and harmless solid gas generating agent can be easily applied to a gas generator for an emergency human body protection device such as an airbag for frontal collision or side collision.

[0026]

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a gas generator of the present invention.

[0027]

FIG. 2 is an experimental apparatus used to evaluate the function of the gas generator of the present invention.

[0028]

FIG. 3 is an example in which the front combustion chamber of the gas generator in Example 1 is replaced with a thin inner cylinder.

[0029]

FIG. 4 is an example in which the shape of the combustion chamber wall of the gas generator in Example 1 is changed.

[0030]

FIG. 5 is an example in which the shape of the combustion chamber wall of the gas generator and the gas injection hole attachment position are changed in the first embodiment.

[0031]

[Explanation of symbols]

1: Adapter 2: Holder 3: Stub detonator 4: Firing pin 5: Front combustion chamber 6: Solid gas generating agent 7: Thin wall portion 8:
Rear combustion chamber 9, 9a, 9b, 9c: Combustion chamber wall 10: Gas ejection hole 11: Front combustion chamber wall 12: Filter 13: Pressure sensor 14: Inner cylinder 15: Hole 16: Membrane

Claims (1)

[Claims] 1. A gas generator for an emergency human body protection apparatus, which uses a solid gas generating agent as a main gas generating source, in which a gas injection hole (10) having a function of controlling a combustion pressure of the solid gas generating agent is arranged. The total volume of the free space in the combustion chamber (5, 8) surrounded by the chamber wall (9) is 3 to 20 times the true volume of the solid gas generating agent before the operation of the gas generator. And a gas generator.