Gas generating compositions for air bag

• US 6,562,161 B1
• Filed: 04/29/1997
• Issued: 05/13/2003
• Est. Priority Date: 03/24/1997
• Status: Expired due to Term

• Current Assignee: Daicel Chemical Industries Limited
• Original Assignee: Daicel Chemical Industries Limited
• Inventors: Ueda, Masayuki, Yamato, Yo, Takahori, Takeshi, Oda, Shingo
• Primary Examiner(s): Carone, Michael J.
• Assistant Examiner(s): FELTON, AILEEN BAKER
• Application Number:
  US08/848,600
• Time in Patent Office: 2,205 Days
• Field of Search: 149/36, 149/45, 149/48, 149/109.2, 149/2, 149/19.4, 149/19.9, 280/241
• US Class Current: 149/45
• CPC Class Codes: B60R 21/2644 using only solid reacting substances, e.g. pellets, powder
• CPC Class Codes: C06B 45/00 Compositions or products which are defined by structure or arrangement of component of product explosive charges of particular form or shape F42B1/00, F42B3/00
• CPC Class Codes: C06D 5/06 by reaction of two or more solids

Abstract

Gas generating pellets for an air bag system causes the initial inflating speed of the air bag to be increased at a reduced rate to prevent a passenger from being injured due to vigorous inflation of the air bag in the initial period, while maintaining sufficient ability to restrict the passenger after 35 to 50 milliseconds from the start of the inflation.

Combustion of the gas generating pellets for an air bag system are controlled such that in a tank test conducted with respect to a gas generator using the pellets, where a desired maximum tank pressure is P (kPa), and a period of time from the start of rising of the tank pressure to the time when the maximum tank pressure P (kPa) is reached is T milliseconds, the tank pressure measured after 0.25×T milliseconds is not higher than 0.20×P (kPa), and the tank pressure measured after 0.80×T milliseconds is not lower than 0.70×P (kPa). In particular, the gas generating pellets may be formed of a non-azide gas generating composition, and each pellet may be formed with a length of L (mm) and a hole having an inside diameter d(mm) of 0.2 to 1.5 (mm), such that the ratio L/d is 3.0 or larger.

Claims

1. A shape of a gas generating pellet used for an air bag gas generator, comprising:

a main body having at least one hole provided therein, an inner diameter d of said at least one hole in a range of 0.2-1.5 mm, and a ratio L/d of a length L of said main body and said inner diameter d being 3 or greater to control an inner surface area of said hole that is initially ignited, relative to an entire inner surface area of said hole,

wherein said gas generating pellet includes a non-azide gas generating composition, and

wherein said non-azide gas generating composition includes

(a) about 25-56% by weight of nitroguanidine,

(b) about 40-65% by weight of an oxidizing agent,

(c) about 1-20% by weight of a slag-forming agent, and

(d) about 3-12% by weight of a binder.

2. The shape of a gas generating pellet according to claim 1, wherein said non-azide gas generating composition includes

(a) about 30-40% by weight of nitroguanidine,

(b) about 40-65% by weight of strontium nitrate,

(c) about 3-10% by weight of acid clay or silica, and

(d) about 4-12% by weight of sodium salt of carboxymethyl cellulose.

3. A gas generator for an air bag system, comprising:

a housing having a combustion chamber and at least one diffuser port; and

gas generating pellets provided in said housing for generating combustion gas, wherein each pellet includes,

a main body having at least one hole provided therein, an inside diameter d of said at least one hole being in a range of 0.2-1.5 mm, and a ratio L/d of a length L of said main body and the inner diameter d being 3 or larger to control an inner surface area of said hole that is initially ignited, relative to an entire inner surface area of said hole, and prevent the airbag from applying excessive impact to a passenger upon inflation of the air bag,

wherein said combustion chamber contains only said gas generating pellets.

4. The gas generator for an air bag system according to claim 3, wherein the gas generator includes

igniting means provided within said housing and igniting said gas generating means to generate combustion gas, and

filter means for cooling said combustion gas and entrapping combustion residues, an outer periphery of said filter means being opposed to an inner surface of an outer circumferential wall of said housing with a space formed therebetween.

5. The gas generator according to claim 3, wherein said main body has an elongated shape.

6. The gas generator according to claim 3, wherein said at least one hole is provided in said main body in a longitudinal direction of said main body.

7. The gas generator according to claim 3, wherein said ratio L/d is set between 3 and 10.

8. A method of attaining a reduced initial inflation speed of an air bag that is inflated by combustion gas generated from a gas generator, comprising:

providing a combustion chamber inside the gas generator;

providing gas generating pellets, each pellet provided with a hole having an inner diameter d of 0.2-1.5 mm, and a ratio L/d of a length L of the main body and the inner diameter d being 3 or greater to control an inner surface area of said hole that is initially ignited, relative to an entire inner surface area of said hole, and prevent the air bag from applying excessive impact to a passenger upon inflation of the air bag; and

providing the combustion chamber only with said gas generating pellets; and

igniting and combusting said gas generating pellets, such that in a 60 liter sealed tank combustion test, in which the gas generator containing said pellets is placed in a 60 liter tank and the gas generator generates a maximum tank pressure of P (kPa) at T milliseconds after an initial rise in the tank pressure due to combustion of said pellets, a pressure at 0.25×

T milliseconds after initial rise in the tank pressure is not higher than 0.25×

P (kPa), and a pressure at 0.8×

T milliseconds after the initial rise is not lower than 0.70×

P (kPa).

9. The gas generator for an air bag system according to claim 8, wherein the maximum tank pressure P (kPa) is in the range of 110 to 220 (kPa), and the time T is in the range of 30 to 50 milliseconds.

10. The method according to claim 8, wherein said main body has an elongated shape.

11. The method according to claim 8, wherein said at least one hole is provided in said main body in a longitudinal direction of said main body.

12. The method, according to claim 8, wherein said step for providing gas generating pellets includes the step of setting said ratio L/d between 3 and 10.

13. Gas generating pellets for an air bag system, comprising:

a main body; and

at least one hole provided in said main body,

wherein in a 60 liter sealed tank combustion test, where a gas generator containing said pellets is placed in a 60 liter tank, and the gas generator generates a maximum tank pressure of P (kPa) at T milliseconds after an initial rise in the tank pressure due to combustion of said pellets, a pressure at 0.2×

T milliseconds after initial rise in the tank pressure is not higher than 0.2×

P (kPa), and a pressure at 0.80×

T milliseconds after the initial rise is not lower than 0.70×

P (kPa),

wherein the pellets include a non-azide gas generating composition, said non-azide gas generating composition comprises

(a) about 25-56% by weight of nitroguanidine,

(b) about 40-65% by weight of an oxidizing agent,

(c) about 1-20% by weight of a slag-forming agent, and

(d) about 3-12% by weight of a binder, and

wherein said non-azide gas generating composition comprises

(a) about 30-40% by weight of nitroguanidine,

(b) about 40-65% by weight of strontium nitrate,

(c) about 3-10% by weight of acid clay or silica, and

(d) about 4-12% by weight of sodium salt of carboxymethyl cellulose.

14. A gas generating pellet for an air bag gas generator, comprising:

a main body having at least one hole provided therein, an inner diameter d of said at least one hole being in a range of 0.2-1.5 mm, and a ratio L/d of a length L of said main body and said inner diameter d being 3 or greater,

wherein said main body includes,

about 25-56% by weight of nitrogen containing compound, and

about 40-65% by weight of an oxidizing agent including a metal element,

wherein, in a 60 liter sealed tank combustion test, where the gas generator having a combustion chamber, in which only a plurality of main bodies are provided, is placed in a 60 litter tank, and the combustion of the main body generates a maximum tank pressure of P (pKa) to T milliseconds after detection of an initial rise in the tank pressure, a pressure at 0.25×

T milliseconds after the detection of the initial rise in the tank pressure is not higher than 0.25×

P (kPa), and a pressure at 0.80×

T milliseconds after the detection of the initial rise is not lower than 0.70×

P (kPa).

15. The gas generating pellet according to claim 14, wherein said main body has a length L of 1.5 to 30 mm, an outside diameter D of 2.4 to 5.0 mm, and said hole has an inside diameter d of 0.4 to 1.0 mm.

16. The gas generating pellet according to claim 14, wherein said main body further includes,

about 1-20% by weight of a slag-forming agent, and

about 3-12% by weight of a binder.

17. The gas generating pellet according to claim 14, wherein said at least one hole penetrates said main body.

18. The gas generating pellet according to claim 14, wherein said main body has an elongated cylindrical shape.

19. The gas generating pellet according to claim 14, wherein said at least one hole is provided in said main body in a longitudinal direction of said main body.

20. The gas generating pellet according to claim 14, wherein said ratio L/d is set between 3 and 10.

21. The gas generating pellet for an air bag gas generator, comprising:

a main body having at least one hole provided therein, an inner diameter d of said at least one hole being in a range of 0.2-1.5 mm, and a ratio L/d of a length L of said main body and said inner diameter d being 3 or greater,

wherein said main body includes,

about 25-56% by weight of nitrogen containing compound, and

about 40-65% by weight of an oxidizing agent including a metal element, wherein said main body includes

about 30-40% by weight of nitroguanidine as said nitrogen containing compound,

about 40-65% by weight of strontium nitrate as said oxidizing agent,

about 3-10% by weight of acid clay or silica as a slag-forming agent, and

about 4-12% by weight of sodium salt of carboxymethyl cellulose as a binder.

22. A gas generating pellet for an air bag gas generator, comprising:

a main body having at least one hole provided therein, an inner diameter d of said at least one hole being in a range of 0.2-1.5 mm, and a ratio L/d of a length L of said main body and said inner diameter d being 3 or greater,

wherein said main body includes nitrogen containing compound and an oxidizing agent including a metal element, and

wherein, in a 60 liter sealed tank combustion test, where the gas generator having a combustion chamber, in which only a plurality of main bodies are provided, is placed in a 60 litter tank, and the combustion of the main body generates a maximum tank pressure of P (pKa) to T milliseconds after detection of an initial rise in the tank pressure, a pressure at 0.25×

T milliseconds after the detection of the initial rise in the tank pressure is not higher than 0.25×

P (kPa), and a pressure at 0.80×

T milliseconds after the detection of the initial rise is not lower than 0.70×

P (kPa).

23. The gas generating pellet according to claim 22, wherein said main body has a length L of 1.5 to 30 mm, an outside diameter D of 2.4 to 5.0 mm, and said hole has an inside diameter d of 0.4 to 1.0 mm.

24. The gas generating pellet according to claim 22, wherein said main body includes,

a slag-forming agent and a binder.

25. The gas generating pellet according to claim 22, wherein said at least one hole penetrates said main body.

26. The gas generating pellet according to claim 22, wherein said main body has an elongated cylindrical shape.

27. The gas generating pellet according to claim 22, wherein said at least one hole is provided in said main body in a longitudinal direction of said main body.

28. The gas generating pellet according to claim 22, wherein said ratio L/d is set between 3 and 10.