Gas generator for multi-stage air bag

• US 7,055,855 B2
• Filed: 06/08/2001
• Issued: 06/06/2006
• Est. Priority Date: 06/12/2000
• Status: Expired due to Term

• Current Assignee: Daicel Chemical Industries Limited (Daicel Corporation)
• Original Assignee: Daicel Chemical Industries Limited (Daicel Corporation)
• Inventors: Katsuda, Nobuyuki, Nakashima, Yoshihiro
• Primary Examiner(s): Dunn, David R.
• Application Number:
  US10/297,172
• Publication Number:
  US 20030137138A1
• Time in Patent Office: 1,824 Days
• Field of Search: 280/736, 280/740, 280/741, 280/742, 102/530, 102/531
• US Class Current: 280/736
• CPC Class Codes: B60R 2021/2633 with a plurality of inflation levels
• CPC Class Codes: B60R 2021/2648 comprising a plurality of combustion chambers or sub-chambers
• CPC Class Codes: B60R 21/2644 using only solid reacting substances, e.g. pellets, powder

Abstract

A multistage type gas generator for an air bag, which has a simple structure and can be easily manufactured and in which combustions of gas generating agents provided in a plurality of combustion chambers do not influence each other, is provided. In the multistage type gas generator, a plurality of the combustion chambers are provided in an axial direction of a cylindrical housing.

Claims

1. A multistage gas generator for an air bag, comprising:

a cylindrical housing having at least one first gas discharging port and at least one second gas discharging port;

a first inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with first flame-transferring holes, both end portions of the first inner cylindrical member being in contact with the cylindrical housing;

a second inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with second flame transferring holes, both end portions of the second inner cylindrical member being in contact with the cylindrical housing;

a first combustion chamber provided inside the cylindrical housing and accommodating a first gas generating agent therein;

a second combustion chamber provided inside the cylindrical housing and on top of the first combustion chamber with respect to an axial direction of the cylindrical housing and accommodating a second gas generating agent therein, the second combustion chamber being defined separately and without communication with the first combustion chamber, such that a first gas generated in the first combustion chamber is discharged only through the at least one first gas discharging port and a second gas generated inside the second combustion chamber is discharged only through the at least one second gas discharging port;

first igniting means adapted to ignite the first gas generating agent accommodated inside the first combustion chamber; and

second igniting means adapted to ignite the second gas generating agent accommodated inside the second combustion chamber.

3. A multistage gas generator for an air bag according to claim 1 or 2,

wherein the first igniting means is accommodated in an inner space of the first inner cylindrical member and the second igniting means is accommodated in an inner space of the second inner cylindrical member.

4. A multistage gas generator for an air bag according to claim 3, wherein the second inner cylindrical member penetrates the first combustion chamber and the second combustion chamber in the axial direction of the cylindrical housing.

5. A multistage gas generator for an air bag according to claim 3, wherein the inner space of the first inner cylindrical member is in communication with the first combustion chamber, and the inner space of the second inner cylindrical member is in communication with the second combustion chamber.

6. A multistage gas generator for an air bag according to claim 3, wherein at least one of the first inner cylindrical member and the second inner cylindrical member is arranged eccentrically in the housing, and an ejecting direction of a flame ejected from the flame-transferring holes of the at least one of the first inner cylindrical member and the second inner cylindrical member is controlled by flame-direction controlling means.

7. A multistage gas generator for an air bag according to claim 1, further comprising:

first cylindrical filter means for one of purifying and cooling the first gas generated by combustion of the first gas generating agent, the first cylindrical filter means surrounding the first combustion chamber; and

second cylindrical filter means for one of purifying and cooling the second gas generated by combustion of the second gas generating agent, the second cylindrical filter means surrounding the second combustion chamber.

8. A multistage gas generator for an air bag according to claim 7, wherein the cylindrical housing includes a cylindrical diffuser shell, having a top wall and a peripheral wall provided with the first gas discharging port and the second gas discharging port, and a closure shell which closes an open end of the diffuser shell, and

an inner diameter of the first cylindrical filter means disposed adjacent to the closure shell is equal to or larger than an inner diameter of the second cylindrical filter means provided further apart from the closure shell.

9. A multistage gas generator for an air bag according to claim 1, wherein the cylindrical housing includes a cylindrical diffuser shell, having a top wall and a peripheral wall provided with the first gas discharging port and the second gas discharging port, and a closure shell which closes an open end of the diffuser shell, and

an outer diameter of the first combustion chamber provided adjacent to the closure shell is equal to or larger than an outer diameter of the second combustion chamber.

10. A multistage gas generator for an air bag according to claim 1, further comprising:

at least one of a heat insulating member and a heat insulating space which blocks conduction of a combustion heat from one of the first combustion chamber and the second combustion chamber to the other of the first combustion chamber and the second combustion chamber.

11. A multistage gas generator for an air bag according to claim 1, wherein the first igniting means and the second igniting means are provided at a predetermined side of the cylindrical housing.

12. A multistage gas generator for an air bag according to claim 1, wherein the first igniting means and the second igniting means are arranged on a common plane of the cylindrical housing.

13. A multistage gas generator for an air bag according to claim 1, wherein the cylindrical housing includes a cylindrical diffuser shell, having a top wall and a peripheral wall provided with the first gas discharging port and the second gas discharging port, and a closure shell which closes an open end of the diffuser shell, and the first igniting means and the second igniting means are arranged on a side closer to the closure shell than the top wall.

14. A multistage gas generator for an air bag according to claim 1, wherein the first combustion chamber and the second combustion chamber are separated from each other by a partition wall made of a plate member.

15. A multistage gas generator for an air bag according to claim 14,

wherein the partition wall abuts against at least one of an inner peripheral surface of the cylindrical housing, an outer peripheral surface of the first inner cylindrical member, and an outer peripheral surface of the second inner cylindrical member.

16. A multistage gas generator for an air bag according to claim 14,

wherein the partition wall is welded to at least one of the cylindrical housing, the first inner cylindrical member, and the second inner cylindrical member.

2. A multistage gas generator for an air bag, comprising:

a cylindrical housing having a plurality of first gas discharging ports provided in an upper half of the cylindrical housing, and a plurality of second gas discharging ports provided in a lower half of the cylindrical housing;

a first inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with first flame-transferring holes, both end portions of the first inner cylindrical member being in contact with the cylindrical housing;

a second inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with second flame transferring holes, both end portions of the second inner cylindrical member being in contact with the cylindrical housing;

a first combustion chamber provided inside the cylindrical housing and accommodating a first gas generating agent therein;

a second combustion chamber provided inside the cylindrical housing and on top of the first combustion chamber with respect to an axial direction of the cylindrical housing and accommodating a second gas generating agent therein, the second combustion chamber being defined separately and without communication with the first combustion chamber, such that a first gas generated in the first combustion chamber is discharged only through the first gas discharging ports and a second gas generated inside the second combustion chamber is discharged only through the second gas discharging ports;

first igniting means adapted to ignite the first gas generating agent accommodated inside the first combustion chamber; and

second igniting means adapted to ignite the second gas generating agent accommodated inside the second combustion chamber.

17. A multistage gas generator for an air bag, comprising:

a cylindrical housing having at least one first gas discharging port and at least one second gas discharging port;

a first combustion chamber provided inside the cylindrical housing;

a second combustion chamber provided inside the cylindrical housing and on top of the first combustion chamber with respect to an axial direction of the cylindrical housing, the second combustion chamber being defined separately and without communication with the first combustion chamber, such that a first gas generated in the first combustion chamber is discharged only through the at least one first gas discharging port and a second gas generated inside the second combustion chamber is discharged only through the at least one second gas discharging port;

a first inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with first flame-transferring holes, both end portions of the first inner cylindrical member being in contact with the cylindrical housing;

a second inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with second flame transferring holes, both end portions of the second inner cylindrical member being in contact with the cylindrical housing;

first igniting means accommodated in an inner space of the first inner cylindrical member;

second igniting means accommodated in an inner space of the second inner cylindrical member;

first gas generating means accommodated inside the first combustion chamber and adapted to be ignited and burnt by the first igniting means; and

second gas generating means accommodated inside the second combustion chamber and adapted to be ignited and burnt by the second igniting means.

18. A multistage gas generator for an air bag according to claim 17, wherein the second inner cylindrical member is provided along the axial direction of the cylindrical housing, and penetrates the first combustion chamber and the second combustion chamber in the axial direction of the cylindrical housing.

19. A multistage gas generator for an air bag according to claim 17 or 18, wherein the inner space of the first inner cylindrical member is in communication with the first combustion chamber, and the inner space of the second inner cylindrical member is in communication with the second combustion chamber.

20. A multistage gas generator for an air bag according to claim 17, wherein at least one of the first inner cylindrical member and the second inner cylindrical member is arranged eccentrically in the housing, and an ejecting direction of a flame ejected from the flame-transferring holes of at least one of the first inner cylindrical member and the second inner cylindrical member is controlled by a flame-direction controlling means.

21. A multistage gas generator for an air bag according to claim 17, further comprising:

first cylindrical filter means for one of purifying and cooling a first gas generated by combustion of the first gas generating means, the first filter means surrounding the first combustion chamber; and

second cylindrical filter means for one of purifying and cooling the second gas generated by combustion of the second gas generating means, the second cylindrical filter means surrounding the second combustion chamber.

22. A multistage gas generator for an air bag according to claim 21, wherein the cylindrical housing includes a cylindrical diffuser shell, having a top wall and a peripheral wall provided with the first gas discharging port and the second gas discharging port, and a closure shell which closes an open end of the diffuser shell, and

an inner diameter of the first cylindrical filter means disposed adjacent to the closure shell is equal to or larger than an inner diameter of the second cylindrical filter means provided further apart from the closure shell.

23. A multistage gas generator for an air bag according to claim 17, wherein the cylindrical housing includes a cylindrical diffuser shell, having a top wall and a peripheral wall provided with the first gas discharging hole and the second gas discharging hole, and a closure shell which closes an open end of the diffuser shell, and

an outer diameter of the first combustion chamber provided adjacent to the closure shell is equal to or larger than an outer diameter of the second combustion chamber.

24. A multistage gas generator for an air bag according to claim 17, further comprising:

at least one of a heat insulating member and a heat insulating space which blocks conduction of a combustion heat from one of the first combustion chamber and the second combustion chamber to the other of the first combustion chamber and the second combustion chamber.

25. A multistage gas generator for an air bag according to claim 17, wherein the first igniting means and the second igniting means are provided at a predetermined side of the cylindrical housing.

26. A multistage gas generator for an air bag according to claim 17, wherein the first igniting means and the second igniting means are arranged on a common plane of the cylindrical housing.

27. A multistage gas generator for an air bag according to claim 17, wherein the cylindrical housing includes a cylindrical diffuser shell, having a top wall and a peripheral wall provided with the first gas discharging port and the second gas discharging port, and a closure shell which closes an open end of the diffuser shell, and the first igniting means and the second igniting means are arranged on a side closer to the closure shell than the top wall.

28. A multistage gas generator for an air bag according to claim 17, wherein the first combustion chamber and the second combustion chamber are separated from each other by a partition wall made of a plate member.

29. A multistage gas generator for an air bag according to claim 28, wherein the partition wall abuts against at least one of an inner peripheral surface of the cylindrical housing, an outer peripheral surface of the first inner cylindrical member, and an outer peripheral surface of the second inner cylindrical member.

30. A multistage gas generator for an air bag according to claim 28 or 29, wherein the partition wall is welded to at least one of the cylindrical housing, the first inner cylindrical member, and the second inner cylindrical member.

31. A multistage gas generator for an air bag, comprising:

a cylindrical housing having a at least one first gas discharging port and at least one second gas discharging port;

a first inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with first flame-transferring holes, both end portions of the first inner cylindrical member being in contact with the cylindrical housing;

a second inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with second flame transferring holes, both end portions of the second inner cylindrical member being in contact with the cylindrical housing;

a first combustion chamber provided inside the cylindrical housing;

a second combustion chamber provided inside the cylindrical housing and on top of the first combustion chamber with respect to an axial direction of the cylindrical housing, the second combustion chamber being defined separately and without communication with the first combustion chamber, such that a first gas generated in the first combustion chamber is discharged only through the at least one first gas discharging port and a second gas generated inside the second combustion chamber is discharged only through the at least one second gas discharging port;

first igniting means accommodated inside the first combustion chamber;

second igniting means accommodated inside the second combustion chamber;

a first gas generating means accommodated inside the first combustion chamber and adapted to be ignited and burnt by the first igniting means;

second gas generating means accommodated inside the second combustion chamber and adapted to be ignited and burnt by the second igniting means;

first cylindrical filter means for one of purifying and cooling a first gas generated by combustion of the first gas generating means, the first cylindrical filter means surrounding the first combustion chamber; and

second cylindrical filter means for one of purifying and cooling the second gas generated by combustion of the second gas generating means, the second cylindrical filter means surrounding the second combustion chamber.

32. A multistage gas generator for an air bag according to claim 31, wherein the cylindrical housing includes a cylindrical diffuser shell, having a top wall and a peripheral wall provided with the first gas discharging port and the second gas discharging port, and a closure shell which closes an open end of the diffuser shell, and

an inner diameter of the first cylindrical filter means disposed adjacent to the closure shell is equal to or larger than an inner diameter of the second cylindrical filter means provided further apart from the closure shell.

33. A multistage gas generator for an air bag according to claim 31, wherein the cylindrical housing includes a cylindrical diffuser shell, having a top wall and a peripheral wall provided with the first gas discharging hole and the second gas discharging hole, and a closure shell which closes an open end of the diffuser shell, and

an outer diameter of the first combustion chamber provided adjacent to the closure shell is equal to or larger than an outer diameter of the second combustion chamber.

34. A multistage gas generator for an air bag according to claim 31, further comprising:

at least one of a heat insulating member and a heat insulating space which blocks conduction of a combustion heat from one of the first combustion chamber and the second combustion chamber to the other of the first combustion chamber and the second combustion chamber.

35. A multistage gas generator for an air bag according to claim 31, wherein the first igniting means and the second igniting means are provided at a predetermined side of the cylindrical housing.

36. A multistage gas generator for an air bag according to claim 31, wherein the first igniting means and the second igniting means are arranged on a common plane of the cylindrical housing.

37. A multistage gas generator for an air bag according to claim 31, wherein the cylindrical housing includes a cylindrical diffuser shell, having a top wall and a peripheral wall provided with the first gas discharging port and the second gas discharging port, and a closure shell which closes an open end of the diffuser shell, and the first igniting means and the second igniting means are arranged on a side closer to the closure shell than the top wall.

38. A multistage gas generator for an air bag according to claim 31, wherein the first combustion chamber and the second combustion chamber are separated from each other by a partition wall made of a plate member.

39. A multistage gas generator for an air bag according to claim 38,

wherein the partition wall abuts against at least one of an inner peripheral surface of the cylindrical housing, an outer peripheral surface of the first inner cylindrical member, and an outer peripheral surface of the second inner cylindrical member.

40. A multistage gas generator for an air bag according to claim 38,

wherein the partition wall is welded to at least one of the cylindrical housing, the first inner cylindrical member, and the second inner cylindrical member.

41. A multistage gas generator for an air bag, comprising:

a cylindrical housing including a cylindrical diffuser shell having a top wall, and a peripheral wall provided with at least one first gas discharging port and at least one second gas discharging port, and a closure shell which closes an open end of the diffuser shell;

a first inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with first flame-transferring holes, a first end portion of the first inner cylindrical member being in contact with the diffuser shell and a second end portion being in contact with the closure shell;

a second inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with second flame transferring holes, a first end portion of the second inner cylindrical member being in contact with the diffuser shell and a second end portion being in contact with the closure shell;

a first combustion chamber provided inside the cylindrical housing;

a second combustion chamber provided inside the cylindrical housing and on top of the first combustion chamber with respect to an axial direction of the cylindrical housing, the second combustion chamber being defined separately and without communication with the first combustion chamber, such that a first gas generated in the first combustion chamber is discharged only through the at least one first gas discharging port and a second gas generated inside the second combustion chamber is discharged only through the at least one second gas discharging port, an inner diameter of the first combustion chamber provided nearest to the closure shell in the cylindrical housing being equal to or larger than a diameter of the second combustion chamber;

first igniting means actuated by a first actuation signal;

a second igniting means actuated by a second actuation signal;

first gas generating means accommodated inside the first combustion chamber and adapted to be ignited and burnt by the first igniting means; and

second gas generating means accommodated inside the second combustion chamber and adapted to be ignited and burnt by the second igniting means.

42. A multistage gas generator for an air bag according to claim 41, further comprising:

at least one of a heat insulating member and a heat insulating space which blocks conduction of a combustion heat from one of the first combustion chamber and the second combustion chamber to the other of the first combustion chamber and the second combustion chamber.

43. A multistage gas generator for an air bag according to any one of claims 41 or 42, wherein the first igniting means and the second igniting means are provided at a predetermined side of the cylindrical housing.

44. A multistage gas generator for an air bag according to claim 41, wherein the first igniting means and the second igniting means are arranged on a common plane of the cylindrical housing.

45. A multistage gas generator for an air bag according to claim 41, wherein the first igniting means and the second igniting means are arranged on a side closer to the closure shell than the top wall.

46. A multistage gas generator for an air bag according to claim 41, wherein the first combustion chamber and the second combustion chamber are separated from each other by a partition wall made of a plate member.

47. A multistage gas generator for an air bag according to claim 46,

wherein the partition wall abuts against at least one of an inner peripheral surface of the cylindrical housing, an outer peripheral surface of the first inner cylindrical member, and an outer peripheral surface of the second inner cylindrical member.

48. A multistage gas generator for an air bag according to claim 46,

wherein the partition wall is welded to at least one of the cylindrical housing, the first inner cylindrical member, and the second inner cylindrical member.

49. A multistage gas generator for an air bag, comprising:

a cylindrical housing having at least one first gas discharging port and at least one second gas discharging port;

a first inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with first flame-transferring holes, both end portions of the first inner cylindrical member being in contact with the cylindrical housing;

a second inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with second flame transferring holes, both end portions of the second inner cylindrical member being in contact with the cylindrical housing;

a first combustion chamber provided inside the cylindrical housing;

a second combustion chamber provided inside the cylindrical housing and on top of the first combustion chamber with respect to an axial direction of the cylindrical housing, the second combustion chamber being defined separately and without communication with the first combustion chamber, such that a first gas generated in the first combustion chamber is discharged only through the at least one first gas discharging port and a second gas generated inside the second combustion chamber is discharged only through the at least one second gas discharging port;

first igniting means adapted to be actuated by a first actuation signal;

second igniting means adapted to be actuated by a second actuation signal;

first gas generating means accommodated inside the first combustion chamber and adapted to be ignited and burnt by the first igniting means;

second gas generating means accommodated inside the second combustion chamber and adapted to be ignited and burnt by the second igniting means; and

at least one of a heat insulating member and a heat insulating space which blocks conduction of a combustion heat from one of the first combustion chamber and the second combustion chamber to the other of the first combustion chamber and the second combustion chamber.

50. A multistage gas generator for an air bag according to claim 49, wherein the first igniting means and the second igniting means are provided at a predetermined side of the cylindrical housing.

51. A multistage gas generator for an air bag according to claim 49 or 50, wherein the first igniting means and the second igniting means are arranged on a common plane of the cylindrical housing.

52. A multistage gas generator for an air bag according to claim 49, wherein the cylindrical housing includes a cylindrical diffuser shell, having a top wall and a peripheral wall provided with the first gas discharging port and the second gas discharging port, and a closure shell which closes an open end of the diffuser shell, and the first igniting means and the second igniting means are arranged on a side closer to the closure shell than the top, wall.

53. A multistage gas generator for an air bag according to claim 49, wherein the first combustion chamber and the second combustion chamber are separated from each other by a partition wall made of a plate member.

54. A multistage gas generator for an air bag according to claim 53,

wherein the partition wall abuts against at least one of an inner peripheral surface of the cylindrical housing, an outer peripheral surface of the first inner cylindrical member, and an outer peripheral surface of the second inner cylindrical member.

55. A multistage gas generator for an air bag according to claim 53,

wherein the partition wall is welded to at least one of the cylindrical housing, the first inner cylindrical member, and the second inner cylindrical member.

56. A multistage gas generator for an air bag, comprising:

a cylindrical housing having at least one first gas discharging port and at least one second gas discharging port;

a first inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with first flame-transferring holes, both end portions of the first inner cylindrical member being in contact with the cylindrical housing;

a second inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with second flame transferring holes, both end portions of the second inner cylindrical member being in contact with the cylindrical housing;

a first combustion chamber provided inside the cylindrical housing;

a second combustion chamber provided inside the cylindrical housing and on top of the first combustion chamber with respect to an axial direction of the cylindrical housing, the second combustion chamber being defined separately and without communication with the first combustion chamber, such that a first gas generated in the first combustion chamber is discharged only through the at least one first gas discharging port and a second gas generated inside the second combustion chamber is discharged only through the at least one second gas discharging port;

first igniting means actuated by a first actuation signal and disposed on a first side of the cylindrical housing;

second igniting means actuated by a second actuation signal and disposed on the first side of the cylindrical housing;

first gas generating means accommodated inside the first combustion chamber and adapted to be ignited and burnt by the first igniting means; and

second gas generating means accommodated inside the second combustion chamber and adapted to be ignited and burnt by the second igniting means.

59. A multistage gas generator for an air bag according to any one of claims 56 to 58, wherein the first combustion chamber and the second combustion chamber are separated from each other by a partition wall made of a plate member.

60. A multistage gas generator for an air bag according to claim 59,

wherein the partition wall abuts against at least one of an inner peripheral surface of the cylindrical housing, an outer peripheral surface of the first inner cylindrical member, and an outer peripheral surface of the second inner cylindrical member.

61. A multistage gas generator for an air bag according to claim 59,

wherein the partition wall is welded to at least one of the cylindrical housing, the first inner cylindrical member, and the second inner cylindrical member.

57. A multistage gas generator for an air bag, comprising:

a cylindrical housing having at least one first gas discharging port and at least one second gas discharging port;

a first inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with first flame-transferring holes, both end portions of the first inner cylindrical member being in contact with the cylindrical housing;

a second inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with second flame transferring holes, both end portions of the second inner cylindrical member being in contact with the cylindrical housing;

a first combustion chamber provided inside the cylindrical housing;

a second combustion chamber provided inside the cylindrical housing and on top of the first combustion chamber with respect to an axial direction of the cylindrical housing, the second combustion chamber being defined separately and without communication with the first combustion chamber, such that a first gas generated in the first combustion chamber is discharged only through the at least one first gas discharging port and a second gas generated inside the second combustion chamber is discharged only through the at least one second gas discharging port;

first igniting means actuated by a first actuation signal and disposed on a first plane of the cylindrical housing;

second igniting means actuated by a second actuation signal and disposed on the first plane of the cylindrical housing;

first gas generating means accommodated inside the first combustion chamber and adapted to be ignited and burnt by the first igniting means; and

second gas generating means accommodated inside the second combustion chamber and adapted to be ignited and burnt by the second igniting means.

58. A multistage gas generator for an air bag, comprising:

a cylindrical housing including a cylindrical diffuser shell having a top wall, and a peripheral wall provided with at least one first gas discharging port and at least one second gas discharging port, and a closure shell which closes a lower opening of the diffuser shell;

a first inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with first flame-transferring holes, a first end portion of the first inner cylindrical member being in contact with the diffuser shell and a second end portion being in contact with the closure shell;

a second inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with second flame transferring holes, a first end portion of the second inner cylindrical member being in contact with the diffuser shell and a second end portion being in contact with the closure shell;

a first combustion chamber provided inside the cylindrical housing;

a second combustion chamber provided inside the cylindrical housing and on top of the first combustion chamber with respect to an axial direction of the cylindrical housing, the second combustion chamber being defined separately and without communication with the first combustion chamber, such that a first gas generated in the first combustion chamber is discharged only through the at least one first gas discharging port and a second gas generated inside the second combustion chamber is discharged only through the at least one second gas discharging port, an inner diameter of the first combustion chamber provided nearest to the closure shell in the cylindrical housing being equal to or larger than a diameter of the second combustion chamber;

first igniting means adapted to be actuated by a first actuation signal;

second igniting means adapted to be actuated by a second actuation signal;

first gas generating means accommodated inside the first combustion chamber and adapted to be ignited and burnt by the first igniting means, the first gas generating means being arranged on a side closer to the top wall than the closure shell;

second gas generating means accommodated inside the second combustion chamber and adapted to be ignited and burnt by the second igniting means, the second gas generating means being arranged on a side closer to the closure shell than the top wall.

62. A multistage gas generator for an air bag, comprising:

a cylindrical housing having at least one first gas discharging port and at least one second gas discharging port;

a first inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with first flame-transferring holes, both end portions of the first inner cylindrical member being in contact with the cylindrical housing;

a second inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with second flame transferring holes, both end portions of the second inner cylindrical member being in contact with the cylindrical housing;

a first combustion chamber provided inside the cylindrical housing;

a second combustion chamber provided inside the cylindrical housing and on top of the first combustion chamber with respect to an axial direction of the cylindrical housing, the second combustion chamber being defined separately and without communication with the first combustion chamber, such that a first gas generated in the first combustion chamber is discharged only through the at least one first gas discharging port and a second gas generated inside the second combustion chamber is discharged only through the at least one second gas discharging port;

a partition wall made of a plate member that separates the first combustion chamber and the second combustion chamber;

first igniting means actuated by a first actuation signal;

second igniting means actuated by a second actuation signal;

first gas generating means accommodated inside the first combustion chamber and adapted to be ignited and burnt by the first igniting means; and

second gas generating means accommodated inside the second combustion chamber and adapted to be ignited and burnt by the second igniting means.

63. A multistage gas generator for an air bag according to claim 62,

wherein the partition wall abuts against at least one of an inner peripheral surface of the cylindrical housing, an outer peripheral surface of the first inner cylindrical member, and an outer peripheral surface of the second inner cylindrical member.

64. A multistage gas generator for an air bag according to claim 62,

wherein the partition wall is welded to at least one of the cylindrical housing, the first inner cylindrical member, and the second inner cylindrical member.

65. A multistage gas generator for an air bag, comprising:

a cylindrical housing having at least one first gas discharging port and at least one second gas discharging port;

a first combustion chamber provided inside the cylindrical housing and accommodating a first gas generating agent therein;

a second combustion chamber provided inside the cylindrical housing and on top of the first combustion chamber with respect to an axial direction of the cylindrical housing and accommodating a second gas generating agent therein, the second combustion chamber being defined separately and without communication with the first combustion chamber, such that a first gas generated in the first combustion chamber is discharged only through the at least one first gas discharging port and a second gas generated inside the second combustion chamber is discharged only through the at least one second gas discharging port;

a first inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with first flame-transferring holes that allow communication between an interior of the first cylindrical member and the first combustion chamber; and

a second inner cylindrical member disposed inside the cylindrical housing and provided, in a peripheral wall thereof, with second flame-transferring holes that allow communication between an interior of the second cylindrical member and the second combustion chamber,

wherein flames are discharged through at least one of the first flame-transferring holes,

wherein the directions of the flames are controlled by not providing said at least one of the first flame-transferring holes and the second flame-transferring holes at a position directly opposing a portion of an inner surface of the cylindrical housing, and

wherein the directions of the flames are controlled by providing a wall between at least one of the first inner cylindrical member and the second inner cylindrical member and a portion of an inner surface of the cylindrical housing.

66. The multistage gas generator for an air bag according to claim 65,

wherein both end portions of the first inner cylindrical member and the second inner cylindrical member are in contact with the cylindrical housing.

67. The multistage gas generator for an air bag according to claim 65,

wherein the wall is provided at a position where said at least one of the first inner cylindrical member and the second inner cylindrical member becomes closest to the inner surface of the cylindrical housing.