Air bag system for an automotive vehicle

• US 5,324,071 A
• Filed: 11/14/1991
• Issued: 06/28/1994
• Est. Priority Date: 03/22/1991
• Status: Expired due to Term

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: Nomura, Yoshinobu, Hirashima, Isao, Kore, Haruhisa, Takayama, Masatoshi, Kohno, Shigefumi, Gotomyo, Yasuo, Muramoto, Hisao
• Primary Examiner(s): Focarino, Margaret A.
• Assistant Examiner(s): DICKSON, PAUL N
• Application Number:
  US07/792,162
• Time in Patent Office: 957 Days
• Field of Search: 280/728, 280/730, 280/735, 280/738, 280/740, 280/742, 280/728 R, 280/728 A, 280/728 B, 280/736, 297/391, 297/394, 297/DIG. 8
• US Class Current: 280/730.1
• CPC Class Codes: B60N 2/02 the seat or part thereof being movable, e.g. adjustable adjustable arm-rests B60N2/75; adjustable head-rests B60N2/806
• CPC Class Codes: B60N 2/879 with additional features not related to head-rest positioning, e.g. heating or cooling devices or loudspeakers
• CPC Class Codes: B60R 2021/0004 Frontal collision
• CPC Class Codes: B60R 2021/2074 in head rests
• CPC Class Codes: B60R 2021/2173 the module or part thereof being movably mounted on the vehicle
• CPC Class Codes: B60R 2021/23153 specially adapted for rear seat passengers
• CPC Class Codes: B60R 2021/23169 specially adapted for knee protection
• CPC Class Codes: B60R 2021/2765 comprising means to control the venting
• CPC Class Codes: B60R 21/01508 detecting forces or pressure in bags or modules
• CPC Class Codes: B60R 21/01516 using force or pressure sensing means
• CPC Class Codes: B60R 21/01554 Seat position sensors
• CPC Class Codes: B60R 21/207 in vehicle seats
• CPC Class Codes: B60R 21/276 with means to vent the inflation fluid source, e.g. in case of overpressure B60R21/30 takes precedence; venting means on inflatable member walls B60R21/239

Abstract

The head rest is detachably mounted to the seat back of the front seat and the air bag unit with an air bag mounted therein is mounted to the head rest. The air bag is expanded toward the passenger seated on the rear seat in response to an explosion signal from the control unit into which signals are entered from impact sensors. The air bag is so disposed as to expand only when the passenger is seated on the rear seat. The posture and position of the air bag unit is adjusted in association with the movement or displacement of the front seat to which the air bag is mounted, thereby improving the ability of the expanded air bag to confine the passenger seated on the rear seat and protecting the passenger in a safer fashion. Further, the air bag unit is mounted to the head rest of the front seat, so that the air bag can be exchanged with ease and at a cheap cost without needing to exchange the front seat itself.

Claims

1. An air bag system for an automotive vehicle having an air bag unit so mounted to a front seat as to expand an air bag accommodated in the air bag unit toward a passenger seated on a rear seat upon impact of the automotive vehicle, comprising:

a head rest detachably mounted to a seat back of the front seat, said air bag unit mounted to the head rest and accommodating the air bag;

front seat status detecting means for detecting a seat status of the front seat;

gas pressure adjusting means for adjusting a distribution of gas pressure within the air bag at a moment of expansion of the air bag; and

gas pressure controlling means for controlling the gas pressure by producing the distribution of the gas pressure so as to expand the air bag in a predetermined direction, including at least one of an upward and downward direction, to bring the air bag into contact with the passenger seated on the rear seat and to cause the air bag to be positioned in accordance with the seat status of the front seat detected by said front seat status detecting means.

2. An air bag system as claimed in claim 1, wherein:

said front seat status detecting means detects a reclined angle at which a seat back of said front seat is reclined; and

said gas pressure controlling means controls the distribution of the gas pressure in accordance with the reclined angle of the seat back of the front seat detected by said front seat status detecting means.

3. An air bag system as claimed in claim 2, wherein said gas pressure controlling means controls the distribution of the gas pressure so as to expand the air bag downward when the reclined angle detected by said front seat status detecting means is smaller than a first predetermined angle.

4. An air bag system as claimed in claim 1, wherein:

said gas pressure adjusting means comprises a plurality of relief holes formed in said air bag unit and a plurality of opening-closing valves disposed in the corresponding relief holes; and

said gas pressure controlling means controls the opening-closing valves to thereby selectively open the opening-closing valves in accordance with the seat status of the front seat detected by said front seat status-detecting means.

5. An air bag system as claimed in claim 4, wherein:

said plurality of relief holes comprise upper relief holes formed at an upper portion of said air bag unit and lower relief holes formed at a lower portion of said air bag unit; and

said plurality of opening-closing valves comprise upper opening-closing valves formed so as to open and close the corresponding upper relief holes and lower opening-closing valves formed so as to open and close the corresponding lower relief holes.

6. An air bag system as claimed in claim 5, wherein:

said front seat status detecting means detects a reclined angle at which the seat back of said front seat is reclined; and

said gas pressure controlling means opens and closes said upper and lower opening-closing valves in accordance with the reclined angle detected by said front seat status detecting means.

7. An air bag system as claimed in claim 6 wherein said gas pressure controlling means opens and closes said opening-closing valves so as to expand the air bag downward when the reclined angle detected by said front seat status detecting means is smaller than a first predetermined angle.

8. An air bag system as claimed in claim 7, wherein said gas pressure controlling means expands the air bag downward by releasing the gas pressure from said upper relief holes by opening said upper opening-closing valves, when the reclined angle detected by said front seat status detecting means is smaller than the first predetermined angle.

9. An air bag system as claimed in claim 6, wherein said gas pressure controlling means opens and closes said opening-closing valves so as to expand the air bag upward when the reclined angle detected by said front seat status detecting means is larger than a second predetermined angle.

10. An air bag system as claimed in claim 9, wherein said gas pressure controlling means expands the air bag upward by releasing the gas pressure from said lower relief holes by opening said lower opening-closing valves, when the reclined angle detected by said front seat status detecting means is larger than the second predetermined angle.

11. An air bag system as claimed in claim 6, wherein said gas pressure controlling means controls said opening-closing valves so as to expand the air bag in a substantially middle position between upward and downward directions when the reclined angle detected by said front seat status detecting means is in a predetermined angular range.

12. An air bag system as claimed in claim 1, wherein:

said front seat status detecting means detects an inclination angle of the head rest at which the head rest of said front seat is inclined; and

said gas pressure controlling means controls the distribution of the gas pressure in accordance with the inclination angle of the head rest of the front seat detected by said front seat status detecting means.

13. An air bag system as claimed in claim 12, wherein said gas pressure controlling means controls the distribution of the gas pressure so as to expand the air bag downward when the inclination angle detected by said front seat status detecting means is smaller than a predetermined value.

14. An air bag system as claimed in claim 5, wherein:

said front seat status detecting means detects an inclination angle of the head rest at which the head rest of said front seat is inclined; and

said gas pressure controlling means opens and closes said upper opening-closing valves and said lower opening-closing valves in accordance with the inclination angle of the head rest of the front seat detected by said front seat status detecting means.

15. An air bag system as claimed in claim 14, wherein said gas pressure controlling means opens and closes said opening-closing valves so as to expand the air bag downward when the inclination angle detected by said front seat status detecting means is smaller than a predetermined value.

16. An air bag system as claimed in claim 15, wherein said gas pressure means expands the air bag downward by releasing the gas pressure from said upper relief holes by opening said upper opening-closing valves, when the inclination angle detected by said front seat status detecting means is smaller than the predetermined value.

17. An air bag system as claimed in claim 14, wherein said gas pressure controlling means opens and closes said opening-closing valves so as to expand the air bag upward when the inclination angle of the head rest detected by said front seat status detecting means is larger than a predetermined angle.

18. An air bag system as claimed in claim 17, wherein said gas pressure controlling means expands the air bag upward by releasing the gas pressure from said lower relief holes by opening said lower opening-closing valves, when the inclination angle of the head rest detected by said front seat status detecting means is larger than the predetermined angle.

19. An air bag system as claimed in claim 14, wherein said gas pressure controlling means controls said opening-closing valves so as to expand the air bag in a substantially middle position between the upward and downward directions when the inclination angle of the head rest detected by said front seat status detecting means is in a predetermined angular range.

20. An air bag system as claimed in claim 1, wherein:

said front seat status detecting means detects a longitudinal position of said front seat; and

said gas pressure controlling means is adapted to control the distribution of the gas pressure in accordance with the longitudinal position of the front seat detected by said front seat status detecting means.

21. An air bag system as claimed in claim 20, wherein said gas pressure controlling means controls the distribution of the gas pressure so as to expand the air bag downward when the longitudinal position detected by said front seat status detecting means is in a position behind a predetermined position.

22. An air bag system as claimed in claim 5, wherein:

said front seat status detecting means detects a longitudinal position of said front seat; and

said gas pressure controlling means is adapted to open and close said upper opening-closing valves and said lower opening-closing valves in accordance with the longitudinal position of said front seat detected by said front seat status detecting means.

23. An air bag system as claimed in claim 22, wherein said gas pressure controlling means opens and closes said opening-closing valves so as to expand the air bag downward when the longitudinal position of said front seat detected by said front seat status detecting means is in a position behind a predetermined position.

24. An air bag system as claimed in claim 23, wherein said gas pressure controlling means expands the air bag downward by releasing the gas pressure from said upper relief holes by opening said upper opening-closing valves, when the longitudinal position detected by said front seat status detecting means is in the position behind the predetermined position.

25. An air bag system as claimed in claim 22, wherein said gas pressure controlling means opens and closes the opening-closing valves so as to expand the air bag upward when the longitudinal position of said front seat detected by said front seat status detecting means is in a position ahead of a predetermined position.

26. An air bag system as claimed in claim 25, wherein said gas pressure controlling means expands the air bag upward by releasing the gas pressure from said lower relief holes by opening said lower opening-closing valves, when the longitudinal position of said front seat detected by said front seat status detecting means is ahead of the predetermined position.

27. An air bag system as claimed in claim 22, wherein said gas pressure controlling means controls said opening-closing valves so as to expand the air bag in a substantially middle position between the upward and downward directions when the longitudinal position of said front seat detected by said front seat status detecting means is in a predetermined range.

28. An air bag system as claimed in claim 1, wherein:

said front seat status detecting means detects a vertical position of a seat cushion of said front seat; and

said gas pressure controlling means controls the distribution of the gas pressure in accordance with the vertical position of the seat cushion of said front seat detected by said front seat status detecting means.

29. An air bag system as claimed in claim 28, wherein said gas pressure controlling means controls the distribution of the gas pressure so as to expand the air bag downward when the vertical position detected by said front seat status detecting mean is in a position higher than a predetermined position.

30. An air bag system as claimed in claim 5, wherein:

said front seat status detecting means detects a vertical position of a seat cushion of said front seat; and

said gas pressure controlling means opens and closes said upper opening-closing valves and said lower opening-closing valves in accordance with the vertical position of the seat cushion of said front seat detected by said front seat status detecting means.

31. An air bag system as claimed in claim 30, wherein said gas pressure controlling means opens and closes said opening-closing valves so as to expand the air bag downward when the vertical position of the seat cushion of said front seat detected by said front seat status detecting means is in a position higher than the predetermined position.

32. An air bag system as claimed in claim 31, wherein said gas pressure controlling means expands the air bag downward by releasing the gas pressure from said upper relief holes by opening said upper opening-closing valves, when the vertical position detected by said front seat status detecting means in the position higher than the predetermined position.

33. An air bag system as claimed in claim 30, wherein said gas pressure controlling means opens and closes the opening-closing valves so as to expand the air bag upward when the vertical position of the seat cushion of said front seat detected by said front seat status detecting means is in a position lower than a predetermined position.

34. An air bag system as claimed in claim 33, wherein said gas pressure controlling means expands the air bag upward by releasing the gas pressure from said lower relief holes by opening said lower opening-closing valves, when the vertical position of the seat cushion of said front seat detected by said front seat status detecting means is lower than the predetermined position.

35. An air bag system as claimed in claim 30, wherein said gas pressure controlling means controls said opening-closing valves so as to expand the air bag in a substantially middle position between the upward and downward directions when the vertical position of the seat cushion of said front seat detected by said front seat status detecting means is in a predetermined range.

36. An air bag system as claimed in claim 1, wherein:

said front seat status detecting means detects a vertical position of a head rest of said front seat; and

said gas pressure controlling means is adapted to control the distribution of the gas pressure in accordance with the vertical position of the head rest of said front seat detected by said front seat status detecting means.

37. An air bag system as claimed in claim 36, wherein said gas pressure controlling means controls the distribution of the gas pressure so as to expand the air bag downward when the vertical position detected by said front seat status detecting means is in a position higher than a predetermined position.

38. An air bag system as claimed in claim 5, wherein:

said front seat status detecting means detects a vertical position of a head rest of said front seat;

nd

said gas pressure controlling means opens and closes said upper opening-closing valves and said lower opening-closing valves in accordance with the vertical position of the head rest of said front seat detected by said front seat status detecting means.

39. An air bag system as claimed in claim 38, wherein said gas pressure controlling means opens and closes said opening-closing valves so as to expand the air bag downward when the vertical position of the head rest of said front seat detected by said front seat status detecting means is in a position higher than a predetermined position.

40. An air bag system as claimed in claim 39, wherein said gas pressure controlling means expands the air bag downward by releasing the gas pressure from said upper relief holes by opening said upper opening-closing valves, when the vertical position detected by said front seat status detecting means is in the position higher than the predetermined position.

41. An air bag system as claimed in claim 38, wherein said gas pressure controlling means opens and closes the opening-closing valves so as to expand the air bag upward when the vertical position of the head rest of said front seat detected by said front seat status detecting means is in a position lower than a predetermined position.

42. An air bag system as claimed in claim 41, wherein said gas pressure controlling means expands the air bag upward by releasing the gas pressure from said lower relief holes by opening said lower opening-closing valves, when the vertical position of the head rest of said front seat detected by said front seat status detecting means is lower than the predetermined position.

43. An air bag system as claimed in claim 38, wherein said gas pressure controlling means controls said opening-closing valves so as to expand the air bag in a substantially middle position between the upward and downward directions when the vertical position of the head rest of said front seat detected by said front seat status detecting means is in a predetermined range.

44. An air bag system for an automotive vehicle having an air bag unit disposed at a front seat so as to expand an air bag accommodated in the air bag unit toward a passenger seated on a rear seat upon impact of the automotive vehicle, comprising:

gas pressure adjusting means for adjusting gas pressure by producing a distribution of gas pressure within the air bag at a moment of expansion of the air bag;

front seat status detecting means for detecting a seat status of the front seat; and

gas pressure controlling means for controlling the gas pressure by producing the distribution of the gas pressure so as to expand the air bag in a predetermined direction, including at least one of an upward and downward direction, to bring the air bag into contact with the passenger seated on the rear seat, in response to a signal from the front seat status detecting means.

45. An air bag system as claimed in claim 44, wherein:

said front seat status detecting means detects a reclined angle at which a seat back of said front seat is reclined; and

said gas pressure controlling means controls the distribution of the gas pressure in accordance with the reclined angle of the seat back of the front seat detected by said front seat status detecting means.

46. An air bag system as claimed in claim 45, wherein said gas pressure controlling means controls the distribution of the gas pressure so as to expand the air bag downward when the reclined angle detected by said front seat status detecting means is smaller than a first predetermined angle.

47. An air bag system as claimed in claim 44, wherein:

said gas pressure adjusting means comprises a plurality of relief holes formed in said air bag unit and a plurality of opening-closing valves disposed in the corresponding relief holes; and

said gas pressure controlling means controls the opening-closing valves to thereby selectively open the opening-closing valves in accordance with the seat status of the front seat detected by said front seat status detecting means.

48. An air bag system as claimed in claim 47, wherein:

said plurality of relief holes comprise upper relief holes formed at an upper portion of said air bag unit and lower relief holes formed at a lower portion of said air bag unit; and

said plurality of opening-closing valves comprise upper opening-closing valves formed so as to open and close the corresponding upper relief holes and lower opening-closing valves formed so as to open and close the corresponding lower relief holes.

49. An air bag system as claimed in claim 48, wherein:

said front seat status detecting means detects a reclined angle at which the seat back of said front seat is reclined; and

said gas pressure controlling means opens and closes said upper and lower opening-closing valves in accordance with the reclined angle detected by said front seat status detecting means.

50. An air bag system as claimed in claim 49, wherein said gas pressure controlling means opens and closes said opening-closing valves so as to expand the air bag downward when the reclined angle detected by said front seat status detecting means is smaller than a first predetermined angle.

51. An air bag system as claimed in claim 50, wherein said gas pressure controlling means expands the air bag downward by releasing the gas pressure from said upper relief holes by opening said upper opening-closing valves, when the reclined angle detected by said front seat status detecting means is smaller than the first predetermined angle.

52. An air bag system as claimed in claim 49, wherein said gas pressure controlling means opens and closes said opening-closing valves so as to expand the air bag upward when the reclined angle detected by said front seat status detecting means is larger than a second predetermined angle.

53. An air bag system as claimed in claim 52, wherein said gas pressure controlling means expands the air bag upward by releasing the gas pressure from said lower relief holes by opening said lower opening-closing valves, when the reclined angle detected by said front seat status detecting means is larger than the second predetermined angle.

54. An air bag system as claimed in claim 49, wherein said gas pressure controlling means controls said opening-closing valves so as to expand the air bag in a substantially middle position between upward and downward directions when the reclined angle detected by said front seat status detecting means is in a predetermined angular range.

55. An air bag system as claimed in claim 44, wherein:

said front seat status detecting means detects an inclination angle of the head rest at which the head rest of said front seat is inclined; and

said gas pressure controlling means controls the distribution of the gas pressure in accordance with the inclination angle of the head rest of the front seat detected by said front seat status detecting means.

56. An air bag system as claimed in claim 55, wherein said gas pressure controlling means controls the distribution of the gas pressure so as to expand the air bag downward when the inclination angle detected by said front seat status detecting mean is smaller than a predetermined value.

57. An air bag system as claimed in claim 48, wherein:

said front seat status detecting means detects an inclination angle of the head rest at which the head rest of said front seat is inclined; and

said gas pressure controlling means opens and closes said upper opening-closing valves and said lower opening-closing valves in accordance with the inclination angle of the head rest of the front seat detected by said front seat status detecting means.

58. An air bag system as claimed in claim 57, wherein said gas pressure controlling means opens and closes said opening-closing valves so as to expand the air bag downward when the inclination angle detected by said front seat status detecting means is smaller than a predetermined value.

59. An air bag system as claimed in claim 58, wherein said gas pressure controlling means expands the air bag downward by releasing the gas pressure from said upper relief holes by opening said upper opening-closing valves, when the inclination angle detected by said front seat status detecting means is smaller than the predetermined value.

60. An air bag system as claimed in claim 57, wherein said gas pressure controlling means opens and closes said opening-closing valves so as to expand the air bag upward when the inclination angle of the head rest detected by said front seat status detecting means is larger than a predetermined angle.

61. An air bag system as claimed in claim 60, wherein said gas pressure controlling means expands the air bag upward by releasing the gas pressure from said lower relief holes by opening said lower opening-closing valves, when the inclination angle of the head rest detected by said front seat status detecting means is larger than the predetermined angle.

62. An air bag system as claimed in claim 57, wherein said gas pressure controlling means controls said opening-closing valves so as to expand the air bag in a substantially middle position between the upward and downward directions when the inclination angle of the head rest detected by said front seat status detecting means is in a predetermined angular range.

63. An air bag system as claimed in claim 44, wherein:

said front seat status detecting means detects a longitudinal position of said front seat; and

said gas pressure controlling means is adapted to control the distribution of the gas pressure in accordance with the longitudinal position of the front seat detected by said front seat status detecting means.

64. An air bag system as claimed in claim 63, wherein said gas pressure controlling means controls the distribution of the gas pressure so as to expand the air bag downward when the longitudinal position detected by said front seat status detecting means is in a position behind a predetermined position.

65. An air bag system as claimed in claim 48, wherein:

said front seat status detecting means detects a longitudinal position of said front seat; and

said gas pressure controlling means is adapted to open and close said upper opening-closing valves and said lower opening-closing valves in accordance with the longitudinal position of said front seat detected by said front seat status detecting means.

66. An air bag system as claimed in claim 65, wherein said gas pressure controlling means opens and closes said opening-closing valves so as to expand the air bag downward when the longitudinal position of said front seat detected by said front seat status detecting means is in a position behind a predetermined position.

67. An air bag system as claimed in claim 66, wherein said gas pressure controlling means expands the air bag downward by releasing the gas pressure from said upper relief holes by opening said upper opening-closing valves, when the longitudinal position detected by said front seat status detecting means is in the position behind the predetermined position.

68. An air bag system as claimed in claim 65, wherein said gas pressure controlling means opens and closes the opening-closing valves so as to expand the air bag upward when the longitudinal position of said front seat detected by said front seat status detecting means is in a position before a predetermined position.

69. An air bag system as claimed in claim 68, wherein said gas pressure controlling means expands the air bag upward by releasing the gas pressure from said lower relief holes by opening said lower opening-closing valves, when the longitudinal position of said front seat detected by said front seat status detecting means is before the predetermined position.

70. An air bag system as claimed in claim 65, wherein said gas pressure controlling means controls said opening-closing values so as to expand the air bag in a substantially middle position between the upward and downward directions when the longitudinal position of said front seat detected by said front seat status detecting means is in a predetermined range.

71. An air bag system as claimed in claim 44, wherein:

said front seat status detecting means detects a vertical position of a seat cushion of said front seat; and

said gas pressure controlling means controls the distribution of the gas pressure in accordance with the vertical position of the seat cushion of said front seat detected by said front seat status detecting means.

72. An air bag system as claimed in claim 71, wherein said gas pressure controlling means controls the distribution of the gas pressure so as to expand the air bag downward when the vertical position detected by said front seat status detecting means is in a position higher than a predetermined position.

73. An air bag system as claimed in claim 48, wherein:

said front seat status detecting means detects a vertical position of a seat cushion of said front seat; and

said gas pressure controlling means opens and closes said upper and opening-closing valves and said lower opening-closing valves in accordance with the vertical position of the seat cushion of said front seat detected by seat front seat status detecting means.

74. An air bag system as claimed in claim 73, wherein said gas pressure controlling means opens and closes said opening-closing valves so as to expand the air bag downward when the vertical position of the seat cushion of said front seat detected by said front seat status detecting means is in a position higher than the predetermined position.

75. An air bag system as claimed in claim 74, wherein said gas pressure controlling means expands the air bag downward by releasing the gas pressure from said upper relief holes by opening said upper opening-closing valves, when the vertical position detected by said front seat status detecting means is in the position higher than the predetermined position.

76. An air bag system as claimed in claim 73, wherein said gas pressure controlling means opens and closes the opening-closing valves so as to expand the air bag upward when the vertical position of the seat cushion of said front seat detected by said front seat status detecting means is in a position lower than a predetermined position.

77. An air bag system as claimed in claim 76, wherein said gas pressure controlling means expands the air bag upward by releasing the gas pressure from said lower relief holes by opening said lower opening-closing valves, when the vertical position of the seat cushion of said front seat detected by said front seat status detecting means is lower than the predetermined position.

78. An air bag system as claimed in claim 73, wherein said gas pressure controlling means controls said opening-closing valves so as to expand the air bag in a substantially middle position between upward and downward directions when the vertical position of the seat cushion of said front seat detected by said front seat status detecting means is in a predetermined range.

79. An air bag system as claimed in claim 44, wherein:

said front seat status detecting means detects a vertical position of a head rest of said front seat; and

said gas pressure controlling means is adapted to control the distribution of the gas pressure in accordance with the vertical position of the head rest of said front seat detected by said front seat status detecting means.

80. An air bag system as claimed in claim 79, wherein said gas pressure controlling means controls the distribution of the gas pressure so as to expand the air bag downward when the vertical position detected by said front seat status detecting means is in a position higher than a predetermined position.

81. An air bag system as claimed in claim 48, wherein:

said front seat status detecting means detects a vertical position of a head rest of said front seat; and

said gas pressure controlling means opens and closes said upper opening-closing valves and said lower opening-closing valves in accordance with the vertical position of the head rest of said front seat detected by said front seat status detecting means.

82. An air bag system as claimed in claim 81, wherein said gas pressure controlling means opens and closes said opening-closing valves so as to expand the air bag downward when the vertical position of the head rest of said front seat detected by said front seat status detecting means is in a position higher than a predetermined position.

83. An air bag system as claimed in claim 82, wherein said gas pressure controlling means expands the air bag downward by releasing the gas pressure from said upper relief holes by opening said upper opening-closing valves, when the vertical position detected by said front seat status detecting means is in the position higher than the predetermined position.

84. An air bag system as claimed in claim 81, wherein said gas pressure controlling means opens and closes the opening-closing valves so as to expand the air bag upward when the vertical position of the head rest of said front seat detected by said front seat status detecting means is in a position lower than a predetermined position.

85. An air bag system as claimed in claim 84, wherein said gas pressure controlling means expands the air bag upward by releasing the gas pressure from said lower relief holes by opening said lower opening-closing valves, when the vertical position of the head rest of said front seat detected by said front seat status detecting means is in a position lower than the predetermined position.

86. An air bag system as claimed in claim 81, wherein said gas pressure controlling means controls said opening-closing valves so as to expand the air bag in a substantially middle position between the upward and downward directions when the vertical position of the head rest of said front seat detected by said front seat status detecting means is in a predetermined range.