Abstract:
An airbag of an airbag apparatus includes an airbag main body capable of expanding in a manner such that the airbag main body covers a steering wheel in front of a driver seated in a driver-side seat, and an upper extending portion that covers a vehicle roof pillar by extending upward from above a left or right side of the airbag main body. The airbag apparatus is designed so as to maintain the airbag shape and position even when the steering wheel is rotated. In the event of an oblique collision, the airbag is capable of preventing a head region of a driver from colliding with the pillar, yet without excessively increasing the required airbag volume.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT  
       [0001]     The present invention relates to an airbag and an airbag apparatus attached to a motor vehicle or the like, and more specifically relates to an airbag and an airbag apparatus configured to prevent a head region of an occupant from colliding with a pillar of the motor vehicle.  
         [0002]     An airbag for protecting an occupant seated on a driver&#39;s seat, a passenger seat, or a rear seat of a motor vehicle, in the event of a crash of the motor vehicle, is known. When the volume of the airbag is increased, most of a head region and an upper half of the body of the occupant can be caught by the airbag, however, a large gas-generation volume is required for an inflator.  
         [0003]     A passenger airbag that prevents the head region of the occupant from colliding with a pillar of the motor vehicle and that attempts to minimize gas volume is described in U.S. Pat. No. 4,474,390.  FIG. 6  illustrates the airbag described in U.S. Pat. No. 4,474,390, in which an airbag apparatus is attached to an instrument panel  2  of the motor vehicle  1 , and the airbag  3  is extended between the instrument panel  2  and the passenger seat in a vertical direction.  
         [0004]     A front face of the airbag  3  faces an occupant seated on the passenger seat and serves as a colliding-face for the occupant that catches the occupant seated on the passenger seat in the event of a crash of the motor vehicle. At a rear face of the airbag  3 , a gas in-flow inlet  4  is provided.  
         [0005]     The airbag  3  has an inverted trapezoid shape. That is, the lower the position one moves from an upper part to a lower part, the smaller a width of the airbag (the width of the airbag in a left-and-right direction of the vehicle body of the motor vehicle  1 ) becomes. Therefore, the volume of a lower portion of the airbag is small. A side  6  of the upper portion of the airbag  3  prevents the occupant seated on the passenger seat from directly colliding with a front pillar  7 , in the event of an oblique crash of the motor vehicle  1 .  
         [0006]     An upper portion of the airbag described in U.S. Pat. No. 4,474,390 laterally overhangs. Therefore, in the event of an oblique crash of the motor vehicle, and when an occupant moves in a manner stretching upward in an obliquely forward direction, there is a possibility that a head region of the occupant collides with a pillar, overleaping the lateral overhanging portion of the airbag. In the airbag having increased lengths in an upper-and-lower direction and a left-and-right direction for preventing the above problem, the volume of the airbag becomes excessive.  
         [0007]     Accordingly, it is an object of the present invention to provide an airbag and an airbag apparatus capable of preventing the head region of the occupant from colliding with the pillar in the event of an oblique crash of the motor vehicle, yet without increasing the volume of the airbag.  
         [0008]     Further objects and advantages of the invention will be apparent from the following description of the invention and the associated drawings.  
       SUMMARY OF THE INVENTION  
       [0009]     An airbag according to one embodiment of the present invention is provided in front of a seat of a motor vehicle and includes an airbag main body configured to be expanded in front of an occupant, and an upper extending portion configured to extend upward from above a left or a right side of the airbag main body.  
         [0010]     The airbag has an extending length L of the upper extending portion from the airbag main body, which, when expanded in a direction parallel to an axial direction of a steering column, is determined to be from 50 to 400 mm.  
         [0011]     The airbag includes a device for limiting a thickness of the upper extending portion, when the upper extending portion is expanded.  
         [0012]     The airbag is for use in a front seat, and the upper extending portion is configured to be slanting toward a backside of the motor vehicle, when the airbag is expanded.  
         [0013]     The upper extending portion is configured to be slanting toward the backside of the motor vehicle, when the airbag is expanded, by connecting the upper extending portion on the occupant side to the airbag main body on the occupant side with a tether belt.  
         [0014]     In another embodiment of the invention, an airbag apparatus includes an airbag according to the above-described embodiment of the invention, and an inflator for expanding the airbag.  
         [0015]     In one embodiment of the airbag apparatus, the airbag apparatus is for use in a driver-side seat, and is configured not to change a posture thereof, even when a steering wheel is rotated.  
         [0016]     In the airbag according to the invention, the upper extending portion is extended upward from above a left or a right side of the airbag main body. Because the upper extending portion, when the airbag is expanded, is extended upward along the pillar and covers the pillar, a head region of the occupant is prevented from colliding with the pillar, even when the occupant moves upward in an obliquely forward direction.  
         [0017]     Particularly, by determining the extending length L of the upper extending portion from the airbag main body, when expanded, in the direction parallel to the axial direction of the steering column to be from 50 to 400 mm, the head region of the occupant is sufficiently prevented from colliding with the pillar.  
         [0018]     When the thickness of the upper extending portion, when expanded, is limited, the volume of the airbag can be reduced to that extent. In addition, the upper extending portion is designed to have a flat or nearly flat shape facing the occupant, and the upper extending portion can be widely expanded. Accordingly, the pillar is covered by the upper extending portion.  
         [0019]     Further, the A pillar of a motor vehicle is usually slanting toward the backside thereof. Therefore, in the airbag for use in a front-side seat, the upper extending portion is preferably configured, when expanded, in a manner so as to be slanting toward the backside of the motor vehicle.  
         [0020]     By connecting the upper extending portion on the occupant side to the airbag main body on the occupant side with the tether belt, the upper extending portion can be expanded in a manner so as to be slanting toward the backside of the vehicle.  
         [0021]     When the airbag apparatus is applied for use in a driver-side seat, the airbag apparatus is configured so as to not change the posture (i.e., shape and position) thereof, even when a steering wheel is rotated. As a result, even when the motor vehicle is crashed while moving through a curve, the upper extending portion is reliably expanded along the A pillar. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]      FIG. 1  is a perspective view illustrating an expanded state of an airbag according to one embodiment of the invention.  
         [0023]      FIG. 2 ( a ) is a vertical cross-section illustrating a first state when the airbag is expanded.  
         [0024]      FIG. 2 ( b ) is a vertical cross-section illustrating a second state when the airbag is expanded.  
         [0025]      FIG. 3  is a plan view illustrating the airbag.  
         [0026]      FIG. 4  is a side view illustrating an interior of a motor vehicle when the airbag is expanded.  
         [0027]      FIG. 5  is a perspective view illustrating a state when an upper extending portion of the airbag catches a head region of an occupant.  
         [0028]      FIG. 6  is a perspective view of a conventional airbag. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]     The embodiments of the present invention will be described below with reference to the accompanying drawings.  
         [0030]      FIG. 1  is a perspective view illustrating an embodiment of an airbag, when expanded;  FIG. 2 ( a ) is a vertical cross-section illustrating the airbag, when a first chamber thereof is expanded;  FIG. 2 ( b ) is a vertical cross-section illustrating the airbag when a second chamber thereof is expanded;  FIG. 3  is a plan view of the airbag;  FIG. 4  is a side view of an interior of a motor vehicle when the airbag is expanded; and  FIG. 5  is a perspective view of the airbag when an upper extending portion thereof catches a head region of an occupant.  
         [0031]     In this embodiment, an airbag  10  is the driver-side airbag mounted on a driver-side airbag apparatus of the motor vehicle. The driver-side airbag apparatus is provided with the airbag  10 , a retainer (not shown), to which the airbag  10  is attached, a gas-generator (not shown) for expanding the airbag  10 , and a module cover (not shown) for covering the folded airbag  10 . The driver-side airbag apparatus is disposed at an occupant side of a central portion  2   a  of a steering wheel  2 .  
         [0032]     Further, in this embodiment, a driver&#39;s seat is located in the left side of the front row in the motor vehicle and an A pillar  1  is disposed in front of the driver&#39;s seat on the oblique left. The A pillar  1  is slanting toward a backside of the motor vehicle, as shown in  FIG. 4 .  
         [0033]     The airbag  10  is provided with an airbag main body  12  that is expanded in a manner to cover the steering wheel  2  in front of the occupant seated on the driver&#39;s seat, and an upper extending portion  14  that covers the A pillar  1  by upwardly extending from the upper part of the left side of the airbag main body  12 .  
         [0034]     An extending length L of the upper extending portion  14  from the airbag main body  12 , when expanded, in a direction parallel to an axial direction of a steering column, is preferably determined to be from 50 to 400 mm, particularly from 150 to 400 mm, and more particularly from 200 to 400 mm.  
         [0035]     As shown in  FIG. 3 , the airbag main body  12  is expanded such that a side peripheral portion thereof overhangs an outer periphery of the steering wheel  2  (in a radial direction). Further, in this embodiment, the amount of overhang of the airbag main body  12  from both a left and a right side part of the outer periphery of the steering wheel  2  in the expanded state of the airbag main body  12  is less than the amount of overhang from an upper end portion and a lower end portion of the outer periphery of the steering wheel  2 .  
         [0036]     In this embodiment, the airbag  10  is formed by stitching a front main panel  16  composed of a series of a surface of the airbag main body  12  on an occupant side and a surface of the upper extending portion  14  on an occupant side, a rear panel  18  composed of a series of a surface of the airbag main body  12  on a steering wheel side and a surface of the upper extending portion  14  on a steering wheel side, and an upper panel  20  disposed at an upper part of the airbag main body  12  on an occupant side together.  
         [0037]     The front main panel  16  and the rear panel  18  are the panels having substantially the same shape and each of respective peripheral edge portions are combined together by a seam (not shown) formed with a thread or the like. The upper panel  20  is overlapped with the front main panel  16  on an occupant side at an upper part of the airbag main body  12 , and a peripheral edge portion of the upper panel  20  is combined with the front main panel  16  by a seam  22 .  
         [0038]     An internal part of the airbag main body  12  is partitioned into a first chamber  12   a  and a second chamber  12   b  by the front main panel  16 , the rear panel  18 , and the upper panel  20 . The first chamber  12   a  is a chamber surrounded by the front main panel  16  and the rear panel  18  and the second chamber  12   b  is a chamber surrounded by the front main panel  16  and the upper panel  20 .  
         [0039]     In the vicinity of a center of the airbag main body  12  on a steering wheel  2  side, a gas inlet (not shown) for receiving gas from the gas generator is provided. The gas inlet communicates with internal space of the first chamber  12   a.    
         [0040]     At both a left and a right side of the second chamber  12   b , a communication opening  24  that allows the first chamber  12   a  to communicate with the second chamber  12   b  (refer to FIGS.  2 ( a ) and  2 ( b )) is formed. Further, in the vicinity of a center of the second chamber  12   b  in a left-and-right direction, a vent hole  26  for allowing the gas in the second chamber  12   b  to be discharged into the first chamber  12   a , when the expanded second chamber  12   b  catches the occupant, is formed. In addition, although not shown, a vent hole for allowing the gas in the first chamber  12   a  to be discharged is formed in the airbag main body  12 .  
         [0041]     Further, in this embodiment, the front main panel  16  and the rear panel  18  are combined together by a tether belt  28  at the upper part of the airbag main body  12 . Thereby, a thickness of an upper part of the first chamber  12   a , when expanded, is limited.  
         [0042]     Furthermore, in this embodiment, in the upper extending portion  14 , the front main panel  16  and the rear panel  18  are also combined by a tether belt (not shown). In this embodiment, the tether belt is provided at two positions along an extending direction of the upper extending portion  14 . A numeral  30  in  FIG. 3  denotes a seam that stitches an end of the tether belt in the upper extending portion  14  on the front main panel  16 . By the tether belt, the upper extending portion  14  is made to have a flat shape widened in a left-and-right direction, when expanded.  
         [0043]     In this embodiment, the upper extending portion  14  on the occupant side, when expanded, is connected to the airbag main body  12  on the occupant side by a tether belt  32  in a manner such that the upper extending portion  14  is slanting toward the backside of the motor vehicle. A numeral  34  (in  FIG. 5 ) denotes a seam that combines each of both ends of the tether belt  32  with the front main panel  16 .  
         [0044]     In the airbag  10 , a peripheral edge portion of the gas inlet is connected to the retainer. In addition, the gas generator is attached to the retainer to allow the gas to be supplied into the airbag  10  through the gas inlet. Further, the airbag  10  is folded and the module cover is attached in a manner to cover the airbag  10 , and thus the airbag apparatus is configured.  
         [0045]     In this embodiment, an attaching base (not shown) whose posture is not changed, even when the steering wheel  2  is rotated, is provided in the central portion  2   a  of the steering wheel  2 . A configuration of the attaching base is not particularly limited. For example, the attaching base may be configured in a manner not to connect to the steering wheel  2  and to connect to a non-rotating member, such as steering column housing or the like, through a connecting member, or other configuration may be applicable.  
         [0046]     The airbag apparatus is attached to the attaching base and is configured not to change the posture, even when the steering wheel  2  is rotated.  
         [0047]     When a motor vehicle, on which the thus configured airbag apparatus for use in a driver-side seat is mounted, is crashed, the gas generator activates, and the gas is blown out and supplied into the airbag  10 . The airbag  10  starts to be expanded by the gas, and pushing open the module cover, the airbag  10  is expanded in front of the occupant seated on the driver-side seat.  
         [0048]     In this embodiment, because the gas blown out from the gas generator is delivered into the first chamber  12   a , the airbag  10  is largely expanded from a central portion of the airbag main body  12  to a lower part thereof first, as shown in  FIG. 2 ( a ). In addition, because an internal volume of the first chamber  12   a  is small in comparison with an entire volume of the airbag  10  and an expansion of the upper part of the first chamber  12   a  toward the occupant side is limited by the tether belt  28 , the airbag main body  12  is immediately expanded from the central part to the lower part thereof. Therefore, a chest region or an abdominal region of the occupant seated on the driver-side seat is first caught by the airbag  10  (airbag main body  12 ).  
         [0049]     The gas delivered into the first chamber  12   a  reaches an upper left part of the airbag main body  12  and flows into the upper extending portion  14  and flows into the second chamber  12   b  passing through each of the communication openings  24 . As a result, each of the upper part of the airbag main body  12  and the upper extending portion  14  is also expanded. The upper extending portion  14  starts to be protrudingly expanded upward along the A pillar  1  from an upper left part of the airbag main body  12  and covers the A pillar  1 .  
         [0050]     Further, in this embodiment, because a thickness of the upper extending portion  14  is limited by the tether belt, the upper extending portion  14  is also immediately expanded. Furthermore, at this moment, because the upper extending portion  14  is expanded in a manner such that it is slanting toward the backside of the motor vehicle by being pulled by the tether belt  32 , the upper extending portion  14  is brought to smoothly cover the A pillar  1 .  
         [0051]     When the head region of the occupant moves straight toward approximately the front side, the head region is caught by an upper part of the expanded airbag main body  12  (the second chamber  12   b ) and thereby, the head region of the occupant is prevented from colliding with a member existing in front of the seat, such as the steering wheel  2  or the like.  
         [0052]     Further, even when the head region of the occupant moves upward in an obliquely left frontward direction, because the expanded upper extending portion  14  covers the A pillar  1 , the head region of the occupant is caught by the upper extending portion  14  and the head region of the occupant is prevented from colliding with the A pillar  1 .  
         [0053]     Furthermore, in this embodiment, by designing the extending length L of the upper extending portion  14  from the airbag main body, when expanded, in the direction parallel to the axial direction of the steering column to be equal to or greater than 50 mm, the head region of the occupant is sufficiently prevented from colliding with the A pillar  1 . In addition, because the extending length L of the upper extending portion  14  from the airbag main body is designed to be 400 mm or less, an interference of the upper extending portion  14  with a roof part of the motor vehicle can be suppressed.  
         [0054]     Furthermore, in this embodiment, because the thickness of the upper extending portion  14 , when expanded, is limited by the tether belt, part of the upper extending portion  14  facing the occupant is brought to have a flat shape or nearly the same shape. As a result, the upper extending portion  14  is widely expanded and the A pillar  1  is brought to be widely covered with the upper extending portion  14 .  
         [0055]     In this embodiment, because the airbag apparatus is configured not to change the posture thereof even when the steering wheel  2  is rotated, even when the motor vehicle is crashed, while moving through a curve, the upper extending portion  14  is reliably expanded along the A pillar  1 .  
         [0056]     The above-described embodiments are illustrative of the invention, and are not to be construed as limiting the invention.  
         [0057]     For example, in the above-described embodiment, because the pillar is disposed at a left side in front of the seat, the upper extending portion is provided at an upper left part of the airbag main body. However, when a pillar is disposed at a right side in front of the seat, the upper extending portion is provided at an upper right part of the airbag main body.  
         [0058]     In this embodiment, an example of applying the present invention to the airbag apparatus for use in the driver-side seat is described. However, the present invention can be also applied to the airbag apparatus for use in a passenger seat or the seat at a row behind the driver-side seat and the passenger seat.  
         [0059]     The disclosure of Japanese Patent Application No. 2005-018538 filed on Jan. 26, 2005, is incorporated herein.