Abstract:
An airbag includes a fabric forming the airbag. The fabric has a vent hole for discharging some of gas introduced into the airbag to the outside. The vent hole is located at a position where the vent hole is not blocked when the airbag protects an occupant. This smoothly discharges gas, thereby improving the occupant protection performance.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to an airbag that is installed in a vehicle to protect an occupant of the vehicle.  
           [0002]    For example, Japanese Examined Patent Publication No. 6-47363 discloses an airbag that is deployed to a predetermined position. Specifically, when protecting an occupant of a vehicle, the airbag is deployed and inflated while contacting structures in the passenger compartment, such as an instrument panel, a windshield, and a pillar garnish. Contacting the structures allows the airbag to be held at the predetermined position.  
           [0003]    The airbag of the publication has vent holes for discharging gas that is supplied to the airbag for inflation and deployment to the outside. The vent holes prevent the internal pressure from being excessively increased, thereby effectively hold and protect an occupant. Normally, the positions of the vent holes are determined such that discharged gas is directed away from the occupant.  
           [0004]    When protecting an occupant, a typical airbag is pushed back by the occupant in a direction opposite to the direction of inflation and deployment. In other cases, the airbag is moved laterally. Accordingly, the airbag can contact structures in the passenger compartment at a relatively large area. This sometimes causes the vent holes to be partly or entirely blocked by the contacting structures. When blocked, the vent holes cannot smoothly discharge gas. It is thus difficult to improve the occupant protection performance of the airbag.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention was made for solving the above problems in the prior art. Accordingly, it is an objective of the present invention to provide an airbag that smoothly discharge gas, thereby improving the occupant protection performance.  
           [0006]    To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, an airbag that is deployed and inflated to protect an occupant on a vehicle when an impact equal to or greater than a predetermined value is applied to the vehicle is provided. The airbag includes a fabric forming the airbag. The fabric has a vent hole for discharging some of gas introduced into the airbag to the outside. The vent hole is located at a position where the vent hole is not blocked when the airbag protects an occupant.  
           [0007]    Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:  
         [0009]    [0009]FIG. 1 is a partial perspective view illustrating a deployed and inflated airbag according to one embodiment of the present invention;  
         [0010]    [0010]FIG. 2 is plan view illustrating fabric forming the airbag of FIG. 1;  
         [0011]    [0011]FIG. 3( a ) is a side view showing a position of a large diameter vent hole;  
         [0012]    [0012]FIG. 3( b ) is a side view showing a position of a small diameter vent hole;  
         [0013]    [0013]FIG. 4( a ) is a side view illustrating the airbag when protecting an occupant, as viewed from a center of the passenger compartment;  
         [0014]    [0014]FIG. 4( a ) is a side view illustrating the airbag when protecting an occupant, as viewed from the outside of the vehicle;  
         [0015]    [0015]FIG. 5 is a plan view illustrating vent holes according to a modified embodiment; and  
         [0016]    [0016]FIG. 6 is a plan view illustrating vent holes according to another modified embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    An airbag  11  for front passenger seat according to one embodiment of the present invention will now be described with reference to FIGS.  1  to  4 . First, an airbag device  10  using the airbag  11  will be described.  
         [0018]    As shown in FIG. 1, the airbag device  10  includes the airbag  11 , an inflator  12  for supplying gas to the airbag  11 , and a case for accommodating the airbag  11  and the inflator  12 . With the airbag  11  and the inflator  12  accommodated therein, the case  13  is fixed to a part of the instrument panel  21  that faces a front passenger seat  22 . Thus, when operating (when the airbag  11  is deployed and inflated), the airbag device  10  holds and protects an occupant in the front passenger seat  22 .  
         [0019]    When the airbag device  10  is activated, the airbag  11 , during its deployment and inflation, breaks the instrument panel  21  at a tear line  21   a  (see FIG. 3) to form an opening of the case  13 . The airbag  11  is then deployed and inflated in the passenger compartment. In this embodiment, the airbag  11  is shaped like a triangular pole when deployed and inflated. That is, the airbag  11  is triangular as viewed from either side of the vehicle and rectangular as viewed from either the front or the rear.  
         [0020]    The airbag  11  is formed of airbag fabric  11 A. When deployed and inflated, the airbag fabric  11 A has an inner side  11   a  facing the lateral center of the passenger compartment and an outer side  11   b  facing the outside of the vehicle. Vent holes  30   a ,  30   b  are formed in the inner side  11   a  and the outer side  11   b , respectively, for discharging gas supplied from the inflator  12  to the outside of the airbag  11 , or to the passenger compartment.  
         [0021]    [0021]FIG. 2 is a development of the airbag fabric  11 A before being sewn. As shown in FIG. 2, the airbag fabric  11 A has an upper side  11   c  and a lower side  11   d  in addition to the inner side  11   a  and the outer side  11   b . The airbag fabric  11 A is folded at a center folding line  11   f  (broken line) and sewn at peripheral sewing lines  11   h  (alternate long and two short dashes lines). An opening  30   c  in the airbag fabric  11 A near the folding line  11   f . The opening  30   c  is used for supplying gas to the airbag  11  from the inflator  12 .  
         [0022]    The vent holes  30   a ,  30   b  are located at positions where the vent holes  30   a ,  30   b  are not blocked by a windshield  23  and a door glass  24  at the front passenger seat  22  from the beginning of deployment and inflation of the airbag  11  to the completion of holding and protection of the occupant.  
         [0023]    As shown in FIGS. 1 and 2, the opening area of the vent hole  30   a  formed in the inner side  11   a  is greater than the opening area of the vent hole  30   b  formed in the outer side  11   b . In this embodiment, the vent holes  30   a ,  30   b  are circular. The diameter d1 of the inner side vent hole  30   a  is 70 mm. The diameter d2 of the outer side vent hole  30   b  is 40 mm.  
         [0024]    The diameters d1, d2 of the vent holes  30   a ,  30   b  are not limited to the above listed values. As long as d1 is greater than d2 (d1&gt;d2), the diameter d1 of the large vent hole  30   a  may be any value between 60 mm and 90 mm, inclusive, and the diameter d2 of the small vent hole  30   b  may be any value less than 60 mm. The ranges of the diameters d1, d2 are changed as necessary according to the arrangement of structures in the passenger compartment, such as the windshield  23 , the door glass  24  at the front passenger seat  22 , and a front pillar garnish  26 .  
         [0025]    If the diameter d1 of the large vent hole  30   a  is less than 60 mm, the vent hole  30   a  cannot discharge sufficient amount of gas in period from deployment and inflation of the airbag  11  to the completion of protection of the occupant. That is, the airbag  11  cannot have a desired gas discharging property.  
         [0026]    If the diameter d1 of the large vent hole  30   a  is more than 90 mm, the amount of discharged gas will be excessive during the period. If the diameter d2 of the small vent hole  30   b  exceeds 60 mm, the area of the vent hole  30   b  is too large. In this case, if the airbag  11  is moved laterally by a load applied by an occupant, the vent hole  30   b  is likely to be blocked by the windshield  23 , the door glass  24 , or the front pillar garnish  26 .  
         [0027]    In this embodiment, the vent holes  30   a ,  30   b  are at the positions described below when the airbag  11  is deployed and inflated.  
         [0028]    Referring to FIG. 3( a ), the large vent hole  30   a  is formed at a position where a distance D1 between the center C 1  of the vent hole  30   a  and a vertical reference plane P 1  is 220 mm. The vertical reference plane P 1  contains the laterally extending tear line  21   a  and extends vertically. Also, a distance D2 between the center C 1  of the vent hole  30   a  and a first horizontal reference plane P 2  is 70 mm. The first horizontal reference plane P 2  contains the laterally extending tear line  21   a  and extends horizontally. Further, a distance D3 between the center C 1  of the vent hole  30   a  and a second horizontal reference plane P 3  is 80 mm. The second horizontal reference plane P 3  contains a line L of intersection of the vertical reference plane P 1  and the windshield  23 , and extends horizontally.  
         [0029]    Referring to FIG. 3( b ), the small vent hole  30   b  is formed at a position where a distance D4 between the center C 2  of the vent hole  30   b  and the vertical reference plane P 1  is 90 mm. Also, a distance D5 between the center C 2  of the vent hole  30   b  and the first horizontal reference plane P 2  is 90 mm. Further, a distance D6 between the center C 2  of the vent hole  30   b  and the second horizontal reference plane P 3  is 60 mm.  
         [0030]    Accordingly, as shown in FIGS.  2  to  3 ( b ), the positions of the vent holes  30   a ,  30   b  are asymmetrical with respect to the lateral direction of the vehicle.  
         [0031]    The distances D1 to D6 between the centers C 1 , C 2  of the vent holes  30   a ,  30   b  and the reference planes P 1  to P 3  are not limited to the values listed above. Regarding the large vent hole  30   a , the distance D1 may be any value between 50 mm and 400 mm, inclusive, the distance D2 may be any value between 50 mm and 200 mm, inclusive, and the distance D3 may be any value between −50 mm and 100 mm inclusive. In FIG. 3( a ), the distance D3 has a negative value if the center C 1  is higher than the second reference plane P 3 , and has a positive value if the center C 1  is lower than the second reference plane P 3 . Regarding the small vent hole  30   b , the distance D4 may be any value between 40 mm and 180 mm, inclusive, the distance D5 may be any value between 40 mm and 110 mm, inclusive, and the distance D6 may be any value between 40 mm and 110 mm inclusive. The distances D1 to D6 are changed as necessary according to the arrangement of the structures in the passenger compartment, such as the windshield  23 , the door glass  24  at the front passenger seat  22 , and the front pillar garnish  26 .  
         [0032]    If at least one of the distances D1 to D3 is out of the above listed ranges, the vent hole  30   a  is partly or entirely blocked with the instrument panel  21  or the windshield  23  temporarily during a period from deployment and inflation of the airbag  11  to the completion of the protection of the occupant. This reduces the amount of discharged gas. In other words, gas is not smoothly discharged.  
         [0033]    If at least one of the distances D4 to D6 is out of the above listed ranges, the vent hole  30   b  is partly or entirely blocked with the windshield  23 , the door glass  24 , or the front pillar garnish  26  during deployment and inflation of the airbag  11  temporarily. This reduces the amount of discharged gas. In other words, gas is not smoothly discharged.  
         [0034]    When the airbag  11  is deployed and inflated, part of the outer side  11   b  contacts the door glass  24  of the passenger seat  22 , part of the upper side  11   c  (see FIG. 1) contacts the windshield  23 , and part of the lower side  11   d  (see FIG. 1) contacts the instrument panel  21 . However, the vent holes  30   a ,  30   b  are scarcely blocked by structures in the passenger compartment, such as the instrument panel  21 , the windshield  23 , the door glass  24 , or the front pillar garnish  26 .  
         [0035]    When the deployed and inflated airbag  11  contacts an occupant in the front passenger seat  22  and starts holding the occupant, the airbag  11  is pushed back frontward. This increases the contacting area between each of the sides  11   a  to  11   d  and the corresponding structure in the passenger compartment.  
         [0036]    As the occupant moves forward into the airbag  11 , the inner side  11   a  of the airbag  11  starts contacting the instrument panel  21  and the windshield  23 . As the occupant moves further forward, the contacting area of the inner side  11   a  increases. However, even if the airbag  11  is holding the occupant, the large vent hole  30   a  is not blocked by the instrument panel  21  or the windshield  23 .  
         [0037]    On the other hand, as shown in FIG. 4( b ), as the occupant moves forward into the airbag  11 , the contacting area between the outer side  11   b  and structures such as the instrument panel  21 , the windshield  23 , and the door glass  24  is increased. At this time, the outer side  11   b  contacts the front pillar garnish  26 . However, even if the airbag  11  is holding the occupant, the small vent hole  30   b  is not blocked by the instrument panel  21 , the windshield  23 , the door glass  24 , or the front pillar garnish  26 . In FIG. 4( b ), an area indicated by S 1  is a part of the outer side  11   b  that contacts the front pillar garnish  26 . An area indicated by S 2  is a part of the outer side  11   b  that contacts the door glass  24 .  
         [0038]    This embodiment has the following advantages.  
         [0039]    (1) In the above illustrated embodiment, the positions of the vent holes  30   a ,  30   b  of the airbag  11  are determined such that the vent holes  30   a ,  30   b  are not blocked by structures in the passenger compartment of the vehicle  20  when the airbag  11  protects an occupant in the front passenger seat  22 , or during a period from when the airbag starts being deployed and inflated to when holding of the occupant is completed. Therefore, when the airbag  11  protects the occupant, gas is smoothly discharged through the vent holes  30   a ,  30   b . This improves the occupant protection performance of the airbag  11 .  
         [0040]    (2) In the above illustrated embodiment, the vent hole  30   a  is formed in the inner side  11   a  of the airbag  11 , which faces the center of the passenger compartment, and the vent hole  30   b  is formed in the outer side  11   b  of the airbag  11 . The diameter of the vent hole  30   a  in the inner side  11   a  is set at 70 mm, and the diameter of the vent hole  30   b  in the outer side  11   b  is set at 40 mm. Therefore, the opening area of the vent hole  30   a  is greater than the opening area of the vent hole  30   b.    
         [0041]    Therefore, although the vent hole  30   b  is formed in the outer side  11   b , which is likely to contact structures in the passenger compartment, such as the door glass  24  and the front pillar garnish  26 , the vent hole  30   b  having a smaller opening area is unlikely to be blocked by those structures. The vent hole  30   a  is formed in the inner side  11   a , which faces fewer structures than the outer side  11   b . The opening area of the vent hole  30   a  is greater than the vent hole  30   b  formed in the outer side  11   b , which permits gas to be smoothly discharged.  
         [0042]    (3) In the above illustrated embodiment, the present invention is applied to the airbag  11  of the airbag device  10  for protecting an occupant in the front passenger seat  22 .  
         [0043]    Generally, in an area of the passenger compartment of the vehicle  20  that corresponds to deployment area of an airbag for the front passenger seat  22 , a number of structures, such as the instrument panel  21 , the windshield  23 , the door glass  24 , and the front pillar garnish  26  are provided. The airbag  11  partly and temporarily contacts structures in the passenger compartment during the period from the beginning of deployment and inflation to the completion of holding of the occupant. Particularly, when holding and protecting the occupant, the airbag  11  is deformed, and the contacting area between the airbag  11  and the structure in the passenger compartment is increased.  
         [0044]    Even if the occupant is held and protected and the contacting area between the airbag  11  and structures in the passenger compartment is increased, the vent holes  30   a ,  30   b  are not blocked. Therefore, gas is smoothly discharged from the airbag  11 . This improves the occupant protection performance. Therefore, the present invention is particularly preferable for the airbag  11  used in the airbag device  10  for the front passenger seat  22 .  
         [0045]    It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the invention may be embodied in the following forms.  
         [0046]    As shown in FIG. 5, a plurality of vent holes  30   a  may be formed in the inner side  11   a  of the airbag fabric  11 A. The total opening area of the vent holes  30   a  is greater than the opening area of the vent hole  30   b  formed in the outer side  11   b . This modification has the advantage (2) of the embodiment of FIGS.  1  to  4 ( b ).  
         [0047]    As shown in FIG. 6, the vent hole  30   b  formed in the outer side  11   b  of the airbag fabric  11 A may be omitted. That is, a vent hole  30   a  may be formed only in the inner side  11   a  of the airbag fabric  11 A. In this configuration, the vent hole  30   a  is easily prevented from being blocked by the structures in the passenger compartment when the airbag  11  protects an occupant.  
         [0048]    In the embodiments of FIGS.  1  to  6 , the vent holes  30   a ,  30   b  need not be circular. The vent holes  30   a ,  30   b  may be, for example, elliptic or polygonal. Alternatively, the vent holes  30   a ,  30   b  may be formed as slits. In the case where the vent holes  30   a ,  30   b  are polygonal or formed as slits, the corners of the vent holes  30   a ,  30   b  are preferably rounded to avoid concentration of stress applied to portions in the vicinity of the vent holes  30   a ,  30   b  during deployment and inflation of the airbag  11 .  
         [0049]    Although, the airbag  11  of the airbag device  10  for front passenger seat is described, the present invention may be applied to other types airbags. For example, the present invention may be applied to the airbag of a side airbag device. Further, the present invention may be applied to the airbag in an airbag device for rear seat, which airbag is deployed and inflated between an occupant in a rear seat and either a driver&#39;s seat or a front passenger seat.  
         [0050]    Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.