Abstract:
An airbag inflating vertically in front of an occupant includes a front portion facing the occupant upon inflation. The front portion has a lower part, a middle part and an upper part. The lower part has a lateral width greater than that of the middle and upper parts. The airbag can receive the occupant&#39;s arms at low cost.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT  
       [0001]     The present invention relates to an airbag and an airbag system for use in automobiles and so forth.  
         [0002]     It is known to provide a driver-seat airbag system to a steering wheel and a passenger airbag system to an instrument panel in front of a passenger seat to restrain the occupants of an automobile in a collision.  
         [0003]     As an airbag system that receives the arms of an occupant with an airbag to restrain the occupant in a collision, an airbag system having a driver-seat airbag and arm bags disposed on the right and left of the lower part of the driver-seat airbag is disclosed in Japanese Unexamined Patent Application Publication No. 2003-182500. However, the airbag system uses three airbags in total, so that it may increase in cost.  
         [0004]     One example is an airbag formed of two front and rear panels. FIGS. 11 to 18 of Japanese Unexamined Patent Application Publication No. 2000-25544 describe an airbag having a large thickness in an inflated state and a procedure for sewing it. The airbag and its sewing procedure will now be described with reference to FIGS.  4  to  11  disclosed in the attached drawings of the specification.  
         [0005]     According to claim  2  of the reference,  
         [0006]     “An airbag comprising two substantially trapezoidal panels A and B sewn together, wherein  
         [0007]     the panel A has a side  2  corresponding to the upper side of the trapezoid, a side  4  corresponding to the bottom of the trapezoid, and sides  1  and  3  ,corresponding to the hypotenuses of the trapezoid, the side  4  having a rectangular cut  5  in the center;  
         [0008]     the panel B has a side  12  corresponding to the upper side of the trapezoid, a side  14  corresponding to the bottom of the trapezoid, and sides  11  and  13  corresponding to the two hypotenuses of the trapezoid, the side  14  having a rectangular projection  15  in the center;  
         [0009]     the projection  15  having sides  15   a  and  15   b  continuing to the side  14 , and a side  15   c  connecting the sides  15   a  and  15   b,    
         [0010]     the side  1  of the panel A having a side if overlapping the side  11  of the panel B and a side  1   r  extending therefrom;  
         [0011]     the side  3  of the panel A having a side  3   f  overlapping the side  13  of the panel B and a side  3   r  extending therefrom;  
         [0012]     the side  4  of the panel A having sides  4   a  and  4   b  on both sides of the rectangular cut  5 ;  
         [0013]     the rectangular cut  5  having sides  51  and  53  continuing to the sides  4   a  and  4   b  and a side  52  connecting the sides  51  and  53 ;  
         [0014]     the side  14  of the panel B having sides  14   a  and  14   b  between the both sides  15   a  and  15   b  of the projection  15  and the sides  11  and  13 ;  
         [0015]     the panels A and B being sewn with a seam  20  along the sides  1   f  and  11 , the sides  2  and  12 , and the sides  3   f  and  13 ;  
         [0016]     the part along the side  4   a  and the part along the side  4   b  of the panel A being sewn up with a seam  30 ;  
         [0017]     the part along the side  15   a  and the part along the side  14   a  of the panel B being sewn with a seam  58 ;  
         [0018]     the part along the side  15   b  of the panel A and the part along the side  14   b  of the panel B being sewn with the seam  58 ;  
         [0019]     the part along the sides  1   r  and  3   r  of the panel A and the part along the side  15   c  of the panel B being sewn up with a seam  48 ;  
         [0020]     the part along the sides  51  and  53  of the rectangular cut  5  and the part along the side  52  of the panel A being sewn with a seam  60 .” 
         [0021]     To manufacture the airbag, as shown in FIGS.  4  ( a ) and  4  ( b ), the two panels A and B are cut from a base fabric and placed one on another. The panel A has the shape of an approximate trapezoid having four sides  1 ,  2 ,  3 , and  4 . The side  4  corresponding to the bottom of the trapezoid is curved in substantially elbow shape, in the center of which the rectangular cut ′ 5  is provided. The side  4  of the panel A has sides  4   a  and  4   b  on both sides of the rectangular cut  5 . The rectangular cut  5  has sides  51  and  53  that continue to the sides  4   b  and  4   a,  respectively, and a side  52  that connects the sides  51  and  53 .  
         [0022]     The sides  1  and  3  corresponding to the hypotenuses of the trapezoid have front sides  1   f  and  3   f  and rear sides  1   r  and  3   r,  respectively. The sides if and  3   f  are substantially equal in length to the sides  11  and  13 .  
         [0023]     The panel A has a gas port  9 .  
         [0024]     The panel B has the shape of an approximate trapezoid having four sides  11 ,  12 ,  13 , and  14 . The side  14  corresponding to the bottom of the trapezoid has a projection  15 . Reference numerals  15   a  and  15   b  indicate sides continuing to the side  14  of the projection  15 . Numeral  15  denotes a side connecting the sides  15   a  and  15   b.  Numerals  14   a  and  14   b  indicate parts of the side  14  extending to both sides of the projection  15 .  
         [0025]     The panels A and B have been put one on the other such that the sides  1   f  and  11 , the sides  2   f  and  12 , and the-sides  3   f  and  13  correspond to each other, and are sewn along the sides  1  to  3  and  11  to  13 , as shown in FIGS.  4  ( c ) and  4  ( d ). Numeral  20  indicates a seam thereof. The sides  1   r  and  3   r  extend over the sides  11  and  13 , respectively, so that they are not sewn to the sides  11  and  13 .  FIG. 4  ( d ) is a cross sectional view taken along line D-D of  FIG. 4  ( c )  
         [0026]     The panels A and B of the sewn body are drawn along the arrow G of  FIG. 4  ( d ).  
         [0027]     Thus, as shown in FIGS.  5  ( a ) and  6 , the panel A is folded in two along the center line g in  FIG. 4  ( c ), so that the sides  4   a  and  4   b  overlap with each other. The panel B is also folded in two along the center line g, and the projection  15  is also folded in two, so that the sides  15   a  and  15   b  overlap with each other, and also the sides  14   a  and  14   b  overlap with each other. Then, as shown in FIGS.  5  ( b ) and  7 , the parts of the panel A along the sides  4   a  and  4   b  are sewn up. Numeral  30  indicates a seam along the sides  4   a  and  4   b.    
         [0028]      FIG. 5  ( c ) is a cross-sectional view taken along line  5  ( c )- 5  ( c ) of  FIG. 5  ( b );  FIG. 5  ( d ) is a cross-sectional view taken along arrow  5  ( d )- 5  ( d ) of  FIG. 5  ( b ).  
         [0029]     As shown in  FIG. 5  ( c ), the sewing portions  21  with the seam  20  are disposed outside the bag.  
         [0030]     The panels A and B of the sewn bag are drawn along arrows E in  FIG. 5  ( d ) and as such, are brought into the state shown in  FIG. 5  ( e ). They are further drawn along arrows F in  FIG. 5  ( e ) into the state shown in FIGS.  5  ( f ) and  8 , in which the sides  1   r  and  3   r  of the panel A are brought into a straight line.  
         [0031]     As shown in  FIGS. 9 and 11 , the side  15   c  of the projection  15  is sewn on the sides  1   r  and  3   r  of the panel A with a seam  48 , and the sides  15   a  and  14   a  and the sides  15   b  and  14   b  are sewn with a seam  58 , respectively.  
         [0032]     Subsequently, as shown in  FIG. 10  ( a ), the left and right corners  5 L and SR of the rectangular cut  5 , at which the sides  52  and  51 , and the sides  52  and  53  intersect, respectively, are drawn along arrows X B . As shown in  FIG. 10  ( b ), the panel A is then sewn along the sides  51 ,  52 , and  53 . Numeral  60  indicates a seam thereof.  
         [0033]     Thus, the airbag shown in  FIG. 11  is completed.  
         [0034]     Accordingly, it is an object of the present invention to provide an airbag capable of receiving occupant&#39;s arms at low cost.  
       SUMMARY OF THE INVENTION  
       [0035]     According to a first aspect of the invention, an airbag inflates vertically in front of an occupant, wherein the lateral width of the lower part upon inflation is larger than that at a part above the lower part.  
         [0036]     According to a second aspect, the airbag of the first aspect has an intermediate part and upper and lower parts, wherein the intermediate part has a relatively small lateral width, and the upper and lower parts having a lateral width larger than that of the intermediate part upon inflation. The relationship is expressed as W 2 &lt;W 1 &lt;W 3 , where W 1  is the maximum lateral width of the upper part, W 2  is the minimum lateral width of the intermediate part, and W 3  is the maximum lateral width of the lower part.  
         [0037]     According to a third aspect, in the airbag of the second aspect, W 1  is larger than W 2  by 50 to 100 mm, and W 3  is larger than W 1  by 100 to 150 mm.  
         [0038]     According to a fourth aspect, an airbag system includes an airbag and an inflator for inflating the airbag, wherein the airbag is one of the first to third aspects.  
         [0039]     With the airbag and the airbag system according to the invention, the lateral width of the lower part of the airbag is large, with which the arms of an occupant can be received. The airbag and the airbag system according to the invention are not required to have an arm bag, so that they can be manufactured at a low cost. Furthermore, because the upper part and intermediate part of the airbag are smaller in lateral width than the lower part, the volume of the airbag can be smaller than that for the case where the whole airbag has a large lateral width.  
         [0040]     According to the second or third aspect, the lateral width of the upper part is larger than that of the intermediate part, so that the performance in restraining the head of an occupant can be improved. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0041]      FIG. 1  ( a ) is a front view of a passenger airbag according to an embodiment of the present invention; and  FIG. 1  ( b ) is a perspective view of the passenger airbag.  
         [0042]      FIG. 2  ( a ) is a front view of a rear panel of the airbag; and  FIG. 2  ( b ) is a front view of a front panel of the airbag.  
         [0043]      FIG. 3  is a perspective view showing the engaging relationship between the rear panel and the front panel.  
         [0044]     FIGS.  4  ( a )- 4  ( d ) are diagrams showing the procedure for sewing an airbag according to Japanese Unexamined Patent Application Publication No. 2000-25544.  
         [0045]     FIGS.  5  ( a )- 5  ( f ) are diagrams showing the procedure for sewing the airbag according to above publication.  
         [0046]      FIG. 6  is a diagram showing the procedure for sewing the airbag according to the above publication  
         [0047]      FIG. 7  is a diagram showing the procedure for sewing the airbag according to the above publication.  
         [0048]      FIG. 8  is a diagram showing the procedure for sewing the airbag according to the above publication.  
         [0049]      FIG. 9  is a diagram showing the procedure for sewing the airbag according to the above publication.  
         [0050]      FIG. 10  is a diagram showing the procedure for sewing the airbag according to the above publication  
         [0051]      FIG. 11  is a perspective view of the airbag sewn according to the above publication.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0052]     Embodiments of the present invention will be described hereinbelow with reference to the drawings.  
         [0053]      FIG. 1  ( a ) is a front view of a passenger airbag  80  according to an embodiment;  FIG. 1  ( b ) is a perspective view of the airbag;  FIG. 2  ( a ) is a front view of a rear panel of the airbag;  FIG. 2  ( b ) is a front view of a front panel of the airbag; and  FIG. 3  is a perspective view showing the engaging relationship between the rear panel and the front panel.  
         [0054]     With the airbag  80  inflated in front of a passenger, the minimum lateral width W 2  of an intermediate part  82  is the minimum, the maximum lateral width W 1  of an upper part  81  is larger than W, and the maximum lateral width W 3  of a lower part  83  is larger than W 1 . That is, the lateral width of the airbag  80  has a relationship W 2 &lt;W 1 &lt;W 3 . Preferably, W 1  is larger than W 2  by 50 to 100 mm, and W 3  is larger than W 1  by 100 to 150 mm. Preferably, W 2  is within the range of 350 to 400 mm, and the vertical length L of the airbag  80  is within the range of 700 to 750 mm.  
         [0055]     The airbag  80  can receive occupant&#39;s arms with laterally projecting portions  83   a  and  83   b  of the lower part  83 . The lateral widths of the intermediate part  82  and the upper part  81  are smaller than that of the lower part  83 , and the lateral width of the intermediate part  82  is smaller than that of the upper part  81 , so that the airbag  80  is small in volume. Thus, a low-capacity inflator can be used.  
         [0056]     The airbag  80  according to the embodiment can provide good performance in restraining the head of the occupant, because the lateral width of the upper part  81  is larger than that of the intermediate part  82 .  
         [0057]     The airbag  80  can be manufactured by sewing the peripheries of a rear panel  80 A and a front panel  80 B. Since the shapes of the rear panel  80 A and the front panel  80 B are substantially the same as those of the panels A and B shown in FIGS.  4  ( a )- 4  ( d ), the same components are given the same reference numerals. The difference between the panels  80 A and  80 B and the panels A and B is that: for the panels A and B, the respective front sides  1   f,    3   f,    11   f,  and  13   f  of the sides  1 ,  3 ,  11 , and  13  are linear; for the panels  80 A and  80 B, the front of the sides  1 ,  3 ,  11 , and  13 , contiguous to the forefront linear sides  1   f,    3   f,    11   f,  and  13   f,  form curves  1   f ′,  3   f ′,  11   f ′, and  13   f ′ curved to the center of the panels  80 A and  80 B.  
         [0058]     The rear panel  80 A has a pair of parallel slits  84  in place of the opening  9 . An inflator is disposed in the airbag  80  through the slits  84 .  
         [0059]     The method of sewing the panels  80 A and  80 B is completely the same as for the panels A and B shown in FIGS.  4  to  11 . Since the curves  1   f ′,  3   f ′,  11   f ′, and  13   f ′ are provided, the intermediate part  82  with a small lateral width can be formed. Since the lateral widths of the sides  1   f ′ and  3   f ′ are smaller than those of the sides  1   r  and  3   r,  and the lateral widths of the sides  11   f ′ and  13   f ′ are smaller than those of the sides  11   r  and  13   r,  the lateral width of the upper part  81  can be made smaller than that of the lower part  83 .  
         [0060]     In the airbag  80  of the invention, when the airbag is inflated, the front surface facing the occupant and formed by the front panel  80 B has the upper part  81 , the intermediate part  82  and the lower part  83 , as explained above. However, the peripheral portion of the front panel  80 B generally extends rearwardly and sewed to the peripheral portion of the rear panel  80 A. Thus, at the sewing portion between the rear and front panels  80 A,  80 B, the lateral sides or width corresponding to the upper part  81  is slightly reduced, and the lateral sides or width corresponding to the intermediate part  82  is slightly enlarged, but the lateral sides of the lower part  83  are generally the same. The sewing portion between the rear and front panels  80 A,  80 B is the largest in lateral size when the airbag is inflated. The inflated condition of the airbag  80  is shown in  FIG. 1  ( b ).  
         [0061]     The disclosure of Japanese Patent Application No. 2005-221247 filed on Jul. 29, 2005 is incorporated herein as a reference.  
         [0062]     While the invention has been explained with reference to the specific embodiment of the invention, the explanation is illustrative and the invention is limited only by the appended claims.