Abstract:
An airbelt wherein a folded body of a bag-like belt is covered with a cover, and the two are sewn together with tear seams, and wherein the tear seams can be torn without the need to use a high-power inflator when the airbelt is inflated, and an airbelt apparatus employing this airbelt are provided. In one form, a mesh webbing and a mesh cover cover the bag-like belt. A plurality of parts of the airbelt in the longitudinal direction are sewn with the tear seams. The tear seams extend in the width direction of the airbelt and curve so as to be convex toward a tongue.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an airbelt configured to inflate a bag-like belt with gas from an inflator in order to restrain a vehicle occupant at the time of a vehicle collision or the like, and an airbelt apparatus employing the same. More specifically, the present invention relates to an airbelt and an airbelt apparatus in which a folded body of a bag-like belt is surrounded with a cover, and the folded body and the cover are sewn together with tear seams. 
       BACKGROUND ART 
       [0002]    Examples of this type of conventional airbelt apparatuses are described in FIG. 6 of Japanese Unexamined Patent Application Publication No. 11-255057, and FIG. 8 of Japanese Unexamined Patent Application Publication No. 2000-203380. 
         [0003]    These are airbelts including a folded body formed by folding a bag-like belt into a belt-like shape, the bag-like belt being to be inflated by introduction of gas, and a cover covering the folded body of the bag-like belt, wherein the folded body and the cover are sewn together with tear seams, and thereby the slip between the two is prevented. 
         [0004]    In such airbelts, the folded body and the cover are sewn together, and the cover does not slip relative to the folded body. The tear seams have such a strength that they tear when the airbelts are inflated. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         PTL 1: Japanese Unexamined Patent Application Publication No. 11-255057 
         PTL 2: Japanese Unexamined Patent Application Publication No. 2000-203380 
       
     
         [0007]    Japanese Unexamined Patent Application Publication No. 11-255057 does not specifically describe the arrangement of the tear seams. 
         [0008]    In Japanese Unexamined Patent Application Publication No. 2000-203380, the tear seams are provided in the longitudinal direction of the airbelt contiguously in a zigzag manner. In the case where tear seams are contiguously provided as described above, sometimes a high-power inflator (an inflator that generates high-pressure gas) is required in order to increase the pressure of gas from the inflator and to thereby tear the tear seams when the airbelt is inflated. 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0009]    An object of the present invention is to provide an airbelt wherein a folded body of a bag-like belt is covered with a cover, and the two are sewn together with tear seams, and wherein the tear seams can be torn without the need to use a high-power inflator when the airbelt is inflated, and an airbelt apparatus employing this airbelt. 
       Solution to Problem 
       [0010]    An airbelt according to a first aspect includes a folded body formed by folding a bag-like belt into a belt-like shape, the bag-like belt being to be inflated by introducing gas from one end thereof in the longitudinal direction, and a cover covering the folded body of the bag-like belt, wherein the folded body and the cover are sewn together with a plurality of tear seams, and wherein the plurality of tear seams extend in the width direction of the airbelt and are spaced in the longitudinal direction of the airbelt. 
         [0011]    An airbelt according to a second aspect is the airbelt according to the first aspect, wherein part of each tear seam extending in the width direction is located closer to the one end of the airbelt than the other parts of each tear seam. 
         [0012]    An airbelt according to a third aspect is the airbelt according to the second aspect, wherein each tear seam extends while curving or bending such that the middle part thereof in the width direction of the airbelt is located on the side of the one end of the airbelt. 
         [0013]    An airbelt according to a fourth aspect is the airbelt according to the third aspect, wherein the distance L between the middle part and the terminal part of each tear seam in the longitudinal direction of the airbelt is from 1 mm to 20 mm. 
         [0014]    An airbelt according to a fifth aspect is the airbelt according to the second aspect, wherein each tear seam extends obliquely to the width direction of the airbelt. 
         [0015]    An airbelt according to a sixth aspect is the airbelt according to the second aspect, wherein each tear seam extends in a zigzag manner such that a plurality of parts thereof in the width direction of the airbelt are located closer to the one end than the other parts. 
         [0016]    An airbelt according to a seventh aspect is the airbelt according to any one of the first to sixth aspects, wherein the width W 1  of the tear seams is from 20% to 100% of the width W 0  of the airbelt. 
         [0017]    An airbelt apparatus according to an eighth aspect includes an inflatable airbelt, and an inflator that supplies gas into the airbelt and thereby inflates the airbelt, wherein the airbelt is that according to any one of the first to seventh aspects. 
       Advantageous Effects of Invention 
       [0018]    In the airbelt of the present invention, a folded body of a bag-like belt and a cover covering this are sewn together with tear seams, and therefore the displacement of the cover relative to the folded body of the bag-like belt is prevented. In the present invention, the tear seams are spaced in the longitudinal direction of the airbelt, and therefore the tear seams can be torn without the need to use a high-power inflator when the airbelt is inflated. 
         [0019]    When part of each tear seam is located closer to one end of the airbelt (more upstream in the gas flow direction) than the other parts, the stress concentrates to the part of each tear seam, and the tear of each tear seam starts in this part. Once the tear starts, the tear spreads throughout each tear seam, and the whole of each tear seam tears in a short time. 
         [0020]    When the airbelt extends so as to curve such that the middle part of each tear seam in the width direction of the airbelt is located on the side of the one end, the shear stress produced in each tear seam when the cover and the folded body of the bag-like belt try to be displaced from each other is distributed throughout each tear seam, and the concentration of shear stress in part of each tear seam is prevented. 
         [0021]    When the distance L between the middle part and the terminal part of each tear seam is 1 mm or more, more specifically 4 mm or more, such an advantageous effect can be sufficiently obtained. 
         [0022]    The percentage (W 1 /W 0 )×100% of the width W 1  of the tear seams to the width W 0  of the airbelt is preferably from about 20% to about 100%, more preferably from about 30% to about 50%. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0023]      FIG. 1  is a perspective view of the inside of an automobile having an airbelt apparatus according to an embodiment. 
           [0024]      FIG. 2  is a perspective view of the airbelt apparatus according to the embodiment with the airbelt inflated. 
           [0025]      FIG. 3  is an exploded perspective view of an airbelt according to the embodiment. 
           [0026]      FIG. 4   a  is a front view of the airbelt apparatus according to the embodiment during manufacture,  FIG. 4   b  is a sectional view taken along line B-B of  FIG. 4   a , and  FIG. 4   c  is a sectional view taken along line C-C of  FIG. 4   b.    
           [0027]      FIG. 5   a  is a front view of the airbelt apparatus according to the embodiment during manufacture, and  FIG. 5   b  is a front view of the airbelt that has been manufactured. 
           [0028]      FIG. 6  is a sectional view taken along line VI-VI of  FIG. 5   b.    
           [0029]      FIG. 7  is a front view of part of the airbelt according to the embodiment. 
           [0030]      FIG. 8  is a perspective view of a tongue part of the airbelt. 
           [0031]      FIG. 9  is a front view of part of an airbelt according to another embodiment. 
           [0032]      FIG. 10  is a front view of part of an airbelt according to still another embodiment. 
           [0033]      FIG. 11  is a front view of part of an airbelt according to a different embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0034]    A first embodiment of the present invention will now be described with reference to  FIG. 1  to  FIG. 8 . 
         [0035]    First, with reference to  FIG. 1  and  FIG. 2 , the overall configuration of a seat having an airbelt apparatus will be described schematically.  FIG. 1  is a perspective view showing the right-side seat and its vicinity of a two-seat (two-seater) automobile equipped with an airbelt apparatus,  FIG. 2  is a perspective view of the airbelt apparatus with the airbelt inflated, and  FIG. 8  is a perspective view of a tongue of this airbelt. 
         [0036]    This seat  1  has a seat cushion  2 , a seat back  3 , and a headrest  4 . This headrest  4  is provided with a slit  5  for passing an airbelt  10 . The slit  5  has such a shape that it extends downward from the upper end of the right side of the seat back  3 . When an occupant is not sitting in the seat  1 , the airbelt  10  hangs from this slit  5  along the right side of the front of the seat back  3 . 
         [0037]    In this embodiment, a retractor  15  for retracting a webbing  14  connected to the airbelt  10  is disposed behind the seat  1 . The webbing  14  reaches the retractor  15  through an opening  7  provided in the vehicle body interior panel  6 . The retractor  15  is fixed to the vehicle body member. 
         [0038]    In this embodiment, a retractor  16  for retracting a lap belt  11  is disposed under the seat cushion  2 , and is fixed to the seat frame. The lap belt  11  is passed through an opening (not shown) provided in the seat cushion  2 . 
         [0039]    The retractors  15  and  16  are both emergency lock retractors (ELRs). 
         [0040]    Since the airbelt  10  hangs along the front of the seat back  3 , when the occupant opens the door and sits in the seat  1  or leaves the seat  1 , the back of the occupant slides on the airbelt  10 , and a folded body of a bag-like belt and a cover in the airbelt  10  try to be displaced from each other. In this embodiment, the folded body of the bag-like belt and the cover  2  of the airbelt  10  are sewn together with tear seams, and thereby this displacement is prevented. 
         [0041]    As shown in  FIG. 2 , the airbelt apparatus has an airbelt  10  forming a shoulder belt portion that goes over one of the shoulders (the right shoulder in this case) of an occupant sitting in the seat  1  and goes over the front of the upper half of the body of the occupant diagonally (from top right to bottom left in this embodiment), a webbing  14  connected to the upper end of the airbelt  10 , a lap belt portion  11  that goes over the waist of the occupant in the horizontal direction, a buckle device  12  installed adjacent to one side (the left side in this embodiment) of the seat, a tongue  13  that is inserted into and engaged with the buckle device  12  when the belt is used, a retractor  15  that retracts the webbing  14 , and a retractor  16  that retracts the lap belt portion  11 . 
         [0042]    The buckle device  12  is provided with an inflator  17 , and gas jetted from the inflator  17  is introduced into the airbelt  10 . 
         [0043]    As shown in  FIG. 8 , the tongue  13  is provided with a tongue plate  13   a  that is inserted into the buckle device  12 , and a nozzle  13   b  for receiving gas from the inflator  17  and guiding the gas into the airbelt  10 . 
         [0044]    To the distal end of the lap belt portion  11 , an anchor plate  11   a  is attached. The anchor plate  11   a  is fixed to the tongue  13  with a bolt. Reference sign  11   b  denotes a decorative cap for concealing the head of this bolt. 
         [0045]    With reference to  FIG. 3  to  FIG. 7 , the configuration of the airbelt  10  will be described in detail. 
         [0046]    As shown in  FIG. 3 , the airbelt  10  includes a bag-like belt  21 , a strap  22  extending from the rear end of the bag-like belt  21 , a mesh webbing  23  covering the bag-like belt  21 , a mesh cover  25  covering the mesh webbing  23 , and a heat-resistant cloth  26  disposed in the bag-like belt  21 . 
         [0047]    The bag-like belt  21  is inflated by gas from the inflator  17 , and is folded into an elongate rectangular belt-like shape as shown in  FIG. 3 . In this embodiment, as shown in  FIG. 2 , the rear end of the bag-like belt  21  is significantly inflated on the right side of the occupant&#39;s head and restrains the head from the right. 
         [0048]    The strap  22  is made of a belt-like cloth and is sewn to the rear end of the bag-like belt  21 . The strap  22  may be formed integrally with the base cloth of the bag-like belt  21 . 
         [0049]    The mesh webbing  23  is an elongate tubular envelope-shaped member that opens at both ends. As shown in  FIG. 4   a  and  FIG. 4   b , the strap  22 , the distal end of the webbing  14 , and the rear end of the mesh webbing  23  are stacked and sewn together using a sewing machine. Reference sign  30  denotes these seams. When the webbing  14  is sewn to the strap  22 , the webbing  14  is not connected to the retractor  15 . 
         [0050]    In this embodiment, as shown in  FIG. 4   c , the strap  22  is folded in two along its longitudinal fold line, and the webbing  14  is sandwiched between the two halves of the strap  22 . However, the strap  22  may be a flat sheet that is not folded in two. The rear end of the mesh webbing  23  is almost coincident with the rear end of the bag-like belt  22 . 
         [0051]    The full length of the mesh webbing  23  is slightly longer than the folded bag-like belt  21 , and the distal end of the mesh webbing  23  extends from the distal end of the bag-like belt  21 . As shown in  FIG. 3 , a narrow neck portion  23   a  is provided near the distal end of the mesh webbing  23 , and the part  23   b  on the distal end side of the neck portion  23   a  is slightly narrower than the main body part of the mesh webbing  23 . In the vicinity of the neck portion  23 , an oblique side  23   c  intersecting obliquely with the longitudinal side of the mesh webbing  23  is formed. The mesh webbing  23  opens at the oblique side  23   c  and thereby an opening is formed. As shown in  FIG. 4   a , the distal end  21   a  of the bag-like belt  21  extends through the opening at the oblique side  23   c  toward the outside of the mesh webbing  23  and is connected to the nozzle  13   b  of the tongue  13 . 
         [0052]    Into the distal end of the bag-like belt  21 , the heat-resistant cloth  26  is inserted. The distal end  26   a  of the heat-resistant cloth  26  and the distal end  21   a  of the bag-like belt  21  are fitted onto the rear end of the nozzle  13   b  and are fixed to the nozzle  13   b  with a securing ring  13   d . The nozzle  13   b  is fixed to a holder portion  13   c  integral with the tongue plate  13   a  by bolting or the like. 
         [0053]    At the rear end of the tongue plate  13   a , an elongate rectangular opening  13   e  is provided. As shown in  FIG. 4   a , the distal end portion  23   b  of the mesh webbing  23  is inserted into the opening  13   e  and is folded back in the neck portion  23   a , and the distal end portion  23   b  is placed on the main body of the mesh webbing  23 . Then, the protruding portion  21   b  of the bag-like belt  21  ( FIG. 3 ), the main body portion of the mesh webbing  23 , and the distal end portion  23   b  of the mesh webbing  23  are sewn together using a sewing machine. Reference sign  27  in  FIG. 4   a  denotes this seam. 
         [0054]    In this manner, the distal end of the mesh webbing  23  is connected to the tongue plate  13   a . As described above, the rear end of the mesh webbing  23  is sewn to the webbing  14  with seams  30 . The mesh webbing  23  is heat-stretched so as not to stretch in the longitudinal direction. For this reason, when a tensile force is applied to the airbelt  10 , the tensile load between the webbing  14  and the tongue plate  13   a  is borne by the mesh webbing  23 . 
         [0055]    The mesh webbing  23  is made of woven fabric, and stretches flexibly in the diameter increasing direction when the bag-like belt  21  is inflated. However, as described above, the mesh webbing  23  is heat-stretched so as not to stretch in the longitudinal direction. For this reason, when the airbelt  10  is inflated, the increase in diameter of the mesh webbing  23  decreases the length of the mesh webbing  23 . Thereby, pre-tension is applied to the airbelt  10  and the webbing  14 . 
         [0056]    As shown in  FIGS. 5 and 6 , the mesh cover  25  is attached so as to cover the mesh webbing  23 . The mesh cover  25  is a flat tubular envelope-shaped member that opens at both ends. The mesh cover  25  is sewn into a tubular shape, and the sewn portion of the mesh cover  25  in the longitudinal direction corresponding to the occupant side is a tear seam  25   t  ( FIG. 1 ) that tears when the bag  10  is inflated. 
         [0057]    The rear end of the mesh cover  25  is caused to protrude slightly from the rear ends of the mesh webbing  23  and the strap  22 , and this protruding portion is sewn to the webbing  14  with a seam  32 . 
         [0058]    The thread forming the seams  30  and  32  is sufficiently strong, and does not break when the bag-like belt  21  is inflated. 
         [0059]    A plurality of parts, in the longitudinal direction, of the integral belt-like airbelt  10  configured as above and including the bag-like belt  21 , the mesh webbing  23 , and the mesh cover  25  are sewn with tear seam  33 . The tear seams  33 , penetrating the airbelt  10  from one surface to the other surface, sew the bag-like belt  21 , the mesh webbing  23 , and the mesh cover  25  together. 
         [0060]    As shown in  FIG. 7 , in this embodiment, each tear seam  33  extends in the width direction of the airbelt  10 . Each tear seam  33  curves such that the middle thereof in the width direction of the airbelt  10  is convex toward the upstream side in the gas flow direction, that is to say, toward the tongue  13 . Although both ends of each tear seam  33  are away from the side edges of the airbelt  10 , they may reach the side edges. As shown in the figure, each tear seam  33  has backstitch portions for preventing raveling. 
         [0061]    The distance L in the longitudinal direction of the airbelt between the middle part of each tear seam  33  and the terminal part of each tear seam  33  is preferably from about 1 mm to about 20 mm, more preferably from about 4 mm to about 20 mm. The length W 1  of each tear seam  33  in the width direction of the airbelt is preferably from about 20% to about 100%, more preferably from about 30% to about 50% of the width W 0  of the airbelt  10 . 
         [0062]    Within this range, the slip between the bag-like belt  21 , the mesh webbing  23 , and the mesh cover  25  can be sufficiently prevented. 
         [0063]    The distance L in the longitudinal direction of the airbelt between the middle part and both ends of each tear seam  33  is preferably from about 2% to about 60%, more preferably from about 8% to about 60% of the width W 1  of each tear seam  33 . Since each tear seam  33  is curved such that the middle part of each tear seam  33  is located on the tongue  13  side, the stress concentrates to the middle part of each tear seam  33  when the airbelt  10  is inflated, and the middle part of each tear seam  33  tears first. That is to say, since gas flows in from the tongue  13  side, the stress concentrates to the middle part of each tear seam  33  closest to the tongue  13 . The middle part of the airbelt  10  in the width direction inflates most easily. Also because of this, the stress concentrates to the middle part of each tear seam  33 . Once the middle part of each tear seam  33  tears, the tear of each tear seam  33  propagates rapidly to both sides, the whole of each tear seam  33  tears rapidly, and the airbelt  10  is inflated. 
         [0064]    The distance between the tear seams  33  is preferably from about 50 mm to about 200 mm, more preferably from about 80 mm to about 120 mm. The number of the tear seams  33  is preferably from about 1 to about 18, more preferably from about 3 to about 10. The intervals between the tear seams  33  may be equal or unequal. 
         [0065]    The above-described mesh cover  25  has such a length that the distal end thereof covers the rear end of the tongue plate  13   a.    
         [0066]    Case halves  13 A and  13 B for the tongue are attached so as to cover the rear part of the tongue plate  13   a  and the distal end of the mesh cover  25 . The case halves  13 A and  13 B are made of synthetic resin. By positioning the case halves  13 A and  13 B face to face and one on top of the other, the rear part of the tongue plate  13   a  and the distal end of the mesh cover  25  are encapsulated. After that, the rear end of the webbing  14  is connected to the retracting shaft of the retractor  15 . 
         [0067]    In the airbelt and airbelt apparatus configured as above, the airbelt  10  is provided with tear seams  33 , and the displacement of the bag-like belt  21 , the mesh webbing  23 , and the mesh cover  25  on the superimposed surfaces is prevented. When the airbelt  10  is inflated, each tear seam  33  tears rapidly. In this embodiment, each tear seam  33  curves gently, and there is no angular part. Therefore, when the superimposed surfaces try to be displaced, the stress applied to each tear seam  33  is distributed throughout each tear seam  33 . 
         [0068]    In the above-described embodiment, each tear seam  33  curves gently. Alternatively, tear seams  34  bent in a dogleg-shape as shown in  FIG. 9  may be provided. Like the W-shaped tear seam  35  shown in  FIG. 10 , a plurality of parts of each tear seam may be located on the tongue side. As shown in  FIG. 11 , linear tear seams  36  intersecting obliquely with the width direction of the airbelt  10  may be provided. 
         [0069]    Although a particular aspect of the present invention has been described in detail, it will be obvious to those skilled in the art that various changes may be made without departing from the intent and scope of the present invention. 
         [0070]    This application is based on Japanese Patent Application No. 2009-217282 filed Sep. 18, 2009, which is incorporated by reference in its entirety.