Abstract:
Opposite end portions of an airbag made of a folded metal plate and formed into a tubular shape are capped by respective end caps and are attached to an attachment surface of a front pillar, and the airbag is deployed along the front pillar by use of gas produced by an inflator, thereby protecting by the airbag a pedestrian that collides with the front pillar. Bolts penetrating through long holes formed in the end portions of the airbag and bolt holes of the end caps are screwed to weld nuts, and thereby the end portions of the airbag are slidably supported by the end caps. Accordingly, when the airbag is deployed the long holes slide with respect to the respective bolts toward inside in a longitudinal direction of the airbag, and a tension in the longitudinal direction of the airbag is prevented from acting on a metal plate of the airbag, thereby enabling the airbag to be deployed reliably near the end caps. Therefore, it is possible to inflate the airbag evenly along its entire length and thereby enhancing the shock absorbing performance when a pedestrian collides.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an airbag system comprising: an airbag made of a folded metal plate; and cap members which respectively cap opposite end portions of the airbag, the cap members being fixed to a vehicle body panel, the airbag system protecting a pedestrian by deploying the airbag by use of gas produced by an inflator. 
     2. Description of the Related Art 
     Japanese Patent Application Laid-open No. 2002-283939 has made publicly known an airbag system for protecting a pedestrian which is configured so that: a folded airbag made of cloth is stored inside a pillar garnish for covering a front surface of a front pillar of an automobile; in collision with a pedestrian, gas produced by an inflator is supplied to the airbag, and thus deploys the airbag along the front surface of the front pillar from a rip which is made when the pillar garnish breaks; and the pedestrian is protected with the airbag thus deployed. 
     In addition, Japanese Patent Application Laid-open No. 2006-282105 has made publicly known a shock absorbing structure for protecting a pedestrian which is configured so that: a pillar garnish for covering a front surface of a front pillar of an automobile is supported by a pillar skeletal member with a link-type pillar driving mechanism being interposed in between; in collision with a pedestrian, the pillar driving mechanism lifts the pillar garnish up from the pillar skeletal member so as to allow the pillar garnish to make stroke motions; and the pillar garnish thus absorbs the collision energy. 
     In the case of the invention disclosed in Japanese Patent Application Laid-open No. 2002-283939, however, it is difficult to keep the airbag deployed for a long time because the airbag is made of cloth; therefore, the airbag may not fully exhibit its shock absorbing effects depending on timing at which the pedestrian collides with the front pillar. 
     In the meantime, the invention disclosed in Japanese Patent Application Laid-open No. 2006-282105 has a problem that: the structure of the link-type pillar driving mechanism for movably supporting the pillar garnish with the pillar skeletal member is complicated; thus, the number of parts increases, and the cost increases. 
     Against this background, through Japanese Patent Application No. 2009-224381, one of the present assignees has already proposed an airbag system which is configured so that: instead of the conventional airbag made of cloth, an airbag made of metal is folded and arranged in a front pillar; and gas produced by an inflator deploys this airbag toward the outside of a vehicle body. 
     In the airbag included in this airbag system, opposite end portions of a metal plate folded in the shape of a tube are inserted into respective openings of box-shaped end caps and are fixed thereto by welding. These end caps are fixed to an attachment surface of the front pillar by bolts. Once the folded airbag is deployed, the airbag begins to contract in the longitudinal direction with an increase in the diameter. However, the above-described conventional airbag is incapable of moving in the longitudinal direction because the opposite end portions of the airbag are fixed to the respective end caps. As a result, the tension of the airbag becomes excessive. This makes it difficult for the airbag to be deployed particularly near the end caps thereof, resulting in the possibility of lowering the shock absorbing performance thereof. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in consideration of the above-described situation. An object of the present invention is to enhance the shock absorbing performance of a metal-made airbag for protecting a pedestrian by making the airbag capable of being deployed evenly through the entire length thereof. 
     In order to achieve the above object, according to a first feature of the present invention, there is provided an airbag system comprising: an airbag made of a folded metal plate; and cap members which respectively cap opposite end portions of the airbag, the cap members being fixed to a vehicle body panel, the airbag system protecting a pedestrian by deploying the airbag by use of gas produced by an inflator, wherein the opposite end portions of the airbag and the respective cap members are connected movably relative to each other when the airbag is deployed. 
     With the foregoing configuration, since the cap members for capping the respective opposite end portions of the airbag made of a folded metal plate are fixed to the vehicle body panel, it is possible to protect a pedestrian by deploying the airbag by use of gas produced by the inflator. When the airbag is deployed, the airbag contracts in the longitudinal direction thereof in accordance with an increase in the diameter. In this respect, it is possible to prevent the tension of the airbag in the longitudinal direction from becoming excessive by allowing the opposite end portions of the airbag to move relative to the respective cap members. This makes the opposite end portions of the airbag, which would otherwise be hard to be deployed, capable of being deployed as well as the middle portion of the airbag. Consequently, an excellent shock absorbing performance can be obtained throughout the length of the airbag. 
     According to a second feature of the present invention, in addition to the first feature, there is provided the airbag system, wherein long holes are formed in the opposite end portions of the airbag, each long hole extending in a longitudinal direction of the airbag, and shaft members fixed to the cap members penetrate the respective long holes. 
     With the foregoing configuration, since the long holes each extending in the longitudinal direction of the airbag are formed in the opposite end portions of the airbag and the shaft members fixed to the cap members penetrate the respective long holes, the long holes can slide relative to the respective shaft members when the airbag is deployed. This makes it possible to prevent the tension of the airbag in the longitudinal direction from becoming excessive, and also to prevent the opposite end portions of the airbag from coming off from the respective cap members. 
     According to a third feature of the present invention, in addition to the second feature, there is provided the airbag system, wherein a space extending along each of the shaft members is formed between an outer surface of the airbag in a folded state and an inner surface of the corresponding cap member, and each of the opposite end portions of the airbag is deployed to make the space disappear. 
     With the foregoing configuration, since the space is formed between the outer surface of the airbag in a folded state and the inner surface of the corresponding cap member so as to extend along the direction of the shaft member, it enables the opposite end portions of the airbag to be deployed further securely by allowing the opposite end portions of the airbag to be deployed in such a way as to make the spaces disappear. 
     According to a fourth feature of the present invention, in addition to any one of the first to third features, there is provided the airbag system, wherein, in the airbag in a folded state, a surface facing in a front-and-rear direction of a vehicle body is flat; and a surface facing in a left-and-right direction of the vehicle body is folded in an accordion shape. 
     With the foregoing configuration, since the airbag in a folded state has a flat surface facing in the front-and-rear direction of the vehicle body and a surface folded in an accordion shape facing in the left-and-right direction of the vehicle body, it enables the airbag to effectively absorb an impact on a pedestrian who collides from the front side by deploying the airbag to a large extent in the front-and-rear direction of the vehicle body. 
     According to a fifth feature of the present invention, in addition to any one of the first to fourth features, there is provided the airbag system, wherein the cap members are each formed of a box shape having an opening to which the corresponding end portion of the airbag in a folded state is inserted. 
     With the foregoing configuration, since each cap member is formed of a box shape which has the opening into which the corresponding end portion of the airbag in a folded state is inserted, it enables the cap members to be fixed to the respective end portions easily and securely. 
     According to a sixth feature of the present invention, in addition to any one of the first to fifth features, there is provided the airbag system, wherein a gap between the shaft member and the long hole functions as a vent hole of the airbag. 
     With the foregoing configuration, since the gap between the shaft member and the long hole functions as a vent hole, it is possible to reduce the processing costs by requiring no formation of special vent hole in the airbag. 
     The above description, other objects, characteristics and advantages of the present invention will be clear from detailed descriptions which will be provided for the preferred embodiments referring to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 to 9B  show a first embodiment of the present invention: 
         FIG. 1  is a plan view of a front part of a vehicle body of an automobile; 
         FIG. 2  is an enlarged cross-sectional view taken along a line  2 - 2  in  FIG. 1 ; 
         FIG. 3A  is a perspective view of an airbag in a non-deployed state; 
         FIG. 3B  is a perspective view of the airbag in a deployed state; 
         FIG. 4  is an enlarged and exploded perspective view of a part indicated by an arrow  4  in  FIG. 3A ; 
         FIG. 5  is an enlarged perspective view of a part indicated by an arrow  5  in  FIG. 3A ; 
         FIG. 6  is a view corresponding to  FIG. 2  and explaining an operation when the airbag deploys; 
         FIG. 7A  is a cross-sectional view taken along a line  7 (A)- 7 (A) in  FIG. 3A ; 
         FIG. 7B  is a cross-sectional view taken along a line  7 (B)- 7 (B) in  FIG. 3B ; 
         FIG. 8  is a cross-sectional view taken along a line  8 - 8  in  FIG. 7 ; 
         FIG. 9A  is a cross-sectional view taken along a line  9 (A)- 9 (A) in  FIG. 7A ; and 
         FIG. 9B  is a cross-sectional view taken along a line  9 (B)- 9 (B) in  FIG. 7B ; 
         FIGS. 10A and 10B  show a second embodiment of the present invention: 
         FIG. 10A  is a view corresponding to  FIG. 7A ; and 
         FIG. 10B  is a view corresponding to  FIG. 7B . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the present invention will be described below based on  FIGS. 1 to 9B . 
     As shown in  FIG. 1 , an automobile has a front windshield  12  in the rear of a hood  11 , and front pillars  15 ,  15  are arranged in a way that the front pillars  15 ,  15  are interposed between left and right edge portions  12   a ,  12   a  of the front windshield  12  and door glasses  14 ,  14  of front doors  13 ,  13 , respectively. 
     As shown in  FIG. 2 , the front pillar  15  is formed in a closed cross section by bonding together an outer panel  16  situated in an outer side of a vehicle body and an inner panel  17  situated in an inner side of the vehicle body. An airbag  18  made of metal, which also serves as a pillar garnish, is folded and arranged in front of a front surface  16   a  of the outer panel  16 . The corresponding edge portion  12   a  of the front windshield  12  is adhered to front faces of joint sections  16   c ,  17   a  of the outer panel  16  and the inner panel  17 , respectively, with an adhesive  21  with a dam rubber  20  being interposed in between. 
     The airbag  18  obtained by folding a metal plate into a tubular shape includes a garnish part  18   a , a windshield-side folded part  18   b , an outer panel-side folded part  18   c  and an inflator supporting part  18   d . The garnish part  18   a  smoothly extends from a side surface  16   b  of the outer panel  16  of the front pillar  15  toward the front windshield  12 , and functions as a pillar garnish arranged between the outer panel  16  and the front windshield  12 . 
     The windshield-side folded part  18   b  and the outer panel-side folded part  18   c  are each folded in an accordion shape behind (in the rear of) the garnish part  18   a  for the purpose of securing the expansion margin of the airbag  18  when it is deployed. At this point, a folded width W 2  of the outer panel-side folded part  18   c  is set larger than a folded width W 1  of the windshield-side folded part  18   b.    
     As clear from  FIGS. 3A ,  3 B,  5  and  7 A to  9 B, the opposite end portions of the airbag  18  in a folded state are molded to be thinner by pressing, and are fitted into openings of boxed-shaped end caps  24 ,  24 , respectively, to be fixed thereto. In this way, since the end caps  24 ,  24  are made into the shape of a box having an opening into which the folded end portion of the airbag  18  is inserted, the end portions of the airbag  18  can be easily and securely fixed to the end caps  24 ,  24 . Note that the folded airbag  18  may have a uniform width over the entire length thereof. 
     Paired stays  25 ,  25  unitarily formed with the end caps  24 ,  24  are fixed to an attachment surface  16   d  of the outer panel  16  of the front pillar  15 . Each stay  25  is one obtained by bending a strip-shaped metal plate into a crank shape. The stay  25  is fixed to the attachment surface  16   d  of the outer panel  16  with a stud bolt  26  and a nut  27 . 
     Two long holes  18   e ,  18   e  each extending in a longitudinal direction of the airbag  8  penetrate the respective end portions of the airbag  18 . Bolts  34 ,  34  respectively inserted in bolt holes  24   a  of the end caps  24  and the long holes  18   e ,  18   e  of the airbag  18  are respectively screwed to weld nuts  35 ,  35  provided to the stay  25 . While the airbag  18  is not deployed as shown in  FIGS. 7A and 9A , the bolts  34 ,  34  are respectively located at inner ends of the long holes  18   e ,  18   e  in the longitudinal direction of the airbag  18 . While the airbag  18  is deployed as shown in  FIGS. 7B and 9B , the long holes  18   e ,  18   e  respectively slide with respect to the bolts  34 ,  34 . As a result, the bolts  34 ,  34  are respectively located at outer ends of the long holes  18   e ,  18   e  in the longitudinal direction of the airbag  18 . 
     As clear from  FIGS. 2 to 4 , an inflator  19  configured to produce gas for deploying the airbag  18  is attached in a lower end portion of the inflator supporting part  18   d  which faces the garnish part  18   a  with the windshield-side folded part  18   b  and the outer panel-side folded part  18   c  interposed therebetween. The inflator  19  having a cylindrical shape is fixed to an inner surface of an attachment bracket  28  having an U-shape cross section with two fastening devices  29 ,  29 . This attachment bracket  28  is overlaid an opening  18   e  formed in the inflator supporting part  18   d  of the airbag  18  from outside and fixed to the inflator supporting part  18   d  with bolts  30  and nuts  31 . 
     As clear from  FIG. 2 , an outer panel-side lip  32  is arranged in a boundary between the garnish part  18   a  and the outer panel-side folded part  18   c  of the airbag  18 . This outer panel-side lip  32  is configured to be in contact with the front surface  16   a  of the outer panel  16 . A windshield-side lip  33  is installed in a boundary between the windshield-side folded part  18   b  and the inflator supporting part  18   d  of the airbag  18 . This windshield-side lip  33  is configured to be in contact with a front surface of the edge portion  12   a  of the front windshield  12 . The outer panel-side lip  32  and the windshield-side lip  33  block rainwater and the like from entering the inflator supporting part  18   d  side of the airbag  18 ; therefore, the inflator  19  can be protected. 
     Next, descriptions will be provided for an operation of the embodiment of the present invention including the foregoing configuration. 
     In a normal time when the airbag  18  is not deployed, the garnish part  18   a  of the airbag  18  smoothly extends toward the side surface  16   b  of the outer panel  16  of the front pillar  15 , and exhibits a pillar garnish function. Accordingly, this makes it possible to abolish a specialized pillar garnish, and thus to reduce parts in number. Furthermore, by replacing the conventional pillar garnish, the airbag  18  can be compactly installed between the front pillar  15  and the front windshield  12 . Therefore, neither case nor cover is required for storing the folded airbag  18 , while a good external appearance around the front pillar  15  is maintained. 
     Once it is detected that the vehicle has collided with a pedestrian, the inflator  19  is actuated, and an internal pressure of the airbag  18  increases due to the gas produced by the inflator  19 . Then, as shown in  FIG. 6 , due to this increase in the internal pressure, the windshield-side folded part  18   b  and the outer panel-side folded part  18   c  of the airbag  18  which are folded in an accordion shape are first inflated toward the outside of the vehicle body, then deployed in the left and right directions in a way that the front surface  16   a  and the side surface  16   b  of the outer panel  16  of the front pillar  15  are covered. 
     At this time, the airbag  18  is deployed to a large extent in the frontward and rearward directions, and is capable of effectively absorbing an impact on a pedestrian who collides from the front side, since the garnish part  18   a  and the inflator supporting part  18   d  forming the front and back surfaces of the folded airbag  18  are flat whereas the windshield-side folded part  18   b  and the outer panel-side folded part  18   c  forming the left and right surfaces of the folded airbag  18  are folded in an accordion shape. 
     In the meantime, once the airbag  18  is deployed, the airbag changes its shape in such a way that the airbag  18  contracts in the longitudinal direction in accordance with an increase in the diameter thereof. As a result, tension occurs within the metal plate of the airbag  18  in the longitudinal direction. For the purpose of obtaining an excellent shock absorbing performance through the entire length of the airbag  18 , it is desirable that the airbag  18  should have an increasing diameter starting immediately from the parts thereof fixed to the end caps  24 ,  24 . However, there is a problem that the opposite end portions of the airbag  18  are hard to be deployed due to the occurrence of the above-described tension. 
     In the present embodiment, however, once the tension occurs in the longitudinal direction with the deployment of the airbag  18 , the long holes  18   e ,  18   e  slide inward with respect to the respective bolts  34 ,  34  in the longitudinal direction of the airbag  18  as shown in  FIGS. 7A ,  7 B,  9 A and  9 B. Accordingly, the opposite end portions of the airbag  18  move inward in the longitudinal direction, inhibiting the occurrence of the tension. Consequently, the opposite end portions of the airbag  18  can be deployed securely; therefore, the airbag  18  can exert the excellent shock absorbing performance through the entire length thereof. 
     Moreover, while the airbag  18  is being deployed, gaps are formed between the bolts  34 ,  34  and the long holes  18   e ,  18   e , and gas leaks from the gaps. When these gaps are used as vent holes of the airbag  18 , no special vent holes need to be formed in the metal plate of the airbag  18 , resulting in a reduction in the processing costs. Alternatively, when vent holes are to be formed in the airbag  18 , the number of the vent holes can be reduced. 
     Furthermore, an airbag system for a pedestrian has a characteristic that time which lapses before the pedestrian collides with the front pillar  15  tends to relatively vary largely depending on the physique of the pedestrian and the velocity at which the vehicle is running at the time of collision. For this reason, a problem with a conventional airbag made of cloth is that an inflator with a large volume, which is configured to produce the gas continuously, is required for the purpose of keeping the airbag deployed for a predetermined length of time. On the contrary, the present embodiment employs the airbag  18  made of metal. Once deployed, the airbag  18  is capable of keeping the deployed state even after the supply of the gas is ended. This plastic deformation allows the airbag  18  to absorb the shock of the collision with a pedestrian. For this reason, the airbag  18  exhibits its shock absorbing capability effectively no matter what timing a pedestrian may collides with the front pillar  15  even with the inflator  19  having a smaller volume. 
     Next, descriptions will be provided for a second embodiment of the present invention based on  FIG. 10 . 
     The second embodiment is an airbag system in which a space α is formed between the front surface of the folded airbag  18  and a front surface  24   c  of each end cap  24  by making the dimensions of each end cap  24  in the front-back directions larger and supporting the back surface of the folded airbag  18  by arbitrary means at a location in which the back surface of the folded airbag  18  is in contact with a back surface  24   b  of each end cap  24 . 
     When the airbag  18  is deployed, not only the long holes  18   e ,  18   e  slides inward along the respective bolts  34 ,  34  in the longitudinal direction of the airbag  18  but also the opposite end portions of the airbag  18  slides frontward along the respective bolts  34 ,  34 . This enables the opposite end portions of the airbag  18  to be deployed more securely; thus, the airbag  18  can exert excellent shock absorbing performance. 
     The embodiments of the present invention have been described above. However, various design changes can be made on the present invention within the scope not departing from the gist of the present invention. 
     For instance, the way of folding the airbag  18  is not limited to the embodiments, and any appropriate way of folding the airbag  18  can be adopted.