Abstract:
A case of an airbag unit includes a case body for forming a storage room for accommodating an airbag, and a movable component attached to the case body for forming at least a part of an edge of an opening of the case body. The movable component has a lower end portion bent in a direction away from the case body. The movable component is movable toward the bottom when an external force is applied to the case.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT  
       [0001]     The present invention relates to an airbag unit used for protecting a passenger in a vehicle, and a case for accommodating an airbag of the airbag unit. In particular, the present invention relates to a case capable of deforming in response to an external force to absorb an impact, and an airbag unit including the case.  
         [0002]     An airbag unit for protecting a passenger is installed in an instrument panel of a vehicle, and includes a case, an airbag accommodated in the case, an inflator for expanding the airbag, and the like. Japanese Patent Publication (Kokai) No. 11-42994 has disclosed a structure having a retractable sliding member fastened with rivets or bolts on a sidewall of a case. When an object hits on an instrument panel, the sliding member retracts by sliding along the sidewall of the case.  
         [0003]     Patent Document 1: Japanese Patent Publication (Kokai) No. 11-42994  
         [0004]     In the airbag unit disclosed in Japanese Patent Publication (Kokai) No. 11-42994, when the sliding member retracts, an end portion thereof is pushed into the sidewall of the case, thereby causing strong resistance.  
         [0005]     In view of the problem described above, an object of the present invention is to provide a case of an airbag unit including a movable component that can always retract smoothly when an external force is applied.  
         [0006]     Another object of the present invention is to provide an airbag unit including the case.  
         [0007]     Further objects and advantages of the invention will be apparent from the following description of the invention.  
       SUMMARY OF THE INVENTION  
       [0008]     In order to achieve the above objects, according to a first aspect of the present invention, a case includes a storage room for accommodating an airbag and an opening facing a vehicle cabin. The case includes a case body functioning as a base end disposed opposite to the opening, and a movable component being at least part of an end portion of the opening and retractable toward the base end along the case body in response to an external force applied to the case. An end portion of the movable component adjacent to the base end is deformed so as to be away from the case body.  
         [0009]     According to a second aspect, in the case in the first aspect, at least part of the end portion of the movable component adjacent to the base end is located adjacent to the vehicle cabin, and is away from an edge of the case body adjacent to the opening before the movable component retracts.  
         [0010]     According to a third aspect, in the case in one of the first and second aspects, the movable component is disposed so as to retract along an outer surface of the case body, and the end portion of the movable component adjacent to the base end is deformed outwardly from the case.  
         [0011]     According to a fourth aspect, an airbag unit includes the case in one of the first to third aspects, an airbag accommodated in the case, and an inflator for expanding the airbag.  
         [0012]     In the case and the airbag unit including the case in the present invention, the end portion of the movable component adjacent to the base end is deformed (for example, bent) so as to be away from the case body. Accordingly, during the retraction of the movable component in response to the external force generated when an object hits on the instrument panel, the rear end portion of the movable component is not subjected to strong resistance from the case body, so that the movable component retracts smoothly.  
         [0013]     In the present invention, it is preferable that at least part of the end portion of the movable component adjacent to the base end is located adjacent to the vehicle cabin and is remote from the case body. With this structure, even when the end portion of the movable component adjacent to the base end contacts the edge of the case body, the movable component can be smoothly guided to the side surface of the case body by the deformed rear end portion, and can smoothly retract along the case body.  
         [0014]     In the present invention, it is preferable that the movable component is disposed so as to retract along the outer surface of the case body, and the end portion of the movable component adjacent to the base end is deformed outwardly from the case. Accordingly, the movable component and the deformed end portion adjacent to the base end smoothly retract without interfering with the airbag in the case. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a perspective view of a case of an airbag unit according to an embodiment of the present invention;  
         [0016]      FIG. 2  is a perspective view of a movable component of the case;  
         [0017]      FIG. 3  is a cross-sectional view taken along line  3 - 3  in  FIG. 2 ;  
         [0018]      FIG. 4  is a perspective view of a case body;  
         [0019]      FIG. 5  is a longitudinal sectional view of the airbag unit; and  
         [0020]      FIG. 6  is a longitudinal sectional view of the airbag unit when an object hits the airbag unit. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0021]     Hereunder, embodiments of the present invention will be described with reference to the accompanying drawings.  FIG. 1  is a perspective view of a case of an airbag unit for a passenger according to an embodiment of the present invention.  FIG. 2  is a perspective view of a movable component of the case.  FIG. 3  is a cross-sectional view taken along line  3 - 3  in  FIG. 2 .  FIG. 4  is a perspective view of a case body.  FIG. 5  is a longitudinal sectional view of the airbag unit.  FIG. 6  is a longitudinal sectional view of the airbag unit when an object hits the airbag unit.  
         [0022]     In the embodiment, the airbag unit is disposed in an instrument panel such that the case has an opening substantially at the top as shown in  FIG. 5 . Accordingly, an upper side of the figures adjacent to a vehicle cabin corresponds to an upper side of the airbag unit, whereas a lower side of the figures corresponds to a lower side of the airbag unit.  
         [0023]     As shown in  FIG. 5 , an airbag unit  1  includes a case  2 , a folded airbag  3  accommodated in the case  2 , an inflator  4  for expanding the airbag  3 , an attachment frame  5  for attaching the airbag  3  and the inflator  4  to the case  2 , and a lid  6  covering the case  2 . The case  2  includes a case body  10  and a movable component  50  attached to the case body  10  shown in  FIGS. 2 and 3 . As shown in  FIGS. 4 and 5 , the case body  10  includes a base  20  having side plates  30  disposed at the left and right sides and a hook plate  40 .  
         [0024]     The base  20  includes a bottom section  21 , a wall  22  extending upwardly from a long side of the bottom section  21 , a comb-shaped wall  23  extending upwardly from the other long side of the bottom section  21 , semicircular concaved portions  24  and semicircular convexed portions  25  in the bottom section  21 , and a concaved portion  26  hollowed around the center of the bottom section  21 . Brackets  28  and  29  for attaching the airbag unit to a vehicle are fixed to the lower surface of the base  20  by welding.  
         [0025]     The airbag unit  1  is mounted in a vehicle such that the wall  22  is adjacent to the front side of the vehicle and the comb-shaped wall  23  is adjacent to the backside of the vehicle. The comb-shaped wall  23  includes a lower portion  23   a  extending along the bottom section  21 , pillars  23   b  and  23   d  extending upwardly from both sides of the lower portion  23   a  in the longitudinal direction, and a pillar  23   c  extending upwardly at the intermediate position between the pillars  23   b  and  23   d . The number and the positions of the pillars are not limited to those described above. The semicircular portions  24  and  25  have a substantially same radius and are disposed coaxially. The inflator  4  is cylindrical, and is disposed such that end portions thereof are fitted into spaces between the semicircular portions  24  and  25 .  
         [0026]     As shown in  FIG. 5 , an end portion of a gas inlet of the airbag  3  and the inflator  4  are held between the attachment frame  5  and the base  20 . The attachment frame  5  is fixed to the base  20  with bolts or rivets (not shown). The side plates  30  are sidewalls disposed at the left and the right sides of the case body  10 . The left and the right sides correspond to the left and the right sides of the vehicle when the airbag unit is put in the instrument panel.  
         [0027]     A semicircular cut-off portion  31  having a radius slightly larger than that of the semicircular portions  25  of the base  20  is provided at the lower end of each side plate  30 . An anchoring piece  32  extending from one side of each side plate  30  is bent. The anchoring pieces  32  are overlapped on the outer surface of the wall  22  of the base  20  and fixed to the wall  22  by spot welding such that the side plates  30  are fixed to the base  20 . No anchoring piece is formed at the other side of each side plate  30 , and the other side of each side plate  30  is not linked to the comb-shaped wall  23  (free). The side plates  30  are located outside the bottom section  21  of the base  20 .  
         [0028]     As described above, the side plates  30  are linked to the base  20  only through the anchoring pieces  32  fixed to the wall  22 , and are not linked to the comb-shaped wall  23 . Moreover, the side plates  30  are located outside the bottom section  21 . Therefore, when a downwardly external force is applied to the side plates  30 , the side plates  30  are deformed around the anchoring pieces  32  such that portions adjacent to the comb-shaped wall  23  are pressed downwardly.  
         [0029]     The hook plate  40  extends along the wall  22  above the wall  22 . Anchoring pieces  41  are bent and extend from both ends of the hook plate  40  in the longitudinal direction. The anchoring pieces  41  are fixed to the side plates  30  by spot welding such that the hook plate  40  is fixed to the side plates  30 . A plurality of hooks  42  protrudes from the upper end of the hook plate  40  in the longitudinal direction with a predetermined spacing therebetween. The hooks  42  extend slightly upwardly from the hook plate  40 , then bend outwardly from the case body  10 , and subsequently bend downwardly.  
         [0030]     As shown in  FIG. 2 , the movable component  50  includes an approximately rectangular main plate  51 ; a plurality of hooks  52  protruding from the upper end of the main plate  51 ; nail-shaped anchoring pieces  53  bent from the left and the right sides of the main plate  51  at a substantially right angle; a deformed section  54  formed at the lower portion of the main plate  51 ; and slits  55  and ribs  56  formed in the main plate  51 . The slits  55  and the ribs  56  extend parallel to the long sides of the main plate  51 . The shapes of the slits and ribs are not limited to those described above. The hooks  52  have a profile similar to that of the hooks  42 , and are disposed on the upper end of the main plate  51  in the longitudinal direction with a spacing therebetween.  
         [0031]     In the embodiment, two anchoring pieces  53  are disposed at each side of the main plate  51 . The number is not limited to two. The deformed section  54  is formed by bending a lower end portion of the main plate  51  such that the lower end portion is away from the comb-shaped wall  23 . The lower end portion of the main plate  51  is bent by an angle θ along a bending line a (see  FIG. 3 ) parallel to the lower side of the main plate  51  so as to form the deformed section  54 . The angle θ is preferably 90° degrees or less. The deformed section  54  may be formed by curving the lower end portion of the main plate  51 .  
         [0032]     The movable component  50  is disposed along the outer surface of the comb-shaped wall  23  of the base  20 , and the anchoring pieces  53  are disposed along the outer surfaces of the side plates  30 . The anchoring pieces  53  are fixed to the side plates  30  by spot welding. In addition, the main plate  51  is fixed to upper portions of the pillars  23   b ,  23   c , and  23   d  of the comb-shaped wall  23  by spot welding.  
         [0033]     As shown in  FIG. 5 , the lid  6  is attached to the case  2  so as to cover the folded airbag  3  accommodated in the case  2 . A leg  6 A adjacent to the front side of the vehicle and a leg  6 B adjacent to the backside of the vehicle protrude from the back side of the lid  6 , and the hooks  42  and  52  are caught in holes  6   a  and  6   b  formed in the legs  6 A and  6 B, respectively. The lid  6  includes a tear line  6   t  to be torn when the airbag  3  is inflated by the inflator  4 .  
         [0034]     The airbag unit  1  having the above-described structure is installed such that the lid  6  is flush with an instrument panel  7 , and the brackets  28  and  29  are fixed to vehicle members (not shown) by bolts and the like. When an object hits and an external force is applied to the lid  6  of the airbag unit  1  in the vicinity of the movable component  50  as indicated by an arrow F shown in  FIG. 6 , the movable component  50  is pushed by the external force and retracts (moves downwardly in the embodiment). At this time, the pillars  23   b ,  23   c , and  23   d  of the comb-shaped wall  23  are deformed so as to be buckled. Moreover, the side plates  30  are deformed around the bases of the anchoring pieces  32  such that the portions adjacent to the comb-shaped wall  23  are pressed downwardly.  
         [0035]     Even though the movable component  50  moves downwardly, the lower portion  23   a  of the comb-shaped wall  23  does not move downwardly due to the firm support of the bottom section  21 . As a result, the movable component  50  moves downwardly while sliding on the outer surface of the lower portion  23   a.    
         [0036]     The deformed section  54  is formed in the lower end portion of the movable component  50  such that the deformed section  54  is away from the comb-shaped wall  23 . Accordingly, the movable component  50  is not caught in the upper end of the lower portion  23   a , and can smoothly move downwardly. As a result, the pillars  23   b  to  23   d  and the side plates  30  can be smoothly deformed, and an impact occurring when the object hits against the lid in the vicinity of the movable component  50  or on the instrument panel can be sufficiently absorbed.  
         [0037]     The above-described embodiment is an example of the present invention, and embodiments other than that shown in the drawings are possible. For example, the comb-shaped wall  23  may be a relatively thin wall component.  
         [0038]     The disclosure of Japanese Patent Application No. 2004-223930, filed on Jul. 30, 2004, is incorporated in the application.  
         [0039]     While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.