Abstract:
An automotive air bag device offers ready installation in an automobile instrument panel while reducing material and assembly costs and maintaining its structural integrity when activated. An air bag inflation opening, formed in the instrument panel, is surrounded by an internal reinforcement wall. An air bag lid, which covers the opening, includes an inwardly directed leg which engages the reinforcement wall. A case, which supports an inflator and a diffuser, is fastened to the leg on the lid.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an automotive air bag device and, more particularly, to an automotive air bag device wherein the air bag inflation opening is formed in an automotive panel such as an instrument panel or a door panel, and this opening is covered with an air bag lid. 
     Referring to FIG. 4, there is shown a conventional passenger-side automotive air bag device  2  disposed in an automobile instrument panel  1 . In the illustration, air bag  2  device is installed at an angle that allows it to be easily viewed in the drawing. This does not necessarily correspond to actual installation angles. 
     Instrument panel  1  is formed of a two-layer material including a core material  1   a  and a surface material  1   b.  A rectangular air bag inflation opening  1   c  is formed at a prescribed position on instrument panel  1 . 
     Air bag device  2  includes a semi-cylindrical metal case  4  fixed to a vehicle body via a bracket  3 . An inflator  5 , housed in case  4 , inflates an air bag  6  when inflator  5  is activated. A metal guide member  8  is fixed to case  4  by a plurality of mechanical fasteners  7 , 7  (only two are shown). An air bag lid  10  is fixed to guide member  8  by a plurality of mechanical fasteners  9 , 9  (only two are shown). These elements are assembled to the vehicle body as a single unit. 
     Air bag lid  10  covers opening  1   c  of instrument panel  1 . Air bag lid  10  includes a main lid unit  10   b  having a scoreline  10   a.  Legs  10   c,  projecting from the back surface of main lid unit  10   b,  are fastened to guide member  8  so as to retain lid  10  when air bag  6  inflates. 
     In air bag device  2 , bracket  3 , case  4 , inflator  5 , air bag  6 , guide member  8 , and air bag lid  10  comprise a subassembly. When installing this subassembly in the vehicle body, the proper alignment of air bag lid  10  with opening  1   c  is difficult to achieve. Proper alignment requires the edges of opening  1   c  and the outer edges of air bag lid  10  be aligned both along the plane of the opening and along the depth axis, i.e. alignment must be performed in three dimensions. If perfect alignment is not achieved, the cosmetic appearance of instrument panel  1  will suffer. 
     Furthermore, the inclusion of guide member  8 , which maintains subassembly integrity when air bag  10  inflates, increases the size of air bag device  2 , thus making the alignment operation described above even more difficult. Finally, the subassembly includes a substantial number of parts, so that material and assembly costs are high. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is a primary object of the present invention to overcome the problems described above by providing an automotive air bag device wherein the air bag lid can be easily aligned with the automotive panel. 
     It is a further object to provide an automotive air bag device which offers reduced material and assembly costs while maintaining its structural integrity when the inflator is activated. 
     Briefly stated, the present invention provides an automotive air bag device which offers ready installation in an automobile instrument panel while reducing material and assembly costs and maintaining its structural integrity when activated. An air bag inflation opening, formed in the instrument panel, is surrounded by an internal reinforcement wall. An air bag lid, which covers the opening, includes an inwardly directed leg which engages the reinforcement wall. A case, which supports an inflator and a diffuser, is fastened to the leg on the lid. 
     According to an embodiment of the invention, there is provided an automotive air bag device comprising: an automotive panel having an inner surface and defining an air bag inflation opening, a reinforcement wall on the inner surface of the instrument panel, surrounding the air bag inflation opening, an air bag lid, a leg projecting from the air bag lid and engageable with the reinforcement wall to retain the air bag lid in covering relation to the air bag inflation opening, a case attached to the leg, and an inflator disposed within the case. 
     According to a feature of the invention, there is provided an automotive air bag installation comprising: an instrument panel, an air bag opening in the instrument panel, an air bag lid, the air bag lid fitting the air bag opening and forming a contiguous portion of the instrument panel, at least one projection on one of the air bag lid and the instrument panel, an engagement portion on the other of the air bag lid and the instrument panel, the projection and the engagement portion interengaging when the air bag lid is inserted into the air bag opening, and a resulting interengagement being effective for retaining the air bag lid in position in the air bag opening whereby the air bag lid is installed by the insertion. 
     These objects are achieved by an air bag device wherein an air bag inflation opening is formed in the automobile panel, with a reinforcement wall surrounding the back side of the opening. An air bag lid, which covers the opening, includes an inwardly directed leg which is fastened to the reinforcement wall. A case, which supports an inflator and a diffuser, is also fastened to the leg on the lid. 
     The above, and other objects and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like numerals designate the same elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-section view of an automotive air bag device according to the present invention. 
     FIG. 2 is a cross-section view illustrating fabrication of the core material of the instrument panel. 
     FIG. 3 is a perspective view of an instrument panel in which the air bag has been installed. 
     FIG. 4 is a cross-section view of a conventional automotive air bag device. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, there is shown an automobile instrument panel  11  fabricated from a core material  12  partially covered by a surface material (elastic pad member)  13 . On the upper surface of instrument panel  11 , toward the passenger seat side, there is disposed an air bag device  14 . 
     A substantially rectangular opening  12   a  is formed in core material  12 . A reinforcement wall  12   c  surrounds a back surface  12   b  of opening  12   a.    
     Walls  12   e,    12   f,  forming a part of reinforcing wall  12   c,  are sloped from surface  12   d  toward the center of opening  12   a.  On walls  12   e,    12   f,  a plurality of comb-like ribs  12   g,    12   h  are formed generally perpendicular to surface  12   d  and have distal edge surfaces substantially parallel to legs  15   d  of air bag lid  15 . 
     A reinforcement wall  12   i  is formed behind wall  12   e  and parallel thereto. A plurality of ribs  12   j  is formed between reinforcement wall  12   i  and wall  12   e.  The end surfaces of ribs  12   j  are formed along surface  12   d  of core material  12 . 
     Referring to FIG. 2, there is shown a parting line PL between upper and lower dies  31 ,  32  used to mold core material  12 . Parting line PL is set to lie on a line connecting the area around the upper end of rib  12   g  and the area around the bottom end of wall  12   f.  Wall  12   e  is positioned so that it is sloped lower than the bottom end of wall  12   f.  Thus, when core material  12  is to be removed from the mold, upper and lower dies are pulled away in the same direction as the incline angle (see arrows P, Q in FIG.  2 ). This prevents undercutting, thus allowing the dies to be made inexpensively and easily without requiring a slide or the like to be disposed on the die. 
     A plurality of ribs  12   k  is formed behind wall  12   f  in a manner similar to ribs  12   h.  A lance  12   m  projects from the surface of wall  12   f.  Ribs  12   g,    12   h  and the portion positioned on a line extending downward from this end surface together form inner wall  12   n.    
     In addition to instrument panel  11  described above, air bag device  14  further includes an air bag lid  15  formed from a thermoplastic elastomer or the like and supported by core material  12  so as to cover opening  12   a.  A case  20  is fastened by brackets  17 ,  18  and a bolt  19  to a steering support member  16 , which is in turn fixed to the vehicle body. A diffuser  22 , supported by case  20 , houses an inflator  21 . A folded air bag  23 , stored in a space defined by case  20  and leg  15   d,  is connected to the gas discharge opening  22   a  of diffuser  22 . Referring to FIG. 1, there is also shown a front window glass  24 . 
     Air bag lid  15  includes a cover  15   a  contiguous and blending smoothly with the surface of instrument panel  11 . A generally H-shaped score line is formed on the back surface  15   b  of cover  15   a  (see FIG. 1, FIG.  3 ). A leg  15   d  projects from back surface  15   b  of cover  15   a  so that it faces inner wall  12   n  of reinforcement wall  12   c.  Engagement openings  15   e,    15   e  (only two are shown) are formed at a plurality of prescribed positions toward the bottom end of leg  15   d.  Engagement piece  15   f  and engagement portion  15   g  project from back surface  15   b  of cover  15   a,  extending out from leg  15   d  which is positioned between rib  12   g  and rib  12   h.  Cover  15   a  is positioned flush with surface material  13 , thus providing improved cosmetic appearance. 
     A lance  15   h,  formed on engagement piece  15   f,  engages the upper end of reinforcement wall  12   c.  A second lance  15   i,  formed on engagement portion  15   g,  engages lance  12   m.  This allows air bag lid  15  to be supported by reinforcement wall  12   c  so that opening  15   a  is covered. It will be appreciated that lance  15   h  can engage reinforcement wall  12   c  without requiring a special engagement opening. Thus, the loss of strength accompanying the presence of an engagement hole is avoided. 
     Hooks  20   a,    20   a,  which engage engagement opening  15   e,  are formed integrally with or are fixed to the end of case  20  to provide a connection with air bag lid  15 . 
     To assemble air bag device  14  described above, opening  12   a  and reinforcement wall  12   c  are formed in core material  12 . Next, lance  15   i  of engagement portion  15   g  is engaged with lance  12   m,  and lance  15   h  is engaged with the upper end of reinforcement wall  12   c.  Thus, air bag lid  15  is supported by reinforcement wall  12   c  so as to cover opening  12   a.  Air bag lid  15  is directly supported by core material  12 . This makes it possible to easily perform three-dimensional alignment of air bag lid  15  relative to opening  12   a.    
     Air bag  23  and diffuser  22  are fixed to cover  20 , with a portion of air bag  23  covering diffuser  22 . Hooks  20   a,    20   a  are then engaged with engagement openings  15   e,    15   e  and cover  20  is mounted on steering support member  16 . 
     The size of engagement opening  15   e  is such that the relative positioning between cover  20  and steering support member  16  remains fixed, and also so that relative positioning between air bag lid  15  and opening  12   a  does not change due to looseness and the like during the assembly process. 
     When inflator  21  is activated, air bag  23  inflates and presses against leg  15   d  and inner wall  12   n,  as well as cover  15   a  of air bag lid  15 . Cover  15   a  breaks open at score line  15   c  so that air bag  23  may inflate outwardly. Thus, subassembly integrity is maintained without the use of guide member  8  shown in the conventional technology. 
     When air bag  23  inflates, upward pressure is generated on cover  15   a,  but this pressure is absorbed by lance  15   h  and hook  20   a  of cover  20 , thus preventing air bag lid  15  from separating from instrument panel  11 . 
     Having described the presently preferred embodiment of the invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiment described, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.