Abstract:
An airbag apparatus is formed of a casing having an opening at an upper part thereof and a side portion, an airbag accommodated in and coupled with the casing, a gas generator for supplying a gas into the airbag and deploying the airbag, and a lid for covering the opening. A thick plate may be formed independently and attached to casing, or formed integrally with the casing. The thick plate has a thickness greater than that of the casing, and includes an upper portion and a lower portion extending from the upper portion. The lower portion and the side portion of the casing secured thereto project outwardly of the casing to be deformed easily when a force is applied thereto.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
     The present invention relates to an airbag apparatus, and more particularly, to an airbag apparatus which is preferably applicable to a passenger side airbag apparatus installed in the instrument panel of a vehicle. More specifically, the present invention relates to an airbag apparatus having a casing with a thick plate portion. Further, the present invention relates to a casing used in the airbag apparatus. 
     There is known an airbag apparatus, wherein a thick plate is attached to a casing, and a lid is locked to hook members of the thick plate, as a passenger-side airbag apparatus. 
     FIG. 9 is a sectional view showing a conventional airbag apparatus. The airbag apparatus  1  is composed of an inflator  2  for generating a gas in a collision of a vehicle and the like, a casing  3  for accommodating the inflator  2 , an airbag  5  accommodated in the casing  3  in a folded state, and a lid  6  for closing an uncovered opening at the upper portion of the casing  3 . The airbag apparatus  1  is attached to an instrument panel  9 . Thick plates  10  and  11  are secured to upper outer surfaces of the casing  3  by spot welding. The thick plates  10  and  11  extend along upper edges of the casing  3 , and a plurality of pawl-shaped hook members  12  is disposed integrally with the thick plates  10  and  11  in the extending direction thereof at appropriate intervals. The legs  7  of the lid  6  have openings  13  corresponding to the hook members  12  to engage therewith. A thin wall section  8  is formed on the inner surface of the lid  6 . 
     When the lid  6  is mounted on the casing  3  to assemble the airbag apparatus  1 , the lid  6  is pushed so as to close the uncovered opening of the upper surface of the casing  3 . With this operation, the legs  7  of the lid  6  pass over the hook members  12  while being elastically deformed externally, and return to their original shapes when the hook members  12  are in conformity with the openings  13 , so that the hook members  12  are caught by the inner edges of the openings  13 . 
     In the airbag apparatus arranged as described above, when the inflator  2  is actuated, the airbag  5  is deployed, and the lid  6  is broken and opened along the thin wall section  8 , whereby the airbag  5  is unfolded into a compartment. 
     The strength required for the casing  3  can be reduced by attaching the thick plates  10  and  11  to the casing  3 , and locking the lid  6  to the hook members  12  of the thick plates  10  and  11 , as shown in FIG.  9 . As a result, it is possible to reduce the wall thickness of the casing  3  and to decrease the weight of the casing  3 . 
     Incidentally, an instrument panel of a vehicle must have a energy absorbing function for absorbing energy generated when a passenger hits thereto in such a manner that the instrument panel is gradually deformed. The casing and the lid of the passenger side airbag apparatus which is installed in the instrument panel also must have the energy absorbing function. 
     Japanese Utility Model Publication (KOKAI) No. 6-22116 discloses that a bent section with an approximately V-shape in a cross section is disposed on a side surface of a casing, and the casing is deformed at the bent section when a passenger hits the airbag apparatus. 
     An object of the present invention is to provide an airbag apparatus having an energy absorbing function which is more enhanced than that disclosed in Japanese Utility Model Publication No. 6-22116 and a casing of the airbag apparatus. 
     SUMMARY OF THE INVENTION 
     In a first aspect of the invention, an airbag apparatus comprises a casing, a front surface of which is arranged as an uncovered opening, an airbag accommodated in and coupled with the casing, a gas generator for supplying a gas into the airbag and deploying the airbag, a thick plate secured to a side surface of the casing, and a lid for covering the uncovered opening. In the airbag apparatus, at least a rear or lower side portion of the thick plate is secured to a side surface or portion of the casing, and the rear side portion of the thick plate and a portion of the side surface of the casing secured to the rear side portion of the thick plate project outwardly. 
     In a second aspect of the present invention, an airbag apparatus comprises a casing, a front surface of which is arranged as an uncovered opening, an airbag accommodated in and coupled with the casing, a gas generator for supplying a gas into the airbag and deploying the airbag, and a lid for covering the uncovered opening. In the airbag apparatus, a front or upper portion, which is near the uncovered opening, of a side surface section of the casing is composed of a thick plate, the thickness being greater than a rear or lower portion of the side surface section, and the rear portion is composed of a thin plate. A rear or lower side of the thick plate and a portion, which is continuous to the rear side, of the thin plate project outwardly of the casing. 
     In a third aspect of the invention, a casing of an airbag apparatus for accommodating an airbag includes an uncovered opening at a front surface or upper portion of the casing, and a thick plate is disposed on a side surface of the casing along an edge of the uncovered opening. In the casing, at least a rear or lower side portion of the thick plate is secured to a side surface or portion of the casing, and the rear side portion of the thick plate and a portion of the side surface of the casing secured to the rear side portion of the thick plate project outwardly. 
     In a fourth aspect of the invention, a casing of an airbag apparatus for accommodating an airbag includes an uncovered opening at a front surface or upper portion of the casing. In the casing, the upper portion, which is near the uncovered opening, of a side surface section of the casing is composed of a thick plate whose thickness is greater than a rear or lower portion of the side surface section, and the rear portion is composed of a thin plate. The rear side portion of the thick plate and a portion continuous to the rear side portion of the thin plate project outwardly of the casing. 
     In the casing and the airbag apparatus using the casing of the present invention, when a passenger hits the casing or the airbag apparatus, the rear or lower side portion of the thick plate is deformed and project outwardly. At the time, the portion of the casing continuous to the thick plate is deformed so as to be drawn externally, whereby an energy is absorbed. 
     It is preferable that the rear side portion of the thick plate is bent obliquely relative to a portion located above the rear side portion. 
     In the present invention, the casing is composed of metal or a synthetic resin. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a casing of an airbag apparatus according to one embodiment of the invention; 
     FIG. 2 is a front view of the casing of the airbag apparatus according to the invention; 
     FIG. 3 is a side view of the casing of the airbag apparatus according to the invention; 
     FIG. 4 is a sectional view taken along ling  4 — 4  in FIG. 2; 
     FIG. 5 is a front view of the airbag apparatus according to the invention; 
     FIG. 6 is a perspective view showing the casing of the airbag apparatus and a thick plate according to the invention; 
     FIG. 7 is a sectional view showing how the casing is deformed; 
     FIG. 8 is a sectional perspective view showing another embodiment; and 
     FIG. 9 is a sectional view of a conventional airbag apparatus. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Embodiments of the invention will be described below with reference to the drawings. 
     FIG. 1 is a perspective view of a casing according to an embodiment; FIG. 2 is a front view of FIG. 1; FIG. 3 is a side view of FIG. 1; FIG. 4 is a sectional view taken along line  4 — 4  in FIG. 2; FIG. 5 is a front view of the airbag apparatus according to the embodiment; FIG. 6 is a perspective view showing a thick plate and an upper portion of the casing; and FIG. 7 is a sectional view showing how the casing is deformed. 
     The passenger side airbag apparatus according to the embodiment includes a casing  20  having an approximately rectangular shape when viewed in a plane, an airbag  22  folded and disposed in the casing  20 , a lid  24  for covering an uncovered or upper opening on the upper surface side of the casing  20 , thick plates  26  and  28  for coupling the lid  24  with the casing  20 , and an approximately columnar inflator  30  for generating a gas for deploying the airbag  22 . 
     The thick plates  26  and  28  are secured to the side surfaces, which extend in a vehicle width direction, of the casing  20  by spot welding. The thick plate  26  is disposed on the side of a seat, whereas the thick plate  28  is disposed on the side of the window shield. 
     The casing  20  and the thick plates  26  and  28  are made of steel, for example, a plated steel sheet or the like. When the thick plates  26  and  28  and the casing  20  are composed of the same type of a steel member, the thickness of each of the thick plates  26  and  28  is set to at least 1.6 times greater than that of the casing  20 , e.g. about 1.6 to 3 times greater that of the casing  20 . 
     A semi-arc-shaped enlarged section  32  projects from the bottom of the casing  20 , and the inflator  30  is engaged with the enlarged section  32  and covered with a press member  34  from an upper side (FIG.  4 ). The press member  34  includes flanges  34   a  which overlap the bottom surface of the casing  20 , and the edge portion of the gas introduction port of the airbag  22  is held between the flanges  34   a  and the bottom surface of the casing  20 . The flanges  34   a  are secured to the casing  20  by bolts  34   b  and nuts  34   c.    
     The thick plates  26  and  28  extend along the upper edges of the casing  20  in the vehicle width direction. The thick plates  26  and  28  are mostly disposed in the casing  20  and secured to the casing  20  by spot welding. It is sufficient that each thick plate is spot welded at 2 to 4 positions, e.g. 3 positions (excluding welding portions between the lower portion  26   a  of the thick plate  26  and a bent section  52 , which will be described later). 
     Approximately L-shaped hook members  36  and  38  extend externally from the upper sides of the thick plates  26  and  28 . Openings  40  and  42  having the number same as that of the hook members  36  are formed in the side surface, which extend in the vehicle width direction, on one side (right side of FIGS. 1,  3  and  4 ) of the casing  20 , whereas openings  44 ,  46  having the number same as that of the hook members  38  are formed in the side surface, which extends in the vehicle width direction, on the other side (left side in FIGS. 1,  3  and  4 ). 
     The openings  40 ,  42  are disposed so that the upper sides thereof have the same height. In the row of the openings  40  and  42 , the openings  42  are disposed on both ends of the row, and the openings  40  are disposed between the openings  42 . The length of the opening  42  in the up and down directions is greater than that of the opening  40  in the up and down directions. The hook members  36  of the thick plate  26  project externally or outwardly of the casing  20  through the openings  40  and  42 . 
     The openings  44 ,  46  are disposed so that the upper sides thereof have the same height. In the row of the openings  44  and  46 , the openings  44  are disposed between the openings  46 . The length of the opening  46  in the up and down directions is greater than the length of the opening  44  in the up and down directions. The hook members  38  of the thick plate  28  project externally or outwardly of the casing  20  through the openings  44  and  46 . 
     Note that the lower portion  26   a  of the thick plate  26  is bent preferably at an angle of 20 to 70 degrees, and particularly preferably at an angle of 30 to 60 degrees, for example, at an angle of about 45 degrees. The lower portion  26   a  extends externally of the casing  20  through a slit (slender opening)  50  of the side surface of the casing  20 . 
     The side surface of the casing  20 , which extends in the vehicle width direction and is located on the side of the seat, has a bent section  52  which extends externally below the slit  50  to have an approximately V-shaped cross section, and the lower portion  26   a  of the thick plate is overlapped with an upper surface  52   a  of the bent section  52  and spot welded thereto at 2 to 4 positions. A lower portion  52   b  of the bent section  52  is bent outwardly approximately perpendicularly from the side surface of the casing  20 . 
     The lid  24  has a pair of leg sections  56  and  58 , and openings  60  and  62  are formed in the respective leg sections  56  and  58 . The hook members  36  and  38  are engaged with the openings  60  and  62  so that the lid  24  is locked to the casing  20 . 
     In the airbag apparatus arranged as described above, when the inflator  30  is actuated to supply a gas, the airbag  22  is deployed and the lid  24  is broken and opened along the thin wall portion  24   a,  whereby the airbag  22  is deployed in a compartment. During the deployment, a pressure is exerted on the thick plates  26  and  28  and the casing  20  from the airbag  22  to expand the casing  20 . However, since the thick plates  26  and  28  are disposed in the casing  20  and the pressure of the airbag  22  is resisted by the thick plates  26  and  28 , the expansion of the casing  20  is prevented. 
     Further, when the airbag  22  is deployed, while a force for moving the lid  24  upward in FIG. 4 is exerted from the airbag  22  to the lid  24 , the force is resisted by the leg sections  56  and  58  and the thick plates  26  and  28 . Since the hook members  36  and  38  of the thick plates  26  and  28  project externally of the casing  20  through the openings  40 ,  42 ,  44  and  46 , the upward drawing force exerted on the thick plates  26  and  28  is transmitted to the casing  20  not only through the portions where the thick plates  26  and  28  are spot welded to the casing  20  but also through the portions where the upper sides of the openings  40 ,  42 ,  44 ,  46  abut against the hook members  36  and  38 . As a result, since the upward drawing force is widely dispersed and transmitted to the casing  20 , the deformation of the casing  20  caused by the upward drawing force also can be prevented. 
     When a passenger hits the airbag apparatus installed in the instrument panel, the casing  20  is deformed in a manner such that the side surface of the casing  20 , which extends in the vehicle width direction and is located on the side of the seat, projects outwardly as shown by the two-dot-and-dash lines  20 ′,  26 ′ and  52 ′ in FIG.  7 . In this case, the thick plate  26  itself is not deformed significantly because it has a high rigidity. Therefore, the lower portion  26   a  moves externally and the overall thick plate  26  is moved downward. As the lower portion  26   a  of the thick plate  26  projects externally, the approximately V-shaped bent section  52  is crushed flat as shown by the reference numeral  52 ′, and the flat surface of the casing  20  is bent as shown by reference numeral  20 ′. When the side surface of the casing  20  is bent as shown by reference numeral  20 ′, an energy or load applied to the passenger is absorbed. 
     In the embodiment, a large number of through holes  66  is formed in the casing  20  so that a larger amount of energy applied to the instrument panel or lid (energy/load applied to the passenger when the passenger hits the instrument panel) can be absorbed. Further, in the embodiment, the lengths of the openings  42  and  46  in the vertical direction are made larger than those of the openings  40 ,  42 , and this arrangement also intends to absorb a larger amount of energy applied to the instrument panel. 
     That is, when a passenger hits approximately the central portion of the lid  24  as shown by an arrow F in FIG. 5, the central portion of the lid  24  is dented in the direction of the arrow F, and the side surfaces of the casing  20  are also deformed in accordance with deformation of the side surfaces, so that the energy from the instrument panel or lid is absorbed. At that time, however, both ends of the casing  20  tend to move upward. Since the openings  40  and  42  at both ends extend long downwardly as shown in FIGS. 1,  2  and  6 , when both sides of the casing  20  are pulled upwardly, both sides of the casing  20  are not subjected to restriction of the thick plates  26  and  28 . Therefore, the casing  20  is deformed smoothly and the larger amount of the energy from the instrument panel or casing is absorbed. 
     Incidentally, though it is not shown, a slit or a slender notch, which extends in the up and down directions, may be formed in the upper surface  52   a  of the bent section  52  so that the bent section  52  can be deformed easily. 
     In the embodiment, although the thick plates  26  and  28 , which are arranged separately from the casing  20 , are secured to the casing  20  by spot welding or the like, a thick plate section  20   a  may be formed integrally with a casing  20 A, as shown in FIG.  8 . That is, it may be successively and integrally formed from the thick plate section  20   a  to a thin plate section  20   b.  In this case, it is preferable to form a bent section  52 A by bending the lower portion of the thick plate section  20   a  and the upper portion of the thin plate section  20   b  externally so that the boundary therebetween is most protruded. 
     In the present invention, the casing is composed of metal, a synthetic resin or the like. 
     As described above, according to the present invention, there is provided the airbag apparatus in which the casing is less deformed when the airbag is deployed. The casing of the airbag apparatus can be easily manufactured because the casing can be made by using the less number of joint positions, such as spot-welded positions and the like. 
     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.