Abstract:
An airbag cover for maintaining a folded shape of an airbag when the airbag is folded and accommodated within a casing, is designed to bulge from an opening formed on a panel constituting a vehicle inner wall for deploying between the panel and an occupant. The airbag cover includes a flat structure for covering at least a side of the airbag facing the opening before a deployment, and a tear line located on the flat structure and facing the opening so as to allow the airbag to bulge from the opening when deployed by cleaving the flat structure. The tear line is located on a side closer to the occupant relative to a center of the airbag cover in a direction of a vehicle length.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
     The present invention relates to an airbag cover for preventing a deformation in folded-state of an airbag for restraining an occupant in case of a collision of a vehicle, such as an automobile, when the airbag is folded and accommodated within a casing, and the invention also relates to an airbag apparatus having the airbag cover. 
     Hitherto, it is known that, in the event of an emergency, such as an automobile collision or rolling, an inflator is operated so as to inflate the airbag for restraining an occupant by gas injected from the inflator. 
     This airbag apparatus includes an airbag that is a simple bag made by stitching a plurality of base clothes together at their edges. In a rest state, the airbag is folded and accommodated within the casing. At the emergency, such as the automobile collision or rolling, upon injecting gas by an operation of the inflator, the gas entirely flows inside the airbag so that the airbag is inflated and developed by its internal pressure. 
     Such an airbag apparatus may include an airbag cover for covering the airbag to be folded and accommodated within the casing (see Patent Document 1: Japanese Unexamined Patent Application Publication No. H11-321515). The airbag cover (flexible protective cover) of a conventional technique includes a pair of flat structures (material webs) each provided transversely to cover the bulging side of the folded and accommodated airbag, and during operating of the inflator, these flat structures allow the airbag to bulge by breaking tearing lines (tearing locations) provided substantially at the center of the flat structures in the longitudinal direction. 
     In the conventional technique mentioned above, the basic configuration of the airbag cover used when the airbag is folded and accommodated within the casing is disclosed. In such a configuration, in order to optimize the development of the airbag, it is required to optimize the position of the tearing lines in the airbag cover. 
     An object of the present invention is to provide an airbag cover and an airbag apparatus capable of improving development properties of the airbag. 
     Further objects and advantages of the invention will be apparent from the following description of the invention. 
     SUMMARY OF THE INVENTION 
     In order to achieve the object mentioned above, according to a first aspect of the invention, an airbag cover for maintaining the folded shape of an airbag when the airbag is folded and accommodated within a casing, is bulged from an opening formed on a panel constituting a vehicle inner wall for inflating and developing between the panel and an occupant, and the airbag cover includes a flat structure for covering at least a side of the airbag facing the opening during non-operating state of an inflator for supplying gas to the airbag; and tear lines located on a side of the occupant in the flat structure facing the opening so as to allow the airbag to be bulged from the opening during the operation of the inflator by cleaving the flat structure. 
     In general, in a passenger airbag apparatus provided on a passenger seat and a knee airbag apparatus for restraining an occupant&#39;s knee, an airbag is to be bulged from an opening formed on a panel constituting a vehicle inner wall to the occupant i.e., in a direction to a rear side of the vehicle. Hence, a lid member for blocking the panel opening in a rest state is configured such that the side of the occupant can be opened by rotating the lid member to its end adjacent to the vehicle front (a side opposite to the occupant), thereby enabling the airbag to smoothly bulge toward the occupant. 
     According to a first aspect of the present invention, during a non-operating state of the inflator, at least the side of the folded airbag facing the panel opening is covered with a flat structure of the airbag cover, and the airbag is accommodated within the casing. Then, upon the operation of the inflator, the flat structure is broken at tear lines, so that the airbag bulges from the panel opening for inflating and developing between the panel and the occupant. 
     At this time, the tear lines are formed to unevenly locate on the side of the occupant in the flat structure facing the panel opening. Thereby, the bulging direction of the airbag after breaking the flat structure can be guided toward the occupant. As a result, the airbag can smoothly bulge in conjunction with the operation of the lid member of which the end adjacent to the occupant is opened by rotating about the end adjacent to the vehicle front (opposite to the occupant), thereby improving the development abilities of the airbag. 
     In the second aspect of the invention, an airbag cover according to the first aspect of the invention further includes a first tongue structure provided inside the flat structure so as to emerge when the flat structure is broken at the tear lines and to intervene in between the end of the opening of the panel adjacent to the occupant and the airbag in the course of inflating and developing of the airbag. 
     Generally, in the airbag apparatus where the airbag bulges from the opening formed on the panel constituting the vehicle inner wall for inflating and developing between the panel and the occupant, a tear line is formed in between the lid member for shielding the panel opening and the end of the panel opening, so that during the developing of the airbag, the lid member is opened by the instant cleaving of the tear line. Hence, burrs and fins may be formed at the end of the panel opening, so that when the airbag is brought into contact with the opening end, the airbag development may be affected or the airbag may be damaged due to sticking. At this time, especially in the passenger airbag apparatus or the knee airbag apparatus, since the airbag bulges from the panel opening toward the occupant, the end of the panel opening adjacent to the occupant tends to contact with the airbag. 
     According to a second aspect of the invention of the present application, in connection with this tendency, the airbag cover further includes a first tongue structure provided inside the flat structure so as to emerge when the flat structure is broken at the tear lines and to intervene in between the end of the opening of the panel adjacent to the occupant and the airbag during inflating and developing of the airbag. Thereby, during the development of the airbag, the contact between the airbag and the end of the panel opening adjacent to the occupant can be avoided, so that developing properties of the airbag can be preferably maintained while the durability can be improved by suppressing the airbag damage. 
     In a third aspect of the invention of an airbag cover, the flat structure according to the second aspect includes a second tongue structure formed to emerge on the side opposite to the occupant after the breaking at the tear lines so as to intervene in between the end of the opening of the panel opposite to the occupant and the airbag during the deployment of the airbag. 
     Since the end of the panel opening opposite to the occupant, as mentioned above, is an axis about which the lid member is rotated, although burrs may not be formed unlike the end adjacent to the occupant mentioned above, the fins may be formed due to the bending of the panel at an acute angle. 
     According to the third aspect of the invention, in connection with this tendency, the second tongue structure emerged on the side opposite to the occupant after the breaking of the flat structure is configured to intervene in between the end of the opening of the panel opposite to the occupant and the airbag during the development of the airbag. Thereby, the contact between the airbag and the end of the panel opening opposite to the occupant can be avoided during the airbag developing, so that developing properties of the airbag can be further preferably maintained while the durability of the airbag can be further improved by further suppressing the airbag damage. 
     According to a fourth aspect of the invention, the first tongue structure in the third aspect includes a pair of side-cover parts covering both sides in the vehicle width direction, respectively, of the airbag folded and accommodated within the casing. 
     According to the fourth aspect of the invention, both sides of the airbag folded and accommodated within the casing in the vehicle width direction are covered with the side-cover parts of the first tongue structure, respectively. Thereby, the perimeter of the folded airbag can be covered with the airbag cover by covering the accommodated airbag in the vehicle front-back direction with the flat structure. As a result, the function maintaining the folded shape when the airbag is accommodated in the casing can be further improved, suppressing the generation of shape collapsing of the airbag during the accommodating. 
     According to a fifth aspect of the invention, the flat structure in the fourth aspect includes through-holes formed at both ends in the longitudinal direction, respectively, to be passed through by fixing members for fixing the casing to the vehicle, and the first tongue structure includes the through-hole formed at the base end to be inserted to the fixing member. 
     According to the fifth aspect of the invention, the through-holes formed at both ends of the flat structure in the longitudinal direction and the through-hole formed at the base end of the first tongue structure are passed through by fixing members, respectively, for fixing the casing to the vehicle. Thereby, the airbag cover composed of the flat structure and the first tongue structure can be fixed in the casing. By diverting the fixing member of the casing to fixing the airbag cover in such a manner, an additional fixing member is not required for fixing the airbag cover, thereby simplifying the structure. 
     According to a sixth aspect of the invention, the flat structure in the fifth aspect includes a connection part formed to emerge adjacently to the occupant after the breakage at the tear lines, said connection part being sewn and connected with the first tongue structure. 
     According to the sixth aspect of the invention, before the operation of the inflator (before the breakage of the flat structure), the flat structure and the first tongue structure are connected together with sewing. After the operation of the inflator, the connection part emerged and separated from the flat structure and the first tongue structure are connected together with sewing. Thereby, throughout the operation of the inflator, the first tongue structure can be stably fixed. 
     In order to achieve the object mentioned above, an airbag apparatus according to a seventh aspect of the invention includes an airbag arranged to bulge from an opening formed on a panel constituting a vehicle inner wall for inflating and developing between the panel and an occupant; the airbag cover according to any one of the first to sixth aspects of the invention for maintaining the folded shape of the airbag when the airbag is folded and accommodated within a casing arranged inside the panel; an inflator for supplying gas to the airbag; and the casing for accommodating the airbag, the airbag cover, and the inflator therein. 
     In general, in a passenger airbag apparatus provided on a passenger seat and a knee airbag apparatus for restraining an occupant knee, an airbag is to bulge from an opening formed on a panel constituting a vehicle inner wall toward an occupant i.e., in a direction of the rear side of the vehicle. Hence, a lid member for blocking the panel opening in the rest state is configured such that the side of the occupant can be opened by rotating the lid member about its end adjacent to the vehicle front (side opposite to the occupant), thereby enabling the airbag to smoothly bulge toward the occupant. 
     According to the seventh aspect of the invention, during non-operating state of an inflator, in a state that at least the side of a folded airbag to a panel opening is covered with a flat structure of an airbag cover, the airbag is accommodated within a casing. Then, upon operating of the inflator, the flat structure is broken at tear lines, so that the airbag is bulged from the panel opening for inflating and developing to between the panel and an occupant. 
     At this time, the tear lines are formed to be unevenly located on the side of the occupant in the flat structure facing the panel opening. Thereby, the bulging direction of the airbag with the broken flat structure can be guided toward the occupant. As a result, the airbag can smoothly bulges in conjunction with the operation of the lid member of which the end adjacent to the occupant is opened by rotating about the end adjacent to the vehicle front (opposite to the occupant), thereby improving the development properties of the airbag. 
     According to the present invention, the development properties of the airbag can be improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1(   a ),  1 ( b ) are side sectional views of a passenger airbag apparatus according to an embodiment of the present invention, showing schematic structures in a rest state and during operation of an inflator. 
         FIG. 2  is a perspective view of a retainer showing a whole structure. 
         FIG. 3  is a side view of an airbag cover for covering an airbag showing a whole structure in a state of being accommodated within the retainer. 
         FIGS. 4(   a ),  4 ( b ),  4 ( c ) are side views and developed plan views of the airbag cover showing a whole structure. 
         FIGS. 5(   a ),  5 ( b ),  5 ( c ),  5 ( d ) are drawings of a passenger airbag apparatus conceptually showing the behavior during operation of the inflator. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments according to the present invention will be described below with reference to the drawings. 
       FIGS. 1(   a ),  1 ( b ) are schematic side sectional views of the structure of an airbag apparatus according to the embodiment of the present invention incorporated in a passenger airbag, in which  FIG. 1(   a ) shows a rest state of an inflator and  FIG. 1(   b ) shows an inflating and developing state of the airbag during operating of the inflator. 
     In  FIGS. 1(   a ) and  1 ( b ), in front (in a vehicle traveling direction, on the right of  FIGS. 1(   a ),  1 ( b )) of an occupant M sitting on a passenger seat S, an instrument panel  12  is arranged, and a passenger airbag apparatus  10  is provided within the instrument panel  12  (panel). The passenger airbag apparatus  10  includes an airbag  16  to bulge from an opening  14  (appropriately referred to a “panel opening” below) so as to inflate and develop between the instrument panel  12  and the occupant M; an airbag cover  18  for maintaining a folded shape of the airbag  16  when the airbag  16  is accommodated in a retainer, which will be described later; an inflator  20  for supplying gas to the airbag  16 ; and a retainer  22  (casing) for accommodating the folded airbag  16  arranged inside the instrument panel  12 , the airbag cover  18  covering the airbag  16 , and the inflator  20  therein. 
     On both sides of the retainer  22  in the vehicle front-back direction, a plurality of claw members  24  are provided. By the plurality of claw members  24  retained to support members  26  provided inside the instrument panel  12 , the retainer  22  is fixed inside the instrument panel  12 . 
     The opening  14  of the instrument panel  12 , as shown in  FIG. 1(   a ), is provided with a lid member  28  for blocking the opening in the rest state. The lid member  28  is configured such that the side of the occupant M can be opened by rotating the lid member  28  about its end adjacent to the vehicle front (side opposite to the occupant M) toward a front windshield  30 . As shown in  FIG. 1(   b ), during the inflator operation, a cleavable tear line (not shown) formed between the lid member  28  and the end of the panel opening  14  is cleaved and the lid member  28  is rotated so as to open the side of the occupant M, thereby enabling the airbag  16  to smoothly bulge toward the occupant M. The structure of the end of the lid member  28  adjacent to the vehicle front (side opposite to the occupant M) serving as the rotational axis of the lid member  28  may be a hinge structure or a structure using the deflection of the member. 
     In a passenger seat airbag apparatus  10  configured in such a manner, in the rest state, as shown in  FIG. 1(   a ), the airbag  16  is folded and accommodated within the retainer  22 . 
     Then, in case of an emergency, such as a vehicle collision, the inflator  20  is operated by receiving a control signal from a control device (not shown) so as to inject combustion compressed gas by igniting an igniting agent provided inside, thereby increasing the internal pressure so as to make the folded airbag  16  inflate and develop. Then, as shown in  FIG. 1(   b ), the airbag  16  cleaves the tear line formed between the lid member  28  and the end of the panel opening  14  with its inflating force so as to open the lid member  28 . Thereby, the airbag  16  bulges outside the retainer  22  and the instrument panel  12  so as to inflate and develop toward the occupant M sitting on the passenger seat S for restraining the upper body of the occupant M with the inflated airbag  16 . 
     Though details will be described later, during the inflation and development of the airbag  16 , as shown in  FIG. 1(   b ), a second tongue structure  42  emerged by the braking of a flat structure  36  of the airbag cover  18  bulges to intervene between the side end of the front windshield  30  in the panel opening  14  and the airbag  16  while a first tongue structure  38  provided inside the flat structure  36  emerges when the flat structure  36  is broken so as to bulges to intervene between the end of the panel opening  14  adjacent to the occupant M and the airbag  16 . 
       FIG. 2  is a perspective view of the retainer  22  showing its whole structure.  FIG. 3  is a side view of the airbag cover  18  for covering the airbag  16  showing its whole structure in a state of being accommodated within the retainer  22 . 
     In  FIGS. 2 and 3 , the retainer  22 , as mentioned above, includes a plurality of the claw members  24  provided on both sides of the retainer  22  in the vehicle front-back direction (lateral direction in  FIG. 2 ), and the retainer  22  is fixed on the vehicle with bolts  31  and  33  (fixing members) inserted into through-holes (not shown) formed on the bottom surface. The retainer  22  also includes an inflator support part  32  arranged adjacent to the bottom surface (downside of  FIG. 2 ) and the retainer  22  supports the inflator  20  inserted into the airbag  16  with the inflator support part  32 . An opening  34  shown in the drawing is for deriving a cable connecting between the inflator  20  and the control device (not shown) for controlling the initiation of the inflator  20 . 
     Also, when the airbag  16  is accommodated within the retainer  22  for maintaining a folded shape of the airbag  16 , it is accommodated by being covered by the airbag cover  18 . At this time, the airbag cover  18  includes the substantially belt-shaped flat structure  36  covering the side of the panel opening  14  (upside of  FIGS. 2 and 3 ) and both sides in the vehicle front-back direction (lateral direction in  FIGS. 2 and 3 ) of the airbag  16 ; and the substantially tongue-shaped first tongue structure  38  arranged inside the flat structure  36  (adjacent to the accommodated airbag) and stitched to the flat structure  36 . 
     The flat structure  36  is provided with slits  40  (breaking locations) formed to be unevenly located on the side of the occupant M (on the left of  FIGS. 2 and 3 ) in the flat structure  36  facing the panel opening  14  (i.e., the upper portion of  FIG. 2  exposed from the retainer  22  and the upper portion of  FIG. 3 ) for allowing the airbag  16  to bulge from the panel opening  14  by cleaving the flat structure  36  during the operation of the inflator  20 . Thereby, the flat structure  36  includes the substantially tongue-shaped second tongue structure  42  formed to emerge oppositely to the occupant M (on the right of  FIGS. 2 and 3 ) after the breakage along the slits  40  of the flat structure  36  so as to intervene between the end of the panel opening  14  adjacent to the front windshield  30  and the airbag  16  during inflating and developing of the airbag  16 ; and a connection part  44  formed to emerge adjacently to the occupant M (on the left of  FIG. 2 ) after the breakage along the slits  40  of the flat structure  36  and sewn and connected with the first tongue structure  38 . 
     The first tongue structure  38  includes a pair of side-cover parts  46 ,  46  covering both sides, respectively, of the folded and accommodated airbag  16  in the vehicle width direction (perpendicular direction to the plane of  FIG. 2 ). The side-cover part  46 , as shown in  FIG. 2 , is formed to have such a size that when the airbag  16  is accommodated within the retainer  22 , the side-cover part  46  slightly protrudes toward the panel opening  14  (upside of  FIG. 2 ). 
     The reason why the flat structure  36  is provided with the slits  40  so as to cleave therealong during the development of the airbag is that the shape maintaining function of the airbag  16  when the airbag  16  is accommodated within the retainer  22  can be improved in comparison with the configuration in that the tongue structures  38 ,  42  are simply placed on the airbag  16 . Furthermore, this configuration has an advantage for improving developing properties by increasing the internal pressure during initiation of the inflating of the airbag to a predetermined pressure. 
       FIGS. 4(   a ),  4 ( b ),  4 ( c ) are explanation views of the airbag cover  18  showing the whole structure, in which  FIG. 4(   a ) is a side view of the airbag  16  in a state of being covered,  FIG. 4(   b ) is a developed plan view of the flat structure  36  in a state of being overlapped on the first tongue structure  38  (in this condition, the airbag cover  18  is wrapped over the airbag  16 ),  FIG. 4(   c ) is a developed plan view of the flat structure  36  in a state of being upwardly turned over (upside in the drawing).  FIG. 4(   a ) corresponds to a simplified view of  FIG. 3 . In  FIG. 4(   a ), the airbag  16  is omitted. 
     In  FIGS. 4(   a ) to  4 ( c ), the airbag cover  18  includes the flat structure  36  and the first tongue structure  38  arranged inside the flat structure  36  (internally perpendicular direction to the plane of  FIGS. 4(   b ) and  4 ( c )). The connection part  44  connects the flat structure  36  and the first tongue structure  38  by sewing therebetween. Reference numeral  48  in the drawing denotes a sewing line (see  FIG. 3) . 
     As mentioned above, the flat structure  36  is provided with the slits  40  formed to be unevenly located on the side of the occupant M in the flat structure  36  facing the panel opening  14 . The flat structure  36  also includes the second tongue structure  42  formed to emerge oppositely to the occupant M (on the right of  FIG. 4(   a ), the downside of  FIGS. 4(   b ) and  4 ( c )) after the breakage along the slits  40  of the flat structure  36  so as to intervene between the end of the panel opening  14  adjacent to the front windshield  30  and the airbag  16  during inflating and developing of the airbag  16  and the connection part  44  formed to emerge adjacently to the occupant M (on the left of  FIG. 4(   a ), the upside of  FIGS. 4(   b ) and  4 ( c )) after the breakage along the slits  40  of the flat structure  36  and sewn and connected with the first tongue structure  38 . As shown in  FIGS. 4(   b ) and  4 ( c ), the flat structure  36  also includes through-holes  50 ,  52 , into which the bolts  31 ,  33  (see  FIG. 2)  for fixing the retainer  22  onto the vehicle can be inserted, on both sides in the longitudinal direction (the vertical direction of  FIGS. 4(   b ) and  4 ( c )), respectively. By inserting the bolts  31 ,  33  into the through-holes  50 ,  52 , respectively, the flat structure  36  is fixed to the retainer  22 . 
     On the other hand, the first tongue structure  38 , as mentioned above, includes a pair of the side-cover parts  46 ,  46  covering both sides, respectively, of the folded and accommodated airbag  16  in the vehicle width direction. The first tongue structure  38  also includes through-holes (not shown), into which the bolts  31  can be inserted, formed at positions of the base end portion (upper end portion of  FIGS. 4(   b ) and  4 ( c )) corresponding to the through-holes  50 , respectively. Furthermore, the side-cover part  46  also includes a through-hole  54 , into which the bolt  33  can be inserted, formed adjacent to the base end (upside of  FIGS. 4(   b ) and ( c )). As a result, by inserting the bolts  31 ,  33  into the through-holes (not shown) in the base end portion of the first tongue structure  38  as well as the through-holes  50  of the flat structure  36  and the through-holes  54  of the side-cover parts  46  as well as the through-holes  52  of the flat structure  36 , respectively, the first tongue structure  38  is fixed to the retainer  22 . 
     The condition of the flat structure  36  being turned over upwardly shown in  FIG. 4(   c ) as described above shows a structure of the airbag cover  18 . In fact, the airbag cover  18  covers the airbag  16  in a state shown in  FIG. 4(   b ) and is accommodated within the retainer  22 . 
       FIGS. 5(   a ), ( b ), ( c ), ( d ) are conceptual drawings of the passenger airbag apparatus  10  showing its behaviors during the operation of the inflator. In  FIGS. 5(   a ), ( b ), ( c ), ( d ), the claw members  24  and the support members  26  are omitted for preventing complication. 
     In the rest state in that the inflator is not operating, as shown in  FIG. 5(   a ), the airbag  16  is folded up and covered with the flat structure  36  and the first tongue structure  38  provided inside the flat structure  36  so as to be accommodated within the retainer  22 . 
     Upon operating the inflator  20 , as shown in  FIG. 5(   b ), the internal pressure is increased by injected gas so as to make the folded airbag  16  inflate and develop. At this time, the flat structure  36  cleaves at the slits  40  formed to be unevenly located on the side of the occupant M (on the left in  FIGS. 5(   a ), ( b ), ( c ), ( d ) in the portion facing the panel opening  14  so as to allow the airbag  16  to bulge, while, due to the breakage of the flat structure  36 , the second tongue structure  42  emerges in the vehicle front direction (on the right of  FIGS. 5(   a ),  5 ( b ),  5 ( c ),  5 ( d )) and the connection part  44  emerges on the side of the occupant M. 
     Then, the lid member  28  is pushed up due to the inflation of the airbag  16 , and the lid member  28 , as shown in  FIG. 5(   c ), is rotated about its end in the vehicle front direction so as to open the side of the occupant M. The first tongue structure  38  also emerges from the broken flat structure  36  so as to bulge together with the airbag  16  from the panel opening  14 . 
     As shown in  FIG. 5(   d ), the airbag  16  is further inflated and finally developed to between the instrument panel  12  and the occupant M. At this time, the first tongue structure  38  intervenes in between the end of the panel opening  14  adjacent to the occupant M and the airbag  16  while the second tongue structure  42  intervenes in between the end of the panel opening  14  in the vehicle front direction and the airbag  16 . 
     From the passenger airbag apparatus  10  according to the embodiment configured as described above, the following advantages can be obtained. 
     Namely, according to the embodiment, the lid member  28  for shielding the panel opening  14  of the instrument panel  12  in the rest state is configured such that the lid member  28  can open up the side of the occupant M by rotating about the end thereof in the vehicle front direction (opposite to the occupant M), so that during the operation of the inflator  20 , the airbag  16  can smoothly bulge toward the occupant M by opening the side of the occupant M. 
     In the passenger airbag apparatus  10  according to the embodiment, during non-operating state of the inflator  20 , in a state where the side of the folded airbag  16  to the panel opening is covered with the flat structure  36  of the airbag cover  18 , the airbag  16  is accommodated within the retainer  22 . Then, upon operation of the inflator  20 , the flat structure  36  is broken across the slits  40 , so that the airbag  16  bulges from the panel opening  14  for inflating and developing between the instrument panel  12  and the occupant M. 
     At this time, the slits  40  are formed to be unevenly located on the side of the occupant M in the flat structure  36  facing the panel opening  14 . Thereby, the bulging direction of the airbag  16  with the broken flat structure  36  can be guided toward the occupant M. As a result, the airbag  16  can smoothly bulge along with the operation of the lid member  28  of which the end adjacent to the occupant M is opened by rotating about the end in the vehicle front direction (opposite to the occupant M), improving the development properties of the airbag. 
     The following advantage can also be achieved especially according to the embodiment. That is, in the passenger airbag apparatus  10  according to the embodiment, a tear line is formed in between the lid member  28  for shielding the panel opening  14  and the end of the panel opening  14 , so that during the airbag developing, the lid member  28  is opened by the instant cleaving of the tear line. Hence, burrs and fins may be formed at the end of the panel opening  14 , so that when the airbag  16  is brought into contact with the end of the panel opening  14 , the airbag development may be affected or the airbag  16  may be damaged due to sticking. Since, in particular, the airbag  16  bulges from the panel opening  14  toward the occupant M, the end of the panel opening  14  adjacent to the occupant M tends to contact with the airbag  16 . 
     According to the embodiment, in view of this tendency, the airbag cover  18  further includes the first tongue structure  38  provided inside the flat structure  36  so as to emerge when the flat structure  36  is broken and to intervene in between the end of the panel opening  14  adjacent to the occupant and the airbag  16  during the airbag developing. Thereby, during the airbag developing, the contact between the airbag  16  and the end of the panel opening  14  adjacent to the occupant M can be avoided, so that developing properties of the airbag  16  can be preferably maintained while the durability the airbag  16  can be improved by suppressing the airbag damage. 
     The following advantage can also be achieved especially according to the embodiment. That is, since the end of the panel opening  14  opposite to the occupant M is an axis about which the lid member  28  is rotated, although burrs may not be formed unlike the end of the panel opening  14  adjacent to the occupant M, fins may be formed due to the bending of the panel at an acute angle. 
     According to the embodiment, in connection with this problem, the second tongue structure  42  emerged after the breaking of the flat structure  36  of the airbag cover  18  is configured to intervene in between the end of the panel opening  14  opposite to the occupant M and the airbag  16  during the airbag developing. Thereby, the contact between the airbag  16  and the end of the panel opening  14  opposite to the occupant M can be avoided during the airbag developing, so that developing properties of the airbag  16  can be further preferably maintained while the durability the airbag  16  can be further improved by further suppressing the airbag damage. 
     In particular, according to the embodiment, both sides of the airbag  16  folded and accommodated within the retainer  22  in the vehicle width direction are covered with the side-cover parts  46  of the first tongue structure  38 , respectively. Thereby, both sides of the accommodated airbag  16  in the vehicle front-back direction can be covered with the flat structure  36  while both sides of the airbag  16  in the vehicle width direction can be covered with the side-cover parts  46 , respectively, so that the perimeter of the folded airbag  16  can be covered with the airbag cover  18 . As a result, the function maintaining the folded shape when the airbag  16  is accommodated in the retainer  22  can be further improved, thereby suppressing the generation of shape collapsing of the airbag  16  during the accommodating. 
     In particular, according to the embodiment, the through-holes  50 ,  52  formed at both ends of the flat structure  36  in the longitudinal direction and the through-hole formed at the base end of the first tongue structure  38  are passed thorough by the bolts  31 ,  33 , respectively, for fixing the retainer  22  to the vehicle. Thereby, the airbag cover  18  composed of the flat structure  36  and the first tongue structure  38  can be fixed in the retainer  22 . By diverting the bolts  31 ,  33  for fixing the retainer  22  to fixing the airbag cover  18  in such a manner, an additional fixing member is not required for fixing the airbag cover  18 , thereby simplifying the structure. 
     In particular, according to the embodiment, before the operation of the inflator  20  (before the breakage of the flat structure  36 ), the flat structure  36  and the first tongue structure  38  are connected together by sewing, and after the operation of the inflator  20 , the connection part  44  emerged and separated from the flat structure  36  and the first tongue structure  38  are connected together by sewing. Thereby, throughout the operation of the inflator  20 , the first tongue structure  38  can be stably fixed. 
     The embodiment described above is an example of a preferred mode of the present invention; however, the invention is not limited to this, so that various modifications can be made within a scope of the present invention. 
     For example, according to the embodiment, the present invention is incorporated in a passenger airbag apparatus; the invention is not limited to this, so that the present invention can also be incorporated in a knee airbag apparatus for protecting an occupant knee and a side airbag apparatus provided at a door or a pillar for inflating and developing between an occupant and a vehicle side wall. 
     The disclosures of Japanese Patent Applications No. 2007-304296 filed on Nov. 26, 2007 and No. 2008-243696 filed on Sep. 24, 2008 are incorporated in the application. 
     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.