Patent Publication Number: US-2011057487-A1

Title: Seat structure of vehicle

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a seat structure of a vehicle comprising a seatback frame provided on a vehicle-inside of a seatback, a side frame extending vertically beside the seatback frame, and a pad member covering the side frame, the pad member forming a shape of the seatback. 
     In general, the seat structure of a vehicle comprises the seatback frame provided on the vehicle-inside of the seatback which is provided at a rear portion of the seat cushion of the seat and supports the back of a passenger seated in the seat, the side frame extending vertically beside the seatback frame, and the pad member covering the side frame, the pad member forming the shape of the seatback. Herein, this seat structure of a vehicle equipped with the side frame has a problem in that when a load (impact load) is inputted to the passenger seated in the seat from the vehicle side at a vehicle side collision, the side frame may hit against a chest portion of the passenger, so that the impact acting on the passenger may become improperly large. 
     Japanese Patent Laid-Open Publication No. 2008-212397 proposes one of the countermeasure structures to solve this problem. Herein, the side frame is configured so that its upper portion is slender to avoid an overlap of the passenger&#39;s chest portion with the side frame in a vehicle side view when the passenger is seated. Further, the U-shaped bar member (see the wire member) is provided at the side frame so as to project forward so that the passenger seated in the seat can be held by this bar member in the vehicle width direction at the normal state, and that the impact acting on the vehicle side face can be absorbed at the vehicle side collision. 
     However, the above-described structure has another problem in that the holding power of the passenger may be insufficient because of the slender upper portion of the side frame and two-part members of the side frame (two members of the side frame and the bar member) may make the structure complex and increase the number of parts and assembling steps. 
     Meanwhile, Japanese Utility Model Laid-Open Publication No. 5-70345 discloses the back frame to absorb the impact load properly at the vehicle collision. Herein, the back frame has the side frames which are arranged on both sides of the back frame, and convex notches are formed at front and rear portions of the side frame so as to extend over an entire width of the side frame. The impact load can be absorbed by the notches. According to this structure, however, even though the impact load at the vehicle frontal or rear collision can be absorbed, it may be impossible that the impact load at the vehicle side collision is absorbed. 
     Further, Japanese Patent Laid-Open Publication No. 2006-110221 discloses the seat structure of a vehicle equipped with the side frame, in which the support pad, which may be made from a synthetic resin, such as hard polyurethane foam, is attached to the front side of the side frame. This support pad extends vertically from a position facing to a shoulder portion of the passenger seated to a position facing to a waist portion of the passenger, and its lower portion facing to the passenger&#39;s waist portion projects forward from its upper portion. According to this structure, the holing of the passenger seated in the seat can be improved by the support pad, but it may not be properly prevented by the support pad that the side frame comes toward the passenger at the vehicle side collision. 
     Moreover, Japanese Patent Laid-Open Publication No. 2000-125988 discloses the structure in which the seatback has the side support portion to support the passenger seated in the seat from the vehicle side, and the energy-absorbing pad is arranged inside the side support portion so as to absorb the impact at the vehicle side collision. However, this energy-absorbing pad is provided on the vehicle-outside of the side frame in the vehicle width direction, so any idea of preventing the side frame from coming toward the passenger by the energy-absorbing pad is not disclosed in the above-described publication. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a seat structure of a vehicle which can reduce the impact load from the vehicle side portion at the vehicle side collision and thereby properly decrease the load inputting to the passenger&#39;s chest portion. 
     According to the present invention, there is provided a seat structure of a vehicle, comprising a seatback frame provided on a vehicle-inside of a seatback (i.e., on an inside of a seatback in a vehicle width direction) which is provided at a rear portion of a seat cushion of a seat and supports a back of a passenger seated in the seat, a side frame extending vertically beside the seatback frame, and a pad member covering the side frame, the pad member forming a shape of the seatback, wherein an impact reduction structure to reduce an impact from a vehicle side is provided. 
     According to the present invention, since the impact reduction structure is provided, the impact load from the vehicle side portion at the vehicle side collision can be reduced, so that the load inputting to the passenger&#39;s chest portion can be decreased. 
     According to an embodiment of the present invention, an impact reduction portion to reduce the impact from the vehicle side is provided at the side frame, which constitutes the impact reduction structure. Herein, the impact reduction portion may be formed by a weak portion, thin portion, opening portion, rigidity-reducing portion or any other portion which causes deformation or split of the side frame at the vehicle side collision. Thereby, since the impact reduction portion is provided at the side frame itself, the above-described effect of the present invention can be properly obtained without making the structure complex or increasing the number of parts and manufacturing steps. 
     According to another embodiment of the present invention, the impact reduction portion causes deformation of the side frame by the impact from the vehicle side. Thereby, the load inputting to the passenger&#39;s chest portion can be properly decreased. Further, since the side frame deforms inside the pad member, the hardness of the side frame can be properly reduced with the pad member. Accordingly, the reduction of the impact load acting on the passenger at the vehicle side collision can be properly achieved. 
     According to another embodiment of the present invention, the impact reduction portion comprises a weak portion which is formed at the side frame so as to extend vertically, the weak portion being deformable by the impact from the vehicle side. Herein, the weak portion may be comprised of a thin portion, an opening portion, such as a slot, or the like. Thereby, since the weak portion as the impact reduction portion extends vertically, the deformation of the side frame is caused by the weak portion easily, so that the reduction of the inputted load to the passenger&#39;s chest portion can be properly achieved. 
     According to another embodiment of the present invention, the weak portion comprises a thin portion formed at the side frame. The thin portion can be easily formed by pressing concurrently with forming the side frame. 
     According to another embodiment of the present invention, another weak portion is further formed so as to extend continuously from the weak portion toward a front end portion of the side frame. Thereby, both the weak portion extending vertically and the weak portion formed at the front end portion of the side frame can cause the split of a specified portion of the side frame which may give the impact to the passenger at the vehicle side collision off a frame body of the side frame. Thus, this specified portion of the side frame may not be restrained by the pad member, so that the impact which the side frame may give to the passenger can be reduced. 
     According to another embodiment of the present invention, the impact reduction portion is formed at a position which corresponds to a chest portion of the passenger seated in the seat. Thereby, the side frame is made deform or split properly at the position corresponding to the passenger&#39;s chest portion, so that the impact given to the passenger&#39;s chest portion can be reduced. Accordingly, the pressing of the chest portion of the passenger can be reduced. 
     According to another embodiment of the present invention, a side airbag device with an airbag which is inflatable beside the passenger when a specified condition is satisfied is attached to the side frame, and an inflator to supply gas for the airbag is arranged at a specified position which is rearward from the impact reduction portion. Herein, the satisfaction of the specified condition may be determined by checking whether the lateral acceleration inputted from the vehicle side exceeds a specified value or not. The inflator is arranged at the specified position which is rearward from the impact reduction portion (where the inflator does not deform), so that the stable inflation of the airbag of the airbag device at the vehicle side collision can be obtained. Further, since the inflator which is a rigidity member is positioned in back of the impact reduction portion which deforms with the impact, any excessive load may not be given to the passenger by the inflator. 
     According to another embodiment of the present invention, the impact reduction portion is provided in back of a passenger-sitting front face of the seatback. Herein, the above-described passenger-sitting front face of the seatback means the front face of the seatback in a state in which the passenger seated leans against the seatback and thereby the pad member has been compressed to a certain degree so that the position of the front face of the seatback moves rearward from its normal position by the certain degree. Thereby, since the impact reduction portion is provided in back of the above-described passenger-sitting front face of the seatback, the impact which the passenger may receive from the deforming side frame at the vehicle side collision can be reduced. 
     According to another embodiment of the present invention, the seat structure of a vehicle further comprising a side support portion which is provided at the seatback so as to support the seated passenger from the vehicle side, wherein the side frame is arranged in back of a passenger-sitting front face of the seatback at a position which corresponds to a chest portion of the passenger seated in the seat, not so as to extend forward beyond the passenger-sitting front face of the seatback, in a plan view and another hard pad member than the pad member is arranged inside the side support portion at a specified position which is located on a vehicle-inside of the side frame, which constitutes the impact reduction structure. Herein, the above-described hard pad member may be made from a hard urethane material. Thereby, since the side frame is arranged in back of the passenger-sitting front face of the seatback, not so as to extend forward beyond the passenger-sitting front face of the seatback, in the plan view, the upper portion of the side frame can be formed to be properly slender. Accordingly, it can be avoided that the side frame contacts the passenger. Further, the passenger can be properly supported from the vehicle side by the pad member arranged along the inward side of the side frame at the normal state. Moreover, since the side frame does not exist at a position in front of the passenger-sitting front face of the seatback, no any particular problem occurs at the vehicle side collision. Further, even if the side frame deforms inward in the vehicle width direction at the vehicle side collision, this deformation may be received by the hard pad member, so that the safety of the passenger can be improved. 
     Other features, aspects, and advantages of the present invention will become apparent from the following description which refers to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view showing a seat structure of a vehicle according to a first embodiment of the present invention. 
         FIG. 2  is a sectional view taken along line A-A of  FIG. 1 . 
         FIG. 3  is a side view of a side frame. 
         FIG. 4  is a sectional view taken along line B-B of  FIG. 3 . 
         FIGS. 5A-5D  are sectional views showing structures of a weak portion. 
         FIG. 6  is an explanatory diagram showing a deformation state of the side frame at a vehicle side collision. 
         FIG. 7  is a side view showing another forming pattern of an impact reduction portion according to a second embodiment. 
         FIG. 8  is a side view showing another impact reduction portion using a slot according to a third embodiment. 
         FIG. 9  is a sectional view showing a seat structure of a vehicle equipped with a side airbag device according to a fourth embodiment. 
         FIG. 10  is a side view of a major part of  FIG. 9 . 
         FIG. 11  is an explanatory diagram at an airbag inflation. 
         FIG. 12  is a side view showing a modification of an inflator arrangement structure. 
         FIG. 13  is a sectional view showing a fifth embodiment in which an inflator is arranged on the vehicle-inside of the side frame. 
         FIG. 14  is an explanatory diagram at the airbag inflation. 
         FIG. 15  is a sectional view showing another impact reduction portion according to a sixth embodiment. 
         FIG. 16  is a sectional view showing a modification of the above-described impact reduction portion. 
         FIG. 17  is a sectional view showing another seat structure of a vehicle according to a seventh embodiment. 
         FIG. 18  is a sectional view showing a modification of the above-described seat structure of a vehicle. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, preferred embodiments of the present invention will be described referring to the accompanying drawings. 
     Embodiment 1 
     A first embodiment of the present invention will be described referring to  FIGS. 1-6 . The figures show a seat structure of a vehicle. In a schematic side view of  FIG. 1 , a seat slide rail  4  is provided on a floor panel  1  via plural seat attaching brackets  2 ,  3 . 
     The seat slide rail  4  comprises a fixed lower rail and a movable upper rail, and a seat  6  is provided at the upper rail via a seat cushion frame  5 . This seat  6  may be any one of a front seat, such as a driver&#39;s seat or a passenger&#39;s seat, a second-row rear seat, or a third-row rear seat, and the seat arranged on the left is shown in the present embodiment. 
     The seat  6  comprises a seat cushion  7  which forms a sitting face for a passenger, a seatback  8  which is connected to a rear portion of the seat cushion  7  and supports a back of the passenger seated in the seat  6  from behind, and a headrest  9  which is provided at an upper portion of the seatback  8  and supports a head of the passenger seated in the seat  6  from behind. Herein, a manikin (a so-called dummy) X is illustrated as the passenger in the figures, which comprises its chest portion X and its ribs Z. 
       FIG. 2  is a sectional view (plan view) taken along line A-A of  FIG. 1 , and  FIG. 3  is a side view of a major part in a state in which  FIG. 2  is viewed from a vehicle outside. As shown in  FIG. 2 , the seatback  8  is equipped with a pair of left and right side support portions  10 ,  11  which supports the passenger (see the manikin X) seated in the seat  6  from the vehicle sides. Further, the seatback  8  comprises a pad member  12  which forms its shape and a surface  13  which covers over the pad member  12  from outside, and it also has a space  14  at its back portion where no pad member exits for the purpose of weight reduction. 
     As shown in  FIGS. 2 and 3 , a seatback frame  15  is provided on a vehicle-inside of the seatback  8 , and this seatback frame  15  comprises a main frame  16  which is formed in a gate shape in an elevation view, and a pair of side frames  17 ,  17  which extends vertically on both sides of the main frame  16 . Further, as shown in  FIGS. 1 and 3 , a pole guide  18  (a so-called support pipe) is provided at an upper portion of the main frame  16 , and a headrest pole  19  of the headrest  9  is supported by the pole guide  18  so as to move vertically. The above-described side frames  17 ,  17  are covered with the pad member  12  as shown in  FIG. 2 . 
       FIG. 4  is a sectional view taken along line B-B of  FIG. 3 , which shows a cross-section structure of the side frame  17 . As shown in  FIG. 4 , the side frame  17  comprises a side portion  17   a  (including a front bead portion  17   c  and a projection portion  17   e , which will be described later) which extends longitudinally, and a rear portion  17   b  (including a rear bead portion  17   d , which will be described later), and this side frame  17  is formed in a L shape in a plan view. The front bead portion  17   c  is formed integrally at a front end of the side portion  17   a  and projects toward the both sides, i.e., inward and outward, in the vehicle width direction. The rear bead portion  17   d  is formed integrally at an inward end of the rear portion  17   b  and projects rearward. The projection portion  17   e  is formed integrally at a rear portion of the side portion  17   a  and projects outward. 
     In other words, as shown by the side view of  FIG. 3 , between the front bead portion  17   c  and the projection portion  17   e  is formed a concave portion  17   f  which extends vertically along the longitudinal direction of the side frame  17 . The sufficient rigidity of the side frame  17  is ensured by forming this concave portion  17   f.    
     Further, a weak portion  20 , which is an example of the impact reduction portion to reduce the impact from the vehicle side, is formed at the side portion  17   a  of the side frame  17  so as to extend vertically as shown in  FIG. 3 . 
     As shown in  FIG. 3 , the weak portion  20  extends vertically from an upper end of the side portion  17   a  of the side frame  17  to a lower portion of the side portion  17   a  through a portion corresponding to the chest portion of the passenger seated in the seat  6 , i.e., right behind the ribs Z of the manikin X shown by an imaginary line. This weak portion  20  causes a deformation of the side portion  17   a  of the side frame  17  by the impact (at the vehicle side collision) from the vehicle side, thereby reducing the impact. While the weak portion  20  shown in  FIG. 3  extends linearly and continuously, it may be formed so as to extend substantially continuously having small vertical gaps. Further, the forming pattern of the weak portion  20  may not necessarily be linear. In the present embodiment, when the impact acts from the vehicle side, the above-described weak portion  20  causes the side portion  17   a  of the side frame  17  to deform outward or inward. 
       FIGS. 5A-5D  are sectional views showing specific structures of the weak portion  20  shown in  FIGS. 3 and 4 . The weak portion  20  shown in  FIG. 5A  has a V-shaped concave portion  20   a  which is formed at one side of the side portion  17   a , and thus a thin portion  20   b  of the side portion  17   a  constitutes the weak portion  20 . 
     The weak portion  20  shown in  FIG. 5B  has V-shaped concave portion  20   a ,  20   a  which are formed at both sides of the side portion  17   a , and thus a thin portion  20   b  of the side portion  17   a  constitutes the weak portion  20 . 
     The weak portion  20  shown in  FIG. 5C  has a U-shaped concave portion  20   c  which is formed at one side of the side portion  17   a , and thus a thin portion  20   b  of the side portion  17   a  constitutes the weak portion  20 . 
     The weak portion  20  shown in  FIG. 5D  has a reverse-trapezoid-shaped concave portion  20   d  which is formed at one side of the side portion  17   a , and thus a thin portion  20   b  of the side portion  17   a  constitutes the weak portion  20 . 
     Any other modifications of the weak portion  20  shown in  FIGS. 5A-5D  may be applied. For example, the concave portions  20   c ,  20   d  shown in  FIGS. 5C ,  5 D may be formed at the both sides. Further, the longitudinal length of the thin portion  20   b  may be longer by prolonging the top portion of the trapezoid of the concave portion  20   d  shown in  FIG. 5D . 
     Any one of the structures shown in  FIGS. 5A-5D  is selected as the weak portion  20 . While a pair of right and loft side frames  17 ,  17  is arranged on both sides of the seatback  8  as shown in  FIG. 2 , it is enough that the weak portion  20  is formed only at the outside-located side frame  17 . Of course, the weak portion  20  may be formed at the both side frames  17 ,  17  and the seat  6  may be installed on the left side or the right side. In the figures, an arrow F shows a forward direction of the vehicle, an arrow R shows a rearward direction of the vehicle, an arrow OUT shows an outward direction of the vehicle, and an arrow IN shows an inward direction of the vehicle. 
     According to the seat structure of the vehicle described above, when the impact is inputted to the seat  6  from the vehicle side at the vehicle side collision, the weak portion  20  causes the deformation of the side portion  17   a  of the side frame  17  as shown in  FIG. 6 , so that the impact load is reduced and thereby the load inputted to the chest portion of the passenger can be decreased. 
     As described above, the seat structure of a vehicle according to the first embodiment shown in  FIGS. 1-6  comprises the seatback frame  15  provided on the vehicle-inside of the seatback  8  which is provided at the rear portion of the seat cushion  7  of the seat  6  and supports the back of the passenger (see the manikin X) seated in the seat  6 , the side frame  17  extending vertically beside the seatback frame  15 , and the pad member  12  covering the side frame  17 , the pad member  12  forming the shape of the seatback  8 , wherein the impact reduction portion (see the weak portion  20 ) to reduce the impact from the vehicle side is provided at the side frame  17  (see  FIGS. 1 ,  2  and  3 ). 
     According to this structure, since the impact reduction portion (see the weak portion  20 ) is provided at the side frame  17  itself, the impact load from the vehicle side portion at the vehicle side collision can be reduced by the impact reduction portion (see the weak portion  20 ), so that the load inputting to the passenger&#39;s chest portion can be decreased. Further, the above-described effect can be obtained without making the structure complex or increasing the number of parts and manufacturing steps. 
     Further, the impact reduction portion (see the weak portion  20 ) causes the deformation of the side frame  17  by the impact from the vehicle side (see  FIG. 6 ). Thereby, the load inputting to the passenger&#39;s chest portion can be properly decreased. 
     Moreover, since the side frame  17  deforms inside the pad member  12 , the hardness of the side frame  17  can be properly reduced with the pad member  12 . Accordingly, the reduction of the impact load acting on the passenger at the vehicle side collision can be properly achieved. 
     Additionally, the impact reduction portion comprises the weak portion  20  which is formed at the side frame  17  so as to extend vertically, the weak portion  20  being deformable by the impact from the vehicle side (see  FIGS. 3 and 6 ). Thereby, since the weak portion  20  of the impact reduction portion extends vertically, the deformation of the side frame  17  (especially, the side portion  17   a ) is caused by the weak portion  20  easily, so that the reduction of the inputted load to the passenger&#39;s chest portion can be properly achieved. 
     Further, the weak portion  20  comprises the thin portion  20   b  which is formed at the side frame  17  (see  FIGS. 4 and 5 ). The thin portion  20   b  can be easily formed by pressing concurrently with forming the side frame  17 . 
     Moreover, the impact reduction portion (see the weak portion  20 ) is formed at the position which corresponds to the chest portion (see the chest portion Y of the manikin X by the imaginary line in  FIG. 3 ) of the passenger seated in the seat  6  (see  FIG. 3 ). Thereby, the side frame  17  is made deform or split properly (“deform” in case of the first embodiment) at the position corresponding to the passenger&#39;s chest portion Y, so that the impact given to the passenger&#39;s chest portion Y can be reduced. Accordingly, the pressing of the chest portion Y of the passenger can be reduced. 
     Embodiment 2 
       FIG. 7  shows another embodiment of the seat structure of a vehicle, in which another weak portion  21  is further formed so as to extend continuously from the above-described weak portion  20  toward a front end portion of the side portion  17   a  of the side frame  17 . That is, the above-described weak portion  20  comprises, at a position where the main frame  16  and sub frame  17  do not overlap with each other in the vehicle width direction, an upper portion  20 A which extends downward from the upper end of the side portion  17   a  to a lower portion corresponding to the lower end of the main frame  16 , a middle portion  20 B which extends obliquely downward and rearward from the lower end of the upper portion  20 A, and a lower portion  20 D which extends downward from the lower end of the middle portion  20 B along the front side of the projection portion  17   e.    
     Further, another weak portion  21  is further formed so as to extend from a lower end  20 E of the above-described weak portion  20  toward the front end portion of the side portion  17   a  of the side frame  17 . Thus, the weak portion  20  and the additional weak portion  21  are made completely continuous from each other. Herein, the additional weak portion  21  is also continuous from the front bead portion  17   c  for the purpose of splitting a front-side portion from the respective weak portions  20 ,  21  at the vehicle side collision. 
     As described above, in the second embodiment shown in  FIG. 7 , the weak portion  21  is further formed so as to extend continuously from the above-described weak portion  20  toward the front end portion of the side frame  17  (see  FIG. 7 ). Thereby, both the weak portion  20  extending vertically and the weak portion  21  formed at the front end portion of the side frame  17  can cause the split of the specified portion of the side frame  17  which may give the impact to the passenger at the vehicle side collision off a frame body of the side frame  17 . Thus, this specified portion of the side frame  17  may not be restrained by the pad member, so that the impact which the side frame  17  may give to the passenger can be reduced. 
     The other structures, operations and effects of the present embodiment are substantially the same as those of the above-described first embodiment, so the same portions as the first embodiment are denoted by the same reference characters in  FIG. 7 , specific descriptions of which are omitted here. The forming pattern of the weak portions  20 ,  21  should not be limited to the ones shown in  FIG. 7  as long as they are formed so as to be continuous from the upper end of the side portion  17   a  of the side frame  17  to the front end of the side portion  17   a  through the position corresponding to the chest portion of the passenger seated in the seat (the position behind the ribs Z of the manikin X). 
     Embodiment 3 
       FIG. 8  shows further another embodiment of the seat structure of a vehicle, in which the impact reduction portion comprises plural slots  22 ,  23 ,  24 ,  25 . That is, the plural slots  22 - 25  as the impact reduction portion to reduce the impact from the vehicle side are formed at the side portion  17   a  of the side frame  17 . The slots  22 - 25  cause the deformation of the side portion  17   a  of the side frame  17  by the impact from the vehicle side, so that the impact can be reduced. 
     In the third embodiment, the first slot  22 , the second slot  23  and an upper portion of the third slot  24  are formed at the side portion  17   a  of the side frame  17  so as to extend vertically, a lower portion of the third slot  24  and the fourth slot  25  are formed in an arc shape, and the fourth slot  25  is formed so as to be positioned on an extension line of the third slot  24  and its lower end extends to near the front end of the side portion  17   a.    
     These slots  22 - 25  (opening portions) are formed so that the side portion  17   a  of the side frame  17  exists between the adjacent slots ( 22  and  23 ,  23  and  24 ,  24  and  25 ), respectively. Thereby, the necessary rigidity of the side frame  7  at the normal state is ensured. That is, in the third embodiment, the first slot  22 , the second slot  23  and the upper portion of the third slot  24  constitute the weak portion extending vertically at the side frame  17 , and the lower portion of the third slot  24  and the fourth slot  25  constitute the other weak portion extending continuously from the above-described weak portion toward the front end portion of the side frame  17 . 
     According to the seat structure of the vehicle described above, when the impact is inputted to the seat  6  from the vehicle side at the vehicle side collision, the slots  22 ,  23 ,  24 ,  25  as the impact reduction portion cause the deformation of the side portion  17   a  of the side frame  17 , so that the impact load is reduced and thereby the load inputted to the chest portion of the passenger can be decreased. 
     The other structures, operations and effects of the third embodiment are substantially the same as those of the above-described embodiments, so the same portions as the previous embodiments are denoted by the same reference characters in  FIG. 8 , specific descriptions of which are omitted here. The forming pattern of the slots  22 - 25  should not be limited to the one shown in  FIG. 7  as long as the slots are formed so as to extend from the upper end of the side portion  17   a  of the side frame  17  to the front end of the side portion  17   a  through the position corresponding to the chest portion of the passenger seated (the position behind the ribs Z of the manikin X). Further, the length or the number of the slots  22 - 25  should not be limited to the ones shown in  FIG. 8 , and the number of the slots may be three, or five or more. 
     Embodiment 4 
       FIGS. 9 ,  10  and  11  show further another embodiment of the seat structure of a vehicle, and  FIG. 9  is a plan view,  FIG. 10  is a side view of its major part, and  FIG. 11  is an explanatory diagram at the airbag inflation. In the fourth embodiment, as shown in  FIG. 9 , a side airbag device  30  is provided on a vehicle-outside of the side portion  17   a  of the side frame  17  (i.e., on an outside of the side portion  17   a  of the side frame in the vehicle width direction). 
     The side airbag device  30  comprises an airbag  31  which is inflatable beside the passenger when a specified condition is satisfied (for example, a lateral acceleration inputted from the vehicle side exceeds a specified value), and an inflator  32  to supply gas for the airbag  31 . The side airbag device  30  is attached to the side frame  17 , and the airbag  31  is stored inside on the vehicle-outside of the side portion  17   a  over the side support portion  10 . Further, a slit  12   a  is formed at a specified portion of the pad member  12  which corresponds to the side of the passenger so that the airbag  31  can inflate forward from the front portion of the side support portion  10  beside the passenger (see  FIG. 11 ). 
     A specific illustration of the folding structure of the airbag  31  is omitted and the airbag  31  is schematically illustrated in  FIG. 9 . In  FIG. 9 , a reference character G denotes a passenger-sitting front face of the seatback  8  (a front face of the seatback  8  in a state in which the passenger leans against the seatback  8  and thereby the pad member  12  has been compressed to a certain degree), and the impact reduction portion  20  as the impact reduction portion is provided in back of the passenger-sitting front face G. 
     The above-described inflator  32  is arranged at a specified position which is rearward from the weak portion  20  as the impact reduction portion. That is, the inflator  32  is provided at the position where the inflator  32  does not deform at the vehicle side collision. Further, the inflator  32  is provided at the height position which corresponds to the middle portion of the side portion  17   a  of the side frame  17  as shown in  FIG. 10 . 
     According to the seat structure of the vehicle described above, when the impact is inputted to the seat  6  from the vehicle side at the vehicle side collision, the gas is supplied into the airbag  31  according to the operation of the inflator  32 , so that the airbag  31  comes out of the slit  12   a  of the side support portion  10  and inflates beside the passenger seated in the seat  6  as shown in  FIG. 11 . The inflation pressure of the airbag  31  makes the weak portion  20  as the impact reduction portion cause the inward deformation of the side portion  17   a  of the side frame  17 . This deformation of the side portion  17   a  reduces the impact load, so that the load inputted to the chest portion of the passenger can be decreased. 
     According to the present embodiment shown in  FIGS. 9 ,  10  and  11 , the side airbag device  30  with the airbag  31  which is inflatable beside the passenger when the specified condition is satisfied is attached to the side frame  17 , and the inflator  32  to supply the gas for the airbag  31  is arranged at the specified position which is rearward from the impact reduction portion (see the weak portion  20 ) (see  FIG. 9 ). Thus, the inflator  32  is arranged at the specified position which is rearward from the impact reduction portion (see the weak portion  20 ), so that the stable inflation of the airbag  31  of the airbag device  30  at the vehicle side collision can be obtained. 
     Further, since the inflator  32  which is a rigidity member is positioned in back of the impact reduction portion (see the weak portion  20 ) which deforms with the impact, any excessive load may not be given to the passenger by the inflator  32 . 
     Further, the impact reduction portion (see the weak portion  20 ) is provided in back of the passenger-sitting front face G of the seatback  8  (see  FIG. 9 ). Thereby, the impact which the passenger may receive from the deforming side frame  17  at the vehicle side collision can be reduced. 
     The other structures, operations and effects of the fourth embodiment shown in  FIGS. 9-11  are substantially the same as those of the above-described embodiments, so the same portions as the previous embodiments are denoted by the same reference characters in  FIGS. 9-11 , specific descriptions of which are omitted here. A structure shown in  FIG. 12  may be applied in place of the structure shown in  FIG. 10 . That is, the inflator  32  is arranged at the specified portion of the side portion  17   a  of the side frame  17  which corresponds to the chest portion of the passenger in  FIG. 10 , but in a modification shown in  FIG. 12 , the inflator  32  is arranged at a specified portion in front of the side portion  17   a  of the side frame  17  which corresponds to the waist portion of the passenger, and a lumber support lever  33  is arranged at a portion of the side portion  17   a  in back of the inflator  32  so as to be apart from the inflator  32 . 
     Further, as shown in  FIG. 12 , the side portion  17   a  of the side frame  17  is configured to be split into a front part and a rear part due to the weak portions  20 ,  21  at the vehicle side collision, and its front part is arranged in a split area, and its rear part, including its lower part, is arranged in a nun-split area (non-deformation area) where the inflator  32  and the lumber support  33  are provided. The inflator  32  is attached to a position below the weak portion  21  which corresponds to the waist portion of the passenger. 
     Thus, since the inflator  32  is attached to the position corresponding to the waist portion of the passenger, it can be prevented that the chest portion of the passenger is hurt by the inflator  32  at the vehicle side collision, and the layout of the inflator  32  and the lumber support lever  33  can be provided, ensuring the front arrangement of the inflator  32 . The other structures, operations and effects of the present embodiment are substantially the same as those of the above-described embodiment shown in  FIGS. 9-11 , so the same portions as the previous embodiments are denoted by the same reference characters in  FIG. 12 , specific descriptions of which are omitted here. 
     Embodiment 5 
       FIGS. 13 and 14  show further another embodiment of the seat structure of a vehicle, and  FIG. 13  is a plan view, and  FIG. 14  is an explanatory diagram at an airbag inflation. In the fifth embodiment, as shown in  FIG. 13 , the side airbag device  30  is provided on the vehicle-inside of the side portion  17   a  of the side frame  17 . 
     The side airbag device  30  comprises the airbag  31  which is inflatable beside the passenger when a specified condition is satisfied (for example, the lateral acceleration inputted from the vehicle side exceeds a specified value), and the inflator  32  to supply the gas for the airbag  31 . 
     The side airbag device  30  is attached to the side frame  17 , and the airbag  31  is stored inside on the vehicle-inside of the side portion  17   a  over the side support portion  10 . Further, the slit  12   a  is formed at a specified portion of the pad member  12  which corresponds to the side of the passenger so that the airbag  31  can inflate forward from the front portion of the side support portion  10  beside the passenger (see  FIG. 14 ). A specific illustration of the folding structure of the airbag  31  is omitted and the airbag  31  is schematically illustrated in  FIG. 13 . In  FIG. 13 , the reference character G denotes the passenger-sitting front face of the seatback  8 , and the impact reduction portion  20  as the impact reduction portion is provided in back of the passenger-sitting front face G. 
     The above-described inflator  32  is arranged at a specified position which is rearward from the weak portion  20  as the impact reduction portion. That is, the inflator  32  is provided at the position where the inflator  32  does not deform at the vehicle side collision. Herein, the arrangement position of the inflator  32  in the vertical direction is the same as the position shown in  FIG. 10 , but the inflator  32  may be arranged at the height position shown in  FIG. 12 . 
     According to the seat structure of the vehicle described above, when the impact is inputted to the seat  6  from the vehicle side at the vehicle side collision, the gas is supplied into the airbag  31  according to the operation of the inflator  32 , so that the airbag  31  comes out of the slit  12   a  of the side support portion  10  and inflates beside the passenger seated in the seat  6  as shown in  FIG. 14 . The inflation pressure of the airbag  31  makes the weak portion  20  as the impact reduction portion cause the outward deformation of the side portion  17   a  of the side frame  17 . This deformation of the side portion  17   a  reduces the impact load, so that the load inputted to the chest portion of the passenger can be decreased. 
     According to the present embodiment shown in  FIGS. 13 and 14 , the side airbag device  30  with the airbag  31  which is inflatable beside the passenger when the specified condition is satisfied is attached to the side frame  17 , and the inflator  32  to supply the gas for the airbag  31  is arranged at the specified position which is rearward from the impact reduction portion (see the weak portion  20 ) (see  FIG. 13 ). Thus, the inflator  32  is arranged at the specified position which is rearward from the impact reduction portion (see the weak portion  20 ), so that the stable inflation of the airbag  31  of the airbag device  30  at the vehicle side collision can be obtained. 
     Further, since the inflator  32  which is the rigidity member is positioned in back of the impact reduction portion (see the weak portion  20 ) which deforms with the impact, the passenger is not hurt by the inflator  32 . Further, the impact reduction portion (see the weak portion  20 ) is provided in back of the passenger-sitting front face G of the seatback  8  (see  FIG. 13 ). 
     Thereby, since the impact reduction portion (see the weak portion  20 ) is provided in back of the passenger-sitting front face G, the impact which the passenger may receive from the deforming side frame  17  at the vehicle side collision can be reduced. The other structures, operations and effects of the fifth embodiment shown in  FIGS. 13 and 14  are substantially the same as those of the above-described fourth embodiment, so the same portions as the previous embodiments are denoted by the same reference characters in  FIGS. 13 and 14 , specific descriptions of which are omitted here. 
     Embodiment 6 
       FIG. 15  shows another embodiment of the side frame  17 . While the weak portion  20 , such as the thin portion, is used as the impact reduction portion in the embodiments shown in  FIGS. 3 ,  7 ,  10 ,  12  and  13  and the plural slots  22 - 25  are used as the impact reduction portion in the embodiment shown in  FIG. 8 , the side frame  17  is configured so that its rigidity portion is formed in a non-rigidity structure in the present embodiment shown in  FIG. 15 . That is, a low-rigidity curve portion (half circular portion)  17   g  is formed in place of the high-rigidity front bead portion  17   c  shown by the imaginary line. This curve portion  17   g  is formed so as not to project outward from the side portion  17   a  as shown, and this portion  17   g  has a low rigidity and thereby functions as the impact reduction portion. 
     As shown in  FIG. 15 , in case the above-described side frame  17  equipped with the low-rigidity curve portion  17   g  is installed to the seatback  8  shown in  FIG. 2 , for example, the low-rigidity curve portion  17   g  absorbs the impact load from the vehicle side at the vehicle side collision by deforming, so that the load inputted to the chest portion of the passenger can be reduced. Herein, the vertical range where the above-described curve portion  17   g  is basically set to an area which only corresponds to the chest portion of the passenger seated in the seat, but that may be set to an entire height area of the side frame  17 , considering easy manufacturing of the side frame  17 . 
     Further, in place of the structure shown in  FIG. 15 , a modification of the side frame  17  is shown in  FIG. 16 . Herein, the modified side frame  17  is configured so that its rigidity portion is formed in the non-rigidity structure as well. That is, a low-rigidity substantially-straight portion  17   h  is formed in place of the high-rigidity front bead portion  17   c  shown by the imaginary line in  FIG. 16 . This substantially-straight portion  17   h  is formed so as to extend almost on an extension line of the side portion  17   a  as shown, and this portion  17   h  has the low rigidity and thereby functions as the impact reduction portion as well. 
     As shown in  FIG. 16 , in case this side frame  17  equipped with the low-rigidity substantially-straight portion  17   h  is installed to the seatback  8  shown in  FIG. 2 , for example, the low-rigidity substantially-straight portion  17   h  absorbs the impact load from the vehicle side at the vehicle side collision by deforming, so that the load inputted to the chest portion of the passenger can be reduced. Herein, the vertical range where the above-described substantially-straight portion  17   h  is basically set to the area which only corresponds to the chest portion of the passenger seated in the seat like the above-described embodiment shown in  FIG. 5 , but that may be set to an entire height area of the side frame  17 , considering the easy manufacturing of the side frame  17 . 
     Herein, since the side frame  17  is equipped with the rear bead portion  17   d  and the projection portion  17   e  in these embodiments shown in  FIGS. 15 and 16  as well, the minimum necessary rigidity of the side frame  17  can be ensured for the normal state (the vehicle non-collision state). The same portions shown in  FIGS. 15 and 16  as the previous embodiment shown in  FIG. 4  are denoted by the same reference characters, specific descriptions of which are omitted here. 
     Embodiment 7 
       FIG. 17  is a sectional view showing further another embodiment of the seat structure of a vehicle. In the present embodiment, the seatback  8  comprises the side support portion  10  which supports the passenger seated in the seat  6  from the vehicle side, and the side frame  17  with the L-shaped cross section which has the side portion  17   a  and the rear portion  17   b . The side frame  17  extends vertically beside the seatback frame  15 . 
     The reference character G shows the passenger-sitting front face of the seatback  8  in  FIG. 17 , and the side frame  17  does not project forward from the passenger-sitting front face G inside the side support portion  10  in the plan view of the seat. That is, the side frame  17  is arranged in back of the above-described passenger-sitting front face G of the seatback  8 . 
     Further, a hard pad member  40  as another impact reduction portion than the above-described pad member  12  is provided inside the side support portion  10  on the vehicle-inside of the side frame  17 . This hard pad member  40 , which may be made of a hard urethane material, is arranged so that its front portion  40   a  projects forward from the passenger-sitting front face G so as to support the passenger seated in the seat  6  from the vehicle side properly. 
     According to the seat structure of a vehicle described above, even when the impact is inputted to the seat  6  from the vehicle side at the vehicle side collision and thereby the side frame  17  deforms inward, the side frame  17  does not project forward from the passenger-sitting front face G, resulting in casing no problem in particular. Even if the side frame  17  deforms inward at the vehicle side collision, the side frame deforming can be received by the hard pad member  40 . Accordingly, the safety of the passenger seated in the seat  6  can be ensured properly. 
     As described above, the seat structure of a vehicle according to the seventh embodiment shown in  FIG. 17  further comprising the side support portion  10  which is provided at the seatback  8  so as to support the seated passenger from the vehicle side, wherein the side frame  17  is arranged in back of the passenger-sitting front face G of the seatback  8  at the position which corresponds to the chest portion of the passenger seated in the seat  6 , not so as to extend forward beyond the passenger-sitting front face G of the seatback  8 , in the plan view and another hard pad member  40  than the pad member  20  is arranged inside the side support portion  10  at the specified position which is located on the vehicle-inside of the side frame  17  (see  FIG. 17  and the previous figure). Thereby, since the side frame  17  is arranged in back of the passenger-sitting front face G of the seatback  8 , not so as to extend forward beyond the passenger-sitting front face G of the seatback  8 , in the plan view of the seat (see  FIG. 17 ), the upper portion of the side frame  17  can be formed to be properly slender. Accordingly, it can be avoided that the side frame  17  contacts the passenger. 
     Further, the passenger can be properly supported from the vehicle side by the hard pad member  40  (the front portion  40   a , in particular) arranged along the inward side of the side frame  17  at the normal state. Moreover, since the side frame  17  does not exist at a position in front of the passenger-sitting front face G of the seatback  8  in the plan view of the seat (see  FIG. 17 ), no any particular problem occurs at the vehicle side collision. Further, even if the side frame  17  deforms inward in the vehicle width direction at the vehicle side collision, this deformation may be received by the hard pad member  40 , so that the safety of the passenger can be improved properly. 
     The other structures, operations and effects of the fourth embodiment shown in  FIG. 17  are substantially the same as those of the above-described embodiments, so the same portions as the previous embodiments are denoted by the same reference characters in  FIG. 17 , specific descriptions of which are omitted here. A structure shown in  FIG. 18  may be applied in place of the structure shown in  FIG. 17 . 
     While the hard pad member  40  is arranged inside the pad member  12  which forms the shape of the seatback  8  on the vehicle-inside of the side frame  17  according to the structure shown in  FIG. 17 , in the example shown in  FIG. 18 , the hard pad member  40  is fixed to the side frame  17 , not being arranged inside the pad member  12 . 
     That is, as shown in  FIG. 18 , plural bolts  40   b  (only one bolt is illustrated in  FIG. 18 ), which may be made from hard urethane, are integrally formed at a rear end portion of the hard pad member  40 . This hard pad member  40  is detachably attached to a front face of the rear portion  17   b  of the side frame  17  by fastening nuts  41  to the bolts  40   b , so that the hard pad member  40  is arranged on the vehicle-inside of the side portion  17   a  of the side frame  17 . Since the structure shown in  FIG. 18  provides substantially the same operations and effects as those of the embodiment shown in  FIG. 17 , the same portions are denoted by the same reference characters in  FIG. 18 , specific descriptions of which are omitted here. 
     The present should not be limited to the above-described embodiments, and any other modifications or improvements can be applied within the scope of a sprit of the present invention. For example, the above-described seat structure of a vehicle may be arranged only on the vehicle-outside of the seatback, or on both sides of the seatback.