Patent Publication Number: US-2009236166-A1

Title: Frame structure of automotive vehicle

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a frame structure of an automotive vehicle, and in particular, relates to the structure for impact absorption. 
     A frame structure of an automotive vehicle comprises, for example, a dash panel which partitions an engine room from a vehicle compartment, and a frame member which is provided in front of the dash panel so as to extend substantially straight in a vehicle longitudinal direction, a rear end portion of which connects to the dash panel. Herein, there is a concern that the dash panel may retreat in case an impact load is inputted to the frame member in the vehicle longitudinal direction at a vehicle front collision or the like. 
     An example of a technology to cope with the above-described concern is disclosed in Japanese Patent Laid-Open Publication No. 2003-220977, for example. According this example, at the frame member is provided a bend portion operative to bend in a vehicle width direction when the impact load is inputted to the frame member in the vehicle longitudinal direction. Thereby, the impact load may be absorbed by bending of the frame member, so that the dash panel can be restrained from retreating properly. 
     Herein, since the bend portion is formed by reinforcing one of the sides of the frame member with a reinforcement member in the above-described example, there is need to provide an additional member of the reinforcement member. This would cause a problem of an increase of the number of members. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a frame structure which can properly provide the bend portion without causing any improper increase of the number of members. 
     According to the present invention, there is provided a frame structure of an automotive vehicle, comprising a frame member provided so as to extend substantially straight in a vehicle longitudinal direction, a rear end portion of which connects to a dash panel, and a bend portion provided at the frame member, the bend portion being operative to bend in a specified direction of a vehicle width direction when an impact load is inputted to the frame member in the vehicle longitudinal direction, wherein the frame member has different cross sections in the vehicle longitudinal direction in such a manner that a centroid of the bend portion of the frame member is offset to the specified direction of the vehicle width direction from a centroid of a different portion of the frame member from the bend portion. 
     According to the present invention, since the centroid of the bend portion of the frame member is offset to the specified direction of the vehicle width direction from the centroid of the different portion of the frame member from the bend portion, the bend portion can be properly provided without causing any improper increase of the number of member. Herein, the centroid is a well-known technical term which is used in the fields of the strength of materials and the like. In case the bend portion of the frame member has offset of the centroid as described above, the input of the impact load may cause a moment which functions so as to rotate the cross section of the bend portion relative to the cross section of the different portion from the bend portion in the plan view. Accordingly, the frame member bends properly. 
     According to an embodiment of the present invention, the frame member comprising a first member and a second member which are located substantially in the vehicle width direction and have a substantially U-shaped cross section respectively, the first and second members being joined to each other via upper and lower flange portions thereof so as to form a closed cross section of the frame member which extends substantially in the vehicle longitudinal direction, and the first and second members have different shapes of the substantially U-shaped cross section in the vehicle longitudinal direction respectively in such a manner that the upper and lower flange portions thereof at the bend portion of the frame member are located offset to the specified direction of the vehicle width direction from the upper and lower flange portions thereof at the different portion of the frame member from the bend portion. Thereby, the offset of the centroid of the bend portion can be materialized easily. 
     According to another embodiment of the present invention, a joining line of the upper and lower flange portions of the first and second members at a front portion in front of the bend portion of the frame member and a rear portion in back of the bend portion of the frame member extends substantially straight and obliquely relative to a longitudinal direction of the frame member in a plan view. Thus, the flange portions turn from side to side at the bend portion in the vehicle width direction, so that the position of the bend portion can be specified surely. Thereby, the frame member bends surely at the bend portion. 
     According to another embodiment of the present invention, a plurality of the bend portions of the frame member which are operative to bend in opposite directions of the vehicle width direction to each other are provided, and the joining line of the upper and lower flange portions of the first and second members at a portion between the bend portions of the frame member extends substantially straight and obliquely relative to the longitudinal direction of the frame member in the plan view. Thereby, the bending of the frame member can be achieved easily compared to a case in which the joining line of the flange portions extends in a curve shape. 
     According to another embodiment of the present invention, the frame member has a substantially rectangular closed cross section which extends substantially in the vehicle longitudinal direction, and both side faces of the bend portion of the frame member have beads which are recessed toward an opposite side thereof respectively in such a manner that a depth of the recessed bead on a specified side face of the frame member which is located on a side of the specified direction of the vehicle width direction is shallower than that of the recessed bead on an opposite side face of the frame member to the specified side face. Thereby, the offset of the centroid of the bend portion can be materialized easily. 
     According to another embodiment of the present invention, respective bottom portions of the recessed beads are joined to each other. Thereby, the impact energy can be properly absorbed by friction of the bottom portions of the recessed beads which occurs at the bending of the frame member. 
     According to another embodiment of the present invention, a vertical length of the recessed bead on the specified side face of the frame member which is located on the side of the specified direction of the vehicle width direction is smaller than that of the recessed bead on the opposite side face of the frame member to the specified side face. Thereby, the offset of the centroid can be achieved properly even in case the width of the frame member is considerably small. 
     According to another embodiment of the present invention, the frame member has a substantially rectangular closed cross section which extends substantially in the vehicle longitudinal direction, and both side faces of the bend portion of the frame member have projections which project outward respectively in such a manner that a projecting height of the projection on a specified side face of the frame member which is located on a side of the specified direction of the vehicle width direction is greater than that of the projection on an opposite side face of the frame member to the specified side face. Thereby, the offset of the centroid of the bend portion can be materialized easily. 
     According to another embodiment of the present invention, a vertical length of the projection on the specified side face of the frame member which is located on the side of the specified direction of the vehicle width direction is greater than that of the projection on the opposite side face of the frame member to the specified side face. Thereby, the offset of the centroid of the bend portion can be provided, restraining the height of the projections properly. 
     According to another embodiment of the present invention, the bend portion of the frame member has a vertical bead on a side face thereof which is opposite to a specified side face thereof which is located on a side of the specified direction of the vehicle width direction, the vertical bead extending vertically and being recessed toward the specified side face of the bend portion. Thereby, the frame member bends surely at the bend portion. 
     According to another embodiment of the present invention, the vehicle has a suspension damper of a suspension member which is located outside the frame member, and the bend portion is located so as to be offset from the suspension damper in the vehicle longitudinal direction. Thereby, the bend portion which bends is prevented from interfering with the suspension damper, so that the proper bending of the frame member can be achieved. 
     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 plan view of a front portion of a vehicle which is equipped with a frame structure of an automotive vehicle according to an embodiment of the present invention. 
         FIG. 2A  is an enlarged plan view of a front side frame on a side which is denoted by an arrow P of  FIG. 1 , and  FIG. 2B  is a side view of the front side frame of  FIG. 2A  when viewed in a direction which is denoted by an arrow L. 
         FIGS. 3A ,  3 B,  3 C,  3 D and  3 E are sectional views of the front side frame taken along lines A-A, B-B, C-C, D-D and E-E respectively of  FIG. 2B . 
         FIG. 4  is an explanatory view of an action when an impact load is inputted. 
         FIG. 5A  is an enlarged plan view of a front side frame of a frame structure of an automotive vehicle according to a second embodiment, which corresponds to  FIG. 2A , and  FIG. 5B  is a sectional view taken along line M-M of  FIG. 5A . 
         FIG. 6  is a sectional view of a front side frame of a frame structure of an automotive vehicle according to a third embodiment, which corresponds to  FIG. 3C . 
         FIG. 7A  is an enlarged plan view of a front side frame of a frame structure of an automotive vehicle according to a fourth embodiment on the side which is denoted by the arrow P of  FIG. 1 , and  FIG. 7B  is a side view of the front side frame of  FIG. 7A  when viewed in a direction which is denoted by an arrow N 
         FIGS. 8A ,  8 B,  8 C,  8 D and  8 E are sectional views of the front side frame taken along lines F-F, G-G, H-H, I-I and J-J respectively of  FIG. 7B . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, a frame structure of an automotive vehicle according to preferred embodiments of the present invention will be described. 
     Embodiment 1 
     A vehicle body of an automotive vehicle  1  according to the present embodiment comprises, as shown in  FIG. 1 , a dash panel  4  which partitions an engine room  2  from a vehicle compartment  3 , a pair of front side frames  5 ,  5  which extends straight in a vehicle longitudinal direction in front of the dash panel  4  on both (light and right) sides, rear end portions of which connect to the dash panel  4 , a bumper reinforcement  7  which is provided at front end portions of the front side frames  5 ,  5  via crush cans  6 ,  6 , hinge pillars  8 ,  8  which are provided at both-side end portions of the dash panel  4  so as to extend vertically and support front end portions of front doors (not illustrated), a dash reinforcement  9  which is provided at a back face of the dash panel  4  so as to interconnect the both-side hinge pillars  8 ,  8 , side sills  10 ,  10  which connect to the lower ends of the hinge pillars  8 ,  8  at front end portions thereof and extend rearward, and floor frames  12 ,  12  which extend in the vehicle longitudinal direction below the floor panel  11  which forms a floor face of the vehicle compartment  3 , front end portions of which connect to rear end portions of the front side frames  5 ,  5 . 
     Herein, when the impact load is inputted to the bumper reinforcement  7  via a bumper face  13  and the like at a vehicle front collision or the like, it is transmitted so as to disperse to members of a vehicle body  4 - 12  via the crush cans  6 ,  6  and front side frames  5 ,  5 . 
     According to the present embodiment, when the impact load is inputted to the vehicle body in the vehicle longitudinal direction, the crush cans  6  crush in an axial direction thereof. The front side frame  5  has a plurality of bend portions T 1 -T 3 , which are operative to bend in a vehicle width direction due to the impact load being inputted (see  FIG. 4 ). Hereinafter, the structure will be described. 
     As shown in  FIGS. 2A ,  2 B and  3 A, the crush can  6  is made of aluminum material, for example, and it has an upper face portion  6   a , a lower face portion  6   b , and left and right side face portions  6   c ,  6   d  so as to form a rectangular closed cross section which extends substantially straight in the vehicle longitudinal direction. At both side face portions  6   c ,  6   d  are formed beads  6   e ,  6   f  which are recessed toward their opposite side face portions  6   d ,  6   c  respectively and extend in the vehicle longitudinal direction. Herein, the depth d 1 , d 2  and the vertical length h 1 , h 2  of these beads  6   e ,  6   f  are the same respectively. Thus, the cross section of the crush can is symmetrical. Further, the thickness and the like of the crush can  6  is configured such that the crush can  6  crushes in an axis direction (a longitudinal direction of the crush can  6 ) so as to have a compressive deformation in bellows shape when the impact load is inputted in the vehicle longitudinal direction. 
     Further, the front side frame  5  comprises, as shown in  FIGS. 2A ,  2 B,  3 C- 3 E, a first member  21  which includes an upper face portion  21   a , a lower face portion  21   b , a side face portion  21   c  and upper and lower flange portions  21   d ,  21   e  so as to have a substantially U-shaped cross section, and a second member  22  which includes an upper face portion  22   a , a lower face portion  22   b , a side face portion  22   c  and upper and lower flange portions  22   d ,  22   e  so as to have a substantially U-shaped cross section. The upper flange portions  21   d ,  22   d  and the lower flange portions  21   e ,  22   e  of the first and second members  21 ,  22  are joined to each other respectively so as to provide the substantially rectangular closed cross section which extends substantially straight in the vehicle longitudinal direction. 
     Further, at both side face portions  21   c ,  22   c  of the first and second members  21 ,  22  are formed beads  21   f ,  22   f  which are recessed toward their opposite side face portions  22   c ,  21   c  respectively and extend in the vehicle longitudinal direction. These beads  21   f ,  22   f  are provided to strengthen the function of absorption of the impact load by the front side frame  5 . 
     Next, the structure of the bend portions T 1 -T 3  will be described. Apparent from  FIGS. 2A ,  2 B and  3 B (a cross section which is located slightly in back of the bend portion T 1 ), the bend portion T 1  is provided at a connection portion of the crush can  6  to the front side frame  5 , specifically at the front end of the front side frame  5 . This bend portion T 1  is configured by a difference in the rigidity between the crush can  6  and the front side frame  5 . A front end  5   a  of the front side frame  5  is formed so as to be slant in such a manner that its outward portion is positioned rearward from its inward portion. Thereby, the front side frame  5  bends outward at the bend portion T 2 . 
     Meanwhile, the centroid of the bend portions T 2 , T 3  of the front side frame  5  is offset to a specified direction of the vehicle width direction from the centroid of the different portion of the front side frame  5  from the bend portions T 2 , T 3 . 
     That is, as apparent from  FIGS. 2A ,  2 B and  3 C, the upper flange portions  21   d ,  22   d  and the lower flange portions  21   e ,  22   e  at the bend portion T 2  are located offset to the above-described specified direction of the vehicle width direction, i.e., outward of the vehicle, from the upper and lower flange portions  21   d ,  22   d ,  21   e ,  22   e  at the different portion from the bend portion T 2 . Further, while a vertical length h 3  of the bead  21   f  is the same as a vertical length h 4  of the bead  22   f  (which is the same as other portions in the longitudinal direction), a depth d 1  of the outside bead  21   f  is shallower than a depth d 2  of the inside bead  22   f . Thus, the centroid Z of the bend portion T 2  is offset toward the side of the side face portion  21   c  of the first member  21  from a middle (center) position C between the side face portions  21   c ,  22   c  of the front side frame  5 . Also, as apparent from  FIG. 2A , the centroid Z of the bend portion T 2  is offset outward of the vehicle from the centroid Z of the different portion from the bend portion T 2 . Herein, as shown in  FIGS. 1 ,  2 A and  4 , the vehicle has a suspension damper D of a suspension member which is located outside the front side frame  5 , and the bend portion T 2  is located so as to be offset from the suspension damper D in the vehicle longitudinal direction. Thereby, the bend portion T 2  which bends is prevented from interfering with the suspension damper D. 
     Further, as apparent from  FIGS. 2A ,  2 B and  3 D, the upper flange portions  21   d ,  22   d  and the lower flange portions  21   e ,  22   e  at the bend portion T 3  are located offset to the above-described specified direction of the vehicle width direction, i.e., inward of the vehicle because the bending direction of the bend portion T 3  is opposite to that of the above-described bend portion T 2 , from the upper and lower flange portions  21   d ,  22   d ,  21   e ,  22   e  at the different portion from the bend portion T 3 . Further, a depth d 2  of the inside bead  22   f  is shallower than a depth d 1  of the outside bead  21   f . Thus, the centroid Z of the bend portion T 3  is offset toward the side of the side face portion  22   c  of the second member  22  from the middle (center) position C between the side face portions  21   c ,  22   c  of the front side frame  5 . That is, the centroid Z of the bend portion T 3  is offset inward of the vehicle from the centroid Z of the different portion from the bend portion T 3 . 
     Further, as apparent from  FIGS. 2A ,  2 B and  3 E, the upper flange portions  21   d ,  22   d  and the lower flange portions  21   e ,  22   e  at a portion of the front side frame  5  which is positioned near its connection portion to the dash panel  4  are located similarly to the bend portion T 2 . A depth d 1  of the outside bead  21   f  is substantially the same as a depth d 2  of the inside bead  22   f . Herein, the front side frame  5  does not bend at this portion near the connection portion to the dash panel. 
     Further, as apparent from  FIG. 2A , a joining line of the upper flange portions  21   d ,  22   d  and the lower flange portions  21   e ,  22   e  at a portion of the front side frame  5  between the bend portions T 2 , T 3  extends substantially straight and obliquely relative to a longitudinal direction of the front side frame  5  in the plan view. 
     The beads  21   f ,  22   f  have bottom portions  21   g ,  22   g  respectively which are formed at the side face portions  21   c ,  22   c , and these bottom portions  21   g ,  22   g  are joined to each other at the bend portions T 2 , T 3 . 
     Hereinafter, the operation of the present embodiment will be described. 
     When the impact load is inputted to the vehicle body in the vehicle longitudinal direction, the crush can  6  crushes so as to deform in the axis direction and the front side frame  5  bends in the vehicle width direction at the bend portions T 1 -T 3  as shown by broken lines in  FIG. 4 . 
     Herein, since the centroid Z of the bend portions T 2 , T 3  of the front side frame  5  is offset in the vehicle width direction from the centroid Z of the different portion of the front side frame  5  from the bend portions T 2 , T 3 , the bend portions T 2 , T 3  can be properly provided without causing any improper increase of the number of member. 
     Also, the above-described offset of the centroid of the bend portions T 2 , T 3  can be materialized easily by the structure in which the upper flange portions  21   d ,  22   d  and the lower flange portions  21   e ,  22   e  at the bend portions T 2 , T 3  are located offset to the above-described specified direction of the vehicle width direction from the upper flange portions  21   d ,  22   d  and the lower flange portions  21   e ,  22   e  at the different portion of the front side frame  5  from the bend portions T 2 , T 3 . 
     Further, since the respective joining lines of the upper flange portions  21   d ,  22   d  and the lower flange portions  21   e ,  22   e  at the front portion in front of the bend portions T 2 , T 3  and the rear portion in back of the bend portions T 2 , T 3  extend substantially straight and obliquely relative to the longitudinal direction of the front side frame  5  in the plan view, these flange portions turn from side to side at the bend portions T 2 , T 3  in the vehicle width direction, so that the position of the bend portions T 2 , T 3  can be specified surely. Thereby, the front side frame  5  bends surely at the bend portions T 2 , T 3 . 
     Also, since the plural bend portions T 2 , T 3  operative to bend in the opposite directions of the vehicle width direction to each other are provided, and the joining line of the upper flange portions  21   d ,  22   d  and the lower flange portions  21   e ,  22   e  at the portion between the bend portions T 2 , T 3  extends substantially straight and obliquely relative to the longitudinal direction of the front side frame  5  in the plan view, the bending of the front side frame  5  can be achieved easily compared to a case in which the joining line of the flange portions extends in a curve shape. 
     Further, the offset of the centroid of the bend portions T 2 , T 3  can be materialized easily by the structure in which the depth of the beads  21   f ,  22   f  is different from each other. 
     Also, since the bottom portions  21   g ,  22   g  of the recessed beads  21   f ,  22   f  are joined to each other, the impact energy can be properly absorbed by friction of the bottom portions  21   g ,  22   g  which occurs at the bending of the front side frame  5 . Further, the deformation of the side face portions  21   c ,  22   c  of the beads  21   f ,  22   f  can be controlled properly. 
     While both the offset joining line provision of the upper flange portions  21   d ,  22   d  and the lower flange portions  21   e ,  22   e  and the different depth d 1 , d 2  of the beads  21   f ,  22   f  are provided to make the offset provision of the centroid Z in the above-described embodiment, either one of these may be applied for the offset of the centroid Z. In this case, the strength of the front side frame  5  may be considered for this application. 
     Embodiment 2 
     In a second embodiment, as shown in  FIG. 5 , the bend portions T 2 , T 3  of a first member  21 ′ and a second member  22 ′ which forms a front side frame  5 ′ has vertical beads  21   h ′,  22   h ′ on their side face portions  21   c ′,  22   c ′. The vertical beads  21   h ′,  22   h ′ extend vertically and are recessed in the bending direction of the bend portions T 2 , T 3 , respectively. Thereby, the front side frame  5 ′ bends surely at the bend portions T 2 , T 3 . 
     Embodiment 3 
     Next, a third embodiment will be described. 
     In the third embodiment, a front side frame  5 ″ has a narrower width W than the first and second embodiments as shown in  FIG. 6 . This is because this frame  5 ″ may be properly applied to a relatively narrow layout space for the frame  5 ″ at the front portion of the vehicle. 
     Herein, a vertical length h 3  of a bead  21   f ″ of a first member  21 ″ which forms a front side frame  5 ″ is not equal to a vertical length h 4  of a bead  22   f ″ of a second member  22 ″. Thus, the centroid Z can be positioned to be offset more toward the first member  21 ″ compared to the case in which the both vertical lengths are equal to each other. Thereby, the offset of the centroid Z can be achieved properly even in case the width W of the front side frame  5  is considerably small. 
     Embodiment 4 
     A fourth embodiment will be described. 
     In the fourth embodiment, as shown in  7 A,  7 B,  8 A- 8 E, a crush can  106  has an upper face portion  106   a , a lower face portion  106   b  and side face portions  106   c ,  106   d  so as to form a substantially rectangular closed cross section which extends substantially straight in the vehicle longitudinal direction. The both side face portions  106   c ,  106   d  have projections  106   e ,  106   f  which project outward respectively. Heights d 1 , d 2  and vertical lengths h 1 , h 2  of the projections  106   e ,  106   f  are equal to each other, respectively, such that the cross section of the crush can  106  is symmetrical. Further, the thickness and the like of the crush can  106  is configured such that the crush can  10  crushes in the axis direction (longitudinal direction of the crush can  106 ) so as to have the compressive deformation in bellows shape when the impact load is inputted in the vehicle longitudinal direction. 
     Further, the front side frame  105  comprises, as shown in  FIGS. 7A ,  7 B,  8 C- 8 E, a first member  121  which includes an upper face portion  121   a , a lower face portion  121   b , a side face portion  121   c  and upper and lower flange portions  121   d ,  121   e  so as to have a substantially U-shaped cross section, and a second member  122  which includes an upper face portion  122   a , a lower face portion  122   b , a side face portion  122   c  and upper and lower flange portions  122   d ,  122   e  so as to have a substantially U-shaped cross section. The upper flange portions  121   d ,  122   d  and the lower flange portions  121   e ,  122   e  of the first and second members  121 ,  122  are joined to each other respectively so as to provide the substantially rectangular closed cross section which extends substantially straight in the vehicle longitudinal direction. 
     Further, at both side face portions  121   c ,  122   c  of the first and second members  121 ,  122  are formed projections  121   f ,  122   f  which project toward the opposite sides to the side face portions  122   c ,  121   c  respectively and extend in the vehicle longitudinal direction. These projections  121   f ,  122   f  are provided to strengthen the function of absorption of the impact load by the front side frame  105 . 
     Next, the structure of the bend portions T 1 -T 3  will be described. Apparent from  FIGS. 7A ,  7 B and  8 B (a cross section which is located slightly in back of the bend portion T 1 ), the bend portion T 1  is provided at a connection portion of the crush can  106  to the front side frame  105 , specifically at the front end of the front side frame  105 . This bend portion T 1  is configured by a difference in the rigidity between the crush can  106  and the front side frame  105 . A front end  105   a  of the front side frame  105  is formed so as to be slant in such a manner that its outward portion is positioned rearward from its inward portion. Thereby, the front side frame  105  bends outward at the bend portion T 2 . 
     That is, as apparent from  FIGS. 7A ,  7 B and  8 C, the upper flange portions  121   d ,  122   d  and the lower flange portions  121   e ,  122   e  at the bend portion T 2  are located offset to the above-described specified direction of the vehicle width direction, i.e., outward of the vehicle, from the upper and lower flange portions  121   d ,  122   d ,  121   e ,  122   e  at the different portion from the bend portion T 2 . Further, a height d 1  of the outside projection  121   f  is greater than a height d 2  of the inside projection  122   f  (the height d 2  is zero at this portion). Thus, the centroid Z of the bend portion T 2  is offset outward of the vehicle from the centroid Z of the different portion from the bend portion T 2 . 
     Further, as apparent from  FIGS. 7A ,  7 B and  8 D, the upper flange portions  121   d ,  122   d  and the lower flange portions  121   e ,  122   e  at the bend portion T 3  are located offset to the above-described specified direction of the vehicle width direction, i.e., inward of the vehicle from the upper and lower flange portions  121   d ,  122   d ,  121   e ,  122   e  at the different portion from the bend portion T 3  (similar to the above-described first embodiment regarding the flange portions). Further, the height d 2  of the inside projection  122   f  is greater than the height d 1  of the outside projection  121   f  (the height d 1  is zero at this portion). Thus, the centroid Z of the bend portion T 3  is offset inward of the vehicle from the centroid Z of the different portion from the bend portion T 3 . 
     Further, as apparent from  FIGS. 7A ,  7 B and  8 E, the upper flange portions  121   d ,  122   d  and the lower flange portions  121   e ,  122   e  at a portion of the front side frame  105  which is positioned near its connection portion to the dash panel  4  are located similarly to the bend portion T 2 . A height d 1  of the outside projection  121   f  is substantially the same as a height d 2  of the inside projection  122   f . Herein, the front side frame  105  does not bend at this portion near the connection portion to the dash panel. 
     According to the present embodiment, the offset of the centroid Z of the bend portions T 2 , T 3  can be materialized easily by the structure in which the height of the projections  121   f ,  122   f  is different from each other. 
     Herein, the vertical length may be set to be different from each other like the above-described third embodiment. Thereby, the centroid may be offset properly, restraining the projection height. 
     While the front side frame is configured to bend in the vehicle width direction in the above-described embodiments, the present invention is applicable to any case in which the front side frame bends vertically or in any angle direction between the lateral direction and the vertical direction. Further, while either the recessed bead or the projection are formed at the both side faces of the front side frame in the above-described embodiments, the combination of these may be applied in such a manner that the projection is formed at the bending-direction side and the recessed bead is formed at the other side. 
     Any other modifications and improvements may be applied in the scope of a sprit of the present invention.