Patent Publication Number: US-10766535-B2

Title: Vehicle body rear part structure

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Priority is claimed on Japanese Patent Application No. 2017-133002, filed on Jul. 6, 2017, the contents of which are incorporated herein by reference. 
     BACKGROUND 
     Field of the Invention 
     The present invention relates to a vehicle body rear part structure. 
     Background 
     Among vehicle body rear part structures, a structure is known in which a rear side frame is provided on both side parts of a vehicle, a lower surface in the vicinity of a rear end part of the rear side frame is formed in a downward slope toward a vehicle body rearward direction, and a rear bumper is provided at a vehicle body rearward position of the rear side frame (for example, refer to Japanese Patent No. 4120200). 
     By forming the lower surface of the rear side frame in a downward slope, for example, when the height dimension of the rear side frame is not matched with the height dimension of the rear bumper, it is possible to match the rear side frame with the rear bumper in a vertical direction. 
     SUMMARY 
     However, when the lower surface of the rear side frame is formed in a downward slope, in the lower surface of the rear side frame, a curved part is formed at a boundary between a slope part of the downward slope and another region. Therefore, for example, when an impact load is input from a vehicle body rearward direction to the rear side frame due to a rear collision, a stress may concentrate on the curved part, and the rear side frame may be deformed at the curved part in the vertical direction. 
     An aspect of the present invention provides a vehicle body rear part structure capable of preventing a rear side frame from being deformed in a vertical direction. 
     (1) A vehicle body rear part structure according to an aspect of the present invention includes: a rear side frame, wherein the rear side frame includes: a general part that extends substantially horizontally in at least one of an upper surface and a lower surface; and a slope part that slopes upward or downward from the general part, the rear side frame includes two components which are a front side member and a rear side member, and a curved part that becomes a boundary between the general part and the slope part is provided on a joint part between the front side member and the rear side member. 
     In this way, the curved part is formed at the boundary between the general part and the slope part. The curved part is provided on the joint part between the front side member and the rear side member. At the joint part between the front side member and the rear side member, the front side member and the rear side member are overlapped with each other. Accordingly, the rigidity of the joint part is ensured. Thereby, it is possible to provide the curved part on the joint part having an ensured rigidity. Therefore, for example, when an impact load is input from a vehicle body rearward direction to the rear side frame due to a rear collision, it is possible to prevent the rear side frame from being deformed in the vertical direction from the curved part. 
     (2) In the vehicle body rear part structure described above, the rear side frame may include a fragile part that facilitates deformation at a time of rear collision, and the curved part may be provided at a more vehicle body frontward position than the fragile part. 
     In this way, the fragile part is provided on the rear side frame. Accordingly, for example, when an impact load is input from a vehicle body rearward direction to the rear side frame due to a rear collision, it is possible to facilitate deformation of the rear side frame from the fragile part by the input impact load. Thereby, it is possible to absorb the impact load that is input to the rear side frame. 
     The curved part is provided at a more vehicle body frontward position than the fragile part of the rear side frame. Thereby, it is possible to reduce the load that is transmitted to the curved part, and it is possible to further favorably prevent the rear side frame from being deformed in the vertical direction from the curved part. 
     (3) The vehicle body rear part structure described above may include: a reinforcement member that reinforces the rear side frame at an inner part of the rear side frame, wherein the reinforcement member may be provided between the curved part and the fragile part in a vehicle body front-to-rear direction. 
     In this way, the reinforcement member is provided between the curved part and the fragile part. Accordingly, the rigidity of the rear side frame at a more vehicle body frontward position than the fragile part is enhanced by the reinforcement member. Thereby, it is possible to further favorably prevent the rear side frame from being deformed in the vertical direction from the curved part by the impact load that is input to the rear side frame. 
     (4) In the vehicle body rear part structure described above, the rear side frame may include at least two joint points that are joined to a vehicle body and that are separated from each other in a vehicle body front-to-rear direction, and the reinforcement member may be arranged between the two joint points. 
     In this way, the reinforcement member is arranged between the two joint points. Accordingly, the reinforcement member can be reinforced by the two joint points. Thereby, it is possible to further enhance the rigidity of the rear side frame by the reinforcement member. 
     (5) In the vehicle body rear part structure described above, the rear side frame may include: a suspension attachment part to which a suspension apparatus is attached; and a suspension stiffener that reinforces the suspension attachment part, wherein the suspension stiffener may be provided to extend from the suspension attachment part to the curved part. 
     In this way, the suspension stiffener is provided to extend from the suspension attachment part to the curved part. Accordingly, it is possible to further reinforce the curved part by the suspension stiffener. Thereby, it is possible to further favorably prevent the rear side frame from being folded from the curved part. 
     (6) The vehicle body rear part structure described above may include an outrigger that extends outward in a vehicle width direction from the rear side frame, wherein an outrigger joint part of the rear side frame and the outrigger may be provided on the curved part. 
     In this way, the outrigger joint part of the rear side frame and the outrigger is provided on the curved part. Accordingly, it is possible to reinforce the curved part by the outrigger. Thereby, it is possible to further favorably prevent the rear side frame from being folded from the curved part. 
     (7) The vehicle body rear part structure described above may include: an inner wheel arch that is provided on an outer side in a vehicle width direction of the outrigger; and a connection member that connects together the outrigger and the inner wheel arch, wherein the outrigger may include a flange that extends continuously from the curved part to the connection member. 
     In this way, the outrigger and the inner wheel arch are connected together by the connection member. Accordingly, it is possible to solidly connect the inner wheel arch to the outrigger by the connection member. Thereby, it is possible to prevent a so-called opening of the inner wheel arch by the connection member. 
     Further, the flange of the outrigger extends continuously from the curved part to the connection member. Accordingly, it is possible to further enhance the rigidity of the curved part by the flange. Thereby, it is possible to further favorably prevent the rear side frame from being folded from the curved part. 
     According to an aspect of the present invention, the curved part is formed at the boundary between the general part and the slope part, and the curved part is provided on the joint part between the front side member and the rear side member. Thereby, it is possible to provide the curved part on the joint part having an ensured rigidity, and it is possible to prevent the rear side frame from being deformed in the vertical direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a bottom view showing a vehicle body rear part structure in an embodiment of the present invention. 
         FIG. 2  is a perspective view showing a state seen from a frontward downward direction of the vehicle body rear part structure in the embodiment of the present invention. 
         FIG. 3  is a bottom view showing an enlarged state of a III part of  FIG. 1  in the embodiment of the present invention. 
         FIG. 4  is a cross-sectional view showing a state broken at a IV-IV line of  FIG. 3  in the embodiment of the present invention. 
         FIG. 5  is a cross-sectional view showing an enlarged state of a V part of  FIG. 4  in the embodiment of the present invention. 
         FIG. 6  is a cross-sectional view showing a state broken at a VI-VI line of  FIG. 5  in the embodiment of the present invention. 
         FIG. 7  is a cross-sectional view showing a state broken at a VII-VII line of  FIG. 5  in the embodiment of the present invention. 
         FIG. 8  is a cross-sectional view showing a state broken at a VIII-VIII line of  FIG. 5  in the embodiment of the present invention. 
         FIG. 9  is a bottom view showing an enlarged state of a IX part of  FIG. 3  in the embodiment of the present invention. 
         FIG. 10  is a bottom view showing an enlarged state of an outrigger of  FIG. 3  in the embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     An embodiment of the present invention will be described with reference to the drawings. In the drawings, an arrow FR indicates a frontward direction of a vehicle, an arrow UP indicates an upward direction of the vehicle, and an arrow LH indicates a leftward direction of the vehicle. 
     As shown in  FIG. 1  and  FIG. 2 , a vehicle body rear part structure  10  includes right and left rear side frames  12 , a rear floor panel  14 , right and left outriggers  16 , and right and left wheel houses  18 . 
     The left rear side frame  12  is provided on a left side of a vehicle body Ve and extends toward a vehicle body rearward direction from a rear end part  21   a  of a left side sill  21 . The right rear side frame  12  is provided on a right side of a vehicle body Ve and extends toward a vehicle body rearward direction from a rear end part  21   a  of the right side sill  21 . 
     A front floor panel  23  is provided between the left side sill  21  and the right side sill  21 . A floor tunnel  24  is provided at a middle position in a vehicle width direction of the front floor panel  23 . 
     A rear floor panel  14  is provided between the left rear side frame  12  and the right rear side frame  12 . A left suspension support part  26  is provided on the left rear side frame  12 . A right suspension support part  26  is provided on the right rear side frame  12 . A subframe  31  of a suspension apparatus  28  is attached to the left suspension support part  26  and the right suspension support part  26 . 
     The left outrigger  16  extends outward in the vehicle width direction from the left rear side frame  12 . 
     The left wheel house  18  is provided on the left rear side frame  12  and the left outrigger  16 . The right outrigger  16  extends outward in the vehicle width direction from the right rear side frame  12 . The right wheel house  18  is provided on the right rear side frame  12  and the right outrigger  16 . 
     The vehicle body rear part structure  10  has a substantially symmetric configuration in the right-to-left direction. Therefore, left configuration members are described, and descriptions of right configuration members are omitted. 
     For ease of understanding of the configuration, the left rear side frame  12  is described as a “rear side frame  12 ”. The left suspension support part  26  is described as a “suspension support part  26 ”. The left outrigger  16  is described as an “outrigger  16 ”. The left wheel house  18  is described as a “wheel house  18 ”. 
     As shown in  FIG. 3 , the outrigger  16  extends outward in the vehicle width direction from the rear side frame  12 . The wheel house  18  is provided on the rear side frame  12  and the outrigger  16 . The wheel house  18  includes an inner wheel  33  and an inner wheel arch  34 . 
     The inner wheel  33  is provided on the rear side frame  12  and the outrigger  16 . The inner wheel arch  34  is provided on an outer side in the vehicle width direction of the inner wheel  33  and the outrigger  16 . 
     As shown in  FIG. 4  and  FIG. 5 , the rear side frame  12  includes an upper side member  35 , a front side member  36 , a rear side member  37 , a reinforcement member  38 , a suspension support part  26 , and a suspension stiffener  41 . The upper side member  35  extends toward a vehicle body rearward direction from the rear end part  21   a  (refer to  FIG. 1 ) of the left side sill  21 . The front side member  36  and the rear side member  37  are provided on a lower side of the upper side member  35 . 
     As shown in  FIG. 5  and  FIG. 6 , the front side member  36  extends toward a vehicle body rearward direction from the rear end part  21   a  (refer to  FIG. 1 ) of the left side sill  21 . The front side member  36  includes a first inner wall  51 , a first outer wall  52 , a general part  53 , a first inner flange  54 , and a first outer flange  55 . 
     The first inner wall  51  is arranged to be spaced inward in the vehicle width direction with respect to the first outer wall  52 . The general part  53  is connected to a lower end part  51   a  of the first inner wall  51  and a lower end part  52   a  of the first outer wall  52 . A first inner flange  54  protrudes inward in the vehicle width direction from an upper end part  51   b  of the first inner wall  51 . A first outer flange  55  protrudes outward in the vehicle width direction from an upper end part  52   b  of the first outer wall  52 . 
     The upper side member  35  includes an inner joint piece  57  and an outer joint piece  58 . The first inner flange  54 , the inner joint piece  57 , and a left part  14   a  of the rear floor panel  14  are in a state of being overlapped with one another and are joined together, for example, by a spot welding. The first outer flange  55 , the outer joint piece  58 , and an inner part  61   a  of an outer panel  61  are in a state of being overlapped with one another and are joined together, for example, by a spot welding. 
     In this state, the general part  53  of a front lower side part  43  is arranged below the rear floor panel  14 . The general part  53  extends parallel with respect to the rear floor panel  14  (that is, substantially horizontally). 
     As shown in  FIG. 5  and  FIG. 7 , the rear side member  37  extends toward a vehicle body rearward direction from a rear end part of the front side member  36 . The rear side member  37  includes a second inner wall  71 , a second outer wall  72 , a slope part  73 , a second inner flange  74 , and a second outer flange  75 . The second inner wall  71  is arranged to be spaced inward in the vehicle width direction with respect to the second outer wall  72 . The slope part  73  is connected to a lower end part  71   a  of the second inner wall  71  and a lower end part  72   a  of the second outer wall  72 . 
     A second inner flange  74  protrudes inward in the vehicle width direction from an upper end part  71   b  of the second inner wall  71 . A second outer flange  75  protrudes outward in the vehicle width direction from an upper end part  72   b  of the second outer wall  72 . 
     The second inner flange  74 , the inner joint piece  57 , and the left part  14   a  of the rear floor panel  14  are in a state of being overlapped with one another and are joined together, for example, by a spot welding. The second outer flange  75 , the outer joint piece  58 , and the inner part  61   a  of the outer panel  61  are in a state of being overlapped with one another and are joined together, for example, by a spot welding. 
     In this state, the slope part  73  of a rear lower side part  64  is arranged below the rear floor panel  14 . The slope part  73  extends so as to be sloped downward from the general part  53  with respect to the rear floor panel  14 . 
     The slope part  73  has a horizontal section  73   a  at a front end portion of the slope part  73 . The horizontal section  73   a  extends horizontally along a rear end section of the general part  53 . The horizontal section  73   a  is in a state of being overlapped with the rear end section  53   a  of the general part  53  and is joined to the rear end section  53   a . In this state, a bent part or curved part  81  is formed at a boundary between the general part  53  and the slope part  73 . 
     As shown in  FIG. 5  and  FIG. 8 , the first inner wall  51  and the second inner wall  71  are joined together in a joint part  39  between the front side member  36  and the rear side member  37 . Further, the first outer wall  52  and the second outer wall  72  are joined together. Further, the rear end section  53   a  of the general part  53  is joined to the horizontal section  73   a  of the slope part  73 . Accordingly, the rigidity of the joint part  39  between the front side member  36  and the rear side member  37  is enhanced. 
     The front side member  36  and the rear side member  37  are joined to the upper side member  35 . Further, the front side member  36  and the rear side member  37  are joined together. Thereby, the rear side frame  12  is formed. 
     That is, the rear side frame  12  includes two components which are the front side member  36  and the rear side member  37 . The rear side frame  12  is formed in a hollow closed cross-section. A lower surface  12   a  of the rear side frame  12  includes the general part  53  and the slope part  73 . 
     The slope part  73  extends so as to be sloped downward and in a vehicle body rearward direction from the general part  53 . Accordingly, the curved part  81  is formed at the boundary between the general part  53  and the slope part  73 . The curved part  81  is provided at the joint part  39  between the front side member  36  and the rear side member  37 . 
     Specifically, in a state where the rear end section  53   a  of the general part  53  and the horizontal section  73   a  of the slope part  73  are overlapped with each other, a downward slope of the slope part  73  is formed from a rear end  53   b  of the rear end section  53   a.    
     The curved part  81  is formed in a region in which the downward slope is formed. 
     The front side member  36  and the rear side member  37  are overlapped with each other, and thereby, the rigidity of the joint part  39  is ensured. That is, the curved part  81  is provided on the joint part  39  having an ensured rigidity. Accordingly, for example, when an impact load F 1  is input from a vehicle body rearward direction to the rear side frame  12  due to a rear collision, it is possible to prevent the rear side frame  12  from being deformed in the vertical direction from the curved part  81 . 
     As shown in  FIG. 4  and  FIG. 9 , a plurality of fragile parts  83  are formed to be spaced from each other in the vehicle body front-to-rear direction on the rear side member  37  of the rear side frame  12 . The plurality of fragile parts  83  are formed on the second inner wall  71  and the second outer wall  72  of the rear side member  37  in a curved shape so as to be recessed to the inner side of the rear side member  37 . The plurality of fragile parts  83  facilitate deformation (specifically, crushing) of the rear side frame  12  by the impact load F 1  that is input from the vehicle body rearward direction due to a rear collision. 
     Accordingly, for example, when an impact load F 1  is input from a vehicle body rearward direction to the rear side frame  12 , it is possible to facilitate crushing of the rear side frame  12  from the fragile part  83  by the input impact load F 1 . Thereby, it is possible to absorb the impact load F 1  that is input to the rear side frame  12 . 
     The plurality of fragile parts  83  are provided at a more vehicle body rearward position than the curved part  81 . In other words, the curved part  81  is provided at a more vehicle body frontward position than the plurality of fragile parts  83 . That is, it is possible to absorb the input impact load F 1  by the crushing of the rear side frame  12  and to transmit the rest of the load to the curved part  81 . 
     Thereby, it is possible to reduce the load that is transmitted to the curved part  81 , and it is possible to favorably prevent the rear side frame  12  from being deformed in the vertical direction from the curved part  81 . 
     The reinforcement member  38  is stored at an inner part  85  of the rear side frame  12 . The reinforcement member  38  has a reinforcement inner wall  86 , a reinforcement outer wall  87 , and a reinforcement bottom part  88 . The reinforcement inner wall  86  is joined to the second inner wall  71  of the rear side member  37  along the second inner wall  71  of the rear side member  37 . The reinforcement outer wall  87  is joined to the second outer wall  72  along the second outer wall  72 . The reinforcement bottom part  88  is joined to the slope part  73  of the rear lower side part  64  along the slope part  73  of the rear lower side part  64 . 
     The reinforcement member  38  is formed of the reinforcement inner wall  86 , the reinforcement outer wall  87 , and the reinforcement bottom part  88  in a U shape in the cross-section. The reinforcement member  38  is provided at the inner part  85  of the rear side frame  12  (in detail, the rear side member  37 ), and thereby, the rear side frame  12  is reinforced by the reinforcement member  38 . 
     The reinforcement member  38  is provided between the curved part  81  and the fragile part  83  in the vehicle body front-to-rear direction. Accordingly, the rigidity of the rear side frame  12  at a more vehicle body frontward position than the fragile part  83  is enhanced by the reinforcement member  38 . Thereby, for example, it is possible to favorably prevent the rear side frame  12  from being deformed in the vertical direction from the curved part  81  by the impact load F 1  that is input to the rear side frame  12  due to a rear collision. 
     As shown in  FIG. 9  and  FIG. 10 , the rear side frame  12  includes, for example, two joint points  91 ,  92 . The two joint points  91 ,  92  are joined to the vehicle body Ve and are provided so as to be separated from each other in the vehicle body front-to-rear direction. In the vehicle body front-to-rear direction, the reinforcement member  38  is provided between the two joint points  91 ,  92 . 
     Accordingly, the reinforcement member  38  is reinforced by the two joint points  91 ,  92 . Thereby, the rigidity of the rear side frame  12  is further enhanced by the reinforcement member  38 . 
     As shown in  FIG. 3 , the suspension support part  26  is provided on the rear side frame  12 . A left end part  31   a  of the subframe  31  is attached to the suspension support part  26 . The suspension support part  26  includes a first suspension attachment part (suspension attachment part)  94  and a second suspension attachment part (suspension attachment part)  95 . 
     The first suspension attachment part  94  is provided on a front end part  12   b  side of the rear side frame  12 . The second suspension attachment part  95  is provided at a vehicle body rearward position of the first suspension attachment part  94  to be spaced from the first suspension attachment part  94 . 
     As shown in  FIG. 5  and  FIG. 6 , a region of the rear side frame  12  (specifically, the front side member  36 ) to which the second suspension attachment part  95  is attached is reinforced by the suspension stiffener  41 . The suspension stiffener  41  is provided to extend to the curved part  81  via the second suspension attachment part  95 . 
     Specifically, the suspension stiffener  41  includes a stiffener inner wall  101 , a stiffener outer wall  102 , a stiffener bottom part  103 , and a stiffener protrusion piece  104  (refer to  FIG. 8 ). 
     The stiffener inner wall  101  is joined to the first inner wall  51  along the first inner wall  51 . The stiffener outer wall  102  is joined to the first outer wall  52  along the first outer wall  52 . The stiffener bottom part  103  is joined to the general part  53  along the general part  53 . The suspension stiffener  41  is formed of the stiffener inner wall  101 , the stiffener outer wall  102 , and the stiffener bottom part  103  in a U shape in the cross-section. 
     Accordingly, a region of the rear side frame  12  (the front side member  36 ) to which the second suspension attachment part  95  is attached is reinforced by the suspension stiffener  41 . 
     The stiffener protrusion piece  104  protrudes from a rear end  103   a  of the stiffener bottom part  103  along the rear end section  53   a  of the general part  53  toward the vehicle body rearward direction. The stiffener protrusion piece  104  is joined to the rear end section  53   a  of the general part  53  and the horizontal section  73   a  of the slope part  73  in a state of being interposed between and held by the rear end section  53   a  of the general part  53  and the horizontal section  73   a  of the slope part  73  (also refer to  FIG. 8 ). 
     Accordingly, the curved part  81  is reinforced by the stiffener protrusion piece  104  (that is, the suspension stiffener  41 ). Thereby, it is possible to favorably prevent the rear side frame  12  from being folded from the curved part  81 . 
     As shown in  FIG. 10 , the outrigger  16  extends outward in the vehicle width direction from the rear side frame  12 . The outrigger  16  has a first side  106 , a second side  107 , and a third side  108  in a bottom view. Hereinafter, the second side  107  is referred to as an “outrigger flange  107  (flange)”. The third side  108  is referred to as a “slope side  108 ”. 
     The outrigger  16  is formed of the first side  106 , the outrigger flange  107 , and the slope side  108  in a substantially triangular shape in a bottom view. 
     The first side  106  extends in the vehicle body front-to-rear direction along the stiffener bottom part  103  and the general part  53  of the front side member  36  and is joined to the general part  53  and the stiffener bottom part  103 . The outrigger flange  107  extends in the vehicle width direction along the outer panel  61  and the curved part  81  of the rear side frame  12  and is joined to the curved part  81  and the outer panel  61 . 
     That is, an outrigger joint part  109  at which the rear side frame  12  and the outrigger  16  are joined together is provided on the curved part  81 . Accordingly, the curved part  81  is reinforced by the outrigger  16 . Thereby, it is possible to favorably prevent the rear side frame  12  from being folded from the curved part  81  by the outrigger  16 . 
     The inner wheel arch  34  is provided on an outer side in the vehicle width direction of the outrigger  16 . The inner wheel arch  34  is connected by a connection member  112 . The connection member  112  has a base part  113  and a support part  114 . The base part  113  is joined to the outrigger flange  107  and a front end  61   b  of the outer panel  61  so as to extend in the vehicle width direction in a state of being interposed between and held by the outrigger flange  107  and the front end  61   b  of the outer panel  61 . 
     The support part  114  extends outward in the vehicle width direction from the base part  113  along the inner wheel arch  34  and is joined to a rear end part  34   a  of the inner wheel arch  34 . Accordingly, the outrigger flange  107  and the inner wheel arch  34  are connected together by the connection member  112 . 
     In this way, the outrigger flange  107  and the inner wheel arch  34  are connected together by the connection member  112 . Accordingly, the inner wheel arch  34  is solidly connected to the outrigger flange  107  by the connection member  112 . Thereby, it is possible to prevent, by the connection member  112 , the inner wheel arch  34  from opening in an arrow A direction. 
     Further, the outrigger flange  107  extends in the vehicle width direction continuously from the curved part  81  to the connection member  112 . Accordingly, it is possible to further enhance the rigidity of the curved part  81  by the outrigger flange  107 . Thereby, it is possible to further favorably prevent the rear side frame  12  from being folded from the curved part  81 . 
     The technical scope of the present invention is not limited to the embodiment described above, and a variety of changes can be added without departing from the scope of the invention. 
     For example, the embodiment is described using an example in which the general part  53  and the slope part  73  are formed on the lower surface  12   a  of the rear side frame  12 , and the curved part  81  is provided on the lower surface  12   a ; however, the embodiment is not limited thereto. As other examples, for example, it is also possible to provide the curved part  81  on an upper surface  12   c  of the rear side frame  12 . 
     The embodiment is described using an example in which the rear end section  53   a  of the general part  53  extends horizontally, the front end part of the slope part  73  is the horizontal section  73   a , and the curved part  81  is formed at a boundary between the rear end  53   b  of the rear end section  53   a  and the rear end of the horizontal section  73   a ; however, the embodiment is not limited thereto. 
     As other examples, for example, it is also possible to extend the rear end section  53   a  of the general part  53  in a slope shape having a downward slope and form the front end part (that is, the horizontal section  73   a ) of the slope part  73  in a slope shape. In this case, the curved part  81  is formed at the boundary between a front end of the rear end section  53   a  and a front end of the horizontal section  73   a.    
     The embodiment is described using an example in which the two joint points  91 ,  92  are provided on the rear side frame  12 ; however, the embodiment is not limited thereto. As other examples, for example, it is also possible to provide three or more joint points on the rear side frame  12 . 
     The embodiment is described using an example in which, when an impact load is input from a vehicle body rearward direction to the rear side frame  12 , crushing of the rear side frame  12  is facilitated by the fragile part  83  of the rear side frame  12 ; however, the embodiment is not limited thereto. As other examples, for example, it is also possible to set the fragile part  83  so as to fold the rear side frame  12  in the vehicle width direction. It is possible to absorb the impact energy by folding the rear side frame  12  in the vehicle width direction.